JPH01318914A - Magnetic rotary sensor - Google Patents

Abstract

PURPOSE:To reduce an even harmonic component contained in an encoder output, by disposing a magnetic sensor at some gap l separate from a magnetic drum. CONSTITUTION:A rotary drum 2 is fixed to a rotating shaft 1 and a magnetic recording medium 3 having magnetic signals recorded at a recording pitch lambdais disposed on the outer periphery of the drum. In opposition to this magnetic recording medium, a magnetic sensor 4 constructed of magnetoresistance effect elements (MR elements) R1 and R2 is disposed at some gap l separate from the medium 3. Accordingly, a recording pitch lambda' on the surface of the magnetic sensor is increased by a dimension obtained by adding a spacing l to the radius of the magnetic drum. By taking the spacing l into consideration when the magnetic sensor is designed, in other words, the occurrence of a phase error due to the recording pitch is prevented. By this constitution, an even harmonic component contained in an encoder output is reduced and a clear sine wave output having no distortion can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotation sensor, and more particularly to a magnetic rotation sensor that obtains a sinusoidal output.

[Conventional technology]

We have previously proposed the invention described in Japanese Patent Application Laid-Open No. 62-204118 as a sinusoidal output encoder using a magnetoresistive element. Here, reduction of odd harmonics among harmonic components included in an encoder output signal is disclosed. but.

No mention is made of measures to reduce even harmonics included in the encoder output signal.

[Problem to be solved by the invention]

The technology that we developed earlier, as described above, does not mention the even harmonic components contained in the encoder output signal, and therefore has the problem of causing errors in the output.

An object of the present invention is to provide a highly accurate magnetic rotation sensor by reducing even harmonic components contained in an output signal of an encoder.

[Means to solve the problem]

The above purpose is 1. For example, to record on the magnetic drum the recording pitch λ' that determines the spacing between the magnetoresistive elements connected with three terminals, the spacing between the magnetic drum and the magnetic sensor to be l, and the radius of the magnetic drum to be 1. This is achieved by calculating and determining the number of magnetic signals in the circumference as P.

[Effect]

A magnetic encoder is composed of a magnetic drum and a magnetic sensor, and the magnetic sensor is arranged at a certain spacing Q from the magnetic drum. Therefore, the recording pitch λ' on the magnetic sensor surface increases by the sum of the magnetic drum radius and the spacing Q. That is, by considering the spacing 2 when designing the magnetic sensor, it is possible to prevent phase errors due to the recording pitch from occurring.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 10. FIG. 1 shows a configuration according to the present invention, in which a rotating drum 2 is fixed to a rotating shaft 1, and a magnetic recording medium 3 on which magnetic signals of a recording pitch λ are recorded is arranged around the outer periphery of the rotating drum 2. Opposed to this, a magnetoresistive element (hereinafter referred to as MR element) R
t, R2 is arranged at a certain distance (hereinafter referred to as spacing) Q from the magnetic recording medium 3. The relationship between the magnetic recording medium 3 and the magnetic sensor 4 shown in FIG. 1 is shown as an expanded view in FIG. 2. In FIG. 2, magnetic signals are recorded on the magnetic recording medium 3 at a recording pitch λ. The magnetic sensor 4 is composed of MR elements Rs and Rz,
Each is arranged at an interval of λ'/2. λ' is a recording pitch determined by considering the spacing Q, which will be described later, and is used to determine the spacing between the MR elements. M of magnetic sensor 4
R element Rt, Rz The electrical resistance changes with respect to the magnetic field, and is made by a method such as vapor deposition of a thin film of Ni-Fe, Ni.Co, etc. on the surface of a glass substrate or the like.

As shown in FIG. 3(a), the resistance changes in proportion to the magnitude of the magnetic field, regardless of the direction of the magnetic field, and saturates at a certain value. Here, the rotating drum 2 rotates, the magnetic recording medium 3 moves, and a magnetic field is applied to the magnetic sensor 4 by the magnetic signal of the magnetic recording medium 3 as shown in FIG.
Assume that it changes as follows. In this case, a large magnetic field is applied to the magnetic sensor 4 so that the resistances of the MR elements Rx and Rz are sufficiently saturated. Therefore, even if the spacing Q changes due to eccentricity of the rotating drum 2, fluctuations in the output amplitude can be reduced. However, the resistance of the MR elements R1r and R2 is
As shown in (c), the resistance changes include even harmonics; on the other hand, M
The R elements R1 and R2 are connected in series with three terminals to the power supply V as shown in FIG. MR element R
By connecting the three terminals 1 and R2, it is canceled out, and a sine wave output eo as shown in FIG. 3 (d) can be obtained. However, previously, the interval λ of the MR element R1t R* of the magnetic encoder that we developed
/2 is determined based on the recording pitch λ of the magnetic signals recorded on the magnetic recording medium 3. However, the actual magnetic sensor 3 is placed apart from the magnetic recording medium 3 by a spacing Q. This situation is shown in FIG.

Therefore, the magnetic sensor surface 4', that is, the MR element Rt.

R2 is the radius r' of the magnetic recording medium 3 by the spacing Q.
The operation is performed at a recording pitch λ' with a large value. For this reason, the recording pitch λ at the time of design and the MR element R1
, Rz are actually operating during the recording pitch λ',
A recording pitch error of 2π72/P as shown in FIG. 5 occurs. here.

P is the number of magnetic signals in one revolution of the magnetic recording medium. An example of the operation waveform in this case is shown in FIG. 6.
The resistance change of R elements R1 and Rz results in a distortion waveform similar to that shown in FIG. 3(c). However, what is different from FIG. 3(C) here is that due to the recording pitch error λ'-λ=□ mentioned above, the output from the MR element R1 is shifted by λ/2. As shown in FIG. 6(b), the voltage is divided into a fundamental wave voltage (sine wave) ell and an even harmonic (second harmonic) ezl. On the other hand, MR element R2
The output from , as shown in Figure 6 (C), is as shown in Figure 6 (B).
The waveform will be similar to that shown in . Therefore, M
As shown in Figure 6 (d), the output waveform obtained from the three-terminal output of R elements Ri and Rz leaves 0 even harmonics (second harmonics) that should be canceled out in opposite phases. For this reason, 3
The output waveform ea of the terminal output becomes a distorted waveform as shown in FIG. 6(E), and the error becomes large. Also, this recording pitch error λ
'-λ also affects the case where, for example, signals having a phase difference of 90 degrees in electrical angle are obtained as encoder outputs. That is, as shown in FIG. 7, MR elements R3 and R4 are arranged at a distance of λ/4 from MR elements R* and Rz.

The MR elements R1 to Ra are connected as shown in FIG. Therefore, the output am obtained from the MR element Rs, Rz (ip3 terminal connection) is the same as the solid line in FIG. 6(e).

Output e obtained from the 3-terminal output of MR element Raw Ra
b shows a shifted waveform of the MR element as shown by the - dotted line in FIG. In this manner, it can be seen that the recording pitch error λ'-λ affects the generation of even harmonics, phase error, and the like. Therefore, when designing the magnetic sensor 4, for example, the M
The recording pitch λ' that determines the interval between the R elements Rz and Rz is preferably determined by taking into consideration the spacing Ω. This situation is shown in FIG. 5. That is, the recording pitch λ' on the magnetic sensor surface 4' is calculated by the radius r' that is the sum of the radius r of the magnetic recording medium 3 and the spacing Q.

Therefore, the MR elements R1t R2 on the magnetic sensor surface 4' operate at a recording pitch λ' with no recording pitch error, and even harmonics can be canceled out. This situation is shown in FIG. 9. As shown in FIG. 9(A), by using the recording pitch λ', the recording pitch error λ'-λ is eliminated, and the MR elements R1 and Rz are accurately adjusted to λ'/2. Out-of-phase resistance changes are obtained. Therefore, the voltage waveforms due to each MR element R1 and R2 are as shown in (b) and (c), respectively, and the fundamental wave @ fl
y e 12 and even harmonic (second harmonic) ezl, ex
It is divided into a.

Here, if we focus on the even harmonics (second harmonics) ext and ezz, they are in opposite phases to each other, so the output waveform e& obtained from the three-terminal output is an even harmonic as shown in Figure 9 (d). Harmonics (second harmonics) are canceled out and a clean sine wave output is obtained in which only the fundamental wave is synthesized. FIG. 10 is an example of experimental results in which the relationship between even harmonic components and the spacing Q was measured using a magnetic sensor prototyped with the spacing Ω taken into consideration. In FIG. 10, the spacing Q of the magnetic sensor 4 is generally set near the optimum spacing 0 m shown in the figure, where the sensor output e& is maximum. Therefore, if we look at this optimal spacing Qt, we can make a prototype (
Compared to the prototype (before the measures) that does not take into account the spacing a, the even-numbered harmonics (second
It can be seen that the ratio of harmonics) is reduced to about 1/3. In this embodiment, the distance between the MR elements R1 and Rz is set to λ'/with respect to the recording pitch λ' taking into account the spacing Ω.
2, but the distance between the MR elements may be selected based on the relationship between the length of the recording pitch λ', the width and number of MR elements, etc., where this is an integer.

FIG. 11 and FIG. 12 show MR elements R1, Rz and Rx.
, Rz shows an example of canceling even harmonics between bridge connections. FIG. 11 is composed of parts having the same function as those in FIG. 2, etc., and 3 is a magnetic recording medium and 4 is a magnetic sensor, each of which is shown as an exploded view. MR elements Rt, Rz', R2 and R constituting the magnetic sensor 4
, t, the distance between the MR elements R1 and R,/ is λ'/
2. R1' and R2 are λ/2 * Rz and R, t are λ'
/2, and the connections shown in Fig. 12 are made, that is, the three terminals of MR elements Rs and R2 are connected in series with the power supply, and the output of the connection point 0 is connected to al, and the MR elements R1' and R , / also make a three-terminal connection in the same way, and the connection point 0'
Let the output of eb be eb. FIG. 13 shows an example of the operating waveform at this time. The waveform ea in FIG. 13 (a) is distorted because it contains even harmonics for the same reason as in FIG. 6 (e). Similarly, the waveform ea' is also a distorted waveform, but
Since the three-terminal outputs e& and 8a' are arranged at an arrangement (λ'/2) taking into account the spacing a, the waveforms have a phase difference of exactly λ/2. Therefore, Fig. 13 (b) (
As shown in c), even harmonics (second harmonics) e&z, eaz
are out of phase with each other and cancel each other out, resulting in the bridge output E
In ^, a clean sine wave can be obtained only for the fundamental wave without even harmonics (second harmonics).

FIG. 14 shows an example of canceling even harmonics using an existing magnetic sensor made without considering the spacing Q. That is, the MR elements R1, R of the magnetic sensor 4
One interval of x is determined from the recording pitch λ of magnetic signals on the magnetic recording medium 3. Therefore, in order to eliminate the recording pitch error caused by the spacing Q, the radius of the existing magnetic recording medium 3 may be reduced by cutting off the radius of the existing magnetic recording medium 3 by the amount of the spacing Q, as shown in the figure. That is, the radius r of the magnetic recording medium 3 is determined by the following equation.

2π Here, P is the number of magnetic signals (N-8) in one round, λ is the recording pitch on the magnetic recording medium 3, and Ω is the spacing.

In this case, countermeasures can be taken by simply adjusting the outer circumference of the magnetic recording medium 3 of the rotating drum 2 using the existing magnetic sensor 4, resulting in cost reduction.

〔Effect of the invention〕

According to the present invention, even harmonic components included in the encoder output are reduced, and a clean sine wave output without distortion can be obtained.

Furthermore, when obtaining a two-phase output, it is possible to obtain an output with an accurate phase difference of, for example, 90 degrees in electrical angle, thereby improving the accuracy of the magnetic rotation sensor.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG. 2 is a configuration diagram showing one embodiment of the present invention.
Figures 3 (a) to 3 (e) are explanatory diagrams of the characteristics and operation of the magnetoresistive effect cable, and Figures 4 and 6 (a) to 6 are diagrams illustrating the relationship between the magnetic recording medium and the magnetic sensor. E) is a developed diagram of a previously developed magnetic recording medium and magnetic sensor and an explanatory diagram of its operation; FIG. 5 is a configuration diagram showing the relationship between the magnetic recording medium and spacing; FIGS. 9 (a) to 2), and FIG. 10 are explanatory diagrams of the operation of the present invention and their characteristic diagrams, and FIGS. 11 to 14. FIG. 3 is an explanatory diagram showing another embodiment. DESCRIPTION OF SYMBOLS 1... Rotating shaft, 2... Rotating drum, 3... Magnetic recording medium, 4... Magnetic sensor, 4'... Magnetic sensor surface, R... Magnetoresistive element, λ... - Recording pitch on the magnetic recording medium, λ'... Recording pitch on the magnetic sensor surface, λ'-λ... Recording pitch error, r... Radius of the magnetic recording medium, P... Magnetic recording Number of magnetic signals in one revolution of the medium, α...Speed height'2 - day 1 concave 8th day person ^g-1 knob 2 Next 13 Figure procedure correction writing method) % formula % 10- cases Indication of 1986 Patent Application No. 150310 Title of the invention Magnetic rotation sensor (Column for a brief explanation of the drawings of the specification subject to the amendment, ILXJI Marunouchi-5-1, Chiyoda-ku, Tokyo.

Claims (1)

[Claims] 1. A magnetic recording medium on which magnetic signals are recorded, carried by a rotating body or a fixed body, and a magnetic recording medium placed on the fixed body or the rotating body at a certain distance (spacing) from the magnetic recording medium. It has a magnetic sensor consisting of a plurality of magnetoresistive elements, and two of the magnetoresistive elements whose internal resistance changes in response to the magnetic field of the magnetic recording medium are connected in series to a power supply, and from the connection point. A device for detecting position and velocity by extracting an output, characterized in that the spacing between the two magnetoresistive elements is selected so that the even harmonic components of each resistance change are in phase. Magnetic rotation sensor. 2. In the device described in claim 1, a recording pitch λ' that determines the spacing between the plurality of magnetoresistive elements
is determined from the sum of the radius r and the spacing l of the magnetic recording medium. 3. In the device described in claim 1, a recording pitch λ' that determines the spacing between the plurality of magnetoresistive elements
is the radius of the magnetic recording medium r, the spacing l, 1
A magnetic rotation sensor characterized in that, where P is the number of circumferential magnetic signals, λ'=[2π(r+l)/P]. 4. In the device according to claim 1, the distance between the plurality of magnetoresistive elements is such that r is the radius of the magnetic recording medium, l is the spacing, and P is the number of magnetic signals in one round.
A magnetic rotation sensor characterized in that, where n is an integer, [2π(r+l)/P](n+1/2). 5. A magnetic recording medium in which magnetic signals are recorded, carried by a rotating body or a fixed body, and a plurality of magnetoresistive elements arranged on the fixed body or the rotating body at a certain distance (spacing) from the magnetic recording medium. The magnetoresistance effect element whose internal resistance changes in response to the magnetic field of the magnetic recording medium is bridge-connected, and the position is detected by extracting an output from the connection point. The magnetic field is characterized in that the spacing between the two sets of magnetoresistive elements connected at three terminals in each of the bridge connections is selected so that even harmonic components of resistance changes are canceled out at the output end of the bridge connection. Rotation sensor. 6. In the device described in claim 5, the recording pitch λ' determines the interval between the two sets of magnetoresistive elements.
is determined from the sum of the radius r and the spacing l of the magnetic recording medium. 7. In the device according to claim 5, a recording pitch λ' that determines the interval between the two sets of magnetoresistive elements
is the radius of the magnetic recording medium r, the spacing l, 1
A magnetic rotation sensor characterized in that the number of circumferential magnetic signals is determined as λ'=2π(r+l)/P, where P is the number of magnetic signals. 8. In the device according to claim 5, the interval between the two sets of magnetoresistive elements is set to the radius of the magnetic recording medium, the spacing is l, and the number of magnetic signals per revolution is P.
A magnetic rotation sensor characterized in that, where n is an integer, [2π(r+l)/P](n+1/2). 9. A magnetic recording medium in which magnetic signals are recorded, which is carried by a rotating body or a fixed body, and a plurality of magnetoresistive elements arranged on the fixed body or the rotating body at a certain distance (spacing) from the magnetic recording medium. a magnetic sensor that detects a position by electrically extracting a change in resistance of the magnetoresistive element whose internal resistance changes in response to the magnetic field of the magnetic recording medium, wherein the plurality of magnetoresistive elements Divide the elements into two groups,
A magnetic rotation sensor characterized in that the spacing between the second group and the first group is selected so that the outputs of each group are accurately out of phase by 90 degrees. 10. In the device according to claim 9, a recording pitch λ' that determines the distance between the first group of magnetoresistive elements and the second group of magnetoresistive elements is determined by the recording pitch λ' of the magnetic recording medium. A magnetic rotation sensor characterized in that the value is obtained by adding a radius r and a spacing l. 11. In the device described in claim 9, a recording pitch λ' that determines the interval between the first group of magnetoresistive elements and the second group of magnetoresistive elements is determined by the recording pitch λ' of the magnetic recording medium. Radius is r, spacing is l, 1
A magnetic rotation sensor characterized by satisfying the relationship λ'=2π(r+l)/P, where P is the number of magnetic signals in the circumference. 12. In claim 9, the interval between the first group of magnetoresistive elements and the second group of magnetoresistive elements is defined by the radius of the magnetic recording medium being r, the spacing being l, The number of magnetic signals in one revolution is P
A magnetic rotation sensor characterized in that, where n is an integer, [2π(r+l)/P](n+1/4). 13. In the item described in claim 1, when the radius of the magnetic recording medium is r, the number of magnetic signals in one revolution is P, the recording pitch of the magnetic signals is λ, and the spacing is l. , r=(Pλ/2π)−l. 14. In the item described in claim 5, when the radius of the magnetic recording medium is r, the number of magnetic signals in one revolution is P, the recording pitch of the magnetic signals is λ, and the spacing is l. , r=(Pλ/2π)−l. 15. In claim 9, if the radius of the magnetic recording medium is r, the number of magnetic signals in one revolution is P, the magnetic signal recording pitch is λ, and the spacing is l, then r= A magnetic rotation sensor characterized in that (Pλ/2π)-l is selected.