FR2948421A1 - Coolant circulation managing method for adjusting temperature of thermal engine of motor vehicle, involves interrupting flow of coolant towards thermal engine in rising phase of temperature of engine corresponding to predetermined time - Google Patents

Abstract

The method involves circulating a coolant in primary and/or secondary main loop of a coolant circuit. The flow of coolant towards a thermal engine (10) is interrupted in a rising phase of temperature of the engine corresponding to a predetermined time after starting the engine and/or in rising phase of a temperature of the engine lower than threshold valve. The temperature of the engine and/or the coolant is maintained at a target value. An independent claim is also included for a device for managing circulation of a coolant in a coolant circuit for adjusting temperature of a thermal engine of a motor vehicle.

Description

METHOD FOR CONTROLLING THE CIRCULATION OF A HEAT PUMP FLUID IN A COOLING CIRCUIT OF A MOTOR VEHICLE HEAT ENGINE.

The present invention relates to the field of temperature management of a motor vehicle engine equipped with an exhaust gas recirculation system, commonly called EGR for Exhaust Gas Re-circulation in English, and of a cooling circuit in which circulates a coolant. More specifically, according to a first of its objects, the invention relates to a method for managing the circulation of a heat transfer fluid in a cooling circuit, for regulating the temperature of a motor vehicle heat engine optionally equipped with a Exhaust gas recirculation system, Such methods are known to those skilled in the art, in particular by the example given in the document of the prior art FR2913057 filed by the applicant.

There is therefore, when the vehicle is equipped with an EGR system, a coupling between the cooling circuit and the EGR system. The temperature of a motor vehicle engine and that of the re-circulated exhaust gas directly influences the polluting emissions (HC for hydrocarbons, CO for carbon monoxide, NOx for nitric oxide, and particulates) and the consumption engine, particularly for a direct injection diesel engine.

Indeed, when an engine is in a temperature increase phase after a cold start, that is to say that the heat transfer fluid, the oil and the metal masses of the engine are not yet at optimum temperature, it is there is overconsumption of the engine due to the higher viscosity of the engine lubricating oil, and high pollutant emissions (HC, CO, particles) due to incomplete combustion due to the low temperature of the walls of the combustion chambers .

In order to reduce pollutant emissions (NOx), according to an EGR system, exhaust gases are re-circulated from downstream of a particulate filter upstream of a (turbo) engine compressor. During this re-circulation, the exhaust gases must be cooled in order to protect the (turbo) compressor and not to penalize its operation. For this purpose, a first gas / liquid exchanger is conventionally used. In addition, downstream of the (turbo) compressor, the exhaust gases are re-circulated to the engine intake, and combined with the intake mixture. However, it is necessary that the temperature of the mixture at the intake is low, to optimize the filling of the combustion chambers. For this purpose, a second exchanger, or supercharged air cooler, is conventionally used. The present invention aims to improve the solutions of the prior art.

With this objective in view, the method according to the invention, moreover, in accordance with the preamble cited above, is essentially characterized in that it comprises the steps of, in the phase of temperature rise of the engine corresponding to a first predetermined delay after starting the engine and / or an engine temperature below a threshold value: 30 - circulating the coolant in a first and / or a second main loop of the cooling circuit, and cut the flow of heat transfer fluid to engine.

In one embodiment, the method further comprises the steps of: determining the temperature of the engine and / or heat transfer fluid, and depending on the temperature determined to circulate the coolant in the engine and the first loop main, and / or circulate the coolant in the engine and the second main loop. In one embodiment, the method further comprises a step of maintaining the temperature of the engine and / or heat transfer fluid at a target value.

In one embodiment, the method further comprises a step of servocontrolling the target value at the operating point of the engine and / or at the outside temperature.

In one embodiment, the motor vehicle is equipped with an exhaust gas recirculation system, the method further comprising the steps of: directing all or part of the re-circulated exhaust gas to a first heat exchanger, then transmit the heat of said first heat exchanger heat transfer fluid, and then direct all or part of the exhaust gas re-circulated to the exhaust.

Preferably, in a cold start phase of the engine corresponding to a second predetermined time after starting the engine and / or an engine temperature below a second threshold value, the method comprises a step of: - circulating the heat transfer fluid in a cooling radiator at low temperature, and a second exchanger of the second main loop, at a flow rate of zero or less than a threshold value.

In one embodiment, after the cold start phase and during the temperature rise phase of the engine, the method further comprises the steps of: circulating the heat transfer fluid in the cooling radiator at low temperature, and the second exchanger of the second main loop, at a non-zero flow rate and greater than said threshold value, and direct all or part of the re-circulated exhaust gas 15 from the first exchanger to a compressor.

According to another of its objects, the invention relates to a device for managing the circulation of a heat transfer fluid in a cooling circuit, for the regulation of the temperature of a motor vehicle engine, possibly equipped with a exhaust gas recirculation system, capable of implementing the method according to the invention.

According to the invention, the device essentially comprises: means for circulating the heat-transfer fluid in a first and / or a second main loop of the cooling circuit, and means for cutting the flow of coolant towards the engine, configured to cut the fluid flow during the engine temperature rise phase corresponding to a first predetermined time after starting the engine and / or an engine temperature below a threshold value.

In one embodiment, the motor vehicle is equipped with an exhaust gas recirculation system, the device further comprising: means for directing all or part of the re-circulated exhaust gases to a first heat exchanger, means for then transmitting the heat of said first exchanger to the coolant, and means for then directing to the exhaust all or part of the re-circulated exhaust gas, means for circulating the coolant in a a low temperature cooling radiator and a second heat exchanger of the second main loop, in a cold start phase of the engine corresponding to a second predetermined time after starting the engine and / or an engine temperature below a second threshold value at a flow rate of zero or less than a threshold value; means for circulating the heat transfer fluid in the low temperature cooling radiator and the second exchanger of the second main loop, after the cold start phase and during a temperature rise phase of the engine, according to a predetermined flow rate; zero and greater than said threshold value; and means for directing all or part of the re-circulated exhaust gas from the first exchanger to the compressor.

The invention also relates to a motor vehicle 30 equipped with the device according to the invention.

Other features and advantages of the present invention will appear more clearly on reading the following description given by way of illustrative and nonlimiting example and with reference to the appended figures in which: FIG. 1 illustrates an embodiment of the (Re) circulation of the exhaust gas according to the prior art, and FIG. 2 illustrates an embodiment of the possible circulation of the coolant according to the invention, FIG. 2A 'illustrates an embodiment of the possible circulation. heat transfer fluid according to the invention in the cold start phase, Figure 2A illustrates an embodiment of the possible circulation of the coolant according to the invention, in the temperature rise phase, within a predetermined time from the start, FIG. 2B illustrates an embodiment of the possible circulation of the heat transfer fluid according to the invention, in the phase of rise in temperature. after a predetermined delay from start-up, FIG. 2C illustrates an embodiment of the possible circulation of the coolant according to the invention in the thermal regulation phase, FIG. 3A illustrates another embodiment of FIG. the possible circulation of the coolant according to the invention, in a temperature rise phase, within a predetermined time from start-up, FIG. 3B illustrates another embodiment of the possible circulation of the coolant according to FIG. In the phase of temperature rise, beyond the predetermined delay from start-up, FIG. 3C illustrates another embodiment of the possible circulation of the coolant according to the invention in the thermal regulation phase.

A vehicle according to the invention comprises: - a heat engine 10, - a particulate filter 17, an exhaust gas recirculation system EGR, - a (turbo) compressor, and - a cooling circuit .

As illustrated in FIG. 1, a current automotive engine 10, in this particular diesel type, is generally turbocharged 14, in particular compressing the fresh air arriving in the engine through an air filter 16. Preferably, the engine 10 of a particulate filter 17. Classically, at the outlet of the particulate filter 17, the exhaust line is equipped with an exhaust flap 12 for closing all or part of the exhaust.

To recycle the exhaust gas, a first recycle loop, referred to as high pressure EGR-HP, is defined connecting the exhaust manifold to the intake manifold. This loop is equipped with a first controllable valve 11. Advantageously, the first loop further comprises cooling means, in this case an air / water cooler 18, for reducing the temperature of the mixture on admission and of improve the engine filling, therefore to promote the amount of gas recycled by said first loop in the engine, thus reduce the amount of NOx produced by controlling the temperature of said mixture.

Thus, the exhaust gas recirculation EGR system comprises: an exhaust flap 12, disposed on the exhaust line downstream of the particulate filter 17, for controlling the exhaust gas flow rate; circulating, in a so-called low-pressure loop EGR-BP, a first exchanger 15 (in this case gas / liquid cooler), arranged between the exhaust flap 12 and the compressor 14, to cool the temperature of the recirculated gases in the so-called low-pressure loop EGR-BP, a second exchanger 18 (in this case an air / water cooler), in this case a supercharged air cooler, arranged between the compressor 14 and the inlet of the engine 10, to cool the intake mixture of the engine, so as not to penalize the filling of the combustion chambers thereof.

Advantageously, the second exchanger 18 is cooled by liquid (in this case water), which greatly reduces the pressure drop of the intake air circuit and to obtain a cooling device of the supercharger air more compact by reducing the size of the intake air hoses because such a second exchanger can then be implanted on the cylinder head of the engine or attached thereto on the side of the intake face.

As illustrated in FIG. 2, one embodiment of the heat transfer fluid cooling circuit comprises: a first main loop, said to be at a high temperature, capable of connecting the engine 10, a passenger air heater 22, a water / oil exchanger 21, the first exchanger 15, and the first controllable valve 11 (shown in the diagrams because it may require permanent cooling); A second main loop, called low temperature, capable of connecting the engine 10, a main cooling radiator 20, a low temperature cooling radiator 19, and the second exchanger 18.

In FIG. 2, the arrows represent the direction of circulation of the coolant in the various branches and loops of the cooling circuit that it is likely to borrow.

The cooling circuit further comprises a pump 23, a controllable valve 24 and a multi-portable pilot valve 25.

Thanks to the invention, only the pump 23 can be used, that is to say that it is not necessary to implement an additional pump for the second main loop.

In other embodiments, provision can be made to equip the bypass cooling circuit of the second exchanger 18 or an EGR system without a second exchanger 18, which makes it possible to improve the rise in temperature of the air at the engine inlet and decrease the 25 pollutant emissions (HC, CO).

The operation of the invention is illustrated in FIGS. 2A to 2D in which the dashed lines represent the branches / loops of the cooling circuit in which the heat transfer fluid does not circulate, and the solid lines in which it circulates.

The invention essentially relates to cold starts and the temperature rise of a heat engine. Thus, after starting the engine 10, it gradually rises in temperature until a target temperature Tc is reached.

The temperature of the engine and / or heat transfer fluid is determined by measurement or by estimation, for example by a sensor arranged in the engine cylinder head, or by a virtual sensor based on a thermal model or by networks of

neurons. According to the invention, a motor temperature rise phase corresponding to a first predetermined delay D1 from the start, in this case 700s, is defined.

and / or an engine temperature lower than a first threshold value T th1, less than or equal to the target temperature Tc. In this phase, FIG. 2A, 2A 'the coolant

circulates in a first and / or a second main loop of the cooling circuit, in this case in the first; and the flow of heat transfer fluid to the engine 10 is cut, in this case by the controlled 4-way valve 25. With this configuration, the temperature of the metal masses and the lubricating oil increases more rapidly, which allows in addition to reducing the consumption of the engine 10. In this phase, all or part of the exhaust gas is re-circulated to the first exchanger 15, in this case all gases.

The heat of said first exchanger 15 can then be transmitted to the heat transfer fluid.

All or part of the re-circulated exhaust gases, in this case all the gases, are then directed, downstream from the said

first exchanger 15, to the exhaust and not to the compressor 14. As illustrated by the combination of arrows and dotted lines 2A ', it is possible to circulate the

heat transfer fluid in a low temperature cooling radiator 19, and the second exchanger 18 of the second main loop, at a DB2 flow rate of zero or less than a threshold value, in this case the DB2 flow rate is 100 1 / h, this which creates a fluid leakage current

coolant for not encountering boiling phenomena in the second exchanger 18. It is possible to implement during this phase a bypass of the second exchanger 18 to not cool the intake air, which allows to reduce polluting emissions (HC, CO).

Preferably, this circulation is performed in a second predetermined time D2 after starting the engine, less than or equal to the first delay D1, in this case 100s, and / or a temperature of the engine less than a second

threshold value T th2 less than or equal to the first threshold value T thl. Beyond the second predetermined delay D2 after starting the engine, or beyond the second threshold value T th2, as illustrated in FIG. 2A, it is necessary to circulate the coolant in the low temperature cooling radiator 19 and the second exchanger 18 of the second main loop, at a predetermined flow rate DB3 nonzero and greater than the value of the flow DB2. During this phase, all or part of the re-circulated exhaust gases are directed from the first exchanger 15 to the compressor 14.

In this case, all the exhaust gases are recirculated by the exhaust flap 12 to the first exchanger 15; then some of these gases are directed

10 to the exhaust, and another part are directed to the compressor 14, for example through a valve 13.

It is therefore necessary to circulate the coolant within the first exchanger 15, which allows to cool the mixture of re-circulated exhaust gas / air

15 admission to the intake of the engine 10.

It will be recalled that in this phase, as well as the previously described phases, the engine has not yet reached its target temperature value Tc. Beyond the first predetermined delay D1 from the start, and / or when reaching or beyond the temperature of the threshold motor T th1, as illustrated in FIG. 2B, the coolant circulates further in the engine 10 and the first main loop.

25

For the regulation of the engine temperature, as illustrated in FIG. 2C, the coolant circulates further in the second main loop, in particular when the engine has reached its target temperature Tc. Advantageously, thanks to the invention, the thermal regulation, aimed at maintaining the temperature of the engine and / or the coolant at a target value Tc, can be implemented at high temperature, in this case a first target temperature Here = 105 ° C (instead of 90 ° C as conventionally). This above-average target temperature

leads to an oil temperature also higher, resulting in a decrease in friction and therefore consumption. In addition, it is possible to enslave the target value Tc

at the operating point of the engine or at the outside temperature. For example, for a hot environment (typically an outdoor temperature above 40 ° C), the target temperature can then switch to a second value Tc2 less than the first Tc1. In this case, the

second value Tc2 is equal to 90 ° C.

Similarly, for a given operating point, for example beyond a target speed (in this case of the order of 120 km / h), the target temperature can then also switch to a second value Tc2 less than the

first Tc1. In this case, the second value Tc2 is equal to 90 ° C. Such a regulation at several target temperatures is possible thanks to the implementation of a controlled thermostat,

replacing a wax thermostat generally used in the prior art. In case of a request for heating the passenger compartment, the circulation of the coolant is that illustrated in FIG.

2B, so as to force the flow of fluid in the motor 10 to have a flow of fluid in the heater 22. A second embodiment is illustrated in Figures 3A to 3D. This variant of the cooling circuit is similar to the previously described circuit but uses an additional electric water pump 27, to circulate the heat transfer fluid within the second main loop (low temperature) of the circuit.

An electric valve 26 at the input of the motor 10 makes it possible to bypass the motor during the temperature rise thereof. Figure 3A is similar to Figure 2A and illustrates

the engine warm-up phase corresponding to a first predetermined delay D1 from the start, and / or an engine temperature below a first threshold value T th1, less than or equal to the target temperature Tc.

In this phase, the heat transfer fluid circulates in a first and / or a second main loop of the cooling circuit; and the flow of coolant to the engine 10 is cut, in this case by-passed through the electric valve 26.

Beyond the second predetermined time D2 after starting the engine, or beyond the second threshold value T th2, as illustrated in FIG. 3A, it is necessary to circulate the coolant in the radiator of the engine.

cooling at low temperature 19 and the second exchanger 18 of the second main loop, at a predetermined flow DB3 non-zero and greater than the value of the flow DB2, in this case thanks to the pump 27.

It is therefore necessary to circulate the heat transfer fluid within the first exchanger 15, which allows to cool the mixture of re-circulated exhaust gas / intake air to the inlet of the engine 10.

Beyond the first predetermined time D1 from the start, and / or reaching or beyond the threshold motor temperature T thl, as shown in FIG 3B (similar to Figure 2B), the coolant flows in besides in the

motor 10 and at least the first main loop, that is to say in this case only the motor and in the first loop, the second main loop being in this case autonomous, the fluid does not circulate between the two loops.

For the regulation of the engine temperature, as illustrated in FIG. 3C (similar to FIG. 2C), the coolant circulates further in the second main loop, in particular when the engine has reached its target temperature Tc.

In case of heating demand in the passenger compartment, the circuit is that illustrated in Figure 3B. The invention can be implemented for engines

spontaneous ignition (diesel) engines with direct injection, but also with direct or indirect injection (gasoline) direct injection. Other embodiments are illustrated in FIGS. 4, 5 and 6. In these figures, the electric valve 26 is positioned no longer at the input but at the output of the motor 10. In these cases, the electric valve 26 is advantageously a two-way valve, less expensive and less complex to implement than the electric valve 26 three or four channels shown in Figures 1 to 3.

In FIG. 4, the first exchanger 15 is no longer mounted between the passenger compartment heater 22 and the first controllable valve 11 as in the figure, for example, but it is mounted bypassing the engine 10.

In FIG. 4A, the electric valve 26 and the controllable valve 24 are both closed during the first predetermined period D1, which makes it possible to increase the temperature of the engine 10 more rapidly. The fluid

coolant circulates only in the first main loop of the cooling circuit.

In FIG. 4B, the electric valve 26 is open and the controllable valve 24 is closed. The coolant then passes through the engine 10 to maintain it in

temperature.

In FIG. 4C, the electric valve 26 and the controllable valve 24 are both open and the heat-transfer fluid then circulates further in the second main loop of the cooling circuit, between the first

and the second main loop of the cooling circuit. In FIG. 5, the first exchanger 15 is mounted on the second main loop, for example in series with the second exchanger 18. In FIG. 5A, the electric valve 26 and the controllable valve 24 are both closed during the first period predetermined value Dl, which makes it possible to increase the

30 temperature of the engine 10 more quickly. The heat transfer fluid circulates only in the second main loop of the cooling circuit, thanks to the electric pump 27 additional, in this case an electric water pump.

In FIG. 5B, the electric valve 26 is open and the controllable valve 24 is closed. The coolant then passes through the engine 10 to maintain it in temperature, thanks to the pump 23. The heat transfer fluid then flows in the first and second main loop of the cooling circuit, without these being connected between they.

In FIG. 5C, the electric valve 26 and the controllable valve 24 are both open and the coolant circulates between the first and the second main loop of the cooling circuit. Figure 6 illustrates a generalization of the invention to a non-EGR engine. There is therefore no first exchanger 15 or second exchanger 18. In FIG. 6A, the electric valve 26 and the controllable valve 24 are both closed during the first predetermined period D1, which makes it possible to increase the

20 temperature of the engine 10 more quickly. The heat transfer fluid does not circulate.

In FIG. 6B, the electric valve 26 is open and the controllable valve 24 is closed. The coolant then passes through the engine 10 to maintain it in

25, the pump 23. The heat transfer fluid then circulates (only) in the first major of the cooling circuit.

In FIG. 6C, the electric valve 26 and the controllable valve 24 are both open and the fluid

30 coolant then circulates between the first and the second main loop of the cooling circuit. 25 30

Claims (10)

REVENDICATIONS1. A method for controlling the circulation of a heat transfer fluid in a cooling circuit, for regulating the temperature of a motor vehicle heat engine (10), characterized in that it comprises steps of, in the phase of engine temperature rise corresponding to a first predetermined delay (D1) after starting the engine and / or an engine temperature below a threshold value (T thl): circulating the heat transfer fluid in a first and / or a second main loop of the cooling circuit, and - cut the flow of heat transfer fluid to the motor 15 (10). 2. The method according to claim 1, further comprising the steps of: determining the temperature of the engine and / or the heat transfer fluid, and as a function of the determined temperature: circulating the coolant in the engine (10); ) and the first main loop, and / or - circulating the coolant in the engine (10) and the second main loop. 3. A method according to any one of the preceding claims, comprising a step of maintaining the temperature of the engine and / or heat transfer fluid to a target value (Tc). The method of any of the preceding claims, further comprising a step of servocontrolling the target value (Tc) at the operating point of the engine and / or at the outside temperature. A method according to any one of the preceding claims, wherein the motor vehicle is equipped with an exhaust gas recirculation system (EGR), the method further comprising the steps of: part of the exhaust gas re-circulated to a first exchanger (15), - then transmit the heat of said first exchanger (15) to the coolant, and - then direct all or part of the exhaust gases to the exhaust -circulés. 6. Method according to claim 5, wherein, in a cold start phase of the engine corresponding to a second predetermined delay (D2) after starting the engine and / or an engine temperature below a second threshold value (T th2). ), the method comprises a step of: - circulating the coolant in a cooling radiator (19) at low temperature, and a second exchanger (18) of the second main loop, at a flow rate of zero or less than a value threshold. 7. The method of claim 5 or 6, wherein after the cold start phase and during the temperature rise phase of the engine, the method further comprises the steps of: - circulating the coolant in the radiator of cooling (19) at low temperature, and the second exchanger of the second main loop (18), at a non-zero flow and greater than said threshold value, and - direct all or part of the re-circulated exhaust gas from the first exchanger (15) to a compressor (14). 8. Device for managing the circulation of a heat transfer fluid in a cooling circuit, for regulating the temperature of a motor vehicle thermal motor (10), capable of implementing the method according to any one of the preceding claim, the device comprising: means (23, 24, 25, 26, 27) for circulating the coolant in a first and / or a second main loop of the cooling circuit, and - means (25, 26) to cut the flow of heat transfer fluid to the engine (10), configured to cut the flow of fluid during engine warm-up phase corresponding to a first predetermined time (D1) after starting the engine and / or a temperature of the engine less than a threshold value (T thl). 9. Device according to claim 8, wherein the motor vehicle is equipped with an exhaust gas recirculation (EGR) system, the device further comprising: means (12) for directing all or part of the exhaust gases; exhaust re-circulated to a first exchanger (15), means for then transmitting the heat of said first exchanger (15) to the coolant, and - means (13) to then direct all or part of the exhaust gas to the exhaust re-circulated exhaust, - means for circulating the coolant in a cooling radiator (19) at a low temperature and a second exchanger (18) of the second main loop, in a cold start phase of the engine corresponding to a second predetermined delay (D2) after starting the engine and / or an engine temperature lower than a second threshold value (T th2), at a rate of zero or less than a threshold value; means for circulating uler the heat transfer fluid in the cooling radiator (19) at low temperature and the second exchanger (18) of the second main loop, after the cold start phase and during a temperature rise phase of the engine, according to a predetermined flow rate non-zero and greater than said threshold value; and means (13) for directing all or part of the exhaust gas re-circulated from the first heat exchanger (15) to the compressor (14). 10. Motor vehicle equipped with the device according to any one of claims 8 or 9.