One-piece integral skirt piston and method of making the same

Details One-piece integral skirt piston and method of making the same One-piece integral skirt piston and method of making the same

1998-07-28

2001-07-17

Look, Edward K. (Department: 3745)

Expansible chamber devices

Piston

Open-ended hollow skirt type

C092S224000, C092S231000

Reexamination Certificate

active

06260472

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a piston for internal combustion engines and in particular, to a one-piece piston having an upper crown and a lower crown with an integral skirt and a method of making the same.
BACKGROUND OF THE INVENTION
It is known to use one-piece pistons for internal combustion engines. Typically, one-piece pistons have a crown connected to a skirt.
It is known to forge the crown and skirt as one-piece. The forged one-piece piston is then machined to form the component parts of the crown such as piston ring grooves and an annular wall having a recess about its periphery. The annular wall is an outer portion which extends downwardly from the bottom of a piston ring zone to an apex of a piston pin bore. The remaining outer portion material defines a skirt.
Forging the crown and skirt as one-piece undesirably requires excess material during the forming process that must later be machined away. To create the annular recess, for example, an area approximately the height of an upper crown must be removed. Machining away the excess to form the component parts of the one-piece piston, therefore, can be both cumbersome and expensive.
The weight of the piston depends on the weight of the single piece of forged material. Using less material, however, may ultimately decrease the utility and strength of the piston. Using commercially available lighter material such as aluminum tends to impose design constraints, such as the depth of the combustion bowls and the location of the ring grooves.
Additionally, the piston crown endures at least two separate loads in service. The upper crown endures both thermal and mechanical loads created by the combustion gas gathered in the combustion bowl at the top of the upper crown. The lower crown, however, endures a side load from the motion of the crankshaft. In the forged piston, the strength needed to endure the two different loads is determined by the strength of the single material chosen. While steel, for example, is strong enough to handle both loads, its weight and expense makes it inefficient for many applications.
SUMMARY OF THE INVENTION
The present invention is directed to a one-piece piston having an upper and a lower crown with an integral skirt and a method of making the same. The upper crown has an upper surface connected to a lower surface by an outer sidewall. The lower crown has an upper surface and first and second downwardly projecting pin bosses for receiving a wrist pin. The first and second pin bosses have corresponding first and second outer surfaces. A first skirt rib extends from the first outer surface of the first pin boss to the corresponding first outer surface of the second pin boss. A second skirt rib extends from the second outer surface of the first pin boss to the corresponding second outer surface of the second pin boss.
A first collar extends downwardly from the lower surface of the upper crown. Similarly, a second collar extends upwardly and defines the upper surface of the lower crown. Finally, the second collar is friction-welded to the first collar in an opposing facing relationship to form the one-piece piston. It should be understood, however, that other means of securing the first and second collars may be employed.
The present invention is made by forming the upper crown from a first material and the lower crown from a second material. It is preferred that the first and second materials be the same. However, they can also be different.
Thus, the present invention increases flexibility in manufacturing and design. The present invention also reduces the amount of scrap material.
Further, the present invention allows flexibility in fabrication techniques and types of material. For instance, without limitation, the upper and lower crowns can be both forged, both cast or one forged and one cast. The present invention also can optimize the weight and load of each component providing the ability to sustain higher peak combustion pressures.
The one-piece integral skirt configuration of the present invention increases the flexibility of design, the ease of manufacturing, and cost-effective, efficient use of material.


REFERENCES:
patent: 4286505 (1981-09-01), Amdall
patent: 4532686 (1985-08-01), Berchem
patent: 4581983 (1986-04-01), Moebus
patent: 4989559 (1991-02-01), Fletcher-Jones
patent: 5150517 (1992-09-01), Martins Leites et al.
patent: 5359922 (1994-11-01), Martins Leites
patent: 5778846 (1998-07-01), Mielke
patent: WO 9620340 (1996-07-01), None

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