JPH05223592A - Origin signal detector - Google Patents

Abstract

PURPOSE:To detect origin signals without requiring high-performance sensors and comparison circuits. CONSTITUTION:The following are provided: a magnetoresistance element 6 map of two pairs of sensors MR1-MR4 connected in series, respectively; a differential amplification circuit which differentially amplifies signals outputted from the respective intermediate points of the series-connected sensors; and a comparison circuit which wave-shapes signals differentially amplified to obtain origin signals; and, the ratio of distance Dy between the sensors MR2, MR3 to width Pz of the magnetizing part of an origin recording signal 10 is set by the value of 0.5. Therefore, manufacture of an encoder is easy, and the component cost can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an origin signal detecting device for detecting an origin recording signal magnetized on a magnetic recording medium such as a magnetic encoder and outputting the origin signal.

[0002]

2. Description of the Related Art Generally, magnetic encoders of both rotary type and linear movement type are designed to output an incremental signal for each predetermined displacement amount and an origin signal indicating an origin position.

FIG. 7 is an electric circuit diagram showing an origin signal detecting device of a conventional magnetic encoder of this kind, FIG. 8 is a diagram showing a structure of a magnetoresistive element provided in the origin signal detecting device of FIG. 7, and FIG. 8 is a perspective view showing a magnetized portion of the origin recording signal of the magnetic recording medium facing the magnetoresistive element of FIG. 8, and FIG.
Timing chart showing the operation of the origin signal detector of
FIG. 11 is a timing chart for explaining the problems of the origin signal detecting device of FIG.

The magnetic recording medium 1 shown in FIG. 9 has an N pole and an S pole.
The origin recording signal 2 having a pair of poles is magnetized. The origin signal detection device shown in FIG. 7 has two detection elements Ra and R.
It is composed of a magnetoresistive element 3 which is composed of b and outputs a signal Va, and a comparison circuit 4 which compares the signal Va with a reference voltage Vrfa. In the magnetoresistive element 3, as shown in FIG. 8, one end of each of the detection elements Ra and Rb is connected in series with a power source Vc to form a current path, and the detection elements Ra and Rb are connected.
Are formed in strips and are arranged in parallel with each other. Further, as shown in FIG. 10A, the detection elements Ra and Rb are provided so as to face the magnetic recording medium 1 and are arranged side by side in the moving direction of the magnetic recording medium 1. When the distance between the center lines of the detection elements Ra and Rb is Da and the width of the magnetized portion of the origin recording signal 2 is Dc, the width Dc is 1.5 of the distance Da.
It is set about twice. The reference voltage Vrfa is
It is set to a level higher than Vc / 2.

In this conventional origin signal detecting device, FIG.
(B), the detecting elements Ra and Rb sense only the magnetic field component H parallel to the magnetic recording medium 1, and the magnetic field component H
As becomes larger, the resistance value becomes smaller as shown in FIG. FIG. 10C shows each detection element R
The change in the resistance value of a and Rb is shown in FIG.
When the magnetic recording medium 1 is moved in the direction indicated by the arrow, the resistance values of the detection elements Ra and Rb have a phase difference corresponding to the distance Da between the detection elements Ra and Rb by sensing the origin recording signal 2 of the magnetic recording medium 1. Change. The detection elements Ra and Rb are shown in FIG.
Since it is connected in series and a voltage Vc is applied to it, Va> Vc / 2 when Rb> Ra, while
When Rb <Ra, Va <Vc / 2, and the output signal Va of the magnetoresistive element 3 becomes as shown in FIG. When the comparison circuit 4 compares the signal Va with the reference voltage Vrfa, a pulse signal having a width P shown in (e) of FIG. 10 is output as the origin signal.

[0006]

By the way, in the above-mentioned conventional origin signal detecting device, the origin signal is obtained from the output signal Va at the midpoint between the pair of detecting elements Ra and Rb having two current paths. Therefore, as shown in (d) of FIG. 10, the amplitude B of the output signal Va is small,
The signal-to-noise ratio of the origin signal obtained based on this signal Va is poor.

Further, since the sensitivity of the detection element of the magnetoresistive element and the strength of the signal magnetic field have a negative temperature characteristic, the amplitude B of the signal Va also has a negative temperature characteristic, and the signal Va has a low temperature characteristic as shown in FIG. The amplitude B is large as shown by the broken line and becomes small as shown by the solid line in FIG. 11 when the temperature is high, that is, the amplitude of the signal Va largely changes due to temperature change. On the other hand, in the above-described conventional origin signal detecting device, the slope of the rising portion and the falling portion that intersects with the reference voltage Vrfa of the signal Va is gentle as in the portion A shown in FIG. Therefore, as a result of the comparison between the signal Va and the reference voltage Vrfa, the pulse width of the output origin signal changes considerably, and as shown in FIG. 11, the pulse width Pa at low temperature and the pulse width Pb at high temperature.
Therefore, the reliability of origin detection is impaired.

Therefore, as described above, since the signal-to-noise ratio of the origin signal is inferior and the pulse width of the origin signal changes considerably, there is a problem that a high-performance detecting element and a comparison circuit are required, and the cost increases. there were.

The present invention has been made in view of the actual situation in the prior art, and an object thereof is to reliably detect the origin signal without requiring a high-performance detection element and a comparison circuit. An object of the present invention is to provide an origin signal detecting device.

[0010]

In order to achieve this object, the present invention comprises a plurality of detecting elements for detecting an origin recording signal magnetized on a magnetic recording medium, and responds to the detection of the origin recording signal. In the origin signal detecting device that outputs the origin signal as a differential signal, a magnetoresistive element including two sets of the detecting elements connected in series, and a signal output from each intermediate point of the detecting elements connected in series are differentiated. A differential amplifier circuit for amplifying and a comparator circuit for waveform-shaping the differentially amplified signal to obtain an origin signal are provided, and between the two sets of the detection elements with respect to the width of the magnetized portion of the origin recording signal. The distance ratio is set to any value of 0.3 to 0.7, and the ratio of the distance between the two sets of the detection elements to the width of the magnetized portion of the origin recording signal is set to a value of 0.5. It has the configuration set in.

[0011]

Since the present invention is configured as described above, the origin recording signal magnetized on the magnetic recording medium is detected by the two sets of detection elements connected in series, and the intermediate points of the detection elements connected in series are detected. The signal output from is differentially amplified by a differential amplifier circuit, and then waveform-shaped by a comparison circuit to obtain an origin signal. As described above, the signals output from the respective intermediate points of the detection elements connected in series are differentially amplified by the differential amplifier circuit, and the width between the two detection elements with respect to the width of the magnetized portion of the origin recording signal is increased. Since the distance ratio is set to a value of 0.5, for example, a signal having a large amplitude and a steep slope can be obtained at the position corresponding to the origin recording signal. This makes it possible to reliably detect the origin signal without requiring a high-performance detecting element and a comparison circuit.

[0012]

Embodiments of the origin signal detecting device of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing a magnetoresistive element provided in an embodiment of the origin signal detecting device of the present invention,
2 is an electric circuit diagram showing the configuration of the origin signal detecting device of the present embodiment, and FIG. 3 is a characteristic diagram showing waveforms of signals output from the differential amplifier circuit provided in the origin signal detecting device shown in FIG.
FIG. 4 is a characteristic diagram showing a magnetic field distribution above the origin recording signal obtained by an experiment, and FIG. 5 is a characteristic diagram showing a relationship between the gap of the detection element and the readable voltage width obtained from the magnetic field distribution shown in FIG. FIG. 6 is a characteristic diagram showing the relationship between the distance between the magnetoresistive elements and the allowable gap range obtained from the graph of FIG.

The origin signal detecting apparatus of the present embodiment shown in FIG. 2 has one set of detection elements MR1 and MR2 connected in series and another set of detection elements MR3 and MR4 connected in series.
And the detection elements MR1 and MR2.
Differential amplifier circuit 7 that differentially amplifies the signals respectively output from the intermediate point of 1 and the intermediate points of the detection elements MR3 and MR4.
And a comparison circuit 8 for waveform-shaping the differentially amplified signal to obtain an origin signal.

The magnetic recording medium 9 shown in FIG. 1 has an N pole and an S pole.
The origin recording signal 10 having a pair of poles is magnetized, and the width Pz of the magnetized portion of the origin recording signal 10 is set to a predetermined dimension, for example, 100 μm. The detection elements MR1 to MR4 are sequentially arranged on the magnetic recording medium 9, and a distance between two sets of the detection elements MR1 to MR4 with respect to the width Pz,
That is, the ratio of the distance Dy between the adjacent detection elements MR2 and MR3 is any value from 0.35 to 0.7, for example, 0.
It is set with a value of 5. Also, one pair of MR1 and M
The distance Dx ₁ between R2 and the other pair of MR3, MR4
The distance Dx ₂ between them is 0.8 with respect to the width Pz.
.About.1.2 times, for example, the same size is set.

In this embodiment, the origin recording signal 10 magnetized on the magnetic recording medium 9 is detected by two sets of detecting elements MR1 to MR4 connected in series, and the detecting element MR is detected.
The differential amplifier circuit 7 differentially amplifies the signals output from the midpoints of 1 and MR2 and the midpoints of the detection elements MR3 and MR4, and then the waveform is shaped by the comparison circuit 8 to obtain the origin signal. ing.

The ratio of the distance Dy to the width Pz described above is such that the distance Dy is 0, 0.3 Pz, 0.5 Pz,
Five types of 0.7 Pz and 1.0 Pz can be set, and comparative examination can be performed based on experimental results in the following procedure.
That is, as the first procedure, 1 is applied to the surface of the magnetic recording medium 9.
A single detection element, a so-called MR sensor, is arranged, the magnetic recording medium 9 is rotated, the resistance change of the detection element is read, and the magnetic field distribution above the origin recording signal 10 is measured. At this time,
A detection element having a resistance change rate of 3% and a sensitivity of 30 Oe was used, the amplification factor of the amplifier was set to 30 times, and the gap between the magnetic recording medium 9 and the detection element was 20 μm from 40 μm to 160 μm.
It was set every other time and the magnetic field distribution in the space was measured. Then D
FIG. 4 shows the origin signal obtained by changing the value of y from 0 to 1.0 Pz by simulation. In FIGS. 4A, 4B, and 4C, the distance Dy is set to 0, 0.5 Pz, and 1.0 Pz, respectively.

As the second procedure, the pulse width Dz of the origin signal of the magnetic encoder is generally required to be 0.5 Pz or more and 1.5 Pz or less, so that as shown in FIG. 3, Dz (min ) = 0.5 Pz, Dz (ma
By plotting so that x) = 1.5 Pz, the readable voltage width is measured from the magnetic field distributions of FIG. 4A, FIG. 4B, and FIG. As a result, when the gap between the magnetic recording medium 9 and the detection element is set to 40 μm as described above, 1.1 V at the distance Dy = 0 and the distance Dy = 0.5P
It is 1.0 V for z and 0 V for the distance Dy = 1.0 Pz. When the readable voltage width thus obtained is taken in the horizontal axis direction and the gap is taken in the vertical axis direction, the distance Dy is 0, 0.3 Pz, 0.5 Pz, 0.7 Pz, 1.0 P, respectively.
The readable voltage range for z is plotted as shown in FIG.

Generally, when the readable voltage width is large, it is desirable in design because an inexpensive IC and sensor having poor drift characteristics can be used, and the allowable gap range of the detection element with respect to the magnetic recording medium is large. Wide,
It is desirable in terms of design because it can be designed with relatively large component tolerances and is easy to assemble. Therefore, as the third procedure, the readable voltage range is set to 0.8V, 1.1V, and 1.4V, and the allowable gap range is measured from the graph of FIG. As a result, when the distance Dy is set in the horizontal axis direction and the allowable gap range is set in the vertical axis direction, the readable voltage width is 0.8.
The allowable gap range for V, 1.1V, 1.4V is
It is constructed as shown in FIG. Therefore, considering the graph of FIG. 6, the allowable gap range is relatively good at 0.35 Pz ≦ distance Dy ≦ 0.7 Pz, and particularly good is the distance Dy = 0.5 Pz. Therefore,
As described above, the distance Dy is set to a value of 0.5 Pz, for example.

In the embodiment thus constructed, the signals output from the respective intermediate points of the one set of detection elements MR1 and MR2 connected in series and the other one set of detection elements MR3 and MR4 connected in series are transmitted. Since the differential amplification circuit 7 performs differential amplification and the ratio of the distance Dy between the detection elements MR2 and MR3 to the width Pz of the magnetized portion of the origin recording signal 10 is set to a value of 0.5, for example, Origin recording signal 10
A signal having a large amplitude and a steep slope is obtained at a position corresponding to, which enables reliable detection of the origin signal without specially requiring a high-performance detection element and a comparison circuit. Although the distance Dy is set to 0.5 Pz in this embodiment, the distance Dy is set to 0.35 Pz as necessary.
It can also be set to any of .about.0.7 Pz. Further, in the present embodiment, the distances Dx ₁ and Dx ₂ are set to ₁ Pz, but the distances Dx ₁ and Dx ₂ are set to 0.8 as required.
It can be set to any of Pz to 1.2Pz, and this can be confirmed by the same experiment as above.

[0020]

Since the present invention is configured as described above, the origin signal can be reliably detected without specially requiring a high-performance detecting element and a comparison circuit. The allowable error range is wide and the manufacturing is easy, and the cost of parts can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a magnetoresistive element included in an embodiment of an origin signal detection device of the present invention.

FIG. 2 is an electric circuit diagram showing a configuration of an origin signal detection device of the present embodiment.

3 is a characteristic diagram showing a waveform of a signal output from a differential amplifier circuit included in the origin signal detection device shown in FIG.

FIG. 4 is a characteristic diagram showing a magnetic field distribution above the origin recording signal obtained by an experiment.

5 is a characteristic diagram showing a relationship between a gap of a detection element and a readable voltage width obtained from the magnetic field distribution shown in FIG.

6 is a characteristic diagram showing a relationship between a distance between magnetoresistive elements and an allowable gap range obtained from the graph of FIG.

FIG. 7 is an electric circuit diagram showing a conventional origin signal detection device for a magnetic encoder.

8 is a diagram showing a configuration of a magnetoresistive element included in the origin signal detection device of FIG.

9 is a perspective view showing a magnetized portion of the origin recording signal of the magnetic recording medium facing the magnetoresistive element of FIG. 8;

10 is a timing chart showing the operation of the origin signal detection device of FIG.

11 is a timing chart for explaining a problem of the origin signal detection device of FIG.

[Explanation of symbols]

 6 Magnetoresistive Element 7 Differential Amplifier Circuit 8 Comparison Circuit 9 Magnetic Recording Medium 10 Origin Recording Signal MR1 to MR4 Detection Element

Claims (2)

[Claims] 1. An origin signal detecting device, comprising a plurality of detection elements for detecting origin recording signals magnetized to a magnetic recording medium, and outputting origin signals in response to detection of the origin recording signals. And a differential amplifier circuit for differentially amplifying signals output from respective intermediate points of the detection elements connected in series, and the differentially amplified signal. And a comparison circuit for waveform-shaping the origin signal to obtain the origin signal, and the ratio of the distance between the two sets of the detection elements to the width of the magnetized portion of the origin recording signal is 0.3 to 0.7. An origin signal detection device characterized by being set by a value. 2. An origin signal detecting device comprising a plurality of detecting elements for detecting origin recording signals magnetized to a magnetic recording medium, and outputting origin signals in response to the detection of the origin recording signals. And a differential amplifier circuit for differentially amplifying signals output from respective intermediate points of the detection elements connected in series, and the differentially amplified signal. And a comparison circuit that obtains an origin signal by waveform shaping, and the ratio of the distance between the two sets of the detection elements to the width of the magnetized portion of the origin recording signal is set to a value of 0.5. Origin signal detector.