GB2479005A

GB2479005A - Rolling Element Bearing Crankshaft with Intermittent Lubricating Oil Supply

Info

Publication number: GB2479005A
Application number: GB201005183A
Authority: GB
Inventors: Dan Merritt
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-03-27
Filing date: 2010-03-27
Publication date: 2011-09-28
Also published as: GB201005183D0

Abstract

The arrangement provides a device for lubricating rolling element bearings inside a reciprocating engine crankcase where it is desired to exclude lubricating oil from the crankcase. The engine has a crankshaft 1 rotating about an axis 2 and supported by rolling element main bearings 3 and a connecting rod 4 attached to the crankshaft by rolling element big end bearing 5. The crankshaft includes an oil inlet manifold 8 and an oil outlet manifold 10, each fitted with seals around the crankshaft and which exclude oil from entering the engine crankcase. Pressurised oil is directed from the supply manifold via a duct 6 within the crankshaft to the oil outlet manifold, en-route providing lubrication to the bearings via orifices 14, 15. The oil supply can be supplied intermittently, under the control of a controller. The arrangement finds application in two-stroke engines that use the crankcase as an air pump, and in four-stroke engines used in situations where the engine may be inverted in use.

Description

INTERNAL COMBUSTION ENGINE

This invention relates to reciprocating combustion engines, in particular it relates to a lubricating system for rolling element bearings attached to the crankshaft.

The invention allows the lubrication of such bearings in a way which avoids discharging oil into the crankcase. This is advantageous in some engines particularly in two stroke engines which use the crankcase as an air pump where oil contamination of pumped air can result in excessive emission of hydrocarbon pollutants in the exhaust.

Accordingly this invention provides an internal combustion reciprocating engine which contains; crankshaft 1 rotating on axis 2 supported by rolling elements main bearings 3; connecting rod 4 attached to the crankshaft by rolling element big end bearings 5; an internal duct 6 in the form of interconnected passages located inside the crankshaft for transmission of oil internally from one end of the crankshaft to its other end; lubricating oil supply means 9 delivering pressurised oil into the crankshaft 1; oil input manifold 8 provided with rotation seal 7 fitted around the crankshaft at one end to supply lubricating oil into the internal duct 6; oil outlet manifold 10 provided with rotation seal 7 fitted around the crankshaft at its other end, the outlet end, constructed to exclude oil from entry into the crankcase; drain means 11 to remove oil from the oil outlet manifold 10 to an oil reservoir separated from the crankcase; crankshaft input orifice 16 to connect the oil input manifold to the internal duct 6; crankshaft outlet orifice 13 to connect the internal duct 6 to the oil output manifold 10; big end bearing orifice 14 for connecting the internal duct 6 with the big end bearing 5; main bearing orifice 15 for connecting the internal duct 6 with the main bearing 3; an interrupter (not shown) for starting and stopping oil supply to the oil input manifold 8; a controller (not shown) to activate and deactivate the interrupter; characterised in that the lubricating oil supply means 9 is controlled to deliver oil intermittently during engine operation, to discharge during such delivery through the crankshaft outlet orifice 13 into the oil outlet manifold 10 and so avoid oil entry into the crankcase and that such delivery is engineered to deposits oil in the internal duct 6 of the crankshaft, to be trapped there after the lubricating oil supply means is interrupted and that such trapped oil is allowed to be propelled by centrifugal force into the big end bearing 5 through the big end bearing orifice 14 during the engine operation after the oil supply is discontinued.

Preferably bearing orifice 14 is restricted in size to control the transfer of oil to the big end bearings to take place over many engine revolutions when the lubricating oil supply means is deactivated.

Preferably bearing orifice 15 is restricted in size to control the quantity of oil transferred to the main bearings over the limited time duration when the lubricating oil supply means is activated.

Preferably the outlet orifice is restricted in size and the lubricating oil supply means is activated for a sufficient duration to ensure the complete filling of the internal duct with oil when the lubricating oil supply means is activated.

Preferably the interrupter is deactivated to provide oil after a predetermined number of engine revolutions.

Preferably the interrupter is activated to stop oil supply after a predetermined time period.

Preferably oil delivery into the crankshaft occurs over a relatively short time period in comparison with the time period when such oil delivery is stopped.

The operation of this invention is described by way of an example using the schematic Figure 1.

Figure 1 illustrates a crankshaft arrangement for a single cylinder engine but this invention is applicable to crankshafts used in multi-cylinder engines as well provided they use rolling element bearings. Other engines, particularly those operating on the four stroke cycle and some two stroke engines use plain bearings which are lubricated by hydrodynamic layer of oil which is constantly pumped under pressure through the bearing to end up in a sump at the bottom of a crankcase.

However engines operating on the two stroke cycle, particularly those which use their crankcase as an air pump, use rolling element bearings on the crankshaft such as ball bearings, roller bearings or needle bearings.

This invention makes use of the fact that rolling element bearings require very little lubrication.

Indeed the continuous pumping of oil through such bearings may cause skidding and even be harmful to their operation. In the past two stroke engines using the crankcase as air pumps, solved their lubrication problems by either mixing oil into gasoline before it was delivered into the crankcase or alternatively, where no fuel was delivered into the crankcase, two stroke engines using their crankcase as an air pump, used fine oil sprayed inside the crankcase to mix with the air passing through the crankcase in order to lubricate the bearings and the pistons. However some modern two stroke engines are seeking to exclude oil presence in the crankcase in order to avoid contamination of the combustion air with oil which may end up as hydrocarbon emissions in the exhaust. This invention offers such engines the capability of lubricating their rolling element bearings with negligible contamination of the air passing through the crankcase. The lubrication of the piston in such engines is the subject of another invention by the current inventor described in a separate U.K. patent application.

Figure 1 shows, by way of a simplified example, crankshaft 1 mounted on ball bearings 3 attached to one connecting rod 4 through ball bearing 5. The crankshaft has an internal duct 6 which allows the transmission of lubricating oil through it from one end of the crankshaft to its other end even when the engine is rotating. Oil is supplied to the duct from the input manifold 8 by the lubricating oil supply means 9, not shown, which supplies pressurised oil. The lubricating oil supply system consists of an oil pump and an interrupter. The interrupter can take the form of an electromagnetic on/off valve which stops the oil flow into the oil input manifold even when the oil pump remains in operation or it can take the form of an electrical switch which can stop the operation of an oil pump itself which can be easily achieved if the pump is driven by an electric motor. The controller which activates the interrupter may do so after the elapse of a given time period or after a predetermined number of engine revolutions or after another signal which indicates the need to supply oil the bearings.

The interruption of oil supply is novel since no other reciprocating engine has been produced to cope with deliberate interruption the lubrication of its bearing over a substantial operational duration.

The internal duct 6 communicates with the bearings through the main bearing orifice 15 and the big end bearing orifice 14. Oil transmition to bearings through internal ducting is common practice for most crankshafts used in reciprocating engines. Engines using plain bearings deliver pressurised oil to such bearings to promote hydrodynamic lubrication but such engines lack the novel features of the crankshaft outlet orifice 13 and the oil outlet manifold 10 shown in Figure 1. These features allow oil to be pumped from the oil inlet manifold to the oil outlet manifold without contaminating the crankcase with lubricating oil. The oil outlet manifold allows the removal of oil through its drain means to return to an oil collection reservoir, not shown, from where it can be delivered to the oil pump when needed.

Another novelty described in this invention is that most of the oil delivery to the big end bearing 5 does not rely on the oil pressure supplied from an oil supply means such as a pump. The pump's task is to fill up the duct with oil and it can then be stopped. The mechanism for pumping the oil into the big end bearing is the centrifugal force produced by the rotation of the crankshaft over its cranked portion. Such a force will vary with engine speed but is capable of generating moderate pressure increases in the oil trapped in the duct which is contained in the crankpin and crank webs. Bearing orifice 14 can then be designed to restrict the delivery of such trapped oil to the bearing to a small quantity, for instance by providing very small diameter holes, by obstructing oil flow with capillary sized passages, for example through metallic sponge, or by using additional restrictions such as by containing a spring loaded one way ball valve which opens after a predetermined engine speed has been reached.

Rolling element bearings need minimal lubrication and can function for long periods after a short lubrication period The lubrication of the main bearing is done through bearing orifice 15. This can be made larger than orifice 14 to allow a small quantity of oil to enter the bearing during the period when moderate oil pressure is applied to the internal duct by the lubricating oil supply means. Any oil leaking from the main bearings can be drained and collected without entering the crankcase.

Claims

* claims 1. An internal combustion reciprocating engine comprising; a crankshaft supported by rolling elements main bearings; a connecting rod attached to the crankshaft by rolling element big end bearings; an internal duct in the form of interconnected passages located inside the crankshaft for transmission of oil internally from one end of the crankshaft to its other end; lubricating oil supply means delivering pressurised oil to the crankshaft; oil input manifold provided with rotation seal fitted around the crankshaft at its inlet end to supply lubricating oil into the internal duct; oil outlet manifold provided with rotation seal fitted around the crankshaft at its other end, the outlet end, constructed to exclude oil from entry into the crankcase; drain means to remove oil from the oil outlet manifold to an oil reservoir separated from the crankcase; crankshaft input orifice to connect the oil input manifold to the internal duct; crankshaft outlet orifice to connect the internal duct to the oil output manifold big end bearing orifice for connecting the internal duct with the big end bearings; main bearing orifice for connecting the internal duct with the main bearing; an interrupter for starting and stopping oil supply to the oil input manifold; a controller for activating and deactivating the interrupter; characterised in that the lubricating oil supply means is controlled to deliver oil intermittently during engine operation, to discharge during such delivery through the crankshaft outlet orifice into the oil outlet manifold and so avoid oil entry into the crankcase, and that such delivery is engineered to deposit oil in the internal duct of the crankshaft, to be trapped there after the lubricating oil supply means is interrupted and that such trapped oil is allowed to be propelled by centrifugal force into the big end bearings through the big end bearing orifice during the engine operation after the oil supply is discontinued.
2. An engine according to claim 1 wherein the big end bearing orifice is restricted in size to reduce the transfer of oil through it so that it takes place over very many engine revolutions as required by the lubrication needs of the big end rolling element bearing;
3. an engine according to claim 1 where in the main bearing orifice is sized to allow sufficient oil into the main bearings during the period when the oil input manifold is pressurised in order to meet the'lubrication needs of the main bearing.

S
4. An engine according to claim 1 wherein the crankshaft outlet orifice is sized to produce sufficient pressure in the internal duct to ensure the filling of the internal duct with oil and the desired lubrication of the main bearings.S. An engine according to claim 1 wherein the interrupter is in the form of an electrically actuated valve to stop and start oil flow through it; 6. An engine according to claim 1 wherein the controller allows oil flow through the interrupter after a pre determined number of engine revolutions.7. An engine according to claim 1 wherein the controller allows oil flow through the interrupter when the engine is first started from rest.8. An engine according to claim 1 wherein oil delivery to the crankshaft occurs over a relatively short time period in comparison with the time period when such oil delivery is stopped.9. An engine according to claim 1 wherein the said engine is operates on the two stroke cycle.10. An engine according to claim 1 wherein the said engine operates on the four stroke cycle.