Multi-part cooled piston for an internal combustion engine

• US 6,763,758 B2
• Filed: 09/18/2002
• Issued: 07/20/2004
• Est. Priority Date: 03/09/2002
• Status: Expired due to Fees

• Current Assignee: Mahle GmbH (MAHLE-STIFTUNG GmbH), United States Secretary of the Army
• Original Assignee: Mahle GmbH (MAHLE-STIFTUNG GmbH)
• Inventors: Kemnitz, Peter, Messmer, Dieter
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): LESLIE, MICHAEL S
• Application Number:
  US10/246,135
• Publication Number:
  US 20030167918A1
• Time in Patent Office: 671 Days
• Field of Search: 921/86, 922/55, 123/193.6, 123/41.35
• US Class Current: 92/186
• CPC Class Codes: F02F 3/0023 the parts being bolted or screwed together
• CPC Class Codes: F02F 3/22 the fluid being liquid

Abstract

A multi-part cooled piston for an internal combustion engine comprises a one-piece piston upper part having a combustion bowl and an annular wall with a piston-ring part, and a one-piece piston lower part having a box-like piston skirt, and bosses to receive the piston pins joining the piston to the connecting rod and boss supports, which are joined to the piston skirt. A cooling channel is formed through the piston upper part and also the piston lower part and is limited thereby in its cross section. A reduction of the compression height and an increase of the heat load can be achieved with this piston despite increasing engine power. The piston can also be assembled without microstructural change. The piston upper part and the piston lower part are provided with support elements having seating faces, which form a first and a second seat. The support element comprising the first seat is provided with threads for screwing the two piston parts together, and in the screwed together condition of the piston upper part and piston lower part, the two piston parts are braced exclusively via the first and second seats.

Claims

1. A multi-part cooled piston for an internal combustion engine, comprising:

a piston upper part having a combustion bowl and an annular wall with a piston-ring part;

a piston lower part having a box-like piston skirt, bosses to receive piston pins joining the piston to a connecting rod and boss supports, which are joined to the piston skirt;

a cooling channel formed by the piston upper part and the piston lower part and being limited thereby in cross section;

support elements on the piston upper part and lower part, said support elements having seating faces which form a first and a second seat, wherein the support element comprising the first seat is provided with threads for screwing the piston upper and lower parts together, said threads being configured as a male thread on a circumferential side of an annular rib disposed radially outward relative to a piston diameter and as a female thread on a circumferential side of an annular load-bearing rib disposed radially inward,

wherein in a screwed together condition of the piston upper part and piston lower part, the two piston parts are supported exclusively via the first and second seats.

2. A multi-part cooled piston according to claim 1, wherein the first and second seats are disposed in respectively different horizontal planes relative to a piston height.

3. A multi-part cooled piston according to claim 1, wherein the first seat is disposed radially inward relative to a piston diameter and forms an inner support for the piston upper part, and the second seat is disposed radially outward relative to the piston diameter and forms an outer support for the piston upper part.

4. A multi-part cooled piston according to claim 1, wherein the support element of the piston upper part comprises one of the seating faces disposed on a bottom side remote from the combustion bowl, a part of a horizontal cross-sectional face of the annular wall and an annular rib, and wherein the support element of the piston lower part comprises an annular load-bearing rib, a cross-sectional face of the annular load-bearing rib, an annular load-bearing ridge and a cross-sectional face of the annular load-bearing ridge.

5. A multi-part cooled piston according to claim 4, wherein the annular rib extending toward the pin boss has in an axial piston direction on at least partly cylindrical or conical portion, which is threaded and oriented parallel to a piston axis (K).

6. A multi-part cooled piston according to claim 4, wherein the seating faces of the first seat comprise the seating face disposed on a bottom side remote from the combustion bowl, and the cross-sectional face of the load-bearing rib.

7. A multi-part cooled piston according to claim 1, wherein the piston upper part is made of an oxidation-resistant or heat-resisting material and the piston lower part is made of a precipitation-hardening ferritic-pearlitic steel or quenched and tempered steel.

8. A multi-part cooled piston for an internal combustion engine, comprising:

a piston upper part having a combustion bowl and an annular wall with a piston-ring part;

a piston lower part having a box-like piston skirt, bosses to receive piston pins joining the piston to a connecting rod and boss supports, which are joined to the piston skirt;

a cooling channel formed by the piston upper part and the piston lower part and being limited thereby in cross section;

support elements on the piston upper part and lower part, said support elements having seating faces which form a first and a second seat, wherein the support element comprising the first seat is provided with threads for screwing the piston upper and lower parts together, and wherein the support element of the piston upper part comprises one of the seating faces disposed on a bottom side remote from the combustion bowl, a part of a horizontal cross-sectional face of the annular wall and an annular rib, and wherein the support element of the piston lower part comprises an annular load-bearing rib, a cross-sectional face of the annular load-bearing rib, an annular load-bearing ridge and a cross-sectional face of the annular load-bearing ridge;

wherein in a screwed together condition of the piston upper part and piston lower part, the two piston parts are supported exclusively via the first and second seats, and wherein the annular rib extending toward the pin boss has in an axial piston direction an at least partly cylindrical on conical portion, which is threaded and oriented parallel to a piston axis (K), and wherein the cylindrical or conical portion of the annular rib is followed in a direction of the combustion bowl by a portion with reduced wall thickness.

9. A multi-part cooled piston for an internal combustion engine, comprising:

a piston upper part having a combustion bowl and an annular wall with a piston-ring part;

a piston lower part having a box-like piston skirt, bosses to receive piston pins joining the piston to a connecting rod and boss supports, which are joined to the piston skirt;

a cooling channel formed by the piston upper part and lower part, said support elements having seating faces which form a first and a second seat, wherein the support element comprising the first seat is provided with threads for screwing the piston upper and lower parts together, wherein the support element of the piston upper part comprises one of the seating faces disposed on a bottom side remote from the combustion bowl, a part of a horizontal cross-sectional face of the annular wall and an annular rib, and wherein the support element of the piston-lower part comprises an annular load-bearing rib, a cross-sectional face of the annular load-bearing rib, an annular load-bearing ridge and a cross-sectional face of the annular load-bearing ridge, wherein in a screwed together condition of the piston upper part and piston lower part, the two piston parts are supported exclusively via the first and second seats,and wherein a radius R_{outer surface} (R_M) of the annular rib lies in a range R_{outer surface}<

R_{middle of boss support} (R_MN) and R_{outer surface}>

R_{inner end of boss support} (R_IEM), all radii being defined as extending from a longitudinal axis (K) of the piston in a radial direction toward an outer surface of the piston and the radii at “

middle of boss support” and

“

inner end of boss support”

being relative to a zenith (N_z) of the boss bore.

10. A multi-part cooled piston for an internal combustion engine, comprising:

a piston upper part having a combustion bowl and an annular wall with a piston-ring part;

a piston lower part having a box-like piston skirt, bosses to receive piston pine joining the piston to a connecting rod and boss supports, which are joined to the piston skirt;

a cooling channel formed by the piston upper part and the piston lower part and being limited thereby in cross section;

support elements on the piston upper part and lower part, said support elements having seating faces which form a first and a second seat, wherein the support element comprising the first seat is provided with threads for screwing the piston upper and lower parts together, wherein the support element of the piston upper part comprises one of the seating faces disposed on a bottom side remote from the combustion bowl, a part of a horizontal cross-sectional face of the annular wall and an annular rib, and wherein the support element of the piston lower part comprises an annular load-bearing rib, a cross-sectional face of the annular load-bearing rib, an annular load-bearing ridge and a cross-sectional face of the annular load-bearing ridge, and wherein the seating faces of the first seat comprise the seating face disposed on a bottom side remote from the combustion bowl, and the cross-sectional face of the load-bearing rib, and wherein in a screwed together condition of the piston upper part and piston lower part, the two piston parts are supported exclusively via the first and second seats, and wherein the first seat is disposed approximately centrally relative to the piston ring part.

11. A multi-part cooled piston for an internal combustion engine, comprising:

a piston upper part having a combustion bowl and an annular wall with a piston-ring part;

a piston lower part having a box-like piston skirt, bosses to receive piston pins joining the piston to a connecting rod and boss support, which are joined to the piston skirt;

a cooling channel formed by the piston upper part and the piston lower part and being limited thereby in cross section;

support elements on the piston upper part and lower part, said support elements having seating faces which form a first and a second seat, wherein the support element comprising the first seat is provided with threads for screwing the piston upper and lower parts together, wherein in a screwed together condition of the piston upper part and piston lower part, the two piston parts are supported exclusively via the first and second seats, and wherein the second seat comprises a part of an entire cross-sectional face of the annular wall and of a cross-sectional face of an annular load-bearing ridge, so that there is obtained a stepped structure of the load-bearing ridge, by which the piston upper part is centered.

12. A multi-part cooled piston according to claim 11, wherein the second seat is disposed underneath a lowest piston-ring groove at a distance.

13. A multi-part cooled piston for an internal combustion engine, comprising:

a piston upper part having a combustion bowl and an annular wall with a piston-ring part;

a piston lower part having a box-like piston skirt, bosses to receive piston pins joining the piston to a connecting rod and boss supports, which are joined to the piston skirt;

a cooling channel formed by the piston upper part and the piston lower part and being limited thereby in cross section;

support elements on the piston upper part and lower part, said support elements having seating faces which form a first and a second seat, wherein the support element comprising the first seat is provided with threads for screwing the piston upper and lower parts together, wherein in a screwed together condition of the piston upper part and piston lower part, the two piston parts are supported exclusively via the first and second seats, and wherein the cooling channel produced when the piston upper part is screwed together with the piston lower part is sealed only by the seating faces.