JP2018074768A - Actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator incorporated with a reverse input shutoff clutch as a brake, which allows a member to be driven to be accurately positioned even when a rotation direction thereof is reversed.SOLUTION: When a rotation direction of an actuator is reversed, in a reverse input shutoff clutch, a gap in the rotation direction between an engagement part 8a of a motor shaft (an input side member) 8 and an inner surface of an engagement hole 9a of an intermediate shaft (an output side member) 9 is backlashed, so that only the motor shaft 8 is rotated when starting rotation. Therefore, even if the motor shaft 8 engages with the intermediate shaft 9 and the intermediate shaft 9 starts to rotate later, rotation of the intermediate shaft 9 and an output shaft connected to the intermediate shaft still delays to rotation of the motor shaft 8. To solve such problem, the actuator is configured so that a control unit for controlling a motor controls the motor, by determining required rotation speed of the motor shaft 8 on the basis of the total of a rotation angle between a position in the rotation direction of the output shaft and a target position and a prescribed rotation-delay angle of the output shaft at the time of reversing the rotation direction, so that delay in rotation of the output shaft is absorbed and a member to be driven can be accurately positioned.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an actuator including a brake that holds a position of a driven member when a motor stops.

  In an actuator that is used for a robot joint or the like and that operates a driven member by driving a motor, when the motor stops due to a power failure or the like, the driven member receives an external force such as gravity to change its position (posture). Various problems may occur due to the change. For this reason, a brake that normally holds the position of the driven member when the motor is stopped (hereinafter, a member having the same function is also simply referred to as a “brake”) is provided.

  As the brake for the actuator as described above, a non-excitation operation type electromagnetic brake that operates when a non-energized state is often used. However, in an actuator incorporating a non-excitation operation type electromagnetic brake, it is necessary to always supply electric power to the electromagnetic brake so that the brake is not applied while the motor is rotating, and there is a problem that power consumption increases.

  On the other hand, when input torque is applied to the input side member, the rotation is transmitted to the output side member, and when reverse input torque is applied to the output side member, the output side member is stopped. An actuator using a clutch (reverse input shut-off mechanism) as a brake (for example, see Patent Document 1) does not require electric power to prevent the brake from being applied during motor rotation. The power consumption can be reduced compared to the built-in one.

JP2015-206455A

  By the way, the reverse input cutoff clutch used as the brake of the actuator as described above is configured such that the input side member rotates between the input side member and the output side member rotating around the same axis as the output side member. Torque transmission means is provided, a fixed outer ring is arranged on the radially outer side of the output side member, a plurality of cam surfaces are provided on the outer peripheral surface of the output side member, and each of the inner peripheral cylindrical surface of the outer ring and the output side member is provided. A wedge-shaped space that gradually narrows on both sides in the circumferential direction is formed between the cam surface, and a pair of rollers and a spring that pushes the pair of rollers into the narrow portion of the wedge-shaped space are incorporated in each wedge-shaped space. In many cases, a column part of an unlocking piece that rotates integrally with the input side member is inserted on both sides in the circumferential direction (positions facing the spring in the circumferential direction with the rollers in between).

  According to this configuration, even when reverse input torque is applied to the output side member, the output side member is locked by engaging the rollers on the rear side in the rotation direction with the outer ring and the output side member. On the other hand, when an input torque is applied to the input side member, the column portion of the unlocking piece that rotates together with the input side member pushes the roller on the rear side in the rotation direction against the elastic portion of the spring to the wide portion of the wedge-shaped space. As a result, the engagement between the roller and the outer ring and the output side member is released and the output side member is released from the locked state, and then the rotation is transmitted from the input side member to the output side member by the torque transmitting means.

  However, in order to transmit rotation to the output side member after unlocking the output side member with respect to the input torque as described above, it is necessary to provide a slight rotational direction gap between the input side member and the output side member. When the rotation direction gap is reversed and the rotation direction is reversed, it is inevitable that rotation delay of the output side member with respect to the input side member occurs.

  For this reason, in the actuator incorporating the reverse input cutoff clutch having the above-described configuration, when the rotation direction is reversed, the control device that controls the motor stops the motor before the driven member reaches the target position. There is a drawback that positioning errors of the driven member occur.

  Accordingly, an object of the present invention is to enable accurate positioning of a driven member even when the rotation direction is reversed in an actuator incorporating a reverse input cutoff clutch as a brake.

  In order to solve the above-described problems, the present invention provides a motor, an output shaft to which rotation is transmitted from the motor shaft of the motor, and a motor shaft necessary for matching the rotational direction position of the output shaft with a target position. And a control device for controlling the motor so that the motor shaft rotates by the number of rotations, and the motor as a brake that holds the rotational direction position of the output shaft when the motor stops In an actuator in which a rotation of the motor shaft is transmitted to the output shaft between the shaft and the output shaft, and a reverse input cutoff clutch for stopping the output shaft against reverse input torque applied to the output shaft is incorporated The control device, when reversing the rotation direction of the motor shaft and the output shaft, and the rotation angle from the rotation direction position of the output shaft to the target position, and a preset reversal time Based on the sum of the rotational delay angle of the power shaft, to employ a configuration in which adjusting the number of rotations of the motor shaft.

  According to the above configuration, when the rotation directions of the motor shaft and the output shaft are reversed, the motor shaft is added to the rotation angle from the rotation direction position of the output shaft to the target position in addition to the preset reversal. Since the rotation corresponding to the rotation delay angle of the output shaft at the time is also rotated, the positioning error of the driven member due to the backlash of the reverse input cutoff clutch incorporated as a brake can be reduced.

  In the above configuration, when the output shaft can be applied with reverse input torque by the weight of the driven member connected to the output shaft, the control device can The number of rotations of the motor shaft is preset when the direction of reverse input torque applied to the output shaft by the weight of the driven member changes from the opposite direction to the same direction as the input torque applied to the motor shaft by the motor. When the direction of the reverse input torque changes from the same direction as the input torque to the reverse direction, the number of rotations of the motor shaft is set to a preset output shaft. It is preferable to increase the amount corresponding to the rotation delay angle. In this way, even when reverse input torque is applied by the weight of the driven member during driving of the motor, the driven member can be accurately positioned.

  As the reverse input cutoff clutch, an input side member receiving input torque from the motor shaft and an output side member receiving reverse input torque from the output shaft are arranged in a state of rotating around the same axis, Torque transmitting means for transmitting the rotation of the input side member to the output side member is provided between the member and the output side member, and a fixed outer ring is disposed on the radially outer side of the output side member, and the output side A plurality of cam surfaces are provided on the outer peripheral surface of the member, and a wedge-shaped space gradually narrowing on both sides in the circumferential direction is formed between the inner peripheral cylindrical surface of the outer ring and each cam surface of the output side member. In each wedge-shaped space, a pair of rollers and an elastic member that is sandwiched between the pair of rollers and pushes each roller into the narrow portion of the wedge-shaped space are incorporated. The unlocking piece has It can be adopted those which are non-rotatably connected to the force member.

  As described above, the actuator of the present invention has a control device that controls the motor so that the rotational position of the output shaft matches the target position. Since the required number of rotations of the motor shaft is adjusted in consideration of the rotation delay, positioning of the driven member connected to the output shaft is accurate even when the rotation direction of the motor shaft and output shaft is reversed. Can be done.

Vertical front view of the actuator of the embodiment The principal part expanded sectional view along the II-II line of FIG. The principal part expanded sectional view along the III-III line of FIG. FIGS. 3A and 3B are cross-sectional views for explaining the operation when driving of the motor is started corresponding to FIG. a and b are sectional views for explaining the operation when the rotation direction is reversed corresponding to FIG. Sectional drawing explaining operation | movement when the direction of reverse input torque changes from the direction opposite to input torque to the same direction during motor drive corresponding to FIG. Sectional drawing explaining operation | movement when the direction of reverse input torque changes from the same direction as input torque to the reverse direction during a motor drive corresponding to FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, this actuator incorporates a reverse input cutoff clutch 2 as a brake, a wave gear device 3 as a speed reduction mechanism, and a cross roller bearing 4 on the output side of the motor 1. The motor 1 is controlled by a control device including an attached encoder (rotation detector) 5 and a controller (not shown). The motor 1 is driven by an output shaft 6 fitted and fixed to the inner periphery of the cross roller bearing 4. An actuated driven member (not shown) is connected.

  The motor 1 has a motor housing 7 fixed to an external member (not shown), and integrally supports the reverse input cutoff clutch 2, the wave gear device 3, and the cross roller bearing 4 as will be described later. . A motor shaft 8 partially protruding from the motor housing 7 is an input side member of the reverse input cutoff clutch 2.

  As shown in FIGS. 1 and 2, the reverse input cutoff clutch 2 is a motor shaft 8 that serves as an input side member, an intermediate shaft 9 that serves as an output side member, and a stationary arrangement that is arranged on the radially outer side of the intermediate shaft 9. The outer ring 10, the unlocking piece 11 having a plurality of column portions 11a inserted between the intermediate shaft 9 and the outer ring 10, the roller 12 incorporated between the intermediate shaft 9 and the outer ring 10, and the coil spring (elastic) Member) 13 and a brake housing 14 in which the outer ring 10 is integrally formed. As the input side member, a shaft-like member that receives input torque from the motor shaft 8 may be incorporated separately from the motor shaft 8. Further, the coil spring can be replaced with another elastic member such as a leaf spring.

  The motor shaft 8 has an engaging portion 8a having a two-sided width formed on the outer periphery thereof inserted into an engaging hole 9a provided in the intermediate shaft 9, and a small-diameter cylindrical portion protruding from the end surface of the engaging portion 8a. The intermediate shaft 9 is slidably fitted into a circular hole provided at the bottom of the engagement hole 9 a and rotates about the same axis as the intermediate shaft 9. On the other hand, one end portion (end portion on the output side) of the intermediate shaft 9 is formed in a semicircular cross section and is connected to the input side of the wave gear device 3 as described later at one end portion of the semicircular cross section. Yes.

  Here, as shown in FIG. 3, the engagement hole 9 a of the intermediate shaft 9 is formed so that a slight clearance in the rotational direction is generated when the engagement portion 8 a of the motor shaft 8 is inserted. Torque transmission means for transmitting the rotation to the intermediate shaft 9 with a slight angular delay is configured. A plurality of cam surfaces 9 b are provided in the circumferential direction on the outer periphery of the intermediate shaft 9, and a wedge-shaped space 15 that gradually narrows on both sides in the circumferential direction between the inner peripheral cylindrical surface of the outer ring 10 and each cam surface 9 b of the intermediate shaft 9. Is formed. A pair of rollers 12 is incorporated in each wedge-shaped space 15, and the coil spring 13 is assembled so as to be sandwiched between the pair of rollers 12, and each roller 12 is pushed into a narrow portion of the wedge-shaped space 15.

  As shown in FIGS. 2 and 3, the pillar portions 11 a of the unlocking pieces 11 are provided on both sides in the circumferential direction of each wedge-shaped space 15 (positions facing the coil springs 13 in the circumferential direction across the rollers 12). The lock release piece 11 is inserted into the outer periphery of the engaging portion 8 a of the motor shaft 8 without a gap, and rotates integrally with the motor shaft 8.

  In this reverse input shut-off clutch 2, each roller 12 is pushed into the narrow portion of the wedge-shaped space 15 by the elasticity of the coil spring 13, so that even if reverse input torque is applied to the intermediate shaft 9, the rollers on the rear side in the rotation direction When 12 engages with the outer ring 10 and the intermediate shaft 9, the intermediate shaft 9 is locked and does not rotate.

  On the other hand, when an input torque is applied to the motor shaft 8, first, as shown in FIG. 4A, as the motor shaft 8 rotates, the column portion 11a of the unlocking piece 11 integrated with the motor shaft 8 is used. When the roller 12 on the rear side in the rotational direction is pushed out against the elasticity of the coil spring 13 to the wide part of the wedge-shaped space 15, the engagement between the roller 12, the outer ring 10 and the intermediate shaft 9 is released, and the intermediate shaft 9 is released from the locked state. As shown in FIG. 4B, when the motor shaft 8 further rotates and the engaging portion 8a of the motor shaft 8 engages with the engaging hole 9a of the intermediate shaft 9, the rotation of the motor shaft 8 is intermediate. (At this time, the roller 12 on the front side in the rotational direction moves relative to the wide portion of the wedge-shaped space 15 and therefore does not engage with the outer ring 10 and the intermediate shaft 9).

  The wave gear device 3 includes a rotation transmission shaft 16 connected to the intermediate shaft 9 of the reverse input cutoff clutch 2 on the input side, a wave generator 17 bolted to the flange portion 16a of the rotation transmission shaft 16, and a wave generator. 17 is provided with a circular spline 18 disposed on the radially outer side of 17, and a flex spline 19 having a large diameter portion sandwiched between the wave generator 17 and the circular spline 18.

  The rotation transmission shaft 16 has a flange portion 16a formed at the input side end, and one end portion of the intermediate shaft 9 of the reverse input cutoff clutch 2 is connected to a semicircular cross-sectional connection hole provided on the input side end surface. By being fitted, it is connected to the intermediate shaft 9 so as not to be relatively rotatable.

  The wave generator 17 is obtained by fitting and fixing an inner ring of a ball bearing 17b on the outer periphery of a cam 17a having a radial cross section formed in an elliptical shape. The circular spline 18 is an annular component having teeth provided on the inner periphery thereof, and an outer peripheral portion thereof is integrated with the brake housing 14 as will be described later. Further, the flex spline 19 is a thin cup-shaped part formed of a metal elastic body, and teeth that mesh with the teeth of the inner periphery of the circular spline 18 are provided on the outer periphery of the large diameter portion, and the cross roller bearing 4 of the small diameter portion. The inner ring 20 is bolted.

  Then, when rotation is transmitted from the intermediate shaft 9 of the reverse input cutoff clutch 2 to the rotation transmission shaft 16 and the wave generator 17 rotates together with the rotation transmission shaft 16, the inner diameter of the large-diameter portion is formed on the outer ring of the ball bearing 17 b of the wave generator 17. The flex spline 19 pressed is elastically deformed to change the meshing position with the circular spline 18, thereby rotating integrally with the inner ring 20 of the cross roller bearing 4 by the difference in the number of teeth with the circular spline 18. A large reduction ratio can be obtained.

  In the cross roller bearing 4, a plurality of rollers 22 are adjacent in the circumferential direction between an inner ring 20 that is bolt-coupled to the small-diameter portion of the flex spline 19 of the wave gear device 3 and an outer ring 21 that is bolt-coupled to the circular spline 18. The matching parts are arranged so as to be orthogonal to each other, and the output shaft 6 is fitted and fixed to the inner circumference of the inner ring 20 and the small diameter portion of the flex spline 19.

  Then, the outer ring 21 of the cross roller bearing 4 and the motor housing 7 are coupled with the brake housing 14 and the bolt 23 passing through the circular spline 18 of the wave gear device 3, so that the reverse input cutoff clutch 2 and the wave gear device 3 A cross roller bearing 4 is integrally supported by a motor housing 7.

  Further, the control device obtains the number of rotations of the motor shaft 8 necessary for making the rotation direction position of the output shaft 6 coincide with the target position by the controller, so that the motor shaft 8 rotates by the number of rotations. The motor 1 is controlled by using the encoder 5, and the control is performed in consideration of the backlash of the reverse input cutoff clutch 2 and the like as will be described later.

  This actuator has the above-described configuration. Next, the operation of this actuator and the function of the control device will be described.

  First, when the motor 1 is driven to rotate the motor shaft 8 from the initial state shown in FIG. 3, the rotation of the motor shaft 8 is transmitted to the intermediate shaft 9 of the reverse input cutoff clutch 2 as described in FIG. Then, after the rotation of the intermediate shaft 9 is decelerated by the wave gear device 3, it is transmitted to the output shaft 6 through the cross roller bearing 4 and the driven member connected to the output shaft 6 is driven.

  Then, after the motor 1 is stopped in the state shown in FIG. 4B, when the motor 1 is driven again, when the motor shaft 8 is rotated in the same direction as before the stop, FIG. The intermediate shaft 9 and the output shaft 6 rotate without being delayed from the motor shaft 8. However, when the motor shaft 8 is rotated in the direction opposite to that before stopping, the rotation direction gap between the engaging portion 8a of the motor shaft 8 and the inner surface of the engaging hole 9a of the intermediate shaft 9 becomes backlash, At the start of rotation, as shown in FIG. 5 (a), only the motor shaft 8 rotates and the intermediate shaft 9 and the output shaft 6 do not rotate. Thereafter, as shown in FIG. Even if the engaging portion 8a engages with the engaging hole 9a of the intermediate shaft 9 and the intermediate shaft 9 and the output shaft 6 start to rotate, a rotation delay of the output shaft 6 with respect to the motor shaft 8 remains.

  Therefore, when reversing the rotation directions of the motor shaft 8 and the output shaft 6, the control device takes into consideration the rotation angle from the rotation direction position of the output shaft 6 to the target position, the backlash of the reverse input cutoff clutch 2, and the like in advance. The rotation angle of the motor shaft 8 is obtained by multiplying the sum of the set rotation delay angle of the output shaft 6 at the time of reversal and the reduction ratio of the wave gear device 3, and this is converted into the number of rotations of the motor shaft 8. . Thereby, the rotation delay of the output shaft 6 is absorbed, and the output shaft 6 can be accurately matched with the target position.

  Further, when reverse input torque is applied to the output shaft 6 due to the weight of the driven member even while the motor 1 is being driven, the control device also performs the following control.

  That is, when the direction of the reverse input torque applied to the output shaft 6 changes from the reverse direction to the same direction as the input torque applied to the motor shaft 8 by the motor 1, the intermediate shaft 9 of the reverse input cutoff clutch 2 is The reverse input torque transmitted from the output shaft 6 via the cross roller bearing 4 and the wave gear device 3 causes the motor shaft 8 to rotate faster than the motor shaft 8 as shown in FIG. 6 from the state shown in FIG. A forward phenomenon occurs (in FIG. 6, for the sake of explanation, only the relative rotation of the intermediate shaft 9 with respect to the motor shaft 8 is indicated by an arrow), and the output shaft 6 also rotates more than the angle corresponding to the number of rotations of the motor shaft 8. . For this reason, the control device reduces the deviation of the output shaft 6 from the target position by reducing the number of rotations of the motor shaft 8 by an amount corresponding to the rotation advance angle of the output shaft 6 set in advance. Yes.

  On the other hand, when the direction of the reverse input torque changes from the same direction as the input torque to the reverse direction, the intermediate shaft 9 of the reverse input cutoff clutch 2 is in the state shown in FIG. 7 also causes a delay phenomenon that is slower than the motor shaft 8 as shown in FIG. 7 (in FIG. 7, only relative rotation of the motor shaft 8 with respect to the intermediate shaft 9 is indicated by an arrow for explanation), the output shaft 6 also The rotation is less than the angle corresponding to the number of rotations of the motor shaft 8. For this reason, the control device increases the number of rotations of the motor shaft 8 by an amount corresponding to a preset rotation delay angle of the output shaft 6 so that the output shaft 6 approaches the target position.

  Further, when the motor 1 is stopped by this actuator, even if reverse input torque is applied, the intermediate shaft 9 of the reverse input cutoff clutch 2 is locked with the outer ring 10 and does not rotate. The rotational position of each member up to the member is maintained. That is, when the motor 1 is stopped due to a power failure or the like, the reverse input cutoff clutch 2 plays a role as a brake.

  As described above, the actuator is configured so that the control device adjusts the number of rotations of the motor shaft 8 in consideration of the rotation delay and the rotation advance of the output shaft 6 due to the backlash of the reverse input cutoff clutch 2 and the like. Since the deviation from the target position of the driven member is reduced, the direction of the reverse input torque applied by the self-weight of the driven member during driving of the motor 1 is changed. Positioning can be performed accurately.

1 Motor 2 Reverse input cutoff clutch (brake)
3 Wave Gearing 4 Cross Roller Bearing 5 Encoder (Rotation Detector)
6 Output shaft 7 Motor housing 8 Motor shaft (input side member of reverse input shut-off clutch)
9 Intermediate shaft (Output side member of reverse input cutoff clutch)
9b Cam surface 10 Outer ring 11 Unlocking piece 11a Column 12 Roller 13 Coil spring (elastic member)
14 Brake housing 15 Wedge-shaped space

Claims (3)

The number of rotations of the motor, the output shaft to which rotation is transmitted from the motor shaft of the motor, and the number of rotations of the motor shaft necessary to match the rotational direction position of the output shaft to the target position are obtained, and the motor shaft is calculated by the number of rotations And a control device for controlling the motor so that the motor rotates.
As a brake that holds the rotational direction position of the output shaft when the motor stops, the rotation of the motor shaft is transmitted to the output shaft between the motor shaft and the output shaft, and applied to the output shaft. For an actuator that incorporates a reverse input cutoff clutch that stops the output shaft for input torque,
The control device, when reversing the rotation direction of the motor shaft and the output shaft, a rotation angle from the rotation direction position of the output shaft to a target position, and a rotation delay angle of the output shaft at the time of reversal set in advance The number of rotations of the motor shaft is adjusted based on the sum of the actuators. The output shaft is applied with reverse input torque by the weight of a driven member connected to the output shaft,
In the control device, the direction of the reverse input torque applied to the output shaft by the weight of the driven member changes from the reverse direction to the same direction as the input torque applied to the motor shaft by the motor during driving of the motor. The number of rotations of the motor shaft is reduced by an amount corresponding to a preset rotation advance angle of the output shaft, and when the direction of the reverse input torque changes from the same direction as the input torque to the reverse direction, 2. The actuator according to claim 1, wherein the number of rotations of the motor shaft is increased by an amount corresponding to a preset rotation delay angle of the output shaft.   The reverse input cutoff clutch is arranged such that an input side member that receives input torque from the motor shaft and an output side member that receives reverse input torque from the output shaft rotate around the same axis, and the input side member Torque transmitting means for transmitting the rotation of the input side member to the output side member is provided between the output side member, and a fixed outer ring is disposed radially outside the output side member, and the output side member A plurality of cam surfaces are provided on the outer peripheral surface of the outer ring, and a wedge-shaped space gradually narrowing on both sides in the circumferential direction is formed between the inner peripheral cylindrical surface of the outer ring and each cam surface of the output side member. Each wedge-shaped space incorporates a pair of rollers and an elastic member that is sandwiched between the pair of rollers and pushes each roller into the narrow portion of the wedge-shaped space, and has column portions that are inserted on both sides in the circumferential direction of each wedge-shaped space. The unlocking piece is on the input side The actuator according to claim 1 or 2, characterized in that those which are non-rotatably connected to the timber.

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