Composite Piston for an Internal Combustion Engine

• US 20080011262A1
• Filed: 06/17/2005
• Published: 01/17/2008
• Est. Priority Date: 06/19/2004
• Status: Active Grant

• Current Assignee: Mahle GmbH (MAHLE-STIFTUNG GmbH)
• Original Assignee: Mahle GmbH (MAHLE-STIFTUNG GmbH)
• Inventors: Scharp, Rainer, Kemnitz, Peter
• Granted Patent: US 7,464,684 B2
• Time in Patent Office: Days
• US Class Current: 123/193.6
• CPC Class Codes: F02F 3/0023 the parts being bolted or screwed together
• CPC Class Codes: F16B 33/02 Shape of thread; Special thread-forms F16B25/00 takes precedence; used to remove paint or dirt layers F16B35/007, F16B37/002; used as screw-locking device F16B39/30
• CPC Class Codes: F16B 5/0275 the screw-threaded element having at least two axially separated threaded portions F16B5/0283 takes precedence

Abstract

The invention relates to an assembled piston (1) for an internal combustion engine, said piston consisting of an upper part (4) and a lower part (5) that are interconnected by means of an internal hexagon screw (6) consisting of an upper half (37) and lower half (38). The upper half (37) of the internal hexagon screw (6) comprises an external thread (39) which is parallel to the external thread (40) of the lower screw half (38) and has a larger lead angle than the same (40). The lead angle resulting from the difference between the lead angles of the two external threads (39, 40) is very small and contributes to a high strength of the screw connection.

Claims

1. Composite piston (1) for an internal combustion engine

consisting of an upper part (4) that forms the piston crown (7),

having a recess (20) disposed on the underside facing away from the piston crown, and circumferential with rotation symmetry relative to the longitudinal piston axis (31), and

having a dead-end bore (32) with inside thread (33) disposed on the underside and coaxial to the longitudinal piston axis (31), and

consisting furthermore of a lower part (5),

having two pin bosses (27, 27′

) disposed on the underside at a distance from one another, each having a pin bore (3, 3′

),

having skirt elements (41, 41′

) that connect the pin bosses (27, 27′

) with one another,

having a recess (21) disposed on the top and circumferential with rotation symmetry relative to the longitudinal piston axis (31), which recess forms an inner cooling channel (22) together with the recess (20) of the upper part (4), and

having a passage bore (34) with thread (35) disposed on the top and coaxial to the longitudinal piston axis (31),

whereby the upper part (4) and the lower part (5) are connected with one another by means of a hexagonal socket screw (6), which consists of an upper half (37) and a lower half (38), each having an outside thread (39, 40) configured in such a manner that the outside thread (39) of the upper screw half (37) can be screwed into the dead-end bore (32) and the outside thread (40) of the lower screw half (38) can be screwed into the passage bore (34), and that the diameter of the outside thread (39) of the upper screw half (37) is smaller, by such a dimension, than the diameter of the outside thread (40) of the lower screw half (38), that the upper screw half (37) can be pushed through the passage bore (34) without hindrance,

wherein

the outside thread (39) of the upper screw half (37) is configured to run in the same direction with the outside thread (40) of the lower screw half (38), and

the outside thread (39) of the upper screw half (37) has a greater pitch angle than the outside thread (40) of the lower screw half (38).

2. Composite piston according to claim 1, wherein the lower piston part (5) is configured to be so thin-walled, in the region (43) of the recess (21), that the region is elastically resilient in the manner of a disk spring.