Engine oil circulation route

Except for the piston and cylinder wall, most of the engine components are lubricated by pressure. The circulation route is: oil pan—→filter—→oil pump—→oil filter. After the oil passes through the filter, a part of the oil enters the engine body. In the main oil passage of the engine, lubricate the crankshaft, connecting rod, etc., and another part of the oil enters the cylinder head to lubricate the camshaft, hydraulic tappet, etc.

Schematic diagram of lubricating oil circuit

 

Oil pump

 

After the oil pump raises the oil to a certain pressure, it is forced to be pressed to the moving surface of each part of the engine. The structure of the oil pump can be divided into two types: gear type and rotor type. The gear-type oil pump has a pair of gears that mesh with each other. As the gears rotate, the oil is sucked into the oil inlet chamber and pressed out from the oil outlet chamber.

 

gear oil pump

 

The rotor oil pump consists of a housing, an inner rotor, an outer rotor, and the like. The inner rotor is directly or indirectly driven by the crankshaft gear. The inner rotor and the outer rotor have a certain eccentricity, so that four working chambers are formed between the inner and outer rotors. With the rotation of the rotor, the volumes of these four working chambers change continuously. The process of oil suction and pressure oil.

 

Rotary oil pump

 

The pressure limiting valve is generally installed on the oil pump, and the pressure limiting valve includes a plunger (or ball valve), a pressure limiting spring and a screw plug. When the main oil pressure exceeds the specified value, the plunger overcomes the spring pressure and is pushed open, and the pressure limiting valve opens to release part of the pressure to maintain the normal oil pressure in the main oil passage.

 

 

Working principle of pressure limiting valve

Oil pressure limiting valve structure

oil pressure switch

The oil pressure switch is usually installed on the oil passage of the cylinder block. When the oil pump failure or other reasons cause the oil pressure to be lower than the specified value, the internal contacts will be closed and the oil pressure warning light on the instrument will light up. When the oil pressure is normal, the oil pressure pushes the diaphragm in the oil pressure switch to disconnect the internal contacts, and the oil pressure warning light goes out.

oil nozzle

 

Oil nozzles Some high-power engines have oil cooling nozzles (or nozzles), which help the pistons cool down and dissipate heat by spraying oil into the piston cavity. If the oil cooling nozzle is blocked, the piston will accumulate heat and heat up, which will easily lead to damage to the top of the piston.

Some engine timing chains are also lubricated by oil nozzles

 

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