DE102016110813A1 - Welding head and method for resistance welding - Google Patents

Abstract

A welding head for a resistance welding device and a method for resistance welding with an electrode holder (14), an electrode (12), a bearing device, over which the electrode holder (14) and the electrode (12) in a receptacle of the welding head (10 ) are stored, and a drive unit described. The electrode holder (14) is rotatably supported by the bearing device about the longitudinal axis of the electrode (12) in the receptacle, wherein the bearing device is a needle bearing. The electrode holder (14) and the electrode (12) are rotatable via the drive unit, wherein the electrode holder (14) and the electrode (12) are rotated by the drive unit about the longitudinal axis of the electrode (12) during a welding operation, to glue the Prevent electrode (12).

Description

A welding head for a resistance welding device with an electrode holder, an electrode, a bearing device, via which the electrode holder and the electrode are mounted in a receptacle of the welding head, and a method for resistance welding are described.

In resistance welding, two electrically conductive workpieces are connected to one another by means of electric current, which is conducted via two opposing electrodes, wherein the workpieces are heated in their connection region by the current flow and enter into a connection.

There are other types of resistance welding. When connecting two workpieces via two opposite, essentially rod-shaped or cylindrical electrodes, the problem frequently arises that the contact surfaces of the electrodes, in particular the electrode, via which the current is introduced, become dirty. The fouling arises, for example, by adhesion of the material of one of the workpieces. After multiple resistance welding then the electrode must be cleaned or replaced. This leads to downtime and increased costs.

DE 10 2006 035 147 A1 discloses a method and apparatus for electrically pulsed workpiece welding, wherein the welder comprises a power source and deliverable electrodes. The workpieces are placed flat on each other for welding and welded to at least one electrode, which has a reduced current-carrying contact surface to the workpiece. As a result, the weld hump previously required for pulse welding can be dispensed with. This in DE 10 2006 035 147 A1 disclosed method is particularly suitable for workpieces or sheets of metallic materials with oxide surfaces, wherein the existing at the contact points between the sheets of oxide layer increases the contact resistance and ensures a temperature increase, which is favorable for the weld. The oxide layer located on the outer workpiece surfaces may be removed prior to or during the welding operation, thereby improving the passage of current from the electrodes to the workpieces. For this purpose, the welding device can have a rotating device or the like, with which the oxide layer can be destroyed and removed via a movement of the pressed-on electrodes.

However, the turning device is from DE 10 2006 035 147 A1 just one way to remove the oxide layer. Instead of a rotating device, a vibrating device and the like may be provided.

A disadvantage of the device known from the prior art and the method, however, is that the rotating device is maintenance-intensive. In order to achieve insulation of the current-carrying electrode and the electrode holder, a plastic sleeve is provided in the prior art. Within the plastic sleeve of the electrode holder is slidably mounted to allow a Nachsenken the electrode holder with the electrode. However, in the course of time, damage to the plastic occurs and thus a great play between the electrode holder and the plastic sleeve, which is provided in a corresponding receptacle of a welding head.

Especially when a subsequent lowering of the electrode, the plastic sleeve is damaged by the relative movement of the electrode holder to the plastic sleeve. The plastic sleeve must then be replaced. This leads to significant downtime and increased costs.

The object is therefore to provide a welding head for a device for resistance welding and a method for resistance welding, wherein contamination of the electrode is prevented, and wherein a reliable and backlash-free displacement of the electrode holder and the electrode are provided without damaging a bearing device.

The object is achieved by a welding head with the technical features specified in claim 1 and by a method having the technical features specified in claim 7. Advantageous developments are specified in the dependent claims in detail.

• – ist der Elektrodenhalter über die Lagereinrichtung drehbar um die Längsachse der Elektrode in der Aufnahme gelagert, wobei die Lagereinrichtung ein Nadellager ist, und
• – der Elektrodenhalter und die Elektrode sind über die Antriebseinheit drehbar.

In a welding head for a resistance welding device which achieves the above object, comprising an electrode holder, an electrode, a bearing device via which the electrode holder and the electrode are mounted in a receptacle of the welding head, and a drive unit,

• - The electrode holder is rotatably mounted about the bearing means about the longitudinal axis of the electrode in the receptacle, wherein the bearing means is a needle bearing, and
• - The electrode holder and the electrode are rotatable via the drive unit.

About the needle bearing play-free storage of the electrode holder is ensured without causing damage to the storage device for the electrode holder. Therefore, can the welding head can be used for a long period of time. The maintenance intervals for the welding head are thereby extended considerably. In addition, a needle bearing allows a lowering movement of the electrode holder and thus a relative, coaxial movement of the electrode holder to the needle bearing, without causing damage to the needle bearing. In conventional storage facilities for a welding head, there is often a tilting and thus damage to the bearing device, which is usually designed as a plastic sleeve. The electrode holder is made of a metal and can easily damage the plastic sleeve. In particular, high temperatures occur during a welding operation. The high temperatures represent an additional burden for plastic sleeves of the prior art. A metal needle roller bearing, however, is not stressed as much by high temperatures as plastic sleeves.

Depending on the design of the needle bearing, in the welding head described herein, coaxial movement of the electrode holder relative to the needle bearing may be performed without damaging the needle bearing.

The storage of the electrode holder via the needle bearing thus ensures over a long period a backlash-free lowering of the electrode holder and twisting of the electrode holder with the electrode. In particular, the welding head allows a rotation of the electrode holder and the electrode in a welding operation, so that sticking of the electrode during the welding process is prevented. At the same time, the electrode is kept clean by the rotational movement, which also extends the cleaning intervals of the electrode. In addition, the electrode must therefore be replaced less frequently, which has a cost effective.

The rotational speed of the electrode may, for example, be in the range between 5 and 20 rpm. The rotation itself is not intended to introduce heat into the connection and can therefore be relatively low. This also results in fewer loads for the needle roller bearing.

In other embodiments, the welding head may have insulation over which the electrode holder and the electrode are electrically insulated from the receptacle of the welding head.

In this case, the insulation may be formed by at least one component of the needle bearing. The needle bearing is usually made of components from a specially designed metal. Needle roller bearings are known from the prior art, wherein, depending on the design of the welding head, especially with regard to the currents and dimensions used, a corresponding needle roller bearing is selected. Likewise, the insulation is to be determined by the at least one component of the needle roller bearing as a function of the current intensity and the dimensions of the welding head or the electrode and the electrode holder.

The needle bearing may comprise an inner ring, a cage and an outer ring and arranged over the cage between the inner ring and the outer ring rolling elements, so-called needle rollers, wherein the outer ring consists of an electrically insulating material or at least one electrically insulating layer. The insulation over the outer ring of the needle bearing, the insulation is not directly in contact with the electrode holder. The effect of heat on the insulation is therefore lower than in the case of insulation over the inner ring of a needle bearing.

The welding head may further comprise a lowering device, via which the electrode holder and the electrode are displaceable along the longitudinal axis of the electrode. The electrode holder is preferably biased by a spring on a housing part of the welding head. In a welding operation, the welding head is positioned so that the upper electrode rests on a workpiece. As the workpiece softens during welding, it is necessary to re-countersink in order to continue the welding process with the set parameters (current, voltage). Without a counterbore, the resistance would change, causing no sufficient heating for the connection of the workpieces takes place. The prestressed spring causes a retraction of the electrode holder, so that essentially the introduced amount of energy remains the same.

For the current transfer between the electrode holder, which is electrically conductive and electrically conductively connected to the electrode, and a stationary, non-rotatable current transfer element, a contact disc or current transfer disc is provided in other embodiments, which consists of a graphite-copper alloy. The contact disk enables reliable power transmission from the stationary power transmission element to the electrode holder without damaging the contact disk over a long period of time. A pure copper disk would be heavily worn even at low rotational speeds. A contact disk made of a graphite-copper alloy allows a rotation of the electrode holder, without causing a fusion of the components ( Power transmission element and electrode holder) comes together.

The contact disk has an opening through which a drive element of the drive unit is guided. The drive element may additionally have an electrical insulation.

A needle bearing is particularly suitable for the rotatable mounting of the electrode holder and for a coaxial, relative movement of the electrode holder to the needle bearing. The re-sinking in a welding process is usually in a range of 1 to 0.1 mm.

A welding head furthermore additionally has cooling channels for a cooling liquid, for example water, via which the electrode and the electrode holder are cooled during a welding operation. In addition, the welding head has a supply for the power supply to the electrode. Preferably, the supply is from above through a central opening. So that no voltage is applied to the housing of the welding head, the housing sections and storage facilities are correspondingly insulated. Such insulations are known as cooling channels for electrode holder and electrode from the prior art.

The above object is also achieved by a method for resistance welding with a welding head according to one of the variants described above, wherein the electrode holder and the electrode are rotated about the longitudinal axis of the electrode via the drive unit during a welding operation.

For this purpose, reference is already made to the procedural aspects of the above description. Preferably, the twisting of the electrode holder and the electrode takes place at a speed of 6 rpm.

However, in other preferred embodiments, the rotational speed of the electrode holder and the electrode may be between 5 and 20 rpm.

Further advantages, features and embodiments will become apparent from the following description of the figures of non-limiting embodiments to be understood.

In the drawings shows:

1 a schematic representation of a welding head in a perspective view;

2 a schematic sectional view of the welding head of 1 ;

3 a further schematic sectional view through components of the welding head of 1 ;

4 a further schematic sectional view through an electrode holder, an electrode and a needle bearing of the welding head of 1 ;

5 a schematic sectional view through a needle bearing of the welding head of 1 ;

6 a further schematic sectional view through a needle bearing for a welding head of 1 ;

7 a schematic plan view of the welding head of 1 ; and

8th a schematic plan view of an electrode holder of the welding head of 1 ,

Substantially numbered components in the drawings essentially correspond to each other unless otherwise specified. Furthermore, it is not intended to describe ingredients which are not essential to the understanding of the teachings disclosed herein.

1 schematically shows a perspective view of a welding head 10 , The welding head 10 has a housing 16 with an upper housing part 29 and a lower housing part 28 on. In addition, the welding head points 10 still further housing sections and connecting elements for arrangement on a welding device, via which a displacement of the welding head 10 for resistance welding.

In the presentation of 1 is the electrode led out from below 12 shown. In addition, there is a channel 18 shown for cooling by means of a cooling liquid during the welding process.

2 shows a schematic sectional view through the welding head 10 from 1 , In 2 are also channels 18 represented, via which a cooling of the electrode holder 14 and the electrode 12 takes place by means of a cooling liquid during a welding process.

The welding head 10 has one in the lower housing part 28 mounted electrode holder 14 and an electrode received therein 12 on. The power supply to the electrode 12 takes place via a contact disc, not shown. The electrode holder 14 is via a needle bearing 30 in a corresponding receptacle of the lower housing part 28 stored. The electrode holder 14 has one of a ring at its upper end 42 surrounded bearing surface 22 on. The opposite housing section has a contact surface 20 on. Between the contact surface 20 and the bearing surface 22 is arranged a spring, not shown. The spring mounted therebetween serves to lower the electrode holder 14 and the electrode 12 during a welding operation, when the material yields to the workpieces to be joined due to the heating. During a welding process, the workpieces heat up strongly in their connection area, which leads to material softening. The countersink ensures that the electrical resistance remains essentially the same.

In the opening 26 Components of a drive unit are received, which is a rotation of the electrode holder 14 and the electrode 12 during a welding process. These are not shown in the figures. The drive unit has, inter alia, a drive shaft, which via a driver in a receptacle 40 into the electrode holder 14 attacks.

3 shows an enlarged view of components of the welding head. About the needle bearing 30 and the drive unit, not shown, are the electrode holder 14 and the electrode 12 during a welding process rotatable about the axis A and can in the direction of the arrow 44 be pressed down over the spring (not shown). The electrode holder is corresponding 14 designed so that it can perform a lowering.

The needle bearing 30 consists of an outer ring 32 a cage 34 , an inner ring 36 and four needles 38 that over the cage 34 are stored. The outer ring 32 It is made of a plastic material and thus provides insulation between the lower housing part 28 and the electrode holder 14 as well as the electrode 12 , Due to the design of the needle bearing 30 becomes a long-lasting operation of the welding head 10 ensured. In addition, the needle bearing allows 30 a relative displacement of the electrode holder 14 in the direction of the arrow 44 during a welding operation or putting on and lifting the welding head 10 ,

A possible embodiment of the needle bearing 30 is in the 4 to 6 shown.

The 7 and 8th show further views on which the rotation of the electrode holder 14 and the electrode 12 is apparent. The electrode holder 14 has a recording for this purpose 40 on. In the recording 40 protrudes a driver of the drive unit. The supply of electricity to the contact disk and possibly a water cooling are not hindered.

In resistance welding, the welding head first becomes 10 positioned so that the electrode 12 rests on a first workpiece. Below this workpiece another workpiece and a corresponding counter-electrode are arranged. The electrodes are first moved to each other in a welding operation and press against two interposed workpieces, for example, a force of 2 kN is applied. Subsequently, the actual welding process takes place, with current flowing through the electrode 12 and the workpieces flow to the counter electrode. Due to the resistance of the workpieces, they heat up and form a connection. So that at least the electrode 12 does not adhere to a workpiece or components of the workpiece to the electrode 12 sticking, becomes the electrode during the welding process 12 rotated at a speed between 5 and 20, preferably 6 U / min.

In addition, in the case of resistance welding, the heating of the workpieces results in yielding thereof, in which case the electrode is applied via the prestressed spring 12 the softening of the workpieces takes into account and a compensating movement takes place. When placing the electrode 12 on the workpiece, the spring is biased. The electrode 12 and the electrode holder 14 will be against the force of the spring in the direction of the arrow 44 pushed up. During welding, the workpieces heat up and change into a doughy state in their connection area. The spring then causes a reprinting of the electrode holder 14 together with the electrode 12 , The selection of the spring takes place as a function of the contact pressure with which the electrode 12 , And if necessary, the counter-electrode are pressed onto the workpieces, as well as the material properties of the workpieces to be joined together.

This ensures that the resistance during resistance welding is kept substantially constant. This is particularly important because deviations of the electrical resistance would not lead to a defined welding result.

In particular, in the resistance welding of components, for example. For a battery, wherein a nickel sponge is to be welded to a nickel strip, a defined reprints during the welding process is required. In conventional prior art welding apparatus, countersinking can also be effected by means of a prestressed spring device, but damage to the bearing device, which is often designed as a plastic sleeve, occurs. This plastic sleeve must then be replaced, resulting in long downtime and costs.

In the welding head described herein, re-countersinking of the electrode holder 14 be carried out without the storage facility, namely the needle roller bearing 30 , is damaged. In addition, the needle bearing allows 30 a backlash-free rotation during the welding process, wherein a gluing of the electrode 12 with the material of the welding article or adhering components thereto to the electrode 12 be prevented.

LIST OF REFERENCE NUMBERS

10

 welding head

12

 electrode

14

 electrode holder

16

 casing

18

 channel

20

 contact surface

22

 bearing surface

24

 channel

26

 opening

28

 housing part

29

 housing part

30

 needle roller bearings

32

 outer ring

34

 Cage

36

 inner ring

38

 needle

40

 admission

42

 ring

44

 arrow

46

 arrow

A

 axis

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006035147 A1 [0004, 0004, 0005]

Claims (8)

Welding head for a resistance welding device with an electrode holder ( 14 ), an electrode ( 12 ), a bearing device, via which the electrode holder ( 14 ) and the electrode ( 12 ) in a receptacle of the welding head ( 10 ), and a drive unit, wherein - the electrode holder ( 14 ) about the bearing means rotatable about the longitudinal axis of the electrode ( 12 ) stored in the receptacle and the bearing device is a needle bearing, and - the electrode holder ( 14 ) and the electrode ( 12 ) are rotatable about the drive unit. Welding head according to claim 1, comprising an insulation, over which the electrode holder ( 14 ) and the electrode ( 12 ) relative to the receiving of the welding head ( 10 ) are electrically isolated. Welding head according to claim 2, wherein the insulation is formed by at least one component of the needle bearing. Welding head according to claim 3, wherein the needle bearing has an inner ring ( 36 ), a cage ( 34 ) and an outer ring ( 32 ) and over the cage ( 34 ) between the inner ring ( 36 ) and the outer ring ( 32 ) arranged rolling elements, and the outer ring ( 32 ) consists of an electrically insulating material or at least one electrically insulating layer. Welding head according to one of claims 1 to 4, comprising a lowering device, via which the electrode holder ( 14 ) and the electrode ( 12 ) along the longitudinal axis of the electrode ( 12 ) are relocatable. Welding head according to one of claims 1 to 5, comprising a contact disk, which consists of a graphite-copper alloy and on the electrode holder ( 14 ) rests. Method for resistance welding with a welding head according to one of Claims 1 to 6, the electrode holder ( 14 ) and the electrode ( 12 ) via the drive unit about the longitudinal axis of the electrode ( 12 ) are rotated during a welding process. Method according to claim 7, wherein the rotational speed of the electrode holder ( 14 ) and the electrode ( 12 ) is between 5 and 20 revolutions per minute.

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