EP2254723A1

EP2254723A1 - Piston for internal combustion engines, produced by means of a multi-orbital friction welding method

Info

Publication number: EP2254723A1
Application number: EP09713945A
Authority: EP
Inventors: Michael Albert Janssen; Gerhard Luz; Volker Gniesmer; Steffen Stork; Martin Weissert
Original assignee: KS Kolbenschmidt GmbH
Current assignee: KS Kolbenschmidt GmbH
Priority date: 2008-02-29
Filing date: 2009-01-30
Publication date: 2010-12-01
Also published as: WO2009106200A1; US8789273B2; DE102008011922A1; US20110119914A1; JP2011514258A

Abstract

The invention relates to a method for producing a piston (1) of an internal combustion engine, designed as a one-piece cooling channel piston. The piston (1) comprises an upper part (2) and a lower part (3) supported by corresponding circumferential joining bosses (11, 12) together forming a joining zone (4). In order to produce a bonded joint of the upper part (2) and the lower part (3), the joining bosses (11, 12) are connected by means of multiorbital friction welding in the region of a rotationally symmetrical or rotationally asymmetrical joining zone (4).

Description

Piston for internal combustion engines, produced by means of a multi-orbital friction welding process

description

The invention relates to a method for producing a piston of an internal combustion engine, which is designed as a finished one-piece cooling channel piston and comprises a lower part and an upper part, which are supported via corresponding joining webs forming a joint zone and which are materially bonded by means of friction welding, according to the features the preamble of independent claims 1 and 2.

Friction welding is based on the principle that sliding movement between two components is produced by relative movement and simultaneous pressure in order to produce the necessary welding energy at the surfaces to be welded in the region of a joining zone. Known rotary friction welding machines use a power chuck and an upsetting device to deliver kinetic energy throughout the welding cycle. For friction welding, two workpieces are rubbed together under pressure with a rotary motion and plasticized by the resulting frictional heat. Preferably, the workpiece used in the driven chuck is rotated relative to the second stationary in the upsetting device held workpiece. Once the temperature required for welding is reached, the upsetting device presses the two workpieces together. Disadvantageously, this method requires that one of the two components rotate at high speed to provide the required energy. From DE 10 2004 061 778 A1, a cooling channel piston is known, consisting of an upper part and a lower part, which are supported via corresponding, each rotationally symmetrical extending and radially spaced joining webs. By means of a friction welding in the region of a joining zone, a cohesive connection of the inner joining webs takes place. The radially outer joining webs are then joined together by means of a separate weld, with no friction welding being provided for this purpose.

US Pat. No. 6,155,157 shows a cooling channel piston with two components that can be produced separately from one another, which are then joined together in a material-locking manner by means of a known friction welding method, to form a one-piece cooling channel piston. This structure allows a relatively simple piston production, wherein the known piston concept is severely limited in terms of geometric freedom, in particular the design of joints.

Based on the known prior art, the present invention seeks to improve a geometric design possibility of pistons by means of an optimized joining technique, in order to achieve a flexible piston production and a reduction in weight.

This object is solved by the features of independent claims 1 and 2.

The invention according to the features of claim 1 relates to a manufacturing method for a piston with rotationally symmetrical or preferably non-rotationally symmetrical joining webs of the lower part and the upper part, which are materially connected in the region of a joining zone by means of a multi-orbital friction welding process. The multi-orbital friction welding envisages that the individual piston components are tightly clamped on both sides adjacent to the joining zones in so-called Reibschweißköpfen and thereby pressed against each other before the joints are vibrated using the Reibschweißköpfe. The joining partners are advantageously moved with the same direction of rotation at a preferred phase offset of 180 ° in the smallest circular orbital movements, which are similar to a sander movement, to generate the frictional heat and swing in particular out of phase. As a result of this motion control, the friction energy is introduced simultaneously in the region of several positions, whereby the previous system limits of friction welding are widened. In the multi-orbital friction welding process, the components to be joined are rubbed against each other over the entire joining zone, which leads to a desired uniform and rapid heating of the entire welding plane. As a result, an optimal, homogeneous energy input is established at each point of the joining zone formed by the piston joining points. Contrary to an exclusively rotating movement of a joining partner in known friction welding processes, which, viewed in the joining zone, causes an inhomogeneous introduction of energy, this energy input is due to a lack of internal speed. With the friction welding method used according to the invention, furthermore, the welding times can advantageously be shortened and follow-up processes can be reduced. In addition, the highest connection quality is achievable, the achievable strength values are close to the material characteristics of the joining partners. The method is also independent of the workpiece shape, the material mass and the symmetry of the welding surface or the joining zone, since the specific welding pressure relative to the surface is always constant. Since multi-orbital friction welding bonds the materials in the plastic state, the temperature level is well below the melting temperatures of conventional friction welding processes. When the joining temperature is reached, the machine system stops to press both workpieces with precise final dimensions. The use according to the invention of the multi-orbital friction welding method simplifies the production of the piston due to a large freedom of design with respect to the position, the orientation and the wall thickness of the joining webs and the resulting joining zone. Since the deflection of the piston components to be joined when rubbing with about 0.3 to 1, 2 mm is low, even thin-walled joining joints can be welded. The use of the multi-orbital friction welding process allows flexible, time-optimized production and thus reduced costs in the production of the piston. Advantageously, the economy of the piston production can be substantially increased by shortened process times by the invention.

Advantageously, the novel manufacturing method allows an improved design of the piston components, since each component taken by itself can be designed in terms of its geometry to achieve optimum fatigue strength, without consideration of cohesive joining technology. Advantageously, it makes sense to interpret the joints only in terms of optimized stiffness or structural strength and a weight-optimized piston. Furthermore, design features can be realized by the welding process, which were previously not feasible due to the required rotationally symmetric geometry of the joining zones in friction welding. At the same time, the invention provides a solution with which the ever increasing demands in terms of thermal and mechanical stress of pistons and the demand for reducing the rotational and oscillating components in internal combustion engines can be met.

The invention of claim 2 relates to a manufacturing method for pistons having at least two mutually radially spaced, connected by means of a multi-orbital friction welding joining zones. Due to the smallest circular Movements of all joining partners is an advantageous synchronous simultaneous joining a plurality of joining webs possible, even if they are relatively close to each other. For example, the multi-orbital friction welding process can be used cost-optimized for the production of a cooling channel piston whose cooling channel, which is bounded on both sides by joints, extends between the lower part and the upper part.

The use according to the invention of the multi-orbital friction welding method on the production of pistons allows a dimensioning of the joining webs adapted to the strength requirements of individual piston regions. Since this method does not require a rotationally symmetrical course, the joining webs on the circumferential side to form variable cross sections on a constant or fluctuating wall thickness. The dimensioning of the joining webs can thus be advantageously adapted to the setting in the individual piston areas, divergent thermal and mechanical loads, which also a weight advantage can be realized.

The multi-orbital friction welding method also allows a height offset of the joining zone, whereby the friction welding can be adapted, for example, to predetermined geometric or special constructive piston concepts. Underlining the diversity of interpretation, it continues to offer, in pistons with two radially spaced joining zones to arrange them together so that the individual joining zones both have a different, not rotationally symmetrical course and a height offset.

The friction welding requires no closed-shaped joining zone, but allows a local to be designated as a passage recess of the joining zone, for example, as a coolant transfer between two cooling channels is usable. This recess can represent an adaptation of the joining web to the loads which occur in the operating state, as a result of which a reduced piston weight can be realized at the same time. In order to meet local strength requirements of the piston, the welding process on the other hand allows partially to provide the joining webs with radially inwardly and / or radially outwardly directed stiffening ribs which extend into the region of the joining zones and are materially connected.

Preferably, the rotationally symmetrical, non-rotationally symmetric or partially approximately parallel to a piston axis extending joining zones are arranged so that they are aligned perpendicular to a piston longitudinal axis. Alternatively, according to the invention, a position or arrangement of the joining zone or the mutually offset joining zones, which deviates from a self-adjusting vertical printing direction of the multi-orbital friction welding. The design also makes it possible that the self-adjusting upsetting axes are aligned in the friction welding orthogonal or not orthogonal to each other.

Advantageously, the multi-orbital friction welding method does not cause any or small welding beads, which remain on the joining zone after completion of the welding or are removed by means of reworking if necessary.

A preferred embodiment of the invention provides that during the Reibschweißvorgangs the cooling channel is closed. Subsequently, by means of a mechanical processing, if necessary, at least one local opening can be introduced into the joining web in order, for example, to allow coolant to enter the cooling channel. For pistons, a combination of several through Include jointed separate cooling channels, it is advisable to provide the joint with at least one also to be designated as a transfer opening passage, which ensures a coolant exchange between the cooling channels.

A further advantageous embodiment according to the invention provides for closing an annular gap provided in the region of the piston outer contour by means of an additional or covering element. The cover element, which encloses, for example, a passage or a transfer opening, can thereby be positively and / or non-positively fastened to the lower part or the upper part of the piston or simultaneously cohesively fixed with the multi-orbital friction welding.

Advantageously, the invention makes it possible to materially connect piston components made of a matching material or of different materials by the multi-orbital friction welding method. Thus, for example, a piston component made of a lightweight material with the main alloying element aluminum may be provided with another piston component made of steel or a ferrous material, e.g. Cast iron can be connected. In addition, it may be considered to manufacture the upper and lower parts in the same or different processes, such as forging, pressing, casting, extrusion and the like.

The following description explains various exemplary embodiments according to the invention shown in FIGS. 1 to 7, the invention not being restricted thereto. Show it:

1 shows a first embodiment of a cooling channel piston according to the invention in a longitudinal section,

FIG. 2 shows a sectional view of the piston according to FIG. 1,

FIG. 3 shows the piston according to FIG. 1 in a longitudinal section rotated by 90 °;

FIG. 4 shows a sectional view of the piston according to FIG. 3,

FIG. 5 shows the piston according to FIG. 1, whose joining zone has a height offset,

6 shows a second embodiment of a cooling channel piston according to the invention in a longitudinal section,

Figure 7: the piston of Figure 6 in a rotated by 90 ° longitudinal section.

1 shows in a longitudinal section a one-piece piston 1, in which an upper part 2 and a lower part 3 via a joining zone 4, which is also to be referred to as a joining surface, are integrally joined together to form a structural unit. A piston head 5 of the upper part 2 includes a combustion bowl 6, which merges circumferentially in a top land 7, to which a ring field 8 is connected for receiving piston rings not shown in FIG. The lower part 3 forms a piston shaft, in which two diametrically opposite pin holes 9 are introduced. In the area of the joining zone 4 are based Correspondingly arranged joining webs 11, 12, which are assigned to the upper part 2 and the lower part 3. To create a cohesive connection, a multi-orbital friction welding is provided in which the joining webs 11, 12 and the associated components, the upper part 2 and the lower part 3, rotates with the same direction of rotation at a preferred phase offset of 180 ° in the smallest circular orbital movements , By this movement, a frictional heat is generated in which sets a homogeneous energy input at each point of the joining zone 4. This special welding weld 13a, 13b forming small welds does not require a rotationally symmetrical arrangement or geometry of the joining zone 4 to a piston axis 10. The joining webs 11, 12 define on the inside and the ring field 8 on the outside a cooling channel 14 integrated in the piston 1. A self-adjusting annular gap 15 between the annular field 8 and the lower part 3 is closed by a separate additional element 16 which is fixed in position by means of a weld or alternatively by a non-positive and / or positive connection to the lower part 3.

FIG. 2, which shows the piston 1 in a sectional view according to the course 2-2 of FIG. 1, illustrates in particular the position of the joining web 11, which at the same time defines the surface or the cross section of the joining zone 4. The course of the joining web 11 shows sections "a" and "b" which extend almost parallel to the axis "y" of the piston 1 and are adjoined by sections "c" and "d" arranged largely concentrically with the center of the piston In this case, the wall thicknesses of the joining web 11 in the individual sections can be dimensioned differently, in accordance with the respective piston loads that are set in the operating state, in which case wall thicknesses of the sections "a" and "b" are the same or different interpreted and execute the other sections "c" and "d" of the joint 11 again equal or different from the section "a" and / or the section "b".

FIG. 3 shows the piston 1 in a longitudinal section offset by 90 ° relative to FIG. 1, and illustrates the design and the course of the joining webs 11, 12 in the sections "c" and "d", which are opposite the sections "a" shown in FIG "and" b "have a reduced wall thickness.

In the figure 4, the piston 1 is shown in a sectional view according to the course 4-4 of Figure 3 and shows a deviating from Figure 2 course of the joint 11. In an approximately parallel to the axis "x" of the piston 1 extending section of the closes Joining ribs 17a, 17b, 17c which are arranged radially offset inwardly from one another and which are in some other direction radially outwardly directed stiffening ribs 18a, 18b, on the side opposite the stiffening ribs 11 openings 19a, 19b staggered with respect to one another are introduced into the joining rib 11 , via which, for example, a coolant exchange can take place from the cooling channel 14 into the inner region 20.

The piston 1 shown in Figure 5 is largely comparable to the piston 1 shown in Figure 1. Consequently, matching components are given the same reference numerals. 5, the joining zone 4 forms a height offset "v", which is made possible by the multi-orbital friction welding method, in order to realize the orbital welding movement, a free space "s" is required for this purpose. The piston 21 according to FIG. 6 is partially comparable to the piston depicted in FIG. 1, therefore matching components have the same reference numerals. The upper part 22, which includes a piston crown 25 with integrated combustion chamber recess 26 and on the outside a top land 27 and a ring field 28, and the bottom part 23 enclosing a pin bore 29 are supported by two radially offset joint pairs. The radially inner joining webs 31, 32 form the joining zone 24a and the radially outer joining webs 33, 34 form the joining zone 24b. By means of the multi-orbital friction welding, the joining webs 31, 32; 33, 34 in the joining zones 24a, 24b integrally connected, wherein in each case on the outside of the joining zones 24a, 24b small Schweißwülste 30a, 30b, 30c form. Underlining the diversity of interpretation, the design of the joining webs 31, 32 or 33, 34 includes different or identical wall thicknesses in opposite sections "a, b" or "e, f". Furthermore, the wall thickness can also be designed differently between the radially spaced joining web pairs. The joining zones 24a, 24b have a height offset "h" relative to one another, the joining zone 24b being arranged at a greater distance from the piston head 25 than the joining zone 24a. In the piston 21, two cooling channels 35, 36 are integrated, which are laterally delimited by joining webs The outer annular cooling channel 35 is bounded on the outside by the annular field 28 or the joining webs 33, 34 and on the inside by the joining webs 31, 32. The central cooling channel 36 extends as far as possible over the region of the piston depression 26 and is formed by passage openings 37 connected to the cooling channel 35.

FIG. 7 shows the piston 21 in a longitudinal section offset by 90 ° to FIG. 6 and illustrates the design of the joining webs 31, 32; 33, 34, wherein the wall thicknesses of the sections "c, d" and "g" differ at least partially from the wall thicknesses of the sections "a, b, e, f" according to FIG. LIST OF REFERENCE NUMBERS

1st piston 20th interior area

2. Upper part 21. Piston

3. lower part 22. upper part

4. joining zone 23. lower part

5. piston bottom 24a. joint zone

6. combustion bowl 24b. joint zone

7. Firestone 25. Piston bottom

8. ring field 26. combustion bowl

9. Bolt Hole 27. Flank

10. Piston axis 28. Ring field

11. Fastening 29. Bolt hole

12th bridge 30a. weld bead

13a. Welding bead 30b. weld bead

13b. Welding bead 30c. weld bead

14. Cooling channel 31. Fügesteg

15. Annular gap 32. Fügesteg

16. Additional element 33. Fügesteg

17a. Stiffening rib 34. Fügesteg

17b. Stiffening rib 35. Cooling channel

17c. Stiffening rib 36. Cooling channel

18a. Stiffening rib 37. Passage

18b. stiffening rib

19a. passage

19b passage

Claims

claims

1. A method for producing a piston (1) of an internal combustion engine, designed as a one-piece cooling channel piston after its manufacture, comprising an upper part (2) and a lower part (3), which via corresponding, a joint zone (4) forming joining webs (11 , 12) are supported and materially connected by friction welding, characterized in that a multi-orbital friction welding is performed to connect the rotationally symmetric or non-rotationally symmetrical joining webs (11, 12) of the piston (1).

2. A method for producing a piston (21) of an internal combustion engine, designed as a one-piece cooling channel piston after its production, comprising an upper part (22) and a lower part (23) via corresponding, a joint zone (24a, 24b) forming joining webs (31, 32, 33, 34) are supported and which are materially connected by means of a friction welding, characterized in that the piston (21) has one or at least two radially spaced-apart, rotationally symmetric or non-rotationally symmetrical joining zones (24a, 24b), their joints (31, 32, 33, 34) are connected by means of a multi-orbital friction welding process.

3. The method according to any one of claims 1 or 2, characterized in that a self-adjusting Schweißwulst (13a, 13b, 30a, 30b, 30c) after completion of friction welding at the joining zones (4; 24a, 24b) remains or is removed.

4. The method according to any one of claims 1 to 3, characterized in that a cooling channel (14) of the piston (1) is closed during the friction welding operation.

5. Piston produced by the method according to one of the preceding claims, characterized in that the joining webs (1 1, 12, 31, 32, 33, 34) circumferentially have a constant or differently designed wall thickness.

6. Piston according to claim 5, characterized in that in the piston (1) circumferentially arranged joining zone (4) has a height offset "v".

7. Piston according to claim 5 or 6, characterized in that between the two radially mutually offset joining zones (24a, 24b) of the piston (21) is provided a height offset "h".

8. Piston according to claim 5, 6 or 7, characterized in that the joining webs (11, 12; 31, 32, 33, 34) are executed circumferentially closed.

9. Piston according to one of claims 5 to 8, characterized in that at least one joining web (11, 31) includes a passage (19a, 19b, 37).

10. Piston according to one of claims 5 to 9, characterized in that at least one joining web (11) has a radially inwardly and / or radially outwardly directed stiffening rib (17a, 17b, 17c, 18a, 18b).

11. Piston according to one of claims 5 to 10, characterized in that at least one rotationally symmetric or non-rotationally symmetrical joining zone (4, 24a, 24b) perpendicular to a piston axis (10).

12. Piston according to one of claims 5 to 11, characterized in that at least a portion of the joining web (11) is partially aligned approximately parallel to an axis "y" of the piston (1).

13. Piston according to one of claims 5 to 12, characterized in that a position of the joining zone (4, 24a, 24b) deviates from a self-adjusting vertical printing direction of the multi-orbital friction welding.

14. Piston according to one of claims 5 to 13, characterized in that compression axes of the multi-orbital friction welding are aligned orthogonally or in a deviating position or direction to each other.

15. Piston according to one of claims 5 to 14, characterized in that the piston (21) includes a combination of an outer cooling channel (14) and an inner cooling channel (20) which are separated by joining webs (31, 32), wherein at least one joining web (31) enclosing a passage (37) forming a transfer opening.

16. Piston according to one of claims 5 to 15, characterized in that the cooling channel (14) of the piston (1) is partially closed with a separate additional element (16) or cover.

17. Piston according to one of claims 5 to 16, characterized in that the form-fitting and / or non-positively or cohesively in the piston (1) inserted additional element (16) or cover has at least one passage.

18. Piston one of claims 5 to 17, characterized in that the piston blanks, the upper part (2, 22) and the lower part (3,23) are made of a matching material or of different materials, being provided as the main alloying element aluminum or steel is.

19. Piston according to one of claims 5 to 18, characterized in that the piston blanks of the piston (1, 21) a forged, cast or by a casting process produced upper part (2, 22) and lower part (3, 23) can be used.