FR2783572A1 - DEVICE FOR DOSING FUEL INTO A CYLINDER OF AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

This fuel metering device comprises a fuel supply device, an injection valve (13), a mixing chamber (14), an air supply device, a mixing injector (15) and a device. adjusting the air pressure in the air supply device according to a fuel pressure in the fuel supply device. The mixing chamber is connected to the air supply device. The injection valve (13) is arranged in the mixing chamber such that fuel is metered into the mixing chamber. The mixture injector (15) communicates with the mixing chamber (14) and is arranged in the cylinder head (10) of the internal combustion engine in such a way that it introduces in a metered manner the mixture present in the chamber. mixture (14) in the cylinder (4).

Description

The present invention relates to a fuel metering device in

  a cylinder of an internal combustion engine, comprising - a fuel supply device connected to an injection valve, - a mixing chamber connected to an air supply device and in which the injection valve is arranged in such a way that the fuel entering the mixing chamber is dosed, and - a mixing injector, which communicates with the mixing chamber and is arranged in the head of the cylinder of the internal combustion engine in such a way that it introduces proportionally the mixture present in

  the mixing chamber in the cylinder.

  Such a device is described in the publication R. Houston, G. Cathart, "Combustion and Emissions Characteristics of Orbital's Combustion Process Applied to Multi-Cylinder Automotive Direct Injected 4-Stroke Engines", Society of Automotive Engineers SAE Document 980153, Volume SP 136 The known device comprises an injection valve, a mixing chamber and a mixing injector. Between the injection valve and the mixing injector, there is a mixing chamber in which pressurized air is mixed

  to fuel which is metered by the injection valve.

  The mixture injector regularly injects the air-fuel mixture which is in the

  mixture in the cylinder of the internal combustion engine.

  The device is characterized by the fact that it allows

  precise stratification of the charge, therefore of the air-

  fuel, in the cylinder. We thus obtain a

  high efficiency of the internal combustion engine.

  In the known device, the air under pressure is adjusted to a given fixed value of the pressure. The fuel pressure in a fuel supply device is adjusted such that a given pressure difference is adjusted between the fuel pressure and the air pressure. The fuel supply device includes a fuel pump, a differential pressure regulator close to the cylinder block of the internal combustion engine and a return line leading from the differential pressure regulator to a fuel tank. Heated fuel almost always returns to the tank during the operation of the internal combustion engine due to the overpressure necessary for regulation and partially evaporates there. The object of the invention is to create a device for metering fuel into a cylinder of an internal combustion engine which is simple and provides for metering.

precise fuel.

  The problem is solved by a device defined in the introduction, characterized in that there is provided a device for adjusting the air pressure in the air supply device as a function of a fuel pressure in the device. food

in fuel.

  The metering device according to the invention also has the following advantageous features: - the air pressure adjustment device is constructed in such a way that the air pressure is adjusted according to a quantity representing the load on the internal combustion engine; - The device includes a regulator whose magnitude set and control is the pressure difference between the fuel pressure and the air pressure; - a differential pressure sensor is provided which measures the difference between the fuel pressure and the air pressure; - There is provided in the air supply device, a throttling device which is an adjustment member for adjusting the air pressure; - the throttling device is placed upstream of a mouth of a pipe communicating with an activated carbon filter which absorbs and desorbs fuel vapors; - a fuel injection duration is determined by the injection valve as a function of the pressure difference and of the quantity representing the

  load on the internal combustion engine.

  The invention is characterized in that, in the fuel supply device, it is possible to dispense with a line returning to a fuel tank. Thus, there is no return of heated fuel to the tank, so that little fuel vaporizes in the fuel tank. By renouncing the return line, the device

becomes more reliable.

  Exemplary embodiments of the invention will be explained in the following with reference to the schematic drawings. FIG. 1 represents an internal combustion engine provided with a fuel metering device, and FIG. 2 represents a control flow diagram

  of the fuel metering device.

  An internal combustion engine (FIG. 1) comprises a suction line 1 with a throttle valve 2, and a block of cylinders 3, which comprises a cylinder 4 and a crankshaft 5. A piston 7 and a connecting rod 8 are associated with the cylinder 4. The connecting rod 8 is connected to the piston

7 and the crankshaft 5.

  There is provided a cylinder head 10, in which is disposed a set of valves comprising at least one intake valve and one exhaust valve. In the cylinder head, is also housed a spark plug 12. An injection valve 13 is arranged in a mixing chamber 14 so that the fuel entering the mixing chamber 14 is metered. A mixing injector 15, which communicates with the mixing chamber 14, is arranged on the cylinder head 10 in such a way that it dosed the mixture which is in the mixing chamber 14 in the

cylinder 4.

  The internal combustion engine further comprises

  an exhaust pipe 16 provided with a catalyst.

  A first pipe 17 goes from an inlet upstream of the throttle valve in the suction line 1 to a compressor 18, which is driven by a camshaft 20 or also by the crankshaft 5, directly or through d 'A chain transmission. In the first pipe 17 is arranged a throttling device 22 which is preferably in the form of a butterfly. However, as a throttling device 22, it is also possible to provide an idling filling regulator or another throttling device known to the specialist. The throttle device 22 is preferably open in the cut-off state of the electrical supply, so as not to have any harmful effect on the supply of air to the compressor in the event of failure of the components. A second pipe 23 goes from the outlet of the compressor 18 to an air pressure container 24. The air pressure container 24 is connected by a

  third pipe 25 to the mixing chamber 14.

  A fuel tank 27 is provided, in which a fuel pump 28 is arranged, which pumps fuel through a fourth pipe 30 to a fuel pressure container 32. The fuel pressure container 32 is connected by a fifth pipe 33 to the

injection valve 13.

  A sixth pipe 34 goes from the fuel tank 27 to an activated carbon filter 35, which adsorbs and desorbs fuel. A seventh pipe 37 goes from the activated carbon filter 35 to the venturi 40 of the first pipe 17. In the seventh pipe 37, there is a degassing valve 38

tank.

  A control device 42 is provided, to which are added sensors which capture different measurement variables and respectively determine the measurement value of the measurement variable. The control device 42 determines as a function of at least one measurement quantity one or more adjustment signals which respectively control an adjustment apparatus. The sensors are a pedal position transmitter 45, which captures a pedal position of the accelerator pedal 47, a throttle valve position transmitter 48, which captures an opening degree of the throttle valve 2, a flow meter air mass 50, which captures a mass air flow and / or a pressure sensor which captures a suction line pressure in the suction line 1, a rotational speed sensor 54, which inputs a speed of rotation N of the crankshaft 5, and a differential pressure sensor 55, which captures the differential pressure of the fuel pressure in the fourth pipe 30 or in the fuel pressure container 32 and the air pressure in the second pipe 23 or the air pressure container 24. Depending on the embodiment of the invention, there can be a choice of a sub-assembly

  indicated sensors or additional sensors.

  The adjustment devices respectively comprise an actuator and an adjustment member. The actuator is an electric motor drive, an electromagnetic drive or another drive known to the specialist. The regulating members are in the form of a throttle valve 2, an injection valve 13, a spark plug 12, a mixture injector 15, a fuel pump 28 or d 'A tank degassing valve 38. In the following, reference will be made respectively to adjustment devices with the associated adjustment member. The control device preferably has the form of an electronic motor control. However, it may also include several control devices connected to each other by conductors

  electric, for example by a bus system.

  Thereafter, the function of the part of the invention of the control device 6 will be described from the flow chart (Figure 2). The program starts at step S1. With a step S2, with a real value PDIFFAV of the differential pressure is associated the value of

  current measurement of differential pressure sensor 55.

  In addition, a set value of a quantity representing the load on the internal combustion engine is determined. For this, it is preferable to determine a setpoint value TQI_SP of the torque as a function of the position of the pedal PV, the speed of rotation N and possibly other operating quantities of the internal combustion engine and, moreover, as a function of the torque requirements of other functions of the internal combustion engine, such as for example an idle speed control, or also of the torque requirements of a gearbox control

  electronic gear or traction control.

  Preferably, the set values are stored in characteristic fields according to the

  quantities indicated and are determined from them

  ci, possibly by interpolation of field of characteristics. At a step S3, a reference value PDIFF SP of the pressure difference is determined as a function of that taken as the reference value TQI_SP of the torque and the speed of rotation N, preferably by means of a characteristic curve or of a field of characteristics. The PDIFFSP setpoint can certainly also be a fixed datum, the previously indicated dependence of the TQI_SP setpoint of the torque has, however, for an appropriate parameterization of the field of characteristics the advantage that a smaller variation of the time of Injection to the injection valve is necessary, so that an inexpensive injection valve can be used with lower linearization requirements between injection time and fuel mass. At a step S4, a setpoint THRSP of the degree of opening of the throttle device 22 is determined as a function of the setpoint PDIFFSP and the actual value PDIFFAV of the pressure difference by means of a regulator which has P. PI, PID or other behavior known to the specialist and corrected according to the speed of

  rotation N and a degassing rate of the CPR tank.

  Thus, the PDIFFSP setpoint for the pressure difference can be precisely adjusted. The degassing rate of the CPR tank is determined according to a

  degree of loading of the activated carbon filter 35.

  At a step S5, an injection time TI is determined as a function of the actual value PDIFFAV of the differential pressure and of the torque setpoint TQISP, preferably from a field of characteristics. At a step S6, adequate adjustment signals are produced to adjust the set point THRSP of the degree of opening of the throttle device 22 and to control the injection valve 13 for the injection duration TI. At one S7 step the program ends. The program is called cyclically or depending on the rotation speed N of the internal combustion engine

  during the operation of the latter.

  By advantageously determining the injection time TI as a function of the actual value PDIFFAV of the pressure difference in accordance with step S5, it is also possible, for short-term deviations of the pressure difference from the set value PDIFF_SP, accurately dose the given mass

  of fuel entering the cylinder 4.

  The mounting of the throttling device 22 as an adjusting member for regulating the air pressure in the air pressure container 24 ensures that with this adjustment, only small losses occur, which are essentially determined by the compressor drive power and are influenced by throttle losses. A compressor is preferably provided, the maximum drive power of which is sufficient to be able to adjust the air pressure, as required, despite series dispersions of the fuel metering device and unfavorable environmental conditions. By the advantageous arrangement of the throttle valve upstream of the venturi 40, in which the seventh pipe 37 opens into the first pipe 17, it is possible by an adequate adjustment of the degree of opening of the throttle device 22 to simply and precisely adjust the rate

tank degassing.

  The use of the differential pressure sensor 55 has the advantage that only a pressure sensor should be provided instead of an absolute pressure sensor for the air pressure and for the fuel pressure respectively. This improves the reliability of the

fuel dosing.

  The first pipe 17, the throttle device 22, the compressor 18, the second pipe 23, the air pressure container 24 and the third, sixth and seventh pipes 25, 34, 37 together form a supply device for air. The fuel tank 27, the fuel pump 28, the fourth pipe 30, the fuel pressure container 32 and the fifth pipe 33 together form a fuel supply device.

Claims (7)

  1. Fuel metering device in a cylinder of an internal combustion engine, comprising: - a fuel supply device connected to an injection valve (13), - a mixing chamber (14), connected to an air supply device and in which the injection valve (13) is arranged such that the fuel entering the mixing chamber (14) is metered, and - a mixing injector (15), which communicates with the mixing chamber (14) and is arranged in the cylinder head (10) of the internal combustion engine in such a way that it dosed the mixture present in the mixing chamber (14) in the cylinder (4) ), characterized in that there is a device for adjusting the air pressure in the air supply device as a function of a pressure of   fuel in the fuel supply system.   2. Device according to claim 1, characterized in that the device for adjusting the air pressure is constituted in such a way that the air pressure is adjusted as a function of a quantity representing the load   on the internal combustion engine.   3. Device according to any one of   previous claims, characterized in that the   device includes a regulator whose controlled and variable control is the pressure difference between the   fuel pressure and air pressure.   4. Device according to claim 3, characterized in that there is provided a differential pressure sensor (55) which measures the pressure difference   between fuel pressure and air pressure.   5. Device according to any one of   previous claims, characterized in that it is   provided in the air supply device a throttle device (22) which is a   adjustment to adjust the air pressure.   6. Device according to claim 5, characterized in that the throttling device is placed upstream of a mouth of a pipe (37), communicating with an activated carbon filter (35), which absorbs and desorbs fuel vapors.   7. Device according to any one of   previous claims, characterized in that   fuel injection time (TI) is determined by the injection valve (13) depending on the pressure difference and the quantity representing the load on the internal combustion engine.