FR2922955A1 - Exhaust gas quantity controlling method for four-stroke diesel type internal combustion engine i.e. diesel type compression ignition engine, of vehicle, involves modifying rule of valve during phases to control quantity of gas in chamber - Google Patents

Abstract

The method involves realizing an opening/closing sequence of one of an exhaust valve (18) or an admission valve (30) during an admission phase and an exhaust phase of a four-stroke diesel type internal combustion engine, where the valve is in the close position. Another opening/closing sequence of the valve is realized during the phases. A raise rule of the other valve is modified during the phases to control the quantity of the exhaust gas in a combustion chamber (12) of a cylinder (10) of the engine.

Description

The present invention relates to a method for controlling the amount of gas recirculated internally of a diesel type internal combustion engine.

As is generally known, the introduction of recirculated exhaust gas (or EGR for Exhaust Gas Recirculation) in greater or lesser amounts at the inlet of an engine makes it possible to reduce, in a non-negligible manner, the amount of oxides of nitrogen (NOx) that is released into the atmosphere.

Usually, this reintroduction can be achieved through a circuit, called external EGR circuit, which allows to introduce exhaust gas to the intake by a pipe connecting the engine exhaust at its intake.

This reintroduction can also be achieved by a method for reintroducing recirculated exhaust gas to the intake of an internal combustion engine without using an external specific circuit. This method makes it possible to carry out an internal recirculation of exhaust gas, usually called IGR for "Internai Gas Recirculation" or "Internai Gas Residual".

As better described in US 2005 // 0081836, such an internal combustion engine comprises a cylinder having a combustion chamber, an exhaust means with an exhaust valve controlled by exhaust control means, and intake means with an intake valve controlled by intake actuating means. For this type of engine operating at low and medium loads, exhaust gases are reintroduced to the intake to mix with the fresh air that arrives there during the intake phase of the engine.

For this, during the intake phase of the engine, the exhaust valve, which is conventionally closed during this phase, is again open for a short period while the intake valve follows its conventional course with an opening beginning in the vicinity of the beginning of the engine intake phase and a closure in the vicinity of the end of this intake phase. Thus, during this intake phase, flue gases present in the exhaust are reintroduced through the exhaust valve and fresh air is admitted into this chamber through the intake valve.

To achieve this double opening (or double lift) of the exhaust valve, the associated control means are constituted by a camshaft actuating device VVA (Variable Valve Actuation), which allows not only to modify the extent of the lifting of the valve but also to change the time of opening and closing of this valve in the engine cycle. In addition, this camshaft WA has the particularity of being able to operate also like a conventional camshaft with a simple opening of the exhaust valve between the beginning of a phase of the engine and the end of this same phase when this engine works at full and heavy loads.

This reintroduction of hot exhaust gas has the effect of reducing the formation and therefore the release into the atmosphere of unburned hydrocarbons (HC) and carbon monoxide (CO).

This arrangement, although satisfactory, nevertheless has significant disadvantages. Indeed, the major disadvantage of such a method is that it is complex and expensive to be able to modulate the amount of recirculated exhaust gas to be introduced into the combustion chamber. For this, it is necessary to be able to vary the phasing and the extent of the second lift and this through the appropriate control means of great sophistication.

The present invention proposes to remedy the drawbacks mentioned above by means of a method of reintroduction of exhaust gas at the intake of an internal combustion engine which makes it possible to be able to control, in a very simple manner, the quantity of gas reintroduced.

To this end, the present invention relates to a method for controlling the amount of gas recirculated internally in a four-cycle diesel type internal combustion engine with an exhaust phase, intake, compression and expansion, said engine comprising a cylinder having a combustion chamber, at least one exhaust means with a type of exhaust valve, controlled by exhaust control means, and at least one intake means with another type valve, said intake, controlled by actuating means, characterized in that it consists, during operation at low or medium engine loads: - to perform at least one opening / closing sequence of the one of the valve types during the operation phase of the engine where this valve is conventionally in the closed position and to perform another opening / closing sequence during the operating phase of the mote where it conventionally follows an opening / closing sequence, - during the phase in which the opening / closing sequence of said one of the valve types is performed, to modify the law of emergence of the other of the valve types during this operating phase of the engine where said other type of valve conventionally executes an opening / closing sequence, so as to control the amount of exhaust gas in said chamber.

The method may consist of: - performing an opening / closing sequence of the exhaust valve during the exhaust phase and performing at least one opening / closing sequence of this valve during the intake phase to reintroduce exhaust gases in the combustion chamber, - to modify the law of emergence of the intake valve during the intake phase to control the amount of exhaust gas to be reintroduced into said chamber.

The method may consist of: - performing at least one opening / closing sequence of the intake valve during the exhaust phase and performing a sequence of opening / closing of this valve during the intake phase, - To modify the law of emergence of the exhaust valve during the exhaust phase to control the amount of exhaust gas to be reintroduced into said chamber. The method may be to modify the law of emergence of the valve by modifying its phasing. The method may be to modify the law of emergence of the valve by modifying the value of its lifting. The method may be to modify the law of emergence of the valve by modifying its spreading.

The method may include changing the valve lift law by initiating its opening movement prior to the opening movement of the valve which is conventionally in the closed position.

The method may include modifying the valve lift law by completing its closing movement substantially simultaneously with the closing movement of the valve which is conventionally in the closed position. The method may include modifying the valve lift law by initiating its opening movement substantially concurrently with the opening movement of the valve which is conventionally in the closed position. The method may include modifying the valve lift law by initiating its opening movement after the valve opening movement which is conventionally in the closed position.

The method may be to modify the valve lift law by completing its closing movement after the closing movement of the valve which is conventionally in the closed position.

The other features and advantages of the invention will now appear on reading the following description, given solely by way of illustration and not limitation, and to which are appended: FIG. 1 which is a diagram showing a motor with internal combustion using the process according to the invention; FIG. 2 which shows curves illustrating the various laws of emergence of the intake and exhaust valves of the engine using the method according to the invention; and FIG. 3 which also shows curves for the various laws for lifting the engines. intake and exhaust valves of the engine using a variant of the method according to the invention. In FIG. 1, the internal combustion engine illustrated is a diesel type auto-ignition engine operating in a four-stroke mode with an intake phase A, compression stage C, expansion stage stage D and exhaust phase stage E. motor comprises at least one cylinder 10, here four cylinders, having a combustion chamber 12 in which occurs the combustion of a fuel mixture.

As is widely known, this fuel mixture can be either a mixture of air (or supercharged air) added to the exhaust with a fuel, or a mixture of air or air supercharged with a fuel .

The cylinder comprises at least one exhaust means 14 of the flue gases, here two, comprising an exhaust pipe 16 and a type of shutter, such as an exhaust valve 18. The exhaust pipes 16 end up in a collector exhaust 20 allowing the evacuation of the burnt gases from the combustion chambers, this manifold being connected to an exhaust line 22. The exhaust valves 18 are controlled in opening and closing by any known means to achieve a fixed double lift of these valves during operation of this engine for low and medium loads, or a simple lift during operation at full and heavy loads. For this, it is used control means 24, VVA camshaft type (Variable Valve Actuation), which allow a permutation between two laws of levies of these valves. A first law makes it possible to carry out an opening / closing sequence of the exhaust valves during the exhaust phase E followed by at least one opening / closing sequence of these valves during the admission phase A where they are conventionally in the closed position while the other law allows to execute only a sequence of opening / closing of the exhaust valves during the exhaust phase E. As a non-limiting example, this camshaft comprises a cam associated with a second cam permitting to ensure the double lift law of these valves during the exhaust phase E and intake A of the engine and a disengagement device making the second cam inoperative to achieve the simple lifting of the exhaust valve during the exhaust phase.

It should be noted that the term "lifting" corresponds to the graphic representation (along two axes) of the movement of a valve from the beginning of its opening until the end of its closure through its full open position. . This cylinder also comprises at least one intake means 26, here two, which comprises an intake manifold 28 associated with another type of closure, such as an intake valve 30. In a conventional manner, a manifold The inlet 32 is connected to the intake manifolds and makes it possible to distribute fresh supercharged or non-supercharged air into the combustion chambers 12.

The intake valves 30 are controlled in opening and closing by actuating means 34 for making a variable distribution or at least for varying the law of lift of these intake valves.

In the case of the example described, these actuating means used are of the VVT (Variable Valve Timing) camshaft type which makes it possible to vary the phasing of the lifting of these valves.

This engine also comprises a computing unit 36, called a motor-calculator, which contains mappings or data tables making it possible to evaluate, as a function of the values of the engine parameters transmitted by data lines 38, as the speed of the engine. engine, its load or the pressures of intake and exhaust, the power that must generate this engine to meet the demand of the driver of the vehicle. This calculator also makes it possible to manage the desired operating conditions of this engine, from low loads to very high loads. More precisely, this engine-calculator makes it possible, according to these operating conditions, to control the exhaust valve lift laws 18 by a control line 40 acting on the means 24 so as to allow a simple lifting or double raising of these valves 18, and control the actuating means 34 for controlling the intake valves 26 by a line 42.

When the engine is operating under conditions that correspond to low or medium loads and therefore require the recirculation of a portion of the exhaust gas at the intake, the engine computer controls the engine so that it operates with such a recirculation .

Thus, the computer 36 controls the control means 24, via the line 40, to perform a double lift of the exhaust valves 18 and also the actuating means 34 of the intake valves 30, via the line 42, to manage the amount of recirculated gas introduced into the combustion chamber during the second lift.

For this, reference is also made to Figure 2 which shows the different laws of lift of the intake and exhaust valves between an open position (0) and closing (F) depending on the angle of crankshaft rotation (° V). More precisely and as better illustrated in this figure, during the exhaust phase E of the engine, the control means 24 are driven by the engine-calculator to open the exhaust valves 18 in the vicinity of the exhaust bottom dead center (PMBe) . The exhaust gases contained in the combustion chamber 12 are discharged through these exhaust valves 18 into the exhaust manifold 20 to be then discharged into the exhaust line 22. These exhaust valves 18 are closed then, still under the influence of the control means 24, in the vicinity of the top dead center (PMHa). Of course, throughout this exhaust phase, the engine computer 36 controls the actuating means 34 of the intake valves 30 by the line 42 so that they remain in the closed position.

During the intake phase A of this engine which follows this exhaust phase, the computer 36 controls the control means 24 of these exhaust valves so that they open again at the point Ve after the PMHa and close before the low compression dead point (PMBc), as illustrated by curve 18a. Preferably, the maximum lift and the maximum extent of these valves is less than that of the exhaust valves during the exhaust phase E. Thus, during this second lift, the exhaust gases contained in the pipes of exhaust 16 and in the exhaust manifold are reintroduced into the combustion chamber 12 under the influence of the piston stroke that usually comprises the cylinder 10. During this admission phase, the computer 36 then controls the means of actuation 34 of the intake valves 30 so as to vary the amount of flue gas reintroduced into the combustion chamber to adapt the rate of flue gas or rate of IGR (rate = mass (grams) of exhaust gas reintroduced / mass (in grams) of air (or supercharged air) introduced).

To arrive at such a result, the computer manages the actuating means 34 to modify the law of emergence of the intake valves 30 during this admission phase A.

In the case of the example described, this modification takes place on the phasing of this law through the use of a camshaft with phase shifter. This modification can also occur on the extent of lifting and / or spreading of this law in association or not with the modification of the phasing.

As illustrated in FIG. 2, the timing of the intake valves 30 oscillates between an OO position and an OO position thereby allowing the internal recirculated gas rate (or IGR rate) to vary between a low rate and a high rate. .

For the position @, which corresponds to a low rate of IGR, the intake valves are open at the point Val before the reopening of the exhaust valves 18a at the point Ve and the exhaust valves close well before the PMBc while the intake valves close in the vicinity of this PMBc. In this case, at the time of the reopening of the exhaust valves 18a, fresh air will have been introduced into the combustion chamber between Val and the point Ve, which limits the possibility of introducing a large quantity of gas. recirculated exhaust in this room. In addition, the fresh gas vein reaches a certain speed due to its inertia, which will limit the return of the recirculated exhaust gas in this chamber. This introduction of recirculated gas will be followed by an admission of fresh air between the closure of the exhaust valves and the closing of the intake valves in the vicinity of the PMBc.

Similarly, to obtain such a low rate, it is possible to open at almost the same time, at point Ve, the intake and exhaust valves and to close the intake valves after closing the exhaust valves. .

In contrast, for the position O which is suitable for a high rate of IGR, the inlet valves 30 are open at point Va2 after the reopening of the exhaust valves 18a at the point Ve and preferably before the closure of these valves. 'exhaust. Therefore, during the intake phase of the engine, only exhaust gases are reintroduced into the combustion chamber between the point Ve and VA2, this reintroduction will be followed by introduction of a mixture of fresh air and recirculated gas between the point Va2 and the closing of the exhaust valves and then only by an intake of fresh air up to the PMBc. As a result, a large amount of flue gas is present in the combustion chamber.

Thanks to the invention, the rate of IGR can be easily controlled by controlling the timing of the intake valves between a setting for a low rate (OO position) and a setting for a high rate (OO position) and that during the intake phase of the engine.

This rate can also be controlled by controlling a variation of lift of the intake valves between a conventional lift and a low lift and / or controlling a variation of the spreading of the lifting of these valves between a conventional spread between two dead spots successive and restricted spreading.

Thus, it is possible, with varying laws of intake valve lift, to control pollutant emissions by adjusting the rate of recirculated flue gas to the operating conditions of the engine. When operating the engine at full load or high loads, it is not necessary to introduce recirculated exhaust gas to the engine intake and the operation of the engine is conventional.

The engine computer 36 then controls, through line 40, the conventional opening and closing of the exhaust valves 18 during the exhaust phase E of the engine between the PMBe and the PMHa. This calculator also controls, during the intake phase A between the PMHa and the PMBc, the control means 24 so as not to make a second lift of the exhaust valves 18 by making the second cam of the shaft inoperative. cams as mentioned above, which keeps in the closed position these exhaust valves.

This engine-calculator also controls the actuating means 34 by the line 42 so that the opening / closing distribution of the intake valves 30 is conventionally performed, as indicated by the dotted curve in FIG. 2.15. The valves thus open in the vicinity of the PMHa and close in the vicinity of the PMBc thus allowing the admission of fresh air only into the combustion chamber.

Thanks to the invention, it is very easy to switch from an engine operation with a reintroduction of exhaust gas with the possibility of adjusting the rate of IGR to conventional operation of this engine, and vice versa.

In the variant of the method as illustrated by the curves of FIG. 3, the quantity of gas re-circulated internally is controlled during the exhaust phase of the engine.

In this variant, the control and actuating means are permuted. Thus, one of the types of valves, here the intake valves 30, is controlled in opening and closing by the control means 24 via the line 40 by making it possible to achieve a fixed double lift of these valves during the operation of the valve. this motor for low and medium loads, or a simple lift during full load operation.

For this, it will also be used control means, VVA camshaft type (Variable Valve Actuation), which allow a permutation between two laws of levies of these valves. Consequently, the other types of valves, the exhaust valves 18, are controlled by the actuating means 34 via the line 42 to open / close by making it possible to produce a variable or at least variable dispensing. law of lifting of these exhaust valves. Also, these actuating means will be of the VVT (Variable Valve Timing) camshaft type which makes it possible to vary the phasing of the lift 30 of these valves.

Thus, when the engine is operating under conditions that require the recirculation of part of the exhaust gases in the combustion chamber, the engine control unit controls the control means 24 and the actuating means 30 to allow them to this recirculation.

Thus, the computer 36 controls the admission control means 24 to perform a double lift of the intake valves 30 by the line 40 and also the actuating means 34 of the exhaust valves 18 to manage the amount of recirculated gas introduced into the combustion chamber during the second lift.

Referring now to Figure 3 which shows the different laws of lift of the intake and exhaust valves of this variant of the process.

As illustrated in this figure, during the exhaust phase E of the engine, the control means 24 are controlled by the engine-calculator to open the intake valves in the vicinity of the PMBe (point Va) and close before the PMHa, as illustrated by curve 30a. The exhaust gases contained in the combustion chamber 12 are evacuated through the intake valves: into the intake manifolds 28 and the intake manifold 32. Of course, the law for lifting the intake valves during this exhaust phase will be established by the skilled person in such a way that these gases can not reach the fresh air intake circuit and more particularly to the air filter (not shown).

During this exhaust phase, the computer 36 also drives the actuating means 34 of the exhaust valves 18 so as to vary the amount of flue gas that is discharged to the intake manifolds and the intake manifold and that can be reintroduced into the combustion chamber during the next intake phase by adapting the rate of IGR to the needs of the engine.

For this, the computer manages the actuating means 34 to modify the law of emergence of the exhaust valves 18 during this exhaust phase E.

As for the example of Figure 2, this change takes place on the phasing of this law through the use of a camshaft with phase shifter. This modification can also occur on the extent of the lifting and / or the spreading of this law in association or not with the modification of the phasing.

The phasage of the exhaust valves 18 oscillates between a position @ and a position O thus making it possible to vary the rate of IGR between a low rate and a high rate.

For the OO position, which corresponds to a low rate of IGR, the exhaust valves 18 open at the point Ve1 before the opening of the intake valves 30a at the point Va which close well before the PMHa while the Exhaust valves arrive at their closed position in the vicinity of this PMHa. In this configuration, the intake valves follow an opening / closing sequence while conventionally they are in the closed position during this exhaust phase. The exhaust gases are thus exhausted in large quantities through the exhaust valves and in small quantities through the intake valves.

It is also possible to open at almost the same time, at point 25 Ve1, the intake and exhaust valves and to close the exhaust valves after the closing of the intake valves.

For the appropriate O position for a high IGR rate, the intake valves 30a are opened at the point Va after the PMBe and the exhaust valves are opened at point Ve2 after this PMBe but before the closure of these valves. intake valves, these exhaust valves being closed in the vicinity of the PMHa. Thus, during this exhaust phase of the engine, only exhaust gases are introduced into the intake manifolds and the intake manifold between point Va and Ve2. The amount of exhaust gas contained in these pipes and the intake manifold is therefore controlled by the law of lift of the exhaust valves.

Thanks to the invention, the rate of IGR can be easily controlled by controlling the setting of the exhaust valves between a setting for a low rate (OO position) and a setting for a high rate (position 02) and this during the exhaust phase E of the engine.

Thus, during the next admission phase A, the intake valves 30 open again in the vicinity of the PMHa and close again in the vicinity of the PMBc. When these intake valves are opened, the exhaust gases contained in the intake manifolds 28 and the intake manifold 32 are reintroduced into combustion chamber 12 through these intake valves. As a result, a mixture of air and recirculated gas is introduced into the combustion chamber during its intake phase.

As already mentioned, during operation of the engine at full load or high loads, it is not necessary to introduce recirculated exhaust gas to the engine inlet and the operation of the latter is conventional.

The engine computer 36 then controls, by the line 42 and the actuating means 34, the conventional opening and closing of the exhaust valves 18 during the exhaust phase E of the engine between the PMBe and the PMHa, as illustrated by the curve in dashed lines. During this exhaust phase, the intake valves are inactive while remaining in their closed position by making the second cam of the camshaft of the control means 24 by the line 40 inoperative.

During the admission phase A, the engine computer also controls the control means 40 via the line 40 so that the opening / closing distribution of the intake valves 30 is conventionally performed, as indicated in FIG. These valves thus open in the vicinity of the PMHa and close in the vicinity of PME3c thus allowing the admission of fresh air only into the combustion chamber.

The present invention is not limited to the example described but encompasses all variants and all equivalents.

Claims (11)

1) Method for controlling the amount of recirculated gas internally in a four-stroke diesel internal combustion engine with an exhaust (E), intake (A), compression (C) and expansion phase (D), said engine comprising a cylinder (10) having a combustion chamber (12), at least one exhaust means (14) with a type of valve, said exhaust (18), controlled by means of exhaust control (24; 34), and at least one intake means (26) with another type of inlet valve (30), controlled by actuating means (34; 24), characterized in that it consists, during operation at low or medium engine loads: - to perform at least one opening / closing sequence of one of the valve types (18, 30) during the phase (A; E) of the engine where this valve is conventionally in the closed position and to perform another opening / closing sequence when the motor operating phase (A; E) where it conventionally follows an opening / closing sequence, - during the phase (A; E) where the opening / closing sequence of said one of the valve types (18, 30) is carried out, to modify the lifting law of the other one of the valve types (30; 18) during this operating phase of the engine wherein said other type of valve conventionally performs an opening / closing sequence, so as to control the amount of exhaust gas in said chamber. 2) A method for controlling the amount of internally recirculated gas according to claim 1, characterized in that it consists in: - performing a sequence of opening / closing of the exhaust valve (18) during the phase of exhaust (E) and to perform at least one opening / closing sequence of this valve during the intake phase (A) to reintroduce exhaust gases into the combustion chamber, - to modify the law of emergence of the intake valve (30) during the intake phase (A) to control the amount of exhaust gas to be reintroduced into said chamber. 3) Process for controlling the amount of internally recirculated gas according to claim 1, characterized in that it consists in: - performing at least one opening / closing sequence of the intake valve (30) during the phase exhaust (E) and to perform a sequence of opening / closing of this valve during the intake phase (A), -to change the law of emergence of the exhaust valve (18) during the phase of exhaust (A) for controlling the amount of exhaust gas to be reintroduced into said chamber. 4) A method for controlling the amount of recirculated gas internally according to one of the preceding claims, characterized in that it consists in modifying the law of lifting of the valve by modifying its phasing. 5) Method for controlling the amount of internally recirculated gas according to one of the preceding claims, characterized in that it consists in modifying the law of lifting of the valve by modifying the value of its lifting. 6) Process for controlling the amount of internally recirculated gas according to one of the preceding claims, characterized in that it consists in modifying the law of lifting of the valve by modifying its spreading. 7) Method for controlling the amount of internally recirculated gas according to one of the preceding claims, characterized in that it consists in modifying the law of lifting of the valve by ending its closing movement substantially simultaneously with the movement closing of the valve which is conventionally in the closed position. 19 8) A method for controlling the intake of an engine according to one of claims 1 to 6, characterized in that it consists in modifying the law of lifting of the valve by completing its closing movement after the closing movement of the valve which is conventionally in the closed position. 9) Process for controlling the amount of internally recirculated gas according to one of the preceding claims, characterized in that it consists in modifying the law of emergence of the valve by beginning its opening movement before the opening movement. of the valve which is conventionally in the closed position. 10) A method for controlling the amount of internally recirculated gas according to one of claims 1 to $, characterized in that it consists in modifying the law of emergence of the valve by beginning its opening movement substantially at the same time that the opening movement of the valve which is conventionally in the closed position. 11) A method for controlling the intake of an engine according to one of claims 1 to 8, characterized in that it consists in modifying the law of emergence of the valve by beginning its opening movement after the movement of opening the valve which is conventionally in the closed position.