Method of controlling recirculation of exhaust gas of internal combustion supercharged engine and engine using such method

The present invention relates to a method of controlling the recirculation of exhaust gas of an internal combustion supercharged engine and an engine using such a method.

The present invention particularly relates to engines that can be operated by such recirculation so as to enhance the reduction of emissions, especially nitrogen oxides (NOx), when the engine operates in a lean fuel mixture.

As shown in Patent Document 1 as an example, it is a common method to recirculate a part of exhaust gas to the intake air of an engine in order to reduce NOx emissions, and this is generally used. Required for engines operating at low or intermediate loads with a lean fuel mixture. In practice, introducing exhaust gas into a cylinder during the intake phase has the effect of reducing the amount of fresh air that can be mixed with the fuel. As a result, the combustion temperature of the fuel mixture can be lowered, and therefore the amount of NOx produced by this combustion can be reduced.

Generally, this recirculation is a pipeline that connects the engine exhaust manifold to the engine intake manifold, and is called an EGR valve valve, which is arranged in this pipeline and regulates the flow rate of gas circulating in the pipeline. It is carried out by a circulation path called an EGR (Exhaust Gas Recirculation) circulation path, which has a valve that enables the operation.<patcit num="1"><text>U.S. Pat. No. 3,982,395</text></patcit>

<p> This circulation has the disadvantages of being very complex with respect to pipeline and valve installation, significantly increasing the additional cost and requiring very high performance EGR valve control means.</p><p> In addition to the drawbacks described above, configurations where engine supercharging is used have far greater drawbacks.</p><p> That is, when it is necessary to rapidly increase the rotation speed of the turbine, the fuel is mixed in a layered form in the cylinder and under lean combustion conditions so as to increase the amount of exhaust gas due to combustion. Mostly understood. Since such an air-fuel mixture causes combustion that generates a large amount of NOx, it is desirable to minimize this NOx generation by exhaust gas recirculation. In addition, such a layered fuel mixture also makes it possible to significantly reduce fuel consumption. However, during the exhaust gas recirculation, a pumping phenomenon occurs due to the pressure conditions required for this recirculation, and such pump loss significantly impairs the expected fuel consumption advantage of the layered fuel mixture.</p><p> An object of the present invention is to make it possible to eliminate the need for recirculation lines and EGR valves while using the necessary and sufficient amount of exhaust gas to allow the NOx emissions to be regulated. A method of controlling recirculation is intended to eliminate the above drawbacks. Furthermore, the pump loss is almost eliminated and the amount of reduction in fuel consumption is increased.</p>

<p> Therefore, the present invention has a combustion cycle in which at least one cylinder of the internal combustion supercharged engine is in the intake stage and at least one other cylinder is in the exhaust stage, each cylinder equipped with an intake valve. An internal combustion supercharged engine having at least one intake means and at least one exhaust means with an exhaust valve, the internal combustion supercharged engine further having an exhaust manifold connected to the exhaust means. In the method of controlling the recirculation of a part of the exhaust gas of the internal combustion supercharged engine, when the internal combustion supercharged engine operates with a lean fuel mixture, it flows from a cylinder in the exhaust stage, and is included in the manifold. Recirculation of a portion of the exhaust gas of an internal combustion supercharged engine, which comprises controlling the opening of the exhaust valve of a cylinder in the intake stage so as to introduce a portion of the exhaust gas that has been exhausted. Regarding how to control.</p><p> Advantageously, the method may comprise controlling the opening of the exhaust valve of the cylinder in the intake stage substantially simultaneously with the opening of the exhaust valve of the cylinder in the exhaust stage.</p><p> Further, this control method may consist of controlling the opening of the intake valve of the cylinder in the intake stage substantially at the same time as the closing of the exhaust valve of the cylinder.</p><p> Alternatively, the method may consist of controlling the opening of the intake valve of the cylinder in the intake stage substantially simultaneously with the opening of the exhaust valve of the cylinder.</p><p> The present invention also includes an internal combustion engine in which each cylinder has at least one intake means provided with an intake valve, at least one exhaust means provided with an exhaust valve, and a manifold connected to the exhaust means of the cylinder. In a supercharged engine, at least in the intake stage so that some of the exhaust gas contained in the manifold, which flows from at least one cylinder in the exhaust stage, is introduced into the cylinder in the intake stage. The present invention relates to an internal combustion supercharged engine, which comprises means for controlling an exhaust valve so as to control the opening of the exhaust valve of one cylinder.</p><p> The control means may have means for changing the lift low of the exhaust valve.</p><p> The lift row changing means may have a VVT type or VVL type control device.</p><p> If the internal combustion engine is a turbocharger that performs intake supercharging into a cylinder in which the turbocharger is in the intake stage, the turbocharger may have a single inlet.</p><p> Other features and advantages of the invention will become apparent by reading the following description, which is given as a non-limiting example, with reference to the accompanying figures.</p>

In particular, the direct fuel injection internal combustion supercharged engine in FIG. 1 has at least four cylinders 10,12,14,16 or multiples of four. Each cylinder has at least one intake means 18 with an intake valve 20 and an intake pipe 22 and at least one exhaust means 24 with an exhaust valve 26 and an exhaust pipe 28. The intake manifold 30 connects the intake pipes 22 to each other while the exhaust pipe 28 is open to the exhaust manifold 32. This exhaust manifold is connected by a conduit 34 to a single inlet of turbine 36 of turbocharger 38. The turbine is connected by a shaft to the compression stage 40 of the turbocharger. Therefore, as is known in the art, this compression stage compresses the atmosphere taken into it and distributes the atmosphere in the compressed state through the conduit 42 into the intake manifold 30.

The opening and closing of the exhaust valves 26 is known as VVT (Variable Valve Timing) or VVL (Variable Valve Lift), which allows the lift lows of these valves to change independently of each other, especially when opening and closing those valves. It is controlled by such means 44. Similarly, the intake valves 20 can also be controlled by means 46 that also allow the lift row of these valves to be varied, preferably VVT or VVL type control means are used. Means 44 and 46 are driven by a control unit 48 that allows the lift low of the valve to be changed according to engine operating conditions such as engine speed and engine load.

As is known in the art, these cylinders are connected to bottom dead center (BDC) by a connecting rod 52 connected to the crankpin of a crankshaft (not shown) typically provided by such engines. It has a piston 50 that reciprocates and translates in the opposite direction between a lower position called the top dead center (TDC) and an upper position called the top dead center (TDC). The cylinder also has a combustion chamber 54 formed by the top surface of the piston and the top surface of the cylinder. All fuel injection means (not shown) that allow the generation of a fuel mixture in the combustion chamber 54, and this, such as spark ignition in the case of a spark ignition engine, that burns this fuel mixture. Like any ignition means for the air-fuel mixture, the intake means 18 and the exhaust means 24 are connected to the combustion chamber (FIGS. 2 and 3).

In this example described with respect to the present invention, the engine has cylinder 10 in the intake phase where piston 50 moves from near its TDC to near its BDC, while cylinder 12 is in the compression phase and cylinder 14 Is in the exhaust stage where the piston moves from near its BDC to near its TDC, and the last cylinder (cylinder 16) is in the expansion stage in the combustion cycle, which is considered to operate at a given crankshaft position, this cycle. Is commonly called 1,4,3,2.

In FIGS. 2 and 3, showing the configuration of cylinders 14 and 10 at the same predetermined crankshaft position, cylinder 14 is in the exhaust stage where piston 50 is near its bottom dead center (BDC), while cylinder 10 is piston. 50 is in the inspiratory phase near top dead center (TDC). The pressure Pe in the combustion chamber 54 of the cylinder 14 corresponds to the pressure of the exhaust gas at the end of the expansion stage, that is, about 5 bar (0.5 MPa), and the pressure Padm in the combustion chamber 54 of the cylinder 10 is higher than this exhaust pressure. Is much lower.

Therefore, in the case of an engine operating at low or intermediate loads, where it is desirable to increase the turbine speed, the engine computer combined with this engine is usually the fuel required to obtain the lean mixture. Obtain the injection parameter and intake parameter. The engine computer also sends instructions to the control unit 48 to achieve recirculation of the exhaust gas in the combustion chamber 54 of the cylinder 10 in the intake stage in order to minimize NOx emissions.

Therefore, a part of the exhaust gas from the cylinder 14 in the exhaust stage is used through the exhaust manifold and injected into the cylinder 10 in the intake stage. More precisely, the exhaust gas flowing from the combustion chamber 54 through the exhaust valve 26 is discharged into the exhaust manifold 32, and then a part of this gas contained in the manifold is discharged from the exhaust valve of the cylinder 10. By controlling the opening of 26, it is supplied into the combustion chamber 54 of the cylinder 10 in the intake stage. The rest of the gas is discharged to the turbine 36 of the turbocharger 38 via the conduit 34.

In order to realize such recirculation, the control unit 48 controls the opening of the valve 26 of the cylinder 14 so as to discharge the gas toward the exhaust manifold 32, and the opening of the exhaust valve 26 of the cylinder 10. However, the control means 44 is controlled so that the exhaust valve 26 is maintained in the open position for a predetermined time and a part of the exhaust gas existing in the exhaust manifold 32 is supplied into the combustion chamber 54 of the cylinder 10. Operates the control means 44 so as to operate the exhaust valve 26. When this amount of exhaust gas is introduced, the means 44 controls the closing of the valve 26 of the cylinder 10 to the valve 26 of the cylinder 14 until substantially the end of the exhaust phase, i.e. the piston 50 of the cylinder 14. Keep opening near top dead center.

After closing the valve 26 of the cylinder 10, the control means 46 operates the intake valve 20 of the cylinder in the intake stage to introduce supercharged air into the combustion chamber 54 of the cylinder.

Of course, it is possible to simultaneously open the intake valve 20 and the exhaust valve 26 of the cylinder 10 in the intake stage to generate a homogeneous air-fuel mixture in the combustion chamber without departing from the scope of the present invention. This is possible because the pressure Padm in the combustion chamber 54 is lower than the pressure Pe of the exhaust gas contained in the manifold, which is slightly higher than the pressure Pe of the gas flowing from the cylinder 14.

Exhaust gas recirculation is not required, especially if the fuel mixture is under theoretical conditions, means 44 and 46 may operate the opening and closing of valves 20 and 26 in the conventional manner or filed by the applicant. As detailed in the French Patent Application No. 03/14967, which has been filed, it enables the scavenging of residual combustion gas.

With this configuration, almost all exhaust gas is used to drive the turbine except for the amount required for recirculation. Moreover, no special configuration is required for this recirculation and only the components commonly present in the engine are used.

The present invention is not limited to the described examples, but includes all equivalents or variants.

In particular, the above description applies to indirect injection engines, especially spark ignition engines, with or without supercharging, and with or without supercharging, with direct injection engines. ..

<figref num="1">It is a figure which shows the 4-cylinder supercharged engine by this invention.</figref><figref num="2">It is a partial cross-sectional view (cross section along AA) of the cylinder in the exhaust stage of the engine of FIG.</figref><figref num="3">It is a partial cross-sectional view (cross section along BB) of another cylinder in the intake stage of the engine of FIG.</figref>

Code description

10,12,14,16 Cylinder 18 Intake means 20 Intake valve 22 Intake pipe 24 Exhaust means 26 Exhaust valve 28 Exhaust pipe 30 Intake manifold 32 Exhaust manifold 34,42 Pipe line 36 Turbine 38 Turbocharger 40 Compression stage 44,46 Control means 48 Control unit 50 Piston 52 Connecting rod 54 Combustion chamber