FR2697869A1 - Motor vehicle internal combustion engine cooling system - has first cooling circuit boiling cooling fluid, and second cooling circuit including heat exchanger connected to vehicle lubricating circuit, pump, heater and control system - Google Patents

Abstract

The engine cooling system includes the first cooling circuit (C1) in which the coolant liquid is brought to the boil. The second cooling circuit (C2) has a heat exchanger (2) connected to the lubrication circuit of the vehicle engine or gearbox. The second circuit includes the supply pump (7), the autonomous heater (4) to accelerate the rise in temperature of the cooling fluid, control valves (11,9) and the control system permitting the flow and temperature of the cooling fluid to be adapted as a function of several operating parameters of the engine. The control system is implemented with analogue or digital electronic circuits or with a microcontroller implementing a suitable algorithm. ADVANTAGE - Improved cooling efficiency while bringing engine up to operating temperature more quickly.

Description

COOLING SYSTEM FOR A MOTOR
INTERNAL COMBUSTION
The present invention relates to a cooling system for an internal combustion engine fitted to a motor vehicle.

The invention relates more particularly to a cooling system by vaporization of the cooling agent comprising means for preheating the latter.

 The standards concerning pollution and consumption of internal combustion engines fitted to motor vehicles are becoming more stringent every day in all industrialized countries. The automotive industry is therefore now busy finding technical solutions to meet these obligations, without penalizing either the performance of the engines or their cost price.

 Cooling systems play an important role in the proper functioning of internal combustion engines and therefore in pollutant emissions.

 Conventionally, cooling systems use a circulation of water (mixed with rust inhibitors and antifreeze) in a closed loop circuit. The water driven by a pump then absorbs the heat from the hot parts of the engine mainly in a water chamber surrounding the cylinders, then is cooled in turn in a radiator where the ambient air circulates, before returning to the engine. This operation is improved by means ensuring temperature regulation, by means of pressurizing the water circuit to avoid cavitation of the pump, etc.

However, such systems have the disadvantage of requiring a large amount of water, which implies a weighing down of the vehicle and a relatively long rise in temperature: hence emissions of unburnt and pollutants. Furthermore, at certain points in the water chamber, the temperatures can reach values high enough to cause an uncontrolled local boiling and therefore the appearance of hot spots generating certain pollutants,
NO and HC in particular.

 For these reasons, other cooling systems have therefore been developed, and in particular two-phase cooling systems of the water-vapor type. One can cite on this subject among the most recent publications, the patents US-A-4,572,115, US-A-4,570,115 and US-A4,367,699 which more particularly describe so-called constant level or boiling cooling systems. stagnant. The principle of these systems is simple: use the evaporation of water to absorb large quantities of engine heat thanks to the latent heat of vaporization of the water. This technique allows with a reduced quantity of liquid to operate an efficient cooling of the engine.

The applicant has therefore developed a new two-phase cooling system, more particularly described in the patent application.
EP-A-489.628. This invention aims to eliminate some of the residual problems of the two-phase cooling circuits, such as the release of vapor to the atmosphere which leads to a progressive consumption of the cooling fluid compromising the autonomy of the vehicle. This system is based on a forced circulation of the cooling fluid where the characteristics of this circulation, flow rate and pressure, are regulated as a function of one or more engine operating parameters. The cooling system makes it possible to regulate the temperature of the walls of the combustion chambers to an optimum value determined according to the characteristics of the engine.

 The object of the present invention is to further improve the efficiency of such a cooling system and more particularly the rapid rise in temperature of the engine when the engine is started so as to reach the optimum temperature as soon as possible, and this in particular by using integrated preheating means selectively controlled.

 The cooling system according to the invention is more particularly intended for internal combustion engines fitted to motor vehicles. This system comprises a first cooling circuit by circulating boiling of the cooling agent which comprises the internal circuit of the engine, a phase separator, at least one heat-condenser exchanger, a supply pump, piloted valves and a control system making it possible to adapt the flow rate and the pressure of the coolant as a function of one or more operating parameters of said engine.

 According to the invention, the cooling system is characterized in that it also comprises a second cooling circuit comprising a heat exchanger connected to the lubrication circuit of the engine or of the gearbox, a supply pump, heating means autonomous, controlled valves and a control system allowing the flow rate and the temperature of the coolant to be adapted as a function of one or more operating parameters of said engine.

 According to another characteristic of the cooling system according to the invention, the first cooling circuit also includes heating means controlled by the circuit control system to allow the temperature of the cooling agent to be adapted according to a or several operating parameters of said engine and in particular to accelerate the rise in temperature of the cooling agent when the engine is started.

 According to another characteristic of the cooling system according to the invention, the controlled heating means are common to the two cooling circuits.

 According to another characteristic of the cooling system according to the invention, a single and same control system controls the operation of the two cooling circuits. This system can for example be the electronic engine control system.

 According to another characteristic of the cooling system according to the invention, the heating means consist of an energy storage device capable of releasing heat energy in contact with the cooling agent when the latter is still cold and to store it in contact with the cooling agent, when the latter has reached a certain temperature.

 According to another characteristic of the cooling system according to the invention, the energy storage device uses elements containing salts with latent heat of fusion, such as barium hydroxide salts.

 According to another characteristic of the cooling system according to the invention, the two cooling circuits communicate and therefore use the same cooling agent.

 According to another characteristic of the cooling system according to the invention, the two cooling circuits are completely separate and therefore do not communicate with each other.

They can therefore use different types of coolants.

The objects, aspects and advantages of the present invention will be better understood from the description given below of an embodiment of the invention applied to an internal combustion engine, this embodiment being given by way of non-limiting example, with reference to the appended drawing, in which
- Figure 1 schematically shows a cooling system according to the invention;
- Figures 2 to 5, similar to Figure 1, specify the operation of the cooling system according to the invention.

 Figure 1 therefore shows a cooling system of an internal combustion engine of the multicylinder type, identified by reference 1 in the drawings, fitted to a motor vehicle. Only the elements necessary for understanding the invention have been shown.

 The cooling system presented mainly consists of two separate circuits C1 and C2 ensuring the selective circulation of a coolant, such as a mixture of water, rust inhibitors and antifreeze.

 The first circuit C1 is mainly intended for cooling the hot walls of the engine. This circuit is more particularly arranged for the implementation of the circulating boiling cooling method described in the aforementioned patent application No. EP-A-489,628.

 This first circuit C1 therefore comprises an internal circuit of the engine or "water chamber". This water chamber conventionally consists of an enclosure defined in the cylinder block, surrounding the walls of the combustion chambers, and extending into the cylinder head. The outlet opening of the water chamber, placed in the upper part of the latter, communicates with a phase separator 3 comprising pressure compensating means controlled by control means and a derating valve. A return pipe connects the lower part of the phase separator 3, where the liquid is collected, to the inlet orifice of the water chamber by means of a supply pump 8 making it possible to ensure a sufficient circulation speed.

 The vapor phase can be treated by two separate condensation radiators 5 and 6. The upper part of the phase separator 3, where the vapor circulates, is connected to a first condenser 5. This heat exchanger 5, of the water / air type, cooperates with a fan not shown, the condensate is collected in an integrated tank fitted with a valve allowing the pressure to be adjusted; a pipe fitted with a valve, connects this reservoir to the return pipe to the water chamber, upstream of the pump 8. The phase separator 3 is also connected to a second condenser or air heater ensuring the transfer of calories to the passenger compartment of the vehicle to heat the latter. A piloted valve 10 makes it possible to direct the flow of steam to one and / or the other of the two condensers 5 and 6.

 The valve 10 as well as the other controlled means, namely the pump 8, the fan and the various pressure regulation means equipping the circuit C1, are controlled by an electronic computer not shown, which may be the computer of the electronic system of engine control. This computer then determines according to different parameters representative of the operation of the engine, such as the speed, the load, the manifold pressure, etc., the operating characteristics of each, according to predetermined strategies specified below.

 The cooling system also includes a second cooling circuit C2 cooperating closely with the first circuit C1 mentioned above. This second circuit C2, which is in particular intended to regulate the temperature of the oil used to lubricate the engine 1 and / or the gearbox, not shown, by means of a water / oil heat exchanger 2, has also for the function of accelerating the rise in temperature of the oil and / or of the walls of the combustion chambers by using autonomous and rechargeable preheating means such as an energy storage device 4.

 The energy storage device 4 makes it possible to store heat energy, taken from the cooling circuit, during the operation of the engine and then to restore this energy during predetermined operating phases, such as the starting phase. It essentially consists of a heat-insulated enclosure in which are sealed tanks, good thermal conductors, containing latent heat salts of fusion whose liquefaction is endothermic and therefore the solidification is strongly exothermic. barium hydroxide whose melting temperature is 780C and whose latent heat of fusion at this temperature is 320 kJ / Kg The enclosure openings are controlled by piloted valves selectively allowing the passage of coolant to the inside the enclosure.

 The second circuit C2 therefore includes a water / oil type heat exchanger 2 connected to the engine lubrication circuit. This heat exchanger 2 is connected by an inlet pipe and a return pipe to the enclosure of the energy storage device 4. A supply pump 7 ensures the circulation of the heat-transfer fluid used in this second circuit.

A bypass pipe also makes it possible to circulate this fluid in the air heater 6 used to heat the passenger compartment of the vehicle.

The air heater comprises two separate parts corresponding respectively to the first and second circuits and thus making it possible not to mix the two heat transfer fluids used in each of the two circuits C1 and C2. One can however provide in another embodiment of the heater 6 a single part common to the two circuits which then involves the use of the same fluid. A piloted valve 9 makes it possible to direct the heat transfer fluid of the second circuit through the exchanger 2 and / or the air heater 6.

 Independently of the possibly common water boxes of the air heater 6, the circuits C1 and C2 are brought together at the energy storage device 4. A bypass pipe makes it possible to circulate the coolant of the first circuit through the energy storage device 4.

This pipe is connected on the one hand to the upper output of the phase separator and on the other hand to the upstream input of the feed pump 8. A pilot-operated valve 11 makes it possible to selectively operate the circulation of the coolant of the first circuit through the energy storage device 4. Here again two possibilities can be envisaged: either the enclosure of the energy storage device is compartmentalized for prevent the communication between the two circuits, ie the enclosure is not compartmentalized and the two circuits C1, C2 are able to communicate.

 The valves 9 and 11 as well as the other piloted means equipping the second circuit C2, namely the pump 7 and the valves controlling the openings of the heat-insulated enclosure of the energy storage device are controlled as for the first circuit C1 by a computer-electronics not shown, which may be the computer of the electronic engine control system. The computer determines, according to various parameters representative of the operation of the engine, such as the speed, the load, the manifold pressure, etc., the operating characteristics of each, according to predetermined strategies specified below.

 According to Figures 2 to 5, the operation of the cooling circuit according to the invention is as follows. In these figures, the unused parts of circuits C1 and C2 are shown hatched.

 When starting the engine, see Figures 2 and 3, the electronic system which controls the cooling circuit according to the invention triggers the circulation of the coolant through the second circuit, between the water / oil exchanger 2 and the device energy storage 4, by activating the pump 7 and in particular controlling the valve 9 and the valves of the device 4. The contact of the cold water inside the enclosure with the molten salt tanks cause solidification of these and a strong release of heat. This results in an extremely rapid rise in the temperature of the coolant and, thanks to the exchanger 2, a corresponding rise in the temperature of the oil which thus very quickly reaches its optimum lubrication temperature, which makes it possible to reduce friction. of the motor.

 With regard to driving the first circuit C1, two strategies are possible. Or, in Figure 3, the first circuit is inactivated so as to naturally accelerate the rise in temperature of the engine, by not operating the circulation of the cooling agent inside the water chamber. Or, Figure 2, to further accelerate the temperature rise, the first circuit is activated by sending the coolant through the energy storage device 4 so as to quickly heat the latter and thus to heat the walls of the engine.

In addition to the engine temperature rise, both of the combustion chambers and of the lubricating oil, it may be important to heat the passenger compartment of the vehicle;
See FIG. 3, directing via the valve 9 the circulation of part of the cooling agent of the second circuit C2, towards the air heater 6, to very quickly obtain the desired temperature in the passenger compartment of the vehicle.

 When the engine is running hot, see Figure 4, the second circuit C2 continues to provide circulation of the coolant, but then it is the coolant which returns the heat energy taken from the 'heat exchanger 2, to the energy storage device 4 by operating the salt fusion, so that the latter reconstitutes these reserves for the next start-up. It is also possible to provide for the circuit C1 to participate, see FIG. 5, in recharging the energy storage device 4, by deriving the cooling agent through the device 4.

 When the engine is stopped, the energy storage device 4 is immediately isolated by closing the openings of the enclosure containing the salts, so as to keep the latter liquefied for as long as possible.

 Of course, the invention is in no way limited to the embodiment described and illustrated, which has been given only by way of example.

 On the contrary, the invention includes all the technical equivalents of the means described and their combinations if these are carried out according to the spirit.

Thus, it is possible to provide specific heating means for each of the cooling circuits. Similarly, it is possible to provide separate control means for each of the circuits C1 and C2. Thus in the case where the cooling circuits C1 and
C2 are completely separate, it is possible to use two coolants with different characteristics.

As regards the production of the control means controlling the engine cooling system which has just been described, it can be produced in various forms
- either with analog electronic components for which summers, comparators and other filters are produced using operational amplifiers
- either with digital electronic components that would perform the function in wired logic
- either by a signal processing algorithm implemented in the form of a software module component of an engine control software system operating the microcontroller of an electronic computer
- Or again, by a specific chip (custom) whose hardware and software resources will have been optimized to carry out the functions which are the subject of the invention: microprogrammable chip or not, encapsulated separately or else all or part of a coprocessor implanted in a microcontroller or microprocessor etc.

 Likewise, the invention includes all the technical equivalents applied to an internal combustion engine whatever its combustion cycle (2-stroke, 4-stroke), the fuel used diesel or petrol or else, the number of cylinders.

Claims (8)

 [1] Cooling system for an internal combustion engine (1) fitted to a motor vehicle, comprising a first cooling circuit (C1) by circulating boiling of the cooling agent comprising the internal circuit of the engine, a phase separator (3 ), at least one heat-condenser exchanger (5,6), a feed pump (8), piloted valves (11,10) and a control system allowing to adapt the flow and the pressure of the coolant as a function of one or more operating parameters of said engine (1), characterized in that it also comprises a second cooling circuit (C2) comprising a heat exchanger (2) connected to the lubrication circuit of the engine (1) or of the gearbox, a feed pump (7), autonomous heating means (4), piloted valves (11,9) and a control system making it possible to adapt the flow rate and the temperature coolant depending on u n or more operating parameters of said motor (1).  [2] Cooling system according to claim 1, characterized in that said first circuit (C1) also includes heating means (4) controlled by the control system of said circuit to allow the temperature of the agent to be adjusted. cooling as a function of one or more operating parameters of said engine (1) and in particular to accelerate the rise in temperature of the cooling agent when the engine starts. [3] Cooling system according to claim 2, characterized in that the controlled heating means (4) are common to the two circuits (C1, C2).  [4] Cooling system according to any one of claims 1 to 2, characterized in that one and the same control system controls the operation of the two cooling circuits (C1, C2). [5] Cooling system according to any one of claims 1 to 4, characterized in that said heating means are constituted by an energy storage device (4) capable of releasing heat energy in contact with the coolant when the latter is still cold and to be stored in contact with the coolant when the latter has reached a certain temperature. [6] Cooling system according to claim 5, characterized in that said energy storage device (4) uses elements containing salts with latent heat of fusion, such as barium hydroxide salts.  [7] Cooling system according to any one of claims 1 to 6, characterized in that the two circuits (C1, C2) communicate and use the same cooling agent. [8] Cooling system according to any one of claims 1 to 6, characterized in that the two circuits (C1, C2) are distinct and do not communicate with each other.