JP4820182B2 - Magnetic encoder - Google Patents

Description

  The present invention relates to a contactless magnetic encoder, and more particularly to a magnetic encoder using a magnetoresistive effect element.

A conventional magnetic encoder includes a disk-shaped magnetic body that is rotatably provided with a rotating shaft, and a pair of Hall elements that are disposed in the vicinity of the outer peripheral surface of the magnetic body. On the outer peripheral side surface 11A of the magnetic body, a magnetic code is formed by alternately magnetizing the N pole and the S pole, and the pair of Hall elements detects a magnetic field generated from the magnetic code. Output the pulse signal to the outside. One Hall element outputs an A-phase pulse signal, and the other Hall element outputs a B-phase pulse signal that is 90 degrees out of phase with the A-phase pulse signal. The number of rotations can be detected (for example, Patent Document 1).
JP-A-9-243399

  However, the magnetic encoder of Patent Document 1 outputs one pulse signal when the Hall element detects a magnetic field in the vertical direction, for example, when any N pole on the magnetic code faces the Hall element. Therefore, the period of the pulse signal (or the number of pulses output during one rotation of the magnetic body) depends on the pitch dimension between the magnetic poles of the magnetic cord (the pitch between the magnetic poles adjacent to the outer peripheral surface of the magnetic body). It will be.

  That is, conventionally, a signal corresponding to one cycle can be obtained unless the magnet is rotated by an angle corresponding to an electrical angle of 360 degrees with respect to the Hall element, N → S → N (or S → N → S). There wasn't.

  For this reason, in order to shorten the period of the pulse signal or increase the number of pulses output during one rotation of the magnetic material, the pitch between the magnetic poles arranged on the outer peripheral surface of the magnetic material is reduced. Therefore, it is necessary to increase the number of magnetic poles.

  However, it is not easy to narrow the pitch between the magnetic poles formed on the outer peripheral surface of the magnetic material, and there is a problem that the cost is greatly increased especially when the pitch is 1 mm or less.

  The present invention has been made to solve the above-described conventional problems, and it is possible to obtain a pulse signal having a double frequency (1/2 period) than the conventional one without reducing the pitch between magnetic poles so much. The purpose is to provide an encoder.

The present invention relates to a rotating body that is rotatably supported, a magnetic body in which a plurality of magnetic poles composed of N poles and S poles are alternately magnetized along the rotation direction on an outer peripheral side surface of the rotating body, and the magnetic A plurality of magnetoresistive effect elements disposed in the vicinity of the body along the rotational direction, and a magnetic encoder comprising:
Each magnetoresistive element has at least a pinned layer and a free layer whose internal magnetization direction changes based on an external magnetic field generated by the magnetic body, and the magnetization direction of the pinned layer is parallel to the outer peripheral side surface and The first direction perpendicular to the rotation direction or the second direction opposite to the first direction is set, and the initial magnetization direction of the free layer is the first direction or the first direction. Is set in the direction of 2,
The arrangement pitch between the magnetoresistive elements is set to λ / 2, where λ is the pitch between the magnetic poles between the N and S poles adjacent to each other in the rotation direction.

  In the present invention, one period of the detection signal that is the output of the magnetic encoder can be shortened to λ as the pitch between the magnetic poles between the N pole and the S pole. For this reason, the frequency can be doubled (double frequency), and the number of pulses output during one rotation of the magnetic material can be doubled.

  In the above, it is preferable that the magnetoresistive effect element includes a hard bias layer that provides a bias magnetic field that sets an initial magnetization direction of the free layer as a reference direction in addition to the pinned layer and the free layer.

  In the above means, since the initial magnetization direction of the free layer is set, the resistance value of the magnetoresistive element is prevented from becoming unstable when the external magnetic field is zero (zero magnetic field) or in a weak magnetic field. it can. For this reason, it is possible to always output an accurate pulse signal.

  In addition, the first to fourth magnetoresistive elements including the first to fourth elements arranged in the rotation direction at the arrangement pitch of λ / 2 and the first and fourth magnetoresistive elements are connected in series. A first connecting portion, a second connecting portion for connecting the second and third magnetoresistive elements in series, the first magnetoresistive element and the second magnetoresistive element, , A power source for applying a predetermined voltage between one end of the third magnetoresistive effect element and one end of the fourth magnetoresistive effect element, and a first detection output from the first connecting portion It is preferable that a detection unit including a binarization unit that converts each of the voltage and the second detection voltage output from the second connection unit into a pulse signal is provided.

  In the above means, since the bridge circuit is configured by using the four magnetoresistive elements, a highly accurate pulse signal can be generated.

Further, with respect to the first detection unit formed by the first to fourth magnetoresistive effect elements arranged with the arrangement pitch of λ / 2, the arrangement pitch λ / 2 corresponding to the first to fourth is used. A second detector formed by the arranged fifth to eighth magnetoresistive elements is provided;
Between each of the first to fourth magnetoresistive effect elements, the fifth to eighth individual magnetoresistive effect elements are arranged one by one, and between adjacent magnetoresistive effect elements. Is preferably set to λ / 4 pitch.

  The above means can generate four types of signals including A phase signals, B phase signals, A phase bar signals, and B phase bar signals having different phases.

  In the magnetic encoder of the present invention, the pitch between the magnetic poles of the magnetic body forming the magnetic code can be shortened. For this reason, it is possible to provide a magnetic encoder in which the magnetic frequency is doubled (double frequency) or the number of pulses output during one rotation of the magnetic body is twice that of the conventional one.

  1 is a plan view showing a magnetic encoder as an embodiment of the present invention, FIG. 2 is a sectional view of the magnetic encoder shown in FIG. 1, and FIG. 3 is a laminated sectional view conceptually showing the basic structure of the magnetoresistive effect element. FIG. 4 is a partially enlarged plan view of a magnetic cord formed on the outer peripheral side surface of the magnetic body, and FIG. 5 is a plan view showing a sensor substrate on which a magnetoresistive effect element is formed. In FIG. 4, for easy understanding, the circular magnetic code array is shown as being converted into an equivalent linear array.

  A magnetic encoder 10 shown in FIGS. 1 and 2 is a device that detects, for example, the number of rotations, the rotation direction, or the rotation speed, and mainly includes a magnetic body 11 and a rotary body 12 that rotatably supports the magnetic body 11. A sensor substrate 20 made of a magnetoresistive effect element is provided.

  The magnetic body 11 has a substantially ring shape, and its inner surface is fixed to the outer peripheral side surface 12b of the rotating body 12 formed in a disc shape. On the outer peripheral side surface 11A side of the magnetic body 11, a magnetic cord is formed by alternately magnetizing a plurality of magnetic poles composed of N poles and S poles. In the following, when the magnetic code is converted into a linear shape, the pitch between magnetic poles (corresponding to an electrical angle of 180 degrees) that is the distance between adjacent N poles and S poles will be described as λ ( (See FIG. 4).

  The magnetic body 11 and the rotating body 12 are arranged in a circular recess 9 </ b> A provided in the housing 9. 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 therethrough. The magnetic body 11 is supported so as to be rotatable 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 casing 9 is formed with a deficient portion 9b in which a part of the concave portion 9A is cut out in the outer peripheral direction, and the sensor substrate 20 is connected to the outer peripheral side surface 11A of the magnetic body 11 in the deficient portion 9b. It is fixed to face each other. The sensor substrate 20 is provided with a plurality of magnetoresistive elements A (indicated as A1, A2, A3, and A4 individually).

  As shown in FIG. 3, the basic structure of the magnetoresistive element A has a pinned layer (fixed layer) 22 provided at the lowermost layer, a nonmagnetic layer 23 laminated thereon, and a laminated layer at the uppermost portion. And the hard bias layers 25a and 25b provided on both sides of each layer, and terminal portions 26 and 26 provided on the hard bias layers 25a and 25b.

  The hard bias layers 25a and 25b are made of, for example, permanent magnets. In FIG. 3, the initial magnetization direction β0 of the free layer 24 is directed to a predetermined reference direction (the first direction (Z2 direction in FIG. 3)). A bias magnetic field γ is given. Therefore, when an external magnetic field is not acting on the magnetoresistive element A, the magnetization direction β of the free layer 24 is in the same first direction (Z2 direction in FIG. 3) as the bias magnetic field γ. It is aligned to face. The initial magnetization direction β0 of the free layer 24 means the magnetization direction β of the entire free layer 24 when the external magnetic field is zero (zero magnetic field).

  The magnetization direction β of the free layer 24 changes according to the vector composition of the external magnetic field (in this application, a magnetic field generated by a magnetic code provided on the magnetic body 11) acting on the free layer 24 and the bias magnetic field γ. . The total resistance value of the magnetoresistive effect element A shown in this embodiment is the case where the magnetization direction β of the free layer 24 is the first direction (Z2 direction) that coincides with the magnetization direction α of the pinned layer 22 (0 degree). In contrast, when the magnetization direction β of the free layer 24 is a second direction (Z1 direction) opposite to the magnetization direction α of the pinned layer 22 (a relationship that is 180 degrees different). ) Is the maximum value. When the angle between the magnetization direction β of the free layer 24 and the magnetization direction α of the pinned layer 22 is perpendicular (90 degrees), that is, the magnetization direction β of the free layer 24 is directed to the rotation direction ra1 or the rotation direction ra2. Sometimes, the total resistance value of the magnetoresistive element A becomes an intermediate value.

  When the total resistance value of the magnetoresistive effect element A is Z, the fixed resistance is R, and the change width of the variable resistance is Δr, the minimum value of the total resistance Z is Zmin = R, and the maximum value is Zmax =. R + Δr and the intermediate value Zmid can be expressed as Zmid = (Zmin + Zmax) / 2 = R + Δr / 2.

  As shown in FIG. 5, the sensor substrate 20 is provided with four magnetoresistive elements A1, A2, A3, A4 including first to fourth along the rotation direction (ra1 or ra2). Yes.

  The magnetization direction α of each pinned layer 22 and the initial magnetization direction β0 of each free layer 24 of the first to fourth magnetoresistive elements A1, A2, A3, A4 in this embodiment are both This is a first direction (Z2 direction) parallel to the outer peripheral side surface 11A and perpendicular to the rotational direction. The magnetization directions of each pinned layer 22 and each free layer 24 may be a second direction (Z1 direction) that is 180 degrees opposite to the first direction. In this embodiment, the arrangement pitch that is the interval in the rotational direction of the magnetoresistive elements A1, A2, A3, and A4 is set to λ / 2 corresponding to half of the pitch λ between the magnetic poles.

FIG. 6 is a circuit configuration diagram showing a detection unit of the magnetic encoder.
As shown in FIG. 6, the detection unit 30 of the magnetic encoder includes the first to fourth magnetoresistive elements A1, A2, A3, A4 and the magnetoresistive element A1 positioned at both ends in the rotational direction. The element A4 is connected in series via the first connection portion T1, and the remaining magnetoresistance effect element A2 and the magnetoresistance effect element A3 are connected in series via the second connection portion T2.

  One end of the first magnetoresistive effect element A1 and one end of the second magnetoresistive effect element A2 are connected to the power supply 31 of the voltage Vcc, and one end of the fourth magnetoresistive effect element A4 and the third magnetoresistive effect element A2 are connected. One end of the magnetoresistive element A3 is grounded to GND. That is, the first to fourth magnetoresistive elements A1, A2, A3, and A4 form a bridge circuit, and the first magnetoresistive element A1 and the fourth magnetoresistive effect connected in series. A voltage Vcc is applied between the element A4 and between the second magnetoresistive element A2 and the third magnetoresistive element A3 connected in series. In the detection unit 30, the first detection voltage V1 and the second detection voltage V2 are output from the first connection unit T1 and the second connection unit T2.

  Binarization units 32A and 32B are provided at the subsequent stage of the first connection unit T1 and the second connection unit T2, respectively. The binarization units 32A and 32B digitally process the first detection voltage V1 and the second detection voltage V2, and convert them into an A-phase signal Sa and a B-phase signal Sb composed of pulse signals. The A-phase signal Sa and the B-phase signal Sb are digital signals whose phases are 90 degrees different from each other when the pitch λ between the adjacent N poles and S poles is an electrical angle of 360 degrees. Further, when a pitch λ / 2 that is half of the pitch λ between the A-phase signal Sa and the B-phase signal Sb magnetic poles is 360 degrees, these are inverted signals whose phases are different from each other by 180 degrees (see FIGS. 8A and 8B).

Hereinafter, the operation of the magnetic encoder of the present invention will be described.
7A to 7C are plan views showing the relationship between the magnetic code and the magnetoresistive effect element as an example of the operation state of the magnetic encoder. FIG. 7A shows the initial state of the magnetic encoder ST1, and FIG. 7B shows the initial state ST2. FIG. 7C shows a state rotated from the state ST1 by the λ / 2 pitch in the rotational direction ra1, and FIG. 7C shows a state further rotated from the ST2 by the λ / 2 pitch in the rotational direction ra1. 8A is a graph showing the relationship between the first detection voltage V1 and the A-phase signal Sa, and FIG. 8B is a graph showing the relationship between the second detection voltage V2 and the B-phase signal Sb. Note that ST means step (STEP). 8A and 8B show a case where the magnetic body is rotated by an angle corresponding to N → S (or S → N) and λ pitch.

  When the rotating shaft 12a is rotated in the rotation direction ra1 or ra2, the rotating body 12 having the magnetic body 11 is rotated. At this time, since the sensor substrate 20 is opposed to the side of the outer peripheral side surface 11A of the magnetic body 11, a plurality of N poles and S poles forming a magnetic code pass in front of the sensor substrate 20 in the rotation direction. To do.

  On the outer peripheral side surface 11A of the magnetic body 11, as shown in FIG. 4, a plurality of magnetic lines of force m from the N pole to the S pole are generated between the adjacent N and S poles. A part reaches the side of the outer peripheral side surface 11A.

  Here, as shown in FIG. 7A, representative magnetic lines of force among m magnetic lines m generated between the N-pole and S-pole magnetic poles adjacent to each other in the rotation direction are m1a, m1b, m2a, and m2b, respectively. That is, the magnetic field lines from the N1 pole to the S1 pole are m1a, the magnetic field lines from the N1 pole to the S2 pole are m1b, the magnetic field lines from the N2 pole to the S2 pole are m2a, and the magnetic field lines from the N2 pole to the S3 pole are m2b. To do. In this case, at the position on the side of the outer peripheral side surface 11A of the magnetic body 11, both the magnetic lines m1a and the magnetic lines m2a face the rotation direction ra1 in the same direction, and both the magnetic lines m1b and the magnetic lines m2b have the same direction. However, the magnetic lines of force m1a and magnetic lines of force m1b are opposite to each other, and the magnetic lines of force m2a and magnetic lines of force m2b are also opposite to each other. That is, magnetic field lines that are alternately opposite to each other are generated between the N pole and the S pole adjacent to each other on the side of the outer peripheral side surface 11A of the magnetic body 11 in the rotation direction.

  As shown in FIGS. 7A to 7C, when the magnetic body 11 is rotated, the magnetic lines of force m1a, m1b, m2a and m2b generated from the magnetic body 11 to the outer peripheral side are changed to the first to fourth magnetic fields. The resistance effect elements A1, A2, A3, A4 are linked in order.

  7A to 7C, the magnetization direction α of the pinned layer 22 and the direction of the bias magnetic field γ of each magnetoresistive element are both parallel to the outer peripheral side surface 11A and in the rotation direction (ra1-ra2). It is set in the first direction (Z2 direction) which is perpendicular to the direction.

  In ST1 shown as an initial state in FIG. 7A, the magnetic lines m1b are linked to the first magnetoresistive element A1, and the magnetic lines m2a are linked to the third magnetoresistive element A3. At this time, an external magnetic field in the rotation direction ra2 acts on the first magnetoresistance effect element A1, and an external magnetic field in the rotation direction ra1 acts on the third magnetoresistance effect element A3. Therefore, the magnetization direction β of the free layer 24 in the first magnetoresistance effect element A1 is directed to the rotation direction ra2, and the magnetization direction β of the free layer 24 in the third magnetoresistance effect element A3 is Oriented in the direction of rotation ra1. At this time, since the angle between the magnetization direction α of the pinned layer 22 and the magnetization direction β of the free layer 24 of the first and third magnetoresistive elements A1 and A3 approaches 90 degrees, the first , 3 magnetoresistive elements A1, A3 are set to a substantially intermediate value Zmid.

  On the other hand, although the magnetic force line m1b and the magnetic force line m2a act on the second magnetoresistive element A2, the magnetic force lines m1b and m2a are opposite to each other and cancel each other. The external magnetic field acting on the effect element A2 is zero (zero magnetic field). Similarly, since the magnetic field lines m2a and m2b cancel each other out with respect to the fourth magnetoresistive element A4, the external magnetic field acting on the fourth magnetoresistive element A4 is zero (zero magnetic field) after all. Become. At this time, the magnetization direction β of the free layer 24 of the second and fourth magnetoresistive elements A2 and A4 is the same as the initial magnetization direction, that is, the first direction (Z2 direction) as the magnetization direction α of the pinned layer 22. Therefore, the resistance values of the second and fourth magnetoresistive elements A2 and A4 are set to the minimum value Zmin.

  ST2 shown in FIG. 7B shows a state in which the magnetic body 11 is rotated by the arrangement pitch λ / 2 in the rotation direction ra1.

  In ST2, since the magnetic lines m2a are linked to the second magnetoresistive element A2 and the magnetic lines m2b are linked to the fourth magnetoresistive element A4, the magnetic lines m2b are linked to the second magnetoresistive element A2. An external magnetic field in the rotation direction ra1 acts, and an external magnetic field in the rotation direction ra2 acts on the fourth magnetoresistive element A4. Therefore, the magnetization direction β of the free layer 24 in the second magnetoresistance effect element A2 is directed to the rotation direction ra1, and the magnetization direction β of the free layer 24 in the fourth magnetoresistance effect element A4 is It is directed in the direction of rotation ra2. Therefore, since the angle between the magnetization direction α of the pinned layer 22 and the magnetization direction β of the free layer 24 of the second and fourth magnetoresistive elements A2 and A4 approaches 90 degrees, The total resistance value of the magnetoresistive effect elements A2 and A4 is set to a substantially intermediate value Zmid.

  On the other hand, the magnetic field lines m1b and m2a cancel each other for the first magnetoresistive element A1, and the magnetic lines m2a and magnetic lines m2b cancel each other for the third magnetoresistive element A3. The external magnetic field acting on the magnetoresistive effect elements A1 and A3 is zero (zero magnetic field). Therefore, the magnetization direction β of the free layer 24 of the first and third magnetoresistive elements A1 and A3 is maintained in the same first direction (Z2 direction) as the magnetization direction α of the pinned layer 22. The total resistance values of the first and third magnetoresistive elements A1 and A3 are set to the minimum value Zmin.

  ST3 shown in FIG. 7C shows a state in which the magnetic body 11 is further rotated in the rotation direction ra1 by the arrangement pitch λ / 2 (total magnetic pole pitch λ (corresponding to an electrical angle of 180 degrees)).

  In ST3, the external magnetic field generated from the magnetic code acts on the first to fourth magnetoresistive elements A1, A2, A3 and A4 in the same state as ST1. For this reason, the resistance values of the first and third magnetoresistive elements A1 and A3 are set to substantially the intermediate value Zmid, and the resistance values of the second and fourth magnetoresistive elements A2 and A4 are set to the minimum value Zmin. Set to

  That is, when the magnetic body 11 is rotated by ST1 → ST2 → ST3 and the magnetic pole pitch λ as described above, the resistance values of the first to fourth magnetoresistive elements A1, A2, A3 and A4, and the The first and second detection voltages V1 and V2 output from the detection unit 30 of the magnetic encoder change as shown in Table 1 below.

  Here, when the pitch is plotted on the horizontal axis and the voltage is plotted on the vertical axis, the first and second detection voltages V1 and V2 are as shown in FIGS. 8A and 8B.

  As shown in FIG. 8A and FIG. 8B, in the magnetic encoder 10 of the present invention, the magnetic body 11 is rotated by a rotation angle (electrical angle 180 degrees) corresponding to the pitch λ between the magnetic poles, so 1, it is possible to output the second detection voltages V1 and V2.

  That is, in the prior art, if the magnet facing the Hall element is not rotated by an angle corresponding to, for example, N → S → N (or S → N → S) and the total pitch 2λ (electrical angle 360 degrees), it corresponds to one cycle. However, in the present invention, it is only necessary to rotate N.fwdarw.S (or S.fwdarw.N) and the conventional half of the magnetic pole pitch .lamda. One cycle of the first and second detection voltages V1 and V2 can be obtained.

  As shown in FIGS. 8A and 8B, the first detection voltage V1 and the second detection voltage V2 are digitally processed by the binarization units 32A and 32B with reference to a predetermined threshold voltage Vth. Are converted into pulse signals composed of the A phase signal Sa and the B phase signal Sb, respectively.

  For this reason, even if the pitch between the magnetic poles of the magnetic cord formed on the magnetic body 11 is not so narrow, the A-phase signal Sa and the B-phase signal Sb having twice the conventional frequency (1/2 period) are obtained. be able to. Therefore, it is not necessary to forcibly narrow the dimension of the magnetic pole pitch λ of the magnetic poles formed on the outer peripheral surface of the magnetic body 11, and it is possible to suppress an increase in cost.

  As shown in FIGS. 8A and 8B, the A-phase signal Sa and the B-phase signal Sb have a 90 degree phase when the pitch λ between the adjacent N poles and S poles is set to an electrical angle of 180 degrees. Depending on whether the rotation direction of the magnetic body 11 is the rotation direction ra1 or the rotation direction ra2, one of the pulse signals is a leading signal with respect to the other. That is, for example, when the rotation direction of the magnetic body 11 is the rotation direction ra1, the A-phase signal Sa is the advance signal, and when the rotation direction is the rotation direction ra2, the B-phase signal Sb is output as the advance signal. The For this reason, it is possible to detect the rotation direction of the magnetic body 11, that is, the rotation direction given to the rotation shaft 12a, from the A-phase signal Sa and the B-phase signal Sb.

  FIG. 9 is a plan view similar to FIG. 7A, conceptually showing a magnetic encoder when four types of signals are output.

  Here, the four types of signals are 45 degrees when the phase angle between the A phase signal Sa and the B phase signal Sb and the A phase signal Sa is λ of the magnetic pole pitch λ is 360 degrees (between the magnetic poles). The phase is 45 degrees with respect to the A phase bar signal Sa−, which is different by 90 degrees when the pitch λ / 2 is set to an electrical angle of 360 degrees, and the B phase signal (the pitch between the magnetic poles λ / 2 is set to 360 degrees). This is a B-phase bar signal Sb- that differs by only 90 degrees.

  In the magnetic encoder shown in FIG. 9, four first to fourth magnetoresistive elements A1, A2, A3, A4 that output an A phase signal Sa and a B phase signal Sb, an A phase bar signal Sa-, and a B phase bar. A total of eight magnetoresistive effect elements B1, B2, B3, and B4 that output the signal Sb- are provided in a line along the rotational direction on one sensor substrate 20. Yes.

  The fifth magnetoresistance effect element B1 is provided between the first magnetoresistance effect element A1 and the second magnetoresistance effect element A2, and the sixth magnetoresistance effect element B2 is the second magnetoresistance effect element B2. An effect element A2 is provided between the third magnetoresistance effect element A3, and the seventh magnetoresistance effect element B3 is provided between the third magnetoresistance effect element A3 and the fourth magnetoresistance effect element A4. The eighth magnetoresistive element B4 is provided so that the fourth magnetoresistive element A4 is positioned between the seventh magnetoresistive element B3 and the eighth magnetoresistive element B4. It has been.

  First to fourth magnetoresistive elements A1, A2, A3, A4 for the A-phase signal Sa and B-phase signal Sb, and fifth to eighth for the A-phase bar signal Sa- and B-phase bar signal Sb-. Similar to the above, the arrangement pitch between the magnetoresistive effect elements B1, B2, B3, and B4 is set to λ / 2. However, between the first magnetoresistive effect element A1 and the fifth magnetoresistive effect element B1, between the fifth magnetoresistive effect element B1 and the second magnetoresistive effect element A2,... As described above, the arrangement pitch between different types of magnetoresistive elements adjacent to each other in the rotation direction is set to λ / 4.

  For this reason, the first to fourth magnetoresistive elements A1, A2, A3, A4 and the fifth to eighth magnetoresistive elements B1, B2, B3, B4 are respectively provided with the detection units 30 shown in FIG. By applying, that is, by forming the first detection unit for the first to fourth magnetoresistive elements A1, A2, A3, A4, the A phase signal and the B phase signal Sb can be obtained. The A-phase bar signal Sa− and the B-phase bar signal Sb− can be obtained by forming a second detection unit for the fifth to eighth magnetoresistive elements B1, B2, B3, and B4.

  In the above embodiment, the plurality of magnetoresistive elements arranged on the sensor substrate 20 all have the same structure (configuration having the same magnetization direction α of the pinned layer 22 and the same magnetization direction γ of the bias magnetic field). The magnetoresistive effect element which becomes can be used.

  In particular, since many magnetoresistive effect elements formed on the same wafer all have the same structure, four or eight magnetoresistive effect elements are cut out as a set from these many magnetoresistive effect elements. Thus, the sensor substrate 20 can be obtained. For this reason, in the magnetic encoder 10 of the present invention, it is not necessary to fix each of the magnetoresistive effect elements cut out separately to the sensor substrate 20 after performing an alignment operation to match the magnetization directions thereof. The assembly process can be facilitated.

  In the above embodiment, the magnetization direction α of the pinned layer 22 and the direction of the bias magnetic field γ of each magnetoresistive element are both parallel to the outer peripheral side surface 11A and with respect to the rotation direction (ra1-ra2). Although the case where the first direction (Z2 direction) is set to be vertical has been described, the present invention is not limited to this, and the second direction (Z1 direction) is opposite to the first direction. May be.

  Further, although the case where the magnetization direction α of the pinned layer 22 is the same as the direction of the bias magnetic field γ has been described, the magnetization direction α of the pinned layer 22 and the direction of the bias magnetic field γ are opposite to each other. It may be set.

The top view which shows the magnetic encoder as embodiment of this invention, Sectional drawing of the magnetic encoder shown in FIG. Laminated cross-sectional view conceptually showing the basic structure of the magnetoresistive element, A partially enlarged plan view of a magnetic cord formed on the outer peripheral side surface of the magnetic body, A plan view showing a sensor substrate on which a magnetoresistive effect element is formed, A circuit configuration diagram showing a detection unit of the magnetic encoder, ST1 indicating the initial state of the magnetic encoder, ST2 indicating a state rotated from the initial state ST1 by the λ / 2 pitch in the rotation direction ra1, ST3 which shows the state rotated in the rotation direction ra1 by λ / 2 pitch from ST2. A graph showing a relationship between the first detection voltage V1 and the A-phase signal Sa; A graph showing a relationship between the second detection voltage V2 and the B-phase signal Sb; FIG. 7A is a plan view conceptually showing a magnetic encoder when outputting four types of signals;

Explanation of symbols

DESCRIPTION OF SYMBOLS 9 Housing | casing 9b Deletion | deletion part 9A Recess 10 Magnetic encoder 11 Magnetic body 11A Outer peripheral side surface 12 Rotating body 12a Rotating shaft 20 Sensor substrate 22 Pin layer (fixed layer)
23 Nonmagnetic layer 24 Free layer 25a, 25b Hard bias layer 26 Terminal part 30 Detection part 31 Power supply 32A, 32B Binarization part A Magnetoresistive effect element A1, A2, A3, A4 1st thru | or 4th magnetoresistive effect element B1, B2, B3, B4 Fifth to eighth magnetoresistive elements N, S Magnetic poles magnetized on the outer peripheral side surface of the magnetic body (magnetic code)
V1 First detection voltage V2 Second detection voltage ra1, ra2 Rotation directions m1a, m1b, m2a, m2b Typical magnetic field lines α Magnetization direction of pinned layer β Magnetization direction of free layer γ Bias magnetic field

Claims (4)

A rotating body supported rotatably, a magnetic body in which a plurality of magnetic poles composed of N and S poles are alternately magnetized along the rotation direction on the outer peripheral side surface of the rotating body, and in the vicinity of the magnetic body A plurality of magnetoresistive elements disposed opposite to each other along the rotation direction, and a magnetic encoder comprising:
Each magnetoresistive element has at least a pinned layer and a free layer whose internal magnetization direction changes based on an external magnetic field generated by the magnetic body, and the magnetization direction of the pinned layer is parallel to the outer peripheral side surface and The first direction perpendicular to the rotation direction or the second direction opposite to the first direction is set, and the initial magnetization direction of the free layer is the first direction or the first direction. Is set in the direction of 2,
A magnetic encoder, wherein an arrangement pitch between magnetoresistive elements is set to λ / 2, where λ is a pitch between magnetic poles between N and S poles adjacent to each other in the rotation direction.   2. The magnetoresistive element includes a hard bias layer that provides a bias magnetic field that sets an initial magnetization direction of the free layer as a reference direction in addition to the pinned layer and the free layer. The magnetic encoder described.   The first to fourth magnetoresistive elements having the arrangement pitch of λ / 2 and arranged in the rotation direction are connected in series to the first and fourth magnetoresistive elements. A first connection portion; a second connection portion connecting the second and third magnetoresistive effect elements in series; and the first magnetoresistive effect element and the second magnetoresistive effect element. A power source that applies a predetermined voltage between one end and one end of the third magnetoresistive element and the fourth magnetoresistive element, and a first detection voltage that is output from the first connection portion And a binarization unit that converts each of the second detection voltage output from the second connection unit and a second detection voltage into a pulse signal. 2. The magnetic encoder according to 2. With respect to the first detectors formed by the first to fourth magnetoresistive elements arranged with the arrangement pitch of λ / 2, they are arranged with the arrangement pitch λ / 2 corresponding to the first to fourth. A second detector formed of fifth to eighth magnetoresistive elements is provided;
Between each of the first to fourth magnetoresistive effect elements, the fifth to eighth individual magnetoresistive effect elements are arranged one by one, and between adjacent magnetoresistive effect elements. 4. The magnetic encoder according to claim 3, wherein the interval is set to λ / 4 pitch.

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