Steel piston for internal combustion engines

Patent metadata

Field	Value
Publication number	US-9051896-B2
Application number	US-201013390717-A
Country	US
Kind code	B2
Filing date	Sep 3, 2010
Priority date	Oct 2, 2009
Publication date	Jun 9, 2015
Grant date	Jun 9, 2015

Abstract

A steel piston with a piston upper part ( 12 ) with combustion chamber recess ( 11 ) and ring wall ( 5 ), and with a piston lower part ( 13 ) with piston body or piston skirt and with connecting rod bearing ( 8 ) for internal combustion engines with cylinder crankcases made of lightweight metal alloys, with at least the piston lower part consisting of a steel alloy which has a coefficient of thermal expansion in the range from 13 to 20×10−6 1/K.

First claim

The invention claimed is:

1. A combustion engine with
steel pistons with
a piston upper part ( 12 ) with a combustion chamber recess ( 11 ) and a ring wall ( 5 ), and
a piston lower part ( 13 ) with a piston body or piston skirt and with a connecting rod bearing ( 8 ) and

a cylinder crankcase made substantially of an aluminum alloy having a coefficient of thermal expansion at 20° C. in the range from 19 to 25×10 −6 /K and having it's cylinder running surface formed as a thermally sprayed layer,
wherein the piston upper part consists of a wear-resistant alloyed heat treatment steel of the group MoCr4, 42CrMo4, CrMo4, 31CrMoV6 or 25MoCr4 and the piston lower part consists of a steel alloy which has a coefficient of thermal expansion at 20° C. in the range from 13 to 20×10 −6 1/K, and
wherein the coefficient of thermal expansion of the piston lower part matches the coefficient of thermal expansion of the cylinder crankcase sufficiently to overcome piston slap.

2. The combustion engine as claimed in claim 1 , wherein at least the steel alloy of the piston lower part has a coefficient of thermal expansion at 20° C. in the range from 15 to 19×10 −6 1/K.

3. The combustion engine as claimed in claim 1 , wherein at least the steel alloy of the piston lower part consists of a high grade steel with a Cr content of 15-26% and an Ni content of 8-15%.

4. The combustion engine as claimed in claim 3 , wherein the piston upper part and piston lower part are joined together by friction welding, laser welding or induction welding.

5. The combustion engine as claimed in claim 1 , wherein the aluminum alloy has a Si content in the range from 7 to 12% by weight.

6. A combustion engine with
steel pistons with
a piston upper part ( 12 ) with a combustion chamber recess ( 11 ) and a ring wall ( 5 ), and
a piston lower part ( 13 ) with a piston body or piston skirt and with a connecting rod bearing ( 8 ) and

a cylinder crankcase made substantially of an aluminum alloy having a coefficient of thermal expansion at 20° C. in the range from 19 to 25×10 −6 /K and having it's cylinder running surface formed as a thermally sprayed layer directly applied to the inner wall of the cylinder bore made from an Al—Si alloy,
wherein the piston upper part consists of a wear-resistant alloyed heat treatment steel of the group MoCr4, 42CrMo4, CrMo4, 31 CrMoV6 or 25MoCr4 and the piston lower part consists of a steel alloy which has a coefficient of thermal expansion at 20° C. in the range from 13 to 20×10 −6 1/K, and
wherein the coefficient of thermal expansion of the piston lower part matches the coefficient of thermal expansion of the cylinder crankcase sufficiently to overcome piston slap.

7. A combustion engine with
steel pistons with
a piston upper part ( 12 ) with a combustion chamber recess ( 11 ) and a ring wall ( 5 ), and
a piston lower part ( 13 ) with a piston body or piston skirt and with a connecting rod bearing ( 8 ) and

a cylinder crankcase made substantially of an aluminum alloy having a coefficient of thermal expansion at 20° C. in the range from 19 to 25×10 −6 /K and having it's cylinder running surface formed as a thermally sprayed layer based on an iron alloy, which is directly applied to the inner wall of the cylinder bore made from an Al—Si alloy,
wherein the piston upper part consists of a wear-resistant alloyed heat treatment steel of the group MoCr4, 42CrMo4, CrMo4, 31 CrMoV6 or 25MoCr4 and the piston lower part consists of a steel alloy which has a coefficient of thermal expansion at 20° C. in the range from 13 to 20×10 −6 1/K, and
wherein the coefficient of thermal expansion of the piston lower part matches the coefficient of thermal expansion of the cylinder crankcase sufficiently to overcome piston slap.

Assignees

• Haug Tilmann
• Daimler Ag

Inventors

• Haug Tilmann

Classifications

• F02F3/02

  having means for accommodating or controlling heat expansion · CPC title

• C22C38/58

  with more than 1.5% by weight of manganese · CPC title

• C22C38/02

  containing silicon · CPC title

• F05C2201/0448

  Steel · CPC title

• F05C2201/021

  Aluminium · CPC title