Encoder and motor

Abstract

This encoder comprises: power generation elements (2a, 2b) that, in accordance with rotation of a magnet (1) attached to a rotation shaft (1a), generates a first pulse by means of wires (21a, 21b), and generates a second pulse by means of coils (22a, 22b); capacitors (3a, 3b, 3c, 3d) that accumulate charges of the first pulse and the second pulse; a pulse detection unit (6) that outputs a pulse detection signal when voltages of the capacitors (3a, 3b, 3c, 3d) exceed a pulse detection threshold; and a control unit (5) that executes count processing for counting multi-rotation data on the basis of the pulse detection signal, wait processing for waiting for a wait time after the count processing, and discharge processing for discharging the capacitors (3a, 3b, 3c, 3d) after the wait processing. The wait time is a time during which accumulation of at least the charges of the first pulse is completed and there is no voltage rise in the capacitors (3a, 3b, 3c, 3d).

Description

Encoder and motor

[0001] The present disclosure relates to an encoder that performs counting processing to count power generation pulses by utilizing electric charge of power generation pulses generated by a power generation element, and a motor including the encoder.

[0002] A known example of a power generating element used in an encoder that performs counting of power generating pulses using the electric charge of the power generating pulses generated by the power generating element is a Wiegand wire that generates power generating pulses using the large Barkhausen effect when the shaft rotates. As disclosed in Patent Document 1, in an encoder that uses a Wiegand wire as a power generating element, the electric charge of the power generating pulses is stored in a capacitor and used as a power source for a counting circuit to perform counting of the pulses generated by the power generating element.

[0003] An encoder that uses a Wiegand wire as a power generating element performs a discharge process to discharge the capacitor after the counting process is completed, thereby becoming ready to detect the next power generating pulse.

[0004] Japanese Patent Application Laid-Open No. 2021-1908

[0005] The charge supply from the power generating element varies greatly depending on conditions such as the rotation speed of the shaft, temperature, and the start position of reverse rotation, and the supply of charge from the power generating element does not necessarily end when the counting process ends. For this reason, in an encoder that uses a Wiegand wire as a power generating element, if a discharge process is performed to discharge the capacitor when the counting process ends and the supply of charge from the power generating element to the capacitor is still ongoing when the counting process ends, charge may accumulate again in the capacitor, resulting in duplicate counts of power generating pulses.

[0006] The present disclosure has been made in view of the above, and has an object to provide an encoder that suppresses duplicate counting of power generation pulses.

[0007] To solve the above-mentioned problems and achieve the object, the present disclosure provides an encoder comprising: a magnet attached to a rotating shaft; a power generating element having a Wiegand wire and a coil wound around the Wiegand wire, disposed opposite the magnet, which generates a first pulse in the Wiegand wire due to the large Barkhausen effect as the magnet rotates; and a second pulse in the coil due to induced electromotive force as the magnet rotates; a capacitor that stores charge from the first pulse and the second pulse; and a pulse detection unit that outputs a pulse detection signal when the voltage of the capacitor exceeds a pulse detection threshold. The encoder is operable with power supplied from the capacitor and includes a control unit that performs a counting process that counts multi-rotation data based on the pulse detection signal, a wait process that waits for a predetermined wait time after the counting process, and a discharge process that discharges the capacitor after the wait process. The wait time is the time during which the accumulation of charge from at least the first pulse has finished and there is no increase in the voltage of the capacitor.

[0008] The encoder according to the present disclosure has the advantage of being able to prevent duplicate counting of power generation pulses.

[0009] FIG. 1 is a diagram showing the configuration of a motor according to embodiment 1; FIG. 2 is a diagram showing an example of a power generation pulse waveform of a power generation element of a battery-less encoder according to embodiment 1; FIG. 3 is a diagram showing an example of a power generation pulse waveform of a capacitor of a battery-less encoder according to embodiment 1; FIG. 4 is a diagram showing a power generation pulse waveform of a capacitor of a battery-less encoder according to a first comparative example of embodiment 1; FIG. 5 is a diagram showing a power generation pulse waveform of a capacitor of a battery-less encoder according to a second comparative example of embodiment 1; FIG. 6 is a diagram showing a power generation pulse waveform of a capacitor of a battery-less encoder according to a third comparative example of embodiment 1;

[0010] An encoder and a motor according to an embodiment will be described in detail below with reference to the drawings.

[0011] Embodiment 1. Figure 1 is a diagram showing the configuration of a motor according to embodiment 1. A motor 200 according to embodiment 1 includes an electric motor 70 having a rotating shaft 1a, and a battery-less encoder 100 that detects the rotation angle of the rotating shaft 1a. The battery-less encoder 100 has a magnet 1 fixed to the rotating shaft 1a, two power generating elements 2a and 2b installed opposite the magnet 1, and a multi-rotation data count circuit 50. The multi-rotation data count circuit 50 includes a half-wave rectifier circuit 23a that rectifies the AC current generated in the power generating element 2a, a half-wave rectifier circuit 23b that rectifies the AC current generated in the power generating element 2b, capacitors 3a and 3b that store the charge of the DC current output by the half-wave rectifier circuit 23a, capacitors 3c and 3d that store the charge of the DC current output by the half-wave rectifier circuit 23b, a constant voltage circuit 4 that outputs a DC current limited to a preset voltage or less, and a discharge circuit 8 that discharges the capacitors 3a, 3b, 3c, and 3d. The battery-less encoder 100 does not have a battery built into the encoder other than the capacitors 3a, 3b, 3c, and 3d. However, the present disclosure can also be applied to encoders that have a battery built into the encoder other than the capacitors 3a, 3b, 3c, and 3d.

[0012] The power generating elements 2a and 2b each include a wire 21a or 21b, which is a Wiegand wire, and a coil 22a or 22b wound around the wire 21a or 21b.

[0013] The multi-rotation data count circuit 50 also includes a pulse detection unit 6 that outputs a pulse detection signal indicating that a pulse has been detected when the voltage of any of the capacitors 3a, 3b, 3c, and 3d, which fluctuates based on the charge accumulated in the capacitors 3a, 3b, 3c, and 3d, exceeds a pulse detection threshold, a storage unit 7 that stores the multi-rotation count data in a non-volatile memory, and a control unit 5 that generates multi-rotation count data based on the multi-rotation count data read from the storage unit 7 and the pulse detection signal input from the pulse detection unit 6, and updates the multi-rotation count data in the storage unit 7. The pulse detection signal is different for each of the capacitors 3a, 3b, 3c, and 3d, and the control unit 5 can identify the location of the pulse generation based on which of the capacitors 3a, 3b, 3c, and 3d the pulse detection signal corresponds to.

[0014] The control unit 5 can operate using power supplied from the capacitors 3a, 3b, 3c, and 3d, or can operate using power supplied from outside the multi-rotation data count circuit 50. The control unit 5 performs a count process that counts multi-rotation data based on the pulse detection signal, a wait process that waits for a preset wait time after the count process, and a discharge process that discharges the capacitors 3a, 3b, 3c, and 3d after the wait process. The control unit 5 performs the count process to detect the rotation angle of the rotating shaft 1a.

[0015] The control unit 5 writes information to the memory unit 7 and reads information from the memory unit 7 through the external circuit interface 11. The control unit 5 can also output count data to a device external to the multi-rotation data count circuit 50 through the external circuit interface 11.

[0016] After the counting process, the control unit 5 performs a wait process and then sends a command to the discharge circuit 8 to discharge the capacitors 3 a, 3 b, 3 c, and 3 d. The wait time can be set separately for when the power is off and no power is supplied from outside the multi-rotation data counting circuit 50, and when the power is on and power is supplied from outside the multi-rotation data counting circuit 50.

[0017] When the DC current output by the constant voltage circuit 4 reaches a specified voltage, the enable circuit 9 releases the reset state in which counting processing based on the pulse detection signal is not performed, and transitions the control unit 5 to a state in which counting processing can be performed.

[0018] When the power is off and the multi-rotation data count circuit 50 is not receiving power from outside, the power supply switching circuit 10 outputs power supplied from the capacitors 3a, 3b, 3c, and 3d to the constant voltage circuit 4. On the other hand, when the power is on and the multi-rotation data count circuit 50 is receiving power from outside, the power supply switching circuit 10 outputs power supplied from outside to the constant voltage circuit 4. Note that, as an example of power supplied from outside the multi-rotation data count circuit 50, power generated within the battery-less encoder 100 based on power supplied from an amplifier (not shown) can be cited, but is not limited to, this. For example, if the encoder has a built-in battery, the power supplied from outside the multi-rotation data count circuit 50 can be power supplied from the battery.

[0019] 2 is a diagram showing an example of a power generation pulse waveform of a power generation element of the battery-less encoder according to embodiment 1. The power generation pulse includes first pulses 12a and 12b generated in association with rotation of magnet 1 due to the large Barkhausen effect of wires 21a and 21b, and second pulses 13a and 13b generated in association with rotation of magnet 1 due to induced electromotive forces in coils 22a and 22b. In FIG. 2, the waveforms of first pulse 12a and second pulse 13a generated in power generation element 2a are shown by solid lines, and the waveforms of first pulse 12b and second pulse 13b generated in power generation element 2b are shown by dashed lines. The amplitude of second pulses 13a and 13b increases as the rotation speed of magnet 1 increases. Since the power generating element 2a and the power generating element 2b are installed in different positions, the timing at which the first pulse 12a is generated is different from the timing at which the first pulse 12b is generated, and the timing at which the second pulse 13a is generated is different from the timing at which the second pulse 13b is generated.

[0020] Although the first pulse 12a and the second pulse 13a have different voltage peak timings, they occur at the same timing corresponding to a specific rotation angle of the magnet 1. Therefore, if the first pulse 12a and the second pulse 13a are counted in overlapping fashion, the number of rotations of the magnet 1 will not be counted accurately. The same is true for the first pulse 12b and the second pulse 13b; if the first pulse 12b and the second pulse 13b are counted in overlapping fashion, the number of rotations of the magnet 1 will not be counted accurately. For this reason, in the batteryless encoder 100 according to the first embodiment, the wait time is set to a time during which the accumulation of electric charge in at least the first pulses 12a, 12b and the second pulses 13a, 13b has finished and there is no voltage rise in the capacitors 3a, 3b, 3c, and 3d.

[0021] 1 will be described in more detail. The batteryless encoder 100 includes four capacitors 3a, 3b, 3c, and 3d. The wait time may be set as a time period during which the accumulation of charges of the first pulses 12a and 12b and the second pulses 13a and 13b in any one of the capacitors 3a, 3b, 3c, and 3d is completed and there is no voltage rise in the capacitors 3a, 3b, 3c, and 3d. Specifically, the wait time may be a time period during which the accumulation of charges of the first pulse 12a and the second pulse 13a in the capacitor 3a is completed and there is no voltage rise in the capacitor 3a. In addition, since the time period during which the accumulation of charges of the first pulse 12a, 12b and the second pulse 13a, 13b is completed in each of the capacitors 3a, 3b, 3c, 3d and there is no voltage rise in the capacitors 3a, 3b, 3c, 3d is the same, the wait time may be set to the time during which the accumulation of charges of the first pulse 12a and the second pulse 13a is completed in the capacitor 3b and there is no voltage rise in the capacitor 3b, or the wait time may be set to the time during which the accumulation of charges of the first pulse 12b and the second pulse 13b is completed in the capacitor 3c and there is no voltage rise in the capacitor 3c, or the wait time may be set to the time during which the accumulation of charges of the first pulse 12b and the second pulse 13b is completed in the capacitor 3d and there is no voltage rise in the capacitor 3d.

[0022] The control unit 5 performs a wait process in which it waits for a preset time after counting the preceding first pulses 12a, 12b. By not performing a count process during the wait process, even if, for example, the first pulses 12a, 12b or the second pulses 13a, 13b exceed the pulse detection threshold, it is possible to prevent duplicate counting of the first pulses 12a, 12b that have already been counted, and to prevent duplicate counting of the first pulses 12a, 12b and the second pulses 13a, 13b.

[0023] However, if the wait process is not completed and the capacitors 3a, 3b, 3c, and 3d are not discharged before the first pulse 12b is generated after the count process of the first pulse 12a, the first pulse 12b will not be counted. Therefore, it is necessary to transition to a state where the first pulse 12b can be counted as soon as possible after the count process of the first pulse 12a is completed. Therefore, it is preferable to set the wait time to approximately the same time as the time when the accumulation of charges from the first pulses 12a and 12b and the second pulses 13a and 13b is completed and no voltage rise occurs in the capacitors 3a, 3b, 3c, and 3d.

[0024] The time width of the first pulses 12a, 12b and the second pulses 13a, 13b becomes shorter as the rotation speed of the magnet 1 becomes faster, so the wait time in the wait processing may be set in stages so that the wait time becomes shorter as the rotation speed of the magnet 1 becomes faster.

[0025] The operation of the batteryless encoder 100 according to the first embodiment will be described using the case where the counting process of the first pulse 12a is performed as an example. FIG. 3 is a diagram showing an example of a waveform of a power generation pulse of the capacitor of the batteryless encoder according to the first embodiment. At time t1, the voltage of the capacitor 3a exceeds the pulse detection threshold Vs, causing the control unit 5 to start the counting process. When the counting process ends at time t2, the control unit 5 performs a wait process. After waiting for a predetermined wait time wt1, at time t3, the control unit 5 performs a discharge process, driving the discharge circuit 8 to discharge the capacitor 3a. The wait time wt1 is the time during which the accumulation of charges from at least the first pulse 12a and the second pulse 13a is completed and there is no voltage rise in the capacitors 3a and 3b. At time t4 when the discharge process ends, the voltage of the capacitor 3a becomes less than the pulse detection threshold Vs, making it possible to detect the first pulses 12a and 12b.

[0026] In the batteryless encoder 100 according to the first embodiment, the control unit 5 discharges the capacitor 3a after the counting process of the first pulse 12a is completed, at the timing when the supply of charge from both the first pulse 12a and the second pulse 13a ceases. Therefore, the charge in the capacitor 3a does not increase after the discharge, preventing the voltage of the capacitor 3a from rising again. This prevents the first pulse 12a that has already been counted from being counted again, and prevents the first pulse 12a and the second pulse 13a from being counted again. Furthermore, the first pulses 12a and 12b can be detected immediately after the discharge process is completed.

[0027] 4 is a diagram showing a waveform of a pulse generated by a capacitor in a batteryless encoder according to a first comparative example of the first embodiment. At time t1, the voltage of the capacitor exceeds the pulse detection threshold Vs, causing the control unit to start a counting process. At time t2, the counting process ends, but the batteryless encoder according to the first comparative example does not perform a discharge process after the counting process of the first pulse ends. Therefore, at time t4, the voltage of the capacitor is equal to or greater than the pulse detection threshold Vs. In this way, if the wait process and discharge process are not performed after the counting process ends, the first pulse cannot be detected until the charge in the capacitor decreases due to natural discharge. Therefore, when the rotation speed of the rotating shaft increases and reaches a certain rotation speed or higher, it becomes difficult to detect the next first pulse.

[0028] FIG. 5 illustrates the waveform of a power generation pulse of a capacitor in a batteryless encoder according to a second comparative example of the first embodiment. At time t1, the capacitor voltage exceeds the pulse detection threshold Vs, causing the control unit to start a counting process. At time t2, the counting process ends, and the control unit performs a wait process. In the batteryless encoder according to the second comparative example of the first embodiment, the wait time wt2 is set to be shorter than the time during which the charge of the first pulse is accumulated in the capacitor and no voltage rise occurs across capacitors 3a, 3b, 3c, and 3d. At time t5, after waiting for the predetermined wait time wt2, the control unit performs a discharge process, driving the discharge circuit to discharge the capacitor. At time t6, when the discharge process ends, the capacitor voltage falls below the pulse detection threshold Vs. However, because charge is still being supplied by the first pulse, the charge in the capacitor increases again, causing the capacitor voltage to rise again. Therefore, at time t4, the capacitor voltage is equal to or greater than the pulse detection threshold Vs.

[0029] The batteryless encoder according to the second comparative example performs a discharge process while supplying charge due to the first pulse after the count process of the first pulse is completed. Therefore, although the charge on the capacitor decreases due to the discharge process, the charge on the capacitor increases again due to the supply of charge to the capacitor due to the first pulse after the discharge process is completed, causing the capacitor voltage to rise again. As the charge on the capacitor increases again, the capacitor voltage exceeds the pulse detection threshold Vs again, causing the control unit to restart the count process. As a result, the batteryless encoder according to the second comparative example repeatedly counts the power generation pulses that have already been counted, resulting in an error in the rotation angle of the rotating shaft. Furthermore, after the charge on the capacitor increases again, the first pulse cannot be detected until the charge on the capacitor decreases due to a re-discharge at time t9. Therefore, when the rotation speed of the rotating shaft increases and reaches a certain rotation speed or higher, it becomes difficult to detect the next first pulse.

[0030] FIG. 6 illustrates the waveform of a power generation pulse of a capacitor in a batteryless encoder according to a third comparative example of the first embodiment. At time t1, the voltage of the capacitor exceeds the pulse detection threshold Vs, causing the control unit to start a counting process. At time t2, the counting process ends, and the control unit performs a wait process. In the batteryless encoder according to the third comparative example of the first embodiment, the wait time wt3 is set to a time that is shorter than the time during which the capacitors 3a, 3b, 3c, and 3d do not increase in voltage due to the charge of the second pulse after the charge of the first pulse has been stored in the capacitors. At time t7, after waiting for the preset wait time wt3, the control unit performs a discharge process, driving the discharge circuit to discharge the capacitors. At time t8, when the discharge process ends, the voltage of the capacitor falls below the pulse detection threshold Vs. However, because the charge of the second pulse is being supplied, the charge of the capacitor increases again, causing the capacitor voltage to rise again. Therefore, at time t4, the voltage of the capacitor is equal to or greater than the pulse detection threshold Vs.

[0031] The batteryless encoder according to the third comparative example performs a discharge process while supplying charge by the second pulse after the count process of the first pulse is completed. Therefore, although the charge on the capacitor decreases during the discharge process, the charge is supplied by the second pulse after the discharge process is completed, causing the charge on the capacitor to increase again, resulting in a re-rise in the capacitor voltage. As the charge on the capacitor increases again, the capacitor voltage exceeds the pulse detection threshold Vs again, causing the control unit to restart the count process. As a result, the batteryless encoder according to the third comparative example counts the first pulse and the second pulse at the same rotation speed of the rotating shaft, resulting in an error in the rotation angle of the rotating shaft. Furthermore, after the charge on the capacitor increases again, the first pulse cannot be detected until the charge on the capacitor decreases due to a re-discharge at time t9. Therefore, when the rotation speed of the rotating shaft reaches a certain rotation speed or higher, it is difficult to detect the next first pulse.

[0032] As described above, if the discharge process is not performed or if the discharge process is performed while the charge is being supplied by the first pulse or the second pulse, the already counted first pulse may be counted twice or the first pulse and the second pulse may be counted twice, resulting in an error in the rotation angle of the rotating shaft. Furthermore, if the time required for the capacitor voltage to decrease to a level at which the subsequent first pulse can be detected increases, causing the rotating shaft to rotate at a high speed exceeding a certain rotation speed, it becomes difficult to detect the next power generation pulse. In contrast, the batteryless encoder 100 according to the first embodiment performs the discharge process when the charge supply from both the first pulse 12 a and the second pulse 13 a has ceased. This prevents the already counted first pulses 12 a and 12 b from being counted twice and prevents the first pulses 12 a and 12 b from being counted twice and the second pulses 13 a and 13 b from being counted twice. Furthermore, the time required for the voltages of the capacitors 3a, 3b, 3c, and 3d to drop to a level at which the first pulses 12a and 12b can be detected is shortened, making it possible to detect high-speed rotation.

[0033] Here, the differences between operation when the power is off and operation when the power is on will be described. First, operation when the power is off will be described. As the magnet 1 attached to the rotating shaft 1a rotates, power generation pulses are generated in the power generation elements 2a and 2b due to the large Barkhausen effect. Of the voltage pulses output by the power generation element 2a, the forward voltage pulses are half-wave rectified by the half-wave rectifier circuit 23a and sent to the capacitor 3a. Of the voltage pulses output by the power generation element 2a, the reverse voltage pulses are half-wave rectified by the half-wave rectifier circuit 23a and sent to the capacitor 3b. Of the voltage pulses output by the power generation element 2b, the forward voltage pulses are half-wave rectified by the half-wave rectifier circuit 23b and sent to the capacitor 3c. Of the voltage pulses output by the power generation element 2b, the reverse voltage pulses are half-wave rectified by the half-wave rectifier circuit 23b and sent to the capacitor 3d. As the magnet 1 rotates, voltage pulses are input to the capacitors 3a, 3b, 3c, and 3d in the order of capacitor 3a, capacitor 3c, capacitor 3b, and capacitor 3d.

[0034] The electric charge stored in the capacitors 3a, 3b, 3c, and 3d by the voltage pulse is converted by the constant voltage circuit 4 into a direct current at or below a preset voltage, and is used as a power source for the control unit 5 and the storage unit 7. The pulse detection unit 6 detects the voltage output from the capacitors 3a, 3b, 3c, and 3d to detect the location where the power generation pulse is generated, i.e., whether the forward voltage or reverse voltage pulse is generated in the power generation element 2a, 2b.

[0035] When a pulse is detected by the pulse detection unit 6, the control unit 5 performs counting processing. In the counting processing, the control unit 5 reads the multiple rotation count data for the previous pulse from the storage unit 7, and generates new multiple rotation count data based on the information on the pulse generation location obtained from the pulse detection unit 6. Furthermore, the control unit 5 writes the newly generated multiple rotation count data into the storage unit 7.

[0036] After performing the counting process, the control unit 5 performs a wait process in which it waits for a preset time, and then drives the discharge circuit 8 to discharge the capacitors 3a, 3b, 3c, and 3d.

[0037] Next, we will explain the operation when the power is on. When power is supplied from an external source, for example, power from an amplifier is supplied to the constant voltage circuit 4, and is used as the power source for the control unit 5 and memory unit 7. The control unit 5 reads from the memory unit 7 the multi-rotation count data from the previous pulse.

[0038] As the magnet 1 attached to the rotating shaft 1a rotates, power generation pulses are generated in the power generation elements 2a and 2b due to the large Barkhausen effect. Of the voltage pulses output by the power generation element 2a, the forward voltage pulses are half-wave rectified by the half-wave rectifier circuit 23a and sent to the capacitor 3a. Of the voltage pulses output by the power generation element 2a, the reverse voltage pulses are half-wave rectified by the half-wave rectifier circuit 23a and sent to the capacitor 3b. Of the voltage pulses output by the power generation element 2b, the forward voltage pulses are half-wave rectified by the half-wave rectifier circuit 23b and sent to the capacitor 3c. Of the voltage pulses output by the power generation element 2b, the reverse voltage pulses are half-wave rectified by the half-wave rectifier circuit 23b and sent to the capacitor 3d. As the magnet 1 rotates, voltage pulses are input to the capacitors 3a, 3b, 3c, and 3d in the order of capacitor 3a, capacitor 3c, capacitor 3b, and capacitor 3d.

[0039] When the electric charge of the power generation pulse is stored in capacitors 3a, 3b, 3c, and 3d, the pulse detection unit 6 detects the location where the power generation pulse was generated, i.e., whether the forward voltage or reverse voltage pulse was generated in power generation element 2a or 2b.

[0040] The control unit 5 generates new multiple rotation count data based on information on the pulse generation locations obtained from the pulse detection unit 6. After performing the counting process, the control unit 5 waits for a preset time and then drives the discharge circuit 8 to discharge the capacitors 3 a, 3 b, 3 c, and 3 d. When the power is turned off, the control unit 5 writes the multiple rotation count data to the memory unit 7.

[0041] Fig. 7 is a diagram showing an example of a generated pulse waveform when the battery-less encoder according to embodiment 1 is powered off. Fig. 8 is a diagram showing an example of a generated pulse waveform when the battery-less encoder according to embodiment 1 is powered on. When the power is off, during counting processing, the control unit 5 reads out the multi-rotation count data for the previous pulse from the storage unit 7, generates new multi-rotation count data based on information about the pulse generation location obtained from the pulse detection unit 6, and writes the multi-rotation count data to the storage unit 7. On the other hand, when the power is on, during counting processing, the control unit 5 only generates new multi-rotation count data based on information about the pulse generation location obtained from the pulse detection unit 6.

[0042] Thus, when the power is off, the charges stored in capacitors 3a, 3b, 3c, and 3d are used as the power source for control unit 5, so the peak voltage Vp1 of the capacitors during the counting process when the power is off is smaller than the peak voltage Vp2 of the capacitors during the counting process when the power is on. On the other hand, because the counting process when the power is off requires more steps than the counting process when the power is on, the time tc1 required to complete the counting process when the power is off is longer than the time tc2 required to complete the counting process when the power is on. Therefore, if the wait time wt11 when the power is off and the wait time wt12 when the power is on are the same, the time t31 at which the discharge process starts when the power is off will be later than the time t32 at which the discharge process starts when the power is on, making it difficult to detect high-speed rotation.

[0043] The batteryless encoder 100 according to the first embodiment can set the wait time wt11 when the power is off and the wait time wt12 when the power is on independently, so that the timing to start the discharge process when the power is off and when the power is on can be the same. Note that it is also possible to set the wait time wt11 when the power is off and the wait time wt12 when the power is on to be the same, but to set the discharge timings to different times.

[0044] As described above, in the batteryless encoder 100 according to the first embodiment, the control unit 5 discharges the capacitor 3a after the counting process of the first pulse 12a is completed and at the timing when the supply of charge from both the first pulse 12a and the second pulse 13a has ceased. Therefore, after the discharge is performed, the charge in the capacitors 3a, 3b, 3c, and 3d does not increase and the voltage of the capacitors does not rise again, and it is possible to prevent duplicate counting of power generation pulses.

[0045] In the above description, the batteryless encoder 100 is described as having two power generating elements 2 a and 2 b, but the number of power generating elements may be one, or three or more. Increasing the number of power generating elements can improve the resolution for detecting the rotation angle of the magnet 1.

[0046] In the batteryless encoder 100 according to the first embodiment described above, the wait time during the wait process by the control unit 5 is set to a time during which the accumulation of charges of at least the first pulses 12a and 12b and the second pulses 13a and 13b has finished and there is no voltage rise in the capacitors 3a, 3b, 3c, and 3d. However, the wait time during the wait process by the control unit 5 may be set to a time different from the above example. For example, the wait time may be set to a time during which the accumulation of charges of at least the first pulse has finished and there is no voltage rise in the capacitors 3a, 3b, 3c, and 3d. Here, the batteryless encoder generates a first pulse as the magnet rotates due to the large Barkhausen effect of the Wiegand wire of the power generating element, and a second pulse as the magnet rotates due to the induced electromotive force in the coil of the power generating element.

[0047] 9 is a diagram showing an example of a power generation pulse waveform of a power generation element of a batteryless encoder according to a modification of the first embodiment. In the batteryless encoder 100 according to the modification of the first embodiment, the wait time is set to a time during which the accumulation of charge of at least the first pulse has finished and there is no voltage increase in the capacitors 3a, 3b, 3c, and 3d. As shown in FIG. 9 , when the rotation speed of the rotating shaft 1a is low or the peak voltage of the second pulses 131a and 131b is small due to the performance of the coils 22a and 22b, the voltage of the capacitors 3a, 3b, 3c, and 3d may not exceed the pulse detection threshold even if the charge of the second pulses 131a and 131b is accumulated in the capacitors 3a, 3b, 3c, and 3d. That is, the batteryless encoder according to the modification of the first embodiment performs a wait process for a preset wait time during which the accumulation of charges of at least the first pulses 12a and 12b shown in FIG. 9 has been completed and there is no voltage rise in the capacitors 3a, 3b, 3c, and 3d, and then performs a discharge process. Even in such a case, the wait time may be set as a wait time during which the accumulation of charges of the first pulses 12a and 12b has been completed in any one of the capacitors 3a, 3b, 3c, and 3d and there is no voltage rise in the capacitors 3a, 3b, 3c, and 3d. Specifically, the wait time may be the time during which the accumulation of charges of the first pulse 12a has been completed in the capacitor 3a and there is no voltage rise in the capacitor 3a.

[0048] In addition, since the time period during which the accumulation of charge of first pulse 12a and 12b is completed in each of capacitors 3a, 3b, 3c, and 3d and there is no voltage rise in capacitors 3a, 3b, 3c, and 3d is the same, the wait time may be set to the time during which the accumulation of charge of first pulse 12a is completed in capacitor 3b and there is no voltage rise in capacitor 3b, or the wait time may be set to the time during which the accumulation of charge of first pulse 12b is completed in capacitor 3c and there is no voltage rise in capacitor 3c, or the wait time may be set to the time during which the accumulation of charge of first pulse 12b is completed in capacitor 3d and there is no voltage rise in capacitor 3d.

[0049] The operation of the batteryless encoder 100 will be described using the modified example shown in FIG. 9 as an example of counting the first pulse 12a. FIG. 10 is a diagram showing an example of a power generation pulse waveform of the capacitor of the batteryless encoder according to the modified example of the first embodiment. At time t1, the voltage of the capacitor 3a exceeds the pulse detection threshold Vs, causing the control unit 5 to start the counting process. When the counting process ends at time t2, the control unit 5 performs a wait process. After waiting for a predetermined wait time wt13, at time t3, the control unit 5 performs a discharge process, driving the discharge circuit 8 to discharge the capacitor 3a. The wait time wt13 is the time during which the accumulation of charge corresponding to at least the first pulse 12a is completed and there is no voltage increase in the capacitor 3a. As shown in FIG. 10, at time t4 when the discharge process ends, the voltage of the capacitor 3a is below the pulse detection threshold Vs, making it possible to detect the first pulses 12a and 12b.

[0050] Even in this modified example, it is possible to prevent duplicate counting of already counted first pulses 12 a, 12 b, and to prevent duplicate counting of first pulses 12 a, 12 b and second pulses 131 a, 131 b. Furthermore, by setting the wait time to the time after the accumulation of electric charge from the power generation pulse has finished and there is no increase in the voltage of capacitors 3 a, 3 b, 3 c, and 3 d, it is not necessary to wait for the time until the voltage of capacitors 3 a, 3 b, 3 c, and 3 d drops below the pulse detection threshold due to natural discharge. This shortens the time until the voltage of capacitors 3 a, 3 b, 3 c, and 3 d drops to a level at which first pulses 12 a, 12 b can be detected, making it possible to more effectively detect high-speed rotation.

[0051] 11 is a diagram showing the hardware configuration of the control unit and storage unit of the battery-less encoder according to the first embodiment and the modification. The control unit 5 is realized by a control circuit 91 designed to execute various processes.

[0052] The control circuit 91 may be an LSI (Large Scale Integration) designed to perform various processes when powered on, and may be an integrated circuit such as an ASIC (Application Specific Integrated Circuit). The control circuit 91 integrates circuits for performing at least counting, waiting, and discharging processes. The storage unit 7 is realized by a nonvolatile memory 92 that retains its memory even without power supply. The nonvolatile memory 92 may be a memory with low power consumption and high processing speed, such as a Ferroelectric Random Access Memory (FeRAM).

[0053] The control circuit 91 may be a semiconductor integrated circuit designed to include the constant voltage circuit 4, the pulse detection unit 6, the discharge circuit 8, the enable circuit 9, the power supply switching circuit 10, and the external circuit interface 11 in addition to the control unit 5. For example, the control circuit 91 may be configured as an ASIC or LSI that includes these circuits. Furthermore, the control circuit 91 may be a semiconductor integrated circuit designed to include the constant voltage circuit 4, the control unit 5, the pulse detection unit 6, the discharge circuit 8, the enable circuit 9, the power supply switching circuit 10, the external circuit interface 11, the capacitors 3a, 3b, 3c, and 3d, the storage unit 7, and the half-wave rectifier circuits 23a and 23b.

[0054] The configurations shown in the above embodiments are merely examples of the content, and may be combined with other known technologies, or parts of the configurations may be omitted or modified without departing from the spirit of the invention.

[0055] 1 magnet, 1a rotating shaft, 2a, 2b power generation element, 3a, 3b, 3c, 3d capacitor, 4 constant voltage circuit, 5 control unit, 6 pulse detection unit, 7 memory unit, 8 discharge circuit, 9 enable circuit, 10 power supply switching circuit, 11 external circuit interface, 12a, 12b first pulse, 13a, 13b, 131a, 131b second pulse, 21a, 21b wire, 22a, 22b coil, 23a, 23b half-wave rectifier circuit, 50 multi-rotation data count circuit, 70 electric motor, 91 control circuit, 92 non-volatile memory, 100 battery-less encoder, 200 motor.

Claims

1. An encoder comprising: a magnet attached to a rotating shaft; a power generating element having a Wiegand wire and a coil wound around the Wiegand wire, installed opposite the magnet, generating a first pulse in the Wiegand wire due to the large Barkhausen effect as the magnet rotates, and a second pulse in the coil due to induced electromotive force as the magnet rotates; a capacitor that stores electric charges of the first pulse and the second pulse; a pulse detection unit that outputs a pulse detection signal when the voltage of the capacitor exceeds a pulse detection threshold; and a control unit that is operable with power supplied from the capacitor and performs a counting process that counts multi-rotation data based on the pulse detection signal, a wait process that waits for a preset wait time after the counting process, and a discharge process that discharges the capacitor after the wait process, wherein the wait time is the time during which accumulation of electric charge of at least the first pulse has finished and there is no increase in the voltage of the capacitor.

2. The encoder according to claim 1, wherein the wait time is a time during which the accumulation of charges of at least the first pulse and the second pulse has finished and there is no voltage rise in the capacitor.

3. The encoder according to claim 2, characterized in that it comprises a plurality of the power generating elements.

4. An encoder as described in any one of claims 1 to 3, characterized in that it is provided with a power supply switching circuit that switches between outputting power supplied from the outside to the control unit and the memory unit that stores the multi-rotation data, or outputting power supplied from the capacitor to the control unit and the memory unit, and the wait time can be set to different times when the power is on and the power supplied from the outside is output to the control unit, and when the power is off and the power supplied from the capacitor is output to the control unit.

5. A motor comprising: an electric motor having the rotating shaft; and the encoder according to any one of claims 1 to 4.

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