Electrode position deviation detection device for resistance welding equipment

Abstract

To provide an electrode positional displacement detection device of a resistance welding device which can detect positional displacements of any of opposing two electrodes.SOLUTION: In a state where electrodes 1 of a resistance welding device attached to, for example, a manipulator of an industrial robot are in a prescribed position, grip members 4 which are brought into prescribed closed states with respect to the electrodes 1 in proper positions are moved simultaneously to external peripheral parts of the electrodes so as to grip both the opposing electrodes 1, and when the grip members 4 are not brought into the prescribed closed state, that is, when the grip members 4 are not closed due to displacements of the electrodes 1, it can be determined that any of the electrodes 1 is displaced. By this constitution, a displacement of any of the opposing two electrodes 1 can be also detected. It can be determined that the grip members 4 are not brought into the prescribed closed states from the fact that determination electrodes 8 arranged at, for example, turning tip parts of the grip members 4 are in non-energization states.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrode position deviation detection device for a resistance welding device, and more particularly to a device for detecting electrode position deviation of a resistance welding device which joins a plurality of workpieces by clamping them and passing current therethrough under pressure. [Background technology]

[0002] Resistance welding, one of the joining methods, has advantages such as little distortion, good appearance, and short welding time, and is widely used in the automotive industry, especially in the manufacture of car bodies. As is well known, resistance welding, also commonly called spot welding, is achieved by melting the joined parts themselves using Joule heat generated mainly by the contact resistance between the parts to be joined. In order to efficiently increase this Joule heat, multiple joined parts (usually two sheets) are sandwiched between opposing electrodes and pressure is applied while electricity is passed through them.

[0003] In mass-produced vehicle body manufacturing, a resistance welding device equipped with the counter electrode and an electrode pressure device is attached to the manipulator of an industrial robot, and the robot is taught to resistance weld various parts of the vehicle body. Generally, one of the counter electrodes is fixed and the other is movable. In mass-produced vehicle body manufacturing using such industrial robots, the position of the electrode (the position in the radial direction of the electrode) may shift due to the electrode colliding with something else or welding of the electrode to the joined member (base material). In particular, if the electrodes are not properly opposed to each other, problems such as poor welding due to reduced current flow efficiency or reduced spatterless function causing spattering may occur.

[0004] Therefore, in the following Patent Document 1, a conductive detection plate is placed within the movable range of a robot, and the detection plate is provided with an allowable hole into which an electrode can be inserted, and is configured to detect electrical continuity between the upper electrode and the detection plate. The robot is then taught to first insert the lower electrode into the allowable hole, and then insert the upper electrode into the allowable hole. If the lower electrode is misaligned relative to the upper electrode in the electrode radial direction and the amount of misalignment becomes larger than the set gap between the allowable hole and the upper electrode, the upper electrode abuts against the detection plate at the periphery of the allowable hole, causing electrical continuity between the two. As a result, if the upper electrode and the detection plate are electrically connected, it is found that the upper electrode is misaligned relative to the lower electrode. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-51003 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the electrode position deviation detection device for the resistance welding apparatus described in the above Patent Document 1 cannot detect deviation of the lower electrode. Since, in principle, deviation of the electrode position can occur in either the upper or lower electrode, there is a need for an electrode position deviation detection device for the resistance welding apparatus that can detect deviation of the electrode position in either the lower or upper electrode.

[0007] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide an electrode position deviation detection device for a resistance welding apparatus that is capable of detecting the position deviation of either of two opposing electrodes. [Means for solving the problem]

[0008] In order to achieve the above object, an electrode position deviation detection device for a resistance welding device is provided, A resistance welding device that joins a plurality of workpieces by sandwiching the workpieces between opposing electrodes and applying pressure and current thereto, the electrode position deviation detection means is provided which is approached simultaneously to outer peripheries of both of the opposing electrodes when the resistance welding device is in a predetermined position, and detects position deviation of the outer peripheries of each electrode, the electrode position deviation detection means comprising: pinching members which are moved toward the outer peripheries of both of the opposing electrodes so as to pinch each electrode from both radially outer sides of the electrodes when the resistance welding device is in the predetermined position, and which are brought into a predetermined closed state when each electrode is in an appropriate position; signal generating means which outputs a movement state signal according to the movement state of the pinching members toward the outer peripheries of the electrodes; and non-closed state detection means which detects, based on the movement state signal of the signal generating means, that the pinching members moved toward the outer peripheries of the electrodes are in a state other than the predetermined closed state. The device is characterized by comprising a position deviation determination means which determines that any of the electrodes is misaligned when the non-closed state detection means detects that the pinching member is in a state other than a predetermined closed state.

[0009] According to this configuration, for example, when a resistance welding device attached to a manipulator of an industrial robot is in a predetermined position, if the clamping members that are simultaneously moved toward the outer periphery of each opposing electrode so as to clamp each of the electrodes are other than in the predetermined closed state, i.e., the clamping members do not close completely due to misalignment of the electrodes, it can be determined that one of the electrodes is misaligned, and thereby any misalignment of either of the two opposing electrodes can be detected.

[0010] Another configuration of the present invention is characterized in that the signal generating means is provided on the clamping member and comprises a determination electrode which abuts against each other when the clamping member moved toward the outer periphery of the electrode is in the specified closed state, and a determination electrode current application means which applies a current between the determination electrodes when the clamping member is moved toward the outer periphery of the electrode, and the non-closed state detection means comprises a non-current detection means which detects that the determination electrodes are in a non-conducting state when current is applied between the determination electrodes by the determination electrode current application means, and the non-current detection means determines that the clamping member is in a state other than the specified closed state when the determination electrodes are in a non-conducting state.

[0011] With this configuration, since the judgment electrode that should come into contact with the clamping member when it is in the specified closed state is in a non-energized state, it can be determined that the clamping member is not in the specified closed state, i.e., that the clamping member is not completely closed due to misalignment of the electrodes, thereby making it possible to reliably detect misalignment of the two opposing electrodes.

[0012] Another aspect of the present invention is a resistance welding apparatus for joining a plurality of workpieces by clamping the workpieces between opposing electrodes and applying pressure and current to the workpieces, comprising: The resistance welding device is characterized in that it is equipped with an electrode position deviation detection means that is approached simultaneously to the outer periphery or tip of both of the opposing electrodes when the resistance welding device is in a predetermined position to detect position deviation of the outer periphery or tip of each electrode, and the electrode position deviation detection means comprises: an electrode distance sensor that is located radially outside the opposing electrodes when the resistance welding device is in the predetermined position and detects the electrode radial distance to the outer periphery or tip of each electrode in a non-contact manner; and a position deviation determination means that determines that the electrode is misaligned when the electrode radial distance detected by the electrode distance sensor is less than a predetermined distance.

[0013] According to this configuration, for example, when a resistance welding device attached to a manipulator of an industrial robot is in a predetermined position, an electrode distance sensor that is simultaneously approached to the outer periphery or tip of each of the opposing electrodes and is located radially outside each electrode detects the radial distance to each electrode in a non-contact manner, and if the detected radial distance to each electrode is less than a predetermined distance, it can be determined that the electrode is misaligned, thereby making it possible to detect misalignment of either of the two opposing electrodes.

[0014] Another configuration of the present invention is characterized in that when the electrode distance sensor detects the radial distance to the tip of each electrode, an electrode position reflecting member is arranged between the tip and the electrode distance sensor and moved in the radial direction of the electrode depending on the position of the tip, and the electrode distance sensor detects the distance to the tip of the electrode by detecting the radial distance to the electrode position reflecting member.

[0015] With this configuration, for example, if the tip of the electrode is spherical or tapered, it is difficult to detect the radial distance to the tip, but the radial distance to the outer periphery of the electrode position reflecting member, which reflects the position of the tip by moving it in the radial direction of the electrode, can be detected relatively easily by the electrode distance sensor, and it is possible to shorten the configuration of the electrode position deviation detection means in the electrode extension direction compared to when the radial distance to the outer periphery of the electrode is detected by the electrode distance sensor. Effect of the Invention

[0016] As described above, according to the present invention, since it is possible to detect any positional deviation between two opposing electrodes, it becomes possible to ensure and improve the quality of resistance welding, particularly in applications such as mass-produced vehicle body manufacturing. [Brief description of the drawings]

[0017] [Figure 1] 1 is a perspective view showing a first embodiment of an electrode position deviation detection device for a resistance welding apparatus according to the present invention. [Diagram 2] 2 is a partially sectional plan view of the electrode position deviation detection device of FIG. 1. [Diagram 3] 3 is an explanatory diagram of the operation of the electrode position deviation detection device of FIG. 1 and FIG. 2. [Figure 4] 2 is a flowchart of a calculation process performed by a control device of the electrode position deviation detection device of FIG. [Diagram 5] FIG. 4 is a schematic diagram showing a second embodiment of an electrode position deviation detection device for a resistance welding apparatus according to the present invention. [Figure 6] 6 is a flowchart of a calculation process performed by a control device of the electrode position deviation detection device of FIG. 5. [Figure 7] 6 is a schematic diagram showing a first modified example of the position shift detection device of FIG. 5. FIG. [Figure 8] 6 is a schematic cross-sectional view showing a second modified example of the position shift detection device of FIG. 5. [Figure 9] 4 is a partially sectional plan view showing a third embodiment of an electrode position deviation detection device for a resistance welding apparatus according to the present invention. FIG. [Figure 10] 10 is an explanatory diagram of the operation of the electrode position deviation detection device of FIG. 9. [Figure 11] 10 is a flowchart of a calculation process performed by a control device of the electrode position deviation detection device of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of an electrode position deviation detection device for a resistance welding device of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing a main part of an electrode position deviation detection device 2 of a first embodiment of the present invention, and FIG. 2 is a partial cross-sectional plan view of the electrode position deviation detection device 2 of FIG. 1, in which FIG. 1(a) and FIG. 2(a) show a state in which a clamping member 4 described later is open, and FIG. 1(b) and FIG. 2(b) show a state in which the clamping member 4 is closed. The resistance welding device of this embodiment, like an existing resistance welding device, clamps a plurality of workpieces (not shown) between the upper and lower electrodes 1 shown in the figure, applies current while pressing them with the electrodes 1, and thereby melts and solidifies (coagulates) the areas near the contact interfaces of the workpieces themselves to weld them. Generally, one of the opposing electrodes 1 is fixed and the other is movable. In the following embodiments including these figures, resistance welding devices other than the electrodes 1 are omitted, but like a general resistance welding device, the resistance welding device of this embodiment is configured with, for example, a pressurizing device for the electrodes 1 (usually also serving as a moving device for the electrodes 1), etc.

[0019] The resistance welding device of this embodiment is attached to the manipulator of an industrial robot (not shown) in the same manner as in the above-mentioned Patent Document 1. In general, an industrial robot called a multi-axis robot can freely move the manipulator within a movable range by teaching, so the resistance welding device and the electrode 1 attached to the manipulator are controlled to various positions and various postures, and in this state, the workpiece is sandwiched between the electrodes 1, and resistance welding is performed by applying pressure and electricity. In this embodiment, as in the above-mentioned Patent Document 1, the electrode 1 (resistance welding device) is moved and fixed to the position of the electrode position deviation detection device 2 shown in the figure, and it is detected whether the electrode 1 is deviated, particularly in the electrode radial direction. This position is specified as a predetermined judgment position (predetermined position). At this predetermined judgment position, the electrodes 1 are fixed at a predetermined close position facing each other. The operation control and judgment of the electrode position deviation detection device 2 are performed by a control device 3 having a calculation function. The control device 3 may be integrated with the control device of the resistance welding device or the industrial robot, or may be separate.

[0020] The electrode position deviation detection device 2 is configured with a clamping member 4 that is moved from both radially outer sides of each electrode 1 of the resistance welding device fixed at the predetermined judgment position toward the outer periphery of each electrode 1. The clamping member 4 in this embodiment is configured of two pairs of members that extend in a direction approximately perpendicular to the extension direction of the electrode 1 on both radially outer sides of each electrode 1, and as shown in FIG. 1, a pair is disposed for each electrode 1 located at the top and bottom of the figure. The clamping member 4 is provided with a semicircular cross-sectional recess 7 that creates a predetermined gap with respect to the outer periphery of the electrode 1 in the appropriate position when it is moved toward the electrode 1 to clamp the electrode 1, as shown in FIG. 2(b), for example. If the side with the recess 7 is defined as the tip side of the clamping member 4 and the opposite side as the base side, a judgment electrode 8 is provided on the opposing surface further to the tip side of the recess 7, and is configured to abut against the electrode 1 in the appropriate position when the clamping member 4 is moved to clamp the electrode 1, as shown in FIG. 2(b). The state of the clamping members 4 is defined as a predetermined closed state. The base ends of the two pairs of clamping members 4 arranged, for example, at the top and bottom of FIG. 1, are connected by a connecting member 9 having a predetermined length in the extension direction of the electrode 1. Furthermore, an arm member 10 extending in the extension direction of each clamping member 4 is connected to the connecting member 9, and a rotating shaft 11 extending in the electrode extension direction is inserted into the middle part of the arm member 10 in the extension direction. A link member 12 is rotatably connected to the end of the arm member 10 opposite the clamping member connection side, and the end of the link member 12 opposite the arm member connection side is rotatably connected to the tip of a rod member 14 of an advancement / retraction device 13. The rod member 14 of the advancement / retraction device 13 extends and contracts in the radial direction of the electrode 1 at the appropriate position, and the advancement / retraction device 13 is composed of, for example, an air cylinder.

[0021] As shown in FIG. 2(a), in a state where the rod member 14 of the advancing / retracting device 13 is extended, the tip portions of the clamping members 4 of each pair are separated from each other, and the recesses 7 of each clamping member 4 are also open to each other, as shown in FIG. 1(a) and FIG. 2(a). In this state, the electrode 1 of the resistance welding device is moved to, for example, the position shown in FIG. 1(a), i.e., a predetermined determination position, and fixed, and in this state, the rod member 14 of the advancing / retracting device 13 is contracted. As a result, the arm member 10 and the clamping member 4 rotate around the rotation axis 11 with the rotational movement of the link member 12 so that the tip portions close to each other, and each pair of clamping members 4 is moved from both radial outsides of the electrode 1 to the outer periphery side of the electrode 1, and the outer periphery of the electrode 1 is clamped by two pairs of clamping members 4 (recesses 7 of the clamping members 4) as shown in FIG. 1(b) and FIG. 2(b). When the electrode 1 in the correct position is accommodated in the recess 7 of the clamping member 4, the clamping member 4 and the electrode 1 do not come into contact with each other, so that each pair of clamping members 4 is in the above-mentioned predetermined closed state, and at that point the determination electrodes 8 provided on each pair of clamping members 4 come into contact with each other. Therefore, if there is electrical current between the determination electrodes 8, each pair of clamping members 4 is in the predetermined closed state, and based on this, it is determined that each electrode 1 is in a predetermined position in the electrode radial direction.

[0022] In contrast, when the electrode 1 is misaligned upward in FIG. 3(a) with respect to the electrode 1 in the proper position shown by the two-dot chain line in FIG. 3(a), the position of the misalignment detection device 2 itself is fixed, so that when each pair of clamping members 4 is closed from the open state shown in FIG. 2(a), the clamping member 4 on the upper side in FIG. 3(a) abuts against the upper side surface of the electrode 1 in the figure, and the pair of clamping members 4 does not close any further. In other words, the predetermined closed state is not reached. If the pair of clamping members 4 does not reach the predetermined closed state in this way, the judgment electrodes 8 do not abut against each other, and therefore the judgment electrodes 8 are in a non-conductive state. Therefore, if the pair of clamping members 4 is in a clamping state with respect to the electrode 1, but the judgment electrodes 8 are in a non-conductive state, it can be determined that one of the electrodes 1 is misaligned. Similarly, when the electrode 1 is misaligned to the right of FIG. 3(b) with respect to the electrode 1 in the correct position shown by the two-dot chain line in FIG. 3(b), the tip of the clamping member 4 abuts against the left side surface of the outer periphery of the electrode 1 in the drawing, and the pair of clamping members 4 does not close any further, and the above-mentioned predetermined closed state is not reached. If the pair of clamping members 4 does not reach the predetermined closed state in this way, the judgment electrodes 8 do not abut against each other, and therefore the judgment electrodes 8 are in a non-conducting state. Therefore, if the pair of clamping members 4 is in a clamping state with respect to the electrode 1, but the judgment electrodes 8 are in a non-conducting state, it can be determined that one of the electrodes 1 is misaligned. When the misalignment of one of the electrodes 1 is determined in this way and the misalignment is notified, it can be determined which electrode 1 is misaligned in which direction by observing the abutment state between the electrode 1 and the clamping member 4. Therefore, it is possible to return to normal resistance welding work by the operator correcting the electrode position after that.

[0023] As described above, the operation control of the electrode position deviation detection device 2 and the electrode position deviation judgment of this embodiment are performed by the control device 3. The control device 3 is configured with an internal computer system for performing arithmetic processing, and is equipped with not only an arithmetic processing device having advanced arithmetic processing functions, but also a storage device for storing programs and data, and an input / output device for controlling input and output with various sensors and external devices. FIG. 4 is a flowchart showing the arithmetic processing for the operation and judgment of the electrode position deviation detection device 2 executed by the control device 3. This arithmetic processing is started with the resistance welding device (opposing electrode 1) fixed at the predetermined judgment position, and first in step S1, the clamping members 4 of each pair are moved to the outer periphery of each electrode 1 to clamp each electrode 1.

[0024] Next, the process proceeds to step S2, where a current is applied between the determination electrodes 8.

[0025] Next, the process proceeds to step S3, where it is determined whether or not there is no current passing between the determination electrodes 8. If there is no current passing between the determination electrodes 8, the process proceeds to step S4, and if not, the process proceeds to step S6.

[0026] In step S4, it is determined that the sandwiching members 4 of each pair are not in the predetermined closed state and that one of the electrodes 1 is misaligned, and then the process proceeds to step S5.

[0027] In step S5, the process ends after notifying the electrode positional deviation by a notifying means (not shown). Examples of such notifying means include a display, a signal lamp, a buzzer, etc.

[0028] On the other hand, in step S6, an instruction to return the resistance welding device to its normal position is issued, and then the device is returned.

[0029] According to this calculation process, when the resistance welding device (opposing electrodes 1) is moved and fixed to a predetermined judgment position, each pair of clamping members 4 is moved toward the outer periphery of each electrode 1 to clamp it, and in this state, electricity is passed through the judgment electrode 8. At this time, if there is electricity passing between the judgment electrodes 8, each pair of clamping members 4 is in a predetermined closed state, so each electrode 1 is in a proper position, and therefore the electrodes 1 are not misaligned. Therefore, the resistance welding device can be returned to its normal position, and mass-produced vehicle body manufacturing can be continued, for example. On the other hand, if there is no electricity passing between the judgment electrodes 8, each pair of clamping members 4 is not in a predetermined closed state, so that each electrode 1 is not in a proper position, and therefore it can be determined that the electrodes 1 are misaligned. Then, when the electrode misalignment is determined, the electrode misalignment is notified, for example, by a display, a signal lamp, a buzzer, or the like. When the electrode misalignment is notified, for example, the worker can correct the misalignment of the electrode 1 and return to normal resistance welding work. This ensures and improves the quality of resistance welding. That is, steps S3 and S4 of the calculation process in FIG. 4 executed by the control device 3 constitute the signal generating means, the determination electrode current applying means, the non-energization detecting means, the non-closed state detecting means, and the position deviation determining means of the present invention.

[0030] The electrode position deviation detection device 2 of this embodiment can be modified as follows. For example, in the case where the advancing / retracting device 13 includes an electric motor, a ball screw attached to the rotating shaft thereof, and a ball screw nut screwed to the ball screw, and the rod member 14 is attached to the ball screw nut that is moved in the extension direction of the ball screw by the thrust of the screw, when the clamping member 4 abuts against the outer periphery of the electrode 1 during the closing operation of the clamping member 4 and cannot move any further, the movement of the ball screw nut is stopped at that point, and the rotation of the ball screw is also stopped at that point. Therefore, for example, the rotation amount of the electric motor rotating the ball screw may be detected by an encoder or the like, and when the rotation amount stops before the rotation amount in the predetermined closed state of the clamping member 4, it may be determined that the clamping member 4 abuts against the outer periphery of the electrode 1, and it may be determined that one of the opposing electrodes 1 is misaligned.

[0031] In this manner, in the electrode position misalignment detection device 2 of the resistance welding device of this embodiment, for example, when the resistance welding device (opposing electrodes 1) attached to the manipulator of an industrial robot is in a predetermined position, the clamping members 4 that are simultaneously moved toward the outer periphery of each opposing electrode 1 so as to clamp each of the opposing electrodes 1 are other than in the predetermined closed state, i.e., the clamping members 4 do not close completely due to a position misalignment of the electrodes 1, so it can be determined that one of the electrodes 1 is misaligned, and thereby any position misalignment of either of the two opposing electrodes 1 can be detected.

[0032] Furthermore, since the judgment electrode 8 which should come into contact with the clamping member 4 in the specified closed state is in a non-conductive state, it can be determined that the clamping member 4 is not in the specified closed state, i.e., that the clamping member 4 is not completely closed due to misalignment of the electrode 1, thereby making it possible to reliably detect the misalignment of the two opposing electrodes 1.

[0033] FIG. 5 is a schematic diagram showing the main part of the electrode position deviation detection device 2 according to the second embodiment of the present invention. The electrode position deviation detection device 2 according to this embodiment is configured with a plurality of electrode distance sensors located radially outside the outer periphery or tip of each electrode 1 when the resistance welding device (opposing electrode 1) is moved and fixed to the predetermined judgment position. The electrode distance sensor is a sensor capable of detecting the distance to the outer periphery or tip of the electrode 1 in a non-contact manner, and is configured with a proximity switch 5 in this embodiment. As is well known, the proximity switch 5 is a sensor that generates a magnetic field around a coil, detects changes in inductance or loss caused by the approach of a metal to this magnetic field, and outputs a signal. For example, when the metal approaches within a predetermined distance, an ON signal is output. That is, the predetermined distance is the distance until the detection signal of the proximity switch 5 turns ON. In FIG. 5, a plurality of (12 in the figure) proximity switches 5 are equally arranged toward the electrode 1 on the radial outside of the outer periphery or tip of the electrode 1 moved and fixed to the predetermined judgment position, and the output signal is read by the control device 3. At this time, the distance in the electrode radial direction from the outer periphery or tip of the electrode 1 in the correct position to each proximity switch 5 is set to the above-mentioned predetermined distance, i.e., the sum of the distance at which the proximity switch 5 is turned on and the predetermined gap in Fig. 1. On the other hand, if the electrode 1 is misaligned in the radial direction, for example by more than the distance equivalent to the predetermined gap in Fig. 1, an ON signal will be output from one of the proximity switches 5, and it can be detected and determined from the ON signal of the proximity switch 5 which electrode 1 is misaligned and in which direction.

[0034] Like the control device 3 of the first embodiment, the control device 3 of this embodiment is also configured with an internal computer system for performing arithmetic processing, and is equipped with not only an arithmetic processing device having advanced arithmetic processing functions, but also a storage device for storing programs and data, and an input / output device for controlling input and output with various sensors and external devices. Fig. 6 is a flowchart showing the operation and judgment arithmetic processing for the electrode position deviation detection device 2 executed by the control device 3. This arithmetic processing is started with the resistance welding device (opposing electrode 1) fixed at the predetermined judgment position, and first in step S11, the detection signals of each of the proximity switches 5 are read.

[0035] Next, proceed to step S12 to determine whether the distance to electrode 1 (its outer periphery or tip) is less than a predetermined distance, i.e., whether the detection signal of proximity switch 5 is an on signal. If the detection signal of proximity switch 5 is an on signal, i.e., the distance to electrode 1 (its outer periphery or tip) is less than the predetermined distance, proceed to step S13; if not, proceed to step S15.

[0036] In the above step S13, it is determined that any electrode 1 whose distance (to the outer periphery or tip) is equal to or less than a predetermined distance is misaligned, and then the process proceeds to step S14.

[0037] In step S14, the electrode position deviation is notified by a notifying means (not shown), and then the process ends. Examples of the notifying means include a display, a signal lamp, a buzzer, and the like.

[0038] On the other hand, in step S15, an instruction to return the resistance welding device to its normal position is issued, and then the device is returned.

[0039] According to this calculation process, when the resistance welding device (opposing electrode 1) is moved and fixed to a predetermined judgment position, the detection signal of each proximity switch 5 is read. At this time, if the detection signals of all the proximity switches 5 are OFF signals, the outer periphery or tip of the electrode 1 is away from the proximity switch 5 by a distance equivalent to or greater than a predetermined distance, so that each electrode 1 is in the correct position, and therefore the electrode 1 is not misaligned. Therefore, the resistance welding device can be returned to the normal position, and mass production of vehicle bodies can be continued, for example. On the other hand, if the detection signal of any of the proximity switches 5 is ON signals, the distance between the outer periphery or tip of the corresponding electrode 1 and the proximity switch 5 outputting the ON signal is equal to or less than a predetermined distance, so that each electrode 1 is not in the correct position, and therefore it can be determined that the electrode 1 is misaligned. Then, when the electrode misalignment is determined, the electrode misalignment is notified, for example, by a display, a signal lamp, a buzzer, or the like. When the electrode misalignment is notified, for example, the worker can correct the misalignment of the electrode 1 and return to normal resistance welding work. This ensures and improves the quality of resistance welding. That is, steps S12 and S13 of the calculation process in FIG. 6 executed by the control device 3 constitute the position deviation determination means of the present invention.

[0040] 5, when the proximity switch 5 is located radially outside the outer periphery or tip of the electrode 1, it is also possible, for example, to move the multiple proximity switches 5 shown in the figure back in the electrode radial direction away from the electrode 1, move and fix the electrode 1 in this state to the position shown in the figure (predetermined judgment position), and then move the proximity switch 5 forward in the electrode radial direction to approach the radially outside of the outer periphery or tip of the electrode 1. However, it is more realistic to fix the proximity switch 5 in the position shown in the figure, bring two electrodes 1 with a wider gap in the opposing direction close to each other at the center position of the multiple proximity switches 5, and operate the robot and resistance welding device so that the multiple proximity switches 5 are located radially outside the outer periphery or tip of the electrode 1.

[0041] FIG. 7 is a modified example of the electrode position deviation detection device 2 of FIG. 5. In the electrode position deviation detection device 2 of FIG. 5, a plurality of proximity switches 5 are arranged evenly on the radially outer side of the outer periphery or tip of the electrode 1, whereas in FIG. 7, a single ring-shaped proximity switch 5 is positioned on the radially outer side of the outer periphery or tip of the electrode 1. This ring-shaped proximity switch 5 outputs, for example, an ON signal when the distance between the inner periphery of the proximity switch 5 and the outer periphery or tip of the electrode 1 becomes equal to or less than a predetermined distance, so that the position deviation of the electrode 1 can be detected in the same manner as the above-mentioned calculation process of FIG. 6. Note that in the electrode position deviation detection device 2 of FIG. 7, the detection signal of the proximity switch 5 alone cannot determine in which direction the electrode 1 is deviated. In addition, in the electrode position deviation detection device 2 of FIG. 7, the electrodes 1, which are spaced apart in the opposing direction, are moved to an inner position of the ring-shaped proximity switch 5 and brought close to each other, so that the electrodes 1 are moved and fixed to a predetermined determination position.

[0042] In this manner, in the electrode position misalignment detection device 2 of the resistance welding device of this embodiment, for example, when the resistance welding device (opposing electrodes 1) attached to the manipulator of an industrial robot is in a predetermined position, the proximity switches 5 (electrode distance sensors) that are simultaneously brought close to the outer periphery or tip of each of the opposing electrodes 1 and located radially outside each electrode 1 detect the electrode radial distance to each electrode 1 in a non-contact manner, and if the detected electrode radial distance to each electrode 1 is less than a predetermined distance, it can be determined that the electrode 1 is misaligned, and therefore it is possible to detect misalignment of either of the two opposing electrodes 1.

[0043] FIG. 8 is a cross-sectional view showing a further modified example of the electrode position deviation detection device 2 of FIG. 5 as seen from the electrode radial direction, and the layout of the proximity switch 5 (electrode distance sensor) as seen from the electrode extension direction is generally the same as that of FIG. 5. In this electrode position deviation detection device 2, the proximity switch 5 is located radially outside the tip of each electrode 1, and an electrode position reflecting member 6 is interposed between the proximity switch 5 and the tip of each electrode 1. This electrode position reflecting member 6 is formed, for example, of a circular metal plate having a predetermined thickness in the electrode extension direction, and the proximity switch 5 is disposed facing the outer circumferential surface of this electrode position reflecting member 6. This electrode position reflecting member 6 is slidably disposed between two support plates 15 spaced apart by a predetermined dimension in the electrode extension direction, and is returned to a position facing the tip of the electrode 1 at the appropriate position by a spring member (not shown). The proximity switch 5 is embedded in a spacing wall portion 16 fixed between the two support plates 15 on the radial outside of the electrode position reflecting member 6. The electrode position reflecting member 6 has a recess (hole) 17 having a tapered truncated cone shape in the electrode extension direction at the center of the plate surface facing the tip of each electrode 1, and the tip of the electrode 1 moved and fixed to the predetermined determination position is inserted into the recess 17. Since the tip of each electrode 1 in this embodiment is hemispherical, when the hemispherical tip is inserted into the recess 17 having a tapered truncated cone shape in the cross section, the electrode position reflecting member 6 is moved in the electrode radial direction according to the position of the tip of each electrode 1. In the figure, the upper electrode 1 is in the correct position, while the lower electrode 1 is shifted to the right in the radial direction. The proximity switch 5 outputs an ON signal when the distance to the outer periphery of the electrode position reflecting member 6, which is moved in the electrode radial direction according to the position of the tip of each electrode 1 in this way, becomes equal to or less than a predetermined distance. Therefore, the electrode position deviation detection device 2 can detect the position deviation of the electrode 1 in the same manner as the calculation process of FIG. 6 described above.

[0044] In this manner, in the electrode position deviation detection device 2 of the resistance welding apparatus of this embodiment, for example, when the tip of the electrode 1 has a hemispherical or tapered shape, it is difficult to detect the electrode radial distance to the tip, but the electrode radial distance to the outer periphery of the electrode position reflecting member 6, which reflects the position of the tip by moving in the electrode radial direction, can be detected relatively easily by the proximity switch 5 (electrode distance sensor), and it is possible to shorten the configuration of the electrode position deviation detection means in the electrode extension direction compared to the case of detecting the electrode radial distance to the outer periphery of the electrode 1.

[0045] Next, a third embodiment of the electrode position deviation detection device 2 of the present invention will be described. The electrode position deviation detection device 2 of this embodiment is a modified example of the first embodiment described above. FIG. 9 is a partial cross-sectional plan view showing a main part of the electrode position deviation detection device 2 of this embodiment, in which FIG. 9(a) shows a state in which the clamping member 4 is open, and FIG. 9(b) shows a state in which the clamping member 4 is closed. The electrode position deviation detection device 2 of this embodiment is similar to the electrode position deviation detection device 2 of the first embodiment, so that the same components are given the same reference numerals and detailed description thereof will be omitted. In this embodiment, the clamping member 4 is extended in the direction opposite to the rotating shaft 11 side, and a movable judgment electrode 21 is added to the extension 4a. In order to distinguish this movable judgment electrode 21 from the fixed judgment electrode 8 described above, the latter (fixed type) is defined as the first judgment electrode 8, and the former (movable type) is defined as the second judgment electrode 21. The configuration on the base end side of the clamping member from the first judgment electrode 8 is the same as that of the first embodiment.

[0046] The extension 4a of the clamping member 4 extends wider in the clamping member opening direction than the attachment portion of the first determination electrode 8, and the shaft of the second determination electrode 21 is inserted into a through hole drilled in the clamping member opening / closing direction in the extension 4a, and a large diameter portion is provided at the end of the shaft in the clamping member opening direction to prevent it from coming off. A hemispherical electrode portion is provided at the tip of the shaft of the second determination electrode 21 in the clamping member closing direction, and a coil spring 22 is interposed between the electrode portion and the extension 4a so as to surround the shaft portion. Therefore, the second determination electrode 21 is biased by the coil spring 22 so that the electrode portion protrudes from the extension 4a in the clamping member closing direction, and slides within the through hole when a force is applied in the clamping member opening direction. A current for determining whether or not electricity is flowing is also applied to the second determination electrode 21 from the control device 3, similar to the first determination electrode 8.

[0047] The position of the protruding tip of the electrode portion of the second determination electrode 21, which is biased by the coil spring 22, is set to a position protruding by a predetermined dimension from the tip of the first determination electrode 8 in the protruding direction. That is, when the opposing clamping members 4 are closed, the second determination electrode 21 abuts on each other earlier than the first determination electrodes 8 by twice the above-mentioned predetermined dimension before the first determination electrodes 8 abut on each other. This means that the second determination electrodes 21 abut on each other even if the opposing clamping members 4 are located far from each other. In addition, after the second determination electrodes 21 abut on each other, if the clamping members 4 can be closed further, the second determination electrode 21 slides along the through hole in the clamping member opening direction. The protruding dimension of the electrode portion of the second determination electrode 21 relative to the first determination electrode 8 can be changed by adjusting the position of the large diameter portion provided at the end of the shaft portion. The position adjustment of the large diameter portion can be made possible, for example, by configuring the large diameter portion as a so-called double nut. 9(b), a predetermined gap (hereinafter, "predetermined gap") is formed between the recess 7 of the clamping member 4 in the closed state and the electrode 1 in the correct position. In other words, when considered in the opening and closing direction of the clamping member, if the electrode 1 is misaligned within the range of this predetermined gap, the first determination electrodes 8 will abut against each other when the clamping member 4 is closed. In this embodiment, if the electrode 1 is present within this predetermined range, it is defined that the electrode 1 is in the correct position.

[0048] In contrast, when the amount of misalignment of the electrode 1 exceeds the predetermined gap between the electrode 1 in the correct position and the recessed portion 7, the first determination electrodes 8 do not come into contact with each other, as shown in Fig. 10(a). However, when the amount of misalignment is within approximately the sum of the protruding dimension of the electrode portion of the second determination electrode 21 from the protruding tip of the first determination electrode 8 and the predetermined gap, the second determination electrodes 21 come into contact with each other. Furthermore, when the amount of misalignment of the electrode 1 exceeds the sum of the predetermined gap between the recessed portion 7 and the electrode 1 in the correct position and the protruding dimension of the electrode portion of the second determination electrode 21 from the protruding tip of the first determination electrode 8, not only the first determination electrodes 8 but also the second determination electrodes 21 do not come into contact with each other, as shown in Fig. 10(b). In this embodiment, similarly to the first embodiment, when a determination current is applied between the first determination electrodes 8 and between the second determination electrodes 21, if the first determination electrodes 8 are not conducting but the second determination electrodes 21 are conducting, it is determined that the electrodes 1 are misaligned within the allowable range and the corresponding resistance welding process is not stopped.

[0049] 11 is a flowchart showing the operation and judgment calculation process of the electrode position deviation detection device 2 of this embodiment, which is executed by the control device 3. This calculation process is started with the resistance welding device (opposing electrode 1) fixed at the above-mentioned predetermined judgment position, and first, in step S21, the clamping members 4 of each pair are moved to the outer periphery of each electrode 1 to clamp each electrode 1.

[0050] Next, the process proceeds to step S22, where a current is applied between the first determination electrodes 8 and between the second determination electrodes 21.

[0051] Next, the process proceeds to step S23, where it is determined whether or not a current is not conducted between the first determination electrodes 8. If a current is not conducted between the first determination electrodes 8, the process proceeds to step S24, and if not, the process proceeds to step S26.

[0052] In step S24, it is determined whether or not a current is not conducted between the second determination electrodes 21. If a current is not conducted between the second determination electrodes 21, the process proceeds to step S27, and if not, the process proceeds to step S25.

[0053] In step S25, a warning is issued if any of the electrodes 1 is misaligned within the allowable range, and the process proceeds to step S26. For this warning, a display, a signal lamp, a buzzer, or the like is used.

[0054] In step S26, an instruction is given to return the resistance welding device to its normal position, and then the device is returned.

[0055] On the other hand, in step S27, it is determined that each pair of clamping members 4 is not in the predetermined closed state and any of the electrodes 1 is misaligned (in this case, beyond the allowable range), and then the process proceeds to step S .

[0056] In step S28, the electrode position deviation is notified by a notifying means (not shown) and then the process is terminated. Examples of such notifying means include a display, a signal lamp, a buzzer, etc. In other words, in this case, the resistance welding device does not return to normal, and the corresponding resistance welding process is stopped.

[0057] According to this arithmetic processing, as in the first embodiment, if the first determination electrodes 8 are energized, each electrode 1 is in a proper position, and therefore the electrodes 1 are not displaced. Therefore, the resistance welding device can be returned to the normal position, and mass production of vehicle bodies can be continued, for example. On the other hand, if the first determination electrodes 8 and the second determination electrodes 21 are not energized, each pair of clamping members 4 is not in the predetermined closed state, and therefore it can be determined that the electrodes 1 are displaced. Then, when the electrode positional deviation is determined, the electrode positional deviation is notified, for example, by a display, a signal lamp, a buzzer, or the like. When the electrode positional deviation is notified, the corresponding resistance welding process is stopped, and therefore, for example, an operator can correct the positional deviation of the electrode 1 and return to normal resistance welding work. This ensures and improves the quality of resistance welding. That is, steps S23, S24, and S27 of the arithmetic processing in FIG. 4 executed by the control device 3 constitute the signal generating means, the determination electrode current applying means, the non-energizing detecting means, the non-closed state detecting means, and the positional deviation determining means of the present invention. In contrast, if the first determination electrodes 8 are not conducting but the second determination electrodes 21 are conducting, it is determined that the electrodes 1 are not in the correct positions and are misaligned, but the amount of misalignment is within an allowable range, and an alarm is issued for the electrode misalignment, for example, by a display, a signal lamp, a buzzer, or the like. In this case, the resistance welding device is returned to its normal position, and mass production of vehicle bodies can be continued. When an alarm is issued for the electrode misalignment, the electrode 1 can be returned to the correct position by correcting the electrode position, for example, at the next shutdown.

[0058] The electrode position deviation detection device 2 of the resistance welding device according to the embodiment has been described above, but the present invention is not limited to the configuration described in the above embodiment, and various modifications are possible within the scope of the gist of the present invention. For example, in the above first embodiment, the opposing clamping members are moved from both radially outer sides so as to clamp each electrode 1 by rotating around the rotating shaft, but the electrode clamping configuration by the clamping members can be configured in other ways. For example, by meshing racks on both radial sides of a pinion attached to the rotating shaft of an electric motor and attaching clamping members to the racks one by one, the two clamping members can be moved toward or away from the electrode 1 from both sides in the electrode diameter direction, so that the electrode 1 can be clamped from the diameter direction by the clamping members with this configuration.

[0059] In addition, the electrode distance sensor that detects the radial distance to the electrode may be a non-contact distance sensor that uses ultrasonic waves, infrared rays, laser light, or the like.

[0060] Furthermore, instead of the coil spring 22 that movably supports second determination electrode 21 in the opening and closing direction of the clamping member in the above third embodiment, a leaf spring member that bends in the opening and closing direction of clamping member 4 may be attached to the tip of clamping member 4, and second determination electrode 21 (the electrode portion thereof) may be rigidly attached to this leaf spring member. In this case, by setting the protruding dimension of second determination electrode 21 (the electrode portion thereof) attached to the leaf spring member relative to first determination electrode 8 to the same as in the above third embodiment, it is possible to obtain the same action and effect.

[0061] Also, instead of the second determination electrode 21 itself in the third embodiment, a load sensor such as a strain gauge can be used. In this case, for example, a leaf spring member that abuts against the second determination electrode 21 at the same timing is provided on each of the clamping members 4, and a load sensor is attached to at least one of the leaf spring members. Then, even if the (first) determination electrodes 8 are not energized, if the load detected by the load sensor is equal to or greater than a threshold value, the electrode 1 is displaced but the amount of the positional displacement is within an allowable range, and a warning is issued. When the electrode positional displacement warning is issued, for example, the electrode position is corrected at the next operation stop, and the electrode 1 is returned to the appropriate position. Also, if the determination electrode 8 is not energized and the detected load is less than the threshold value, the amount of the positional displacement of the electrode 1 is deemed to exceed the allowable range, and the operation is stopped, so that the same action and effect as the third embodiment can be obtained. In addition, when a piezoelectric element is used as the load sensor, for example, a load sensor can be attached to the seat surface of the coil spring 22 in the third embodiment.

[0062] Also, instead of this load sensor, a non-contact distance sensor as used in the second embodiment can be used. In this case, for example, a non-contact distance sensor is provided on one of the extensions 4a of the clamping member 4, and a distance detection target member detectable by the non-contact distance sensor is provided on the other. For example, if the non-contact distance sensor is a proximity switch 5, a metal member to which the proximity switch 5 reacts is attached to the extension 4a at the opposing position. Then, even if the (first) determination electrodes 8 are in a non-conductive state, if the distance detected by this distance sensor is less than a threshold value, a warning is issued that the electrode 1 is misaligned but the amount of misalignment is within a tolerable range. When the electrode misalignment warning is issued, for example, the electrode position is corrected at the next operation stop to return the electrode 1 to the appropriate position. Also, if the determination electrode 8 is in a non-conductive state and the detection distance is equal to or greater than the threshold value, the operation is stopped because the amount of misalignment of the electrode 1 exceeds the tolerable range, and the same action and effect as the third embodiment can be obtained. [Explanation of symbols]

[0063] 1 Electrode (resistance welding device) 2. Electrode position deviation detection device 3. Control device 4 Clamping member 5 Proximity switch (electrode distance sensor) 6 Electrode position reflecting member 8 Judgment electrode (1st judgment electrode) 21 Second judgment electrode

Claims

1. A resistance welding device that joins a plurality of workpieces by sandwiching the workpieces between opposing electrodes and applying pressure and current thereto, an electrode position deviation detection means for detecting a position deviation of the outer periphery of each of the electrodes, the electrode position deviation detection means being brought into close proximity with the outer periphery of each of the opposing electrodes at the same time when the resistance welding device is in a predetermined position; The electrode position deviation detection means a clamping member that is moved toward the outer periphery of each of the opposing electrodes so as to clamp each electrode from both radially outer sides of the opposing electrodes when the resistance welding device is in the predetermined position, and that is in a predetermined closed state when each electrode is in an appropriate position; a signal generating means for outputting a movement state signal corresponding to a movement state of the clamping member toward the outer periphery of the electrode; a non-closed state detection means for detecting, based on a movement state signal from the signal generation means, that the pinching member moved toward the outer periphery of the electrode is in a state other than the predetermined closed state; and a position deviation determination means for determining that one of the electrodes is misaligned when the non-closed state detection means detects that the clamping member is in a state other than a predetermined closed state.

2. The signal generating means a determination electrode provided on the pinching member and abutting against the electrode when the pinching member is moved toward the outer periphery of the electrode and is in the predetermined closed state; a current application means for applying a current between the determination electrodes in a state in which the pinching member is moved to the outer periphery of the electrodes, The non-closed state detection means a non-current-passing detection means for detecting a non-current passing state between the reference electrodes when a current is being applied between the reference electrodes by the reference electrode current application means, 2. The electrode position deviation detection device for a resistance welding apparatus according to claim 1, wherein said non-energization detection means determines that said pinching member is in a state other than a predetermined closed state when said determination electrodes are in a non-energized state.

3. A resistance welding device that joins a plurality of workpieces by sandwiching the workpieces between opposing electrodes and applying pressure and current thereto, an electrode position deviation detection means for detecting a position deviation of each of the outer periphery or the tip end of each of the electrodes, which is simultaneously approached to the outer periphery or the tip end of each of the opposing electrodes when the resistance welding device is in a predetermined position; The electrode position deviation detection means an electrode distance sensor that is located radially outward of the opposing electrodes when the resistance welding device is in the predetermined position and that detects the distance in the electrode radial direction to an outer periphery or a tip end of each electrode in a non-contact manner; and a position deviation determination means for determining that the electrode is misaligned when the distance to the electrode in the electrode radial direction detected by the electrode distance sensor is equal to or shorter than a predetermined distance.

4. an electrode position reflecting member that is disposed between the tip and the electrode distance sensor when the electrode distance sensor detects a distance in a radial direction of the electrode to the tip of each electrode and is moved in the radial direction of the electrode according to a position of the tip; 4. The electrode position deviation detection device for a resistance welding apparatus according to claim 3, wherein the electrode distance sensor detects the distance in the electrode radial direction to the electrode position reflecting member, thereby detecting the distance in the electrode radial direction to the tip of the electrode.

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