JPH0616810U - Rotation angle detector - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the reliability by minimizing the detection phase error of the rotation angle detection device with a relatively simple configuration. [Constitution] 1/2 of the inner diameter of the circumference where the tips of the exciting salient pole pairs are arranged is LR, 1/2 of the outer diameter of the rotor is SR, and the amount of eccentricity from the rotation center of the eccentric rotor is d. When I did
While setting d / LR in the range of 0.05 ± 0.02,
SR / LR was set in the range of 0.86 ± 0.02, and the width SW of the tip of each exciting salient pole expressed by the angle viewed from the rotation center of the eccentric rotor was set to 20 ° ≦ SW ≦ 50 °. thing.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a variable reluctance type rotation angle detection device for detecting a rotation angle by changing the reluctance of a magnetic path according to the rotation angle.

[0002]

[Prior art]

 In a conventional variable reluctance type rotation angle detecting device described in Japanese Patent Publication No. 62-58445, a stator (iron core) around which an exciting coil (primary winding) and a detecting coil (secondary winding) are wound. ) And a rotor (iron core) facing the stator by opening a proper gear to form an electromagnetic detection device. Then, a phase shift detection signal corresponding to the rotation angle of the rotor is obtained between the applied excitation AC signal and the output signal obtained through the detection coil.

For example, in the case where a cylindrical eccentric rotor is used as shown in FIG. 3, the cylindrical rotor 2 that is rotationally driven inside the stator 1 having a hollow cylindrical shape is the rotor 2 itself. It is eccentrically arranged so that the center of rotation is a position displaced from the center of the shape by a predetermined amount. The air gap distance between the circumferential side surface of the cylindrical rotor 2 and the tip surfaces of the four exciting salient poles A, B, C, D provided on the stator 1 is the magnetic resistance of the rotor 2. It is configured to change with rotation. The change in the magnetic resistance in this case is a function of the rotation angle of the rotor 2 and is converted into an electric signal as rotation position information.

At this time, two exciting coils (primary windings) 3 and 3 are differentially wound around each exciting salient poles A, B, C and D of the stator 1. The detection coil (secondary winding) 4 is wound so as to be connected in series. The total detection voltage V _out is given by the sum of the induced voltages e _{A to} e _D of the respective poles. That is, as is apparent from the equivalent circuit of FIG. 4, when the numbers of turns of the exciting coil 5 and the detecting coil 7 are N ₁ and N ₂ , respectively, the detection voltage V _out is represented by the following equation.

[Equation 1] Here, from Kirchhoff's law (φ _A + φ _B + φ _C + φ _D = 0), φ _B + φ _D = − (φ _A + φ _C )

[Equation 2] Here again, using Kirchhoff's law,

[Equation 3] Therefore

[Equation 4] Substituting equation 4 into equation 2 and rearranging,

[Equation 5] here,

[Equation 6] Equation 5 above is a basic equation of input / output characteristics of a variable reluctance type rotation angle detection device using an eccentric rotor. Here, the functional forms of (P _A −P _C ) (P _B ＋ P _D ) and (P _A ＋ P _C ) (P _B −P _D ), which are obtained from the combination of the rotation angle dependence of the permeance of each exciting salient pole, are respectively

[Equation 7] Is the ideal state, and only in that case

[Equation 8]

[0005]

[Problems to be solved by the device]

However, in reality, a rotor having a true circular cross-sectional area cannot be exactly in the ideal state as described above, and the essential principle derived from the operating principle of a variable reluctance type rotation angle detection device using an eccentric rotor is essential. There is a problem that a detection error, that is, a phase error due to the structure of the mechanical section essentially occurs. This phase error ε (θ) is derived by obtaining the phase difference in the above equations (5) and (8), and permeance P _A (θ) to P _D (θ) determined by the dimensional conditions of the mechanism section. It is expressed as a function of.

[Equation 9]

Therefore, it is an object of the present invention to provide a rotation angle detecting device which has a relatively simple structure and which can minimize a detected phase error.

[0007]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention has a plurality of pairs of exciting salient poles in which an exciting coil is differentially wound at predetermined angular intervals in the circumferential direction, and detects the induced voltage by each exciting salient pole. A stator provided with a coil and an eccentric rotor having a shape that changes the reluctance of a magnetic path passing through each stator exciting salient pole according to a rotation angle are provided. A plurality of alternating current signals with phase shifts corresponding to the intervals are separately excited, whereby an alternating current signal with a phase shift corresponding to the rotation angle of the eccentric rotor is output from the secondary winding. In the rotation angle detection device, LR is 1/2 of the inner diameter of the circumference where the tips of the exciting salient pole pairs are arranged, SR is 1/2 of the outer diameter of the eccentric rotor, and the rotation center of the eccentric rotor is Eccentricity of Then, d / LR was set in the range of 0.05 ± 0.02, SR / LR was set in the range of 0.86 ± 0.02, and the angle was viewed from the center of rotation of the eccentric rotor. The width SW of the tip portion of each of the exciting salient poles is set to 20 ° ≦ SW ≦ 50 °.

[0008]

According to the dimensional conditions of the mechanism section in such means, the detected phase error is minimized.

[0009]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The basic structure of the rotation angle detecting device in the present invention is the same as the conventional product. That is, as shown in FIG. 3, the inner wall portion of the hollow cylindrical stator (iron core) 1 has four exciting salient poles A, B from four sides toward the cylindrical center O of the stator 1. C and D are formed so as to project. These exciting salient poles A, B, C, D are arranged at intervals of 90 degrees in the circumferential direction, and two exciting salient poles A and C facing each other in the radial direction form one pair, Exciting salient poles B and D form another pair. Further, as shown in FIG. 1, the tip portions of the exciting salient poles A, B, C, D are arranged on the circumference of a broken line formed as a concentric circle of the center O of the stator.

A solid cylindrical rotor (iron core) 2 is rotated by a drive mechanism (not shown) in an area on the inner side of a broken circle, which is the arrangement circle of these exciting salient poles A, B, C, and D. It is arranged so that The center of rotation of the rotor 2 is set to the center of the circumference of the broken line, that is, the center O of the stator, but the center O ′ of the cylindrical shape of the rotor 2 is displaced from the center O of rotation by a distance d. Is set to. That is, the positional relationship is eccentric by the distance d.

Returning to FIG. 3, the exciting salient pole pairs A and C (or 2B and 3D) in the stator 1 are provided with exciting coils (primary windings) 3A and 3C (or 2B and 3D), respectively. In addition to being differentially wound, the detection coils (secondary windings) 7A and 7C (or 7B and 7D) are wound so as to be connected in series.

In this case, when the direction of the magnetic flux toward the inner end side of each of the exciting salient poles A, B, C, D is a positive phase, the exciting coils 3A and 3C (or 3B and 3D) are The magnetic fluxes generated by the windings are wound so that they have opposite phases. More specifically, when a magnetic flux is generated in the exciting salient pole A by the exciting coil 3A in the direction of exiting from the extreme portion as shown by the arrow x, the exciting salient pole C forming a pair with the magnetic flux generates an arrow x by the exciting coil 3C. The exciting coils 3A and 3C are differentially wound so that a magnetic flux is formed in the direction of entering the extreme portion as shown in FIG. Therefore, a magnetic flux flow in the same direction is formed in the exciting salient pole pairs A and C via the rotor 2 arranged in the central space of the stator 1. Similarly, for the other exciting salient pole pair B and D, the exciting coils 3B and 3D are differentially wound. The reason why the exciting coil is differentially wound around the exciting salient pole pairs A and C (or B and D) in this way is that each exciting salient pole pair A and C or B and D is different in alternating current as will be described later. This is because it is excited by a signal, and the flow of magnetic flux is guaranteed between poles (A and C or B and C) that are excited by the same AC signal.

The rotor 2 facing the end portions of the exciting salient poles A to D with an appropriate gap interposed therebetween is rotated integrally with the rotating shaft 5. The rotation shaft 5 is provided coaxially with the rotation center O, and is given a rotation angle θ which is a detection target. Further, as described above, the rotor 2 has a cylindrical shape that is eccentrically attached to the rotation center O of the rotary shaft 5, and the magnets passing through the excitation salient poles A, B, C, D of the stator 1 are connected to each other. It is configured to change the reluctance of the road according to the rotation angle θ. By the rotational driving of the eccentrically arranged cylindrical rotor 2, the distance of the gap interposed between the cylindrical side surface of the rotor 2 and the tip of each exciting salient pole A, B, C, D is rotated. It is changed according to the angle θ. Then, due to the change in the gap, a reluctance change corresponding to one cycle per one rotation of the rotor 2 is brought to the exciting salient poles A, B, C and D.

On the other hand, the magnetic excitation salient pole pairs A and C and the magnetic excitation salient pole pairs B and D are separately excited by an alternating signal whose phase is shifted by 90 degrees. In this embodiment, the exciting coils 3A and 3C corresponding to the exciting salient pole pairs A and C are connected in series, and the cosine wave signal i _a = Icos ωt is applied from the oscillator 5 arranged in the middle thereof. Further, the exciting coils 3B and 3D of the exciting salient pole pairs B and D are connected in series, and the sine wave signal ib = Isin ωt is applied from the oscillator 6 arranged in the middle of the exciting coils 3B and 3D. If only the exciting coils 3A and 3C are extracted, both appear as in-phase series connection, but the directions of the exciting salient pole pairs A and C around which they are wound, that is, the direction of the magnetic flux generated by both Considering the above, both are substantially connected in anti-phase series. In other words, both are differentially wound. The same applies to the exciting coils 3B and 3D.

Further, the detection coil (secondary winding) 4 is wound in order to extract the voltages respectively induced by the exciting salient poles A, B, C and D. In this embodiment, the detection coils 4A and 4C are wound in phase with the excitation salient poles A and C, respectively, and the detection coils 4B and 4D are wound in phase with the excitation salient poles B and D, respectively. Therefore, the detection coils 4A and 4C and the detection coils 4B and 4D have opposite phases. These detection coils 4A to 4D are connected in series, and are configured so that the combined signal E of the voltages respectively induced at the respective exciting salient poles A, B, C and D can be taken out. The output signal E becomes an AC signal having a phase shift corresponding to the rotation angle θ of the rotor 2 with respect to the excitation AC signal i _a = Icos ωt or i _b = Isin ωt. This point will be described below.

Here, the dimensional conditions of the mechanical section in the present embodiment are defined as follows. First, as shown in FIG. 1, the radius of the broken line circle that is the arrangement circle of the exciting salient poles A, B, C, D is LR, the outer radius of the rotor 2 is SR, and the eccentricity of the rotor 2 is d. The width of the exciting salient poles of the stator 1 is SW at an angle from the rotation center O of the rotor 2. Then, the ratio d / LR, which is the ratio of the radius LR of the arrangement circle of the exciting salient poles A, B, C, D and the eccentricity d of the rotor 2, is set in the range of 0.05 ± 0.02. In addition, SR / LR, which is the ratio of the radius LR of the circle in which the salient magnetic poles A, B, C, D are arranged and the radius SR of the rotor 2, is set in the range of 086 ± 0.02, and The width SW of the tip end portion of the exciting salient pole is set to 20 ° ≦ SW ≦ 50 °.

As described in the above-mentioned prior art, the essential error due to the variable reluctance type rotation angle detecting device using the eccentric rotor is that the permeance angle dependence P _A (θ) to P _B (θ) Determined by Next, let us consider how this permeance is governed by the dimensional conditions of the mechanical section. As a premise for the consideration, strict discussion on the spread of the magnetic flux in the air gap magnetic path and the leakage magnetic flux between the exciting salient poles is omitted, and only the gap length between the exciting salient poles facing the rotor side surface is omitted. It is assumed that each permeance is determined.

First, as shown in FIG. 1, as the mechanical unit sizing parameters that determine the behavior of permeance, LR (stator radius), SR (rotor radius), d ( Consider eccentricity), SW (width of stator exciting salient pole) and θ (rotation angle). Since the four exciting salient poles A, B, C, and D are symmetrically arranged at 90 ° mechanical angles, if the angle dependence of permeance corresponding to one exciting salient pole is obtained, the remaining exciting salient poles are obtained. The angle dependence of permeance corresponding to a pole can be obtained by adding a phase difference of 90 degrees to each of the obtained results.

Here, as shown in FIG. 2, the origin of the mechanical angle θ is defined as a state in which the gap length between the exciting salient pole A and the rotor 2 is the shortest, and the angular dependence P _A (θ of the permeance with respect to the exciting salient pole A P (θ ). First, in order to obtain the gap length between the exciting salient pole A and the rotor 2 at an arbitrary rotation angle θ from the rotation center O of the rotor 2, a geometrical circle corresponding to the rotor 2 and an eccentric position (d, The intersection (x ₀ , y ₀ ) of the straight line passing through ₀ ) is obtained. this is,

[Equation 10] The following simultaneous equations are solved to obtain as follows.

[Equation 11] Here, y ₀ > 0 when 0 ° <θ <180 °, and y ₀ <0 when 180 ° <θ <360 °.

Since the distance between the obtained point (x ₀ , y ₀ ) and the origin O corresponds to the distance from the rotation center O at the rotation angle θ to the outer circumference of the rotor 2, the gap length G ( θ) is calculated by the following equation.

[Equation 12]

On the other hand, since the magnetic resistance R _m (θ) is proportional to the gap length and inversely proportional to the magnetic path cross-sectional area, the required permeance P _A (θ) is

[Equation 13] Given in.

In the above equation, the inner radius of the stator; LR, the outer radius of the rotor; SR, the amount of eccentricity; d, the stator exciting salient poles are used as the dimensional parameters of the mechanical portion of the rotation angle detection device that affects the permeance, that is, the value of the phase error. Width; SW, but the permeance functional form is calculated from the calculation of the rotational angle dependence of the simple geometrical void length, so the same result is obtained for similar mechanical parts. Will be obtained. Therefore, here, the outer radius of the rotor and the eccentricity are standardized with the inner radius of the stator, and the three parameters of SR / LR, d / LR, and SW are examined.

When discussing the error as a real problem, the maximum value ε _max (phase delay; positive value) and the minimum value ε _min (phase lead; negative value) of one rotation of the rotor 2 are used. Difference, that is, the magnitude of the error width | ε _max −ε _min | is the criterion for error width judgment. The dependence of this error width on the stator salient pole width SW is calculated using the rotor radius SR and the eccentricity d as parameters, and the results are shown in FIGS. 5 (a) and 5 (b). From this figure, the dimensional conditions of the mechanical part in this embodiment, that is, d / LR is set in the range of 0.05 ± 0.02, SR / LR is set in the range of 086 ± 0.02, and According to the mechanical condition in which the width SW of the tip portion of the exciting salient pole expressed by the angle viewed from the rotation center O of the eccentric rotor 2 is set to 20 ° ≦ SW ≦ 50 °, the error width | ε _max −ε It turns out that _min | is minimized.

Although four exciting salient poles are provided in this embodiment, the number of exciting salient poles is not limited to this.

[0025]

[Effect of device]

 As described above, according to the size condition of the mechanism section in the rotation angle detection device of the present invention, the detection phase error can be minimized with a relatively simple structure, and the reliability of the rotation angle detection device can be improved. it can.

[Brief description of drawings]

FIG. 1 is a partially enlarged cross-sectional explanatory view showing a main part of a rotation angle detection device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for deriving a gap length.

FIG. 3 is a cross-sectional explanatory diagram showing the overall configuration of a rotation angle detection device.

FIG. 4 is a diagram showing an equivalent circuit of a magnetic circuit.

FIG. 5 is a diagram showing the dependence of an error on a stator salient pole.

[Explanation of symbols]

 1 Stator 2 Rotor A, B, C, D Exciting salient pole 3 Exciting coil 4 Detection coil

Claims (1)

[Scope of utility model registration request] 1. An exciting coil having a plurality of pairs of exciting salient poles wound differentially at a predetermined angular interval in the circumferential direction, and a detection coil for extracting an induced voltage by each exciting salient pole. A stator and an eccentric rotor having a shape that changes the reluctance of a magnetic path passing through each of the stator exciting salient poles in accordance with a rotation angle, and each of the exciting salient poles has a phase corresponding to an angular interval of the exciting salient poles. In the rotation angle detecting device in which the plurality of AC signals having the deviation are separately excited, and the AC signal having the phase deviation corresponding to the rotation angle of the eccentric rotor is output from the secondary winding. 1/1 of the inner diameter of the circumference where the tip of the exciting salient pole pair is placed
2 is LR, 1/2 of the outer diameter of the eccentric rotor is SR, and the amount of eccentricity from the center of rotation of the eccentric rotor is d. D / LR is set to 0.05 ± 0.02 and
SR / LR was set in the range of 0.86 ± 0.02, and the width SW of the tip of each exciting salient pole expressed by the angle viewed from the rotation center of the eccentric rotor was set to 20 ° ≦ SW ≦ 50 °. A rotation angle detection device characterized by the above.