JP2009082946A - Spot-welding system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spot-welding system with which even in the case of it becomes impossible for a pressurizing force sensor to use caused by any trouble, immediately, the spot-welding can be restarted. <P>SOLUTION: Since a motor instructing electric current value in the case of fitting a pressurizing force sensor 2 and normally working the sensor is recorded in a motor-instructing electric current value recording part 8, thereafter, even in the case of normally non-working the pressurizing force sensor 2, or taking out the pressurizing force sensor 2, based on the motor instructing electric current value recorder in the motor instructing current recording part 8 and the practical electrical motor current value flown in a servo-motor 7 detected with an electric current detector 10, the servo-control part 13 is successively made to be controlled. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a spot welding system adapted to perform spot welding work with a spot welding gun.

  In a spot welding system having a spot welding gun such as a spot welding robot, in general, one electrode (moving side electrode) is operated by a drive source such as an air cylinder or a servo motor, and the other electrode (fixed) is paired with this electrode. After the work piece is pressed and clamped to the side electrode), a predetermined welding operation is performed by passing a current through both electrodes. At this time, when the drive source of the moving electrode is a servo motor, the force that presses and clamps the workpiece to be welded, so-called pressure, depends on the motor command current value transmitted to the servo control unit that drives and controls the servo motor. It will be.

  In controlling the pressure of the spot welding gun, a form using a pressure sensor for measuring the pressure of the spot welding gun is conventionally known. FIG. 2 is a block diagram showing a spot welding system including such a control device 1 in the prior art. In FIG. 2, reference numeral 3 denotes one electrode (moving side electrode) which is operated, and after pressing the object to be welded against the other electrode (fixed side electrode) which is paired with this electrode, A spot welding gun that performs welding work by passing an electric current, 2 is a pressure sensor that measures the actual pressure of the spot welding gun 3, and 4 reads the actual pressure measured by the pressure sensor 2. A sensor reading unit, 5 is a pressurizing force control unit, 6 is a servo control unit, and 7 is a servo motor that drives the moving-side electrode provided in the spot welding gun 3.

  As an operation in this spot welding system, the actual pressurizing force of the spot welding gun 3 measured by the pressurizing sensor 2 is read by the sensor reading unit 4 and fed back to the pressurizing control unit 5. The pressure control unit 5 calculates a difference between the actual feedback force fed back and the commanded pressure (desired pressure), and calculates a motor command current value that fills this difference. The servo control unit 4 drives the servo motor 7 based on the calculated motor command current value, and thereby the moving electrode provided in the spot welding gun 3 is operated. The applied pressure is controlled.

  On the other hand, the thing of the form which does not use the pressurization sensor 2 other than the form which uses the pressurization sensor 2 like the above-mentioned spot welding system is also known conventionally. A typical example in which the pressure sensor 2 is not used is that the pressure is converted into a motor command current value based on the pressure table data set in advance, and the motor command current value is converted into a servo control unit. 6 to generate a desired pressure for each welding position. Here, the pressurizing force table is a graph showing the relationship between the pressurizing force and the feedback current value (the aforementioned motor command current value) as shown in FIG. 6, and is prepared in advance. As a method for creating this pressure table, the spot welding gun 3 is actually operated, the force applied by the external device is measured, and the feedback current value (motor) to the servo motor 7 that drives the moving electrode at that time is measured. (Command current value) is measured, and this measurement is made for a plurality of different pressures within the range of pressures actually used. The pressure table is disclosed in, for example, Patent Document 1.

Japanese Patent No. 2596722

  However, the above-described two forms, that is, the form using the pressurizing table and the form using the pressurizing sensor 2 have the following problems. First, for the configuration using the pressure table, the current value must be measured for a plurality of pressures when creating the pressure table as described above, but high-precision pressure control is performed. Therefore, there is a problem that it is necessary to plot the current value at as much pressure as possible by finely changing the pressure, and this work requires a lot of man-hours. Further, in the configuration using the pressurizing table due to the change in the relationship between the pressurizing force and the feedback current value (motor command current value) shown in FIG. There is a problem that the pressure table must be updated regularly. On the other hand, the configuration using the pressure sensor 2 does not cause a problem when the above-described pressure table is created, but the pressure sensor 2 itself may break down during the operation of the spot welding system. When a failure related to the pressure sensor occurs, such as the cable connecting the pressure sensor 2 and the control device 1 is disconnected, it is necessary to immediately stop the production line including the spot welding system and take measures against the failure. There's a problem.

  The present invention has been made to solve the above-described problems of the prior art, and in a spot welding system having a pressure sensor, spot welding work is immediately performed even when the pressure sensor becomes unusable due to a failure or the like. An object of the present invention is to provide a spot welding system capable of resuming.

  In order to achieve such an object, in the invention according to claim 1, one electrode, that is, the moving side electrode is operated, and the work piece is connected to the other electrode, that is, the fixed side electrode that is paired with this moving side electrode. A spot welding gun that performs welding work by applying current to both electrodes after pressing and clamping, and an actual pressure applied when the workpiece is pressed and clamped while being detachably attached to the spot welding gun. Measured by a pressure sensor, a servo motor for driving the moving electrode, a current detector for detecting an actual motor current value flowing through the servo motor, and the pressure sensor When there is input of data regarding the actual applied pressure, a pressure control unit that generates a motor command current value based on the input actual pressure, and the pressure generated by the pressure control unit A servo control unit that drives the servo motor based on the current command current value and the actual motor current value detected by the current detector, and input of data relating to the actual pressurizing force to the pressurizing control unit A motor command current value recording unit that records the motor command current value when there is a motor command current value recording unit when there is no data input related to the actual pressure force A spot welding system is provided in which a motor command current value is input when there is an input of data relating to the actual pressurizing force recorded in the section, and this is output to the servo control section.

  By having such a configuration, the following effects are exhibited. First, when the input of the data related to the actual pressing force measured by the pressing force sensor is in the pressing force control unit, specifically, when the pressing force sensor is installed and operating normally, the pressing force control The motor command current value is generated based on the input data on the actual pressurizing force, the servo control unit is driven by the motor command current value, and the motor command current value at this time is stored in the motor command current value recording unit. To be recorded. On the other hand, if the input of the data related to the actual pressing force is no longer input to the pressing force control unit, specifically, if the pressing force sensor does not operate normally or the pressing force sensor is removed, the servo control unit Then, the control is continued based on the motor command current value recorded in the motor command current recording unit.

  Furthermore, in the invention according to claim 2, in the invention according to claim 1, the motor command current value recorded in the motor command current value recording unit is input of data relating to the actual pressurizing force to the pressurizing control unit. The average value of the motor command current value n times (where n is an integer of 2 or more) in the case of By adopting such a configuration, there is no variation in the motor command current value, and the value can be leveled, so the input data on the actual pressure force is no longer input to the pressure control unit with no pressure variation. Control of the case can be continued.

  According to the present invention, since the motor command current value is recorded in the motor command current value recording unit when the pressure sensor is attached and is operating normally, the pressure sensor 2 is normally operated thereafter. Even if the operation is stopped or the pressure sensor is removed, the servo control unit actually flows to the servo motor 7 detected by the motor command current value recorded in the motor command current recording unit and the current detector. It is controlled continuously based on the motor current value. Therefore, it is necessary to prepare in advance data based on the pressure table that was generally required in the spot welding process without a pressure sensor in case the pressure sensor suddenly becomes unusable due to a failure, etc. The spot welding process can be resumed immediately.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a spot welding system according to the present embodiment. In FIG. 1, the same reference numerals are given to components having the same functions as those of FIG. 2 shown in the above-described prior art. In FIG. 1, reference numeral 3 denotes an electrode (moving side electrode) that is operated, and after pressing the object to be welded against the other electrode (fixed side electrode) paired therewith, This is a spot welding gun that performs a welding operation by passing an electric current through it. Reference numeral 2 denotes a pressure sensor that measures the actual pressure of the spot welding gun 3, that is, the pressure when an object to be welded is pressed between both electrodes. The pressure sensor 2 is detachably attached to the spot welding gun 3. ing. Reference numeral 4 denotes a sensor reading unit that reads the above-described actual pressing force measured by the pressing force sensor 2 and feeds it back to the pressing force control unit 12 described later.

  Reference numeral 7 denotes a servo motor that drives the above-described moving-side electrode provided in the spot welding gun 3. Reference numeral 10 denotes a current detector that detects an actual motor current value flowing through the servomotor 7. A current reading unit 11 reads the above-described actual motor current value detected by the current detector 10 and feeds it back to a servo control unit 13 described later.

  Reference numeral 8 denotes a motor command current value recording unit that records a motor command current value generated by a pressurizing force control unit 12 described later in a program file described later in the internal memory of the control device 1. Reference numeral 9 denotes a motor command current value output unit that reads the motor command current value recorded in the motor command current value recording unit 8 and outputs the read motor command current value to the pressure control unit 12.

  Reference numeral 12 denotes a pressure control unit that performs pressure control, but unlike the pressure control unit 5 shown in FIG. 2 of the prior art, feedback from the sensor reading unit 4 to the pressure control unit 12 is performed. The following functions are performed with and without. First, the function of the pressurization control unit 12 when there is feedback from the sensor reading unit 4 to the pressurization control unit 12, that is, when the pressurization sensor 2 is attached and operating normally will be described. In this case, the pressurizing control unit 12 is the same as the pressurizing control unit 5 shown in FIG. 2 of the prior art described above, and the actual pressurizing force fed back from the sensor reading unit 4 and the commanding pressurizing force (desired pressurizing force). The motor command current value is calculated so as to fill the difference. The calculated motor command current value is output to a servo control unit 13 described later. Further, in this case, the applied pressure control unit 12 outputs the generated motor command current value to the motor command current value recording unit 8, and the motor command current value recording unit 8 outputs the applied pressure as described above. The motor command current value input from the control unit 12 is recorded in a program file (described later) existing in the internal memory of the control device 1.

  Next, when there is no feedback from the sensor reading unit 4 to the pressure control unit 12, that is, when the pressure sensor 2 is shifted from a normally operating state to a state where it does not operate normally, or a pressing force is applied. The function of the pressure control unit 12 when the sensor 2 is attached to the removed state will be described. In this case, the pressurizing control unit 12 receives a motor command in a state where the feedback from the sensor reading unit 4 described above to the pressurizing control unit 12 is present, that is, in a state where the pressurizing sensor 2 is attached and operates normally. The motor command current value recorded in the current value recording unit 8 is used. Specifically, in this case, the motor command current value recorded in a program file (described later) existing in the internal memory of the control device 1 in a state where the feedback from the sensor reading unit 4 to the pressure control unit 12 is received. The motor command current value output unit 9 reads out and outputs this to the pressure control unit 12. The pressurizing control unit 12 outputs the motor command current value input from the motor command current value output unit 9 as it is to a servo control unit 13 described later.

  The servo control unit 13 drives the servo motor 7 based on the motor command current value input from the pressure control unit 12 and the actual motor current value input as feedback from the current reading unit. As a result, the above-mentioned moving-side electrode of the spot welding gun 3 is operated, whereby the applied pressure of the spot welding gun 3 is controlled.

  Next, the structure of the above-described program file existing in the internal memory of the control device 1 will be described with reference to FIG. FIG. 3 is a diagram showing the structure of a program file existing in the internal memory of the control device 1. The program file records the welding spot information necessary for each welding spot. The welding spot information is identified by a unique identification number 101 given for each welding spot, and necessary welding spot information is edited. Here, the necessary welding spot information represents at least welding conditions such as pressure position information 102 indicating the pressure position of the moving electrode provided in the spot welding gun 3 and welding current commanded to the spot welding gun 3. It consists of welding condition information 103 and motor command current average value information 104 representing the average value of the calculated motor command current values. Among these, for the pressurization position information 102 and the welding condition information 103, it is necessary to input initial data in advance before actually operating the spot welding system.

  Next, the actual processing contents in this embodiment will be described with reference to the flowcharts shown in FIGS. First, the processing contents when there is feedback from the sensor reading unit 4 to the pressure control unit 12, that is, when the pressure sensor 2 is attached and operating normally, will be described with reference to the flowchart shown in FIG. To do.

  In this case, first, when the servo motor 7 is driven, the moving side electrode of the spot welding gun 3 moves toward the pressurizing position (step S201). Note that the pressure position at this time is determined based on the pressure position information 102 recorded in the program file described above. While the moving side electrode of the spot welding gun 3 is moving toward the pressurizing position, the applied pressure measured by the applied pressure sensor 2 is fed back to the applied pressure control unit 12 in the scan time period of the control device 1. By continuing, the applied pressure of the spot welding gun 3 is sequentially controlled.

  In the pressurizing control in step S201 described above, feedback control is repeated until a desired pressurizing force is generated at the pressurizing position (step S202: No), but when the desired pressurizing force is generated at the pressurizing position. (Step S202: Yes), the motor command current value recording unit 8 acquires the motor command current value generated by the pressure control unit 12 at the time when the pressure is generated (Step S203). Further, the motor command current value recording unit 8 is used for leveling the obtained actual motor command current value in the past n times (n is an integer equal to or greater than 2) in which a desired pressure is generated at this pressurization position. ) Is calculated (step S204).

  Thereafter, the motor command current value recording unit 8 records the following two data in the program file with reference to the identification number 101 given for each welding spot information in the program file shown in FIG. (Step S205). That is, the average value of the motor command current value calculated in step S204 as the first data is recorded in the motor command current average value information 104 in the program file shown in FIG. Further, data representing the pressure position when the desired pressure is generated in step S202 as the second data is recorded in the pressure position information 102 in the program file shown in FIG. When these data are recorded, the data that has already been recorded including the initial data is overwritten.

  Next, when there is no feedback from the sensor reading unit 4 to the pressure control unit 12, that is, when the pressure sensor 2 is shifted from a normally operating state to a state where it does not operate normally, or a pressing force is applied. Processing contents when the sensor 2 is attached to the removed state will be described with reference to the flowchart shown in FIG.

  In this case, first, the motor command current value output unit 9 refers to the identification number 101 given for each welding spot information in the program file, and the motor command in the welding spot information corresponding to the above-described step S205. The average value of the motor command current value recorded in the current average value information 104 is read (step S301). Next, the motor command current value output unit 9 outputs the average value of the motor command current values read out in step S301 to the pressurization control unit 12, and the pressurization control unit 12 outputs the motor command current value output unit. The average value of the motor command current value input from 9 is output as it is to the servo control unit 13 described later as the motor command current value (step S302).

  Next, the servo control unit 13 inputs the motor command current value output in step S302. In the servo control unit 13, the motor command current value input from the pressure control unit 12 and the feedback input from the current reading unit 11 are input. Based on the actual motor current value, the servo motor 7 is driven, whereby the above-mentioned moving electrode provided in the spot welding gun 3 starts moving toward the pressurizing position (step S303). In addition, about the pressurization position here, the data of the pressurization position recorded on the pressurization position information 102 in the welding spot information corresponding in the above-mentioned step S205 are used.

  Next, in step S304, after the movement of the movable electrode to the pressurization position is completed, pressurization is started, and pressurization control is performed to determine whether or not a desired pressurization has occurred. However, unlike the process of step S202 in the case where the pressure sensor 2 is attached and operates normally, feedback control using the pressure sensor 2 cannot be performed in this case, so this step S304. The determination as to whether or not the desired applied pressure has occurred is performed as follows. That is, first, the current detector 10 detects an actual motor current value flowing through the servo motor 7, and the current reading unit 11 reads the detected actual motor current value and outputs it to the servo control unit 13. Then, the servo control unit 13 performs control so that the difference between the motor command current value output to the pressure control unit 12 in step S302 and the read actual motor current value falls within a preset allowable value. When the difference enters an allowable value, it is determined that a desired pressure is generated.

  In the process in step S304, this control process is continued until it is confirmed that the pressure is applied with the desired pressure (step S304: No), and it is confirmed that the desired pressure is generated. After that (step S304: Yes), a welding command is issued to the spot welding gun 3. In addition, about welding instruction here, the welding current etc. with respect to the spot welding gun 3 when the desired pressurization generate | occur | produced recorded on the welding condition information 103 in the welding spot information corresponding in the above-mentioned step S205, etc. are shown. Use welding condition data.

  The embodiment of the present invention has been described above. In the above-described embodiment, the average value of the past n times of pressing force at the pressurizing position is calculated and recorded. However, the calculation of the average value of the past n times of pressing force itself is not necessary. It is not an essential requirement in the invention. For example, the pressurizing force of the spot welding gun 3 is controlled using only the motor command current value when the desired pressurizing force is generated at the pressurizing position immediately before the pressurizing sensor 2 becomes unusable due to failure or the like. Nevertheless, the present invention can be implemented.

  In addition, “when the pressure sensor 2 is attached to the removed state” in the above-described embodiment is, for example, the following usage pattern. That is, since the pressure sensor 2 is generally expensive, it is difficult to attach one pressure sensor 2 to one spot welding system from the start to the end of the spot welding operation. Since the number of pressure sensors 2 is required, the burden on the cost increases. Therefore, the applied pressure is measured using the applied pressure sensor 2 only at the start-up stage of the production line including the spot welding system, and the applied pressure sensor 2 is removed at the subsequent spot welding stage and is recorded at the start-up stage of the production line. A subsequent spot welding operation may be performed using the above-described data such as the motor command current value.

  Further, in addition to the above-described form, a plurality of pressures are acquired using the pressure sensor 2 for the purpose of confirming the pressure force every time a certain time elapses, and then the pressure sensor 2 is removed again. Then, the spot welding operation may be performed again in the same manner as described above. Thereby, it is not necessary to attach the pressure sensor 2 from the start to the end of the spot welding operation for one spot welding system, and one pressure sensor 2 is used in a plurality of spot welding systems. Therefore, it is possible to reduce the cost burden related to the purchase and the like of the pressure sensor 2.

  According to the present embodiment, the motor command current value when the pressure sensor 2 is attached and operating normally is recorded in the motor command current value recording unit 8, and thereafter the pressure sensor Servo motor detected by the current detector 10 and the motor command current value recorded in the motor command current recording unit 8 by the servo control unit 13 even when the pressure sensor 2 does not operate normally or the pressure sensor 2 is removed. 7 is continuously controlled based on the actual motor current value flowing through the motor 7. Therefore, data based on the pressure table generally required in the spot welding process without the pressure sensor 2 is created in advance for the case where the pressure sensor 2 cannot be used suddenly due to a failure or the like. The spot welding process can be resumed immediately.

  Further, the motor command current value recorded in the motor command current value recording unit 8 is recorded by setting the average value of the motor command current values of the past n times (n is an integer of 2 or more) at the pressurization position. Since the value of the motor command current value can be leveled, spot welding work using a uniform pressure can be performed.

  The embodiment according to the present invention has been described above. However, the present invention is not limited to the embodiment, and various modifications can be made to the described embodiment within the definition of the appended claims. Needless to say.

It is a block diagram which shows the spot welding system in one Embodiment of this invention. It is a block diagram which shows the spot welding system in a prior art. It is a figure which shows the structure of the program file in one Embodiment of this invention. It is a flowchart which shows the processing content at the time of use of the pressurization sensor 2 which is one Embodiment of this invention. It is a flowchart which shows the processing content when the pressurization sensor 2 which is one Embodiment of this invention becomes non-use later. It is a figure which shows an example of the pressurization table in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control apparatus 2 Pressure sensor 3 Spot welding gun 4 Sensor reading part 5 Pressure control part 6 Servo control part 7 Servo motor 8 Motor command current value recording part 9 Motor command current value output part 10 Current detector 11 Current reading part 12 Pressurizing control unit 13 Servo control unit 101 Identification number 102 Pressurizing position information 103 Welding condition information 104 Motor command current average value information

Claims (2)

Welding is performed by operating one electrode, i.e., the moving electrode, and pressurizing the workpiece to be welded to the other electrode, i.e., the fixed electrode, which is paired with the moving electrode, and then passing a current through both electrodes A spot welding gun to do the work,
A pressure sensor that is detachably attached to the spot welding gun, and is configured to measure an actual pressure when the workpiece is pressed and clamped;
A servo motor for driving the moving electrode;
A current detector for detecting an actual motor current value flowing through the servo motor;
A pressure control unit that generates a motor command current value based on the input actual pressing force when there is input of data relating to the actual pressing force measured by the pressing force sensor;
A servo control unit that drives the servo motor based on the motor command current value generated by the pressure control unit and the actual motor current value detected by the current detector;
A motor command current value recording unit for recording the motor command current value when there is an input of data relating to actual pressing force to the pressing force control unit;
Have
In the pressurizing force control unit, when there is no input of data relating to the actual pressurizing force, the motor command current value when the data relating to the actual pressurizing force recorded in the motor command current value recording unit is input. A spot welding system characterized in that it is inputted and outputted to the servo control unit.   The motor command current value recorded in the motor command current value recording unit is n times (n is an integer of 2 or more) motor command currents when data relating to actual pressurizing force is input to the pressurizing control unit. The spot welding system according to claim 1, wherein the spot welding system is an average value.

Images