JPS629218A - Magnetic rotation detector - Google Patents

Abstract

PURPOSE:To detect a rotational state accurately by making the magnetic patterns in the straight stripe shapes and narrowing the widths of the stripes of a magneto-resistance effect element in a different direction from one side respectively and reducing being influenced by a variation of the spacing. CONSTITUTION:The trapezoidal stripes 41-44 of the magneto-resistance effect element whose widths are narrowed in the different direction from one hand with respect to a longitudinal direction are arranged in opposition to the straight striped magnetic patterns 51-54 on the cylindrical outside peripheral surface of a permanent magnet drum 2 rotating in an arrow direction in figure. Hereby, for instance, the stripes 41 and 43 are situated at the position with the same phase with respect to the magnetic patterns 51-55, and the stripes 42 and 44 are situated at the position with the same phase delayed semicircularly from the stripes 41 and 43. Hereby, as to one stripe, since the time to start being influenced or the time to be free from being influenced by the magnetic flux from the magnetic patterns on its each part can be shifted little by little, the influencing by the variation of the spacing is reduced and an output voltage signal close to a sine wave is taken out stably and the rotational state can be accurately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a magnetic rotation detector. ``A magnetic rotation detector is a device that uses a multi-pole magnetized permanent magnet drum or disk attached to the rotating shaft, and detects the magnetized pattern on the surface with a magnetically sensitive element placed nearby to determine the rotational state. It is.

[Conventional technology]

An example of such a magnetic rotation detector is a "magnetic detector using a magnetoresistive element (hereinafter referred to as MR sensor)" (1981 National Conference of the Institute of Electrical and Communication Engineers, Prefi 161).

This magnetic detector corresponds to the A phase and B phase by arranging each stripe of the MR sensor 1/4p apart and connecting each stripe with a bridge, where p is the magnetization pitch of the permanent magnet. This is to obtain an increment signal output.

A pseudo sine wave signal appears at the terminal of the Pritsuno, and is generally amplified and waveform-shaped to obtain a desired rectangular wave signal.

Some magnetic rotation detectors do not require a rectangular wave output as an output signal, but an output that is as close to a sine wave as possible. In such cases, conventional detectors could not adequately cope with the situation. In other words, the peak value of the sine wave signal is greatly affected by the distance between the sensor and the permanent magnet (hereinafter referred to as spacing), and if the spacing changes due to eccentricity of the drum during rotation, this will cause the output voltage to change. There was a drawback that manifested itself in fluctuations.

The cause of this will be explained below.

FIG. 4 is a perspective view of the main parts showing the configuration of the most basic detector, in which 2 is a permanent magnet drum rotating in the opposite direction;
23 is a magnetization pattern magnetized with pitch p.

*11 to 14 are MR censuses and drives arranged at a pitch of p/2.

Now, if the 0 magnetization pattern (for example, 21), which is of interest only for the sensor stripe 11, is directly below the stripe 11, the magnetic flux will not cross the magnetization pattern 21, so the resistance value of the stripe 11 will be the same as in the absence of a magnetic field. However, as the permanent magnet drum 2 rotates and the magnetized butterfly 21 shifts from directly below the stripe 11, the stripe 11 changes into two magnetized patterns ( For example, it comes to be influenced by the magnetic flux between 21 and 22), and its resistance value decreases. Then, as the next magnetized pattern (for example, 22) approaches just below the stripe 11, the stripe 11 becomes unaffected by the magnetic flux again, and the resistance value increases to the original value R*.

FIG. 5 shows this situation, where the resistance value of the stripes changes periodically as the drum rotates (moves).

The curve shown by the solid line A in FIG. 5 shows the case where the set spacing is relatively small, and when the magnetization pattern deviates slightly from the sensor stripe, sufficient magnetic flux crosses the stripe, so the resistance value decreases. The resistance value decreases rapidly, and even if the magnetic flux further increases thereafter, the magnetoresistance effect is saturated, so the resistance value hardly decreases and -1 almost reaches the saturation value Rs.

The resistance change in such a case takes the form of a steep peak appearing at the pitch p, as shown by the solid line A.

Next, the curve indicated by dotted line B will be explained.

This white line is when the setting spacing is large,
Since the magnetic flux from the magnetized pattern does not sufficiently reach the sensor stripe, the resistance value of the stripe does not decrease to its saturation value Rs.

Note that in such a region, if the spacing changes while the drum is rotating, the fluctuation directly affects the waveform of the change in resistance value. For example, if the spacing is slightly reduced,
The change waveform of the resistance value is as shown by the dashed line C in the figure.

FIG. 6 shows how the output voltage in the bridge circuit shown in FIG. 4 changes when the resistance value of the sensor stripe changes as shown in FIG. 5.

In FIG. 6, there are three output voltage curves A + , B +
, C3 correspond to the conditions of curves A, B, and C in FIG. 5, respectively. As you can see by comparing Figures 5 and 16, drum turn 11! The change in the resistance value of the stripe and the change in the output voltage of the Pritsuno circuit with respect to (movement) are curves with similar shapes in that the peak appears at each pitch p.

The fact that the curves in FIGS. 5 and 6 have similar shapes at the above points can be explained as follows.

The resistance values of the stripes 11 to 14 in FIG. 4 each reach the minimum value (saturation value) Rs when the external magnetic field R1 is sufficiently strong in the absence of external magnetic flux.

This rate of decrease in resistance value (R-Rs)/R is usually a small value of about 2 to 4%. *If you take a moment,
Since the relative position to the magnetization pattern is the same,
The resistance values of stripes 11 and 13 are equal, and the resistance values of stripes 12 and 14 are equal, so the resistance value R, of stripes 11 and 13 at a certain moment is (1-a
)R, the resistance value R2 of stripes 12 and 14 is (1-β)
It can be expressed as R (α.

β is the resistance reduction rate. And its maximum value is 0°02～
It is a small value of 0.04, and constantly changes periodically due to the rotation of the drum).

From this condition, the output voltage of the bridge circuit at this time is calculated, and as shown in FIG.
Since a1β is small, V can be calculated by omitting the terms of second order or higher. In other words, the output voltage waveform of the 1977 circuit is the resistance change waveform of stripes 11.13 and (/12.14) in the opposite direction. It can be seen that it is superimposed on .

Also, from Figure 6, the setting spacing can be adjusted to
The output voltage waveform is close to a sine wave as shown in the curve M c +, but the output voltage is small and easily affected by variations in spacing (also, if the set spacing is small, the output voltage will be large). , and is less affected by spacing variations, but it can be seen that the waveform is far from a sine wave with a sharp tip.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic rotation detector that is less affected by spacing variations, stably extracts an output voltage signal close to a sine wave, and can accurately detect rotational conditions. That is.

[Means for solving problems]

To achieve this goal, the magnetic flux across the sensor stripe must be large enough at its maximum to saturate the reduction in resistance of the sensor stripe, at a minimum near zero, and at intermediate times the magnetic flux across the sensor stripe is large enough to saturate the decrease in resistance of the sensor stripe. It is necessary to partially saturate the resistance value.

Therefore, as a means to satisfy this requirement, on the sensor stripe side, it is necessary to determine the time at which each part of a sensor stripe begins to be influenced by the magnetic flux from the magnetization pattern, or the time at which it ceases to be influenced by the magnetic flux from the magnetization pattern. All you have to do is shift it slightly.

The present invention is characterized in that the magnetization pattern is linearly striped, and the width of each sex drive is narrowed from one side toward the other in the longitudinal direction.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a perspective view showing an embodiment of the present invention, in which magnetized butter 151 g 52 * 53 v 54 and a trapezoidal sensor stripe 41 . 42°43. In order to make it easier to understand the state in which it faces 44, the outer cylindrical curved surface is shown open at 71 in a plane.

In this embodiment, the pitch p0 of the sensor stripes 41 to 44 and the magnetization pattern 5 on the outer peripheral surface of the permanent magnet drum 2 are
The relationship with the pitch p of 1 to 55 is different from the example in Fig. 4,
The relationship is po=1.5p. The sensor stripes 41 and 43 are in the same phase position with respect to the magnetized patterns 51 to 55, and the sensor stripes 42 and 44 are in the same phase position delayed by half a period from 41.43, and the output voltage is the same as that in Fig. 4. can get.

Therefore, in this embodiment, p=100μ and the width of the sensor stripe is WI=eop theory.

By setting 12=15μ, it was possible to make the waveform of the output voltage close to a sine wave as shown in the curve MD of the IJss diagram.

Note that by adopting the arrangement as in this embodiment, the width of the sensor stripe can be set relatively freely.

FIG. 2 shows another embodiment of the present invention, and is a perspective view showing only the sensor stripe.

Sensor stripe 31 in this embodiment.

32. 33. 34 is one in which the width is narrowed midway in the longitudinal direction, that is, the width is narrowed in stages.

In this case as well, it is possible to obtain a waveform of the output voltage close to a sine wave as shown in the line E in FIG. 3.

〔Effect of the invention〕

As described above, the present invention reduces the width of each sensor stripe from one longitudinal end to the other.
It is possible to stably extract an output voltage signal close to a sine wave, which is less affected by variations in spacing, and to accurately detect the rotational state.

[Brief explanation of drawings]

Fig. 1 is a perspective view of an embodiment of the present invention showing the main parts developed, Fig. 2 is a perspective view of only the sensor stripe in another embodiment, and Fig. 3 shows the output voltage of the Britno circuit and the drum. Figure 4 is a perspective view of the main part showing the basic configuration of a magnetic rotation detector, and Figure 5 is a diagram showing the relationship between the resistance value of one sensor stripe and the travel amount of the drum. Figure shown, t
Figures J&8 are diagrams showing the relationship between the output voltage of a bridge circuit composed of four sensor stripes and the amount of movement of the drum. 2: Permanent magnet drum, 31. 32. 33°34
．． 41, 42, 43, 44: Censust 2 Eve, 51. 52. 53. 54: Magnetization pattern agent Patent attorney Takashi Honma
)

Claims (3)

[Claims] (1) A permanent magnet drum whose cylindrical outer circumferential surface is multi-pole magnetized and which is attached to a rotating shaft and rotates in synchronization with the rotating shaft, and a permanent magnet drum that is provided close to the cylindrical outer circumferential surface of the permanent magnet drum. In a magnetic rotation detector equipped with a magnetoresistive element, the magnetized pattern magnetized on the outer circumferential surface of the cylinder is linear striped, and the width of the magnetoresistive element is set to one side with respect to its longitudinal direction. A magnetic rotation detector characterized by narrowing from one side toward the other side. (2) The magnetic rotation detector according to claim 1, wherein the width of the magnetoresistive element is linearly narrowed from one side to the other. (3) The magnetic rotation detector according to claim 1, wherein the width of the magnetoresistive element is gradually narrowed from one side to the other.