Patent Application
20090026015
1. Technical Field
The present disclosure relates to an internal combustion engine having an oil pan with an internal tunnel to manage oil drain-back flow and air flow.
2. Background Art
Lubrication systems for internal combustion engines that power various types of vehicles often use an oil pan with a wet sump to collect and store lubricating oil until it is recirculated through the lubricating circuits of the engine by an oil pump. Many systems rely only on the force of gravity to return oil to the sump where the pick-up tube for the oil pump is located. Packaging constraints often result in portions of the crankshaft rotating in a relatively shallow area of the oil pan. The rotation of the crankshaft, particularly at high speed, may result in windage, or oil clinging to and splashing against the crankshaft. This generally reduces available power and inhibits oil return to the sump, which may result in oil starvation, i.e. insufficient oil available to lubricate the engine. This problem has been ameliorated by the use of a windage tray, scrapers, screens, louvers, baffles, etc. and/or optimizing the oil drain-back placement to facilitate the return of a sufficient quantity of oil to the sump. One strategy for directing oil flow disclosed in DE 4139195-A1 uses air pulses from the rotating crankshaft to direct oil through a corresponding passage toward the oil pump intake.
The present disclosure recognizes another factor that may contribute to oil aeration and/or oil starvation during high speed operation. Empirical data have indicated that air pulses from the high-speed rotation/reciprocation of components within the shallow portion of the oil pan create a localized high pressure or high turbulence region. This localized high pressure region hinders the return of oil to the sump while also inhibiting crankcase gases from flowing through the high pressure region and out the PCV (positive crankcase ventilation) valve. Crankcase pressure may increase to a level that blow-by gas bubbles or percolates up through the oil drain-back channels further inhibiting oil return to the sump and potentially leading to oil starvation.
A system and method for managing return oil flow and crankcase gas flow in a multiple cylinder internal combustion engine having a plurality of pistons reciprocating within corresponding cylinders of an engine block to rotate a crankshaft include an oil pan having a shallow portion and a deeper sump portion, wherein the shallow portion includes at least one tunnel extending between the shallow portion and the sump portion to block airflow generated by rotation of the crankshaft and facilitate oil flow through a localized high pressure region between the shallow portion and the sump portion.
In one embodiment, an oil pan includes a generally flat plate extending from the bottom to an adjoining side with a first lateral opening beyond the first crank pin of the crankshaft and a second lateral opening near the sump portion. In another embodiment, the tunnel is implemented by a cylinder or tube extending between the shallow portion and the sump portion of the pan. Ribs or other flow diverters may be provided on the top surface of the tunnel to direct oil flow toward the sump portion.
The present disclosure includes embodiments having various advantages. For example, the communication tunnel of the present disclosure blocks turbulent airflow that inhibits return oil flow by providing a passage for return oil flow in addition to crankcase gas flow by venting of blow-by gases through the localized high pressure region created by crankshaft rotation over the shallow portion of the pan. A communication tunnel according to the present disclosure separates the crankcase into two separate regions, which allows more aggressive scraping of a windage tray while preserving a semi-quiescent flow of oil and blow-by gases fore and aft within the tunnel.
The above advantages and other advantages and features will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings.
As those of ordinary skill in the art will understand, various features of the embodiments illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce alternative embodiments that may not be explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations. The representative embodiments used in the illustrations relate generally to a four-stroke, multi-cylinder, internal combustion engine with a gravity return wet sump lubrication system. Those of ordinary skill in the art may recognize similar applications or implementations with other engine/vehicle technologies.
A representative embodiment of an internal combustion engine having an oil pan with a tunnel according to the present disclosure is illustrated generally in
Engine 12 is generally of conventional design with the exception of oil pan 10. Engine 12 includes an oil pump 22 that pumps lubricating oil from the relatively deeper sump portion 24 of oil pan 10 through an oil pick-up tube (not shown) and through oil filter 26 to pressurize various oil delivery passages in engine block 14 during engine operation. Pressurized lubricating oil is then delivered to various engine components. Gravity return passages within block 14 return oil to one or more locations within oil pan 10, which may include one or more locations in shallow portion 30 of oil pan 10.
As shown in
Shallow portion 30 includes at least one tunnel 50 extending between shallow portion 30 and sump portion 24. In the embodiment illustrated in
Empirical data gathered by the present inventors indicated that air pulses from the rotating crankshaft, reciprocating pistons and other rotating components, particularly at higher engine speeds, created a localized high pressure region within shallow portion 30 of oil pan 10. This localized high pressure region hindered or blocked oil draining into shallow portion 30 from one or more gravity return passages from traveling toward sump portion 36. In addition, the high pressure region hindered or blocked blow-by gas from venting through the PCV valve, which instead was bubbling or percolating up through the oil return passages, further inhibiting oil return to sump portion 24. Tunnel 50 functions to block crankshaft generated air flow within the tunnel passage extending between shallow portion 30 and sump portion 24 of oil pan 10 to facilitate oil return flow through tunnel 50 to sump portion 24. As such, tunnel 50 separates the crankcase into two separate regions, which allows more aggressive scraping of any windage tray while preserving a semi-quiescent flow of oil and blow-by gases fore and aft within the tunnel. Tunnel 50 is particularly suited for applications that include a chain-drive cam system that have to drain/return oil from their lubrication systems. These cams are typically driven by a sprocket located on the front or “nose” of the crankshaft so that the systems are positioned in front of the engine such that return oil travels past the high pressure zone within the oil pan.
As the various embodiments illustrate, at least one communication tunnel disposed within the oil pan according to the teachings of the present disclosure blocks turbulent airflow that inhibits return oil flow by providing a passage for return oil flow from the shallow portion to the sump portion of the pan. In addition, the tunnel(s) facilitate positive crankcase ventilation by directing ventilation airflow through the localized high pressure region created by crankshaft rotation over the shallow portion of the pan. A communication tunnel according to the present disclosure separates the crankcase into two separate regions, which allows more aggressive scraping of oil in applications having a windage tray while preserving a semi-quiescent flow of oil and ventilation gases fore and aft in the oil pan through the tunnel.
While the best mode has been described in detail, those familiar with the art will recognize various alternative designs and embodiments within the scope of the following claims. Several embodiments have been compared and contrasted. Some embodiments have been described as providing advantages or being preferred over other embodiments in regard to one or more desired characteristics. However, as one skilled in the art is aware, different characteristics may provide advantages and be preferred in some applications while being considered less desirable or disadvantageous in other applications. These attributes include, but are not limited to: cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, any embodiments described herein as being preferred or advantageous with respect to one or more characteristics do not preclude embodiments or implementations that may be less desirable or advantageous but are also within the scope of the disclosure.
