JP3047567B2 - Orientation sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an azimuth sensor for applying an appropriate bias magnetic field to a magnetoresistive element and detecting the terrestrial magnetism to determine the azimuth.

[0002]

2. Description of the Related Art In general, sensors for detecting geomagnetism include those using a rotatable magnet, those using a core wound with a detection coil, and those using a magnetoresistive element. The one using a rotatable magnet generally supports the center point of the N and S poles of a permanent magnet rotatably, and the N and S poles always point north and south along the direction of geomagnetism. Is detected. However, this method is difficult to downsize the element due to the presence of the movable portion, and it is difficult to apply the detection result to an electric signal and combine it with another use. In addition, the thing which wound the coil for detection on the core,
By detecting the geomagnetic signal with a coil and processing the circuit,
Although the azimuth is detected, it is also difficult to reduce the size.

On the other hand, a direction sensor using a ferromagnetic magnetoresistive element having good weak magnetic field sensitivity can easily process a detection signal and can be applied to other electric controls. Further, there is an advantage that the size can be reduced, and a direction sensor using a magnetoresistive element has been considered.

FIG. 4 shows a conventional direction sensor using a magnetoresistive element. The direction sensor includes two sensor units A and B. In FIG. 6, reference numerals 11a and 11b denote magnetoresistive elements, and the pattern directions of the elements are the same.
FIG. 7A shows how the magnetoresistive elements 11a and 11b change their resistance values with respect to an external magnetic field. When a magnetic field is applied to the element pattern in the rotational direction as shown in FIG. This is a change in the resistance value. Reference numerals 12a and 12b denote permanent magnets for generating a bias magnetic field, and the magnetic fields Ha and Hb applied to the magnetoresistive elements 11a and 11b are orthogonal to each other as shown in the drawing. Now, the direction of the geomagnetic He is shown in FIG.
, The magnetic field felt by each of the magnetoresistive elements 11a and 11b is a combined magnetic field Ht of the magnetic fields Ha, Hb and He.
a, Htb. That is, assuming that the angle between the bias magnetic field of the sensor A and the terrestrial magnetism is θ, the angle between the sensor B and the terrestrial magnetism is θ + 90 °,
If θ is known, the azimuth can be detected.

When the A and B sensors are rotated in the same plane to detect terrestrial magnetism, the output of the sensor is theoretically shifted to a waveform as shown in FIG. Become. That is, each output of the sensors A and B can be expressed as Va = Asinθ Vb = Bcosθ. From this, the directional angle of the terrestrial magnetism with respect to the sensor is tanθ = sinθ / cosθ = (Va × B) / (vb × A) Is obtained as This calculation can be easily performed using a microcomputer.

[0006]

However, in the conventional direction sensor using the above-described magnetoresistive elements 11a and 11b, an error tends to occur in the direction indicated by the following points. First,
Since the azimuth is determined by the ratio of the outputs from the two magnetoresistive elements 11a and 11b, an error occurs unless the sensitivity of each sensor is the same. That is, the magnetic characteristics between the magnetoresistive elements must be the same. Next, the combined magnetic field applied to the element must be the same, the magnitude of the bias magnetic field,
The direction for each magnetoresistive element must be constant.

However, it is difficult to actually produce the magnetoresistive elements 11a and 11b whose characteristics completely match as shown in FIG. In addition, it is difficult to accurately install the bias magnet, and as shown in the characteristic diagram of FIG. 9, the operation centers of the respective elements are different, the output is reduced, and the output between the sensors varies as described above. This causes a problem that an error occurs in the direction detection.

Further, since the bias magnetic fields Ha and Hb are formed by permanent magnets, the respective bias magnetic fields Ha and Hb influence each other, so that it is impossible to obtain bias magnetic fields Ha and Hb which are orthogonal to each other. As described above, the conventional direction sensor has a problem that the detected direction tends to include an error.

There is also a problem that the size of the sensor is increased by using two magnetoresistive elements.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a small and accurate azimuth sensor which detects geomagnetism with a simple structure and shows an accurate azimuth.

[0011]

In order to achieve this object, an azimuth sensor according to the present invention is arranged such that when an electric current is applied to an insulating substrate having four orthogonal sides in the longitudinal direction of a pattern, an electric resistance of the magnetic field is perpendicular to the pattern. Four magnetoresistive elements that change according to the strength are arranged so that the longitudinal directions of the patterns are orthogonal to each other and are oriented at 45 ° to each side of the insulating substrate, and are connected in series with each other. A magnetoresistive element configured by providing an input terminal and an output terminal, and a pedestal for installing the magnetoresistive element such that the surface on which the magnetoresistive element is formed is located at the center thereof, and A first groove for winding a first bias coil for applying a bias magnetic field in a 45 ° direction at a predetermined distance from the magnetoresistive element; A holder having a second groove for forming a second bias coil orthogonal to the coil at a predetermined position so as not to touch the first bias coil, and a predetermined number of turns on the holder. And two bias coils.

[0012]

According to the present invention, the magneto-resistive element uses a magneto-resistive element composed of magneto-resistive elements formed at very close and adjacent positions under the same forming conditions, and is orthogonal to the external magnetic field. The output characteristics with respect to the combined magnetic field with the bias magnetic field are the same for all magnetoresistive elements.

In addition, the bias magnetic field instantaneously switches ON and OFF of the current flowing through each bias coil, and only one of the two bias coils detects the direction by applying the bias magnetic field. There is no possibility that the other bias magnetic field influences and shifts in the bias magnetic field application direction to cause an error. The magnetoresistive element is held by a holder that forms a bias coil, and is previously set on a pedestal such that the magnetoresistive element comes to the center of a bias coil that is formed outside. Can also be maintained at a predetermined value. Further, since the outer-wound bias coil is not directly wound around the inner-wound coil, the shape of the coil is stabilized and the generated magnetic field is also stabilized. In addition, since the number of turns of each bias coil is set to a predetermined number, the same magnetic field can be obtained even when excited by the same constant current source.

In addition, 45 ° with respect to the magnetoresistive element
Bias coil to apply a bias magnetic field in the
When winding, the longitudinal direction of the magnetoresistive element is
Formed so as to be in a 45 ° direction with respect to the four sides of the plate
In this case, if it is formed parallel to the four sides of the insulating substrate,
The size of the sensor as a whole can be made smaller than in the case of the above .

This makes it possible to realize an azimuth sensor which detects geomagnetism and indicates an accurate azimuth with a simple configuration.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an orientation sensor according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 (a), (b)
2A and 2B are a perspective view and a plan view, respectively, showing the outer shape of the direction sensor according to the present embodiment, and FIG. 2A is a cross-sectional view in which the upper surface of the sensor is cut away. FIG. 2B is a side sectional view of the sensor. In the figure, reference numeral 1 denotes a magneto-resistive element, which is composed of four magneto-resistive elements 3 whose longitudinal directions are perpendicular to each other and are connected in series with each other, formed on an insulating substrate made of glass on a rectangular flat plate. The four magnetoresistive elements 3 are formed by vacuum-depositing NiFe to a film thickness of 1000 ° and then processing the same into a predetermined pattern by photolithography and etching. °
The direction is set. Reference numeral 3a denotes a magnetoresistive element terminal. Reference numerals 2a and 2b denote bias coils for generating a bias magnetic field. After the magnetoresistive element 1 is installed on a mounting table 4a in a box-shaped element holder 4, coil grooves 4b and 4c provided on the element holder 4 are provided. A predetermined number of insulated wires were wound around the wire. Here, the depths of the coil grooves 4b and 4c of the element holder 4 are h ₁ and h _{2 as} shown in FIGS. 3A and 3B, respectively. Is deeper. In addition, the position of the outer winding groove is changed in advance by d1 in consideration of the thickness d1 of the inner coil.
(H ₁ −h ₂ = Δh ≧ d ₁ ) Each bias coil 2a, 2b
Are orthogonal to each other, and each bias coil 2
The angles formed by the elements a and 2b and the magnetoresistive element 3 are determined by the element holder 4 so as to be at 45 ° to each other.

The operation of the azimuth sensor having such a configuration is as follows. As for the output, a constant voltage is applied between terminals T1 and T3 shown in FIG. 2A, and the output voltage between terminals T2 and T4 is further processed by an amplifier circuit. Now, when a predetermined current is applied to one of the bias coils 2a and 2b and this sensor is rotated once in the same plane to detect terrestrial magnetism, the output becomes as shown in FIG. Moreover, a waveform having the same amplitude can be obtained. Therefore, the direction of terrestrial magnetism can be accurately detected from the following equation.

Tan θ = sin θ / cos θ = va / Vb As described above, according to the present embodiment, the magneto-resistive element 1 is constituted by the magneto-resistive element 3 formed at an extremely close position under the same forming conditions. Only one magnetoresistive element 1 is used, and all magnetoresistive elements 3 have the same output characteristics with respect to the combined magnetic field of the external magnetic field and each of the orthogonal bias magnetic fields.

The bias magnetic field is switched by turning on and off the current flowing through each of the bias coils 2a and 2b instantaneously, and only one of the two bias coils 2a and 2b applies a bias magnetic field. Is detected, there is no possibility that the bias magnetic field of the other will affect and shift in the bias magnetic field application direction. Further, since the positional relationship between the bias magnetic field and the magnetoresistive element is determined in advance by the element holder 4, and the magnitude of the bias magnetic field is determined at a predetermined position and the number of turns, the variation is reduced. In addition, the magnetoresistive elements 3 are connected in series such that each element has its pattern direction orthogonal to each other, and 4
Applying a bias magnetic field in the 5 ° direction causes the same operation for all magnetoresistive elements. Also, the application of the bias magnetic field in the 45 ° direction is as follows.
Since the characteristic detection is performed in a region where the characteristic dynamically changes with respect to the minute magnetic field, the stability against a slight error is improved.

In addition, 45 ° with respect to the magnetoresistive element
Bias coil to apply a bias magnetic field in the
In case of winding, as shown in FIG.
45 ° to the four sides of the insulating substrate
When formed so that they are oriented in the same direction, as shown in FIG.
The size of the entire sensor can be reduced as compared with the case where the edge substrate is formed in parallel with the four sides . (2.8 × X <
X: routing and electrode pattern width in the magnetoresistive element>)

[0021]

As described above, according to the present invention, a bias magnetic field is separately applied to one magnetoresistive element by a bias coil from directions different from 90 °, and the magnetic field direction and the direction of the magnetoresistive element are set to 45 °. In addition, by setting the positional relationship between the bias magnetic field and the magnetoresistive element and the number of turns of the coil, it becomes possible to accurately measure the detection of terrestrial magnetism. Further, since the longitudinal direction of the magnetoresistive element is formed at a direction of 45 ° with respect to the four sides of the insulating substrate, the size of the sensor is reduced.

[Brief description of the drawings]

1A is a perspective view of an orientation sensor according to an embodiment of the present invention, and FIG.

2A is a cross-sectional view of FIG. 2B is a cross-sectional view of FIG.

FIGS. 3A and 3B are cross-sectional views of the element holder of the same embodiment.

FIG. 4 is an output waveform diagram of geomagnetism detection in the embodiment.

FIGS. 5A and 5B are plan views showing arrangement directions of a magnetoresistive element and comparison of a sensor shape;

FIG. 6 is an external view of a conventional direction sensor.

7A is a diagram showing a magnetoresistive characteristic of a magnetoresistive element. FIG. 7B is an explanatory diagram showing a relationship between a current i flowing through the magnetoresistive element and a magnetic field H applied.

FIG. 8 is an output waveform diagram of geomagnetism detection of a conventional direction sensor.

FIG. 9 is an output waveform diagram of the sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetoresistive element 2a, 2b Bias coil 3 Magnetoresistive element 3a Magnetoresistive element terminal 4 Element holder 4a Installation base 4b, 4c Coil groove

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01C 17/30 G01C 17/28

Claims (1)

(57) [Claims] When a current is applied to an insulating substrate having four orthogonal sides in the longitudinal direction of a pattern, four magnetoresistive elements whose electric resistance changes according to the strength of a magnetic field orthogonal to the pattern are formed in the longitudinal direction of the pattern. Are arranged so as to be orthogonal to each other and oriented at 45 ° to each side of the insulating substrate, connected in series with each other, and provided with predetermined input terminals and output terminals; A holder having a pedestal for mounting the magnetoresistive element such that the surface on which the element is formed is located at the center thereof; and two bias coils formed with a predetermined number of turns in each of the holders. A first bias coil for applying a bias magnetic field in a 45 ° direction to the resistive element is wound at a predetermined distance from the magnetoresistive element. And a second groove for forming a second bias coil orthogonal to the first bias coil at a predetermined position so as not to touch the first bias coil. Orientation sensor.