JP2019087328A - Spark plug, and manufacturing method of spark plug - Google Patents

Abstract

To improve a spark plug, and a manufacturing method thereof.SOLUTION: A spark plug 1 has a holding mechanism 20 for holding an insulator 8 while engaging in the body 2. Consequently, the insulator 8 is pressed in the longitudinal direction 5 toward a seal pedestal base 17 by applied pressure Fv, and a passage 6 is sealed so as not to pass combustion gas flow. A fixing mechanism 30 overlapping the opposite side to the front end 3 of the body 2, out of the holding mechanism 20, at least partially is installed on the body 2 and attached thereto. The insulator 8 is provided to project from the opposite side to the front end 3 of the body 2, out of the fixing mechanism 30, the fixing mechanism 30 overlaps the holding mechanism 20 and forms a gap 41 therebetween, and forms a gap 40 with the insulator 8.SELECTED DRAWING: Figure 1

Description

  The technology disclosed herein relates generally to spark plugs, and more particularly to spark plugs for internal combustion engines.

  The technology disclosed herein relates to a spark plug having the features defined in the preamble of claim 1 and a method of manufacturing a spark plug having the features defined in claim 12.

  The spark plug disclosed in DE 10 2012 101 168 A1 comprises a main body having a passage in which an insulator is inserted in an airtight manner. After insertion of the insulator, at the rear end of the body, the edge of the body is folded inward as a retention mechanism for the insulator and engaged with the insulator shoulder. The body has a contraction area of reduced cross section. The contraction area is heated by the current pulse and is simultaneously upset by applying an axial force. Subsequent cooling causes the body to shrink in the shrink zone and the insulator is clamped in the body by the axial pressure. This known method is in fact often used and is also called "electrical upset processing". The passage is thus sealed in such a way that the combustion gases acting at the front end of the spark plug which contact the combustion chamber during operation of the internal combustion engine do not pass through the passage in the body, in particular the intermediate space between the insulator and the body. ing.

German patent application 102012101168A1 specification German Patent Application Publication No. 102006043593 B3 German Patent Application Publication No. 102008040285 A1 German Patent Application Publication No. 10227371A1 U.S. Patent Application No. 2300646 European Patent Publication No. 1265328 A1

  During relatively long periods of operation of the spark plug, if the longitudinally acting pressure is reduced, for example due to fatigue of the body material and / or accidental overheating of the body, the combustion gas will flow between the insulator and the body. There is the possibility of entering an intermediate space or leaking out of the combustion chamber of the internal combustion engine through the passage. This is not desirable. The hot combustion gas flow through the passage leads to overheating of the spark plug, which reduces the force at the flange edge at the rear end of the body and may even push the insulator back from the body. Injection of the insulator by the high pressure combustion gas can cause considerable damage.

  A spark plug of the kind originally mentioned and a method of manufacture are known from DE 102006043593 B3. The known spark plug comprises a body having an insulator located therein and having a passageway which is held under pressure by the engagement and holding mechanism. The main body is fitted with an engaging and fixing mechanism that overlaps on the opposite side far from the front end of the holding mechanism. The fixing mechanism comprises a cylindrical housing and a hex portion welded on the rear end, which causes parts of the spark plug, in particular the insulator, to fail in the holding mechanism due to dangerous levels of maximum pressure It is provided to prevent the case from popping out of the cylindrical housing. The cylindrical housing is provided with at least one vent hole on the side, which allows the excess pressure to be relieved in the radial direction. A Teflon seal ring is provided at the rear of the cylindrical housing to prevent leakage gas from entering the rear area where the central conductor protrudes from the rear end of the insulator. Since the cylindrical housing has a smooth inner wall which continues to the hexagonal portion, if the insulator pops out in the event of failure, the insulator is first accelerated over a relatively long distance, and then the hexagonal portion It will collide with the narrow part formed at high speed.

  DE 102 00 040 285 A1 discloses a special shape of spark plug which optimizes the installation space, which requires a special design of the cylinder head. Here, the body does not have an external thread for screwing into the cylinder head. Instead, a clamp nut is provided in the rear end region of the body, the clamp nut having an external thread. The male thread is screwed into the corresponding female thread of the cylinder head to press the body of the spark plug towards the combustion chamber towards the seal seat. By proper design of the insulator, the clamp nut prevents the insulator from popping back from the body in the event of a failure.

  German patent application DE 102 27 371 A1 discloses a spark plug having a piezoelectric sensor. A sensor is closely spaced between the insulator retaining mechanism and the sleeve overlying the insulator back end to measure the deformation of the retaining mechanism that occurs with changes in combustion pressure. The sleeve is oriented towards the front end of the body and has a sharply reduced end which is welded to the cylindrical portion of the body. This thin-walled end of the sleeve is not robust enough to stop the insulator being accelerated back from the body in the event of failure of the retention mechanism. U.S. Pat. No. 2,300,646 discloses a spark plug having a main body and an insulator holding mechanism, and a rubber cap overlapping the holding mechanism is disposed on the rear end of the main body. Such rubber caps are likewise not suitable for preventing the insulator from popping out in case of failure of the holding mechanism. European Patent Publication No. 1,265,328 A1 discloses a spark plug comprising a body formed by assembling a plurality of parts and having an insulator held therein. The housing parts are pressurized with one another in the contact area by a welding process and the insulator is sealed within the body.

  German patent application DE 102 27 371 A1 discloses a spark plug having a piezoelectric sensor. A sensor is closely spaced between the insulator retaining mechanism and the sleeve overlying the insulator back end to measure the deformation of the retaining mechanism that occurs with changes in combustion pressure. The sleeve is oriented towards the front end of the body and has a sharply reduced end which is welded to the cylindrical portion of the body. This thin-walled end of the sleeve is not robust enough to stop the insulator being accelerated back from the body in the event of failure of the retention mechanism. U.S. Pat. No. 2,300,646 discloses a spark plug having a main body and an insulator holding mechanism, and a rubber cap overlapping the holding mechanism is disposed on the rear end of the main body. Such rubber caps are likewise not suitable for preventing the insulator from popping out in case of failure of the holding mechanism. European Patent Publication No. 1,265,328 A1 discloses a spark plug comprising a body formed by assembling a plurality of parts and having an insulator held therein. The housing parts are pressurized with one another in the contact area by a welding process and the insulator is sealed within the body.

  The technology disclosed herein is directed to improving the spark plug of the type originally described and the method of manufacturing the spark plug.

  This object can be achieved by a spark plug having the features of claim 1 and a method having the features of claim 12. Useful improvements are as described in the dependent claims.

  The spark plug comprises a metal body having a front end, a rear end, a longitudinal direction, and a longitudinally extending passage. At least one ground electrode conductively connected to the body may be located at the front end. An insulator comprising a central electrode is located in the passage. The central electrode may project from the insulator in the front end region and may form, with the at least one ground electrode, a spark gap or spark gap. At its front end area, the body has a sealing seat for the insulator located in the passage. The body has at its rear end area a retention mechanism which engages the insulator and holds it in the body, whereby the insulator is pressed longitudinally towards the seal pedestal by pressure and the combustion gas flow does not pass The passage is sealed. The retention mechanism can be designed as an annular shape, in particular as a continuous annular shape surrounding the insulator. The retention mechanism can be formed by a constriction of the passage in the body. The retention mechanism can be formed, in particular, by flanging the edge of the body after insertion of the insulator. The insulator may have an insulator shoulder that is oriented towards the rear end and engaged by the retention mechanism of the body. The body extends at least from the seal seat to the holding mechanism, and in particular the part comprising the seal seat and the holding mechanism can be designed as a single continuous part.

  The insulator may have a shoulder facing the front end of the body and resting on the seal pedestal of the body, inter alia through the seal ring. The insulator may likewise comprise a channel extending longitudinally and inside which the central electrode is located. An igniter can be located in the insulator passage that projects from the back end of the insulator and can be used to connect a power line. The igniter and the central electrode are connected to each other inside the insulator passage by a conductive molten glass element, and the molten glass element simultaneously seals the in-insulator passage so that the combustion gas flow does not flow.

  An engagement locking mechanism is mounted to the body that at least partially overlaps the side opposite to the front end of the retention mechanism. According to one embodiment, the insulator projects from the side opposite to the front end of the fastening mechanism. The securing mechanism overlaps the retaining mechanism, forming a gap with the retaining mechanism, and a gap with the insulator. Both gaps are small. The gap between the locking mechanism and the holding mechanism and / or the gap between the locking mechanism and the insulator is at most 2 mm, in particular at most 1 mm is preferred. The body can be provided with an outer shoulder which is oriented towards the rear end and on which the locking mechanism is mounted. The securing mechanism may comprise a torus that forms a gap to surround the insulator and forms a gap to overlap the retaining mechanism. The inner shape of the annulus of the fixing mechanism can in particular be matched to the outer shape of the holding mechanism and / or the insulator projecting from the rear end of the main body.

  In a method of manufacturing a spark plug, first, an insulator is placed in a main body having a passage, and fixed at a predetermined position inside by an engagement holding mechanism. The formation of the holding mechanism and the fixing of the insulator in place can be carried out in a known manner, for example by flanging the edge of the rear end of the body after the insulator has been inserted. Next, the engagement and fixing mechanism is installed on the main body so as to at least partially overlap the holding mechanism and coupled to the main body. At the time of installation, the fixing mechanism is slipped in the longitudinal direction, and the insulator is mounted on the main body so that the insulator protrudes from the opposite side to the front end of the fixing mechanism. In addition, the securing mechanism contacts the outer shoulder of the body, in particular without gaps, while the portion overlapping the retaining mechanism of the securing mechanism is slip mounted so as to form a gap between each of the retaining mechanism and the insulator. Do. The fixing mechanism can be connected by welding to the body, in particular to the outer shoulder thereof. The fixing mechanism and the body can be welded to one another in the circumferential direction of the body, in particular by means of a welding seam mechanism around the entire circumference of the body. In particular, after insertion of the insulator, the body can be longitudinally set in a longitudinal direction between the outer shoulder and the holding mechanism so that the fixing mechanism can not be installed and mounted until the setting completion.

One or more embodiments may have the following important advantages.
・ If the holding mechanism fails, the fixing mechanism securely fixes the insulator in the main body. Failure of the holding mechanism can occur, for example, due to material fatigue or spark plug overheating, and as mentioned above, there is a high safety risk.
• If the holding mechanism fails, the fixing mechanism has a small gap so that it immediately catches the insulator and prevents the insulator from being accelerated at high speeds or jumping out of the main body over a long distance. Insulators are prevented from flying around.
The method of installing the insulator on the main body by producing a pressure acting on the insulator in the longitudinal direction of the spark plug by forming the flange on the rear end edge of the main body and applying the electrical upset processing to the contraction area is known and proven. As a method, it can continue to be used, especially before the fixing mechanism is in place.
The fixing mechanism can be mounted, for example in the form of a fixing sleeve, at the rear end of the main body without great effort.
-The fixing mechanism works with high reliability, especially at high temperatures reaching 700 ° C.
The gap, in particular the annular gap between the fastening mechanism and the insulator, ensures a hot gas in the event of a failure which has previously occurred in spark plugs without fastening mechanism known from DE 10 2012 101 168 A1. In the axial direction. It is not necessary to provide additional holes in the fixing mechanism to weaken the cross section, as in DE-A 102 0060 4 359 B3. In addition, this narrow gap provides some degree of insulation centering in the event of a failure. In contrast, in normal operation, the presence of the gap does not cause the securing mechanism to exert undesirable forces on the insulator. This mechanism can improve the overall safety.
-If the inner shape of the fixing mechanism conforms to the outer shape of the holding mechanism, the holding mechanism, which expands backward in the event of a failure, strikes on the fixing mechanism immediately after passing a slight gap, and is securely supported. The insulator is not strongly accelerated.
The gap between the locking mechanism and the holding mechanism ensures that the locking mechanism slides on the body into contact with the outer shoulder, where a reliable joint, in particular a welded joint, can be formed. In particular, the clearance between the fixing mechanism and the holding mechanism is determined in such a way that the fixing mechanism does not touch the holding mechanism, even if the individual parts have manufacturing tolerances, that the part overlapping the holding mechanism of the fixing mechanism does not touch the holding mechanism. It is chosen to be large enough to touch the outer shoulder of the body. In this way, reliable spark plug production can be ensured.

  In one embodiment, the locking mechanism can have a locking sleeve located on the rear end of the body. The fixed sleeve can in particular be crimped or screwed to the rear end of the body. It can be welded to the body for attachment of the fixed sleeve. The body may be cylindrically shaped at its rear end in order to crimp the fixed sleeve. The annular part of the fixing mechanism can be formed by a particularly continuous ring-shaped constriction of the inner shape of the fixing sleeve. The constriction and the opposite end of the fixation sleeve can be welded to the outer shoulder of the body. The combination of the outer shoulder and the fixed sleeve mounted on it allows the spark plug to maintain its profile corresponding to the existing standard that can subsequently be used with a standard cylinder head.

  In another embodiment, the spark plug may comprise a screwing mechanism and an external thread located at the front end of the body for screwing the spark plug into the internal combustion engine. The screw-in mechanism is arranged on the fixed sleeve and can be formed, for example, by a hexagonal engagement surface, in particular by means of an engagement surface with a wrench. The outer shape of the body at the rear end and the corresponding inner shape of the fixed sleeve can have a groove other than circular, in particular, a longitudinally extending groove or a longitudinal toothed cross section. In this way, it is possible to improve the torque transfer from the screwing mechanism located on the fixed sleeve to the body. The body can include a contraction area for electrical upset processing located between the male screw and the retention mechanism. The retraction zone can in particular be located between the retention mechanism and the rearwardly facing outer shoulder for mounting of the fastening device. The fixing sleeve covers the contraction zone and can be connected, in particular welded, to the body between the contraction zone and the external thread. This design allows the locking sleeve as well as the retention mechanism to protect the shrinking area where the body cross section is decreasing. This enhances the material fatigue of the body and the function of preventing the popping out of the insulator. As a result, the stress of the fastening torque when screwing in the spark plug is not applied to the contraction region. This avoids the contraction zone being subjected to undesirable damage that can cause leaks.

  The main body has an outer shoulder between the external thread and the fixing mechanism mounting portion, which is directed toward the front end of the main body to limit the process of screwing the spark plug into the internal combustion engine and seal the spark plug from the internal combustion engine. Can. The spark plug can include a seat ring resting on the shoulder. The external thread and the outer shoulder of the body allow heat to be removed from the spark plug to the internal combustion engine to provide a cooling circuit located within the engine.

  The securing mechanism can be designed as a single continuous part, at least the part overlapping the retaining mechanism, in particular from the torus to the attachment point to the body. In particular, the locking mechanism can be designed entirely as a single part. The fastening mechanism, in particular the fastening sleeve, can be made of high heat resistance, in particular of a nickel alloy. Material numbers 2.4816 (also known as Inconel 600) and 2.4851 (also known as Inconel 601) are particularly suitable. This design of the locking mechanism can improve stability and safety.

1 is a partial cross-sectional view of a spark plug according to an embodiment.

<One embodiment>
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the figure, the same elements are denoted by the same reference numerals.

  FIG. 1 partially shows a spark plug 1 provided with a metal body 2. The body 2 has a front end 3 and a rear end 4, and also a longitudinal direction 5 and a passage 6 extending in the longitudinal direction 5. A ground electrode 7 is welded to the surface of the front end 3 of the main body 2. Within the passage 6 is located an insulator 8 comprising a central electrode 9, an igniter 10 and a molten glass element 11. The central electrode 9 projects from the insulator 8 in the region of the front end 3 and forms a spark gap 13 with the ground electrode 7. The insulator 8 has a passage 12 in which the central electrode 9, the igniter 10 and the molten glass element 11 are located. The body 2 has at its front end 3 an external thread 14 for screwing the spark plug 1 into the internal combustion engine, this external thread 14 being adjacent to the outer shoulder 15 facing the front end 3 side The seal ring 16 is mounted. In other words, the seal ring 16 is disposed on the surface of the outer shoulder 15 facing downward in FIG.

  The body 2 has in the area of the front end 3 a sealing seat 17 located in the passage 6 in the form of an inner shoulder, the insulator 8 being placed on this shoulder (sealing seat 17) via the sealing ring 18 Be done. The main body 2 is formed in the area of the rear end 4 by forming the rear edge of the main body 2 in a flange shape on the inside, and has a holding mechanism 20 that rests on the shoulder 19 of the insulator 8. The body 2 further comprises a contraction area 25 representing a reduction in area. The main body 2 is designed as a single part including at least the seal pedestal 17, the holding mechanism 20, and the contraction area 25.

  At the rear end 4 of the body 2 a fastening mechanism 30 is fastened in the form of a fastening sleeve 31 which engages with the fastening mechanism 20 and anchors the fastening mechanism 20 for this purpose The fixed sleeve 31 overlaps the front end 3 of the main body 2 in the holding mechanism 20. The insulator 8 protrudes in the opposite direction to the front end 3 of the main body 2 from the side of the fixing mechanism 30 opposite to the front end 3 of the main body 2. The fixing mechanism 30 comprises an annular portion 32. The annular portion 32 is formed by a continuous annular narrow portion of the inner shape of the fixed sleeve 31, and in the region where the insulator 8 protrudes from the rear end 4, a gap 40 is formed to surround the insulator. In FIG. 1, the cylindrical gap 41 is not visible in continuous form because it is so small. The annular portion 32 forms a gap 41 and overlaps the holding mechanism 20, and captures the shoulder 19 of the insulator 8 when the holding mechanism 20 can not hold the insulator 8 due to material destruction. The fixing mechanism 30 thus suppresses the possibility of the insulator 8 popping out of the rear end 4 of the main body 2 due to the high combustion pressure rising in the combustion chamber of the internal combustion engine when the holding mechanism 20 breaks down.

  The fixing sleeve 31 is pressed onto the rear end 4 and welded to the body 2 in the region between the external thread 14 and the contraction zone 25. The weld seam is shown at 33 and is located between the shrink area 25 and the outer shoulder 15. As a result, the fixing sleeve 31 reliably covers the contraction area 25 and likewise its cross-sectional reduction is protected. The fixing sleeve 31 comprises a screwing mechanism 34 in the form of an outer hex for applying a fastener. The fastening torque is transmitted to the main body 2 through the fixing sleeve 31 and the welding joint 33 and through the cross-sectional reduction of the contraction area 25.

  At the time of manufacture of the spark plug 1, the rear edge of the main body 2 (the area indicated by the reference numeral 20 in FIG. 1) is not initially flanged yet, and the passage 6 has a constriction at its rear end 4 I do not have it. The seal ring 18 and the insulator 8 are inserted into the passage 6. The trailing edge of the body 2 is then flanged to form a retention mechanism 20 for the insulator 8. Thereafter, while applying an axial force between the front end 3 and the rear end 4, the contraction region 25 is heated by the current pulse flowing through the main body 2. In this way, the material in the area of the contraction area 25 is upset. The contraction zone 25 is further shrunk during cooling, and the insulator 8 is axially clamped within the main body 2 of the spark plug 1 as indicated by the applied pressure Fv, and the insulator 8 is pressed against the seal pedestal 17 Therefore, the passage 6 is sealed so that the combustion gas from the combustion chamber of the internal combustion engine does not enter or pass through. Next, the fixing mechanism 30 is placed on the rear end 4 of the main body 2 and joined by the welding joint 33. The weld seam 33 extends around the entire circumference of the body 2 and the fixing sleeve 31.

  The main body 2 has an outer shoulder 45 directed to the rear end 4 side. When the fixed sleeve 31 is set in place, it contacts the outer shoulder 45. In other words, the fixing sleeve 31 is placed on the surface of the outer shoulder 45 facing upward in FIG. 1. When the fixing sleeve 31 contacts the outer shoulder 45, the gap 41 between the inner shape of the annular portion 32 and the holding mechanism 20 allows the fixing mechanism 30 to be fixed at a predetermined position without excessively defining the fixing position statically. It can be installed securely. In this way it is possible to provide a particularly stable and reliable weld seam 33 with virtually no gaps in the contact line between the bottom edge of the fixing sleeve 31 and the outer shoulder 45. In order for the stationary sleeve 31 to actually perform its safety function, it is important to have a stable weld seam 33 without breaks or bubbles.

  Of course, the foregoing is a description of one or more preferred embodiments of the present invention. The present invention is not limited to the specific embodiments disclosed herein, but is only defined by the following claims. Furthermore, the descriptions contained in the above description relate to specific embodiments, and unless the terms and phrases are clearly defined above, the definition of terms within the scope of the present invention or the claims. It should not be interpreted as limiting. Various other embodiments and various changes and modifications to the disclosed embodiments will be apparent to the parties. Such other embodiments, changes and modifications are intended to be included within the scope of the appended claims.

  The words "for example", "for example", "for example", "like" and "like" as used in the present specification and embodiments, and the words "include", "have", "include" and others When used in conjunction with one or more parts or a list of other items, the verb form of should be interpreted as open-ended, that is, not to exclude additional parts or items other than those listed. It is. Other terms should be interpreted rationally in the broadest sense, unless they are used in contexts that require different interpretations.

1: spark plug 2: body 3: front end 4: rear end 5: longitudinal direction 6: passage 7: ground electrode 8: insulator 9: central electrode 10: igniter 11: molten glass element 12: passage 13: spark gap 14 A male screw 15: an outer shoulder 16: a seal ring 17: a seal seat 18: a seal ring 19: a shoulder 20: a holding mechanism 25: a contraction area 30: a fixing mechanism 31: a fixing sleeve 32: a ring 33: a welding joint 34: Screwing mechanism 40: gap 41: gap 45: outer shoulder Fv: pressurization

Claims (14)

A metallic body having a front end, a rear end, a longitudinal direction, and the longitudinally extending passage;
An insulator located in the passage and comprising a central electrode projecting in the area of the front end,
The body is located in the passage in the area of the front end and has a sealing seat for the insulator, the body sealing the passage from the flow of combustion gas in the area of the rear end A holding mechanism for holding the insulator in the main body by engagement so that the insulator is pressed against the seal pedestal in the longitudinal direction by pressure;
A fixing mechanism is mounted on the body that at least partially overlaps and engages on the opposite side to the front end of the holding mechanism, the insulator projects from the side opposite to the front end of the fixing mechanism, the fixing mechanism And the holding mechanism, wherein a gap is formed between the fixing mechanism and the holding mechanism, and a gap is formed between the fixing mechanism and the insulator.   The spark plug according to claim 1, wherein the main body includes an outer shoulder facing the rear end side, and the fixing mechanism is attached to the outer shoulder.   3. At least one ground electrode located at the front end of the body and conductively connected to the body to form a spark gap with the central electrode according to claim 1 or 2. Spark plug.   The gap between the locking mechanism and the holding mechanism and / or the gap between the locking mechanism and the insulator is at most 2 mm, in particular preferably at most 1 mm. A spark plug according to any one of claims 1 to 3.   5. The fastening mechanism according to claim 1, wherein the fastening mechanism is designed as a single continuous part, in particular from the part overlapping at least the holding mechanism to the attachment point to the body, and in particular as a single piece in general. The spark plug according to any one of the preceding claims.   The body according to any one of the preceding claims, wherein the body extends at least from the seal seat to the holding mechanism and the part comprising the seal seat and the holding mechanism is designed as a single continuous piece. Spark plug as described in.   The said fixing mechanism is an annular ring part which encloses the said insulator, forms the said gap | interval, and overlaps with the said holding | maintenance mechanism and forms the said gap | interval, It is described in any one of Claims 1-6. Spark plug.   The spark plug according to claim 7, wherein an inner shape of the annular portion conforms to an outer shape of the holding mechanism and / or the insulator.   9. The fastening mechanism according to any one of claims 2 to 8, wherein the fastening mechanism is disposed on the outer shoulder of the main body and has a fastening sleeve welded to the outer shoulder by means of a weld seam extending over the entire circumference. The spark plug according to one item.   The screwing mechanism according to claim 9, further comprising a screwing mechanism and an external thread located at the front end of the main body, for screwing the spark plug into an internal combustion engine, wherein the screwing mechanism is disposed in the fixed sleeve. Spark plug. The body has a contraction zone located between the male screw and the holding mechanism;
11. The spark plug according to claim 10, wherein the fixing sleeve covers the contraction area and is coupled to the body between the contraction area and the external thread. Placing an insulator within a body having a passageway and securing the insulator in position within the passageway by a retention mechanism engaged with the body;
Placing a locking mechanism in engagement with the body on an outer shoulder of the body at least partially overlapping the holding mechanism;
Combining the outer shoulder and the securing mechanism;
When the fixing mechanism is disposed, a portion of the fixing mechanism overlapping the holding mechanism is a gap between the insulator and the holding mechanism so that the insulator protrudes to the side opposite to the front end of the mechanism. Forming a gap between the locking mechanism and the insulator, while the locking mechanism contacts the outer shoulder without a gap, the locking mechanism along the longitudinal direction A method of manufacturing a spark plug in which the main body is slid and mounted.   The method for manufacturing a spark plug according to claim 12, wherein the fixing mechanism is coupled to the outer shoulder by forming a welded joint around the entire circumference of the main body by welding.   The insertion process according to claim 12 or 13, wherein after insertion of the insulator, the main body is longitudinally set between the outer shoulder and the holding mechanism, and the fixing mechanism is installed and mounted after the setting. The manufacturing method of the spark plug as described in.

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