Patent Application
20090095248
None.
This disclosure relates to a reciprocating internal combustion engine having an in-cylinder structure for removing deposits from the top land of the piston.
Internal combustion engines, particularly diesel or other compression-ignition internal combustion engines, are often required to operate on fuels having widely differing compositions. Unfortunately, some fuels such as marine diesel oil (MDO), or vegetable oils, or other heavy fuels, produce excessive carbon deposits which adhere to the top land of the piston. Such carbon deposits, if sufficiently thick, will rub on the bore of the cylinder and polish the cylinder bore, removing the crosshatched honing marks which are necessary for the provision of adequate piston ring lubrication. If piston rings are not lubricated properly, wear will occur, and the engine will not run properly because it will be unable to develop sufficient compression in the cylinders. Moreover, this type of deposit buildup has been observed even with diesel engines operated on lighter distillate fuels such as diesel No. 2.
It would be desirable to provide a robust, cost-effective device for scraping carbon from the top land of pistons. Such a device would be particularly useful in the context of engines having a welded cylinder heads not permitting use of an inserted deposit scraper ring.
According to one aspect of the present invention, a power assembly for an internal combustion engine includes a cylinder having a circular wall defining a first inside diameter and a piston reciprocably housed within the cylinder. A connecting rod and wrist pin attach the piston to a crankshaft which is mounted within a cylinder block. A cylinder head is attached to an end of the cylinder. An integral piston deposit scraper is formed in a portion of the cylinder wall. The piston deposit scraper defines a second inside diameter which is less than the first inside diameter.
According to another aspect of the present invention, the piston deposit scraper extends downwardly into the cylinder for a distance which is proximate the height of the top land. Accordingly, the piston scraper extends substantially coextensively with the top land when the piston is at a top dead center position.
According to another aspect of the present invention, the piston scraper is formed by upsetting material from the parent metal of the cylinder, whether it be a parent bore cylinder in the cylinder block or a cylinder liner. This upsetting may be accomplished, according to an aspect of the present invention, through the use of a knurling tool.
According to another aspect of the present invention, the upsetting of metal of the cylinder bore results in a number of open top cells having walls, which act as scraper elements to remove combustion deposits from the top land of the piston as the piston reciprocates within the cylinder. The cells may be arranged as a repeating pattern having common walls which act as the scraper elements.
It is an advantage of a system, according to the present invention, that an engine may be reliably operated on heavy fuels which create large amounts of deposits, but without the problem of excessive cylinder bore wear experienced with other types of piston and cylinder combinations.
It is another advantage of a power assembly, according to the present invention, that the maintenance costs of such an engine will be reduced because of the absence of a need to disassemble the engine to remove carbon deposits from the upper part of the engine's cylinders.
It is another advantage that this system may be used with a welded cylinder head not suitable for the application of an inserted scraper ring.
It is another advantage that the present system reduces the cylinder's crevice volume, which aids in the reduction of certain regulated exhaust emissions.
Other advantages, as well as features, of the present invention will become apparent to the reader of this specification.
As shown in
Piston 22 is attached to crankshaft 38 by means of connecting rod 34 and wrist pin 30. Conventional poppet valves 44 handle the ingress and egress of air and exhaust gasses from engine cylinder 14. Fuel injector 43 sprays into combustion chamber 49. Those skilled in the art will appreciate, in view of this disclosure, that the particular type of valving arrangements and the use of injectors, whether in-cylinder, or in-port, are matters not committed to the current invention.
As further shown in
Piston scraper 50 has an installed height (H1,
In the illustrated embodiment, piston scraper 50 is installed or formed in engine 10 by first welding cylinder 14 to cylinder head 46 and then by honing cylinder 14 and, finally, by applying knurling with a knurling machine shown in part in
The foregoing invention has been described in accordance with the relevant legal standards, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and fall within the scope of the invention. Accordingly the scope of legal protection afforded this invention can only be determined by studying the following claims.
