JP6544822B2 - One side spot welding apparatus and one side spot welding method - Google Patents

Description

  The present invention relates to a one-sided spot welding apparatus and a one-sided spot welding method in which a welding electrode is pressed against one surface of a workpiece to be welded and a ground electrode is pressed against a position different from the position facing the welding electrode to perform spot welding. .

  2. Description of the Related Art Direct spot welding is known, in which a workpiece to be welded consisting of a plurality of superposed plate members is sandwiched between a welding electrode and an earth electrode, and current is applied in a plate thickness direction to apply welding. In addition, in the case of forming a work to be welded by superimposing a plurality of press-formed panels, such as a car body (vehicle body), etc., it is possible to use a welding electrode and an earth electrode for reasons of vehicle design and function. In many cases, a portion where it is difficult to hold the work to be welded is formed. In such a case, one-sided spot welding is often employed in which the welding electrode is pressed to a predetermined hitting point position, and the earth electrode is pressed against a position different from the welding electrode for joining.

  For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2012-76144), an earth electrode to be pressed against the back surface of a work to be welded is supported swingably with respect to a shaft portion, and this shaft portion is a tip of a robot arm. A technique is disclosed which is connected to the cylinder unit provided in.

  In the technique disclosed in this document, since the ground electrode is swingably supported by the shaft portion, when the cylinder unit is made to project and the ground electrode is pressed against the work, the ground follows the surface shape of the work. The electrode is inclined, and the earth electrode can be brought into contact with the work always in the correct posture.

JP 2012-76144 A

  However, in the case of a workpiece that is bent or formed into a complicated shape like an automobile body or has a step difference, it is difficult to correctly press the ground electrode against the workpiece surface, resulting in an increase in electrical resistance or contact failure. There is a disadvantage that occurs. Therefore, a shift mechanism is required to move the ground electrode to an optimum ground point according to the workpiece shape, which results in an increase in equipment cost.

  In addition, when the ground electrode is a copper mesh wire braided with a copper wire, the ground electrode can be deformed according to the shape of the work surface when pressed against the work surface. However, continuous use of the copper mesh wire tends to cause a setback, and in order to ensure good deformability always along the workpiece shape, it is necessary to shorten the earth electrode replacement cycle for a short time. There is a disadvantage that the cost is high.

  In view of the above circumstances, the present invention does not require a shift mechanism for moving the ground electrode to the optimum spot point, and even if the ground electrode is deformed according to the surface shape of the work, it is difficult to cause setback and replacement cycle One-sided spot welding apparatus and one-sided spot welding that can reduce the running cost and can always set the resistance value between the ground electrode and the work surface to an appropriate value. Intended to provide a method.

  According to the first aspect of the present invention, a welding electrode is pressed against a welding portion set to a work to be welded formed by superimposing a plurality of plate members, and an earth electrode body is pressed against a position different from the welding portion. In the single-sided spot welding apparatus for spot welding the welding portion, the ground electrode pressing unit for injecting a fluid into the ground electrode assembly is provided, and the ground electrode assembly is formed by the fluid injected from the ground electrode pressing unit. A bulging bulging member, and a deformable earth electrode member which is coated on the outer surface of the bulging member and is pressed against the workpiece to be welded following the bulging of the bulging member.

  According to a second aspect of the present invention, a welding electrode is pressed against a welding portion set to a work to be welded formed by superimposing a plurality of plate members, and an earth electrode body is pressed against a position different from the welding portion. In the one-side spot welding method for spot welding the welding portion, a fluid is injected into a bulging member provided on the ground electrode body to cause the bulging member to bulge and ground the outer periphery of the bulging member The first step of pressing the electrode member against the work to be welded, and the lower limit pressure value of the fluid set in advance when the pressure of the ground electrode member is pressed against the work to be welded by the expansion of the bulging member And a second step of starting the spot welding operation.

  According to a third aspect of the present invention, a welding electrode is pressed against a welding portion set to a work to be welded formed by superimposing a plurality of plate members, and an earth electrode body is pressed against a position different from the welding portion. In the one-side spot welding method for spot welding the welding portion, a target pressure of a fluid injected into a bulging member provided in the earth electrode body, a hit point position where the welding electrode of the work to be welded contacts, and the earth electrode A third step of obtaining based on the current-carrying distance to the contact position, and injecting a fluid into the bulging member provided on the earth electrode body to cause the bulging member to be bulging out, and the outer surface of the bulging member A fourth step of pressing the coated ground electrode member against the workpiece to be welded, and a fifth step of starting a spot welding operation after the fluid pressure injected into the bulging member reaches the target pressure.

  According to the present invention, the earth electrode body to be pressed against the work to be welded is covered with the expansion member which can expand by the fluid injected from the earth electrode pressing unit and the outer surface of the expansion member, and expansion is performed. Since the deformable earth electrode member is configured to be in pressure contact with the work to be welded following the expansion of the member, when the expansion member is expanded to press the ground electrode member against the work to be welded, Since the ground electrode member deforms in accordance with the surface shape of the work to be welded, a shift mechanism for moving to the optimum ground point is not necessary, and the equipment cost can be reduced.

  In addition, since the bulging member is bulging by the fluid injected from the earth electrode pressurizing unit, the aging stagnation does not easily occur, so that the earth electrode body replacement cycle can be extended, and the running cost can be reduced. Can be Furthermore, by adjusting the pressure of the fluid that causes the bulging member to expand, the pressure at the time of pressing the ground electrode member against the work to be welded can be variably set. Therefore, between the ground electrode member and the work surface The resistance between them can always be set to an appropriate value.

A schematic plan view of the one-side spot welding apparatus provided in the welding process of a car body assembly line according to the first embodiment Also, a schematic configuration diagram of the ground electrode pressing unit provided in the one side spot welding apparatus Same, cross-sectional plan view of earth electrode contact body The same, (a) is a cross-sectional view of the ground electrode contact body at the time of pressure reduction, (b) is a cross-sectional view of the ground electrode contact body at the time of pressurization Same as the construction diagram of earth electrode pressure control system Flow chart showing the same ground electrode pressure setting routine Similarly, a characteristic diagram showing the relationship between the fluid pressure pressing the ground electrode network against the vehicle body and the resistance value of the contact surface The schematic block diagram of the earth electrode pressurizing unit provided in the one-side spot welding apparatus according to the second embodiment Flow chart showing the same ground electrode pressure setting routine

  Hereinafter, an embodiment of the present invention will be described based on the drawings.

First Embodiment
1 to 7 show a first embodiment of the present invention. FIG. 1 shows a body assembly line 1 provided in the middle of a vehicle assembly line. In the body assembly line 1, a vehicle body W as a work to be welded which is configured by overlapping a plurality of plate members (panels) press-formed in a predetermined manner is mainly joined by spot welding. A transport conveyor 2 such as a chain conveyor extending to the front and rear work lines is penetrated in the body assembly line 1, and a vehicle body W is mounted on the transport conveyor 2.

  In addition, a pair of line blocks 3 are disposed opposite to each other on both sides of the body assembly line 1. The line block 3 is disposed along the moving direction of the body assembly line 1, and as shown in FIG. 2, a step 3a is formed at a predetermined depth on the upper surface of the opposing surface. .

  Furthermore, a single-sided spot welding device 11 is disposed in the body assembly line 1. The one-side spot welding apparatus 11 includes a welding electrode 12, an earth electrode body 13, and an earth electrode pressing unit 14.

  The welding electrodes 12 are attached to the end of the robot arm 5 a of each welding robot 5 installed on both sides of the body assembly line 1. Further, a predetermined distance is provided between the inner wall of the stepped portion 3a formed on the line block 3 and the opposing surface of the vehicle body W, and the ground electrode body 13 is disposed on the stepped portion 3a. The pair of ground electrode bodies 13 are disposed opposite to each other on the left and right line blocks 3, but only one is disposed in either one of them, or three or more as shown by a broken line in FIG. It may be done. However, in the present embodiment, it is assumed that the ground electrode body 13 is disposed as a left-right pair.

  As shown in FIGS. 1 and 2, on the inner surface of the stepped portion 3a facing the ground electrode body 13, a support member 4 formed of a material having electrical insulation and heat resistance such as ceramic is laid. There is. As shown in FIG. 3, the ground electrode body 13 has a pressure bag 13a as a bulging member and a ground electrode network 13b as a ground electrode member coated on the outer surface of the pressure bag 13a. There is.

  The pressure bag 13a is formed of a material having high stretchability and heat resistance, such as silicone rubber, in a state in which the sealability is maintained. Further, the ground electrode network 13b is formed in a net shape by braiding wires having high conductivity such as copper wires, aluminum wires, etc., and in a state covered with the pressure bag 13a, expansion and contraction of the pressure bag 13a It is made deformable corresponding to

  Further, as shown in FIG. 2, the ground electrode pressurizing unit 14 injects a fluid such as water, oil or the like stored in the storage tank 15 into the pressure bag 13 a, whereby the ground electrode network 13 b for the vehicle body W is Control the pressing pressure of A branch passage 19a and a drain passage 20a, which will be described later, are connected to the pressure bags 13a, respectively. Furthermore, an earth wire 13c is connected to the earth electrode network 13b, and a welding current conduction path is formed by bringing the earth electrode network 13b and the welding electrode 12 into contact with the vehicle body W.

  Hereinafter, the configuration of the ground electrode pressurizing unit 14 will be specifically described. The suction port side of the electric pump 16 faces the storage tank 15 in which fluid such as water is stored via the suction passage 17a, and the feed passage 17b communicating with the discharge side of the electric pump 16 has an electromagnetic switching valve. The pressure supply passage 19 is in communication with the pressure supply passage 18.

  The electromagnetic switching valve 18 selectively causes the pressure supply passage 19 to communicate with the supply passage 17 b and the drain passage 20 a facing the storage tank 15. The drive signal is turned on / off. Note that FIG. 2 shows the electromagnetic switching valve 18 in the OFF state, and in this state, the pressure supply passage 19 is in communication with the drain passage 20a. On the other hand, when the electromagnetic switching valve 18 is turned on, the feed passage 17b and the pressure supply passage 19 are communicated.

  Further, pressure bags 13a provided on the ground electrode body 13 are in communication with the pressure supply passage 19 via the branch passages 19a. Further, the upstream side of the relief passage 20b is communicated with each pressurizing bag 13a, and the downstream side of each relief passage 20b is gathered and exposed to the storage tank 15. Furthermore, a relief valve 21 that forcibly drains when the fluid pressure P exceeds a preset relief pressure Pr (see FIG. 7) is interposed in each relief passage 20b. Further, a pressure sensor 22 is exposed to the pressure supply passage 19. The parameters detected by the information input means 23 represented by the pressure sensor 22 are read by the electrode pressure control unit 31.

  The electrode pressure control unit 31 is mainly composed of a well-known microcomputer, and as shown in FIG. 5, the information input means 23 and the control panel 24 are connected to the input side, and an electric motor is connected to the output side. The pump 16, the electromagnetic switching valve 18, and the display board 25 are connected. Furthermore, the robot control unit 36 that controls the welding robot 5 is connected to be capable of bi-directional communication.

  The operation panel 24 is provided with a power switch or the like for turning on / off the one-side spot welding apparatus 11. In addition, a display unit 25 displays a vehicle number or the like indicating the type of the vehicle body W, lights up when the fluid pressure supplied to the ground electrode body 13 reaches a set pressure, or the lighting color changes from red to green The lamp etc. which show the pressurization state of the fluid, etc. are arrange | positioned by changing. The information input means 23 includes, in addition to the pressure sensor 22, position detection means and the like including a phototube sensor or the like for detecting a state in which the vehicle body W is carried into the body assembly line 1 and stopped at a fixed position.

  When the vehicle body W is carried into the body assembly line 1 and stopped at a fixed position, the electrode pressure control unit 31 first injects a fluid into the pressure bag 13a of the ground electrode body 13 and causes it to bulge and coat the outer surface The pressed ground electrode network 13b is pressed against the vehicle body W, and then spot welding by the welding robot 5 is started.

  Specifically, the control operation of pressing the ground electrode network 13b to the vehicle body W executed by the electrode pressure control unit 31 is performed according to a ground electrode pressure setting routine shown in FIG.

  In this routine, first, in step S1, based on the position detection signal from the position detection means, etc., the vehicle body W stands by until it is carried into the body assembly line 1 and stopped at a fixed position. Then, when it is detected that the vehicle body W is stopped at the fixed position in the body assembly line 1, the process proceeds to step S2, and after the electric pump 16 is turned on, the electromagnetic switching valve 18 is turned on in step S3. Let

  Then, a fluid such as water or oil stored in the storage tank 15 is sucked by the drive of the electric pump 16, and the feed passage connected to the discharge side of the electric pump 16 by the ON operation of the electromagnetic switching valve 18 The pressure supply passage 19 is in communication with the pressure supply passage 17 b. As a result, the fluid sucked up by the electric pump 16 flows into the pressure supply passage 19 through the electromagnetic switching valve 18, and is supplied to the pressure bag 13a of the ground electrode body 13 through each branch passage 19a. The processing in step S3 corresponds to the first step of the present invention.

  The ground electrode body 13 is disposed between the step portion 3a of the line block 3 disposed on both sides of the body assembly line 1 and the vehicle body W, and when fluid is supplied to the pressure bag 13a, It gradually bulges out from the contracted state shown in FIG. Then, as shown in FIG. 6B, the ground electrode body 13 is pressed against the support member 4 fixed to the line block 3, and the reaction force presses the vehicle body W to cover the outer surface. The ground electrode network 13 b is in pressure contact with the vehicle body W. Since earth electrode body 13 is deformable, the earth point (the position where earth electrode body 13 contacts) of vehicle body W has a curved surface or when it bulges even if a step is formed. In order to be deformed according to the surface shape of the vehicle body W, contact failure or insufficient contact area does not occur.

  Next, the process proceeds to step S4, the fluid pressure P supplied to the pressure supply passage 19 detected by the pressure sensor 22 is detected, and compared with a preset pressurization lower limit value P0. Then, the process waits until the fluid pressure P becomes equal to or higher than the preset pressurization lower limit value P0, and when P0 ≧ P, the process proceeds to step S5.

  As shown in FIG. 7, for example, a vehicle body W is formed by joining two sheets of a first welded panel W1 and a second welded panel W2 and is a welding point position which is a welding portion of the first welded panel W1. When the tip of the welding electrode 12 is pressed against and the ground electrode network 13b of the ground electrode body 13 is pressed against the second welded panel W2, the joint between the panels W1 and W2 is properly welded. The resistance value R1 of the contact surface between the welding electrode 12 and the first welded panel W1 and the second welded panel W2 and the ground electrode body 13 are provided in comparison with the resistance value R0 of the joint portion. It is necessary to adjust the resistance value R2 of the contact surface with the ground electrode network 13b to a low value.

  Here, the resistance value R1 can be easily adjusted by the pressure applied to the first welded panel W1 of the welding electrode 12. On the other hand, resistance value R2 is adjusted with the pressing force with respect to the 2nd to-be-welded panel W2 of earth electrode network 13b. The characteristic values shown in FIG. 7 indicate changes in the fluid pressure P applied to the pressure bag 13a and the resistance value R2, and the resistance value R2 increases as the fluid pressure P applied to the pressure bag 13a increases. The curve decreases in inverse proportion.

  Therefore, in the present embodiment, the fluid pressure P at which the resistance value R2 is equal to the resistance value R0 is obtained from simulation or the like, and this is set as the pressurization lower limit value P0. When the fluid pressure P exceeds the relief pressure Pr, the relief valve 21 is opened, excess fluid passes through the relief passage 20b, is reduced to the storage tank 15, and the pressure is adjusted. Therefore, the welding operation by the welding robot 5 described later is performed in a state where the fluid pressure P is between the pressurization lower limit value P0 and the relief pressure Pr. Thereafter, the process proceeds to step S5, a welding operation start signal is transmitted to the robot control unit 36, and the welding operation is started. The processes in steps S4 and S5 correspond to the second process of the present invention.

  Then, the robot arm 5a of each welding robot 5 standing by at the standby position is operated, and the welding electrode 12 attached to the tip is pressed against the predetermined hit point position of the vehicle body W with a predetermined pressure. , Start spot welding work. Next, the process proceeds to step S6, and it is checked whether the welding operation by all the welding robots 5 is completed. For example, it is determined based on the welding end signal from the robot control unit 36 whether the welding operation is completed.

  Then, if the welding operation is not completed, the process returns to step S5, and the welding operation is continued. On the other hand, when spot welding by all the welding robots 5 is finished in a predetermined manner, the process proceeds to step S7, the electromagnetic switching valve 18 is turned off, and the electric pump 16 is turned off in step S8 to end the routine. . When the welding operation is completed, each welding robot 5 returns the robot arm 5a to a preset standby position to prepare for the next welding operation.

  Further, when the electromagnetic switching valve 18 is turned OFF, the upstream side of the pressure supply passage 19 is in communication with the drain passage 20a, so the fluid in the pressure bag 13a is pressure supplied by the contraction pressure of the pressure bag 13a. And is reduced to the storage tank 15 through the drain passage 20a. Then, the ground electrode body 13 is contracted from the state of pressing the support member 4 and the vehicle body W shown in FIG. 4B, and as shown in FIG. 4A, the support member 4 and the vehicle body It is separated from W. In this case, the ground electrode body 13 may be fixed on the support member 4 side and may be separated only from the vehicle body W side.

  As described above, in the present embodiment, the ground electrode body 13 is constituted by the stretchable pressure bag 13a and the ground electrode network 13b covering the outer surface, and the fluid is supplied to the pressure bag 13a. The ground electrode network 13b is brought into pressure contact with the vehicle body W by bulging, and moreover, since the ground electrode body 13 is made deformable according to the surface shape of the vehicle body W, the type of the ground electrode is made There is no need to move to the most suitable earth point. As a result, the conventional shift mechanism becomes unnecessary, and the equipment cost can be reduced.

  Further, since the earth electrode body 13 is expanded by supplying a fluid to the pressure bag 13a, the earth electrode body 13 can be operated intermittently even if the earth electrode pressurization unit 14 is operated intermittently for a long time. As a result, it is possible to reduce the running cost and to obtain high reliability.

  Further, by adjusting the fluid pressure P supplied to the pressure bag 13a, the resistance value R2 between the ground electrode network 13b and the vehicle body W can be always maintained in an appropriate range. In the spot welding operation, a fluid such as water or oil is always supplied to the pressurizing bag 13a, and the fluid pressure P is circulated when it exceeds the relief pressure Pr, so that the earth electrode network 13b is cooled by this fluid. Since the heating can be suppressed, the durability of the ground electrode body 13 can be enhanced.

Second Embodiment
8 and 9 show a second embodiment of the present invention. In the first embodiment described above, the fluid pressure P supplied to the pressure bag 13a provided to the ground electrode body 13 at the time of welding operation is adjusted within the range of P0 ≦ P ≦ Pr. However, in the present embodiment The target pressure Ps of the fluid pressure P is set, and spot welding is performed in a state where the fluid pressure P is within the range of the target pressure Ps ± α. The same components as those of the first embodiment are designated by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, as shown in FIG. 8, a variable solenoid valve 41 is interposed instead of the electromagnetic switching valve 18 of the first embodiment. The variable solenoid valve 41 controls the fluid pressure P supplied to the pressure supply passage 19 by reducing a part of the fluid supplied from the supply passage 17b to the storage tank 15 through the drain passage 20a. It is. When the variable solenoid valve 41 is off, the pressure supply passage 19 and the drain passage 20a communicate with each other.

  In addition, a check valve 42 and an accumulator 43 are provided from the upstream side in the feed passage 17 b communicating the variable solenoid valve 41 with the electric pump 16. The check valve 42 prevents the backflow of fluid from the accumulator 43 to the electric pump 16 side. Further, the accumulator 43 accumulates the fluid supplied from the electric pump 16 and suppresses large pressure fluctuation of the fluid supplied to the variable solenoid valve 41. The variable solenoid valve 41 is operated by a drive signal from the electrode pressure control unit 31 (see the drawing).

  Next, a control operation of pressing the ground electrode network 13b performed by the electrode pressure control unit 31 against the vehicle body W will be described along a ground electrode pressure setting routine shown in FIG.

  In this routine, first, in step S11, the vehicle body W is carried into the body assembly line 1 and waits until it is stopped at a fixed position, and the position detection means detects that the vehicle body W is stopped at a fixed position. Then, the process proceeds to step S12, and the electric pump 16 is turned on.

  Thereafter, the process proceeds to step S13, and a conductive distance (a distance between the hit point and the ground) L from the hit point position of the vehicle body W (the position where spot welding is performed by the welding electrode 12) set in advance is obtained. If there are a plurality of hit positions, the hit position at the position farthest from the earth point is extracted as the current hit position.

  Next, the process proceeds to step S14, and a resistance value R2 (see FIG. 7) between the ground electrode body 13 and the vehicle body W is determined by map reference or the like based on the hit-ground distance L. In the case where the distance L between the hit point and the ground is long, it is natural that the current path is long and the electrical loss is increased. Therefore, by setting the resistance value R2 to a lower value as the distance L between the hit point and the ground becomes longer, the electrical conductivity between the ground electrode network 13a and the vehicle body W becomes good, and the overall electrical loss becomes Suppress.

  Thereafter, in step S15, a target value (target pressure) Ps of the fluid pressure P corresponding to the resistance value R2 is determined by table search or the like. In this table, a higher target pressure Ps is set as the resistance value R2 is higher. Therefore, as the fluid pressure P is set higher, the degree of adhesion of the ground electrode network 13b to the vehicle body W becomes higher, and the resistance value R2 decreases. The processing of steps S12 to S15 corresponds to the third step of the present invention.

  Subsequently, the process proceeds to step S16, and a drive signal corresponding to the target pressure Ps is output to the variable solenoid valve 41 to perform the valve opening operation. Then, the fluid discharged from the electric pump 16 passes through the check valve 42 and the pressure fluctuation is suppressed by the accumulator 43 and then flows into the variable solenoid valve 41.

  The variable solenoid valve 41 squeezes the flow passage in response to the drive signal, and discharges the fluid from the drain passage 20 a to the storage tank 15 to send the adjusted fluid pressure P to the pressure supply passage 19. Then, the fluid pressure P flows into the pressure bag 13 a of the earth electrode body 13 to cause the earth electrode body 13 to swell, and the earth electrode body 13 presses the support member 4 fixed to the line block 3. Then, the vehicle body W is pressed by the reaction force (see FIG. 4B). The processing in this step corresponds to the fourth step of the present invention.

  Thereafter, the process proceeds to step S17 and waits until the fluid pressure P reaches a predetermined width α with the target pressure Ps as a median value. When the fluid pressure P reaches the target fluid pressure area Ps ± α, the process proceeds to step S18. In step S18, a welding operation start signal is transmitted to the robot control unit 36, and the welding operation is started in the same manner as the processing in step S5 of the first embodiment. The predetermined width α is a fixed value obtained from an experiment or the like. The processing in steps S17 and S18 corresponds to the fifth step of the present invention.

  Thereafter, the process proceeds to step S19, and it is determined based on a signal from robot control unit 36 whether or not the welding operation of all welding robots 5 is completed. If the welding operation is not completed, the process branches to step S20. Then, it is checked whether the fluid pressure P is within the target fluid pressure region Ps ± α. If the fluid pressure P is within the target fluid pressure region Ps ± α (P = Ps ± α), the welding process in step S18 is repeated. On the other hand, when the fluid pressure P is out of the target fluid pressure region Ps ± α (P <Ps ± α, or P> Ps ± α), the process returns to step S16, and the fluid pressure P becomes the target fluid pressure region Ps ± α. The variable solenoid valve 41 is driven to be accommodated to adjust the flow rate of the fluid flowing to the pressure supply passage 19.

  If it is determined in step S19 that the welding operation by all the welding robots 5 is completed, the process proceeds to step S21, the variable solenoid valve 41 is turned OFF, and is returned to the initial position. It makes it communicate with 20a. Then, the process proceeds to step S22, the electric pump 16 is turned OFF, and the routine ends.

  When the variable solenoid valve 41 is turned OFF, the pressure supply passage 19 and the drain passage 20a are communicated with each other, so the fluid in the pressure bag 13a is reduced to the contraction pressure of the pressure bag 13a as in the first embodiment. Then, the pressure supply passage 19 is reversely flowed, and is reduced to the storage tank 15 through the drain passage 20a. As a result, the ground electrode body 13 contracts and is separated from the support member 4 and the vehicle body W (see FIG. 4A).

  As described above, in the present embodiment, the contact point position where the welding electrode 12 held by the welding robot 5 contacts the fluid pressure P supplied to the pressure bag 13 a of the ground electrode body 13 and the ground electrode of the ground electrode body 13 Since the setting is made based on the conductive distance (dot-ground distance) L with the ground point with which the mesh 13b contacts, if the dot-ground distance L is long, the fluid pressure P is set high to ground The degree of adhesion of the electrode network 13b to the vehicle body W can be increased, and the resistance value R2 can be relatively reduced. As a result, in addition to the effects of the first embodiment described above, the electrical loss can be reduced.

  Furthermore, since the fluid pressure P supplied to the pressure bag 13a is variable based on the distance L between the hit point and the ground, the vehicle body W has variations or a vehicle body whose vehicle type has been changed in the middle of the production line. Even when W is transported to the body assembly line 1, the resistance value R2 can always be maintained at an appropriate value. As a result, not only heat generation and melting loss of the ground electrode network 13b can be prevented but also the welded portion can be always formed in an appropriate shape.

  The present invention is not limited to the above-described embodiments. For example, the line blocks 3 disposed opposite to each other on both sides of the body assembly line 1 can be advanced and retracted in the direction orthogonal to the body assembly line 1. Even for different vehicle bodies W, the distance between the vehicle body W and the support member 4 may be kept constant at all times.

  Further, the fluid which is a pressurized medium is not limited to liquid such as water and oil, and may be gas such as air. When the fluid is air, the storage tank 15 is not necessary. Furthermore, the work to be welded may be configured by joining three or more plate members.

1 ... body assembly line,
3a ... stage,
4 ... support member,
5 ... Welding robot,
5a ... Robot arm,
11 ... One side spot welding device,
12 ... welding electrode,
13: Earth electrode body,
13a ... pressure bag,
13b: Earth electrode network,
13c ... Earth wire,
14: Earth electrode pressure unit,
15 ... Reservoir,
16: Electric pump,
17a ... suction passage,
17b ... feed passage,
18 ... electromagnetic switching valve,
19 ... pressure supply passage,
20a ... drain passage,
20b ... relief passage,
21 ... relief valve,
22 ... pressure sensor,
23 ... Information input means,
31 ... electrode pressure control unit,
36: Robot control unit,
41 ... Variable solenoid valve,
L ... distance between batting and earth,
P: Fluid pressure,
Ps: Target pressure,
P0 ... pressure lower limit value,
Pr ... relief pressure,
Ps ± α ... target pressure area,
R0, R1, R2 ... resistance value,
W: Vehicle body,
W1 ... 1st welded panel,
W2 ... 2nd welded panel

Claims (10)

A welding electrode is pressed against a welding portion set to a work to be welded formed by superimposing a plurality of plate members, and an earth electrode body is pressed against a position different from the welding portion to spot weld the welding portion One-sided spot welding equipment
And an earth electrode pressurizing unit for injecting a fluid into the earth electrode body,
The earth electrode body is
A bulging member capable of bulging by the fluid injected from the earth electrode pressurizing unit;
And a deformable ground electrode member coated on the outer surface of the bulging member and pressed against the work to be welded following the bulging of the bulging member. The single-sided spot welding apparatus according to claim 1, wherein the ground electrode member is formed in a net shape by braiding wires having conductivity. The single-sided spot welding apparatus according to claim 1 or 2, wherein one or more ground electrode bodies are disposed around the workpiece to be welded. The ground electrode body is disposed between the workpiece to be welded and a support member having an electrical insulating property facing the workpiece to be welded at a predetermined distance, and the ground electrode member is the bulged member The one side spot welding apparatus according to any one of claims 1 to 3, characterized in that the workpiece to be welded is brought into pressure contact with a reaction force when it is pressed against the support member by the bulging of the metal. The bulging member causes the ground electrode pressing unit to press fluid pressure so that a resistance value between the ground electrode member and the work to be welded is lower than a resistance value generated at a joint portion of the welding portion. The one side spot welding apparatus according to any one of claims 1 to 4, wherein the single side spot welding apparatus The earth electrode pressure unit, the pressure of the fluid injected into the bulging member is set based the energization distance between the contact position of the the strike position ground electrode body in which the welding electrode of the welding workpiece contacts The one side spot welding apparatus according to claim 5, characterized in that: A welding electrode is pressed against a welding portion set to a work to be welded formed by superimposing a plurality of plate members, and an earth electrode body is pressed against a position different from the welding portion to spot weld the welding portion One side spot welding method
First step of injecting a fluid into a bulging member provided on the ground electrode body to cause the bulging member to swell and pressing the ground electrode member coated on the outer surface of the bulging member against the work to be welded When,
A second step of starting a spot welding operation after the pressure of the fluid at the time of pressing the ground electrode member against the work to be welded by the bulging of the bulging member exceeds a predetermined pressurization lower limit value; One side spot welding method characterized by having. The pressure lower limit value is set to a value such that the resistance value of the contact surface, which is changed by pressing the ground electrode member against the workpiece to be welded, is equal to the resistance value of the welding portion. The one side spot welding method according to claim 7. A welding electrode is pressed against a welding portion set to a work to be welded formed by superimposing a plurality of plate members, and an earth electrode body is pressed against a position different from the welding portion to spot weld the welding portion One side spot welding method
The target pressure of the fluid to be injected into the bulging member provided in the earth electrode body is determined based on the distance between the contact point of the workpiece to be welded and the contact position of the earth electrode body . Process,
A fourth step of injecting a fluid into the bulging member provided on the earth electrode body to cause the bulging member to swell and pressing the ground electrode member coated on the outer surface of the bulging member against the work to be welded When,
And a fifth step of starting a spot welding operation after the fluid pressure injected to the bulging member reaches the target pressure. The ground electrode body is disposed between the workpiece to be welded and a support member having an electrical insulating property facing the workpiece to be welded at a predetermined distance, and the ground electrode member is bulged. The one-side spot welding method according to any one of claims 7 to 9, wherein the workpiece is pressed to the workpiece by a reaction force when the member is pressed against the supporting member by bulging of the member .

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