WO2009154157A1 - Magnetic sensor and magnetic encoder - Google Patents

Abstract

Provided are a magnetic sensor and a magnetic encoder wherein the duty ratio of a high/low binary signal is constant and a stable output is ensured. The magnetic sensor is disposed in a position away from the magnetized surface of a magnet in which an N pole and an S pole are alternated in a relative movement direction.  The magnetic sensor has a sensor unit (bridge circuit) (55) comprising a magnetic sensing element having an electric resistance value which varies with the external magnetic field and a control unit (integrated circuit) (56) for generating a high/low binary signal according to the sensor output from the sensor unit (55).  The magnetic sensor is characterized in that the control unit (56) has a comparator (59) for obtaining the binary signal by comparison of the sensor output with a threshold value and a threshold value setting circuit (53) for setting the threshold value according to the maximum peak and the minimum peak of the sensor outputs two outputs before.

Description

Magnetic sensor and magnetic encoder

The present invention particularly relates to a magnetic sensor and a magnetic encoder capable of obtaining a stable output with a constant duty ratio of a high / low binary signal.

The magnetic encoder is provided with a magnet in which N poles and S poles are alternately magnetized in the relative movement direction, and a position away from the magnet, and includes, for example, a GMR element (giant magnetoresistive effect element). And a sensor.

The magnetic encoder is known to have a double frequency mode in which an output of two pulses can be obtained with respect to a relative movement of one period λ, where the distance λ between the centers of the N and S poles is one period. This double frequency mode is characterized in that detection can be performed with higher accuracy than the single frequency mode in which an output for one pulse can be obtained in one cycle (λ).

7 is a plan view of a conventional rotary magnetic encoder, FIG. 8 is a side view of the rotary magnetic encoder as viewed from the direction of arrow a, and FIG. 9 is a rotary magnetic encoder of FIG. It is the front view of the rotary magnetic encoder which looked at the encoder from the arrow b direction.

Reference numeral 1 shown in FIG. 7 is a rotating drum type magnet. For example, in the form of FIG. 7, the side surface 1a of the magnet 1 is a magnetized surface (radial magnetized magnet), and the N pole and the S pole are alternately magnetized. Has been. Reference numeral 2 denotes a magnetic sensor, and the magnetic sensor 2 is provided at a position away from the side surface 1a of the magnet 1 by a predetermined distance. The magnetic sensor 2 is supported by a support plate 3. For example, the magnet 1 rotates around the axis center O1. Then, since the magnetic field from the magnet 1 acting on the magnetic sensor 2 changes, the electric resistance value of the GMR element changes. A sensor output based on a change in the electrical resistance of the GMR element is converted into a high / low binary signal by a comparator having a threshold set by an integrated circuit (IC) provided in the magnetic sensor 2.

8 and 9, the center O2 of the magnetic sensor 2 is in a positional relationship facing the center line CL of the side surface 1a of the magnet 1. However, in the magnetic encoder in the double frequency mode, the center 2 of the magnetic sensor 2 is When the center line CL is shifted in the vertical direction, or when at least one of the rotation modes α, β, γ shown in FIGS. It has been found that the duty ratio of the binary signal varies and, in the worst case, a detection error occurs.

10 shows the sensor output when the magnetic sensor 2 has a rotation mode γ of 10 ° with the Y axis direction as the rotation center from the normal state of FIG. 8, and FIG. 11 shows the magnetic sensor 2 from the normal state of FIG. Is the sensor output when a rotation mode β of 10 ° occurs with the Z-axis direction as the center of rotation. 10 and 11 show both actual measurement values and simulation results.

As is clear from FIGS. 10 and 11, the sensor output is distorted. Therefore, if the threshold value for generating the high / low binary signal is fixed, the duty ratio of the high / low binary signal varies as shown in FIG. Further, in order to suppress the occurrence of chattering, it is desirable to set the threshold value as close to the maximum peak and minimum peak of the sensor output as possible. However, when the sensor output is distorted as shown in FIG. 11 and variations occur in the maximum peak and the minimum peak of the sensor output, for example, a fixed threshold is set in accordance with the high maximum peak (high), and this fixed threshold is set. Is larger than the low maximum peak (low), a signal cannot be generated at the protruding waveform portion having the maximum peak (low), and a detection error occurs. Therefore, conventionally, the threshold value cannot be set to a value close to the maximum peak and the minimum peak of the sensor output and must be reduced, and a stable output cannot be obtained.

Patent Document 1 describes an invention in which a peak of a sensor output immediately before is detected, and thereby a threshold is set as needed.

However, the method described in Patent Document 1 cannot cope with threshold correction for sensor output distortion in the double-frequency mode, cannot make the duty ratio of the binary signal of high / low constant, and causes a detection error. There is a possibility.
JP 2005-91073 A

Accordingly, the present invention is to solve the above-described conventional problems, and in particular, to provide a magnetic sensor and a magnetic encoder capable of obtaining a stable output with a constant duty ratio of a high / low binary signal. With the goal.

In the present invention, a magnetic field generating member having a magnetized surface in which N and S poles are alternately magnetized in the relative movement direction is disposed at a position away from the magnetized surface, and has an electric resistance value with respect to an external magnetic field. In a magnetic sensor comprising: a sensor unit including a magnetic detection element that changes; and a control unit for generating a high / low binary signal based on a sensor output from the sensor unit.
The control unit compares the sensor output with a threshold value to obtain the binary signal, and a threshold setting circuit that sets the threshold value based on the maximum peak and the minimum peak of the two previous sensor outputs It is characterized by having. As a result, a stable output with a constant duty ratio of the high / low binary signal can be obtained.

In the present invention, the threshold setting circuit includes a peak detection unit that detects a maximum peak and a minimum peak of the sensor output, a first storage unit that stores a maximum peak and a minimum peak of the previous sensor output, and 2 It is preferable to have a second storage unit that stores a maximum peak and a minimum peak of the previous sensor output, and a threshold generation unit that generates the threshold based on data in the second storage unit. As a result, the threshold value can be dynamically set based on the maximum peak and the minimum peak of the sensor output two times before by a simple circuit.

In the present invention, it is preferable that the magnetic detection element is an MR element utilizing a magnetoresistive effect.

Further, a magnetic encoder according to the present invention includes any one of the magnetic sensors described above and the magnetic field generating member. The present invention can be used for a single-frequency magnetic encoder, but can be preferably applied to a double-frequency configuration that outputs two pulses in one cycle.

In a magnetic encoder having a double-frequency configuration, when the magnetic sensor is displaced from the magnetic field generating member, two different output waveforms appear alternately in the sensor output as shown in FIGS. all right. Therefore, as in the case of the magnetic sensor of the present invention, the threshold value is set based on the maximum peak and the minimum peak of the sensor output two times before, so that even if the magnetic sensor causes a positional deviation or the like with respect to the magnetic field generating member, A stable output with a constant duty ratio of the / low binary signal can be obtained.

According to the present invention, it is possible to obtain a stable output with a constant duty ratio of a high / low binary signal.

1 is a perspective view of the magnetic encoder of the present embodiment, FIG. 2 is a partial cross-sectional view of the magnetic detection element of the present embodiment, FIG. 3 is a circuit configuration diagram of the magnetic sensor of the present embodiment, and FIG. FIG. 5 is a circuit configuration diagram of a magnetic sensor in the embodiment, and FIG. 5 is a diagram for explaining output processing from sensor output to comparator output (conversion to a binary signal) in this embodiment. b) Maximum peak detection (digital value), (c) Minimum peak (digital value), (d) Comparator threshold value (e) A diagram showing a comparator output.

In each figure, the X1-X2 direction, the Y1-Y2 direction, and the Z1-Z2 direction are orthogonal to the remaining two directions. The Y1-Y2 direction is the relative movement direction of the magnet 21 and the magnetic sensor 22, and is the lateral direction of the substrate 23 constituting the magnetic sensor 22. In this embodiment, unless otherwise specified, the “relative movement direction” refers to the relative movement direction of the magnetic sensor. In this embodiment, the relative movement direction of the magnetic sensor 22 is the Y1 direction. Therefore, when the magnet 21 is fixed and the magnetic sensor 22 is moved, the magnetic sensor 22 is moved in the Y1 direction. When the magnetic sensor 22 is fixed and the magnet 21 is moved, the magnet 21 is moved in the Y2 direction. Note that both the magnet 21 and the magnetic sensor 22 may move. The X1-X2 direction is the longitudinal direction of the magnetic sensor 22 orthogonal to the relative movement direction in the plane of the substrate 23. The Z1-Z2 direction is a height direction in which the magnet 21 and the magnetic sensor 22 face each other with a predetermined interval.

As shown in FIG. 1, the magnetic encoder 20 includes a magnet (magnetic field generating member) 21 and a magnetic sensor 22.

The magnet 21 has a rod shape extending in the Y1-Y2 direction shown in the figure, and the magnetized surface in which the facing surface 21a facing the magnetic sensor 22 is alternately magnetized with N and S poles with a predetermined width in the Y1-Y2 direction shown in the figure. It is. The center-to-center distance (pitch) between the N pole and the S pole is λ.

As shown in FIG. 1, the magnetic sensor 22 has a substrate 23 and a plurality of magnetic detection elements A1, A2, B1, and B2 provided on a surface 23a (a surface facing the magnet 21) of the common substrate 23. Composed.

As shown in FIG. 1, the eight magnetic detection elements A1, A2, B1, and B2 are arranged in a matrix with four elements in the Y1-Y2 direction and two elements in the X1-X2 direction. As shown in FIG. 1, the interval between the centers of adjacent magnetic detection elements in the Y1-Y2 direction is λ / 4.

As shown in FIG. 2, each of the magnetic detection elements A1, A2, B1, and B2 is laminated in order of an antiferromagnetic layer 7, a fixed magnetic layer 8, a nonmagnetic layer 9, a free magnetic layer 10, and a protective layer 11 from the bottom. It is formed with the structure. However, the laminated structure of FIG. 2 is an example. For example, the pinned magnetic layer 8 may be formed with a laminated ferrimagnetic structure. For example, the antiferromagnetic layer 7 is made of IrMn, the pinned magnetic layer 8 is made of CoFe, the nonmagnetic layer 9 is made of Cu, the free magnetic layer 10 is made of NiFe, and the protective layer 11 is made of Ta.

The magnetic detection elements A1, A2, B1, and B2 include a laminated portion in which at least the pinned magnetic layer 8 and the free magnetic layer 10 are laminated with the nonmagnetic layer 9 interposed therebetween. An exchange coupling magnetic field (Hex) is generated between the antiferromagnetic layer 7 and the pinned magnetic layer 8, and the magnetization direction (P direction) of the pinned magnetic layer 8 is pinned in one direction. On the other hand, the magnetization direction (F direction) of the free magnetic layer 10 is not fixed as in the fixed magnetic layer 8 and easily changes in magnetization due to the external magnetic field H.

In the present embodiment, the interface between the free magnetic layer 10 and the nonmagnetic layer 9 constituting the magnetic detection elements A1, A2, B1, B2 is a plane direction (XY) parallel to the magnetized surface 21a of the magnet 21. Face direction).

The above configuration is a configuration of a giant magnetoresistive effect element (GMR element) in which the nonmagnetic layer 9 is formed of Cu. For example, when the nonmagnetic layer 9 is formed of an insulating material such as Al ₂ O ₃ or MgO. And configured as a tunnel type magnetoresistive effect element (TMR element). Further, the magnetic detection elements A1, A2, B1, and B2 of the present embodiment may be anisotropic magnetoresistive elements (AMR elements) using the anisotropic magnetoresistive effect.

1 and 2, the magnetization direction (P direction) of the pinned magnetic layer 8 of each of the magnetic detection elements A1, A2, B1, and B2 is the X1 direction.

In this embodiment, the magnetization direction (F direction) of the free magnetic layer 10 is the same as the magnetization direction (P direction) of the pinned magnetic layer 8 in the absence of a magnetic field (a state in which no external magnetic field is applied). By adjusting the interlayer coupling magnetic field (Hin) generated between the free magnetic layer 10 and the pinned magnetic layer 8, the magnetization direction (F direction) of the free magnetic layer 10 is changed to the magnetization direction (P direction) of the pinned magnetic layer 8. It can be in the same direction or in the opposite direction.

As shown in FIG. 3, an A-phase bridge circuit (sensor unit) 55 is constituted by the two magnetic detection elements A1 and the two magnetic detection elements A2. One magnetic detection element A1 and one magnetic detection element A2 are connected in series via an A-phase first output terminal (Va1) 50. The other magnetic detection element A1 and the other magnetic detection element A2 are connected in series via the A-phase second output terminal (Va2) 51. Reference numeral 52 is an input terminal, and reference numeral 60 is a ground terminal.

The bridge circuit 55 is connected to an integrated circuit (IC) 56 that is a control unit.
As shown in FIG. 3, the integrated circuit 56 includes a main signal circuit 57 and a threshold setting circuit 53.

As shown in FIG. 3, the main signal circuit 57 includes an amplifier 58 and a comparator 59. As shown in FIG. 3, the A-phase first output terminal (Va1) 50 and the A-phase second output terminal (Va2) 51 are connected to the input section of the amplifier 58, and the output section of the amplifier 58 is the input section of the comparator 59. It is connected to the.

As shown in FIG. 3, the threshold setting circuit 53 includes a peak detection unit 61, an A / D converter 62, a first storage unit (Shift Register) 63, a second storage unit (Shift Register) 64, and a D / A converter. 65 and a threshold generation unit 66. As shown in FIG. 3, the threshold setting circuit 53 branches from the main signal circuit 57, and the input unit of the peak detection unit 61 constituting the threshold setting circuit 53 is connected to the output unit of the amplifier 58 to configure the threshold setting circuit 53. The output unit of the threshold generation unit 66 is connected to the input unit of the comparator 59.
Although not shown, the B phase also constitutes a circuit similar to FIG.

The magnetic encoder 20 shown in FIG. 1 has a double frequency configuration (outputs two pulses in one period (λ)), and the interval between the centers of the magnetic detection elements connected in series in the bridge circuit shown in FIG. 2

When the magnetic sensor 22 moves relative to the magnet 21 in the Y1 direction, the external magnetic fields H1, H2 enter the magnetic detection elements A1, A2, B1, B2 from the magnetized surface 21a of the magnet 21. As shown in FIG. 1, the directions of the external magnetic field H1 and the external magnetic field H2 are different, and when the magnetic detection element is positioned on the magnetic pole, the perpendicular magnetic field is dominant in the magnetic field component with respect to the magnetic detection element, and the external magnetic field is zero. (No magnetic field state).

As a representative example, a state in which an external magnetic field enters the magnetic detection element A1 and the magnetic detection element A2 that constitute an A-phase bridge circuit and are connected in series will be described.

The magnetic detection element A1 and the magnetic detection element A2 are separated from each other by λ / 2 in the relative movement direction (Y1 direction). When the magnetic detection element A1 is positioned on the magnetic pole in the non-magnetic state, the magnetization direction (P Direction) and the magnetization direction (F direction) of the free magnetic layer 10 are parallel to each other, so that the electric resistance value is a minimum value. On the other hand, the magnetic detection element A2 receives the external magnetic field H1 or the external magnetic field H2, and the electrical resistance value increases from the minimum value.

Further, when the magnetic detection element A2 is positioned on the magnetic pole in the non-magnetic field state and the electric resistance value is the minimum value, the magnetic detection element A1 receives the external magnetic field H1 or the external magnetic field H2, and the electric resistance value is the minimum value. It grows from.

The sensor output shown in FIG. 5 (a) is the sensor output (analog value) amplified by the amplifier 58. The sensor output shown in FIG. 5A is an actual measurement value when the magnetic sensor 22 of the double frequency configuration travels away from a position opposite to the center line of the magnet 21.

As shown in FIG. 5A, when the magnetic sensor 22 relatively moves in the Y1 direction from the initial position (0), a sensor output in which a maximum peak and a minimum peak appear twice each in one period (λ). can get. As shown in FIG. 5A, for example, it can be seen that the maximum peak A and the maximum peak C have different output values. Further, as shown in FIG. 5A, it can be seen that the minimum peak B and the minimum peak D have different output values. For example, the output waveform (1) reaching the minimum peak B, the maximum peak C, and the minimum peak D is different from the output waveform (2) reaching the minimum peak D, the maximum peak E, and the minimum peak F, and the output waveform ( It can be seen that 1) and the output waveform (2) appear alternately.

The sensor output amplified by the amplifier 58 is sent to both the comparator 59 and the peak detection unit 61 constituting the threshold setting circuit 53.

The peak detector 61 detects the maximum peak output value (Vmax) of the sensor output. Further, the peak detection unit 61 detects the output value (Vmin) of the minimum peak of the sensor output. The output value detected by the peak detector 61 is preferably an analog value for reliable detection, but the analog value is converted to a digital value by the A / D converter 62 in order to maintain the peak value for a long period of time. Is preferred. FIG. 5B shows a digitized maximum peak, and FIG. 5C shows a digitized minimum peak.

In the initial stage (when starting to move from a stationary state), a comparator threshold value is preset as an initial setting value. A rising threshold value (VTH1) and a falling threshold value (VTL1) are set as initial threshold values (see FIG. 5D). The threshold values (VTH1, VTL1) in the initial setting are all set to small values close to the reference level.

When the magnetic sensor 22 starts relative movement in the Y1 direction from the stationary state, the sensor output gradually increases from the initial position (0), and when the sensor output exceeds the rising threshold value (VTH1), (1) in FIG. ), The comparator output becomes a high level.

Among them, the sensor output passes the maximum peak A. At this time, the peak detection unit 61 detects the maximum peak A and holds the value of the maximum peak A digitized by the A / D converter 62.

When the sensor output gradually decreases from the maximum peak A and falls below the falling threshold value (VTL1) in the initial setting, the comparator output becomes the low level as shown in (2) of FIG. At this time, the held value of the maximum peak A is stored in the maximum storage portion of the first storage unit 63. At the same time, the detection level of the maximum peak is returned to the initial state (FIG. 5B).

Subsequently, the sensor output passes through the minimum peak B. At this time, the minimum peak B is detected by the peak detector 61 and the value of the minimum peak B digitized by the A / D converter 62 is held.

When the sensor output gradually rises from the minimum peak B and exceeds the rising threshold value (VTH1) in the initial setting, the comparator output becomes a high level as shown in (3) of FIG. At this time, the held minimum peak B is stored in the minimum storage portion of the first storage unit 63. At the same time, the detection level of the minimum peak is returned to the initial state (FIG. 5C).

Subsequently, the sensor output passes through the maximum peak C. At this time, the peak detection unit 61 detects the maximum peak C and holds the maximum peak C digitized by the A / D converter 62.

When the sensor output gradually decreases from the maximum peak C and falls below the falling threshold value (VTL1) in the initial setting, the comparator output becomes a low level as shown in (4) of FIG.

At this time, the held maximum peak C is stored in the maximum storage portion of the first storage unit 63, but the maximum peak A stored in the first storage unit 63 is stored in the second storage unit. Forwarded to the department. At the same time, the detection level of the maximum peak is returned to the initial state (FIG. 5B).

The data of the maximum peak A transferred to the second storage unit 64 is D / A converted by the D / A converter 65 shown in FIG. 3, and based on this value, the threshold value generation unit 66 sets a new rising threshold value (VTH2). generate. This rising threshold value (VTH2) is set as the next comparator threshold value. At this time, the minimum peak has not yet been stored in the second storage unit 64, and thus the complete threshold value has not been set.

Subsequently, the sensor output passes through the minimum peak D. At this time, the minimum peak D is detected by the peak detector 61 and the minimum peak D digitized by the A / D converter 62 is held.

When the sensor output gradually rises from the minimum peak D and exceeds the rising threshold value (VTH2), the comparator output becomes a high level as shown in (5) of FIG.

At this time, the held minimum peak D is stored in the minimum storage portion of the first storage unit 63, but the minimum peak B stored in the first storage unit 63 is stored in the minimum storage of the second storage unit. Forwarded to the department. At the same time, the detection level of the minimum peak is returned to the initial state (FIG. 5C).

The data of the minimum peak B transferred to the second storage unit 64 is D / A converted by the D / A converter 65 shown in FIG. 3, and based on this value, the threshold value generation unit 66 generates a new falling threshold value (VTL3). Is generated. This falling threshold value (VTL3) is sent to the comparator 59 and set to the next comparator threshold value.

Here, a threshold value that does not exceed the minimum peak B and is as close as possible to the minimum peak B is set. From here, a completely dynamic threshold setting is performed.

Subsequently, the sensor output passes through the maximum peak E. At this time, the peak detection unit 61 detects the maximum peak E and holds the maximum peak E digitized by the A / D converter 62.

When the sensor output gradually decreases from the maximum peak E and falls below the falling threshold value (VTL3), the comparator output becomes a low level as shown in (6) of FIG.

At this time, the held maximum peak E is stored in the maximum storage portion of the first storage unit 63, but the maximum peak C stored in the first storage unit 63 is stored in the maximum storage of the second storage unit. Forwarded to the department. At the same time, the detection level of the maximum peak is returned to the initial state (FIG. 5B).

The data of the maximum peak C transferred to the second storage unit 64 is D / A converted by the D / A converter 65 shown in FIG. 3, and based on this value, the threshold value generation unit 66 sets a new rising threshold value (VTH3). generate. This rising threshold value (VTH3) is sent to the comparator 59 and set to the next comparator threshold value. Here, a threshold value that does not exceed the maximum peak C and is as close as possible to the maximum peak C is set.

In the present embodiment, the dynamic threshold setting based on the maximum peak and the minimum peak of the sensor output described above is repeated to obtain the comparator output shown in FIG.

The rising threshold value (VTH4) shown in FIG. 5 (d) is a threshold value generated based on the maximum peak E ·· having a smaller protruding amount than the maximum peaks C and G ··. Further, the falling threshold value (VTL4) shown in FIG. 5 (d) is a threshold value generated based on the minimum peak D ·· having a smaller protruding amount than the minimum peaks B and F ··.

The threshold value in the present embodiment described above is generated based on the previous maximum peak and minimum peak. For example, the rising threshold value (VTH3) for the protruding waveform portion of the maximum peak G is generated based on the maximum peak C two times before the maximum peak G. The same applies to the minimum peak. For example, the falling threshold value (VTL3) for the protruding waveform portion of the minimum peak F is generated based on the maximum peak B two times before the minimum peak F.

As described above, in the double frequency configuration, different output waveforms (1) and output waveforms (2) appear alternately in the sensor output, and almost the same maximum peak and minimum peak appear alternately (see FIG. 5). (See (a)). Therefore, as shown in the present embodiment, by setting the threshold based on the previous maximum peak and minimum peak, binary values of high / low as shown in the comparator output after (5) of FIG. The duty ratio of the signal can be made constant.

Further, although the duty ratio is slightly reduced from the resting state to several pulses (two pulses in FIG. 5E), thereafter, the threshold value is based on the two previous maximum and minimum peaks as in this embodiment. By setting the threshold, the threshold value can be dynamically changed close to the maximum peak and minimum peak, chattering can be prevented, and stable output can be obtained without causing detection errors as in the past. Is possible.

As shown in FIG. 5D, it is preferable that the initial setting value of the comparator threshold is a value close to the reference level assuming the minimum value of the sensor output peak. As a result, the duty ratio decreases as described above, but a high / low binary signal can be reliably output from the beginning.

In addition, when the operation is stopped after the operation and then restarted for a while, and the stop time is short, the threshold value may be set based on the maximum peak and the minimum peak stored in the second storage. Since the maximum peak and the minimum peak stored in the second storage may be different from the original maximum peak and minimum peak due to drift, when the operation stops for a predetermined time or more, the first storage 63 and the second storage It is preferable to perform dynamic threshold setting again after erasing the data in the device 64 and using the initial threshold value described with reference to FIG.

In this embodiment, only the A phase may be used, but by using both the A phase and the B phase, it is possible to know the moving direction in addition to the moving speed and the moving distance.

Further, as shown in FIG. 4, in the B phase and the A phase, the A / D converter 62 and the D / A converter 65 having a relatively large circuit scale can be shared by time-division driving, so that a threshold setting circuit is configured. One A / D converter 62 and one D / A converter 65 may be provided. As a result, the circuit can be made smaller. 4, the same reference numerals as those in FIG. 3 denote the same components. 4, reference numeral 70 is a B-phase amplifier, reference numeral 71 is a B-phase comparator, reference numeral 72 is a B-phase peak detection unit, reference numeral 73 is a first B-phase storage unit, and reference numeral 74 is a second B-phase signal. A storage unit, reference numeral 75 is a B-phase threshold generation unit.

In the magnetic encoder 20 of the present embodiment, the magnetic sensor 22 linearly moves relative to the magnet 21 as shown in FIG. 1, but as shown in FIG. This is a rotary magnetic encoder having a rotating drum magnet 80 and magnetic sensor 22 alternately magnetized with S poles, and the rotation speed, rotation speed, and rotation direction are determined by the output obtained by rotation of the magnet 80. It may be a rotary magnetic encoder that can be detected.

The magnet may be either a radial type or an axial type.
In the rotary magnetic encoder, even if the magnetic sensor 22 is displaced in the vertical direction from the center line of the side surface 80a of the magnet 80, or the same variation as in the prior art shown in FIGS. By setting the threshold based on the previous maximum peak and minimum peak, the duty ratio of the high / low binary signal is constant and a stable output can be obtained.

The perspective view of the magnetic encoder of this embodiment, Partial sectional view of the magnetic detection element of the present embodiment, The circuit configuration diagram of the magnetic sensor of the present embodiment, The circuit block diagram of the magnetic sensor in other embodiment, It is for demonstrating the output process from the sensor output in this embodiment to a comparator output (conversion to a binary signal), (a) Sensor output (b) Peak detection (maximum value), (c) Peak detection (Minimum value) (d) Comparator threshold (e) Diagram showing comparator output, A plan view of the rotary magnetic encoder of the present embodiment, Plan view of a conventional rotary magnetic encoder, FIG. 7 is a side view of the rotary magnetic encoder as viewed from the direction of arrow a. The front view of the rotary magnetic encoder which looked at the rotary magnetic encoder of FIG. 7 from the arrow b direction, The sensor output when the 10 ° rotation mode γ is generated from the normal state of FIG. The sensor output when the magnetic sensor 2 has a rotation mode β of 10 ° with the Z-axis direction as the rotation center from the normal state of FIG. The figure which shows the conventional comparator output (binary signal),

7 Antiferromagnetic layer 8 Pinned magnetic layer 9 Nonmagnetic layer 10 Free magnetic layer 11 Protective layer 20 Magnetic encoder 21, 80 Magnet 22 Magnetic sensor 23 Substrate 53 Threshold setting circuit 55 Sensor unit (bridge circuit)
56 Control unit (integrated circuit)
57 Main signal circuit 58, 70 Amplifier 59, 71 Comparator 61, 72 Peak detector 62 A / D converter 63, 73 First storage 64, 74 Second storage 65 D / A converter 66, 75 Threshold generator A1, A2, B1, B2 Magnetic detection elements A, C, E, G Maximum peaks B, D, F Minimum peaks H1, H2 External magnetic field

Claims (5)

A magnetic field generating member having a magnetized surface in which N and S poles are alternately magnetized in the relative movement direction is disposed at a position away from the magnetized surface, and the magnetic resistance value changes with respect to an external magnetic field. In a magnetic sensor comprising a sensor unit having a detection element and a control unit for generating a high / low binary signal based on a sensor output from the sensor unit,
The control unit compares the sensor output with a threshold value to obtain the binary signal, and a threshold setting circuit that sets the threshold value based on the maximum peak and the minimum peak of the two previous sensor outputs And a magnetic sensor. The threshold setting circuit includes a peak detection unit that detects a maximum peak and a minimum peak of the sensor output, a first storage unit that stores a maximum peak and a minimum peak of the previous sensor output, and a second previous The magnetic sensor according to claim 1, further comprising: a second storage unit that stores a maximum peak and a minimum peak of the sensor output; and a threshold generation unit that generates the threshold based on data stored in the second storage unit. The magnetic sensor according to claim 1, wherein the magnetic detection element is an MR element using a magnetoresistive effect. A magnetic encoder comprising the magnetic sensor according to claim 1 and the magnetic field generating member. 5. The magnetic encoder according to claim 4, wherein the magnetic encoder has a double frequency configuration that outputs two pulses in one cycle.

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