JPH02229680A - Welding state judging system - Google Patents

Abstract

PURPOSE:To exactly judge a welding state with simple processing by detecting the surface temp. of a weld zone by a temp. sensor, comparing the temp. with a set prescribed temp. and judging the normal/defective condition of the welding state. CONSTITUTION:A control device 15 is inputted with the surface temp. of the weld zone of members 1 to be welded via the temp. sensor 12, a temp. amplifier unit 13 and an A/D converter 14. The control device 15 reads out the critical temp. preset and stored in an internal memory and compares the surface temp. with the critical temp. The control device outputs an NG signal to a display device via an I/O circuit 17 when the device judges that the surface temp. is not above the critical temp. and the welding is defective as a nugget 11 is not sufficiently formed. The welding in a defective state is thus displayed on a display device 16. Further, the control device 15 outputs a firing signal to a thyristor 6 via the I/O circuit 17 to execute the current control to increase the external electric power to be supplied to a transformer 3 and to increase the welding current so that the welding to be executed next is satisfactorily executed. The processing is thus ended.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is capable of accurately detecting the welding state of, for example, spot welding, laser welding, and electron beam welding, and thereby accurately detecting the welding state. Concerning a welding condition determination system that can determine whether it is good or bad.

(Prior Art) Generally, a welding device that performs so-called spot welding can be simplified and represented as shown in FIG.

The welding device shown in the figure is equipped with an electrode tip 2 for performing spot welding on superimposed members 1 to be welded, for example, thin plates such as mild steel. The workpiece 1 to be welded by a cylinder etc.
It is designed to be pressed against.

Further, the electrode tip 2 is connected to the secondary coil 4 of the transformer 3.
A large current is applied to the welded member 1 in response to external power input to the primary coil 5 of the transformer 3 to weld the welded member.

The current applied to the welded member 1 via the electrode tip 2 can be adjusted by a thyristor 6 that adjusts the power supplied to the primary coil 5 of the transformer 3.

This thyristor 6 is adapted to adjust the so-called ignition phase of the external current by a control device 7 that performs overall control of the welding equipment, and to adjust the current input to the primary coil 5 of the transformer 3. The current output from the secondary coil 4 to the electrode tip 2 can be adjusted.

Furthermore, the control device 7 is connected to a current detector 8 that detects the current values flowing through the primary coil 5 and the secondary coil 4, and by inputting the current values flowing through the respective coils,
The welding state is determined, and the thyristor 6 is operated according to this state to control the welding current flowing between the electrode tips 2.

As described above, some conventional methods indirectly determine the welding state of spot welding by detecting the welding current or the like.

In addition, conventionally, in addition to this, for example, there are devices that detect the voltage between the electrode tips 2, devices that detect the resistance between the electrode tips, and devices that calculate the welding energy from the current value and voltage. What determines the condition, and furthermore,
Since the member to be welded 1 is displaced by welding, there are some devices that detect this and determine the welding state.

(Problems to be Solved by the Invention) However, these conventional methods for determining whether the welding condition is bad have the following problems in each case.

For example, in a device that detects the value of the current flowing through the primary and secondary coils of a transformer, the current flowing through the secondary coil is shunted depending on the contact state between the electrode tip and the workpiece during welding. Values may change and
The contact area of the electrode tip with the workpiece changes due to wear, etc., and the value of the current passing through it changes, so it is difficult to accurately judge the welding condition by detecting the value of the current flowing through the coil. Met.

In addition, even with devices that detect the voltage between electrode tips, it is possible to detect the amount of heat generated in the thickness direction of the weld, but the size of the nugget that is formed in the weld and directly affects the welding condition. Also, as mentioned above, even if the electrode tip wears and the energized area changes, the voltage will not change, so by detecting the voltage as above, it is possible to accurately determine the welding state. It was difficult to judge.

Furthermore, in devices that detect the resistance value between electrode tips, the resistance value changes as the contact area of the tips of the tips wears out, making it similarly impossible to accurately judge the welding state.

Furthermore, even in methods that calculate welding energy, since the calculation is based on welding current and tip-to-tip voltage, it includes uncertainties in each, and similarly it has been impossible to accurately judge the welding state.

Furthermore, in devices that detect displacement of parts to be welded by welding, the displacement may be affected by effects other than welding, such as the rigidity of the tip and the mechanical system that operates it. Accuracy was insufficient.

In this way, in the past, the welding condition of spot welding was indirectly detected using the welding current, inter-tip voltage, resistance, displacement, etc., and the welding condition was judged, but the welding condition directly affected the welding condition. There was nothing to detect the size of the nugget, making it difficult to accurately judge the welding state.

The present invention was made to solve these conventional problems, and it is an object of the present invention to accurately detect the size of a nugget formed by welding and accurately judge whether the welding condition is good or bad. The purpose is to provide a welding condition determination system that can perform

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a welding device that connects each of the welded members by melting the welded portion of the welded member to form a fused portion. , a temperature sensor that detects the surface temperature of the welded part, and the surface temperature is input based on the temperature sensor, and when the surface temperature is not higher than a preset temperature, the molten part is sufficiently The welding state can be accurately determined by detecting the surface temperature of the welded member.

Further, an electrode tip is provided that faces and contacts the surface of each welded part of the laminated members to be welded, and supplies current to the welded part, and melts the welded part by the energization to form a molten part. a welding device for connecting each of the members to be welded; a temperature sensor for detecting the surface temperature of the welding portion; a moving means for moving the temperature sensor in a direction in which the electrode tip faces; and a displacement sensor that detects the amount of displacement of the workpiece to be welded, and outputs a movement signal to the moving means to move the temperature sensor according to the amount of displacement based on the displacement sensor; and determining means for determining that the welding is in a defective state in which the fusion zone is not sufficiently formed when the surface temperature is not higher than a preset predetermined temperature. ,
It is characterized by being able to accurately judge the welding condition.

Further, it includes an electrode tip that faces and contacts the surface of each welded part of the laminated members to be welded and energizes the welded part,
a welding device that connects each of the members to be welded by melting the welded portion by the energization to form a fused portion; a temperature sensor that detects the surface temperature of the welded portion;
A displacement sensor that detects the amount of displacement of the welded member due to wear of the electrode tip, and a correction value that corrects a critical temperature that is preset as a reference value for determining the welding state according to the amount of displacement. The critical temperature is corrected by the correction value corresponding to the amount of displacement detected by the displacement sensor, and if the surface temperature is not equal to or higher than the corrected critical temperature based on the temperature sensor, the melted portion is sufficiently The present invention is characterized in that the welding condition can be accurately determined by detecting the surface temperature of the welded member.

Further, an electrode tip is provided that contacts the surface of the welded part of the laminated members to be welded and energizes the welded part, and by melting the welded part by the energization and forming a fused part, each of the members to be welded is a temperature sensor that detects the surface temperature of the welding part; A bracket capable of adjusting a sensor, and inputting the surface temperature based on the temperature sensor, and when the surface temperature is not higher than a predetermined temperature, the welding defect is caused by the welding part not being sufficiently formed. by adjusting the temperature sensor in the displacement direction, the surface temperature is detected within an allowable range with respect to the displacement of the welded member, and the welding condition is accurately determined. It is characterized by being able to be determined.

Further, it includes an electrode tip that faces and contacts the surface of each welded part of the laminated members to be welded and energizes the welded part,
A welding device connects each of the members to be welded by melting the welded portion to form a fused portion by the energization; a temperature sensor that detects the surface temperature of the welded portion; and a temperature sensor that detects the surface temperature of the welded portion, and Rotating the temperature sensor within a predetermined angular range in a displacement direction in which a detection position of the temperature sensor is displaced due to displacement of the welded member;
a moving means that enables the temperature sensor to detect the surface temperature in the displacement direction; and a moving means that outputs a movement signal for moving the temperature sensor to the moving means, and a maximum temperature of the surface temperature detected by the temperature sensor. determination means for determining that the welding is in a defective state in which the molten part is not sufficiently formed when the temperature is lower than a preset predetermined temperature; It is characterized in that the welding state can be accurately determined by detecting the surface temperature by rotating in the displacement direction.

(Function) The present invention configured as described above functions as follows.

The temperature sensor detects the surface temperature of the welded part, which changes in temperature depending on the size of the fused part, and outputs this surface temperature to the determination means.

Then, the judgment means compares the input surface temperature with a preset predetermined temperature, and if the surface temperature is not higher than the predetermined temperature, the fusion zone is not sufficiently formed and the welding is defective. I judge that there is.

Therefore, the formation state of the molten part can be determined by detecting the surface temperature of the welded part, and the welded state can be accurately determined.

Further, the displacement sensor detects the amount of displacement of the welded member caused by wear of the electrode tip, and outputs this amount of displacement to the determining means.

Then, the determining means outputs a movement signal to the moving means to move the temperature sensor in the same direction by the same amount as the displacement amount in accordance with the input displacement amount, and moves the temperature sensor to correct the detected position.

Furthermore, the determination means inputs the surface temperature by detecting the surface temperature of the welding part of the welded member by this temperature sensor, compares it with a predetermined temperature set in advance, and determines whether the surface temperature is equal to or less than this predetermined temperature. If the temperature is not higher than that, it is determined that the fusion zone is not sufficiently formed and the welding is defective.

Therefore, even if the workpiece to be welded is displaced, the temperature sensor can be moved according to the amount of displacement and the detection position can be corrected, so the surface temperature can always be accurately detected, which improves the welding condition. can always be judged accurately.

Furthermore, when the displacement sensor detects the amount of displacement of the workpiece to be welded due to wear of the electrode tip, the determining means determines the appropriate correction value among the preset critical temperature correction values according to the amount of displacement. Correct the critical temperature by the value.

Then, when the temperature sensor detects the surface temperature of the welded part, the judgment means compares this surface temperature with the corrected critical temperature, and if the surface temperature is not higher than this critical temperature, the molten part is sufficiently It is determined that the weld is not formed and the welding is defective.

Therefore, even if the detection position of the temperature sensor changes due to displacement of the workpiece to be welded, a critical temperature corresponding to the surface temperature detected by the temperature sensor can be obtained, and the surface temperature is compared based on this critical temperature. By doing so, the welding condition can always be accurately determined.

In addition, the temperature sensor is adjusted in advance in the displacement direction using a bracket so that the amount of change in surface temperature caused by the change in the detection position of the temperature sensor depending on the displacement of the welded member is within a predetermined tolerance range. I'll keep it.

Then, when the temperature sensor adjusted in this way detects the surface temperature of the welding part, the determination means compares the surface temperature with a predetermined temperature set in advance, and determines that the surface temperature is not higher than this predetermined temperature. In this case, it is determined that the fusion zone is not sufficiently formed and the welding is defective.

Therefore, the amount of change in the surface temperature with respect to the displacement of the welded member can be kept within an allowable range, and by detecting this surface temperature, the welding state can be accurately determined.

Furthermore, the determining means outputs a movement signal to the moving means, so that the moving means rotates the temperature sensor within a predetermined angular range in the displacement direction.

The temperature sensor sequentially detects the surface temperature in the direction of displacement and outputs these to the determining means.

The judgment means compares the maximum temperature of these input surface temperatures with a preset predetermined temperature, and if the surface temperature is not higher than this predetermined temperature, it is determined that the fusion zone is not sufficiently formed and there is a defective welding condition. It is determined that

Therefore, by rotating the temperature sensor in the direction in which the detection position of the temperature sensor shifts in response to the displacement of the workpiece, even if the detection position shifts, the surface temperature of the welding part can be accurately measured. can be detected and the welding condition can be accurately determined.

(Example) Below, a welding condition determination system according to the present invention will be explained in detail based on the drawings.

FIG. 1 shows a first embodiment of the welding condition determination system in a schematic configuration diagram, and the same members as those described in the related art are given the same reference numerals.

The figure shows a system in a so-called spot welding machine 10 that determines the welding state by detecting the surface temperature of the workpiece 1 to be welded, and displays whether the welding is good or bad as a result of this determination. There is.

This spot welding machine 10 is provided with electrode tips 2 facing each other, which contact the welded part of the welded part 1 while being pressed by an air cylinder, and weld the welded part 1 by energizing the welded part. ing.

These electrode tips 2 are connected to a transformer 3 that converts the current supplied from an external power source into the welding current necessary for welding.
are connected to both ends of the secondary coils 4, respectively, so that the welding current can be passed between the members 1 to be welded to weld the members 1 to be welded.

Furthermore, the primary coil 5 of this transformer 3 is connected to an external power supply via a thyristor 6, and this thyristor 6
The current supplied to the primary coil 5 is controlled by adjusting the ignition phase and the energization time, thereby controlling the welding current output from the secondary coil 4. It is possible to control the current and adjust the welding condition.

Furthermore, the spot welding machine 10 is provided with a temperature sensor 12 for detecting the surface temperature of the welding part of the welded member 1, with its focal point located on the surface of the welding part at a predetermined distance from the center of the electrode tip 2. has been done.

This temperature sensor 12 is a so-called infrared temperature sensor, which outputs an electric signal according to the temperature on the focal point, and when a welding current is applied, each coating is applied to the joint surface of the workpiece 1. The surface temperature of the heated welding part can be detected by the nugget 11 formed by melting the welding member. That is, this temperature sensor 12 can detect the surface temperature of the welded portion depending on the size of the nugget 11.

This temperature sensor 12 is connected to the temperature amplifier unit 1.
3, and this temperature amplifier unit 13 is connected to
The electrical signal output by the temperature sensor 12 is amplified to form an analog signal, and is output to an A/D converter 14 that converts this signal into a digital signal.

Furthermore, this A/D converter 14 outputs the converted digital signal to a control device 15 that collectively controls this system, and the control device 15 controls these temperature sensors 12, temperature Amplifier unit 13 and
The surface temperature of the weld zone can be input via the A/D converter 14.

The control device 15 is constituted by a so-called microcomputer, etc., and compares the input surface temperature with a preset critical temperature, and if the surface temperature is not higher than this critical temperature, that is, the critical temperature In the case of lower temperature, I/I as a conversion circuit that converts the signal form.
An NG signal is outputted to the display 16 via the O circuit 17 to indicate a welding defect.

This critical temperature is a temperature determined in advance through experiments and the like, and is stored in advance in the internal memory of the control device 15.

As shown in FIG. 2, the critical temperature is at a position a predetermined distance (8 mm) from the center of the electrode tip 2, as shown in the relationship diagram between the diameter of the nugget 11 and the surface temperature of the welded part. Therefore, the surface temperature (
In other words, depending on whether the surface temperature is above this critical temperature, it is determined whether the size of the nugget 11 is sufficient for welding. This is the temperature that serves as the standard for determining.

Therefore, if the surface temperature is not higher than this critical temperature, the nugget 11 is not sufficiently formed and the welding is insufficient, so the control device 15 causes the display 16 to display a welding defect. It has become.

Further, in this case, the control device 15 outputs a firing signal to the thyristor 6 via the I/O circuit 17 to increase the current supplied to the primary coil 5, and this firing signal The thyristor 6 that receives the input adjusts the firing phase of the current supplied to the primary coil 5 so that the current value increases, increases the welding current, and enlarges the nugget 11 to ensure welding. It is now possible to do so.

Further, when the input surface temperature is equal to or higher than the critical temperature, the control device 15 outputs an OK signal to the display 16 via the I/O circuit 17 to indicate that welding has been reliably performed, The display 16 is designed to display that the welding has passed.

Therefore, by detecting the surface temperature of the welded part that changes depending on the size of the nugget 11, the control device 15 determines that welding is insufficient if this surface temperature is not higher than a predetermined critical temperature. In addition to displaying a welding defect, the welding current can be increased to ensure welding.

The welding state determination system according to the present invention configured as described above operates based on the operation flowchart shown in FIG.

First, the control device 15 inputs the surface temperature of the welded portion of the welded member 1 via the temperature sensor 12, temperature amplifier unit 13, and A/D converter 14 (step 1).

Next, the control device 15 is configured in advance in the internal memory, and
Read out the stored critical temperature (step 2).

Then, the control device 15 compares the input surface temperature with the read critical temperature, and determines that the surface temperature is not higher than the critical temperature, that the nugget 11 is not sufficiently formed, and that the welding is insufficient. (Step 3), an NG signal is output to the display 16 via the I/O circuit 17, and the display 16 indicates that the welding is defective (Step 4).
.

Further, the control device 15 outputs an ignition signal to the thyristor 6 via the I/O circuit 17, increases the external current supplied to the transformer 3, performs current adjustment to increase the welding current, and performs a current adjustment to increase the welding current. Ensure sufficient welding (
Step 5), end the process.

On the other hand, if the control device 15 determines in step 3 that the surface temperature is higher than the critical temperature and that welding has been successfully performed, the control device 15 displays an output signal on the display 16 via the I/O circuit 17.
A K signal is output, a welding pass indication is displayed on the display 16 (step 6), and the process is ended.

Therefore, the control device 15 can judge whether the welding condition is good or bad simply by comparing the surface temperature of the welded portion with the critical temperature, and can make this judgment relatively easily and accurately.

Furthermore, the welding condition determination system according to the present invention can be used not only in the system described in the first embodiment above, but also in so-called laser welding equipment, electron beam welding equipment, etc. as shown in FIG. 4, for example. It is possible.

This figure shows a schematic diagram of a laser welding device that welds a member to be welded 1 from one side using laser beams emitted from a laser emitting device 18.

In this welding apparatus, the temperature sensor 12 is arranged so as to be able to detect the surface temperature of the back surface of the welded part of the welded member 1, as shown in a in the figure, and the case in which the temperature sensor 12 is arranged so as to be able to detect the surface temperature of the back surface of the welded part of the welded member 1, as shown in the figure b. In both cases, the temperature sensor 12 detects the temperature in accordance with the size of the bead formed by welding. Since the temperature at which the welding occurs changes, the welding state can be accurately determined by detecting each temperature.

Next, a second embodiment of the welding condition determination system according to the present invention will be described based on FIG.

Incidentally, the same members as those described in the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

In the same figure, a displacement sensor 2 detects the amount of displacement of the workpiece 1 due to wear of the electrode tip 2 in the system described in the first embodiment.
A slider 21 and its displacement sensor 20 are shown for detecting the temperature at 0 and moving the temperature sensor 12 according to the amount of displacement.

The spot welding machine 10 is equipped with a displacement sensor 20 that detects the amount of displacement of the workpiece 1 to be welded. The amount of displacement of the member 1 in response to this wear is detected.

Further, the displacement sensor 20 can detect the wear state of the electrode tip 2 by detecting the amount of displacement thereof, and has a function as a wear detection sensor for the electrode tip 2.

Further, the temperature sensor 12 is attached to the spot welding machine 10 via a slider 21.
is composed of a moving mechanism capable of moving the temperature sensor 12 in the displacement direction of the welding member 1, that is, the direction in which the electrode tip faces, and a drive member such as a motor that operates the side of this moving machine. The temperature sensor 12 can be moved to follow the displacement.

This is to correct the position shift of the focal point of the temperature sensor 12 due to the displacement of the welded member 1 in the vertical direction in the figure due to wear of the electrode tip 2.

Temperature sensor 1 whose focus has shifted due to displacement of workpiece 1 to be welded
The surface temperature detected in step 2 no longer corresponds to the critical temperature for determining the welding state, and the welding state cannot be accurately determined. This is because the heat transferred from the nugget 11 changes depending on the distance from the nugget 11 to the surface of the weld, so this temperature sensor is misaligned with respect to the critical temperature set under certain conditions. This is because the surface temperature detected by the control device 12 does not meet this condition, so even if the control device 15 compares this surface temperature with the critical temperature, it does not mean that it has accurately recognized the welding state.

Therefore, the temperature sensor 12 can be moved by the slider 21 in accordance with the amount of displacement of the welded member 1 by the same amount and in the same direction.

The displacement sensor 20 converts the detected displacement amount into an electrical signal and outputs it to the displacement amplifier unit 22. The displacement amplifier unit 22 amplifies the input electrical signal and converts it into an analog signal. Along with forming
A/D converter 23 that converts this signal into a digital signal
It is designed to output to .

Further, the A/D converter 23 outputs the converted digital signal to the control device 15, and the control device 15 controls the displacement sensor 20, the displacement amplifier unit 22, and the A/D converter 23. The amount of displacement of the member to be welded 1 can be input via the converter 23.

Based on this input displacement amount, the control device 15 calculates the amount of movement to move the temperature sensor 12 by the same amount and in the same direction as the displacement amount.

Further, the control device 15 outputs a movement signal to the drive unit 24 via the I/O circuit 17 to move the temperature sensor 12 by the amount of movement.

The drive unit 24 is configured to supply drive power to the drive member of the slider 21 based on the input movement signal, and operates the drive member to adjust the temperature sensor 12 to the temperature calculated by the control device 15. It can be moved by the amount of movement.

Therefore, when the workpiece 1 is displaced due to wear of the electrode tip 2 and the focus of the temperature sensor 12 shifts from the proper detection position, the control device 15 detects the amount of displacement of the workpiece 1 using the displacement sensor 20. However, the temperature sensor 12 can be moved by the same amount and in the same direction as this displacement amount.

The system thus constructed operates based on the operation flowchart shown in FIG.

The control device 15 inputs the amount of displacement of the welded member 1 via the displacement sensor 20, displacement amplifier unit 22, and A/D converter 23 (step 10).

Next, the control device 15 calculates a movement amount to move the temperature sensor 12 in the same direction as the displacement amount based on the input displacement amount (step 11).

Then, the control device 15 outputs a movement signal for moving the temperature sensor 12 by the amount of movement to the drive unit 24 via the I/O circuit 17, and the drive unit 24, based on the input movement signal, By supplying driving power to the driving member of the slider 21, this driving member is actuated to move the temperature sensor 12 the calculated distance (step 12).

From then on, proceed to step 1 of the flowchart in FIG. 3, perform the processing as explained in the first embodiment, and
The welding condition is determined by comparing the surface temperature of the welded part detected by step 2 with the critical temperature, and whether the welding is good or bad is displayed, and if the welding is bad, the thyristor 6 is controlled to adjust the welding current.

Therefore, the control device 15 controls the temperature sensor 12 according to the amount of displacement of the welded member 1 caused by the wear of the electrode tip 2.
The focus of the temperature sensor 12 can always be located at the appropriate detection position by moving the temperature sensor 12, so that the temperature sensor 12 can always accurately detect the surface temperature of the welding part.
The control device 15 can always accurately judge the welding state.

Next, a third embodiment of the welding condition determination system according to the present invention will be described based on FIG. 7.

Incidentally, the same members as those described in the first embodiment and the second embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

This figure shows a system in which a displacement sensor 20 for detecting the amount of displacement of the welded member 1 due to wear of the electrode tip 2 is added to the system described in the first embodiment.

As explained in the second embodiment, this displacement sensor 20 is connected to the control device 15 via the displacement amplifier unit 22 and the A/D converter 23, and sends the detected displacement amount of the welded member 1 to the control device 15. It is designed to be output.

The internal memory of the control device 15 that inputs this displacement amount stores in advance a table of critical temperature correction values according to this displacement amount, and the control device 15 uses this correction value to It is read out based on the amount and added to the critical temperature to correct the critical temperature.

This correction value is determined by the temperature sensor 1 due to the displacement of the workpiece 1 in the vertical direction in the figure due to wear of the electrode tip 2.
2 shifts from the detection position a predetermined distance away from the center of the electrode tip 2, and the critical temperature field for the surface temperature detected by the temperature sensor 12 changes, so this critical temperature is corrected according to the displacement of the welded member 1. It is something to do.

This is because, as described above, the critical temperature is preset with respect to the surface temperature at a position a predetermined distance from the center of the electrode tip 2, and the critical temperature is detected by the temperature sensor 12 based on the displacement of the welded member 1. If the position to perform deviates from this position,
This is because the critical temperature relative to the detected surface temperature changes, so it is necessary to correct the critical temperature by the amount of this change.

Then, the control device 15 compares the input surface temperature with the corrected critical temperature, determines whether the welding is good or bad, and displays the result, as in the first embodiment. If the welding is bad, the control device 15 changes the welding current. It is designed to be adjusted.

Therefore, the control device 15 corrects the critical temperature according to the displacement amount of the welded member 1 detected by the displacement sensor 20,
By comparing the surface temperature of the welded part detected by the temperature sensor 12 with this corrected critical temperature, it is possible to accurately determine whether welding is good or bad.

The system configured in this way operates based on the operation flowchart shown in FIG.

The control device 15 inputs the amount of displacement of the welded member 1 via the displacement sensor 20, displacement amplifier unit 22, and A/D converter 23 (step 20).

Next, the control device 15 reads from the memory the correction value of the critical temperature corresponding to this input displacement amount (step 21
).

Then, the control device 15 inputs the surface temperature of the welded portion via the temperature sensor 12, temperature amplifier unit 13, and A/D converter 14 (step 22).

Furthermore, the control device 15 reads the critical temperature corresponding to the input surface temperature from the memory (step 23), and corrects the critical temperature by adding the correction value read in step 21 to this critical temperature (step 24).

After that, proceed to step 3 of the flowchart in FIG. 3, perform the processing as explained in the first embodiment, and
The welding condition is determined by comparing the surface temperature of the welded part detected in step 2 with the corrected critical temperature, and whether the welding is good or bad is displayed, and if the welding is bad, the thyristor 6 is controlled to adjust the welding current to: Section A.

Therefore, the control device 15 corrects the critical temperature according to the amount of displacement of the welded member 1 caused by the wear of the electrode tip 2, and compares the surface temperature of the weld zone detected by the temperature sensor 12 with this corrected critical temperature. By doing so, even if the welded member 1 is displaced, the welding state can always be accurately determined based on the surface temperature detected by the temperature sensor 12.

Next, a fourth embodiment of the welding state detection system according to the present invention will be described based on FIG. 9. In this figure, (a) is a front view of the spot welding machine 10, and (b) is a side view thereof.

Incidentally, the same members as those described in the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

In the same figure, a temperature sensor 12 is attached to the spot welding machine 10 described in the first embodiment so that the detection axis can be adjusted, and by adjusting the detection axis, the temperature sensor 12 is It is shown that the amount of change in surface temperature detected by can be set within an allowable range for determining the welding condition.

The temperature sensor 12 is attached to the spot welding machine 10 via a bracket 30, and is also connected to a temperature amplifier unit 13, which is connected to the temperature amplifier unit 13 and an A/D converter 14 (not shown) as in the first embodiment. The surface temperature of the welded portion is output to the control device l5 via the control device l5.

The bracket 30 is configured so that the angle of the detection axis of the temperature sensor 12 can be adjusted with respect to the central axis of the electrode tip 2, as shown in FIG. can also be adjusted in the direction of its detection axis, and the focal length can also be adjusted.

Further, as shown in FIG.
can be adjusted, and as shown in Figure (a),
The distance from the central axis of the electrode tip 2 to the focal point of the temperature sensor 12 is also adjustable.

Therefore, this bracket 30 allows the temperature sensor 1
As shown in FIG.
r) Adjustable in the circumferential tangential direction centering on the electrode tip 2 at separate positions.

Next, the temperature sensor 12 is connected by such a bracket 30.
This section explains how to adjust the installation.

First, as shown in FIG. 9(b), the angle between the central axis of the electrode tip 2 and the detection axis of the temperature sensor 12 is θ, and the distance from the detection part of the temperature sensor 12 to the weld surface is y. At the same time, if the displacement amount of the welded member 1 is Δy, the amount X by which the focal point of the temperature sensor 12 shifts from the center of the electrode tip 2 (hereinafter referred to as the displacement amount) according to this displacement amount Δy is:
x=(y+Δy)tanθ−ytanθ;Δytanθ
...It can be expressed as the following formula.

Moreover, as shown in FIG. 10(a) and FIG.
is located on the distance r from the center of the electrode tip 2 to the detection axis of the temperature sensor 12, and occurs in the tangential direction of the circumference of the radius r centered on the electrode tip 2. Therefore, from the electrode tip 2 to the temperature sensor The distance r+Δr to the focal point of l2 can be expressed as (r+Δr) 2=x2+r2, and here, from equation (2), it can be expressed as (r+Δr)−(Δytanθ)2+r2.

Then, when this formula is expanded, r +2Δr−r+Δr2=(Δytanθ)20r
2, Δr is tiny with respect to y, and Δr2 is
Since it may be omitted, ``+2Δr*r=(Δytanθ)2+,2.

Therefore, it can be expressed as Δr=(Δytanθ)2/2r...■ Formula. In other words, this Δr varies from the center of the electrode tip 2 to the temperature sensor 2, which changes depending on the displacement of the welded member 1.
This corresponds to the amount of change in the distance to the focal point.

Furthermore, the relationship between the distance from the center of the electrode tip 2 and the surface temperature of the welded part can be found through experiments, etc. For example, as shown in FIG. As can be seen from the surface temperature graph, it has a predetermined rate of change ΔT/Δr=22°C/mm, and from this rate of change Δr can be expressed as Δr=ΔT/22... ■■ Formula .

Therefore, from the formulas (2) and (2), the following formula is obtained: ΔT/22=(Δytanθ)2/2r...

Here, for example, r is set to 10InII1, the displacement Δy of the welded member 1 is 51III1 or less, and in practice, the change matrix ΔT of the surface temperature detected by the temperature sensor 12 with respect to the displacement of the welded member 1 If we try to keep it within the allowable range of 5°C or less, by substituting the respective values into equation (2), we get 5/22=(5tanθ)2/2・10tanθ=0.
426 θ=23' is obtained.

Therefore, in the above case, if the angle between the central axis of the electrode tip 2 and the detection axis of the temperature sensor 12 is set to 23 degrees or less, the change in the surface temperature detected by the temperature sensor 12 with respect to the amount of displacement of the workpiece 1 The amount ΔT can be set within a permissible range of 5° C. or less.

In this way, based on the temperature sensor 12 whose detection axis is adjusted by the bracket 30, the control device 15
The process is carried out as explained in the first embodiment, and the surface temperature of the welded part detected by this temperature sensor 12 is compared with a predetermined critical temperature to judge the welding condition and to display whether the weld is good or bad. In case of failure, the thyristor 6 is controlled to adjust the welding current.

Therefore, the control device 15 can accurately determine the welding state based on the surface temperature of the welded portion detected by the temperature sensor 12 within an allowable range with respect to the amount of displacement of the welded member 1.

Next, a fifth embodiment of the welding condition determination system according to the present invention will be described based on FIG. 12.

Incidentally, the same members as those described in the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

This figure shows a system in which a scanner 40 that rotates the temperature sensor 12 within a predetermined angle range (so-called scanning) is added to the system described in the first embodiment.

The temperature sensor 12 is attached to the spot welding machine 10 via a scanner 40, and as shown in the figure, the scanner 40 is movable so as to scan the detection axis of the temperature sensor 12 in a predetermined angular range. It is depicted by a mechanism and a driving member such as a motor that operates the moving mechanism.

Then, by scanning the temperature sensor 12, this scanner 40 detects the detection position of the temperature sensor 12 on the circumferential tangent line centered on the electrode tip 2, which is on the surface of the welding part and similar to the third embodiment. It is designed to move back and forth in the direction.

That is, this scanner 40 is configured to scan its detection axis in the direction of displacement in which the detection position of the temperature sensor 12 is displaced due to displacement of the member 1 to be welded.

On the other hand, the control device 15 controls the I/O circuit 17 at the end of welding.
A scanning signal for causing the temperature sensor 12 to scan is output to the drive unit 41 via the drive unit 41 .

The drive unit 41 is configured to supply drive power to the drive member of the scanner 40 based on the input scanning signal, and operates the drive member.
The temperature sensor 12 can be scanned in a predetermined angle range.

The temperature sensor 12 scanned by the scanner 40 transmits the surface temperature detected during this scanning to the temperature amplifier unit 13 and the A/D converter 14.
The control device 15 sequentially outputs the following information to the control device 15 via the
The input surface temperature is sequentially stored in the internal memory according to the scanning angle.

Then, the control device 15 controls, for example, as shown in FIG. 13, among the stored surface temperatures according to the scanning angle,
By determining the maximum temperature, it is possible to detect the surface temperature corresponding to the critical temperature even if the detection position of the temperature sensor 12 is displaced in accordance with the displacement of the welded member 1.

As shown in the figure, in the case of the surface temperature detected according to the scanning angle, the scanning angle at which the maximum temperature is obtained changes as the detection position of the temperature sensor 12 is displaced, but the maximum temperature Since it does not change,
By comparing this maximum temperature with the critical temperature, it is possible to accurately determine whether the welding condition is good or bad.

Then, the control device 15 reads the highest temperature among the stored surface temperatures, compares this highest temperature with the critical temperature, and determines the welding state.

Therefore, even if the welded member 1 is displaced due to wear of the electrode tip 2 and the detection position of the temperature sensor 12 is displaced, the control device 15 causes the temperature sensor 12 to scan within a predetermined angle range, and during this period By comparing the highest temperature among the surface temperatures detected by the temperature sensor 12 with the critical temperature, the welding state can be accurately determined.

The system configured in this way operates based on the operation flowchart shown in FIG.

When welding is completed, the control device 15 outputs a scanning signal to the drive unit 41 via the I/O circuit 17, and the drive unit 41 controls the drive member of the scanner 40 based on the input scanning signal. By supplying driving power to the drive member, the drive member is actuated to scan the temperature sensor 12 in a predetermined angular range in the displacement direction (step 30).

Then, the control device 15 sequentially stores the surface temperature of the welded portion detected by the temperature sensor 12 during this scanning in the internal memory according to the scanning angle (step 31).

Furthermore, the control device 15 reads out the highest temperature among the surface temperatures stored in its memory (step 32), and thereafter proceeds to step 2 of the flowchart in FIG. 3 and carries out the processing as explained in the first embodiment. The welding condition is judged by comparing the maximum temperature with the critical temperature, and whether the welding is good or bad is displayed. If the welding is bad, the thyristor 6 is controlled to adjust the welding current.

Therefore, the control device 15 controls the temperature sensor 1 with respect to the amount of displacement of the welded member 1 caused by the wear of the electrode tip 2.
2, and by comparing the maximum surface temperature input during this scanning with the critical temperature, the welding state can always be accurately determined.

(Effect of the invention) As is clear from the above explanation, the present invention has the following features:
It has the following effects.

A temperature sensor detects the surface temperature of the weld zone, which changes depending on the size of the molten zone, which directly affects the weld condition. By comparing this surface temperature with a preset temperature, the quality of the weld condition can be checked. Since defects are determined, it is possible to accurately judge the welding condition with a relatively simple process, and the time required to judge the welding condition can be shortened, making it possible to quickly and accurately obtain welding results. It becomes possible.

In addition, the displacement sensor detects the amount of displacement of the welded member caused by wear of the electrode tip, moves the temperature sensor according to this amount of displacement, and corrects the detection position of the temperature sensor, thereby achieving the above effect. In addition, the welding state can always be accurately determined based on the displacement of the welded member.

Furthermore, the amount of displacement of the workpiece to be welded is detected by a displacement sensor, and a correction value corresponding to this amount of displacement is used to correct the critical temperature for determining the welding state.
Since the welding condition is judged, it is possible to accurately judge the welding condition with a relatively simple process, reducing the time required to judge the welding condition, and even when the welded member is displaced. , the welding condition can be determined accurately,
It becomes possible to obtain welding results quickly and always accurately.

In addition, the temperature sensor is adjusted in advance using a bracket so that the amount of change in surface temperature that occurs due to the change in the detection position of the temperature sensor depending on the displacement of the welded member is within an allowable range, and this temperature sensor detects the Since the welding condition is judged based on the surface temperature, it is not only possible to obtain welding results quickly and always accurately, but also
This eliminates the need for any member or process to correct the displacement of the welded member, resulting in excellent economic efficiency.

Furthermore, by rotating the temperature sensor within a predetermined angular range in the direction of displacement in which the detection position of the temperature sensor is displaced due to the displacement of the welded member, the temperature can be adjusted based on the maximum surface temperature detected by the temperature sensor. Since the welding condition is judged, it is possible to accurately judge the welding condition with a relatively simple process, reducing the time required to judge the welding condition, and even when the welded member is displaced. , it becomes possible to obtain welding results quickly and always accurately.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the welding condition determination system according to the present invention, FIG. 2 is a relationship diagram between surface temperature and nugget diameter, and FIG. 3 is a welding condition according to the present invention. Operation flowchart in the first embodiment of the judgment system, 4th
FIG. 5 is an explanatory diagram of a welding condition determination system according to the present invention applied to a laser welding device, FIG. 5 is a schematic configuration diagram showing a second embodiment of the welding condition determination system according to the present invention, and FIG.
The figure is an operation flowchart of a second embodiment of the welding condition determination system according to the present invention, and FIG. 7 is a schematic diagram showing a third embodiment of the welding condition determination system according to the present invention.
FIG. 8 is an operation flowchart of a third embodiment of the welding condition determination system according to the present invention, FIG. 9 is a schematic configuration diagram showing a fourth embodiment of the welding condition determination system according to the present invention, and FIG. Figure TS11 is an explanatory diagram of adjusting the temperature sensor in the fourth embodiment of the welding condition determination system according to the present invention, and FIG. 12 is a schematic diagram showing the fifth embodiment of the welding condition determination system according to the present invention. The configuration diagram, FIG. 13, shows a fifth embodiment of the welding condition determination system according to the present invention,
FIG. 14 is an explanatory diagram for detecting surface temperature, and FIG. 14 is an operation flowchart in a fifth embodiment of the welding state determination system according to the present invention. FIG. 15 is an explanatory diagram of a conventional welding device. DESCRIPTION OF SYMBOLS 1... Member to be welded, 2... Electrode tip, 3... Transformer, 6... Thyristor, 10... Spot welder (welding device), 11... Nugget (melted part), 12
...Temperature sensor, 15...Control device (judgment means),
20... Displacement sensor, 21... Slider (moving means), 24... Drive unit (moving means), 30...
Bracket, 40... Scanner (transportation means), 41.
... Drive unit (transportation means). Patent applicant Nissan Motor Co., Ltd.

Claims (5)

[Claims] (1) A welding device that connects each of the welded parts by melting the welded part of the welded part to form a fused part, a temperature sensor that detects the surface temperature of the welded part, and a temperature sensor that detects the surface temperature of the welded part. Input the surface temperature based on
and a determination means for determining that the welding is in a defective state in which the fusion zone is not sufficiently formed when the surface temperature is not higher than a preset predetermined temperature, and detecting the surface temperature of the welded member. A welding condition judgment system is characterized in that it is possible to accurately judge a welding condition. (2) By providing an electrode tip that faces and contacts the surface of each welded part of the stacked members to be welded and energizes the welded part, and melts the welded part by the energization to form a fused part, A welding device that connects each of the members to be welded, a temperature sensor that detects the surface temperature of the welded part, a moving means that moves the temperature sensor in a direction where the electrode tip faces, and a welding device that connects each of the members to be welded. a displacement sensor that detects the amount of displacement of the welded member; and a displacement sensor that outputs a movement signal that moves the temperature sensor according to the amount of displacement to the moving means based on the displacement sensor; and a determination means for determining that the welding is in a defective state in which the fusion zone is not sufficiently formed when the surface temperature is not higher than a preset predetermined temperature, and detecting the surface temperature of the welded member. A welding condition judgment system is characterized in that it is possible to accurately judge a welding condition. (3) Providing an electrode tip that faces and contacts the surface of each welded part of the laminated members to be welded and energizes the welded part, and melts the welded part by the energization to form a fused part, A welding device that connects each of the welded members, a temperature sensor that detects the surface temperature of the welded part, a displacement sensor that detects the amount of displacement of the welded member due to wear of the electrode tip, and determines the welding state. The critical temperature is corrected by the correction value corresponding to the displacement detected by the displacement sensor among the correction values for correcting the critical temperature, which is preset as a reference value for The surface temperature based on a temperature sensor is
and a determination means for determining that the welding is defective in that the fusion zone is not sufficiently formed when the temperature is not higher than the corrected critical temperature, and the welding state is determined by detecting the surface temperature of the welded member. A welding condition judgment system that is characterized by its ability to accurately judge. (4) Provided with an electrode tip that contacts the surface of the welded part of the laminated members to be welded and energizes the welded part, and melts the welded part by the energization to form a molten part. a welding device that connects each, a temperature sensor that detects the surface temperature of the welding part, and a temperature sensor that detects the welding part in a direction of displacement in which the detection position of the temperature sensor is displaced due to displacement of the welded member due to wear of the electrode tip. A bracket capable of adjusting a temperature sensor; and a welding method in which the surface temperature is inputted based on the temperature sensor, and the molten part is not sufficiently formed when the surface temperature is not higher than a preset temperature. and determining means for determining that the welding state is in a defective state, and by adjusting the temperature sensor in the displacement direction, the surface temperature is detected within an allowable range with respect to the displacement of the welded member, and the welding state is determined. A welding condition judgment system that is characterized by its ability to accurately judge. (5) An electrode tip is provided which faces and contacts the surface of each welded part of the laminated members to be welded and energizes the welded part, and the welded part is melted by the energization to form a fused part. a welding device that connects each of the members to be welded;
A temperature sensor detects the surface temperature of the welding part, and the temperature sensor is moved in a predetermined angular range in a displacement direction in which a detection position of the temperature sensor is displaced due to displacement of the welded member due to wear of the electrode tip. a moving means that rotates the temperature sensor so that the temperature sensor can detect the surface temperature in the displacement direction; and a moving means that outputs a movement signal that causes the temperature sensor to move to the moving means; and determining means for determining that the welding is defective in that the fusion zone is not sufficiently formed when the maximum temperature of the surface temperature is not higher than a preset predetermined temperature. The welding condition determination system is characterized in that the welding condition can be accurately determined by rotating the temperature sensor in the displacement direction and detecting the surface temperature.