Multipiece piston

• US 6,622,613 B1
• Filed: 09/06/2001
• Issued: 09/23/2003
• Est. Priority Date: 03/10/1999
• Status: Expired due to Term

• Current Assignee: Mahle GmbH (MAHLE-STIFTUNG GmbH)
• Original Assignee: Mahle GmbH (MAHLE-STIFTUNG GmbH)
• Inventors: Kortas, Jochen, Lipp, Stefan, Sander, Wilfried
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): Kershteyn, Igor
• Application Number:
  US09/914,973
• Time in Patent Office: 747 Days
• Field of Search: 922/20, 922/22, 922/23, 922/24, 922/25, 922/26, 922/27, 922/28, 922/29, 922/30
• US Class Current: 92/223
• CPC Class Codes: F02F 2200/04 Forging of engine parts
• CPC Class Codes: F02F 3/0023 the parts being bolted or screwed together
• CPC Class Codes: F02F 3/003 the parts being connected by casting, brazing, welding or clamping
• CPC Class Codes: F02F 3/22 the fluid being liquid
• CPC Class Codes: F05C 2201/021 Aluminium
• CPC Class Codes: F05C 2201/0448 Steel

Abstract

A multipiece piston comprises a steel upper part and a lower part which is screwed to the upper part and which contains the hubs. The design of the piston improves the strength of the lower part and its resistance to material defects, and reduces production cost. The lower part of the piston consists of a precipitation-hardened ferrite-pearlite steel, preferably according to EN 10267 and with added titanium. The hubs of the lower part are preferably not reinforced with bushings.

Claims

1. A multipiece piston with an upper part made of steel and a lower part screwed to the upper part, said lower part containing hubs and a material different from the upper part, wherein the lower part consists of precipitation-hardened, ferrite-pearlite steel (AFP steel) and is extruded or forged.

2. The multipiece piston according to claim 1, where in the material of the lower part is a precipitation-hardened, ferrite-pearlite steel according to steel-iron data sheet EN 10267.

3. The multipiece piston according to claim 1, wherein the precipitation-hardened, ferrite-pearlite steel also has a titanium content of 0.01-0.05 weight percent.

4. The multipiece piston according to claim 1, wherein the hubs of the piston are not reinforced with bushings and pins and/or hub borings of the piston are coated.

5. The multipiece piston according to claim 4, wherein the hub borings and/or the pins of the piston are phosphatized.

6. The multipiece piston according to claim 1, wherein the maximum surface pressure occuring in the hubs is >

85 n/mm.

7. The multipiece piston according to claim 1, wherein the lower part has at least one recess in a region neighboring the upper part for receiving cooling oil, said at least one recess being produced through machining.

8. The multipiece piston according to claim 1, wherein a diameter of the lower part measures at least 160 mm.

9. The multipiece piston according to claim 1, wherein a diameter of the lower part measures at least 250 mm.