Volume Control Valve and High Pressure Pump

Volume Control Valve And High Pressure Pump

Volume control valve and high pressure pump
The fuel is delivered to the high pressure pump via the inlet with delivery pressure generated by the fuel pump. The fuel is then directed into the fuel chamber of the pump element via the quantity control valve. In this pump element, the fuel is pressurized by a piston and delivered to the high-pressure connection via the high-pressure non-return valve. The high pressure pump is screwed to the cylinder head and is driven by the camshaft via a triple cam.

Functional description
As soon as the engine is running, the triple cam continuously moves the piston to make its stroke. Fuel is thus pressurized for as long as new fuel is delivered into the high pressure pump via the quantity control valve. The quantity control valve is activated by the engine control system; it specifies the delivered volume of fuel. Pressure regulation takes place via the quantity control valve in that it is opened or closed by the pump element towards the fuel feed. In the induction stroke, the fuel is sucked in via the opened quantity control valve and delivered back again in the compression stroke into the feed until the quantity control valve closes. The closing time initiates the actual delivery stroke and determines the volume of fuel that is pumped through the non-return valve into the high pressure line.







The quantity control valve controls the fuel pressure in the rail. In addition, the pressure limiting valve provides the possibility to reduce the pressure in the rail. Here, the fuel is fed out of the high-pressure system back into the pump element.

Structure and inner electrical connection
The quantity control valve is a solenoid valve. The quantity control valve is activated via a pulse-width modulated signal (PWM signal) from the engine control system. Depending on the activation signal, the ratio between return delivery in the low-pressure range and delivery stroke in the high-pressure range changes. This sets the necessary fuel mass flow for each load point. The quantity control valve is powered by the quantity control valve relay using terminal 15N. The engine control system activates the relay.







Schematic overview and setpoint values
The maximum pressure in the high-pressure range is restricted to 245 bar. if such a high pressure arises, the high-pressure circuit is relaxed to the low-pressure range by a pressure limiting valve. The pressure change does not cause a change in the fuel volume. The resulting pressure peak is compensated for by the low-pressure damper when entering the low-pressure range.







Observe the following setpoint values for the quantity control valve:

Size Value
Minimum supply voltage at engine 6 Volts
start
System pressure of high pressure 5 to 20 MPa
pump
Power consumption 4.5 A
Resistance at 20 °C 0.5 Ohms
Response time 3.2 ms
Temperature range -30 °C to 140 °C

Diagnosis instructions

Failure of the component
If the quantity control valve fails, the following behavior is to be expected:
- Fault entry in the engine control unit
- Emergency operation with substitute value

General notes
In the event of mechanical failure when the quantity control valve is closed,engine operation is no longer possible:
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