JP5860281B2 - Spot welding equipment - Google Patents

Description

  The present invention relates to a spot welding apparatus that spot welds a member to be welded, and more particularly to a spot welding apparatus that spot welds a member to be welded in a plate set in which plate members having different rigidity are overlapped.

  In general, spot welding in which a large current is applied between a pair of welding electrodes and a large amount of current is applied for a certain period of time is widely used for joining plate members such as stacked steel plates.

  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. 6, 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. 6A, first, a nugget N is formed at the joint between the first thick plate 102 and the second thick plate 103, and then the nugget N gradually increases as shown in FIG. 6B. The thin plate 101 and the first thick plate 102 are welded together. 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. As shown in FIG. 7, in this spot welding apparatus, a spot welding apparatus 120 is mounted on a wrist portion 116 of a welding robot 115, and the welding robot 115 is spotted at each hit point position of a member to be welded 100 supported by a clamper 118. The welding gun 120 is moved 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 with no bias is generated 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 a state where the clamp position of the member 100 to be welded by the clamper 118 and the welding position are separated from each other, the member 100 to be welded is bent and deformed, and the applied pressure FL by the fixed electrode 124 and the applied pressure FU by the movable electrode 125 vary. The stable contact resistance between the thin plate 101 and the first thick plate 102 and the contact resistance between the first thick plate 102 and the second thick plate 103 is difficult to secure, and the current density at the joint varies. There is a concern about the deterioration of the quality of spot welding.

  Accordingly, an object of the present invention made in view of such a point is to provide a spot welding apparatus capable of obtaining excellent welding quality when spot-welding a member to be welded in a plate assembly in which plate members having different rigidity are overlapped. is there.

  The invention of the spot welding apparatus according to claim 1, which achieves the above object, includes a first welding electrode and a second welding electrode that abuts the member to be welded and clamps the member to be welded in cooperation with the first welding electrode. A pressure actuator for moving the welding electrode to the welded member to apply pressure and a retracting position for moving the welding electrode away from the member to be welded, and a sub-pressurizing unit abutting the welded member to make a secondary application A sub-pressurizing position that applies pressure and a sub-pressurizing actuator that moves to a retracted position away from the member to be welded, and the member to be welded is sandwiched between the first welding electrode and the second welding electrode by the pressure actuator. A spot welding apparatus that pressurizes and applies a sub-pressurizing force by a sub-pressurizing actuator to energize the first welding electrode and the second welding electrode to weld a member to be welded. In Sub-pressurization detecting means for detecting the actual sub-pressurizing force applied, and in the operating state in which the sub-pressurizing portion is in contact with the member to be welded to apply the sub-pressurizing force, Welding control means is provided for controlling the sub-pressurizing actuator so that the sub-pressurizing force becomes the set sub-pressurizing force by the detected actual sub-pressing force and the preset sub-pressing force set in advance.

  According to this, the first welding electrode and the second welding electrode are obtained by applying the sub-pressurizing force from the sub-pressurizing portion to the member to be welded to which the pressing force is applied by the first welding electrode and the second welding electrode by the sub-pressurizing actuator. In spot welding of the welded member by controlling the applied pressure, the secondary pressure detection means detects the actual secondary pressure applied to the welded member from the secondary pressurization part and is detected by the secondary pressure detection means. The sub-pressurization actuator so that the sub-pressurization force becomes the set sub-pressurization force by the actual sub-pressurization force and the preset set sub-pressurization force, that is, the difference between the actual sub-pressurization force and the set sub-pressurization force is reduced. By controlling the above, the influence of internal mechanical loss etc. of the sub-pressurization actuator etc. is avoided, the preset high-precision sub-pressurizing force is applied, and excellent welding to the member to be welded on which plate materials with different rigidity are stacked Quality is obtained

  According to a second aspect of the present invention, in the spot welding apparatus according to the first aspect, the auxiliary pressure detection means is a load cell interposed between the auxiliary pressure unit and the auxiliary pressure actuator. To do.

  According to this, the sub-pressurization detecting means for detecting the sub-pressurizing force by the sub-pressurizing unit can be constituted by a load cell interposed between the sub-pressurizing unit and the sub-pressurizing actuator and is influenced by the sub-pressurizing actuator. Without this, the actual sub-pressurizing force of the sub-pressurizing unit can be detected by the load cell.

  According to a third aspect of the present invention, in the spot welding apparatus according to the first or second aspect, the sub-pressurizing actuator has a servo motor, and the servo motor corresponds to a sub-pressurizing force corresponding to the supplied motor current. Is applied to the sub-pressurizing section, and the welding control means sets the sub-pressurizing force by the servo motor based on the actual sub-pressing force detected by the sub-pressurizing detecting means and the preset sub-pressing force set in advance. The motor current is controlled so that

  According to this, the motor current supplied to the third motor is changed from the sub-pressurizing force by the servo motor to the set sub-pressing force based on the actual sub-pressing force detected by the sub-pressurization detecting unit and the set sub-pressing force by the welding control unit. By controlling so as to be, a preset high-precision sub-pressurizing force is applied to the member to be welded, and excellent welding quality for the member to be welded is obtained.

  According to the present invention, the first welding electrode and the second welding are applied to the member to be welded to which the pressurizing force is applied by the first welding electrode and the second welding electrode by the subpressurizing actuator from the subpressurizing portion. In spot welding of the welded member by controlling the pressure applied by the electrode, the secondary pressure detection means detects the actual secondary pressure applied to the welded member from the secondary pressure part, and the secondary pressure detection means detects it. By controlling the sub-pressurization actuator so that the sub-pressurization force becomes the set sub-pressurization force by the actual sub-pressurization force and the preset sub-pressurization force, due to internal mechanical loss etc. of the sub-pressurization actuator etc. A preset high-precision sub-pressurizing force is applied without being affected, and excellent welding quality can be obtained for a member to be welded in which plate materials having different rigidity are stacked.

It is a lineblock diagram of a spot welding device in one embodiment. It is the A section enlarged view of FIG. FIG. 2 is an explanatory diagram of a load cell arrangement structure, in which (a) is an enlarged view of a portion B in FIG. 1 and (b) is a cross-sectional view taken along the line CC in (a). It is an operation | movement outline explanatory drawing. It is arrangement | positioning structure explanatory drawing of a load cell, (a) is a principal part perspective view, (b) is the DD sectional view taken on the line of (a). 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.

  An embodiment of the present invention will be described with reference to FIGS. 1 is a configuration diagram of a spot welding apparatus, FIG. 2 is an enlarged perspective view of part A in FIG. 1, FIG. 3 is an explanatory view of an arrangement structure of a load cell, FIG. 1 (a) is an enlarged view of part B in FIG. ) Is a cross-sectional view taken along the line CC of FIG. 4A, and FIG.

  Prior to the description of the spot welding apparatus 1, the member to be welded 100 will be described. As shown in FIG. 2, the welded member 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 than the thin plate 101 and has a higher rigidity. The first thick plate 102 and the second thick plate 103 are composed of a three-layered plate set.

  The spot welding apparatus 1 has a rectangular base portion 3 attached to a wrist portion of a welding robot (not shown) via an equalizer unit, and a pair of side portions 4 bent downward from both sides of the base portion 3 and opposed to each other. The fixed arm 10, the pressure actuator 20, the sub-pressurizing application means 30, and the welding transformer 50 are attached to and supported by the support bracket 2.

  The fixed arm 10 is formed with a fixed arm main body 11 extending at a base end thereof coupled to both side portions 4 of the support bracket 2 and an electrode holding portion 12 bent in an L shape at the distal end of the fixed arm main body 11. The fixed electrode 15 as the first welding electrode is attached to the electrode holding portion 12 with the top end 15a facing upward.

  The pressurizing actuator 20 has a linear motion part 22 composed of a servo motor 21 and a ball screw feed mechanism, and the rod of the linear motion part 22 moves up and down by the operation of the servo motor 21. An electrode arm 23 is provided at the lower end of the rod of the linear motion portion 22, and is coaxial with the fixed side electrode 15 provided on the fixed arm 10 at the tip of the electrode arm 23, that is, faces the fixed side electrode 15 on the central axis L. A movable electrode 25 that is a second welding electrode is provided. Accordingly, the movable side electrode 25 cooperates with the fixed side electrode 15 by the operation of the servo motor 21 of the pressure actuator 20, and the pressurizing position where the pressing force is applied and the fixed side electrode 15. It moves along the central axis L between the retracted position that separates upward.

  The applied pressure by the movable side electrode 25 and the fixed side electrode 15 is determined by the rotational torque of the servo motor 21, and the desired applied pressure can be obtained by controlling the rotational torque of the servo motor 21. That is, when the member to be welded 100 is sandwiched between the movable side electrode 25 and the fixed side electrode 15 by the downward movement of the movable side electrode 25 by the servo motor 21, the load on the servo motor 21 increases and flows to the servo motor 21. Motor current rises. Then, when the motor current rises to the set current value set in accordance with the desired set pressing force, the welding controller 51 serving as a welding control means to be described later regulates the further increase in the motor current to control the member to be welded 100. Pressurization can be performed with a set pressure.

  The sub-pressurizing application means 30 is a straight motor constituted by a servo motor 32 attached to a substrate 6 provided on a U-shaped attachment bracket 5 having both ends coupled to both side portions 4 of the support bracket 2 and a ball screw feed mechanism. The actuator 34 has a sub-pressurizing application actuator 31 having a moving portion 33, and the rod 34 of the linear motion portion 33 moves up and down by the operation of the servo motor 32, and a load cell 40 that is a sub-pressure detecting means is attached to the tip of the rod 34. A movable shaft 35 is provided.

  The movable shaft 35 includes a pair of sub movable shafts 35a and 35b arranged to face the tip, and a sub pressure applying arm 36 is provided at the tip of the sub movable shafts 35a and 35b. The sub-pressurizing application arm 36 includes a base end arm portion 37 extending in a substantially horizontal direction with base end portions coupled to the front ends of the sub movable shafts 35 a and 35 b, and a base end portion at the front end portion of the base end arm portion 37. Are coupled to each other, and the arm portion 38 extends downward in the axial direction of the fixed electrode 15, that is, in the direction of the central axis L. A sub-pressurizing portion 39 is provided at the tip of the arm portion 38.

  The sub-pressurizing portion 39 has a rectangular plate shape whose base end portion is coupled to the lower mounting flange portion 38A of the arm portion 38 by a bolt and extends in the direction of the central axis L, and is coaxial with the central axis L at the tip. Thus, a contact part 39a having a semicircular cross section that allows the fixed electrode 15 to pass therethrough, that is, a half cylinder, is provided.

  FIG. 3 shows an arrangement structure of the load cell 40. 3A is an enlarged view of a portion B in FIG. 1, and FIG. 3B is a cross-sectional view taken along the line CC in FIG.

  The load cell 40 has a cylindrical shape having an upper surface 40a and a lower surface 40b, and is provided with a screw shaft shape, that is, a bolt-shaped upper shaft 41A that projects coaxially with the central axis L at the center portion of the upper surface 40a. A lower shaft 41B having a screw shaft shape that projects coaxially with the central axis L is provided at the portion.

  On the other hand, a cylindrical shaft accommodating portion 42 that allows insertion of the upper shaft 41A provided in the load cell 40 is formed at the lower end of the rod 34 of the linear motion portion 33, and the upper shaft 41A is screwed into the tip of the rod 34. A fixing nut 43 having a screw hole 43a is provided. A fixing nut in which a shaft accommodating portion 44 into which the lower shaft 41B of the load cell 40 is inserted is formed at the upper end of the movable shaft 35, and a screw hole 45a into which the lower shaft 41B is screwed into the distal end of the movable shaft 35. 45 is provided.

  The upper shaft 41A and the lower shaft 41B provided on the load cell 40 are screwed and fastened to the fixing nut 43 provided on the rod 34 and the fixing nut 45 provided on the movable shaft 35, respectively. A load cell 40 is arranged between

  The sub-pressurizing application arm 36 configured in this way is a contact portion of the sub-pressurizing unit 39 from below on the member to be welded 100 sandwiched between the fixed side electrode 15 and the movable side electrode 25 by the operation of the servo motor 32. A sub-pressurizing position where 39a abuts to apply the sub-pressurizing force f, and a retreat position where the abutting portion 39a of the sub-pressurizing portion 39 is below the top end 15a of the fixed electrode 15 and separates from the welded member 100. Move along the central axis L.

  The sub-pressurizing force by the sub-pressurizing unit 39 can be obtained by controlling the rotational torque of the servo motor 32. That is, when the sub-pressurizing unit 39 comes into contact with the member to be welded 100 by the upward movement of the sub-pressurizing unit 39 by the servomotor 32, the load on the servomotor 32 increases and the motor current flowing through the servomotor 32 increases. Then, the motor current is feedback-controlled so that the difference between the actual applied pressure detected by the load cell 40 by the welding controller 51, that is, the so-called actual auxiliary applied pressure and a preset desired auxiliary applied pressure is reduced.

  That is, the operation of the servo motor 32 moves the auxiliary pressure portion 39 from the retracted position to the auxiliary pressure position where the contact portion 39a contacts the welded member 100, and further activates the servo motor 32 to activate the auxiliary pressure portion 39. When the secondary pressurizing force is applied to the member to be welded 100 and a secondary pressurizing force is generated, a reaction force of the secondary pressurizing force that is actually applied to the welded member 100 by the secondary pressurizing unit 39, a so-called actual secondary pressurizing force is applied to the load cell 40 by the movable shaft 35. To enter. Here, the load cell 40 generates an electric charge proportional to the amount of increase in the applied pressure, and the change in the output voltage is measured as an actual auxiliary pressure, and the change in the output voltage is measured by the welding controller 51 as the auxiliary pressure detection signal. By controlling the motor current supplied to the servomotor 32, the sub-pressurizing force applied to the welded member 100 from the sub-pressurizing unit 39 can be adjusted. Specifically, when the actual auxiliary pressure detected by the load cell 40 is smaller than a preset set pressure, the motor current flowing to the servo motor 32 is increased by the welding controller 51 to increase the rotational torque of the servo motor 32. The sub-pressurizing unit 39 increases the sub-pressurizing force f, and when the actual sub-pressurizing force is larger than the set sub-pressurizing force, the motor current flowing to the servomotor 32 is decreased to reduce the rotational torque of the servomotor 32 and to subpressurize. The auxiliary pressure f by the portion 39 is decreased.

  One output terminal of the welding transformer 50 serving as a power source is connected to the fixed side electrode 15 through the bus bar and the fixed arm 10 so as to be energized, and the other output terminal is connected to the movable side electrode 25 through the bus bar and the electrode arm 23 and the like. Is connected to be energized.

  Further, the welding controller 51 is provided. The welding controller 51 includes an operation program for the spot welding apparatus 1 and a pressurization control unit 52 that controls the pressurization actuator 20 based on each operation stroke set in the operation program, and a sub-pressurization actuator. A sub-pressurization control unit 53 for controlling 31 is included. Further, the welding controller 51 controls the servo motor 32 by comparing the sub pressure detection signal from the load cell 40 with a preset sub pressure. That is, by controlling the motor current flowing through the servo motor 32 according to the sub pressure detected by the load cell 40, the sub pressure can be controlled to be a preset sub pressure.

  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. A welding controller (not shown) includes an operation program for the welding apparatus 1 and a pressure actuator 20, a control pressure applying means 30, and an operation control for the welding transformer 50.

  Next, the operation of the spot welding apparatus 1 will be described with reference to the operation outline explanatory diagram of FIG.

  In spot welding of the member to be welded 100, according to a preset program, the movable side electrode 25 is at the retracted position where it is separated from the fixed side electrode 15, and the sub-pressurizing portion 39 of the sub-pressurizing application means 30 is held at the retracted position. In this state, the robot controller operates the welding robot to bring the top end 15a of the fixed side electrode 15 into contact with the striking position as the welding position of the member to be welded 100 as shown in FIG. Positioning.

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

  Next, as shown in FIG. 4B, the movable side electrode 25 is retracted by the operation of the servo motor 21 of the pressure actuator 20 with the fixed side electrode 15 in contact with the thin plate 101 of the member to be welded 100. From the upper side, the second thick plate 103 is brought into contact with the second thick plate 103 by moving in the direction of the pressurizing position approaching the fixed side electrode 15. Further, the servo motor 21 is operated until a predetermined torque is reached, and the movable electrode 25 is pressed against the second thick plate 103. That is, when the load of the servo motor 21 increases and the motor current flowing through the servo motor 21 rises to the set current value set in accordance with the set pressure, further increase of the motor current is restricted. As a result, the pressure applied by the pressure actuator 20 acts on the fixed side electrode 15 via the movable side electrode 25 and the fixed arm 10, and the movable side electrode 25 and the fixed side electrode 15 hold the welded portion of the member to be welded 100. And pressurize.

  On the other hand, the sub-pressurizing portion 39 by the operation of the servo motor 32 of the sub-pressurizing application means 30 is brought into contact with the thin plate 101 of the member to be welded 100 adjacent to the fixed electrode 15 from the retracted position. Move to position. Further, the servo motor 32 is operated to increase the sub-pressurizing force f that presses the sub-pressurizing portion 39 against the thin plate 101. Here, when the sub-pressurizing part 39 is pressed against the member 100 to be welded and a sub-pressurizing force f is generated, the sub-pressurizing part 39 is movable via the sub-pressurizing part 39 and the sub-pressurizing application arm 36 by the reaction force of the sub-pressurizing force f. A pressing force corresponding to the actual sub pressing force is input from the shaft 35 to the load cell 40. The load cell 40 generates a charge proportional to the amount of increase in the applied pressure, measures the change in the output voltage as an actual auxiliary pressure, and controls the servo motor 32 using the output voltage change as the auxiliary pressure detection signal. Thus, the sub-pressurizing force f applied to the welded member 100 from the sub-pressurizing unit 39 is controlled. That is, when the actual auxiliary pressure detected by the load cell 40 is smaller than the preset auxiliary pressure, the welding controller 51 increases the motor current flowing through the servo motor 32 to increase the rotational torque of the servo motor 32 and increase the auxiliary torque. When the sub-pressing force f by the pressurizing unit 39 is increased and the actual sub-pressing force is larger than the set sub-pressing force, the motor current flowing through the servo motor 32 is decreased to reduce the rotational torque of the servo motor 32 and the sub-pressurizing unit. The auxiliary pressure f by 39 is decreased. The auxiliary pressure f is set by directly detecting the reaction force of the auxiliary pressure unit 39 by the load cell 40 and controlling the servo motor 32. The mechanical resistance of the servo motor 32 and the ball screw mechanism of the linear motion unit or the like is set. That is, a preset high-precision sub-pressurizing force is applied without being affected by internal mechanical loss or the like.

  In this state, the member 100 to be welded is sandwiched and pressed by the fixed side electrode 15 and the movable side electrode 25, and the sub-pressurizing portion 38 is applied to the thin plate 101 adjacent to the fixed side electrode 15 from the lower side. As shown in FIG. 5 (c), a pressing force FU by the movable side electrode 25 is applied to the second thick plate 103 of the member to be welded 100 from above, and the pressing force FL by the fixed side electrode 15 and the sub pressurizing part 39. Is applied to the thin plate 101 adjacently.

  In this case, the pressure applied by the pressure actuator 20 acts on the movable side electrode 25 via the electrode arm 23 and the like, and acts on the fixed side electrode 15 via the fixed arm 10 so as to face the movable side electrode 25. In the auxiliary pressure applying means 30, the urging force of the servo motor 32 acts on the auxiliary pressure applying portion 39 via the auxiliary pressure applying arm 35 and the like, and the applied pressure by the movable side electrode 25 acting on the second thick plate 103 from above. The sum of the pressing force FL by the fixed side electrode 15 acting on the thin plate 101 from below and the sub pressing force f by the sub pressurizing unit 39 is equal (FU = FL + f).

  As a result, the member to be welded 100 has a pressing force FU of the movable side electrode 25 acting on the second thick plate 103 side from above, and a pressing force FL and a sub-pressing force of the fixed side electrode 15 acting on the thin plate 101 side from below. It is held and held in a stable state by the auxiliary pressure f of the portion 39.

  On the other hand, a pressure FU is applied to the second thick plate 103 from the movable side electrode 25 and a pressure FL of the fixed side electrode 15 is applied to the thin plate 101 to the welded portion of the member 100 to be welded, and a sub-pressurization unit. Since the auxiliary pressure f is applied from 39, the applied pressure FL acting on the thin plate 101 from the fixed electrode 15 is obtained by subtracting the auxiliary pressure f of the auxiliary pressure unit 39 from the applied pressure FU of the movable electrode 25. A pressing force is applied (FL = FU−f).

  In this way, the pressing force FL from the fixed electrode 15 acting on the thin plate 101 side is made smaller (FL <FU) than the pressing force FU of the movable electrode 25 acting on the second thick plate 103 side, so that the thin plate 101 and The contact pressure at the joint of the first thick plate 102 is smaller than the contact pressure at the weld between the first thick plate 102 and the second thick plate 103, and the contact resistance between the thin plate 101 and the first thick plate 102 is relatively large. Increases and the contact resistance between the first thick plate 102 and the second thick plate 103 decreases.

  Next, the member 100 to be welded is sandwiched and pressed by the movable side electrode 25, the fixed side electrode 15 and the sub-pressurizing portion 39, and the pressing force FL of the fixed side electrode 15 located on the thin plate 101 side is changed to the second thick plate 103 side. In a state where the pressure is less than the pressure FU of the movable side electrode 25 positioned at the position, the welding transformer 50 is energized and welded to the movable side electrode 25 and the fixed side electrode 15 for a predetermined time.

  When the movable side electrode 25 and the fixed side electrode 15 are energized, the contact resistance at the joint between the thin plate 101 and the first thick plate 102 is relatively large and the current density is increased. The contact resistance between the two thick plates 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. A good nugget with no uneven current density is formed over the thick plate 103, and the welding strength of the thin plate 101 can be ensured.

  Thereafter, the energization of the movable side electrode 25 and the fixed side electrode 15 is terminated, and the operation of the servo motor 21 of the pressure actuator 20 moves the movable side electrode 25 from the pressure position to the retracted position. The clamping of the member 100 to be welded by the movable electrode 25 is released, and the sub-pressurizing unit 39 is retracted from the sub-pressurizing position to the retracted position by the operation of the servo motor 32 of the sub-pressurizing actuator 31. 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 sub-pressurizing portion 39 applies the sub-pressurizing force f to the welded member 100 to which the pressurizing force is applied by the fixed-side electrode 15 and the movable-side electrode 25. Is applied between the sub-pressurizing actuator 31 and the sub-pressurizing portion 39 when spot welding the member 100 to be welded by controlling the applied pressures FL and FU by the fixed-side electrode 15 and the fixed-side electrode 25. The actual sub-pressurizing force applied to the welded member 100 from the sub-pressurizing unit 39 is detected by the load cell 40, and the actual sub-pressing force detected by the load cell 40 is compared with the preset sub-pressing force. By controlling the sub pressurizing force by the pressurizing actuator 31 to be the set subpressing force, there is no influence by internal mechanical loss of the sub pressurizing actuator 31 and the like, and a preset high pressure is applied. Each time sub-pressure f is applied to, excellent weld quality with respect to the welding member of repeated different plate rigidity is obtained.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of invention. For example, another example of the mounting structure of the load cell 40 disposed between the rod 34 of the linear motion portion 33 and the movable shaft 35 in the above embodiment will be described with reference to FIG.

  Fig.5 (a) is a perspective view which shows an outline | summary, (b) is the DD sectional view taken on the line of (a). An upper flange 46A in which a plurality of mounting holes 46Aa are perforated and a lower flange 46B in which a plurality of mounting holes 46Ba are perforated are provided on the upper surface 40a and the lower surface 40b of the cylindrical load cell 40.

  On the other hand, an upper mounting flange 47 in which a plurality of mounting holes 47a are formed in a plate shape is provided at the lower end of the rod 34 of the linear motion portion 33, and a plurality of mounting holes 48a are formed in a plate shape in the upper end of the movable shaft 36. A lower mounting flange 48 is provided.

  The upper flange 46A provided on the load cell 40 is superposed on the upper attachment flange 47 provided on the rod 34 and fastened by bolts 49a and nuts 49b inserted into the attachment holes 47a and 46Aa. Similarly, a lower flange 46B provided on the load cell 40 is overlapped with a lower attachment flange 48 provided on the movable shaft 36 and fastened by a bolt 49a and a nut 49b inserted into the attachment holes 48a and 46Ba. In this way, the load cell 40 disposed between the rod 34 and the movable shaft 36 has a reaction force from the sub-pressurizing unit 39, that is, an actual sub-pressurizing force, and a lower mounting flange 48 provided on the movable shaft 36 and Input to the load cell 40 via the lower flange 46B.

  Further, for example, in the above embodiment, the load cell 40 is disposed between the rod 34 of the linear motion portion 33 and the movable shaft 35. It can be disposed between the pressure unit 39 and the sub-pressure applying arm 36. Moreover, it can replace with the load cell 40 and subloading detection means, such as another load cell, can also be used.

DESCRIPTION OF SYMBOLS 1 Spot welding apparatus 10 Fixed arm 15 Fixed side electrode (1st welding electrode)
20 Pressurizing Actuator 21 Servo Motor 22 Linear Motion Part 23 Electrode Arm 25 Movable Side Electrode (Second Welding Electrode)
30 Sub-pressure applying means 31 Sub-pressure applying actuator 32 Servo motor 33 Linear motion part 34 Rod 35 Movable shaft 36 Sub-pressure applying arm 39 Sub-pressure part 40 Load cell (sub-pressure detecting means)
51 Welding controller (welding control means)

Claims (3)

A first welding electrode;
A pressurizing position where the second welding electrode which contacts the member to be welded and cooperates with the first welding electrode to clamp the member to be welded contacts the member to be welded to apply pressure is separated from the member to be welded. A pressure actuator that is moved to a retracted position,
A sub-pressurizing portion that abuts the sub-pressurizing portion on the member to be welded to apply a sub-pressurizing force, and a sub-pressurizing actuator that moves the sub-pressurizing portion to a retracted position away from the member to be welded.
The member to be welded is clamped and pressed by the first welding electrode and the second welding electrode by the pressurizing actuator, and the first welding electrode and the second welding electrode are energized by applying the sub-pressurizing force by the sub-pressurizing actuator. A spot welding apparatus for welding a member to be welded,
Having a sub-pressurization detecting means for detecting an actual sub-pressurizing force applied to the member to be welded from the sub-pressurizing portion;
In an operating state in which the sub-pressurizing unit is in contact with the member to be welded and a sub-pressurizing force is applied, a sub-pressurizing force is detected by an actual sub-pressing force detected by the sub-pressurizing detecting means and a preset sub-pressurizing force. A spot welding apparatus comprising welding control means for controlling a sub-pressurizing actuator so that the pressure becomes a set sub-pressurizing force.   The spot welding apparatus according to claim 1, wherein the sub-pressurization detecting means is a load cell interposed between the sub-pressurization unit and the sub-pressurization actuator. The sub-pressurizing actuator has a servo motor, and the servo motor applies a sub-pressurizing force corresponding to the supplied motor current to the sub-pressurizing unit,
The welding control means controls the motor current so that the sub pressure applied by the servo motor becomes the set sub pressure by the actual sub pressure detected by the sub pressure detection means and a preset set sub pressure. The spot welding apparatus according to claim 1 or 2, wherein

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