spark plug

Abstract

A spark plug (1, 201, 301, 401, 501, 601) comprising: a cylindrical insulator (10, 210, 410, 510) with an axially extending axial hole (20, 220, 520) and a rearwardly directed surface (22A) formed in the axial hole (20, 220, 520); a cylindrical metal casing (30, 330, 630) arranged on an outer periphery of the insulator (10, 210, 410, 510); and a central electrode (50) arranged at a front end in the axial hole (20, 220, 520), wherein the central electrode (50) has a large-diameter section (52) with an outer diameter that is the largest in the central electrode (50), the large-diameter section (52) being held at the rearward-facing surface (22A), and wherein the metal shell (30, 330, 630) has a diameter-enlarged section (36) at a rear end with respect to the central electrode (50),wherein the enlarged diameter section (36) has an inner diameter that is enlarged towards the rear end, wherein the insulator (10, 210, 410, 510) has a first section (70, 270, 470, 570) which is a section of the insulator (10, 210, 410, 510) in a region (AR) from a rear end of the rearward-facing surface (22A) to a front end of the enlarged diameter section (36), the first section (70, 270, 470, 570) having a thickness (X1) which is the greatest in the region (AR), and is arranged at least on an outer periphery of the large-diameter section (52), the insulator (10, 210, 410, 510) being connected to the metal shell (30, 330, 630) by a seal (45) is held at the front face with respect to the first section (70, 270, 470, 570) and the insulator (10, 210, 410, 510) has a second section (80, 280, 480, 580) at the rear end face with respect to the first section (70, 270, 470, 570) in the area (AR),wherein the second section (80, 280, 480, 580) has an outer diameter (B) that is smaller than an outer diameter (A) of the first section (70, 270, 470, 570), wherein the first section (70, 270, 470, 570) is arranged at least at an outer periphery of an entire region in the axial direction of a section of the central electrode (50) that is arranged in the region (AR).

Description

Technical area

[0001] The present invention relates to a spark plug. Technical background

[0002] A spark plug used for an internal combustion engine (engine), such as the spark plug disclosed in PTL 1, typically comprises a cylindrical insulator with an axial hole extending in the axial direction, a cylindrical metal shell provided at an outer periphery of the insulator, and a rod-shaped center electrode extending in the axial direction. In the spark plug disclosed in PTL 1, the center electrode is located at a front end face in the axial hole formed in the insulator, and a ground electrode is provided at a front end face of the metal shell, so that a spark discharge is generated between the center electrode and the ground electrode.

[0003] In a spark plug of this type, a large-diameter section is provided in a predetermined area of ​​the center electrode in the axial direction; the outer diameter of this section is larger than that of the other section. Additionally, the axial hole of the insulator has a rearward-facing surface. The center electrode, positioned within the axial hole, is arranged so that the large-diameter section is held against this rearward-facing surface. Citation list - Patent literature

[0004] PTL 1: Published Japanese patent application no. 2019-3721 Summary of the invention: Technical problem

[0005] In recent years, engines with increased turbocharging, higher compression, etc., have been proposed to improve fuel economy and comply with environmental regulations. When using this type of engine, the pressure in the combustion chamber is increased during operation, which necessitates an increased spark discharge voltage to generate a spark discharge. However, increasing the spark discharge voltage increases the likelihood of a spark penetrating the insulator (spark breakdown) between the large-diameter section of the center electrode and the metal casing, potentially disrupting a normal spark discharge.

[0006] One method for suppressing such sparking is to increase the thickness of the insulator to improve its voltage resistance. However, simply increasing the insulator thickness increases the diameter of the metal casing by the same amount as the increase in insulator thickness, consequently increasing the overall size of the candle.

[0007] The present invention was made to solve at least one of the problems described above, and an object of the invention is to provide a spark plug that is able to further suppress a spark penetrating an insulator while suppressing an increase in the diameter of a metal casing. Solution to the problem

[0008] A spark plug according to one aspect of the present invention comprises a cylindrical insulator with an axially extending hole and a rearward-facing surface formed in the axial hole; a cylindrical metal casing arranged on an outer periphery of the insulator; and a central electrode located at a front end in the axial hole, wherein the central electrode has a large-diameter section with an outer diameter which is the largest in the central electrode, wherein the large-diameter section is held against the rearward-facing surface, and wherein the metal shell has a section with an increased diameter on a rear end face in relation to the central electrode, wherein the section with an increased diameter has an inner diameter that is increased towards the rear end face, wherein the insulator has a first section which is part of the insulator in an area from a rear end of the rearward-facing surface to a front end of the section enlarged in diameter, the first section has a thickness that is the greatest in the area, and is located at least on an outer periphery of the large-diameter section, the insulator is held to the metal casing by a seal at the front end in relation to the first section and The insulator has a second section on the rear end face relative to the first section in the area, the second section having an outer diameter that is smaller than the outer diameter of the first section.

[0009] In the spark plug, the first section is located on one side close to the seal (a component that positions the insulator while being supported by the metal casing), and the second section is located on a side farther from the seal than the first section. Furthermore, the first section is positioned at the outer periphery of the large-diameter center electrode section and is thicker than the second section.

[0010] With such a configuration, the effect of suppressing spark penetration can be enhanced near the large diameter section, where a countermeasure against spark penetration is more necessary.

[0011] Furthermore, the side near the seal has the property that "the insulator is held more stably and its position relative to the metal casing is hardly displaced." Therefore, this property can be effectively utilized when positioning the first section on the side near the seal. That is, on the side near the seal, even though the first section has a relatively large outer diameter, and therefore the gap between the outer periphery of the insulator (the outer periphery of the first section) and the inner circumferential surface of the metal casing is relatively small, positional displacement of the insulator is suppressed, and therefore the insulator hardly comes into contact with the metal casing.Therefore, on the side near the seal, by using both the structure in which the position of the insulator is hardly displaced, and the first section together, both the prevention of contact and the suppression of spark penetration can be ensured.

[0012] On the side facing away from the seal, the second section has a relatively small outer diameter, ensuring a larger gap between the outer periphery of the insulator (the outer periphery of the second section) and the inner circumferential surface of the metal casing. This means that on the side facing away from the seal, there is more clearance for the insulator's positional displacement, making it less likely that the insulator will come into contact with the metal casing even with a certain degree of displacement. In this way, the contact prevention effect can be enhanced.

[0013] In the case of the spark plug, the first section can be located at least on an outer periphery of an entire area in the axial direction of the center electrode in that area.

[0014] When the spark plug is configured as described above, the entire axial area of ​​a section of the center electrode located in this region (the area from the rear end of the rearward-facing surface to the front end of the enlarged diameter section) can be surrounded by the first section. In this way, spark ingress in the section described above, where it might otherwise occur, can be further effectively suppressed, and the dielectric strength can be further improved.

[0015] In the case of a spark plug, the inner diameter of the insulator can be smallest in the first section of the area.

[0016] In a spark plug, the inner diameter of the insulator is smallest in the first section. This largely ensures the clearance between the metal casing and the center electrode, while maintaining the thickness of the first section, thus suppressing electrostatic capacitance near this section. Consequently, wear on the center and ground electrodes is reduced.

[0017] In a spark plug, the metal casing can have an inner diameter section, which is a portion of the metal casing within that area. This inner diameter section can have the largest inner diameter in that area and can be located at least on an outer periphery of the first section.

[0018] In the spark plug, the section of the metal casing located in the area (the area from the rear end of the rearward-facing surface to the front end of the enlarged diameter section) with the largest inner diameter (inner diameter section) is positioned at least at the outer periphery of the first section. Thus, near the first section, the distance between the metal casing and the center electrode is largely maintained due to the presence of the inner diameter section, further suppressing electrostatic capacitance. Consequently, wear on the center and ground electrodes is further reduced.The inner diameter section (the section with the largest inner diameter) is not provided across the entire area (the area from the rear end of the rearward-facing surface to the front end of the enlarged diameter section), but selectively only in a portion of the area. Therefore, a decrease in the strength of the metal shell compared to a configuration where the inner diameter section is provided across the entire area is suppressed.

[0019] In the spark plug, a section in the axial hole on the rear end, relative to the rearward-facing surface, can be filled with a front sealing element that is in contact with an inner circumferential surface of the insulator and the center electrode and contains an electrically conductive material. This first section can extend at least from the rear end of the rearward-facing surface to the rear end of the front sealing element.

[0020] In a spark plug where the gap between an insulator and a center electrode is filled with an electrically conductive front sealing element, the front sealing element transmits a spark from the center electrode to the insulator. If the spark's energy is high, it can penetrate the insulator, resulting in a discharge. However, in the spark plug described above, the thickness of the insulator near the center electrode and the front sealing element is increased, thus suppressing spark penetration. Advantageous effects of the invention

[0021] According to the present invention, a spark plug can be provided which is able to further suppress a spark penetrating an insulator, while suppressing an increase in the diameter of a metal casing. Brief description of the drawings [ Fig. 1] Fig. Figure 1 is a partial section showing a spark plug according to a first embodiment. [ Fig. 2] Fig. 2 is an enlarged section showing part of the spark plug in Fig. 1 is enlarged and corresponds to a section drawn from a one-point catenary K in Fig. 1 is surrounded. [ Fig. 3] Fig. 3 is an enlarged section showing a magnified part of a spark plug according to a second embodiment. [ Fig. 4] Fig. Figure 4 is an enlarged section showing a part of a spark plug according to a third embodiment in an enlarged view. [ Fig. 5] Fig. 5 is an enlarged section showing a magnified part of a spark plug according to a first modification of another embodiment. [ Fig. 6] Fig. Figure 6 is an enlarged cross-sectional view showing a magnified part of a spark plug according to a second modification of another embodiment. [ Fig. 7] Fig. Figure 7 is an enlarged cross-sectional view showing a magnified part of a spark plug according to a third modification of another embodiment. Description of the embodiments: First embodiment 1. General configuration of the spark plug

[0022] A spark plug 1 after an initial in Fig. The embodiment shown in Figure 1 is installed in an internal combustion engine (not shown) and serves to ignite a combustion gas in a combustion chamber of the internal combustion engine. The spark plug 1includes an insulator 10 , a metal casing 30 , a central electrode 50 , a metal terminal 60 and a resistor 61. The description specifies a direction along an axial line. X (central axis) of the spark plug 1 as axial direction. In the axial direction, a side on which a ground electrode 42 is provided is referred to as the front end, and a side opposite it (a side on which the metal terminal 60 faces the outside of the insulator) 10 The side that is exposed) is referred to as the rear end. Fig. 1 will be a front end (front tip end) of the spark plug 1 The spark plug is designated with the reference symbol F and the rear end with the reference symbol R. A subside is designated for each component in Fig. 1 is referred to as the front end and a top side as the back end in the following description. Furthermore, the axial direction is also referred to as the front-back direction. The front end is also referred to as the front and the back end as the back.

[0023] As in Fig. The insulator shown in 1 is... 10 a cylindrical element with an axial hole 20 , which extends in the axial direction. The insulator 10 It is produced by firing an insulating ceramic material, e.g., aluminum oxide. The insulator 10 is fixed in a state in which it is inserted into a through hole 31 of the metal casing 30 is inserted. The front end of the insulator. 10 protrudes in relation to the front end of the metal casing 30 towards the front end. The rear end of the insulator. 10 protrudes in relation to the rear end of the metal casing 30towards the rear end.

[0024] As in Fig. The axial hole is shown in 1. 20 designed as a hole section into which the central electrode 50 The metal connector 60, the resistor 61, a front sealing element 62, a rear sealing element 63, etc., are inserted. The axial hole 20 extends in the axial direction through the insulator 10 and extends from the front end to the rear end of the insulator. 10 The axial hole 20 has a small diameter hole section 21, a stepped section 22 and a large diameter hole section 23 in that order from the side of the front end.

[0025] As in Fig. As shown in Figure 1, the inner diameter of the small-diameter hole section 21 is smaller than the inner diameter of the large-diameter hole section 23. The rear end of the small-diameter hole section 21 is located at the front end of the step section 22. The front end of the small-diameter hole section 21 is located at the front end of the insulator. 10 The inner diameter of the small-diameter hole section 21 is constant in a predetermined range in the axial direction (a range from the front end of the step section 22 to the front end of the insulator). 10 The front end of the large-diameter hole section 23 is located at the rear end of the step section 22. The rear end of the large-diameter hole section 23 is located at the rear end of the insulator. 10The inner diameter of the large-diameter hole section 23 is in a predetermined range from the rear end of the step section 22 to a position near the rear end of the insulator. 10 constant.

[0026] As in Fig. As shown in Figure 1, the step section 22 is provided between the small diameter hole section 21 and the large diameter hole section 23 and has an inclined surface (rearward-facing surface). 22A ), which is chamfered in such a way that the inner diameter decreases from the rear end to the front end. The rearward-facing surface 22A is a surface that forms the rear end of the spark plug 1 is directed towards, is formed in a forward fuselage section 14 and is designed to align with the axial line X is facing (pointing obliquely inwards). The rearward-facing surface 22Ais a conically tapered surface that is chamfered such that the outer diameter (the diameter in a section perpendicular to the axial line) X ) gradually increases towards the rear end.

[0027] A section of the insulator 10 , which is the center electrode 50 surroundings has a stepped section 13 ( Fig. 2). The step section 13 is via a ring-shaped seal 45 on a protruding section 35 of the metal casing 30 held. The step section 13 has a beveled surface 13A ( Fig. 2), which is beveled in such a way that the diameter decreases towards the front end.

[0028] As in Fig. As shown in 1, the insulator has 10 a leg section 12, which is located at the front end side in relation to the step section 13 is planned ( Fig. 2), and has the front fuselage section 14, which is located at the rear end in relation to the step section 13 The leg section 12 is a section that extends in the axial direction such that it is located from the front end position of the step section. 13 is continuous in the axial direction up to the front end. Leg section 12 is a section that, in a state where the spark plug 1 is installed in the internal combustion engine and is exposed to a combustion chamber. The leg section 12 is thinner than the front fuselage section 14. The front fuselage section 14 is a section that extends axially from the rear end position of the stage section. 13 extends further in the axial direction to the front end position of a flange section 15.

[0029] As in Fig. As shown in 1, the insulator has 10The flange section 15 is located at the rear end relative to the front fuselage section 14. The flange section 15 is situated essentially in the center of the insulator in the axial direction. 10 and has a flange shape that projects outwards in a radial direction with respect to the front fuselage section 14 and a rear fuselage section 16.

[0030] As in Fig. As shown in 1, the insulator has 10 the rear fuselage section 16, which is provided at the rear end face with respect to the flange section 15. The outer peripheral surface of the rear fuselage section 16 is a cylindrical surface that is aligned along the axial line. XThe outer diameter (the diameter of the outer peripheral surface) of the rear fuselage section 16 is constant within a predetermined range from the rear end of the flange section 15. The outer diameter of the flange section 15 is larger than the outer diameters of the front fuselage section 14 and the rear fuselage section 16.

[0031] The metal casing 30 It is made of an electrically conductive metal material (e.g., low-carbon steel). The metal casing 30 is a metal part for attaching the spark plug 1 on the cylinder head of an internal combustion engine. The metal casing 30 It has a cylindrical shape through which the through-hole 31 extends in the axial direction. The metal casing 30 is located at the outer periphery of the insulator 10 arranged and is crimped onto the insulator. 10 attached.

[0032] As in Fig. 1 shown, contains the metal casing 30 a tool engagement section 32, which is equipped with a tool (spark plug wrench) for mounting the metal casing 30 The tool engages with the motor head. The outer peripheral surface of the tool engagement section 32 has a polygonal shape into which the tool engages. A thin crimp section 33 is provided on the rear side of the tool engagement section 32. The crimp section 33 comes into close contact with the rear body section 16 of the insulator. 10 , if the metal casing 30 on the insulator 10 is crimped.

[0033] As in Fig. As shown in 1, the metal shell 30A screw section 34 (external thread section) is inserted into and secured in a screw hole (internal thread section, not shown) provided in the internal combustion engine. A threaded groove (external thread groove) is formed in the outer peripheral surface of the screw section 34. The projecting section 35 is formed in the inner circumferential surface of the screw section 34 such that it projects inwards along its entire circumferential direction. The projecting section 35 serves to seal the 45 together with the one in the insulator 10 planned stage section 13 ( Fig. 2) to arrange them in a sandwich-like manner.

[0034] As in Fig. 1 shown, contains the metal casing 30A flange-shaped seat section 37 is located at the rear end of the screw section 34. A thin compression section 38 is provided between the seat section 37 and the tool engagement section 32. A filled section 49 is located between the inner circumferential surfaces of the tool engagement section 32 and the crimp section 33, and the outer circumferential surface of the rear body section 16 of the insulator. 10 The filled section 49 is filled with talc powder. The filled section 49 is sealed with ring-shaped sealing elements (linear seals) 41.

[0035] As in Fig. The section shown in 1 has been enlarged in diameter. 36 , whose inner diameter is enlarged, on the inner circumferential section of the seat section 37 of the metal shell 30 planned. The section with increased diameter 36 is at the rear end in relation to the center electrode50 arranged and has an inner diameter that increases towards the rear end. The section with increased diameter 36 is shaped such that the inner diameter gradually increases from the front end to the rear end in the seat section 37. The inner circumferential surface of the section with the increased diameter 36 is a tapered surface that is chamfered such that the inner diameter (the diameter in a section perpendicular to the axial line) X ) gradually increases towards the rear end. The front end position of the inclined surface (sloping surface) described above in the axial direction corresponds to an example of the front end position of the section enlarged in diameter. 36 The flange section 15 is partially within the section with the increased diameter. 36 arranged.

[0036] The insulator 10In the through-hole 31, via the sealing elements 41 and the talc, due to the pressure deformation of the pressure deformation section 38 of the metal shell, the pressure deformation section 38 is formed. 30 Pressed towards the front end. The seal 45 is in close contact with an inclined surface (inclined surface of the preceding section) 35A of the preceding section 35, which faces the rear end side, and an inclined surface (inclined surface of the step section) 13A of the step section 13 , which faces the front end, and is clamped between the inclined surfaces 35A and 13A. In the configuration where the seal 45 In this sandwich-like arrangement, the gas in the combustion chamber is forced through a gap between the metal shell. 30 and the insulator 10 prevented from escaping towards the rear end.

[0037] The ground electrode 42 is connected, for example, to the front end of the metal casing by resistance welding.30 connected. Between the ground electrode 42 and the center electrode 50 A spark gap is created, which is a gap for generating a spark.

[0038] The center electrode 50 It is formed by using a metal with high corrosion resistance and high heat resistance, for example nickel (Ni) or an alloy containing nickel as its main component. The center electrode 50 It has a rod shape extending in the axial direction and is located in the axial hole at the end side. 20 of the insulator 10 arranged. The front end of the center electrode 50 protrudes in relation to the front end of the insulator 10 towards the front end. The rear end of the center electrode 50 is located in the forward fuselage section 14.

[0039] The center electrode 50 includes a leg section 51, a section with a large diameter 52and a head section 53 in this order from the front end in the axial direction. The outer diameter of the large-diameter section 52 is larger than the outer diameter of the leg section 51 and the outer diameter of the head section 53. The large-diameter section 52 is a section with an outer diameter that is the largest in the center electrode 50 is and at the rear end surface 22A of the insulator 10 is held. The large-diameter section 52 The device has a columnar section 54 with an outer diameter (the diameter of the outer peripheral surface) that is constant in the axial direction within a predetermined range, and a tapered section 56 with an outer diameter that gradually decreases towards the front end. The outer diameter of the columnar section 54 is the largest in the central electrode. 50The rear end of the columnar section 54 is a rear end 55 of the section 52 with a large diameter. The rear end 55 is located in the same position as the front end of the head section 53 in the axial direction. The tapered section 56 is a section that is in contact with the rearward-facing surface. 22A stands and is supported by it, and is a section that extends from the front end of the column-shaped section 54 to the side of the front end.

[0040] The metal connector 60 is formed from an electrically conductive metal material (e.g., low-carbon steel). The metal connector 60 is a rod-shaped element that extends in the axial direction and is inserted into the axial hole on the back side. 20 of the insulator 10 is arranged. A rear end section of the metal terminal 60 projects in relation to the insulator. 10towards the rear end. A high voltage to generate a spark discharge is applied from a power supply element to the metal terminal 60.

[0041] The resistor 61 is in the axial hole 20 between the center electrode 50 and the metal terminal 60. The resistor 61 is made of a composition that contains, for example, an electrically conductive material, glass particles and ceramic particles other than the glass particles.

[0042] In the axial hole 20 is the gap between the resistor 61 and the center electrode 50 The front sealing element 62 is filled with an electrically conductive material. The filling with the front sealing element 62 is located in the axial hole. 20 on the rear end side in relation to the rearward-facing surface 22AThe front sealing element 62 is in contact with the inner circumferential surface of the insulator. 10 , the center electrode 50 and the resistor 61. The front sealing element 62 separates the center electrode. 50 and the resistance 61 from each other. The front sealing element 62 is an element that seals the insulator. 10 and the center electrode 50 seals and secures.

[0043] In the axial hole 20 The gap between the resistor 61 and the metal terminal 60 is filled with the rear sealing element 63, which is electrically conductive. The rear sealing element 63 is in contact with the metal terminal 60 and the resistor 61, separating them. The rear sealing element 63 is an element that forms the insulator. 10and seals and secures the metal connection 60. The front sealing element 62 and the rear sealing element 63 connect the center electrode. 50 and the metal connection 60 are electrically and physically connected to each other via the resistor 61. The front sealing element 62 and the rear sealing element 63 are made of an electrically conductive material, e.g., a composition containing glass and metal particles. 2. Specific configurations of the insulator and other components

[0044] The specific configurations of the isolator and other components are described in detail below.

[0045] At the insulator 10 The forward fuselage section 14 has a feature configuration. The forward fuselage section 14 is a section that is arranged such that it extends from the rear end position of the step section. 13continues axially to the front end position of the flange section 15. At least one section of the front fuselage section 14 is within the screw section 34 of the metal shell. 30 arranged. The forward fuselage section 14 comprises a first section 70 with an outer peripheral surface that forms a first structure, and a second section 80 with an outer peripheral surface that forms a second structure.

[0046] The first section 70 is a section of the insulator 10 in an area AR from the rear end of the rearward-facing surface 22A to the front end of the section with the increased diameter 36 The first section 70 has a thickness that is in the area AR is largest, and is at least at the outer periphery of the section 52arranged with a large diameter. In particular, the first section 70 on the outer circumference of the entire area in the axial direction of the center electrode 50 in the area AR arranged. The rear end of the first section is located in the axial direction. 70 on the rear end side in relation to the rear end 55 of the section 52 with a large diameter and is located on the rear end side in relation to the rear end of the center electrode 50 The front end of the first section 70 is located on the side of the front end in relation to the front end of the section 52 with a large diameter and is located on the side of the front end in relation to the rear end of the backward-facing surface 22A The first section 70 is at least in an area from the rear end of the rear frontal surface 22Aarranged up to the rear end of the front sealing element 62.

[0047] A length M of the first section 70 in the axial direction is greater than a length N from the rear end of the step section 13 to the rear end of the front sealing element 62 in the axial direction and is greater than a length L from the rear end of the step section 13 to the rear end of the center electrode 50 in an axial direction. The rear end of the front sealing element 62 is located relative to the rear end of the center electrode. 50 on the side of the rear end. The rear end of the first section. 70 is located on the rear end side with respect to the rear end of the front sealing element 62. The front end of the first section 70 is located on the side of the front end in relation to the front end of the front sealing element 62.

[0048] The first section 70 is on the rear end side in relation to the seal 45 arranged. That is, the insulator 10 is via the seal 45 on the metal casing 30 held, namely on the front end side in relation to the first section 70 .

[0049] In the area AR is the inner diameter of the insulator 10 constant in the axial direction. The hole of the insulator. 10 is a cylindrical surface that covers the entire area of ​​the area AR in the axial direction on the axial line X is centered, and the inner diameter of the insulator 10 is throughout the entire area of ​​the area AR constant. Thus, in the area AR the inner diameter of the insulator 10 in the first section 70 smallest.

[0050] The second section 80 is a section of the insulator 10, which is on the back end page in relation to the first section 70 in the area AR is arranged, and is a section with an outer diameter B that is smaller than an outer diameter A of the first section. 70 .

[0051] In the axial direction, the position of the rear end of the first section is 70 the same as the position of the front end of the second section 80 , and the position of the front end of the first section 70 is the same as the position of the rear end of the step section 13 (the position of the rear end of the inclined surface 13A). In the axial direction, the position of the rear end of the second section is 80the same as the position of the front end of the flange section 15 (the position of the front end of the inclined surface provided on the front end side of the flange section 15), and the position of the front end of the second section 80 is the same as the position of the rear end of the first section 70 .

[0052] The outer diameter A (the diameter of the outer peripheral surface) of the first section 70 is larger than the outer diameter B (the diameter of the outer peripheral surface) of the second section 80 The outer peripheral surface of the first section 70 is a cylindrical surface that lies on the axial line X is centered. The outer peripheral surface of the second section 80 is a cylindrical surface that lies on the axial line X is centered.

[0053] The outer diameter A of the first section 70and the outer diameter B of the second section 80 are larger than the outer diameter (the diameter of the outer peripheral surface) of leg section 12. The outer diameter A of the first section 70 is from the rear end of the step section 13 to the front end of the second section 80 constant in the axial direction. At every position in the axial direction, a section of the first section has a cross-section. 70 , which is in a direction perpendicular to the axial line X cut, a circular outer shape that lies on the axial line X centered with the predetermined diameter A (the same diameter). The outer diameter B of the second section 80 is from the rear end of the first section 70 The axial length is constant up to the front end of flange section 15. At each position in the axial direction, a section of the second section has a cross-sectional area. 80, which is in a direction perpendicular to the axial line X cut, a circular outer shape that lies on the axial line X is centered with the predetermined diameter B (the same diameter). 3. Examples of effects

[0054] in the spark plug 1 is the first section 70 on one side near the seal 45 arranged (a component that forms the insulator) 10 positioned while it is removed from the metal casing 30 is supported), and the second section 80 is located on a side that is further away from the seal 45 is further away than the first section 70 Furthermore, the first section has a thickness X1. 70 in the radial direction greater than a thickness Y1 of the second section 80 in a radial direction. The first section 70 is on the outer periphery of the section 52arranged with a large diameter and has a greater thickness than the second section 80 .

[0055] With such a configuration, the effect of suppressing spark penetration near the large-diameter section can be achieved. 52 intensification is needed where countermeasures against spark penetration are more necessary.

[0056] Furthermore, the side near the seal indicates 45 the property that "the insulator 10 is held more stably and its position relative to the metal shell 30 "has hardly shifted." So, if one considers the first section 70 on the side near the seal 45 This feature can be used effectively if the design provides for it. That is, on the side near the seal. 45 , although the first section 70 is arranged with a relatively large outer diameter, and therefore the gap between the outer peripheral surface of the insulator10 (the outer peripheral surface of the first section 70 ) and the inner circumferential surface of the metal casing 30 relatively small, the insulator comes into play. 10 hardly with the metal casing 30 in contact. Therefore, on the side near the seal. 45 by using the structure in which the position of the insulator 10 has hardly shifted, and of the first section 70 Together, both contact prevention and the suppression of spark ingress are provided.

[0057] In contrast, on the side of the seal 45 far side of the second section 80 arranged with a relatively small outer diameter, resulting in a larger gap between the outer peripheral surface of the insulator. 10 (the outer peripheral surface of the second section 80 ) and the inner peripheral surface of the metal shell 30is guaranteed. That is, based on the seal. 45 The opposite side provides the scope for the insulator's positional displacement. 10 larger, so that the insulator 10 even with a certain displacement of the insulator 10 less likely to come into contact with the metal casing30. In this way, the contact prevention effect can be increased.

[0058] If, in such a configuration, during the use of the spark plug 1 When a vibration or similar is applied, this is a situation in which the insulator 10 with the metal casing 30 comes into contact near the first section 70 and the second section 80 less likely.

[0059] at the spark plug 1 is the first section 70 at least at the outer periphery of the entire area in the axial direction of the central electrode 50 in the area AR arranged. In the spark plug 1 The entire area in the axial direction can be defined by "a section of the center electrode". 50 , which is in the area AR is arranged" from the first section 70 be surrounded. In this way, in the section described above, where sparks may penetrate, the ingress of sparks can be further effectively suppressed and the dielectric strength can be further improved.

[0060] In particular, the first section 70 The electrodes are positioned outside the edge sections 57A, 57B, 57C, and 57D to surround all edge sections 57A, 57B, 57C, and 57D where sparking is likely to originate. In this way, spark penetration can be further effectively suppressed. Edge section 57A is an outer circumferential edge at the rear end of the center electrode. 50(the rear end of head section 53). Edge section 57B is an outer circumferential edge at the front end of head section 53. Edge section 57C is an outer circumferential edge at the rear end of the section. 52 with a large diameter. The edge section 57D is an outer circumferential edge at the front end of the columnar section 54 of the large-diameter section. 52 .

[0061] Since the spark plug 1 the inner diameter of the insulator 10 in the first section 70 The smallest one can be found at the spark plug. 1 the distance between the metal casing 30 and the center electrode 50 largely ensured, while the thickness of the first section 70 largely preserved, thus maintaining the electrostatic capacitance near the first section 70 is suppressed. This reduces wear on the center electrode. 50and the ground electrode 42 is suppressed.

[0062] at the spark plug 1 is the section in the axial hole 20 on the rear end side in relation to the rearward-facing surface 22A The front sealing element 62 is filled with an electrically conductive material. The front sealing element 62 is in contact with the inner circumferential surface of the insulator. 10 and the center electrode 50 The first section 70 is in an area from the rear end of the rearward-facing surface 22Aup to the rear end of the front sealing element 62. In a spark plug where the gap between an insulator and a center electrode is filled with an electrically conductive front sealing element, the front sealing element, being electrically conductive, transmits a spark from the center electrode, and the spark reaches the insulator. If the energy of the spark is high, the spark can penetrate the insulator and a discharge can occur. However, since in the spark plug 1 the thickness of the insulator 10 near the center electrode 50 and the front sealing element 62 is increased, can be seen at the spark plug 1 The penetration of the spark is suppressed. Second embodiment

[0063] A spark plug 201 According to a second embodiment, the following mainly refers to Fig. 3 described.

[0064] The spark plug 201 according to the present, in Fig. The embodiment shown in 3 is the same as the spark plug. 1 according to the first embodiment, except that the insulator 10 ( Fig. 2) into an insulator 210 has changed. Specifically, the spark plug. 201 the same as the spark plug 1 according to the first embodiment, except that the axial hole 20 ( Fig. 2) into an axial hole 220 The design is changed. Therefore, the same reference numeral is applied to the configuration similar to the first embodiment, and the redundant description is omitted.

[0065] For example, the configuration in Fig. 1 with the exception of the internal structure, which is characterized by area K, the same as that of the in Fig. 1 spark plug shown 1 In the following description, the other one is referred to as the one in Fig. 3. Area shown, possibly with reference to Fig. 1 described.

[0066] The in Fig. 3 spark plug shown 201 differs from the spark plug 1 ( Fig. 2) only because the hole section 23 has a large diameter ( Fig. 2) is changed to a hole section 223 with a large diameter. Specifically, the spark plug differs 201 from the spark plug 1 ( Fig. 2) only by virtue of an inner diameter D of a first section 270 throughout the entire area on the rear end side in relation to the rearward-facing surface 22A is smaller than an inner diameter C of the second section 80 .

[0067] At the in Fig. 3 spark plugs shown 201 is the inner diameter of the insulator 210 in the area AR (the area from the rear end of the rearward-facing surface 22Ato the front end of the section with the increased diameter 36 ( Fig. 1) in axial direction) in the first section 270 smallest. The second section 80 has the same form as the second section 80 the spark plug 1 ( Fig. 2). The first section 270 differs from the first section 70 ( Fig. 2) only by virtue of the fact that the inner diameter of the first section 270 in the area AR is smaller than the inner diameter of the first section 70 the spark plug 1 ( Fig. 2) in the area AR The inner circumferential surface of the first section 270 is a cylindrical surface 223A with the constant inner diameter D, which lies on the axial line X on the rear end side in relation to the rearward-facing surface 22A is centered. An inner circumferential surface 223B of the second section 80is a cylindrical surface with the constant inner diameter C, which lies on the axial line X is centered. The inner diameter D is smaller than the inner diameter C. The rear end of the cylindrical surface 223A with the constant inner diameter D can be positioned at the rear end of the first section. 270 located on the front end side in relation to the rear end of the first section 270 located or may be on the rear end side in relation to the rear end of the first section 270 condition.

[0068] The spark plug configured as described above 201 also achieved in terms of its similar properties to the spark plug 1 a beneficial effect ( Fig. 2).

[0069] Furthermore, the spark plug 201 the inner diameter of the insulator 210 in the area AR in the first section 270the smallest. Specifically, a section of the first section 270 with the inner diameter D, which is smaller than the inner diameter C of a second section 280, in the area AR provided for. In this way, the thickness of the first section can be adjusted. 270 further sufficiently ensured and the electrostatic capacitance near the first section 270 will continue to be suppressed. Third embodiment

[0070] A spark plug 301 According to a third embodiment, the following will mainly refer to Fig. 4 described.

[0071] The spark plug 301 according to the present, in Fig. The embodiment shown in section 4 is the same as the spark plug. 201 according to the second embodiment, except that the metal casing 30 ( Fig. 3) into a metal casing 330 is being changed. Specifically, the spark plug. 301According to the second embodiment, the same as the spark plug. 201 , except that the through hole 31 ( Fig. 3) is changed to a through-hole 331. Therefore, the same reference numeral is applied to the configuration similar to the second embodiment, and the redundant description is omitted. For example, the configuration in Fig. 1 with the exception of the internal structure, which is characterized by area K, the same as that of the in Fig. 1 spark plug shown 1 In the following description, the other one is referred to as the one in Fig. 4. Area shown, possibly with reference to Fig. 1 described.

[0072] The in Fig. 4 metal casings shown 330 the spark plug 301 differs from the metal casing 30 the spark plug 201 ( Fig. 3) only by the fact that a first inner diameter section 331A with a first inner diameter F and a second inner diameter section 331B with a second inner diameter E in the area AR are provided for, instead of the configuration in which the inner circumferential section has a constant inner diameter in the area AR has.

[0073] As in Fig. As shown in section 4, the first inner diameter section 331A represents a section of the metal shell. 330 in the area AR ( Fig. 1) and has an inner diameter that is larger than that of the second inner diameter section 331 B, which forms another section of the metal casing 330 in the area AR The first inner diameter section 331A corresponds to an example of an inner diameter section and is a section with the largest inner diameter in a section of the metal casing. 330 in the area AR ( Fig. 1) It is sufficient that the first inner diameter section 331A is at least at the outer periphery of the first section 70 is arranged. In the example in Fig. 4 the first inner diameter section331A is arranged such that it covers the entire area in the axial direction of the first section 70 surrounds.

[0074] The inner circumferential surface of the first inner diameter section 331A is a cylindrical surface with the constant inner diameter F, which lies on the axial line X on the rear end side in relation to the step section 13 is centered. The inner circumferential surface of the second inner diameter section 331B is a cylindrical surface with the constant inner diameter E, which lies on the axial line. Xon the rear end face with respect to the first inner diameter section 331A. Both the inner diameter F and the inner diameter E are larger than either the outer diameter A or the outer diameter B. The inner diameter F is larger than the inner diameter E. It is desirable that the rear end of the first inner diameter section 331A be centered at a position on the rear end face with respect to the rear end of the first section. 70 is arranged at a predetermined distance in the axial direction. Furthermore, it is desirable that the front end of the first inner diameter section 331A be located at a position on the front end face relative to the front end of the first section. 70 is arranged at a predetermined distance in the axial direction.

[0075] The spark plug configured as described above 301 also achieved in terms of the similar property to the spark plug1 ( Fig. 2) an advantageous effect similar to that of the spark plug 1 similar.

[0076] at the spark plug 301 The first internal diameter section 331A is “an internal diameter section with an internal diameter that is the largest in a section of the metal casing 330 is, who is in the area AR is arranged ( Fig. 1)”, and such an inner diameter section is located at the outer periphery of the first section 70 arranged. Thus, it is located near the first section. 70 the distance between the metal casing 30 and the center electrode 50 In the radial direction, the presence of the first inner diameter section 331A (the inner diameter section) largely ensures continued protection. Similarly, a distance Z3 between the metal shell is maintained. 30and the front sealing element 62 in the radial direction is still largely ensured. As a result, the electrostatic capacitance is further suppressed. Accordingly, the wear of the center electrode can be reduced. 50 and the ground electrode 42 is further suppressed. At the spark plug 301 The first inner diameter section 331A (the section with the largest inner diameter) is not in the entirety of the range AR planned ( Fig. 1), but selectively only in a part of the area AR Therefore, a decrease in the strength of the metal casing will occur. 30 compared to a configuration where the first inner diameter section is 331A across the entire range AR is intended to be suppressed ( Fig. 1). Another example

[0077] The new invention is not limited to aspects and modifications of the embodiments described and can be implemented through various configurations within the scope that does not deviate from the spirit of the present invention. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in the aspects described in the "Summary of the Invention" section can be exchanged or combined if this is necessary to partially or completely solve the problems described above or to partially or completely achieve the advantageous effects described above. In particular, the various technical features can be desirablely combined within a non-contradictory scope, according to the embodiments described above or embodiments described later.If the technical features are not described as essential in the description, they can be omitted if necessary. Modifications include, for example, the following.

[0078] In the embodiments described above, the front or rear end of the outer peripheral surface of the first section, or the front end of the outer peripheral surface of the second section, is designed as an angled corner section (edge ​​section). However, such a corner section can be chamfered, for example, to be round, as in a spark plug. 401 the in Fig. Figure 5 shows that in this configuration, no angular section is required near the first section (the large-diameter section) of the insulator, which is advantageous in terms of strength. The in Fig. 5 spark plugs shown 401 is the same as the spark plug 301according to the third embodiment, except that the insulator 210 ( Fig. 4) into an insulator 410 will be changed. Specifically, the first section 470 the same as the first section 270 the spark plug 301 ( Fig. 4), except that a round section 470A is located at the outer circumferential edge of the rear end of the outer peripheral surface of the first section. 470 and a round section 470B at the outer circumferential edge of the front end of the outer peripheral surface of the first section 470 is planned. A second section 480 is the same as the second section 80 the spark plug 301 ( Fig. 4), except that a round section 470C is provided. The round section 470A, the round section 470B and the round section 470C are sections that are chamfered so that they are round.

[0079] In the embodiments described above, the rear end of the first section is located at the rear end face with respect to the rear end of the front sealing element 62 (the front end of the resistor 61). However, it is sufficient that the first section is located at the outer periphery of the section 52 is arranged with a large diameter. For example, the rear end of the first section can lie in the axial direction in the area of ​​the head section.

[0080] According to the second and third embodiments, etc., the step is formed at the boundary between the inner circumferential surface of the first section. 270 and the inner circumferential surface of the second section 80 formed, like a spark plug. 501 , which in Fig. As shown in Figure 6, an inner circumferential surface can be inclined in such a way that it diverges from a first section. 570 to a second section 580 extends. In the example in Fig. 6 The inner circumferential surface of a large-diameter hole section 523 has a conical shape with an inner diameter that increases from the front end to the rear end. Since the inner circumferential surface of the insulator has no step, the stress concentration is reduced, which has a beneficial effect on the strength. The in Fig. 6 spark plugs shown 501 is the same as the spark plug 1 ( Fig. 2), except that the insulator 10 ( Fig. 2) into an insulator 510 will be changed.

[0081] More precisely, the configuration is the same as in Fig. 2, except that the axial hole 20 into an axial hole 520 is changed (more precisely, the large-diameter hole section 23 is changed to the large-diameter hole section 523). The first section 570 is the same as the first section 70 in Fig. 2, with the exception of the shape of the inner circumferential surface. The second section 580 is the same as the second section 80 in Fig. 2 with the exception of the shape of the inner circumferential surface. The inclination of the inner circumferential surface of the large-diameter hole section 523 is desirablely determined such that, for example, the angle of the inner circumferential surface of the large-diameter hole section 523 with respect to the axial line X in a section in each through the axial line X the direction in which the direction is greater than 0 degrees and partially or completely less than 20 degrees ( Fig. 1).

[0082] According to the third embodiment, etc., the step is formed at the boundary between the inner circumferential surface of the first inner diameter section and the inner circumferential surface of the second inner diameter section of the metal shell. As in the Fig. 7 spark plug shown 601However, for example, an inner circumferential surface of the metal shell at the rear end, with respect to the preceding section 35, can have a conical shape with an inner diameter that gradually decreases towards the rear end. In such a configuration, the stress concentration is reduced, which has a beneficial effect on the strength. Furthermore, the inner diameter of the metal shell near the section can be 52 The outer diameter is relatively large, while the inner diameter of the metal casing at the rear end is made relatively small. This is advantageous for preventing spark penetration and also for increasing strength at the rear end.

[0083] The in Fig. 7 spark plug shown 601 is the same as the spark plug 1 according to the first embodiment, except that the metal casing 30 ( Fig. 2) through a metal casing 630 It has been replaced. Specifically, the configuration is the same as in Fig. 2, except that the through hole 31 is changed to a through hole 631. The inclination of the inner circumferential surface of the through hole 631 is desirablely set such that, for example, the angle of the inner circumferential surface of the through hole 631 with respect to the axial line X in a section in each through the axial line X the direction in which the direction is greater than 0 degrees and partially or completely less than 20 degrees ( Fig. 1). Reference symbol list 1, 201, 301, 401, 501, 601 Spark plug 10, 210, 410, 510 Insulator 13th stage section 20, 220, 520 axial hole 22A rear-facing surface 30, 330, 630 metal casing 36 diameter enlarged section 45 Seal 50 Center electrode 52 Large diameter section 70, 270, 470, 570 first section 80, 480, 580 second section X axial line AR area QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2019003721

[0004]

Claims

[1] Containing a spark plug: a cylindrical insulator with an axially extending hole and a rearward-facing surface formed in the axial hole; a cylindrical metal casing arranged on an outer periphery of the insulator; and a central electrode located at a front end in the axial hole, wherein the central electrode has a large diameter section with an outer diameter which is the largest in the central electrode, wherein the large diameter section is held against the rearward-facing surface, and wherein the metal shell has a section with an increased diameter on a rear end face in relation to the central electrode, wherein the section with an increased diameter has an inner diameter that is increased towards the rear end face, wherein the insulator has a first section which is a section of the insulator in an area from a rear end of the rearward-facing surface to a front end of the diameter-enlarged section, the first section has a thickness that is the greatest in the area, and is located at least on an outer periphery of the large-diameter section, the insulator is held to the metal casing by a seal on the front face in relation to the first section and The insulator has a second section on the rear end face relative to the first section in the area, the second section having an outer diameter that is smaller than the outer diameter of the first section. [2] Spark plug according to claim 1, wherein the first section is arranged at least on an outer periphery of an entire region in the axial direction of the central electrode in that region. [3] The spark plug according to claim 1 or 2, wherein the inner diameter of the insulator in the first section is smallest in that area. [4] The spark plug according to any one of claims 1 to 3, wherein the metal shell has a section of the inner diameter that is a section of the metal shell in that area, and the section with the inner diameter has an inner diameter that is the largest in the area and is located at least on an outer periphery of the first section. [5] The spark plug according to any one of claims 1 to 4, wherein a section in the axial hole on the rear end face, in relation to the rearward-facing surface, is filled with a front sealing element that is in contact with an inner peripheral surface of the insulator and the center electrode and contains an electrically conductive material, and the first section is arranged at least in an area from the rear end of the rearward-facing surface to a rear end of the front sealing element.