Encoder

Abstract

An encoder is provided with: a magnet attached to a measurement object at a rotational position; the power generation element is used for converting magnetic energy of the magnet into electric pulse by utilizing Barkhausen characteristics; a magnetic sensor for measuring the magnetization polarity of the magnet; an estimation unit that estimates a rotation count and a rotation position of the measurement object on the basis of the power generation polarity of the power generation element, the magnetization polarity of the magnetic sensor, and the rotation position estimated last time; and a non-volatile storage unit that stores the rotation count and the rotation position estimated by the estimation unit.

Description

Technical Field

[0001] The present invention relates to encoders. Background Art

[0002] Patent Document 1 discloses a method for synchronizing a segment counter having a single pulse wire (Wiegand wire) sensor with a precision position sensor.

[0003] <Prior Art Literature>

[0004] <Patent Documents>

[0005] Patent Document 1: Japanese Patent No. 5730809 Summary of the invention

[0006] <Problems to be Solved by the Invention>

[0007] As a battery-free encoder, a power generation element that uses the Barkhausen characteristic to generate electricity is sometimes used. The power generation element that uses the Barkhausen characteristic to generate electricity has hysteresis. Since the power generation element that uses the Barkhausen characteristic to generate electricity has hysteresis, after generating electricity in one direction, if sufficient magnetic saturation is not achieved, the power generation in the opposite direction may decrease. In the power generation element, when the power generation is small, the encoder rotation error may occur.

[0008] The present invention provides an encoder that suppresses the generation of errors.

[0009] <Methods used to solve the problem>

[0010] According to one embodiment of the present invention, an encoder is provided, comprising: a magnet mounted on a measurement object of a rotational position; a generating element that utilizes the Barkhausen characteristic to convert the magnetic energy of the magnet into an electrical pulse; a magnetic sensor that measures the magnetization polarity of the magnet; an estimating unit that estimates the rotation count and the rotational position of the measurement object based on the generating polarity of the generating element, the magnetization polarity of the magnetic sensor, and the last estimated rotational position; and a non-volatile storage unit that stores the rotation count and the rotational position estimated by the estimating unit.

[0011] <Effects of the Invention>

[0012] According to the encoder of the present invention, it is possible to suppress the occurrence of errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a diagram for explaining a servo motor system using the encoder according to the first embodiment.

[0014] Figure 2It is a diagram for explaining the structure of a servo motor using the encoder according to the first embodiment.

[0015] Figure 3 It is a diagram for explaining the circuit configuration of the encoder according to the first embodiment.

[0016] Figure 4 It is a diagram for explaining the circuit configuration of the encoder according to the first embodiment.

[0017] Figure 5 It is a diagram for explaining the circuit configuration of the encoder according to the first embodiment.

[0018] Figure 6 This is a diagram for explaining the configuration of the encoder according to the first embodiment.

[0019] Figure 7 This is a diagram for explaining the configuration of the encoder according to the first embodiment.

[0020] Figure 8 This is a diagram for explaining the operation of the encoder according to the first embodiment.

[0021] Fig. 9 This is a diagram for explaining the operation of the encoder according to the first embodiment.

[0022] Fig.10 This is a diagram for explaining the operation of the encoder according to the first embodiment.

[0023] Fig.11 This is a diagram for explaining the operation of the encoder according to the first embodiment.

[0024] Fig.12 It is a diagram for explaining the structure of a servo motor using an encoder according to a second embodiment.

[0025] Fig.13 This is a diagram for explaining the configuration of an encoder according to the second embodiment.

[0026] Fig.14 This is a diagram for explaining the operation of the encoder according to the second embodiment.

[0027] Fig.15 This is a diagram for explaining the operation of the encoder according to the second embodiment.

[0028] Fig.16 A flowchart illustrating processing of the encoder according to the second embodiment. DETAILED DESCRIPTION

[0029] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, in the descriptions and drawings related to each embodiment, for components having substantially the same or corresponding functional structures, repeated descriptions are sometimes omitted by marking the same symbols. In addition, for ease of understanding, the scale of each part in the drawings is sometimes different from the actual scale.

[0030] 《First Implementation Mode》

[0031] <Servo Motor System>

[0032] First, a servo motor system using the encoder according to the present embodiment will be described. Figure 1 It is a diagram for explaining a servo motor system 1 using an encoder 12 according to the present embodiment.

[0033] The servo motor system 1 includes a servo motor 10 and a servo controller 20. The servo controller 20 acquires at least one of position information and rotation information of a rotating shaft 11a from the servo motor 10. The servo controller 20 controls the servo motor 10 using at least one of the acquired position information and rotation information.

[0034] The servo motor 10 includes a motor 11 and an encoder 12. The motor 11 is connected to a servo controller 20 via a wiring L1. The encoder 12 is connected to the servo controller 20 via a wiring L2.

[0035] The motor 11 rotates the rotating shaft 11a in the direction of the arrow AR based on the command from the servo controller 20. Specifically, the motor 11 rotates the rotating shaft 11a in the direction of the arrow AR based on the power supplied from the servo controller 20. The servo controller 20 controls the motor 11 by supplying the controlled power from the wiring L1. The motor 11 is, for example, an AC (Alternating Current) motor, a DC (Direct Current) motor, or the like.

[0036] The encoder 12 detects the change of the magnetic field to detect at least one of the position information and the rotation information of the object such as the rotating shaft 11a of the motor 11. In addition, the encoder 12 outputs at least one of the detected position information and the rotation information to the servo controller 20 via the wiring L2. In addition, the so-called position information of the rotating shaft 11a is, for example, the angle of the rotation direction of the rotating shaft 11a. The so-called rotation information of the rotating shaft 11a is, for example, the rotation speed of the rotating shaft 11a or the number of rotations indicating how many times the rotating shaft 11a has rotated since a given time point.

[0037] <Servo motor 10>

[0038] Next, the structure of the servo motor 10 using the encoder 12 according to the present embodiment will be described. Figure 2 1 is a diagram for explaining the configuration of a servo motor 10 using an encoder 12 according to the present embodiment. In addition, arrowed lines indicate the flow of supply of electric power or current.

[0039] [Motor 11]

[0040] The motor 11 includes a disk 11d provided on the encoder 12 side of the rotating shaft 11a, and a magnet 11m provided on the disk 11d. In addition to the rotating shaft 11a, the disk 11d, and the magnet 11m, the motor 11 also includes known elements such as a bearing for supporting the rotating shaft 11a, a winding for constituting a stator for rotating the rotating shaft 11a, an iron core, and a permanent magnet constituting a rotor, but the description thereof is omitted here.

[0041] The disk 11d is fixed to the rotating shaft 11a. The disk 11d rotates together with the rotating shaft 11a as the rotating shaft 11a rotates in the direction of the arrow AR. A magnet 11m is fixed to the surface of the disk 11d on the encoder 12 side.

[0042] The magnet 11m is a permanent magnet formed of neodymium, etc. The magnet 11m is provided to have an N pole and an S pole in a direction parallel to the surface of the disk 11d. When the magnet 11m rotates together with the disk 11d, the magnetic field on the encoder 12 side changes.

[0043] [Encoder 12]

[0044] The encoder 12 is described. The encoder 12 detects at least one of the position information and the rotation information of the rotating shaft 11a by means of a magnetic field that changes with the rotation of the magnet 11m. The encoder 12 is an absolute encoder. The encoder 12 involved in this embodiment operates at least as a multi-turn encoder. That is, the encoder 12 counts how many turns the rotating shaft 11a has rotated. In addition, the encoder 12 generates the power required to operate the encoder 12 by means of a magnetic field that changes with the rotation of the magnet 11m.

[0045] The encoder 12 includes a power generation element 12g, a rectifier circuit 12a, a stabilized power supply circuit 12b, a polarity detection circuit 12d, a drive circuit 12e, a Hall element 12h, a signal processing circuit 12f, a control circuit 12p, and a storage unit 12r. In addition, the rectifier circuit 12a and the stabilized power supply circuit 12b are collectively referred to as a power supply circuit 12n. In addition, the polarity detection circuit 12d, the drive circuit 12e, and the signal processing circuit 12f are collectively referred to as a rotation detection circuit 12m.

[0046] The encoder 12 includes a power generation element 12g that generates power by changing the magnetic flux caused by movement, and a Hall element 12h that detects a magnetic field. The power generation element 12g and the Hall element 12h are respectively provided on the motor 11 side of the encoder 12 so as to be easily affected by the magnetic field generated by the magnet 11m.

[0047] [Power generation element 12g]

[0048] The power generation element 12g is an element that converts magnetic energy into electric pulses to generate electricity. The power generation element 12g is an element that generates electricity using Barkhausen characteristics. The power generation element 12g is, for example, a Wiegand wire that is an environmental generator (EHG: Energy Harvest Generator).

[0049] The power generation element 12g includes a hard core and a soft layer wound around the hard core. The hard core is formed of a material with a large coercive force. The soft layer is formed of a material with a small coercive force. When the direction of the external magnetic field is reversed, the power generation element 12g generates a power generation pulse.

[0050] For example, the Wiegand wire generates an electric pulse near the zero point of the external magnetic field reversal, independent of the speed of change of the external magnetic flux. Therefore, the Wiegand wire generates constant power regardless of the rotation speed of the rotating shaft 11a. The Wiegand wire generates a stable electric pulse (voltage pulse) even when the magnetic flux changes slowly due to low-speed rotation (movement). The Wiegand wire generates an electric pulse at the timing of the magnetic field reversal.

[0051] By using an environmental generator in the power generation element 12g, the encoder 12 does not require a battery or an external power supply. That is, the encoder 12 is a battery-free encoder. Since the Wiegand wire generates constant power regardless of the rotation speed of the rotating shaft 11a, and a stable power generation waveform can be obtained even at a low speed rotation, it is suitable for use as the power generation element 12g of the encoder 12 of the battery-free encoder.

[0052] The power generation element 12g is not limited to the Wiegand wire, and any power generation element that generates power using the Barkhausen characteristic may be used.

[0053] [Hall element 12h]

[0054] The Hall element 12h detects the magnetic field of the semiconductor element across the driving current. In the encoder 12, the Hall element 12h mainly detects the magnetic field generated by the magnet 11m. The Hall element 12h is composed of semiconductor elements such as indium antimonide (InSb) and gallium arsenide (GaAs). The Hall element 12h outputs a voltage proportional to the driving current and the magnetic flux density across the driving current.

[0055] The Hall element 12h outputs a detection signal of the magnetic field to the signal processing circuit 12f. The Hall element 12h is supplied with a constant current Idr from the drive circuit 12e.

[0056] The electric power generated by the power generating element 12g is rectified by the rectifier circuit 12a, and the electric current (constant current Idr) made constant by the drive circuit 12e is supplied to the Hall element 12h.

[0057] In addition, the encoder 12 has one Hall element, but the number of Hall elements is not limited to one. The encoder 12 may also have multiple Hall elements. In addition, the measurement of the magnetic field can be performed by any element that can detect magnetism (magnetic detection element), and is not limited to the Hall element. For example, a magnetoresistive effect element may be used instead of the Hall element 12h.

[0058] Regarding the circuit structure of the encoder 12, based on Figure 3 To explain. Figure 3 It is a diagram for explaining the circuit configuration of the encoder 12 according to the present embodiment.

[0059] [Rectifier circuit 12a]

[0060] The rectifier circuit 12a rectifies the electric power generated by the power generation element 12g to generate a positive voltage. The rectifier circuit 12a includes a full-wave rectifier circuit 12a1 and a capacitor 12a2.

[0061] The full-wave rectifier circuit 12a1 rectifies the positive and negative pulses of the voltage Vgn generated by the power generation element 12g into positive pulses. The full-wave rectifier circuit 12a1 is a so-called diode bridge circuit. For example, when the power generation element 12g is a Wiegand wire, the power generation element 12g generates positive and negative pulses. The full-wave rectifier circuit 12a1 converts the positive and negative pulses generated by the power generation element 12g into positive pulses.

[0062] The capacitor 12a2 stores the electric power generated by the power generation element 12g. In addition, the capacitor 12a2 smoothes the positive pulse generated by the full-wave rectifier circuit 12a1. The capacitor 12a2 is provided between the output terminal of the full-wave rectifier circuit 12a1 and the common potential. The positive pulse is smoothed by the capacitor 12a2, and the smoothed voltage Vrc is output from the rectifier circuit 12a.

[0063] [Stabilized power supply circuit 12b]

[0064] The stabilized power supply circuit 12b makes the voltage outputted from the rectifier circuit 12a substantially constant and outputs the voltage. The stabilized power supply circuit 12b includes a regulator 12b1. The regulator 12b1 is, for example, an LDO (Low Dropout) regulator.

[0065] When a voltage of a given magnitude is input, the stabilized power supply circuit 12 b outputs a substantially constant voltage Vdd.

[0066] [Polarity detection circuit 12d]

[0067] The polarity detection circuit 12d detects the polarity of the electric power generated by the power generation element 12g. Figure 4 1 is a diagram for explaining the circuit structure of the polarity detection circuit 12d in the encoder 12 according to the present embodiment. The polarity detection circuit 12d includes a comparator 12d1, a filter circuit 12d2, and a diode 12d3. The diode 12d3 is used to prevent current from flowing from the polarity detection circuit 12d to the power generation element 12g. The filter circuit 12d2 is a low-pass filter including a resistor 12d2a and a capacitor 12d2b.

[0068] The comparator 12d1 compares the voltage Vgns with a potential (reference potential Vref2) serving as a reference, and outputs the comparison result to the control circuit 12p. The comparator 12d1 is a so-called comparator. The comparator 12d1 includes a differential amplifier 12d1a, a resistor 12d1b, a resistor 12d1c, and a resistor 12d1d. The power of the voltage Vdd is supplied to the differential amplifier 12d1a from the stabilized power supply circuit 12b. The differential amplifier 12d1a compares the voltage Vgns after the voltage Vgn outputted by the power generating element 12g is smoothed by the filter circuit 12d2 with the reference potential Vref2 generated by dividing the voltage Vdd by the resistors 12d1c and 12d1d. Furthermore, the differential amplifier 12d1a outputs the comparison result as a polarity signal Sp1 serving as a voltage signal to the control circuit 12p. The resistor 12d1b is a feedback resistor.

[0069] [Drive circuit 12e]

[0070] The drive circuit 12e is a so-called constant current circuit that supplies a constant current Idr to the Hall element 12h. The drive circuit 12e operates as a constant current source. The encoder 12 drives the Hall element 12h with a constant current Idr. The drive circuit 12e supplies drive power to the Hall element 12h so that the constant current flows through the Hall element 12h as a drive current. Figure 5 1 is a diagram for explaining the circuit configuration of the drive circuit 12e and the Hall element 12h in the encoder 12 according to the present embodiment. Figure 5 In FIG. 1 , the Hall element 12h is equivalently represented by using a bridge circuit including a resistor 12h1 , a resistor 12h2 , a resistor 12h3 , and a resistor 12h4 .

[0071] The drive circuit 12e includes a transistor 12e1, a current detection resistor 12e2, and a differential amplifier 12e3. The drive circuit 12e also includes a resistor 12e4, a Zener diode 12e5, and a capacitor 12e6.

[0072] The transistor 12e1 is controlled so that a constant current flows through the Hall element 12h. The output terminal of the differential amplifier 12e3 is connected to the gate terminal of the transistor 12e1. The differential amplifier 12e3 outputs a voltage based on the potential difference between the + terminal and the - terminal from the output terminal. The drive circuit 12e is controlled so that a constant current (constant current Idr) based on the voltage input to the + terminal and the resistance value of the current detection resistor 12e2 flows between the drain and the source of the transistor 12e1.

[0073] The Hall element 12h is driven by the constant current Idr, and outputs a voltage Vh+ and a voltage Vh- that are proportional to the constant current Idr and the magnetic flux density that crosses the Hall element 12h.

[0074] In addition, the driving circuit 12e is driven by the voltage Vdd supplied from the stabilized power supply circuit 12b.

[0075] [Signal processing circuit 12f]

[0076] The signal processing circuit 12f processes the detection signal from the Hall element 12h to detect the direction of the magnetic field of the magnet 11m. Figure 3 The signal processing circuit 12f will be described.

[0077] The signal processing circuit 12f includes a differential amplifier 12f1 and a comparator 12f2.

[0078] (Differential amplifier 12f1)

[0079] The differential amplifier 12f1 amplifies the potential difference between the voltage Vh+ and the voltage Vh- outputted from the Hall element 12h and outputs a voltage Vd to the comparator 12f2. The differential amplifier 12f1 is supplied with power of the voltage Vdd from the stabilized power supply circuit 12b.

[0080] (Comparator 12f2)

[0081] The comparator 12f2 compares the voltage Vd output from the differential amplifier 12f1 with the potential (reference potential Vref) as a reference, and outputs the comparison result to the control circuit 12p. The comparator 12f2 is a so-called comparator. The comparator 12f2 includes a differential amplifier 12f2a, a resistor 12f2b, a resistor 12f2c, and a resistor 12f2d. The power of the voltage Vdd is supplied to the differential amplifier 12f2a from the stabilized power supply circuit 12b. The differential amplifier 12f2a compares the voltage Vd output from the differential amplifier 12f1 with the reference potential Vref generated by dividing the voltage Vdd with the resistors 12f2c and 12f2d, and outputs the comparison result as a magnetic pole signal Smg as a voltage signal to the control circuit 12p. The resistor 12f2b is a feedback resistor.

[0082] [Control circuit 12p]

[0083] The control circuit 12p calculates at least one of the position information and the rotation information, such as the rotation position and the rotation speed, of the rotating shaft 11a of the motor 11 based on the input from the signal processing circuit 12f. In addition, the control circuit 12p records at least one of the position information and the rotation information of the rotating shaft 11a of the motor 11 detected, or transmits it to an external control system such as a servo controller 20.

[0084] The control circuit 12p is, for example, a microcomputer, an ASIC (application specific integrated circuit), etc. Alternatively, the control circuit 12p may be, for example, an FPGA (Field-Programmable Gate Array), a PLD (Programmable Logic Device), etc.

[0085] The control circuit 12p is connected to a storage unit 12r provided outside. Alternatively, the control circuit 12p may include a nonvolatile memory such as a ferroelectric memory inside, instead of the external storage unit 12r.

[0086] The control circuit 12p includes at least a terminal PWR, a terminal SIG1, and a terminal SIG2.

[0087] The terminal PWR of the control circuit 12p is a terminal to which a positive power supply is supplied. Power of the voltage Vdd is supplied from the stabilized power supply circuit 12b to the terminal PWR. The control circuit 12p operates by supplying power to the terminal PWR.

[0088] The terminal SIG1 and the terminal SIG2 of the control circuit 12p are terminals for inputting signals from the outside.

[0089] The terminal SIG1 is connected to the signal processing circuit 12f. A magnetic pole signal Smg, which is a detection result detected by the signal processing circuit 12f, is input from the terminal SIG1. The magnetic pole signal Smg is a signal indicating the direction of the magnetic field detected by the Hall element 12h.

[0090] The terminal SIG2 is connected to the polarity detection circuit 12d. A polarity signal Sp1, which is a detection result by the polarity detection circuit 12d, is input from the terminal SIG2. The polarity signal Sp1 is a signal indicating the power generation polarity of the power generation element 12g.

[0091] The encoder 12 involved in this embodiment counts the number of revolutions of the rotating shaft 11a. The control circuit 12p uses the magnetic pole signal Smg and the polarity signal Spl to count the number of revolutions of the rotating shaft 11a. In addition, the control circuit 12p uses the magnetic pole signal Smg and the polarity signal Spl to detect in which area the rotating shaft 11a is located in the area divided into 90 degrees for one circle. And the control circuit 12p stores the result of counting the number of revolutions of the rotating shaft 11a and the result of detecting in which area the rotating shaft is located in the storage unit 12r. In addition, the control circuit 12p stores the last detected magnetic pole signal Smg and polarity signal Spl in the storage unit 12r.

[0092] [Storage unit 12r]

[0093] The storage unit 12r stores, for example, a rotation count, etc. The storage unit 12r is, for example, a ferroelectric memory. The control circuit 12p stores at least a count value indicating how many times the rotating shaft 11a has rotated, the position of the rotating shaft, and the last detected magnetic pole signal Smg and polarity signal Spl in the storage unit 12r.

[0094] <Structure of encoder 12>

[0095] The structure of the encoder 12 will be described. Figure 6 as well as Figure 7 This is a diagram for explaining the configuration of the encoder 12 according to the first embodiment. Figure 6 It is a perspective view for explaining the arrangement of the power generating element 12 g and the Hall element 12 h in the encoder 12 . Figure 7 It is a plan view for explaining the arrangement of the power generating element 12 g and the Hall element 12 h in the encoder 12 .

[0096] The power generation element 12g is arranged at the center of the upper surface of the substrate 12j. The Hall element 12h is arranged on the lower surface of the substrate 12j. Figure 7As shown, Figure 7 The case where the horizontal axis on the right side of the image is set to an angle of 0 degrees and the angle is defined counterclockwise is described. The Hall element 12h is arranged on the axis with an angle of 0 degrees. The power generation element 12g is arranged on the axis with an angle of Figure 7 It has a long side direction in the longitudinal direction.

[0097] The magnet 11m is provided on a disk 11d fixed to the rotating shaft 11a in the motor 11. When the rotating shaft 11a rotates, the magnet 11m also rotates. The encoder 12 measures the rotation angle of the rotating shaft 11a. That is, the rotating shaft 11a is an example of an object of measuring the rotation position.

[0098] The generating polarity of the power generating element 12g and the magnetizing polarity of the Hall element 12h when the magnet 11m rotates will be described.

[0099] Figure 8 1 is a diagram for explaining the operation of the encoder 12 according to the first embodiment. Figure 8 In the case where a Wiegand wire is provided as the power generating device of the power generating element 12g, power is generated at every 180 degrees as the magnet 11m rotates. Figure 8 In the case of the configuration shown, when the angle is around 0 degrees, it is negative power generation when it is rotated clockwise, and it is positive power generation when it is rotated counterclockwise. On the other hand, when the angle is around 180 degrees, it is positive power generation when it is rotated clockwise, and it is negative power generation when it is rotated counterclockwise.

[0100] In addition, if Figure 8 The sensor polarity of the Hall element 12h configured as shown is between an angle of 0 degree and an angle of 90 degrees and an angle of 270 degrees and an angle of 360 degrees (angle 0 degree), that is, Fig.11 The right half of is N. On the other hand, the sensor polarity of the Hall element 12h is between an angle of 90 degrees and an angle of 270 degrees, that is, Figure 8 The left half of is S.

[0101] Therefore, the position can be detected at an angle of 90 degrees based on the generating polarity of the generating element 12g and the sensor polarity of the Hall element 12h. Position detection with an angle resolution of 90 degrees is performed at the timing of power generation (near an angle of 0 degrees and near an angle of 180 degrees).

[0102] Specifically, when the generating polarity of the generating element 12g is positive and the sensor polarity of the Hall element 12h is N, the position of the rotating shaft 11a is determined to be in the range of angles from 0 to 90 degrees, that is, position POS1 (first quadrant). When the generating polarity of the generating element 12g is positive and the sensor polarity of the Hall element 12h is S, the position of the rotating shaft 11a is determined to be in the range of angles from 90 to 180 degrees, that is, position POS2 (second quadrant).

[0103] When the generating polarity of the generating element 12g is negative and the sensor polarity of the Hall element 12h is S, the position of the rotating shaft 11a is determined to be in the range of 180 degrees to 270 degrees, that is, position POS3 (third quadrant). When the generating polarity of the generating element 12g is negative and the sensor polarity of the Hall element 12h is N, the position of the rotating shaft 11a is determined to be in the range of 270 degrees to 360 degrees (0 degrees), that is, position POS4 (fourth quadrant).

[0104] The above is summarized in Table 1. Table 1 shows the position (quadrant) in which the encoder 12 determines the N pole of the magnet 11m is located when the encoder 12 detects the generating polarity (GP) and the magnetic pole (MP). In addition, Table 1 also shows the direction in which the magnet 11m rotates. Hereinafter, the position of the N pole of the magnet 11m is referred to as the position of the magnet 11m.

[0105]

Table 1

[0106]

[0107] For example, when the generating polarity (GP) detected by the polarity detection circuit 12d is positive (+) and the magnetic pole (MP) detected by the Hall element 12h is the N pole, the control circuit 12p determines that the position of the magnet 11m is at the position POS1 (first quadrant). In addition, in the case of the position POS1, since the counterclockwise (CCW) rotation passes through the reference angle 0 degrees, the rotation count value stored in the storage unit 12r is increased by 1, and the updated rotation count value is stored in the storage unit 12r.

[0108] When the generating polarity (GP) detected by the polarity detection circuit 12d is positive (+) and the magnetic pole (MP) detected by the Hall element 12h is the S pole, the control circuit 12p determines that the position of the magnet 11m is at the position POS2 (second quadrant). In addition, when at the position POS2, the magnet 11m rotates clockwise (CW) and passes through an angle of 180 degrees.

[0109] When the generating polarity (GP) detected by the polarity detection circuit 12d is negative (-) and the magnetic pole (MP) detected by the Hall element 12h is the S pole, the control circuit 12p determines that the position of the magnet 11m is at position POS3 (third quadrant). In the case of position POS3, the counterclockwise (CCW) rotation passes through an angle of 180 degrees.

[0110] When the generating polarity (GP) detected by the polarity detection circuit 12d is negative (-) and the magnetic pole (MP) detected by the Hall element 12h is the N pole, the control circuit 12p determines that the position of the magnet 11m is at the position POS4 (fourth quadrant). In addition, in the case of the position POS4, since the clockwise (CW) rotation passes through the reference angle 0 degrees, the rotation count value stored in the storage unit 12r is subtracted by 1, and the updated rotation count value is stored in the storage unit 12r.

[0111] Then, the rotation speed is obtained when, for example, the angle 0 degrees is positive in the counterclockwise direction, based on the generating polarity of the generating element 12g and the sensor polarity of the Hall element 12h. Regarding the position detection of the encoder 12 involved in this embodiment, during the power generation of the generating element 12g, two pulses are generated when one rotation is performed. The two pulses generated are one positive pulse and one negative pulse. In addition, the polarity of the generated pulse becomes the opposite sign when the reverse rotation is performed to that when the forward rotation is performed.

[0112] The position cannot be detected within the 360-degree angle range by only the polarity of the power generation pulse, but by configuring the Hall element 12h at a position 90 degrees out of phase with the power generation pulse, the 90-degree phase can be detected using the polarity of the power generation pulse and the polarity of the Hall element 12h. In addition, by comparing the last power generation position with the current power generation position, when the angle 0 is used as the reference angle, it is possible to determine how many times the reference angle has been rotated.

[0113] As described above, the encoder 12 according to the first embodiment is an encoder having an angular resolution of 90 degrees.

[0114] Next, the power generating element 12g when the encoder 12 is operated will be described. Fig. 9 This is a diagram for explaining the state of the power generating element 12g when the encoder 12 according to the present embodiment is operated. Fig. 9 This is a diagram for explaining the magnetization characteristics (BH curve) of the power generating element 12g having the Barkhausen characteristic with respect to the external magnetic field.

[0115] Fig. 9 The horizontal axis represents the external magnetic field Hext in the power generating element 12g. Fig. 9 The line La shows the magnetization state of the power generating element 12g when rotating in one direction.

[0116] In addition, Fig. 9In order to explain the magnetization state of the power generation element 12g, simplified diagrams PS1, PS2, AS1, and AS2 are shown. In each of the simplified diagrams PS1, PS2, AS1, and AS2, the central cylinder represents the hard core HC, and the outer cylinder represents the soft layer SL. In addition, the arrows in each of the hard core HC and the soft layer SL represent the directions of their respective magnetization.

[0117] In addition, the simplified diagram PS1 shows a state in which the magnetization of the hard core HC and the soft layer SL are oriented in the same direction relative to the positive external magnetic field (parallel state). The simplified diagram PS2 shows a state in which the magnetization of the hard core HC and the soft layer SL are oriented in the same direction relative to the negative external magnetic field (parallel state). The simplified diagram AS1 shows a state in which the hard core HC is oriented in the direction of the positive external magnetic field and the soft layer SL is oriented in the direction of the negative external magnetic field, and they are oriented in opposite directions to each other (antiparallel state). The simplified diagram AS2 shows a state in which the hard core HC is oriented in the direction of the negative external magnetic field and the soft layer SL is oriented in the direction of the positive external magnetic field, and they are oriented in opposite directions to each other (antiparallel state).

[0118] First, the characteristics of the power generation element 12g when rotating in one direction are described. Here, the case of rotating in one direction from point A is described. In addition, point A represents the state where the maximum external magnetic field is applied to the power generation element 12g. Point A is equivalent to Figure 8 The angle in is 90 degrees. At point A, both the hard core HC and the soft layer SL of the power generating element 12g are magnetized in the direction of the positive external magnetic field (parallel state).

[0119] When the magnet rotates, the magnetization state of the power generation element 12g changes from point A along the arrow B. Then, when the external magnetic field Hext changes from positive to negative, the magnetization changes sharply as shown by the arrow C due to the Wiegand effect. The sharp change in magnetization is caused by a large Barkhausen jump that occurs when the magnetization of the soft layer SL is reversed. As shown by the arrow C, a large power generation pulse is generated in the power generation element 12g due to the sharp change in magnetization. In addition, as shown in the simplified diagram AS1, the power generation element 12g becomes antiparallel.

[0120] Then, when the magnet further rotates, the magnetization state of the power generating element 12g changes along the arrow D. When reaching point E, as shown in the simplified diagram PS2, the power generating element 12g is in a parallel state.

[0121] Then, similarly to the above description, the magnetization state of the power generation element 12g changes from point E along the arrow F. Then, when the external magnetic field Hext changes from negative to positive, the magnetization changes sharply as shown by the arrow G due to the Wiegand effect. As shown by the arrow G, a large power generation pulse is generated in the power generation element 12g due to the sharp change in magnetization. In addition, as shown in the simplified diagram AS2, the power generation element 12g becomes an antiparallel state. Then, the magnetization state changes along the arrow H.

[0122] In this way, when the magnetization state of the power generation element 12g changes along a loop (main loop) such as the line La, as shown by arrows C and G, a large power generation pulse is generated.

[0123] Here, for example, a case where a large power generation pulse is generated as indicated by arrow C and then the rotation is reversed at point X, that is, a case where the rotation is reversed at point X will be described.

[0124] When reversing at point X, the state changes as shown by line Lz. When reversing at point X, the magnetization state of the power generation element 12g changes along the arrow M. In addition, when reversing at point X, the external magnetic field Hext changes in the opposite direction before becoming a parallel state as shown in the simplified diagram PS2. That is, before the power generation element 12g is fully magnetized, an external magnetic field Hext is applied in the opposite direction. Therefore, as shown by arrow N, the magnetization changes slightly. As shown by arrow N, the power generation pulse caused by the small magnetization change is called a short pulse (RuntPulse). Then, after the short pulse is generated, the remaining part changes as shown by arrow P and arrow Q.

[0125] When a short pulse is generated, the amount of power generated is small, so the reverse rotation is not counted, resulting in a rotation error.

[0126] The short pulse power generation is changing from Fig. 9 It occurs when the main loop of the magnetization characteristic (BH curve) relative to the external magnetic field deviates. For example, it occurs when the reversal occurs immediately after normal power generation occurs. For example, it occurs when the N pole in the magnet 11m passes through the angle 0 degree from the angle 90 degrees and reverses immediately after a negative pulse is generated due to the Barkhausen jump. When the reversal occurs immediately after a negative pulse is generated due to the Barkhausen jump, since the magnetization state is not set to an angle of 270 degrees, there is no Barkhausen jump, and a short pulse is generated instead of a normal pulse. Therefore, a positive pulse should have been generated at an angle of 0 degrees, but a normal pulse was not generated.

[0127] However, according to the above mechanism, the power generation failure of the power generation element 12g as the Wiegand wire is not fully magnetized and occurs only when it does not pass through the angle near 90 degrees or the angle near 270 degrees and reverses. On the other hand, when the N pole passes through the angle near 90 degrees or the angle near 270 degrees, the above power generation failure does not occur.

[0128] That is, except for the case of reciprocating motion at an angle of 0 or 180, two consecutive power generation failures will not occur. In addition, in the case of reciprocating motion near an angle of 0 or 180, as long as only the last state is detected, the number of reciprocating times in the middle does not affect the count update, so there is no need to consider it.

[0129] The inventors used the above mechanism of the power generation element 12g as a Wiegand wire and found that when the power generation element 12g generates electricity and detects a position, the rotation count value caused by poor power generation can be updated based on the relationship with the most recently generated and detected position (the last estimated rotation position).

[0130] The relationship between the position detected when the power generation element 12g generates power (the position of this power generation) and the position detected when the power generation element 12g generated power most recently (the position of the last power generation: the last rotation position) is summarized in Table 2. In addition, regarding the example shown in Table 2, the diagram summarizing the position detected in the encoder 12 and how the magnet 11m moves is shown in FIG. Fig.10 as well as Fig.11 .

[0131] In addition, Fig.10 , Fig.11 In the figure, the inner circular mark indicates the position at the last power generation (the position at the last power generation), and the outer circular mark indicates the position at the current power generation (the position at the current power generation). The inner arrow line indicates the movement of the N pole of the magnet 11m at the last power generation. The outer arrow line indicates the movement of the N pole of the magnet 11m at the current power generation.

[0132]

Table 2

[0133]

[0134] A typical example will be described. For example, in case 3, that is, when the position of the previous power generation is in the first quadrant and the position of the current power generation is in the third quadrant, it is determined that normal power generation is performed in the encoder 12. In the case of case 3, since the reference angle 0 degree is not passed, the rotation count value stored in the storage unit 12r is not updated.

[0135] In case 4, when the position of the previous power generation is the first quadrant and the position of the current power generation is the fourth quadrant, it is determined that normal power generation is performed in the encoder 12. In the case of case 4, since the reference angle 0 degrees is passed, 1 is subtracted from the rotation count value stored in the storage unit 12r, and the updated rotation count value is stored in the storage unit 12r.

[0136] On the other hand, in case 1, that is, the position of the last power generation is the first quadrant and the position of the current power generation is the first quadrant, it is assumed that power generation failure occurs twice in succession at an angle of 180 degrees and an angle of 0 degrees. However, as described above, since two consecutive power generation failures will not occur, a situation like case 1 will not actually occur, and the count value is not updated but remains unchanged. In addition, in a case like case 1, an error may be output.

[0137] In case 2, when the position of the last power generation is the first quadrant and the position of the current power generation is the second quadrant, it is assumed that power generation failure occurs at an angle of 0 degrees and power generation is performed normally at an angle of 180 degrees. In case 2, since the reference angle of 0 degrees is passed, 1 is subtracted from the rotation count value stored in the storage unit 12r, and the updated rotation count value is stored in the storage unit 12r.

[0138] In the above description, examples 1, 2, 3, and 4 are described, but the same is true for other examples. By updating the count value according to the transfer table (update table) shown in Table 2, it is possible to suppress the occurrence of errors in the rotation count value based on power generation.

[0139] The encoder according to the first embodiment can suppress the occurrence of errors due to abnormal power generation caused by abnormal power generation by performing the above-described processing.

[0140] Second Implementation Method

[0141] A servo motor 110 according to a second embodiment will be described. The servo motor 110 according to the second embodiment is obtained by further including a position detection unit 112 s in addition to the servo motor 10 according to the first embodiment.

[0142] <Servo motor 110>

[0143] Next, the structure of the servo motor 110 according to the second embodiment will be described. Fig.12 1 is a diagram for explaining the structure of a servo motor 110 using an encoder 112 according to the second embodiment. Arrow lines indicate the flow of power or current supply. The servo motor 110 is connected to a servo controller 120 .

[0144] The servo motor 110 includes a motor 111 and an encoder 112. Note that, regarding the same configuration as the servo motor 10 according to the first embodiment, reference can be made to the description of the servo motor 10, and here, differences from the servo motor 10 will be described.

[0145] [Motor 111]

[0146] The motor 111 includes a disk 111 d provided on the encoder 12 side of the rotating shaft 11 a and a magnet 11 m provided on the disk 111 d .

[0147] The disk 111d has a plurality of slits 111s arranged in a predetermined pattern on the surface on the encoder 112 side. The slits 111s are used to detect the position by the position detection unit 112s. The slits 111s are formed on the surface of the disk 111d in an M-series pattern, for example.

[0148] [Encoder 112]

[0149] The encoder 112 further includes a position detection unit 112s in the encoder 12. In addition, along with the position detection unit 112s, the encoder 112 includes a control circuit 112p instead of the control circuit 12p, and includes a storage unit 112r instead of the storage unit 12r.

[0150] [Position detection unit 112s]

[0151] The position detection unit 112s has an angular resolution higher than the angular resolution of the encoder 12. For example, the position detection unit 112s has a resolution of about 20 to 24 bits in the circumferential direction. The position detection unit 112s is, for example, an angular position sensor. In addition, the position detection unit 112s is a so-called single-turn encoder. The position detection unit 112s is operated by supplying power from the servo controller 120.

[0152] The position detection unit 112s includes a light emitting unit 112s1 and a light receiving unit 112s2. The light emitting unit 112s1 irradiates light to a portion of the surface of the disk 111d where the slit 111s is formed. The light emitting unit 112s1 includes a light emitting element, such as an LED (Light Emitting Diode) or an LD (Laser Diode). The light receiving unit 112s2 receives light reflected from the slit 111s on the surface of the disk 111d. The light receiving unit 112s2 includes a light receiving element, such as a PD (Photo Detector).

[0153] The position detection unit 112s detects the intensity of light irradiated from the light emitting unit 112s1, reflected at the slit 111s, and received by the light receiving unit 112s2. Then, the position detection unit 112s detects the position of the slit 111s on the disk 111d at the portion where the light is reflected, based on the intensity of the light received by the light receiving unit 112s2. The position detection unit 112s detects the position of the magnet 11m fixed to the disk 111d (the position of the N pole of the magnet 11m) based on the position of the slit 111s.

[0154] [Control circuit 112p]

[0155] In addition to the function of the control circuit 12p, the control circuit 112p acquires position information from the position detection unit 112s and processes the information.

[0156] [Storage unit 112r]

[0157] The storage unit 112r stores information related to the position detection unit 112s in addition to the function of the storage unit 12r.

[0158] <Configuration of encoder 112>

[0159] The structure of the encoder 112 will be described. Fig.13 This is a diagram for explaining the configuration of the encoder 112 according to the second embodiment. Fig.13 It is a plan view for explaining the arrangement of the power generating element 12g, the Hall element 12h, and the position detecting unit 112s in the encoder 112.

[0160] The position detection unit 112s is disposed on the lower surface of the substrate 112j. The position detection unit 112s is provided at a location that does not overlap with the power generation element 12g and the Hall element 12h, for example, at an angle of 180 degrees.

[0161] <Operation of encoder 112>

[0162] Next, the operation of the encoder 112 will be described. When external power is supplied from the servo controller 120 to the position detection unit 112s in the encoder 112, the processing when the position of the power generating element 12g is misaligned during power generation will be described.

[0163] The basic concept is the same as that of the first embodiment, but the difference is that the position information of the position detected by the position detection unit 112s is used. In other words, the transfer of the magnet 11m is estimated based on the last position information obtained by power generation and the position information of the position detection unit 112s when the external power is turned on to the position detection unit 112s, and the rotation count value is corrected in consideration of the missing power generation pulse such as the short pulse generation. If normal power generation is performed in the power generation element 12g, the last correct position information obtained by power generation is already stored in the storage unit 112r. Therefore, the transfer of the magnet 11m can be estimated based on the last position information obtained by power generation and the position information of the position detection unit 112s when the external power is turned on to the position detection unit 112s.

[0164] Table 3 shows the relationship between the position detected when the power generation element 12g generates power (position information of MT) and the position detected by the position detection unit 112s after the external power is supplied to the position detection unit 112s and before the power generation of the power generation element 12g (position information of ST). In addition, regarding the example shown in Table 3, the diagram summarizing the position detected by the encoder 112 and how the magnet 11m moves is for Fig.14 as well as Fig.15 .

[0165]

Table 3

[0166]

[0167] In addition, Fig.14 , Fig.15 In the figure, the inner circular mark indicates the position detected when the power generation element 12g generates power (the position information of MT), and the outer circular mark indicates the position detected by the position detection unit 112s (the position information of ST). The inner arrow line indicates the movement of the N pole of the magnet 11m when the power generation element 12g generates power. The outer arrow line indicates the movement of the N pole of the magnet 11m when the position detection unit 112s detects. The outermost line with two arrows indicates the range of correction of the position information of MT. That is, the position information of MT is changed to the position information of ST. In other words, the position information of MT is regarded as the correct position information of ST and is changed to the position information of ST.

[0168] A typical example will be described. For example, in case 1, that is, when the position information of MT is the first quadrant and the position information of ST is the first quadrant, the control circuit 112p determines that the position of the magnet 11m has not changed. That is, in the case of case 1, the control circuit 112p determines that it is operating normally. Because the position of the magnet 11m has not changed, the control circuit 112p does not change the rotation count value stored in the storage unit 112r.

[0169] In case scenario 2, i.e., when the position information of MT is the first quadrant and the position information of ST is the second quadrant, the control circuit 112p determines that it is operating normally. In case scenario 2, the position information of MT is the first quadrant, which is the result of normal power generation, so it can be inferred that it is coming counterclockwise from the fourth quadrant. In addition, it can be inferred that the power supply to the position detection unit 112s is turned on, and the second quadrant is obtained through the high-resolution position detection of the position detection unit 112s. Because there is no normal power generation transfer from the first quadrant to the second quadrant, it can be inferred that it is shifted counterclockwise. In the case of case scenario 2, since the angle of intersection is not 0 degrees, the control circuit 112p does not change the rotation count value stored in the storage unit 112r.

[0170] On the other hand, in case 3, i.e., when the position information of MT is the first quadrant and the position information of ST is the third quadrant, the control circuit 112p determines that abnormal power generation has occurred. In case 3, the position information of MT is the first quadrant, which is the result of normal power generation, so it can be inferred that it came from the fourth quadrant counterclockwise. In addition, it can be inferred that the power supply of the position detection unit 112s is turned on, and the third quadrant is obtained through the high-resolution position detection of the position detection unit 112s. Since power generation occurs when the position of the magnet 11m moves counterclockwise from the first quadrant to the third quadrant, it can be inferred that the position of the magnet 11m moves clockwise from the first quadrant to the third quadrant. In addition, it can be inferred that abnormal power generation has occurred when the position of the magnet 11m passes through the angle of 0 degrees. Therefore, in order to correct the false detection caused by abnormal power generation, the control circuit 112p subtracts 1 from the rotation count value stored in the storage unit 112r, and stores the updated rotation count value in the storage unit 112r.

[0171] In case 4, i.e., when the position information of MT is the first quadrant and the position information of ST is the fourth quadrant, the control circuit 112p determines that abnormal power generation has occurred. In case 4, the position information of MT is the first quadrant, which is the result of normal power generation, so it can be inferred that it came from the fourth quadrant counterclockwise. In addition, it can be inferred that the fourth quadrant was obtained by turning on the position detection unit 112s and detecting the position with high resolution of the position detection unit 112s. Since power generation occurs when the position of the magnet 11m moves counterclockwise from the first quadrant to the fourth quadrant, it can be inferred that the position of the magnet 11m moves clockwise from the first quadrant to the fourth quadrant. In addition, it can be inferred that abnormal power generation has occurred when the position of the magnet 11m passes through an angle of 0 degrees. Therefore, in order to correct the false detection caused by abnormal power generation, the control circuit 112p subtracts 1 from the rotation count value stored in the storage unit 112r, and stores the updated rotation count value in the storage unit 112r.

[0172] <Processing in Encoder 112>

[0173] The processing in the encoder 112 is described. Fig.16 This is a flowchart for explaining the processing of the encoder 112 according to the second embodiment.

[0174] (Step S10)

[0175] First, power is supplied from the servo controller 120 to the position detection unit 112s (a process of supplying power from the host control unit). When power is supplied, the position detection unit 112s detects a position.

[0176] (Step S20)

[0177] Next, the control circuit 112p acquires position information from the position detection unit 112s (a step of acquiring position information from the position detection unit). The control circuit 112p acquires position information (position information of ST, first rotation position) from the position detection unit 112s.

[0178] (Step S30)

[0179] In parallel with step S20, the control circuit 112p obtains the position information measured at the last power generation and the rotation count value as the rotation information from the storage unit 112r (the step of obtaining the position information and the rotation information from the storage unit). The control circuit 112p obtains the position information (the position information of the MT) and the rotation count value from the storage unit 112r.

[0180] (Step S40)

[0181] Next, the control circuit 112p corrects the position information and the rotation information (a step of correcting the position information and the rotation information). The control circuit 112p corrects the rotation count value based on a correction table such as that shown in Table 3.

[0182] In addition, the timing of reading the position information stored in the storage unit 112r and the timing of measuring the position by the position detection unit 112s and reading the position information are set to be simultaneous.

[0183] The encoder according to the second embodiment can suppress the occurrence of errors due to abnormal power generation by performing the above-mentioned processing.

[0184] The Hall element 12h is an example of a magnetic sensor. The control circuit 12p or the control circuit 112p is an example of an estimation unit.

[0185] It should be understood that the embodiments disclosed herein are illustrative in all aspects and are not restrictive. The above embodiments may be omitted, replaced, or modified in various ways without departing from the scope of the appended claims and the gist thereof.

[0186] This application claims the priority of basic patent application No. 2022-207340 filed with the Japan Patent Office on December 23, 2022, the entire contents of which are incorporated herein by reference.

[0187] Explanation of symbols

[0188] 1: Servo motor system

[0189] 10, 110: Servo motor

[0190] 11, 111: Electric motor

[0191] 11a: Rotation axis

[0192] 11d, 111d: disk

[0193] 11m: Magnet

[0194] 12: Encoder

[0195] 12g: Power generation element

[0196] 12h: Hall element

[0197] 12p, 112p: Control circuit

[0198] 12r, 112r: Storage unit

[0199] 20, 120: Servo controller

[0200] 111s: Slit

[0201] 112s: Position detection unit

[0202] 120: Servo controller.

Claims

1. An encoder, comprising: A magnet mounted on the rotational position of the object to be measured; A power generation element, which utilizes the Barkhausen characteristic to convert the magnetic energy of the magnet into an electrical pulse; a magnetic sensor that measures the magnetization polarity of the magnet; an estimating unit that estimates a rotation count and a rotation position of the measurement object based on the generation polarity of the power generation element, the magnetization polarity of the magnetic sensor, and the last estimated rotation position; and A nonvolatile storage unit stores the rotation count and the rotation position estimated by the estimating unit.

2. The encoder according to claim 1, wherein When the generating polarity is + and the magnetizing polarity is N, the estimating unit estimates that the rotation position is in the first quadrant. When the generating polarity is + and the magnetizing polarity is S, the estimating unit estimates that the rotation position is in the second quadrant. When the generating polarity is - and the magnetizing polarity is S, the estimating unit estimates that the rotation position is located in the third quadrant. When the generating polarity is - and the magnetizing polarity is N, the estimating unit estimates that the rotation position is located in the fourth quadrant.

3. The encoder according to claim 1 or 2, wherein: The rotational position has a resolution of 90 degrees.

4. The encoder according to claim 1 or 2, wherein: The estimating unit estimates the rotation count and the rotation position when the power generating element generates power.

5. The encoder according to claim 4, wherein: When the power generating element generates power, the estimating unit reads the rotational position when the power generating element generated power last time from the storage unit as the last rotational position, and estimates the rotational position based on the last rotational position, the power generating polarity of the power generating element, and the magnetization polarity of the magnetic sensor.

6. The encoder according to claim 5, wherein: When the power generating element generates power, the estimating unit reads the rotation position when the power generating element generated power last time from the storage unit as the last rotation position, and updates the rotation count based on the last rotation position, the power generating polarity of the power generating element, and the magnetization polarity of the magnetic sensor.

7. The encoder according to claim 5, wherein: The estimating unit corrects the rotation count when an error occurs in the rotation count due to a power generation failure in the power generating element.

8. The encoder according to claim 7, wherein: The estimating unit corrects the rotation count based on a correction table.

9. The encoder according to claim 4, wherein: The encoder further includes an angular position sensor.

10. The encoder according to claim 9, wherein: The estimating unit estimates the rotational position based on the last estimated rotational position and the rotational position detected by the angular position sensor when power is supplied to the angular position sensor.

11. The encoder according to claim 10, wherein: When power is supplied to the angular position sensor, the estimating unit corrects the rotation count based on the rotation position estimated last and the rotation position detected by the angular position sensor.

12. The encoder according to claim 10, wherein: The estimating unit corrects the rotation count based on a correction table.

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