JPH10217167A - Scalar type robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve rectilinear propagation precision by installing a seesaw type tensioner in an upper arm inside and providing a mechanism to actuate an idler in the opposite direction and at the same stroke in the case when tension varies. SOLUTION: A tensioner provided with a seesaw type plate 8 inside of an upper arm 1 and an idler 6 on its both ends is provided, a pre-load is constantly applied on a side surface of a belt by a spring on the tensioner, and the idler 6 is pressed on the belt 4. When both of pitch diameters of pulleys are constant, a fulcrum 7 of the seesaw type tensioner is set at a position properly offset from an intermediate point of both of the idlers, and it is possible to press the idler on the belt 4 constantly moving the idler in the opposite direction by the same stroke by fixing the fulcrum on an axis between the pulleys.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scalar robot for transporting a semiconductor wafer or a liquid crystal glass substrate.

[0002]

2. Description of the Related Art A scalar robot is used for transferring a semiconductor wafer or a glass substrate for liquid crystal to a processing apparatus and a cassette or another apparatus. Generally, when transferring a semiconductor wafer or a glass substrate for liquid crystal, the clearance between the cassette and the wall of the processing chamber is small. . In order to achieve this performance, the overall rigidity of the mechanism is generally improved, and the belt tension used to prevent the backlash of the power transmission elements of the belt and pulley used to link the links inside the robot arm is increased. However, this problem has been dealt with by improving the coaxiality and the positional accuracy of the arm, shaft and pulley. Of these, as for the tension adjustment mechanism of the upper arm belt, a structure as shown in FIG. 3 is used, and measures have been taken to eliminate the backlash by applying the tension of the belt and to eliminate the error of the rotation angle. However, let us consider a case where an error due to machining and assembly occurs and the distance between the pulleys is increased or decreased. FIG. 3 shows the eccentricity of the fixed pulley 1 with respect to the arm rotation shaft 3 for simplification. In a method as shown in FIG. 3A in which the idler 6 is pressed from one side via a spring 5b from one direction, the driven pulley 11 and the forearm 12 rotate so that the tensions of the belts 4 above and below the pulley shown in FIG.
Deviates from the original rotation angle. As a result, the position 15 of the hand shifts, and the straight traveling accuracy of the hand deteriorates. In this case, when the spring is removed, the upper and lower tensions of the pulley shown in the figure are appropriately tensioned at a certain point, but when the pulley is loosened, backlash occurs, and the positional deviation of the hand further increases. In the method shown in FIG. 3B, the side surfaces of the belt hanging on both ends of the pulley are pushed by the idler via the springs 5c or 5d, so that the straight running accuracy is improved as compared with the method shown in FIG. 3A. . However, even if 5c and 5d are created so as to have the same spring constant, it is difficult to always match the respective spring constants k1 and k2. As shown in FIG.
If the belts are sandwiched between idlers by the tension of the book spring, and the upper and lower belts in the figure are linearly stretched, the structure shown in FIG.
The deviation of the hand position 15 is further reduced, but when the hand is loosened, backlash occurs in the rotation angle of the driven pulley 11.

[0003]

In order to increase the straight traveling accuracy of a SCARA type robot, measures have conventionally been taken to improve the coaxiality and positional accuracy of arms, shafts and pulleys. However, as a practical matter, there are always processing tolerances in the production of robots. FIG. 2 illustrates a case where a deviation occurs between the center axis 2 of the fixed pulley in the upper arm and the rotation center 3 of the upper arm. Assuming that the rotation angle of the arm 14 is θ, the rotation angle of a straight line connecting the axes of the pulleys due to axis deviation is θ1. Assuming that the pitch radius of the fixed pulley 1 is 2r and the radius of the driven pulley 11 is r, the rotation angle of the forearm 12 with respect to the upper arm 14 is originally 2θ.
However, it changes to 2θ1, and the position 15 of the hand changes. At this time, since the distance between the shafts of the pulleys varies depending on the rotation angle θ, the rotation error Δθ2 is further reduced by the conventional transmission component tension adjusting method for the reason described above.
Is added.

When the distance between the shafts of the pulley is ΔL = (the distance between the shafts when the rotation angle = 0) − (the rotation angle θ
, The rotation error Δθ2 = ΔL / r [rad]
Is generated. This has a greater effect as r is reduced, and is sufficiently greater than the effect of θ1. Therefore, Δθ2
Reduces the straightness of the hand.

[0005]

According to the present invention, even if the distance between the pulleys caused by the misalignment between the fixed pulley center shaft 1 and the arm rotating shaft 2 fluctuates, the rotation error of the driven pulley described above is obtained. An object of the present invention is to improve the straight traveling accuracy of a SCARA robot by uniformly and automatically adjusting the belt tension without generating Δθ2.

In a SCARA type robot, as shown in FIG. 1, an idler 6 is provided on both sides of a tensioner 8, and a seesaw type tensioner having a structure in which a side of a belt is always sandwiched from both sides by a spring is mounted inside the upper arm of the SCARA type robot. When the tension fluctuates, the idler has a mechanism that operates in the reverse direction and the same stroke.

According to the above configuration, even if the belt in the upper arm of the SCARA type robot becomes slack, the slack can be absorbed without giving a rotation angle error of the driven pulley, so that the influence on the straightness of the hand can be reduced. It is.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a seesaw-shaped plate 8 and a tensioner provided with idlers 6 at both ends thereof are provided inside the upper arm 1 of the SCARA robot, and the tensioner is always preloaded on the side of the belt by a spring. Press the idler against the belt. If the pitch diameter of both pulleys is constant, set the fulcrum of the seesaw tensioner at a position appropriately offset from the midpoint of both idlers, and fix the fulcrum on the axis between the pulleys, so that it is always the same. It is possible to push the idler against the belt while moving it in the opposite direction by the stroke.

When the pulley does not have a constant pitch radius like a cam, as shown in FIG. 4, a part of the belt is guided by a guide roller 18 so that the belt is parallel to the axis of the pulley and symmetrical with the object. Run 4. Also, by providing a fulcrum at the midpoint between the two idlers 6 and providing a seesaw-type tensioner that fixes the fulcrum on the pulley axis, the idler 6 is always pressed against the belt 4 while moving in the opposite direction by the same stroke. Is possible.

[0011]

By using the above-mentioned seesaw type tensioner, even if the center distance fluctuates due to a processing error or the tension fluctuates greatly by using a non-circular pulley, the tensioner makes the belt tension uniform. Does not occur, and the meandering width of the hand can be reduced.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a SCARA robot according to the present invention.

FIG. 2 is a diagram illustrating an influence of a displacement of an axis of rotation of a fixed pulley upper arm on a hand position when a rotation error due to slack of a belt is not considered.

FIG. 3 is an explanatory diagram of a rotation error due to slack of a belt in a conventional tensioner.

FIG. 4 shows another embodiment of a robot having a non-circular pulley.

[Explanation of symbols]

1: Upper arm fixed pulley, 2: Upper arm fixed pulley central axis, 3: Upper arm rotation axis, 4: Belt, 5a, b,
c, d: tensioner spring, 6: idler, 7: seesaw type tensioner fulcrum, 8: tensioner, 9 ...
Central axis of driven pulley in upper arm, 10 ... Rotation axis of forearm, 1
DESCRIPTION OF SYMBOLS 1 ... Pulley inside upper arm, 12 ... Forearm, 13 ... Hand, 14 ... Upper arm, 15 ... Hand position, 16
... non-circular fixed pulley in the upper arm, 17 ... non-circular driven pulley in the upper arm, 18 ... guide roller, 19 ... spring post

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yutaka Saito 3300 Hayano, Mobara-shi, Chiba Electronic Device Division, Hitachi, Ltd.

Claims (2)

[Claims] 1. A scalar type robot for transmitting power using a belt and a pulley, wherein a belt is hung on the two pulleys, and when the belt bends, the same stroke is applied to a portion of the belt not in contact with the pulley. A scalar type robot characterized by pressing an idler with a quantity. 2. A scalar robot for transmitting power using a belt and a pulley, wherein a belt is hung on the two pulleys, a part of the belt not in contact with the pulley is run in parallel, and a parallel portion of the belt is formed. A scalar robot characterized by a mechanism for pressing the idler with the same stroke.