Spark Plug with Improved Ground Electrode

Abstract

【Means for Solving the Problem】 The present invention relates to a spark plug, and includes a metal housing (2), an insulator (3), a center electrode (4), and a ground electrode (5) that is installed laterally with respect to the center electrode (4) and has a main body (5') and a noble metal member (6). The main body (5') has a fixing region (50) for fixing the ground electrode to the housing (2) and a welding region (51). The noble metal member (6) is disposed in the welding region (51) by a welding bond (7). A first transition region (52) is disposed between the fixing region (50) and the welding region (51). The cross-sectional area of the fixing region (50) is larger than the cross-sectional area of the welding region (51). The first transition region (52) has a predetermined extension in the axial direction Y-Y of the ground electrode (5), providing a geometric connection and a functional separation between the fixing region (50) and the welding region (51).

Description

Technical Field

[0001] The present invention relates to a spark plug having an improved ground electrode. In particular, the present invention relates to a pre-chamber spark plug having an improved ground electrode.

Background Art

[0002] Spark plugs are known in a variety of different configurations from the prior art. For example, in the case of a side-mounted ground electrode disposed at an angle of 90° with respect to the center electrode of the spark plug, when a noble metal member is used on the end face of the ground electrode facing the center electrode, on the one hand, problems occur during the attachment of the noble metal member and, on the other hand, during the original attachment of the ground electrode. The ground electrode is usually fixed to the housing of the spark plug. The noble metal member is usually joined to the base material of the ground electrode by a welding bond. In particular, due to the welding bond between the noble metal member and the base material of the ground electrode, undesirable changes in the base material may occur, especially in the region where the ground electrode is to be attached. However, as a result, in addition to assembly problems that may occur due to a deteriorated joint between the base material and the housing of the spark plug, other problems related to heat conduction and current conduction also occur.

Summary of the Invention

[0003] The spark plug of the present invention having the constituent elements of claim 1 has the advantage that a functional separation is possible between, on the one hand, the fixing of the ground electrode to the housing and, on the other hand, the attachment of the noble metal member to the ground electrode. At this time, according to the present invention, a geometric separation is made between the fixing region where the ground electrode is fixed to the housing and the welding region where the noble metal member is welded to the main body of the ground electrode. Thereby, in the present invention, based on the separation between the fixing region and the welding region by a special geometric measure, it is possible to optimize the respective joints of these regions independently of each other. That is, for the fixing of the ground electrode, the fixing region can obtain the best geometric form. For the attachment of the noble metal member, the welding region can have the best geometric form. Furthermore, since other functionalities of these regions, that is, heat conduction, current conduction, the strength of each region, etc. can also be optimized, the ground electrode can be designed especially for the entire service life of the spark plug. Another great advantage of the spark plug according to the present invention is that the ground electrode can be assembled to the housing without the occurrence of any adverse effects that may be considered in the welding region of the ground electrode. In particular, the spark plug according to the present invention enables the ground electrode to be fixed to the housing before the attachment of the noble metal member. As an alternative, the spark plug according to the present invention also enables an assembly in which first the noble metal member is attached to the main body of the ground electrode and then the ground electrode provided with the noble metal member is fixed to the housing.

[0004] According to the present invention, this is achieved by the spark plug including a metal housing, an insulator, a center electrode, and a ground electrode having a main body and a noble metal member. The ground electrode is installed laterally with respect to the center electrode. The main body of the ground electrode includes a fixing region for fixing the ground electrode to the housing and a welding region where the noble metal member, particularly a cylindrical noble metal pin, is attached by a welding bond. Between the fixing region and the welding region of the ground electrode, a first transition region having a predetermined extension in the axial direction Y-Y of the ground electrode is arranged. At this time, the cross-sectional area of the fixing region of the ground electrode is larger than the cross-sectional area of the welding region. Further, the first transition region ensures a geometric connection and a functional separation between the fixing region and the welding region.

[0005] The dependent claims show preferred developments of the present invention.

[0006] It is particularly preferred that the main body of the ground electrode to which the noble metal member is attached is a molded part. Thereby, the main body of the ground electrode can be manufactured at a particularly low cost, and various regions of the main body can be optimally optimized by the molding process from the viewpoint of their respective functionality. For example, the mounting region can be optimized by the molding process from the viewpoint of mounting characteristics related to geometric dimensions and surface quality. The welding region can also be optimized geometrically and with respect to surface quality from the viewpoint of the functionality for welding the noble metal member.

[0007] It is particularly preferred that the fixing region of the ground electrode is configured as a cylinder having a first diameter D1 and the welding region is configured as a cylinder having a second diameter D2. At this time, the first transition region is preferably intended to be a frustum of a cone, and D1 > D2.

[0008] Furthermore, it is preferable that the first axial length L1 of the fixed region in the axial direction Y - Y is greater than the second axial length L2 of the welding region. Thereby, the fixed region becomes longer than the welding region, and it is ensured that simple and reliable fixing becomes possible in this way. As an alternative thereto, the first length L1 is greater than the third length L3 of the first transition region, and the third length L3 is greater than the second length L2 of the welding region. Thereby, a sufficient interval between the welding region and the fixed region is realized, whereby the attachment of the noble metal member by welding does not affect the fixed region unfavorably. As a further alternative, the first length L1 of the fixed region is greater than the second length L2 of the welding region, and the second length L2 of the welding region is greater than the third length L3 of the first transition region. At this time, the third length L3 is selected so that the adverse influence of the welding process for attaching the noble metal member does not affect the fixed region in particular.

[0009] In another preferred embodiment of the present invention, the ground electrode further includes a cylindrical intermediate region disposed between the fixed region and the welding region. By providing an additional cylindrical intermediate region, it is possible to achieve a further improved separation between the functionality of the fixed region and the welding region.

[0010] The first transition region is preferably disposed between the cylindrical intermediate region and the fixed region and directly connects these regions to each other. As an alternative thereto, the first transition region is disposed between the cylindrical intermediate region and the welding region and directly connects these regions to each other.

[0011] In another preferred alternative, the first transition region is disposed between the cylindrical intermediate region and the fixed region, and the second transition region is disposed between the cylindrical region and the welding region.

[0012] In yet another alternative of the present invention, the welding region is disposed directly in the intermediate region. That is, no transition region is provided between the welding region and the intermediate region.

[0013] Furthermore, the welding area is preferably configured as a frustum of a cone. Thereby, in particular, during the welding process for attaching the noble metal member, it is possible to prevent an unfavorable heat injection into the fixing area.

[0014] Furthermore, it is preferable that a through hole through which the ground electrode is fixed therein by the fixing area is formed in the housing. At this time, the first length L1 of the fixing area is preferably larger than the axial length L0 of the through hole.

[0015] Furthermore, the ground electrode preferably has a copper core material. The copper core material is preferably cylindrical and extends through the entire body of the ground electrode to the noble metal member.

[0016] Furthermore, the housing preferably includes a thread area set up for screwing together with the cylinder head. At this time, the through hole is preferably formed in the thread area, or alternatively, the through hole is arranged outside the thread area.

[0017] Furthermore, it is preferable that one or more transition parts between the respective areas of the ground electrode are chamfered. Thereby, a non-abrupt transition between the individual areas of the ground electrode becomes possible, and thereby, in particular, the assembly of the ground electrode to the housing can be significantly simplified.

[0018] Furthermore, the first and / or the second transition area is preferably configured as a frustum of a cone.

[0019] It is preferable to use a nickel alloy as the material of the ground electrode.

[0020] Furthermore, the spark plug is configured as a pre-chamber spark plug having a pre-chamber in which the ground electrode is arranged. The pre-chamber is preferably at least partially defined by a cap in which an overflow hole is formed.

[0021] Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following are shown in the drawings.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0023] Hereinafter, with reference to FIGS. 1 and 2, the spark plug 1 based on the first preferred embodiment of the present invention will be described in detail.

[0024] As is apparent from FIG. 1, the spark plug 1 of the first embodiment is a pre-chamber spark plug.

[0025] The spark plug 1 includes a metal housing 2 and an insulator 3. Further, the spark plug includes a center electrode 4 and a ground electrode 5.

[0026] The ground electrode 5 is installed laterally with respect to the center electrode 4.

[0027] Furthermore, the spark plug includes a cap 9 that defines a prechamber 90 together with each part of the housing 2. The ground electrode 5 and the center electrode 4 are arranged here in the prechamber 90.

[0028] Furthermore, the housing 2 includes an external thread 21 that is set up to be screwed into the cylinder head of an internal combustion engine.

[0029] As is apparent from FIG. 1, a through hole 20 is formed in the housing 2 in the region of the thread 21, and the ground electrode 5 is arranged therein.

[0030] A plurality of overflow holes 91 are formed in the cap 9. X-X represents the central axis of the spark plug.

[0031] The ground electrode 5 will be described in detail with reference to FIG. 2. Here, the ground electrode 5 includes a main body 5' having a cylindrical fixing region 50 and a cylindrical welding region 51, and a noble metal member 6. The fixing region 50 is set up to fix the ground electrode to the housing 2. More specifically, as is apparent from FIG. 2, the fixing region 50 is arranged in the through hole 20 of the housing 2. Here, a press fit 8 is formed between the through hole 20 and the fixing region 50.

[0032] A first transition region 52 is formed between the fixing region 50 and the welding region 51. As is apparent from FIG. 2, the first transition region 52 is configured as a frustum of a cone. The fixing region 50 is a first cylinder, and the welding region 51 is a second cylinder. Here, the fixing region 50 has a first diameter D1 that is larger than the second diameter D2 of the welding region 51.

[0033] The transition region 52 has a predetermined extension in the axial direction Y-Y of the ground electrode 5.

[0034] In this way, the first transition region 52 directly connects the fixed region 50 to the welding region 51, and the frustum-shaped first transition region 52 decreases its diameter from the first diameter D1 to the second diameter D2. In this manner, a seamless transition occurs from the fixed region 50 to the first transition region 52, and it is ensured that the transition from the first transition region 52 to the welding region 51 is also configured without a step. At this time, the transition portions between the respective partial regions of the ground electrode 5 may be chamfered.

[0035] A noble metal member 6 is fixed to the welding region 51. Here, a welding joint 7 is formed between the noble metal member 6 configured as a cylindrical noble metal pin and the welding region 51. In this way, the noble metal member 6 is welded to the welding region 51.

[0036] As is apparent from FIG. 2, the cross-sectional area of the fixed region 50 is larger than the cross-sectional area of the welding region 51. That is, the first transition region 52 provides a geometric connection between the fixed region 50 and the welding region 51, and the first transition region 52 also provides a functional separation between the fixed region 50 and the welding region 51.

[0037] Furthermore, a cylindrical copper core 10 is disposed in the main body 5' of the ground electrode 5. The copper core 10 extends from the end face of the welding region 51 to the free end of the fixed region 50. The copper core 10 is in direct contact with the noble metal member 6 after the noble metal member 6 is welded.

[0038] Here, the function of the fixed region 50 is to securely fix the ground electrode 5 to the housing 2. The function of the welding region 51 is to securely fix the noble metal member 6 to the ground electrode 5.

[0039] Thus, the ground electrode 5 includes a noble metal member 6 and a main body 5'. The main body includes a fixed region 50, a welding region 51, and a first transition region 52. Here, the main body 5' is integrally manufactured as a molded part, so that there is no need for a welded connection between the individual partial regions of the main body. Therefore, when manufacturing the ground electrode, the main body can be provided by a molding process. At this time, in particular, the outer dimensions and length of the fixed region 50 can be adjusted very precisely.

[0040] Thereby, a reliable press fit between the fixed region 50 and the through-hole 20 can be provided in a simple manner. In a similar manner, the welding region 51 can also be optimally designed for welding to the noble metal member 6 by a molding process.

[0041] In this way, a geometric separation of each functional joint of the ground electrode can be realized, whereby each partial region of the ground electrode can be optimized independently of each other. Thereby, for example, when the ground electrode is fixed to the housing 2 in the fixed region, or when the noble metal member 6 is welded to the welding region 51, only a significantly reduced influence occurs.

[0042] Thereby, not only advantages are obtained from the perspective of fixing the ground electrode or attaching the noble metal member 6, but also advantages regarding heat conduction and / or current conduction and / or the strength of the main body of the ground electrode are realized. For example, during the welding process for attaching the noble metal member 6, the fixed region 50 is not affected. In that case, it is possible to attach the noble metal member 6 to the main body 5' of the ground electrode before assembling the ground electrode to the housing, or it is possible to first attach the main body 5' to the housing and then weld the noble metal member 6.

[0043] In this way, the accuracy of the cylindrical shape of the fixed region 50 can be enhanced, and based on fabrication by the molding process, improved coaxiality between the respective partial regions of the grounding electrode can also be achieved, and improvements can also be realized from the perspective of heat conduction between the fixed region and the housing 2. Thereby, an unacceptable temperature rise of the grounding electrode during operation is reliably prevented.

[0044] During the welding process of the noble metal member 6 to the welding region 51, based on the separation according to the present invention for each region, a possible change in the diameter of the welding region 51, particularly an increase in diameter, becomes acceptable. This is because it does not affect the fixed region 50. Thereby, it becomes possible to apply a quick and low-cost welding method for fixing the noble metal member to the welding region. This is because the risk of geometric changes in the fixed region due to welding is eliminated.

[0045] Furthermore, when fabricating the main body 5' of the grounding electrode 5, in the first step, the fixed region 50 can be fabricated with the highest degree of accuracy, particularly by molding, and then the welding region 51 is fabricated only afterwards. Thereby, it is possible to fabricate the grounding electrode with an even higher shape tolerance for individual regions, and the accuracy of the component is increased.

[0046] The transition region 52 of the first embodiment is configured in a tapered shape. However, it should be noted that other geometric shapes are also possible. However, it is preferable that the grounding electrode be fabricated in rotational symmetry, which significantly reduces the manufacturing cost.

[0047] Furthermore, as is apparent from FIG. 2, the first axial length L1 of the fixed region 50 in the axial direction Y - Y of the grounding electrode 5 is greater than the second axial length L2 of the welding region 51. Furthermore, the first length L1 is greater than the third axial length L3 of the first transition region 52.

[0048] The axial length L0 of the through-hole 20, which corresponds to the thickness of the housing in the region of the pre-chamber, is also smaller than the first length L1 of the fixed region 50. Thereby, for example, in addition to the press fit 8 between the fixed region 50 and the through-hole 20, it is possible in a simple manner to further embody the welding connections 80, 81 between the fixed region 50 and the housing 2. At this time, the welding connection can be performed at the free end of the fixed region 50 located on the outer surface of the housing 2 and / or at the inner surface of the housing in contact with the fixed region 50.

[0049] In this way, the body of the ground electrode 5 can be manufactured from a single workpiece, preferably first the fixed region 50, and only then the first transition region 52 and the welding region 51, preferably by a forming process.

[0050] Figures 3 and 4 show the ground electrode 5 of a spark plug according to a second embodiment of the invention. The same reference numerals as in the first embodiment are given to the same or functionally identical parts.

[0051] As is apparent from FIG. 3, the structure of the ground electrode 5 of the second embodiment is different.

[0052] The ground electrode 5 of the second embodiment further additionally includes a cylindrical intermediate region 53 and a second transition region 54 in addition to the fixed region 50, the welding region 51, and the first transition region 52. The cylindrical intermediate region 53 is arranged between the fixed region 50 and the welding region 51. Here, the first transition region 52 directly connects the fixed region 50 to the cylindrical intermediate region 53. The second transition region 54 directly connects the cylindrical intermediate region 53 to the welding region 51. A noble metal member 6 is fixed to the end face of the welding region 51 by a welding connection 7. The noble metal member 6 has a fourth diameter D4 that is smaller than the second diameter D2 of the welding region 51.

[0053] Figure 4 shows the main body 5' in detail. Here, the first axial length L1 of the fixed region 50 is greater than the second axial length L2 of the welding region 51, and the first length L1 is also greater than the fourth axial length L4 of the cylindrical intermediate region 53. It is also preferable that the taper of the first transition region 52 is the same under an angle smaller than the angle of the second transition region 54 having the fifth length L5.

[0054] The main body 5' of the grounding electrode 5 of the second embodiment is preferably an integral component that is also manufactured from a primary product by a plurality of forming processes.

[0055] Furthermore, the first diameter D1 of the fixed region 50 is larger than the second diameter D2 of the welding region 51, and is also larger than the third diameter D3 of the cylindrical intermediate region 53. Furthermore, the third diameter D3 is larger than the second diameter D2.

[0056] Figures 5 and 6 show the grounding electrode of the spark plug according to the third embodiment of the present invention. The same or functionally identical parts are denoted by the same reference numerals as in the preceding embodiments.

[0057] The third embodiment substantially corresponds to the second embodiment, but different from the second embodiment, the third embodiment is not provided with the second transition region. As is apparent from FIGS. 5 and 6, the welding region 51 is directly arranged on the cylindrical intermediate region 53. Thus, the second transition region can be omitted. Here, the welding region 51 is configured as a frustum of a cone. Furthermore, the main body 5' is an integral component manufactured from a primary product in a plurality of forming steps. And after the production of the main body, the noble metal member 6 can be welded to the end face of the welding region 51.

[0058] In other respects, this embodiment corresponds to the preceding embodiments, so reference can be made to the explanations made there.

[0059] FIG. 7 shows a ground electrode of a spark plug according to a fourth embodiment of the present invention. The same reference numerals are given to the same or functionally equivalent parts as those in the previous embodiments.

[0060] As is apparent from FIG. 7, the fourth embodiment substantially corresponds to the second embodiment. However, unlike the second embodiment, in the fourth embodiment, the welding region 51 is configured as a frustum of a cone. Here, the frustum-shaped welding region 51 directly follows the first transition region 52. Here, the cone angles of the frustum-shaped welding region 51 and the transition region 52 are equal. However, it should be noted that the angles can be selected differently.

Description of Reference Numerals

[0061] 2 Housing 3 Insulator 4 Center electrode 5 Ground electrode 5’ Body 6 Noble metal member 7 Weld joint 8 Press fit 10 Copper core material 20 Through hole 21 Threaded area 50 Fixed area 51 Welding region 52 First transition region 53 Cylindrical intermediate region 54 Second transition region 90 Prechamber

Claims

1. In a spark plug, a metal housing (2), an insulator (3), a center electrode (4), and a ground electrode (5) disposed laterally with respect to the center electrode (4) and having a body (5') and a noble metal member (6), the body (5') has a fixing region (50) for fixing the ground electrode to the housing (2) and a welding region (51), and the noble metal member (6) is disposed in the welding region (51) by a welding bond (7), a first transition region (52) is disposed between the fixing region (50) and the welding region (51), the cross-sectional area of the fixing region (50) is larger than the cross-sectional area of the welding region (51), the first transition region (52) has a predetermined extension in the axial direction Y - Y of the ground electrode (5), and provides a geometric connection and a functional separation between the fixing region (50) and the welding region (51), a spark plug.

2. The spark plug according to claim 1, wherein the body (5') of the ground electrode (5) is an integral molded part.

3. The spark plug according to claim 1 or 2, wherein the fixing region (50) is a cylinder having a first diameter D1, the welding region (51) is a cylinder having a second diameter D2, and the first transition region (52) is a frustum of a cone.

4. The first length L1 of the fixing region (50) in the axial direction Y - Y is greater than the second length L2 of the welding region (51), or the first length L1 of the fixing region (50) in the axial direction Y - Y is greater than the third length L3 of the first transition region (52), and the third length L3 is greater than the second length L2 of the welding region, or the first length L1 of the fixing region (50) in the axial direction Y - Y is greater than the second length L2 of the welding region (51), and the second length L2 is greater than the third length L3 of the first transition region (52), the spark plug according to any one of claims 1 to 3.

5. The spark plug according to any one of claims 1 to 4, further comprising a cylindrical intermediate region (53) disposed between the fixing region (50) and the welding region (51).

6. The first transition region (52) connects the cylindrical intermediate region (53) to the fixing region (50), or the first transition region (52) connects the cylindrical intermediate region (53) to the welding region (51), the spark plug according to claim 5.

7. The first transition region (52) connects the cylindrical intermediate region (53) to the fixed region (50), and the second transition region (54) connects the cylindrical intermediate region (53) to the welding region (51), the spark plug according to claim 5.

8. The welding region (51) is disposed directly on the cylindrical intermediate region (53), the spark plug according to claim 5.

9. The welding region (51) is configured as a frustum of a cone, the spark plug according to any one of claims 1, 2 or 4 to 8.

10. A through hole (20) in which the ground electrode (5) is fixed therein by press fitting (8) is formed in the housing (2), and / or the ground electrode (5) is coupled to the housing (2) by one or more welded joints, the spark plug according to any one of claims 1 to 9.

11. The first length L1 of the fixed region (50) is greater than the axial length L0 of the through hole (20), the spark plug according to claim 10.

12. The ground electrode (5) has a copper core (10), the spark plug according to any one of claims 1 to 11.

13. The housing (2) has a threaded region (21), and the ground electrode (5) is attached to the region of the threaded region (21), the spark plug according to any one of claims 1 to 12.

14. The spark plug is configured as a prechamber spark plug having a prechamber (90), the spark plug according to any one of claims 1 to 13.

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