JP3734108B2 - Resistance welding machine and resistance welding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention is a resistance welding machine.And resistance welding methodIn particular, resistance welding machines that can be used when performing resistance welding such as spot welding, projection welding, and seam weldingAnd resistance welding methodAbout.
[0002]
[Prior art]
Conventionally, resistance welding has been used as a method for joining metal members. For example, spot welding is used when two steel plates are stacked and joined. In this spot welding, an electrode is energized while a workpiece is sandwiched between a pair of electrodes to cause a current to flow directly through the workpiece, and the contact electrical resistance between the electrode and the workpiece and the electrical resistance of the workpiece itself are used. This is done by heating the work to be welded using the generated Joule heat and melting and solidifying the joint of the work to be welded.
[0003]
In general, the amount of Joule heat generated when a current flows through a conductor is proportional to the square of the current intensity and the resistance of the conductor (Joule's law). In the spot welding, the contact resistance tends to decrease as the electrode pressing force and the welding current increase. Furthermore, if welding is performed for a long time with a reduced current, heat does not concentrate, so that satisfactory welding cannot be performed. Therefore, in resistance welding such as spot welding, it is important to properly set three conditions of electrode pressing force, welding current, and energization time.
[0004]
As a resistance welding machine for performing such spot welding, Japanese Patent Laid-Open No. 4-178275 discloses one shown in FIG. This resistance welder includes a pair of electrodes 81a and 81b, a resistance welding power source 82 that supplies a welding current to the electrodes 81a and 81b, a pressure cylinder 83 that applies electrode pressure to one electrode, and a pressure cylinder 83. And an electro-pneumatic proportional valve 84 for adjusting the pressure applied to the electrode 81a, 81b from the resistance welding power source 82 while the workpiece 85 is clamped between the pair of electrodes 81a, 81b by the operation of the pressurizing cylinder 83. Spot welding is performed by supplying a welding current. In this resistance welding machine, the average temperature and the current-carrying diameter of the welded portion are determined from the inter-chip voltage detected by the detection cable 86, the welding current detected by the current detector 87, and the amount of electrode movement detected by the detector 88. Are sequentially identified by the signal processing unit 89 and the estimation unit 90, and based on the result of comparing the energized diameter and the heat generation density determined therefrom with each standard increase pattern determined in advance, the signal generation unit 91 and the control units 92 and 93 Thus, adaptive control of the welding current and the electrode pressing force in real time is repeated to always ensure an appropriate nugget growth state, and the energization end time is determined based on the predicted nugget dimension at the same time.
[0005]
[Problems to be solved by the invention]
In the conventional resistance welding machine, the electrode pressurizing force is controlled only on one electrode 81a by a single pressurizing cylinder 83, and the pressurizing force of each electrode 81a, 81b is controlled independently. I can't. For this reason, in the conventional resistance welding machine, the nugget formation position cannot be adjusted in the opposing direction of the pair of electrodes 81a and 81b (the plate thickness direction of the workpiece 85). was there.
[0006]
First, when two steel plates having different plate thicknesses are overlapped and spot-welded, it is necessary to adjust the nugget formation position in the plate thickness direction according to the difference in plate thickness. Here, the nugget formation position can be adjusted by the pressure applied to each workpiece 85 from the electrodes 81a and 81b. That is, since the amount of Joule heat generated between the electrode and the workpiece is different when the magnitude of the applied pressure is different, the magnitude of the applied pressure from the one electrode 81a to the workpiece 85 and the measured pressure from the other electrode 81b are different. By changing the magnitude of the pressure applied to the weldment 85, the nugget formation position can be shifted. However, in the conventional resistance welding machine, the pressure applied to the workpiece 85 from one electrode 81a cannot be different from the pressure applied to the workpiece 85 from the other electrode 81b. The nugget formation position could not be adjusted in the plate thickness direction, and it was impossible to satisfactorily weld two workpieces having different thicknesses.
[0007]
Further, the conventional welding resistance machine that controls the electrode pressing force only with respect to one electrode 81a by a single pressurizing cylinder 83 has a problem in that poor bonding or weld cracking occurs due to nugget bias. . That is, in the conventional resistance welding machine, for example, when an external force that presses the workpiece 85 toward the one electrode 81a acts on the workpiece 85, the electrode pressure applied from the one electrode 81a to the workpiece 85 Becomes larger than the electrode pressing force applied to the workpiece from the other electrode 81b. Then, the Joule heat generated between the one electrode 81a and the workpiece 85 becomes smaller than the Joule heat generated between the other electrode 81b and the workpiece, and as a result, the nugget is biased toward the other electrode 81b. It will be formed at the position, causing joint failure and weld cracking.
[0008]
  The present invention has been made in view of the above circumstances, and a resistance welding machine capable of adjusting the nugget formation position in the opposing direction of each electrode.And resistance welding methodIt is a technical problem to be solved.
[0009]
[Means for Solving the Problems]
  The resistance welding machine according to claim 1, which solves the above problem, is a resistance welding machine that welds the workpiece by energizing each electrode while sandwiching the workpiece with a pair of electrodes. A pair of pressure applying means for independently applying pressure to the workpiece, and a pair of pressure detecting means for independently detecting the pressure applied from the electrodes to the workpiece, And controlling each of the pressure applying means independently based on a detection result of each of the pressure detecting means, and a control means for controlling energization to each of the electrodes. Based on the interrelationship between the value of the pressure difference A applied to the work piece from the above and the offset amount of the nugget formation position, the difference in the thickness of the work piece was determined.Not zeroThe value of the difference A when the predetermined offset amount is reached is predetermined as a set value, and the control means compares the detection signals sent from the respective pressure detection means and compares the pressure difference. It is determined whether or not the value of A is the set value, and each pressing force applying means is controlled so that the value of the difference A becomes the set value, and the value of the difference A is set to the set value. In this case, each electrode is energized to start welding.
[0010]
  In this resistance welder, the pressure can be applied independently from each electrode to the workpiece by the pair of pressure application means. For this reason, for example, when the pressure applied to one electrode is larger than the pressure applied to the other electrode, Joule heat generated between the one electrode and the work piece is generated between the other electrode and the work piece. As a result, the amount of heat generated between the electrode and the work piece is unbalanced, so that the nugget formation position can be shifted to the other (smaller pressing force) electrode side. . Therefore, the nugget formation position can be arbitrarily adjusted by adjusting the pressure applied from each electrode to the workpiece, for example, according to the difference in the thickness of the workpiece.
  Further, in this resistance welding machine, the applied pressure applied from each electrode to the workpiece is detected by the applied pressure detection means, and the applied pressure applied from each electrode to the workpiece is determined based on the detection result. Can be controlled independently. For this reason, for example, an external force that presses the work piece to one electrode side acts on the work piece, the magnitude of the pressure applied from the one electrode to the work piece, and the other electrode to the work piece. When the applied pressure is different from the applied pressure, the control means applies each applied pressure applying means according to the difference in applied pressure from each electrode to the workpiece based on the detection result of each applied pressure detecting means. By controlling the above, it is possible to adjust the pressure applied from each electrode to the workpiece, and thus to adjust the nugget formation position. Therefore, for example, an external force that presses the work piece to one electrode side acts on the work piece, and the amount of pressure applied from the one electrode to the work piece and the other electrode to the work piece are applied. Even when the applied pressure is different from the magnitude of the applied pressure, it is possible to prevent poor bonding and weld cracking due to the nugget bias.
  Further, in this resistance welding machine, the pressure applied to the work piece from each electrode is detected by the pressure detection means, and each pressure application means is operated by the control of the control means based on the detection result. Thus, it is possible to independently control each electrode pressure applied from each electrode to the workpiece. For this reason, for example, even when two workpieces having different plate thicknesses are welded, the nugget formation position can be adjusted in accordance with the difference in the plate thickness of the workpieces. Thus, it is possible to reliably form a nugget at the boundary portion and perform good welding.
  In the resistance welding machine according to claim 1, the control means is based on the interrelationship between the value of the sum B of the applied pressures from the electrodes to the work piece and the diameter of the nugget. The value of the sum B when the nugget becomes a predetermined size is determined in advance as a set value, and the control means outputs a detection signal sent from each of the pressure detection means during welding. Based on this, it is determined whether or not the value of the sum B of the applied pressures is the set value, and when the value of the sum B reaches the set value, the energization to each of the electrodes is stopped to end the welding. It is preferable that it is comprised.
  According to this aspect, during welding, it is possible to reliably detect that the nugget diameter has reached a predetermined size by controlling the nugget growth process in real time based on detection signals from the respective pressure detection means. it can. For this reason, excessive cracking of the nugget can be surely prevented, and extra electricity consumption can be avoided to contribute to energy saving. Further, it is not necessary to separately provide a displacement sensor for observing nugget growth.
[0011]
  The resistance welding machine according to claim 3, which solves the above-described problem, is a resistance welding machine that welds the workpiece by energizing each electrode while sandwiching the workpiece with a pair of electrodes. A pair of pressure detection means for independently detecting the pressure applied to the work piece from each other, a shift means for moving at least each of the electrodes relative to the work piece in a facing direction, The shift means is controlled based on the detection result of the pressurizing force detection means, and control means for controlling energization to each of the electrodes is provided. Based on the interphase relationship between the value of the applied pressure difference A and the offset amount of the nugget formation position, the difference in the plate thickness of the workpieces was determined.Not zeroThe value of the difference A when the predetermined offset amount is reached is predetermined as a set value, and the control means compares the detection signals sent from the respective pressure detection means and compares the pressure difference. It is determined whether or not the value of A is the set value, and the shift means is controlled so that the value of the difference A becomes the set value, and the value of the difference A becomes the set value. In some cases, the electrodes are configured to start welding by energizing each of the electrodes.
[0012]
  In this resistance welding machine, the applied pressure applied to the work piece from each electrode can be detected by the pressure detection means, so that, for example, an external force that presses the work piece against one electrode side is subjected to the work piece. If the magnitude of the pressure applied from one electrode to the workpiece is different from the magnitude of the pressure applied from the other electrode to the workpiece, the electrodes are transferred from the electrodes to the workpiece. The difference in applied pressure can be detected by each applied pressure detection means. For this reason, based on the detection result of each applied pressure detection means, depending on the difference in the applied pressure from each electrode to the workpiece, at least each electrode is moved relative to the workpiece in the opposite direction by the operation of the shift means. Thus, the applied pressure from each electrode to the workpiece, and thus the nugget formation position, can be adjusted. Therefore, for example, an external force that presses the work piece to one electrode side acts on the work piece, and the amount of pressure applied from the one electrode to the work piece and the other electrode to the work piece are applied. Even when the applied pressure is different from the magnitude of the applied pressure, it is possible to prevent poor bonding and weld cracking due to the nugget bias. For example, even when two workpieces having different plate thicknesses are welded, the nugget formation position can be adjusted according to the difference in the plate thickness of the workpieces. It is possible to reliably form a nugget at the boundary and perform good welding.
  In the resistance welding machine according to claim 3, the control means is based on the interrelationship between the value of the sum B of the applied pressures applied from the electrodes to the work piece and the diameter of the nugget. The value of the sum B when the nugget becomes a predetermined size is determined in advance as a set value, and the control means outputs a detection signal sent from each of the pressure detection means during welding. Based on this, it is determined whether or not the value of the sum B of the applied pressures is the set value, and when the value of the sum B reaches the set value, the energization to each of the electrodes is stopped to end the welding. It is preferable that it is comprised.
  The resistance welding method according to claim 5, which solves the above-described problem, is a resistance welding method in which a welding object is welded by energizing each electrode while sandwiching the object to be welded by a pair of electrodes. In a state where an object is sandwiched between the electrodes, the applied pressure from each electrode to the workpiece is detected, and each electrode is applied to the workpiece based on the detection result. A welding preparation step for adjusting the nugget formation position in the plate thickness direction of the workpiece by adjusting the applied pressure, and the nugget formation position in the plate thickness direction of the workpiece to be welded in the welding preparation step And a welding process for starting welding by energizing each of the electrodes and welding the workpieces.In the welding preparation step, the value of the pressure difference A applied from each electrode to the workpiece is based on the correlation between the value of the pressure difference A and the offset amount of the nugget formation position. Each of the electrodes is applied to the work piece so as to be a set value of the difference A when a predetermined non-zero offset amount corresponding to a difference in thickness of the work piece is set in advance. Adjust the pressureIt is characterized by this.
  The resistance welding method according to claim 5.,in frontIn the welding process, during welding, the pressure applied to each of the workpieces from each of the electrodes is detected, and the value of the sum B of the pressures based on the detection result is the value of the sum B of the pressures. When the set value of the sum B when the nugget is set to a predetermined size based on the correlation between the diameter of the nugget and the diameter of the nugget is reached, the energization to each electrode is stopped and welding is performed. It is preferable to end.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described.
(Embodiment 1)
In the resistance welding machine according to the present embodiment shown in FIG. 1, an upper hydraulic cylinder 3 and a lower hydraulic cylinder 4 are fixed to an upper arm 1 and a lower arm 2 as pressure applying means, respectively. An upper electrode 6 is connected to the upper hydraulic cylinder 3 via an upper load cell 5 as a pressure detection means, and a lower electrode 8 is also connected to the lower hydraulic cylinder 4 via a lower load cell 7. The upper electrode 6 and the lower electrode 8 can be energized by a welding power source 9.
[0016]
The detection signals of the upper load cell 5 and the lower load cell 7 are respectively sent to the control device 10, and the control device 10 sends the upper hydraulic cylinder 3 via the upper electromagnetic proportional valve 11 and the lower electromagnetic proportional valve 12 based on these detection signals. The lower hydraulic cylinder 4 can be controlled. The welding power source 9 can also be controlled by the control device 10.
[0017]
(When forming a nugget at the center of the work piece)
A case where two welding objects (steel plates) W having the same thickness are overlapped and welded using the resistance welder according to the first embodiment having the above configuration will be described below. The workpiece W is clamped between the upper electrode 6 and the lower electrode 8, and a flowchart before welding is shown in FIG. 2, and a flowchart during welding is shown in FIG.
[0018]
After the two workpieces W are overlapped and placed between the upper electrode 6 and the lower electrode 8, a predetermined signal is sent from the control means 10 to the upper electromagnetic proportional valve 11 and the lower electromagnetic proportional valve 12, respectively. The hydraulic cylinder 3 and the lower hydraulic cylinder 4 were operated, and the workpiece W was clamped between the upper electrode 6 and the lower electrode 8. At this time, the stroke amounts of the upper hydraulic cylinder 3 and the lower hydraulic cylinder 4 were made equal. The work piece W is fixed by a clip device (not shown). In this state, the upper electrode pressure F applied to the workpiece W from the upper electrode 6_UIs detected by the upper load cell 5 and this detection signal is sent to the control means 10 and the lower electrode pressure F applied to the workpiece W from the lower electrode 8._DIs detected by the lower load cell 7 and this detection signal is sent to the control means 10. The control device 10 compares the detection signals sent from the upper load cell 5 and the lower load cell 7, respectively,
A = (Upper electrode pressure F_U)-(Lower electrode pressure F_D)
It is determined whether or not the value of is zero. If the value of A is not zero, a signal is sent to the upper electromagnetic proportional valve 11 or the lower electromagnetic proportional valve 12 according to the value of A to operate the upper hydraulic cylinder 3 or the lower hydraulic cylinder 4.
[0019]
For example, when an external force pressing the workpiece W toward the upper electrode 6 is acting on the workpiece W, the upper electrode pressure F applied from the upper electrode 6 to the workpiece W_UIs applied to the workpiece W from the lower electrode 8._DSince A> 0, the control device 10 sends a signal to the upper electrode proportional valve 11 to reduce the stroke amount of the upper hydraulic cylinder 3 by a predetermined amount or lower according to the value of A. A signal is sent to the electrode proportional valve 12 to increase the stroke amount of the lower hydraulic cylinder 4 by a predetermined amount.
[0020]
Through this process, when the value of A becomes zero, the upper electrode pressure F applied from the upper electrode 6 to the workpiece W_UAnd lower electrode pressure F applied to the workpiece W from the lower electrode 8_DAnd the preparation for welding to form the nugget at the center of the workpiece W is completed, the control device 10 sends a signal to the welding power source 9, and the welding power source 9 sends the signal to the upper electrode 6 and the lower electrode 8. A predetermined current is supplied to start welding.
[0021]
During this welding, a nugget is formed at the boundary of the workpiece W. Then, when the nugget grows and expands in the workpiece W, the pressure accompanying the nugget expansion is equally applied from the workpiece W to the upper electrode 6 and the lower electrode 8. This pressure increases as the nugget grows. For this reason, the pressure applied to the upper electrode 6 and the lower electrode 8 from the workpiece W is determined as the upper electrode pressure F._UAnd lower electrode pressure F_DAnd detected by the upper load cell 5 and the lower load cell 7, respectively, and this detection signal is sent to the control device 10. In the control apparatus 10, based on the detection signals sent from the upper load cell 5 and the lower load cell 7, respectively,
B = (Upper electrode pressure F_U) + (Bottom electrode pressure F_D)
It is determined whether the value of is a set value. A correlation between the size of the nugget diameter and the value of B is obtained in advance, and the value of B when the nugget becomes a predetermined size is preset in the control device 10 based on the correlation. Yes. When the value B becomes a preset value, a power-off signal is sent from the control device 10 to the welding power source 9, and the welding is terminated.
[0022]
Thus, according to the welding resistance machine of this embodiment, the upper electrode pressure F applied to the workpiece W from the upper electrode 6 and the lower electrode 8._ULower electrode pressure F_DIs detected by the upper load cell 5 and the lower load cell 7, and the upper hydraulic cylinder 3 or the lower hydraulic cylinder 4 is operated via the upper electromagnetic proportional valve 11 or the lower electromagnetic proportional valve 12 under the control of the control device 10 based on the detection result. The upper electrode pressure F applied to the workpiece W from the upper electrode 6 and the lower electrode 8 respectively._ULower electrode pressure F_DCan be controlled independently. Therefore, for example, even when an external force that presses the work piece W toward the upper electrode 6 is acting on the work piece W, the upper electrode pressure applied to the work piece W from the upper electrode 6 and the lower electrode 8. F_UAnd lower electrode pressure F_DCan be made equal, and the nugget formation position can be reliably set at the center of the work W. Therefore, it is possible to prevent poor bonding and weld cracking due to the nugget bias.
[0023]
Moreover, according to the welding resistance machine of this embodiment, the nugget growth process can be controlled in real time based on the detection signals of the upper load cell 5 and the lower load cell 7. For this reason, it is possible to reliably detect that the nugget diameter has become a predetermined size, so that it is possible to reliably prevent over-cracking of the nugget and to contribute to energy saving by avoiding excessive electricity consumption. You can also. Further, it is not necessary to provide a separate displacement sensor or the like for observing nugget growth.
[0024]
(When offsetting nuggets)
A case where two welding objects (steel plates) W having different thicknesses are overlapped and welded using the resistance welder according to the first embodiment will be described below.
Similar to the case where the nugget is formed at the center, two workpieces W fixed by a clip device (not shown) are overlapped so that the stroke amounts of the upper hydraulic cylinder 3 and the lower hydraulic cylinder 4 are equal. The upper electrode 6 and the lower electrode 8 were sandwiched with each other. In this state, the upper electrode pressure F applied to the workpiece W from the upper electrode 6_UIs detected by the upper load cell 5 and this detection signal is sent to the control means 10 and the lower electrode pressure F applied to the workpiece W from the lower electrode 8._DIs detected by the lower load cell 7 and this detection signal is sent to the control means 10. The control device 10 compares the detection signals sent from the upper load cell 5 and the lower load cell 7, respectively,
A = (Upper electrode pressure F_U)-(Lower electrode pressure F_D)
It is determined whether the value of is a set value. A correlation between the value A and the offset amount of the nugget formation position is obtained in advance, and based on the correlation, a predetermined offset amount corresponding to the difference in the thickness of the two workpieces W is obtained. The value of A at that time is preset in the control device 10. If the value A is not a set value, a signal is sent to the upper electromagnetic proportional valve 11 or the lower electromagnetic proportional valve 12 according to the value A to operate the upper hydraulic cylinder 3 or the lower hydraulic cylinder 4.
[0025]
Through such a process, if the value of A becomes a set value, preparation for welding for forming a nugget at a predetermined offset position, that is, a boundary portion of the workpiece W, is completed. A signal is sent to the welding power source 9 and a predetermined current is supplied from the welding power source 9 to the upper electrode 6 and the lower electrode 8 to start welding.
During this welding, as in the case where the nugget is formed at the center, the pressure increase due to the nugget expansion is increased by the upper electrode pressure F_UAnd lower electrode pressure F_DAnd detecting by the upper load cell 5 and the lower load cell 7, respectively, and detecting that the nugget has become a predetermined size based on the detection signal, and the welding can be finished.
[0026]
Thus, according to the welding resistance machine of this embodiment, the upper electrode pressure F applied to the workpiece W from the upper electrode 6 and the lower electrode 8._ULower electrode pressure F_DIs detected by the upper load cell 5 and the lower load cell 7, and the upper hydraulic cylinder 3 or the lower hydraulic cylinder 4 is operated via the upper electromagnetic proportional valve 11 or the lower electromagnetic proportional valve 12 under the control of the control device 10 based on the detection result. The upper electrode pressure F applied to the workpiece W from the upper electrode 6 and the lower electrode 8 respectively._ULower electrode pressure F_DCan be controlled independently. For this reason, for example, even when two workpieces W having different plate thicknesses are welded, the nugget formation position can be adjusted according to the difference in the plate thickness of the workpieces W. It is possible to reliably form a nugget at the boundary portion of the object W and perform good welding.
[0027]
Further, for example, even when an external force that presses the work piece W toward the upper electrode 6 acts on the work piece W, the upper load cell 5 and the lower load cell 7 are used to add the effect of the external force. Since the nugget can be surely formed at the boundary portion between the two workpieces W, good welding can be performed.
In addition, in the said Embodiment 1, when the structure which eliminated the load cells 5 and 7 as a pressure detection means is employ | adopted, the external force which presses the to-be-welded object W to the upper electrode 6 side, for example to this to-be-welded object W On the condition that it does not act, it is possible to reliably form a nugget at the boundary portion between two workpieces W having different plate thicknesses and perform good welding.
[0028]
(Embodiment 2)
In the resistance welding machine according to the present embodiment shown in FIG. 4, an upper hydraulic cylinder 3 and a base 13 as pressing force application means are fixed to the upper arm 1 and the lower arm 2 that are connected to each other. An upper electrode 6 is connected to the upper hydraulic cylinder 3 via an upper load cell 5 as a pressure detecting means, and a lower electrode 8 is also connected to the base 13 via a lower load cell 7. The upper electrode 6 and the lower electrode 8 can be energized by a welding power source 9. Further, the upper arm 1 and the lower arm 2 connected to each other can be moved up and down by an arm hydraulic cylinder 14 as a shift means.
[0029]
The detection signals of the upper load cell 5 and the lower load cell 7 are respectively sent to the control device 10, and the control device 10 can control the arm hydraulic cylinder 14 via the electromagnetic proportional valve 15 based on these detection signals. Yes. The upper hydraulic cylinder 3 can also be controlled by the control device 10 via the upper electromagnetic proportional valve 11, and the welding power source 9 can also be controlled by the control device 10.
[0030]
Even when the resistance welding machine according to the second embodiment having the above-described configuration is used, as in the first embodiment, the nugget is welded while being reliably formed at the center of the workpiece W, or two sheets having different plate thicknesses are used. It is possible to weld the workpiece to be welded satisfactorily.
That is, in the resistance welding machine of this embodiment, the upper electrode pressure F_UAnd lower electrode pressure F_DAre detected by the upper load cell 5 and the lower load cell 7, respectively, and this detection signal is sent to the control device 10. The control device 10 compares these detection signals in the same manner as in the first embodiment,
A = (Upper electrode pressure F_U)-(Lower electrode pressure F_D)
In response to the value of, a signal is sent to the electromagnetic proportional valve 15 to activate the arm hydraulic cylinder 14.
[0031]
  For example, when an external force pressing the workpiece W toward the upper electrode 6 is acting on the workpiece W, the upper electrode pressure F applied from the upper electrode 6 to the workpiece W_UIs applied to the workpiece W from the lower electrode 8._DSince A> 0, the control device 10 sends a signal to the electrode proportional valve 15 according to the value of A.Hydraulic cylinder for arm 14And the upper arm 1 and the lower arm 2 are integrally raised. The workpiece W is fixed by a clip device (not shown). As a result, the upper electrode 6 connected to the upper arm 1 via the upper hydraulic cylinder 3 and the upper load cell 5 and the lower electrode 8 connected to the lower arm 2 via the base 13 and the lower load cell 7 are 6 and the lower electrode 8 are moved relative to the workpiece W in the opposing direction (vertical direction). As a result, the upper electrode pressure F is compared with that before the movement._UAnd the lower electrode pressure F_DBecomes larger.
[0032]
Through such a process, the nugget formation position can be arbitrarily adjusted by adjusting the value A. Therefore, even when welding workpieces W having the same thickness, or when welding workpieces W having different thicknesses, a nugget is reliably formed at the boundary of the workpieces W. It becomes possible to do.
Of course, also in the welding resistance machine according to the second embodiment, the nugget growth process during welding can be observed and controlled based on the detection signals of the upper load cell 5 and the lower load cell 7.
[0033]
In the second embodiment, the example in which the workpiece W is fixed and the upper electrode 6 and the lower electrode 8 are moved relative to the workpiece W has been described. It is also possible to fix the electrode 8 and move the workpiece W relative to the upper electrode 6 and the lower electrode 8. In this case, the clip device or the like that holds the workpiece W can be moved up and down by a hydraulic cylinder or the like as a shift means.
[0034]
【The invention's effect】
  As described in detail above, the resistance welder according to claims 1 to 4 or claim 5., 6According to the described resistance welding method, for example, it is possible to arbitrarily adjust the nugget formation position according to the difference in the thickness of the workpieces, and reliably weld the nuggets even in workpieces having different thicknesses. Good welding is possible by forming at the boundary of objects.
[Brief description of the drawings]
FIG. 1 is a side view schematically showing an overall configuration of a resistance welding machine according to a first embodiment.
FIG. 2 is a flowchart for explaining control of electrode pressing force before welding.
FIG. 3 is a flowchart for explaining control of a nugget diameter during welding.
FIG. 4 is a side view schematically showing the overall configuration of a resistance welding machine according to a second embodiment.
FIG. 5 is a side view schematically showing the overall configuration of a conventional resistance welder.
[Explanation of symbols]
1 is upper arm, 2 is lower arm, 3 is upper hydraulic cylinder, 4 is lower hydraulic cylinder, 5 is upper load cell, 6 is upper electrode, 7 is lower load cell, 8 is lower electrode, 9 is welding power source, 10 is control 11 is an upper electromagnetic proportional valve, 12 is a lower electromagnetic proportional valve, 13 is a base, 14 is a hydraulic cylinder for arm, and 15 is an electromagnetic proportional valve.

Claims (6)

A resistance welding machine that welds the workpiece by energizing each electrode while sandwiching the workpiece with a pair of electrodes,
A pair of pressure applying means for applying pressure independently from each of the electrodes to the workpiece;
A pair of pressure detection means for independently detecting the pressure applied to each workpiece from each of the electrodes;
Controlling each pressure application means independently based on the detection result of each pressure detection means, and a control means for controlling the energization to each electrode,
The control means includes a difference in plate thickness of the workpieces based on the interrelationship between the value A of the applied pressure applied from the electrodes to the workpiece and the offset amount of the nugget formation position. The value of the difference A when a predetermined non-zero offset amount according to is set as a set value,
The control means compares the detection signals sent from the respective pressure detection means to determine whether or not the value of the pressure difference A is the set value, and the value of the difference A is Each pressurizing force applying means is controlled to become the set value, and when the value of the difference A reaches the set value, the electrodes are energized to start welding. Features resistance welding machine. When the nugget has a predetermined size based on the interrelationship between the value of the sum B of the applied pressures applied from the electrodes to the workpiece and the size of the nugget diameter, The value of the sum B is determined in advance as a set value,
The control means determines whether or not the value of the sum B of the applied pressure is the set value based on the detection signal sent from each of the applied pressure detecting means during welding. 2. The resistance welding machine according to claim 1, wherein when the value of becomes the set value, the energization to each of the electrodes is stopped and the welding is finished. A resistance welding machine that welds the workpiece by energizing each electrode while sandwiching the workpiece with a pair of electrodes,
A pair of pressure detection means for independently detecting the pressure applied to each workpiece from each of the electrodes;
Shift means for moving at least each of the electrodes relative to the work piece in a facing direction;
The shift means is controlled based on the detection result of each pressurizing force detection means, and includes a control means for controlling energization to each electrode.
The control means includes a difference in plate thickness of the workpieces based on the interrelationship between the value A of the applied pressure applied from the electrodes to the workpiece and the offset amount of the nugget formation position. The value of the difference A when a predetermined non-zero offset amount according to is set as a set value,
The control means compares the detection signals sent from the respective pressure detection means to determine whether or not the value of the pressure difference A is the set value, and the value of the difference A is The shift means is controlled to become the set value, and when the value of the difference A reaches the set value, the electrodes are energized to start welding. Resistance welding machine. When the nugget has a predetermined size based on the interrelationship between the value of the sum B of the applied pressures applied from the electrodes to the workpiece and the size of the nugget diameter, The value of the sum B is determined in advance as a set value,
The control means determines whether or not the value of the sum B of the applied pressure is the set value based on the detection signal sent from each of the applied pressure detecting means during welding. The resistance welding machine according to claim 3, wherein when the value of becomes the set value, the energization to each of the electrodes is stopped to end the welding. A resistance welding method of welding the workpiece by energizing each electrode while sandwiching the workpiece with a pair of electrodes,
In a state where the workpiece is sandwiched between the electrodes, the pressure applied from the electrodes to the workpiece is detected, and the workpiece is detected from the electrodes based on the detection result. A welding preparation step of adjusting the nugget formation position in the plate thickness direction of the workpiece by adjusting the applied pressure respectively to
After adjusting the nugget formation position in the plate thickness direction of the workpiece to be welded in the welding preparation step, the welding step starts welding by energizing each electrode and welding the workpiece ,
In the welding preparation step, the value of the pressure difference A applied from each of the electrodes to the workpiece is previously determined based on the correlation between the value of the pressure difference A and the offset amount of the nugget formation position. Addition applied from each electrode to the work piece so as to be a set value of the difference A when a predetermined non-zero offset amount corresponding to the set thickness difference of the work piece is obtained. A resistance welding method characterized by adjusting pressure . In the welding process, during welding, the applied pressure applied from the electrodes to the workpiece is detected, and the value of the applied pressure B based on the detection result is the value of the applied pressure B. When the set value of the sum B when the nugget is set to a predetermined size based on the correlation between the diameter of the nugget and the diameter of the nugget is reached, the current supply to each electrode is stopped and welding is performed The resistance welding method according to claim 5 , wherein the resistance welding method is terminated.

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