Spark plug with improved sealing properties

Abstract

The invention relates to a spark plug, comprising a center electrode (4) and a ground electrode (5), an insulating body (2), a metal housing (3), and a metal sealing ring (6) arranged on the outer side of the housing (3) for sealing on a cylinder head (8), the sealing ring (6) has a first annular region (61), which is oriented perpendicularly to the central axis X-X of the spark plug, and a second annular region (62), which is oriented at an acute angle alpha to the central axis X-X of the spark plug, the first annular region (61) being parallel to the shoulder (34) on the housing (3) and the second annular region (62) being arranged on the inner periphery of the first annular region (61).

Description

Technical Field

[0001] The invention relates to a spark plug having improved sealing properties on an outer housing of the spark plug when the spark plug is screwed onto a cylinder head or the like, for example. Background Art

[0002] Spark plugs of various designs are known from the prior art. A series of problems in spark plugs is that a spark plug arranged in a spark plug hole in a cylinder head must also provide a seal between the spark plug and the cylinder head at the outer periphery of the spark plug. For this purpose, a gasket-shaped sealing ring made of metal is usually used. Here, for example, DE 10 2016 110 880 A1 shows a spark plug with a sealing ring in the form of a gasket, which is pushed onto the housing and shrinks in a subsequent reshaping step so that it is held on the spark plug in a detachable manner by a threaded section of the housing. Summary of the invention

[0003] The spark plug according to the invention having the features of claim 1 has the advantage that the seal between the spark plug and the cylinder head is significantly improved by means of the metallic sealing ring. This makes it possible to reliably prevent the gas from reaching the outside through the gap between the cylinder head and the spark plug from the combustion chamber. According to the invention, this is achieved in that the spark plug has a center electrode and a ground electrode, between which an ignition gap is formed. In addition, the spark plug includes an insulator and a metallic housing and a metallic sealing ring arranged on the outside of the housing. The sealing ring is set to seal between the cylinder head and the spark plug. The metallic sealing ring has a first annular area and a second annular area. The first annular area is oriented perpendicularly to the central axis XX of the spark plug, and the second annular area is oriented at an acute angle α to the central axis XX of the spark plug. Here, the first annular area oriented perpendicularly to the central axis is oriented parallel to the shoulder on the housing. The second annular area is arranged at the inner periphery of the first annular area. The first and second annular areas of the metal sealing ring thus achieve that, instead of having only one sealing structure in a plane perpendicular to the central axis of the spark plug as in the gasket, two different sealing areas are provided at the metal sealing ring. The first sealing area at the first annular area of ​​the sealing ring is perpendicular to the central axis of the spark plug and is therefore provided as in the prior art when the gasket is used as a sealing ring. The second annular area is arranged at an acute angle α to the central axis, thereby achieving an additional second sealing area in another plane. Here, the second sealing area at the second annular area is conical. As a whole, the sealing surface between the metal sealing ring and the spark plug or the cylinder head can therefore be increased.

[0004] The dependent claims reveal preferred developments of the invention.

[0005] The housing preferably has a recess in which the sealing ring is completely arranged. The metallic sealing ring can thus be arranged on the housing of the spark plug in a detachably secured manner, which significantly simplifies the assembly of the spark plug. The metallic sealing ring is thus integrated into the housing by means of the recess in the housing.

[0006] Preferably, a thread is formed adjacent to the recess in the housing in the direction of the combustion chamber side of the spark plug, which thread is used to screw the spark plug into the cylinder head.

[0007] Furthermore, the recess formed in the housing is preferably configured as a circumferential groove having a first and a second wall and a bottom with three bottom areas. The first wall is preferably oriented parallel to the central axis of the spark plug. The second wall is preferably oriented at an angle or at right angles to the central axis of the spark plug. The three bottom areas are preferably arranged in such a way that the bottom has a first area perpendicular to the central axis, a second area parallel to the central axis, and a third area, which is arranged at an angle to the central axis and connects the first and second areas to each other.

[0008] According to a particularly preferred embodiment of the present invention, the surface roughness of the metal sealing ring is greater than the surface roughness of the housing and / or the cylinder head. The different surface roughnesses achieve improved sealing during assembly of the spark plug, since the higher surface roughness increases the sealing surface between the housing and the metal sealing ring and between the metal sealing ring and the cylinder head.

[0009] Furthermore, the metallic sealing ring is preferably designed such that a first side length L1 of the first annular region is greater than or equal to a second side length L2 of the second annular region.

[0010] Furthermore, it is preferred that the first and second annular regions of the metallic sealing ring have the same thickness and / or the same mass.

[0011] The angle α between the second annular region and the central axis is preferably in the range of 40° to 50° and particularly preferably 45°.

[0012] The spark plug is preferably a hook spark plug or a pre-combustion chamber spark plug or a spark plug with an ignition gap in the housing. The housing of the spark plug is preferably made of a metal material, wherein the housing preferably has a greater hardness than a metal sealing ring. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the accompanying drawings:

[0014] Figure 1 A schematic partially cutaway view of a spark plug according to a preferred embodiment of the present invention is shown,

[0015] Figure 2 A schematic diagram is shown in a sectional view of a spark plug mounted in a cylinder head, wherein only the cylinder head, the housing and the sealing ring are shown for better clarity, and

[0016] Figure 3 Shows Figure 1 and Figure 2 Schematic cross-sectional view of a metal sealing ring. DETAILED DESCRIPTION

[0017] Next reference Figures 1 to 3 A spark plug 1 according to a preferred embodiment of the present invention will be described in detail.

[0018] As from Figure 1 As is evident, the spark plug 1 is a hook-shaped spark plug having an insulator 2, preferably made of a ceramic material, and a metallic housing 3. The spark plug 1 further comprises a center electrode 4 and a ground electrode 5, which are connected to the housing 3. An ignition gap is formed between the center electrode 4 and the ground electrode 5 in a known manner.

[0019] The spark plug 1 further comprises a metallic sealing ring 6 which is arranged on the outside of the housing 3 . The metallic sealing ring 6 is provided for sealing on the cylinder head 8 .

[0020] Sealing by means of metallic sealing ring 6 is necessary in order to prevent gases from the combustion chamber from escaping into the environment through the gap between spark plug 1 and cylinder head 8 .

[0021] The metal sealing ring 6 is composed in detail of Figure 2 and Figure 3 It is obvious that the sealing ring 6 includes a first annular region 61 and a second annular region 62 and is configured as an integral component. The second annular region 62 is arranged at the inner circumference of the first annular region 61 .

[0022] The first annular region 61 and the second annular region 62 are arranged such that the first annular region 61 is arranged perpendicular to the central axis XX and the second annular region 62 is arranged at an acute angle α of 45° relative to the central axis XX. Figure 3 As is obvious, in this case the first side length L1 of the first annular region 61 is equal to the second side length L2 of the second annular region 62 .

[0023] The metallic sealing ring 6 having the first and second annular regions 61 , 62 can be produced, for example, by a forming process.

[0024] If especially by Figure 1 and Figure 2As is obvious, a recess 30 for receiving a metallic sealing ring 6 is formed in the housing 3. The recess 30 on the housing 3 is arranged at the transition area between a shoulder 34 of the housing 3 and a fixing area 35 of the housing 3, in particular a threaded area, which is used to fix the spark plug on the cylinder head 8.

[0025] Recess 30 comprises a first wall 31 oriented parallel to the central axis XX of the spark plug, a second wall 32 oriented perpendicularly or in particular at an angle of 45° to the central axis XX, and a bottom 33. Bottom 33 connects first wall 31 to second wall 32.

[0026] The bottom 33 comprises a first region 33a perpendicular to the central axis XX, a second region 33b parallel to the central axis XX and a third region 33c at an acute angle to the central axis XX, wherein the third region 33c connects the first region to the second region. Here, the angle corresponds to the angle α between the first and second annular regions 61, 62 at the metal sealing ring.

[0027] Especially from Figure 2 As is evident, the metallic sealing ring 6 is completely received in the recess 30. As a result, the metallic sealing ring 6 is positioned on the housing 3 in a manner that prevents it from separating. This facilitates the assembly of the spark plug in the cylinder head 8.

[0028] So from outside Figure 2 As is obvious, in the installed state of the metallic sealing ring 6, an empty receiving area 7 is obtained in the recess 30. The receiving area 7 is substantially formed at the second area 30b of the recess 30 and serves as a free area to receive the material displaced due to the deformation of the metallic sealing ring 6 when the spark plug is installed in the cylinder head 8.

[0029] As from Figure 2 As is evident, in the assembled state of the spark plug 1 in the cylinder head 8, a first sealing area 11 is obtained between the first annular area 61 and the sealing shoulder 81 on the cylinder head 8, and a second sealing area 12 is obtained between the chamfer 82 on the cylinder head and the second annular area 62. The sealing surface between the sealing ring 6 and the cylinder head 8 can thus be enlarged.

[0030] In addition, the surface roughness of the sealing ring 6 is greater than the surface roughness of the cylinder head 8. This further enhances the sealing performance between the sealing ring and the cylinder head.

[0031] Furthermore, the surface roughness of the sealing ring 6 is preferably also greater than the surface roughness of the housing 3 , whereby the seal between the housing and the sealing ring 6 is likewise improved.

[0032] Furthermore, the design of sealing ring 6 according to the invention allows for an improved heat transfer between spark plug and cylinder head.

[0033] The receiving area 7 in the recess 30 also enables a defined deformation of the sealing ring 6 during assembly, so that a reliable seal between the spark plug and the cylinder head can be achieved. The sealing ring 6 can also be assembled very easily into the recess. Since the sealing ring 6 is seated in the recess 30, it is also not necessary to carry out further steps, such as shrinking, etc., in order to mount the sealing ring 6 on the spark plug in a detachable manner.

Claims

1. A spark plug comprising: - a central electrode (4) and a ground electrode (5), - an insulator (2), - a metal housing (3), and a metallic sealing ring (6) arranged on the outer side of the housing (3), which is provided for sealing at the cylinder head (8), - wherein the sealing ring (6) has a first annular region (61) oriented perpendicularly to the central axis XX of the spark plug and a second annular region (62) oriented at an acute angle α to the central axis XX of the spark plug, wherein the first annular region (61) is parallel to the shoulder (34) on the housing (3) and the second annular region (62) is arranged at the inner periphery of the first annular region (61).

2. The spark plug according to claim 1, wherein: The housing (3) has a recess (30) in which the metallic sealing ring (6) is completely arranged.

3. The spark plug according to claim 2, wherein: The recess (30) in the housing (3) is a circumferential groove having a first wall (31), a second wall (32) and a bottom (33) with three bottom areas.

4. The spark plug according to claim 2 or 3, wherein: The bottom (33) has a first area (33a) perpendicular to the central axis XX, a second area (33b) parallel to the central axis XX, and a third area (33c) forming an acute angle with respect to the central axis XX, wherein the third area (33c) connects the first area with the second area (33a, 33b).

5. The spark plug according to claim 4, wherein: The recess (30) has a receiving area (7) not filled by the sealing ring (6), which is designed as a material receiving area in order to receive deformed material of the sealing ring (6) when the spark plug is mounted on the cylinder head.

6. A spark plug according to any one of the preceding claims, wherein The surface roughness of the sealing ring (6) is greater than the surface roughness of the housing (3) and / or the surface roughness of the cylinder head (8).

7. A spark plug according to any one of the preceding claims, wherein The first side length L1 of the first annular area (61) is greater than or equal to the second side length L2 of the second annular area (62).

8. A spark plug according to any one of the preceding claims, wherein The first annular region (61) and the second annular region (62) have the same thickness, and / or the first annular region (61) and the second annular region (62) have the same mass.

9. A spark plug according to any one of the preceding claims, wherein: The acute angle α between the first annular region and the second annular region (61, 62) is 45°.

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