초록 ▼

Control method for an overpressure valve in a common-rail fuel supply system, the method including the phases of: delivering fuel under pressure, via a high-pressure pump, to a common rail equipped with the overpressure valve that is set to discharge the fuel present in the common rail into a discha

Control method for an overpressure valve in a common-rail fuel supply system, the method including the phases of: delivering fuel under pressure, via a high-pressure pump, to a common rail equipped with the overpressure valve that is set to discharge the fuel present in the common rail into a discharge line when the fuel pressure inside the common rail exceeds a safety value; piloting, during a diagnostic test, the high-pressure pump to increase the fuel pressure inside the common rail beyond the safety value in order to trigger operation of the overpressure valve; determining, during the diagnostic test, the flow of the high-pressure pump and/or the fuel pressure inside the common rail; and comparing the flow of the high-pressure pump and/or the fuel pressure inside the common rail during the diagnostic test with respective threshold values.

대표청구항 ▼

The invention claimed is: 1. Control method for an overpressure valve in a common-rail fuel supply system, the method including: delivering fuel under pressure, via a high-pressure pump, to a common rail equipped with the overpressure valve that is set to discharge the fuel present in the common ra

The invention claimed is: 1. Control method for an overpressure valve in a common-rail fuel supply system, the method including: delivering fuel under pressure, via a high-pressure pump, to a common rail equipped with the overpressure valve that is set to discharge the fuel present in the common rail into a discharge line when the fuel pressure inside the common rail exceeds a safety value (psafety) which guarantees the tightness and safety of the injection system; determining, during a normal use, the fuel pressure inside the common rail; feedback-piloting, during the normal use, the high-pressure pump in function of the fuel pressure inside the common rail to keep the fuel pressure inside the common rail to a desired level which is always lower than the safety value (psafety); piloting, during a diagnostic test performed with the internal combustion engine in cut-off condition, the high-pressure pump to increase the fuel pressure inside the common rail beyond the safety value (psafety) to reach a target pressure (ptarget) having a higher value that the safety value (psafety) in order to trigger operation of the overpressure valve; determining, during the diagnostic test, the flow (mHP) of the high-pressure pump and/or the fuel pressure inside the common rail; comparing the flow (mHP) of the high-pressure pump and/or the fuel pressure inside the common rail during the diagnostic test with respective threshold values (mtest and ptest); and diagnosing malfunctioning of the overpressure valve if the flow (mHP) of the high-pressure pump is less than a respective flow threshold value (mtest) and/or the fuel pressure inside the common rail is greater than a respective pressure threshold (ptest). 2. Method according to claim 1, wherein during the diagnostic test the high-pressure pump is piloted having at least the pressure threshold value (ptest) as the target pressure (ptarget). 3. Method according to claim 1, wherein the pressure threshold value (ptest) is at least equal to the safety value (psafety) incremented by the pressure tolerance of the overpressure valve. 4. Method according to claim 1, wherein the flow threshold value (mtest) is greater than the fuel flow (mLeak) lost due to leaks on the injectors. 5. Method according to claim 1, wherein the flow threshold value (mtest) increases as the number of revs of the internal combustion engine rises. 6. Method according to claim 1, wherein the diagnostic test is performed during a cut-off condition in which the fuel pressure inside the common rail is close to the maximum operating value. 7. Method according to claim 1, wherein malfunctioning of the overpressure valve is diagnosed after a certain time interval from the start of the diagnostic test. 8. Method according to claim 7, wherein after the certain time interval from the start of the diagnostic test, the flow (mHP) of the high-pressure pump and/or the fuel pressure inside the common rail have substantially stable values.