JP4255356B2 - Resistance welding machine - Google Patents

Description

  The present invention relates to a pressurizing device that linearly drives electrodes of a stationary spot welder, a welding gun, a projection welder, and the like. More specifically, when spot welding is performed, there is no foreign matter between the workpiece and the electrode. The present invention relates to a device for ensuring safety when a handle is sandwiched.

Conventionally, as a safety device known for a spot welder or the like, for example, there is an invention previously filed by the applicant of the present application. This prior art detects the amount of displacement of the movable electrode with a sensor at a predetermined position just before the movable electrode pressurizes the workpiece, and when the detected displacement is determined to be abnormal, the movable electrode is used to press the electrode after a short time. This is a pressurizing device that opens to the return side of the cylinder (Patent Document 1).

In addition, a pressurization control method for a resistance welder that detects the inclusion of foreign matter between electrodes and avoids moving the movable electrode side in the open direction has been disclosed.
In this type of conventional invention method, in order to weld the nut to the panel work placed on the lower electrode, when the upper electrode approaches the nut and reaches the welding start position, the gap between the upper electrode and the lower electrode is reached. If the current is confirmed at the welding start position, the controller determines that there is no foreign material between the upper electrode and the lower electrode and continues to pressurize with the upper electrode. Perform the welding process. If continuity cannot be confirmed, it is determined that foreign matter is caught between the upper electrode and the lower electrode, and the upper electrode is stopped moving in the pressurizing direction during the operation of the electrode sinking mechanism and moved in the opposite direction. , Detection and avoidance operation of foreign object pinching is performed (Patent Document 2).

However, although the device of Patent Document 1 is excellent as a simple safety device that does not require the number of parts, it has been considered difficult to cope with the case where it is desired to increase the speed when the electrode descends due to the weight reduction of the pressure cylinder.

Further, in the method of Patent Document 2, when welding is performed with a workpiece sandwiched between a pair of electrodes, it is determined whether or not a foreign object or the like is sandwiched between the electrodes in order to confirm conduction by energization between the pair of electrodes. And a means for temporarily suppressing the movement of the electrode in the pressurizing direction against the driving force supplied during the operation of the electrode, that is, a point where an energization detection circuit for the energization conduction confirmation device (sensor) is provided between the electrodes It is necessary to provide the insertion mechanism in the electrode part, and the electrode structure and control become complicated.
JP 2002-35954 A JP 2002-205174 A

  The present invention uses a composite cylinder in which a large-diameter cylinder for electrode pressurization and a small-diameter cylinder for low pressurization in a resistance welder are connected to a pressurizing unit, and is movable by pressurizing with the differential pressure of the piston of the small-diameter cylinder. The descending speed until the electrode touches the workpiece can be increased, the low pressurization overload can be reduced, the switching position from low pressurization to main pressurization (welding pressurization) can be set arbitrarily, and welding is started When a predetermined time or more has elapsed from the start position to the switching position, it is determined that a foreign object has been caught between the workpiece and the upper and lower electrodes, and immediately the movement of the movable electrode in the pressurizing direction is stopped and the electrode is opened or removed. The warning is to solve the above-mentioned conventional problems.

Therefore, the present invention takes the following technical means to achieve the above object. In other words, the invention of claim 1 is a pressure resistance welding machine that moves at least one movable electrode, sandwiches a work between the other fixed electrodes, generates a necessary pressurizing force, and energizes and welds. A large-diameter cylinder for pressurizing an electrode disposed in an air supply circuit for adjusting the pressure of the movable electrode from an air source, and a small-diameter cylinder for low pressurization connected to the large-diameter cylinder, A first solenoid valve (SOL1) is connected to the air supply circuit of the small diameter cylinder, and a second solenoid valve (SOL2) is connected to the air supply circuit of the large diameter cylinder, and the large and small pistons are connected to the piston of the small diameter cylinder. By providing both rods with different diameters concentrically with the cylinder and operating the first solenoid valve , air pressure acts on both piston surfaces of the small-diameter cylinder to cope with the area difference between the piston surfaces of the small-diameter cylinder. The piston is pushed downward with a slight force, and a linear detection area is provided in the range of movement from the pressure reference point within the movable area of the movable electrode to the backward side and from the reference point to the forward side. On the basis of the displacement amount of the displacement sensor at the displacement position of the movable electrode set in the linear detection region provided on the reverse side from the low pressure, it is possible to switch from the low pressurization to the main pressurization. If the movable electrode does not reach the displacement position of the movable electrode set in the linear detection region provided on the backward side from the pressure reference point from the position, the welding control device controls the welding machine. The condition is that the movable electrode is stopped and / or opened by a signal .

Next, the invention of claim 2 is based on the condition that the switching point from the low pressurization to the main pressurization in the linear detection region can be arbitrarily set by the welding control device.

According to a third aspect of the present invention, the displacement of the amount of wear of the electrode is measured from position information when the movable electrode reaches the pressure reference point within the linear detection region, and the switching position from the low pressure to the main pressure is measured. It has an automatic correction function that always matches the (distance from the fixed electrode) with the set value.

According to a fourth aspect of the present invention, the amount of penetration of the workpiece by welding is measured and displayed on the basis of the position information of the movable electrode before starting welding and the position information of the movable electrode during energization and after energization within the linear detection region. And a function for determining and displaying whether or not the amount of penetration has reached a settable reference value.

The invention of claim 5 measures the thickness and height of a part to be welded such as a nut from the position information when the movable electrode reaches the workpiece in the linear detection region, and compares it with a settable missing part judgment reference position. Therefore, it has an automatic judgment function for the presence or absence of parts to be welded.

According to the first aspect of the present invention , the linear detection region is provided in the moving range from the pressure reference point in the movable region of the movable electrode to the backward side and from the reference point to the forward side,
Based on the displacement amount of the displacement sensor at the displacement position of the movable electrode set in the linear detection area provided on the backward side from the pressurization reference point, switching from low pressurization to main pressurization is possible. Welding that controls the welding machine when the movable electrode does not reach the displacement position of the movable electrode set in the linear detection area provided on the backward side from the pressure reference point from the retracted position of the movable electrode. Whether the movable electrode is stopped and / or opened by a signal from the control device, so that when a workpiece is sandwiched between a pair of electrodes and welding is performed, foreign matter or the like is sandwiched between the electrodes. Compared with the invention of Patent Document 2 to see the judgment, the energization detection circuit for confirming the conduction by energization between the pair of electrodes and the movement of the electrodes in the pressurizing direction against the driving force supplied during the operation of the electrodes. one The electrode structure and control need not be provided to the electrode portion becomes easy to suppress means clogging electrode sinking mechanism or the like.

  According to the invention of claim 2, the output of the sensor can be taken into the welding control device, and the switching point from the low pressurization to the main pressurization within the linear detection region can be arbitrarily set by the welding control device. By doing so, the digital setting of the switching point can be set electrically on the operation panel of the welding control device, that is, at the same level as the welding condition setting. The linear detection position of the linear gauge can be corrected according to the change of the pressurization reference point Q depending on the amount of electrode wear from the welding control device.

According to the third aspect of the present invention, it is not necessary to change the set value for manual correction by automatically correcting the deviation of the contamination determination position S (pressure switching position) caused by electrode wear. Convenience is increased and safety is improved because an appropriate foreign matter contamination determination position can be secured at all times.

According to invention of Claim 4, the information which determines the success or failure of welding with respect to a user by carrying out the monitor display of the welding amount of the workpiece | work by welding, and determining whether the settable reference value was reached or not is displayed. Can be provided.

According to the invention of claim 5, it is possible to prevent the occurrence of defective products by notifying the user of the shortage of the parts to be welded.

  The embodiment of the present invention is used in a pressurizing device of a stationary resistance spot welder, and is useful for a safety device of a fluid pressure cylinder in which an electrode is linearly driven by expansion energy such as compressed air.

  FIG. 1 is an external view of a stationary resistance spot welder. FIG. 2 shows only a part of the pressure device and the displacement sensor of Example 1 in an enlarged manner. FIG. 3 is a sequence chart showing a low force sequence operation of the present invention. FIG. 4 shows a connection circuit between the functional unit of the welding control device of the present invention device and the pneumatic piping system of the pressure unit.

In FIG. 1, an upper arm 2 and a lower arm 3 are arranged on the front surface of the main body 1. A guide case 4 is fixed to the tip of the upper arm. A pressure unit is fixed to the upper surface of the guide case 4. The pressurizing unit is a unit in which a large-diameter cylinder 6 for electrode pressurization and a small-diameter cylinder 22 for low pressurization are connected. The movable ram 5 in the guide case 4 moves up and down by the operation of the large and small cylinders 6. A movable electrode 8 is supported at the tip of the movable ram 5 via an upper conductor 7. On the other hand, a fixed electrode 9 opposite to the movable electrode 8 is supported on the lower arm 3 via a lower conductor 10. A welding transformer (not shown) housed in the main body is connected to the movable copper plate 11 and the conductive member 12.

Figure 6 shows an embodiment for an increase in the operating speed of the pressurized圧初phase of the movable electrode of the present invention apparatus supplementarily, enlarged cross-sectional view showing a part of a structure of inserting the scan flops ring inside of the small-diameter cylinder It is. In the figure, with the pressure chamber C side to the elastic member of the small-diameter cylinder 22, for example a spring 30 is provided so as to surround the outer periphery of the rods 24, the gel direction under pressing spring force is always piston 23 It is energized. Thus, the piston 23 is pushed down at the moment when the compressed air supply is switched to the pressurization side of the small cylinder 22 so that the operation speed of the movable electrode 8 at the initial pressurization can be supplementarily increased.

  The welding control device 13 controls the time of mechanical and electrical operations by a sequence program of the stationary spot welding machine and the controller 14, and is installed in the welding machine main body.

In FIG. 4, the air supply circuit of the large diameter cylinder 6 for generating the pressure of the spot welder is provided with an air pressure reducing valve 16 for adjusting the pressure of the movable electrode from the air source 15 on the primary side. The secondary side of the second solenoid valve (SOL2) connected to the air supply circuit is connected to the pressurizing chamber A of the large-diameter cylinder 6.

On the other hand, the first solenoid valve (SOL1) is connected to the return chamber B and the air supply circuit of the pressurizing chamber C of the small diameter cylinder 22 for low pressurization. The return chamber B of the small diameter cylinder 22 is connected via an air pressure reducing valve 17 from an air supply circuit of the air pressure reducing valve 16.

  The pressurizing unit of the present invention comprises a large-diameter cylinder 6 for electrode pressurization and a small-diameter cylinder 22 for low pressurization. The large-diameter cylinder 6 is pressurized by a second solenoid valve (SOL2), and the small-diameter cylinder 22 is pressurized. The first solenoid valve (SOL1) lowers and releases the pressure. The air source is directly connected to the bottom and connected to the head via the first solenoid valve (SOL1). The low-pressure small-diameter cylinder 22 has rods 24 and 25 having different diameters at both ends of the small-diameter piston 23, and the area on the upper side of the small-diameter piston 23 is slightly larger than the lower side.

In the embodiment shown in FIG. 2, the entire stroke of the pressurizing device is 70 mm, and the position from the start start point O until the movable electrode 8 moves and normally contacts the fixed electrode 9, that is, to the pressurization reference point Q. When the stroke is set to 55 mm, the low force (low pressurization) control range is about 15 mm from the pressurization reference point Q to the moving distance P including the thickness of the workpiece to be moved backward. Furthermore, the movement range between PR, which is 15 mm from the pressing reference point Q to the moving distance R taking into account the amount of pushing of the movable electrode due to nugget expansion after welding and the amount of consumption of the electrode tip, that is, the linear detection region is 30 mm. The whole range is monitored.

In the case of this embodiment, the displacement sensor 27 (RG1) is a digital displacement amount detecting means (hereinafter referred to as a product name: linear gauge) for monitoring linear movement. Here, the linear gauge 27 generates one pulse from the pulse generator every time the movable part of the spindle 28 moves by a predetermined amount or rotates by a predetermined angle, and counts up the generated pulse to the current position count according to the moving direction. Alternatively, it is an incremental method in which the count value of the current position counter is displayed as the current position of the machine movable part.

The linear gauge 27 is attached to the outside of the pressure unit and covered with a unit cover 29. The linear gauge 27 is installed so as to detect the amount of displacement of both rods 24 protruding outward from the small diameter cylinder 22 connected to the large diameter cylinder 6. The monitoring limit point of the linear gauge is a position that can prevent damage when foreign matter is caught between the electrodes, for example, the movable electrode 8 is about 6 mm from the pressurization reference point Q as a switching point between low pressurization and main pressurization. If the movable electrode passes through the limit point of 6 mm within the set time by setting it in the retracted position, the pressurization valve is normally operated to start substantial welding, but the movable electrode is in the detection zone of 6 mm. When the time until passing the limit point exceeds a certain time, it is determined that a foreign object is sandwiched between the electrodes, and the operation of immediately opening the movable electrode is started.

The welding control device 13 shown in FIG. 4 incorporates a welding condition setting unit such as a pressing force, a welding current value, and an energizing time, a reference value storage unit, a calculation unit, and the like. In addition to the timer unit that executes the welding sequence control, a counter unit that receives a pulse signal from the linear gauge 27 and converts it into a displacement is detected, and the linear gauge is included in the output stage of the pulse input driver of the counter unit. 27 is connected.

The welding control device 13 controls the input / output signals for switching ON / OFF of the first solenoid valve (SOL1) of the small cylinder for stroke and the second solenoid valve (SOL2) of the large cylinder for main pressurization to perform two-stage pressurization. Built-in I / O unit for control.

  The welding control device 13 detects an electrode pressurization reference point Q for each welding hit point by the linear gauge 27, detects the wear amount of the movable electrode and the fixed electrode, and gradually changes the wear reference point. The function of correcting the limit point of 6 mm by adjusting the amount of electrode stroke and the function of appropriately detecting the dressing timing of the tip of the electrode tip and the replacement timing of a new electrode tip.

Next, the operation of the low force sequence of the pressurizing apparatus of the present invention will be described based on the sequence chart of FIG.

Set the panel work on the fixed electrode on the lower side of the open electrode, set the mating welding nut or bolt on the welding position of the panel work, and then step on the foot switch (start switch) of the welding machine. 1 Solenoid valve (SOL1) is activated and air is supplied to both sides of the piston 23 (return chamber B and pressurizing chamber C).

The piston 23 of the small-diameter cylinder 22 is slightly pushed downward, and the movable electrode 8 is lowered by applying its own weight, such as a movable ram of the large-diameter cylinder 6, other arm supports, and a round arm. Contrary to this descent, the air control (balanced air) supplied to the bottom applies pressure in the direction of pushing up from the lower side of the piston 23, so that the descent is performed at a low pressure while there is speed. The movable electrode 8 descends at a low pressure up to a stroke of 40 mm.

When the movable electrode is lowered by 40 mm, the dog 26 fixed to the external tip of both rods 24 comes into contact with the tip of the spindle 28 of the linear gauge 27 from 15 mm before the pressurization reference point Q and pushes it in, and the spindle 28 is squeezed. Whether or not it passes through the limit point 6 mm of the linear detection area to the point where it is turned on within the time is detected by a change in the position output of the linear gauge 27. The squeeze time confirms that the movable electrode 8 is operating normally. When the movable electrode 8 normally comes into contact with the workpiece within a predetermined time, the second solenoid valve (SOL2) is activated and air is sent to the pressurizing chamber A of the large-diameter cylinder 6 to raise the pressure necessary for welding. It becomes the main pressurization to raise.

  Subsequently, the current position of the linear gauge 27 before the start of energization is measured linearly with the electrode pressurized, the welding current is supplied between the electrodes, and the current position output of the linear gauge 27 is real-time after the end of energization. It is measured. Complementary increment output from the linear gauge 27 is taken into the welding control device 13 one by one, and the difference from the position before energization is stored (displayed) in the monitor circuit as the pushing amount of the welded portion melted and softened even during welding. Check the quality of the weld.

If a foreign object is caught at the descending end of the movable electrode 8 within the squeeze time, the linear gauge 27 receives resistance due to the thickness of the foreign object and detects it as an abnormal displacement amount of the movable electrode 8 and remains OFF. If the linear gauge 27 does not turn on even after the limit point 6mm set in the linear detection area PQ has started for a certain period of time (1-2 seconds after the start-up) after starting, Since the movement in the direction is delayed due to resistance, the first solenoid valve (SOL1) is turned OFF and air is supplied to the return chamber B of the small-diameter cylinder 22 so that the obstacle can be removed. The electrode 8 is opened immediately.

As described above, when a finger or the like is mistakenly sandwiched between the electrodes, the linear gauge 27 is determined to be abnormal because the predetermined time for passing through the linear detection region of the movable electrode 8 is exceeded, and is not turned ON. As a result, the first solenoid valve (SOL1) is turned off and the movable electrode 8 is immediately raised and opened after a predetermined time of 1 to 2 seconds has elapsed since the start.

Further, according to the embodiment shown in FIG. 5, the current position of the linear gauge 27 before the start of energization in a state where the electrodes are completely pressed is measured, and the missing item determination point T is set with respect to the pressing reference point Q. This makes it possible to detect a missing part of the welded part.

When the parts to be welded are correctly placed, the movable electrode 8 stops at the normal completion position U when the pressurization is completed, but proceeds to the abnormal completion position V when there are no parts to be welded. These stop positions can be measured by the linear gauge 27. By setting (storing) an appropriate position between the normal completion position U and the abnormal completion position V in the welding control device 13 as the shortage determination point T, the welding control device can obtain position information from the linear gauge 27 and By comparing the set values, it is possible to clearly indicate to the user whether there are parts to be welded.

  In the embodiments of the present invention, the safety system of the pressurization device of the stationary resistance welding machine has been described. However, the C type or X type welding gun, seam welding machine, upset welding machine, etc. other than the welding machine field are mounted on the robot. In addition, it is also useful for improving the safety of the machine movable part of a pressurizing apparatus required for metal plastic working such as a die press machine.

It is a front view of the whole welding machine which shows the Example which used this invention for the pressurization apparatus of the resistance spot welding machine. It is an enlarged view which shows embodiment of the pressurization apparatus and linear gauge of the Example of this invention. It is a welding sequence chart figure of the Example of this invention. It is an air supply circuit diagram of the pressurization system concerning the example of the present invention. It is explanatory drawing in the case of detecting the missing part of a to-be-welded part in the Example of this invention. FIG. 5 is an enlarged sectional view showing a part of a structure in which a spilling is inserted into a small-diameter cylinder, showing an embodiment for supplementarily increasing the operation speed of the movable electrode of the present invention in the initial stage of pressurization.

Explanation of symbols

1 Welding Machine Body 2 Upper Arm 3 Lower Arm 4 Guide Case
5 Movable Ram 6 Large Diameter Cylinder 7 Upper Conductor 8 Movable Electrode 9 Fixed Electrode 10 Lower Conductor 11 Movable Copper Plate
12 Conductive Member 13 Welding Control Device 14 Controller
22 Small-diameter cylinder 23 Piston 24 and 25 rods 26 Dog 27 Linear gauge 28 Spindle 29 Unit cover

Claims (5)

A pressure resistance welding machine that moves at least one movable electrode and sandwiches a workpiece between the other fixed electrodes to generate a necessary pressure and energizes and welds the welded electrode from an air source. A large-diameter cylinder for electrode pressurization arranged in an air supply circuit for adjusting pressure, and a small-diameter cylinder for low pressurization connected to the large-diameter cylinder, and the air supply circuit for the small-diameter cylinder includes The first solenoid valve (SOL1) is connected to the air supply circuit of the large-diameter cylinder, and the second solenoid valve (SOL2) is connected to the large-diameter cylinder air supply circuit. By providing a rod and operating the first solenoid valve , air pressure acts on both piston surfaces of the small-diameter cylinder, and the piston is lowered by a slight force according to the area difference between the piston surfaces of the small-diameter cylinder. A linear detection region is provided in the moving range from the pressure reference point in the movable region of the movable electrode to the backward side and the forward side from the reference point in the movable region of the movable electrode;
Based on the displacement amount of the displacement sensor at the displacement position of the movable electrode set in the linear detection area provided on the backward side from the pressurization reference point, switching from low pressurization to main pressurization is possible. Welding that controls the welding machine when the movable electrode does not reach the displacement position of the movable electrode set in the linear detection area provided on the backward side from the pressure reference point from the retracted position of the movable electrode. A resistance welding machine provided that the movable electrode is stopped and / or opened by a signal from a control device . 2. The resistance welding machine according to claim 1, wherein a switching position from low pressurization to main pressurization within the linear detection region can be arbitrarily set by a welding control device. In Claim 1, the displacement of the amount of wear of the electrode is measured from position information when the movable electrode reaches the pressure reference point in the linear detection region, and the switching position (fixed) from the low pressure to the main pressure is measured. Resistance welding machine with an automatic correction function that always matches the distance from the electrode with the set value. In Claim 1, the amount of penetration of a workpiece is measured and displayed for each welding based on the position information of the movable electrode before starting welding and the position information of the movable electrode during energization and after energization in the linear detection region. A resistance welding machine having a function and a function for determining whether or not a reference value at which the penetration amount can be set is reached and displayed. In Claim 1, by measuring the thickness and height of a workpiece to be welded such as a nut from the position information when the movable electrode reaches the workpiece in the linear detection region, and comparing the thickness and height with a settable shortage determination reference position , Resistance welding machine with automatic judgment function for presence / absence of parts to be welded.

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