JP2013132660A - Pressure control method for spot welding apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure control method for a spot welding apparatus that can obtain excellent welding quality by controlling pressing force and sub-pressing force by a welding electrode acting on a member to be welded.SOLUTION: The spot welding apparatus includes a pressing actuator 20 for applying the pressing force F to a fixed side electrode 15 and a movable side electrode 25, and a sub-pressing actuator 31 allowing a sub-pressing part 39 to abut on the member 100 to be welded, to apply the sub-pressing force f. The member 100 to be welded is held and pressed with the pressing force F by the fixed side electrode 15 and the movable side electrode 25, and a current is applied for a predetermined time between the fixed side electrode 15 and the movable side electrode 25. The sub-pressing part 39 is allowed to abut on the member 100 to be welded at an initial predetermined time within the current applying time to apply the sub-pressing force f by the sub-pressing actuator 31.

Description

  The present invention relates to a pressure control method for a spot welding apparatus for spot welding a member to be welded.

  In general, when joining plate materials such as stacked steel plates, a spot where a large current is passed between the electrodes for a certain period of time while applying pressure between a pair of welding electrodes, and the joint is heated to a substantially melting temperature and joined. Welding is widely performed.

  In spot welding, when the applied pressure and energization time by both welding electrodes are constant, the nugget diameter gradually increases as the current increases, but if the current value is excessive, the amount of heat generation increases and molten metal is present between the plate materials. Causes scattering. That is, it causes a reduction in strength as the plate thickness decreases at the joint. On the other hand, when the current is too small, the nugget becomes small and sufficient bonding strength cannot be obtained. In addition, when the applied pressure is small, the contact area between the plate materials is reduced, the current density is increased, and scattering due to overheating is caused. On the other hand, if the applied pressure is too large, the contact area of the joint is increased, the current density is reduced, the heat generation is reduced, the nugget is reduced, and the welding strength is reduced.

  Here, as shown in FIG. 10, spot welding is performed on a member to be welded 100 in which three sheets of a thin plate 101 having low rigidity and a first thick plate 102 and a second thick plate 103 having higher rigidity than the thin plate 101 are overlapped. In the state where the plate members 101, 102, and 103 are in close contact with each other, when the member to be welded 100 is pressed by the movable side electrode 111 and the fixed side electrode 112 and energized by the power source 113, the movable side electrode 111 and The current density in the energization path between the fixed side electrodes 112 is substantially uniform, and a good nugget is formed from the thin plate 101 to the second thick plate 103, so that welding strength can be obtained.

  However, actually, when the member to be welded 100 is pressed by the movable side electrode 111 and the fixed side electrode 112, the thin plate 101 and the first thick plate 102 having low rigidity bend upward, and the thin plate 101 and the first thickness are bent. A gap is generated between the plates 102 and between the first thick plate 102 and the second thick plate 103. In this case, the contact area between the movable electrode 111 and the thin plate 101 is increased by the bending of the thin plate 101, whereas between the thin plate 101 and the first thick plate 102 and between the first thick plate 102 and the second thick plate 103. The contact area of the joint becomes smaller.

  For this reason, the current density between the movable side electrode 111 and the fixed side electrode 112 is higher on the second thick plate 103 side than on the thin plate 101 side, and the first thick plate 102 and the first thick plate 102 are larger than between the thin plate 101 and the first thick plate 102. The amount of heat generated locally between the two thick plates 103 increases. As a result, as shown in FIG. 10A, first, the nugget N is formed at the joint portion between the first thick plate 102 and the second thick plate 103, and the nugget N gradually becomes larger and then shown in FIG. 10B. In this way, the thin plate 101 and the first thick plate 102 are welded. However, the amount of penetration between the thin plate 101 and the first thick plate 102 is small, the welding strength is unstable, the peeling of the thin plate 101 is a concern, and the welding quality varies. This problem is particularly noticeable because the nugget N is less likely to reach between the first thick plate 102 and the thin plate 101 as the first thick plate 102 and the second thick plate 103 are thicker.

  As a countermeasure, for example, there is a spot welding apparatus disclosed in Patent Document 1. In this spot welding apparatus, a spot welding apparatus 120 is mounted on a wrist portion 116 of a welding robot 115 as shown in FIG. The spot welding gun 120 is moved to each spot position of the member to be welded 100 supported by the clamper 118, and spot welding of the member to be welded 100 is performed.

  The spot welding device 120 includes a base portion 122 supported by a linear guide 121 fixed to a gun support bracket 117 attached to the wrist portion 116 so as to be movable up and down, and a fixed arm 123 extending downward is provided on the base portion 122. The fixed side electrode 124 is provided at the lower end tip of the fixed arm 123. A pressure actuator 126 is mounted on the upper end of the base portion 122, and the movable electrode 125 is attached to the lower end of the rod 127 that moves up and down by the pressure actuator 126. A servo motor 128 is mounted on the upper end of the gun support bracket 117, and the operation of the servo motor 128 causes the base portion 122 to move up and down via a ball screw mechanism.

  Here, in accordance with teaching data stored in advance in a controller (not shown), the pressure FU applied by the movable electrode 125 located on the thin plate 101 side is made smaller than the pressure FL applied by the fixed electrode 124 (FU <FL).

  In order to make the pressure FU applied by the movable electrode 125 smaller than the pressure FL applied by the fixed electrode 124 in this way, first, the base portion 122 is raised by the servo motor 128 to connect the fixed electrode 124 to the lower surface of the member 100 to be welded. The movable side electrode 125 is lowered by the pressure actuator 126 and is brought into contact with the upper surface of the member to be welded 100 for pressurization. Next, the base portion 122 is pushed up by the servo motor 128. As the base portion 122 is pushed up, the pressing force FL of the fixed side electrode 124 is increased by the pushing amount of the base portion 122, and the pressing force FU by the movable side electrode 125 becomes smaller than the pressing force FL by the fixed side electrode 124.

  As a result, when the movable side electrode 125 and the fixed side electrode 124 are energized, the current density at the joint between the thin plate 101 and the first thick plate 102 is increased, and the amount of heat generated is the first thick plate 102 and the second thickness. It increases relative to the amount of heat generated at the joint of the plate 103. Thereby, a good nugget without bias is formed from the thin plate 101 to the second thick plate 103, and the welding strength can be ensured.

JP 2003-251469 A

  According to Patent Document 1, the current density between the thin plate 101 and the first thick plate 102 is relatively increased by making the applied pressure FU on the movable side electrode 125 side smaller than the applied pressure FL of the fixed side electrode 124. The amount of heat generated at the joint between the thin plate 101 and the first thick plate 102 can be secured, the amount of penetration increases, and the welding strength increases.

  However, the member to be welded 100 clamped and held by the clamper 118 is moved between the fixed side electrode 124 and the movable side electrode 125 while the base part 122 is moved and the movable side electrode 125 is moved by the pressure FL of the fixed side electrode 124. In order to reduce the applied pressure FU caused by the above, a large load is required for the clamper 118 that clamps and holds the member to be welded 100. On the other hand, in the state where the clamp position of the member 100 to be welded by the clamper 118 and the welding position are largely separated from each other, the member 100 to be welded is bent and deformed, and the applied pressure FL by the fixed side electrode 124 and the applied pressure FU by the movable side electrode 125 vary. It is difficult to secure a stable contact resistance between the thin plate 101 and the first thick plate 102 and a contact resistance between the first thick plate 102 and the second thick plate 103 due to the occurrence of There is a concern that the quality of spot welding may deteriorate due to variations.

  Therefore, the applicant of the present patent application, as shown in FIG. 12 in Japanese Patent Application No. 2010-200633, welds the member to be welded 100 between the fixed electrode 132 and the movable electrode 131 operated by the pressure actuator. The portion is clamped and pressurized by a predetermined pressure F, that is, the pressure FU of the movable side electrode 132 and the pressure FL of the fixed side electrode 132 (F = FU + FL). By pressing 133 to the thin plate 101 of the member to be welded 100 and applying the sub-pressing force f, the movable side electrode 131 that applies the pressing force of the fixed side electrode 132 acting on the thin plate 101 side to the second thick plate 103 side. A spot welding apparatus has been proposed in which welding is performed by energizing between the movable side electrode 131 and the fixed side electrode 132 while controlling the applied pressure to be smaller than the applied pressure.

  As a result of diligent experiments and the like, in this spot welding apparatus, the member to be welded 100 is sandwiched and pressurized with the applied force F set by the movable electrode 131 and the fixed electrode 132, and the movable member 100 is movable with the auxiliary applied force f applied. Since the welding is performed by energizing the side electrode 131 and the fixed side electrode 132 for a predetermined time, the welding portion is heated by this energization and the welded portion is softened, and the pressure applied by the movable side electrode 131 and the fixed side electrode 132 during the welding is performed. Decreases, the contact area between the first plank 102 and the second plank 103 decreases, the nugget diameter becomes smaller than the intended diameter, and the place between the first plank 102 and the second plank 103 is reduced. There is concern that the welding strength of the initial stage cannot be achieved.

  Accordingly, an object of the present invention made in view of such a point is to provide a pressurizing control method for a spot welding apparatus in which excellent welding quality can be obtained by controlling the pressing force and the sub-pressing force by the welding electrode acting on the member to be welded. Is to provide.

  The invention of the pressurization control method for a spot welding apparatus according to claim 1, which achieves the above object, is applied to a first welding electrode and a second welding electrode that holds the member to be welded in cooperation with the first electrode. A pressure actuator for applying pressure; and a sub-pressurization actuator for applying a sub-pressurizing force by contacting a sub-pressurizing portion to the member to be welded. The welding member is clamped and pressurized with a preset pressure, energized between the first welding electrode and the second welding electrode, and welded with a secondary pressure applied by the secondary pressure unit. A pressurizing control method for a spot welding apparatus, wherein the welded member is sandwiched and pressed between a first welding electrode and a second welding electrode by a pressurizing actuator with a preset pressurizing force. 2 Energizing time to energize the welding electrode for a predetermined time Characterized by imparting secondary pressure to FukuKa pressure part to be welded member abuts by the sub-pressure actuator in some predetermined time.

  According to this, the energization time in which the first welding electrode and the second welding electrode are energized for a predetermined time by sandwiching and pressurizing the member to be welded with the first welding electrode and the second welding electrode with a preset pressing force by the pressurizing actuator. Welding by applying a pressurizing force by the uniform first welding electrode and the second welding electrode by applying a subpressing force by a subpressurizing actuator while abutting the subpressurizing portion on the member to be welded for a predetermined period of time Spot welding with characteristics and spot welding with welding characteristics in which the pressing force of the first welding electrode and the second welding electrode is controlled by the sub-pressurizing force by the sub-pressurizing part can be obtained continuously, and excellent welding quality can be obtained. . For example, the first welding electrode and the second welding electrode are formed by sandwiching and pressurizing the member to be melted by the first welding electrode and the second welding electrode, which is configured by a three-layered plate assembly in which a thin plate is superimposed on one of two thick plates. The pressure applied by the welding electrode is ensured, and the generation of nuggets between the two thick plates is promoted to obtain a sufficient nugget diameter between the two thick plates, and the member to be welded is applied by the first welding electrode and the second welding electrode. By holding and pressurizing with pressure and applying a sub-pressurizing force by the sub-pressurizing unit, the contact resistance between the thin plate and the thick plate is relatively increased and the contact resistance between the both thick plates is controlled to be relatively small. A nugget extending from the thin plate side to both thick plates is formed, so that the welding strength of the thin plate can be secured and excellent welding quality can be obtained.

  According to a second aspect of the present invention, in the pressurization control method for the spot welding apparatus according to the first aspect, a sub-pressurizing portion is brought into contact with the member to be welded to apply a sub-pressurizing force by a sub-pressurizing actuator. The predetermined time is set to an initial range within the energization time.

  According to this, the member to be welded is sandwiched and pressed by the first welding electrode and the second welding electrode and energized for a predetermined time, and the sub-pressurizing unit applies the sub-pressurizing force only for a predetermined time to the initial range of the energizing time. By controlling the pressure applied by the fixed side electrode and the movable side electrode, the welding quality with respect to the member to be welded on which the plate materials having different rigidity are stacked is improved. For example, the member to be welded is composed of a three-layered plate assembly in which a thin plate is superposed on one of two thick plates, and a member to be welded is sandwiched and pressurized by a first welding electrode and a second welding electrode and applied by a sub-pressurizing unit. By applying the sub-pressing force, the contact resistance between the thin plate and the thick plate is relatively increased and the contact resistance between the two thick plates is controlled to be relatively small. There is no bias, and a nugget extending from the thin plate side to both thickness holding plates is formed, and the welding strength of the thin plate can be ensured. On the other hand, as the welding progresses, the joints of the two thick plates and the surroundings of the joints are heated and softened, the pressurizing force between the two thick plates is reduced, and the nugget growth is suppressed. By releasing the pressure, the pressurization by the first welding electrode and the second welding electrode is increased, the contact area between the two thick plates is secured, the generation of the nugget is promoted, and a sufficient nugget diameter between the two thick plates is secured. Excellent welding quality can be obtained.

  According to a third aspect of the present invention, in the pressurization control method for the spot welding apparatus according to the first aspect, a sub-pressurizing portion is brought into contact with the member to be welded to apply a sub-pressurizing force by a sub-pressurizing actuator. The predetermined time is set in a later period within the energization time.

  According to this, the latter part of the energization time which clamps and presses a to-be-welded member with the 1st welding electrode and the 2nd welding electrode, energizes for a predetermined time between the 1st welding electrode and the 2nd welding electrode, and welds the to-be-welded member. By applying the sub-pressurizing force to the range by the sub-pressurizing portion for a predetermined time and controlling the pressurizing force by the fixed side electrode and the movable side electrode, the welding quality for the member to be welded on which the plate materials having different rigidity are overlapped is improved. For example, the member to be welded is formed by a three-layered plate assembly in which a thin plate is superposed on one of two thick plates, and both members are sandwiched and pressurized by a relatively large pressure applied by a first welding electrode and a second welding electrode. By generating sufficient nugget between the thick plates to ensure the welding strength of both thick plates, and by applying the sub-pressurizing force by the sub-pressurizing part, the generation of nuggets at the junction between the thin plate and the thick plate is promoted Excellent welding quality can be obtained.

  According to the present invention, the first welding electrode and the second welding electrode are energized for a predetermined time by sandwiching and pressurizing the member to be welded with the first welding electrode and the second welding electrode with a preset pressure. By applying the additional pressure by the uniform first welding electrode and the second welding electrode by abutting the auxiliary pressure member on the member to be welded and applying the auxiliary pressure force by the auxiliary pressure actuator at a predetermined time within the time. Spot welding with welding characteristics, and spot welding with welding characteristics in which the pressurizing force of the first welding electrode and the second welding electrode is controlled by the sub-pressurizing force by the sub-pressurizing part, are continuously obtained, complementing each other's welding characteristics Excellent welding quality can be obtained.

It is a block diagram of the spot welding apparatus in 1st Embodiment. It is A arrow directional view of FIG. It is the B section enlarged perspective view of FIG. It is a time chart in a welding operation cycle. It is an operation | movement outline explanatory drawing. It is an operation | movement outline explanatory drawing. It is a time chart in the welding operation cycle in 2nd Embodiment. It is an operation | movement outline explanatory drawing. It is an operation | movement outline explanatory drawing. It is explanatory drawing which shows the outline | summary of the conventional spot welding. It is explanatory drawing which shows the outline | summary of the conventional spot welding. It is outline | summary explanatory drawing of a spot welding apparatus.

(First embodiment)
A first embodiment of a pressure control method for a spot welding apparatus according to the present invention will be described with reference to FIGS. 1 is a configuration diagram of a spot welding apparatus, FIG. 2 is a view as seen from an arrow A in FIG. 1, FIG. 3 is an enlarged perspective view of part A in FIG. 1, FIG. 4 is an explanatory diagram of operation program data, and FIGS. FIG.

  Prior to the description of the spot welding apparatus 1, the member to be welded 100 will be described. As shown in FIG. 3, the member to be welded 100 is a thin plate 101 having a lower rigidity in order from the bottom, in which a thin plate is superposed on one of two stacked thick plates, and the thickness is larger and higher than the thin plate 101. The first thick plate 102 and the second thick plate 103 are composed of a three-layered plate set.

  As shown in FIGS. 1 to 3, the spot welding apparatus 1 includes a base portion 3 attached to a wrist portion of a welding robot (not shown) via an equalizer unit, and side portions 4 extending opposite from both sides of the base portion 3, A support bracket 2 with 5. The fixed arm 10 is attached to the opposite side portions 4 and 5 of the support bracket 2, and the pressure actuator 20 is attached to the front end portions 4 a and 5 a of the side portions 4 and 5 via the bracket 6. Further, the auxiliary pressure actuator 31 of the auxiliary pressure applying means 30 and the welding transformer 40 are attached and supported between the side portions 4 and 5.

  The fixed arm 10 includes a fixed arm body 11 having a base end coupled to both side portions 4 and 5 of the support bracket 2 and extending downward, and an electrode holding portion 12 bent in an L shape from the distal end of the fixed arm body 11. The fixed electrode 15 that is formed and that is the first welding electrode is mounted on the electrode holding portion 12 with the top end 15a facing upward.

  The pressure actuator 20 includes a servo motor 21 configured by a hollow motor having a hollow rotor that is rotatably accommodated in a motor housing, and includes a ball screw mounted on the hollow rotor and a rod 23 that is screwed to the ball screw. It has a linear motion part 22, and the rod 23 of the linear motion part 22 reciprocates up and down by the operation of the servo motor 21. An electrode arm 24 is provided at the lower end of the rod 23 of the linear motion portion 22, and the fixed side electrode is coaxial with the top end 15 a of the fixed side electrode 15 provided on the fixed arm 10 at the tip of the electrode arm 24, that is, on the central axis L. A movable side electrode 25 which is a second welding electrode is provided opposite to 15.

  Thus, the movable side electrode 25 is moved away from the fixed side electrode 15 by the operation of the servo motor 21 of the pressurizing actuator 20, and the member to be welded 100 is clamped in cooperation with the fixed side electrode 15, and pressure is applied. It moves along the central axis L between the pressurizing position. The pressure F applied to the welded member 100 by the fixed side electrode 15 and the movable side electrode 25, that is, the pressure FL by the fixed side electrode 15 and the pressure FU by the movable side electrode 25 are determined by the rotational torque of the servo motor 21. A desired pressure can be obtained by controlling the rotational torque of the motor 21.

  The sub-pressurizing application means 30 includes a sub-pressurizing actuator 31 that is held between the side portions 4 and 5 of the support bracket 2 via the support member 7 and a sub-pressurizing application arm provided with a sub-pressurizing unit 38 at the tip. 35. The sub-pressurizing actuator 31 includes a servo motor 32 configured by a hollow motor having a hollow rotor that is rotatably accommodated in a motor housing, and includes a ball screw mounted on the hollow rotor and a rod 34 screwed to the ball screw. The rod 34 of the linear motion portion 33 is reciprocated up and down by the operation of the servo motor 32. A sub-pressure applying arm 35 is provided on the rod 34 of the linear motion portion 33.

  The auxiliary pressure applying arm 35 has a proximal end portion coupled to the distal end of the rod 34, extends downward between the fixed arm 10 and the electrode arm 24, and bends in the direction of the central axis L from the distal end. The auxiliary pressure member holding member 38 is provided at the distal end portion 37 of the arm portion 36.

  The auxiliary pressure member holding member 38 has a rectangular plate shape in which the base end portion 38A is coupled to the distal end portion 37 of the arm portion 36 and extends in the direction of the central axis L, and is coaxial with the central axis L at the distal end. A sub-pressurizing portion 39 having a semicircular arc shape, that is, a half-cylindrical cylinder shape, is provided in which the tip 39a protrudes upward to allow the fixed side electrode 15 to pass therethrough.

  In the sub-pressure applying arm 35 configured as described above, the tip 39 a of the sub-pressing portion 39 provided at the tip of the sub-pressure applying arm 35 by the operation of the servo motor 32 is lower than the top end 15 a of the fixed side electrode 15. Centered between a retracted position that is separated from the member to be welded 100 and a sub-pressurizing position that abuts the member to be welded 100 sandwiched between the fixed side electrode 15 and the movable side electrode 25 from below and applies a sub-pressurizing force. It moves along the axis L. This auxiliary pressure is determined by the rotational torque of the servo motor 32, and the desired auxiliary pressure f is obtained by controlling the rotational torque of the servo motor 32.

  One output terminal of the welding transformer 40 serving as a power source is connected to the fixed side electrode 15 via the bus bar and the fixed arm 10 and the like, and the other output terminal is connected to the movable side electrode 25 via the bus bar and the electrode arm 24 and the like. Is connected to be energized.

  Further, the welding controller 41 is provided. The welding controller 41 includes an operation program for the spot welding apparatus 1 and a pressurization control unit 42 that controls the pressurization actuator 20 based on each operation stroke set in the operation program, and a sub-pressurization actuator. A sub-pressurizing control unit 43 for controlling 31 is included.

  The welding controller 41 has a welding operation cycle as operation program data. As a welding operation cycle, a pressurization start step S11 for pressurizing the member 100 to be welded by the movable side electrode 25 and the fixed side electrode 15, a pressurization holding step S12 for maintaining the pressurization state, and a pressure release for releasing the pressurization Step S13, sub-pressurization start step S21 for sub-pressurizing the member 100 to be welded by the sub-pressurization unit 39, sub-pressurization holding step S22 for retaining the sub-pressurization state, and sub-pressurization for releasing the sub-pressurization It has cancellation | release process S23, the electricity supply start process S31 which supplies with electricity to the movable side electrode 25, and the fixed side electrode 15, the electricity supply holding process S32 which hold | maintains electricity supply, and the electricity supply completion | finish process S33 which complete | finishes electricity supply. The time chart in this welding operation cycle is shown in FIG.

  In addition, the welding controller 41 receives the rotation torque of the servomotor 21 when pressurizing the member 100 to be welded by the fixed side electrode 15 and the movable side electrode 25 with the preset pressure F, that is, the pressure setting rotation torque and the preset value. The rotational torque of the servo motor 32 when the sub-pressurizing unit 39 sub-pressurizes the welded member 100 with the set sub-pressurizing force f, that is, the sub-pressurizing set rotational torque is set.

  In the pressurization start step S11, the servo motor 21 is operated until reaching a preset pressurization setting rotational torque, and the member to be welded 100 is sandwiched and pressed by the fixed electrode 15 and the movable electrode 25 with a predetermined pressure F. In the subsequent pressurizing and holding step S12, the servo motor 21 is held in a state where the set rotational torque is held. In the pressurization releasing step S13, the movable side electrode 25 is moved from the pressurizing position to the retracted position by the operation of the servo motor 21. Here, the pressurizing force F in the pressurizing and holding step S12 is the sum of the pressurizing force of the fixed side electrode 15 and the pressurizing force of the movable side electrode 25 that pressurize the member to be welded 100, and is the optimum required during welding. This is the total applied pressure (F = FL + FU) of the applied pressure FL of the fixed electrode 15 and the applied pressure FU of the movable electrode 25, and is preferably set in advance through experiments, simulations, or the like.

  In the sub-pressurization start step S21, the servo motor 32 is operated until a preset sub-pressurization set rotational torque is reached, and the member to be welded 100 is pressurized by the sub-pressurization unit 39 with a predetermined sub-pressurizing force f. In the sub pressure holding step S22, the servo motor 32 is held in a state where the set rotational torque is held. In the sub pressure release step S23, the servo motor 32 is operated to move the sub pressure portion 39 from the sub pressure position to a retracted position away from the member to be welded 100. It is preferable to set in advance through experiments, simulations, or the like. Here, when the auxiliary pressure f is applied in a state where the pressing force F is applied to the member to be welded 100 by the fixed side electrode 15 and the movable side electrode 25, the pressing force by the movable side electrode 25 acting on the member to be welded 100 from above. The sum of the pressing force FL by the fixed electrode 15 acting on the welded member 100 from below and the sub-pressing force f by the sub-pressurizing unit 39 becomes equal (FU = FL + f). In other words, the pressurizing force FL that acts on the member to be welded 100 from the fixed electrode 15 is applied by subtracting the subpressurizing force f by the subpressurizing unit 39 from the pressurizing force FU by the movable electrode 25 (FL). = FU-f). Thus, the applied pressure FL from the fixed electrode 15 acting on the member to be welded 100 is controlled to be smaller than the applied pressure FU of the movable electrode 25 acting on the member to be welded 100 (FL <FU).

  In the energization start step S31, energization between the fixed side electrode 15 and the movable side electrode 25 is started. In the energization holding step S32, the energization state between the fixed side electrode 15 and the movable side electrode 25 is maintained, and energization is performed in the energization end step S33. Stop.

  A welding robot controller (not shown) stores teaching data of the welding robot, and the teaching data includes an operation program for sequentially spot welding the welding spot positions of the member to be welded 100 and each welding spot, that is, the welding position. The position and attitude of the spot welding apparatus 1 in FIG.

  Next, the operation of the spot welding apparatus 1 will be described with reference to the time chart in the welding operation cycle shown in FIG. 4 and the operation outline explanatory diagrams of FIGS.

  In spot welding of the member to be welded 100, according to a preset program, as shown in FIG. 1, the movable side electrode 25 is at a retracted position away from the fixed side electrode 15, and the auxiliary pressure applying unit 39 of the auxiliary pressure applying means 30. Is held at the retracted position, the robot controller operates the welding robot, and the top end 15a of the fixed-side electrode 15 is brought into contact with the striking position as the welding position of the welded member 100 as shown in FIG. Then, the spot welding apparatus 1 is positioned at the welding position.

  In the state where the spot welding device 1 is positioned at the welding position, the top end 15a of the fixed electrode 15 of the spot welding device 1 abuts on the thin plate 101 of the member to be welded 100 from below as shown in FIG. The top end 25a of the movable electrode 25 is opposed to the second thick plate 103 with a gap, and the tip 39a of the sub-pressing portion 39 is opposed to the thin plate 101 with a gap.

  Next, in a state where the fixed side electrode 15 is in contact with the thin plate 101 of the member to be welded 100, the movable side electrode 25 is moved from the retracted position by the operation of the servo motor 21 of the pressure actuator 20 in the pressurizing step S11. As shown in FIG. 5B, the second thick plate 103 is brought into contact with the second thick plate 103 from above and the servo motor 21 of the pressure actuator 20 is operated until the pressure setting rotational torque is reached. The member to be welded 100 is sandwiched and pressurized with the applied pressure F between the movable side electrode 25 and the fixed side electrode 15. In the subsequent pressurizing and holding step S12, the servo motor 21 is stopped and held in this position, and the state in which the member to be welded 100 is sandwiched and pressed between the movable side electrode 25 and the fixed side electrode 15 by the pressing force F is held. To do.

  In the initial stage of the pressurizing and holding step S12 in which the member to be welded 100 is pressed and held with the applied pressure F between the movable side electrode 25 and the fixed side electrode 15, the welding side transformer 40 and the movable side electrode 25 are fixed in the energization start step S31. Energization is performed between the side electrode 15 and the energization state between the movable side electrode 25 and the fixed side electrode 15 is retained for a predetermined time in a current retention step S32.

  The servo motor 32 of the sub-pressurization actuator 31 is operated until reaching the sub-pressurization setting rotational torque in the sub-pressurization start step S21 immediately after the start of the energization holding step S32. As a result, the sub-pressurizing portion 39 moves from the retracted position to the sub-pressurizing position and is welded in a state in which it is sandwiched and pressed between the movable electrode 25 and the fixed electrode 15 as shown in FIG. The tip 39a of the sub-pressurizing unit 39 is brought into pressure contact with the thin plate 101 of the member 100 from below to apply the sub-pressurizing force f from below, and the servo motor 32 is energized within the sub-pressurizing and holding step S22. After maintaining the sub-pressurization section 39 to apply and hold the sub-pressurizing force f for a predetermined time in the initial range, the servo-motor 32 is operated in the sub-pressurization releasing step S23, and FIG. As shown, the sub-pressurizing unit 39 is moved to a retracted position away from the welded member 100.

  In this sub-pressurizing and holding step S22, the sub-pressurizing section 39 adjoins the member to be welded 100 that has been pressed with the pressing force FL of the fixed-side electrode 15 and the pressing force FU of the movable-side electrode 25, adjacent to the fixed-side electrode 15. In a state where the pressing force f is applied, the pressing force FU by the movable side electrode 25 acting on the second thick plate 103 from above, the pressing force FL by the fixed side electrode 15 acting on the thin plate 101 from below, and the sub pressurizing unit 39. The total sum of the sub pressures f becomes equal (FU = FL + f). In other words, the applied pressure FL acting on the thin plate 101 from the fixed side electrode 15 is applied by adding the applied pressure FU by the movable side electrode 25 to the sub applied pressure f by the auxiliary pressurizing unit 39 (FL = FU). -F).

  Thus, the thin plate 101 is controlled by controlling the pressure FL from the fixed side electrode 15 acting on the thin plate 101 side smaller than the pressure FU of the movable side electrode 25 acting on the second thick plate 103 side (FL <FU). The contact pressure between the first thick plate 102 and the first thick plate 102 is smaller than the contact pressure at the welded portion between the first thick plate 102 and the second thick plate 103, and the contact between the thin plate 101 and the first thick plate 102 is relatively small. As the resistance increases, the contact resistance between the first thick plate 102 and the second thick plate 103 decreases.

  The movable electrode 25, the fixed electrode 15, and the sub-pressurizing unit 39 sandwich and press the member to be welded 100 so that the pressing force FL of the fixed electrode 15 positioned on the thin plate 101 side is positioned on the second thick plate 103 side. In a state where the applied pressure FU of the movable side electrode 25 is smaller than that of the movable side electrode 25, current is passed between the movable side electrode 25 and the fixed side electrode 15 for a predetermined time, thereby relatively joining the thin plate 101 and the first thick plate 102. The contact resistance at the portion is large and the current density is high, and the contact resistance between the first thick plate 102 and the second thick plate 103 is kept small. As a result, the amount of heat generated at the joint between the thin plate 101 and the first thick plate 102 is relatively increased with respect to the amount of heat generated at the joint between the first thick plate 102 and the second thick plate 103, and the second from the thin plate 101. There is no bias in current density over the thick plate 103, and a relatively cylindrical nugget N is formed on the second pressure plate 103 from the thin plate 101 side as shown in FIG. 6A, so that the welding strength of the thin plate 101 can be ensured. .

  As the welding progresses, the joint between the first pressure plate 102 and the second thick plate 103 and the periphery of the joint are heated and softened, and the applied pressure between the first thick plate 102 and the second thick plate 103 decreases. The growth of the nugget N between the first thick plate 102 and the second thick plate 103 is suppressed. Here, the servo motor 32 is operated in the sub-pressurization releasing step S23 to move the sub-pressurization part 39 from the sub-pressurization position to the retracted position away from the welded member 100 as shown in FIG. A predetermined pressure F is applied to the member to be welded 100 from which the application of the sub-pressurizing force f by the sub-pressurizing unit 39 is released by the fixed-side electrode 15 and the movable-side electrode 25 in a state where the set rotational torque of the servomotor 21 is maintained. Is increased to the pressing force FL of the fixed electrode 15 and the pressing force FU of the movable electrode 25, and the contact area between the first thick plate 102 and the second thick plate 103 is ensured, and the nugget N The generation is promoted to secure a sufficient diameter of the nugget N between the first thick plate 102 and the second thick plate 103, and the thin plate 101 and the first thick plate 102 are joined as shown in FIG. The nugget N having a diameter that gradually increases as the transition from the first portion to the joining portion of the first thick plate 102 and the second thick plate 103 is generated, and the welding strength of the first thick plate 102 and the second thick plate 103 is obtained. .

  Thereafter, the energization of the movable side electrode 25 and the fixed side electrode 15 is terminated in the energization end step S33, and the movable side electrode 25 is moved from the pressurization position by the operation of the servo motor 21 of the pressure actuator 20 in the pressure release step S13. As shown in FIG. 5E, the member to be welded 100 is held between the fixed side electrode 15 and the movable side electrode 25 as shown in FIG.

  Next, the welding robot is operated according to the operation program, and the spot welding apparatus 1 is retracted from the spot position of the welded member 100 and moved to the spot position of the next welded member 100.

  According to the present embodiment configured as described above, the welding target 100 is sandwiched and pressed by the fixed electrode 15 and the movable electrode 25 to start energization or immediately after the start of welding, that is, in the initial range of energization time for a predetermined time. By applying the sub-pressurizing force f by the sub-pressurizing unit 39, the pressing force FL from the fixed-side electrode 15 acting on the thin plate 101 side is applied to the movable plate electrode 25 acting on the second thick plate 103 side. The contact resistance between the thin plate 101 and the first thick plate 102 is large and the current density is increased, and the contact resistance between the first thick plate 102 and the second thick plate 103 is kept small. There is no bias in current density from 101 to the second thick plate 103, a relatively cylindrical nugget N is formed on the second pressure plate 103 from the thin plate 101 side, and the welding strength of the thin plate 101 is ensured. Addition By canceling the application of the sub-pressing force f by the portion 39, the pressing force F is increased by the fixed electrode 15 and the movable electrode 25, and the contact area between the first thick plate 102 and the second thick plate 103 is secured. Generation of the nugget N is promoted, a sufficient diameter of the nugget N between the first thick plate 102 and the second thick plate 103 is ensured, and the first thickness from the joint portion of the thin plate 101 and the first thick plate 102 is secured. A nugget N having a diameter that gradually increases as the transition to the joint between the plate 102 and the second thick plate 103 is generated, and the welding strength of the first thick plate 102 and the second thick plate 103 is obtained.

  Accordingly, the member to be welded 100 is sandwiched and pressurized by the fixed side electrode 15 and the movable side electrode 25, and the initial period within the energization time for welding the member to be welded 100 by energizing the fixed member 15 and the movable side electrode 25 for a predetermined time. A member to be welded 100 in which plate materials having different rigidity are overlapped by applying a sub-pressurizing force f by the sub-pressurizing unit 39 to the range for a predetermined time and controlling the pressing forces FL and FU by the fixed side electrode 15 and the movable side electrode 25. This improves the welding quality against. That is, the spot welding based on the welding characteristics by applying the pressing force F by the uniform fixed electrode 15 and the movable side electrode 25 and the pressing force FL of the fixed side electrode 15 and the moving side electrode 25 by the sub pressing force f by the sub pressurizing unit 39. Spot welding with a welding characteristic in which the pressure FU is controlled is continuously obtained, and the welding characteristics of each other are complemented to obtain excellent welding quality.

(Second Embodiment)
A second embodiment of the pressure control method for a spot welding apparatus according to the present invention will be described with reference to FIGS. The present embodiment is different from the first embodiment in the operation program, and other configurations are the same as those in the first embodiment, and detailed descriptions of the parts are omitted by attaching corresponding reference numerals.

  As shown in the time chart of the welding operation cycle in FIG. 7, as the welding operation cycle, a pressurization start step S111 in which the member to be welded 100 is pressed by the movable side electrode 25 and the fixed side electrode 15, and the pressurizing state is maintained. Pressure holding step S112, pressure releasing step S113 for releasing pressure, sub-pressurizing start step S121 for sub-pressurizing the member to be welded 100 by the sub-pressurizing unit 39, and sub-pressurizing for maintaining the sub-pressurized state Holding step S122, sub-pressurization releasing step S123 for releasing the sub-pressurization, energization start step S131 for energizing the movable side electrode 25 and the fixed side electrode 15, an energization holding step S132 for retaining energization, and energization And an energization end step S133 to be ended.

  The operation of the spot welding apparatus 1 will be described with reference to the time chart in the welding operation cycle shown in FIG. 7 and the operation outline explanatory diagrams of FIGS.

  In spot welding of the member to be welded 100, according to a preset program, as shown in FIG. 8A, the top end 15a of the fixed side electrode 15 is brought into contact with the spot position as the welding position of the member to be welded 100, and spot welding is performed. The device 1 is positioned at the welding position.

  Next, in the pressurizing step S111, the movable side electrode 25 is moved to the pressurizing position approaching the fixed side electrode 15 by the operation of the servo motor 21 of the pressurizing actuator 20, and the second thick plate as shown in FIG. The contact member 103 is contacted from above and the servo motor 21 of the pressurizing actuator 20 is operated until the pressurizing set rotational torque is reached, so that the member to be welded 100 is applied with the pressurizing force F between the movable side electrode 25 and the fixed side electrode 15. The state in which the member to be welded 100 is sandwiched and pressurized with the applied pressure F is held between the movable electrode 25 and the fixed electrode 15 in the subsequent pressurization and holding step S112.

  In the initial stage of the pressurization and holding step S111 in which the member to be welded 100 is pressed and held with the applied pressure F between the movable side electrode 25 and the fixed side electrode 15, the movable side electrode 25 and the fixed side electrode 15 are In the energization holding step S132, the energized state is maintained between the movable side electrode 25 and the fixed side electrode 15 for a preset energizing time.

  When the member to be welded 100 is pressurized by the movable side electrode 25 and the fixed side electrode 15, the thin plate 101 and the first thick plate 102 having low rigidity are bent downward, and between the thin plate 101 and the first thick plate 102 and A gap is generated between the first thick plate 102 and the second thick plate 103, and the current density between the fixed side electrode 15 and the movable side electrode 25 is higher on the second thick plate 103 side than on the thin plate 101 side. As schematically shown in (a), a nugget N is formed at the joint between the first thick plate 102 and the second thick plate 103, and the nugget N gradually increases until the thin plate 101 and the first thick plate 102 are welded. Is done. As the welding progresses, the joint between the first pressure plate 102 and the second thick plate 103 and between the first thick plate 102 and the thin plate 101 and the periphery of the joint are heated and softened, and the pressurizing force is lowered to generate the nugget N. Is suppressed.

  Thereafter, in the sub-pressurization start step S121 in the latter stage of energization, the servo motor 32 of the sub-pressurization actuator 31 is operated until the sub-pressurization setting rotational torque is reached. As a result, as shown in FIG. 8C, the thin plate 101 of the member to be welded 100 is sandwiched and pressed between the movable side electrode 25 and the fixed side electrode 15 so as to be adjacent to the fixed side electrode 15 from below. The pressurizing unit 39 is pressed to apply the sub-pressurizing force f, and is held in a stopped state for a predetermined time within the energizing time in the sub-pressurizing and holding step S122, and the sub-pressurizing unit 39 applies and holds the sub-pressurizing force f. Thereafter, the servo motor 32 is operated in the sub-pressurization releasing step S123 to move the sub-pressurization unit 39 from the sub-pressurization position to the retracted position away from the welded member 100 as shown in FIG.

  In the sub-pressurizing and holding step S122, in the state where the sub-pressurizing portion 39 applies the sub-pressurizing force f to the member 100 to be welded that has been pressed with the pressing force FL of the fixed electrode 15 and the pressing force FU of the movable electrode 25. The applied pressure FL acting on the thin plate 101 from the fixed side electrode 15 is applied by subtracting the auxiliary pressure f by the auxiliary pressure unit 39 from the pressure FU by the movable electrode 25 (FL = FU−f). . That is, by controlling the applied pressure FL from the fixed side electrode 15 acting on the thin plate 101 side to be smaller than the applied force FU of the movable side electrode 25 acting on the second thick plate 103 side (FL <FU), the thin plate 101 and the first plate 101 are controlled. The contact pressure at the joint portion of the first thick plate 102 is smaller than the contact pressure at the weld portion between the first thick plate 102 and the second thick plate 103, and relatively at the joint portion between the thin plate 101 and the first thick plate 102. The contact resistance is large and the current density is increased, so that the generation of nugget N at the joint between the thin plate 101 and the first thick plate 102 is promoted, and the joint between the thin plate 101 and the first thick plate 102 as shown in FIG. From the first thick plate 102 and the second thick plate 103, a nugget N having a diameter that gradually increases as the transition is made to the joining portion of the first thick plate 102 and the second thick plate 103 is generated.

  Thereafter, the energization to the movable side electrode 25 and the fixed side electrode 15 is terminated in the energization end step S133, and the movable side electrode 25 is moved from the pressurization position by the operation of the servo motor 21 of the pressure actuator 20 in the pressure release step S113. As shown in FIG. 8D, the member to be welded 100 is held between the fixed side electrode 15 and the movable side electrode 25 as shown in FIG. Next, the welding robot is operated according to the operation program, and the spot welding apparatus 1 is retracted from the spot position of the welded member 100 and moved to the spot position of the next welded member 100.

  According to the present embodiment configured as described above, the fixed side electrode 15 and the movable side electrode 25 are relatively large in the initial stage in which the member to be welded 100 is sandwiched and pressurized by the fixed side electrode 15 and the movable side electrode 25 and energized. By sandwiching and pressing with the applied pressure F, sufficient nugget N is generated between the first thick plate 102 and the second thick plate 103 to ensure the welding strength between the first thick plate 102 and the second thick plate 103. In the later stage, by applying the sub-pressurizing force f by the sub-pressurization 39 for a predetermined time, the generation of the nugget N at the junction between the thin plate 101 and the first thick plate 102 is promoted, and the thin plate 101 and the first thick plate The nugget N having a diameter that gradually increases as the transition from the joint with 102 to the joint between the first thick plate 102 and the second thick plate 103 is generated, and the first thick plate 102 and the second thick plate 103 are welded. Strength is obtained.

  Accordingly, the member to be welded 100 is sandwiched and pressurized by the fixed side electrode 15 and the movable side electrode 25, and energized for a predetermined time between the fixed side electrode 15 and the movable side electrode 25 to weld the member to be welded 100. A member to be welded in which plate materials having different rigidity are stacked by applying a sub-pressurizing force f by the sub-pressurizing unit 39 to the latter range for a predetermined time and controlling the pressing forces FL and FU by the fixed side electrode 15 and the movable side electrode 25. The welding quality with respect to 100 is improved.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention. For example, in the embodiment described above, the member to be welded 100 is sandwiched and pressurized by the fixed side electrode 15 and the movable side electrode 25, and the member to be welded 100 is energized for a predetermined time between the fixed side electrode 15 and the movable side electrode 25. The sub-pressurizing portion 39 applied the sub-pressurizing force f at a predetermined time within the energizing time to be welded for a predetermined time to control the pressurizing force F by the fixed side electrode 15 and the movable side electrode 25. The auxiliary pressurizing force 39 can be applied to the intermediate range excluding the initial period and the latter period by the auxiliary pressure unit 39 over a predetermined time.

1 Spot Welding Device 15 Fixed Electrode (First Welding Electrode)
20 Pressure actuator 25 Movable electrode (second welding electrode)
30 Sub-pressurizing application means 31 Sub-pressurizing actuator 39 Sub-pressurizing part 100 Member to be welded 101 Thin plate 102 First thick plate 103 Second thick plate F Pressurizing force f Subpressing pressure N Nugget

Claims (3)

A first welding electrode;
A pressure actuator that applies pressure to the second welding electrode that sandwiches the member to be welded in cooperation with the first electrode;
A sub-pressurizing actuator that abuts the sub-pressurizing portion on the member to be welded and applies a sub-pressurizing force;
The member to be welded is sandwiched and pressed with a preset pressure by the first welding electrode and the second welding electrode, and energized between the first welding electrode and the second welding electrode. A pressurization control method for a spot welding apparatus for welding by applying a preset sub-pressing force,
Within the energization time in which the first welding electrode and the second welding electrode are sandwiched and pressed by the pressurizing actuator by the first welding electrode and the second welding electrode with a preset pressure, and the first welding electrode and the second welding electrode are energized for a predetermined time. A pressurizing control method for a spot welding apparatus, wherein a subpressurizing part is brought into contact with a member to be welded for a predetermined time to apply a subpressing force by a subpressurizing actuator.   The partial predetermined time for applying a sub-pressurizing force by a sub-pressurizing actuator by abutting a sub-pressurizing portion on the member to be welded is set to an initial range within an energizing time. A pressure control method for a spot welding apparatus.   The partial predetermined time for applying a sub-pressurizing force by a sub-pressurizing actuator by abutting a sub-pressurizing portion to the welded member is set to a late range within an energization time. A pressure control method for a spot welding apparatus.

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