JPH07332912A - Non-contact potentiometer and displacement sensor of moving body - Google Patents

Abstract

PURPOSE:To accurately measure by winding a primary coil and two secondary differential coils having the same number of turns on a soft magnetic core of an open magnetic path at both the longitudinal outer edges, and longitudinally operating a moving body to be detected. CONSTITUTION:When an AC voltage is applied to a primary coil 1, an alternating magnetic field is generated in a soft magnetic core 13, and induced voltages e1, e2 are obtained from secondary coils 2a, 2b by electromagnetic coupling. In this case, when the wired parts of the two coils 2a, 2b are disposed accurately symmetrically with respect to the center of the core 13, a differential output voltage (e) obtained between the coils 2a and 2b becomes '0' since the amplitudes of the voltages e1 and e2 are equal and the phases of the voltages e1, e2 are different at 180 degrees. When a moving body 14 to be detected is disposed near the longitudinal center of the core 13, a DC bias magnetic field is applied to the part of the core 13 to lower its permeability, but the permeabilities of the cores 13 of the coils 2a, 2b have no difference, and the voltage (e) becomes '0'. When the body 14 is approached to and separated from the end of the magnetic flux 13, a difference occurs between the voltages e1 and e2, thereby obtaining a differential output voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact potentiometer for magnetically detecting a rotation angle or a linear movement amount of an object that rotates or linearly moves, and a displacement sensor of a moving body using the non-contact potentiometer. .

[0002]

2. Description of the Related Art Two semiconductor magnetoresistive elements connected in series to an angle sensor, a rotation sensor, a linear displacement sensor, etc. for automotive electrical components and FA, a permanent magnet and a yoke for applying a magnetic field thereto. When the permanent magnets or the yokes are arranged so as to face each other and are moved relative to each other between the two semiconductor magnetoresistive elements, the differential from the midpoint connection portion of the semiconductor magnetoresistive element is detected depending on the strength of the magnetic coupling degree on the moved side. A non-contact potentiometer capable of taking out an output signal has been widely proposed in the past (for example, JP-A-59-159).
578).

The non-contact potentiometer using a semiconductor magnetoresistive element has many advantages as compared with a contact type potentiometer, such as high reliability against noise and vibration, and excellent high-speed response. The improvement of temperature drift in this type of non-contact potentiometer is disclosed, for example, in Japanese Patent Publication No. 63-56713. According to this, two semiconductor magnetoresistive elements having the same temperature characteristic are formed as a bridge circuit, and the difference between the individual outputs is made the output of the potentiometer, so that the temperature error of the output is reduced.

[0004]

A conventional non-contact potentiometer using a semiconductor magnetoresistive element must be expensive and must compensate for an error due to the temperature characteristic of the element.

The present invention provides a non-contact potentiometer having a novel structure which is inexpensive and has good temperature characteristics, and is capable of detecting a rotation angle or a linear displacement in a wide range and with high accuracy. Further, the non-contact potentiometer is used to move the non-contact potentiometer. It is intended to provide a body displacement sensor.

[0006]

In order to achieve the above object, the non-contact potentiometer of the present invention is a differential magnetic coil having the same number of turns as the primary coil on a soft magnetic core whose outer edges at both longitudinal ends are open magnetic paths. Two moving secondary coils, each of which is wound around the soft magnetic core, and the moving body to be detected, which is composed of magnetic field generating means arranged close to each other in the longitudinal direction of the soft magnetic core, forms a magnetic circuit. It is designed to work with.

The soft magnetic core is preferably a ferromagnetic material having a high magnetic permeability, a small coercive force, and a high specific resistance, and the movable body to be detected is preferably a permanent magnet having a high maximum energy product. Preferably.

Further, the soft magnetic core is substantially ring-shaped including a missing portion forming an open magnetic path, and the moving body to be detected is substantially rod-shaped with different magnetic poles arranged at both ends in the longitudinal direction. It is effective to have.

Further, the soft magnetic core has a substantially annular shape including a missing portion forming an open magnetic path, and the detected moving body has different magnetic poles arranged at both ends of the substantially annular shape including the missing portion. That is effective.

Further, in the moving body to be detected, a plurality of the moving bodies to be detected are arranged in proximity to the side surfaces in the longitudinal direction of the soft magnetic core, and a required magnetic circuit is provided in the longitudinal direction of the soft magnetic core. Is effective.

The displacement sensor of the moving body of the present invention is
The non-contact potentiometer includes a means for applying an AC voltage to the primary coil of the non-contact potentiometer to process a differential output between the two secondary coils into an electric signal representing a displacement of the detected moving body. It is designed to operate in the longitudinal direction of the soft magnetic core.

[0012]

When an AC voltage is applied to the primary coil of the non-contact potentiometer constructed as described above, an alternating magnetic field is generated in the soft magnetic core, and an output voltage is obtained from the two secondary coils by electromagnetic coupling. When the detected moving body including a magnetic field generating means for applying a DC bias magnetic field to a part of the soft magnetic core in the longitudinal direction is arranged close to the outer edge of the center of the soft magnetic core in the longitudinal direction, the soft magnetic core The magnetic permeability of the central portion of the core is reduced, the outputs of two differential secondary coils having the same number of turns are also reduced at the same rate, and the differential output voltage becomes zero. ◆ When the object to be detected, which is a magnetic field generating means, moves from the longitudinal center of the soft magnetic core toward one of the end portions depending on the object whose displacement needs to be detected, the magnetic permeability of the soft magnetic core is detected. It decreases when the moving body moves and increases when it moves away. Therefore, a difference occurs in the output voltage of the two secondary coils,
It is detected as a differential output voltage and functions as a non-contact potentiometer.

When the magnetic permeability of the soft magnetic core is high, a change in the bias magnetic field due to the moving body to be detected can be detected as a highly sensitive differential output from the secondary coil, and the soft magnetic core functions as a highly accurate non-contact potentiometer. When an alternating magnetic field is applied to the soft magnetic core, heat is generated due to hysteresis loss and eddy current loss of the magnetic core. This hysteresis loss is proportional to the area surrounded by the hysteresis loop, and the eddy current loss is proportional to the specific resistance.
Using a soft magnetic core with low coercive force and high specific resistance,
Heat generation due to hysteresis loss and eddy current loss is reduced, and a non-contact potentiometer with stable characteristics can be obtained. Further, when the moving body to be detected is a permanent magnet having a high maximum energy product, a strong bias magnetic field can be applied to the soft magnetic core, a highly sensitive differential output can be detected from the secondary coil, and high accuracy is achieved. Function as a simple non-contact potentiometer.

Further, the soft magnetic core has a substantially annular shape including a missing portion forming an open magnetic path, and the moving body to be detected is provided with different magnetic poles at both ends in the longitudinal direction along the soft magnetic core. In the case of a substantially rod shape, a bias magnetic field is applied to a part of the soft magnetic core with a small and simple structure to function as a highly accurate non-contact potentiometer.

On the other hand, the soft magnetic core has a substantially annular shape including a missing portion forming an open magnetic path, and the moving body to be detected has different end portions along the substantially annular soft magnetic core including the missing portion. When the magnetic poles are provided, the distance between the magnetic poles is generally longer than that of the substantially rod-shaped moving body to be detected, so that the demagnetizing field inside the moving body to be detected, which is composed of the magnetic field generating means, is relatively weak and the magnetic field is incorporated in the magnetic circuit. The bias magnetic field is effectively increased when it is released. Further, since the magnetic flux efficiently passes through the soft magnetic core, it becomes possible to detect a more sensitive differential output from the secondary coil, which functions as a non-contact potentiometer that detects the rotation angle with higher accuracy.

Further, when the plurality of substantially rod-shaped or substantially annular moving bodies to be detected including the cutout portions are respectively arranged close to the longitudinal side surfaces of the soft magnetic core, a magnetic circuit is provided in the longitudinal direction of the soft magnetic core. Since it is installed side by side and a wide range of bias magnetic field can be taken, it functions as a non-contact potentiometer capable of detecting a rotation angle or linear displacement in a wide range and with high accuracy.

Then, an AC voltage is applied to the primary coil of the non-contact potentiometer according to the present invention, and a member to be detected which is a magnetic field generating means is made of a soft magnetic material by a member interlocking with the movement of an object which requires displacement detection. When moving from the center of the magnetic core in the longitudinal direction to either one of the ends, the bias magnetic field in this portion becomes large, and a differential output is generated between the two secondary coils. By processing this differential output with an AC amplifier, a synchronous detection, and a rectifying circuit including smoothing, it functions as a displacement sensor of the moving body.

Embodiments will be described below with reference to the drawings.
◆

[0019]

FIG. 1 is a connection diagram in which an AC power source is added to the basic structure of the non-contact potentiometer of the present invention. The non-contact potentiometer of FIG. 1 has a soft magnetic core 13 forming an open magnetic path, a primary coil 1, and two secondary coils 2
a moving body 14 to be detected including a and 2b and magnetic field generating means
And, it is basically configured.

A soft magnetic core 13 forming an open magnetic path,
The primary coil 1 and the two secondary coils 2a and 2b having the same number of turns, which are differentially wound from both ends of the soft magnetic core 13 in the longitudinal direction at both ends so that there is no density, are fixed transformers. It constitutes part 8.

The moving body 14 to be detected is arranged in the longitudinal direction of the soft magnetic core 13 so as to form a required magnetic circuit in the longitudinal direction of the soft magnetic core 13. The moving body to be detected 14 is interlocked with any one of the end portions from the center of the soft magnetic core 13 in the longitudinal direction along with the movement of an object that requires displacement detection.

By applying an AC voltage to the primary coil 1, an alternating magnetic field is generated in the soft magnetic core 13, and induced voltages e1 and e2 are obtained from the secondary coils 2a and 2b by electromagnetic coupling. At this time, when the connection parts of the two secondary coils 2a and 2b are arranged symmetrically with respect to the center of the soft magnetic core 13 with high accuracy, the differential output voltage e obtained between the secondary coils 2a and 2b becomes the induced voltage. The magnitudes of e1 and e2 are equal and the phase is 18
It is 0 because it is 0 degrees different. When the moving body to be detected 14 is disposed close to the center of the soft magnetic core 13 in the longitudinal direction, the soft magnetic core 13 is placed.
Although a DC bias magnetic field is applied to a part of the magnetic field to reduce the magnetic permeability, the magnetic permeability of the soft magnetic cores 13 in the secondary coils 2a and 2b is substantially the same and the differential output voltage e is zero. Next, when the detected moving body 14 is displaced toward one of the ends of the soft magnetic core 13 by an object that requires displacement detection,
The DC bias magnetic field increases and the permeability decreases in the approaching place. On the other hand, in the distant place, the bias magnetic field decreases and the magnetic permeability increases. As a result, the secondary coils 2a, 2b
There is a difference in the magnitudes of the induced voltages e1 and e2 of the two, and a differential output voltage is generated.

FIG. 2 shows the relationship between the displacement X of the moving body 14 to be detected and the induced voltages e1 and e2 of the secondary coils 2a and 2b and the differential output voltage e. The absolute values of the outputs appear symmetrically with respect to the longitudinal center (X = 0) of the position of the moving body 14 to be detected, but the phases are different from each other by 180 degrees, so the differential output when the phase is added. The voltage e is as shown in FIG. -By the above technical means, a non-contact potentiometer capable of detecting a wide range of rotation angles or a wide range of linear displacement with high accuracy can be obtained.

Since the soft magnetic core applies an AC voltage to the primary coil, it is required that hysteresis loss and eddy current loss be small. Therefore, coercive force is small and specific resistance is large.
Further, it is preferable to use a soft magnetic material having a high magnetic permeability at a high frequency, such as amorphous, permalloy or silicon steel.

In addition, the moving body to be detected which is composed of the magnetic field generating means has Sm1Co5 system and Sm2Co1 system in order to obtain responsiveness and high accuracy.
It is preferable to use a permanent magnet having a high maximum energy product such as 7 series, ferrite, alnico, NdFeB series.

FIG. 4 is an enlarged perspective view of the non-contact potentiometer in the rotation axis direction according to the embodiment of the present invention. FIG. 5 is a diagram showing a positional relationship of main components for explaining the operation of the embodiment shown in FIG. ◆ The fixed transformer section 28 shown in FIG. 4 is a soft magnetic core that constitutes an open magnetic path.
As shown in FIG. 5, a primary coil and two secondary coils having the same number of turns are wound in the directions a and b from the center of the soft magnetic core so as to be differential and not dense. Either of these primary and secondary coils may be wound in the upper layer. However, this configuration is not shown in FIG.

The fixed transformer section 28 shown in FIG. 4 is fixed to the non-magnetic fixed transformer section supporting member 5. Sm2C
The moving body 24 to be detected, which comprises an o17-based permanent magnet, has magnetic poles N and S on a surface that is substantially parallel to the surface passing through the rotation axis at the end in the longitudinal direction, and the nonmagnetic magnet support member 26 can detect displacement. It is attached to a member 7 that interlocks with the required movement of an object, and is rotatable by a bearing 9.

As shown in FIG. 5, the soft magnetic core 23 has an annular shape having an open magnetic path. FIG. 6 shows the moving body 2 to be detected.
4 is an enlarged view showing the vicinity of magnetic poles N and S of FIG. In the open magnetic path, the magnetic flux of the magnetic path B shown by the broken line is changed to the magnetic path A shown by the solid line.
It is effective in reducing the magnetic flux to a negligible level.

FIG. 7 shows, in the embodiment of FIG. 4, the rotation angles of the magnetic poles N and S and the differential output voltage e of the induced voltages e1 and e2 of the two secondary coils when an AC voltage of 50 Hz is applied to the primary coil. The absolute value of | e | The absolute value of the output can be regarded as a straight line up to ± 45 degrees. Further, the outputs appear symmetrically with respect to the center position of the secondary coil differentially connected, but the phases are different from each other by 180 degrees,
When the phase is taken into consideration, the same tendency as in FIG. 3 is shown.

The amount of change in permeability changes proportionally depending on the size of the moving body 24 to be detected, that is, the angle of the magnetic poles N and S with respect to the rotation axis. In the case of a moving object to be detected, it is almost 45
It is possible to change the angle by about 45 degrees to the left and about 90 degrees in total.

In the embodiment of FIG. 4, the moving body to be detected 24 is detected.
Is easier to miniaturize and has a simple shape compared to the moving body to be detected shown in FIG.

FIG. 8 is a perspective view showing another embodiment of the present invention in which a non-contact potentiometer is enlarged in the rotation axis direction.
Different magnetic poles are arranged at both ends of the ring including the cutout portion, and the detected moving body 34 made of, for example, a Sm2Co17 system permanent magnet has a configuration in which the magnetic poles N and S are opened 90 degrees with respect to the rotation axis. ◆ In the case of this detected moving body 34, FIG.
In comparison with the detected moving body 24 shown in FIG. 3, even if the detected moving body has the same rotation angle, the differential output obtained between the secondary coils is larger when the detected moving body 34 is used. Accurate position detection is possible. This is because the demagnetizing field is relatively weak, so that the effective bias magnetic field is high, and when the generated magnetic flux from the moving body to be detected 34 is substantially annular, it efficiently passes through the soft magnetic core. In the case of the detection moving body 24, this is due to the large amount of leakage magnetic flux that does not pass through the soft magnetic core.

FIG. 9 is still another embodiment of the present invention, and is a perspective view of a non-contact potentiometer which is enlarged in the direction of the rotation axis. Non-movable magnetic bodies 44a and 44b, which are composed of two permanent magnets, are arranged close to each other in the longitudinal direction of the soft magnetic core so as to be sandwiched therebetween, and a required magnetic circuit is provided in the longitudinal direction of the soft magnetic core. It is a contact potentiometer.

The differential output obtained by this structure is about 60 degrees in the right direction and about 60 degrees in the left direction, and the differential output is about 1 in total.
A 20 degree change is possible.

FIG. 10 is still another embodiment of the present invention, which is a perspective view of a non-contact potentiometer enlarged in the direction of the rotation axis, in which two fixed magnets with the fixed transformer portion 58 opened at an angle of 60 degrees with respect to the rotation axis. In the non-contact potentiometer, the missing portions of 54a and 54b are arranged close to each other so as to be sandwiched by the longitudinal side surfaces of the soft magnetic core, and a required magnetic circuit is provided side by side in the longitudinal direction of the soft magnetic core.

With this structure, the magnetic flux generated from the moving body to be detected efficiently passes through the soft magnetic core as described in the description of FIG. 8, and further, the displacement detection of 120 degrees can be performed as in FIG. is there.

FIG. 11 is a block diagram showing an example of an electric circuit used together with a non-contact potentiometer as a displacement sensor for a moving body.

First, an AC voltage is applied to the primary coil by the oscillator. When the moving body to be detected, which is the magnetic field generating means, is interlocked with any of the longitudinal directions of the soft magnetic core due to the movement of the object whose displacement is required to be detected, the change in the magnetic permeability due to the bias magnetic field in this portion is changed into two. It is detected as a differential output voltage from the next coil, and this signal is detected by the AC amplifier, synchronous detection,
It is output as an electric signal indicating the position of the moving object to be detected via a rectifying circuit including smoothing.

The AC voltage applied to the primary coil preferably has a high frequency in order to obtain responsiveness and high accuracy.

The waveform of the applied alternating current and the waveform output from the secondary coil are compared, and the waveforms of only the positive direction and only the negative direction are obtained by the synchronous detection. The direction of rotation can be known by predetermining the waveform in the positive direction when the moving body to be detected, which is the magnetic flux generating means, is on the right and the waveform in the negative direction when it is on the left. The smoothing circuit can output the differential voltage depending on the rotation angle by the waveform in which only the positive and the negative are taken.

[0041]

As described above, according to the present invention, the following effects can be obtained. ◆ (a) Two differential secondary coils with the same number of turns as the primary coil are wound around a soft magnetic core whose both ends in the longitudinal direction are open magnetic fields, and the magnetic field is generated by the movement of an object that requires displacement detection. Since the moving body to be detected composed of the generating means is operated between both longitudinal ends of the soft magnetic core, a non-contact potentiometer capable of detecting a wide angle of rotation or a wide range of linear displacement with high accuracy can be obtained. .

(B) Compared with the conventional semiconductor magnetoresistive element, an expensive semiconductor magnetoresistive element is not used, and in the manufacturing process, the semiconductor magnetoresistive element and the magnet are used.
Since it is not necessary to strictly control the magnetic gap between the yokes, the cost of the non-contact potentiometer can be reduced.

(C) Since the coil is wound around a soft magnetic core having a small coercive force and a high specific resistance as compared with the conventional semiconductor magnetoresistive element, the temperature of the detection sensitivity is increased. It is possible to obtain a non-contact potentiometer capable of detecting a wide angle of rotation or a wide range of linear displacement with a high degree of accuracy, which changes little and can be sufficiently used even under a wide range of temperature conditions.

The temperature change of the detection sensitivity is about 0.02% per 1 ° C., which is one tenth of the semiconductor magnetoresistive element, and it can be sufficiently used in a wide range of temperature conditions.

(D) In the case where the moving body to be detected, which is composed of the magnetic field generating means, is provided with different magnetic poles at both ends of the substantially rod-like shape, a small and wide rotation angle or a wide range of linear displacement can be obtained with high accuracy. And a non-contact potentiometer capable of detecting

(E) On the other hand, when the moving body to be detected which comprises the magnetic field generating means is provided with different magnetic poles at both ends of the substantially annular shape including the missing portion, the effective bias magnetic field becomes high, Moreover, a non-contact potentiometer capable of more efficiently magnetically saturating a part of the soft magnetic core from both magnetic poles and detecting a wide angle of rotation with higher accuracy can be obtained.

(F) Furthermore, the detected moving body composed of the magnetic field generating means is a plurality of substantially rod-shaped detected moving bodies, or a substantially annular detected moving body including a plurality of missing portions, and has a soft magnetic core. When the required magnetic circuits are arranged side by side in the longitudinal direction of the soft magnetic core, the bias magnetic field can be set in a wider range, so that a wider rotation angle or more A non-contact potentiometer capable of detecting a wide range of linear displacement is obtained.

(G) An AC voltage is applied to the primary coil of the non-contact potentiometer according to the present invention, and a moving body to be detected, which is magnetic field generating means, is moved by movement of a material requiring displacement detection. When moving from the center of the longitudinal direction toward one of the ends, a differential output is detected from the two secondary coils, and this detection signal is detected by the AC amplifier, the synchronous detection,
The displacement sensor of the moving body, which is output via the rectifying circuit including smoothing and has the above effects, is obtained.

[Brief description of drawings]

FIG. 1 is a connection diagram showing a basic structure of an embodiment of a non-contact potentiometer.

FIG. 2 is a diagram showing a relationship between displacement X of a moving body to be detected, induced voltages e1 and e2 of secondary coils 2a and 2b, and a differential voltage e in the embodiment of FIG.

FIG. 3 is a diagram in the case of considering the phase of the relationship between the displacement X of the moving body to be detected shown in FIG. 2 and the differential voltage E of the secondary coils 2a and 2b.

FIG. 4 is a perspective view in which a non-contact potentiometer according to an embodiment of the present invention is enlarged in a rotation axis direction.

5 is a diagram showing a positional relationship of main components of the embodiment of FIG.

6 is an enlarged view around magnetic poles N and S of a moving body to be detected 24 made of a permanent magnet shown in FIG.

7 is a diagram showing a relationship between a rotation angle and a differential voltage in the embodiment of FIG. 4 according to the present invention.

FIG. 8 is a perspective view in which another embodiment of the non-contact potentiometer according to the present invention is enlarged in the rotation axis direction.

FIG. 9 is a perspective view showing an embodiment of a non-contact potentiometer sandwiched by two rod-shaped permanent magnets from above and below.

FIG. 10 is a perspective view showing an embodiment of a non-contact potentiometer sandwiched by two substantially annular permanent magnets from above and below.

FIG. 11 is a diagram showing an example of a processing circuit by synchronous rectification used together with a non-contact potentiometer as a displacement sensor of a moving body according to the present invention.

[Explanation of symbols]

1 Primary coil 2a Secondary coil a 2b Secondary coil b 13,23 Soft magnetic core 14, 24, 34, 44a, 44b, 54a, 54b
Detected moving body 5 Fixed differential transformer section supporting member 26, 36 Magnet supporting member 7 Member interlocking with movement of object requiring displacement detection 8, 28, 38, 48, 58 Fixed differential transformer section 9 Bearing

Claims (6)

[Claims] 1. A soft magnetic core whose outer edges at both ends in the longitudinal direction are open magnetic paths, and a primary coil wound around the soft magnetic core.
Two secondary coils that are wound around the soft magnetic core and are differential in number with the same number of turns, and magnetic field generating means that are closely arranged to form a magnetic circuit in the longitudinal direction of the soft magnetic core. A non-contact potentiometer including a detection moving body,
A non-contact potentiometer, wherein the moving body to be detected operates in a longitudinal direction of the soft magnetic core. 2. The non-contact potentiometer according to claim 1, wherein the soft magnetic core is preferably a ferromagnetic material having a high magnetic permeability, a low coercive force, and a high specific resistance, Non-contact potentiometer, characterized in that the body is preferably a permanent magnet with a high maximum energy product. 3. The non-contact potentiometer according to claim 1, wherein the soft magnetic core has a substantially annular shape including a cutout portion forming an open magnetic path, and the detected moving body comprises:
A non-contact potentiometer having a substantially rod shape in which different magnetic poles are arranged at both ends in the longitudinal direction. 4. The non-contact potentiometer according to claim 1, wherein the soft magnetic core has a substantially annular shape including a cutout portion forming an open magnetic path, and the moving body to be detected includes:
A non-contact potentiometer in which different magnetic poles are provided at both ends of a substantially annular shape including a cutout portion. 5. The non-contact potentiometer according to any one of claims 1 to 4, wherein the plurality of moving bodies to be detected are arranged in proximity to side surfaces in a longitudinal direction of a soft magnetic core. A non-contact potentiometer having a required magnetic circuit provided along the longitudinal direction of a soft magnetic core. 6. The non-contact potentiometer according to any one of claims 1 to 5, means for applying an AC voltage to the primary coil, and a differential output between the two secondary coils for displacement of the detected moving body. A displacement sensor for a moving body, comprising: a means for processing into an electric signal represented by the moving body, wherein the detected moving body operates in a longitudinal direction of the soft magnetic core.