PISTON WITH A COOLING CHANNEL INSERT

Abstract

A piston for an internal combustion engine has a lower piston part and an upper piston part connected with the lower piston part by welding to form jointly a circumferential cooling channel having inner and outer circumferential walls. The welding process forms weld seams that curl outwards on the inner and outer circumferential walls. An insert is disposed in the circumferential cooling channel. The insert is placed in the cooling channel prior to welding of the upper and lower piston parts, and is clamped in place by at least one of the weld seams that projects into the cooling channel. This way, no additional fabrication or steps need to be taken to hold the insert securely in place in the cooling channel.

Claims

1. A piston for an internal combustion engine, comprising: a lower piston part; and an upper piston part connected with the lower piston part by welding to form jointly a circumferential cooling channel having inner and outer circumferential walls, said upper piston part having a circumferential ring belt provided with ring grooves, wherein the inner circumferential wall has an inner weld seam and the outer circumferential wall has an outer weld seam, each of the weld seams having weld beads protruding therefrom; and an insert disposed in the circumferential cooling channel, said insert being placed in the cooling channel prior to welding of the upper and lower piston parts, and being held in place by at least one of the weld beads.

2. The piston according to claim 1, wherein the insert is formed of aluminum.

3. The piston according to claim 1, wherein the insert extends around a full circumference of the cooling channel.

4. The piston according to claim 1, wherein the insert is held in place by the inner weld seam.

5. The piston according to claim 1, wherein the insert has an L-shaped cross-section.

6. The piston according to claim 1, wherein the insert is configured with at least one vertical bore running therethrough.

7. The piston according to claim 1, wherein the insert has a channel formed on a top surface thereof.

8. The piston according to claim 1, wherein the insert has at least one oil ramp extending upwards into the cooling channel.

9. The piston according to claim 1, wherein the a shape of the cross-section of the insert varies throughout a circumference of the insert.

10. A method for manufacturing a piston, comprising: forming an upper piston part having a piston crown, an outer circumferential wall and an inner circumferential wall; forming a lower piston part having a skirt and pin bosses, an outer circumferential wall and an inner circumferential wall and a cooling channel bottom between the outer circumferential wall and inner circumferential wall; placing an insert into the cooling channel bottom; thereafter connecting the outer and inner circumferential walls of the upper piston part to the outer and inner circumferential walls of the lower piston part by welding, with the formation of weld beads at weld seams and the formation of a closed circumferential cooling channel with the insert disposed therein; wherein the insert is held in place by at least one of the weld beads.

11. The method according to claim 10, wherein the upper and lower piston parts are connected by friction welding.

12. The method according to claim 10, further comprising finishing the piston by machining after the step of connecting.

13. The method according to claim 10, wherein the insert extends around a full circumference of the cooling channel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention.

[0020] In the drawings, wherein similar reference characters denote similar elements throughout the several views:

[0021] FIG. 1 shows a cross-sectional view of the piston according to the invention prior to welding of the two piston parts, and with an insert placed in the cooling channel.

[0022] FIG. 2 shows a cross-sectional view of a finished piston according to the invention having an insert in the cooling channel, with two different cross-sections; and

[0023] FIG. 3 shows another cross-sectional view of a finished piston according to the invention having an insert with two different cross-sections.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0024] Referring now in detail to the drawings, FIG. 1 shows a piston 100 according to the invention. Piston 10 consists of an upper part 10 and a lower part 20. Upper part 10 has the piston crown 11 with a combustion bowl 12, an inner circumferential wall 13 and an outer circumferential wall 14. The upper part of a cooling channel 30 is formed between inner circumferential wall 13 and outer circumferential wall 14.

[0025] Piston lower part 20 consists of a skirt 21, a pin boss 22, and an inner circumferential wall 24 and an outer circumferential wall 25. The lower part of cooling channel 30 is formed between inner circumferential wall 24 and outer circumferential wall 25. An insert 31 is placed in the lower part of cooling channel 30 in lower piston part 20. Insert 31 extends entirely around the circumference of piston 100 and is formed of a material that has a higher thermal coefficient than that of the piston itself. For example, if the piston is made of iron or steel, the insert may be made of aluminum.

[0026] Once insert 31 is placed into lower piston part 20, the upper and lower piston parts are welded together using any suitable welding method, such as friction welding.

[0027] The fully welded piston 100 is shown in FIGS. 2 and 3. Once welded, the finished piston 100 contains a closed circumferential cooling channel 30 and after finish machining, a ring carrier 36. FIGS. 2 and 3 show the piston 100 according to the invention with four different insert shapes 31a, 31b, 31c and 31d. The inserts 31 can have the same shape throughout the entire circumference of the insert, or the shape can change across the circumference. The shapes shown here do not necessarily have to be combined in the manner shown, but can be used alone or in any combination with the other shapes shown.

[0028] During the welding process, weld beads 41 are formed at the weld seams 40 between the outer circumferential walls 14, 25 and weld beads 42 are formed at the weld seam 43 between the inner circumferential walls 13, 24. As can be seen in FIGS. 2 and 3, weld bead 42 is formed directly on top of the inner portion of inserts 31 and essentially clamps them in place within the cooling channel 30, so that any axial motion of the insert 31 is prevented.

[0029] By this process, no additional methods or devices are required to secure the insert within the cooling channel. The present invention provides a simple an inexpensive way to provide a piston with a cooling channel insert that is securely held within the cooling channel.

[0030] The insert 31 can take on various geometries 31a, 31b, 31c and 31d, as shown in FIGS. 2 and 3. In geometry 31a, the insert can take on a basic sheet metal structure that forms a heat sink within the cooling channel 30. The size of the insert can be structured to optimize the shaker volume within the cooling channel.

[0031] Geometry 31b includes an oil ramp 32 that extends upwards from the insert 31. This oil ramp can direct the cooling oil to desired parts of the cooling channel to optimize heat transfer. Geometry 31c includes an integrated shield 33 in the form of a scoop, which also serves to direct the cooling oil in such a way so as to maximize heat transfer. In geometry 31d, a standpipe structure is shown, with a bore 34 through the insert 31. In this geometry, the insert usually has two bores located on opposite sides of the piston. The oil can drain through the bores. In each of the geometries of insert 31, the insert has a lip 36 that extends underneath the weld bead 42 and is clamped in place by weld bead 42. In this embodiment, the weld seams 40 and 43 are located vertically offset from each other, with weld seam 43 being located closer to the bottom of the cooling channel 30. However, the piston could be constructed with any arrangement of the weld seams, as long as one of the weld beads is located so as to clamp the insert in place after welding. For example, in an alternative arrangement, outer weld bead 41 can clamp the insert 31 in place.

[0032] Accordingly, while only a few embodiments of the present invention have been shown and described, it is obvious that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.