Encoder

Abstract

To provide an encoder that can be operated with less electric power.SOLUTION: An encoder detects variation in a magnetic field and detects position information on an object. The encoder comprises: a power generation circuit including a Wiegand wire generating power by a change in magnetic flux due to movement; a polarity detection circuit that detects a polarity of output from the power generation circuit; a switching circuit that switches the power from the power generation circuit to the polarity detection circuit between supply and cutoff; and an arithmetic circuit that calculates the position information. The switching circuit switches the power from the power generation circuit to the polarity detection circuit from the cutoff to the supply when the voltage of the power generation circuit is a threshold voltage value or more, and the arithmetic circuit calculates the position information on the basis of a detection result of the polarity detection circuit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an encoder device that includes a signal generating unit that generates a detection signal based on the movement of a moving unit, a state detecting unit that detects the state of a power supply unit, and a switching unit that switches on and off the supply of power from the power supply unit to the state detecting unit based on the detection signal. Patent Document 1 also discloses that the power supply unit includes a battery, and that consumption of the power supply unit is suppressed by detecting the state of the power supply unit while reducing the power consumption of the power supply unit.

[0003] Patent Document 2 discloses an encoder device that includes a position detection unit that detects position information of a moving unit, and a cutoff unit that cuts off the supply of power from a power supply unit to the position detection unit based on a trigger signal that indicates the end of operation of the position detection unit. Patent Document 2 discloses that by cutting off the power supply from the power supply unit to the position detection unit upon receiving a trigger signal that indicates the end of operation of the position detection unit, it is possible to reduce consumption of the power supply unit, such as a battery. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 188084 [Patent Document 2] Patent Publication No. 2021-001908 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, an encoder using an energy harvesting element is known, and it is desirable to operate the encoder with lower power consumption.

[0006] An object of the present disclosure is to provide an encoder that can operate with low power consumption. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, there is provided an encoder that detects fluctuations in a magnetic field to detect position information of an object, the encoder comprising: a power generation circuit having a Wiegand wire that generates power through changes in magnetic flux due to movement; a polarity detection circuit that detects the polarity of the output from the power generation circuit; a switching circuit that switches between supplying and cutting off power from the power generation circuit to the polarity detection circuit; and a calculation circuit that calculates the position information, wherein the switching circuit switches from cutting off to supplying power from the power generation circuit to the polarity detection circuit when the voltage of the power generation circuit reaches a threshold voltage value or higher, and the calculation circuit calculates the position information based on the detection result of the polarity detection circuit. [Effects of the Invention]

[0008] The encoder of the present disclosure can operate with low power consumption. [Brief explanation of the drawings]

[0009] [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 using 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 diagram illustrating the circuit configuration of the encoder according to this embodiment. [Figure 7] FIG. 7 is a diagram illustrating the processing of the encoder according to this embodiment. [Figure 8] FIG. 8 is a diagram illustrating the operation of the encoder according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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.

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

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

[0017] [Motor 11] The motor 11 includes a disk 11d provided on the rotary shaft 11a facing the encoder 12, and a magnet 11m provided on the disk 11d. In addition to the rotary shaft 11a, the disk 11d, and the magnet 11m, the motor 11 also includes well-known elements such as bearings that support the rotary shaft 11a, windings that form a stator for rotating the rotary shaft 11a, an iron core, and permanent magnets that form a rotor, but a description of these elements will be omitted here.

[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. Magnet 11m is fixed to the surface of disk 11d on the encoder 12 side.

[0019] The magnet 11m is a permanent magnet made of neodymium or the like. The magnet 11m is provided so as 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.

[0020] [Encoder 12] The encoder 12 detects at least one of position information and rotation information of the rotating shaft 11a based on the magnetic field that changes with the rotation of the magnet 11m. The encoder 12 also generates the power required to operate the encoder 12 based on the magnetic field that changes with the rotation of the magnet 11m.

[0021] The encoder 12 includes a power generation circuit 12g, a rectifier circuit 12a, a stabilization circuit 12b, a switching circuit 12c, a polarity detection circuit 12d, a drive circuit 12e, a Hall element 12h, a signal processing circuit 12f, and a control circuit 12p. The polarity detection circuit 12d, the drive circuit 12e, the Hall element 12h, and the signal processing circuit 12f are collectively referred to as an analog processing circuit 12m.

[0022] The encoder 12 includes a power generation circuit 12g that generates power using a change in magnetic flux due to movement, and a Hall element 12h that measures the magnetic field. The power generation circuit 12g and the Hall element 12h are provided on the motor 11 side of the encoder 12 so that they are easily affected by the magnetic field generated by the magnet 11m.

[0023] [Generator circuit 12g] The power generation circuit 12g is, for example, a Wiegand wire, which is an energy harvest generator (EHG). The Wiegand wire generates a power generation pulse near the zero point where the external magnetic field reverses, regardless of the rate of change of the external magnetic flux. Therefore, the Wiegand wire generates a constant amount of power regardless of the rotation speed of the rotating shaft 11a.

[0024] By using an environmental power generator in the power generation circuit 12g, the encoder 12 does not require a battery or external power source. In other words, the encoder 12 is 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 in particular, so it is suitable for use in the power generation circuit 12g of the battery-less encoder 12.

[0025] [Hall element 12h] The Hall element 12h detects the magnetic field that crosses the semiconductor element through which the drive current flows. In the encoder 12, the Hall element 12h mainly detects the magnetic field generated by the magnet 11m. The Hall element 12h is made of a semiconductor element such as indium antimonide (InSb) or gallium arsenide (GaAs). The Hall element 12h outputs a voltage proportional to the drive current and the magnetic flux density that crosses the drive current.

[0026] The Hall element 12h outputs a detection signal of the magnetic field to the signal processing circuit 12f. A constant current Idr is supplied to the Hall element 12h from the drive circuit 12e.

[0027] The Hall element 12h is supplied with a current (constant current Idr) that is obtained by rectifying the power generated by the power generating circuit 12g in the rectifying circuit 12a and then making it constant in the driving circuit 12e.

[0028] Although the encoder 12 includes one Hall element, the number of Hall elements is not limited to one. The encoder 12 may include multiple Hall elements. Furthermore, the measurement of the magnetic field is not limited to the 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 instead of the Hall element 12h.

[0029] 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 according to this embodiment.

[0030] [Rectifier circuit 12a] The rectifier circuit 12a rectifies the power generated by the power generation circuit 12g to generate a positive voltage. The rectifier circuit 12a includes a full-wave rectifier circuit 12a1 and a smoothing capacitor 12a2.

[0031] The full-wave rectifier circuit 12a1 rectifies the positive and negative pulses of the voltage Vgn generated by the power generation circuit 12g into positive pulses. The full-wave rectifier circuit 12a1 is a so-called diode bridge circuit. For example, when the power generation circuit 12g is a Wiegand wire, the power generation circuit 12g generates positive and negative pulses. The full-wave rectifier circuit 12a1 converts the positive and negative pulses generated by the power generation circuit 12g into positive pulses.

[0032] Smoothing capacitor 12a2 smoothes the positive pulse generated by full-wave rectifier circuit 12a1. Smoothing capacitor 12a2 is provided between the output terminal of full-wave rectifier circuit 12a1 and a common potential. By smoothing the positive pulse by smoothing capacitor 12a2, a smoothed voltage Vrc is output from rectifier circuit 12a.

[0033] [Stabilization circuit 12b] The stabilization circuit 12b converts the voltage output from the rectification circuit 12a into a substantially constant voltage and outputs it. The stabilization circuit 12b includes a regulator 12b1. The regulator 12b1 is, for example, an LDO (Low Dropout) regulator.

[0034] When a voltage of a predetermined magnitude is input, the stabilization circuit 12b outputs a substantially constant voltage Vdd.

[0035] [Switching circuit 12c] The switching circuit 12c switches between interrupting and supplying power from the power generation circuit 12g to the analog processing circuit 12m based on the voltage Vrc in the rectifier circuit 12a and a control signal Cst from the control circuit 12p. Specifically, the switching circuit 12c switches between interrupting and supplying power from the power generation circuit 12g to the analog processing circuit 12m via the rectifier circuit 12a and the stabilization circuit 12b based on the voltage Vrc in the rectifier circuit 12a and a control signal Cst from the control circuit 12p. FIG. 4 is a diagram illustrating the circuit configuration of the switching circuit 12c of the encoder 12 according to this embodiment. The switching circuit 12c includes a changeover switch 12c1 and a changeover signal generation circuit 12c2. The changeover signal generation circuit 12c2 generates a changeover signal Csw that controls the changeover of the changeover switch 12c1.

[0036] (Switch 12c1) The changeover switch 12c1 switches between connection and disconnection based on the changeover signal Csw. The changeover switch 12c1 is provided between the wiring Wvdd and the wiring Wva. When the changeover switch 12c1 switches from disconnection to connection based on the changeover signal Csw, the wiring Wvdd and the wiring Wva are connected. When the wiring Wvdd and the wiring Wva are connected, the voltage Va supplied to the analog processing circuit 12m becomes equal to the voltage Vdd supplied from the stabilization circuit 12b. When the wiring Wvdd and the wiring Wva are connected, power is supplied from the stabilization circuit 12b to the analog processing circuit 12m. When power is supplied from the stabilization circuit 12b to the analog processing circuit 12m, the analog processing circuit 12m starts operating.

[0037] (Switching signal generating circuit 12c2) The switching signal generating circuit 12c2 generates the switching signal Csw based on the voltage Vrc output by the rectifier circuit 12a and the control signal Cst. The switching signal generating circuit 12c2 includes a comparator 12c2A and a logic circuit 12c2B.

[0038] Comparator 12c2A compares voltage Vrc with a reference potential (threshold voltage Vth (see FIG. 8)) and outputs the comparison result to logic circuit 12c2B. Comparator 12c2A is a so-called comparator. Comparator 12c2A includes differential amplifier 12c2a and resistors 12c2b, 12c2c, and 12c2d. Resistor 12c2b is a feedback resistor. Power of voltage Vdd is supplied to differential amplifier 12c2a from stabilization circuit 12b. Comparator 12c2A divides voltage Vdd using resistors 12c2c and 12c2d to generate threshold voltage Vth.

[0039] The differential amplifier 12c2a compares the voltage Vrc output from the rectifier circuit 12a with a threshold voltage Vth, and outputs a comparison signal Scmp, which is a voltage signal, to the logic circuit 12c2B if the voltage Vrc is equal to or greater than the threshold voltage.

[0040] Furthermore, the differential amplifier 12c2a compares the voltage Vrc output from the rectifier circuit 12a with the threshold voltage Vth, and stops outputting the comparison signal Scmp, which is a voltage signal, to the logic circuit 12c2B if the voltage Vrc is less than the threshold voltage value.

[0041] The logic circuit 12c2B generates a switching signal Csw based on the comparison signal Scmp and the control signal Cst. The logic circuit 12c2B outputs the switching signal Csw when both the comparison signal Scmp and the control signal Cst satisfy the conditions. For example, if the comparison signal Scmp is a high voltage until the acquisition of the measurement results is completed and a low voltage after the acquisition is completed, the logic circuit 12c2B outputs the logical product of the comparison signal Scmp and the control signal Cst as the switching signal Csw. When a high voltage is output as the switching signal Csw, the selector switch 12c1 connects the wiring Wvdd and the wiring Wva. The logic circuit 12c2B is supplied with power of the voltage Vdd from the stabilization circuit 12b.

[0042] [Polarity detection circuit 12d] The polarity detection circuit 12d detects the polarity of the power generated by the power generation circuit 12g. Figure 5 is a diagram illustrating the circuit configuration of the polarity detection circuit 12d of the encoder 12 according to this embodiment. 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 generation circuit 12g. The filter circuit 12d2 is a low-pass filter including a resistor 12d2a and a capacitor 12d2b.

[0043] Comparator 12d1 compares voltage Vgn 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 Va is supplied to differential amplifier 12d1a from wiring Wva. Differential amplifier 12d1a compares voltage Vgns, which is obtained by smoothing voltage Vgn from power generation circuit 12g using filter circuit 12d2, with reference potential Vref2, which is generated by dividing voltage Va 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.

[0044] [Driver circuit 12e] 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 the constant current Idr. The drive circuit 12e supplies drive power to the Hall element 12h so that a constant current flows through the Hall element 12h as a drive current. Figure 6 is a diagram showing the circuit configuration of the drive circuit 12e and the Hall element 12h. In Figure 6, the Hall element 12h is equivalently represented using a bridge circuit including resistors 12h1, 12h2, 12h3, and 12h4.

[0045] 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.

[0046] The transistor 12e1 is controlled so that a constant current flows through the Hall element 12h. The gate terminal of the transistor 12e1 is connected to the output terminal of the differential amplifier 12e3. The differential amplifier 12e3 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 12e2 flows between the source and gate of the transistor 12e1.

[0047] The Hall element 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 Hall element 12h.

[0048] The driving circuit 12e is driven by a voltage Va supplied from a wiring Wva.

[0049] [Signal processing circuit 12f] 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. The signal processing circuit 12f will be described with reference to FIG.

[0050] The signal processing circuit 12f includes a differential amplifier 12f1 and a comparator 12f2.

[0051] (Differential amplifier 12f1) The differential amplifier 12f1 amplifies the potential difference between the voltage Vh+ and the voltage Vh- output from the Hall element 12h to generate a voltage Vd, which is output to the comparator 12f2. The differential amplifier 12f1 is supplied with power of the voltage Va from a wiring Wva.

[0052] (Comparator 12f2) The comparator 12f2 compares the voltage Vd output from the differential amplifier 12f1 with a reference potential (reference potential Vref1) 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 and resistors 12f2b, 12f2c, and 12f2d. The differential amplifier 12f2a receives power of voltage Va from a wiring Wva. The differential amplifier 12f2a compares the voltage Vd output from the differential amplifier 12f1 with a reference potential Vref1 generated by dividing the voltage Va using resistors 12f2c and 12f2d, and outputs the comparison result to the control circuit 12p as a magnetic pole signal Smg, which is a voltage signal. The resistor 12f2b is a feedback resistor.

[0053] [Control circuit 12p] Based on inputs from the polarity detection circuit 12d and the signal processing circuit 12f, 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.

[0054] The control circuit 12p is, for example, a microcomputer, an ASIC (application specific integrated circuit), etc. The control circuit 12p may also be, for example, an FPGA (field-programmable gate array), a PLD (programmable logic device), etc. Furthermore, the control circuit 12p may include a nonvolatile memory such as a ferroelectric memory. The control circuit 12p may also be connected to an externally provided nonvolatile memory such as a ferroelectric memory.

[0055] The control circuit 12p includes at least a terminal PWR, a terminal CTL1, a terminal SIG1, and a terminal SIG2.

[0056] The terminal PWR of the control circuit 12p is a terminal to which positive power is supplied. The terminal PWR is connected to the wiring Wvdd. The control circuit 12p is supplied with power of voltage Vdd from the terminal PWR. The control circuit 12p operates when power is supplied to the terminal PWR.

[0057] The terminal CTL1 of the control circuit 12p is a terminal that outputs a signal to the outside. The terminal CTL1 is connected to a switching signal generation circuit 12c2 provided in the switching circuit 12c. The terminal CTL1 outputs a control signal Cst. The control signal Cst is a signal that indicates that the control circuit 12p has completed taking in the measurement results.

[0058] Terminals SIG1 and SIG2 of the control circuit 12p are terminals to which signals are input from the outside. The terminal SIG1 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 SIG1. The polarity signal Sp1 is a signal indicating the polarity of the power generation circuit 12g. The terminal SIG2 is connected to the signal processing circuit 12f. A magnetic pole signal Smg, which is the detection result detected by the signal processing circuit 12f, is input from the terminal SIG2. The magnetic pole signal Smg is a signal indicating the direction of the magnetic field detected by the Hall element 12h.

[0059] The control circuit 12p is an example of an arithmetic circuit.

[0060] <Encoder 12 processing> Fig. 7 is a diagram illustrating the processing of the encoder 12 according to this embodiment. When the Wiegand wire, which is the power generation device of the power generation circuit 12g, is arranged as shown in Fig. 7, power is generated every 180 degrees as the magnet 11m rotates. In the arrangement shown in Fig. 7, clockwise rotation near an angle of 0 degrees results in negative power generation, and counterclockwise rotation results in positive power generation. On the other hand, near an angle of 180 degrees, clockwise rotation results in positive power generation, and counterclockwise rotation results in negative power generation.

[0061] The output polarity of the Hall element 12h arranged as shown in Fig. 7 is negative from an angle of 0 degrees to an angle of 90 degrees and from an angle of 270 degrees to an angle of 360 degrees (angle 0 degrees), i.e., in the right half of Fig. 7. On the other hand, the output polarity of the Hall element 12h is positive from an angle of 90 degrees to an angle of 270 degrees, i.e., in the left half of Fig. 7.

[0062] Therefore, the position can be detected at an angle of 90 degrees from the power generation polarity of the power generation circuit 12g and the sensor polarity of the Hall element 12h. By detecting the position at an angle of 90 degrees at the timing of power generation (near an angle of 0 degrees and an angle of 180 degrees), it is possible to determine the number of rotations, for example, when the angle of 0 degrees is defined as clockwise positive.

[0063] In the position detection of the encoder 12 according to this embodiment, two pulses are generated per rotation during power generation in the power generation circuit 12g. The two pulses generated are one positive pulse and one negative pulse. Furthermore, the polarity of the generated pulses during reverse rotation is opposite to that during forward rotation.

[0064] Although the position cannot be detected within a 360-degree angle range using only the polarity of the power generation pulse, by placing the Hall element 12h at a position that is 90 degrees out of phase with the power generation pulse, it is possible to detect the 90-degree phase using the polarity of the power generation pulse and the polarity of the Hall element 12h.In addition, by comparing the previous power generation position with the current power generation position, it is possible to determine how many times the reference angle has been rotated, assuming an angle of 0 degrees.

[0065] Once position detection is complete, the signal from the analog processing circuit 12m is no longer needed, so the supply of power to the analog processing circuit 12m is stopped.Then, the control circuit 12p reads the previous number of rotations from memory, compares it with the current position, and if it is necessary to update the number of rotations, updates it and writes the new data to memory.While the control circuit 12p is performing the process of reading and writing from and to the memory, there is no need to supply power to the analog processing circuit 12m.

[0066] <Encoder 12 Operation> The operation of the encoder 12 according to this embodiment will now be described. FIG. 8 is a diagram illustrating the operation of the encoder 12 according to this embodiment. Specifically, the power supply management timing of the analog processing circuit 12m will be described based on the power generation voltage waveform generated by the power generation circuit 12g. The vertical axis of FIG. 8 represents voltage. The horizontal axis of FIG. 8 represents the time (time) since the start of operation.

[0067] When the Wiegand wire in the power generating circuit 12g generates power, it generates electricity by avalanche-like reversal of magnetic domains due to a large Barkhausen jump. Therefore, when using a Wiegand wire, a nearly constant power generation signal is obtained regardless of the rate of change of the generated magnetic flux. The voltage Vgn of the power generation signal from the power generating circuit 12g is shown by the line LVgn in Figure 8. Note that Figure 8 shows a positive pulse generated by the power generating circuit 12g.

[0068] The voltage Vrc obtained by full-wave rectifying the power generation signal in the power generation circuit 12g in the rectifier circuit 12a is shown as line LVrc. The voltage Vdd obtained by stabilizing the full-wave rectified voltage Vrc in the stabilization circuit 12b is shown as line LVdd. Note that FIG. 8 shows the result of regulating the voltage Vrc to voltage Vldo (1.8 volts) in the stabilization circuit 12b. The voltage Va on the wiring Wva is shown as line LVa.

[0069] At time T1, the output voltage Vdd of the stabilization circuit 12b starts to rise. At time T2, the output voltage Vdd of the stabilization circuit 12b becomes the voltage Vldo, and a constant voltage Vdd is output from the stabilization circuit 12b.

[0070] At time T3, when the voltage Vgn becomes greater than the threshold voltage Vth, the switching circuit 12c connects the wiring Wvdd and the wiring Wva. When the switching circuit 12c connects the wiring Wvdd and the wiring Wva, the voltage Va becomes equal to the voltage Vdd, and power is supplied to the analog processing circuit 12m. When power is supplied to the analog processing circuit 12m, measurements become possible in the polarity detection circuit 12d and the signal processing circuit 12f.

[0071] Next, assume that measurements are performed by the polarity detection circuit 12d and the signal processing circuit 12f from time T3, and that the control circuit 12p finishes acquiring the measurement results at time T4. At time T4, the encoder 12 outputs a control signal Cst to cause the switching circuit 12c to disconnect the wiring Wvdd and the wiring Wva.

[0072] At time T5 when the voltage Vgn becomes lower than the threshold voltage Vth, the switching circuit 12c may disconnect the wiring Wvdd and the wiring Wva. In the encoder 12 according to this embodiment, in the switching signal generation circuit 12c2 of the switching circuit 12c, the logic circuit 12c2B switches the switching signal Csw at the earliest timing of either the comparison signal Scmp or the control signal Cst. The logic circuit 12c2B switches the switching signal Csw based on the comparison signal Scmp and the control signal Cst, thereby switching the switching circuit 12c at the earliest timing of either the timing when the control circuit 12p finishes acquiring the measurement result or the timing when the voltage Vgn becomes lower than the threshold voltage Vth.

[0073] The encoder 12 includes a smoothing capacitor 12a2. Generally, capacitors are arranged before and after the regulator used in the stabilization circuit 12b. Therefore, as shown by line LVrc in FIG. 8, a constant voltage Vdd is output from the stabilization circuit 12b until time T6. The encoder 12 obtains a stable power supply for the time Tsup from time T2 to time T6, that is, for a time longer than the power generation pulse (line LVgn) in the power generation circuit 12g.

[0074] In order to perform position detection in the encoder 12, it is necessary to detect the polarity at the timing when the generated pulse is generated by the polarity detection circuit 12d. In the encoder 12 according to this embodiment, the switching circuit 12c uses the voltage level of the generated pulse voltage Vgn to supply power to the polarity detection circuit 12d. By using the voltage level of the generated pulse voltage Vgn to supply power to the polarity detection circuit 12d, it is possible to operate the polarity detection circuit 12d at the timing when the generated pulse is generated.

[0075] <Actions and Effects> According to the encoder 12 of this embodiment, by managing the power supply timing using the power generation waveform, power is supplied to the analog processing circuit 12m only during the period when the analog processing circuit 12m requires power, thereby enabling operation with less power.

[0076] For example, if the timing of supplying power to the analog processing circuit 12m is managed by the control circuit 12p, a timer is required inside the control circuit 12p. When the timing of supplying power to the analog processing circuit 12m is managed by a timer, the period during which power is supplied to the analog processing circuit 12m must be set with a sufficient margin. Therefore, power is supplied to the analog processing circuit 12m even during periods when the analog processing circuit 12m does not require power, which increases power consumption. Furthermore, using a timer in the control circuit 12p increases the circuit size of the control circuit 12p, and the power consumption of the control circuit 12p also increases.

[0077] According to the encoder 12 of this embodiment, power is supplied from the stabilization circuit 12b at the timing required for the operation of the analog processing circuit 12m, thereby saving power. For example, since the analog processing circuit 12m simultaneously reads the signal from the power generation device, it is sufficient that power is supplied only at a certain timing when the generated power is available. According to the encoder 12 of this embodiment, the switching circuit 12c can supply power to the analog processing circuit 12m at the timing required for the operation of the analog processing circuit 12m.

[0078] According to the encoder 12 of this embodiment, power supply control for analog circuits, which conventionally required timer control, can now be controlled simply by detecting the voltage level, allowing for simplification of the circuitry and reduction of power consumption.

[0079] Furthermore, according to the encoder 12 of this embodiment, the timing for cutting off the power supply to the analog processing circuit 12m can be set to the earlier of the time when the position information is read or the time when the generated voltage level drops below a predetermined level.

[0080] Although the servo motor 10 according to this embodiment includes the magnet 11m in the motor 11, a magnet that rotates together with the rotary shaft 11a may be provided inside the encoder 12 instead of the magnet 11m.

[0081] 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]

[0082] 1. Servo motor system 10 Servo motor 11 Motor 12 Encoders 12a rectifier circuit 12a1 full wave rectifier circuit 12a2 smoothing capacitor 12b Stabilization circuit 12b1 regulator 12c Switching circuit 12c1 changeover switch 12c2 Switching signal generation circuit 12c2A comparator 12c2B logic circuit 12d Polarity detection circuit 12d1 Comparator 12d2 filter circuit 12d3 diode 12e Drive circuit 12f signal processing circuit 12g power generation circuit 12h Hall element 12m analog processing circuit 12p control circuit 20 Servo Controller

Claims

1. An encoder that detects a change in a magnetic field to detect position information of an object, a power generation circuit including a Wiegand wire that generates electricity by changing magnetic flux due to movement; a polarity detection circuit for detecting the polarity of an output from the power generation circuit; a switching circuit for switching between supplying and cutting off power from the power generating circuit to the polarity detection circuit; a calculation circuit for calculating the position information; Equipped with the switching circuit switches from cutting off power to supplying power from the power generating circuit to the polarity detection circuit when the voltage of the power generating circuit becomes equal to or greater than a threshold voltage value; the arithmetic circuit calculates the position information based on the detection result of the polarity detection circuit. Encoder.

2. a magnetic detection element; and a signal processing circuit connected to the magnetic detection element and configured to detect the direction of a magnetic field detected by the magnetic detection element, the switching circuit further switches between supplying and cutting off power from the power generation circuit to the signal processing circuit; the switching circuit switches from cutting off to supplying power from the power generating circuit to the polarity detection circuit and the signal processing circuit when the voltage of the power generating circuit becomes equal to or greater than the threshold voltage value; the arithmetic circuit calculates the position information based on the detection result of the polarity detection circuit and the detection result of the signal processing circuit. The encoder of claim 1 .

3. the magnetic detection element is a Hall element; The encoder of claim 2 .

4. a rectifier circuit that rectifies the power from the power generation circuit; a stabilization circuit that stabilizes the power rectified by the rectification circuit to a constant voltage, the switching circuit switches the power from the power generation circuit through the stabilization circuit; The encoder according to any one of claims 1 to 3.

5. the stabilization circuit supplies power to the switching circuit and the arithmetic circuit; The encoder of claim 4.

6. the switching circuit switches from supplying power from the power generating circuit to the polarity detection circuit to cutting it off when the voltage of the power generating circuit becomes less than the threshold voltage value. The encoder according to any one of claims 1 to 5.

7. the switching circuit switches from supplying power from the power generation circuit to the polarity detection circuit to cutting it off when the arithmetic circuit has completed obtaining the detection result from the polarity detection circuit. An encoder according to any one of claims 1 to 6.

Images