Patent Application
20160201595
The present disclosure relates generally to the field of combustion engines, and more particularly, to a crankcase ventilation system for use in connection with such combustion engines which lessen the amount of oil entrained in the combustion blow-by gases that are pulled into the crankcase ventilation system.
Internal combustion engines generally consist of a bank of cylinders where the combustion of a fuel/air mixture takes place. The cylinders generally act as a sleeve for housing the piston for reciprocating movement caused by fuel/air combustion in the cylinder. This reciprocating movement is then translated into rotational movement of a crankshaft through the use of connecting rods that are pivotally attached on one end to the bottom of the piston and pivotally attached on the other end to the crankshaft.
The movement of all of these attached parts can create a tremendous amount of heat and friction which needs to be dissipated. Accordingly, it is common to encase the crankshaft and the bottom of the piston assemblies with a crankcase, the crankcase providing an enclosed area for the circulation of engine oil to parts of the crankshaft, the walls of the cylinders, the valves, rockers, etc.
It has been found that most internal combustion engines, particularly larger ones, require a crankcase ventilation system comprised of a one way pasage for release of gases from the crankcase. The crankcase ventilation system is provided to allow gases to escape the crankcase in a controlled manner because internal combustion inevitably involves a small but continual amount of blow-by, namely the leaking of combustion gases from the combustion chamber past the piston rings, turbo seals, valve stem seals, etc. Accordingly, for control of the pressure inside the crankcase, it is generally known to provide a crankcase ventilation system.
It is further known to provide the cylinder head with an oil return passage for returning oil from the cylinder head back to the oil sump through a drain-back opening. This passage needs to be in fluid communication with the crankcase ventilation system, in order to allow blow-by gases to be released from the crankcase. Further, this passage needs to be connected to the oil sump, to allow the oil to properly drain back to the oil sump for recirculation. However, the use of this passage for both oil and gas circulation can create some issues.
Specifically, the blow-by gas flow can be at a relatively high flow rate. Given the tight restrictions in the oil drain back passage and the high velocity of blow-by gases, oil can become undesirably entrained in the gas and pulled into the crankcase ventilation system. Such a system is undesirable as it can result in fouling of the system. Another shortcoming is that oil foaming can occur from the blow-by gases flowing past the draining oil. In addition to fouling the equipment, these problems can also contribute to oil oxidation and contamination, which can be detrimental to engine life.
There have been prior attempts to resolve issues related to this problem. For example, Pub. No. US 2009/0314230 A1 to Nagenkogl et al. entitled Crankcase Breathing System discloses the use of a preliminary separator arranged integrally with a main separator wherein the main separator is formed by a cyclone separator with the outlet of the preliminary separator being arranged in a tangential way relative to the main separator. Additionally, the Nagenkogl reference discloses the use of at least one baffle plate in the preliminary separator between the inlet and the outlet of the preliminary separator wherein the baffle plate is spaced from the outlet of the preliminary separator.
While the system disclosed in the Nagenkogl reference may be useful in removing some entrained oil from the blow-by gases, there is still desired a crankcase ventilation system that utilizes an improved and/or optimized geometry to reduce oil entrainment in blow-by combustion gases.
According to the present disclosure, an internal combustion engine having an improved crankcase ventilation system is provded. More specifically, a cylinder block having at least one cylinder therein for housing a reciprocating piston, a crankshaft operably connected to the piston, the crankshaft being located in a crankcase, the crankcase further including an oil sump is disclosed. In accordance therewith a cylinder head may be attached to the cylinder block and may have at least a portion of a crankcase ventilation system attached thereto. The cylinder head my have an oil drain opening therein, the oil drain opening connecting to an oil drain passage providing for the return of oil to the oil sump and the escape of gases into the crankcase ventilation system. In accordance with the disclosure, the oil drain opening may be shaped such that velocity of blow-by gas flow through the drain opening may be controlled such that entrained oil caught therein is limited. Further, the oil drain passage may provide a volume such that velocity of the blow-by gas through the drain opening is limited.
There has thus been outlined, rather broadly, certain aspects of the disclosure in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional aspects of the disclosure that will be described below and which will form the subject matter of the claims appended hereto.
According to an exemplary embodiment of the present disclosure, a crankcase ventilation system 110 for allowing blow-by engine gases to be filtered and properly vented may be integrated as part of the valve cover assembly 112 or may be provided as a separate unit (not shown). The crankcase ventilation system 110 may be used to relieve the pressure in the crankcase 106 caused by blow-by gases and may also act to filter and return some entrained particulates, such as entrained oil, therefrom to return to the crankcase 106. The entrained oil may come from oil dripping back to the sump from the crankcase ventilation system 110 and may also comprise oil that is being used to lubricate various portions of the rocker mechanisms and/or valve mechanisms (not shown). The rocker mechanisms/valve mechanisms may be housed in the rocker box 114 and may be attached to the cylinder head 116. The valve cover assembly 112 may be attached to the rocker box 114. In accordance with embodiments of the disclosure, some cylinder heads 116 may have standard valve cover assemblies attached thereto (not shown) while others may include valve cover assemblies 112 including crankcase ventilation systems 110 attached thereto (depending on the amont of crankcase ventilation required by the specific application).
In accordance with the disclosure, the crankcase ventilation system 110 may include an integrated breather 118. The integrated breather 118 may comprise a pre-separator for helping to remove entrained oil from the blow-by gases and, as such may include an oil condensing mesh, a foil pack, and/or other known condensation aids packed therein. The integrated breather 118 may have an outlet cover 120 having a vapor outlet 122 for directing blow-by gases to a central filtration mechanism (not shown) or otherwise out of the engine 100.
As best shown in
In accordance with the foregoing,
In accordance with aspects of the disclosure, it has been found that the oil drain opening 128 located in the cylinder head 116, and more particularly, the specific geometry of that opening 128, as well as the cross-sectional area of oil drain passage 117 just below the opening 128 may critically effect the amount of that oil becomes undesirably entrained in the blow-by gases. More specifically, it has been determined that if the specific velocity of the blow-by gases can be kept below approximately 1200 mm/s as they travel thourgh the oil drain opening 128 at typical operating flow rates from the crankcase 106, that the amount of oil entrained in the blow-by gases may be maintained at an acceptable level.
In accordance therewith with respect to the opening 128 geometry,
Similarly,
As best shown in
In response thereto, higher cross-sectional areas in this section of oil drain passage 117 have been determined to decrease predicted velocities of the blow-by gases to a more acceptable level at opening 128, 128′. More specifically, it has been determined that cross-sectional areas of approximately 1700 mm2 (or greater) taken at 140, 1800 mm2 (or greater) taken at 142, 1800 mm2 (or greater) taken at 144, 2100 mm2 (or greater) taken at 146 (20 degree position), 2100 mm2 (or greater) taken at 148, and 2200 mm2 taken at 150 may contribute significantly to desired predicted velocities at opening 128, 128′. Even more specifically, it has been determined that cross-sectional areas of approximately 1800 mm2 (or greater) taken at 140, 1900 mm2 (or greater) taken at 142, 1800 mm2 (or greater) taken at 144, 2300 mm2 (or greater) taken at 146 (20 degree position), 2500 mm2 (or greater) taken at 148, and 2600 mm2 taken at 150 may contribute even more significantly to desired predicted velocities at opening 128, 128′.
As will be understood to those of ordinary skill in the art, increases in volume in the oil drain passage 117 discussed herein will decrease velocities at opening 128, 128′. In accordance therewith, changes to the discussed specific area measurements disclosed herein may be made while still generally increasing the volume of the oil drain passage 117 without departing from the scope of the present disclosure.
The industrial applicability of the crankcase ventilation system geometry disclosed herein will be readily appreciated from the foregoing discussion. Specifically, referring to the figures in general, in operation, the crankcase ventilation system 110 may be used to allow blow- by gases to be vented from the cylinder block while simultaneously operating to segregate the oil particles from exhaust of the crankcase 106. More specifically, the geometry of the oil drain opening 128 and oil drain passage 117 disclosed herein may allow for the flow of oil downward therethrough into the crankcase 106 while simultaneously allowing blow-by gases to enter into the crankcase ventilation system 110 at a velocity through the opening 128 such that an undesirable amount of oil does not become entrained in the blow-by gases. In accordance with the disclosure, the geometry optimization may provide a cost-effective method for preventing fouling of the interior 119 of the integrated breather 118, and more specifically, the condensation materials packed therein.
More generally, in accordance with the foregoing, the present disclosure operates to allow blow-by gases to be released from the crankcase 106 while simultaneously allowing oil, including entrained oil, to drip back to the oil sump. In accordance with the optimized geometry provided herein, the amount of entrained oil being carried up to the integrated breather 118 and/or out through the vapor outlet 122 may be signficiantly reduced.
The many features and advantages of the disclosure are apparent from the detailed specification, and, thus, it is intended by the appended claims to cover all such features and advantages of the disclosure which fall within the true spirit and scope of the disclosure. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the disclosure to the exact construction and operation illustrated and described, and, accordingly, all suitable modifications and equivalents may be resorted to that fall within the scope of the disclosure.
