EP3775517A1

EP3775517A1 - Cooling circuit for an internal combustion engine provided with an exhaust gas recirculation circuit and control method therefor

Info

Publication number: EP3775517A1
Application number: EP19711953.0A
Authority: EP
Inventors: Adrien PICARD; Estelle BECQUET; Johan LEFEBVRE; Dominique Lecroq
Original assignee: Renault SAS
Current assignee: New H Powertrain Holding SLU
Priority date: 2018-03-27
Filing date: 2019-03-26
Publication date: 2021-02-17
Also published as: WO2019185663A1; FR3079558A1; FR3079558B1

Abstract

The invention relates to a cooling circuit (10) for an internal combustion engine (12) provided with an exhaust gas recirculation circuit, comprising at least one first, cooling loop (14) associated with the engine (12), a second, heating loop (30) comprising at least one unit heater (34), and a third loop (40) for cooling the exhaust gases, which comprises at least one heat exchanger (42) for cooling the exhaust gases of said recirculation circuit, characterised in that said third loop (40) for cooling the exhaust gases comprises at least one pump (44), heating means (46) for selectively heating the cooling liquid circulating in said third loop (40), and control means (48) which are selectively controlled for isolating the third loop (40) from the rest of the cooling circuit (10). The invention also relates to a method for controlling such a cooling circuit (10).

Description

"Cooling circuit for an internal combustion engine equipped with an exhaust gas recirculation circuit and its control method"

TECHNICAL FIELD OF THE INVENTION

The invention relates to a cooling circuit for an internal combustion engine, in particular for a motor vehicle, equipped with an exhaust gas recirculation circuit and its control method.

The invention more particularly relates to a cooling circuit for an internal combustion engine equipped with an exhaust gas recirculation circuit, in which is intended to circulate a cooling liquid, said cooling circuit comprising at least:

a first cooling loop associated with the engine which comprises at least one pump, means for regulating the circulation of the cooling liquid and a cooling radiator,

a second heating loop which is selectively connected to said first loop by said regulating means and which comprises at least one heater, and

a third exhaust gas cooling loop which, associated with said exhaust gas recirculation circuit, comprises at least one heat exchanger for cooling the exhaust gases of said recirculation circuit.

The invention also relates to a method for controlling such a cooling circuit for an internal combustion engine equipped with an exhaust gas recirculation circuit. STATE OF THE TECH N IQU E

Exemplary of such a cooling circuit for an internal combustion engine which is equipped with an exhaust gas recirculation circuit, commonly known as "EGR", an acronym for "Exhaust", are known from the state of the art. Gas Recirculation "in English.

In an ever more restrictive regulatory context, for example that defined by the future Euro6d and Euro7 European standards, motor vehicles will have to comply with emission thresholds of ever lower pollutants.

These emissions of pollutants such as nitrogen oxides or "NOx", must be in all operating conditions, especially almost from the start of the engine.

In order to meet the standards in force, various solutions have already been developed, such as, for example, equipping the engine exhaust of a vehicle with at least one nitrogen oxides (NOx) aftertreatment system. is in the exhaust gases so as to mimic the discharges into the outside atmosphere of these pollutants.

Non-imitative manner, such as an example of such a post-treatment system, a nitrogen oxide trap or a selective reduction of nitrogen oxides (NOx) catalyst.

However, as the efficiency of these aftertreatment systems is limited, both engines and supercharged diesel engines are generally also equipped with an "EGR" circuit for the recirculation of exhaust gases to the engine intake. .

In known manner, such an "EGR" circuit is able to take part of the exhaust gas (or combustion) of the engine and reintroduce them into the engine air intake circuit, by mixing them with the engine. fresh air admitted into the engine. Advantageously, this results in a lower emission of nitrogen oxides (NOx) in the exhaust gases of the engine, ie at the source, which subsequently makes it possible to reduce the reduction portion. NOx realized by the post-treatment system.

For example, a "high pressure" exhaust gas recirculation circuit further comprises a recirculation duct, connected at one end to the exhaust flow of the engine, at a point upstream of the turbine. a turbocharger of the engine, and at its other end to the engine intake circuit, at a point downstream of the compressor of the turbocharger.

An EGR circuit further includes a valve, commonly referred to as an EGR valve, to control the proportion of exhaust gas that is recycled to the engine intake.

In addition, the temperature of all or part of these exhaust gas recirculated is advantageously controlled using at least one heat exchanger, also called "EGR cooler".

In operation of such an exhaust gas recirculation circuit (EGR), the appearance of a "lacquering phenomenon" explained below is observed.

This lacquering phenomenon occurs more particularly in conditions of use of the engine called "low temperatures", that is to say when the temperatures of the coolant of the engine and / or the engine. ambient air are below 0 ° C, for example between -30 ° C and 0 ° C.

In fact, these conditions of low ambient air temperatures and / or of the engine cooling fluid favor the occurrence of fouling of the EGR valve by unburnt hydrocarbons (HC) which are present in the engine. the exhaust gas. In contact with the cold walls of the recirculation pipe and the EGR valve, these unburnt hydrocarbons (HC) are condensed and then polymerized into very adherent heavy compounds.

Thus, during a cold start in particular, the exhaust gas recirculation circuit is traversed by exhaust gases that are not sufficiently hot (for example at a temperature below 150.degree. clean up these unburnt hydrocarbon deposits.

It is this phenomenon of fouling that is further referred to as "lacquering phenomenon". However, a lacquering of the EGR valve results in a bonding of the shutter of the valve (usually a valve or a flap) on its seat, which prevents the opening of the valve and thus the dosing of gases. recycled exhaust.

This then temporarily or permanently prevents the proper functioning of the exhaust gas recirculation circuit, the user can even be forced to proceed to change the EGR valve.

In addition to the fouling of the EGR valve, there is also the clogging of the heat exchanger associated with the EGR circuit which results in a loss of cooling efficiency, or even clogging.

To fouling is added the formation of acid condensates in the EGR circuit which cause corrosion problems of the elements of the EGR circuit, in particular but not exclusively of the heat exchanger.

Indeed, the use of a cooling fluid at a temperature too cold causes the condensation of a portion of the exhaust gas passing through the heat exchanger.

This is the reason why the heat exchanger associated with the EGR circuit is not generally used until the coolant has reached a certain temperature. However, if a delayed use of the heat exchanger associated with the EGR circuit is justified in the light of the various problems just described, the ever-increasing severity of the legislation requires that the EGR circuit be used inversely. at the earliest, in order to mimic the emissions of nitrogen oxides (NOx) to meet ever more stringent regulatory standards.

As explained above, the most difficult conditions are those of use at low temperatures, especially when the temperatures of the engine coolant and / or the ambient air are below 0 ° C. .

Solutions are therefore being sought to make it possible, on the one hand, to use the heat exchanger associated with the EGR circuit more rapidly in order to be able to reduce the emissions of nitrogen oxides (NOx) so as to meet the standards in terms of emission especially in low temperature conditions, and on the other hand to avoid problems such as lacquering and corrosion.

The object of the invention is in particular to propose a new design of a cooling circuit for an internal combustion engine to solve the aforementioned drawbacks of the state of the art.

BRIEF SUMMARY OF THE INVENTION

For this purpose, the invention proposes a cooling circuit of the type described above, characterized in that said third exhaust gas cooling loop comprises at least one pump, heating means constituted by an immersion heater or an electric heater. adapted to heat the cooling liquid circulating in said third loop and controlled control means selectively to isolate the third loop from the rest of the cooling circuit.

Advantageously, the third exhaust gas cooling loop is temporarily isolated to form a closed loop so as to raise the temperature of the cooling liquid more rapidly by means of associated heating means and independently of the rest of the cooling circuit. .

Thanks to this acceleration of the temperature rise of the cooling fluid in the third cooling loop of the exhaust gas, the heat exchanger can be used more quickly to cool the part of the exhaust gases that are put in recirculation through the exhaust gas recirculation circuit equipping the engine.

Advantageously, the emissions of pollutants such as nitrogen oxides (NOx) are then imitated because of the faster use of the exhaust gas recirculation circuit and this especially in low temperature conditions. in particular cold start of the engine.

Advantageously, the cooling solution reaches more quickly the first threshold temperature at which the cooling of the exhaust gas is started by the heat exchanger so that the cooling is obtained more quickly without exposing itself. the aforementioned drawbacks as the phenomenon of lacquering or corrosion resulting from a condensation of the exhaust gas cooled by the heat exchanger.

According to other features of the circu it of the invention:

the control means of the third loop are selectively controlled between at least one closing position in which the said control means isolate the third loop from the rest of the cooling circuit so that the third loop operates in a closed loop, and an open position in which the third exhaust gas cooling loop is in communication with at least one other loop of the cooling circuit;

the control means are capable of occupying at least one intermediate position between said open and closed positions;

the heating means of the third loop are selectively controlled between an inactive state and an active state in which said heating means heat the cooling liquid;

the cooling circuit comprises means for measuring the temperature for measuring the temperature of the cooling liquid in the third loop as well as the first loop and / or the second loop;

the third exhaust gas cooling loop is connected to the second heating loop;

the first cooling loop associated with the engine comprises at least a first branch, of high temperature, comprising at least the cooling radiator, and a second branch, said low temperature, comprising at least one other cooling radiator. the third exhaust gas cooling loop is connected to the second low temperature branch of the first cooling loop;

the first high temperature branch and the second low temperature branch of the first cooling loop are connected to each other;

the first high temperature branch and the second low temperature branch of the first cooling loop are independent of one another.

The invention also proposes a method for controlling a cooling circuit of an internal combustion engine said cooling circuit comprising at least temperature measuring means capable of measuring the temperature of the cooling element in the third loop, a temperature comparator, said third loop comprising a pump, control means capable of being placed in at least one open position or in a closed position, heating means selectively controlled between an active state and an inactive state, characterized in that said control method comprises at least:

a step of comparing the temperature of the cooling liquid of the third cooling loop with a first temperature of

a control step which consists, when the temperature of the cooling liquid is lower than said first temperature of threshold, to control at least:

The control means in the closed position to isolate the third cooling loop from the rest of the cooling circuit,

The heating means in said active state for heating the cooling liquid to increase the temperature until at least the first temperature is reached; and

• the pump in a running state to ensure circulation of the coolant in the third closed-loop cooling loop.

According to other characteristics of the control method according to the invention:

the control method comprises at least one control step consisting, when the temperature of the cooling liquid is at least equal to the first temperature of the temperature, in controlling the circulating flow of the exhaust gas the engine to establish a circulation desd its exhaust gases through the heat exchanger of the third loop to cool the recirculating exhaust gas;

when the temperature of the cooling liquid is at least equal to the first temperature of the temperature, the control method comprises a control step of controlling at least the heating means in the inactive state to stop heat the cooling liquid;

when the temperature of the cooling liquid is at least equal to the first temperature of the temperature, the control method comprises a control step of controlling at least the heating means in the active state to continue to heating the cooling liquid for a specified period of time or until the temperature of the coolant reaches a given value, such as a second threshold temperature above the first temperature;

when the temperature of the cooling liquid is at least equal to a second threshold temperature higher than the first threshold temperature, the control method comprises a control step of at least controlling the control means in an intermediate position; between the said full open and closed positions to bring the third cooling loop partially in communication with at least one other loop of the cooling circuit having a cooling liquid;

when the temperature of the cooling liquid is at least equal to a second threshold temperature greater than the first temperature of the sensor, the control method comprises a control step of at least controlling the control means in position; opening to fully bring the third cooling loop into communication with at least one other loop of the cooling circuit. BRIEF DESCRIPTION OF F IGU RES

Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

FIG. 1 is a diagrammatic view showing a first embodiment of a cooling circuit according to the invention comprising respectively a first cooling loop of the motor, a second heating loop and a third cooling loop. exhaust gases of an EGR circulating motor and illustrating, with the engine stopped, a circu it in which the third loop of cooling of the exhaust gas is selectively connected by means control at the second heating loop;

FIG. 2 is a schematic view showing the cooling circuit according to FIG. 1 during a first operating phase corresponding to a cold start in low temperature conditions and which illustrates the control means of the third an exhaust gas cooling loop in a closed position in which said third loop is isolated from the remainder of the cooling circuit to operate in a closed loop to accelerate the temperature rise of the cooling die, said cooling fluid passing through the heat exchanger being circulated by the pump and heated by the associated heating means until at least a first threshold temperature is reached from which starts a second operating phase in which a circulation exhaust gas is established through the heat exchanger for cooling with the aid of the cooling liquid; FIG. 3 is a schematic view showing a cooling circuit according to FIG. 1 during a third operating phase during which the temperature of the cooling liquid of the third exhaust gas cooling loop continues to to increase until reaching a second threshold temperature and which illustrates the control means of the third loop occupying at least one of the intermediate positions between said opening and closing positions allowing in this first embodiment to gradually bring said third loop in fluidic relation with the second heating loop, once said second threshold temperature reached by the coolant;

FIG. 4 is a schematic view showing a cooling circuit according to FIG. 1 during a fourth operating phase during which the cooling liquid of the third exhaust gas cooling loop is at a higher temperature; at the second threshold temperature and which illustrates the control means of the third loop occupying an open position in which said third loop is fully in communication with the second heating loop of the cooling circuit;

FIG. 5 is a graph which, for the first embodiment, represents on the ordinate the temperature (in degrees Celsius: ° C) of the coolant as a function of time (in seconds: s) is plotted on the abscissa and which respectively illustrates by a curve (CEGR) the evolution of the coolant temperature in the third cooling loop, by a curve (CMOT) the change in the temperature of the coolant in the first cooling loop and the opening progressive valve forming the regulating means of the third loop; FIG. 6 is a schematic view showing a second embodiment of a cooling circuit according to the invention in which the third exhaust gas cooling loop is connected to a second low temperature branch of the first cooling loop and illustrating another implementation of the third exhaust gas cooling loop than that of the first embodiment of FIGS. 1 to 4;

FIG. 7 is a diagrammatic view that represents a variant embodiment of the cooling circuit according to the second embodiment of FIG. 6 in which the first high temperature branch and the second low temperature branch of the first heating loop. Engine-related cooling is independent of each other.

DETAIL DESCRIPTION LLEE OF F IGU RES

FIGS. 1 to 4 show an example of a cooling circuit 10 for an internal combustion engine 12, especially a motor vehicle, in which a cooling fluid is intended to be selectively circulated.

The cooling circuit 10 is equipped with an exhaust gas recirculation circuit (not shown), commonly known as EGR circulation.

In the remainder of the present description, the term "cooling liquid" should be interpreted broadly as referring to a coolant fluid that can be used not only to cool but also to heat up while realizing calorie intake.

The cooling circuit 10 comprises at least a first cooling loop 14 which is associated with the internal combustion engine 12. The first cooling loop 14 comprises at least one pump 16 for circulating the cooling liquid in the cooling circuit.

The first cooling loop 14 comprises at least a first pipe 18 which is connected to the internal combustion engine 12 to ensure cooling during its operation.

Preferably, the pump 16 is arranged in said first pipe 18, upstream of the internal combustion engine 12. The first cooling loop 14 comprises regulation means 20 for controlling the circulation of the cooling liquid, in particular as a function of operating parameters. of the engine 12.

Preferably, the means 20 for regulating the first cooling loop 14 is a thermostat (or thermostatic valve).

The thermostat is for example of the passive type, that is to say controlled in opening by the coolant when a given threshold temperature is reached. In a variant, the thermostat is controlled so that it can be controlled in opening for more than one threshold temperature.

The regulation means 20 are arranged at the junction of the first pipe 18 with a second pipe 22 in which is arranged a cooling radiator 24.

Advantageously, the first cooling loop 14 comprises a bypass line 26, said bypass, said bypass line 26 being connected to the second pipe 22 respectively upstream and downstream of the radiator 24 cooling.

Preferably, the branch pipe 26 comprises a jar 28 degassing. The cooling circuit 10 comprises a second heating loop 30 comprising at least one main duct 32 in which is arranged a heater 34.

The second heating loop 30 is connected selectively to the first first loop 14, in particular via the regulation means 20.

The main pipe 32 of the second heating loop 30 is connected to the first pipe 18 of the first loop 14, respectively to the level of the regulation means 20 formed by the thermostat and upstream of the pump 16.

The second heating loop 30 comprises at least a first pipe 36 and a second pipe 38 of the iaison with a third loop 40 for cooling the exhaust gas.

The third exhaust gas cooling loop 40 is associated with the circu it (not shown) of exhaust gas recirculation equipping the engine 12.

The third exhaust gas cooling loop 40 comprises at least one heat exchanger 42 for cooling the exhaust gases of said recirculation circuit.

According to the invention, the third exhaust gas cooling loop 40 comprises at least one pump 44 and heating means 46 able to heat the cooling liquid flowing in said third loop.

The pump 44 of the third loop 40 is selectively controlled between a standby state and a running state in which the pump 44 circulates the cooling liquid at least in the third exhaust gas cooling loop 40. .

The means 46 for heating the third exhaust gas cooling loop 40 are selectively controlled between an inactive state and an active state in which said heating means 46 heat the cooling liquid.

The heating means 46 is intended to transfer calories to the cooling liquid of the third loop 40 so as to increase the temperature thereof.

Thanks to the heating means 46, it is possible to accelerate the rise in temperature of the cooling l id and thereby make it possible to use the heat exchanger 42 more rapidly to cool at least part of the exhaust gases. recirculated through the EGR circulation.

The means 46 for heating the third loop 40 are for example selected from a list comprising means such as an immersion heater, an electric heater, an energy storage jar.

Preferably, the heating means 46 of the third loop 40 comprise at least one immersion heater.

The means 46 for heating the third loop 40 may however be constituted by any source capable of transferring calories to the cooling liquid.

The means 46 for heating could also be constituted by a heat recovery device of the type "EH RS" acronym for ("Energy Recovery Heat System") in English.

The third exhaust gas cooling loop 40 has control means 48 which are selectively controlled to isolate the third loop 40 from the rest of the cooling circuit 10, particularly with respect to the part at which the third loop 40 is connected.

The control means 48 for controlling the third loop 40 are selectively controlled between at least:

a closing position in which said control means 48 isolate the third loop 40 from the remainder of the circuit 1 0 of coolant so that the third loop 40 operates in a closed loop, and

an opening position in which the third exhaust gas cooling loop 40 is in fluid connection with at least one other loop of the cooling circuit.

Advantageously, the control means 48 are capable of occupying at least one intermediate position between the said opening and closing positions.

Preferably, the control means 48 consist of at least one valve, such as a three-way valve.

Advantageously, the control means 48 are capable of successively occupying several intermediate positions in order to progressively establish communication between the third loop 40 and the cooling circuit 10 after the third loop 40 has been isolated in order to operate. in closed loop.

Alternatively, the control means 48 are constituted by a thermostat, controlled or not in opening, or any other equivalent control means.

The cooling circuit 10 comprises temperature measuring means for measuring the temperature of the cooling liquid in the third loop 40 and in the first loop 14 and / or the second loop 30.

The third exhaust gas cooling loop 40 comprises temperature measuring means 50, such as at least one sensor, for measuring the temperature of the cooling fluid circulating in said third loop 40.

Preferably, the means 50 for measuring temperature associated with said third loop 40 are arranged upstream of the heat exchanger 42 along the direction of circulation of the cooling liquid. Advantageously, the cooling circuit 1 0 comprises means 52 for measuring temperature, such as at least one sensor, for measuring the temperature of the cooling liquid in at least one of the first and second loop desd ites.

Preferably, the means 52 for measuring temperature are arranged in the first conduit 18, downstream of the engine 1 2.

The means 52 for measuring the temperature are able to measure the temperature of the cooling liquid circulating in the first reactor 18 which is connected on the one hand to the second heating loop 30 and, on the other hand, selectively at the first cooling loop 14 depending on the position of the control means 20.

In this first embodiment, the third exhaust gas cooling loop 40 is selectively connected to the second heating loop 30 through said first condensate 36 and the second condensate conduit 38.

The third exhaust gas cooling loop 40 is intended to operate either in a closed loop or an open loop when said third loop 40 is in total or partial communication with the second heating loop 30.

We will now describe the operation of a cooling circuit 1 0 according to the first embodiment for an internal combustion engine 12 e ipe EGR circuit.

The invention also relates to a method for controlling a cooling circuit 10 for an internal combustion engine 12 with an EGR circulating circuit.

In FIGS. 2 to 4, certain parts of the cooling circuit 10 have been shown with a thicker line in order to facilitate understanding by illustrating the circulation of the cooling element during the different operating phases. As explained in the preamble, the most critical operating conditions correspond to use at low temperatures when the outside temperature and / or that of the coolant is below 0 ° C.

Such conditions are encountered in particular in winter and during a cold start of the engine 12.

The control method comprises at least one step of comparing the temperature T of the cooling solution with a first threshold temperature TS1, preferably the temperature T of the coolant of the third cooling loop 40.

In the example illustrated in FIG. 5, the value of the second threshold temperature TS1 is approximately 20 ° C.

Alternatively, the temperature T of the coolant is measured elsewhere in the cooling circuit.

The temperature T of the cooling fluid of the third cooling loop 40 is advantageously determined by the means 50 for measuring the temperature.

The first temperature TS1 is a reference temperature from which the heat exchanger 42 is used to cool the exhaust gases of said exhaust gas recirculation circuit.

When the temperature T of the cooling liquid is greater than or equal to said first threshold temperature TS1, the control means 48 are then controlled in the open position and the circulating circuit EGR so that the heat exchanger 42 the third loop 40 is traversed by the exhaust gas recirculation to cool them.

On the other hand, when the temperature T of the cooling liquid in the third cooling loop 40 is lower than the first threshold temperature TS1, the heat exchanger 42 of the third loop 40 is not used to cool the cooling gases. 'exhaust. This will also be the case in the low temperature, typically winter conditions, the heat exchanger 42 then not being preferentially used to cool the exhaust gas EGR circuit.

Indeed, the use of the heat exchanger 42 under such conditions would result in problems such as lacquering (fouling) or corrosion in the EGR circuit.

In the absence of use of the EGR circuit with the heat exchanger 42, the amount of pollutants, and especially nitrogen oxides (NOx) emitted by the engine 12, is higher than that obtained when the Heat exchanger 42 is used to cool the exhaust gas.

To remedy this, the invention proposes to accelerate the rise in temperature of the cooling fluid circulating in the third cooling loop 40 in order to be able to use the heat exchanger 42 and thus the EGR circuit more rapidly so as to reduce emissions of nitrogen oxides (NOx).

When the temperature T of the coolant is smaller than said first temperature TS1 of threshold 11, the control method comprises a control step of controlling at least the control means 48 in the closed position.

Controlling the control means 48 in the closed position has the consequence of isolating the third cooling loop 40 from the rest of the cooling circuit 10.

The heating means 46 are then controlled in an active state to heat the cooling liquid to increase the temperature T until it reaches at least the first threshold temperature TS1.

The pump 44 is controlled in a running state to ensure a circulation of the cooling liquid in the third cooling loop 40 which operates in a closed loop.

In a first phase of operation, the third loop 40 is temporarily isolated to form a closed loop so as to accelerate the rise in temperature of the cooling liquid through the heating means 46.

Advantageously, the calories delivered by the heating means 46 are used solely for heating the cooling liquid of the third loop 40, independently of the rest of the cooling circuit 10.

Thanks to this acceleration of the temperature rise of the coolant in the third loop 40, said coolant liqu ide will reach faster the first threshold temperature TS1.

Thus, the heat exchanger 42 can be used more quickly to cool the exhaust gas recirculated through the exhaust gas recirculation circuit equipping the motor 1 2.

Advantageously, the exhaust gas recirculation circuit is then also used more quickly, which is accompanied, according to the desired purpose, a imitation of pollutant emissions such as nitrogen oxides (NOx).

By comparing respectively the curves CEGR and CM OT shown in FIG. 5, it can be seen that the temperature rise of the coolant in the third cooling loop 40 is faster than in the remainder of the circuit 1 0, here in FIG. Conduit 1 8 of the first loop comprising the means 52 for measuring temperature.

Initially, the valve forming the control means 48 being in the closed position, the curve Cv corresponding to the percentage (%) of opening of the valve is at a zero value, equal to zero. The temperature of the cooling liquid in the third cooling loop 40 will increase until at least the first temperature TS1 is reached.

In a second phase of operation, when the temperature T of the cooling fluid is at least equal to said first temperature TS1 de seu il, the control method comprises at least a step of controlling the exhaust gas recirculation circuit Equipping the engine 12 to establish a circulation of its exhaust gas through the heat exchanger 42 of the third loop 40 to cool the exhaust gas recirculation.

Preferably, when the temperature T of the cooling liquid is at least equal to the first temperature TS1 of threshold 11, the control method comprises a control step of controlling at least the heating means 46 in an inactive state. .

The cooling liquid then ceases to be heated with the heating means 46.

The temperature T of the cooling liquid will continue to increase because the exhaust gas cooled in the heat exchanger 42 then transfer calories to it.

As a variant, when the temperature T of the cooling liquid is at least equal to the first temperature TS1 of threshold 11, the control method comprises a control step of keeping the heating means 46 in an active state.

In this variant, the cooling liquid is then heated with the heating means 46, for example for at least a predetermined period of time or until the temperature of the cooling liquid reaches a given value.

As a non-imitative example, the value given is that of a second temperature of only TS2. The cooling fluid of the third loop 40 is then respectively heated by the heating means 46 and by the exhaust gases of the EGR circuit which pass through the heat exchanger 42 to be cooled.

The cooling circuit 10 starts a third phase of operation when the temperature T of the cooling liquid is at least equal to a second threshold temperature TS2.

In the example illustrated in FIG. 5, the value of the second threshold temperature TS2 is approximately 50 ° C.

As illustrated by FIG. 3, the control method then preferably comprises a control step of controlling at least the control means 48 in at least one intermediate position to put the third cooling loop 40 partially in communication with one another. with at least one other loop of the cooling circuit 10.

In the first embodiment, the third cooling loop 40 is gradually brought into communication with the second heating loop 30.

The cooling fluid of the third loop 40 mixes with the cooling liquid of the second heating loop 30.

The temperature of the cooling fluid of the second heating loop 30 is lower than the temperature of the cooling liquid of the third loop 40, ie lower than said second threshold temperature TS2.

The cooling fluid of the third loop 40 will therefore transfer, to the second heating loop 30 comprising the heater 34, the calories absorbed through the heat exchanger 42 during cooling of the exhaust gas EGR circuit.

Advantageously, the increase in the temperature of the cooling cylinder is beneficial for the engine 12 in terms of consumption because it helps to reduce friction and is likely to provide thermal comfort in case of demand.

As illustrated in FIG. 5, the control means 48, advantageously formed by the valve, are controlled to partially open and allow a progressive circulation through the first conduction 36 of the Iaison, the third loop 40 to the second heating loop 30.

After reaching the second temperature TS2 only, the temperature T of the cooling liquid continues to grow.

As illustrated in FIG. 4, the control method then comprises a control step consisting of controlling the control means 48 in the open position to completely bring the third cooling loop 40 in fluid relation with at least one other loop of the cooling circuit.

The cooling fluid circulating in the third exhaust gas cooling loop 40 is then circulated in the remainder of the cooling circuit 10 so that its rise in temperature continues with the operation of the engine 12.

For the remainder, the operation of the cooling circuit 10 is carried out conventionally with, when the temperature of the cooling liquid reaches a given value, the opening of the regulating means 20 to ensure a circulation of the liquid of cooling through at least the cooling radiator 24.

FIG. 6 shows a second embodiment of a cooling circuit 10 according to the invention.

This second embodiment is described below by comparison with the first embodiment, the means designated by the same references being identical or similar to those described above for FIGS. 1 to 4. In this second embodiment, the cooling circuit 10 comprises a first cooling loop 14 associated with the motor 12 which differs from that of the first embodiment.

Indeed, the first cooling loop 14 associated with the motor 12 comprises at least a first branch 14A, said high temperature (similar to the first cooling loop described above), and further comprises a second branch 14B, said low temperature.

In what follows, the term "high temperature" designates a part of the cooling circuit in which the coolant circulates at a temperature which is higher than that of the coolant circulating in another part of the cooling circuit, then qualified by comparison of "low temperature".

The first branch 14A comprises at least the radiator 24 cooling, said high temperature radiator (or HT).

The second branch 14B comprises at least one other radiator 54 cooling, said low-temperature radiator (or BT).

As illustrated by FIG. 6, the third exhaust gas cooling loop 40 is here connected to the second low temperature branch 14B of the first cooling loop 14.

The second branch 14B low temperature comprises at least one pipe 56 in which is arranged the radiator 54 cooling.

The pipe 56 is connected at one end, downstream, to the third cooling loop 40, preferably at the level of the control means 48.

According to a characteristic of this second embodiment, the first branch 14A high temperature and the second branch 14B low temperature of the first loop 14 are connected, fluently connected to one another.

The pipe 56 is connected at the other end, upstream, to the second pipe 22 of the first high temperature branch 14A, preferably downstream of the high temperature cooling radiator 24.

The third exhaust gas cooling loop 40 is connected to the remainder of the cooling circuit 10 via the pipe 56 communicating with the second leg 14B on the one hand and by a pipe 58 on the other hand.

The pipe 58 is connected to the second pipe 22 of the first branch 14A of the first cooling loop 14. The pipe 58 is the one through which the return of the cooling liquid, when the third loop 40 does not work in a closed loop.

The operating phases of the third exhaust gas cooling loop 40 in this second embodiment are similar to those described for the first embodiment.

The first embodiment illustrated in FIGS. 1 to 4 and the second embodiment of FIG. 6 are non-imitative examples of implementation of an exhaust gas cooling loop associated with a circulating EGR of FIG. a motor 1 2 to internal combustion.

FIG. 7 shows a variant of real isation of the second embodiment which has just been described.

In comparison with this second embodiment shown in FIG. 6, the first high temperature branch 14A and the second low temperature branch 14B of the first cooling loop 14 are here independent of each other.

Indeed, a portion of the pipe 56 connects the input of the radiator 54 cooling low temperature to the third loop 40 tand is that the other party connects as previously the output of the radiator 54 to the third loop 40, here at the level of the control means 48.

In such a variant embodiment, the maximum temperature reached by the cooling fluid circulating in the second low temperature branch 14B of the first loop 14 and in the third loop 40 will advantageously be less than the maximum temperature that can be reached by the coolant liquid in the first branch 14A high temperature.

In summary, the invention proposes a cooling circuit 10 for an internal combustion engine 12 equipped with an exhaust gas recirculation circuit, comprising at least a first cooling loop 14 associated with the engine 12. a second heating loop 30 which comprises at least one heater 34, and a third exhaust gas cooling loop 40 which comprises at least one heat exchanger 42 for cooling the exhaust gases from the recirculation circuit circuit 10 wherein said third exhaust gas cooling loop 40 comprises at least one pump 44, heating means 46 for selectively heating the cooling fluid flowing in said third loop 40 and control means 48 selectively controlled to isolate the third loop 40 from the remainder of the cooling circuit 10, and a method of controlling such a circuit uit 10 of cooling.

Claims

REVEN DICATIONS

1. Cooling circuit (1 0) for an internal combustion engine (12) with an exhaust gas recirculation circuit, in which a cooling circuit is circulated, it circulates ( 1 0) comprising at least:

- a first cooling loop (14) associated with the engine (12) which comprises at least one pump (1 6), means (20) for regulating the circulation of the cooling liquid and a radiator (24) cooling,

a second heating loop (30) which is selectively connected to said first loop (14) by said regulating means (20) and which comprises at least one heater (34), and - a third loop (40) an exhaust gas cooling system which, associated with the exhaust gas recirculation circuit, comprises at least one heat exchanger (42) for cooling the exhaust gases of said recirculation circuit, characterized in that said third an exhaust gas cooling loop (40) comprises at least one pump (44), heating means (46) consisting of an immersion heater or an electric heater capable of heating the cooling fluid circulating in said third loop ( 40) and selectively controlled control means (48) for isolating the third loop (40) from the remainder of the cooling circuit.

2. Cooling circuit according to claim 1, characterized in that the means (48) for controlling the third loop (40) are selectively controlled between at least:

a closing position in which said means

(48) isolate the third loop (40) from the remainder of the cooling circuit (10) so that the third loop (40) operates in a closed loop, and an opening position in which the third exhaust gas cooling loop (40) is in communication with at least one other loop (30, 1 0) of the cooling circuit (1 0).

3. Cooling circuit according to revendication 2, characterized in that the means (48) of control are likely to occupy at least one intermediate position betweenddis open and closed positions.

4. cooling circuit according to one of claims 1 to 3, characterized in that the means (46) for heating the third loop (40) are selectively controlled between an inactive state and an active state wherein said means (46) heat the cooling liquid.

5. Cooling circuit according to any one of the preceding revendications, characterized in that the cooling circuit (1 0) comprises means (50, 52) for measuring the temperature to measure the temperature of the liquid. in the third loop (40) as well as in the first loop (14) and / or the second loop (20).

6. Cooling circuit according to claim 1 or 2, characterized in that the third loop (40) for cooling the exhaust gas is connected to the second heating loop (30).

7. Circu it cooling according to one of revendications ications 1 to 5, wherein the first loop (14) cooling issement associated with the motor (1 2) comprises at least a first branch (14A), dite high temperature, comprising at least the radiator (24) cooling, and a second branch (14B), d ite low temperature, having at least one other radator (54) cooling, characterized in that the third loop (40) exhaust gas cooling system is connected to the second low temperature branch (14B) of the first cooling loop (14).

Cooling circuit according to Claim 7, characterized in that the first high temperature branch (14A) and the second low temperature branch (14B) of the first cooling loop (14) are connected to each other. 'other.

9. Cooling circuit according to revendication 7, characterized in that the first branch (14A) high temperature and the second branch (14B) low temperature of the first loop (14) of cooling are independent one of the other.

1 0. Control method for a cooling circuit (10) for an internal combustion engine (1 2), said cooling circuit (1 0) comprising at least means (50) for measuring the temperature suitable for measuring the temperature of the coolant in the third loop (40), a temperature comparator, said third loop (40) having a pump (44), control means (48) capable of being placed in at least one an open position or in a closed position, heating means (46) selectively controlled between an active state and an inactive state, characterized in that said control method comprises at least:

a step of comparing the temperature of the cooling fluid of the third cooling loop (40) with a first temperature (TS 1) of only 10,

a control step which consists, when the temperature (T) of the cooling liquid is lower than the first temperature (TS1) of threshold, to control at least:

The closing position control means (48) for isolating the third cooling loop (40) from the remainder of the cooling circuit (10),

Heating means (46) in said active state for heating the cooling liquid to increase its temperature until at least said first temperature (TS1) is reached; and • the pump (44) in a running state to ensure circulation of the coolant in the third closed loop cooling loop (40).

11. Control method according to claim 10, characterized in that the control method comprises at least one control step consisting, when the temperature (T) of the coolant is at least equal to said first temperature (TS1) of threshold controlling the exhaust gas recirculation circuit of the engine to establish a flow of said exhaust gas through the heat exchanger (42) of the third loop (40) to cool the exhaust gas recirculation .

12. Control method according to claim 10 or 11, characterized in that, when the temperature (T) of the coolant is at least equal to said first threshold temperature (TS1), the control method comprises a control step comprising controlling at least the heating means (46) in said inactive state to stop heating the coolant.

13. Control method according to claim 10 or 11, characterized in that, when the temperature (T) of the coolant is at least equal to said first threshold temperature (TS1), the control method comprises a control step controlling at least the heating means (46) in said active state to continue heating the coolant for a specified period of time or until the coolant temperature (T) reaches a given value, such as a second threshold temperature (TS2) greater than the first threshold temperature (TS1).

14. Control method according to one of claims 10 to 13, characterized in that, when the temperature (T) of the coolant is at least equal to a second temperature (TS2) threshold greater than the first threshold temperature (TS1), the control method comprises a control step of at least controlling the control means (48) in an intermediate position between the said opening positions and at least one other closed loop for cooling the third cooling loop (40) in communication with at least one other loop (30, 14B) of the cooling circuit.

5. Control method according to one of claims 10 to 13, characterized in that, when the temperature (T) of the cooling liquid is at least equal to a second temperature (TS2) upper threshold to the first threshold temperature (TS1), the control method comprises a control step of at least controlling the control means (48) in the open position to fully set the third cooling loop (40) in common ication with at least one other loop (20, 14B) of the cooling circuit.