MICROMETRY OF CYLINDER LINERS OF YAMZ ENGINES

Abstract

The most important part that limits the engine life is the cylinder liner. Before fault finding in the cylinder liners, it is necessary to carry out the micrometry of their surface to identify the areas of greatest and least wear. For carrying out the micrometry and testing it on new and worn cylinder liners, 40 cylinder liners of YaMZ engines were used. The working surface of the cylinder liners was controlled by the inner diameter, which was measured in eight sections and two planes. The micrometry was carried out with an indicating hole gauge with a digital head of increased accuracy with a sensitivity of 0.001 mm; ten new cylinder liners met the technical requirements. The micrometry of thirty cylinder liners showed that the greatest wear was 253 μm in the connecting rod oscillation plane and 189 μm in the perpendicular plane. It was found that liner micrometry should be particularly thoroughly carried out at the top of the cylinder liners. The greatest wear occurs at the top piston ring stop at the start of the expansion stroke, with more intensive wear in the connecting rod oscillation plane due to the normal force. The uppermost part of the cylinder liners is the wear-free liner flange, the diameter of which indicates the original dimensions of the liner bore. However, it must also be measured due to the effects of high temperatures, changes in the crystal pattern of the material, oxidation and the presence of combustion products in the form of carbon deposits. The lower part of the cylinder liner is subject to wear due to the friction of the piston skirt against its surface. However, due to the lower temperature, the better lubrication, the much larger contact surface and the correspondingly lower pressure, increased wear here can only occur if there are misalignments in the crank mechanism: the misaligned crankshaft axle or the bent connecting rod.