EP2066884B1 - Cooling circuit for the thermal engine of an automotive vehicle - Google Patents

Abstract

A cooling circuit for the thermal engine of an automotive vehicle includes a main loop that includes a first exchanger for collecting the heat from a first heat source, a first radiator and a pump connected in series by ducts for the circulation of a cooling liquid, the temperature of the cooling liquid being kept under normal operation conditions at a temperature lower than or equal to a predetermined threshold value. The cooling circuit includes a first bypass of the main loop in parallel relative to said first radiator, the first bypass including sequentially, in the circulation direction of the cooling liquid, a second exchanger for collecting the heat from a second heat source and a second radiator connected in series by ducts for the circulation of the cooling liquid, the temperature of said cooling liquid at the outlet of said second exchanger being set, under normal operation conditions, at a temperature higher than or equal to the predetermined threshold value.

Description

Technical area

The invention relates to the field of cooling motor vehicle engines such as passenger cars, trucks, buses or construction site machines. A cooling circuit generally passes through a plurality of mechanical members to be cooled and may also heat some heat-energy consuming elements, connected by tubings or other flexible or rigid conduits in which circulates a heat transfer fluid commonly referred to by the term of cooling liquid.

The invention more particularly relates to a particular arrangement of the cooling circuit for more effectively dissipating heat to the atmosphere and to improve the overall efficiency of heat exchange between the various mechanical components and elements to be heated of the motor vehicle.

Prior art

In general, the cooling circuit of a motor vehicle engine comprises a main circuit called "high temperature" for cooling and regulating the temperature of the engine. Such a main circuit thus comprises a radiator for discharging the heat energy released by the engine and conveyed by the coolant. This radiator allows a heat exchange with an ambient air flow depending on the speed of the vehicle and / or the actuation of the fan. A pump is also part of this main circuit and allows to adjust the flow of coolant in the circuit. A thermostat arranged on the main circuit makes it possible to short-circuit the radiator and thus to heat the coolant more quickly

Moreover, the main engine cooling circuit can also be used for different applications, and in particular to cool different equipment. Among these elements are for example and in particular a condenser of the air conditioning circuit of the passenger compartment of the motor vehicle, but also a heat exchanger of the engine cooling oil circuit, the gearbox cooling oil circuit, the circuit compressed air supercharging or the exhaust gas recirculation circuit also called "Exhaust Gas Recycling" (EGR).

To cool these different elements, secondary circuits can be connected to the main cooling circuit. The coolant can, in a first embodiment as described in the document FR 2,832,185 , go into a radiator dedicated to this secondary loop to lower its temperature below that of the coolant in the main circuit. The coolant then passes into the equipment to be cooled. Such a secondary loop is generally referred to as a "low temperature loop" since the coolant temperature is lowered before it is used to cool equipment.

However, the different equipment to be cooled do not need to be cooled at low temperature and can be cooled by the main circuit called "high temperature". Thus, the exhaust gas recirculation system (EGR) can be cooled directly by the coolant circulating in the main loop whose maximum temperature is of the order of 110 ° C. Indeed, the cooling circuit of the recycled gas must allow to lower the temperature of the exhaust gas from a temperature of 600 ° C to about 180 ° C, and therefore a fluid at 110 ° C allows such cooling. It is the same for the cooling circuit of the charge air which must allow to cool the compressed air whose compressor outlet temperature is about 200 ° C to 250 ° C.

Thus, in this prior art, the ventilation air evacuates, in the radiators, all the heat energy generated by the heat sources. The air does not however, it may heat up above the temperature of the cooling liquid in the main circuit.

According to another prior art, the secondary circuits may also be devoid of radiators. In this case, the main circuit radiator must discharge the additional amount of heat supplied to the coolant.

However, it is necessary to increase the heat exchange surface of the radiator, which may be incompatible with the space available at the front of the vehicle.

It is also known, and as described in the document US-5,244,256 , motor vehicle cooling circuits having two separate cooling loops, one being specifically dedicated to the cooling of the exhaust gas recirculation (EGR) device.

However, such an installation requires to multiply the elements specific to each independent cooling loop, such as pumps and expansion vessels.

Thus, the object of the invention is to improve the cooling of a thermal installation formed by an engine and all of its ancillary equipment.

A second object of the invention is to reduce the number of elements, in particular by using a single pump, a single expansion tank and a single degassing system for the two cooling circuits.

Presentation of the invention

The invention therefore relates to a cooling circuit of a motor vehicle engine comprising a main loop comprising a first heat exchanger capturing the heat of a first heat source. This exchange is generally carried out inside ducts in the engine block at the cylinder or in the cylinder head at the combustion chambers. The main loop also includes a first radiator and a pump for ensuring a flow rate sufficient to evacuate the heat energy released by the combustion inside the engine. The various elements of the main loop are connected in series by means of hoses for the circulation of the coolant. Under normal operating conditions, the temperature of the liquid is maintained at a temperature less than or equal to a predetermined threshold value.

According to the invention, the cooling circuit is characterized in that it comprises a first branch of the main loop arranged in parallel with respect to the first radiator. This first branch comprises successively, in the flow direction of the coolant flow, a second heat exchanger capturing the heat of a second heat source and a second radiator connected in series by means of hoses for the circulation of the coolant. Under normal operating conditions, the temperature of the coolant at the outlet of the second exchanger is raised to a temperature greater than or equal to the predetermined threshold value.

In other words, the heated coolant is used by passing inside the lines of the engine to directly cool or heat particular equipment of the vehicle with a coolant at higher temperatures. Indeed, some equipment does not require the use of a coolant whose temperature is regulated below the predetermined threshold value. The coolant is, in this derivation, brought to a temperature higher than that of the liquid in the main loop. Thus, the main loop may be referred to as a "high temperature" loop, while the bypass may be referred to as a "very high temperature" bypass.

Specifically, in the main loop, the coolant temperature must be kept below the predetermined threshold value of about 110 ° C. Overheating of the engine could have detrimental consequences on the motor seals or on the internal clearances allowing the sliding of the pistons inside the cylinders, and in general on the lubrication of the various mechanical parts in movement. However, the different equipment connected to this "very high temperature" bypass does not require such temperature regulation, and can withstand much higher temperatures. Thus, the temperature of the coolant at the outlet of the second exchanger is greater than the temperature of the coolant in the main circuit, in rated speed.

Such a cooling circuit thus makes it possible to improve the heat exchange between the ventilation air passing through the radiators and the cooling liquid, in particular by increasing the temperature difference between these two fluids.

As already mentioned, the heat sources, some of the heat energy is removed in the second heat exchanger, may be of different natures. The different sources can then be used independently or in combination according to various embodiments of the second exchanger.

According to a first embodiment of the invention, the second heat source of the second heat exchanger may comprise a circuit of the exhaust gas recirculation system.

In this case, the second exchanger is, for example, of the liquid / gas type in which the gases released during combustion inside the engine, are recovered and cooled by means of the exchanger and pass from a temperature of about 600 ° C to about 180 ° C. This lowering temperature is due to the heat exchange with the coolant entering the first branch of the main loop of the cooling circuit. At the exit of the second exchanger, the Coolant is therefore at a higher temperature than in the main circuit.

According to a second embodiment, the second heat source of the second heat exchanger may comprise a circuit of the lubricating oil of the heat engine. In this case, the second exchanger is of the liquid / liquid type in which the coolant is heated by the engine lubricating oil.

According to a third embodiment, the second heat source of the second heat exchanger may comprise a supercharged compressed air circuit.

In this case, the second exchanger is, for example, of the liquid / gas type in which the coolant stores heat energy conveyed by the air previously compressed by a device of the compressor or turbocharger type. Indeed, the temperature of the air at the outlet of this type of device is generally of the order of 200 to 250 ° C.

These different embodiments may, when combined, be integrated within a single multi-channel exchanger, for conveying a plurality of fluids and being separated by means of a heat exchange surface. Many types of exchangers can be used, such as for example "plate type" exchangers, or tubular exchangers.

The use of a separate radiator for the bypass makes it possible to improve the efficiency of the heat exchange between the air and the fluid to be cooled to a higher temperature. In fact, at a given ventilation air flow rate, this independent radiator makes it possible to dissipate more heat by increasing the temperature difference between the inlet and the outlet of the exchangers. In addition, this arrangement reduces the size of the radiator of the main circuit.

Furthermore, the radiators of the main loop and the "very high temperature" bypass, can be arranged relative to each other in various ways.

According to a first variant, these radiators can be arranged aeraulically in series. In this case, the air captured by the front face of the vehicle enters successively through the cooling fins of the radiator of the main loop and the first bypass. In other words, the two radiators are arranged one behind the other, for example perpendicular to the direction of travel of the vehicle corresponding to the direction of the air flow.

In this case, the air which makes it possible to cool the second radiator is at a temperature higher than that of the outside air, for example about 100 ° C. when the outside air is at 40 ° C. This increase in air temperature is not detrimental, however, since the coolant circulating in the second radiator is also at a higher temperature. Thus the air, even heated, can, in the second radiator, cool the coolant.

Furthermore, the second radiator preferably has dimensions smaller than or equal to the first radiator, and thus does not generate an increase in the overall width and height of the air intake surface on the front of the vehicle. Thus, with equal total frontal area, such a cooling circuit comprising a "very high temperature" bypass makes it possible to increase the dissipated thermal power.

According to a second variant, the first and second radiators may be arranged aeraulically in parallel. In this case, the two radiators can be cooled by separate air flows, which generates an overall exchange surface greater than the size of the larger of the two radiators. This arrangement, however, makes it possible to improve the overall efficiency of the cooling since, in this case, the flow of air passing through the two radiators is at the same temperature corresponding to the temperature of the external environment.

The two radiators can also be cooled by the same flow of air deflected after passing through the first radiator. In this case, the flow of air passing through the second radiator is at a temperature greater than that of the air flow passing through the first radiator.

In order to improve the rate of rise in temperature of the coolant in the main loop, a thermostat can be positioned on this loop so as to regulate the coolant flow rate as a function of its temperature.

According to a first embodiment, the first branch can be arranged downstream, in the direction of flow of the coolant, the thermostat arranged on the main circuit. In this case, when the thermostat blocks the circulation of the coolant inside the first radiator, it also blocks the circulation of the coolant in the first bypass. The coolant is not cooled and circulates in closed circuit in the first exchanger.

According to a second embodiment, the first branch may be arranged upstream, always in the direction of circulation of the coolant, a thermostat arranged on the main circuit. In this case, when the thermostat is actuated, the coolant no longer circulates in the first radiator, but it can however flow in the first bypass.

Advantageously, in this case, the first branch may comprise a second thermostat. In this way, it is possible to increase the speed of heating the coolant, by circulating it in the first and second heat exchangers without cooling in the first and second radiators.

Moreover, the first branch may comprise a control valve. Such a valve thus makes it possible to regulate the flow rate of the cooling liquid in the first bypass.

According to a particular embodiment, the cooling circuit may comprise a second branch of the main loop, arranged in parallel with respect to the first radiator and the first heat exchange, this second bypass may have successively in a direction of circulation of the liquid of cooling, a third radiator and a third heat exchanger capturing the heat of a third heat source connected in series by means of hoses for the circulation of the coolant.

Indeed, the cooling circuit may also include a second branch to provide heat at a lower temperature than the main loop. This second derivation then plays the role of derivation "low temperature". In this case, the cooling of the charge air can in particular be carried out in two stages. A first cooling by means of the second exchanger of the first bypass "very high temperature" allows a first lowering in contact with the cooling fluid at high temperature. A second cooling of the charge air in the third exchanger of the second bypass makes it possible to take advantage of a cooling fluid at low temperature. Analogous cycles of using the second heat exchanger as " pre-cooler " and the third heat exchanger as " cooler " can also be used to cool the engine oil or the exhaust gases of the recycling system.

In practice, the first bypass may also include a fourth heat exchanger connected to a circuit for heating the ventilation air of the vehicle cabin.

Indeed, and especially in winter, it may be necessary to quickly heat the vehicle cabin. This heat exchanger can be arranged parallel to the second radiator, especially at the output of the second heat exchanger of the high temperature loop. Indeed, in this case, the coolant is heated to a very high temperature, before entering the fourth heat exchanger. This supply of heat energy makes it possible in particular to improve the efficiency of the heat transfer.

Brief description of the figures

• ■ la figure 1 est une représentation schématique d'un circuit de refroidissement conforme à l'invention ;
• ■ la figure 2 est une représentation schématique d'un second échangeur de chaleur captant la chaleur dégagée par différents éléments du véhicule ;
• ■ les figures 3 à 5 représentent différentes variantes du circuit de refroidissement conforme à l'invention.

The manner of carrying out the invention as well as the advantages which result therefrom, will emerge clearly from the description of the embodiment which follows, given by way of indication and not limitation, in support of the appended figures in which:

• ■ the figure 1 is a schematic representation of a cooling circuit according to the invention;
• ■ the figure 2 is a schematic representation of a second heat exchanger capturing the heat released by different elements of the vehicle;
• ■ the Figures 3 to 5 represent different variants of the cooling circuit according to the invention.

Way of realizing the invention

As already mentioned, the invention relates to a cooling circuit of a motor vehicle engine. Such a circuit can be reported in particular in the engine compartment of a car, a truck, a coach, a bus or a construction vehicle in particular.

As shown in figure 1 , the cooling circuit can decompose into a main loop 1 on which is reported a bypass 11. The main loop 1 comprises a first heat exchanger 2 sensing the heat of a first heat source, a radiator 3 and a pump 4. These different elements are connected in series by means of the hoses 5,6,7,8,9. Thus, the pump 4 makes it possible to circulate the coolant both in the main loop 1 and in the first bypass 11. Moreover, the pump 4 can be arranged anywhere in the main loop 1 or in one of its derivations.

The first branch 11 is then arranged in parallel with the first radiator 3. "T" connections are then arranged at the junction between the hoses 5 and 6, and 7 and 8 so as to connect the hoses 15 and 17 of the first branch. 11 with the main loop 1. The downstream end of the bypass 11 thus opens between the exit of the radiator 3 and the inlet of the first exchanger 2.

This first branch 11 comprises a second heat exchanger 12 sensing the heat of a second heat source and a second radiator 13. These two elements are connected in series by means of the hose 16.

In the main loop 1, the coolant temperature must not exceed a predetermined threshold value T0, generally 110 ° C. Thus, the temperature of the coolant at the outlet of the first heat exchanger 2 and thus in the hoses 5, 6 and 15 is regulated at temperature T1.

Furthermore, due to the circulation of the liquid in the second heat exchanger 12, the temperature T2 of the coolant in the hose 16 downstream of the second heat exchanger 12 is greater than the temperature T1 of the coolant in the hose 15 upstream of it. However, when the vehicle is in normal operating conditions, the temperature T1 of the coolant in the main loop is substantially equal to the threshold value T0. Therefore, the temperature T2 of the coolant in the bypass 11 is greater than or equal to the predetermined threshold value T0 once the engine is at temperature.

Moreover, and as shown in this embodiment, the first and second radiators 13 may be arranged aeraulically in series. Thus, the flow of air passing through the first radiator 3 then passes through the second radiator 13 without the need to deflect it. In extreme cases the outside temperature can be around 40 ° C. It is then raised after the passage through the first radiator 3. This particular arrangement of the two radiators 3.13 one behind the other, limits the air intake surface on the front of the vehicle.

As shown in figure 2 , the second heat exchanger 12 positioned on the branch 11, can capture heat from a plurality of different heat sources arranged in parallel or in series. The heat energy captured by the coolant in this exchanger 12 switches the coolant from the temperature T1 to the temperature T2 in the hose 16.

The one or more heat sources may be formed by, in particular, a circuit 50 of the exhaust gas recirculation system and / or a circuit 60 of the engine lubricating oil and / or a compressed air circuit 70. overeating. Indeed, the temperature of these fluids is much higher than the temperature T1 of the coolant. The temperature difference with the coolant in the high temperature loop is sufficient to ensure satisfactory cooling of the coolant in the second radiator. In this way, the overall efficiency of the heat exchange between the different heat sources and the ventilation air is improved.

As shown in figure 3 the second radiator 33 of the bypass 11 can also be offset laterally with respect to the rear surface of the first radiator 3. In this case, the air flow passing through the first radiator 3 can be deflected to cool the second radiator 33 , either directly evacuated. In the case where the outside air is used to cool the second radiator 33, the amount of heat evacuated with equal capture surface is then increased. Indeed, the ventilation air can be captured laterally with respect to the front face of the vehicle and this arrangement makes it possible to improve the efficiency of the heat exchange in the "very high temperature" loop.

Furthermore, the first bypass 11 may comprise a valve 20 for regulating the flow of the coolant inside the first bypass 11. This regulating valve 20 allows, when the latter is closed, to rapidly heat the temperature of the liquid of the cooling liquid in the exchanger 12. When the valve 21 is open, the heat exchanger 12 then dissipates a maximum heat energy.

Furthermore, the main loop 1 may include a thermostat 19, the first bypass 11 being arranged downstream of the thermostat 19. Such a thermostat 19 increases the speed of rise in temperature of the coolant in the main loop 1 to by means of a hose 49 "short-circuiting" the first radiator 3 and the first bypass 11. Thus, the first heat exchanger 2 is a closed circuit with the pump 4 and the heat stored by the coolant is not exchanged with the air from the outside environment.

As shown in figure 4 , the cooling circuit may also comprise a second branch 21 arranged in parallel with the first heat exchanger 2 and the first radiator 3 of the main loop 1. This second branch 21 comprises successively a third radiator and a third heat exchanger 22 sensing the heat of a third source of heat. These two elements are connected in series by means of the hose 27 and connected to the main loop 1 by means of the three hoses 25, 26 and 28. This second bypass 21 makes it possible in particular to lower the temperature of the regulated coolant in the loop. at a temperature T1, so as to cool a fluid that may be a particular gas or a liquid in the third heat exchanger 22. In this configuration, the second heat exchanger 12 can be used to "pre-cool" air supercharging tablet, the third heat exchanger 2 being used as a "cooler" output of the "pre-cooler".

The three radiators 3, 13, 23 can be arranged in various configurations, namely aeraulically in series or in parallel.

As shown in figure 5 , the first branch 11 can be arranged upstream of the first thermostat 29 arranged on the main circuit 1. way, when the first radiator 3 is bypassed by means of the hose 59, the coolant passes inside the first bypass 11, and in particular through the second heat exchanger 12. to increase the rate of rise in temperature of the coolant since it is no longer cooled by the first radiator 3 of the main loop 1.

Furthermore, a second thermostat 39 can be arranged inside the first bypass 11. This second thermostat 39 can "short-circuit" the second radiator 13 by means of a hose 69 directly connecting the hose 15 with the hose 18.

Furthermore, a fourth heat exchanger 32 may be arranged in parallel with the second radiator 13 on the first bypass 11 downstream of the second heat exchanger. This fourth heat exchanger 32 can be connected to a circuit for heating the ventilation air of the vehicle cabin.

This embodiment allows in particular to obtain rapid heating of the cabin, which can be advantageous for defrosting a windshield quickly or simply improve the comfort of the vehicle. It also improves the efficiency of the heat exchange in the fourth heat exchanger 32 since the fluid passing through it is at a temperature greater than that of the main loop 1 on which it is generally arranged.

• ■ il permet d'améliorer le rendement global d'un échange thermique généré par l'ensemble des équipements chauffants ou à chauffer du véhicule ;
• ■ à rendement équivalent, il permet de réduire la surface de captation en air frais au niveau de la surface avant du véhicule ;
• ■ il permet d'améliorer le confort général du véhicule en améliorant la rapidité de chauffage de la cabine notamment.

It follows from the foregoing that a cooling circuit according to the invention has many advantages, in particular:

• It makes it possible to improve the overall efficiency of a heat exchange generated by all the heating or heating equipment of the vehicle;
• ■ with equivalent efficiency, it reduces the fresh air intake area at the front surface of the vehicle;
• ■ It improves the overall comfort of the vehicle by improving the speed of heating the cabin in particular.

Claims (12)

1. A cooling circuit for a motor vehicle combustion engine, comprising a main loop (1) comprising a first exchanger (2) that collects the heat from a first heat source, a first radiator (3) and a pump (4) which are connected in series using hoses (5, 6, 7, 8) allowing the circulation of a liquid coolant, the temperature of said coolant being, under normal operating conditions, kept at a temperature (T1) lower than or equal to a predetermined threshold value (T0), a first bypass (11) of the main loop (1) arranged in parallel with said first radiator (3), characterized in that said first bypass (11) comprises, in succession, in the direction in which the coolant flows, a second exchanger (12) collecting heat from a second heat source and a second radiator (13), these being connected in series by means of hoses (15-18) allowing the circulation of said liquid coolant, the temperature of said coolant leaving said second exchanger (12) being, under normal operating conditions, raised to a temperature (T2) higher than or equal to the predetermined threshold value (T0).
2. The cooling circuit as claimed in claim 1, characterized in that the second heat source of the second exchanger (12) comprises a circuit (50) of the exhaust gas recirculation system.
3. The cooling circuit as claimed in claim 1, characterized in that the second heat source of the second exchanger (12) comprises a circuit (60) of the combustion engine lubricating oil.
4. The cooling circuit as claimed in claim 1, characterized in that the second heat source of the second exchanger comprises a compressed charge air circuit (70).
5. The cooling circuit as claimed in claim 1, characterized in that said first (3) and second (13) radiators are arranged, in terms of air flow, in series.
6. The cooling circuit as claimed in claim 1, characterized in that said first (3) and second (33) radiators are arranged, in terms of air flow, in parallel.
7. The cooling circuit as claimed in claim 1, characterized in that the first bypass (11) is arranged downstream, in the direction in which the coolant flows, of a first thermostat (19) arranged on the main circuit (1).
8. The cooling circuit as claimed in claim 1, characterized in that the first bypass (11) is arranged upstream, in the direction in which the coolant flows, of a first thermostat (29) arranged on the main circuit (1).
9. The cooling circuit as claimed in claim 8, characterized in that the first bypass (11) comprises a second thermostat (39).
10. The cooling circuit as claimed in claim 1, characterized in that the first bypass (11) comprises a regulating valve (20).
11. The cooling circuit as claimed in claim 1, characterized in that it comprises a second bypass (21) of the main loop (1), arranged in parallel with respect to said first radiator (3) and to said first heat exchanger (2), said second bypass (21) comprising, in succession, in the direction in which the coolant flows, a third radiator (23) and a third exchanger (22) collecting heat from a third heat source, these being connected in series by means of hoses (25-28) allowing the circulation of said liquid coolant.
12. The cooling circuit as claimed in claim 1, characterized in that the first bypass (11) comprises a fourth heat exchanger (32) connected to a circuit for heating the air with which the cab or cabin of the vehicle is ventilated.

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