JP2001099681A - Magnetic encoder apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic encoder apparatus whose magnetization for Z-phase detection is contrived, in which a high-accuracy Z-phase signal can be obtained even when a magnetoresistance effect element is arranged so as to be brought close to, or moved away from, a magnetization body, in which a processing operation by an electric circuit is not required and which does not have a cause of an increase in costs. SOLUTION: A magnetization body is provided in such a way that it is composed of constant-wavelength signal parts 11 in which a repetitive magnetic signal at a set wavelength λ is magnetized and recorded and that it is composed of discontinuous magnetization parts 12 which are formed between the constantwavelength signal parts 11 and which are at a discontinuous interval of λ/2 with reference to the constant-wavelength signal parts 11. A detection part is provided in such a way that it comprises two magnetoresistance effect elements MR1, MR2 which are installed so as to be separated at an interval of, λ/2 with reference to the magnetization body and that it comprises an output terminal part which is connected across the magnetoresistance effect elements. Only signals which correspond to the discontinuous magnetization parts 12 are output from the output terminal part. The output signals are used as a Z-phase signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic encoder device which can be used for a rotation detector, a linear movement detector, and the like, and more particularly to the detection of an origin position called a Z phase.

[0002]

2. Description of the Related Art In a magnetic encoder device, a magnetized body is magnetized at a constant interval, and a magnetic signal of the magnetized portion is phase-shifted by nine.
A pair of magnetoresistive elements arranged at 0 degrees are used to obtain A-phase and B-phase detection signals, and the A-phase and B-phase detection signals are processed and counted, whereby the rotation amount or movement of the detection target is obtained. The amount of rotation is detected, and the direction of rotation or the direction of movement is detected based on the phase shift between the A phase and the B phase.

However, the rotation amount and the movement amount from the reference position cannot be determined only by the A-phase and B-phase detection signals. In addition, even if the reference position is known at first, errors occur in the rotation amount and the movement amount from the reference position due to accumulation of detection errors and detection errors while repeating rotation and movement. Will be. Therefore, in addition to the above-described magnetizing at a fixed interval, the magnetized body is magnetized to obtain a so-called Z-phase signal for detecting the origin, and this is detected by a Z-phase detecting magnetoresistive element. ing.

[0004] As described in Japanese Patent Publication No. 8-20271, for example, a conventional magnetic encoder device includes a magnetized body having a first track for detecting A and B phases and a second track for detecting Z phases. The tracks for A and B phases are formed by repeated magnetization of a certain wavelength, and the magnetization for Z phase detection is
It comprises a single magnetized part 20 at a predetermined position as shown in FIG. The magnetized body rotates or moves linearly, and a magnetic sensor such as a magnetoresistive element is disposed so as to face a position where the magnetized body passes through the single magnetized section 20. The opposed position of the magnetic sensor is set to the single magnetized section. When 20 passes, a Z-phase detection signal can be obtained from the magnetic sensor.

[0005]

However, if the magnetization for detecting the Z phase is solely magnetized as in the prior art, the following problems occur. That is, as shown in FIG. 4B, the component from the N pole to the S pole of the single magnetized portion 20 is defined as the X component, and the component exits from the N pole of the single magnetized portion 20 and becomes the single magnetized portion 20.
Looking at the magnetic flux returning to the S-pole, when first going out of the N-pole, it has a direction against the X component, that is, the component of -X, then has the X component, and when heading to the S-pole, it again has the -X Has components. Assuming that such a magnetic flux is detected by the magnetoresistive element, the magnetoresistive element detects magnetism irrespective of the polarity. Therefore, as shown in FIG. The detection signal has three peaks.

In order to obtain a Z-phase signal from such a detection signal having three peaks, it is necessary to avoid the influence of signals of small peaks on both sides of the large peak. This is because the signal of the small peak is output from a position shifted from the origin detection position, and if it is affected, an accurate Z-phase signal cannot be obtained. Therefore, as a conventional countermeasure, there is a method in which a magnetoresistive element as a magnetic sensor is moved away from a magnetized body to detect only a strong X component at the center and not detect a weak X component on both sides. However, there are restrictions on the arrangement that the magnetoresistive element must be arranged away from the magnetized body, and there is a disadvantage that the effective output range at the center is narrow.

As another countermeasure, a detection signal of a magnetoresistive element as shown in FIG. 4C is electrically processed to obtain a Z-phase signal based on only one large central signal. Some have been made. However, since it is necessary to perform processing like an electric circuit, there is a problem that causes an increase in cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it has been proposed to detect a Z-phase so that three peaks are not generated in a detection signal by a magnetoresistive element for detecting a Z-phase. Even if the magnetizing effect is devised and the magnetoresistive effect element is arranged close to the magnetized body or arranged away from the magnetized body, an accurate Z-phase signal can be obtained. An object of the present invention is to provide a magnetic encoder device that does not require processing and does not cause a cost increase.

[0009]

According to the first aspect of the present invention,
A constant wavelength signal section in which a repetitive magnetic signal of a constant wavelength λ is magnetized and recorded; and a discontinuous magnetization section formed between the constant wavelength signal section and discontinuous with respect to the constant wavelength signal section at an interval of λ / 2. Comprising: a magnetized body comprising: a magnetized body; two magnetoresistive elements connected in series separated by λ / 2 from the magnetized body and connected in series; and an output terminal connected between the magnetoresistive elements. Wherein only a signal corresponding to the discontinuous magnetized portion is output from the output terminal portion, and this output signal is used as a Z-phase signal.

According to a second aspect of the present invention, in the first aspect of the present invention, the discontinuous magnetized portion has a fixed magnetized shape or a different magnetized size to change the magnetized pattern to λ. The repetitive magnetic signal of the constant wavelength λ is made different as a non-repetitive waveform only at the interval of / 2, so that one signal corresponding to the discontinuous magnetized portion is formed from the output terminal portion.

According to a third aspect of the present invention, in the second aspect of the present invention, another pair of two magnetoresistive elements provided in series with each other and separated by λ / 2 from the magnetized body are provided, Two sets of magnetoresistive elements are provided apart from each other within the range of λ / 2, and a differential output between output terminals connected between the two magnetoresistive elements is taken out.
The differential output is used as a Z-phase signal.

According to a fourth aspect of the present invention, in the third aspect of the invention, the two magnetoresistive elements and the output terminal connected between the two magnetoresistive elements are provided with a repetitive magnetic field having a constant wavelength λ. A signal of a constant level is output for the signal, and one output different from the signal of the constant level is formed for the discontinuous magnetized portion.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a magnetic encoder device according to the present invention will be described with reference to the drawings. In FIG. 1, a sinusoidal signal waveform 1 is an example of a Z-phase detection magnetization waveform recorded on a magnetized body (not shown). The signal waveform 1 has a constant wavelength signal portion 11 in which a repetitive magnetic signal having a constant sinusoidal wavelength λ and a period of 2a is magnetized and recorded, and a wavelength λ / 2 formed between the constant wavelength signal portions 11, that is, an interval is set. a, a discontinuous magnetized portion 12 discontinuous with respect to the constant wavelength signal portion 11. In this example, the discontinuous magnetized portion 12 is a constant magnetized portion that remains unchanged at a constant level.

Two magnetoresistive elements MR1 and MR2 are opposed to the magnetized body at an interval of λ / 2, that is, the same interval as the interval a. Similarly, two magnetoresistive elements MR3 and MR4 are arranged facing each other at an interval of λ / 2, that is, at an interval a. The interval b between these two sets of magnetoresistive elements, that is, one set of magnetoresistive elements MR1 and MR2 and the other set of magnetoresistive elements MR3 and MR4 is within the above-mentioned λ / 2 (= a) interval. More specifically, it is in the range of 0 ≦ b ≦ a, and the detection element section is provided separated in this range.

FIG. 3 shows an example of a detection circuit using each of the above magnetoresistive elements. In FIG. 3, a pair of magnetoresistive elements MR1 and MR2 are connected in series, one end of the series connection is connected to a power supply Vcc and the other end is connected to ground. The output terminal is connected between them. Another pair of magnetoresistive elements MR3 and MR4 are also connected in series. One end of the series connection is connected to the power supply Vcc and the other end is connected to ground. An output terminal is connected to the MR4. These four magnetoresistive elements are bridge-connected, the magnetoresistive elements MR1 and MR4 are at diagonals of the bridge, and the magnetoresistive elements MR2 and MR3 are connected to another pair of bridges. On the corner.

An output terminal between the magnetoresistive element MR1 and the magnetoresistive element MR2 is connected to a minus input terminal of the operational amplifier 10, and an output terminal between the magnetoresistive elements MR3 and MR4 is an operational amplifier. It is connected to 10 positive input terminals. The operational amplifier 10 constitutes a subtraction circuit 8, and the magnetoresistive element MR
1, the output V1 between MR2 and the magnetoresistive elements MR3, M
A signal Vout of a difference from the output V2 between R4 is output.

In FIG. 1, the detection output of each magnetoresistive effect element is considered assuming that the detection element portion relatively moves to the right with respect to the magnetization waveform as shown by the arrow. FIG. 2 shows four magnetoresistive elements MR1, MR2, MR3,
3 shows an output waveform of MR4. First, the detection output of each of the magnetoresistive elements MR1 and MR2 will be considered. Reference numeral 30 indicates a detection output of the magnetoresistive element MR1, and reference numeral 40 indicates a detection output of the magnetoresistive element MR2. The detection output 30 of the magnetoresistive element MR1 is shown in FIG.
Is formed between the constant wavelength detection signal section 31 corresponding to the sinusoidal constant wavelength signal section 11 having the constant wavelength λ and the constant wavelength detection signal section 31 according to the magnetization waveform 1 for Z phase detection shown in FIG. ,
A discontinuous detection signal section 32 corresponding to the discontinuous magnetized section 12 which is a constant magnetized section which remains unchanged at a constant level. Similarly, the detection output 40 of the magnetoresistive effect element MR2 follows the magnetization waveform 1 between the constant wavelength detection signal section 41 corresponding to the constant wavelength signal section 11 and the constant wavelength detection signal section 41. And a discontinuous detection signal section 42 corresponding to the discontinuous magnetized section 12. The above detection output 3
0, 40, the magnetoresistive effect elements MR1, MR2
Has a phase shift of λ / 2 corresponding to the shift of the arrangement position.

As described above and as shown in FIG. 4 (a), the magnetized waveform 1 for Z-phase detection magnetized and recorded on the magnetized body is obtained by magnetizing and recording a repetitive magnetic signal of a constant wavelength λ. Each of the magnetized portions is composed of a constant-wavelength signal portion 11 and a discontinuous magnetized portion 12 formed between the fixed-wavelength signal portion 11 and discontinuous with respect to the constant-wavelength signal portion 11 at an interval of λ / 2. Are formed adjacent to each other, and the magnetic flux coming out of the N pole of one magnetized portion and reaching the S pole is pushed by the magnetic flux of the adjacent magnetized portion, as shown in FIG. There is no wraparound and there is only one direction component. Therefore, there is only one peak of the detection output of the magnetoresistive element corresponding to each magnetized portion, and FIG.
There are no three peaks as shown in FIG.

As shown in FIG. 2, the detection outputs of the magnetoresistive elements MR3 and MR4 also have a magnetization waveform 1 for Z-phase detection.
The waveforms are the same as those of the detection outputs 30 and 40 following the above.
However, the detection signal is output at a phase corresponding to the arrangement position of the magnetoresistive elements MR3 and MR4.

FIG. 2A shows a voltage V1 between the magnetoresistive elements MR1 and MR2 connected in series and a voltage V2 between the magnetoresistive elements MR3 and MR4. As can be seen from FIG. 2A, the portions corresponding to the constant wavelength detection signal portions 31 and 41 in the detection outputs 30 and 40 of the magnetoresistive elements MR1 and MR2 are in a state where the waveforms overlap each other. The voltage V1 does not change at a constant voltage level, and an alternating signal for one cycle different from the constant voltage level is formed at a portion corresponding to the discontinuity detection signal units 32 and 42. Similarly, in the voltage V2 between the magnetoresistive elements MR3 and MR4, an alternating signal of one cycle different from a constant voltage level is formed in a portion corresponding to the discontinuity detection signal portion. Between the alternating signals of the voltages V1 and V2, a phase difference corresponding to the displacement of one set of magnetoresistive elements MR1 and MR2 and another set of magnetoresistive elements MR3 and MR4 occurs. ing.

As described above, a set of magnetoresistive elements M
From the output terminal connected between R1 and MR2, the curve V1 shown in FIG.
Since the alternating signal as shown by the symbol is output, a Z-phase signal can be obtained from the alternating signal by obtaining a rectangular wave by setting a predetermined threshold value, for example. The above-mentioned alternating signal is only for one cycle, and is not a detection signal having three peaks following a small peak on both sides of a large peak as shown in FIG. 4C. It is not necessary to move the resistance effect element away from the magnetized body,
Since it is not necessary to electrically process the detection signal of the magnetoresistive effect element and obtain a Z-phase signal based on only one large central signal, it is easy and reliable to detect the magnetized portion, In addition, it is possible to obtain a low-cost magnetic encoder device without causing any cost increase.

Another set of magnetoresistive elements MR3, MR
4 from the output terminal connected between the
2 (a) is output only at the position corresponding to the square wave, so that, for example, a predetermined threshold value is set from the alternating signal as in the above-described example. , A Z-phase signal can be obtained, and the same effect as described above can be obtained.

As described above, a set of magnetoresistive effect elements MR
1, a Z-phase signal can be obtained from MR2 and from another set of magnetoresistive elements MR3 and MR4.
As in the circuit example shown in FIG. 3, two sets of magnetoresistive elements are bridge-connected to form one set of magnetoresistive elements MR1 and MR1.
2 and an output terminal connected between another pair of magnetoresistive elements MR3 and MR4, that is, a differential output of the voltages V1 and V2. , May be taken out from the subtraction circuit 8 including the operational amplifier 10 and used as a Z-phase signal.

The curve shown in FIG.
0 indicates an output Vout. Since there is a phase difference between the voltages V1 and V2, the differential output between the voltages V1 and V2 becomes a signal having a valley on both sides of a central high mountain as shown in FIG. become. The high peak at the center corresponds to the position of the discontinuous magnetized portion 12. An appropriate threshold value is set for the central high mountain portion to obtain a square wave, which can be used as a Z-phase signal.
The width of the rectangular wave obtained from the output Vout is a width substantially close to the mutual interval a between a pair of magnetoresistive elements, that is, λ / 2.

The output Vout of the operational amplifier 10 has a high peak in the center and valleys on both sides as described above, and a small peak on both sides of a large peak as shown in FIG. Since the detection signal does not have three peaks following the peak, it is not necessary to move the magnetoresistive effect element away from the magnetized body unlike the related art, and the detection signal of the magnetoresistive effect element is electrically processed. It is not necessary to obtain a Z-phase signal based on only one large central signal. Therefore, it is possible to obtain a low-cost magnetic encoder device that can easily detect a magnetized portion, has high reliability, and has no cost increase factor.

Further, as shown in FIG. 3, in the case where the differential output Vout between the voltages V1 and V2 obtained from the two sets of magnetoresistive elements is used as the Z-phase signal, the voltage is higher than the voltages V1 and V2. Differential output Vout with large amplitude
Is obtained. Therefore, the detection of magnetization by the magnetoresistive effect element is easy, and the reliability of the detection can be improved.
From another viewpoint, it is possible to detect the magnetized portion even if the magnetoresistive effect element is arranged away from the magnetized body. Therefore, dust hardly accumulates between the magnetized body and the magnetoresistive effect element, and a highly reliable magnetic encoder device can be obtained in this respect as well.

A set of magnetoresistive effect elements MR1, MR2
And the distance between the other set of magnetoresistive elements MR3 and MR4 is b, this distance b is 0 ≦
What is necessary is just to be in the range of b ≦ a. Accordingly, there is no difference between the positions of one set of magnetoresistive elements MR1 and MR2 and the other set of magnetoresistive elements MR3 and MR4, and they may overlap each other. As described above, when b = 0, the differential output Vout is a voltage obtained by combining the voltage V1 and the voltage V2, that is, an output that is at most twice V1 or at most twice V2.

In contrast to a constant-wavelength signal portion in which a repetitive magnetic signal of a fixed wavelength λ of a magnetized body is recorded by magnetization, a discontinuous-magnetization portion at an interval of λ / 2 is not necessarily required to be a constant magnetization. It suffices that the magnitude of the magnetization differs for the signal portion. For example, in the waveform shown in FIG.
As shown in A, a discontinuous magnetized portion may be formed as a magnetized waveform protruding greatly from the constant wavelength signal portion 11. One or two sets of magnetoresistive elements are disposed opposite to the magnetized body in the same manner as in the above-described embodiment.
A detection signal as shown in FIG. 3 is obtained from each set of magnetoresistive elements only at positions corresponding to the discontinuous magnetized portions, and can be used as a Z-phase signal.

[0029]

According to the first aspect of the present invention, there is provided a constant-wavelength signal section in which a repetitive magnetic signal of a constant wavelength λ is magnetized and recorded, and the constant-wavelength signal section formed between the fixed-wavelength signal section is incompatible with the constant-wavelength signal section. A magnetized body consisting of discontinuous magnetized portions at continuous λ / 2 intervals;
A detecting unit having two magnetoresistive elements connected in series and separated from each other by λ / 2 with respect to the magnetized body and having an output terminal connected between the magnetoresistive elements; Only a signal corresponding to the discontinuous magnetized portion is output from the output terminal portion, and this output signal is used as a Z-phase signal. Since the magnetization for obtaining the Z-phase signal is continuous magnetization, the detection output from the output terminal connected between the two magnetoresistive elements connected in series to detect this is the same as in the prior art. In addition, since the detection signal does not have three peaks followed by the small peaks on both sides of the large peak, it is not necessary to move the magnetoresistive effect element away from the magnetized body, and the detection signal of the magnetoresistive effect element is electrically transmitted. And it is not necessary to obtain a Z-phase signal based on only one large central signal. for that reason,
It is possible to obtain a low-cost magnetic encoder device which can easily detect the magnetized portion, has high reliability, and has no cost increase factor.

According to a second aspect of the present invention, in the first aspect of the invention, the discontinuous magnetized portion has a constant magnetized state, or
By changing the magnitude of the magnetization, the magnetization pattern is made different from the repetition magnetic signal of a constant wavelength λ as a non-repetitive waveform only at intervals of λ / 2, and the signal corresponding to the discontinuous magnetization portion is output from the output terminal portion. Since one is formed, the same effect as the first aspect of the invention can be obtained.

According to a third aspect of the present invention, in the first aspect of the present invention, another pair of two magnetoresistive effect elements provided in a manner separated by λ / 2 from the magnetized body and connected in series are provided. Two sets of magnetoresistive elements are provided apart from each other within the range of λ / 2, and a differential output between output terminals connected between the two magnetoresistive elements is taken out.
This differential output is used as a Z-phase signal. According to the present invention, the above differential output having an amplitude larger than the voltage obtained from the two magnetoresistive elements can be obtained. Therefore, the detection of magnetization by the magnetoresistive effect element is easy, and the reliability of the detection can be improved. In other words, the magnetized portion can be detected even if the magnetoresistive element is arranged away from the magnetized body. Therefore, dust hardly accumulates between the magnetized body and the magnetoresistive effect element, and a highly reliable magnetic encoder device can be obtained in this respect as well.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the two magnetoresistive elements and an output terminal connected between the two magnetoresistive elements are provided with a repetitive magnetic field having a constant wavelength λ. The invention according to claim 4, wherein a signal of a constant level is output for the signal, and one output different from the signal of the constant level is formed for the discontinuous magnetized portion. According to this, the same effect as that of the third aspect can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a magnetization waveform and a layout diagram of a magnetoresistive effect element, conceptually showing an embodiment of a magnetic encoder device according to the present invention.

FIG. 2 is a waveform diagram showing an example of a detection signal obtained from the magnetoresistive element and an example of a differential output of signals obtained from two sets of magnetoresistive elements.

FIG. 3 is a circuit diagram illustrating an example of a detection circuit that can be used in the present invention.

4A is a conceptual diagram showing an example of a magnetization pattern of a magnetized body according to the present invention, FIG. 4B is a conceptual diagram showing an example of a conventional magnetization for Z-phase detection, and FIG. It is a perspective view showing an example of a detection signal of a magnetoresistive effect element obtained from magnetization for Z phase detection.

[Explanation of symbols]

 11 constant wavelength signal section 12 discontinuous magnetized section 12A discontinuous magnetized section MR1 magnetoresistive element MR2 magnetoresistive element MR3 magnetoresistive element MR4 magnetoresistive element

Claims (4)

[Claims] 1. A constant-wavelength signal section in which a repetitive magnetic signal of a constant wavelength λ is magnetized and recorded, and a non-continuous λ / 2 interval formed between the constant-wavelength signal section and the discontinuous λ / 2 signal section. A magnetized body composed of a continuous magnetized portion and a λ /
Two magnetoresistive elements connected in series and separated from each other, and a detector having an output terminal connected between the magnetoresistive elements. A magnetic encoder device that outputs only a signal corresponding to a continuous magnetized portion and uses the output signal as a Z-phase signal. 2. A repetitive magnetic signal of a constant wavelength λ, wherein the discontinuous magnetized portion is made to have a constant magnetization or by making the magnitude of the magnetization different so that the magnetization pattern has a non-repetitive waveform only at intervals of λ / 2. 2. The magnetic encoder device according to claim 1, wherein one signal corresponding to the discontinuous magnetized portion is formed from the output terminal portion. 3. A pair of two magnetoresistive elements, which are provided at an interval of λ / 2 from the magnetized body and are connected in series, and two sets of the magnetoresistive elements are arranged within the above λ / 2 interval. The differential output between the output terminals connected between the two magnetoresistive elements is taken out, and the differential output is used as a Z-phase signal. Magnetic encoder device. 4. A signal of a fixed level is output to two magnetoresistive elements and an output terminal connected between the two magnetoresistive elements, for a repetitive magnetic signal of a constant wavelength λ. 4. The magnetic encoder device according to claim 3, wherein one output different from a signal of a fixed level is formed for the continuous magnetized portion.