JPS6152995A - Robot for spot welding - Google Patents

Abstract

PURPOSE:To reduce impact force that acts on a robot and improve accuracy of positioning by bringing a movable electrode into contact with a work by low pressure and pressing by high pressing force at the time of welding. CONSTITUTION:When starting welding work, pressure of compressed air from an air source 27 is reduced by a pressure regulator 25 and supplied to a cylinder 9 through a shuttle valve 24 and an air passage 32, and the tip of an electrode 8 is brought into contact at relatively small first set pressure. When it comes into contact with a reinforcing member to which a movable electrode is connected, a solenoid valve 31 for high pressure of a fluid supplying device for pressing 28 is switched by a switching signal from a timer 33 after switching of a solenoid valve 26. Then, compressed air from the air source 27 is supplied to the cylinder 9 without reducing its pressure. At this time, a return passage 30 is opened to the air, and thereby the first and second pistons are pressed by greater pressure. Consequently, pressing is made at the second set pressure which is pressing force of normal welding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spot welding robot used, for example, in manufacturing automobile bodies.

[Prior art]

In recent years, in spot welding of automatic car bodies, etc., a robot moves a welding electrode to the part of the workpiece to be welded, and the electrode applies a predetermined pressure to the workpiece, e.g.
The workpieces are clamped with a force of 300 kg, and in this state, electricity is applied between the electrodes to weld the workpieces. Therefore, when the pressure is applied, a large reaction force is generated on the electrodes.

By the way, there are various types of structures of the above-mentioned spot welding robots depending on the shape of the workpiece, the position to be welded, etc. For example, a robot with a C-type gun or an X-type gun has a movable electrode and a gun frame on the robot. A fixed electrode is provided, and the gun frame is configured to be supported by a support arm of the robot. In such a robot,
The reaction force generated on the electrode during the pressurization is absorbed by the gun frame, so that no shock due to the reaction force acts on the robot body.

However, when spot welding parts to the tunnel part of a floor panel, for example, if you try to use the C-type gun mentioned above, the arm of the gun body needs to be very long, which reduces the rigidity of the frame. Therefore, instead of such a C-type gun type, only a movable electrode is attached to the support arm of the robot, and the workpiece is held between the movable electrode and a backing metal that is a fixed electrode provided on the underside of the workpiece. A robot equipped with a so-called stud welding gun is used. In such Skusod type welding robots, the reaction force during pressurization is naturally not absorbed by the gun frame, and as a result, the impact of this reaction force acts on the robot body.As a result, in this conventional stand type welding robot, There is a problem in that the reaction force tends to cause looseness in the rotating portion of the robot, which tends to reduce positioning accuracy during welding.

[Purpose of the invention]

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a spot welding robot that can improve positioning accuracy by alleviating the induction impact force that acts on the robot during welding.

[Structure of the invention]

As mentioned above, in spot welding, it is necessary to hold the workpiece under a predetermined pressure, but this is sufficient as long as the predetermined pressure is applied when both electrodes are energized and welded. We focused on the fact that the high pressure required during welding is not required when welding. That is, in the spot welding robot that supports only the movable electrode, the present invention first applies a pressure lower than the welding pressure to the movable electrode until the movable electrode contacts the workpiece, and then applies a pressure higher than the above pressure to the movable electrode. The welding force is applied to the movable electrode, which causes the movable electrode to come into weak contact with the workpiece, thereby reducing the impact force acting on the robot body.

〔Example〕

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

FIGS. 1 and 2 show an embodiment of the present invention. In the figures, 1 is a spot welding robot, and its base 2
is fixed on the floor 3. A support column 4 is pivotally supported on the base 2 so as to be swingable in the front and rear (left and right directions in FIG. 2) about a rotation shaft 5. 5 Further, an arm part 6 is pivotally supported at the upper end of the column part 4 so as to be able to swing vertically about a rotation shaft 7, and a movable electrode is provided at the tip of the arm part 6. Cylinder 9 is attached.

The cylinder body 13 of the cylinder 9 is the first cylinder. It has a cylindrical shape consisting of a second working chamber 10, 1.1 and a guide section 12, and has a cylindrical shape. Inside the second working chamber 10.11 is a sliding member 14.
1st. A second piston 15.16 is slidably inserted into the first piston. A communication passage 18 is formed in the connecting portion 17 that connects the second piston 15, 16, and the communication passage 18 allows the first and second pistons to connect to each other. The first working chamber 10.11 of the second working chamber 10.11. second piston 15,
16 upper parts communicate with each other. Further, a piston rod 19 fixed to the second piston 16 projects outward through the guide portion 12, and a movable electrode 8 is attached to the piston rod 19.

Further, a work jig 20 is disposed in front of the robot 1, and the work jig 20 is for holding a work, and a fixing member, which is a backing metal, is provided at a portion corresponding to the welding part of the work. An electrode 21 is provided, and the spot welding robot 1 is configured to sandwich a workpiece between the fixed electrode 21 and the movable electrode 8.

An air passage 32 is connected to the upper end of the first working chamber 10 of the cylinder 9 as shown in the figure, and one connection port of a shuttle valve 24 connected to the air passage 32 supplies low-pressure compressed air to the cylinder 9. A low pressure passage 23 of a contact fluid supply device 22 is connected thereto. A pressure regulator 2 is provided between the shuttle valve 24 of the low pressure passage 23 and the air #i27.
5 and a low-pressure solenoid valve 26 are inserted and connected, and the pressure regulator 25 is composed of a pressure setting valve 25a, a check valve 25b, and a pressure gauge 25C. In this embodiment, the air pressure is 'l kg/ It is set to cJ.

Further, a high pressure passage 29 of a pressurized fluid supply device 28 is connected to the other connection port of the shuttle valve 24, and a return passage 30 of the supply device 28 is connected to the lower end of the first working chamber 10 of the cylinder 9. The return passage 30. The high pressure passage 29 is connected to the air source 27 via a high pressure solenoid valve 31. In addition, each of the above-mentioned solenoid valves 26.
An on/off control signal from a timer 33 is input to 31.

Next, the operation and effect will be explained with reference to FIGS. 1 to 3.

Floor panel 3 which is a workpiece by robot 1 of this embodiment
To explain the case where the reinforcing member 35 is connected to the tunnel portion 34a of No. 4 by spot welding, at the start of the welding work, both the electromagnetic valves 26 and 31 of the robot 1 of this embodiment are turned off and the state shown in FIG. Therefore, the cylinder 9 is contracted as shown by the dashed line in the figure. In order to weld the floor panel 34 in this state, the workpiece is first placed and set on the jig 20 so that the part to be welded is on the fixed electrode 21. Next, the reinforcing member 35 is placed in the position where the floor panel 34 is to be attached.

Then, the robot 1 moves the cylinder 9 to the movable electrode 8.
is moved to face the fixed electrode 21 via the welded portion of the floor panel 34 reinforcing member 35, and in this state, the solenoid valve 26 of the contact fluid supply device 22 is switched in the opposite direction to that shown in FIG. It can be switched to the state of Then, the compressed air from the air source 27 is passed through the pressure regulator 25.
) The pressure is reduced to 2 kg/a+l, and this reduced pressure compressed air for contact is supplied to the cylinder 9 through the shuttle valve 24 and the air passage 32, and is then supplied to the cylinder 9 through the shuttle valve 24 and the air passage 32. 2nd piston 15°16
is pressurized, which causes the piston rod 19 to move towards the movable electrode 8
At the same time, the tip of the electrode 8 comes into contact with the reinforcing member 35 with a first set pressure of a relatively small force vl (100 kg) (see FIG. 3 (al)).

In this case, an upward force due to the compressed air from the turn passage 30 is acting on the lower surface of the first piston 15, but the second piston 15.
Since the area of the upper surface of piston rod 16 is large, piston rod 19 descends as described above.

As described above, the movable electrode 8 is attached to the reinforcing member 35.
5, when the solenoid valve 26 is switched, the high pressure solenoid valve 31 of the pressurizing fluid supply device 28 is activated by the timer 3.
The switching signal from 3 causes the state to be switched to the opposite state to that shown in FIG. Then, the compressed air from the air source 27 is supplied to the cylinder 9 through the shuttle valve 24 at a pressure of 4 kg/ant without being depressurized, and at this time, the return passage 30 is opened to the atmosphere. 1. The second piston is pressurized with even greater pressure, and as a result, the tunnel portion 34a of the floor panel 34 and the ? ili strong member 3
5 is pressurized and clamped between the movable electrode 8 and the fixed electrode 21 at a second set pressure of 2 (250 kg), which is the normal welding force (see Fig. 3 (bl)).

In this state, a spot welding current is applied between the movable electrode 8 and the fixed electrode 21, thereby performing spot welding.

When the spot welding is performed, both the solenoid valves 26.
31 is switched to the state shown in FIG. 1, whereby compressed air is supplied to the high pressure solenoid valve 31. The movable electrode 8 is supplied to the lower side of the first piston 15 in the first working chamber 10 of the cylinder 9 through the return passage 30, and as a result, the movable electrode 8 rises together with the piston rod 19, completing the spot welding operation.

In this embodiment, the movable electrode cylinder 9 is first expanded with low-pressure compressed air until the movable electrode 8 comes into contact with the reinforcing member 35, and then with compressed air at normal pressure for spot welding. The movable electrode 8 is reinforced by the reinforcing member 35
Since the pressure is applied to the robot, the reaction force generated on the electrode portion during welding can be reduced, and therefore the impact force acting on the robot due to the reaction force can be reduced.

In the above embodiment, the case where the cylinder 9 has a 2N piston structure has been described, but this cylinder 9
Of course, the electrode may be of the usual type having one piston, but in the present invention, the point is that the movable electrode is lowered with a small pressure until it contacts the workpiece, and after the contact, the electrode is passed through the air. The electrode may be used to press the workpiece with a welding pressure of .

Further, although an air cylinder is provided in the above embodiment, it may of course be a hydraulic cylinder.

〔Effect of the invention〕

As described above, according to the spot welding robot according to the present invention, after the movable electrode is brought into contact with the workpiece at a low first set pressure, during welding, the movable electrode is applied with a second set pressure higher than the first set pressure. Since pressure is applied, it is possible to reduce the impact force acting on the robot due to the reaction force generated in the electrode part, which has the effect of improving positioning accuracy during welding.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a spot welding robot according to an embodiment of the present invention, FIG. 2 is an overall diagram thereof, and FIG. 3 is a diagram for explaining its operation. DESCRIPTION OF SYMBOLS 1... Spot welding robot, 6... Support arm, 8... Movable electrode, 9... Cylinder, 21... Back metal, 22... Contact fluid supply device, 28... Machining Pressure fluid supply device. Patent applicant: Mazda Motor Corporation agent, patent attorney Ken Hayase - Figure 1 Figure 2

Claims (1)

[Claims] (1) Attach only the movable electrode to the support arm of the robot,
The robot performs spot welding of the workpiece by sandwiching the workpiece between the movable electrode and a back metal on the lower side of the workpiece, and when the movable electrode is brought into contact with the workpiece, a pressing force of a first set pressure is applied to the movable electrode. At the same time, when welding, the above-mentioned first
A spot welding robot characterized by being provided with a pressurizing force control device that applies a pressurizing force of a second set pressure higher than the set pressure to the movable electrode.