阅读说明：本技术 火花塞壳体及其制造方法 (Spark plug shell and manufacturing method thereof ) 是由 马书伟 理查德·凯勒 于 2020-04-09 设计创作，主要内容包括：一种用于火花塞(10)的金属壳体(16)由钢材料制成,所述钢材料具有增加的碳含量并且在一些实施例中还具有硼。所述钢材料因其延展性而非常适合挤压,同时保持必要的强度。火花塞壳体可以在压接的热锁区域(40)处具有减小的外径(OD-(HL)),诸如在壳体用于例如M8和M10插塞的较小直径的火花塞时的情况。根据非限制性示例,火花塞壳体钢材料包含0.20至0.55wt％的碳,包括端值。(A metal shell (16) for a spark plug (10) is made of a steel material having an increased carbon content and, in some embodiments, also having boron. The steel material is very suitable for extrusion due to its ductility, while maintaining the necessary strength. The spark plug shell may have a reduced Outer Diameter (OD) at a crimped heat lock region (40) HL ) Such as is the case when the housing is used for smaller diameter spark plugs such as M8 and M10 plugs. According to a non-limiting example, the spark plug housing steel material includes 0.20 to 0.55 wt% carbon, inclusive.)

1. A spark plug housing (16) comprising:

a tubular body (28) of steel material, the tubular body having an axial bore (26), the axial bore (26) having a longitudinal axis (L)_Shell)，

Wherein the steel material comprises 0.20 to 0.55 wt% carbon, inclusive, and includes a grain structure (66) having a plurality of grains (70), each grain of the plurality of grains in the grain structure including a longitudinal axis (L) along a longest extent of the grain_G) For a majority of the plurality of grains in the grain structure, a longitudinal axis (L) of the grain_G) A longitudinal axis (L) with the axial hole of the housing_Shell) And (6) aligning.

2. The spark plug housing (16) of claim 1, wherein the steel material includes 0.45 to 0.50 wt% carbon, inclusive.

3. The spark plug housing (16) of claim 1, wherein said steel material further includes boron.

4. The spark plug housing (16) of claim 3, wherein the steel material includes 5 to 30ppm boron, inclusive.

5. The spark plug housing (16) of claim 1, wherein the steel material further includes 0.30 to 1.00 wt% manganese, inclusive.

6. The spark plug housing (16) of claim 1, wherein the steel material further comprises 0.001 to 0.10 wt% titanium, inclusive.

7. The spark plug housing (16) of claim 1, wherein the steel material further comprises at least one of 0.02 to 0.06 wt% aluminum or 0.01 to 0.30 wt% silicon, wherein each numerical range is inclusive.

8. As in claimThe spark plug housing (16) of claim 1, wherein the tubular body (28) includes a tip (32), a free end (30), and a heat lock region (40) between the tip and the free end, wherein an Outer Diameter (OD) of the heat lock region_HL) Between 0.40 and 0.50 inches, inclusive.

9. The spark plug housing (16) of claim 1, wherein the tubular body (28) includes a tip (32), a free end (30), and a threaded region (34) between the tip and the free end, wherein an Outer Diameter (OD) of the threaded region_Shell) Between 0.30 and 0.425 inches, inclusive.

10. A spark plug (10) comprising:

the spark plug housing (16) of claim 1;

an insulator (14) having an axial bore (24) and disposed at least partially within the axial bore (26) of the spark plug housing;

a center electrode (12) disposed at least partially within the axial bore of the insulator; and

a ground electrode (18) attached to the spark plug housing.

11. A spark plug housing (16) comprising:

a tubular body (28) of steel material having an axial bore (26) with a longitudinal axis (L)_Shell)，

Wherein the steel material comprises the balance iron, 0.45 to 0.50 wt% carbon, 5 to 30ppm boron, 0.30 to 1.00 wt% manganese, 0.001 to 0.10 wt% titanium, and at least one of 0.02 to 0.06 wt% aluminum or 0.01 to 0.30 wt% silicon, wherein each wt% is inclusive.

12. The spark plug housing (16) of claim 11 wherein said tubular body (28) includes a tip (32), a free end (30) and a portion therebetweenA heat-lock region (40), wherein an Outer Diameter (OD) of the heat-lock region_HL) Between 0.40 and 0.50 inches, inclusive.

13. The spark plug housing (16) of claim 11, wherein the tubular body (28) includes a tip (32), a free end (30), and a threaded region (34) between the tip and the free end, wherein an Outer Diameter (OD) of the threaded region_Shell) Between 0.30 and 0.425 inches, inclusive.

14. A spark plug (10) comprising:

the spark plug housing (16) of claim 11;

an insulator (14) having an axial bore (24) and disposed at least partially within the axial bore (26) of the spark plug housing;

a center electrode (12) disposed at least partially within the axial bore of the insulator; and

a ground electrode (18) attached to the spark plug housing.

15. A method of manufacturing a spark plug housing (16), comprising the steps of:

extruding a tubular body (28) from a steel material, wherein the steel material comprises 0.20 to 0.55 wt% carbon, inclusive, and the tubular body comprises a tubular body having a longitudinal axis (L)_Shell) An axial bore (26); and

crimping a heat-lock region (40) in the tubular body once an insulator (14) has been inserted into the axial bore, wherein an Outer Diameter (OD) of the heat-lock region_HL) Between 0.40 inches and 0.50 inches, inclusive.

Technical Field

The present invention relates generally to spark plugs and, more particularly, to a metal shell for a spark plug.

Background

Low carbon steels (e.g., C1005, C1008, and C1010 steels) have traditionally been used as the material for extruded spark plug housings. These materials have lower strength and higher ductility, making them more suitable for deep extrusion. Typically, these mild steels are widely used for M12 spark plugs (shell outer diameter of 12 mm or 0.485 inch) and larger size spark plugs.

With the demand for downsizing engines, the spark plugs are also downsized accordingly, and the spark plugs of sizes such as M8, M10, etc. are used more frequently. As dimensions decrease, there is also a trend to use thicker ceramic insulators to increase the voltage capability of the spark plug. This requires the use of thinner but stronger housing materials. To meet these requirements, the housing requires a higher strength steel material. However, as one example, higher strength steels are generally more difficult to manufacture in processes such as extrusion.

Disclosure of Invention

According to one example, there is provided a spark plug housing comprising: a tubular body of steel material having an axial bore with a longitudinal axis (L)_Shell) Wherein the steel material comprises 0.20 to 0.55 wt% (weight percent) carbon, inclusive, and includes a grain structure having a plurality of grains, each grain of the plurality of grains in the grain structure including a longitudinal axis (L) along a longest extent of the grain_G) For most of the plurality of grains in the grain structure, the longitudinal axis (L) of the grain_G) Longitudinal axis (L) of the axial bore of the housing_Shell) And (6) aligning.

According to various embodiments, the spark plug housing may further comprise any one of the following features or any technically feasible combination of some or all of these features:

the steel material comprises 0.45 to 0.50 wt% carbon, inclusive;

the steel material also contains boron;

the steel material contains 5 to 30ppm of boron, inclusive;

the steel material further comprises 0.30 to 1.00 wt% manganese, inclusive;

the steel material further comprises 0.001 to 0.10 wt% titanium, inclusive;

the steel material further comprises at least one of 0.02 to 0.06 wt.% aluminium, inclusive, or 0.01 to 0.30 wt.% silicon, inclusive;

the tubular body comprises a distal end, a free end, and a heat-lock region between the distal end and the free end, wherein the heat-lock region has an Outer Diameter (OD)_HL) Between 0.40 and 0.50 inches, inclusive;

the tubular body comprises a terminal end, a free end and a threaded region between the terminal end and the free end, wherein the Outer Diameter (OD) of the threaded region_Shell) Between 0.30 and 0.425 inches, inclusive;

a spark plug comprising: the spark plug housing of claim 1; an insulator having an axial bore and disposed at least partially within the axial bore of the spark plug housing; a center electrode at least partially disposed within the axial bore of the insulator; and a ground electrode attached to the spark plug shell.

According to another example, there is provided a spark plug housing comprising: a tubular body of steel material having an axial bore with a longitudinal axis (L)_Shell) Wherein the steel material comprises the balance iron, 0.45 to 0.50 wt% carbon, 5 to 30ppm boron, 0.30 to 1.00 wt% manganese, 0.001 to 0.10 wt% titanium, and at least one of 0.02 to 0.06 wt% aluminum or 0.01 to 0.30 wt% silicon, wherein each wt% is inclusive.

According to various embodiments, the spark plug housing may further comprise any one of the following features or any technically feasible combination of some or all of these features:

the tubular body comprises a distal end, a free end, and a heat-lock region between the distal end and the free end, wherein the heat-lock region has an Outer Diameter (OD)_HL) Between 0.40 and 0.50 inches, inclusive;

the tubular body comprises a terminal end, a free end and a threaded region between the terminal end and the free end, wherein the Outer Diameter (OD) of the threaded region_Shell) Between 0.30 and 0.425 inches, inclusive;

a spark plug comprising: the spark plug housing of claim 11; an insulator having an axial bore and disposed at least partially within the axial bore of the spark plug housing; a center electrode at least partially disposed within the axial bore of the insulator; and a ground electrode attached to the spark plug shell.

According to another example, there is provided a method of manufacturing a spark plug housing, comprising the steps of: extruding a tubular body from a steel material, wherein the steel material comprises 0.20 to 0.55 wt% carbon, inclusive, and the tubular body comprises a tubular body having a longitudinal axis (L)_Shell) The axial bore of (a); and crimping a heat-lock region in the tubular body once the insulator has been inserted into the axial bore, wherein an Outer Diameter (OD) of the heat-lock region_HL) Between 0.40 inches and 0.50 inches, inclusive.

Drawings

Preferred exemplary embodiments will hereinafter be described in conjunction with the appended drawings, wherein like designations denote like elements, and wherein:

FIG. 1 is a partial cross-sectional view illustrating an example spark plug having an extruded spark plug shell;

FIG. 2 is another cross-sectional view of the spark plug of FIG. 1, taken along line 2-2 of FIG. 1;

FIG. 3 is another cross-sectional view of the spark plug of FIGS. 1 and 2, taken along line 3-3 of FIG. 1; and

fig. 4 schematically illustrates an extrusion process that may be used to manufacture a shell for a spark plug, such as the spark plugs shown in fig. 1-3.

Detailed Description

The spark plug described herein includes a metal shell made of a steel material having an increased carbon content and advantageously with the addition of boron. The steel material used for the spark plug housing is well suited for extrusion due to its ductility, while maintaining the necessary strength. The spark plug housings described herein have a reduced outer diameter at the crimped heat lock region. In contrast to the M12 and M14 plugs, the proportional diameter reduction may be more pronounced in smaller spark plugs, such as M8 and M10 plugs, particularly at the hot lock region. The presently described steel material and extruded spark plug housing may help compensate for this reduction in diameter at the thermal lock area.

Fig. 1 shows an embodiment of a spark plug, in which the housing consists of an advantageous, extruded steel material. In this particular embodiment, the spark plug 10 includes a center electrode 12, an insulator 14, a metal shell 16, and a ground electrode 18. Other spark plug components may include posts, internal resistors, various gaskets, internal seals, etc., all of which are known to those skilled in the art. The center electrode 12 is a conductive member and is generally disposed within the axial bore 24 of the insulator 14, and the center electrode 12 may have an end exposed to the exterior of the insulator near the firing end of the spark plug 10. The insulator 14 is generally disposed within the axial bore 26 of the shell 16 and may have an end nose portion exposed to the exterior of the shell near the firing end of the spark plug 10. Insulator 14 is preferably made of an insulating material, such as a ceramic composition, that electrically isolates center electrode 12 from metal shell 16. Depending on the desired spark plug design, the firing tips 20, 22 may be attached to the center electrode 12 and/or the ground electrode 18, respectively, and may assist in forming a spark gap where a spark initiates the combustion process during engine operation. The firing tips 20, 22 may include any number of suitable precious metal alloys (e.g., iridium-based, platinum-based, ruthenium-based, etc. alloys), and the firing tips 20, 22 may be a single piece component or multiple piece components and may be arranged according to any number of suitable shapes (e.g., flat pads, discs, rivets, cylindrical tips, cones, etc.). However, firing tips 20 and/or 22 are optional as the spark gap may be defined by a spark surface from center electrode 12, ground electrode 18, or both. The electrodes 12, 18 and their associated firing tips 20, 22 may have a common J-gap configuration as shown, or they may have some other configuration, including multiple ground or ring electrodes and firing tips, to name a few. Spark plug 10 may even be a pre-chamber type spark plug in which the spark gap is surrounded by a pre-chamber cover having an opening for communication with the combustion chamber of the engine.

The center electrode 12 and/or the ground electrode 18 may include a nickel-based outer cladding and a copper-based inner thermally conductive core. Some non-limiting examples of nickel-based materials that may be used with center electrode 12 and/or ground electrode 18 include alloys composed of nickel (Ni), chromium (Cr), iron (Fe), aluminum (Al), manganese (Mn), silicon (Si), and any suitable alloy or combination thereof (e.g., inconel 600, 601). The inner thermally conductive core may be made of pure copper, copper-based alloys, or other materials having suitable thermal conductivity. Of course, other materials are certainly possible, including center and/or ground electrodes having more than one internal conductive core or no internal conductive core at all.

The spark plug housing 16 provides the outer structure for the spark plug 10. Housing 16 includes a main tubular body 28 extending axially between a free end 30 and a tip end 32. The tubular body 28 includes an axial bore 26 for receiving the insulator 14, which may include various steps, seats, etc., and a longitudinal axis L of the tubular body 28_ShellGenerally corresponding to the longitudinal axis L of the spark plug_plug. In one advantageous embodiment, the housing 16 is extruded with various features, such as steps, threads, etc., machined into the extrusion body 28. However, in some embodiments, the body 28 of the housing 16 may be fully machined. The housing 16 may also include other features not shown in the figures, such as a nickel-based or zinc-based coating or cladding, to name a few. Tubular body 28 of housing 16 includes a plurality of regions along the axial extent of housing 16 between free end 30 and tip 32: a threaded region 34, a sealing region 36, a seat region 38, a heat-lock region 40, a hex region 42, and a crimp region 44.

The threaded region 34 is designed to be installed into the engine such that the firing end extends into the combustion chamber. The threaded region 34 may include a plurality of threads 46 (only a few of which are labeled in fig. 1). Threads 46 may be threaded into the cylinder head to provide mechanical retention of the spark plug and electrical ground to the engine. The threaded region 34 generally corresponds to an axial portion of the spark plug housing 16 located within the cylinder head. The sealing region 36 may include a gasket 48, or in some embodiments, may have a tapered configuration or the like, with or without a separate gasket. The sealing region 36 engages a complementary shoulder or other sealing surface in the engine and, according to the illustrated embodiment, compresses the gasket 48 therebetween to form a seal between the spark plug and the engine. The heat-lock region 40 is located between the seat region 38 and the hex region 42 and forms a seal between the outer surface of the insulator 14 and the inner surface of the shell 16. The heat-lock region 40 includes a heat-lock slot 50, the heat-lock slot 50 being generally defined between radially inwardly extending walls 52, 54. The heat-lock region 40 may be created in a heat-lock crimping process that establishes a structurally sound assembly for holding the insulator 14 in a gas-tight manner to help prevent leakage of combustion gases during use.

Fig. 2 is a cross-sectional view of the thread region 34 taken along line 2-2 in fig. 1, and fig. 3 is a cross-sectional view of the heat-lock region 40 taken along line 3-3 in fig. 1. In one advantageous embodiment, the spark plug 10 is an M10 plug, an M8 plug, or even an M6 or smaller plug. Thus, at the threaded region 34 as shown in FIG. 2, the outer diameter OD of the housing_ShellAbout 0.405 inches (e.g., M10) or 0.350 inches (e.g., M8). They are much smaller than the more standard M12 plug, which is about 0.485 inches for M12 plugs. For smaller OD_ShellInsulator diameter OD_InsMust be correspondingly smaller. For M12 plug, OD_InsAbout 0.37 inches, but for M10 and M8 plugs, OD_InsAbout 0.296 inches and 0.25 inches, respectively. In order to maintain the necessary level of dielectric capacity, it may be desirable to reduce the thickness T of the housing_ShellTo accommodate larger or thicker insulators 14. Thus, for the M12 plug, T_ShellAbout 0.0575 inches, but for M10 and M8 plugs, T_ShellAbout 0.0545 inches and 0.05 inches, respectively.

Fig. 3 and the following table show that the effect of the reduction in diameter of the housing 16 is more pronounced in the heat-lock region 40 than in the threaded region 34, as described above.

TABLE 1

As shown, from M12 to M8 plug, OD at threaded region 34_ShellFrom about 0.485 "to about 0.350". Further, from M12 to M8 plug, T at threaded region 34_ShellAlso reduced from about 0.0575 "to about 0.0500". At the heat-lock area 40, although the thickness T_HLApproximately the same between various plug sizes, but from M12 to M8 plugs, the outer diameter OD_HLFrom 0.557 "to 0.494". Advantageously, for the M8 and M10 plugs, the spark plug 10 has a thread region outside diameter OD of between about 0.30 "and 0.425" inches, inclusive_ShellAnd a thermal lock outside diameter OD of between about 0.40 "and 0.50", inclusive_HL. As the plug size decreases, the OD for a given pop-up load or untwist torque load applied to the plug 10_HLCan greatly increase the local stress level. In order to maintain the same (or increase) unscrewing ability and/or spring-up strength, an increase in the strength of the steel material of around 20 to 30% is required. In one embodiment, in order to transition from the M12 size to the M8 size in the above table, an increase in steel strength of 27% is required.

The steel material and the grain structure of the steel material in the body 28 of the housing 16 help to increase the steel strength and provide better structural reinforcement, particularly in the heat lock region 40 where the proportional straight reduction is small and more pronounced. In some advantageous embodiments, the steel material has a higher proportion of carbon than other steels commonly used for spark plug housings. In other advantageous embodiments, the steel material includes a certain amount of co-addition of carbon and boron to increase ductility while increasing strength. Further, in connection with one or more embodiments described herein, the steel material may have a particular grain structure to help impart force resistance. The grain structure described may be imparted via specific manufacturing processes (such as extrusion) that are not feasible for certain steel types that do not have the necessary ductility.

Generally, the steel material used for the spark plug housing 16 includes a balance of iron (Fe), a carbon (C) content of 0.20 to 0.55 weight percent, and a manganese (Mn) content of 0.30 to 1.00 weight percent (all example ranges described herein are inclusive). In a more advantageous embodiment, the carbon content is between 0.45 and 0.50 weight percent, preferably 0.45 weight percent, to obtain the mechanical strength required to at least partially offset the diameter reduction of the heat-lock region 40. Manganese may be added to steel materials to deoxidize the steel melt and may help form manganese sulfide (MnS) with sulfur to facilitate machining while also helping to balance potential brittleness from sulfur. In some embodiments, the steel material used for the housing 16 contains no or trace amounts of nickel (Ni), chromium (Cr), vanadium (V), and molybdenum (Mo).

Advantageously, in some embodiments, the steel material comprises boron (B). The addition of boron can improve strength through hardenability. The amount of boron is preferably 5 to 30 parts per million (ppm). To promote the mechanical strengthening effect of boron, titanium (Ti) and aluminum (Al) or silicon (Si) may be added to fix nitrogen and oxygen in steel.

In a particular embodiment, the steel material has a balance of iron, a carbon content of 0.20 to 0.55 weight percent, a manganese content of 0.30 to 1.00 weight percent, boron in the range of 5 to 30ppm, a titanium content of 0.001 to 0.10 weight percent, and an aluminum content of 0.02 to 0.06 weight percent or a silicon content of 0.01 to 0.30 weight percent. In another particular embodiment, the steel material has a balance of iron, a carbon content of 0.25 to 0.55 weight percent, a manganese content of 0.60 to 0.90 weight percent, boron in a range of 5 to 30ppm, a titanium content of 0.01 to 0.05 weight percent, and an aluminum content of 0.02 to 0.06 weight percent. In yet another embodiment, the steel material has a balance of iron, a carbon content of 0.40 to 0.50 weight percent, a manganese content of 0.60 to 0.90 weight percent, boron in the range of 5 to 30ppm, a titanium content of 0.01 to 0.10 weight percent, and an aluminum content of 0.02 to 0.06 weight percent. In all of these embodiments, the carbon content may be advantageously limited to 0.45 to 0.50 weight percent, particularly with a total addition of 5 to 30ppm boron, to help achieve the mechanical strength necessary to at least partially offset the diameter reduction of the heat-lock region 40.

Taking a typical M12 plug using 1008/1010 steel as an example, the tensile strength is about 300 to 350 MPa. The example materials disclosed above have a tensile strength of 450 to 500MPa to provide greater structural mechanical strength to a reduced diameter region of the shell 16, such as the heat-lock region 40. Additionally, in some embodiments, the steel material may be annealed. For the annealed material, the tensile strength was about 450MPa, and the yield strength was about 280 MPa. For unannealed steels, the tensile strength is about 600 to 700MPa, and the yield strength is about 350 to 400 MPa. If the housing 16 is to be machined rather than manufactured using a deep extrusion process, the steel material does not need to be annealed to maintain its high strength. If an extrusion process is used, it may be necessary to anneal the steel material.

Fig. 4 schematically illustrates an extrusion process that may be used to manufacture the body 28 of the spark plug housing 16. The steel material described herein has the necessary strength to accommodate the reduction in diameter of the various parts (such as at the threaded region 34 and the heat-lock region 40) while still having a quality that accommodates the extrusion process. Extrusion may be advantageous from a manufacturing perspective as well as from a structural perspective of the resulting elongated grain structure of the manufactured shell.

As schematically shown in fig. 4, bulk steel material 60 includes a grain structure 62 and extruded steel material 64 includes a grain structure 66. Each grain structure 62, 66 includes a plurality of pre-extruded grains 68 or post-extruded grains 70, respectively (only a few grains are labeled for clarity). Each grain 68, 70 includes a longitudinal axis L along the longest extent of each grain_GSome of which are schematically shown in fig. 4. Extrusion die 72 helps to produce elongated grain structure 66 in which for each grain 70, most of axis L_GLongitudinal axis (L) of the axial bore with the housing 16_Shell) And (6) aligning. As used herein, the longitudinal axis L of the axial bore with the housing_ShellLongitudinal direction of "aligned" grainsAxis L_GMeaning the grain axis L_GAt the axial hole axis L with the housing_ShellWithin +/-15 of parallel. The elongated grain structure 66 has an axial bore axis L with the housing_ShellAligned majority grain axes L_GThe extruded steel material 64 of (a) may be used to form the metal shell 16 of the spark plug 10. As shown, grains 70 in elongated grain structure 66 have a higher aspect ratio (i.e., the ratio of the longest axis divided by the shortest axis) than grains in grain structure 62 of bulk steel material 60. The elongated grain structure 66 may impart structural benefits, such as when a crimping force F is applied to form a heat-lock region. Since the crimping force F is generally associated with most of the crystal grain axes L_GOrthogonal, therefore, the extruded steel material 64 or extrusion may be less susceptible to stress or fracture.

It should be understood that the foregoing is a description of one or more preferred exemplary embodiments of the invention and that the drawings are examples that are not necessarily drawn to scale. The present invention is not limited to the specific embodiments disclosed herein, but is only limited by the following claims. Furthermore, statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments, as well as various changes and modifications to the disclosed embodiments, will be apparent to persons skilled in the art. All such other embodiments, changes and modifications are intended to fall within the scope of the appended claims.

As used in this specification and claims, the terms "for example," "for instance," "such as," and "like," and the verbs "comprising," "having," "including," and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that listing is not to be considered as excluding other, additional components or items. Unless other terms are used in a context that requires a different interpretation, they should be interpreted using their broadest reasonable meaning.