JP5115309B2 - Industrial robot and method of operation - Google Patents

Description

  The present invention relates to an industrial robot provided with an arm balance device.

Conventionally, in an industrial robot, as a second axis lower arm auxiliary device, an arm balance device using a compression spring is generally provided for the purpose of reducing the load on the second axis lower arm. A conventional industrial robot having such a configuration will be described with reference to the drawings.
FIG. 4 is a side view showing a conventional industrial robot, and FIG. 5 is a side sectional view of an arm balance device using a conventional compression spring.
In FIG. 4, the industrial robot 1 includes a fixed base 2, a turning head 3, a second axis lower arm 4, a third axis upper arm 5, a wrist 6, and an arm balance device 7. The swivel head 3 is supported by the fixed base 2 so as to be pivotable about the vertical axis S and is swiveled. The second shaft lower arm 4 is supported at the lower end thereof by the swivel head 3 so as to be rotatable around the horizontal axis L, and is driven to swing back and forth. The third shaft upper arm 5 is supported at the upper end of the second shaft lower arm 4 so as to be rotatable around the horizontal axis U, and is driven to swing up and down. The wrist 6 is supported at the tip of the third shaft upper arm 5 so as to be rotatable about the horizontal axis B. FIG. 5 shows an arm balance device using a compression spring. Reference numeral 7 denotes an arm balance device that creates a reaction force against the second shaft lower arm when the second shaft lower arm tilts. It is a balancer comprising a cylinder 73 that slides the member on its inner peripheral surface. As described above, the conventional arm balance device assists the tilting of the second shaft lower arm using the repulsive force of the spring for the purpose of reducing the load.
Further, as an industrial robot provided with an arm balance device using a compression spring, a robot using a cylinder mechanism has been proposed (for example, see Patent Document 1). In this industrial robot, the lower arm moves when a ball nut screwed with a ball screw rotated by a motor moves. Also, springs are arranged at both ends of the ball nut, and the action of tension compression occurs by the operation of the ball nut, so that the operation of tilting the lower arm is assisted.
Japanese Patent Laid-Open No. 61-109677

Industrial robots work in factories such as assembly, welding, and painting. As described above, robots used in factories are required to improve productivity by reducing the footprint and arranging them closely.
However, the conventional industrial robot has a problem that the arm balance device is large and it is difficult to reduce the size. In addition, the arm balance device has a very complicated structure, which increases the number of assembly steps, leading to an increase in cost. Since a dedicated jig is required for maintenance, there is a problem with maintainability. Also, since the compression spring is used, in the case of assisting the second shaft lower arm, the torque depends on the spring constant, and depending on the posture of the arm, the load on the motor that drives the second shaft lower arm is reversed. There was also a problem of becoming.
The present invention has been made in view of such problems, and an object of the present invention is to provide an industrial robot that can be miniaturized and has good operability.

In order to solve the above problem, the present invention is configured as follows.
The present invention provides an industrial robot having a lower arm that is supported by a base and that tilts back and forth to perform work, and includes a balancer that assists the tilting load of the lower arm, and the balancer is driven by an electric motor. It is a thing.
In the present invention, one end of the balancer is attached to the fixed portion, and the other end is attached to the lower arm.
In the present invention, the balancer includes a mechanism that converts the rotational motion of the electric motor into a linear motion by a feed screw mechanism.
Further, the present invention is a mechanism in which the balancer converts a rotational motion of the electric motor into a linear motion by a feed screw mechanism, and a hollow actuator is used for the electric motor.
Further, the present invention is a mechanism in which the balancer converts a rotational motion of the electric motor into a linear motion by a feed screw mechanism, and a nut used in the feed screw mechanism is attached to the rod, and the rod is It is attached to the lower arm.
Further, the present invention is a mechanism in which the balancer converts a rotational motion of the electric motor into a linear motion by a feed screw mechanism, wherein a hollow actuator is used in the electric motor, and a rod of the feed screw mechanism is the hollow It is pulled into the hollow part of the motor.
In addition, the present invention provides an industrial arm that includes a lower arm that is supported by a base and that tilts back and forth to work, a balancer that assists the tilting load of the lower arm, and controls the operation of the lower arm. In the operation method of the robot, the electric motor that drives the balancer is driven in synchronization with the electric motor that drives the lower arm.
In the present invention, the electric motor that drives the balancer is controlled by a command value based on an encoder signal of the electric motor that drives the lower arm.
In the present invention, the electric motor that drives the balancer is torque-controlled in synchronization with the inclination angle of the lower arm.

According to the present invention, the structure can be simplified, and the cost can be reduced by downsizing and reducing the number of assembly steps. In particular, when a hollow actuator is used in an electric motor, the rod can be pulled into the hollow portion of the hollow actuator. Is possible.
Moreover, by operating synchronously the electric motor and an electric motor for driving the lower arm for driving the balancer, in order to be able to control the balancer synchronized with the inclination angle of the lower arm, of the motor for driving the lower arm A balancer with good operability can be obtained without causing a load.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an industrial robot of the present invention. 1 is an industrial robot, 2 is a fixed base, 3 is a turning head, 4 is a lower arm, 5 is an upper arm, 6 is a wrist, and 8 is a balancer. The industrial robot 1 has a turning head 3 attached to a fixed base 2, a lower arm 4 attached to the turning head 3, and an electric balancer 8.
Further, the upper arm 5 is provided with a wrist shaft at the tip, and is rotatably provided on the lower arm. As described above, the present invention will be described using an industrial robot having a 6-axis configuration.
The part where the present invention is different from the prior art is a part in which the structure is simplified and a balancer having a torque control function is provided in the swivel head.
Next, the operation of each part of the industrial robot will be described. The industrial robot 1 has a turning head 3 mounted on a fixed base 2 and rotates around the Z axis. The lower arm 4 provided on the swivel head 3 rotates around the X axis and tilts. The upper arm 5 has a wrist shaft that rotates around the X axis and the Y axis at the tip, and the upper arm itself also rotates around the X axis.
Next, details of the balancer 8 will be described with reference to FIG. 81 is a driving motor, 82 is a ball screw, 83 is a nut, and 84 is a rod. The drive motor 81 is an electric motor, and in the present invention, a hollow motor will be described as an example. The output shaft of the drive motor 81 is coupled to the ball screw 82 via a coupling 85, and the rotation of the drive motor 81 is transmitted. The ball screw 82 is screwed with a nut 83, and a rod 84 attached to the lower arm is attached to the outer periphery of the nut 83.
When the driving motor 81 is rotated, the ball screw 82 is also rotated, and the nut 83 and the rod 84 that are screwed into the ball screw 82 are moved forward or backward. Here, if a hollow motor is used as the drive motor 81 and the hollow portion of the hollow motor is formed with a diameter wider than the diameter of the rod 84 as shown in FIG. It can be drawn into the hollow part. For this reason, the balancer 8 can be further downsized.
Next, the relationship between the operation of the lower arm and the balancer will be described with reference to FIG. 10 is a robot controller, 11 is a robot controller, 12 is a lower arm drive motor, 13 is a lower arm drive encoder, 14 is a balancer controller, 15 is a balancer drive motor, 16 is a balancer drive encoder, and 17 is a computation It is a vessel. An operation command from the robot controller 10 is instructed to the robot controller 11 and the balancer controller 14, and the robot controller 11 performs PID control using a movement amount corresponding to the operation as a command value, and supplies current to the lower arm drive motor 12. Is supplied to move the lower arm. Further, the movement amount at this time is detected by the lower arm driving encoder 13 and fed back to the robot controller 11 and the balancer controller 14. The amount of movement detected by the lower drive encoder 13 is calculated by the calculator 17 so as to be a position command for the balancer controller 14, and the balancer controller 14 is also PID-controlled so that current is supplied to the balancer drive motor 15. Is done. The amount of movement by the balancer drive motor 15 is detected by the balancer drive encoder 16 and fed back to the balancer controller 14.
As described above, regarding the positional relationship between the lower arm and the balancer, the command value calculated from the signal of the lower arm driving encoder 13 is used as the balancer position command, so that the lower arm and the balancer can operate in synchronization. It is.
Further, the thrust at each position of the balancer rod is obtained from the inclination angle of the lower arm, the moment load from the rotation center, and the like, and a current gain corresponding to this is given by the balancer controller 14, whereby the balancer drive motor The current value to 15 is also given a considerable value. Here, since the thrust of the rod is obtained from the ball screw lead and the torque of the driving motor, the thrust of the rod can be controlled by controlling the current value of the driving motor.
Here, the position command to the balancer controller has been described using the value generated from the signal of the lower arm drive encoder. However, a value determined by the robot controller may be given, in which case the balancer drive motor By controlling in the torque control mode so as to manage only this torque, a current to the balancer driving motor corresponding to the inclination angle of the lower arm is supplied.

  Since the arm balance device has a simplified structure, it can be applied to a vertical multi-indirect robot that needs assistance for tilting all the second axis arms.

Side sectional view of an industrial robot showing an embodiment of the present invention Side sectional view of an arm balance device showing an embodiment of the present invention The block diagram which shows the Example of this invention Side view showing a conventional industrial robot Side sectional view of a conventional arm balance device using a compression spring

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Industrial robot 2 Fixed base 3 Turning head 4 Lower arm 5 Upper arm 6 Wrist part 7 Balancer 8 Balancer 10 Robot controller 11 Robot controller 12 Lower arm drive motor 13 Lower arm drive encoder 14 Balancer controller 15 Balancer drive Motor 16 Balancer drive encoder 17 Calculator 71 Rod 72 Spring 73 Cylinder 81 Electric motor 82 Ball screw 83 Nut 84 Rod 85 Coupling

Claims (9)

An industrial robot comprising a lower arm that is supported by a base and that tilts back and forth to perform work, and a balancer that assists the tilting load of the lower arm,
The balancer is driven by a rotary electric motor ,
The industrial robot according to claim 1, wherein a linear motion shaft of the balancer is parallel to an output shaft of the rotary electric motor . One end of the balancer, industrial robot according to claim 1, wherein attached to the base, characterized in that the other end is attached to the lower arm. The balancer industrial robot according to claim 1 or 2, characterized in that it comprises a mechanism for converting the linear motion by the rotary electric motor feed screw mechanism the rotational movement of the. Prior Symbol rotary motors, industrial robot according to claim 1, 2 or 3, characterized in that the hollow actuator. The balancer before Symbol mounted on nut rod used in the feed screw mechanism, the rod industrial robot according to claim 4, characterized in that attached to the lower arm. The balancer industrial robot according to claim 5, characterized in that the rod before Symbol feed screw mechanism is drawn into the hollow portion of the hollow actuator. In an operation method of an industrial robot that is supported by a base and includes a lower arm that tilts back and forth to perform work, a balancer that assists a tilting load of the lower arm, and controls the operation of the lower arm.
The balancer is driven by a rotary electric motor ,
The linear motion shaft of the balancer is parallel to the output shaft of the rotary electric motor,
The method for operating an industrial robot, wherein the rotary electric motor for driving the balancer is driven in synchronization with the electric motor for driving the lower arm. 8. The method of operating an industrial robot according to claim 7 , wherein the rotary electric motor that drives the balancer is controlled by a command value based on an encoder signal of the electric motor that drives the lower arm. . The rotary electric motor, the operation method of the industrial robot according to claim 7 or 8, characterized in that it is the torque control in synchronism with the inclination angle of the lower arm for driving said balancer.

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