Method of assessing operation of an internal combustion engine common-rail injection system

• US 6,502,551 B2
• Filed: 01/18/2001
• Issued: 01/07/2003
• Est. Priority Date: 01/18/2000
• Status: Expired due to Term

• Current Assignee: C.R.F. Societa Consortile Per Azioni
• Original Assignee: C.R.F. Societa Consortile Per Azioni
• Inventors: Osella, Massimo, Sottano, Sara, Davide, Cristiana, Antonioli, Pierpaolo
• Primary Examiner(s): Moulis, Thomas N.
• Application Number:
  US09/761,744
• Publication Number:
  US 20010025626A1
• Time in Patent Office: 719 Days
• Field of Search: 123/359, 123/446, 123/456, 123/479, 123/497, 123/198.D, 123/198.DB, 731/19.A
• US Class Current: 123/456
• CPC Class Codes: F02D 2041/224 Diagnosis of the fuel system
• CPC Class Codes: F02D 2200/0602 Fuel pressure
• CPC Class Codes: F02D 41/221 relating to the failure of actuators or electrically driven elements
• CPC Class Codes: F02D 41/3836 Controlling the fuel pressure

Abstract

A method of assessing operation of a common-rail injection system of an internal combustion engine; the injection system having a number of injectors, a high-pressure circuit supplying high-pressure fuel to the injectors, and a low-pressure circuit supplying fuel to the high-pressure circuit; and the method including the steps of hydraulically isolating the high-pressure circuit from the low-pressure circuit and the engine; and assessing operation of the injection system as a function of the fuel pressure drop in the high-pressure circuit.

Claims

1. A method of assessing operation of a common-rail injection system of an internal combustion engine;

said injection system comprising a number of injectors, a high-pressure circuit supplying high-pressure fuel to said injectors, and a low-pressure circuit supplying fuel to said high-pressure circuit;

the method comprising the steps of;

hydraulically isolating said high-pressure circuit from said low-pressure circuit and said engine; and

assessing operation of said injection system as a function of the fuel pressure drop in said high-pressure circuit.

2. A method as claimed in claim 1, wherein said step of hydraulically isolating said high-pressure circuit from said low-pressure circuit and said engine comprises the steps of:

cutting off fuel supply from said low-pressure circuit to said high-pressure circuit; and

cutting off fuel supply from said injectors to said engine.

3. A method as claimed in claim 1, wherein said step of assessing operation of said injection system comprises the steps of:

determining the fuel pressure drop in said high-pressure circuit;

comparing said determined pressure drop with a reference pressure drop;

determining a fault in said high-pressure circuit when a first predetermined relationship exists between said determined pressure drop and said reference pressure drop; and

determining a fault in said low-pressure circuit in the absence of said first predetermined relationship between said determined pressure drop and said reference pressure drop.

4. A method as claimed in claim 3, wherein said first predetermined relationship is defined by the condition that said determined pressure drop be greater than said reference pressure drop.

5. A method of assessing operation of a common-rail injection system of an internal combustion engine;

said injection system comprising a number of injectors, a high-pressure circuit supplying high-pressure fuel to said injectors, and a low-pressure circuit supplying fuel to said high-pressure circuit;

the method comprising the steps of;

hydraulically isolating said high-pressure circuit from said low-pressure circuit and said engine;

assessing operation of said injection system as a function of the fuel pressure drop in said high-pressure circuit; and

wherein said step of assessing operation of said injection system comprises the steps of;

determining the fuel pressure drop in said high-pressure circuit;

comparing said determined pressure drop with a reference pressure drop;

determining a fault in said high-pressure circuit when a first predetermined relationship exists between said determined pressure drop and said reference pressure drop;

determining a fault in said low-pressure circuit in the absence of said first predetermined relationship between said determined pressure drop and said reference pressure drop;

determining a limit pressure value;

comparing the instantaneous pressure value of the fuel in said high-pressure circuit with said limit pressure value for a predetermined time interval;

determining said fault in said low-pressure circuit when a second predetermined relationship exists between said instantaneous pressure value and said limit pressure value throughout said time interval; and

determining said fault in said high-pressure circuit in the absence of said second predetermined relationship between said instantaneous pressure value and said limit pressure value during said time interval.

6. A method as claimed in claim 5, wherein said second predetermined relationship is defined by the condition that said instantaneous pressure value be greater than said limit pressure value throughout said time interval.

7. A method as claimed in claim 5, wherein said step of determining a limit pressure value comprises the step of:

determining said limit pressure value as a function of the instantaneous pressure value of said fuel in said high-pressure circuit.

8. A method of assessing operation of a common-rail injection system of an internal combustion engine;

said injection system comprising a number of injectors, a high-pressure circuit supplying high-pressure fuel to said injectors, and a low-pressure circuit supplying fuel to said high-pressure circuit;

the method comprising the steps of;

hydraulically isolating said high-pressure circuit from said low-pressure circuit and said engine;

assessing operation of said injection system as a function of the fuel pressure drop in said high-pressure circuit;

wherein said step of assessing operation of said injection system comprises the steps of;

determining the fuel pressure drop in said high-pressure circuit;

comparing said determined pressure drop with a reference pressure drop;

determining a fault in said high-pressure circuit when a first predetermined relationship exists between said determined pressure drop and said reference pressure drop;

determining a fault in said low-pressure circuit in the absence of said first predetermined relationship between said determined pressure drop and said reference pressure drop;

the method further comprising the steps of;

turning off said engine in the event said fault in said high-pressure circuit is determined; and

limiting the performance of said engine in the event said fault condition in said low-pressure circuit is determined.

9. A method as claimed in claim 8, wherein said step of limiting the performance of said engine comprises the steps of:

limiting the maximum fuel quantity injectable by said injectors; and

limiting the maximum permissible pressure of said fuel in said high-pressure circuit.

10. A method of assessing operation of a common-rail injection system of an internal combustion engine;

said injection system comprising a number of injectors, a high-pressure circuit supplying high-pressure fuel to said injectors, and a low-pressure circuit supplying fuel to said high-pressure circuit;

the method comprising the steps of;

hydraulically isolating said high-pressure circuit from said low-pressure circuit and said engine;

assessing operation of said injection system as a function of the fuel pressure drop in said high-pressure circuit; and

wherein said step of assessing operation of said injection system comprises the steps of;

determining the fuel pressure drop in said injection system; and

classifying said injection system as a function of said determined pressure drop.

11. A method of assessing operation of a common-rail injection system of an internal combustion engine;

said injection system comprising a number of injectors, a high-pressure circuit supplying high-pressure fuel to said injectors, and a low-pressure circuit supplying fuel to said high-pressure circuit;

the method comprising the steps of;

hydraulically isolating said high-pressure circuit from said low-pressure circuit and said engine;

assessing operation of said injection system as a function of the fuel pressure drop in said high-pressure circuit; and

wherein said step of assessing operation of said injection system comprises the steps of;

determining the fuel pressure drop in said high- pressure circuit;

generating an aging index of said injection system as a function of said determined pressure drop.

12. A method as claimed in claim 11, further comprising the step of periodically repeating said step of determining the fuel pressure drop in said high-pressure circuit and said step of generating an aging index of said injection system as a function of said determined pressure drop;

said I aging index being calculated as a function of the pressure drops determined.

13. A method as claimed in claim 12, wherein said aging index is calculated, at each determination, as a moving mean of the determined pressure drop value and a previous pressure drop value.

14. A method of assessing operation of a common-rail injection system of an internal combustion engine;

said injection system comprising a number of injectors, a high-pressure circuit supplying high-pressure fuel to said injectors, and a low-pressure circuit supplying fuel to said high-pressure circuit;

the method comprising the steps of;

hydraulically isolating said high-pressure circuit from said low-pressure circuit and said engine;

assessing operation of said injection system as a function of the fuel pressure drop in said high-pressure circuit; and

wherein said high-pressure circuit comprises a common rail connected to said injectors and to said low-pressure circuit by high-pressure conduits, and wherein said step of hydraulically isolating said high-pressure circuit comprises the step of;

hydraulically isolating said common rail and said high-pressure conduits.

15. A method as claimed in claim 14, wherein said low-pressure circuit comprises a supply pump for drawing fuel from a tank, a high-pressure pump connected to said supply pump and to said common rail, and a pressure regulator for regulating the fuel pressure in said high-pressure circuit, characterized in that said step of hydraulically isolating said high-pressure circuit from said low-pressure circuit and said engine comprises the steps of:

disabling said supply pump;

closing said pressure regulator; and

cutting off injection by said injectors.

16. A method of assessing operation of a common-rail injection system of an internal combustion engine;

said injection system comprising a number of injectors, a high-pressure circuit supplying high-pressure fuel to said injectors, and a low-pressure circuit supplying fuel to said high-pressure circuit;

the method comprising the steps of;

hydraulically isolating said high-pressure circuit from said low-pressure circuit and said engine;

assessing operation of said injection system as a function of the fuel pressure drop in said high-pressure circuit;

determining the presence of a jammed-open injector condition;

turning off said engine if said jammed-open injector condition is determined; and

performing said step of hydraulically isolating said high-pressure circuit and said step of assessing operation of said injection system if said jammed-open injector condition is not determined.