WO2019154925A1

WO2019154925A1 - Method and device for introducing a joint element

Info

Publication number: WO2019154925A1
Application number: PCT/EP2019/053032
Authority: WO
Inventors: Vitalij JANZEN; Dominik FRÖHLICH
Original assignee: Arnold Umformtechnik Gmbh & Co. Kg
Priority date: 2018-02-12
Filing date: 2019-02-07
Publication date: 2019-08-15
Also published as: DE102018202140A1

Abstract

The invention relates to a method for introducing a joint element into at least one workpiece made of a high-strength steel sheet with a tensile strength of more than 700 N/mm², in particular more than 1,200 N/mm and less than 2,200 N/mm², wherein at least the workpiece, which faces the joint element prior to introducing the joint element, is locally heated prior to placing the joint element at the provided joining location, wherein the joint element consists of a material with a bainite microstructure.

Description

Method and device for introducing a joining element

The invention relates to a method for introducing a joining element into at least one workpiece made of high-strength sheet steel, wherein the steel sheet has a tensile strength of more than 700 N / mm ² , in particular more than 1 .200 N / mm ² , and less than 2,200 N / mm ² wherein at least the workpiece facing the joining element prior to insertion is locally heated prior to placement of the joining element at the intended joint.

German Offenlegungsschrift DE 10 2010 024 000 A1 discloses a method for setting non-cutting self-perforating connecting elements in one or more sheets. The sheets are to be heated by electrical energy shortly before the start of the setting process, wherein the heating takes place via an induction coil, which is arranged in the vicinity of a location on the sheet or plates on which the connecting element is placed. The method is suitable for introducing non-cutting self-perforating fasteners in high-strength steel sheets without pre-drilling.

From the German patent DE 196 30 488 C2, a method for joining two overlapping arranged joining parts is known in which prior to joining, for example by clinching, the joining parts are heated contactlessly by means of induction loops. It is also intended to form hold-down as a heating plate and to transfer the heat when placed on the parts to be joined.

With the invention, a method and a device for introducing a joining element to be improved.

According to the invention, a method with the features of claim 1 and a device with the features of claim 8 are provided for this purpose.

In the method according to the invention for introducing a joining element into at least one workpiece made of high-strength steel sheet having a tensile strength of more than 700 N / mm ² , in particular more than 1 .200 N / mm ² , and less than 2,200 N / mm ^{2, it} is provided that the workpiece facing the joining element prior to introduction is locally heated prior to fitting of the joining element at the intended joint and that the joining element consists of a material with bainite structure. Bainite structure is also referred to as Zwischenstufengefüge and gives the joining element in addition to a high strength and very good toughness properties. By a Bainitgefüge or Zwischenstufengefüge are Surprisingly, joining elements made of steel are particularly suitable for being introduced into workpieces made of high-strength sheet steel. A local heating of the workpiece made of high-strength steel sheet facilitates the penetration of the joining element into the workpiece, but by the bainitic structure or interstitial structure of the joining element this is at the same time so temperature stable that the joining element itself is not or only slightly deformed mechanically during insertion. Even if the mechanical properties of the high-strength steel sheet fluctuate over the spatial extent of the intended joint as a result of local heating, a joining element with bainite structure or interstage structure facilitates penetration into the workpiece. The inventive method can be applied to unperforated or pre-punched workpieces.

In a development of the invention, the connection of at least two workpieces is provided by introducing a flow-hole-forming joining element into the workpieces.

For example, in the body shop, two workpieces can be reliably connected to one another by means of the method according to the invention in a very simple and fast manner.

In a further development of the invention, the local heating of the joint is effected by means of induction prior to placement of the joining element.

By means of induction, a very rapid heating of the workpiece can take place in a locally limited area. In a further development of the invention, the local heating of the joint takes place prior to placement of the joining element by means of laser, ultrasound and / or resistive, ie by introducing an electrical current into the workpiece at the intended joint.

Just a heating by means of laser has the advantage that on the one hand the workpiece does not have to be contacted and on the other hand, the introduction of the heat energy can be made obliquely to a joint axis. For example, by means of an obliquely incident laser light beam, the intended joint can be heated and the joining element can already be placed at a small distance immediately in front of the joint.

In a further development of the invention, the placement of a device for heating the joint to the joining element facing the workpiece and the moving away of the Means provided for heating of the joint before the introduction of the joining element.

For example, an induction coil, a heated component, an electrode or even a burner flame can be placed on the joint and before putting the joining element on the joint, the means for heating is moved away again.

In a further development of the invention, the heating of the joining element facing

Workpiece provided at the intended joint within a circular area with a diameter between 7 mm and 13 mm.

In this way, the workpiece facing the joining element can be locally heated extremely limited, it has been found that a diameter of the heated area between 7 mm and 13 mm is completely sufficient for setting a joining element. This is only possible because a wing element consists of a steel material with bainite structure. The mechanical properties of the high-strength steel sheet are changed by the local heating only very local limited in the area of the intended joint.

Workpiece at the intended joint within a maximum of 5 seconds to a temperature between 200 ° C and 1000 ° C provided.

By such a rapid heating can be prevented that the workpiece is heated over a large area. For example, heating within five seconds, in particular within two seconds, in particular within one second to a temperature between 200 ° C. and 1000 ° C., in particular between 200 ° C. and 500 ° C., can be provided. The heating to a temperature between 200 ° C and 1000 ° C readily enough to use a joining element with bainite.

In a further development of the invention, a non-contact temperature measurement of the intended joint during heating and the generation of a start signal for the introduction of the joining element after reaching the predefined temperature are provided.

In this way, a high process reliability is achieved because the joining element is introduced only when the joint has reached the intended temperature. If the intended and predefined temperature has not yet been reached, further heating or automatic reheating is carried out as part of the temperature monitoring Joint causes so that the predefined temperature is reached. This is also called readjustment.

According to the invention, a device is also provided for introducing a joining element into at least one workpiece with the method according to the invention, wherein the device has a device for introducing a joining element and a device for locally heating at least the workpiece facing the joining element at the intended joint.

In addition to the device for local heating, means may be provided for actively and / or passively cooling the device, in particular the hold-down device of the device and other components of the joining system adjoining the heating zone. The hold-down is provided for holding down or pressing together the two workpieces during the joining process. The means for active and / or passive cooling may have cooling rib-like contours on the hold-down device and on other components of the joining system adjoining the heating zone, thereby causing passive cooling. Alternatively or additionally, lines for coolant can also be led through the hold-down device and through further components of the joining system adjoining the heating zone in order to effect active cooling. In the context of the invention, such lines for coolant can of course also be guided around the hold-down or around the hold-down device as well as further components adjoining the heating zone. For example, the combined use of cooling fins in conjunction with the targeted blowing with cooling air is possible. By means of active and / or passive cooling, on the one hand, the life of the device can be extended and, on the other hand, the device can also be operated in continuous operation or continuous use.

In a development of the invention, the device for local heating has at least one induction coil, which is movable relative to the device for introducing the joining element.

In a further development of the invention, the device for heating is movable perpendicular or obliquely to a joining direction of the joining element.

In a development of the invention, the device for heating is movable parallel to a joining direction of the joining element. In a development of the invention, the device for heating has an induction coil which surrounds the joining element in an annular manner.

In a development of the invention, the device for heating has a rod-like element, in particular an induction coil or an electrode, which can be moved through in and against the joining direction by a holder for the joining element in the device for introducing the joining element.

In a further development of the invention, the rod-like element is moved through a hole in a Drehantriebs- and holding mechanism training for the joining element of the device for setting, in other words, the rod-like element is moved through a hole in the joint with the device for introducing the Fügelements.

In a development of the invention, the device for heating has a laser light source or an ultrasound source.

Non-contact heating is possible by means of laser and ultrasound, it being possible, especially in the case of a laser, for the device for heating to be relatively far away from the joint. For example, laser beams can also be directed obliquely onto the joint, so that the joining element can already be arranged in the joining axis and just above the joint. As a result, very short cycle times can be achieved when introducing joining elements.

Further features and advantages of the invention will become apparent from the claims and the following description of preferred embodiments of the invention in conjunction with the drawings. Individual features of the different, illustrated and described embodiments can be combined with one another in an arbitrary manner without exceeding the scope of the invention. This also applies to the combination of individual features with other individual features without the other features with which the individual features are described in context. In the drawings show:

1 to 3 each individual steps of the method according to the invention for introducing a joining element into a workpiece in a schematic representation,

4 to 6 each individual steps of the method according to the invention according to a further embodiment for introducing a joining element into a workpiece in a schematic representation, 7 to 9 each individual steps of the method according to the invention according to a further embodiment for introducing a joining element into a workpiece in a schematic representation,

10 to 12 each individual steps of the method according to the invention for introducing a joining element into a workpiece according to a further embodiment in a schematic representation,

FIGS. 13 to 18 different joining elements for use with the invention

Method,

19 is an exemplary illustration of a bainite structure and

Fig. 20 is a schematic representation of the steps in the introduction of a flow-hole-forming joining element for connecting two workpieces.

Fig. 20 shows schematically the introduction of a joining element in two unperforated workpieces to connect these two workpieces together. In this case, a flow-hole-forming connecting element 10, as for example also shown in FIG. 16, is placed on the joint of two unperforated workpieces. Before placing the joining element, at least the workpiece 12 facing the joining element is locally heated at the joint. At least one of the two workpieces 12, 14 to be joined consists of high-strength steel sheet with a tensile strength of more than 700 N / mm ² , in particular more than 1200 N / mm ² , and less than 2200 N / mm ² . The joining element 10 is made of steel and has a bainite structure or interstage structure.

After placement on the intended joint, the joining element 10 is pressed in the axial direction of the workpiece 12 and simultaneously set in rotation. The non-threaded tip of the threaded element 10 has a polygonal shape with rounded corners. Due to the axial pressure and the simultaneous rotation of the workpiece 12 and at the same time the underlying workpiece 14 in the region of the joint 16 is further heated, so that the rounded tip of the joining element 10 can penetrate into the workpieces 12, 14. This state is shown on the left in FIG. Simultaneously with the penetration of the threadless tip into the workpieces 12, 14, a draft is generated.

As soon as the threaded portion of the joining element 10 penetrates into the workpiece 12, the axial pressure and optionally also the rotational speed of the joining element 10 is reduced. The Threaded portion of the joining element 10 now fear a thread in the previously generated passage of the workpieces 12, 14 a.

This state is shown in Fig. 20 as the second from the left. The threaded portion now feared, as described, a thread in the passage and as a result, the joining element 10 can be screwed into the passage formed and consequently passes through both workpieces 12, 14. This step is in Fig. 20 as the third from the left shown.

The screwing of the joining element is continued until the underside of the head of the joining element 10 rests on the upper side of the upper workpiece 12. As soon as the underside of the head of the joining element 10 touches the upper side of the upper workpiece 12, the joining element 10 is further rotated by a certain angle of rotation to attract the joining element 10 in the threaded hole formed and reliably secure the two workpieces 12, 14 together. This step is shown in Fig. 20 as fourth from the left.

1 to 3 show different process steps during the introduction of the joining element 10 in the superposed workpieces 12, 14. In the state of FIG. 1, the joining element 10 is arranged on the underside of a screw 20. With the screw 20 shown schematically, the joining element 10 can be placed on the joint 16 and rotated. In the state of FIG. 1, the tip of the joining element 10 is still spaced from the joint 16.

A first hold-down 22 is placed in Fig. 1 to the right of the joint 16 on the upper workpiece 12 and a second hold-down 24 is placed on the left of the joint 16 on the top of the workpiece 12. With the hold-downs 22, 24, the upper workpiece 12 is held and pressed against the lower workpiece 14, for example. A support for the lower workpiece 14 is not shown in the schematic representation of FIG. 1 for the sake of clarity.

Both the first hold-down 22 and the second hold-down 24 have at their lower, placed on the workpiece 12 each end a coil 26 and 28, respectively. The two induction coils 26, 28 are current-flowing in the state of FIG. 1 and thereby generate a magnetic field whose field lines are shown schematically in FIG. 1 and designated by the reference numeral 30. The current flow through the induction coils 26, 28 is directed so that the field lines from the first coil 26 through the first workpiece 12 into the second Workpiece and then back into the first workpiece and the second induction coil 28 extend. As a result of the induction, the joint 16 is heated as well. The course of the magnetic field lines 30 is shown schematically only for clarity. It is crucial that the two workpieces 12, 14 are locally heated in the region of the joint 16 by means of the induction coils 26, 28.

Alternatively, the two down holders 22, 24 together form a ring which surrounds the joint 16. At the bottom of this ring then only a single induction coil would be arranged. The magnetic field lines, which are generated by this single induction coil, then run directly through the joint 16 and thus also heat the two workpieces 12, 14 in the region of the joint 16.

According to a further alternative, the joint 16 can be heated by means of a laser light beam 18, which impinges obliquely on the joint 16 in the illustrated embodiment. The joining element 10 is not heated and can already be arranged just above the joint 16.

In the method step according to FIG. 1, therefore, the two workpieces 12, 14 are heated in the region of the joint 16, which is indicated by the warning symbol 32.

In the subsequent state of FIG. 2, the joint 16 is heated, wherein the heated area is indicated by lines 34, between which the workpieces 12, 14 are heated. This area, which surrounds the joint 16, has a diameter which corresponds approximately to the distance of the two downholders 22, 24, and a heating of the workpieces 12, 14 in this area is carried out at a temperature between 200 ° C and 500 ° C. The heating takes place advantageously within only one second.

In the state of Fig. 2, the joining element 10 has been placed on the joint 16 by the screw 20 was moved down. The hold-downs 22, 24 remain in their position in which they rest on the top of the upper workpiece 12. The induction coils 26, 28 are no longer current-carrying, so that no further heating takes place.

Starting from the state of FIG. 2, the joining element 10 is now, as described with reference to FIG. 20, introduced into the two workpieces 12, 14 in order to securely connect them together. The fully inserted state of the joining element 10 is shown in Fig. 3. Subsequent to the state of FIG. 3, both the hold-downs 22, 24 and the screw 20 are lifted and another joining element 10 can be set.

The representations of FIGS. 4 to 6 show steps of a method according to the invention according to a further embodiment of the invention.

According to FIG. 4, a joining element 40, which is shown only schematically as a block, is to be introduced into a workpiece 42. The joining element 40 may be formed, for example, as a punching nut or the like. The joining element 40 is introduced by means of a setting device 44. In the state of FIG. 4, the joining element 40 is still located above the intended joint 46. The setting device has an annular holding-down device 48 which surrounds the joining element 40 and, in the state of FIG. 4, is still located at a short distance from the workpiece 42 , The joining element 40 is made of steel and has a bainite structure or interstage structure.

In order to heat the workpiece 42 before introducing the joining element 40, a device 50 with an induction coil 52 is provided. The device 50 is of annular design and the windings of the coil 52 are parallel to the annular device 50. If the induction coil 52 is traversed by current, a magnetic field 54 is formed, which passes through the workpiece 42 in the region of the joint 46 and thereby heated. The magnetic field 54 is shown only schematically in FIG. 4. The magnetic field lines pass through the coil 52 and heat the workpiece 42 exactly in the region of the joint 46.

In the subsequent step, which is shown in Fig. 5, the device 50 has been moved away laterally from the joint 46 and the joining element 40 is now placed with its underside on top of the workpiece 42. In the region of the joint 46, a heated region 56 has now formed, which is only slightly larger than the joining element or the joining element 40. The hold-down 48 has been lowered onto the upper side of the workpiece 42.

Starting from the state of FIG. 5, the joining element 40 can now be set.

6 shows the state after the setting of the connecting element 40. It can be seen that the joining element 40 now penetrates the workpiece 42 and is now anchored in the workpiece 42 in a manner not shown. When setting the joining element 40, a slug 58 has formed, which is now discharged downward. The hold-down 48 is still sitting on the surface of the workpiece 42 and the setting device 44 is still connected to the joining element 40 in connection. The heating device 50 is arranged unchanged at the side of the joint and also at the side of the hold-down 48. Since the material of the joining element 40 has a bainitic structure, the heating of the workpiece 42 in the region 56 to a temperature between 200 ° and 500 ° is sufficient to be able to easily insert the joining element 40 into the workpiece 42 made of high-strength sheet steel.

Following the state of FIG. 6, the hold-down 48, the setting device 44 and the device 50 are lifted off and another joining process can begin.

FIGS. 7 to 9 show steps of a method according to the invention according to a further embodiment of the invention.

According to FIG. 7, two unperforated workpieces 12, 14 made of high-strength sheet steel are connected to one another by means of a joining element 10, see FIG. 8. The workpieces 12, 14 are pressed against each other by means of a hold-down 60 and the joining element 10 is to be used by means of a screwdriver 62. The screwdriver 62 has a joining bit 64 which is adapted to the drive configuration of the joining element 10.

In the state of FIG. 7 there is still no joining element in the screwdriver 62.

The screwdriver 62 has a through hole which also extends through the joining bit 64 and in which a rod-shaped element 66 is slidably disposed in and opposite to the joining direction. The rod-shaped element 66 can be heated at its lower end. In the state of FIG. 7, the rod-shaped element 66 is placed with its lower end on the intended joint 66. The rod-shaped element 68 is heated shortly before or immediately after fitting at its lower end and thus heats the two workpieces 12, 14 in the region of the intended joint 66. This is indicated by circular-segment-shaped lines 70, which in the workpieces 12, 14 symbolize penetrating heat energy.

By the rod-shaped element 68, the joint 66 can be heated in a locally extremely limited area. As has been stated, this localized area around the intended joint 66 has a diameter of only 7 mm to 13 mm and is heated to a temperature between 200 ° C and 500 ° C within about 1 s.

This heated area around the joint 66 is indicated schematically in FIG. 8. The rod-shaped element 68 may, for example, also be formed as an electrode, in order to effect a flow of current through the joint 66 and thereby a heating of the joint 66. The rod-shaped element can also be designed as an ultrasonic vibrator or rod-shaped inductor to heat the joint 66. After heating the area surrounding the joint 66, the rod-shaped element 68 is retracted again and then, as shown in FIG. 8, the joining element 10 is inserted into the joining bit 64 of the screwdriver 62. The rod-shaped element 68 has been withdrawn so far that the joining element 10 can be inserted into the joining bit 64.

In the state of FIG. 8, the tip of the joining element 10 has already been placed on the joint 66 and can then be introduced into the two workpieces 12, 14 by means of the screwdriver 62 and as explained in connection with FIG.

The hold-down 60 remains unchanged in the position in which he presses the two workpieces 12, 14 against each other.

In the subsequent state of FIG. 9, the joining element 10 passes through the two workpieces 12, 14 completely. In the region of the joint 66 has in the two workpieces 12, 14 a

Passage formed in which the joining element 10 now, as explained with reference to FIG. 20, is anchored.

Subsequent to the state of FIG. 9, the hold-down device 60 and the screwdriver 62 can then be lifted off the joining element 10 and a further joining process can begin. FIGS. 10 to 12 show several steps of a method according to the invention according to a further embodiment.

A joining element 40, see Fig. 1 1, is to be introduced with a setting device 44 in an unperforated workpiece 42 made of high-strength steel. The joining element 40 is formed, for example, as a punch nut, made of steel and has a bainite structure or interstage structure.

In the state of FIG. 10, the joining element 40 is not yet in the setting device 44. A device for heating 70 radially surrounds the setting device 44 and is arranged between the setting device 44 and a hold-down 48. The heating device 70 may include, for example, induction coils to locally heat the workpiece 42. The Device 70 can be displaced relative to the setting device 44 in and against the joining direction. The hold-down 48 surrounds the setting device 44 and the device 70 in the radial direction. The workpiece 42 rests on a base 72. The base 72 may be an anvil, a die, or a support structure for the joining operation. The holding-down device 48, the setting device 44 and also the device 70 for heating can be provided with means not shown in FIG. 10 for the active and / or passive cooling of the hold-down 48, the setting device 44 and / or the device 70. These can be realized, for example, by means of lines through which cooling liquid flows, cooling fins and / or cooling fans. By means of active and / or passive cooling, the life of the device is increased and a continuous operation becomes possible.

In the state of Fig. 10, the means 70 for heating has been lowered so far that it contacts the top of the workpiece 42, if required by the type of heating or the heating mechanism. Induction coils in the device 70 are now energized, so that the workpiece 42 is heated by a magnetic field 74.

In the state of FIG. 11, the joining element 40 has now been introduced into the setting device 44, and the joining element 40 rests with its underside on the upper side of the workpiece 42. An area 76 of the workpiece 42 was heated.

Starting from the state of FIG. 1 1, the joining element 40 can now be set. The set state of the joining element 40 is shown in FIG. 12. When setting the joining element 40, a slug 78 can form, which is discharged downwards.

As can be seen with reference to FIGS. 10 to 12, the setting device 44 can be displaced relative to the device 70 in and against the joining direction. This makes it possible first to heat the workpiece 42 locally and then to move the setting device 44 inside the device 70 for heating to set the joining element 40 downwards, in the direction of the workpiece 42.

The representations of FIGS. 13 to 18 show various joining elements which can be set with the method according to the invention and the device according to the invention or introduced into workpieces made of high-strength sheet steel.

Fig. 13 shows a Einpresschraube 80. Fig. 14 shows a threaded bolt 82 which is introduced with a punching section 84 in a workpiece on high-strength steel sheet. Fig. 15 shows a punch nut 86.

FIG. 16 shows the already described flow-hole-forming joining element 10.

FIG. 17 shows a punch rivet as a semi-hollow punch rivet 88.

FIG. 18 shows a further punch rivet as a solid punch rivet 90. FIG. 19 shows a microsection of a joining element with bainite structure or interstage structure.

Claims

claims

1. A method for introducing a Fügelements in at least one workpiece made of high strength steel sheet having a tensile strength of more than 700N / mm ^2, in particular more than 1,200N / mm ^2, and less than 2,200 N / mm ^2, wherein at least the, prior to the introduction Fühlement facing workpiece before placing the

Fühlements is locally heated at the intended joint, characterized in that the Fügelement consists of a material with bainite.

2. The method according to claim 1, characterized by connecting at least two workpieces by introducing a flow-hole-forming joining element in the workpieces.

3. The method according to claim 1 or 2, characterized in that the local heating of the joint is effected prior to placement of the joining element by means of induction.

4. The method according to at least one of the preceding claims, characterized by placing a device for heating the joint to the Fügelement facing workpiece and moving away the device for heating of the joint before introducing the joining element.

5. The method according to at least one of the preceding claims, characterized by heating the joining element facing the workpiece at the intended joint within a circular area with a diameter between 7mm and 13 mm.

6. The method according to at least one of the preceding claims, characterized by heating the joining element facing the workpiece at the intended joint within a maximum of five seconds, in particular a maximum of two seconds, in particular a maximum of one second to a temperature between 200 degrees Celsius and 1000 degrees Celsius, in particular between 200 degrees Celsius and 500 degrees Celsius.

7. The method according to at least one of the preceding claims, characterized by non-contact temperature measurement of the provided joint during heating and generating a start signal for the introduction of the Fügelements after reaching a predefined temperature.

8. An apparatus for introducing a joining element into at least one workpiece according to a method according to at least one of the preceding claims, with a device for introducing a joining element and with a device for locally heating at least the before the introduction of the Fügelement facing workpiece at the intended joint.

9. Apparatus according to claim 8, characterized in that the means for local heating comprises at least one induction coil which is movable relative to the means for introducing the Fügelements.

10. Apparatus according to claim 8 or 9, characterized in that the means for heating is movable perpendicular or obliquely to a joining direction of the pad member.

1 1. Apparatus according to claim 8 or 9, characterized in that the means for heating is movable parallel to a joining direction of the pad member.

12. The device according to at least one of claims 8 to 11, characterized in that the means for heating comprises an induction coil which surrounds the Fügelement or a setting device for the joining element annular.

13. The device according to at least one of claims 8 to 11, characterized in that the means for heating a rod-like element, in particular an induction coil or an electrode comprising, in and against the joining direction by a holder for the Fügelement in the device for introducing is movable through the Fügelements.

14. The device according to claim 13, characterized in that the rod-like element is moved through a bore in a rotary drive and holding mechanism training for the Fügelement the device for setting.

15. The device according to at least one of claims 8 to 14, characterized in that means are provided for active and / or passive cooling of the device.