JP2539470B2 - Device that magnetically detects position and speed - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for magnetically detecting the position and speed of a moving body, and in particular, using a magnetoresistive effect element (hereinafter abbreviated as MR element) The present invention relates to a device for detecting speed.

[Conventional technology]

Japanese Patent Publication Sho 60
-There is one described in Japanese Patent No. 45804.

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

[Problems to be solved by the invention]

It has been experimentally confirmed that the MR element of this type used in the present invention and the prior art exhibits hysteresis in resistance change depending on the direction of an applied magnetic field. This hysteresis has a large variation depending on the manufacturing process and the width of the manufactured MR element.

When the MR element is about 5 μm and very thin, there is almost no hysteresis, but when it is set to a width of about 20 to 30 μm, the hysteresis appears remarkably. On the other hand, since the output based on the resistance change rate is larger when it is wider, it is inevitable to use a wide MR element even if there is hysteresis.

This hysteresis means that when the magnetic field from the same magnetic pole acts on the same MR sensor, when this magnetic field acts from the right direction of the MR sensor and when it acts from the left direction,
This means that the resistance change of the MR sensor is different.

This hysteresis becomes an obstacle when trying to obtain a highly accurate and high resolution device by increasing the number of output pulses per revolution or unit length. That is, even if there is hysteresis, it is necessary to detect the magnetic poles separately from the adjacent magnetic poles, and therefore the magnetizing pitch of the magnetic poles cannot be made too small.

The state of hysteresis will be described with reference to FIGS. 11 to 13.

FIG. 11 is a development view showing the relationship between the magnetic sensor 4 and the recording medium 3. On the recording medium 3, a magnetic track T ₁ composed of a magnetic signal of the NS magnetic pole of the recording pitch λ is arranged, while the magnetic sensor 4 is arranged by separating the MR elements R _{1 to} R ₄ by λ / 2. are doing. These MR elements R _{1 to} R ₄ are bridge-connected as shown in FIG. At this time, if the recording medium 3 moves, the resistance changes of the MR elements R _{1 to} R ₄ become as shown in FIG. FIG. 13 shows static characteristics showing the resistance change of the MR element with respect to the magnetic field.
As shown in the figure, the magnetic field has a hysteresis having different resistance changes in the positive and negative directions. Here, if the magnetic field applied to the MR element by the magnetic track T ₁ by moving the recording medium 3 is the input magnetic field Hi as shown in the figure, the MR element R ₁ changes with the position as shown in the upper right R _{1 in} the figure. . MR element R ₂ is an MR element
Since it is 1λ / 2 away from R ₁ , the change is as shown in R ₂ . These resistance changes of R ₁ and R ₂ are large or small every cycle due to the influence of the static characteristics of the MR element. Therefore, the 3-terminal output e ₁ composed of MR elements R ₁ and R ₂ is
With the waveform of e _1, the amplitude of the output and the size of the cycle occur every cycle. Similarly, the 3-terminal output of MR elements R ₃ and R ₄ is also shown in the figure e ₂
Therefore, the bridge output e is the output e at the lower right of the figure. This output also repeats the magnitude of the amplitude and the cycle for each cycle, resulting in a large error.

The above-mentioned prior art has not disclosed that the static characteristic of the MR element has a hysteresis in which the resistance change is different between positive and negative magnetic fields, and therefore there is a problem that an error occurs in the output.

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

[Means for solving problems]

The present invention has been made in view of the above, and includes a first member, a second member that move with a relatively small gap, and a first member.
A magnetic recording medium carried by the member, a magnetic track having a large number of magnetic poles arranged in a predetermined pitch in the moving direction of the magnetic recording medium, and a magnetic track carried by the second member and brought close to the magnetic recording medium. The base of the magnetic sensor, the magnetoresistance effect element (hereinafter abbreviated as MR element) carried on the base whose internal resistance changes in response to the magnetic field of the magnetic pole, and the resistance change of this MR element are used as an electric signal. In the one for taking out and detecting the position and speed of the first and second members, at least two rows of the magnetic tracks are provided, and each magnetic track is displaced from each other by a pitch λ with respect to each other. Each magnetic pole is provided, and the magnetic sensor base is provided with a linear MR element that is sensitive to the magnetic fields of the two tracks. Even if the relative movement directions of the two members change, an output signal indicating the correct position can be obtained. It is those that you have configured.

[Action]

As described above, since each MR element operates in a positive or negative magnetic field, the hysteresis is averaged out. As a result, the amplitude of each cycle is compensated, so that an error does not 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 structure of the present invention. This drawing is an example of a rotation sensor, in which a first member, for example, a rotary drum 2 is fixed to a rotary shaft 1, and the magnetic signals of the N and S magnetic poles of the recording pitch λ are all around the magnetic recording medium 3 around the first member. Recorded in 2
The two magnetic tracks T ₁ and T ₂ are arranged such that the recording positions of the magnetic poles which become magnetic signals are shifted from each other by λ. The magnetic sensor 4 including a second member composed of the MR elements R ₁ , R ₂ , R ₃ and R ₄ facing this, for example, a magnetic sensor base 41, is connected to the magnetic track T _1.
And T _{2 with} a certain spacing. The relationship between the magnetic tracks T ₁ and T ₂ on the magnetic recording medium 3 of FIG. ₁ and the magnetic sensor 4 is shown in FIG. 2 (A) as a developed view. Second
In the drawing, as described above, the magnetic signals of the N and S magnetic poles are recorded on the magnetic tracks T ₁ and T ₂ on the magnetic recording medium 3 by the recording pitch λ. The magnetic tracks T ₁ and T ₂ are MR elements R ₁
To compensate for hysteresis to R _4, the magnetic signal of the magnetic track T _1, the magnetic signal of the magnetic track T ₂ are are shifted λ the recording position in the movement direction. Magnetic sensor 4 is an MR element
Is composed of R ₁ to R _4, each MR element are opposed to each lambda / 2 away both as receiving a magnetic signal from the magnetic track T ₁ and T ₂ in the same way to track. These four MR elements R ₁
Connect ~ R _{4 as} shown in Fig. 3. On the other hand, since the magnetic signal of the MR element R ₁ to R ₄ are magnetic tracks T ₁ and T ₂ as shown in FIGS. 1 and 2 are shifted by contact each other lambda, for example, in MR elements R ₁ In other words, the magnetic tracks T ₁ and T ₂ cause the MR element of R ₁ to operate so that the upper half and the lower half receive the positive magnetic field and the negative magnetic field in the same manner. That is, the upper half of the R ₁ is N · S pole of the magnetic track T ₁ when in the magnetic field of the (S · N pole), S · N pole of the magnetic track T ₂ are the lower half of R ₁ (N · S pole) Receive a magnetic field. Therefore, the MR element of R ₁ has a magnetic field of R ₁₁ that receives the magnetic field from magnetic track T ₁ and a magnetic field of R ₁₂ that receives the magnetic field of magnetic track T ₂ .
Consider it as a series connection of MR elements. Similarly, the MR element of R ₂ is R ₂₁ and R
_Since the MR element of ₂₂ and R ₃ can be considered to be the series connection of R ₃₁ and the MR element of R ₃₂ and R ₄ to R ₄₁ and R ₄₂ , the connection diagram of FIG.
Replaced by the connection diagram in the figure. Here, it is assumed that the static characteristic of the magnetoresistive element has a hysteresis characteristic as shown in FIG. When the magnetic drum 2 rotates, each magnetoresistive element R ₁
Magnetic field corresponding to a magnetic signal from the magnetic track T ₁ and T ₂ are added in to R _4. For example, if the magnetic field applied to the magnetoresistive element R ₁₁ by the magnetic track T ₁ is an input magnetic field H _i as shown in the figure, this magnetic field changes positively and negatively depending on the position (rotational position of the magnetic drum 2). Correspondingly, the resistance of the magnetoresistive element R ₁₁ changes as shown by the solid line in the upper right of the figure. This resistance change is large or small every cycle due to the influence of the hysteresis of the magnetoresistive element. In addition, the resistance change occurs in two cycles in one cycle of the input magnetic field Hi. On the other hand, the magnetoresistive element R ₁₂
Receives the magnetic field from the magnetic track T _{2 that} shifts the recording position of the magnetic signal by λ with respect to the magnetic signal of the magnetic track T ₁ , the input magnetic field Hi is shifted by 180 degrees, and the resistance change is similar to the broken line R ₁₂ . Become. If you compare the resistance changes of R ₁₁ and R ₁₂ , J
The phase of the resistance change is shifted by one cycle. Therefore, when the magnetoresistive elements R ₁₁ and R ₁₂ are added in series as shown in FIG. 4, the resistance of the MR element R ₁ shown in FIG. 3 is as shown in FIG. 5 (R ₁₁ + R ₁₂ ). Waveform, the magnetoresistive element R ₁₁
And the averaged waveform of the resistance change of R ₁₂ , the amplitude of each cycle disappears. Similarly, MR element
The combined output of R ₂₁ and R ₂₂ is the resistance change of the broken line (R ₂₁ + R ₂₂ ) in FIG. Therefore, the three-terminal output e _{1 in} FIG. 4 has a waveform as shown by the solid line e _{1 in} the right part of FIG. In addition, MR elements R ₃₁ , R ₃₂
The three-terminal output e ₂ constituted by R ₄₁ and R ₄₂ is exactly the same except that the phase is shifted by 180 degrees, and becomes like the broken line e _{2 in} the right side of FIG. Therefore, the output of the bridge becomes the difference e between e ₁ and e ₂ as shown by e in the lower right of FIG. This output does not have a large amplitude or a small cycle for each cycle, and a highly accurate output can be obtained.

As shown in FIG. 2 (B), the magnetic tracks T ₁ , T ₂
There is no magnetic pole between them. Therefore, it is meaningless to have the magnetic sensitive portion of the MR element in this portion, and it becomes a resistance, which in turn causes a decrease in output. As a countermeasure against this, FIG. 2B shows that this portion is widened. According to this, a large output can be obtained because the wide portion R ₁ ′ does not become a resistance.

The above is an example of two magnetic tracks, but another embodiment constituted by three or more magnetic tracks is shown in FIGS. 6 and 7. FIG. 6 is a development view showing the relationship between the magnetic track and the magnetic sensor. The magnetic track is three T ₁ through T ₃ constitutes in (odd number), the odd-numbered T ₁ and T ₃ of the magnetic track magnetic signal recording positions of even-numbered T ₂ the same magnetic track The recording position of the magnetic signal is shifted by λ with respect to the magnetic signals of T ₁ and T ₃ . On the other hand, the MR element of the magnetic sensor 4
R ₁ is the arrangement of to R ₄ are the same as those shown in FIGS. 1 and 2, the width of the length L ₁ of the MR element is one magnetic track T _L with respect to L ₁ ≒ 2T _L Both ends of the MR element are magnetic tracks T ₁
And T ₃ are set to face each other by almost half. Positive and negative longitudinal direction of the MR element is also displaced occurs R ₁ to R ₄ of the MR element between the magnetic sensor 4 and the magnetic tracks T ₁ through T ₃ With this manner receives from the magnetic track T ₁ through T ₃ You can equalize the magnitude of the magnetic field. That is, for example, at the position of point P of the magnetic signal,
If the magnetic sensor 4 is displaced to the magnetic track T ₁ side, MR
In the elements R _{1 to} R ₄ , the magnetic field of the S / N magnetic poles received from the magnetic track T ₃ decreases, but the magnetic field of the S / N magnetic poles received from the magnetic track T ₁ increases, so that the elements R _{1 to} R ₄ receive the N from the magnetic track T _2.
・ S received from the magnetic field of the S magnetic pole and the magnetic tracks T ₁ and T ₂
Since the magnetic fields of the N magnetic poles can be made equal to each other, hysteresis of the MR element can be compensated even if the longitudinal displacement of the magnetoresistive element occurs.

FIG. 7 shows an example in which the magnetic tracks are composed of four (even number) T _{1 to} T ₄ , and the magnetic signal recording positions of the odd-numbered magnetic half-tracks T ₁ and T ₃ are the same as in FIG. Although the same, the magnetic signal of the even-numbered magnetic tracks T ₂ and T ₄ are, T ₁ and T ₃
The recording position is shifted by λ with respect to the magnetic signal of. The arrangement and the like of the four MR elements R _{a1 to} R _a4 of the magnetic sensor 4 are the same as those in FIG. 6, but the length L ₁ of the MR elements R _{a1 to} R _a2 is four (even number) of magnetic fields. The track width T _L2 of the innermost two magnetic tracks T ₂ and T ₃ of the tracks is made substantially the same. By doing so, even if the MR element is displaced in the longitudinal direction as in the case of FIG. 6, the MR elements R _{a1 to} R _a4 are N.
Since the magnetic fields of the S magnetic pole and the S / N magnetic pole are evenly received, the hysteresis of the MR element can be compensated.

Further, in the above description, the magnetic sensor 4 is described as an example of one-phase output, but FIG. 8 shows another embodiment of two-phase output. Magnetic tracks T ₁ and T ₂ on the magnetic recording medium 3 of FIG.
4 is a development view showing the relationship between the magnetic sensor 4 and the magnetic sensor 4. The structure of the magnetic tracks T ₁ and T ₂ is the same as that of the embodiment shown in FIG. The MR elements of the magnetic sensor 4 are R _a1 , R _a2 , R _a3 , R _a4 , R _b1 , R _b2 , R _b3 and R
It is composed of eight _b4 , and the MR elements are arranged with a gap of λ / 4. The 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, MR elements R _b1 , R _b2 ,
Since R _b3 and R _a4 are arranged so that the MR elements R _a1 , R _a2 , R _a3 and R _a4 are displaced from each other by λ / 4 position, only the phase difference is shifted by 90 degrees from e _a . The output e _b is obtained. According to this embodiment, since the outputs of the magnetic sensors are two-phase outputs which are deviated from each other by 90 degrees, it can be used as a rotation sensor capable of discriminating the rotating direction of the rotating body.

FIG. 10 shows an example in which the magnetic tracks T ₁ and T ₂ are composed of separate rotating drums 2 and 2 ', respectively. In this way, there is no need to newly create a rotary drum, and thus there is an effect that the rotary drum that has been used conventionally can be diverted.

In the above example, the example of the rotating body has been described, but the same effect can be obtained by using the rotating body other than the rotating body to detect the position. The same applies even if the entire rotary drum is made of a permanent magnet such as a plastic magnet.

〔The invention's effect〕

As described above, according to the present invention, the first and second members that move with a relatively small gap, the magnetic recording medium carried by the first member, and the predetermined direction in the moving direction of the magnetic recording medium are provided. A magnetic track having a large number of magnetic poles arranged by a pitch;
Of the magnetic sensor, which is carried by the member of (1) and which is brought close to the magnetic recording medium, and the magnetoresistive effect element (hereinafter referred to as MR element) carried by the base whose internal resistance changes in response to the magnetic field of the magnetic pole. Abbreviated), the resistance change of the MR element is extracted as an electric signal to detect the position and speed of the first and second members, and at least two rows of the magnetic tracks are provided, and each magnetic track is provided in each of the magnetic tracks. Are provided with magnetic poles shifted from each other by pitch λ with respect to each other, and a linear MR element sensitive to the magnetic fields of the two tracks is provided on the magnetic sensor base. Since the hysteresis can be eliminated, the accurate relative position and correct velocity of the first and second members can be detected even if the relative movement directions of the first and second members change.

[Brief description of drawings]

1 is a block diagram showing an embodiment of the present invention, FIG. 2 (A) is a development view showing the relationship between the magnetic recording medium of FIG. 1 and a magnetic sensor, and FIG. 2 (B) is an improved magnetic sensor. Fig. 3 is a connection diagram of the MR element, Fig. 4 is an equivalent connection diagram when the MR element is operating, Fig. 5 is an operation explanatory diagram of the present invention, and Figs. FIG. 9 is a development view of a magnetic recording medium and a magnetic sensor according to another embodiment of the figure, FIG. 9 is a connection diagram of an MR element according to another embodiment, FIG. 10 is a configuration diagram showing another embodiment, and FIG. FIG. 12 is a development view of a magnetic recording medium and a magnetic sensor of the technology, FIG. 12 is a connection diagram of a MR element of the related art, and FIG. 13 is an operation explanatory diagram of the related art. 1 ... Rotating shaft, 2, 2 '... Rotating drum, 3 ... Magnetic recording medium, 4 ... Magnetic sensor, R ... Magnetoresistive effect element, λ
…… Magnetic signal recording pitch, T ₁ , T ₂ …… Magnetic track, e
₁ , e ₂ , e _a1 , e _a2 , e _b1 , e _b2 …… 3-terminal output voltage, e, e _a , e _b …
… Bridge output voltage, Hi …… Input magnetic field.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-58-154612 (JP, A) JP-A-62-192615 (JP, A) JP-A 64-16924 (JP, A)

Claims (4)

(57) [Claims] 1. A first device that moves with a relatively small gap,
A second member, a magnetic recording medium carried by the first member, a magnetic track having a large number of magnetic poles arranged in a predetermined pitch in the moving direction of the magnetic recording medium, and carried by the second member, A base of a magnetic sensor which is placed close to the magnetic recording medium, a magnetoresistive effect element (hereinafter abbreviated as MR element) carried on the base whose internal resistance changes in response to the magnetic field of the magnetic pole, and the MR In a device for detecting a change in resistance of an element as an electric signal to detect a position and a velocity between the first and second members, at least two rows of the magnetic tracks are provided, and each magnetic track mutually has another magnetic track. A magnetic position and velocity detecting device characterized in that magnetic poles are provided by being shifted by pitch λ with respect to each other, and linear MR elements that are sensitive to the magnetic fields of the two tracks are provided on the magnetic sensor base body. . 2. The apparatus according to claim 1, wherein the magnetic tracks are provided in three or more rows, and adjacent magnetic tracks are arranged with magnetic poles shifted from each other by pitch λ. On the other hand, the length of the MR element is set to be twice as long as the width of one magnetic track, and the center of the MR element is arranged so as to be aligned with the center of the magnetic track or a magnetic track near the center. A device that magnetically detects position and speed. 3. An apparatus for magnetically detecting a position and velocity according to claim 1, wherein a plurality of magnetic tracks are formed on the same magnetic recording medium. 4. An apparatus for magnetically detecting position and velocity according to claim 1, wherein the plurality of magnetic tracks are formed on independent magnetic recording media.