JP4881180B2 - Spot welding inspection method and inspection apparatus - Google Patents

Description

  The present invention relates to an inspection method and an inspection apparatus for estimating the size of a melted portion by making a transverse wave ultrasonic wave incident on a workpiece during spot welding.

  A reflection method and a transmission method are known as this type of inspection method.

  In the reflection method, correlation data relating to the maximum value of the intensity of the reflected wave and the size of the melted part is collected in advance, and welding is performed while monitoring the intensity of the reflected wave from the melted part. The intensity of the reflected wave increases as the melted part grows and decreases as the melted part solidifies, so the maximum value of the reflected wave intensity is correlated with the correlation data to increase the size of the melted part. Ask.

  In addition, a method has been proposed in which the size of the melted part is determined not from the maximum value of the reflected wave intensity but from the propagation time of the ultrasonic wave in the workpiece. In this method, first, the time until the ultrasonic wave is reflected by the melted portion and returns to the sensor is measured. On the other hand, the temperature of the workpiece is estimated from the welding current value, energization time, etc., and the speed of sound in the workpiece is obtained. And the distance from a sensor to a fusion | melting part is calculated | required from the relationship between a sound speed and propagation time, and the thickness of a fusion | melting part is calculated | required from the thickness of a workpiece | work.

  In the transmission method, correlation data relating to the minimum value of the transmitted wave intensity and the size of the melted portion is collected in advance. Then, welding is performed while monitoring the intensity of ultrasonic waves that pass through the workpiece. The intensity of the transmitted wave decreases as the melted portion grows and increases as the melted portion solidifies, so the minimum value of the transmitted wave intensity is correlated with the correlation data to increase the size of the melted portion. Ask.

  A method for obtaining the size of the melted part from the attenuation of the transmitted wave has also been proposed (see Patent Document 1). In this method, the speed of sound in the work is obtained from the transmittance of ultrasonic waves, the temperature of the work is obtained from the value, and the time when the melting point of the work is reached is obtained from the value. Then, the attenuation amount of the transmittance after reaching the melting point is obtained, and the size of the melted portion corresponding to the value is obtained from the correlation data.

Japanese Patent No. 3644958

  However, in any method, if the ultrasonic wave does not enter the workpiece perpendicularly due to the inclination of the electrode tip, the intensity of the reflected wave and the transmitted wave is lowered, and the accuracy of determination of the melted part volume is deteriorated. Further, when the thickness of the melted part is obtained from the propagation time of the ultrasonic wave, there is a problem that measurement accuracy of the workpiece temperature and propagation time has a great influence on the determination accuracy of the melted part volume.

  When the workpiece is a galvanized steel sheet, the melting point of zinc is lower than the melting point of iron. Therefore, when the melting of iron starts, the zinc is already melted. That is, since the ultrasonic wave is reflected by the molten plating layer, neither the transmitted wave nor the reflected wave from the base material melting portion can be detected, and the inspection by any method becomes impossible.

  In view of such circumstances, the present invention is a spot welding inspection method and inspection capable of accurately estimating the size of the melted part without being affected by the change in the incident angle of the ultrasonic wave or the workpiece temperature on the workpiece. An object is to provide an apparatus.

  As a spot welding inspection method of the present invention for solving the above-mentioned problems, a first inspection method using a reflected wave from a molten part and a transmitted wave from a molten part are used to estimate the size of the molten part. There are two inspection methods.

  The first inspection method for spot welding according to the present invention is a method for estimating the size of a melted portion by injecting ultrasonic waves into a workpiece being spot welded. A step of detecting the reflected wave, a step of detecting a first time at which energization of the welding current to the workpiece is stopped, and a second time at which the intensity of the reflected wave from the melted portion is reduced to a predetermined value. The difference between the process and the first time and the second time is set as the solidification time of the molten portion, and the solidification time is compared with correlation data regarding the size of the molten portion and the solidification time. And an estimating step.

  According to this configuration, when the size of the melted portion increases, the intensity of the reflected wave increases accordingly. When the energization of the welding current is stopped, the size of the melted portion is maximized. After the energization of the welding current is stopped, when the solidification of the melted portion proceeds, the intensity of the reflected wave decreases accordingly. When the solidification of the molten part is completed, the intensity of the reflected wave is reduced to a predetermined value. When the ultrasonic wave is incident obliquely on the workpiece, the intensity of the reflected wave from the melted portion decreases, but the time required for solidification of the melted portion does not change. In other words, the first time when the welding current is not supplied to the workpiece and the second time when the intensity of the reflected wave from the melted portion is reduced to a predetermined value are detected, and the first time and the second time are detected. Is the solidification time of the melted part, and the solidification time is compared with the correlation data to estimate the size of the melted part. Can be obtained accurately.

  When welding a galvanized steel sheet, ultrasonic waves are reflected by the hot-dip plating layer, and the reflected wave from the base metal melting portion cannot be detected. Further, when the diameter of the sensor used for detecting the reflected wave is smaller than the maximum diameter of the melted part, it is impossible to detect the reflected wave from the end part exceeding the sensor diameter in the melted part. Therefore, in these cases, it is effective to use the time when the energization of the welding current to the workpiece is stopped as described above as the first time.

  In the first inspection method, the time when the intensity of the reflected wave from the melted portion becomes maximum can be used as the first time. That is, another first inspection method for spot welding according to the present invention is a method for estimating the size of a melted portion by injecting ultrasonic waves into a workpiece during spot welding, and applying ultrasonic waves of transverse waves to the workpiece. Detecting the reflected wave from the melting part, detecting the first time at which the intensity of the reflected wave from the melting part becomes maximum, and reducing the intensity of the reflected wave from the melting part to a predetermined value. By detecting the time of 2 and the difference between the first time and the second time as the solidification time of the melted portion, and comparing the solidification time with correlation data relating to the size of the melted portion and the solidification time And a step of estimating the size of the melting part.

  According to such a configuration, when the size of the melted portion is maximized, the intensity of the reflected wave reaches the maximum value. When the ultrasonic wave is incident obliquely on the workpiece, the intensity of the reflected wave decreases, but the time when the value reaches the maximum value does not change. That is, the coagulation time may be obtained starting from the time when the intensity of the reflected wave reaches the maximum value. Such a configuration is effective when a galvanized steel sheet is not used or when the diameter of the sensor is equal to or larger than the maximum diameter of the melted part.

  The second inspection method for spot welding according to the present invention is a method for estimating the size of the melted part by injecting ultrasonic waves into the workpiece during spot welding, and injecting the ultrasonic wave of the transverse wave into the work from the melted part. A step of detecting a transmitted wave, a step of detecting a first time at which energization of the welding current to the workpiece is stopped, and a second time at which the intensity of the transmitted wave from the melting portion increases to a predetermined value. The difference between the process and the first time and the second time is set as the solidification time of the molten portion, and the solidification time is compared with correlation data regarding the size of the molten portion and the solidification time. And an estimating step.

  According to this configuration, when the size of the melted portion increases, the intensity of the transmitted wave decreases accordingly. When the energization of the welding current is stopped, the size of the melted portion is maximized. After the energization of the welding current is stopped, as the solidification of the molten portion proceeds, the intensity of the transmitted wave increases accordingly. When the solidification of the molten part is completed, the intensity of the transmitted wave has increased to a predetermined value. When the ultrasonic wave is incident obliquely on the workpiece, the intensity of the transmitted wave from the melted portion decreases, but the time required for solidification of the melted portion does not change. That is, the first time at which the energization of the welding current to the workpiece is stopped and the second time at which the intensity of the transmitted wave from the molten portion increases to a predetermined value are detected, and the first time and the second time are detected. Is the solidification time of the melted part, and the solidification time is compared with the correlation data to estimate the size of the melted part. Can be obtained accurately.

  When welding a galvanized steel sheet, the ultrasonic wave is reflected by the hot-dip plating layer, and the transmitted wave from the base metal melting portion cannot be detected. Further, when the diameter of the sensor used for detecting the transmitted wave is smaller than the maximum diameter of the melted portion, the transmitted wave from the end portion exceeding the sensor diameter in the portion corresponding to the melted portion of the workpiece cannot be detected. Therefore, in these cases, it is effective to use the time when the energization of the welding current to the workpiece is stopped as described above as the first time.

  In the second inspection method, the time when the intensity of the transmitted wave from the melted portion is minimized can be used as the first time. That is, another second inspection method for spot welding according to the present invention is a method for estimating the size of a melted portion by injecting ultrasonic waves into a workpiece during spot welding, and injecting ultrasonic waves of transverse waves into the workpiece. Detecting the transmitted wave from the melting part, detecting the first time at which the intensity of the transmitted wave from the melting part is minimized, and increasing the intensity of the transmitted wave from the melting part to a predetermined value. By detecting the time of 2 and the difference between the first time and the second time as the solidification time of the melted portion, and comparing the solidification time with correlation data relating to the size of the melted portion and the solidification time And a step of estimating the size of the melting part.

  According to this configuration, when the size of the melted portion is maximized, the intensity of the transmitted wave reaches the minimum value. When the ultrasonic wave is incident obliquely on the workpiece, the intensity of the transmitted wave is reduced, but the time when the value reaches the minimum value does not change. That is, the coagulation time may be obtained starting from the time when the intensity of the transmitted wave reaches the minimum value. Such a configuration is effective when a galvanized steel sheet is not used or when the diameter of the sensor is equal to or larger than the maximum diameter of the melted part.

  As the spot welding inspection apparatus of the present invention, there are a first inspection apparatus using the first inspection method of the present invention and a second inspection apparatus using the second inspection method of the present invention.

  The first inspection apparatus for spot welding according to the present invention is an apparatus for estimating the size of a molten part by injecting ultrasonic waves into a workpiece during spot welding, and stores correlation data regarding the size of the molten part and the solidification time. Storage means, a sensor for detecting a reflected wave from the melted part by injecting a transverse wave ultrasonic wave into the work, a first time at which energization of the welding current to the work is stopped, and a reflected wave from the melted part By detecting the second time when the intensity decreases to a predetermined value, the difference between the first time and the second time is set as the solidification time of the melted portion, and the solidification time is collated with correlation data And a judging means for estimating the size of the melted portion. With such a configuration, the same operation and effect as the first inspection method of the present invention can be obtained.

  The second inspection apparatus for spot welding according to the present invention is an apparatus for estimating the size of a melted portion by injecting ultrasonic waves into a workpiece during spot welding, and stores correlation data relating to the size of the melted portion and the solidification time. Storage means, ultrasonic wave generating means for injecting ultrasonic waves of a transverse wave into the work, a sensor for detecting a transmitted wave from the melting part, a first time at which energization of the welding current to the work is stopped, and from the melting part Detecting means for detecting the second time at which the intensity of the transmitted wave increases to a predetermined value, and the difference between the first time and the second time as the solidification time of the melted portion, and the solidification time as the correlation data And a judging means for estimating the size of the melted part by collation. With such a configuration, it is possible to obtain the same operation and effect as the second inspection method of the present invention.

  According to the present invention, since the size of the melted portion is estimated not from the intensity of the reflected wave or the transmitted wave but from the solidification time of the melted portion, the change in the incident angle of the ultrasonic wave to the workpiece or the change in the workpiece temperature The size of the melted part can be accurately estimated without being affected by the above.

(1) 1st Embodiment Hereinafter, 1st Embodiment of this invention is described in detail based on an accompanying drawing. FIG. 1 shows a block diagram of an inspection apparatus according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an electrode tip of a spot welding gun, which incorporates a sensor 2 that makes ultrasonic waves incident on a workpiece W. The welding current from the electrode tip 1 to the workpiece W and the energization time thereof are controlled by a welding timer (not shown). The sensor 2 receives a pulse signal from the ultrasonic transmitter / receiver 3, generates a transverse ultrasonic wave, converts the reflected wave into an electric signal, and returns it to the ultrasonic transmitter / receiver 3. The reflected wave signal is amplified by the ultrasonic transmitter / receiver 3 and sent to the detecting means 4.

  The detection means 4 detects the first time when the intensity of the reflected wave becomes maximum and the second time when the intensity of the reflected wave decreases to a predetermined value, and sends the signal to the determination means 5. The determination means 5 obtains the solidification time of the melted part from the difference between the first and second times, compares this with the correlation data in the storage means 6 and obtains the size of the melted part corresponding to the solidification time. The storage means 6 stores correlation data regarding the size of the melted portion and the solidification time. The size of the melted part means the diameter or volume of the melted part.

  Next, a method for estimating the size of the melted part from the intensity of the reflected wave will be described in detail with reference to FIGS. FIG. 2 is a diagram showing changes with time in reflected wave intensity and welding current. FIGS. 9A to 9D are schematic views showing transition of a state in which a transverse ultrasonic wave is incident on a workpiece during spot welding.

First, as shown in FIG. 1, to start the energization of the welding current pressed across the workpiece W at the electrode tip 1,1, at time t _s. In FIG. 2, a solid line A indicates a change in welding current. Although the reflected wave before fusion zone generated in the workpiece W is not observed (FIG. 9 (a)), the workpiece W is heated melted by energization of the welding current, the reflected wave from the melting portion L at time t ₀ is observed The As the size of the melted portion L increases, the intensity of the reflected wave increases accordingly. In FIG. 2, a solid line B indicates a change in the intensity of the reflected wave. As the melting progresses, the distance from the sensor 2 to the melting portion L decreases, and the appearance time of the reflected wave decreases. In FIG. 2, a dotted line C indicates the appearance time of the reflected wave. Incidentally, shows the appearance time of the reflected wave, the ultrasonic wave transmitted from the sensor 2 is reflected by the melt portion L, refers to a time to come back to the sensor 2, in t _a in reflection waveform diagram of FIG. 2 upper Has been. In Figure 2, the time t _a, although the time until the rise of the reflected wave corresponding to each incident wave, but is not limited thereto. For example, at the peak of the intensity of the reflected wave, the time until the middle point of the rising of the reflected wave and its disappearance may be time t _a. In the graph showing the time course of the reflected wave intensity and the welding current in FIG. 2 lower part, it is assumed that the observation time of the reflected wave, the sum of the time t _a the transmission time of the reflected wave.

If you stop the energization of the welding current at time t _1, the solidification section M is generated begin solidification of the molten portion L, the intensity of the reflected wave starts to decrease. In other words, the strength of the size and the reflected wave of the molten portion L at time t ₁ of energization stop is maximized (Fig. 9 (b)). When solidification of the melted portion proceeds (FIG. 9C), the intensity of the reflected wave decreases correspondingly, and the appearance time of the reflected wave increases. At time t ₃ the solidification of the molten portion is completed, the reflected wave is disappeared, the intensity becomes zero (FIG. 9 (d)).

The solidification time of the melted part L is calculated with the time t ₁ when the intensity of the reflected wave becomes maximum as the start (first time) and the time t ₃ when the intensity of the reflected wave becomes zero as the end (second time). do it. However, when the time t ₃ to the end, tends to occur a measurement error due to noise. Therefore, a threshold value slightly larger than zero may be set, and the time t ₂ (second time) when the intensity of the reflected wave reaches the threshold value may be the end of the coagulation time.

In this case, the coagulation time T is slightly shorter than the true value (t ₃ -t ₁ ). However, if the above value (t ₂ -t ₁ ) is used as the coagulation time when creating the correlation data, There is almost no influence on the determination accuracy of the molten part.

Since the sensor 2 cannot detect a reflected wave from a portion of the workpiece W exceeding the sensor diameter, the detection limit of the reflected wave intensity from the melted portion L is defined by the sensor diameter of the sensor 2. That is, as shown in FIGS. 9A to 9D, when the sensor diameter is equal to or larger than the maximum diameter of the melted part L, the sensor 2 can detect the reflected wave from all parts of the melted part L. Therefore, the sensor 2 can detect the maximum value of the reflected wave intensity (the solid line B in FIG. 2 and the broken line B in FIG. 3). Therefore, in this case, the time t _{1 at} which the intensity of the reflected wave becomes maximum as described above can be used as the start (first time).

On the other hand, as shown in FIGS. 10A and 10B, when the sensor diameter is smaller than the maximum diameter of the melted portion L, the sensor 2 detects reflected waves from both ends exceeding the sensor diameter in the melted portion L. Can not do it. In this case, the sensor diameter is equal to or greater than the maximum diameter of the melted part L before the diameter of the melted part L matches the sensor diameter during energization and after the diameter of the melted part L matches the sensor diameter during cooling after the end of energization. Although the same change as the case shown by the broken line B in FIG. 3 is shown, until the diameter of the melted portion L matches the sensor diameter during energization until the diameter of the melted portion L matches the sensor diameter during cooling after the end of energization. As shown by the solid line B ′ in FIG. 3, the intensity of the reflected wave is constant. As described above, the intensity of the reflected wave does not reflect a change in the diameter of the melted portion exceeding the sensor diameter. Therefore, in this case, the time t ₁ when the energization of the welding current is stopped is the start of the solidification time T. Since the size of the melted portion L reaches the maximum when the welding current is stopped, this time can be used as the start of the solidification time T. In this case, using the time t ₅ the diameter of the melted portion L is equal to the sensor size during cooling after application end may be a (t 5 _{-t 1)} clotting time T.

  Then, the size of the melted portion is estimated by comparing the solidification time T with the correlation data (see FIG. 5).

  Correlation data relating to the size of the melted part and the solidification time is prepared as follows.

  Spot welding is performed on a large number of workpieces by changing the welding conditions (current value, energization time, etc.), and the solidification time T of the molten part is measured and recorded each time. Destructive inspection of the welded workpiece is performed, and the size V of the molten part is obtained from the vertical and horizontal cross sections of the molten part. Then, correlation data is created by associating the size of the melted portion with the solidification time T.

Now, the slope of the electrode tip 1, the ultrasonic wave is obliquely incident on the workpiece, the intensity of the reflected wave decreases, the first time t ₁ the intensity of the reflected wave is maximum does not change. Meanwhile, since in the vicinity of the threshold value hardly occurs the intensity difference of the reflected wave, a second difference between the time t ₂ when the intensity of the reflected wave reaches the threshold becomes negligibly small. In FIG. 6, the intensity of the reflected wave when the ultrasonic wave is incident obliquely is indicated by a one-dot chain line. That is, since the time T required for solidification of the melted portion does not change, the size of the melted portion can be accurately estimated without being affected by the change in the incident angle of the ultrasonic wave on the workpiece. Also, it is not affected by the temperature change of the workpiece.

  By the way, when the workpiece is a galvanized steel sheet, since the melting point of zinc is lower than the melting point of iron, the plating layer between the workpieces first melts, and then the base material begins to melt. For this reason, as shown in FIG. 4 (a), when energization of the welding current is started, a reflected wave D is first generated from the hot dipped layer between the workpieces.

  The plating layer between the workpieces will eventually evaporate, but the base material will begin to melt around that time. When the energization current value is high and the melting portion is large, heat is transferred to the electrode tip 1 side, and the plating layer on the electrode tip 1 side may melt. In this case, as shown in FIG. 4B, a reflected wave E from the plating layer on the electrode chip 1 side is generated, and the ultrasonic wave does not enter the base material. For this reason, it becomes impossible to detect the peak of the intensity of the reflected wave B that should be reflected from the base metal melting portion.

Therefore, the time t _{1 at} which the welding current is stopped is set as the start of the solidification time T. That is, when the welding current is stopped, the size of the melted portion reaches the maximum, and this time can be used as the start of the solidification time T.

When reflected from the plating layer of the electrode chip 1 side is eliminated at time t _4, since appears reflected waves B from the base metal molten portion, the end of the clotting time T, as in the normal work, the reflected wave B strength may be set to a time t ₂ to decrease to the threshold. The method for estimating the size of the melted part from the solidification time T is as described above.

(2) Second Embodiment The second embodiment is the same as the first embodiment, except that a transmitted wave from the melted part is used instead of a reflected wave from the melted part to estimate the size of the melted part. . FIG. 7 shows a block diagram of an inspection apparatus according to the second embodiment of the present invention. Note that, in the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description of the configuration and operation thereof is omitted.

  In the second embodiment, as shown in FIG. 7, the sensor 7 that receives the transmitted wave from the melting portion is provided on the electrode tip 1 on the lower side of the work W. The sensor 7 has, for example, the same diameter as the sensor 2 and is disposed at a position symmetrical to the sensor 2 with respect to the workpiece W. The sensor 2 (ultrasonic wave generating means) receives the pulse signal from the ultrasonic wave transmitter / receiver 3 and generates a transverse ultrasonic wave. The sensor 7 receives the transmitted wave from the melting part, converts the transmitted wave into an electric signal, and returns it to the ultrasonic transceiver 3. The transmitted wave signal is amplified by the ultrasonic transmitter / receiver 3 and sent to the detection means 4.

  The detection means 4 detects a first time when the intensity of the transmitted wave is minimum and a second time when the intensity of the transmitted wave increases to a predetermined value, and sends the signal to the determination means 5. The determination means 5 obtains the solidification time of the melted part from the difference between the first and second times, compares this with the correlation data in the storage means 6 and obtains the size of the melted part corresponding to the solidification time.

  Next, a method for estimating the size of the melted part from the intensity of the transmitted wave will be described in detail with reference to FIGS. 7, 8, 9 (a) to (d). FIG. 8 is a diagram showing temporal changes in transmitted wave intensity and welding current. In addition, illustration of the sensor 7 is abbreviate | omitted in Fig.9 (a)-(d).

First, pressurized by sandwiching the first embodiment similarly to the workpiece W of the electrode tip 1,1, it starts energization of the welding current at time t _s. In FIG. 8, a solid line A indicates a change in welding current. Since the ultrasonic wave is not reflected by the workpiece W before the melted portion L is generated in the workpiece W, the intensity of the transmitted wave at this time is the maximum (FIG. 9A). When the workpiece W by energizing the welding current generates heat melt, because ultrasound is reflected by the melt portion L, the transmitted wave from the melting portion L at time t ₀ is reduced. As the size of the melted portion L increases, the intensity of the transmitted wave decreases accordingly. In FIG. 8, a broken line F indicates a change in the intensity of the transmitted wave.

If you stop the energization of the welding current at time t _1, the solidified portion M begins solidification of the molten portion L is produced, the intensity of the transmitted wave changes to increase. In other words, the size of the fused portion at the time t ₁ of energization stopping up the intensity of the transmitted wave is minimized (FIG. 9 (b)). As the solidification of the melted portion L proceeds (FIG. 9C), the intensity of the transmitted wave increases accordingly. At time t ₃ the solidification of the molten portion L is completed, the intensity of the transmitted wave is maximized again ((FIG. 9 (d)).

The solidification time of the melted portion L is calculated with the time t ₁ when the intensity of the transmitted wave is minimized as the start (first time) and the time t ₃ when the intensity of the transmitted wave is maximized as the end (second time). do it. However, when the time t ₃ to the end, tends to occur a measurement error due to noise. Therefore, a threshold value slightly smaller than the maximum intensity of the transmitted wave may be set, and the time t ₂ (second time) when the intensity of the transmitted wave reaches the threshold value may be set as the end of the coagulation time.

In this case, the coagulation time T is slightly shorter than the true value (t ₃ -t ₁ ). However, if the above value (t ₂ -t ₁ ) is used as the coagulation time when creating the correlation data, There is almost no influence on the determination accuracy of the molten part.

In addition, since the sensor 7 cannot detect the transmitted wave from the part exceeding the sensor diameter in the workpiece | work W, the detection limit of the transmitted wave intensity from the fusion | melting part L is the same as that of the case of the reflected wave of 1st Embodiment. Further, it is defined by the sensor diameter of the sensor 7. That is, when the sensor diameter is equal to or larger than the maximum diameter of the melted part L, the sensor 7 can detect transmitted waves from all parts corresponding to the melted part L in the workpiece W. The minimum value can be detected (broken line F in FIG. 8). Therefore, in this case, the time t _{1 at} which the intensity of the transmitted wave is minimized as described above can be used as the start (first time).

On the other hand, when the sensor diameter is smaller than the maximum diameter of the melted part L, the sensor 7 cannot detect transmitted waves from the portions corresponding to both ends of the melted part L exceeding the sensor diameter in the workpiece W. The transmitted wave intensity curve in this case is a curve obtained by translating the curve shown by the broken line F in FIG. 8 in the case where the sensor diameter is equal to or larger than the maximum diameter of the melted portion L downward in the time axis direction (FIG. 8 The solid line F ′), the intensity of the transmitted wave becomes zero until the diameter of the melted portion L coincides with the sensor diameter during cooling after the energization ends after the diameter of the melted portion L coincides with the sensor diameter. As described above, the intensity of the transmitted wave does not reflect the change in the diameter of the melted portion exceeding the sensor diameter. Therefore, in this case, the time t ₁ when the energization of the welding current is stopped is the start of the solidification time T. Since the size of the melted portion L reaches the maximum when the welding current is stopped, this time can be used as the start of the solidification time T. In this case, using the time t ₅ the diameter of the melted portion L is equal to the sensor size during cooling after application end may be a (t 5 _{-t 1)} clotting time T.

  Then, similarly to the first embodiment, the solidification time T is collated with the correlation data to estimate the size of the molten part (see FIG. 5).

Now, the slope of the electrode tip 1, the ultrasonic wave is obliquely incident on the workpiece, the intensity of the transmitted wave is degraded, the first time t ₁ the intensity of the transmitted wave is minimized does not change. Meanwhile, since in the vicinity of the threshold value hardly occurs the intensity difference between the transmitted wave, a second difference between the time t ₂ when the intensity of the transmitted wave reaches the threshold becomes negligibly small. That is, since the time T required for solidification of the molten part does not change, the size of the molten part can be accurately estimated without being affected by the change in the incident angle of the ultrasonic wave with respect to the workpiece W. Also, it is not affected by the temperature change of the workpiece.

By the way, when the workpiece is a galvanized steel sheet, the time t ₁ when the energization of the welding current is stopped is set as the start of the solidification time T as in the first embodiment using a reflected wave. That is, when the welding current is stopped, the size of the melted portion reaches the maximum, and this time can be used as the start of the solidification time T.

1 is a block diagram of an inspection apparatus according to a first embodiment of the present invention. The figure which shows the time-dependent change of reflected wave intensity and welding current. The figure which shows the dependence to the relationship between the sensor diameter of reflected wave intensity, and the maximum diameter of a fusion | melting part. The figure which added the reflected wave from a hot dipped layer to FIG. The figure which shows the correlation data regarding the magnitude | size of a fusion | melting part, and solidification time. The figure explaining the influence which the inclination of an electrode tip has on reflected wave intensity. The block diagram of the inspection apparatus of 2nd Embodiment which concerns on this invention. The figure which shows the time-dependent change of transmitted wave intensity and welding current. It is the schematic which shows the transition of the state which has injected the ultrasonic wave of the transverse wave into the workpiece | work in spot welding when a sensor diameter is more than the maximum diameter of a fusion | melting part, (a) is the state before electricity supply, (b) is The state at the end of energization, (c) is the state during cooling, (d) is a diagram showing the state at the end of cooling. It is the schematic which shows the transition of the state which has injected the ultrasonic wave of the transverse wave into the workpiece | work in spot welding when a sensor diameter is smaller than the maximum diameter of a fusion | melting part, (a) is a state at the time of completion | finish of electricity supply, (b) FIG. 4 is a diagram showing a state during cooling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrode chip | tip, 2,7 ... Sensor, 3 ... Ultrasonic transmitter / receiver, 4 ... Detection means, 5 ... Determination means, 6 ... Memory | storage means, A ... Welding current, B, B '... Reflected wave intensity, F, F '... transmitted wave intensity, L ... melting part, M ... solidification part, W ... workpiece, t ₁ ... first time, t ₂ ... second time

Claims (6)

In the method of estimating the size of the melted part by injecting ultrasonic waves into the workpiece being spot welded,
Detecting a reflected wave from the melted portion by injecting a transverse ultrasonic wave into the workpiece;
Detecting a first time to stop energization of the welding current to the workpiece;
Detecting a second time when the intensity of the reflected wave from the melted portion decreases to a predetermined value;
The difference between the first time and the second time is defined as the solidification time of the melted portion, and the solidification time is compared with correlation data relating to the size of the melted portion and the solidification time. And a method for estimating spot welding. In the method of estimating the size of the melted part by injecting ultrasonic waves into the workpiece being spot welded,
Detecting a reflected wave from the melted portion by injecting a transverse ultrasonic wave into the workpiece;
Detecting a first time at which the intensity of the reflected wave from the melted portion is maximized;
Detecting a second time when the intensity of the reflected wave from the melted portion decreases to a predetermined value;
The difference between the first time and the second time is defined as the solidification time of the melted portion, and the solidification time is compared with correlation data relating to the size of the melted portion and the solidification time. And a method for estimating spot welding. In the method of estimating the size of the melted part by injecting ultrasonic waves into the workpiece being spot welded,
A process of detecting a transmitted wave from the melted portion by injecting a transverse wave ultrasonic wave into the workpiece;
Detecting a first time to stop energization of the welding current to the workpiece;
Detecting a second time at which the intensity of the transmitted wave from the melting portion increases to a predetermined value;
The difference between the first time and the second time is defined as the solidification time of the melted portion, and the solidification time is compared with correlation data relating to the size of the melted portion and the solidification time. And a method for estimating spot welding. In the method of estimating the size of the melted part by injecting ultrasonic waves into the workpiece being spot welded,
A process of detecting a transmitted wave from the melted portion by injecting a transverse wave ultrasonic wave into the workpiece;
Detecting a first time at which the intensity of the transmitted wave from the melting portion is minimized;
Detecting a second time at which the intensity of the transmitted wave from the melting portion increases to a predetermined value;
The difference between the first time and the second time is defined as the solidification time of the melted portion, and the solidification time is compared with correlation data relating to the size of the melted portion and the solidification time. And a method for estimating spot welding. In an apparatus that estimates the size of the melted part by injecting ultrasonic waves into the workpiece being spot welded,
Storage means for storing correlation data relating to the size of the melted portion and the solidification time;
A sensor that detects a reflected wave from the melted portion by injecting a transverse ultrasonic wave into the workpiece;
Detection means for detecting a first time at which energization of the welding current to the workpiece is stopped and a second time at which the intensity of the reflected wave from the melted portion decreases to a predetermined value;
And a determination means for estimating a size of the melted portion by comparing the solidification time with the correlation data using the difference between the first time and the second time as the solidification time of the melted portion. Spot welding inspection device characterized by. In an apparatus that estimates the size of the melted part by injecting ultrasonic waves into the workpiece being spot welded,
Storage means for storing correlation data regarding the size of the melted part and the solidification time;
Ultrasonic wave generation means for injecting ultrasonic waves of transverse waves to the workpiece;
A sensor for detecting a transmitted wave from the melting part;
Detection means for detecting a first time at which energization of the welding current to the workpiece is stopped and a second time at which the intensity of the transmitted wave from the melted portion increases to a predetermined value;
A determination unit that estimates a difference between the first time and the second time as a solidification time of the melted portion and estimates the size of the melted portion by comparing the solidification time with the correlation data; A spot welding inspection apparatus characterized by the above.

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