1. The cause of "biased cylinder"
1) Deformation of the cylinder block or cylinder liner causes the cylinder centerline to exceed the perpendicularity tolerance relative to the crankshaft main bearing bore centerline, resulting in cylinder misalignment.
2) Bend or twist deformation of the crankshaft that is not inspected and repaired according to technical standards causes the parallelism tolerance between the connecting rod diameter centerline and the main shaft diameter centerline to exceed the tolerance, or the two centerlines, while parallel, are not in the same horizontal plane, causing piston misalignment.
3) Bend or twist deformation of the connecting rod that is not corrected according to technical specifications causes piston misalignment.
4) The flatness of the mating surface between the cylinder liner support step and the cylinder liner does not meet standard requirements, or there is debris trapped between the two, which can also cause piston misalignment in the cylinder.
5) Exceeding the tolerance of the connecting rod diameter cylindricity causes the connecting rod to be non-perpendicular to the crankshaft main shaft diameter centerline, causing the piston to press against the front and rear sides of the cylinder wall, resulting in piston misalignment.
6) Connecting rod bushing machining does not meet technical requirements, or the centerline of the connecting rod head hole is not parallel to the centerline of the connecting rod bushing during boring, resulting in cylinder misalignment after installation.
7) Piston pin hole machining does not meet standard specifications, causing the centerline of the piston pin hole to be non-perpendicular to the centerline of the piston skirt, leading to piston misalignment and cylinder misalignment.
8) The piston does not misalign when stationary, but does so before and after movement. This is caused by excessive crankshaft end clearance or the thrust bearing seat and bearing side edges not meeting technical requirements.
2. Measures to prevent cylinder deviation
A: Before final assembly, the technical conditions of the following parts must be strictly checked and must meet the standard requirements before assembly.
(1) The technical condition of the cylinder block should be checked as appropriate, especially for engines that have been used for a long time and have problems such as burning, sticking, and seizing. They should be carefully checked and, if necessary, reshaped to meet the technical requirements.
(2) The perpendicularity error of the center line of the processed cylinder to the crankshaft bearing hole should meet the standard requirements.
(3) Check and correct the bending and twisting deformation of the connecting rod to meet the technical requirements.
(4) The parallelism error between the center line of the crankshaft connecting rod diameter and the center line of the main shaft diameter, and the cylindricity error of the connecting rod diameter should meet the standard requirements.
(5) The perpendicularity error between the center line of the piston pin seat hole or the center line of the connecting rod small end and the center line of the piston skirt should meet the technical requirements.
B: Assemble the piston and connecting rod assembly according to the assembly process requirements to ensure assembly quality. After the connecting rod, piston pin, and piston are assembled according to the specified process, in addition to measuring the cylindricity error of the piston skirt, the perpendicularity between the piston skirt generatrix and the connecting rod big end should also be checked on a connecting rod tester to ensure that they meet the standard requirements. Otherwise, the relevant parts should be inspected separately. Only when they meet the technical requirements can the piston and connecting rod be assembled into the cylinder.
