JP6640006B2 - Displacement sensor - Google Patents

Description

  The present invention relates to a displacement sensor including a coil and a magnetic core.

  Non-contact displacement sensors are used for measuring the rotation angle of a rotating body, the position of a moving body, and the like. For example, Patent Document 1 discloses a sensor target eccentrically mounted on a rotor, a stator coil unit for measuring a radial position of the sensor target, an oscillator for supplying a carrier signal to the stator coil unit, and a stator coil. A rotation angle detector of a rotation shaft including means for detecting an induced voltage is described.

JP-A-11-94589

  The displacement sensor using such a coil has a problem that the sensor output fluctuates when the temperature changes, and the measurement error increases.

  As a method to prevent this, a method of compensating for temperature using a bridge circuit and an arithmetic circuit using two sets of sensor targets and coils, or installing a temperature sensor and using correlation data between temperature and sensor output There is a correction method.

  However, variations in sensor output when the temperature changes include variations due to variations in characteristics of each coil, and cannot be corrected by the above method.

  Thus, the present invention provides a displacement sensor that suppresses sensor output fluctuations due to variations in characteristics of each coil and has a small measurement error.

The present invention in order to solve the above problems, a magnetic material is inserted inside the coil, which is part of the outer periphery of at least the coil of the inner surface and the magnetic material is arranged at a predetermined interval, the coil and the magnetic The first direction is a direction connecting the center of one magnetic body and the center of the other magnetic body, and at least one of the distance between the inner surface of the coil and the outer surface of the magnetic material in at least the first direction is: A displacement sensor that is shorter than one of a distance between an inner surface of a coil and an outer surface of a magnetic body in a direction substantially perpendicular to the first direction .

  Advantageous Effects of Invention According to the present invention, it is possible to provide a displacement sensor that suppresses sensor output fluctuation due to variation in characteristics of each coil and has a small measurement error.

FIG. 2 is a cross-sectional view illustrating a configuration of a displacement sensor according to the first embodiment. FIG. 3 is a diagram illustrating a structure of a coil and a magnetic core according to the first embodiment. FIG. 4 is a diagram illustrating a state of a magnetic flux in the first embodiment. FIG. 4 is a cross-sectional view illustrating another example of the magnetic core according to the first embodiment. FIG. 9 is a diagram illustrating a configuration of a displacement sensor and a sensor target according to a second embodiment. FIG. 13 is a diagram illustrating a configuration of a displacement sensor and a sensor target according to a third embodiment. FIG. 14 is a diagram illustrating a configuration of a displacement sensor and a sensor target according to a fourth embodiment. FIG. 14 is a diagram illustrating a configuration of a displacement sensor and a sensor target according to a fifth embodiment. FIG. 14 is a diagram illustrating a configuration of a displacement sensor and a sensor target according to a sixth embodiment. FIG. 21 is a diagram illustrating another example of the sensor target according to the sixth embodiment. It is a figure showing another example of a coil shape in the present invention. FIG. 21 is a diagram showing another example of the shape of the magnetic core in the sixth embodiment.

  Hereinafter, embodiments of a displacement sensor according to the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating a configuration of the displacement sensor according to the first embodiment of the present invention.

  The displacement sensor 1 according to the first embodiment includes a coil 2, a magnetic core 3, and a circuit unit 4, which are housed inside a housing 5.

  The circuit section 4 includes an oscillation circuit that generates an AC voltage to the coil 2 and an output circuit that outputs a predetermined voltage corresponding to a change in the impedance of the coil 2.

  FIG. 2 is a diagram of the coil 2 and the magnetic core 3 according to the first embodiment viewed from the detection surface.

  The magnetic core 3 is made of a magnetic metal such as iron or a magnetic ceramic such as ferrite. The magnetic core 3 is formed in a shape surrounding the coil 2 except for a detection surface, and further, an insertion portion inserted inside the coil 2. 3a.

  The coil 2 is wound in a circular shape around the center of the insertion portion 3a. A gap 6 is provided between the inner surface of the coil 2 and the outer surface of the insertion portion 3a of the magnetic core 3.

  The cavity 6 is made of a material having a low magnetic permeability, such as a space, a resin, a non-magnetic glass, a non-magnetic ceramic, and a non-magnetic metal.

  Here, the effect of the gap 6 will be described.

  As a result of investigating the cause of the variation in sensor output variation when the temperature changes, it was found that the rate of change in the inductance of the coil differs for each coil, and this is the factor of the variation in sensor output variation. Furthermore, it was found that the variation in the change rate of the inductance of the coil was caused by the variation in the change rate of the magnetic permeability of the magnetic core inserted into the coil.

  Here, when the gap 6 is provided, the magnetic flux amplified by the magnetic core 3 is reduced as compared with the case where the inside of the coil 2 is filled with the insertion portion 3a of the magnetic core 3 without providing the gap 6. As a result, the inductance decreases. That is, the influence of the magnetic permeability of the magnetic core 3 on the inductance is reduced. As a result, the influence of the variation in the rate of change of the magnetic permeability of the magnetic core 3 on the inductance when the temperature changes is reduced, so that the variation in the rate of change in the inductance is reduced, and the variation in the sensor output variation can be reduced.

  In addition, the maximum measurement distance when the gap 6 is provided and the maximum measurement distance when the gap 6 is filled with the insertion portion 3a of the magnetic core 3 without the gap 6 are almost equal, and the measurement performance is not impaired. . The reason will be described with reference to FIG. 3A shows the state of the magnetic flux when the gap 6 is provided, and FIG. 3B shows the state of the magnetic flux when the inside of the coil 2 is filled with the insertion portion 3a of the magnetic core 3 without providing the gap 6. FIG. Since the magnetic flux concentrates on the magnetic core 3 having high magnetic permeability, the magnetic flux passing through the gap 6 is small, and most of the magnetic flux passes through the insertion portion 3 a of the magnetic core 3. Since the magnetic flux passing through the insertion portion 3a of the magnetic core 3 has a long distance from the coil 2, the magnetic flux is large and the magnetic flux spreads far. The spread of the magnetic flux is the same as that of the magnetic flux that is spread most when the gap 6 is not provided as shown in FIG. Therefore, even when the air gap 6 is provided, the reach distance of the magnetic flux is the same as when the air gap 6 is not provided, and as a result, the maximum measurement distance is the same.

  As described above, according to the present embodiment, it is possible to reduce the sensor output fluctuation at the time of temperature change while suppressing the influence on the maximum measurement distance.

  In the present embodiment, the example of the shape of the magnetic core, which surrounds the coil 2 except for the detection surface, has been described. However, the shape of the magnetic core does not include the outer protrusion as shown in FIG. May be. By removing the outer protruding portion, the ratio of the magnetic path orbiting around the coil 2 passing through the inside of the magnetic core 8 is reduced, and the inductance is reduced, so that variation in sensor output fluctuation can be reduced. Further, when the size of the sensor is reduced, the coil diameter can be increased by removing the protrusion outside the magnetic core, so that the magnetic flux can be expanded and the measurement sensitivity can be improved.

  Similar effects can be expected even if the magnetic core has a rod shape as shown in FIG. 4B. Further, as another example of the magnetic core, shapes as shown in FIGS. 4C to 4E may be used.

  In this embodiment, it is desirable that the cross-sectional shape of the coil 2 be smaller in the detection direction than in the detection surface. Since the ratio of the magnetic path orbiting around the coil 2 passing through the inside of the magnetic core is reduced and the inductance is reduced, the influence of the variation in the rate of change of the permeability of the magnetic core on the inductance is reduced, and the sensor output fluctuation is reduced. Variation can be reduced.

  In the present embodiment, an example will be described in which the measurement sensitivity can be improved in the displacement sensor described in the first embodiment.

  FIG. 5 is a diagram illustrating the configuration of the displacement sensor and the sensor target according to the present embodiment. 5A is a cross-sectional view taken along line BB of FIG. 5B viewed from the side, FIG. 5B is a cross-sectional view taken along line AA of FIG. 5A viewed from the front, and FIG. It is the figure which looked at the displacement sensor from the detection surface. The materials of the magnetic core 13 and the gap 6 in the present embodiment are the same as those of the first embodiment, and therefore the description is omitted.

  The sensor target 14 is fixed to a rotating shaft 15. The distance from the center of the rotation shaft 15 to the outer surface of the sensor target 14 is configured to change depending on the rotation angle of the rotation shaft 15. As a result, since the distance between the sensor target 14 and the displacement sensor changes depending on the rotation angle, the rotation angle can be measured by measuring this distance with the displacement sensor.

  The magnetic core 13 has an insertion portion 13 a inserted inside the coil 2. The insertion portion 13a is formed in an elliptical shape, and has a major axis oriented in the rotation direction of the sensor target 14.

  The coil 2 is wound in a circular shape around the center of the insertion portion 13a. The gap 6 is provided between the inner surface of the coil 2 and the outer surface of the insertion portion 13a.

  In this embodiment, since the insertion portion 13a is formed so as to face the sensor target 14, a large amount of magnetic flux can be sent to the sensor target 14. Furthermore, since the gap 6 is provided in a region that does not face the sensor target 14, magnetic flux that does not pass through the sensor target 14 can be reduced. Thereby, the magnetic flux can be efficiently sent to the sensor target 14, so that the measurement sensitivity can be improved.

  In the present embodiment, an example in which the insertion portion 13a has an elliptical shape is described, but any shape having a longitudinal direction in the rotation direction of the sensor target 14, such as a rectangle or a track, may be used.

  In this embodiment, an example will be described in which the measurement accuracy of the displacement sensor described in the first embodiment can be improved.

  FIG. 6 is a diagram illustrating the configuration of the displacement sensor and the sensor target according to the present embodiment. 6A is a cross-sectional view taken along the line BB of FIG. 6B viewed from the side, FIG. 6B is a cross-sectional view taken along the line AA of FIG. 6A viewed from the front, and FIG. It is the figure which looked at the displacement sensor from the detection surface. Note that the materials of the magnetic core 16 and the gap 6 in the present embodiment are the same as those of the first embodiment, and a description thereof will be omitted.

  The magnetic core 16 has an insertion portion 16 a inserted inside the coil 2. The insertion portion 16a is formed in an elliptical shape, and has a major axis oriented in the rotation axis direction of the sensor target 17.

  The coil 2 is wound in a circular shape around the center of the insertion portion 16a. The gap 6 is provided between the inner surface of the coil 2 and the outer surface of the insertion portion 16a.

  In this embodiment, since the insertion portion 16a is formed so as to have a narrow width facing the rotation direction of the sensor target 17, the spread of the magnetic flux in the rotation direction of the sensor target 17 is suppressed, and the Can be sent. This makes it possible to detect the distance of the region facing the vicinity of the center of the displacement sensor, and thus to measure the rotation angle with high accuracy.

  In the present embodiment, an example in which the insertion portion 16a has an elliptical shape is described, but any shape having a longitudinal direction in a direction orthogonal to the rotation direction of the sensor target 17 such as a rectangle or a track may be used.

  In this embodiment, an example will be described in which the displacement sensor described in the first embodiment is configured with two coils and two sensor targets to improve measurement accuracy.

  FIG. 7 is a diagram illustrating the configuration of the displacement sensor and the sensor target according to the present embodiment. 7A is a sectional view taken along the line BB of FIG. 7B viewed from the side, FIG. 7B is a sectional view taken along the line AA of FIG. 7A viewed from the front, and FIG. FIG. 7 is a view of the displacement sensor as viewed from a detection surface, and in FIG. 7A, a target 20b is indicated by a dotted line to facilitate understanding of the configuration. Note that the materials of the magnetic core 18 and the gap 6 in the present embodiment are the same as those of the first embodiment, and a description thereof will be omitted.

  The sensor target 20 includes two targets 20a and 20b, and is fixed to the rotating shaft 15. At least one of the targets is configured such that the distance from the center of the rotation shaft 15 to the outer surface of the target changes depending on the rotation angle of the rotation shaft 15, and the target, the displacement sensor, and the like depend on the rotation angle. Distance changes. Further, assuming that the distance between the target 20a and the displacement sensor is a gap a and the distance between the target 20b and the displacement sensor is a gap b, the difference between the gap a and the gap b varies depending on the rotation angle of the rotating shaft 15. Is configured.

  The magnetic cores 18a and 18b include insertion portions 18c and 18d inserted inside the coils 19a and 19b, respectively.

  The coils 19a and 19b are arranged to detect the sensor targets 20a and 20b, respectively. The insertion portions 18c and 18d of the magnetic cores 18a and 18b are disposed eccentrically toward the center of the sensor inside the coils 19a and 19b. The gap 6 is provided between the inner surfaces of the coils 19a and 19b and the outer surfaces of the insertion portions 18c and 18d of the magnetic cores 18a and 18b.

  In this embodiment, two coils 19a and 19b are used to measure the distances to the targets 20a and 20b, respectively, and the difference or ratio between the measured values is used to calculate the temperature characteristics of the coils and the target and the displacement sensor. Fluctuations in the sensor output due to variations and fluctuations in the distance between the sensor and the rotating shaft 15 can be compensated. Furthermore, by disposing the insertion portion of the magnetic core 18 eccentrically toward the center of the sensor, a large amount of magnetic flux is sent to the sensor target 20, so that the measurement sensitivity can be improved.

  In the present embodiment, as an example of a method of measuring the rotation angle of the rotating shaft 15, an example has been described in which the distance to the target is measured by two coils and the difference or ratio between the two is used. It may be connected and the voltage at the midpoint may be used.

  In the present embodiment, an example in which the displacement sensor described in the fourth embodiment can be downsized will be described.

  FIG. 8 is a diagram illustrating a configuration of the displacement sensor and the sensor target according to the present embodiment. 8A is a sectional view taken along the line BB of FIG. 8B viewed from the side, FIG. 8B is a sectional view taken along the line AA of FIG. 8A viewed from the front, and FIG. FIG. 8A is a view of the displacement sensor as viewed from a detection surface, and in FIG. 8A, a target 20b is indicated by a dotted line to facilitate understanding of the configuration. The sensor target 20 according to the present embodiment is the same as that according to the fourth embodiment, and a description thereof will be omitted. The materials of the magnetic core 21 and the gap 6 are the same as those of the first embodiment, and the description is omitted.

  The coils 22a and 22b are wound in an elliptical shape with the rotation direction of the sensor targets 20a and 20b as the major axis, and are arranged to detect the sensor targets 20a and 20b, respectively. The insertion portions 21c and 21d of the magnetic cores 21a and 21b are arranged inside the coils 22a and 22b with the centers of the coils 22a and 22b as centers. The gap 6 is provided between the inner surfaces of the coils 22a and 22b and the outer surfaces of the insertion portions 21c and 21d of the magnetic cores 21a and 21b.

  In this embodiment, the width of the gap 6 in the direction in which the two coils are juxtaposed (x direction) is reduced, while the width of the gap 6 in the direction perpendicular to the x direction (y direction) is increased. . Thereby, the sensor width from the center of the displacement sensor to the outermost part of the coil can be reduced. On the other hand, by securing the gap 6 in the y direction, the sensor output fluctuation at the time of temperature change can be reduced. .

  In this embodiment, an example will be described in which the displacement sensor described in the fifth embodiment can suppress a decrease in measurement accuracy.

  FIG. 9 is a diagram illustrating a configuration of a displacement sensor and a sensor target according to the present embodiment. 9A is a sectional view taken along the line BB of FIG. 9B viewed from the side, FIG. 9B is a sectional view taken along the line AA of FIG. 9A viewed from the front, and FIG. FIG. 9A is a view of the displacement sensor as viewed from a detection surface, and in FIG. 9A, a target 20b is indicated by a dotted line to facilitate understanding of the configuration. The sensor target 20 and the coil 22 according to the present embodiment are the same as those according to the fifth embodiment, and thus description thereof is omitted. Further, the materials of the magnetic core 23 and the gap 6 are the same as those of the first embodiment, and the description is omitted.

  The coils 22a and 22b are wound in an elliptical shape with the rotation direction of the sensor targets 20a and 20b as the major axis, and are arranged to detect the sensor targets 20a and 20b, respectively. The insertion portions 23c and 23d of the magnetic cores 23a and 23b are eccentrically arranged outside the displacement sensor inside the coil. The air gap 6 is provided between the inner surface of the coil and the outer surface of the insertion portion of the magnetic core.

  In the present embodiment, by disposing the insertion portions 23c and 23d of the magnetic cores 23a and 23b eccentrically outside the displacement sensor, a part of the magnetic flux emitted from the coils 22a and 22b is adjacent to the corresponding target. Leakage to the target 20b, 20a. As a result, the distance from the target corresponding to each of the coils 22a and 22b can be accurately measured.

  Further, a sensor target having a shape shown in FIG. 10 may be used. The sensor target 24 includes two targets 24a and 24b, and is disposed at a position facing the magnetic cores 23a and 23b with an interval. At least one of the targets is configured such that the distance from the center of the rotation shaft 15 to the outer surface of the target changes depending on the rotation angle of the rotation shaft 15, and the target, the displacement sensor, and the like depend on the rotation angle. Distance changes. Further, assuming that the distance between the target 24a and the displacement sensor is a gap a and the distance between the target 24b and the displacement sensor is a gap b, the difference between the gap a and the gap b varies depending on the rotation angle of the rotary shaft 15. Is configured.

  By providing an interval between the targets in this manner, a part of the magnetic flux emitted from the coils 22a and 22b can be suppressed from leaking to the targets 24b and 24a adjacent to the corresponding targets. As a result, the distance from the target corresponding to each of the coils 22a and 22b can be accurately measured.

  In the above embodiment, the example of the coil shape is a circle or an ellipse. However, the coil may be a semicircle as shown in FIG. 11A or a rectangle as shown in FIG. 11B. As the area inside the coil increases, the area of the gap 6 increases, and the influence of the variation in the rate of change of the magnetic permeability of the magnetic core on the inductance decreases, so that the variation in sensor output variation can be reduced.

  Further, in the above-described embodiment, the example of the shape of the insertion portion of the magnetic core is circular or elliptical. However, as shown by 27a and 28b in FIG. May be filled in. As the area facing the target is larger, more magnetic flux is sent from the coil to the target, so that the measurement sensitivity is improved.

  Further, in the above-described embodiment, the example of the rotating body is shown as the sensor target. However, the sensor target is fixed to the parallel moving body and the distance from the displacement sensor changes depending on the moving position. It may be the one that moves to.

DESCRIPTION OF SYMBOLS 1 Displacement sensor 2, 19, 22, 25, 26 Coil 3, 8-13, 16, 18, 21, 23, 27 Magnetic core 4 Circuit part 5 Housing 6 Air gap part 7 Magnetic flux 14, 17, 20, 24 Sensor Target 15 Rotation axis

Claims (7)

In a displacement sensor with a magnetic material inserted inside the coil,
At least a part of the inner surface of the coil and the outer periphery of the magnetic body are arranged at a predetermined interval ,
Comprising two sets of the coil and the magnetic material,
The direction connecting the center of one magnetic body and the center of the other magnetic body is the first direction, and at least one of the distance between the inner surface of the coil and the outer surface of the magnetic material in the first direction is the first direction. A displacement sensor that is shorter than one of the distance between the inner surface of the coil and the outer surface of the magnetic body in a direction substantially perpendicular to the direction .   2. The displacement sensor according to claim 1, wherein the magnetic body has different widths in two different directions within a detection surface of the sensor. 3.   3. The displacement sensor according to claim 2, wherein a longitudinal direction of the magnetic body substantially coincides with a longitudinal direction of a sensor target facing the displacement sensor.   3. The displacement sensor according to claim 2, wherein a longitudinal direction of the magnetic body substantially coincides with a lateral direction of a sensor target facing the displacement sensor. 2. The displacement sensor according to claim 1 , wherein the center of at least one magnetic body is eccentric from the center of the coil. The displacement sensor according to claim 5 , wherein the center of the magnetic body whose center is eccentric from the center of the coil is eccentric in a direction closer to the other magnetic body. 6. The displacement sensor according to claim 5 , wherein the center of the magnetic body whose center is eccentric from the center of the coil is eccentric in a direction away from the other magnetic body.

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