EP0775822B1 - Starting aid method and apparatus for internal combustion engine - Google Patents

Description

The present invention relates to the field of cold starting of vehicles automobiles having an internal combustion engine.

Given the increasingly severe standards in force or to come, emissions pollutants must be reduced, especially cold, during the first minutes engine operation. We know that most pollutants (80%) are emitted within this period, when the conversion catalyst placed in the line exhaust is not yet sufficiently heated by the exhaust gases to be efficient.

It is currently well known that one of the major obstacles for the depollution of motor vehicles is in the warm-up phase following a cold start.

There are several reasons for this, the first in order of importance being the enormous increase in viscosity of cold lubricants, which can exceed 1000 cSt below 0 ° C, resulting in very high friction levels in the engine, resulting in no less high overconsumption. This fact is aggravated by feeding difficulties at low temperatures, poor quality fuel mixtures from insufficient spraying and evaporation fuel in the air intake, which is compensated as best as possible by a enrichment of the fuel load. Overconsumption is naturally accompanied by high emissions of basic pollutants, carbon monoxide and unburnt, consequences of too rich mixtures and incomplete combustions, and that cannot exhaust the exhaust catalyst as long as its temperature is not reached, which may take several minutes.

In addition, improvements in the design of combustion chambers have resulted in a real increase in thermodynamic efficiency for engines recent, with the corollary a decrease in the heat transferred through the cylinder walls, therefore an additional difficulty in heating up the engine, and thereby the interior of the vehicle, exploiting the heat in a natural way contained in cooling water.

Many studies have therefore already focused on the problem of starting motor vehicle cold. There are basically two types of solutions: those outside the engine and those aimed directly at the engine.

Solutions affecting the engine concern for example pre-evaporation fuel, improving fuel atomization or the homogenization of the load. By way of example, patent FR 2 706 184 describes a such a fuel vaporization device.

Solutions "external" to the engine notably concern the line specifically the reduction of the time required to initiate the (or) catalyst (s) placed in the exhaust.

One known way is to cover the catalyst with a layer intended to lower the temperature at which the catalyst begins to be active.

Another solution may consist in injecting additional air, by upstream of the catalyst which thus receives additional energy and heats up more quickly.

The electric heating of the catalyst can also be considered as by example in patent EP-B1-605479. This solution is certainly effective since totally dedicated to heating the catalytic converter. However, this system is energy consumer since it consumes at least three or four kilowatts on the battery. An additional battery should be considered. The energy balance is therefore not completely satisfactory and the overall yield is very low.

Thus recent developments have sought to reduce the electrical capacity necessary for heating the catalyst.

The solutions which go in this direction consist in choosing an element catalytic converter and put it in the right place.

Other technological solutions have been considered such as for example the preheating of the catalytic converter by hot gases generated by a burner placed in upstream of said pot as described in document DE 4208621, this burner also allowing to heat the passenger compartment of the vehicle thanks to an exchanger. The WO 95/14852 describes another arrangement for preheating the pot Catalytic. The thermal power of such a unit is high, of the order of 15 kW of so that the catalyst can be activated in about 20 seconds. The advantage is good yield of this system, close to 100%.

However, one of the problems of this type of solution is to require a element here the burner whose sole function is to heat the catalyst (s).

In addition, both for electric heating and for space heating burner, a problem of premature and / or unpredictable catalyst aging may arise, this problem being due to the strong and brief thermal stresses of the catalyst.

In addition, it is also known from document DE-A-3 341 097 to link the engine cooling system to a source of calories, such as a fuel tank storage of a hot fluid, so as to introduce, at startup, this hot fluid into the engine circuit.

As shown by this document, the heating of the intake air is carried out by another circuit separate from the main engine circuit which results in a complication of the device.

The present invention overcomes in particular the problems of the art previous stated above.

Thus the present invention provides a method for improving both the consumption and anti-pollution of cold engines.

One of the advantages of the present invention is to provide a means of heating whose consumption can be compensated in order not to degrade the thermal and economic balance.

Thus the subject of the present invention is a method of starting assistance with cold for motor vehicles with internal combustion engine comprising a catalyst placed in the engine exhaust line consisting of using a burner and a gas-liquid exchanger integrated into the coolant circuit, said burner being used to directly heat the exhaust gases, the catalyst and exchanger integrated in the cooling circuit, characterized in that we use the calories from said burner and conveyed by the liquid cooling to heat the air admitted to the engine and then to heat the oil of the engine, the metallic mass of the engine and the air for heating the passenger compartment.

According to the invention, the method is used for a determined period, basically when the engine is cold.

In addition, the method according to the invention can be used for a period determined based on engine speed and load.

In particular, the burner is supplied with the same fuel as the engine.

The catalyst can be placed between the burner and the heat exchanger.

Without departing from the scope of the invention, the heat exchanger can be arranged between the burner and the catalyst.

The present invention further relates to a starting aid device for cold of motor vehicles with internal combustion engine comprising a catalyst placed in the engine exhaust line and a fluid circuit cooling, said device comprising a burner and a gas-liquid exchanger integrated in the coolant circuit, said burner being placed in such a way that it directly heats the exhaust gases, the catalyst and the gas-liquid exchanger integrated in the cooling circuit, characterized by which it also includes means for transferring calories conveyed by the coolant to the engine intake air and then to the engine oil, the metallic earth of the engine and the air for heating the passenger compartment of the vehicle.

Advantageously, the burner is supplied with the same fuel as the engine.

According to one of its characteristics, the burner is put into operation for a fixed period, mainly when the engine is cold.

According to another characteristic, the burner is put into operation for a fixed duration, depending on the engine speed and load.

Other characteristics, advantages and particularities of the present invention will appear better on reading the description which follows, given by way of illustration and in no way limitative with reference to the single appended figure.

This figure shows schematically an internal combustion engine 1 and the associated cooling circuit 7.

Usually, the coolant circulates thanks to a pump 2 through several elements for heat exchange: in addition to the metallic mass of the engine 1 itself, the water exchanges calories with the oil via an oil-water exchanger 3, with the intake air via an air-water exchanger 11, and with the passenger compartment via a air heater 4. A thermostat 9 also makes it possible to regulate the flow of circulating water in a radiator 10 and the oil-water exchanger 3.

According to the invention, at least one burner 5 is placed on the circuit cooling so that it can heat a gas-liquid exchanger 6 integrated in the cooling circuit 7 of the engine 1. The exchanger 6 is arranged on the exhaust 8, so that the combustion gases from the burner 5 pass through the exchanger 6 then are evacuated with the exhaust gases which they heat. So the combustion gases from the burner 5 can be used to heat a catalyst (not referenced) placed in the exhaust 8. Once the catalyst is primed, the gases are converted by it.

In other words, part of the heat from the combustion gases of the burner 5 is thus captured by the coolant which, via the usual organs of the cooling circuit 7, will transfer this heat to the oil (via the exchanger 3), to the intake air, to the passenger compartment (via the air heater 4) and to earth metallic motor 1.

The other part of the heat from the burner 5, having passed through the exchanger 6, will therefore mix with the exhaust gases from engine 1 as indicated above.

Without departing from the scope of the present invention, the catalyst (not referenced) can be placed in front of the exchanger 6 integrated in the cooling circuit 7.

The calculations show that we can hope for a recovery in this way. of heat of the order of 10 kW in the cooling circuit 7 of an engine middle-class automobile, which results in a decrease of one factor 2 of the temperature rise time of the fluids, while ensuring a adequate interior heating with 5 kW available on average at the heater. This is valid for conditions of activation at low revs and low load, which are most affected by the problems already mentioned.

The operating time of the burner 5 will naturally depend on the outside temperature, but also of the speed and the load imposed on the engine 1. In all cases, only the first minutes of starting must be assisted in this way, a compromise must be sought in order not to increase the overconsumption.

Commonly, the engine is considered to be cold when the cooling system temperature is less than about 50 ° C.

One or more temperature sensors will be provided on the engine, associated with a burner control element in order to activate it beyond a certain temperature.

Under these conditions, we can at least hope for an unchanged balance sheet as regards relates to consumption, i.e. the fuel used in the burner may be offset by the engine efficiency gains achieved through a rapid reduction in friction, consequence of a higher temperature rapid lubricant, and thanks to improved carburetion.

The economic balance of the system will be all the more favorable as the temperature at start-up will be lower, the increase in friction being almost exponential with the decrease in temperature.

Thus, the essential advantage of the device lies in the improvement of the depollution, carried out globally by accelerated heating of all parts of the engine, in particular that of the air admitted for better carburetion, and exhaust catalyst for faster priming. Finally, the heating of the passenger compartment can be secured at a level sufficient to not require any other additional means of heating.

Claims (10)

1. Process for cold start assistance for motor vehicles with an internal combustion engine including a catalyst placed in the exhaust line of the engine consisting of using a burner and a gas-liquid exchanger integrated in the cooling liquid circuit, the said burner being used to directly heat the exhaust gases, the catalyst and the exchanger integrated in the cooling circuit, characterised by the fact that the calories coming from the said burner and transported by the cooling liquid are used to heat the air taken into the engine and then to heat the engine oil, the metal mass of the engine and the air for heating the passenger space.
2. Process as described in claim 1, characterised by the fact that it is used for a determined duration, essentially when the engine is cold.
3. Process as described in any one of the preceding claims, characterised by the fact that it is used for a duration determined as a function of the running conditions and load of the engine (1).
4. Process as described in any one of the preceding claims, characterised by the fact that the burner (5) is supplied with the same fuel as the engine (1).
5. Process as described in any one of the preceding claims, characterised by the fact that the said catalyst is arranged between the burner (5) and the exchanger (6).
6. Process as described in any one of the preceding claims, characterised by the fact that the exchanger (6) is arranged between the said burner (5) and the said catalyst.
7. Device for cold start assistance for motor vehicles with an internal combustion engine (1) including a catalyst placed in the exhaust line of the engine and a cooling liquid circuit, the said device including a burner (5) and a gas-liquid exchanger (6) integrated in the cooling liquid circuit, the said burner being positioned in such a manner that it directly heats the exhaust gases, the catalyst and the gas-liquid exchanger (6) integrated in the cooling circuit, characterised by the fact that it also includes means permitting transfer of calories transported by the cooling liquid to the induction air of the engine and then to the engine oil, to the metal mass of the engine and to the air for heating the passenger space of the vehicle.
8. Device as described in claim 7, characterised by the fact that the burner (5) is supplied with the same fuel as the engine (1).
9. Device as described in any one of claims 7 to 8, characterised by the fact that the burner (5) is operated for a determined duration, essentially when the engine is cold.
10. Device as described in any one of claims 7 to 9, characterised by the fact that the burner (5) is operated for a determined duration, as a function of the running conditions and load of the engine.

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