EP1556932A1

EP1556932A1 - Precombustion chamber ignition device made of a material with high thermal conductivity for an internal combustion engine, and precombustion chamber igniter

Info

Publication number: EP1556932A1
Application number: EP03778403A
Authority: EP
Inventors: Cyril Robinet; Nicolas Tourteaux
Original assignee: Peugeot Citroen Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2002-10-18
Filing date: 2003-10-17
Publication date: 2005-07-27
Anticipated expiration: 2023-10-17
Also published as: FR2846042B1; US7104245B2; FR2846042A1; JP2006503218A; EP1556932B1; ATE400912T1; WO2004036709A1; ES2307997T3; US20050268882A1; DE60322089D1

Abstract

An ignition system for an internal combustion engine comprises: (a) a main combustion chamber (1) destined to contain a main fuel mixture, and equipped with a compression system; (b) an ignitor (11) incorporating a precombustion chamber (2) destined to receive some reactives and an ignition system (13, 14) for the reactives contained in the precombustion chamber; (c) the precombustion chamber is defined by a body (12) having a head (12a) incorporating at least one passage (15); (d) the head separates the precombustion chamber from the main chamber, which are connected by passages in the head; (e) the body of the precombustion chamber is made in a material with a thermal conductivity at 20 degrees Celsius of at least 10 W/K/m. An Independent claim is also included for an ignitor for an internal combustion engine incorporating a precombustion chamber.

Description

Prechamber ignition device made of a material with high thermal conductivity, for an internal combustion engine, and prechamber igniter

The present invention relates to an ignition device for an internal combustion engine, as well as to a prechamber igniter.

The ignition device according to the invention comprises a prechamber igniter which can be screwed in place of a conventional spark plug without modification of the cylinder head of the internal combustion engine (diameter less than or equal to 14 mm), the means for igniting an oxidant and fuel mixture being contained in a prechamber defined by a body the head of which is provided with passages.

Thus, when the prechamber igniter is mounted in the cylinder head of the engine, the igniter prechamber is separated from the main combustion chamber of the engine by the head of the prechamber body and communicates with the main combustion chamber through the intermediate passages made in this head.

The prechamber igniter may optionally be provided with means making it possible to introduce the reactants directly into the prechamber. US Patent 4,926,818 describes a device and a method for generating pulsed jets intended to form vortex combustion pockets. The device described comprises a main chamber containing a main fuel mixture in which moves a piston and a prechamber receiving reagents and communicating with the main chamber through orifices made in a wall. The ignition of the reactants in the prechamber produces jets of gas in combustion, which ignite the main mixture contained in the main chamber by convection of the flame front.

Patent application FR 2 781 840 describes an ignition device for an internal combustion engine comprising:

a main chamber intended to contain a main combustible mixture, and provided with a system for compressing said mixture,

a prechamber intended to receive reagents and communicating with the main chamber through orifices made in a wall separating the main chamber from the prechamber, - an ignition system for the reagents contained in the prechamber. In such a device, which is generally satisfactory, the orifices are of small diameter and able to prevent the passage of a flame front while allowing the passage of unstable compounds originating from the combustion of the reagents contained in the prechamber. The compression system and the seeding of the main mixture with unstable compounds allow mass self-ignition of the initial mixture.

Patent application FR 2 810 692 also relates to an ignition device of an internal combustion engine comprising a prechamber of generally cylindrical shape, similar to that described in application FR 2 781 840, but whose passages communicating with the chamber main combustion are circumscribed by a circular curve passing through the outermost passage centers, the diameter of this circular curve being in a ratio less than or equal to VI with the diameter of the cylindrical prechamber. This arrangement allows the engine to operate with a small quantity of combustion air, in particular when the composition of the air-fuel mixture in the main chamber is stoichiometric, for reasons of pollution control with a three-way catalyst. These devices can be further improved. In particular, the present invention relates to an ignition device for an internal combustion engine which can have the following advantages: - reduction in the fuel enrichment of the air-fuel mixture when the engine is running at full load,

- reduction or even elimination of rattling, which makes it possible to increase the volumetric ratio of the engine,

- better efficiency in the use of oxidizer and fuel. To this end, the invention relates to an ignition device of an internal combustion engine, comprising:

a main chamber intended to contain a main combustible mixture, and provided with a system for compressing said mixture, an igniter comprising a prechamber intended to receive reagents and a system for igniting the reagents contained in the prechamber, said prechamber being defined by a prechamber body having a head comprising at least one passage, said head of the prechamber body separating the prechamber of the main bedroom and communicating the prechamber and the main bedroom through the passage (s). According to the invention, said prechamber body is made of a material having a thermal conductivity at 20 ° C of at least 10 W / K / m. Preferably, the prechamber body is made of a material having a thermal conductivity at 20 ° C of at least 30 W / K / m, better still at least 50 W / K / m.

Generally, the thermal conductivity at 20 ° C of the material from which the body of the prechamber is made does not exceed 350 W / K / m. To produce the prechamber body according to the invention, one can use any type of material whose thermal conductivity is as defined above and which is capable of withstanding the temperature and pressure constraints due to the operation of the ignition device. In particular, copper alloys can be used. Preferably, the material constituting the prechamber body according to the invention is chosen from binary brasses, cupro-nickel, cupro-aluminum and nickel silver.

In particular, the alloys CuZn5, CuZn10, CuZn15, CuZn30, CuZn33, CuZn36, CuZn36, CuNi44Mn, CuNiδF, CuAI5, CuNi2, CuNi21, CuNi10 CuZnδ alloy whose thermal conductivity at 20 ° C is 234 W / (mK). The composition of these alloys is given by standard NF A51 -101

A particularly preferred material for the prechamber body according to the invention is the alloy CuCrI Zr, the thermal conductivity of which

20 ° C is 320 W / K / m. This alloy comprises, by weight, more than 0.4% of chromium, from 0.02 to 0.1% of zirconium, the complement to 100% being copper. These alloys with high thermal conductivity are particularly suitable for prechamber igniters intended to be used with highly supercharged internal combustion engines, that is to say having an effective average pressure greater than or equal to 13 bars. Mention may be made, for example, of motors for compressors or turbochargers.

The use of such a material according to the invention makes it possible to better dissipate the energy at the level of the body of the prechamber and thus to avoid the appearance of hot spots. The combustion mode resulting from the use of the ignition device according to the invention ensures a combustion speed sufficient to dispense with an increase in the combustion speed via aerodynamics.

This allows in particular to considerably reduce the rattling. This reduction in knocking makes possible a high volumetric ratio of the motor, advantageously between 8 and 14.

In addition, this reduction in knocking allows a better efficiency in the use of the oxidizer and the fuel.

In fact, when the engine is limited by knocking (in particular at high load), that is to say when the combustion speed too low makes it possible to reach in certain parts of the chamber the conditions of self-ignition of the mixture before these could have been burned by the flame front, the setting applied in terms of ignition advance is degraded compared to the optimal case. The amount of air and fuel introduced into the combustion chamber is not used with optimum efficiency.

When the rattling phenomenon is inhibited, it is possible to adjust the engine with an ignition advance closer to the optimum efficiency, which allows better use of oxidant and fuel.

According to a first embodiment, the main mixture contained in the main chamber is ignited by convection of the flame front resulting from the ignition of the reagents contained in the prechamber. In this case, the passage or passages are preferably of cylindrical shape and of diameter greater than 1 mm.

According to a second embodiment, the passage or passages are capable of preventing the propagation of a flame front while allowing the propagation of unstable compounds originating from the combustion of the reagents contained in the prechamber, the compression system of the main chamber and seeding the main mixture with said unstable compounds allowing mass self-ignition of the main mixture. Self-ignition in a large volume allows a very rapid pressure build-up, a reduction in knocking and good repeatability.

In this case, the said passage or passages are preferably of cylindrical shape and of diameter less than or equal to 1 mm. More preferably, the said passage or passages have a length less than or equal to their diameter. By length is meant the dimension of the passages in a direction perpendicular to the surface of the partition wall. In this way, the least possible of unstable compounds are trapped on the walls. Generally, the number of passage (s) is between 1 and 20, preferably between 3 and 15.

In the case of self-ignition of the mixture by seeding the main mixture into unstable compounds, according to a preferred embodiment: - the upper part of the prechamber body, not attached to the main chamber, has the shape of a cylinder of internal diameter Φ, and

- The head of the prechamber body comprises several passages, said passages being circumscribed by a circular curve of diameter d ₂ passing through the centers of the outermost passages, the ratio d ₂ / Φ being less than or equal to 0.5.

Preferably, the ratio d ₂ / Φ is less than or equal to 1/3.

Advantageously, the center of the curve passing through the centers of the outermost passages is located on the axis of symmetry of the prechamber. However, according to another embodiment, the center of the curve passing through the centers of the outermost passages can be located at a distance d ₃ from the axis of symmetry of the prechamber, equal to or greater than a quarter of the diameter Φ of the prechamber. This configuration makes it possible to preferentially direct the jets of flame or of unstable compounds towards a particular zone of the combustion chamber, as a function of the position of said center of the curve relative to the axis of symmetry of the prechamber.

The invention also relates to an igniter for an internal combustion engine comprising a prechamber defined by a prechamber body having a head provided with at least one passage, the prechamber being intended to contain a combustible mixture, and a system for igniting the mixture. fuel contained in the prechamber, said prechamber body being made of a material having a thermal conductivity at 20 ° C of at least 10 W / K / m, preferably at least 30 W / K / m, better at least 50 W / K / m, and less than or equal to 350 W / K / m.

Preferably, the prechamber body is made of a copper alloy. More preferably, the material constituting the prechamber body according to the invention is chosen from binary brasses, cupro-nickel, cupro-aluminum and nickel silver.

In particular, the alloys CuZnδ, CuZn10, CuZn15, CuZn30, CuZn33, CuZn36, CuZn36, CuNi44Mn, CuNiδF, CuAI5, CuNi2, CuNi21, CuNi10 CuZnδ alloy whose thermal conductivity at 20 ° C is 234 W / (mK).

A particularly preferred material for the prechamber body of the igniter according to the invention is the CuCrIZr alloy, the thermal conductivity of which at 20 ° C. is 320 W / K / m.

The invention will be better understood and other objects, advantages and characteristics thereof will appear more clearly on reading the description which follows, given with reference to the appended drawings. Figure 1 shows a schematic view, partially in section, of an ignition device comprising a prechamber igniter according to the invention.

Figure 2 shows a schematic view in vertical section of the prechamber body of an igniter according to the invention.

Figure 3 is a bottom view of the head of a prechamber body of an igniter according to the invention.

A cylinder of an internal combustion engine, shown in the

Figure 1, comprises a main chamber 1 delimited by a jacket (not shown) and closed above by a cylinder head 10. As is conventional, the main chamber 1 contains a piston (not shown) actuated in translation by a connecting rod (not shown) .

An igniter 11 with prechamber according to the invention is fixed in the cylinder head 10 so as to be adjacent to the main chamber 1, for example by screwing into a thread 10a of the cylinder head 10.

The igniter 1 1 comprises a prechamber body 12, of generally tubular shape, comprising a head 12a, preferably having the shape of a spherical cap, defining a prechamber 2.

The head 12a of the prechamber body 12 constitutes a partition wall between the main chamber 1 and the prechamber 2. The head 12a communicates the prechamber 2 with the main chamber 1 via passages (15).

The prechamber body 12 is made of a material having a thermal conductivity at 20 ° C of at least 10 W / K / m, preferably at least 20 W / K / m, better still at least 50 W / K / m. Generally, the thermal conductivity at 20 ° C of the material from which the prechamber body is made does not exceed 350 W / K / m. Advantageously, the prechamber body 12 is produced from the CuCrIZr alloy, the thermal conductivity of which at 20 ° C. is 320 W / K / m. Generally, the prechamber 2 has a volume of between 0.2 cm ³ and 2 cm ³ , preferably between 0.5 cm ³ and 1.5 cm ³ .

In general, the S / V ratio between the sum of the sections of the passages 1δ of the prechamber and the volume of the prechamber is between 10 ^"3 mm ^{" 1} and δ.10 ^"2 mm ^{" 1} . Optionally, the igniter may also include an inlet (not shown) allowing the pre-chamber 2 to be supplied with a mixture of air-fuel reagents formed upstream or to introduce fuel, the air being mixed with the fuel in the pre-chamber 2. The prechamber is provided with an ignition system comprising a central electrode 13 and a ground electrode 14. The interelectrode space is for example of the order of 0.7 mm.

When the main mixture is ignited by convection of the flame front coming from the prechamber, the passages 15 are orifices preferably having a diameter greater than 1 mm.

When it is desired to prevent, during ignition, the passage of a flame front while allowing the passage of unstable compounds (ignition of the main mixture by self-ignition), the passages 15 then have a small diameter, generally less than 1 mm, and, advantageously, a length less than their diameter.

In the case of self-ignition of the main mixture, as shown in Figure 2, the passages 1δ advantageously belong to a circle of diameter d ₂ corresponding substantially to half the diameter Φ of the prechamber. The center of this circle can be on the axis of symmetry 2b of the prechamber 2, as shown in Figure 2.

The center of this circle can also be located at a distance d ₃ from the axis of symmetry 2b of the prechamber 2, as shown in Figure 3, on which passages 15 8 in number have been shown.

An air-fuel mixture is introduced into the main chamber and the prechamber 2 is supplied. A spark is then produced between the electrodes 13 and 14, thereby initiating combustion in the prechamber 2, so that the temperature and the pressure increase. her breast.

Under the effect of the higher pressure in the prechamber 2 than in the main chamber 1, the flames, or the unstable compounds in the case where the size of the passages prevents the propagation of the flame front, are expelled in the form of jets towards bedroom main 1. Thus the main mixture contained in the main chamber 1 is ignited.

In both cases (ignition of the main mixture by convection of the flame front or by self-ignition), the high thermal conductivity of the prechamber body allows energy to be evacuated at the level of the prechamber body and thus avoids the appearance of hot spots.

The resulting combustion mode ensures a sufficient combustion speed to dispense with an increase in the combustion speed via aerodynamics. We can thus reduce the enrichment when the engine is running at full load. The phenomenon of rattling is also considerably reduced.

Claims

1. An ignition device of an internal combustion engine, comprising: - a main chamber (1) intended to contain a main combustible mixture, and provided with a system for compressing said mixture, an igniter (11) comprising a prechamber (2) intended to receive reagents and an ignition system (13,14) of the reagents contained in the prechamber, said prechamber (2) being defined by a prechamber body (12) having a head (12a) comprising at least a passage (15), said head (12a) of the prechamber body separating the prechamber (2) from the main chamber (1) and making the prechamber (2) and the main chamber (1) communicate via the one or more passages (15), characterized in that said prechamber body (12) is made of a material having a thermal conductivity at 20 ° C of at least 10 W / K / m.

2. An ignition device according to claim 1 characterized in that said prechamber body (12) is made of a material having a thermal conductivity at 20 ° C of at least 30 W / K / m, preferably of minus 50 W / K / m.

3. An ignition device according to any one of the preceding claims, characterized in that said prechamber body (12) is made of a material having a thermal conductivity at 20 ° C less than or equal to 350 W / K / m.

4. An ignition device according to any one of the preceding claims, characterized in that the material constituting said prechamber body (12) is chosen from copper alloys.

5. An ignition device according to claim 4 characterized in that the material constituting the prechamber body according to the invention is chosen from binary brasses, cupro-nickel, cupro-aluminum and nickel silver.

6. An ignition device according to claim δ characterized in that the material constituting the prechamber body according to the invention is chosen from the alloys CuZnδ, CuZnIO, CuZnlδ, CuZn20, CuZn30, CuZn33, CuZn36, CuZn37, CuZn40, CuNi44Mn, CuNiδFe, CuAlδ, CuAI6, CuAIIOFeδNiδ, CuNi10Zn27, CuNi12Zn24, CuNi1δZn21, CuNi18Zn20, CuNi18Zn27, CuNin19

7. An ignition device according to claim 4 characterized in that the material constituting said prechamber body (12) is CuCrIZr.

8. Ignition device according to any one of the preceding claims, characterized in that the said passage or passages (1δ) are of cylindrical shape and of diameter greater than 1 mm.

9. An ignition device according to any one of claims

1 to 7 characterized in that the said passage (s) (1δ) are capable of preventing the propagation of a flame front while allowing the propagation of unstable compounds originating from the combustion of the reagents contained in the prechamber (2), the system compression of the main chamber (1) and the seeding of the main mixture into said unstable compounds allowing self-ignition in mass of the main mixture.

10. An ignition device according to claim 9 characterized in that the said passage or passages (1δ) are of cylindrical shape and of diameter less than or equal to 1 mm.

11. An ignition device according to claim 9 or 10 characterized in that the said passage or passages (1δ) have a length less than or equal to their diameter.

12. An ignition device according to claim 9, 10 or 11 characterized in that

the upper part of the prechamber body (12), not attached to the main chamber, has the shape of a cylinder with an internal diameter Φ, and

- The head of the prechamber body comprises several passages (1δ), said passages being circumscribed by a circular curve of diameter d ₂ passing through the centers of the outermost passages (1δ), the ratio d ₂ / Φ being less than or equal to 0.5.

13. An ignition device according to the preceding claim characterized in that the ratio d ₂ / Φ is less than or equal to 1/3.

14. An ignition device according to claim 12 or 13 characterized in that the center of the curve passing through the centers of outermost passages (15) is located on the axis of symmetry (2b) of the prechamber (2).

15. An ignition device according to claim 12 or 13 characterized in that the center of the curve passing through the centers of the outermost passages is located at a distance d ₃ from the axis of symmetry (2b) of the prechamber ( 2), said distance d ₃ being equal to or greater than a quarter of the diameter Φ of the prechamber (2).

16. Igniter for internal combustion engine comprising a prechamber (2) defined by a prechamber body (12) having a head (12a) provided with at least one passage (15), the prechamber being intended to contain a combustible mixture, and an ignition system (13,14) of the combustible mixture contained in the prechamber (2), characterized in that the prechamber body (2) is made of a material having a thermal conductivity greater than 10 W / K / m .

17. An igniter according to claim 16 characterized in that said prechamber body (12) is made of a material having a thermal conductivity greater than 10 W / K / m, preferably greater than 30 W / K / m.

18. Igniter according to claim 16 or 17 characterized in that said prechamber body (12) is made of a material having a thermal conductivity less than or equal to 350 W / K / m.

19. Igniter according to any one of claims 16 to 18 characterized in that the material constituting said prechamber body (12) is chosen from copper alloys.

20. An igniter according to claim 19 characterized in that the material constituting said prechamber body (12) is chosen from binary brasses, cupro-nickel, cupro-aluminum and nickel silver.

21. An igniter according to claim 20 characterized in that the material constituting said prechamber body (12) is chosen from the alloys CuZnδ, CuZnI O, CuZnlδ, CuZn20, CuZn30, CuZn33, CuZn36, CuZn37, CuZn40, CuNi44Mn, CuNiδFe, CuAlδ , CuAI6, CuAH OFeδNiδ, CuNi10Zn27, CuNi12Zn24, CuNi1 δZn21, CuNi18Zn20, CuNi18Zn27, CuNi10Zn42Pb2 and CuNi18Zn19Pb1, preferably the CuZnδ alloy.

22. Igniter according to claim 19, characterized in that the material constituting said prechamber body (12) is the CuCrIZr alloy.