EP2010769A1

EP2010769A1 - System and method for controlling the temperature of a supercharged engine comprising an exhaust gas recycling circuit

Info

Publication number: EP2010769A1
Application number: EP07731913A
Authority: EP
Inventors: Cedric Rouaud; André FRANCE; Robert Yu
Original assignee: Renault SAS
Current assignee: Renault SAS
Priority date: 2006-04-21
Filing date: 2007-04-19
Publication date: 2009-01-07
Also published as: WO2007122345A1; FR2900197A1; FR2900197B1

Abstract

A temperature control system for a supercharged engine (11) contains an exhaust gas recycling circuit, a first cooling circuit (1) comprising a main radiator (10) to cool the engine (11), a second circuit (2a) comprising a supercharging air radiator (22), a secondary pump (24) and a secondary radiator (20), and also a recycled gas radiator (21). Control method for such a system.

Description

System and method for controlling the temperature of a supercharged engine and having an exhaust gas recirculation circuit

The invention relates to a system for controlling the temperature of an engine, and the control method of this system. More particularly, it relates to a motor which is supercharged and which comprises an exhaust gas recirculation circuit.

In an internal combustion engine, supercharged for example by a turbocharger, it is known to recycle a portion of the exhaust gas to the intake circuit. This improves the combustion conditions by better control of the temperature during combustion and gaseous compositions, to reduce the source of gaseous pollutants and increase the efficiency of the engine.

To further improve the operation of such an engine, we note that it is interesting to operate with an even higher rate of recycled gas than currently practiced. However, increasing the recycled gases, it becomes more difficult to control the ^"temperature of the gases entering the engine. In particular, if the temperature increases too much, there is a risk of damaging engine components and increasing the production of nitrogen oxides.

One of the ways commonly used to control the temperature of the gases at the intake is to place a radiator on the charge air circuit at the outlet of the compressor. The document FR 2 463 860 discloses, for example, a cooling system for an engine comprising a first cooling circuit in which a coolant circulates. In this circuit, the fluid flows in a primary radiator, is discharged by a pump, on the one hand to the engine, and on the other hand to a first charge air radiator before returning to the primary radiator. A second cooling circuit includes a secondary radiator and a second charge air radiator positioned downstream of the first. The use of a second cooling circuit makes it possible to operate with a coolant temperature lower than that of the first circuit, and thus to better cool the charge air.

However, when using an engine with a high rate of recycled gas, the cooling of the charge air is no longer sufficient for the cooling of the intake gases.

WO2005 / 073535 discloses a system for controlling the temperature of a motor with two cooling circuits. At a low temperature first cooling circuit comprises a secondary radiator, an electric pump, a radiator ^r supercharging air, a gas radiator recycled and a valve. A second conventional circuit allows the cooling of the engine. The valve allows the flow rates to be distributed between the charge air cooler and the recycled gas heater, but without the possibility of canceling the flow in the charge air cooler when the electric pump is running. The permanent circulation of water in the secondary radiator does not prevent cooling of the charge air during the temperature rise phase of the engine. If the electric pump is stopped, the coolant may boil in the recycled gas radiator in particular.

It is therefore an objective to provide a system for controlling the temperature of a supercharged engine and comprising an exhaust gas recirculation circuit making it possible to optimize the temperature of the gases at the intake.

With this objective in view, the invention relates to a system for controlling the temperature of a supercharged engine and comprising an exhaust gas recirculation circuit, the system comprising a first cooling circuit comprising a main radiator, for cooling the engine, a second circuit comprising a charge air radiator, a recycled gas radiator, a secondary pump and a secondary radiator. It further comprises bypass means for short-circuiting the secondary radiator on command.

The use of two cooling circuits makes it possible to work with different temperature levels. In particular, the second circuit contains coolant whose average temperature is lower than that in the first circuit. Indeed, the level of the average temperature in the first circuit is conditioned by the operation of the engine. By releasing this constraint with the second circuit, it is possible to cool the gases admission to a sufficiently low temperature level. Moreover, by also cooling the recycled gases, it is possible to control the temperature of the gases on admission over a larger range, whatever the rate of recycling of the exhaust gases. Finally, by cooling the recycled gases, their density is increased, which also makes it possible to increase the limit of the rate of these recycled gases. Admission gas cooling is provided in all configurations, be it high load, where the charge air temperature is high at the compressor outlet, or when the recycling rate is high.

The bypass means prevent the secondary radiator from being in use when the temperature in the first circuit is still insufficient. The dissipation of calories is thus avoided, allowing a faster temperature setting.

According to a first particular provision, the bypass means comprises a first bypass in parallel with the secondary radiator, and selection means for directing a cooling fluid to the secondary radiator or to the first bypass. Thus, it is possible to loop the second circuit on the radiator ^r supercharging air, the radiator of the recycled gases and the pump, by putting out of the circuit the secondary radiator. This mode of operation is particularly interesting during a start-up phase of the engine, allowing rapid heating of the second circuit. Indeed, when the engine is cold, it may be advantageous not to decrease, or even increase the temperature of the inlet gas, to improve the combustion conditions. It is then useful not to dissipate calories by the secondary radiator.

The selection means are for example selected from a three-way valve, or a valve input to the secondary radiator combined with a nozzle on the bypass, or a pair of valves, a double-acting thermostat or a controlled thermostat combined with a nozzle. The three-way valve has one inlet and two outlets, one to the bypass and the other to the secondary radiator, and directs the coolant to one or the other of the elements. According to a particular embodiment, the fluid can be divided into two more or less balanced flows. Other means may replace the three-way valve, such as a pair of valves disposed at the respective inlet of the secondary radiator and the bypass. The thermostats are valves whose control is carried out according to the temperature of the fluid passing through them.

According to a first embodiment, the charge air radiator and the recycled gas radiator are arranged in parallel. They are each powered by the coolant at the lowest temperature, that at the output of the secondary radiator, which allows to obtain the lowest possible temperature level for the air or the cooled gases.

According to an improvement, the system comprises a first valve for isolating the air radiator from overeating. The first valve cuts or reduces the flow of fluid in the charge air cooler. This is interesting during the warm-up phase, where it is useful not to cool the charge air to improve combustion. The stagnant fluid in the charge air cooler is not replaced by cooler fluid. On the other hand, when the engine is hot and at low load, the temperature of the charge air may be lower than that of the fluid in the second circuit. In this case, by shutting off the circulation in the charge air cooler, it avoids the heating of the charge air.

According to another improvement, the system comprises a second valve for isolating the radiator from recycled gases. This allows, during the temperature rise phase, to cancel or reduce the flow of fluid in the recycled gas radiator and consequently reduce the cooling of the gases recycled in said radiator. The circulation of the fluid is reestablished as soon as a risk of boiling of the fluid is detected.

According to a second particular provision, in combination or not with the first, the bypass means comprise a second bypass in the second circuit for looping the pump and the radiator of recycled gas. In this arrangement, when said loop is established, the charge air radiator and the secondary radiator are outside the flow of the fluid. said loop is very short, which makes it possible to obtain a temperature rise in the radiator of recycled gas fairly fast, by limiting the mass of the fluid and the elements to be heated. This is particularly interesting in the engine warm-up phase.

According to an improvement, the charge air radiator is disposed upstream of the recycled gas radiator. The temperature level of the compressed air is often lower than that of the recycled exhaust gases. Also, it is more efficient to direct the fluid leaving the secondary radiator to the charge air radiator and then to the recycled gas radiator, rather than the opposite. The temperature of the fluid at the outlet of the recycled gas radiator may not allow cooling of the charge air.

According to a third particular arrangement, the bypass means comprise two branch lines for connecting the second circuit in parallel with the first circuit. With such an arrangement, it is possible to involve the second circuit in raising the temperature of the first circuit in the starting phase. The bypass lines are closed when the temperature of the first circuit is sufficiently high.

According to an improvement, the first circuit comprises a cabin heating heater, the second circuit being connected in parallel with the heater, selection means for looping the pornpe _? the recycled gas radiator and the air heater. According to a complementary improvement, a separation valve makes it possible to isolate the heater from the first circuit. In this configuration, the heater is switched on in particular with the recycled gas heater. Thus, during the engine warm-up phase, all the calories of the engine are used for this warm-up, while the calories recovered by the recycled gas radiator are transferred into the passenger compartment via the heater, in order to rapidly increase the temperature inside the passenger compartment.

In the third arrangement of the system, the recycled gas radiator and the charge air radiator may be arranged in parallel, or the recycled gas radiator may be disposed downstream of the charge air radiator.

The invention also relates to a control method of a system as described above, wherein the secondary radiator is in use if at least one of the following conditions is met: the engine is hot; the temperature of the fluid in the second circuit is greater than a predetermined threshold; the motor load is greater than a predetermined threshold,

If none of the above conditions is fulfilled, the flow of liquid in the secondary radiator is canceled or reduced, which limits the cooling of the charge air or recycled gas.

When the engine is hot, it is useful to minimize the temperature of the intake gas, and thus to remove the calories from the intake air and the gases recycled by the secondary radiator. It is determined that the engine is hot for example by measuring the temperature of the cooling fluid at the motor output. If this temperature exceeds for example 70 ⁰ C, it is considered that the engine is hot. The temperature threshold may be different depending on the engine.

In addition, it is necessary to prevent the coolant from boiling. Also, it is useful to take into account the temperature at at least one point of the second circuit, such as at the entrance of the secondary radiator, ^r in one of the radiators or their output to activate the secondary radiator.

Finally, when the engine load is high, the charge air is heavily compressed and its temperature is high. To optimize the filling of the engine, it is useful to cool the charge air to make it denser. This situation can occur even if the engine is not yet warm or if the fluid temperature of the second circuit is still low.

The method according to the invention is implemented for example by an electronic control unit which receives information from the system and the engine and which drives valves to determine the circulation paths of the fluid in the circuits. When the second circuit comprises the first valve, the latter is closed when at least one of the following conditions is met: the engine is cold and the temperature representative of the charge air radiator is lower than the air temperature overeating; the engine is hot, the engine load is low and the temperature representative of the charge air radiator is higher than the charge air temperature.

The first valve isolates the charge air radiator when heat exchange is not desired. This is the case when the engine is cold and it is desirable to have the admission gases that are the hottest possible, to improve the combustion conditions and limit the formation of unburned gases. Circulation of the fluid in this phase would cool the charge air, which is undesirable.

This is also the case when the engine is hot and you do not want to heat the intake air. If the fluid is warmer than the intake air, it would heat the air while circulating in the charge air cooler, which is undesirable at this time.

Alternatively, the first valve is closed when at least one of the following conditions is met: - the engine is cold, the engine load is low, the temperature representative of the radiator the charge air is below a predetermined threshold and the charge air temperature is below a predetermined threshold; the engine is hot, the engine load is low and the temperature representative of the charge air radiator is higher than the temperature of the engine ^; supercharging air; the temperature representative of the charge air radiator is below a predetermined threshold.

The representative temperature of the ^? one of the radiators may be a temperature measured at a point of the radiator, but it will generally take the temperature of the heat transfer fluid measured at the radiator outlet.

When the second circuit comprises the second valve, the latter is open when the temperature representative of the recycled gas radiator is greater than a predetermined threshold. Thus, as soon as a risk of boiling is detected, the valve is open to circulate the fluid and avoid this risk. On the other hand, the second valve can be closed when the engine is cold and the temperature of the gases at the intake is lower than a predetermined threshold, or when the rate of recycled gases is zero.

In the case of a system according to the second arrangement, the recycled gas pump and radiator are connected in a loop only when the representative temperature of the gas radiator recycled is below a predetermined threshold. Thus, as soon as a risk of boiling is detected by crossing the predetermined threshold during the temperature rise phase of the engine, the second circuit is expanded to involve other heat exchange with the charge air radiator or the secondary radiator and avoid this risk. When the pump and the radiator of recycled gas are connected in boude _? a rapid rise in the temperature of the recycled gas radiator is obtained.

If, in addition, the system includes the first bypass, the recycled gas radiator, the pump and the charge air radiator are connected in a loop when the engine load is below a predetermined threshold and the temperature representative of the air radiator. boost is less than another predetermined threshold. Thus, after the temperature rise of the recycled gas radiator, or the heat transfer fluid that comes out, the charge air radiator is also warmed up without calories being dissipated in the secondary radiator.

The invention will be better understood and other features and advantages will appear on reading the description which follows, the description referring to the appended drawings in which: FIG. 1 is a schematic view of a system according to a first embodiment embodiment of the invention; Figure 2 is a view similar to Figure 1 of a variant of the first embodiment; Figure 3 is a schematic view of a system according to a second embodiment of the invention; Figure 4 is a view similar to Figure 3 of a variant of the second embodiment; Figures 5 and 6 are schematic views of a system according to a third embodiment of the invention, in two different modes of operation; - Figures 7 and 8 are schematic views of a system according to a variant of the third embodiment of the invention, in two different modes of operation.

A first embodiment of the invention is shown in FIG.

11 for the motorization of a motor vehicle is supplied with intake air via an air filter 7, a compressor 31 of a turbocharger 3 and a charge air radiator 22. The heat engine 11 generates exhaust gases that are discharged by a turbine 30 of the turbocharger 3 and a treatment device 8. Part of the exhaust gas can be recycled by a bypass 19 placed upstream of the turbine 30 and connected downstream of the charge air radiator 22, a recycled gas radiator 21 is placed on the branch 19.

The system according to the invention comprises a first circuit 1 for controlling the temperature of the engine 11. This first circuit 1 allows the circulation of a cooling fluid between the engine 11 and a main radiator 10 placed in a flow of air from outside the vehicle. The first circuit 1 conventionally comprises a thermostat 15 at the output of the engine 11 which directs the fluid to a main bypass 16 or to the main radiator 10. A main pump 14, placed at the inlet of the engine 11, circulates the fluid in The first circuit 1. A heater 13, for heating the passenger compartment of the vehicle, is placed in parallel with the main bypass 16,

The system comprises a second temperature control circuit 2a independent of the first circuit 1. This second circuit 2a comprises a secondary pump 24, a secondary radiator 20, also placed in the air flow coming from the outside of the vehicle, the radiator of charge air 22 and the radiator of recycled gas 21, the charge air heaters 22 and recycled gas 21 are air / water exchangers in which heat exchange takes place between a heat transfer liquid which circulates in the second circuit 2a and respectively the intake air and the recycled gases circulating in the bypass 19.

According to the first embodiment, the output of the secondary pump 24 is connected to the inputs of the recycled gas radiator 21 and the charge air cooler 22, arranged in parallel. The output of the charge air cooler 22 is connected to a first valve 61, of the two-way type. The output of the recycled gas radiator 21 and the outlet of the first valve 61 are connected to the inlet of a three-way valve 25, the two outlets of the three-way valve 25 are respectively connected to the input of the secondary radiator 20 and the input of a first bypass 23, placed in parallel with the secondary radiator 20.

The system comprises an electronic computer or central unit 5 which receives data on the state of the system, and which controls the three-way valve 25 and the first valve 61. It receives for example a temperature T1 of the output coolant. of the engine 11, a temperature T2 of the liquid in the second circuit 2a upstream of the three-way valve 25, a temperature 13 of the mixture of the intake air and recycled gases, a temperature 14 of the coolant at the outlet of the charge air cooler, representative of the temperature of the charge air cooler 22, a coolant temperature T5 of the output of the recycled gas heater, representative of the temperature of the recycled gas heater, a pressure P in the intake manifold, representative of the load of the engine 11, and a quantity of fuel injected.

The secondary pump 24 continuously circulates the liquid in the second circuit 2a. The direction of circulation from the secondary pump 24 is directed towards the charge air heaters 22 and recycled gas 21, the three-way valve 25, the secondary radiator 20 or the first bypass 23, before returning to the secondary pump 24,

When starting the engine 11, when this is cold, the three-way valve directs the flow of liquid in the first bypass 23, thus turning off the secondary radiator 20. The first valve 61 is closed. Thus, the liquid circulates in a loop between the recycled gas radiator 21 and the secondary pump 24 and rises rather quickly in temperature thanks to the calories provided by the recycled gases. The temperature T3 increases quite rapidly, which makes it possible to limit the emission of unburned gases. The charge air is not cooled since the liquid does not circulate in the charge air radiator 22.

If the temperature level of the liquid in the charge air cooler 22 rises with the risk of causing the liquid to boil, the first valve 61 is opened. This can occur when the engine 11 is operating at a high load. , and that the temperature of the charge air rises up to 200 ^° C., The criterion for opening the first valve 61 is, for example, a temperature T4 greater than 115 ^° C. It is also possible to take an indication of the load of the motor 11, such as the exceeding of a threshold on the boost pressure P or on the quantity of fuel Q injected, these values possibly being filtered. The temperature T4 can be given by a sensor or a digital temperature model of the wall of the charge air cooler 22 taking into account the operation of the engine 11 and its environment.

When it is considered that the engine 11 is hot _f or that the temperature of the liquid in the 1?

second circuit 2a is high enough _f the three-way valve 25 is controlled to guide at least partially the flow of liquid to the secondary radiator 20, can be seen here that the engine 11 is warm when the coolant temperature T at the output of motor 11 is greater than 80 ⁰ C. at this time, the second circuit 2a cools the recycled gases and the charge air in order to optimize operation of the engine 11. Optionally, the temperature T3 of the inlet gas can be measured and regulated by modulating the orientation of the three-way valve 25. The three-way valve 25 can be in all-or-nothing operation, that is to say binary, or continuously variable mode, it is to say progressive. The set point for the temperature T3 can be determined as a function of the operating point of the motor 11, for example by means of a mapping,

One variant of the first embodiment is shown in FIG. 2. The second circuit 2b differs from that 2a of FIG. 1 by the addition of a second valve 62 of the two-way type downstream of the recycled gas radiator 21, allowing to reduce or cut the flow of liquid in the latter.

In this variant, the control unit 5 controls the closing of the second valve 62 when the engine 11 is cold and a temperature T5 of the liquid at the outlet of the recycled gas radiator 21 is less than a predetermined threshold, for example 90 ⁰ C. the temperature can be measured directly on a wall of the radiator 21, or into the liquid in or out of the radiator 21. the cooling recycled gas at the beginning of the temperature rise phase of the engine 11 is thus limited.

According to a second embodiment of the invention, represented in FIG. 3, the first circuit 1 is identical to that of the first embodiment. The second circuit 2c comprises in loop, in the direction of the flow of liquid, the secondary pump 24, a third valve 63 of the two-way type, a fourth valve 64 of the two-way type, the secondary radiator 20, the air radiator of The first bypass 23 is connected upstream of the fourth valve 64 and opens upstream of the charge air radiator 22. A second bypass 26 is connected upstream of the third valve 63 and opens between the charge air radiator 22 and the recycled gas radiator 21. A nozzle, making a restriction of the passage of the liquid, is provided on the first 23 and the second bypass 26.

When starting the engine 11, when it is cold, the third valve 63 is closed. Thus, the liquid circulates in a loop between the recycled gas heater 21 and the secondary pump 24 and rises quite rapidly in temperature thanks to the calories provided by the recycled gases. The loop is very short, which limits the thermal inertia of it. The temperature increases rapidly enough, which makes it possible to limit the emission of unburned gases. The charge air is not cooled since the liquid does not circulate in the charge air radiator 22.

If the temperature level of the liquid in the booster air radiator 22 rises, with the risk of boiling the liquid, opens the third valve 63 by maintaining the fourth valve 64 closed. The same criteria as in the first embodiment are used. Due to the presence of a nozzle in the second bypass 26, the liquid at least partially flows through the third valve 63, the first bypass 23 and the charge air radiator 22.

When it is considered that the motor 11 is hot, or that the temperature of the liquid in the second circuit is sufficiently high, the fourth valve 64 is opened to direct the flow of liquid towards the secondary radiator 20. Due to the presence of a nozzle in the second bypass 26, the liquid preferably circulates in the secondary radiator 20. At this time, the second circuit can cool the recycled gas and the charge air to optimize the operation of the engine 11. The same transition criteria as in the first embodiment can be applied to the second embodiment.

In general, the recycled gas heater is smaller than the charge air radiator. In addition, in case of operation of the vehicle over an urban cycle, the engine works at low load and high rate of recycled gas. Also, by performing the loop on the secondary pump 24 and the recycled gas radiator 21, with a reduced volume of liquid, the temperature rise in the secondary circuit 2c will be obtained the fastest, while avoiding the boiling of the liquid of cooling. Finally, as the cooling liquid circulates in the radiator not supercharging air, the ^f intake air is not cooled.

In a variant of the second embodiment, shown in FIG. 4, the second circuit 2d is simplified by the deletion of the first bypass 23 and the fourth valve 64. In this configuration, as soon as the liquid circulating in a loop in the radiator recycled gas 21 and the secondary pump 24 is hot, for example with a temperature above 90 ⁰ C, the third valve 63 is open and the secondary radiator 20 is put into operation. The transient phase with the loop comprising the secondary pump 24, the third valve 63 the charge air radiator 22 and the recycled gas radiator 21 is eliminated. This simpler and less expensive circuit is interesting for highly turbocharged engines. Indeed, for these engines, the charge air temperature is generally quite high, and it is not disadvantageous to supply the charge air radiator 22 only liquid cooled by the passage in the secondary radiator 20.

In a third embodiment of the invention, shown in Figures 5 and 6, the first circuit 1 is identical to that of the first embodiment. The second circuit 2 comprises, in a loop and in the direction of liquid flow, the secondary pump 24, the cooler ^# supercharging air 22 and the gas cooler recycled 21 placed in parallel, a fifth valve 65 of the type two-way the secondary radiator 20. A first bypass line 90 is connected between the upstream of the fifth valve 65 and the downstream of the heater 13 of the first circuit 1. A second bypass line 91 is connected between the downstream of the secondary radiator 20 and the upstream of the heater 13. A sixth valve 66 of the two-way type is placed on the first bypass line 90, so as to be able to cut off the circulation in said duct 90.

When the engine 11 is cold, the fifth valve 65 is closed and the sixth valve 66 is open, as shown in Figure 5. The liquid driven by the secondary pump 24 then flows through the charge air heaters 22 or recycled gas 21, the sixth valve 66, in the first circuit 1, then returns to the secondary pump 24. The secondary pump 24 may optionally be stopped, the flow of fluid being activated by the main pump 14. The calories captured by the recycled gas radiators 21 and charge air 22 are transferred to the engine 11 to accelerate the warm-up of the engine 11 and the cockpit.

When the engine 11 is hot, the state of the valves is switched, that is to say that the fifth valve 65 is open and the sixth valve 86 is closed, as shown in Figure 6. The two circuits 1, 2e are then isolated from each other and the second circuit provides cooling of the charge air cooler 22 and the recycled gas radiator 21.

The fifth and sixth valves 66 can be replaced by a three-way valve placed for example upstream of the secondary radiator 20 to direct the fluid to the first bypass line 90 or to the secondary radiator 20.

In a variant of the third embodiment, shown in FIGS. 7 and 8, the first circuit If further comprises a separation valve 67 placed between the start of the second bypass pipe 91 and the upstream of the main bypass 16. the second circuit 2f, the charge air radiator 22 is not in parallel with the recycled gas radiator 21, but downstream of the secondary radiator 20 and upstream of the return of the second bypass line 91.

In the warm-up phase of the engine 11, if the need for heating of the passenger compartment is felt, the separation valve 67 is closed, the fifth valve 65 is closed and the sixth valve 66 is open, as shown in FIG. 7. The liquid driven by the secondary pump 24 then circulates through the recycled gas heater 21, the sixth valve 66, the heater 11, then returns to the secondary pump 24 by the second bypass pipe 91 "Calories are then quickly transferred to heat the cabin, faster than if the heater 13 was powered by the first circuit If. In addition, all the calories developed by the motor 11 are stored in the first circuit If to accelerate the warm-up.

Always during the heating phase, if the heating need does not exist or is limited, the separation valve 67 is open and the recycled gas radiator 21 participates in the temperature rise of the first circuit 1 and the motor 11.

If the temperature in the charge air radiator 22 is likely to cause boiling, then the fifth valve 65 is at least partially opened to circulate a portion of the liquid in the secondary radiator 20 and in the charge air radiator. .

Once the motor 11 is warm, the separation valve 67 is opened, the fifth valve 65 is opened and the sixth valve 66 is closed, as shown in Figure 8. The two circuits are then isolated and fulfill their respective roles.

Other variants of the third embodiment may be designed. The charge air radiator 22 and the recycled gas radiator 21 may be placed in parallel as in FIG. 5 or separated as in FIG. 7, the first case being more suitable when the engine 11 is heavily supercharged. The second case requires managing the risk of boiling, but is more efficient for the rise in temperature.

Note that the valves whose control is a function of the temperature of the liquid flowing through them can be controlled by the thermal expansion of a wax contained in a container placed in the flow of liquid. For this type of valve, it is necessary to maintain a minimum flow, so that the valve is sensitive to the temperature of the liquid. Also, even when considering in the previous explanations that the valve is closed, there is a flow of heat transfer liquid through the valve. The switching of the valve can be anticipated at a temperature level below the predetermined threshold by a heating resistor that heats the wax. This is called a piloted thermostat.

The invention is not limited to the embodiments which have been described solely by way of example. Other combinations of variants, such as the arrangement of the radiators and the technology of the binary or progressive valves, can be used effectively.

Claims

A system for controlling the temperature of a supercharged engine (11) having an exhaust gas recirculation circuit, the system comprising a first cooling circuit (1) having a main radiator (10) for cooling the engine. motor (115), a second circuit comprising a charge air radiator (22), a recycled gas radiator (21), a secondary pump (24) and a secondary radiator (20), characterized in that II comprises in addition to bypass means (23, 26, 90) for short-circuiting the secondary radiator on command.

2. System according to claim 1, characterized in that the bypass means comprises a first bypass (23) in parallel with the secondary radiator (20), and selection means (25) for directing a cooling fluid to the radiator secondary (20) or to the first bypass (23).

The system of claim 2, wherein the selecting means is selected from a three-way valve (25), or an inlet valve of the secondary radiator combined with a bypass nozzle (23), or a pair of valves, a double-acting thermostat or a controlled thermostat combined with a nozzle.

4. The system of claim 2, wherein the radiator ^f charge air (22) and the recycled gas radiator (21) are arranged in parallel.

5. System according to claim 4, characterized in that it comprises a first valve (61) for isolating the charge air radiator (22).

6. System according to claim 4, characterized in that ^r II includes a second valve (62) to isolate the gas recycled radiator (21).

7. System according to claim 1 or 2, wherein the bypass means comprise a second bypass (26) in the second circuit (2c, 2d) for looping the secondary pump (24) and the radiator of recycled gases ( 21).

8. System according to claim 1, wherein the charge air radiator (22) is disposed upstream of the recycled gas radiator (21).

9. System according to claim 1, characterized in that the derivation means comprise two branch lines for connecting the second circuit (2e, 2f) in parallel with the first circuit (1, If).

10. System according to claim 9, wherein the first circuit (1, If) comprises a cabin heater heater (13), the second circuit (2e, 2f) being connected in parallel with the heater (13), selection means (65, 66, 67) for looping the secondary pump (24), the recycled gas heater (21) and the heater (13).

11. System according to claim 10, wherein a separating valve (67) isolates the heater (13) from the first circuit (If).

12. System according to claim 9, wherein the recycled gas radiator (21) and the charge air radiator (22) are arranged in parallel.

13. The system of claim 9, wherein the recycled gas radiator (21) is disposed downstream of the charge air radiator (22).

14. A method of controlling a system according to one of claims 2 or 9, characterized in that the secondary radiator (20) is in use if at least one of the following conditions is met: - the engine (11) is hot ; the temperature of the fluid at the inlet of the secondary radiator (20) is greater than a predetermined threshold; the load of the motor (11) is greater than a predetermined threshold.

15. The method of claim 14 for controlling a system according to claim 5, wherein the first valve (61) is closed when at least one of the following conditions is met: the engine (11) is cold and the temperature representative of the charge air cooler (T4) is lower than the charge air temperature; the engine (11) is hot, the engine load (11) is low and the representative temperature of the charge air cooler (T4) is higher than the charge air temperature.

The method of claim 14 for controlling a system according to claim 5, wherein the first valve (61) is closed when at least one of the following conditions is met: the engine (11) is cold, the engine load is low, the temperature representative of the charge air cooler (T4) is below a predetermined threshold and the charge air temperature (22) is below a predetermined threshold; the engine (11) is hot, the load of the engine (11) is low and the temperature representative of the charge air cooler (T4) is higher than the temperature of the charge air; the representative temperature of the charge air radiator (22) is below a predetermined threshold.

17. The method of claim 14 for controlling a system according to claim 6, wherein the second valve (62) is open when the representative temperature of the recycled gas radiator (T5) is greater than a predetermined threshold.

The method of claim 14 for controlling a system according to claim 7, wherein the secondary pump (24) and the recycled gas radiator (21) are connected in a loop only. when the representative temperature of the recycled gas radiator (T5) is below a predetermined threshold.

19. The method of claim 18 for controlling a system according to claims 2 and 7 taken in combination, wherein the recycled gas radiator (21), the secondary pump (24) and the charge air radiator (22). ) are connected in a loop when the load of the motor (11) is below a predetermined threshold and the temperature representative of the charge air radiator (14) is lower than another predetermined threshold.