This article continues to introduce the knowledge of the crankshaft connecting rod mechanism and the crankcase ventilation device of diesel generators.
Crankshaft - flywheel group
There are seven main bearings. The fourth bearing is equipped with thrust washers. The thrust washers should be installed according to the specified method; otherwise, an incorrect axial clearance will be obtained. After installation, check the thrust clearance of the crankshaft, and the axial clearance of the crankshaft must be between 0.15 - 0.344 mm.
The front crankshaft oil seal is installed on the front oil - seal seat, and the front oil - seal seat is installed at the front end of the diesel engine block, as shown in Figure 3.10. The rear oil seal is installed on the rear oil - seal seat, and the rear oil - seal seat is installed on the flywheel housing.
When pressing in the front and rear oil seals, use special tooling to ensure that the oil seals are installed in place reliably. When tightening the front and rear oil - seal seats, tighten the bolts diagonally and cross - wise, and tighten them in two steps. The first step is to tighten to 10 - 13 N.m, and the second step is to tighten to 20 - 30 N.m. The sealing surface of the rear oil seal is mated with the timing gear. When installing the rear oil seal, first tighten the timing gear on the crankshaft with bolts to facilitate the assembly of the flywheel and prevent the O - ring from misaligning.
The flywheel is positioned and assembled with the rear flange of the crankshaft. During assembly, keep the mating surface clean and intact. Tighten the flywheel fastening bolts diagonally and cross - wise, and tighten them evenly in three steps as required in Table 2 - 5.
First step: Tighten to 150 N.m.
Second step: Tighten to 300 N.m.
Third step: Tighten to (520 - 560) N.m.
Note: After each tightening, rotate the crankshaft to check its flexibility.
The crankshaft pulley damper is connected to the crankshaft with bolts. Tighten the bolts diagonally and cross - wise, and also tighten them in three steps according to the requirements in Table 2 - 5.
When the engine is working, a part of the combustible mixture and exhaust gas leaks into the crankcase through the piston rings. The gasoline vapor that leaks into the crankcase will condense and dilute the engine oil, deteriorating its performance. The exhaust gas contains water vapor and sulfur dioxide. The water vapor will condense in the engine oil to form foam, which will disrupt the oil supply. This phenomenon is particularly serious in winter. Sulfur dioxide reacts with water to form sulfurous acid, and sulfurous acid reacts with oxygen in the air to form sulfuric acid. The presence of these acidic substances not only deteriorates the engine oil but also corrodes the parts. Due to the leakage of the combustible mixture and exhaust gas into the crankcase, the pressure in the crankcase will increase, and the engine oil will leak out from the crankshaft oil seal, the crankcase gasket, etc. The engine - oil vapor that leaks into the atmosphere will increase the engine's pollution to the atmosphere. Installing a crankcase ventilation device on the engine can avoid or mitigate the above - mentioned phenomena. Therefore, the functions of the engine crankcase ventilation device are: 1) to prevent the engine oil from deteriorating; 2) to prevent the crankshaft oil seal and the crankcase gasket from leaking.
The oil - gas separator is installed on the tappet - chamber cover on the right side of the front section of the engine block. When the engine is working, the oil - gas mixture that leaks into the crankcase enters the oil - gas separator through the pipeline. The oil - gas separator separates the oil and gas sucked from the crankcase, allowing the liquid oil to flow back to the oil pan and discharging the gaseous oil - gas mixture. This can reduce the consumption of engine oil.
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