spark plug

Abstract

Spark plug (10), with: a metal casing (16); an insulator (314) which is at least partially surrounded by the metal shell (16); a central electrode (12) arranged within a bore of the insulator (314); and a ground electrode (18) which is attached to the metal shell (16); wherein the insulator (314) has a first outer surface (366) at least partially along an exposed section (350) and a second outer surface (368) at least partially along a non-exposed section (348), wherein the second outer surface (368) is a curved surface with variable radius, wherein the exposed section (350) includes a section of the insulator (314) extending from an interface (354) between exposed and non-exposed to a tip of the insulator (314), wherein the first outer surface (366) extends between the interface (354) between exposed and non-exposed towards a tip transition section adjacent to a distal end of the insulator (314), wherein the first outer surface (366) and the second outer surface (368) meet at a nasal surface transition (362), wherein at the nose surface transition (370) the first outer surface (366) is arranged at a first angle (A1) with respect to a central axis (C) of the spark plug, and the second outer surface (68) is arranged at a second angle (A2) with respect to the central axis (C) of the spark plug, wherein the first angle (A1) is greater than the second angle (A2), wherein the second angle (A2) is not zero, such that the first surface (366) forms a first conical region within the exposed section (350) of the insulator (314), and wherein the second angle (A2) forms a second conical region within the non-exposed section (348) of the insulator (314), and wherein the nasal surface transition (370) is arranged within the non-exposed section (348) or at the interface (354) between exposed and non-exposed.

Description

AREA

[0001] The present disclosure relates in general to a spark plug and relates in particular to a spark plug having an insulator having an enlarged cone or angular surface along a section where the insulator projects beyond the spark plug casing. BACKGROUND

[0002] During operation, spark plugs are subjected to explosive forces, or pressure forces, generated by the combustion of fuel within the combustion chamber. These explosive forces are exerted against the parts of the spark plug that protrude into the combustion chamber, including the exposed portion of the insulator. The non-exposed portion of the insulator is held in place within a bore in the cylinder head by the spark plug casing. The explosive forces act on the exposed portion of the insulator while the non-exposed portion is held in place, resulting in a bending moment or force on the insulator, which can lead to weakening or breakage.

[0003] Examples of known spark plugs are disclosed in documents DE 10 2007 055 731 A1, EP 2 259 393 A1, EP 2 933 888 A1, JP S60 - 232 679 A and DE 101 19 310 A1. OVERVIEW

[0004] It is the task of revelation to provide an improved spark plug.

[0005] This problem is solved by a spark plug according to claim 1, by a spark plug according to claim 10 and by a spark plug according to claim 11.

[0006] According to one embodiment, a spark plug is provided comprising: a metal casing; an insulator that is at least partially enclosed by the metal casing; a center electrode arranged within a bore of the insulator; and a ground electrode attached to the metal casing. The insulator includes a first outer surface, extending at least partially along an exposed portion, and a second outer surface, extending at least partially along a non-exposed portion. The exposed portion includes a section of the insulator extending from an interface between the exposed and non-exposed portions to a tip or end of the insulator. The first outer surface extends from the interface between the exposed and non-exposed portions to a tip transition section adjacent to a distal end of the insulator.The first outer surface and the second outer surface meet at a nose surface junction. At the nose surface junction, the first outer surface is arranged at a first angle with respect to a central axis of the spark plug, and the second outer surface is arranged at a second angle with respect to the central axis of the spark plug. The first angle is greater than the second angle, and the nose surface junction is located within the non-exposed section or at the interface between exposed and non-exposed areas.

[0007] According to various embodiments, this spark plug may further include any of the following features or any technically feasible combination of some or all of these features: • the second outer surface extends parallel for a large part of the unexposed section; • the second angle is non-zero, such that the first surface forms a first conical region within the exposed section of the insulator, and the second angle forms a second conical region within the non-exposed section of the insulator, according to claim 1; • the second outer surface is a curved surface with a variable radius, according to claim 1; • the insulator includes a third outer surface along the non-exposed section, which is arranged at an angle or at an angle to the central axis of the spark plug at a third angle, wherein the third angle is not equal to the second angle, according to claim 11; • the third angle is smaller than the second angle; • the second angle is smaller than the third angle and the third angle is smaller than the first angle; • a radial distance between the metal casing and the insulator is greater than or equal to 1 mm and greater than a spark gap formed between the center electrode and the ground electrode, the radial distance being measured along a line passing through the nose surface transition, the line being orthogonal to the central axis of the spark plug; • A radial distance between the metal shell and the insulator is at a maximum compared to other radial distances measured between the metal shell and the insulator on the non-exposed section, and the radial distance is measured along a line passing through the nose surface transition and orthogonal to the central axis of the spark plug, and the other radial distances are measured along other lines, each of which is parallel to the line passing through the nose surface transition, the line being orthogonal to the central axis of the spark plug; • The diameter of the insulator decreases with its extension from the unexposed section to the exposed section; • Between an inner surface of the metal casing and the insulator, a gap exists on the non-exposed section; • A nasal surface transition is located at the interface between exposed and non-exposed areas; • the nasal junction has a circumferential or circumferential apex; • the first outer surface is conical between the nasal surface transition and the distal end of the insulator; • The first angle lies between 1° and 30°, inclusive; and / or • The second angle lies between 0° and 15°, inclusive.

[0008] According to claim 10, a spark plug is provided comprising: a metal casing; an insulator that is at least partially surrounded by the metal casing; a center electrode arranged within a bore of the insulator; and a ground electrode attached to the metal casing. The insulator comprises a first outer surface, at least partially along an exposed portion, and a second outer surface, at least partially along a non-exposed portion. The exposed portion comprises a section of the insulator extending from an interface between the exposed and non-exposed portions to a tip of the insulator. The first outer surface and the second outer surface meet at a nasal surface transition. The first outer surface is conical between the nasal surface transition and a distal end of the insulator.At the nose surface transition, the first outer surface is arranged at a first angle with respect to a central axis of the spark plug, and the second outer surface is arranged at a second angle with respect to the central axis of the spark plug. The first angle is larger than the second angle, and the difference between the first and second angles is between 1° and 10°.

[0009] According to claim 11, a spark plug is provided comprising: a metal casing; an insulator that is at least partially surrounded by the metal casing; a center electrode arranged within a bore of the insulator; and a ground electrode attached to the metal casing. The insulator comprises a first outer surface, at least partially along an exposed portion, and a second outer surface, at least partially along a non-exposed portion, and a third outer surface, at least partially along the non-exposed portion. The exposed portion comprises a section of the insulator extending from an interface between the exposed and non-exposed portions to a tip of the insulator.The first outer surface and the second outer surface meet at a first nose surface transition, and the second outer surface and the third outer surface meet at a second nose surface transition. At the first nose surface transition, the first outer surface is arranged at a first angle with respect to a central axis of the spark plug, and the second outer surface is arranged at a second angle with respect to the central axis of the spark plug. The first angle is greater than the second angle, and the second nose surface transition is located within the non-exposed portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Preferred exemplary embodiments of the invention are described below in conjunction with the accompanying drawing, wherein the same reference numerals denote the same elements and wherein: Fig. 1 is a cross-sectional view of an exemplary spark plug as installed in an internal combustion engine (ICE); Fig. 2 a cross-sectional view of an end section of the exemplary spark plug of the Fig. 1 is; Fig. 3 is a diagram that represents forces exerted by the spark plug of the Fig. 1. will be experienced when it is used in an internal combustion engine; Fig. 4 is a graphical representation showing relative magnitudes of compressive forces and tensile stresses experienced by an insulator during a test in which mechanical forces were applied to different insulators on an exposed section with an angular surface; Fig. 5 is a cross-sectional view of a second embodiment of a spark plug with an exemplary insulator; Fig. 6 is a cross-sectional view of a third embodiment of a spark plug with an exemplary insulator; Fig. 7 is a cross-sectional view of a fourth embodiment of a spark plug with an exemplary insulator; and Fig. Figure 8 shows a cross-sectional view of a fifth embodiment of a spark plug with an exemplary insulator. DETAILED DESCRIPTION

[0011] The spark plug described herein includes a conical insulator that incorporates an additional conical or angular surface at or around a point where the insulator projects from the spark plug casing (an exposed section of the insulator). In many embodiments, this additional conical surface includes a surface arranged at an angle greater than that of the insulator surface that does not project from the spark plug casing (a non-exposed section of the insulator). This change in angle at the exposed section along an outer insulator surface allows the insulator to maintain a certain thickness at the non-exposed section within the casing, while enabling the exposed section of the insulator to resist forces resulting from the combustion of gas or gasoline within the combustion chamber.In this way, the insulator can maintain dielectric strength or voltage resistance while helping to mitigate damage caused by explosive forces generated within the combustion chamber.

[0012] When a spark plug is in use within an internal combustion engine, it experiences forces from the combustion of fuel within the combustion chamber, such as explosion forces. These forces act against the insulator (predominantly at the exposed portion of the insulator) and can cause a bending force or moment to be exerted on the insulator, potentially leading to weakening or breakage. To counteract this bending force, the exposed insulator surface (or at least a portion thereof) may be angled or conical with respect to the central axis of the spark plug.The use of an increased or relatively large angle on this exposed insulator face can result in a smaller exposed cross-sectional area, which refers to a cross-section or profiled surface exposed to a gas flow perpendicular to the central axis of the spark plug. In other words, the exposed cross-sectional area coincides with a plane perpendicular to the central axis of the spark plug along the principal force direction of the insulator core nose. Furthermore, the use of a larger angle for this exposed insulator face causes a greater proportion of the explosive forces to be directed upwards in a pressure-exerting manner, counteracting the bending forces experienced by the insulator.Consequently, the larger the angle of the exposed insulator surface, the more the forces are distributed as compression forces and the less as bending forces. Furthermore, it is generally the case that using this larger angle (and consequently a smaller exposed cross-sectional area) can lead to a reduction in the total force applied to the insulator. In at least some embodiments, to maximize this angle without reducing the mechanical, electrical, and thermal performance of the insulator, it is advantageous to maintain the insulator's diameter at all locations within the casing.When providing a set internal bore thickness or diameter of the metal casing, the thickness of the insulator at the non-exposed section should not be oriented at the relatively high angle of the exposed insulator section, as this would necessitate an unacceptably thin insulator, resulting in a corresponding decrease in mechanical, thermal, and especially electrical performance. Outside the grounded metal casing, however, these considerations are secondary with respect to the forces caused by gas movement, and an increase in the angle is desirable. Consequently, at least according to one embodiment, the result is that it is advantageous to provide a change in the angle where the insulator passes through the end of the casing, where the angle of the exposed section of the insulator is greater than at the non-exposed section.

[0013] With reference to Fig. Figure 1 shows a spark plug 10 comprising a center electrode 12, an insulator 14, a metal sheath 16, and a ground electrode 18. The spark plug 10 is shown installed in a cylinder head 20 of an internal combustion engine (ICE). The center electrode 12, which may be a single, one-piece component or may comprise a number of separate components, is arranged or positioned at least partially within an inner bore 22 of the insulator 14, extending along the axial length of the insulator 14. As shown, the inner bore 22 includes one or more internal step sections 24 extending circumferentially around the interior of the bore and designed to accommodate complementary external step sections 26 of the center electrode 12. In the exemplary embodiment of the Fig. In the first embodiment, the inner bore 22 contains only a single internal step or shoulder section 24; however, it is possible that the inner bore contains additional internal step sections at different axial positions along its length, or that the inner bore contains no internal step sections at all. The insulator 14 is arranged at least partially within an inner bore 28 of the metal shell 16, and the inner bore 28 extends along the length of the metal shell and is generally coaxial with the inner bore 22. In the particular embodiment shown, the insulator 14 extends partially from and projects beyond the end of the inner bore 28 of the metal shell, and a tip end of the center electrode 12 extends from and projects beyond the inner bore 22 of the insulator.

[0014] The center electrode 12 protrudes from the casing 16 of the spark plug 10 and includes a tip 13 ( Fig. 2) The tip 13 of the central electrode 12 forms a connection with a corresponding tip 19 ( Fig. 2) a spark gap G at the ground electrode 18. In the embodiment of the Fig. 1 and Fig. 2. Both the center and ground electrode tips 13, 19 are noble metal ignition elements, but this is optional and not required. The ground electrode 18 extends from the end of the metal casing 16 and projects beyond one end of the insulator 14. In this example, the ground electrode 18 forms a J-gap with the center electrode 12, but other ground electrode configurations are possible. The spark gap G is formed such that the spark follows a path between the tip 13 of the center electrode and the tip 19 of the ground electrode.

[0015] The insulator 14 is an elongated and generally cylindrical component made of an electrically insulating material and designed to insulate the center electrode 12 from the metal shell 16, so that high-voltage ignition pulses in the center electrode are directed to the spark gap G. The insulator 14 can comprise any functional ceramic-based material and, in one embodiment, comprises an aluminum oxide (Al₂O₃)-based ceramic material. Aluminum oxide-based ceramics tend to have relatively high mechanical and dielectric strength, as well as high electrical resistance and low dielectric loss, and are known to maintain these properties over a relatively wide temperature range.

[0016] The insulator 14 includes a nose section 30, an intermediate section 32, and an end section 34; however, other configurations or embodiments may be implemented. The intermediate section 32 of the insulator extends axially between an external step 36 and an external locking feature 38. In the Fig. In the particular embodiment shown in Figure 1, the predominant part of the intermediate section 32 is arranged and held within the inner bore 28 of the metal casing 16. The external locking feature 38 can have a diametrically enlarged shape so that an open end or flange 40 of the metal casing can be folded over it during an assembly process for the spark plug, or can be mechanically deformed in some other way to securely hold the insulator 14 in place. The folded flange 40 also holds an annular seal or seal assembly 42 between an outer surface 43 of the insulator 14 and an inner surface of the metal casing 16, thus achieving a certain amount of sealing. In another embodiment, a seal assembly 42 can include one or more metallic seals or seal assemblies and optionally a compacted powder seal.Other features of the intermediate section are of course also possible.

[0017] The end section 34 is located at the end of the insulator 14 opposite the nose section 30, and the end section 34 extends axially between the external locking feature 38 and a distal end 44. In the illustrated embodiment, the end section 34 is quite long; however, it can be shorter and / or can have any number of other features, such as annular ribs. The spark plug 10 is not limited to the illustrated embodiment and can use any combination of other known spark plug components, such as terminal bolts, internal resistors, internal seals, various gasket packages, precious metal elements, etc., to name just a few possibilities. It should be noted that the spark plug 10 is merely a non-limiting example of a spark plug that can use the insulator described herein.The insulator can be used in conjunction with any number of other types of spark plugs and / or ignition devices, including, but not limited to, those incorporating: a J-gap, annular gap, single gap, multiple gap, and / or other types of spark gap arrangements; precious metal tips on both the center and ground electrodes; precious metal tips on only one of the center or ground electrodes; no precious metal tips; multi-piece precious metal tip arrangements; one-piece precious metal tips; precious metal tips in the form of rivets, rods, cylinders, discs, pads, projections, annular rings, annular sleeves, and / or other embodiments; as well as any other suitable spark plug and / or ignition device configuration. The insulator described herein is not limited to any particular spark plug or ignition device.

[0018] Fig. Figure 2 is an enlarged view of the nose section 30 of the spark plug 10. The nose section 30 of the insulator 14 extends in the axial or longitudinal direction between a nose stem section or nose root section 56 on the outer surface 43 of the insulator and a tip 46 of the insulator 14. The nose section 30 includes a non-exposed section 48 and an exposed section 50. The non-exposed section 48 is the portion of the nose section 30 that lies within the bore of the casing 16, and may be that portion of the nose section 30 that extends from the external step 36 to a plane B, as shown in Fig. Figure 2 shows that plane B can be coplanar with the end 52 of the shell 16. The exposed section 50 of the nasal section 30 is that part of the nasal section 30 which extends from the end 52 of the shell 16 (or plane B) to the nasal tip 46 of the nasal section 30. In this way, the exposed section 50 is that part or section of the nasal section 30 which extends beyond the shell 16 into the combustion chamber (when the spark plug 10 is in use). In some cases, the exposed section 50 may be referred to as the 'protrusion' of the nasal section 30. An interface or region between the non-exposed section 48 and the exposed section 50 is referred to as an exposed-non-exposed interface 54. Regarding the exact position orThere can be some slight variations in the exact location of the interface 54 between exposed and non-exposed parts of the insulator. For example, the insulator 14 may bear against the internal sealing pack, which compresses over time, such that the location of the interface 54 between exposed and non-exposed parts on the insulator, or its alignment with it, changes slightly. To address this, instead of assuming that the interface 54 between exposed and non-exposed parts is a planar boundary located exactly between the exposed and non-exposed sections 50, 48 of the insulator, directly at the distal end 52 of the shell 16, the interface 54 between exposed and non-exposed parts is assumed to be a small axially extending region or area on the insulator that is within a tolerance (e.g.,± one millimeter, ± two millimeters) of plane B is arranged along the central axis C, with plane B being coplanar with the end 52 of the shell 16. Unless otherwise specified, the tolerance used here is ± two millimeters. Accordingly, a nasal surface transition 70 can occur at an interface 54 between exposed and non-exposed areas, located anywhere within two millimeters of the distal end 52 of the shell 16. In a particular embodiment, the nasal surface transition occurs at an interface 54 between exposed and non-exposed areas located 1.75 mm below the distal end 52 of the shell 16 (closer to the center of the combustion chamber). In another embodiment, which is shown in more detail in the figures, the nasal surface transition 70 occurs at the interface 54 between exposed and non-exposed areas directly at the distal end 52 of the shell 16.

[0019] A radial distance L between the inner surface of the casing 16 and the outer surface of the insulator 14 (such as at the interface 54 between exposed and non-exposed areas or at the nose surface transition 70) can be greater than 1 mm (millimeters), or in some embodiments, equal to 1 mm. In addition, a radial distance L applied at the interface 54 between exposed and non-exposed areas (or at the nose surface transition 70) can, in at least some embodiments, be greater than the spark gap G. The radial distance L can be greatest at the interface 54 between exposed and non-exposed areas (or at the end 52 of the casing 16) compared to a radial distance applied at any other point of the non-exposed section 48 along an outer surface of the insulator.Furthermore, the radial distance L, compared to any other radial distances between the ground electrode and the insulator at any other point of the exposed section 50 along an outer face of the insulator, may be smallest at the interface 54 between exposed and non-exposed areas (or the nose surface transition 70). In such a case, these radial distances are measured along an axis orthogonal to the central axis C (i.e., along a radial direction with respect to the central axis C). Although the radial distance is typically used to describe a distance between an inner face of the metal shell 16 and an outer face of the insulator 14, there may be axial locations where the metal shell 16 is not present, such as axial locations corresponding to the exposed section 50.In such cases, the radial distance in a radial direction between an outer surface of the insulator 14 and an inner surface of the ground electrode 18 can be measured.

[0020] As it is in Fig. As shown in Figure 2, the radial distance L at the interface 54 between exposed and non-exposed areas (or the nose surface transition 70) is not at a local minimum; that is, the radial distance L at the interface 54 between exposed and non-exposed areas (or at the nose surface transition 70) is not smaller than both an adjacent non-exposed radial distance and an adjacent exposed radial distance. The adjacent non-exposed radial distance is a radial distance (i.e., a distance measured in a radial direction with respect to the central axis C) measured between an inner surface of the shell 16 and an outer surface of the insulator 14, at a point adjacent to the interface 54 between exposed and non-exposed areas and within the non-exposed section 48.The adjacent exposed radial distance is a radial distance that is set between an inner surface of the ground electrode 18 and an outer surface of the insulator 14, at a point adjacent to the interface 54 between exposed and non-exposed and within the exposed section 50.

[0021] The adjacent non-exposed radial distance and the adjacent exposed radial distance are measured along separate lines, each extending radially with respect to the central axis C. In addition, the insulator 14 includes a diameter D that decreases (or at least does not increase or remain constant) with the extension of the insulator from the non-exposed section (and / or the nasal trunk section 56) to the exposed section (and / or the nasal tip 46).

[0022] The exposed section 50 of the nose section 30 of the spark plug 10 is exposed to the combustion chamber and to thermal and mechanical forces within it. The thickness of the insulator 14 can be adjusted at any point to meet the mechanical strength, thermal behavior, and dielectric strength or dielectric strength requirements of the system in which the insulator 14 (or the spark plug 10) is to be used. In many cases, adjusting the thickness of the insulator 14 results in a trade-off between the dielectric strength of the insulator 14 (as at sections located within the casing 16) and the forces generated by gas movement acting on the nose section 30, particularly at the exposed section 50 of the nose section 30. In some cases, using a thicker insulator 14 allows the insulator 14 to withstand higher mechanical and electrical loads or dielectric strength.While it resists stresses, it also leads to an increased exposed cross-sectional area, which can result in increased bending forces because the area exposed to combustion forces is larger. The exposed cross-sectional area refers to that cross-sectional or profile area of ​​the exposed section 50 which is attached to (or cut off from) the center of the insulator 14, viewed in the radial direction, as in the view described in . Fig. 2 is shown.

[0023] The extent to which the nasal section 30 extends axially or projects beyond the end of the metal sheath 16 may be greater or lesser than that shown in Fig. 1 is shown. As in Fig. As shown in Figure 2, the nose section 30 can be conical (or substantially conical) with respect to the central axis C of the spark plug 10. The central axis C of the spark plug 10 can be located with respect to the mean longitudinal axis of the inner bore 28 of the casing 16, or with respect to the inner bore 22 of the insulator 14. In particular, both the non-exposed section 48 and the exposed section 50 can be conical (or substantially conical). This conical shape is advantageous, especially with respect to the exposed section 50, because it can provide an improved response to applied bending forces.In other embodiments, however, the non-exposed section 48 and the exposed section 50 may each or both have different configurations, such as a fixed-radius curvature, a variable-radius curvature, a multi-part shape, or any combination thereof. Some of these different embodiments are discussed in greater detail below, particularly with regard to the . Fig. 5 to 8.

[0024] The non-exposed section 48 of the nose section 30 includes a nose stem section 56 and a non-exposed body section 58. The nose stem section 56 serves as a transition from the external step (or sealing pack seat) 36 of the insulator 14 and the non-exposed body section 58, and may serve as a first end of the nose section 30. The external step 36 may be or include a surface that serves to abut an internal sealing pack 60, which seals the inner bore 28 of the casing 16 to prevent gases from the combustion chamber from entering the inner bore 28 when the spark plug 10 is in use.

[0025] The exposed section 50 of the nose section 30 comprises the nose tip 46, a tip transition section 62, and an exposed body section 64. The nose section 46 may include a surface that is orthogonal (or substantially orthogonal) to the central axis C. The nose tip 46 projects into the combustion chamber and beyond the shell 16. In many cases, this projection allows a well-formed spark to be generated at the spark gap G to provide a suitable ignition source for the fuel-air mixture in the combustion chamber. The surface of the exposed body section 64 transitions into the nose tip 46 at the tip transition section 62, which is a rounded or radiused surface located between the exposed body section 64 and the nose tip 46.In other embodiments, the tip transition section can be omitted, and a hard edge can be formed between the exposed body section 64 and the nose tip 46. Other implementations of the nose tip 46 and the tip transition section 62 can be used.

[0026] The nose section 30 has a first outer surface 66 and a second outer surface 68. In many embodiments, the first outer surface 66 includes at least a portion of the exposed body section 64, and the second outer surface 68 includes at least a portion of the non-exposed body section 58. In the illustrated embodiment, the first outer surface 66 coincides with the exposed body section 64, and the second outer surface 68 coincides with the exposed body section 58. Furthermore, the first outer surface 66 (and also the exposed body section 64) is angled or inclined at a first angle A1 with respect to the central axis C of the spark plug 10 and can therefore be referred to as the first angled surface.Similarly, the second outer surface 68 (and also the non-exposed body section 58) is angled or inclined at a second angle A2 with respect to the central axis C of the spark plug 10, and can therefore be referred to as a second angled surface. At least in this embodiment, the first angle A1 can be referred to as an exposed nose angle A1, and the second angle A2 can be referred to as a non-exposed nose angle A2. As shown in the illustrated embodiment, the exposed nose angle A1 is larger than the non-exposed nose angle A2, and consequently, the nose section 30 incorporates a positive angle change ΔA. 1,2 The angle change ΔA 1,2 The difference between the exposed nasal angle (or first angle) A1 and the non-exposed nasal angle (or second angle) A2 can be expressed as (A1 - A2). This change in angle ΔA 1,2can be positive, as shown in the illustrated embodiment. Generally, the angle of the insulator surface increases at the transition or interface 54 from the non-exposed region to the exposed region, and this transition is largely coplanar with the end 52 of the shell 16. Advantageously, in many embodiments, neither the first outer surface 66 nor the second outer surface 68 is parallel to the central axis C.

[0027] As discussed above, the nasal section 30 of the insulator 14 is tapered or conical at both the non-exposed section 48 and the exposed section 50. The exposed body section 64 (or the exposed section 50) is shown with a continuous and uniform conical shape along its axial extent and is angled below the exposed nasal angle A1. Similarly, the non-exposed body section 58 (or the non-exposed section 48) is shown with a continuous and uniform conical shape along its axial extent and is angled below the non-exposed nasal angle A2. In many embodiments, the non-exposed body section 48 is not tangential with respect to the exposed body section 50.This arrangement can maximize an insulator volume at the non-exposed section 48 while improving flexural strength at the exposed section 50, particularly compared with exposed sections having exposed surfaces that are generally parallel or aligned with the central axis C.

[0028] The angle of the nasal section 30 transitions abruptly at the interface 54 between exposed and non-exposed areas from the exposed nasal angle A1 to the non-exposed nasal angle A2, and this transition can be referred to as a nasal surface transition 70. Accordingly, in the illustrated embodiment, the interface 54 between exposed and non-exposed areas coincides with the nasal surface transition 70 and includes a circumferential apex (or sharp edge). In many embodiments, this circumferential apex extends outwards or is convex with respect to the outer surface of the insulator, in contrast to transitions at the interface between exposed and non-exposed areas, which have a more concave configuration.In other embodiments, the nasal surface transition 70 between the exposed nasal angle A1 and the non-exposed nasal angle A2 can be gradual and can, in particular, be provided with a radius or be rounded. Furthermore, in alternative embodiments, the nasal surface transition 70 between the exposed nasal angle A1 and the non-exposed nasal angle A2 can include a concave groove, a chamfer, multiple sharp edges, or the like. In other embodiments, a different nasal surface transition can occur at a point other than the interface 54 between the exposed and non-exposed areas. For example, a nasal surface transition can occur at a point within the sheath 16 and / or at a point within the non-exposed body section 58. Or a nasal surface transition can occur at a point outside the sheath 16 and at a point within the exposed body section 64.And in other embodiments, a variety of nose surface transitions can be used.

[0029] In some cases, the non-exposed nose angle A2 is narrow or small (and in some cases zero), so that the thickness of the insulator 14 at the non-exposed section 48 can be sufficiently thick to withstand forces exerted during engine operation, as well as to maintain dielectric integrity between the ground electrode 18 and the center electrode 12 to prevent electrical failure of the spark plug 10. Furthermore, the length of the non-exposed section 48 can be extended in various embodiments, and in such cases, using a small (or zero) non-exposed nose angle A2 along the non-exposed body section 58 can maintain sufficient insulator thickness.Furthermore, other requirements can be taken into account when setting or selecting the insulator thickness and / or the non-exposed nose angle A2, including the sleeve thread diameter.

[0030] With reference to Fig. Figure 3 shows a diagram illustrating the forces that can be experienced by the spark plug 10 when used in an internal combustion engine. A force F, such as an explosive force generated by the combustion of an air-fuel mixture, can be exerted on the exposed section 50 on the insulator 14. This force F is equal to the reaction force F. react , which can be decomposed into its orthogonal components, including a compression force F comp and a reaction normal force F norm In many cases, the magnitude of the compression force F compdepending on the angle A1 of the exposed body section 64, and in particular the magnitude of the compression force F comp This occurs when angle A1 increases. Furthermore, in such cases, this greater compression force F acts. comp , to reduce the traction force on the nasal trunk section 56 ( Fig. 2) is exerted. As mentioned above, this additional conical shape (or first outer surface 66) on the exposed section 50 of the nose section 30 allows the exposed nose section 50 to be angled at a larger (or more significant) angle relative to the non-exposed section 60, thereby enabling the insulator 14 to maintain its dielectric strength or dielectric strength at sections within the shell 16, while simultaneously reducing the likelihood of possible damage to the insulator 14 (as at the nose stem section 56) due to explosive forces experienced by the exposed section 50.

[0031] With reference to Fig. Figure 4 shows a graphic representation of 100, which represents the compressive forces F. compand represents tensile stresses experienced by the insulator 14 during a test in which mechanical forces are applied to the insulator 14 at the exposed section 50. The graphical representation 100 includes an x-axis 102, which represents the first angle A1 of the exposed body section 64, and a first y-axis 104, which represents the compressive force F. comp The first y-axis represents a proportion of the applied force F, and a second y-axis 106 represents the maximum tensile stress, compared to simulations where the first angle A1 is zero. The dashed line 108 corresponds to the first y-axis 104, and the solid line 110 corresponds to the second y-axis 106. As mentioned above, the tensile stress is in many cases a function of the compressive force F. comp , which is ultimately a function of the first angle A1. Line 108 represents that a maximum value of F compThe minimum tensile stress on the nose stem section 56 is experienced when the first angle A1 is at or around 45°. Furthermore, the minimum tensile stress is experienced when the first angle A1 is at or around 45°. In one embodiment, the insulator 14 includes a first outer surface angled at a first angle A1 between 30° and 50°. In another embodiment, the insulator 14 includes a first outer surface angled at a first angle A1 between 40° and 50°. In yet another embodiment, the insulator 14 includes a first outer surface angled at a first angle A1 of 45°. Additionally, in one embodiment, the insulator 14 includes an angle change ΔA. 1,2 , which lies between 1° and 30°. In yet another embodiment, the insulator 14 incorporates an angular change ΔA 1,2, which lies between 1° and 20°. In yet another embodiment, the insulator 14 incorporates an angular change ΔA 1,2 , which lies between 1° and 10°. Although providing the first angle A1 between 30° and 50° can help to minimize tensile stress, it may be advantageous to maintain a larger diameter on the exposed section to give the insulator 14 greater strength. Accordingly, in some embodiments, the first angle A1 may lie between 1° and 30°, inclusive, and preferably between 5° and 20°, inclusive. Additionally or alternatively, in some embodiments, the second angle A2 may lie between 0° and 15°, inclusive, and preferably between 0° and 12°, inclusive.

[0032] As mentioned above, the exposed cross-sectional area is a function of the first angle A1, such that when the first angle A1 increases, the exposed cross-sectional area decreases. As mentioned above, the exposed cross-sectional area refers to a cross-sectional or profile area experienced by a gas flow that is orthogonal to the central axis of the spark plug. In many cases, the force F experienced by the insulator 14 is reduced when the exposed cross-sectional area is reduced. Consequently, increasing the first angle (or exposed nose angle) A1 (and thus reducing the exposed cross-sectional area) reduces the experienced force F.

[0033] With reference to the Fig. Figures 5 to 8 show further embodiments of an insulator 314, 414, 514, 614, which can be used in conjunction with the spark plug 10. These insulators 314, 414, 514, 614 may be the same as or similar to the insulator 14, provided that such a discussion of the insulator 14 does not contradict the discussion of insulators 314, 414, 514, 614 below.

[0034] With particular reference to Fig. Figure 5 shows an insulator 314 that can be used with the spark plug 10. The insulator 314 includes a nasal section 330, and the nasal section 330 includes a non-exposed section 348 and an exposed section 350. The exposed section 350 of the insulator 314 includes a nasal tip 346, a nasal transition section 362, and an exposed body section 364. The non-exposed section 348 includes a non-exposed body section 358, which has a variable-radius curve. As used herein, a “variable-radius curve” refers to a surface that is curved with different or varying radii, such as in an elliptical or non-circular manner. Furthermore, the non-exposed body section 358 gradually transitions into the nasal stem section 356, which then transitions into the external stage 336.

[0035] The nasal section 330 includes an interface 354 between exposed and non-exposed areas, in which a nasal surface transition 370 is located between a first outer surface 366 and a second outer surface 368. The first outer surface 366 can be angled or inclined at a first angle A1, and the second outer surface 368 can be angled or beveled at a second angle A2. It should be noted that, at least in the illustrated embodiment, the first outer surface 366 coincides with (and consequently partially contains) the exposed body section 364, and that the second outer surface 368 coincides with (and consequently partially contains) the non-exposed body section 358.Accordingly, in this embodiment, the second outer surface 368 at the nasal surface transition 370 is parallel to the central axis C, and the second outer surface 368 is angled at a non-zero angle at a section located near the nasal stem section 356. In other embodiments, however, the nasal surface transition 370 may be located within either the non-exposed section 348 or within the exposed section 350. In such cases, the first outer surface 366 or the second outer surface 368 may include the interface 354 between the exposed and non-exposed areas.

[0036] With particular reference to Fig. Figure 6 shows an insulator 414 that can be used with the spark plug 10. The insulator 414 includes a nose section 430, and the nose section 430 includes a non-exposed section 448 and an exposed section 450. The non-exposed section 448 includes a non-exposed body section 458 and a nose stem section 456. The exposed section 450 includes a nose tip 446, a tip transition section 462, and an exposed body section 464. The exposed body section 464 can be angled or inclined at a first angle A1. The exposed section 450 includes a first outer surface 466 that is inclined at the first angle, which can be referred to as an exposed nose angle A1, at least in this embodiment.

[0037] The nasal section 430 includes an interface 454 between exposed and non-exposed areas, in which a nasal surface transition 470 is located between the first outer surface 466 and a second outer surface 468. The first outer surface 466 can be angled or inclined at the first angle A1, and the second outer surface 468 can be angled or inclined at a second angle A2. It should be noted that, at least in the embodiment shown, the first outer surface 466 coincides with (and consequently at least partially includes) the exposed body section 464, and that the second outer surface 468 coincides with (and consequently at least partially includes) the non-exposed body section 458. In other embodiments, however, the nasal surface transition 470 can be arranged within either the non-exposed section 448 or the exposed section 450.In such cases, the first outer surface 466 or the second outer surface 468 can include the interface 454 between exposed and non-exposed areas. In this embodiment, the second outer surface 468 transitions gradually into the nasal stem section 456. Furthermore, the nasal stem section 456 gradually transitions into an external step 436 and includes a surface 457 with a radius of curvature larger than that of the insulator 14. Fig. 2.

[0038] With particular reference to Fig. Figure 7 shows an insulator 514 that can be used with the spark plug 10. The insulator 514 includes a non-exposed section 548 and an exposed section 550. The exposed section 550 includes a nose tip 546 and an exposed body section 564. The exposed body section 564 may be chamfered or angled at a first angle A1. The exposed section 550 lacks a tip transition section (or is formed without one). However, in other embodiments, a tip transition section may be included between the nose tip 546 and the exposed body section 564. The exposed section 550 includes a first outer surface 566 that is chamfered at the first angle A1 (also referred to as an exposed nose angle in this embodiment).

[0039] The non-exposed section 548 includes a non-exposed body section 558 and a nasal trunk section 556. The non-exposed body section 558 includes a second outer surface (or first non-exposed surface) 568 and a third outer surface (or second non-exposed surface) 572. The second outer surface 568 forms a first nasal surface transition 570 with the first outer surface 566 at an exposed-non-exposed interface 554. Furthermore, the second outer surface 568 forms a second nasal surface transition 574 with the third outer surface 572. Consequently, the second nasal surface transition 574 lies along a plane D that is orthogonal to the central axis C and is located within the non-exposed section 548 of the insulator 514.The second outer surface 568 can be a surface of the non-exposed section 548 located between the exposed and non-exposed interface 554 (or the first nasal surface transition 570) and the second nasal surface transition 574. The third outer surface 572 can be a surface of the non-exposed section 548 located between the second nasal surface transition 574 and a nasal stem section 556. In other embodiments, the first nasal surface transition 570 can be located within the exposed section 550, such that a surface (under a second angle A2 (also referred to as a first exposed nasal angle in this embodiment)) between the first and second nasal surface transitions 570, 574 includes at least a portion of the non-exposed section 548 and at least a portion of the exposed section 550.

[0040] The second outer surface 568 can be angled or inclined at the second angle A2, and the third outer surface 572 can be angled, beveled, or inclined at a third angle A3 (also referred to as a second non-exposing nose angle in this embodiment). In an embodiment such as that shown in the illustrated embodiment of the Fig. As shown in Figure 8, the angles of the insulator can be constructed according to the following formula: A1 > A2 > A3. In a special configuration, the third angle A3 can be zero or parallel to the central axis C. In another embodiment, the angles of the insulator can be constructed as follows: A1 > A3 > A2. The first nose surface transition 570 and / or the second nose surface transition 574 can include a circumferential vertex (or a sharp edge), or can include a rounded or radiused edge, a fillet, a chamfer, multiple sharp edges, or the like.

[0041] With reference to Fig. Figure 8 shows an insulator 614 that can be used with the spark plug 10. The insulator 614 includes a non-exposed section 648 and an exposed section 650. The exposed section 650 of the insulator 614 includes a nose tip 646, a tip transition section 662, and an exposed body section 664. The tip transition section 662 includes a rounded or radiused surface that forms a transition between the nose tip 646 and the exposed body section 664. The non-exposed section 648 includes a non-exposed body section 658 that runs parallel with respect to the central axis C. Furthermore, the non-exposed body section 658 gradually transitions into the nose stem section 656, which then transitions into the external stage 636.

[0042] The nasal section 30 includes an interface 654 between exposed and non-exposed areas, in which a nasal surface transition 670 is located between a first outer surface 666 and a second outer surface 668. The first outer surface 666 can be angled or inclined at a first angle A1, and the second outer surface 668 can be angled or inclined at a second angle A2. It should be noted that, at least in the illustrated embodiment, the first outer surface 666 coincides with (and consequently at least partially includes) the exposed body section 664, and that the second outer surface 668 coincides with (and consequently at least partially includes) the exposed body section 658. Therefore, in this embodiment, the second outer surface 668 is parallel to the central axis C.In other embodiments, however, the nose surface transition 670 can be arranged within either the non-exposed section 648 or the exposed section 650. In such cases, the first outer surface 666 or the second outer surface 668 can include the interface 654 between exposed and non-exposed areas. In the embodiment of the . Fig. 8 The second outer surface 668 is a continuously curved section such that the radius varies continuously along this section of the insulator. Consequently, the second angle A2 can vary continuously along the second outer surface 668 from the nose surface transition 670 over the remaining part of the core nose section up past the sealing pack 60.

[0043] It is understood that the foregoing description is not a definition of the invention, but rather a description of one or more preferred exemplary embodiments of the invention. The invention is not limited to the embodiment(s) disclosed herein, but is defined exclusively by the following claims. Furthermore, the statements contained in the foregoing description refer to specific embodiments and are not to be construed as limiting the scope of protection of the invention or the definition of terms used in the claims, unless a term or phrase is expressly defined above.

[0044] As used in this specification and the claims, the terms "for example," "e.g.," "such as," "as," and "equal," as well as the verbs "to exhibit," "to contain," and their other verb forms, when used in conjunction with a list of one or more components or other elements, are each to be interpreted as open-ended or non-exhaustive, meaning that the list is not to be considered as excluding other, additional components or elements. Other terms are to be interpreted according to their broadest reasonable meaning unless they are used in a context that requires a different interpretation. In addition, the term "and / or" is to be understood as an inclusive OR. Thus, for example, the phrase "A, B, and / or C" is to be understood as covering all of the following alternatives: "A"; "B"; "C"; "A and B"; "A and C"; "B and C"; and "A, B, and C."

Claims

[1] Spark plug (10), with: a metal shell (16); an insulator (314) at least partially surrounded by the metal shell (16); a center electrode (12) disposed within a bore of the insulator (314); and a ground electrode (18) attached to the metal shell (16); wherein the insulator (314) has a first outer surface (366) at least partially along an exposed portion (350), and a second outer surface (368) at least partially along a non-exposed portion (348), the second outer surface (368) being a variable radius curved surface, the exposed portion (350) including a portion of the insulator (314) extending from an exposed-non-exposed interface (354) to a tip of the insulator (314), wherein the first outer surface (366) extends between the exposed and non-exposed interface (354) to a tip transition portion adjacent a distal end of the insulator (314), wherein the first outer surface (366) and the second outer surface (368) meet at a nose surface transition (362), wherein at the nose surface transition (370) the first outer surface (366) is arranged at a first angle (A1) with respect to a central axis (C) of the spark plug, and the second outer surface (68) is arranged at a second angle (A2) with respect to the central axis (C) of the spark plug, the first angle (A1) being greater than the second angle (A2), wherein the second angle (A2) is not zero, such that the first surface (366) forms a first conical region within the exposed portion (350) of the insulator (314), and wherein the second angle (A2) forms a second conical region within the non-exposed portion (348) of the insulator (314), and wherein the nasal surface transition (370) is disposed within the non-exposed portion (348) or at the interface (354) between exposed and non-exposed. [2] Spark plug according to claim 1, wherein a radial distance between the metal shell (16) and the insulator (314) is greater than or equal to 1 mm and is greater than a spark gap (G) formed between the center electrode (12) and the ground electrode (18), the radial distance being measured along a line passing through the nose surface transition (370), the line being orthogonal to the central axis (C) of the spark plug (10). [3] The spark plug of claim 1, wherein a radial distance between the metal shell (16) and the insulator (14) is at a maximum when compared to other radial distances between the metal shell (16) and the insulator (14) at the non-exposed portion (348), the radial distance being measured along a line passing through the nose surface transition (370) and being orthogonal to the central axis (C) of the spark plug (10), and the other radial distances being measured along other lines, each of which is parallel to the line passing through the nose surface transition (370) and being orthogonal to the central axis (C) of the spark plug (10). [4] The spark plug of claim 1, wherein a diameter of the insulator (314) decreases as it extends from the non-exposed portion (348) toward the exposed portion (350). [5] The spark plug according to claim 1, wherein a gap is present between an inner surface of the metal shell (16) and the insulator (314) at the non-exposed portion (348). [6] Spark plug according to claim 1, wherein the nose surface transition (370) has a circumferential apex. [7] The spark plug of claim 1, wherein the first outer surface (366) is tapered between the nose surface transition (370) and the distal end of the insulator (314). [8] Spark plug according to claim 1, wherein the first angle (A1) is between 1° and 30°, inclusive. [9] Spark plug according to claim 1, wherein the second angle (A2) is between greater than 0° and less than or equal to 15°. [10] Spark plug (10), with: a metal shell (16); an insulator (314) at least partially surrounded by the metal shell (16); a center electrode (12) disposed within a bore of the insulator (314); and a ground electrode (18) attached to the metal shell (16); wherein the insulator (314) has a first outer surface (366) at least partially along an exposed portion (350) and a second outer surface (368) at least partially along a non-exposed portion (348), wherein the exposed portion (350) includes a portion of the insulator (314) extending from an exposed-non-exposed interface (354) to a tip of the insulator (314), wherein the first outer surface (366) and the second outer surface (368) meet at a nose surface transition (370), wherein the first outer surface (366) between the nose surface transition (370) and a distal end of the insulator (314) is conical, wherein at the nose surface transition (370) the first outer surface (366) is arranged at a first angle (A1) with respect to a central axis (C) of the spark plug (10), and the second outer surface (368) is arranged at a second angle (A2) not equal to zero with respect to the central axis (C) of the spark plug (10), and wherein the first angle (A1) is greater than the second angle (A2) and wherein a difference between the first angle (A1) and the second angle (A2) is between 1° and 10°, inclusive. [11] Spark plug, with: a metal shell (16); an insulator (514) at least partially surrounded by the metal shell (16); a center electrode (12) disposed within a bore of the insulator (514); and a ground electrode (18) attached to the metal shell (16); wherein the insulator (514) has a first outer surface (566) at least partially along an exposed portion (550), and a second outer surface (568) at least partially along a non-exposed portion (548), and a third outer surface (572) at least partially along the non-exposed portion (548), wherein the exposed portion (550) includes a portion of the insulator (514) extending from an exposed-non-exposed interface (554) to a tip of the insulator (14), wherein the first outer surface (566) and the second outer surface (568) meet at a first nose surface transition (570), and wherein the second outer surface (568) and the third outer surface (572) meet at a second nose surface transition (574), wherein at the first nose surface transition (570) the first outer surface (566) is arranged at a first angle (A1) with respect to a central axis (C) of the spark plug (10) and the second outer surface (568) is arranged at a second angle (A2) with respect to the central axis (C) of the spark plug (10), and where the first angle (A1) is greater than the second angle (A2), wherein the third outer surface (572) is oriented at a third angle (A3) with respect to the central axis (C) of the spark plug (10), wherein the first angle (A1) is not zero, such that the first surface (566) forms a first conical region within the exposed portion (550) of the insulator (14), and wherein the second angle (A2) forms a second conical region within the non-exposed portion (548) of the insulator (14), where the third angle (A3) is not equal to the second angle (A2), and wherein the second nose surface transition (574) is disposed within the non-exposed portion (548). [12] Spark plug according to claim 11, wherein the third angle (A3) is smaller than the second angle (A2). [13] Spark plug according to claim 11, wherein the second angle (A2) is smaller than the third angle (A3) and the third angle (A3) is smaller than the first angle (A1).

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