JPS58154612A - Detector of displacement quantity - Google Patents

Abstract

PURPOSE:To obtain a precise differential output and to detect a displacement quantity more precisely by arraying at least two magnetic resistance effect elements (MR elements) in the direction intersected with the displacement direction so as to be opposed to magnetic recording tracks forming their magnetic patterns with different phases each other. CONSTITUTION:A magnetic recording medium 10 is composed of two recording tracks 11a, 11b and records a magnetic pattern by shifting it by a half of a pitch P. When the magnetic recording medium 10 is displaced, the resistance values R of the MR elements are changed as shown by curves 13a, 13b. The differential output voltage shown by the curve 14 is obtained by finding the difference between the output signals of the MR elements 12, 12b. Since the MR elements 12a, 12b are arrayed in the direction intersected with the displacing direction, the detection does not depend upon the pitch P of the magnetic pattern and the magnetic sensor can be used in common also for the magnetic patterns with different pitches P.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a displacement detection device that can be used as a rotary encoder or a linear encoder. This relates to a displacement detection device that obtains a differential output. For example, a disk or cylinder having a magnetic recording medium attached to a rotating shaft records magnetization in the form of a pattern with equally spaced bit lengths. A so-called rotary encoder is known, which detects the rotation angle of one rotating shaft by reading a magnetic signal generated by the magnetic field with a magnetic sensor including a ferromagnetic magnetoresistive element (hereinafter abbreviated as MR element). In a rotary encoder like this, a single MR element basically detects a magnetic signal and can determine the amount of displacement, but it has drawbacks such as a small output voltage and the output voltage drifting due to temperature changes. Therefore, it is common to differentially couple eight or more MR elements to obtain an output. For example, in Japanese Patent Publication No. 54-115257, two MR elements are arranged at an interval equal to an integral multiple of the pitch of the magnetic pattern on a magnetic recording medium, and the difference in the outputs of these MR elements is calculated as a differential signal. An angle detector using an amplifier is described.

Also, [Nikkei Electronics J, June 1981, issue gg, page 88 contains the 18th! i! As shown in , four MR elements A0 to A4 . Two groups of magnetic sensors are provided for growing B, ~B4, and the MR elements of each group are connected to a magnetic recording medium M.
The MR elements of one group are arranged to be separated by the corner i of the pitch P of the magnetization patterns, and the MR elements of one group are arranged shifted by τ from the MR elements of the other group, as shown in Fig. 2. The four MR elements of the group are connected as a bridge circuit,
The difference in the output voltages appearing at the diagonal points of each bridge circuit is calculated by the differential amplifiers D A and D A!, respectively. An angle detection device is shown in which the amount and direction of displacement are detected by determining the amount of displacement and the direction of displacement. Adopting such a differential coupling method has the advantage of increasing the output amplitude and canceling out the effects of drift.

However, in such a conventional angle detection device, two or more MR elements are arranged in the displacement direction, that is, in the arrangement direction of the magnetic patterns, at intervals of an integral multiple or an integral fraction of the pitch P of the magnetization pattern. It is necessary to prepare magnetic sensors with MR elements arranged at predetermined intervals for magnetic media with magnetization patterns of various pitches, which limits the degree of freedom in design. In addition, when a magnetic recording medium is provided on a cylindrical surface, if multiple MR elements are formed on a flat substrate, the distances between each MR element and the magnetic recording medium are not equal, and the output signal of each MR element is There is a drawback that the amplitude of the MR element varies, which causes an error in the differential output.In order to solve this problem, changing the width of the MR element is disclosed in Japanese Patent Publication No. 56-85011; It is troublesome to manufacture such an MR element, and if the above-mentioned distance changes, it is necessary to manufacture an MR element with a corresponding width, which has the disadvantage of lacking in versatility. 2 or more M
If the R element is shifted in the direction in which the magnetization pattern of the magnetic recording medium is arranged, the size of the magnetic sensor will inevitably increase, and the overall size of the detection device will also tend to increase.

An object of the present invention is to eliminate the above-mentioned drawbacks, to provide a displacement detection device that does not require MR elements to be arranged apart in the direction of arrangement of magnetization patterns of a magnetic recording medium, and that can provide differential output. This is what I am trying to do.

The displacement detection device of the present invention includes a member K that is displaced in a predetermined direction, and at least two magnetic recording tracks extending in the direction of the displacement, and these recording tracks are arranged in phase with each other when viewed in the direction of displacement. A magnetization pattern is formed by shifting the magnetic recording tracks, and at least two magnetoresistive elements are arranged side by side in a direction orthogonal to the direction of displacement, facing the magnetic recording tracks.

The present invention will be described in detail below with reference to the drawings.

FIG. 8 is a plan view showing the configuration of an example of the displacement amount detection device of the present invention. In this example, two recording tracks lla and llb are provided on the magnetic recording medium 10, and magnetization patterns are recorded on these recording tracks shifted by half the pitch P thereof.

First and second ferromagnetic magneto-resistance effect elements 12a and 12b are arranged opposite to these recording tracks 111) in a direction perpendicular to the arrangement direction of the magnetization pattern, that is, the displacement direction.

In such a configuration, when the magnetic recording medium 1o is displaced in the direction shown by the arrow, the magnetic field acting on the first and eighth MR elements 12a and 11bK changes, and in response to the change in the magnetic field, the resistance value R of these MR elements changes. are converted to 5Kffi as shown by curves 18a and 18b, respectively, in FIG. That is, the changes in this resistance 01R are 180° out of phase with each other.

Therefore, these first and 217th) MR elements 12a
By taking the differential of the output signals of and 12b, a differential output voltage as shown by curve 1114 in FIG. 6 is obtained. In the present invention, the first and second M
Since the R elements 12a and 12b are arranged in a direction perpendicular to the arrangement direction of the magnetization pattern, that is, the displacement direction, detection no longer depends on the pitch P of the magnetization pattern, and the detection is no longer dependent on the pitch P of the magnetization pattern. Magnetic sensors can also be used in common.

FIG. 6 is a perspective view showing a modification of the displacement detection device of the present invention. This example is also similar to the previous example in that two recording tracks 21a and 21b are provided on the magnetic recording medium 2o, and magnetization patterns are formed on these tracks by shifting them by a pitch P when viewed in the displacement direction indicated by the arrow. In this example, the substrate 21 extends perpendicularly to the magnetic recording medium 20 in a direction perpendicular to the displacement direction! Four MR elements 28a-2 on top
An insulating layer 25ali is interposed between the MR elements 28a, 24&, and (7), and an insulating layer g5b is interposed between the MR elements 2db and 24b. 61st i! ! Although the MR element and the insulating layer are shown in a large area in order to make the drawings brighter, they are actually extremely thin. 4 pieces (
7) MR element! 21a, g8b, 24a and 24i)
is assembled into a bridge circuit as shown in Fig. 7, and the MR element 2
Connect the connection point between 8a and 24k) to the power supply upper terminal +E,
The connection point between the R elements 2δb and 2A is connected to the power supply negative terminal -E, the connection point between the MR elements 24i) and 24& is connected to the positive input terminal of the differential amplifier 26, and )l[R element 28& and 2
By connecting the connection point 8b to the negative input terminal of the differential amplifier 26, a differential output signal is obtained at the output terminal 27. In this example, the MR elements are arranged perpendicularly to the surface of the magnetic recording medium 20, but of course they may be arranged parallel to the front row.

The substrate 81i of the magnetic sensor used in the implementation row of the displacement detection device of the present invention shown in FIG. 6 is a glass plate, and the MR
The elements 28a, 28b, 24a, and 24b are formed by vapor-depositing FeNi alloy (permalloy) to a thickness of about 600 mm,
The insulating films 25a and 25b are 810 and 100θ to 2000
It can be formed by vapor deposition to a thickness of A. In this way, magnetic sensors can be easily manufactured by vapor deposition and are therefore inexpensive.

FIGS. 8 and 9 show modified examples of the magnetization pattern recorded on the magnetic recording medium used in the displacement detection device of the present invention. In the example shown in FIG.
02 recording tracks 81a and 81bK pitch P1
．． P and magnetization patterns different from P are recorded while being shifted by their respective pitches. Further, in the example shown in FIG. 9, the two recording tracks 41& and 41b of the magnetic recording medium 40 are recorded by changing the pitch of the two recording tracks 41& and 41b gradually so that the magnetization pattern is shifted by 4 pitches.

Although a magnetic recording medium in which the pitch of the magnetization pattern has changed in this way cannot be used in a conventional magnetic sensor, it can be used in the present invention because the MR elements are arranged side by side in a direction perpendicular to the direction of displacement. Such a magnetic recording medium is effective, for example, in IJ near encoding, where detection accuracy is changed during displacement.

The present invention is not limited to the above-mentioned example, and many modifications are possible. For example, although the above example is shown as a linear encoder, the rotation angle can also be detected as a rotary encoder. Further, in the example described above, two recording tracks were formed and the magnetization patterns were shifted by half the pitch, but three or more recording tracks could also be provided. For example, if you set up four recording tracks,
A magnetization pattern can be formed by shifting these by a pitch. In this case, four or eight MR elements may be arranged side by side in a direction perpendicular to the direction in which the tracks extend. Furthermore, in the example shown in FIG.
a, 28b and 24&.

24b are provided in one layer, but they can also be arranged in a line in a direction perpendicular to the displacement direction for power distribution. In this case, an MR element 2 is placed above one recording track 1lla.
8a and 24a are arranged side by side in a direction perpendicular to the displacement direction, and the MR element 28 is placed above the other recording track 21b.
b and 24b meet by arranging them side by side in the same way. Further, in the above example, the recording tracks are formed on the same magnetic recording medium, but they may be formed on separate magnetic recording media.

According to the displacement detection device of the present invention described above, a plurality of MR
Since the elements are arranged in the direction perpendicular to the displacement direction, detection is possible regardless of the pinch of the magnetization pattern formed on the magnetic recording medium. The advantage is that magnetic sensors can be used in common, and magnetic recording media having magnetization patterns with different pitches can also be used. When applied to a rotary encoder that has a magnetic recording medium on the side wall of a cylinder or disk, all M
Since the distance between the R element and the magnetic recording medium is reduced, the effect of the magnetic field on all MR elements becomes equal, resulting in more accurate differential output and therefore more accurate displacement detection. There are advantages that can be achieved. Furthermore, since the plurality of MR elements are arranged in a direction perpendicular to the displacement direction, the dimensions of the magnetic sensor can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of an example of a conventional displacement detection device, FIG. 2 is a circuit diagram showing a bridge circuit made of a magnetoresistive element, and FIG. 8 is a diagram of a displacement detection device of the present invention. A plan view showing the configuration of an example, FIG. 4 is a waveform diagram showing the simplified resistance value of the magnetoresistive element, FIG. 5 is a waveform diagram showing the differential output signal of the magnetoresistive element, and FIG.
The figure is a perspective view showing the configuration of another example of the displacement detection device of the present invention, FIG. 7 is a circuit diagram showing a bridge circuit similarly configured by the magnetoresistive element, and FIGS. 8 and 9 are the same according to the present invention. FIG. 3 is a plan view showing another example of the magnetization pattern on the magnetic recording medium used in the displacement detection device of FIG. No, 5!0.30.40...Magnetic recording medium, 11a
, llb, 21a, 21b, 81a, 81b. 41a, 41b...recording track, 12a, 12b, 23a, 28b, 24a, 24b-magnetoresistive element, 26a, 25b...insulating film, 26...differential amplifier. Patent applicant: Copal Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Procedural amendment June 9, 1982 1. Indication of the case 1982 Patent Application No. 36640 2. Amount of name displacement of the invention Detection device 3, relationship with the case of the person making the amendments Patent applicant Co., Ltd. Corrections are made to Figure 2 of the drawing center cylinder as shown in the attached sheet. (iT il L; 6 ” Fig. 2

Claims (1)

[Claims] t At least two magnetic recording tracks extending in the direction of displacement are arranged in parallel on a member that is displaced in a predetermined direction, and magnetization patterns are formed on these recording tracks with phases shifted from each other when viewed in the direction of displacement. , A displacement amount detection device having a 4I feature in which at least two magnetoresistive elements are arranged in parallel in a direction orthogonal to the displacement direction, facing these magnetic recording tracks.