DE102016113606A1 - A method of controlling the temperature of an intake manifold of a supercharged internal combustion engine provided with an EGR circuit for returning the exhaust gases at low pressure - Google Patents

Abstract

A method of controlling the temperature of an intake manifold (4) of a supercharged internal combustion engine (1) provided with an EGR circuit (EGRLP) for returning the exhaust gases at low pressure, which provides the saturated vapor temperature (TS) of the exhaust gas Suction line (6) coming gas mixture, which flows through the intake collector (4), and determine the temperature of the Ansaugkollektors (4) in dependence on the comparison between the temperature (TS) of saturated vapor of the suction line (6) coming gas mixture and a desired To control the value of the temperature of the intake collector (4).

Description

Field of engineering

The present invention relates to a method for controlling the temperature of an intake manifold of a supercharged internal combustion engine provided with an EGR circuit for returning the exhaust gases at low pressure.

State of the art

As is known, an internal combustion engine, which is supercharged by means of a turbocharged supercharging system, includes a number of cylinders, each of which is connected to an intake manifold via at least one intake valve and to an exhaust collector via at least one respective exhaust valve. The intake manifold receives via a suction line, a gas mixture, both exhaust gases and exhaust gases and fresh air, d. H. from outside air. Finally, connected to the outlet collector is an outlet conduit which delivers the exhaust gases produced by the combustion to an exhaust system which discharges the gases produced by the combustion into the atmosphere. The internal combustion engine is controlled by an electronic control unit which monitors the functioning of all components of the internal combustion engine.

The supercharging system of the internal combustion engine includes a turbo-compressor provided with a turbine disposed along the exhaust passage to rotate at high speed under the effect of the exhaust gases discharged from the cylinders, and a compressor which is longitudinally driven. disposed in the intake passage and mechanically connected to the turbine to be rotated by the turbine to increase the pressure of existing in the supply line air.

The internal combustion engine also usually includes a high pressure EGR circuit and / or a low pressure EGR circuit, which in turn includes a bypass line provided along the exhaust passage and connected in parallel with the turbo compressor. More specifically, the low-pressure EGR _LP circuit includes a bypass passage that extends from an exhaust passage and opens into the intake passage; In the bypass passage, an EGR valve for regulating the flow rate of the exhaust gases passing through the bypass passage is arranged, and further, in the bypass passage upstream of the EGR valve, there is disposed a heat exchanger having the function of the gases exiting the outlet collector and entering the compressor to cool.

However, the combustion engines described so far, which are provided with the low-pressure EGR circuit, have the serious disadvantage that they are characterized by the formation of condensation, especially in the intake, by the effect of passage of the throughput of the low pressure EGR circuit passing exhaust gases; The formation of condensation is absolutely to be avoided as it can seriously damage the components of the internal combustion engine.

Description of the invention

It is an object of the present invention to provide a method for controlling the temperature of an intake manifold of a supercharged internal combustion engine provided with an EGR circuit for returning the exhaust gases at low pressure, and wherein the disadvantages of the prior art are not present and which is at the same time of simple and economical implementation.

According to the invention, there is provided a method of controlling the temperature of an intake manifold of a supercharged internal combustion engine provided with an EGR circuit for returning the exhaust gases at low pressure, as defined in the appended claims.

Short description of the drawing

The present invention will now be described with reference to the accompanying drawings which illustrate a non-limiting embodiment in which:

the 1 schematically illustrates a supercharged internal combustion engine, which is provided with a low-pressure EGR circuit and with an electronic control unit, which implements the inventive method;

the 2 an enlarged detail of the internal combustion engine of 1 represents; and

the 3 represents the course of the saturation temperature as a function of the saturation pressure.

Preferred embodiments of the invention

In 1 is with the number 1 in its entirety denotes an internal combustion engine which is charged by means of a turbocharger charging system.

The internal combustion engine 1 includes four injectors (injectors) 2 taking the fuel, preferably gasoline, directly into four cylinders 3 injecting each of which has at least one respective intake valve (not shown) with an intake manifold 4 and via at least one respective outlet valve (not shown) with an outlet collector 5 connected is.

The intake collector 4 receives a gas mixture comprising both outlet gases (as described better below) and fresh air, ie ambient air, via a suction line 6 that with an air filter 7 is provided for the fresh air flow and through a throttle 8th is controlled. Longitudinal or in the suction line 6 downstream of the air filter 7 is also an air mass meter 7 * (better known as Air Flow Meter, in 2 shown).

Longitudinal or in the suction line 6 is a charge air cooler (Intercooler) 9 arranged, which has the function of cooling the sucked air and preferably in the suction collector 4 is integrated, as in 2 is shown better. As well as in 2 shown is the intercooler 9 with a conditioning circuit in the intercooler 9 connected cooling liquid, which provides a heat exchanger, a supply pump and a regulating valve, the longitudinal or in a line parallel to the intercooler 9 are arranged. With the outlet collector 5 is an outlet pipe 10 which supplies the exhaust gases produced by the combustion to an exhaust system which discharges the gases produced by the combustion into the atmosphere and normally at least one catalyst 11 (possibly provided with a particulate filter) and at least one (not shown) muffler downstream of the catalyst 11 is arranged.

The supply system of the internal combustion engine 1 includes a turbo compressor 12 that with a turbine 13 is provided, the longitudinal or in the outlet 10 is arranged to move at high speed under the action of the cylinders 3 To turn out exhaust gases emitted, and a compressor 14 , the longitudinal or in the suction line 6 arranged and mechanically with the turbine 13 connected to the turbine 13 to be set in rotation, so that in the supply line 6 existing air pressure is increased.

In or along the outlet pipe 10 is a bypass line 15 provided parallel to the turbine 13 is connected so that its ends upstream or downstream of the turbine 13 are connected; along or in the bypass line 15 is a wastegate valve 16 arranged, which is adapted to regulate the flow or throughput of the outlet gases passing through the bypass line 15 flow, and that of an electric valve 17 is controlled.

The internal combustion engine 1 also includes a bypass line 18 , the longitudinal or in the suction line 6 is provided; the bypass line 18 is parallel to the compressor 14 switched so that their ends upstream or downstream of the compressor 14 are connected. In the bypass line is a valve Poff 19 arranged, which is adapted to regulate the flow of air through the bypass line 18 flows, and that by an electric actuator 20 is controlled.

The internal combustion engine 1 is through an electronic control unit 22 controlled, which the functioning of all components of the internal combustion engine 1 supervised or supervised. The electronic control unit 22 is with sensors 21 connected to the temperature and pressure in the suction line 6 upstream of the compressor 14 measure, and with a sensor 23 which determines the temperature and pressure of the suction line 6 existing gas mixture upstream of the throttle 8th measures, and with a sensor 24 that determines the temperature and pressure inside the suction collector 4 measures, and with a sensor 25 (typically a linear oxygen probe of the UHEGO or UEGO type) of known type and not described in detail and in US Pat 2 shown), the ratio of air / fuel of the exhaust gases upstream of the catalyst 11 measures.

In addition, the electronic control unit 21 be connected to other sensors, for example, the angular position (and thus the speed) of a motor shaft of the engine 1 or to measure the phase of the intake and / or exhaust valves.

The internal combustion engine 1 Finally, it includes a low pressure EGR _LP circuit, which in turn is a bypass line 26 includes that from the outlet pipe 10 , preferably downstream of the catalyst 11 , goes out and in the intake pipe 6 downstream of the air mass meter 7 * opens; the bypass line 26 is parallel to the turbocompressor 12 connected. In the bypass line 26 is an EGR valve 27 arranged, which is adapted to regulate the flow of the outlet gases, which the bypass line 26 flow through. In the bypass line 26 is upstream of the valve 27 also a heat exchanger 29 arranged, which has the function coming out of the outlet collector 5 exiting and in the compressor 14 to cool incoming gases.

Finally, the electronic control unit 22 with a sensor 30 connected, which measures the amount of oxygen that is present in the gas mixture in the intake line 6 flows, and in the intake duct upstream of both the intercooler 9 as well as the throttle 8th is arranged.

As shown in 2 is defined a series of nodes, designated S ₀ , S ₁ , S ₂ , S _3, and S ₄ , which are used to determine the maximum flow rate of the exhaust gases present in the low pressure EGR _LP circuit is returned.

The node S ₀ is located in the intake pipe 6 immediately downstream of the air mass meter 7 * and immediately upstream of the point where the bypass line 26 in the intake pipe 6 empties. The air mass meter 7 * is configured to have at least some characteristic magnitudes of that of the internal combustion engine 1 sucked fresh air flow detected; in particular, the air mass meter 7 * configured to detect the flow rate m _{0 of} the intake fresh air flow, the temperature T _{0 of} the intake fresh air flow, the pressure P _{0 of} the intake fresh air flow, and the psychometric degree φ (or relative humidity) of the intake fresh air flow.

Depending on the temperature T _{0 of} the intake fresh air flow, it is possible, the saturation vapor pressure P _{S0 of} the intake fresh air flow on the in 3 to determine the graphic shown.

X₀

Feuchte des angesaugten Frischluftstroms;

φ

psychometrischer Grad (oder relative Feuchte) des angesaugten Frischluftstroms;

P_S0

Sättigungsdampfdruck des angesaugten Frischluftstroms.

Once the saturation vapor pressure P _{S0 of} the intake fresh air flow is determined, the humidity (il titolo) X _{0 of} the intake fresh air flow can be easily obtained by the following formula: X ₀ = 0.622 × φ × P _S0 / (P ₀ -φ × P _S0 ) [1]

X ₀

Humidity of the intake fresh air stream;

φ

psychometric degree (or relative humidity) of the intake fresh air flow;

P _S0

Saturation vapor pressure of the intake fresh air flow.

m₀

Massendurchsatz des angesaugten Frischluftstroms;

X₀

Feuchte des des angesaugten Frischluftstroms;

m_0A

Durchsatz an trockener Luft des angesaugten Frischluftstroms; und

m_0V

Durchsatz an Dampf des angesaugten Frischluftstroms.

If the humidity x _{0 of} the intake fresh air flow is known, it is possible to obtain both the flow rate m _0A of dry air of the intake fresh air flow and the flow rate m _0V of saturated vapor of the intake fresh air flow through the formulas: m _0A = m ₀ / (1 + X ₀ ) [2] m _0V = m ₀ × X ₀ / (1 + X ₀ ) [3]

m ₀

Mass flow rate of the intake fresh air flow;

X ₀

Humidity of the intake fresh air stream;

m _0A

Throughput of dry air of the intake fresh air stream; and

m _0V

Throughput of steam of the intake fresh air flow.

The node S ₃ is located in the outlet line 10 immediately downstream of the catalyst 11 and immediately upstream of the point at which the bypass line 26 from the drainage line 10a emanates.

m

Gesamtmassendurchsatz an Luft, der den Verbrennungsmotor 1 durchströmt;

m_t

Massendurchsatz an feuchter Luft, die in den Zylindern 3 eingeschlossen ist; und

m_SCAV

Massendurchsatz des ”scavenging” (Spülung); in anderen Worten der Massendurchsatz an Luft, der von der Ansaugleitung 6 über die Zylinder 3 in die Auslassleitung 10 geführt wird, ohne an der Verbrennung teilzunehmen.

In node S ₃ , the relation holds: m = m _t + m _SCAV [4]

m

Total mass flow rate of air, the internal combustion engine 1 flow through;

m _t

Mass flow of moist air in the cylinders 3 is included; and

m _SCAV

Mass flow rate of "scavenging"(flushing); in other words, the mass flow rate of air from the intake pipe 6 over the cylinders 3 in the outlet pipe 10 guided without participating in the combustion.

m_COMBV

Durchsatz an durch die Verbrennung erzeugtem gesättigtem Dampf;

m_t

Massendurchsatz an feuchter Luft, die in den Zylindern 3 eingeschlossen ist;

STECH

stöchiometrisches Verhältnis zwischen der Masse der Luft und der Masse an in die Zylinder eingespritztem Brennstoff, das eine stöchiometrische Verbrennung des Gemischs liefert;

λ

vom Sensor 25 gemessenes Verhältnis Luft/Brennstoff der Auslassgase stromaufwärts des Katalysators 11;

X

Feuchte des Gesamtmassendurchsatzes an Luft, der den Verbrennungsmotor 1 durchströmt; und

á

molares Verhältnis des Dampfs/verbrannten Brennstoffs, unter Betrachtung von Isooktan als verwendetem Brennstoff und gleich 18H₂O/2C₈H₁₈.

The throughput m _{COMBV of} saturated steam produced by the combustion can be calculated as follows: m _COMBV m = _t / (HOLLY · min (1, λ)) * 1 / (1 + X) * A [5]

m _COMBV

Throughput of saturated vapor produced by the combustion;

m _t

Mass flow of moist air in the cylinders 3 is included;

HOLLY

stoichiometric ratio between the mass of the air and the mass of fuel injected into the cylinders that provides stoichiometric combustion of the mixture;

λ

from the sensor 25 measured ratio air / fuel of the outlet gases upstream of the catalyst 11 ;

X

Humidity of the total mass flow rate of air, of the internal combustion engine 1 flow through; and

á

molar ratio of steam / burned fuel, considering isooctane as fuel used and equal to 18H ₂ O / 2C ₈ H ₁₈ .

m_V

Durchsatz an gesättigtem Dampf am Eingang des Verbrennungsmotors 1;

m

Gesamtmassendurchsatz an Luft, der den Verbrennungsmotor 1 durchströmt; und

X

Feuchte des Gesamtmassendurchsatzes an Luft, der den Verbrennungsmotor 1 durchströmt.

The throughput m _V at saturated steam at the entrance of the internal combustion engine 1 is determined by the formula: m _V = m × X / (1 + X) [6]

m _V

Throughput of saturated steam at the entrance of the internal combustion engine 1 ;

m

Total mass flow rate of air, the internal combustion engine 1 flow through; and

X

Humidity of the total mass flow rate of air, of the internal combustion engine 1 flows through.

m_EXV

Durchsatz an gesättigtem Dampf am Auslass;

m_COMBV

Durchsatz an durch die Verbrennung erzeugtem gesättigtem Dampf; und

m_V

Durchsatz an gesättigtem Dampf am Eingang des Verbrennungsmotors 1.

Therefore, the flow m _EXV of saturated vapor at the outlet (ie, in correspondence to the node S ₃ ) can be calculated as follows: m _EXV = m _COMBV + m _V [7]

m _EXV

Throughput of saturated vapor at the outlet;

m _COMBV

Throughput of saturated vapor produced by the combustion; and

m _V

Throughput of saturated steam at the entrance of the internal combustion engine 1 ,

m_COMBV

Durchsatz an durch die Verbrennung erzeugtem gesättigtem Dampf;

m_t

Massendurchsatz an feuchter Luft, die in den Zylindern 3 eingeschlossen ist;

STECH

stöchiometrisches Verhältnis zwischen der Masse der Luft und der Masse an in die Zylinder eingespritztem Brennstoff, das eine stöchiometrische Verbrennung des Gemischs liefert;

λ

von Sensor 25 gemessenes Verhältnis Luft/Brennstoff der Auslassgase stromaufwärts des Katalysators 11;

X

Feuchte des Gesamtmassendurchsatzes an Luft, der den Verbrennungsmotor 1 durchströmt;

á

molares Verhältnis des Dampfs/verbrannten Brennstoffs, unter Betrachtung von Isooktan als verwendetem Brennstoff und gleich 18H₂O/2C₈H₁₈.

m_V

Durchsatz an gesättigtem Dampf am Eingang des Verbrennungsmotors 1;

m

Gesamtmassendurchsatz an Luft, der den Verbrennungsmotor 1 durchströmt; und

X

Feuchte des Gesamtmassendurchsatzes an Luft, die den Verbrennungsmotor 1 durchströmt.

Substituting equations [5] and [6] into equation [7], the saturated vapor _output m _EXV at the outlet is expressed as follows: _EXV m = m _t / (HOLLY · min (1, λ)) * 1 / (1 + X) * A + M · X / (1 + X) [8]

m _COMBV

Throughput of saturated vapor produced by the combustion;

m _t

Mass flow of moist air in the cylinders 3 is included;

HOLLY

stoichiometric ratio between the mass of the air and the mass of fuel injected into the cylinders that provides stoichiometric combustion of the mixture;

λ

from sensor 25 measured ratio air / fuel of the outlet gases upstream of the catalyst 11 ;

X

Humidity of the total mass flow rate of air, of the internal combustion engine 1 flow through;

á

molar ratio of steam / burned fuel, considering isooctane as fuel used and equal to 18H ₂ O / 2C ₈ H ₁₈ .

m _V

Throughput of saturated steam at the entrance of the internal combustion engine 1 ;

m

Total mass flow rate of air, the internal combustion engine 1 flow through; and

X

Humidity of the total mass flow rate of air, the internal combustion engine 1 flows through.

m_EXA

Durchsatz an trockener Luft am Auslass;

m_t

Massendurchsatz an feuchter Luft, die in den Zylindern 3 eingeschlossen ist;

λ

von Sensor 25 gemessenes Verhältnis Luft/Brennstoff der Auslassgase stromaufwärts des Katalysators 11;

X

Feuchte des Gesamtmassendurchsatzes an Luft, der den Verbrennungsmotor 1 durchströmt.

The throughput m _EXA of dry air at the outlet (ie in correspondence with the node S ₃ can be calculated as follows: m _EXA = _mt / (1 + X) * max (0, (λ-1) / λ) [9]

m _EXA

Throughput of dry air at the outlet;

m _t

Mass flow of moist air in the cylinders 3 is included;

λ

from sensor 25 measured ratio air / fuel of the outlet gases upstream of the catalyst 11 ;

X

Humidity of the total mass flow rate of air, of the internal combustion engine 1 flows through.

The node S4 is found in the bypass line 26 immediately downstream of the EGR valve 27 , which is designed to regulate the flow rate of the exhaust gases that bypass the bypass 26 through, and immediately upstream of the point at which the bypass line 26 in the outlet pipe 10 empties.

m

Gesamtmassendurchsatz an Luft, der den Verbrennungsmotor 1 durchströmt;

m_C

Durchsatz an in die Zylinder 3 injiziertem Brennstoff; und

m_SCAV

Massendurchsatz des ”scavenging” (Spülung); in anderen Worten der Massendurchsatz an Luft, der von der Ansaugleitung 6 über die Zylinder 3 in die Auslassleitung 10 geführt wird, ohne an der Verbrennung teilzunehmen.

In node S ₄ , the relation holds: m _EX = m + m _C [10]

m

Total mass flow rate of air, the internal combustion engine 1 flow through;

m _C

Throughput in the cylinder 3 injected fuel; and

m _SCAV

Mass flow rate of "scavenging"(flushing); in other words, the mass flow rate of air from the intake pipe 6 over the cylinders 3 in the outlet pipe 10 guided without participating in the combustion.

m_EGRA

Durchsatz an trockener Luft der Auslassgase, die im EGR_LP-Kreis mit niedrigem Druck zurückgeführt werden;

m_EGRV

Durchsatz an gesättigtem Dampf der Auslassgase, die im EGR_LP-Kreis mit niedrigem Druck zurückgeführt werden;

m_EGR

Gesamtdurchsatz der Auslassgase, die im EGR_LP-Kreis mit niedrigem Druck zurückgeführt werden;

m_EXA

Durchsatz an trockener Luft am Auslass;

m_EXV

Durchsatz an gesättigtem Dampf am Auslass; und

m_EXV

Durchsatz an gesättigtem Dampf am Auslass.

It is also possible, both the throughput m _EGRA of dry air to the exhaust gases which are recirculated in the EGR _LP circle with a low pressure, as well as the throughput m _EGRV of saturated vapor of the exhaust gases, the recirculated in the EGR _LP circle at low pressure to get over the formulas: m _EGRA = m _EXA · m _EGR / m _EX [11] m _EGRV = m _EXV · m _EGR / m _EX [12]

in _EGRA

Throughput of dry air of the outlet gases, which are recycled in the low pressure EGR _LP circuit;

in the _EGRV

Throughput of saturated vapor of the outlet gases recycled in the EGR _LP circuit at low pressure;

in _EGR

Total flow rate of the outlet gases recycled in the EGR _LP circuit at low pressure;

m _EXA

Throughput of dry air at the outlet;

m _EXV

Throughput of saturated vapor at the outlet; and

m _EXV

Throughput of saturated vapor at the outlet.

X_EGR

Feuchte der in dem EGR_LP-Kreis mit niedrigem Druck zurückgeführten Auslassgase;

m_EGRA

Durchsatz an trockener Luft des Stroms von Auslassgasen, der im EGR_LP-Kreis mit niedrigem Druck zurückgeführt wird;

m_EGRV

Durchsatz an gesättigtem Dampf des Stroms von Auslassgasen, der im im

EGR_LP-Kreis

mit niedrigem Druck zurückgeführt wird.

Der Knoten S₁ befindet sich in der Ansaugleitung 6 unmittelbar stromaufwärts des Kompressors 14 und unmittelbar stromabwärts des Punkts, an dem die Bypassleitung 26 in die Ansaugleitung 6 mündet.Once the throughput m _EGRA of dry air and the throughput m _EGRV of saturated vapor of the exhaust _{gases recirculated} in the low pressure EGR _LP circuit are determined, it is possible to determine the _{exhaust gas} humidity X _EGR in the EGR _LP Circuit with low pressure, using the following formula: X _EGR = m _EGRV / m _EGRA [13]

X _EGR

Humidity of exhaust gases recycled in the EGR _LP circuit at low pressure;

in _EGRA

Dry air flow rate of outlet gases recycled in the EGR _LP circuit at low pressure;

in the _EGRV

Throughput of saturated steam of the stream of outlet gases, which in im

EGR _LP circle

is returned at low pressure.

The node S ₁ is located in the intake pipe 6 immediately upstream of the compressor 14 and immediately downstream of the point at which the bypass line 26 in the intake pipe 6 empties.

m_EGRV

Durchsatz an gesättigtem Dampf des Stroms von Auslassgasen, der im EGR_LP-Kreis mit niedrigem Druck zurückgeführt wird;

m_V

Durchsatz an gesättigtem Dampf des Gasstroms unmittelbar stromaufwärts des Kompressors 14; und

m_0V

Durchsatz an Dampf des angesaugten Frischluftstroms.

For the flow rate m _V at saturated steam of the stream immediately upstream of the compressor 14 the relation applies: m _V = m _EGRV + m _0V [15]

in the _EGRV

Saturated vapor flow rate of outlet gases recycled in the EGR _LP circuit at low pressure;

m _V

Throughput of saturated vapor of the gas stream immediately upstream of the compressor 14 ; and

m _0V

Throughput of steam of the intake fresh air flow.

m_EGRA

Durchsatz an trockener Luft des Stroms von Auslassgasen, der im EGR_LP-Kreis mit niedrigem Druck zurückgeführt wird;

m_A

Durchsatz an trockener Luft des Gasstroms unmittelbar stromaufwärts des Kompressors 14; und

m_0A

Durchsatz an trockener Luft des angesaugten Frischluftstroms.

For the throughput m _A of dry air of the stream immediately upstream of the compressor 14 on the other hand, the relation holds: m _A = m _EGRA + m _0A [16]

in _EGRA

Dry air flow rate of outlet gases recycled in the EGR _LP circuit at low pressure;

m _A

Throughput of dry air of the gas flow immediately upstream of the compressor 14 ; and

m _0A

Throughput of dry air of the intake fresh air flow.

By substituting Equations [12] and [3] into Equation [15], the saturated steam flow rate m _V of the stream immediately upstream of the compressor 14 be determined.

By substituting the equations [11] and [2] into the equation [16], on the other hand, the throughput m _A of dry air of the stream immediately upstream of the compressor can 14 be determined.

X

Feuchte des Gasstroms unmittelbar stromaufwärts des Kompressors 14;

m_A

mittels der Formel [16] berechneter Durchsatz an trockener Luft des Gasstroms unmittelbar stromaufwärts des Kompressors 14; und

m_V

mittels der Formel [15] berechneter Durchsatz an gesättigtem Dampf des Gasstroms unmittelbar stromaufwärts des Kompressors 14.

The humidity X of the gas flow immediately upstream of the compressor 14 can be calculated using the following formula: X = m _V / m _A [17]

X

Humidity of the gas flow immediately upstream of the compressor 14 ;

m _A

throughput of dry air calculated from the formula [16] of the gas flow immediately upstream of the compressor 14 ; and

m _V

By the formula [15] calculated throughput of saturated vapor of the gas stream immediately upstream of the compressor 14 ,

The humidity X of the gas flow immediately upstream of the compressor 14 can be considered the same as the humidity of the gas stream, the intake collector 4 flows through, assuming that from the compressor 14 up to the cylinders 3 no formation of condensation occurs.

X

Feuchte des Gasstroms, der den Ansaugkollektor 4 durchströmt;

P

Druck des Gasstroms, der den Ansaugkollektor 4 durchströmt; und

P_S

Sättigungsdampfdruck des Gasstroms, der den Ansaugkollektor 4 durchströmt.

Once the humidity X of the gas flow immediately upstream of the compressor 14 and thus the humidity X of the gas flow, the suction collector 14 flows through, is determined, can be determined by means of its derivation from the formula [1], the saturation pressure P _{S of} the gas stream, the suction collector 4 flows through, assuming that the psychometric degree φ (or relative humidity) of the gas flow, the intake collector 4 flows through, equal to 1, by means of the following formula: P _s = (P x) / (0.622 - X) [18]

X

Humidity of the gas flow, the intake collector 4 flow through;

P

Pressure of the gas flow, the intake collector 4 flow through; and

P _S

Saturation vapor pressure of the gas flow, the suction collector 4 flows through.

Depending on the saturation vapor pressure P _S of the intake manifold calculated by the formula [18] 4 permeate gas flow, it is possible, the temperature T _{S of} the saturated steam of the intake manifold 4 flowing gas stream over the in 3 to determine the graphic shown.

The temperature T _{S of} the saturated steam of the intake collector 4 flowing gas flow affects the temperature and flow rate of the cooling liquid in the through the in the suction collector 4 integrated intercooler 9 formed arrangement is used.

The following describes the strategy used by the electronic control unit 22 is implemented to the desired temperature T _obj inside the intake manifold 4 to investigate.

The electronic control unit 22 is set to the desired temperature T _obj inside the intake manifold 4 also depends on the saturated steam temperature T _S of the intake collector 4 to determine flowing gas stream. More specifically, the electronic control unit 22 set to a value of a target temperature T _{E_obj} inside the Ansaugkollektors 4 depending on the engine point investigated; that is, the target temperature T _{E_obj provided} by the engine _controller in the interior of the intake manifold 4 is determined depending on the speed n of the internal combustion engine and the intake power η _ASP . The intake capacity η _ASP is equal to the ratio between the mass of one cylinder 3 for each combustion cycle of trapped air and the mass of reference air (ie the mass of air in the volume of the cylinder contents, uniform with respect to the pressure and the reference temperature). Alternatively, it is possible to replace the intake power η _ASP by the target intake power η _{ASP_obj} provided by the engine controller and by the electronic control unit 22 is determined. Alternatively, it is possible to replace the suction power η _ASP by the torque or the average pressure (indirectly or effectively).

The target temperature T _obj inside the suction collector 4 is thus by the electronic control unit 22 determined as follows: T _obj = max (T _{E_obj} , T _S + Δ) [19] In other words, the target temperature T _obj is inside the intake manifold 4 highest value saturated between the target temperature T _{E_obj} delivered by the engine control unit inside the intake manifold 4 and the sum of the temperature T _{S of} the saturated vapor of the intake collector 4 flowing gas stream with a safety value Δ, preferably a constant size, which is determined experimentally.

The following is from the electronic control unit 22 implemented strategy for avoiding condensation in correspondence of the node S ₁ , located in the suction line 6 immediately upstream of the compressor 14 and immediately downstream of the point at which the bypass line 26 in the intake pipe 6 empties. In other words, below is the one of the electronic control unit 22 described modality to determine the maximum throughput of the outlet gases, which is returned in the EGR _LP circuit with low pressure, which makes it possible to prevent the formation of condensation in correspondence of the node S ₁ , located in the intake pipe 6 immediately upstream of the compressor 14 and immediately downstream of the point at which the bypass line 26 in the intake pipe 6 empties.

T_mix

Temperatur des Gemischs der zwei Gasströme, die sich in Korrespondenz des Knotens S₁ vereinigen;

m_EGR

Durchsatz des Auslassgasstroms, der in dem EGR_LP-Kreis mit niedrigem Druck zurückgeführt wird;

m₀

Druchsatz des angesaugten Frischluftstroms;

T_E

Temperatur des Auslassgasstroms, der in dem EGR_LP-Kreis mit niedrigem Druck zurückgeführt wird; und

T₀

von dem Luftmassenmesser 7* erhaltene Temperatur des angesaugten Frischluftstroms.

To prevent the formation of condensation in correspondence of the node S ₁ , located in the suction line 6 immediately upstream of the compressor 14 and immediately downstream of the point at which the bypass line 26 in the intake pipe 6 First, it is necessary to estimate the temperature T _{mix of} the mixture of the two gas streams merging in correspondence of the node S ₁ according to the following formula: T _mix = (m _EGR * T _E + m ₀ * T ₀ ) / (m _EGR + m ₀ ) [20]

T _mix

Temperature of the mixture of the two gas streams, which unite in correspondence of the node S ₁ ;

in _EGR

Throughput of the outlet gas stream recirculated in the low pressure EGR _LP circuit;

m ₀

Druchsatz of the sucked fresh air flow;

T _E

Temperature of the outlet gas stream recirculated in the low pressure EGR _LP circuit; and

T ₀

from the air mass meter 7 * obtained temperature of the sucked fresh air flow.

Depending on the temperature T _{mix of} the mixture of the two gas streams, which unite in correspondence of the node S ₁ , it is possible, the saturation vapor pressure P _{Smix of} the mixture of the two gas streams, which unite in correspondence of the node S ₁ , over that in the 3 to determine the graphic shown.

X_Smix

Feuchte des Gemischs der zwei Gasströme, die sich in Korrespondenz des Knotens S₁ vereinigen;

φ

psychometrischer Grad (oder relative Feuchte) des Gemischs der zwei Gasströme, die sich in Korrespondenz des Knotens S₁ vereinigen, ist gleich 1;

P_mix

Druck des Gemischs der zwei Gasströme, die sich in Korrespondenz des Knotens S₁ vereinigen; und

P_Smix

Druck der zwei Gasströme, die sich in Korrespondenz des Knotens S₁ vereinigen.

Once the saturation vapor pressure P _{Smix of} the mixture of the two gas streams, which unite in correspondence of the node S ₁ , is determined the moisture X _{Smix of} the mixture of the two gas streams which combine in correspondence of the node S _{1 can be} easily obtained by means of the following formula: X _Smix = 0.622 · φ · P _Smix / (P _mix - φ · P _Smix ) [21]

X _Smix

Humidity of the mixture of the two gas streams which unite in correspondence of the node S ₁ ;

φ

psychometric degree (or relative humidity) of the mixture of the two gas streams which unite in correspondence of the node S ₁ is equal to 1;

P _mix

Pressure of the mixture of the two gas streams, which unite in correspondence of the node S ₁ ; and

P _Smix

Pressure of the two gas streams, which unite in correspondence of the node S ₁ .

m_Vlim

maximaler Durchsatz des gesättigten Dampfs des Gemischs der zwei Gasströme, die sich in Korrespondenz des Knotens S₁ vereinigen;

X_Smix

Feuchte des Gemischs der zwei Gasströme, die sich in Korrespondenz des Knotens S₁ vereinigen; und

m_a

mittels der Formel [14] berechneter Durchsatz an trockener Luft des Gasstroms unmittelbar stromaufwärts des Kompressors 14.

If the humidity X _{Smix of} the mixture of the two gas streams _merging in correspondence of the node S _{1 is} known, it is possible to determine the maximum flow rate m _{Vlim of} the saturated vapor of the mixture of the two gas streams which are in correspondence of the node S ₁ unite to get over the formula: m _Vlim = X _Smix · m _a [22]

m _Vlim

maximum flow rate of the saturated vapor of the mixture of the two gas streams which combine in correspondence of the node S ₁ ;

X _Smix

Humidity of the mixture of the two gas streams which unite in correspondence of the node S ₁ ; and

m _a

throughput of dry air calculated from the formula [14] of the gas flow immediately upstream of the compressor 14 ,

The maximum flow rate m _Vlim of saturated vapor of the mixture of the two gas streams which unite in correspondence of the node S ₁ is therefore accompanied by the product of the moisture X _{Smix of} the mixture of the two gas streams which unite in correspondence with the node S ₁ the throughput m _{a of} the dry air of the gas stream obtained by the formula [14] immediately upstream of the compressor 14 receive.

m_EGRVlim

Durchsatz an gesättigtem Dampf der in dem EGR_LP-Kreis mit niedrigem Druck zurückgeführten Auslassgase;

m_Vlim

maximaler Durchsatz an gesättigtem Dampf des Gemischs der zwei Gasströme, die sich in Korrespondenz des Knotens S₁ vereinigen; und

m_0V

Durchsatz an gesättigtem Dampf des angesaugten Frischluftstroms.

Once the maximum flow rate m _Vlim of saturated vapor of the mixture of the two gas streams _merging in correspondence of the node S _{1 is} determined, it is possible to determine the maximum saturated vapor flow rate of the exhaust _{gases recycled} in the low pressure EGR _LP circuit to get over the formula: m _EGRVlim = m _Vlim - m _0V [23]

m _EGRVlim

Saturated vapor flow rate of the exhaust gases recycled in the EGR _LP circuit at low pressure;

m _Vlim

maximum saturated vapor flow rate of the mixture of the two gas streams combining in correspondence of node S ₁ ; and

m _0V

Throughput of saturated steam of the intake fresh air flow.

m_EGRlim

maximaler Durchsatz der in dem EGR_LP-Kreis mit niedrigem Druck zurückgeführten Auslassgase;

m_EGRVlim

Durchsatz an gesättigtem Dampf der in dem EGR_LP-Kreis mit niedrigem Druck zurückgeführten Auslassgase; und

X_EGR

Feuchte der in dem EGR_LP-Kreis mit niedrigem Druck zurückgeführten Auslassgase.

The maximum flow rate m _EGRlim of the exhaust _{gases recycled} in the EGR _LP circuit at low pressure is therefore obtained by the formula: m _EGRlim = m _EGRVlim * (1-X _EGR ) / X _EGR [24]

m _EGRlim

maximum flow rate of exhaust gases recycled in the EGR _LP circuit at low pressure;

m _EGRVlim

Saturated vapor flow rate of the exhaust gases recycled in the EGR _LP circuit at low pressure; and

X _EGR

Moisture of exhaust gases recycled in the EGR _LP circuit at low pressure.

The electronic control unit 22 is thus designed to determine the target throughput m _EGRobj of the exhaust _{gases recirculated} in the low pressure EGR _{LP circuit} also as a function of the maximum flow rate m _EGRlim of the exhaust _{gases recycled} in the low pressure EGR _{LP circuit} . More specifically, the electronic control unit 22 configured to determine a target flow rate value m _EGRobj of the EGR _LP cycle at low pressure supplied by the vehicle _control in order to optimize consumption and performance. The value of the target flow rate m _EGRengobj of the exhaust _{gases returned} in the EGR _LP circuit at low pressure is determined depending on the engine point under investigation; that is, the targeted value m _{EGRengobj provided} by the engine controller of the _{exhaust gases recirculated} in the low pressure EGR _{LP circuit is determined} depending on the engine speed n and the intake power η _ASP . The intake capacity η _ASP is equal to the ratio between the mass of one cylinder 3 for each combustion cycle of trapped air and the mass of standard reference air present in each cylinder 3 is to be included for each combustion cycle. Alternatively, it is possible to replace the intake power η _ASP by the target intake power η _{ASP_obj} provided by the engine controller and by the electronic control unit 22 is determined. Alternatively it is possible to use the suction power η _ASP to replace the torque or mean pressure (indirect or effective).

The desired flow rate _EGRobj of the exhaust _{gases recirculated} in the EGR _LP circuit at low pressure is therefore provided by the electronic control unit 22 determined as follows: m _EGRobj = min (m _EGRengobj , m _EGRlim + Δ _EGR (T _H2O )) [25] In other words, the target flow rate m _{EGRobj of the exhaust gases recirculated} in the low pressure EGR _{LP circuit} is saturated with the smaller value of the target flow rate m _{EGRengobj provided} by the engine control and the _{exhaust gases discharged} in the low pressure EGR _{LP circuit} the sum of the maximum flow rate m _EGRlim of the exhaust _{gases returned} in the low pressure EGR _{LP circuit} and a safety value Δ _EGR . According to a preferred variant, the safety value Δ _{EGR is} variable as a function of the temperature of the internal combustion engine 1 or from the temperature T _{H2O of} the cooling liquid of the internal combustion engine 1 ,

m_EGR

Durchsatz der in dem EGR_LP-Kreis mit niedrigem Druck zurückgeführten Auslassgase; und

m

Gesamtmassendurchsatz an Luft und Auslassgasen, die im EGR_LP-Kreis mit niedrigem Druck zurückgeführt werden, der den Verbrennungsmotor 1 durchströmt.

Also defined in the following manner is the size R _EGR , which indicates the incidence of the low pressure EGR _LP cycle on the total mass of the gas mixture in the intake manifold 6 flows: R _EGR = m _EGR / m [26]

in _EGR

Flow rate of exhaust gases recycled in the EGR _LP circuit at low pressure; and

m

Total mass flow rate of air and exhaust gases that are returned to the EGR _LP circuit at low pressure, the internal combustion engine 1 flows through.

The electronic control unit 22 is therefore designed to determine the target value of the quantity R _EGRobj , which indicates the low pressure EGR _{LP cycle} incidence on the total mass of the gas mixture in the intake line 6 depending on the maximum flow rate m _EGRlim of the exhaust _{gases recirculated} in the low pressure EGR _{LP circuit} , particularly depending on the ratio between the maximum flow rate m _EGRlim of the exhaust _{gases recirculated} in the low pressure EGR _{LP circuit} and the total mass flow rate m in the air, the internal combustion engine 1 flows through. More specifically, the electronic control unit 22 _configured to determine a value of the quantity R _EGRengobj supplied by the engine control, which indicates the incidence of the EGR _LP circuit with low pressure on the total mass of the gas mixture in the intake line 6 flows to optimize consumption and performance. The value of the size R _EGRengobj , which indicates the low pressure EGR _{LP cycle} incidence on the total mass of the gas mixture in the suction line 6 flows, is determined depending on the examined engine point; that is, the value of the quantity R _{EGRengobj provided} by the engine control, which indicates the incidence of the low pressure EGR _LP cycle on the total mass of the gas mixture, in the intake manifold 6 flows, depending on the speed n of the internal combustion engine and the intake power η _{ASP is} determined. Alternatively, it is also possible in this case to replace the suction power η _ASP by the aspired suction power η _{ASP_obj} provided by the engine controller and by the electronic control unit 22 is determined. Alternatively, it is possible to replace the suction power η _ASP by the torque or the average pressure (indirectly or effectively).

The target value of the size R _EGRobj , which indicates the low pressure EGR _{LP cycle} incidence on the total mass of the gas mixture in the intake manifold 6 flows, is thus from the electronic control unit 22 determined as follows: R _EGRobj = min (R _EGRengobj , m _EGRlim / m + Δ _EGR (T _H2O )) [27] In other words, the quantity R _{EGRobj indicating} the incidence of the low pressure EGR _LP circuit on the total mass of the mixed gas is that in the intake line 6 at the smaller value supplied by the engine control, flows between the quantity R _{EGRengobj indicating} the incidence of the low pressure EGR _LP cycle on the total mass of the gas mixture in the intake manifold 6 and the sum given by a safety value Δ _EGR and a ratio between the maximum flow rate m _EGRlim of the exhaust _{gases recirculated} in the low pressure EGR _{LP circuit} and the total mass flow rate m of air of the internal combustion engine 1 flows through. Also in this case, according to a preferred variant, the safety value Δ _{EGR is} variably dependent on the temperature of the internal combustion engine 1 or the temperature T _{H2O of} the cooling liquid of the internal combustion engine 1 ,

According to a first variant, it is possible, in the preceding discussion, to replace the temperature T _{mix of} the mixture of the two gas streams which unite in correspondence of the node S ₁ with the temperature T _{CAC of} the cooling liquid which is in the intake collector 4 Integrated intercooler is included. In this way it is possible to prevent the formation of condensation in the suction collector 4 to prevent; in other words, the strategy described in the previous discussion allows the temperature T _CAC the cooling liquid used in the in the suction collector 4 integrated charge air cooler is included to determine the maximum flow rate of the exhaust gases recycled in the EGR _LP circuit at low pressure so that the formation of condensation in the intake manifold 4 is prevented.

According to a further variant, it is possible, in the preceding discussion, to replace the temperature T _{mix of} the mixture of the two gas streams which unite in correspondence of the node S ₁ with the temperature of the gas stream in correspondence of the node S ₂ . The node S ₂ is in correspondence of the suction collector 4 downstream of the intercooler integrated in its interior 9 , In this way it is possible the formation of precipitate in the suction collector 4 to avoid; in other words, the strategy described in the previous discussion, which uses the temperature of the gas flow in correspondence of the node S ₂ , allows to determine the maximum flow rate of the exhaust gases recycled in the low pressure EGR _LP circuit to prevent the formation of precipitation the suction collector 4 to avoid.

The following describes the strategy adopted by the electronic control unit 22 and implementing the low pressure EGR _LP circuit start-up sequence to avoid the formation of condensed water, particularly at the coldest components of the internal combustion engine 1 ,

The low pressure EGR _LP circuit is kept off (in other words, the EGR valve becomes 27 for regulating the flow rate in the bypass line 26 _{recirculated exhaust gases are} kept closed, and the flow rate m _EGR of the exhaust gases recirculated in the EGR _LP circuit at low pressure is zero) during the entire time in which the temperature of the internal combustion engine 1 is smaller than a safety value S ₁ , ie, during the entire time in which the temperature T _{H2O of} the cooling liquid of the internal combustion engine is smaller than the safety value S ₁ .

In addition, the EGR _LP circuit is kept off at low pressure (in other words, the EGR valve becomes 27 for regulating the flow rate through the bypass line 26 flowing outlet gases are kept closed, and the flow rate m _EGR of the exhaust gases recirculated in the EGR _LP circuit at low pressure is zero) throughout the time in which the difference between the temperature T _{t of} the gas flow in the intake passage 6 at a point immediately downstream of the compressor 14 and upstream of the suction collector 4 (upstream also the throttle 8th ) and the temperature T ₀ of the air mass meter 7 * detected sucked fresh air flow is less than a safety value S ₂ . The safety values S ₁ and S ₂ are preferably constant values, which are determined experimentally.

The electronic control unit 22 is also configured to measure, via the variable T _off, the time during which the low pressure EGR _LP circuit is kept off (in other words, the time during which the EGR valve is turned off) 27 for regulating the flow rate through the bypass line 26 flowing outlet gases are kept closed and the flow rate m _EGR of the exhaust gases returned in the EGR _LP circuit at low pressure is zero). The variable T _off , which provides an indication of the time taken by the internal combustion engine 1 It is also possible to estimate the amount of condensate that might have formed in the low pressure EGR _LP cycle. At each turn-off, the variable T _{off is} stored in the non-volatile memory of the electronic control unit of the internal combustion engine in the variable T _{off_EE} .

The variable _{Toff_EE} is initialized to zero each time the internal combustion engine is turned on, or as will be better described below, each time the subsequent cleaning phase ends.

At each run of the internal combustion engine, the variable T _off at the smaller value becomes saturated between a variable T _{offMAX indicating} the maximum time during which the low pressure EGR _{LP circuit} is kept off, and the sum of the variable T _{off_EE} and a value Δt _OFF , which measures the dwell time in the off state during the current run.

In other words, the variable T _off at each run of the internal combustion engine 1 calculated as follows: T _off = min (T + .DELTA.t _{off_EE OFF,} T _offMAX) [28] In this way, the variable T _{off is} able to provide an indication of the time taken by the internal combustion engine 1 is consumed to heat up and estimate the amount of condensed water even in the case of a plurality of energizations that are short in time, that may have formed in the low pressure EGR _LP circuit.

Once the internal combustion engine 1 has warmed up, it is possible to gradually open the EGR _LP circuit at low pressure, thereby initiating the cleaning phase. More specifically, the electronic control unit 22 configured to recognize that the internal combustion engine 1 is sufficiently heated when the temperature of the internal combustion engine 1 greater than the safety value S ₁ (ie, when the temperature T _{H2O of} the cooling liquid of the internal combustion engine 1 greater than the safety value S ₁ ) and at the same time the difference between the temperature T _{t of} the gas flow in the intake pipe 6 at a point immediately downstream of the compressor 14 and upstream of the throttle 8th and the temperature T ₀ of the air mass meter 7 * detected intake fresh air flow is greater than the safety value S ₂ .

The low pressure EGR _LP circuit is gradually and progressively opened to allow any condensate that may be present in the low pressure EGR _LP circuit to be purged. In other words, during the cleaning phase, the opening degree of the EGR valve 27 to regulate the bypass line 26 exhaust gases passing through are variable (neither zero nor fully open), and the flow rate m _EGR of the exhaust gases returned in the low pressure EGR _LP circuit is variable (neither zero nor maximum).

The duration of the cleaning phase characterized by a gradual opening of the low pressure EGR _LP circuit is variable depending on the variable T _off , ie the duration of the cleaning phase is determined as a function of the time during which the EGR _LP circuit is low Pressure has remained off.

T_imer

verbliebene Zeit bei der Beendigung der Reinigungsphase;

T_PURCHING

Gesamtdauer der Reinigungsphase und variabel in Abhängigkeit von der Variablen T_off;

Δt

ab dem Beginn der Reinigungsphase verstrichene Zeit; und

Δt_EE

Dauer der Reinigungsphasen der vorhergehenden Einschaltzyklen, bei denen die Funktion g einen umgekehrt proportionalen Verlauf zum Sicherheitswert Δt_OFF aufweist.

In addition, the variable T _{imer is} introduced, which represents the remaining time of the purification _phase and is expressed as follows: T _imer = T _PURGING - Δt - Δt _EE · g (Δt _OFF ) [29]

T _imer

remaining time at the completion of the cleaning phase;

T _PURCHING

Total duration of the cleaning phase and variable depending on the variable T _off ;

.delta.t

elapsed time from the beginning of the cleaning phase; and

Δt _EE

Duration of the cleaning phases of the previous switch-on cycles, in which the function g has an inversely proportional progression to the safety value Δt _OFF .

Δt_EE

Dauer der Reinigungsphasen der vorhergehenden Einschaltzyklen;

Δt

ab dem Beginn der Reinigungsphase verstrichene Zeit; und

Δt_EEold

Dauer der Reinigungsphasen der vorhergehenden Einschaltzyklen, die zuvor in dem nicht flüchtigen Speicher des elektronischen Steuergeräts 22 gespeichert wurde.

The duration .DELTA.t _{EE of} the cleaning phases of the preceding switch-on cycles is in each non-volatile memory of the electronic control unit each time the internal combustion engine 22 saved and is the same: Δt _EE = Δt + Δt _EEold [30]

Δt _EE

Duration of the cleaning phases of the previous switch-on cycles;

.delta.t

elapsed time from the beginning of the cleaning phase; and

Δt _EEold

Duration of the cleaning phases of the previous power cycles, previously in the non-volatile memory of the electronic control unit 22 was saved.

R_EGRengobj

von der Motorsteuerung gelieferte Größe, welche die Inzidenz des EGR_LP-Kreises mit niedrigem Druck auf die Gesamtmasse des Gasgemischs angibt, das in der Ansaugleitung 6 strömt;

R_EGRengobjc

von der Motorsteuerung gelieferte Größe, welche die Inzidenz des EGR_LP-Kreises mit niedrigem Druck auf die Gesamtmasse des Gasgemischs angibt, das in der Ansaugleitung 6 strömt, um die Verbrennung, die Verbräuche und die Emissionen zu optimieren;

R_EGRMAX

maximale Größe, welche die Inzidenz des EGR_LP-Kreises mit niedrigem Druck auf die Gesamtmasse des Gasgemischs angibt, das in der Ansaugleitung 6 strömt, in Abhängigkeit von der Variablen T_imer.

Once the variable T _{imer is} defined, it is possible to determine the value of the quantity R _EGRengobj supplied by the engine control, which indicates the incidence of the low pressure EGR _LP circuit on the total mass of the gas mixture in the intake manifold 6 flows as follows: R _EGRengobj = min (R _EGRengobjc · K (T _imer ), R _EGRMAX (T _imer )) [31]

R _EGRengobj

magnitude provided by the engine control, which indicates the low pressure EGR _LP cycle incidence on the total mass of the gas mixture in the intake manifold 6 flows;

R _EGRengobjc

magnitude provided by the engine control, which indicates the low pressure EGR _LP cycle incidence on the total mass of the gas mixture in the intake manifold 6 flows to optimize combustion, consumption and emissions;

R _EGRMAX

maximum size, which indicates the low pressure EGR _LP cycle incidence on the total mass of the gas mixture in the intake manifold 6 flows, depending on the variable T _imer .

In other words, the R _{EGRengobj provided} by the engine control, which indicates the low pressure EGR _{LP cycle} incidence on the total mass of the mixed gas, is in the intake manifold 6 is equal to the smaller value between the quantity R _EGRengobj supplied by the engine control, which indicates the incidence of the low pressure EGR _LP circuit on the total mass of the gas mixture in the intake pipe 6 flows to optimize the combustion multiplied by the function K (T _imer ), and the maximum size R _EGRMAX , which indicates the incidence of the low pressure EGR _LP circuit on the total mass of the gas mixture in the intake line 6 flows, as a function of the variable T _imer .

The function K (T _imer ) has a gradient that tends to be inversely proportional to the variable T _imer . More specifically, the function K (T _imer ) _assumes a value equal to zero at the beginning of the _{purge phase of the} low pressure EGR _{LP circuit and progressively increases as the purge phase terminates} until it reaches a value of 1 reached at the end of the cleaning phase.

Once the cleaning phase is completed, the EGR _LP circuit is fully opened at low pressure. More specifically, the electronic control unit 22 configured to recognize that the cleaning _phase is completed when the variable T _imer , which represents the remaining time of the cleaning _phase , is zero and the function K (T _imer ) assumes the value 1. Opening the EGR valve 27 for regulating the flow rate of the bypass line 26 _{effluent exhaust gases} (ie, the flow rate _EGR of the exhaust gases returned in the low pressure EGR _LP circuit) are determined as a function of the target value of the quantity R _EGRengobj , which is the incidence of the low pressure EGR _LP circuit on the total mass of the exhaust gas the suction line 6 indicates flowing gas mixture, as calculated for example by means of the formula [27].

Each time the supercharged internal combustion engine is switched off 1 the variable T _{off is} stored in a non-volatile memory in a variable T _{off_EE} . The value .DELTA.t _OFF, which counts the time of staying in the off state to the run is each time the internal combustion engine 1 set to zero. The variable T _off is determined as the minimum value between a maximum value T _offMAX and the sum of the variable T _{off_EE} and the value Δt _off indicating the time of remaining in the off state. The variable T _{off_EE} is _activated each time the internal combustion engine is switched on 1 set to zero. The variable T _{off_EE} is _set to zero at the end of the cleaning _interval T _purging .

And the procedure envisages the time since the end of the closing phase of the EGR valve 27 has elapsed, and to measure the time Δt of remaining in the cleaning phase; at the end of the run, the sum of the elapsed time from the end of the closing phase of the EGR valve 27 and to store the time Δt of remaining in the cleaning phase in a variable Δt _EE ; the difference between the duration of the cleaning _interval T _purching and the elapsed time since the end of the closing phase of the EGR valve 27 to calculate equal to the time .DELTA.t of remaining in the cleaning phase and the variable .DELTA.t _EE multiplied by a function of the value of .DELTA.t _off, indicating the time of staying in the off state, and storing it in a variable T _imer.

The modality of the low pressure EGR _LP circuit starting process of the electronic control unit 22 implemented and described so far, it is possible to avoid or at least limit the formation of condensation, especially in the coldest components of the internal combustion engine 1 ie in the suction line 6 and in the part of the compressor 14 up to the cylinders 3 ,

Claims (9)

Method for controlling the mass flow rate of an EGR Circuit (EGR _LP ) for the recirculation of low pressure exhaust gases of a supercharged internal combustion engine ( 1 ), wherein the suction collector ( 4 ) via a suction line ( 6 ) receives a mixture of externally-drawn intake fresh air and exhaust gases returned from the EGR circuit (EGR _LP ) for returning the exhaust gases at low pressure; and the supercharged internal combustion engine ( 1 ) a number of cylinders ( 3 ) and a turbocompressor ( 12 ) equipped with a turbine ( 13 ) and a compressor ( 14 ) provided in the suction line ( 6 ) is arranged; the method _{comprising the} steps of: determining a limit value (m _EGRlim ) of the mass flow rate of the EGR circuit (EGR _LP ) for recirculating the outlet gases at low pressure such that the formation of condensed water in the intake line ( 6 ) upstream of the compressor ( 14 ) is prevented; Determining a desired value (m _EGRengobj ) of the mass flow rate of the EGR circuit (EGR _LP ) for returning the exhaust gases at low pressure as a function of the supercharged internal combustion engine ( 1 ) and thus depending on the speed (n) and the suction power (η _ASP ) of the suction equal to the ratio between the in each cylinder ( 3 ) for each combustion cycle trapped air mass and the reference air mass; Comparing the threshold value (m _EGRlim) the mass flow rate of the EGR circuit (EGR _LP) for recycling the exhaust gases at low pressure with the desired value (m _EGRengobj) the mass flow rate of the EGR circuit (EGR _LP) for recycling the exhaust gases at low pressure; and controlling the mass flow rate of the EGR circuit (EGR _LP) for recycling the exhaust gases at low pressure in dependence on the comparison between the limit value (m _EGRlim) the mass flow rate of the EGR circuit (EGR _LP) for recycling the exhaust gases at low pressure and the desired Value (m _EGRengobj ) of the mass flow rate of the EGR circuit (EGR _LP ) for the recirculation of the outlet gases at low pressure; the method being characterized in that the step of determining the limit value (m _EGRlim ) of the mass flow rate of the EGR circuit (EGR _LP ) for returning the outlet gases at low pressure such that the formation of condensed water in the intake line ( 6 ) upstream of the compressor ( 14 ), comprising the following substeps: calculating the maximum flow rate (m _Vlim ) of saturated vapor of the mixture of fresh air drawn in from outside and exhaust gas recirculated from the EGR circuit (EGR _LP ) for the recirculation of the outlet gases at low pressure, by means of the product of the moisture (X _Smix ) of the mixture of fresh air drawn in from outside and of exhaust gas recirculated from the EGR circuit (EGR _LP ) for the recirculation of the outlet gases at low pressure and the throughput (m _A ) of dry one Air of the mixture of outside drawn-in air and outlet gases returned from the EGR circuit (EGR _LP ) for returning the outlet gases at low pressure; Calculate the maximum flow rate (m _EGRVlim ) of _{exhaust gas} vapor returned through the EGR _loop (EGR _LP ) to return the low pressure _{exhaust gases} by the difference between the maximum flow rate (m _Vlim ) of saturated vapor of the mixture fresh air drawn in from the outside and exhaust gases recirculated from the EGR circuit (EGR _LP ) for recirculation of the exhaust gases at low pressure, and the flow rate (m _0V ) to the vapor of the fresh air flow taken in from outside; Calculating the limit value (m _EGRlim ) of the mass flow rate of the EGR circuit (EGR _LP ) for the recirculation of the outlet gases at low pressure such that the formation of condensed water in the intake line ( 6 ) upstream of the compressor ( 14 ) is prevented by means of the maximum flow rate (m _EGRVlim ) of vapor from the exhaust _{gases recirculated} via the EGR circuit (EGR _LP ) to recirculate the exhaust gases at low pressure and the humidity (X _EGR ) of the exhaust _{gases passing} through the exhaust _gases EGR circuit (EGR _LP ) at low pressure. The method of claim 1, and comprising the further step of limiting the EGR circuit mass flow rate (EGR _LP ) to return the low pressure _{exhaust gases} to the smaller value between the EGR circuit mass flow rate limit (m _EGRlim ) (EGR _LP ) for returning the low pressure _{discharge gases} and the target value (m _EGRengobj ) of the mass flow rate of the EGR circuit (EGR _LP ) for returning the exhaust gases at low pressure. A method according to claim 1 or 2, and comprising the further step of summing, to the limit (m _EGRlim ), the mass flow rate of the EGR circuit (EGR _LP ) for returning the low pressure _{discharge gases} , a safety value (Δ), preferably variable depending on the temperature of the internal combustion engine ( 1 ) or the temperature (T _H2O ) of the cooling liquid of the internal combustion engine ( 1 ). Method according to one of the preceding claims, wherein the moisture (X _Smix ) of the mixture of fresh air drawn in from the outside and exhaust _{gases returned} from the EGR circuit (EGR _LP ) for the recirculation of the outlet gases at low pressure is determined by the formula: X _Smix = 0.622 · φ · P _Smix / (P _mix - P _Smix ) [21] X _Smix Moisture _{content of} the mixture of fresh air drawn in from outside and outlet _{gases recirculated} from the EGR circuit (EGR _LP ) for the recirculation of the outlet gases at low pressure; φ psychometric degree (or relative humidity) of the mix of the mixture of outside intake fresh air and outlet gases returned from the EGR circuit (EGR _LP ) for returning the outlet gases at low pressure, equal to 1; P _mix Pressure of the mixture of outside intake fresh air and outlet _gases returned from the EGR circuit (EGR _LP ) for returning the exhaust _gases at low pressure, and P _Smix saturated vapor pressure of the mixture of outside drawn fresh air and exhaust gases , which are returned by the EGR circuit (EGR _LP ) for the recirculation of the outlet gases at low pressure. A method according to claim 4, _{wherein the} saturated steam pressure (P _Smix ) of the external fresh air drawn in and exhaust gas recirculated from the EGR circuit (EGR _LP ) to return the exhaust gases at low pressure vary depending on the Temperature (T _mix ) of the mixture of fresh air drawn in from outside and outlet gases which are returned by the EGR circuit (EGR _LP ) for the recirculation of the outlet gases at low pressure. A method according to claim 5, _wherein the temperature (T _mix ) of the mixture of outside intake fresh air and outlet gases returned from the EGR circuit (EGR _LP ) for recirculating exhaust gases at low pressure is calculated by: T _mix = (m _EGR * T _E + m ₀ * T ₀ ) / (m _EGR + m ₀ ) [20] T _mix temperature of the mixture of fresh air drawn in from outside and outlet gases returned by the EGR circuit (EGR _LP ) for the recirculation of the outlet gases at low pressure; m _EGR flow rate of exhaust gas recirculated from the EGR (EGR _LP ) circuit to recirculate the exhaust gases at low pressure; m ₀ throughput of fresh air intake; T _E temperature of the outlet gas flow recirculated through the EGR circuit (EGR _LP ) for returning the exhaust gases at low pressure; and T ₀ temperature of the sucked fresh air flow. A method according to any one of claims 1 to 4, wherein the pressure (P _Smix ) of saturated vapor of the mixture of outside drawn fresh air and outlet _{gases returned} from the EGR circuit (EGR _LP ) for returning the outlet gases at low pressure Depending on the temperature (T _CAC ) of the cooling liquid is determined in a in the intake collector ( 4 ) integrated intercooler ( 9 ) is used. A method according to any one of claims 1 to 4, _{wherein the} saturated vapor pressure (P _Smix ) of the mixture of outside intake fresh air and outlet _{gases returned} from the EGR circuit (EGR _LP ) for returning the outlet gases at low pressure, depending on the temperature of the gas flow inside the intake collector ( 4 ) and downstream of a charge air cooler ( 9 ), which is inside the suction collector ( 4 ) is integrated. A method according to any one of the preceding claims, wherein the dry air flow rate (m _A ) of the mixture of outside intake fresh air and outlet gases recirculated in the EGR circuit (EGR _LP ) to recycle the low pressure discharge gases the sum of the flow rate (m _EGRA ) of dry air of the outlet _{gas flow recirculated} through the EGR circuit (EGR _LP ) for recirculation of the low pressure _{exhaust gases} and a flow rate (m _0A ) of dry air of the intake fresh air flow.

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