Expansible chamber devices – Piston – Open-ended hollow skirt type
Patent
1989-10-02
1991-03-19
Dolinar, Andrew M.
Expansible chamber devices
Piston
Open-ended hollow skirt type
123193P, F02F 300
Patent
active
050000780
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a light metal trunk piston for internal combustion engines.
2. Prior Art
Such pistons are known from GB-PS No. 12 56 242. In each of the prior art pistons, a control strip is inserted at the top end of the skirt and is of a width which varies over its periphery. The width varies in that the radial thickness of the control strip is at its smallest on the pressure side of the piston and at its greatest on the counter-pressure side. Consequently, on the counter-pressure side of the skirt there is a smaller radial expansion of the upper part of the skirt than there is on the pressure side. Due to the lesser expansion of the upper portion of the skirt on the counter-pressure side under temperature, it is possible to achieve a very close running tolerance of the skirt when it is cold. Linked with the closer running tolerance is a reduction in the running noise when cold, which is greatly influenced by the top land on the counter-pressure side striking the cylinder liner when the engine is cold.
SUMMARY OF THE INVENTION
It is on this premise that the invention is based on the problem, in the case of a piston of the type mentioned at the outset, of still further reducing the noise caused by the piston head striking the cylinder liner on the counter-pressure side when the piston is cold.
In the case of a piston of the type mentioned at the outset, this problem is resolved by an embodiment of piston skirt according to the characterising features described hereinafter.
Expedient further developments of the invention are the object of the sub-Claims. Particular significance attaches to the teaching according to claim 2, and this will be dealt with in greater detail hereinafter.
As a result of the design and outer form of the piston skirt, when it is cold, the piston assumes a position in the engine cylinder in which the piston head has its top end on the pressure side so inclined in relation to the cylinder liner that in the region of the top land the clearance in respect of the cylinder liner is greater on the counter-pressure side than it is on the pressure side. Consequently, when the engine has just been started and when it is running on partial load, when the piston is still at a relatively low temperature, noise build-up due to the ring portion striking the counter-pressure side can be avoided.
The indicated inclination of the piston head when the piston is cold in the engine cylinder is achieved in that the outer surface on the counter-pressure side is inclined from the top downwardly vis-a-vis the longitudinal axis of the piston, the radial distance in respect of the piston axis diminishing, in fact, towards the bottom end of the piston skirt. Bearing of the piston on the thus inclined outer surface on the counter-pressure side is further favored by reason of the inclination of the outer surface of the piston skirt which according to claim 2 is orientated in the opposite direction on the pressure side. This statement again relates to the situation when cold.
The pattern of the generatrix which is substantially rectilinear over a wide portion on the counter-pressure side is advantageous to the attainment of the inclined attitude of the piston which is desired for partial loading of the engine.
As the piston skirt becomes increasingly heated, the control strip inserted on the counter-pressure side in the upper end portion of the skirt impedes the expansion of the light metal under heat in this area of the skirt, while the lower portion of the skirt on the counter-pressure side can expand considerably more since it is not impeded by a control strip. Thus, the generatrix on the counter-pressure side of the skirt when the engine is under full load assumes a pattern which is orientated substantially parallel with the longitudinal axis of the piston head. Therefore, the piston head then also runs centrally in the cylinder bore.
The other control strip which is provided on the pressure side, in the lower portion of the skirt, exerts an
REFERENCES:
patent: 1825750 (1931-10-01), McCoy
patent: 2086677 (1937-07-01), Nelson
patent: 2110346 (1938-03-01), Teetor
patent: 2551488 (1951-05-01), Deming
patent: 3908521 (1975-09-01), Cockcroft
patent: 4074617 (1978-02-01), Cockcroft
patent: 4669366 (1987-06-01), Ellermann et al.
patent: 4890543 (1990-01-01), Kudou et al.
Dolinar Andrew M.
Macy M.
Mahle GmbH
Wray James C.
LandOfFree
Light metal trunk piston for internal combustion engines does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Light metal trunk piston for internal combustion engines, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Light metal trunk piston for internal combustion engines will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2001816