JPH0128402Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to a variable magnetic resistance type rotation angle detection device. Conventional electromagnetic rotation angle detection devices such as resolvers and microsynths include a primary winding and a secondary winding, and an output signal corresponding to the rotation angle is extracted from the secondary winding. By the way, the winding occupies a relatively large space in the structure of the detector.
The larger the number of windings, the larger the detector. Furthermore, the larger the number of windings, the more manufacturing steps will be required, resulting in higher costs. Therefore, if an electromagnetic detector could be constructed using only the primary winding without the need for a secondary winding, the structure would be greatly simplified and the detector could be made smaller. Many effects can be expected, such as , and the omission of manufacturing processes. The present invention has been made in view of the above points, and an object of the present invention is to provide an electromagnetic rotation angle detection device that does not require a secondary winding. A stator including a plurality of magnetic poles and an excitation winding wound around each of these magnetic poles, and a shape that faces the stator magnetic poles via a suitable gap and changes the magnetic resistance of each of the magnetic poles according to the rotation angle. A detection device is configured in combination with the rotor, which drives each excitation winding at a constant voltage or constant current, and sends a signal indicating a current or voltage according to the impedance of each excitation winding to a circuit that drives each excitation winding. The rotation angle is detected based on these signals. Since the impedance of each excitation winding changes in accordance with the change in magnetic resistance of each magnetic pole, it is possible to extract a signal corresponding to the rotation angle from a part of the circuit that drives each excitation winding. An embodiment of this invention will be described in detail below with reference to the accompanying drawings. In Figure 1, a stator (iron core) 1 has four excitation poles A, B, C, and D arranged at 90 degree intervals in the circumferential direction, and each magnetic pole A, B, C, and D has a winding. 2
A, 2B, 2C, and 2D are wound. Constant voltage or constant current AC signals having a phase shift of 90 degrees are applied to each of the windings 2A to 2D. In the figure, the winding 2A of pole A has a sine wave signal e _a = e _p sinωt, the winding 2B of pole B has a cosine wave signal e _b = e _p cosωt, and the winding 2C of pole C has an inverted sine wave signal e _c = -e _p sinωt, and an inverted cosine wave signal _ed = -e _p cosωt is applied to the winding 2D of the pole D at a constant voltage. The windings 2A to 2D are wound so that the magnetic fluxes generated at the magnetic poles A and C (or B and D) facing each other in the radial direction are directed in the same direction. That is, when the winding 2A generates a magnetic flux at the pole A in the direction of exiting from the extreme end as shown by the arrow x, the opposite pole C
The windings 2A and 2C are wound in such a way that the winding 2C generates a magnetic flux in the direction toward the extreme end as shown by the arrow. The windings 2B and 2C of the other radially opposing magnetic poles B and D are similarly wound. The rotor 3 faces the ends of each of the excitation poles A to D with a suitable gap interposed therebetween, and rotates integrally with the rotating shaft 4. A rotation angle θ to be detected is given to this rotation axis 4. The rotor 3 has a shape that changes the reluctance of the magnetic path passing through each stator excitation pole A, B, C, and D according to the rotation angle θ. In the example shown in FIG. 1, the rotor 3 has a cylindrical shape and is mounted eccentrically with respect to the center of the rotating shaft 4. As shown in FIG. Due to this eccentric cylindrical shape, the gap distance between the cylindrical side surface of the rotor 3 and the end of each pole A, B, C, and D changes depending on the rotation angle θ. Due to this change in gap, the reluctance of the magnetic path passing through each pole A to D changes, and the impedance (inductance) La, Lb,
Change Lc and Ld. Here, by appropriately selecting the mechanical dimensions and shapes of the stator 1 and rotor 3, it is possible to make the change in impedance of the windings 2A to 2D become a trigonometric function as shown in the following equation. L ₀ and k are constants determined by the structures of the stator 1 and rotor 3 and the frequency (ω/2π) of the excitation signal. In the above equation (1), as shown in FIG. 1b, the rotation angle θ is set to 0 degrees when the gap distance between the magnetic pole A and the rotor 3 is maximum. AC signals e _a to e _d applied to each winding 2A to 2D
Since is a constant voltage, the currents i _a to i _d that are inversely proportional to the impedance changes of each winding 2A to 2D are
Flows from A to 2D. These currents i _a , i _b , i _c , and i _d can be expressed as in the following equations. In this way, the current i _a ~ flowing through each winding 2A ~ 2D
Since i _d is a function of angle θ, these currents i _a ~
By detecting i _d and performing appropriate arithmetic processing, the rotation angle θ of the rotor 3 can be determined. for example,
A phase modulation signal corresponding to the rotation angle θ can be obtained by adding and combining the current signals i _a to i _d as shown in the following equation. I=i _a +i _b +i _c +i _d =2e _p k/L _p (cosθ・sinωt+sinθ・cosωt) =2e _p k/L _p sin(ωt+θ) …(3) As is clear from the above equation (3) The signal I obtained by adding and combining i _a to i _d is an AC signal whose phase is shifted by the phase angle corresponding to the rotation angle θ with respect to the excitation signal e _a = e _p sinωt, and therefore, this composite signal I and the excitation signal signal
The rotation angle θ can be determined by detecting the phase difference with e _a . FIG. 2 is an example of a circuit for applying a constant voltage alternating current signal to an excitation winding and detecting the current flowing through the winding. In Figure 2, only the winding 2A is shown as a representative, but the same thing is shown in each winding 2A.
Individually provided for each of A to 2D. In FIG. 2, an amplifier 5 is used to apply a constant voltage to a winding 2A, and a reference resistor R for current detection and a winding 2A are connected in series to its output. The amplifier 5 operates so that the excitation signal e _p sinωt is applied to the winding 2A at a constant voltage. The amplifier 6 is for detecting the voltage across the resistor R. Since the same current i _a flows through the resistor R and the winding 2A, the voltage across R is proportional to the current flowing through the winding 2A. Therefore, the amplifier 6 outputs a voltage signal _{R a} proportional to the current i _a flowing through the winding 2A. With the configuration shown in FIG. 2, each winding 2A~
Voltage signals Ri _a to Ri _d proportional to the currents i _a to i _d flowing through them can be extracted for each 2D. These signals Ri _a to Ri _d output from each magnetic pole A to D
The rotation angle θ can be determined by performing appropriate calculation processing. For example, as described above, in order to obtain a phase modulation signal corresponding to the rotation angle θ, these output signals Ri _a to Ri _d may be added and combined. The rotation angle θ is determined by detecting the phase difference between the phase modulation signal Ksin(ωt+θ) (where K is a constant) obtained by addition and synthesis and the excitation signal sinωt. There are various types of circuits that detect phase differences, but for example,
The processing circuit shown in No. 147425 or Japanese Patent Application No. 56-22075 can be used. According to the former processing circuit, the angle θ is obtained as a digital signal, and according to the latter, the angle θ is obtained as an analog signal. On the other hand, since the voltage signals Ri _{a to} Ri _d proportional to the currents i a to i _d show level changes according to the rotation angle θ, as is clear from equation (2), they can be calculated based on their amplitude values. The rotation angle θ can also be determined by for example,
Using the method shown in Japanese Patent Application No. 135325-1980,
Portions with good linearity of amplitude changes in the output signals of the respective magnetic poles may be complementarily synthesized. Note that when the output of each magnetic pole is determined based on the amplitude value of its voltage or current, each magnetic pole may be excited by only either a sine wave signal or a cosine wave signal. In the above embodiment, the excitation signal to each of the windings 2A to 2D is applied as a constant voltage, but it may be applied as a constant current. In that case, the terminal voltage of each winding 2A to 2D will change according to the rotation angle θ, so if this terminal voltage is detected and the appropriate arithmetic processing is performed as described above, the terminal voltage will change according to the rotation angle θ. I can get a signal. Note that the shapes of the stator 1 and rotor 3 are not limited to those shown in the first part, and can be arbitrarily changed in design without departing from the gist of this invention. For example, the magnetic pole of stator 1 in Figure 1 is 90
There are 4 pieces arranged at 45 degree intervals, but the design can be changed to 8 pieces at 45 degree intervals. Even in this manner, a reluctance change corresponding to the rotation angle θ is obtained between the rotor 3 and each magnetic pole, and an impedance change is brought about in each winding with a phase shift of 45 degrees. That is, the number of magnetic poles of the stator is not limited to four, but may be a plurality of N. In that case, each excitation winding of each magnetic pole of the stator is shifted in phase from each other by a phase angle corresponding to the deviation in the arrangement angle of each magnetic pole. Constant voltage or constant current driving may be performed using a plurality of alternating current signals. Let the number of magnetic poles of the stator be N, and the above formula (1),
The generalization of equation (2) is as follows. 1/L ₁ = 1/L ₀ (1+kcosθ) 1/L ₂ = 1/L ₀ {1+kcos(θ−2π/N)} 1/L ₃ =1/L ₀ {1+kcos(θ−4π/N)} 1/L ₄ = 1/L ₀ {1+kcos (θ-6π/N)} 〓 1/Li=1/L ₀ {1+kcos (θ-2π×i-1/N)} 〓 1/L _N = 1/ L ₀ {1+kcos(θ−2π×N−1/N)}
…(4) i ₁ = 1/L ₁ e ₁ = e ₀ /L ₀ (1+kcosθ) sinωt i ₂ = 1/L ₂ e ₂ =e ₀ /L ₀ {1+kcos(θ−2π/N)}s
in(ωt+2π/N) i ₃ =1/L ₃ e ₃ =e ₀ /L ₀ {1+kcos(θ−4π/N)}s
in(ωt+4π/N) i ₄ =1/L ₄ e ₄ =e ₀ /L ₀ {1+kcos(θ−6π/N)}s
in(ωt+6π/N) 〓 ii=1/Liei=e ₀ /L ₀ {1+kcos(θ−2π×i−1
/N)}sin(ωt+2π×i−1/N) 〓 i _N =1/L _N eN=e ₀ /L ₀ {1+kcos(θ−2π×N−1
/N)}sin(ωt+2π×N-1/N)...(5) Here, the signal I obtained by adding and combining i ₁ to i _N is I=i ₁ +i ₂ +i ₃ +i ₄ +...+ii+...+i _N = _N 〓 ⁱ⁼¹ ii, and if ii is expressed as a complex number, then from Euler's formula, Therefore, I is It can be expressed as here,

[Formula] is the sum of complex numbers obtained by dividing 2π into N equal parts, so it is 0 when N>1, and similarly,

[Formula] (where N>1) be. Also,

[Formula] is 0 when N>2. can be,

[Formula] is also 0 when N>2. Therefore, rearranging the above equation (6) results in the following. I= _N 〓 〓 ⁱ⁼¹ ii=e ₀ /L ₀・1/2j [k/2・N{e ^j( 〓 ^t+ 〓 ⁾ −e ^-j
( 〓 ^t+ 〓 ⁾ ｝〕 =N/2・e ₀ k／L ₀・1/2j{e ^j( 〓 ^t+ 〓 ⁾ −e ^-j( 〓 ^t
+ 〓 ⁾ }...(7) The above equation (7) can be converted as follows using Euler's formula. I=N/2・e ₀ k/L ₀・1/2j [cos(ωt+θ)+jsi
n(ωt+θ)−{cos(ωt+θ)−jsin(ωt+θ)}
] =N/2・e ₀ k/L ₀・1/2j {2jsin(ωt+θ)}
=N/2·e ₀ k/L ₀ ·sin (ωt+θ) (8) Therefore, a signal I is obtained by phase-modulating the excitation signal according to the rotation angle θ. Note that, as is clear from the above, in the above equation (8), N is an integer of 3 or more. As explained above, according to the present invention, it is possible to provide an electromagnetic rotation angle detection device that does not require a secondary winding. Compared to this, it has excellent effects in that manufacturing steps can be omitted, miniaturization can be promoted, and costs can be reduced.

[Brief explanation of drawings]

Fig. 1a is a diagram schematically showing a side cross section of an embodiment of the rotation angle detection device according to this invention, Fig. 1b is a schematic front view of a, and Fig. 2 is a diagram showing the application of a constant voltage alternating current signal to the excitation winding. FIG. 2 is a circuit diagram showing an example of a circuit and a circuit for detecting a current in the winding. 1...Stator, 2A-2D...Winding, 3...
Rotor, 4... Rotating shaft, A, B, C, D... Excitation pole, 5, 6... Amplifier, R... Reference resistor for current detection.

Claims (1)

[Claims for Utility Model Registration] A stator including a plurality of magnetic poles (an integer of 3 or more) arranged circumferentially at a predetermined angle and an excitation winding wound around each of these magnetic poles, and the stator magnetic poles. and a rotor that faces each other through a suitable gap and has a shape that changes the magnetic resistance of each of the magnetic poles according to the rotation angle, and the excitation windings are adapted to accommodate deviations in the arrangement angles of the magnetic poles. A part of a circuit that drives each excitation winding at a constant voltage or constant current using a plurality of alternating current signals that are out of phase with each other by a phase angle, and that drives each excitation winding with a signal indicating a current or voltage according to the impedance of the excitation winding. A rotation angle detection device characterized in that a signal obtained by phase modulating the excitation signal according to a rotation angle is obtained by additively combining the signals taken out from each winding.