Arc stud welding device and arc stud welding method

Abstract

To provide a technique that can suppress variation in welding time, in arc stud welding.SOLUTION: An arc stud welding device, which generates an arc between a base material and a stud material to weld the materials to each other, comprises: a stud gun that holds the stud material, executes, for each of a plurality of weld points, a separating-operation of separating the stud material from the base material after starting welding and an approaching-operation of making the stud material approach the base material after the separating-operation; an obtaining section that obtains a required time after when starting the approaching-operation until a contact time point when the stud material comes into contact with the base material; a determining section that determines whether or not there is a time difference between the required time obtained by the obtaining section and a predetermined reference time; and an operation control section that controls the approaching-operation and the separating-operation by the stud gun. The operation control section, when it is determined that the time difference occurs, controls the required time by adjusting a starting time point in succeeding welding so as to reduce the time difference.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to an arc stud welding apparatus and an arc stud welding method. [Background technology]

[0002] Conventionally, a technique is known for joining a stud attached to a stud gun to a base material by arc stud welding (Patent Document 1). In arc stud welding, first, with the base end of the stud in contact with the base material, current is passed between the stud and the base material to separate the stud from the base material, generating an arc between the stud and the base material. Next, when the base material reaches a desired molten state due to the arc generated between the stud and the base material, the stud is brought closer to the base material by the moving mechanism of the stud gun, and the stud and base material are brought into contact with each other, thereby joining the stud to the base material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-105141 A Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present application discovered that the cause of variation in weld quality in arc stud welding is the variation in the required time due to sliding resistance in the stud gun's movement mechanism and wear of the base metal holder provided on the stud gun. The required time is the time from when the stud starts to approach the base metal after the arc is generated until the stud and base metal come into contact. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms. (1) According to one aspect of the present disclosure, there is provided an arc stud welding apparatus that generates an arc between a base metal and a stud material to perform welding, the arc stud gun gripping the stud material performs, for each of a plurality of welding points, a separating action to separate the stud material from the base metal after starting welding, and an approaching action to bring the stud material closer to the base metal after the separating action, an acquisition unit that acquires the time required from the start of the approaching action to the contacting point where the stud material and the base metal come into contact, and a time between the required time acquired by the acquisition unit and a predetermined reference time. the operation control unit controls the approaching and separating operations of the stud gun, wherein the acquisition unit determines the time of contact using a detection signal from a sensor that detects the amount of displacement of the tip of the stud material and acquires as the required time the time until the amount of displacement becomes the same as the separation distance between the tip of the stud material and the base material at the start of the approaching operation, and when it is determined that a time difference has occurred, the operation control unit controls the required time by adjusting the start point of a subsequent welding so as to reduce the time difference. (2) According to another aspect of the present disclosure, there is provided an arc stud welding method. This arc stud welding method is an arc stud welding method for welding a base metal and a stud material by generating an arc between the base metal and the stud material, and includes a separating step of separating the stud material from the base metal after starting welding with a stud gun which holds the stud material, and an approaching step of bringing the stud material closer to the base metal after the separating step, for each of a plurality of welding points, and further includes an acquiring step of acquiring a required time from a start point of the approaching step to a contact point at which the stud material and the base metal come into contact, and a determining step of determining whether or not a time difference occurs between the required time acquired by the acquiring step and a predetermined reference time, in which the acquiring step determines the contact point using a detection signal from a sensor which detects an amount of displacement of the tip of the stud material, and acquires as the required time the time until the amount of displacement becomes the same as the separation distance between the tip of the stud material and the base metal at the start point of the approaching operation, and the approaching step includes a step of controlling the required time by adjusting the start point of a subsequent welding so as to reduce the time difference if it is determined that the time difference occurs.

[0006] (1) According to one aspect of the present disclosure, there is provided an arc stud welding apparatus that generates an arc between a base material and a stud material to perform welding, the arc stud welding apparatus comprising: a stud gun that holds the stud material and that, after starting welding, performs a separating action to separate the stud material from the base material and an approaching action to bring the stud material closer to the base material after the separating action, for each of a plurality of welding points; an acquisition unit that acquires a required time from a start point of the approaching action to a contact point at which the stud material and the base material come into contact; a determination unit that determines whether or not a time difference occurs between the required time acquired by the acquisition unit and a predetermined reference time; and an operation control unit that controls the approaching action and the separating action of the stud gun, and when it is determined that the time difference occurs, the operation control unit controls the required time by adjusting the start point of a subsequent welding so as to reduce the time difference. According to this aspect, by adjusting the start time of the approaching motion by the motion control unit to reduce the time difference, the time required from the start time of the approaching motion to the contact time can be made closer to the reference time, thereby suppressing variation in welding quality in arc stud welding. (2) In the above aspect, when the required time is longer than the reference time, the operation control unit may control the required time by adjusting the start time earlier in accordance with the time difference. According to this aspect, when the required time is longer than the reference time, the start time of the approaching operation is adjusted earlier in accordance with the time difference, so that the required time can be brought closer to the reference time. (3) In the above aspect, when the required time is shorter than the reference time, the operation control unit may control the required time by adjusting the start time later in accordance with the time difference. According to this aspect, when the required time is shorter than the reference time, the start time of the approaching operation is adjusted later in accordance with the time difference, so that the required time can be brought closer to the reference time. (4) In the above embodiment, the plurality of welding points may be located at different positions on the same base material, the acquisition unit may acquire the required time for each of the plurality of welding points, the determination unit may perform the determination for each of the plurality of welding points, and the operation control unit may control the required time for each of the plurality of welding points. According to this embodiment, when welding a stud material to a plurality of welding points, the required time for each of the plurality of welding points can be made to approach a reference time. (5) In the above aspect, the determination unit may perform the determination using an average time difference that is a difference between an average time of the required times for each of the plurality of welding points and the reference time, and the operation control unit may adjust the start time of the subsequent welding so as to reduce the average time difference. According to this aspect, the start time of the subsequent welding can be adjusted in consideration of the required times for the plurality of welding points. (6) In the above embodiment, the number of the welding points may be N or more (N is an integer equal to or greater than 2), the welding to the welding points may be performed in order from the first welding point to the Nth welding point, and the determination unit may use, as the average time difference, a difference between an average time of the required time for each of the welding points from the previous welding point to the welding point M points before (M is an integer smaller than N) and the reference time. According to this embodiment, the start time of subsequent welding can be adjusted taking into account the required times for the welding points. (7) In the above embodiment, the number of base materials may be two or more, each of the plurality of welding points may be formed at a corresponding position on the two or more base materials, the acquisition unit may acquire the required time for each of the plurality of welding points, the determination unit may perform the determination for each of the plurality of welding points, and the operation control unit may control the required time for each of the plurality of welding points. According to this embodiment, when welding is performed on a plurality of welding points formed at corresponding positions on two or more base materials, the start time of the subsequent welding can be adjusted taking into consideration the characteristics and tendencies of each of the plurality of welding points. (8) In the above embodiment, the determination unit may perform the determination using an average time difference that is a difference between an average time of the required times for each of the plurality of welding points and the reference time, and the operation control unit may adjust the start time of the subsequent welding so as to reduce the average time difference. According to this embodiment, when welding is performed on a plurality of welding points formed at corresponding positions among two or more base materials, the start time of the subsequent welding can be adjusted taking into consideration the characteristics and tendencies of each of the plurality of welding points. (9) In the above embodiment, the arc stud welding apparatus may further include a base metal presser for holding down the base metal. According to this embodiment, welding can be performed in a state in which the base metal to be welded is fixed by the base metal presser. Therefore, the stud gun and the base metal can be brought into contact in a stable position. (10) According to another aspect of the present disclosure, there is provided an arc stud welding method. The arc stud welding method is an arc stud welding method for welding by generating an arc between a base material and a stud material, and includes a separating step of separating the stud material from the base material by a stud gun that holds the stud material after starting welding, and an approaching step of bringing the stud material closer to the base material after the separating step, for each of a plurality of welding points, and further includes an acquisition step of acquiring a required time from a start point of the approaching step to a contact point at which the stud material and the base material come into contact, and a determination step of determining whether or not a time difference occurs between the required time acquired by the acquisition step and a predetermined reference time, and the approaching step includes a step of controlling the required time by adjusting the start point of a subsequent welding so as to reduce the time difference when it is determined that the time difference occurs. According to this aspect, the operation control unit adjusts the start point of the approaching step so as to reduce the time difference, so that the required time from the start point of the approaching step to the contact point can be brought closer to the reference time. As a result, variation in welding quality in arc stud welding can be suppressed. The present disclosure may be realized in various forms other than the above-described arc stud welding apparatus and arc stud welding method, for example, in the form of a manufacturing method for an arc stud welding apparatus, a control method for an arc stud welding apparatus, a computer program for implementing the control method, a non-transitory recording medium on which the computer program is recorded, etc. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing a schematic configuration of an arc stud welding device according to an embodiment of the present invention; [Diagram 2] Schematic diagram showing the structure of a stud gun. [Diagram 3] 5A to 5C are diagrams for explaining an arc stud welding process in the present embodiment. [Figure 4] 5 is a schematic diagram showing a state of current flow during welding and a transition of the gun position. FIG. [Diagram 5] Graph showing the variation in welding time due to individual differences in stud guns and the passage of time during use. [Figure 6] FIG. 4 is a conceptual diagram for explaining a method for controlling a required time in the first embodiment. [Figure 7] 11 is a graph for explaining a control method when a required time is longer than a reference time. [Figure 8] 11 is a graph for explaining a control method when a required time is shorter than a reference time. [Figure 9] A graph showing the time required for each welding point for multiple base materials. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] A. First embodiment: Fig. 1 is a schematic diagram showing the general configuration of an arc stud welding apparatus 1 of this embodiment. Fig. 1 shows the arc stud welding apparatus 1 placed on a horizontal installation surface F. The arc stud welding apparatus 1 generates an arc A between a base material W and a stud material B to perform welding. The arc stud welding apparatus 1 is used, for example, in the manufacturing process of a vehicle when welding a stud material B to a metal part such as a panel.

[0009] The base material W is made of a metal, for example, aluminum or an alloy. The base material W has a welding surface WS as a surface to which the stud material B is joined by arc stud welding (hereinafter, welding). In this embodiment, the base material W is in the form of a plate.

[0010] The stud material B is a member for joining the base material W to another member different from the base material W when it is welded to the base material W by welding. The stud material B is a so-called stud bolt or stud nut. The stud material B is made of metal and has a rod shape. In this embodiment, the stud material B is a stud bolt with a base.

[0011] The arc stud welding apparatus 1 includes a stud gun 2, a robot 3, a control device 4, a bolt feeder 6, a power supply device 7, a base material support stand 9, and a sensor 11.

[0012] FIG. 2 is a schematic diagram showing the configuration of the stud gun 2. FIG. 2 shows a schematic cross section of the stud gun 2 and the base material W. FIG. 2 also shows the positional relationship between the stud gun 2 and the base material W in step (2) shown in FIG. 3 described later. The stud material B described above has a head B1, a shaft B2, and a protruding portion B3. The head B1 is held by a chuck 27 of the stud gun 2 described later. The protruding portion B3 comes into contact with the welding surface WS of the base material W during welding. The shaft B2 is located between the head B1 and the protruding portion B3. After welding, when the base material W is joined to another member, the shaft B2 is fitted to the other member via the head B1 of the stud material B, thereby joining the base material W to the other member. The shape of the stud material B is not limited to this. The stud material B may be formed with a screw thread or a groove for fitting with the other member. The head B1 and the shaft B2 may be integrally formed with the same diameter. In the following description, the side of the stud material B where the head B1 is located is referred to as the base end Ba of the stud material B, and the side where the protruding portion B3 is located is referred to as the tip Bb of the stud material B.

[0013] The stud gun 2 grips the stud material B, and in response to commands from the control device 4, performs a separating operation to separate the stud material B from the base material W, and then an approaching operation to bring the stud material B closer to the base material W, for each of a plurality of welding points. One end 2a of the stud gun 2 is supported by a stud gun support section 37 (FIG. 1), which will be described later. The stud gun 2 is electrically connected to the control device 4 via the robot 3. The stud gun 2 includes a case 20, a gun coil 21, a fixed magnetic pole member 22, a cylinder 23, a movable magnetic pole member 24, a biasing member 25, a chuck 27, and a base material presser 29.

[0014] The case 20 is a cylindrical member forming the outer shell of the stud gun 2. The case 20 houses a gun coil 21, a fixed magnetic pole member 22, a cylinder 23, a movable magnetic pole member 24, a biasing member 25, and a chuck 27. The other end 2b, which is located opposite to the one end 2a of the stud gun 2 in the vertical direction, faces the welding surface WS of the base material W. In this embodiment, the fixed magnetic pole member 22, the cylinder 23, the movable magnetic pole member 24, and the chuck 27 are provided in this order in the direction from the one end 2a of the stud gun 2 toward the other end 2b.

[0015] The gun coil 21 is provided around the fixed magnetic pole member 22 on the inner circumferential surface of the case 20, on one end 2a side of the stud gun 2. The gun coil 21 is a coil made of a metallic wire such as a copper wire wound into a cylindrical shape, and generates a magnetic field by a gun coil voltage supplied from the power supply 7. Note that, during welding, the specific operations of each component in a state where the gun coil 21 is energized (hereinafter, energized state) and a state where the gun coil 21 is not energized (hereinafter, non-energized state) will be described later with reference to Figures 3 and 4.

[0016] The fixed magnetic pole member 22 is provided inside the case 20, on the one end 2a side of the stud gun 2 and inside the gun coil 21. In other words, the fixed magnetic pole member 22 is located in the center of the one end 2a side of the case 20 extending in the horizontal direction. The fixed magnetic pole member 22 is a magnetic body, and is formed of a metal that can function as a magnetic body, such as iron. The fixed magnetic pole member 22 becomes a magnetized electromagnet due to the magnetic field generated by the excited gun coil 21.

[0017] The cylinder 23 is a cylindrical member that slidably accommodates the movable magnetic pole member 24. The cylinder 23 is provided inside the case 20 at a position closer to the fixed magnetic pole member 22 than the fixed magnetic pole member 22 on the other end 2b side. One bottom surface of the cylinder 23 is located on the one end 2a side, and the other bottom surface is located on the other end 2b side. The bottom surface on the other end 2b side of the cylinder 23 is provided with an opening for slidably accommodating a rod 242 (described later) between the one end 2a side and the other end 2b side. The diameter of this opening is provided to be smaller than the diameter of a head 241 (described later). In addition, the inner peripheral surface of the side surface of the cylinder 23 is a sliding surface on which the movable magnetic pole member 24 slides. In FIG. 2, a part of the side surface of the cylinder 23 is provided at a position facing the gun coil 21.

[0018] The movable magnetic pole member 24 is slidably provided inside the cylinder 23. The movable magnetic pole member 24 is a magnetic body, and is formed of a metal that can function as a magnetic body, such as iron. Therefore, when the fixed magnetic pole member 22 is in a magnetized state, the movable magnetic pole member 24 is electromagnetically attracted to the fixed magnetic pole member 22. The movable magnetic pole member 24 includes a head 241, a rod 242, and a tail 243. The head 241 is disk-shaped. The rod 242 is rod-shaped. The tail 243 is disk-shaped. The movable magnetic pole member 24 is a so-called piston in which the head 241, the rod 242, and the tail 243 are integrally configured in this order. The diameter of the head 241 is smaller than the diameter of the cylinder 23 and larger than the diameter of the opening of the cylinder 23. The diameter of the rod 242 is smaller than the diameter of the head 241 and smaller than the diameter of the opening of the cylinder 23. This allows the movable magnetic pole member 24 to slide without coming off the opening of the cylinder 23. Furthermore, by providing the tail 243 on the other end 2b side, the biasing member 25 can be extended and retracted. In Fig. 2, the region where the movable magnetic pole member 24 slides inside the cylinder 23 is illustrated as a sliding region S. The sliding region S refers to the range between one bottom surface and the other bottom surface of the cylinder 23 described above in the vertical direction.

[0019] The biasing member 25 biases the movable magnetic pole member 24 toward the other end 2b of the stud gun 2. The biasing member 25 is a so-called coil spring. The biasing member 25 expands and contracts in response to the sliding of the movable magnetic pole member 24 in the sliding region S.

[0020] The chuck 27 grips the stud material B. Specifically, the chuck 27 grips the head B1 of the stud material B located on the one end 2a side. The chuck 27 is attached to the tail 243 so as to be integrated with the tail 243, and is provided on the other end 2b side of the tail 243. The chuck 27 has a gripping portion 271 for gripping the stud material B. In FIG. 2, two gripping portions 271 are provided facing each other in the horizontal direction, and one gripping portion 271 and the other gripping portion 271 grip the head B1 of the stud material B by sandwiching it between them. Therefore, the position of the stud material B changes following the sliding of the movable magnetic pole member 24 by sliding the movable magnetic pole member 24. In this way, the chuck 27 of the stud gun 2 equipped with a solenoid mechanism grips the stud material B, and the stud material B approaches or moves away from the base material W.

[0021] The base material presser 29 is disposed on the outer surface of the case 20, on the other end 2b side facing the welding surface WS of the base material W. The base material presser 29 is rod-shaped and has a contact surface 29a that comes into contact with the base material W. When the contact surface 29a of the base material presser 29 comes into contact with a portion of the welding surface WS of the base material W, the stud gun 2 can move the stud material B toward or away from the base material W in a stable position. The base material presser 29 is formed, for example, from copper.

[0022] However, the components and arrangement of the stud gun 2 are not limited to those described above. The stud gun 2 only needs to have a mechanism for gripping the stud material B and performing approaching and separating operations, and for generating an arc A from the other end 2b of the stud gun 2 that faces the base material W. Furthermore, the base material presser 29 is not an essential component of the stud gun 2.

[0023] As shown in Figure 1, the robot 3 is a mobile mechanism that supports one end 2a of the stud gun 2 and changes the position and posture of the stud gun 2. In the example shown in Figure 1, the robot 3 is an articulated robot, and includes an arm 30 that is placed on an installation surface F, a base 35, and a stud gun support part 37. The stud gun support part 37 is provided at the tip of the arm 30, and supports the stud gun 2.

[0024] The control device 4 controls the robot 3, the bolt feeder 6, and the power supply 7, and also controls the operation of the stud gun 2 via the robot 3. The control device 4 includes a CPU 40 and a storage unit 47 that stores various programs. The control device 4 is electrically connected to the robot 3, the bolt feeder 6, and the power supply 7. The control device 4 functions as an acquisition unit 41, a determination unit 43, and an operation control unit 45 by deploying the various programs stored in the storage unit 47. At least some of the functions of the CPU 40 may be realized by hardware circuits.

[0025] The acquisition unit 41 acquires the time T1 required from the start of the approaching operation to the contact time when the tip Bb of the stud material B comes into contact with the welding surface WS of the base material W. Specifically, the acquisition unit 41 acquires a detection signal from the sensor 11 shown in FIG. 1, and uses the acquired detection signal to determine the contact time when the tip Bb of the stud material B comes into contact with the welding surface WS of the base material W. The sensor 11 detects information regarding the position of the stud material B. The sensor 11 is, for example, a displacement sensor such as a laser displacement meter, and detects the amount of displacement of the tip Bb of the stud material B. The distance between the tip Bb of the stud material B and the welding surface WS of the base material W at the start of the approaching operation is determined in advance or measured in advance and stored in the memory unit 47. The acquisition unit 41 acquires the time T1 required until the amount of displacement of the tip Bb of the stud material B acquired from the sensor 11 becomes equal to the separation distance L (FIG. 3) at the start of the approaching operation by measuring it with a timer (not shown) of the control device 4. The sensor 11 is not limited to a displacement sensor. For example, an imaging device may be used as the sensor 11. In this case, the stud material B and the base material W may be imaged at regular intervals, and the acquisition unit 41 may use the captured images as detection signals to determine the contact time point, thereby acquiring the required time T1.

[0026] The determination unit 43 determines whether or not a time difference T2 occurs between the required time T1 acquired by the acquisition unit 41 and a predetermined reference time TS. Specifically, the determination unit 43 calculates the difference between the required time T1 and the reference time TS, and determines that the time difference T2 occurs when the difference is not zero. Note that, in other embodiments, the determination unit 43 may determine that the time difference T2 occurs when the difference is equal to or greater than a predetermined threshold value.

[0027] The operation control unit 45 controls the approaching and separating operations of the stud gun 2. Specifically, the operation control unit 45 controls the operation of the power supply unit 7 by transmitting a control signal and a gun signal, which will be described later. As a result, the operation control unit 45 controls the operation of the stud gun 2 by controlling the voltage and current supplied from the power supply unit 7 to the stud gun 2. Furthermore, when the determination unit 43 determines that the time difference T2 has occurred, the operation control unit 45 executes control to bring the required time T1 closer to the reference time TS by adjusting the start point of the approaching operation in the later welding in order to reduce the time difference T2. Specifically, when the required time T1 is longer than the reference time TS, the operation control unit 45 adjusts the start point of the approaching operation in the later welding to be earlier in accordance with the time difference T2, thereby bringing the required time T1 closer to the reference time TS. Furthermore, when the required time T1 is shorter than the reference time TS, the operation control unit 45 controls the required time T1 by adjusting the start point of the approaching operation in the later welding to be later in accordance with the time difference T2. In this way, by adjusting the start point of the approaching action in accordance with the time difference T2, it is possible to bring the required time T1 closer to the reference time TS.

[0028] The storage unit 47 is composed of storage devices such as RAM and ROM. The storage unit 47 stores various programs and data for controlling the operation of the arc stud welding apparatus 1. The storage unit 47 also stores data relating to the base metal W, such as the material, shape, and size of the base metal W, and data such as welding conditions when welding the stud material B to the base metal W.

[0029] The bolt feeder 6 supplies the stud material B to the stud gun 2 in response to an instruction from the control device 4. The bolt feeder 6 is communicatively connected to the stud gun 2 via the control device 4. When the bolt feeder 6 receives an instruction from the control device 4 to supply the stud material B, it supplies the stud material B to the stud gun 2 via a transport path (not shown).

[0030] The power supply device 7 is a current supply device during welding. Specifically, the power supply device 7 has a function as a welding power supply and a function as a gun coil power supply. The function as a welding power supply is an operation of applying a welding voltage to the stud gun 2 to generate an arc A between the base material W and the stud material B during welding. The function as a gun coil power supply is an operation of applying a gun coil voltage to the gun coil 21. The power supply device 7 receives from the control device 4 a control signal that controls whether or not a welding voltage is applied and the applied voltage, and a gun signal that controls whether or not a gun coil voltage is applied. When at least one of the control signal and the gun signal is received, the power supply device 7 applies a voltage according to a signal indicating the control content from the control device 4.

[0031] The base material support stage 9 is a stage that supports the base material W. In the example shown in Fig. 1, the base material support stage 9 has a rectangular parallelepiped shape. The base material support stage 9, like the robot 3, is placed on the horizontal installation surface F.

[0032] The configuration, functions, etc. of the arc stud welding apparatus 1 are not limited to those disclosed herein. In the arc stud welding apparatus 1, there may be a plurality of stud guns 2 and robots 3 electrically connected to the control device 4. For example, the arc stud welding apparatus 1 may be provided with a plurality of robots 3 for one control device 4, and each of the plurality of robots 3 may be equipped with a stud gun 2. In this case, the apparatus may be configured so that welding can be performed on a plurality of base materials W simultaneously by each of the plurality of robots 3 and the plurality of stud guns 2.

[0033] FIG. 3 is a diagram for explaining the arc stud welding process in this embodiment. FIG. 4 is a schematic diagram showing the state of current flow during welding in this embodiment and the transition of the gun position. In FIG. 3, the arc stud welding process in which the base material W and the stud material B are welded using the arc stud welding device 1 is illustrated as being divided into five steps, step (1) to step (5). The steps in FIG. 3 are executed in the order of step (1), step (2), step (3), step (4), and step (5). In FIG. 4, step numbers corresponding to steps (1) to (5) in FIG. 3 are assigned. The graph in FIG. 4 shows, from the top, the transition of the welding current, welding voltage, gun coil voltage, and gun position in steps (1) to (5). The welding current is a current supplied to the stud gun 2 in response to the application of the welding voltage. In FIG. 4, the transitions of the welding current, welding voltage, and gun coil voltage show the change in value when the start of step (2) in FIG. 3 is set as the reference (zero). In addition, the gun position in Figure 4 represents the change in position of the tip Bb of the stud material B in the vertical direction when the state in which the welding surface WS of the base material W and the tip Bb of the stud material B are in contact is taken as the reference (zero).

[0034] Step (1) is a preparation step before the start of welding. In this embodiment, before the start of welding, the position of the tip Bb of the stud material B protrudes in a direction approaching the base material W from the position of the contact surface 29a of the base material holder 29. In step (1), the tip Bb of the stud material B and the contact surface 29a of the base material holder 29 are not in contact with the welding surface WS of the base material W. In addition, since step (1) is before the start of welding, the welding voltage and the gun coil voltage are not applied to the stud gun 2. Therefore, as shown in FIG. 4, the welding current, welding voltage, and gun coil voltage show constant values ​​of zero. In addition, since the gun position is based on the state in which the tip Bb of the stud material B contacts the welding surface WS of the base material W, step (1) is not illustrated.

[0035] As shown in FIG. 3, step (2) is a step of moving the stud gun 2 gripping the stud material B to an initial position. In step (2), the contact surface 29a of the base material holder 29 of the stud gun 2 is brought into contact with the welding surface WS of the base material W. At this time, the movable magnetic pole member 24 is integrated with the stud material B via the chuck 27. Therefore, in the above-mentioned step (1), the movable magnetic pole member 24 is in a state of moving toward the one end 2a of the stud gun 2 by an amount that the tip Bb of the stud material B protruded from the contact surface 29a of the base material holder 29. In step (2), the biasing member 25 is in a state of being further compressed with the movement of the movable magnetic pole member 24. As a result, the contact surface 29a of the base material holder 29 is placed on the welding surface WS of the base material W, so that the tip Bb of the stud material B and the welding surface WS of the base material W are in contact with each other. In the following, the position of the tip Bb of the stud gun 2 in this state is referred to as the initial position. Therefore, the above-mentioned gun position can also be said to represent the height position of the stud material B in the vertical direction when the initial position is taken as the reference (zero), i.e., the distance L between the tip Bb of the stud material B and the base material W.

[0036] In step (3), a welding voltage is applied to the stud gun 2 to generate a weak arc A between the welding surface WS of the base metal W and the tip Bb of the stud material B. As shown in FIG. 4, at the start of step (3), a weak welding current is supplied to the stud gun 2 by applying a welding voltage. This weak welding current is continuously supplied, and an arc A is generated between the welding surface WS of the base metal W and the tip Bb of the stud material B. The arc A generated in step (3) is an arc A that induces a main arc as the arc A generated in step (4), and is a so-called pilot arc. Due to the generation of this arc A, a repulsive force is generated between the welding surface WS of the base metal W and the stud material B. Due to this repulsive force, the stud material B rises in a direction away from the welding surface WS of the base metal W against the biasing force of the biasing member 25. In other words, step (3) can also be said to be a separation step in which a separation operation is performed.

[0037] Here, the stud material B is held by a chuck 27 attached to the movable magnetic pole member 24 of the stud gun 2. That is, the position of the stud material B in the vertical direction (advance / retract direction) relative to the welding surface WS of the base material W changes following the sliding of the movable magnetic pole member 24 in the sliding area S shown in FIG. 2. Therefore, when a repulsive force is generated between the base material W and the stud material B by the generation of the arc A, the movable magnetic pole member 24 moves from the other end 2b side of the stud gun 2 toward the one end 2a side against the biasing force of the biasing member 25. In step (3) of FIG. 3, the distance in the vertical direction (advance / retract direction) generated between the welding surface WS of the base material W and the tip Bb of the stud material B by the separation operation is shown as a separation distance L. The separation distance L coincides with the distance that the head 241 of the movable magnetic pole member 24 moves from the other end 2b side to the one end 2a side within the range of the sliding area S.

[0038] As shown in Fig. 4, in step (4), the welding voltage applied to the stud gun 2 is increased more than in step (3) to generate an arc A over a wider range than in step (3), and a gun coil voltage is applied to maintain the stud material B and the welding surface WS of the base material W apart. As a result, the arc A discharged from the stud gun 2 spreads from the other end 2b side of the stud gun 2 toward the welding surface WS of the base material W, as shown in step (4) of Fig. 3, and is discharged over a wider range than the arc A (pilot arc) in step (3). The arc A generated in step (4) is a so-called main arc for melting the base material W and generating a molten pool by applying heat to the welding surface WS of the base material W. In Fig. 4, the amount of heat applied to the base material W by the arc A (main arc) in step (4) is shown as a heat input.

[0039] As shown in FIG. 4, at the start of step (4), a gun coil voltage is applied to the gun coil 21 of the stud gun 2. During step (4), the energized state is maintained. As described above, the gun coil 21 is excited when energized to generate a magnetic field. The fixed magnetic pole member 22 (FIG. 2) formed around the gun coil 21 is magnetized by the excited gun coil 21 to generate an electromagnetic attraction force. The movable magnetic pole member 24 is electromagnetically attracted to the one end 2a of the stud gun 2 where the fixed magnetic pole member 22 is located, against the biasing force of the biasing member 25, by the magnetic force of the magnetized fixed magnetic pole member 22. In this way, the fixed magnetic pole member 22, which functions as an electromagnet when energized, is used to attract the movable magnetic pole member 24 to the one end 2a of the stud gun 2 within the range of the sliding region S, thereby maintaining the position of the stud material B with respect to the welding surface WS of the base material W.

[0040] In step (4), the gun coil 21 is maintained in an energized state as shown in Fig. 4. Therefore, the distance L between the stud material B and the welding surface WS of the base material W is kept constant as shown in the gun position graph in Fig. 4. From the above, the gun position is constant during step (3) as shown in Fig. 4.

[0041] Step (5), which is an actual welding step, includes a step of performing an approaching operation of bringing the stud material B close to the welding surface WS of the base material W, and a step of performing a welding operation after the approaching operation. In step (5), the operation control unit 45 performs the approaching operation, and presses the stud material B against the molten pool formed on the welding surface WS of the base material W by the arc A, thereby welding the stud material B to the base material W. In step (5), as shown in FIG. 4, the operation control unit 45 performs the approaching operation by stopping the application of the gun coil voltage to the gun coil 21. Specifically, at the start of step (5), the operation control unit 45 stops the supply of the gun signal to the power supply device 7. This stopping of the supply of the gun signal stops the application of the gun coil voltage. As a result, the gun coil 21 switches from a conducting state to a non-conducting state. In the non-conducting state, the excited gun coil 21 is demagnetized. Therefore, the fixed magnetic pole member 22, which functions as an electromagnet in the conducting state, loses its electromagnetic attraction force as the gun coil 21 is demagnetized. As a result, the movable magnetic pole member 24 moves from the one end 2a side to the other end 2b side by the biasing force of the biasing member 25. As a result, the stud material B is pressed against the welding surface WS of the base material W by the biasing force of the biasing member 25. The welding operation is an operation in which the state in which the stud material B is pressed against the welding surface WS of the base material W is maintained until the molten pool is cooled and solidified. As a result, the molten pool is solidified, and the stud material B and the base material W are joined. As described above, the operation control unit 45 maintains the state in which the stud material B is pressed against the welding surface WS of the base material W by the biasing force of the biasing member 25 for a predetermined time after stopping the application of the welding voltage and the gun coil voltage to the stud gun 2 and ending the approaching operation. In step (5) of FIG. 3, the part where the base material W and the stud material B are welded is illustrated as a welding point 100.

[0042] 4, the welding voltage is continuously applied to the stud gun 2 until the tip Bb of the stud material B contacts the welding surface WS of the base metal W by the approaching operation, i.e., until the gun position becomes zero. In other words, the arc A (main arc) is continuously discharged even after the approaching operation starts, and continues to melt the base metal W. When the gun position becomes zero, the application of the welding voltage is stopped, and then the welding current gradually decreases to zero.

[0043] In this embodiment, the welding time T is the time required from the start of the separating operation to the end of the approaching operation. That is, the welding time T refers to the time from the start of the application of the welding voltage (the start of step (3)) in Fig. 4 to the contact point where the base material W and the stud material B come into contact with each other (the point where the gun position becomes zero).

[0044] In the arc stud welding described above, the inventors of the present application found that there is variation in the welding time T from when the arc A is generated to start welding until the separation distance L between the base material W and the stud material B becomes zero. FIG. 5 is a graph showing the variation in the welding time T with the individual difference of the stud gun 2 and the passage of the period of use. In FIG. 5, in order to show the individual difference of the stud gun 2, data related to the welding time T when two stud guns X and Y are used and each is used continuously is shown. The horizontal axis of FIG. 5 shows the period of use of the stud gun X and the stud gun Y. In FIG. 5, the unit of the period of use is one month. Also, the vertical axis of FIG. 5 shows the welding time T. In FIG. 5, the unit of the welding time T is expressed in milliseconds (ms). In this measurement, the predetermined recommended time for the welding time T is 41.0 milliseconds. Also, in this measurement, the condition for a non-defective product is when the difference from the recommended time is within 2.0 milliseconds. In FIG. 5, the range from 39.0 ms to 43.0 ms, which is within 2.0 ms of the recommended time of 41.0 ms, is shown as a non-defective condition, and is indicated by hatching.

[0045] As data on the welding time T, Fig. 5 shows the average and the variation. The average in Fig. 5 is the average value of each welding time T when multiple welding operations are performed in one day. The variation in Fig. 5 is the standard deviation for each average. In Fig. 5, the variation for each average is calculated within a range of 4σ as the variation value. In the measurement shown in Fig. 5, the welding time T of at least one of the stud gun X and the stud gun Y is measured at any timing within five months after the start of use, and the average and the variation value are calculated.

[0046] In this measurement, at least three patterns were found as trends in the welding time T. The first pattern is, for example, a case where the average welding time T is outside the range of the non-defective condition. The first pattern is prominent in the portion where the period of use is 3 to 5 months in the measurement using the stud gun Y. The second pattern is, for example, a case where the average welding time T is within the range of the non-defective condition, but the variation value for the average is outside the range of the non-defective condition. The second pattern is prominent in the portion where the period of use is 0 to 1 month in the measurement using the stud gun Y. The third pattern is, for example, a case where a difference occurs in the welding time T due to an individual difference of the stud gun 2. Specifically, when comparing the stud gun X and the stud gun Y, the degree of the average and the variation value differs between the two.

[0047] Two factors are considered to be the causes of the variation in welding time T found in this measurement. The first factor is the change in sliding resistance in the sliding region S of the stud gun 2. As described above, the arc stud welding equipment 1 performs approaching and separating operations by sliding of the movable magnetic pole member 24 within the range of the sliding region S. There may be cases where the sliding resistance during sliding between this movable magnetic pole member 24 and the sliding surface that forms the inner surface of the cylinder 23 changes over time. Generally, sliding resistance often increases as the period of use passes.

[0048] The second factor is the change in the separation distance L due to wear of the base metal holder 29. The contact surface 29a of the base metal holder 29 is in contact with the welding surface WS of the base metal W during welding. That is, when heat is applied to the welding surface WS of the base metal W by the generation of the arc A, the base metal holder 29 is located near the location where the arc A is generated. Therefore, the contact surface 29a side of the base metal holder 29 is easily deteriorated as the usage period passes. Furthermore, since the base metal holder 29 supports the stud gun 2 by contacting the base metal W every time welding is performed, it is easily subjected to load. Due to various factors including these, the base metal holder 29 gradually wears out from the contact surface 29a side as the usage period passes. That is, the length of the base metal holder 29 becomes shorter as the usage period passes. As the length of the base metal holder 29 becomes shorter, the separation distance L becomes shorter by the amount that the base metal holder 29 is worn out, even if welding is performed under the same conditions. As a result, the distance L between the tip Bb of the stud material B and the welding surface WS of the base material W becomes shorter after the base material presser 29 has been worn out compared to before the base material presser 29 was worn out. The shorter the distance L, the shorter the time required to bring the stud material B closer together in the approaching operation.

[0049] Fluctuations in the welding time T are one of the factors that affect the welding quality. Specifically, when the required time T1 of the welding time T fluctuates, a difference occurs in the amount of heat given to the base metal W according to the fluctuation of the required time T1. This may result in the welding quality not being constant, and a stable quality may not be ensured. Therefore, even when performing arc stud welding, it is desirable to suppress the fluctuations in the welding time T. Therefore, in this embodiment, the control device 4 executes control to suppress the fluctuations in the required time T1. A method of controlling the required time T1 in this embodiment will be described below.

[0050] The arc stud welding equipment 1 controls the required time T1 by adjusting the start time of the approaching operation using the acquisition unit 41, the determination unit 43, and the operation control unit 45. First, the acquisition unit 41 acquires the required time T1. Next, the determination unit 43 determines whether or not a time difference T2 occurs between the required time T1 acquired by the acquisition unit 41 and the reference time TS. If the determination unit 43 determines that the time difference T2 occurs, the operation control unit 45 adjusts the start time of the approaching operation in the subsequent welding in order to reduce the time difference T2. This brings the required time T1 closer to the reference time TS.

[0051] In actual welding, the sliding resistance of the stud gun 2 and wear of the base material holder 29 may change over time. That is, in welding, factors that make the required time T1 shorter than the reference time TS and factors that make it longer coexist. Furthermore, when multiple robots 3 and stud guns 2 are connected to the control device 4 and multiple base materials W are welded simultaneously, individual differences in the stud guns 2 also cause variations in the welding time T. Therefore, in this embodiment, for ease of understanding, a case will be described in which one of the factors that make the required time T1 shorter than the reference time TS and the factors that make the required time T1 longer than the reference time TS is dominant.

[0052] FIG. 6 is a conceptual diagram for explaining a method for controlling the required time T1 in this embodiment. In FIG. 6, step numbers corresponding to steps (2) to (5) in FIG. 3 and FIG. 4 are assigned. In FIG. 6, the transition of the gun coil voltage from the start to the end of the welding time T and the required time T1 are illustrated in three patterns: the setting state, the past routine, and the current routine. The vertical axis of FIG. 6 indicates the fluctuation of the gun coil voltage. FIG. 6 shows the change in value when the gun coil voltage before the start of step (3) is set as the reference (zero). The horizontal axis of FIG. 6 shows the progress of the welding time T. In FIG. 6, the progress of the welding time T is expressed in milliseconds (ms).

[0053] The setting state in Fig. 6 is a reference state in the control method of this embodiment. The graph of the setting state indicates a case where the required time T1 coincides with the reference time TS. In other words, the reference time TS is a time that is predetermined as a recommended value for the required time T1. In Fig. 6, the reference time TS is set to N milliseconds.

[0054] The past routine in Fig. 6 is data for welding performed in a routine before the welding to be controlled is performed. Data relating to the required time T1 in the past routine is used as the required time T1 when the determination unit 43 calculates the time difference T2. In the past routine, a case is illustrated in which the required time T1 is 1 millisecond longer than the reference time TS of N milliseconds. In other words, the required time T1 in the past routine is N+1 milliseconds. In the graph of the past routine, the reference time TS, the required time T1, and the time difference T2 are each illustrated.

[0055] This routine in FIG. 6 shows the required time T1 when the start time of the approaching operation is adjusted by the operation control unit 45 using the required time T1 of the past routine. In FIG. 6, the required time T1 in the past routine is longer than the reference time TS by 1 millisecond. In order to bring the time difference T2 of 1 millisecond closer to the reference time TS, in FIG. 6, the operation control unit 45 adjusts the start time of the approaching operation to be earlier by 1 millisecond corresponding to the time difference T2. That is, the operation control unit 45 refers to the required time T1 of the past routine and reflects the time difference T2 calculated from the past routine in the start time of the approaching operation in the subsequent welding to be controlled. By this control, in FIG. 6, the approaching operation in the subsequent welding starts earlier by 1 millisecond corresponding to the time difference T2. Therefore, the required time T1 can be brought closer to the reference time TS, and the fluctuation of the required time T1 is suppressed.

[0056] At this time, when there are multiple pieces of data related to the required time T1 of the past routine, the determination unit 43 may be set to select any one of the multiple pieces of data and calculate the time difference T2. The determination unit 43 may calculate the time difference T2 by using, for example, an average time obtained by averaging multiple pieces of data related to the required time T1 of the past routine as the required time T1. The time difference T2 calculated using the average time corresponds to, for example, a first average time difference D1, a second average time difference D2, or a third average time difference D3, which will be described later. The determination unit 43 may also be set to select any one of the data and calculate the time difference T2. In other words, the past routine referred to in this routine may be a single piece of data or a plurality of pieces of data. Furthermore, the data selected as the past routine may be data related to either a non-corrected state in which the start time of the approaching operation is not adjusted by the operation control unit 45, or a controlled state in which the start time of the approaching operation is adjusted by the operation control unit 45.

[0057] In this embodiment, as described above, the approaching operation starts from the point in time when the supply of the gun signal is stopped to stop the application of the gun coil voltage ("gun signal OFF" in FIG. 6). Therefore, in this embodiment, the operation control unit 45 adjusts the start point of the approaching operation by switching the gun signal between ON and OFF. Note that the method of adjusting the start point of the approaching operation is not limited to this.

[0058] In the following, a specific control method of this embodiment will be described by taking as an example a case where a stud material B is welded to a plurality of welding points 100. FIG. 7 is a graph for explaining a control method when the required time T1 is longer than the reference time TS. FIG. 8 is a graph for explaining a control method when the required time T1 is shorter than the reference time TS. The horizontal axis of FIG. 7 and FIG. 8 indicates which of the welding points 100 is welded among the welding points 100 that are welded. FIG. 7 and FIG. 8 show a case where ten welding points 100 are welded. The vertical axis of FIG. 7 and FIG. 8 indicates the required time T1 of each welding point 100 that is performed in order from the first welding point 100 to the tenth welding point 100. In FIG. 7 and FIG. 8, the unit of the required time T1 is milliseconds (ms). In FIG. 7 and FIG. 8, the reference time TS is 38.0 milliseconds.

[0059] In this embodiment, the multiple welding points 100 are present at different positions in the same base material W. The number of welding points 100 is N or more (N is an integer of 2 or more). Welding to the multiple welding points 100 is performed in order from the first point to the Nth point (the tenth point in this embodiment).

[0060] The determination unit 43 uses the required time T1 (past routine) for each of the multiple welding points 100 performed at a time point before the welding to be controlled is performed to determine whether or not a time difference T2 occurs for each of the welding points 100. If it is determined that a time difference T2 occurs, the operation control unit 45 executes control to bring the required time T1 closer to the reference time TS by adjusting the start time of the approach operation for each of the multiple welding points 100. In this embodiment, the sixth to tenth welding points 100 are targeted for control.

[0061] When the operation control unit 45 adjusts the start time of the approaching operation, the determination unit 43 uses, as the required time T1, the average time of the required time T1 acquired for each of the multiple welding points 100 where welding was performed before this routine. In other words, the average time is the average of the required times T1 from the welding point 100 one point before to the welding point 100 M points before (M is an integer smaller than N) when welding is performed in sequence from the first point to the Nth point (N is an integer equal to or greater than 2). This average time corresponds to the past routine described above. In the example shown in FIG. 7 and FIG. 8, when welding is performed in sequence from the welding point 100 one point before to the welding point 100 five points before, the average time is used. In FIG. 7 and FIG. 8, the transition of the required time T1 at each welding point when the operation control unit 45 adjusts the start time of the approaching operation is illustrated by a two-dot chain line as this routine.

[0062] In this embodiment, the acquisition unit 41 acquires the required time T1 for each of the multiple welding points 100. The determination unit 43 calculates average time differences D1, D2 as the difference between the average time and a predetermined reference time TS. Furthermore, the determination unit 43 determines whether or not a time difference T2 occurs using the average time differences D1, D2. The operation control unit 45 adjusts the start time of the approaching operation at the subsequent welding point 100 to be controlled by advancing or delaying the start time using the average time differences D1, D2. Specifically, when the required time T1 is longer than the reference time TS, the operation control unit 45 adjusts the start time of the approaching operation in the subsequent welding to be advanced according to a first average time difference D1 to be described later. Furthermore, when the required time T1 is shorter than the reference time TS, the operation control unit 45 adjusts the start time of the approaching operation to be delayed according to a second average time difference D2 to be described later. Therefore, the control in this embodiment for bringing the required time T1 closer to the reference time TS is a correction control for bringing the required time T1 closer to the reference time TS by feeding back the average time differences D1 and D2 during subsequent welding at the welding point 100.

[0063] First, a control method in the case where the required time T1 is longer than the reference time TS will be described with reference to Fig. 7. In Fig. 7, the transition of the required time T1 when no correction control is performed is shown by a dotted line as a non-correction state. In the graph of the non-correction state in Fig. 7, the required time T1 for the first to fifth welding points 100 represents an actual measurement value. Also, in the graph of the non-correction state in Fig. 7, the required time T1 for the sixth to tenth welding points 100 represents the required time T1 expected when no correction control is performed by the operation control unit 45.

[0064] In Fig. 7, the average time of the required time T1 acquired for each of the multiple welding points 100 is shown as the first average time. In Fig. 7, the transition of the first average time is shown by a dashed line. The first average time here is the average of the required times T1 from the previous welding point 100 to the fifth previous welding point 100. The first average time difference D1 is the difference between the first average time at each welding point 100 and a reference time TS.

[0065] FIG. 7 illustrates a case where the correction control is executed for the sixth and subsequent welding points 100 in order. For example, for the sixth welding point 100, the first average time and the first average time difference D1 are calculated by the determination unit 43 based on the required time T1 from the first to the fifth welding points 100. The first average time from the first to the fifth welding points 100 in FIG. 7 is 40.4 milliseconds. Therefore, the first average time difference D1 from the first to the fifth welding points 100 is 2.4 milliseconds. Therefore, in the example illustrated in FIG. 7, the operation control unit 45 adjusts the start time of the approaching operation at the sixth welding point 100 to start 2.4 milliseconds earlier than the start time of the approaching operation in the set state (a state in which the required time T1 coincides with the reference time TS). By this correction control, the required time T1 at the sixth welding point 100 becomes 40.6 milliseconds. That is, the correction control makes it possible to bring the required time T1 at the sixth welding point 100 closer to the reference time TS by the first average time difference D1, 2.4 milliseconds in this case, compared to the required time T1 (uncorrected state) expected when the correction control is not executed. Note that the required time T1 in the uncorrected state at the sixth welding point 100 in Fig. 7 is 43.0 milliseconds. Therefore, as shown by the arrow at the sixth welding point 100 in Fig. 7, the required time T1 of this routine can be brought closer to the reference time TS compared to the required time T1 in the uncorrected state.

[0066] When the seventh welding point 100 is the target of the correction control, the first average time difference D1 may be calculated using the required times T1 from the second welding point 100 to the sixth welding point 100. As shown in the graph of this routine in Fig. 7, when the required time T1 in the non-corrected state is longer than the reference time TS, the correction control is executed to make the required time T1 in the subsequent welding closer to the reference time TS. This suppresses fluctuations in the required time T1.

[0067] Next, a control method in the case where the required time T1 is shorter than the reference time TS will be described with reference to Fig. 8. Descriptions of the same parts as in Fig. 7 will be omitted where appropriate. The non-correction state in Fig. 8 is the same as in Fig. 7.

[0068] In Fig. 8, the average time of the required time T1 acquired for each of the multiple welding points 100 is shown as the second average time. In Fig. 8, the transition of the second average time is shown by a dashed line. The second average time here is the average of the required times T1 from the previous welding point 100 to the fifth previous welding point 100. The second average time difference D2 is the difference between the second average time and the reference time TS.

[0069] FIG. 8 illustrates a case where the correction control is executed sequentially for the sixth and subsequent welding points 100. For example, for the sixth welding point 100, the second average time and the second average time difference D2 are calculated by the determination unit 43 based on the required time T1 from the first to the fifth welding points 100. The second average time from the first to the fifth welding points 100 in FIG. 8 is 35.8 milliseconds. Therefore, the second average time difference D2 from the first to the fifth welding points 100 is 2.2 milliseconds. Therefore, in the example illustrated in FIG. 8, the operation control unit 45 adjusts the start time of the approach operation at the sixth welding point 100 to start later by 2.2 milliseconds. By this correction control, the required time T1 at the sixth welding point 100 becomes 36.2 milliseconds. That is, the correction control makes it possible to bring the required time T1 at the sixth welding point 100 closer to the reference time TS by the second average time difference D2, 2.2 milliseconds in this case, compared to the required time T1 (uncorrected state) expected when the correction control is not executed. Note that the required time T1 in the uncorrected state at the sixth welding point 100 in Fig. 8 is 34.0 milliseconds. Therefore, as shown by the arrow at the sixth welding point 100 in Fig. 8, the required time T1 of this routine can be brought closer to the reference time TS compared to the required time T1 in the uncorrected state.

[0070] When the seventh welding point 100 is the target of the correction control, the second average time difference D2 may be calculated using the required times T1 from the second welding point 100 to the sixth welding point 100. As shown in the graph of this routine in Fig. 8, even if the required time T1 in the non-corrected state is shorter than the reference time TS, the required time T1 in the subsequent welding can be made to approach the reference time TS by executing the correction control. This suppresses fluctuations in the required time T1.

[0071] According to the above embodiment, the acquisition unit 41 acquires the required time T1 from the start of the approaching operation to the contact time when the stud material B and the base material W come into contact with each other. Next, the determination unit 43 determines whether or not a time difference T2 occurs between the required time T1 acquired by the acquisition unit 41 and a predetermined reference time TS. When it is determined that the time difference T2 occurs, the operation control unit 45 adjusts the start time of the approaching operation in the later welding so as to reduce the time difference T2. When the required time T1 is longer than the reference time TS, the start time of the approaching operation in the later welding is adjusted to be earlier according to the time difference T2. As a result, when the required time T1 is longer than the reference time TS, the start time of the approaching operation is adjusted according to the time difference T2, so that the required time T1 can be brought closer to the reference time TS. Also, when the required time T1 is shorter than the reference time TS, the start time of the approaching operation in the later welding is adjusted to be later according to the time difference T2. In this way, when the required time T1 is shorter than the reference time TS, the start point of the approaching action is adjusted according to the time difference T2, so that the required time T1 can be brought closer to the reference time TS. As a result, fluctuations in the required time T1 are suppressed.

[0072] Furthermore, according to the above embodiment, when it is determined that the time difference T2 occurs, the operation control unit 45 adjusts the start time of the approaching operation in the subsequent welding for each of the multiple welding points 100 so as to reduce the time difference T2. In this way, by adjusting the start time of the approaching operation for each of the multiple welding points 100 in accordance with the time difference T2, it is possible to bring the required time T1 closer to the reference time TS.

[0073] According to the above embodiment, the determination unit 43 determines whether or not a time difference T2 occurs by using the average time difference D1, D2, which is the difference between the average time of the required time T1 for each of the multiple welding points 100 and the reference time TS. This allows the start time of the subsequent welding to be adjusted in consideration of the required time T1 for each of the multiple welding points 100. That is, the required time T1 can be brought closer to the reference time TS while taking into account the tendency of the required time T1 at the multiple welding points 100 when welding using the stud gun 2. Also, the average time that is the median of the required time T1 at the multiple welding points 100 can be brought closer to the reference time TS. For example, this is effective when an extreme difference is observed in the required time T1 at the multiple welding points 100 compared to the other welding points 100 (hereinafter, abnormal value). In this case, the determination unit 43 does not calculate the time difference T2 based only on the abnormal value, so that the possibility of a large time difference T2 occurring between the required time T1 in this routine and the reference time TS can be reduced.

[0074] Furthermore, according to the above embodiment, when the required time T1 is longer than the reference time TS, the operation control unit 45 adjusts the start time of the approaching action in the later welding to be earlier in accordance with the first average time difference D1, thereby bringing the required time T1 closer to the reference time TS. When the required time T1 is shorter than the reference time TS, the operation control unit 45 adjusts the start time of the approaching action in the later welding to be later in accordance with the second average time difference D2, thereby bringing the required time T1 closer to the reference time TS. As a result, even when the determination unit 43 calculates the time difference T2 using the average time differences D1 and D2, the required time T1 in the later welding can be brought closer to the reference time TS in both cases where the required time T1 is longer and shorter than the reference time TS.

[0075] According to the above embodiment, when welding is performed in order from the first welding point 100 to the Nth welding point 100 (N is an integer equal to or greater than 2), the determination unit 43 determines the time difference T2 using average time differences D1 and D2, which are the differences between the average time T1 of each of the welding points 100 from the previous welding point 100 to the welding point 100 M points before (M is an integer smaller than N) and the reference time TS. As a result, even if the required time T1 varies due to the passage of time of use, the determination unit 43 can select data at any welding point 100 and use it as a past routine, and calculate the time difference T2 by referring to this past routine. For example, if the required time T1 varies significantly as the time of use passes compared to when the use started, the average time may not match the actual situation even if the average time is calculated using data from a time when the required time T1 had a different tendency. In contrast, in this embodiment, if the judgment unit 43 calculates the time difference T2 using the required time T1 for any welding point 100 in the past routine, the operation control unit 45 can adjust the start time of the approach operation in the subsequent welding based on desired data, such as the most recent data.

[0076] The method of controlling the required time T1 by the arc stud welding apparatus 1 is not limited to this. For example, the multiple welding points 100 may be provided at 11 or more points on the same base material W. The determination unit 43 may calculate average time differences D1, D2 from the required times T1 of the previous welding point 100 and the welding point 100 three points before as an arbitrary welding point 100. In addition, it is not essential to use the average time when calculating the time difference T2. For example, when welding is performed at five welding points 100, the determination unit 43 may set the difference between the required time T1 at the previous welding point 100 and the reference time TS as the time difference T2.

[0077] B. Second embodiment: In this embodiment, a method for controlling the required time T1 when welding stud material B to a plurality of welding points 100 for each of two or more base materials W will be described. The configuration of the arc stud welding apparatus 1 in this embodiment is similar to that in the first embodiment, and therefore a description thereof will be omitted. Also, in this embodiment, the method for controlling the required time T1 is different from that in the first embodiment.

[0078] FIG. 9 is a graph showing the required time T1 for each welding point 100 for two or more base materials W. In the example shown in FIG. 9, car numbers are attached to identify the two or more base materials W. In this embodiment, welding is performed on a first base material W which is a part of car P, a second base material W which is a part of car P+1, and a third base material W which is a part of car P+2, in that order. The first to third base materials W are made of the same shape and the same material. The first to third base materials W are, for example, the same parts used for each vehicle when manufacturing multiple vehicles.

[0079] The first to third base metals W are welded in order from the first welding point 100 to the Nth welding point 100 (N is an integer of 2 or more). In FIG. 9, the first base metal W (car P) is welded in order from the first welding point 100 to the fifth welding point 100. Thereafter, the second base metal W (car P+1) is welded in order from the first welding point 100 to the fifth welding point 100. The horizontal axis of FIG. 9 shows the first welding point 100 to the fifth welding point 100 in chronological order. The vertical axis of FIG. 9 shows the required time T1. In FIG. 9, the unit of the required time T1 is milliseconds (ms). In FIG. 9, the required times T1 for the first to fifth welding points 100 on the first base metal W and the first to fifth welding points 100 on the second base metal W are plotted. In this embodiment, the required time T1 at each welding point 100 of the first base material W (car P) and the second base material W (car P+1) corresponds to the past routine when welding each welding point 100 of the third base material W (car P+2). In Fig. 9, the progress of the required time T1 at the first base material W and the second base material W is shown by a dotted line as the past routine.

[0080] Each of the multiple welding points 100 is formed at a corresponding position in two or more base materials W. In this embodiment, each of the multiple welding points 100 is formed at the same position in two or more base materials W. For example, the Qth welding point 100 (Q is an integer between 1 and N) in the first base material W (car P), the Qth welding point 100 in the second base material W (car P+1), and the Qth welding point 100 in the third base material W (car P+2) are formed at the same position in each base material W. That is, the third welding point 100 in the first base material W (car P), the third welding point 100 in the second base material W (car P+1), and the third welding point 100 in the third base material W (car P+2) in FIG. 9 are formed at the same position.

[0081] Here, when welding is performed on the welding points 100 formed at the same positions of the first to third base materials W that are made of the same shape and the same material, a certain tendency may be observed for each welding point 100 with respect to the required time T1. For example, in FIG. 9, a similar tendency is observed for the required time T1 at the welding points 100 formed at the same positions of the first base material W (car P) and the second base material W (car P+1). The similar tendency is whether the required time T1 is shorter or longer than the reference time TS, or the difference between the required time T1 and the reference time TS. Therefore, when welding is performed on the welding points 100 formed at the same positions of the base materials W that are made of the same shape and the same material, it is preferable to consider the characteristics and tendency of each welding point 100. Therefore, in this embodiment, a more preferable correction control of the required time T1 is executed.

[0082] In this embodiment, the acquisition unit 41 acquires the required time T1 for each of the multiple welding points 100. When adjusting the start time of the approaching operation by the operation control unit 45, the determination unit 43 calculates a third average time as an average time of the required times T1 of the welding points 100 formed at the same position among the required times T1 acquired for each welding point 100 in two or more base materials W. Furthermore, the determination unit 43 determines whether or not a time difference T2 occurs using a third average time difference D3 that is the difference between the third average time and the reference time TS. The third average time is an average time of the required times T1 at the Qth welding point 100 as the welding point 100 formed at the same position among the required times T1 from the first welding point 100 to the Nth welding point 100 (N is an integer of 2 or more) for each of the first base material W (car P) and the second base material W (car P+1). In the example shown in Fig. 9, the required time T1 at the third welding point 100 on the first base material W (car P) is 47.0 milliseconds. Also, the required time T1 at the third welding point 100 on the second base material W (car P+1) is 46.0 milliseconds. Therefore, in Fig. 9, the third average time at the third welding point 100 is 46.5 milliseconds. In Fig. 9, the third average time is shown by a triangular plot.

[0083] In the example shown in Fig. 9, the third average time difference at the third welding point 100 is 46.5 milliseconds, the reference time TS is 38.0 milliseconds, and the third average time difference D3 is 8.5 milliseconds. In Fig. 9, at the third welding point 100, the third average time is delayed by 8.5 milliseconds with respect to the reference time TS.

[0084] The operation control unit 45 adjusts the start time of the approaching operation of the stud gun 2 to the welding point 100 formed at the same position as the welding point 100 for which the third average time was calculated among the two or more base materials W to be welded in sequence. That is, the third average time difference D3 at the Qth welding point 100 calculated from the past routine is reflected in the start time when welding is performed on the Qth welding point 100 of the base material W to be welded later. At this time, when the required time T1 is longer than the reference time TS, the operation control unit 45 adjusts the start time of the approaching operation in the later welding earlier according to the third average time difference D3. Also, when the required time T1 is shorter than the reference time TS, the operation control unit 45 adjusts the start time of the approaching operation in the later welding later according to the third average time difference D3.

[0085] In the example shown in FIG. 9, the third average time difference at the third welding point 100 calculated from the required time T1 for the first base material W (car P) and the second base material W (car P+1) is 8.5 milliseconds. Also, in the example shown in FIG. 9, the third average time is longer than the reference time TS. Therefore, when welding the third welding point 100 of the third base material W (car P+2) to be welded later, the operation control unit 45 starts the approach operation 8.5 milliseconds earlier. Note that the same correction control is performed for the first, second, fourth, and fifth welding points 100 as the other welding points 100.

[0086] The positions at which the multiple welding points 100 are formed are not limited to this. Each of the multiple welding points 100 may be formed at a corresponding position among two or more base materials W. For example, consider a case where the thickness of the plate-shaped base materials is different among two or more plate-shaped base materials having the same material and shape. In this case, each of the multiple welding points 100 may be formed at a part of the two or more plate-shaped base materials having the same thickness. For example, consider a case where the strength of the base materials differs depending on the part among two or more base materials having the same material and shape. In this case, each of the multiple welding points 100 may be formed at a part of the two or more base materials having the same strength. In this way, each of the multiple welding points 100 may be formed at a corresponding position among two or more base materials W.

[0087] According to the above embodiment, the acquisition unit 41 acquires the required time T1 for each of the multiple welding points 100 in two or more base materials W. Next, the determination unit 43 calculates an average time (third average time) of the required times T1 acquired for each of the multiple welding points 100 in two or more base materials W for the welding points 100 formed at the corresponding positions. Furthermore, the determination unit 43 uses a third average time difference D3, which is the difference between the third average time and the reference time TS, to determine whether or not a time difference T2 has occurred. For the multiple base materials W to be welded in sequence, the operation control unit 45 adjusts the start time of the approaching operation for the welding point 100 formed at the position corresponding to the welding point 100 for which the third average time as the average time has been calculated among the base materials W to be welded later. Specifically, when the required time T1 is longer than the reference time TS, the operation control unit 45 adjusts the start time of the approaching operation in the later welding earlier according to the third average time difference D3. When the required time T1 is shorter than the reference time TS, the operation control unit 45 adjusts the start time of the approaching operation in the subsequent welding to be later in accordance with the third average time difference D3. This allows the required time T1 to be brought closer to the reference time TS in welding using the arc stud welding apparatus 1, taking into account the characteristics and tendencies of each welding point 100. As a result, fluctuations in the required time T1 are suppressed.

[0088] The number of base materials W to be welded in sequence and the number of welding points 100 are not limited to this. For example, the number of base materials W to be welded in sequence may be 50. In this case, the determination unit 43 may calculate the third average time difference D3 using the required time T1 of each welding point 100 from the first base material W to the 49th base material W in welding the 50th base material W. The determination unit 43 may also calculate the third average time difference D3 using the required time T1 of each welding point 100 from the previous base material W to an arbitrary number, for example, the fifth previous base material W. In addition, it is not essential to use the average time when the determination unit 43 calculates the time difference T2. For example, consider a case where welding is performed on one welding point formed at a corresponding position for each of five base materials W. In this case, the determination unit 43 may calculate the time difference T2 using only the required time T1 for the third base material W when welding the fifth base material W.

[0089] According to all the embodiments described above, in both cases where the base metal W to be the object of arc stud welding is a single one and where there are multiple base metals W, the operation control unit 45 adjusts the start point of the approaching operation, so that the required time T1 can be made to approach the reference time TS. Therefore, regardless of the number of base metals W to be the object of welding, the required time T1 can be made to approach the reference time TS.

[0090] The present disclosure is not limited to the above-mentioned embodiment, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features of the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention can be appropriately replaced or combined to solve some or all of the above-mentioned problems or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0091] 1...arc stud welding device, 2...stud gun, 2a...one end, 2b...other end, 3...robot, 4...control device, 6...bolt feeder, 7...power supply device, 9...workpiece support, 11...sensor, 20...case, 21...gun coil, 22...fixed magnetic pole member, 23...cylinder, 24...movable magnetic pole member, 25...biasing member, 27...chuck, 29...workpiece holder, 29a...contact surface, 30...arm, 35...base, 37...stud gun support, 40...CPU, 41...acquisition unit, 43 ...determination unit, 45...operation control unit, 47...storage unit, 100...welding point, 241...head, 242...rod, 243...tail, 271...gripping unit, A...arc, B...stud material, B1...head, B2...shaft, B3...projection, Ba...base end, Bb...tip, D1...first average time difference, D2...second average time difference, D3...third average time difference, F...installation surface, L...separation distance, S...sliding area, T...welding time, T1...required time, T2...time difference, TS...reference time, W...base material, WS...welding surface

Claims

1. An arc stud welding device that generates an arc between a base material and a stud material to weld, a stud gun which holds the stud material, and which, after starting welding, executes a separating operation for separating the stud material from the base material, and an approaching operation for bringing the stud material closer to the base material after the separating operation, for each of a plurality of welding points; an acquisition unit that acquires a required time from a start point of the approaching motion to a contact point where the stud material and the base material come into contact with each other; a determination unit that determines whether or not a time difference occurs between the required time acquired by the acquisition unit and a predetermined reference time; an operation control unit that controls the approaching operation and the separating operation of the stud gun, the acquisition unit determines the time point of contact using a detection signal from a sensor that detects a displacement amount of the tip of the stud, and acquires as the required time a time until the displacement amount becomes equal to a separation distance between the tip of the stud and the base material at the start point of the approaching motion; When it is determined that the time difference exists, the operation control unit controls the required time by adjusting the start time of the subsequent welding so as to reduce the time difference.

2. 2. The arc stud welding apparatus according to claim 1, When the required time is longer than the reference time, the operation control unit controls the required time by adjusting the start time earlier in accordance with the time difference.

3. The arc stud welding apparatus according to claim 1 or 2, When the required time is shorter than the reference time, the operation control unit controls the required time by adjusting the start time later in accordance with the time difference.

4. The arc stud welding apparatus according to any one of claims 1 to 3, the plurality of weld points are located at different positions in the same base material, The acquisition unit acquires the required time for each of the plurality of welding points, The determination unit performs the determination for each of the plurality of welding points, The operation control unit controls the required time for each of the plurality of welding points.

5. 5. The arc stud welding apparatus according to claim 4, the determination unit performs the determination using an average time difference that is a difference between an average time of the required times for each of the plurality of welding points and the reference time, The operation control unit adjusts the start time of the subsequent welding so as to reduce the average time difference.

6. 6. The arc stud welding apparatus according to claim 5, The number of welding points is N or more (N is an integer of 2 or more), The welding to the plurality of welding points is performed in order from a first point to an Nth point, the determination unit uses, as the average time difference, a difference between an average time of the required time for each of the plurality of welding points from the welding point one point before to the welding point M points before (M is an integer smaller than N) and the reference time.

7. The arc stud welding apparatus according to any one of claims 1 to 3, The number of the base materials is two or more, Each of the plurality of weld points is formed at a corresponding position in the two or more base materials, The acquisition unit acquires the required time for each of the plurality of welding points, The determination unit performs the determination for each of the plurality of welding points, The operation control unit controls the required time for each of the plurality of welding points.

8. 8. The arc stud welding apparatus according to claim 7, the determination unit performs the determination using an average time difference that is a difference between an average time of the required times for each of the plurality of welding points and the reference time, The operation control unit adjusts the start time of the subsequent welding so as to reduce the average time difference.

9. 9. The arc stud welding apparatus according to claim 1, The arc stud welding apparatus further comprises a base metal presser for pressing the base metal.

10. An arc stud welding method for welding by generating an arc between a base material and a stud material, comprising the steps of: a separating step of separating the stud material from the base material after starting welding with a stud gun that holds the stud material; After the separating step, a process of bringing the stud material closer to the base material is performed for each of the plurality of welding points, and further an acquisition step of acquiring a time required from a start point of the approach step to a contact point of the stud material and the base material; a determination step of determining whether or not a time difference occurs between the required time acquired by the acquisition step and a predetermined reference time, In the obtaining step, the contact time point is determined using a detection signal from a sensor that detects a displacement amount of the tip of the stud, and the time until the displacement amount becomes equal to the separation distance between the tip of the stud and the base material at the start point of the approaching step is obtained as the required time, the approaching step includes a step of controlling the required time by adjusting the start time of the subsequent welding step so as to reduce the time difference when it is determined that the time difference exists.

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