Method for attaching a ring element to a piston for an internal combustion engine

• US 7,971,355 B2
• Filed: 12/09/2008
• Issued: 07/05/2011
• Est. Priority Date: 12/20/2007
• Status: Expired due to Fees

• Current Assignee: Mahle International GmbH (MAHLE-STIFTUNG GmbH)
• Original Assignee: Mahle International GmbH (MAHLE-STIFTUNG GmbH)
• Inventors: Scharp, Rainer
• Primary Examiner(s): Bryant; David P
• Assistant Examiner(s): Walters; Ryan J
• Application Number:
  US12/316,017
• Publication Number:
  US 20090158925A1
• Time in Patent Office: 938 Days
• Field of Search: 298/880.42, 298/880.4, 298/880.44, 298/880.48, 298/880.49, 294/18, 921/76, 922/16, 922/22, 123/193.6
• US Class Current: 29/888.042
• 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: Y10T 29/49249 Piston making
• CPC Class Codes: Y10T 29/49252 Multi-element piston making
• CPC Class Codes: Y10T 29/49256 with assembly or composite article making
• CPC Class Codes: Y10T 29/49263 by coating or cladding
• CPC Class Codes: Y10T 29/49799 Providing transitory integral holding or handling portion

Abstract

A method for attaching a ring element to a piston for an internal combustion engine, in which the ring element is screwed onto the piston body by a thread applied to the radially outer surface of a part of the piston crown, a circumferential groove that is open towards the top is formed into the piston crown in the region of the thread, the groove is filled with solder material, the piston is heated until the solder material liquefies and flows between the thread channels of the thread and subsequently, the piston is cooled. As a result, a secure screw connection between the basic piston body and the ring element is obtained. Furthermore, the cooling channel is sealed with regard to the combustion gases, which stand under high pressure and act on the piston crown.

Claims

1. A method for attaching a ring element to a piston for an internal combustion engine, the piston having a basic piston body that forms a radially inner part of a piston crown, and having two pin bosses each connected with the piston crown by way of a pin boss support, which pin bosses are connected with one another by way of two skirt elements, wherein a ring element is connected with the basic piston body by way of a thread applied to a radially outer surface of the inner part of the piston crown, said ring element forming a radially outer part of the piston crown, and, together with the basic piston body, forms a circumferential cooling channel disposed radially on the outside and close to the piston crown, and wherein a lower face surface of the ring element comes into contact with a piston-crown-side surface of a circumferential molded-on part affixed to the radially outer surface of the piston, at a level of the pin boss supports, the method comprising the following steps:

providing a projection on the molded-on part, said projection widening the piston-crown-side surface of the molded-on part radially to an outside;

providing a radially outer edge of the inner part and a radially inner edge of the outer part of the piston crown with a bevel;

screwing the ring element onto the basic piston body by way of the thread, wherein the two bevels of the inner and the outer part of the piston crown form a groove that is V-shaped in cross-section;

filling the groove and covering a piston-crown-side surface of the projection with solder material;

heating the piston until the solder material liquefies and flows between thread channels of the thread and between the lower face surface of the ring element and the piston-crown-side surface of the molded-on part;

cooling the piston; and

removing a part of the projection that projects beyond the radially outer surface of the ring element.

2. The method according to claim 1, wherein the basic piston body and ring element are made of AFP steel, the solder material contains copper or nickel, the piston is heated to a temperature between 1050°

C. and 1250°

C., and the piston is cooled to a temperature of less than 600°

C., at a cool-off speed of 5 to 50°

K/min, in an oxygen-free atmosphere.

3. The method according to claim 2, wherein said step of cooling takes place in a vacuum.

4. The method according to claim 2, wherein said step of cooling takes place in a reducing atmosphere.

5. The method according to claim 1, wherein the solder material is in the form of a solder paste.

6. The method according to claim 1, wherein the solder material is in the form of a solder wire.

7. The method according to claim 1, wherein the solder material is in the form of a solder foil.