WO2008012452A2

WO2008012452A2 - Method for reducing hydrocarbon emissions from a cold engine with external fuel injection and engine for the implementation of said method

Info

Publication number: WO2008012452A2
Application number: PCT/FR2007/051448
Authority: WO
Inventors: Jean-Bruno Zimmermann; Eric Hamon; Frédéric Gourves
Original assignee: Peugeot Citroën Automobiles SA
Priority date: 2006-07-25
Filing date: 2007-06-15
Publication date: 2008-01-31
Also published as: FR2904370B1; FR2904370A1; EP2044312A2; WO2008012452A3

Abstract

The invention relates to a method for reducing unburned hydrocarbon emissions from a cold engine with external fuel injection. Preferably, the method comprises three successive phases (I, II, III) after the cold engine is started: a first phase (I) of high pressure fuel injection (HP) during the intake, the intake valves open, a second phase (II) comprising a principal fuel injection at high pressure during the intake, the intake valves at least partly open and a secondary fuel injection at high pressure during the exhaust, intake valves closed, and a third phase (III) of injection at low pressure (BP), during the exhaust, intake valves closed. The invention also relates to an engine for the implementation of the method.

Description

METHOD OF REDUCING HYDROCARBON EMISSIONS OF A COLD ENGINE WITH INDIRECT FUEL INJECTION AND ENGINE FOR THE IMPLEMENTATION

WORK OF THIS METHOD

The invention relates to a process for reducing hydrocarbon emissions from a cold engine with indirect fuel injection.

It also relates to an indirect fuel injection engine for the implementation of the method. The pollution of the environment caused by the rejection of internal combustion engines is a concern that has led the authorities to provide ever more stringent standards that must be respected by car manufacturers. In particular, the level of release of hydrocarbons into the atmosphere must be substantially reduced. For this purpose, it is common, on the one hand, to use catalysis to improve the combustion of the exhaust gases of internal combustion engines and, on the other hand, to improve combustion in combustion engines. internal.

It has been found in particular that the majority of unburned hydrocarbon emissions occur when the engine is cold, that is to say generally at startup, because, in this situation, the catalyst or catalysts are not active, the quality of the mixture of air and fuel and the thermodynamic conditions in the cylinder are not optimal, which does not allow a good atomization / vaporization of the fuel mixture. As a result, the combustion does not proceed properly, which greatly increases the formation of pollutants produced by the engine. More precisely, it can be seen that, for gasoline-powered vehicles, most of the vehicle's pollutant emissions take place during the first seconds of engine operation, when the catalyst is not primed when it is cold. Typically, according to the standard homologation cycle, up to 90% of the unburned hydrocarbon emissions are during the first tens of seconds of operation of the engine, these cycles comprising a phase of idling engine operation, particularly conducive to releases of unburned hydrocarbon pollutants. Figure 1 appended to this description illustrates very schematically the configuration of an indirect fuel injection engine. This figure shows only a single cylinder 1, in partial section of this engine.

Usually, an engine of this type comprises one, two, three or four cylinders or more.

The cylinder 1 comprises a cylindrical wall 10 allowing a reciprocating vertical movement of a piston 11, surmounted by a combustion chamber 18. This chamber is supplied with an "air-fuel" mixture, referenced Airet Ess, respectively, via a conduit The indirect injection mode implies that the injector 14 associated with this cylinder sprays the fuel on the walls of the intake duct and / or on the intake valve or valves 15, and not directly. in the combustion chamber 18. The engine being of the type called "four-stroke cycle", this mixture is admitted through an intake valve 15 during the so-called admission time. Symmetrically, after the compression and combustion times, the flue gases Ge are ejected in an exhaust duct 13 via an exhaust valve 16, during the exhaust time. A spark plug 17 provides sparks for igniting the fuel mixture at the end of the compression time.

From the foregoing, it is easily understood that, during a first start, cold engine, the intake duct 12 and the corresponding valve 15 are not yet hot. The essence hardly evaporates due to a lack of heat input from the walls and / or the valve 15 and tends to re-condense.

Measurements carried out on a test bench make it possible to highlight this phenomenon.

FIG. 1A, appended to the present description, is a curve showing the variations in the level of unburned hydrocarbon emissions as a function of time, after a first start of the engine, that is to say a cold engine. The vertical axis is graduated in ppmC unburned hydrocarbons and the horizontal axis in number of engine cycles.

It can be seen from this curve that unburned hydrocarbon emissions are very important during the very first engine cycles after a cold start. It is therefore essential to improve the damping of this type of cold engine, that is to say, to control the starting of this engine and in particular the injection that will condition the preparation of the air / fuel mixture.

In the known art, various methods have been proposed to improve the combustion conditions during this cold start phase, and thereby reduce the pollution produced by the engine.

A commonly used solution consists in reducing the average diameter of drops injected into the combustion chamber 18, which diameter is characterized by the so-called Sauter average diameter value. This physical quantity is better known by the abbreviation "SMD" used hereafter (for "Sauter Mean Diameter"). To do this, we increase the injection pressure to provide the largest possible exchange surface with the ambient air to vaporize and ensure the most homogeneous mixture possible.

In this connection, it has been found that unburned hydrocarbon emissions during cold engine operation are particularly important in the case where the engine uses camless type valves (absence of camshaft). replaced by an electrically controlled device, in particular electromagnetic or electrohydraulic). They are nevertheless also prohibitive in the case of engines using a conventional distribution camshaft.

The Holder has been able to demonstrate that this higher emission of unburnt hydrocarbons from the cold engine in the case of electrically actuated or hydraulic valves finds part of its origin in the fact that the opening of the intake valve performs more quickly with such an electrical control with a conventional cam control, which limits the tearing effect of the fluid film of fuel deposited on the intake ducts: tearing related to the increase of the speeds of gas at low valve openings that allows atomization of fuel drops. However, this tearing effect remains insufficient in the case of a conventional camshaft distribution to limit the discharge of pollutants.

Taking advantage of this observation, the Holder, in the French patent application No. 0505507, filed on April 5, 2005, proposed a method and a device based on the increase of the fuel intake pressure during the start-up phase. at Engine coolant, applicable for camshaft or electrically or hydraulically operated valves.

Figures 2 and 3 placed at the end of the present description can briefly illustrate this process. In both cases, the start of the lift phase of the intake valve 15-15 'is illustrated when the fuel Ess is sprayed onto the walls of the duct 12 and the air supplied by this air. leads.

In the first case (Rg.2), it is an electrically controlled inlet valve 15. The opening is brutal, which results in a section of opening S quickly important. It follows that the pressure decreases very quickly, the mixture is imperfect: droplets G associated with a "MDS" important.

On the other hand, in the case of a mechanically driven intake valve 15 '(camshaft), the start-up phase is longer. The intake section is narrower, which increases the pressure during this phase. The "MDS" of droplets G'obtenues is lower and the mixture more homogeneous. More specifically, according to the method taught by the aforementioned patent application, the opening of the intake valve is controlled in two phases: a first phase devoted mainly to the admission of fuel and a second phase devoted mainly to admission of air, the opening of the valve being substantially lower in the first phase than in the second phase, so that the fuel is sprayed in the form of fine droplets during this first phase.

In summary, this process makes it possible to obtain finer droplets and thereby greatly reduce the emission of hydrocarbons, especially when the engine is cold.

However, this process necessarily requires the use of electrically controlled valve technology, which can lead to a higher cost than the use of a more conventional technology.

Finally, it is possible to obtain droplets of lower "SMD", which will correlatively achieve an even greater decrease in hydrocarbon emissions.

This is the main purpose of the invention. The invention therefore relates to an improved process for reducing hydrocarbon emissions from a cold engine.

For this purpose, according to an important characteristic of the invention, in a engine called "four-stroke", it implements a multiple fuel injection (gasoline) characterized by at least two distinct injection pressures, namely: an injection called "high pressure" during the so-called "admission time"", the intake valve being open during the first cold engine cycles; and an injection called "low pressure" during the so-called "exhaust" time, the intake valve being closed. In the context of the invention, "low pressure" corresponds in amplitude to a "standard" type of pressure, that is to say of the order of magnitude of that used in engines of the prior art. .

The injection of fuel at high pressure allows both a low "SMD" and a good homogenization of the mixture "air-fuel", despite the intake valve is fully open.

By cons, this mode of operation has the disadvantage of inducing a higher fuel consumption, related to the use of a device increasing the injection pressure. Also, once the engine is warm, it is possible to return to the conventional mode, that is to say in "low pressure" (or standard pressure) injection mode and with closed intake valves.

In any case, as shown in Figure 1A, unburned hydrocarbon emissions have dropped significantly after a limited number of engine cycles and it becomes unnecessary to resort to high pressure.

The number of high pressure cycles necessary to obtain the desired effect of the invention naturally depends on the particular characteristics of a given engine.

The moment of transition between the two phases depends mainly on the boiling point of the fuel, or "TVR" parameter, which can typically vary from 30 to 200 ^° C., the fuel being brought to this temperature essentially by heat exchange with the fuel. intake duct and / or the intake valve when it settles in. This temperature depends in particular on: the quality of the fuel used - the conditions of pressure and inlet temperature.

In a preferred embodiment, instead of providing a sudden transition between the two modes of operation (high and low injection phases pressures, respectively), an intermediate phase can be provided during which the transition between the two modes is progressive.

According to this variant embodiment, which comprises three phases, during the second phase or intermediate phase, the amplitude of the fuel injection pressure gradually drops until it reaches the standard pressure. In addition, fuel is still injected, injection valve open, but it is also possible to make small fuel injections, closed valve, so as to take advantage of the first available calories to vaporize the fuel. Indeed, at this stage, the engine temperature begins to grow strongly, even if it has not yet reached its cruising temperature. In yet another embodiment, it is also possible to use the electric type valve control technology used in the above-mentioned French patent application and implemented according to the teachings of this patent application. This embodiment, combining the two teachings, allows even more efficient operation and better elimination of unburned hydrocarbons when the engine is cold.

The subject of the invention is therefore a process for reducing hydrocarbon emissions from a cold engine with indirect fuel injection, said engine operating in a four-stroke cycle, called combustion, exhaust, intake and compression, the engine comprising at least one cylinder provided with at least one intake valve of an air-fuel mixture, characterized in that it comprises at least two successive phases of operation after starting the cold engine:

a first gasoline injection phase under a high pressure during the admission time, each intake valve being fully open; and a second low pressure injection phase during the exhaust time, each intake valve being closed; the second phase being initiated after a determined number of engine cycles.

The invention also relates to an indirect fuel injection engine for the implementation of this method. The invention will now be described in more detail with reference to the accompanying drawings, in which: Figure 1 illustrates very schematically the configuration of an indirect fuel injection engine; FIG. 1A is a curve illustrating the hydrocarbon emission variations as a function of the number of engine cycles, during a cold start;

Figures 2 and 3 schematically illustrate the fuel intake when the valve lift is low (start of admission or partial lift: Figure 3) and that the effect of increasing gas velocities improves vaporization and when lifting valve is important (Figure 2); Figures 4A to 4C schematically illustrate the phases of the method of the invention in a preferred embodiment; FIGS. 5A and 5B are curves explaining the fuel injection pressure variations during the phases of the method of the invention; and

Figure 6 schematically illustrates the configuration of an indirect fuel injection engine for the implementation of the method according to the invention.

In what follows the elements common to several figures bear the same references and will be re-described only as necessary.

A preferred embodiment of the process for reducing unburned hydrocarbon emission from an indirect fuel injection engine during a cold start will now be described with reference to the description of FIGS. 4A to 4C.

In itself, the configuration of an engine usable in the context of the invention is quite similar to that of an engine of the prior art. The engine does not require any modification of the fuel injection and the timing of the valve openings. These aspects will appear more clearly in the following. It will therefore be assumed that the engine is of the type described with reference to FIG. 1. Although only one cylinder 1 has been shown, it is clear that the invention relates to engines having one or more cylinders. As it has also been recalled, the control of the valves can be indifferently of conventional type (camshaft), or type said "camless" (absence camshaft replaced by an electrical or hydraulic valve control device).

The preferred embodiment of the method of the invention comprises three main phases. Figure 4A illustrates the first phase, referenced I, that is to say during the cold start of the engine.

During this phase, the first gasoline injections are made during the admission time, the intake valve fully open and, according to the main feature of the invention, at high injection pressure. In FIG. 4A (as well as in FIGS. 4B and 4C), the four operating times of the engine are shown: combustion, exhaust, admission and compression, as well as the so-called "High Death" points ("PM / - /"). ) and "Death Low"("PM? ¹ ) successive, corresponding to the positions of the piston 11 (Figure 1) in the cylinder 10 of the engine 1 during these four times.

The high-pressure injection period is also referred to as "ppal HP Injection", which can take up almost the entire intake time interval depending on the operating point of the engine.

After a few engine cycles, phase II is initialized. This phase II is illustrated in Figure 4B.

As before, we proceed to an injection of fuel called "main", high pressure and open intake valve. The duration of the fuel injection "Injection HP HP" is however shorter than previously and gradually decreases, from one engine cycle to the next, the amplitude of the injection pressure.

In addition, in a preferred embodiment, a so-called "secondary" fuel injection, referenced in FIG. 4B "Dry injection", is carried out, the characteristics of which are as follows: it is carried out with a closed intake valve, that is, during the escape time, and it is of relatively short duration. The amplitude of the secondary injection pressure is the same as that of the main pressure.

Alternatively, during this phase II and during the high pressure main injection, the inlet valve may only be partially open and the valve lift gradually decrease from one engine cycle to the next.

For the sake of clarity, the valve lift can typically vary between 0 and 2 mm. In this way, we take advantage of the progressive warming of the engine and we begin to use the first available calories to vaporize the fuel, by thermal contact with the metal surfaces of the duct 12 (Rg.1) and the intake valve 15. Finally, when the engine reaches its cruising temperature (warm engine), phase III is initialized. This phase III is illustrated in Figure 4C.

This phase III is characterized by a so-called "main" fuel injection, at low pressure, referenced "ppal BF injection" in Figure 4C, closed intake valve, that is to say during the exhaust time. The duration of the main injection at low pressure can occupy almost the entire interval of the exhaust time, depending on the engine operating point.

During this phase, the inlet valve and the ducts are now hot. They reached their "cruising" temperature. In fact, during this phase, the engine operates as a conventional engine of the known art. The injection pressure may be that implemented in such an engine.

Figure 5A schematically illustrates the variation of the fuel injection pressure as a function of the number of NCM engine cycles. The presence of a first level of constant pressure (high HF pressure) is observed during phase I, then a progressive decrease, a priori linear, during phase II, until reaching a second level of constant pressure (low pressure). BF), during phase III.

For the sake of clarity, in the example described, which is specific to a particular type of engine, phase I lasts five motor cycles [NCM = 1 to 5], the second ten motor cycles [NCM = 5 to 15], and phase III starts from the NCM = 15 engine cycle. It must be clear, however, that these values are dependent on each application and are subject to a specific calibration.

FIG. 5B very schematically illustrates the transition between a cold engine operation (phase I) and a hot engine operation (phase II), the pivot point being NCM = 10, in the illustrated example.

For the sake of clarity, the high injection pressure is typically greater than or equal to 9 bars (9 10 ⁵ Pascals) and the low injection pressure substantially equal to 3.5 bars.

(3.5-10 ⁵ Pascals). It must be clear, however, that depending on the type of engine and operating conditions, the so-called "high" injection pressure may be less than 9 bar, but remains higher in all cases at the so-called low injection pressure.

The number of NCM engine cycles at high pressure depends on the particular engine considered, the start temperature, the heating conditions of this engine, load conditions thereof after starting. In practice, an adapted control strategy is implemented taking into account these parameters and making it possible to define the transition moment between operations with a high injection pressure and with a conventional injection pressure.

As a main point, the moment that characterizes the transition between these modes of operation is the boiling point of the fuel, a parameter known by the acronym "TVR." This temperature typically varies between 30 and 200 ° C. It essentially depends on:

- the quality of the fuel used; and

- conditions of pressure and temperature of the admission.

In practice, a suitable behavior model for a given data engine is determined during its design.

In operational operation of the engine, data measured in real time by different sensors is used. These sensors are usually present on recent technology engines, which does not involve additional cost and / or complexity. This aspect is a further advantage of the invention which uses only conventional technologies implemented on modern engines. The measurements made by the sensors are processed by an on-board control unit, for example a digital program recorded computer, also present on most modern vehicles.

For the purposes of the invention, particular use is made of water temperature, oil temperature, and number of NCM engine cycles performed since the start of the engine cold.

As just described, the method according to the preferred embodiment of the invention comprises three phases, which allows a good optimization.

However, the method may, without departing from the scope of the invention, include only two phases: phase I and phase III.

In a further variant embodiment, one can combine the teachings of the invention and those of the aforementioned French patent application No. 05 05507, filed April 5, 2005. These last lessons were briefly recalled in the preamble of the present description, with reference to Figure 3.

This patent application teaches a method of controlling an internal combustion engine having at least one electrically controlled intake valve, characterized in that, to reduce unburned hydrocarbon emissions from the cold internal combustion engine, the The opening of the valve is controlled in two successive phases, the first phase corresponding mainly to the admission of the fuel and the second phase mainly to the admission of air, the opening of the valve being substantially lower during the first phase. phase than during the second phase so that the fuel is sprayed in the form of fine droplets during this first phase.

In a variant of this method, the valve is opened twice during the intake time of the engine, at least one of the openings being controlled in two phases.

In a variant still, the second opening, called the main lift, comprises the two phases, the first phase being performed at low opening, mainly to admit fuel.

We will now describe an example of a motor configuration M indirect fuel injection with reference to Figure 6.

In itself, this configuration is very similar to that of a conventional engine of the known art, as will be seen. The differences will be explained below.

To fix ideas, the motor M is assumed to have four cylinders in the example described, 1 a to 1 d. Each cylinder (such as the cylinder 1 represented in a dashed box) is similar if not identical to the cylinder shown in FIG.

Also, not to overload Figure 6, only the elements essential to the understanding of the invention have been referenced again.

The cylinders, for example the cylinder 1a, are fed with an "air-gasoline" mixture (references: Airei Ess) via the discharge valve 15. The spark plug 17 (FIG. 1) is supplied with electrical energy by a coil 170 The flue gases Ge are ejected via the exhaust valve 16 to an exhaust pipe 22 - 23. Between the two sections of this exhaust pipe is inserted in a conventional manner, a catalyst 8, so as to improve the aftertreatment of the exhaust gas. The exhaust pipe, 22 - 23, is usually provided with two oxygen content probes, 80 and 81.

The engine M comprises a conventional fuel tank 3 equipped with a fuel level sensor 30. Ess gasoline is transported by a pipe 31 to the intake ducts of each cylinder, for example to the intake duct 12 ( figure 1 ).

The air air is transported by a pipe 90 to be injected into the inlet duct of each cylinder, for example the duct 12 (FIG. 1) of the cylinder 1 a, via an air filter 9 and a motorized butterfly 21, and mixed with fuel Ess. An air temperature sensor 20 is usually provided on the air supply.

The engine M may also include a secondary air pump 7, exhaust side.

There is usually a member 50, called a "canister" and a purge 50, arranged between the air supply line Air and the fuel tank 3. There is also provided one or more water temperature sensors. , 25, and oil, 26, respectively.

Finally, according to an important feature of the invention, means are provided for injecting fuel Ess under variable pressure.

In the embodiment illustrated in Figure 6, there is provided an injection pump (not explicitly shown) provided with two separate gasoline pressure regulators: a low pressure regulator 6a, and a high pressure regulator 6b. Depending on the activation of one or the other of these regulators, 6a or 6b, and during the activation intervals, the injectors, for example the injector 14 of the cylinder 1a, are supplied with fuel Ess, under low pressure (especially during phase III: FIG. 4C) or high pressure, respectively (in particular during phase I: FIG. 4A).

In another variant embodiment (not shown), two separate injection pumps are provided. Each pump delivers fuel Ess, one under high pressure, the other under low pressure, according to the time diagram of Figures 4A to 4C.

Furthermore, as has been indicated, in some embodiments of the method according to the invention, the amplitude of the pressure can be modulated in time (for example, during phase II: FIG. 4B). The measurements made on the motor M using the different sensors are usually processed by an electronic control unit 4, for example a digital computer with a registered program. Such an organ may be, in itself, of a quite conventional type. Only the "hardware" arrangements of electronic circuits and / or programs ("software") must be modified and / or supplemented to implement the method according to the invention.

The control unit 4 comprises in particular links 41 receiving measurement signals from the various sensors that have been previously described, links 42 enabling analog-to-digital conversions, and actuator control links 40 (not shown). various engine members M: injectors, for example 14 (Figure 1), valves, for example 16, etc., which again is conventional in itself.

However, more specifically to the method of the invention, the controller 4 generates the control signals 40 of the actuators (for example acting on the pressure regulators, 6a or 6a, so that the injectors (for example FIG. are fed with fuel Ess, low or high pressure, according to a given time diagram (Figures 4A to 4C), according to the measurement signals from the various sensors, including the number of engine cycles NCM, and measured temperatures.

In certain embodiments (phase II: FIG. 4B), the timing diagram of fuel supply of the injectors, the amplitude of the injection pressure, and / or the amplitude of the intake valve lifts, translate by also specific actuator control signals

Finally, in a further embodiment, combining the teachings of the present invention and those aforementioned French patent application No. 05 05507, the levers of intake valves are also specifically controlled according to a diagram. predefined time. More particularly, the opening of the intake valves is controlled in two successive phases, the first phase corresponding mainly to the intake of fuel Ess and the second phase mainly to the air intake Air, as has been recalled. Naturally, including in this embodiment variant, according to the main characteristic of the method of the invention, during a given number of engine cycles NCM, the injection of fuel Ess, called the main fuel, that is to say that carried out during the admission time, is carried out at high pressure (phase I: FIG. 4A, and phase II: FIG. 4B).

It can be seen from the foregoing that the invention achieves the goals it has set for itself. It has many advantages, it makes it possible to achieve a very high reduction of unburned hydrocarbon emissions from a cold engine with indirect injection of gasoline, without requiring significant modifications of the constituent parts of the engine, or to resort to complex and expensive solutions. In fact, if a software solution is used (digital program recorded computer) for the processing of the signals acquired by the sensors and the generation of control signals of the various actuators, the modifications required by the method of the invention are summarized, essentially, an adaptation of the programs implemented in the memory means of the computer.

The invention is however not limited to only the embodiments which have been explicitly described, with particular reference to FIGS. 4A to 6.

Similarly, specific numerical examples have been given only to better highlight the essential characteristics of the invention and result only from a technological choice, in itself within the reach of the skilled person. They can not limit in any way the scope of the invention.

Claims

1. A method for reducing unburned hydrocarbon emissions from a cold engine with indirect fuel injection, said engine operating in a four-cycle cycle, said combustion, exhaust, intake and compression, the engine comprising at least one cylinder provided with at least one intake valve of an air-fuel mixture, characterized in that it comprises at least two successive phases of operation after starting the cold engine: a first phase (I) with fuel injection under high pressure (HF) during the admission time, each intake valve (15) being fully open; and a second low pressure injection (LP) phase (III) during the exhaust time, each intake valve (15) being closed; the second phase being initiated after a determined number of engine cycles (NCM).

2. Method according to claim 1, characterized in that it comprises an intermediate operating phase (II) between the first (I) and second (III) phases, this intermediate phase (II) comprising a fuel injection (Ess ) said main under high pressure (HF) during the admission time, each intake valve (15) being at least partially open and a so-called high pressure (HF) secondary fuel injection (Ess) during the exhaust time, each intake valve (15) being closed.

3. Method according to claim 2, characterized in that the amplitude of the pressure of the main fuel injection (Ess) during the intermediate phase (II) gradually decreases from one engine cycle to the next.

4. Method according to one of claims 2 or 3, characterized in that the amplitude of the opening of each intake valve (15), said lift, during the intermediate operating phase (II), during the main injection, gradually decreases from one engine cycle to the next.

5. Method according to claim 4, characterized in that the lifting amplitude of each intake valve (15) varies between 0 and 2 mm.

6. Method according to any one of the preceding claims, characterized in that the amplitude of the high pressure (HF) equal to or greater than 9 10 ⁵ Pascals and the amplitude of the low pressure (BF) is substantially equal to 3 , 5 10 ⁵ Pascals.

7. Method according to any one of claims 2 to 6, characterized in that the moments controlling the transitions between the operating phases (I, II, III) are determined from a motor behavior model (M). elaborated during design and processing by a calculation unit of measurements (4) acquired by a plurality of sensors (20, 25, 26) of physical quantities related to the operation of the motor [M].

The method according to claim 7, characterized in that, the motor [M] being cooled by water and lubricated with oil, the measured physical quantities comprise the measurement of the water temperatures (25) and oil (26), and the number of motor cycles [NCM] performed since a cold start of the engine [M].

9. Method according to claim 8, characterized in that the first phase of operation (I) lasts five motor cycles, the intermediate phase (II) of operation ten motor cycles and the second phase of operation (III) begins after fifteen engine cycles. .

10. Method according to any one of the preceding claims, characterized in that each of the intake valves (15) being electrically controlled, the opening of each valve (15) is controlled in two successive phases, the corresponding first phase. mainly to the gasoline intake (Ess) and the second phase mainly to the air intake (Air), the opening of each valve being substantially lower in the first phase than in the second phase.

11. The method of claim 10, characterized in that each inlet valve (15) is open twice during the intake time of the motor [M], at least one of the openings being controlled in two phases.

12. The method of claim 11, characterized in that the second opening, said main lift, comprises the two phases, with the first low-opening phase mainly for the admission of gasoline [Ess).

13. Indirect fuel injection engine for implementing the process for reducing unburned hydrocarbon emissions from a cold engine with indirect fuel injection according to any one of the preceding claims, characterized in that comprises at least gasoline injection control means (6a, 6b) under at least two distinct pressure amplitudes, said high [HF] and low [BF] pressures, distributed according to a given temporal scheme, in particular function the number of motor cycles performed [NCM] after a cold start.

14. Motor according to claim 13, characterized in that the fuel injection control means under at least two distinct pressure amplitudes comprise a fuel pump associated with two pressure regulators (6a, 6b), a first regulator [6b] delivering gasoline under high pressure and a second regulator (6a) under low pressure.

15. Motor according to claim 13, characterized in that the fuel injection control means under at least two distinct pressure amplitudes. include two gas pumps, the first delivering gasoline (Ess) under high pressure [HP] and the second under low pressure [BP].

16. Motor according to any one of claims 13 to 15, characterized in that it comprises, a plurality of actuators acting on fuel injectors (14) and on each of the intake valves (15), a a plurality of sensors (20, 25, 26) of physical quantities related to the operation of the motor [M) and calculation and control means (4) developing from these physical quantities and from a model of the behavior of the motor [M ), established during its design, control signals (40) of the actuators, so as to obtain the determined temporal pattern.

17. Motor according to claim 16, characterized in that the calculation and control means comprise a registered program digital calculator (4).