JPS6133678B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wrist mechanism attached to the tip of an arm of a robot, manipulator, etc., and is particularly intended to reduce the size of the wrist portion and even the entire device, and to prevent tools and the like attached to the wrist from becoming obstacles. This relates to a wrist mechanism equipped with a safety device in case of a collision.

In general, robots, manipulators, etc. have an arm part for moving a working tool, etc. to an arbitrary position in space, and a wrist mechanism for determining the posture of the tool, etc. with respect to the work object. Since each mechanism independently has a plurality of degrees of freedom, it is possible to take any posture at any position in space. In this way, when an arm, wrist, etc. has multiple degrees of freedom, it is easy in design to attach the actuator directly to the rotating part to cause rotation corresponding to each degree of freedom.
It is often desirable to use such a structure when space and weight constraints are less restrictive. However, when driving a large tool by attaching it to the tip of the wrist, the weight of the tool and the weight of the actuator are superimposed, and in order to secure multiple degrees of freedom, a large Due to the load, the entire actuator must be made larger, the entire wrist mechanism becomes larger and heavier, and the arm that supports it is also required to be large and highly rigid, making the entire device larger and increasing the work space. , which causes an increase in costs.

For example, in the case of a scarfing manipulator for removing scratches from hot slab material shown in Fig. 1, the arm part is composed of a vertical arm 1 and a horizontal arm 2 that is swingably connected to the vertical arm 1, and the horizontal Arm 2
A scarfing nozzle 4 is attached to the lower end of the wrist 3 attached to the tip of the wrist 3, and the rotation movement θ1 is centered around the vertical axis 5 passing through the center of the wrist 3 and the horizontal axis 6 attached to the lower end of the wrist 3. However, since the scarfing nozzle 4 is large and heavy due to its heat-resistant structure, the rotation axis that causes the rotation of θ1 is If another actuator was attached to the lower end of the tool to cause the tool to swing as in the past, the weight of the tip would be much greater than the wrist 3, making the entire machine larger and heavier. There is a possibility that

In addition, if the object to be worked on is a heavy object such as a hot slab material, such as a manibrator for scarfing, if the tool collides with it, the object side cannot be pushed away, so the tool, There is a risk of damage to the wrist, arm, etc. or destruction of the actuator due to overload, so a reasonable safety device is required depending on each wrist mechanism.

In view of the above-mentioned points, the present invention aims to provide a wrist mechanism that is most suitable for the wrist of robots, manipulators, etc. that work with large tools. A hollow shaft for the tool is rotated to impart a turning motion to the tool, and a reciprocating shaft that passes through the hollow shaft and is connected at one end to a tool swinging mechanism and is relatively rotatably connected at an intermediate portion is reciprocated. In a wrist mechanism of a robot, manipulator, etc. that causes a tool to swing, there is provided a reciprocating hydraulic cylinder device with one end connected to the other end of the advance/retreat shaft, and the other end of the reciprocating hydraulic cylinder device. a piston rod having one end connected to the piston rod and a head having a larger diameter than the intermediate body formed at the other end; An overload prevention hydraulic cylinder having first and second cylinder chambers coaxially formed in series with a small-diameter stepped portion in between, and an overload prevention hydraulic cylinder that is slidably fitted into the intermediate body of the piston rod, and whose outer diameter is the same as the small diameter. a cylindrical first floating piston having a larger diameter than the stepped portion and slidably mounted in the first cylinder chamber; and a second cylinder having an outer diameter larger than the small diameter stepped portion. The present invention provides a wrist mechanism for a robot, a manipulator, etc., characterized in that it is equipped with a second floating piston that is slidable within a room by being pushed by the head of the piston rod.

Next, an embodiment in which the present invention is applied to a scarfing manipulator will be described in detail with reference to the accompanying drawings starting from FIG. 2 is a perspective view of the wrist mechanism of the scarfing manipulator, and FIG. 3 is a side sectional view of the wrist mechanism, including a hydraulic circuit diagram for controlling the mechanism. Moreover, FIG. 4 is a sectional view taken along the line A--A in FIG. 3.

The wrist mechanism shown in FIG. 2 is a detailed depiction of the wrist 3 of the scarfing manipulator shown in FIG. In FIG. 2, the link rod 7 moves in the direction of the arrow 9 in accordance with the rotation movement of the entire manipulator with respect to the base 8 shown in FIG.
This constitutes a direction correction mechanism for rotating the nozzle 4 by the same angle in the direction opposite to the rotation of the entire manipulator to keep the direction of the nozzle constant at all times. That is, the entire manipulator is θ1 with respect to the base 8.
This rotation is transmitted to the link rod 7 via a parallel link mechanism (not shown), moves the link rod 7 in the direction of the arrow 9, and the shaft 1 connected to the link rod 7 via the lever 11 moves.
Rotate 0. Rotation of shaft 10 is sprocket 1
The power is transmitted to the drive shaft 15 of the sprocket 13 via the chain 14 that is wound around the sprockets 2 and 13 and both sprockets. The drive shaft 15 has a bevel gear 16 integrally,
A bevel gear 17 of the same size facing this bevel gear 16 is rotatably provided, and this bevel gear 17 is coaxially integrated with a large bevel gear 18. It is connected to a servo motor 20. Further, as shown in FIG. 4, the drive shaft 15 has a swing shaft 21 located between the bevel gears 16 and 17 that can swing freely around the drive shaft 15. The bevel gear 22 is rotatably attached to the bevel gear 1 described above.
6 and 17, and connects bevel gears 16 and 17. A gear 23 is fixed to the output shaft side of the rotary servo motor 20.
is engaged with a gear 26 fixed to the upper end of a vertical hollow shaft 25 fixed to a nozzle attachment part 24 having a nozzle 4 swingably therein.

A hydraulic cylinder 27, which is an example of a hydraulic cylinder device for reciprocating motion, is disposed coaxially with the upper part of the hollow shaft 25, and a piston rod 28 that projects and retracts downward from the hydraulic cylinder 27 and the hollow shaft 25 are disposed coaxially with the hollow shaft 25. The upper end of a forward and backward shaft 29 coaxially inserted therein is integrally connected to each other in the axial direction so as to be able to rotate relative to each other via a thrust bearing 30. The lower end of the advance/retreat shaft 29 is connected via a link 31 to a lever 32 fixed to the swing center shaft 6 of the nozzle 4, and the arm is 32. The swing center shaft 6 and the nozzle 4 integrally attached to the swing center shaft 6 swing around the swing center shaft 6 to perform a swing motion of the nozzle.

Further, as shown in FIG. 3, a piston rod 34 having a large head 33 at the upper end is attached to the upper end of the hydraulic cylinder 27 so as to be able to swing slightly. is inserted movably into a hydraulic cylinder 35, which is an example of an upper and lower two-stage overload prevention hydraulic cylinder provided coaxially with the hydraulic cylinder 27, and the two-stage hydraulic cylinder 35 is connected to a small-diameter stage provided in the center. The first and second
It is divided into a lower chamber 36b and an upper chamber 36a, which are an example of a cylinder chamber, and a slidable floating piston 37a is installed in 36a.
Inside the lower chamber 36b is a floating piston 3 that is slidably fitted around the outer periphery of the piston rod 34.
7 (second floating piston) b is slidably mounted, and the upper floating piston 37a collides with the small diameter portion 35a at the lowest position shown in the figure, and does not move further downward. cannot advance, and the lower floating piston 3
At the uppermost position shown in the figure, 7b collides with the lower surface of the small diameter portion 35a and is prevented from moving further upward. Pressure oil is supplied to the upper chamber 36a and the lower chamber 36b, respectively, and both the floating pistons 37a and 37b are always pressed against the small diameter portion 35a.
The head 33 of the piston rod 34, which has the same width in the vertical direction as the width of a, is held in the vertical direction,
The outer diameter of the head 33 is slightly narrower than the inner diameter of the small diameter portion 35a, slightly larger than the inner diameter of the floating piston 37b, and slightly smaller than the outer diameter of the upper floating piston 37a. Therefore, when the piston rod 34 moves upward, the floating piston 37b collides with the small diameter portion 35a and stops at the position shown in the figure, but the floating piston 37a is pushed by the head 33 of the piston rod 34 and moves upward. It is possible to move upward within the chamber 36a. Conversely, when the piston rod 34 moves downward, the floating piston 37a comes into contact with the small diameter portion 35a and stops at the position shown in the figure, and the lower floating piston 37b is pushed by the head 33 and moves downward. Move to.

The control circuit of the hydraulic system in the above configuration is as shown in FIG.
The rotation direction of the rotary servo motor 20 is determined by the direction of the flow of pressure oil sent from the hydraulic unit 38 through the piping 39, and the rotation of the rotary servo motor 20 is determined by switching the solenoid valve 40 connected in the middle of the piping 39. The direction can be switched. Also hydraulic piston 27
Pressure oil is sent from the hydraulic unit 38 to the pipe 42 having a solenoid valve 41 in the middle.
By switching the solenoid valve 41, the piston 2
8 advances or retreats are made. Also provided at the top 2
Regarding the piping to the hydraulic cylinder 35 of the stage, pressure oil is supplied to the upper chamber 36a and the lower chamber 36b through safety circuits 44a and 44b by piping 43a and 43b branched from the high-pressure side piping of the piping 39, respectively. ing. Moreover, the pressure switches 45a and 45b provided in each safety circuit are switch mechanisms for detecting an increase in the oil pressure in the upper chamber 36a or lower chamber 36b and issuing an alarm when the nozzle 4 collides with the workpiece W.

Next, the above wrist mechanism nozzle direction correction operation, nozzle direction change operation, cutting surface switching operation,
and the overload prevention operation due to nozzle collision will be explained respectively.

(1) Nozzle direction correction operation When the manipulator described above rotates by θ1 with respect to the base, the link rod 7,
The sprocket 12, chain 14, and sprocket 13 rotate one after another, and at the same time, the drive shaft 15 rotates the manipulator by an amount corresponding to the turning angle. When the drive shaft 15 rotates, the rotation is transmitted to the bevel gear 19 attached to the input shaft of the rotary servo motor 20 via the bevel gears 16, 22, 17, and 18, and the rotational force is amplified by the rotary servo motor 20. and is transmitted to the gear 23. The rotation of the gear 23 is transmitted to the gear 26 and the hollow shaft 25 integrated therewith, and the nozzle attachment part 24 and the nozzle 4 attached to the lower end of the hollow shaft 25
is pivoted around the axis of the hollow shaft 25 (vertical shaft 5 shown in FIG. 1). The turning angle of the nozzle 4 is set to be the same as the turning angle of the entire manipulator by appropriately adjusting the ratio of the number of teeth between the bevel gears 18 and 17 and the ratio of the number of teeth between the gears 23 and 26. By appropriately selecting the above-mentioned combination of gears,
The turning direction is set to be opposite to the turning direction of the entire manipulator, so when the entire manipulator turns clockwise by θ1, the nozzle 4 turns counterclockwise by −θ1,
In this state, the nozzle is always oriented in a fixed direction regardless of the rotation of the entire manipulator.

(2) Nozzle direction changing operation From the above explanation, we understand the mechanism that corrects the nozzle direction with respect to the rotation of the entire manipulator and keeps the nozzle direction constant at all times. In reality, it is necessary to rotate the nozzle in an arbitrary direction based on . In the case of manipulators for scarfing, it is important to keep the direction of the nozzle constant, but it is also possible to change the direction of the nozzle as necessary to avoid various problems that occur on the surface of the hot slab material. It becomes possible to carry out scarfing work to deal with scratches. Such a change in the angle of the nozzle is achieved by the swing motion of the swing shaft 21 about the drive shaft 15, and the swing of the swing shaft 21 is performed by a small hydraulic cylinder 46. That is, considering the state where the drive shaft 15 is now stopped, the swing shaft 21 can be rotated around the drive shaft 15 by moving the piston rod 47 of the hydraulic cylinder 46 back and forth, and by this rotation, Bevel gear 16
The meshing point between and 22 moves, the bevel gear 22 rotates relatively, and this rotation is transmitted to the bevel gear 17, and the bevel gear 19 is driven by the bevel gear 19 via the bevel gear 18 integrated with the bevel gear 17. The rotary servo motor 20 is rotated.

In this way, by appropriately controlling the amount of advance of the piston rod 47 of the hydraulic cylinder 46, the rotation angle of the bevel gear 22, that is, the rotation angle of the rotary servo motor 20 interlocked with the bevel gear 22 can be arbitrarily controlled. The direction can be changed arbitrarily. The above-mentioned rotation of the nozzle around the hollow shaft 25 also causes the forward/backward shaft 29 to turn, but the hydraulic cylinder 27 cannot rotate, so the hydraulic cylinder and the forward/backward shaft 29 are made relatively rotatable. I have to keep it. Thrust bearing 30 described above
is in line with this purpose.

(3) Changing the cutting surface of the nozzle As shown in Fig. 3, the nozzle 4 can remove scratches generated on the top surface Wa and side surface Wb of the workpiece W by cutting, respectively. It must be swung around the swiveling center axis 6. The hydraulic cylinder 27 is for this purpose.
By switching the solenoid valve 41, the piston rod 28 of the hydraulic cylinder 27 advances or retreats. Due to this reciprocating movement of the piston rod, the advance/retreat shaft 29 advances or retreats via the thrust bearing 30, and the arm 32, the swing center shaft 6 to which it is fixed, and the nozzle 4 move through the link 31 to the swing center shaft 6. The welding surface is switched by swinging around the .

(4) Overload prevention operation As mentioned above, the top surface Wa or side surface Wb of the workpiece W
Consider a case where the nozzle 4 collides with the workpiece W while the workpiece is being melt-cut, for example, a case where the nozzle 4 descends more than necessary and collides with the upper surface Wa.
In this case, since the nozzle 4 is at the most rotated position in the clockwise direction, the piston rod 28 of the hydraulic cylinder 27 is in the most retracted state, that is, at the upper limit position, and in this state, when the nozzle descends and collides with the upper surface Wa of the workpiece. Since the piston rod 28 cannot escape any further, the hydraulic cylinder 27 itself must escape upwards. When the hydraulic cylinder 27 receives upward force due to the collision of the nozzles, the piston rod 34 attached to the upper part of the hydraulic cylinder 27 pushes up the floating piston 37a attached to the upper chamber 36a of the hydraulic cylinder 35, and the upper chamber 36a
The piston 34 rises against the hydraulic pressure within the piston 6a, allowing the hydraulic cylinder 27 to escape upward without being destroyed. When the floating piston 37a rises in this way, the upper chamber 36
The pressure inside a increases, and the pressure switch 45a
By turning on, the nozzle will
An alarm will be issued to notify you that you have hit Wa. Conversely, when the nozzle 4 collides with the workpiece when the nozzle 4 is rotated most counterclockwise, that is, when the side surface Wb of the workpiece W is being cut,
A counterclockwise load is applied to the nozzle, and the piston rod 28 attempts to be pulled downward, but in this state, the piston rod 28 is at its lowest position and cannot be lowered any further.
The hydraulic cylinder 27 itself is pulled downward, and the piston rod 34 integrally connected to the hydraulic cylinder 27 pushes down the floating piston 37b and moves, thereby preventing the nozzle 4 from being destroyed. In this case, the pressure in the lower chamber 36b increases, the pressure switch 45b is turned on, and an alarm is issued to notify that the nozzle has come into contact with the side surface of the workpiece.

As described above, according to the present invention, a hollow shaft for attaching a tool provided at the tip of the wrist is rotated to give a turning motion to the tool, and the hollow shaft is passed through the hollow shaft and one end is connected to the tool swing mechanism. In the wrist mechanism of a robot, manipulator, etc., which causes a tool to swing motion by reciprocating a forward/backward shaft that is relatively rotatably connected at an intermediate portion, one end is connected to the other end of the forward/backward shaft. a reciprocating hydraulic cylinder device; a piston rod having one end connected to the other end of the reciprocating hydraulic cylinder device and a head having a larger diameter than the intermediate body portion formed at the other end; Slidably attached,
A hydraulic cylinder for overload prevention has first and second cylinder chambers formed in series and coaxially across a small-diameter stepped portion having a larger diameter than the head formed in the middle, and a hydraulic cylinder that slides on the intermediate body of the piston rod. a cylindrical first cylinder that is freely fitted and has an outer diameter larger than the small diameter stepped portion and is slidably installed in the first cylinder chamber;
a floating piston, and a second floating piston having an outer diameter larger than that of the small-diameter stepped portion and slidable within the second cylinder chamber by being pushed by the head of the piston rod. Since the wrist mechanism of robots, manipulators, etc. is characterized by the fact that This is not necessary, and instead of a floating mechanism that allows free swinging as in the past, the floating mechanism uses two floating pistons to ensure accurate positioning at all times, and only releases the fixed state when overloaded. This feature allows accurate positioning at all times, making it possible to make the wrist mechanism and arm part smaller and lighter, and to prevent tools, etc. installed at the tip of the wrist from colliding with work objects or obstacles. Even in such a case, there is no risk of overloading the actuator or damage to the wrist portion, etc., and it is suitable for application to, for example, a manipulator for scarfing.

[Brief explanation of the drawing]

Fig. 1 is a side view of a manipulator for scarfing which is an embodiment of the present invention, Fig. 2 is a perspective view of the wrist mechanism of the manipulator, and Fig. 3 is a side sectional view of the wrist mechanism (controlling the mechanism). 4 is a sectional view taken along the line A-A in FIG. 3. (Explanation of symbols), 3...Wrist, 4...Tool, 2
0...Hollow shaft, 29...Advance/retreat axis, 31, 32...
Tool swing mechanism, 30... Thrust bearing, 27...
Hydraulic cylinder, 37a, 37b...floating piston.

Claims (1)

[Scope of Claims] 1. A hollow shaft for attaching a tool provided at the tip of the wrist is rotated to give a turning motion to the tool, and the hollow shaft passes through the hollow shaft and one end is connected to a tool swinging mechanism, and an intermediate portion In wrist mechanisms such as robots and manipulators that cause swinging motion in tools by reciprocating the forward and backward shafts that are connected to each other so as to be relatively rotatable, the reciprocating shaft has one end connected to the other end of the forward and backward shaft. a hydraulic cylinder device; a piston rod having one end connected to the other end of the reciprocating hydraulic cylinder device and a head having a larger diameter than the intermediate body portion formed at the other end; the piston rod being slidable in the axial direction; an overload prevention hydraulic cylinder having first and second cylinder chambers formed in series and coaxially across a small-diameter stepped portion having a larger diameter than the head formed in the middle; and an intermediate body of the piston rod. The first step has an outer diameter larger than the small-diameter stepped portion.
a cylindrical first floating piston slidably mounted in a cylinder chamber of the cylinder;
A wrist mechanism for a robot, a manipulator, etc., comprising a second floating piston that is slidable by being pushed by the head of the piston rod in the cylinder chamber of the robot.