CONTROL METHOD OF A COMMON-RAIL TYPE SYSTEM FOR DIRECT FUEL INJECTION INTO AN INTERNAL COMBUSTION ENGINE

• US 20070144490A1
• Filed: 12/21/2006
• Published: 06/28/2007
• Est. Priority Date: 12/28/2005
• Status: Abandoned Application

• Current Assignee: Magneti Marelli Powertrain S.p.A. (Magneti Marelli S.p.A.)
• Original Assignee: Magneti Marelli Powertrain S.p.A. (Magneti Marelli S.p.A.)
• Inventors: De Cesare, Matteo, Serra, Gabriele
• Application Number:
  US11/614,247
• Publication Number:
  US 20070144490A1
• Time in Patent Office: Days
• US Class Current: 123/458
• CPC Class Codes: F02D 2250/31 Control of the fuel pressure
• CPC Class Codes: F02D 41/123 the fuel injection being cut-off
• CPC Class Codes: F02D 41/3872 characterised by leakage flow in injectors
• CPC Class Codes: F02M 47/027 Electrically actuated valves draining the chamber to release the closing pressure
• CPC Class Codes: F02M 63/0225 Fuel-injection apparatus having a common rail feeding several injectors F02M63/0003 takes precedence; Means for varying pressure in common rails; Pumps feeding common rails

Abstract

A control method for a direct fuel injection system into an internal combustion engine provided with a number of cylinders; the method presents the stages of: supplying pressurised fuel to a common rail by means of a high-pressure pump; cyclically driving a number of hydraulically actuated injectors having an hydraulically actuated needle to inject fuel into the cylinders; establishing a desired fuel pressure level within the common rail; determining a threshold value for the injectors so that no fuel is injected by each injector if it is driven for a time interval shorter than the threshold value; and reducing the actual fuel pressure within the common rail by driving the injectors for a driving time interval shorter than the threshold value.

Claims

1. ) A control method for a direct fuel injection system (1) into an internal combustion engine (2) provided with a number of cylinders (3);

the method comprises the stages of;

supplying pressurised fuel to a common rail (5) by means of a high-pressure pump (6);

cyclically driving a number of injectors (4) having an hydraulically actuated needle (21) and connected to the common rail (5) to inject fuel directly into the cylinders (3);

establishing a desired fuel pressure level within the common rail (5); and

regulating the actual fuel pressure level within the common rail (5) according to the desired level by regulating the fuel flow rate (m_HP) from the high-pressure pump (6) during the compression or pumping stage of the high-pressure pump (6) itself;

the method is characterised in that it comprises the further stages of;

determining a threshold value (ETmin) for the injectors (4) so that no fuel is injected by each injector (4) if it is driven for a time interval shorter than the threshold value (ETmin); and

reducing the actual fuel pressure within the common rail (5) according to the desired level by driving the injectors (4) for a driving time interval (ETred) shorter than the threshold value (ETmin) when the injectors (4) themselves are not used to inject the fuel required by the combustion process.

2. ) A method according to claim 1, wherein the driving time interval (ETred) is shorter than the threshold value (ETmin) and close to the threshold value (ETmin) itself.

3. ) A method according to claim 1, and comprising the further stage of optimising the driving time interval (ETred) so as to ensure that the driving time interval (ETred) is shorter than the threshold value (ETmin).

4. ) A method according to claim 1, wherein the actual fuel pressure level within the common rail (5) is reduced by driving the injectors (4) for the driving time interval (ETred) shorter than the threshold value (ETmin) during an injection cut-off stage.

5. ) A method according to claim 4, wherein the optimisation stage comprising the further stages of:

detecting the possible presence of undesired fuel injections within the cylinders (3) during the injection cut-off stage; and

decreasing the driving time interval (ETred) in the presence of undesired fuel injections within the cylinders (3) during injection cut-off stage.

6. ) A method according to claim 5, wherein the optimisation stage comprises the further stage of:

increasing the driving time interval (ETred) of the injectors (4) in the case of prolonged absence of undesired fuel injections within the cylinders (3) during injection cut-off stage.

7. ) A method according to claim 5, wherein the presence of undesired fuel injections within the cylinders (3) during the injection cut-off stage is determined by detecting possible accelerations of a crankshaft of the engine.

8. ) A method according to claim 5, wherein the presence of undesired fuel injections within the cylinders (3) during the injection cut-off stage is determined by detecting possible sudden increases of pressure within the cylinders (3) themselves.

9. ) A method according to claim 5, wherein the presence of undesired fuel injections within the cylinders (3) during the injection cut-off stage is determined by observing the Air/Fuel ratio in exhaust.

10. ) A method according to claim 5, wherein the presence of undesired fuel injections within the cylinders (3) during the injection cut-off stage is determined by observing the quantity of exhaust gas by means of a linear oxygen probe.

11. ) A method according to claim 1, wherein, in order to reduce the actual fuel pressure level within the common rail (5), a single injector (4) is driven at a time and the driving of each injector (4) is timed with respect to the respective cylinder (3).

12. ) A method according to claim 11, wherein the driving of each injector (4) is timed with the compression stroke of the respective cylinder (3).

13. ) A method according to claim 1, wherein, in order to reduce the actual fuel pressure level within the common rail (5), the injectors (4) are not driven in a timed manner with respect to the cylinders (3).

14. ) A method according to claim 13, wherein several injectors (4) are driven simultaneously.

15. ) A method according to claim 1, wherein no regulating action on the fuel pressure within the common rail (5) is taken if the actual fuel pressure level within the common rail (5) is lower than the desired level.

16. ) A method according to claim 1, wherein each injector (4) is connected to a discharge channel (14) having a substantially ambient pressure;

if an injector (4) is controlled for a time interval shorter than the threshold value (ETmin), then an output of fuel to the discharge channel (14) may occur but no fuel is injected into the cylinder (3).

17. ) A method according to claim 1, wherein the fuel flow rate (m_HP) from the high-pressure pump is regulated by varying the closure instant of an intake valve of the high-pressure pump 6 itself.