# US 2009/0260593 A1 · Two-part piston for an internal combustion engine

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- Number: US 2009/0260593 A1
- Document ID: US20090260593A1
- Status: Published application
- Kind: A1
- Application number: 11/991,238
- Filed: 2006-08-31
- Published: 2009-10-22
- Earliest claimed: 2005-09-01
- Assignees: Mahle International GmbH
- Inventors: Dieter Messmer
- Web page: https://patentgrep.com/patent/US20090260593A1

## CPC

- F02F 3/0023: {the parts being bolted or screwed together}
- F02F: CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES

## Abstract

A two-piece piston for an internal combustion engine has an upper piece and a lower piece, the lower piece having an upper base part with an opening lying coaxial to the piston axis into which a pin on the upper piece is inserted. The upper piece is connected to the lower piece with a hexagonal nut screwed onto the pin. A resilient sleeve is arranged between the upper piece and the lower piece comprising an inwardly directed collar on the against which the upper face of the hexagonal nut lies and in the region facing away from the piston crown, a contact surface facing the piston crown lying on a surface on the inner side of the opening. An economically produced two-piece piston results with a resilient sleeve between both screwed piston pieces which exerts a pre-tensioning and thus provides security for the screw connection.

## Claims

### Claim at position 1

1: Two-part piston (1, 1″) for an internal combustion engine,
having an upper part (2, 2″) that forms a piston crown (4, 4′),
whereby a cylindrical pin (31) having an outside thread (32) and lying coaxial to the piston axis (12) is formed onto the underside of the upper part (2, 2″), on the side facing away from the piston crown (4, 4″), and
having a lower part (3, 3″), on the underside of which pin bosses (9, 9′) having pin bores (10, 10′) and skirt elements (13) that connected the pin bosses (9, 9′) with one another are disposed,
whereby the lower part (3, 3′, 3″) has an upper crown part (25, 25′) with an opening (27, 27′) that lies coaxial to the piston axis (12), into which opening the pin (31) is introduced, by way of which pin the upper part (2, 2″) is screwed to the lower part (3, 3″) by means of a hexagonal nut (29) screwed onto the pin (31),
wherein
the radial inside of the opening (27) has a ring-shaped surface (21) disposed on the skirt side, which lies further removed from the piston crown (4) than the upper face surface (23) of the hexagonal nut (29), and
that an expansion sleeve (26) is disposed between the face surface (23) and the surface (21), which sleeve, for one thing, has a collar (28) directed radially inward, disposed on its side facing the piston crown, this collar having a radially oriented inside surface (20) on its side facing away from the piston crown, against which surface the face surface (23) of the hexagonal nut (29) rests, and, for another thing, has a contact surface (19) that faces the piston crown in its region that faces away from the piston crown, which surface rests against the surface (21).

### Claim at position 2 (depends on 1)

2: Piston according to claim 1, wherein the contact surface (19) in the region of the expansion sleeve (26) facing away from the piston crown and the surface (21) on the radial inside of the opening (27) are configured to widen conically outward in the direction facing away from the piston crown.

### Claim at position 3 (depends on 1)

3: Piston according to claim 1, wherein the contact surface (19) in the region of the expansion sleeve (26) facing away from the piston crown is configured to be spherical.

### Claim at position 4 (depends on 1)

4: Piston according to claim 1, wherein the contact surface (19) in the region of the expansion sleeve (26) facing away from the piston crown is configured to be ball-shaped.

### Claim at position 5 (depends on 1)

5: Piston according to claim 1,
whereby the piston (1, 1″) has a ring-shaped, outer cooling channel (22) in its edge region on the piston crown side, which channel is connected with the piston interior (36) by way of at least one oil feed channel (52),
whereby the piston (1, 1″) has a ring-shaped, inner cooling channel (24), within the outer cooling channel (22), disposed coaxial to the piston axis (12), delimited radially on the inside by the pin (31), which channel is connected with the outer cooling channel (22) by way of at least one overflow channel (37, 37′), and
whereby a ring-shaped gap (33) is situated between the collar (28) of the expansion sleeve (26, 26″) and the pin (31),
wherein
the hexagonal nut (29) has at least one radially disposed groove (34, 34′, 34″, 34′″) in its upper face surface (23), which groove opens radially on the inside, into the gap (33),
that an interstice (35) is situated between the hexagonal nut (29) and the expansion sleeve (26, 26″), the end of which interstice, on the piston crown side, stands in connection with the at least one groove (34, 34′, 34″, 34′″),
that the end of the interstice (35) facing away from the piston crown opens into the piston interior (36), and
that a continuous oil channel occurs, proceeding from the oil feed channel (52), by way of the outer cooling channel (22), by way of the at least one overflow channel (37, 37′), by way of the inner cooling channel (24), by way of the gap (33) between the collar (28) and the pin (31), by way of the at least one groove (34, 34′, 34″, 34′″) in the face surface (23) of the hexagonal nut (29), and by way of the interstice (35) between the hexagonal nut (29) and the pin (31).

### Claim at position 6 (depends on 5)

6: Piston according to claim 5, wherein the hexagonal nut (29) has four radially disposed grooves (34, 34′, 34″, 34′″) distributed uniformly over its circumference, on its upper face surface (23).

### Claim at position 7 (depends on 1)

7: Piston according to claim 1, wherein a collar (44) directed radially outward is disposed on the end of the expansion sleeve (26″) facing away from the piston crown, which collar has a radially oriented contact surface (19′) on the piston crown side, and that a cantilever (45) that narrows conically radially inward in the direction facing away from the piston crown and is elastically resilient is formed onto the inside wall of the opening (27′), which cantilever has a radially oriented surface (21′) on its side facing away from the piston crown, against which surface the contact surface (19′) rests.

### Claim at position 8

8: Two-part piston (1′) for an internal combustion engine,
having an upper part (2′) that forms a piston crown (4″),
whereby a dead-end hole bore (49) with inside thread, which lies coaxial to the piston axis (12), is disposed on the underside of the upper part (2′) facing away from the piston crown (4″), and
having a lower part (3′), on the underside of which pin bosses (9″, 9′″) with pin bores (10″, 10′″) and skirt elements (13′) that connect the pin bosses (9″, 9′″) with one another are disposed,
whereby the lower part (3′) has an upper crown part (25″) having an opening (27″) that lies coaxial to the piston axis (12), by way of which the upper part (2′) is connected with the lower part (3′) by means of a hexagonal screw (39)
wherein
the radial inside of the opening (27″) has a ring-shaped surface (21″) disposed on the skirt side,
that the head (40) of the hexagonal screw (39) has a contact surface (51) radially on the outside, on the piston crown side,
that a tube-shaped intermediate piece (41) with an upper face surface (50) is disposed on the contact surface (51), whereby the face surface (50) lies closer to the piston crown (4″) than the surface (21″), and
that an expansion sleeve (26) are disposed between the face surface (50) of the intermediate piece (41) and the surface (21″), which sleeve, for one thing, has a collar (28′) directed radially inward on its side facing the piston crown, this collar having a radially oriented inside surface (20) disposed on its side facing away from the piston crown, which surface rests on the face surface (50), and, for another thing, has a contact surface (19) that faces the piston crown in its region that faces away from the piston crown, which surface rests against the surface (21″).

### Claim at position 9 (depends on 8)

9: Piston according to claim 8,
whereby the piston (1′) has a ring-shaped, outer cooling channel (22′) in its edge region, on the piston crown side, which channel is connected with the piston interior (36′) by way of at least one oil feed channel (52′).
whereby the piston (1′) has a ring-shaped, inner cooling channel (24′), within the outer cooling channel (22′), disposed coaxial to the piston axis (12), delimited radially on the inside by the hexagonal screw (39), which channel is connected with the outer cooling channel (22′) by way of at least one overflow channel (37″), and
whereby a ring-shaped gap (33′) is situated between the collar (28′) of the expansion sleeve (26′) and the shaft of the hexagonal screw (39),
wherein
a tube-shaped intermediate piece (41) is disposed between the head (40) of the hexagonal screw (39) and the collar 28′),
whereby the radial inside diameter of the intermediate piece (41) is greater than the radial outside diameter of the shaft of the hexagonal screw (39), so that a first interstice (53) occurs between them,
whereby the radial outside diameter of the intermediate piece (41) is smaller than the radial inside diameter of the expansion sleeve (26′), so that a second interstice (54) occurs between them, and
whereby the intermediate piece (41) has a least one continuous, radially lying bore (42, 42′) as a connection between the first interstice (53) and the second interstice (54),
that the radial diameter of the head (40) of the hexagonal screw (39) is smaller than the radial inside diameter of the expansion sleeve (26′), so that a third interstice (35′) occurs between the head (40) and the expansion sleeve (26′), and
that a continuous oil channel occurs, proceeding from the oil feed channel (52′), by way of the outer cooling channel (22′), by way of the at least one overflow channel (37″), by way of the inner cooling channel (24′), by way of the gap (33′), by way of the first interstice (53), by way of the at least one bore (42, 42′) in the intermediate piece (41), by way of the second interstice (54), and by way of the third interstice (35′).