JP2015027680A - Upper electrode device of spot welder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an upper electrode device of a spot welder which can detect precisely inappropriate set states of to-be-welded objects, e.g. steel sheets or nuts, in a spot welder.SOLUTION: An upper-part electrode device of a spot welder holds a to-be-welded object between an upper electrode 1 capable of ascending and descending freely by a cylinder 4 and a fixed lower electrode 2 and performs welding by pressure application and electrification. A potentiometer 6 for measuring a descending position of the upper electrode 1 is provided in the side of the upper electrode. A set defect of the object is detected by providing defect detection means 10 of determining whether or not a measurement of the potentiometer 6 exceeds a threshold value from a reference point, with the descending position of the upper electrode when the object is set in a normal state as the reference point, and generating a defect signal when the measurement exceeds the threshold value.

Description

  The present invention relates to an upper electrode device of a spot welder that can accurately detect an inappropriate set state of an object to be welded such as a steel plate or a nut in a spot welder.

  Conventionally, a spot welder has been widely used to manufacture automobile parts such as a panel in which two steel plates are welded or a nut is welded to a steel plate. This spot welder uses the resistance heat of the workpiece to be melted by setting the steel plate and nut between the upper and lower electrodes between the two steel plates to be welded and applying pressure and energization. Adhere. In general, the steel plate and nut are automatically supplied and the welding process is performed automatically and continuously.

  At this time, if the steel plate and the nut are supplied as scheduled, the welding process is performed without any problem. However, the nut may be supplied in various states other than the normal state, such as being supplied in a state where the nut is displaced, or in a state where there is no steel plate or in a state where they are overlapped. If the welding process is performed in such a state other than the normal state, defective automobile parts are provided, and troubles such as being unable to be assembled in the subsequent vehicle assembly process occur.

Therefore, as shown in Patent Documents 1 to 3, the present applicant has developed and put into practical use a set failure detection device such as various patterns of nuts. These set defect detection devices described in Patent Documents 1 to 3 are all based on the fixed lower electrode 2, and the position displacement of the positioning center pin 3 that moves up and down the center of the lower electrode 2. A defect is detected by measuring the amount.
That is, as shown in FIG. 9, when the position of the center pin 3 when the steel plate (W1) and the nut (W2) are set in a normal state is used as a reference point, for example, the nut (W2) is displaced. In this case, since the center pin 3 does not rise to the normal position, the amount of displacement is negative (see FIG. 10). Further, when the nut (W2) is large, the center pin 3 rises to the normal position or more, so that the displacement amount is positive (not shown). In this way, the amount of displacement of the center pin 3 is measured, and when it exceeds a certain threshold value, it is determined as defective and the supply of defective products to the subsequent process is stopped.

However, in the set defect detection device described in Patent Documents 1 to 3, if a non-standard nut having the same inner and outer diameter and different height is supplied in the state of a double nut, the center pin is Since it rises to the normal position, a normal signal is output even though it is actually defective. Also, when welding steel plates, the upper and lower electrodes with cap tips attached to the tips are used, and there is no center pin. There has been a problem that it cannot be judged as defective when, for example, two steel sheets are in close contact with each other.
On the other hand, since the upper electrode moves up and down to pressurize and energize, the general idea is that it is not suitable for measuring the amount of displacement of the position, and a set defect detection device using the upper electrode has been put to practical use. Not.

JP 2006-21226 A JP 2011-161502 A JP2013-6192A

  The present invention solves the above problems and incorporates a position displacement amount measuring device into the upper electrode, which has been considered inappropriate in the past, to supply a double nut that could not be detected in the past. Spot welder that can detect the inappropriate setting state of workpieces such as steel plates and nuts in spot welders, such as the supply of three-layer steel plates, and can easily set the reference point with a push button It is an object of the present invention to provide an upper electrode device.

  The upper electrode device of the spot welding machine of the present invention made to solve the above-mentioned problem is to sandwich an object to be welded between an upper electrode that can be raised and lowered by a cylinder and a fixed lower electrode, This is an upper electrode device of a spot welding machine that conducts welding by energizing, and a potentiometer that measures the descending position of the upper electrode is provided on the upper electrode side, and the measured value of the potentiometer is in a normal state to be welded. When a lowering position of the upper electrode when set is used as a reference point, it is determined whether or not a threshold value is exceeded from this reference point, and a defect detection means for generating a defect signal when the threshold value is exceeded is provided, This is characterized in that a defective set of an object is detected.

  The potentiometer is installed in parallel with the cylinder, and the detection shaft of the potentiometer is connected to the rod of the cylinder so that the amount of movement of the detection shaft and the rod is equal, and the lowering position of the upper electrode is measured with the potentiometer What is made possible is preferable, and this is the invention according to claim 2.

  Moreover, it is preferable that a center pin that can be moved up and down is built in the center of the lower electrode, and the workpieces are preferably a steel plate and a nut, and this is the invention according to claim 3.

  Moreover, it is preferable that the cap chip | tip is each attached to the front-end | tip of an upper electrode and a lower electrode, and it is preferable that a to-be-welded object is steel plates, and let this be the invention which concerns on Claim 4.

In the invention according to claim 1, an upper electrode device of a spot welder that performs welding by holding an object to be welded between an upper electrode that can be moved up and down by a cylinder and a fixed lower electrode, and performing welding by applying pressure and energization. A potentiometer for measuring the lowering position of the upper electrode is provided on the upper electrode side, and the measured value of the potentiometer is based on the lowering position of the upper electrode when the work piece is set in a normal state. In this case, it is determined whether or not the threshold value is exceeded from this reference point, and a defect detection means that issues a defect signal when the threshold value is exceeded is provided so as to detect a set defect of the work piece. It is now possible to detect set failures such as supply of double nuts and supply of three-layer steel plates, which could not be detected by measurement on the lower electrode side.

  In the invention according to claim 2, the potentiometer is provided in parallel with the cylinder, and the detection shaft of the potentiometer is connected to the rod of the cylinder so that the amount of movement of the detection shaft and the rod is equal, and the upper electrode Since the lowering position of the upper electrode can be measured with a potentiometer, the amount of change in the lowering position of the upper electrode can be accurately measured, and the structure is simple and can be easily incorporated on the upper electrode side.

  Moreover, in the invention which concerns on Claim 3, since the center pin which can be raised-lowered is incorporated in the center part of a lower electrode, and the to-be-welded object is a steel plate and a nut, the double nut of the former which was undetectable conventionally A set failure such as supply or supply of nuts of different heights can be detected.

  Moreover, in the invention which concerns on Claim 4, since the cap chip | tip is each mounted | worn at the front-end | tip of an upper electrode and a lower electrode and the to-be-welded object is steel plates, the two-ply steel plate which was undetectable conventionally It is possible to detect a defective set such as supply.

It is the schematic which shows embodiment of this invention. It is a front view of the electrode device which shows the form which set the steel plate and the nut in the regular state. It is a front view of the electrode apparatus which shows the form with which a steel plate and a nut are inadequately set. It is a front view of the electrode apparatus which shows the form with which a steel plate and a nut are inadequately set. It is a front view of the electrode apparatus which shows the form with which a steel plate and a nut are inadequately set. It is a front view of the electrode apparatus which shows the form which set the steel plates in the regular state. It is a front view of the electrode device in which the steel plate shows a form in which the set is defective. It is a front view of the electrode device in which the steel plate shows a form in which the set is defective. It is explanatory drawing of the principal part which shows the form which set the steel plate and the nut in the regular state with the electrode of the prior art example. It is explanatory drawing of the principal part which shows the form in which a steel plate and a nut are poorly set with the electrode of a prior art example.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic explanatory view of an electrode device showing a form in which a steel plate (W1) and a nut (W2) are set in a regular state, in which 1 is an upper electrode and 2 is a lower electrode. The upper electrode 1 is movable up and down by a cylinder 4, but the lower electrode 2 has a fixed structure. Reference numeral 5 denotes a drive source for the cylinder 4, and the above configuration is basically the same as that of a conventional electrode apparatus of this type of spot welder.
1 to 5 is a type in which a center pin 3 (see FIG. 9) that can be moved up and down for positioning the work piece is inserted in the center of the lower electrode 2. FIG. 8 shows a type in which a cap chip is attached to the tip of an electrode.

A potentiometer 6 for measuring the lowered position of the upper electrode 1 is provided on the upper electrode side, and the measured value of the potentiometer 6 indicates that the upper electrode 1 when the workpiece is set in a normal state. Defect detection means 10 is provided for determining whether or not a predetermined threshold (both ±) is exceeded from the reference point when the lowered position is a reference point, and for generating a defect signal when the threshold is exceeded. Yes.
Conventionally, as a means for detecting the set failure of the work piece, one based on the lower electrode 2 in a fixed state has been common. That is, the defective set is detected by measuring the position displacement amount of the positioning center pin 3 that moves up and down the central portion of the lower electrode 2. However, in this case, there is a problem that a set failure such as supply of a double nut or supply of two or more steel sheets cannot be detected.In the present invention, by using the upper electrode 1 that moves up and down instead of the lower electrode, This makes it possible to detect a set defect of an object to be welded such as supply of a double nut, which could not be detected conventionally. The detection process will be described later.

  The potentiometer 6 is provided in parallel with the cylinder 4. Further, the tip of the detection shaft 6a of the potentiometer 6 is connected to the tip of the rod 4a of the cylinder 4 by the connecting bracket 7, so that the amount of movement of the detection shaft 6a and the rod 4a is equal. ing. As a result, the lowered position of the upper electrode 1 can be accurately measured by the potentiometer 6.

  As the potentiometer 6, a general linear motion variable resistance type can be used. This is because a contact made of a good conductor such as copper or copper alloy is attached to the base end of the detection shaft 6a, and this contact makes the two resistors arranged in parallel in the housing conductive. The lowering position is detected by measuring the partial pressure at that time, and the vertical position can be accurately detected without being affected by the magnetic field generated during welding.

Whether the defect detection means 10 exceeds a predetermined threshold from the reference point (zero point) when the lowering of the upper electrode 1 when the work piece is set in a normal state is set as the reference point (zero point). It is configured to determine whether or not and issue a failure signal when a threshold value is exceeded. The defect detection means 10 is housed in the control unit 11.
In addition, the control unit 11 adjusts the supply controller for the workpiece such as a steel plate and a nut, the supply controller for circulating water for cooling the electrodes, and the timing of clamping and pressurizing and energizing the workpiece. It is the same as in the prior art in that various controllers such as a controller and a controller that receives a defect signal from the defect detection means 10 and instructs the discharge of defective products are housed.

Below, the detection process of the set defect of a to-be-welded object is demonstrated.
2 to 5 show a case where a center pin (see FIG. 9) that can be raised and lowered is built in the center of the lower electrode 2, and a steel plate (W1) and a nut (W2) are welded as objects to be welded. Show.
FIG. 2 shows a form in which a steel plate and a nut are set in a normal state. The lower position (H) of the lower end surface of the upper electrode at this time is used as a reference, and the position measurement value of the detection shaft 6a of the potentiometer 6 in this case is set as a reference point (zero point). If the position measurement value of the potentiometer 6 when the upper electrode 1 is lowered and the workpiece is clamped is zero, it can be determined that the steel plate and the nut are set in a normal state, so the welding process is performed as it is. On the other hand, if the position measurement value of the potentiometer 6 is not zero, it can be determined that the steel plate and the nut are not set in a normal state in principle. However, considering the undulation of the steel plate (W1), it can be determined that the steel plate and the nut are set in a normal state if the position measurement value is within a predetermined numerical range.
Accordingly, a predetermined threshold value is set as an absolute value, it is determined whether or not the position measurement value of the potentiometer 6 exceeds the threshold value, and a defect signal is generated when the threshold value is exceeded. Note that the threshold value can be arbitrarily set at the site corresponding to the product with reference to the following pattern or the like.

FIG. 3 shows a form in which the nut (W2) is set in a state of being supplied twice. In this case, in the case of the detection mechanism using the conventional lower electrode 2, the center pin is raised to the normal position, so that a normal signal is output although it is actually defective.
On the other hand, in the present invention, the lower end surface of the upper electrode stops at a position higher than the normal lowered position (H) by the height (B) of the nut (W2), and as a result, the potentiometer 6 connected to the rod 4a of the cylinder 4 is obtained. Since the detection shaft 6a is also higher than the reference point by (B), the position measurement value of the potentiometer 6 is “B”. Accordingly, if the threshold value is set to a value smaller than “B”, for example, it is determined that the steel plate and the nut are not set in a normal state, and a defect signal can be immediately issued.
In addition to this, for example, even when nuts having the same inner and outer diameters and different heights are set, the detection mechanism using the conventional lower electrode 2 cannot be detected, but according to the present invention, the threshold value is either plus or minus. Or appropriately set as an absolute value to reliably issue a failure signal.

  FIG. 4 shows a configuration in which the nut (W2) is not supplied and only the steel plate (W1) is supplied. In this case, the lower end surface of the upper electrode stops at a position lower than the normal lowered position (H) by the height (B) of the nut (W2), and as a result, the detection shaft 6a of the potentiometer 6 is also moved from the reference point (B ), The position measurement value of the potentiometer 6 is “minus B”.

Moreover, FIG. 5 has shown the form set in the state in which only the nut (W2) was supplied, without supplying a steel plate (W1). In this case, the lower end surface of the upper electrode stops at a position lower than the normal descending position (H) by the thickness (A) of the steel plate (W1). As a result, the detection shaft 6a of the potentiometer 6 is also (A) from the reference point. Therefore, the position measurement value of the potentiometer 6 is “minus A”.
Therefore, in the case of FIGS. 4 to 5, if the threshold value is set to a value smaller than “A” or “B”, it is determined that the steel plate or the nut is not set in a normal state, and the defect is immediately detected. A signal can be emitted. Of course, both can be detected by setting a smaller threshold. 4 to 5 can also be detected by a conventional detection mechanism using the lower electrode 2. FIG.

Next, FIGS. 6 to 8 show cases where cap tips 3a and 3a are attached to the tips of the upper electrode 1 and the lower electrode 2, respectively, and the workpieces are steel plates (W1).
FIG. 6 shows a form in which two steel plates are set in a normal state. In this case, the lowering position (H) of the lower end surface of the upper electrode is used as a reference, and the position measurement value of the detection shaft 6a of the potentiometer 6 in this case is set as a reference point (zero point) as described above. . And if the position measurement value of the potentiometer 6 when the upper electrode 1 is lowered and the workpiece is clamped is zero, it can be determined that the two steel plates are set in a normal state, so the welding process is performed as it is. Do.

  FIG. 7 shows a form in which a total of three steel plates are set by supplying steel plates in close contact with oil. In this case, the lower end surface of the upper electrode stops at a position higher than the normal lowered position (H) by the height (A) of the steel plate (W1). As a result, the detection shaft 6a of the potentiometer 6 connected to the rod 4a Since the position is higher by (A) than the reference point, the position measurement value of the potentiometer 6 is “A”. Therefore, if the threshold value is set to a value smaller than “A”, for example, it is determined that the steel sheet is not set in a normal state, and a defect signal can be immediately issued. Of course, it can also be detected when four or more steel plates are supplied.

FIG. 8 shows a form in which only one steel plate is supplied. In this case, the lower end surface of the upper electrode stops at a position lower than the normal descending position (H) by the thickness (A) of the steel plate (W1). As a result, the detection shaft 6a of the potentiometer 6 is also (A) from the reference point. Therefore, the position measurement value of the potentiometer 6 is “minus A”.
Therefore, in the case of FIGS. 7 to 8, if the threshold value is set to a value smaller than “A”, it is determined that the steel plate is not set in a normal state, and a defect signal can be immediately issued. . Further, since the steel plate (W1) has undulations, it is preferable to set the threshold value to, for example, about “plus or minus A / 2” so as not to generate a failure signal for the undulations. Of course, it is possible to detect the case where the steel plate is not supplied.
7 to 8 cannot be detected by a conventional detection mechanism using the lower electrode 2 because there is no center pin insertion hole in the steel plate.

  As is clear from the above description, the present invention is a device for detecting a set defect of an object to be welded using an upper electrode that has been conventionally considered to be not suitable for measuring the amount of displacement because it moves up and down, A potentiometer for measuring the lowering position of the upper electrode is provided on the upper electrode side, and a defect detection means for determining whether or not the measured value of the potentiometer exceeds a predetermined threshold and generating a defect signal when the threshold is exceeded is provided. It is provided and configured to detect a set failure of the workpiece. And with such a configuration, it is possible to detect set failures such as supply of double nuts, supply of two-layer steel sheets, and insufficient supply of steel sheets, which could not be detected by conventional measurement on the lower electrode side It is possible to achieve a remarkable effect of doing.

DESCRIPTION OF SYMBOLS 1 Upper electrode 2 Lower electrode 3 Center pin 3a Cap chip 4 Cylinder 4a Rod 5 Drive source 6 Potentiometer 6a Detection shaft 7 Connection bracket 10 Defect detection means 11 Control part A Steel plate thickness B Nut height H Upper part in a normal state Lower position of electrode lower end surface W1 Steel plate W2 Nut

Claims (4)

  An upper electrode device of a spot welder that sandwiches an object to be welded between an upper electrode that can be raised and lowered by a cylinder and a fixed lower electrode, and performs welding by applying pressure and energization, A potentiometer that measures the lowering position of the upper electrode is provided, and when the measured value of the potentiometer is the lower electrode's lowering position when the work piece is set in a normal state, the reference point is An upper electrode of a spot welder characterized in that a defect detection means for determining whether or not a threshold value is exceeded and generating a defect signal when the threshold value is exceeded is provided to detect a set defect of the workpiece. apparatus.   A potentiometer is provided in parallel with the cylinder, and the detection shaft of the potentiometer is connected to the rod of the cylinder so that the amount of movement of the detection shaft and the rod is equal, and the lowering position of the upper electrode can be measured with the potentiometer The upper electrode apparatus of the spot welder according to claim 1, which is configured as described above.   The upper electrode device for a spot welder according to claim 1 or 2, wherein a center pin that can be moved up and down is built in the center of the lower electrode, and the workpiece is a steel plate and a nut.   The upper electrode device for a spot welder according to claim 1 or 2, wherein cap tips are respectively attached to the tips of the upper electrode and the lower electrode, and the workpieces are steel plates.

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