FR2888284A3 - Internal combustion engine for motor vehicle, has injector with nozzle, whose free end comprises secondary orifice for supplying fuel to primary orifices, where axis of secondary orifice is oriented towards end of preheater plug - Google Patents

Abstract

The engine has a preheater plug with a free end penetrating in a combustion chamber. An injector (9) has a nozzle (10), whose free end (19) is extended into the chamber. The end (19) comprises a secondary orifice (18) for supplying fuel to primary orifices, where the diameter of the orifice (18) is greater than 80 microns and is lower than the diameter of the primary orifices. The orifice (18) has an axis (A21) oriented towards the end of the preheater plug.

Description

TECHNICAL FIELD TO WHICH THE INVENTION REFERS

  The present invention generally relates to internal combustion engines.

  The invention relates more particularly to an internal combustion engine of a motor vehicle comprising a combustion chamber in which extends a free heating end of a preheating element and a free end of a nozzle of a fuel injector provided with a row of primary fuel jet orifices arranged circumferentially around the axis of the injector.

  The invention finds a particularly advantageous application for the cold start of compression-ignition internal combustion engines of the diesel type.

BACKGROUND

  Diesel fuel injection direct injection engine engines generally comprise a fuel injector arranged in a combustion chamber of a cylinder in which a piston slides. The fuel injector discharges into the combustion chamber a certain volume of fuel, a fraction of which is vaporized and mixes with a volume of fresh air admitted by an intake manifold into the combustion chamber, to form a mixture of fresh gas.

  The thermodynamic conditions favorable to the ignition of the fresh gas mixture are a function of the richness, the temperature and the pressure of the fresh gas mixture. Thus, for a given richness of the mixture of fresh gas, it automatically ignites under a certain pressure and a certain temperature.

  Currently, the compression ratio of the fresh gas mixture in the combustion chamber of diesel direct injection engines is low, in order to increase the power of the engine.

  This low compression ratio of the fresh gas mixture leads to a deterioration of the thermodynamic conditions in the combustion chamber allowing the automatic ignition of the fresh gas mixture. It follows, starting difficulties when the engine is still cold, that is to say, when the mixture of fresh gas in the combustion chamber is cold.

  To correct this cold start problem, it is known to use a glow plug, positioned in the combustion chamber to increase the temperature in the combustion chamber to compensate for the decrease in the compression ratio of the fresh gas mixture. However, the use of a glow plug requires a warm-up time which is even more important that the temperature of the fresh gas mixture before starting the engine is low. In addition, the preheating time generates a significant electrical energy consumption.

  It is still known to bring the glow plug of one of the orifices of the free end of the nozzle of the fuel injector to increase the temperature in the zone where the mixture of fresh gas is made.

  When the free end of the nozzle of the fuel injector has a single row of fuel jet orifices, it is left free regardless of the operating state of the engine. The glow plug is then positioned near a free-left orifice belonging to the row of orifices of the free end of the nozzle. The free end of the nozzle may also have several rows of fuel spray ports used depending on engine speed. These rows are independent of each other and, at least one moment of operation of the motor, the different orifices of the different rows are closed by a closure member cooperating with the nozzle of the injector. It follows that the orifice located near the glow plug, close to it, is at a given time closed as well as the other holes of the row to which it belongs.

  However, a reconciliation of the spark plug of the fuel injector, penalizes engine performance after startup, because the candle is an obstacle to the vortex flow of fresh air into the combustion chamber.

  Finally, it is known to increase the amount of fuel injected at the start in order to increase the richness of the fresh gas mixture. Indeed, when the temperature is low in the combustion chamber, only a small fraction of the injected fuel volume is vaporized and can then mix with the volume of fresh air. It is then necessary to inject a large volume of fuel to have a larger volume of vaporized fuel. However, this solution leads to overconsumption and a significant emission of pollutants.

  OBJECT OF THE INVENTION In order to overcome the drawbacks of the prior art, the present invention proposes a new direct injection engine in which there is provided a fuel injector suitable for promoting the starting of the engine.

  For this purpose, it is proposed according to the invention an internal combustion engine of a motor vehicle comprising a combustion chamber in which extends a free heating end of a preheating element and a free end of a nozzle of an injector fuel nozzle provided with a row of primary fuel jet orifices circumferentially disposed about the axis of the injector, wherein said free end of the nozzle of the injector comprises, outside of said row of primary orifices nozzle, a secondary orifice, adapted to be supplied with fuel simultaneously with the primary orifices of said row, whose axis is oriented substantially towards said free heating end of the preheating element.

  Due to the orientation of the axis of the secondary orifice substantially towards the free heating end of the preheating element, the gas mixture is produced, at startup, near this heating free end. The gas mixture then has a satisfactory richness and a temperature sufficient to satisfy the thermodynamic conditions of ignition of the gas mixture, thus compensating for the degradation of the thermodynamic conditions resulting from the low compression ratio of the gas mixture in the combustion chamber.

  In addition, this sufficient temperature of the gas mixture is reached, due to the proximity of the free heating end of the heating element, after a short preheating period, which reduces the consumption of electrical energy and therefore fuel.

  In particular, during the cold start of the engine where the low temperature of the combustion chamber and therefore of the gas mixture penalizes the ignition of the gas mixture, the use of the secondary orifice according to the invention injecting the fuel with proximity of the heating end of the preheating element thus promotes the ignition of the gas mixture.

  In addition, the orientation of the axis of the secondary orifice makes it possible to penetrate only slightly the free heating end of the preheating element in the combustion chamber. Thus, thanks to the secondary orifice of the nozzle of the injector according to the invention, the preheating element does not hinder the vortex flow of air to promote the homogenization of the gas mixture.

  Finally, the secondary fuel jet orifice located outside the row of primary orifices is mainly dedicated to starting the engine, but remains fueled at the same time as the primary orifices, which makes it possible to have a simple operating mechanism for the injector.

  Thus, the use of a secondary orifice according to the invention promotes the starting of the engine and reduces the constraints of space and consumption to which it is subjected during its operation after startup.

  According to a first advantageous characteristic of the engine according to the invention, the diameter of the secondary orifice is smaller than the diameter of the primary orifices.

  According to another advantageous characteristic of the engine according to the invention, the diameter of the secondary orifice is at most 80 microns.

  According to another advantageous characteristic of the engine according to the invention, the secondary orifice is disposed above the row of primary orifices for spraying, with respect to the center of the combustion chamber.

  According to another advantageous characteristic of the engine according to the invention, the axis of the secondary orifice makes an angle of between 80 and 90 with the axis of a piston arranged in the combustion chamber.

  According to another advantageous characteristic of the engine according to the invention, the secondary orifice is disposed below the row of primary spraying orifices relative to the center of the combustion chamber.

  DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

  The following description with reference to the accompanying drawings of an embodiment, given by way of non-limiting example, will make it clear what the invention consists of and how it can be achieved.

  In the accompanying drawings: FIG. 1 is a sectional view of a part of an engine according to the invention in which are arranged a fuel injector and a preheating element; FIG. 2 is a front view of the free end of the nozzle of the injector of the engine of FIG. 1; FIG. 3 is a view along section A-A of FIG.

  In Figure 1, there is shown a portion of a direct injection diesel engine internal combustion engine with direct injection. This engine comprises a cylinder 5 in which a piston 7 slides. The upper wall of the cylinder 5 delimits, with the outer hollow face 71 of the piston head 7, a combustion chamber 6. A free heating end 28 of a preheating element 8 and a free end 19 of a nozzle 10 of a fuel injector 9 extend into the combustion chamber 6, opposite the piston 7.

  Here, this preheating element 8 is a glow plug 8 whose free heating end 28 penetrates weakly into the combustion chamber 6 so as not to impede a swirling air flow intended to promote the homogenization of the gas mixture.

  On the one hand, the fuel injector 9 and its nozzle 10, and on the other hand, the piston 7, have axes A9, A7 which, here, are merged. As shown in FIG. 2, the free end 19 of the nozzle 10 comprises a row 17 of fuel injection orifices 11, 12, 13, 14, 15, 16, called primary orifices, distributed circumferentially about the axis. A9 of the nozzle 10 of the fuel injector 9. Each of these primary orifices 11, 12, 13, 14, 15, 16 has an axis A20, A20 'which makes an angle B20 of the order of 70 with the axis A7 of the piston 7 (see FIG. 3). These primary orifices 11, 12, 13, 14, 15, 16 make it possible to inject fuel in jets 20, 20 'directed towards the sunken face 71 of the piston head 7 (see FIG. 1).

  Advantageously according to the invention, as shown in FIG. 2, said free end 19 of the nozzle 10 of the injector 9 comprises a secondary orifice 18 intended for the injection of fuel for starting the engine and able to be supplied with fuel. simultaneously with the primary orifices of the row 17. This secondary orifice 18 is located above the row 17 of primary orifices 11, 12, 13, 14, 15, 16 of spray, with respect to the center of the combustion chamber 6 .

  The diameter of at most 80 microns of the secondary orifice 18 is smaller than the diameter of the primary orifices 11, 12, 13, 14, 15, 16 of the row 17.

  This secondary orifice 18 has an axis A21 oriented substantially towards said free heating end 28 of the preheating element 8 and then makes an angle B21 of the order of 85 with the axis A7 of the piston 7 sliding in the combustion chamber 6 here confused with the axis A9 of the nozzle 10 of the injector 9 (see Figure 1).

  The operation of the engine according to the invention is described below. Before the cold start of the engine, the temperature of the combustion chamber 6 is low and therefore penalizes the ignition of the gas mixture. When starting the engine, the fuel arriving through the injector 9 springs, on the one hand, through the primary orifices 11, 12, 13, 14, 15, 16 of the row 17, and on the other hand, according to the invention. by the secondary orifice 18 situated above the row 17 of primary orifices 11, 12, 13, 14, 15, 16, in a jet 21 directed towards the free heating end 28 of the spark plug 8.

  Advantageously, thanks to the orientation of the axis A21 of the secondary orifice 18 substantially towards the free heating end 28 of the preheating element 8, the gas mixture is produced near this free heating end 28. The gas mixture then has a satisfactory richness and a temperature sufficient to satisfy the thermodynamic conditions of ignition of the gas mixture, thus compensating for the degradation of the thermodynamic conditions resulting from a low compression ratio of the gas mixture in the combustion chamber. by the piston 7.

  Due to the small diameter of the secondary orifice 18 according to the invention, the vaporization of the fuel injected by this secondary orifice 18 of spray is improved. A larger volume of vaporized fuel then participates in producing the gas mixture near the free heating end 28 of the preheating element 8, thus providing a richness and a temperature of the gas mixture favorable to its ignition.

  Due to the small diameter of the secondary orifice 18 according to the invention, the penetration of the liquid and the vapor of the jet of fuel injected by this secondary orifice 18 is reduced. Penetration of the jet being low, the dilution of the fuel in the oil film present on the cylinder 5 is very limited. There is therefore no alteration of the quality of the oil.

  In addition, the vaporization of the fuel through its passage in the secondary orifice 18 is important, it is not necessary to inject, especially at engine start, a large volume of liquid fuel to obtain a large volume of vaporized fuel . Thus, at startup, the pollutant emissions are reduced.

  Then, after the ignition of the gas mixture near the heating end 28 of the spark plug 8, the ignition is propagated to the injected fuel, through the primary orifices 11, 12, 13, 14, 15, 16 of larger diameters in the combustion chamber 6.

  After the cold start of the engine, the fuel continues to flow not only through the primary orifices 11,12,13,14,15,16 but also through the secondary orifice 18. After starting the engine, the fuel injection by the primary orifices 11, 12, 13, 14, 15, 16 depending on the jets 20, 20 ', each oriented by the angle B20 with respect to the axis A7 of the piston 7, makes it possible to optimize the combustion of the mixture of gas in the combustion chamber 6. The flow of fuel continuing to flow from the secondary orifice 18 is small compared to that springing from the primary orifices 11,12,13,14,15,16 and this secondary orifice can therefore remain powered by fuel simultaneously to the primary ports during the entire operation of the engine, which simplifies the operation of the fuel injector 9.

  The present invention is not limited to the embodiment described and shown, but the art can apply any variant within his mind.

  Alternatively, it is possible to provide that the secondary orifice is located below the row of primary spray orifices relative to the center of the combustion chamber. The angle between the axis of this secondary orifice and the axis of the piston is then adapted so that the axis of this secondary orifice is oriented substantially towards said free heating end of the preheating element.

  It is also possible to use an injector whose free end of the nozzle comprises several rows of primary orifices. These different rows are then closed according to the operating mode of the motor by a closure member cooperating with the nozzle of the injector, independently of the secondary orifice directed towards the glow plug.

  It may also be advantageous to provide a large number of primary orifices on the corresponding row in order to better distribute the fuel injection in the central part of the combustion chamber. This then improves the distribution of the gas mixture in the combustion chamber and thus allows, during operation of the engine after startup, to optimize the performance of said engine. In addition, the greater the number of primary orifices is less the addition of a secondary orifice will penalize the flow of fuel in the primary row of orifices necessary for operation of the engine after startup.

Claims (1)

9 CLAIMS   Motor vehicle internal combustion engine comprising a combustion chamber (6) in which extends a free heating end (28) of a preheating element (8) and a free end (19) of a nozzle ( 10) of a fuel injector (9) provided with a row (17) of primary fuel injection orifices (11, 12, 13, 14, 15, 16) arranged circumferentially about the axis (A9) of the injector (9), characterized in that said free end (19) of the nozzle (10) of the injector (9) comprises, outside said row (17) of primary spraying orifices, an orifice secondary valve (18), able to be supplied with fuel simultaneously with the primary orifices (11, 12, 13, 14, 15, 16) of said row (17), whose axis (A21) is oriented substantially towards said free heating end (28) of the preheating element (8), and in that the diameter of the secondary orifice (18) is at most 80 microns.   2. Motor according to claim 1, characterized in that the diameter of the secondary orifice (18) is smaller than the diameter of the primary orifices (11,12,13,14,15,16).   3. Motor according to one of the preceding claims, characterized in that the secondary orifice (18) is disposed above the row (17) of orifices (11,12,13,14,15,16) of spray, relative to the center of the combustion chamber (6).   4. Motor according to the preceding claim, characterized in that the axis (A21) of the secondary orifice (18) makes an angle (B21) between 80 and 90 with the axis (A7) of a piston (7). ) arranged in the combustion chamber (6).   5. Motor according to one of claims 1 and 2, characterized in that the secondary orifice (18) is disposed below the row (17) of primary orifices (11,12,13,14,15,16 ) of spray, relative to the center of the combustion chamber (6).