Encoder and motor

Abstract

The encoder includes power generating elements (2a, 2b) that generate a first pulse in wires (21a, 21b) and generate a second pulse in coils (22a, 22b) as a magnet (1) attached to a rotating shaft (1a) rotates, capacitors (3a, 3b, 3c, 3d) that store electric charges of the first pulse and the second pulse, a pulse detection unit (6) that outputs a pulse detection signal when the voltage of the capacitors (3a, 3b, 3c, 3d) exceeds a pulse detection threshold, and a control unit (5) that performs a counting process of counting multi-rotation data based on the pulse detection signal, a wait process of waiting for a wait time after the counting process, and a discharge process of discharging the capacitors (3a, 3b, 3c, 3d) after the wait process. The wait time is a time during which the accumulation of electric charges of at least the first pulse is completed and there is no increase in the voltage of the capacitors (3a, 3b, 3c, 3d).

Description

[Technical field]

[0001] The present disclosure relates to an encoder that performs a counting process for counting generated pulses by utilizing electric charge of a generated pulse by a power generating element, and a motor including the encoder. [Background technology]

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

[0003] An encoder that uses a Wiegand wire as a power generating element becomes capable of detecting the next power generating pulse by performing a discharge process that discharges the capacitor after the counting process ends. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-1908 Summary of the Invention [Problem to be solved by the invention]

[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 the 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 using a Wiegand wire as a power generating element, when a discharge process is performed to discharge the capacitor when the counting process ends, if the supply of charge from the power generating element to the capacitor is still continuing when the counting process ends, charge may accumulate again in the capacitor, resulting in duplicate counting 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. [Means for solving the problem]

[0007] In order to solve the above problems and achieve the object, the encoder according to the present disclosure includes a magnet attached to a rotating shaft, a power generating element having a Wiegand wire and a coil wound around the Wiegand wire, which is installed facing the magnet and generates a first pulse in the Wiegand wire by the large Barkhausen effect as the magnet rotates and a second pulse in the coil by induced electromotive force as the magnet rotates, a capacitor that accumulates the electric charge of 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 by power supplied from the capacitor, and includes a control unit that 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 capacitor after the wait process. The wait time is a time during which the accumulation of the electric charge of at least the first pulse is completed and there is no voltage rise in the capacitor. Effect of the Invention

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

[0009] [Figure 1] FIG. 1 is a diagram showing a configuration of a motor according to a first embodiment; [Diagram 2] FIG. 1 is a diagram showing an example of a power generation pulse waveform of a power generation element of a battery-less encoder according to the first embodiment; [Diagram 3] FIG. 1 is a diagram showing an example of a power generation pulse waveform of a capacitor of the batteryless encoder according to the first embodiment; [Figure 4] FIG. 13 is a diagram showing a power generation pulse waveform of a capacitor of a batteryless encoder according to a first comparative example of the first embodiment; [Diagram 5] FIG. 13 is a diagram showing a power generation pulse waveform of a capacitor of a batteryless encoder according to a second comparative example of the first embodiment; [Figure 6] FIG. 13 is a diagram showing a power generation pulse waveform of a capacitor of a batteryless encoder according to a third comparative example of the first embodiment. [Figure 7] FIG. 13 is a diagram showing an example of a generated pulse waveform when the power supply of the battery-less encoder according to the first embodiment is off; [Figure 8] FIG. 13 is a diagram showing an example of a power generation pulse waveform when the battery-less encoder according to the first embodiment is powered on; [Figure 9] FIG. 13 is a diagram showing an example of a power generation pulse waveform of a power generation element of a battery-less encoder according to a modification of the first embodiment; [Figure 10] FIG. 13 is a diagram showing an example of a power generation pulse waveform of a capacitor of a batteryless encoder according to a modification of the first embodiment; [Figure 11] FIG. 1 is a diagram showing the hardware configuration of a control unit and a storage unit of a battery-less encoder according to the first embodiment and a modification example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An encoder and a motor according to an embodiment will be described in detail below with reference to the drawings.

[0011] Embodiment 1 FIG. 1 is a diagram showing the configuration of a motor according to the first embodiment. The motor 200 according to the first embodiment includes an electric motor 70 having a rotating shaft 1a, and a batteryless encoder 100 for detecting the rotation angle of the rotating shaft 1a. The batteryless encoder 100 includes a magnet 1 fixed to the rotating shaft 1a, two power generating elements 2a and 2b arranged to face 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 for rectifying an AC current generated in the power generating element 2a, a half-wave rectifier circuit 23b for rectifying an AC current generated in the power generating element 2b, capacitors 3a and 3b for storing the charge of the DC current output by the half-wave rectifier circuit 23a, capacitors 3c and 3d for storing the charge of the DC current output by the half-wave rectifier circuit 23b, a constant voltage circuit 4 for outputting a DC current limited to a voltage equal to or lower than a preset voltage, and a discharge circuit 8 for discharging the capacitors 3a, 3b, 3c, and 3d. The batteryless encoder 100 is an encoder that does not have a battery built in the encoder other than the capacitors 3a, 3b, 3c, and 3d. However, the present disclosure can also be applied to an encoder that has a battery built in 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 varies based on the charges stored 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 a different signal 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 with power supplied from the capacitors 3a, 3b, 3c, and 3d, or with power supplied from outside the multi-rotation data count circuit 50. The control unit 5 performs a count process for counting multi-rotation data based on a pulse detection signal, a wait process for waiting for a preset wait time after the count process, and a discharge process for discharging 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 storage unit 7 and reads information from the storage unit 7 through the external circuit interface 11. In addition, the control unit 5 can output the 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 3a, 3b, 3c, and 3d. The wait time can be set separately for when the power is off and no power is being supplied from outside the multi-rotation data count circuit 50, and when the power is on and power is being supplied from outside the multi-rotation data count 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 count processing based on the pulse detection signal is not performed, and transitions the control unit 5 to a state in which count processing can be performed.

[0018] When the power supply is off and the multi-rotation data count circuit 50 is not receiving power from the outside, the power supply switching circuit 10 outputs the power supplied from the capacitors 3a, 3b, 3c, and 3d to the constant voltage circuit 4. On the other hand, when the power supply is on and the multi-rotation data count circuit 50 is receiving power from the outside, the power supply switching circuit 10 outputs the power supplied from the outside to the constant voltage circuit 4. Note that, as the power supplied from the outside of the multi-rotation data count circuit 50, power generated in the batteryless encoder 100 based on power supplied from an amplifier (not shown) can be cited as an example, but is not limited to this. For example, when the encoder has a built-in battery, the power supplied from the outside of 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 the first embodiment. The power generation pulse includes first pulses 12a, 12b generated with the rotation of the magnet 1 due to the Large Barkhausen effect of the wires 21a, 21b, and second pulses 13a, 13b generated with the rotation of the magnet 1 due to the induced electromotive force of the coils 22a, 22b. In FIG. 2, the waveforms of the first pulse 12a and the second pulse 13a generated in the power generation element 2a are shown by solid lines, and the waveforms of the first pulse 12b and the second pulse 13b generated in the power generation element 2b are shown by dashed lines. The second pulses 13a, 13b have a larger amplitude when the rotation speed of the 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 an overlapping manner, the number of rotations of the magnet 1 is not 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 an overlapping manner, the number of rotations of the magnet 1 is not 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 the charges of at least the first pulses 12a, 12b and the second pulses 13a, 13b is completed and there is no voltage rise in the capacitors 3a, 3b, 3c, and 3d.

[0021] 1 in more detail, the batteryless encoder 100 includes four capacitors 3a, 3b, 3c, and 3d, and the wait time may be set to a time when the charge storage of the first pulse 12a, 12b and the second pulse 13a, 13b is 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 a time when the charge storage of the first pulse 12a and the second pulse 13a is completed in the capacitor 3a and there is no voltage rise in the capacitor 3a. In addition, since the time when 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 in the capacitor 3b to the time when the accumulation of charges of the first pulse 12a and the second pulse 13a is completed and there is no voltage rise in the capacitor 3b, the wait time may be set in the capacitor 3c to the time when the accumulation of charges of the first pulse 12b and the second pulse 13b is completed and there is no voltage rise in the capacitor 3c, or the wait time may be set in the capacitor 3d to the time when the accumulation of charges of the first pulse 12b and the second pulse 13b is completed 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 performing a count process of the preceding first pulses 12a, 12b, and thereby does not perform a count process even if, for example, the first pulses 12a, 12b or the second pulses 13a, 13b exceed the pulse detection threshold during the wait process. This prevents duplicate counting of the already counted first pulses 12a, 12b and prevents 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 occurs 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 in which 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 the charges of the first pulses 12a, 12b and the second pulses 13a, 13b is completed and the voltage of the capacitors 3a, 3b, 3c, and 3d is no longer increased.

[0024] Since 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, the wait time in the wait process 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 by taking the case where the count 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, and the control unit 5 starts the count process. At time t2, when the count process ends, the control unit 5 performs a wait process. At time t3 after waiting for a preset wait time wt1, the control unit 5 performs a discharge process and drives the discharge circuit 8 to discharge the capacitor 3a. The wait time wt1 is a time during which the accumulation of the charges of 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, and the first pulses 12a and 12b can be detected.

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

[0027] FIG. 4 is a diagram showing a power generation pulse waveform of a capacitor of 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, and the control unit starts the 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 higher than the pulse detection threshold Vs. In this way, if the wait process and the discharge process are not performed after the counting process ends, the first pulse cannot be detected until the charge of 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 is difficult to detect the next first pulse.

[0028] FIG. 5 is a diagram showing a power generation pulse waveform of a capacitor of a batteryless encoder according to a second comparative example of the first embodiment. At time t1, the voltage of the capacitor exceeds the pulse detection threshold Vs, and the control unit starts a counting process. At time t2, when the counting process ends, 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 a time shorter than the time during which the charge of the first pulse is accumulated in the capacitor and there is no voltage rise in the capacitors 3a, 3b, 3c, and 3d. At time t5 after waiting for the preset wait time wt2, the control unit performs a discharge process and drives the discharge circuit to discharge the capacitor. At time t6 when the discharge process ends, the voltage of the capacitor becomes less than the pulse detection threshold Vs, but since the charge is being supplied by the first pulse, the charge of the capacitor increases again, and the voltage of the capacitor rises again. Therefore, at time t4, the voltage of the capacitor is equal to or greater than the pulse detection threshold Vs.

[0029] In the batteryless encoder according to the second comparative example, after the counting process of the first pulse is completed, the discharge process is performed while the charge is being supplied by the first pulse, so that the charge of the capacitor is reduced by the discharge process, but since the charge of the capacitor is supplied by the first pulse after the discharge process is completed, the charge of the capacitor increases again and the voltage of the capacitor rises again. When the charge of the capacitor increases again, the voltage of the capacitor exceeds the pulse detection threshold Vs again, and the control unit starts the counting process again. As a result, the batteryless encoder according to the second comparative example counts the power generation pulses that have already been counted redundantly, causing an error in the rotation angle of the rotating shaft. In addition, after the charge of the capacitor increases again, the first pulse cannot be detected until the charge of the capacitor is discharged again at time t9 and decreases, so that when the rotation speed of the rotating shaft increases and reaches a certain rotation speed or higher, it is difficult to detect the next first pulse.

[0030] FIG. 6 is a diagram showing a power generation pulse waveform of a capacitor of 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, and the control unit starts a counting process. At time t2, when the counting process ends, 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 shorter than the time during which the charge of the first pulse is accumulated in the capacitor and then the charge of the second pulse is accumulated in the capacitor, and there is no voltage rise in the capacitors 3a, 3b, 3c, and 3d due to the accumulation of the charge of the second pulse. At time t7 after waiting for the preset wait time wt3, the control unit performs a discharge process and drives the discharge circuit to discharge the capacitor. At time t8 when the discharge process ends, the voltage of the capacitor becomes less than the pulse detection threshold Vs, but since the charge is being supplied by the second pulse, the charge of the capacitor increases again, and the voltage of the capacitor rises again. Therefore, at time t4, the voltage of the capacitor is equal to or greater than the pulse detection threshold Vs.

[0031] In the batteryless encoder according to the third comparative example, after the counting process of the first pulse is completed, the discharge process is performed while the charge is being supplied by the second pulse, so that the charge of the capacitor decreases by the discharge process, but since the charge is supplied by the second pulse after the discharge process is completed, the charge of the capacitor increases again and the voltage of the capacitor rises again. When the charge of the capacitor increases again, the voltage of the capacitor exceeds the pulse detection threshold Vs again, and the control unit starts the counting process again. As a result, the batteryless encoder according to the third comparative example counts the first pulse and the second pulse in the same number of rotations of the rotating shaft, and an error occurs in the rotation angle of the rotating shaft. In addition, after the charge of the capacitor increases again, the first pulse cannot be detected until the charge of the capacitor decreases by being discharged again at time t9, so that when the number of rotations of the rotating shaft becomes a high speed rotation exceeding a certain number of rotations, it is difficult to detect the next first pulse.

[0032] In this way, if the discharge process is not performed or if the discharge process is performed during the charge supply by the first pulse or the second pulse, the already counted first pulse may be counted repeatedly, or the first pulse and the second pulse may be counted repeatedly, resulting in an error in the rotation angle of the rotating shaft. In addition, if the time required for the voltage of the capacitor to drop to a level at which the subsequent first pulse can be detected becomes long and the number of rotations of the rotating shaft increases, and the rotation speed becomes high at a certain rotation speed or higher, it is difficult to detect the next power generation pulse. In contrast, the batteryless encoder 100 according to the first embodiment performs the discharge process at the timing when the charge supply from both the first pulse 12a and the second pulse 13a ceases, so that it is possible to suppress the already counted first pulses 12a and 12b from being counted repeatedly, and to suppress the first pulses 12a and 12b from being counted repeatedly and the second pulses 13a and 13b from being counted repeatedly. 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 difference between the operation when the power is off and the operation when the power is on will be described. First, the operation when the power is off will be described. As the magnet 1 attached to the rotating shaft 1a rotates, a power generation pulse is 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 pulse is 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 pulse is 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 pulse is 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 pulse is half-wave rectified by the half-wave rectifier circuit 23b and sent to the capacitor 3d. As the magnet 1 rotates, a voltage pulse is input to the capacitors 3a, 3b, 3c, and 3d in the order of the capacitor 3a, the capacitor 3c, the capacitor 3b, and the 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 was generated, i.e., whether the forward voltage or reverse voltage pulse was 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 a counting process. In the counting process, the control unit 5 reads out the multiple rotation count data at the previous pulse from the storage unit 7, and generates new multiple rotation count data based on the information on the occurrence location of the pulse 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, the operation when the power is on will be described. 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 the memory unit 7. The control unit 5 reads out the multi-rotation count data from the previous pulse from the memory unit 7.

[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, 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 at power generation element 2a or 2b.

[0040] The control unit 5 generates new multiple rotation count data based on the information on the pulse generation location 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 3a, 3b, 3c, and 3d. 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 the first embodiment is powered off. Fig. 8 is a diagram showing an example of a generated pulse waveform when the battery-less encoder according to the first embodiment is powered on. When the power is off, during count processing, the control unit 5 reads out the multi-rotation count data at the time of the previous pulse from the storage unit 7, generates new multi-rotation count data based on information on the location of the pulse generated 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 count processing, the control unit 5 only generates new multi-rotation count data based on information on the location of the pulse generated obtained from the pulse detection unit 6.

[0042] In this way, when the power is off, the charges stored in the capacitors 3a, 3b, 3c, and 3d are used as the power source for the control unit 5, so that the peak voltage Vp1 of the capacitor during the counting process when the power is off is smaller than the peak voltage Vp2 of the capacitor during the counting process when the power is on. On the other hand, the counting process when the power is off requires more man-hours than the counting process when the power is on, so 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. For this reason, 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 is 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] In the batteryless encoder 100 according to the first embodiment, the wait time wt11 when the power is off and the wait time wt12 when the power is on can be set independently, so that the timing for starting 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, and set the timing for discharging to be different.

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

[0045] In the above description, the batteryless encoder 100 is configured to include two power generating elements 2a and 2b, but the number of power generating elements may be one, or three or more. By increasing the number of power generating elements, the resolution for detecting the rotation angle of the magnet 1 can be improved.

[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 charge of the first pulse 12a, 12b and the second pulse 13a, 13b is accumulated 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 charge of the first pulse is accumulated and there is no voltage rise in the capacitors 3a, 3b, 3c, and 3d. Here, the batteryless encoder generates a first pulse as a power generation pulse due to the large Barkhausen effect of the Wiegand wire of the power generation element and generates a second pulse as a power generation pulse due to the induced electromotive force of the coil of the power generation 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 charge of at least the first pulse is accumulated and there is no voltage rise 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 of the 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 when the charge accumulation of at least the first pulses 12a and 12b shown in FIG. 9 is 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 to a wait time when the charge accumulation of the first pulses 12a and 12b is 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 when the charge accumulation of the first pulses 12a is completed in the capacitor 3a and there is no voltage rise in the capacitor 3a.

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

[0049] The operation of the batteryless encoder 100 will be described with reference to the modified example shown in FIG. 9, taking the case of performing count processing of the first pulse 12a as an example. FIG. 10 is a diagram showing an example of a waveform of a power generation pulse of a capacitor of a batteryless encoder according to a modified example of the first embodiment. At time t1, the voltage of the capacitor 3a exceeds the pulse detection threshold Vs, and the control unit 5 starts count processing. At time t2, when the count processing ends, the control unit 5 performs a wait processing. At time t3 after waiting for a preset wait time wt13, the control unit 5 performs a discharge processing and drives the discharge circuit 8 to discharge the capacitor 3a. The wait time wt13 is a time during which the accumulation of the charge of at least the first pulse 12a ends and there is no voltage rise of the capacitor 3a. As shown in FIG. 10, at time t4 when the discharge processing ends, the capacitor voltage of the capacitor 3a becomes less than the pulse detection threshold Vs, and the first pulses 12a and 12b become detectable.

[0050] Even in this modified example, it is possible to prevent the first pulses 12a, 12b that have already been counted from being counted again, and to prevent the first pulses 12a, 12b and the second pulses 131a, 131b from being counted again. In addition, by setting the wait time to a time during which the accumulation of the electric charge of the power generation pulse is completed and there is no voltage rise in the capacitors 3a, 3b, 3c, 3d, it is not necessary to wait for the time until the voltage of the capacitors 3a, 3b, 3c, 3d drops below the pulse detection threshold due to natural discharge, and the time until the voltage of the capacitors 3a, 3b, 3c, 3d drops to a level at which the first pulses 12a, 12b can be detected is shortened, making it possible to more effectively detect high-speed rotation.

[0051] 11 is a diagram showing the hardware configuration of a control unit and a storage unit of the battery-less encoder according to the first embodiment and the modifications. 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 execute various processes when energized, and may be, for example, an integrated circuit such as an ASIC (Application Specific Integrated Circuit). The control circuit 91 has integrated therein circuits for executing at least counting, waiting, and discharging processes. The storage unit 7 is realized by a non-volatile memory 92 that retains memory even without a power supply. The non-volatile memory 92 may be a memory with low power consumption and high processing speed, and may be, for example, 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 including each of 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 contents, and may be combined with other known technologies. Parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0055] 1 magnet, 1a rotating shaft, 2a, 2b power generating 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. A magnet attached to a rotating shaft, a Weigand wire and a coil wound around the Weigand wire, which is installed facing the magnet, generates a first pulse in the Weigand wire as the magnet rotates due to the large Barkhausen effect, and generates a second pulse in the coil as the magnet rotates due to the induced electromotive force, a power generation element; a capacitor that accumulates the 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; a control unit that is operable by the power supplied from the capacitor, performs a count process of counting multi-rotation data based on the pulse detection signal, a wait process of waiting for a preset wait time after the count process, and a discharge process of discharging the capacitor after the wait process; The encoder is characterized in that the wait time is a time when at least the accumulation of the charge of the first pulse is completed 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 when at least the accumulation of the charges of the first pulse and the second pulse is completed and there is no increase in the voltage of the capacitor.

3. The encoder according to claim 2, characterized in that a plurality of the power generation elements are provided.

4. A power supply switching circuit that switches between outputting the power supplied from the outside to the control unit and the storage unit that stores the multi-rotation data, or outputting the power supplied from the capacitor to the control unit and the storage unit; The encoder according to claim 1, characterized in that the wait time can be set to different times depending on whether the power supplied from the outside is output to the control unit (when the power is on) or the power supplied from the capacitor is output to the control unit (when the power is off).

5. A power supply switching circuit that switches between outputting the power supplied from the outside to the control unit and the storage unit that stores the multi-rotation data, or outputting the power supplied from the capacitor to the control unit and the storage unit; The encoder according to claim 2, characterized in that the wait time can be set to different times depending on whether the power supplied from the outside is output to the control unit (when the power is on) or whether the power supplied from the capacitor is output to the control unit (when the power is off). **Claim 6**: A power supply switching circuit is provided for switching between outputting the power supplied from the outside to the control unit and the storage unit that stores the multi-rotation data, or outputting the power supplied from the capacitor to the control unit and the storage unit. The encoder according to claim 3, characterized in that the wait time can be set to different times depending on whether the power supplied from the outside is output to the control unit (when the power is on) or whether the power supplied from the capacitor is output to the control unit (when the power is off). **Claim 7** A motor, characterized by comprising a motor having the rotating shaft and the encoder according to any one of claims 1 to 6.

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