JPH01136018A - Apparatus for magnetically detecting position and speed - Google Patents

Abstract

PURPOSE:To perform accurate detection by preventing the generation of histeresis in the direction signal of an MR element, in a position and speed detection apparatus using the MR element, by using two rows of magnetic tracks shifted by a predetermined pitch. CONSTITUTION:Two rows of magnetic tracks T1, T2 shifted by a predetermined pitch lambda are provided in the moving direction of a magnetic recording medium 3 and linear MR elements (magnetoresistance effect elements) R1-R4 are provided to a magnetic sensor substrate 41. By this constitution, since the MR elements R1-R4 are operated by positive and negative magnetic fields by the aforementioned respective magnetic tracks T1, T2, even when there is histeresis in the static characteristics of the MR elements R1-R4, said characteristics are averaged. Therefore, the error of encoder output based on histeresis can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device for magnetically detecting the position and speed of a moving object, and in particular, the present invention relates to a device for magnetically detecting the position and speed of a moving object, and in particular, detecting the position and speed using a magnetoresistive element (hereinafter abbreviated as MR element). The present invention relates to a device for detecting speed.

[Conventional technology]

To detect the angle using an MR element,
There is one described in Publication No. 0-45804.

This publication mainly describes the relative arrangement relationship between the MR element and the magnetic recording medium that generates a periodic magnetic field.

[Problem that the invention seeks to solve]

It has been experimentally confirmed that in this type of MR element used in the present invention and the prior art, hysteresis appears in the resistance change depending on the direction of the applied magnetic field.

This hysteresis has large variations depending on the manufacturing process and the width of the manufactured MR element.

When the MR element is very thin, about 5 μm, there is almost no hysteresis, but when the width is about 20 to 30 μm, hysteresis becomes noticeable. on the other hand.

The output based on the rate of change in resistance is greater when the width is wider, so
Even if there is hysteresis, it is necessary to use a wide MR element.

This hysteresis means that when a magnetic field from the same magnetic pole acts on the same MR sensor, the change in resistance of the MR sensor will be different depending on whether the magnetic field acts from the right side or the left side of the MR sensor. That's true.

Increase the number of output pulses per revolution or unit length,
This hysteresis becomes an obstacle when trying to obtain a high-precision, high-resolution device. That is, even if there is hysteresis, it is necessary to detect the magnetic poles separately from adjacent magnetic poles, so the magnetization pitch of the magnetic poles cannot be made very small.

The state of hysteresis will be explained based on FIGS. 11 to 13.

FIG. 11 is a developed view showing the relationship between the magnetic sensor 4 and the recording medium 3. A magnetic track Tz consisting of magnetic signals of N-S magnetic poles with a recording pitch λ is arranged on the recording medium 3, and the magnetic sensor 4 has MR elements R1 to R4 arranged at a distance of λ/2 from each other. ing. These MR elements R
1 to R4 are bridge-connected as shown in FIG. At this time,
When the recording medium 3 moves, the resistance changes of the MR elements R1-R4 become as shown in FIG. FIG. 13 shows the static characteristics of the MR element showing the resistance change with respect to the magnetic field. As shown in the figure, it has a characteristic of having hysteresis in which the resistance changes are different when the magnetic field is in the positive direction and in the negative direction. Here, suppose that the magnetic field applied to the MR element by the magnetic track T1 as the recording medium 3 moves becomes an input magnetic field Hi as shown in the figure.

The MR element R1 changes with position as shown in the upper right R1 in the figure. Furthermore, the MR element Rz is 1λ/
Since the change is 2tll, the change will be as shown in R2 in the diagram. The resistance changes of these R1 and R2 change in magnitude every cycle as shown in the figure due to the static characteristics of the MR element. For this reason,
The three-terminal output e1 composed of the MR elements R1 and R2 has a waveform of 01 in the diagram, and the output amplitude and period vary in magnitude for each cycle. Similarly, since the three-terminal outputs of the MR elements R3 and R4 are as shown in e2 in the figure, the bridge output e becomes the output e at the lower right in the figure. This output also repeats the amplitude and period in each cycle, resulting in a large error.

The above-mentioned conventional technology does not indicate that the static characteristics of the MR element have hysteresis, in which resistance changes differ depending on positive and negative magnetic fields, and therefore there is a problem in that errors occur in the output.

An object of the present invention is to provide a position detection device that does not cause errors in encoder output even if there is hysteresis in the static characteristics of an MR element.

[Means for solving problems]

The present invention has been made focusing on the above, and includes first and second members that relatively move with a minute gap, a magnetic recording medium supported by the first member, and movement of the magnetic recording medium. a magnetic track having a large number of magnetic poles arranged at a predetermined pitch in a direction; a base body of a magnetic sensor carried by the second member and placed close to the magnetic recording medium; A magnetoresistive element (hereinafter abbreviated as MR element) that changes and is supported on the base, and this MR
The change in resistance of the element is extracted as an electrical signal and used as the first signal. In the device for detecting the mutual positions and speeds of the second members, at least two rows of the magnetic tracks are provided, each magnetic track is provided with a magnetic pole shifted by a pitch λ with respect to the other magnetic track, and the magnetic The sensor base is provided with a linear MR element that is sensitive to the magnetic fields of both tracks, so that even if the direction of relative movement of the two members changes, an output signal indicating the correct position can be obtained.

[Effect]

As described above, since each MR element operates with positive and negative magnetic fields, their hysteresis is averaged out. This acts to compensate for the magnitude of the amplitude for each cycle, so that no errors occur in the position detection output.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5. FIG. 1 shows the configuration of the present invention.

This figure shows an example of a rotation sensor, in which a first member such as a rotating drum 2 is fixed to a rotating shaft 1, and a magnetic signal of N-3 magnetic poles with a recording pitch λ is transmitted to a magnetic recording medium 3 on the outer circumference of the first member, for example, a rotating drum 2. The two magnetic tracks Tl and T2 recorded on the magnetic tracks T1 and T2 are arranged such that the recording positions of the magnetic poles, which serve as magnetic signals, are shifted from each other by λ. Opposing this, MR elements R1, R21R3 and R4
A second member, such as a magnetic sensor 4 including a magnetic sensor substrate 41, is arranged at a certain distance spacing from the magnetic tracks TI and T2. The relationship between the magnetic tracks Tl and T2 on the magnetic recording medium 3 in FIG. 1 and the magnetic sensor 4 is shown in a developed view in FIG. 2(A). In Figure 2,
As mentioned above, the magnetic track T1 of the magnetic recording medium 3I-
And in T2, magnetic signals of N, S8 & poles are recorded at a recording pitch λ. In the magnetic tracks Tz and T2, in order to compensate for the hysteresis of the MR elements R1 to R4, the recording position of the magnetic signal of the magnetic track T2 is shifted by λ in the movement direction with respect to the magnetic signal of the magnetic track T1. The magnetic sensor 4 is composed of MR elements R1 to R4, and each MR element is spaced apart from each other by λ/2 and faces the magnetic tracks T1 and T2 so as to receive the magnetic signals from the tracks in the same manner. These four MR elements R1 to R4 are connected as shown in FIG. On the other hand, the MR elements R1 to R4 are shown in FIGS.
As shown in the figure, the magnetic signals of the magnetic tracks T1 and T2 are shifted by λ, so for example, in the case of the MR element of R1, the MR element of R1 is divided into the upper half and the lower half by the magnetic tracks T1 and T2. It operates in such a way that it receives both positive and negative magnetic fields. That is, when the upper half of Ri is in the magnetic field of the N-3 magnetic pole (S-N magnetic pole) of the magnetic track T+, the lower half of R1 is in the magnetic field of the N-3 magnetic pole (S-N magnetic pole) of the magnetic track T2.
It receives a magnetic field of 8faViA). Therefore.

The MR element of Ri receives the magnetic field from the magnetic track T1, and the MR element of Rlz receives the magnetic field from the magnetic track T2.
Think of it as a series connection of elements. Similarly, the MR element of R2 is Rz
Since the MR elements of 1, Rzz, and Ra can be considered to be a series connection of Rat and R3Z, and the MR element of R4 is a series connection of Ras and R42, the connection diagram of FIG. 3 can be replaced with the connection diagram of FIG. 4. Here, it is assumed that the static characteristics of the magnetoresistive element have hysteresis as shown in FIG. When the magnetic drum 2 rotates, a magnetic field corresponding to the magnetic signals from the magnetic tracks T1 and T2 is applied to each of the magnetoresistive elements R1 to R4. For example, the magnetic track Tl causes the magnetoresistive element R1 to
If the magnetic field applied to t is the input magnetic field H1 as shown in the figure, this magnetic field changes from positive to negative depending on the position (rotational position Jiff of the magnetic drum 2), so the resistance of the magnetoresistive element Rss corresponds to It changes like a solid line. This resistance change varies in size every cycle due to the hysteresis of the magnetoresistive element. Furthermore, two cycles of resistance change occur in one cycle of the input magnetic field Hi. On the other hand, the magnetoresistive element R12 receives a magnetic field from the magnetic track T2 in which the recording position of the magnetic signal is shifted by λ with respect to the magnetic signal of the magnetic track TI, so the input magnetic field Hi is shifted by 180 degrees and the resistance change is also as indicated by the broken line Rrz. It will look like this. Comparing the resistance changes of R11 and Rsx, it appears that the phase of the resistance change is shifted by J degrees by one cycle. Therefore.

When magnetoresistive elements R11 and R12 are connected in series and added together as shown in Fig. 4, the resistance of MR element R1 shown in Fig. 3 has a waveform as shown in Fig. 5 (R11+R12), and magnetoresistive element Rrt and The waveform becomes an average of the resistance change of R12, and the amplitude of each cycle is not large or small. Also,
Similarly, the combined output of MR elements R21 and R22 is the fifth
The resistance change is shown by the broken line (Rzx + R2z) in the figure. Therefore, the three-terminal output e1 in FIG. 4 is the solid line e in the cloth in FIG.
It will have a waveform like 1.

In addition, MR elements Rsl, R32 and R4□, R4□
The three-terminal output e2 configured as shown in FIG.

Therefore, the bridge output becomes the difference between el and 02 as shown in e in the lower right corner of FIG. This output has no amplitude or cycle size for each cycle, and a highly accurate output can be obtained.

In addition, as shown in FIG. 2(B), the magnetic troughs 11, 1
There are no magnetic poles between the two. therefore.

There is no point in having a magnetically sensitive part of the MR element in this part, and it becomes a resistance and causes a decrease in the output. As a countermeasure, this part was made wider as shown in Fig. 2 (B). According to this, a large output can be obtained since the first wide portion Rz' does not act as a resistance.

Although the above example uses two magnetic tracks, other embodiments configured with three or more magnetic tracks are shown in FIGS. 6 and 7. FIG. 6 is a developed view showing the relationship between the magnetic track and the magnetic sensor. The magnetic tracks are composed of three (odd number) T1 to T8, and the recording positions of the magnetic signals of the odd-numbered magnetic tracks T1 and T3 are the same, and the magnetic signals of the even-numbered magnetic tracks T2 are the same. The recording position is shifted by λ with respect to the magnetic signal of T3. On the other hand, the arrangement of the MR element Rl''R4 of the magnetic sensor 4 is the same as that shown in Figs. 1 and 2, but the length Ll of the MR element is different from the width T of one magnetic track. As L L''F2TL, both ends of the MR element are arranged to face approximately half of the magnetic tracks Tr and T3. In this way, even if there is a shift in the longitudinal direction of the MR element between the magnetic sensor 4 and the magnetic tracks T1 to T8, the magnitude of the positive and negative magnetic fields that the MR element Rs''R4 receives from the magnetic tracks T1 to T3 can be equalized. Can be done.

That is, for example, if the magnetic sensor 4 is shifted toward the magnetic track Ti at the position of point P of the magnetic signal, the MR
Elements R1-R4 receive S-N from magnetic track T3.
Although the magnetic field of the magnetic pole decreases, the magnetic field of the S-N magnetic pole received from the magnetic track T1 increases, so that the magnetic field of the N-3 magnetic pole received from the magnetic track T2 and the magnetic tracks T1 and T2
Since the magnetic fields of the S and N magnetic poles received from the magneto-resistance element can be made equal, the hysteresis of the MR element can be compensated for even if the longitudinal positional deviation of the magnetoresistive element occurs.

Figure 7 shows the magnetic track T! ~4 T4 (even number)
Similarly to FIG. 6, the recording positions of the magnetic signals of the odd-numbered magnetic half tracks T1 and T3 are the same, but the magnetic signals of the even-numbered magnetic tracks T2 and T4 are The recording position is shifted by λ with respect to the magnetic signal. Four MR elements Rai to R of the magnetic sensor 4
The arrangement of at is the same as that in Fig. 6, but the length Ll of the MR element Ra i '' Ra 2 is set to the innermost two magnetic tracks T2 and Tδ of the four (even number) magnetic tracks. It is made almost the same as the track width Tbz.In this way, even if there is a positional shift in the longitudinal direction of the MR element like the one in FIG.
-3 magnetic pole and S-N magnetic pole are equally received, so M
The hysteresis of the R element can be compensated for.

Further, in the above description, the magnetic sensor 4 has been described as an example of a one-phase output, but FIG. 8 shows another embodiment of a two-phase output.

Magnetic tracks T1 and T2 on the magnetic recording medium 3 in FIG.
FIG. The configuration of magnetic tracks T1 and T2 is the same as in the embodiment of FIG.

The MR element of the magnetic sensor 4 is Raae Raat Raa
It is composed of eight MR elements: e Raat Rb1y RbZ+Rba and Rb4, and the intervals between the respective MR elements are shifted by λ/4. These eight MR elements are connected as shown in FIG. The resistance change of each MR element is the same as in the previous embodiment. In FIG. 8, in order to obtain a two-phase output, the MR element Rb
s HRb 2 gRl, 3 and R1, 4 as MR element R
at+ Raz+ Raa and Ra4 are arranged with their positions shifted by λ/4.

An output eb similar to that shown in FIG. 5 is obtained in which only the phase difference is shifted by 90 degrees from ea. According to this embodiment, since the output of the magnetic sensor is a two-phase output that is shifted by 90 degrees from each other, it can be used as a rotation sensor capable of determining the rotation direction of a rotating body.

FIG. 10 shows an example in which the magnetic tracks TI and Tl are constructed from separate rotating drums 2 and 2', respectively. In this way, there is no need to create a new rotating drum, so there is an effect that the previously used rotating drum can be used.

In the above example, an example of a single rotating body has been explained, but the same effect can be obtained even if it is used to detect the position of an object other than a rotating body that performs linear motion. Further, the same effect can be obtained even if the entire rotating drum is made of a permanent magnet such as a plastic magnet.

〔Effect of the invention〕

As explained above, the present invention provides a first lens that moves with a relatively small gap. a second member, a 6J1 recording medium supported by the first member, a magnetic track having a large number of magnetic poles arranged at a predetermined pitch in the direction of movement of the magnetic recording medium, and a magnetic track supported by the second member; and a base body of a magnetic sensor placed close to the magnetic recording medium; a magnetoresistive element (hereinafter abbreviated as MR element) whose internal resistance changes in response to the magnetic field of the magnetic pole and supported on the base body; The resistance change of the MR element is extracted as an electrical signal and the first. In the device for detecting the mutual positions and speeds of the second members, at least two rows of the magnetic tracks are provided, each magnetic track is provided with a magnetic pole shifted by a pitch λ with respect to the other magnetic track, and the magnetic Since the sensor base is provided with a linear MR element that is sensitive to the magnetic fields of both tracks, hysteresis can be removed from the detection signal of the MR element. Even if the relative movement direction of the second member changes, the first member. The accurate relative position and correct speed of the second member can be detected.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 (A) is a developed view showing the relationship between the magnetic recording medium and the magnetic sensor in FIG. 1, and FIG. 2 (B) is an improved magnetic sensor. Developed diagram, 3rd
The figure is a connection diagram of the MR element, FIG. 4 is an equivalent connection diagram when the MR element is operating, and FIG. 5 is a diagram explaining the operation of the present invention.
FIGS. 6 to 8 are developed views of the magnetic recording medium, magnetic sensor, and magnetic sensor according to other embodiments, and FIG. 12 is the conventional M
The connection diagram of the R element, FIG. 13, is an explanatory diagram of the operation of the prior art. 1... Rotating shaft, 2, 2'... Rotating drum, 3...
Magnetic recording medium, 4... Magnetic sensor, R... Magnetoresistive element, λ... Recording pitch of magnetic signal, Tl, Tl
...magnetic track, ex, e2. eal+e
a2. ebl+ebz"'3 terminal output voltage, e, ea
, eb...Bridge output voltage, Hi...Input magnetic field.

Claims (1)

[Claims] 1. First and second members that move with a relatively small gap, a magnetic recording medium supported by the first member, and a predetermined pitch in the direction of movement of the magnetic recording medium. a magnetic track having a large number of magnetic poles arranged thereon; a base body of a magnetic sensor carried by the second member and brought close to the magnetic recording medium; Magnetoresistive element (hereinafter abbreviated as MR element) supported on the base
The resistance change of the MR element is extracted as an electric signal to detect the mutual position and speed of the first and second members, wherein at least two rows of the magnetic tracks are provided, and each magnetic track has a Magnetic position and velocity characterized in that magnetic poles are provided on each magnetic track shifted by a pitch λ with respect to other magnetic tracks, and a linear MR element sensitive to the magnetic fields of both tracks is provided on the magnetic sensor base. A device that detects 2. In the device according to claim 1, the magnetic tracks are provided in three or more rows, and the magnetic poles of adjacent magnetic tracks are shifted from each other by a pitch λ with respect to the other magnetic tracks. The length of the MR element is approximately twice the width of one magnetic track, and the MR element is arranged so that the center of the MR element is aligned with the center or a magnetic track near the center of the magnetic tracks. A device that magnetically detects position and speed. 3. An apparatus for magnetically detecting position and velocity according to claim 1, characterized in that a plurality of magnetic tracks are formed on the same magnetic recording medium. 4. The device according to claim 1, wherein the plurality of magnetic tracks are formed on independent magnetic recording media.