JP2554472B2 - Rotation position detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase type rotational position detector, and more particularly, to an improvement of a detector that has a rotor having concave and convex teeth to detect rotational position with high resolution.

[Conventional technology]

A multi-tooth type variable magnetic resistance type rotational position detector in which a plurality of concave and convex teeth are provided around the rotor to cause a plurality of cycles of magnetic resistance change per rotation to each pole of the stator is disclosed in Japanese Patent Laid-Open No. 57883883. No. specification. As an example of such a detector, as shown in FIG. 6, there is a detector including a 6-pole type stator 1 and an 8-tooth rotor 2. In this detector, the stator poles A ₁ , B ₁ , C ₁ arranged at intervals of 60 degrees and the rotor teeth correspond to each other in terms of the magnetoresistance change of 12
It is designed to be sequentially shifted by 0 degrees (in this case, one cycle of magnetic resistance change, that is, 360 degrees corresponds to rotational displacement of one pitch of rotor teeth), and stator poles are arranged at intervals of 60 degrees. The correspondence between the poles at A ₂ , B ₂ and C ₂ and the rotor teeth is such that the change in their magnetic resistance is sequentially shifted by 120 degrees. Therefore, A ₁ and A ₂ are in phase, B ₁ and B ₂ are in phase, and C ₁ and C ₂ are in phase. Here, the primary coils of A ₁ and A ₂ are excited by sin ωt, the primary coils of B ₁ and B ₂ are excited by sin (ωt−120 °), and the primary coils of C ₁ and C ₂ are sine. By exciting at (ωt-240 °) and synthesizing the secondary coil output signals of each pole, it is possible to obtain an output signal Y that can be approximately expressed by the following formula: Y = K sin (ωt−Nθ) (1) You can do it. Here, K is a constant, N is the number of teeth of the rotor 2, and θ is a rotation angle. By measuring the phase shift Nθ in the output signal Y, the rotational position within 1 / N rotation can be detected.

[Problems to be solved by the invention]

In such a case, the magnetic resistance change at each pole is a simple trigonometric function (eg sin N
θ) and includes an error of the second harmonic (sin 2Nθ) or the third harmonic (sin 3Nθ). In the 6-pole detector, the magnetic resistance error component of the third harmonic wave is finally canceled out (see, for example, Japanese Utility Model Laid-Open No. 59-161023), but the magnetic resistance error component of the second harmonic wave remains. Further, when the primary side is driven with a constant voltage, the exciting current fluctuates due to the impedance change, and accordingly, a double wave error occurs. Due to the presence of such an error of the second harmonic, the phase shift component in the final output signal Y does not simply become a linear function Nθ with respect to θ as in the above equation, but as in the following equation (2). Will contain an error component of the third harmonic. Note that e is a coefficient of the error component.

Y = K sin (ωt−Nθ + e sin 3Nθ) (2) The present invention has been made in view of the above points, and in a rotational position detector including a multi-tooth rotor, the phase error as described above is generated. The purpose is to eliminate the component and improve the position detection accuracy.

[Means for solving problems]

The present invention is directed to a stator having a plurality of poles provided at predetermined intervals in the circumferential direction, and a plurality of n arranged facing each pole of the stator through a gap at predetermined equal intervals in the circumferential direction. Therefore, one pitch of the uneven teeth is 36
0 degree / n, a rotor that changes the magnetic resistance of each pole by changing the correspondence between each pole of the stator and the teeth according to a given rotation, and an induction corresponding to the magnetic resistance of each pole of the stator. In a rotational position detector comprising a plurality of coils provided on the side of the stator for generating an electric current, the poles of the stator are composed of a plurality of poles provided at a predetermined first interval P. A first pole group and a second pole group consisting of the same number of poles as the poles of this first pole group and equidistantly arranged, wherein the arrangement of the first pole group and the second pole group is One of the concave and convex teeth should correspond to the rotor teeth in opposite phases.
The pitch is shifted by a predetermined angle corresponding to an integral multiple of the pitch plus 0.5 pitch of the uneven tooth, and the first interval P is an integral multiple of 1 pitch of the uneven tooth plus 1 / m pitch of the uneven tooth ( m is an interval corresponding to an arbitrary number), each pole of the first pole group is excited by a plurality of alternating current signals whose electrical phases are sequentially shifted by 360 degrees / m, and the second pole
The respective poles of the first pole group are also excited by a plurality of AC signals whose electrical phases are sequentially shifted by 360 degrees / m, whereby the rotor corresponding to each of the first pole group and the second pole group. Output signals whose phases have been shifted according to the rotational positions of the respective pole groups, and the output signals corresponding to the respective pole groups are differentially combined to generate the final output signal.

[Action]

Assuming that the output signal obtained from the coil corresponding to the first pole group is Y ₁ and the output signal obtained from the coil corresponding to the second pole group is Y ₂ , the two are in opposite phase, and therefore the respective amplitude values are Since the sign of is the opposite polarity and the phase error appears in the opposite phase, Y ₁ = K sin (ωt−Nθ + e sin 3Nθ) (3) Y ₂ = −K sin (ωt −Nθ−e sin 3Nθ) (4) The output signals Y ₁ and Y _{2 of} both groups are combined differentially (that is, subtractively), so that the final output signal is Y ₁ −Y ₂ = K sin (ωt−Nθ + e sin 3Nθ) − {−K sin (ωt−Nθ−e sin 3Nθ)} = 2K sin (ωt−Nθ) cos (e sin 3Nθ) (5) In the above equation, cos (e sin 3Nθ) takes a value of “1” or a value close to “1” to slightly change the amplitude of 2K sin (ωt−Nθ), but does not affect the phase. Therefore, the equation (5) is substantially the same as the equation (1) in the phase component. In this way, an output signal in which the phase error component e sin 3Nθ is substantially canceled is obtained. Of course, phase error components other than the third harmonic can be similarly canceled.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the rotational position detector according to the present invention. The stator 1 of this rotational position detector has six poles A _{1 to} A ₆ arranged at equal intervals (that is, at intervals of 60 degrees).
A first pole group consisting of
Six second pole groups of pole B ₁ .about.B ₆ of arranged at intervals) of each 60 ° are provided. The rotor 2 is provided with 16 pitch convex rotor teeth at equal intervals (that is, at intervals of 22.5 degrees), and each pole A _{1 to} A _{6 of} the first pole group.
And the respective poles B _{1 to} B ₆ of the second pole group are respectively
They are arranged offset by an angle corresponding to 1 1/2 pitch (that is, 33.75 degrees). With this arrangement, as is apparent from the figure, the first pole group and the second pole group correspond to the rotor teeth in opposite phases.

Although only the pole A ₁ is designated by the reference numeral and the others are omitted, in FIG. 1, each of the poles A _{1 to} A ₆ , B _{1 to} B ₆ of the stator 1 has a primary coil L ₁ and a secondary coil. Each L ₂ is rolled.

Next, the detection principle of this rotational position detector will be described.

A function of the magnetoresistance change of each pole A _{1 to} A ₆ of the first pole group, that is, the permeance P with respect to the rotation angle θ of the rotor 2.
Ideally, the functions of _{A1 to} P _A6 are as follows. Where:
The unit of angle is “degree”, N is the number of teeth of the rotor 2, P ₀ , P
₁ is a constant.

Let the primary signals of poles A ₁ and A _{4 be} E _a1 and the primary signals of poles A ₂ and A _{5 be} E _{a1.
Let a2} be the primary signal of poles A ₃ and A _{6 be} E _a3, and set these as follows.

That is, each pole group is excited by an AC signal having a phase shift corresponding to the phase shift of the magnetic resistance change. The polarities of the primary signals E _{a1 to} E _a3 of the poles A _{1 to} A ₆ are set so that the magnetic circuit passes from one pole to the other pole in the pole group.

If the combined value Y ₁ of the output signals induced in the secondary coils of the poles A _{1 to} A ₆ of the _first group is obtained under the conditions of the above equations (6) and (7), ideally, Y ₁ = K sin (ωt−Nθ) should be obtained as in the equation (1), but as described above, the phase error of the third harmonic is actually included, so Y ₁ is actually Then, as in the equation (3), Y ₁ = K sin (ωt−Nθ + e sin 3Nθ).

On the other hand, the permeance P of the poles B _{1 to} B ₆ of the second pole group
The functions of _{B1 to} P _B6 are as follows because the first pole group and the second pole group have opposite phases.

P _B1 = P _B4 = P ₀ + P ₁ sin (Nθ-180 °) = P ₀ -P ₁ sin Nθ P _B2 = P _B5 = P ₀ + P ₁ sin (Nθ-120 ° -180 °) = P ₀ -P ₁ sin (Nθ-120 °) P _B3 = P _B6 = P ₀ + P ₁ sin (Nθ-240 ° -180 °) = P ₀ -P ₁ sin (Nθ-240 °) Primary of poles B ₁ and B _{4 Let} B _b1 be the signal and E be the primary signal of poles B ₂ and B _5.
and _b2, and E _b3 primary signal pole B _3, B _6, to set these as follows.

E _b1 = E _a1 = sin ωt E _b2 = E _a2 = sin (ωt-120 °) E _b3 = E _a3 = sin (ωt-240 °) Each pole B _{1 to} B of the second group, subject to the above equation _When the composite value Y ₂ of the output signal induced in the secondary coil of ₆ is obtained, ideally Y ₂ = −K sin (ωt−Nθ) as described above, but as described above, Actually, the phase error of the third harmonic wave opposite to Y ₁ is included, so that Y ₂ becomes Y ₂ = −K sin (ωt−Nθ−e sin 3Nθ) as in (4) above. .

The output signals Y ₁ and Y ₂ of each group are differentially combined to generate an output signal Y in which the influence of the phase error component e sin 3Nθ on the AC signal phase is eliminated, as in the equation (5). .

Y = Y ₁ −Y ₂ = 2K sin (ωt−Nθ) cos (e sin 3Nθ) The AC component in the output signal Y thus obtained is sin
(Ωt−Nθ), and the electrical phase shift amount with respect to the reference AC signal sinωt is Nθ. As described above, the final phase shift Nθ in the output signal Y is a linear function with respect to the rotation angle θ of the rotor 2 and does not include an error component. As is apparent, this electrical phase shift angle Nθ is the number of teeth times the actual rotation angle θ (N = 16 in FIG. 1).
And the resolution is expanded.

2 and 3 show poles A _{1 to} A ₆ and B _{1 to} B ₆ of each group.
3 shows respective connection examples of the primary coil L ₁ of FIG. By this connection, two AC signals sin ωt, s 60 degrees out of phase
Just by using in (ωt-60),
It is possible to generate three AC signals E _{a1 to} E _a3 and E _{b1 to} E _b3 which are 120 degrees out of phase, and to excite the primary coil of a predetermined pole by these.

4 and 5 show the poles A _{1 to} A ₆ and B _{1 to} B ₆ of each group.
2 shows an example of connection of the secondary coil L ₂ . Fourth
In the figure, the secondary coil connections of the first group and the second group are connected in antiphase series, and in FIG. 5, the secondary coil connections of both groups are connected in antiphase parallel. In both cases,
An output signal Y ₁ of the first group output signals Y ₂ of the second group differentially synthesized, Y ₁ as the final output signal Y -
I am trying to get Y ₂ .

The finally obtained output signal Y is supplied to a phase shift measuring circuit (not shown), the phase shift Nθ is measured there, and data corresponding to the rotation angle θ of the rotor 2 is obtained by the phase shift measurement.

In the above embodiment, the primary signal E _a1 of the first pole group
~ E _a3 and the primary signals E _{b1 to} E _{b3 of} the second pole group are in phase, and the combined value of the output signals in the first pole group
Although Y ₁ and the composite value Y ₂ of the output signals in the second pole group are subtractively combined, E _{a1 to} E _a3 and E _{b1 to} E _b3 are in opposite phases, and Y ₁ and Y ₂ are combined. The same result can be obtained by the addition and synthesis.

Also, in this embodiment, the first pole group and the second pole group each consist of 6 poles, the rotor teeth are 16 pitches, and the arrangement of the first pole group and the second pole group is rotor teeth. However, the number of poles in the pole group, the number of pitches of the rotor teeth, the arrangement of the first pole group and the second pole group are not limited to this. . The point is that the first pole group consists of a plurality of poles provided at a predetermined equal interval, and the second pole group consists of the same number of poles as the poles of the first pole group. Therefore, the arrangement of the first pole group and the second pole group may be displaced by a predetermined angle so as to correspond to the rotor teeth in opposite phases.

〔The invention's effect〕

As described above, according to the rotational position detector of the present invention, the phase error component can be removed from the output signal. Therefore, when detecting the rotational position in accordance with the phase shift between the output signal and the reference AC signal, This has an effect that the position detection accuracy can be further improved.

[Brief description of drawings]

FIG. 1 is a radial cross-sectional view showing an embodiment of the rotational position detector according to the present invention, and FIGS. 2 and 3 are connection examples of primary coils of respective poles of the rotational position detector of FIG. Figures shown respectively, 4th
FIG. 5 and FIG. 5 are views showing examples of connecting secondary coils of respective poles of the rotary position detector of FIG. 1, respectively, and FIG. 6 is a typical example of a conventional multi-tooth type variable reluctance rotary position detector. It is a radial direction sectional view shown. 1 ...... stator, 2 ...... rotor, A ₁ to A ₆ ...... first pole group, B ₁ .about.B ₆ ...... second pole group, L ₁ ...... 1 primary coil, L ₂ ...... 2 primary coil.

Claims (2)

(57) [Claims] 1. A stator having a plurality of poles provided at a predetermined interval in the circumferential direction, and a plurality of stators facing each pole of the stator via a gap and arranged at a predetermined equal interval in the circumferential direction. Including n concave and convex teeth,
Therefore, one pitch of the concavo-convex teeth is 360 degrees / n, and the rotor that changes the magnetic resistance of each pole by changing the correspondence between each stator pole and each tooth according to the given rotation; And a plurality of coils provided on the stator side to generate an induced current according to the magnetic resistance of the poles, wherein the poles in the stator have a predetermined first interval P
A first pole group consisting of a plurality of poles provided in the first pole group and a second pole group consisting of the same number of poles provided at equal intervals as the poles of the first pole group. And the arrangement of the second pole group are shifted by a predetermined angle corresponding to an integer multiple of one pitch of the uneven teeth plus 0.5 pitch of the uneven teeth so as to correspond to the rotor teeth in opposite phases. And, the first interval P is 1 of the uneven teeth.
A pitch corresponding to an integer multiple of the pitch plus 1 / m pitch (where m is an arbitrary number) of the uneven teeth, and each pole of the first pole group is sequentially shifted in electrical phase by 360 degrees / m. Each of the poles of the second pole group is excited by an AC signal, and each of the poles of the second pole group is also excited by a plurality of AC signals sequentially shifted in electrical phase by 360 degrees / m, whereby the first pole group and the second pole group are excited. Output signals that are phase-shifted according to the rotational position of the rotor corresponding to each of the pole groups, and output signals corresponding to each pole group are differentially combined to generate a final output signal. A rotary position detector characterized in that 2. The first pole group and the second pole group each have 6 poles, the rotor teeth have 16 pitches, and the arrangement of the first pole group and the second pole group is the rotor. The rotational position detector according to claim 1, wherein the rotational position detector is offset by an angle corresponding to the 3/2 pitch of the teeth.