JP2648291B2 - Electrode drive of spot welding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spot welding machine for performing spot welding by sandwiching a work between a fixed electrode and a movable electrode and applying a pressurized current to the work. The present invention relates to an electrode driving device for a spot welding machine for moving the movable electrode up and down.

[0002]

2. Description of the Related Art Normally, spot welding is performed by sandwiching a work between a fixed electrode and a movable electrode and applying a current under pressure. The movable electrode can be moved up and down with respect to the work on the fixed electrode by an air cylinder, and the pressure is changed by the air cylinder. That is, the switching of the pressing force is performed by supplying / exhausting air to / from the head side and the rod side of the air cylinder for moving the movable electrode up and down by a five-way solenoid valve or the like. At this time, if the movement of the movable electrode is accelerated in order to shorten the cycle time, the impact when the movable electrode comes into contact with the work increases, and the shock causes deformation of the work, noise, damage to the electrode chip, and the like. .

To solve this problem, Japanese Utility Model Application Laid-Open No. 3-10
No. 6,277 discloses a pressurizing device for a spot welding gun that changes supply pressure by adjusting electromagnetic valves on a head side and a rod side. According to this, when lowering the movable electrode stopped at the rising end toward the work, first, the original pressure is applied to the head side of the air cylinder, and the rod side is released to the atmosphere at a high speed. Immediately before reaching the workpiece, the pressure on the head side is reduced and the pressure on the rod side is increased (however, the head side pressure is larger than the rod side pressure) to lower the pressure at a low speed. Then, the movable electrode reaches the work while descending at a low speed. Therefore, both impacts are small. Thereafter, the pressure on the head side is increased to press the movable electrode against the work, and pressure welding is performed.

[0004]

However, in the pressurizing device of the spot welding gun disclosed in Japanese Utility Model Laid-Open No. 3-106277, no consideration is given to the switching timing of each electromagnetic valve. Change in stroke due to
B) Fluctuation of the arrival time to the work due to fluctuations in the supply air c) Similarly, wear of the sliding parts, especially fluctuations in the arrival time of the work due to changes in the sliding resistance due to the packings d) Clogging of the exhaust port muffler There is a problem that the initially set switching timing becomes inappropriate as time passes due to fluctuations in the arrival time due to a change in the exhaust speed due to the change in the exhaust speed.

For example, while the electrode tip is new, the stroke is short and the time for the movable electrode to reach the work is short, but when the electrode tip is old, the stroke is long and the time for the movable electrode to reach the work is long. Become. For this reason, when the movable electrode is lowered at a high speed for the initially set time, and then the solenoid valve is switched and lowered at a low speed, the cycle time was appropriate while the electrode tip was new. And the cycle time becomes longer as a result. On the other hand, in order to prevent the cycle time from becoming long even when the electrode tip becomes old, it is only necessary to set the speed at the time of low-speed descent too low.However, in this case, the impact between the movable electrode and the work must be sufficiently reduced. There was a problem that it could not be relieved.

That is, if the cycle time is shortened, the impact of the work cannot be sufficiently reduced, and if the impact of the work is sufficiently reduced, the cycle time cannot be shortened. The present invention has been made in order to solve the above-described problems, and has as its object to provide an electrode drive device of a spot welding machine that can always sufficiently reduce the impact between a movable electrode and a work and shorten the cycle time. .

[0007]

In order to solve the above-mentioned problems, the present invention is provided in a spot welding machine for sandwiching a work between a fixed electrode and a movable electrode and performing spot welding by applying an electric current under pressure. An electrode driving device for a spot welding machine for moving the movable electrode up and down with respect to the work on the fixed electrode, wherein a high power applying means for applying high power to the movable electrode; A low-power applying means for applying power; and a high-power applying means for applying a high power for a time TD to the movable electrode disposed above the workpiece to lower the movable electrode at a high speed. Low power is applied to the electrode by the low power applying means to lower the movable electrode at a low speed to reach the work, and thereafter, high power is applied to the movable electrode by the high power applying means. Power application control means for pressing the movable electrode against the work, and an arrival time for measuring a time TR from when the low power application means starts applying low power to the movable electrode until the movable electrode reaches the work. A time measuring means, and a time TD when the time TR measured by the arrival time measuring means is shorter than a predetermined time.
And a high-speed descent time output means for outputting the time TD to the power supply control means after extending the time TD when the time TR is longer than a predetermined time. .

Here, the movable electrode is provided at a tip of a rod of an air cylinder, and the high power applying means and the low power applying means supply air to the air cylinder of the movable electrode to supply air to the movable electrode. An air supply device that applies high power or low power to the air supply device may be used. At this time,
The power supply control means supplies high power to the movable electrode disposed above the work for a time TD by supplying air from the air supply device to the air cylinder, thereby causing the movable electrode to move at a high speed. By lowering the pressure in the rod chamber of the air cylinder higher than the head chamber, and then supplying air from the air supply device to the air cylinder so that the pressure in the rod chamber is lower than that in the head chamber. By applying a low power to the movable electrode to lower the movable electrode at a low speed to reach the work, and then supply air to the air cylinder from the air supply device to pressurize the work by the movable electrode. May be configured.

[0009]

The electrode driving apparatus of the spot welding machine according to the present invention is provided in a spot welding machine which performs spot welding by sandwiching a work between a fixed electrode and a movable electrode and applying an electric current under pressure. The movable electrode is moved up and down with respect to the work on the electrode. In such an electrode driving device, the power application control means applies high power for a time TD to the movable electrode disposed above the workpiece by the high power application means to lower the movable electrode at a high speed. A low power is applied to the movable electrode by applying a low power to the work by lowering the movable electrode at a low speed so that the movable electrode reaches the workpiece. Press against the work and pressurize. Also,
The arrival time measuring means measures a time TR from when the low power applying means starts applying low power to the movable electrode until the movable electrode reaches the workpiece. Then, the high-speed falling time output means outputs the time TR measured by the arrival time measuring means.
Is smaller than the predetermined time, the time TD is shortened,
If the time TR is longer than the predetermined time, the time TD is extended, and then the time TD is output to the power application control means. As a result, in the next cycle, when the high power is applied to the movable electrode disposed above the workpiece by the high power applying means, the power applying control means performs only the time TD output by the high speed descent time output means. It will give high power.

Here, the high-speed descent time output means is provided when the time TR from when the low power applying means starts applying low power to the movable electrode to when the movable electrode reaches the workpiece is shorter than a predetermined time. Before reaching a sufficiently low speed, it may reach the workpiece and give a large impact to the workpiece.
The time TD for performing the high-speed descent is shortened to eliminate the fear. On the other hand, if the time TR is longer than the predetermined time, the time required for the movable electrode to reach the workpiece after the speed is sufficiently reduced may be too long, and the cycle time may be prolonged. The fear is eliminated.

Therefore, according to the electrode driving apparatus of the spot welding machine of the present invention, it is possible to obtain the effect that the impact between the movable electrode and the work can be always sufficiently reduced and the cycle time can be shortened.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a first embodiment, FIGS. 2 to 5 are explanatory diagrams of a switching valve for applying a supply pressure, an exhaust pressure, a harmonic pressure, and a low pressure regulation, respectively, and FIG. FIG. 7 is a block diagram showing a connection, and FIG. 7 is an explanatory diagram showing one cycle of the first embodiment.

The spot welding pressurizing device (electrode driving device) of the first embodiment includes a fixed electrode 2, a movable electrode 3, and a welding gun 3.
0, head side switching valve 40a, rod side switching valve 4
0b, a pressure controller 70, a landing detection device 71, an air supply source 80, and the like.

The fixed electrode 2 is removably provided on the upper end of a rod 1c suspended from the lower arm 1a of the jig 1 having a substantially U-shape via an insulator 2a. On the other hand, the movable electrode 3 is disposed so as to face the fixed electrode 2, penetrates the upper arm 1 b of the jig 1, and is supported so as to be movable in the vertical direction. The movable electrode 3 is provided on the lower end of a piston rod 33 of a welding gun 30 (described later) fixed to the upper surface of the upper arm 1 b of the jig 1.
It is provided detachably via a. The fixed electrode 2 and the movable electrode 3 can sandwich a pair of works 4 and 5 therebetween, and the works 4 and 5 are pressurized and energized by the electrodes 2 and 3 to perform spot welding. In addition, both electrodes 2, 3
Lead wires 2b and 3b respectively extend from the electrodes, and when the electrodes 2 and 3 sandwich the workpieces 4 and 5, electricity is supplied between the electrodes 2 and 3. The conductors 2b and 3b are connected to the landing detection device 71.
The landing detection device 71 outputs a landing detection signal to the pressure controller 70 when the conduction between the movable electrode 3 and the fixed electrode 2 is established.

The welding gun 30 is fixed to the upper surface of the upper arm 1b of the jig 1 and includes a cylinder 31, a piston 32, and a piston rod 33 penetrating vertically through the cylinder 31. The head-side air chamber 31a and the rod-side air chamber 31b of the cylinder 31 communicate with the head-side switching valve 40a and the rod-side switching valve 40 via communication passages 34 and 35, respectively.
b and the secondary ports 60a and 60b.

Since the head-side switching valve 40a and the rod-side switching valve 40b have the same structure, the switching valve 40 is hereinafter simply referred to as a switching valve 40, and a,
The description of b will be omitted. The switching valve 40 includes a main body 41 and first and second solenoid valves 65 and 66. The main body 41 of the switching valve 40 is formed in a cylindrical shape whose upper and lower ends are closed, and a spring chamber 42, an exhaust chamber 43, a pressure regulating chamber 62, and an air supply chamber 44 are formed from the upper part in FIG.

In the spring chamber 42, a spring pressurizing piston 45 is disposed slidably up and down on the upper side, and a pressure adjusting piston 46 is slidable up and down on the lower side. Further, a spring 47 is provided between the spring pressurizing piston 45 and the pressure adjusting piston 46 so as to urge it in a direction to widen the interval between them. In the spring chamber 42, the spring pressurizing piston 4
The communication path 48 connected to the second solenoid valve 66 is provided on the upper surface
A communication passage 49 communicating with the atmosphere is provided on the lower surface side of the spring pressurizing piston 45, and a communication passage 50 connected to the first solenoid valve 65 is provided on the lower surface side of the pressure regulating piston 46. .

In the exhaust chamber 43, an exhaust valve body 51 having a hole penetrating the upper and lower surfaces is disposed so as to be slidable up and down, and the exhaust valve body 51 is moved by a spring 52 provided on the outer periphery thereof. , So as to abut against the valve seat 68. A rod 53 connected to the pressure adjusting piston 46 penetrates the center of the exhaust valve body 51 so as to be slidable up and down. At the lower end of the rod 53, a stem 54 having a diameter larger than the rod diameter is provided. Therefore, when the pressure adjustment piston 46 slides upward, the exhaust valve body 51 engages with the stem 54 and is pulled upward. The exhaust chamber 43 includes an exhaust valve body 5.
An exhaust port 55 that communicates with the atmosphere is provided on the lower surface side of 1.

In the air supply chamber 44, an air supply valve body 56 having a hole penetrating the upper and lower surfaces is disposed so as to be slidable up and down. The air supply valve body 56 is formed by a spring 57 provided on the outer periphery thereof. It is urged to abut the valve seat 69 of the air supply chamber 44. The lower surface of a stem 54 provided on the rod 53 is arranged at the center of the air supply valve body 56 so as to be able to abut. For this reason,
When the pressure adjustment piston 46 slides downward, the air supply valve body 56 is pressed by the stem 54 and is pushed downward. The air supply source 8 is provided on the upper surface side of the air supply valve body 56.
An air supply port 58 communicated with the solenoid valve 0 and a communication passage 59 connected to the second solenoid valve 66 are provided.

The pressure regulating chamber 62 is provided between the exhaust chamber 43 and the air supply chamber 44, and has a secondary port 60 connected to the cylinder 31 and a communication passage 61 connected to the first solenoid valve 65. I have. When the exhaust valve body 51 is in contact with the valve seat 68, the communication between the exhaust chamber 43 and the pressure regulating chamber 62 is interrupted,
When the exhaust valve body 51 is separated from the valve seat 68, the exhaust chamber 43 and the pressure regulating chamber 62 are communicated. In addition, the air supply valve body 56
Is in contact with the valve seat 69, the communication between the air supply chamber 44 and the pressure regulating chamber 62 is cut off, and when the air supply valve body 56 is separated from the valve seat 69, the air supply chamber 44 and the pressure regulating chamber 62 Is communicated.

The first and second solenoid valves 65 and 66 are connected to the communication passage 4.
8, 50, 59 and 61 are set for the communication state. The first and second solenoid valves 65 and 66 are positioned by driving a solenoid according to an output signal from a pressure controller 70 described later. As shown in FIG. 1, the air supply source 80 is connected to an air supply port 58a of the head side switching valve 40a and an air supply port 58b of the rod side switching valve 40b via a mist separator 81 and a pressure reducing valve 82.

As shown in FIG. 6, the pressure controller 70 includes a well-known CPU 74, a ROM 75, a RAM 76, a backup RAM 77, a clock 78, and an input / output port 79.
And these are connected by a bus.
The pressurization controller 70 is connected so that a landing detection signal from the landing detection device 71 can be input via the input / output port 79, and the first and second solenoid valves 65a, 65b, 66a, 66b
Is connected so as to be able to output a control signal via an input / output port 79.

Next, adjustment of the air pressure by the switching valve 40 will be described. The switching valve 40 can be set to any one of four pressures: supply pressure, exhaust pressure, harmonic pressure, and low pressure regulation. When the switching valve 40 is set to the supply pressure, as shown in FIG. 2, the first and second solenoid valves 65 and 66 are both turned on, the communication path 48 and the communication path 59 are connected, and the communication path 50 is The communication path 61 is cut off, communicating with the atmosphere. At this time, the air from the air supply port 58 is supplied to the spring chamber 42 via the air supply chamber 44, the communication passage 59, the second solenoid valve 66, and the communication passage 48.
To act on the upper surface of the spring pressing piston 45, the spring pressing piston 45 is pushed down. Then, the pressure adjustment piston 46 is also pushed down together with the rod 53 and the stem 54 via the spring 47, so that the air supply valve body 56 is pushed down against the urging force of the spring 57. On the other hand, the exhaust valve body 51 is in contact with a valve seat 68 by a spring 52. As a result, the air from the air supply port 58 is supplied from the air supply chamber 44 to the secondary port 60 as it is through the gap between the valve seat 69 and the air supply valve body 56.

When the switching valve 40 is set to the exhaust pressure, as shown in FIG. 3, the first solenoid valve 65 is on, the second solenoid valve 66 is off, the communication passage 48 communicates with the atmosphere, and the communication passage 48 communicates with the atmosphere. The communication path 50 and the communication path 59 are communicated, and the communication path 61 is shut off. At this time, the air from the air supply port 58 is supplied to the air supply chamber 4.
4. Since the pressure control piston 46 acts on the lower surface of the pressure control piston 46 of the spring chamber 42 via the communication path 59, the second solenoid valve 66, the first solenoid valve 65, and the communication path 50, the pressure control piston 46 is moved together with the rod 53 and the stem 54. Pushed up. Therefore, the exhaust valve body 51
Engages with the stem 54 and rises against the urging force of the spring 52. On the other hand, the air supply valve body 56 is in contact with a valve seat 69 by a spring 57. As a result, the air from the secondary port 60 passes through the gap between the valve seat 68 and the exhaust valve body 51 from the exhaust chamber 43 and is discharged to the atmosphere via the exhaust port 55.

When the switching valve 40 is set to the higher pressure, as shown in FIG. 4, the first solenoid valve 65 is off, the second solenoid valve 66 is on, and the communication passage 48 and the communication passage 59 are communicated. , The communication path 50 and the communication path 61 are communicated. At this time, the air from the air supply port 58 is supplied to the spring chamber 42 via the air supply chamber 44, the communication passage 59, the second solenoid valve 66, and the communication passage 48.
To act on the upper surface of the spring pressing piston 45, the spring pressing piston 45 is pushed down. Then, the pressure adjustment piston 46 is also pushed down together with the rod 53 and the stem 54 via the spring 47, so that the air supply valve body 56 is pushed down against the urging force of the spring 57. Then, air from the air supply port 58 passes from the air supply chamber 44 to the pressure regulating chamber 62 through the gap between the valve seat 69 and the air supply valve body 56, and further communicates with the communication passage 61, the first solenoid valve 65, It acts on the lower surface of the pressure adjustment piston 46 via the passage 50 to push up the pressure adjustment piston 46. In this manner, the main body 41 constitutes a pressure reducing valve mechanism, and a pressure adjustment balanced with the pressing force of the spring 47 (the pressing force is high because the spring pressing piston 45 is lowered) is generated in the pressure adjusting chamber 62. Then, the higher pressure is supplied to the secondary port 60.

When the switching valve 40 is set to a low pressure regulation, as shown in FIG. 5, the first and second solenoid valves 65 and 66 are both off, the communication passage 48 communicates with the atmosphere, and the communication passage 50 communicates with the atmosphere.
And the communication path 61 is communicated, and the communication path 59 is shut off. Also in this case, as in the case of the harmonic pressure, since the pressure regulating chamber 62 and the lower surface of the pressure regulating piston 46 communicate with each other, the main body 41 constitutes a pressure reducing valve mechanism, and the pressing force of the spring 47 (the spring pressurizing piston 4
5 is raised, the pressure is low), and a pressure adjustment matching the pressure is generated in the pressure adjustment chamber 62, and the low pressure adjustment is supplied to the secondary port 60.

Next, the operation of the pressurizing device of the spot welding machine according to the present embodiment will be described. The pressure controller 70
As shown in FIG. 7, regarding the state of the movable electrode, stop, high speed descent, deceleration descent (reverse pressure), low speed descent, pressure welding, high speed rise, deceleration rise (reverse pressure), and low speed rise are executed as one cycle. (Note that, in FIG. 7, although there is a slight response delay for the position of the movable electrode, it is ignored and displayed). This pressurization controller 70 stores the information in FIG.
The spot welding process is performed according to the flowchart of FIG.
Note that the backup RAM77 of the pressure controller 70, the value of TD ₁ is stored as an initial value in advance fast fall time.

The spot welding process shown in FIG. 8 is started when a power supply (not shown) of the pressure controller 70 is turned on. When this process is started, the pressurization controller 70 sets the first solenoid valve 65a of the head-side switching valve 40a.
Is turned off, the second solenoid valve 66a is turned off to supply a low pressure regulation to the head side air chamber 31a (see FIG. 5), the first solenoid valve 65b of the rod side switching valve 40b is turned off, and the second solenoid valve 66 is turned off.
The movable electrode 3 is stopped at the rising end by turning on b to supply the harmonic pressure to the rod-side air chamber 31b (see FIG. 4) (S10).

Subsequently, it is determined whether or not a work switch (not shown) of the pressure controller 70 is turned on (S1).
2) If the switch is not turned on (NO in S12), the process waits until the switch is turned on. On the other hand, if the switch is turned on (YES in S12), the counter value n of the RAM 76 is set to 1 (S14), and it is determined whether a predetermined stop time has elapsed (S16). Again S1
Returning to step S6, if it has elapsed, the process proceeds to step S18. In S18,
The pressurization controller 70 turns on the first solenoid valve 65a and the second solenoid valve 66a of the head-side switching valve 40a to supply the supply air pressure to the head-side air chamber 31a (see FIG. 2). By turning on the first solenoid valve 65b of 40b and turning off the second solenoid valve 66b to supply the exhaust pressure to the rod side air chamber 31b (see FIG. 3), the movable electrode 3 is moved toward the workpieces 4, 5 at high speed. Lower (S1
8).

[0030] Then, it is determined whether or not the high-speed descent time TD _n has elapsed (S20), it has not elapsed (S20
NO at S20), and returns to S20 again, and if it has elapsed (YES at S20), proceeds to S22. In S22, the pressurization controller 70 operates the first solenoid valve 65a of the head-side switching valve 40a.
Is turned off, the second solenoid valve 66a is turned off to supply a low pressure regulation to the head side air chamber 31a (see FIG. 5), the first solenoid valve 65b of the rod side switching valve 40b is turned off, and the second solenoid valve 66 is turned off.
b is turned on to supply the harmonic pressure to the rod-side air chamber 31b (see FIG. 4), and this state is maintained for a predetermined deceleration descent time (S22). Thus, contrary to the high-speed descent, the air pressure in the rod-side air chamber 31b becomes higher than the head-side air chamber 31a (reverse pressure), and the descent speed of the movable electrode 3 is rapidly reduced.

Subsequently, at S24, the pressure controller 70
Turns off the first solenoid valve 65a of the head-side switching valve 40a and turns on the second solenoid valve 66a to supply the harmonic pressure to the head-side air chamber 31a (see FIG. 4). The solenoid valve 65b is turned off, the second solenoid valve 66b is turned off, and a low pressure is supplied to the rod side air chamber 31b (see FIG. 5), whereby the movable electrode 3 is lowered at a low speed (S24). Then, the pressure controller 70 determines whether or not a landing detection signal has been input from the landing detection device 71 (S26). If not (NO in S26), the process returns to S26 again, and if it has been input (S26). YES) S2
Proceed to 8. In S28, the temporarily stored in RAM76 time TR _n from the start of deceleration down to the landing detection signal is input. The measurement of the time TR _n is performed by the clock 78.

Subsequently, at S30, the pressure controller 70
Turns on the first solenoid valve 65a and the second solenoid valve 66a of the head-side switching valve 40a to supply the supply air pressure to the head-side air chamber 31a (see FIG. 2). By turning on the solenoid valve 65b and turning off the second solenoid valve 66b to supply the exhaust pressure to the rod side air chamber 31b (see FIG. 3), the workpieces 4, 5 are moved between the movable electrode 3 and the fixed electrode 2. Spot welding is performed by sandwiching and applying pressure (S30).

Subsequently, in S32, the pressure controller 70
Turns on the first solenoid valve 65a of the head-side switching valve 40a and turns off the second solenoid valve 66a to supply the exhaust pressure to the head-side air chamber 31a (see FIG. 3). By turning on the solenoid valve 65b and turning on the second solenoid valve 66b to supply the supply air pressure to the rod-side air chamber 31b (see FIG. 2), the movable electrode 3 is quickly raised above the works 4, 5 (S32). ).

[0034] Then, it is determined whether or not the high-speed rise time TU _n has elapsed (S34), it has not elapsed (S34
NO at S34), and if it has elapsed (YES at S34), the process proceeds to S36. Here, TU _n is a value calculated as a function of TD _n (TU _n = f (TD _n )).

In S36, the pressurizing controller 70 turns off the first solenoid valve 65a and turns on the second solenoid valve 66a of the head-side switching valve 40a to turn on the harmonic pressure to the head-side air chamber 31.
a (see FIG. 4), and the rod-side switching valve 40b
The first solenoid valve 65b is turned off and the second solenoid valve 66b is turned off to supply a low pressure regulation to the rod side air chamber 31b (see FIG. 5), and this state is maintained for a predetermined deceleration rising time (S
36). As a result, contrary to the high-speed rise, the air pressure in the rod-side air chamber 31b becomes lower than the head-side air chamber 31a (reverse pressure), and the rising speed of the movable electrode 3 is rapidly reduced.

Subsequently, at S38, the pressure controller 70
Turns off the first solenoid valve 65a and the second solenoid valve 66a of the head-side switching valve 40a to supply a low pressure regulation to the head-side air chamber 31a (see FIG. 5), and the first of the rod-side switching valve 40b. By turning off the solenoid valve 65b and turning on the second solenoid valve 66b to supply the harmonic pressure to the rod-side air chamber 31b (see FIG. 4), the movable electrode 3 is slowly raised.

Subsequently, it is determined whether or not the movable electrode 3 has reached the rising end (S40). If it has not reached the rising end (NO in S40), the process returns to S40 again, and if it has reached the rising end. (YES in S40) Proceed to S42. The determination as to whether or not the movable electrode 3 has reached the rising end is made by a rising end reaching detecting means such as a limit switch.

In S42, the counter value n of the RAM 76 is incremented (S42), and it is determined whether or not the time TR _n-1 stored in the RAM 76 in S28 is equal to or less than a predetermined time t (S44). Here, the predetermined time t is an optimal time for decelerating the speed of the movable electrode 3 at the time of high-speed descent and allowing the movable electrode 3 to reach the workpieces 4 and 5 in a sufficiently low speed state. It is what I sought.

If the time TR _n-1 is equal to or less than the predetermined time t in S44 (YES in S44), the movable electrode 3 may reach the works 4 and 5 before the movable electrode 3 sufficiently slows down and give a large impact to the works 4 and 5. It is therefore also set shorter by α faster falling time TD _n previous value TD _n-1 (S46). On the other hand, if the time TR _n-1 exceeds the predetermined time t in S44 (NO in S44), the movable electrode 3 reaches the works 4 and 5 after being sufficiently slowed down, but the slow down time tends to be too long. There because cycle time may result in prolonged, which to be set longer by α faster after falling time TD _n previous value TD _n-1 to solve (S48).

Thereafter, in S50, the pressure controller 70
It is determined whether or not the work switch (not shown) is turned off to determine whether or not to end the spot welding process (S50). If not (NO in S50),
The processing after S16 is executed again. On the other hand, if the process is to be terminated (YES in S50), the spot welding process is terminated.

As described above, according to the pressurizing device of the spot welding machine of the present embodiment, the effect that the impact between the movable electrode 3 and the works 4 and 5 can always be sufficiently reduced and the cycle time can be shortened. can get. Further, when shifting from the high speed descent to the low speed descent, the time for shifting from the high speed descent to the low speed descent is shortened by setting the air pressure of the head side air chamber 31a to be lower (reverse pressure) than the rod side air chamber 31b. Therefore, the value of the predetermined time t can be set small, and the effect that the cycle time can be shortened can be obtained.

Here, the air supply source 80, the head-side switching valve 40a, and the rod-side switching valve 40b of the present embodiment correspond to the air supply device (high power supply means and low power supply means) of the present invention, When the air pressure is supplied to the air chamber 31a and the exhaust pressure is supplied to the rod-side air chamber 31b, high power is applied to the movable electrode 3 ("high-speed descent" in FIG. 6), and low pressure adjustment or harmonic pressure is applied to the head-side air chamber 31a. , Rod side air chamber 31b
When the harmonic pressure or the low regulated pressure is supplied to the movable electrode 3, low power is applied to the movable electrode 3 ("deceleration down" and "low speed down" in FIG. 6). Further, the pressurizing controller 70 corresponds to the power application control means and the high-speed descent time output means of the present invention, and the landing detection device 71 and the clock 78 correspond to the arrival time measuring means.

Next, a second embodiment will be described. Second
In the embodiment, except that the configuration of the landing detection device 71 is such that a landing detection signal is output to the pressure controller 70 by a pressure change instead of outputting a landing detection signal to the pressure controller 70 by conduction of electric current, Since this embodiment is the same as the first embodiment, the same reference numerals are given to the same components, and the description thereof will be omitted. As shown in FIG. 9, the pressure diagram at the moment when the movable electrode 3 lands on the workpieces 4 and 5 is such that the harmonic pressure of the head side air chamber 31 a increases by a minute amount d, and the low pressure adjustment of the rod side air chamber 31 b decreases. It falls by an amount d '. Therefore, these minute amounts are stored in advance, and the head side air chamber 31 is stored.
a, these minute amounts d and d ′ are in the rod side air chamber 31b.
Is detected by the pressure switches 72a and 72b when there is a pressure change of a value in which a certain allowable width is taken into account.
It may be configured to output to the pressure controller 70 (see FIG. 10). Since the operation and effect of the second embodiment are almost the same as those of the first embodiment, the description thereof will be omitted.

It is needless to say that the present invention is not limited to the above-described embodiments, and can be implemented in various modes without departing from the technical scope of the present invention. For example, FIG.
As described above, when the welding gun 30 having the piston rod 33 skewed into the cylinder 31 is used, the head-side and rod-side pistons 32 have the same area,
Head side switching valve 40a and rod side switching valve 40b
The urging force (pressing force) of the springs 47a and 47b may be the same, but if a welding gun having a piston rod penetrating only one side of the cylinder 31 is used, the area of the piston on the head side and that on the rod side differ. 11A, the spring 47 is moved up and down with respect to the spring pressurizing piston 45 by the screw 91 as shown in FIG. 11A to make the biasing force of the spring 47 variable, or as shown in FIG. It is preferable that the biasing force of the high-pressure and low-pressure springs 47 is made variable by moving the rising end position of the spring pressurizing piston 45 up and down by 92. In this case, one of the head-side switching valve 40a and the rod-side switching valve 40b may be of a variable type, or both may be of a variable type.

In S44 of the flowchart of FIG. 8, the lower limit time t1 and the upper limit time t are substituted for the predetermined time t.
Defines 2, TR if _n-1 is in the range of t1~t2 fast fall time TD _n uses the previous value TR _n-1, TR _n-1 is t
If it is less than 1 fast fall time TD _n is the previous value TR _n-1
Also set shorter by α than, may be TR _n-1 is set fast fall time TD _n if it exceeds t2 only α than the previous value TR _n-1 long.

Further, in the welding gun 30 of the above embodiment, the movable electrode 3 is moved up and down using an air cylinder. However, a hydraulic cylinder may be used, or the movable electrode 3 may be moved to the lower end of the rod on the male screw side of the ball screw. The electrode 3 may be attached, and the movable electrode 3 may be moved up and down using a drive motor that rotates the ball screw.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment.

FIG. 2 is an explanatory diagram of a switching valve when a supply air pressure is applied.

FIG. 3 is an explanatory diagram of a switching valve when applying exhaust pressure.

FIG. 4 is an explanatory diagram of a switching valve when applying a harmonic pressure.

FIG. 5 is an explanatory diagram of a switching valve when a low pressure adjustment is applied.

FIG. 6 is a block diagram showing an electrical connection of a pressure controller.

FIG. 7 is an explanatory diagram showing one cycle.

FIG. 8 is a flowchart of a spot welding process.

FIG. 9 is a pressure change diagram of the second embodiment.

FIG. 10 is a schematic configuration diagram of a second embodiment.

FIG. 11 is a partial explanatory view of a welding gun according to another embodiment.

FIG. 12 is an explanatory diagram showing a change in a stroke due to wear of an electrode tip.

[Explanation of symbols]

2 ... fixed electrode 3 ... movable electrode
4, 5 ... Work, 30 ... Welding gun, 31a ... Head side air chamber, 31b ... Rod side air chamber, 40a ... Head side switching valve, 40
b: rod-side switching valve, 42: spring chamber,
43 ... exhaust chamber, 44 ... air supply chamber,
45: Spring pressure piston, 46: Pressure adjustment piston, 51: Exhaust valve body, 53:
Rod, 54 ... Stem, 55 ...
Exhaust port, 56 ... air supply valve, 58 ...
・ Air supply port, 60 ... secondary port, 62
... pressure regulating chamber, 65 ... first solenoid valve,
66 second solenoid valve 70 pressurized controller 71 landing detection device 80
・ Air supply source,

Claims (2)

(57) [Claims] 1. A spot welding machine for sandwiching a workpiece between a fixed electrode and a movable electrode and applying a pressure to perform spot welding to move the movable electrode up and down with respect to the workpiece on the fixed electrode. In the electrode driving device of the spot welding machine, a high power applying means for applying high power to the movable electrode, a low power applying means for applying low power to the movable electrode, and disposed above the work. High power is applied to the movable electrode by the high power applying means for a time TD to lower the movable electrode at high speed, and then low power is applied to the movable electrode by the low power applying means. A power applying control means for lowering the movable electrode at a low speed to reach the work, and thereafter applying high power to the movable electrode by the high power applying means to press the movable electrode against the work. A step, arrival time measuring means for measuring a time TR from the start of applying low power to the movable electrode by the low power applying means until the movable electrode reaches the work, and the arrival time measuring means If the measured time TR is shorter than the predetermined time, the time TD is shortened and the time T
An electrode for a spot welding machine, comprising: a high-speed descent time output means for outputting the time TD to the power application control means after extending the time TD when R is longer than a predetermined time. Drive. 2. The movable electrode is provided at a tip end of a rod of an air cylinder, and the high power applying means and the low power applying means supply air to the air cylinder of the movable electrode to supply air to the movable electrode. The electrode drive device for a spot welding machine according to claim 1, wherein the electrode drive device is an air supply device for applying high power or low power.