JPS60223669A - Pressing force control device of resistance welding machine - Google Patents

Abstract

PURPOSE:To provide the titled control device capable of fitting correctly the pressing force of a welding gun specially to the established pressure by constituting the device so that the established pressure is changed by an electrical signal and the pressure control means to stop the supply of compressed air are connected between a pressing cylinder and direction changing valve, etc. CONSTITUTION:The supply of air to the inside of air room 2a of extension side is performed until the inner pressure of the room 2a reaches the established pressure after a pressing cylinder 2 acted a welding gun 1 and a work was held between an electrode tip 1a of the gun 1. The most suitable pressure to the work by the tip 1a is thus brought. On the other hand in case the inner pressure of the room 2a reaches the established pressure the spool of pressure reducing valve 22 is acted against a pilot pressure and the supply of compressed air is directly shut off, so the supply of compressed air is quickly stopped and the inside of the room 2a is maintained to the prescribed set-up pressure. After the prescribed spot welding is subjected to the work with the maintaining condition that the inner pressure of the room 2a is brought to, then, a changing valve 3 of electromagnetic direction is acted and the discharging of air of from the room 2a of the cylinder 2 and the supply of compressed air of to the air room of the opposite side are performed and the releasing motion of the tip 1a of the gun 1 is performed.

Description

Detailed Description of the Invention (Technical Field) The present invention provides a resistance welding machine, for example, a spot welding machine, by appropriately adjusting the pressure force of a welding gun on a workpiece as required to always achieve optimal welding conditions. This relates to a control device.

(Prior Art) As a conventionally known pressurizing force control device of this type, there is one shown in FIG. 1, for example.

This is a pressure cylinder 2 attached to the welding gun 1 of the spot welding machine.
The electromagnetic directional control valve 3 and the compressed air supply source 4 are connected in sequence to the pressurizing cylinder 2, and the welding gun is applied to the pressurizing cylinder 2 between the pressurizing cylinder 2 and the directional switching valve 3. A pressure control means 8 consisting of a directly operated pressure reducing valve 6 and a check valve 7 which are arranged in parallel is connected to a compressed air supply/discharge passage 5 communicating with the pressure side.

Note that 9 in the figure indicates a silencer.

According to such a pressurizing force control device, the pressurizing force of the welding gun 1 is set by the electromagnetic directional control valve 3 and the directly actuated pressure reducing valve 6.
This can be done by manually adjusting the directly actuated pressure reducing valve 6 before supplying air from the compressed air supply source 4 to the welding gun pressurizing side of the pressurizing cylinder 2 through the pressure control means here. 8 is a semi-fixed type in which the set pressure is directly adjusted by manual operation, so for example,
When welding is performed sequentially and rapidly at multiple points on a workpiece whose thickness, material, etc. change, as in the case of welding work using a robot, the set pressure of the pressure control means 8 must be adjusted so that it is always applied to the welding area of the workpiece. It is virtually impossible to frequently adjust the pressure to the appropriate optimum pressure, and as a result, there is a problem in that excellent welding results cannot be obtained under optimum welding conditions.

Therefore, as a solution to this problem with the conventional technology,
Japanese Unexamined Patent Publication No. 58-84686 (Patent Application No. 1826-1982)
A pressurizing force adjusting device as shown in No. 35) has been proposed.

As shown in FIG. 2, this device connects a pressurizing cylinder 2 provided in association with a welding gun 1 to a compressed air supply source 4 via a three-position electromagnetic directional control valve 3a, and A compressed air supply/discharge passage 5 that communicates with the welding gun pressurizing side of the pressurizing cylinder 2 between the cylinder 2 and the directional control valve 3a,
A pressure sensor 10 that can remotely control the set pressure is connected, and when the internal pressure of the extension side air chamber 2a of the pressurizing cylinder 2 reaches the required pressure set remotely, the pressure sensor 1
0, the electromagnetic directional switching valve 3a is operated to the illustrated position to stop the supply of compressed air, while maintaining the welding gun 1 pressing the workpiece 11 at the required pressure.

However, in the disclosed technology, the pressure sensor 10 detects the pressure in the pressurizing cylinder 2, and when the pressure reaches a predetermined level, it sends a signal to operate the electromagnetic directional control valve 3a, and finally closes the valve. Therefore, due to the long response delay, there is a problem that the cycle time to complete the - welding work becomes longer and work efficiency decreases, and the pressure sensor 10 does not operate. There was a problem in that the pressurizing force of the welding gun 1 became higher than the set pressure due to the time delay from when the supply of compressed air was stopped until the supply of compressed air was stopped.

Here, the cycle time of this device will be explained in detail based on FIG. 3. In this graph, in which the horizontal axis represents time t and the vertical axis represents air pressure p, the electromagnetic directional valve response delay time (1 Pressurized cylinder operating time t2 Cylinder pressure rise time t3 Set pressure holding time t4.t6 Welding current energization time t5 Pressure cylinder return time t7 Pressure drop holding time t8 Welding gun moving time 9 Electromagnetic directional valve closing time t□.

The cycle time is T, and the other times t1 to t3 and tl excluding the time 14 to t9 essential for welding work are the cycle time T.
o is considerably long due to the response delay of the device.

(Object of the Invention) In view of the problems of the prior art, the present invention enables remote control of the set pressure, reduces cycle time, and accurately matches the pressure of the welding gun to the set pressure. The present invention provides a pressurizing force control device for a resistance welding machine.

(Structure of the Invention) The pressurizing force control device for a resistance welding machine of the present invention particularly provides a setting pressure between a pressurizing cylinder and a directional control valve, or between a directional control valve and a compressed air supply source by an electric signal. is modified by connecting a pressure control means which results in the cessation of the supply of compressed air.

According to this pressurizing force control device, for example, by constructing a sequence circuit according to the type of pressurizing force and automatically selecting a set pressure for each welding point and inputting it to the pressure control means, remote control of the set pressure can be quickly performed. Moreover, since welding is performed reliably, welding can always be performed under optimal conditions. In addition, with this device, when the internal pressure of the pressurized cylinder reaches the set pressure, there is no need to wait for the electromagnetic directional control valve to operate in response to a signal from the pressure sensor. Since the air supply can be stopped and the responsiveness of the stop is extremely high, it is possible to supply compressed air at a high flow rate into the pressurized cylinder, shortening the cycle time, and reducing the pressurizing force of the welding gun. This effectively prevents the pressure from rising above the set pressure.

(Example) The present invention will be explained below based on the drawings.

FIG. 4 is a circuit diagram showing an embodiment of the present invention, in which parts equivalent to those shown in FIGS. 1 and 2 are designated by the same numbers. Further, here, the air passages are shown by solid lines, and the pressure propagation passages are shown by broken lines.

In this example, a pressure control means 21 is provided in a compressed air supply/discharge passage 5 that communicates the extension side air chamber 2a of the pressurizing cylinder 2 with the two-position electromagnetic directional switching valve 3.

This pressure control means 21 here includes pilot operated pressure reducing valves 2 connected in parallel to each other in the compression empty supply/discharge passage 5.
2 and check valve 23, for example, three pressure setting valves 25, 26, 27 connected in parallel to the pressure propagation passage 24 branching from the secondary side of the electromagnetic directional control valve 3, and each of these pressure setting valves 25. , 26. Solenoid valve 2 connected to 27
8, 29.30, and each solenoid valve 28, 29.30 on the negative side
It also comprises a shuttle valve 31 whose secondary side is connected to the pilot-operated pressure reducing valve 22, and the pressure on the secondary side of the shuttle valve 31 is used as the pilot pressure of the pilot-operated pressure reducing valve 22.

In this pressure control means 21, three pressure setting valves 25.2
6.27 are manually adjusted in advance to various set pressures, and by operating one of the solenoid valves by an electric signal based on the selection as required, the selected set pressure is set to the shuttle valve 31. It can then be led to the pilot-operated pressure reducing valve 22.

Here, the pressure setting valves 25, 26, 27 operate to cut off the respective pressure propagation passages when a pressure higher than the respective set pressure acts on their secondary sides,
Further, the pilot-operated pressure reducing valve 22 acts to stop the supply of compressed air when a pressure higher than the pilot pressure acts on its secondary side.

When performing resistance welding, in this case spot welding, on a workpiece based on the operation of the apparatus configured as described above, the electromagnetic directional control valve 3 is moved to a position different from that shown in the figure by an electric signal from a control circuit (not shown). At the same time, a negative solenoid valve, such as the solenoid valve 28, is selectively operated.

As a result, the pressure set by the pressure setting valve 25 is supplied to the pilot operated pressure reducing valve 22 as a pilot pressure, and the compressed air from the compressed air supply source 4 is supplied to the electromagnetic directional control valve 3 and the pilot operated pressure reducing valve. 22 and is supplied to the extension side air chamber 2a of the pressurizing cylinder 2.

Here, air is supplied into the extension side air chamber 2a after the pressurizing cylinder 2 operates the welding gun 1 and the electrode tip 1a of the welding gun 1 clamps a workpiece (not shown). The internal pressure is brought up until it reaches the set pressure, which results in the optimal pressing force on the workpiece by the electrode tip 1a.

On the other hand, when the internal pressure of the extension side air chamber 2a reaches the set pressure, the spool of the pilot-operated pressure reducing valve 22 is operated against the pilot pressure and directly cuts off the supply of compressed air. This resulted in a rapid supply disruption of
The inside of the extension side air chamber 2a is maintained at a predetermined set pressure.

After performing predetermined spot welding on the work while maintaining the internal pressure of the extension side air chamber 2a, the electromagnetic directional control valve 3
By operating to the illustrated position, air is discharged from the extension side air chamber 28 of the pressurizing cylinder 2 and compressed air is supplied to the opposite side air chamber, thereby opening the electrode tip 1a of the welding gun 1. bring about.

The welding gun 1 is then moved, for example by a robot arm, to the next welding point position, where it waits for the next welding operation similar to that described above.

In addition, if the optimal pressing force for the workpiece in the next welding operation is different from that in the previous welding operation, at the start of the operation,
By selectively operating other electromagnetic valves, the pilot pressure of the pilot-operated pressure reducing valve 22 can be easily and remotely changed.

Therefore, according to this device, the set pressure according to the number of pressure setting valves can be quickly and remotely selected, and the internal pressure of the extension side air chamber 2a can be accurately matched to the set pressure, so that it is always optimal. Welding can be performed under pressurized conditions, and furthermore, cycle time can be shortened and work efficiency can be improved.

FIG. 5 is a graph showing the cycle time of the apparatus of this example, in which the horizontal axis represents time t and the vertical axis represents air pressure p.

Further, parts equivalent to those shown in FIG. 3 are designated by the same reference numerals. The length of the cycle time of the embodiment of the present invention and the prior art will be evaluated by comparing the time t of FIG. 5 and FIG. 3 in detail below.

(1) First, regarding the response delay time t1 of the electromagnetic directional control valve, in the conventional technology, the solenoid valve has three positions, but in the embodiment of the present invention, it has two positions. is shorter than that of the conventional technology.

(2) j+ to t9 is the time essential for welding work in the cycle time T, and the embodiment of the present invention and the prior art are equal.

(3) Regarding the pressurizing cylinder operating time t2 and the rise time t3 of the cylinder internal pressure, in the conventional technology, the pressure sensor 10
detects the pressure in the pressurized cylinder 2, and when the pressure reaches a predetermined level, it sends a signal to operate the electromagnetic directional control valve 3a and finally close it, which causes a long response delay. On the other hand, in the embodiment of the present invention, the pressure of the pressurizing cylinder 2 is not controlled by the pressure sensor 10, but pressurizing is performed using a pressurizing force set in advance by a remote instruction, so there is no response delay like in the conventional technology. It takes less time.

(4) The closing time t1o of the electromagnetic directional control valve of the prior art shown in FIG. 3 is unnecessary due to the structure of the embodiment of the present invention.

From the above explanation, the embodiments of the present invention and the prior art are 14 to 19.
They are the same, but tl, tz, t3゜t. Since each of these is shorter in the embodiment of the present invention than in the prior art, the overall cycle time T of the embodiment of the present invention is significantly shorter than in the prior art.

FIG. 6 is a circuit diagram showing another embodiment of the present invention. In this example, a variable pressure proportional control solenoid valve 32 is connected in series to a pressure propagation passage 24 branching from the secondary side of the solenoid directional control valve 3. The secondary side thereof is connected to a pilot-operated pressure reducing valve 22, and these and a check valve 23 constitute a pressure control means 21.

In this device, by changing the magnitude of the current supplied to the pressure variable proportional control solenoid valve 32, the set pressure, in other words, the pilot pressure, can be changed steplessly. By supplying a current of the same magnitude to the pressure variable proportional control solenoid valve 32, an appropriate set pressure can always be selected. Note that here, the supply of compressed air is quickly and reliably stopped in the same manner as in the example described above.

FIG. 7 is a circuit diagram showing still another embodiment of the present invention, and the device of this example can function almost similarly to the pressure variable proportional control solenoid valve 32 described in FIG. 6, and has a larger capacity. A proportional control solenoid valve 33 having the same function as the pilot-operated pressure reducing valve 22 is connected to the compressed air supply/discharge passage 5 instead of the pilot-operated pressure reducing valve 22. Therefore, in this example, the pressure control means 21 is composed of the proportional control solenoid valve 33 and the check valve 23.

According to this example, by controlling the current supplied to the proportional control solenoid valve 33, the air pressure supplied to the extension side air chamber 2a of the pressurizing cylinder 2 is directly set,
Further, when the internal pressure of the extension side air chamber 2a reaches the set pressure, the spool of the proportional control solenoid valve 33 is operated.
The supply of compressed air can be shut off quickly and reliably.

FIGS. 8(a) and 8(b) are circuit diagrams showing further embodiments of the present invention, and FIG. 8(a) shows the pressure control means 21 shown in FIG. Figure (b)
The pressure control means 21 shown in FIG. 6 is connected between the electromagnetic directional control valve 3 and the compressed air supply source 4, and the check valve 23 is omitted.

Each of the above-described modifications operates in substantially the same manner as the embodiment described with reference to FIG. 4, and can produce the same effects. In particular, in the modified example shown in FIG. 8, the pressure control means 21 is operated not only when the welding gun 1 is operated in the closing direction, in other words, in the pressurizing direction of the workpiece, but also when the welding gun 1 is operated in the opening direction. Therefore, it is possible to effectively prevent damage to the welding gun 1 due to unexpected interference between the welding gun 1 and an obstacle, for example.

FIG. 9 is a perspective view showing an application example of the pressure control device described above, and in this example, the arm 35 of the welding robot 34 is
An electromagnetic directional control valve 3 and a pressure control means 21 are attached to the robot hand, and a pressure cylinder 2 and a welding gun 1 are attached to the robot hand, and a pneumatic hose 36 connects the pressure cylinder 2 to the compressed air supply 1lIii 4 (not shown). At the same time, the welding gun 1 and a welding transformer 37 suspended and supported above the robot 34 are connected by a welding cable 38.

Although not shown, the electromagnetic directional control valve 3 and the pressure i i
Of course, each of the 611 means 21 is connected to a signal cable for inputting an electric signal from a control panel, which is also not shown.

According to this application example, in addition to bringing about the unique functions and effects of this pressurizing force control device as described above, in particular, by arranging the electromagnetic directional control valve 3 and the pressure control means 21 on the robot arm 35. , since the piping distance from them to the pressurizing cylinder 2 is shortened, the electromagnetic directional valve 3
It is possible to shorten the time from when the welding gun 1 is activated until the workpiece pressurizing force reaches a predetermined value, resulting in a further improvement in welding work efficiency.

Incidentally, the one shown in FIG. 10 is a conventional example in which the pressurizing force control device shown in FIG. 37. Therefore, the electromagnetic directional control valve 3 and the pressure control means 21 according to the present invention are located at the positions of the electromagnetic directional control valve 3 and the pressure control means 8.
However, in this case, the air hose 36 from the electromagnetic directional control valve 3 to the pressurizing cylinder 2
The piping distance becomes considerably long and the response becomes poor.

Although the present invention has been described above based on the illustrated example, the pressure control means shown in FIG. 7 can also be arranged as shown in FIG. 8. Further, the pressurizing force control device of the present invention can be applied to resistance welding machines other than spot welding machines, and can also be applied to welding machines other than robots. Furthermore, when applying it to a spot welding machine,
The type, shape, etc. of the welding gun other than those shown in the drawings can be appropriately selected as required.

(Effects of the Invention) Therefore, according to the present invention, the set pressure can be changed by an electric signal between the pressurized cylinder and the directional control valve, or between the directional control valve and the compressed air supply source, and the compressed air By connecting a pressure control means that directly stops the supply of The stop operation of the supply of compressed air by the control means itself increases the responsiveness of the supply stop, so that the flow rate of the supply of compressed air into the pressurizing cylinder can be increased and the cycle time can be shortened.

In addition, when the pressure control means is connected between the electromagnetic directional valve and the pressurized air supply source, it is possible to effectively prevent damage to the welding gun during opening operation, and furthermore, the electromagnetic directional valve When the pressure control means is attached to a part near the welding gun, such as a robot arm, it is possible to particularly improve responsiveness when compressed air is supplied, thereby further improving work efficiency.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams showing conventional examples, FIG. 3 is a graph showing the cycle time of the device shown in FIG. 2, FIG. 4 is a circuit diagram showing an embodiment of the present invention, and FIG. FIG. 4 is a graph showing the cycle time of the device shown in FIG. FIG. 2 is a perspective view showing an example of application of the device shown in FIG. 1; 1... Welding gun 1a... Electrode tip 2... Pressure cylinder 2a... Extension side air chamber 3... Electromagnetic directional control valve 4... Compressed air supply source 5... Compressed air supply Discharge passage 21...Pressure control means 22...Pilot operated pressure reducing valve 23...Check valve 24...Pressure propagation passage 2
5.26.27... Pressure setting valve 28.29.30... Solenoid valve 31... Shuttle valve 32... Pressure variable proportional control solenoid valve 33... Proportional control solenoid valve Figure 1, Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 0 Figure 8

Claims (1)

[Claims] 1. A pressurizing cylinder (2) that controls the operation of the resistance welding machine, an electromagnetic directional control valve (3) that supplies and discharges compressed air to and from the pressurizing cylinder (2), and a compressed air In a pressurizing device for a resistance welding machine in which a supply source (4) is sequentially connected, there is a supply voltage between a pressurizing cylinder (2) and an electromagnetic directional control valve (3), or between an electromagnetic directional control valve (3) and compressed air. Pressure force control for a resistance welding machine, characterized in that a pressure control means (21) is connected between a supply source (4) and a pressure control means (21) whose set pressure is changed by an electric signal and which causes the supply of compressed air to be stopped. Device.