JP2722605B2 - Magnetic encoder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic encoder for detecting a rotation angle of a rotating body or a position of a moving body.

[Conventional technology]

2. Description of the Related Art Conventionally, as an encoder for detecting a rotation angle of a rotating body or a position of a moving body, a magnetoresistive element (hereinafter, referred to as MR) which is closely opposed to a rotating body or a moving body having an incremental signal magnetic track and a reference position signal magnetic track.
2. Description of the Related Art A magnetic encoder that reads a rotational position and a moving speed by a magnetic sensor including a magnetic sensor is known, and utilizes a change in electric resistance of an MR element in a changing magnetic field.

FIG. 5 (a) shows the arrangement of magnetic poles on an incremental signal magnetic track (hereinafter referred to as a magnetic track) 52 of one example and eight MR elements R on a corresponding magnetic sensor 51.
₁₁ to R _14, shows the sequence context of R ₂₁ to R _24, FIG. 5 (b) shows a connected signal output circuit of the MR elements R ₁₁ to R _24. The length of the set of NS poles on the magnetic track 52 in the moving direction is λ
Then, as the magnetic track 52 moves, the magnetic sensor 51
The wavelength of the signal generated in each MR element above is λ, and
The spacing between the MR elements is 1 / 2λ or 3 / 4λ as shown. As outputs of this magnetic encoder, MR elements R ₁₁ , R
A, phase A signal e _A is output from the bridge composed of R ₁₄ , R ₁₂ and R ₁₃
A B-phase signal e _B is output from the bridge composed of the elements R ₂₁ , R ₂₄ , R ₂₂ , and R _{23 with} a phase difference of λ / 4.

FIG. 6 (a) is an improved example of the magnetic encoder shown in FIG. 5 (a) (IEEJ Transactions on Electronics, Vol. 107, No. 6, 1987, No. 751).
Shows the pole on a magnetic track 62 having a page), the sequence status of the corresponding eight MR elements R ₁₁ on the magnetic sensor 61 to to R _14, R ₂₁ to R _24, FIG. 6 (b) is the signal The output circuit is shown. In this example, the half bridge R ₁₂ −
The R _13, R ₂₂ -R _23, another half-bridge R ₁₁ -R _14, R ₂₁ -
Against R ₂₄ are disposed with a phase difference of 2/3 [lambda], is aimed at excluding the third harmonic from the output.

FIG. 7 (a) shows an example of generating a higher output voltage.
The magnetic sensor 61 shown in FIG. 6A is further provided with eight MR elements R _31.
To R _34, shows what was added to R ₄₁ to R _44, FIG. 7 (b)
Indicates the signal output circuit. Each half-bridge _{R 11 -R 14, R 42 -R} 43 output signal e ₁ to e ₈ from is from the adder 75 and the differential 76 shown in Figure No. 7 (c) circuit of the signal output circuit of the magnetic encoder , Sine wave signals of the A phase and the B phase can be obtained.

[Problems to be solved by the invention]

The output of the conventional magnetic encoder shown in FIG. 5 (a) is generally a square-wave pulse output. Therefore, to improve the resolution, it is necessary to increase the number of pulse outputs, but to increase the number of pulses, it is necessary to increase the number of recording magnetic poles, which are incremental signals on a magnetic track,
Accordingly, it is necessary to improve the manufacturing accuracy, which is not practical. For this reason, there is a method in which a sine wave output is generated as a magnetic encoder used with higher resolution, and the resolution is increased by circuit processing. However, since the MR element of the magnetic sensor as shown in FIG. 5 (a) is affected by magnetic saturation and the like, the output waveforms e _A and e _B have third harmonics as shown in FIG. 5 (c). There is a disadvantage in that a distorted waveform including an odd harmonic component such as the fifth harmonic is generated, and high resolution cannot be implemented by circuit processing.

The magnetic encoder shown in FIG. 6A is similar to the magnetic encoder shown in FIG.
The output of this magnetic encoder is similar to a sine wave by removing the third harmonic. However, while the output e of the conventional magnetic encoder in which the harmonics are not removed in FIG. 5A is expressed by e = 2Acos ωt (A is a constant), it is shown in FIG. 6A. The magnetic encoder from which the third harmonic has been removed is, for example, an MR element for each of the MR elements R ₁₁ and R ₁₄ in order to remove the third harmonic.
R ₁₃ and R ₁₂ are arranged with a phase difference of 1 / 6λ, respectively.
The output e is Where the output voltage is 14% lower than the output voltage of a conventional magnetic encoder without harmonics. For this reason, there is a drawback in that it is susceptible to external noise and the frequency of malfunctions increases when used in a servomotor or the like.

In order to obtain a high output voltage, a magnetic encoder shown in FIG. 7 (a) is conceivable, which is twice the output voltage of the magnetic encoder shown in FIG. 6 (a). It is possible to obtain However, since the number of MR elements in the magnetic encoder of FIG. 7A increases, for example, in the case of a rotary type magnetic encoder, as shown in FIG. 8, the MR element (for example, R ₄₂ , R ₁₃ ) and the MR element at the end (for example, R ₁₁ and R ₄₄ ) have different distances from the magnetic track 72, causing a difference in the strength of the magnetic field and a large output difference. In the MR element, the magnetized pitch becomes shorter due to the curvature of the magnetic track, causing distortion in the output waveform.Also, the output waveform often becomes distorted due to slight fluctuations in the spacing between the magnetic track and the magnetic sensor. There is a disadvantage of doing so.

It is an object of the present invention to provide a magnetic encoder that generates a stable sine wave output at a high output voltage.

[Means for solving the problem]

In the magnetic encoder of the present invention, the one according to claim 1 has a phase of λ / 6, −λ / 6, λ / 10, −λ / 10 with respect to the phase of an incremental signal on one incremental signal magnetic track. At least one of which one of the recorded incremental signals is shifted
Two other incremental signal magnetic tracks, and a plurality of magnetoresistive element rows respectively corresponding to each incremental signal magnetic track, and a magnetic sensor in which the arrangement of each magnetoresistive element row is in phase with each other. 3. The method according to claim 2, wherein at least one other incremental signal recorded with an incremental signal having a phase shifted by λ / 6 or −λ / 6 with respect to the phase of the incremental signal on one incremental signal magnetic track. For the signal magnetic track and the incremental signal magnetic track whose phase is shifted by λ / 6 or −λ / 6,
At least one incremental signal magnetic track that is λ / 10 or −λ / 10 out of phase, and for this incremental signal magnetic track that is λ / 10 or −λ / 10 out of phase, Or -λ / 6
Incremental signal magnetic tracks that are shifted, and a plurality of magnetoresistive element rows corresponding to each of the incremental signal magnetic tracks, and a magnetic sensor in which the arrangement of each magnetoresistive element row is in phase with each other. I have.

[Action]

Conventional magnetic encoders have only one incremental signal magnetic track on the moving magnetic recording medium, and therefore the MR elements on the magnetic sensor that are in close proximity to the incremental signal magnetic track are also arranged in a single row. On the other hand, the magnetic encoder of the present invention is provided with a plurality of incremental signal magnetic tracks, and also has a plurality of rows of corresponding MR elements disposed close to and opposed thereto, and a phase difference between the incremental signal magnetic tracks, By appropriately shifting λ / 6 or λ / 10, the length of the MR element array on the magnetic sensor is shortened to prevent output differences and waveform distortion due to differences or fluctuations in the distance from the incremental signal magnetic track. In addition, the third or fifth harmonic can be easily extracted from the output signal (in the case of claim 1) or both of them (in the case of claim 1). Since in the case), except may be a sine wave shape, of a high output strong stable to external noise can be obtained and high resolution can be achieved by the circuit process.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Perspective view of a first embodiment of a magnetic encoder in Figure 1 the present invention, FIG. 2 (a), (b), respectively, 16 of the MR elements R ₁₁ ~ with the magnetic sensor 1 of the present embodiment R _14, R ₂₁ ~R
_24, and _{R 31 ~R 34, R 41 ~R} 44, showing the arrangement pattern of the incremental signal magnetic track 2 and 3 on the pole in two rows formed on the side surface of the magnetic drum 4, a signal output circuit diagram FIG. 3 is a comparison diagram between the output voltage characteristic of the present embodiment and that of the conventional example.

The magnetic drum 4 is directly connected to a rotating body whose rotation angle is to be measured, and is arranged on its side face in parallel with the circumferential direction.
A ferromagnetic film with a thickness of about several tens of μm is formed,
Two incremental signal magnetic tracks (hereinafter referred to as magnetic tracks) 2 and 3 are magnetized at a magnetization pitch of μm. Assuming that the magnetization pitch is λ, the length of λ is
Equal to one wavelength of the incremental signal generated MR element R ₁₁ to R _44, two magnetic tracks as shown in FIG. 2 (a)
The phase difference between 2 and 3 is λ / 6. The magnetic sensor 1 is disposed in close proximity to the magnetic tracks 2 and 3, and eight MR elements R ₁₁ , R ₁₂ , R _{21 to} R ₂₄ , R ₁₄ , and R ₁₃ are provided on the magnetic track 2. Correspondingly, the other eight MR elements R ₃₁ , R ₃₂ , R
_{41 ~R 44, R 34, R} 33 is corresponding to the magnetic track 3, second
They are arranged at intervals as shown in FIG. From each of the set of the MR element corresponding to the set and the magnetic track 3 of the MR element corresponding to the magnetic track 2, four half-bridge R ₁₁ and connect the MR element every two -R _14, R ₁₂ - R ₁₃ , R ₂₁
−R ₂₄ , R ₂₂ −R ₂₃ and the other four half bridges R ₃₁ −
R ₃₄ , R ₃₂ -R ₃₃ , R ₄₁ -R ₄₄ , R ₄₂ -R ₄₃ are made, and each half bridge is connected in parallel to the power supply 5, and signals e ₁ , e ₃ , e from the middle point thereof, respectively. _{5, e 7, e 2,} e 4, e 6, e 8 is taken out. 1 / 6λ between magnetic track 2 and magnetic track 3
, The signals e ₁ and e ₂ , e ₃ and e ₄ , e ₅ and e ₆ , and e ₇ and e ₈ output from each half bridge are also λ / 6 , The contained third-order harmonics have an opposite phase relationship to each other. Therefore, if the signals e ₁ and e ₂ , e ₃ and e ₄ , e ₅ and e ₆ , and e ₇ and e ₈ are respectively added, the third harmonic is eliminated, and then the signals e ₁ and e ₂
Taking the differential of the sum of the sum value and the signal e ₃ and e ₂ of the A-phase output of the sine wave is obtained. Similarly, the signal e ₅ as well as B-phase output of the sinusoidal Taking the differential of the sum of the sum value and the signal e ₇ and e ₈ and e ₆ is obtained.

The maximum output of the conventional magnetic encoder from which the third harmonic of FIG. 6 was removed was about 90 mV when the spacing between the magnetic drum and the magnetic sensor was 140 μm, but the maximum output was about 90 mV in the magnetic encoder of this embodiment. It was 180 mV. Also, the third
The figure shows the case of the conventional magnetic encoder in which the harmonics are not removed in FIG. 5 (curve A) and the case of the conventional magnetic encoder in which the third harmonic is removed in FIG. 6 (curve A). B) and the case of this embodiment (curve C) show the dependence of the respective output voltages on the spacing. The magnetic encoder of this embodiment makes the output voltage significantly higher than that of the conventional example. Can be a third as described above
It can be seen that the output voltage is about twice as high as that of the conventional magnetic encoder from which the second harmonic is removed. Further, the following Table 1
Shows the sine wave distortion rate (%) of the magnetic encoder (B) of the conventional example and the magnetic encoder (C) of the present embodiment from which the third harmonic was removed at each spacing (μm). It can be seen that the distortion rate of the magnetic encoder of this embodiment is almost the same as that of the conventional encoder.

Therefore, the magnetic encoder of this embodiment can significantly increase the output voltage without increasing the sine wave distortion factor as compared with the conventional magnetic encoder, and can be a magnetic encoder resistant to external noise.

In this embodiment, the third harmonic is removed by shifting the magnetic track 3 by 1 / 6λ with respect to the magnetic track 2;
It is apparent that the same result can be obtained even if the shift is made, and if the shift is + λ / 10 or −λ / 10, only the fifth harmonic can be removed, and the sine wave distortion rate of the output waveform decreases.

FIGS. 4A and 4B respectively show 32 MRs of the magnetic sensor 41 of the magnetic encoder according to the second embodiment of the present invention.
The arrangement pattern of such elements R _11, it is a diagram showing a magnetization pattern of the magnetic poles of the magnetic drum 42 magnetic tracks of four rows formed on 11,12,13,14.

The phase difference between the magnetic tracks 11 and 12 is λ / 6, as in the first embodiment described above, and the phase difference between the magnetic tracks 13 and 14 is −λ / 6. The magnetic track 13 is out of phase with the magnetic track 12 by λ / 10. 32 MR element R _11, etc. on the magnetic sensor 41, and respectively adjacent opposed by eight within the magnetic track 11, 12, 13, 14 are arranged at the same intervals as in the first embodiment . Then, as in the case of the first embodiment, these
Make a half-bridge from the MR element R _11, etc., by taking the differential adds the outputs of the midpoint of their half-bridge, is easily understood can be removed 3rd and 5th harmonics. Therefore, as shown in the following Table 2, in the case of the second embodiment (D), the sine wave distortion rate (%) in each spacing (μm) is compared with the case of the first embodiment (C). Was further reduced, and a sinusoidal output waveform was obtained.

A similar result is obtained when -λ / 6 is used instead of the phase difference λ / 6 between the magnetic track 11 and the magnetic track 12 of the present embodiment, and the phase difference -λ / 6 between the magnetic track 13 and the magnetic track 14 is obtained. Alternatively, it may be λ / 6. Further, similar results can be obtained by setting -λ / 10 instead of the phase difference λ / 10 between the magnetic tracks 12 and 13.

Table 3 below shows the conventional magnetic encoder (B) shown in FIG. 6 (a) from which the third harmonic was removed and the magnetic encoder (C) of the first embodiment shown in FIG. 2 (a). , And when the magnetic encoder (D) of the second embodiment, from which the fifth harmonic is removed, is combined with a servomotor,
It indicates the number of malfunctions due to noise.

That is, in the actual measurement example in which each magnetic encoder was operated together with the servo motor for one day in a real environment, the conventional magnetic encoder often had malfunctions due to a low output voltage, and was completely unreliable. The magnetic encoder of the example had no malfunction.

〔The invention's effect〕

As described above, according to the present invention, the incremental signal magnetic track and the magnetoresistive element array adjacent to the incremental signal magnetic track are arranged as a plurality of rows, and the phase difference between the incremental signal magnetic tracks is λ / 6, −λ / 6. , λ / 10, -λ / 10, the array length of the MR element array on the magnetic sensor is shortened, so that it is possible to prevent the output from dropping and the occurrence of waveform distortion. Since the tertiary or fifth harmonic or both of them can be removed to form a sinusoidal waveform, a high output voltage, high resistance to external noise, and a high resolution magnetic encoder can be obtained. There is.

[Brief description of the drawings]

Perspective view of a first embodiment of a magnetic encoder in Figure 1 the present invention, FIG. 2 (a), (b), respectively, 16 of the MR elements R ₁₁ ~ with the magnetic sensor 1 of the present embodiment R ₁₄ , R ₂₁ 〜
An array pattern of R ₂₄ , R _{31 to} R ₃₄ , R _{41 to} R _{44 and} an array pattern of two rows of incremental signal magnetic tracks 2 and 3 formed on the side surface of the magnetic drum 4 and magnetic poles on
FIG. 3 is a diagram showing a signal output circuit, FIG. 3 is a comparison diagram of output voltage characteristics between the first embodiment and the conventional example, and FIGS. 4 (a) and (b) are second diagrams of the magnetic encoder of the present invention, respectively. The figure which shows the arrangement | sequence pattern of 32 MR elements R11 _grade etc. which the magnetic sensor 41 of an Example has, and the magnetic pole arrangement | sequence on four rows of incremental signal magnetic tracks 11,12,13,14 formed on the magnetic drum 42. 5 (a) and 5 (b) show an incremental signal magnetic track 52 of a conventional magnetic encoder.
Eight MR elements R ₁₁ on the magnetic sensor 51 corresponding to the upper magnetic pole
The arrangement pattern of the to R _24, shows signal output circuit, FIG. 5 (c) is an output signal waveform diagram, Figure 6 (a),
(B) shows the arrangement pattern of the magnetic poles on the incremental magnetic track 62 and the corresponding eight MR elements R _{11 to} R ₂₄ on the magnetic sensor 61 of the conventional magnetic encoder from which the third harmonic has been removed. 7 (a), 7 (b) and 7 (c) show a magnetic pole on an incremental signal magnetic track 72 and a magnetic pole on a magnetic sensor 71 of a conventional magnetic encoder for obtaining a higher output voltage. 16 MRs
Shows the arrangement pattern of the elements R ₁₁ to R _44, and a signal output circuit, a signal processing circuit, FIG. 8 is a magnetic drum of the prior art
FIG. 28 is a diagram showing a positional relationship between a cross section of 84 and the magnetic sensor 71. 1,41,51,61,71 …… magnetic sensor, 2,3,11,12,13,14,52,6
2,72 …… Incremental signal magnetic track, 4,42,74
…… Magnetic drum, 75 …… Adder, 76 …… Differential unit, λ ……
Magnetization pitch, N, S ...... _{pole, R 11 ~R 14, R 21} ~R 24, R 31 ~
_{R 34, R 41 ~R 44,} 10 ...... magnetoresistive element, e ₁ ~e ₈ ...... output signal, e _A ...... _A-phase signal, e _B ...... _B-phase signal, A, B, C ...... curve .

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-154612 (JP, A) JP-A-1-297507 (JP, A) JP-A-59-187713 (JP, U) 35246 (JP, B2) Patent 2529960 (JP, B2)

Claims (2)

(57) [Claims] 1. An incremental signal which is repeatedly recorded at a constant wavelength λ on an incremental signal magnetic track parallel to a moving direction on a moving magnetic recording medium using a magnetoresistive element whose electric resistance changes according to a change in a magnetic field as a sensor. In a magnetic encoder that detects a signal and detects a moving amount and a moving direction of the magnetic recording medium, a phase is λ / 6, −λ / 6, λ with respect to a phase of an incremental signal on one magnetic track. / 1
At least one other incremental signal magnetic track on which an incremental signal shifted by one of 0, -λ / 10 is recorded, and a plurality of magnetoresistive element arrays respectively corresponding to each incremental signal magnetic track. And a magnetic sensor in which the arrangement of each of the magnetoresistive element rows has a magnetic sensor in phase with each other. 2. Incremental signals parallel to the moving direction on a moving magnetic recording medium using a magnetoresistive element whose electric resistance changes according to a change in a magnetic field as a sensor. Incremental signals repeatedly recorded at a constant wavelength on a magnetic track. In the magnetic encoder for detecting the moving amount and the moving direction of the magnetic recording medium, the phase is λ / 6 or −λ / 6 with respect to the phase of the incremental signal on one magnetic signal magnetic track.
At least one other incremental signal magnetic track on which the shifted incremental signal is recorded, and a phase of λ / 10 or- at least one incremental signal magnetic track that is λ / 10 shifted, and whose phase is λ / 10 or −
With respect to the incremental signal magnetic track shifted by λ / 10, an incremental signal magnetic track whose phase is further shifted by λ / 6 or −λ / 6, and a plurality of magnetoresistive element arrays respectively corresponding to each incremental signal magnetic track. And a magnetic sensor in which the arrangement of the magnetoresistive element rows is in phase with each other.