Welding device and storage medium

Abstract

The purpose is to shorten the operation time for correcting the relationship between applied pressure and torque. The welding apparatus 1 includes: a unit that prompts the user to input a command indicating that the applied pressure between the movable electrode head 35 and the fixed electrode head 34 reaches two applied pressures respectively; a unit that determines the torque generated by the servo motor 36 and the amount of movement of the movable electrode head at the time the command is input; a unit that derives the relationship between applied pressure and movement; a unit that uses the relationship to estimate the amount of movement of the movable electrode head required to generate other applied pressures; and a unit that determines the torque required to move the estimated amount of movement of the movable electrode head and registers it in correspondence with other applied pressures.

Description

Technical Field

[0001] This invention relates to a welding apparatus and a process. Background Technology

[0002] In recent years, robotic devices equipped with spot welding guns have been widely used for welding automotive bodies and other components. In spot welding operations, two workpieces are clamped between a movable electrode head and a fixed electrode head, and current flows through the movable and fixed electrode heads under a specified applied pressure, enabling the welding of the two workpieces. Regarding welding using a spot welding gun, Patent Document 1 discloses a spot welding system that can accurately and easily calculate the elastic displacement of the gun arm when pressure is applied to the workpieces to suppress a decrease in welding accuracy.

[0003] To prevent a decrease in welding precision, it is crucial to apply the correct pressure, adjusted according to the thickness and material of the workpiece being welded and the required weld strength. This pressure is adjusted based on the torque of the servo motor that drives the movement of the movable electrode head. To adjust the pressure via torque, the relationship between pressure and torque is pre-registered. However, this relationship can change due to factors such as servo motor deterioration or electrode head deterioration. Therefore, the relationship between pressure and torque needs to be calibrated before using the spot welding torch.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2015-217436 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] To obtain the relationship between applied pressure and torque with high accuracy, a known method involves using a pressure sensor to actually measure the applied pressure generated between the movable and fixed electrode heads, and obtaining the torque generated by the servo motor when the applied pressure between the movable and fixed electrode heads reaches a predetermined applied pressure. However, this method requires performing the above operation multiple times for each predetermined applied pressure, thus consuming a significant amount of time. Therefore, it is desirable to shorten the operation time for correcting the relationship between applied pressure and torque.

[0009] means for solving problems

[0010] One aspect of the welding apparatus disclosed herein is equipped with a welding torch having a servo motor that generates power to bring the movable electrode head closer to and further away from the fixed electrode head in order to apply pressure and weld the workpiece between a movable electrode head and a fixed electrode head. The welding apparatus includes: a unit that prompts the user to input multiple pressures to be used in welding; a unit that prompts the user to input commands indicating that the pressure between the movable electrode head and the fixed electrode head reaches two of the multiple pressures; a unit that determines the torque generated by the servo motor at the time the command is input; a unit that determines the amount of movement of the movable electrode head required for the pressure between the movable electrode head and the fixed electrode head to reach the two pressures; a unit that derives a formula relating the pressure and the movement based on the two pressures and the movement; a unit that uses the formula to estimate the amount of movement required to generate other pressures between the movable electrode head and the fixed electrode head, excluding the two of the multiple pressures; a unit that determines the torque required to move the estimated amount of movement of the movable electrode head; and a unit that registers the torque required to move the estimated amount of movement as the torque required to generate other pressures between the movable electrode head and the fixed electrode head.

[0011] The effects of the invention

[0012] According to one aspect of this disclosure, the operation time for correcting the relationship between applied pressure and torque can be shortened. Attached Figure Description

[0013] Figure 1 This is a diagram illustrating an example of the welding apparatus of this embodiment.

[0014] Figure 2 yes Figure 1 An enlarged view of the spot welding gun.

[0015] Figure 3 This is a frame structure diagram of the welding apparatus of this embodiment.

[0016] Figure 4 This is a flowchart illustrating an example of the correction sequence performed by the welding apparatus of this embodiment.

[0017] Figure 5 It is shown that... Figure 4 A diagram showing an example of a calibration screen corresponding to the calibration sequence process S11.

[0018] Figure 6 It is shown that... Figure 4 An example diagram of the calibration screen corresponding to the calibration sequence steps S12, S15, and S16.

[0019] Figure 7 It is used to explain and Figure 4Supplementary diagram of the internal processing of the control device corresponding to the correction sequence steps S13 and S14.

[0020] Explanation of reference numerals in the attached figures

[0021] 30: Spot welding gun; 31: Base; 32: Fixed arm; 33: Movable arm; 34: Fixed electrode head; 35: Movable electrode head; 36: Servo motor; 37: Encoder; 38: Torque sensor; 39: Motor driver; 50: Control device; 51: Torque determination unit; 52: Movement determination unit; 53: Formula processing unit; 54: Movement estimation unit; 55: Screen generation unit; 56: Motor control unit; 70: Teach pendant; 71: Input unit; 72: Display unit. Detailed Implementation

[0022] Hereinafter, a welding apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings. In the following description, structural elements having substantially the same function and structure will be given the same reference numerals and will be described repeatedly only where necessary.

[0023] The welding apparatus of this embodiment is a device that equips a spot welding gun on a robotic arm mechanism in a manner that allows the position and orientation of the spot welding gun to be changed. However, one feature of the welding apparatus of this embodiment is the method for calibrating the spot welding gun. Therefore, the welding apparatus can also equip the spot welding gun on other mechanisms that allow the position and orientation of the spot welding gun to be changed. In addition, if the spot welding gun can be used for welding operations, the spot welding gun can also be used as a separate welding device.

[0024] like Figure 1 As shown, the welding device 1 includes: a robotic arm mechanism 10, a spot welding gun 30 mounted on the robotic arm mechanism 10, a control device 50 for controlling the movement of the robotic arm mechanism 10 and the spot welding gun 30, and a teach pendant 70 that is connected to the control device 50 in a communicative manner.

[0025] like Figure 2 As shown, the spot welding gun 30 has a base 31, a fixed arm 32, a movable arm 33, and a pair of electrode heads. One of the pair of electrode heads 34 and 35 (referred to as the fixed electrode head 34) is mounted on the front end of the fixed arm 32, and the other of the pair of electrode heads 34 and 35 (referred to as the movable electrode head 35) is mounted on the front end of the movable arm 33. The shape, orientation, and position of the base 31, the fixed arm 32, and the movable arm 33 are designed so that the pair of electrode heads 34 and 35 can be arranged facing each other on the gun shaft Ax.

[0026] For example, the base portion 31 is configured as a rectangular plate. At the front end of the base portion 31, a rod-shaped movable arm 33 is configured to move along the gun axis Ax. At the rear end of the base portion 31, a fixed arm 32 is integrally formed with the base portion 31. The fixed arm 32 is configured as a rod, for example, bent into a roughly U-shape, such that a fixed electrode head 34 is disposed on the gun axis Ax at its front end and faces a movable electrode head 35 mounted at the front end of the movable arm 33.

[0027] The movement of the movable arm 33 is driven by a drive mechanism. The drive mechanism includes a servo motor 36 mounted on the base 31 that generates the power to move the movable arm 33, and a conversion mechanism (not shown) that converts the rotational motion of the servo motor 36 into linear motion along the gun axis Ax of the movable arm 33. The conversion mechanism can be any mechanism such as a gear mechanism, a belt / pulley mechanism, or a combination thereof. By driving the servo motor 36, the movable electrode head 35 reciprocates along the gun axis Ax together with the movable arm 33, approaching and moving away from the fixed electrode head 34.

[0028] The servo motor 36 is driven by current supplied from the motor driver 39. An encoder 37 for detecting the rotational position of the drive shaft of the servo motor 36 and a torque sensor 38 for detecting the torque generated on the drive shaft of the servo motor 36 are provided on the servo motor 36. The encoder 37 detects the rotational position of the drive shaft of the servo motor 36 and sends it to the control device 50. The encoder 37 functions as a position detection unit that detects the position of the movable arm 33 by detecting the rotational position of the drive shaft of the servo motor 36. Alternatively, a Hall element can be used as the position detection unit instead of the encoder 37. The torque sensor 38 can be any existing sensor, such as a strain gauge type or a non-contact type. The torque sensor 38 detects the actual torque generated on the drive shaft of the servo motor 36 and sends it to the control device 50.

[0029] Under the control of the control device 50, the workpiece to be welded is positioned between a pair of electrodes 34 and 35 of the spot welding gun 30 via the robotic arm mechanism 10. Subsequently, the control device 50 controls the servo motor 36 to move the movable electrode head 35 toward the fixed electrode head 34, clamping the workpiece between the movable and fixed electrode heads 34 and applying pressure with a predetermined force. Under the control of the control device 50, the fixed and movable electrode heads 34 are energized, and the workpiece clamped between them is spot welded.

[0030] The control device 50 has the same hardware as a typical PC (Personal Computer). Specifically, the control device 50 has a processor consisting of a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit), RAM (Random Access Memory) which functions as the processor's main memory and workspace, and a storage device that stores various programs and setting information. The storage device stores a calibration program for the pressure / torque of the welding torch 30, a control program for maneuvering the robot device including the welding torch 30 and the robotic arm mechanism 10, and data such as constants, variables, and setpoints required when the welding torch 30 moves.

[0031] When the correction program is executed by the processor, the control device 50 functions as a torque determination unit 51, a movement amount determination unit 52, a formula processing unit 53, a movement amount estimation unit 54, a screen generation unit 55, and a motor control unit 56.

[0032] The torque determination unit 51 is a unit that determines the torque generated on the drive shaft of the servo motor 36 based on the output of the torque sensor 38. Specifically, the torque determination unit 51 determines the torque of the drive shaft of the servo motor 36. However, if it can be correlated with the torque generated by the servo motor 36, the torque determined by the torque determination unit 51 is not limited to the torque of the drive shaft of the servo motor 36. For example, the torque determination unit 51 may also determine the torque of other shafts based on the output of torque sensors mounted on other shafts that transmit the rotation of the servo motor 36. Additionally, the torque determination unit 51 may also determine the torque as the torque command value sent from the motor control unit 56 to the motor driver 39. The torque determination unit 51 estimates the torque for moving the movable electrode head 35 by the amount of movement estimated by the movement amount estimation unit 54 (described later).

[0033] The movement amount determination unit 52 determines the movement amount (first movement amount) of the movable electrode head 35, which moves along the gun axis Ax, based on the output of the encoder 37. This movement amount is a parameter indicating the extent to which the movable electrode head 35 is pushed in from its position of contact with the workpiece being welded, the pressure sensor 100, the fixed electrode head 34, or other contacted objects. The point at which the movable electrode head 35 contacts the contacted object can be determined based on, for example, the output of the torque sensor 38. Of course, the means are not limited to this; if it is possible to detect that the movable electrode head 35 has contacted the contacted object, a contact sensor, an external image sensor, etc., can be used. Since it is based on the output of the encoder 37, the movement amount of the movable electrode head 35 is not a physical movement amount, but rather equivalent to the rotation amount of the drive shaft of the servo motor 36. Hereinafter, only the movement amount referred to as the movement amount refers to the movement amount of the movable electrode head 35.

[0034] The formula processing unit 53 is a unit that formulates the relationship between the applied pressure and the amount of movement when the applied pressure is generated between at least two applied pressures and the movable electrode head 35 and the fixed electrode head 34. For example, the formula processing unit 53 maintains a linear function formula as a model of the relation, and calculates the constant of the linear function formula by applying two applied pressures and the amount of movement when the applied pressure is applied, and then formulates the formula. The model of the relation is not limited to a linear function, and any formula can be used. Based on the model of the relation, the number of points of change in applied pressure / movement required to calculate the constant is determined.

[0035] The movement estimation unit 54 estimates the movement amount (second movement amount) of the movable electrode head 35 for generating other applied pressures based on at least two applied pressures and the movement amount when the applied pressure is generated between the movable electrode head 35 and the fixed electrode head 34. Specifically, the movement estimation unit 54 estimates the movement amount (second movement amount) for achieving a predetermined applied pressure between the movable electrode head 35 and the fixed electrode head 34 using the relationship between applied pressure and movement amount formulated by the formulating processing unit 53.

[0036] The image generation unit 55 generates image data to be displayed on the display unit of the teach pendant 70. Specifically, it generates a correction image 200 (see reference) for correcting the relationship between applied pressure and torque. Figure 5 The data in (a), etc. Additionally, when determining the torque in the specified applied pressure using the pressure sensor 100, a measurement window 300 is generated for measuring the specified applied pressure (see reference). Figure 5 (c) Figure 6 The data in (a)). The calibration screen 200 corresponds to a unit that prompts the user to input multiple pressures to be used in welding. In addition, the measurement window 300 corresponds to a unit that prompts the user to input instructions indicating that the pressure between the movable electrode head 35 and the fixed electrode head 34 reaches two of the multiple pressures.

[0037] In order to control the servo motor 36, the motor control unit 56 sends a torque command to the motor driver 39 of the servo motor 36. The motor driver 39 supplies current to the servo motor 36 corresponding to the torque command received from the motor control unit 56. As a result, the servo motor 36 is driven with a predetermined torque. In this embodiment, the motor control unit 56 controls the servo motor 36 to gradually increase the torque based on the click of the start button of the measurement window 300 displayed on the teach pendant 70. In addition, the motor control unit 56 controls the servo motor 36 to gradually increase the torque based on the click of the calibration button of the calibration screen 200 displayed on the teach pendant 70, until the movement amount of the movable electrode head 35 determined by the movement amount determination unit 52 reaches the movement amount estimated by the movement amount estimation unit 54.

[0038] The teach pendant 70 functions as a display unit 72 for the user to view various information from the control device 50 and an input unit 71 for the user to input various information into the control device 50. The display unit 72 is composed of an LCD (Liquid Crystal Display) or the like. The input unit 71 is composed of a keyboard or the like. Of course, it can also be composed of a touch-screen display panel that combines the functions of an input unit 71 and a display unit 72.

[0039] The input unit 71 allows the user to input multiple pressures intended for use in welding. These pressures can be input directly by the user, or multiple tables containing pre-registered pressures can be imported from the user-selected tables. Furthermore, during trial runs where the torque of the servo motor 36 is gradually increased, the input unit 71 receives commands from the user indicating that the pressure between the movable electrode head 35 and the fixed electrode head 34 has reached the minimum and maximum pressures, respectively. Thus, the control device 50 receives the specified pressures and whether the pressure between the movable electrode head 35 and the fixed electrode head 34 has reached two of the specified pressures via the input unit 71. The display unit 72 displays the calibration screen 200, measurement window 300, etc., generated by the screen generation unit 55 of the control device 50.

[0040] The following is for reference Figures 4 to 7 This describes the method for correcting the relationship between applied pressure and torque. The correction of applied pressure / torque can be performed via user operation displayed on the correction screen 200 and measurement window 300 on the teach pendant 70. The correction screen 200... Figure 5 (a) Figure 5 (b) Figure 5 (c) Figure 6 (a) Figure 6 (b) Figure 6 The order of (c) in the text changes.

[0041] like Figure 5 As shown in (a), the calibration screen 200 includes a selection button for selecting data tables related to multiple pre-registered applied pressures, a display area for a list of applied pressures of the calibration object, a graph showing the relationship between applied pressure and torque, a calibration button for starting automatic calibration, and a save button for saving the relationship between applied pressure and the calibrated torque. The measurement window 300 is overlaid on the calibration screen 200 by clicking on the applied pressure points plotted on the graph. Figure 5 As shown in (c), the measurement window 300 includes a display area for applied pressure, a display area for torque before calibration, a display area for current torque, a start button for initiating the closing action (pressurizing action) of the spot welding gun 30, a stop button for stopping the closing action (pressurizing action) of the spot welding gun 30, and a register button for registering the current torque.

[0042] like Figure 4 As shown, if pressure / torque calibration begins, the control device 50 registers multiple pressures Pr1, Pr2, Pr3, Pr4, and Pr5 of the calibration target input by the user (S11). Specifically, if the user clicks the selection button on the calibration screen 200, multiple files recording the predetermined pressures are displayed. If the user selects a specific file (aaaaa.txt) from the multiple files, the multiple pressures recorded in that specific file are input to the control device 50 as the pressures of the calibration target. Thus, the process of step S11 is completed, as... Figure 5 As shown in (b), multiple applied pressures Pr1, Pr2, Pr3, Pr4, and Pr5 recorded in a defined file are displayed on the applied pressure display area. The minimum applied pressure Pr1 and the maximum applied pressure Pr5 from these multiple applied pressures are automatically extracted, and the applied pressure and torque are plotted on a two-axis graph. At this time, the torques Tr1 and Tr5 corresponding to applied pressures Pr1 and Pr5, respectively, are the torques before calibration. The two applied pressures Pr1 and Pr5 are the applied pressures of the calibration object that actually used the applied pressure sensor 100.

[0043] Return to instructions Figure 4 After the processing in step S11, the welding device 1 registers the torques Tr1′, Tr5′ and the displacements Gm1, Gm5 when the pressure between the movable electrode head 35 and the fixed electrode head 34 reaches the minimum pressure Pr1 and the maximum pressure Pr5, respectively (S12). Step S12 is the step that intervenes in the operation of the user using the pressure sensor 100.

[0044] The user's operating sequence for using the pressure sensor 100 is as follows. The user places the sensor body of the pressure sensor 100 between the movable electrode head 35 and the fixed electrode head 34. Next, through operations on the calibration screen 200, the user selects the pressure to be calibrated using the pressure sensor 100. For example, as... Figure 5 As shown in (b), by clicking the point corresponding to the minimum applied pressure Pr1, the minimum applied pressure Pr1 can be selected as the calibration applied pressure. If the point corresponding to the minimum applied pressure Pr1 is clicked, the measurement window 300 is displayed.

[0045] like Figure 5 As shown in (c), if the start button of the measurement window 300 is clicked by the user, the torque of the servo motor 36 is gradually increased by the control device 50, and the pressure value measured by the pressure sensor 100 gradually increases. The user monitors the pressure value measured by the pressure sensor 100, and when the pressure value reaches the minimum pressure Pr1, clicks the stop button of the measurement window 300 to stop the control of the servo motor 36. The control device 50 determines the torque Tr11 at the time the stop button is clicked based on the output of the torque sensor 38, and determines the movement Gm based on the output of the encoder 37.

[0046] like Figure 6 As shown in (a), the torque Tr11 at the time the stop button is clicked is displayed in the current torque display area of ​​the measurement window 300. When the user clicks the registration button in the measurement window 300, the torque Tr11 and the movement Gm at the time the stop button is clicked are registered as the torque Tr1′ and the movement Gm1 when the minimum applied pressure Pr1 is applied.

[0047] Return to instructions Figure 4 After the processing in step S12, the control device 50 uses the minimum applied pressure Pr1, the maximum applied pressure Pr5, the movement amount Gm1 when the minimum applied pressure Pr1 is applied, and the movement amount Gm5 when the maximum applied pressure Pr5 is applied to derive the relationship between applied pressure and movement amount (S13).

[0048] After the processing in step S13, the control device 50 uses the relationship between the applied pressure and the amount of movement to estimate the amount of movement Gm2, Gm3, and Gm4 when the other applied pressures Pr2, Pr3, and Pr4 (excluding the minimum applied pressure Pr1 and the maximum applied pressure Pr5) of the multiple applied pressures Pr1, Pr2, Pr3, Pr4, and Pr5 of the calibration object are applied between the movable electrode head 35 and the fixed electrode head 34 (S14).

[0049] Processes S13 and S14 are internal processes of the control device 50. See below for reference. Figure 7 Explain the processing of steps S13 and S14. For example... Figure 7 As shown in (a), at the end of process S12, the movement Gm1 when pressure Pr1 is applied and the movement Gm5 when pressure Pr5 is applied are registered inside the control device 50. Therefore, two points can be plotted on a graph with pressure and movement as the X and Y axes, respectively. Assuming the relationship between pressure and movement is linear, the constants (A, B) of the linear function ((pressure) = A × (movement) + B) can be obtained from the above two points. By obtaining the constants (for example, by obtaining constant A = A1 and constant B = B1), as... Figure 7 As shown in (b), the relationship between applied pressure and displacement ((applied pressure) = A1 × (displacement) + B1) can be formulated (step S13). By formulating the relationship between applied pressure and displacement, the applied pressures Pr2, Pr3, and Pr4, which are not corrected by this relationship, can be substituted into the formula, thereby estimating the displacements Gm2, Gm3, and Gm4 (step S14).

[0050] Return to instructions Figure 4 After the processing of step S14, the control device 50 controls the opening and closing of the spot welding gun 30, automatically determines the torque when the movement of the movable electrode head 35 reaches the movement Gm2, Gm3, and Gm4 estimated by step S14 (S15), and registers the automatically determined torque as the torque Tr2′, Tr3′, and Tr4′ when the applied pressure Pr2, Pr3, and Pr4 are applied (S16).

[0051] Specifically, such as Figure 6 As shown in (b), if the user clicks the calibration button on the calibration screen 200, the control device 50 controls the servo motor 36 to gradually increase the torque from a state where the movable electrode head 35 is in contact with the fixed electrode head 34. During this period, the control device 50 monitors the amount of movement of the movable electrode head 35 based on the output of the encoder 37 and monitors the torque generated on the drive shaft of the servo motor 36 based on the output of the torque sensor 38. The control device 50 determines the torque at the time points when the amount of movement of the movable electrode head 35 reaches the amount of movement Gm2, Gm3, and Gm4 estimated by process S14. The amount of movement Gm2, Gm3, and Gm4 are estimated using the relationship between applied pressure and amount of movement as the amount of movement when applied pressure Pr2, Pr3, and Pr4 are applied. Therefore, the torque at the time points when the amount of movement Gm2, Gm3, and Gm4 estimated by process S14 can be regarded as the torque Tr2′, Tr3′, and Tr4′ when applied pressure Pr2, Pr3, and Pr4 are applied. After the processing in step S15, such as Figure 6 As shown in (c), the torques Tr1′, Tr2′, Tr3′, Tr4′, and Tr5′ corresponding to the predetermined pressures Pr1, Pr2, Pr3, Pr4, and Pr5 used as the calibration objects are obtained, respectively.

[0052] Through processes S11 to S16, the relationship between applied pressure and torque is corrected.

[0053] For reference Figures 4 to 7 As explained, according to the welding apparatus 1 of this embodiment, for at least two of the multiple applied pressures, the pressure / torque relationship can be manually corrected using the pressure sensor 100, and the welding apparatus 1 can automatically correct the pressure / torque relationship for the other applied pressures instead of manually correcting them. Therefore, even if the number of applied pressures intended to be used in the welding operation is as many as 30 points, the user only needs to use the pressure sensor 100 to correct the pressure / torque relationship for two of them. If the number of applied pressures intended to be used in the welding operation is 30 points, compared to the conventional method of repeatedly manually correcting all 30 points using the pressure sensor 100, the time required for the correction operation can be significantly reduced.

[0054] To achieve the aforementioned effects, the inventors focused on the correlation between applied pressure and the amount of movement of the movable electrode head 35. In step S12, the amounts of movement Gm1 and Gm5, which are internal parameters of the welding apparatus 1, were obtained together with the torques Tr1′ and Tr5′ when applied pressures Pr1 and Pr5. Then, by formulating the relationship between applied pressure and the amount of movement, the amount of movement required to obtain a specific applied pressure can be estimated. Thus, a feature of this application is that the external parameter, i.e., applied pressure, which can only be measured by the external pressure sensor 100, is replaced by the internal parameter, i.e., the amount of movement of the movable electrode head 35, which can be determined based on the output of the internal encoder 37. If the amount of movement required to obtain a specific applied pressure can be estimated, the torque can be gradually increased from the state where the movable electrode head 35 is in contact with the fixed electrode head 34, and the torque at which the amount of movement of the movable electrode head 35 reaches the estimated amount of movement can be obtained as the torque required to obtain the specific applied pressure. Although the initial two applied pressures must be manually calibrated for the applied pressure / torque, the process of obtaining the torque required to obtain the other applied pressures does not require user operation or assistance using the pressure sensor 100, thus significantly reducing the time required for user calibration.

[0055] In this embodiment, the functions of the input unit 71 and the display unit 72 are provided by the teach pendant 70 connected to the control device 50. However, as long as the user can input input information to the control device 50, its structure is not limited to this embodiment. For example, the functions of the input unit 71 and the display unit 72 may also be provided by the control device 50. In addition, an external device that can be communicatively connected to the control device 50 may also be configured to have some of the functions of the internal calculation and processing of the control device 50.

[0056] In this embodiment, the control device 50 controls the movement of the spot welding gun 30, but its form is not limited as long as it can control the movement of the spot welding gun 30. For example, the teach pendant 70 may have the function of the control device 50, and the spot welding gun 30 may be controlled by the teach pendant 70.

[0057] In this embodiment, the minimum and maximum applied pressures among the multiple applied pressures are automatically extracted as objects for manual calibration. However, the user can also select any two applied pressures from among the multiple applied pressures. The user's selection of two applied pressures can be performed via the calibration screen 200.

[0058] In this embodiment, the case where the movable electrode head 34 moves linearly along the gun axis Ax (represented by a straight line) is described. However, if the movable electrode head 35 can approach and move away from the fixed electrode head 34, and when the movable electrode head 35 approaches the fixed electrode head 34, it faces the fixed electrode head 34 along the gun axis Ax, holding the workpiece to be welded between the movable electrode head 35 and the fixed electrode head 34, then the approach and away path of the movable electrode head 34 may not be a straight line. Furthermore, in this embodiment, one of the pair of electrode heads 34 and 35 is movable, while the other electrode head 35 is fixed. However, it is also possible that one electrode head 34 is fixed and the other electrode head 35 is movable, or both of the electrode heads 34 and 35 are movable. If the structure has a pair of movable electrode heads 34 and 35 and two servo motors, then the pressure / torque correction described in this embodiment can be performed on each of the two servo motors.

[0059] While some embodiments of the invention have been described, these embodiments are given by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments or variations thereof are included within the scope or spirit of the invention as well as within the scope of the invention as set forth in the claims and its equivalents.

Claims

1. A welding apparatus equipped with a welding torch, the welding torch having a servo motor, wherein, in order to apply pressure and weld a workpiece between a movable electrode head and a fixed electrode head, the servo motor generates a force for moving the movable electrode head closer to and further away from the fixed electrode head, wherein... The welding apparatus has the following features: The user is prompted to enter the number of pressure units to be used in the welding process. The unit prompts the user to input instructions indicating that the pressure applied between the movable electrode head and the fixed electrode head reaches two of the plurality of pressures. A unit that determines the torque generated by the servo motor at the point in time when the instruction is input. A unit for determining the amount of movement of the movable electrode head required to achieve the two applied pressures between the movable electrode head and the fixed electrode head. The unit that derives the relationship between the applied pressure and the displacement based on the two applied pressures and the displacement. The unit that estimates the amount of movement required to generate the remaining pressure after removing two of the plurality of applied pressures between the movable electrode head and the fixed electrode head using the aforementioned relationship is used. A unit for determining the torque required to move the movable electrode head by the estimated amount of movement, and The torque required to move the estimated amount of movement is registered as a unit of torque required to generate the other applied pressure between the movable electrode head and the fixed electrode head.

2. The welding apparatus according to claim 1, wherein, The two applied pressures are the minimum and maximum applied pressures among the plurality of applied pressures.

3. The welding apparatus according to claim 1, wherein, It also has a unit that prompts the user to select two of the multiple pressures to be used in the welding process.

4. The welding apparatus according to claim 1, wherein, The unit that determines the torque determines the torque based on the output of the torque sensor installed in the servo motor.

5. The welding apparatus according to claim 1, wherein, The unit that determines the amount of movement determines the amount of movement based on the output of the encoder installed in the servo motor.

6. The welding apparatus according to claim 1, wherein, A unit that determines the torque required to move the movable electrode head by the estimated amount of movement controls the servo motor in a manner that gradually increases the torque from a state in which the movable electrode head is in contact with the fixed electrode head, and determines the torque at which the amount of movement of the movable electrode head reaches the estimated amount of movement as the required torque.

7. The welding apparatus according to claim 1, wherein, The unit that derives the relation maintains a linear model of a linear function. Based on the two applied pressures and the amount of movement until the two applied pressures are generated respectively, the constants of the linear model are determined, thereby deriving the relation between the applied pressure and the amount of movement.

8. A welding apparatus comprising a control device that controls a servo motor to apply pressure and weld a workpiece between a movable electrode head and a fixed electrode head, wherein the servo motor generates a force for moving the movable electrode head closer to and further away from the fixed electrode head, wherein... The control device is configured to perform the following: The system receives multiple specified pressure applications and determines whether the pressure between the movable electrode head and the fixed electrode head reaches two of the specified pressure applications. A first movement of the movable electrode head is obtained to achieve the two applied pressures. Based on the two applied pressures and the first movement, a relationship between the applied pressure and the movement is derived. Using this relationship, a second movement of the movable electrode head for generating other applied pressures different from the two applied pressures among the plurality of applied pressures is estimated. The torque used to move the movable electrode head by the second amount of movement is estimated.

9. A storage medium storing a program that enables a computer to act as a control device for controlling a welding torch having a servo motor, wherein, in order to apply pressure and weld a workpiece between a movable electrode head and a fixed electrode head, the servo motor generates a force for moving the movable electrode head closer to and further away from the fixed electrode head, wherein... The program enables the computer to function as the following unit: The user is prompted to enter the number of pressure units to be used in the welding process. The unit prompts the user to input instructions indicating that the pressure applied between the movable electrode head and the fixed electrode head reaches two of the plurality of pressures. A unit that determines the torque generated by the servo motor at the point in time when the instruction is input. A unit for determining the amount of movement of the movable electrode head required to achieve the two applied pressures between the movable electrode head and the fixed electrode head. The unit that derives the relationship between the applied pressure and the displacement based on the two applied pressures and the displacement. The unit that estimates the amount of movement required to generate the remaining pressure after removing two of the plurality of applied pressures between the movable electrode head and the fixed electrode head using the aforementioned relationship is used. A unit for determining the torque required to move the movable electrode head by the estimated amount of movement, and The torque required to move the estimated amount of movement is registered as a unit of torque required to generate the other applied pressure between the movable electrode head and the fixed electrode head.

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