JPH0369676B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an arm for a work robot, and more particularly, to an arm for a work robot that can move in a gravity-balanced manner over its entire range of motion.

As shown in Fig. 1, a conventional work robot, for example, a painting robot, has a rotary body 2 installed on a base 1 so as to be rotatable in the left-right direction (θ direction). It consists of a vertical arm 3 that can swing vertically and a horizontal arm 5 that can swing vertically (in the φ direction) about a pin 4 at the top of the vertical arm 3. , is configured to move in the ψ direction.

However, in order to drive a working robot, such as a painting robot, teaching must be performed, and a person must hold the end of the arm to operate the robot. For this purpose, it is necessary to maintain the gravity balance of the arm over the entire range of motion, and conventionally
As shown in the figure, the vertical arm 3 is configured to be able to swing in the ψ direction about the shaft portion 2b on the support rack 2a on the rotary body 2, and the pins between the top portion 2c of the support rack 2a and the vertical arm 3. A spring 6 is stretched between the pin 4 and the angle 7, and the angle 7 is rotatably attached to the pin 4.
A spring 8 is stretched between the top of a and the tip of the horizontal arm 5. Also, the tip of the side 7b and the top 7 of the rotating body 2
The balance rod 10 is arranged so that it can rotate around the fulcrum 9 provided at the same distance as the length of the shaft part 2b and at the same height as the shaft part 2b, and the side 7 of the angle 7 is
b, a parallelogram link is formed between the vertical arm 3 and the sides 2b-9.

Therefore, no matter what angle (φ) the horizontal arm 5 is moved up and down, the restoring force of the spring 8 acts on the horizontal arm 5 to return it to its old position. Further, the vertical arm 3 is connected to the shaft portion 2 of the support frame 2a.
Although it swings around b, the spring 9
Since the rotation center of is the top of the support frame 2a, when the vertical arm 3 tilts back and forth (in the ψ direction), the spring 6 stretches according to the tilt angle, and at the same time a restoring force is generated within the spring 6, causing the vertical arm 3 to There is a force working to return it to its old position.

However, in the case of the gravity balance structure mentioned above,
The restoring force generated differs depending on the amount of extension of the spring, and even if it is balanced at a certain amount of extension, it is not necessarily balanced at other points, and the structure was not designed to be balanced over the entire range of arm movement. . In addition, since the gravity balance spring is placed on the arm, the weight of the arm increases, resulting in an increase in inertia.
It had a drawback that made it difficult to operate during teaching.

The present invention was made in order to eliminate such drawbacks of the conventional gravity balance structure of a work robot arm, and provides a work robot that can move in a gravity balanced manner over the entire operating range of the arm. The purpose is to provide an arm for use.

The arm for a work robot according to the present invention is an arm for a work robot driven by a rotary actuator, and includes an eccentric ring having a radius _R1 disposed at a constant distance from the vertical arm, and one end supported on the periphery of the vertical arm. A means for transmitting the tensile force f ₁ of a vertical arm whose end is supported on the circumferential surface of the eccentric wheel, and a radius R ₂ that is provided on the same rotation axis as the rotation axis of the eccentric wheel and rotates in synchronization with the rotation axis. balance means of a vertical arm consisting of a circular ring of radius R ₂ and an elastic means with a spring force f ₂ supported at one end on the circumferential side of the circular ring with radius R 2 and the other end supported on a fixed end; means for transmitting the tensile force f ₃ of a horizontal arm supported and whose other end is supported on the circumferential side of an eccentric wheel with radius R ₃ ; A balance means of a horizontal arm consisting of a circular ring with a radius R ₄ which rotates as a horizontal arm, and an elastic means with a spring force f ₄ whose one end is supported on the circumferential side of the circular ring with a radius R ₄ and the other end is supported by a fixed end. The radii R ₁ and R ₃ from the rotational axis of the eccentric ring to the circumferential side of the eccentric ring are R ₁ = f ₂ / f ₁ × R ₂ and R ₃ = f ₄ / f ₃ × R ₄ , respectively. It is characterized by having the dimensions indicated. However, in this specification, the radius of the eccentric ring means the dimension from the rotation axis to the ring periphery.

EMBODIMENT OF THE INVENTION Hereinafter, the arm for a work robot of the present invention will be explained based on an example.

Figure 3 shows the overall structure of a work robot incorporating the work robot arm of the present invention.
A is a top view, b is a side view, and c is a rear view.

The arm for a work robot according to the present invention, like a general work robot, has a joint arm system consisting of a vertical arm 3 and a horizontal arm 5, and these arms 3 and 5 are capable of moving in the θ, φ, and ψ directions. is provided on the rotating body 2.

Motor units 11 and 12 as rotary actuators are arranged on the rotary body 2, and by rotating a drive lever 13 directly connected to the output shaft of the motor unit 11, the horizontal arm is connected via a connecting lever 14. 5 up and down in the φ direction. Further, the motor unit 12 tilts the vertical arm 3 directly connected to its output shaft to perform a swinging operation in the ψ direction. Furthermore, the motor unit 15 in the base 1 moves the horizontal arm 5 in the left and right direction (θ direction).
This is a motor unit for driving the rotary body 2, and has a structure in which the rotary body 2 is caused to perform a turning motion using a pinion and a gear (not shown).

Further, at the rear of the vertical arm 3, as _shown in FIG. Radius R ₂ that rotates synchronously with
a circular ring 19 and a vertical arm 3
A chain 16 is stretched, with one end supported by the arm edge 2d at a distance L ₀ from the rotating shaft 2b to the eccentric wheel 17 side, and the other end supported by the circumferential side of the eccentric wheel 17. In addition, a coil spring 21 with a spring force f ₂ is attached so that one end is supported on the fixed end 20 on the rotating body 2 described above and the other end is supported on the circumferential side of the circular ring 19, and the vertical arm 3 is balanced. will be established.

If the above-mentioned balance structure is provided in the vertical arm 3, when the arm 3 is tilted in the ψ direction, a tensile force corresponding to the tilt of the arm is generated in the chain 16 and the eccentric wheel 17, and the eccentricity is The ring 17 rotates in the direction of the tensile force f ₁ .

As a result, the circular ring 19 fixed to the same rotating shaft 18 as the eccentric ring 17 also rotates, and the radius of the circular ring 19 is
Spring 21 by an amount corresponding to R ₂ and its slope
expands and contracts.

Therefore, if the radius R ₁ of the eccentric ring 17 is of the shape R ₁ = f ₂ / f ₁ × R ₂ , R ₂ changes depending on the inclination angle of the vertical arm 3, and the arm 3 can be tilted to any angle ψ, it is possible to provide a structure that returns to the old position.

Further, as shown in FIG. 5, the lever 23 is fixed to the end of the rotating shaft 22 of the connecting lever 14 on the horizontal arm 5 side, and is configured to rotate in synchronization with the rotation of the rotating shaft 22. A function is provided to convert the vertical movement (φ direction movement) of the arm 5 into left and right direction movement (ψ direction movement). Further, the lever 23 is mounted on the rotating shaft 22 at a position orthogonal to the connecting lever 14, and an eccentric wheel 24 with a radius R ₃ is mounted on the rear side of the lever 23, and on the same rotating shaft 25 as the eccentric wheel 24, the rotating shaft 25 A circular ring 26 of radius R ₄ is arranged which is synchronized with the rotation of . Further, a chain 27 is installed between the lever 23 and the circumferential side of the eccentric ring 24, and a coil spring 29 with a spring force f ₄ is installed between the circumferential side of the circular ring 26 and the fixed end 28 of the rotating body 2. The structure is such that the vertical movement of the horizontal arm 5 is balanced.

If the horizontal arm 5 is provided with the above-mentioned balance structure, when the arm 5 is moved up and down, the drive lever 13 also moves up and down, the connection lever 14 is rotated, the lever 13 swings, and the chain 27 and the eccentric wheel 24, a tensile force _f3 of an amount corresponding to the vertical movement of the arm 5 is generated, and the eccentric wheel 24 rotates in the direction in which the tensile force _f3 is applied.

As a result, the circular ring 26 attached to the same rotating shaft 25 as the eccentric ring 24 also rotates, and the spring 29 expands and contracts by an amount corresponding to the radius R ₄ of the circular ring 26 and its inclination.

Therefore, if the radius R ₃ of the eccentric ring 24 is formed to have a dimension of R ₃ =f ₄ /f ₃ ×R ₄ ,
Balanced movement can be achieved no matter how the horizontal arm 5 is moved up and down.

Note that the eccentric wheels 17 and 24 described above are not limited to so-called off-axis circular plates in which the rotation center of the circular plate is shifted from the center of the circle, and may also include modified triangular plates instead of circular plates, etc.
This includes all cases where the distance from the center of rotation to the periphery of the plate (ring) varies depending on the rotation angle.

As is clear from the above description, the arm for a work robot of the present invention uses a chain and an eccentric wheel in addition to a spring in the balance mechanism of the arm, so that (1) the amount of inclination or movement of the horizontal arm of the vertical arm is reduced; By absorbing the property that the spring force changes depending on the amount of tension and the amount of expansion and contraction into an eccentric ring of an appropriate radius, it was possible to achieve balance over the entire operating range of the arm.

(2) Additionally, the balance spring is placed on the arm and is not driven together with the arm, which reduces the weight of the arm and reduces inertia, making it easier to operate the arm during teaching.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the overall structure of a work robot, Fig. 2 is a sectional view of main parts showing the gravity balance structure of a conventional work robot arm, and Fig. 3 is a work robot equipped with the work robot arm of the present invention. 3A is a top view, FIG. 3B is a side view, and FIG. 5 is a rear view, and FIGS. 4 and 5 are views showing the vertical and horizontal arms of the work robot arm according to the present invention. FIG. 3 is a cross-sectional view of main parts showing the balance structure of the arm. In the figure, 1...base, 2...rotating body, 3...
Vertical arm, 5...Horizontal arm, 11, 12, 1
5...Motor unit, 13...Drive lever, 1
4...Connection lever, 16, 27...Chain, 1
7, 24... Eccentric wheel, 19, 26... Circular ring, 1
8, 22, 25... Rotating shaft, 21, 29... Coil spring, 23... Lever.

Claims (1)

[Claims] 1. An arm for a work robot driven by a rotary actuator, which includes an eccentric ring with a radius R ₁ disposed at a constant distance from the vertical arm, and an eccentric ring with one end supported on the periphery of the vertical arm and the other end eccentric. means for transmitting the tensile force f ₁ of a vertical arm supported on the circumferential side; a circular ring with a radius R ₂ that is provided on the same rotation axis as the rotation axis of the eccentric wheel and rotates in synchronization with the rotation axis;
Balancing means of a vertical arm consisting of an elastic means with a spring force f ₂ supported at one end by a circular circumferential side surface of radius R ₂ and the other end supported by a fixed end; means for transmitting the tensile force f ₃ of a horizontal arm supported on the circumferential side of an eccentric wheel with radius R ₃ , and a means for transmitting the tensile force f 3 of a horizontal arm supported on the circumferential side of an eccentric wheel with a radius R 3, and a means of transmitting the tensile force f 3 of a horizontal arm supported on the circumferential side of an eccentric wheel with a radius
A circular ring with radius R ₄ and a spring force whose one end is supported by the side surface of the circular ring with radius R ₄ and the other end is supported by a fixed end.
radii R ₁ and R ₃ from the rotation axis of the eccentric wheel to the circumferential surface _of the eccentric wheel are respectively R ₁ = f ₂ /f ₁ ×R. _2. An arm for a work robot, characterized in that it has dimensions expressed as: 2, R ₃ =f ₄ /f ₃ ×R ₄ .