JPH10132604A - Position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain two-phase signals for controlling the position and speed of an AC servo motor and three-shape signals for controlling magnetic field from one scale by the same encoder. SOLUTION: Sensors (a), (b), V, and W are provided along a scale SC on which gradations are marked at pitched so that the sensors can be displaced relatively to a scale 1. The sensor (b) is separated from the sensor (a) by a distance which is (n+1)/4 times as long as the period so that the sensor (b) can detect two-phase periodic signals cos(2πx/λ) and sin(2πx/λ) having a phase difference of 90 deg. between them in cooperation with the sensor (a) and, at the same time, separated from the sensors V and W by the distances, which are (n+1)/6 and (n+1)/3 times as long as of the period, respectively, so that the sensor (b) can detect three-phase periodic signals, sin(2πx/λ-λ/6), and sin(2πx/λ-λ/3) having a phase different of 60 deg. between each of them to sin(2πx/λ) in cooperation with the sensors V and W.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device for detecting the amount of displacement of two members which are relatively displaced in, for example, a machine tool or a precision measuring device, and more particularly to simplification of the structure of the device itself and the entire servo mechanism. The present invention relates to a technique for improving the accuracy of servomotor control.

[0002]

2. Description of the Related Art Generally, in a machine tool, a precision measuring device, or the like, in order to make the position of two members relatively displaced coincide with a target position, the amount of displacement between the two members is detected and the detection result is used as a control amount. A servo mechanism to be used is provided.
In recent years, in this servo mechanism, the use of an AC servomotor as a servomotor has become mainstream.

In order to control an AC servomotor, a digital two-phase signal (an A / B phase signal having a phase difference of 90 degrees or an UP / DOWN signal) for controlling position and speed is usually used.
Signal) and a digital three-phase signal for controlling the magnetic field (U-, V-, and W-phase signals having a phase difference of 120 degrees each other) need to be supplied to the AC servomotor. However, the two-phase signal for position / velocity control must be a signal with a relatively short period (length in micrometer) to enable fine control, whereas the three-phase signal for magnetic field control is required. Since the signals have a period corresponding to the pitch of the motor slot (generally, the length in millimeters), the periods of both signals are greatly different.

Conventionally, there are two types of scales, a scale on which a pitch scale corresponding to a two-phase signal for position / speed control is recorded and a scale on which a pitch scale corresponding to a three-phase signal for magnetic field control is recorded. A scale is provided, and a two-phase signal for position / speed control and a three-phase signal for magnetic field control are obtained based on periodic signals detected from these separate scales.

When a linear AC servomotor is used, the encoder itself for encoding the relative displacement between the scale and the sensor (detection head) is also required to obtain a two-phase signal for position / speed control. A device for obtaining a three-phase signal for magnetic field control is provided separately.

[0006]

However, providing two scales, one for position / speed control and one for magnetic field control, complicates the structure of the servo mechanism and the adjustment points when the servo mechanism is mounted. There has been a problem that the number of assembling steps is increased.

In order to obtain the two-phase signal for position / velocity control and the three-phase signal for magnetic field control from different scales as described above, it is necessary to provide a two-phase signal for position / velocity control and a three-phase signal for magnetic field control. There is a problem that it is difficult to match the phase difference with the three-phase signal with high accuracy, and the yield is deteriorated.

Further, when two encoders for position / speed control and magnetic field control are provided as in a linear AC servomotor, the structure becomes complicated and the number of adjustment points and the number of assembling steps are further increased. was there.

The present invention has been made in view of the above points, and simplifies the structure of a servomechanism using an AC servomotor, reduces the number of adjustment points and the number of assembling steps at the time of mounting, and further reduces the position / speed control. It is an object of the present invention to provide a position detecting device capable of adjusting the phase difference between the two-phase signal and the three-phase signal for controlling the magnetic field with high accuracy.

[0010]

A position detecting device according to the present invention has a scale on which a scale of a predetermined pitch is recorded and a sensor for detecting a periodic signal corresponding to a relative position with respect to the scale. In the first sensor,
For this first sensor, n + 1 / of the period of the periodic signal
A second sensor disposed at a distance of four times the distance, and n + of the period of the periodic signal with respect to the second sensor.
A third sensor and a fourth sensor which are arranged at a distance of (a predetermined number of times) and n + (a number of times a predetermined number of times), and a period is determined by the first sensor and the second sensor; A two-phase periodic signal having a phase shifted by 1/4 of the periodicity of the periodicity signal is detected, and the second sensor, the third sensor, and the fourth sensor detect a predetermined fraction of the periodicity of the periodicity signal. It is characterized in that three-phase periodic signals whose phases are shifted from one another are detected.

According to this position detecting device, while the second sensor is also used as a sensor for detecting a two-phase periodic signal and a sensor for detecting a three-phase periodic signal, these periodic signals are Both are detected. Therefore, these two phases, 3
Based on the phase periodic signal, a two-phase signal having a phase difference of 90 degrees for controlling the position and speed of the AC servomotor and a three-phase signal having a phase difference of 120 degrees for controlling the magnetic field can be obtained.

Since the distance between the second, third and fourth sensors is a predetermined fraction of the period of the periodic signal, the phase difference between the three-phase signals detected from these sensors is equal to the predetermined period of the period. It is a fraction and not necessarily 120 degrees. However, if the predetermined number is 3 (that is, if the distance between the second, third and fourth sensors is 1/3 of the period of the periodic signal), the phase difference is 12
It goes without saying that a three-phase signal of 0 degree is detected, for example, the predetermined number is set to 6 (that is, the distance between the second, third, and fourth sensors is set to 1/6 of the period of the periodic signal). Do)
Accordingly, even when a three-phase signal having a phase difference of 60 degrees is detected, a three-phase signal having a phase difference of 120 degrees is obtained from a three-phase signal having a phase difference of 60 degrees. By inverting the signal from the third sensor). In addition, by setting the distance between the second, third, and fourth sensors to be 1/6 of the period of the periodic signal, the distance between the second, the third, and the fourth sensor can be reduced by a factor of 2, Since the distance between the third and fourth sensors can be reduced, the size of the position detection device can be reduced.

In this manner, the two-phase signal for position / speed control and the three-phase signal for magnetic field control can be obtained from one scale by the same encoder, thereby simplifying the structure of the servo mechanism. Adjustment points and assembly man-hours at the time of installation are reduced.

Further, by obtaining a two-phase signal for position / velocity control and a three-phase signal for magnetic field control based on the periodic signal detected from the same scale as described above, the difference in the phase difference between the two signals is obtained. Disappears.

In addition, since the second sensor is also used as a sensor for detecting a two-phase periodic signal and a sensor for detecting a three-phase periodic signal, the sensor for detecting a two-phase periodic signal is used. As compared with the case where sensors for detecting periodic signals of three phases are separately provided, the number of sensors is reduced, so that the size of the position detecting device itself and the structure thereof are simplified.

[0016]

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

FIG. 1 shows a basic configuration when the present invention is applied to a magnetic linear position detecting device (linear encoder). Scale SC with magnetic scale recorded at a given pitch λ
Along the four sensors a, b, V and W are scale SC
Is provided so as to be able to be displaced relative to. Sensor a,
The detection method using b, V, and W may be a known detection method.

The sensors a and b may be those conventionally provided in a linear position detecting apparatus for detecting a two-phase periodic signal corresponding to the relative displacement x between the scale SC and the sensor SC. Therefore, the distance between them is n + ／ times the period of the periodic signal (in the figure, 1/4)
Twice the distance). Here, it is assumed that the period of this periodic signal is equal to the pitch λ, and the sensors a and b
From the cos (2πx / λ) and sin
(2πx / λ).

The sensors V and W are provided in the present invention, and distances from the sensor b by n + 1/6 times and n + ／ times the period of the periodic signal (1/1 in the figure).
(6 times, 1/3 times the distance). Therefore, from the sensors V and W, the signal si from the sensor b is output.
n (2πx / λ), the phase difference is 1 for the period λ.
Ｓ times (= λ / 6) signal sin (2πx / λ−λ)
/ 6) and sin (2πx / λ−λ / 3) are detected.

In this way, from one scale SC, the sensor b is used for both the detection of the two-phase periodic signal and the detection of the three-phase periodic signal. A signal is detected.

Next, the present invention is applied to an MR element (magnetic resistance element).
FIG. 2 shows an embodiment in which the present invention is applied to a magnetic position detecting device using a sensor as a sensor. Along a scale 1 on which magnetic scales are recorded at a predetermined pitch λ (for example, a pitch of several millimeters), four sets of MR heads 2, 3, 4, and 5 are provided so as to be relatively displaceable with respect to the scale 1.

In the figure, the MR heads 2 to 5 are abstracted for convenience, but each of these MR heads has a well-known configuration in which a bridge structure is formed by a pair of MR elements. That is, taking the MR head 2 as an example, a pair of M
As shown in the broken line on the right side of the figure, the R elements MR1 and MR2 are arranged along the scale 1 at a distance of の of a period λ ₁ of a periodic signal to be described later, and are connected to a terminal on the MR element MR1 side. and by applying a voltage between the MR element MR2 side terminal, based on the resistance change due to relative displacement between the scale 1, periodic signals corresponding to the relative displacement amount x ₁ is MR
It is derived from the midpoint of connection between elements MR1 and MR2.

The heads 2 and 3 are arranged along the scale 1 at a distance of n + ／ times the period of the periodic signal. The heads 3, 4 and 5 have n +
They are spaced apart by a distance of 1/6. As is well known, the period of the periodic signal is equal to the pitch λ or equal to the pitch λ depending on the presence and magnitude of the bias magnetic field.
/ 2, but here, it is assumed that a bias magnetic field having a magnitude (including 0) with a period λ ₁ = λ / 2 is applied. Therefore, the distance between the heads 2 and 3 is λ ₁ = λ
/ 2 + n + 1/4 times (1/4 times in the figure), and the distance between the heads 3, 4, and 5 is n + 1 / of λ ₁ = λ / 2, respectively.
It is 6 times (in the figure, 1/6 times).

[0024] Thus, 1/4 phase difference of the periodic lambda ₁ from the head _{2,3 (= λ 1/4)} 2 -phase periodic signal c
os (2πx ₁ / λ ₁ ) and sin (2πx ₁ / λ ₁ ) are detected, and the signal sin (2π
x ₁ / λ ₁ ), the phase difference is 1/1 of the period λ ₁
6 times _{(= λ 1/6),} 1/3 times (= λ _1/3) of the periodic signal sin (2πx ₁ / λ ₁ over _{λ 1/6), sin (} 2
πx ₁ / λ ₁ over lambda _1/3) is detected from the heads 4 and 5. (Note that, even when a bias magnetic field whose period λ ₁ is equal to the pitch λ is applied, the distance between the heads 2 and 3 is set to n + ／ times λ and the distance between the heads 3 and 4 Are respectively set to n + 1/6 times of λ, and the MR of each head is
If the distance between the elements is set to λ / 2, the two-phase periodic signal having a phase difference of λ / 4 can be detected from the heads 2 and 3 in exactly the same manner, and the phase difference λ / 6 can be detected from the heads 3, 4, and 5.
Of course, three-phase periodic signals can be detected. )

The signal cos (2πx ₁ / λ ₁ ), sin
(2πx ₁ / λ ₁ ) is input to the interpolation circuit 10 via the amplifiers 6 and 7, respectively. The interpolation circuit 10 executes a well-known interpolation method using these signals, thereby obtaining the signal shown in FIG.
A and B-phase signals having a phase difference of 90 degrees obtained by dividing the period λ ₁ into a predetermined number, as exemplified in A and B, are output. This A phase,
The B-phase signal is sent to an AC servomotor (not shown) of the servo mechanism as a digital two-phase signal for position / speed control.

The signal sin (2πx
₁ / λ ₁ ) is also input to the comparator 11 and is quantized by being compared with a predetermined threshold value in the comparator 11. Similarly, sin (2πx ₁ / λ ₁ −λ _{1
/ 6), sin (2πx 1} / λ 1 over lambda _1/3) are also quantized by the comparator 12 through the amplifier 8 and 9, respectively.

Thus, the comparators 11, 12, 13
Outputs a rectangular wave signal having a period λ ₁ with a phase shift of 60 degrees. The output signal of the comparator 12 is inverted by the inverter 14 and phase-shifted by 180 degrees.
C, D, E, U, V,
A W-phase signal is obtained. The U, V, and W phase signals are sent to the AC servomotor of the servo mechanism as digital three-phase signals for magnetic field control.

Thus, the two-phase signal for controlling the position and speed of the AC servomotor and the three-phase signal for controlling the magnetic field are
It is obtained from one scale 1 based on a periodic signal detected by the same encoder. This simplifies the structure of the servo mechanism and reduces the number of adjustment points and the number of assembling steps when mounting the servo mechanism.

Since the number of heads can be reduced by using the head 3 as a head for detecting a two-phase periodic signal and a head for detecting a three-phase periodic signal, the number of heads can be reduced. Compared to a case where a signal detection head and a three-phase periodic signal detection head are separately provided, the size of the position detecting device itself and the structure thereof are simplified.

The distance between the heads 3, 4, and 5 is shown in FIG.
Instead of the n + 1/6 times the cycle lambda ₁ as may be the n + 1/3 times the period lambda _1. In that case,
Since the phase difference is periodic signals of 1/3 times the period _{λ 1 (= λ 1/3} ) is detected by these heads, each as a phase difference 120 degrees output signal from the comparator 11, 12, 13 U, V, and W phase signals, and therefore the inverter 14 becomes unnecessary. However, by adopting the configuration as shown in FIG. 2, the distance between the heads 3, 4, and 5 can be further reduced, so that the size of the position detecting device itself can be further reduced.

Incidentally, in the magnetic type position detecting device using the MR element as a sensor, the pitch of the scale is relatively coarse (the pitch is on the order of millimeters), but the pitch of the slot in the linear AC servomotor is about the same ( About several millimeters). Therefore, the scale for the MR element is suitable for use in obtaining a digital three-phase signal for controlling the magnetic field of the linear AC servomotor based on the periodic signal detected therefrom. On the other hand, since the interpolation technology with high resolution has been developed today, even from a periodic signal detected from such a coarse pitch scale, a digital 2 micrometer unit suitable for position / speed control of an AC servomotor is used. It is quite possible to obtain a phase signal. Therefore, it is particularly preferable that the present invention be applied to a magnetic position detecting device using an MR element as in the above-described embodiments and used to control a linear AC servomotor.

On the other hand, according to recent advances in micromachining technology, a small linear AC servomotor with a slot pitch reduced to about several hundreds to several tens of micrometers can be realized. . Therefore, the present invention relates to a magnetic position detecting device that detects a periodic signal using a magnetic flux response type magnetic head from a scale on which magnetic scales are recorded at a pitch of, for example, a micrometer, or a micrometer to a scale grid plate and a scanning plate. The present invention may be applied to an optical position detecting device of a photoelectric scanning system in which slits are provided at a unit pitch. Hereinafter, such an embodiment will be described.

FIG. 4 shows the case where the present invention is applied to a magnetic position detecting device using a magnetic flux responsive head as a sensor, and has a predetermined pitch λ ₂ (for example, a pitch of several hundreds to several tens of micrometers). Scale 2 with magnetic scale
1, a magnetic flux response type multi-gap magnetic head 22
To 25 are provided so as to be displaceable relative to the scale 21.

The heads 22 and 23 are n + ｎ times the magnetic scale pitch λ ₂ of the scale 21 (1/4 times = λ in the figure).
_2/4) at a distance of being disposed. Head 2
3,24,25, the pitch lambda ₂ of n + 1/6-fold (in the figure 1/6 = λ _2/6) are spaced apart by a distance.

To the heads 22 to 25, signals obtained by reducing the frequency of the AC signal from the oscillator 26 to に よ り by the frequency divider 27 and then amplifying by the amplifier 28 are supplied as excitation signals. Thus, in accordance with the relative displacement amount x ₂ between the scale 21, 1/4 phase difference of the periodic lambda ₂ from the head 22,23 (= λ _2/4) of the two-phase periodic signals cos ( 2πx ₂ / λ ₂ ), sin (2πx ₂
/ Λ ₂ ) is detected and si from the head 23 is detected.
n (2πx ₂ / λ ₂ ) has a phase difference of λ
1/6 of _{2 (= λ 2/6)} , 1/3 times (= λ _2/3)
Periodic signal sin (2πx ₂ / λ ₂ over λ _2/6), s
in (2πx ₂ / _{λ 2} over λ _2/3) the head 24, 25
Is detected from.

Since the period of these periodic signals is equal to the pitch λ ₂ of the magnetic scale of the scale 21, the distance between the heads 22 and 23 is 1/4 of this period (= λ ₂ /).
4), and the distance between the heads 23, 24, and 25 is _１ ／ times (= λ 2/6) the period.

The periodic signals from the heads 22 to 25 are multiplied by the AC signals from the oscillator 26 in the multipliers 32 to 29, respectively, and then harmonic components are removed by the low-pass filters 36 to 33.

Signal c from low-pass filters 36 and 35
os (2πx ₂ / λ ₂ ), sin (2πx ₂ / λ ₂ )
Are input to the interpolation circuit 37, respectively. Interpolation circuit 37
Performs a well-known interpolation method using these signals, thereby outputting A-phase and B-phase signals having a phase difference of 90 degrees obtained by dividing the period λ ₂ into a predetermined number.

The signal s from the low-pass filter 35
in (2πx ₂ / λ ₂ ) is also input to the comparator 40 and is quantized by being compared with a predetermined threshold value in the comparator 40. Similarly, the signal from the low-pass filter 34,33 sin (2πx ₂ / _{λ 2} over lambda ₂ /
_{6), sin (2πx 2 /} λ 2 over lambda _2/3) are also quantized by the respective comparators 39 and 38.

Thus, the comparators 38, 39, 40
Outputs a rectangular wave signal having a period λ ₂ with a phase shift of 60 degrees. The output signal of the comparator 39 is inverted by the inverter 41 and phase-shifted by 180 degrees, whereby the comparator 40, the inverter 41, and the comparator 38
Thus, U, V, and W phase signals having a phase difference of 120 degrees are obtained.

Thus, the two-phase signal for controlling the position and speed of the AC servomotor and the three-phase signal for controlling the magnetic field are
It is obtained from one scale 21 based on a periodic signal detected by the same encoder. This simplifies the structure of the servo mechanism and reduces the number of adjustment points and the number of assembling steps when mounting the servo mechanism.

Further, the number of heads can be reduced by using the head 23 as a head for detecting a two-phase periodic signal and a head for detecting a three-phase periodic signal.
As compared with the case where a head for detecting a phase periodic signal and a head for detecting a three-phase periodic signal are separately provided, the size of the position detecting device itself and the structure thereof are also simplified.

[0043] Also, since the interval between the amount corresponding to the distance between the head 23, 24 and 25 to lambda _2/6 of half instead lambda _2/3 each head 23, 24, 25 is narrowed,
Again, the size of the position detecting device itself can be further reduced.

FIG. 5 shows the optical scanning type optical position detecting device to which the present invention is applied.
1a to graduations plate 51 arranged at a pitch lambda ₃ and slits 52b with release slit 52a, the distance between 52b only _{n + λ 3/4, 52c} , a distance between 52 d n
Scanning plate 52 is provided which is arranged + λ _3/6 each apart.

Scale grating by light source and lens not shown
The plate 51 is illuminated and each slit 51a of the scale grid plate 51
The light passing through is irradiated on the scanning plate 52. This allows
Relative displacement x with respect to the scale grid plate 51_ThreeAccording to the slit
52a and 52b have a phase difference of λ_Three1/4 times (= λ_Three
/ 4) two-phase periodic optical signal cos (2πx_Three/ Λ_Three)
And sin (2πx_Three/ Λ_Three) Is passed,
The optical signal sin (2πx_Three/
λ_Three) Has a phase difference of λ_Three1/6 times of
(= Λ_Three/ 6), 1/3 times (= λ_Three/ 3) periodic signal
sin (2πx_Three/ Λ _Three-Λ_Three/ 6), sin (2πx
_Three/ Λ_Three-Λ_Three/ 3) passes through slits 52c and 52d
I do.

The optical signals passing through the slits 52a to 52d are converted into current signals ia to id by being received by separate photoelectric elements, and then converted into voltage signals va to vd by an operational amplifier and a resistor. (In the figure, for convenience, the photoelectric element 5 for the optical signal that has passed through the slit 52a
3, only the operational amplifier 54 and the resistor 55 are shown, and the illustration of the remaining photoelectric elements, the operational amplifier and the resistor is omitted).

The voltage signal va = cos (2πx ₃ /
λ ₃ ) and vb = sin (2πx ₃ / λ ₃ ) are interpolated in the same manner as shown in FIGS. 2 and 4, whereby the A phase having a 90 ° phase difference obtained by dividing the period λ ₃ into a predetermined number is obtained. ,
A B-phase signal is obtained.

Also, vb = sin (2πx_Three/ Λ_Three),
vc = sin (2πx_Three/ Λ_Three-Λ _Three/ 6), vd = s
in (2πx_Three/ Λ_Three-Λ_Three/ 3) is shown in FIGS. 2 and 4.
Is quantized in the same manner as described above, and the quantized signal of vc is
In the same way, the phase is inverted by 120 degrees.
U, V, and W phase signals are obtained.

Thus, the two-phase signal for controlling the position and speed of the AC servomotor and the three-phase signal for controlling the magnetic field are
It is obtained from one scale grid plate 51 based on an optical signal detected by the same scanning plate 52. This simplifies the structure of the servo mechanism and reduces the number of adjustment points and the number of assembling steps when mounting the servo mechanism.

Since the number of slits can be reduced by using the slit 52b as a slit for detecting a two-phase periodic signal and a slit for detecting a three-phase periodic signal, the number of slits can be reduced. Compared to a case where a slit for detecting a signal and a slit for detecting a three-phase periodic signal are separately provided, the size of the scanning plate 52 is reduced, and the size of the position detecting device itself is reduced.

[0051] The slit 52 b, 52c, the distance half rather than lambda _3/3 each between 52 d lambda _3/6
Since the distance between the slits 52b, 52c, and 52d becomes narrower and the scanning plate 52 becomes smaller, the size of the position detecting device can be further reduced.

In the above embodiment, the present invention is applied to a magnetic position detecting device or a photoelectric scanning type optical position detecting device. For example, a laser beam may be used with a finer graduation pitch. The present invention may be applied to an interferometer-type position detection device or the like described above.

In each of the above embodiments, the present invention is applied to a linear position detecting device (linear encoder). However, the present invention may be applied to a rotational position detecting device (rotary encoder). It is. FIG. 6 shows a basic configuration when the present invention is applied to a magnetic rotational position detecting device in comparison with FIG.
Along the scale SC on which the magnetic scale is recorded at (a pitch that divides the circumference into eight as an example), four sensors a, b, and
V and W are provided so as to be displaceable relative to the scale SC. Sensor a, b is the period lambda ₁ = lambda / 2 of the two-phase periodic signal _{cos (2πx / λ 1),} sin (2πx /
λ ₁ ) is conventionally provided to detect λ ₁ ). The sensors V and W are located at a distance of n + 倍 and n + ／ times the period λ ₁ of the periodic signal with respect to the sensor b. Are only located away. Therefore, the sensor V,
From W, the signal sin from sensor b (2πx / λ ₁ )
The phase difference is 1/6 times the period λ ₁ (= λ ₁
/ 6) by the signal sin (2πx / λ ₁ over lambda _1/6),
sin (2πx / λ ₁ over lambda _1/3) is detected. Thus, a two-phase periodic signal and a three-phase periodic signal are detected in the same manner as in the case of the linear position detecting device.

The present invention is not limited to the above embodiment,
It goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0055]

As described above, according to the position detecting device of the present invention, two-phase signals for position / velocity control and three-phase signals for magnetic field control are obtained from one scale by the same encoder. be able to. As a result, it is possible to simplify the structure of the servo mechanism and reduce its cost, and it is possible to reduce the number of adjustment points and the number of assembling steps when mounting the servo mechanism.

By obtaining a two-phase signal for controlling the position and speed of the AC servomotor and a three-phase signal for controlling the magnetic field on the basis of the periodic signal detected from the same scale, the positions of both signals are obtained. Since the deviation of the phase difference can be eliminated, there is an effect that the AC servomotor can be controlled with high accuracy.

Further, one sensor (second sensor) is
Since it is also used as a sensor for detecting the periodic signal of the phase and a sensor for detecting the periodic signal of the three phases, the sensor for detecting the periodic signal of the two phases and the sensor for detecting the periodic signal of the three phases are used. As compared with the case where the sensors are separately provided, there is an effect that the size of the position detecting device itself can be reduced and the structure thereof can be simplified by reducing the number of sensors.

When the distance between the second, third and fourth sensors is set to 1/6 of the period of the periodic signal,
Since the distance between the second, third, and fourth sensors can be reduced, the size of the position detection device can be further reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a basic configuration of the present invention.

FIG. 2 is a diagram showing one embodiment of the present invention.

FIG. 3 is a diagram showing an example of an A / B phase signal and U, V, W phase signals.

FIG. 4 is a diagram showing another embodiment of the present invention.

FIG. 5 is a diagram showing another embodiment of the present invention.

FIG. 6 is a diagram showing another example of the basic configuration of the present invention.

[Explanation of symbols]

SC, 1,21 scale, a, b, U, V sensor, 2,3,4,5 MR head, 10,37 interpolation circuit, 11,12,13,38,39,40 comparator, 14,41 inverter, 22,23,2
4,25 magnetic flux response type multi-gap magnetic head, 5
1 scale grid plate, 52 scanning plate, 52a, 52b,
52c, 52d slit

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H02P 5/00 101 H02P 5/00 101Z 6/16 6/02 351N

Claims (2)

[Claims] 1. A position detecting device comprising: a scale on which graduations having a predetermined pitch are recorded; and a sensor for detecting a periodic signal corresponding to a relative position with respect to the scale, wherein: a first sensor; and the first sensor. A second sensor disposed at a distance of n + ／ times the period of the periodic signal (n is an integer equal to or greater than 0), and a second signal of the periodic signal with respect to the second sensor. A third sensor and a fourth sensor which are arranged at a distance of n + (one-predetermined number) times and n + (two-predetermined times) times the period, wherein the first sensor and the fourth The two sensors detect two-phase periodic signals whose phases are shifted by 1/4 of the period, and the second sensor, the third sensor, and the fourth sensor detect a predetermined number of the period. The three-phase periodic signal whose phase is shifted by 1 Position detecting device is characterized in that so as to output. 2. The position detecting device according to claim 1, wherein the third sensor and the fourth sensor are each provided with n + 1 of the period of the periodic signal with respect to the second sensor.
A position detecting device, which is disposed at a distance of / 6 times and n + ／ times.