The two sets of opposing plungers are driven by the inner cam via the rollers. The inner cam is driven by the engine via the timing belt. The inside of the inner cam, which is elliptic, comes in contact with the roller. As the inner cam rotates, it causes the plunger to move reciprocally, and the resulting suction and pumping of fuel generates pressure.
The rotation of the eccentric cam causes the ring cam to rotate with an offset axis. The ring cam rotates and pushes one of the two plungers upward as it pulls the other plunger upward or vice versa for the downward direction. For the supply pump, plunger B is pushed down to compress the fuel and send it into the common-rail when plunger A is pulled downward to draw the fuel in. Conversely, when plunger A is pushed up to compress the fuel and send it to the common-rail, plunger B is pulled up to draw the fuel up.
Regulation of the Fuel Pressure by the Supply Pump
2. Check valve
4. Inner cam
5. Delivery valve
The fuel that has been fed by the feed pump travels via the SCV and the check valve, becomes pressurized by the plunger, and is pumped via the delivery valve to the common-rail.
SCV Control of the Supply Pump
The SCV operates under the duty-cycle control of the ECU.
At the same time, current control is effected to limit the amount of electrical current that flows during the ON period, thus preventing the coil in the SCV from damage.
2KD-FTV and 1ND-TV Engine
The fuel supplied by the feed pump is drawn through the SCV (or MPROP) and the check valve. Then, it is compressed by the plunger, and is pumped up through the check valve via the delivery valve to the common-rail.
SCV opening/closing time: long
SCV opening/closing time: short
To regulate the generation of fuel pressure, the volume of fuel that enters the supply pump is regulated by varying the opening/closing time of the SCV or MPROP.
Construction of Common-rail
The common-rail stores the high-pressure fuel that has been generated by the supply pump and distributes the fuel via the injection pipes to the injectors of the cylinders. Because the fuel is under extremely high pressure, proper care must be taken to prevent leaks.
Fuel pressure sensor
Detects the pressure in the rail and feeds it back to the ECU.
In case of a system failure in which the pressure in the common-rail rises to an abnormal level, this valve opens to release the pressure. Returns to the fuel tank.
Operation of the Pressure Limiter
The pressure limiter operated mechanically to release the pressure in case the pressure in the common-rail rises to
an abnormal level.
Pressure limiter inactive
Pressure limiter active