GB2114223A

GB2114223A - Air and liquid cooling system of an I.C. engine

Info

Publication number: GB2114223A
Application number: GB08301899A
Authority: GB
Inventors: Roberto Bosisio
Original assignee: Same SpA
Current assignee: Same SpA
Priority date: 1982-02-04
Filing date: 1983-01-24
Publication date: 1983-08-17
Also published as: GB8301899D0; FR2520802A1; ES8501840A1; IT1150173B; DE3303347A1; IT8219447A0; ES519333A0

Abstract

Each engine cylinder 11 comprises a finned upper part 14 projecting from the engine crankcase 10, and a lower part 15 inserted into the crankcase to form therewith a chamber 16 into which cooling oil is fed. <IMAGE>

Description

SPECIFICATION Cooling system for l.C.

In air-cooled reciprocating internal combustion engines, the air is made to directly cool the engine head and cylinders, which are suitably provided with finned surfaces.

With regard to the cylinder, it is usually necessary to remove heat over a region equal to the stroke ofthe top ofthe piston which, being at a highertemperature, tends to transfer heat to the walls and could raise their temperatureto unacceptable levels.

In multi-cylinder engines, the cylinder geometry is usually such as to provide almost uniform passage of cooling air overthe entire height of the region to be cooled, whereas the quantity of heattransferred to the inner wall of the cylinder is greatest in its upper part, a minimum in its central region and somewhat higher in its terminal region where the piston speed becomes zero.

Underthese conditions, the cylinder is excessively cooled in its central and lower part, leading to deformation problems and excessive energy removal.

The object ofthe present invention is to obviate the aforesaid drawback by providing a cooling system able to cool the cylinders in a uniform manner, by taking into account the differenttemperaturesto which the lower, central and upper cylinder regions are heated.

This object is attained according to the present invention bya reciprocating internal combustion engine characterised in that each cylinder comprises a finned upper part projecting from the engine block, and a lower part inserted into the engine block to form therewith a jacket into which cooling liquid is fed by feed means.

In this manner, the air directly cools only the upper part ofthe cylinder, which is not in direct contact with any cooling fluid overthe region corresponding to the middle ofthe piston stroke, whereas over its lower part it is grazed by oil, the throughput of which is suitably adjusted to remove only that quantity of heat strictly necessary to maintain the cylindertempera- ture within the limits of acceptability.

This results in a smallertemperaturevariation along the cylinder axis and a lower energy subtraction.

The structural and operational characteristics of the invention and its advantages will be more apparent from the description given hereinafter by way of example with reference to the accompanying di agrammaticdrawings, in which: Figures 1,2 and 3 are sectional views illustrating three possible embodiments ofthe invention.

In Figure 1 of the drawings, the reference numeral 10 indicates an engine block, 11 one ofthe cylinders, 12the relative piston and 13 the engine head.

According to the present invention, the cylinder 11 comprises an upper finned part 14 projecting from the block 10 and a lower smooth part 15 which is inserted into the block to form therewith an interspace 16 through which the cooling oil circulates.

The oil can be circulated through the interspace or jacket 16 in various ways, for example as shown in Figures2 and 3.

In Figure 2,the oil is withdrawn from the sump by the pump 17 ofthe lubrication circuit, and is pumped to a header channel 18through a duct 19 provided in the block 10. The oil is fed into the lower region of the jacket 16 from the header 18 through radial bores 20, and returns to the sump afterwetting the entire cylinder region concerned, by passing through dis charge apertures 21 provided in the upper region of the jacket. Avalve 22 for setting the oil pressure is provided in the duct 19.

In the embodiment of Figure 3, the oil is pumped to a header 23 and then sprayed into the interspace 16 through apertures 26 by means of sprayers 24 with which sprayers 25 are associated for cooling the piston.

A reciprocating internal combustion engine is thus provided, cha racterised buy a mixed cooling system using air directly and engine oil as the intermediate fluid, the system being conceived in such a manner as to cool the engine head and part ofthe engine (generallythe upper part, i.e. from the top dead centre ofthe region in which the piston attains its maximum speed of movement) with direct air, but to cool the outer wall ofthe cylinder over its lower part (from the point of maximum speed to the bottom dead centre) with engine lubricating oil, which itself is then cooled either by air by means of a radiator or by simple radiation from the peripheral surfaces wetted by said oil.

The height ofthe engine block (from the drive axle to the cylinder support plane) increases as a consequence of choosing this cooling system, and this is normally preferable because it enablestheflexural and torsional rigidity to be increased without having to lengthen the engine in the part below the axle, which would increase overall size, deformation and noise.

Moreover, the said cooling method reduces the finned area and provides part of the cylinder with an oil chamber, which further reduces noise.

In an engine with a cooling system ofthetype heretofore described, the quantity of heat removed from the lower part ofthe cylinder (from approximatelythe middle of the stroke to the bottom dead centre) can be made less than the quantity of heat removed from the upper part, so as to keep the temperature and thus the cylinder expansion along its axis more uniform, and generally reducethe energy subtracted, leading to improved thermodynamic efficiency.

The finned cylinder area and consequently the noise emission can also be reduced.

1. A reciprocating internal combustion engine characterised in that each cylinder comprises an upper finned part projecting from the engine block, and a lower part inserted into said engine block and forming therewith a jacket into which a cooling liquid is fed by feed means.

2. An engine as claimed in claim 1, characterised in that said feed means comprise a pump which feeds oil under pressure into a header channel which communicates with the lower region of said jacket byway of a plurality of radial bores, said oil being discharged into the sump through discharge apertures provided in the upper region of said jacket.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Cooling system for l.C. In air-cooled reciprocating internal combustion engines, the air is made to directly cool the engine head and cylinders, which are suitably provided with finned surfaces. With regard to the cylinder, it is usually necessary to remove heat over a region equal to the stroke ofthe top ofthe piston which, being at a highertemperature, tends to transfer heat to the walls and could raise their temperatureto unacceptable levels. In multi-cylinder engines, the cylinder geometry is usually such as to provide almost uniform passage of cooling air overthe entire height of the region to be cooled, whereas the quantity of heattransferred to the inner wall of the cylinder is greatest in its upper part, a minimum in its central region and somewhat higher in its terminal region where the piston speed becomes zero. Underthese conditions, the cylinder is excessively cooled in its central and lower part, leading to deformation problems and excessive energy removal. The object ofthe present invention is to obviate the aforesaid drawback by providing a cooling system able to cool the cylinders in a uniform manner, by taking into account the differenttemperaturesto which the lower, central and upper cylinder regions are heated. This object is attained according to the present invention bya reciprocating internal combustion engine characterised in that each cylinder comprises a finned upper part projecting from the engine block, and a lower part inserted into the engine block to form therewith a jacket into which cooling liquid is fed by feed means. In this manner, the air directly cools only the upper part ofthe cylinder, which is not in direct contact with any cooling fluid overthe region corresponding to the middle ofthe piston stroke, whereas over its lower part it is grazed by oil, the throughput of which is suitably adjusted to remove only that quantity of heat strictly necessary to maintain the cylindertempera- ture within the limits of acceptability. This results in a smallertemperaturevariation along the cylinder axis and a lower energy subtraction. The structural and operational characteristics of the invention and its advantages will be more apparent from the description given hereinafter by way of example with reference to the accompanying di agrammaticdrawings, in which: Figures 1,2 and 3 are sectional views illustrating three possible embodiments ofthe invention. In Figure 1 of the drawings, the reference numeral 10 indicates an engine block, 11 one ofthe cylinders, 12the relative piston and 13 the engine head. According to the present invention, the cylinder 11 comprises an upper finned part 14 projecting from the block 10 and a lower smooth part 15 which is inserted into the block to form therewith an interspace 16 through which the cooling oil circulates. The oil can be circulated through the interspace or jacket 16 in various ways, for example as shown in Figures2 and 3. In Figure 2,the oil is withdrawn from the sump by the pump 17 ofthe lubrication circuit, and is pumped to a header channel 18through a duct 19 provided in the block 10. The oil is fed into the lower region of the jacket 16 from the header 18 through radial bores 20, and returns to the sump afterwetting the entire cylinder region concerned, by passing through dis charge apertures 21 provided in the upper region of the jacket. Avalve 22 for setting the oil pressure is provided in the duct 19. In the embodiment of Figure 3, the oil is pumped to a header 23 and then sprayed into the interspace 16 through apertures 26 by means of sprayers 24 with which sprayers 25 are associated for cooling the piston. A reciprocating internal combustion engine is thus provided, cha racterised buy a mixed cooling system using air directly and engine oil as the intermediate fluid, the system being conceived in such a manner as to cool the engine head and part ofthe engine (generallythe upper part, i.e. from the top dead centre ofthe region in which the piston attains its maximum speed of movement) with direct air, but to cool the outer wall ofthe cylinder over its lower part (from the point of maximum speed to the bottom dead centre) with engine lubricating oil, which itself is then cooled either by air by means of a radiator or by simple radiation from the peripheral surfaces wetted by said oil. The height ofthe engine block (from the drive axle to the cylinder support plane) increases as a consequence of choosing this cooling system, and this is normally preferable because it enablestheflexural and torsional rigidity to be increased without having to lengthen the engine in the part below the axle, which would increase overall size, deformation and noise. Moreover, the said cooling method reduces the finned area and provides part of the cylinder with an oil chamber, which further reduces noise. In an engine with a cooling system ofthetype heretofore described, the quantity of heat removed from the lower part ofthe cylinder (from approximatelythe middle of the stroke to the bottom dead centre) can be made less than the quantity of heat removed from the upper part, so as to keep the temperature and thus the cylinder expansion along its axis more uniform, and generally reducethe energy subtracted, leading to improved thermodynamic efficiency. The finned cylinder area and consequently the noise emission can also be reduced. CLAIMS

3. An engine as claimed in claim 1, characterised in that said feed means comprise sprayers which spray oil under pressure into said jacket through apertures provided between the cylinder and the engine block, said oil falling back into the sump by gravity, by passing through analogous apertures.

4. An engine as claimed in claim 1, characterised in that at least one valve for regulating the cooling liquid throughput cooperates with said feed means.

5. A reciprocating internal combustion engine substantially as hereinbefore described with reference to the accompanying drawings.