JP5054586B2 - Magnetic encoder - Google Patents

Description

  The present invention relates to a magnetic encoder, and more particularly to a magnetic encoder including a GMR sensor using a GMR element as a magnetic sensor.

  Conventionally, a magnetic encoder using a magnetoresistive effect element (GMR (giant magneto resistive) element) using a giant magnetoresistive effect has been used as a sensor for detecting the rotation direction and rotation angle of a rotor such as a stepping motor. Yes. In this magnetic encoder, the output of the AB2 phase is provided, and the rotation direction is detected by the phase difference between the A phase and the B phase.

For example, as shown in FIGS. 13 and 14, A-phase GMR elements 2a to 2d and B-layer GMR elements 3a to 3d are provided, and a disk-shaped multipolar magnet body facing these GMR elements is rotated. Thus, an A phase output and a B phase output are obtained. Based on the timing difference between the rise of the A-phase output waveform and the rise of the B-phase output waveform, the rotation direction of the disk-shaped multipolar magnet body is detected.
Japanese Patent Laid-Open No. 2007-199007

  By the way, in a general encoder, AB both-phase GMR sensors can be arranged in a row, but in a high-density encoder, the number of GMR elements per magnetization pitch of the disk-shaped multipole magnet body is large. It was difficult to line up in a row. Therefore, in the high-density encoder, there is a problem that the outer shape becomes large because it is necessary to provide a sensor for two phases AB.

  The present invention has been made in view of such problems, and an object thereof is to provide a magnetic encoder that is much smaller.

The magnetic encoder of the present invention moves in a predetermined direction, a magnet body in which a plurality of magnetic poles composed of N poles and S poles are alternately magnetized along the moving direction, and in the moving direction in the vicinity of the magnet body. A plurality of magnetoresistive elements, the plurality of magnetoresistive elements are connected in series, one end of which is connected to the power supply terminal, and the other end is connected to the magnetic sensor. While connecting to the ground terminal, the middle point dividing the plurality of magnetoresistive effect elements connected in series into the same number as the output terminal of the magnetic sensor, the magnetoresistive element closer to the power supply terminal than the middle point, The magnetoresistive elements on the ground terminal side are alternately arranged along the moving direction,
The moving direction of the magnet body is detected by detecting whether the pulse voltage output from the output terminal increases or decreases as the magnet body moves.

  According to the above magnetic encoder, since the direction of movement can be detected using a single-phase magnetoresistive element, a much smaller magnetic encoder can be realized.

  In the magnetic encoder, it is preferable that the magnet body is a rotating body, and an N pole and an S pole are magnetized along the rotation direction on the outer peripheral side surface of the rotating body. In this case, since the rotation direction can be detected using a single-phase magnetoresistive element, a much smaller rotary magnetic encoder can be realized.

  In the magnetic encoder, it is preferable that the plurality of magnetoresistive elements of the magnetic sensor are arranged so that the resistance value becomes larger or smaller in the order of arrangement in the moving direction. In this case, since the change in the output voltage value of the output terminal becomes significant as the magnet body moves, the moving direction can be detected more easily.

  In the magnetic encoder, it is preferable that the plurality of magnetoresistive elements of the magnetic sensor are arranged within a range corresponding to one pole of magnetization of the magnet body. In this case, pulses corresponding to the number of magnetoresistive elements can be obtained while the magnet body moves by one pole. The moving direction can be detected based on the change in the peak value of the pulse.

  According to the present invention, a much smaller magnetic encoder can be provided.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
As shown in FIG. 1, the magnetic encoder 10 is a device that detects, for example, a rotation angle, a rotation direction, a rotation speed, or the like, and mainly includes a magnet body 11 and a rotating body 12 that rotatably supports the magnet body 11. It has a housing 9 that rotatably supports the rotating body 12 and a magnetic sensor 20 made of a magnetoresistive effect element.

  The magnet body 11 is formed in a ring shape, and its inner surface is fixed to the outer peripheral side surface of the rotating body 12 formed in a disk shape. On the outer peripheral side surface 11A of the magnet body 11, a magnetic pattern in which a plurality of magnetic poles composed of N poles and S poles are alternately magnetized is formed.

  The magnet body 11 and the rotating body 12 are disposed in a circular recess 9 </ b> A provided in the housing 9. As shown in FIG. 2, a center hole 9 a is formed at the center of the housing 9, and a rotating shaft 12 a formed at the center of the rotating body 12 is inserted. The magnet body 11 is rotatably supported in the rotation direction ra1 or the rotation direction ra2 in the recess 9A with the rotation shaft 12a of the rotation body 12 as an axis center.

  The housing 9 is formed with a notch 9b in which a part of the recess 9A is notched in the outer circumferential direction, and the magnetic sensor 20 faces the outer circumferential surface 11A of the magnet body 11 in the notch 9b. So that it is fixed. The magnetic sensor 20 is provided with a plurality of magnetoresistive elements A (individually indicated as R11, R21, R12, R22, R13, R23).

  As shown in FIG. 3, the magnetic sensor 20 includes a plurality of magnetoresistive elements R11 to R23 arranged in a line, and every other one of the magnetoresistive elements R11 to R23 arranged in the line. The arranged magnetoresistive effect elements R11, R12 and R13 are connected in series, and every other arranged magnetoresistive effect elements R21, R22 and R23 are connected in series.

  In addition, the magnetoresistive effect elements R11 to R13 and R21 to R23 connected in series are connected in series as a whole by connecting the magnetoresistive effect elements R11 and R21. An output terminal TO is connected between the magnetoresistive elements R11 and R21. The magnetoresistive element R13 is connected to a power supply terminal T1, and the magnetoresistive element R23 is connected to a ground terminal T2.

  In addition, these magnetoresistive effect elements R13 to R23 provided in the magnetic sensor 20 are arranged so as to be within a range of one pole of the N pole (or S pole) of the magnet body 11.

  FIG. 4 is a diagram illustrating a connection state of the magnetoresistive elements R11 to R23, the output terminal TO, the power supply terminal T1, and the ground terminal T2 arranged in the magnetic sensor 20 illustrated in FIG. As shown in FIG. 4, six magnetoresistive elements R11 to R23 having the same resistance value are connected in series between the power supply terminal T1 and the ground terminal T2, and the three magnetoresistive elements R11 to R13 are connected in series. The output terminal TO is connected to a position where the three magnetoresistive elements R21 to R23 are separated (between the magnetoresistive elements R11 and R21).

  That is, the plurality of magnetoresistive effect elements R11 to R23 are connected in series between the power supply terminal T1 and the ground terminal T2, and the midpoint is divided to divide the series connected magnetoresistive effect elements R11 to R23 into the same number. Output terminal TO, and the magnetoresistive elements R11, R12, R13 on the power supply terminal T1 side from the midpoint and the magnetoresistive elements R21, R22, R23 on the ground terminal T2 side in the rotation direction of the magnet body 11 Alternatingly arranged along.

  Thereby, in the initial state where all the magnetoresistive elements R11 to R23 have the same resistance value (for example, the resistance values of all the magnetoresistive elements R11 to R23 are “Low”), first, the magnetoresistive elements R11 When the resistance value changes, the output voltage of the output terminal TO changes by the change amount. Second, when the resistance value of the magnetoresistive element R21 further changes while the resistance value of the magnetoresistive element R11 changes, With the output terminal TO as the center, the combined resistance value on the magnetoresistive effect elements R11 to R13 side and the combined resistance value on the magnetoresistive effect elements R21 to R23 side become equivalent resistance values, whereby the output voltage of the output terminal TO Will return to the output voltage in the initial state.

  Third, when the resistance value of the magnetoresistive effect element R12 changes from this state, the output voltage of the output terminal TO changes from the initial state by the change amount.

  In this way, the magnetoresistive effect elements R11 to R23 change in the order of R11, R21, R12, R22, R13, and R23 in the order of arrangement, so that the output voltage of the output terminal TO is, for example, the initial state and the H level. It will change repeatedly between. That is, as the magnet body 11 rotates, the magnetoresistive elements R11 to R23 change in the order of R11, R21, R12, R22, R13, and R23, and the output voltage of the output terminal TO is, for example, an initial value The state repeatedly changes between the H level (or L level).

  Here, as a characteristic of a magnetic sensor using a plurality of magnetoresistive effect elements, in a state where the plurality of magnetoresistive effect elements R11 to R23 are arranged, one of them is sequentially “High” (the resistance value is high). State), the voltage change at the output terminal TO when the next magnetoresistive element becomes “High” as the number of magnetoresistive elements that have already changed to “High” increases. (Voltage change with respect to the initial state) is reduced.

  In the present embodiment, in order to utilize such characteristics of the magnetoresistive effect element, the length L1 (FIG. 3) corresponding to one pole of the N pole (S pole) of the magnet body 11 is included. , The power-side magnetoresistive elements R11 to R13 and the ground-side magnetoresistive elements R21 to R23 are alternately arranged with the output terminal TO as a boundary. By configuring so that the resistance value of the resistive element changes, the output voltage of the output terminal TO repeatedly changes between the initial state and the “High” level (or “Low” level). In this case, since all of the magnetoresistive elements R11 to R23 are arranged within a range of one magnetic pole (N pole or S pole) of the magnet body 11, the resistance value is once "High". ”(Or“ Low ”), the resistance values of the magnetoresistive effect elements arrive at positions where all the magnetoresistive effect elements R11 to R23 face the one magnetic pole of the magnet body 11, and these resistance values Is maintained until “High” (or “Low”).

  Thereby, the characteristics of the magnetoresistive effect element can be used, and the output voltage of the output terminal TO is obtained while one pole of the N pole (S pole) of the magnet body 11 crosses the front of the magnetic sensor 20. The voltage change with respect to the initial state of the peak voltage of the sequentially generated pulse waveform is sequentially reduced (or increased), so that this change is detected by the detector 30 to determine the rotation direction.

  5 shows an output voltage Out [V] output from the output terminal TO of the magnetic sensor 20 when the magnet body 11 is rotated in the direction of the arrow ra1 (FIG. 3) with the configuration shown in FIGS. FIG. 6 is a signal waveform diagram thereof.

  As shown in FIG. 5, when the resistance values of the magnetoresistive elements R <b> 11 to R <b> 23 are all “Low”, the magnet body 11 rotates in the direction indicated by the arrow ra <b> 1 (FIG. 3) to For example, when the N pole (S pole) reaches a position crossing these magnetoresistive elements R11 to R23, first, the resistance value of the magnetoresistive element R11 on the upstream side in the rotation direction ra1 is changed from “Low” to “High”. To change. As a result, the output voltage Out [V] of the output terminal TO changes from 2.500 [V] to 2.582 [V]. When the resistance value of the magnetoresistive effect element R21 changes from “Low” to “High” following the magnetoresistive effect element R11, the midpoint voltage between the magnetoresistive effect elements R11, R12, R13 and R21, R22, R23 The output voltage of the output terminal TO is returned to the initial state of 2.500 [V].

  Further, when the resistance value of the magnetoresistive element R12 changes from “Low” to “High”, the output voltage Out [V] of the output terminal TO changes from 2.500 [V] to 2.579 [V]. In this case, the resistance value of one magnetoresistive effect element R11 has already changed to “High” and is maintained at “High”, so that the first magnetoresistive effect element R11 depends on the characteristics of the magnetoresistive effect element. When the resistance value becomes “High”, the output voltage becomes a value lower than 2.582 [V] (a voltage change from the initial state is small). When the resistance value of the magnetoresistive effect element R22 changes from “Low” to “High” following the magnetoresistive effect element R12, the midpoint voltage between the magnetoresistive effect elements R11, R12, R13 and R21, R22, R23 The output voltage of the output terminal TO is returned to the initial state of 2.500 [V].

  Further, when the resistance value of the magnetoresistive effect element R13 changes from “Low” to “High”, the output voltage Out [V] of the output terminal TO changes from 2.500 [V] to 2.577 [V]. In this case, since the resistance values of the two magnetoresistive elements R11 and R12 have already changed to "High" and are maintained at "High", the first magnetoresistive effect is obtained according to the characteristics of the magnetoresistive element. The output voltage is 2.582 [V] when the resistance value of the element R11 is “High” and lower than the output voltage 2.579 [V] when the resistance value of the third magnetoresistive element R12 is “High”. Value (value with a small voltage change from the initial state). When the resistance value of the magnetoresistive effect element R23 changes from “Low” to “High” following the magnetoresistive effect element R13, the midpoint voltage between the magnetoresistive effect elements R11, R12, R13 and R21, R22, R23 The output voltage of the output terminal TO is returned to the initial state of 2.500 [V].

  Thus, by rotation of the magnet body 11, all the magnetoresistive effect elements R11 to R23 are opposed to the length of one pole of the N pole (S pole) of the magnet body 11, In a state where the resistance values of the magnetoresistive elements R11 to R23 have changed to “High”, the magnet body 11 further rotates in the direction of the arrow ra1, and the S pole (N pole) of the magnet body 11 crosses the magnetic sensor 20 When approached, first, the resistance value of the magnetoresistive element R11 on the upstream side in the rotation direction ra1 changes from “High” to “Low”. As a result, the output voltage Out [V] of the output terminal TO changes from 2.500 [V] to 2.423 [V]. When the resistance value of the magnetoresistive effect element R21 changes from “High” to “Low” following the magnetoresistive effect element R11, the midpoint voltage between the magnetoresistive effect elements R11, R12, R13 and R21, R22, R23 The output voltage of the output terminal TO is returned to the initial state of 2.500 [V].

  Furthermore, when the resistance value of the magnetoresistive element R12 changes from “High” to “Low”, the output voltage Out [V] of the output terminal TO changes from 2.500 [V] to 2.421 [V]. In this case, as compared with the above-described case where the resistance value of the magnetoresistive effect element R11 is changed from “High” to “Low”, the number of elements that are “High” is reduced, and thus the output voltage Becomes a low value (a value with a large change from the initial state). When the resistance value of the magnetoresistive effect element R22 changes from “High” to “Low” following the magnetoresistive effect element R12, the midpoint voltage between the magnetoresistive effect elements R11, R12, R13 and R21, R22, R23 The output voltage of the output terminal TO is returned to the initial state of 2.500 [V].

  Further, when the resistance value of the magnetoresistive element R13 changes from “High” to “Low”, the output voltage Out [V] of the output terminal TO changes from 2.500 to 2.418 [V]. In this case, as compared with the above-described case where the resistance value of the magnetoresistive effect element R11 is changed from “High” to “Low”, the number of elements that are “High” is further reduced, so that the output The voltage becomes a low value (a value with a large change from the initial state).

  On the other hand, FIGS. 7 and 8 show changes in the resistance values of the magnetoresistive elements R11 to R23 when the magnet body 11 is rotated in the reverse direction (arrow ra2 direction (FIG. 3)), and the output terminal TO. It is a figure which shows the output voltage in.

  In this case, as the magnet body 11 rotates, the resistance value changes in the order of the magnetoresistive effect elements R23, R13, R22, R12, R21, and R11, and as shown in FIG. The value changes in the order of 2.418 [V], 2.421 [V], 2.423 [V], 2.577 [V], 2.579 [V], 2.582 [V].

  Thus, based on the voltage value of the output terminal TO, the output voltage when the resistance values of the magnetoresistive elements R11, R12, R13 change (changes in the peak value of every three pulses) is detected. Thus, as this change, when the difference from the initial state (2.500 [V]) is a small change (FIGS. 5 and 6) or a large change (FIGS. 7 and 8), The direction of rotation (ra1 or ra2) can be determined.

  In the above-described embodiment, the case where all the magnetoresistive effect elements R11 to R23 are set to the same initial resistance value and is changed with the rotation of the magnet body 11 is described. However, the present invention is not limited to this. The initial resistance value may be different for each of the magnetoresistive effect elements R11 to R23. In this way, the voltage change at the output terminal TO accompanying the rotation of the magnet body 11 becomes more prominent, so that the voltage change can be detected more easily.

  For example, in FIGS. 9 and 10, the magnetoresistive elements R12 and R22 are set to 1000Ω, R11 and R21 are set to 1200Ω, R13 and R23 are set to 833Ω, and the magnet body 11 is rotated in the arrow ra1 direction (forward direction). FIG. 11 and FIG. 12 are diagrams showing changes in the output terminal TO when the magnet body 11 is rotated in the arrow ra2 direction (reverse direction) under the same conditions.

  In this way, the peak voltage value is different between the high voltage side and the low voltage side than the intermediate voltage (2.5 [V]), but the other peak is higher than the maximum peak voltage value on the high voltage side than the intermediate voltage. The values are 19.5% and 34.8%, respectively, and on the lower voltage side than the intermediate voltage are 13.8% and 26.0%. When such a voltage difference occurs, it is easy to electrically determine the magnitude of the peak voltage.

  In the above-described embodiment, the case where the present invention is applied to an encoder used as a sensor for detecting a rotation direction and a rotation angle has been described. However, the application target is not limited to this, and a linear encoder is used. It can also be applied to.

It is a top view which shows one Embodiment of the magnetic encoder of this invention. It is sectional drawing of the magnetic encoder of FIG. It is a figure which shows the structure of the magnetic sensor of the magnetic encoder of FIG. It is a figure which shows the connection state of the magnetoresistive effect element of the magnetic sensor of FIG. It is a figure which shows the output voltage at the time of forward rotation in case the resistance value of all the magnetoresistive effect elements is the same. It is a signal waveform diagram which shows the output voltage at the time of forward rotation in case the resistance value of all the magnetoresistive effect elements is the same. It is a figure which shows the output voltage at the time of reverse rotation in case the resistance value of all the magnetoresistive effect elements is the same. It is a signal waveform diagram which shows the output voltage at the time of reverse rotation in case the resistance value of all the magnetoresistive effect elements is the same. It is a figure which shows the output voltage at the time of forward rotation when changing the resistance value of a magnetoresistive effect element in arrangement order. It is a signal waveform diagram which shows the output voltage at the time of forward rotation when the resistance value of a magnetoresistive effect element is changed in order of arrangement. It is a figure which shows the output voltage at the time of reverse rotation when changing the resistance value of a magnetoresistive effect element in order of arrangement. It is a signal waveform diagram which shows the output voltage at the time of reverse rotation when changing the resistance value of a magnetoresistive effect element in order of arrangement. It is a figure for demonstrating the conventional magnetic encoder. It is a figure for demonstrating the conventional magnetic encoder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnetic encoder 11 Magnet body 12 Rotating body R11, R21, R12, R22, R13, R23 Magnetoresistive effect element TO Output terminal T1 Power supply terminal T2 Ground terminal

Claims (4)

A magnet body that moves in a predetermined direction and is alternately magnetized with a plurality of magnetic poles composed of N and S poles along the moving direction;
A magnetic sensor disposed in the vicinity of the magnet body and facing the moving direction;
The magnetic sensor is composed of a plurality of magnetoresistive effect elements, and the plurality of magnetoresistive effect elements are connected in series with one end connected to a power supply terminal and the other end connected to a ground terminal, while the plurality of series connected magnetoresistive effect elements. The middle point dividing the magnetoresistive effect elements into the same number is used as the output terminal of the magnetic sensor, and the magnetoresistive element on the power supply terminal side and the magnetoresistive element on the ground terminal side from the midpoint are in the moving direction. Are arranged alternately along the
A magnetic encoder for detecting a moving direction of the magnet body by detecting whether a pulse voltage output from the output terminal increases or decreases as the magnet body moves.   The magnetic encoder according to claim 1, wherein the magnet body is a rotating body, and the N pole and the S pole are magnetized along a rotation direction on an outer peripheral side surface of the rotating body.   3. The magnetic encoder according to claim 1, wherein the plurality of magnetoresistive elements of the magnetic sensor are arranged so that the resistance value is increased or decreased in the order of arrangement in the moving direction. .   4. The magnetic encoder according to claim 1, wherein the plurality of magnetoresistive elements of the magnetic sensor are arranged within a range corresponding to one pole of magnetization of the magnet body. 5. .

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