Method for Producing a Monoblock Piston, and Monoblock Piston

Abstract

Disclosed is a monoblock or cooling channel piston and a method for producing a monoblock piston for use in an internal combustion engine. A piston blank includes a circumferential collar protruding radially in the region of the piston crown is first produced and the collar is then shaped. A contact region on a top region of the piston skirts and the collar is shaped such that the outer circumferential edge thereof points at a distance to the contact region and forms a defined gap. The gap is then sealed by a closure element in order to form a closed cooling channel.

Claims

1. A method for producing a cooling duct piston for an internal combustion engine, which cooling duct piston has a cooling duct in its piston crown, the piston crown being adjoined by a piston lower part with piston bosses, pin bores and piston skirts, a piston blank having a circumferential collar which projects radially in the region of the piston crown first of all being produced, and the collar subsequently being reshaped, characterized in that a bearing region is provided on an upper region of the piston skirts, and the collar is reshaped in such a way that the outer circumferential edge points toward the bearing region at a spacing defining a gap, the gap subsequently being closed by way of a closure element, in order to form a closed cooling duct.

2. The method as claimed in claim 1, characterized in that the piston blank is produced using a forging method.

3. The method as claimed in claim 1 wherein the closure element comprises two or more pieces each having ends, the method further comprising arranging the two or more closure element pieces ends in abutting engagement with one another at a setpoint position in the gap; and connecting the abuttingly engaged ends of the two or more closure elements.

4. The method as claimed in claim 1, characterized in that the closure element is not connected in an integrally joined manner to the piston blank.

5. The method as claimed in claim 1, characterized in that boundaries for a contact of the closure element are provided on one of the bearing region or the outer circumferential edge of the collar.

6. A cooling duct piston for an internal combustion engine, which cooling duct piston has a cooling duct in its piston crown, the piston crown being adjoined by a piston lower part with piston bosses, pin bores and piston skirts, a piston blank having a circumferential collar which projects radially in the region of the piston crown first of all being produced, and the collar subsequently being reshaped, characterized in that a bearing region is provided on an upper region of the piston skirts, and the collar is reshaped in such a way that a outer circumferential edge points toward the bearing region at a spacing defining a gap, the gap being closed by way of a closure element operable to form a closed cooling duct.

7. The cooling duct piston as claimed in claim 6, characterized in that the closure element comprises two or more pieces each having abutting ends, the abutting ends are connected to one another after the two or more pieces are positioned at a setpoint position in the defined gap.

8. The cooling duct piston as claimed in claim 6, characterized in that the closure element is not connected in an integrally joined manner to the piston blank.

9. The cooling duct piston as claimed in claim 6, characterized in that boundaries for a contact of the closure element are positioned on one of the bearing region or the outer circumferential edge of the collar.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIGS. 1 to 4 show the individual steps of the method according to the invention for producing the cooling duct piston.

[0017] FIG. 5 shows a detailed view of a closure element which is inserted into a gap.

DETAILED DESCRIPTION

[0018] Referring to FIG. 1, the designation 1 shows a piston blank which is produced, for example, using a casting or forging method. These can also be other production methods for a piston blank, such as the extrusion method. The method, by way of which the piston blank 1 is produced, is as a rule based on the design of the piston and the strength requirements made of the piston. The piston blank 1 which is shown in FIG. 1 has a piston crown 2 (upper part), a collar 3 projecting from the piston crown 2 in a radially circumferential manner. Piston bosses 4 with piston skirts and pin bores and possibly further elements which together form a piston lower part are situated on the piston crown 2 toward the bottom.

[0019] There is a bearing region 5 (with an indicated step or else without one) in a transition region between the piston crown 2 and the piston lower part, preferably on the lower circumferential edge of the piston bosses 4, which bearing region 5 (as has already been illustrated) is situated in a transition region 6 between the piston crown 2 and the piston lower part. Said transition region 6 is configured approximately as a circumferential land in the case of the piston blank 1 according to FIG. 1, but can also have different geometries in the case of other piston designs. The bearing region 5 serves to form a gap after it has been reshaped. A closure element is inserted subsequently into said gap (see FIGS. 3 and 4). In order for it to be possible to define the setpoint position of the closure element in an improved manner, there is/are a radially circumferential land 7 or part regions of a land in the bearing region 5 according to FIG. 2, it being possible for the land 7 to be produced, for example, by way of machining with the removal of material. This embodiment is shown in FIG. 2, it also being possible for there to be a simple step in the bearing region 5, with which step the closure element can come into contact when it is inserted into the gap.

[0020] FIG. 3 shows the collar 3 after being reshaped. It can be seen that the outer radially circumferential part of the collar 3 is angled away by approximately 90. A radially circumferential cooling duct 8 and a defined gap 9 are formed by way of said reshaping and the corresponding forming of the piston crown 2 with the projecting collar 3 which is present there, it being of particular significance that the inner wall of the transition region 6 merges into the collar 3 in a rounded manner, in order to ensure the subsequent cross-sectional shape of the cooling duct 8.

[0021] After the piston blank 1 has been produced according to FIG. 3, it can be subjected to final machining, with the result that, after said final machining, the finished cooling duct piston with closure element 10 which is inserted in the gap 9 is available, which finished cooling duct piston or monoblock piston 11 is provided with the designation 11 in FIG. 4. In the case of said design of the cooling duct piston 11 which is shown in the exemplary embodiment, a combustion chamber recess 12 is also made in the piston crown 2. Ring grooves of a ring zone 13 are made in the region of the piston crown 2 and therefore also at least partially in the region of the reshaped collar 3. In the case of said finished cooling duct piston 11, a pin bore is provided with the designation 14 and a piston skirt is provided with the designation 15. At least one opening 16 (bore) is likewise provided for the exchange of cooling medium into the cooling duct 8 and out of it again, which opening 16 has been made parallel to the piston stroke axis 17 in the direction of the cooling duct 8.

[0022] FIG. 5 shows details of the finished one-piece cooling duct piston 11, in which the two-piece or multiple-piece closure element 10 has been inserted into the gap 9. Said closure element 10 is joined together merely at its abutting ends, but is not connected in an integrally joined manner to the piston blank 1 (piston main body). It is therefore, in particular, not welded to the piston blank 1. The gap 9 is closed completely at the top and bottom (in the case of the view of FIG. 4) by way of the closure element 10, or a residual gap can remain, as can be seen clearly in FIG. 4. The land 7 serves to limit the position of the closure element 10. After the closure element 10 has been inserted into the gap 9 and its abutting ends have been joined together, final machining of the cooling duct piston 11 can take place only subsequent to or in addition to a preceding machining operation of the piston blank 1.

[0023] Finally, it is also to be noted that the piston blank 1 or the cooling duct piston 11 is shown in FIGS. 1 to 4 along the piston stroke axis 17 in two different views (in one case on the left and in one case on the right of the piston stroke axis 17).