FR3058472A1 - METHOD FOR CONTROLLING A SUPERIOR THERMAL MOTOR EQUIPPED WITH A CYLINDER DISCONNECTING MECHANISM - Google Patents

Abstract

The invention relates to a method for controlling a supercharged engine comprising a cylinder disconnection mechanism and a turbocharger, in which a value of engine torque is determined (E0) before disconnection of the cylinders, said torque value corresponding to a first boost pressure setpoint (psural (4)) in an intake manifold connected to the cylinders, one disconnects (E1) a portion of the cylinders and the boost pressure is regulated by acting on a control of the turbocharger, from a second boost pressure setpoint (Psural (2)) necessary to reach said determined torque value before disconnection of the cylinders. An additional compressor is also provided in series with the compressor of the turbocharger, the additional compressor is activated during the disconnection of the cylinders, and the boost pressure is regulated (E3) from said second supercharging pressure setpoint, by acting simultaneously on a control of the additional compressor.

Description

® FRENCH REPUBLIC

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY © Publication number: 3,058,472 (to be used only for reproduction orders) (© National registration number: 16 60707

COURBEVOIE © IntCI ⁸ : F 02 D 23/00 (2017.01), F 02 D 17/00

A1 PATENT APPLICATION

(© Date of filing: 04.11.16. (© Applicant (s): RENAULT S.A.S Joint-stock company (© Priority: simplified - FR. @ Inventor (s): LEFEBVRE ALAIN. (© Date of public availability of the request: 11.05.18 Bulletin 18/19. ©) List of documents cited in the report preliminary research: Refer to end of present booklet (© References to other national documents (73) Holder (s): RENAULT S.A.S Société par actions sim- related: folded. ©) Extension request (s): © Agent (s): RENAULT SAS.

METHOD FOR CONTROLLING A SUPERCHARGED THERMAL ENGINE EQUIPPED WITH A CYLINDER DISCONNECTION MECHANISM.

FR 3 058 472 - A1 (tv) The invention relates to a method for controlling a supercharged combustion engine comprising a cylinder disconnection mechanism and a turbocharger, in which a value of engine torque is determined before disconnection of the cylinders , said torque value corresponding to a first boost pressure setpoint (psural (4)) in an intake manifold connected to the cylinders, a part of the cylinders is disconnected (E 1) and the boost pressure is regulated by acting on a turbocharger control, from a second boost pressure setpoint (Psural (2)) necessary to reach said determined torque value before disconnection of the cylinders. An additional compressor is also provided in series with the turbocharger compressor, the additional compressor is activated when the cylinders are disconnected, and the boost pressure is regulated (E3) from said second boost pressure set point, by acting simultaneously on a command from the additional compressor.

P1

Method for controlling a supercharged combustion engine equipped with a cylinder disconnection mechanism

The present invention relates generally to the field of control of turbocharging systems of internal combustion engines equipped with a cylinder disconnection mechanism allowing the selective disconnection of the engine cylinders.

It relates more particularly to a method for controlling a supercharged thermal engine, the engine comprising combustion cylinders associated with a cylinder disconnection mechanism, and a turbocharger composed of a turbine driven by the exhaust gases at the outlet. cylinders and a compressor coupled in rotation to the turbine in order to increase the quantity of air admitted into the engine cylinders, the method comprising steps of:

- determination of a value of engine torque before the disconnection of a part of the cylinders, said value of engine torque corresponding to a first boost pressure setpoint from which the boost pressure is regulated in a connected intake manifold to cylinders;

- disconnection of part of the cylinders by means of the cylinder disconnection mechanism,

- regulation of the boost pressure by acting on a control of the turbocharger, from a second boost pressure setpoint necessary to reach said value of engine torque determined before disconnection of said part of the cylinders.

In a manner known per se, the cylinder disconnection mechanism associated with the engine cylinders is intended to reduce consumption during certain operating phases, and in particular at partial load. The purpose of this disconnection mechanism, when the engine is operating under predetermined conditions, is to disconnect (that is to say, to stop operating) at least one of the engine cylinders and to operate the engine on only the cylinders remaining, that is to say to produce the engine torque by these only cylinders. The cylinders are disconnected by shutting down the gas intake and exhaust valves.

In the case of an engine supercharged by turbocharger, the disconnection phase of the cylinders causes a certain response time of the turbo5 compressor before it reaches its rotational speed necessary to restore the same level of engine torque as with all cylinders before disconnection, which causes a drop in torque, which is detrimental to the approval of the vehicle.

If the engine operating limits are not reached (richness lower than the maximum admissible richness, injection or ignition advances lower than the maximum advance, etc.), this drop in torque can then be compensated , for example by temporarily increasing wealth, but at the cost of increased consumption and polluting emissions. On the other hand, if the operating limits of the engine are reached, the cylinder disconnection mechanism cannot simply be used, unless the drop in torque, also known as the torque hole, is felt by the driver (in the form of jerks), which is not desirable.

In other words, due to the inertia of the turbocharger supercharging system, the disconnection of the cylinders cannot be effected in all of the engine's operating ranges, but only in those that compensate for the drop in torque linked to the time of response of the turbocharger during monitoring of the boost pressure setpoint allowing the engine torque level to be recovered before disconnection, knowing that such compensation results in peaks of pollutant emission and consumption, which are detrimental to compliance anti-pollution standards.

Also, there is a need to optimize the use of the cylinder disconnection mechanism in an engine supercharged by turbocharger, without degrading engine consumption and without emitting additional pollutants.

To this end, the process of the invention, moreover in accordance with the generic definition given in the preamble above, is essentially characterized in that in that it comprises:

- the provision of an additional compressor in series with the turbocharger compressor,

- the activation of the additional compressor when the cylinders are disconnected, and

- regulation of the boost pressure from the second boost pressure setpoint, acting simultaneously on a command from the additional compressor.

Advantageously, the additional compressor is activated up to its maximum rotation speed when the cylinders are disconnected.

îo Advantageously, the additional compressor is deactivated and short-circuited when the boost pressure reaches the second boost pressure setpoint.

Preferably, the value of engine torque before the disconnection of a part of the cylinders is determined from a map of the boost pressure setpoint in an operating mode of the engine with all the cylinders connected, said map being established in dependent on engine speed and engine torque.

Preferably, the second boost pressure setpoint is determined from a map of the boost pressure setpoint in an engine operating mode with part of the cylinders disconnected, said map being established as a function of the rotation speed of the engine and engine torque.

the invention also relates to a supercharged combustion engine, the engine comprising combustion cylinders associated with a cylinder disconnection mechanism, and a turbocharger composed of a turbine driven by the exhaust gases at the outlet of the cylinders and a compressor coupled in rotation to the turbine in order to increase the quantity of air admitted into the engine cylinders, the engine further comprising an additional compressor in series with the turbocharger compressor and an electronic control unit adapted to implement the process as described above.

Advantageously, the additional compressor is an electric compressor.

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

Other features and advantages of the invention will emerge on reading the description given below, given for information but not limitation, with reference to the accompanying drawings in which:

- Figure 1 schematically illustrates an example of diesel engine architecture, on which the control method of the invention can be implemented;

- Figure 2 is a flowchart describing the control method îo according to the invention.

- Figures 3 and 4 illustrate an example of operation of the supercharging system with and without implementation of the control method of the invention.

FIG. 1 illustrates a supercharged thermal engine 1, of the type with four combustion cylinders 10, 12, 14, 16 in line in the example illustrated. The engine cylinders are associated with a cylinder disconnection mechanism which can be activated to disconnect at least one cylinder in four, for example two cylinders. Disconnected cylinders have their intake and exhaust valves closed and therefore no gas flows through them. As for the non-disconnected cylinders that remain active, they must produce greater torque and therefore require a greater flow of gas at the intake, which requires increasing the pressure at the intake. The engine 1 comprises an intake gas 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 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 gasoline engine, and an intake distributor or intake manifold 24 connected to an intake inlet of the cylinders.

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 post-treatment systems 32, and an exhaust outlet 37 provided with an exhaust flap 38. For example, the post-treatment system 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 turbocharger turbine 31 is coupled in rotation to the main compressor 21 by means of a drive shaft, and it makes it possible to drive the main compressor 21 in rotation when the turbocharger turbine 31 is driven in rotation by the gases d exhaust coming from the exhaust manifold 30.

The turbine 31 is for example 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 fins 310 can be controlled in different closing states so as to modify (decrease or increase) the cross section of the exhaust gases to the turbine 31 and thus modulate the power supplied by the exhaust gases to the turbine 31.

The control signals for this actuator are supplied by an electronic engine control unit, for example a computer (not shown), so as to control the boost pressure prevailing in the intake manifold. The manifold pressure setpoint value is calculated by the electronic control unit. The actual value of the pressure Pcol is measured by means of a pressure sensor placed in the intake manifold 24.

Here, the engine 1 also includes 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 includes 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, between the intake flap 23 and the manifold admission 24.

This EGR-HP circuit 33 makes it possible to take a part of the gases circulating in the exhaust circuit 3 and to reinject them into the engine cylinders in order to reduce the polluting emissions of the engine, more particularly the emissions of nitrogen oxides. This EGR-HP circuit 33 includes an EGR-HP valve 34 for regulating the flow of EGR gas opening into the intake manifold 24.

îo 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.

According to the invention, the heat engine also comprises 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 placed downstream of the main compressor

21, here is preferably an electric compressor driven in rotation by means of an electric motor (not shown). Alternatively, it could also be a mechanical compressor. Unlike the turbocharger, the operation of the additional compressor is independent of the exhaust gases and allows a large amount of air to be supplied to the intake regardless of the engine load level, especially at low load and at low revs.

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 additional compressor 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 electronic control unit implements the control method, which will now be described with reference to FIG. 2, used to regulate the boost pressure during a phase of disconnection of the cylinders, for example when the engine passes from d '' four-cylinder operation towards two-cylinder operation.

In a step E0, the value of the requested engine torque is first determined before the cylinders are disconnected. This engine torque value corresponds to a Psural boost pressure setpoint (4) from which the boost pressure is regulated in the operating mode of the four-cylinder engine, ie with all the cylinders activated.

The boost pressure setpoint value can be mapped according to the engine rotation speed and engine torque.

This map of the boost pressure setpoint in the operating mode of the four-cylinder engine, ie with all the cylinders connected, is stored in the electronic control unit and is used as parameter P1 for characterizing the engine. Knowing the engine speed and the boost pressure, the value of the torque required is determined before the cylinders are disconnected.

In a step E1, the electronic engine control unit controls the disconnection of two cylinders via the cylinder disconnection mechanism, whereby the engine switches from the four-cylinder operating mode to a two-cylinder operating mode.

When the two cylinders are disconnected, the electronic engine control unit controls, in a step E3, the activation of the electric compressor 25, which is therefore put into operation. The boost pressure is then regulated by acting simultaneously on the control of the turbocharger and on the control of the additional compressor so as to allow the response time to be suppressed to reach a boost pressure set point value Psural (2) îo necessary to achieve the same engine torque in the two-cylinder operating mode as that achieved in the four-cylinder operating mode, as determined in step E0.

The Psural boost pressure setpoint (2) to be reached in the two-cylinder operating mode can also be mapped according to the engine rotation speed and engine torque. This map of the boost pressure setpoint in the operating mode of the two-cylinder engine, ie with two cylinders disconnected, is stored in the electronic control unit and is used as parameter P2 for characterizing the engine. Knowing the engine speed and the engine torque required before the cylinders are disconnected, as determined in step E0, the value of the boost pressure pressure Psural (2) to be determined to achieve this torque in the two-cylinder mode is determined. and the boost pressure is regulated from this pressure setpoint by simultaneously controlling the turbocharger and the additional compressor.

Figures 3 and 4 illustrate an example of operation of the supercharging system with and without implementation of the control method of the invention. FIG. 3 illustrates more precisely the evolution of the speed of the turbocharger as a function of time during a disconnection phase of the cylinders and FIG. 4 illustrates the evolution of the boost pressure as a function of time during this same phase.

As illustrated in FIG. 3, without the control method of the invention, when changing from an operating mode of the engine from four to two cylinders after the disconnection of two cylinders, the speed of the turbocharger which is 40,000 rpm / min in the four-cylinder operating mode according to the example, will take approximately 2.5 seconds to reach the speed of 100,000 rpm, necessary to reach the pressure setpoint making it possible to achieve the same level of torque with two cylinders instead of four cylinders before disconnection.

As illustrated in FIG. 4, this results in a response time when monitoring the Psural boost pressure setpoint (2), which will also take 2.5 seconds before reaching the value of 1.8 bar îo necessary according to the example to achieve the same torque as with four cylinders. This response time is due to the inertia of the turbocharger which does not allow instant reaction. This response time will result either in a torque dip harmful to driving pleasure, or by the need to increase the richness of the engine to compensate for this torque dip.

With the control method of the invention, when the engine changes from four-cylinder operation to two-cylinder operation, the electric compressor is activated. The electric compressor has a very short response time, which allows it to compensate for the inertia of the turbocharger and virtually eliminate the response time of the supercharging system to reach the required Psural (2) supercharging pressure setpoint. to achieve the same torque with two cylinders as with four cylinders. As a result, the boost pressure increases almost instantly to the value of 1.8 bar necessary to achieve the same torque as with four cylinders. The virtual absence of response time from the supercharging system thus makes it possible to avoid a sudden drop in torque, which can be fully compensated for by the activation of the electric compressor without degrading engine consumption and without emitting additional pollutants.

Before disconnecting the two cylinders for switching from the four-cylinder operating mode to the two-cylinder operating mode, the additional compressor is in standby, with a rotation speed close to 0 rpm, for example fixed around 10 000 rpm. When the two cylinders are disconnected, the additional compressor is activated and its command consists in activating the additional compressor up to its maximum rotation speed, for example around 70,000 rpm.

In a step E4, once this speed has been reached by the additional compressor, and once the Psural pressure setpoint (2) has been reached to achieve the required engine torque before disconnection, the additional compressor is deactivated and short-circuited. The boost pressure is then ensured by the turbocharger, as is the regulation of this pressure around the Psural pressure setpoint (2).

îo Thanks to the control method of the invention, the drop in torque inherent in the inertia of the turbocharger when a part of the engine cylinders is disconnected, can be compensated for by the actuation of the additional compressor, so that there is almost no more limitation by the maximum admissible wealth. When the control method is implemented, the richness in the cylinders hardly changes when the cylinders are disconnected. The method of the invention therefore makes it possible to extend the use of the cylinder disconnection mechanism to higher speed and load levels, which makes it possible to obtain greater consumption gains.

Claims (8)

1. Method for controlling a supercharged heat engine (1), the engine comprising combustion cylinders (10, 12, 14, 16) associated with a 5 cylinder disconnection mechanism, and a turbocharger composed of a turbine (31) driven by the exhaust gases at the outlet of the cylinders and a compressor (21) coupled in rotation to the turbine in order to increase the quantity of air admitted into the engine cylinders, the method comprising steps of: îo determination (E0) of a value of engine torque before the disconnection of a part of the cylinders, said value of engine torque corresponding to a first boost pressure setpoint (psural (4)) from which the pressure is regulated supercharging in an intake manifold connected to the cylinders; 15 disconnection (E1) of a part of the cylinders by means of the cylinder disconnection mechanism, regulation of the boost pressure by acting on a control of the turbocharger, from a second boost pressure setpoint (Psural ( 2)) necessary to reach said value 20 of engine torque determined before the disconnection of said part of the cylinders, the method being characterized in that it comprises: the provision of an additional compressor (25) in series with the compressor of the turbocharger, 25 activation (E2) of the additional compressor when the cylinders are disconnected, and regulation (E3) of the boost pressure from the second boost pressure setpoint (Psural (2)), acting simultaneously on an additional compressor control. 2. Method according to claim 1, characterized in that the additional compressor (25) is activated up to its maximum rotation speed when the cylinders are disconnected. 3. Method according to claim 1 or 2, characterized in that the additional compressor is deactivated and short-circuited when the boost pressure reaches the second boost pressure setpoint (Psural (2)). 5 4. Method according to any one of the preceding claims, characterized in that the value of engine torque before the disconnection of a part of the cylinders is determined from a map of the boost pressure setpoint in a mode of operation of the engine with all the cylinders connected, said mapping being established as a function of the engine rotation speed and the engine torque. 5. Method according to any one of the preceding claims, characterized in that the second boost pressure setpoint (Psural (2)) is determined from a map of the boost pressure setpoint in an operating mode of the motor with 15 part of the cylinders disconnected, said mapping being established as a function of the engine rotation speed and the engine torque. 6. Supercharged heat engine (1), the engine comprising combustion cylinders (10, 12, 14, 16) associated with a cylinder disconnection mechanism, and a turbocharger composed of a turbine (31) 20 driven by the exhaust gases at the outlet of the cylinders and of a compressor (21) rotatably coupled to the turbine in order to increase the quantity of air admitted into the engine cylinders, the engine further comprising a compressor additional (25) in series with the turbocharger compressor and an electronic control unit adapted to 25 implements the method according to any one of the preceding claims. 7. Motor according to claim 6, characterized in that the additional compressor is an electric compressor. 8. Motor vehicle, characterized in that it comprises an engine according to claim 6 or 7. 1/2 10 12 ¹⁴ Λ VhTp © οσο SW JUUJ r37