WO2017170273A1 - 内燃機関用の点火プラグ及びその製造方法 - Google Patents

内燃機関用の点火プラグ及びその製造方法 Download PDF

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Publication number
WO2017170273A1
WO2017170273A1 PCT/JP2017/012156 JP2017012156W WO2017170273A1 WO 2017170273 A1 WO2017170273 A1 WO 2017170273A1 JP 2017012156 W JP2017012156 W JP 2017012156W WO 2017170273 A1 WO2017170273 A1 WO 2017170273A1
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WO
WIPO (PCT)
Prior art keywords
electrode
base
internal combustion
combustion engine
covering portion
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2017/012156
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English (en)
French (fr)
Japanese (ja)
Inventor
正行 田村
阿部　信男
柴田　正道
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Denso Corp
Original Assignee
Denso Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Denso Corp filed Critical Denso Corp
Priority to US16/088,971 priority Critical patent/US10439367B2/en
Priority to DE112017001680.0T priority patent/DE112017001680T5/de
Publication of WO2017170273A1 publication Critical patent/WO2017170273A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
    • H01T13/39—Selection of materials for electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/02—Details
    • H01T13/08—Mounting, fixing or sealing of sparking plugs, e.g. in combustion chamber
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
    • H01T13/32—Sparking plugs characterised by features of the electrodes or insulation characterised by features of the earthed electrode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T21/00—Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T21/00—Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs
    • H01T21/02—Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs of sparking plugs

Definitions

  • the present disclosure relates to an ignition plug for an internal combustion engine and a manufacturing method thereof.
  • Patent Document 1 discloses a spark plug in which a needle tip is formed on a ground electrode to improve ignitability.
  • the tip base material is formed of an inexpensive metal, and the end face and part of the side face of the chip are covered with a noble metal, thereby suppressing the consumption of the needle tip due to spark discharge and reducing the cost.
  • the tip since the tip is needle-shaped, it is easily affected by temperature change in the cylinder, and the temperature change of the tip itself becomes significant. Since the chip is composed of a noble metal having a different linear expansion coefficient and an inexpensive base metal, a large thermal stress is generated in the chip due to a temperature change of the chip itself. The thermal stress is likely to concentrate at the corner between the end surface of the base metal and the side surface of the base metal at the joint between the noble metal and the base metal, causing a crack in the noble metal joined to the corner. There is a case to let you.
  • the cracked portion is oxidized at a high temperature by the high temperature corrosive atmosphere in the cylinder, and a part of the noble metal is peeled off or the noble metal is dropped, thereby shortening the life of the spark plug.
  • the present disclosure is intended to provide a spark plug for an internal combustion engine that can extend the life and improve the ignitability, and a method for manufacturing the same.
  • a spark plug for an internal combustion engine having an electrode protrusion protruding
  • the electrode protrusion has a base portion formed integrally with the electrode base material, and a covering portion that is joined to the base portion and faces the discharge gap,
  • the base has an end surface in the protruding direction and a side peripheral surface connected to the electrode base material from the outer edge of the end surface, and the outer edge of the end surface forms a curved surface
  • the covering portion is made of a noble metal or a noble metal alloy having a lower linear expansion coefficient than the forming material of the base, and covers at least a part of the side peripheral surface and the end surface
  • a protrusion is formed on the outer surface of the portion of the covering portion that covers the side peripheral surface of the base portion when the electrode protrusion portion is attached to the internal combustion engine and cooled after being heated in the
  • Another aspect of the present disclosure includes a center electrode and a ground electrode disposed to face the center electrode so as to form a discharge gap between the center electrode and the electrode base material of the ground electrode.
  • a method of manufacturing a spark plug for an internal combustion engine having an electrode protrusion protruding toward a discharge gap, A joining step of joining a covering portion rough material made of a noble metal or a noble metal alloy having a linear expansion coefficient lower than that of the electrode base material to the electrode base material by resistance welding;
  • the electrode protruding portion has a coating portion made of a noble metal or a noble metal alloy at the portion facing the discharge gap, the consumption due to spark discharge is small, and the life of the ignition plug is extended. Furthermore, since the base forming material in the electrode protruding portion can be made of a material that is less expensive than the covering portion, the manufacturing cost can be reduced compared to the case where the entire electrode protruding portion is made of the covering portion forming material. it can.
  • the noble metal or the noble metal alloy forming the covering portion has a lower linear expansion coefficient than that of the base forming material, a difference between the two linear expansion coefficients is generated.
  • the outer edge of the end surface in the protruding direction of the base portion is a curved surface, a corner portion is hardly formed at the joint portion with the covering portion covering the base portion. For this reason, excessive concentration of the thermal stress caused by the difference in the linear expansion coefficient is suppressed.
  • the life of the spark plug can be extended from this viewpoint.
  • the covering portion is formed with a protrusion at a portion covering the side peripheral surface of the base portion. . Therefore, in a lean combustion engine with a fast in-cylinder airflow, even if the spark discharge generated in the discharge gap tries to move to the base side of the chip by the high-speed airflow, the spark discharge is applied to the protruding portion of the portion covering the side peripheral surface of the base. It is easy to concentrate and the discharge path is prevented from becoming excessively long. Thereby, the blow-off of the spark discharge is suppressed. As a result, the ignitability is improved.
  • the protrusion is configured to be formed due to a difference in linear expansion coefficient of the forming material between the base and the covering.
  • the covering portion rough material is joined to the electrode base material by resistance welding. Therefore, unlike the laser welding, electron beam welding, or the like, an intermediate layer formed by melting and mixing both of the covering portion rough material and the electrode base material is not formed. An interface is formed. Therefore, when the spark plug for the internal combustion engine is attached to the internal combustion engine and heated in the cylinder and then cooled, the difference in the linear expansion coefficient exists between the two forming materials, so that the protrusion is formed. It is surely formed. Thereby, the ignition plug for the internal combustion engine can be easily manufactured.
  • an ignition plug for an internal combustion engine and a method for manufacturing the same, which can extend the life and improve the ignitability.
  • the side inserted into the combustion chamber is the front end side, and the opposite side is the base end side.
  • the plug axial direction means the axial direction of the spark plug
  • the plug radial direction means the radial direction of the spark plug
  • the plug circumferential direction means the circumferential direction of the spark plug.
  • FIG. 1 is a partial cross-sectional front view of a spark plug in Embodiment 1.
  • FIG. 2 is a partially enlarged sectional view in the vicinity of the discharge gap in the first embodiment.
  • FIG. 3 is a partially enlarged cross-sectional view of the vicinity of the discharge gap after heating and cooling in Embodiment 1.
  • FIG. 4 is a partially enlarged cross-sectional view of the vicinity of the discharge gap for explaining the formation process of the protrusions in the first embodiment.
  • FIG. 5 is a diagram for explaining the formation process of the protrusions in the first embodiment.
  • FIG. 6 is a schematic diagram illustrating a spark discharge occurrence state in the first embodiment.
  • FIG. 7 is a schematic diagram illustrating a spark discharge occurrence state in the first embodiment.
  • FIG. 8 is a schematic diagram illustrating a manufacturing process of a spark plug in Embodiment 1.
  • FIG. 9 is a diagram showing the results of evaluation test 1
  • FIG. 10 is a diagram showing the results of evaluation test 2
  • FIG. 11 is a partially enlarged cross-sectional view in the vicinity of the discharge gap in the first modification.
  • An ignition plug 1 for an internal combustion engine according to the present embodiment (hereinafter also referred to as “ignition plug 1” in the present specification) includes a center electrode 2 and a ground electrode 3 as shown in FIG.
  • the ground electrode 3 is disposed to face the center electrode 2 so as to form a discharge gap G between the ground electrode 3 and the center electrode 2.
  • the ground electrode 3 has an electrode protrusion 30 that protrudes from the electrode base material 3 a toward the discharge gap G.
  • the electrode protrusion 30 has a base portion 31 and a covering portion 32.
  • the base 31 is formed integrally with the electrode base material 3a.
  • the covering portion 32 is bonded to the base portion 31 and faces the discharge gap G.
  • the base 31 has an end surface 33 in the protruding direction Y2 and a side peripheral surface 35 connected to the electrode base material 3a from the outer edge 34 of the end surface 33, and the outer edge 34 of the end surface 33 forms a curved surface.
  • the covering portion 32 is made of a noble metal or a noble metal alloy having a lower linear expansion coefficient than the forming material of the base portion 31 and covers at least a part of the side peripheral surface 35 and the end surface 33. As shown in FIG.
  • the spark plug 1 for an internal combustion engine is attached to an internal combustion engine (not shown) and the electrode protrusion 30 is heated in the cylinder and then cooled, the base 31 in the covering portion 32 is provided.
  • a protrusion 36 is formed on the outer surface 37 of the portion covering the side peripheral surface 35 of the first and second surfaces.
  • the spark plug 1 of the present embodiment has a cylindrical housing 4 extending in the plug axial direction Y.
  • a mounting screw portion 41 for screwing into an internal combustion engine (not shown) is formed on the outer peripheral surface of the housing 4.
  • the spark plug 1 is attached to the internal combustion engine so that the discharge gap G is exposed to a combustion chamber (not shown) of the internal combustion engine by screwing the attachment screw portion 41 into the internal combustion engine.
  • a cylindrical insulator 5 is provided inside the housing 4, and a rod-shaped center electrode 2 is provided inside the insulator 5.
  • a distal end portion 2 a that is an end portion on the distal end side Y 1 in the plug axial direction Y of the center electrode 2 protrudes from the insulator 5 to the distal end side Y 1 in the plug axial direction Y.
  • An electrode tip 20 is provided at the distal end portion 2a.
  • the electrode tip 20 has a needle shape protruding toward the tip end Y1 in the plug axial direction Y.
  • the ground electrode 3 extends from the distal end surface 42, which is the end portion of the distal end side Y ⁇ b> 1 in the plug axial direction Y of the housing 40, to the distal end side Y ⁇ b> 1. It is bent so as to form a discharge gap G at a predetermined interval in the axial direction Y. And the ground electrode 3 has the electrode protrusion part 30 which protrudes toward the discharge gap G from the electrode base material 3a on the plug center axis
  • the electrode protruding portion 30 has a base portion 31 and a covering portion 32.
  • the base 31 is formed integrally with the electrode base material 3 a of the ground electrode 3.
  • the base 31 is substantially cylindrical and protrudes toward the discharge gap G. That is, the base 31 protrudes toward the base end side Y2 in the plug axial direction Y.
  • the end surface 33 of the base portion 31 in the protruding direction Y2 has a flat shape except for the outer edge 34 thereof.
  • the base 31 is made of the same forming material as the electrode base material 3 a and forms a part of the electrode protrusion 30.
  • the outer edge 34 of the end surface 33 is a curved surface so as to be continuous with the side peripheral surface 35 substantially parallel to the protruding direction Y2.
  • the radius of curvature R of the outer edge 34 is preferably 0.1 mm ⁇ R, more preferably 0.1 mm ⁇ R ⁇ 0.45 mm.
  • the covering portion 32 covers the base portion 31.
  • the covering portion 32 covers the end surface 33, the outer edge 34, and the side peripheral surface 35.
  • the end surface 33, the outer edge 34, and the side peripheral surface 35 form an interface between the base portion 31 and the covering portion 32.
  • the thickness of the covering portion 32 that covers the side peripheral surface 35 is shown larger than the actual thickness.
  • the covering portion 32 that covers the side peripheral surface 35 is actually thin. In FIG. 2, for convenience of explanation, it is as described above. However, as shown in FIG. 2, the covering portion 32 that covers the side peripheral surface 35 may be formed thick.
  • the covering portion 32 is made of a noble metal or a noble metal alloy having a lower linear expansion coefficient than the material for forming the base portion 31.
  • the material for forming the base 31 is, for example, nickel (Ni) having a linear expansion coefficient (10 ⁇ 6 / K) of 13.3, or a linear expansion coefficient (10 ⁇ 6 / K) of 16.5.
  • Ni nickel
  • 10 ⁇ 6 / K linear expansion coefficient
  • Cu copper
  • the linear expansion coefficient (10 ⁇ 6 / K) is about 10 to 18
  • a nickel alloy, a copper alloy, an iron alloy, or the like can be used.
  • Inconel 600 (INCONEL" is a registered trademark) of Special Metallized Co., which is a nickel alloy having a linear expansion coefficient (10 -6 / K) of 12.8 is used. .
  • the forming material of the covering portion 32 is, for example, platinum (Pt) having a linear expansion coefficient (10 ⁇ 6 / K) of 8.9 or a linear expansion coefficient (10 ⁇ 6 / K) of 6.5.
  • Platinum or noble metal alloys such as iridium (Ir), platinum alloys having a linear expansion coefficient (10 ⁇ 6 / K) of less than 10, iridium alloys, and platinum iridium alloys can be used.
  • Pt is used as a material for forming the covering portion 32.
  • the difference ⁇ in the linear expansion coefficient between the forming material of the covering portion 32 and the forming material of the base portion 31 preferably satisfies 3.3 ⁇ 10 ⁇ 6 /K ⁇ 4.5 ⁇ 10 ⁇ 6 / K. In the embodiment, it is 3.9 ⁇ 10 ⁇ 6 / K.
  • the spark plug 1 of this embodiment when the spark plug 1 of this embodiment is attached to an internal combustion engine (not shown) and heated in the cylinder and then cooled, the portion of the covering portion 32 that covers the side peripheral surface 35 of the base portion 31 is covered.
  • a protrusion 36 is formed on the outer surface 37.
  • the projecting portion 36 is formed in the entire area in the plug circumferential direction of the outer surface 37 of the covering portion 32 and has an annular shape.
  • the formation process of the protrusion 36 is as follows. First, as shown in FIG. 4A, FIG. 5A, and FIG. 5B, no protrusions 36 are formed on the outer surface 37 of the covering portion 32 in the initial state.
  • the spark plug 1 is attached to an internal combustion engine (not shown), and the electrode protrusion 30 is heated by being exposed to a high temperature in the cylinder, whereby the base 31 and the covering portion 32 are expanded. For example, the expansion occurs when heated to about 800 ° C.
  • the covering portion 32 Since the covering portion 32 is made of a material having a lower linear expansion coefficient than the forming material of the base portion 31, the covering portion 32 has a smaller expansion amount when heated than the base portion 31. Therefore, as shown in FIG. 4 (b), on the outer surface 37 of the covering portion 32, the first outer surface 371 located on the distal end side Y1 in the plug axial direction Y with respect to the end surface 33 of the base portion 31 is an expanded base portion. 31 is pushed out of the plug radial direction X by the side peripheral surface 351 of the base 31, and is expanded in the plug radial direction X from the second outer surface 372 located on the base end side Y2 in the plug axial direction Y from the end surface 33 of the base 31. To do.
  • the covering portion 32 is plastically deformed, and a step portion 361 is formed between the first outer surface 371 and the second outer surface 372.
  • the broken line in FIG.4 (b) has shown the shape of the electrode protrusion 30 before the expansion
  • the base 31 and the covering portion 32 which have expanded are both contracted to return to the initial state.
  • the protrusion 36 is formed as shown in FIG.
  • a force toward the outer side of the plug radial direction X is generated at the outer edge 34 of the base 31 when the protrusion 36 is contracted, as shown in FIG.
  • the outer edge 341 slightly bulges outward in the plug radial direction.
  • the radius of curvature R of the outer edge 34 refers to that in the initial state shown in FIG.
  • the electrode protrusion 30 is substantially cylindrical, the height T0 is 0.8 mm, and the diameter D0 is 0.7 mm.
  • the height T1 of the base portion 31 is 0.5 mm, and substantially coincides with the height of the apex position of the protruding portion 36 in the protruding direction X.
  • the recessed part 38 is substantially cylindrical shape, and the diameter D1 of the opening part is 0.8 mm.
  • the height H (mm) of the protrusion 36 is expressed by the curvature radius of the outer edge 34 as R (mm). Then, it is preferable that H ⁇ ⁇ 0.067R + 0.227 is satisfied. In this embodiment, H is 0.2 mm.
  • a usage mode in the spark plug 1 of the present embodiment will be described with reference to FIGS. 6 and 7.
  • the spark plug 1 of this embodiment is attached to an internal combustion engine (not shown).
  • the internal combustion engine is a lean combustion engine. Then, when a high voltage is applied to the center electrode at a predetermined timing, the discharge gap G between the electrode protrusion 20 of the center electrode 2 and the electrode protrusion 30 of the ground electrode 3 is applied as shown in FIG. A spark discharge P is generated.
  • the spark discharge P is caused to flow in the traveling direction of the airflow S by the airflow S of the air-fuel mixture in the cylinder.
  • the spark discharge P is applied to the protrusion 36. You will concentrate. As a result, the spark discharge P is suppressed from flowing to the electrode base material 3 a side of the ground electrode 3.
  • the method for manufacturing the spark plug 1 includes a joining step S1, a preparation step S2, and an extrusion step S3.
  • joining process S1 as shown to Fig.8 (a), the coating
  • the covering portion rough material 32a is made of platinum, which is a noble metal having a lower linear expansion coefficient than Inconel 600 ("INCONEL" is a registered trademark) of Special Metallize Co., which is a material for forming the electrode base material 3a.
  • the covering portion rough member 32a joined to the electrode base material 3a is placed along the first jig 51 having the recess 50, thereby covering the covering portion rough portion.
  • a space 50 a is formed between the material 32 a and the recess 50.
  • FIG.8 (c), FIG.8 (d) it is opening of the recessed part 50 in the part 3c on the opposite side to the part 3b where the coating
  • tool 52 which has the convex part 53 larger than the part 50b is pressed toward the recessed part 50.
  • FIG. As a result, the rough material joining portion 3b is pushed out into the space 50a to form the convex base 31, and the covering portion rough material 32a has at least a part of the side peripheral surface 35 of the base 31 and the end surface 33 in the protruding direction.
  • the covering portion 32 is formed to form the electrode protruding portion 30.
  • a concave portion 38 is formed along the outer shape of the convex portion 53 of the second jig 52 at a portion of the ground electrode 3 opposite to the electrode protruding portion 30.
  • the convex portion 53 in the second jig 52 is larger than the opening 50 b of the concave portion 50 in the first jig 51.
  • the base material 3a is pushed into the recess 50 to form the base portion 31, the outer edge 34 of the end surface 33 of the base portion 31 is formed into a curved surface.
  • the recessed part 50 is cylindrical, and the convex part 53 is substantially cylindrical.
  • the diameter w ⁇ b> 2 of the convex portion 53 is larger than the opening diameter w ⁇ b> 1 of the opening portion 50 b of the concave portion 50.
  • the first jig 51 is configured such that the covering portion coarse material 32 a covers the opening 50 b of the recess 50 of the first jig 51 in the preparation step S ⁇ b> 2. Is along.
  • evaluation test The following evaluation test 1 and evaluation test 2 were performed on the spark plug 1 of the first embodiment. First, in the evaluation test 1, in the configuration of the spark plug 1 of the first embodiment, the presence or absence of cracks in the protrusion 36 when the radius of curvature R of the outer edge 34 and the height H of the protrusion 36 are changed is evaluated. did.
  • Test Examples 1 to 3 in Evaluation Test 1 are as follows. That is, in the configuration of the spark plug 1 of the first embodiment, the example in which the difference ⁇ of the linear expansion coefficient between the base portion 31 and the covering portion 32 is 3.3 ⁇ 10 ⁇ 6 / K is defined as Test Example 1, and ⁇ is A sample having 3.8 ⁇ 10 ⁇ 6 / K was designated as Test Example 2, and a sample having ⁇ of 4.5 ⁇ 10 ⁇ 6 / K was designated as Test Example 3.
  • the test condition is that the ignition plug in Test Examples 1 to 3 is set on a temperature-controllable cooling and heating bench, the temperature is raised from room temperature to 900 ° C., and then cooled to room temperature again as one cycle. This was performed 200 cycles. During the execution of 200 cycles, the case where no cracks occurred in the protrusions 36 was good (O), and the case where the protrusions 36 were cracked was bad (X). The results are shown in Table 1 below. The graph is shown in FIG.
  • the evaluation test 2 the relationship between the height of the protrusion 36 and the ignitability was evaluated.
  • the height H of the protrusion 36 after heating and cooling is set to 0.03 mm, 0.05 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, and What prepared 0.5 mm was prepared.
  • a projection having a height H of 0 mm, that is, having no projection 36 was prepared.
  • the test condition is that the spark plugs of the test example and the comparative example are attached to a 1800 cc, 4-cylinder internal combustion engine, the engine speed is 2000 rpm, and the Pmi fluctuation rate is 3% or more under the condition of Pmi of 0.28 MPa.
  • the A / F at the time was determined as the lean limit A / F.
  • FIG. 10 shows a graph in which the height H of the protrusion 36 and the lean limit A / F in the evaluation test 2 are plotted.
  • the evaluation test 2 as shown in FIG. 10, when the height H of the protrusion 36 as the test example is 0.03 mm, compared with the case where the height H of the protrusion 36 as the comparative example is 0 mm.
  • the lean limit A / F was only slightly increased and the ignitability was not improved.
  • the height H of the protrusion 36 as the test example is 0.05 mm or more, the lean limit A / F is sufficiently increased as compared with the case where the height H of the protrusion 36 as the comparative example is 0 mm. It was confirmed that the ignitability was improved.
  • the difference ⁇ in the linear expansion coefficient between the forming material of the covering portion 32 and the forming material of the base portion 31 is 3.3 ⁇ 10 ⁇ 6 /K ⁇ 4.5 ⁇ 10. It was shown that by satisfying ⁇ 6 / K, the difference ⁇ of the linear expansion coefficient was secured, and the protrusion 36 was reliably formed by heating and cooling.
  • the protrusion 36 does not crack and is ignitable. Has been shown to improve.
  • the effect of the ignition plug 1 for the internal combustion engine of the present embodiment will be described in detail.
  • the electrode protrusion 30 has the covering portion 32 made of a noble metal or a noble metal alloy at the portion facing the discharge gap G, there is little consumption due to spark discharge, and the spark plug 1 has a long life. Is achieved.
  • the material for forming the base 31 in the electrode protrusion 30 can be a cheaper material than the cover 32, the manufacturing cost is lower than when the entire electrode protrusion 30 is made of the material for forming the cover 32. Can be reduced.
  • the noble metal or the noble metal alloy forming the covering portion 32 has a lower linear expansion coefficient than the material for forming the base portion 31, a difference ⁇ between the linear expansion coefficients of both occurs.
  • the outer edge 34 of the end surface 33 in the protruding direction of the base portion 31 is a curved surface, a corner portion is hardly formed at the joint portion with the covering portion 32 that covers the outer surface of the base portion 31. For this reason, excessive concentration of thermal stress caused by the difference ⁇ in the linear expansion coefficient is suppressed.
  • the life of the spark plug 1 can be extended from this viewpoint.
  • the covering portion 32 has a protrusion on the portion 37 that covers the side peripheral surface 35 of the base 31. 36 is formed. Therefore, in the lean combustion engine having a fast in-cylinder airflow, even if the spark discharge P generated in the discharge gap G tries to move to the base 31 side by the high-speed airflow, the spark discharge P covers the side peripheral surface 35 of the base 31. It is easy to concentrate on the protrusion 36 of 37, and the discharge path is prevented from becoming excessively long. Thereby, the blow-off of the spark discharge P is suppressed. As a result, the ignitability is improved.
  • the protrusion part 36 is comprised so that it may be formed in the base 31 and the coating
  • the forming material of the base portion 31 is a nickel alloy
  • the forming material of the covering portion 31 is platinum.
  • the difference ⁇ between the expansion coefficients of the two can satisfy the above-mentioned 3.3 ⁇ 10 ⁇ 6 /K ⁇ 4.5 ⁇ 10 ⁇ 6 / K.
  • a difference ⁇ in the linear expansion coefficient is ensured, and the protrusion 36 is reliably formed by heating and cooling.
  • the covering portion rough material 32a is joined to the electrode base material 3a by resistance welding in the joining step S1. Therefore, an intermediate layer formed by melting and mixing the covering portion rough material 32a and the electrode base material 3a is not formed between the covering portion rough material 32a and the electrode base material 3a as in laser welding or electron beam welding. An interface with the material 3a is formed. Therefore, when the spark plug 1 is attached to the internal combustion engine and the electrode protrusion 30 is cooled after being heated in the cylinder, the difference 36 in the linear expansion coefficient exists between the two forming materials, and thus the protrusion 36. Will be formed reliably. Thereby, according to the said manufacturing method, the spark plug 1 of this embodiment can be manufactured easily.
  • the covering portion rough material 32 a is placed along the first jig 51 so as to cover the opening 50 b of the concave portion 50 of the first jig 51.
  • the covering portion 32 formed from the covering portion rough material 32 a covers the entire area of the end surface 33 and the side peripheral surface 35 of the base portion 31. Therefore, consumption of the electrode protrusion 30 due to spark discharge can be further suppressed.
  • the covering portion 32 is formed so as to cover the end surface 33 of the base portion 31 and the entire area of the side peripheral surface 35.
  • a modification 1 shown in FIG. 11 may be used as long as the effect of suppressing the consumption of the electrode protrusion 30 is obtained.
  • the protruding portion 36 is formed in the entire circumferential direction of the covering portion 32, but a part of the side peripheral surface 35 of the base portion 31 is not covered by the covering portion 32. It may be. Even in such a case, the same effects as those of the present embodiment can be obtained.
  • a spark plug 1 for an internal combustion engine and a method for manufacturing the same, which can extend the life and improve the ignitability.

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  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
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PCT/JP2017/012156 2016-03-29 2017-03-24 内燃機関用の点火プラグ及びその製造方法 Ceased WO2017170273A1 (ja)

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Application Number Priority Date Filing Date Title
US16/088,971 US10439367B2 (en) 2016-03-29 2017-03-24 Ignition plug for an internal combustion engine and method for manufacturing the same
DE112017001680.0T DE112017001680T5 (de) 2016-03-29 2017-03-24 Zündkerze für eine Verbrennungskraftmaschine und Verfahren zum Herstellen derselben

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JP2016-066269 2016-03-29
JP2016066269A JP6645314B2 (ja) 2016-03-29 2016-03-29 内燃機関用の点火プラグ及びその製造方法

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