JP2022053616A - Encoder and motor - Google Patents

Abstract

To suppress the deterioration in encoder detection accuracy even when an electromagnetic brake is not used as specified with an inexpensive configuration.SOLUTION: A motor 1 includes a rotor 2, a stator 3, an electromagnetic brake 7, and an encoder 10. The encoder 10 holds a magnet 12 at a position in which a predetermined air gap G is provided between the encoder and a tip surface 24 of a rotation shaft 20. Further, a peripheral wall 112 of a magnet holder 11 includes a first annular step portion 114 provided on the inner peripheral side of an annular protrusion 113 provided at the tip of one side L1 in an axial direction L, and the magnet 12 fits into a second annular step portion 115 provided on the inner peripheral side of the first annular step portion 114. An encoder circuit 17 includes a correction unit 18 that performs correction processing, for a detection angle obtained from the output of a magnetic sensor 13, of cancelling a detection error due to the influence of the brake magnetic field generated when the electromagnetic brake 7 is driven at a voltage lower than a specified voltage.SELECTED DRAWING: Figure 1

Description

The present invention relates to encoders and motors.

In a motor that houses a stator and a rotor in a tubular motor case, a motor with an encoder that holds an encoder that detects the rotation of the rotor inside the encoder case by fixing the encoder case to the end on the opposite output side of the motor case. It is used. Patent Documents 1 and 2 disclose this type of motor.

The motors of Patent Documents 1 and 2 include an electromagnetic brake arranged on the side opposite to the stator with respect to the stator. In the motor of Patent Document 1, the electromagnetic brake attracts the friction plate fixed to the rotating shaft (motor shaft), the armature pressed against the friction plate by the spring, and the armature in the direction opposite to the urging force of the spring. It is equipped with a brake stator that generates magnetic attraction.

In a motor with a brake, the encoder that detects the rotation of the rotor may be affected by the leakage flux generated from the electromagnetic brake. In the motor of Patent Document 1, a partition plate made of a magnetic member is arranged at the end of the brake case on the non-output side to absorb the leakage flux from the brake to the encoder side. Further, the leakage flux is further reduced by forming a step portion on the inner peripheral surface of the partition plate and the outer peripheral surface of the rotating shaft to form a labyrinth structure, and by using a magnetic member for the substrate holder holding the encoder substrate.

Further, in the motor of Patent Document 2, the output of the encoder is corrected in advance so as to eliminate the influence of the leakage flux on the premise that the leakage flux generated from the electromagnetic brake exists, so that the encoder due to the influence of the leakage flux is used. Suppress the deterioration of detection accuracy.

Japanese Patent No. 5943694 Japanese Unexamined Patent Publication No. 9-2433998

Due to the improvement of the resolution of the encoder, even if the measures as in Patent Document 1 are taken, the influence of the leakage flux on the detection accuracy may become a problem. In order to further reduce the leakage flux, measures are taken to prevent the magnetic flux from leaking to the encoder side via the rotation shaft by using different materials for the non-output side and output side of the rotation shaft, but the component cost There is a problem that it becomes high.

In addition, the motor with an electromagnetic brake may not be used by the user at a voltage according to the brake specifications. For example, it may be used at a voltage lower than the specified voltage for the purpose of reducing heat generation and power consumption of the electromagnetic brake. Further, since the electromagnetic brake operates even if it is connected with the polarity reversed, it may be connected with the wrong polarity and used as it is. As in Patent Document 2, when the influence of the leakage magnetic flux generated from the electromagnetic brake is canceled by the correction, the error of the detection angle due to the leakage magnetic flux can be canceled by the correction when the user uses the voltage and the polarity according to the brake specifications. However, when the user uses the voltage different from the brake specifications, the correction amount does not match the error of the detection angle due to the leakage magnetic flux, and the influence of the leakage magnetic flux cannot be canceled out as targeted. Further, when the user uses the vehicle with the polarity opposite to that of the brake specifications, the correction may cause an overadjustment that greatly increases the error of the detection angle.

In view of the above problems, an object of the present invention is to suppress a decrease in the detection accuracy of the encoder with an inexpensive configuration even when the electromagnetic brake is not used according to the specifications.

In order to solve the above problems, the present invention presents a rotor having a rotating shaft, a stator facing the rotor in the radial direction, and an electromagnetic field arranged on one side of the rotating shaft in the axial direction with respect to the stator. An encoder that detects the rotation of a motor with a brake provided with a brake, a magnet holder fixed to one end of the rotation axis on one side in the axial direction, and a magnet held by the magnet holder. The magnet has a magnetic sensor facing the magnet from one side in the axial direction, a sensor substrate on which the magnetic sensor is arranged, and a correction unit for correcting a detection angle obtained from the output of the magnetic sensor. The magnet holder includes a peripheral wall surrounding the outer peripheral side of the magnet, and holds the magnet at a position where a predetermined gap is provided between the tip surface of the rotating shaft and the magnet, and the peripheral wall holds the magnet at a position where a predetermined gap is provided. An annular protrusion provided at the tip on one side in the axial direction and a first annular step portion provided on the inner peripheral side of the annular protrusion are provided, and the said is provided on the inner peripheral side of the first annular step. A second annular step portion into which a magnet is fitted is provided, and the correction portion is affected by a braking magnetic field generated when the electromagnetic brake is energized with a second voltage lower than the first voltage which is the specification voltage of the electromagnetic brake. It is characterized by making a correction that cancels the detection error due to.

According to the present invention, since the magnet of the encoder is not in contact with the rotating shaft, the leakage flux generated from the end of the rotating shaft 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 of the magnet can be stabilized, it is possible to suppress a decrease in the detection accuracy of the encoder due to the leakage flux from the electromagnetic brake.

Further, according to the present invention, the first annular step portion is provided at the tip of the peripheral wall of the magnet holder, and the magnet fits 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 and the magnet. The magnetic path through which the leakage magnetic flux of the electromagnetic brake passes includes a rotating shaft and a magnet holder. However, in the present invention, a gap is secured between the end of the magnet holder on the magnetic sensor side and the magnet. , The magnetic flux leakage 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, it is possible to suppress a decrease in the detection accuracy of the encoder due to the leakage flux from the electromagnetic brake.

Further, according to the present invention, it is assumed that the leakage magnetic flux from the electromagnetic brake affects the output of the magnetic sensor even if the above structural measures are taken, and the electromagnetic brake is applied to the detection angle of the encoder. Is corrected to cancel the detection error due to the influence of the brake magnetic field that occurs when the brake magnetic field is energized at a voltage lower than the specified voltage. By doing so, the influence of the leakage flux on the detection accuracy of the encoder is reduced even when the user uses the electromagnetic brake at a voltage lower than the specified voltage or when the electromagnetic brake is used with the polarity reversed. It is possible to prevent the detection accuracy of the encoder from deteriorating significantly. In addition, it is possible to suppress over-adjustment in which the detection error becomes large due to the correction. Therefore, it is possible to suppress a decrease in the detection accuracy of the encoder due to the leakage flux from the electromagnetic brake even when the electromagnetic brake is not used according to the specifications without using expensive parts.

In the present invention, it is preferable that an air gap of 0.5 mm or more is provided between the tip surface of the rotating shaft and the magnet. By providing the air gap, it is possible to give magnetic resistance to the path through which the leakage flux of the brake is transmitted from the rotation axis to the magnet, and it is possible to attenuate the continuation of leakage toward the magnet. Therefore, it is possible to reduce the disturbance of the magnetic flux of the magnet due to the leakage flux from the brake.

In the present invention, the second voltage is preferably a voltage that is 75% of the first voltage. In this way, if the electromagnetic brake can be used at a voltage of 50% of the specified voltage, the detection error will be corrected by any voltage between the specified voltage and the voltage of 50% of the specified voltage. Can be reduced, and the influence of the leakage magnetic flux on the detection accuracy of the encoder is unlikely to increase. Further, according to the verification by the present inventors, even when the electromagnetic brakes are connected with opposite polarities, the detection error can be reduced by the correction, and the influence of the leakage flux on the detection accuracy of the encoder is unlikely to increase. Therefore, the detection accuracy of the encoder is unlikely to be significantly reduced.

In the present invention, it is preferable that the annular protrusion protrudes on one side in the axial direction from the surface on one side in the axial direction of the magnet. In this way, the leakage flux from the brake is more likely to collect at the tip of the peripheral wall than the magnet. Therefore, the influence of the leakage 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 protrusion and the magnet is an adhesive reservoir in which the adhesive for fixing the magnet is housed. In this way, the fixing strength of the magnet can be increased by utilizing the structure for reducing the influence of the leakage flux from the electromagnetic brake.

In the present invention, the magnet holder is preferably made of 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 comprises a rotor provided with a rotating shaft, a stator facing the rotor in the radial direction, and an electromagnetic brake arranged on one side of the rotating shaft in the axial direction with respect to the stator. It is characterized by being a motor with a brake equipped with an encoder.

According to the present invention, the leakage flux generated from the end of the rotating shaft is less likely to directly interfere with the magnet, and the magnetic field of the magnet is less likely to be disturbed. Further, according to the present invention, since a gap is secured between the end portion of the magnet holder on the magnetic sensor side and the magnet, the leakage magnetic flux from the electromagnetic brake is unlikely to directly interfere with the magnet and disturbs the magnetic field of the magnet. Hateful. Therefore, since the magnetic flux detected by the magnetic sensor can be stabilized, it is possible to suppress a decrease in the detection accuracy of the encoder due to the leakage flux from the electromagnetic brake.

Further, according to the present invention, it is assumed that the leakage magnetic flux from the electromagnetic brake affects the output of the magnetic sensor even if the above structural measures are taken, and the electromagnetic brake is applied to the detection angle of the encoder. Is corrected to cancel the detection error due to the influence of the brake magnetic field that occurs when the brake magnetic field is energized at a voltage lower than the specified voltage. By doing so, the detection accuracy of the encoder is unlikely to be significantly reduced in various usage modes. In addition, it is possible to suppress over-adjustment in which the detection error becomes large due to the correction. Therefore, it is possible to suppress a decrease in the detection accuracy of the encoder due to the leakage flux from the electromagnetic brake even when the electromagnetic brake is not used according to the specifications without using expensive parts.

It is sectional drawing of the motor provided with the encoder which concerns on this invention. It is an enlarged sectional view of the main part of an encoder. It is a plan view of a magnet and a magnet holder, and is also a plan view of a sensor board. It is a block diagram which shows typically the signal processing circuit of an encoder. It is a graph which shows the influence of the leakage flux from an electromagnetic brake on the detection error of an encoder.

(overall structure)
Hereinafter, embodiments of a motor to which the present invention is applied will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a motor 1 provided with an encoder 10 according to 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 rotating shaft 20, a stator 3 arranged on the outer peripheral side of the rotor 2, a tubular motor case 4 accommodating the stator 3, and a motor case 4. A bearing holder 5 fixed to one end of the motor case 4, a brake case 6 fixed to the other end of the motor case 4, an electromagnetic brake 7 housed in the brake case 6, and an encoder 10 for detecting the rotation of the rotor 2 are provided. The encoder 10 is housed in the encoder case 8.

The rotary shaft 20 extends in the axial direction L at the radial center of the motor 1. In the present specification, one side of the axial direction L is L1 and the other side of the axial direction L is L2. The bearing holder 5 is fixed to the end of L2 on the other side of the motor case 4 in the axial direction L. The rotating 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 counter-output side.

The rotor 2 includes a rotary shaft 20 and a rotor magnet 21 fixed to the outer peripheral surface of the rotary shaft 20. The rotating shaft 20 is made of a magnetic material. The rotary shaft 20 is rotatably held by a first bearing 22 held in a recess formed in the center of the bearing holder 5 and a second bearing 23 held in the brake case 6. In this embodiment, the first bearing 22 and the second bearing 23 are ball bearings.

The motor case 4 is made of a metal such as aluminum. The stator 3 includes a stator core 30 made of a laminated core and a coil 33 wound around each of a 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 arranged on one side L1 of the stator 3. The wiring board 34 is electrically connected to the coil 33 via a terminal pin 35 protruding from the insulator 32.

A lead wire holder 41 that covers the notch 40 formed in the motor case 4 is fixed to the side surface of the motor case 4. The lead wire (not shown) for supplying power to the coil 33 is routed inside the lead wire holder 41, drawn from the notch 40 into the inside of the motor case 4, 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 a three-phase coil 33. In this embodiment, the number of slots in which the coil 33 is arranged is 12. Further, the rotor magnet 21 is an 8-pole magnetizing magnet in which N poles and S poles are alternately magnetized in the circumferential direction on the outer peripheral surface. That is, the motor 1 of this embodiment has 8 poles and 12 slots. The number of poles and the number of slots of the motor 1 may be different from the above.

The brake case 6 is made of a metal such as aluminum. The brake case 6 includes a thick-walled bottom portion 61 having a recess formed in the center for holding the second bearing 23, 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. At the tip of the side wall portion 62, a small diameter portion 63 that fits on the inner peripheral side of the motor case 4 is formed. Further, an annular rib 51 that fits on 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 assembling the bearing holder 5 and the brake case 6 to both ends of the motor case 4, the gap between the small diameter portion 63 and the annular rib 51 and the motor case 4 is sealed with a sealing material (not shown).

The electromagnetic brake 7 includes a friction plate 71 that rotates integrally with the rotating shaft 20, an armature 72 that faces the friction plate 71 from one side L1 in the axial direction L, and a torque spring that urges the armature 72 toward the friction plate 71. (Not shown), a plate 73 facing the friction plate 71 from the other side L2 in the axial direction L, and a brake stator 74 arranged on the one side L1 in the axial direction L with respect to the armature 72. The brake stator 74 is fixed to the brake case 6.

In the electromagnetic brake 7, when the coil of the brake stator 74 is not energized, the armature 72 is pressed against the friction plate 71 by a torque spring, and a rotational load is applied to the rotary shaft 20. Therefore, a braking force is generated. Further, when 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 torque spring, so that a gap is generated between the armature 72 and the friction plate 71. .. Therefore, since the rotational load due to friction is not applied to the rotary shaft 20, the braking force is released.

The encoder case 8 is made of a non-magnetic resin. The encoder case 8 includes a bottom portion 81 facing the bottom portion 61 of the brake case 6 in the axial direction L, and a side wall portion 82 rising from the outer peripheral edge of the bottom portion 81 toward the bottom portion 61 toward the other side L2. The gap between the tip of the side wall portion 82 and the bottom portion 61 is sealed by the sealing material 9. The side wall portion 82 is provided with an encoder wiring take-out portion 83 for drawing out 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 rotating shaft 20 via a magnet holder 11 and a magnetic sensor 13 facing the magnet 12 from one side L1 in the axial direction L. The magnet holder 11 is made of a magnetic material. The magnet 12 has one north pole and one south pole magnetized on the magnetizing surface facing the magnetic sensor 13.

The sensor board 14 on which the magnetic sensor 13 is arranged is fixed to the bottom 61 of the brake case 6 via the board 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 by a cup-shaped shield member 16 fixed to the inside of the encoder case 8 on the outer peripheral side and one side L1. The shield member 16 is made of magnetic metal.

FIG. 2 is an enlarged cross-sectional view of a main part of the encoder 10. FIG. 3A is a plan view of the magnet 12 and the magnet holder 11 as viewed from one side L1 in the axial direction L. FIG. 3B is a plan view of the sensor substrate 14 and is a view seen from the other side L2 in the axial direction L. As shown in FIGS. 2 and 3A, the magnet holder 11 has a circular holding portion 110 when viewed from the axial direction L, and a cylindrical shape protruding from the center of the holding portion 110 to the other side L2 in the axial direction L. A fixing portion 120 is provided. The end of L1 on one side of the rotating shaft 20 is fitted in a center hole 130 penetrating the radial center of the holding portion 110 and the fixing portion 120.

As shown in FIG. 3B, the magnetic sensor 13 includes a magnetic sensing element 131 arranged in the center of the sensor substrate 14 and two Hall elements 132 arranged in the vicinity of the magnetic sensing element 131. The two Hall elements 132 are arranged at an angle position 90 degrees apart.

The holding portion 110 includes a circular bottom portion 111 and a peripheral wall 112 projecting from the outer peripheral edge of the bottom portion 111 to one side L1 in the axial direction L. An annular protrusion 113 projecting to one side L1 is provided at the tip of the peripheral wall 112, and a first annular step 114 recessing to the other side L2 is provided on the inner peripheral side of the annular protrusion 113. The magnet 12 fits into the second annular step 115 provided on the inner peripheral side of the first annular step 114. As shown in FIG. 2, an air gap G having a predetermined dimension is provided between the tip surface 24 of one side L1 of the rotating shaft 20 and the magnet 12.

In this embodiment, when assembling the encoder 10, the magnet holder 11 is positioned at the tip of the rotating shaft 20 by using a jig. At that time, the magnet with respect to the rotating shaft 20 so that the air gap G between the tip surface 24 of the rotating shaft 20 and the magnet 12 has a dimension of 0.5 mm or more, preferably 0.6 mm or more and 1.0 mm or less. Position the holder 11. As a result, an air gap G is secured between the magnet 12 and the tip surface 24 of the rotating shaft 20.

In this embodiment, the peripheral wall 112 of the magnet holder 11 is provided with stepped portions in two stages, and the magnet 12 is fitted in the second annular stepped portion 115 which is the stepped portion on the inner peripheral side. It is radially separated from the annular protrusion 113. The magnet 12 is fixed to the magnet holder 11 by an adhesive, and the first annular step portion 114 is used as an adhesive reservoir for arranging an adhesive (not shown) for fixing the magnet 12. Therefore, the fixing strength of the magnet 12 is ensured.

As shown in FIG. 2, in the present embodiment, the tip of the annular protrusion 113 protrudes from the surface 12A on one side L1 in the axial direction L of the magnet 12 toward L1 on one side. When the magnetic flux generated by the electromagnetic brake 7 passes through the rotating shaft 20 and the magnet holder 11 and becomes a leakage magnetic flux, the peripheral wall 112 surrounding the magnet 12 becomes a magnetic path and leaks from the annular protrusion 113 to the outside of the magnet holder 11. The magnetic flux is emitted toward the magnetic sensor side, but in this embodiment, since the peripheral wall 112 is provided with the first annular step portion 114, the annular protrusion 113 is radially separated from the magnet 12. Further, the tip of the annular protrusion 113 is located on one side L1 of the axial direction L with respect to the surface 12A of the magnet 12. Therefore, since the magnetic path is configured so that the leakage flux is generated from a position away from the magnet 12, the influence of the leakage flux on the magnetic field of the magnet 12 is small.

The encoder 10 rotates the magnet 12 with the rotation of the rotating shaft 20, and detects a change in the magnetic field due to the rotation of the magnet 12 from the output of the magnetic sensor 13. The encoder 10 functions as an absolute encoder that detects the rotation position of the rotor 2 by discriminating the output cycle of the magnetic sensing element 131 obtained in one rotation from the outputs of the two Hall elements 132.

(Encoder angle correction)
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 arranged on the sensor board 14. The encoder circuit 17 includes a correction unit 18 that corrects a 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 the encoder wiring 19 connected to the connector on the sensor board 14.

The correction unit 18 performs a process of correcting the detection angle so as to cancel the leakage flux on the premise that the leakage flux generated from the electromagnetic brake 7 exists. In the present embodiment, the correction unit 18 makes corrections to cancel the influence of the brake magnetic field generated when the electromagnetic brake 7 is driven with a second voltage lower than the first voltage which is the specification voltage of the electromagnetic brake 7. Here, the second voltage is a voltage that is 75% of the specified voltage of the electromagnetic brake 7. For example, when 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 flux from the electromagnetic brake 7 on the detection error of the encoder 10. The horizontal axis of FIG. 5 is the rotation position of the rotor 2. The vertical axis represents the detection error and is indicated by the number of encoder pulse counts. The data of FIG. 5 is the data of the detection error obtained when the electromagnetic brake 7 is driven in the following six types when the first voltage (specification voltage) is 24V.
(1) Drive voltage 24V, Regular connection (2) Drive voltage 18V, Regular connection (3) Drive voltage 12V, Regular 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 feeding wiring is connected to the electromagnetic brake 7 with the polarity reversed. As shown in FIG. 5, when the connection is reversed, the detection error greatly varies depending on the rotation position of the rotor 2. On the other hand, in the normal connection, the fluctuation of the detection error is small, and the absolute value of the detection error is smaller than in the case of the reverse connection. Further, in both the normal connection and the reverse connection, the absolute value of the detection error due to the leakage flux from the electromagnetic brake 7 becomes smaller as the driving voltage of the electromagnetic brake 7 becomes smaller.

The correction unit 18 stores the data of the detection error generated at each rotation position, and corrects the detection angle output from the encoder circuit 17 to cancel the detection error. At that time, not the data of the detection error when the electromagnetic brake 7 is driven by the first voltage (24V), but the data of the detection error when the electromagnetic brake 7 is driven by the second voltage (18V) is used as the correction value. By doing so, the detection error can be reduced not only when the electromagnetic brake 7 is driven at the specified voltage (24V) but also when the electromagnetic brake 7 is driven at a voltage different from the specified voltage (18V, 12V).

That is, in the present embodiment, when the electromagnetic brake 7 is driven in the aspect of (2) above, the correction is performed with the correction value according to the detection error that occurs, so that the detection error can be minimized. Next, when the electromagnetic brake 7 is driven in the mode of (1) above, the detection error that occurs is larger than the correction value. Therefore, although a part of the detection error cannot be removed, the detection error can be reduced. Further, when the electromagnetic brake 7 is driven in the aspect of (3) above, the detection error that occurs is smaller than the correction value. Therefore, although a detection error in which the positive and negative directions are opposite remains, the absolute value of the detection error can be reduced.

Next, when the electromagnetic brake 7 is driven in the manners (4) to (6) above, the detection error can be reduced except in the range where the positive and negative of the detected error and the correction value are opposite to each other. can. According to the data of FIG. 5, in the range where the positive and negative of the detection error and the correction value are reversed, the detection error is conversely increased by the correction, but such a range is small. Further, since the correction value is set small (that is, the detection error when the electromagnetic brake 7 is driven at 18V, which is lower than the specified voltage of 24V, is used as the correction value), over-adjustment can be reduced. ..

(Main effect of this form)
As described above, the motor 1 of the present embodiment includes the rotor 2 provided with the rotating shaft 20, the stator 3 that faces the rotor 2 in the radial direction, and L1 on one side of the axial direction L of the rotating shaft 20 with respect to the stator 3. It is a motor with a brake provided with an electromagnetic brake 7 arranged in, and includes an encoder 10 for detecting the rotation of the rotor 2. The encoder 10 of the present embodiment has a magnet holder 11 fixed to the end of L1 on one side of the axial direction L of the rotating shaft 20, a magnet 12 held by the magnet holder 11, and one side of the axial direction L on the magnet 12. It has a magnetic sensor 13 facing from L1, a sensor substrate 14 on which the magnetic sensor 13 is arranged, and a correction unit 18 for correcting a detection angle obtained from the output of the magnetic sensor 13. The magnet holder 11 includes a peripheral wall 112 that surrounds the outer peripheral side of the magnet 12, and a magnet at a position where a predetermined gap (air gap G in this embodiment) is provided between the tip surface 24 of the rotating shaft 20 and the magnet 12. Holds twelve. Further, the peripheral wall 112 includes an annular protrusion 113 provided at the tip of L1 on one side of the axial direction L, and a first annular step 114 provided on the inner peripheral side of the annular protrusion 113. A second annular step 115 into which the magnet 12 is fitted is provided on the inner peripheral side of the annular step 114. Further, the correction unit 18 makes corrections to cancel the influence of the brake magnetic field generated when the electromagnetic brake 7 is energized with a second voltage lower than the first voltage which is the specification voltage of the electromagnetic brake 7.

In this embodiment, since the magnet 12 of the encoder 10 and the rotating shaft 20 are not in contact with each other, the leakage flux generated from the end of the rotating shaft 20 is less likely to directly interfere with the magnet 12, and the magnetic field of the magnet 12 is less likely to be disturbed. Therefore, since the magnetic flux of the magnet 12 can be stabilized, it is possible to suppress a decrease in the detection accuracy of the encoder 10 due to the leakage flux from the electromagnetic brake 7.

Further, in the present embodiment, the first annular step portion 114 is provided at the tip of the peripheral wall 112 of the magnet holder 11, and the magnet 12 is arranged on the second annular step portion 115 provided on the inner peripheral side of the first annular step portion 114. Therefore, a radial gap is secured between the magnet holder 11 and the magnet 12, and a gap is secured between the magnetic path through which the leakage magnetic flux from the electromagnetic brake 7 passes and the magnet 12. Therefore, the leakage flux is less likely to directly interfere with the magnet 12, and the magnetic field of the magnet 12 is less likely to be disturbed. Therefore, it is possible to suppress a decrease in the detection accuracy of the encoder 10 due to the leakage flux from the electromagnetic brake 7.

Further, in this embodiment, it is assumed that the leakage magnetic flux from the electromagnetic brake 7 affects the output of the magnetic sensor 13 even if the above structural measures are taken, and the electromagnetic field is applied to the detection angle of the encoder 10. The correction is performed to cancel the detection error due to the influence of the brake magnetic field generated when the brake 7 is driven by the second voltage lower than the specified voltage (first voltage). As a result, it is possible to reduce the influence of the leakage flux on the detection accuracy of the encoder 10 even when the encoder 10 is used at a voltage lower than the specified voltage or the polarity is reversed. In addition, it is possible to suppress over-adjustment in which the detection error becomes large due to the correction. Therefore, it is possible to suppress a decrease in the detection accuracy of the encoder 10 due to the leakage flux from the electromagnetic brake 7 even when the electromagnetic brake 7 is not used according to the specifications without using expensive parts.

In this embodiment, an air gap G of 0.5 mm or more is provided between the tip surface 24 of the rotating shaft 20 and the magnet 12. By providing the air gap G, magnetic resistance can be provided in the path in which the leakage flux from the electromagnetic brake 7 is transmitted from the rotating shaft 20 to the magnet 12, and the leakage continuation toward the magnet 12 can be attenuated. Therefore, it is possible to reduce the disturbance of the magnetic flux of the magnet 12 due to the leakage flux from the electromagnetic brake 7. The gap between the tip surface 24 of the rotating shaft 20 and the magnet 12 does not have to be the air gap G, and may be filled with a non-magnetic adhesive.

In this embodiment, the second voltage is a voltage that is 75% of the first voltage. When the correction value is set in this way, even when the electromagnetic brake 7 is used at a voltage different from the specified voltage, the influence of the leakage flux on the detection accuracy of the encoder 10 is unlikely to be large, and the detection error can be reduced. For example, the minimum voltage at which the brake can be released varies depending on the brake, but if the user has the possibility of using the electromagnetic brake 7 by lowering it to 50% of the specified voltage, the specified voltage and 50% of the specified voltage may be used. By setting the voltage in the middle of the voltage to the second voltage, the detection error of the encoder 10 is minimized regardless of whether the voltage is between the specified voltage and the voltage of 50% of the specified voltage. can do. Further, even when the electromagnetic brake 7 is connected with the opposite polarity, the influence of the leakage flux on the detection accuracy of the encoder 10 is unlikely to increase by using such a correction value. Therefore, the detection accuracy of the encoder 10 is unlikely to be significantly reduced.

In this embodiment, the annular protrusion 113 projects from the surface 12A of one side L1 of the axial direction L of the magnet 12 to the one side L1 of the axial direction L. Since the annular protrusion 113 constitutes a magnetic path through which the magnetic flux of the electromagnetic brake 7 passes, if the tip of the annular protrusion 113 is away from the magnet 12, the leakage flux is discharged from a position away from the magnet 12. Get out. Therefore, since the influence of the leakage flux on the magnetic field of the magnet 12 is small, it is possible to suppress the deterioration of the detection accuracy of the encoder 10 due to the leakage flux from the electromagnetic brake 7.

In the present embodiment, the gap between the annular protrusion 113 and the magnet 12 is an adhesive pool in which the adhesive for fixing the magnet 12 is housed. Therefore, the fixing strength of the magnet 12 can be increased by utilizing the structure for reducing the influence of the leakage flux from the electromagnetic brake 7.

1 ... motor, 2 ... rotor, 3 ... stator, 4 ... motor case, 5 ... holder, 6 ... brake case, 7 ... electromagnetic brake, 8 ... encoder case, 9 ... sealing material, 10 ... encoder, 11 ... magnet holder, 12 ... Magnet, 12A ... One surface in the axial direction of the magnet, 13 ... Magnetic sensor, 14 ... Sensor board, 15 ... Board holder, 16 ... Shield member, 17 ... Encoder circuit, 18 ... Correction unit, 19 ... Encoder wiring , 20 ... rotary shaft, 20A ... output shaft, 21 ... rotor magnet, 22 ... first bearing, 23 ... second bearing, 24 ... tip surface, 30 ... stator core, 31 ... salient pole, 32 ... insulator, 33 ... coil, 34 ... wiring board, 35 ... terminal pin, 40 ... notch, 41 ... lead wire holder, 51 ... annular rib, 61 ... bottom, 62 ... side wall, 63 ... small diameter, 71 ... friction plate, 72 ... armature, 73 ... plate, 74 ... brake stator, 81 ... bottom, 82 ... side wall, 83 ... encoder wiring take-out part, 110 ... holding part, 111 ... bottom, 112 ... peripheral wall, 113 ... annular protrusion, 114 ... first annular Step portion, 115 ... Second annular step portion, 120 ... Fixed portion, 130 ... Center hole, 131 ... Magnetic element, 132 ... Hall element, G ... Air gap, L ... Axial direction, L1 ... One side in the axial direction, L2 ... The other side in the axial direction

Claims (7)

Rotation of a motor with a brake including a rotor provided with a rotating shaft, a stator facing the rotor in the radial direction, and an electromagnetic brake arranged on one side of the rotating shaft in the axial direction with respect to the stator. An encoder that detects
A magnet holder fixed to one end of the rotating shaft on one side in the axial direction,
The magnet held in the magnet holder and
A magnetic sensor facing the magnet from one side in the axial direction, and a sensor substrate on which the magnetic sensor is arranged.
It has a correction unit that corrects the detection angle obtained from the output of the magnetic sensor.
The magnet holder includes a peripheral wall surrounding the outer peripheral side of the magnet, and holds the magnet at a position where a predetermined gap is provided between the tip surface of the rotating shaft and the magnet.
The peripheral wall includes an annular protrusion provided at the tip on one side in the axial direction and a first annular step provided on the inner peripheral side of the annular protrusion, and the peripheral wall comprises the first annular step. A second annular step portion into which the magnet is fitted is provided on the inner peripheral side.
The correction unit is characterized in that it performs correction for canceling a detection error due to the influence of a brake magnetic field generated when the electromagnetic brake is energized with a second voltage lower than the first voltage which is a specification voltage of the electromagnetic brake. Encoder. The encoder according to claim 1, wherein an air gap of 0.5 mm or more is provided between the tip surface of the rotating shaft and the magnet. The encoder according to claim 1 or 2, wherein the second voltage is a voltage that is 75% of the first voltage. The encoder according to any one of claims 1 to 3, wherein the annular protrusion protrudes from the surface of the magnet on one side in the axial direction to one side in the axial direction. The encoder according to any one of claims 1 to 4, wherein the gap between the annular protrusion and the magnet is an adhesive reservoir in which an adhesive for fixing the magnet is housed. The encoder according to any one of claims 1 to 5, wherein the magnet holder is a magnetic material. A rotor provided with a rotating shaft, a stator facing the rotor in the radial direction, an electromagnetic brake arranged on one side of the rotating shaft in the axial direction with respect to the stator, and any one of claims 1 to 6. A motor comprising the encoders described in the section.

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