JPH09218053A - Magnetic type encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve resolutions of a magnetic type encoder. SOLUTION: The interval δd between magnetoresistance effect elements R1 and R2 and a magnetic recording medium 2 is so set that magnetic characteristics of the magnetoresistance effect elements R1 and R2 becomes unsaturated to output roughly a sine wave with limited distortion from the magnetoresistance effect elements R1 and R2 , which enable the multiplying of the roughly sine wave with the limited distortion. Utilizing this, for example, a shaping of a waveform is made by a waveform shaping circuit 4a and the results are multiplied by a multiplying circuit 4b. Thus, the number of pulse waveforms to be outputted is multiplied more than ever.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to a magnetic encoder device.

[0002]

2. Description of the Related Art For example, a motor such as an AC servo motor is provided with a magnetic encoder device for detecting a rotation angle and a rotation speed of a rotating body. This magnetic encoder device has a disk-shaped magnetic recording surface on which a repetitive signal having a constant wavelength λ is magnetized, and a magnetic recording medium that rotates together with the rotating body, and a magnetic field arranged to face the magnetic recording medium. Has an MR element as a magnetoresistive effect element whose resistance value changes according to the change of the magnetic field, and the MR element processes a signal output from the MR sensor having a one-bridge or full-bridge configuration, for example. And a signal processing unit.

In the magnetic encoder device having such a structure, the magnetic signal from the magnetic recording medium is detected by the MR element, and the magnetic signal detected by the MR element is converted into a pulse waveform by the signal processing section. It has become so. Then, based on the converted output, the processing circuit connected to the signal processing unit detects the rotation angle and the rotation speed of the rotating body.

[0004]

In the above magnetic encoder device, when the diameter of the magnetic recording medium is 35 mm, for example, the number of output pulse waveforms is about 2000 ppr (pulse / revolution) per track. ) Is the limit, and there is a problem that the resolution is lower than that of the optical encoder device.

Therefore, it is an object of the present invention to provide a magnetic encoder device having improved resolution.

[0006]

In order to achieve the above object, a magnetic encoder device according to a first aspect of the present invention includes a magnetic recording medium that is movably provided and generates a magnetic signal, and a magnetic recording surface of the magnetic recording medium. A magnetic sensor having a magnetoresistive effect element that is provided to face the magnetic sensor and that detects the magnetic signal; and a signal processing unit that converts the magnetic signal detected by the magnetoresistive element into a pulse waveform and outputs the pulse waveform. In the magnetic encoder device provided, the distance between the magnetoresistive effect element and the magnetic recording medium is set to an interval at which the magnetic characteristic of the magnetoresistive effect element is in an unsaturated state.

In order to achieve the above object, in the magnetic encoder device according to a second aspect of the present invention, in addition to the first aspect, the signal processing section includes a waveform shaping circuit for shaping the waveform of the magnetic signal, and a waveform shaping circuit from the waveform shaping circuit. And a multiplying circuit for multiplying the output signal.

In order to achieve the above object, in the magnetic encoder device according to a third aspect, in addition to the first aspect, the distance between the magnetoresistive effect element and the magnetic recording medium is about 80 to 130 μm.
It is characterized by being.

According to the magnetic encoder device of the first and second aspects, the distance between the magnetoresistive effect element and the magnetic recording medium is set to an interval at which the magnetic characteristic of the magnetoresistive effect element is in an unsaturated state. Then, the magnetoresistive effect element outputs a substantially sine wave with less distortion, and the substantially sine wave with less distortion can be multiplied.
As described in 1, the waveform is shaped by the waveform shaping circuit and then multiplied by the multiplying circuit. Therefore, the number of output pulse waveforms is the conventional multiplication.

At this time, for example, as described in claim 3,
The distance between the magnetoresistive effect element and the magnetic recording medium is approximately 80 to 1.
When set to 30 μm, the substantially sine wave is made into a substantially sine wave with little distortion within the range in which multiplication can be performed by the multiplication circuit.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic perspective view showing a magnetic encoder device according to an embodiment of the present invention, and the magnetic encoder device is provided, for example, in an AC servomotor.

In FIG. 1, reference numeral 1 denotes a motor spindle, and the motor spindle 1 has a disk-shaped magnetic recording medium 2
Is attached. As the magnetic recording medium 2,
In this embodiment, a mold type ferrite containing PPS (polyphenol sulfide resin) is used. On the outer peripheral surface of the magnetic recording medium 2, N is generated so as to generate a repetitive signal (magnetic signal) having a constant wavelength λ.
A magnetic recording surface 2a is formed in which poles and S poles are alternately magnetized.

At a position facing the magnetic recording surface 2a,
The MR elements R1 and R2 forming the magnetic sensor 3 have λ
They are arranged side by side so as to be spaced apart by / 4. The distance between the MR elements R1 and R2 and the magnetic recording medium 2, that is, the detection gap δd, is determined by the MR elements R1 and R2.
Is set to a value between about 80 and 130 μm, for example, as an interval value at which the magnetic characteristics of (1) become unsaturated.

The magnetic sensor 3 includes the MR element R.
1, R2 has a single bridge configuration wiring,
The signal processing unit 4 is connected to the output terminal. The signal processing unit 4 multiplies the output signal from the waveform shaping circuit 4a having a well-known configuration for shaping the output signal from the magnetic sensor 3 into a pulse waveform by a comparator (multiplies the frequency). And a multiplying circuit 4b having a known configuration.

Here, the detection gap is about 80 to 130.
The reason for setting the value in the range of μm will be described below based on the experimental data conducted by the present inventor. In carrying out this experiment, an experimental apparatus as shown in FIG. 2 is prepared. That is, this apparatus has a magnetic recording medium 2 having the same structure as shown in FIG. 1, a magnetizing head 5 for magnetizing the magnetic recording surface 2a of the magnetic recording medium 2, and the magnetic recording surface 2
This MR element R is provided with an MR element R3 arranged to face a.
3 is connected in series with the resistor Rs, and the MR element R
3. Magnetic sensor 6 configured to apply voltage E ₀ to resistor Rs
And

Then, using such a device, the magnetic recording medium 2 was rotated at a speed of v = 0.5 s ⁻¹ and magnetized by the magnetizing head 5 with a sine wave current of 125 Hz. At this time, the resistance Rs was 1.2 kΩ, the voltage E _{0 was} 10 V, and the voltage across the MR element R3 was the output voltage V ₀ . Then, the change of the output voltage V ₀ was measured by changing the magnetizing current Im, the magnetizing gap (distance between the magnetizing head 5 and the magnetic recording medium 2) δm, and the detection gap δd.

The output voltage waveform V ₀ of the MR element R3 at this time
Is shown in FIGS. 3 (a) and 3 (b), and FIG.
3 shows the case where the MR element R3 is brought close to the magnetic recording medium 2 and the detection gap δd = 30 μm.
(B) is a case where the MR element R3 is moved away from the magnetic recording medium 2 and has δd = 150 μm.

As is clear from the figure, when the MR element R3 is brought close to the magnetic recording medium 2, the output voltage waveform V ₀ is as shown in FIG.
As shown in (a), the sine wave was folded back and became saturated around the peak. After that, when the MR element R3 is moved away from the magnetic recording medium 2, the output voltage waveform V ₀ becomes as shown in FIG.
As shown in (b), a sine wave having a frequency twice the magnetization frequency was obtained. As described above, it was found that the output voltage waveform V ₀ has a sinusoidal shape at any magnetizing current Im when the MR element R3 is moved away from the magnetic recording medium 2 (for these values). See below).

At this time, the output voltage V ₀ and the detection gap δd
FIG. 4 is a diagram showing the relational data with and using the magnetizing current Im as a parameter. As is clear from the figure, any magnetizing current Im (= 100, 200, 300, 400 mA)
Also, the maximum value of the output voltage V ₀ was about 40 mV. Further, when the detection gap δd is made small, the output voltage V ₀ is saturated, but then decreases. It is considered that this is because the magnetic field becomes stronger as the detection gap δd becomes smaller, and the change in the average resistance value of the MR element width becomes smaller.

Next, the harmonic component of the output voltage waveform V ₀ is F
It investigated using the FT analyzer. The results are shown in FIG. 5, where the reference symbol f1 is the fundamental wave, f2 is the second harmonic, f3 is the third harmonic, and f4 is the first / second harmonic.
Each is shown. As is clear from the figure, the fundamental wave f
The ratio of the second harmonic f2 to 1 was the largest. The present inventor has confirmed through experiments that the second harmonic is due to saturation of the magnetic characteristics of the MR element 3. That is, the output voltage waveform V ₀ is distorted by the second harmonic. Therefore, the output voltage V ₀ near the detection gap (δd = 120 μm) where the second harmonic becomes _0.
Is supposed to be sinusoidal.

Here, the degree of distortion of the output voltage waveform V ₀ is defined as a distortion rate kd, and this distortion rate kd is used as an index indicating how sinusoidal the waveform is (for example, the waveform shown in FIG. 3A). Distortion rate kd is considerably large), and distortion rate kd
Is 0 when it is a completely sinusoidal wave. This distortion rate kd
Is expressed by the following equation when the effective value of the fundamental wave is E ₁ (V) and the effective value of the nth harmonic is En (V).

[Equation 1]

Then, the present inventor obtained the distortion rate kd of the output voltage shown in FIG. 6 through the experiment and the above-mentioned equation 1 (at this time, the magnetization gap δm = 0). As is clear from the figure, the distortion rate kd is the detection gap δd as estimated above.
Was the minimum around = 120 μm (however, the magnetizing current Im
= Excluding 100 mA). Further, the detection gap δd = 12
At 0 μm or more, the fundamental wave f1 itself becomes small as shown in FIG. 5, so that the distortion rate kd becomes large as shown in FIG.

By the way, in order to perform the multiplication by the multiplication circuit 4b, a substantially sine wave with less distortion is required. Therefore, in order to reduce the strain rate kd with respect to other magnetizing currents other than the magnetizing current Im = 100 mA, it is determined that the detection gap δd should be a value within the range of about 80 to 130 μm. If the value is within this range, it is considered that a substantially sinusoidal wave with little distortion can be obtained.

In order to obtain a highly accurate sine wave, the distortion rate kd is required to be 10% or less. Therefore, for the strain rate kd = 10% or less shown in FIG. 6, the magnetization gap δm, the detection gap δd, and the magnetization current I
FIG. 7 shows the relationship of m. As is apparent from the figure, the range in which the strain rate kd = 10% or less has a characteristic that the strain decreases linearly with respect to the magnetization gap δm and is distributed in a band shape. For example, if magnetization is performed with a magnetization current Im of 300 mA, for example, even if the magnetization gap δm is arbitrarily set up to 50 μm, an output with a distortion rate kd = 10% or less can be obtained only by adjusting the detection gap δd. It became clear that the voltage V ₀ can be obtained.

Now, returning to FIG. 1 again, in the magnetic encoder device shown in FIG. 1, the detection gap δd is an interval in which the magnetic characteristics of the MR elements R1 and R2 are in a non-saturated state, that is, the output distortion is reduced. As a value, for example, about 80-1
It is set to a value between 30 μm. That is, since the intervals are similar to those described above, the signal processing unit 4
A substantially sinusoidal wave with less distortion is input to this, and the substantially sinusoidal wave with less distortion is shaped into a pulse waveform by the waveform shaping circuit 4a and then multiplied by the multiplication circuit 4b. That is, the resolution is increased.

As described above, in this embodiment, the detection gap δd is set to a value between about 80 to 130 μm, for example, as an interval at which the magnetic characteristics of the MR elements R1 and R2 are in a non-saturated state. Utilizing the fact that the elements R1 and R2 output a substantially sinusoidal wave with little distortion, and that the substantially sinusoidal wave with little distortion can be multiplied, the waveform is shaped by the waveform shaping circuit 4a, and then the multiplication circuit 4b is used. Since the number of pulse waveforms that are multiplied and output is the same as the conventional multiplication, it is possible to improve the resolution of the magnetic encoder device.

Further, in the present embodiment, even if the number of MR elements is two, it is possible to obtain a substantially sine wave with little distortion (little harmonic components). In comparison with a configuration (shown in FIG. 8 to be described later) that obtains a substantially sinusoidal wave with less distortion by using a large number of
Cost reduction is possible.

The magnetic sensor 3 shown in FIG.
If the magnetic sensor 6 shown in FIG. 2 is replaced, the resolution can be increased, but since there is only one MR element, the direction cannot be detected due to the phase relationship.

FIG. 8 shows another embodiment of the magnetic sensor in the above magnetic encoder device. Since the configuration other than the magnetic sensor is the same as that of the above embodiment, the description thereof is omitted here. .

MR elements R4, R5, R6 and R7 are arranged in parallel at a position facing the magnetic recording surface 2a of the magnetic sensor 7. The MR elements R5 and R6 in the center are separated from each other by a distance of λ / 2, and the MR elements R4 and R4 on both sides are separated from each other.
R7 is (2n ± 1) with respect to the central MR elements R5 and R6
・ The distance of λ / 4 is separated. Further, the magnetic sensor 7 is provided with wiring for making the MR elements R4 to R7 into a full bridge configuration, and the signal processing section 4 is connected to the output terminal thereof.

It goes without saying that even if the magnetic sensor 7 is constructed as described above, the same effects as those of the above-described embodiment can be obtained, and in addition, the MR elements R4 to R7 have a full bridge construction, and Also, since the harmonic components are cancelled, it is possible to obtain a substantially sinusoidal wave with less distortion as compared with the previous embodiment.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the invention. Needless to say, for example, in the above-described embodiment, the distance between the MR element and the magnetic recording medium 2 is set to a value between about 80 and 130 μm, for example. As is clear from FIG. 9, it changes depending on the magnetizing current Im and the magnetizing gap δm, and also changes depending on the material of the magnetic recording medium 2 and so on, and is not limited to the above values. The point is that the interval value is such that the magnetic characteristics of the MR element are in a non-saturated state.

[0033]

As described above, according to the magnetic encoder device of the first and second aspects, the gap between the magnetoresistive effect element and the magnetic recording medium is set such that the magnetic characteristic of the magnetoresistive effect element is in a non-saturated state. By setting the interval so that the magnetoresistive effect element outputs a substantially sinusoidal wave with little distortion, and utilizing that the substantially sinusoidal wave with little distortion can be multiplied,
For example, as described in claim 2, the waveform is shaped by the waveform shaping circuit, then multiplied by the multiplying circuit, and the number of pulse waveforms to be output is configured to be the conventional multiplication. It is possible to improve the resolution of.

At this time, as described in claim 3, the distance between the magnetoresistive effect element and the magnetic recording medium is about 80 to 130 μm.
When set to m, the substantially sine wave becomes a substantially sine wave with little distortion within a range in which multiplication can be performed by the multiplication circuit, and the above effect can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a magnetic encoder device according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view showing an apparatus for analyzing the characteristics of a magnetic encoder apparatus.

3A and 3B are voltage waveform diagrams showing an output voltage of the MR element in the apparatus shown in FIG. 2, where FIG. 3A is a case where the MR element is brought close to a magnetic recording medium, and FIG. This is when the recording medium is moved away from the recording medium.

FIG. 4 is a diagram showing relational data between an output voltage of an MR element and a detection gap in the device shown in FIG. 2 with a magnetizing current as a parameter.

5 is a diagram showing relational data between an output voltage of an MR element and a detection gap in the device shown in FIG. 2 divided into a fundamental wave and a harmonic wave.

FIG. 6 is a diagram showing relational data between a distortion rate of an output voltage of an MR element and a detection gap in the device shown in FIG. 2 with a magnetizing current as a parameter.

FIG. 7 is a diagram showing a relationship between a magnetizing gap, a detection gap, and a magnetizing current for a strain rate of 10% or less shown in FIG.

FIG. 8 is a front view showing another embodiment of the magnetic sensor in the magnetic encoder device shown in FIG.

[Explanation of symbols]

 2 magnetic recording medium 2a magnetic recording surface 3,6,7 magnetic sensor 4 signal processing unit 4a waveform shaping circuit 4b multiplication circuit R1, R2-R7 magnetoresistive effect element δd distance between magnetoresistive effect element and magnetic recording medium

Claims (3)

[Claims] 1. A magnetic recording medium that is movably provided to generate a magnetic signal, and a magnetic sensor that is provided facing a magnetic recording surface of the magnetic recording medium and that includes a magnetoresistive effect element that detects the magnetic signal. A signal processing unit that converts the magnetic signal detected by the magnetoresistive effect element into a pulse waveform and outputs the pulse waveform, wherein a gap between the magnetoresistive effect element and the magnetic recording medium is ,
A magnetic encoder device, wherein the magnetic characteristic of the magnetoresistive effect element is set to an interval at which the magnetic characteristic is in a non-saturated state. 2. The magnetic system according to claim 1, wherein the signal processing unit has a waveform shaping circuit for shaping the waveform of the magnetic signal and a multiplication circuit for multiplying the output signal from the waveform shaping circuit. Encoder device. 3. The magnetic encoder device according to claim 1, wherein the gap between the magnetoresistive effect element and the magnetic recording medium is about 80 to 130 μm.