EP2971716A1

EP2971716A1 - Two-part steel piston, joining process

Info

Publication number: EP2971716A1
Application number: EP14711950.7A
Authority: EP
Inventors: Robert KÜHNEL
Original assignee: KS Kolbenschmidt GmbH
Current assignee: KS Kolbenschmidt GmbH
Priority date: 2013-03-15
Filing date: 2014-03-14
Publication date: 2016-01-20
Also published as: WO2014140287A1; DE102014204774A1; US20160069294A1; CN105189999A

Abstract

The invention relates to a piston (10), in particular a cooling channel piston, for an internal combustion engine, comprising at least one lower part (2) and one upper part (3), a combustion chamber (13) and at least one annular groove (11), wherein the upper part (3) or the lower part (2) is fastened by means of at least one undercut on the lower part (2) or on the upper part (3), characterised in that the upper part (3) comprises at least one combustion chamber (13) and at least one annular groove (11). The invention further relates to a method for producing such a piston.

Description

DESCRIPTION

Two-piece steel piston, joining process

The invention relates to a piston and a method for producing a two-part piston from an upper part and a lower part, according to the features of the respective preamble of the independent claims.

EP 1 878 902 A2 describes the construction of a piston comprising an upper part and a lower part, which are supported via joining webs in the region of contact zones and connected to one another. A clamping connection arises here by a rotation of the upper part to the lower part, comparable to a clutch. This is very complicated to handle.

From DE 10 2005 030 556 B4 the production of a connection between the upper part and lower part of a piston for an internal combustion engine by positive locking is known. The disadvantage here is that the joined by positive fit upper part only forms part of the piston crown.

The piston, in particular the cooling channel piston, consists of an upper part and a lower part. In the upper part can, but does not have to be introduced a cooling channel. The upper part comprises the surface facing the combustion chamber of the cylinder, in known per se, the ring field and optionally a combustion bowl. The lower part consists of opposite supporting shaft wall sections, connecting walls, which connect the skirt wall sections, wherein in the connecting walls in known per se, the bolt holes are arranged. The two parts can be made of the same or different material. If the piston is a cooling channel piston, a cover for the cooling channel can be provided before joining the upper part and the lower part, this cover being provided by joining the two parts to one another Destination is determined. Alternatively or additionally, even after the joining of the two parts, the cover can be arranged independently of the clamping process or even if it was clamped by the upper and lower part, by additional measures such. As welding or the like, set at their destination and sealed by these additional measures. The two parts can in the same process or in different processes, such. As forging, casting or the like, be prepared.

The invention is therefore based on the object to abolish the disadvantageous parting plane between the lower part and upper part of a piston.

The object is achieved by a piston and by a method having the features of the independent claims.

It is proposed to manufacture the upper part with combustion chamber recess and ring field as well as an optional cooling channel in one piece.

Compared to the prior art, it is advantageous to strive for a joining direction.

According to the invention, it is provided that the upper part comprises at least one combustion chamber and at least one annular groove. A connection in which at least two components to be connected mechanically interlock and because of their geometric shape of the components to be connected in the connection region, the connection remains, is referred to as positive locking. Even if there is no power transmission between the components to be connected or the power transmission between the components to be connected is interrupted, the connection is maintained. Connections with undercut, riveted joints or dovetail joints are, for example, attributed to the positive connections. The invention relates to a piston, in particular a cooling channel piston, for an internal combustion engine, with at least one lower part and an upper part, and a combustion chamber and with at least one annular groove, wherein the upper part or the

Lower part is fixed with at least one undercut on the lower part or on the upper part, wherein the upper part comprises at least one combustion chamber and at least one annular groove.

Furthermore, the invention provides that the at least one undercut is part of the wall of an opening. The undercut can be advantageously prepared in one step with the opening.

Furthermore, the invention provides that at least one pin engages after forming in the undercut. Thus, a robust positive connection is created by including the undercut. The compound is almost insoluble and can only be solved, if at all, with a very high cost.

Furthermore, the invention provides that the volume of the pin corresponds almost exactly to the volume of the opening. This ensures that the pin fills the entire, for example, cylindrical opening. This leads to a secure high-strength connection. The opening is made almost cylindrical, wherein it has a smaller diameter in the inlet area of the pin than on the opposite side. The opening is bounded by a wall which corresponds to the mantle of a truncated cone, the truncated cone pointing to the "tip" in the direction of the peg. "Almost exactly" in this context means that the volume of the peg (ie the volume which is in the opening is to be placed) may be less than or equal to the volume of the opening. Furthermore, the invention provides that for closing a cooling channel, at least one closure element, in particular a ring, is provided.

Such a closure element is in one piece, but may also be multi-part, e.g. from two or more than two parts, be configured. In addition, depending on the shape of the cooling channel, the at least one closure element of the geometry of the cooling channel is adapted. Is the cooling channel rotationally symmetrical (for example, based on the

Kolbenhubachse), is also formed a part of the closure element (or the plurality of parts which form the closure element) rotationally symmetrical. If, however, the geometry of the cooling channel is not rotationally symmetrical (for example oval, elliptical or other geometries), the at least one closure element is correspondingly also adapted, that is also not rotationally symmetrical.

The invention provides a method for producing a two-part piston, in particular a cooling channel piston, for an internal combustion engine, having a lower part and an upper part, comprising the following steps,

Supply of the lower part having at least one opening or at least one pin, supply of the upper part having at least one pin or at least one opening, wherein the at least one pin under force the undercut of the at least one opening fills.

Furthermore, the invention provides that at least the at least one pin is heated to a temperature well above room temperature before joining. Thus, the joining process is supported because the material to be joined is easier to deform.

The term "room temperature" as a rule means the temperatures at which the production process of such pistons takes place, ie temperatures that are sustainable for the persons who work in such production halls the at least one pin is heated before joining, thus significantly above this room temperature, at clearly more than 100 degrees Celsius. If cold joining or hot forging takes place as a joining process, it is possible to consider it well above 200 degrees Celsius. For example, in the half-warm forging in the

Temperature range above 300 degrees Celsius (+/- 20%) worked. In hot forging, the temperatures are still significantly higher.

Furthermore, the invention provides that prior to the joining of lower part and upper part of a ring to form a cooling channel is inserted. Thus, optionally, a piston can be produced with a cooling channel, without tool change.

Furthermore, the invention provides that at least one annular groove is introduced after the joining in the upper part. Ring grooves are used to accommodate piston rings for use at least one piston in an internal combustion engine.

Furthermore, the invention provides that an insoluble, positive connection between the lower part and upper part is created. This creates a quasi one-piece piston, which can be made of different materials. These materials need not be accessible to a cohesive connection, since according to the invention a high-strength positive connection is created.

Trained is the positive connection according to the invention such that it counteracts the forces exposed during operation in an internal combustion engine. These are predominantly forces whose vector is parallel to the central longitudinal axis of the piston.

Further details of the invention will be explained in connection with the figures. Show it:

1 A to 1 D show the sequence for preparing the joining process between the lower and upper part of a piston,

Fig. 2A to 2D show schematically the sequence of the joining process for a

Piston. Fig. 3 shows a sectional view of a piston blank and the

4A to 4B show several views of the piston parts.

In the following description of the figures, terms such as top, bottom, left, right, front, back, etc. refer exclusively to the example representation and position of the device and other elements selected in the respective figures. These terms are not intended to be limiting, that is to say that different positions and / or mirror-symmetrical design or the like may change these references.

FIGS. 1A to 2D show the joining process according to the invention using the example of a cooling channel piston. The method is not limited to cooling channel pistons, also pistons without cooling channel can be manufactured by the method according to the invention.

All Figures 1A to 1 D show a plan view of the underside (in the operating position) of an upper part 3 of a piston blank. 1

In FIG. 1A, a ring 4 is introduced into the upside-down upper part 3 to form a cooling channel 7. If later the lower part 2 is supplied and the connection method of the invention has been used, the ring 4 is fixed between the lower part 2 and upper part 3. The ring 4 then closes the underlying (in the operating position overlying) cavity to form the cooling channel 7 tightly.

Figure 1 B shows the upper part 3 with inserted ring 4 and pin 5 before joining the lower part 2. Clearly visible in this case four pins 5 for producing a positive connection between the lower part 2 and upper part 3. However, there may only two Pin 5 or more than four pins 5 are provided. The supply of the lower part 2 before joining is shown in FIG. 1C. For joining, in particular the pins 5 can be heated to a temperature well above the ambient temperature. This supports the subsequent forming process of the pin 5.

Figure 1 D shows the now one-piece piston blank 1, made of the lower part 2 and the upper part 3. Due to the transparent representation of the lower part 2, the deformation of the pin 5 can be seen after joining.

FIGS. 2A to 2D show sectional views in the region of the connection according to the invention analogous to FIGS. 1A to 1D. FIG. 2D clearly shows that the pin 5 completely fills the counter-shape of an opening 6 after the forming.

Figures 2A and 2B show the feeding of the lower part 2 before joining. FIG. 2B furthermore shows that the dimension x of the pin 5 before the joining is greater than the dimension y drawn in FIG. 2D after the joining. These dimensions x and y refer to the height of the pin 5 measured from the parting plane 8. The "excess" material of the pin 5 is calculated so that it completely fills the opening 6 after the joining process drawn angle α illustrates that the opening has an undercut 6. In the region of the undercut, the "excess" material of the pin 5 is pressed during the joining process. The amount of material of the pin 5 must be matched exactly to the volume of the opening 6, so that the upper part 3 and the lower part 2 in the parting plane 8 can be joined plan superimposed. The volume of the pin 5 before and after the joining process thus corresponds exactly to the volume of the opening 6. At least the pin 5 can be heated to a temperature well above room temperature before the joining process, this facilitates the forming process and leaves the material of the pin 5 almost in the opening 6 flow. After completion of the joining process, the lower part 2 and the upper part 3 are permanently connected to a piston blank 1. In further process steps, for example, the annular grooves are introduced into the upper part 3. In Figure 3, the piston blank 1 is shown in section through the junction point according to the invention. Plotted is a line 9 which represents the later outer contour of a piston 10. It can also be seen that the connection points lie above next to a pin bore 12. Here is enough material available to ensure a solid, secure connection between the lower part 2 and upper part 3. 8, the separating plane between the lower part 2 and upper part 3 is marked in FIG.

Figure 4A shows a perspective view of a piston 10 according to the invention, wherein the lower part 2 and the upper part 3 are shown spaced. FIG. 4B, in turn, shows a plan view of the lower part 2 and the upper part 2 in the parting plane 8. On the upper part 3, ring grooves 1 marked by the line 9 are already worked out in FIG. Mentally when components 2 and 3 are joined, a finished piston 10 is present.

Both in the general description part and in the description of the figures, the term "opening" (denoted by the reference numeral 6 in the part of the figure descriptions) is used in the sense that in the upper part (general) and in the upper part 3 (according to FIG 1) in which the pin (general) or reference numeral 5 is introduced and deformed in the description of the figure, whereby the pin is formed by the lower part (general or lower part 2 in the exemplary embodiment) is also that the at least one recess in the lower part and the at least one corresponding pin part of the upper part is essential., It is essential that pin and recess (or opening) are coordinated so that the volume of the pin after forming the volume of the By the resulting deformation of the pin "digs" this in the recess, so that dadurc h upper part and lower part are inseparably connected to each other in the sense that they are no longer arranged relatively movable to each other. Only by not occurring in operation and thus unusually high forces, it would be possible to separate lower part and upper part of each other. LIST OF REFERENCE NUMBERS

1 piston blank

2 lower part

3 shell

4 ring

5 cones

6 opening

7 cooling channel

8 parting plane

9 line

10 pistons

1 1 ring groove

12 pin hole

13 Combustion chamber x dimension before joining y Dimension after joining α angle

Claims

PATENT APPLICATIONS Two-piece steel piston, joining process

1 . Piston (10), in particular cooling channel piston, for an internal combustion engine, with at least one lower part (2) and an upper part (3), and a combustion chamber (13) and with at least one annular groove (1 1), wherein the upper part (3) or Lower part (2) with at least one undercut on the lower part (2) or on the upper part (3) is fixed, characterized in that the upper part (3) at least one combustion chamber (13) and at least one annular groove (1 1).

2. Piston according to claim 1, characterized in that the at least one undercut is part of the wall of an opening (6).

3. Piston according to one of the preceding claims, characterized in that at least one pin (5) engages after forming in the undercut.

4. Piston according to one of the preceding claims, characterized in that the volume of the pin (5) corresponds almost exactly to the volume of the opening (6).

5. Piston according to one of the preceding claims, characterized in that for closing a cooling channel (7) at least one closure element, in particular a ring (4) is provided.

6. A method for producing a two-part piston, in particular cooling channel piston, for an internal combustion engine, with a lower part (2) and an upper part (3) comprising the following steps,

Feeding the lower part (2) having at least one opening (6) or at least one pin (5), Feeding the upper part (2) comprising at least one pin (5) or at least one opening (6), characterized in that the at least one pin (5) under force the undercut of the at least one opening (6) fills.

7. The method according to claim (6), characterized in that at least the at least one pin (5) is heated to a temperature well above room temperature before joining.

8. The method according to claim 6 or 7, characterized in that prior to the joining of lower part (2) and upper part (3), a ring (4) for forming a cooling channel (7) is inserted.

9. The method according to any one of claims 6 to 8, characterized in that at least one annular groove (1 1) is introduced after joining in the upper part (3).

10. The method according to any one of claims 6 to 9, characterized in that an insoluble, positive connection between the lower part (2) and upper part (3) is provided.