JPH05209761A - Rotation detecting apparatus - Google Patents

Abstract

PURPOSE:To obtain a rotation detecting apparatus, which can obtain the rotation speed data and the position data signal in high resolution without using a frequency generator having a fine magnetizing pitch. CONSTITUTION:A sine-wave voltage (sintheta) and a cosine-wave voltage (costheta) are obtained with a magnetism-sensitive element 2. The carrier wave signal V0=sin(2pi/T)t, which is obtained from an oscillator 5, is supplied to the magnetism-sensitive element 2. Among the output voltages, which are obtained by the multiplication in the magnetism sensitive element 2, the voltage of V3= sintheta.cos(2pi/T)t is obtained by delaying the phase of the carrier component of V1=sintheta.sin(2pi/T)t by 90 degrees with a phase shifting circuit 6. The value V3 and V2=costheta.sin(2pi/T)t are added with an adder 7, and V4=sin(2pit/T+theta) is obtained. The phase difference between V4 and the carrier wave signal V0 is detected with a phase comparing circuit 8, and the value of theta (rotating position data) is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation detection device for detecting the rotation speed, rotation phase, etc. of a rotating body, and is particularly suitable for use in a frequency generator (FG) such as a small motor.

[0002]

2. Description of the Related Art A conventional frequency generator for detecting the rotation speed of a brushless motor or the like is a magnet formed by periodically magnetizing N-poles and S-poles on the peripheral surface of a rotor to about 400 to 500 poles. By detecting the signal with the magnetic sensitive element, a detection signal having a frequency corresponding to the rotation speed is obtained. In such a frequency generator (FG), accuracy is required in the magnetic pitch of the magnetic signal, and especially when the motor becomes small, the magnetic pitch becomes about 100 microns, and it is very difficult to obtain the accuracy. ing.

Conventionally, there is a method of using a multiplier in order to obtain a rotation detection signal (low speed high resolution signal) of high frequency without using the fine magnetizing pitch, that is, without increasing the wave number of the frequency generator of the motor. A method of adding two carrier waves to the power source of the MR element (Japanese Patent Laid-Open No. 60-188853) has been proposed. However, at present, the multiplier is expensive, and the method of adding two carrier waves to the MR power source is quite difficult to align the two MR elements. To avoid this, a special MR element is not made. must not.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rotation detecting device which can obtain a rotation frequency information and a position information signal of a rotating body having a high frequency (high resolution) without using the fine magnetizing pitch. ..

[0005]

According to the present invention, a sine wave voltage and a cosine wave voltage are obtained in accordance with the rotation of a rotating body, the sine wave voltage and the cosine wave voltage are multiplied by the same carrier, respectively, and the sine wave voltage is obtained. The voltage is delayed by 90 degrees with respect to the cosine wave voltage by the carrier wave, the voltage obtained by the phase delay and the cosine wave voltage are added, and the position of the signal obtained by the addition and the carrier wave is added. The feature is that the position of the rotating body is obtained by obtaining the phase difference.

[0006]

EXAMPLE As shown in FIG. 2, a sine wave voltage V _S = Ksi is detected by detecting the rotation of a rotor 1 magnetized at a predetermined pitch by a magnetic sensitive element 2 to which a constant voltage is applied.
Obtain nθ and the cosine wave voltage V _C = cos θ. In order to obtain these voltages V _S and V _C by, for example, the method shown in FIG. 2, the two detectors 3 and 4 of the magnetically sensitive element 2 are electrically separated by 90 degrees with respect to one cycle of the magnetizing pitch. It is arranged so as to have a phase difference. As the magnetic sensitive element 2 used here, a magnetoresistive effect element (MR element), a Hall element or the like is used.

Next, in the block diagram shown in FIG. 1, the carrier signal V obtained from the oscillator 5 is applied to the magnetic sensitive element 2.
_{When O 0} = sin (2π / T) t is used as a power supply voltage and V ₀ and a phase-reversed (−V ₀ ) are supplied, at this time, output voltages V ₁ and V ₂ obtained by multiplication from the magnetosensitive element 2 are obtained.
V ₁ = sin θ · sin (2π / T) t V ₂ = cos θ · sin (2π / T) t, and when θ = (1/30) · (2π / T) t, it is shown in FIG. Such output voltage waveforms of V ₁ and V ₂ are obtained. Here, θ = (1/30) · (2π / T) t
Means that when θ and (2π / T) t change synchronously, the output phase of the magneto-sensitive element 2 changes at a speed of 1/30 of the carrier phase change speed (2π / T) t. That is, while θ changes from 0 degree to 360 degrees, (2π / T) t
Means that it changes from 0 degree to (360 × 30) degrees.

[0008] Of this, the output voltage V _1, the output voltage V ₃ obtained by delaying the phase of 90 degrees sin (2π / T) by the phase shifting circuit 6 is approximately _{V 3 ≒ sinθ · cos (2π} / T ) T. This phase shift causes a time difference between the signals handled by the output voltages V ₁ and V ₂ , but the error due to this causes no practical problem by increasing the carrier frequency.

Here, when the output voltages V ₂ and V ₃ are added by the adder 7 and this output voltage is V ₄ , V ₄ = V ₂ + V ₃ ≈cos θ · sin (2π / T) t + sin θ · cos (2π / T) t = sin (2πt / T + θ), and set the output voltage waveform (θ = (1/100) · (2π / T) t as shown in FIG. 5 to increase the carrier frequency. Can obtain θ with a more accurate value). As a result,
The output voltage V ₄ of the adder 7 has a form in which a function having a time variable of sin (2π / T) t is phase-modulated by the position variable θ, and the output voltage V ₄ and the output voltage V ₀ = s of the oscillator 5 are
The phase difference φ of in (2π / T) t can be detected by the phase comparison circuit 8 to obtain the value of θ, that is, the rotational position information.
A more accurate value can be obtained for the value of θ by setting the carrier frequency higher.

As a concrete method for detecting the phase difference by the phase comparison circuit 8, since the frequency of the output voltage V ₀ of the oscillator 5 is constant, V _{0 is obtained} by using a counter (timer) 9 such as a microcomputer. The waveform of V ₄ is compared with 0, converted into a rectangular wave, and the phase difference between V ₀ and V ₄ is measured as a time difference at the rising or falling edge of the waveform to convert it into a phase.

[0011] In the above embodiment, the V ₁ sin (2π /
Although the phase of T) t is delayed by 90 degrees using the phase shift circuit 6, as another embodiment, the high pass filter 10 and the low pass filter 11 are provided as shown in FIG. 3 so that the gain and the phase can be easily adjusted. The output voltage V ₁ of the magnetic sensitive element 2 is input to the high-pass filter 10 by utilizing the phase characteristic of
The sin (2π / T) t of the output voltage V ₁ is advanced 45 degrees,
Similarly, V ₂ is input to the low-pass filter 11, and sin (2π / T) t of V ₂ is delayed by 45 degrees, resulting in a phase difference of 90 degrees, which is added at the output parts of both filters. It is input to the phase comparison circuit 6 and the phase difference from the output voltage V ₀ of the oscillator 5 is detected.

[0012]

According to the present invention, by interpolating the signal obtained from the rotation detection element (FG or the like) of the rotating body, the rotation position detection signal of high frequency (high resolution) can be obtained at low cost. .. In addition, a magnetic resistance element (M
When the R element is used, since the carrier waves applied to the two phases may be the same, a general MR element having a common power supply and ground and having two phases combined can be used without phase matching.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a method of obtaining a sine wave voltage and a cosine wave voltage according to the rotation of a rotating body.

FIG. 3 is a circuit diagram of another embodiment of the present invention.

FIG. 4 is an output waveform diagram of a main part of FIGS. 1 and 3.

5 is an output waveform diagram of a main part of FIGS. 1 and 3. FIG.

[Explanation of symbols]

1 ... Rotating body 2 Magnetic sensing element 5 Oscillator 6
・ Phase shift circuit 7 ・ ・ Adder 8 ・ ・ Phase comparison circuit

Claims (1)

[Claims] 1. A sine wave voltage and a cosine wave voltage are obtained according to the rotation of a rotating body, the sine wave voltage and the cosine wave voltage are respectively multiplied by the same carrier, and the sine wave voltage is compared with the cosine wave voltage. Of the rotating body by delaying the carrier wave by 90 degrees, adding the voltage obtained by the delay and the cosine wave voltage, and obtaining the phase difference between the signal obtained by the addition and the carrier wave. A rotation detection device characterized by obtaining a position.