JPH0615587A - Robot arm - Google Patents

Abstract

PURPOSE:To control the motion of a robot arm being driven by a servomotor accurately with a speed reducer 41 simple in structure. CONSTITUTION:A nut 22 is screwed in a ball screw 21 rotated and driven by a servomotor 18. This nut 22 is attached tight to a toothed belt 16 stretched across in a pair of wheels 14 and 15 and its rotation is stopped. When the ball screw 21 is rotated therewith, the nut 22 is moved in company with the toothed belt 16, and thereby the paired wheels 14, 15 are rotated as well. In succession, a robot arm is rotated.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a robot arm.

[0002]

2. Description of the Related Art An arm of a conventional robot is designed to be moved by a servomotor through a speed reducer composed of a large number of gears. A special link mechanism is provided so that the posture can be kept constant.

The arm of the robot is also provided with a large number of cords composed of electric signal lines and the like necessary for controlling the robot, many of which are attached to the outside of the arm but are placed inside the arm. Some have been set up.

[0004]

As described above, the arm of the conventional robot is designed to be moved through the speed reducer equipped with a large number of various gears. Therefore, there is a drawback that the backlash is large and the structure of the speed reducer becomes more complicated as the reduction ratio is increased, and the size becomes bulky and the weight becomes large.

Moreover, the arm of the conventional robot has a special link mechanism so that the posture of the hand can be kept constant when the arm turns, which makes the structure more complicated. One of the design problems is to wire the code consisting of many electric signal lines required for controlling the robot so that it does not interfere with the moving parts of the robot arm and does not damage the appearance of the robot. Has become.

A first object of the present invention is to solve the above problems and to provide an arm of a robot having a simple structure that can be controlled with high accuracy. A second object of the present invention is to rotate the arm. At times, it aims to provide a robot arm having a simple structure that can keep the hand posture constant.
A third object of the present invention is to easily wire a cord composed of a large number of electric signal lines or the like necessary for controlling the robot so as not to obstruct the moving parts of the robot and not to hurt the enjoyment of the robot. It is intended to provide a robot arm that can.

[0007]

A robot arm for achieving the first object is rotatably supported by a threaded shaft which is rotationally driven by a servomotor, a nut which is screwed to the threaded shaft. A power transmission means comprising a set of wheels and an endless rope such as a belt, a wire or a chain that is stretched between the wheels, and the nut is fixed to a portion extending along the threaded shaft of the rope. It consists of and.

The second object is achieved by matching the diameters of both wheels used for the arm. A robot arm for achieving the third object is a robot arm in which one arm is rotatably connected to one arm by a rotation shaft fixed to the other arm. The other arm is rotatably supported and the other arm is rotatably supported.A male connector and a female connector are provided, and one of the connectors is used as the rotary shaft and the other connector is connected. One end of the cord attached to the mounting portion and passed through the rotating shaft is connected to the one connector, and the other end of the cord extending from the rotating shaft is connected to the other connector.

[0009]

In the robot arm for achieving the first object, when the threaded shaft is rotationally driven by the servomotor, the nut fixed to the rope and prevented from rotating performs linear motion along the threaded shaft. Move the rope in one direction and rotate the wheel. As a result, the arm fixed to the shaft rotates via the shaft fixed to the wheel. As described above, the motor is decelerated by the screw shaft, the nut, and the wheel, and there is less rattling compared to the conventional reducer that uses a large number of gears, and the reduction ratio can be achieved only by the screw shaft, the nut, and the wheel. It can be made large, and its reduction ratio increases as the diameter of the wheel increases.

Incidentally, when the distance (pitch) that the nut advances by one rotation of the threaded shaft is P and the diameter of the wheel is D, the reduction ratio Z is Z = πD / P, and P = 1 mm, D
= 50 mm, the reduction ratio Z is 157, and a torque 157 times the rated torque of the motor can be obtained. Further, by making the diameters of both wheels the same, the rotation angles of both wheels become equal, and the relative movement between the wheel and the rope is eliminated, so that the wheels function as one link. Therefore, as shown in FIG.
When the wheel a of the wheel rotates by the angle θ, the arm b and the second wheel c also rotate by the angle θ, and the wheel shaft d that is integrated with the wheel c.
Since the fixed wrist e and the hand f are relatively rotated with respect to the arm b by an angle θ, the same posture is maintained.

In the arm of the robot for achieving the third object, when connecting the arms of the robot, the cord is connected by inserting the male connector into the female connector, so that the cord is wired. The work is extremely easy, and the modularity of the robot arm is improved. Moreover, since the cord is passed through the rotary shaft, it does not obstruct the movable part, and if it is passed through the arm, the robot is refreshed without being impaired.

[0012]

EXAMPLE FIG. 3 shows an example of an articulated robot. A first arm 2 pivotally supported on the upper end of a column 1 so as to be horizontally rotatable, and a first arm 2 connected to the arm 2 to move around a vertical axis. Rotatable second
Arm 3, a third arm 4 connected to the arm 3 and rotatable about a vertical axis and a horizontal axis, a servomotor 5 with a speed reducer attached to the arm 4, and a servomotor 5 The wrist 6 is fixed to the output shaft, and the hand 7 is rotatably supported up and down. Each arm 2, 3 and 4 has the following structure.

This will be explained with reference to FIGS. 1 and 2. Mounting plates 9 and 10 are attached to the left and right front and back, respectively, to a case-shaped cover 8 whose left and right ends are semicircular.
Rotating shafts 12 and 13 are rotatably supported by and 10, and a part of the rotating shaft 12 and 13 protrudes in the reverse direction. Each rotating shaft 1
Wheels 14 and 15 having the same diameter are fixed to 2 and 13, respectively, and a toothed belt 16 is stretched between the wheels.

Mounting base 1 fixed to a case-shaped cover 8
A ball screw 21 rotatably driven by the servo motor 18 via gears 19 and 20 is axially supported in parallel with the toothed belt 16 at the servo motor 18. A nut 22 is screwed onto the ball screw 21, and the nut 22 is connected to the toothed belt 16 by a jig 23.

Each of the arms 2, 3 and 4 is constructed as described above. When the servo motor 18 is driven to rotate forward or backward, the ball screw 21 rotates via the gears 19 and 20 and the toothed belt 16 The nut 22, which is connected to and is prevented from rotating, advances and retreats along the ball screw 21. Along with this, the toothed belt 16 moves, and the wheels 14 and 15 and the rotary shafts 12 and 13 rotate. Incidentally, the speed reduction ratio Z between the servo motor 18 and the wheels 14 and 15 in this case is πDη / P. Here, D is the diameter of the wheels 14 and 15, η is the reduction ratio of the gears 19 and 20, and P is the pitch of the ball screw.

FIGS. 5 and 6 show an example of a robot arm in which a cord made of an electric signal line for controlling a robot is wired. Mounting plates 26 attached to the left and right of a case-shaped cover 25, Of the 27, one side 26 has a cylindrical rotary shaft 28
Is rotatably supported, a rotary shaft 29 is fixed to the other front mounting plate 27, and a female connector 30 is fixed to the rear mounting plate 27 '. A wheel 31 is rotatably supported on the rotary shaft 28, and a wheel 32 is fixed to the rotary shaft 29. A toothed belt (not shown) similar to that of the above-described embodiment is wound between both wheels. There is.

A male connector 33 is attached to the front end of the rotary shaft 28 so that the connector 3
A bundle 34 of cords, which are connected to 0 and are arranged in the cover, including electric signal lines for controlling the robot, is once taken out of the cover and then inserted into the rotary shaft 28, and the connector 3
It is connected to 3. The portion of the cord bundle 34 protruding outside the cover may be covered with an arm cover or the cord bundle 34
Can be inserted into the rotary shaft through a hole provided in the peripheral wall of the rotary shaft so as not to be exposed from the cover.

The arm of the robot constructed as described above is
As shown in FIG. 7, the male connector 33 is inserted into the female connector 30, and the flange portion 29 'at the end of the rotary shaft 29 is connected to the mounting plate 27' by bolts to connect the two connectors. The cords of each arm are connected by connecting. It should be noted that FIG. 3 shows the arms of an articulated robot having 7 degrees of freedom, or depending on the industrial application, each arm may be, for example, a SCARA robot having a first arm and a second arm. A variety of robots can be constructed by combining the above, and it can also be widely used as a constituent element of all automatic machines for the purpose of automation and labor saving in addition to general robots.

[0019]

The present invention is constructed as described above and has the following effects. The robot arm according to claim 1, wherein movement of the robot arm driven by a servomotor is:
It is designed to be decelerated by a threaded shaft to which a nut is screwed and a wheel of a power transmission means having an endless rope that connects the nut, and is decelerated by a conventional speed reducer equipped with various gears. Compared to the other types, the amount of backlash is small, so that the robot arm can be controlled with high precision, and the reduction ratio can be increased with a simple structure.

As in the robot arm according to the second aspect of the present invention, if both wheels have the same diameter, the hand can be kept in the same posture even while the arms are turning, and a special link mechanism as in the prior art is used. do not need. According to the arm of the robot of claim 3, since the cord formed of the electric signal line and the like can be hidden inside the arm, the appearance of the arm of the robot is improved neatly, and the connector is connected when connecting the arms. By simply doing so, a cord composed of an electric signal line or the like can be connected, which facilitates the wiring work and improves the modularity of the robot arm. Therefore, if various robots are manufactured according to the application using this module as a basic constituent element, the cost of the robot can be reduced and the spread of the robot can be promoted.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a robot arm.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a perspective view showing an example of an articulated robot.

FIG. 4 is a diagram showing a posture of a hand when an arm is turned.

FIG. 5 is a cross-sectional view of a main part of an arm in which a cord is wired.

6 is a sectional view taken along line BB of FIG.

FIG. 7 is a cross-sectional view showing a state in which the arms are connected.

[Explanation of symbols]

 2, 3, 4 Arms 5, 18 Servo motor 7 Hands 14, 15 Wheels 16 Toothed belt 21 Ball screw 22 Nuts 30, 33 Connectors 31, 32 Wheels 34 A bundle of cords consisting of electric signal lines, etc.

Claims (3)

[Claims] 1. A screw shaft rotatably driven by a servomotor, a nut screwed to the screw shaft, a pair of wheels rotatably supported, and a belt stretched between the wheels. A robot arm comprising an endless cord such as a wire or a chain, and a power transmission means for fixing the nut to a portion extending along a threaded shaft of the cord. 2. The robot arm according to claim 1, wherein both wheels have the same diameter. 3. An arm of a robot in which an arm and an arm are rotatably connected to one arm by a rotary shaft fixed to the one arm, and the rotary shaft is tubular and is attachable to and detachable from a mounting portion of the one arm. The other arm is rotatably supported, and a male connector and a female connector are provided, and one of the connectors is attached to the rotary shaft and the other connector is attached to the mounting portion. A robot arm in which one end of a cord passed through a rotating shaft is connected to the one connector, and the other end of the cord extending from the rotating shaft is connected to the other connector.