EP3420615B1 - Prechamber spark plug - Google Patents

Description

The present invention relates to an antechamber spark plug with a housing, a ground electrode and an antechamber defined by the housing and a cap, a center electrode being arranged within the antechamber.

Pre-chamber spark plugs of the type in question have been known from practice for years. For example, prechamber spark plugs are used in internal combustion engines that operate on the lean-burn principle. Pre-chamber spark plugs have a pre-chamber which interacts with the combustion chamber of an internal combustion engine through transfer openings. The fuel-air mixture is ignited by means of ignition sparks in the prechamber, after which the combustion continues in the form of ignition torches through the transfer openings into the combustion chamber of the internal combustion engine, where the mixture ignites.

A prechamber spark plug is, for example, from WO 2007/092972 A1 known. This spark plug has an antechamber provided with an antechamber wall and a cover surface. The antechamber wall comprises a cylindrical part to which rectangular ground electrodes are also attached by means of rectangular ground electrode supports. The ground electrodes are assigned rectangular ignition electrodes which are attached to a central ignition electrode carrier. Several pairs of ignition surfaces are thus created with which ignition is to take place as centrally as possible with respect to the prechamber.

The known prechamber spark plugs have the disadvantage that relatively high wall heat losses occur. Another disadvantage is the insufficient flame spread, which leads to a low degree of efficiency of the prechamber spark plug.

The present invention is therefore based on the object of designing and developing a prechamber spark plug of the type mentioned at the beginning in such a way that the function of the prechamber spark plug is improved with structurally simple means.

According to the invention, the above object is achieved by the features of claim 1. Accordingly, the prechamber spark plug in question is characterized in that the ratio V / D of the prechamber volume V to the largest inner diameter D of the prechamber is in the range from 30 mm ² to 95 mm ² .

The invention is based on the knowledge that the layout of the prechamber has significant effects on the functionality of the prechamber spark plug. In particular, it has been recognized that a sufficiently spherical design of the antechamber results in optimal flame propagation and reduced wall heat losses. To achieve the underlying problem, the ratio V / D between the prechamber volume V enclosed by the prechamber and the largest inner diameter D of the prechamber is optimized, namely in the range from 40 mm ² to 70 mm ² . With such a ratio of V / D, the functionality of the prechamber spark plug is optimized in an ideal way.

At this point, it should be noted that the term "prechamber volume" is to be understood as the volume of the prechamber enclosed by the inner wall of the housing and the cap or the electrodes without the overflow bores or transfer passages.

To further improve the ignition properties, at least one corner and / or edge formed on the inside of the antechamber can be rounded. In particular, it is conceivable that all of the corners and / or edges formed on the inside of the antechamber are rounded. The rounded design avoids hot spots in the antechamber. This has the advantage that uncontrolled ignition of the fuel-air mixture on such a hot surface is largely prevented.

In a further advantageous manner, it is conceivable that the rounded corner or the rounded corners have a radius R _E of greater than or equal to 0.4 mm, ie R 0.4 mm and / or an angle β in the range of greater than or equal to 90 Define °.

Alternatively or additionally, at least one of the edges formed on the inside of the antechamber can have an angle β ′ in the range from greater than or equal to 90 ° to less than 100 ° and / or have a radius R _K of greater than or equal to 0.8 mm, ie 90 ° ≤ β '<100 ° and R _K ≥ 0.8 mm. In a particularly advantageous manner, the angle β 'is in the range from greater than or equal to 100 ° to less than 120 ° and / or the radius R _{K is} in a range greater than or equal to 0.6 mm, ie 100 ° ≤ β'<120 ° and R _K ≥ 0.6 mm.

In a further advantageous manner, the radius R _{K can be} in a range of greater than or equal to 0.4 mm and / or the angle β 'can be configured to be greater than or equal to 120 °, ie β' β 120 ° and R 0.4 mm.

In order to minimize the heat input into the spark plug via the cap surface protruding into the combustion chamber, the ratio y / D _a between the protrusion dimension y and the largest outer diameter D _{a of} the cap can be in the range from 0.2 to 1.0. The protrusion dimension y is defined as the length of the area of the prechamber spark plug which protrudes beyond the combustion chamber roof into the combustion chamber.

To protect the weld seam connecting the cap to the housing, the weld seam can be at the same level as or above the combustion chamber roof when the prechamber spark plug is arranged in the combustion chamber roof. This ensures that the weld seam is not subject to excessive erosion due to contact with the gases and flames in the combustion chamber.

It should be noted that the invention in question here also comprises a set consisting of a combustion chamber roof and an antechamber spark plug with a housing, a ground electrode and an antechamber defined by the housing and a cap, a center electrode being arranged within the antechamber and wherein in the state of the prechamber spark plug arranged in the combustion chamber roof, the ratio y / D _a between protrusion dimension y and maximum The outer diameter D _{a of} the cap is in the range from 0.2 to 1.0 and / or the weld seam connecting the cap to the housing is at the same level or above the combustion chamber roof. Furthermore, the prechamber spark plug of the set can have one or more features of claims 1 to 10 and the description of the figures below.

The invention in question also relates to an antechamber spark plug with a housing, a ground electrode and an antechamber defined by the housing and a cap, a center electrode being arranged within the antechamber and the ratio y / D _a in the state of the antechamber spark plug in the combustion chamber roof between the protrusion dimension y and the largest outer diameter D _{a of} the cap is in the range from 0.2 to 1.0 and / or the weld seam connecting the cap to the housing is at the same level or above the combustion chamber roof. Such a spark plug can have one or more of the features of claims 1 to 10 and the description of the figures below.

The present invention also relates to an antechamber spark plug with a housing, a ground electrode and an antechamber defined by the housing and a cap, a center electrode being arranged within the antechamber, with at least one corner and / or edge formed on the inside of the antechamber being rounded. Such a prechamber spark plug can also have one or more features of claims 1 to 9 and the following description of the figures.

Fig. 1

in einer schematischen Darstellung ein Ausführungsbeispiel einer erfindungsgemäßen Vorkammerzündkerze,

Fig. 2

in einer vergrößerten Darstellung einen Ausschnitt aus Fig. 1, und

Fig. 3

in einer schematischen Darstellung die erfindungsgemäße Vorkammerzündkerze gemäß Fig. 1 im in ein Brennraumdach angeordneten Zustand.

There are now various possibilities for designing and developing the teaching of the present invention in an advantageous manner. For this purpose, on the one hand, reference is made to the claims subordinate to claim 1 and, on the other hand, to the following explanation of preferred exemplary embodiments of the invention with reference to the drawing. In connection with the explanation of the preferred exemplary embodiments of the invention with reference to the drawing, generally preferred embodiments and developments of the teaching are also explained. Show in the drawing

Fig. 1

in a schematic representation an embodiment of a prechamber spark plug according to the invention,

Fig. 2

an enlarged view of a section Fig. 1 , and

Fig. 3

in a schematic representation the prechamber spark plug according to the invention according to Fig. 1 in the state arranged in a combustion chamber roof.

The Figs. 1 to 3 show in a schematic representation an embodiment of a prechamber spark plug according to the invention. The prechamber spark plug has a housing 3 formed from a first housing part 1 and a second housing part 2. The housing parts 1, 2 are connected to one another via a weld seam. The housing 1 surrounds part of an insulator 4. A supply line (not shown) is arranged inside the insulator 4 and supplies the central electrode 6 provided within the antechamber 5 with electrical voltage. The center electrode 6 comprises a total of four electrode arms 7. The center electrode 6 can, however, also have a different geometry. It should also be pointed out that the housing 3 can also be designed in one piece.

In the exemplary embodiment shown here, the first housing part 1 serves as a ground electrode and has an external thread 8 in order to fix the prechamber spark plug in a housing cover which defines the combustion chamber roof 9, as shown in FIG Fig. 3 is shown. The prechamber 5 is closed by the cap 10 in the direction of the main combustion chamber. The cap 10 is connected to the first housing part 1 via a weld 11. It is conceivable that the cap 10 extends as far as the center electrode 6 and serves as a ground electrode. The cap 10 has a plurality of passage passages 12 which can be arranged around the cap 10 in the circumferential direction.

In Fig. 2 the largest inner diameter D of the prechamber 5 is shown. It is essential that the ratio of the prechamber volume V to the largest inner diameter D of the prechamber is in the range from 30 mm ² to 95 mm ² , in particular in the range from 35 mm ² to 90 mm ² , preferably in the range from 40 mm ² to 70 mm ² .

In addition, the Fig. 2 and 3 the largest outer diameter D _{a of} the cap 10 is shown. Furthermore goes out Fig. 3 the protrusion y of the prechamber spark plug arranged in the combustion chamber roof 9 emerges. The ratio y / D _a between the protrusion dimension y and the largest outside diameter D _{a of} the cap 5 is advantageously in the range from 0.2 to 1.0.

In Fig. 3 it is also shown that the weld seam 11, which connects the cap 10 to the first housing part 1, is at the same height as the combustion chamber roof 9. Alternatively, it is conceivable that the weld seam 11 is arranged above the combustion chamber roof 9, so that only part of the cap 10 protrudes into the combustion chamber.

Furthermore, in Fig. 3 to see that the corners 13 and edges 14 realized on the inside of the antechamber 5 are rounded. In concrete terms, the corners 13 can have a radius R _E of greater than or equal to 0.4 mm and / or an angle β of greater than or equal to 90 °. In the exemplary embodiment shown here, the angle β measures approximately 120 °. An angle greater than 90 ° has the advantage that the radius can be made smaller, so that less reworking is necessary. The angle β 'formed by the edges 14 can be in the range from greater than or equal to 90 ° to less than 100 ° and / or the edges 14 can have a radius R _K of greater than or equal to 0.8 mm. It is also conceivable that the angle β ′ is in the range from greater than or equal to 100 ° to less than 120 ° and / or that the edges 14 have a radius R _K of greater than or equal to 0.6 mm. According to a further embodiment, the edges can have a radius R _K of greater than or equal to 0.4 mm and / or the angle β ′ can be in the range of greater than or equal to 120 °. The angles β and β 'can be designed as alternating angles.

With regard to further advantageous embodiments of the device according to the invention, reference is made to the general part of the description and to the appended claims in order to avoid repetition.

Finally, it should be expressly pointed out that the above-described exemplary embodiments of the device according to the invention only serve to explain the teaching claimed, but do not restrict them to the exemplary embodiments.

List of reference symbols

1

first housing part

2

second housing part

3

casing

4th

insulator

5

Antechamber

6th

Center electrode

7th

Electrode arms

8th

External thread

9

Combustion chamber roof

10

cap

11

Weld

12

Transfer passage

13

corner

14th

Edge

Claims (9)

1. Pre-chamber spark plug having a housing (3), an earth electrode and a pre-chamber (5) which is defined by the housing (3) and a cover (10), wherein a central electrode (6) is arranged within the pre-chamber (5),
   characterised in that the ratio V/D of pre-chamber volume V to the largest inner diameter D of the pre-chamber (5) is in the range from 40 mm² to 70 mm².
2. Pre-chamber spark plug according to claim 1, characterised in that at least one corner (13) and/or edge (14) formed on the inner side of the pre-chamber (5) is rounded.
3. Pre-chamber spark plug according to claim 1 or claim 2, characterised in that all of the corners (13) and/or edges (14) formed on the inner side of the pre-chamber (5) are rounded.
4. Pre-chamber spark plug according to claim 2 or claim 3, characterised in that the corner (13) or the corners (13) has/have a radius R_E greater than or equal to 0.4 mm and/or have an angle β in the range greater than or equal to 90°.
5. Pre-chamber spark plug according to any one of claims 1 to 4, characterised in that at least one of the edges (14) formed on the inner side of the pre-chamber (5) has an angle β' in the range from greater than or equal to 90° to less than 100° and/or has a radius R_K greater than or equal to 0.8 mm.
6. Pre-chamber spark plug according to any one of claims 1 to 5, characterised in that at least one of the edges (14) formed on the inner side of the pre-chamber (5) has an angle β' in the range from greater than or equal to 100° to less than 120° and/or has a radius R_K greater than or equal to 0.6 mm.
7. Pre-chamber spark plug according to any one of claims 1 to 5, characterised in that at least one of the edges (14) formed on the inner side of the pre-chamber (5) has an angle β' in the range greater than or equal to 120° and/or a radius R_K greater than or equal to 0.4 mm.
8. Pre-chamber spark plug according to any one of claims 1 to 7, characterised in that in the state arranged in a combustion chamber roof (9) the ratio y/D_a between the degree of protrusion y and the largest outer diameter D_a of the cover (10) is in the range from 0.2 to 1.0.
9. Pre-chamber spark plug according to any one of claims 1 to 8, characterised in that in the state arranged in a combustion chamber roof (9) the weld seam (11) which connects the cover (14) to the housing (3) is at the same height as or above the combustion chamber roof (9).

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