GB2292417A

GB2292417A - I.c. engine lubrication system

Info

Publication number: GB2292417A
Application number: GB9416627A
Authority: GB
Inventors: Thomas Tsoi-Hei Ma
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1994-08-17
Filing date: 1994-08-17
Publication date: 1996-02-21
Anticipated expiration: 2014-08-17
Also published as: GB2292417B; GB9416627D0

Abstract

A circulation pump 10 draws oil from a sump 16 and delivers to galleries 12 and 14 supplying upper and lower engine parts and a regulating valve 20 limits the pressure of the oil in circulation by returning directly to the sump 16 a proportion of the oil delivered by the pump. The return oil from the gallery 12 and the valve 20 are grouped together and returned to the sump by a common pipe 28 that discharges into the sump 16 under gravity separately from the oil returned from the gallery 14. The suction pipe 18 of the pump 10 is arranged to draw the major proportion of the oil to be circulated from the heated oil discharged by the return pipe 28. The pipes 18 and 28 may be insulated within the sump. A coolant heat exchanger may be combined with an oil filter immediately downstream of the pump 10. <IMAGE>

Description

Engine Lubrication System Field of the invention The present invention relates to an engine lubrication system and is particularly concerned with a lubrication system for promoting rapid oil warm-up.

Background of the invention GB-A-2,251,889 and US-A-4,616,609 describe lubrication systems that have the same aim as the present invention of achieving rapid oil warm up, and achieve this aim by heating only a proportion of the oil in the engine sump during the first few minutes after starting the engine from cold.

However, steps are taken to ensure that over a longer time period, all the oil in the sump is circulated at a slower rate in order to prolong oil life.

US-A-4,616,609 collects all the return oil and directs some of the oil to a small compartment containing the suction pipe of the oil pump. The remainder of the oil is returned to the main sump at a rate that increases as the oil temperature rises. In this way, when the oil is cold the same small volume of oil is circulated, and as the oil warms up more and more oil is circulated via the main sump. This prior art system requires a drip pan to collect the return oil and a device for diverting the oil flow in dependence upon the oil temperature.

In GB-A-2,251,889 all the collected return oil is directed to a first compartment before allowing a proportion of the oil to overflow from the first smaller compartment to the main sump. This again requires a drip pan to collect the return oil and a pump with a divided intake that draws different proportions of oil from the two compartments.

It is inconvenient to provide an additional collection pan as this requires the bottom end of the engine to be redesigned and cannot readily be achieved without increasing the height of the engine. The collection pan has other disadvantages in that a large amount of oil will adhere to its surface, especially when the oil is cold and viscous, and it will itself draw heat from the oil in circulation thereby detracting from the desired object of achieving more rapid warm-up of the engine oil.

Summary of the invention In order to mitigate the foregoing disadvantages, the present invention provides an internal combustion engine having an oil lubrication system for lubricating and cooling first surfaces in the upper part of the engine and second surfaces in the lower part of the engine, the lubrication system comprising a circulation pump for drawing oil from a sump and delivering oil to the first and second surfaces and a regulating valve for limiting the pressure of the oil in circulation by returning directly to the sump a proportion of the oil delivered by the circulation pump, wherein the return oil from the first surfaces and the regulating valve are grouped together and returned to the sump by a common pipe that discharges into the sump under gravity separately from the oil returned from the second surfaces and wherein the suction pipe of the circulation pump is arranged to draw the major proportion of the oil to be circulated from the oil discharged by the return pipe common to the first surfaces and the regulating valve.

In the invention, a major proportion of the return oil is channelled through a pipe network and is drained lender gravity towards the suction pipe of the oil pump to make sure that substantially all this flow is immediately drawn back into the pump. The remainder of the return oil from the second surfaces is allowed to drip conventionally directly into the oil sump. As there is no need for a drip pan to collect the return oil, the invention offers effective oil temperature management with the simplest design with no moving part and no complicated partitioning of the oil sump.

The first surfaces are all the surfaces to be found near or in the cylinder head notably the surfaces associated with the valve train, amongst them the camshaft cams and bearings, the cam followers, rockers, hydraulic tappets etc.

These are the surfaces which take the major proportion of the oil delivery from the circulation pump. The second surfaces are the bearings associated with the crankshaft, namely the big end bearings and the crankshaft main bearings and in some engines these surfaces may include the piston skirts and cylinder walls which may be sprayed with oil to assist in their cooling.

In a conventional engine, there are two drain holes, one at each end of the engine, to drain the oil from the cylinder head back into the sump. The present invention may be easily realised in practice by connecting these drain holes to a pipe, the latter pipe also being used to return to the sump the oil spilled by the regulating valve in order to regulate the oil pressure.

In the invention, the main oil in circulation is not the entire volume of oil in the sump but just the quantity of oil required to lubricate the first bearing surfaces. A much lesser amount of oil for lubricating the second surfaces is drawn from the sump and this smaller amount also ensures a lesser circulation for mixing that is required to prolong the life of the lubricating oil, all the oil in the sump being eventually cycled after a period of time.

In a preferred embodiment of the invention, a heat exchanger is provided to transfer heat between the oil supplied to the first surfaces and the engine coolant. This can assist in raising the temperature of the oil during warm-up and also preventing overheating of the oil during normal operation.

The heat exchanger may conveniently be combined with an oil filter and be located in the part of the lubricating circuit between the regulating valve and the first surfaces.

Brief descriDtion of the drawing The invention will now be described further, by way of example, with reference to the accompanying drawing, in which the single figure shows a schematic diagram of an engine lubricating system embodying the invention.

Detailed descriDtion of the preferred embodiment In the drawing an oil circulating pump 10 has a suction pipe 18 opening in the main sump 16 of the engine and has a delivery pipe that discharges into two oil galleries designated 12 and 14 respectively. A pressure regulating valve 20 opens automatically when the pressure in the delivery side of the pump 10 exceeds a given value and spills oil directly back into the sump 16 and regulating in this manner the pressure in the galleries 12 and 14.

The gallery 12 is arranged in the cylinder head and delivers oil to the surfaces in the cylinder head that require lubrication and cooling, notably all the surfaces associated with the valve train such as camshaft bearings, cams, followers, hydraulic tappets etc. The oil from the cylinder head falls under gravity through two drainage holes 22 and 24 and would in a conventional engine fall back into the main body of the sump. In the present invention, however, pipes 26 and 28 are connected to the drainage holes so that the return oil from the cylinder head does not merely fall into the sump 16 but flows directly into a small catchment volume 30 submerged in the sump and surrounding the suction pipe 18 of the circulation pump 10.The oil spilled over by the pressure regulating valve 20 is also returned to this catchment volume 30 through the pipe 28 and it is only the oil from the second gallery 14, used for lubricating and cooling the bottom end of the engine, that drains back into the main body of the sump 16.

In operation, oil drawn from the sump catchment volume 30 is delivered by the pump 10 after being regulated by the valve 20 to the two oil galleries 12 and 14. The oil from the gallery 12 and the oil spilled by the regulating valve 20 are immediately returned to the catchment volume 30 through the pipes 26 and 28 and once again drawn into the suction pipe 18 of the pump 10. The same oil therefore keeps in circulation and warms up rapidly. At the same time the oil through the gallery 14 drips back in the normal way into the main sump 16. A volume of oil equal to the return from the gallery 14 is drawn into the catchment volume 30 from the surrounding oil in the sump to compensate for the loss of the oil from the delivery side of the pump to the gallery 14. This achieves a longer term mixing of all the oil in the sump 16 so that the life of the oil is prolonged.

An oil filter may be arranged between the pump 10 and the oil galleries 12 and 14, and if desired, an oil-to-coolant heat exchanger may be combined with the filter housing. The effect of the heat exchanger would be to increase the speed of warm up of the oil while ensuring that it does not overheat during normal operation. Because only a small amount of oil is in constant circulation, the heat drawn from the coolant when the engine is cold is not excessive and does not interfere significantly with the warming up of the coolant.

Because the oil in the lubrication circuit is returned through pipes to the sump, a substantial head of oil may be developed assuring a rapid return of the oil under gravity and minimising the volume of oil used to wet all the surfaces over which the oil flows on its return to the sump.

It is preferred to provide thermal insulation of the parts of the lubrication circuit that is submerged in the oil in the sump to prevent the hot oil that is circulated from losing its heat to the colder oil in the sump.

The effect of achieving of a more rapid rise of the temperature of the lubricating oil during cold starts is to reduce engine friction. In this way, fuel consumption and exhaust emissions during cold starts are reduced.

Claims

1. An internal combustion engine having an oil lubrication system for lubricating and cooling first surfaces in the upper part of the engine and second surfaces in the lower part of the engine, the lubrication system comprising a circulation pump for drawing oil from a sump and delivering oil to the first and second surfaces and a regulating valve for limiting the pressure of the oil in circulation by returning directly to the sump a proportion of the oil delivered by the circulation pump, wherein the return oil from the first surfaces and the regulating valve are grouped together and returned to the sump by a common pipe that discharges into the sump under gravity separately from the oil returned from the second surfaces and wherein the suction pipe of the circulation pump is arranged to draw the major proportion of the oil to be circulated from the oil discharged by the return pipe common to the first surfaces and the regulating valve.

2. An internal combustion engine as claimed in claim 1, wherein the first surfaces are all the surfaces to be found near or in the cylinder head and the second surfaces are the surfaces at the bottom end of the engine.

3. An internal combustion engine as claimed in claim 2, wherein oil from the cylinder head flows under gravity via drainage holes into pipes leading directly to a catchment volume submerged in the oil sump and surrounding the end of the suction pipe of the oil pump.

4. An internal combustion engine as claimed in any preceding claim, wherein a heat exchanger is provided to transfer heat between the oil supplied to the first surfaces and the engine coolant.

5. An internal combustion engine as claimed in claim 4, wherein the heat exchanger is combined with an oil filter located in the part of the lubricating circuit between the regulating valve and the first surfaces.

6. An internal combustion engine as claimed in any preceding claim, wherein the parts of the pipes of the lubricating circuit immersed in the oil in the sump are thermally insulated.

7. An internal combustion engine constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.