Pre-chamber spark plug having an improved function

Abstract

The invention relates to a pre-chamber spark plug comprising a housing (2) and a cap (6), wherein the cap (6) has at least one cap hole (7, 8, 9) which establishes a connection between a pre-chamber (16) and an outer region of the cap, and the cap (6) has, on an inner wall region, at least one conical wall surface (61, 62, 63, 64) which forms an angle α relative to a plane E which is perpendicular to the central axis X-X of the pre-chamber spark plug.

Description

[0001] Description

[0002] title

[0003] Pre-chamber spark plug with improved function

[0004] State of the art

[0005] The present invention relates to a prechamber spark plug with an improved function, in particular a gas exchange in the prechamber during a gas exchange.

[0006] Pre-chamber spark plugs are known from the prior art in various designs. Pre-chamber spark plugs usually have a cap that defines a pre-chamber, whereby the cap has so-called cap holes that create a connection between the pre-chamber and a combustion chamber of an internal combustion engine. The cap holes must ensure gas exchange in the pre-chamber. After ignition in the pre-chamber, so-called torch jets spread through the cap holes into the combustion chamber, where the main ignition of a gas-air mixture then occurs. After ignition, the pre-chamber must be purged in order to be ready for the next ignition. The problem is that every internal combustion engine has different conditions, so that individual pre-chamber spark plugs are often necessary for different internal combustion engines.In particular, a position between the injector and the cap holes of the cap in the respective internal combustion engine must be ensured in a coordinated manner in order to achieve optimal function.

[0007] Disclosure of the invention

[0008] The prechamber spark plug according to the invention with the features of claim 1 has the advantage that a particularly effective charge exchange is possible within a prechamber of the prechamber spark plug. In particular, the invention reduces turbulence when gas flows into the prechamber. Furthermore, the inflow of gas can be introduced with significantly less pressure loss and in a defined direction. This also enables efficient purging of combusted gas from the prechamber.

[0009] This is achieved according to the invention in that the pre-chamber spark plug comprises a housing and a cap. The cap has at least one cap hole. Furthermore, the cap defines a pre-chamber, wherein the cap has at least one conical wall surface on an inner wall region. The conical wall surface has a first wall angle α, in particular an acute angle, to a plane E, wherein the plane E is perpendicular to a central axis XX of the pre-chamber spark plug. As a result, a flow within the pre-chamber can be deflected in a streamlined manner as it flows in and strikes the inner wall surface of the cap, without significant turbulence or pressure losses occurring. Thus, a fresh gas mixture can be optimally introduced between a center electrode and a ground electrode of the pre-chamber spark plug as it flows in, so that an ignitable mixture is reliably present in an ignition region between the center electrode and the ground electrode.

[0010] The subclaims show preferred developments of the invention.

[0011] Preferably, the cap hole opens into the inner wall area of ​​the cap at the conical wall surface. The opening of the cap hole preferably lies entirely within a conical wall surface of the inner wall area of ​​the cap.

[0012] Further preferably, several conical wall surfaces with different wall angles are provided. This allows for a significant optimization of the flow of fresh gas into the combustion chamber.

[0013] If several conical wall surfaces are provided, these preferably have different dimensions in the direction of the central axis XX. For example, the width of the wall surfaces differs in the direction of a central axis of the pre-chamber spark plug. This can further reduce turbulence when fresh gas flows into the pre-chamber. Particularly preferably, the cap hole is designed to be straight with a central axis Y, wherein a hole angle ß is present between the central axis Y and a plane E which is perpendicular to the central axis XX. The angle ß differs from the wall angle α of the conical wall surface which is intersected by the central axis Y by a maximum of 75°. For example, the angles α and β differ by 45°. In this case, bore axes which do not meet a conical surface on the opposite side are preferably shifted in parallel until the next wall surface is met.

[0014] Accordingly, if there are several cap holes, the cap holes are straight and each have a central axis Y1, Y2, Y3, whereby a hole angle ß1, ß2, ß3 is present between the respective central axis Y1, Y2, Y3 and the plane E. The respective angle ß1, ß2, ß3 differs from the wall angle a of the conical wall surface that is intersected by the respective central axis Y1, Y2, Y3 by a maximum of 75°. For example, the angles a and ß differ by 45°. In this case, hole axes that do not meet a conical surface on the opposite side are preferably shifted parallel until the next wall surface is met.

[0015] More preferably, the second hole angle ß is smaller than each wall angle a.

[0016] In a further preferred embodiment of the invention, the inner wall region of the cap is formed with a base. The base is arranged perpendicular to the center axis of the prechamber spark plug.

[0017] Starting from the base, the inner wall area of ​​the cap has exclusively one or more conical wall surfaces until the cap transitions into an inner wall of the housing, which is parallel to the central axis XX. Preferably, a rounded portion is provided at the transition between the base and a conical wall surface immediately adjacent to the base.

[0018] With multiple conical wall surfaces, the first wall angle a between the conical wall surfaces and the plane E, which is perpendicular to the central axis XX, increases continuously. In one embodiment, the cap has a cylindrical section and a transition from the cylindrical section to the inner wall of the housing, which transition is executed without a step.

[0019] More preferably, the pre-chamber spark plug comprises one or more ground electrodes and at least one center electrode.

[0020] Short description of the drawings

[0021] Embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing:

[0022] Figure 1 is a schematic partial sectional view of a spark plug according to a first embodiment,

[0023] Figure 2 is a schematic partial sectional view of a cap of the pre-chamber spark plug of Figure 1 in a first sectional plane,

[0024] Figure 3 is a schematic partial sectional view of a cap of the pre-chamber spark plug of Figure 1 in a second sectional plane,

[0025] Figure 4 is a schematic sectional view of a cap of a pre-chamber spark plug according to a second embodiment of the invention, and

[0026] Figure 5 is a schematic sectional view of a cap of a pre-chamber spark plug according to a third embodiment of the invention.

[0027] Preferred embodiments of the invention

[0028] A pre-chamber spark plug 1 according to a first preferred embodiment of the invention is described in detail below with reference to Figures 1 to 3.

[0029] The prechamber spark plug has, as shown in Figure 1, a metallic housing 2 and an insulator 3. Furthermore, the prechamber spark plug comprises a center electrode 4, which lies along a center axis XX of the prechamber spark plug, and at least one laterally positioned ground electrode 5.

[0030] An external thread 21 is formed on the housing 2, which is designed to screw the spark plug into a cylinder head of an internal combustion engine.

[0031] The prechamber spark plug further comprises a cap 6, which, together with a part of the housing 2, defines a prechamber 16. The center electrode 4 and the ground electrode 5 are arranged in the prechamber 16.

[0032] The cap 6 has a plurality of cap holes that enable fluid communication between the prechamber 16 and a combustion chamber 10 of an internal combustion engine. Figures 2 and 3 show three cap holes: a first cap hole 7, a second cap hole 8, and a third cap hole 9.

[0033] The housing 2 has an inner wall 20, which can be seen in Figures 1 to 3, and in particular continuously merges into an inner wall region of the cap 6.

[0034] The inner wall region of the cap 6 is shown in detail in Figures 2 and 3. The inner wall region has a base 60 arranged perpendicular to the central axis XX. Furthermore, the inner wall region has a first conical wall surface 61 and a second conical wall surface 62.

[0035] At the transition between the base 60 and the first conical wall surface 61 there is a rounded transition area 66.

[0036] A cylindrical section 67 is provided at the transition between the inner wall area of ​​the cap 6 and the inner wall 20 of the housing 2 (see Figures 2 and 3). The transition is formed without a step.

[0037] The first conical wall surface 61 is arranged at a first wall angle o1 to a plane E, which is perpendicular to the central axis XX. The second conical wall surface 62 is arranged at a second wall angle a2 to a plane E, which is perpendicular to the central axis XX. The first wall angle o1 is smaller than the second wall angle a2. The difference between the first wall angle o1 and the second wall angle a2 is a maximum of 15°. Thus, an inner wall region of the cap 6 has two conical wall surfaces 61, 62, which enable improved outflow and also improved inflow of gas.

[0038] As shown in Figure 2, the first cap hole 7 is a straight bore and an opening 7a of the first cap hole 7 lies completely in the first conical wall surface 61. A central axis Y1 of the first cap hole 7 lies at a first hole angle ß1 to a plane E which is perpendicular to the central axis XX. The second cap hole 8 lies, as shown in Figure 2, with a central axis Y2 at a second hole angle ß2 to a plane E which is perpendicular to the central axis XX. An opening 8a of the second overflow opening 8 lies completely in the rounded transition region 66 between the base 60 and the first conical wall surface 61. The second hole angle ß2 is smaller than the first hole angle ß1.

[0039] Figure 2 shows the outflow behavior of gas from the prechamber 16. The smaller hole angle ß2, which is located near the bottom 60, significantly improves the outflow from the prechamber 16 in this area. The slightly larger hole angle ß1 compared to the second hole angle ß2 also improves the outflow in the area of ​​the first conical wall surface 61. In Figure 2, the arrows schematically show the outflow behavior from the prechamber 16.

[0040] In Figure 3, the inflow behavior of gas is schematically represented by the arrows. The third cap hole 9 is arranged similarly to the second cap hole 8 such that an opening 9a lies completely in the rounded transition region 66 of the inner wall region of the cap 6. A central axis Y3 of the third cap hole 9 is arranged at a third hole angle ß3 to a plane E, which is perpendicular to the central axis XX, and is relatively flat. This achieves very good inflow behavior of gas into the prechamber 16. In particular, turbulence during the inflow process of gas into the prechamber 16 can be reduced. The design of the third cap hole 9 allows the inflow to be carried out with significantly reduced pressure loss and in a predefined direction. This predefined direction of the inflowing gas can, in particular, enable efficient purging of combusted gas from the prechamber 16.By arranging the orifices 7a, 8a, and 9a at the rounded transition area and the conical wall surfaces, a large opening cross-section can be achieved at the orifices. This supports gas exchange in the prechamber 16.

[0041] Furthermore, the relatively flat design of the cap holes 7, 8, 9 allows a relatively long flow path to be achieved in the cap holes 7, 8, 9. This reduces turbulence both during inflow and outflow. The flatter the angle of the cap holes 7, 8, 9 to plane E, the lower the turbulence generated and also the pressure loss at the inner wall region of the cap 6. This leads to particular advantages when an ignitable gas mixture flows into the prechamber 16. In particular, the rounded transition region 66 allows, as shown schematically in Figure 3, very good application of the gas flow during inflow to the inner wall region of the cap 6 and subsequently to the inner wall 20 of the housing 2.

[0042] Thus, by selecting the hole angles for the cap holes and the wall angles for the conical wall surfaces, individual adaptation to the specific conditions of internal combustion engines from different manufacturers can be achieved. With regard to flow optimization, an internal geometry of the cap 6 with different conical wall surfaces can achieve flows with low turbulence in the antechamber 16.

[0043] Figure 4 schematically illustrates a cap 6 of a prechamber spark plug of a second exemplary embodiment. The same reference numerals in the second exemplary embodiment denote the same components as in the first exemplary embodiment.

[0044] As shown in Figure 4, the inner wall region of the cap 6 is constructed differently from the first exemplary embodiment. Starting from a base 60, which has a relatively small area, a total of four conical wall surfaces are arranged, namely a first conical wall surface 61, a second conical wall surface 62, a third conical wall surface 63 and a fourth conical wall surface 64. The conical wall surfaces are each arranged at different wall angles a1, a2, a3 and a4 to planes E, which are perpendicular to the central axis XX of the pre-chamber spark plug. The angles a1 and a2 for the first and second wall surfaces 61, 62 are shown as examples. The angles increase continuously from the first wall angle a1 to the fourth wall angle a4. This is shown schematically in Figure 5. Figure 4 also shows the first hole angle ß1 of the first cap hole 7 to plane E.

[0045] The fourth wall angle a4 is almost 90°. By way of example, the first hole angle ß1 is approximately 10° and the first wall angle cd of the first conical wall surface 61 is approximately 15°. The second wall angle a2 of the second conical wall surface is approximately 25° and the third wall angle a3 of the third conical wall surface is approximately 50°. It should be noted that these are only example values ​​and that, depending on the internal combustion engine and the desired inflow and outflow behavior, the wall and hole angles can also be selected differently. The number of conical wall surfaces of the cap 6 can also be freely selected and is preferably in a range from two conical wall surfaces to ten conical wall surfaces or more.

[0046] Figure 5 shows a cap 6 of a pre-chamber spark plug according to a third embodiment of the invention, wherein identical or functionally identical parts are designated by the same reference numerals.

[0047] As can be seen from Figure 5, the cap 6 has a base 60, a first conical wall surface 61, and a second conical wall surface 62. A first cap hole 7 is formed at a transition between a base 60 and the first conical wall surface 61. A central axis Y of the first cap hole 7 intersects the second conical wall surface 62 (see Figure 6). A hole angle ß of the first cap hole 7 is equal to or smaller than a first wall angle a1 of the first conical wall surface and a second wall angle α2 of the second conical wall surface. The second angle a2 is greater than the first angle a1 (preferably approximately twice as large).

Claims

Claims 1. Pre-chamber spark plug comprising a housing (2) and a cap (6), wherein the cap (6) has at least one cap hole (7, 8, 9) which establishes a connection between a pre-chamber (16) and an outer region of the cap, and wherein the cap (6) has at least one conical wall surface (61, 62, 63, 64) on an inner wall region with a wall angle a to a plane E which is perpendicular to a central axis XX of the pre-chamber spark plug.

2. Pre-chamber spark plug according to claim 1, wherein the cap hole (7) opens at the conical wall surface (61).

3. Pre-chamber spark plug according to one of the preceding claims, comprising a plurality of conical wall surfaces with different wall angles a.

4. Pre-chamber spark plug according to claim 3, wherein the conical wall surfaces have different dimensions in the direction of the central axis XX.

5. Prechamber spark plug according to one of the preceding claims, wherein the cap holes (7, 8, 9) are rectilinear and have a central axis (Y1, Y2, Y3), wherein a hole angle ß between the central axis (Y1, Y2, Y3) and the plane E differs from the wall angle α of the conical wall surface (61, 62, 63, 64) which is intersected by the central axis (Y1, Y2, Y3) by a maximum of 75°.

6. Pre-chamber spark plug according to claim 5, wherein the hole angle ß of the cap holes is smaller than the wall angle α of the conical wall surfaces of the cap (6).

7. Prechamber spark plug according to one of the preceding claims, wherein the inner wall region of the cap (6) has a base (60) formed perpendicular to the central axis XX.

8. Prechamber spark plug according to claim 7, wherein the inner wall region of the cap (6) is formed exclusively with conical wall surfaces (61, 62, 63, 64) starting from the bottom up to an inner wall (20) of the housing (2).

9. Prechamber spark plug according to claim 7 or 8, wherein a transition between the base (60) and a conical wall surface (61) adjacent to the base (60) is rounded by a rounded transition region (66).

10. Pre-chamber spark plug according to one of the preceding claims, wherein the cap (6) has a cylindrical portion (67) and a transition from the cylindrical portion (67) to the inner wall (20) of the housing is designed without a step.

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