JPH0325317B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to a multi-joint robot equipped with a weight balance device that uses the force of a spring to balance the weight of a horizontally supported arm, particularly for direct teaching operations. It's about something that can be done easily.

(Prior Art) It is known to employ direct teaching in order to facilitate teaching, such as in hydraulic painting robots.

In addition, in the case of vertically articulated robots, springs or fluid pressure are used to balance the weight of the arms horizontally supported on the main body around the horizontal axis, reducing the load on the drive source during playback, and Consideration has also been given to not placing a large burden on the operator during direct teaching.

For example, in a device that utilizes fluid pressure, a cylinder device is pivotally supported between the main body and the arm, an accumulator is connected to one chamber of the cylinder device, the other chamber is open to the atmosphere, and the accumulator is under pressure. Some are filled with oil and pressure gas. However, according to this, the relationship between the stroke of the cylinder device and the cylinder pressure (gas pressure) due to the rotation of the arm is an inclined, almost linear relationship, and accordingly, the torque with respect to the rotation angle of the arm is also almost linear. This is a relationship. On the other hand, the rotational torque around the horizontal axis due to the weight of the arm draws a cosine curve with respect to the rotation angle of the arm. Therefore, the maximum value of the difference (absolute value) between the two torques becomes large. Further, as a device using a spring, a winding wheel is provided on the horizontal shaft, one end of a winding body such as a chain is fixed to the arm, and the other end is provided on the main body side via the winding body. There are things that can be pulled by compression springs. Moreover, it has also been considered that the winding body is formed as a cam, and the weight of the arm is balanced at any rotational position by the force of the compression spring. However, when the load acting on the tip of the arm changes, it is necessary to prepare a variety of cams and replace them with the most suitable one according to the load, which is extremely difficult. .

(Problem to be Solved) This invention has been made in view of the above-mentioned circumstances, and there is no need to prepare many types of cams or to replace them, and moreover, the horizontal movement due to the weight of the arm The aim is to provide an articulated robot that allows the operator to perform direct teaching operations easily by minimizing the maximum value of the difference (absolute value) between the rotational torque around the axis and the torque that balances it. be.

(Means for Solving the Problems) This invention provides a device that horizontally supports an arm on a main body, balances the weight of the arm around the horizontal axis by the force of a spring, and projects a lever on the horizontal axis. and a first cylinder device is provided between the lever and a location remote from the horizontal axis of the arm. Further, a first selection device is provided so as to be able to switch the first cylinder device between a fully contracted locking state and a constant pressure operating state. Further, the spring of the weight balance device can be switched between a balance operation state and a balance non-operation state.
A second selection device is provided that includes a cylinder device.

(Function) During teaching, the first cylinder device is set to a constant pressure operating state, and the second cylinder device is set to a balanced non-operating state, so that the fluid pressure for any rotation angle of the arm is adjusted. The torque caused by the weight of the arm is made almost constant, and the minimum value of the difference (absolute value) from the rotational torque caused by the weight of the arm is made small.

Further, during regeneration, the first cylinder device selects the most contracted locking state, and the second cylinder device selects the spring in the balanced operating state.

(Example) Examples will be described in detail below. Although this embodiment will be described as a five-axis articulated robot for arc welding, the present invention is not limited to this embodiment.

1 is the base of the multi-jointed robot, and on the top thereof there is a main body 2 that can rotate around a vertical axis (α ₁ direction).
(a rotating table) is supported by a shaft 2a. The drive source M ₁ for the α ₁ axis is a direct drive motor in the embodiment. R is a resolver (position detector) for the _α1 axis.

Further, a first arm 3 is pivotally supported on the upper part of the rotating table 2 so as to be rotatable around a horizontal axis (in the _α2 direction). M ₂ is an electric motor for the α ₂ axis, and
A lever 5 supported on a shaft 3a is rotatably connected via a known transmission mechanism 4.
A first cylinder device A is pivotally supported between the tip of the lever 5 and the tip of the arm 3.
Further, a cylinder 7a is attached to the rotary table 2 in the direction of the axis 2a, and a spring 7b (compression spring in the embodiment) is provided inside the cylinder 7a. Moreover, a sliding body 7c is inserted into the cylinder 7a, and this sliding body 7c is also formed as a receiving plate for the lower end of the spring 7b. A string-like body 7e (chain in the embodiment) is stretched between the arm 3 and the sliding body 7c via a winding wheel 7d (sprocket in the embodiment) supported on the shaft 3a. Further, a second cylinder device B is provided between the upper end of the cylinder 7a and the sliding body 7c, and this cylinder device B has one end (cylinder side) supported by the cylinder 7a and the other end (piston rod side). ) is slidably supported by the sliding body 7c. A protrusion Ba is provided at the tip of the piston rod to raise the sliding body 7c against the force of the spring 7b when the cylinder device B contracts. Note that 7 above
Weight balance device 7 around the axis 3a of the arm 3 in a to 7e
It is configured as. _E2 is an encoder (position detector) for the _α2 axis.

Further, at the tip of the arm 3, the middle of the _second arm 8 (the position of the center of gravity including the arm 8 and the rotating body 10 and holder 11, etc., which will be described later) is rotatable in the α 3 direction by a shaft 8a parallel to the shaft 3a. Supported. _M3 is an electric motor for the _α3 axis, which is mounted on the rotating table 2, and a clutch _C3 is connected to its output shaft. The clutch _C3 is connected to the arm 8 by a known transmission mechanism 9. E ₃ is an encoder (position detector) for the α ₃ axis.

Furthermore, at the tip of the arm 8, there is a shaft 10 parallel to the shaft 8a.
A rotating body 10 is supported so as to be rotatable in the _α4 direction. _M4 is an electric motor for the _α4 axis, which is attached to the arm 8, and a clutch _C4 is connected to its output shaft. The clutch _C4 is connected to the rotating body 10 by a known transmission mechanism (not shown). _E4 is an encoder (position detector) for the _α4 axis.

Furthermore, a torch holder 11 is supported on the rotary body 10 so as to be rotatable in the _α5 direction by a shaft 11a orthogonal to the shaft 10a. _M5 is an electric motor for the _α5 axis, which is attached to the arm 8, and a clutch _C5 is connected to its output shaft. The clutch _C5 is connected to the holder 11 by a known transmission mechanism (not shown). The holder 11 holds a welding torch T. _E5 is an encoder (position detector) for the _α5 axis.

Reference numeral 12 denotes a first switching valve that is piped to the cylinder device A and switches the cylinder device A to a contraction locking state or a constant pressure operating state, and SL ₁ is a solenoid thereof. 13 is a relief valve for maintaining the constant pressure state. 14 is a second switching valve that is piped to the cylinder device B and switches the cylinder device B to a free state or a contracted and locked state;
SL ₂ is that solenoid. And cylinder devices A, B, switching valves 12, 14, relief valve 13
is, together with a pressure source 15 (in the embodiment, a pneumatic source), a check valve 16, and a filter 17, arranged in piping as shown in FIG.

The cylinder device A, the switching valve 12, the relief valve 13, and the check valve 16 constitute a first selection device _S1 for selecting a state in which the arm ₃ is connected or not connected to its drive source, that is, the motor M2. There is. Furthermore, the cylinder device B and the switching valve 14 constitute a second selection device _S2 for selecting the weight balance device 7 into an operating state or a non-operating state.

18 is a control device including a central processing unit CPU and a memory MEM, and this control device includes a motor
M ₁ to M ₅ , clutches C ₃ to C ₅ , resolver R, encoders E ₂ to _{E 5} , solenoids SL ₁ and SL ₂ are bus lines
Connected via BL.

Furthermore, the operation of this embodiment will be described.

First, if you want to teach with this robot, disconnect each clutch C ₃ to C ₅ and disconnect the arm 8, rotating body 10, and holder 11 from the motors M ₃ to _{M 5} , so that they can rotate freely. state.
Furthermore, both switching valves 12 and 14 are switched to the right position. Then, in the case of cylinder device A, pressure source 1
The pressure of the high pressure air from 5 is regulated by the relief valve 13 and flows into the piston rod side, creating a state where the torque around the shaft 3a due to the weight of the arm 3 is pressure balanced, and the arm 3 is disconnected from the motor _M2 . Ru. In addition, in the case of cylinder device B, high pressure air from pressure source 15 directly flows into its piston rod side, cylinder device B contracts against the force of spring 7b as shown in FIG. 5, and eventually chain 7e Due to the slack, the weight balancer 7 becomes inactive.

Therefore, the operator directly determines the position and orientation of the torch T with respect to the workpiece (not shown) by holding the arm 8 and the holder 11, and outputs information on the position and orientation from the resolver R and encoders _E3 to _E5. The value may be recorded in the control device 18.

At this time, the rotational torque around the axis 3a due to the weight of the arm 3 is the _T1 curve in Figure 6, but on the other hand,
The torque due to the pressure acting on the piston rod side of cylinder device A is a straight line T ₂ in Figure 6, and T ₁ and T ₂
The maximum value of the difference (absolute value) between the torque T ₁ and the torque T ₃ caused by the spring 7b is smaller than the maximum value (absolute value) of the difference between the torque T 1 and the torque T 3 caused by the spring 7b, and direct teaching can be performed easily.

Next, if you want to regenerate the robot based on the taught program, each clutch C ₃
～C ₅ is in contact, arm 8, rotating body 10, holder 11
are connected to those motors M ₃ to _{M 5} . Furthermore, both switching valves 12 and 14 are switched to the left position. Then, in the cylinder device A, the high pressure air from the pressure source 15 flows directly into the piston rod side, and the cylinder device A is locked in the retracted position.
Eventually, the arm 3 becomes connected to the motor _M2 . Further, in the case of the cylinder device B, air from the pressure source 15 does not flow into the cylinder device B, and the cylinder device B is in a free state, so that the chain 7e is moved by the force of the spring 7b as shown in FIG. The weight balance device 7 is put into operation.

Then, the reproduction may be started. At this time, the rotational torque T ₁ around the axis 3a due to the weight of the arm 3 is:
This is done to balance the torque T ₃ due to the force of the spring 7b, and the load acting on the motor M ₂ is reduced.

The above description is an example, and replacement of each configuration with an equivalent is also included within the technical scope of the present invention.

As described above, in this invention, when the robot is regenerated, the first cylinder device A is in the most contracted and locked state,
The second cylinder device B is a driving source for the arm 3 by selecting the spring 7b to be in a balanced operating state.
The load acting on _M2 can be reduced. Moreover, during direct teaching, the first cylinder device A is in a constant pressure operating state, and the second cylinder device B is in a state where the spring 7b is applied.
By selecting the equilibrium non-operating state, the rotational torque T ₁ due to the weight of the arm 3 is supported by the constant pressure torque T ₂ , so both torques T ₁
The maximum value of the _difference ( _absolute value) between Teaching operations become easier. In addition, there is no need to prepare multiple types of cams, unlike the conventional cams mentioned above.
There is no need to replace them.

[Brief explanation of the drawing]

Each of the figures shows an embodiment of the present invention.
The figure is a partial vertical side view of the articulated robot, Figure 2 is an explanatory diagram of the main parts of Figure 1, Figure 3 is a piping diagram, Figure 4 is a block diagram of the control device, and Figure 5 is the function of the main parts. The explanatory diagram, FIG. 6, is a torque diagram. In the figure, 2... main body (rotating table in the example),
3...Arm (first arm), 3a...Horizontal axis, _M2 ...Drive source (electric motor in the example), 7...Weight balance device, 7a...Cylinder body, 7b...Spring, 7c... ...Sliding body, 7e... String-like body (chain in the example),
A...First cylinder device, B...Second cylinder device, 12...First switching valve, 13...Relief valve,
14... Second switching valve, S ₁ ... First selection device, S ₂ ...
...a second selection device.

Claims (1)

[Claims] 1 An arm 3 rotatably supported horizontally on the main body 2
and the horizontal shaft 3 is connected to the main body 2 via a drive device.
a lever 5 rotatably supported around a; and a first lever 6a, 6b swingably supported between the tip of the lever 5 and a location remote from the horizontal axis 3a of the arm 3;
a first selection device S ₁ including a first switching valve 12 and a relief valve 13 capable of switching the cylinder device A and the first cylinder device A to the most contracted locking state or the constant pressure acting state; the main body 2 and the arm 3; and a device 7 for balancing the weight of the arm 3 around the horizontal axis 3a by the force of a spring 7b, and switching the spring 7b of the weight balancing device 7 to a balance operating state or a balance non-operating state. A second cylinder device B and a second selection device _S2 possibly including a second switching valve 14 are provided, and during teaching, the first cylinder device A is in a constant pressure operating state, and the second cylinder device B is in a constant pressure operating state. The spring 7b is selected to be in an equilibrium non-operating state, and during regeneration, the first cylinder device A is selected to be in a fully contracted locking state, and the second cylinder device B is selected to be in an equilibrium operating state with the spring 7b. A multi-jointed robot.