Pre-chamber spark plug

Abstract

The invention relates to a pre-chamber spark plug comprising: a housing (2); a central electrode (3); a ground electrode (4), the central electrode (3) and the ground electrode (4) being arranged in a pre-chamber (5); an insulator (7); and a cap (6) which closes the prechamber in the direction of the combustion chamber (11), the insulating body (7) having: a side wall region (70) which extends substantially coaxially to a central axis (X-X) of the prechamber spark plug; an end region (71) substantially perpendicular to the central axis (X-X), on which end region the central electrode (3) protrudes; and a connection region (72) that connects the side wall region (70) and the end region (71) and has a distance defined between the center electrode (3) and the ground electrode (4).

Description

Technical Field

[0001] The invention relates to a pre-combustion chamber spark plug, which has improved ignition performance and longer service life, and in particular reduces the risk of sparks generated at the weld of the pre-combustion chamber spark plug. Background Art

[0002] Pre-chamber spark plugs are known from the prior art in various designs. The pre-chamber of a pre-chamber spark plug is typically defined by a housing area and a cap. However, the cap prevents the combustible mixture from directly contacting the spark gap and igniting. Therefore, so-called cap holes are typically provided in the cap to ensure that the ignitable mixture reaches the pre-chamber, specifically the ignition gap between the center electrode and the ground electrode. However, a problem with this is that internal combustion engine manufacturers often have different design options and design conditions, particularly regarding the position of the pre-chamber spark plug relative to the fuel injection jet. Therefore, the cap of the pre-chamber spark plug must be precisely positioned to ensure optimal gas exchange within the pre-chamber. Improper cap positioning, and therefore imperfect gas exchange for introducing the combustible mixture, often leads to the risk of sparking from the pre-chamber spark plug weld. This, however, significantly shortens the service life of the pre-chamber spark plug. Summary of the Invention

[0003] In contrast, the pre-chamber spark plug according to the present invention having the features of claim 1 has the advantage that, by adhering to the prescribed parameters of the pre-chamber spark plug components, a targeted flow can be achieved in the pre-chamber, resulting in better ignition in the pre-chamber. In particular, the spark position can be directed in a targeted manner away from welds or similar areas, thereby significantly extending the service life of the pre-chamber spark plug. According to the present invention, the flow velocity within the pre-chamber can also be increased, thereby making the air flow in the pre-chamber more turbulent and improving the ignition effect at the ignition moment. In particular, the ignition performance can be achieved by a stronger spark deflection and the resulting increase in the volume between the spark and the combustible mixture in the pre-chamber.

[0004] According to the present invention, this effect is achieved by having a pre-chamber spark plug comprising a housing, a center electrode, and a ground electrode. The center electrode and the ground electrode are arranged in a pre-chamber. Furthermore, the pre-chamber spark plug comprises an insulator and a cap that closes the pre-chamber toward the combustion chamber of the internal combustion engine. The insulator comprises a side wall region parallel to the central axis XX of the pre-chamber spark plug; an end region substantially perpendicular to the central axis, on which the center electrode is arranged, in particular, protrudes; and a connecting region between the connecting wall region and the end region. A first point K is defined at the transition between the side wall region and the connecting region of the insulator. A second point M is defined at the transition between the connecting region and the end region of the insulator. A third point I is defined at the free end of the center electrode, wherein the third point I is the point on the free end of the center electrode that is farthest from the ground electrode. A fourth point P is defined at the free end of the ground electrode. The fourth point P is the point on the free end of the ground electrode that is farthest from the center electrode. A first straight line KI extends through the first point K and the third point I. A second straight line KP extends through the first point K and the fourth point P. An angle bisector W is located between the first and second straight lines. A third straight line KM extends through the first and second points K and M on the insulator. The angle α between the angle bisector W and the third straight line KM is within the range of +20° ≤ α ≤ -20°. Therefore, the angle α is within the range of ±20° around the angle bisector W. Therefore, by adhering to these geometrical regulations, the spark deflection between the center electrode and the ground electrode can be enhanced, thereby increasing the volume between the spark and the combustible mixture in the pre-combustion chamber. This results in better ignition of the combustible mixture in the pre-combustion chamber.

[0005] The dependent claims reveal preferred further developments of the invention.

[0006] The angle α is preferably in the range of +15°≤α≤-15°, more preferably in the range of +10°≤α≤-10°, and even more preferably in the range of +5°≤α≤-5°, and is particularly preferably 0°. It is particularly advantageous that the flame front in the combustion chamber expands when the angle bisector W and the third straight line KM coincide and the angle α is 0°.

[0007] According to a further preferred design of the present invention, the distance Q between the third point I and the fourth point P is in the range of 1 mm to 3 mm, preferably in the range of 1.5 mm to 2.5 mm.

[0008] Further preferably, the pre-chamber spark plug has a plurality of ground electrodes, wherein a fourth point P is respectively provided on each of the plurality of ground electrodes, and all the ground electrodes comply with the geometrical provisions of the present invention relative to the central center electrode.

[0009] According to a further preferred embodiment of the present invention, the ground electrode has a cylindrical noble metal needle defining a free end of the ground electrode, and / or the center electrode has a cylindrical noble metal needle defining a free end of the center electrode.

[0010] Preferably, the cross section of the connecting region on the insulating body between the first point K and the second point M is straight and / or convex and / or concave and / or freely selectable. Particularly preferably, the connecting region begins with a concave curve at point K, changes to a convex curve at a turning point, and ends at point M of the insulating body, which is located at the transition between the end region and the connecting region perpendicular to the central axis XX.

[0011] In order to achieve a better flow guidance effect in the pre-combustion chamber, the pre-combustion chamber spark plug preferably has a flow guidance element on the inner wall of the housing.

[0012] The flow-guiding element is preferably a region protruding radially inward from the inner wall, for example a material accumulation.

[0013] The flow-guiding element is preferably arranged below the ground electrode. If a plurality of ground electrodes are provided, a flow-guiding element is preferably arranged below each ground electrode.

[0014] Particularly preferably, the flow guide element ends at or close to a plane E, which is perpendicular to the center axis XX of the pre-chamber spark plug and leads through a second point M on the insulator.

[0015] According to a preferred embodiment of the present invention, the flow-guiding element comprises a recess in the inner wall of the housing, preferably below the ground electrode. The recess is preferably formed at the level of the connection region of the insulator and preferably ends at the level of the first point K. The flow-guiding element preferably comprises a material accumulation and a recess.

[0016] The pre-chamber spark plug preferably has exactly one central electrode, which is arranged on the central axis of the pre-chamber spark plug. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the accompanying drawings:

[0018] Figure 1 shows a schematic cross-sectional view of a pre-chamber spark plug according to a first embodiment of the present invention,

[0019] Figure 2 shows a schematic cross-sectional view of a pre-chamber spark plug according to a second embodiment of the present invention, and

[0020] Figure 3 A schematic cross-sectional view shows a pre-chamber spark plug according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0021] Refer to the following Figure 1 A pre-chamber spark plug 1 according to a first preferred embodiment of the present invention will be described in detail.

[0022] As from Figure 1 It can be seen that the pre-combustion chamber spark plug 1 includes a housing 2 and a cap 6. The housing 2 and the cap 6 together define a pre-combustion chamber 5.

[0023] A plurality of cap holes 60 are provided in the cap 6 for gas exchange between the pre-combustion chamber 5 and the combustion chamber 11 .

[0024] The pre-combustion chamber spark plug 1 further comprises a center electrode 3 and a ground electrode 4. The center electrode 3 is arranged on the center axis XX of the pre-combustion chamber spark plug. The ground electrode 4 is arranged in the housing at a right angle to the center electrode 3.

[0025] The center electrode 3 includes a cylindrical noble metal needle 30 on which a planar, flat free end 30a is defined. The ground electrode 4 also includes a cylindrical noble metal needle 40 on which a planar free end 40a is defined.

[0026] Ground electrode 4 is fixed in housing 2 , for example, by means of a welded connection.

[0027] The center electrode 3 is arranged in an insulator 7, which electrically insulates the housing 2 and thus the ground electrode 4 from the center electrode 3. The center electrode 3 is connected in a known manner to an electrical terminal of a pre-chamber spark plug (not shown).

[0028] The pre-chamber spark plug 1 is therefore arranged directly on the combustion chamber 11 of the internal combustion engine. Due to the use of the cap 6, the combustible mixture formed in the combustion chamber 11 does not come into direct contact with the spark gap between the center electrode 3 and the ground electrode 4. Therefore, the pre-chamber spark plug and especially the cap 6 must be aligned so that Figure 1 A gas flow 10 schematically indicated in FIG. 1 reaches the pre-chamber 5 and in particular into the spark gap between the center electrode and the ground electrode in order to provide a combustible mixture there when the ignition spark is generated.

[0029] If further from Figure 1 As can be seen, the insulator 7 has a side wall region 70, an end region 71 at the top end, and a connecting region 72, which connects the wall region 70 and the end region 71. The connecting region 72 is a straight line in cross section. Different embodiments of the connecting region can also have a concave or convex shape. This means that the insulator 7 has a substantially truncated cone shape at its end facing the pre-chamber 5.

[0030] The side wall region 70 extends parallel to the inner wall 20 of the housing 2 . This means that the inner wall 20 and the side wall region 70 are cylindrical. Alternatively, the wall region 70 of the insulating body rests directly on the inner wall 20 .

[0031] If further from Figure 1 It can be seen that a first point K is defined at the transition between the side wall region 70 and the connecting region 72 .

[0032] A second point M is defined at the transition between the connecting region 72 and the end region 71 .

[0033] A third point I is defined on the free end of the center electrode 3 , more precisely on the cylindrical noble metal needle 30 , wherein the third point I is the point at which the free end 30 a of the center electrode 3 is farthest from the ground electrode 4 .

[0034] A fourth point P is defined on the free end 40a of the ground electrode 4. The fourth point P is the point on the free end 40a of the cylindrical noble metal needle 40 that is farthest from the center electrode.

[0035] Furthermore, the pre-chamber spark plug 1 includes a first straight line KI extending through the first point K and the third point I.

[0036] A second straight line KP passing through the first point K and the fourth point P is also defined.

[0037] Furthermore, the angle bisector W is located between the first straight line KI and the second straight line KP.

[0038] The third straight line KM extends through the first point K and the second point M on the insulating body 7 .

[0039] The angle α between the angle bisector W and the third straight line KM on the insulating body 7 is preferably in the range of +20°≤α≤-20° and is 5° in this embodiment. If the straight line KM extends between points P and I, the angle α is positive.

[0040] Furthermore, a distance Q is defined between a third point I on the center electrode and a fourth point P on the ground electrode. The angle bisector W intersects at half the distance Q.

[0041] like Figure 1 As shown in FIG, sparks 9 generated between center electrode 3 and ground electrode 4 are deflected by air flow 10, which is directed toward cap 6. Consequently, during the combustion time, sparks 9 are deflected by air flow 10 from their starting point between center electrode 3 and ground electrode 4, where the distance between them is typically at its shortest. The targeted air flow 10 also increases the flow velocity within pre-chamber 5, which has a beneficial effect on accelerating combustion by generating higher turbulence within pre-chamber 5. Air flow 10 ensures that sparks do not propagate toward a weld seam, which may exist between ground electrode 4 and inner wall 20 of housing 2. This significantly extends the service life of the spark plug.

[0042] Therefore, by means of targeted expansion of the spark plug 9 by means of the air flow 10, the volume of the flame front in the pre-combustion chamber 5 can be increased, which has a favorable effect on the ignition inside the pre-combustion chamber 5 and thus on the flame jet that is subsequently ejected through the cap hole 60 for igniting the combustible mixture in the combustion chamber 11.

[0043] Figure 2 A second embodiment of a pre-chamber spark plug 1 according to the present invention is shown. Identical or functionally identical components are provided with the same reference numerals as in the first embodiment.

[0044] from Figure 2 As can be seen, the second embodiment essentially corresponds to the first embodiment. Unlike the first embodiment, in the second embodiment, a flow guide element 8 is arranged on the inner wall 20 of the housing 2. In this embodiment, the flow guide element 8 is a material accumulation 80. The flow guide element 8 is arranged below the ground electrode 4. The flow guide element 8 is positioned between the plane E where the end region 71 of the insulator 7 lies and the ground electrode 4. The flow guide element 8 terminates at plane E. The flow guide element 8 is shaped in a flow-optimizing manner to deflect the airflow 10 toward the spark gap between the center electrode 3 and the ground electrode 4. This allows for more targeted guidance of the airflow 10.

[0045] Figure 3 A third embodiment of a pre-chamber spark plug 1 according to the present invention is shown. Identical or functionally identical components are provided with the same reference numerals as in the preceding embodiments.

[0046] The third embodiment essentially corresponds to the second embodiment and also features an air guide element 8 . However, the air guide element 8 in the third embodiment is a recess 81 in the inner wall 20 of the housing 2 . Recess 81 is again formed below the ground electrode 4 . Recess 81 also serves to redirect the airflow 10 , thereby improving the flow of air 10 into the ignition gap between the center electrode 3 and the ground electrode 4 . Otherwise, this embodiment corresponds to the second embodiment, and reference is made to the description of the second embodiment.

Claims

1. Pre-chamber spark plug, including: - a housing (2), - a central electrode (3), - a ground electrode (4), wherein the central electrode (3) and the ground electrode (4) are arranged in a pre-combustion chamber (5), - an insulator (7), and - a cap (6) which closes the pre-chamber in the direction of the combustion chamber (11), - wherein the insulator (7) comprises: a side wall region (70) extending substantially coaxially with the center axis (XX) of the pre-chamber spark plug; an end region (71) substantially perpendicular to the center axis (XX) and on which the center electrode (3) protrudes; and a connecting region (72) connecting the side wall region (70) to the end region (71), wherein a first point K is defined at the transition between the side wall region (70) and the connecting region (72), wherein a second point M is defined at the transition between the connecting region (72) and the end region (71), - wherein a third point I is defined on the free end (30a) of the central electrode (3), the third point being the point farthest from the end region (40a) of the ground electrode (4), - wherein a fourth point P is defined on the free end (40a) of the ground electrode (4), the fourth point being the point farthest from the free end (30a) of the central electrode (3), wherein a first straight line KI extends through the first point K and the third point I, wherein a second straight line KP extends through the first point K and the fourth point P, - wherein an angle bisector W extends between the first straight line KI and the second straight line KP, - wherein a third straight line KM extends through the first point K and the second point M on the insulator (7), and - wherein the angle α between the angle bisector W and the third straight line KM is in the range of +20°≤α≤-20°.

2. The pre-combustion chamber spark plug according to claim 1, wherein: The angle α is in the range of +15°≤α≤−15°, particularly in the range of +10°≤α≤−10°, and further particularly in the range of +5°≤α≤−5°, and is particularly preferably zero.

3. A pre-chamber spark plug according to any one of the preceding claims, wherein: A distance Q between the third point I and the fourth point P is in the range of 1 mm to 3 mm, preferably in the range of 1.5 mm to 2.5 mm.

4. A pre-chamber spark plug according to any one of the preceding claims, wherein: A plurality of grounding electrodes (4) are arranged on the housing (2), each of the grounding electrodes having a fourth point P.

5. A pre-chamber spark plug according to any one of the preceding claims, wherein: The ground electrode (4) has a noble metal needle (40) on which the free end (40a) is defined, and / or wherein: The central electrode (3) has a noble metal needle (30) on which the free end (30a) is defined.

6. A pre-chamber spark plug according to any one of the preceding claims, wherein: The cross section of the connecting region (72) between the first point K and the second point M on the insulating body (7) extends straight and / or convexly and / or concavely and / or freely selectably.

7. A pre-chamber spark plug according to any one of the preceding claims, wherein: A flow guide element (8) is arranged on the inner wall (20) of the housing (2).

8. The pre-chamber spark plug according to claim 7, wherein: The flow guide element (8) is a region (80) that protrudes radially inward from the inner wall (20) of the housing.

9. The pre-combustion chamber spark plug according to claim 7 or 8, wherein: The flow guide element (8) is arranged on a plane E or between the ground electrode (4) and the plane E, wherein the plane E extends perpendicularly to the center axis (XX) of the pre-chamber spark plug 1 and through a second point M on the insulator (7).

10. The pre-chamber spark plug according to any one of claims 7 to 9, wherein: The flow guide (8) comprises a recess (81) in the inner wall (20) of the housing (2).

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