FR2920826A1 - Internal combustion engine e.g. direct injection petrol engine, for motor vehicle, involves injecting air into engine by intake valve, injecting fuel into cylinders by another intake valve, and rotating air/fuel mixture injected into engine - Google Patents

Abstract

The method involves intersecting intake valves (A1, A2) and exhaust valves (E) of an internal combustion engine. The air is injected into the engine by one of the intake valves during intersection of the valves for evacuating residual burnt gas. The fuel is injected into cylinders (C) by another intake valve along a direction opposite to rotation movement of the air. The air/fuel mixture injected into the engine is rotated. An independent claim is also included for an internal combustion engine for a motor vehicle.

Description

B07-0896 - ODE / EVH

Anonyme known as: RENAULT s.a.s. A method of controlling the operation of an internal combustion engine and internal combustion engine implementing this method. Invention of: Said SOLTANI Alexandre MICHEL 1 Method for controlling the operation of an internal combustion engine and internal combustion engine implementing this method The invention relates, in general, to controlling the operation of an internal combustion engine of a motor vehicle. More particularly, the invention relates to the control of the operation of an internal combustion engine provided with a turbocharger supercharger and provided with a plurality of intake valves, for example at least two intake valves. In engines of this type, and in particular in turbocharged engines capable of delivering a very high torque, a scanning phase is often implemented, which consists in driving off the residual burnt gases by admitting fresh air into the cylinders. during the crossing phase of the intake and exhaust valves, particularly when the pressure in the intake lines is greater than the pressure in the cylinders. In addition to the evacuation of the residual burnt gases, this scanning phase makes it possible to increase the filling of the cylinders and to improve the combustion by reducing the phenomenon of rattling. However, in indirect injection petrol engines, the scavenging phase is performed with a mixture of air and fuel, which significantly increases the unburned fuel fraction at the exhaust by shorting a portion of the fuel. flow admitted into the cylinders directly to the exhaust. There is then an increase in emissions of HC hydrocarbon components and a degradation of the specific consumption. Although these drawbacks are particularly marked in indirect injection engines, they are also found in direct injection engines.

It has been proposed to reduce the emission of HC exhaust by controlling the intake of fuel in the cylinders according to the law of displacement of the exhaust valves. Referring to FIGS. 1 and 2 on which a cylinder of an internal combustion engine with two intake valves A1 and A2 associated with two intake ducts C1 and C2 and with an injector I and its two exhaust valves E, on the one hand, and the lift laws L1 and L2 of the intake valves A1 and A2 and exhaust E, respectively, it has for example been proposed to inject fuel into the intake lines when the intake valves are open and stop injection when the intake valves are closed so that the sweeping phase can only be performed by air injection , without fuel. But this requires to provide a relatively high injection pressure in order to inject a sufficient amount of fuel during the intake phase. In addition, the preparation of the mixture may be degraded if the injection is carried out too late during the cycle. Referring to FIGS. 3 and 4, in which the cylinder C of the engine, provided with its intake valves A1 and A2, associated with an injector I and with the intake ducts C1 and C2 and its valves Exhaust E, on the one hand, and the laws of emergence of exhaust valves E and intake valves Al and A2, it has been proposed, alternatively, to proceed with the injection of fuel only in the one of the intake pipes C2 and to make a shift of the opening of the intake valves A1 and A2.

In particular, the duct C1 is devoid of injector and is used to implement the sweeping phase with fresh air, without fuel, while implementing an opening opening at the inlet for this valve Al in order to provide a crossover of the valves during the sweep, while the fuel injection is performed while the exhaust valves are closed, to avoid any short circuit.

These control techniques nonetheless generate poor combustion yields and, in particular, an increase in the specific consumption, as well as an increase in unburned fractions, in particular an increase in HC at the exhaust. It will also be possible to refer to the document FR-A-2 781 011 which proposes to implement a crossover of the intake and exhaust valves, to carry out the sweep during the crossing phase and to perform the injection of fuel after the closing of the exhaust valves. The document US-B-6, 397, 813 proposes, for its part, to limit the pollutant emissions and the combustion noise by implementing a rotational movement of the gaseous mixture admitted into the cylinders of the engine. In view of the foregoing, the object of the invention is to take full advantage of the effect of scanning, particularly at low speeds, while avoiding problems related to solutions of the state of the art. The invention thus proposes, according to a first aspect, a method for controlling the operation of an internal combustion engine with at least two intake valves, in which a crossing of the intake and exhaust valves is carried out and in which which air is injected into the engine by one of the intake valves substantially at the crossing of the valves so as to evacuate the residual burnt gases, and then fuel is injected into the cylinders by the other valve of the engine. 'admission.

In addition, the air / fuel mixture injected into the engine is rotated.

It has been found that, thanks to this rotational movement of the mixture in the cylinders of the engine, the air / fuel mixture is optimized and homogenized, particularly at the end of compression, at the moment of the initiation of the combustion. It is therefore conceivable that the combustion is greatly improved and the unburnt fractions, the HC and, consequently, the consumption are significantly reduced. In one embodiment, the rotation of the air / fuel mixture is performed by injecting the fuel so as to obtain said rotational movement.

In addition, the air can be injected into the engine by using an intake duct provided with a member for rotating the air in the engine. Alternatively, according to another embodiment, the rotation of the air / fuel mixture is performed by injecting air into the engine so as to obtain said rotational movement. For example, the fuel is injected in a general direction substantially opposite to the rotational movement of the air. According to another characteristic of the invention, for example, a system for modifying the valve lift laws is used. For example, the fuel is injected substantially at the closing of the exhaust valves of the engine. It is also possible to shift the entire law of lift of the fuel injection valve relative to the law of lift of the air injection valve. The subject of the invention is also, according to a second aspect, an internal combustion engine of a motor vehicle comprising at least two intake valves and at least one exhaust valve, means for controlling the displacement of the intake valves and exhaust able to achieve a crossing of the intake and exhaust valves and means for controlling the injection of air into the engine by one of the intake and fuel injection valves by the other intake valve, so as to inject the air into the engine substantially during the crossing of the valves and then to inject the fuel. This engine further comprises means for causing rotation of the air / fuel mixture injected into the engine. According to another general characteristic of this engine, it further comprises a valve lift law modification system adapted to inject the fuel substantially to the closing of the exhaust valves of the engine.

Other objects, features and advantages of the invention will become apparent on reading the following description, given solely by way of nonlimiting example, and with reference to the appended drawings, in which: FIGS. 1 to 4, of which it has already been mentioned, illustrate examples of control techniques of the operation of supercharged internal combustion engines according to the state of the art; FIG. 5 very schematically illustrates an internal combustion engine equipped with a control device according to the invention; FIG. 6 schematically shows a cylinder of the engine of FIG. 5 illustrating a first embodiment of a control method according to the invention; FIGS. 7 and 8 are intake and exhaust valve lift laws, respectively at low speeds and at high speeds, corresponding to the embodiment of FIG. 6; FIG. 9 very schematically shows a cylinder of the engine of FIG. 5 illustrating another embodiment of a control method according to the invention; FIGS. 10 and 11 respectively show intake and exhaust valve lift laws corresponding to the mode of implementation of FIG. 9 at low and high speeds, respectively; FIG. 12 very schematically illustrates a cylinder of the engine of FIG. 5 showing a third embodiment of a control method according to the invention; and FIGS. 13 and 14 illustrate intake and exhaust valve lift laws corresponding to the embodiment of FIG. 12 at low speeds and at high speeds, respectively. FIG. 15 very schematically illustrates a cylinder of the engine of FIG. 5 showing a fourth embodiment of a control method according to the invention; and FIGS. 16 and 17 illustrate intake and exhaust valve lift laws corresponding to the embodiment of FIG. 15 at low speeds and at high speeds, respectively.

FIG. 5 very schematically illustrates a turbocharged motor vehicle internal combustion engine designated by the general numerical reference numeral 1. In the exemplary embodiment, the engine 1 is provided with four cylinders fed by a mixture of air and fuel flowing in an intake pipe 2, while the exhaust gases from the engine are conveyed by an exhaust pipe 3. A fuel injector I is associated with each of the cylinders 20 20 .

As seen, the engine 1 is associated with an electronic control unit 4 which controls the operation of the engine, in particular from a set of control signals from sensors (not shown). In particular, the electronic control unit 4 controls the admission of air into the cylinders of the engine, the injection of fuel by the injectors I and also controls the displacement of the intake and exhaust valves which are provided each cylinder according to lift laws, for example stored in memory or developed according to the operating parameters of the engine, in particular depending on the speed. The control unit 4 comprises for this purpose all the hardware and software means for controlling the operation of the engine 1. According to a characteristic of the invention, the control unit 4 implements scanning phases, which consist of flushing the residual flue gases by admission of fresh air into the cylinders when the pressure in the intake duct 2 is greater than the pressure in the cylinders during the crossing phase of the intake and exhaust valves, while limiting HC emissions and specific consumption. A first embodiment of the control method implemented by the control unit 4 will now be described with reference to FIGS. 6 to 8. In FIG. 6, one of the cylinders C of the engine is recognized. provided with at least two intake valves A1 and A2, here two in number, and at least one exhaust valve E, here also two in number. The intake valves are associated with intake ducts C1 and C2 connected to the duct 2 (FIG. 5). The exhaust valves E are also connected to the exhaust pipe 3 (Figure 5).

As can be seen, in this embodiment, the inlet ducts are separated. One of the pipes, namely the pipe C1, comprises a fuel injector I. It is intended for the injection of fuel into the cylinder C. The other pipe, namely the pipe C2, is intended for injection C. As can be seen in FIGS. 7 and 8, the intake valve lift laws A1 and A2, L1 and L1, respectively, are shifted at low speeds and at high speeds so that to open, respectively close, the valve A2 before the valve Al.

Thus, fresh air is injected into the cylinder C before fuel injection. The control unit 4 controls the valve A2 so as to implement an opening opening on admission and to implement a scanning phase substantially at the crossing of the valves. In addition, the pipe C1 is shaped so as to cause a rotational movement along the arrow F of the air / fuel mixture in the cylinder. In other words, according to the mode of implementation, one proceeds, at low speeds, on the one hand to an opening advance admission with respect to the valve A2 so as to inject air cool in the cylinders during the crossing phase of the valves to scan the residual burnt gases. Furthermore, it maintains a rotational movement of the air / fuel mixture in the cylinder. This rotational movement can be completed by providing the air intake pipe C2 with a suitable device D, known per se, of the guillotine type, plug, butterfly, ... in order to vary the rotational movement continuously. . The pipe C2 of such a device D will preferably be provided in order to minimize the disturbance of the air flow in the pipe C1 carrying the injector I. Thanks to the combined action of the rotational movement and the sweep during the crossing of the valves, the mixture is improved in order to obtain a homogeneous charge at the end of compression, at the moment of the initiation of the combustion.

In the exemplary embodiment shown, the rotational movement is maintained using a helical-shaped conduit C 1. It is also possible, alternatively, to use a judiciously oriented tangential pipe. It would also be possible, in other embodiments, to use for this purpose any other suitable device. Finally, with reference to FIG. 8, it will be noted that, with regard to the high speeds, the control unit 4 controls the valves so as to increase the closing delay at the intake, both with regard to the valve A1 fuel intake that the air intake valve A2. We will now describe with reference to Figures 9 to 11 another embodiment of a control method according to the invention. FIG. 9 shows the cylinder C provided with its intake valves A1 and A2 associated with the intake ducts C1 and C2 and its exhaust valves E. In this embodiment, one of the ducts C2 is provided with an injector I, the other pipe C1, intended for the admission of fresh air into the cylinders, being provided with a device D intended to maintain a rotational movement of the air / fuel mixture in the cylinder C according to the arrow F. The pipe C l is then shaped in the same manner as the pipe C 1 described above with reference to FIG. 6, that is to say helical or a tangentially oriented pipe. The control unit 4 controls the valves A1 and A2 so as to open, respectively close, the line C1 dedicated to the admission of fresh air into the cylinder C before the fuel injection pipe C2. Likewise, the control unit 4 causes an opening opening at the inlet, with respect to the air intake valve A1, so as to cause a sweep during the crossing phase of the valves, to low diets. At high speeds (FIG. 11), the control unit 4 provides a closing delay on admission, both with regard to the valve A1 and the valve A2. Finally, as in the embodiment described above with reference to FIGS. 6 to 8, the fuel intake starts after the closing of the exhaust valves E. In this embodiment, the pipe C1 generates a flow capable of maintaining a rotation of the air / fuel mixture in the cylinder C, the fuel injection being carried out in the opposite direction to the rotational movement generated by this pipe C1. This variant is advantageous when it is desired to modify the amount of rotational movement by the shift effect of the intake valve lifts while ensuring a good quality of the mixture. As illustrated in the embodiment shown in FIGS. 12 to 14, the control unit 4 may be associated with a valve lift law modification system, for example by variation of lift and spreading of the lift laws to the admission to further optimize the operation of the engine. In the exemplary embodiment shown, the arrangement of FIG. 12 corresponds to the embodiment of FIG. 9. Thus, for example, the pipe C1 associated with the fresh air admission valve A1 in the cylinder is used. for rotating the air / fuel mixture, the other line C2, associated with the valve A2 being used for the injection of fuel into the cylinder.

As shown in FIG. 13, at low speeds, the lift law of the valve A1 is modified so as to open the valve A1 before the valve A2 so as to implement a sweeping phase during the crossing phase of the valves. In other words, at low speeds, the opening of the valve A2 is delayed to avoid sending fuel to the exhaust during the scan. In contrast, the closing delay at the inlet of the valve A2 is unchanged so that the two intake valves A1 and A2 are closed simultaneously. In other words, it avoids the repression after the bottom dead center. On the other hand, at high speeds, the levy laws of the valves A1 and A2 are combined (see Figure 14).

Maintaining the intake closure delay with respect to the fuel admission valve can also be implemented in the arrangement described above with reference to FIG. 6. In other words, as illustrated in FIGS. at 17, in a cylinder arrangement in which the pipe C1 having an injector I for injecting fuel into the cylinder C is shaped to maintain rotational movement of the air / fuel mixture, wherein the other pipe C2 associated with the intake valve A2 dedicated to the intake of fresh air into the cylinders C ensures a sweep during the crossing phase and in which the fuel injection is performed after closing the exhaust valves E, on maintains the intake closing delay, with respect to the fuel intake valve A1 at an optimum value to maximize the filling for the relevant regime.

In this mode of implementation, the delay of closing on admission is maintained as well with regard to the low speeds as the high speeds. Finally, it should be noted that in the different embodiments envisaged, it is also possible to use a variable exhaust valve system, known as VVT or VVA, acting in parallel on the valve lift laws described above in order to 'fully achieve the specific performance, clean-up and consumption objectives of the engine.

Claims (10)

A method of controlling the operation of an internal combustion engine with at least two intake valves, in which a crossing of the intake (Al, A2) and exhaust (E) valves is carried out and wherein injects air into the engine through one of the intake valves substantially at the crossing of the valves so as to evacuate the residual burnt gases, then fuel is injected into the cylinders (C) by the other valve intake, characterized in that it causes a rotation of the air / fuel mixture injected into the engine. 2. Method according to claim 1, wherein the rotation of the air / fuel mixture is performed by injecting the fuel so as to obtain said rotational movement. 3. Method according to claim 2, wherein the air is further injected into the engine by using an intake pipe (A1, A2) provided with a member (D) for rotating the air in the engine. engine. 4. The method of claim 1, wherein the rotation of the air / fuel mixture is performed by injecting air into the engine so as to obtain said rotational movement. 5. Method according to claim 4, wherein the fuel is injected in a general direction substantially opposite to the rotational movement of the air. 6. Process according to any one of Claims 1 to 5, characterized in that a system for modifying the laws for lifting the valves is also implemented. 7. The method of claim 6, wherein the fuel is injected substantially at the closure of the exhaust valves of the engine. 8. Method according to one of claims 6 and 7, wherein the entire law of lifting of the fuel injection valve is shifted relative to the law of lift of the air injection valve. 9. Internal combustion engine of a motor vehicle comprising at least two intake valves (A1, A2) and at least one exhaust valve (E), means for controlling the displacement of the intake and exhaust valves capable of to make a crossing of the intake (Al, A2) and exhaust (E) valves and means for controlling the injection of air into the engine by one of the intake and injection valves of fuel by the other intake valve so as to inject the air into the engine substantially during the crossing of the valves and to inject the fuel, characterized in that it further comprises means for causing rotation of the air mixture / fuel injected into the engine. 10. Motor according to claim 9, characterized in that it further comprises a valve lift law modification system adapted to inject the fuel substantially to the closure of the exhaust valves of the engine.