JP6726557B2 - Spot welder and spot welding method - Google Patents

Description

The present invention relates to a spot welding machine and a spot welding method.

Spot welding is known as one of the methods for welding overlapping works (see, for example, Patent Document 1). The welding method described in Patent Document 1 is referred to as indirect spot welding, in which the electrodes are brought into contact with one side of the work and the other side of the work, and a welding current is passed between the electrodes to perform spot welding. To form.

Japanese Patent No. 4209570

In spot welding, for example, welding is performed in a state in which the electrode is pressed against the work by the pressure of the air cylinder. However, in spot welding, it has been a problem that the electrode is pushed into the work softened by the temperature rise due to the energization, so that an indentation is generated on the work. When the indentation is conspicuous on the work, the appearance quality of the work may be deteriorated.

Therefore, an object of the present invention is to provide a spot welding machine and a spot welding method capable of suppressing the indentation of a work.

The spot welder of the present invention is a spot welder in which a pair of electrodes are brought into contact with the stacked work pieces and a spot welding portion is formed by passing a welding current between the electrodes, and one electrode is attached to the work piece. The control unit includes a servo cylinder that is moved with respect to each other, and a control unit that controls the operation of the servo cylinder and the welding current between the electrodes. One of the electrodes is preset in the workpiece at the initial position at the start of welding. The servo cylinder is controlled so as to be pressed by a pressing force, and the servo cylinder is controlled so that the position of one electrode is maintained at the initial position while the welding current is flowing between the electrodes after the start of welding.

In this spot welding machine, the servo cylinder is controlled so that one electrode is pressed against the work piece by a preset pressing force at the initial position at the start of welding, and after starting welding, a welding current flows between the electrodes. During this period, the servo cylinder is controlled so that the position of one electrode is maintained at the initial position at the start of welding. By controlling the servo cylinder in this manner, it is possible to prevent one electrode from being pushed into a softened work due to a temperature rise caused by energization. Therefore, the indentation of the work due to the pushing of the electrode can be suppressed.

Further, the control unit further includes a detection unit that detects a contact state between the one electrode and the work, and the control unit determines that the one electrode and the work are not in contact with each other during execution of the control for maintaining the position of the one electrode. When is detected by the detection unit, the welding current may be stopped. In this case, formation of an unhealthy weld can be prevented.

The spot welding method of the present invention is a spot welding method in which a pair of electrodes are brought into contact with the overlapped works and a spot welding portion is formed by passing a welding current between the electrodes, and the initial position at the start of welding. In the step of controlling the servo cylinder so that one electrode is pressed against the workpiece with a preset pressing force, the position of one electrode is set to the initial position while welding current is flowing between the electrodes after starting welding. Controlling the servo cylinder to be maintained at.

In this spot welding method, the servo cylinder is controlled so that one electrode is pressed against the workpiece with a preset pressing force at the initial position at the start of welding, and after starting welding, a welding current flows between the electrodes. During this period, the servo cylinder is controlled so that the position of one electrode is maintained at the initial position at the start of welding. By controlling the servo cylinder in this manner, it is possible to prevent one electrode from being pushed into a softened work due to a temperature rise caused by energization. Therefore, the indentation of the work due to the pushing of the electrode can be suppressed.

Further, when the detection unit detects that one of the electrodes is not in contact with the work during the control for maintaining the position of the one electrode, the welding current may be stopped. In this case, formation of an unhealthy weld can be prevented.

ADVANTAGE OF THE INVENTION According to this invention, the spot welding machine and spot welding method which can suppress the indentation of a workpiece can be provided.

It is a schematic diagram showing a spot welding machine concerning an embodiment. It is a flow chart which shows processing by a spot welding machine. It is a schematic diagram showing a spot welding machine at the time of welding.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding elements will be denoted by the same reference symbols, without redundant description.

The spot welding machine 1 shown in FIG. 1 abuts a pair of electrodes 4 and 5 on the plate-shaped works 2 and 3 that are overlapped with each other, and applies a welding current C between the electrodes 4 and 5 to form a spot welding portion. It is a welding machine which forms W (FIG. 3). The work 2 is, for example, a side structure that constitutes a side portion of the railcar structure, and the work 3 is, for example, an underframe that forms a bottom portion of the railcar structure. The work 3 has an extending portion that extends from the overlapping portion with the work 2 and is curved toward the opposite side of the work 2. The spot welding machine 1 here is configured as a welding machine for performing indirect spot welding, in which electrodes 4 and 5 are brought into contact with one surface 2a of the work 2 and one surface 3a of the work 3, respectively. Weld. The works 2 and 3 are held by holding means (not shown).

The spot welding machine 1 includes a first servo cylinder 11, a second servo cylinder 12, a detection unit 13, and a control unit 14. Each of the first servo cylinder 11, the second servo cylinder 12, and the detection unit 13 is electrically connected to the control unit 14.

The first servo cylinder 11 has a cylinder portion 11a and a piston rod 11b. An electrode 4 (one electrode) is provided at the tip of the piston rod 11b, and the first servo cylinder 11 moves the electrode 4 with respect to the work 2 by moving the piston rod 11b back and forth with respect to the cylinder portion 11a. To move. The first servo cylinder 11 is, for example, an electric cylinder using a servo motor, and controls the pressure of the electrode 4 (control of the axial load acting on the piston rod 11b) and the electrode according to a control signal from the control unit 14. 4 position control (control of the protrusion amount of the piston rod 11b from the cylinder portion 11a).

The second servo cylinder 12 has, for example, the same configuration as the first servo cylinder 11, and includes a cylinder portion 12a and a piston rod 12b having an electrode 5 at the tip thereof. The second servo cylinder 12 moves the electrode 5 with respect to the work 3 by moving the piston rod 12b forward and backward with respect to the cylinder portion 12a. The second servo cylinder 12 is, for example, an electric cylinder using a servo motor, and controls the pressure of the electrode 5 and the position of the electrode 5 according to a control signal from the control unit 14. The first servo cylinder 11 and the second servo cylinder 12 are fixed to a support mechanism (not shown), for example.

The detection unit 13 detects a contact state between the electrode 4 and the work 2. The detection unit 13 is configured to include, for example, an imaging unit (camera) that images the contact position between the electrode 4 and the work 2, and detects the contact state between the electrode 4 and the work 2 by analyzing the acquired image. .. The detection unit 13 sequentially outputs the detection result to the control unit 14. The control unit 14 may determine the contact state between the electrode 4 and the work 2 based on the image received from the imaging unit. In this case, the imaging unit and the control unit 14 configure a detection unit that detects the contact state between the electrode 4 and the work 2. Further, the detection unit 13 may be realized by detection means other than the image pickup unit.

The control unit 14 is, for example, a computer including a CPU, a memory, a communication interface, a hard disk, and the like. The control unit 14 controls the operation of each unit of the spot welding machine 1. For example, the control unit 14 controls the operations of the first servo cylinder 11 and the second servo cylinder 12. Further, the control unit 14 controls on/off of the welding current C flowing between the electrodes 4 and 5 by controlling a power supply device (not shown).

Subsequently, a processing flow executed at the time of welding will be described with reference to FIGS. 2 and 3. At the start of the process shown in FIG. 2, the works 2 and 3 are held by the holding means, and the electrodes 4 and 5 are separated from the works 2 and 3.

After the processing is started, the control unit 14 first controls the first servo cylinder 11 so that the electrode 4 is pressed against the work 2 (step S1). As a result, the electrode 4 contacts the work 2. In parallel with step S1, the control unit 14 controls the second servo cylinder 12 so that the electrode 5 is pressed against the work 3. As a result, the electrode 5 contacts the work 3. The control of the second servo cylinder 12 may be executed at any timing after the start of the process and before the start of energization in step S4 described later, and may be executed, for example, before step S1. Alternatively, the electrode 5 may be in contact with the work 3 in advance at the start of processing.

Subsequently, the control unit 14 controls the first servo cylinder 11 so that the pressure applied to the electrode 4 increases at a preset rate (step S2). For example, in step S2, the first servo cylinder 11 is controlled so that the pressure applied to the electrode 4 increases by a predetermined value. The predetermined value is preset based on welding conditions, specifications of the first servo cylinder 11, and the like.

Subsequently, the control unit 14 determines whether the pressure applied to the electrode 4 is equal to the target value (step S3). This target value is a value that defines the pressing force that acts on the electrode 4 at the start of energization in step S4, which will be described later, and is set in advance based on welding conditions, specifications of the first servo cylinder 11, and the like. In addition, in step S4, the control unit 14 may determine whether the pressure applied to the electrode 4 is within the target range.

As a result of the determination in step S3, when the control unit 14 determines that the pressure applied to the electrode 4 is equal to the target value (YES in step S3), the process proceeds to step S4, and the pressure applied to the electrode 4 is the target value. When it is determined that it is not equal to (lower than the target value) (NO in step S3), the process returns to step S2. As a result, at the start of energization in step S4, that is, at the start of welding, the electrode 4 is pressed against the work 2 with a preset pressure.

In step S4, the control unit 14 controls the power supply device so that the welding current C is started to flow between the electrodes 4 and 5. As a result, welding of the works 2 and 3 is started. Further, the control unit 14 starts energizing the welding current C in step S4, and simultaneously starts control for maintaining the position of the electrode 4 (step S5).

During execution of this control, the control unit 14 controls the first servo cylinder 11 so that the position of the electrode 4 is maintained at the initial position at the start of welding. For example, even if the work 2 tries to expand at the welding location due to the temperature rise due to the energization and the load acting on the electrode 4 from the work 2 increases, the position of the electrode 4 is changed by increasing the pressing force acting on the electrode 4. The first servo cylinder 11 is controlled so as to be maintained (fixed) at the initial position at the start of welding. Further, even if the work 2 contracts at the welding location, the first servo cylinder 11 is configured so that the position of the electrode 4 is maintained at the initial position at the start of welding, regardless of the increase or decrease in the pressure applied to the electrode 4. To control.

Subsequently, the control unit 14 determines whether or not the electrode 4 and the work 2 are in contact with each other based on the detection result of the detection unit 13 (step S6). As a result of the determination, when it is determined that the electrode 4 and the work 2 are not in contact (NO in step S6), the process proceeds to step S7, and when it is determined that the electrode 4 and the work 2 are in contact with each other. (YES in step S6), the process proceeds to step S8. In step S7, the control unit 14 stops the conduction of the welding current C between the electrodes 4 and 5, and also stops the control for maintaining the position of the electrode 4.

In step S8, the control unit 14 determines whether or not a predetermined time has elapsed after the start of energization. As a result of the determination, when it is determined that the predetermined time has elapsed after the start of energization (YES in step S8), the process proceeds to step S9, and when it is determined that the predetermined time has not elapsed after the start of energization (in step S8). If NO, the process returns to step S6. This predetermined time is a welding time and is preset based on welding conditions and the like.

In step S9, the control unit 14 stops the supply of the welding current C between the electrodes 4 and 5. This completes the welding of the works 2 and 3. Subsequently, the control unit 14 stops the control for maintaining the position of the electrode 4 and controls the first servo cylinder 11 so that the electrode 4 is separated from the work 2 (step S10). In parallel with step S10, the control unit 14 controls the second servo cylinder 12 so that the electrode 5 is separated from the work 3. The control of the second servo cylinder 12 may be executed at any timing after the stop of energization.

Through the series of processes described above, welding is performed while the electrode 4 is pressed against the work 2 by the pressing force of the first servo cylinder 11, and the spot welded portion W is formed on the works 2 and 3.

In the spot welding machine 1 described above, the first servo cylinder 11 is controlled so that the electrode 4 is pressed against the work 2 with a preset pressing force at the initial position at the start of welding (steps S1 to S3), After the start of welding, while the welding current C is flowing between the electrodes, the first servo cylinder 11 is controlled so that the position of the electrode 4 is maintained at the initial position at the start of welding (steps S4 to S10). .. By controlling the first servo cylinder 11 in this manner, it is possible to prevent the electrode 4 from being pushed into the work 2 that has been softened due to the temperature rise due to energization. Therefore, the indentation of the work 2 due to the pushing of the electrode 4 can be suppressed.

In the spot welder 1, the control unit 14 detects that the electrode 4 and the work 2 are not in contact with each other during the position control of the electrode 4 (NO in step S6). In the case), the energization of the welding current C is stopped (step S7). This can prevent the formation of an unhealthy weld.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, although the side structures and the underframes are illustrated as the works 2 and 3 in the above-described embodiment, the works 2 and 3 may constitute other parts of the railway vehicle structure. Further, the works 2 and 3 are not limited to those constituting the railcar structure, and the present invention is widely applicable to spot welding of superposed works. Further, in the above embodiment, the spot welder 1 is configured as a welder that performs indirect spot welding. However, for example, it is assumed that the spot welder 1 performs direct spot welding by sandwiching the overlapped works with a pair of electrodes and performing welding. It may be configured.

1... Spot welder, 2, 3... Work, 4... Electrode (one electrode), 5... Electrode, 11... 1st servo cylinder, 11a... Cylinder part, 13... Detection part, 14... Control part, C... Welding current, W... Spot weld.

Claims (2)

A spot welder that forms a spot weld by contacting a pair of electrodes to the overlapped works and applying a welding current between the electrodes,
A servo cylinder for moving one of the electrodes with respect to the work;
A controller that controls the operation of the servo cylinder and the welding current between the electrodes;
A detection unit that detects a contact state between the one electrode and the work ,
The control unit is
While controlling the servo cylinder so that the one electrode is pressed against the workpiece with a preset pressing force at the initial position at the start of welding,
After starting welding, while the welding current is flowing between the electrodes, the servo cylinder is controlled so that the position of the one electrode is maintained at the initial position ,
When it is detected by the detector that the one electrode and the work piece are not in contact with each other during the control for maintaining the position of the one electrode, the energization of the welding current is stopped , Spot welder. A spot welding method of forming a spot welded portion by contacting a pair of electrodes to the overlapped works and applying a welding current between the electrodes,
A step of controlling the servo cylinder so that one of the electrodes is pressed against the workpiece with a preset pressure at the initial position at the start of welding;
After starting welding, seen including the steps of: controlling the servo cylinder as between, the position of the one electrode is maintained in the initial position in which the welding current flows between the electrodes,
When it is detected by the detection unit that the one electrode and the work piece are not in contact with each other during the execution of the control for maintaining the position of the one electrode, the energization of the welding current is stopped , the spot Welding method.

Images