Spark plug for spark-ignition engine.

Abstract

Spark plug for a spark-ignition engine. Spark plug (10) for a spark-ignition engine comprising: - a first electrode (1), - a second electrode (2), - a third electrode (13), - a fourth electrode (23), - a first inter-electrode gap (14) located between the first electrode (1) and the third electrode (13), - a second inter-electrode gap (24) located between the second electrode (2) and the fourth electrode (23), and - a base (8), particularly in the lower part of the spark plug, the third and fourth electrodes (13, 23) forming part of the base (8). Figure for the abbreviation: 1

Description

Title of the invention: Spark plug for spark-ignition engine.

[0001] The invention relates to a spark plug for a spark-ignition engine. The invention also relates to a spark-ignition system comprising such a spark plug. The invention also relates to a cylinder head for a spark-ignition engine comprising such a spark plug. The invention also relates to a spark-ignition engine comprising such a cylinder head. The invention also relates to a vehicle comprising such an engine. The invention also relates to a method of operating a spark-ignition engine comprising such a cylinder head.

[0002] Improving the efficiency of spark-ignition internal combustion engines is one of the challenges of the evolution of the automotive industry. In particular, increasing the compression ratio of spark-ignition engines constitutes a key area of ​​progress in this field.

[0003] The technical solutions considered so far for increasing the compression ratio of an internal combustion engine encounter implementation difficulties. Indeed, an increase in the compression ratio can induce fuel auto-ignition phenomena, otherwise known as knocking, which can damage the engine.

[0004] The use of a pre-chambered spark plug reduces the phenomenon of engine knock. This type of spark plug, used in stationary gas engines and Formula 1 engines, allows for faster fuel combustion than with a standard spark plug, thus delaying the onset of knock, for the same combustion chamber volume. However, the pre-chambered spark plug is less efficient than a standard spark plug under certain operating conditions of a passenger vehicle engine, such as cold starting or aftertreatment warm-up phases.

[0005] US publication 2019 / 0323415-Al proposes an arrangement in a cylinder head of a thermal engine with a first spark plug with a pre-chamber associated with a second spark plug arranged laterally.

[0006] Such an arrangement requires two different holes in the cylinder head for the insertion of the two spark plugs as well as good positioning of the spark plugs relative to each other, which increases the overall size of the cylinder head and the internal combustion engine.

[0007] The object of the invention is to provide a spark plug for a spark-ignition engine that overcomes the above drawbacks and improves upon spark plugs for spark-ignition engines known in the prior art. In particular, the invention relates to a spark plug for a spark-ignition engine that allows the engine's compression ratio to be increased while limiting the knocking phenomenon, and that is adapted to the operating conditions of a private vehicle engine by controlling the bulk generated by the spark plug arrangement.

[0008] To this end, the invention relates to a spark plug for a spark-ignition engine comprising: - a first electrode, - a second electrode, - a third electrode, - a fourth electrode, - a first inter-electrode space located between the first electrode and the third electrode, - a second inter-electrode space located between the second and fourth electrodes, and - a base, particularly in the lower part of the spark plug, the third and fourth electrodes being part of the base.

[0009] In one embodiment the first and second electrodes are electrically isolated from each other and the two inter-electrode spaces allow a spark to be independently directed towards one or the other or both of the inter-electrode spaces.

[0010] In one embodiment, the spark plug includes a pre-chamber arranged so that the first inter-electrode space is located in the pre-chamber and the second inter-electrode space is located outside the pre-chamber.

[0011] In one embodiment, the candle comprises: - a washer welded to the base of the spark plug, said washer having two openings, a first opening being made to allow the passage of a first electrode and a second opening being made to allow the passage of a second electrode, and - a capsule, welded to the washer and covering the first opening made on the washer, said capsule having at least two orifices allowing a fuel to enter the pre-combustion chamber.

[0012] In one embodiment, the third and fourth electrodes are carried by the capsule.

[0013] In one embodiment, the washer and the capsule are part of the base.

[0014] In one embodiment, the spark plug includes a two-prong connector designed to receive a cap allowing each of the first and second electrodes to be controlled individually.

[0015] In one embodiment, the first and second electrodes are straight and they are inserted respectively into two parallel housings made in an insulating ceramic.

[0016] The invention also relates to a spark-ignition engine cylinder head comprising a spark plug according to the invention: - the spark plug fits into a location in the cylinder head designed for a standard spark plug, and - at least two openings in the pre-chamber capsule of the spark plug allowing fuel contained in the cylinder head to enter the pre-chamber, - the second inter-electrode space of the spark plug located in the cylinder head.

[0017] The invention also relates to a controlled ignition system comprising an ignition control unit and a spark plug according to the invention.

[0018] The invention further relates to a spark-ignition engine comprising a cylinder head according to the invention.

[0019] The invention further relates to a motor vehicle comprising a spark-ignition engine according to the invention.

[0020] The invention relates to a method of operating a spark-ignition engine according to the invention or a spark-ignition system according to the invention, comprising: - a spark production step per engine cycle and per spark plug in a first inter-electrode space, and / or - a spark production step per engine cycle and per spark plug in a second inter-electrode space, and / or - a stage of producing two sparks per engine cycle and per spark plug respectively in the first and second inter-electrode spaces, these two sparks being able to be offset in time from each other.

[0021] These objects, features and advantages of the present invention will be described in detail in the following description of a particular embodiment, given by way of non-limiting example, with reference to the accompanying figures, among which:

[0022] [Fig-1] Figure [Fig.1] represents an embodiment of a vehicle according to the invention, where a candle is shown in longitudinal section.

[0023] [Fig.2] Fig.2 represents a bottom view of one embodiment of the spark plug according to the invention.

[0024] [Fig.3] Fig.3 presents a perspective view of an embodiment of a pre-combustion chamber according to the invention.

[0025] An embodiment of a motor vehicle 300 according to the invention is described below with reference to [Fig. 1]. The motor vehicle 300 is a motor vehicle of any type, in particular a passenger vehicle or a commercial vehicle.

[0026] The motor vehicle 300 is equipped with a spark-ignition engine 200 according to the invention. The spark-ignition engine is of any type.

[0027] The spark-ignition engine 200 includes an ignition system 150. The ignition system includes an ignition control unit 160 and a spark plug 10 according to the invention.

[0028] The spark-ignition engine 200 comprises a cylinder head 100 according to the invention. The cylinder head 100 comprises a spark plug 10 according to the invention.

[0029] An embodiment of a spark plug 10 for a spark-ignition engine is described below with reference to figures 1 to 3.

[0030] The spark plug 10 comprises a base 8 into which an insulating ceramic 7 is inserted. The base 8 and the ceramic 7 have a common longitudinal axis 101, which is also the longitudinal axis of the spark plug 10. The base 8 covers the ceramic 7 substantially over the first half of the length of the spark plug 10, referred to as the lower part or half of the spark plug 10. Over substantially the other half of the length of the spark plug 10, referred to as the upper part or half of the spark plug 10, the insulating ceramic is exposed. The base is preferably externally threaded to allow it to be screwed into a tapped hole in the cylinder head.

[0031] The insulating ceramic 7 has two straight recesses parallel to the longitudinal axis 101 of the spark plug 10.

[0032] The spark plug 10 also includes a first and a second electrode 1, 2. They are, for example, straight and fit respectively into the two straight recesses of the insulating ceramic 7. The first and second electrodes 1, 2 therefore pass longitudinally through the insulating ceramic 7.

[0033] In the upper half of the spark plug 10, the ceramic 7 has two recesses 71, 72 which allow the upper end 12, 22 of the first and second electrodes 1, 2 to protrude. The recesses 71, 72 thus constitute a two-pin connector 9 intended to receive a two-pin cap enabling a galvanic connection of the upper ends 12, 22 of the electrodes to the ignition control unit 160, in order to control one or the other or both of the first and second electrodes 1, 2.

[0034] In the lower half of the spark plug 10, the lower ends 11, 21 of the first and second electrodes 1, 2 protrude from the ceramic.

[0035] The lower end of the spark plug 10 also includes a third and a fourth electrode 13, 23, which respectively define - a first inter-electrode space 14 located between the third electrode 13 and the lower end 11 of the first electrode 1, and - a second inter-electrode space 24 located between the fourth electrode 23 and the lower end 21 of the second electrode 2.

[0036] The inter-electrode space is defined as an interstice separating two electrodes not in contact, this interstice being intended to be the site of sparks between the two electrodes.

[0037] At the lower end of the first electrode 1, a pre-combustion chamber 3 (more specifically represented in [Fig.3]) can be formed by means of a pre-chamber washer 4 and a pre-chamber capsule 5 welded onto the washer 4.

[0038] The washer 4 is welded to the lower end of the base 8. It has two openings 41, 42 which allow the lower ends 11, 21 of the first and second electrodes 1, 2 to pass through respectively, as well as the insulating ceramic which envelops a portion of these lower ends 11, 21.

[0039] A seal 6 can be placed between the washer 4 and a shoulder made in the insulating ceramic 7 around the lower end 11 of the first electrode 1.

[0040] A prechamber capsule 5 is advantageously welded onto the washer 4 opposite the opening 41 made in the washer 4 to allow the lower end 11 of the first electrode 1 to pass through. The prechamber capsule 5 thus delimits a prechamber volume around the lower end 11 of the first electrode 1. Orifices 51, 52 are arranged on the prechamber capsule 5 in order to allow the prechamber volume to communicate with the outside of the prechamber.

[0041] According to another embodiment, said washer 4 and capsule 5 are part of the base 8, in particular washer 4 and capsule 5 are made from the same piece with the base 8.

[0042] The third and fourth electrodes 13, 23 are respectively arranged opposite and at a distance from each of the lower ends 11,21 of the first and second electrodes 1, 2. In the remainder of the document, the third and fourth electrodes are referred to as ground electrodes.

[0043] Preferably, the third and fourth ground electrodes are carried by the capsule 5 and therefore by the base 8. This arrangement allows optimal compactness of the spark plug.

[0044] The ground electrode 13 associated with the first electrode 1 is located inside the pre-combustion chamber.

[0045] In the embodiment shown in [Fig. 1], the ground electrode 23 associated with the second electrode 2 is located on the outer face of the prechamber capsule 5, opposite the lower end 21 of the second electrode 2. In In this embodiment, the first electrode 1 opening onto the prechamber 3 is slightly shorter than the second electrode 2.

[0046] The two ground electrodes are connected directly or indirectly to the base 8 of the spark plug 10. In the embodiment presented, the two ground electrodes 13, 23 are fixed to the capsule 5 which is connected to the base 8 via the washer 4.

[0047] A space called inter-electrode space 14, 24 separates each of the lower ends 11, 21 of the first and second electrodes 1, 2, from the ground electrode associated with it 13, 23.

[0048] The spark plug 10 thus allows the first and second electrodes 1, 2, electrically isolated from each other, to be controlled independently or simultaneously, resulting in independent or simultaneous ignition of the fuel from two distinct spaces, the pre-combustion chamber 3 and / or the combustion chamber.

[0049] Ignition of the fuel from the pre-combustion chamber 3 is achieved by applying a high voltage between the upper end 12 of the electrode 1 via the connector 9 and ground. An electric arc then forms in the inter-electrode space 14 located in the pre-combustion chamber. Since the pre-chamber is filled with a flammable mixture, the occurrence of this spark causes the fuel to ignite.

[0050] Ignition of the fuel directly in the combustion chamber delimited by the cylinder head is achieved by applying a high voltage between the upper end 22 of the electrode 2 via the connector 9 and ground. An electric arc then forms in the inter-electrode space 24 located in the combustion chamber, creating the ignition of the fuel from this spark.

[0051] An embodiment of a method for operating a spark-ignition engine or a spark-ignition system according to the invention is described below. The method comprises: - a first mode of operation with production of a spark per spark plug and per engine cycle in a first inter-electrode space 14, 24, and / or - a second operating mode with production of a spark per spark plug and per engine cycle in a second inter-electrode space 14, 24, and / or - a third mode of operation with production of two sparks per spark plug and per engine cycle respectively in the first and second inter-electrode spaces 14, 24, these two sparks being able to be offset in time from each other.

[0052] Fuel ignition can therefore be selectively controlled from the most suitable space, pre-combustion chamber 3 or combustion chamber, depending on the engine operating conditions.

[0053] Under normal engine operating conditions that do not risk damaging the pre-combustion chamber, ignition can be controlled via electrode 1 opening into the pre-combustion chamber 3. The spark plug 10 will offer the same advantages as a pre-chambered spark plug. In particular, the spark plug 10 will increase the engine's volumetric efficiency while limiting the occurrence of knocking.

[0054] During specific engine operating phases—such as a cold start or a warm-up phase for the aftertreatment system—ignition can be controlled via electrode 2 opening into the combustion chamber. The spark plug 10 will thus provide improved performance in applications where a pre-chambered spark plug would be inefficient.

[0055] In the operating mode where two sparks are produced per spark plug and per engine cycle, the two sparks can be offset in time by a duration corresponding to a given degree of crankshaft rotation of the engine.

[0056] Thus, by combining the operation of a pre-chamber spark plug and a standard spark plug, the spark plug 10 makes it possible to increase the volumetric efficiency of a heat engine.

[0057] Furthermore, the spark plug 10 was designed taking into account the constraints related to its integration into a cylinder head and combustion chamber of an engine. In particular, the spark plug 10 was designed so that it could be integrated into a bore intended to receive a standard spark plug.

Claims

Demands

1. Spark plug (10) for a spark-ignition engine comprising: - a first electrode (1), - a second electrode (2), - a third electrode (13), - a fourth electrode (23), - a first inter-electrode gap (14) located between the first electrode (1) and the third electrode (13), - a second inter-electrode gap (24) located between the second electrode (2) and the fourth electrode (23), - a base (8), in particular in the lower part of the spark plug, the third and fourth electrodes (13, 23) forming part of the base (8), and - a pre-chamber (3) arranged such that the first inter-electrode gap (14) is located in the pre-chamber (3) and the second inter-electrode gap (24) is located outside the pre-chamber,the first and second electrodes being electrically isolated from each other and the two inter-electrode spaces allowing a spark to be independently directed towards either or both inter-electrode spaces.

2. Spark plug (10) for spark-ignition engine according to the preceding claim, characterized in that the base (8) comprises: - a washer (4) having two openings, a first opening (41) being provided to allow a first electrode (1) to pass through and a second opening (42) being provided to allow a second electrode (2) to pass through, and - a capsule (5) covering the first opening (41) provided on the washer (4), said capsule (5) having at least two orifices (51, 52) allowing a fuel to enter the pre-combustion chamber (3).

3. Spark plug (10) for spark-ignition engine according to claim 2, characterized in that the third and fourth electrodes are carried by the capsule (5).

4. Spark plug (10) for a spark-ignition engine according to any one of the preceding claims, characterized in that it includes a two-pin connector (9) intended to receive a cap enabling individual control of each of the first and second electrodes (1,2).

5. Spark plug (10) for spark-ignition engine according to any one of the preceding claims, characterized in that the first and second electrodes (1,2) are straight and in that they fit respectively into two parallel housings made in an insulating ceramic (7).

6. Engine cylinder head (100) with spark ignition comprising a spark plug (10) according to any one of the preceding claims, characterized in that: - said spark plug (10) is inserted into a location in the cylinder head provided for a standard spark plug, and - the at least two orifices (51, 52) of the prechamber capsule of said spark plug (10) allow fuel contained in the cylinder head to enter the prechamber (3), and - the second inter-electrode space (24) of said spark plug (10) is located in the cylinder head.

7. Controlled ignition system (150) comprising an ignition control unit (160) and a spark plug (10) according to any one of claims 1 to 5.

8. Spark-ignition engine (200) comprising a cylinder head according to claim 6.

9. Motor vehicle (300) comprising a spark-ignition engine according to the preceding claim.

10. A method of operating a spark-ignition engine according to claim 8 or a spark-ignition system according to claim 7, comprising: - a step of producing one spark per engine cycle and per spark plug in a first inter-electrode space, and / or - a step of producing one spark per engine cycle and per spark plug in a second inter-electrode space, and / or - a step of producing two sparks per engine cycle and per spark plug respectively in the first and second inter-electrode spaces, these two sparks being able to be offset in time from each other.

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