Internal-combustion engines – Cooling – With jacketed head and/or cylinder
Utility Patent
1999-06-15
2001-01-02
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Cooling
With jacketed head and/or cylinder
C123S041840
Utility Patent
active
06167847
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a cylinder liner for a liquid-cooled internal combustion engine, with a cylinder liner collar which is adjacent to a cylinder head sealing plane and in which at least one circular cooling duct is formed.
There are two boundary conditions for the cooling in the construction of cylinder liners. In order to prevent hot erosion, the surface temperature of the cylinder liner should not exceed approx. 190° C. in the entire working area of the piston rings. On the other hand, cold corrosion occurs by the sulphur in the fuel when the surface temperature of the cylinder liner drops below approx. 140° C. in the zone of the combustion chamber. Since the permitted temperature window is relatively small, the precise control and monitoring of the temperature of the cylinder liner is very important.
DESCRIPTION OF THE PRIOR ART
It is known to provide the collar of the cylinder liner with circular annular grooves which, in combination with the cylinder block, form cooling ducts extending in the circumferential direction. Moreover, it is known from U.S. Pat. No. 4,093,842 A to form cooling ducts into the collar of the cylinder liner, with the cooling ducts having an even width. The cross section of the cooling duct is formed by an open profile line. As a result of the even width of the cooling duct and the even wall thickness of the cylinder liner in the zone of the cooling duct, there will be an approximately linear drop of temperature, which leads to the consequence that the minimum temperature for preventing sulphur corrosion is not reached in a number of zones of the cylinder liner.
SUMMARY OF THE INVENTION
It is the object of the present invention to avoid such disadvantages and to improve the cooling of the cylinder liner in such a way that overheating and/or undercooling can be excluded.
This occurs in accordance with the invention in such a way that the cross section of the cooling duct is formed, within the cylinder liner collar, by a closed profile line having at least an inner, an outer and an upper section, and the cross section of the cooling duct is provided with a substantially oblong shape whose height as measured substantially in the direction of the cylinder liner axis is larger than its maximum width as measured substantially in the radial direction of the cylinder liner, with the arrangement and/or the cross-sectional shape of the cooling duct being provided in such a way that the cooling of the cylinder liner collar is higher in an upper zone which is closest to the cylinder head sealing plane than in a lower zone of the cooling duct which is disposed remotest from the cylinder head sealing plane. Preferably, the shape of the profile line and/or the wall thickness between cooling duct and inner jacket surface of the cylinder liner is a function of the combustion chamber temperature, the gas forces, the heat transmission coefficient between combustion gas and cylinder axis on the one hand and between cylinder liner and coolant on the other hand, the coolant temperature, the coolant pressure and/or the assembly force in the design point of the internal combustion engine. The shape of the cross section can thus be optimally adapted to the respective conditions and requirements.
It is preferably further provided that the width of the cooling water duct decreases, preferably continuously, from the upper zone with maximum width to the lower zone with minimum width. In this way it is possible to adequately cool the uppermost region of the cylinder liner in order to prevent any exceeding of the maximum permissible temperature. The cooling performance decreases with the distance from the cylinder head plane, so that thermally less stressed areas are cooled less.
A further embodiment of the invention provides that the liner wall thickness as measured between the inner section of the profile line and the inner jacket surface of the cylinder liner increases from a minimum liner wall thickness in the upper zone of the cooling duct to the lower zone. Accordingly, a better cooling is produced in high-temperature zones than in zones with lower liner temperature.
It can be provided within the scope of the invention that the cooling duct is provided with a substantially trapezoid, triangular or oval cross section.
Particularly when the cooling duct is designed with a strongly curved top surface area, high tensions in the liner wall can occur in the zone of the cooling chamber as a result of the assembly forces and the combustion forces. When tightening the cylinder head studs, axial pressure forces will occur which cause high tensile stress in the zone of the top surface area of the cooling duct. Additionally, compressive strain caused by radial combustion forces act at the same location on the cylinder liner in the zone of the top surface area of the cooling duct, thus giving rise to high peak tensile forces and respectively reducing the security factor. In order to achieve an overlapping of the peak tensile forces and a reduction of the tension amplitudes, it is advantageous if the profile line in the zone of the upper section forming the top surface area is curved less strongly than in the zone of the transition to the inner and/or outer section, with the upper section preferably being formed at least partly by a straight line which particularly preferably extends substantially parallel to the cylinder head sealing plane. In this way the peak tensile forces which are caused by the assembly forces and the combustion forces are mutually separated, with the maximum of the bending stress occurring in the middle zone of the top surface area and the maximum of the compressive strain caused by the combustion forces occurring at the edge zones of the top surface area or the transitional areas into the lateral profile lines.
In order to achieve an optimal progress of the cooling it is particularly advantageous if the inner profile line is inclined between 60° and 90°, preferably between 65° and 80°, and particularly preferably between 70° and 75°, to a normal plane on the cylinder liner axis. Best cooling results within the permitted temperature window are obtained when the inner section and the outer section of the profile line are inclined towards one another and preferably open up an angle of between 5° and 10°.
REFERENCES:
patent: 4093842 (1978-06-01), Scott
patent: 4370952 (1983-02-01), Mettig et al.
patent: 5746161 (1998-05-01), Boggs
patent: 480536 (1969-12-01), None
patent: 1955140 (1971-04-01), None
patent: 123218 (1976-05-01), None
patent: 6346783 (1994-12-01), None
Ergezen Ugur
Melde-Tuczai Helmut
Tanska Tuomas
AVL List GmbH
Dolinar Andrew M.
Dykema Gossett PLLC
Harris Katrina B.
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