Common Rail System on S05C-TB Engine
The control system can be divided into three conventional parts: sensors, an electronic control unit (computer) and actuators.
The electronic control unit uses signals from sensors installed on the engine and in the transmission to calculate the time (moment) of power supply and the duration of power supply to the solenoid valve of the nozzle.
Description of the system “Common Rail”
The Common Rail system consists of a fuel pump, a fuel manifold, nozzles, an electronic control unit that controls all these parts and various sensors.
The fuel pump delivers high pressure fuel to the fuel manifold. The fuel pressure is regulated by the flow rate to the fuel manifold. The flow rate is controlled by switching on / off the bypass valve, controlled by signals from the electronic unit.
The fuel manifold receives fuel under the pressure generated by the fuel pump and distributes it among the engine cylinders. Fuel pressure is detected by a pressure sensor installed in the fuel manifold. The feedback is arranged so that the actual pressure is consistent with the calculated value in accordance with the crankshaft speed and engine load.
Fuel under pressure from the fuel manifold through the fuel pipes enters the nozzles.
The nozzles control the magnitude of the cyclic feed and the angle of advance of the injection by turning the control valve on and off. When voltage is applied to the valve winding, fuel flows out of the control chamber through the nozzle, the sprayer needle rises, and injection begins. When the voltage supply to the valve winding is stopped, the fuel pressure in the control chamber rises, the needle moves down, and the injection ends.
The injection advance angle is controlled by the moment (time) of voltage supply to the control valve winding, and the cyclic feed rate is controlled by the duration of voltage supply to the valve winding.
Operation of the “Common Rail” system
Description of the fuel pump
The fuel pump has a high-pressure fuel production system similar to conventional in-line fuel pumps and is equipped with an overflow valve that controls the amount of fuel delivered to each section..
The number of fuel pump sections is half the number of engine cylinders due to two cams. The amount of supply to the fuel manifold is the same for all injectors, which ensures the same and constant pressure in the fuel manifold.
A. When the plunger moves down, the bypass valve opens and fuel is pumped into the supraplunger cavity at low pressure through the bypass valve.
IN. Even when the plunger goes up, fuel returns through the bypass valve without increasing pressure while the valve is open (without energizing the valve coil).
FROM. When voltage is applied to the valve winding, the valve closes at the appropriate time for the required supply quantity, and the fuel pressure in the plunger chamber increases. Thus, fuel enters through the discharge valve (check valve) into the fuel manifold. In other words, the stroke of the plunger after closing the bypass valve determines the flow rate and, by changing the duration of closing the bypass valve (preliminary stroke), the flow rate can be changed and the pressure in the fuel manifold can be adjusted.
A’ When the plunger reaches its maximum rise, it begins to move downward and the pressure in the supra-plunger cavity begins to drop. At this time, the discharge valve closes and the fuel supply stops. As soon as the voltage supply to the bypass valve winding is interrupted, the valve opens and the fuel enters the plunger chamber under low pressure.
The scheme of the fuel pump
The bypass valve adjusts the amount of fuel supplied by the fuel pump in accordance with the pressure in
fuel manifold. The flow rate from the fuel pump to the fuel manifold is determined by the duration of the voltage supply to the solenoid valve.
Fuel manifold, pressure limiter, dampers
The fuel manifold serves to distribute high pressure to the nozzles of each cylinder. A pressure sensor, pressure limiter and damper are installed in the fuel manifold.
The pressure limiter opens at high pressure and allows you to reset it to a predetermined value. When the pressure in the fuel manifold exceeds 171 MPa, the restrictor valve opens and the pressure is relieved by 35 MPa, then the restrictor valve closes and the pressure is maintained at that level.
Damper operation scheme
Dampers are installed at the inlet to the high pressure pipes connecting the fuel manifold and the injector. Dampers are used to reduce the pulsation of the fuel pressure in the fuel pipe and the supply of fuel under constant pressure to the nozzle. They also provide fuel (fuel channel) cut-off in case of excessive pressure to prevent abnormal fuel flow.
The damper works as follows: for example, in the case of high pressure, the damper piston moves to the right and reaches the seat, thus closing the fuel line to the nozzle.
The function of the nozzle is to inject fuel under high pressure in the fuel manifold, in accordance with the signal of the electronic control unit corresponding to the angle of advance of injection, the magnitude of the cyclic feed, the injection speed. The nozzle diagram is shown in the figure:
Nozzle circuit. 1 – ECU, 2 – fuel pressure sensor, 3 – control valve, 4 – drain, 5 – fuel collector, 6 – “feeding” nozzle, 7 – nozzle of the control chamber, 8 – control chamber, 9 – plunger, 10 – spray gun, 11 – needle, 12 – spray chamber, 13 – fuel pump, 14 – bypass valve.
With the nozzle closed, no power is supplied to the solenoid valve. The valve needle is pressed under the action of a spring and hydraulic pressure, and the valve seat is closed. While the fuel from the fuel manifold enters the control chamber, the nozzle is closed and there is no injection.
When voltage is applied to the control valve coil, the valve needle rises and the valve seat opens. As a result, fuel flows out of the control chamber through the nozzle and the pressure in the chamber decreases, so that the nozzle needle rises and injection begins. Fuel consumption through the nozzle affects the injection speed, gradually increasing it. With continuous voltage supply to the valve coil, a maximum injection speed can be achieved..
Nozzle closes (end of injection)
When the voltage supply to the valve winding is interrupted, the valve needle closes the valve seat under the action of a spring and hydraulic pressure. At this moment, fuel from the fuel manifold enters the control chamber, the nozzle needle instantly lowers, and the injection stops.
1 – valve spring, 2 – ECU, 3 – control valve, 4 – valve needle, 5 – valve seat, 6 – control chamber nozzle, 7 – control chamber, 8 – plunger, 9 – fuel manifold, 10 – “feed “jet.
A description of the repair, diagnostic and maintenance procedures for this engine can be found in the book “HINO engines J05C, S05C, S05C-B, S05C-TA, S05C-TB, S05D”
J05C J05C-TD J08C (TP / TR)
S05C S05C-B S05C (TA / TB) S05D
Diagnostics. Repairs. Maintenance.
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