Spark plug

Abstract

The application provides a spark plug, which comprises a center electrode and a ground electrode, the ground electrode is arranged opposite to the center electrode, and a spark gap is formed between one end of the center electrode and a corresponding end of the ground electrode, wherein at least one of the one end of the center electrode and the corresponding end of the ground electrode is configured with a noble metal tip, the noble metal tip is in a single-piece integrated structure and is fixedly connected with the corresponding center electrode or ground electrode through welding, the noble metal tip has one end side facing away from the spark gap and the other end side facing the spark gap, and the one end side has a reduced cross-sectional area relative to the other end side. Compared with conventional spark plugs, the spark plug has the advantages of simple structure, low manufacturing cost, long service life and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a spark plug, and more particularly to a spark plug having an improved electrode structure. BACKGROUND

[0002] As an important component of an ignition system, a spark plug has a wide range of applications in, for example, spark-ignition internal combustion engines (e.g., gasoline engines) for motor vehicles. Generally, the main function of a spark plug used in an internal combustion engine during its service life is to discharge a pulse of high voltage from a high tension lead to produce a spark by breaking down the air in a spark gap (or discharge gap) formed between a center electrode and a ground electrode of the spark plug, thereby igniting the combustible mixture in the combustion chamber of the internal combustion engine. However, during the process of producing a spark, the electrode material will inevitably be lost due to vaporization, ablation, etc. because of the characteristics of the electrode material, and so on, thereby resulting in an increasing spark gap and an increasing required ignition voltage as the service time of the spark plug increases, until the limit of the voltage capacity that can be provided by the ignition coil is reached. Thus, the spark plug can no longer produce a spark, resulting in misfire of the engine.

[0003] In order to reduce the loss rate of the electrode material and prolong the service life of the spark plug, it is known that a noble metal material having excellent corrosion resistance and thus a very low erosion rate can be introduced at the end portion of the electrode of the spark plug. For example, a noble metal tip can be fixedly connected to the center electrode at the end portion of the center electrode of the spark plug by laser welding to improve the reliability, corrosion resistance, etc. of the center electrode by the use of the noble metal material, and thereby reduce the loss of the electrode material and improve the service life of the spark plug. Generally, the noble metal tip on the center electrode of a conventional spark plug is in the shape of a substantially cylindrical body having a constant cross-sectional dimension. During the welding process, the noble metal tip and the base portion of the center electrode are fused together to form a fixed connection. As the requirements for the service life of the spark plug are gradually increased, the diameter of the noble metal tip also needs to be increased. However, the inventors of the present application have found that the required workpiece dimension at the welding location when welding the noble metal tip to the base portion of the electrode (e.g., the center electrode) of the spark plug does not necessarily require to be large. In this case, if the noble metal tip having a cylindrical shape, for example, is still used in the conventional manner, a large amount of noble metal material will be wasted or lost during the welding process, thereby resulting in unnecessary cost increase.

[0004] Therefore, there is a need to improve the existing spark plug. SUMMARY

[0005] It is an object of the present application to provide a spark plug having an improved electrode structure to overcome the problems or deficiencies in the existing spark plug.

[0006] To this end, according to an aspect of the present application, there is provided a spark plug comprising:

[0007] a center electrode; and

[0008] a ground electrode disposed opposite to the center electrode and forming a spark gap between one end of the center electrode and a corresponding end of the ground electrode;

[0009] wherein at least one of the one end of the center electrode and the corresponding end of the ground electrode is configured with a noble metal tip in a single-piece integral structure and fixedly connected to the corresponding center electrode or ground electrode by welding, the noble metal tip having one end side (i.e., a welding side) facing away from the spark gap and another end side (i.e., a discharge side) facing the spark gap, the one end side having a reduced cross-sectional area relative to the another end side.

[0010] With the above technical solution, the present application ingeniously changes the structural design of the noble metal tip used in the spark plug under the premise of meeting the production process and use requirements, i.e., appropriately reducing the size of the welding side of the noble metal tip in a single-piece integral structure, so that the welding side of the noble metal tip has a reduced cross-sectional area relative to the discharge side thereof, thereby being able to significantly reduce the volume of the welding area of the noble metal tip when welding is performed through a simple structural change, and thus as much as possible to reduce the waste of noble metal material and improve its utilization rate, so as to ultimately reduce the manufacturing cost of the spark plug and improve its economy. BRIEF DESCRIPTION OF DRAWINGS

[0011] The features, advantages, and characteristics of the present application will be more clearly understood from the following more detailed description of the application, given by way of example and illustrated in the accompanying drawings in which:

[0012] Figure 1 is a schematic view of a typical configuration of a discharge portion of a spark plug used in an internal combustion engine;

[0013] Figure 2 is a schematic view of a microstructure near a welding area of a noble metal tip welded to an electrode base of a spark plug;

[0014] Figure 3 schematically shows a noble metal tip and a corresponding center electrode base portion in a combined state before welding according to a first embodiment of the present application;

[0015] Figure 4 schematically shows a noble metal tip and a corresponding center electrode base portion in a combined state before welding according to a second embodiment of the present application;

[0016] Figure 5 The diagram schematically illustrates the noble metal tip and corresponding center electrode substrate portion according to the third embodiment of this application, and their combined state before welding.

[0017] Figure 6 The illustration schematically shows the noble metal tip and the corresponding center electrode substrate portion according to the fourth embodiment of this application, and their combined state before welding.

[0018] Figure 7 The illustration schematically shows the noble metal tip and the corresponding center electrode substrate portion according to the fifth embodiment of this application, and their combined state before welding. Detailed Implementation

[0019] The embodiments of this application and other details are described in detail below with reference to the accompanying drawings. It should be understood that the embodiments described below are exemplary and do not constitute a limitation of this application.

[0020] Furthermore, it should be noted that the same reference numerals in different figures denote substantially the same or similar parts (or components) to avoid repetitive descriptions as much as possible. It should be understood that the dimensions, positions, etc., of the parts in the figures are not strictly drawn to scale, and the dimensions, scale relationships, and number of parts should not be construed as limitations on this application.

[0021] Figure 1 The schematic diagram illustrates a typical construction of the discharge section of a spark plug used, for example, in an internal combustion engine for motor vehicles.

[0022] like Figure 1 As shown, the spark plug typically includes, for example, a generally cylindrical center electrode 1 and a generally L-shaped ground electrode 2, which is disposed opposite to the center electrode 1, and a spark gap is formed between one end of the center electrode 1 (i.e., the front end or ignition end) and the corresponding end of the ground electrode 2. To reduce the wear rate of the electrode material and extend the service life of the spark plug, a precious metal tip 3 may be attached, for example, welded to the front end or ignition end of the center electrode 1. Additionally, if necessary, a precious metal tip 4 may also be attached, for example, welded to the corresponding end of the ground electrode 2.

[0023] The inventors of this application, through extensive experimentation and research, discovered that, taking the central electrode as an example, when a noble metal end is fixedly connected to the central electrode by, for example, laser welding, after welding is completed, metallographic observation typically reveals the following pattern near the welding area: Figure 2 The microstructure shown in the photomicrographs, in which... Figure 2In the gray-white area shown, the lighter-colored areas at the top and middle represent the precious metal tip, while the darker-colored area at the bottom represents the central electrode substrate.

[0024] from Figure 2 As can be seen, the precious metal end after welding can be basically divided into three regions from top to bottom: the undamaged region, the partially molten region, and the fully molten region. The precious metal end has a total length L; the undamaged region has a length L1, representing the effective precious metal length; the partially molten and fully molten regions together have a length L2, representing the weld length; and the fully molten region has a length L3. Additionally, as... Figure 2 As shown, the noble metal end has a diameter D.

[0025] After conducting welding tests with different electrode substrates and noble metal tips, the inventors of this application found that, generally, under the condition of meeting welding process requirements, the lengths L1, L2 and L3 will fall within the following numerical range: 2mm ≥ L1 ≥ 100μm, L2 ≥ 200μm and L3 ≥ 20μm.

[0026] As can be seen from the above, when the precious metal tip is welded to the electrode substrate, a certain amount of precious metal material will be consumed in the welding area, resulting in a certain degree of waste or loss of precious metal material. If the structure of the precious metal tip can be redesigned while meeting lifespan and production requirements, for example, by making the cross-sectional area of ​​the side of the precious metal tip away from the spark gap (hereinafter referred to as the welding side) smaller than that of the other side facing the spark gap (hereinafter referred to as the discharge side), the waste or loss of precious metal material during the welding process can be reduced in a targeted manner, thereby effectively reducing the overall manufacturing cost of the spark plug and improving its economy.

[0027] Furthermore, the inventors of this application have noted that during the use of spark plugs equipped with precious metal tips, as the usage time of the spark plug gradually increases, the spark plug electrode (more specifically, the precious metal tip) will be gradually consumed or worn. The height difference between the spark plug electrode before and after use, i.e., the wear height (or wear amount), changes substantially linearly with the increase of usage time. That is, as the usage time gradually increases, the wear height of the spark plug electrode (more specifically, the precious metal tip) increases linearly until a predetermined wear height is reached, i.e., the predetermined life limit of the spark plug is reached. Generally, to ensure the ideal service life of the spark plug, the effective height or working height of the precious metal tip on the spark plug (which substantially corresponds to the length L1 as described above) should be at least 200 μm. That is, to meet usage requirements, the effective height of the precious metal tip should be greater than or equal to 200 μm.

[0028] Based on the above background and understanding, this application improves the structure of the spark plug electrode on the basis of existing spark plugs. That is, while keeping other structures or dimensions basically unchanged, a noble metal end with a single-piece structure is adopted, and the welding side of the noble metal end is designed to have a reduced cross-sectional area relative to its discharge side.

[0029] According to this application, by making the welding side of the precious metal terminal, which is a single-piece structure, have a smaller cross-sectional area relative to its discharge side (i.e., selectively making the welding side of the precious metal terminal have a smaller cross-sectional area compared to its discharge side), the volume of the welding area of ​​the precious metal terminal can be significantly reduced through a simple structural change, thereby reducing the waste or loss of precious metal materials during the welding process. This minimizes the amount of precious metal materials used and increases their utilization rate, ultimately reducing the overall manufacturing cost of the spark plug and improving its economy.

[0030] Advantageously, from the other end to the first end, the precious metal end sequentially includes or is divided into a working portion and a welding portion, the working portion having a predetermined working length, the welding portion having a predetermined welding length, and the precious metal end having a total length, wherein one or more of the following are satisfied:

[0031] The predetermined working length is greater than or equal to 0.2 mm and less than or equal to 2 mm;

[0032] The predetermined welding length is greater than or equal to 0.2 mm and less than or equal to 1 mm;

[0033] The total length is greater than or equal to 0.4 mm and less than or equal to 3 mm.

[0034] As can be seen from the above description, the main improvement or design feature of this application lies in the structural design of the precious metal tip used in the spark plug. Therefore, for the sake of brevity, the specification and accompanying drawings of this application will focus on describing or presenting the content related to the improvement or design feature of this application, while omitting descriptions of other components or structures.

[0035] To better understand the features, advantages, and other aspects of this application, the application will be described in more detail below with reference to the accompanying drawings and exemplary embodiments, wherein... Figures 3 to 7 The noble metal tip and corresponding center electrode substrate portions, and their pre-welding assembly, are schematically shown in cross-sectional views in some exemplary embodiments according to this application. It should be noted that, for simplicity, the following embodiments are described exemplarily by welding the noble metal tip onto the center electrode, but the invention is obviously not limited thereto.

[0036] First Embodiment

[0037] Reference Figure 3 In the first embodiment of this application, the noble metal end piece, which has a single integrated structure, is generally indicated by reference numeral 10, and the corresponding central electrode substrate portion (or central electrode head) is generally indicated by reference numeral 100. In the finished product state, the noble metal end piece 10 is fixed to the central electrode substrate portion 100 by welding, for example, laser welding. Figure 3 The precious metal tip 10, the central electrode substrate portion 100, and their combined state before welding are shown in exploded and combined state diagrams, respectively.

[0038] According to a first embodiment of this application, the precious metal end 10 has an end side extending through which it faces away from the spark gap in its service state. Figure 1 The right side of the middle) and the other side facing the spark gap in the operating state ( Figure 1 The central axis (on the left side) is a block shape with rotational symmetry around the central axis. Figure 3 As seen in the cross-sectional view along the central axis, the precious metal end 10 has cross-sectional dimensions that vary along the central axis.

[0039] More specifically, such as Figure 3 As shown, the precious metal end 10 in the first embodiment of this application is generally T-shaped and consists of a first columnar portion (i.e., the working portion) 11 and a second columnar portion (i.e., the welding portion) 12, each having a constant cross-sectional dimension along the central axis. The first columnar portion 11 is disposed close to the spark gap in the use state, and the second columnar portion 12 is disposed away from the spark gap and adjacent to the first columnar portion 12 in the use state. Both the first columnar portion 11 and the second columnar portion 12 are preferably cylindrical. In a cross-sectional view through the central axis, the first columnar portion 11 has a first diameter D1, and the second columnar portion 12 has a second diameter D2. The first diameter D1 and the second diameter D2 preferably satisfy the following relationship:

[0040] 5mm≥D1>D2≥0.1mm.

[0041] In addition, such as Figure 3 As shown, according to the first embodiment of this application, in a cross-sectional view through the central axis, the first columnar portion 11 has a first length L. 11 The second columnar portion 12 has a second length L 12 Preferably, 2mm ≥ L 11 ≥0.2mm and 1mm≥L 12 ≥0.2mm.

[0042] In addition, such as Figure 3 As shown, according to the first embodiment of this application, the central electrode substrate portion 100 corresponding to the noble metal end 10 also has a central axis, and as observed in a cross-sectional view through the central axis, the central electrode substrate portion 100 may also have a cross-sectional dimension that varies along the central axis. In particular, as observed in a cross-sectional view through the central axis, the central electrode substrate portion 100 may form a reduced-diameter portion corresponding to the noble metal end 10.

[0043] More specifically, such as Figure 3 As shown, the generally cylindrical central electrode substrate portion 100 has a third diameter D3 on the side near the noble metal end 10, and a fourth diameter D4 on the side away from the noble metal end 10. When the noble metal end 10 is welded to the central electrode substrate portion 100, the central axis of the noble metal end 10 is aligned with the central axis of the central electrode substrate portion 100, and the second diameter D2, the third diameter D3, and the fourth diameter D4 preferably satisfy the following relationship:

[0044] D2≤D3 <D4。

[0045] After their respective forming or processing is completed, the noble metal end 10 and the central electrode substrate portion 100 in the first embodiment of this application can be processed as follows: Figure 3 The rightmost way is combined together, and then as shown in the example Figure 3 Welding is performed in the combined state shown, thereby reliably fixing the precious metal end 10 to the central electrode substrate portion 100.

[0046] The dimensions of the various components (or parts) in the first embodiment of this application can be selected in accordance with the manner or principle described below.

[0047] The first diameter D1 (also known as the wear diameter or working diameter) is determined based on the intended service life of the spark plug and user requirements, and is preferably at least 0.5 mm (i.e., D1 ≥ 0.5 mm), and preferably at most 5 mm (i.e., D1 ≤ 5 mm). Furthermore, typically, depending on the spark plug installation requirements, the first diameter D1 ≤ the fourth diameter D4.

[0048] Second diameter D2 (also known as welding diameter): Based on the applicant's research and welding process requirements and practice, the second diameter D2 is preferably at least 0.1 mm (i.e., D2 ≥ 0.1 mm), otherwise it will be difficult to successfully complete the required welding process and obtain sufficient weld strength. Furthermore, as mentioned above, based on welding process and installation requirements, it is preferable that the first diameter D1 > the third diameter D3 ≥ the second diameter D2.

[0049] First length L 11 (Also known as the predetermined wear length or predetermined working length): Determined based on the predetermined service life of the spark plug and user requirements, it is preferably at least 0.2 mm (i.e., L). 11 ≥0.2mm), and preferably at most 2mm (i.e., L 11 ≤2mm).

[0050] Second length L 12 (Also known as the predetermined welding length): Based on the applicant's research and welding process requirements and practice, the second length L 12 It should generally be at least equal to the length L2 as described above. Therefore, the second length L 12 It should typically be at least 0.2 mm (i.e., 200 μm). In other words, L 12 ≥0.2mm. Otherwise, the first columnar portion 11 of the precious metal end 10 may melt during welding, thus affecting its service life. Furthermore, in order to minimize the waste of precious metal material while meeting welding requirements, the second length L... 12 Preferably, the maximum thickness is 1 mm (i.e., L). 12 ≤1mm).

[0051] As an example of the first embodiment, the noble metal end cap 10 of the present invention includes a cylindrical first columnar portion 11 and a second columnar portion 12, wherein the first columnar portion 11 and the second columnar portion 12 respectively have a first diameter D1 and a first length L. 11 Second diameter D2, second length L 12 Where, D1 = 1.2 mm, L 11 =0.7mm, D2=0.5mm, L 12 =0.3mm. Under these conditions, the total volume V of the precious metal tip 10 is calculated to be... 新 0.85mm 3 .

[0052] Correspondingly, as a comparative example, the conventionally designed precious metal end is in the shape of a cylinder with a constant cross-sectional area along its central axis, having a diameter of 1.2 mm and a length (height) of 1.0 mm, and its volume V is calculated to be... 常规 It is 1.13mm 3 .

[0053] In this case, V 新 / V 常规=0.85 / 1.13≈75%. It can be seen that, compared to the conventional design described above, the volume of the precious metal end, as an example of the first embodiment of this application, is reduced by approximately 25%, which means that approximately 25% of the precious metal material cost can be saved. In particular, compared to the precious metal end using a conventional design, the precious metal end of the example of the first embodiment of this application has a welded portion (i.e., the second columnar portion 12) with significantly reduced overall size and volume.

[0054] Second Embodiment

[0055] The following reference Figure 4 The second embodiment of this application is described below. Except for the structural design of the noble metal tip, this second embodiment is substantially the same as the remaining parts of the first embodiment described above (e.g., the central electrode substrate portion and the combination and welding process of the noble metal tip and the central electrode substrate portion, etc.). Therefore, the following description will mainly focus on the differences from the first embodiment, omitting descriptions of other parts; this also applies to the third to fifth embodiments described subsequently.

[0056] like Figure 4 As shown, the precious metal end piece with a single, integrated structure in the second embodiment of this application is generally indicated by reference numeral 20. From Figure 4 As can be seen, similar to the first embodiment, the precious metal end 20 has an extension through the side facing away from the spark gap in its operating state. Figure 4 The right side of the middle) and the side facing the spark gap in the operating state ( Figure 4 The central axis of the noble metal end 20 is located on the left side of the central axis, and the noble metal end 20 is generally a truncated cone with a cross-sectional shape that varies linearly along its central axis. In a cross-sectional view through the central axis, the side of the noble metal end 20 facing the spark gap has a first diameter D1, and the side of the noble metal end 20 away from the spark gap has a second diameter D2. The dimensions or ranges of the first diameter D1 and the second diameter D2 can be determined or selected in the same manner as in the first embodiment, and preferably satisfy the following relationship:

[0057] 5mm≥D1>D2≥0.1mm.

[0058] In addition, from Figure 4 As can be seen from left to right, the truncated cone of the precious metal end 20 shown in this second embodiment can be sequentially divided into a working portion 21 and a welding portion 22 by the dotted lines in the figure. The welding portion 22 has a reduced cross-sectional area relative to the working portion 21, and the working portion 21 has a predetermined working length L. 21 The welded portion 22 has a predetermined weld length L 22The predetermined working length L 21 and the predetermined welding length L 22 It can be in accordance with the first length L in the first embodiment 11 Second length L 12 The design or selection is carried out in a similar manner or according to similar principles (e.g., in this second embodiment, the predetermined working length L). 21 Similarly, a minimum of 0.2 mm and a maximum of 2 mm are preferred; additionally, the predetermined welding length L 22 Similarly, it is preferred to be at least 0.2 mm and preferably at most 1 mm, which will not be elaborated here.

[0059] In addition, such as Figure 4 As shown, the precious metal end 20 has a total length L, and the total length L can be selected according to the following described methods or principles:

[0060] The total length L should be at least equal to the sum of the lengths L1 and L2 as described above (and equal to the predetermined working length L). 21 and the predetermined welding length L 22 The total length L is preferably not less than 0.4mm, i.e., L≥0.4mm, considering factors such as the expected service life of the spark plug and user needs. Otherwise, the service life may be affected due to the melting of too much precious metal material during the welding process. The total length L is preferably at most 3mm (i.e., L≤3mm).

[0061] As an example of the second embodiment, the noble metal end 20 of the present invention is generally shaped like a truncated cone as described above, and accordingly has a first diameter D1, a second diameter D2, and a total length L, wherein D1 = 1.0 mm, D2 = 0.5 mm, and L = 1.0 mm. In this case, the total volume V of the noble metal end 20 is calculated to be... 新 It is 0.458mm 3 .

[0062] Correspondingly, as a comparative example, the conventionally designed precious metal end is in the shape of a cylinder with a constant cross-sectional area along its central axis, and has a diameter equal to 1.0 mm and a length (height) equal to 1.0 mm. Its volume V is calculated to be... 常规 It is 0.785mm 3 .

[0063] In this case, V 新 / V 常规=0.458 / 0.785≈58%. It can be seen that, compared to the conventional design described above, the volume of the precious metal end, as an example of the second embodiment of this application, is reduced by approximately 42%, which means that approximately 42% of the precious metal material cost can be saved. In particular, compared to the precious metal end using a conventional design, the precious metal end of the example of the second embodiment of this application has a welded portion (i.e., welded portion 22) with significantly reduced overall size and volume.

[0064] Third Embodiment

[0065] The following reference Figure 5 The third embodiment of this application is described. The third embodiment is basically similar to the first embodiment, both of which design the precious metal end to include two different parts. The main difference lies in the structure or composition of the two parts.

[0066] More specifically, such as Figure 5 As shown, the precious metal end piece with a single-piece integrated structure in the third embodiment of this application is generally indicated by reference numeral 30 and consists of a columnar portion (i.e., the working portion) 31 with a constant cross-sectional dimension along the central axis and a variable cross-sectional portion (i.e., the welding portion) 32 with a continuously varying cross-sectional dimension along the central axis. The columnar portion 31 is positioned close to the spark gap in the use state, and the variable cross-sectional portion 32 is positioned away from the spark gap and adjacent to the columnar portion 31 in the use state. The columnar portion 31 is preferably cylindrical, and the variable cross-sectional portion 32 is preferably a truncated cone with a linearly varying cross-sectional shape along its central axis. Viewed in a cross-sectional view through the central axis, the columnar portion 31 has a first diameter D1, and the variable cross-sectional portion 32 has a second diameter D2 at its farthest side away from the spark gap. Furthermore, as... Figure 5 As shown, in a cross-sectional view passing through its central axis, the columnar portion 31 has a length L. 31 The variable cross-section portion 32 has a length L 32 .

[0067] The dimensions of the various components (or parts) in the third embodiment of this application can be selected in a similar manner or principle to the first embodiment (for example, in the third embodiment, the first diameter D1 and the second diameter D2 preferably satisfy the following relationship: 5mm ≥ D1 > D2 ≥ 0.1mm; furthermore, 2mm ≥ L 31 ≥0.2mm and 1mm≥L 32 (≥0.2mm), which will not be elaborated here.

[0068] As an example of the third embodiment, the noble metal end 30 of the present invention includes a cylindrical columnar portion 31 and a truncated conical variable cross-section portion 32, wherein the columnar portion 31 and the variable cross-section portion 32 respectively have a first diameter D1 and a first length L. 31 Second diameter D2, second length L 32 Where, D1 = 1.0 mm, L 31 =0.5mm, D2=0.2mm, L 32 =0.3mm. Under these circumstances, the total volume V of the precious metal tip 30 is calculated to be... 新 It is 0.515mm 3 .

[0069] In contrast, as a comparative example, the conventionally designed precious metal end is cylindrical with a constant cross-sectional area along its central axis, having a diameter of 1.0 mm and a length (height) of 0.8 mm. Its calculated volume V... 常规 It is 0.628mm 3 .

[0070] In this case, V 新 / V 常规 =0.515 / 0.628≈82%. It can be seen that, compared to the conventional design described above, the volume of the precious metal end, as an example of the third embodiment of this application, is reduced by approximately 18%, which means that approximately 18% of the precious metal material cost can be saved. In particular, compared to the precious metal end using a conventional design, the precious metal end of the example of the third embodiment of this application has a welded portion (i.e., the variable cross-section portion 32) with significantly reduced overall size and volume.

[0071] Fourth embodiment

[0072] The following reference Figure 6 The fourth embodiment of this application is described, which differs from the first to third embodiments in that the precious metal end is designed to include three different parts.

[0073] More specifically, such as Figure 6As shown, the precious metal end piece with a single-piece integrated structure in the fourth embodiment of this application is generally indicated by reference numeral 40. It is generally funnel-shaped and consists of a first columnar portion (i.e., the working portion) 41 with a constant cross-sectional dimension along the central axis, a second columnar portion 43 with a constant cross-sectional dimension along the central axis, and a variable cross-section portion 42 located between the first columnar portion 41 and the second columnar portion 43. The variable cross-section portion 42 has a continuously varying cross-sectional dimension along the central axis. The first columnar portion 41 is positioned close to the spark gap in the use state, and the second columnar portion 43 is positioned away from the spark gap in the use state. Both the first columnar portion 41 and the second columnar portion 43 are preferably cylindrical, and the variable cross-section portion 42 is preferably a truncated cone with a linearly varying cross-sectional shape along the central axis. The variable cross-section portion 42 and the second columnar portion 43 together correspond to the welding portion. In a cross-sectional view along the central axis, the first columnar portion 41 has a first diameter D1, and the second columnar portion 43 has a second diameter D2. Furthermore, as... Figure 6 As shown, in a cross-sectional view passing through the central axis, the first columnar portion 41 has a length L. 41 The variable cross-section portion 42 and the second columnar portion 43 together have a length L 42+43 And the second columnar portion 43 has a length L 43 .

[0074] The first diameter D1 and the second diameter D2 in the fourth embodiment of this application can be selected in the same manner or principle as in the first embodiment, and will not be repeated here.

[0075] Furthermore, the length L in the fourth embodiment of this application 41 L 42+43 and length L 43 You can choose according to the methods or principles described below.

[0076] Length L 41 (Also known as the predetermined wear length or predetermined working length): Determined based on the predetermined service life of the spark plug and user requirements, it is preferably at least 0.2 mm (i.e., L). 41 ≥0.2mm), and preferably at most 2mm (i.e., L 41 ≤2mm).

[0077] Length L 42+43 (Also known as the predetermined welding length): Based on the applicant's research and welding process requirements and practices, the length L... 42+43 It should generally be at least equal to the length L2 as described above. Therefore, the length L 42+43It should be at least 0.2 mm (i.e., 200 μm). In other words, L 42+43 ≥0.2mm. Otherwise, the first columnar portion 41 of the precious metal end 40 may melt during welding, thus affecting its service life. Furthermore, in order to minimize the waste of precious metal material while meeting welding requirements, the length L... 42+43 Preferably, the maximum thickness is 1 mm (i.e., L). 42+43 ≤1mm).

[0078] Length L 43 (Also known as the predetermined complete melting length): Based on the applicant's research and welding process requirements and practices, the length L 43 It should generally be at least equal to the length L3 as described above. Therefore, L 43 It should be at least 0.02 mm (i.e., 20 μm). In other words, L 43 ≥0.02mm. Otherwise, it may affect the welding process and quality, and may cause the first columnar portion 41 of the precious metal end 40 to melt during the welding process, thereby affecting its service life. In addition, considering factors such as welding reliability and cost, the length L 43 Preferably, the maximum thickness is 1 mm (i.e., L). 43 ≤1mm).

[0079] As an example of the fourth embodiment, the noble metal end 40 of the present invention includes a cylindrical first columnar portion 41, a truncated conical variable cross-section portion 42, and a cylindrical second columnar portion 43, wherein the first columnar portion 41 and the second columnar portion 43 respectively have a first diameter D1 and a length L. 41 Second diameter D2, length L 43 The variable cross-section portion 42 and the second columnar portion 43 together have a length L 42+43 Where, D1=0.8mm, L 41 =0.3mm, D2=0.2mm, L 42+43 =0.2mm, L 43 =0.1mm. Under these conditions, the total volume V of the precious metal tip 40 is calculated to be... 新 It is 0.174mm 3 .

[0080] In contrast, as a comparative example, the conventionally designed precious metal end is cylindrical with a constant cross-sectional area along its central axis, having a diameter of 0.8 mm and a length (height) of 0.5 mm. Its calculated volume V... 常规 It is 0.251mm 3 .

[0081] In this case, V新 / V 常规 =0.174 / 0.251≈69%. It can be seen that, compared to the conventional design described above, the volume of the precious metal end, as an example of the fourth embodiment of this application, is reduced by approximately 31%, which means that approximately 31% of the precious metal material cost can be saved. In particular, compared to the precious metal end using a conventional design, the precious metal end of the example of the fourth embodiment of this application has a welded portion (i.e., the variable cross-section portion 42 and the second columnar portion 43) with significantly reduced overall size and volume.

[0082] Fifth embodiment

[0083] The following reference Figure 7 The fifth embodiment of this application is described, which is essentially a variation of the second embodiment. The main difference between the fifth and second embodiments is that the linear transition method in the precious metal end of the second embodiment is replaced with a non-linear transition method (especially an arc transition method).

[0084] More specifically, such as Figure 7 As shown, the precious metal end piece with a single, integrated structure in the fifth embodiment of this application is generally indicated by reference numeral 50. From Figure 7 As can be seen, similar to the second embodiment, the precious metal end 50 has an extension through the side facing away from the spark gap in its operating state. Figure 7 The right side of the middle) and the side facing the spark gap in the operating state ( Figure 7 The precious metal end 50 is generally shaped like a trumpet with an arc-shaped cross-section along the central axis. In a cross-sectional view through the central axis, the side of the precious metal end 50 facing the spark gap has a first diameter D1, the side of the precious metal end 50 away from the spark gap has a second diameter D2, and the precious metal end 50 has a total length L.

[0085] In addition, from Figure 7 As can be seen from left to right, the horn body of the precious metal end 50 shown in this fifth embodiment can be sequentially divided into a working part 51 and a welding part 52 by the dotted lines in the figure. The welding part 52 has a reduced cross-sectional area relative to the working part 51, and the working part 51 has a predetermined working length L. 51 The welded portion 52 has a predetermined weld length L 52 The predetermined working length L 51 and the predetermined welding length L 52 It can be done according to the predetermined working length L in the second embodiment. 21 and the predetermined welding length L 22The design or selection is carried out in a similar manner or according to similar principles (for example, in this fifth embodiment, the predetermined working length L). 51 Similarly, a minimum of 0.2 mm and a maximum of 2 mm are preferred; additionally, the predetermined welding length L 52 Similarly, it is preferred to be at least 0.2 mm and preferably at most 1 mm, which will not be elaborated here.

[0086] Furthermore, the first diameter D1, the second diameter D2, and the total length L in the fifth embodiment of this application can be selected in the same manner or principle as in the second embodiment, and will not be repeated here. As an example of the fifth embodiment, the noble metal end 50 of the newly designed present invention is generally in the shape of a flared body as described above, and accordingly has a first diameter D1, a second diameter D2, and a total length L, wherein D1 = 0.5 mm, D2 = 0.2 mm, and L = 0.5 mm. In this case, the total volume V of the noble metal end 50 is calculated to be... 新 It is 0.038mm 3 .

[0087] Correspondingly, as a comparative example, the conventionally designed precious metal end is in the shape of a cylinder with a constant cross-sectional area along its central axis, and has a diameter of 0.5 mm and a length (height) of 0.5 mm. Its volume V is calculated to be... 常规 It is 0.098mm 3 .

[0088] In this case, V 新 / V 常规 =0.038 / 0.098≈39%. It can be seen that, compared to the conventional design described above, the volume of the precious metal end, as an example of the fifth embodiment of this application, is reduced by approximately 61%, which means that approximately 61% of the precious metal material cost can be saved. In particular, compared to the precious metal end using a conventional design, the precious metal end of the example of the fifth embodiment of this application has a welded portion (i.e., welded portion 52) with significantly reduced overall size and volume.

[0089] It should be noted that the arc-shaped transition method in the fifth embodiment described above can also be selectively applied to other embodiments of this application (e.g., the variable cross-section portion 32 in the third embodiment and the variable cross-section portion 42 in the fourth embodiment) in a similar manner, thereby constituting advantageous optional variations of these embodiments, which will not be elaborated here. In fact, without conflict with each other, other features in the various embodiments of this application can also be combined or varied with each other, thereby producing other variations or improvements not shown here.

[0090] As can be clearly seen from the above description, this application addresses the shortcomings of traditional precious metal tips (which typically have a constant cross-sectional size), such as the significant waste of precious metal material during the welding process. This is achieved through specific optimization of the structure and dimensions of the precious metal tip (e.g., making the welding side of the single-piece precious metal tip have a reduced cross-sectional area relative to its discharge side, and dividing the precious metal tip into a working part and a welding part, and differentiating and rationally selecting them based on their different functions, especially making the welding part have a significantly reduced cross-sectional area, overall size, and volume compared to the prior art). This cleverly reduces the volume of the welding area of ​​the precious metal tip through simple structural changes, thereby reducing the waste or loss of precious metal material during welding. This minimizes the amount of precious metal material used and maximizes its utilization rate, ultimately reducing the overall manufacturing cost of the spark plug and improving its economic efficiency. The structural design of this application is applicable to various types of spark plugs equipped with precious metal tips and can be widely used in various applications, such as internal combustion engines in motor vehicles. Compared with conventional spark plugs, spark plugs using the unique structural design of this application have advantages such as simple structure, low manufacturing cost, and long service life.

[0091] The precious metal tips in the above embodiments of this application can be manufactured by machining methods such as cutting (the resulting chips can be collected for recycling), and then the manufactured precious metal tips can be fixedly connected to the spark plug electrode base by laser welding or resistance welding to ensure connection strength and reliability. Preferably, the precious metal tips are integrally formed (e.g., molded) before welding, thereby simplifying the production process and further reducing manufacturing costs.

[0092] Furthermore, the materials and welding processes of the precious metal tip and the corresponding spark plug electrode substrate in this application can be selected or implemented in accordance with methods known in the art. Moreover, without conflicting with the spirit or scope of this application, those skilled in the art can freely select or apply the relevant components based on specific applications, working environments, usage requirements, and relevant knowledge known in the art. For example, the precious metal tip can typically be made of a precious metal (e.g., platinum, iridium, ruthenium, rhodium) that is resistant to high temperatures and has excellent wear resistance and corrosion resistance, or an alloy with the precious metal as the main component. The spark plug electrode (center electrode or ground electrode) substrate can typically be made of a metal or alloy with high corrosion resistance (e.g., nickel alloy). Moreover, without departing from the basic spirit and principles of this application, those skilled in the art can appropriately change or adjust the dimensions of the various parts (especially the working part and the welding part) of the precious metal tip in this application according to different application environments, user needs, and selected materials.

[0093] Furthermore, in the above description of the various embodiments and related examples, the example of welding a precious metal tip to a central electrode is mainly used as an example. The precious metal tip is, for example, in the form of a cone with a varying cross-section or a block-shaped object combining a cone and a cylinder. It is preferably fixed to the central electrode substrate portion (i.e., the front end or welding end of the central electrode) with a corresponding reduced diameter portion by laser welding. This allows for convenient and quick welding operations using a pulsed laser, and offers advantages such as safety and reliability. However, it is clear that this application is not limited to this. For example, when the precious metal tip of this application is configured on a ground electrode, the precious metal tip may be in the form of a sheet and can be fixedly connected to the ground electrode, for example, by resistance welding. Furthermore, without affecting the welding performance and process, the precious metal tip may have a portion different from a cylinder or cone (e.g., a square prism, hexagonal prism, or pyramidal portion), and the corresponding ground electrode may not have a corresponding reduced diameter portion.

[0094] The present application has been described in detail above with reference to specific embodiments and variations thereof. It is obvious that, as stated above, the description and embodiments shown in the accompanying drawings should be understood as exemplary and not as limiting the present application. Those skilled in the art can make various modifications or variations without departing from the spirit of the present application. Obviously, these modifications or variations do not depart from the scope of the present application.

Claims

1. A spark plug comprising: Central electrode; as well as A grounding electrode is disposed opposite to the center electrode, and a spark gap is formed between one end of the center electrode and the corresponding end of the grounding electrode. At least one of the ends of the center electrode and the corresponding end of the ground electrode is provided with a noble metal tip. The noble metal tip is a single-piece integral structure and is fixedly connected to the corresponding center electrode or ground electrode by welding. The noble metal tip has one end side facing away from the spark gap and another end side facing the spark gap. The one end side has a reduced cross-sectional area relative to the other end side. From one end to the other end, the precious metal end is divided into a working part and a welding part. The working part has a predetermined working length, which is greater than or equal to 0.2 mm and less than or equal to 2 mm. The welding part has a predetermined welding length, which is greater than or equal to 0.2 mm and less than or equal to 1 mm.

2. The spark plug according to claim 1, characterized in that, The precious metal end has a central axis extending through one end side and the other end side of the precious metal end, and is in the form of a block or sheet body with rotational symmetry about the central axis. When viewed in a cross-sectional view through the central axis, the precious metal end has a cross-sectional dimension that varies along the central axis.

3. The spark plug according to claim 2, characterized in that, The precious metal end is generally T-shaped and consists of a first columnar portion and a second columnar portion, each having a constant cross-sectional dimension along the central axis. The first columnar portion corresponds to the working portion and is positioned close to the spark gap. The second columnar portion corresponds to the welding portion and is positioned away from the spark gap and adjacent to the first columnar portion. In a cross-sectional view along the central axis, the first columnar portion has a first diameter D1, and the second columnar portion has a second diameter D2. The first diameter D1 and the second diameter D2 satisfy the following relationship: 5 mm ≥ D1 > D2 ≥ 0.1 mm.

4. The spark plug according to claim 3, characterized in that, Viewed in a cross-sectional view passing through the central axis, the first columnar portion has a first length L. 11 The second columnar portion has a second length L 12 , where 2 mm ≥ L 11 ≥ 0.2 mm and 1 mm ≥ L 12 ≥ 0.2 mm.

5. The spark plug according to claim 2, characterized in that, The precious metal end is generally shaped like a truncated cone with a linearly varying cross-sectional shape along the central axis, or like a trumpet with an arc-shaped cross-sectional shape along the central axis. From one end to the other, each of the truncated cone and the trumpet is sequentially divided into a working part and a welding part. In a cross-sectional view along the central axis, the side of the precious metal end facing the spark gap has a first diameter D1, and the side of the precious metal end facing away from the spark gap has a second diameter D2. The first diameter D1 and the second diameter D2 satisfy the following relationship: 5 mm ≥ D1 > D2 ≥ 0.1 mm; and / or The working part has a predetermined working length L. 21 or L 51 The welded portion has a predetermined weld length L 22 or L 52 The precious metal end has a total length L, where 2 mm ≥ L 21 or L 51 ≥ 0.2 mm, 1 mm ≥ L 22 or L 52 ≥0.2 mm and 3 mm ≥ L ≥ 0.4 mm.

6. The spark plug according to claim 2, characterized in that, The precious metal end cap consists of a columnar portion having a constant cross-sectional dimension along the central axis and a variable cross-sectional portion having a continuously varying cross-sectional dimension along the central axis. The columnar portion corresponds to the working portion and is positioned close to the spark gap. The variable cross-sectional portion corresponds to the welding portion and is positioned away from the spark gap and adjacent to the columnar portion. Viewed in a cross-sectional view through the central axis, the columnar portion has a first diameter D1, and the variable cross-sectional portion has a second diameter D2 at its farthest point away from the spark gap. The first diameter D1 and the second diameter D2 satisfy the following relationship: 5 mm ≥ D1 > D2 ≥ 0.1 mm.

7. The spark plug according to claim 6, characterized in that, Viewed in a cross-sectional view passing through the central axis, the columnar portion has a length L. 31 The variable cross-section portion has a length L 32 Where 2 mm ≥ L 31 ≥ 0.2 mm and 1 mm ≥ L 32 ≥ 0.2 mm.

8. The spark plug according to claim 2, characterized in that, The precious metal end is generally funnel-shaped and consists of a first columnar portion with a constant cross-sectional dimension along the central axis, a second columnar portion with a constant cross-sectional dimension along the central axis, and a variable cross-section portion located between the first and second columnar portions. The variable cross-section portion has a continuously varying cross-sectional dimension along the central axis. The first columnar portion corresponds to the working portion and is positioned close to the spark gap, while the second columnar portion is positioned away from the spark gap. The variable cross-section portion and the second columnar portion together correspond to the welding portion. In a cross-sectional view through the central axis, the first columnar portion has a first diameter D1, and the second columnar portion has a second diameter D2. The first diameter D1 and the second diameter D2 satisfy the following relationship: 5 mm ≥ D1 > D2 ≥ 0.1 mm.

9. The spark plug according to claim 8, characterized in that, Viewed in a cross-sectional view passing through the central axis, the first columnar portion has a length L. 41 The second columnar portion has a length L 43 The variable cross-section portion and the second columnar portion together have a length L 42+43 Where 2 mm ≥ L 41 ≥ 0.2 mm, 1 mm ≥ L 42+43 ≥ 0.2 mm and 1 mm ≥ L 43 ≥ 0.02 mm.

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