JP2015089566A - Resistance welding apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resistance welding apparatus that does not require flatness of an end surface of a welded member, and can perform resistance welding having sufficient welding strength in a relatively short time.SOLUTION: The resistance welding apparatus comprises: clamping means that clamps a pair of welded members 10, 11 so that end surfaces 10a, 11a of their weld parts face each other; first pressure application means for maintaining the end surfaces 10a, 11a in a state of being in contact with each other; voltage application means that applies a first voltage, in a state where a first pressure is applied, to generate a flash between the end surfaces 10a, 11a, and applies a second voltage effectively lower than the first voltage continuously after the application of the first voltage for a predetermined period of time; and second pressure application means that, when the clamping means is moved by a first set distance by the application of the second voltage and the application of the first pressure, applies a second pressure higher than the first pressure to the clamping means so that the end surfaces 10a, 11a of the pair of welded members 10, 11 are pressed against each other by higher pressure. The pair of welded members 10, 11 are upset welded by applying the second voltage and the second pressure.

Description

  The present invention relates to a resistance welding apparatus that performs resistance welding by butting members to be welded together.

  The most representative butt resistance welding method is the upset welding method (see, for example, Non-Patent Document 1). In this upset welding method, welding is performed by resistance heat generation while the end surfaces of the members to be welded are pressed against each other and pressed and energized. Since the resistance heat generation is used, the thermal time constant is large and therefore the current density is small. However, sufficient welding strength can be obtained.

JISZ3001-6: 2013 welding terms

  However, in the upset welding method, the energization time is relatively long, the heating range is widened, and the butt end surfaces of the members to be welded are required to be flat so that they are in good contact with each other. Is required to be clean.

  On the other hand, flash welding is known as one of resistance welding methods. In this flash welding method, strong pressure is not applied to the member to be welded at the initial stage of energization, and the contact part is sparked (flashed) through the welding current simply by making contact, and the entire weld surface is scattered. This is a resistance welding method in which a strong pressure is applied when sufficiently heated. According to the flash welding method, the flatness of the butted end face of the member to be welded is not required.

  The advantage that the end face does not have to be flat in the flash welding method cannot be obtained by the upset welding method as described above. In the first place, the upset welding method is a resistance welding method that is completely different from the flash welding method, and resistance welding equipment that has the advantages of both the upset welding method and the flash welding method has never existed. There wasn't.

  An object of the present invention is to provide a resistance welding apparatus capable of performing resistance welding having sufficient welding strength in a relatively short time without requiring flatness of an end face.

  Another object of the present invention is to provide a resistance welding apparatus that does not require flatness of the end face, can be constructed at a relatively low cost, and can perform resistance welding having sufficient welding strength.

  Still another object of the present invention is to provide a resistance welding apparatus capable of performing resistance welding in which flatness of the end face is not required, reliability is high, and the shape of the welded portion is stabilized.

  According to the present invention, the gripping means for gripping the pair of welded members such that the end surfaces of the welded portions face each other, and the first for maintaining the end surfaces of the pair of welded members in contact with each other. Applying a first voltage between a pair of members to be welded in a state in which the first pressure is applied by the first pressure applying unit The flash is generated between the end faces of the pair of members to be welded, and the second voltage which is effectively lower than the first voltage is continuously applied after the first voltage is applied for a predetermined period. When the gripping means is moved by the first set distance by the application of the second voltage and the application of the first pressure, the end surfaces of the pair of members to be welded with each other at a higher pressure. A second pressure higher than the first pressure is applied to the gripping means so as to be pressed. And a second pressure applying means for pressing, a pair of weld members resistance welding apparatus is upset welding by the second voltage and the second pressure is applied is provided.

  In a state where the first pressure is applied, a first voltage is applied between the pair of members to be welded by the voltage applying means, and a flash is generated. The end surface of the member to be welded is purified by this flash, dirt, oxides and impurities are removed, and the surface is smoothed. Furthermore, the entire end face is soaked. After the first voltage is applied for a predetermined period, a second voltage that is effectively lower than the first voltage is subsequently applied. When the member to be welded moves by the first set distance by applying the second voltage and the first pressure, a second pressure higher than the first pressure is applied, and the second voltage and the first pressure are applied. By applying both of the two pressures, the pair of welded members are upset welded. Since the upset welding is performed continuously after the temperature is equalized by the generation of flash, resistance welding having sufficient welding strength can be performed in a relatively short time. In addition, because upset welding is performed after heat equalization due to flash generation, the quality of the joint is stabilized and highly reliable resistance welding can be performed, and the shape of the end face is not easily affected. Stabilized resistance welding can be performed. Further, since the flash is generated not for completing the welding process by the generation of the flash but for cleaning, smoothing and soaking the end face, a large-scale power supply device is unnecessary, A resistance welding apparatus can be configured at low cost.

  It is preferable that the voltage applying means is configured to apply the first voltage intermittently. When the first voltage, which is a high voltage, is continuously applied, the temperature of the end face of the member to be welded may suddenly rise in whole or in part. For this reason, such a high voltage is continuously applied. Control applied to is not preferable. On the other hand, by applying the first voltage intermittently, it is possible to prevent an overall or partial rapid temperature increase, and as a result, it is possible to generate a flash over the entire end face. It becomes possible to purify and soaking the end faces.

  It is also preferable that the voltage application means is configured to control the first voltage and the second voltage by controlling the firing angle of the applied voltage. By controlling the firing angle and controlling the effective voltage, it is possible to perform switching control from the first voltage to the second voltage continuously and easily.

  The voltage application means is configured to finish applying the second voltage between the pair of welded members when the gripping means moves a second set distance greater than the first set distance. Is also preferable. Since the application of the second voltage is terminated according to the distance moved, it is possible to accurately control the end of welding.

  In this case, the second pressure applying means applies the second pressure to the gripping means after a predetermined time has elapsed since the gripping means has moved the second set distance (that is, application of the second voltage). It is more preferable to be configured to end the process. Since the second pressure can be applied even after the second voltage application is completed, the formation of the bumps in the welded portion can be advanced by the residual heat.

  The gripping means includes a first clamp electrode member and a second clamp electrode member that respectively hold a pair of members to be welded and also serve as electrodes, and the first pressure applying means is provided on the first clamp electrode member. It is also preferred to have a first pressure cylinder member configured to apply a first pressure.

  In this case, the movable rod of the first pressure cylinder member is fixed to the first clamp electrode member, and the first clamp electrode member is pressed toward the second clamp electrode member with the first pressure. More preferably.

  More preferably, the first pressure cylinder member is configured to always press the first clamp electrode member with the first pressure during the welding operation of the resistance welding apparatus.

  The direction in which the first pressure cylinder member pulls the first clamp electrode member away from the second clamp electrode member after the gripping of the pair of welded members by the first clamp electrode member and the second clamp electrode member is completed. It is also preferable to be configured so as to be driven.

  The gripping means includes a first clamp electrode member and a second clamp electrode member that respectively hold a pair of members to be welded and also serve as electrodes, and the second pressure applying means is provided on the first clamp electrode member. It is also preferred to have a second pressure cylinder member configured to apply a second pressure.

  In this case, the movable rod of the second pressure cylinder member is in contact with the first clamp electrode member, and is configured to press the first clamp electrode member toward the second clamp electrode member with the second pressure. More preferably.

  It is also preferable to further include a third pressure cylinder member configured to apply to the gripping means a force that cancels the force applied to the gripping means from the pair of welded members. By providing such a third pressure cylinder member, it becomes possible to always apply the first pressure to the member to be welded without depending on the member to be welded, and therefore it is possible to generate a stable flash. .

  According to the present invention, the end face of the member to be welded is purified by the occurrence of flash, dirt, oxides and impurities are removed, and the surface is smoothed. Furthermore, the entire end face is soaked. Since the upset welding is performed continuously after the temperature is equalized by the generation of flash, resistance welding having sufficient welding strength can be performed in a relatively short time. In addition, because upset welding is performed after heat equalization due to flash generation, the quality of the joint is stabilized and highly reliable resistance welding can be performed, and the shape of the end face is not easily affected. Stabilized resistance welding can be performed. Further, since the flash is generated not for completing the welding process by the generation of the flash but for cleaning, smoothing and soaking the end face, a large-scale power supply device is unnecessary, A resistance welding apparatus can be configured at low cost.

It is a perspective view showing roughly the appearance composition of a resistance welding device in one embodiment of the present invention. It is a block diagram which shows roughly each element of the resistance welding apparatus of FIG. FIG. 3 is a block diagram schematically showing a configuration of a welding operation control circuit shown in FIG. 2. It is a figure for demonstrating the margin for welding. It is a figure explaining the voltage waveform applied to the steel materials which should be welded. It is a flowchart explaining the control operation of the welding operation control circuit shown in FIG. It is a figure explaining the applied voltage and applied pressure which are controlled by the welding operation control circuit shown in FIG. It is a figure explaining the direction of the applied pressure from each cylinder. It is a figure explaining flash operation.

  FIG. 1 schematically shows an external configuration of a resistance welding apparatus according to an embodiment of the present invention, and FIG. 2 schematically shows each element of the resistance welding apparatus.

  In the present embodiment, it is assumed that a member to be welded is a high-strength steel material (for example, 10 to 16 mmφ) used for a closed type reinforcing bar. Of course, the resistance welding apparatus according to the present invention includes members having other diameters and other members such as other steel materials, high carbon wires such as PC steel wires, spring wires, various stainless steel wires, and various welding rod wires. , Alloy steel wire, PC steel stranded wire, steel tire cord, copper wire for electric conduction, oxygen-free copper wire for electric conduction, aluminum wire for electric conduction, non-ferrous rectangular wire for electric conduction, brass wire, non-ferrous stranded wire, or dissimilar It can be used for welding metal wires.

  As shown in FIGS. 1 and 2, the resistance welding apparatus according to the present embodiment has a pair of steel materials (corresponding to the welded members of the present invention) 10 and 11 to be welded and their end faces 10a and 11a are mutually connected. A first clamp electrode member 12 and a second clamp electrode member 13 are provided to be gripped (clamped) on the rear side of the end faces 10a and 11a so as to face each other. The first clamp electrode member 12 and the second clamp electrode member 13 also serve as electrodes for supplying a current during a flash operation and an upset welding operation, which will be described later, to the steel materials 10 and 11, and are clamped. It can be exchanged according to the diameter and shape of the steel material. An output of an output transformer 14 for applying a flash voltage and an upset welding voltage is electrically connected to the first clamp electrode member 12 and the second clamp electrode member 13. Is electrically connected to the firing angle / energization control circuit 15.

  The first clamp electrode member 12 is attached so as to be integrated with the moving side block 16, and the second clamp electrode member 13 is attached so as to be integrated with the fixed side block 17. The moving side block 16 is movable in the axial direction, and the fixed side block 17 is fixed to the pedestal 18 and is not movable. In this specification, “axial direction” refers to the axial direction passing through the welded portions of the steel materials 10 and 11 to be welded, and “forward direction” refers to the axial direction from the moving side block 16 to the fixed side block. 17 is a direction opposite to the front axis direction, that is, an axial direction, which is a direction from the fixed side block 17 toward the moving side block 16.

  The moving side block 16 includes a distal end portion of a movable rod 19a of a primary cylinder 19 (corresponding to the first pressure cylinder member of the present invention) 19 that pushes and pulls the moving side block 16 forward and backward. Is fixed, and the tip of the movable rod 21a of the secondary cylinder 21 (corresponding to the second pressure cylinder member of the present invention) that presses the moving block 16 in the axial direction is in contact. Furthermore, the tip of the movable rod 23a of the balance cylinder (corresponding to the third pressure cylinder member of the present invention) 23 that presses the moving side block 16 in the axial rear direction is configured to come into contact. Yes. The primary cylinder 19, the secondary cylinder 21 and the balance cylinder 23 are all air cylinders that are operated by air pressure, and the air pressure and the applied pressure and the operating direction are the first solenoid valve 20, the second solenoid valve 22, and the third one. The solenoid valves 24 are respectively controlled.

  The clamp operation of the first clamp electrode member 12 and the second clamp electrode member 13 with respect to the steel materials 10 and 11 to be welded is performed by driving clamp cylinders 25 and 26, which are air cylinders operated by air pressure, respectively.

  The primary cylinder 19, the secondary cylinder 21, the balance cylinder 23, and the clamp cylinders 25 and 26 may be hydraulic cylinders that are driven by hydraulic pressure such as hydraulic pressure, or actuators that are electrically or magnetically controlled. Or a motor may be sufficient.

  The moving distance measuring device 27 is a device that measures the moving distance of the moving side block 16, and is configured by an encoder or the like, for example. The operation display panel 28 is an operation and display device for performing various displays as well as setting and operating the resistance welding apparatus. As shown in FIG. 1, the operation display panel 28 includes a touch panel 28a for electrical setting and display, a counter 28b for setting the movement position of the moving side block 16, an operation power switch 28c, an emergency stop switch 28d, A next cylinder operation switch 28e, a clamp system changeover switch 28f, a main power supply lamp 28g, a thyristor temperature rise lamp 28h, a cooling water flow shortage lamp 28i, and the like are provided. The left clamp open / close switch 29 and the right clamp open / close switch 30 are foot switches that operate the clamp cylinders 25 and 26 when an operator steps on the foot. The welding start switch 31 is a foot switch that starts the welding operation of the resistance welding apparatus when an operator steps on the foot.

  The firing angle / energization control circuit 15, the first solenoid valve 20, the second solenoid valve 22, the third solenoid valve 24, the clamp cylinders 25 and 26, the movement distance measuring device 27, the operation display panel 28, described above. The left clamp opening / closing switch 29, the right clamp opening / closing switch 30, and the welding start switch 31 are electrically connected to a welding operation control circuit 32 mainly composed of a computer, and instructions output from the welding operation control circuit 32 In addition to the operation by the signal, the measurement signal and the operation signal are sent to the welding operation control circuit 32.

  FIG. 3 schematically shows the configuration of the welding operation control circuit 32. As shown in the figure, the welding operation control circuit 32 includes a central processing unit (CPU) 32b, a read only memory (ROM) 32c, a random access memory (RAM) 32d, which are connected to each other via a bus 32a. The computer comprises at least an input / output interface 32e and a program for operating the computer.

  The CPU 32b is configured to execute a program stored in the ROM 32c according to a basic program such as an operation system (OS) or a boot program stored in the ROM 32c to perform the processing of this embodiment. The CPU 32b is configured to control operations of the RAM 32d and the input / output interface 32e.

  The RAM 32d is used as a main memory of the resistance welding apparatus, and is configured to store programs and data transferred from the ROM 32c and the like. The RAM 32d is also used as a work area for temporarily storing various data during program execution.

  The input / output interface 32e includes an ignition angle / energization control circuit 15, a first solenoid valve 20, a second solenoid valve 22, a third solenoid valve 24, clamp cylinders 25 and 26, a travel distance measuring device 27, an operation display. Data exchange among the board 28, the left clamp opening / closing switch 29, the right clamp opening / closing switch 30, and the welding start switch 31 and the CPU 32b or RAM 32d is controlled.

  In the computer having such a configuration, when starting the program, the CPU 32b first secures a program storage area, a data storage area, and a work area in the RAM 32d, and fetches the program and data from the ROM 32c or the outside, Store in the data storage area. Next, a process flow to be described later is executed based on the program stored in the program storage area.

  Hereinafter, the operation and operation of the resistance welding apparatus in the present embodiment including the operation of the welding operation control circuit 32 will be described in detail.

  Before performing the welding operation, the resistance welding apparatus is set. This setting is performed by the operator operating the touch panel, counter, and / or air pressure regulator of the operation display panel 28.

(1) Setting of mechanical configuration The mechanical configuration of the resistance welding apparatus is set as necessary at the time of initial operation or when the diameters of the steel materials 10 and 11 are changed. Specifically, the first clamp electrode member 12 and the second clamp electrode member 13 that clamp the steel materials 10 and 11 are selected as clamp electrode members having concave clamp surfaces that match the diameters of the steel materials 10 and 11 or Exchange.

  Furthermore, the initial interval between the moving side block 16 and the fixed side block 17 is adjusted in consideration of the welding margin of the steel materials 10 and 11. When the steel material to be welded is a closed type reinforcing bar, the welding margin is the length of the portion where both ends thereof overlap each other as shown in FIG. As shown in FIG. 4 (B), the operator forcibly opens the closed-type reinforcing bar as shown by an arrow and abuts both end faces, and in this state, the first clamp electrode member 12 and the second clamp electrode member 13 Clamp to As shown in the upper part of FIG. 4 (C), welding is performed in this state. As a result, when the first clamp electrode member 12 of the moving block moves as shown in the lower part of FIG. The moving length of the first clamp electrode member 12 (moving side block 16) becomes a margin for welding.

  Further, in the initial state, the protruding position of the adjustment bolt (not shown) of the moving side block 16 is adjusted so that the tip of the movable rod 21a of the secondary cylinder 21 is in contact with the moving side block 16, and The advance stroke of the secondary cylinder 21 in the axial direction is adjusted.

(2) a first set distance L ₁ is a movement position of the movable block 16 which corresponds to the second pressure application start time from the threshold setting secondary cylinder 21 of the moving distance, application end timing of the upset welding current a set distance L ₂ second is a movement position of the movable block 16 corresponding to the set if necessary such as when the diameter of the initial operation time and steel 10 and 11 is changed. This setting is performed by the operator operating a counter 28b provided on the operation display panel 28.

(3) Cylinder air pressure setting The pressure of the air sent to the primary cylinder 19, the secondary cylinder 21 and the balance cylinder 23 is set as necessary when the diameter of the steel materials 10 and 11 is changed during initial operation. . The primary air pressure to the primary cylinder 19 is set by the operator operating the regulator 34 while looking at the pressure gauge 33, and the secondary air pressure to the secondary cylinder 21 is set while the operator looks at the pressure gauge 35. The regulator 36 is set by operating the balance 36, and the balance air pressure to the balance cylinder 23 is set by the operator operating the regulator 38 while looking at the pressure gauge 37.

When air of 0.1 MPa is supplied as the primary air pressure, if the inner diameter of the primary cylinder 19 is 50 mm (cross-sectional area is approximately 20 cm ² ), a pressure of 200 N is applied from the primary cylinder 19 to the moving side block 16. To be applied. In practice, it is desirable to apply a pressure of less than 100 N to the moving block 16.

When air of 0.5 MPa is supplied as the secondary air pressure, if the cylinder inner diameter of the secondary cylinder 21 is 175 mm (the cross-sectional area is about 240 cm ² ), a pressure of 12 kN is transferred from the secondary cylinder 21 to the moving side. Applied to block 16. Actually, it is desirable that a pressure of about 5 to 12 kN is applied to the moving block 16.

Further, when air of 0.1 MPa is supplied as the balance air pressure, if the cylinder inner diameter of the balance cylinder 23 is 32 mm (cross-sectional area is about 8 cm ² ), a pressure of 80 N is applied to the moving side block 16 from the balance cylinder 23. The pressure is applied in the direction opposite to the pressure from the primary cylinder 19. Assuming that the pressure applied to the moving side block 16 from the steel materials 10 and 11 side, that is, the force to return from the closed rebar forcibly opened and clamped is about 160 N, the balance pneumatic pressure of 0.2 MPa. Is supplied to the balance cylinder 23, a pressure of 160 N is applied from the balance cylinder 23 to the moving block 16 in the reverse direction.

(4) Settings relating to applied voltage The applied voltage during flash operation and the applied voltage during upset welding operation, the heat cycle period and cool cycle period during flash operation, the total number of cycles of flash operation, and the hold time value It is set as necessary when the initial operation is performed or when the diameters of the steel materials 10 and 11 are changed. This setting is performed by the operator operating the touch panel 28a provided on the operation display panel 28.

  The effective value of the voltage applied between the steel materials 10 and 11 from the output transformer 14 via the first clamp electrode member 12 and the second clamp electrode member 13 is, for example, an ignition angle composed of a thyristor and its ignition control circuit. It is controlled by the energization control circuit 15. That is, as shown in FIGS. 5A and 5B, the firing angle / energization control circuit 15 controls the firing angle of the sine wave applied voltage to control its effective value. That is, the effective value of the applied voltage can be increased by increasing the firing angle as shown in FIG. 5A, and the effective value of the applied voltage can be increased by delaying the firing angle as shown in FIG. The value can be lowered. Therefore, the effective value of the applied voltage during the flash operation and the upset welding operation can be set by setting the firing angle.

  In addition, the firing angle / energization control circuit 15 also applies the energization and non-energization periods of the voltage applied between the steel materials 10 and 11 from the output transformer 14 via the first clamp electrode member 12 and the second clamp electrode member 13. Be controlled. That is, as shown in FIG. 5C, by setting the number of cycles of the heat cycle and the number of cycles of the cool cycle, the mode of intermittent voltage application during the flash operation can be set.

  Furthermore, the total number of cycles and the hold time of the flash operation that is the flash energization period are set. For example, a numerical value of 99 or less is set as the total number of cycles. For example, 2 seconds is set as the hold time.

  In the present embodiment, a plurality of patterns are set in advance, such as the applied voltage during the flash operation and the upset welding operation, the heat and cool cycles during the flash operation, the total number of cycles of the flash operation, and the hold time. It is stored as pattern data in a ROM 32c of a computer, for example. Therefore, at the time of this setting operation, it is only necessary to select desired pattern data. Of course, this pattern data can be reset.

  FIG. 6 shows the flow of the control operation of the welding operation control circuit 32, and FIG. 7 shows the applied voltage and applied pressure controlled by the welding operation control circuit 32. The welding operation of the resistance welding apparatus in the present embodiment will be described below with reference to these drawings.

  First, the worker clamps the steel materials 10 and 11 of the closed rebar to be welded to the first clamp electrode member 12 and the second clamp electrode member 13. In this clamping operation, the steel materials 10 and 11 are held by hand at the positions of the first clamp electrode member 12 and the second clamp electrode member 13 so that the end surfaces 10a and 11a face each other, and the left clamp open / close switch 29 and / or the right clamp opening / closing switch 30 is stepped on with a foot. When the left clamp open / close switch 29 and the right clamp open / close switch 30 are stepped on, the corresponding clamp cylinders 25 and 26 are operated, and the first clamp electrode member 12 and the second clamp electrode member 13 individually perform the clamp operation. . In order to release the clamp, the left clamp open / close switch 29 and the right clamp open / close switch 30 may be depressed once more. To clamp again, just step on these switches again. It should be noted that by operating the clamp system changeover switch 28f, if either the left clamp open / close switch 29 or the right clamp open / close switch 30 is stepped on, both the first clamp electrode member 12 and the second clamp electrode member 13 are clamped simultaneously. It is possible to switch to a clamping method as described above.

  Thereafter, when the worker steps on the welding start switch 31, the welding operation starts (starts). That is, the control process of the welding operation control circuit 32 is executed according to the flow shown in FIG.

  First, the welding operation control circuit 32 controls the first electromagnetic valve 20 to send air of a set pressure to the primary cylinder 19 and urge the movable rod 19a in the axial direction. Since the distal end portion of the movable rod 19a is fixed to the moving side block 16, a first pressure of less than 100 N is applied to the moving side block 16 from the primary cylinder 19 (step S1). FIG. 7 shows that the application of the first pressure from the primary cylinder 19 is started at this start point.

  Next, the welding operation control circuit 32 controls the third electromagnetic valve 24, sends air of the set pressure to the balance cylinder 23, and biases the movable rod 23a in the rear axis direction. Since the tip of the movable rod 23a is configured to come into contact with the moving block 16, the moving block 16 is moved from the balance cylinder 23 to, for example, about 160 N in a direction opposite to the first pressure of the primary cylinder 19. The third pressure is applied (step S2). FIG. 7 shows that the application of the third pressure from the balance cylinder 23 is started at this start point.

  As shown in FIG. 8, the pressure application direction from the primary cylinder 19 to the moving side block 16 is the front axis direction, while the steel materials 10 and 11 (closed reinforcing bars) are applied to the moving side block 16. The direction of “force to return” is the front axis direction, and the pressure application direction from the balance cylinder 23 to the moving block 16 is the rear axis direction opposite to these directions. Therefore, the balance cylinder 23 can cancel the “force to return” from the closed type reinforcing bar, and the first pressure from the primary cylinder 19 is not affected by the force from the closed type reinforcing bar. Applied to block 16. The “force to return” from the closed rebar differs depending on the hoop size and diameter, but if the third pressure from the balance cylinder 23 is set to a value corresponding to this, the type of the closed rebar is determined. A stable flash operation can always be performed without dependence.

  By such functions of the primary cylinder 19 and the balance cylinder 23, the end faces 10a and 11a of the steel materials 10 and 11 are always in contact with each other at an appropriate pressure (first pressure), and are in contact with each other during the flash operation period. Is preserved.

  Next, the welding operation control circuit 32 lowers the front cover (not shown) that prevents the flash from flying in the direction of the operator by covering the front surface of the welded portion of the resistance welding apparatus (step S3).

  Thereafter, the welding operation control circuit 32 determines whether or not a squeeze time of, for example, about 1 second has elapsed since the start (start) of the welding operation (step S4).

  Only when it is determined that the squeeze time has elapsed (in the case of YES), flash energization is started as shown in FIG. 7 (step S5). That is, the welding operation control circuit 32 controls the firing angle of the sine wave applied voltage to an early angle as shown in FIG. 5A by the firing angle / energization control circuit 15 so that the effective value is 10 V or less. The set flash energization voltage is applied between the steel materials 10 and 11 via the output transformer 14 and further via the first clamp electrode member 12 and the second clamp electrode member 13. Further, the flash energization period is controlled by the firing angle / energization control circuit 15 and the voltage application is intermittently performed. That is, as shown in FIG. 5C and FIG. 7, the number of heat cycles in which energization and non-energization are set, for example, two cycles of heat (energization) and then one cycle cool (non-energization) are performed. And control to the number of cool cycles. In the example of FIG. 5C, one cool cycle is repeated after two heat cycles, but the number of heat cycles and the number of cool cycles can be set to arbitrary optimum values. As will be described later, a sufficient flash can be generated over the entire welded portion by intermittently applying the voltage in this manner.

  By applying an appropriate pressure (first pressure) of less than 100 N from the primary cylinder 19, flash energization is started in a state in which the end faces 10a and 11a of the steel materials 10 and 11 are in contact with each other to a slight degree. Then, flash occurs between the end surfaces (welded surfaces) 10a and 11a of the steel materials 10 and 11. In this case, however, if the pressure is too strong, no or little flash will occur.

  In general, the end faces 10a and 11a of the steel materials 10 and 11 are not smooth surfaces when viewed microscopically (see the end face 11a), as shown in FIG. It is not a surface perpendicular to the axial direction (see end surface 10a). When flash energization is performed in a state in which a part of the end faces 10a and 11a are in contact with each other by the application of the first pressure from the primary cylinder 19, the portion that protrudes most and contacts the opposite surface is locally applied. Current flows and flashover occurs because there is not enough cross-sectional area. For example, as shown in FIG. 9B, the current flows through the portion a that is in contact with each other because it protrudes most between the end faces 10a and 11a, and flashover occurs. When the protruding portion is blown off by this flashover, the first block 19 is applied with the first pressure, so that the moving block 16 slightly moves in the axial direction. As a result, current flows through the portions b that protrude at the next height and come into contact with each other, and the protruding portions are blown off by flashover. Thereafter, the flashover occurs in succession to the portions c and d. A flash occurs continuously over the entire surface. Such flushing removes dirt, oxidized parts and impurities, purifies the welded surface (cleaning), smoothes the entire welded surface, and equalizes the entire surface of the welded surface.

  Moreover, according to this embodiment, since the voltage of the flash energization period is intermittently applied, it is possible to generate a sufficient flash at the welded portion. The reason for this is that if a high voltage is continuously applied during the flash operation, the temperature of the welded portion may rise suddenly in whole or in part. Is not preferred. On the other hand, by intermittently applying voltage, the temperature of the welded part does not rise completely or partially even at high voltage, and as a result, sufficient flash is generated on the entire welded surface. To do. In addition, if the flash does not occur on the entire welded surface, the cleaning of the end surface becomes insufficient, and this tendency becomes prominent particularly when a part of the end surface is inclined to face each other. Furthermore, if the flash is insufficient, the heat does not spread over the entire surface, so that the soaking operation is not performed. That is, according to the present embodiment, since the flash can be generated on the entire welded surface, it is possible to purify the entire welded surface and to equalize the entire surface of the welded surface.

  Next, the welding operation control circuit 32 determines whether or not the flash energization for all the preset number of cycles has been performed (step S6).

  Only when it is determined that the total number of cycles has been completed (in the case of YES), as shown in FIG. 7, the applied voltage is changed from a high voltage for flash energization (flash voltage) to a low voltage for energization of upset welding (upset welding). Voltage) (step S7). That is, the welding operation control circuit 32 controls the firing angle of the sine wave applied voltage to a slow angle as shown in FIG. 5B by the firing angle / energization control circuit 15, and the effective value is higher than the flash energizing voltage. A lower applied voltage is applied between the steel materials 10 and 11 via the output transformer 14 and further via the first clamp electrode member 12 and the second clamp electrode member 13. In this embodiment, since the firing angle is controlled in this way, the applied voltage can be switched continuously and smoothly.

Then, the welding operation control circuit 32, the moving distance of the movable block 16 it is determined whether or not a first set distance L ₁ that is set in advance (step S8).

If the moving distance is determined to become the first set distance L ₁ only (if YES), terminates the application of the third pressure from the balance cylinder 23 (step S9), and further, from the secondary cylinder 21 Application of the second pressure is started (step S10). Since the first pressure is continuously applied from the primary cylinder 19 to the moving side block 16, the welded portions of the steel materials 10 and 11 generate heat and form a bump gradually or abruptly when energized. Moves in front of the axis. For example by measuring the moving distance of the movable block 16 by the moving distance measuring instrument 27 is an encoder, when the measured value becomes equal to the first predetermined distance L _1, as shown in FIG. 7, the balance cylinder 23 The third pressure application is finished, and the second pressure application from the secondary cylinder 21 is started. Thus, in the state where the welding surface and its periphery are soaked by the Joule heat of the large current of the upset energization subsequent to the flash energization, a strong pressure (second pressure) of about 5 to 12 kN from the secondary cylinder 21 is obtained. ) Is applied, and reliable upset welding is performed. That is, the quality of the joint can be stabilized and resistance welding with high reliability can be performed, and resistance welding that is not easily affected by the shape of the end face can be performed.

Thereafter, the welding operation control circuit 32 determines whether or not the moving distance of the moving block 16 has reached a _second set distance L2 set in advance (step S11).

If the moving distance is determined to become the second set distance L ₂ only (in the case of YES), as shown in FIG. 7, it ends the upset welding operation (step S12). Even after the application of the upset welding voltage is completed, since the residual heat and the strong pressure (second pressure) from the secondary cylinder 21 are applied, bumps are formed in the welded portions of the steel materials 10 and 11. .

Then, the welding operation control circuit 32, since the moving distance becomes a second set distance L _2, i.e., from the time of upset welding operation ends, for example, a predetermined time such as 2 seconds (hold time) has elapsed It is determined whether or not (step S13).

  Only when it is determined that the set hold time has elapsed since the end of upset welding energization (in the case of YES), the application of the second pressure from the secondary cylinder 21 is terminated as shown in FIG. 7 (step S14). ), The clamp cylinders 25 and 26 are actuated to release the clamps of the steel materials 10 and 11 by the first clamp electrode member 12 and the second clamp electrode member 13, and the front cover is raised (step S15). The application of the first pressure from the next cylinder 19 is terminated (step S16), and the moving block 16 is pulled back in the axial rear direction. This makes it possible to remove the welded steel materials 10 and 11 from the resistance welding apparatus.

  The lowering and raising timing of the front cover is not limited to the timing described above as long as the front of the welded portion is covered by the front cover while flushing is performed.

  As described in detail above, according to the present embodiment, first, the flash operation is performed, thereby cleaning the end face of the steel material to be welded, removing dirt, oxides and impurities, and smoothing the surface. Is done. Furthermore, the entire end face is soaked. Since the upset welding is continuously performed after the temperature is equalized by the generation of flash, resistance welding having sufficient welding strength can be performed in a relatively short time. In that case, since the effective voltage value is changed by the firing angle control, the device configuration can be greatly simplified. In addition, because upset welding is performed after heat equalization by flash, the quality of the joint is stabilized, highly reliable resistance welding can be performed, and it is difficult to be affected by the shape of the end face. Resistance welding can be performed. Further, since the flash is generated not for completing the welding process by the generation of the flash but for cleaning, smoothing and soaking the end face, a large-scale power supply device is unnecessary, A resistance welding apparatus can be configured at low cost.

  In the above-described embodiment, the hold time, which is the application time of the second pressure from the secondary cylinder 21, is managed by an internal timer by a computer program, but this hold time is managed by an external timer. Also good. Even in this case, it is desirable that the hold time can be set by operating the touch panel 28a provided on the operation display panel 28.

  Furthermore, in the above-described embodiment, after the flash is generated, the second pressure that is a single pressure value is applied to perform the upset welding. However, after the flash is generated, the pressure is stepwise or continuous. Alternatively, upset welding may be performed by applying a plurality of pressure values that change with time.

  All the embodiments described above are illustrative of the present invention and are not intended to be limiting, and the present invention can be implemented in other various modifications and changes. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

DESCRIPTION OF SYMBOLS 10, 11 Steel materials 10a, 11a End surface 12 1st clamp electrode member 13 2nd clamp electrode member 14 Output transformer 15 Firing angle and electricity supply control circuit 16 Moving side block 17 Fixed side block 18 Base 19 Primary cylinder 19a, 21a , 23a Movable rod 20 First solenoid valve 21 Secondary cylinder 22 Second solenoid valve 23 Balance cylinder 24 Third solenoid valve 25, 26 Clamp cylinder 27 Moving distance measuring device 28 Operation display panel 28a Touch panel 28b For moving position setting 28c Operation power switch 28d Emergency stop switch 28e Primary cylinder operation switch 28f Clamp switching switch 28g Main power lamp 28h Thyristor temperature rise lamp 28i Cooling water flow shortage lamp 29 Left clamp open / close switch 30 Right clamp open Switch 31 welding start switch 32 the welding operation control circuit 32a bus 32 b CPU
32c ROM
32d RAM
32e I / O interface 33, 35, 37 Pressure gauge 34, 36, 38 Regulator

Claims (12)

  The gripping means for gripping the pair of welded members so that the end surfaces of the welded portions face each other, and the first pressure for maintaining the end surfaces of the pair of welded members in contact with each other Applying a first voltage between the pair of members to be welded in a state in which the first pressure is applied by the first pressure applying means and the first pressure applying means. A flash is generated between the end faces of the pair of welded members, and a second voltage that is effectively lower than the first voltage is continuously applied after the first voltage is applied for a predetermined period. And a pair of members to be welded when the gripping means is moved by a first set distance by applying the second voltage and applying the first pressure. So that the end faces of each other are pressed against each other with higher pressure And a second pressure applying means for applying a second pressure higher than the first pressure to the holding means, and the pair of welded members are applied with the second voltage and the second pressure. Resistance welding apparatus, wherein upset welding is performed.   The resistance welding apparatus according to claim 1, wherein the voltage applying unit is configured to intermittently apply the first voltage.   The resistance welding apparatus according to claim 1 or 2, wherein the voltage application means is configured to control the first voltage and the second voltage by controlling an ignition angle of the applied voltage. .   The voltage application means ends the application of the second voltage between the pair of welded members when the gripping means moves a second set distance larger than the first set distance. The resistance welding apparatus according to claim 1, wherein the resistance welding apparatus is configured.   The second pressure application unit is configured to end the application of the second pressure to the gripping unit after a predetermined time has elapsed since the gripping unit has moved the second set distance. The resistance welding apparatus according to claim 4.   The gripping means includes a first clamp electrode member and a second clamp electrode member that also serve as electrodes while holding the pair of welded members, respectively, and the first pressure applying means is the first pressure applying means. The resistance welding apparatus according to claim 1, further comprising a first pressure cylinder member configured to apply the first pressure to the clamp electrode member.   The movable rod of the first pressure cylinder member is fixed to the first clamp electrode member so that the first clamp electrode member is pressed toward the second clamp electrode member with the first pressure. The resistance welding apparatus according to claim 6, wherein the resistance welding apparatus is configured.   7. The welding apparatus according to claim 6, wherein the first pressure cylinder member constantly presses the first clamp electrode member with the first pressure during the welding operation of the resistance welding apparatus. 7. The resistance welding apparatus according to 7.   After gripping the pair of welded members by the first clamp electrode member and the second clamp electrode member, the first pressure cylinder member moves the first clamp electrode member to the second clamp electrode member. The resistance welding apparatus according to any one of claims 6 to 8, wherein the resistance welding apparatus is configured to be driven in a direction away from the clamp electrode member.   The gripping means includes a first clamp electrode member and a second clamp electrode member that both hold the pair of members to be welded and also serve as electrodes, and the second pressure application means includes the first pressure application member. The resistance welding apparatus according to claim 1, further comprising a second pressure cylinder member configured to apply the second pressure to the clamp electrode member.   The movable rod of the second pressure cylinder member is in contact with the first clamp electrode member, and is configured to press the first clamp electrode member toward the second clamp electrode member with the second pressure. The resistance welding apparatus according to claim 10, wherein the resistance welding apparatus is provided.   A third pressure cylinder member configured to apply to the gripping means a force that cancels a force applied to the gripping means from the pair of welded members. Item 12. The resistance welding apparatus according to any one of Items 1 to 11.

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