The principle of operation of the fuel quantity meter
1 - pressure disk; 2 - distribution plunger; 3 - axis of the lever; 4 - to intake valves
The principle of operation of the dispenser-distributor of fuel
1 - valve spring; 2 - diaphragm; 3 - distribution plunger; 4 - slotted sleeve of the distribution plunger; 5 - lower chamber; 6 - upper chamber; 7 - fuel supply to the nozzles; 8 - control edge of the distribution plunger
The dispenser-distributor regulates the amount of fuel supplied to the injectors in proportion to the amount of air supplied.
The fuel dispenser-distributor consists of a pressure regulator, a distribution plunger, differential pressure valves and a control pressure circuit.
Pressure regulator
The pressure regulator regulates the fuel supply pressure in the range of 4.5-5.2 kg/cm2. Excess fuel is returned to the tank through the drain pipe.
When the engine is stopped, the pressure regulator reduces the fuel pressure in the system to a value slightly less than 3.3 kg / cm2, i.e. nozzle opening pressure. This eliminates the possibility of self-ignition of the working mixture.
Distribution plunger
The amount of fuel supplied to the engine cylinders varies depending on the position of the distribution plunger, in the walls of which there are rectangular slots, the flow area of which changes as the plunger moves relative to the windows (one window per cylinder), made in the plunger sleeve.
The fuel dispensed in this way (proportional to air flow) is fed into the upper chambers of the differential pressure valves.
Differential pressure valves
Four differential pressure valves (one per cylinder) have two chambers separated by a diaphragm. Regardless of the amount of fuel supplied, they maintain a constant pressure drop at the level of the distribution plunger slots, thanks to which the fuel pressure in the system and the pressure of the fuel supplied to the injectors is maintained at a constant level.
With an increase in the fuel supply to the upper chambers, the pressure increases, the diaphragm bends down, completely opening the fuel supply holes to the injectors.
With a decrease in the fuel supply to the upper chambers, the diaphragm bends upward, reducing the flow area of the fuel supply holes to the injectors.
Pilot pressure circuit
The pressure in the control circuit is regulated by a pressure regulator and can vary from 0.5 kg/cm2 on a cold engine to 3.4-3.8 kg/cm2 on a warm engine. At wide open throttle, the control pressure drops to 2.9 kg/cm2, causing the mixture to become richer at full engine load.
To prevent uncontrolled beats of the pressure plate of the air flow meter under the influence of air flow pulsations (at low engine speed or at full engine load) shock-absorbing throttle constriction is provided.
Pilot pressure regulator
The control pressure regulator ensures the enrichment of the working mixture entering the combustion chambers when the engine warms up. On a cold engine, the bimetal spring compresses the diaphragm valve spring, opening the fuel drain channel, which leads to a decrease in resistance on the distribution plunger. A decrease in control pressure at a constant air flow causes an increase in the stroke of the pressure disc. As a result, the distribution plunger is additionally raised, increasing the amount of fuel supplied to the injectors.
As the bimetal spring heats up, the pressure on the diaphragm valve spring of the control pressure regulator decreases and the drain channel slowly closes. The control pressure reaches a normal value and the enrichment of the combustible mixture stops.
The pilot pressure regulator is mounted on the cylinder block, so that its temperature changes at the same time as the engine temperature. This eliminates excessive enrichment of the working mixture at an average temperature.
Operating principle of the pilot pressure regulator
A - on a cold engine; B - on a hot engine; 1 - bimetallic spring; 2 - fuel drain; 3 - control pressure supply; 4 - thermal winding of a bimetallic spring
Auxiliary air valves
This valve is used to increase the engine speed during engine warm-up. When starting a cold engine, the additional air supply channel is opened by a rotary valve flap, which moves when the bimetallic spring is heated. As it warms up, the additional air supply channel gradually closes.
In addition, the supply of additional air is regulated by the pressure disk of the air quantity meter, the movement of which leads to a corresponding rise in the distribution plunger, which also contributes to an increase in the crankshaft speed (with closed throttle).
When starting a cold engine, an electromagnetic starting injector, controlled by a thermal time switch, atomizes additional fuel into the intake manifold.
Fuel to the starting nozzle is supplied directly from the dispenser-distributor under a pressure of about 4.7 kg / cm2.
The maximum operating time of the nozzle at a temperature of minus 20°C is 8 s. If the coolant temperature is above 15°C, the starting injector does not turn on.