JPH0791980A - Magnetic encoder - Google Patents

Abstract

PURPOSE:To relax the mechanical accuracy of a rotary magnetization body to improve the mass productivity by compensating the duty ratio of the output pulse train of a magnetic encoder. CONSTITUTION:By a magnetic resistance element 3 utilizing a bamboo blind type magnetic resistance element which is laid out opposingly to a rotary magnetization body 1 where a magnetization pattern 2 is laid out, the voltage of each two connection middle points of the bamboo blind type magnetic resistance element is acquired and the acquired voltage is input to a voltage comparator 4 to output a rectangular wave pulse. The duty ratio of the rectangular wave pulse is compensated by a duty ratio compensation circuit 5 and the scattering of the duty ratio based on the limit of the mechanical accuracy of the rotary magnetization body 1 is compensated.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a magnetic encoder,
In particular, the present invention relates to a magnetic encoder using a slack type magnetoresistive element.

[0002]

2. Description of the Related Art A conventional magnetic encoder of this type is shown in FIG.
As shown in FIG. 1, a rotating magnetized body 1 having a magnetization pattern 2
And a magnetoresistive element 3 that uses a sloppy magnetoresistive element that detects a change in the magnetic field due to the rotating magnetized body 1 and outputs a potential change signal, and a voltage comparator 4.

The magnetization pattern 2 of the rotary magnetized body 1 is
As shown in FIG. 4, an N pole and an S pole are formed on the circumferential side surface of the rotary magnetized body 1.
The poles and the poles are alternately magnetized.

Next, the operation of the conventional magnetic encoder will be described.

As shown in FIG. 4 (a), the four dull magnetoresistive elements MRE1 to MRE4 are λ / 4 (λ: wavelength).
They are arranged at a pitch, and as shown in FIG.
The potentials Va and Vb at the midpoints of the two magnetoresistive elements RE1 and MRE2 and MRE3 and MRE4 show potential changes as shown in FIGS. 5B and 5C.

In FIG. 5, (a) shows the magnetic field of the rotating magnetized body 1 with respect to the dull magnetoresistive element MRE1.
(B) shows the midpoint potential Va, (c) shows the midpoint potential Vb, and (d) shows the output voltage Vout of the voltage comparator 4. The voltage comparator 4 compares the potentials Va and Vb and outputs them as a rectangular wave pulse of + Vcc when Va> Vb and an OV potential when Va <Vb.

[0007]

In this conventional magnetic encoder, the magnetization pattern is magnetized on the circumferential side surface of the rotating magnetized body, and the distance from the magnetoresistive element for detecting the magnetic field by the magnetization pattern is kept constant. There is a need. This is to prevent the midpoint potential signal from changing when the distance from the magnetoresistive element changes, which causes a change in the duty ratio of the pulse voltage output from the voltage comparator.

Therefore, in order to reduce the change in the duty ratio, it is necessary to bring the rotating magnetized body close to a perfect circle to reduce the eccentricity and to make the side surfaces smooth. That is, it is necessary to improve the mechanical accuracy of the rotary magnetized body, but there is a limit to that, and there is a problem that there is also a limit to the reduction of the change in the duty ratio.

The object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a magnetic encoder that can remarkably reduce the conditions relating to the mechanical accuracy of a rotating magnetized body.

[0010]

SUMMARY OF THE INVENTION A magnetic encoder according to the present invention comprises a rotary magnetized body having a magnetization pattern, and a magnetic resistance which is arranged to face the rotary magnetized body and outputs a potential change signal due to a magnetic field formed by the rotary magnetized body. An element, a voltage comparator for inputting the potential change signal by the magnetoresistive element and transmitting an output pulse of a rectangular wave pulse train, and a mechanical accuracy of the rotary magnetized body for correcting the duty ratio with the output pulse as an input. And a duty correction circuit for correcting the change of the duty ratio based on the above.

The magnetic encoder of the present invention has a structure in which a differential amplifier for increasing the input level of the voltage comparator is interposed between the voltage comparator and the rotary magnetized body.

Further, in the magnetic encoder of the present invention, each of the magnetic resistance element, the voltage comparator, the duty correction circuit, or the magnetic resistance element, the voltage comparator, the duty correction circuit, and the differential amplifier is provided as one chip. It has a configuration of one module.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a magnetic encoder according to a first embodiment of the present invention.

In the first embodiment, a rotary magnetized body 1, a magnetization pattern 2 arranged by magnetizing a plurality of magnets on the circumferential side surface of the rotary magnetized body 1, and a magnetoresistive element using a dull magnetoresistive element. 3, a voltage comparator 4, and a duty ratio correction circuit 5, and a portion indicated by a dotted line is an integrated configuration of one chip or one module.

The magnetization number of the magnetization pattern 2 is the same as that of the rotating magnetized body 1.
Is determined by the relationship with the number of output pulses generated during one rotation of, and, for example, ones of about 100 to 200 are used.

Since the mechanical accuracy of the rotary magnetized body 1 is limited, the duty ratio of the output pulse of the voltage comparator 4 is strictly different and varies. These voltage comparators 4
The output pulse of is input to the duty ratio correction circuit 5.

The duty ratio correction circuit 5 is preset with a circuit constant so as to output an output pulse having a desired duty ratio. As a concrete configuration example of the duty ratio correction circuit 5, there is, for example, a monostable multivibrator circuit, and by appropriately selecting the time constants of the capacitors and resistors of the circuit constituent elements, if there is an input signal, a constant pulse width It is possible to output a pulse with a constant duty ratio. By appropriately selecting the time constant, the duty ratio can be set over a variable range of approximately 5% to 95%.

In the first embodiment, the signal voltage input to the voltage comparator 4 can be sufficiently secured, but when the signal voltage input to the voltage comparator 4 is small, the second signal shown in FIG. The differential amplifier 6 is interposed between the magnetoresistive element 3 and the voltage comparator 4 to generate a signal voltage of a sufficient level and input to the voltage comparator 4 to ensure stable operation as shown in the embodiment of FIG. can do.

[0020]

As described above, according to the present invention, by performing duty correction on the output pulse of the magnetic encoder, the condition of mechanical accuracy for the rotating magnetized body, which has been conventionally required, is greatly relaxed, and the present invention is mass-produced. And the duty ratio of the output pulse can be freely set to a desired value.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a magnetic encoder according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a magnetic encoder according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional magnetic encoder.

FIG. 4 is a diagram showing an arrangement example (a) and a connection example (b) of magnetoresistive elements.

5 is a waveform diagram showing a potential change and a voltage comparison output of each part of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotating magnetized body 2 magnetization pattern 3 magnetoresistive element 4 voltage comparator 5 duty ratio correction circuit 6 differential amplifier

Claims (3)

[Claims] 1. A rotary magnetized body having a magnetization pattern, a magnetoresistive element which is arranged to face the rotary magnetized body and outputs a potential change signal according to a magnetic field formed by the rotary magnetized body, and the potential change by the magnetoresistive element. A voltage comparator that inputs a signal and outputs an output pulse of a rectangular wave pulse train, and a duty that corrects the duty ratio of the output pulse as an input and corrects the change of the duty ratio based on the mechanical accuracy of the rotating magnetized body. A magnetic encoder comprising a correction circuit. 2. The magnetic encoder according to claim 1, further comprising a differential amplifier interposed between the voltage comparator and the rotary magnetized body for increasing an input level of the voltage comparator. 3. The magnetoresistive element, the voltage comparator, and the duty correction circuit, or the magnetoresistive element, the voltage comparator, the duty correction circuit, and the differential amplifier are configured as one chip or one module, respectively. The magnetic encoder according to claim 1 or 2, characterized in that.