METHOD FOR JOINING TWO WORKPIECES

Description

[0001] The invention relates to a method for joining two preferably flat workpieces, in particular two metal sheets, according to the preamble of claim 1.

[0002] Such a method is described, for example, in DE 10 2006 039 718 A1. In known methods of this type, hybrid connections are usually used to join two flat workpieces, for example sheet metal or the like. These hybrid connections use connecting elements such as rivets and a viscous adhesive to connect the workpieces. To join the workpieces, the adhesive is first applied to a joining surface of a workpiece. The two workpieces are then arranged one above the other, defining a gap between them in which the adhesive is arranged. The two workpieces are then fixed to one another using the connecting elements. The adhesive can then harden. When the connecting elements are inserted, air can be forced into the adhesive-filled gap. This can create air chambers or air outlet channels filled with air in the adhesive.These may be exposed to the atmosphere, allowing moisture to penetrate, for example. This makes the connection susceptible to corrosion. Similar problems arise when other connecting elements, such as welded joints, are used instead of the connecting bodies. US 2012 / 0124805 A1 discloses a method for joining workpieces by applying a flat layer of adhesive and additionally creating clinch joints. Excess adhesive is subsequently removed before the clinch joints are created.

[0003] The object of the invention is therefore to further develop a method of the type mentioned at the outset in such a way that a better connection of the workpieces is achieved.

[0004] This problem is solved by the technical teaching of claim 1.

[0005] The basic idea of ​​the present invention is that the amount of adhesive applied per unit length measured in the application direction in the hybrid bonding areas, in which the workpieces are each joined together by means of an additional connecting means, is smaller than the amount of adhesive applied per unit length measured in the application direction in the bonding areas. Therefore, less adhesive is arranged per unit length in the hybrid bonding areas than in the bonding areas in which the workpieces are joined together solely by means of the adhesive. The adhesive arranged in the intermediate gap can be distributed more effectively in the hybrid bonding areas due to the reduced amount of adhesive. This has the effect that less adhesive is required to cover the bonding surfaces than with conventional methods.Furthermore, this has the effect that, when the two workpieces are fixed, the adhesive is distributed evenly and extensively across the hybrid bonding areas and the bonding areas, i.e., across the bonding surfaces. This results in a high degree of adhesive coverage of the bonding surfaces, for example, up to 95%, while simultaneously reducing adhesive consumption. Furthermore, bulging of the workpieces in the bonding areas transverse to the application direction, which is also referred to as "quilting" or "formation of adhesive pockets," can be reduced due to unevenly distributed adhesive quantities. In contrast, in the prior art, a uniform adhesive application or a reduction in the adhesive quantity in the area between the rivets or weld points is considered advantageous in this regard.

[0006] The disclosure further relates to an arrangement of at least two workpieces arranged in pairs at least partially opposite one another and defining an intermediate gap. An adhesive is arranged in at least one of the intermediate gaps, which adhesive is applied to a first joining surface of a workpiece in the manner described above in order to join the workpieces together. The workpieces are additionally joined together by means of further joining means, such as joining bodies or weld points.

[0007] The method according to the invention can be applied in particular to thin workpieces, which can be flat or curved. Two workpieces made of the same material or two workpieces made of different materials can be joined together. In particular, sheet metal, for example, made of steel, aluminum, or magnesium, die-cast parts, or workpieces made of carbon fiber-reinforced plastic are suitable.

[0008] Preferably, the adhesive strand forms a pattern with a wave, zigzag, or sawtooth shape, such that it is applied in an oscillating manner around a centerline of the application path. Oscillating means that the adhesive strand oscillates around the centerline, so that the adhesive strand intersects the centerline. The pattern allows for the air introduced via the additional bonding means to be diverted to the environment, thus at least reducing the formation of disruptive air channels when the adhesive is cured.

[0009] The pattern has a component transverse to the application direction. The application path can be straight or curved along the first bonding surface, so that the application direction relative to the first bonding surface is constant or can change selectively or continuously. Preferably, the center line is interspersed with the additional bonding means.

[0010] Preferably, the distance between two consecutive intersection points of the pattern and the center line is greater in the hybrid bonding areas than in the bonding areas. As a result, less adhesive mass is applied per unit length in the application direction in the hybrid bonding areas. The distance between two consecutive intersection points of the pattern and the center line can define a frequency at which the adhesive strand is applied to the first bonding surface, a strand frequency, so to speak. The strand frequency is then lower in the hybrid bonding areas than in the bonding areas. The pattern can, in particular, correspond to a sinusoidal oscillation.

[0011] Alternatively or additionally, the maximum deflection of the pattern relative to the centerline can be smaller in the hybrid bonding areas than in the bonding areas. This has the effect that less adhesive is applied per unit length in the application direction in the hybrid bonding areas than in the bonding areas. The maximum deflection of the pattern relative to the centerline can also be referred to as the amplitude of the pattern. In particular, the amplitude and / or frequency of the pattern in the hybrid bonding areas can be practically zero in magnitude, so that the mass strand here has the shape of a thin line that coincides with the centerline.

[0012] A preferred concept provides that the distance between two consecutive intersection points of the pattern with the center line is constant within the hybrid bonding areas and the bonding areas, and / or that the maximum deflection of the pattern with respect to the center line is constant within the hybrid bonding areas and the bonding areas. Furthermore, a transition region can be arranged between each hybrid bonding area and each bonding area, in which the maximum deflection of the pattern with respect to the center line and / or the distance between two consecutive intersection points of the pattern with the center line changes continuously or abruptly.

[0013] According to the invention, the mass strand can also have a variable strand cross-section, with the strand cross-section being smaller in the hybrid bonding areas than in the bonding areas. This also has the effect that less adhesive or adhesive mass is applied in the hybrid bonding areas than in the bonding areas.

[0014] To reduce the applied adhesive or adhesive mass in the hybrid bonding areas, a combination of two or all of the measures described above is preferred, namely that the mass strand has a variable strand cross-section, the maximum deflection of the pattern with respect to the center line is smaller in the hybrid bonding areas than in the bonding areas and the distance between two consecutive intersection points of the pattern with the center line is greater in the hybrid bonding areas than in the bonding areas.

[0015] Preferably, after the adhesive has been applied to the first joining surface, the workpieces are fixed to one another, in particular pressed together. This can be done by means of a hold-down device of the self-piercing riveting device, which is also used to insert the additional connecting means if these are designed as self-piercing rivets, or by means of separate clamping devices. The connecting surfaces lie opposite one another and delimit the intermediate gap in which the mass strand is arranged, whereby an adhesive curing phase of the adhesive begins. The workpieces are then expediently joined to one another by means of the additional connecting means after the start of the adhesive curing phase, but in particular before the adhesive has cured.

[0016] Preferably, the hybrid adhesive regions have a length in the application direction that corresponds at least to a cross-sectional area of ​​the additional connecting means. For example, the length can correspond approximately to 1.5 times, 2 times, or 3 times the cross-sectional area of ​​the additional connecting means. Furthermore, the hybrid adhesive regions are preferably of approximately the same length in the application direction.

[0017] Preferably, the adhesive regions have a length in the application direction that corresponds at least to the cross-section of the mass strand. The narrowest adhesive region is at least as wide as the cross-section of the mass strand.

[0018] Preferably, the adhesive areas are approximately 1.5 times, 2 times or 3 times the length of the hybrid adhesive areas and are preferably of approximately the same length in the application direction.

[0019] The additional connecting means can be welded joints, particularly spot welds. These are expediently arranged along the application path. However, the additional connecting means can also be connecting elements that are inserted through the workpieces and the mass strand, with rivets preferably being used, practically punch rivets. The use of both spot welds and connecting elements is also possible, with spot welds being used, for example, in a first section of the application path and connecting elements in a second section of the application path.

[0020] At least one additional workpiece is expediently connected to at least one of the two workpieces, either simultaneously with the connection of the two workpieces or at a different time. Individual or all connecting elements can also penetrate more than two workpieces. The at least one additional workpiece can be attached in a conventional manner or by means of the method according to the invention.

[0021] The invention is explained in more detail below with reference to the exemplary embodiments schematically illustrated in the drawings. They show: Figure 1 is a schematic plan view of a joining surface of a workpiece to which a ground strand is applied in a first wave pattern, Figure 2 is a schematic plan view of a joining surface of a workpiece to which a ground strand is applied in a second wave pattern, Figure 3 is a schematic plan view of a joining surface of a workpiece to which a ground strand is applied in a third wave pattern.

[0022] The drawing schematically shows a workpiece 10 being joined to a second workpiece (not shown in detail). It has a flat shape and is, in particular, a sheet metal. The workpiece 10 further has a joining surface 20, which is also referred to as the first joining surface 20. It comprises a plurality of alternately arranged hybrid adhesive regions 80 and adhesive regions 90, wherein the hybrid adhesive regions 80 are characterized in that they are each intended to receive a connecting body 70 which, in addition to the adhesive, serves to join the two workpieces 10, so that a hybrid connection is produced in the hybrid adhesive regions 80.

[0023] A mass strand 30 consisting of a viscous adhesive is applied to the connecting surface 20 in the area of ​​the hybrid adhesive areas 80 and the adhesive areas 90, which is used to bond the two workpieces 10. The mass strand 30 is applied continuously along an application path 50 extending in an application direction 40. The application path 50 is, for example, a straight line. It could also be curved or wavy or have a kink. The mass strand 30 is applied in an oscillating manner around a center line 55 of the application path 50, wherein in the first embodiment it is applied according to Figure 1 a first wave pattern 60, in the second embodiment according to Figure 2 a second wave pattern 61 and in the third embodiment according to Figure 3 a third wave pattern 62 forms.

[0024] The amount of adhesive applied in the hybrid adhesive areas 80 relative to their length in the application direction 40 should be smaller than the amount of adhesive applied in the adhesive areas 90 relative to their length in the application direction 40. This means that the amount of adhesive applied in the hybrid adhesive areas 80 per unit length in the application direction 40 is smaller than the amount of adhesive applied in the adhesive areas 90 per unit length in the application direction 40. In order to reduce the amount of adhesive applied in the hybrid adhesive areas 80, it is provided that the wave pattern 60 is designed differently in the hybrid adhesive areas 80 and the adhesive areas 90.

[0025] For this purpose, the distance between two consecutive intersection points 65 of the first wave pattern 60 and the center line 55 in the hybrid bonding areas 80 and / or the bonding areas 90 is varied. The distance between two consecutive intersection points 65 of the first wave pattern 60 and the center line 55 is greater in the hybrid bonding areas 80 than in the bonding areas 90. The first wave pattern 60 has, so to speak, a lower frequency in the hybrid bonding areas 80 than in the bonding areas 90. Overall, a shorter ground strand 30 can thus be realized in the hybrid bonding areas 80.

[0026] Furthermore, each wave pattern 60, 61, 62 has a maximum deflection 67 with respect to the center line 55 in a transverse direction 41 running transversely to the application direction 40. In the second wave pattern 61 ( Figure 2), in addition to the reduced frequency, the maximum deflection 67, which can also be referred to as amplitude, is smaller in the hybrid bonding areas 80 than in the bonding areas 90. This measure further shortens the mass strand 30 in the hybrid bonding areas 80 compared to the first wave pattern 60.

[0027] A transition region 95 is arranged between each hybrid adhesive region 80 and each adhesive region 90. In the transition regions 95, the maximum deflection 67 of the second wave pattern 61 relative to the center line 55 changes continuously or abruptly. In the transition regions 95, the distance between two consecutive intersection points 65, 66 of both the first wave pattern 60 and the second wave pattern 61 also changes continuously or abruptly. Thus, the adhesive application in the hybrid adhesive regions 80 can be particularly small.

[0028] According to Figure 3A third wave pattern 62 is shown, which represents a special case. The third wave pattern 62 has a maximum deflection 67 in the hybrid bonding areas 80 and a distance between two consecutive intersection points 65, 66 that are almost zero in magnitude. This measure allows the adhesive application in the hybrid bonding areas 80 to be further reduced compared to the bonding areas 90.

[0029] It can also be provided that the mass strand 30 has a variable strand cross-section. In order to apply less adhesive in the hybrid bonding areas 80, the strand cross-section of the mass strand 30 can be set smaller in the hybrid bonding areas 80 than in the bonding areas 90. This results in a smaller adhesive volume, so to speak, a smaller mass strand 30, in the hybrid bonding areas 90.

[0030] After the adhesive is applied to the first joining surface 20, the workpieces 10 are fixed to one another with opposing joining surfaces 20. For example, the workpieces 10 are pressed together. After fixing, the adhesive begins to cure. During this curing phase, connecting bodies 70, indicated by dash-dotted lines, are inserted through the workpieces 10. The connecting bodies 70 are rivets, preferably self-piercing rivets, such as those used in the hybrid joining of sheet metal parts or the like. The connecting bodies 70 are inserted into each hybrid bonding area 80 in order to fix the workpieces 10 to one another.

[0031] The hybrid adhesive regions 80 have a length in the application direction 40 that corresponds at least to a cross-sectional area 71 of the connecting body 70. The hybrid adhesive regions 80 can also be longer in the application direction 40, for example, 1.5 times, 2 times, or 3 times as long.

[0032] Preferably, the adhesive region 90 is at least as long in the application direction 40 as the width of a strand cross-section of the mass strand. However, the adhesive region 90 is preferably at least as long as a hybrid adhesive region 80, preferably 1.5 times, 2 times, or 3 times as long.

[0033] The use of connecting bodies 70 in the present embodiment is not the only possibility for creating a hybrid connection. In particular, the self-piercing rivets 70 shown in the drawing can be completely or partially replaced by welded connections, particularly in the form of spot welds.

Claims

1. Method for joining two workpieces (10), in particular two metal sheets, which each have a joining surface (20) for joining the workpieces (10), wherein a viscous adhesive in the form of a continuous material strand (30) is applied to a first joining surface (20), along an application track (50) that extends in an application direction (40), wherein the joining surfaces (20) are arranged to lie opposite one another so as to delimit an intermediate gap in which the material strand (30) is arranged, wherein the workpieces (10) are joined to one another in the region of the material strand (30), with the aid of at least one further joining means (70), wherein the first joining surface (20) comprises multiple alternately arranged hybrid adhesion regions (80) and adhesion regions (90), and wherein a further joining means (70) is arranged in each hybrid adhesion region (80), characterized in that the amount of adhesive applied in the hybrid adhesion regions (80), per length unit measured in the application direction (40), is less than the amount of adhesive applied in the adhesion regions (90), per length unit measured in the application direction (40).

2. Method according to claim 1, characterized in that the material strand (30) forms a pattern (60, 61, 62) having a wave, zigzag or saw-tooth shape, in such a manner that it is applied oscillating about a center line (55) of the application track (50).

3. Method according to claim 2, characterized in that the distance between two consecutive intersection points (65, 66) of the pattern (60, 61, 62) with the center line (55) is greater in the hybrid adhesion regions (80) than in the adhesion regions (90).

4. Method according to claim 2 or 3, characterized in that the maximum deflection (67) of the pattern (61, 62) with reference to the center line (55) is less in the hybrid adhesion regions (80) than in the adhesion regions (90).

5. Method according to one of claims 3 or 4, characterized in that the distance between two consecutive intersection points (65, 66) of the pattern (60, 61, 62) with the center line (55) is constant within the hybrid adhesion regions (80) and the adhesion regions (90), in each instance, and / or that the maximum deflection (67) of the pattern (60, 61, 62) with reference to the center line (55) is constant within the hybrid adhesion regions (80) and the adhesion regions (90), in each instance.

6. Method according to one of claim 2 to 5, characterized in that a transition region (95) is arranged between a hybrid adhesion region (80) and an adhesion region (90), in each instance, in which transition region (95) the maximum deflection (67) of the pattern (60, 61, 62) with reference to the center line (55) and / or the distance between two consecutive intersection points (65, 66) of the pattern (60, 61, 62) with the center line (55) changes continuously or suddenly.

7. Method according to one of the preceding claims, characterized in that the material strand (30) has a variable strand cross-section, wherein the strand cross-section is smaller in the hybrid adhesion regions (80) than in the adhesion regions (90).

8. Method according to one of the preceding claims, characterized in that the workpieces (10) are fixed in place on one another after application of the adhesive to the first joining surface (20), in particular pressed onto one another, so that the joining surfaces (20) lie opposite one another and delimit the intermediate gap in which the material strand (30) is arranged, so that an adhesive hardening phase of the adhesive begins, wherein the workpieces (10) are joined to one another after the start of the adhesive hardening phase, in terms of time, by means of the further joining means (70), and preferably before the end of the adhesive hardening phase.

9. Method according to one of the preceding claims, characterized in that the hybrid adhesion regions (80) have a length in the application direction (40) that at least corresponds to a cross-section surface (71) of the further joining means (70).

10. Method according to one of the preceding claims, characterized in that the adhesion regions (90) have a length in the application direction (40) that at least corresponds to a strand cross-section of the material strand (30).

11. Method according to one of the preceding claims, characterized in that the further joining means are weld connections and, in particular, weld points, at least in part.

12. Method according to claim 11, characterized in that the weld connections are arranged along the application track (50).

13. Method according to one of the preceding claims, characterized in that the further joining means are joining bodies (70), at least in part, which are introduced through the workpieces (10) and the material strand (30).

14. Method according to claim 13, characterized in that the joining bodies (70) are rivets.

15. Method according to one of the preceding claims, characterized in that at least one further workpiece is joined to at least one of the workpieces (10).