JP2001300738A - Method and device for controlling motor-driven servo type resistance welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method and a control device for a motor-driven servo type resistance welding equipment by which a welding condition required for welding can be made common to those of other pressure systems regardless of a difference in the pressure system by which a material to be welded is pressed by electrodes. SOLUTION: The control device is equipped with a drive force transmission mechanism 14 transmitting a drive force being generated by a servomotor 13 to an electrode 11, a pressure force command means issuing a command to the servomotor so that materials W1, W2 to be welded are pressured by the above electrodes 11 with a prescribed pressure force and a weld command means 31 instructing the start of welding. By a displacement quantity detection means 15 detecting the displacement quantity of the electrode 11 by the thermal expansion of the materials W1, W2 to be welded from the starting time of energizing by the electrode 11 and a pressure force command correction means 34 correcting a pressure force command issued by the above pressure force command means 32 so that the increase of the pressure force by the thermal expansion of the materials W1, W2 to be welded, is eliminated by referring to a motive power transmission characteristic in the drive force transmission mechanism 14 when a detected displacement quantity has reached a prescribed quantity, the pressure force during spot welding is made to be almost constant.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric servo type resistance melting device.
The present invention relates to a control method and a control device for a contact device. Further details
In other words, eliminates the effect of the thermal expansion of the material to be welded on the energized state
And an electric sensor that automatically detects the spots where welding defects occur.
Control method and control apparatus for resistance welding equipment
You. [0002] Conventionally, a material to be welded is pressed by an electrode.
In spot welding where resistance welding is performed, servo motors are used.
Electric to press the material to be welded by driving the electrode with
Servo method and air pressure
A method has been implemented. Electric servo system is now air system
The pressure control accuracy and responsiveness are
Electric servo method is frequently used in spot welding by bots
Have been. However, electric servo type resistance welding
Welding by electric equipment (electric servo type resistance welding equipment)
Now, transmit the rotational driving force generated by the servo motor to the electrodes
The driving force transmission system is an air-type resistance welding device (air-type
Resistance welding equipment).
The following problems occur. That is, as shown in FIG.
In the dynamic servo resistance welding apparatus 100, the upper electrode 101
Between the lower electrode 102 and a pair of materials to be welded (hereinafter, work
W)₁´, W_Two′ Are placed one on top of the other
For example, the upper electrode 101 is driven by the rotational driving force of the motor 103.
Driving up and down, the work W₁´, W_Two′ For each electrode 10
Welding while applying pressure at a predetermined pressure according to 1, 102
It is being done. Rotary drive generated by servo motor 103
Power is timing belts, gears, chains and cups
Via a power transmission mechanism 104 composed of a member such as a ring
Transmitted to the ball screw 105,
It is converted into a linear driving force in the vertical direction. However, such a conventional electric servo type
In the resistance welding apparatus 100, the driving force of the ball screw 105
Loss in direction change and friction in the power transmission mechanism 104
Rotation driving force of the servo motor 103
100% is not transmitted to the pole side,
100% of the reaction force acting on the end is transmitted to the servo motor 103 side
It will not be. Therefore, the rotation of the servo motor 103
Only by keeping the driving force constant, the work W
₁´, W_TwoThe pressure applied by each of the electrodes 101 and 102 is
It cannot be fixed. That is, as shown in FIG.
Each workpiece W at a constant pressure Fc '₁´, W_Two′ For each electrode 10
As shown in FIG.
As shown in FIG.₁´, W_Two´ energized part
Is thermally expanded, and the reaction force Fe ′ generated by this thermal expansion is
Acts to push up the pole 101. At this time,
Each work W facing the poles 101 and 102₁´, W_TwoWith ´
The pressurizing force Fj 'acting therebetween is represented by the following equation (7). Fj ′ = Fc ′ + (1−η ′) Fe ′ (7) where η ′ is the power transmission mechanism 104 and
Driving force transmission efficiency of the ball screw 105 (η ′ <
1). That is, the servo motor 103
When the rotational driving force applied is constant, the actual pressing force Fj ′ becomes
The force (1-η ') Fe' is larger than the predetermined pressure Fc '.
It will be good. The friction of the power transmission mechanism 104, especially static
The loss due to friction is smaller than the loss in the ball screw 105.
Since it is negligible, the transmission efficiency η 'is substantially
Transmission efficiency of the ball screw 105
You can think. As described above, the actual pressing force Fj 'is
When the pressure becomes larger than the applied pressure Fc ′, each electrode 101,
102 tip and each work W₁´, W_TwoThe contact area between ´
As a result, the welding current density during energization starts
It falls below the point. Therefore, the conventional electric servo type
In the resistance welding apparatus 100, a decrease in welding current density during energization
It is necessary to set welding conditions (such as energizing time) in consideration of
is there. On the other hand, in an air resistance welding apparatus, an air pressure
Transmission system is simpler than an electric servo type,
The transmission efficiency η 'in the pressure transmission system can be considered to be approximately 1.
Can be. For this reason, the electrode pressurizes the material to be welded.
The force is almost constant during energization, and the contact surface between the electrode and the workpiece
The product does not change significantly, so the welding current
Can be considered to be almost constant from the start of energization.
it can. Therefore, the electric servo type resistance welding apparatus and
Same principle as air type resistance welding equipment due to difference in pressurization method
The welding current density is the welding condition
Completely different from other welding strips.
It is necessary to perform welding according to the requirements. However, welding
Conditions are determined in consideration of various factors such as the material of the material to be welded
It takes a lot of time to derive it.
In order to derive individual welding conditions for
Is a hindrance to increasing the efficiency of the welding process
There is a problem. Further, a conventional electric servo type resistance welding apparatus is used.
In spot welding using
The flow value is constant and the energizing time is constant at all points
Therefore, the following problem occurs. That is, the materials to be welded such as steel plates are made of the same material.
Even so, there is a slight difference in the surface condition for each welding location,
Also, the composition of each welded material differs slightly.
Normal. Therefore, a certain amount of
Even when the welding current is applied for a certain period of time, the
The amount of energy applied depending on the degree of the surface state difference,
In other words, excess or deficiency occurs at each point of the heat quantity, and
No get is formed, and poor welding may occur. For this reason, welding is properly performed at all the spots.
In order to detect whether the welding process has
Need to inspect all the spots, in this case
Inspectors need empirical skills to determine quality,
In the case of a large number of points, it takes a lot of time for inspection
There is a problem. [0015] The present invention relates to such a conventional technique.
The electrode is made in consideration of the operation
Regardless of the difference in the pressurizing method to press
Welding conditions can be made common with those of other pressurized systems
Method and Control Device for Electric Servo Resistance Welding Apparatus
One purpose is to provide In addition, the present invention
Automatically determine good welds and bad welds when welding
Of electric servo type resistance welding equipment that can detect
Another object is to provide a control method and a control device.
You. An electric servo type resistor according to the present invention is provided.
The first form of the control method of the anti-welding apparatus is that the servo motor
The material to be welded is pressurized by the
Control method of an electric servo type resistance welding apparatus for performing a spot welding.
Thus, the material to be welded from the start of energization by the electrode
The amount of displacement of the same electrode due to thermal expansion of the
When the displacement reaches a predetermined displacement, the thermal expansion of the material to be welded is performed.
Servo mode so as to eliminate the increase in pressure due to tension.
The driving force of the motor is adjusted. Control of the electric servo type resistance welding apparatus of the present invention
In a first embodiment of the method, the adjustment of the driving force of the servomotor is performed.
The clause is made based on, for example, the following equation. F_mc= F_m・ (1-η) / η^{Two [ 0019 ]} Where F_mc： Pressure adjustment amount F_m: Rotational driving force of servo motor η: transmission efficiency of driving force Electric servo type resistance welding apparatus of the present invention
The second form of the control method of the first embodiment is an electric motor driven by a servomotor.
Conducts spot welding by applying current while pressing the material to be welded with the poles.
A method for controlling an electric servo resistance welding apparatus, comprising:
The thermal expansion of the material to be welded from the start of energization by the electrode
The amount of displacement of the same electrode is detected, and during the detected energization,
Based on the displacement amount at the end of welding and the displacement amount at the end of welding.
Detecting defective parts and / or types of welding defects
It is characterized by. Control of the electric servo type resistance welding apparatus of the present invention
In a second form of the method, the welding failure and / or
Indicates that the type of welding failure is detected, for example
Based on the displacement of the electrode due to the thermal expansion of the workpiece
The welding condition is determined by the welding condition
If the parameters are within the specified range, a proper nugget will be formed
And the welding state determination parameter exceeds the predetermined value.
If there is, it is assumed that dust has occurred inside the nugget and the welding state
If the judgment parameter does not reach the predetermined value, nugget
And shallow penetration. On the other hand, the electric servo type resistance welding apparatus of the present invention
The first form of the control device is a drive generated by a servomotor.
A driving force transmitting mechanism for transmitting a force to the electrode, and the electrode
The servo motor is pressed so as to press the workpiece with a predetermined pressure.
Pressure command means for issuing a command to the
Electric servo type resistance welding comprising welding command means
A control device of the contact device, at the time of starting energization by the electrode
Detects the displacement of the same electrode due to thermal expansion of the workpiece from a point
Means for detecting the amount of displacement,
When the pressure reaches the maximum, the pressure increases due to the thermal expansion of the material to be welded.
Refer to the power transmission characteristics of the driving force transmission mechanism
The pressing force generated by the pressing force command means so as to remove
A pressure command correction means for correcting the command.
It is characterized by. Control of the electric servo type resistance welding apparatus of the present invention
In the first embodiment of the device, the pressure command correction means
The correction is performed based on, for example, the following equation. F_mc= F_m・ (1-η) / η^{Two [ 0025 ]} Where F_mc： Pressure adjustment amount F_m: Rotational driving force of servo motor η: transmission efficiency of driving force Also, the electric servo resistance welding apparatus of the present invention
The second form of the control device is an electric motor driven by a servomotor.
Energize while applying pressure to the work piece by the specified pressure with the poles
Of electric servo resistance welding equipment for spot welding
A device, which is a material to be welded from a time point at which energization by an electrode is started.
Displacement detecting means for detecting the displacement of the electrode due to thermal expansion of the electrode
And the detected displacement during energization and the end time of welding.
Welding location and / or welding
Equipped with welding state detecting means for detecting the type of connection failure
It is characterized by the following. Control of the electric servo type resistance welding apparatus of the present invention
In the second embodiment of the apparatus, the welding state detecting means
Detection of defective welding spots and / or types of defective welding
For example, thermal expansion of the material to be welded from the start of energization by the electrode
The welding condition judgment parameter based on the displacement of the electrode
The welding condition determination parameter is within the specified range.
If a proper nugget has been formed,
If the parameter exceeds the specified value, dust inside the nugget
Occurs, and the welding state determination parameter reaches a predetermined value.
If not, assume that the nugget has a shallow penetration. Control of the electric servo type resistance welding apparatus of the present invention
In the second embodiment of the apparatus, the detection by the welding state detecting means is performed.
It is preferable to provide a notification unit for notifying the output result. The electric servo resistance welding of the present invention
The control unit of the equipment is mounted on the electric servo resistance welding equipment.
The electric servo resistance welding equipment is mounted on a robot.
Will be posted. The present invention is constructed as described above,
The energizing pressure is applied regardless of the thermal expansion of the welded part.
It can be substantially constant from the beginning, resulting in a weld
Can be made substantially constant. Further, according to the present invention, during welding, welding is performed.
Defective parts and types of welding defects can be detected. Hereinafter, the present invention will be described with reference to the accompanying drawings.
The present invention will be described based on an embodiment, but the present invention
It is not limited only to the embodiment. [0033] An electric servo resistor according to one embodiment of the present invention.
FIG. 1 shows a schematic configuration of an anti-welding device (hereinafter, referred to as a welding device).
The welding apparatus 10 includes a pair of materials to be welded (hereinafter, work pieces).
W)₁, W_TwoSpot welding, e.g. robot
Servo gun G attached to the hand of
Welding power supply 20 for supplying force, servo gun G and welding
A control device 30 for controlling the operation of the power supply 20;
You. The servo gun G has a work W₁, W_TwoBetween
Work W₁, W_TwoAre arranged above and below
Arc W₁, W_TwoIs energized while pressurizing with a predetermined pressure
The upper electrode 11, the lower electrode 12, and the upper electrode 11 are driven.
Servo motor 13 that generates rotational driving force for moving
And the rotational driving force generated by the servo motor 13 in the vertical direction.
Which is converted into a linear driving force and transmitted to the upper electrode 11
The rotation angle position of the force transmission mechanism 14 and the servo motor 13;
That is, a signal corresponding to the vertical position of the upper electrode 11 is output.
It is composed of an encoder (displacement amount detecting means) 15 for outputting.
Is done. The control device 30 turns on the welding power source 20.
・ Welding command means 31 for commanding off and servo motor 1
Pressurizing command means for commanding the generated rotational driving force to 3
32 and each work based on the output signal of the encoder 15.
W₁, W_TwoDetects the state of thermal expansion of the melted part (current-carrying part)
Fusion part state detection means (displacement amount detection means) 33;
Eliminates the increase in the pressing force of each electrode 11 and 12 due to thermal expansion of
Force command issued by the force command means 32 so that
Force adjustment amount calculator that calculates the force adjustment amount to perform
Stage (pressurizing force command correcting means) 34 and melting portion state detecting means
Upper electrode due to thermal expansion of the fusion zone detected by 33
11 and the displacement at the end of welding.
Nugget formation status based on the nugget formation status
Determination means (welding state detection means) 35
You. FIG. 2 shows a hardware configuration of the control device 30.
Is shown. The control device 30 includes the above-mentioned units 31, 32,
33, 34 and 35 are programs for performing various processes.
ROM (read only memory) 41 for storing the
Various according to the program read from OM41
CPU (Central Processing Unit) 42 for executing calculations
And R for temporarily storing the calculation result in the CPU 42.
AM (writable / readable memory) 43 and servo
Between motor 13, encoder 15 and welding power source 20
I / O interface 44 that mediates the exchange of signals
Input to the CPU 42 via the input / output interface 44.
A / that converts the input analog signal into a digital signal
Input / output interface from D converter 45 and CPU 42
The digital signal output via 44 is converted to an analog signal.
D / A converter 46 that converts the data into the data, and each configuration of the control device 30
The clock that generates the basic clock that operates the elements synchronously
And a clock generator 47. FIG. 3 shows a detailed configuration of the driving force transmission mechanism 14.
Show. The driving force transmission mechanism 14 includes a servo motor 13
Transmits the rotational driving force generated by changing the number of rotations, shown
Omit timing belts, gears, chains and brackets.
Rotational driving force transmission unit composed of each member such as a spring
14a and the rotation transmitted by the rotational driving force transmission unit 14a.
A linear drive for driving the upper electrode 11 in the vertical direction
And a ball screw 14b for converting power. Thus, as shown in FIG.
The servo motor 13 is rotated by a command from the force command means 32.
A power is generated, and each of the electrodes 11 and 12 is driven at a predetermined pressure Fc.
Work W₁, W_TwoIs pressurized, the welding command means 31
A power supply of a predetermined voltage is opened to each electrode 11 and 12 to the power supply 20.
To start. Each electrode 1 is controlled by a command from the welding command means 31.
When energization by 1 and 12 is started, the state shown in FIG.
So each work W₁, W_TwoHeat is generated in the current-carrying part of the
Starts, and a nugget N is formed
I will go. Due to this thermal expansion, the upper electrode 11
The force Fe acts, during which the servomotor 13 is generated
Rotational driving force (hereinafter, symbol F_mIs constant)
Therefore, the upper electrode 11 is pushed up. On the upper electrode 11 due to such thermal expansion
Displacement is melted via the output signal of encoder 15
The part state detecting means 33 is monitoring the
Upper electrode 1 from the start of energization detected by stage 33
1 is a predetermined displacement M_r(See Fig. 6)
At this time, the pressing force adjustment amount calculating means 34
And each work W₁, W_TwoIncrease of the actual pressure Fj acting between
The command by the pressing force command means 32 is supplemented so as to eliminate large
Pressing force adjustment amount F to correct_mcIs calculated. That is, the pressing force Fj is₁, W_Twoof
In order to keep it almost constant regardless of thermal expansion, a driving force transmission device
Considering the drive force transmission efficiency η (η <1) in the structure 14
Thus, the pressing force adjustment amount F such that the following equation (3) holds._mcTo
The pressing force adjustment amount is calculated by the pressing force adjustment amount calculating means 34.
F_mcIt is necessary to correct the command of the pressurizing
You. Fj = η (F_m-F_mc) + (1−η) Fe = ηF_m (1) Fc = ηF_m (2) Since equation (1) is_mcSolving for: F_mc= F_m・ (1-η) / η^Two (3) The following relationship is obtained. That is, the driving force transmission mechanism 14
By referring to the transmission efficiency η of the driving force
W₁, W_TwoOf increase in pressure Fj due to thermal expansion of
Drive force of servo motor 13 can be adjusted
Becomes Note that the rotational driving force F_mAnd pressure adjustment amount F
_mcIs determined by referring to the torque constant specific to the servo motor 13.
Operate the command value to command the supply current value to the servo motor 13
Is a controllable element. FIG. 5 shows the flow of processing in the control device 30.
Show. This process is executed by the CPU 42 every predetermined time.
It is. First, detection is performed based on the output signal of the encoder 15.
The amount of displacement M of the output upper electrode 11 from the start of energization is
Predetermined displacement amount M_rIs determined (step
S1). M value is M_rIf the value exceeds the value,₁, W_Two
The amount of pressure adjustment F_mcIs calculated
Issue (Step S2). Next, the calculated pressure adjustment amount F_mcIn response to the
The pressure command issued by the pressure command means 32 is corrected (step
Step S3), it is determined whether or not the welding is completed (step S3).
S4). If the welding is not completed, the step S
Returning to the processing of step 1, this processing is ended when the processing is completed. In step S1, the displacement amount M is determined to be a predetermined value.
Displacement M_rIf the current does not exceed
The process proceeds to step S4 assuming that there is no data. FIG. 6 is a time chart of the processing described above.
Is shown. In the figure, the vertical position of the upper electrode 11 is
Output signal value of the encoder 15 (hereinafter also referred to as an encoder value).
U) is indicated by E. Time t₀The upper electrode 11 starts to descend
You. Time t₁Each electrode 11 and 12 is connected to each work W₁, W_TwoWhen
The electrodes 11 and 12 come into contact with each other, and pressurization by the electrodes 11 and 12 is started. Time
Time t_TwoThe rotational driving force of the servo motor 13
Rotational driving force F corresponding to Fc_mReaches the upper electrode 1
The descent of 1 stops. The encoder value at this time is E₁When
I do. Time t_ThreeThrough the electrodes 11 and 12
Is started, and the encoder value E starts increasing. Time t
_FourTo the encoder value E₁The amount of rise from the value is the prescribed displacement
M_rIs exceeded, the pressure adjustment amount F_mcTo
Of the rotational driving force of the servo motor 13 is started.
You. Time t_FiveWhen the power supply to the
The energized part starts contracting. Time t₆The encoder value E
E₁The amount of rise from the value is a predetermined displacement M_rThe corresponding rise
If it is less than the amount, the pressure adjustment amount F_mcServo motor 1 by
The adjustment of the rotational driving force of No. 3 is completed. Time t₇Energized
Complete welding work to stop the shrinkage of the part and form the nugget N
Assuming that the process has been completed, the upper electrode 11 is moved to the initial position.
Evacuation is started. In the following, the nugget formation judging means 35
The process of determining the quality of the state will be described. FIGS. 7, 8 and 9 show the quality of the welding condition.
Shows the state of formation of the nugget N corresponding to FIG. Nugget N
The formation state is the work W via the electrodes 11 and 12.₁, W_TwoTo
The electric energy (or heat) of the applied welding current
Quantity) determines its quality. That is, if the energy amount is appropriate,
As shown in FIG. 7, the nugget N₁Got
It is. When the energy amount is insufficient, as shown in FIG.
Nugget N with shallow penetration_TwoIs formed. Ma
If the amount of energy is excessive, as shown in FIG.
Get N_ThreeA cavity V appears in the inside, and dust is generated. FIG. 10 corresponds to each state of formation of the nugget N.
7 shows how the encoder value E changes. That is to say, a proper nugget with a proper energy amount
N₁Is formed (solid line L₁) Start energizing
Time t_ThreeImmediately after and during energization, the encoder value E is
Encoder value E₁Large change, and the end of welding
Time point (electrode evacuation start time) t₇Encoder value E at
Also the encoder value E₁And the amount of change is about half of
Become. On the other hand, the energy amount is insufficient and
Bad nugget N_TwoIs formed (dotted line
L_Two) Indicates a proper nugget N with a proper energy amount.₁Formed
(Solid line L₁), Compared to)
t_ThreeEncoder value E immediately after and during energization is
Loader value E₁And the change is small at the end of welding
Point t₇The encoder value E at₁Against
Therefore, the amount of change is small. On the other hand, dust was generated due to excessive energy.
Nugget N_ThreeIs formed (dotted line L_Three) Energized
Start time t_ThreeEncoder value E immediately after and during energization
Is the encoder value E₁Is large, but the
End time t₇Is the encoder value E₁To
On the other hand, the change amount is small. Therefore, the encoder value E₁Through
Encoder value E and encoder value E during electricity₁Against
Based on the encoder value E at the end of welding,
It is possible to detect the types of occurrence and welding defects.
You. This will be specifically described below. Power supply start time t_ThreeEncoder value E₁Based on
The value is stored in the RAM 43 as a value. Energized encoder
Value E_TwoReference value E₁ΔE_wInto the following equation (4)
And the maximum value ΔE_wmaxIs stored in the RAM 43.
Let ΔE_w= E_Two-E₁ (4) Next, the electrode retreat start time t₇En in
Coder value E_ThreeReference value E₁Displacement ΔE_eIs the following equation
It is calculated by (5). ΔE_e= E_Three-E₁ (5) ΔE_wmaxOccurs in the nugget N during energization
The degree of thermal expansion was taken as the amount of change in the encoder value E
And ΔE_eAt the end of welding of nugget N
The degree of shrinkage as an amount of change in the encoder value E
Things. Then, β defined by the following equation (6)
Is a parameter representing the state of formation of the nugget N (weld state determination
Parameter). Β = (ΔE_wmax−ΔE_e) / ΔE_wmax (6) That is, the parameter β is within the predetermined range.
If the hit point, a proper nugget N is formed
Is determined, and the parameter β is not in the predetermined range,
At this point, a proper nugget N was not formed and welding failure occurred.
It is determined that there is. Further, if the parameter β falls within the predetermined range,
(See Fig. 11)
Type, that is, whether the amount of energy is excessive or insufficient
It is also possible to determine whether or not there is. As described above, in the welding apparatus 10 of the present embodiment,
Means that the displacement M of the upper electrode 11 from the start of energization is a predetermined value.
Displacement M_rWhen the work W₁, W_TwoEnergized part of
Is issued by the pressing force command means 32 assuming that
The command is a pressurization calculated by the pressing force adjustment amount calculating means 34.
Force adjustment amount F_mcIs corrected according to the
The increase in the pressing force Fj due to the expansion can be eliminated.
Thereby, the pressing force in the electric servo welding device 10
Fj is kept substantially constant during welding regardless of the thermal expansion of the energized part.
Can be The energized encoder value E_TwoEnergized open
Start time t_ThreeEncoder value E at₁ΔE_w
Maximum value ΔE_wmaxAnd welding end time t₇Enko in
Loader value E_ThreeReference value E₁ΔE_eAnd based on
Define the parameter β and use this parameter β
Automatically determines when welding is performed.
It is possible to determine the welding state of all the spots. The present invention will now be described by way of more specific examples.
This will be described more specifically. FIG. 11 shows a SUS304 steel plate having a thickness of 2 mm.
Work W₁, W_TwoPlace used as
And a 1 mm thick 301L-MT steel sheet
Work W₁, W_TwoEach when used as
, The welding power source 2 with the pressing force Fj kept constant.
0 when the welding current value I supplied from 0 is changed.
This shows how the parameter β changes. As shown in FIG.
If the contact state is good, the parameter β is within a predetermined range (0.5
<Β <0.7). Also, the welding current
If the value I is small and the state of formation of the nugget N is insufficient,
Parameter β deviates from the predetermined range in a small
If the contact current value I is large and dust is generated,
Is deviated from the predetermined range in a larger direction. Thus, an appropriate value for the parameter β
By determining the good welding area (predetermined range), the nugget N
Automatically and appropriately judge the quality of the formed state
Becomes Also, the setting of the good welding area is
Has a certain margin, and the material and plate thickness of the material to be welded
Because a substantially constant range can be used regardless of the
It is not necessary to perform complicated setting work for each pot welding process condition
Absent. The nugget determined in this way
The result of the determination of the state of formation of N
A control device is provided to notify operators and weld quality inspectors
It may be provided in the device 10. The present invention has been described based on the embodiments and examples.
The present invention has been described with reference to such an embodiment and
The present invention is not limited to the embodiments, and various modifications are possible.
You. For example, in this embodiment, the welding device is a servo gun.
Although the application of the present invention is limited to the servo gun,
Instead, it can be applied to various electric spot welding equipment.
You. As described in detail above, according to the present invention,
The electrode presses the welding force to press the workpiece
It can be almost constant until the end of contact,
Pressurizing welding conditions in electric servo type resistance welding equipment to other pressure
Can be used in common with welding conditions
It has excellent effects. Further, when the spot welding is executed, the welding state is changed.
Automatic judgment can be made, thereby checking the welding condition
It is said that work efficiency in the process can be improved
It also has excellent effects.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a control device of an electric servo resistance welding apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a hardware configuration of a control device.

FIG. 3 is a schematic diagram showing details of a drive system for driving an upper electrode.

FIG. 4 is a schematic diagram showing a state of a change in a current-carrying part during execution of welding.

FIG. 5 is a flowchart showing a procedure of a process executed by the control device.

FIG. 6 is a time chart of the same process, in which (a) shows a change in an encoder value and (b) shows a change in a rotational driving force.

FIG. 7 is a schematic diagram showing a state of forming a nugget N when an energy amount is appropriate.

FIG. 8 is a schematic diagram showing a state of forming a nugget N when the energy amount is insufficient.

FIG. 9 is a schematic diagram showing a state of forming a nugget N when the amount of energy is excessive.

FIG. 10 is an explanatory diagram for explaining a principle of determining a formation state of a nugget N.

FIG. 11 is a graph showing an example.

FIG. 12 is a schematic diagram showing details of a drive system of a conventional electric servo type resistance welding apparatus.

FIG. 13 is a schematic diagram showing a state of a change in a current-carrying part when welding is performed in a conventional electric servo type resistance welding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Welding apparatus 11 Upper electrode 12 Lower electrode 13 Servo motor 15 Encoder 14 Driving force transmission mechanism 14b Ball screw 20 Welding power supply 30 Control device 31 Welding command means 32 Pressing force commanding means 33 Melting part state detecting device 34 Pressing force adjustment amount calculating means 35 Nugget formation status determination means G Servo gun N Nugget V Cavity W Work

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takao Yamaguchi 1-1, Kawasakicho, Akashi-shi Inside the Akashi Plant of Kawasaki Heavy Industries, Ltd. Kawasaki Heavy Industries, Ltd. Kobe Factory F-term (reference) 4E065 AA05 BA06

Claims (11)

[Claims] 1. A control method for an electric servo resistance welding apparatus for spot welding by applying a current while pressurizing a material to be welded by an electrode driven by a servomotor, wherein the welding is performed from the start of energization by the electrode. The amount of displacement of the same electrode due to thermal expansion of the material is detected, and when the detected amount of displacement reaches a predetermined amount of displacement, the servomotor is controlled so as to eliminate an increase in pressure due to thermal expansion of the material to be welded. A method for controlling an electric servo type resistance welding apparatus, wherein a driving force is adjusted. 2. The control method for an electric servo resistance welding apparatus according to claim 1, wherein the driving force of the servomotor is adjusted based on the following equation. F _mc = F _m · (1−η) / η ² where F _mc : adjustment amount of pressing force F _m : rotational driving force of servo motor η: drive force transmission efficiency 3. A control method of an electric servo resistance welding apparatus for spot welding by applying a current while pressurizing a material to be welded by an electrode driven by a servomotor, wherein the welding is performed from the start of energization by the electrode. The amount of displacement of the same electrode due to thermal expansion of the material is detected, and based on the detected amount of displacement during energization and the amount of displacement at the end of welding,
A method for controlling an electric servo type resistance welding apparatus, characterized by detecting a defective welding location and / or a type of defective welding. 4. Detection of a defective welding location and / or a type of defective welding is performed based on a welding state determination parameter based on a displacement amount of the electrode due to thermal expansion of a material to be welded from the start of energization by the electrode. Is within a predetermined range, it is determined that a proper nugget has been formed, and if the welding state determination parameter exceeds a predetermined value, it is determined that dust has occurred inside the nugget, and if the welding state determination parameter has not reached the predetermined value. 4. The control method for an electric servo type resistance welding apparatus according to claim 3, wherein the penetration of the nugget is shallow. 5. A driving force transmitting mechanism for transmitting a driving force generated by a servo motor to an electrode, and a pressing force command means for issuing a command to the servo motor so as to press the workpiece with a predetermined pressing force by the electrode. And a welding instruction means for instructing the start of welding, a control device of the electric servo type resistance welding device, comprising: A displacement amount detecting means for detecting, when the detected displacement amount reaches a predetermined displacement amount, an increase in the pressing force due to the thermal expansion of the material to be welded is removed by referring to a power transmission characteristic of the driving force transmission mechanism. A control device for an electric servo type resistance welding apparatus, comprising: a pressing force command correcting means for correcting a pressing force command generated by the pressing force command means. 6. The control device for an electric servo resistance welding apparatus according to claim 5, wherein the correction by the pressure command correction means is performed based on the following equation. F _mc = F _m · (1−η) / η ² where F _mc : adjustment amount of pressing force F _m : rotational driving force of servo motor η: drive force transmission efficiency 7. A control device for an electric servo resistance welding apparatus for spot welding by applying a current while pressurizing a material to be welded by an electrode driven by a servomotor with a predetermined pressing force, and starting from the time when the current is applied by the electrodes. A displacement detecting means for detecting a displacement of the electrode due to thermal expansion of the material to be welded, and a defective welding location and / or a defective welding based on the detected displacement during energization and the displacement at the end of welding. And a welding state detecting means for detecting the type of the electric motor. 8. The welding state detecting means detects the location of a defective welding and / or the type of a defective welding by using a welding state determination parameter based on a displacement amount of the electrode due to a thermal expansion of a material to be welded from a start of energization by the electrode. If the welding state determination parameter is within a predetermined range, it is determined that a proper nugget has been formed, and if the welding state determination parameter exceeds a predetermined value, it is determined that dust has occurred inside the nugget, and the welding state determination parameter has a predetermined value. 8. The control device for an electric servo-type resistance welding apparatus according to claim 7, wherein the nugget has a shallow penetration if it has not reached the maximum value. 9. The control device for an electric servo-type resistance welding apparatus according to claim 7, further comprising a notifying means for notifying a detection result by the welding state detecting means. 10. An electric servo resistance welding apparatus comprising the control device according to claim 5. Description: 11. A robot comprising the electric servo resistance welding apparatus according to claim 10.