Internal combustion engine

Abstract: An internal combustion engine includes separated oil drain-back and crankcase ventilation passages (20,22). The oil drain-back passages (20) extend from the cylinder head (12) to a position below the top level of oil in the engine's crankcase (24). The crankcase ventilation passages (22) extend from passages formed in the main bearing bulkheads from positions above the oil level in the crankcase (24) and ultimately through the cylinder head (12). Oil dams (36) surrounding the uppermost portions of the crankcase ventilation passages (22) prevent oil from running downwardly through the crankcase ventilation passages (22).

Description: The present invention relates to a system for separating the oil drain-back passages and crankcase ventilation passages in an internal combustion engine. The working gases of an internal combustion engine are generally confined to the combustion chamber and the intake and exhaust ports. A small portion of the working gases, however, escapes from the combustion chamber past the piston rings to the crankcase. These gases are referred to as blow-by and are vented back to the intake system to be recycled through the combustion process. A convenient manner for accomplishing this venting requires that the gases pass upwardly through passages in the engine block and cylinder head. Then, the gases are collected from under a camshaft or rocker arm cover. Of course, lubrication of the bearings and sliding surfaces is a required function in an engine. And, lubrication must be furnished to the upper portion of the engine, including the valve gear, such as camshafts, rocker arms, finger followers, lash adjusters, valve lifters, and other types of hardware known to those skilled in the art and suggested by this disclosure. Lubrication oil is fed from the oil sump via a pump through pressurised passages to the cylinder block and the cylinder head. In the cylinder head, the oil lubricates the camshaft bearings and other valve gear and then drains back to the oil sump. In current state-of-the-art engines, the crankcase ventilation and oil drain functions utilise the same internal passages. That is, oil drains down from the cylinder head to the sump, generally flowing down the walls of the passage, while blow-by gases are vented up from the crankcase and through the cylinder head, generally flowing up the centre of the passage. In such a system the rising blow-by gases can entrain small oil droplets from the oil flow that is draining down to the oil sump. As some of this entrained oil gets past the oil separator it flows into the intake system and contributes to deposits and fouling which adversely effects engine durability. Another shortcoming is that oil foaming can occur from the blow-by gases flowing past the draining oil. Both of these problems contribute to oil oxidation and contamination, which can be detrimental to engine life. The present solution to the problems caused by common crankcase ventilation and oil drain passages is to separate the passages that vent the crankcase gases to the cylinder head from those passages which drain the oil from the cylinder head to the oil sump while, still using internal passages. Although internal, yet separate, crankcase vents and oil drains has been previously attempted, this earlier effort relied on inclination of the engine to concentrate the oil drainage function on the front passages and the venting function to the rear passages. Unfortunately, the engine had no geometrical features which force the oil to drain in one set of passages while crankcase gases are vented in another set of passages. As such, if the angle of inclination of the engine is not proper, the system will be defeated. Other engines have been known to use external passages to separate the venting and drainage functions. External passages present several shortcomings however, because they generally lack long term durability, they are more expensive, they increase weight, and they increase the warm-up time of the engine compared to an engine with internal passages. PCT Application No. WO 96/19655 of Rover Group Limited filed 19 December 1995 describes an internal combustion engine comprising an iron block and an aluminium head held together by bolts. The bolts extend through oil drainage passages in the head and through bores in the block and engage with the block at a point substantially spaced from the head/block interface. According to the present invention, there is provided an internal combustion engine, comprising: a cylinder block; a cylinder head mounted upon the cylinder block, with said cylinder head having an upper deck for collecting oil furnished to the upper part of the engine; a crankcase containing a supply of oil for lubricating the engine; at least one oil drain-back passage extending through the cylinder block and the upper deck; and at least one crankcase vent passage extending through the cylinder block and cylinder head; characterised in that said oil drain-back passage and said crankcase vent passage are functionally separate from each other; said oil drain-back passage extends from a submerged position within the crankcase; and said crankcase vent passage extends from the crankcase at a position which is above the oil level in the crankcase and emerges from the cylinder head at a position which is above the upper deck, wherein portions of said oil drain-back passage and said crankcase vent passage comprise main bearing cap retaining bolt passages formed in said cylinder block (14). Portions of the oil drain-back passages and the crankcase vent passages may conveniently be formed in main bearing bulkheads of the engine. As an aid to manufacturing, these passages may have identical geometries, at least as far as the cylinder block itself is concerned. In an engine embodying the invention portions of the oil drain-back passages and the crankcase vent passages may comprise main bearing cap retaining bolt passages formed in the cylinder block. Portions of the oil drain-back passages and the crankcase vent passages are preferably formed in a bedplate attached to a lower surface of the cylinder block. A system according to the present invention offers the advantage that separation of the venting and drainage functions is assured at any desired engine inclination. An engine constructed according to the present specification will benefit from less sludging of the intake manifold and inlet valves, because less oil will be entrained in the inlet air entering the engine's cylinders. In addition, oil drainage to the sump is ensured for a wide range of engine inclinations and any rate of blow-by flow. The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of an engine cylinder head having passages according to the present invention; Figure 2 is a section of a engine having a cylinder head, cylinder block, and bedplate according to the present invention. The portion of Figure 2 pertaining to the cylinder head is taken along line 2-2 of Figure 1; Figure 3 is a second section of a engine having a cylinder head, cylinder block, and bedplate according to the present invention. The portion of Figure 3 pertaining to the cylinder head is taken along line 3-3 of Figure 1; and Figure 4 illustrates a section of a cylinder head and the uppermost portion of a cylinder block according to the present invention. This Figure is taken along the line 4-4 of Figure 1. Figure 1 is a plan view of engine cylinder head 12 according to the present invention, which is shown in this example as an inline-4 cylinder engine. Those skilled in the art will appreciate, in view of this disclosure, that the present inventive concept applies to engines with any number of cylinders. Figure 1 shows the uppermost parts of a plurality of oil drain-back passages 20, which extend through cylinder head 12. Note that passages 20 are located on opposite sides of some of cylinder head bolt bosses 15. The purpose of oil drain-back passages 20 is to permit lubricating oil which has been furnished to the valve gear (not shown) which is mounted on top of cylinder head 12 in the upper part of the engine to return to the crankcase (Figure 2). Figure 1 further illustrates a plurality of crankcase vent passages 22, which are located on opposite sides of the remaining head bolt bosses 15. The purpose of crankcase vent passages 22 is to permit blow-by gases to exit the crankcase without coming in contact with lubricating oil draining down from cylinder head 12. Figure 2 shows a cross-section of Figure 1 in a plane containing oil drain-back passages 20. Oil flowing from the upper part of the engine falls upon upper deck 28 and then flows through the portion of passages 20 in cylinder head 12 which adjoin head bolt bosses 15. Then, the oil falls through bolt passages 38 formed in cylinder block 14 and into passages 13a formed in the cylinder block's main bearing bulkheads. Thereafter, the oil passes through passages 17 formed in bedplate 16 and into oil pan 24. Because the lower outlets of passages 17 extend below the top level of oil 26 within the crankcase, the blow-by gases cannot escape from the crankcase through oil drain passages 20. Thus, blow-by gases are not entrained in the oil, which reduces the possibility of oil foaming. This result is desirable, because oil foaming can lead to inadequate lubrication of bearing surfaces. An additional benefit resides in the fact that oil is not entrained in the blow-by gases, which may cause intake system deposits and fouling. Figure 3 shows a cross-section of Figure 1 in a plane containing crankcase vent passages 22. The construction of crankcase vent passages 22 is such that the bottom portions of passages 22 are above the uppermost level of oil 26 within oil pan 26. Beginning with passages 19 formed in bedplate 16, crankcase gases pass through the bedplate and into passages 13b formed in cylinder block 14. The geometrical configuration and size of passages 13a and 13b are identical, which is desirable for ease of manufacturing. Having flowed through passages 13b, the crankcase gases pass through bolt passages 38 and up through cylinder head 12. Figure 4 illustrates an important difference between oil drain-back passages 20 and crankcase vent passages 22. In order to prevent oil and crankcase gases from mixing as gases pass upwardly through passages 22, an oil dam 36 is positioned about the upper portion of each of passages 22. Dams 36, which are formed integrally as part of the base casting of cylinder head 12, prevent oil from flowing from upper deck 28 into passages 22. Construction of an engine in the manner herein described assures separated crankcase venting and oil drainage functions at any desired angle of the engine. The distances of the top of the passages above the cylinder head deck and the bottom of the passages from the bottom of the engine determine the maximum angle to which the engine can be inclined and still have separate venting and oil drainage functions. These distances may of course be adjusted to accommodate various engine mounting attitudes. As noted above, crankcase vent passages 22 and the drain passages 20 can be identical in cylinder block 14. This is useful in an engine with a short-skirted cylinder block and a bedplate because the bedplate and cylinder head determine the function of the passages. The present invention is illustrated as being applied to an engine with through-bolted construction where long bolts extend into and clamp together the cylinder head, block, and bedplate instead of using two separate sets of bolts, one clamping the cylinder head to the block and another set clamping the bedplate (or crankshaft main bearing caps) to the block.

Claims: An internal combustion engine, comprising: a cylinder block (14); a cylinder head (12) mounted upon the cylinder block (14), with said cylinder head (12) having an upper deck (28) for collecting oil furnished to the upper part of the engine; a crankcase (24) containing a supply of oil for lubricating the engine; at least one oil drain-back passage (20) extending through the cylinder block (14) and the upper deck (28); and at least one crankcase vent passage (22) extending through the cylinder block (14) and cylinder head (12); Said oil drain-back passage (20) and said crankcase vent passage (22) are functionally separate from each other; said oil drain-back passage (20) extends from a submerged position within the crankcase (24); and said crankcase vent passage (22) extends from the crankcase (24) at a position which is above the oil level in the crankcase (24) and emerges from the cylinder head (12) at a position which is above the upper deck (28), wherein portions of said oil drain-back passage (20) and said crankcase vent passage (22) comprise main bearing cap retaining bolt passages (38) formed in said cylinder block (14) ; characterized in that portions of said oil drain-back passage (20) and said crankcase vent passage (22) are formed in a bedplate (16) attached to a lower surface of said cylinder block (14). An engine according to Claim 1, wherein portions of said oil drain-back passage (20) and said crankcase vent passage (22) are formed in main bearing bulkheads of said engine. An engine according to Claims 1 or 2, wherein the portions of said oil drain-back passage (20) and said crankcase vent passage (22) which are formed in the cylinder block (14) have identical geometrical configurations. An engine according to any one of the preceding claims, wherein said portions of said oil drain-back passage (20) and said crankcase vent passage (22) comprising main bearing cap retaining bolt passages (38) are formed in main bearing bulkheads of said cylinder block (14). An engine according to any one of the preceding claims, wherein the cylinder head (12), the cylinder block (14), and the bedplate (16) are fastened together by means of a plurality of bolts (18) extending through the cylinder head (12) and cylinder block (14) and into the bedplate (16). An engine according to Claim 5 wherein at least one of bolts (18) extends through an oil drain-back passage (20) formed in the cylinder block (14) and at least another one of said bolts (18) extends through a crankcase vent passage (22) formed in the cylinder block (14). An engine according to any one of the preceding claims, having a plurality of said oil drain-back passages (20) and a plurality of said crankcase vent passages (22). An engine according to any one of the preceding claims, wherein the portion of said crankcase vent passage (22) above the upper deck (28) is protected by an oil dam (36).

Inventors: BARASZU DANIEL JAMES, BOGGS DAVID LEE, FOULKES DAVID MARK, GOMES ENIO GOYANNES, BARASZU, DANIEL JAMES, BOGGS, DAVID LEE, FOULKES, DAVID MARK, GOMES, ENIO GOYANNES
Applicants: FORD GLOBAL TECH INC, FORD GLOBAL TECHNOLOGIES, INC.
Application year: 1998
Main classification: F01M13
IPC codes: F01M13, F01M11, F02F7, F02B75