FR2887304A1 - Diesel type direct injection combustion ignition engine for motor vehicle, has gas pump nozzle`s free end with circumferential row whose angular sector has secondary orifice having axis oriented towards free end of preheating unit - Google Patents

Abstract

The engine has a combustion chamber (6) in which a free end (28) of a preheating unit (8) and a free end (19) of a gas pump nozzle (10) extend. The free end (19) has a circumferential row, which has one angular sector less than 180 degrees having a secondary orifice, with an axis oriented towards the free end (28), and another angular sector without an orifice. A unit closes the primary orifices and allows the fuel to gush out via a secondary orifice during the start of an engine and closes the secondary orifice and lets the fuel gush out via the primary orifices, after starting the engine.

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 area where the mixture of fresh gas is made. The orifice near the heating end of the spark plug then forms part of a row comprising several orifices distributed over the entire corresponding circumference of the free end of the nozzle.

  When the free end of the nozzle has several rows of primary orifices, the free heating end of the candle is approximated to a primary orifice of the row farthest from the center of the combustion chamber. The injection through these orifices is performed at different times during the operation of the engine, generally during passages at low engine speeds. When the free end of the nozzle has a single row of primary orifices this row is left free regardless of the operating state of the engine.

  Whatever the number of rows of orifices present on the free end of the nozzle, the approach of the spark plug of the fuel injector facilitates the starting of the engine, but penalizes the engine performance after startup, because the candle is then an obstacle to the vortex circulation of the fresh air in 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 at least one row of primary fuel jet orifices disposed circumferentially about the axis of the injector, wherein said free end of the nozzle of the injector comprises, at an axial level different from that of said row of primary orifices, another circumferential row whose angular sector less than 180 is provided with at least one secondary orifice whose axis is oriented substantially towards said free heating end of the preheating element, and whose complementary angular sector is free of orifice, and in which there is provided a closure member intended, on the one hand, at startup, to close the orifices imary and let the fuel gush through each secondary orifice, and secondly, after starting the engine, to seal each secondary orifice and let the fuel gush through at least some primary orifices.

  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 thus 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 here left free at engine start and then closed after starting. The secondary orifice is thus dedicated to starting the engine, which makes it possible to reduce the fuel consumption.

  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 each secondary orifice is greater than or equal to the diameter of the primary orifices.

  According to another advantageous characteristic of the engine according to the invention, said other secondary orifice row is disposed above the row of primary spray orifices relative to the center of the combustion chamber.

  According to another advantageous characteristic of the engine according to the invention, the axis of each secondary orifice makes an angle of between 80 and 90 with the axis 25 of a piston arranged in the combustion chamber.

  According to another embodiment of the invention, said other secondary orifice row is disposed below the row of primary spray 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: - Figure 1 is a sectional view of a portion of an engine according to the invention in which are arranged a fuel injector and a preheating element, at the start of the engine; FIG. 2 is a view from below of the preheating element of FIG. 1 according to the invention, at the start of the engine; - Figure 3 is a view of Figure 1, after starting the engine; Figure 4 is a front view of the free end of the nozzle of the fuel injector according to the invention; Figure 5 is a view according to section A-A of Figure 4, after starting the engine; - Figure 6 is a view according to section BB of Figure 4, when starting the engine.

  In Figure 1, there is shown a portion of a direct injection diesel type internal combustion engine. This engine comprises a cylinder 5 in which a piston 7 slides. The upper wall of the cylinder 5 delimits, with the outer hollowed surface 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, vis-à-vis 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 22 intended to promote the homogenization of the gas mixture ( Figure 2).

  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. Of course, it can be provided to use an injector whose axis is offset and inclined relative to the axis of the piston bowl and / or relative to the axis of the piston which coincides with the axis of the cylinder. As shown in FIG. 4, 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. 5).

  Advantageously according to the invention, as shown in FIG. 4, said free end 19 of the nozzle 10 of the injector 9 comprises, at an axial level different from that of said row 17 of primary orifices 11, 12, 13, 14 , 15,16, a row of which an angular sector S1 is provided here with a secondary orifice 18 dedicated to starting the engine. The complementary angular sector S2 of said angular sector S1 of said row is free of orifice. This angular sector S1 here has an angular aperture of the order of 30.

  The injector also comprises a shutter member 30 intended to shut off, depending on the operating state of the engine, the various orifices 11, 12, 13, 14, 15, 16, 18 present on the free end 19 of the nozzle 10 of FIG. the fuel injector 9 (see Figures 5 and 6).

  The secondary orifice 18 present on the angular sector S1 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 the secondary orifice 18 is greater than or equal to the diameter of the primary orifices 11, 12, 13, 14, 15, 16 of the row 17.

  This secondary orifice 18 has an axis A21 (see FIG. 6) 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 coinciding here 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. At the start of the engine, the closure member 30 is rotated about the axis A9 of the injector 9 so that it closes the primary orifices 11, 12, 13, 14, 15, 16 of the spray nozzle. the row 17 and that it has vis-à-vis the secondary port 18 a 33 fuel inlet channel (see Figure 6).

  As represented in FIG. 1, the fuel arriving via the injector 9 then flows through the secondary orifice 18 situated above the row 17 of primary orifices 11, 12, 13, 14, 15, 16, in one jet. 21 directed towards the free heating end 28 of the candle 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.

  Due to the large diameter of the secondary orifice 18 according to the invention, the volume of fuel injected by this secondary orifice 18 spraying at startup is important. The vaporized portion of this large volume of 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 .

  In addition, since the volume of fuel spouting from the secondary orifice 18 is large, it is not necessary to inject fuel through the primary orifices 11, 12, 13, 14, 15, distributed circumferentially about the axis. A9 of the nozzle 10 and a number of which is oriented opposite the heating end 28 of the spark plug 8. Thus, at the start, thanks to the secondary orifice 18 according to the invention, the fuel consumption and 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 maintained by the remainder of the large volume of fuel injected into the combustion chamber 6.

  It can be provided that the angular sector comprises several orifices, including the secondary orifice as described above. The other orifices belonging to this angular sector then have axes oriented towards the upstream part of the swirling air movement, close to the glow plug.

  After the cold start of the engine, the shutter member 30 is rotated about the axis A9 of the fuel injector 9 so that it closes the secondary orifice 18 and that it has screw-in -vis primary orifices 11,12,13,14,15,16 spraying row 17, 31,32 channels of fuel arrival. The fuel then gushes only primary orifices 11,12,13,14,15,16. Thus, after starting the engine, the injection of the fuel through the primary orifices 11, 12, 13, 14, 15, 16 in jets 20 each oriented at the angle B20 with respect to the axis A7 of the piston 7, allows to optimize the combustion of the gas mixture in the combustion chamber 6 (Figure 3).

  The present invention is not limited to the embodiments described and shown, but the skilled person will be able to make 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 engine. At startup, all the primary orifices are closed and the fuel spurts through each secondary orifice. After starting the engine, each secondary orifice is closed and the fuel flows through at least some primary orifices, that is to say that all the primary orifices of at least one of the rows of primary orifices are open while the others rows of primary orifices are closed.

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) a fuel injector (9) provided with at least one row (17) of primary fuel-jet primary orifices (1, 1, 12, 13, 14, 15, 16) disposed 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, at an axial level different from that of said row (17) of primary orifices (11,12,13,14,15,16), another circumferential row of which an angular sector (Si) less than 180 is provided with at least one secondary orifice (18) whose axis (A21) is oriented substantially towards said free heating end (28) of the preheating element (8), and whose complementary angular sector (S2) is free of orifice, and in that there is provided a shutter member (30) intended, on the one hand, at startup, to close the primary orifices (11, 12, 13, 14, 15, 16) and to allow the fuel to flow through each secondary orifice (18 ), and, secondly, after starting the engine, closing each secondary orifice (18) and let the fuel flow through at least some primary orifices (11,12,13,14, 15,16).   2. Motor according to claim 1, characterized in that the diameter of each secondary orifice (18) is greater than or equal to the diameter of the primary orifices (11,12,13,14,15,16).   3. Motor according to one of the preceding claims, characterized in that said other secondary orifice row (18) is disposed above the row of primary 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 of each secondary orifice (18) is an angle of 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 or 2, characterized in that said other row of secondary orifice (18) is disposed below the row of primary orifices (11,12,13,14,15,16 ) of spray, relative to the center of the combustion chamber (6).