FR2669377A1 - Internal combustion engine fuelled by two different injection modes - Google Patents

Abstract

The invention relates to an internal combustion engine of any type whatsoever, more particularly to the supply of such an engine with fuel. An engine (1) comprises a first system (200) for supplying fuel, operating according to a first injection mode, and is equipped with a second supply system (300) operating according to a second injection mode which is different from the first injection mode, and control means coupled to at least one of the feed systems (200, 300) for selectively switching on or off one and/or other system. The invention applies to single-cylinder or multi-cylinder internal combustion engines operating on a two- or four-stroke cycle.

Description

 The present invention relates to an internal combustion engine of any type, and relates more particularly to the fuel supply system of such an engine.

 Various fuel supply systems for internal combustion engines are already known, such as injection supply systems. Currently, there are mainly two modes of fuel injection.

 The first of these injection methods is commonly called "homogenization". According to this mode, a homogeneous mixture of air and fuel is injected into the cylinder. In other words, the fuel is distributed regularly within an air flow injected into the cylinder and the proportion of fuel in the mixture is chosen to provide optimal combustion. This injection mode provides excellent performance when the engine to which it is applied operates at high loads.

 The second most common mode of injection is generally called "stratification". It consists in injecting a flow of air and fuel into the cylinder so that an area particularly rich in fuel is located in the vicinity of an ignition member such as for example a spark plug. This injection mode promotes good performance at low engine load, and is frequently obtained by direct injection of fuel into the engine's combustion chamber.

 However, current injection fueled engines are powered by one or the other exclusively of these injection modes. Therefore, it is very difficult to obtain optimal performance under all the load and speed conditions of such engines.

 The object of the invention is to remedy this drawback in particular by proposing an internal combustion engine which offers excellent performance, whatever the load and speed conditions of the engine.

 To this end, the invention relates to an internal combustion engine of the type comprising a first fuel supply system operating according to a first injection mode, characterized in that it is equipped with a second supply operating according to a second injection mode which is different from the first injection mode, and control means connected to at least one of the supply systems for selectively switching on or off one and / or the other of the systems.

 The invention is further characterized in that one of the supply modes is said to be "homogenization" and consists in injecting into each cylinder of the engine an air flow to which the fuel is homogeneously mixed, the other mode supply being called "stratification" and consisting in injecting into each cylinder a flow of air and fuel which has a particularly rich fuel area.

 The invention is further characterized in that the first supply system operates by stratification and comprises at least one high pressure injector connected to each cylinder of the engine, the second system operating by homogenization and comprising at least one low pressure injector.

 The engine according to the invention is characterized in that each high pressure injector is arranged at the upper part of the cylinder, near an ignition member such as a spark plug, and each low pressure injector is arranged at the part lower of the cylinder, so as to direct the homogeneous mixture towards said upper part.

 According to one embodiment, the invention applies to a two-stroke engine of the type comprising a pump casing connected to each cylinder by at least one transfer duct, characterized in that each low pressure injector opens into one of these conduits.

 According to another embodiment, the invention applies to a two-stroke engine of the type comprising a pump casing connected to each cylinder by at least one transfer duct, characterized in that each low pressure injector opens into a duct supplied with pressurized air which is separated from the transfer duct and which opens into the cylinder.

 It will be specified here that the motor is characterized in that the aforementioned control means act on a shutter mounted in the duct supplied with pressurized air, so as to selectively close or open the latter.

 The engine is further characterized in that the aforementioned conduit communicates with the casing and is supplied with pressurized air by the latter.

 According to an alternative embodiment, the motor is characterized in that the aforementioned duct is connected to an external source of pressurized air supply.

 In the case where the engine is of the multi-cylinder type, the second supply system comprises a single low-pressure injector which is connected to all the cylinders.

 According to a characteristic of the invention, the control means are manual.

 According to another characteristic of the invention, the control means are connected to at least one sensor sensitive to an engine operating parameter, as a function of which said means automatically vary the mode of supply of the engine.

 It will be noted here that each sensor is sensitive to one of the parameters among engine speed, engine load and timing, temperature of the intake air and of the coolant and ambient atmospheric pressure.

 In addition, said control means comprise an electronic control connected on the one hand to at least one injector and on the other hand to each of the sensors.

 The two supply systems are connected to the same fuel supply circuit which includes a booster pump connected on the one hand to a fuel tank and on the other hand to the low pressure injector, a low pressure regulator allowing maintain the supply pressure of the low pressure injector at a constant value, this regulator being connected to a high pressure pump which is itself connected to the high pressure injector via a high pressure regulator.

However, other advantages and characteristics of the invention will appear better on reading the detailed description given solely by way of example which follows and refers to the accompanying drawings in which
- Figure 1 is a sectional view, partial and schematic, of a two-stroke engine according to a first embodiment of the present invention
- Figure 2 is a view similar to that of Figure 1 and according to a second embodiment of the invention; and
- Figure 3 is a view schematically illustrating an example of a fuel supply circuit for an engine in accordance with the invention.

 Referring first to Figures 1 and 2, we see an internal combustion engine 1, of the two-stroke type.

 For the purpose of simplification, only one cylinder 2 has been illustrated in these figures. It goes without saying that the invention is in no way limited to these examples, and that it can be applied for example to engines. single-cylinder or multi-cylinder internal combustion engine, operating on a two-stroke or four-stroke cycle.

 A piston 3 can slide inside the cylinder 2 in a back-and-forth movement, defining inside it a variable-volume chamber 4.

 The piston 3 is shown in a position where the chamber 4 has a maximum volume. This position is called "bottom dead center", since the piston is then in the lower or lower part of cylinder 2. Obviously, this terminology can be used regardless of the orientation of cylinder 2.

 Similarly, the upper part of the cylinder 2 is called the part of the latter which is opposite to the lower part described above and to which a cylinder head 5 is fixed (for example using screws not shown). Usually, a member d ignition such as a spark plug 6 is mounted on the cylinder head 5 by screwing in a threaded bore 7.

 It is common in two-stroke engines that the variation in volume of the casing, due to the displacement of the piston, acts as a pump by which the chamber 4 can be supplied with air under pressure. Motors of this type are shown in FIGS. 1 and 2. For this purpose, transfer channels or conduits 8 and 9 are formed in the lower part of the cylinder 2. These transfer conduits 8 and 9 communicate by their lower ends with the casing of the motor 1 and open, by their upper ends, into the chamber 4. Although in the examples illustrated the cylinder 2 is shown with two transfer conduits, an engine may also include a different number of transfer conduits .

 It will also be noted in the figures that the cylinder 2 of the engine 1 has an orifice 10 which is diametrically opposite the transfer duct 8. This orifice is an exhaust port which puts the lower part of the chamber 4 into communication with a duct exhaust 11, when the piston 3 is, as shown, at "bottom dead center".

 Internal combustion engines of the type described above are generally supplied with fuel via a carburetor or an injection system. The internal combustion engine according to the present invention is of the type comprising a first fuel supply system 200 which operates according to a first injection mode. This engine is characterized in that it is equipped with a second supply system 300 which, in turn, operates according to a second injection mode.

 More particularly, the supply system 200 operates according to the so-called "stratification" injection mode, which consists in injecting directly into the combustion chamber 4 a flow of air and fuel having a fuel-rich zone, while the rest of the flow is relatively poor.

 The supply system 300 operates for its part according to the so-called "homogenization" injection mode. This second injection mode is different from the first in that the fuel is regularly and homogeneously mixed with the air injected into the cylinder.

 It is known that stratification promotes good engine performance when it is operating at low speed and at low load, while homogenization provides excellent performance at high engine loads.

 According to a first embodiment of the invention visible in FIG. 1, the fuel supply system 200 is mainly constituted by a high pressure injector designated by the reference 20. The injector 20 is connected to a fuel source by via a fuel supply circuit which will be explained in detail later (Figure 3).

 A nozzle 21 of the injector 20 opens into the chamber 4, at the cylinder head 5. More precisely, the injection nozzle 21 is mounted in a bore 51 formed in the cylinder head 5, near the spark plug 6. The nozzle 21 is oriented so that the flow injected by it into the chamber 4 is oriented in the area of the spark plug 6 in order to obtain the desired stratification. In addition, it will be noted that it is also advantageous, according to this mode of supply, to inject the fuel into the chamber 4 just before ignition.

 The supply system 300 comprises a low pressure injector 30, which is also connected to a fuel supply circuit. The injector 30 comprises a nozzle 31 opening into the transfer duct 8 which connects the engine casing 1 to the lower part of the cylinder 2. The casing thus forms a source of pressurized air which supplies an air flow M. The injection nozzle 31 is therefore disposed at the bottom of the cylinder 2 and is oriented so as to propel from below upwards a jet of fuel sprayed into the air flow M.

To obtain optimum performance from the engine 1 when it is supplied by the nozzle 31, the flow rate of the injector 30 should be adjusted according to the operating conditions of the engine and the arrangement and characteristics of the nozzle should be chosen. injection 31 so that the sprayed fuel mixes perfectly homogeneously with the flow M of pressurized air.

In addition, it is preferable that the injector 30 is mounted in a transfer duct which opens at a location on the periphery of the chamber 4 which is diametrically opposite to the exhaust port 10, so that the "fresh" gases injected in the cylinder 2 sweep the combustion gases towards the exhaust pipe 11.

 Referring to Figure 3, a fuel supply circuit to the injectors 20 and 30 will now be described. This figure shows the injectors 20 and 30, as well as a fuel tank 40. The tank 40 is connected to a booster pump 50 via a pipe 12. In operation, the booster pump 50 draws a fuel such as gasoline from the tank 40, and forces this gasoline under a relatively low pressure along a line 13 towards a filter 52. The fuel filter 52 into which the line 13 opens is connected to the using a pipe 15, on the one hand to a low pressure regulator 54, and on the other hand to the injector 30 of the b300 supply system. The presence of the regulator 54 makes it possible to supply the injector 30 under constant pressure and to avoid jolts in the operation of the booster pump 50.

It can be seen in FIG. 3 that the regulator 54 is connected to a fuel return line 14, which is connected to the tank 40 to recover the excess petrol supplied by the pump 50.

 The low pressure regulator 54 is also connected at the output to a high pressure pump 60, via a pipe 16. Consequently, the booster pump 50 and the regulator 54 not only make it possible to supply fuel to the injector. 30, but additionally supply the high pressure pump 60 with gasoline at a low and constant pressure. Such an arrangement guarantees easy priming of the pump 60 which cannot directly draw from the reservoir 40. It should be noted here that the pump 60 can also be supplied with priming by means of a separate booster pump. , whether or not fitted with a regulator.

 The reference 62 designates a high pressure regulator which is directly connected to the outlet of the pump 60. Like the pressure regulator 54, the regulator 62 is connected to the reservoir 40 by the return line 14. The outlet of the high regulator pressure 62 is connected by a line 17 to the injector 20 of the supply system 200 so as to supply the latter with fuel under high pressure.

 It will be understood that the engine 1 must also include means for controlling the supply systems 200 and 300, in order to selectively cause the starting or stopping of these systems, for example according to the speed and the load of the engine 1. It will be noted here that the transition from one injection mode to another must imperatively be carried out without interruption of supply, so that it is necessary to provide, for each of these mode changes, a transient phase during which the engine 1 is simultaneously fed by homogenization and by stratification.

 The control means of the systems 200, 300 comprise an electronic shoemaker 100 which automatically manages the fuel supply to the engine 1.

Although the example illustrated relates to automatic control means, these can also be manual without departing from the scope of the present invention.

 It can be seen in FIGS. 1 and 3 that the injectors 20, 30 are respectively connected to cables 22 and 32 which are themselves connected to the electronic control unit 100.

 Furthermore, the control bolt 100 is connected by cables identified in A, B, C, D, E and F to sensors (not shown) which are respectively sensitive to an operating parameter of the engine. For example, cable A is connected to a sensor sensitive to engine speed, cable B to a sensor sensitive to its load, cable C to a sensor measuring the temperature of the engine coolant, cable D to a sensor measuring the temperature of the intake air and the cables E and F are respectively connected to a sensor indicating the engine stalling and to a sensor sensitive to ambient atmospheric pressure.

 The parameters measured by these sensors are transmitted via cables A, B, C, D, E and F to the control unit 100 which processes them so as to determine the most appropriate mode or modes of supply of the motor in based on the information provided by these sensors. It should be noted here that the number and type of sensors can vary as required, and that the control can be of any known type, for example of the type comprising a microprocessor.

 The control unit 100 transmits periodically and according to the information it has just processed a signal, for example electrical, to mechanical or electromechanical means forming shutters of the injectors 20 and 30, so as to control the opening or closing of these shutters and thus to select the power supply mode for motor 1.

 FIG. 2 illustrates a second embodiment of the internal combustion engine according to the present invention. This motor 1 is identical to that described above and shown in FIG. 1 and can also be supplied by means of a circuit substantially similar to that visible in FIG. 3.

Elements identical or similar to those explained above are designated by the same reference numerals and will therefore not be described again.

 The engine 1 visible in FIG. 2 differs from that shown in FIG. 1 in that the injector 30 opens into a supply duct 33 and not into the transfer duct 8. The supply duct 33 is produced in the lower part of the cylinder 2, with one end which opens into the chamber 4, substantially opposite the nozzle 21 of the injector 20 and at a location diametrically opposite to the exhaust port 10. This duct 33 is connected to a source of air under external pressure such as for example a variable pressure compressor.

 Note in FIG. 2 that the duct 33 comprises, near its end opening into the combustion chamber 4 and downstream of the nozzle 31 in the direction of flow of the air flow M, a mechanical or electromagnetic shutter 34 This shutter is connected to the control system so as to be in phase with the engine, which makes it possible to supply the chamber 4 with pressurized air coming either from the crankcase or from an external pressure source such as by example a variable pressure compressor. It is therefore understood that according to this embodiment, the opening and closing of the duct are controlled synchronously with the engine so that air and gasoline are injected into the combustion chamber at the time when they will provide the engine optimal performance.

 In addition, with such a supply conduit 33 separate from the transfer conduits 8 and 9, it will be easy for a multi-cylinder engine to provide a single low pressure injector for all of the cylinders of this engine. More specifically, such an arrangement will include a single injector 30 delivering through a conduit 33 connected to each of the combustion chambers of the engine. In this case, a low pressure injector of the single point type should be provided.

 It will also be noted here that the shape of the combustion chamber 4, and more particularly that of the cylinder head 5 are preferably designed in a manner suitable both for a supply by homogenization and for a supply by stratification.

 In accordance with the invention, an internal combustion engine was therefore obtained, exhibiting particularly remarkable performance at all operating speeds and loads.

 Of course, the invention is in no way limited to the embodiments described and illustrated. On the contrary, it includes all the technological means equivalent to those described as well as their combinations, if these are carried out according to the spirit.

Claims (15)

 1 Internal combustion engine of the type comprising a first fuel supply system (200) operating according to a first injection mode, characterized in that it is equipped with a second supply system (300) operating according to a second injection mode which is different from the first injection mode, and control means (100) connected to at least one of the supply systems (200, 300) for selectively switching on or off one and / or the other of the systems (200, 300).  2. Engine according to claim 1, characterized in that one of the supply modes is said to be "homogenization" and consists in injecting (30) into each cylinder (2) of the engine (1) an air flow (M ) to which the fuel is homogeneously mixed, the other mode of supply being called "stratification" and consisting in injecting (20) into each cylinder (2) a flow of air and fuel which has a particularly rich zone in fuel.  3. Engine according to claim 2, characterized in that the first supply system (200) operates by stratification and comprises at least one high pressure injector (20) connected to each cylinder (2) of the engine (1), the second system (300) operating by homogenization and comprising at least one low pressure injector (30).  4. Engine according to claim 3, characterized in that each high pressure injector (20) is disposed at the upper part (5) of the cylinder (2), near an ignition member such as a spark plug (6 ), and each low pressure injector (30) is arranged at the lower part of the cylinder (2), so as to direct the homogeneous mixture towards said upper part (5).  5. Two-stroke engine according to claim 3 or 4, and of the type comprising a pump casing connected to each cylinder by at least one transfer duct (8, 9), characterized in that each low pressure injector (30) opens out. in one (8) of these conduits (8, 9).  6. Two-stroke engine according to claim 3 or 4 and of the type comprising a pump casing connected to each cylinder (2) by at least one transfer duct (8, 9), characterized in that each low-pressure injector (30 ! opens into a duct (33) supplied with pressurized air which is separated from the transfer duct (8, 9) and which opens into the cylinder (2).  7. Motor according to claim 2, characterized in that the aforementioned control means (100) act on a shutter (34) mounted in the duct (33) supplied with pressurized air, so as to selectively close or open it .  8. Motor according to claim 6 or 7, characterized in that the aforementioned conduit (33) communicates with the casing and is supplied with pressurized air by the latter.  9. Motor according to claim 6 or 7, characterized in that the aforementioned conduit (33) is connected to an external source of pressurized air supply.  10. Engine according to any one of claims 3 and 9, and of the multi-cylinder type, characterized in that the second supply system (300) comprises a single low-pressure injector (30) which is connected to all the cylinders (2).  11. Motor according to any one of claims 1 to 10, characterized in that the control means are manual.  12. Motor according to any one of claims 1 to 10, characterized in that the control means (100) are connected (A, B, C, D, E, F) to at least one sensor sensitive to a parameter of operation of the motor (1), according to which said means (100) automatically vary the mode of supply of the motor (1).  13. Engine according to claim 12, characterized in that each sensor is sensitive to one of the parameters among engine speed, engine load and timing, temperature of the intake air and coolant, and atmospheric pressure.  14. Motor according to claim 12 and one of claims 3 to 10, characterized in that said control means (100) comprise an electronic control (100) connected on the one hand to at least one injector (20, 30) and on the other hand to each of the sensors.  15. Engine according to any one of claims 3 to 14, characterized in that the two supply systems (200, 300) are connected to the same fuel supply circuit which comprises a booster pump (50) connected on the one hand to a fuel tank (40) and on the other hand to the low pressure injector (30), a low pressure regulator (54) making it possible to maintain the supply pressure of the low pressure injector (30 ) at a constant value, this regulator (54) being connected to a high pressure pump (60) which is itself connected (17) to the high pressure injector (20), by means of a high pressure regulator (62).