FR3058471A1 - METHOD FOR CONTROLLING A SUPERIOR THERMAL MOTOR COMPRISING AN EXHAUST GAS RECIRCULATION LINE - Google Patents

Abstract

The invention relates to a method for controlling a supercharged engine comprising an intake gas intake circuit (2), a turbocharger compressor (21) and an additional compressor (25), an exhaust system (3) with a variable geometry turbocharger turbine (31) rotatably coupled to the turbocharger compressor (21), and an exhaust gas recirculation circuit (33) to an intake manifold (25) of the exhaust circuit (21). 'admission. In case of activation of the exhaust gas recirculation circuit, if the additional compressor is in operation, geometry change elements (310) of the variable geometry turbine (31) are controlled so as to increase the pressure ( PAVT) at the outlet upstream of the variable geometry turbine, so as to restore a positive pressure difference between the exhaust pressure upstream of the variable geometry turbine and a supercharging pressure in the intake manifold .

Description

® FRENCH REPUBLIC

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY © Publication number:

(to be used only for reproduction orders)

©) National registration number

058 471

60705

COURBEVOIE © IntCI ⁸ : F02 D 21/08 (2017.01), F 02 D 23/00, F 02 M 26/08, 26/10, F 02 B 37/24

A1 PATENT APPLICATION

(§) Date of filing: 04.11.16. (© Applicant (s): RENAULT S.A.S Joint-stock company (30) Priority: simplified - FR and NISSAN MOTOR CO., LTD - JP. @ Inventor (s): LEFEBVRE ALAI. (© Date of public availability of the request: 11.05.18 Bulletin 18/19. (© List of documents cited in the report of preliminary research: Refer to end of present booklet (© References to other national documents (© Holder (s): RENAULT S.A.S Société par actions sim- related: NISSAN MOTOR CO., LTD. ©) Extension request (s): © Agent (s): RENAULT SAS.

METHOD FOR CONTROLLING A SUPERCHARGED THERMAL ENGINE INCLUDING A LINE OF RECIRCULATION OF EXHAUST GASES.

FR 3 058 471 - A1

The invention relates to a method for controlling a supercharged combustion engine comprising an intake gas intake circuit (2), with a turbocharger compressor (21) and an additional compressor (25), an exhaust circuit. (3) with a variable geometry turbocharger turbine (31) rotatably coupled to the turbocharger compressor (21), and an exhaust gas recirculation circuit (33) to an intake manifold (25) of the circuit d 'admission. When the exhaust gas recirculation circuit is activated, if the additional compressor is in operation, elements (310) for changing the geometry of the variable geometry turbine (31) are controlled so as to increase the pressure ( PAVT) at the exhaust upstream of the variable geometry turbine, so as to restore a positive pressure difference between the exhaust pressure upstream of the variable geometry turbine and a boost pressure in the intake manifold .

Γ ¹

1-Λ PCOLL

22 (

23 ^l (24 _{10 12} 14

g ^{21 31} ^ ^etro ' ^sseur |

38

Method for controlling a supercharged combustion engine comprising an exhaust gas recirculation line

The present invention relates generally to the field of recirculation of exhaust gases from the exhaust to the intake of an internal combustion engine.

It relates more particularly to a method for controlling a supercharged combustion engine, the engine comprising:

- combustion cylinders, îo - an intake gas intake circuit comprising a turbocharger compressor and an additional compressor for increasing the quantity of intake gas supplied to an intake manifold of the intake circuit connected to the cylinders,

an exhaust circuit comprising an exhaust manifold connected to the cylinders and a variable geometry turbocharger turbine at the outlet of the exhaust manifold and coupled in rotation to the turbocharger compressor, the engine further comprising a recirculation circuit of the exhaust gas from the exhaust system, between the exhaust manifold and the variable geometry turbocharger turbine, to the intake manifold.

In the case of a supercharged engine as described above, the additional compressor, whether it is an electric compressor driven in rotation by means of an electric motor or a mechanical compressor, which can for example being coupled to the engine crankshaft, cannot be used to increase the quantity of air sent to the intake during certain engine operating phases and, in particular, during the operating phases where the gas recirculation circuit exhaust is activated.

When the additional compressor operates in addition to the turbocharger, the pressure in the intake manifold, called intake pressure, becomes greater than the exhaust pressure. Also, in this configuration, it is no longer possible to have a driving pressure between the exhaust and the intake capable of forcing the flow of gases in the exhaust gas recirculation circuit from the exhaust circuit. exhaust to the intake manifold.

This is why it is not possible to use the additional compressor in phases where the recirculation of exhaust gases to the intake is activated, nor to activate this recirculation when the additional compressor is operating.

The present invention seeks to overcome this limitation.

This objective is achieved by a control method, moreover in accordance with the generic definition given in the preamble above, in which, in the event of activation of the exhaust gas recirculation circuit, if the additional compressor is in operation, elements for changing the geometry of the variable geometry turbine are controlled so as to increase the exhaust pressure upstream of the variable geometry turbine, so as to restore a positive pressure difference between the pressure at the exhaust upstream of the variable geometry turbine and a boost pressure in the intake manifold.

In this way, it is possible to ensure that the exhaust gas recirculation circuit is used simultaneously with the operation of the additional compressor.

Advantageously, elements for changing the geometry of the turbine with variable geometry are controlled from the determination of the pressure upstream of the turbine, for example by means of a pressure sensor disposed in the exhaust circuit upstream of the turbine.

Advantageously, the elements for changing the geometry of the variable geometry turbine comprising movable fins with variable orientation at the inlet of the turbine adapted to be controlled in different closed states so as to modify an exhaust gas passage section towards the turbine, a state of greater closing of the fins is controlled compared to a closing state normally used as a function of the engine speed.

Preferably, the rate of exhaust gas present in the intake gases entering the intake manifold is regulated by means of elements for changing the geometry of the turbine with variable geometry with respect to a setpoint difference between the pressures in the exhaust system upstream of the variable geometry turbocharger turbine and at the intake manifold.

As a variant, it is possible to regulate the rate of exhaust gases present in the intake gases entering the intake manifold by means of the geometry change elements of the variable geometry turbine relative to a gas rate setpoint. exhaust.

Advantageously, the boost pressure is regulated by means of the turbocharger and the additional compressor on a boost pressure setpoint.

The invention also relates to a supercharged heat engine comprising:

- combustion cylinders,

- an intake gas intake circuit comprising a turbocharger and an additional compressor to increase the quantity of intake gas supplied to an intake manifold of the intake circuit connected to the cylinders,

an exhaust circuit comprising an exhaust manifold connected to the cylinders and a variable geometry turbocharger turbine at the outlet of the exhaust manifold and coupled in rotation to the turbocharger compressor, the engine further comprising a recirculation circuit of the exhaust gas from the exhaust system, between the exhaust manifold and the variable geometry turbocharger turbine, to the intake manifold, the engine being characterized in that it comprises control means adapted to control elements for changing the geometry of the variable geometry turbine so as to increase the exhaust pressure upstream of the variable geometry turbine, so as to restore a positive pressure difference between the exhaust pressure upstream of variable geometry turbine and boost pressure at the intake manifold when the exhaust gas recirculation circuit is activated and the additional compressor is in operation.

The invention also relates to a motor vehicle characterized in that it comprises a supercharged heat engine as described above.

- Figure 1 schematically illustrates an internal combustion engine architecture supercharged with air by a turbocharger and comprising an additional compressor, according to a first embodiment according to the invention;

- Figure 2 is a flowchart describing the method of controlling the motor according to the invention.

FIG. 1 illustrates a supercharged thermal engine 1 according to a first embodiment of the invention, of the type with four combustion cylinders 10, 12, 14, 16 in line in the example illustrated. The engine comprises an air intake circuit 2 comprising from upstream to downstream (relative to the direction of flow of the gases): an air filter 20, a turbocharger compressor 21, called the main compressor, which sucks in the ambient air at atmospheric pressure and sends it under pressure to the engine intake, a supercharged air cooler 22 (or RAS), an intake flap 23, such as for example a throttle body in the case of a petrol engine, and an intake manifold or intake manifold 24.

Furthermore, the engine 1 also has an exhaust circuit 3 connected to an exhaust outlet of the engine cylinders, comprising from upstream to downstream (relative to the direction of gas flow): a manifold exhaust 30, a turbocharger turbine 31, one or more exhaust gas after-treatment systems 32 and an exhaust outlet 37 provided with an exhaust flap 38. For example, the after-treatment system for exhaust gas 32 includes a catalyst 320 and a particulate filter 321 located immediately after the catalyst. It may also include a nitrogen oxide (NOx) trap. The exhaust flap 38 makes it possible in particular to control the flow of exhaust gases at the outlet of the exhaust circuit.

The turbocharger turbine 31 is coupled in rotation to the main compressor 21 by means of a drive shaft, and makes it possible to drive the main compressor 21 in rotation to compress the air which enters the intake manifold when the turbine 31 of the turbocharger is driven in rotation by the exhaust gases leaving the exhaust manifold 30.

The turbine 31 is of variable geometry. It includes movable fins with variable orientation 310 at the inlet of the turbine, making it possible to modify the geometry of the turbine so as to influence the flow of exhaust gases on the turbine 31. An actuator (not shown) ) is used to control the orientation of the fins 310 of the turbine. The control signals of this actuator are supplied by an electronic engine control unit, for example a computer. The fins 310 can be controlled in different closed states so as to modify (decrease or increase) the cross section of the exhaust gases towards the turbine and thus modulate the power supplied by the exhaust gases to the turbine.

Here, the engine 1 also comprises a circuit 33 for recirculating the high-pressure exhaust gases, from the exhaust circuit 3 to the intake circuit 2. This recirculation circuit is commonly called the EGR-HP circuit, in accordance with the acronym “Exhaust Gaz”

Recirculation - High Pressure ”. It comprises an inlet which begins in the exhaust circuit 3, between the exhaust manifold 30 and the turbine 31, and an outlet which opens into the intake circuit 2, directly upstream of the intake manifold 24, between the intake flap 23 and the manifold 24.

This EGR-HP circuit 33 makes it possible to take a portion of the gases circulating in the exhaust circuit 3 and to reinject these into the engine cylinders in order to reduce the polluting emissions of the engine, more particularly the emissions of oxides of nitrogen. This EGR-HP circuit 33 includes an EGR-HP valve 34 for regulating the flow of EGR gas opening into the intake manifold 24. When the valve 34 is closed, no EGR gas is introduced into the intake circuit via the EGR-HP 34 circuit. On the other hand, when it is necessary to introduce EGR gases into the fresh air intake circuit via the EGR-HP 34 circuit, the EGR-HP 34 circuit is activated by controlling the opening the valve 34, allowing the passage of a greater or lesser flow of exhaust gas to the intake circuit.

In addition, this EGR-HP circuit 33 is here supplemented by a low pressure exhaust gas recirculation circuit 35, commonly known as the EGR-LP circuit in accordance with the English acronym for "Exhaust Gas Recirculation - Low Pressure" . This EGR-LP circuit begins in the exhaust circuit 3, at the outlet of the post-treatment system 32, and opens into the intake circuit 2, between the air filter 20 and the main compressor 21. This circuit EGR-LP 35 includes an EGR-LP 36 valve to regulate the flow of EGR gas opening into the intake circuit 2.

The heat engine also includes an additional compressor

25, arranged in the intake circuit 2 in series with the main compressor 21. According to the example of FIG. 1, the additional compressor 25 is arranged downstream of the main compressor 21. As a variant, it could be arranged upstream of the main compressor 21 in the intake circuit.

The additional compressor 25 is here an electric compressor driven in rotation by means of an electric motor (not shown). It can also be a mechanical compressor, driven for example by the engine crankshaft. Unlike the turbocharger, the operation of the additional compressor is independent of the exhaust gases and makes it possible to increase the quantity of air at the intake regardless of the engine load level, especially at low load and low speed.

This additional compressor has an inlet 26 and an outlet 27, said inlet 26 being connected in the air intake circuit 2 downstream of the main compressor 21, ie at the outlet of the latter, according to the example in FIG. 1 , and said outlet 27 opening upstream of the air cooler 22.

The additional compressor 25 can be associated with a bypass duct 28 of the intake circuit extending between the inlet 26 and the outlet 27 of the additional compressor 25 and in which a bypass valve 29 is arranged. Thus, when the compressor additional valve 25 is deactivated, by controlling the opening of the bypass valve 29, the additional compressor 25 is short-circuited. On the other hand, when the additional compressor 25 is activated, the bypass valve 29 is closed and the air having the object of a first compression in the main compressor 21, undergoes a second compression in the additional compressor 25.

The engine also includes control means (not shown), which have as input a measurement of the PAVT pressure upstream of the turbine 31 (ie at the input of the EGR-HP circuit 33), obtained by means of '' a pressure sensor, or alternatively, a measure of the EGR rate, i.e. the proportion of exhaust gases present in the intake gases entering the engine's intake manifold 25 via the EGR-HP circuit 33 , and / or an estimate of the pressure difference PAVT-PCOLL between the pressure îo PAVT at the exhaust upstream of the turbine 31 and the pressure PCOLL prevailing in the intake manifold 25. The control means also have for input data a boost pressure setpoint Psural_cible in the intake manifold, developed for example according to the engine speed, and a pressure difference setpoint PAVT-PCOLL_cible between the PAVT pressure at the exhaust upstream of the turbine 31 and the press ion PCOLL in the intake manifold 25 or alternatively an EGR rate setpoint. The control means are adapted to deliver a first control signal making it possible to control the turbocharger and the additional compressor in order to regulate the boost pressure relative to the setpoint. The control means are also suitable for delivering a second control signal making it possible to control the state of closure of the blades with variable orientation of the turbine to ensure the regulation of the EGR rate.

FIG. 2 illustrates the engine control method according to the invention making it possible to provide pollution control via the activation of the EGR-HP circuit 33 and this, simultaneously with the operation of the additional compressor 25.

If a need for activation of the EGR-HP circuit 33 is identified in a step E0, in other words if the introduction of exhaust gases into the intake circuit via the EGR-HP 33 circuit is required to limit the emissions of 'nitrogen oxides of the engine, it is first determined in a step E1, whether the additional compressor 25 is in operation or must be used.

If this is the case, in a step E2, the blades of the turbine 31 are controlled so as to impose a state of closure of the fins, known as the state of greatest closure, corresponding to a state of closure of the fins greater than the closing state normally used to obtain a desired engine load value for a given engine speed value. This state of greatest closure is defined from a first mapping of pre-positioning of the fins which delivers a value of pre-positioning of the fins which can for example be expressed as a percentage of full opening of the fins according to the speed.

On the other hand, if the additional compressor 25 is not in operation, in a step E2 ′ the state of closing of the fins normally used is controlled as a function of the same engine load for an identical speed, for example by means of '' a second map of fin prepositioning mapping.

The state of greater closure of the fins controlled at the inlet of the turbine 31 in step E2 makes it possible to greatly increase the pressure PAVT at the exhaust upstream of the turbine 31, where the EGRHP circuit 33 arises, for a same pressure level PCOLL in the intake manifold 25, downstream of which the EGR-HP line 33 opens. As a result, the pressure difference PAVT-PCOLL becomes positive again, generating a difference in driving pressure between the two ends d line entry and exit

EGR-HP 33, respectively at the exhaust and at the intake, allowing to force the circulation of the recirculation gases through the EGR-HP 33 circuit from the exhaust to the intake.

The control of the fins of the turbine 31 is ensured from the determination of the PAVT pressure at the exhaust upstream of the turbine 31, for example by means of a pressure sensor disposed in the exhaust circuit upstream of the turbine, at the end of the inlet of the EGRHP 33 circuit, capable of supplying a pressure measured at this location. However, the use of this pressure sensor upstream of the turbine can be avoided if other means are available to measure the EGR rate, i.e. the proportion of exhaust gases present in the intake gases. entering the engine intake manifold 25 via the EGR-HP circuit 33, and / or the PAVT-PCOLL pressure difference.

In a step E3, a phase of regulating the boost pressure Psural of the intake gases in the intake manifold is implemented, where the turbocharger and the additional compressor are controlled to constantly reduce the pressure measured in the manifold d admission to the target value Psural_cible.

At the same time, an EGR rate regulation phase is implemented, where the fins of the turbine 31 are controlled to constantly reduce the PAVT-PCOLL pressure difference determined for example from pressure measurements upstream on the one hand, and on the intake manifold îo, on the other hand, on the difference between these pressures PAVTPCOLL_cible. As a variant, in this regulation phase, the fins of the turbine 31 are controlled by measuring the EGR rate, in order to constantly reduce this measured rate to the EGR rate setpoint rate_ of EGR_target.

In a step E4, when the EGR-HP circuit 33 is deactivated, the control process is stopped and the regulations of step E3 are interrupted.

Claims (8)

1. Method for controlling a supercharged heat engine, the engine comprising: 5 - combustion cylinders (10, 12, 14, 16), - an intake gas intake circuit (2) comprising a turbocharger compressor (21) and an additional compressor (25) to increase the quantity of intake gas supplied to an intake manifold (24) of the circuit intake connected to the cylinders, îo - an exhaust circuit (3) comprising an exhaust manifold (30) connected to the cylinders and a turbocharger turbine (31) with variable geometry at the outlet of the exhaust manifold (30 ) and coupled in rotation to the turbocharger compressor (21), the engine further comprising an exhaust gas recirculation circuit (33) from the exhaust circuit, between the exhaust manifold (30) and the turbine variable geometry turbocharger (31), to the intake manifold (24), the method being characterized in that, in the event of activation (E0) of the exhaust gas recirculation circuit, if the additional compressor ( 25) es t 20 in operation, control (E2) is made of elements (310) for changing the geometry of the variable geometry turbine (31) so as to increase the pressure (PAVT) at the exhaust upstream of the variable geometry turbine, so as to restore a positive pressure difference between the exhaust pressure upstream of the variable geometry turbine and a pressure of 25 supercharging in the intake manifold. 2. Method according to claim 1, characterized in that elements (310) for changing the geometry of the variable geometry turbine (31) are controlled from the determination of the pressure (PAVT) upstream of the turbine ( 31), for example by means of a pressure sensor 30 arranged in the exhaust circuit (2) upstream of the turbine (31). 3. Method according to claim 1 or 2, characterized in that the elements (310) for changing the geometry of the variable geometry turbine (31) comprising movable fins with variable orientation at the inlet of the turbine adapted to be controlled in different closing states so as to modify a section for passage of the exhaust gases towards the turbine, a state of greater closing of the fins is controlled (E2) compared to a closing state normally used depending on the speed 5 motor. 4. Method according to any one of claims 1 to 3, characterized in that regulates (E3) the rate of exhaust gas present in the intake gases entering the intake manifold (25) by means elements for changing the geometry of the variable geometry turbine relative to a deviation setpoint (PAVT-PCOLL_target) between the pressures in the exhaust circuit upstream of the variable geometry turbocharger turbine (31) intake manifold level. 5. Method according to any one of claims 1 to 3, characterized in that one regulates (E3) the rate of exhaust gas present 15 in the intake gases entering the intake manifold (25) by means of elements for changing the geometry of the turbine with variable geometry with respect to an exhaust gas rate setpoint (target_EGR_ rate). 6. Method according to any one of claims 4 or 5, characterized in that the boost pressure is controlled by means of the 20 turbocharger and additional compressor on a boost pressure setpoint (Psural_cible). 7. Supercharged heat engine including: - combustion cylinders (10, 12, 14, 16), - an intake gas intake circuit (2) comprising a 25 turbocharger compressor (21) and an additional compressor (25) to increase the quantity of intake gas supplied to an intake manifold (24) of the intake circuit connected to the cylinders, - an exhaust circuit (3) comprising an exhaust manifold (30) connected to the cylinders and a turbocharger turbine (31) with geometry 30 variable at the outlet of the exhaust manifold (30) and coupled in rotation to the turbocharger compressor (21), the engine further comprising an exhaust gas recirculation circuit (33) from the exhaust circuit, between the exhaust manifold (30) and the variable geometry turbocharger turbine (31), towards the intake manifold (24), the engine being characterized in that it comprises control means adapted to control elements ( 310) change of 5 geometry of the variable geometry turbine (31) so as to increase the exhaust pressure (PAVT) upstream of the variable geometry turbine, so as to restore a positive pressure difference between the exhaust pressure in upstream of the variable geometry turbine and a boost pressure at the intake manifold, when the exhaust gas recirculation circuit is activated and the additional compressor (25) is in operation. 8. Motor vehicle characterized in that it comprises a supercharged heat engine according to claim 7. 1/1