JP2017044625A - Encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an encoder in which influence of an offset voltage to temperature characteristics of a magnetoresistive element is decreased.SOLUTION: Under operation of the encoder, an offset adjustment unit 94 successively records, in a memory 95, an offset voltage and a temperature of the magneto-sensitive element as a pair. The offset adjustment unit 94 derives an approximate expression on the basis of data in the memory 95, and calculates the temperature characteristics of the offset voltage. When the encoder is started next time, the offset adjustment unit 94 calculates the offset voltage just after the start on the basis of detection results of a temperature monitoring resistance film and a temperature calculation unit 93 and the temperature characteristics.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an encoder, and more particularly to an encoder including a magnetic sensor device.

  In an encoder that detects the rotation of a rotating body, for example, there is a magnetic sensor device provided with a magnet on the rotating body side and a magnetoresistive element (hereinafter referred to as “MR element”) or a Hall element on the fixed body side. Provided. In this magnetic sensor device, a magnetosensitive film made of a magnetoresistive film is formed on one surface of a substrate, and based on an output output from a two-phase (A phase and B phase) bridge circuit configured by the magnetosensitive film. Thus, the angular velocity and angular position of the rotating body are detected.

  Here, in general, the resistance value of the magnetosensitive film used for the MR element and the Hall element used in the magnetic sensor device varies depending on the temperature. Therefore, a technique for obtaining stable detection accuracy even when the ambient temperature changes has been proposed (see, for example, Patent Document 1). Specifically, a temperature monitoring resistance film and a heating resistance film (heater pattern) are formed on the substrate on which the magnetosensitive film is formed. Then, the temperature difference and temperature change from the set temperature are monitored by the resistance value of the temperature monitoring resistance film, and the heating resistance film is supplied based on the monitoring result to heat the magnetosensitive film to the set temperature. Therefore, when a change in the environmental temperature occurs, even if the resistance change due to the effect of stress or the resistance change due to the difference in film quality is different, it is difficult to be affected by the environmental temperature. However, stable detection accuracy can be obtained.

JP 2014-194360 A

  By the way, in the technique disclosed in Patent Document 1, temperature control is performed by a heater pattern to keep the MR element at a constant temperature. (1) At startup, it takes time until the temperature of the MR element becomes constant, or (2 ) Because the temperature sensor and the magnetic sensitive film are arranged differently, the temperature in the chip is not the same and an error due to temperature distribution is likely to occur, or (3) MR corresponding to the secular change of the offset voltage Although the offset voltage at the previous operation is used as the element offset voltage, there is a problem that the temperature characteristic is not considered. For example, offset is recorded at a high temperature during operation, but there is a problem that the error is large because the temperature is low at startup.

  The present invention has been made in view of such a situation, and an object thereof is to provide an encoder in which the influence of the temperature characteristics of the MR element is reduced.

  The encoder of the present invention includes a magnetoresistive element formed on a substrate, an offset voltage detector that detects an offset voltage of the magnetoresistive element, a temperature detector that detects a temperature of the magnetoresistive element, and the offset voltage And a temperature of the magnetoresistive element from the data of the offset voltage and the temperature of the magnetoresistive element recorded in the memory unit An approximate expression indicating the relationship is calculated, and at the time of start-up, the current offset voltage is estimated from the temperature of the magnetoresistive element based on the approximate expression, and the estimated offset voltage is used as a new offset voltage. An offset voltage determination unit. Therefore, it is not necessary to perform constant temperature control by heating the element at the time of start-up, and a suitable offset value can be acquired even if there is no time until a constant temperature is reached. That is, a highly accurate output can be realized immediately after startup.

  The temperature detecting unit may be provided on the same substrate on which the magnetoresistive element is formed. Therefore, substantially the temperature detection of the magnetoresistive element itself, that is, the temperature detection with high accuracy is possible.

  Further, when the offset voltage and the temperature of the magnetoresistive element are recorded in the storage unit in association with each other, the temperature range is divided into predetermined ranges, and the detected offset voltage within the temperature range is averaged. Also good. Therefore, the data capacity can be suppressed by averaging and recording the offset voltage separately for each predetermined temperature range. For example, a storage unit having a small capacity can be selected, data can be recorded over a long period, and long-term data can be corrected.

  Further, the offset voltage determination unit calculates a new approximate expression based on new data when the relationship between the measured offset voltage and the temperature of the magnetoresistive element is more than a predetermined amount away from the approximate expression. It may be calculated. Therefore, when the offset voltage largely deviates due to an external factor or the like, the offset voltage suitable for the situation can be obtained by once resetting the approximate expression, that is, the temperature characteristic of the magnetoresistive element.

  The temperature detector may calculate a resistance value of the magnetoresistive element and detect a current temperature from the calculated resistance value. Therefore, since the resistance value of the magnetoresistive element itself is used, there is no need to provide a separate temperature detection unit. In addition, since the temperature of the magnetosensitive portion of the magnetoresistive element can be detected, errors due to temperature distribution within the chip are reduced.

  The temperature detection unit detects the temperature of the magnetoresistive element once every communication cycle with an external control device, and the offset voltage determination unit calculates the approximate expression in the communication cycle. Also good. That is, the temperature calculation process is executed between the start of the angle response and the request from the next control device. In this way, by performing temperature detection for each communication cycle, the processing can be simplified compared to non-periodic processing such as interrupt processing. That is, a sufficient processing time can be secured, so that the temperature calculation process can be surely terminated.

  The temperature detector may include a temperature monitoring resistance film formed on the substrate on which the magnetoresistive element is formed. Therefore, the temperature distribution in the chip (on the substrate) can be ascertained by using the temperature monitoring resistive film in addition to detecting the temperature of the magnetosensitive element of the magnetoresistive element. Can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the encoder which reduced the influence of the temperature characteristic of a magnetoresistive element regarding an offset voltage can be provided.

It is a figure which shows the principle in the magnetic sensor apparatus and rotary encoder based on 1st Embodiment. It is a figure which shows the electrical connection structure of the magnetic sensitive film of the magnetic sensitive element used for the magnetic sensor apparatus and rotary encoder based on 1st Embodiment. It is a figure which shows the plane structure of the magnetosensitive element of the magnetic sensor apparatus based on 1st Embodiment. It is a block diagram of a control part concerning a 1st embodiment. It is the graph which showed the relationship between the temperature of a magnetosensitive element, and an offset voltage based on 1st Embodiment. It is a figure which shows the electrical connection structure of the magnetosensitive film of the magnetosensitive element used for the magnetic sensor apparatus and rotary encoder based on 2nd Embodiment.

  Embodiments of a magnetic sensor device and a rotary encoder to which the present invention is applied will be described below with reference to the drawings. In the rotary encoder, when detecting the rotation of the rotating body with respect to the fixed body, the fixed body is provided with a magnet, the rotating body is provided with a magnetic sensitive element, and the fixed body is provided with a magnetic sensitive element. Any of the configurations in which the magnet is provided may be adopted. However, in the following description, the description will focus on the configuration in which the magnetosensitive element is provided in the fixed body and the magnet is provided in the rotating body.

<First Embodiment>
FIG. 1 is an explanatory diagram showing the principle in the magnetic sensor device 10 and the rotary encoder 1 according to the first embodiment of the present invention. FIG. 1A illustrates a signal processing system for the magnetosensitive element 4 and the like. FIG. 1B is a diagram illustrating a signal output from the magnetosensitive element 4. FIG. 1C is a diagram showing the relationship between the signal and the angular position (electrical angle) of the rotating body 2. FIG. 2 is a diagram for explaining an electrical connection structure of the magnetosensitive films 41 to 44 (magnetoresistive films) of the magnetosensitive element 4 used in the magnetic sensor device 10 and the rotary encoder 1. FIG. 2A shows a diagram of the bridge circuit 4a formed by the + A phase magnetosensitive film 43 and the -A phase magnetosensitive film 41. FIG. FIG. 2B shows a diagram of the bridge circuit 4b formed by the + B phase magnetosensitive film 44 and the -B phase magnetosensitive film 42.

  A rotary encoder 1 shown in FIG. 1 is a device that magnetically detects a rotation around an axis (rotation axis) of a rotary body 2 with respect to a fixed body (not shown) by a magnetic sensor device 10. The fixed body is fixed to a frame or the like of the motor device, and the rotating body 2 is used in a state of being connected to a rotation output shaft or the like of the motor device. On the rotating body 2 side, a magnet 20 is held that directs the magnetized surface 21 in which the N pole and the S pole are magnetized one by one in the circumferential direction to one side in the rotation axis direction L. The magnet 20 rotates around the rotation axis integrally with the rotating body 2.

  On the fixed body side, there is a magnetic sensor device 10 including a magnetosensitive element 4 that faces the magnetized surface 21 of the magnet 20 on one side in the rotation axis direction L, a control unit 90 that performs processing to be described later, and the like. Is provided. Further, the magnetic sensor device 10 includes a first hall element 61 and a second hall element 62 at a position facing the magnet 20. The second Hall element 62 is located at a position that is shifted by 90 ° in mechanical angle in the circumferential direction with respect to the first Hall element 61.

  The magnetosensitive element 4 includes a two-phase magnetosensitive film (A phase (SIN) magnetosensitive film and B phase (COS) sensitive) having a phase difference of 90 ° with respect to the phase of the substrate 40 and the magnet 20. Magnetoresistive element provided with a magnetic film). Specifically, the A phase magnetosensitive film includes a + A phase (SIN +) magnetosensitive film 43 that detects movement of the rotating body 2 with a phase difference of 180 °, and a −A phase (SIN−) magnetosensitive film. 41 is provided. Similarly, the B-phase magnetosensitive film includes a + B-phase (COS +) magnetosensitive film 44 and a -B-phase (COS-) magnetosensitive film 42 that detect the movement of the rotating body 2 with a phase difference of 180 °. Prepare.

  As shown in FIG. 2A, the + A phase magnetic sensitive film 43 and the -A phase magnetic sensitive film 41 have one end connected to the A phase power supply terminal VccA and the other end connected to the A phase ground. It is connected to the terminal GNDA. An output terminal + A from which the + A phase is output is provided at the midpoint position of the + A phase magnetosensitive film 43. At the midpoint position of the -A phase magnetosensitive film 41, an output terminal -A from which the -A phase is output is provided.

  As shown in FIG. 2B, the + B phase magnetic sensitive film 44 and the −B phase magnetic sensitive film 42 are similar to the + A phase magnetic sensitive film 44 and the −A phase magnetic sensitive film 41 at one end. The B-phase power supply terminal VccB is connected, and the other end is connected to the B-phase ground terminal GNDB. An output terminal + B from which a + B phase is output is provided at the midpoint position of the + B phase magnetosensitive film 44, and an output from which the −B phase is output at the midpoint position of the −B phase magnetosensitive film 42. Terminal -B is provided.

  In FIG. 2, for convenience, the A-phase power supply terminal VccA and the B-phase power supply terminal VccB are shown, but the A-phase power supply terminal VccA and the B-phase power supply terminal VccB are common. May be. For convenience, FIG. 2 shows the A-phase ground terminal GNDA and the B-phase ground terminal GNDB, but the A-phase ground terminal GNDA and the B-phase ground terminal GNDB are common. May be.

  As shown in FIG. 1A, the magnetic sensing element 4 having such a configuration is arranged at a position where the magnet 20 overlaps the magnetization boundary portion in the rotation axis direction L. For this reason, the magnetic sensitive films 41 to 44 of the magnetic sensitive element 4 are rotated so that the direction of the magnetic sensitive films 41 to 44 changes in the in-plane direction of the magnetized surface 21 with a magnetic field strength equal to or higher than the saturation sensitivity region of the resistance value of each of the magnetic sensitive films 41 to 44. A magnetic field can be detected. That is, a rotating magnetic field whose direction in the in-plane direction changes with a magnetic field strength equal to or higher than the saturation sensitivity region of the resistance value of each of the magnetic sensitive films 41 to 44 is generated at the magnetization boundary line portion.

Here, the saturation sensitivity region generally refers to a region other than the region in which the resistance value change amount k can be approximately expressed by the magnetic field strength H and the expression “k∝H 2”. The principle of detecting the direction of the rotating magnetic field (rotation of the magnetic vector) with a magnetic field strength equal to or higher than the saturation sensitivity region is that a magnetic field strength that saturates the resistance value is applied while the magnetic sensitive films 41 to 44 are energized. At this time, the fact that there is a relationship expressed by the following equation between the angle θ formed by the magnetic field and the current direction and the resistance value R of the magnetosensitive films 41 to 44 is utilized.
R = R ₀ −k × sin 2θ
R ₀ : resistance value in the absence of a magnetic field k: resistance value change amount (a constant when the saturation sensitivity region is exceeded)
If the rotating magnetic field is detected based on such a principle, the resistance value R changes along the sine wave when the angle θ changes, so that an A-phase output and a B-phase output with high waveform quality can be obtained.

  As shown in FIG. 1A, a control unit 90 is connected to the magnetic sensor device 10. Specifically, the magnetosensitive element 4 is connected to the control unit 90 via the amplifier circuits 31 and 32, and to the first Hall element 61 and the second Hall element 62 via the amplifier circuits 35 and 36. Has been.

  The control unit 90 includes a CPU (arithmetic circuit) that performs interpolation processing and various arithmetic processing on the sine wave signals sin and cos output from the magnetic sensor device 10, and includes the magnetic sensitive element 4, the first hall element 61, and the first. Based on the output from the two-hole element 62, the rotational angle position of the rotating body 2 with respect to the fixed body is obtained.

  More specifically, in the rotary encoder 1, when the rotating body 2 makes one rotation, the sine wave signals sin and cos shown in FIG. 1B are output from the magnetosensitive element 4 (magnetoresistance element) for two cycles. Is done. The control unit 90 obtains the Lissajous diagram shown in FIG. 1C from the sine wave signals sin and cos amplified by the amplifier circuits 31 and 32, and further, θ = tan −1 (sin / cos) from the sine wave signals sin and cos. ) To calculate the angular position θ of the rotation output shaft.

  In the present embodiment, the first Hall element 61 and the second Hall element 62 are arranged at a position shifted by 90 ° from the center of the magnet 20. For this reason, it can be seen from the combination of the outputs of the first Hall element 61 and the second Hall element 62 which section of the sine wave signal sin or cos the current position is located. As a result, the rotary encoder 1 generates absolute angular position information of the rotating body 2 based on the detection result of the magnetosensitive element 4, the detection result of the first Hall element 61, and the detection result of the second Hall element 62. The absolute operation can be performed.

  FIG. 3 is a diagram for explaining the magnetosensitive element 4 of the magnetic sensor device 10. Here, the planar configuration of the magnetosensitive element 4 is illustrated, and the temperature monitoring resistance film 47 is provided with a slanting line with a lower right for convenience.

  As shown in the figure, in the magnetic sensor device 10, the magnetosensitive element 4 includes a substrate 40 and magnetosensitive films 41 to 44 formed on one surface 40 a of the substrate 40. The magnetosensitive films 41 to 44 form a circular magnetosensitive area 45 in the center of the substrate 40 by the portions extending while being folded back. The substrate 40 is, for example, a silicon substrate having a square planar shape.

  A wiring portion extends integrally from the magnetic sensitive films 41 to 44, and an A-phase power supply terminal VccA, an A-phase ground terminal GNDA, and an output terminal for + A-phase output are provided at the ends of the wiring portions. + A, -A phase output terminal -A, B phase power supply terminal VccB, B phase ground terminal GNDB, + B phase output terminal + B, and -B phase output terminal -B Is provided.

  In addition, a temperature monitoring resistance film 47 is formed on one surface 40 a of the substrate 40. The resistance film 47 for temperature monitoring is provided in the lower right region of the substrate 40 in the figure, and is close to the magnetosensitive region 45. The temperature monitoring resistance film 47 has a planar shape extending while being folded a plurality of times. Here, in the plan view shown in the drawing, the temperature monitoring resistance film 47 partially overlaps the wiring portion of the magnetosensitive film 44, but in a region shifted in the in-plane direction of the substrate 40 from the magnetosensitive area 45. It is formed and does not overlap with the magnetic sensitive region 45.

  The temperature monitoring resistance film 47 is a conductive film that does not exhibit a magnetoresistance effect. For this reason, even if the magnetic flux density with respect to the temperature monitoring resistive film 47 changes, the temperature can be accurately monitored. In addition, since the temperature monitoring resistance film 47 is formed adjacent to the magnetosensitive element 4 (the magnetosensitive films 41 to 44) on the same substrate, the temperature of the magnetosensitive element 4 can be detected with high accuracy and sensitivity. Can do.

  A temperature monitoring power supply terminal VccS is formed at one end of the temperature monitoring resistance film 47. The other end of the temperature monitoring resistance film 47 is connected to a B-phase ground terminal GNDB. For this reason, the B-phase ground terminal GNDB is also used as the ground terminal GNDS for the temperature monitoring resistance film 47.

  FIG. 4 is a block diagram of the control unit 90. The control unit 90 includes an ADC unit 91, a signal processing unit 92, a temperature calculation unit 93, an offset adjustment unit 94, and a memory 95.

  The ADC unit 91 converts an analog signal into a digital signal by A / D conversion of the output from the magnetic sensor device 10. The signal processing unit 92 detects the rotation angle position, rotation speed, and the like of the magnet 20 based on the A / D converted signal.

  The temperature calculation unit 93 performs temperature calculation processing on the magnetosensitive element 4 and detects a temperature difference from the set temperature and a temperature change based on the resistance value of the temperature monitoring resistance film 47.

  As temperature detection timing, for example, detection is performed once every communication cycle with a predetermined control device (higher-order device) that controls the rotary encoder 1, and temperature calculation processing is performed in the communication cycle. That is, the temperature calculation process is executed between the start of the angle response and the request from the next control device. Since the temperature calculation process is completed in several tens of μs, the process is surely completed within a communication cycle having a period sufficiently longer than that. By performing temperature detection for each communication cycle, processing can be simplified compared to non-periodic processing such as interrupt processing.

  The offset adjustment unit 94 sequentially records the offset voltage obtained based on the output of the magnetosensitive element 4 and the temperature of the element detected by the temperature calculation unit 93 in the memory 95. Then, the offset adjusting unit 94 calculates the temperature characteristics of the offset voltage based on the data recorded in the memory 95 at the time of startup, and calculates the offset voltage at the time of startup from the current temperature. When the amount of writing in the memory 95 becomes full, the oldest data is overwritten with the latest data.

  FIG. 5 is a graph showing the relationship between the temperature of the magnetosensitive element 4 and the offset voltage. The offset voltage adjustment process will be described with reference to this graph. The horizontal axis indicates the temperature of the magnetosensitive element 4 (detection result by the temperature monitoring resistance film 47 and the temperature calculation unit 93). The vertical axis represents the offset voltage of the magnetosensitive element 4.

  As described above, during operation of the rotary encoder 1, the offset adjustment unit 94 records the offset voltage and the temperature of the magnetosensitive element 4 in pairs in the memory 95 sequentially. For example, in FIG. 5, the first to fourth data D1 to D4 are represented on the graph.

  The offset adjustment unit 94 calculates an approximate expression (here, an approximate straight line AL) based on the first to fourth data D1 to D4, and calculates a temperature characteristic of the offset voltage. For example, the intercept and slope of the approximate straight line AL are calculated as the temperature specification.

  Then, when the rotary encoder 1 is activated next time, the offset adjusting unit 94 calculates the offset voltage immediately after activation based on the temperature characteristics based on the detection results of the temperature monitoring resistance film 47 and the temperature calculating unit 93. . As a result, the offset voltage can be calculated appropriately immediately after startup, and the output error of the rotary encoder 1, that is, the angle error can be reduced. In addition, even when the offset voltage changes with time or when the offset voltage temperature characteristic changes with time, it can be corrected sequentially. That is, the offset adjusting unit 94 can calculate the offset voltage immediately after startup with high accuracy and sensitivity by learning the offset voltage temperature characteristic.

  When the offset voltage and the temperature of the magnetosensitive element 4 are recorded in the memory 95 as a pair, the temperature range is divided into predetermined ranges, and the offset voltage detected within the temperature range is averaged and stored. Also good. Since the required capacity can be suppressed, it is effective when the capacity of the available memory 95 is limited. In another aspect, the period until data is overwritten can be lengthened, and data over a long period can be used.

  When the data indicated by the offset voltage and the temperature of the magnetosensitive element 4 is detected at a predetermined value or more away from the approximate straight line AL, the offset adjustment unit 94 determines that an error has occurred and resets the existing temperature characteristics. Also good. That is, the offset adjustment unit 94 performs learning initialization.

For example, as shown in the figure, the error data D _error (Dx) is a value lower than the approximate straight line AL by ΔV. In this case, a malfunction such as element deformation may occur in the magnetosensitive element 4, and the output characteristics of the magnetosensitive element 4 may have changed. Therefore, in such a case, the offset adjustment unit 94 discards the existing data and records and uses new data acquired thereafter. Further, when the initialization of learning frequently occurs, the offset adjustment unit 94 may determine that a failure has occurred in the rotary encoder 1 and notify the fact by a predetermined warning unit (display unit or the like).

<Second Embodiment>
In the present embodiment, the temperature of the magnetosensitive element itself is directly detected based on the current flowing through the magnetosensitive element (MR element), and the offset voltage of the temperature is calculated. Since the configuration other than the temperature measurement technique of the magnetosensitive element (MR element) can be realized with the same configuration and function as the first embodiment, the characteristic technique of this embodiment will be described and the same configuration will be described.・ Functions are denoted by the same reference numerals and description thereof is omitted as appropriate.

  FIG. 6 is a diagram for explaining an electrical connection structure of the magnetosensitive films 41 to 44 (magnetoresistive films) of the magnetosensitive element 4 used in the magnetic sensor device 10 and the rotary encoder 1. Here, the bridge circuit 4a on the A phase side is shown, and the current detection circuit 150 is added to the configuration of FIG. 2A of the first embodiment.

  As shown in the figure, a current detection circuit 150 is provided in the middle of the path between the A-phase power supply terminal VccA and the A-phase side bridge circuit 4a, that is, on the high side. Note that the configuration of the current detection circuit 150 shown here shows a basic circuit configuration for current detection for ease of explanation. In practice, a dedicated current detection IC is generally used, and the same applies to the present embodiment. Further, current detection may be performed not only on the high side but also on the low side.

  The current detection circuit 150 includes a current detection resistor 151 and a current detection amplifier 152. The current detection resistor 151 is inserted in series along the path between the A-phase power supply terminal VccA and the A-phase side bridge circuit 4a. Here, when the resistance values of the magnetosensitive films 41 and 43 are 500 to 1000Ω, the resistance value of the current detection resistor 151 is set to several tens of Ω so that the S / N ratio is not substantially decreased without reducing the current. Detection is possible.

  Both ends of the current detection resistor 151 are connected to two inputs (+/−) of the current detection amplifier 152. The output (Vout) of the current detection amplifier 152 is connected to the control unit 90.

Next, the temperature detection process will be described. This is realized by the same configuration as the control unit 90 of FIG. In the memory 95, the resistance temperature coefficient α and the offset value (resistance value R _0MR at a certain temperature) of the _{magnetosensitive} element ₄ are recorded. Temperature calculation section 93 calculates the resistance value R _MR of magnetic sensing element 4 based on the current and the applied voltage flows through the sensitive element 4, with reference to the memory 95, calculates the temperature t of the current sensitive element 4 To do. The current temperature t of the magnetosensitive element 4 is derived from the following relational expression.
R _MR = R _0MR + α (t−t ₀ )
α: Resistance temperature coefficient of magnetosensitive element 4 R _0MR : Resistance value of magnetosensitive element 4 at predetermined temperature t ₀

  Here, the resistance value of each element (the magnetosensitive films 41 and 43) constituting the resistance bridge in the magnetosensitive element 4 varies depending on the application direction of the external magnetic flux, but the bridge configuration (the magnetosensitive film 41 shown in FIG. 3). 43), the fact that the total resistance becomes almost constant is utilized. The same applies to the B-phase side elements (magnetic films 42 and 44). The offset adjustment unit 94 obtains the offset voltage of the magnetosensitive element 4 using the obtained temperature. Note that the temperature characteristics of the offset voltage are recorded in the memory 95 in advance.

  By providing the temperature monitoring resistance film 47 of the first embodiment together with the current detection circuit 150, the temperature distribution in the magnetic sensor device 10, that is, on the substrate 40 can be grasped accurately. It is possible to calculate the temperature condition. The CPU mounted on the rotary encoder 1 incorporates a temperature sensor, but the temperature sensor output is not calibrated. Therefore, the current detection circuit 150 can also be used as an internal calibration temperature sensor.

  Although the present invention has been described based on the embodiment, this embodiment is an exemplification, and various modifications can be made to combinations of the respective components, and such modifications are also included in the present invention. It will be understood by those skilled in the art that it is in the range.

DESCRIPTION OF SYMBOLS 1 Rotary encoder 2 Rotating body 4 Magnetosensitive element 4a, 4b Bridge circuit 10 Magnetic sensor apparatus 20 Magnet 21 Magnetized surface 31, 32, 35, 36 Amplifier circuit 40 Board | substrate 41, 42, 43, 44 Magnetosensitive film 45 Magnetosensitive area (Magnetic part)
47 Resistive film for temperature monitoring (temperature detector)
61 1st Hall element 62 2nd Hall element 90 Control part 91 ADC part 92 Signal processing part 93 Temperature calculation part (temperature detection part)
94 Offset adjustment unit 95 Memory 150 Current detection circuit (temperature detection unit)
151 Current detection resistor 152 Current detection amplifier

Claims (7)

A magnetoresistive element formed on the substrate;
An offset voltage detector for detecting an offset voltage of the magnetoresistive element;
A temperature detector for detecting the temperature of the magnetoresistive element;
A storage unit that records the offset voltage and the temperature of the magnetoresistive element in association with each other;
From the data of the offset voltage and the temperature of the magnetoresistive element recorded in the storage unit, an approximate expression indicating the relationship between the offset voltage and the temperature of the magnetoresistive element is calculated. An offset voltage determination unit that estimates the current offset voltage from the temperature of the resistance element based on the approximate expression, and uses the estimated offset voltage as a new offset voltage;
The encoder characterized by having.   The encoder according to claim 1, wherein the temperature detection unit is provided on the same substrate on which the magnetoresistive element is formed.   When the offset voltage and the temperature of the magnetoresistive element are recorded in the storage unit in association with each other, the temperature range is divided into predetermined ranges, and the offset voltage detected within the temperature range is averaged. The encoder according to claim 1 or 2, characterized in that   The offset voltage determination unit calculates a new approximate expression based on new data when the relationship between the measured offset voltage and the temperature of the magnetoresistive element is separated from the approximate expression by a predetermined amount or more. The encoder according to any one of claims 1 to 3, wherein   The encoder according to any one of claims 1 to 4, wherein the temperature detection unit calculates a resistance value of the magnetoresistive element and detects a current temperature from the calculated resistance value. The temperature detection unit detects the temperature of the magnetoresistive element once every communication cycle with an external control device,
The encoder according to any one of claims 1 to 5, wherein the offset voltage determination unit calculates the approximate expression in the communication cycle.   The encoder according to any one of claims 1 to 6, wherein the temperature detection unit includes a temperature monitoring resistive film formed on the substrate on which the magnetoresistive element is formed.

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