JPH0477246B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetic rotation sensor, in particular, a magnetic signal obtained from a magnetic pattern magnetized at equal intervals on a magnetic recording medium disposed around the entire circumference of a rotating body. The present invention relates to a magnetic rotation sensor that detects the rotation angle of a rotating body by reading it as an electric signal using a magnetoresistive element arranged in the same manner.

[Prior art]

Generally, in this type of magnetic rotation sensor, the higher the number of output signals per rotation of the rotating body, the more accurate measurement can be performed. Just make it smaller.

However, when the pitch of the magnetic pattern is reduced in this way, the magnetic signal obtained from the pattern also becomes smaller, so it becomes necessary to reduce the spacing between the magnetic pattern and the magnetoresistive element that detects it. However, if this spacing is made small, there is a risk of crushing between the magnetic recording medium and the magnetoresistive element, and there is a limit in terms of mechanical accuracy.

By the way, in this kind of magnetic rotation sensor,
Instead of increasing the number of magnetic poles of a magnetic recording medium, the number of magnetoresistive elements placed opposite to the magnetic recording medium is increased, and the output voltages obtained from each magnetoresistive element are combined, thereby achieving high precision. Means for detecting rotation are known, and examples of this means include, for example, Utility Model Application No. 55-51797;
One example is disclosed in Utility Model Application Publication No. 56-58513.

However, it is very clear that even with the above-mentioned means, there is a limit to the number of magnetoresistive elements that can be increased mechanically or precisely.

[Purpose of the invention]

Therefore, the present invention has been made in view of the above-mentioned situation, and its purpose is to provide a magnetic recording medium and a magnetoresistive element without narrowing the distance between the magnetic recording medium and the magnetoresistive element.
Another object of the present invention is to provide a magnetic rotation sensor in which many magnetoresistive elements can be arranged without considering the mutual spacing between the magnetoresistive elements.

[Summary of the invention]

In order to achieve the above object, the present invention provides a magnetic recording medium having a plurality of magnetic poles provided on the entire circumferential surface of a rotating body and alternately magnetized in different directions with a constant pitch; comprising a plurality of magnetoresistive elements spaced apart from each other in positions facing the medium and arranged in parallel at regular intervals in the rotational direction of the rotating body;
In a magnetic rotation sensor that detects a periodically fluctuating magnetic field based on a magnetic pattern formed by the plurality of magnetic poles as a periodic change in electrical resistance by the plurality of magnetoresistive elements, the plurality of magnetoresistive elements , the magnetoresistive elements are arranged side by side across a plurality of pitches in the plurality of magnetic poles and arranged in a multilayer structure with an insulator interposed therebetween, and each magnetoresistive element has a center spacing between adjacent magnetoresistive elements with the insulator interposed therebetween. A plurality of magnetic detection circuits are configured by sequentially bridge-connecting the plurality of magnetoresistive elements in a predetermined order, and from these plurality of magnetic detection circuits, a plurality of magnetic detection circuits having different phases are selected. This is to obtain a detection signal.

[Embodiments of the invention]

Next, embodiments of the present invention will be described in detail using the drawings.

FIG. 1 is a sectional side view of a main part of an example of a magnetic rotation sensor according to the present invention. In the figure, a magnetic drum 3 is mounted on a shaft 2 driven by a motor 1, and is equipped with a magnetic recording medium having a magnetic pattern magnetized at a constant pitch λ over the entire circumference.
are combined. Further, a substrate 5 is fixed on a support base 4 fixed to the housing of the rotating body, and a thin film-like magnetoresistive element 6 is formed on the surface of this substrate 5. A certain distance 7 from the magnetic recording medium on the circumferential surface of the magnetic drum 3
They are facing each other across the street.

FIG. 2 shows an example of a combination of the magnetic drum 3 and the magnetoresistive element 6. In the figure, arrow A indicates the rotation direction of the magnetic drum 3, and a plurality of N-
Magnetoresistive elements 6 ₁ to 6 ₁₄ and 6 ₁ ' to 6 ₁₄ ' are formed and arranged at a ratio of 14 for each magnetic pole pitch λ along the rotational direction A of the magnetic track 3a consisting of S magnetic poles. And these magnetoresistive elements 6
₁ to 6 ₁₄ , 6 ₁ ′ to 6 ₁₄ ′ are combined as a set of 4 wires in each period of 7 across two continuously arranged N-S magnetic poles, as shown in Figure 3 a and b. A magnetic detection circuit 6A consisting of magnetic resistance elements 6 ₁ , 6 ₈ , 6 ₁ ′, 6 ₈ ′ is bridge-connected to the magnetic detection circuit 6A, and a magnetic detection circuit 6A consisting of magnetic resistance elements 6 ₂ , 6 9 , 6 _{2 ′} , 6 ₉ ′ is bridge-connected to the magnetic detection circuit 6A. Magnetic detection circuit 6B
Seven sets are constructed in the same way.

In such a configuration, when the magnetic drum 3 is rotated, the magnetic field applied to the magnetoresistive element 6 changes periodically in accordance with the magnetic pattern magnetized on the magnetic recording medium. As a result, seven sets of magnetic detection circuits 7
Since the electrical resistances of the magnetic detection circuits 7A, 7B, ... also change periodically, by shaping the currents flowing through these magnetic detection circuits 7A, 7B, ... into waveforms, the electrical resistances of the magnetic detection circuits 7A, 7B, ..., which have different phases as shown in FIG. Output signals with various pulse waveforms can be obtained.

In this case, since the pitch of the magnetic pattern is λ, the period of the obtained output signal is also λ, but the seven sets of magnetic detection circuits 7A, 7B, ... 7G are connected to each other along the rotation direction A of the magnetic drum 3. λ/(2
×7), so the phase is
Seven sets of output signals shifted by 25.7° are obtained. Then, as shown in FIG. 4a, 28 magnetoresistive elements 6 ₁ to 6 ₁₄ , 6 ₁ ′ to 6 ₁₄ ′ constituting seven sets of magnetic detection circuits 7A, 7B, ... 7G are mounted on the substrate 5. When arranging, the width of each magnetoresistive element 6 ₁ to 6 ₁₄ , 6 ₁ ′ to 6 ₁₄ ′ is defined as W, and the center distance between adjacent magnetoresistive elements 6 ₁ to 6 ₁₄ , 6 ₁ ′ to 6 ₁₄ ′ is When W>P is selected, each magnetoresistive element 6 ₁
Although the magnetoresistive elements 6 1 to _{6 14} , 6 ₁ ′ to 6 ₁₄ ′ are overlapped with each other, in this embodiment, each of the magnetoresistive elements 6 ₁ to 6 ₁₄ , 6 ₁ ′ to 6 ₁₄ ′ are connected to one another through the insulator 8. Specifically, the magnetoresistive elements 6 ₁ , 6 ₃ , 6 ₅ , 6 ₇ , ... are placed on the lower side, and the magnetoresistive elements 6 ₂ , 6 ₄ , ... 6 ₆ , 6 ₈ , . . . are arranged on the upper side.

In this case, as shown in FIG. 4b, the magnetic resistance elements 6 ₁ , 6 ₃ , 6 ₅ , 6
₇ , ... on one side, magnetoresistive elements 6 ₂ , 6 ₄ , 6 ₆ ,
It is also possible to alternately arrange the magnetoresistive elements 6 ₁ to 6 ₁₄ and 6 ₁ ′ to 6 ₁₄ ′ in combination, such as 6 ₈ , . . . on the other side. Therefore, it is possible to accurately match the phase difference between the outputs from each of the seven sets of magnetic detection circuits 7A, 7B, . . . , 7G.

In rotation sensors generally used for machine tools, etc., a magnetic drum 3 with a diameter of approximately 50 mm produces approximately 5000 ppr.
(pulse per revolution), the interval 7 between the magnetic drum 3 and the magnetoresistive element 6 is required to be approximately 0.2 mm. When the magnetic drum 3 is magnetized to about 5000 ppr, the magnetization pitch becomes about 31.4 μm, and it is extremely difficult to set the interval 7 to about 0.2 mm. Therefore, according to the above configuration, the magnetization pitch λ is set to approximately
126μm and outputs as a 7-phase output signal (at this time, the phase difference between each phase is 180/7 = 25.71°)
As a result, it has become possible to detect and output a magnetic field of about 20 Gauss even if the distance 7 is about 0.2 mm. In addition, since it is necessary to properly control the phase difference of each output signal, in order to always maintain the correct phase difference or the order of the 7-phase output, it is necessary to Bridge detection type magnetic detection circuit 7A, 7
By arranging B, . . . , the phase difference can be accurately controlled. In this case, since it is a 7-phase output, if 14 magnetic detection elements 6 ₁ to 6 ₁₄ are arranged within one magnetic pole pitch λ, the pitch between each element is approximately
It becomes 15.7μ. On the other hand, in order to improve the detection sensitivity of the magnetoresistive element 6 in a low magnetic field, the pattern width of the magnetoresistive element 6 needs to be approximately 15 μm or more. 6 ₁
This can be easily realized by forming a two-layer structure in which 67 to ₆₇ are alternately arranged in parallel.

In the above-mentioned embodiment, a bridge detection type magnetic detection circuit was provided within a two-magnetic pole pitch, but the present invention is not limited to a two-magnetic pole pitch; Of course, even if a magnetic detection circuit having a three-terminal configuration of a dynamic detection type is provided, the same effect as described above can be obtained.

Further, in the above-mentioned embodiments, the case where the magnetic recording medium is provided on the magnetic drum has been explained, but the present invention is not limited to this, and the present invention can be similarly applied to the case where a magnetic disk is used, for example. It goes without saying that this effect can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, since a plurality of magnetoresistive elements are arranged side by side in a multilayer structure with an insulator interposed between them, it is necessary to reduce the distance between the magnetic recording medium and the magnetoresistive elements. This makes it possible to increase the number of magnetoresistive elements arranged in parallel. Increasing the number of magnetoresistive elements has the effect of improving measurement accuracy and making it possible to obtain high resolution. Furthermore, when increasing the number of magnetoresistive elements,
Another advantage is that the process can be carried out without any restrictions on mechanical processing conditions or assembly conditions.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional configuration diagram of essential parts showing an example of a magnetic rotation sensor according to the present invention, Fig. 2 is a plan view showing an example of a combination arrangement of a magnetic drum and a magnetic resistance element, and Figs. 3 a and b are magnetic detection circuits. Figures 4a and 4b are cross-sectional views and plan views of main parts showing examples of the arrangement of magnetoresistive elements, and Figures 5a to 5g are when the arrangement examples of Figures 2 and 3 are used. FIG. 3 is an output signal waveform diagram obtained in FIG. 1...Motor, 2...Shaft, 3...Magnetic drum, 4...Support stand, 5...Substrate, 6,6 ₁ to 6
₁₄ , 6 ₁ ' to 6 ₁₄ '... Magnetoresistive element, 6A, 6B...
...Magnetic detection circuit, 7... Spacing, 8... Insulating layer, 9
...Lead section.

Claims (1)

[Claims] 1. A magnetic recording medium having a plurality of magnetic poles provided on the entire circumferential surface of a rotating body and alternately magnetized in different directions with a constant pitch; It consists of a plurality of magnetoresistive elements arranged in parallel at regular intervals in the rotational direction of a rotating body, and periodically fluctuates a magnetic field based on a magnetic pattern formed by the plurality of magnetic poles by the plurality of magnetoresistive elements. In a magnetic rotation sensor that detects a change in electrical resistance, the plurality of magnetoresistive elements are arranged side by side across a plurality of pitches in the plurality of magnetic poles and in a multilayer structure with an insulator interposed therebetween, and , the center spacing between adjacent magnetoresistive elements via the insulator is selected to be smaller than the width of each magnetoresistive element, and the plurality of magnetoresistive elements in a predetermined order are sequentially bridge-connected. A magnetic rotation sensor comprising a plurality of magnetic detection circuits and obtaining a plurality of detection signals having mutually different phases from the plurality of magnetic detection circuits.