The vehicle's lubrication system is designed to reduce friction, eliminate wear products and cool surfaces. The supply of oil into the gap between the contacting (rubbing) surfaces - the cylinder and the piston - increases the compression of the motor and makes the connection more tight.
The oil used in the lubrication system has different requirements. It should have a certain viscosity index, minimum pour point, high thermo-oxidizing ability, maximum flash point. In addition, the lubricant must have a minimum coke number. It should be purified - it should not contain impurities (alkalis, mineral acids, sulfur, water) and other mechanical impurities.
The listed requirements are more consistent with materials derived from oil. Synthetic oils are also quite common. However, they, in comparison with mineral ones, are of great value, but, at the same time, surpass them in quality.
The engine lubrication system provides several options for supplying oil. The material can be fed by gravity, under pressure or by spraying. In the designs of modern cars, as a rule, all types of oil supply are used. Such a system is called a “combined engine lubrication system”. In this case, as a rule, oil does not accumulate at the bottom of the cavity where the crank rotates. The combined method is most widely used in the design of four-stroke engines, which use a dry sump circulation lubrication system.
Oil from the crankshaft (connecting rod journals) through special holes can be supplied to the piston pin or from the connecting rod channel to the engine cylinder walls if the channels of the connecting rod journal and connecting rod coincide. From here, oil can also be sprayed onto the cams of the camshaft at its lower position. When friction parts that are lubricated under pressure flow out in the contact zone, the lubricant enters the timing parts (pushers, valve stem, rods, drive chain) by gravity. Rotating, the crankshaft breaks up drops of oil and creates a “fog”. This helps to reduce the friction of the contacting parts.
The oil supplied by the pump has rather stringent requirements for the degree of purification. In this regard, the engine lubrication system is equipped with a number of filters.
The first, usually mesh, filter is installed on the oil intake of the pump. The following are several cleaning methods:
- All oil can be supplied to the lubrication system through one filter. This cleaning method is called full-flow.
- Partial oil cleaning is also provided. In this case, a certain amount of oil is sent from the pump or its section to the filter through a parallel channel with further discharge to the sump.
The engine lubrication system is also equipped with devices designed to maintain the optimum temperature of the system, as well as providing emergency operation. The main parameters that determine functioning include temperature and pressure. Taking into account the type of motor design, the optimal pressure indicator is also determined (within 1-8 kg / cm2).
In addition, the limit values are determined in accordance with the operating mode of the engine. Provides pressure maintenance at the right level pressure reducing valve. This part helps to limit the pressure to the required rate. Installation of this valve is carried out in the main line or on the oil pump directly.
In case of failure of a full-flow filter, a bypass valve is provided in the design . It allows oil to be passed past the filter.
The necessary thermal conditions are maintained by transferring part of the oil through a special channel to the cooling radiator from the pump.