FR2796419A1 - PROCESS FOR DIAGNOSING A FUEL SUPPLY SYSTEM OF AN INTERNAL COMBUSTION ENGINE, ESPECIALLY FOR A MOTOR VEHICLE - Google Patents

Abstract

The invention provides a method for diagnosing a fuel supply system of a vehicle internal combustion engine. The fuel is injected directly into a combustion chamber by injectors (7). The engine is operated in a mode in which the pressure increase to high pressure is disabled. The pre-supply pressure prevailing in a fuel distribution tube (4) of the fuel supply system is recorded using a pressure sensor (5) fitted to this tube.

Description

I

State of the art.

  The present invention relates to a method for diagnosing a fuel supply system of a mo-

  internal combustion engine, in particular of an auto-5 bile vehicle, according to which the fuel can be injected directly

  in a combustion chamber by injectors.

  The invention also relates to a system for

  automatic diagnosis, designed for the implementation of the

  dice and an external diagnostic system for the implementation

of the process.

  In the case of petrol engines with electronic injection, a fuel pressure of the order of

  3 to 10 bars. This pressure is supplied by an electric pump

  fuel stick, and regulated by a pressure regulator

  mechanical. Direct injection petrol engines require

  also try such pressure as pre-

  high pressure pump supply.

  As in gasoline injection engines

  known electronics, there is no monitoring or regulation

  electronic pre-supply pressure, it is also not possible to diagnose using a

  control device or workshop control device.

  In direct injection petrol engines, pre-supply pressure is mainly required

  to supply the high pressure pump. This pres-

  There is no strict condition because it is enough

  that it exists to allow high pressure.

  But there are also operating ranges, for example

  example when starting the engine, for which it is necessary to

  work with the pre-feed pump even in the

  petrol with direct injection. For this reason, even for direct injection petrol engines, the pre-supply pressure is an important parameter to allow

faultless operation.

  The present invention aims to develop

  a method for diagnosing a fuel supply system

  of an internal combustion engine with direct petrol injection, allowing monitoring or diagnosis of the

pre-feed pressure.

  To this end, the invention relates to a method of

  type defined above, characterized in that it operates-

  ner the internal combustion engine in an operating mode for which the pressure increase is deactivated

  towards a high pressure, and we enter a pre-

  supply to a fuel distribution tube of the system

  fuel supply using a fuel sensor

pressure fitted to this tube.

  Thus, according to the invention, the pressure sensor necessarily existing in each supply system with

  fuel from a direct injection petrol engine is used

  used for the diagnosis of the pre-supply pressure.

  For this, the engine must operate in a mode in the-

  which high pressure setting is disabled.

  There are two different concepts for this purpose for high pressure regulation of direct injection internal combustion engines. In both cases, however,

  a mode of operation for which high pressure

  is deactivated so that the pre-

  supply can be detected using the pressure sensor fitted to the fuel distribution tube. This makes it possible to diagnose the pre-supply pressure in the fuel supply system without intervening in the assembly of the engine. According to other advantageous characteristics of the invention: * for diagnosing a fuel supply system

  pressure-regulated, comprising a pressure relief valve

  pressure control, the pressure control valve is fully opened; * to diagnose a fuel supply system with consumption control, having a flow control valve, a few injections are provided before the diagnosis so that there is no high pressure in the fuel distribution tube, and regulates the flow control valve so as not to have a high pressure transfer;

  pre-supply pressure for the fuel system

  Unloaded fuel rate is determined during starter operation with closed injectors or when the fuel supply system is loaded, the pre-supply pressure is entered before

  defining different injection durations for injections

  teurs. The invention also relates to a system for

  automatic diagnosis of a fuel supply system

  of an internal combustion engine, particularly a vehicle

  motor vehicle, in which the fuel can be injected directly into a combustion chamber, characterized in that the output of a pressure sensor intended to capture the pressure prevailing in a fuel distribution tube is connected to an inlet of a central control unit which

  allows the method according to the invention to be carried out.

  The invention further provides a diag-

  external diagnosis, in particular of workshop diagnosis, of a system

  fuel supply stage of a motor vehicle according to which fuel is injected directly into a combustion chamber, characterized in that the output of a pressure sensor which detects the pressure prevailing in a fuel distribution tube is connected at an entry of a

  central control unit, which allows the process to be carried out

  die according to the invention; an external diagnostic device, in particular a workshop controller, forces in particular by the central control device, the operating mode of the internal combustion engine so as to deactivate

  the pressure increase towards high pressure.

  The present invention will be described below from

  in more detail using an embodiment

  shown schematically in the accompanying drawings in the-

  which: FIG. 1 is a block diagram of a fuel supply system with pressure regulation of a

  internal combustion engine, in particular of a motor vehicle

  mobile, Figure 2 is a block diagram of a system

  fuel supply with consumption control

  of an internal combustion engine, particularly a vehicle

car cule.

  The two figures show a configuration of

  based. This can be extended in different realizations

  tions by additional valves and / or connections, by

  example to realize particular means such as the re-

cooling or ventilation.

  In the fuel supply system with pressure regulation shown in FIG. 1, the petrol is transferred from a tank 1 by an electric fuel pump 2 comprising a mechanical pressure regulator, with a pre-supply pressure to a high pump

  pressure 3. From there the fuel enters the repair tube.

  tition of fuel (common rail) 4 fitted with a fuel sensor

  pressure 5 and from this ramp the fuel supplies the various

  rents injectors 7. In the fuel supply system

  With pressure regulation, a regulation circuit 8 comprising a pressure control valve 6 ensures a permanent flow. The quantities of fuel to be injected into the combustion chambers of the internal combustion engine,

  through the injectors 7, represent large

  disturbing dors for this regulation circuit 8. The pressure prevailing in the fuel distribution tube 4 (common rail) is regulated using the regulation circuit 8 by a variation of the flow rate in the distribution tube of

fuel 4.

  For the implementation of the diagnostic process

  according to the invention of the fuel pre-supply system

  rant, in the fuel supply system to be regulated

  pressure according to FIG. 1, the control valve for

  pressure 6 is fully open.

  When the fuel system

  is not loaded, the pre-supply pressure is detected

  ted when the starter is running, the injectors being closed, and at that time the diagnosis is made. In a fuel system under load, to diagnose the

  pre-supply pressure, the preset control unit

  nit different injection times for the injectors 7. In the fuel supply system according to

  Figure 2, with consumption control, the electric pump

  that fuel 2, equipped with a mechanical pressure regulator, takes gasoline from tank 1 to supply gasoline at the pre-supply pressure to a pump

  high pressure fitted with a flow control valve 13.

  The fuel distribution tube 4, transfers by the flow control valve 13, only the quantities of fuel necessary for the injectors 7. It is possible to have a combined high pressure regulation (not shown) ensuring fine adjustment. The combination of the high pressure pump 3 and the flow control valve 13 allows precise control of the dosage of the quantity of fuel necessary for

  injection. In addition, in the fuel supply line

  burant, between the flow control valve 13 and the fuel distribution tube 4, there is a non-return valve 10. The fuel distribution tube 4 has a pressure sensor 5 as in the fuel supply system

  with pressure regulation shown in figure 1.

  To diagnose pre-

  feed into the fuel-controlled fuel supply system shown in Figure 2, first injections are performed by the injectors to ensure that there is no high pressure in the distribution tube fuel 4. Depending on the design of the high pressure pump 3 and the flow control valve 13, there

  order the flow control valve 13 for the diag-

  nostic, so as not to have transfer at high pressure.

  In this situation, the fuel distribution tube 4

  is then supplied by the pre-supply system from

  shot from the electric supply pump 2. The diagnosis of the pre-supply pressure in the fuel supply system, not under load, is made with the starter, the injectors 7 being closed. The diagnosis of the pre-supply pressure is done in the system

  fuel supply under load by predefining dif-

different injection times.

  For automatic diagnosis of the pre-supply pressure, a control device, not shown in FIGS. 1 and 2, is coupled to the pressure sensor 5 and receives the pressure signals from the fuel distribution tube 4, signals supplied by the pressure sensor 5. The control unit performs the various process steps and

  diagnoses the pre-supply pressure using the

  pressure signals supplied by the pressure sensor 5.

  In the case of an external diagnosis, for example a workshop diagnosis, a workshop diagnosis system (not shown) coupled to the control unit (also not shown) forces the control unit to operating state in which the pre-supply pressure can be detected using the pressure sensor 5.

Claims (5)

R E V E N D I C A T IONS   1) Method for diagnosing a fuel supply system   of an internal combustion engine, in particular of a vehicle   motor vehicle, according to which the fuel can be injected directly into a combustion chamber by injectors (7), characterized in that * the internal combustion engine is operated in an operating mode for which the increase in pressure towards a high pressure, and * a pre-supply pressure is entered in a fuel distribution tube (4) of the fuel supply system using a pressure sensor (5) fitted this tube.   2) A diagnostic method according to claim 1, characterized in that to diagnose a pressure regulated fuel supply system, comprising a pressure control valve (6), the control valve is completely opened. pressure (6).   3) diagnostic method according to claim 1, characterized in that * for diagnosing a fuel supply system with consumption control, having a control valve of   flow (13), a few injections are provided before the diag-   nostic so that there is no high pressure in the fuel distribution tube (4), and * the flow control valve (13) is adjusted so as not to   have high pressure transfer.   4) diagnostic method according to claim 1 or 2, characterized in that   pre-supply pressure for the fuel system   Unloaded fuel consumption is determined during the   starter operation with injectors (7) closed.    ) A diagnostic method according to claim 2 or 3, characterized in that when the fuel supply system is loaded, the pre-supply pressure is entered by predefining different injection times for the injectors (7). 6) System for automatically diagnosing a fuel supply system of an internal combustion engine, in particular of a motor vehicle, into which the fuel can be injected directly into a combustion chamber, characterized in that the outlet a pressure sensor (5) intended to capture the pressure prevailing in a fuel distribution tube (4) is connected to an input of a central control device and the control device makes it possible to carry out the process according to one of claims 1 to 5.   7) External diagnostic system, especially diagnostic   workshop, a fuel supply system for a vehicle   automobile vehicle according to which direct fuel is injected   in a combustion chamber, characterized in that   the output of a pressure sensor (5) which detects the pressure   sion reigning in a fuel distribution tube (4) is connected to an input of a central control device, the control device allows the process to be carried out according to one of claims 1 to 5, and   an external diagnostic device, in particular a controller   workshop, in particular by the central control unit   tral, the operating mode of the internal combustion engine   dull so as to deactivate the pressure increase towards high pressure.