WO2010098259A1

WO2010098259A1 - Magnetic encoder

Info

Publication number: WO2010098259A1
Application number: PCT/JP2010/052532
Authority: WO
Inventors: 眞喜人瀧川; 幸光山田; 賢川畑
Original assignee: アルプス電気株式会社
Priority date: 2009-02-26
Filing date: 2010-02-19
Publication date: 2010-09-02

Abstract

Provided is a magnetic encoder equipped with a signal processing circuit with lower number of elements than that of circuitry equipped with an absolute value circuit. A plurality of magnetic detection elements (R11 to R23) configure a series circuit equipped with an output part (T0) in the midpoint. An output area (A) of a high output voltage (H1) higher than an intermediate voltage (V0), and an output area (B) of a low output voltage (L1) lower than the intermediate voltage (V0) are alternately obtained from the output part (T0). An integrated circuit (21) is configured by comprising a differential amplifier (26), a first comparator (22) having a first threshold voltage (V1) and a second comparator (23) having a second threshold voltage (V2), which are bifurcated and connected from the output part side of the differential amplifier (26), respectively, and an OR circuit (24) which is connected to the respective output sides of the first comparator (22) and the second comparator (23), and combines the pulse signal from the first comparator and the pulse signal from the second comparator.

Description

Magnetic encoder

The present invention relates to a signal processing circuit for a magnetic encoder.

FIG. 6 is a signal processing circuit diagram and an output waveform diagram of a high resolution magnetic encoder using a magnetic sensor formed by combining a plurality of magnetic detection elements, which the present inventors considered. In the following description, for the sake of convenience, the configuration in FIG. 6 may be referred to as “conventional configuration” or “conventional circuit configuration”.

As shown in FIG. 6, a plurality of magnetic detection elements R1 to R6 are connected in series, and an output voltage from a midpoint that divides the plurality of magnetic detection elements R1 to R6 into the same number is input to the differential amplifier 1. Further, as shown in FIG. 6, an absolute value circuit (ABS circuit) 2 is connected to the output side of the differential amplifier 1, and a comparator 3 is connected between the output side of the absolute value circuit 2 and the output terminal 4. .

(A) in FIG. 6 shows output voltages from the plurality of magnetic detection elements R1 to R6. The output voltage is amplified by the differential amplifier 1 as shown in FIG.

As shown in the example of FIG. 7, the absolute value circuit 2 has a configuration in which an adder circuit is connected to the subsequent stage of the ideal diode circuit.

In the ideal diode circuit 7 provided in the previous stage of the absolute value circuit 2, the low output voltage lower than the reference voltage is inverted to the high output side with the reference voltage as the axis of symmetry (higher than the reference voltage depending on the direction of the diode). The high output voltage can be inverted), and the adder circuit 8 in the subsequent stage adds the inverted output voltage and the non-inverted output voltage that is originally higher than the reference voltage (absolute value shown in FIG. 6). (Refer waveform (c) from circuit 2).

As described above, in the absolute value circuit 2, all output voltages are processed so as to be obtained on either the high output side or the low output side of the reference voltage.

The comparator 3 compares a predetermined threshold voltage with the output voltage input from the absolute value circuit 2, and outputs a signal when an output voltage equal to or higher than the threshold voltage is input, as shown in FIG. A pulse signal (digital value) is obtained.

As shown in FIG. 7, the absolute value circuit 2 is not a simple diode circuit, but uses two operational amplifiers 5 and 6.
The operational amplifier is composed of a number of transistors as shown in FIG.

Japanese Patent Laid-Open No. 7-183591 JP-A-4-69986

However, in the conventional circuit configuration in which signal processing is performed by the absolute value circuit 2 and the comparator 3, the number of elements increases due to the increase in the number of operational amplifiers, the burden on ASIC (Application Specific Integrated Circuit) design increases, the size of the signal processing circuit increases, and the manufacturing cost. The problem of increasing

Patent Document 1 discloses a circuit configuration in which the output voltage from the MRE bridge circuit 2 is input to the differential amplifier 5 and the amplified output voltage is input to the binarization circuit 4. Further, an output correction circuit 3 is provided, and this output correction circuit 3 is provided with an upper limit value setting comparator 6a, a lower limit value setting comparator 6b, an OR circuit 7, and the like.

The output correction circuit 3 is for correcting the output of the magnetic detection sensor to operate the binarization circuit 4 stably. On the main circuit for waveform shaping from the differential amplifier to the external connection terminal. It does not exist. In the invention described in Patent Document 1, a region having a higher output voltage than the reference voltage and a region having a lower output voltage than the reference voltage, which are obtained from the series circuit of the magnetic detection elements R1 to R6, are alternately repeated. Signal processing for obtaining the final waveform shown in FIG. 6D is not performed on the output voltage. The same applies to Patent Document 2.

Therefore, the present invention is to solve the problem in the circuit configuration of FIG. 6 described above, and in particular, provides a magnetic encoder including a signal processing circuit having a smaller number of elements than a circuit configuration including an absolute value circuit. For the purpose.

The present invention includes a magnetic field generating member having a magnetized surface in which N and S poles are alternately magnetized in the relative movement direction, and a position away from the magnetized surface of the magnetic field generating member. In contrast, a magnetic encoder including a magnetic sensor having an integrated circuit and a magnetic detection element whose electrical characteristics change,
A plurality of the magnetic detection elements are provided in the magnetic sensor, and the plurality of magnetic detection elements constitute a series circuit having an output portion at a midpoint, and are used for relative movement of the magnetic field generating member with respect to the magnetic sensor. Accordingly, a high output region where a high output voltage higher than the intermediate voltage is output and a low output region where a low output voltage lower than the intermediate voltage is output are alternately obtained,
A first comparator having a first threshold voltage between the high output voltage and the intermediate voltage, connected to the integrated circuit in a bifurcated manner from the output part side of the series circuit, and the low output voltage And a second comparator having a second threshold voltage between the intermediate voltage and the first comparator and the output side of the second comparator and an external output terminal, and obtained from the first comparator. And an OR circuit for combining the pulse signal obtained from the second comparator and the pulse signal obtained from the second comparator.

With the above configuration, one operational amplifier can be reduced compared to a circuit configuration having an absolute value circuit. In the present invention, an OR circuit is used. The OR circuit can be composed of several transistors, or can be composed of a so-called wired OR that does not use transistors. Therefore, the ASIC design can be facilitated as compared with the circuit configuration using the absolute value circuit, and the signal processing circuit can be downsized and the manufacturing cost can be reduced.

Further, in the high output region and the low output region, the high output voltage and the low output voltage are output a plurality of times through the intermediate voltage, so that a large number of pulse signals can be obtained. Therefore, a high-resolution magnetic encoder can be configured. In addition, the output voltage is not stepped up or down to a plurality of levels, but a plurality of high output voltages or low output voltages can be obtained via an intermediate voltage, making it easy to set the threshold voltage of the comparator. .

In this case, in the present invention, the plurality of magnetic detection elements are connected in series to one side with respect to the midpoint of the series circuit and in series with the other side with respect to the midpoint. The number of second magnetic detection elements is the same as the number of the first magnetic detection elements connected, and the first magnetic detection element and the second magnetic detection element are in the relative movement direction of the magnetic field generating member. The magnetic detection elements are arranged in a range of one pole of N or S poles in the relative movement direction of the magnetic field generating member. As a result, a configuration in which a high output voltage and a low output voltage are output a plurality of times via an intermediate voltage in a high output region and a low output region can be easily achieved by arranging and connecting a plurality of magnetic detection elements. Obtainable.

In the present invention, it is preferable that an amplifier circuit is provided between the output unit of the series circuit and the first comparator and the second comparator. As a result, the threshold voltage of the comparator can be set more easily.

In the present invention, the magnetic sensing element is preferably a GMR element (giant magnetoresistive element).

The GMR element has a large resistance change rate and detects the direction, not the magnitude of the magnetic field, so that the output voltage can be increased and the detection accuracy can be improved effectively.

According to the magnetic encoder of the present invention, operational amplifiers can be reduced as compared with a circuit configuration having an absolute value circuit. In the present invention, an OR circuit is used. The OR circuit can be composed of several transistors, or can be composed of a so-called wired OR that does not use transistors. Therefore, the ASIC design can be facilitated as compared with the circuit configuration using the absolute value circuit, and the signal processing circuit can be downsized and the manufacturing cost can be reduced.

The top view of the magnetic encoder of this embodiment, Sectional drawing of the magnetic encoder shown in FIG. FIG. 1 is a configuration diagram of a magnetic sensor (magnetic detection element) in the magnetic encoder shown in FIG. 1 and a schematic diagram showing a relationship with a magnet; The circuit block diagram of the magnetic sensor in this embodiment, A more specific circuit configuration diagram of an integrated circuit provided in the magnetic sensor in the present embodiment, A circuit configuration diagram of a magnetic sensor having an absolute value circuit, A circuit configuration diagram of an absolute value circuit (ABS circuit), Operational amplifier circuit configuration diagram,

1 is a plan view of the magnetic encoder of the present embodiment, FIG. 2 is a cross-sectional view of the magnetic encoder shown in FIG. 1, and FIG. 3 is a configuration diagram of a magnetic sensor (magnetic detection element) in the magnetic encoder shown in FIG. 4 is a schematic diagram showing a relationship with a magnet, FIG. 4 is a circuit configuration diagram of a magnetic sensor in the present embodiment, and FIG. 5 is a more specific circuit configuration diagram of an integrated circuit provided in the magnetic sensor in the present embodiment. . In this embodiment, the magnet 11 has a ring shape as shown in FIG. 1, but in FIG. 3, the positional relationship between the magnet 11 and the magnetic detection element constituting the magnetic sensor by expanding the magnetized surface of the magnet 11 on a plane. Is shown.

The magnetic encoder 10 in this embodiment is a device that detects a rotation angle, a rotation direction, a rotation speed, or the like. The magnetic encoder 10 includes a magnet 11 that is a magnetic field generating member, a rotating body 12 that rotatably supports the magnet 11, a housing 9 that rotatably supports the rotating body 12, a magnetic sensor 20 that includes a magnetic detection element and an integrated circuit. It is comprised.

For example, the magnet 11 has a ring shape, and the outer peripheral surface of the rotating body 12 is fixed to the inner surface side thereof. A plurality of magnetic poles composed of N poles and S poles are alternately magnetized on the outer peripheral surface 11A of the magnet 11 at equal intervals (equal angular intervals).

The magnet 11 and the rotating body 12 are arranged in a circular recess 9A provided in the housing 9. As shown in FIG. 2, a through hole 9 a is formed at the center of the housing 9. A rotating shaft 12a provided at the center of the rotating body 12 is inserted through the through hole 9a.

The magnet 11 is supported so as to be rotatable in the counterclockwise direction ra1 and the clockwise direction ra2 in the recess 9A with the rotation axis 12a of the rotating body 12 as an axis center. That is, in this embodiment, the magnet 11 moves relative to the magnetic sensor 20 described later in the circumferential direction.

The housing 9 is formed with a notch 9b in which a part of the recess 9A is notched in the outer peripheral direction. The magnetic sensor 20 is fixed in the notch 9b via a substrate (silicon substrate) (not shown), and faces the outer peripheral surface 11A, which is the magnetized surface of the magnet 11, in a separated state. That is, a predetermined interval is provided between the magnetic sensor 20 and the outer peripheral surface 11A, and the magnetic sensor 20 is disposed in the vicinity of the outer peripheral surface of the outer peripheral surface 11A.

As shown in FIG. 3, the magnetic sensor 20 is provided with a plurality of magnetic detection elements R11 to R23. In the present embodiment, the magnetic detection element is, for example, a GMR element (giant magnetoresistive effect element), and has a basic laminated structure of antiferromagnetic layer / fixed magnetic layer / nonmagnetic layer / free magnetic layer. For example, the magnetization of the fixed magnetic layer is fixed in a tangential direction with respect to the rotation direction of the magnet 11. Note that the magnetization directions of the pinned magnetic layers in all the magnetic detection elements R11 to R23 are the same.

As shown in FIG. 3, the magnetic detection elements R11 to R23 are arranged in a row in the rotational tangential direction, which is the direction along the relative movement direction of the magnet 11. As shown in FIG. 3, every other magnetic detection element R11, R12, R13 is connected in series, and every other magnetic detection element R21, R22, R23 is connected in series. ing.

In addition, as shown in FIG. 3 described above, the magnetic detection element R11 and the magnetic detection element R21 are connected via the output unit T0, whereby all the magnetic detection elements R11 to R23 are connected in series. As shown in FIG. 3, an input terminal (power supply terminal) T1 is connected to the magnetic detection element R13, and a ground terminal T2 is connected to the magnetic detection element R23.

As shown in FIG. 3, all the magnetic detection elements R11 to R23 provided in the magnetic sensor 20 are arranged so as to be within the range of one pole of the N pole (or S pole) in the relative movement direction of the magnet 11. ing. In this embodiment, since the magnet 11 is ring-shaped and rotates, all the magnetic detection elements R11 are within an angular range of one pole from the rotation center of the magnet 11 to the N pole (or S pole). Contains R23.

As shown in FIG. 4, six magnetic detecting elements R11 to R23 having the same resistance value are connected in series between the input terminal T1 and the ground terminal T2. An output unit T0 is provided at a midpoint that divides the three magnetic detection elements R11, R12, and R13 and the three magnetic detection elements R21, R22, and R23. Accordingly, the three magnetic detection elements R11, R12, and R13 connected in series between the output portion T0 and the input terminal T1, which are the midpoints of the series circuit of the six magnetic detection elements R11 to R23, are connected to the first magnetic detection element. The three magnetic detection elements R21, R22, and R23, which are elements and are connected in series between the output unit T0 and the ground terminal T2, serve as second magnetic detection elements. Although the number of magnetic detection elements is not limited to six, an even number of magnetic detection elements are provided, and an output unit T0 is provided at a midpoint that divides the magnetic detection elements into the same number.

The direction of the magnetic field by the magnet 11 acting on all the magnetic detection elements R11 to R23 is the same (for example, the direction along the magnetization direction of the fixed magnetic layer), and the resistance values of all the magnetic detection elements R11 to R23 are the same. In the initial state (for example, the resistance values of all the magnetic detection elements R11 to R23 are the minimum resistance value), when the magnet 11 rotates, for example, in the ra1 direction of FIG. 3, the direction of the magnetic field acting on the magnetic detection element R11 is, for example, reversed. Change. Accordingly, when the resistance value of the magnetic detection element R11 changes, the output voltage from the output unit T0 changes by an amount corresponding to the resistance change of the magnetic detection element R11. Subsequently, when the magnet 11 rotates in the same direction and the resistance value of the magnetic detection element R21 changes together with the magnetic detection element R11, the combined resistance value on the magnetic detection elements R11 to R13 side with the output unit T0 as the center, As the combined resistance value on the detection elements R21 to R23 side becomes the same resistance value, the output voltage of the output unit T0 returns to the output voltage in the initial state.

Further, when the magnet 11 rotates and the resistance value of the magnetic detection element R12 changes together with the magnetic detection elements R11 and R21, the output voltage of the output unit T0 is changed from the initial state by an amount corresponding to the resistance change of the magnetic detection element R12. Change.

FIG. 4A shows an output voltage from the output unit T0. As shown in FIG. 4, the high output voltage H1 higher than the intermediate voltage V0 is output three times, the high output region A repeatedly output via the intermediate voltage V0, and the low output voltage L1 lower than the intermediate voltage V0 is output three times. Low output regions B that are repeatedly output via the intermediate voltage V0 are alternately obtained from the output unit T0. When Vdd is applied as a power supply voltage between the input terminal T1 and the ground terminal T2, the intermediate voltage V0 is Vdd / 2. Three high output voltages H1 are output to the high output region A and three low output voltages L1 are output to the low output region B because six magnetic detection elements R11 to R23 are provided in total. It is. Therefore, if the number of the magnetic detection elements R11 to R23 is changed, the number of outputs of the high output voltage H1 and the low output voltage L1 also changes. Then, by setting so that a plurality of output voltages can be obtained in the high output region A and the low output region B and detecting the plurality of output voltages, it is possible to appropriately function as a high resolution magnetic encoder.

As shown in FIG. 4, the integrated circuit 21 is provided with a differential amplifier 26, a first comparator 22, a second comparator 23, an OR circuit 24, an external output terminal 25, and the like. Note that all the magnetic detection elements R11 to R23 and the integrated circuit 21 are provided on the same substrate (silicon substrate) (not shown) and constitute the magnetic sensor 20.

As shown in FIG. 4, the differential amplifier 26, which is an amplifier circuit, is connected to the output section T0 of the series circuit of the magnetic detection elements R11 to R23. As shown in FIG. 4B, the output voltage is amplified by the differential amplifier 26. As a result, the high output voltage H1 shown in (a) is amplified to H2, and the low output voltage L1 is amplified to L2. At this time, the intermediate voltage V0 is also amplified, but for convenience, the intermediate voltage after amplification is also described as “intermediate voltage V0”.

Next, as shown in FIG. 4, the output side of the differential amplifier 26 is divided into two branches, one connected to the first comparator 22 and the other connected to the second comparator 23.

In the first comparator 22 shown in FIG. 4, as shown in (c), the first threshold voltage V1 is set between the amplified high output voltage H2 and the intermediate voltage V0. In the second comparator 23, as shown in (d), the second threshold voltage V2 is set between the amplified low output voltage L2 and the intermediate voltage V0.

Then, the first comparator 22 compares the input output voltage with the first threshold voltage V1, and controls to output a signal with an output voltage exceeding the first threshold voltage V1, (e) The pulse signal shown in FIG. For example, as shown in (e), when the output voltage is lower than the first threshold voltage V1, the signal is “Low” level, and when the output voltage is higher than the first threshold voltage V1, the signal of “High” level is output. Further, the second comparator 23 compares the input output voltage with the second threshold voltage V2, and controls to output a signal with an output voltage lower than the second threshold voltage V2, and (f) The pulse signal shown in FIG. As shown in (f), when the output voltage exceeds the second threshold voltage V2, a signal is output at the “Low” level, and when the output voltage is lower than the second threshold voltage V2, a signal at the “High” level is output.

As shown in FIG. 4, an OR circuit 24 is connected between the output sides of the first comparator 22 and the second comparator 23 and the external output terminal 25.

The pulse signal generated by the first comparator 22 shown in (e) and the pulse signal generated by the second comparator 23 shown in (f) are combined by the OR circuit 24 and shown in (g), etc. A continuous pulse signal is generated at intervals.

In this embodiment, as shown in FIGS. 4 and 5, an absolute value circuit (ABS circuit) is not used unlike the conventional circuit configuration shown in FIG. In this embodiment, two

comparators

22 and 23 are used. However, in the conventional configuration, an absolute value circuit (ABS circuit) using two operational amplifiers and a comparator are provided (see FIGS. 6 and 7). In the embodiment, one operational amplifier can be reduced compared to the conventional circuit configuration. Further, the OR circuit 24 composed of TTL needs only to use about four transistors. Further, in the present embodiment shown in FIG. 5, an OR circuit is configured by a so-called wired OR that connects the output terminals of the

comparators

22 and 23. In this case, a transistor is also unnecessary. Therefore, according to the signal processing circuit of this embodiment, the ASIC design can be facilitated more easily than the conventional configuration, and the signal processing circuit can be downsized and the manufacturing cost can be reduced.

4 and 5, the configuration of the magnetic detection element and the integrated circuit is, for example, the A phase. Although not shown, the B phase having the same configuration exists. However, one B-phase magnetic detection element is arranged between the magnetic detection elements R11 to R23 shown in FIG. 3 and one outside the magnetic detection elements R11 and R23. As a result, since the output timing of the pulse signal shown in FIG. 4E is shifted between the A phase and the B phase, the rotation direction of the magnet 11 can be known from the output states of the A phase pulse signal and the B phase pulse signal. it can. Further, the rotation angle and the rotation speed can be detected by the pulse signal obtained from the external output terminal 25.

Examples of the magnetic detection elements R11 to R23 include a Hall element and an AMR element. However, by using a GMR element that has a large resistance change rate and detects a direction instead of the magnitude of the magnetic field, the output voltage can be increased and the detection accuracy can be increased. It is possible to improve.

In the above-described embodiment, a rotary magnetic encoder in which the circular magnet 11 is rotated is used. However, for example, a magnetic encoder in which the magnet 11 is linearly moved in a rod shape may be used. Further, the magnet may be fixed and the magnetic sensor may be moved.

R11 to R23 Magnetic detection element T0 Output unit V0 Intermediate voltage V1 First threshold voltage V2 Second threshold voltage 10 Magnetic encoder 11 Magnet 12 Rotating body 20 Magnetic sensor 21 Integrated circuit 22 First comparator 23 Second comparator 24 OR Circuit 25 External output terminal 26 Differential amplifier

Claims

A magnetic field generating member having a magnetized surface in which N and S poles are alternately magnetized in the relative movement direction; and a magnetic field generating member disposed at a position away from the magnetized surface of the magnetic field generating member. In a magnetic encoder configured to include a magnetic detection element that changes and a magnetic sensor including an integrated circuit,
A plurality of the magnetic detection elements are provided in the magnetic sensor, and the plurality of magnetic detection elements constitute a series circuit having an output portion at a midpoint, and are used for relative movement of the magnetic field generating member with respect to the magnetic sensor. Accordingly, a high output region where a high output voltage higher than the intermediate voltage is output and a low output region where a low output voltage lower than the intermediate voltage is output are alternately obtained,
A first comparator having a first threshold voltage between the high output voltage and the intermediate voltage, connected to the integrated circuit in a bifurcated manner from the output part side of the series circuit, and the low output voltage And a second comparator having a second threshold voltage between the intermediate voltage and the first comparator and the output side of the second comparator and an external output terminal, and obtained from the first comparator. A magnetic encoder comprising: an OR circuit that synthesizes the obtained pulse signal and the pulse signal obtained from the second comparator.
The magnetic encoder according to claim 1, wherein the high output voltage and the low output voltage are output a plurality of times via the intermediate voltage in the high output region and the low output region, respectively.
The plurality of magnetic detection elements are connected in series on the other side with respect to the midpoint, and a plurality of first magnetic detection elements connected in series on one side with respect to the midpoint of the series circuit. The number of second magnetic detection elements is the same as the number of magnetic detection elements, and the first magnetic detection elements and the second magnetic detection elements are alternately arranged along the relative movement direction of the magnetic field generating member. 3. The magnetic encoder according to claim 2, wherein the plurality of magnetic detection elements are housed in a range of one pole of N pole or S pole in the relative movement direction of the magnetic field generating member.
4. The magnetic encoder according to claim 1, wherein an amplifier circuit is provided between the output unit of the series circuit and the first comparator and the second comparator. 5.
5. The magnetic encoder according to claim 1, wherein the magnetic detection element is a GMR element (giant magnetoresistive element).