Delphi-Common Rail System – High-pressure chamber

1 Inlet valve
2 Cam ring
3 Roller with roller support
4 High-pressure chamber
5 Outlet valve
6 Pump plunger

The storage pressure required for the fuel rail is generated in the high pressure chamber of the high pressure pump.

The system uses the radial piston method of operation and consists of one inlet and one outlet valve, both of which are fitted with a non-return valve, two pump plungers with rollers and roller supports and a cam ring. The cam ring forms part of the drive shaft.

The rotational movement of the drive shaft causes the cam ring to rotate as a result of which the pump plungers are moved backwards and forwards to the centre of the pump.

High-pressure chamber filling

If the transfer pressure exceeds the internal pressure of the high-pressure chamber, the inlet valve opens. Fuel flows into the high-pressure chamber and pushes the pump plungers via the rollers and roller supports outwards against the cam track of the cam ring (cams run along the rollers of the pump plungers). The outlet valve remains closed because the pressure in the high pressure channel, which is behind it, is higher.

Generation of high pressure in the high pressure chamber

1 Inlet valve
2 Cam ring
3 Roller with roller support
4 High-pressure chamber
5 Outlet valve
6 To the high pressure channel/high pressure connection
7 Pump plunger

If a cam now starts to run along the roller support of the pump plunger, the plungers moves to the centre of the high-pressure chamber. As this occurs, the delivery pressure of the pump plungers exceeds the transfer pressure and the inlet valve is closed.

As soon as the pressure in the high pressure chamber exceeds the pressure in the high pressure channel, the outlet valve opens and fuel is supplied to the fuel rail through the high pressure connection.

The delivery phase lasts until the apex of the cam has reached the roller of the roller support and the pump plungers have covered the maximum delivery path.

At this moment the pressure in the high pressure chamber drops below that in the high pressure channel.

The higher pressure in the high-pressure channel closes the outlet valve again and the fuel delivery phase ends. The amount of fuel delivered depends on the cross-section of the opening of the fuel metering valve.

02. August 2018 by Ron
Categories: Common Rail | Comments Off on Delphi-Common Rail System – High-pressure chamber