Method and system for regulating the combustion of an internal combustion engine

Abstract

A method for regulating the combustion of an internal combustion engine comprising, on the one hand, an air supply duct equipped with means for regulating the airflow in said duct and, on the other hand, a single cylinder associated with said regulating means, comprising the following steps: - determining the engine speed and / or load, and - when the engine speed is below a predetermined value and / or the engine load is below a predetermined value, the means for regulating the airflow in the supply duct are controlled such that the airflow is reduced at least temporarily while an intake valve for introducing air into the corresponding cylinder from said supply duct is open. Abstract figure: Figure 6

Description

Title of the invention: Method and system for regulating the combustion of an internal combustion engine

[0001] The present disclosure relates to a method and a corresponding system for controlling the combustion of an internal combustion engine. This disclosure relates rather to controlling an engine at low load and low speed. Technical field

[0002] The present disclosure relates to the field of combustion management of an internal combustion engine. It relates more particularly to single-cylinder engines or more generally to engines comprising a throttle valve for each cylinder. This type of engine is most often spark-ignition. Prior art

[0003] In the design of an internal combustion engine, when high performance is sought, the characteristics of the engine to achieve this high performance most often go against the stability of combustion at low speed and low load. In this type of engine, at low speed and low load, it is most often found, due to the structure of the engine, that burnt gases remain in the combustion chamber at the end of the intake phase. As a result, if no measures are taken, the residual burnt gases slow down the combustion speed and as a result the engine speed becomes unstable.

[0004] Among the known solutions to remedy this problem, one solution consists of injecting fresh air at the exhaust. Thus, the air / fuel mixture can remain rich at the combustion chamber when the exhaust gases remain generally such that the lambda probe detects an overall richness of 1. Thus a three-way catalytic converter fitted to the corresponding engine can continue to operate efficiently.

[0005] This first solution involves adding means to the engine for injecting fresh air into the exhaust and therefore involves an additional cost in the manufacture of the engine.

[0006] Another solution consists of adapting the shape of the combustion chamber to promote turbulence and thus better sweeping of the combustion chamber at the end of combustion.

[0007] This solution makes it possible at low cost to promote engine stability at low speeds and low loads but is detrimental to performance at high speeds and high loads.

[0008] The present disclosure therefore aims to provide a solution enabling to improve the stability of an engine at low speed and low load at low cost and without deterioration of engine performance at other operating points. Summary

[0009] The present disclosure improves the situation.

[0010] Firstly, a method for regulating the combustion of an internal combustion engine is proposed, comprising, on the one hand, an air supply pipe provided with means for regulating the air flow in said pipe and, on the other hand, a single cylinder associated with said regulating means.

[0011] According to the present disclosure, it is proposed that said method comprises the following steps:

[0012] - determination of the engine speed and / or load, and

[0013] - when the speed is below a predetermined value and / or the load of the engine is below a predetermined value, the means for regulating the air flow in the supply line are controlled such that the air flow is reduced at least temporarily while an intake valve for introducing air into the corresponding cylinder from said supply line is open.

[0014] Thus, during the entire opening of the intake valve or at least during a part of this opening time, the air supply is limited. This creates a depression upstream of the intake valve which subsequently promotes better air filling upstream of the intake valve by creating a suction when the means for regulating the air flow in the supply line return to a position allowing a higher air flow.

[0015] In the proposed regulation method, the air flow may for example be reduced in the supply line for a period corresponding to at least 180°CRK.

[0016] According to an embodiment allowing efficient and rapid control of the means for regulating the air flow in the air supply pipe, the latter comprise for example a butterfly valve, the reduction of the air flow being obtained by pivoting said butterfly valve without closing it.

[0017] According to a variant, the regulation method according to the present disclosure comprises the following steps:

[0018] - determination of engine speed and load,

[0019] - determination of a quantity of fuel to be injected and a corresponding mass of air laying,

[0020] - determination of an average position command for the regulation means of the air flow in the supply line allowing to obtain the air mass determined during an engine cycle,

[0021] - position control of said regulating means to limit the air flow in the supply line relative to the mid-position control at least temporarily during the opening of the intake valve, and

[0022] - position control of said regulating means when the air flow is not limited so that the airflow in the supply line over an engine cycle is sufficient to supply the determined air mass.

[0023] According to this variant embodiment of the regulation method according to the present disclosure, the air flow can be limited in the supply line at least for 180°CRK corresponding to the passage through a top dead center until the passage through the next bottom dead center, an intake valve being open.

[0024] The present disclosure further relates to:

[0025] - a computer program product, comprising a series of code instructions for the implementation of a method for regulating the combustion of an internal combustion engine described above, when it is implemented by a computer;

[0026] - a computer adapted for regulating the combustion of an engine internal combustion comprising, on the one hand, an air supply duct provided with means for regulating the air flow in said duct and, on the other hand, a single cylinder associated with said regulation means, characterized in that said computer is also adapted for implementing each of the steps of a regulation method described above;

[0027] - an internal combustion engine comprising, on the one hand, a pipe air supply provided with means for regulating the air flow in said pipe and, on the other hand, a single cylinder associated with said regulation means, characterized in that it further comprises a computer defined in the preceding paragraph: in such an engine, the means for regulating the air flow in the supply pipe advantageously comprise a motorized butterfly valve. Brief description of the drawings

[0028] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawing, in which: Fig.l

[0029] [Fig.l] shows schematically a single-cylinder engine in section. Fig. 2

[0030] [Fig.2] schematically shows the pressure variations at the inlet of the cylinder of the engine of [Fig.l] with prior art management. Fig. 3

[0031] [Fig.3] schematically shows the control signal for a butterfly valve of the engine of [Fig.l] with prior art management. Fig. 4

[0032] [Fig.4] shows schematically the pressure variations at the inlet of the cylinder of the engine of [Fig.l] with management according to the present disclosure in comparison with the variations of [Fig.2]. Fig. 5

[0033] [Fig.5] schematically shows the control signal for the butterfly valve of the engine of [Fig.l] with management according to the present disclosure. Fig. 6

[0034] [Fig.6] shows an example of a flowchart for the implementation of a mode of realization of a process corresponding to the control signal of [Fig.5]. Description of the embodiments

[0035] Reference is now made to [Fig.l]. The person skilled in the art will recognize here a single-cylinder engine shown schematically in section. This engine thus comprises a cylinder 2 in which slides a piston 4 above which is located a combustion chamber 6. The piston 4 is connected by a connecting rod 8 to a flywheel 10. A position sensor 12 makes it possible to know the angular position of the flywheel 10 as well as the rotation speed RPM of this flywheel, which corresponds to the rotation speed, or speed, of the engine.

[0036] The combustion chamber 6 is supplied, on the one hand, with fuel and, on the other hand, with fresh air. A fuel supply line, shown diagrammatically by an arrow 14, supplies a fuel injection system 16 into the combustion chamber.

[0037] Air is brought to the combustion chamber 6 by an intake manifold 18. At least one intake valve 20 controls the entry of air into the combustion chamber. It will be assumed hereinafter that there is only one intake valve 20. The air flow in the intake manifold 18 is regulated by a motorized butterfly valve 22. The space in the intake manifold located between the motorized butterfly valve 22 and the combustion chamber 6 (or the intake valve 20) is called the manifold 24 (also known as the English “manifold”). A pressure sensor 26 makes it possible to know the pressure in this manifold 24.

[0038] In the illustrated example, the engine is an engine with ignition controlled by a spark plug 28.

[0039] An electronic control unit 30, commonly called ECU, makes it possible to control and command the engine. This unit is connected in particular to the injection system 16, to the spark plug 28 (or more generally to an ignition system), to the position sensor 12, to the pressure sensor 26 and to the motorized throttle valve 22 (which also integrates at least one throttle position sensor).

[0040] [Fig.l] does not show in particular the exhaust system of the engine since the present disclosure relates more particularly to an air intake system in an engine. However, the person skilled in the art knows exhaust systems as well as other elements of an engine not illustrated here in this schematic figure.

[0041] The present disclosure relates more particularly to the operation of the engine of [Fig.l] when the engine speed RPM is low and / or the engine load L is also low. Under these conditions, burnt gases remain present in the combustion chamber during an intake of fresh air. Indeed, it is generally provided that the exhaust valve and the intake valve are open for the same period of time at the start of the intake of fresh air. At high speed and / or under load, this allows the fresh air entering the combustion chamber to expel the burnt gases remaining there. At low speed and / or under low load, the fresh air entering does not have enough energy to expel all the burnt gases.The mixture in the combustion chamber then partially contains burnt gases which slow down combustion and the engine speed therefore becomes unstable, i.e. it varies significantly (and uncontrolled).

[0042] Figures 2 and 3 illustrate the usual operation of the engine of [Fig.l] according to the state of the art prior to the present disclosure. [Fig.2] illustrates by a curve 100 the pressure in the manifold 24 as seen by the pressure sensor 26. As long as the intake valve 20 is closed, this pressure increases to reach a maximum value (corresponding substantially to the atmospheric pressure in a non-supercharged engine) a little after the intake valve 20 begins to open. The two pressure maxima illustrated in [Fig.2] are 720°CRK apart in the case of an engine operating according to a four-stroke cycle.

[0043] [Fig. 3] illustrates the angular position of a butterfly valve 32 used to modify the passage section in the intake manifold 18. This butterfly valve 32 is pivotally mounted (and controlled by a motor) around an axis transverse to the intake manifold 18 and it is considered that it pivots between two extremes 0° and 90° (which are not necessarily reached in practice), 0° corresponding to the smallest possible passage section while 90° corresponds to a maximum opening and therefore the largest possible passage section.

[0044] The position of the butterfly valve 32 in its housing, i.e. in the motorized butterfly valve 22, is hereinafter called PAP. In the state of the art prior to the present disclosure, the butterfly valve 32 remains in the same angular position MOY throughout the engine cycle (intake, compression, expansion and exhaust). In the example illustrated, MOY is for example 8°. This angular value is determined by the electronic control unit 30 so that the mass of air admitted into the combustion chamber 6 corresponds to the mass of fuel in order to obtain complete combustion of the latter.

[0045] In an original manner, it is proposed to improve combustion in the engine - at low speed and / or at low load, in a preferred embodiment, at low speed and at low load - and to improve the stability of combustion, to act quickly on the motorized butterfly valve 22 to vary the angular position of its butterfly 32 during the combustion cycle so as to reduce the passage section in the intake manifold during the admission of air into the combustion chamber (compared to the position of this butterfly 32 during the other phases of the cycle). It is therefore a question of varying the position of the butterfly 32, the latter being more closed during the admission of air into the combustion chamber.

[0046] In order for the quantity (mass) of air entering the combustion chamber to correspond to the quantity of fuel injected, it is necessary to adapt the opening angle of the butterfly valve 32 outside the intake phase.

[0047] [Fig. 5] illustrates a throttle opening command 32 corresponding to conditions in all respects similar to those of figures 2 and 3. The RPM and the load L of the engine are the same and it is assumed that the same quantity of fuel must be injected. Therefore, the same mass of air must be admitted into the engine.

[0048] For the record, in the configuration of figures 2 and 3, to admit the correct mass of air, it was determined that the butterfly 32 had to be open at an angle PAP=MOY. For purely illustrative and non-limiting purposes, we have for example PAP=MOY=8°.

[0049] Under similar conditions, it is provided in [Fig.5] to close the butterfly 32 so that its angular position is PAP=MIN with MIN <M0Y. A titre illustratif (et non limitatif), on aura par exemple MIN=5°. Cette position n’est prise par le papillon 32 par exemple uniquement lorsque la soupape d’admission 20 est ouverte. Lorsque la soupape d’admission 20 est fermée, le papillon 32 prend une position angulaire PAP=MAX avec MAX> M0Y. As an illustrative and non-limiting example, we can for example have MAX=9°.

[0050] By controlling the motorized butterfly valve 22 in this way, it is noted that the pressure curve in the manifold 24 varies. In [Fig. 4], a curve 200 represents the pressure variations in the manifold 24 corresponding to this mode of controlling the motorized butterfly valve 22. This [Fig. 4] also uses the curve 100 of [Fig. 2] for comparison. It is noted in particular that just before the opening of the intake valve 20, the pressure in the manifold 24 is higher than the pressure observed when the butterfly 32 maintains a constant angular position. This “overpressure” is of the order of approximately 100 mbar. When the intake valve opens, it prevents the return of burnt gases which are in the exhaust, substantially at atmospheric pressure, and also facilitates, to a lesser extent, the entry of fresh air into the combustion chamber. In other words, Fresh air arriving with higher pressure more efficiently expels burnt gases from the combustion chamber.

[0051] Generally, the intake valve 20 opens a little before the passage to the corresponding top dead center of the piston 4 and closes after the following passage to the bottom dead center of this piston 4. It is advantageously provided that the butterfly 32 is in its closed position (PAP=MIN) at least between the passage of the piston 4 from the top dead center to the bottom dead center corresponding to an air intake.

[0052] The "closed" position of the throttle is not a position fixed once and for all. It depends on the quantity of air to be admitted into the engine at each cycle. Similarly, the "open" position is not fixed but determined according to the quantity of air to be admitted into the engine.

[0053] The range in which the butterfly 32 takes its closed position can be, as indicated above, for example, a range of 180°CRK going from a top dead center to a bottom dead center during which the intake valve 20 is open.

[0054] This range may be different. It may correspond to the opening range of the intake valve (for example 10°CRK before top dead center to 60°CRK after bottom dead center). It may be reduced relative to the opening range of the intake valve, it may be greater than the opening range of the intake valve or it may straddle an opening phase and a closing phase of the intake valve. For example, it is provided that the range in which the section of the intake manifold is limited by the “closed” position of the throttle valve 32 corresponds to at least 90°CRK during which the intake valve is open, advantageously at least 135°CRK and preferably at least 180°CRK.

[0055] The description is given above for a single-cylinder engine. Those skilled in the art also understand that it can be carried out for an engine comprising several cylinders with a motorized butterfly valve (or equivalent) to control the air flow supplying each cylinder.

[0056] [Fig.6] is a flowchart summarizing a method for achieving stable combustion of an engine at low speed and low load according to the present disclosure.

[0057] The electronic control unit 30 knows the engine speed RPM and load L. These values ​​are compared to a predetermined speed value RPMo and to a predetermined load value Lo.

[0058] If the RPM speed is greater than RPMo or if the load L is greater than Lo, then the motorized butterfly valve 22 is controlled such that its butterfly 32 maintains a constant angular position (PAP=MOY) for each air mass setpoint.

[0059] On the other hand, if the RPM is lower than RPMo and the engine load is lower than Lo, then the throttle 32 will have a variable angular position for the same air mass instruction.

[0060] In the simplified embodiment illustrated here, it is determined as a function of the angular position of the engine (°CRK) whether the engine is in the intake phase or not. If necessary, the motorized butterfly valve is controlled so that the butterfly takes the angular position PAP=MIN and otherwise a command is sent so that the position of the butterfly is PAP=MAX. Industrial application

[0061] These technical solutions can be applied in particular to the management of an internal combustion engine.

[0062] The solution proposed by the present disclosure makes it possible to improve the stability of an engine without having to equip it with additional elements. The modifications to be made are simply software-related.

[0063] The proposed solution does not require an increase in fuel consumption. It allows for combustion optimization and improves engine efficiency at low speeds and / or low loads.

[0064] Finally, the stability of the engine at low speed and / or low load is not at the expense of engine performance.

[0065] The present disclosure is not limited to the examples of methods and systems described above and to the variants described above, only as examples, but it encompasses all the variants that may be envisaged by those skilled in the art within the framework of the protection sought.

Claims

Claims

1. Method for regulating the combustion of an internal combustion engine of the single-cylinder type or comprising a throttle valve for each cylinder, said engine comprising, on the one hand, an air supply duct (18) provided with means (22) for regulating the air flow in said duct and, on the other hand, a single cylinder (2) associated with said regulating means (22), said engine operating on the basis of an engine cycle comprising four phases, characterized in that said method comprises the following steps: - determining the engine speed and / or load, and - when the speed is below a predetermined value and / or the engine load is below a predetermined value, either when the engine is operating at low load and / or at low speed,the means (22) for regulating the air flow in the supply line (18) are controlled in such a way that the air flow is temporarily reduced during the engine cycle relative to the position of said throttle valve during the other phases of the engine cycle, while an intake valve (20) for introducing air into the corresponding cylinder (2) from said supply line (18) is open or at least for part of the opening time.,

2. A control method according to claim 1, characterized in that the air flow is reduced in the supply line (18) for a period corresponding to at least 180°CRK.

3. A method of regulation according to one of claims 1 or 2, characterized in that the means (22) for regulating the air flow in the air supply line comprise a butterfly valve, the reduction of the air flow is obtained by pivoting said butterfly valve without closing it.

4. Regulation method according to one of claims 1 to 3, characterized in that it comprises the following steps: - determination of the engine speed and load, - determination of a quantity of fuel to be injected and a corresponding air mass, - determination of an average position command for the means (22) for regulating the air flow in the supply line making it possible to obtain the determined air mass during a cycle engine, - position control of said regulating means (22) to limit the air flow in the supply line relative to the average position control temporarily during the opening of the intake valve (20), and - position control of said regulating means (22) when the air flow is not limited so that the air flow in the supply line on an engine cycle makes it possible to supply the determined air mass.

5. Control method according to claim 4, characterized in that the air flow is limited in the supply line (18) at least for 180°CRK corresponding to the passage through a top dead center until the passage through the next bottom dead center, an inlet valve (20) being open.

6. Computer program product, comprising a series of code instructions for implementing a method for regulating the combustion of an internal combustion engine according to one of claims 1 to 5, when it is implemented by a computer.

7. A computer adapted for regulating the combustion of an internal combustion engine comprising, on the one hand, an air supply pipe (18) provided with means (22) for regulating the air flow in said pipe and, on the other hand, a single cylinder (2) associated with said regulating means (22), characterized in that said computer is also adapted for implementing each of the steps of a method according to one of claims 1 to 5.

8. Internal combustion engine comprising, on the one hand, an air supply duct (18) provided with means (22) for regulating the air flow in said duct and, on the other hand, a single cylinder (2) associated with said regulating means (22), characterized in that it further comprises a computer (30) according to claim 7.

9. Engine according to claim 8, characterized in that the means (22) for regulating the air flow in the supply line comprise a motorized butterfly valve.

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