Superimposed pressure control of the common rail system

1. A method for pressure control of a common rail injection system of an internal combustion engine, comprising a high-pressure pump for delivering fuel to a common rail accumulator connected to an injector, a volume control valve (VCV) which is disposed upstream of the high-pressure pump and configured for adjusting a volume flow of fuel through said volume control valve into the high-pressure pump, and a pressure control valve (PCV) downstream of the high-pressure pump, the method comprising:

using a processor to implement a VCV closed-loop control mode for controlling the pressure of fuel in the common rail injection system, wherein in the VCV closed-loop control mode the VCV is controlled in a closed-loop control manner and the PCV is controlled in an open-loop control manner;

upon detecting a predefined operating point of the internal combustion engine, automatically activating a switch to activate a PCV closed-loop control mode while in the VCV closed-loop control mode, wherein both the PCV and the VCV are controlled in a closed-loop control manner;

upon achieving a desired pressure control according to the PCV closed-loop control mode, automatically activating the switch to deactivate the PCV closed-loop control mode, thereby returning to the VCV closed-loop control mode, wherein the VCV is controlled in a closed-loop control manner and the PCV is controlled in an open-loop control manner.

2. The method according to claim 1 , wherein the PCV is controlled in an open-loop control manner as offset control during the VCV closed-loop control mode.

3. A device for controlling pressure in a common rail injection system of an internal combustion engine comprising a high-pressure pump for delivering fuel to a common rail accumulator connected to an injector, a volume control valve (VCV) upstream of the high-pressure pump and configured for adjusting a volume flow of fuel through said volume control valve into the high-pressure pump, and a pressure control valve (PCV) downstream of the high-pressure pump, the control device comprising:

a processor programmed to:

implement a VCV closed-loop control mode for controlling the pressure of fuel in the common rail injection system, wherein in the VCV closed-loop control mode the VCV is controlled in a closed-loop control manner and the PCV is controlled in an open-loop control manner;

upon detecting a predefined operating point of the internal combustion engine, automatically activate a switch to activate a PCV closed-loop control mode while in the VCV closed-loop control mode, wherein both the PCV and the VCV are controlled in a closed-loop control manner;

upon achieving a desired pressure control according to the PCV closed-loop control mode, automatically activate the switch to deactivate the PCV closed-loop control mode, thereby returning to the VCV closed-loop control mode, wherein the VCV is controlled in a closed-loop control manner and the PCV is controlled in an open-loop control manner.

4. The device according to claim 3 , wherein the PCV is controlled in an open-loop control manner as offset control during the VCV closed-loop control mode.

5. The device according to claim 3 , comprising a common rail pressure coordination block configured to select between the VCV closed-loop control mode and the PCV closed-loop control mode.

6. The device according to claim 3 , comprising a pressure control valve coordination block configured to select between the VCV closed-loop control mode and the PCV closed-loop control mode.

7. The device according to claim 6 , wherein the pressure control valve coordination block comprises a switch for implementing at least one of a ramp transition and an exponential transition.

8. A system for pressure control of a common rail injection system of an internal combustion engine, comprising:

a high-pressure pump for delivering fuel to a common rail accumulator connected to an injector,

a volume control valve (VCV) which is disposed upstream of the high-pressure pump and configured to adjust a volume flow of fuel through said volume control valve into the high-pressure pump,

a pressure control valve (PCV) downstream of the high-pressure pump, and

a pressure control unit configured to:

implement a VCV closed-loop control mode for controlling the pressure of fuel in the common rail injection system, wherein in the VCV closed-loop control mode the VCV is controlled in a closed-loop control manner and the PCV is controlled in an open-loop control manner;

upon detecting a predefined operating point of the internal combustion engine, automatically activate a switch to activate a PCV closed-loop control mode while in the VCV closed-loop control mode, wherein both the PCV and the VCV are controlled in a closed-loop control manner;

upon achieving a desired pressure control according to the PCV closed-loop control mode, automatically activate the switch to deactivate the PCV closed-loop control mode, thereby returning to the VCV closed-loop control mode, wherein the VCV is controlled in a closed-loop control manner and the PCV is controlled in an open-loop control manner.

9. The system according to claim 8 , wherein the PCV is controlled in an open-loop control manner as offset control during the VCV closed-loop control mode.

10. The system according to claim 8 , comprising a common rail pressure coordination block configured to select between the VCV closed-loop control mode and the PCV closed-loop control mode.

11. The system according to claim 8 , wherein the pressure control unit comprises a pressure control valve coordination block configured to select between the VCV closed-loop control mode and the PCV closed-loop control mode.

12. The system according to claim 11 , wherein the pressure control valve coordination block comprises a switch for implementing at least one of a ramp transition and an exponential transition.