Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/30—Controlling fuel injection
  • F02D41/38—Controlling fuel injection of the high pressure type
  • F02D41/3809—Common rail control systems
  • F02D41/3836—Controlling the fuel pressure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/22—Safety or indicating devices for abnormal conditions
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/20—Output circuits, e.g. for controlling currents in command coils
  • F02D2041/202—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit
  • F02D2041/2024—Output circuits, e.g. for controlling currents in command coils characterised by the control of the circuit the control switching a load after time-on and time-off pulses
  • F02D2041/2027—Control of the current by pulse width modulation or duty cycle control
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/22—Safety or indicating devices for abnormal conditions
  • F02D41/222—Safety or indicating devices for abnormal conditions relating to the failure of sensors or parameter detection devices
  • F02D2041/223—Diagnosis of fuel pressure sensors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/22—Safety or indicating devices for abnormal conditions
  • F02D2041/224—Diagnosis of the fuel system
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/22—Safety or indicating devices for abnormal conditions
  • F02D2041/224—Diagnosis of the fuel system
  • F02D2041/225—Leakage detection
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/22—Safety or indicating devices for abnormal conditions
  • F02D2041/228—Warning displays
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2200/00—Input parameters for engine control
  • F02D2200/02—Input parameters for engine control the parameters being related to the engine
  • F02D2200/06—Fuel or fuel supply system parameters
  • F02D2200/0602—Fuel pressure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2250/00—Engine control related to specific problems or objectives
  • F02D2250/31—Control of the fuel pressure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/30—Controlling fuel injection
  • F02D41/38—Controlling fuel injection of the high pressure type
  • F02D41/3809—Common rail control systems

Definitions

• the present invention relates to -a- method of diagnosing malfunctioning of the high-pressure circuit of internal combustion engine high-pressure injection systems.
• a high-pressure injection system substantially comprises a fuel tank, and a high-pressure injector supply circuit in turn comprising a pump for supplying fuel at high pressure to a manifold in turn supplying a number of injectors.
• the pump presents a pressure regulating solenoid valve for supplying fuel at a predetermined pressure.
• the high-pressure circuit be monitored continually to prevent operation of the system from being impair e d by a shift in the pressure sensor setting, jamiu. ig or malfunctioning of the control members or injectors, or leakage in the circuit.
• a method of diagnosing malfunctioning of the high-pressure circuit of internal combustion engine high-pressure injection systems comprising a high-pressure pump for supplying fuel at a pressure value controlled by means of control cycles; characterized in that it comprises the- steps of monitoring quantities correlated to the pressure generated by said pump in successive control cycles; comparing the pattern of said quantities in said successive control cycles with reference values; and generating fault signals in the event said pattern fails to present a predetermined relationship with said reference values.
• Figure 1 shows an overall diagram of the hydraulic system of an injection system to which the diagnosis method according to the present invention is applied;
• Figure 2 shows a detail of the pressure regulator of the Figure 1 system
• Figure 3 shows a -block diagram of the method according to the present invention
• Figure 4 shows a maximum and minimum reference pressure graph as a function of engine speed
• Figures 5A, 5B and 5C show pressure and duty cycle graphs with an injector locked in the open position and in three different operating conditions
• Figure 6 shows the pressure/duty cycle relationship used for congruency testing.
• a general descri; ion will now be given, with reference to Figure 1, of a high-pressure injection system for internal combustion engines.
• the system indicated by 1, comprises a tank 2 at atmospheric pressure, connected by a delivery line 5 to a radial-piston pump 6 presenting a pressure regulating solenoid valve (or pressure regulator) 7 connected by drain line 8 to tank 2.
• Manifold 10 feeds the fuel at high pressure along line ii to a manifold 10 which provides for distributing the fuel to the injectors and damping any fluctuation in pressure caused by the action of the pump and opening of the injectors.
• Manifold 10 consists of a steel body preferably in the form of a parallelepipedon and in which is formed a cylindrical cavity extending along the length of the manifold and connected to line 11 by a central hole 12.
• Manifold 10 also presents four holes .:3 spaced along the length of the manifold and connected to four high-pressure (up to- 1500 bar) supply conduits 14 of four injectors 15 of an engine 16. Each injector 15 is also connected to a conduit 17 for recirculating the fuel (for operating the injector) into tank 2.
• Manifold 10 is fitted at one end with a known pressure sensor 18.
• Pressure regulator 7 is conveniently formed as shown in Figure 2, and comprises a body 20 defining a conical seat 21 for a spherical shutter 22.
• shutter 22 is subjected to the combined force of a spring 24 and a solenoid 25 which " cooperates with a core 26 integral with a rod 27 in turn integral with push rod 23.
• Shutter 22 separates an inlet conduit 28, connected to the body of pump 6, from an outlet conduit 29, connected to line 8; and varying the current supply to solenoid 25 regulates the force exerted on shutter 22 in the closing direction and, hence, the output pressure of pump 6.
• Pressure is regulated by supplying solenoid 25 with a current whose duty cycle is modulated at a fixed oscillation frequency (PWM - Pulse Width Modulation - technique) and using a closed regulating loop which takes into account the actual pressure measured by pressure sensor 18, and the desired pressure value.
• the method according to the present invention provides for periodically checking operation of the system 1 components, and more specifically for determining: the ability of pump 6 to generate the required pressure; correct- tightness of regulator 7; the absence of leakage in the circuit; the presence of injectors locked in the open position; correct operation of the electric circuit controlling regulator 7; and the sensitivity and correct operation of pressure sensor 18. According to a preferred embodiment shown schematically in Figure 3, four tests are performed periodically: maximum measured pressure (block 30) ; minimum measured pressure (block 31) ; duty cycle controlling the pressure regulator (block 32) ; and measured pressure/duty cycle congruency (block 33) .
• the maximum measured pressure test (block 30) consists in determining the pressure measured by sensor 18 in manifold 10 does not exceed a maximum permissible externally set value, e.g. 1600 bar, in a predetermined number of consecutive checks (e.g. five) .
• a pressure in excess of the maximum permissible value (shown by line A in Figure 4) indicates the following types of fault: a shift in the setting of sensor 18 (measuring error) ; or regulator 7 locked in the closed position (a fault on the regulator preventing or greatly reducing pressurized fuel flow from conduit 28 to conduit 29 of regulator 7) .
• the minimum measured pressure test (block 31) consists in determining the measured pressure does not fall below a minimum permissible value in a predetermined number of consecutive checks, e.g. five.
• the minimum permissible value varies according to engine speed, as shown by curve B in Figure 4; and a pressure below the minimum permissible value indicates the following types of fault: an injector locked in the open position; a fault on the pump (fails to ensure the required fuel flow) ; leakage in the circuit; or a shift in the sensor setting.
• the increase in the minimum permissible value alongside engine speed is important for detecting the presence of an injector locked in the open position, in that, at high engine speed, even with an injector locked in the open position, pressure may fail to fall below values which are acceptable and correspond to efficient operation at low engine speed.
• Testing of the duty cycle controlling the pressure regulator consists in determining the duty cycle (percentage measurement) does not exceed a predetermined maximum value K2 (e.g. 97%) or fall below a predetermined minimum value Kl (e»g. 2%) in a predetermined number of consecutive checks (e.g. five for the maximum and 25 for the minimum value) .
• a duty cycle repeatedly in excess of the maximum value means the measured pressure in this period is permanently below the reference value of the system controlling the regulator, and indicates the same faults as the minimum pressure test as well as, possibly, malfunctioning of the electric circuit regulating the duty cycle.
• a repeatedly low duty cycle value means the measured pressure is permanently in excess of the reference value of the system controlling the regulator, and indicates a shift in- the setting of sensor 18 or overtightness of regulator 7.
• Figures 5A, 5B and 5C show the pressure curve (dotted line) and duty cycle curve (continuous line) in three different conditions following locking of the injector at cycle 2 of the engine. More specifically, Figure 5A relates to a high-pressure condition, in which case, the fault is detected on the basis of the duty cycle remaining repeatedly in excess of the predetermined limit; Figure 5B relates to a medium-pressure condition, in which case, the fault is again detected on the basis of the excessively high duty cycle value, though more slowly than in Figure 5A; and Figure 5C relates to a low-pressure condition, in which case, the fault is detected by detecting too low a pressure value a given number of times.
• the measured pressure/duty cycle congruency test exploits the relationship between the duty cycle (or more specifically the effective current supplied to regulator 7) and the pressure measured in manifold 10, which relationship is as shown by curve C in Figure 6 which shows reference pressure PR as a function of effective current. Since curve C varies within certain limits according to the regulator used, reference value PR is assigned an upper and lower tolerance value T (e.g. 300 bar) to give two curves Dl, D2 defining a given acceptance range.
• T e.g. 300 bar
• the congruency test consists in determining the duty cycle value of the current supply to solenoid valve 7 according to conveniently proportional-integral algorithms and as a function of actual measured pressure and required pressure (the latter calculated as provided for, e.g. on the basis of engine parameters as described in a further patent application filed by the present Applicant) .
• the reference value PR corresponding to the determined duty cycle is determined; and a check is made to determine whether the value of the pressure measured by sensor 18 corresponds to reference value PR within the given tolerance (i.e. whether the measured pressure value falls within the given tolerance range) .
• a pressure value outside the given range in a given number of consecutive checks substantially indicates a shift in the setting of sensor 18 in that, the congruency test being slower than the others, other types of fault are generally detected earlier.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
• Combined Controls Of Internal Combustion Engines (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=11411710

Family Applications (1)

Country Status (5)

Cited By (3)

Families Citing this family (28)

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• 1993
  • 1993-09-03 IT ITTO930646A patent/IT1261575B/it active IP Right Grant
• 1994
  • 1994-09-02 WO PCT/EP1994/002922 patent/WO1995006814A1/en active IP Right Grant
  • 1994-09-02 JP JP50796095A patent/JP3727339B2/ja not_active Expired - Lifetime
  • 1994-09-02 EP EP94927543A patent/EP0668966B1/de not_active Expired - Lifetime
  • 1994-09-02 DE DE69409222T patent/DE69409222T2/de not_active Expired - Lifetime

Non-Patent Citations (1)

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