JP5965620B2 - Resistance welding quality control method and resistance welding apparatus - Google Patents

Description

  The present invention relates to a resistance welding quality control method and a resistance welding apparatus, and in particular, holds a plurality of electric wires between a pair of electrodes in a state in which the wires are pressed toward each other, and a welding current is applied between the pair of electrodes. The present invention relates to a resistance welding quality control method and a resistance welding apparatus in which a plurality of electric wires are thermocompression bonded to each other using resistance heat generated by energization of the welding current.

  In general, in resistance welding equipment that joins steel plates, the voltage between a pair of electrodes and the amount of subsidence of the steel plates are monitored, and electrode dressing (mechanical shaping of the electrode surface and tip is performed according to the usage of the electrodes. To produce under the same manufacturing conditions. However, when a resistance welding apparatus is used for joining the above-described wires, not only quality but also high productivity is required. Therefore, when dressing is performed by removing an electrode made of an expensive material such as tungsten, high productivity is achieved. There was a problem that it was difficult to secure.

  Therefore, electrode dressing is performed for each lot, and a tensile test for adhesion force is performed to confirm that the product is a non-defective product, thus ensuring quality. In that case, there are two problems, that is, it is necessary to perform a tensile inspection of the fixing force every certain number of productions, and it is impossible to detect defects in the lot. Therefore, in order to solve the above problems, the calorific value and resistance value are calculated by measuring the voltage and welding current between a pair of electrodes, and the calculated calorific value and resistance value are monitored to determine whether the product is good or defective. A resistance welding apparatus having a quality control function is proposed (Patent Documents 1 to 3).

  However, in the resistance welding apparatus having the above-described conventional quality control function, a defective product is mixed in a product determined to be a non-defective product depending on the type of the electric wire, or it is determined to be a defective product. There was a problem that non-defective products were mixed in the product, and it was impossible to accurately determine whether the product was non-defective or defective. When the inventors diligently investigated the cause of this, the appearance of an oxide film or organic film attached to the electrode differs depending on the type of the wire, and as a result, contact between the electrode and the wire used for thermocompression bonding. It has been found that this is because the resistance is reduced and the resistance component of the electrode itself cannot be ignored.

Japanese Patent No. 3540125 Japanese Patent No. 3540127 Japanese Patent No. 37605434

  Then, this invention makes it a subject to provide the quality control method and resistance welding apparatus of resistance welding which can test | inspect a welding state correctly irrespective of the state of an electrode.

  The invention according to claim 1 for solving the above-mentioned problem is to hold a plurality of electric wires between the pair of electrodes in a state in which they are brought close to each other, and to pass a welding current between the pair of electrodes, In the resistance welding quality control method in which the plurality of electric wires are thermocompression bonded to each other using the resistance heat generated by energization of the welding current, measurement is performed to measure a voltage generated between the pair of electrodes when the welding current is energized. Based on a comparison between the measured value that is one of the measured pair of interelectrode voltages or the measured pair of interelectrode voltages and the welding current, and the upper and lower thresholds An inspection step for inspecting the welding state of the electric wires, and before the inspection step, the measurement that is generated by the resistance component of each of the pair of electrodes at the temporary upper limit threshold and the temporary lower limit threshold that are set and stored in advance. It consists in the quality control method of resistance welding, wherein a value obtained by adding the increment value performs an addition process to the upper threshold and the lower threshold.

  The invention according to claim 2 lies in the quality control method for resistance welding according to claim 1, wherein the increment of the added measurement value is a value that varies in accordance with the welding current. .

  According to a third aspect of the present invention, a plurality of electric wires are pressed between a pair of electrodes while being pressed in a direction approaching each other, a welding current is passed between the pair of electrodes, and a resistance heat is generated by passing the welding current. In the resistance welding apparatus that thermocompression-bonds the plurality of electric wires using voltage, a voltage measuring unit that measures a voltage generated between the pair of electrodes when the welding current is applied, and a distance between the measured pair of electrodes Inspecting means for inspecting the welding state of the electric wire based on a comparison between a voltage or a measured value which is one of the measured voltage between the pair of electrodes and the welding current, and an upper threshold and a lower threshold And an adder that uses the upper limit threshold and the lower limit threshold as values obtained by adding the increments of the measured value generated by the resistance component of each of the pair of electrodes to the preset upper limit threshold and the temporary lower limit threshold. If, it consists in the resistance welding apparatus comprising the.

  According to a fourth aspect of the present invention, there is provided storage means for storing in advance a unit upper limit calorie per unit conductor area given to the electric wire, a unit lower limit calorie per unit conductor area given to the electric wire, and a resistance component of a pair of electrodes, And an input means for inputting the total conductor area of the electric wire, and calculating the upper limit heat amount by multiplying the unit upper limit heat amount by the total conductor area, and multiplying the unit lower limit heat amount by the total conductor area to obtain the lower limit heat amount. A calculation means and a value obtained by converting the obtained upper limit heat amount into the measured value are set and stored as the temporary upper limit threshold value, and a value obtained by converting the obtained lower limit heat amount into the measured value is set as the temporary lower limit threshold value. Further, the resistance welding apparatus according to claim 3, further comprising a threshold setting unit that stores the threshold value.

  As described above, according to the first to third aspects of the present invention, the upper limit threshold and the lower limit threshold are values obtained by adding the increments of the measured values generated by the resistance components of each of the pair of electrodes to the temporary upper limit threshold and the temporary lower limit threshold. Then, the welding state is inspected based on the comparison between the upper and lower threshold values and the measured values. Therefore, even if the contact resistance between the electrode and the electric wire becomes small depending on the state of the electrode and the resistance component of the electrode becomes not negligible, the threshold value can be set in consideration of the increase in the measured value due to the resistance component of the electrode. Therefore, the welding state can be accurately inspected regardless of the state of the electrode.

  According to the invention of claim 4, the calorie calculating means obtains the upper limit calorie by multiplying the unit upper limit calorie by the total conductor area, obtains the lower limit calorie by multiplying the unit lower limit calorie by the total conductor area, and the threshold setting means The calculated upper limit calorie is converted into a measured value and set as a temporary upper limit threshold and stored, and the obtained lower limit calorie is converted into a measured value and set as a temporary lower limit threshold and stored. Even if the total conductor area is changed, it is possible to accurately inspect the welding state.

It is a side view which shows one Embodiment of the resistance welding apparatus of this invention. It is a block diagram which shows the structure of the principal part of the resistance welding apparatus shown in FIG. Prepare multiple sample products consisting of multiple wires, join these multiple sample products using the resistance welding equipment shown in Fig. 1, measure the welding current-electrode voltage, and plot the power against welding current ² It is a graph which shows the result. It is a figure which shows the resistance which arises between a pair of electrodes which comprise the resistance welding apparatus shown in FIG. It is a graph for demonstrating the relationship between upper limit power consumption and lower limit power consumption, and a non-defective product and defective product inspection. It is a flowchart which shows the welding current setting process sequence of the control apparatus in 1st Embodiment. It is a flowchart which shows the manufacturing process procedure of the control apparatus in 1st Embodiment. Prepare a plurality of sample products consisting of a plurality of electric wires, join each of these sample products using the resistance welding device shown in FIG. 1, measure the welding current-electrode voltage, and calculate the interelectrode voltage relative to the welding current. It is a graph which shows the plotted result. It is a graph for demonstrating the relationship between an upper limit voltage and a lower limit voltage, and a non-defective product and defective product inspection. It is a flowchart which shows the welding current setting process sequence of the control apparatus in 2nd Embodiment. It is a flowchart which shows the manufacturing process procedure of the control apparatus in 2nd Embodiment.

First Embodiment Hereinafter, a resistance welding apparatus 1 according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. The resistance welding apparatus 1 shown in FIG. 1 has a resistance by overlapping a core wire of one electric wire made of a plurality of copper wire rods twisted with each other and a core wire of the other electric wire made of a plurality of copper wire wires twisted together. It is a welding device.

  As shown in FIG. 1, the resistance welding apparatus 1 includes a base part 2 mounted on a factory floor, an arm part 3 extending upward from the base part 2, and air as a pressurizing means. A cylinder 4, a pair of electrodes 5a and 5b, a voltage measurement sensor 6 as a voltage measurement means, a current measurement sensor 7 as a current measurement means, a welding transformer 8 as a power source, a control device 9 and the like are provided. .

  The base part 2 includes a flat part 2a that is flat when viewed from the side. The arm part 3 extends upward from the flat part 2a of the base part 2, and extends along the horizontal direction from the upper end part 3a toward the operator side, for example. The flat end portion 2a and the arm portion 3 are formed in a U shape when viewed from the side.

  The air cylinder 4 includes a cylinder body 4a, a piston rod 4b that is extendable from the cylinder body 4a, and an electromagnetic valve 4c (shown in FIG. 2). The air cylinder 4 has a cylinder body 4a provided at the tip of the arm portion 3 so that the piston rod 4b extends downward.

  A pressurized gas is supplied into the cylinder body 4a from a pressurized gas supply source (not shown). The piston rod 4b extends from the cylinder body 4a when pressurized gas is supplied into the cylinder body 4a. The electromagnetic valve 4c is connected to the pressurized gas supply source, and opens and closes to start supplying pressurized gas into the cylinder body 4a and stop supplying the gas. have. The electromagnetic valve 4 c is connected to the control device 9.

  One electrode 5a of the pair of electrodes 5a and 5b is attached to the tip of the piston rod 4b via an electrode holder 10. The other electrode 5b is attached to the flat portion 2a. The pair of electrodes 5a and 5b are disposed to face each other along the vertical direction. The one electrode 5a is electrically connected to the welding transformer 8 via an ounce copper plate 11 or the like, and the other electrode 5b is electrically connected to the welding transformer 8.

  The electrodes 5a and 5b include a columnar chrome copper plate attached to the tip end portion and the flat portion 2a of the piston rod 4b, and a tungsten chip protruding from the chrome copper plate, and these tungsten chips face each other. Is provided. The electrodes 5a and 5b sandwich and hold a core wire of the electric wire to be welded between the tungsten tips. An oxide film is formed by repeating welding on at least the surface of the tungsten tip that contacts the core wire. An electric wire setting jig 12 is provided in the vicinity of the electrode 5b. The electric wire setting jig 12 prevents the misalignment of the core wires held between the electrodes 5a and 5b and pressed in a direction approaching each other by the air cylinder 4 or the like, and these core wires are placed between the electrodes 5a and 5b. It has a function to hold.

  The voltage measurement sensor 6 is electrically connected to each of the pair of electrodes 5a and 5b, and measures the voltage between the electrodes 5a and 5b. The voltage measurement sensor 6 outputs the measured voltage between the pair of electrodes 5 a and 5 b to the control device 9. The current measurement sensor 7 is provided between the welding transformer 8 and the electrode 5a, and measures a welding current flowing between the electrodes 5a and 5b. The current measuring sensor 7 outputs the measured welding current to the control device 9.

  The welding transformer 8 is connected to the control device 9 via a welding timer 13 (shown in FIG. 2). The welding timer 13 has a function of controlling the energization time of the welding current. The welding apparatus 1 includes an operation panel 14 as input means. The operation panel 14 is provided with a plurality of setting buttons for performing various operation instructions and various settings for the welding apparatus 1. The operation panel 14 is connected to each other, for example, the energization time from the start of energization of the welding current energized between the electrodes 5a and 5b from the welding transformer 8 to the end of energization, the pressurizing force by which the air cylinder 4 presses the core wires toward each other. The total conductor area of multiple wires can be entered.

Next, the principle of the present invention will be described with reference to FIGS. First, the present inventors prepare a plurality of sample products composed of a plurality of electric wires, respectively join the plurality of sample products using the resistance welding apparatus 1, and determine the voltage V between the welding current I and the electrodes 5a and 5b. Measurements were made and the power VI versus welding current ² = I ² was plotted. The results are shown in FIG. Each sample product has the same conductor area, and the energization time of the welding current is the same time. In FIG. 3, “OK” is a non-defective product that satisfies the fixing force between the core wires, and “NG” is a defective product that does not satisfy the fixing force between the core wires due to insufficient heat or excessive heat.

  When the electric power of 2000 W to 2500 W is supplied to the core wire, the sampled electric wire is obtained as a good product by obtaining a good fixing force. However, as shown in FIG. 3, some out of the range of 2000 W to 2500 W are non-defective. The present inventors diligently searched for this cause and found the following. That is, as shown in FIG. 4, when a welding current I is passed between the pair of electrodes 5a and 5b with the core wire of the wire interposed therebetween, the resistance component Ra of the electrode 5a, the contact resistance Rt between the electrodes 5a and 5b and the wire, and the electrode The welding current I flows through the resistance component Rb of 5b. When the welding current I flows through the contact resistance Rt and power is consumed by the contact resistance Rt, heat is applied to the core of the electric wire, which can be used for thermocompression bonding. However, even if the welding current I flows through the resistance components Ra and Rb and power is consumed by the resistance components Ra and Rb, the electrodes 5a and 5b only generate heat, and this hardly adds heat to the core wire.

  Since the voltage measuring sensor 6 measures the voltage V between the electrodes 5a and 5b, the power consumption calculated by the measured voltage is not only that consumed by the contact resistance Rt, but also by the resistance components Ra and Rb. Even power consumption is included. When the contact resistance Rt is small, the power consumed by these resistance components Ra and Rb cannot be ignored, so it has been found that it is necessary to consider these as the upper limit power consumption and the lower limit power consumption.

Therefore, in the present invention, the upper limit power consumption PU (= upper limit threshold) and the lower limit power consumption PL (= lower limit threshold) are set as shown in the expressions (1) and (2), and the voltage measurement sensor 6 and the current measurement sensor are set. The measured power consumption P (= measured value) obtained from the voltage V (hereinafter measured voltage V) between the pair of electrodes 5a and 5b measured by 7 and the welding current I is compared with the upper limit power consumption PU and the lower limit power consumption PL. Then, inspect for good and defective products.
Upper limit power consumption PU (W) = upper limit heat quantity QU (J) / energization time T (sec) + (Ra + Rb) × I ² (1)
Lower limit power consumption PL (W) = lower limit heat quantity QL (J) / energization time T (sec) + (Ra + Rb) × I ² (2)
The upper limit calorie QU and the lower limit calorie QL are the upper limit and lower limit of the range of heat given to the electric wire core wire so that a good fixing force can be obtained.

According to the above formulas (1) and (2), the increase in the measured power consumption P caused by the resistance component of each of the pair of electrodes 5a and 5b at the upper limit heat quantity QU / energization time T and the lower limit heat quantity QL / energization time T. A value obtained by adding (Ra + Rb) I ² which is a minute is defined as an upper limit power consumption PU (W) and a lower limit power consumption PL (W). When this upper limit power consumption PU is plotted in FIG. 3, the slope is (Ra + Rb) and the intercept is a straight line of the upper limit heat quantity QU / energization time T. When the lower limit power consumption PL is plotted in FIG. 3, the slope is (Ra + Rb), and the intercept is a straight line of the lower limit heat quantity QL / energization time T.

  Based on this, the control device 9 will be described. The control device 9 is a computer equipped with a well-known RAM, ROM, CPU, etc., and is connected to the air cylinder 4, the voltage measurement sensor 6, the current measurement sensor 7, the welding transformer 8, and the like to control these operations. Thus, the entire welding apparatus 1 is controlled. As illustrated in FIG. 2, the control device 9 includes a display unit 21, a storage unit 22 as a storage unit, a calculation unit 23, an inspection unit 24, and the like. The display unit 21 has a function of displaying the energization time of the welding current, the setting state of the resistance welding apparatus 1, the determination result of the welding quality of the wire that has been welded as will be described later by the inspection unit 24, and the like. ing.

  The storage unit 22 has a unit upper limit calorie qU per unit conductor area given to the core of the electric wire, a unit lower limit calorie qL per unit conductor area given to the core of the electric wire, and a resistance component (Ra + Rb) of the pair of electrodes 5a and 5b. Are stored in advance. The unit upper limit calorie qU and the unit lower limit calorie qL are an upper limit and a lower limit of a calorie range per unit conductor area given to the electric wire core wire so that a good fixing force can be obtained.

  The calculation unit 23 calculates the measured power consumption P = IV from the measurement voltage V measured by the voltage measurement sensor 6 and the welding current I measured by the current measurement sensor 7, and calculates the upper limit power consumption PU and the lower limit power consumption PL. To do. The inspection unit 24 compares the obtained measured power consumption P with the upper limit power consumption PU and the lower limit power consumption PL, and as shown in FIG. 5, the measured power consumption P falls within the range of the upper limit power consumption PU and the lower limit power consumption PL. If it is within the range, it is determined to be a non-defective product, and if it exceeds the upper limit power consumption PU, it is determined to be over-welded and defective, and if it falls below the lower limit power consumption PL, it is determined to be non-welded and defective.

  Next, detailed operation of the resistance welding apparatus 1 described in the above outline will be described with reference to FIGS. The resistance welding apparatus 1 is set to any one of a welding current setting mode for setting the welding current I by operation of the operation panel 14 and a manufacturing mode for performing resistance welding of the electric wire to determine whether the product is good or defective. it can. When the welding current setting mode is selected by operating the operation panel 14, the control device 9 starts the welding current setting process shown in FIG. 6 and first inputs the total conductor area S and the energization time T of the electric wire to be welded. A screen is displayed on the display unit 21 (step S1). When the operator inputs the total conductor area S or the like using the operation panel 14 in accordance with this display, the calculation unit 23 functions as a heat amount calculation means, and the total upper limit heat amount qU stored in the storage unit 22 is input. The upper limit heat quantity QU is obtained by multiplying the conductor area S, and the lower limit heat quantity QL is obtained by multiplying the unit lower limit heat quantity qL by the total conductor area S (step S2). That is, in step S2, the intercept of the upper limit power consumption PU and the lower limit power consumption PL is obtained.

  Thereafter, the operator superimposes core wires of a plurality of electric wires as sample products between the pair of electrodes 5a and 5b and holds the core wires by the electric wire setting jig 12, and then operates the energizing button on the operation panel 14. Then, the control device 9 controls the air cylinder 4 to move one electrode 5a toward the other electrode 5b, and pressurizes these core wires with the pair of electrodes 5a and 5b (step S3). Thereafter, the control device 9 starts the welding timer 13 and at the same time controls the welding transformer 8 to pass the welding current I between the electrodes 5a and 5b to energize it (step S4). When this welding current I flows through the contact resistance Rt, heat is generated between the electrodes 5a, 5b and the core wire, and the core wires are thermocompression-bonded (or diffusion-bonded) to each other by this heat and resistance welding is performed.

When the welding current I is energized, the control device 9 measures the measurement voltage V and the welding current I using the voltage measurement sensor 6 and the current measurement sensor 7 (step S5). Thereafter, when the energization time T when the welding timer 13 is input is reached, the calculation unit 23 of the control device 9 functions as a threshold setting means and an addition means, and stops energization of the welding current I (step S6). Thereafter, the control device 9 divides the upper limit heat quantity QU and the lower limit heat quantity QL obtained in step S2 by the input energization time T to convert to power consumption, and the electrodes 5a and 5b input to the values converted to power consumption. A value obtained by multiplying the resistance component (Ra + Rb) by the measured welding current I ² is added to obtain an upper limit power consumption PU and a lower limit power consumption PL (step S7).

The (Ra + Rb) × I ² is an increase in power consumption caused by the welding current I flowing through the resistance component (Ra + Rb) of the electrodes 5a, 5b, and is a value that varies according to the welding current I. In step S7, the upper limit heat quantity QU / energization time T and the lower limit heat quantity QL / energization time T are set and stored as temporary upper limit power consumption and temporary lower limit power consumption (= temporary upper limit threshold, temporary lower limit threshold), and resistance components ( A value obtained by adding the power consumption (Ra + Rb) × I2 generated when the welding current I flows to Ra + Rb) is defined as the upper limit power consumption PU and the lower limit power consumption PL.

  Thereafter, the control device 9 obtains the measured power consumption P = VI from the measured voltage V and welding current I measured in step S5 (step S8), and the measured power consumption P is within the upper limit power consumption PU and lower limit power consumption PU. If there is (Yes in Step S9), the display unit 21 is notified that the joining conditions such as the welding current I are appropriate (Step S10), and the process is terminated. On the other hand, when the measured power consumption P exceeds the upper limit power consumption PU (N in step S9 and Y in step S11), the control device 9 notifies the display unit 21 by displaying the welding current I so as to decrease it. (Step S12), and the process ends. Further, when the measured power consumption P is lower than the lower limit power consumption PL (N in step S9 and N in step S11), the control device 9 notifies the display unit 21 by increasing the welding current I or the like. (Step S13), and the process ends.

  On the other hand, when the manufacturing mode is selected by operating the operation panel 14, the control device 9 starts the manufacturing process shown in FIG. In FIG. 7, steps equivalent to the welding current setting process shown in FIG. 6 described above are denoted by the same reference numerals and description thereof is omitted. When the manufacturing process starts, the control device 9 performs steps S1 to S8 similar to the welding current setting process. Thereafter, the inspection unit 24 of the control device 9 functions as an inspection unit, and if the measured power consumption P is within the range between the upper limit power consumption PU and the lower limit power consumption PL (Y in step S9), a display unit indicating that the product is a non-defective product. 21 and so on (step S14), and the process returns to step S3. On the other hand, when the measured power consumption P exceeds the upper limit power consumption PU or falls below the lower limit power consumption PL (N in step S9), the control device 9 displays on the display unit 21 that the product is defective. (Step S1), and the process ends.

According to the first embodiment described above, the measured upper power consumption (= QU / T) and lower limit power consumption (QL / T) of the measured power consumption P generated by the resistance components Ra and Rb of the pair of electrodes 5a and 5b, respectively. The value obtained by adding the increment (= (Ra + Rb) × I ² ) is set as the upper limit power consumption PU and the lower limit power consumption PL, and the welding state based on the comparison between the upper limit power consumption PU, the lower limit power consumption PL, and the measured power consumption P Perform the inspection. Therefore, even if the contact resistance Rt between the electrodes 5a and 5b and the electric wire is reduced depending on the state of the electrodes 5a and 5b and the resistance component (Ra + Rb) of the electrodes 5a and 5b becomes a non-negligible magnitude, the resistance of the electrodes 5a and 5b Since the threshold value can be set in consideration of the increase in the measured power consumption P due to the component (Ra + Rb), the welding state can be accurately inspected regardless of the state of the electrodes 5a and 5b.

Moreover, according to 1st Embodiment mentioned above, while the control apparatus 9 multiplies the unit upper limit calorie | heat amount qU by the total conductor area S and calculates | requires upper limit calorie | heat amount QU (= qUxS), the unit lower limit calorie | heat amount qL adds to the total conductor area. Multiply S to obtain the lower limit heat quantity QL (= qL × S), convert the obtained upper limit heat quantity QU into power consumption QU / T and set it as the temporary upper limit power consumption, and set the obtained lower limit heat quantity QL to power consumption QL / Converted to T and set as the temporary lower limit power consumption, and (Ra + Rb) × I ² is added to the temporary upper limit power consumption (= QU / T) and the temporary lower limit power consumption (= QL / T). Even if the total conductor area S of the electric wire is changed, the welding state can be accurately inspected.

  Moreover, according to 1st Embodiment mentioned above, when the control apparatus 9 has the measurement power consumption P in the range of upper limit power consumption PU and lower limit power consumption PL at the time of welding current setting mode, welding current I is optimal. If the upper limit power consumption PU is exceeded, a notification is made to decrease the welding current I. If the lower limit power consumption PL is below the lower limit power consumption PL, a notification is made to increase the welding current I. Is in the range of the upper limit power consumption PU and the lower limit power consumption PL, it is notified that it is a non-defective product, and if it is below the lower limit power consumption PL or exceeds the upper limit power consumption PU, it is notified that it is a defective product. Therefore, the optimum welding current I can be set in the welding current setting mode, and defective products can be rejected in the manufacturing mode.

Second Embodiment Next, a second embodiment will be described. Since the configuration of the resistance welding apparatus 1 in the second embodiment is the same as that of the first embodiment, detailed description thereof is omitted. In the first embodiment described above, the measured power consumption P is obtained from the measured voltage V and the welding current I, and the obtained measured power consumption P is compared with the upper limit power consumption PU and the lower limit power consumption PL. However, the present invention is not limited to this. For example, the measurement voltage V, the upper limit voltage VU, and the lower limit voltage VL may be compared to inspect non-defective / defective products.

In this case, the upper limit voltage VU and the lower limit voltage VL can be set by the following equations (3) and (4).
Upper limit voltage VU = QU / (T × I) + (Ra + Rb) × I (3)
Lower limit voltage VL = QL / (T × I) + (Ra + Rb) × I (4)
As described above, QU: upper limit heat amount, QL: lower limit heat amount, T: energization time, I: welding current, Ra: resistance component of electrode 5a, Rb: resistance component of electrode 5b.

  According to the above-described equations (3) and (4), QU / (T × I) and QL / (T × I) are increments of the measurement voltage V generated by the resistance components of the pair of electrodes 5a and 5b. A value obtained by adding (Ra + Rb) × I is defined as an upper limit voltage VU and a lower limit voltage VL.

  Next, the present inventors prepare a plurality of sample products composed of a plurality of electric wires, respectively join the plurality of sample products using the resistance welding apparatus 1, and measure the welding current I-measurement voltage V. While plotting the measured voltage V against the welding current I, the upper limit voltage VU and the lower limit voltage VL were plotted. The results are shown in FIG. As is clear from FIG. 8, if the measured voltage V is within the range of the upper limit voltage VU and the lower limit voltage VL, it is determined to be a non-defective product, and if the measured voltage V exceeds the upper limit voltage VU, it is determined to be overwelded and defective. It can be seen that if the voltage is lower than the lower limit voltage VL, it is not welded and it is determined as a defective product (see FIG. 9).

  Next, detailed operation of the resistance welding apparatus 1 in the second embodiment will be described below with reference to FIGS. 10 and 11. Similar to the first embodiment, the resistance welding apparatus 1 includes a welding current setting mode for setting the welding current I by the operation of the operation panel 14 and a manufacturing mode for performing resistance welding of the electric wire to determine a good product or a defective product. And can be set to either mode. When the welding current setting mode is selected by operating the operation panel 14, the control device 9 starts the welding current setting process shown in FIG. In FIG. 10, steps equivalent to the welding current setting process shown in FIG. 6 described above are denoted by the same reference numerals and description thereof is omitted.

  When the welding current setting process starts, the control device 9 performs steps S1 to S6 similar to the welding current setting process described in the first embodiment. Thereafter, the control device 9 converts the upper limit heat quantity QU and the lower limit heat quantity QL obtained in step S2 by the input energization time T and the measured welding current I, and converts them to the measured voltage V, and then measures. A value obtained by multiplying the resistance component (Ra + Rb) of the electrodes 5a and 5b input to the value converted into the voltage V and the measured welding current I is added to obtain an upper limit voltage VU and a lower limit voltage VL (step S16).

  The above (Ra + Rb) × I is a voltage drop caused by the welding current I flowing through the resistance component (Ra + Rb) of the electrodes 5a, 5b, and is a value that varies according to the welding current I. In step S16, the upper limit heat quantity QU / (welding current I × energization time T) and the lower limit heat quantity QL / (welding current I × energization time T) are obtained as temporary upper limit voltage and temporary lower limit voltage, and the resistance component (Ra + Rb) is obtained. The upper limit voltage VU and the lower limit voltage VL are values obtained by adding a voltage drop (Ra + Rb) × I caused by the welding current I flowing.

  After that, if the measured voltage V measured in step S5 is within the range of the upper limit voltage VU and the lower limit voltage VL (Y in step S17), the control device 9 displays that the joining conditions such as the welding current I are appropriate. The information is displayed on the unit 21 (step S18), and the process is terminated. On the other hand, when the measured voltage V exceeds the upper limit voltage VU (N in step S18 and Y in step S19), the control device 9 notifies the display unit 21 by displaying it on the display unit 21 so as to decrease the welding current I. (Step S20), the process ends. Further, when the measured voltage P is lower than the upper limit voltage VU (N in step S18 and N in step S19), the control device 9 notifies the display unit 21 so as to increase the welding current I. (Step S21), the process ends.

  On the other hand, when the manufacturing mode is selected by operating the operation panel 14, the control device 9 starts the manufacturing process shown in FIG. In FIG. 11, steps equivalent to the welding current setting process shown in FIG. 10 described above are denoted by the same reference numerals and description thereof is omitted. When the manufacturing process starts, the control device 9 performs steps S1 to S6 and S16 similar to the welding current setting process. Thereafter, if the measurement voltage V is within the range between the upper limit voltage VU and the lower limit voltage VL (Y in step 17), the inspection unit 24 of the control device 9 notifies the display unit 21 that it is a non-defective product. Then (step S22), the process returns to step S3. On the other hand, when the measured voltage V exceeds the upper limit voltage VU or is lower than the lower limit voltage VL (N in step S17), the control device 9 notifies the display unit 21 that the product is defective. (Step S23), and the process ends.

  According to the second embodiment described above, the non-defective product and the defective product can be inspected from the measurement voltage V itself.

  Further, in the first embodiment described above, the measured power consumption P is obtained from the measured voltage V and the welding current I, and the obtained measured power consumption P is compared with the upper limit power consumption PU and the lower limit power consumption PL. Although defective products have been inspected, the present invention is not limited to this. In addition, for example, the measured calorific value Q ′ per unit time is obtained from the measured voltage V and the welding current I, and the obtained measured calorific value Q ′ is compared with the upper limit calorific value QU ′ and the lower limit calorific value QL ′. It is also possible to inspect non-defective / defective products.

The upper limit heat generation amount QU ′ and the lower limit heat generation amount QL ′ are obtained from the following formulas (5) and (6).
Upper limit calorific value QU ′ = QU ′ + 0.24 × (Ra + Rb) × I ² (5)
Lower limit calorific value QL ′ = QL ′ + 0.24 × (Ra + Rb) × I ² (6)

  Further, the above-described embodiments are merely representative forms of the present invention, and the present invention is not limited to the embodiments. That is, various modifications can be made without departing from the scope of the present invention.

1 Resistance welding equipment 6 Voltage measurement sensor (voltage measurement means)
9 Control device (first notification means, second notification means)
14 Operation panel (input means)
22 Storage unit (storage means)
23 Calculation unit (adding means, heat quantity calculating means, threshold setting means)
24 Inspection Department (Inspection means)

Claims (4)

A plurality of electric wires are held between the pair of electrodes in a state where they are pressed in a direction approaching each other, a welding current is passed between the pair of electrodes, and resistance heating due to the conduction of the welding current is used to In the quality control method of resistance welding in which wires are thermocompression bonded together,
A measurement step of measuring a voltage generated between the pair of electrodes when the welding current is applied;
Based on a comparison between a measured value that is one of the measured pair of interelectrode voltages or a value obtained from the measured pair of interelectrode voltages and the welding current, and an upper threshold and a lower threshold, The inspection process for inspecting the welding state is sequentially performed,
Prior to the inspection step, a value obtained by adding an increment of the measured value generated by the resistance component of each of the pair of electrodes to a preset upper limit threshold and a temporary lower limit threshold that are set and stored in advance is referred to as the upper limit threshold and the lower limit threshold. A quality control method for resistance welding, characterized by performing an adding step. The quality control method for resistance welding according to claim 1, wherein the increment of the measured value to be added is a value that varies according to the welding current. A plurality of electric wires are held between the pair of electrodes in a state where they are pressed in a direction approaching each other, a welding current is passed between the pair of electrodes, and resistance heating due to the conduction of the welding current is used to In resistance welding equipment that thermocompresses wires together,
Voltage measuring means for measuring a voltage generated between the pair of electrodes when the welding current is applied;
Based on a comparison between a measured value that is one of the measured pair of interelectrode voltages or a value obtained from the measured pair of interelectrode voltages and the welding current, and an upper threshold and a lower threshold, Inspection means for inspecting the welding state;
Adding means for setting the upper limit threshold and the lower limit threshold to a value obtained by adding the increment of the measurement value generated by the resistance component of each of the pair of electrodes to the preset upper limit threshold and the temporary lower limit threshold stored;
A resistance welding apparatus comprising: Storage means for storing in advance a unit upper limit heat amount per unit conductor area given to the electric wire, a unit lower limit heat amount per unit conductor area given to the electric wire, and a resistance component of a pair of electrodes
Input means for inputting a total conductor area of the plurality of electric wires;
A calorie calculating means for multiplying the unit upper limit calorie by the total conductor area to obtain an upper limit calorie, and multiplying the unit lower limit calorie by the total conductor area to obtain a lower limit calorie,
A value obtained by converting the obtained upper limit heat amount into the measured value is set and stored as the temporary upper limit threshold value, and a value obtained by converting the obtained lower limit heat amount into the measured value is set and stored as the temporary lower limit threshold value. Threshold setting means;
The resistance welding apparatus according to claim 3, further comprising:

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