New honing technique reduces oil consumption | air filter supplier
Low oil consumption and a consequent reduction in harmful pollutant emissions from internal combustion engines are the principal objectives in the development of new techniques for honing piston raceways. These objectives can be met with slide honing, or, better still, helical slide honing. These three-stage processes are comparable with plateau honing and can be implemented on existing honing machines. Report by G. Haasis and U.-P Weigmann.
A longside reductions in fuel consumption and noise levels, lower emission of harmful pollutants is one of the principai objectives in engine development. The permitter level of sooty emissions from diesel engined passenger vehicles, for example, jas been reduced from 0.18 g/km to 0.05 g/km in the year 2005.
Harmful emissions are determined by a number of factors, e.g. ity of the fuel used, driving conditions, etc, A not inconsiderable proportion of the pollutants emitted stems directly or indirectly from the oil used in the engine for lubricating the moving parts. A crtical point within the engine is the combustion chamber itself. Burning oil during the combustion phase of the cycle leads to the emission of burnt oil particles. In addition, the temperatures reached in the combustion chamber can lead to the evaporation of the more volatile elements in the oil (e.g. benzine) and thus, as HC emissions, impair the harmful emission balance of the system.
Oil can enter the combustion chamber either through non-tight valve guides from above, or, from below, through the spaces between the piston, piston ring and cylinder bearing surfaces. Valve guides which are not tight are not a factor in new engines, On the other hand, the piston rings need a certain minimum amount of oil to be able to run properly over the surface of the cylinder wall in order to avoid metal to metal contact. The oil, which is thus of necessity present in the combustion chamber, has a detrimental effect on the performance of the engine”s exhaust system.
Reducing the amount of oil in the combustion chamber is therefore important for reducing harmful emissions, The honed cylinder bore surfaces have a particular part to play in this, They must hold a sufficient quantity of oil to prevent metal to metal contact between the friction pairs, but, on the other hand, excess oil has the detrimental effect on emissions referred to above, A development is presented below which reduces the quantity of oil on the cylinder bearing surfaces and, as a result, leads to a reduction in oil consumption and consequently to a reduction in the quantity of pollutants emitter by the engine. air filter supplier
