EP2010778A1

EP2010778A1 - Device for distributing incoming gases in an internal combustion air supply system

Info

Publication number: EP2010778A1
Application number: EP07731883A
Authority: EP
Inventors: Bertrand Maunoury
Original assignee: Peugeot Citroen Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2006-04-21
Filing date: 2007-04-06
Publication date: 2009-01-07
Also published as: FR2900203B1; WO2007125233A1; JP2009534573A; US20090173320A1; FR2900203A1; US8020539B2

Abstract

The invention relates to a device for distributing the incoming gases in an internal combustion air supply system. This system comprises a fresh air intake pipe (1) and an exhaust gas recirculation intake pipe (2) and the internal combustion engine comprises, for each cylinder, a cylinder head that forms a lid over it, at least one inlet gas intake valve (3, 4) and at least one exhaust valve (5) which are mounted in the cylinder head and, in the case of a multi-cylinder engine, a distributor (7) connecting at least the fresh air intake pipe (1) to the cylinders. In this device, the fresh air intake pipe (1) and the exhaust gas recirculation intake pipe (2) are connected to each of the cylinders independently of one another, each of them (1, 2) via an intake valve (3, 4) dedicated to it (1, 2).

Description

"Apparatus for distributing input gases in an air supply system of an internal combustion engine"

The present invention claims the priority of the French application 0651398 filed on April 21, 2006, the content of which

(description, claims, drawings) is incorporated herein by reference.

The present invention relates to an inlet gas distribution device in an air supply system of an internal combustion engine having one or more cylinders, with recirculation of the exhaust gas.

The present invention applies equally to compression ignition engines as to spark ignition engines.

With regard to the operation of compression ignition engines, also called diesel engines, the recirculation of exhaust gas makes it possible to reduce the discharge of pollutant gases, mainly nitrogen oxides, gases whose thresholds are standardized.

The re-circulation of the exhaust gas, that is to say the reintroduction of a portion of the exhaust gas together with fresh air reduces the emissions of gaseous pollutants. The granting of more and more stringent emission standards makes the use of the process of recirculation of the exhaust gas systematically diesel engine type. It is common to see recirculation rates of the order of 50%, which means that half of the gases drawn by a cylinder of an internal combustion engine are re-circulated exhaust gases.

An internal combustion engine, or heat engine, having one or more cylinders comprises for each cylinder a cylinder head, forming a cover above it, at least one fresh air intake valve and at least one an exhaust valve climb in the breech. Fresh air is supplied to the valves through a volume called plenum or dispatcher. The latter is generally in communication with the exhaust via a valve or a valve. We then speak of an EGR circuit (the English term "exhaust gas recirculation").

While the use of EGR is not yet systematic in spark-ignition type engines, and the recirculation rates are not generally at the high level of diesel engines, its use is seriously considered on a large scale in the long term, particularly for combustion modes based on spontaneous ignition and no longer controlled, the load. The expected benefits of using EGR are mainly associated with a reduction in fuel consumption that allows a lean burn.

The exhaust gas recirculation technique is thus commonly accepted and generally appears satisfactory. However, more in-depth studies of the operation of an internal combustion engine under recirculated air + exhaust gas regimes show that combustion is very sensitive to the heterogeneities of this mixture and to the evolution of the proportion of EGR in the mass of gas admitted into the cylinder.

To improve the homogeneity of air + exhaust gas mixtures, more and more complex systems are developed. In some systems, for example in that used for the diesel engine described in US-A-

6301888, the fresh air is re-circulated to the engine intake valves, to improve the responsiveness of the system.

However, the air supply systems with recirculation of exhaust gas have certain disadvantages related to the conditions necessary for the supply of recirculated exhaust gas from the engine. If the air is admitted with a pressure P in the engine, and that the exhaust gas is discharged at a pressure P ', the flow of the re-circulated exhaust gas will be introduced from the exhaust to the admission only if P 'is greater than P. It can of course play on the acoustics of gases, but it does not allow to install a flow of exhaust fumes re-circulated at high flow. Therefore, the increase of the level of the re-circulated exhaust gases is only possible with the increase of the pressure differential (P '-P).

However, the difference (P '-P) influences the fuel consumption by entering the calculation of the work of the low-pressure loop of the engine cycle, and therefore in its performance.

The object of the invention is to provide simpler means than those used to date for the air supply of an internal combustion engine with re-circulation of the exhaust gas.

The object of the invention is achieved with an inlet gas distribution device in an air supply system of an internal combustion engine having one or more cylinders, the system comprising an intake manifold fresh air and an exhaust gas intake pipe re-circulated, and the internal combustion engine comprising for each cylinder a cylinder head forming a lid above it, at least one gas admission valve inlet and at least one exhaust valve mounted in the cylinder head, and, in the case of a multi-cylinder engine, a distributor connecting at least the fresh air intake manifold to the cylinders. According to the invention, the fresh air inlet pipe and the re-circulated exhaust gas intake pipe are connected to the single cylinder or to each of the cylinders independently of one another, each by a intake valve reserved for her.

[0014] The invention allows more particularly to increase the rate of recirculation of the exhaust gas and thus reduce pollutant emissions. Such an increase can be achieved without inducing a high fuel consumption related to the difference (P '-P), generally necessary to introduce this flow. Similarly, the invention improves the operation and performance of an internal combustion engine, compression ignition or spark ignition, when admitted with a mixture of air + exhaust gas re-circulated. The invention finally makes it possible to improve the transient behavior of the engine during a passage from an operating point with re-circulated exhaust gas to an operating point without re-circulated exhaust gas, and more generally during strong variations of the pressure differential (P'-P).

The device of the invention is shaped to operate essentially according to the principle that the fresh air flow is established only via the pressure P and that the flow of re-circulated exhaust gas is established only via the pressure P .

This arrangement allows to operate with the re-circulated exhaust gas while the pressures P 'and P are equal, which is interesting from a fuel consumption point of view, because it minimizes the work of the loop low pressure of the engine cycle. In addition, this arrangement makes it possible to increase the rate of re-circulated exhaust gases in the cylinder, since the re-circulated exhaust gas flow rate is no longer introduced by the pressure differential (P'-P). but only by the pressure P '.

The device of the invention also improves the homogeneity of the cylinder-by-cylinder inlet gas dosage without having to resort to complex homogenization tools for the two gas streams, respectively the fresh air and the exhaust gases. exhaust re-circulated.

In addition, the device of the invention provides a re-circulated exhaust gas distribution dedicated to each of the engine cylinders. internal combustion. The exhaust valves of the gases lead directly, apart from the possible distributor, to the re-circulated gas admission valves.

This is why the present invention proposes to use, in a multi-cylinder engine, an intake distributor for each flow. At the same time, this design of the invention makes it possible, for the transient aspects, to use a steering strategy of a butterfly valve disposed at the inlet of the re-circulated exhaust gas distributor.

One of the two distributors is in communication with the exhaust via a conventional recirculated exhaust gas circuit: valve or valve with or without water / gas exchanger.

The flow of the exhaust gas re-circulated in the cylinders is therefore directly at the following conditions (P'-Pcyl) -dP where

• P 'is the average pressure in the exhaust manifold,

• Pcyl, the pressure in the cylinder and

• dP the pressure drop in the re-circulated exhaust gas system, adjustable by the previously mentioned valve or valve.

By this device, the re-circulated exhaust gas filling is not dependent on the pressure difference established across the cylinders (P'-P), but (P'-Pcyl).

By means of a throttle, which will be tried to keep closed over most of the range of use of the recirculated exhaust gas, this distributor can also be in communication with the fresh air. In this way, when one will not want to operate with re-circulated exhaust gas, this distributor can be used to bring air to the intake valves dedicated thereto. In a variant of the invention, the throttle may be controlled during the change of engine mode: air + exhaust gas recirculated to air only.

The other distributor is, meanwhile, connected to the fresh air intake line. It is possible to add a butterfly, preferably placed upstream of the two distributors. It will then serve to damp the motor during the stopping phases, or pressure regulator P of the fresh air flow.

By this split distributor device, the air filling is not disturbed by the flow of re-circulated exhaust gas and is performed under the conditions (P-Pcyl).

With this splitter device split in two, the re-circulated exhaust gas arrive directly to the valves via its dedicated distributor, ensuring a good distribution of air and exhaust gas re-circulated cylinder cylinder, without resort to a complex homogenization device. The two mixing and homogenizing functions of the "air" and "recirculated exhaust" streams are provided by the cylinder itself.

The distributor dedicated to the re-circulated exhaust gas will have a suitable volume to support the entire range of use of the engine its demand flow recirculated exhaust gas: typically a volume type aC / N where

• C is the total displacement of the engine,

• N is the number of cylinders, and

A is chosen between 0.3 and 3, preferably around 1.5. The sensitivity related to the volume remaining in the primary ducts: between the valves and the distributor.

The second splitter will have substantially the same volume and will be dedicated to supply the cylinder or cylinders in fresh air. As stated above, a variant of the invention will, using the throttle upstream of the re-circulated exhaust gas distributor (referenced 6 in the drawings), operate by opening it somewhat . This is particularly the case where the air requirements of the cylinders will be such that the flow will not be able to pass through the only distributor dedicated to the air, typically for cases of full load or very high partial loads, or even high speeds. .

In another variant of the invention, the throttle may be controlled during the change of intake mode of the engine (air + exhaust gas re-circulated to air only), in order to gain in dynamics, the gain being all the more important as the rate of re-circulated gas is important.

When passing air + exhaust gas re-circulated to air alone, the butterfly will remain closed until the air distributor is close to its operating conditions, that is to say up to its saturation in volume flow. After that, the distributor initially dedicated to the re-circulated exhaust gas can be opened to fresh air. This increases the reactivity of the air loop by minimizing the recirculated exhaust gas flow effect of the dedicated distributor.

Depending on the dynamics of the re-circulated exhaust butterfly, it will be necessary to anticipate the saturation. In this case, the test dQ / dt> 0 will be replaced by dQ / dt> n, n being a setpoint value calibrated as representative of the need for approval.

Finally, advantageously, the system thus described may be associated with a variable valve-by-valve distribution system making it possible to better control the flow rates of air and re-circulated exhaust gas and thus the gas rate of exhaust recirculated in the cylinder. In the accompanying drawings, the main features of the present invention will be represented as follows:

FIG. 1 schematically represents a device of the invention in operating position with recirculated exhaust gas,

[0038] FIG. 2 shows the device of FIG. 1 in operation with fresh air alone,

FIG. 3 is an exemplary embodiment of a device of the invention and,

[0040] Figure 4 shows a diagram of the control logic of a butterfly valve EGR.

The inlet gas distribution device according to the invention is shown in Figures 1 and 2 for a two-cylinder engine C1 and C2. The system comprises a fresh air intake manifold 1, a re-circulated exhaust gas intake manifold 2, and an exhaust manifold 11 from which the gas intake manifold is derived. re-circulated exhaust. The engine further comprises for each cylinder a cylinder head forming a lid above it, two inlet gas inlet valves 3, 4 and an exhaust valve 5 mounted in the cylinder head. The fresh inlet manifold 1 is connected to the cylinders C1, C2 by means of a distributor 7 and, likewise, the re-circulated exhaust gas intake pipe 2 is connected to the cylinders C1, C2 with a distributor 8.

According to the invention, the fresh air inlet pipe 1 is connected to the cylinders C1, C2, furthermore by the distributor 7 with its two branches 7A, 7B, by dedicated intake valves 3. similarly, the re-circulated exhaust gas intake pipe 2 is connected to the cylinders C1, C2, further by the distributor 8 with its two branches 8A, 8B, by dedicated valves 4.

Thus, each of the two branches of the two distributors 7 and 8 is connected to the corresponding cylinder C1 or C2 respectively by the first intake valves 3 or by second intake valves 4.

Advantageously, as shown in Figures 1 and 2, the re-circulated exhaust gas intake pipe 2 comprises a first butterfly valve 6 for controlling a passage between the fresh air inlet pipe 1 and the re-circulated exhaust manifold 2. The first butterfly valve 6 is controlled, for example, by the on-board computer or its shaped portion to control the various control functions necessary for the proper operation of the engine.

As clearly shown in Figures 1 and 2, the system of the invention may be equipped with a second butterfly valve 9 disposed in the fresh air intake pipe 1 upstream of the first butterfly valve 6 of the intake manifold of the re-circulated exhaust manifold 2. The second throttle valve 9 is intended to be actuated, for example, during the stopping phases of the engine.

The flow of the part of exhaust gas that is re-circulated is influenced by an EGR valve 10.

When the engine is operating normally with recirculation of the exhaust gas, the EGR valve 10 is open depending on the percentage of exhaust gas in the exhaust gas / fresh air mixture to be reached in the cylinders.

When the engine must be powered only with fresh air, the EGR valve 10 is closed and the first butterfly valve 6 is fully open so that the fresh air, after having passed the second valve 9, may be spread on the fresh air intake manifold 7 and the recirculated gas inlet manifold 8. Figure 3 shows very schematically an intake assembly for a four-cylinder engine. It is more particularly seen the fresh air intake distributor 7 and the exhaust gas distributor re-circulated 8 with the branches respectively referenced 7A, 7B, IC, 7D for the fresh air distributor and the branches referenced 8A, 8B, 8C, 8D for the exhaust gas distributor 8.

FIG. 4 shows a diagram of the piloting logic of an EGR butterfly valve in the case of a transient operation of the "air + exhaust gases re-circulated" zone towards the "annular" zone. This diagram includes the test test dQ / dt> 0 which, as explained above, can be replaced by the test dQ / dt> n, where n is a setpoint value calibrated as representative of the need for approval.

Claims

1. Apparatus for distributing the inlet gases in an air supply system of an internal combustion engine having one or more cylinders (C1, C2), the system comprising a fresh air intake manifold (1 ) and a re-circulated exhaust gas intake manifold (2), and the internal combustion engine comprising for each cylinder a cylinder head forming a lid above it, at least one gas intake valve inlet (3, 4) and at least one exhaust valve (5) mounted in the cylinder head, the exhaust valves (5) being associated with an exhaust manifold (11) from which a manifold of admission of recirculated exhaust gas, and, in the case of a multi-cylinder engine, a distributor (7) connecting at least the fresh air intake manifold (1) to the cylinders, characterized in that the fresh air inlet pipe (1) and re-circulated exhaust gas pipe (2) are connected to the cylinder dre unique or each cylinder independently of each other, each (1, 2) by an inlet valve (3, 4) reserved for it (1, 2).

2. Device according to claim 1 adapted to an internal combustion engine having at least two cylinders, characterized in that it comprises two distributors (7, 8) one of which (7) connects the air intake manifold cool (1) to the cylinders by first intake valves (3) and the other (8) connects the re-circulated exhaust gas intake (2) to the cylinders by second intake valves (4).

3. Device according to claim 1 or 2, characterized in that the re-circulated exhaust gas intake manifold (2) comprises a first butterfly valve (6) intended to control a passage between the intake manifold. fresh air (1) and the re-circulated exhaust gas manifold (2).

4. Device according to claim 3, characterized in that the fresh air intake pipe (1) comprises a second butterfly valve (9) disposed upstream of the first butterfly valve (6) of the intake manifold. recirculated exhaust gas (2).

5. Device according to claim 3 or 4, characterized in that it comprises control means for controlling the first butterfly valve (6) so as to open the valve (6) entirely during a change of operating mode Mixed air fresh air motor plus exhaust gas recirculates to fresh air only.

6. Device according to any one of claims 2 to 5, characterized in that the two distributors (7, 8) have at least approximately the same volume.

7. Device according to claim 3 or 4, characterized in that it comprises control means for controlling the first butterfly valve (6) so as to open the valve (6) somewhat when the motor is loaded under full load , in high partial load or at high speed.

8. Device according to any one of claims 1 to 7, characterized in that it comprises a variable valve valve distribution system, for controlling cylinder by cylinder respective flow rates of fresh air and exhaust gas re -circulés.

9. Motor vehicle, characterized in that it comprises a device according to any one of claims 1 to 8.