Piston and method for manufacturing piston

Patent metadata

Field	Value
Publication number	US-10132268-B2
Application number	US-201415032584-A
Country	US
Kind code	B2
Filing date	Oct 22, 2014
Priority date	Oct 30, 2013
Publication date	Nov 20, 2018
Grant date	Nov 20, 2018

Abstract

This piston includes a piston main body made of aluminum or an aluminum alloy, used in an internal combustion and a modified layer formed on a surface of a strength reinforced portion of the piston main body, having a surface made of aluminum oxide by plasma oxidation, to which compressive residual stress is applied.

First claim

The invention claimed is:

1. A method for manufacturing a piston, comprising:
preparing a piston main body made of aluminum or an aluminum alloy, used in an internal combustion;
generating plasma by emission of laser light of ultrashort pulse high peak output density, having a pulse width of not more than 100 nanoseconds, to a surface of a strength reinforced portion of the piston main body under a prescribed emission condition and performing laser peening treatment on the strength reinforced portion of the piston main body with pressure of the plasma that is generated to form a surface made of aluminum oxide by plasma oxidation, to which compressive residual stress is applied;
causing, on the surface of the strength reinforced portion of the piston main body, work-hardening caused by an increase in dislocation density;
causing, on the surface of the strength reinforced portion of the piston main body, strain age hardening caused by congregation of a fine precipitate containing a constituent element of the piston man body in a dislocation by performing thermal treatment after the laser peening treatment has been performed; and
forming a modified layer on the surface of the strength reinforced portion of the piston main body by the strain age hardening and the work-hardening.

2. The method for manufacturing a piston according to claim 1 ,
wherein forming the modified layer includes forming the modified layer having the surface made of the aluminum oxide by the plasma oxidation, to which the compressive residual stress is applied, on the surface of the strength reinforced portion of the piston main body by performing the laser peening treatment on the strength reinforced portion of the piston main body in a state where a liquid film is arranged on the surface of the strength reinforced portion of the piston main body.

3. The method for manufacturing a piston according to claim 1 , wherein the modified layer has hardness larger than hardness of a base material of the piston main body.

4. The method for manufacturing a piston according to claim 1 , wherein
the piston main body is made of cast metal of the aluminum or the aluminum alloy, and
forming the modified layer includes melting and resolidifying a casting surface of the strength reinforced portion of the piston main body made of the cast metal and forming the modified layer having the surface made of the aluminum oxide by the plasma oxidation, to which the compressive residual stress is applied, by performing the laser peening treatment on the strength reinforced portion of the piston main body.

5. The method for manufacturing a piston according to claim 1 , wherein forming the modified layer includes forming the modified layer on an inner surface of a top portion of the piston main body by performing the laser peening treatment on at least the inner surface of the top portion of the piston main body.

6. The method for manufacturing a piston according to claim 1 , wherein
preparing the piston main body includes forming a cutting surface on the piston main body by cutting; and
forming the modified layer includes melting and resolidifying the cutting surface of the strength reinforced portion of the piston main body and forming the modified layer having the surface made of the aluminum oxide by the plasma oxidation, to which the compressive residual stress is applied, by performing the laser peening treatment on the strength reinforced portion of the piston main body.

7. The method for manufacturing a piston according to claim 1 , wherein forming the modified layer includes forming the modified layer by scanning the surface of the strength reinforced portion of the piston main body a plurality of times with the laser light and performing the laser peening treatment on the strength reinforced portion of the piston main body.

Assignees

• Aisin Seiki
• Advanced Laser Tech Research Center Co Ltd
• Advanced Laser Tech Research Center Co Ltd

Inventors

• Niimi Takuya
• Okamoto Akihiro
• Sugano Keiki
• Okazaki Ryo
• Kutsuna Muneharu
• Saito Kiyotaka

Classifications

• B23P15/10

  pistons · CPC title

• F02F2200/00

  Manufacturing · CPC title

• F02F3/10 Primary

  having surface coverings (F02F3/02 takes precedence) · CPC title

• F02F3/0084 Primary

  the pistons being constructed from specific materials · CPC title

• F05C2251/10

  Hardness · CPC title