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The Role Of Camshaft And Common Faults

2021-09-09

The camshaft is one of the key parts of the engine. The main body of the camshaft is a cylindrical rod with approximately the same length as the cylinder group. There are several cams on it to drive the valves. Therefore, the main function of the camshaft is to control the opening and closing of the valve.
The contact stress between the cam and the tappet is very high, and the relative sliding speed is also very high, so the wear of the cam working surface is more serious. In response to this situation, the camshaft journal and cam working surface should have high dimensional accuracy, small surface roughness and sufficient rigidity, as well as high wear resistance and good lubrication.

Common malfunctions

Common failures of camshafts include abnormal wear, abnormal noise, and breakage. Symptoms of abnormal wear often occur before abnormal noise and breakage occur.
(1) The camshaft is almost at the end of the engine's lubrication system, so the lubrication status is not optimistic. If the oil pump has insufficient oil supply pressure due to excessive use time, etc., or the lubricating oil passage is blocked and the lubricating oil cannot reach the camshaft, or the tightening torque of the bearing cap fastening bolts is too large and the lubricating oil cannot enter the camshaft gap, it will Cause abnormal wear of the camshaft.
(2) Abnormal wear of the camshaft will cause the gap between the camshaft and the bearing seat to increase, and the camshaft will undergo axial displacement when it moves, resulting in abnormal noise. Abnormal wear will also cause the gap between the drive cam and the hydraulic tappet to increase. When the cam is combined with the hydraulic tappet, an impact will occur, which will cause abnormal noise.
(3) The camshaft sometimes has serious failures such as fractures. The common causes are hydraulic tappet cracking or severe wear, severe poor lubrication, poor camshaft quality, and camshaft timing gear rupture.
(4) In some cases, the failure of the camshaft is caused by man-made reasons, especially when the camshaft is not properly disassembled and assembled when the engine is repaired. For example, when removing the camshaft bearing cap, use a hammer or a screwdriver to pry pressure, or when installing the bearing cap, the position of the bearing cap does not match with the bearing seat, or the tightening torque of the fastening bolt of the bearing cap is too large. When installing the bearing cover, pay attention to the direction arrow and position number on the surface of the bearing cover, and use a torque wrench to tighten the bearing cover fastening bolts in strict accordance with the specified torque.