JP2019150914A - Wrist unit of robot - Google Patents

Abstract

To provide a wrist unit of a robot that can perform turning motion of a first wrist and a second wrist around one shaft of two shafts orthogonal to each other, and turning motion of the second wrist around the other shaft independently from each other, using one driving motor.SOLUTION: A wrist unit of a robot, in which a second wrist 6 is rotatably mounted on a first wrist 5, is provided with a planetary gear mechanism 4 which is equipped with a sun gear 16 formed integrally with an input shaft 3, a carrier 19, formed integrally with a first wrist shaft 1, which rotatably supports a planetary gear 18 and an inner gear 17 which is connected through a pair of bevel gears 2a and 17b to a second wrist shaft 2 orthogonal to the first wrist shaft 1. The unit can perform turning motion of both wrists 5 and 6 around the first wrist shaft 1 and rotating motion of the second wrist 6 around the second wrist shaft 2 independently from each other, using one driving motor that applies input torque to the input shaft 3, by selectively releasing a first brake 7 for the first wrist shaft 1 and a second brake 8 for the second wrist shaft 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wrist unit provided at an arm tip of an industrial robot.

  At the tip of the arm of the industrial robot, there is a first wrist that rotates around one of two axes orthogonal to each other, a first wrist that rotates together with the first wrist, Provided with a wrist unit that rotates around the axis of the wrist and that positions the end effector attached to the second wrist by rotating both wrists together and rotating the second wrist. It is often done.

  However, in such a wrist unit of the robot, when the first wrist and the second wrist are rotated together around one axis, the second wrist also rotates around the other axis. In the case of such a structure, the control for moving the end effector to the target position becomes complicated. For this reason, conventionally, a wrist unit that can rotate both wrists around one axis and the second wrist around the other axis independently using two drive motors. Have been devised.

  For example, the wrist unit proposed in Patent Document 1 has an inner drive shaft driven by a second motor inside an outer drive shaft driven by a first motor, and rotates in a posture orthogonal to both drive shafts. A rotation center first gear (bevel gear) meshed with the bevel gear fixed to the outer drive shaft on the outer periphery of the rotation center shaft that can be installed, and a rotation center second gear meshed with the bevel gear fixed to the inner drive shaft (Bevel gear) is attached rotatably, and the rotation center shaft (corresponding to the first wrist) is fixed to the rotation center shaft in a posture orthogonal to the rotation center shaft. A fixed rotation shaft (corresponding to the second wrist) is rotatably mounted, one of the two bevel gears fixed to the rotation shaft is meshed with the rotation center first gear, and the other is meshed with the rotation center second gear. It is a combination.

  With the above configuration, when one of the first motor and the second motor is driven alone, the rotation shaft and the suction hand rotate around the rotation center axis and simultaneously rotate around the rotation center axis. When both the first motor and the second motor are driven at the same rotational speed, the rotation direction of the rotation shaft and the suction hand is offset by the rotation direction, and the rotation around the rotation center axis is offset. Only the rotation operation is performed, or the rotation operation about the rotation center axis is performed by canceling the rotation operation about the rotation center axis.

JP 2017-1003009 A

  In the wrist unit of Patent Document 1 described above, the rotation center axis and the rotation center axis are orthogonal to each other, and the two drive motors are simultaneously driven at the same rotation speed, whereby the rotation center axis ( The rotation operation of the first wrist) and the rotation shaft (second wrist) and the rotation operation of the rotation shaft around the rotation center axis can be performed independently of each other.

  However, the wrist unit incorporating two drive motors in this way has a problem that it is difficult to reduce the size of the entire unit because the installation space for the drive motor becomes large. In addition, since there are a large number of large-diameter power cables and communication cables for the drive motor, there is also a problem that it takes time for wiring work during assembly.

  Therefore, the present invention provides a rotation operation of the first wrist and the second wrist around one of the two axes orthogonal to each other and the rotation of the second wrist around the other axis with one drive motor. It is an object of the present invention to provide a wrist unit for a robot that can perform operations independently of each other.

  In order to solve the above problems, a wrist unit of a robot according to the present invention includes an input shaft to which an input torque is applied from a drive motor, and a first shaft connected to the input shaft via a planetary gear mechanism and extending in directions orthogonal to each other. A wrist shaft and a second wrist shaft, a first wrist connected to the first wrist shaft so as to be able to transmit rotation, and a first wrist connected to the first wrist so as to be rotatable, and connected to the second wrist shaft so as to be able to transmit rotation. The second wrist, when not operated, the first wrist shaft is restrained so as not to rotate, and the first wrist shaft is rotatably released by a release operation, and the first wrist is incorporated into the first wrist and is not operated. A second brake that restrains the second wrist shaft so as not to rotate relative to the first wrist and releases the second wrist shaft so as to rotate relative to the first wrist by a release operation, and the planetary gear mechanism includes: It is connected to the input shaft so that rotation can be transmitted. A sun gear, an internal gear arranged radially outside the sun gear, a plurality of planetary gears meshed with both the sun gear and the internal gear, and a carrier that supports the planetary gears so as to be capable of rotating, The carrier is connected to the first wrist shaft so as to be able to transmit rotation, and the internal gear is connected to the second wrist shaft so as to be able to transmit rotation via a pair of bevel gears engaged with each other, and the first brake is released. When an input torque is applied to the input shaft in a state in which the second brake is not operated, the first wrist rotates together with the second wrist around the first wrist shaft, When an input torque is applied to the input shaft while one brake is not operated and the second brake is released, the second wrist rotates about the second wrist shaft.

  That is, a planetary gear mechanism in which a second wrist connected to a second wrist shaft orthogonal to the first wrist shaft is rotatably incorporated in a first wrist connected to the first wrist shaft, and a sun gear is connected to the input shaft. When the carrier of the planetary gear mechanism is connected to the second wrist shaft via a pair of bevel gears and the input torque is applied to the input shaft by one drive motor, When the first brake is released to release the first wrist shaft and the second brake is not operated and the second wrist shaft is restrained, the first wrist and the second wrist are integrated around the first wrist shaft. If the first wrist is not operated and the first wrist shaft is restrained and the second brake is released to release the second wrist shaft, the first wrist is stopped and the first wrist is stopped. Rotating two wrists around the second wrist axis Than it was to kill.

  In the above configuration, a non-excitation electromagnetic brake can be adopted as the first brake and the second brake.

  Further, if a reduction mechanism is provided between the first wrist shaft and the first wrist and between the second wrist shaft and the second wrist, the space between the drive motor and each wrist is provided. The positioning error of each wrist due to the backlash of the planetary gear mechanism or the like in the rotation transmission path can be reduced.

  Further, two absolute encoders are provided for detecting the rotational positions of the first wrist and the second wrist, respectively, and a detection value of each absolute encoder and a detection value of an encoder provided in the drive motor are provided. On the basis of this, if the configuration is such that the first wrist and the second wrist are positioned by controlling the drive motor, the first brake and the second brake, the positioning accuracy of each wrist can be improved.

  As described above, the wrist unit of the robot according to the present invention is configured to rotate the first wrist and the second wrist around the first wrist axis and the second wrist around the second wrist axis with one drive motor. Therefore, the installation space for the drive motor and its driver device is small compared to a conventional wrist unit incorporating two drive motors, and the overall size and size of the unit are reduced. Costs can be reduced, and the number of power cables and communication cables for the drive motor is reduced, so that wiring work during assembly can be performed efficiently.

Longitudinal front view of the wrist unit of the embodiment in a state where the first brake is energized Sectional drawing which shows the operation | movement seen from the axial direction one end side of the planetary gear mechanism of FIG. Right side view of FIG. Longitudinal front view of the wrist unit of the embodiment in a state where the second brake is energized Sectional drawing which shows the operation | movement seen from the axial direction one end side of the planetary gear mechanism of FIG. Top view of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the wrist unit of the robot of this embodiment is in a state of being coaxial with the first wrist shaft 1 and the second wrist shaft 2 arranged in a posture extending in directions orthogonal to each other, and the first wrist shaft 1. An input shaft 3 arranged, a planetary gear mechanism 4 for transmitting the rotation of the input shaft 3 to the first wrist shaft 1 and the second wrist shaft 2, and a first wrist connected to the first wrist shaft 1 so as to be able to transmit the rotation. 5, a second wrist 6 rotatably incorporated in the first wrist 5 and coupled to the second wrist shaft 2 so as to be able to transmit rotation, a first brake 7 for the first wrist shaft 1, and a second wrist shaft A second brake 8 for 2 and a frame 9 for rotatably supporting the first wrist shaft 1 and the input shaft 3. The second wrist shaft 2 is formed in a hollow shape so that the wiring of an end effector (not shown) attached to the second wrist 6 is passed therethrough.

  A pulley 10 is fitted and fixed to the outer periphery of the input shaft 3, and a drive motor (not shown) is connected via a belt 11 wound around the pulley 10 in a state of passing through the pulley 10 and a part of the frame 9. The input torque can be applied. And the one end part is rotatably supported by the 1st pillar 9a provided in the one end of the flame | frame 9 via the bearing, and the other end part is provided in the one end of the 1st wrist axis | shaft 1 via the bearing. It is fitted in the hole 1a so as to be relatively rotatable.

  The first wrist shaft 1 is connected to the planetary gear mechanism 4 as will be described later, and one end thereof is rotatably supported by a second column 9b provided in the center of the frame 9 via a bearing. The small diameter portion 1b formed on the end side is rotatably supported by a third column 9c provided on the other end of the frame 9 via a bearing. The first wrist 5 is connected to the small diameter portion 1 b via the first speed reduction mechanism 12.

  Here, the first speed reduction mechanism 12 includes a wave generator 12a fixed to the small diameter portion 1b of the first wrist shaft 1 and a part of the inner ring of the first cross roller bearing 13 disposed on the radially outer side of the wave generator 12a. And a sprocket 12c that is partly sandwiched between the wave generator 12a and the circular spline 12b. Then, the circular spline 12b is fixed to the first wrist 5, and the flex spline 12c is fixed to the third column 9c of the frame 9, so that the rotation of the first wrist shaft 1 is decelerated and the first from the circular spline 12b. It is transmitted to the wrist 5.

  The first wrist 5 includes tongue-shaped attachment portions 5a and 5b disposed at both ends, and a flat plate portion 5c that connects the attachment portions 5a and 5b (see FIGS. 3 and 6). The attachment portion 5a on one end side is attached to the outer periphery of the input shaft 3 via a bearing so as to be relatively rotatable. Further, the attachment portion 5b on the other end side is attached to the outer periphery of the small diameter portion 1b of the first wrist shaft 1 via a bearing so as to be relatively rotatable, and the third cross roller bearing 13 is used for the third portion of the frame 9. The column 9c is rotatably supported. And the 2nd wrist 6 is incorporated in the center part of the flat plate part 5c via the 2nd cross roller bearing 14 so that rotation is possible.

  The second wrist 6 is an annular body arranged in a state of partially protruding from an opening opened in the center of the flat plate portion 5c of the first wrist 5, and is connected to the planetary gear mechanism 4 as described later. It is connected to the wrist shaft 2 via a second reduction mechanism 15 and is attached to the outer periphery of the second wrist shaft 2 so as to be relatively rotatable via a bearing.

  Here, the second speed reduction mechanism 15 is a wave gear device having the same structure as the first speed reduction mechanism 12, and the wave generator 15 a is integrated with the second wrist shaft 2 and a part of the inner ring of the second cross roller bearing 14. The formed circular spline 15b is fixed to the second wrist 6, and the flex spline 15c sandwiched between the wave generator 15a and the circular spline 15b is fixed to the flat plate portion 5c of the first wrist 5, respectively. The rotation of the wrist shaft 2 is decelerated and transmitted from the circular spline 15b to the second wrist 6.

  As shown in FIG. 2, the planetary gear mechanism 4 includes a sun gear 16 integrally formed on the outer periphery of the central portion of the input shaft 3, an internal gear 17 disposed radially outside the sun gear 16, A plurality of planetary gears 18 meshing with both the gear 16 and the internal gear 17, and an annular carrier 19 that supports each planetary gear 18 so as to be capable of rotating.

  The carrier 19 of the planetary gear mechanism 4 has a plurality of support shafts 19a provided on one end side fitted in the center holes of the planetary gears 18 via bearings so as to be rotatable relative to each other. Is formed integrally with the first wrist shaft 1 in a state of being connected to one end of the first wrist shaft 1. The internal gear 17 has a lid portion 17a fixed to the inner periphery on one end side so as to be relatively rotatable on the outer periphery of the input shaft 3 via a bearing, and a bevel gear 17b integrally formed on the other end side. It meshes with a bevel gear 2 a formed integrally with the flange portion of the second wrist shaft 2. The sun gear 16 may be formed separately from the input shaft 3 and connected to be able to transmit rotation, and the carrier 19 may be formed separately from the first wrist shaft 1 and connected to be able to transmit rotation. .

  The first brake 7 is formed of a flexible material, and has a brake plate 20 whose inner peripheral portion is fixed to the first wrist shaft 1, and an armature 21 that axially faces one side surface of the brake plate 20. The brake plate 20 is opposed to the other side surface of the brake plate 20 in the axial direction, the plurality of brake springs 23 press the armature 21 against the brake plate 20, and the armature 21 is energized against the elasticity of the brake spring 23 by energization. This is a non-excitation electromagnetic brake provided with an electromagnet 24 that is separated from the magnet.

  The friction plate 22 of the first brake 7 is fixed to one side surface of the third column 9c of the frame 9, and the electromagnet 24 is fitted on the outer periphery of the first wrist shaft 1 via the bearing and the seal member 25. Thus, it is bolted to the third column 9c of the frame 9. Further, the brake spring 23 is held in an elastically compressed state in a concave portion provided on the surface of the electromagnet 24 facing the armature 21 and presses the armature 21.

  When the electromagnet 24 is not energized, the brake spring 23 presses the armature 21 against the brake plate 20 so that the brake plate 20 pressed by the armature 21 is pressed against the friction plate 22 fixed to the frame 9 (see FIG. 4 state), when the electromagnet 24 is energized, the electromagnet 24 attracts the armature 21 to move in the axial direction against the elastic force of the brake spring 23 and is separated from the brake plate 20 (state of FIG. 1). That is, when not energized (when not operated), the brake plate 20 and the first wrist shaft 1 connected thereto are restrained so as not to rotate, and the brake plate 20 and the first wrist shaft 1 can be rotated by energization (release operation). To be released.

  The second brake 8 is a non-excited electromagnetic brake having the same structure as that of the first brake 7 and is formed of a flexible material and includes a brake plate 26 fixed to the second wrist shaft 2 and a brake plate 26. An armature 27 and a friction plate 28 that are opposed to each other in the axial direction are provided, a plurality of brake springs 29 that press the armature 27 against the brake plate 26, and an electromagnet 30 that separates the armature 27 from the brake plate 26 when energized. The friction plate 28 and the electromagnet 30 are bolted together with the outer ring of the second cross roller bearing 14 to the opening edge of the center of the flat plate portion 5c of the first wrist 5. The electromagnet 30 is fitted on the outer periphery of the second wrist shaft 2 via a bearing and a seal member 31.

  When the electromagnet 30 is not energized (during non-operation), the brake plate 26 and the second wrist shaft 2 are restrained so as not to rotate relative to the first wrist 5 (state of FIG. 1), and the electromagnet 30 is energized. At the time (at the time of release operation), the brake plate 26 and the second wrist shaft 2 are released so as to be rotatable relative to the first wrist 5 (state shown in FIG. 4).

  Further, the wrist unit is provided with two absolute encoders 32 and 33 for detecting the rotational direction positions of the first wrist 5 and the second wrist 6, respectively.

  The absolute encoder 32 for the first wrist 5 is attached to the first column 9a of the frame 9 so as to face the code wheel 32a and the code wheel 32a attached to the inner surface of the one end side attachment portion 5a of the first wrist 5. Sensor 32b and base 32c. The absolute encoder 33 for the second wrist 6 includes a code wheel 33a attached to the outer peripheral surface of the second wrist 6, a sensor 33b attached to the flat plate portion 5c of the first wrist 5 so as to face the code wheel 33a, and It consists of a base 33c.

  Then, the first wrist 5 and the second wrist 6 are positioned based on detection values of the absolute encoders 32 and 33 and detection values of encoders (not shown) provided in the drive motor. ing.

  Next, the operation of this wrist unit will be described. When the wrist effector is driven to move the end effector attached to the second wrist 6 to the target position, usually, as a first step, the electromagnet 24 of the first brake 7 is energized to the electromagnet of the second brake 8. 30 is not energized, that is, as shown in FIG. 1, the first wrist shaft 1 is released so as to be rotatable, and the second wrist shaft 2 is restrained so as not to rotate relative to the first wrist 5, and this state Then, an input torque is applied to the input shaft 3 from the drive motor.

  In this first step, first, as shown in FIGS. 1 and 2, the sun gear 16 of the planetary gear mechanism 4 rotates together with the input shaft 3, and the planetary gear 18 revolves while rotating. Then, the revolution of the planetary gear 18 is transmitted to the first wrist shaft 1 integrated with the carrier 19, and the rotation of the first wrist shaft 1 is decelerated by the first reduction mechanism 12 and transmitted to the first wrist 5. Thereby, as shown in FIGS. 1 and 3, the first wrist 5 rotates around the first wrist shaft 1 integrally with the second wrist 6.

  At this time, the second wrist shaft 2 to which the second wrist 6 is attached also rotates around the first wrist shaft 1, and accordingly, as shown in FIGS. 1 and 2, the second wrist shaft 2 is rotated. The internal gear 17 of the planetary gear mechanism 4 connected to the shaft 2 by the pair of bevel gears 2a and 17b rotates, and the rotation speed and revolution speed of the planetary gear 18 according to the rotational speed difference between the internal gear 17 and the sun gear 16. Is now decided.

  Next, as a second step, the state where the electromagnet 24 of the first brake 7 is stopped and the electromagnet 30 of the second brake 8 is energized, that is, as shown in FIG. 4, the first wrist shaft 1 is rotated. In this state, the second wrist shaft 2 is released so as to be rotatable relative to the first wrist 5, and in this state, input torque is applied to the input shaft 3 from the drive motor.

  In this second step, since the carrier 19 integrated with the first wrist shaft 1 which is restrained so as not to rotate does not rotate, as shown in FIGS. 4 and 5, when the sun gear 16 rotates together with the input shaft 3, The planetary gear 18 only rotates, and the internal gear 17 rotates in the opposite direction to the sun gear 16. The rotation of the internal gear 17 is transmitted to the second wrist shaft 2 through the pair of bevel gears 17b and 2a, and the rotation of the second wrist shaft 2 is decelerated by the second reduction mechanism 15 and transmitted to the second wrist 6. The As a result, as shown in FIGS. 4 and 6, the second wrist 6 rotates around the second wrist shaft 2 with the first wrist 5 stopped.

  The first step and the second step described above are based on the detection values of the absolute encoders 32 and 33 for the first wrist 5 and the second wrist 6 and the detection values of the encoder on the drive motor side, By controlling the 1st brake 7 and the 2nd brake 8, it repeats a required number of times. Finally, the first wrist 5 and the second wrist 6 are positioned, the drive motor is stopped, the energization to the first brake 7 and the second brake 8 is stopped, and the end effector stops at the target position. Will do.

  As described above, the wrist unit rotatably incorporates the second wrist 6 connected to the second wrist shaft 2 orthogonal to the first wrist shaft 1 into the first wrist 5 connected to the first wrist shaft 1, A sun gear 16 formed integrally with the input shaft 3, a carrier 19 formed integrally with the first wrist shaft 1 and rotatably supporting the planetary gear 18, and a pair of bevel gears 2a, 17b on the second wrist shaft 2. A planetary gear mechanism 4 having an internal gear 17 connected thereto is provided to selectively release the first brake 7 for the first wrist shaft 1 and the second brake 8 for the second wrist shaft 2. Thus, with one drive motor that applies input torque to the input shaft 3, the two wrists 5, 6 around the first wrist shaft 1 rotate together, and the second wrist 6 around the second wrist shaft 2 rotates. Rotating operations can be performed independently of each other.

  Therefore, compared with the conventional one incorporating two drive motors, the installation space for the drive motor and its driver device is small, the entire unit can be reduced in size and cost, and power cables and communication cables for the drive motor are also available. Since there are few, wiring work at the time of an assembly can be performed efficiently.

  Since the first reduction mechanism 12 is provided between the first wrist shaft 1 and the first wrist 5, and the second reduction mechanism 15 is provided between the second wrist shaft 2 and the second wrist 6, respectively. Positioning errors of the wrists 5 and 6 due to backlash of the planetary gear mechanism 4 and the like in the rotation transmission path from the drive motor to the first wrist 5 and the second wrist 6 are small. In addition, the positioning operation of the wrists 5 and 6 is controlled based on the absolute encoders 32 and 33 that detect the rotational position of the wrists 5 and 6 and the detection value of the encoder of the drive motor. The position can be stopped with high accuracy.

  In the above-described embodiment, the non-excitation electromagnetic brake is used for the first brake and the second brake, and the wave gear device is used for the first reduction mechanism and the second reduction mechanism. The present invention is not limited to the embodiment, and various types can be adopted.

DESCRIPTION OF SYMBOLS 1 1st wrist axis | shaft 2 2nd wrist axis | shaft 2a Bevel gear 3 Input shaft 4 Planetary gear mechanism 5 1st wrist 6 2nd wrist 7 1st brake (non-excitation type electromagnetic brake)
8 Second brake (non-excitation electromagnetic brake)
9 Frame 12 First reduction mechanism (wave gear device)
13 First cross roller bearing 14 Second cross roller bearing 15 Second reduction mechanism (wave gear device)
16 Sun gear 17 Internal gear 17b Bevel gear 18 Planetary gear 19 Carrier 32, 33 Absolute encoder

Claims (4)

An input shaft to which input torque is applied from a drive motor, a first wrist shaft and a second wrist shaft that are connected to the input shaft through a planetary gear mechanism and extend in directions orthogonal to each other, and rotation transmission to the first wrist shaft A first wrist connected to the first wrist, a second wrist rotatably incorporated in the first wrist, and connected to the second wrist shaft so as to be able to transmit rotation; and the first wrist shaft when not operating. 1st brake which restrains impossible and releases the 1st wrist axis by release operation, and it is built in the 1st wrist, and when it is not operated, the 2nd wrist axis is restrained so that it cannot rotate relative to the 1st wrist And a second brake that releases the second wrist shaft so as to be rotatable relative to the first wrist by a release operation,
The planetary gear mechanism includes a sun gear coupled to the input shaft so as to be able to transmit rotation, an internal gear disposed radially outside the sun gear, and a plurality of planetary gears meshing with both the sun gear and the internal gear. And a carrier that rotatably supports the planetary gears, the carrier is connected to the first wrist shaft so as to be able to transmit rotation, and the second wrist is connected via a pair of bevel gears that mesh with each other. It is connected to the shaft so that rotation can be transmitted,
When input torque is applied to the input shaft in a state where the first brake is released and the second brake is not operated, the first wrist is integrated with the second wrist around the first wrist shaft. When the input torque is applied to the input shaft in a state where the first brake is not operated and the second brake is released, the second wrist rotates around the second wrist shaft. The robot wrist unit.   The wrist unit of the robot according to claim 1, wherein the first brake and the second brake are non-excitation electromagnetic brakes.   The robot according to claim 1, wherein a speed reduction mechanism is provided between the first wrist axis and the first wrist and between the second wrist axis and the second wrist. Wrist unit.   Two absolute encoders are provided for detecting the rotational direction positions of the first wrist and the second wrist, respectively, and based on the detection value of each absolute encoder and the detection value of the encoder provided in the drive motor. 4. The positioning of the first wrist and the second wrist is performed by controlling the drive motor, the first brake, and the second brake. 5. Robot wrist unit.

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