Spark plug

Abstract

A spark plug includes an insulator provided with a shaft hole formed therein, a metal fitting caulked to support the insulator from an outer peripheral side of the insulator, and a talc material filled in an annular space provided between an outer peripheral surface of the insulator and an inner peripheral surface of the metal fitting. First and second annular members are provided at end portions of the annular space on a center electrode side along a central axis in the annular space, the second annular member being in contact with the first annular member from an opposite side of the center electrode.

Description

Technical Field

[0001] This disclosure relates to a spark plug. Background Technology

[0002] The internal combustion engine of a vehicle is equipped with a spark plug for igniting its internal fuel. The spark plug includes an insulator that supports the center electrode and a metal fitting (i.e., a housing) that supports the insulator from the outside. The metal fitting is fastened and secured to the internal combustion engine. A connecting portion is provided on the side surface of the metal fitting, which allows tools such as spark plug wrenches to engage with it when the spark plug is connected to the internal combustion engine.

[0003] Japanese Patent No. 3502936 discloses a spark plug having an annular space located within the aforementioned connection portion between the outer peripheral surface of an insulator and the inner peripheral surface of a metal fitting. Talc material, which is powdered talc, is filled into the annular space. The talc material is used to enhance the spark plug's impact resistance during internal combustion engine operation and to prevent gas leakage from the internal combustion engine to the outside. Within the annular space, annular members are provided at two locations along the central axis of the spark plug to support the talc material within the annular space.

[0004] In spark plug manufacturing, the metal fitting is fastened to the insulator with talc material and a pair of annular members housed within an annular space. At this point, the talc material is compressed. The metal fitting receives forces from the compressed talc material along the direction of outward expansion.

[0005] In recent years, the limited space near the internal combustion engine due to component arrangement has necessitated smaller ignition coils. Consequently, the width between the two facing surfaces of the connection has become smaller compared to conventional technologies. With such a small width, the metal fittings may deform due to the force of the talc material, resulting in a reduced thickness of the connection.

[0006] If the metal fittings are deformed, it may be difficult to engage the spark plug with the tool when attaching it to the internal combustion engine. Furthermore, deformation of the metal fittings reduces the sealing performance of the talc material, which could cause gases from the internal combustion engine to leak out through the talc material.

[0007] The aforementioned patent document, Japanese Patent No. 3502936, discloses defining the dimensions (e.g., length and thickness) of the annular space filled with talc material to suppress deformation of metal fittings due to the force exerted by the talc material. However, based on experimental results conducted by the inventors of this disclosure, it was found that using only the structure disclosed in the aforementioned patent document is insufficient to adequately prevent deformation of metal fittings.

[0008] The inventors of this disclosure have discovered that the annular member, through which the talc material applies force, exerts a force on the metal fitting to expand outward according to the shape of the insulator, thereby causing further deformation of the metal fitting. In this respect, the aforementioned patent documents do not suggest or mention suppressing the deformation of the metal fitting caused by the force transmitted through the annular member. Summary of the Invention

[0009] This disclosure provides a spark plug capable of suppressing deformation of metal fittings.

[0010] The spark plug according to this disclosure includes: an insulator having a bore formed therein; a center electrode supported by the insulator at one end of the bore along its central axis; a metal fitting filled to support the insulator from its outer peripheral side; a ground electrode extending from the metal fitting, a portion of the ground electrode facing the center electrode; and a talc material filled in an annular space between the outer peripheral surface of the insulator and the inner peripheral surface of the metal fitting.

[0011] The first and second annular components are disposed at the ends of the annular space, which are located on the side of the central electrode along the central axis in the annular space. The second annular component contacts the first annular component from the opposite side of the central electrode.

[0012] In the spark plug constructed as described above, a first annular member and a second annular member are disposed at the ends of the annular space, located on the side of the center electrode along the central axis within the annular space. The second annular member contacts the first annular member from the opposite side of the center electrode. This construction suppresses the force exerted on the metal fitting from the annular member compared to conventional constructions that use a single annular member at the aforementioned location. Consequently, deformation of the metal fitting can be suppressed compared to conventional techniques.

[0013] According to this disclosure, a spark plug capable of suppressing deformation of metal fittings can be provided. Attached Figure Description

[0014] In the attached diagram:

[0015] Figure 1 This is a diagram showing the internal structure of the spark plug according to this embodiment;

[0016] Figure 2 It is shown Figure 1 A diagram of the enlarged portion of the structure shown;

[0017] Figure 3A and Figure 3B Each diagram shows the force applied from the annular member in the spark plug to the metal fitting according to a comparative example;

[0018] Figure 4 This is a diagram illustrating the force applied from the annular member in the spark plug to the metal fitting according to this embodiment;

[0019] Figure 5 It is a graph showing the relationship between the overlap width between the first and second annular members and the expansion amount of the two sides of the connection.

[0020] Figure 6A and Figure 6B Each diagram shows the force applied from the annular member in the spark plug to the metal fitting according to a comparative example;

[0021] Figure 7 It is a graph showing the relationship between the overlap width between the first and second annular members and the angle θ; and

[0022] Figure 8 This is a diagram showing the location of the connecting part. Detailed Implementation

[0023] This embodiment will be described with reference to the accompanying drawings. For ease of understanding, the same reference numerals will be used as much as possible for the same components in each drawing, and repeated descriptions will be omitted.

[0024] Reference Figure 1 The construction of the spark plug according to this embodiment will be described. Figure 1 The image shows spark plug 10, in which... Figure 1 The left side shows a cross-section taken along a surface including the central axis CX, which will be described later. For the center electrode 30 and terminal fitting 40, which constitute the components of spark plug 10, each outline is shown without showing a cross-section.

[0025] Spark plugs 10 are disposed at each cylinder in an internal combustion engine (not shown) and ignite the air-fuel mixture in the combustion chamber of each cylinder. Spark plugs 10 are provided with an insulator 20, a center electrode 30, a terminal fitting 40, a metal fitting 50, and a ground electrode 60.

[0026] Insulator 20 is a cylindrical member formed of an insulating material such as alumina. A shaft hole 200 is formed in insulator 20. The shaft hole 200 is configured to penetrate the central axis of insulator 20. The central axis of shaft hole 200 corresponds to the central axis of insulator 20. Hereinafter, the central axis of shaft hole 200 is also referred to as the central axis CX. When insulator 20 is traversed along a line perpendicular to the central axis CX, the cross-sectional shape of shaft hole 200 is circular.

[0027] The center electrode 30 is made of metal and is located at one end of the shaft hole 200 along the central axis CX. Figure 1The lower end is supported by an insulator 20. The center electrode 30 is a rod-shaped member, and most of it is arranged within the shaft hole 200. A portion of the center electrode 30 protrudes from the shaft hole 200 to the outside of the insulator 20, and the discharge chip 31 is attached to the front end of the portion protruding from the shaft hole 200.

[0028] Terminal fitting 40 is a metal component, and is located at the second end of the shaft hole 200 along the central axis CX. Figure 1 The upper end of the terminal fitting 40 is supported by glass or similar material inside the insulator 200. The terminal fitting 40 is a rod-shaped member, and most of it is disposed within the shaft hole 200. A portion of the terminal fitting 40 protrudes outside the insulator 20. This protruding portion serves as an electrode terminal to which voltage is applied from an external power source (not shown).

[0029] In insulator 20, the area along the central axis CX where the center electrode 30 is attached can be referred to as the front end side. Furthermore, in insulator 20, the area along the central axis CX where the terminal fitting 40 is attached can be referred to as the rear end side.

[0030] A resistor 71 is disposed in the shaft hole 200 between the terminal fitting 40 and the center electrode 30. The resistor 71 is configured to adjust the resistance of the electrical path from the terminal fitting 40 to the center electrode. The resistor 71 is made of a material in which a predetermined amount of carbon powder is added to powdered glass and zirconium oxide. The resistance of the resistor 71 is adjusted by the amount of carbon added. The resistor 71 is disposed at the electrical path between the terminal fitting 40 and the center electrode 30 to suppress electromagnetic noise associated with the spark discharge of the spark plug 10. The resistor 71 and the center electrode 30 are electrically connected via a conductive sealing layer 72. Similarly, the terminal fitting 40 and the resistor 71 are electrically connected via a conductive sealing layer 73. Each of the conductive sealing layers 72 and 73 is a conductive layer formed of a material in which copper powder is added to the powdered glass.

[0031] The metal fitting 50 is constructed as a cylindrical member that is positioned to cover a portion of the insulator 20 from its outer periphery. The entire body of the metal fitting 50 is made of metal. As described later, the metal fitting 50 is secured to and supports the insulator 20 by caulking. The metal fitting 50 includes a connecting portion 52, a flange portion 55, and an insertion portion 56.

[0032] The connecting portion 52 is the part that engages with a tool such as a spark plug wrench when the spark plug 10 is attached to the internal combustion engine. When viewed along the central axis CX, the connecting portion 52 is hexagonal in shape. According to this embodiment, the width between two facing surfaces (width between the two surfaces) in the connecting portion 52 is 16 mm. Note that the connecting portion 52 may have a double hexagonal shape when viewed along the central axis CX.

[0033] When the spark plug 10 is attached to the internal combustion engine, the flange portion 55 contacts the outer surface of the internal combustion engine via the gasket GK. The flange portion 55 is located on the front end side where the connecting portion 52 is located and protrudes towards the outer periphery. A deformable portion 54 is located between the flange portion 55 and the connecting portion 52, which will be described later.

[0034] The insertion portion 56 is located on the front end side where the flange portion 55 is located, and is inserted into the insertion hole (not shown) formed in the internal combustion engine. An external thread is formed on the outer peripheral surface of the insertion portion 56. When the spark plug 10 is attached to the internal combustion engine, the connecting portion 52 rotates around the central axis CX under the force applied by a tool. Therefore, the internal thread formed on the inner peripheral surface of the insertion hole and the external thread 561 of the insertion portion 56 engage with each other. Thus, the spark plug 10 is tightened and fixed to the internal combustion engine. With the spark plug 10 attached to the internal combustion engine, the potential of the metal fitting 50 is the same as the ground potential of the internal combustion engine.

[0035] The ground electrode 60 is made of metal and is formed to extend from the end of the metal fitting 50 to a more distant front end. The ground electrode 60 is bent and a portion thereof faces the discharge chip 31 of the center electrode 30 along the central axis CX. The ground-side chip 61 is attached to the portion of the ground electrode 60 facing the discharge chip 31. The gap formed between the ground-side chip 61 and the discharge chip 31 serves as a discharge gap.

[0036] like Figure 1 As shown, an annular space SP is formed inside the connecting portion 52 between the outer peripheral surface of the insulator 20 and the inner peripheral surface of the metal fitting 50. The annular space SP is a space having an annular shape and formed around the central axis CX. The end of the annular space SP on the front end side is separated by a protrusion 211 (see...). Figure 2 The annular space SP is separated at its rear end by a filler portion 51 of the metal fitting 50. The filler portion 51 is positioned in the metal fitting 50 closer to the rear end than the connecting portion 52. The filler portion 51 deforms toward the inner circumference when being filled.

[0037] Talc material, in the form of powdered talc, is filled into the annular space SP. The talc material TC enhances the impact resistance of the spark plug 10 when attached to the internal combustion engine and prevents gas from the internal combustion engine from leaking toward the rear end.

[0038] In the annular space SP, the annular member 90 is disposed at the end on the rear end side (i.e., the opposite side of the central electrode 30) along the central axis CX. Furthermore, in the annular space SP, the first annular member 81 and the second annular member 82 are disposed in contact with each other at their ends on the front end side (i.e., the side of the central electrode 30) along the central axis CX. Each of the annular member 90, the first annular member 81, and the second annular member 82 is formed in an annular shape to surround the central axis CX. For example, each of the annular member 90, the first annular member 81, and the second annular member 82 is made of a hard metal material such as carbon steel. The cross-sectional shape of each of the annular member 90, the first annular member 81, and the second annular member 82, when cross-sectioned at the surface including the central axis CX, is circular.

[0039] Therefore, according to this embodiment, a single annular member 90 is provided on the rear end side of the talc material TC, but multiple annular members (first annular member 81 and second annular member 82) are provided on the front end side of the talc material TC. The reason for this arrangement will be described later.

[0040] The method of securing the metal fitting 50 to the insulator 30 will be described. First, the insulator 20 is inserted into the metal fitting 50 from the rear end side. At this time, as... Figure 1 As shown, the filler portion 51 has not yet deformed, but extends linearly on the rear end side. In other words, the rear end side of the annular space SP faces the external opening.

[0041] A protrusion 562 is formed on the inner circumferential surface of the insertion portion 56 of the metal fitting 50. The insulator 20 inserted into the metal fitting 50 stops in contact with the protrusion 562 at the stepped portion formed on its outer circumference. Subsequently, the first annular member 81, the second annular member 82, the talc material TC, and the annular member 90 are arranged in the annular space SP in this order.

[0042] Next, a force is applied between the bottom surface of the flange portion 55 (the surface that will contact the washer Gk) and the front end of the filler portion 51 along the central axis CX to compress it therebetween. This force deforms the filler portion 51 to displace it toward the inner circumferential side, as... Figure 1 As shown.

[0043] Furthermore, since the deformed portion 54 formed between the connecting portion 52 and the flange portion 55 is relatively thin, the deformed portion 54 is bent. Therefore, since the distance from the caulking portion 51 to the protrusion 562 is shortened, the insulator 20 is forcefully pressed against the protrusion 562 by the force via the talc TC. Using the above method, the metal fitting 50 is caulked to support the insulator 20 from the outer peripheral side of the spark plug 10, thereby fixing it to the insulator 20.

[0044] In such Figure 1With the metal fitting 50 in the sealed state, compressive force has been applied to the talc material TC. In this state, the talc material absorbs vibrations from the internal combustion engine, thus enhancing the shock resistance of the spark plug 10. Furthermore, the talc material TC becomes denser due to the compressive force, thereby functioning as a sealing material to prevent gas leakage from the internal combustion engine to the rear end.

[0045] refer to Figure 2 The following will describe the first annular member 81 and the second annular member 82, as well as the structures near the first annular member 81 and the second annular member 82. Figure 2 This is a magnified image, which is enlarged. Figure 1 Part of it. Figure 2 The portion referred to as 210 in the accompanying drawings is the outer peripheral surface of the insulator 20. In the following text, the outer peripheral surface is also referred to as outer peripheral surface 210.

[0046] In the insulator 20, a protrusion 211 is formed in the portion near the end of the annular space SP on the front end side. The protrusion 211 protrudes such that the diameter of the outer peripheral surface 210 increases the closer it is to the front end side (i.e., the side of the central electrode 30) along the central axis CX. Figure 2 In the cross-section shown, the line representing the outer peripheral surface of the protrusion 211 is an arc-shaped line protruding towards the front end. The protrusion 211 supports the first annular member 81 from the top end side. In the portion closer to the rear end side than the protrusion 211, the line representing the outer peripheral surface 210 of the insulator 20 is a straight line extending parallel to the central axis CX.

[0047] The first annular member 81 is positioned closer to the front end than the second annular member 82. The center diameter CD1 of the first annular member 81 is larger than the center diameter CD2 of the second annular member 82. The center diameter CD1 can also be described as being equal to twice the distance from the center of the cross-section of the first annular member 81 to the central axis CX. Figure 2 As shown. Furthermore, the center diameter CD2 can also be described as a dimension equal to twice the distance from the center of the cross-section of the second annular member 82 to the central axis CX, as... Figure 2 As shown.

[0048] exist Figure 2 In the accompanying drawing, the portion referred to as 520 is the inner circumferential surface of the metal fitting 50. In the following text, the inner circumferential surface may also be referred to as inner circumferential surface 520. Figure 2 In the cross-section shown, the line representing the inner circumferential surface 520 of the metal fitting 50 is a straight line extending parallel to the central axis CX.

[0049] Figure 2The “T” shown refers to the distance from the outer peripheral surface 210 to the inner peripheral surface 520 along the direction perpendicular to the central axis CX, that is, the width dimension of the part in the annular space SP that is different from the protrusion 211. Figure 2 The “t” shown is the distance from the front end of the protrusion 211 to the inner peripheral surface 520, that is, the width dimension of the gap formed in the front end side of the protrusion 211.

[0050] exist Figure 2 In this configuration, the diameter SD1 of the cross-section of the first annular member 81 is smaller than T and larger than t. Furthermore, the first annular member 81 contacts both the outer peripheral surface of the protrusion 211 and the inner peripheral surface 520 of the metal fitting 50. This configuration prevents leakage of talc material TC from the portion between the first annular member 81 and the inner peripheral surface 520. Additionally, the first annular member 81 cannot be located in the portion formed on the front end side of the protrusion 211.

[0051] The second annular member 82 is in contact with the first annular member 81 from the opposite side of the central electrode 30 (i.e., from the rear end side). Figure 2 In this context, the diameter SD2 of the cross-section of the second annular member 82 is smaller than the diameter SD1 of the cross-section of the first annular member 81. However, the diameter SD2 may be larger than the diameter SD1, or the diameters SD1 and SD2 may be the same, provided that the overlap width OL, which will be described later, is within a predetermined range.

[0052] The second annular member 82 contacts both the first annular member 81 and the outer peripheral surface 210. Note that the portion of the outer peripheral surface 210 that contacts the second annular member 82 may be in an area where the protrusion 211 is not formed or in an area where the protrusion 211 is formed.

[0053] Figure 2 The ID1 shown represents the inner diameter of the first annular member 81. In the following text, this inner diameter may be referred to as the inner diameter ID1. The inner diameter ID1 may also be described as a dimension equal to twice the distance from the innermost circumferential portion of the first annular member 81 to the central axis CX.

[0054] Figure 2 The OD1 shown represents the outer diameter of the first annular member 81. Hereinafter, this outer diameter may be referred to as the outer diameter OD1. The outer diameter OD1 may also be described as a dimension equal to twice the distance from the outermost portion of the first annular member 81 to the central axis CX. According to this embodiment, the outer diameter OD1 is equal to the inner diameter of the inner circumferential surface 520.

[0055] Figure 2The ID2 shown represents the inner diameter of the second annular member 82. Hereinafter, this inner diameter may be referred to as inner diameter ID2. Inner diameter ID2 may also be referred to as a dimension equal to twice the distance from the innermost portion of the second annular member 82 to the central axis CX. According to this embodiment, inner diameter ID2 is equal to the outer diameter of the portion of the outer circumferential surface 210 where the protrusion 211 is not formed.

[0056] Figure 2 The OD2 shown represents the outer diameter of the second annular member 82. In the following text, this outer diameter may be referred to as the outer diameter OD2. The outer diameter OD2 may also be described as a dimension equal to twice the distance from the outermost portion of the second annular member 82 to the central axis CX.

[0057] According to this embodiment, the outer diameter OD2 of the second annular member 82 is larger than the inner diameter ID1 of the first annular member 81. Therefore, when viewed along the central axis CX, a portion of the first annular member 81 and a portion of the second annular member 82 overlap. Figure 2 The overlap width OL shown refers to the width of a portion of the aforementioned overlapping portion along a direction perpendicular to the central axis CX. The overlap width OL can also refer to the distance from the innermost portion of the first annular member 81 to the outermost portion of the second annular member 82 along a direction perpendicular to the central axis CX in a cross-section of the spark plug 10 taken along the surface including the central axis CX. The overlap width OL is equal to half the outer diameter OD2 minus the inner diameter ID1. According to the construction of this embodiment, the overlap width OL is equal to the value calculated by the equation (SD2 - (T - SD1)).

[0058] Figure 2 The dotted line DL1 shown is a virtual line passing through the center of the cross-section of the first annular member 81 and the center of the cross-section of the second annular member 82. Furthermore, in Figure 2 In the diagram, the dashed line CX' is a straight line parallel to the central axis CX (not shown). Figure 2 The angle θ shown is the angle formed between the dashed line DL1 and the dashed line CX'. This angle θ can also be referred to as the angle formed between the straight line connecting the center of the cross-section of the first annular member 81 and the center of the cross-section of the second annular member 82 and the central axis CX.

[0059] Figure 2 The cross-section shown is the cross-section of spark plug 10, which is cut along a surface perpendicular to the two facing surfaces in the connection portion 52 and including the central axis CX. Furthermore, Figure 2 The dashed line DL52 shown represents the outline of the connector 52 in the cross-section of the spark plug 10 along the surface passing through the vertices of the hexagonal connector 52 and including the central axis CX.

[0060] In the metal fitting 50, the portion adjacent to the connecting portion 52 on the front end side (i.e., the portion marked with reference numeral 53) is formed such that the diameter of the outer peripheral surface of the metal fitting 50 decreases as it gets closer to the front end side along the central axis CX. Hereinafter, this portion may be referred to as the reduced portion. Figure 2 The dashed line DL13 shown indicates the vertex position of the hexagonal portion located at the rear end side along the central axis CX in the reduced portion, that is, the portion at the rear end side of the reduced portion 53 in the cross-section represented by the dashed line DL52 mentioned above. Furthermore, Figure 2 The dashed line DL13' shown represents the hexagonal planar portion located at the rear end side along the central axis CX in the reduced portion 53, that is, in Figure 2 The portion at the very end of the narrowed section 53 shown in the cross-section.

[0061] The reduced portion 53 is formed to extend until Figure 2 The dashed line DL11 indicates the location. In the portion further from the dashed line DL11 towards the front end, the diameter of the outer circumference of the metal fitting 50 is set such that the diameter increases as it approaches the front end along the central axis CX. The portion further from the dashed line DL11 towards the front end connects to... Figure 1 The deformed portion 54 is shown. In other words, the dashed line DL11 can be referred to as the line representing the portion along the foremost side of the central axis CX. Figure 2 In the cross-section shown, the line representing the outer periphery of the reduced portion 53 is an arc curve within the range from dashed line DL11 to dashed line DL12. The line representing the outer periphery of the reduced portion 53 is a straight line within the range from dashed line DL12 to dashed line DL13.

[0062] In this embodiment, a comparative example similar to conventional technology will first be described to illustrate the advantages of the two annular members (i.e., the first annular member 81 and the second annular member 82) arranged on the front end side of the talc material TC. Figure 3A and Figure 3B As shown, according to the comparative example, only a single annular member 80 is provided on the front end side of the talc material TC. Constructions other than this comparative example are similar to, for example... Figure 2 The construction shown in this embodiment is the same.

[0063] Figure 3A The diagram shows the state immediately following the caulking of the metal fitting 50. As described above, when the metal fitting 50 is caulked, compressive force is applied to the talc material TC. Therefore, the annular member 80 receives force from the talc material TC in the direction toward the front end side. Figure 3A In the diagram, the force applied to the ring member 80 by the talc material TC is represented by multiple arrows AR1.

[0064] The force from the talc material TC presses the annular member 80 against the protrusion 211. Therefore, the protrusion 211 receives the force in a direction substantially toward the front end side from the annular member 80. Figure 3A The arrow AR2 shown indicates the force applied from the annular member 80 to the protrusion 211.

[0065] Talc material TC is also present in the portion between the annular member 80 and the protrusion 211. In addition to the force in the direction toward the front end, the annular member 80 receives a force in the direction from the talc material present between the annular member 80 and the protrusion 211 toward the metal fitting 50 on its outer side. Therefore, the inner circumferential surface 520 of the metal fitting 50 receives a force in the direction substantially toward the outer circumferential side from the annular member 80. Figure 3A Arrow AR3 indicates the force applied from the annular member 80 to the inner circumferential surface 520.

[0066] The protrusion 211 is inclined such that the diameter of the outer peripheral surface 210 increases as it approaches the front end along the central axis CX. Therefore, as the annular member 80 pressing against the protrusion 211 moves outward along the protrusion 211, the annular member 80 is further pressed forcefully against the inner peripheral surface 520 of the metal fitting 50. The direction of the force indicated by arrow AR3 is substantially the same as the direction of the tangent (not shown), which touches the portion of the protrusion 211 that contacts the annular member 80.

[0067] As described, the annular member 80, which receives force from the talc material TC, applies force to the metal fitting 50 in an outwardly expanding direction. According to the comparative example, the reduced portion 53, i.e., the portion of the metal fitting 50 with a small thickness, exists near the portion of the metal fitting 50 from which force is applied. This structure is similar to that of this embodiment. Therefore, when the force indicated by arrow AR3 increases due to the caulking, the metal fitting 50 may deform, such as… Figure 3B As shown. In Figure 3B In the example shown, the outer peripheral surface of the contact portion 52 deforms to expand slightly outward. Figure 3B In the diagram, the shape of the metal fitting 50 before deformation is represented by dashed lines.

[0068] This deformation of the metal fitting 50 may cause problems where the tool cannot engage with the connection 52 when attaching the spark plug to the internal combustion engine. Furthermore, as the talc material TC softens due to the deformation of the metal fitting 50, the sealing performance of the talc decreases, allowing gases from the internal combustion engine to leak out through the talc material TC.

[0069] Therefore, according to this embodiment, the first annular member 81 and the second annular member 82 are arranged to overlap each other under the talc material TC, thereby preventing the metal fitting 50 from deforming during caulking. Figure 4 With similar Figure 3AThe method illustrates the state immediately following the filling of the metal fitting 50 according to this embodiment.

[0070] Furthermore, according to this embodiment, similar to the comparative example shown in FIG3, when the metal fitting 50 is filled, the first annular member 81 and the second annular member 82 are each subjected to force in a direction from the talc material TC toward the front end side (indicated by arrow AR1). Using this force, the first annular member 81 is pressed against the protrusion 211.

[0071] like Figure 4 As shown, according to the configuration of this embodiment, the second annular member 82 contacts the first annular member 81 from the rear end side and the inner circumferential side. Therefore, since the inner circumferential portion of the first annular member 81 in the annular space SP (i.e., the portion labeled SP0) is covered by the second annular member 82 from the rear end side, the talc material TC is not present in the inner circumferential portion of the first annular member 81. Therefore, the amplitude of the force received by the second annular member 82 from the talc material TC toward the outer circumferential side is less than that shown. Figure 3A The magnitude of the force in the comparative example is shown. As a result, the force (arrow AR3) applied from the first annular member 81 to the inner circumferential surface 520 is also less than... Figure 3A The force of the comparative example shown.

[0072] Note that, according to this embodiment, the first annular member 81 is forcefully pressed against the protrusion 211 by a force from the second annular member 82 disposed on the rear end side. Therefore, the force (arrow AR2) applied from the first annular member 81 to the protrusion 211 is greater than that of the second annular member 82. Figure 3A The force of the comparative example shown.

[0073] Therefore, according to this embodiment, the first annular member 81 and the second annular member 82 are arranged to overlap each other below the talc material TC, thereby linking / achieving the balance of forces indicated by arrows AR2 and AR3. As a result, compared with conventional techniques, the force applied from the first annular member 81 to the inner circumferential surface 520 can be suppressed, and the deformation of the metal fitting 50 can be suppressed compared with conventional techniques.

[0074] The magnitude of the force applied from the first annular member 81 to the inner circumferential surface 520 varies according to the corresponding shapes of the first annular member 81 and the second annular member 82. Through experiments with various shapes of the first annular member 81 and the second annular member 82, the inventors of this disclosure have discovered that the magnitude of the force varies according to the aforementioned overlap width OL (see [link to original text]). Figure 2 And change.

[0075] Figure 5The relationship between the overlap width OL (horizontal axis) and the expansion of the two-sided width (vertical axis) is shown. The expansion of the two-sided width refers to the increase in the width of the two sides of the connection 52 when the metal fitting 50 is filled to secure it to the insulator 20. Figure 5 The graph shows the increase in the width of both sides of the connecting portion 52 when the diameter SD1 of the first annular member 81 is fixed at 1 mm and the diameter SD2 of the second annular member 82 is changed to various values. In the corresponding measurements, the first annular member 81 contacts the inner circumferential surface 520 of the metal fitting 50, and the second annular member 82 contacts the outer circumferential surface 210 of the insulator 20.

[0076] Figure 5 The line 16 shown represents the measured value of the expansion of the two-sided width for a sample with an initial two-sided width of 16 mm for the connecting part 52. Figure 5 The dW1 shown represents the expansion of the width of the two sides of a sample with a similar structure to the comparative example shown in Figure 3 (in which the connecting part 52 has an initial width of 16 mm on both sides). Figure 5 As shown, when the overlap width OL is in the range of 0.06 mm to 0.88 mm, the expansion of the width of both sides is the normal value (dW1) or less. When the overlap width OL is 0.06 mm and 0.88 mm, the expansion of the width of both sides is the same as the normal value (dW1).

[0077] Figure 5 The line 14 shown represents the measured value of the expansion of the two-sided width of a sample with an initial two-sided width of 14 mm for the connecting part 52. Figure 5 The dW2 shown represents the expansion amount of the two-sided width of a sample constructed similarly to the comparative example shown in Figure 3, where the connecting portion 52 has an initial two-sided width of 14 mm. Similarly, in this case, when the overlap width OL is in the range of 0.06 mm to 0.88 mm, the expansion amount of the two-sided width is the conventional value (dW2) or less. When the overlap width OL is 0.06 mm and 0.88 mm, the expansion amount of the two-sided width is the same as the conventional value (dW2).

[0078] When the overlap width is less than 0.06 mm, the expansion of the width on both sides becomes greater than that of conventional techniques. The reason is as follows. In this case, as... Figure 6A As shown, the second annular member 82 is deeply located inside between the first annular member 81 and the protrusion 211. Therefore, as indicated by arrow AR10, the force exerted by the second annular member 82 on the first annular member 81 in the vertical direction relative to the central axis CX becomes larger. As a result, the first annular member 81 is forcefully pressed against the inner circumferential surface 520 by arrow AR3, and this may cause an increase in the amount of expansion of both surfaces.

[0079] Furthermore, when the overlap width OL is greater than 0.88 mm, the expansion of the width on both sides becomes greater than that of conventional techniques. The reason is as follows. In this case, as... Figure 6B As shown, the gap between the second annular member 82 and the outer peripheral surface 210 widens, and talc material TC fills this gap. Therefore, the talc material TC filling this gap exerts a force on the second annular member 82 in the direction toward the outer metal fitting 50. This force is transmitted via the first annular member 81 to the inner peripheral surface 520 and may cause an increase in the expansion of both surfaces.

[0080] As described, by adjusting the corresponding shapes of the first annular member 81 and the second annular member 82 so that the overlap width OL is within the range of 0.06 mm to 0.88 mm, deformation of the connecting portion 52 can be suppressed. The aforementioned range of the overlap width OL is the same as when the diameter of the first annular member 81 is set to a value other than 1 mm. Furthermore, this also applies when the cross-sectional shape of at least the first annular member 81 or the second annular member 82 is not circular.

[0081] Note that, according to this embodiment, when the cross-sectional shape of the first annular member 81 and the second annular member 82 is circular, the aforementioned range of the overlap width OL can be expressed as follows: Figure 2 The angle θ is shown. Figure 7 The relationship between the overlap width OL (horizontal axis) and the angle θ (vertical axis) is shown. A configuration with an overlap width OL of 0.06 mm corresponds to a configuration with an angle θ of 77°. Therefore, when the shapes of the first annular member 81 and the second annular member 82 are adjusted to make the angle range from 13° to 77°, deformation of the connecting portion 52 can be suppressed compared to conventional techniques.

[0082] Note that when the width of both sides of the connecting portion 52 is greater than 16 mm, the effects and advantages obtained from the overlapping structure of the first annular member 81 and the second annular member 82 are less due to the high rigidity of the connecting portion 52 or the portion near the connecting portion 52. On the other hand, when the width of both sides of the connecting portion 52 is less than or equal to 16 mm, the rigidity of the connecting portion 52 or the portion near it decreases even if its size is reduced. In this respect, significant effects and advantages can be obtained using the structure of this embodiment. Therefore, the structure of this embodiment can be preferably applied to spark plugs 10 provided with connecting portions 52 with a width of less than or equal to 16 mm.

[0083] Figure 8 With Figure 2 The same view shows a cross-section of the spark plug 10 according to this embodiment. Figure 8 The dotted line DL21 shown represents the tangent of the portion of the protrusion 211 that contacts the first annular member 81.

[0084] When the metal fitting 50 is filled, the first annular member 81 tends to expand along the outer peripheral surface of the protrusion 211. Therefore, the direction of the force applied from the first annular member 81 to the inner peripheral surface 520 is along the direction of the dotted line DL21, which is a tangent.

[0085] Assuming the entire reduced portion is positioned further on the front end side than the portion indicated by the dashed line DL21, deformation of the metal fitting 50 including the connecting portion 52 is unlikely to occur because most of the force along the dashed line DL21 is applied to the highly rigid portion (connecting portion 52). In this case, even with the overlapping construction of the first annular member 81 and the second annular member 82 of this disclosure, the effect obtained is less significant.

[0086] On the other hand, such as Figure 8 As shown, according to this embodiment, at least a portion of the reduced portion 53 is positioned further on the rear end side than the portion indicated by the dashed line DL 21. In other words, the connecting portion 52 according to this embodiment is formed at a portion further on the rear end side than the portion indicated by the dashed line DL 21. With this configuration, since a force along the dashed line DL 21 is applied to the portion of the metal fitting 50 with low rigidity (the reduced portion 53), this portion may deform. Therefore, the connecting portion 52 may also deform. Therefore, with this configuration, significant effects can be obtained when the first annular member 81 and the second annular member 82 of this embodiment overlap.

[0087] The dashed line DL22 represents a tangent at the outermost peripheral portion of the protrusion 211, i.e., a virtual line where the shape of the protrusion extends further outward toward the peripheral side. According to this embodiment, at least a portion of the reduced portion 53 is positioned further on the rear end side than the portion shown by the dashed line DL22. In this case, even when the first annular member 81 contacts any point on the protrusion 211, at least a portion of the reduced portion 53 is always positioned further on the rear end side than the portion shown by the dashed line DL21. Therefore, as described above, significant effects can be obtained when utilizing the overlapping structure of the first annular member 81 and the second annular member 82 of this embodiment.

[0088] In the above embodiments, the case where each cross-sectional shape of the first annular member 81 and the second annular member 82 is circular is exemplified. However, at least either cross-sectional shape can be a shape other than circular. Even in this case, the outer diameter of the second annular member 82 is set to be larger than the inner circumferential surface of the first annular member 81, and the overlap width OL is set in the range of 0.06 mm to 0.88 mm, thereby suppressing deformation of the connecting portion 52.

[0089] In the above embodiment, the example illustrates a case where the center diameter CD1 of the first annular member 81 is larger than the center diameter CD2 of the second annular member 82. However, this configuration is not limited to, and the center diameter CD1 of the first annular member 81 can be set to be smaller than the center diameter CD2 of the second annular member 82. Even with this configuration, the force applied to the inner circumferential surface from the second annular member 82 can be changed, thereby suppressing deformation of the connecting portion 52.

[0090] In addition to the first annular member 81 and the second annular member 82, the plurality of annular members arranged below the talc material TC may also include other annular members. Specifically, three or more annular members may be provided below the talc material TC.

[0091] This embodiment has been described with reference to specific examples. However, this disclosure is not limited to these specific examples. This disclosure may include constructions modified by those skilled in the art based on the above specific examples, as long as they include the features of this disclosure. The elements, arrangements, conditions, and shapes included in the respective specific examples are not limited to exemplary constructions but may be appropriately modified. The various elements included in the above specific examples may be appropriately combined as long as there is no technical inconsistency.

Claims

1. A spark plug, comprising: An insulator having a shaft hole formed therein; The center electrode is supported by the insulator at one end of the shaft hole along its central axis; Metal fittings, which are slit to support the insulator from the outer peripheral side of the insulator; A grounding electrode extends from the metal fitting, a portion of which faces the center electrode; as well as Talc material is used to fill the annular space between the outer peripheral surface of the insulator and the inner peripheral surface of the metal fitting. in The first annular member and the second annular member are disposed at the ends of the annular space, the ends being positioned in the annular space along the central electrode side of the central axis. The second annular member contacts the first annular member from the opposite side of the central electrode side, and The second annular member contacts both the first annular member and the outer peripheral surface of the insulator, and the first annular member and the second annular member are arranged to have an overlapping width below the talc material.

2. The spark plug as claimed in claim 1, wherein... The center diameter of the first annular component is larger than the center diameter of the second annular component.

3. The spark plug as claimed in claim 1 or 2, wherein... The inner diameter of the first annular component is smaller than the outer diameter of the second annular component.

4. The spark plug as claimed in claim 3, wherein The overlap width is defined as the distance from the innermost portion of the first annular member to the outermost portion of the second annular member in a cross-section taken along the surface including the central axis of the spark plug, in a direction perpendicular to the central axis. The overlap width is in the range of 0.06 mm to 0.88 mm.

5. The spark plug as claimed in claim 3, wherein... The first annular member and the second annular member each have a circular cross-sectional shape in the cross-section of the spark plug taken along the surface including the central axis; The angle (θ) formed between the straight line connecting the center of the cross section of the first annular member and the center of the cross section of the second annular member and the central axis is in the range of 13° to 77°.

6. The spark plug as claimed in claim 1 or 2, wherein The metal fitting includes a connection portion on the outer periphery of the annular space, which allows a tool to engage with the spark plug when it is attached; and The width between the two facing surfaces in the connecting part is 16mm.

7. The spark plug as claimed in claim 1 or 2, wherein The metal fitting includes a connection in the outer peripheral side of the annular space, which allows a tool to engage with the spark plug when it is attached. The insulator includes protrusions that project such that the diameter of their outer circumferential surfaces increases towards the central electrode side along the central axis, and the protrusions support the first annular member from the central electrode side; and The connection is formed at a portion located further than the tangent on the opposite side of the central electrode, where the tangent touches the portion of the protrusion that contacts the first annular member.

Images