Internal combustion engines

An internal combustion engine of the reciprocating piston type has oil jets for cooling the pistons. The jets are fed by the pump which supplies oil to the engine's lubrication system. A valve in the feed line to the jets is arranged to close automatically when the pressure of oil flowing through it falls below a determined value due to the engine and thus the pump running temporarily at low speed, so as to give priority to the lubrication system at such times.

BACKGROUND OF INVENTION 
The invention relates to internal combustion engines of the type having at 
least one cylinder in which there is reciprocable a piston, and a 
pressurised bearing lubrication system. 
The object of the invention is to employ lubricating oil to cool the piston 
or pistons without starving the bearings of lubricating oil. 
SUMMARY OF INVENTION 
According to the invention an internal combustion engine, of the type 
having at least one cylinder in which there is reciprocable a piston, 
comprises a lubrication system including a pump delivering oil under 
pressure through a first feed line to the engine's bearings, a second feed 
line connecting the first feed line to at least one oil jet directed into 
the or each cylinder for cooling the piston therein, and a valve in the 
second feed line for closing said line to prevent the flow of oil to the 
oil jet or jets when the pressure acting on said valve is less than a 
determined value.

DESCRIPTION OF PREFERRED EMBODIMENT 
Referring now to the drawings, a multi-cylinder in-line internal combustion 
engine is provided with a conventional lubrication system comprising a 
pump 10 driven by the engine, which draws oil from a sump 11 and delivers 
it under pressure through a feed line 12 to a main oil gallery 13 in the 
engine's cylinder block 14, said gallery being connected to lubricate the 
engine's bearings (including the big-end bearings 15), tappets (not shown) 
and the like. A filter 16 is interposed in the feed line 12 between the 
pump 10 and the oil gallery 13, and a spring-closed maximum pressure 
relief valve 17 disposed between the pump 10 and the filter 16 is arranged 
to open so as to connect the feed line 12 to the sump 11 at a pressure of, 
say, approximately 45 pounds per square inch. 
In order to cool the engine's pistons 18, oil jets 19 of, say, 5/64" 
diameter and, say 60.degree. inclination above the horizontal are formed 
in cylindrical members 20 disposed near the lower ends of the cylinders 
21. Each member 20 has one jet 19 at each of its ends, and thus serves to 
cool the pistons 18 in two adjacent cylinders 21. Each piston 18 is 
connected in well-known manner to the engine's crankshaft 22 by means of a 
gudgeon pin 23 and a connecting rod 24. The members 20 are connected by 
respective pipes 25 to a subsidiary oil gallery 26 in the cylinder block 
14, said gallery being connected in its turn to a point in the 
afore-mentioned feed line 12 (hereinafter called the first feed line) 
between the filter 16 and the main oil gallery 13 by way of a second feed 
line 27. A spring-closed low pressure relief valve 28 interposed in the 
second feed line 27 is arranged to open said line at a pressure of, say, 
approximately 30 pounds per square inch. A tab 29 secured to each pipe 25 
is bent into contact with a surface 30 in the cylinder block 14 to prevent 
each member 20 from moving out of its operative position. 
An oil cooler may be provided in the system to extract excess heat from the 
oil. 
In a modification, the oil jets may be formed directly in the walls in the 
cylinders, near their lower ends. 
In operation, when the engine speed is low the flow rate and pressure of 
the discharge of the pump 10 are correspondingly low. To avoid the risk of 
starving the bearings, tappets and the like of oil in these circumstances, 
the low pressure relief valve 28 holds the second feed line 27 closed to 
prevent the flow of oil to the oil jets 29 until such time as an increase 
in engine speed causes a pressure of approximately 30 pounds per square 
inch to be attained in the first feed line 12 between the filter 16 and 
the main oil gallery 13, whereupon the valve 28 opens and permits oil to 
be supplied to the jets 19 as shown in FIG. 3. Oil sprayed from the jets 
19 thus impinges upon the internal surfaces of the pistons 18 and 
abstracts excess heat therefrom, and then drains from the cylinders 21 
into the sump 11 for recirculation. In the course of recirculation it 
passes through the oil cooler if one is provided. At engine speeds lower 
than that capable of producing and oil pressure of approximately 30 pounds 
per square inch the pistons 18 do not require cooling, because excessively 
hot conditions only occur at higher engine speeds.