Method to control a high-pressure fuel pump for a direct injection system

Patent metadata

Field	Value
Publication number	US-11041447-B2
Application number	US-202016927551-A
Country	US
Kind code	B2
Filing date	Jul 13, 2020
Priority date	Jul 18, 2019
Publication date	Jun 22, 2021
Grant date	Jun 22, 2021

Abstract

The invention relates to a method to control a fuel pump for a direct injection system of a heat engine provided with a common rail comprising the steps of determining a minimum threshold based on the pressure in the common rail and on the speed of the heat engine, on the temperature of the high-pressure pump and on the inlet pressure of the high-pressure pump; calculating the objective fuel flow rate to be fed by the high-pressure pump to the common rail instant by instant in order to have the desired pressure value inside the common rail; comparing the objective fuel flow rate with the minimum threshold; and controlling the high-pressure pump based on the comparison between the objective fuel flow rate and the minimum threshold.

First claim

The invention claimed is:

1. A method to control a fuel pump ( 4 ) for a direct injection system of a heat engine ( 1 ) provided with a common rail ( 3 ) comprising the steps of:
determining a minimum threshold (Q MIN , Q TEMP ) of fuel to be fed by the high-pressure pump ( 4 );
calculating the objective fuel flow rate (M ref ) to be fed by the high-pressure pump ( 4 ) to the common rail ( 3 ) instant by instant in order to have the desired pressure value (P TARGET ) inside the common rail ( 3 );
comparing the objective fuel flow rate (M ref ) with the minimum threshold (Q MIN , Q TEMP ); and
controlling the high-pressure pump ( 4 ) based on the comparison between the objective fuel flow rate (M ref ) and the minimum threshold (Q MIN , Q TEMP );
the method is characterized in that the step of determining a minimum threshold (Q MIN , Q TEMP ) comprises the sub-steps of:
determining a first contribution (Q MIN_COLD ) and a second contribution (Q MIN_HOT ) based on the pressure (P RAIL ) in the common rail ( 3 ) and on the speed (n) of the heat engine ( 1 ); wherein the first contribution (Q MIN_COLD ) is the minimum threshold of fluid to be pumped under cold conditions that are far from the triggering of cavitation phenomena for given values of the pressure (P RAIL ) in the common rail ( 3 ) and of the speed (n) of the heat engine ( 1 ), and the second contribution (Q MIN_HOT ) is the minimum threshold of fuel to be pumped under hot conditions that are close to the triggering of cavitation phenomena for given values of the pressure (P RAIL ) in the common rail ( 3 ) and of the speed (n) of the heat engine ( 1 );
determining a coefficient (K) based on the temperature (T PUMP ) of the high-pressure pump ( 4 ) and on the inlet pressure (P LOW ) of the high-pressure pump ( 4 ); wherein said coefficient (K) expresses the closeness of the high-pressure pump ( 4 ) to the condition of triggering of cavitation phenomena; and
determining said minimum threshold (Q MIN , Q TEMP ) based on the first contribution (Q MIN_COLD ), on the second contribution (Q MIN_HOT ) and on the coefficient (K).

2. A method according to claim 1 and comprising the further steps of:
determining a third contribution (Q EEff ) to increase energy efficiency based on the pressure (P RAIL ) in the common rail ( 3 ) and on the injected fuel quantity (Q F_INJ );
determining a fourth contribution (Q DAM ) to decrease possible risks of damaging the high-pressure pump ( 4 ) based on the pressure (P RAIL ) in the common rail ( 3 ) and on the speed (n) of the heat engine ( 1 ); and
determining said minimum threshold (Q MIN ) based on the third contribution (Q EEff ) and on the fourth contribution (Q DAM ).

3. A method according to claim 2 , wherein the third contribution (Q EEff ) is determined depending on a driving mode (DV) chosen for the vehicle provided with the heat engine ( 1 ); preferably, depending on the position of a hand lever among a plurality of possible positions.

4. A method according to claim 2 and comprising the further steps of:
determining a fifth contribution (Q TEMP ) to contain the temperature variation generated during the pumping phase in the high-pressure pump ( 4 ) based on the first contribution (Q MIN_COLD ), on the second contribution (Q MIN_HOT ) and on the coefficient (K); and
determining said minimum threshold (Q MIN ) based on the comparison among the fifth contribution (Q TEMP ), the third contribution (Q EEff ) and the fourth contribution (Q DAM ).

5. A method according to claim 4 , wherein the fifth contribution (Q TEMP ) is calculated as follows:
Q TEMP =(1− K )* Q MIN_COLD +K*Q MIN_HOT   [6]

Q TEMP fifth contribution;
K coefficient;
Q MIN_COLD first contribution; and
Q MIN_HOT second contribution.

6. A method according to claim 4 , wherein the minimum threshold (Q MIN ) corresponds to the greatest value among the fifth contribution (Q TEMP ), the third contribution (Q EEff ) and the fourth contribution (Q DAM ).

7. A method according to claim 1 and comprising the further step of controlling the high-pressure pump ( 4 ) so as to deliver the objective fuel flow rate (M ref ) only in case the objective fuel flow rate (M ref ) is greater than the minimum threshold (Q MIN , Q TEMP ); and controlling the high-pressure pump ( 4 ) so as not to deliver fuel in case the objective fuel flow rate (M ref ) is smaller than the minimum threshold (Q MIN , Q TEMP ).

8. A method according to claim 1 , wherein the step of determining a minimum threshold (Q MIN , Q TEMP ) comprises the sub-steps of:
calculating an energy index (I), which gives an indication of the closeness—or lack thereof—to the triggering o cavitation phenomena in the high-pressure pump ( 4 ) based on the intensity of the perturbation of the signal concerning the pressure (P RAIL ) in the common rail ( 3 ) detected in real time by a pressure sensor ( 11 ), wherein the perturbation is assessed by means of an integral within an observation time window; and
calculating the minimum threshold (Q MIN , Q TEMP ) based on said energy index (I).

9. A method according to claim 8 and comprising the further step of decreasing the desired pressure value (P TARGET ) inside the common rail ( 3 ) by a first quantity (ΔP TARGET ) and for a first amount of time in case the energy index (I) exceeds a first threshold value.

10. A method according to claim 9 , wherein the first quantity (ΔP TARGET ) is equal to at least 10 bar and preferably is independent of the difference between the energy index (I) and the first threshold value.

11. A method according to claim 8 and comprising the further step of increasing the minimum threshold (Q MIN , Q TEMP ) by a second quantity (ΔQ MIN ) in case the energy index (I) exceeds a first threshold value.

12. A method according to claim 11 , wherein the second quantity (ΔQ MIN ) is equal to at least 20 mg and preferably is independent of the difference between the energy index (I) and the first threshold value.

13. A method according to claim 8 , wherein the energy index (I 1 ) in case the objective fuel flow rate (M ref ) is delivered is calculated as:
I 1 =∫ t 1 t 2 ( P TARGET −P RAIL ) 2 dt   [2]

wherein
t 1 , t 2 instants defining an observation time window;
P RAIL actual pressure in the common rail ( 3 );
P TARGET desired pressure value in the common rail ( 3 ).

14. A method according to claim 8 , wherein the energy index (I 2 ) in case the objective fuel flow rate (M ref ) is delivered is calculated as:
I 2 =∫ t 1 t 2 ( P RAIL_M −P RAIL ) 2 dt   [3]

wherein
t 1 , t 2 instants defining an observation time window;
P RAIL actual pressure in the common rail ( 3 ); and
P RAIL_M actual mean pressure in the common rail ( 3 ) and within the observation window.

15. A method according to claim 8 , wherein the energy index (I 3 ) is calculated as:
I 3 =∫ t 1 t 2 ( INT M −INT ) 2 dt   [4]

wherein:
t 1 , t 2 instants defining an observation time window;
INT value of the integral component of the closed loop of the pressure control;
INT M mean value of the integral component of the closed loop of the pressure control within the observation window.

Assignees

• Marelli Europe Spa

Inventors

• Parotto Marco
• De Cesare Matteo
• Morelli Marco
• Prodi Giovanni
• Cardellini Tommaso

Classifications

• F02D1/16 Primary

  Adjustment of injection timing (F02D1/02 takes precedence) · CPC title

• F02D2200/0602

  Fuel pressure · CPC title

• F02D2041/226

  Fail safe control for fuel injection pump · CPC title

• F02M63/027

  More than one high pressure pump feeding a single common rail · CPC title

• F02M55/025 Primary

  Common rails · CPC title