JP2018189485A - Angle detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an angle detector that can obtain a high detection gain for a high-frequency excitation current while having a coil with a simple configuration.SOLUTION: An angle detector 10 includes: a stator 20 having excitation coil parts 22 and detection coil parts 23 located at regular angular intervals; and a rotor 30 rotatable with respect to the stator 20, the rotor including a conductor. In the rotor 30, an eddy current flows to interrupt change of a magnetic flux generated by the excitation coil parts 22. In the detection coil parts 23, an inductive voltage is induced by the excitation coil parts 22. The conductor is formed so that the amplitude of the magnetic flux at a position in the predetermined circumferential direction of the stator 20 forms a sine wave according to the angle of the rotation of the rotor 30.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an angle detector, and more particularly to an angle detector that utilizes sin and cos signals induced in a plurality of detection coils.

  The voltage induced in the detection winding by the electromotive force of the excitation winding is determined by appropriately selecting the shape of the rotor, which is a magnetic material, and the number of turns of each detection coil, and the sin waveform and cos depending on the rotation angle of the rotor. Obtained as a waveform signal.

  5 and 6 show examples of the configuration of such an angle detector. FIG. 5 shows the shape of the stator core viewed from the axial direction, and FIG. 6 shows the shape of the rotor core viewed from the axial direction. An example of such an angle detector is disclosed in Patent Document 1.

  When a material with high permeability such as an electromagnetic steel plate is used for the rotor, the magnetic resistance of the magnetic path is small for a coil in which the gap length between the rotor and the stator is short, and the gap length is long. For a certain coil, the magnetic resistance of the magnetic path increases. Using this, a coil having a number of turns defined so that the voltage induced in the detection winding has a sin waveform (sin winding) and a coil having a number of turns defined to have a cos waveform ( cos windings) were prepared, and the rotor angle was detected from the voltage ratio induced in these two windings.

  Further, as a conventional angle detector having a configuration different from that shown in FIGS. 5 and 6, there is known one using an eddy current flowing in a rotor. An example of such an angle detector is disclosed in Patent Document 2.

JP-A-8-178611 JP 2011-202966 A

  However, the conventional technique has a problem that it is difficult to obtain a high detection gain with respect to a high-frequency excitation current while simplifying the configuration of the coil.

  For example, as in Japanese Patent Application Laid-Open No. H11-260260, the conventional technique that utilizes the fact that the rotor permeability is larger than the gap portion (vacuum permeability) for the principle of angle detection has a high gain for high-frequency excitation current. Is difficult to get. The induced voltage of the detection coil is proportional to the magnetomotive force of the exciting current, and a large induced voltage can be obtained if the frequency of the current flowing through the exciting coil is high. On the other hand, the magnetic substance such as an electromagnetic steel sheet has a low magnetic permeability when the frequency is high, and the magnetic permeability is almost the same as the vacuum magnetic permeability for a frequency higher than a certain value. Therefore, in such a conventional technique, when the frequency of the excitation current is increased above a certain value, the detection gain is lowered.

  For example, the configuration of Patent Document 2 uses eddy current, but the configuration of the coil is complicated. Specifically, it is necessary to arrange the coil patterns so that the coil patterns are alternately alternated or to form an annular shape over the entire circumference of the rotor.

  The present invention has been made to solve such problems, and provides an angle detector capable of obtaining a high detection gain with respect to a high-frequency excitation current while simplifying a coil configuration. Objective.

The angle detector according to the present invention is:
A ring-shaped stator having excitation coil portions and detection coil portions provided at predetermined angular intervals;
A ring-shaped rotor including a conductor that is rotatable with respect to the ring-shaped stator; and
In an angle detector having
An eddy current flows through the annular rotor so as to block a change in magnetic flux generated by the excitation coil unit, and an induced voltage is induced in the detection coil unit by the excitation coil unit,
The conductor is shaped so that the amplitude of the magnetic flux at a predetermined circumferential position of the annular stator is sinusoidal according to the rotation angle of the annular rotor.
It is characterized by that.
According to a particular embodiment,
The ring-shaped rotor is arranged to be spaced apart in the axial direction with respect to the ring-shaped stator,
The ring-shaped rotor includes a concavo-convex portion that is formed on the outer periphery and whose radial length changes.
According to a particular embodiment, the conductor contained in the annular rotor is non-magnetic.
According to a particular embodiment, the excitation coil part and the detection coil part are a conductive pattern or a magnet coil on the annular stator.

  Since the angle detector according to the present invention uses an eddy current that can follow a high-frequency excitation current, a high detection gain can be obtained with respect to the high-frequency excitation current. Further, since the conductor is formed so that the amplitude of the magnetic flux is sinusoidal, the configuration of the coil can be simplified. As a result, it is possible to obtain a high detection gain for a high-frequency excitation current while simplifying the configuration of the coil.

It is sectional drawing by the plane perpendicular | vertical to an axis | shaft of the angle detector which concerns on Embodiment 1 of this invention. It is sectional drawing by the plane parallel to an axis | shaft of the angle detector of FIG. FIG. 2 is a vector diagram of eddy current generated in a rotor in the embodiment of the angle detector of FIG. 1. FIG. 2 is a vector diagram of magnetic flux density interlinking with a detection coil unit in the embodiment of the angle detector of FIG. 1. It is a figure which shows the shape which looked at the stator core of the conventional angle detector from the axial direction. It is a figure which shows the shape which looked at the rotor core of the conventional angle detector from the axial direction.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
1 and 2 show examples of the configuration of the angle detector 10 according to Embodiment 1 of the present invention. FIG. 1 is a cross-sectional view of the angle detector 10 by a plane perpendicular to the axis of the angle detector 10, and FIG. 2 is a cross-sectional view of the angle detector 10 by a plane parallel to the axis of the angle detector 10. In particular, FIG. 1 is a cross section taken along line II in FIG. 2, and FIG. 2 is a cross section taken along line II-II in FIG.

  The angle detector 10 may be a so-called resolver. The angle detector 10 includes a stator 20 and a rotor 30. The stator 20 includes a stator body 21, an excitation coil unit 22, and a detection coil unit 23. The stator body 21 is formed in a ring shape, for example, and in that case, the entire stator 20 is ring-shaped. The rotor 30 is also formed in a ring shape, for example. The rotor 30 is provided so as to be rotatable with respect to the stator 20. Further, as shown in FIG. 2, the rotor 30 is arranged to be separated from the stator 20 in the axial direction. That is, in the angle detector 10, the stator 20 and the rotor 30 are arranged in an axial type.

  The rotor 30 is fixed to a rotating shaft (not shown) and rotates with respect to the stator 20 together with the rotating shaft. The angle detector 10 is configured to detect a rotation angle (angular position) of the rotor 30 with respect to the stator 20. In the example of FIGS. 1 and 2, the inner and outer peripheral surfaces of the stator 20 and the inner peripheral surface of the rotor 30 are both cylindrical, and the respective axes are common.

  The excitation coil unit 22 and the detection coil unit 23 are configured as a conductive pattern on the stator 20. The exciting coil unit 22 is provided at predetermined angular intervals in the circumferential direction of the stator body 21. The detection coil portions 23 are also provided at predetermined angular intervals in the circumferential direction of the stator body 21. In FIG. 1 and FIG. 2, the excitation coil unit 22 and the detection coil unit 23 are disposed so as to substantially overlap each other at the same circumferential position, but their positional relationship is not limited to that illustrated. In FIGS. 1 and 2, the loop formed by the detection coil unit 23 is arranged immediately inside the loop formed by the excitation coil unit 22, but the positional relationship between them is not limited to that illustrated.

  The rotor 30 includes a conductor. In the present embodiment, the entire rotor 30 is made of a conductor. For this reason, an eddy current flows through the rotor 30 so as to block the change in magnetic flux generated by the exciting coil unit 22. In addition, the conductor included in the rotor 30 includes a nonmagnetic material in the present embodiment. In the present embodiment, the entire conductor of the rotor 30 is nonmagnetic.

  In the stator 20, an alternating current flows through the exciting coil unit 22, and the exciting coil unit 22 generates a magnetic flux that changes in accordance with the flowing of the alternating current. In response to the magnetic flux changing in this way, an induced voltage is induced in the detection coil unit 23. That is, an induced voltage is induced in the detection coil unit 23 by the excitation coil unit 22.

  A description of a configuration for supplying current to the exciting coil unit 22 (power source or the like) and a configuration for detecting an induced voltage in the detection coil unit 23 (such as a voltmeter or a control device) will be omitted. For example, it is possible to design based on a known configuration.

  The rotor 30 is shaped so that the amplitude of the magnetic flux at a predetermined circumferential position of the stator 20 is sinusoidal according to the rotation angle of the rotor 30. Such a specific configuration and shape of the rotor 30 can be realized, for example, by changing the diameter of the rotor 30 according to the circumferential position as shown in FIGS. 1 and 2. In the illustrated embodiment, the rotor 30 includes an uneven portion 31. The concavo-convex portion 31 is a portion that is formed on the outer periphery of the rotor 30 and whose radial length changes. For example, the uneven part 31 includes a large diameter part 31a and a small diameter part 31b. 1 and 2 are schematic diagrams for explaining the principle of the present invention, and the dimensions of each part (particularly the length in the radial direction of the rotor 30) are not strict.

  The operation of the rotor 30 having such a shape is as follows. For example, when the large-diameter portion 31a of the concavo-convex portion 31 is located at a specific circumferential position of the stator 20 (a circumferential position corresponding to a specific excitation coil portion 22 and detection coil portion 23), The eddy current flowing through the rotor 30 at the circumferential position increases, and the action of blocking the change in magnetic flux generated by the exciting coil unit 22 becomes stronger. As a result, the magnetic flux amplitude at the circumferential position is reduced.

  On the other hand, when the small-diameter portion 31b of the concavo-convex portion 31 is located at the circumferential position, the eddy current flowing through the rotor 30 at the circumferential position is reduced, and the change in magnetic flux generated by the exciting coil portion 22 is reduced. The action of blocking is weakened. As a result, the magnetic flux amplitude at the circumferential position increases.

  Further, when a portion between the large diameter portion 31a and the small diameter portion 31b of the uneven portion 31 is located at the circumferential position, the circumferential position according to the radial length of the portion. At this time, the magnitude of the eddy current flowing through the rotor 30 changes, and the strength of the action that blocks the change in magnetic flux generated by the exciting coil section 22 changes. As a result, the amplitude of the magnetic flux at the circumferential position changes according to the length of the rotor 30 in the radial direction.

  In this way, the amplitude of the magnetic flux at each circumferential position of the stator 20 changes according to the rotation angle of the rotor 30. The magnetic flux amplitude at each circumferential position can be detected or calculated based on the amplitude of the induced voltage induced in the detection coil section 23 at the circumferential position.

  For example, the shape of the rotor 30 as shown in FIG. 1 can be determined as follows. First, the small diameter portion 31b is arranged every 2π / X [rad] starting from a certain circumferential position 0 [rad]. However, X is an integer greater than or equal to 1 representing the shaft angle multiplier of the rotor 30, and X = 4 in the example of FIG. X corresponds to the number of small diameter portions 31b. In addition, the large-diameter portion 31a is arranged every 2π / X [rad] starting from the circumferential position π / X [rad]. That is, the number of the large diameter portions 31a and the number of the small diameter portions 31b are equal, and these are alternately arranged in the circumferential direction.

  With respect to the detection coil portion 23 arranged at a specific circumferential position of the stator 20, it is assumed that the small diameter portion 31b is positioned in the detection coil portion 23 when the rotation angle of the rotor 30 is θr = 0 [rad]. At this time, the amplitude of the magnetic flux acting on the detection coil unit 23 becomes the maximum value. This maximum value is assumed to be Φmax [Wb]. In this case, when the rotation angle of the rotor 30 is θr = π / X [rad], the large diameter portion 31a is located in the detection coil portion 23, and the amplitude of the magnetic flux takes the minimum value. Let this minimum value be Φmin [Wb].

  The shape of the rotor 30 (particularly, the length in the radial direction at each circumferential position) is designed so that the amplitude of the magnetic flux in the detection coil portion 23 becomes a sine wave shape according to the rotation angle θr of the rotor 30. Can do. For example, with respect to the rotation angle θr [rad] of the rotor 30 (where 0 ≦ θr ≦ 2π / X), the magnetic flux amplitude in the detection coil unit 23 may satisfy the following expression.

  The angle detector 10 has a signal processing unit (not shown). A signal detected by each detection coil unit 23 is input to the signal processing unit. This input can be configured in parallel for each detection coil section 23. The signal processing unit generates a sin signal and a cos signal by multiplying the signals input from the detection coil units 23 by different coefficients and then taking the sum.

The coefficient used for the multiplication for generating the sin signal is defined as follows, for example. For the mth detection coil unit 23, the coefficient N1 (m) multiplied by the signal of the detection coil unit 23 is
N1 (m) = p · N _M · K (m) · sin {θm + α (m)}
And However,
p is p = 1 when m is odd, and p = −1 when m is even;
N _M is a constant coefficient for determining the maximum value of the coefficient,
K (m) is a value determined according to the number of turns of the coil in the m-th detection coil unit 23. For example, the number of turns may be used as it is, and the number of turns of all the detection coil units 23 is the same. If you want, you can omit it.
θm is a constant representing an angle formed by two adjacent detection coil units 23 (that is, a difference in circumferential position),
α (m) is an offset value representing the circumferential position of the m-th detection coil unit 23.

Moreover, the coefficient used for the multiplication for producing | generating a cos signal is defined as follows, for example. For the mth detection coil unit 23, the coefficient N2 (m) multiplied by the signal of the detection coil unit 23 is
N2 (m) = p · N _M · K (m) · cos {θm + α (m)}
And

The amplitude Esin (θr) of the sin signal generated by the signal processing unit for the rotation angle θr of the rotor 30 satisfies the following expression.
Esin (θr) = Emax · sin (X · θr + β)
Here, β is an offset value that serves as a reference for the rotation angle θr of the rotor 30.

Further, the amplitude Ecos (θr) of the cos signal generated by the signal processing unit for the rotation angle θr of the rotor 30 satisfies the following expression.
Ecos (θr) = Emax · cos (X · θr + β)

Thus, the rotation angle θr of the rotor 30 can be obtained by calculating the ratio of Esin (θr) and Ecos (θr). For example, θr = arctan {Esin (θr) / Ecos (θr)}

  FIG. 3 and FIG. 4 show the analysis results by the finite element method for one embodiment of the angle detector 10. FIG. 3 is a vector diagram of eddy current generated in the rotor 30, and FIG. 4 is a vector diagram of magnetic flux density interlinking with the detection coil unit 23.

  As described above, according to the angle detector 10 according to the first embodiment of the present invention, since the change in magnetic flux is detected based on the eddy current, the change in magnetic flux that depends on the magnetic permeability of the rotor is detected. As compared with, the detection gain can be maintained with respect to the excitation current having a higher frequency. Moreover, according to the angle detector 10, since the rotor 30 is shape | molded so that the amplitude of magnetic flux may become a sine wave shape, the structure of the detection coil part 23 can be simplified. As a result, it is possible to obtain a high detection gain with respect to a high-frequency excitation current while simplifying the configuration of the detection coil unit 23.

  In general, in order to increase the induced voltage, it is necessary to increase the areas of the excitation coil unit 22 and the detection coil unit 23, but according to the angle detector 10 according to the first embodiment of the present invention. Since the stator 20 and the rotor 30 are arranged in the axial type, it is possible to obtain a large coil area with a thinner configuration as compared with the radial type arrangement.

  That is, in the conventional configuration, it is necessary to use laminated steel plates for the stator and the rotor in order to prevent the magnetic flux from decreasing due to the eddy current flowing through the rotor. Therefore, in addition to the thickness of the laminated stator and the thickness of the rotor, at least the thickness of the coil end portion of the coil wound around the stator is required, and it is difficult to reduce the overall configuration. On the other hand, according to the angle detector 10 according to the first embodiment of the present invention, it is not necessary to suppress eddy currents, so there is no need to use laminated steel plates, and the stator 20 and the rotor 30 are configured thinner than before. can do. Moreover, since the exciting coil part 22 and the detection coil part 23 can be wound in a plane perpendicular to the axis, the coil can also be made thinner than before. In this way, the angle detector 10 can be thinned.

  In the prior art, in order to pass the magnetic flux through the rotor, it is necessary to thicken the rotor to some extent. However, the angle detector 10 according to Embodiment 1 of the present invention uses eddy current, No substantial thickness is required for flow. Therefore, the thickness of the rotor 30 can be reduced to the minimum thickness required for structural strength, and the angle detector 10 can be thinned.

  Further, in the prior art, since the winding (magnet coil) is used for the excitation coil and the detection coil, it is difficult to reduce the cost of the winding, and the cost of the connector part connecting the winding and the circuit. It was also difficult to reduce this. On the other hand, in the angle detector 10 according to the first embodiment of the present invention, the excitation coil unit 22 and the detection coil unit 23 can be realized by a pattern on the substrate, thereby further reducing the thickness and reducing the cost. Is possible.

  In the prior art, two independent windings, a sin winding and a cos winding, are used. For this reason, the imbalance between the sin winding and the cos winding occurs due to the winding order, and the mutual interference between the sin winding and the cos winding is large. On the other hand, in the angle detector 10 according to the first embodiment of the present invention, the signal from one detection coil unit 23 is commonly used for the generation of the sin signal and the generation of the cos signal. There is no balance, and mutual interference between the windings can be suppressed.

  In the prior art, two signals of a sin signal and a cos signal are generated by changing the number of turns according to the position where the coil is wound. For this reason, even if there is a sufficient space for the winding, the detection coil cannot be wound with a number of turns greater than the specified number, and there is a limit to the improvement in detection gain. In addition, rationalization errors of the windings were also generated. On the other hand, in the angle detector 10 according to the first embodiment of the present invention, the sin waveform and the cosine waveform are generated by the calculation based on the signal output from each detection coil unit 23. Therefore, the excitation coil unit 22 and the detection coil The number of turns and the pattern of the portion 23 can be defined as long as space permits, the detection gain can be increased, and rationalization errors can be eliminated in principle.

In the first embodiment, the following modifications can be made.
The signal processing unit can be configured using a digital circuit, or can be configured using an analog circuit. Further, the signal processing unit may be omitted. In that case, if the number of turns is varied depending on the position of the detection coil unit 23 and the detection coil units 23 are connected in series, the sin signal and the cos signal can be directly generated based on the output. it can.

  In the first embodiment, the excitation coil unit 22 and the detection coil unit 23 are conductive patterns, but as a modification, they may be magnet coils.

  In the first embodiment, the stator 20 and the rotor 30 are arranged in an axial type, but they may be arranged in a radial type. For example, the rotor may be arranged on the radially inner side of the stator. In that case, the shape of the rotor may be the same as that of the first embodiment, or may be another shape. For example, the magnitude of the eddy current can also be changed by making the length of the rotor in the radial direction constant and changing the thickness in accordance with the circumferential position.

  In the first embodiment, the rotor 30 is entirely made of a conductor, but an insulator may be included in a part of the rotor. In the first embodiment, the conductor included in the rotor 30 is entirely non-magnetic, but a part of the conductor may be magnetic. If at least a part of the rotor contains a nonmagnetic conductor, the angle detector according to the principle of the present invention is realized by configuring the magnetic flux amplitude to be sinusoidal according to the rotation angle of the rotor. It is possible.

  DESCRIPTION OF SYMBOLS 10 Angle detector, 20 Stator (annular stator), 22 Excitation coil part, 23 Detection coil part, 30 Rotor (annular rotor), 31 Uneven part.

Claims (4)

A ring-shaped stator having excitation coil portions and detection coil portions provided at predetermined angular intervals;
A ring-shaped rotor including a conductor that is rotatable with respect to the ring-shaped stator; and
In an angle detector having
An eddy current flows through the annular rotor so as to block a change in magnetic flux generated by the excitation coil unit, and an induced voltage is induced in the detection coil unit by the excitation coil unit,
The conductor is shaped so that the amplitude of the magnetic flux at a predetermined circumferential position of the annular stator is sinusoidal according to the rotation angle of the annular rotor.
An angle detector characterized by that. The ring-shaped rotor is arranged to be axially spaced from the ring-shaped stator,
The ring-shaped rotor includes a concavo-convex portion that is formed on the outer periphery and changes in length in the radial direction.
The angle detector according to claim 1.   The angle detector according to claim 1, wherein the conductor included in the annular rotor is nonmagnetic.   The angle detector according to any one of claims 1 to 3, wherein the excitation coil unit and the detection coil unit are a conductive pattern or a magnet coil on the annular stator.

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