SPARK PLUG

Abstract

Spark plug (100) comprising: a center electrode (20; 20S) extending in one direction of an axis (AX) of the spark plug (100); an insulator (10; 10B) having an axial hole (12; 12B) formed therein in the direction of the axis (AX) to retain the center electrode (20; 20S) in a front end face of the axial hole (12; 12B); a cylindrical metal housing (2; 2B) arranged around an outer circumference of the insulator (10; 10B) and having a sealing element (SP) which is brought into contact directly or via another element (8) with an outer circumferential surface of the insulator (10; 10B); a ground electrode (30; 30B) arranged to form a gap (G) with the center electrode (20; 20B); and a cap (90; 90B) connected to a front end part (61) of the metal housing (2; 2B) to form a front end opening (50o, 60o) of the metal housing (2;2B) to cover and to define therein an auxiliary combustion chamber (BS) in which the gap (G) is formed, wherein the cap (90; 90B) has at least one through-hole (95a to 95d; 95aB, 95bB) formed in it to establish a connection between the auxiliary combustion chamber (BS) and the outside, wherein a central axis (L2) of the at least one through-hole (95a to 95d; 95aB, 95bB) passes through the gap (GP), and wherein the condition (B / A) ≤ 0.25 is satisfied, wherein an imaginary plane extending perpendicular to the axis (AX) to close a front-end opening (12o; 12oB) of the axial hole (12; 12B) of the insulator (10; 10B) is called a first imaginary plane (VS1); an imaginary plane which has a minimal area to close an inner surface opening (95ao to 95do; 95aoB to 95boB) of the at least one through hole (95a to 95d; 95aB, 95bB) of the cap (90; 90B) is referred to as a second imaginary plane (VS2a to VS2d);A represents a volume of an imaginary space (VV) defined by an inner surface (90i) of the cap (90; 90B), a surface (50s, 50u, 50i) of the metal housing (2; 2B), a surface (13o, 13s) of the insulator (10; 10B), the first imaginary plane (VS1) and the second imaginary plane (VS2a to VS2d); and B represents a volume of parts (VP) of the center and ground electrodes (20, 30; 20B, 30B) located in the imaginary space (VV).

Description

GENERAL STATE OF THE ART

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

[0002] Spark plugs are traditionally used in internal combustion engines such as gasoline and gas engines. Japanese Patent Application No. 2017-103179 discloses a spark plug of the type that has an auxiliary combustion chamber. In this spark plug, a cap is attached to the front end of a metal housing, so that the auxiliary combustion chamber is defined within the cap. A hole is formed in the cap, creating a connection between the auxiliary combustion chamber and the outside. An air-fuel mixture is introduced into the auxiliary combustion chamber through the hole in the cap. Furthermore, a center electrode and a ground electrode are arranged in the auxiliary combustion chamber. When a spark discharge is generated in a gap between the center electrode and the ground electrode, the air-fuel mixture introduced into the auxiliary combustion chamber is ignited by the spark discharge.Upon ignition, a flame develops and spreads through the hole in the cap to the outside, that is, into the combustion chamber of the internal combustion engine. This flame propagation combusts the air-fuel mixture in the combustion chamber. SUMMARY

[0003] However, it cannot be said that the spark plug type disclosed above has been sufficiently developed to reduce the heat and pressure losses in the auxiliary combustion chamber. Therefore, there is a possibility that the heat and pressure losses in the auxiliary combustion chamber could increase excessively, potentially preventing the spark plug from achieving sufficient ignition capability (e.g., combustion stability).

[0004] A major advantage of the present invention is that a spark plug of the type having an auxiliary combustion chamber is provided which is able to achieve improved ignition capability.

[0005] According to one aspect of the present invention, a spark plug is provided which comprises: a center electrode extending in one direction along an axis of the spark plug; an insulator having an axial hole formed in the direction of the axis to hold the center electrode in a front end face of the axial hole; a cylindrical metal housing arranged around an outer circumference of the insulator and having a sealing element that is in contact with an outer circumferential surface of the insulator, either directly or via another element; a ground electrode arranged to form a gap with the center electrode;and a cap connected to a front end part of the metal housing to cover a front end opening of the metal housing and to define an auxiliary combustion chamber in it in which the gap is formed, the cap having at least one through-hole formed in it to establish a connection between the auxiliary combustion chamber and the outside, wherein the condition (B / A) ≤ 0.25 is satisfied, wherein an imaginary plane extending perpendicular to the axis to close a front end opening of the axial hole of the insulator is called a first imaginary plane; an imaginary plane having a minimal area to close an inner surface opening of the through-hole of the cap is called a second imaginary plane;A represents a volume of an imaginary space defined by an inner surface of the cap, a surface of the metal casing, a surface of the insulator, the first imaginary plane, and the second imaginary plane; and B represents a volume of portions of the center and ground electrodes located in the imaginary space.

[0006] It is understood that the present invention can be implemented in various forms, such as not only as a spark plug, but also as an ignition device with a spark plug, an internal combustion engine with a spark plug, and the like.

[0007] The other tasks and features of the present invention will also become apparent from the following description. List of characters Fig. Figure 1 is a sectional view (cross-sectional view) of a spark plug 100 according to one embodiment of the present invention. Fig. 2 is an end view of the spark plug 100 , in one direction from front to back along an axis AX the spark plug 100 seen. Fig. Figure 3 is a sectional view (cross-sectional view) of a front end part of the spark plug. 100 along the line A-A from Fig. 2. Fig. 4A and Fig. 4B are schematic views to explain the volume. A one in the spark plug 100 defined imaginary space. Fig. 5A and Fig. 5B are schematic views to explain the volume B of parts of a ground and a center electrode of the spark plug 100 , which are located in the imaginary space. Fig. Figure 6 is a sectional view (cross-sectional view) of a front end part of a spark plug according to a modified example of the embodiment of the present invention. DETAILED DESCRIPTION

[0008] The present invention will now be described in detail with reference to the drawings. FORM OF EXECUTION

[0009] Fig. Figure 1 is a sectional view (cross-sectional view) of a spark plug 100 according to one embodiment of the present invention. In the present description, a direction parallel to an axis is defined. AX the spark plug 100 (i.e. a vertical direction in Fig. 1) also referred to as "axial direction"; a direction of a radius of a circle that lies on a plane perpendicular to the axis AX A direction drawn perpendicular to and centered on the plane is also called the "radial direction"; and a direction along the circumference of the circle is also called the "circumferential direction". Furthermore, the top and bottom sides are distinguished in Fig. 1 as the rear or front side of the spark plug 100A direction towards the front is called a "forward direction". FD “ is referred to as, and a direction towards the rear is called “reverse direction” BD " designated.

[0010] The spark plug 100 It is designed for use in an internal combustion engine, such as a gas engine, to ignite a fuel gas in a combustion chamber of the engine. As in Fig. As shown in 1, the spark plug 100 an insulator 10 , a central electrode 20 , a ground electrode 30 , a connecting electrode 40 , a metal casing 2 with an inner and an outer metal housing part 50 and 60 , a resistance 70 conductive sealing elements 80A and 80B and a cap 90 on.

[0011] The insulator 10 It has an essentially cylindrical shape with an axial hole 12, passing through him along the axis AX is designed. In the present embodiment, the insulator is 10 Made from a ceramic material such as aluminum oxide. The insulator 10 features a federal section 19 , a posterior body section 18 , a front part of the body 17 , a section with decreasing outer diameter 15 and a foot section 13 on.

[0012] The federal section 19 is located in the axial direction at an essentially central part of the insulator 10 The posterior body section 18 is located behind the federal section 19 and has an outer diameter that is smaller than that of the collar section 19 is the anterior body section 17 is located in front of the federal section 19and has an outer diameter that is smaller than that of the posterior body section 18 is the foot section 13 It is located in front of the anterior body section 17 and has an outer diameter that is smaller than that of the anterior body section. 17 is and gradually decreases towards the front. The section with decreasing outer diameter 15 is located between the foot section 13 and the anterior body section 17 and has an outer diameter that gradually decreases from back to front.

[0013] The insulator 10 Its configuration of the inner circumference indicates an area with a large inner diameter. 12L , an area with a small inner diameter 12S and an area with decreasing inner diameter 16 on. The area with a large inner diameter 12L is located at one rear end of the insulator10 The area with a small inner diameter 12S is located in front of the area with a large inner diameter 17 and has a smaller inner diameter than the area with a large inner diameter 12L The area with decreasing inner diameter 16 is located between the area with a large inner diameter 12L and the area with a small inner diameter 12S , so that its inner diameter gradually decreases from back to front. In the present embodiment, the position of the area with decreasing inner diameter corresponds to 16 in the axial direction of the position of an anterior end part of the anterior body section 17 in the axial direction.

[0014] The inner metal housing part 50 consists of a conductive metallic material such as low-carbon steel and has a cylindrical shape, with a [missing information] along the axis AX through which it formed a passage hole 59 The inner metal housing part 50 is around an outer circumference of the insulator 10 arranged around it so that it forms the insulator 10 surrounds in the radial direction. In other words, the insulator 10 is in the through hole 59 of the inner metal housing part 50 inserted and held in it, with a front end part of the insulator 10 (foot section) 13 ) from a front end of the inner metal housing part 50 protrudes forward and forms a rear end part of the insulator. 10 from a rear end of the inner metal housing part 50 protrudes backwards.

[0015] The inner metal housing part 50 features a hexagonal, column-shaped tool engagement section 51 on, which is designed for the attachment of a spark plug wrench, a fastening thread section52 , which has an external thread for attaching the outer metal housing part 60 is formed on it, and has a bundle-shaped seat section 54 , which is between the tool engagement section 51 and the mounting thread section 52 is designed. In the present embodiment, the fastening thread section has 52 a nominal diameter of e.g. M8 until M14 on.

[0016] A metallic inner sealing ring 5A is on part of the inner metal housing 50 between the fastening thread section 52 and the seating section 54 attached to create a game between the seating section 54 of the inner metal housing part 50 and the seating area mentioned below 64 of the outer metal housing part 60 to seal.

[0017] The inner metal housing part 50It also features a thin crimp section 53 on, which is behind the tool engagement section 51 is provided for, and a thin compression deformation section 58 , which is between the seat section 54 and the tool engagement section 51 is provided. Ring-shaped sealing packings. 6 and 7 are located in an annular space between an inner circumferential surface of a part of the inner metal housing part 50 from the tool engagement section 51 up to the crimp section 53 and an outer circumferential surface of the posterior body section 18 of the insulator 10 arranged. Part of the annular space between these two sealing packings 6 and 7 is with a talcum powder 9 filled. One rear end of the crimp section. 53 is radially inwardly flanged and on the outer circumferential surface of the insulator 10fastened. The compression deformation section 58 It will be deformed by compression if pressure is applied to the outer circumferential surface of the insulator. 10 attached crimp section 53 during the manufacture of the spark plug 100 is pushed forward. With this compression deformation of the compression deformation section 58 The insulator will be 10 about the sealing packs 6 and 7 and the talc 9 inside the metal housing part 50 pushed forward. The inner metal housing part 50 It also features a step section 56 on which is formed on its inner circumference at a position corresponding to the fastening thread section 52 corresponds. If the insulator 10 As it is pushed forward, the section with decreasing outer diameter 15 of the insulator 10 via a ring-shaped plate packing 8 against the step section 56pressed. The record pack 8 Therefore, a distinction is made between the section with decreasing outer diameter. 15 and the stage section 56 held so that it prevents gas from escaping from the combustion chamber of the internal combustion engine through a gap between the inner metal housing part 50 and the insulator 10 prevented.

[0018] This involves part of the stage section. 56 , which is connected to the outer circumferential surface of the insulator 10 (more precisely, with the outer circumferential surface of the section with decreasing outer diameter) 15 ) about the plate pack 8 It is brought into contact with, also referred to as "sealing part SP".

[0019] The outer metal housing part 60 is made of a conductive metal material, which is the same as that of the inner metal housing part. 50or similar to this, and has a cylindrical shape, with a length along the axis AX through which it formed a passage hole 69 The outer metal housing part 60 is on an outer circumference of the inner metal housing part 50 at a position in front of the seat section 54 of the inner metal housing part 50 arranged. An internal thread 66 is located on an inner circumferential surface of the outer metal housing part 60 formed and is aligned with the external thread of the fastening thread section 52 of the inner metal housing part 50 in engagement. Through the engagement of the external thread and the internal thread. 66 is part of the inner metal housing section 50 , which is in front of the seating section 54 is located in the through hole 69 of the outer metal housing part 60 used and is held in it.

[0020] The outer metal housing part 60 has a fastening thread section 62 and a seating area 64 , which is located in a position behind the mounting thread section 62 is trained, as in Fig. 1 shown. In the present embodiment, the fastening thread section 62 a nominal diameter of e.g. M10 until M18 on. On an outer circumferential surface of the fastening thread section 62 An external thread is formed so that the spark plug 100 It is attached to the cylinder head of the internal combustion engine by screwing the external thread into a spark plug hole of the cylinder head.

[0021] A ring-shaped metallic outer seal 5B is on part of the outer metal housing part 60 between the fastening thread section 62 and the seating section 64 attached to, when the spark plug100 attached to the internal combustion engine, a gap between the spark plug 100 and to seal the internal combustion engine (cylinder head).

[0022] The cap 90 is with a front end part 61 of the outer metal housing part 60 connected, so that they have front-end openings 60o and 50o of the outer and inner metal housing parts 50 and 60 closes. The design of the cap 90 This will be explained in more detail below. Through the cap 90 An auxiliary combustion chamber BS is defined, so that the gap mentioned below G BS is formed in the auxiliary combustion chamber.

[0023] The cap 90 is made of a highly corrosion- and heat-resistant metal material such as nickel (Ni), a Ni-based alloy (such as NCF) 600 , NCF 601etc.) or tungsten (W). In the present embodiment, the outer metal housing part is 60 made from a nickel alloy, and the cap 90 is with the outer metal housing part 60 Made from a single piece. In other words, the outer metal housing part 60 and the cap 90 are manufactured as a single piece from the same material. Alternatively, the cap can be 90 separate from the outer metal housing part 60 shaped and welded to the front end part 61 of the outer metal housing part 60 be connected.

[0024] The center electrode 20 has a rod shape that extends along the axis AX extends. In the present embodiment, the central electrode 20made from a highly corrosion- and heat-resistant metal material such as nickel (Ni) or a Ni-based alloy (such as NCF) 600 , NCF 601 etc.). Alternatively, the center electrode can be used. 20 They have a double-layered structure comprising an electrode base, made, for example, of nickel or a nickel alloy, and a core embedded in the electrode base, made, for example, of copper (Cu) or a Cu-based alloy with a thermal conductivity higher than that of the electrode base. The central electrode 20 is in a front end face of the axial hole 12 of the insulator 10 deployed and is held in this position.

[0025] The center electrode 20 features a federal section 24 , which is formed at a predetermined position in the axial direction, a head section 23(as an electrode head) located behind the fret section 24 is located, and a foot section 25 (as an electrode foot) located in front of the fret section 24 is located on. The federal section 24 is formed from its front end by the section with decreasing inner diameter 16 of the insulator 10 supported, i.e. on the section with decreasing inner diameter 16 of the insulator 10 held. A rear end part of the foot section. 25 is in the axial hole 12 arranged (area with small inner diameter) 12S) , while a front end part of the foot section 25 from a front end of the insulator 10 protrudes. A front end surface of the foot section 25 serves as a first discharge area 20S , which is connected to the second discharge surface mentioned below 30S the ground electrode 30a gap G educates.

[0026] The connecting electrode 40 It has a rod shape that extends in the axial direction. The connecting electrode 40 is inserted into the axial hole from the rear end 12 of the insulator 10 inserted and is located behind the center electrode 20 in the axial hole 12 The connecting electrode 40 It is made of a conductive material such as low-carbon steel. To prevent corrosion, a plating of nickel, etc., is applied to one surface of the terminal electrode. 40 upset.

[0027] The connecting electrode 40 features a federal section 42 (as a connecting collar) which is formed at a predetermined position in the axial direction, a cap fastening section 41 , which is located behind the federal section 42 is located, and a foot section 43(as a connecting foot) which is located in front of the federal section 42 is located on. The cap fastening section 41 protrudes from the rear side of the insulator 10 out, while the foot section 43 into the axial hole 12 of the insulator 12 inserted and arranged within it. Although not explicitly shown in the drawings, a spark plug cap with a high-voltage cable is attached to the cap mounting section. 41 attached to apply a high voltage to generate a spark discharge.

[0028] The resistance 70 is between a front end of the terminal electrode 40 and a rear end of the center electrode 20 within the axial hole 12 of the insulator 10 arranged. The resistance 70 has a resistance value of, for example, 1 kΩ or more (in the present embodiment) 5kΩ) and serves to reduce radio interference caused by the generation of a spark discharge. The resistance 70 It is made, for example, from a composition which contains glass particles as the main component, particles made of a ceramic material other than glass, and a conductive material.

[0029] A space between resistance 70 and the center electrode 20 within the axial hole 12 is equipped with the conductive sealing element 80A filled; and a space between the resistance 70 and the connecting electrode 40 within the axial hole 12 is equipped with the conductive sealing element 80B filled. In other words, the sealing element 80A is connected to the center electrode 20 and with the resistance 70 brought into contact, so that it is the center electrode 20 and the resistance 70keeps them apart; and the sealing element 80B will be with the resistance 70 and the connecting electrode 40 brought into contact, so that it encountered resistance 70 and the connecting electrode 40 This keeps the sealing elements apart. 80A and 80B arranged so that they form the central electrode 20 and the connecting electrode 40 about the resistance 70 connect them electrically and physically. Each of the sealing elements 80A and 80B is made from a conductive material, such as a composition containing particles of glass (such as B2O3-SiO2 glass) and particles of metallic material (such as Cu or Fe).

[0030] The ground electrode 30 It has the form of a column with a rectangular cross-section, with two end sections: a connecting end section 32 and a free end section31 , which is opposite the connecting end section 32 is located. The connecting end section 32 is e.g. by resistance welding to the front end of the inner metal housing part 50 connected. The metal casing 2 (inner and outer metal housing part) 50 and 60 ) and the ground electrode 30 are therefore electrically and physically connected to each other. Furthermore, the ground electrode 30 bent at a middle part of it by about 90 degrees, so that part of the ground electrode 30 near the end section of the connection 32 in a direction parallel to the axis AX extends, while part of the ground electrode 30 near the free end section 31 in a direction perpendicular to the axis AX extends.

[0031] The ground electrode 30is made of a highly corrosion- and heat-resistant metal material such as nickel or a nickel-based alloy (such as NCF) 600 , NCF 601 etc.) manufactured. As in the case of the center electrode 20 can the ground electrode 30 Alternatively, they may have a double-layered structure comprising an electrode base, e.g., made of Ni or a Ni alloy, and a core embedded in the electrode base, made of a metallic material (such as Cu) with a thermal conductivity higher than that of the electrode base. A rear surface of the free end section 31 serves as a second discharge surface 30S , which with the first discharge surface 20S the center electrode 20 the gap G forms. The first and second discharge surfaces 20S and 30S lie in the direction of the axis. AX They are opposite each other and facing each other. The gap G is a so-called discharge gap in which a spark discharge is generated.

[0032] Fig. 2 is an end view of the spark plug 100 , from the front end in a backward direction BD along the axis AX seen. As in Fig. As shown in 2, the cap 90 several (four in the present embodiment) through holes formed through them 95a until 95d to create a connection between the auxiliary combustion chamber BS and the outside. The through holes 95a until 95d are spaced apart from each other in the circumferential direction. In Fig. 2 are openings 95ao to 95do of the through holes for illustrative purposes. 95a until 95d on an inner circumferential surface of the cap 90 (also referred to here as "openings on the inner surface") 95ao until 95do “” and the main points CPa until CPd the openings 95ao until 95do depicted.

[0033] This involves a direction which is defined by the axis AX runs and in which the free end section 31 the ground electrode 30 extends as a first direction D1 designated, and a direction perpendicular to the first direction D1 is considered a second direction D2 designated. In the present embodiment, each of the four through holes is 95a until 95d arranged at a circumferential position, which is aligned with the first and second directions D1 and D2 forms an angle of 45°. For this reason, the through holes 95a until 95d in Fig. 1 not visible.

[0034] Fig. Figure 3 is a sectional view (cross-sectional view) of a front end part of the spark plug. 100along the line A-A from Fig. 2. More precisely, Fig. Figure 3 shows a section (cross-sectional view) CF1 of the front end part of the spark plug 100 along a plane which is the axis AX , the center of gravity CPa of the inner surface opening 95ao of the through hole 95a and the focus CPb the opening on the inner surface 95bo of the through hole 95b contains. As in Fig. As shown in 3, the cap 90 It has an essentially hemispherical, hollow shape. The auxiliary combustion chamber BS is accordingly essentially hemispherical.

[0035] The front end part of the foot section 13 (Insulator 10 ), the ground electrode 30 and the front end part of the foot section 25 (center electrode) 20 ) are located within the auxiliary combustion chamber BS. Furthermore, the gap is located G in the auxiliary combustion chamber BS.

[0036] In the present embodiment, the cap 90 no through holes at the positions of the cut with the axis AX trained, as in Fig. 2 and Fig. Figure 3 shows the positions of the four through holes. 95a until 95d in the axial direction they essentially correspond to the position of the free end section 31 the ground electrode 30 in the axial direction and the position of the gap G in the axial direction.

[0037] As in Fig. 3. Indicated by dashed lines, an imaginary plane is shown, which is perpendicular to the axis. AX extends to create a front-end opening 12o of the axial hole 12 of the insulator 10 to conclude, as a first imaginary level VS1 designated; and imaginary planes that have minimal areas to accommodate the openings on the inner surfaces. 95ao until 95do the through holes 95a until 95d To conclude, each is considered a second imaginary level. VS2a until VS2d designated. In Fig. 2 are the four second imaginary planes VS2a until VS2d , which are the four openings on the inner surface 95ao until 95do correspond, indicated by hatching. In Fig. 3 are the two second imaginary planes VS2a and VS2b , which are the two openings on the inner surface 95ao and 95bo Corresponding lines are indicated by dashed lines.

[0038] Fig. 4A, Fig. 4B, Fig. 5A and Fig. 5B are schematic views to explain the volume A one in the spark plug 100 defined imaginary space W and volume B of parts VP the ground and center electrode 30 and 20 , which are located in the imaginary space W. More precisely, Fig. 4A and Fig. 5A each show the section (cross-section) CF1 of the front end part of the spark plug 100 ; and Fig. 4B and Fig. Figures 5B each show a section (cross-section). CF2 of the front end part of the spark plug 100 along the line B-B from Fig. 2, i.e. along a plane which contains the axis AX and is parallel to the first direction D1 extends into which the free end section 31 the ground electrode 30 extends.

[0039] As in Fig. 4A and Fig. 4B, represented by hatching, shows the imaginary space W at a location in front of the sealing part SP through an inner surface 90i the cap 90 , an area of ​​the metal casing 2 (e.g. a front end face) 50s and an inner and an outer circumferential surface 50i and 50u of the inner metal housing part 50), an area of ​​the insulator 10 (e.g. a front end face) 13a and an outer circumferential surface 13o of the foot section 13 ), the first imaginary level VS1 and the second imaginary levels VS2a until VS2d defined. The imaginary space. W is considered the space which is the auxiliary combustion chamber BS serves as an illustration. For illustrative purposes, the following are included: Fig. 4A and Fig. 4B Parts of the spark plug 100 , which do not belong to the imaginary space W (auxiliary combustion chamber BS), are not marked with hatching.

[0040] As in Fig. 5A and Fig. 5B, represented by hatching, are the parts VP the ground and center electrode 30 and 20 in imaginary space W arranged. For illustrative purposes, the spark plug 100 , which do not belong to the parts VP belong, not marked with hatching.

[0041] In the present embodiment, the spark plug 100 as follows. The spark plug 100 It is used by attaching it to the internal combustion engine, such as a gas engine, as mentioned above. In this case, the internal combustion engine is equipped with an ignition system (such as a fully transistorized ignition system) that has a predetermined current source. When the ignition system applies a voltage between the ground electrode 30 and the center electrode 20 the spark plug 100 When applied, a spark discharge occurs in the gap. G between the ground electrode 30 and the center electrode 20 generated, that is, in the auxiliary combustion chamber BS inside the cap 9 On the other hand, a fuel gas in the combustion chamber of the internal combustion engine passes through the through holes. 95a until 95d the cap 90 through into the auxiliary combustion chamber BS introduced. The fuel gas in the auxiliary combustion chamber BS It is then ignited by the resulting spark discharge. The combustion of the ignited fuel gas produces a flame, which spreads through the through-holes. 95a until 95d the cap 90 The gas escapes to the outside, that is, into the combustion chamber of the internal combustion engine. The fuel gas in the combustion chamber is ignited by the spreading flame. As a result, all the fuel gas in the combustion chamber is rapidly combusted, even in an internal combustion engine where the combustion chamber has a relatively large volume.

[0042] In the event that the flame is in imaginary space W developed, with the ground electrode 30 or the center electrode 20 within the imaginary space W, before they pass through the through holes 95a until 95d the cap 90As the heat spreads through to the combustion chamber of the internal combustion engine, a heat loss (loss of thermal energy) of the flame occurs due to the quenching effect of the electrode. 30 , 20 The heat loss from the flame leads to a deterioration in its ignitability, causing the combustion gas in the combustion chamber of the internal combustion engine to ignite. In the case that the flame is located in an imaginary space... W developed, with the ground electrode 30 or the center electrode 20 within the imaginary space W, before they pass through the through holes 95a until 95d the cap 90 Furthermore, as the flame spreads through to the combustion chamber of the internal combustion engine, a pressure loss of the flame occurs due to contact between the flame and the electrode. 30 , 20The pressure drop of the flame causes a reduction in its kinetic energy. As a result of this reduction in kinetic energy, flame growth in the combustion chamber of the internal combustion engine becomes more difficult. The pressure drop of the flame thus also leads to a deterioration in ignition.

[0043] In the present embodiment, the spark plug 100 designed to satisfy the condition (B / A) ≤ 0.25, thereby increasing the volume B the parts VP the ground and center electrode 30 and 20 , which are located in imaginary space W are located relative to the volume A of imaginary space W (as the auxiliary combustion chamber BS ) is sufficiently small. Consequently, the heat and pressure losses that occur through contact in the imaginary space are W developed flame with the electrode 30 , 20The ignition capability of the spark plug is reduced. 100 will therefore be improved.

[0044] Preferably, in the present embodiment, the condition (B / A) ≤ 0.15 is met. In this design, the volume B the parts VP the ground and center electrode 30 and 20 , which are located in imaginary space W are located relative to the volume A of imaginary space W especially small. The heat and pressure losses that occur through contact between the flame, which developed in the imaginary space W, and the electrode 30 , 20 The resulting emissions are therefore reduced even further. This improves the spark plug's ignition capacity. 100 improved even further.

[0045] Preferably, in the present embodiment, the condition 0.005 ≤ (B / A) is also fulfilled. In this design, the volume B the parts VP the ground and center electrode 30 and 20 , which are located in imaginary space W are located relative to the volume A of imaginary space W not excessively small. This prevents the wear resistance of the ground and center electrodes from being compromised. 30 and 20 is reduced too much.

[0046] Furthermore, in the present embodiment, the width of the gap is preferably G between the center electrode 20 and the ground electrode 30 in the axial direction, that is, the distance between the first discharge surface 20S and the second discharge area 30S , 0.2 mm or more. If the gap L is small, the flame that is in the gap will G developed, with the electrode 20 , 30 Contact occurs at the stage where the core of the flame is small. The extinguishing effect of the electrode.30 , 20 The gap becomes larger, which results in a significant amount of energy being drawn from the flame. In other words, the smaller the gap, the more energy is drawn from the flame. G The smaller the electrode, the slower the flame growth. The extinguishing effect of the electrodes 30 and 20 The amount of heat transferred from the spark plug is effectively reduced when the gap width is 0.2 mm or greater, compared to when the gap width is less than 0.2 mm. 100 The amount of gas released into the combustion chamber of the internal combustion engine is consequently increased, thus increasing the combustion velocity of the fuel gas. This improves the ignition capability of the spark plug. 100 further improved. ASSESSMENT TESTS

[0047] The following evaluation tests were carried out to verify the effects of the above embodiment.

[0048] For the evaluation test, 30 types of spark plug samples were prepared, in which the number of parts in the cap 90 formed through holes (hereinafter also simply referred to as "number of holes"), the diameter R1 the respective through holes (hereinafter also simply referred to as "hole diameter") R1 “ denoted, see Fig. 2), the arrangement angle θ of the respective through holes (see Fig. 3) the volume A of the imaginary space W (see Fig. 4), the volume B of parts VP (see Fig. 5) and / or the width of the column G in the axial direction (hereinafter also simply referred to as "gap width").

[0049] Here, the arrangement angle θ is determined with reference to Fig. 3 explained, where the through hole 95a is used as an example. In section (cross-section) CF1 ( Fig. 3), which runs along the plane which is the axis AX and the center of gravity CPa of the inner surface opening 95ao of the through hole 95a Contains a point that lies on the axis AX lies and from the first discharge surface 20S and the second discharge area 30S is equidistant, as a splitting center GP denoted; a ray emanating from the slit center GP exits and leads to the through hole 95a towards the axis AX extending in a vertical direction, it is considered the first ray. L1 designated; and a ray emanating from the slit center GP originates and is centered on CPa the opening on the inner surface 95ao of the through hole 95a It runs as a second beam L2 The angle θ of the through-hole is designated. 95a is an angle that is in the section (cross-section) CF1 between the first and second beam L1 and L2 is formed.

[0050] The hole diameter R1 The thickness was chosen to be 1 mm or 2 mm. The number of holes was chosen to be 2, 4, 6, or 8. The arrangement angle θ was chosen to be 15 degrees, 30 degrees, 45 degrees, 60 degrees, or 75 degrees. The volume A was achieved by adjusting the inner diameter of the cap 90 and the length of the cap 90 in the direction of the axis AX with 350 mm 3 , 450 mm 3 , 550 mm 3 or 650 mm 3 The volume B was chosen by adjusting the outer diameter. R2 of the foot section 25 the center electrode 20 (see Fig. 3) the overhang length H2 of the foot section 25 the center electrode 20 regarding the front end of the insulator 10 (see Fig. 3) the length H1 of the free end section 31the ground electrode 30 in the direction of the AX axis (see Fig. 3) and the length W of the free end section 31 the ground electrode 30 in the second direction D2 (see Fig. 2) with 1.4 mm 3 , 2.4 mm 3 , 3.3 mm 3 , 4.1 mm 3 , 7.3 mm 3 , 15 mm 3 , 23.1 mm 3 , 37.9 mm 3 , 47.5 mm 3 , 52.5 mm 3 , 54.8 mm 3 , 68 mm 3 , 87.5 mm 3 or 87.8 mm 3 selected. The width of the column. G The dimensions chosen were 0.7 mm, 0.6 mm, 0.5 mm, 0.4 mm, 0.3 mm, 0.2 mm or 0.1 mm.

[0051] The hole diameter R1 , the number of holes, the arrangement angle θ, the volume A , the volume B and the gap width of the respective patterns are together with the ratio of the volume A to the volume B(hereinafter also referred to as "volume ratio B / A") in TABLE 1 specified. Table 1 Nr. Lochdurchmesser (mm) Löcheranzahl Anordnungswinkel (Grad) Volumen A (mm 3 ) Volumen B (mm 3 ) (B / A) Spaltbreite (mm) Verbrennungsstabilität Verschleißbeständigkeit Brenngeschwindigkeit 1 1 4 15 350 1,4 0,004 0,7 A B A 2 1 4 30 350 2,4 0,007 0,7 A A A 3 1 4 45 350 4,1 0,012 0,7 A A A 4 1 4 60 350 7,3 0,021 0,7 A A A 5 1 4 75 350 15 0,043 0,7 A A A 6 1 4 45 350 23,1 0,066 0,7 A A A 7 1 4 45 350 37,9 0,108 0,7 A A A 8 1 4 45 350 47,5 0,136 0,7 A A A 9 1 4 45 350 52,5 0,15 0,7 A A A 10 1 4 45 350 54,8 0,157 0,7 B A A 11 1 4 45 350 68 0,194 0,7 B A A 12 1 4 45 350 87,5 0,25 0,7 B A A 13 1 4 45 350 87,8 0,251 0,7 C A A 14 1 4 45 450 87,8 0,195 0,7 B A A 15 1 4 45 550 87,8 0,160 0,7 B A A 16 1 4 45 650 87,8 0,135 0,7 A A A 17 1 4 45 650 3,3 0,005 0,7 A A A 18 1 4 45 650 2,4 0,004 0,7 A B A 19 1 2 45 350 15 0,043 0,7 A A A 20 1 6 45 350 15 0,043 0,7 A A A 21 1 8 45 350 15 0,043 0,7 A A A 22 0,5 4 45 350 15 0,043 0,7 A A A 23 1,5 4 45 350 15 0,043 0,7 A A A 24 2 4 45 350 15 0,043 0,7 A A A 25 1 4 45 350 52,5 0,15 0,6 A A A 26 1 4 45 350 52,5 0,15 0,5 A A A 27 1 4 45 350 52,5 0,15 0,4 A A A 28 1 4 45 350 52,5 0,15 0,3 A A A 29 1 4 45 350 52,5 0,15 0,2 A A A 30 1 4 45 350 52,5 0,15 0,1 A A B

[0052] The inner diameter of the inner metal housing part 50 A uniform measurement of 7.2 mm was chosen for all samples.

[0053] Using the above prepared spark plug samples, the combustion stability test, the wear resistance test, and the burning rate test were carried out.

[0054] In the combustion stability test, each sample was tested by installing the sample in a real 1.6-liter four-cylinder in-line direct-injection gasoline engine with a supercharger and running the gasoline engine 3000Cycles were run under conditions of an engine speed of 2000 rpm, an indicated mean effective pressure (NMEP) of 1200 kPa, and an air-fuel ratio (A / F) of 14.5. The coefficient of variation (COV) of the indicated mean effective pressure during operation of the gasoline engine was then determined. The lower the coefficient of variation of the indicated mean effective pressure, the lower the probability of misfires and the higher the ignitability of the fuel mixture.

[0055] The criteria for evaluating combustion stability were as follows: “A” if the coefficient of variation of the indicated mean effective pressure was less than 1%; “B” if the coefficient of variation of the indicated mean effective pressure was greater than or equal to 1% and less than 2%; and “C” if the coefficient of variation of the indicated mean effective pressure was greater than or equal to 2%. The results of the combustion stability evaluation of the respective samples are also shown in TABLE. 1 specified.

[0056] The combustion stability was rated "A" or "B" for all samples Nos. 1 to 12 and 14 to 30 that met the condition (B / A) ≤ 0.25. In contrast, the combustion stability for sample No. 13, which met the condition (B / A) > 0.25, was rated "C". These results show that the spark plug 100 Improved ignition capability is achieved by fulfilling the condition (B / A) ≤ 0.25.

[0057] Among samples 1 to 12 and 14 to 30 that met the condition (B / A) ≤ 0.25, the combustion stability for samples 1 to 9 and 16 to 30 that met the condition (B / A) ≤ 0.15 was rated "A", while the combustion stability for samples 10 to 12, 14, and 15 that met the condition (B / A) > 0.15 was rated "B". These results show that the spark plug 100 By fulfilling the condition (B / A) ≤ 0.15, a further improved ignition capability is achieved.

[0058] In the wear resistance test, each sample was tested by installing the sample in a real 2-liter four-cylinder in-line direct-injection gasoline engine with a supercharger and running the gasoline engine 100The test was conducted for several hours under conditions of 4000 rpm, wide-open throttle (WOT), an indicated mean effective pressure of 190 kPa, and an air-fuel ratio (A / F) of 12. After running the gasoline engine, the amount of increase in the gap width was measured. The smaller the increase in gap width, the higher the wear resistance of the sample.

[0059] The criteria for assessing wear resistance were as follows: “A” if the increase in gap width was less than 0.2 mm; and “B” if the increase in gap width was greater than or equal to 0.2 mm and less than 0.3 mm. No sample had a gap width increase of 0.3 mm or more. The results of the wear resistance assessment for each sample are also shown in TABLE. 1 specified.

[0060] The wear resistance was rated "A" for all samples Nos. 2 to 17 and 19 to 30 that met the condition 0.005 ≤ (B / A). In contrast, the wear resistance for samples Nos. 1 and 18 that met the condition 0.005 > (B / A) was rated "B". These results demonstrate that meeting the condition 0.005 ≤ (B / A) prevents the wear resistance of the spark plug from decreasing. 100 reduced too much.

[0061] In the combustion speed test, each sample was tested by installing the sample in a real 1.6-liter four-cylinder in-line direct-injection gasoline engine with a supercharger and running the gasoline engine 3000Cycles were run under conditions of an engine speed of 2000 rpm, an indicated mean effective pressure (NMEP) of 1200 kPa, and an air-fuel ratio (A / F) of 14.5. The time required to change the mass fraction burned (MFB) of the fuel from 10% to 90% was then measured during operation of the gasoline engine. The shorter the measured time, the higher the combustion rate of the sample.

[0062] Furthermore, an ordinary spark plug without a cap was used. 90 (that is, a standard spark plug for a test gasoline engine) was prepared as a comparison example and tested in the same way as above. The percentage by which the time measured for the sample had decreased compared to the time measured for the comparison example was determined (hereinafter referred to as the "depreciation rate").

[0063] The criteria for evaluating the burning rate were as follows: “A” if the decay rate was higher than 20%; and “B” if the decay rate was greater than or equal to 10% and lower than 20%. No sample had a decay rate lower than 10%. The results of the burning rate evaluation for each sample are also shown in TABLE. 1 specified.

[0064] The combustion rate was rated "A" for all samples No. 1 to 29 where the gap width was greater than or equal to 0.2 mm. In contrast, the combustion rate for sample No. 30, where the gap width was less than 0.2 mm, was rated "B". These results demonstrate that the spark plug achieves improved ignition performance by controlling the gap width to 0.2 mm or more. MODIFIED EXAMPLES

[0065] The special design of the spark plug explained above100 This is merely one embodiment, and it is not intended to limit the present invention to it.

[0066] Fig. Figure 6 is a sectional view (cross-sectional view) of a modified example of the above embodiment of the present invention, which corresponds to the view in Fig. 3 corresponds. The modified example of Fig. 6 is similar in structure to the embodiment described above, except for a metal housing. 2B , a cap 90B , a ground electrode 30B and an insulator 10B , as in Fig. 6 shown. (1) The metal casing 2B It is made from a single piece and not divided into two parts. The cap 90B is welded to a front end face of the metal housing 2B connected. Furthermore, the ground electrode is 30B in the form of a round rod (a bar) along the axis AX formed. A rear end face of the ground electrode 30B serves as a second discharge surface 30S A front end face of the ground electrode 30B is by welding to an inner surface of the cap 90B connected. The ground electrode 30B is therefore over the cap 90B with the metal casing 2B electrically connected. In this way, the cap and the metal housing can be varied into different shapes. (2) In the Fig. As seen in the section view shown in 6, a front end surface is 13sB of the insulator 10B (foot section) 13 ) not perpendicular to the axis AX , but is with respect to the axis AX inclined. A front-end opening 12oB of the axial hole 12B of the insulator 10B is therefore inclined in the same way as the front end face 13sB of the insulator 10BIn this case, an imaginary plane passing through a rear end of the opening is used. 12oB runs and is perpendicular to the axis AX extends, as in Fig. 6 is shown as a first imaginary plane VS1 designated. (3) Since the openings 95aoB and 95boB of the through holes are located on the inner surface sides 95aB and 95bB the cap 90B Beveled areas FR are provided, as in Fig. Figure 6 shows the diameter of the through holes. 95aB and 95bB partially enlarged. In this case, imaginary planes with minimal areas are used to represent the innermost parts of the through holes. 95aB and 95bB with the exception of the beveled areas FR, to close as second imaginary planes VS2a and VS2b designated.

[0067] Although this is not specifically shown in the drawings, the cap can 90In the above embodiment, instead of being in a hemispherical shape, it is formed in a cylindrical shape. In this case, the front end region of the imaginary space W a cylindrical shape.

[0068] In the above embodiment, the outer circumferential surface of the section decreases with decreasing outer diameter. 15 of the insulator 10 and the sealing part SP of the stage section 56 of the inner metal housing part 50 about the record pack 8 They are brought into contact with each other. Alternatively, the outer circumferential surface of the section can be reduced with decreasing outer diameter. 15 of the insulator 10 and the sealing part SP of the stage section 56 of the inner metal housing part 50 be brought into direct contact with each other.

[0069] The materials, shapes and dimensions of the respective spark plug components, such as the center electrode 20, the connecting electrode 40 , the ground electrode 30 and the metal casing 2 , can be varied as needed. Although in the above embodiment the center electrode 20 and the ground electrode 30 each made of only one material can be used to form the center electrode 20 and the ground electrode 30 Alternatively, they can be designed to comprise an electrode body and an electrode tip connected to the electrode body and made of a material that has a higher resistance to spark discharge than the material (e.g., a nickel alloy) of the electrode body. Examples of such tip materials are precious metals such as iridium (Ir) and platinum (Pt), tungsten (W), and an alloy containing at least one of these metals. In this case, a surface of the electrode tip serves as the discharge surface.

[0070] Although the present invention has been described above with reference to the specific embodiment and the examples, the embodiment and examples described above are intended to facilitate understanding of the present invention and not to limit the present invention to them. Various changes and modifications can be made to the embodiment and examples described above without altering the scope of protection of the present invention. The present invention includes equivalents thereof.

[0071] The entire content of Japanese patent applications No. 2018-158069 (filed on August 27, 2018) and No. 2019-095225 (filed on May 21, 2019) is incorporated herein by cross-reference. The scope of protection of the present invention is defined by the following claims. 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 2017103179

[0002] JP 2018158069

[0071]

Claims

[1] Spark plug (100), comprising: a center electrode (20; 20S) extending in one direction along an axis (AX) of the spark plug (100); an insulator (10; 10B) having an axial hole (12; 12B) formed therein in the direction of the axis (AX) to hold the central electrode (20; 20S) in a front end side of the axial hole (12; 12B); a cylindrical metal housing (2; 2B) arranged around an outer circumference of the insulator (10; 10B) and having a sealing element (SP) which is brought into contact with an outer circumferential surface of the insulator (10; 10B) directly or via another element (8); a ground electrode (30; 30B) arranged such that it forms a gap (G) with the center electrode (20; 20B); and a cap (90; 90B) connected to a front end part (61) of the metal housing (2; 2B) to cover a front end opening (50o, 60o) of the metal housing (2; 2B) and to define an auxiliary combustion chamber (BS) therein in which the gap (G) is formed, wherein the cap (90; 90B) has at least one through-hole (95a to 95d; 95aB, 95bB) formed in it to establish a connection between the auxiliary combustion chamber (BS) and the outside, where the condition (B / A) ≤ 0.25 is satisfied, wherein an imaginary plane extending perpendicular to the axis (AX) to close a front-end opening (12o; 12oB) of the axial hole (12; 12B) of the insulator (10; 10B) is called a first imaginary plane (VS1); an imaginary plane having a minimal area to close an inner-surface opening (95ao to 95do; 95aoB to 95boB) of the at least one through-hole (95a to 95d; 95aB, 95bB) of the cap (90; 90B) is called a second imaginary plane (VS2a to VS2d); A represents a volume of an imaginary space (W) defined by an inner surface (90i) of the cap (90; 90B), a surface (50s, 50u, 50i) of the metal housing (2; 2B), a surface (13o, 13s) of the insulator (10; 10B), the first imaginary plane (VS1) and the second imaginary plane (VS2a to VS2d); and B represents a volume of parts (VP) of the center and ground electrodes (20, 30;20B, 30B) represent, which are located in the imaginary space (W).; [2] Spark plug (100) according to claim 1, wherein the condition (B / A) ≤ 0.15 is satisfied. [3] Spark plug (100) according to claim 1 or 2, wherein the condition (B / A) ≥ 0.005 is satisfied. [4] Spark plug according to any one of claims 1 to 3, wherein the width of the gap (G) between the center electrode (20; 20B) and the ground electrode (30; 30B) in the direction of the axis (AX) is 0.2 mm or more.