JP2629884B2 - Robot hand - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a robot for stacking articles and transporting the stacked articles to another place. Of the equipped robot,
The present invention relates to a robot hand having an improved safety joint at a connecting portion between the arm and the grasping unit.

(Prior Art) A grasping part for grasping an article provided at the tip of a robot arm is provided with an external force greater than a stress normally caused by grasping and a load greater than a natural load of the article (overload). There is a robot provided with a safety joint for preventing damage to the arm and the grasping body of the robot in the direction of avoiding overload when ()) is applied. For example, as shown in FIG. 5 (a), a groove 3a is provided along the outer periphery of the connecting portion 3 provided between the robot arm 1 and the article grasping portion 2, and the connecting portion 3 has a smaller diameter than the arm 1. And grasping part 2
When the overload is applied to the grasping portion side by making the structural strength weaker than that of the above, the connecting portion 3 is broken from the groove portion 3a, so that the overload is not transmitted to the arm 1 and the grasping portion 2 side. Or a bracket 4 is provided at the tip of the arm 1 as shown in (b), a shaft mounting portion 2a is provided on the grasping portion 2, and the bracket 4 is provided with a shaft 4b via a support shaft 4b. The arm 1 and the grasping part 2 are connected by supporting the mounting part 2a. When an overload is applied to the grasping portion 2, the support shaft 4 b is broken so that the overload is not transmitted to the arm 1, and as shown in FIG. A guide plate 5 is provided at the distal end, and holes 5a are provided vertically at four places of the plate 5, and shafts 6 each having a notch 6a having a larger diameter than the hole 5a are provided at the respective holes. 5a, the shaft 6 is hung on the guide plate 5 by a notch 6a at the upper end, and the gripper 2 is integrally attached to the lower end of the shaft 6, and the relative space between the guide plate 5 and the gripper 2 And a spring 7 for urging the guide plate and the grasping portion in the separating direction, so that when the grasping portion 2 is overloaded,
The distance between the grasping portion 2 and the guide plate 5 is reduced against the urging force of the spring 7 so that one of the fitted shafts 6
In some cases, it is possible to freely move upward in the hole portion 5a, so that transmission of an overload to the arm 1 side can be prevented and the grasping portion 2 can be prevented from being broken. However, in the above cases (a) and (b), parts such as the direct connection part and the spindle part are destroyed, so parts need to be replaced, and it takes time and effort to recover from the trouble, and Until the parts are destroyed, the robot body cannot detect the occurrence of overload. In the case of the above (c), since there is no broken portion, the recovery is quick, but since the joint itself is supported by the buffer spring, the joint is supported against an abnormal force from the grasping portion 2 side to the arm 1 side. The sensitivity is reduced by the spring force. Further, the spring to be used is designed so that the spring is easily deformed by the inertial force applied to the grasping portion 2 side by the movement operation of the arm 1 so that no malfunction occurs in the positioning between the grasping portion and the article and the position detecting operation of the article. Therefore, it is necessary to use a relatively strong spring and reduce the amount of displacement of the grasping portion with respect to the arm due to the buffering action.

(Object of the Invention) The present invention does not use a spring at a connection portion between a robot arm and a grasping portion, and easily displaces the grasping portion by a small inertia force applied when the arm is moved. A robot which sets a permissible value of a load applied to a grasping unit in a grasping operation by a detector, and performs an article grasping / conveying operation according to a load allowable amount in a range set by the detector. It is a hand.

(Constitution of the Invention) The present invention provides a guide plate 5 at the distal end of a robot main body operating arm, a hole 5a formed in the guide plate 5 at an equal distance from the center of the arm 1, and a hole formed in each of the holes. A shaft 6 suspended vertically and freely in 5a, a support plate 2b integrally attached to a lower end portion of the shaft 6, and a grasping unit 2 integrally and downwardly provided below the support plate 2b. A detector 8 is provided in a notch above the shaft 6 to perform a control operation such as stop or reverse deceleration based on a detection signal of the detector 8, and a distance a from the center of the arm 1 to the shaft 6 is: When the distance 1 from the upper surface of the guide plate 5 to the composite center of gravity G of the grasping portion 2 and the work W, the gravitational acceleration g, and the maximum operation acceleration α of the arm 1 are set to have a relationship of a / l ≧ α / g. A robot band characterized by:

(Operation of the Invention) The present invention does not use a buffer spring at the connection between the robot arm and the grasping unit, and can hold the posture of the grasping unit in the vertical gravity direction by the action of natural gravity under normal load conditions. The displacement of the grasping part caused by the overload applied to the grasping part can be detected by the detector. Based on the detection signal, the arm operation of the robot body is stopped or retreated, and the arm moving speed is reduced. It is possible to control various operations such as a switching operation in the direction.

(Example) If the present invention is explained in detail according to an example, FIG. 1 is a front view explaining the outline of the robot hand of the present invention.
A guide plate 5 is provided at the distal end of the robot arm 1, and a circular shape vertically penetrating three or four or more places equidistant and equally spaced around the arm 1 of the guide plate 5. A hole 5a is provided. A shaft 6 having a circular notch 6a having a diameter larger than the diameter of the hole is provided in the hole 5a and suspended vertically downward in a freely fitted state.
At the lower end of the shaft 6, a support plate 2b for attaching the gripper 2
Are provided integrally, and the grasping unit 2 is integrally provided downwardly below the support plate 2b. A funnel-shaped follower 6b is provided between the notch 6a and the shaft 6. And the notch
Limit switch 8 radially integrated outside the outer circumference of 6a
Is provided. The contact terminal portion 8a of the switch 8
Is in a normal vertical state, it is in contact with the upper surface of the guide plate 5 in a pressed state, and the switch 8 itself is in a closing operation. FIG. 2 is a partially enlarged view of FIG.

Since the grasping unit 2 is attached to the leading end of the robot arm 1, it receives various forces due to the operation of the robot. The connecting portion between the arm 1 and the grasping portion 2 in the present invention is such that when the body of the grasping portion 2 hits an obstacle and overloads in the left-right direction, the grasping portion 2 shifts in the lateral direction and the shaft 6
The upper follower portion 6b of the guide plate 5 is slid up along the guide portion 5b having a right angle or an inclined surface of the guide plate 5, and is detected by the limit switch 8 attached to the integral notch 6a on the upper side of the follower portion 6b. Control to stop the operation of the robot main body arm 1 or to perform other operations based on the above. in this case,
Even if an overload is applied from any direction, up, down, left, right, front and back, any one of the shafts 6 slides up and the guide plate 5
Further, the contact terminal portion 8a of the limit switch 8 moves in a direction in which the contact terminal portion 8a moves away, and the switch 8 eventually performs an electrically separating operation. Also, in cases other than the collision with an obstacle, that is, during the operation of the robot, the body of the grasping unit 2 has a sufficient weight so that none of the shafts 6 slides above the guide plate 5 and does not malfunction. However, in the present invention, a response as sensitive as possible to an upward overload on the grasping unit 2 can be exhibited at the same time.

The robot hand of the present invention includes three or more shafts 6. When the notch 6a of the shaft 6 separates from the guide plate 5 when an external force is applied, the guide plate 5
The hole 5a is sufficiently larger than the diameter of the shaft 6, and the arm 1 is stopped by detection of the detector 8 at the time of contact with an emergency obstacle at the normal operation speed of the robot arm 1. This can be set by variously changing the inclination angle of the funnel-shaped truncated cone of the follower portion 6b so that no malfunction occurs due to inertia. In addition, the detection by the limit switch 8 is performed in such a manner that the operation is sensitive to an overload in the vertical direction, and the clearance between the shafts 6 is set to an appropriate distance in order to allow sufficient margin for the overload in the horizontal direction. , For example, by opening more than necessary dimensions.

Here, in FIG. 3, the distance a from the center of the arm 1 of the robot hand to the shaft 6 is a, the distance from the upper surface of the support guide plate 5 to the composite center G of the grasping unit 2 and the article (work) W is 1 and the grasping unit. Assuming that the total mass of the workpiece 2 and the workpiece W is m, the optimum separation distance of the shaft 6 is calculated. For example, in the case where the external force F acts and the limit switch 8 performs the detection operation, the shaft 6 is moved from the guide plate 5 at a point A (one contact portion between the notch 6a and the hole 5a) in FIG. Rising up,
At this time, the point B at the other end (the other portion of the contact portion between the notch 6a and the hole portion 5a) is the center of rotation. At points A and B, 1/2 mg of gravity is applied downward, and at point B, external force F
Generates a bending moment M. Assuming that the upward force generated by M is f, M = lF and M = 2af, so that f = M / 2a = (l / 2a) × F where F is the normal (normal use) of the robot arm 1 in the lateral direction. ), F = mα. The necessary condition is that the position of the combined center of gravity G of the work W and the grasping unit 2 when the work W is grasped by F does not move. In order not to move, the upward force f applied to the point A becomes A
Since it is necessary that the total gravity of the grasping part 2 and the workpiece W itself at the point is equal to or less than 1/2 mg, f ≦ (1/2) mg.

 From the above, when the relationship between a and l is obtained, lmα / 2a ≦ (1/2) mg from (l / 2a) × F ≦ (1/2) mg, so that a / l ≧ α / g is sufficient.

Next, the relationship between the diameter of the hole 5a of the guide plate 5 and the diameter of the shaft 6 is calculated.

If the robot is stopped urgently by receiving an external force from the lateral direction during operation, as shown in FIG. 4 (b), between the guide plate 5, the shaft 6 and the support plate 2b shown in FIG. A phenomenon in which the support plate 2b slides up occurs. If the user does not move from the state (a) to the state (b) without being caught, there is a high risk of damaging the grasping unit 2 and the obstacle itself. Therefore, an appropriate amount of gap δ is required between the hole portion 5a of the guide plate 5 and the shaft 6. Here, the parallel distance between the guide plate 5 and the support plate 2b is e, the diameter of the shaft 6 is D1, and the diameter of the notch 6a is
Assuming that D2 (provided that there is a margin such that D2> D1 + δ), the gap δ is the horizontal displacement of the point Y with the point X as the center of rotation, so that δ = ▲ ▼-▲ ▼ cosθ Where ▲ ▼ cosθ = (1/2) D1 + 2a + (1/2) D2 So that Becomes

(Effect of the Invention) According to the present invention, when a predetermined normal load is applied to the joint between the arm and the grasping portion of the robot hand body, the grasping portion is determined by the own weight of the grasping portion and the own weight of the grasped article (work). The position of the gripper can be maintained constant in the direction of gravitational load, and when an overload is applied from the outside, the fitting / connecting part that can displace the position of the grasping part against the load applied in the direction of gravitational force is provided. Damage to the robot arm, grasping part, and work due to load can be avoided, and a detector that detects the occurrence of displacement is provided at the fitting connection part, and a displacement generation signal is sent from the detector when overload is applied As a result, it is possible to control so as to perform an appropriate processing operation such as stopping the operation of the robot arm body based on the signal, and a robot hand having a safety device against overload can be provided. It has a remarkable effect.

[Brief description of the drawings]

1 is a front view of the apparatus of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, FIG. 3 is a schematic view of the entire apparatus of the present invention, and FIG. FIG. 5 is a front view of a conventional robot hand. DESCRIPTION OF SYMBOLS 1 ... Robot arm 2, ... Grasping part 3 ... Connection part 4, ... Bracket 5 ... Guide plate, 6 ... Shaft 7 ... Spring, 8 ... Detector

Claims (1)

(57) [Claims] 1. A guide plate 5 at the end of an operating arm of a robot body, holes 5a formed in the guide plate 5 at equal distances from the center of the arm 1, and a vertical hole in each of the holes 5a. A shaft 6 suspended in a free-fitting state in a direction, a support plate 2b integrally attached to a lower end of the shaft 6, and a grasping portion 2 integrally and downwardly provided below the support plate 2b. A detector 8 is provided in a notch on the upper part of the arm 6 to perform a control operation such as stop or reverse deceleration based on a detection signal of the detector 8, and a distance a from the center of the arm 1 to the shaft 6 is changed by a guide plate 5. Grasp part 2 and work W from top
The robot hand is set to have a relationship of a / l ≧ α / g when a distance l to the combined center of gravity G, a gravitational acceleration g, and a maximum operation acceleration α of the arm 1 are set.