CN114257045B - Encoder and motor - Google Patents
Encoder and motor Download PDFInfo
- Publication number
- CN114257045B CN114257045B CN202111116908.5A CN202111116908A CN114257045B CN 114257045 B CN114257045 B CN 114257045B CN 202111116908 A CN202111116908 A CN 202111116908A CN 114257045 B CN114257045 B CN 114257045B
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- magnet
- encoder
- electromagnetic brake
- brake
- voltage
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- 238000001514 detection method Methods 0.000 claims abstract description 77
- 230000002093 peripheral effect Effects 0.000 claims abstract description 42
- 239000000758 substrate Substances 0.000 claims description 16
- 239000000853 adhesive Substances 0.000 claims description 10
- 230000001070 adhesive effect Effects 0.000 claims description 10
- 239000000696 magnetic material Substances 0.000 claims description 4
- 230000009467 reduction Effects 0.000 abstract description 4
- 230000004907 flux Effects 0.000 description 68
- 230000007423 decrease Effects 0.000 description 7
- 239000012212 insulator Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical group [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005192 partition Methods 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 239000003566 sealing material Substances 0.000 description 2
- 240000001973 Ficus microcarpa Species 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 230000005415 magnetization Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
- H02K11/20—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection for measuring, monitoring, testing, protecting or switching
- H02K11/21—Devices for sensing speed or position, or actuated thereby
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
- H02K7/10—Structural association with clutches, brakes, gears, pulleys or mechanical starters
- H02K7/102—Structural association with clutches, brakes, gears, pulleys or mechanical starters with friction brakes
- H02K7/1021—Magnetically influenced friction brakes
- H02K7/1023—Magnetically influenced friction brakes using electromagnets
- H02K7/1025—Magnetically influenced friction brakes using electromagnets using axial electromagnets with generally annular air gap
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)
Abstract
An encoder and a motor are provided, which can restrain the reduction of the detection precision of the encoder even if an electromagnetic brake is not used according to the specification with a low-cost structure. The motor is provided with: a rotor and a stator; an electromagnetic brake; an encoder. A position holding magnet of the encoder is provided with a prescribed air gap between the encoder and the front end surface of the rotary shaft. The peripheral wall (112) of the magnet holder (11) is provided with a first annular step (114) provided on the inner peripheral side of an annular protrusion (113) provided at the front end on one side in the axial direction, and the magnet is fitted into a second annular step (115) provided on the inner peripheral side of the first annular step. The encoder circuit (17) is provided with a correction unit (18) that performs correction processing for removing a detection error caused by the influence of a brake magnetic field generated when the electromagnetic brake is driven by a voltage lower than the standard voltage, the detection angle being obtained from the output of the magnetic sensor (13).
Description
Technical Field
The present invention relates to an encoder and a motor.
Background
In a motor in which a stator and a rotor are accommodated in a cylindrical motor case, an encoder-equipped motor is used in which an encoder case is fixed to an end portion of the motor case opposite to the output side, and an encoder for detecting rotation of the rotor is accommodated in the encoder case. Such motors are disclosed in patent documents 1 and 2.
The motors of patent documents 1 and 2 include electromagnetic brakes arranged on the opposite output side with respect to the stator. The motor of patent document 1 includes: a friction plate fixed to a rotary shaft (motor shaft); an armature pressed against the friction plate by a spring; and a stator for a brake that generates a magnetic attraction force that attracts the armature in a direction opposite to the urging force of the spring.
An encoder of the motor with a brake that detects rotation of the rotor may be affected by leakage magnetic flux generated from the electromagnetic brake. The motor of patent document 1 has a partition plate made of a magnetic member disposed at an end portion of a brake case opposite to an output side thereof to absorb leakage magnetic flux from a brake toward an encoder side. The step portions are formed on the inner peripheral surface of the partition plate and the outer peripheral surface of the rotary shaft, and the labyrinth structure is formed, and the substrate holder for holding the substrate of the encoder is also formed as a magnetic member, thereby further reducing the leakage magnetic flux.
The motor of patent document 2 corrects the output of the encoder on the premise that there is leakage magnetic flux generated from the electromagnetic brake, so as to eliminate the influence of the leakage magnetic flux, thereby suppressing the degradation of the detection accuracy of the encoder due to the influence of the leakage magnetic flux.
Prior art literature
Patent literature
Patent document 1: japanese patent No. 5943694
Patent document 2: japanese patent laid-open No. 9-243398
Disclosure of Invention
Technical problem to be solved by the invention
Due to the improvement of the resolution of the encoder, even when countermeasures such as patent document 1 are taken, the influence of the leakage magnetic flux on the detection accuracy may reach a level that is problematic. In order to further reduce the leakage magnetic flux, countermeasures have been taken to suppress the leakage of the magnetic flux to the encoder side via the rotary shaft by making the opposite output side and the output side of the rotary shaft different in material, but there is a problem that the component cost becomes high.
In addition, there are cases where the user does not use the motor with the electromagnetic brake at a voltage conforming to the brake specification. For example, the electromagnetic brake may be used at a voltage lower than the standard voltage for the purpose of reducing heat generation and power consumption. Further, since the electromagnetic brake operates even when the polarity is reversed, the electromagnetic brake may be connected with the wrong polarity and used as it is. In the case of eliminating the influence of the leakage magnetic flux generated from the electromagnetic brake by correction as in patent document 2, although the error of the detection angle caused by the leakage magnetic flux can be eliminated by correction when the user uses the brake with a voltage and polarity that meet the brake specification, the influence of the leakage magnetic flux cannot be eliminated in accordance with the target because the correction amount does not coincide with the error of the detection angle caused by the leakage magnetic flux when the user uses the brake with a voltage that is different from the brake specification. In addition, when the user uses the brake with a polarity opposite to the brake specification, there is a case where the error of the detection angle is excessively adjusted by correction, which increases considerably.
In view of the above, an object of the present invention is to suppress a decrease in the detection accuracy of an encoder even when an electromagnetic brake is not used in accordance with specifications, with an inexpensive structure.
Technical proposal adopted for solving the technical problems
In order to solve the above-described problems, the present invention provides an encoder for detecting rotation of a motor with a brake, the motor with a brake including: a rotor including a rotation shaft; a stator that is radially opposed to the rotor; and an electromagnetic brake disposed on one side of the stator in the axial direction of the rotary shaft, wherein the encoder includes: a magnet holder fixed to an end portion of the rotating shaft on one side in the axial direction; a magnet held by the magnet holder; a magnetic sensor facing the magnet from one side in the axial direction, and a sensor substrate on which the magnetic sensor is disposed; and a correction unit that corrects a detection angle obtained from an output of the magnetic sensor, wherein the magnet holder includes a peripheral wall surrounding an outer peripheral side of the magnet, the magnet is held at a position where a predetermined gap is provided between a front end surface of the rotating shaft and the magnet, the peripheral wall includes an annular protrusion provided at a front end of one side in the axial direction and a first annular step provided on an inner peripheral side of the annular protrusion, and a second annular step into which the magnet is fitted is provided on an inner peripheral side of the first annular step, and the correction unit corrects a detection error caused by an influence of a brake magnetic field generated when the electromagnetic brake is energized by a second voltage lower than a first voltage, which is a standard voltage of the electromagnetic brake.
According to the present invention, since the magnet of the encoder and the rotary shaft are not in contact with each other, the leakage magnetic flux emitted from the end of the rotary shaft does not easily interfere with the magnet directly, and the magnetic field of the magnet is not easily disturbed. Therefore, since the magnetic flux of the magnet can be stabilized, the deterioration of the detection accuracy of the encoder due to the leakage magnetic flux from the electromagnetic brake can be suppressed.
In addition, according to the present invention, since the first annular step portion is provided at the front end of the peripheral wall of the magnet holder and the magnet is fitted into the second annular step portion provided on the inner peripheral side of the first annular step portion, a gap is secured between the peripheral wall of the magnet holder and the magnet. The magnetic circuit through which the leakage magnetic flux from the electromagnetic brake passes is constituted by a rotary shaft and a magnet holder, but in the present invention, since a gap is secured between the end of the magnet holder on the magnetic sensor side and the magnet, the leakage magnetic flux from the electromagnetic brake is less likely to directly interfere with the magnet and the magnetic field of the magnet is less likely to be disturbed. Therefore, since the magnetic flux detected by the magnetic sensor can be stabilized, a decrease in the detection accuracy of the encoder due to the leakage magnetic flux from the electromagnetic brake can be suppressed.
Further, according to the present invention, even if the above-described structural countermeasure is taken, the output of the magnetic sensor is affected by the leakage magnetic flux from the electromagnetic brake, and the detection angle of the encoder is corrected so as to eliminate the detection error caused by the influence of the brake magnetic field generated when the electromagnetic brake is energized at a voltage lower than the standard voltage. In this way, even when the user uses the electromagnetic brake at a voltage lower than the standard voltage or when the electromagnetic brake is used by reversing the polarity, the influence of the leakage magnetic flux on the detection accuracy of the encoder can be reduced, and the detection accuracy of the encoder is not easily lowered significantly. In addition, excessive adjustment in which the detection error is increased by correction can be suppressed. Therefore, the reduction in the detection accuracy of the encoder due to the leakage magnetic flux from the electromagnetic brake can be suppressed without using expensive components, including the case where the electromagnetic brake is not used in the specification.
In the present invention, an air gap of 0.5mm or more is preferably provided between the front end surface of the rotating shaft and the magnet. By providing the air gap, the path through which the leakage magnetic flux of the brake is transmitted from the rotating shaft to the magnet can have magnetic resistance, and leakage to the magnet can be continuously attenuated. Therefore, the disturbance of the magnetic flux of the magnet caused by the leakage magnetic flux from the brake can be reduced.
In the present invention, it is preferable that the second voltage is a voltage of 75% of the first voltage. In this way, when the electromagnetic brake can be used at a voltage of 50% of the specification voltage, even when the electromagnetic brake is used at any voltage between the specification voltage and the voltage of 50% of the specification voltage, the detection error can be reduced by correction, and the influence of the leakage magnetic flux on the detection accuracy of the encoder is less likely to increase. In addition, according to the verification by the present inventors, even in the case where the electromagnetic brake is connected in the opposite polarity, the detection error can be reduced by correction, and the influence of the leakage magnetic flux on the detection accuracy of the encoder is not easily increased. Therefore, the detection accuracy of the encoder is not likely to be significantly reduced.
In the present invention, it is preferable that the annular projection projects further to one side in the axial direction than the surface of the magnet on one side in the axial direction. In this way, the leakage magnetic flux from the brake is more concentrated at the tip of the peripheral wall than the magnet. Therefore, the influence of the leakage magnetic flux from the electromagnetic brake on the magnetic flux of the magnet can be reduced.
In the present invention, it is preferable that the gap between the annular projection and the magnet is an adhesive reservoir chamber in which an adhesive for fixing the magnet is contained. In this way, the fixing strength of the magnet can be improved by the structure for reducing the influence of the leakage magnetic flux from the electromagnetic brake.
In the present invention, it is preferable that the magnet holder is a magnetic material. In this way, the magnet holder functions as a yoke for the magnet, so that the sensor magnetic flux detected by the magnetic sensor can be stabilized.
Next, the present invention provides a motor with a brake, comprising: a rotor including a rotation shaft; a stator that is radially opposed to the rotor; an electromagnetic brake disposed on one side of the stator in the axial direction of the rotating shaft; an encoder as described above.
Effects of the invention
According to the present invention, the leakage magnetic flux emitted from the end portion of the rotation shaft is less likely to directly interfere with the magnet, and the magnetic field of the magnet is less likely to be disturbed. In addition, according to the present invention, since a gap is secured between the end of the magnet holder on the magnetic sensor side and the magnet, the leakage magnetic flux from the electromagnetic brake is less likely to directly interfere with the magnet, and the magnetic field of the magnet is less likely to be disturbed. Therefore, since the magnetic flux detected by the magnetic sensor can be stabilized, a decrease in the detection accuracy of the encoder due to the leakage magnetic flux from the electromagnetic brake can be suppressed.
Further, according to the present invention, even if the above-described structural countermeasure is taken, the output of the magnetic sensor is affected by the leakage magnetic flux from the electromagnetic brake, and the detection angle of the encoder is corrected to eliminate the detection error caused by the influence of the brake magnetic field generated when the electromagnetic brake is energized at a voltage lower than the standard voltage. In this way, in various usage modes, the detection accuracy of the encoder is not likely to be significantly reduced. In addition, excessive adjustment in which the detection error is increased by correction can be suppressed. Therefore, the reduction in the detection accuracy of the encoder due to the leakage magnetic flux from the electromagnetic brake can be suppressed without using expensive components, including the case where the electromagnetic brake is not used in the specification.
Drawings
Fig. 1 is a cross-sectional view of an electric motor provided with an encoder of the present invention.
Fig. 2 is an enlarged cross-sectional view of a main portion of the encoder.
Fig. 3 is a plan view of the magnet and the magnet holder, and a plan view of the sensor substrate.
Fig. 4 is a block diagram schematically showing a signal processing circuit of the encoder.
Fig. 5 is a graph showing the influence of leakage magnetic flux from the electromagnetic brake on detection errors of the encoder.
Description of the reference numerals
A 1 … motor; 2 … rotor; 3 … stator; 4 … motor housing; 5 … cage; 6 … brake housing; 7 … electromagnetic brake; 8 … encoder housing; 9 … seal material; 10 … encoder; 11 … magnet holder; 12 … magnets; a surface of one side of the 12a … magnet in the axial direction; 13 … magnetic sensor; 14 … sensor substrate; 15 … substrate holder; 16 … shielding member; 17 … encoder circuit; 18 … correction unit; 19 … encoder wiring; 20 … rotation axis; 20a … output shaft; 21 … rotor magnets; 22 … first bearing; 23 … second bearings; 24 … front end face; 30 … stator core; 31 … protruding poles; 32 … insulator; 33 … coil; 34 … wiring board; 35 … terminal pins; 40 … notch portion; 41 … lead holder; 51 … annular ribs; 61 … bottom; 62 … side wall portions; 63 … minor diameter; 71 … friction plate; 72 … armature; 73 … plate; a stator for a 74 … brake; 81 … bottom; 82 … side wall portions; 83 … encoder wiring take-out section; 110 … holding portion; 111 … bottom; 112 … peripheral wall; 113 … annular projection; 114 … first annular step; 115 … second annular step; 120 … fixing portions; 130 … central bore; 131 … magneto-sensitive element; 132 … hall element; g … air gap; l … axis direction; one side in the axial direction of L1 …; l2 … on the other side in the axial direction.
Detailed Description
(integral structure)
An embodiment of a motor to which the present invention is applied will be described below with reference to the drawings. Fig. 1 is a cross-sectional view of a motor 1 provided with an encoder 10 of the present invention. The motor 1 is a motor with a brake. As shown in fig. 1, the motor 1 includes: a rotor 2 provided with a rotation shaft 20; a stator 3 disposed on the outer peripheral side of the rotor 2; a cylindrical motor case 4 accommodating the stator 3; a bearing holder 5 fixed to one end of the motor housing 4; a brake housing 6 fixed to the other end of the motor housing 4; an electromagnetic brake 7 accommodated in the brake housing 6; and an encoder 10 that detects the rotation of the rotor 2. The encoder 10 is accommodated in the encoder housing 8.
The rotary shaft 20 extends in the axial direction L at the center of the motor 1 in the radial direction. In the present specification, one side in the axial direction L is L1, and the other side in the axial direction L is L2. The bearing holder 5 is fixed to an end portion of the other side L2 in the axial direction L of the motor housing 4. The rotary shaft 20 includes an output shaft 20A protruding from the bearing holder 5 to the other side L2 in the axial direction L. Therefore, in this embodiment, the other side L2 in the axial direction L is the output side, and the one side L1 in the axial direction L is the opposite output side.
The rotor 2 includes a rotary shaft 20 and rotor magnets 21 fixed to the outer peripheral surface of the rotary shaft 20. The rotation shaft 20 is made of a magnetic material. The rotation shaft 20 is rotatably held by a first bearing 22 and a second bearing 23, the first bearing 22 is held by a recess formed in the center of the bearing holder 5, and the second bearing 23 is held by the brake housing 6. In this embodiment, the first bearing 22 and the second bearing 23 are ball bearings.
The motor case 4 is made of metal such as aluminum. The stator 3 includes: a stator core 30, the stator core 30 being formed of a laminated core; and a coil 33, wherein the coil 33 is wound around each of the plurality of salient poles 31 provided on the stator core 30 via an insulator 32. The stator core 30 is fixed to the inside of the motor case 4 by shrink fitting or press fitting. An annular wiring board 34 is disposed on one side L1 of the stator 3. The wiring board 34 is electrically connected to the coil 33 via terminal pins 35 protruding from the insulator 32.
A lead holder 41 is fixed to a side surface of the motor case 4, and the lead holder 41 covers the notch 40 formed in the motor case 4. Leads (not shown) for supplying power to the coil 33 are inserted into the lead holder 41, introduced into the motor case 4 from the notch 40, and connected to the wiring board 34. The lead wire connected to the wiring board 34 includes a lead wire for supplying power to the electromagnetic brake 7.
The motor 1 is an AC servomotor, and the stator 3 includes three-phase coils 33. In this embodiment, the number of slots in which the coil 33 is disposed is 12. The rotor magnet 21 is an 8-pole magnetized magnet having N poles and S poles alternately magnetized in the circumferential direction on the outer peripheral surface. That is, the motor 1 of the present embodiment is an 8-pole 12-slot motor. The number of poles and slots of the motor 1 may be different from those described above.
The brake housing 6 is made of metal such as aluminum. The brake housing 6 includes: a thick bottom 61 having a concave portion for holding the second bearing 23 formed in the center; and a side wall portion 62 extending from the outer peripheral edge of the bottom portion 61 to the other side L2 in the axial direction L. A small diameter portion 63 fitted into the inner peripheral side of the motor case 4 is formed at the front end of the side wall portion 62. Further, an annular rib 51 fitted into the inner peripheral side of the motor case 4 is formed on the surface of one side L1 of the bearing holder 5 in the axial direction L. When the bearing holder 5 and the brake housing 6 are assembled to both ends of the motor housing 4, the small diameter portion 63 and the gap between the annular rib 51 and the motor housing 4 are sealed with a sealing material, not shown.
The electromagnetic brake 7 includes: a friction plate 71 that rotates integrally with the rotation shaft 20; an armature 72 facing the friction plate 71 from one side L1 in the axial direction L; a torsion spring (not shown) that biases the armature 72 toward the friction plate 71; a plate 73 opposed to the friction plate 71 from the other side L2 in the axial direction L; and a brake stator 74 disposed on one side L1 of the armature 72 in the axial direction L. The brake stator 74 is fixed to the brake housing 6.
The electromagnetic brake 7 applies a rotational load to the rotating shaft 20 by pressing the armature 72 against the friction plate 71 by the torsion spring in a state where the coil of the brake stator 74 is not energized. Thus, a braking force is generated. In addition, in a state where the coil of the brake stator 74 is energized, the armature 72 is attracted to the brake stator 74 against the urging force of the torsion spring, so that a gap is generated between the armature 72 and the friction plate 71. Therefore, the rotational load due to friction is not applied to the rotational shaft 20, so the braking force is released.
The encoder housing 8 is made of a nonmagnetic resin. The encoder housing 8 includes: a bottom 81 opposed to the bottom 61 of the brake housing 6 in the axial direction L; and a side wall portion 82 rising from the outer periphery of the bottom portion 81 toward the bottom portion 61 toward the other side L2. The gap between the front end of the side wall portion 82 and the bottom portion 61 is sealed by the sealing material 9. The side wall 82 is provided with an encoder wiring extracting unit 83 for extracting the encoder wiring 19 connected to the encoder 10 to the outside.
(encoder)
The encoder 10 is a magnetic encoder. The encoder 10 includes: a magnet 12 fixed to the rotary shaft 20 via a magnet holder 11; and a magnetic sensor 13 facing the magnet 12 from one side L1 in the axis direction L. The magnet holder 11 is made of a magnetic material. The magnet 12 has one N pole and one S pole magnetized on each magnetization surface facing the magnetic sensor 13.
The sensor substrate 14 on which the magnetic sensor 13 is disposed is fixed to the bottom 61 of the brake housing 6 via the substrate holder 15. The substrate holder 15 is formed of an insulating material such as resin. The magnet 12 and the sensor substrate 14 are surrounded on the outer peripheral side and one side L1 by a cup-shaped shielding member 16 fixed to the inside of the encoder housing 8. The shielding member 16 is made of a magnetic metal.
Fig. 2 is an enlarged cross-sectional view of a main portion of the encoder 10. Fig. 3 (a) is a plan view of the magnet 12 and the magnet holder 11, and is a view as seen from one side L1 in the axial direction L. Fig. 3 (b) is a plan view of the sensor substrate 14, and is a view as seen from the other side L2 in the axial direction L. As shown in fig. 2 and 3 (a), the magnet holder 11 includes: a circular holding portion 110 as viewed in the axial direction L; and a cylindrical fixing portion 120 protruding from the center of the holding portion 110 toward the other side L2 in the axial direction L. The end of one side L1 of the rotation shaft 20 is fitted into a center hole 130 penetrating the center of the holding portion 110 and the fixing portion 120 in the radial direction.
As shown in fig. 3 (b), the magnetic sensor 13 includes: a magneto-sensitive element 131 arranged in the center of the sensor substrate 14; and two hall elements 132 disposed in the vicinity of the magneto-sensitive element 131. The two hall elements 132 are arranged at angular positions separated by 90 degrees.
The holding portion 110 includes a circular bottom 111 and a peripheral wall 112 protruding from an outer peripheral edge of the bottom 111 to one side L1 in the axial direction L. An annular projection 113 projecting toward one side L1 is provided at the front end of the peripheral wall 112, and a first annular step 114 recessed toward the other side L2 is provided on the inner peripheral side of the annular projection 113. The magnet 12 is fitted into a second annular step portion 115 provided on the inner peripheral side of the first annular step portion 114. As shown in fig. 2, an air gap G of a predetermined size is provided between the front end surface 24 of one side L1 of the rotary shaft 20 and the magnet 12.
In this embodiment, when the encoder 10 is assembled, the magnet holder 11 is positioned to the front end of the rotation shaft 20 using a jig. At this time, the magnet holder 11 is positioned relative to the rotary shaft 20 so that the air gap G between the front end surface 24 of the rotary shaft 20 and the magnet 12 is 0.5mm or more, preferably 0.6mm or more and 1.0mm or less. Thereby, an air gap G is secured between the magnet 12 and the front end surface 24 of the rotary shaft 20.
In this embodiment, since the two-stage stepped portion is provided on the peripheral wall 112 of the magnet holder 11, and the magnet 12 is fitted into the second annular stepped portion 115 which is the stepped portion on the inner peripheral side, the magnet 12 is radially distant from the annular protrusion 113. The magnet 12 is fixed to the magnet holder 11 by an adhesive, and the first annular step 114 is used as an adhesive reservoir for an adhesive (not shown) for fixing the magnet 12. Thus, the fixing strength of the magnet 12 is ensured.
As shown in fig. 2, in this embodiment, the tip of the annular projection 113 projects to one side L1 than the surface 12A of one side L1 in the axial direction L of the magnet 12. When the magnetic flux generated by the electromagnetic brake 7 becomes leakage flux through the rotary shaft 20 and the magnet holder 11, the peripheral wall 112 surrounding the magnet 12 becomes a magnetic path, and the leakage flux leaks from the annular protrusion 113 to the outside of the magnet holder 11 and toward the magnetic sensor side, but in this embodiment, the annular protrusion 113 is radially distant from the magnet 12 because the first annular step 114 is provided on the peripheral wall 112. The tip of the annular projection 113 is located on the side L1 in the axial direction L with respect to the surface 12A of the magnet 12. Therefore, the magnetic circuit is configured such that the leakage magnetic flux leaks from a position away from the magnet 12, and therefore the influence of the leakage magnetic flux on the magnetic field of the magnet 12 is small.
In the encoder 10, the magnet 12 rotates with the rotation of the rotary shaft 20, and a change in the magnetic field caused by the rotation of the magnet 12 is detected from the output of the magnetic sensor 13. The encoder 10 functions as an absolute encoder that discriminates the period of the output of the magneto-sensitive element 131 obtained in one rotation from the outputs of the two hall elements 132, thereby detecting the rotational position of the rotor 2.
(Angle correction of encoder)
Fig. 4 is a block diagram schematically showing a signal processing circuit of the encoder 10. The encoder 10 includes an encoder circuit 17 to which the output of the magnetic sensor 13 is input. The encoder circuit 17 is composed of circuit elements and wiring patterns disposed on the sensor substrate 14. The encoder circuit 17 includes a correction unit 18 for correcting the detection angle obtained from the output of the magnetic sensor 13. The detection angle corrected by the correction unit 18 is output to the outside via an encoder wiring 19 connected to a connector on the sensor substrate 14.
The correction unit 18 performs a process of correcting the detection angle so as to eliminate the leakage magnetic flux, on the assumption that the leakage magnetic flux generated from the electromagnetic brake 7 exists. In the present embodiment, the correction unit 18 performs correction for eliminating the influence of the brake magnetic field generated when the electromagnetic brake 7 is driven by the second voltage lower than the first voltage, which is the specification voltage of the electromagnetic brake 7. Here, the second voltage is 75% of the specification voltage of the electromagnetic brake 7. For example, in the case where the first voltage of the electromagnetic brake 7 is 24V, the second voltage is 75% of the first voltage, which is 18V.
Fig. 5 is a graph showing the influence of the leakage magnetic flux from the electromagnetic brake 7 on the detection error of the encoder 10. The horizontal axis of fig. 5 is the rotational position of the rotor 2. The vertical axis is the detection error, represented by the count value of the encoder pulse. The data of fig. 5 are data of detection errors obtained when the electromagnetic brake 7 is driven in the following six ways in the case where the first voltage (specification voltage) is 24V.
(1) Drive voltage 24V, conventional connection
(2) Drive voltage 18V, conventional connection
(3) Drive voltage 12V, conventional connection
(4) Drive voltage 24V, reverse connection
(5) Drive voltage 18V, reverse connection
(6) Drive voltage 12V, reverse connection
The reverse connection is a state in which the power supply wiring is connected to the electromagnetic brake 7 in a polarity reversing manner. As shown in fig. 5, in the case of reverse connection, the detection error varies greatly depending on the rotational position of the rotor 2. On the other hand, in the conventional connection, the variation of the detection error is small, and the absolute value of the detection error is also smaller than in the case of the reverse connection. In addition, in the case of either one of the normal connection and the reverse connection, as the drive voltage of the electromagnetic brake 7 decreases, the absolute value of the detection error caused by the leakage magnetic flux from the electromagnetic brake 7 decreases.
The correction unit 18 stores data of detection errors generated at the respective rotational positions, and corrects the detection angles outputted from the encoder circuit 17 so as to eliminate the detection errors. At this time, the data of the detection error when the electromagnetic brake 7 is driven at the second voltage (18V) is used as the correction value, instead of the data of the detection error when the electromagnetic brake 7 is driven at the first voltage (24V). In this way, not only when the electromagnetic brake 7 is driven at the standard voltage (24V), but also when the electromagnetic brake is driven at voltages (18V, 12V) different from the standard voltage, the detection error can be reduced.
That is, in this embodiment, when the electromagnetic brake 7 is driven in the manner of (2), the correction is performed in accordance with the correction value corresponding to the detection error generated, so that the detection error can be minimized. Next, in the case where the electromagnetic brake 7 is driven in the manner of the above (1), the detection error generated is larger than the correction value. Therefore, although a part of the detection error cannot be removed, the detection error can be reduced. In the case where the electromagnetic brake 7 is driven in the manner of (3), the detection error generated is smaller than the correction value. Therefore, although the detection error having the opposite sign is remained, the absolute value of the detection error can be reduced.
Next, when the electromagnetic brake 7 is driven in the modes (4) to (6), the detection error can be reduced except for the range where the positive and negative of the generated detection error and the correction value are reversed. According to the data of fig. 5, the detection error is excessively adjusted in such a way that the detection error is increased by correction in the range where the positive and negative of the generated detection error and the correction value are opposite to each other, but such a range is small. In addition, since the correction value is set small (i.e., the detection error when the electromagnetic brake 7 is driven at 18V lower than the specification voltage, that is, 24V, is used as the correction value), the overshoot can be reduced.
(main effects of the present embodiment)
As described above, the motor 1 according to the present embodiment is a motor with a brake, and includes: a rotor 2 provided with a rotation shaft 20; a stator 3 radially opposed to the rotor 2; and an electromagnetic brake 7 disposed on one side L1 of the axis direction L of the rotary shaft 20 with respect to the stator 3, wherein an encoder 10 for detecting the rotation of the rotor 2 is provided. The encoder 10 of the present embodiment includes: a magnet holder 11 fixed to an end portion of one side L1 of the rotation shaft 20 in the axial direction L; a magnet 12 held by the magnet holder 11; a magnetic sensor 13 facing the magnet 12 from one side L1 in the axis direction L, and a sensor substrate 14 on which the magnetic sensor 13 is disposed; and a correction unit 18 for correcting the detection angle obtained from the output of the magnetic sensor 13. The magnet holder 11 includes a peripheral wall 112 surrounding the outer periphery of the magnet 12, and holds the magnet 12 at a position where a predetermined gap (in this embodiment, an air gap G) is provided between the front end surface 24 of the rotary shaft 20 and the magnet 12. The peripheral wall 112 includes an annular projection 113 provided at the front end of one side L1 in the axial direction L, and a first annular step 114 provided on the inner peripheral side of the annular projection 113, and a second annular step 115 into which the magnet 12 is fitted is provided on the inner peripheral side of the first annular step 114. The correction unit 18 corrects the influence of the second voltage lower than the first voltage, which is the specification voltage of the electromagnetic brake 7, on the brake magnetic field generated when the electromagnetic brake 7 is energized.
In this embodiment, since the magnet 12 of the encoder 10 and the rotary shaft 20 are not in contact with each other, the leakage magnetic flux emitted from the end of the rotary shaft 20 does not easily interfere with the magnet 12 directly, and the magnetic field of the magnet 12 is not easily disturbed. Therefore, since the magnetic flux of the magnet 12 can be stabilized, a decrease in the detection accuracy of the encoder 10 due to the leakage magnetic flux from the electromagnetic brake 7 can be suppressed.
In the present embodiment, since the first annular step 114 is provided at the front end of the peripheral wall 112 of the magnet holder 11 and the magnet 12 is disposed in the second annular step 115 provided on the inner peripheral side of the first annular step 114, a radial gap is secured between the magnet holder 11 and the magnet 12, and a gap is secured between the magnetic circuit through which the leakage magnetic flux from the electromagnetic brake 7 passes and the magnet 12. Therefore, the leakage magnetic flux does not easily interfere with the magnet 12 directly, and the magnetic field of the magnet 12 is not easily disturbed. This can suppress a decrease in the detection accuracy of the encoder 10 caused by the leakage magnetic flux from the electromagnetic brake 7.
In this embodiment, on the premise that the output of the magnetic sensor 13 is affected by the leakage magnetic flux from the electromagnetic brake 7 even if the above-described structural countermeasure is taken, correction of detection errors due to the influence of the brake magnetic field generated when the electromagnetic brake 7 is driven at the second voltage lower than the standard voltage (first voltage) is performed to cancel the detection angle of the encoder 10. Thus, even when the voltage lower than the standard voltage is used or the polarity is reversed, the influence of the leakage magnetic flux on the detection accuracy of the encoder 10 can be reduced. In addition, excessive adjustment in which the detection error is increased by correction can be suppressed. Therefore, the reduction in the detection accuracy of the encoder 10 due to the leakage magnetic flux from the electromagnetic brake 7 can be suppressed without using expensive components, including the case where the electromagnetic brake 7 is not used in the specification.
In this embodiment, an air gap G of 0.5mm or more is provided between the front end surface 24 of the rotary shaft 20 and the magnet 12. By providing the air gap G, the path through which the leakage magnetic flux from the electromagnetic brake 7 is transmitted from the rotary shaft 20 to the magnet 12 can be made magnetoresistive, and leakage to the magnet 12 can be continuously attenuated. Therefore, the disturbance of the magnetic flux of the magnet 12 caused by the leakage magnetic flux from the electromagnetic brake 7 can be reduced. The gap between the front end surface 24 of the rotary shaft 20 and the magnet 12 may be not the air gap G, but may be filled with a non-magnetic adhesive.
In this embodiment, the second voltage is 75% of the first voltage. If the correction value is set in this way, even when the electromagnetic brake 7 is used at a voltage different from the standard voltage, the influence of the leakage magnetic flux on the detection accuracy of the encoder 10 is less likely to increase, and the detection error can be reduced. For example, although the minimum voltage at which braking can be released varies depending on the brake, if there is a possibility that the user uses the electromagnetic brake 7 by dropping the voltage to 50% of the standard voltage, by setting the voltage that is the middle of the standard voltage and the voltage that is 50% of the standard voltage to the second voltage, even if the electromagnetic brake is used at any voltage between the standard voltage and the voltage that is 50% of the standard voltage, detection errors of the encoder 10 can be minimized. In addition, when the electromagnetic brake 7 is connected in the opposite polarity, the influence of the leakage magnetic flux on the detection accuracy of the encoder 10 is not easily increased by using such a correction value. Therefore, the detection accuracy of the encoder 10 is not likely to be significantly reduced.
In this embodiment, the annular projection 113 projects toward the one side L1 in the axial direction L than the surface 12A of the one side L1 in the axial direction L of the magnet 12. The annular protrusion 113 constitutes a magnetic path through which the magnetic flux of the electromagnetic brake 7 passes, so if the tip of the annular protrusion 113 is away from the magnet 12, the leakage magnetic flux leaks to the outside from a position away from the magnet 12. Therefore, since the influence of the leakage magnetic flux on the magnetic field of the magnet 12 is small, the degradation of the detection accuracy of the encoder 10 due to the leakage magnetic flux from the electromagnetic brake 7 can be suppressed.
In this embodiment, the gap between the annular protrusion 113 and the magnet 12 is an adhesive reservoir for accommodating the adhesive for fixing the magnet 12. Therefore, the fixing strength of the magnet 12 can be improved by using a structure for reducing the influence of the leakage magnetic flux from the electromagnetic brake 7.
Claims (7)
1. An encoder that detects rotation of a motor with a brake, the motor with a brake comprising: a rotor including a rotation shaft; a stator that is radially opposed to the rotor; and an electromagnetic brake disposed on one side of the stator in the axial direction of the rotating shaft, the electromagnetic brake including:
a magnet holder fixed to an end portion of the rotating shaft on one side in the axial direction;
a magnet held by the magnet holder;
a magnetic sensor facing the magnet from one side in the axial direction, and a sensor substrate on which the magnetic sensor is disposed; and
a correction unit that corrects a detection angle obtained from an output of the magnetic sensor,
the magnet holder includes a peripheral wall surrounding an outer peripheral side of the magnet, and holds the magnet at a position where a predetermined gap is provided between a front end surface of the rotary shaft and the magnet,
the peripheral wall includes an annular protrusion provided at a front end of one side in the axial direction and a first annular step provided on an inner peripheral side of the annular protrusion, a second annular step provided on an inner peripheral side of the first annular step for the magnet to fit in,
the correction unit corrects the electromagnetic brake to eliminate a detection error caused by an influence of a brake magnetic field generated when the electromagnetic brake is energized with a second voltage lower than a first voltage which is a specification voltage of the electromagnetic brake.
2. The encoder of claim 1, wherein the encoder further comprises a decoder,
an air gap of 0.5mm or more is provided between the front end surface of the rotating shaft and the magnet.
3. An encoder according to claim 1 or 2, characterized in that,
the second voltage is 75% of the first voltage.
4. An encoder according to claim 1 or 2, characterized in that,
the annular projection projects further to one side in the axial direction than a surface of the magnet on one side in the axial direction.
5. An encoder according to claim 1 or 2, characterized in that,
the gap between the annular protrusion and the magnet is an adhesive reservoir chamber in which an adhesive for fixing the magnet is contained.
6. An encoder according to claim 1 or 2, characterized in that,
the magnet holder is a magnetic material.
7. An electric motor, comprising:
a rotor including a rotation shaft;
a stator that is radially opposed to the rotor;
an electromagnetic brake disposed on one side of the stator in the axial direction of the rotating shaft; and
an encoder as claimed in any one of claims 1 to 6.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
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| JP2020-160336 | 2020-09-25 | ||
| JP2020160336A JP7517927B2 (en) | 2020-09-25 | 2020-09-25 | Encoders and Motors |
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| CN114257045A CN114257045A (en) | 2022-03-29 |
| CN114257045B true CN114257045B (en) | 2023-11-14 |
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| CN (1) | CN114257045B (en) |
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Also Published As
| Publication number | Publication date |
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| JP7517927B2 (en) | 2024-07-17 |
| JP2022053616A (en) | 2022-04-06 |
| CN114257045A (en) | 2022-03-29 |
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