JPH07186079A - Automatic tool change device - Google Patents

Abstract

PURPOSE:To reduce the weight and bulk of an automatic tool change device by detecting by means of a sensor the displacement of the size of a coupling gap between a robot side fixing plate and a tool plate, deciding overload due to operation force such as rotation, torsion and tensile in the direction of the tool plate being separated. CONSTITUTION:When compressed air is fed to a cylinder bore 1a from a feed/ discharge port 1b, an actuator 3 is descended, and lock balls 4 are kept on being pushed into a joining seat 1d, and when the actuator 3 descends to the final position and the lock balls 4 come to face the restraining taper of an aligning ring 5, the lock balls 4 are pressed against a core side on the joining taper surface of the actuator 3, and this pressing force acts on the restraining taper of the aligning ring 5, so as fixing plate 1 and a tool plate 2 are coupled mutually. At this time, tensile force in regard to the tool plate 2 acts on as overload, and when a coupling opening is enlarged, this change is detected by means of a sensor 6, and the operation of a robot is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic tool changer which can be used for a robot hand or the like to automatically change tools.

[0002]

2. Description of the Related Art An arm of an industrial robot is equipped with an automatic tool changer for changing a tool for machining. This automatic tool changer is capable of aligning and connecting a tool plate with a tool integrated with a fixed plate connected to an arm of a robot.

In such an automatic tool changer, in order to connect the fixed plate and the tool plate, a mechanism for positioning and fastening them is necessary. For example, as a positioning mechanism, as described in Japanese Patent Laid-Open No. 4-63688, a positioning shaft is projected at a position apart from the core of the tool plate in parallel with the axis of the tool plate, and these positioning members are positioned on the fixed plate side. A hole into which the shaft fits can be provided, and the fitting between the positioning shaft and the hole can be used.

In addition to such a positioning mechanism, between the robot arm and the automatic tool changer, an abnormal load is generated when a tool is mounted while the positioning is still poor, and a workpiece is not machined during machining. It is necessary to provide an overload prevention device for absorbing reaction force due to poor posture setting or the like. If such an overload prevention device is not provided, a large load is applied to the arm side of the robot at the time of mounting a tool or machining a workpiece, causing damage or affecting the operation accuracy.

[0005]

Conventionally, most automatic tool changers have mainly adopted a function for tool change, and have adopted a system in which a tool can be quickly attached / detached by a floating mechanism or the like. For this reason, the overload prevention device is usually designed to be installed between the arms of the robot separately from the automatic tool changer.

However, if the automatic tool changing device and the overload preventing device are separately provided and arranged side by side from the robot side to the tool side, the distance from the arm to the tool plate becomes long. Therefore, the distance from the output flange on the robot side to the tool also becomes long, and the influence of inertial weight and the like during operation becomes large.

As described above, since the conventional automatic tool changer is separately provided with the overload preventive device, the motion performance of the robot at the time of operation is affected by the increase in inertial weight.
There was also a limit to the size and weight reduction.

The problem to be solved in the present invention is to reduce the size and weight by integrally providing the overload prevention device with the automatic tool changer, and further improve the motion performance of the robot.

[0009]

The present invention comprises a combination of a fixed plate connected to an arm of a robot hand and the like, and a tool plate for attaching and detaching a tool. An automatic tool changer for fastening, wherein one of the fixed plate and the tool plate is provided with detection means for detecting the size of the gap between the plates, and the fixed plate and the tool plate are detected by the detection means. It is characterized by comprising a system capable of detecting an overload from the tool plate by comparing the size of the gap between the tool plate and the steady value of the gap at the time of proper fastening.

[0010]

With respect to the steady value of the gap between the fixed plate and the tool plate when they are properly fastened, the detecting means is used, for example, when the tool plate is pulled and the gap becomes large. Detects this and determines whether or not an overload is applied from the tool plate to the fixed plate by comparing with the above steady value. When it is determined that the overload is applied, the operation of the robot is stopped to prevent the automatic tool changer including the fixed plate and the tool plate from being damaged.

Further, not only the displacement due to the pulling of the tool plate but also the external force causing the twisting, the inclination in the axial direction, etc. is detected, and the size of the gap between the plates is detected by the detecting means to cause an overload. You can know if you are doing.

[0012]

1 is a schematic vertical sectional view showing an embodiment of an automatic tool changer of the present invention, and FIG. 2 is a horizontal sectional view taken along the line AA of FIG.

In the figure, with respect to the fixed plate 1 connected to the tip of the arm (not shown) of the robot hand,
A tool plate 2 integrated with a tool (not shown) can be detachably mounted.

The fixed plate 1 has a circular cross section, and a cylinder bore 1a having an annular cross section is formed therein, and supply / discharge ports 1b, 1c for supplying air as a working fluid to the cylinder bore 1a are provided therein. Further, an actuator 3 is coaxially connected to the fixed plate 1, and its piston 3a is slidably incorporated in the cylinder bore 1a.

On the lower surface of the fixed plate 1, a hollow joint seat 1d surrounded by a cylinder bore 1a is coaxially provided, and a plurality of tapered positioning holes 1e having a triangular vertical cross section are provided at the edges. A plurality of lock balls 4 are rotatably incorporated in the peripheral wall of the joint seat 1d, and the lock balls 4 do not come out to the outer edge of the opening of the joint seat 1d supporting the lock balls 4. A small protrusion (not shown) is provided.

The actuator 3, as shown in FIG.
A guide tapered surface 3b, a stopper 3d, a copying tapered surface 3e, and a coupling taper 3c are formed from the tip side. At the time of coupling, the stroke of the actuator 3 is determined so that the peripheral surface of the lock ball 4 comes into point contact with the coupling taper 3c.

Returning to FIG. 1, the tool plate 2 is provided with a connector rod 2a, which is smaller than the inner diameter of the joint seat 1d of the fixed plate 1 and is coaxially projected. This connector 2a
Has a guide 2b whose outer peripheral surface at the upper end has a tapered surface, a small diameter portion 2c is provided at the lower portion thereof, and an alignment ring 5 is externally fitted around the small diameter portion 2c.

The aligning ring 5 is an annular body having an inner diameter larger than the outer diameter of the small diameter portion 2c, and the lower half of the outer peripheral surface thereof has a restraining taper tapering toward the lower end side as shown in FIG. 5a is formed and a tapered guide surface 5b having a gentle slope is provided in the upper half.

Further, on the upper surface of the tool plate 2, a steel ball 2d fitted in the positioning hole 1e of the fixed plate 1 is incorporated. These steel balls 2d are capable of being aligned with the tapered positioning hole 1e of the fixed plate 1.

Here, when the tool plate 2 is attached to the fixed plate 1 and when machining is performed by a tool (not shown) set on the tool plate 2, the robot moves from the fixed plate 1 to the robot via the tool plate 2. A system is provided for detecting an overload applied to the side by knowing the change in the size of the gap between the fixed plate 1 and the tool plate 2.

As this detection system, an optical sensor 6 is incorporated in the tool plate 1 and its tip is fixed to the fixed plate 1.
The optical axis is parallel to the axis of the tool plate 1. As shown in FIG. 1, the sensor 6 can detect the fastening gap between the fixed plate 1 and the tool plate 2 by an optical system. Then, the detection signal of the change in the fastening gap by the sensor 6 is input to the controller that controls the robot,
Establish a control system that stops the robot operation when an overload occurs.

If the sensor 6 has a steady value S corresponding to the fastening gap shown in FIG. 1, the controller determines that the fastening of the fixed plate 1 and the tool plate 2 is complete and that there is no overload, and the interval is It is determined that the fastening between the fixed plate 1 and the tool plate 2 has been released when the fixed value C becomes equal to or more than a certain value. When the fastening gap becomes smaller than the steady value S or the change between the steady value S and the constant value C is detected, it is determined that the controller is overloaded from the tool plate 2 to the fixed plate 1 side. Judge and stop the operation of the robot.

FIG. 4 shows an attempt to connect the fixed plate 1 to the tool plate 2 which is stocked at a predetermined position before the fastening by fixing the fixed plate 1 to the tool plate 2 by operating the robot. Indicates the status. Before fastening, the actuator 3 retracts to the uppermost end as shown in the drawing by supplying air to the cylinder bore 1a from the supply / discharge port 1c, and the guide tapered surface 3b at the lower end abuts the lock ball 4.

When compressed air is supplied to the cylinder bore 1a from the supply / discharge port 1b in this state, the actuator 3 descends as shown in FIG. 1, and the lock ball 4 is gradually held in the lock ball 4a. 4 for joint 1
Push it into d.

By moving the lock ball 4 to the core side,
When the actuator 3 descends to the final position, the lock ball 4 comes into contact with the restraining taper 5 a of the aligning ring 5. Since the lock ball 4 is pressed toward the core side by the connecting tapered surface 3c of the actuator 3, this pressing force acts on the restraining taper 5a from the lock ball 4. Therefore, the fixed plate 1 and the tool plate 2 are axially constrained and fastened to each other by the engaging force between the lock ball 4 and the centering ring 5.

FIG. 5 is a vertical cross-sectional view showing a situation where the tool plate 2 receives a downward pulling force in the drawing to apply an overload to the fixed plate 1.

When the tool plate 2 is pulled in the direction away from the fixed plate 1, an acting force by the vector shown in FIG. 3 is generated. That is, the overload that acts is F
_{When set to 1} , the acting force when pushing the lock ball 4 outward can be expressed as F ₂ . If the angles formed by the tapered surface 5a of the aligning link 5 and the coupling taper 3c of the actuator 3 with respect to the axes are θ ₁ and θ ₂ , respectively, F ₃ = F ₂ · tan θ ₂ = F ₁ · tan θ ₁ · ta
nθ ₂ acts as an acting force that raises the actuator 3 due to overload. Therefore, if the pressing force of the actuator 3 is F _4, and under the condition of F ₄ <F ₃ , the actuator 3 moves upward in the drawing, and the fastening gap between the fixed plate 1 and the tool plate 2 is It becomes larger than the steady value S.

As described above, when the tensile force acting on the tool plate 2 acts as an overload and the fastening gap is expanded, the sensor 6 detects the change in the fastening gap,
This detection signal is input to the controller to stop the operation of the robot.

FIG. 6 is a diagram showing a case where a torque for rotating the tool plate 2 around its axis is generated and this torque acts as an overload.

When the position of the fixed plate 1 is fixed and the tool plate 2 is displaced in the direction around its axis, the steel balls 2d for positioning the fixed plate 1 and the tool plate 2 are positioned. The position changes with respect to the positioning hole 1e of the fixed plate 1. Since the positioning hole 1e has a conical shape, the steel ball 2d is located in the positioning hole 1e.
If it deviates from the center of e, the fastening gap between the fixed plate 1 and the tool plate 2 becomes larger than the steady value S. In such a situation, the tool plate 2 tends to move away from the fixed plate 1 and the actuator 3 is pushed back upward from its steady position.

When the fastening gap is widened in this way, the sensor 6 detects a change in the fastening gap and inputs it to the controller, as in the previous example, thereby stopping the operation of the robot.

FIG. 7 shows an example of a case where an acting force for inclining the axis of the tool plate 2 acts.

In the example shown in the figure, the right side of the tool plate 2 is overloaded such that it tilts downward, and the actuator 3 is pushed back up from the steady position in FIG. 1 via the lock ball 4. At this time, on the side where the sensor 6 is incorporated,
The fastening gap between the fixed plate 1 and the tool plate 2 becomes larger than the steady value S. Therefore, the sensor 6 detects the change in the fastening gap and inputs it to the controller to stop the operation of the robot.

The tool plate 2 is not only subjected to the oblique posture shown in the drawing, but is also subjected to an overload such as tilting to the downward left posture, and the posture is changed three-dimensionally. Such a change in the posture causes a phenomenon in which a portion of the fastening gap detected by the sensor 6 becomes larger or smaller than the steady value S. Therefore, no matter which direction the lean is tilted, when the fastening gap is detected by the sensor 6, the fastening gap is detected. The operation of the robot is immediately stopped by detecting the deviation from the steady value S of.

FIG. 8 is an example showing a state in which an overload is applied to the tool plate 2 from left to right in a direction orthogonal to the axis.

By pushing the tool plate 2 to the right side, the positioning steel ball 2d moves in the direction of coming out of the positioning hole 1e of the fixed plate 1 as in the case of FIG. The fastening gap with the tool plate 2 expands. Then, due to the overload, the actuator 3 is pushed back up from the steady position in FIG.

Even in this case, since the fastening gap between the plates 1 and 2 is expanded with respect to the steady value S, the sensor 6 detects the displacement, and the controller stops the operation of the robot.

FIG. 9 is a longitudinal sectional view of the essential part showing another embodiment. The same members as those in the previous example are designated by common reference numerals, and detailed description thereof will be omitted.

A connecting rod 10 (corresponding to the connector rod 2a in the previous example) is coaxially arranged on the tool plate 2 so as to be slidable in the axial direction thereof, and the centering ring 5 is attached to the small diameter portion 10a provided at the upper end thereof. Is loosely fitted so that its center can be displaced. Further, a flange 10a is formed at the lower end of the connecting rod 10, and this flange 10a portion is housed in a chamber 2e provided in a hollow shape at the lower end of the tool plate 2, and a disc spring is provided between the flange 10a and the inner wall of the chamber 2e. 11 is installed.

The disc spring 11 is pre-compressed and pre-loaded in a steady state when fastening the fixed plate 1 and the tool plate 2 in FIG. 9, and contracts when a compression force of a certain level or more is applied. Let the spring constant deform.

In FIG. 9, the fixed plate 1 and the tool plate 2
Are properly fastened, and the fastening gap is maintained at a steady value S. Then, the sensor 6 detects the distance from the facing surface of the tool plate 2 to input to the controller that the robot is in an operable state.

FIG. 10 is a vertical sectional view showing a state where the tool plate 2 is pulled in the axial direction.

When the tool plate 2 is displaced in the direction away from the fixed plate 1, the disc spring 11 contracts when the displacement amount corresponds to the load of the compressive force exceeding the bending limit of the disc spring 11. In this case, although the tool plate 2 is displaced,
The position of the connecting rod 10 does not change due to the contraction of the disc spring 11, and the action force for pushing the actuator 3 upward is absorbed by the disc spring 11. When the sensor 6 detects the displacement of the tool plate 2 and a fastening gap exceeding a certain critical value from the steady value S is detected, the controller immediately stops the operation of the robot as in the previous example.

FIG. 11 shows when the tool plate 2 is subjected to the rotational torsional load about its axis, FIG. 12 shows when the tool plate 2 is loaded in the direction in which its axis is tilted, and FIG. In the case of receiving a load pushed from left to right in. These are the same as the situations of FIGS. 6, 7 and 8 described in the previous example, and the sensor 6 detects the displacement of the tool plate 2 and detects the displacement amount of the fastening gap with respect to the steady value S. , Input the overload condition to the controller to stop the robot operation.

Also in these examples of FIGS. 11 to 13,
The disc spring 11 absorbs the displacement so as not to change the relative position of the connecting rod 10 with respect to the fixed plate 1.
However, when the displacement amount is too large to be absorbed by the disc spring 11, the actuator 3 is returned upward as shown by the arrows in FIGS. 1 and 13, for example.

[0046]

According to the present invention, the sensor detects the displacement of the size of the fastening gap between the fixed plate on the robot side and the tool plate for mounting the tool, thereby pulling or twisting the tool plate in the direction of separation. It is possible to judge overload due to the action force such as rotation, and the volume and weight of the device are reduced compared to the conventional one in which the tool changer and the overload preventer are separated, and the robot's motion performance is reduced. Can be improved.

Further, since the distance from the tip of the robot arm to the tool mounting surface of the tool plate is shortened, the influence of inertial weight due to the turning motion of the arm can be reduced, and the motion and positioning accuracy of the robot can be reduced. improves.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of an automatic tool changer of the present invention in a state where a fixed plate and a tool plate are properly fastened.

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

FIG. 3 is an enlarged vertical cross-sectional view of a main part showing the positional relationship between the centering ring, the lock ball, and the engagement surface of the actuator in the state of FIG.

FIG. 4 is a vertical cross-sectional view showing a state before the fastening, in which the fixed plate and the tool plate are separated from each other.

FIG. 5 is a vertical cross-sectional view showing enlargement of the fastening gap when a tensile overload acts on the tool plate in the axial direction thereof.

FIG. 6 is a vertical cross-sectional view showing enlargement of the fastening gap when an overload is applied to the tool plate to rotate it about its axis. It is a cross-sectional view of the main part showing the engagement.

FIG. 7 is a vertical cross-sectional view showing expansion and contraction of the fastening gap when an overload is applied to displace the tool plate in a posture in which the axis of the tool plate is inclined.

FIG. 8 is a vertical cross-sectional view showing enlargement of a fastening gap when a tool plate is overloaded in a direction orthogonal to its axis.

FIG. 9 is a vertical cross-sectional view showing another example in which a connecting rod is slidably provided on a tool plate and is biased and held by a disc spring.

FIG. 10 is a vertical cross-sectional view showing an enlargement of the fastening gap when a tensile overload acts on the tool plate in the axial direction in the example of FIG. 9.

FIG. 11 is a vertical cross-sectional view showing an enlargement of the fastening gap when an overload is applied to the tool plate to rotate it about its axis in the example of FIG. 9;

FIG. 12 is a vertical cross-sectional view showing enlargement and reduction of the fastening gap when an overload is applied to displace the tool plate in a posture in which the axis of the tool plate is tilted in the example of FIG. 9;

FIG. 13 is a vertical cross-sectional view showing the enlargement of the fastening gap when the tool plate is overloaded in the direction orthogonal to its axis in the example of FIG. 9.

[Explanation of symbols]

 1 Fixed Plate 1a Cylinder Bore 1d Joint Seat 1e Positioning Hole 2 Tool Plate 2a Connector Rod 2d Steel Ball 3 Actuator 4 Lock Ball 5 Alignment Ring 6 Sensor 10 Connecting Rod 11 Disc Spring

Claims (1)

[Claims] 1. An automatic tool changer comprising a combination of a fixed plate connected to an arm of a robot hand and a tool plate for attaching / detaching a tool, wherein the plates are positioned and fastened by concavo-convex fitting. A detection means for detecting the size of the gap between the fixed plate and the tool plate, and the size of the gap between the fixed plate and the tool plate by the detection means. An automatic tool changer comprising a system capable of detecting an overload from the tool plate by comparing with a steady value of a clearance during proper fastening.