Encoder

Abstract

To provide a technique for improving the reliability of an encoder to detect malfunction.SOLUTION: The encoder detects angular displacement of rotation axis of a motor, and comprises: a first detection section including a power generation element; a second detection section detecting the center of one rotation in the rotation axis by an optical pattern; and a control section detecting whether at least any of the first detection section or the second detection section has malfunction on the basis of output of the second detection section generated by the power generation element.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to encoders. [Background technology]

[0002] Patent document 1 discloses an encoder device that includes a rotating part, a first detection part that detects first rotation information of the rotating part, a second detection part that detects second rotation information of the rotating part, and a control part that detects whether or not there is an abnormality in the detection results of the first detection part or the second detection part. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-149312 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a need to improve the reliability of anomaly detection in encoders.

[0005] The present disclosure provides techniques for improving the reliability of anomaly detection in encoders. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided an encoder that detects angular displacement of a rotating shaft of a motor, the encoder comprising: a first detection unit having a power generating element; a second detection unit that detects the position of the rotating shaft during one rotation using an optical pattern; and a control unit that detects the presence or absence of an abnormality in at least one of the first detection unit and the second detection unit based on the output of the second detection unit when the power generating element generates power. [Effects of the Invention]

[0007] According to the encoder of the present disclosure, the reliability of abnormality detection can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a servo motor system using an encoder according to this embodiment. [Figure 2] FIG. 2 is a diagram illustrating the configuration of a servo motor that uses the encoder according to this embodiment. [Figure 3] FIG. 3 is a diagram illustrating the circuit configuration of the encoder according to this embodiment. [Figure 4] FIG. 4 is a diagram illustrating the circuit configuration of the encoder according to this embodiment. [Figure 5] FIG. 5 is a diagram illustrating the circuit configuration of the encoder according to this embodiment. [Figure 6] FIG. 6 is a perspective view illustrating the configuration of the encoder according to this embodiment. [Figure 7] FIG. 7 is a diagram illustrating the functional configuration of the encoder according to this embodiment. [Figure 8] FIG. 8 is a diagram illustrating the processing of the first detection unit in the encoder according to this embodiment. [Figure 9] FIG. 9 is a diagram illustrating the processing of the first detection unit in the encoder according to this embodiment. [Figure 10] FIG. 10 is a diagram illustrating the processing of the second detection unit in the encoder according to this embodiment. [Figure 11] FIG. 11 is a diagram illustrating the processing of the second detection unit in the encoder according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that, in the description of the specification and drawings relating to each embodiment, components having substantially the same or corresponding functional configurations may be designated by the same reference numerals, and redundant description may be omitted. Furthermore, to facilitate understanding, the scale of each part in the drawings may differ from the actual scale.

[0010] An encoder according to this embodiment will be described. The encoder according to this embodiment is an encoder that detects the angular displacement of the rotating shaft of a motor. The encoder according to this embodiment includes a first detection unit having a power generating element, and a second detection unit that detects the position of the rotating shaft during one rotation using an optical pattern. The encoder according to this embodiment also includes a control unit that detects the presence or absence of an abnormality in at least one of the first detection unit and the second detection unit based on the output of the second detection unit when the power generating element generates power.

[0011] <Servo motor system> First, a servo motor system using an encoder according to this embodiment will be described. Fig. 1 is a diagram illustrating a servo motor system 1 using an encoder 12, which is an example of an encoder according to this embodiment.

[0012] 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 the rotation 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.

[0013] The servo motor 10 includes a motor 11 and an encoder 12. The motor 11 is connected to a servo controller 20 via a wire L1. The encoder 12 is connected to the servo controller 20 via a wire L2.

[0014] The motor 11 rotates the rotary shaft 11a in the direction of the arrow AR based on a command from the servo controller 20. Specifically, the motor 11 rotates the rotary shaft 11a in the direction of the arrow AR based on power supplied from the servo controller 20. The servo controller 20 controls the motor 11 by supplying controlled power from a wiring L1. The motor 11 is, for example, an alternating current (AC) motor, a direct current (DC) motor, or the like.

[0015] The encoder 12 detects magnetic field fluctuations (magnetic field patterns) to detect at least one of position information and rotation information of an object such as the rotating shaft 11a of the motor 11. The encoder 12 also outputs the detected position information and / or rotation information to the servo controller 20 via the wiring L2. The position information of the rotating shaft 11a is, for example, the angle (angular displacement) in the rotation direction of the rotating shaft 11a. The 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 predetermined point in time.

[0016] <Servo motor 10> Next, the configuration of the servo motor 10 using the encoder 12, which is an example of the encoder according to this embodiment, will be described. Figure 2 is a diagram illustrating the configuration of the servo motor 10 using the encoder 12, which is an example of the encoder according to this embodiment. Note that lines with arrows indicate the flow of power or current supply.

[0017] [Motor 11] The motor 11 rotates a rotating shaft 11a. The motor 11 includes well-known elements, such as bearings that support the rotating shaft 11a, windings and an iron core that form a stator for rotating the rotating shaft 11a, and permanent magnets that form a rotor, but these will not be described here. The motor 11 also includes a disk 11d that is provided on the encoder 12 side of the rotating shaft 11a. As will be described later, a first magnet 12m1 is provided symmetrically on the rotating shaft 11a, and a second magnet 12m2 is provided adjacent to the rotating shaft 11a in the circumferential direction. These magnets are mounted on the disk 11d. The first magnet 12m1 and the second magnet 12m2 rotate around the rotating shaft 11a.

[0018] Disk 11d is fixed to rotating shaft 11a. Disk 11d rotates together with rotating shaft 11a as rotating shaft 11a rotates in the direction of arrow AR. A first magnet 12m1 and a second magnet 12m2 are fixed to the surface of disk 11d facing the encoder 12.

[0019] Each of the first magnet 12m1 and the second magnet 12m2 is a permanent magnet made of neodymium, etc. When each of the first magnet 12m1 and the second magnet 12m2 rotates together with the disk 11d, the magnetic field on the encoder 12 side changes.

[0020] The first magnet 12m1 is provided so as to have an N pole and an S pole in a direction parallel to the surface of the disk 11d. The first magnet 12m1 generates a magnetic field that is detected by each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2.

[0021] The second magnets 12m2 generate a magnetic field that causes the power generating element 12g to generate power. The second magnets 12m2 are provided continuously in the circumferential direction of the rotation shaft 11a. Details of the second magnets 12m2 will be described later.

[0022] The disk 11d also has a plurality of slits 11s arranged in a predetermined optical pattern on its surface facing the encoder 12. The slits 11s are used to detect the position by a position detection circuit 12s. The slits 11s are formed on the surface of the disk 11d so as to form, for example, a light-dark pattern that constitutes an M sequence or Gray code in the circumferential direction.

[0023] [Encoder 12] The encoder 12 will now be described. The encoder 12 detects at least one of position information and rotation information of the rotating shaft 11a by using a magnetic field that changes with the rotation of the first magnet 12m1 and the second magnet 12m2. The encoder 12 also functions as an absolute encoder. The encoder 12 operates at least as a multi-turn encoder. That is, the encoder 12 counts the number of rotations of the rotating shaft 11a. The encoder 12 also generates the power required to operate at least the multi-turn detection unit of the encoder 12 (the portion of the encoder 12 other than the position detection circuit 12s) by using a magnetic field that changes with the rotation of the second magnet 12m2.

[0024] The encoder 12 detects position information of the rotating shaft 11a using a position detection circuit 12s. For example, the position detection circuit 12s has a resolution of about 5 bits in the circumferential direction. The position detection circuit 12s is, for example, an angular position sensor. By using the position detection circuit 12s, the encoder 12 functions as a so-called single-turn encoder. The position detection circuit 12s operates by receiving power from the servo controller 20. The number of bits of resolution in the position detection circuit 12s is not limited to the above example. For example, the number of bits of resolution in the position detection circuit 12s may be any number in the range of 5 bits to 24 bits.

[0025] The encoder 12 includes a power generating element 12g, a rectifier circuit 12a, a stabilized power supply circuit 12b, and a polarity detection circuit 12d. The encoder 12 also includes drive circuits 12e1 and 12e2, a first magnetic sensor 12h1 and a second magnetic sensor 12h2, signal processing circuits 12f1 and 12f2, a position detection circuit 12s, a control circuit 12p, and a storage unit 12r. The encoder 12 also includes a first magnet 12m1 and a second magnet 12m2. The rectifier circuit 12a and the stabilized power supply circuit 12b are collectively referred to as a power supply circuit 12n. The polarity detection circuit 12d, the drive circuits 12e1 and 12e2, and the signal processing circuits 12f1 and 12f2 are collectively referred to as a rotation detection circuit 12k. The first magnetic sensor 12h1 and the second magnetic sensor 12h2 are collectively referred to as a magnetic sensor 12w.

[0026] The encoder 12 includes a power generating element 12g that generates power using a change in magnetic flux due to movement, and a first magnetic sensor 12h1 and a second magnetic sensor 12h2 that measure the magnetic field. The power generating element 12g, the first magnetic sensor 12h1, and the second magnetic sensor 12h2 are provided on the motor 11 side of the encoder 12 so as to be easily affected by the magnetic fields generated by the first magnet 12m1 and the second magnet 12m2, respectively.

[0027] [Power generating element 12g] The power generating element 12g is an element that generates electricity by converting magnetic energy into an electric pulse. The power generating element 12g is an element that generates electricity by utilizing the Barkhausen characteristic. The power generating element 12g is, for example, a Wiegand wire that is an energy harvest generator (EHG).

[0028] The power generating element 12g includes a hard core and a soft layer wound around the hard core. The hard core is made of a material with a high coercive force. The soft layer is made of a material with a low coercive force. The power generating element 12g generates a power generation pulse when the direction of the external magnetic field reverses.

[0029] For example, a Wiegand wire generates an electric pulse near the zero point where the external magnetic field reverses, regardless of the rate of change of the external magnetic flux. Therefore, a Wiegand wire generates a constant power regardless of the rotation speed of the rotating shaft 11a. A Wiegand wire generates a stable electric pulse (voltage pulse) even with a gradual change in magnetic flux due to slow rotation (movement). A Wiegand wire generates an electric pulse at the timing when the magnetic field reverses.

[0030] By using an environmental power generator in the power generating element 12g, the encoder 12 can count the rotations of the rotating shaft 11a, for example, without a battery or external power source. In other words, the encoder 12 can also function as a battery-less encoder. Wiegand wire generates a constant amount of power regardless of the rotation speed of the rotating shaft 11a, and a stable power generation waveform can be obtained even at low rotation speeds, making it suitable for use as the power generating element 12g when the encoder 12 is used as a battery-less encoder.

[0031] The power generating element 12g is not limited to a Wiegand wire, and may be any power generating element that generates electricity by utilizing the Barkhausen characteristic.

[0032] The power generating element 12g generates power using the magnetic field generated by the second magnet 12m2.

[0033] [First magnetic sensor 12h1 and second magnetic sensor 12h2 (magnetic sensor 12w)] The magnetic sensor 12w includes a first magnetic sensor 12h1 and a second magnetic sensor 12h2. Each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2 detects a magnetic field. More specifically, each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2 detects a magnetic field generated by a first magnet 12m1 (described later).

[0034] Each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2 is, for example, a Hall element. The Hall element detects a magnetic field that crosses a semiconductor element through which a drive current flows. In the encoder 12, each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2 mainly detects the magnetic field generated by the first magnet 12m1. The Hall elements that constitute each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2 are made of semiconductor elements such as indium antimonide (InSb) and gallium arsenide (GaAs). The Hall elements output a voltage proportional to the drive current and the magnetic flux density that crosses the drive current.

[0035] The first magnetic sensor 12h1 outputs a magnetic field detection signal to the signal processing circuit 12f1. The first magnetic sensor 12h1 is supplied with a constant current Idr from the drive circuit 12e1. The second magnetic sensor 12h2 outputs a magnetic field detection signal to the signal processing circuit 12f2. The second magnetic sensor 12h2 is supplied with a constant current Idr from the drive circuit 12e2.

[0036] The first magnetic sensor 12h1 is supplied with a current (constant current Idr) that is obtained by rectifying the power generated by the power generating element 12g with the rectifier circuit 12a and further making it constant with the drive circuit 12e1. The second magnetic sensor 12h2 is supplied with a current (constant current Idr) that is obtained by rectifying the power generated by the power generating element 12g with the rectifier circuit 12a and further making it constant with the drive circuit 12e2.

[0037] The second magnetic sensor 12h2 has a magnetic sensitivity direction that is 90 degrees out of phase with the first magnetic sensor 12h1. The encoder 12 has magnetic sensitivity directions that are 90 degrees out of phase with each other due to the first magnetic sensor 12h1 and the second magnetic sensor 12h2. In other words, the magnetic sensors 12w (first magnetic sensor 12h1 and second magnetic sensor 12h2) in the encoder 12 have magnetic sensitivity directions that are 90 degrees out of phase with each other.

[0038] The magnetic sensor 12w comprises a first magnetic sensor 12h1 and a second magnetic sensor 12h2 having magnetic sensitivity directions with a phase difference of 90 degrees from each other, and detects changes in the magnetic field of the first magnet 12m1 as two-phase electrical signals with a phase difference of 90 degrees.

[0039] Although the encoder 12 includes two magnetic sensors, the number of magnetic sensors is not limited to two. The encoder 12 may include three or more magnetic sensors. Furthermore, the magnetic field measurement is not limited to a Hall element as long as it is an element capable of detecting magnetism (magnetic detection element). For example, a magnetoresistance effect element or the like may be used as the magnetic sensor.

[0040] The circuit configuration of the encoder 12 will be described with reference to Fig. 3. Fig. 3 is a diagram illustrating the circuit configuration of the encoder 12, which is an example of an encoder according to this embodiment.

[0041] [Rectifier circuit 12a] The rectifier circuit 12a rectifies the power generated by the power generating element 12g to generate a positive voltage. The rectifier circuit 12a includes a full-wave rectifier circuit 12a1 and a capacitor 12a2.

[0042] The full-wave rectifier circuit 12a1 rectifies the positive and negative pulses of the voltage Vgn generated by the power generating element 12g into positive pulses. The full-wave rectifier circuit 12a1 is a so-called diode bridge circuit. For example, when the power generating element 12g is a Wiegand wire, the power generating element 12g generates positive and negative pulses. The full-wave rectifier circuit 12a1 converts the positive and negative pulses generated by the power generating element 12g into positive pulses.

[0043] Capacitor 12a2 stores the power generated by power generating element 12g. Capacitor 12a2 also smooths the positive pulse generated by full-wave rectifier circuit 12a1. Capacitor 12a2 is provided between the output terminal of full-wave rectifier circuit 12a1 and a common potential. By smoothing the positive pulse by capacitor 12a2, a smoothed voltage Vrc is output from rectifier circuit 12a.

[0044] [Stabilized power supply circuit 12b] The stabilized power supply circuit 12b converts the voltage output from the rectifier circuit 12a into a substantially constant voltage 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.

[0045] When a voltage of a predetermined magnitude is input, the stabilized power supply circuit 12b outputs a substantially constant voltage Vdd.

[0046] [Polarity detection circuit 12d] The polarity detection circuit 12d detects the polarity of the power generated by the power generating element 12g. Figure 4 is a diagram illustrating the circuit configuration of the polarity detection circuit 12d in the encoder 12. The polarity detection circuit 12d includes a comparator 12d1, a filter circuit 12d2, and a diode 12d3. The diode 12d3 prevents current from flowing from the polarity detection circuit 12d to the power generating element 12g. The filter circuit 12d2 is a low-pass filter including a resistor 12d2a and a capacitor 12d2b.

[0047] Comparator 12d1 compares voltage Vgns with a reference potential (reference potential Vref2) and outputs the comparison result to control circuit 12p. Comparator 12d1 is a so-called comparator. Comparator 12d1 includes differential amplifier 12d1a and resistors 12d1b, 12d1c, and 12d1d. Power of voltage Vdd is supplied to differential amplifier 12d1a from stabilized power supply circuit 12b. Differential amplifier 12d1a compares voltage Vgns, which is obtained by smoothing voltage Vgn of the output of power generating element 12g using filter circuit 12d2, with reference potential Vref2, which is generated by dividing voltage Vdd using resistors 12d1c and 12d1d. Differential amplifier 12d1a then outputs the comparison result to control circuit 12p as a polarity signal Sp1, which is a voltage signal. Resistor 12d1b is a feedback resistor.

[0048] [Driver circuit 12e1 and driver circuit 12e2] The drive circuits 12e1 and 12e2 are so-called constant current circuits that supply a constant current Idr to the first magnetic sensor 12h1 and the second magnetic sensor 12h2, respectively. The drive circuits 12e1 and 12e2 operate as constant current sources. The encoder 12 drives the first magnetic sensor 12h1 and the second magnetic sensor 12h2, which are Hall elements, with the constant current Idr.

[0049] The drive circuit 12e1 supplies drive power to the first magnetic sensor 12h1, which is a Hall element, so that a constant current flows as a drive current through the first magnetic sensor 12h1, which is a Hall element. The drive circuit 12e2 supplies drive power to the second magnetic sensor 12h2, which is a Hall element, so that a constant current flows as a drive current through the second magnetic sensor 12h2.

[0050] Fig. 5 is a diagram illustrating the circuit configuration of the drive circuit and magnetic sensors in encoder 12, which is an example of an encoder according to this embodiment. Since drive circuit 12e1 and drive circuit 12e2 have the same circuit configuration, drive circuit 12e1 and drive circuit 12e2 will each be described as drive circuit 12e in Fig. 5. Also, in Fig. 5, first magnetic sensor 12h1 and second magnetic sensor 12h2, which are Hall elements, are each equivalently illustrated as magnetic sensor 12h using a bridge circuit including resistors 12ha, 12hb, 12hc, and 12hd.

[0051] The drive circuit 12e includes a transistor 12ea, a current detection resistor 12eb, and a differential amplifier 12ec. The drive circuit 12e also includes a resistor 12ed, a Zener diode 12ee, and a capacitor 12ef.

[0052] The transistor 12ea is controlled so that a constant current flows through the magnetic sensor 12h. The gate terminal of the transistor 12ea is connected to the output terminal of the differential amplifier 12ec. The differential amplifier 12ec outputs a voltage based on the potential difference between the positive terminal and the negative 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 positive terminal and the resistance value of the current detection resistor 12eb flows between the drain and source of the transistor 12ea.

[0053] The magnetic sensor 12h is driven by a 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 magnetic sensor 12h.

[0054] The drive circuit 12e is driven by the voltage Vdd supplied from the stabilized power supply circuit 12b.

[0055] [Signal Processing Circuit 12f1 and Signal Processing Circuit 12f2] The signal processing circuits 12f1 and 12f2 process the detection signals from the first magnetic sensor 12h1 and the second magnetic sensor 12h2, respectively, to detect the direction of the magnetic field of the first magnet 12m1. Furthermore, the signal processing circuits 12f1 and 12f2 output the strength of the magnetic field of the first magnet 12m1 to the control circuit 12p based on the detection signals from the first magnetic sensor 12h1 and the second magnetic sensor 12h2, respectively. The signal processing circuits 12f1 and 12f2 will be described with reference to FIG. 3. Since the signal processing circuits 12f1 and 12f2 have the same circuit configuration, the signal processing circuits 12f1 will be used for description in FIG. 3.

[0056] The signal processing circuit 12f1 includes a differential amplifier 12fa, a comparator 12fb, and a quantizer 12fc.

[0057] (Differential amplifier 12fa) The differential amplifier 12fa amplifies the potential difference between the voltage Vh+ and the voltage Vh− output from the magnetic sensor 12h to generate a voltage Vd, and outputs the amplified voltage Vd to the comparator 12fb. The differential amplifier 12fa is supplied with power at the voltage Vdd from the stabilized power supply circuit 12b.

[0058] (Comparator 12fb) The comparator 12fb compares the voltage Vd output from the differential amplifier 12fa with a reference potential (reference potential Vref) and outputs the comparison result to the control circuit 12p. The comparator 12fb is a so-called comparator. The comparator 12fb includes a differential amplifier 12fb1 and resistors 12fb2, 12fb3, and 12fb4. The differential amplifier 12fb1 receives power of voltage Vdd from the stabilized power supply circuit 12b. The differential amplifier 12fb1 compares the voltage Vd output from the differential amplifier 12fa with a reference potential Vref generated by dividing the voltage Vdd using resistors 12fb3 and 12fb4, and outputs the comparison result to the control circuit 12p as a magnetic pole signal Smg1, which is a voltage signal. The resistor 12fb2 is a feedback resistor.

[0059] (quantizer 12fc) The quantizer 12fc quantizes the voltage Vd output from the differential amplifier 12fa and outputs the quantized result to the control circuit 12p. The quantizer 12fc is a so-called analog-to-digital converter (AD converter). The quantizer 12fc quantizes the voltage Vd output from the differential amplifier 12fa and outputs, for example, an 8-bit digital value as a magnetic field intensity signal Dmg1 to the control circuit 12p.

[0060] [Position detection circuit 12s] The position detection circuit 12s and the slit 11s constitute a so-called optical encoder. The position detection circuit 12s includes a light-emitting unit 12s1 and a light-receiving unit 12s2. The light-emitting unit 12s1 irradiates light onto a portion of the surface of the disc 11d where the slit 11s is formed. The light-emitting unit 12s1 includes a light-emitting element, such as an LED (Light Emitting Diode) or an LD (Laser Diode). The light-receiving unit 12s2 receives light reflected from the slit 11s on the surface of the disc 11d. The light-receiving unit 12s2 includes a light-receiving element, such as a PD (Photo Detector). The light-receiving unit 12s2 includes multiple light-receiving elements. For example, when light is received using an n-bit M sequence, the light-receiving unit 12s2 includes n light-receiving elements.

[0061] The position detection circuit 12s detects the intensity of light emitted from the light-emitting unit 12s1, reflected by the slit 11s, and received by the light-receiving unit 12s2. The position detection circuit 12s then detects the position of the slit 11s on the disk 11d where the light is reflected, based on the intensity of the light received by the light-receiving unit 12s2. The position detection circuit 12s detects the rotational position based on the position of the slit 11s.

[0062] [Control circuit 12p] Based on inputs from the polarity detection circuit 12d, the signal processing circuits 12f1, and the signal processing circuits 12f2, the control circuit 12p calculates at least one of position information and rotation information, such as the rotation position and rotation speed, of the rotating shaft 11a of the motor 11. The control circuit 12p also records at least one of the detected position information and rotation information of the rotating shaft 11a of the motor 11, and transmits it to an external control system, for example, the servo controller 20.

[0063] The control circuit 12p is, for example, a microcomputer, an application specific integrated circuit (ASIC), etc. Alternatively, the control circuit 12p may be, for example, a field-programmable gate array (FPGA), a programmable logic device (PLD), etc.

[0064] The control circuit 12p is connected to an externally provided storage unit 12r. The control circuit 12p may include a nonvolatile memory such as a ferroelectric memory inside instead of the external storage unit 12r.

[0065] The control circuit 12p includes at least a terminal PWR, a terminal SIG1, a terminal row SIG1d, a terminal SIG2, a terminal row SIG2d, a terminal SIG3, and a terminal row SIG4d.

[0066] The terminal PWR of the control circuit 12p is a terminal to which positive power is supplied. The terminal PWR is supplied with power of voltage Vdd from the stabilized power supply circuit 12b. The control circuit 12p operates when power is supplied to the terminal PWR.

[0067] The terminals SIG1, SIG2, and SIG3 of the control circuit 12p are terminals to which signals are input from the outside. The terminal rows SIG1d, SIG2d, and SIG4d of the control circuit 12p are terminal rows to which multi-bit signals are input from the outside.

[0068] The terminal SIG1 is connected to the signal processing circuit 12f1. A magnetic pole signal Smg1, which is the detection result detected by the signal processing circuit 12f1, is input from the terminal SIG1. The magnetic pole signal Smg1 is a signal that indicates the direction of the magnetic field detected by the first magnetic sensor 12h1. The terminal SIG2 is connected to the signal processing circuit 12f2. A magnetic pole signal Smg2, which is the detection result detected by the signal processing circuit 12f2, is input from the terminal SIG2. The magnetic pole signal Smg2 is a signal that indicates the direction of the magnetic field detected by the second magnetic sensor 12h2.

[0069] The terminal row SIG1d is connected to the signal processing circuit 12f1. A magnetic field intensity signal Dmg1, which is the detection result detected by the signal processing circuit 12f1, is input from the terminal row SIG1d. The magnetic field intensity signal Dmg1 is a signal indicating the intensity of the magnetic field detected by the first magnetic sensor 12h1. The terminal row SIG2d is connected to the signal processing circuit 12f2. A magnetic field intensity signal Dmg2, which is the detection result detected by the signal processing circuit 12f2, is input from the terminal row SIG2d. The magnetic field intensity signal Dmg2 is a signal indicating the intensity of the magnetic field detected by the second magnetic sensor 12h2.

[0070] The terminal SIG3 is connected to the polarity detection circuit 12d. A polarity signal Sp1, which is the detection result detected by the polarity detection circuit 12d, is input from the terminal SIG3. The polarity signal Sp1 is a signal that indicates the power generation polarity of the power generation element 12g.

[0071] The terminal array SIG4d is connected to the position detection circuit 12s. A position detection signal Ds, which is the detection result of the position detection circuit 12s, is input from the terminal array SIG4d. The position detection signal Ds is a signal that indicates the rotational position of the rotary shaft 11a.

[0072] The encoder 12 counts the number of rotations of the rotating shaft 11a. The control circuit 12p counts the number of rotations of the rotating shaft 11a using the magnetic pole signal Smg1 and the polarity signal Sp1. The control circuit 12p also uses the magnetic pole signal Smg1 and the polarity signal Sp1 to detect which of the 90-degree regions the rotating shaft 11a is in. The control circuit 12p then stores the results of counting the number of rotations of the rotating shaft 11a and the results of detecting which region the rotating shaft is in in the memory unit 12r. The control circuit 12p also stores the most recently detected magnetic pole signals Smg1, Smg2, and polarity signal Sp1 in the memory unit 12r.

[0073] Furthermore, the control circuit 12p uses the magnetic field strength signals Dmg1 and Dmg2 to determine the rotation angle of the rotating shaft 11a. For example, the control circuit 12p calculates the rotation angle of the rotating shaft 11a using an arctangent function from the ratio between the magnetic field strength signals Dmg1 and Dmg2.

[0074] Furthermore, the control circuit 12p calculates the rotation angle of the rotary shaft 11a based on the position detection signal Ds.

[0075] The control circuit 12p detects whether or not there is an abnormality in the counting of the number of rotations by the magnetic sensor 12w and the position detection by the position detection circuit 12s.

[0076] [Storage section 12r] The memory unit 12r stores, for example, a rotation count and the like. The memory unit 12r is, for example, a ferroelectric memory. The control circuit 12p stores, in the memory unit 12r, at least a count value indicating the number of rotations of the rotating shaft 11a, the position of the rotating shaft, and the last detected magnetic pole signal Smg1, magnetic pole signal Smg2, and polarity signal Sp1.

[0077] <Encoder configuration> The configuration of the encoder 12 will now be described in detail.

[0078] FIG. 6 is a perspective view illustrating the configuration of an encoder 12, which is an example of an encoder according to this embodiment.

[0079] A circuit board 12j is provided facing the disk 11d. A power generating element 12g is disposed on the upper surface of the circuit board 12j. The power generating element 12g is provided outside the position facing the second magnet 12m2. The power generating element 12g is preferably provided within a range of 1.2 to 1.5 times the radius of the second magnet 12m2. By providing the power generating element 12g outside the position facing the second magnet 12m2, the power generation efficiency of the power generating element 12g can be increased.

[0080] A position detection circuit 12s and a magnetic sensor 12w are provided on the lower surface of the circuit board 12j. The position detection circuit 12s is provided at a position facing the slit 11s in the disk 11d. The magnetic sensor 12w is provided at a position facing the first magnet 12m1.

[0081] The disk 11d is fixed to the rotating shaft 11a. The disk 11d rotates in synchronization with the rotation of the rotating shaft 11a. Figure 6 shows the arrangement of the magnets at a certain point in time.

[0082] The encoder 12 includes a rotationally symmetric first magnet 12m1 provided on the disk 11d, and a rotationally symmetric second magnet 12m2 provided outside the rotation axis of the first magnet 12m1. The first magnet 12m1 has two poles, an S pole and an N pole, and is a magnet with one rotational symmetry. In this embodiment, the second magnet 12m2 has four poles and is a magnet with two rotational symmetry. By making the first magnet 12m1 and the second magnet 12m2 rotationally symmetric in this way, the rotational torque (moment) is smaller than that of rotationally asymmetric magnets, which has the effect of reducing the load on the motor 11.

[0083] The encoder 12 may include a magnetic body between the first magnet 12m1 and the second magnet 12m2. By including a magnetic body between the first magnet 12m1 and the second magnet 12m2, the encoder 12 can prevent the magnetic forces of the first magnet 12m1 and the second magnet 12m2 from interfering with each other and weakening the magnetic field.

[0084] The encoder 12 includes, as the second magnet 12m2, C-shaped unit magnets 12m2a, 12m2b, 12m2c, and 12m2d. The second magnet 12m2 is a magnet formed by combining C-shaped unit magnets 12m2a, 12m2b, 12m2c, and 12m2d in a ring shape. The second magnet 12m2 is integrally arranged in the circumferential direction. By arranging the second magnet 12m2 integrally in the circumferential direction, the area efficiency and volume efficiency for generating a magnetic field by the second magnet 12m2 can be improved. By improving the area efficiency and volume efficiency for generating a magnetic field by the second magnet 12m2, the power generation efficiency of the power generation element 12g can be improved.

[0085] The second magnet 12m2 includes four unit magnets, but the number of unit magnets is not limited to four. The second magnet may be a magnet made up of a combination of 2×n (n is an integer of 1 or greater) C-shaped unit magnets.

[0086] Each of the unit magnets 12m2a, 12m2b, 12m2c, and 12m2d has a magnetization direction perpendicular to the rotation axis direction.

[0087] By configuring the second magnet 12m2 by combining unit magnets each having a C-shape, the magnet can be easily assembled. For example, when assembling magnets, the assembly work can be difficult due to the attraction and repulsion of the magnets. According to the encoder 12, by combining unit magnets each having a C-shape and arranging them continuously in the circumferential direction, assembly can be made easier. Furthermore, according to the encoder 12, by combining unit magnets each having a C-shape and arranging them continuously in the circumferential direction, the area efficiency and volume efficiency for generating a magnetic field can be improved compared to when magnets are arranged dispersed in the circumferential direction. Furthermore, C-shaped unit magnets are widely available, inexpensive, and easily available.

[0088] The first magnet 12m1 has a magnetization direction in the direction of zero magnetic field in the second magnet 12m2, that is, in the direction between adjacent unit magnets, more specifically, in the direction between unit magnet 12m2a and unit magnet 12m2d.

[0089] Furthermore, in the above example, the second magnet is a combination of C-shaped unit magnets, but the second magnet may also be a ring magnet with 2×n poles (n is an integer greater than or equal to 1). A ring magnet is easier to manufacture and assemble onto disk 11d than when a combination of C-shaped unit magnets is used.

[0090] Next, the functional configuration of the encoder according to this embodiment will be described. Fig. 7 is a diagram illustrating the functional configuration of the encoder 12, which is an example of the encoder according to this embodiment.

[0091] The encoder 12 includes a control unit 12A, a first detection unit 12B, and a second detection unit 12C.

[0092] The first detection unit 12B includes a first magnet 12m1, a second magnet 12m2, a power generation element 12g, a magnetic sensor 12w, and a control circuit 12p. The control circuit 12p executes a process to calculate the number of rotations of the rotating shaft 11a based on the magnetic pattern generated by the first magnet 12m1 detected by the magnetic sensor 12w. The control circuit 12p executes a process to calculate the number of rotations of the rotating shaft 11a based on the magnetic pattern generated by the first magnet 12m1 detected by the magnetic sensor 12w, and the first detection unit 12B detects the number of rotations of the rotating shaft 11a. The first detection unit 12B also outputs a sine wave with a phase shift of 90 degrees representing the change in the magnetic field of the second magnet 12m2 detected by the first magnetic sensor 12h1 and the second magnetic sensor 12h2 in the magnetic sensor 12w.

[0093] The second detection unit 12C includes a slit 11s, a position detection circuit 12s, and a control circuit 12p. The control circuit 12p executes a process to calculate the position (angle, angular displacement) of the rotating shaft 11a during one rotation from the optical pattern generated by the slit 11s detected by the position detection circuit 12s. The control circuit 12p executes a process to calculate the position (angle, angular displacement) of the rotating shaft 11a during one rotation from the optical pattern generated by the slit 11s detected by the position detection circuit 12s, whereby the second detection unit 12C detects the position (angle, angular displacement) of the rotating shaft 11a during one rotation.

[0094] Next, the processing of the first detection unit 12B in the encoder 12 will be described. Figures 8 and 9 are diagrams illustrating signal waveforms of the encoder 12, which is an example of an encoder according to this embodiment. Figure 8 shows waveforms when the first magnet 12m1 and the second magnet 12m2 in Figure 6 rotate counterclockwise as viewed from above. Figure 9 shows waveforms when the first magnet 12m1 and the second magnet 12m2 in Figure 6 rotate clockwise as viewed from above.

[0095] It is assumed that the first magnetic sensor 12h1 has a magnetic sensitivity direction in the horizontal direction in FIG. 6, and the second magnetic sensor 12h2 has a magnetic sensitivity direction in the front-rear direction in FIG.

[0096] 8 and 9, the horizontal axis represents the angle θ, and the vertical axis represents the signal intensity normalized so that the maximum is 1. Line Lc represents the signal output from the first magnetic sensor 12h1, line Ls represents the signal output from the second magnetic sensor 12h2, line Lg1 represents the signal generated by the power generating element 12g in the counterclockwise direction, and line Lg2 represents the signal generated by the power generating element 12g in the clockwise direction.

[0097] As shown in FIGS. 8 and 9, the magnetic field generated by the first magnet 12m1 causes the first magnetic sensor 12h1 and the second magnetic sensor 12h2 to output sine waves with a phase difference of 90 degrees. Furthermore, the power generating element 12g generates electricity near angles that are multiples of 45 degrees. The polarity of the generated electricity differs depending on the direction of rotation. The polarity of the generated electrical pulse (generated pulse) during counterclockwise rotation is opposite to that during clockwise rotation. Specifically, as shown in FIG. 8, the polarity of the generated electrical pulse during counterclockwise rotation is positive near 45 degrees, 225 degrees, and negative near 135 degrees, 315 degrees, and conversely, as shown in FIG. 9, the polarity of the generated electrical pulse during clockwise rotation is negative near 45 degrees, 225 degrees, and positive near 135 degrees, 315 degrees, and Furthermore, because the power generation characteristics of the power generation element 12g have hysteresis, the angle at which the power generation element 12g generates an electric pulse is shifted by a certain number of degrees (α degrees) from an angle that is a multiple of 45 degrees. For example, when rotating counterclockwise at 45 degrees, an electric pulse is generated at 45 + α degrees. Note that the direction of the shift when rotating counterclockwise is opposite to the direction of the shift when rotating clockwise. For example, when rotating clockwise at 45 degrees, an electric pulse is generated at 45 - α degrees.

[0098] As shown in Figures 8 and 9, the first magnetic sensor 12h1 and the second magnetic sensor 12h2 each output a sine wave that is 90 degrees out of phase with each other, and the power generating element 12g generates power. As a result, as shown in Table 1, the encoder 12 can measure the rotation direction and the rotation position with an angular resolution of 90 degrees.

[0099] [Table 1]

[0100] Next, a description will be given of the processing of the second detection unit 12C in the encoder 12. Figures 10 and 11 are diagrams for explaining the processing of the second detection unit in the encoder 12, which is an example of an encoder according to this embodiment. In each of the examples in Figures 10 and 11, a case will be described in which a 5-bit M sequence is used.

[0101] The positions in FIG. 10 indicate numbers that represent positions (angles, angular displacements) when the circumferential position (angle, angular displacement) on the rotating shaft 11a (disk 11d) is divided into 32 parts. The M-sequence waveform in FIG. 10 indicates the waveform received by the position detection circuit 12s. mqs[0] to msq[4] in FIG. 10 indicate the waveforms received by each of the five light receiving elements in the position detection circuit 12s. mqs[4:0] in FIG. 10 indicates the result of encoding the received light and expressing it in hexadecimal notation. The interpolated waveform in FIG. 10 indicates a sine wave with one period equal to the resolution of the M-sequence. Note that in FIG. 10, sine and cosine are used to indicate two-phase sine waves with a phase difference of 90 degrees.

[0102] FIG. 11 shows a conversion table between the M sequence waveform (M sequence read value) detected by the position detection circuit 12s and the position (angle, angular displacement). The M sequence read value in FIG. 11 shows the read value expressed in both binary and hexadecimal when the rotating shaft 11a is at the position (angle, angular displacement) indicated by the number. The rotating shaft position in FIG. 11 shows the number indicating the position of the rotating shaft 11a detected by the position detection circuit 12s and the angle at that time. Note that the angle is set to 0 degrees when the number of the rotating shaft position is 0.

[0103] By using the conversion table shown in FIG. 11, the position (angle, angular displacement) of the rotation axis 11a can be determined with a resolution of approximately 11.61 degrees (=360 degrees / 31).

[0104] Furthermore, by using an interpolated waveform and performing an arctangent operation, it is possible to specify a position (angle, angular displacement) with even greater precision than the resolution of the M sequence.

[0105] A specific example of the process will be described below: For example, a case where the position is detected by the position detection circuit 12s at the position of the line P in FIG.

[0106] The control circuit 12p acquires the value of msq[4:0] from the position detection circuit 12s. When the control circuit 12p acquires the value of msq[4:0] from the position detection circuit 12s at line P in FIG. 10, the value of msq[4:0] is 19h (hexadecimal). Therefore, the control circuit 12p determines that the position of the rotating shaft 11a is at position 12. The control circuit 12p then determines that the angle of the rotating shaft 11a is 139.35 degrees (=360×(12 / 31)).

[0107] Furthermore, the control circuit 12p acquires values ​​of the interpolated waveform from the position detection circuit 12s. At the position of line P in Figure 10, for example, if sin is 0.5 and cos is 0.866, the control circuit 12p determines using an arctangent function that the position (angle, angular displacement) of the rotating shaft 11a is 60 degrees in one interpolation cycle. Therefore, the control circuit 12p calculates the angle of the rotating shaft 11a as 141.29 degrees (= 360 × (12 / 31) + (360 / 31) × (60 / 360)).

[0108] The abnormality detection method of first detection unit 12B and second detection unit 12C in control unit 12A will be described below. Here, the description will be made assuming that the 0 degree positions of first detection unit 12B and second detection unit 12C are the same.

[0109] As shown by line Lg1 in Fig. 8 and line Lg2 in Fig. 9, the electric pulse of the power generating element 12g rises very steeply near angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees. If the position of the power generating element 12g is read by the second detection unit 12C at the timing when the electric pulse of the power generating element 12g rises very steeply near angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees, the value will be close to any of the angles 45 degrees, 135 degrees, 225 degrees, and 315 degrees if the second detection unit 12C is normal.

[0110] Therefore, if the detection result of the second detection unit 12C at the time when the power generation element 12g generates an electrical pulse is a value close to any of the angles 45 degrees, 135 degrees, 225 degrees, and 315 degrees, the control unit 12A determines that both the first detection unit 12B and the second detection unit 12C are normal.

[0111] However, if an error occurs in the detection result of the second detection unit 12C in the position detection circuit 12s due to, for example, dirt on the slit 11s, the detection result of the second detection unit 12C at the timing when the power generating element 12g generates an electric pulse will have an error from a value near any of the angles 45 degrees, 135 degrees, 225 degrees, and 315 degrees. Therefore, by setting in advance an allowable value for the error from a value near the angles 45 degrees, 135 degrees, 225 degrees, and 315 degrees as a judgment value, the control unit 12A can compare the timing when the power generating element 12g generates an electric pulse with the detection result of the second detection unit 12C and detect an abnormality if the error exceeds the judgment value.

[0112] Furthermore, by comparing the power generation timing of the power generation element 12g, the detection polarities of the two-phase electrical signals with different phase differences detected by the first magnetic sensor 12h1 and the second magnetic sensor 12h2, and the detection result of the second detection unit 12C, more precise abnormality detection becomes possible. As described above, the change in the magnetic field of the second magnet 12m2 detected by the first magnetic sensor 12h1 and the second magnetic sensor 12h2 in the magnetic sensor 12w is output as a sine wave with a phase shift of 90 degrees.

[0113] Therefore, the first detection unit 12B can detect the position with a resolution of 90 degrees, based on the power generation polarity at the timing when the electric pulse of the power generation element 12g rises and the detection polarity of each of the two-phase electric signals with different phase differences detected by the first magnetic sensor 12h1 and the second magnetic sensor 12h2 at that time, as shown in Table 1. In other words, the first detection unit 12B can identify which angle of 45 degrees, 135 degrees, 225 degrees, or 315 degrees the position is near, based on the power generation polarity of the power generation element 12g and the detection polarity of each of the first magnetic sensor 12h1 and the second magnetic sensor 12h2.

[0114] Therefore, when the detection result of the first detection unit 12B at the timing when the power generation element 12g generates an electric pulse is, for example, near an angle of 45 degrees, if the detection result of the second detection unit 12C is also a value near an angle of 45 degrees, the control unit 12A will determine that both the first detection unit 12B and the second detection unit 12C are normal.

[0115] However, when the detection result of the first detection unit 12B at the timing when the power generation element 12g generates an electric pulse is, for example, near an angle of 45 degrees, if the detection result of the second detection unit 12C has an error that exceeds a predetermined judgment value from the value near an angle of 45 degrees, the control unit 12A determines that at least one of the first detection unit 12B and the second detection unit 12C is abnormal.

[0116] In this way, by presetting the allowable error value from values ​​near angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees as the judgment value, the control unit 12A can compare the detection result with 90-degree resolution output by the first detection unit 12B with the detection result of the second detection unit 12C, and detect an abnormality if the error between both detection results exceeds the judgment value.

[0117] It should be noted that even if a malfunction occurs in the first detection unit 12B, the abnormality can be detected by the same process.

[0118] As shown by line Lg1 in Fig. 8 and line Lg2 in Fig. 9, the power generating element 12g produces electric pulses that rise very steeply near angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees. Because the power generating element 12g produces electric pulses that rise very steeply near angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees, there is little change in timing with respect to temperature, making it possible to diagnose abnormalities with accurate timing. Furthermore, because the power generating element 12g produces electric pulses that rise very steeply near angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees, it is possible to diagnose abnormalities even when the rotating shaft 11a is rotating at high speed.

[0119] As mentioned above, the waveform of the power generating element 12g deviates by α degrees from an angle that is a multiple of 45 degrees when rotating clockwise and counterclockwise. However, because the angle deviation due to the direction of rotation has little dependency on the rotation speed or temperature, more accurate diagnosis can be achieved by setting separate judgment values ​​for clockwise and counterclockwise rotations. Accurate diagnosis improves reliability.

[0120] Furthermore, by increasing the number of poles (2n) of the second magnet 12m2, more precise abnormality detection becomes possible. More precise abnormality detection improves reliability. For example, in the examples shown in Figures 8 and 9, the second magnet has four poles (n = 2), so there are four detection timings every 90 degrees per motor rotation. However, by increasing the number of poles (n = 4), for example, there can be eight detection timings every 45 degrees.

[0121] The encoder according to this embodiment can improve the reliability of abnormality detection. For example, the Hall elements used in multi-turn encoders have poor temperature characteristics, resulting in variations in detection results. Because the detection results of the Hall elements vary, it is necessary to set stricter judgment values ​​to take these variations into account, narrowing the tolerance for error. Furthermore, because the detection delay time of the Hall elements is long, the tolerance for error becomes even narrower when the motor is rotating at high speed. The encoder according to this embodiment can minimize the effects of temperature and stably detect abnormalities by comparing the outputs of the first and second detection units when the power generating element generates power to detect whether or not an abnormality exists. The encoder according to this embodiment can improve reliability by stably detecting abnormalities.

[0122] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0123] 1. Servo motor system 10 Servo motor 11 Motor 11a Rotation axis 11d disc 11s slit 12 Encoders 12g power generating element 12w magnetic sensor 12h1 First magnetic sensor 12h2 Second magnetic sensor 12m1 1st magnet 12m2 2nd magnet 12p control circuit 12s Position detection circuit 12A Control unit 12B First detection unit 12C Second detection unit 20 Servo Controller

Claims

1. An encoder that detects angular displacement of a rotating shaft of a motor, a first detection unit including a power generation element; a second detection unit that detects a position of the rotation shaft during one rotation using an optical pattern; a control unit that detects whether or not there is an abnormality in at least one of the first detection unit and the second detection unit based on an output of the second detection unit when the power generation element generates power; Equipped with Encoder.

2. the first detection unit includes a second magnet with 2×n poles (n is an integer equal to or greater than 1) that is symmetrically arranged with respect to the rotation axis, The power generating element generates power by a change in the magnetic field of the second magnet. The encoder of claim 1 .

3. An encoder that detects angular displacement of a rotating shaft of a motor, a first detection unit including a power generating element and a magnetic sensor that detects the number of rotations of the rotation shaft based on a magnetic pattern; a second detection unit that detects a position of the rotation shaft during one rotation using an optical pattern; a control unit that compares outputs of the first detection unit and the second detection unit when the power generation element generates power, and detects whether or not there is an abnormality in at least one of the first detection unit and the second detection unit; Equipped with Encoder.

4. The first detection unit a first magnet having two poles symmetrically disposed on the rotation axis; a second magnet having 2×n poles (n is an integer of 1 or more) arranged symmetrically with respect to the rotation axis; a magnetic sensor that detects a change in the magnetic field of the first magnet as two-phase electrical signals with a phase difference of 90 degrees; Equipped with The power generating element generates power by a change in the magnetic field of the second magnet. The encoder of claim 3 .

5. the control unit detects the presence or absence of an abnormality in at least one of the first detection unit and the second detection unit by comparing the power generation timing of the power generation element, the detection polarities of the two-phase electrical signals detected by the magnetic sensor, and the detection result of the second detection unit. The encoder of claim 4.

6. The power generating element generates power by utilizing the Barkhausen characteristic. The encoder according to any one of claims 1 to 5.

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