Spark plug with improved ground electrode
By setting a fixed area, welding area and transition area in the ground electrode base of the spark plug, the problem of non-separation of the ground electrode fixation and precious metal thermocouple tightening functions is solved, and better thermal conduction, current conduction and overall strength are achieved.
Patent Information
- Application Number
- CN202380054693.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-07-18
- Filing Date
- 2023-07-13
- Publication Date
- 2025-03-07
AI Technical Summary
In existing spark plugs, there is a problem of functional non-separation between the fixation of the ground electrode and the fastening of the noble metal thermocouple, resulting in poor heat conduction and current conduction, and undesirable material changes in the welding area may occur.
By providing a fixed area and a welding area in the base of the ground electrode and a first transition area between the two, geometric separation and functional separation are achieved, ensuring that the fixation of the ground electrode and the fastening of the noble metal thermocouple can be independently optimized.
The stable fixation of the ground electrode and the optimized installation of precious metal thermocouples are achieved, the heat conduction, current conduction and overall strength are improved, and the negative impact of the welding area on the fixed area is avoided.
Smart Images
Figure CN119585962A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a spark plug having an improved ground electrode, and in particular to a pre-chamber spark plug having an improved ground electrode. Background Art
[0002] Spark plugs of various designs are known from the prior art. In the case of a laterally mounted ground electrode, which is arranged at an angle of 90° to the center electrode of the spark plug, for example, when a precious metal thermocouple is used at the end side of the ground electrode pointing toward the center electrode, problems arise on the one hand in fastening the precious metal thermocouple and on the other hand in actually fastening the ground electrode. The ground electrode is usually fixed to the housing of the spark plug. The precious metal thermocouple is usually connected to the base material of the ground electrode by means of a welded connection. In particular, due to the welded connection between the precious metal thermocouple and the base material of the ground electrode, undesirable changes in the base material may occur, especially in the following areas, in which the ground electrode should be fastened. However, in addition to possible assembly problems, this leads to further problems, for example due to a deteriorated connection point between the base material and the housing of the spark plug, which further problems relate to the conduction of heat or current. Summary of the invention
[0003] The spark plug according to the invention having the features of claim 1 has the advantage that a functional separation can be achieved between the fixing of the ground electrode to the housing on the one hand and the fastening of the noble metal thermocouple to the ground electrode on the other hand. According to the invention, a geometric separation of the fixing area, where the ground electrode is fixed to the housing, and the welding area, where the noble metal thermocouple is welded to the base body of the ground electrode, is achieved. It is thus possible according to the invention to optimize the respective connection positions of these areas independently of one another based on the separation between the fixing area and the welding area achieved by special geometric measures. That is, the fixing area can obtain an optimal geometry for the fixing of the ground electrode. The welding area can have an optimal geometry for the installation of the noble metal thermocouple. In addition, other functionalities of these areas, such as heat conduction, current conduction, and strength of these areas, can also be optimized, so that the ground electrode can be designed in particular for the entire service life of the spark plug. Another great advantage of the spark plug according to the invention is that the ground electrode can be mounted on the housing without any possible negative influence on the welding area of the ground electrode. In particular, the spark plug according to the invention can be implemented by fixing the ground electrode to the housing before the noble metal thermocouple is installed. Alternatively, the spark plug according to the invention can also be assembled in such a way that first the noble metal thermocouple is fastened to the base of the ground electrode and then the ground electrode provided with the noble metal thermocouple is fixed to the housing.
[0004] According to the present invention, this is achieved in the following manner, namely: the spark plug includes a metal shell, an insulator, a center electrode and a ground electrode having a base and a precious metal thermocouple. The ground electrode is placed laterally relative to the center electrode. The base of the ground electrode includes a fixing area for fixing the ground electrode to the shell and a welding area, at which a precious metal thermocouple, especially a cylindrical precious metal pin, is fastened by means of a welding connection. A first transition area is arranged between the fixing area and the welding area of the ground electrode, and the first transition area has a predetermined extension along the axial direction YY of the ground electrode. Here, the cross-sectional area of the fixing area of the ground electrode is larger than the cross-sectional area of the welding area. In addition, the first transition area ensures the geometric connection and functional separation between the fixing area and the welding area.
[0005] The dependent claims reveal preferred developments of the invention.
[0006] Particularly preferably, the noble metal thermocouple is fastened to a base body of the ground electrode, which is a molded part. This makes it possible to manufacture the base body of the ground electrode particularly cost-effectively and to optimize different regions of the base body with respect to their respective functionality by means of a molding process. For example, the fastening region can be optimized with respect to its fastening properties with respect to geometric dimensions and surface quality by means of a molding process. The welding region can also be optimized with respect to its functionality for welding the noble metal thermocouple geometrically and with respect to its surface properties.
[0007] Particularly preferably, the fastening region of the ground electrode is designed as a cylinder with a first diameter D1 and the welding region is designed as a cylinder with a second diameter D2. In this case, the first transition region is preferably designed as a truncated cone, wherein D1>D2.
[0008] Furthermore, preferably, the first axial length L1 of the fixing area along the axial direction YY is greater than the second axial length L2 of the welding area. This ensures that the fixing area is longer than the welding area and that simple and reliable fixing can therefore be achieved. Alternatively, the first length L1 is greater than the third length L3 of the first transition area and the third length L3 is greater than the second length L2 of the welding area. This achieves a sufficient spacing between the welding area and the fixing area so that the installation of the precious metal thermocouple by means of welding does not have a negative impact on the fixing area. Furthermore, alternatively, the first length L1 of the fixing area is greater than the second length L2 of the welding area, and the second length L2 of the welding area is greater than the third length L3 of the first transition area. Here, the third length L3 is selected in particular so that the negative impact of the welding process for fastening the precious metal thermocouple does not act on the fixing area.
[0009] According to another preferred embodiment of the present invention, the ground electrode further comprises a cylindrical intermediate region, which is arranged between the fixing region and the welding region. By providing an additional cylindrical intermediate region, an even better separation between the functionality of the fixing region and the welding region can be achieved.
[0010] Preferably, the first transition region is arranged between the cylindrical middle region and the fixing region and connects these regions directly to one another. Alternatively, the first transition region is arranged between the cylindrical middle region and the welding region and connects these regions directly to one another.
[0011] According to a further preferred alternative, the first transition region is arranged between the cylindrical middle region and the fastening region, and the second transition region is arranged between the cylindrical region and the welding region.
[0012] According to another alternative of the present invention, the welding area is directly arranged at the middle area. That is to say, there is no transition area between the welding area and the middle area.
[0013] Furthermore, the welding region is preferably designed as a truncated cone. In particular, a possible negative heat input into the fastening region can be prevented during a welding process for fastening the noble metal thermocouple.
[0014] Furthermore, preferably, a through-opening is formed in the housing, in which the ground electrode is fixed by means of the fixing region. Preferably, a first length L1 of the fixing region is greater than an axial length L0 of the through-opening.
[0015] Furthermore, the ground electrode preferably has a copper core. The copper core is preferably cylindrical and extends through the entire base body of the ground electrode as far as the noble metal thermocouple.
[0016] Furthermore, the housing preferably comprises a threaded section which is provided for a threaded connection with the cylinder head. Here, the through-opening is preferably configured in the threaded section, or the through-opening is alternatively arranged outside the threaded section.
[0017] Furthermore, one or more transitions between the regions on the ground electrode are preferably designed to be rounded, thereby making it possible to achieve edgeless transitions between the individual regions of the ground electrode, so that in particular the installation of the ground electrode in the housing can be significantly simplified.
[0018] Furthermore, it is preferred that the first and / or the second transition region is designed as a truncated cone.
[0019] A nickel alloy is preferably used as the material of the ground electrode.
[0020] Furthermore, the spark plug is preferably designed 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 delimited by a cap, in which the flow bore is formed. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the accompanying drawings:
[0022] Figure 1 shows a schematic cross-sectional view of a spark plug according to a first embodiment of the present invention,
[0023] Figure 2 Shows Figure 1 A schematic enlarged partial cross-sectional view of a ground electrode of a spark plug,
[0024] Figure 3 A schematic partial cross-sectional view showing a ground electrode of a spark plug according to a second embodiment of the present invention,
[0025] Figure 4 Shows Figure 3 Schematic diagram of the ground electrode,
[0026] Figure 5 A schematic cross-sectional view showing a ground electrode of a spark plug according to a third embodiment of the present invention,
[0027] Figure 6 Shows Figure 5 A schematic diagram of the ground electrode, and
[0028] Figure 7 A schematic enlarged partial sectional view shows a ground electrode of a spark plug according to a fourth embodiment of the present invention. DETAILED DESCRIPTION
[0029] Next reference Figure 1 and Figure 2 A spark plug 1 according to a preferred first embodiment of the present invention will be described in detail.
[0030] As Figure 1 As is apparent, the spark plug 1 of the first embodiment is a pre-chamber spark plug.
[0031] The spark plug 1 includes a metal housing 2 and an insulator 3. In addition, the spark plug includes a center electrode 4 and a ground electrode 5.
[0032] The ground electrode 5 is arranged laterally with respect to the center electrode 4 .
[0033] The spark plug further comprises a cap 9 which, together with parts of the housing 2, defines a pre-combustion chamber 90. In this case, the ground electrode 5 and the center electrode 4 are arranged in the pre-combustion chamber 90.
[0034] The housing 2 further comprises an external thread 21 which is provided for being screwed into a cylinder head of an internal combustion engine.
[0035] As Figure 1 As is evident, a through-opening 20 is formed in the housing 2 in the region of the thread 21 , in which the ground electrode 5 is arranged.
[0036] A plurality of flow bores 91 are formed in the cover 9. XX denotes the center axis of the spark plug.
[0037] The ground electrode 5 is composed in detail of Figure 2 It is obvious. Here, the ground electrode 5 comprises a base body 5' having a columnar fixing area 50 and a columnar welding area 51 and a noble metal thermocouple 6. The fixing area 50 is provided for fixing the ground electrode to the housing 2. More precisely, as shown by Figure 2 As is evident, the fastening region 50 is arranged in the through-opening 20 in the housing 2. In this case, a press-fit connection 8 is formed between the through-opening 20 and the fastening region 50.
[0038] A first transition region 52 is formed between the fixing region 50 and the welding region 51. Figure 2 As is evident, the first transition region 52 is designed as a truncated cone. The fixing region 50 is a first cylinder and the welding region 51 is a second cylinder. The fixing region 50 has a first diameter D1 which is greater than a second diameter D2 of the welding region 51 .
[0039] Transition region 52 has a predetermined extension along axial direction YY of ground electrode 5 .
[0040] The first transition region 52 thus directly connects the fastening region 50 to the welding region 51, wherein the truncated cone-shaped first transition region 52 reduces its diameter from the first diameter D1 to the second diameter D2. This ensures that there is a stepless transition from the fastening region 50 to the first transition region 52, and that the transition from the first transition region 52 to the welding region 51 is also designed to be stepless. In this case, the transitions between the partial regions of the ground electrode 5 can also be rounded.
[0041] The noble metal thermocouple 6 is fixed to the welding region 51. In this case, a weld connection 7 is formed between the noble metal thermocouple 6, which is designed as a cylindrical noble metal pin, and the welding region 51. The noble metal thermocouple 6 is thus welded to the welding region 51.
[0042] As Figure 2As becomes apparent, the cross-sectional area of the fixing region 50 is greater than the cross-sectional area of the welding region 51. The first transition region 52 thus provides a geometric connection between the fixing region 50 and the welding region 51, wherein the first transition region 52 also provides a functional separation between the fixing region 50 and the welding region 51.
[0043] Furthermore, a cylindrical copper core 10 is arranged in the base body 5' of the ground electrode 5. The copper core 10 extends from the end face of the welding region 51 to a free end at the fastening region 50. The copper core 10 is in direct contact with the noble metal thermocouple 6 after welding the noble metal thermocouple 6.
[0044] Here, the function of the fixing 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 thermocouple 6 to the ground electrode 5 .
[0045] The ground electrode 5 thus comprises a noble metal thermocouple 6 and a base body 5 ′, which comprises a fastening region 50, a welding region 51 and a first transition region 52. The base body 5 ′ is produced in one piece as a molded part, so that no welded connections are required between the individual subregions of the base body. The base body can thus be provided by a molding process during the production of the ground electrode. In particular, the outer dimensions and the length of the fastening region 50 can be set very accurately.
[0046] As a result, a reliable press-fit connection between the fastening region 50 and the through-opening 20 can be easily provided. In the same way, the welding region 51 can also be optimally designed for a welding connection to the noble metal thermocouple 6 by means of a forming process.
[0047] This allows a geometric separation of the functional connection points at the ground electrode, so that the corresponding sub-regions of the ground electrode can be optimized independently of one another. This significantly reduces the effects, for example, when the ground electrode is fixed to the housing 2 at the fixing region or when the noble metal thermocouple 6 is welded to the welding region 51.
[0048] This not only achieves advantages in terms of fixing the ground electrode or fastening the noble metal thermocouple 6, but also in terms of heat conduction and / or current conduction and / or strength of the base body of the ground electrode. For example, the fixing region 50 is not affected during a welding process for fastening the noble metal thermocouple 6. It is possible to fasten the noble metal thermocouple 6 to the base body 5' of the ground electrode before the ground electrode is installed in the housing, or to first fasten the base body 5' to the housing and then weld the noble metal thermocouple 6.
[0049] The accuracy of the cylindrical shape of fastening region 50 can thus be increased and, due to the production by means of a forming process, an improved coaxiality between subregions of the ground electrode and an improvement in the heat conduction between fastening region and housing 2 can also be achieved. Inadmissible temperature increases of the ground electrode during operation are thereby reliably prevented.
[0050] During the welding process of the noble metal thermocouple 6 to the welding region 51, due to the separation of said region according to the invention, a possible change in the diameter of the welding region 51, in particular an increase in the diameter, can be tolerated, since this has no effect on the fixing region 50. This makes it possible to use a fast and cost-effective welding method for fixing the noble metal thermocouple at the welding region, since the risk of a geometric change of the fixing region caused by welding is eliminated.
[0051] Furthermore, when producing base body 5 ′ of ground electrode 5 , the advantage is that fastening region 50 can be produced with the highest precision in a first step, in particular by forming, and only subsequently welding region 51 can be produced. This allows the ground electrode to be produced with increased shape tolerances of the individual regions and increases the precision of the component.
[0052] The transition region 52 of the first exemplary embodiment is designed to be conical. However, it should be noted that other geometries are also possible. However, it is preferred that the ground electrode is produced rotationally symmetrically, which significantly reduces the production costs.
[0053] So outside Figure 2 As is apparent, the first axial length L1 of the fixing region 50 along the axial direction YY of the ground electrode 5 is greater than the second axial length L2 of the welding region 51 . In addition, the first length L1 is also greater than the third axial length L3 of the first transition region 52 .
[0054] The axial length L0 of the through-opening 20 corresponds to the thickness of the housing in the region of the pre-chamber and is also smaller than the first length L1 of the fastening region 50. It is thus possible, for example, in a simple manner to realize, in addition to the press-fit connection 8 between the fastening region 50 and the through-opening 20, a welded connection 80, 81 between the fastening region 50 and the housing 2. The welded connection can be realized at the free end of the fastening region 50, which is located on the outside of the housing 2 and / or at the fastening region 50 on the inside of the housing.
[0055] The base body of ground electrode 5 can thus be produced from one workpiece, wherein preferably first fastening region 50 and only then first transition region 52 and welding region 51 are produced, preferably by means of a forming process.
[0056] Figure 3 and Figure 4A ground electrode 5 of a spark plug according to a second exemplary embodiment of the present invention is shown. Identical or functionally identical parts are denoted by the same reference numerals as in the first exemplary embodiment.
[0057] If Figure 3 As is obvious, the structure of the ground electrode 5 of the second embodiment is different.
[0058] The ground electrode 5 of the second embodiment includes, in addition to the fixing region 50, the welding region 51 and the first transition region 52, a columnar middle region 53 and a second transition region 54. The columnar middle region 53 is arranged between the fixing region 50 and the welding region 51. Here, the first transition region 52 directly connects the fixing region 50 with the columnar middle region 53. The second transition region 54 directly connects the columnar middle region 53 with the welding region 51. The noble metal thermocouple 6 is fixed at its end side at the welding region 51 by means of a welding connection 7. The noble metal thermocouple 6 has a fourth diameter D4, which is smaller than the second diameter D2 of the welding region 51.
[0059] Figure 4 The base body 5' is shown in detail. Here, the first axial length L1 of the fixing 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 middle region 53. The same is preferably true for the taper of the first transition region 52, which is at a smaller angle than the taper of the second transition region 54, which has a fifth length L5.
[0060] Main body 5 ′ of ground electrode 5 of the second exemplary embodiment is preferably likewise a one-piece component which is produced from a prefabricated product by means of a plurality of forming processes.
[0061] The first diameter D1 of the fixing region 50 is also greater than the second diameter D2 of the welding region 51 and also greater than the third diameter D3 of the cylindrical middle region 53. The third diameter D3 is also greater than the second diameter D2.
[0062] Figure 5 and Figure 6 A ground electrode of a spark plug according to a third embodiment of the present invention is shown. The same or functionally the same parts are denoted by the same reference numerals as in the above-mentioned embodiments.
[0063] The third embodiment corresponds substantially to the second embodiment, wherein, unlike the second embodiment, no second transition region is provided in the third embodiment. Figure 5 and Figure 6As is obvious, the welding region 51 is arranged directly at the cylindrical middle region 53. Therefore, the second transition region can be omitted. Here, the welding region 51 is designed as a truncated cone. The base body 5 ′ is again a one-piece component, which is manufactured from a prefabricated product in multiple forming steps. After the base body is manufactured, the precious metal thermocouple 6 can be welded to the end side of the welding region 51.
[0064] Otherwise this exemplary embodiment corresponds to the above exemplary embodiment, so that reference is made to the description provided there.
[0065] Figure 7 A ground electrode of a spark plug according to a fourth embodiment of the present invention is shown. The same or functionally the same parts are denoted by the same reference numerals as in the above-mentioned embodiments.
[0066] If Figure 7 As is evident, the fourth embodiment corresponds essentially to the second embodiment, wherein, unlike the second embodiment, in the fourth embodiment the welding region 51 is designed as a truncated cone. Here, the truncated cone-shaped welding region 51 directly adjoins the first transition region 52. Here, the truncated cone apex angles of the welding region 51 and the transition region 52 are identical. However, it should be noted that this angle can also be selected differently.
Claims
1. A spark plug comprising: - a metal housing (2), - an insulator (3), - a central electrode (4), and a ground electrode (5) which is arranged laterally relative to the central electrode (4) and has a base body (5') and a noble metal thermocouple (6), wherein the base body (5′) has a fastening region (50) for fastening the ground electrode to the housing (2) and a welding region (51), wherein the noble metal thermocouple (6) is arranged at the welding region (51) by means of a welded connection (7), wherein a first transition region (52) is arranged between the fixing region (50) and the welding region (51), - wherein the cross-sectional area of the fixing region (50) is greater than the cross-sectional area of the welding region (51), and - wherein the first transition region (52) has a predetermined extension along the axial direction YY of the ground electrode (5) and provides a geometric connection and a functional separation between the fixing region (50) and the welding region (51).
2. The spark plug according to claim 1, wherein: The base body (5') of the ground electrode (5) is a one-piece molded part.
3. A spark plug according to any one of the preceding claims, 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 truncated cone.
4. Spark plug according to any one of the preceding claims, -in, A first length L1 of the fixing region (50) along the axial direction YY is greater than a second length L2 of the welding region (51), or wherein a first length L1 of the fixing region (50) along the axial direction YY is greater than a third length L3 of the first transition region (52) and the third length L3 is greater than a second length L2 of the welding region, or - wherein a first length L1 of the fixing region (50) along the axial direction YY is greater than a second length L2 of the welding region (51) and the second length L2 is greater than a third length L3 of the first transition region (52).
5. The spark plug according to claim 1, further comprising a cylindrical middle region (53) which is arranged between the fastening region (50) and the welding region (51).
6. The spark plug according to claim 5, - wherein the first transition region (52) connects the cylindrical intermediate region (53) to the fixing region (50), or -in, The first transition region (52) connects the columnar middle region (53) to the welding region (51).
7. The spark plug according to claim 5, - wherein the first transition region (52) connects the cylindrical middle region (53) to the fixing region (50), and -in, A second transition region (54) connects the cylindrical middle region (53) to the welding region (51).
8. The spark plug according to claim 5, wherein: The welding region (51) is arranged directly at the cylindrical middle region (53).
9. The spark plug according to any one of claims 1, 2 or 4 to 8, wherein: The welding region (51) is configured as a truncated cone.
10. Spark plug according to any one of the preceding claims, wherein a through opening (20) is formed in the housing (2), the ground electrode (5) being fixed in the through opening by means of a press-fit connection (8), and / or -in, The ground electrode (5) is connected to the housing (2) by means of one or more welded connections.
11. The spark plug according to claim 10, wherein: The first length L1 of the fixing area (50) is greater than the axial length L0 of the through opening (20).
12. A spark plug according to any one of the preceding claims, wherein The ground electrode (5) has a copper core (10).
13. A spark plug according to any one of the preceding claims, wherein The housing (2) has a threaded section (21), and the ground electrode (5) is fastened in the region of the threaded section (21).
14. A spark plug according to any one of the preceding claims, wherein The spark plug is designed as a pre-combustion chamber spark plug having a pre-combustion chamber (90).