JPH11291060A - Resistance welding method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resistance welding method and its device dispensing with the control of a welding electrode length, facilitating operation and improving welding quality. SOLUTION: A pressurizing mechanism 13 is lowered by energizing a servo motor 32, holding objects to be welded 90, 92 between the upper and lower welding electrodes.12, 14. In this case, the pressurizing force of the upper electrode 12 to the object 92 is measured by a load cell 86. At the point of time when this pressurizing force becomes a prescribed set value, the lowering of the pressurizing mechanism 13 is stopped. As a result, the objects 90, 92 to be welded are kept in the state pressurized at the set value. Then, with the welding current flowing from the welding power source 20 to the upper and lower electrodes 12, 14, welding is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance welding method and apparatus for obtaining good welding quality by measuring the magnitude of the pressure of a welding electrode on an object to be welded.

[0002]

2. Description of the Related Art In resistance welding, two types of workpieces are brought into contact with each other and a large current is applied while mechanically pressing the workpieces.
The contact resistance of the pressurized part between the workpieces becomes lower than the contact resistance of the other metal parts, the welding current is concentrated and Joule heat is generated, and as a result, the molten state of the metal parts is obtained, The basic principle is that welding is performed in combination with the pressing force.

[0003] In this case, the welding electrode, which is controlled to a fixed length by a jig or the like, is displaced by a constant displacement amount by a pressing mechanism, so that the welding electrode is brought into contact with the work to be welded at a constant pressing force. There is a resistance welding method in which a current is passed from a welding electrode to a workpiece to perform welding.

[0004]

However, in the above-described conventional resistance welding method, it is necessary for an operator to always manage the length of the electrode, and the operation is complicated.

Japanese Patent Application Laid-Open No. 9-248676 discloses that the displacement of a welding electrode when the welding electrode is brought into contact with a strain gauge is measured in advance, and the welding electrode is distorted again after performing welding several times. The length of the welding electrode is calculated by measuring the wear of the welding electrode from the amount of displacement of the welding electrode at this time, and the resistance that controls the voltage applied to the electrode, the welding time, and the pressing force is calculated based on this length. A welding device is disclosed. However, this resistance welding apparatus has a problem that the control for measuring the length of the welding electrode is complicated, and the efficiency of the operation is poor because the length of the electrode is measured every several weldings.

Further, in the pressurizing device of a resistance welding machine disclosed in Japanese Patent Application Laid-Open No. 61-253189, an electric motor is driven to bring an electrode into contact with an object to be welded so that the torque of the electric motor is made constant. Thus, the pressing force is made constant, and the height of the electrode tip is freely changed to improve the workability.

However, in this method, an error occurs in the pressing force due to the sliding resistance between the screw shaft and the ball screw connected to the electric motor, the guide rod for guiding the electrode tip and the guide, etc. There is a problem that it is difficult to perform welding due to pressure and that welding quality is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is not necessary to control the length of a welding electrode, so that the work is easy, and a resistance welding method capable of improving welding quality. It is intended to provide the device.

[0009]

In order to achieve the above object, the present invention provides a step of pressing a welding electrode for resistance welding against an object to be welded, and a step of applying the welding electrode to the object to be welded. The pressure is measured by a pressure sensor, and the pressing operation of the welding electrode is stopped when the pressing force reaches a predetermined pressing force set value, and a step of maintaining the pressing force, and a welding current is applied to the workpiece. Energizing and welding.

[0010] According to the present invention, since the pressing force of the welding electrode to the workpiece is kept constant, the control of the welding current, welding time and the like becomes easy.

[0011] The present invention also provides a step of pressing a welding electrode for resistance welding against an object to be welded, and measuring a pressing force of the welding electrode on the object to be welded by a pressure sensor.
The pressing operation of the welding electrode is stopped when the pressing force reaches the first pressing force set value, and a step of maintaining the pressing force, and applying a temporary welding current to the workpiece to perform the temporary welding. Applying, and pressing the welding electrode against the workpiece again, measuring the pressure of the welding electrode against the workpiece, and determining when the pressure reaches a second pressure setting value. And a step of stopping the pressing operation of the welding electrode and maintaining the pressing force, and a step of applying a main welding current to the workpiece to perform the main welding.

According to the present invention, since the pressing force of the welding electrode against the workpiece is kept constant, the control of the welding current, the welding time and the like becomes easy. Further, the contact resistance of the workpiece is sufficiently reduced by the temporary welding, and the main welding is performed in this state, so that the workpiece can be favorably welded.

Further, according to the present invention, a welding electrode for resistance welding is pressed against an object to be welded, and the pressure of the welding electrode on the object to be welded is measured by a pressure sensor. At the time when the set pressure is reached, a welding current is applied to the work to be welded to perform welding, and the welding electrode is pressed against the work so that the pressing force is maintained at the set pressure. Thus, it is possible to prevent poor welding due to a decrease in the pressing force during welding, which is preferable.

Further, according to the present invention, a step of pressing a welding electrode for resistance welding against an object to be welded, and the pressure of the welding electrode against the object to be welded are measured by a pressure sensor. Stopping the pressing operation of the welding electrode at the time when the welding pressure set value is reached, maintaining the welding force, applying a welding current to the workpiece to perform welding, Measuring the thickness displacement amount, and performing the welding until the displacement amount reaches a predetermined value.When the displacement amount reaches a predetermined value, the welding is completed. It is possible to obtain a proper welding state.

Further, the present invention includes a pressing mechanism for pressing a welding electrode for resistance welding against a workpiece, and a displacement mechanism for displacing the pressing mechanism toward the workpiece. Has a linear actuator capable of stopping the pressing mechanism at an arbitrary position. On the other hand, the pressing mechanism has a pressing force transmission to which the welding electrode is mounted and which is urged to the workpiece through an elastic member. It is characterized by having a shaft and a pressure sensor connected to the elastic member and measuring a pressure applied to the welding electrode.

According to the present invention, the pressing mechanism is displaced by the linear actuator to press the welding electrode against the workpiece, and the pressure of the welding electrode against the workpiece detected by the pressure sensor becomes a predetermined value. By stopping the linear actuator at the point in time, the pressing force of the welding electrode against the workpiece is maintained constant, so that the control of the welding current, welding time, and the like is facilitated.

In this case, the linear actuator is
When a servomotor, a feed screw connected to the rotation shaft of the servomotor, and a feed nut that converts the rotational motion of the feed screw into a linear motion and is connected to the pressing mechanism, the pressing mechanism can accurately perform the pressing mechanism. This can be stopped at a predetermined position, which is preferable.

In this case, it is preferable that the pressure sensor is a load cell, because the structure of the pressing mechanism can be simplified.

Further, in this case, if the pressing mechanism has a displacement sensor for detecting a displacement amount of the pressurizing force transmission shaft at the time of pressurization, a change in the thickness of the workpiece is detected at the time of welding. The welding can be performed so that the change in thickness becomes a predetermined value, which is more preferable.

Further, in this case, if the displacement sensor is a magnetic induction type displacement sensor, the responsiveness of the welding electrode to a change in the thickness of the workpiece is good, and the thickness of the workpiece is reduced while welding. This is suitable because the displacement can be measured with high accuracy.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a resistance welding method according to the present invention will be described in detail with reference to the accompanying drawings in relation to an apparatus for performing the method.

In FIG. 1, reference numeral 10 indicates a resistance welding apparatus according to a first embodiment of the present invention. The resistance welding apparatus 10 includes a displacement mechanism 16 that displaces a pressing mechanism 13 provided with an upper welding electrode 12 in a direction to approach or separate from a lower welding electrode 14, a controller 18 that controls the displacement mechanism 16, A welding power source 20 for supplying a welding current to the welding electrode 12 and the lower welding electrode 14 is provided.

The controller 18 is provided with an LCD display 18a for displaying the operation status and the like of the resistance welding apparatus 10, and a plurality of switches 18b for setting and operating the resistance welding apparatus 10. Further, a first pressure setting value P ₁ and a second pressure setting value P ₂ of the upper welding electrode 12 for the workpiece are stored in a memory (not shown) of the controller 18.

The displacement mechanism 16 has a base 22, as shown in FIG. The lower electrode holder 24 is fixed to the base 22, and the lower welding electrode 14 is fixed to the lower electrode holder 24. An electric wire 26 for supplying a welding current from the welding power source 20 to the lower welding electrode 14 is connected to the lower electrode holder 24.

A support 28 is erected on the base 22.
A servo motor 32 constituting the linear actuator 30 is provided on the upper part of the reference numeral 8. The servo motor 32 is controlled by the controller 18. A ball screw 36, which is a feed screw, is connected to a rotary shaft 34 of the servo motor 32. Both ends of the ball screw 36 are supported by shaft support members 38a, 38b.
It is rotatably supported by. A ball nut 40 as a feed nut is engaged with the ball screw 36, and the rotational motion of the ball screw 36 is converted into a linear motion by the ball nut 40.

A housing 42 constituting the pressing mechanism 13 is fixed to the ball nut 40, and the ball screw 36 is inserted into a hole 44 formed in the housing 42. A plurality of guide blocks 46a and 46b are fixed to the housing 42, and the guide blocks 46a and 46b are slidably engaged with guide rails 48 fixed to the sides of the columns 28.

A chamber 50 is defined inside the housing 42.
The case 42 is covered with a shield 52 made of iron or an iron alloy, and noise such as electromagnetic waves and magnetism is prevented from entering the inside of the case 42. Holes 54 and 56 are formed in the housing 42 so as to extend coaxially and vertically,
Bushings 58, 60 are provided in the holes 54, 56. A pressure transmitting shaft 62 is slidably inserted through the bushings 58 and 60. The upper welding electrode 12 is attached to a lower portion of the pressure transmission shaft 62 via an upper electrode holder 64. An electric wire 66 for supplying a welding current from the welding power source 20 to the upper welding electrode 12 is connected to the upper electrode holder 64.

A plate-like member 68 disposed inside the chamber 50 is fixed to the pressing force transmission shaft 62.
Is a bar-shaped magnet 7 constituting the magnetic induction type displacement sensor 70.
2 is fixed parallel to the pressure transmission shaft 62. The magnet 72 is configured to be able to pass through the inside of the coil 74 of the magnetic induction type displacement sensor 70 fixed to the housing 42. Although not shown, a primary coil and a secondary coil are wound around the coil 74. When an AC reference voltage such as a sine wave is applied from the controller 18 to the primary coil, the magnet 72 An AC signal whose phase is deviated from the reference voltage according to the displacement amount is output.

A flange portion 78 is formed on the upper portion of the pressure transmitting shaft 62, and the pressure transmitting shaft 62 is prevented from coming off when the flange portion 78 comes into contact with the upper portion of the housing 42. A pressing force transmission shaft 62 is provided at an upper portion of the housing 42.
The casing 80 is fixed above the. Casing 80
, A coil spring 82 is disposed, and one end of the coil spring 82 is seated on the flange portion 78. The upper part of the coil spring 82 is seated on a seating member 84 provided inside the casing 80. A load cell 86 as a pressure sensor is disposed above the seat member 84, and the load cell 86 is slidable on the inner wall of the casing 80.
The upper part of the load cell 86 contacts the lower part of the screw 88 screwed into the screw hole on the upper part of the casing 80, and when the screw 88 is rotated, the load cell 86 displaces inside the casing 80.

Magnetic displacement sensor 70, load cell 8
6 is connected to the controller 18 by electric wires 87 and 89 as shown in FIG.

The resistance welding apparatus 10 according to the first embodiment
Is basically configured as described above. Next, its operation and operation and effect will be described in relation to the resistance welding method according to the first embodiment.

As shown in FIG. 2, the upper welding electrode 1
The objects to be welded 90 and 92 are placed between the lower electrode 2 and the lower welding electrode 14 (Step S1 in FIG. 3).

When the servo motor 32 is energized under the control of the controller 18 through the above-described preparation steps, the ball screw 36 rotates, and this rotational motion is converted into linear motion by the ball nut 40. The pressing mechanism 13 descends (Step S2). For this reason, the upper welding electrode 1
2 is in contact with the upper surface of the workpiece 92,
Is sandwiched between the upper welding electrode 12 and the lower welding electrode 14 (see FIG. 7A).

The upper welding electrode 12 presses the workpiece 92 under the further lowering action of the pressing mechanism 13, and the pressing force transmission shaft 62 relatively rises against the elastic force of the coil spring 82. Therefore, the coil spring 82 contracts, and the pressing force P of the upper welding electrode 12 against the workpiece 92 is reduced.
Gradually increases. The pressing force P is transmitted to the load cell 86, and the load cell 86 outputs an electric signal corresponding to the pressing force P to the controller 18.

The controller 18 compares the pressure setpoint P ₁ of the pressure P and the first (step S3), and pressure P if the first pressure set value P ₁ is smaller than returns to step S2 , The pressing mechanism 13 is further lowered, and the pressing force P
At the time when the pressure becomes equal to the _first pressure setting value P1, the rotation of the servomotor 32 is stopped, and the lowering of the pressing mechanism 13 is stopped (step S4). Therefore, the upper welding electrode 12 is maintained in a state in which the workpiece 92 is pressed at the _first pressure setting value P1. As described above, since the workpieces 90 and 92 are sandwiched between the upper welding electrode 12 and the lower welding electrode 14 at the first pressing force set value P ₁ , the gap between the upper welding electrode 12 and the workpiece 92 is The contact resistance between the workpiece 90 and the workpiece 92 and between the workpiece 90 and the lower welding electrode 14 are maintained at predetermined values.

Next, the controller 18 controls the workpiece 9
0 and 92 are welded. This welding method will be described in detail with reference to the flowchart of FIG. 4. First, the controller 18 outputs a temporary welding command signal to the welding power source 20. Therefore, the welding power source 20 supplies a temporary welding current between the upper welding electrode 12 and the lower welding electrode 14 in accordance with the temporary welding command signal, thereby performing temporary welding on the workpieces 90 and 92 (step S10). ). In this state, the strength is insufficient due to insufficient welding, but the contact resistance between the workpiece 90 and the workpiece 92 is sufficiently small. Further, even if the contact resistance varies when the workpieces 90 and 92 are sandwiched between the upper welding electrode 12 and the lower welding electrode 14, the contact resistance becomes substantially constant by temporary welding.

At this time, the thickness of the workpieces 90 and 92 is slightly reduced by the temporary welding, and the pressure P of the upper welding electrode 12 on the workpieces 90 and 92 is set to the first pressure setting value P _1.
Smaller than. Therefore, the controller 18 measures the pressing force P using the load cell 86 while the servo motor 3
2 to lower the pressing mechanism 13 (step S1).
1). The controller 18 compares the pressure setpoint P ₂ and pressure P of the second (step S12), the applied pressure P second
Stopping the descent of the pressing mechanism 13 at the time of the match with the pressure set value P ₂ in (step S13).

Next, the controller 18 outputs a main welding command signal to the welding power source 20, and the welding power source 20 applies a main welding current between the upper welding electrode 12 and the lower welding electrode 14,
The main welding is performed on the workpieces 90 and 92 (step S14). At this time, since the contact resistance between the workpiece 90 and the workpiece 92 is sufficiently small and does not vary due to the temporary welding, a nugget 94 having a predetermined size is formed by the main welding current as shown in FIG. 7B. And good welding is performed.

Then, the controller 18 urges the servo motor 32 to raise the pressing mechanism 13, and the workpieces 90 and 92 having been welded are taken out (step S1).
5).

According to the first embodiment, the load cell 8
6, the pressing force P of the upper welding electrode 12 against the workpieces 90 and 92 is measured, and welding is performed when the pressing force P reaches the first pressing force set value P _1. It is easy, and there is no need to control the lengths of the upper welding electrode 12 and the lower welding electrode 14, so that the welding operation is facilitated and the number of maintenance steps is reduced.

Further, since the workpieces 90 and 92 are provisionally welded, the contact resistance between the workpiece 90 and the workpiece 92 is small and the variation is small, so that good welding can be performed in the main welding. . Furthermore, even when the surface roughness of the workpieces 90 and 92 is rough, the variation in the contact resistance can be reduced by the temporary welding and good welding can be performed regardless of the state of the surface roughness.

Further, the pressing force P of the upper welding electrode 12
The pressure transmission shaft 62 for transmitting the
, The error of the pressing force P transmitted to the load cell 86 is small, and the welding can be controlled by accurately managing the pressing force P.

In the above-described first embodiment, the welding is performed in two steps: the temporary welding and the main welding. However, the welding may be performed only once. In this case, work time can be reduced.

Next, a resistance welding method according to the second embodiment will be described with reference to the flowchart of FIG. Since the resistance welding apparatus 10 used in this resistance welding method has the same configuration as that of the first embodiment, a detailed description thereof will be omitted.

First, similarly to the resistance welding method according to the first embodiment, the objects to be welded 90 and 92 are disposed so as to overlap between the upper welding electrode 12 and the lower welding electrode 14 (step S1 in FIG. 3). ), The pressing mechanism 13 is lowered to clamp the workpieces 90 and 92 between the upper welding electrode 12 and the lower welding electrode 14 (step S2, see FIG. 7A). And the workpiece 9
The pressing force P of the upper welding electrode 12 with respect to No. 2 is compared with the pressing force set value P ₀ stored in the controller 18 (step S3), and when the pressing force P matches the pressing force set value P ₀ , the pressing mechanism is pressed. 13 is stopped (step S
4).

Next, the controller 18 controls the load cell 86
To output a welding command signal to the welding power source 20 while measuring the pressing force P of the upper welding electrode 12 against the workpiece 92. For this reason, the welding power source 20 supplies a welding current between the upper welding electrode 12 and the lower welding electrode 14 and
0, 92 welding is started (step S2)
1). At this time, the controller 18 starts measuring the welding time t.

When welding is started, the thickness D of the objects to be welded 90, 92 is reduced, so that the pressing force P is reduced (FIG. 7B).
reference). Therefore, the controller 18 compares the pressing force P measured by the load cell 86 with the pressing force set value P ₀ (step S22), and when the pressing force P becomes smaller than the pressing force set value P ₀ , the controller 18 controls the servo motor 32. The pressing mechanism 13 is urged to move down (step S23), and the pressing force P is increased. Then, comparing the weld time set value T ₁ that is stored in the welding time t and the controller 18 (step S24). If welding time t has not reached the welding time set value T _1, the process returns to step S22, and compares the pressure P and the pressure setpoint P _0.

When the pressing force P and the pressing force set value P ₀ coincide with each other, the lowering of the pressing mechanism 13 is stopped (step S25), and the welding time t and the welding time set value T ₁ are compared again (step S25). Step S24). Further, the pressing force P may become larger than the pressing force set value P ₀ under the lowering operation of the pressing mechanism 13. In such a case, the pressing mechanism 13 is raised to reduce the pressing force P (Step S26).

As described above, the pressure P is controlled so as to coincide with the pressure set value P ₀ .

In this case, the controller 18 uses the pressure setting value P ₀ as a target value signal, the pressure P as a feedback signal, and the control signal of the servomotor 32 as an output signal to generate a PI.
Control operation such as D control may be performed to control the displacement of the pressing mechanism 13.

When the welding time t matches the welding time set value T _{1 in} step S 24, the controller 18 stops outputting the welding command signal to the welding power source 20. Therefore, the supply of the welding current from the welding power source 20 to the upper welding electrode 12 and the lower welding electrode 14 is stopped, and the welding is completed (step S25). Then, the pressing mechanism 13 is raised to take out the welded workpieces 90 and 92 (step S26).

In the second embodiment, since welding is performed while maintaining the applied pressure P constant, the applied pressure P does not become insufficient during welding, and good welding quality can be obtained.

Next, a resistance welding method according to a third embodiment will be described with reference to the flowchart of FIG.

First, similarly to the resistance welding method according to the first and second embodiments, the objects to be welded 90 and 92 are disposed between the upper welding electrode 12 and the lower welding electrode 14 in an overlapping manner (FIG. 4). Step S1), the pressing mechanism 13 is lowered, and the workpieces 90 and 92 are sandwiched between the upper welding electrode 12 and the lower welding electrode 14 (Step S2, see FIG. 7A). Then, the pressing force P of the upper welding electrode 12 with respect to the workpiece 92 is compared with the pressing force set value P ₀ (step S3), and when the pressing force P matches the pressing force set value P ₀ , the pressing mechanism 13 The descent is stopped (step S4).

Next, the magnetic induction type displacement sensor 7 at this time is
The output signal of 0 is input to the controller 18, and the controller 18 sets this output signal to the reference value 0 (step S31). For this reason, the output of the magnetic induction type displacement sensor 70 is hereinafter referred to as the displacement amount Δ of the thickness D of the workpieces 90 and 92.
D.

Next, the controller 18 controls the welding power source 20.
To output the welding command signal. Therefore, the welding power source 20 supplies a welding current between the upper welding electrode 12 and the lower welding electrode 14 for a certain period of time in accordance with the welding command signal, and
0 and 92 are welded (step S32). Therefore, as shown in FIG. 7B, a nugget 94 is formed on the workpieces 90 and 92, and the thickness D of the workpieces 90 and 92 is reduced. At this time, the upper welding electrode 12 is displaced with the change of the thickness D of the workpieces 90 and 92 under the elasticity of the coil spring 82. This displacement is transmitted from the pressure transmitting shaft 62 to the magnet 72, and the magnet 72 displaces inside the coil 74. Therefore, the displacement amount ΔD is measured by the magnetic induction type displacement sensor 70 (step S33). In this case, the displacement ΔD is the sum of the displacement ΔD _d of the thickness D of one workpiece 90 and the displacement ΔD _u of the other workpiece 92.

The controller 18 compares the displacement ΔD with the displacement set value ΔD ₁ stored in the controller 18 (step S34). If the displacement amount [Delta] D is less than the displacement amount set value [Delta] D ₁ returns to step S32, performs welding again. For this reason, welding progresses further and nugget 9
4 increases, and the thickness D of the workpieces 90 and 92 further decreases.

[0058] It this way repeatedly welding, nugget 94 becomes satisfactory size when measured displacement amount ΔD in step S33 becomes the displacement amount set value D ₁ or more, it is determined that the welding is completed Therefore, the controller 18 raises the pressing mechanism 13 and the workpieces 90, 92
Is taken out (step S35).

In the third embodiment, the workpieces 90, 9
By repeating welding until the displacement amount ΔD of the thickness D of 2 reaches the displacement amount set value ΔD ₁ , welding can be completed in a good welding state.

Further, since the displacement .DELTA.D of the upper welding electrode 12 is measured by the magnetic induction type displacement sensor 70 having good responsiveness, the displacement .DELTA.D can be accurately determined despite the short welding time.
Can be measured. Further, since the magnetic induction type displacement sensor 70 is covered by the shield 52, there is no concern that an error occurs in the output signal of the magnetic induction type displacement sensor 70 due to electromagnetic noise or magnetic noise.

In the third embodiment, the quality of welding is managed only by the displacement amount ΔD, but may be managed by the displacement amount ΔD and the pressing force P. For example, during welding, after the upper welding electrode 12 is displaced by the displacement amount ΔD (<ΔD ₁ ), the load P is applied to the workpiece 92 of the upper welding electrode 12 with the load cell 86, and the applied pressure P is measured. The pressing mechanism 13 is displaced so as to reach the pressing force set value P ₀ . After the upper welding electrode 12 is displaced again by the displacement amount ΔD (<ΔD ₁ −ΔD), the pressing force P is measured, and the pressing mechanism 13 is operated so that the pressing force P becomes the pressing force set value P _0. By performing the welding by repeating the step of displacing, welding can be performed while maintaining the pressing force P constant, and a desired displacement amount ΔD ₁ can be obtained, so that good welding quality can be obtained. Becomes

[0062]

According to the resistance welding method and apparatus of the present invention, the following effects and advantages can be obtained.

In order to perform welding by pressing the welding electrode while measuring the pressing force of the welding electrode against the workpiece by the load cell, and stopping the displacement of the welding electrode when the pressing force reaches a predetermined pressing force set value. In addition, it becomes easy to control the pressing force. Further, it is not necessary to control the length of the welding electrode, so that the welding operation is facilitated and the number of maintenance steps is reduced.
Therefore, work efficiency is improved.

Further, by performing the temporary welding on the workpiece, the contact resistance of the workpiece is small and the variation is reduced, so that a good welding can be performed at the time of the main welding, and further, the state of the surface roughness can be improved. Regardless, since the variation in contact resistance can be reduced by the temporary welding, good welding can be performed even on a workpiece having a rough surface roughness.

Further, by performing welding while keeping the pressing force constant, a good welding quality can be obtained without insufficient pressing force during welding.

Further, by measuring the amount of displacement of the thickness of the workpiece and repeating welding until the amount of displacement reaches the set value of displacement, welding can be completed in a good welding state.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a resistance welding apparatus according to an embodiment of the present invention.

FIG. 2 is a side view showing a displacement mechanism of the resistance welding apparatus of FIG.

FIG. 3 is a flowchart illustrating a resistance welding method according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating a resistance welding method according to the first embodiment of the present invention.

FIG. 5 is a flowchart illustrating a resistance welding method according to a second embodiment of the present invention.

FIG. 6 is a flowchart illustrating a resistance welding method according to a third embodiment of the present invention.

7 is a partially enlarged longitudinal sectional view showing a workpiece to be welded by the resistance welding apparatus of FIG. 1, and FIG. 7A shows a state where the workpiece is sandwiched between an upper welding electrode and a lower welding electrode; FIG. 7B is a diagram showing a state where the workpiece is welded.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Resistance welding apparatus 12, 14 ... Welding electrode 13 ... Pressing mechanism 16 ... Displacement mechanism 18 ... Controller 30 ... Linear actuator 32 ... Servo motor 36 ... Ball screw 40 ... Ball nut 52 ... Shield 62 ... Force transmission shaft 70 ... Magnetic Inductive displacement sensor 82: Coil spring 86: Load cell 90, 92: Workpiece

Claims (9)

[Claims] 1. A step of pressing a welding electrode for resistance welding against an object to be welded, and the pressure of the welding electrode against the object to be welded is measured by a pressure sensor. A step of stopping the pressing operation of the welding electrode at the time when the value becomes a value, and maintaining the pressing force; and a step of applying a welding current to the workpiece to perform welding. Welding method. 2. A step of pressing a welding electrode for resistance welding against an object to be welded, and the pressure of the welding electrode against the object to be welded is measured by a pressure sensor. The pressing operation of the welding electrode is stopped when the set value is reached, a step of maintaining the pressing force, a step of applying a temporary welding current to the workpiece to perform the temporary welding, and A step of pressing against the workpiece; measuring a pressing force of the welding electrode against the workpiece; stopping the pressing operation of the welding electrode when the pressing force reaches a second pressing force set value; A step of maintaining the pressure, and a step of applying a main welding current to the workpiece to perform the main welding. 3. A welding electrode for resistance welding is pressed against an object to be welded, and a pressing force of the welding electrode against the object to be welded is measured by a pressure sensor. When the welding current is applied, the welding current is applied to the workpiece to perform welding, and the welding electrode is pressed against the workpiece so that the pressing force is maintained at the pressing force set value. Resistance welding method. 4. A step of pressing a welding electrode for resistance welding against an object to be welded, and the pressure of the welding electrode against the object to be welded is measured by a pressure sensor. Stopping the pressing operation of the welding electrode at the time when the value becomes a value, maintaining the pressing force, applying a welding current to the workpiece, and performing welding; and Measuring the amount of displacement; and performing the welding until the amount of displacement reaches a predetermined value. 5. A pressing mechanism for pressing a welding electrode for resistance welding against an object to be welded, and a displacement mechanism for displacing the pressing mechanism toward the object to be welded, wherein the displacement mechanism includes the pressing mechanism. A pressing force transmission shaft, on which the welding electrode is mounted and which is urged to the workpiece through an elastic member, connected to the member, the resistance welding apparatus characterized by having a pressure sensor for measuring such pressure to the welding electrode. 6. The resistance welding apparatus according to claim 5, wherein the linear actuator converts a servomotor, a feed screw connected to a rotary shaft of the servomotor, and a rotary motion of the feed screw into a linear motion. And a feed nut connected to the pressing mechanism. 7. The resistance welding apparatus according to claim 5, wherein the pressure sensor is a load cell. 8. The resistance welding apparatus according to claim 5, wherein the pressing mechanism has a displacement sensor that detects a displacement amount of the pressurizing force transmission shaft when pressurizing. Resistance welding equipment. 9. The resistance welding apparatus according to claim 8, wherein the displacement sensor is a magnetic induction type displacement sensor.