Crankcase ventilation system: device, types, operating principle

At present, despite the rapid development of technology, it is not possible to create a perfectly sealed pair of friction parts - the cylinder and the piston ring. Therefore, in combustion engines, combustion products accumulate during operation.

In the pallet crankcase gases pass through the piston rings, which adjoin the cylinders loosely. As a result, heat is removed worse, the service life of the lubricating fluid is shortened, and excessive pressure is applied to all block seals. The crankcase ventilation system prevents excessive crankcase pressure.

Development of the device

In the beginning, the mechanism looked like this: from the crankcase, a tube was simply output that discharged gases into the atmospheric air and contaminated it. But the regulations on the emission of gases from vehicles have been seriously tightened. Therefore, the crankcase ventilation system was forcedly developed by the manufacturers.

Principle of operation of the mechanism

In the form in which the system is known at present, gases are not simply released into the atmosphere. They are sent to the motor by means of a withdrawn tube from the crankcase, the other end of which is connected to the intake manifold. From there, gases are sent to the combustion chamber. At the time of the outbreak, some of them burn out, and the other part is thrown out through the release mechanism. Only a small fraction of these gases re-enter the crankcase. So the process takes place without a break.

Types of the crankcase recirculation system

There are two types of system:

• Open;
• Closed.

In the first case, as described in the beginning of the article, the gases are taken away simply into the atmosphere. In the second they are sucked into the intake manifold. The closed crankcase ventilation system: VAZ and Lada, BMW and Mercedes, Japanese and Americans, is mainly used now.

In addition, closed systems are with variable or constant flow. The first type is more precisely able to regulate the recirculation of the crankcase. It varies depending on the amount of gas supplied.

Device

At the top is the oil separator of the crankcase ventilation system, and inside it there is an oil reflector. Its task is to release gases from oil particles. The oil separator of the crankcase ventilation system has an outlet with a pipeline. During normal operation of the motor in the crankcase, a certain rarefaction must occur at all times. The valve can operate in three versions.

Forced crankcase ventilation: valve

Let's consider briefly all three of these options.

1. Behind the throttle a low pressure is formed from 500 to 700 mbar. The crankcase ventilation system does not stand this mode. And the piston, under the influence of rarefaction, closes the valve.
2. If the throttle is fully open, then the pressure there is the same with the atmospheric or even higher. When the flow reaches 500-700 mbar, the piston closes the valve to pass the gases.
3. In the middle position, the normal piston pressure is ensured.

If the operation of the valve raises questions, then its serviceability is easy to verify. For this purpose, a sheet of paper is placed on the idle at the neck where the oil is poured. If it will go down and rise together with the membrane movement, then the valve is serviceable.

The normal functioning can also be checked in another way. In idle mode, remove the ventilation hose and close it with your finger: the suction should be felt.

Pressure Reducing Valve

If the motor is operating at high speed, a pressure appears in the intake manifold, which has an equal value with the atmospheric pressure or exceeds it. In this case, more gases enter the crankcase. If there is a turbocharger in the inlet, the vacuum will be too high and it should be balanced.

To do this, a pressure relief valve is provided that works in the intake manifold when the damper opens. The mechanism, consisting of a diaphragm and a spring, is inserted into the plastic housing, in which there are inlet and outlet fittings.

Operation of the reduction valve

At normal underpressure, the spring is not loaded. At the same time, the membrane is raised and gases are passed freely.

Under reduced pressure, the diaphragm descends and closes the outlet, overcoming the action of the spring. Then the gases begin to move through the bypass path - a channel with a calibrated hole.

Unfortunately, acting positively on the one hand, the crankcase ventilation system creates a problem with the other. Leaving the sump, gases capture and particles of grease, thus contaminating the intake system. In addition, they settle on the surfaces of the exit channels and the parts of the recirculation valve. This leads to narrowing of the channels and may cause malfunctions in the operation of the injection. If the diaphragm jams, the oil consumption will increase. Then you have to change the valve.

Also, one should not forget about another important detail and in time to change the hose of the crankcase ventilation system - this is usually done together with recirculating valves. Otherwise, it forms cracks and tears.

To prevent expensive repairs, it is necessary to pay attention to the emerging stains on the engine seals, the increase in the consumption of the fuel and lubricating fluid and the unstable functioning of the motor. If you arrive at the service center in time, the problem will be solved in the embryo, until it has had time to cause significant harm to the unit.