Encoder and motor

Abstract

The present invention facilitates provision of an encoder that enables more backups without depending on rotational speed that can be maintained by a multi-turn data detection element. The encoder includes: a multi-turn data detection element capable of detecting rotational speed of a motor; a memory reset signal generation circuit that generates a reset signal to reset the rotational speed detected by the multi-turn data detection element; a position detection circuit that detects rotational speed and rotational angle of the motor while a main power supply is on; and an operation switching unit that detects whether the main power supply is on or off and switches to backup operation when the main power supply is off. The memory reset signal generation circuit generates a reset signal if the operation switching unit detects that the main power supply is turned off.

Description

Encoder and motor

[0001] The present disclosure relates to an encoder and a motor.

[0002] An encoder (rotary encoder) attached to a servo motor or the like is required to backup the number of rotations (number of rotation times) in order to hold the origin position, but an external battery is often necessary for the backup.

[0003] Conventionally, various proposals have been made as backup methods for holding the origin position in an encoder attached to a servo motor or the like.

[0004] Japanese Patent Application Laid-Open No. 2003-315099, Japanese Patent Application Laid-Open No. 2009-300354, Japanese Patent Application Laid-Open No. 2016-036216

[0005] As described above, in order to hold the origin position of an encoder attached to a servo motor or the like, it is usually backed up using a battery. However, using an external battery for backup requires holding and replacing the battery, which is troublesome, and a backup method that can eliminate the need for replacing the external battery has been studied.

[0006] Also, as a prior art, elements that can detect the number of rotations without power supply by applying various detection principles have been proposed. However, due to limitations such as the capacity of the memory built into the element itself and the limitation of the number of rotations that can be stored due to the detection method, there is a problem that the maximum value of the number of rotations during the main power supply ON is limited.

[0007] Therefore, there is a demand for providing an encoder and a motor capable of backing up the number of rotations without depending on the memory capacity of an element that can detect the number of rotations without power supply and the limitation of the number of rotations that can be stored.

[0008] According to one embodiment of the present disclosure, the present invention provides an encoder that generates a reset signal when the operation switching unit detects that the main power supply is turned off, and the memory reset signal generation circuit is provided that generates a reset signal to reset the rotation speed detected by the multi-turn data detection circuit, a position detection circuit that detects the rotation speed and rotation angle of the motor while the main power supply is on, and an operation switching unit that detects whether the main power supply is on or off and switches to backup operation when the main power supply is off, wherein the memory reset signal generation circuit is provided that generates a reset signal when the operation switching unit detects that the main power supply is off.

[0009] Figure 1 is a diagram illustrating a schematic example of a conventional encoder. Figure 2 is a diagram illustrating an example of operation when the main power is ON in one embodiment of the encoder according to this embodiment. Figure 3 is a diagram illustrating an example of operation when the main power is OFF in one embodiment of the encoder according to this embodiment. Figure 4 is a diagram illustrating a modified example of the operation when the main power is OFF shown in Figure 3. Figure 5 is a block diagram illustrating a schematic example of the encoder according to this embodiment. Figure 6 is a flowchart illustrating the operation of the first embodiment of the encoder according to this embodiment. Figure 7 is a flowchart illustrating the operation of the second embodiment of the encoder according to this embodiment. Figure 8 is a flowchart illustrating the operation of the third embodiment of the encoder according to this embodiment.

[0010] Before detailing the embodiments of the encoder and motor according to this embodiment, an example of a conventional encoder will be described. First, in a battery-backed encoder that is backed up by an external battery, the A and B phase signals are in a phase-shift relationship of 90° from each other. For example, by plotting the A phase as the X-axis and the B phase as the Y-axis, a Lissajous waveform that completes one rotation in one slit can be generated. Furthermore, by splitting the A phase and B phase with an AD converter, one point in the Lissajous waveform can be determined and its angle can be calculated. Therefore, the angle within one slit can be further divided to obtain the position (interpolated data) within one slit.

[0011] Here, the AB phase signal is generated by the rotating slit and the fixed slit. For example, by counting each slit, the rotation angle (data within one rotation) can be detected based on which slit it is from the reference position (Z phase). The Z phase signal is used to determine the reference position for one rotation.

[0012] Next, an example of a conventional encoder will be explained with reference to Figure 1. Figure 1 is a diagram that schematically illustrates an example of a conventional encoder, and is intended to illustrate an example of an absolute type encoder installed on the rotating shaft of a motor (servo motor), etc.

[0013] As shown in Figure 1, an example of a conventional encoder includes a multi-turn data detection element (Z phase) S101 and a single-turn data generation circuit (AB phase) S104. The encoder generates absolute position data S102 by combining the single-turn data S105 (which is obtained by combining interpolated data (position data within one slit) S106 with the single-turn data generation circuit S104) and the rotational speed generated by the multi-turn data detection element S101, and transmits this data to the motor drive unit S103. Here, the multi-turn data detection element S101 is an element that detects the Z phase and can store the rotational speed without external power supply. Examples of multi-turn data detection elements S101 include those utilizing Wiegand wire or gears.

[0014] The one-rotation data generation circuit S104 is a circuit that generates slit position data within one rotation using M-sequences, Gray codes, and Vernier methods, and assigns address information to each slit using the bit sequence such as the M-sequence. This makes it possible to calculate the rotation angle within one rotation even without information on the reference position of one rotation.

[0015] In conventional technology, absolute position data is generated by combining the output of a multi-turn data detection element with data within a single rotation. Therefore, if the number of rotations that the multi-turn data detection element can store is small, the number of rotations that the motor can rotate in one direction will also be limited. In other words, in the example of a conventional encoder described with reference to Figure 1, if the output of the multi-turn data detection element (S101) is used directly as the number of rotations for absolute position data, even when the encoder's main power is on, the upper limit of the rotation speed depends on the memory capacity of the element and the number of teeth on the gear. For example, if the number of rotations that the element itself can store is small, it will overflow during operation while the power is on.

[0016] Hereinafter, embodiments of the encoder and motor according to this embodiment will be described in detail with reference to the accompanying drawings. In each drawing, identical or similar components are denoted by the same or similar reference numerals. Furthermore, the embodiments described below do not limit the technical scope of the invention as described in the claims or the meaning of the terms used.

[0017] Figure 2 is a diagram illustrating an example of operation when the main power is turned on in one embodiment of the encoder according to this embodiment. As shown in Figure 2, the encoder comprises a power supply (main power supply) 1, an operation switching unit 2, and a position detection circuit 3. The position detection circuit 3 comprises a total rotation speed storage unit 31, a calculation unit (rotation speed calculation unit) 32, a multi-rotation data detection element (Z phase) 34, a reference signal generation circuit (Z phase) 35, a single rotation data generation circuit (AB phase) 36, and interpolation data (position within one slit) 37. The position data generated by the position detection circuit 3 is transmitted to a motor drive device, etc., via a communication unit 4. Reference numeral 6 indicates a communication unit for transmitting the position data calculated by the calculation unit 32 to a motor drive device, etc.

[0018] In the encoder embodiment shown in Figure 2, when the main power supply (power supply 1) is on, the reference signal generation circuit 35 is used, and the calculation unit 32 updates the rotational speed. At this time, the output of the multi-turn data detection element (rotational speed detection element) 34 may be masked, and instead of the reference signal generation circuit 35, the count-up / count-down of the multi-turn data detection element 34 may be used as a trigger signal to update the counter of the calculation unit 32. Also, the transfer (update) of the data "total rotational speed" from the calculation unit 32 to the total rotational speed storage unit 31 may be performed either during continuous update or just before transitioning to backup operation. Note that the rotational speed that the total rotational speed storage unit 31 can count is set to be greater than the rotational speed that the multi-turn data detection element 34 can store.

[0019] In the encoder shown in Figure 2, the multi-turn data detection element 34 may be configured not to be used when the power supply 1 is on, that is, to be used only when the power supply 1 is off.

[0020] In this embodiment, assuming that the counter that counts the number of rotations of the multi-turn data detection element 34 will overflow when the storage capacity of the multi-turn data detection element 34 is small while the power supply 1 is on, the position data including the number of rotations is updated using the total rotation storage unit 31 and the calculation unit 32 without using the multi-turn data detection element 34 while the operation switching unit 2 determines that the power supply is on.

[0021] Figure 3 is a diagram illustrating an example of operation when the main power is off in one embodiment of the encoder according to this embodiment, and reference numeral 30 indicates a memory reset signal generation circuit. As shown in Figure 3, when the main power (power) switches from on to off, (1) the rotational speed (total rotational speed) calculated by the calculation unit 32 is sent to the total rotational speed storage unit 31. That is, the total rotational speed storage unit 31 stores the total rotational speed at the time the encoder power is switched from on to off. Here, the total rotational speed storage unit 31 is a non-volatile memory and can retain the rotational speed even when the power is off.

[0022] The operation switching unit 2 (2) generates a signal via the memory reset signal generation circuit 30 to reset the rotation count (number of Z-phase detections) stored in the multi-turn data detection element 34. Furthermore, (3) when the power is turned on next time, the rotation count stored in (1) above, which was recorded when the power was switched from on to off, is added to and updated by the rotation count that the multi-turn data detection element 34 counted while the main power was off. Here, the addition and update processing in the calculation unit 32 is performed when the power is turned on next time (3).

[0023] Figure 4 is a diagram illustrating a modified version of the operation shown in Figure 3 when the main power supply is off. Here, as is clear from comparing Figure 4 and Figure 3, the modified version shown in Figure 4 differs from the embodiment shown in Figure 3 above in that an emergency power supply 4 is added.

[0024] As shown in Figure 4, in this modified example, if the motor moves by inertia when the main power is switched from on to off, the emergency power supply 4 is used to operate the position detection circuit 3 until the motor's rotational speed falls below a threshold. Once it falls below the threshold, the processes described in (1) and (2) above are executed, and then the system switches to backup operation.

[0025] Figure 5 is a schematic block diagram showing one embodiment of the encoder according to this embodiment. In Figure 5, reference numeral 2 denotes an operation switching unit, 3 denotes a position detection circuit, and 5 denotes a rotation speed detection element unit. One embodiment of the encoder according to this embodiment has a memory reset signal generation circuit 30, an emergency power supply 4, a total rotation speed storage unit 31, a calculation unit (rotation speed calculation unit) 32, and a rotation speed detection element unit 5 including a rotation speed storage unit 51, a rotation speed detection unit 52, and a multi-turn data detection element 34. Here, the total rotation speed storage unit 31 and the calculation unit 32 can also be configured as external components not included inside the encoder.

[0026] As shown in Figure 5, one embodiment of the encoder according to this embodiment includes a total rotation count storage unit 31 that stores the rotation count counted while the power is on, and when the power is turned off, the memory (rotation count storage unit 51) of the multi-turn data detection element 34 is cleared, and when the power is turned on next time, the count count of the total rotation count storage unit 31 is updated with the count count of the multi-turn data detection element 34 that was counted during backup. If the multi-turn data detection element 34 is of a type that outputs an error flag or the like when the counter overflows, the error flag or the like is also cleared (initialized).

[0027] Furthermore, one embodiment of the encoder according to this embodiment may include an emergency power supply 4, which, when the motor is coasting when the power is off, uses the emergency power supply 4 to drive the power-on circuit, and when the motor's rotation speed falls below a threshold, writes the total rotations to memory and switches to backup operation. At this time, the count in the total rotations storage unit 31 is continuously updated until just before switching to backup operation, and when switching to backup operation, a signal is generated via the memory reset signal generation circuit 30 to reset the rotations (number of Z-phase detections) stored in the multi-turn data detection element. For example, an electric double-layer capacitor or a secondary battery can be used as the emergency power supply 4, and a non-volatile memory can be used as the memory.

[0028] Figure 6 is a flowchart illustrating the operation of the first embodiment of the encoder according to this embodiment. As shown in Figure 6, when the operation switching unit 2 detects that the main power supply 1 is turned off, in step ST11 the integrated value of the rotations is written to the total rotations storage unit 31, and the process proceeds to step ST12 to clear the memory (rotations storage unit) 51 of the multi-turn data detection element 34.

[0029] Furthermore, the process proceeds to step ST13 to determine whether the encoder's main power supply is on. If it is determined in step ST13 that the encoder's main power supply is on (Yes), the process proceeds to step ST14. If it is determined that the encoder's main power supply is not on (No), the process proceeds to step ST15.

[0030] In step ST14, the total rotation counts are added to the total rotation count storage unit 31, and the system returns to normal operation. Meanwhile, in step ST15, the rotation count is monitored using the multi-rotation data detection element 34, and the system returns to step ST13 to continue the same process. Here, the rotation count may take both positive and negative values ​​depending on the direction of rotation.

[0031] Figure 7 is a flowchart illustrating the operation of a second embodiment of the encoder according to this embodiment. As shown in Figure 7, when the operation switching unit 2 detects that the main power supply 1 is off, in step ST21 it is determined whether the motor rotation speed is below a threshold. If it is determined in step ST21 that the motor rotation speed is below a threshold (Yes), the process proceeds to step ST22. If it is determined that the motor rotation speed is not below a threshold (No), the process proceeds to step ST24.

[0032] In step ST22, the accumulated value of the rotation speed is written to the total rotation speed storage unit 31, and the process proceeds to step ST23. In step ST23, the memory (rotation speed storage unit) 51 of the multi-turn data detection element 34 is cleared, and the process proceeds to step ST25. Meanwhile, in step ST24, the position detection circuit 3 is driven using the emergency power supply 4, and the processes of steps ST21 and ST24 are repeated until the motor's rotation speed falls below a threshold.

[0033] In step ST25, it is determined whether the encoder's main power supply 1 is on. If it is determined that the encoder's main power supply 1 is on (Yes), the process proceeds to step ST26. If it is determined that the encoder's main power supply 1 is not on (No), the process proceeds to step ST27. In step ST26, the rotation count of the multi-turn data detection element 34 is added to the total rotation count storage unit 31, and normal operation is performed. Meanwhile, in step ST27, the rotation count is monitored using the multi-turn data detection element 34, and the processes of steps ST25 and ST27 are repeated until the encoder's main power supply is turned on.

[0034] Figure 8 is a flowchart illustrating the operation of the third embodiment of the encoder according to this embodiment, and is intended to explain the process when the multi-turn data detection element 34 is also used to detect the rotational speed while the power is on. As shown in Figure 8, in step ST31, the encoder, which is in normal operation, determines whether the rotational speed counted by the multi-turn data detection element 34 is within 90% of the element's memory limit. If it determines that the rotational speed counted by the multi-turn data detection element 34 is within 90% of the element's memory limit (Yes), it terminates the process of the third embodiment and continues normal operation.

[0035] On the other hand, in step ST31, if it is determined that the number of rotations counted by the multi-turn data detection element 34 is not within 90% of the element's memory limit (No), the process proceeds to step ST32 to determine whether the motor's rotation speed is within a threshold. In step ST32, if it is determined that the motor's rotation speed is not within a threshold (No), the process is repeated until it is determined that it is within a threshold (Yes). Also, in step ST32, if it is determined that the motor's rotation speed is within a threshold (Yes), the process proceeds to step ST33.

[0036] In step ST33, the accumulated value of the rotations is written to the total rotations memory unit 31, and the process proceeds to step ST34. In step ST34, the rotations memory unit 51 of the multi-turn data detection element 34 is cleared, and the process proceeds to step ST35, where the rotations counted by the multi-turn data detection element 34 are added to the rotations in the total rotations memory unit 31, and then normal operation is performed.

[0037] Here, the determination of whether the rotational speed in step ST32 is within the threshold is made, for example, based on whether the threshold is "time required to clear memory < time required for one rotation of the motor". Also, since the encoder stores the rotational speed when it exceeds the range that the multi-turn data detection element 34 can store, if the multi-turn data detection element 34 is used for the signal corresponding to the Z phase, it is not a problem to update the total rotational speed while the power supply 1 is on. Furthermore, for example, in the case of a gear type, instead of the sequence of "clearing the memory 51 of the multi-turn data detection element 34", it is also possible to monitor the rotational speed detected by the multi-turn data detection element 34 at regular intervals and add or subtract the difference from the previously detected rotational speed to the total rotational speed to create a backup.

[0038] In this case, the interval t (seconds) for monitoring the rotation speed can be selected within the range satisfying t < (N / 2) × (60 / v), where N (times) is the total number of rotations that the multi-turn data detection element 34 can store and v (rpm) is the maximum rotation speed of the motor. This is because, when the motor is rotating at its maximum rotation speed, if it rotates more than half (N / 2 times) of the number of rotations that the multi-turn data detection element 34 can store in t seconds, the direction of rotation cannot be determined. At this time, if the number of rotations detected by the multi-turn data detection element 34 at time T is represented as N(T), the difference ΔN from time T to time T+t can be expressed by the following equation. When N(T+t)-N(T)>N / 2, ΔN=-N+N(T+t)-N(T); When -N / 2<N(T+t)-N(T)≤N / 2, ΔN=N(T+t)-N(T); When N(T+t)-N(T)<-N / 2, ΔN=N-N(T+t)+N(T).

[0039] As detailed above, when starting the backup operation, the encoder or controller records the multi-turn data immediately before switching to the backup operation, and initializes the rotation count of the rotation speed detection element. This allows the multi-turn data detection element to be used only for rotation speed detection during the backup operation. As a result, the amount of multi-turn data that the multi-turn data detection element is required to hold is limited to the rotation speed during the backup operation, thus broadening the range of element selection. In other words, the encoder and motor according to the embodiment described above make it possible to back up a larger number of rotation speeds, regardless of the rotation speed that the multi-turn data detection element can hold.

[0040] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. Furthermore, these embodiments can be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above.

[0041] With respect to the above embodiments and modifications, the following additional notes are disclosed. [Addendum 1] An encoder comprising: a multi-turn data detection element (34) capable of detecting the rotational speed of a motor; a memory reset signal generation circuit (30) that generates a reset signal for resetting the rotational speed detected by the multi-turn data detection element (34); a position detection circuit (3) that detects the rotational speed and rotational angle of the motor while the main power supply (1) is on; and an operation switching unit (2) that detects whether the main power supply (1) is on or off and switches to backup operation if the main power supply (1) is off, wherein the memory reset signal generation circuit (30) generates the reset signal when the operation switching unit (2) detects that the main power supply (1) is off. [Note 2] The encoder according to Note 1, further comprising: a total rotation count storage unit (31) that stores the total number of rotations since the establishment of the origin; and a calculation unit (32) that adds or subtracts the number of rotations counted by the multi-turn data detection element (34) during the backup operation from the total number of rotations, wherein the total rotation count storage unit (31) updates the total number of rotations to the value calculated by the calculation unit (32) when the main power supply (1) is switched from off to on. [Note 3] The encoder according to Note 2, wherein the number of rotations that the total rotation count storage unit (31) can count is greater than the number of rotations that the multi-turn data detection element (34) can store. [Note 4] The encoder according to Note 2 or Note 3, further comprising an emergency power supply (4), wherein when the operation switching unit (2) detects that the main power supply (1) is off, it supplies power to the position detection circuit (3) using the emergency power supply (4) as a power source instead of the main power supply (1), thereby storing the total rotations at the time the backup operation starts in the total rotations storage unit (31). [Note 5] The encoder according to Note 4, wherein when the operation switching unit (2) detects that the main power supply (1) is off, it supplies power to the position detection circuit (3) using the emergency power supply (4) as a power source instead of the main power supply (1) while the motor rotation speed calculated from the motor rotation angle detected by the position detection circuit (3) exceeds a threshold, thereby storing the total rotations at the time the backup operation starts in the total rotations storage unit (31).[Note 6] The encoder according to any one of Notes 2 to 5, wherein the total rotation count storage unit (31) holds the rotation count counted while the main power supply (1) is ON, clears the rotation count storage unit (51) of the multi-turn data detection element (34) when the main power supply (1) is OFF, and updates the count count of the total rotation count storage unit (31) with the count count of the multi-turn data detection element (34) counted during backup when the power is turned on next time. [Note 7] The encoder according to any one of Notes 1 to 6, wherein the multi-turn data detection element (34) is not used when the main power supply (1) is ON, and is used only when the main power supply (1) is OFF. [Note 8] The encoder according to any one of Notes 1 to 7, wherein the memory of the multi-turn data detection element (34) is cleared immediately before transitioning to the backup operation, and the multi-turn data detection element (34) is used only during the backup operation. [Note 9] An encoder according to Note 8, which generates absolute position data by adding the number of rotations counted by the multi-turn data detection element (34) when the power is turned on and the number of rotations backed up on the encoder side. [Note 10] A motor that drives a rotating shaft, wherein an encoder according to any one of Notes 1 to 9 is attached to the rotating shaft.

[0042] 1 Power supply (main power supply) 2 Operation switching unit 3 Position detection circuit 4 Emergency power supply 5 Rotation speed detection element unit 6 Communication unit 20 Memory reset signal 30 Memory reset signal generation circuit 31 Total rotation speed storage unit 32 Calculation unit 34 Multi-rotation data detection element 35 Reference signal generation circuit 36 ​​Data generation circuit within one rotation 37 Internal data 51 Rotation speed storage unit (memory) 52 Rotation speed detection unit

Claims

1. An encoder comprising: a multi-turn data detection element capable of detecting the rotational speed of a motor; a memory reset signal generation circuit that generates a reset signal to reset the rotational speed detected by the multi-turn data detection element; a position detection circuit that detects the rotational speed and rotational angle of the motor while the main power supply is on; and an operation switching unit that detects whether the main power supply is on or off and switches to backup operation if the main power supply is off, wherein the memory reset signal generation circuit generates the reset signal when the operation switching unit detects that the main power supply is off.

2. The encoder according to claim 1, further comprising: a total rotation count storage unit that stores the total number of rotations since the establishment of the origin; and a calculation unit that adds or subtracts the number of rotations counted by the multi-rotation data detection element and the total number of rotations during the backup operation, wherein the total rotation count storage unit updates the total number of rotations to the value calculated by the calculation unit when the main power supply is switched from off to on.

3. The encoder according to claim 2, wherein the total number of rotations that the total number of rotations storage unit can count is greater than the number of rotations that the multi-rotation data detection element can store.

4. The encoder according to claim 2 or 3, further comprising an emergency power supply, wherein when the operation switching unit detects that the main power supply is turned off, it supplies power to the position detection circuit using the emergency power supply as a power source instead of the main power supply, thereby storing the total rotations at the time the backup operation starts in the total rotations storage unit.

5. The encoder according to claim 4, wherein when the operation switching unit detects that the main power supply is off, while the motor rotation speed calculated from the motor rotation angle detected by the position detection circuit exceeds a threshold, the unit supplies power to the position detection circuit using the emergency power supply instead of the main power supply, thereby causing the total rotation speed at the time the backup operation starts to be stored in the total rotation speed storage unit.

6. The encoder according to any one of claims 2 to 5, wherein the total rotation speed storage unit holds the rotation speed counted while the main power supply is ON, clears the rotation speed storage unit of the multi-turn data detection element when the main power supply is OFF, and updates the count of the total rotation speed storage unit with the count of the multi-turn data detection element counted during backup when the power is turned on next time.

7. The encoder according to any one of claims 1 to 6, wherein the multi-turn data detection element is not used when the main power supply is on, and is used only when the main power supply is off.

8. The encoder according to any one of claims 1 to 7, wherein the memory of the multi-turn data detection element is cleared immediately before transitioning to the backup operation, and the multi-turn data detection element is used only during the backup operation.

9. The encoder according to claim 8, wherein absolute position data is generated by summing the number of rotations counted by the multi-turn data detection element and the number of rotations backed up by the encoder when the power is turned on.

10. A motor for driving a rotating shaft, wherein an encoder according to any one of claims 1 to 9 is attached to the rotating shaft.

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