WO2015063987A1 - スパークプラグ - Google Patents
スパークプラグ Download PDFInfo
- Publication number
- WO2015063987A1 WO2015063987A1 PCT/JP2014/004262 JP2014004262W WO2015063987A1 WO 2015063987 A1 WO2015063987 A1 WO 2015063987A1 JP 2014004262 W JP2014004262 W JP 2014004262W WO 2015063987 A1 WO2015063987 A1 WO 2015063987A1
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- WIPO (PCT)
- Prior art keywords
- insulator
- tip
- spark plug
- peripheral surface
- curved surface
- Prior art date
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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
-
- 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
- H01T13/38—Selection of materials for insulation
Definitions
- the present invention relates to a spark plug used for ignition in an internal combustion engine or the like.
- the spark plug applies a voltage to the center electrode and the ground electrode which are insulated from each other by an insulator, thereby causing a spark discharge in a spark gap formed between the tip of the center electrode and the tip of the ground electrode. Is generated.
- the insulator that insulates the center electrode and the ground electrode is broken through by the applied voltage, a current flows through the portion that has been broken through, which may cause a problem that no spark discharge occurs in the spark gap.
- An object of the present invention is to provide a spark plug that can suppress the penetration failure of an insulator.
- a spark plug An insulator having a through hole extending in the direction of the axis; A rod-shaped center electrode inserted in the through hole and extending in the direction of the axis; and A metal shell disposed on the outer periphery of the insulator; A ground electrode that is electrically connected to the metal shell and forms a gap with the center electrode;
- a spark plug comprising: The front end portion of the insulator has a front end surface, an outer peripheral surface extending from the front end surface toward the rear end in the axial direction, and a curved surface portion formed between the front end surface and the outer peripheral surface.
- the spark plug has a radius of curvature of the curved surface portion of 0.2 mm (millimeters) or more and 0.8 mm (millimeters) or less.
- tip of the internal peripheral surface of a metal shell opposes the curved surface part of the front-end
- the curvature radius of a curved-surface part shall be 0.2 mm (millimeter) or more and 0.8 mm (millimeter) or less.
- the curvature radius of the curved surface portion is set to a range of 0.2 mm (millimeters) or more and 0.8 mm (millimeters) or less, thereby increasing the possibility that the path of the spark discharge becomes a creeping path. It is possible to effectively suppress the insulator from being broken through.
- the volume of the insulator becomes smaller as it is closer to the tip.
- the temperature in the vicinity of the insulator can be made higher as it is closer to the front end of the insulator and lowered toward the rear end.
- the acute angle formed by the two outer peripheral surfaces of the insulator (hereinafter also referred to as the taper angle of the insulator) is 5 degrees or more.
- the taper angle of the insulator is 30 degrees or less, the temperature at the tip of the insulator can be prevented from becoming excessively high. As a result, it is possible to reduce the possibility of erroneous ignition due to an overheated tip, for example, preignition, during use in an internal combustion engine.
- the present invention can be realized in various aspects, for example, in aspects such as a spark plug and an internal combustion engine equipped with the spark plug.
- FIG. 2 is a cross-sectional view of the vicinity of a tip of a spark plug 100.
- FIG. 3 is a view for explaining the configuration near the tip of a spark plug 100.
- FIG. 1 is a cross-sectional view of a spark plug 100 of the present embodiment.
- the dashed line in FIG. 1 indicates the axis CO (also referred to as axis CO) of the spark plug 100.
- a direction parallel to the axis CO (vertical direction in FIG. 1) is also referred to as an axis direction.
- the radial direction of the circle centered on the axis CO is simply referred to as “radial direction”
- the circumferential direction of the circle centered on the axis CO is also simply referred to as “circumferential direction”.
- the spark plug 100 includes an insulator 10 as an insulator, a center electrode 20, a ground electrode 30, a terminal fitting 40, and a metal shell 50. *
- the insulator 10 is formed by firing alumina or the like.
- the insulator 10 is a substantially cylindrical member that extends along the axial direction and has a through hole 12 (shaft hole) that penetrates the insulator 10.
- the insulator 10 includes a flange part 19, a rear end side body part 18, a front end side body part 17, a step part 15, and a leg length part 13.
- the rear end side body portion 18 is located on the rear end side of the flange portion 19 and has an outer diameter smaller than the outer diameter of the flange portion 19.
- the distal end side body portion 17 is located on the distal end side from the flange portion 19 and has an outer diameter smaller than the outer diameter of the flange portion 19.
- the long leg portion 13 is positioned on the distal end side from the distal end side body portion 17 and has an outer diameter smaller than the outer diameter of the distal end side body portion 17.
- the leg portion 13 is exposed to the combustion chamber when the spark plug 100 is attached to an internal combustion engine (not shown).
- the step portion 15 is formed between the leg long portion 13 and the distal end side body portion 17.
- the metal shell 50 is formed of a conductive metal material (for example, a low carbon steel material) and is a cylindrical metal fitting for fixing the spark plug 100 to an engine head (not shown) of an internal combustion engine.
- the metal shell 50 is formed with an insertion hole 59 penetrating along the axis CO.
- the metal shell 50 is disposed on the outer periphery of the insulator 10. That is, the insulator 10 is inserted and held in the insertion hole 59 of the metal shell 50.
- the axial position of the tip of the insulator 10 is substantially the same as the axial position of the tip of the metal shell 50, as will be described in detail later.
- the rear end of the insulator 10 protrudes toward the rear end side from the rear end of the metal shell 50. *
- the metal shell 50 is formed between a hexagonal column-shaped tool engagement portion 51 with which a spark plug wrench engages, an attachment screw portion 52 for attachment to an internal combustion engine, and the tool engagement portion 51 and the attachment screw portion 52. And a bowl-shaped seat portion 54.
- the nominal diameter of the mounting screw portion 52 is, for example, one of M8 (8 mm (millimeters)), M10, M12, M14, and M18. *
- An annular gasket 5 formed by bending a metal plate is fitted between the mounting screw portion 52 and the seat portion 54 of the metal shell 50.
- the gasket 5 seals a gap between the spark plug 100 and the internal combustion engine (engine head) when the spark plug 100 is attached to the internal combustion engine.
- the metal shell 50 further includes a thin caulking portion 53 provided on the rear end side of the tool engaging portion 51, and a thin compression deformation portion 58 provided between the seat portion 54 and the tool engaging portion 51. And.
- An annular region formed between the inner peripheral surface of the portion of the metal shell 50 from the tool engaging portion 51 to the crimping portion 53 and the outer peripheral surface of the rear end side body portion 18 of the insulator 10 has an annular shape.
- Ring members 6 and 7 are arranged. Between the two ring members 6 and 7 in the region, talc (talc) 9 powder is filled. The rear end of the crimped portion 53 is bent radially inward and fixed to the outer peripheral surface of the insulator 10.
- the compression deforming portion 58 of the metal shell 50 is compressed and deformed when the crimping portion 53 fixed to the outer peripheral surface of the insulator 10 is pressed toward the distal end during manufacture.
- the insulator 10 is pressed toward the front end side in the metal shell 50 through the ring members 6 and 7 and the talc 9 by the compression deformation of the compression deformation portion 58.
- a step portion 15 (insulator side step) of the insulator 10 is formed by a step portion 56 (metal side step portion) formed on the inner periphery of the mounting screw portion 52 of the metal shell 50 through the metal annular plate packing 8. Part) is pressed.
- the gas in the combustion chamber of the internal combustion engine is prevented by the plate packing 8 from leaking outside through the gap between the metal shell 50 and the insulator 10. *
- the center electrode 20 is a rod-like member extending along the axis CO, and is inserted into the through hole 12 of the insulator 10.
- the center electrode 20 has a structure including an electrode base material 21 and a core material 22 embedded in the electrode base material 21.
- the electrode base material 21 is formed of nickel or an alloy containing nickel as a main component (such as Inconel (registered trademark) 600).
- the core material 22 is made of copper or an alloy containing copper as a main component, which has better thermal conductivity than the alloy forming the electrode base material 21.
- the tip of the center electrode 20 is exposed on the tip side of the insulator 10. *
- the center electrode 20 has a flange portion 24 (also referred to as an electrode flange portion or a flange portion) provided at a predetermined position in the axial direction, and a head portion 23 (electrode head) that is a portion on the rear end side of the flange portion 24. Part) and a leg part 25 (electrode leg part) which is a part on the tip side of the collar part 24.
- the flange 24 is supported by the step 16 of the insulator 10.
- the distal end portion of the leg portion 25 protrudes toward the distal end side from the distal end of the insulator 10.
- An electrode tip 29 is joined to the tip portion of the leg 25 by, for example, laser welding.
- the electrode tip 29 is formed of a material mainly composed of a high melting point noble metal.
- a material of the electrode tip 29 for example, iridium (Ir) or an alloy containing Ir as a main component is used. Specifically, an Ir-5Pt alloy (iridium alloy containing 5% by mass of platinum) or the like is used. Is used. *
- the ground electrode 30 includes an electrode body 31 and an electrode tip 33, and is joined to the tip of the metal shell 50.
- the electrode body 31 is made of a metal having high corrosion resistance, for example, a nickel alloy such as Inconel (registered trademark) 600.
- the base end portion 31 b of the electrode body 31 is joined to the distal end surface of the metal shell 50 by welding. As a result, the ground electrode 30 is electrically connected to the metal shell 50.
- the electrode body 31 is bent, and one side surface of the end portion 31a opposite to the base end portion 31b of the electrode body 31 faces the electrode tip 29 of the center electrode 20 in the axial direction on the axis CO. Yes.
- An electrode tip 33 is welded to one side surface of the end 31 a of the electrode body 31 at a position facing the electrode tip 29 of the center electrode 20.
- the electrode tip 33 for example, Pt (platinum) or an alloy containing Pt as a main component, specifically, a Pt-20Ir alloy (a platinum alloy containing 20% by mass of iridium) or the like is used.
- a spark gap is formed between the electrode tip 29 of the center electrode 20 and the electrode tip 33 of the ground electrode 30.
- the terminal fitting 40 is a rod-shaped member that extends along the axis CO.
- the terminal fitting 40 is formed of a conductive metal material (for example, low carbon steel), and a metal layer (for example, Ni layer) for corrosion protection is formed on the surface of the terminal fitting 40 by plating or the like.
- the terminal fitting 40 includes a collar part 42 (terminal jaw part) formed at a predetermined position in the axial direction, a cap mounting part 41 located on the rear end side of the collar part 42, and a leg part 43 on the distal side of the collar part 42. (Terminal leg).
- the cap mounting portion 41 of the terminal fitting 40 is exposed to the rear end side from the insulator 10.
- the leg portion 43 of the terminal fitting 40 is inserted (press-fitted) into the through hole 12 of the insulator 10.
- a plug cap to which a high voltage cable (not shown) is connected is attached to the cap attaching portion 41, and a high voltage for generating a spark discharge is applied.
- a resistor 70 for reduction is arranged.
- the resistor is made of, for example, a composition containing glass particles as a main component, ceramic particles other than glass, and a conductive material.
- a gap between the resistor 70 and the center electrode 20 is filled with a conductive seal 60.
- a gap between the resistor 70 and the terminal fitting 40 is filled with a conductive seal 80.
- the conductive seals 60 and 80 are made of, for example, a composition containing glass particles such as B 2 O 3 —SiO 2 and metal particles (Cu, Fe, etc.).
- FIG. 2A is a cross-sectional view of the vicinity of the tip of the spark plug 100 taken along a plane including the axis CO.
- FIG. 2B is an enlarged view of a portion surrounded by a dashed line EA in FIG. FIG. 2 is illustrated with the front end direction D1 facing upward and the rear end direction D2 facing downward.
- the cross section in the vicinity of the tip of the spark plug 100 shown in FIG. 2A has a line-symmetric shape with the axis CO as the target axis except for the ground electrode 30.
- description will be made centering on the portion on the right side of the axis CO in the cross section of FIG. 2A, but the portion on the left side of the axis CO has the same configuration. is doing. *
- the distal end portion of the long leg portion 13 has a distal end surface 13A, an outer peripheral surface 13B, and a curved surface portion 13C.
- the tip surface 13A is a surface perpendicular to the axis CO.
- the outer peripheral surface 13B is located on the rear end side from the front end surface 13A and extends toward the rear end (rear end direction D2) in the axial direction.
- the curved surface portion 13C is formed between the tip surface 13A and the outer peripheral surface 13B.
- the point P1 is a point located on the outer edge of the tip surface 13A.
- the point P1 can also be said to be a point located at the tip of the curved surface portion 13C.
- Point P2 is a point located at the tip of outer peripheral surface 13B.
- the point P2 can also be said to be a point located at the rear end of the curved surface portion 13C.
- an imaginary line (a line perpendicular to the axis CO) obtained by extending the tip surface 13A in the cross section of FIG.
- an imaginary line obtained by extending the outer peripheral surface 13B is defined as HL2. It can be said that the curved surface portion 13 ⁇ / b> C is a portion away from the two virtual lines HL ⁇ b> 1 and HL ⁇ b> 2 on the outer surface of the insulator 10 in the cross section of FIG. *
- the length in the axial direction of the curved surface portion 13C that is, the length in the axial direction from the front end P1 of the curved surface portion 13C to the rear end P2 of the curved surface portion 13C is defined as H1.
- the curved surface portion 13 ⁇ / b> C is formed when the outer shape of the insulator 10 is adjusted by grinding the insulator 10 before firing using a grinding wheel when the insulator 10 is formed.
- the curved surface portion 13 ⁇ / b> C is formed in an annular shape over the entire circumference of the outer edge of the distal end portion of the leg long portion 13.
- the curvature radius R of the curved surface portion 13C is expressed by using the radius of an arc representing the curved surface portion 13C in the cross section of FIG. *
- an intersection of the above-described virtual line HL1 extending the tip surface 13A and the virtual line HL2 extending the outer peripheral surface 13B is defined as P4. Further, in the cross section of FIG. 2B, among the points on the outer peripheral surface 13B, a point where the axial distance from the tip surface 13A of the insulator 10 is 1 mm is P3. *
- the double of the radial distance from the axis CO to the point P4 is defined as the first outer diameter ⁇ 1 (also referred to as the tip diameter ⁇ 1) of the insulator 10 (the long leg portion 13).
- the outer diameter of the insulator 10 at twice the radial distance from the axis CO to the point P3, that is, at a position 1 mm away from the tip surface 13A in the axial direction is the second outer diameter ⁇ 2 of the insulator 10.
- the second outer diameter ⁇ 2 is larger than the first outer diameter ⁇ 1 ( ⁇ 2> ⁇ 1).
- the outer diameter of the outer peripheral surface 13B of the long leg portion 13 of the insulator 10 increases from the front end toward the rear end.
- the leg long portion 13 has a tapered shape that expands from the front end toward the rear end.
- the second outer diameter ⁇ 2 may be equal to the first outer diameter ⁇ 1.
- two lines representing the outer peripheral surface 13B of the insulator 10 appear on both sides of the axis CO in the cross section.
- the angle between these two lines that is, the acute angle formed by the two outer peripheral surfaces on the cross section of FIG. ⁇ 1 is also referred to as a taper angle near the tip of the insulator 10.
- the first outer diameter ⁇ 1 of the insulator 10 is not limited to this, but is preferably 3.0 mm or more and 5.5 mm or less, for example, 3.6 mm or more and 4.3 mm or less. Is particularly preferred.
- the inner diameter ⁇ 4 (the inner diameter of the portion where the leg portion 25 of the center electrode 20 is inserted) of the tip portion of the insulator 10 is not limited to this, but is, for example, 3.1 mm or more and 5.55 mm or less. It is preferable that it is 3.7 mm or more and 4.35 mm or less. *
- the front end portion of the metal shell 50 has a front end surface 50A, an inner peripheral surface 50B, and a chamfered portion 50C formed between the front end surface 50A and the inner peripheral surface 50B.
- the inner diameter of the inner peripheral surface 50B of the metal shell 50 (the inner diameter of the insertion hole 59) is a constant value ⁇ 3 at the tip end side of the step portion 56 in FIG.
- ⁇ 3 is also referred to as an inner diameter ⁇ 3 in the vicinity of the tip of the metal shell 50.
- the inner diameter ⁇ 3 is not limited to this, but is preferably, for example, from 5.5 mm to 8.5 mm, and particularly preferably from 7.0 mm to 7.5 mm.
- the diameters ⁇ 1 to ⁇ 4 described above represent not the radius but the diameter. *
- the point P5 is a point located at the tip of the inner peripheral surface 50B.
- the point P5 can also be said to be a point located at the rear end of the chamfered portion 50C.
- the distal end P5 of the inner peripheral surface 50B is an intersection of the distal end surface 50A and the inner peripheral surface 50B.
- ⁇ H The position in the axial direction of the tip surface 13A of the insulator 10 with respect to the position in the axial direction of the tip P5 of the inner peripheral surface 50B of the metal shell 50 is represented using ⁇ H (FIG. 2B).
- ⁇ H can also be said to be the position of the tip P1 of the curved surface portion 13C of the insulator 10 with reference to the axial position of the tip P5 of the inner peripheral surface 50B of the metal shell 50.
- the value of ⁇ H is a positive value.
- the distal end P5 of the inner peripheral surface 50B of the metal shell 50 has a curved surface of the insulator 10. It means that it is located at the rear end side from the front end P1 of the portion 13C and at the front end side from the rear end P2 of the curved surface portion 13C.
- 0 ⁇ ⁇ H ⁇ H1 means that the tip P5 of the inner peripheral surface 50B of the metal shell 50 faces the curved surface portion 13C of the insulator 10 in a direction perpendicular to the axial direction. ing. In the example of FIG. 2B, 0 ⁇ ⁇ H ⁇ H1 is satisfied. *
- FIG. 3 is a view for explaining the configuration in the vicinity of the tip of the spark plug 100.
- the front end surface 50A of the metal shell 50 is located at the position indicated by the broken line VL1 in FIG. 3, the front end (P5a in FIG. 3) of the inner peripheral surface 50B is more than the front end P1 of the curved surface portion 13C of the insulator 10. Since it is located on the side, ⁇ H ⁇ 0. *
- ⁇ H is larger than the length H1 in the axial direction of the curved surface portion 13C ( ⁇ H> H1), so that the front end P5 of the inner peripheral surface 50B of the metal shell 50 is behind the rear end P2 of the curved surface portion 13C of the insulator 10. It means that it is located on the end side.
- the front end (P5b in FIG. 3) of the inner peripheral surface 50B is from the rear end P2 of the curved surface portion 13C of the insulator 10. Since it is located on the rear end side, ⁇ H> H1.
- the radius of curvature R of the curved surface portion 13C, the first outer diameter ⁇ 1, and the second outer diameter ⁇ 2 is different.
- the curvature radius R is set to any one of 0.1 mm, 0.2 mm, 0.4 mm, 0.8 mm, and 0.9 mm.
- the first outer diameter ⁇ 1 is set to any value of 4.1 mm and 4.5 mm.
- the second outer diameter ⁇ 2 is any value of 4.1 mm, 4.3 mm, 4.5 mm, and 4.7 mm. *
- the value of ⁇ H is any one of ⁇ 0.1 mm, 0 mm, 0.05 mm, 0.35 mm, 0.4 mm, 0.7 mm, and 0.75 mm.
- the length H1 in the axial direction of the curved surface portion 13C is a value determined by the curvature radius R, the first outer diameter ⁇ 1, and the second outer diameter ⁇ 2.
- Samples 1-2 to 1-4, 1-6, and 1-8 to 1-16 satisfy 0 ⁇ ⁇ H ⁇ H1. That is, in Samples 1-2 to 1-4, 1-6, and 1-8 to 1-16, the tip P5 of the inner peripheral surface 50B of the metal shell 50 is perpendicular to the curved surface portion 13C of the insulator 10 and the axial direction. Opposite direction. *
- test A a discharge test for generating 60 spark discharges per second in a chamber pressurized to 5 MPa was performed for 20 hours. The spark discharge was performed while heating using a burner so that the temperature of the tip of the sample insulator 10 was 900 degrees Celsius.
- test B the discharge test was performed under conditions more severe than test A. Specifically, test B was performed in a chamber pressurized to 10 MPa. Other conditions for test B are the same as for test A. As the pressure in the chamber is higher, normal discharge in the spark gap between the electrode tip 29 of the center electrode 20 and the electrode tip 33 of the ground electrode 30 is less likely to occur. Become. *
- each sample was disassembled, and it was evaluated whether or not penetration failure occurred in the insulator 10. Specifically, the presence or absence of penetration failure was confirmed visually after applying a red check solution to the insulator 10 to visualize the cracks in the insulator 10 due to penetration failure. *
- Table 1 shows the presence or absence of penetration failure in each of test A and test B.
- the evaluation of the sample by which the penetration fracture was recognized in the test A and the penetration fracture was recognized in the test B was set to "x".
- the evaluation of the sample in which the penetration failure was not recognized in the test A and the penetration failure was recognized in the test B was set as “ ⁇ ”.
- the evaluation of a sample in which no penetration failure was observed in Test A and no penetration failure was observed in Test B was evaluated as “ ⁇ ”.
- a spark discharge may occur between the tip P5 of the inner peripheral surface 50B of the metal shell 50 and the center electrode 20. Most likely. This is because a sharp portion (edge portion) such as the tip P5 of the inner peripheral surface 50B of the metal shell 50 is likely to be the starting point of spark discharge because the electric field tends to concentrate.
- 0 ⁇ ⁇ H ⁇ H1 is satisfied, that is, the tip P5 of the inner peripheral surface 50B of the metal shell 50 faces the curved surface portion 13C of the insulator 10 in a direction perpendicular to the axial direction.
- An unintended spark discharge path is likely to be the creeping path RT1 in FIG. That is, an unintended spark discharge path tends to be a path from the tip P5 of the inner peripheral surface 50B of the metal shell 50 to the center electrode 20 through the curved surface portion 13C of the insulator 10 and the tip surface 13A. This is because the spark discharge is induced to the tip surface 13A by the curved surface portion 13C.
- the unintended spark discharge path is the creeping path RT1
- the penetration failure of the insulator 10 does not occur.
- ⁇ H ⁇ 0 that is, if the tip P5 of the inner peripheral surface 50B of the metal shell 50 is located on the tip side of the tip P1 of the curved surface portion 13C of the insulator 10, the inner circumference of the metal shell 50 will be described.
- the distance from the front end P5 of the surface 50B to the surface (the outer peripheral surface 13B or the front end surface 13A) of the insulator 10 becomes longer (see FIG. 3).
- the starting point of the unintended spark discharge is likely to be not the front end P5 of the inner peripheral surface 50B of the metal shell 50 but the rear end side portion of the inner peripheral surface 50B of the metal shell 50 from the front end P5.
- the unintended spark discharge path is likely to be the through-path RT2 in FIG.
- penetration breakage of the insulator 10 is likely to occur as a result. *
- the tip P5 of the inner peripheral surface 50B of the metal shell 50 faces the curved surface portion 13C of the insulator 10 in a direction perpendicular to the axial direction, and the curvature radius R of the curved surface portion 13C is 0.2 mm (millimeters). ) And preferably 0.8 mm (millimeters) or less. If it carries out like this, it can suppress effectively that the insulator 10 breaks through. *
- 11 types of samples 1-2 to 1-4, 1-6, 1-9, 1-10, 1-12 to 1 satisfying 0 ⁇ ⁇ H ⁇ H1 and 0.2 mm ⁇ R ⁇ 0.8 mm -16 will be described in detail.
- the evaluation of ⁇ 16 was “ ⁇ ”.
- the evaluation of the three types of samples 1-12, 1-14, and 1-15 in which the second outer diameter ⁇ 2 is equal to or smaller than the first outer diameter ⁇ 1 was “ ⁇ ”.
- the reason is estimated as follows. The higher the temperature, the lower the density of air in the vicinity, and the lower the electrical resistance and spark discharge is likely to occur. Conversely, the lower the temperature, the higher the density of the nearby air, so that the electrical resistance increases and spark discharge is less likely to occur.
- the second outer diameter ⁇ 2 is larger than the first outer diameter ⁇ 1 in the vicinity of the tip portion of the insulator 10
- the volume of the insulator 10 becomes smaller as it is closer to the tip.
- the temperature in the vicinity of the insulator 10 increases as it approaches the tip of the insulator 10 and decreases as it approaches the rear end.
- the second outer diameter ⁇ 2 is more preferably larger than the first outer diameter ⁇ 1.
- the outer diameter of the outer peripheral surface 13B of the insulator 10 is more preferably increased from the front end to the rear end of the outer peripheral surface 13B. If it carries out like this, it can suppress more effectively that the insulator 10 breaks through.
- the six types of samples have different taper angles ⁇ 1 described above. Specifically, the taper angles ⁇ 1 of the samples 2-1 to 2-6 are 0 degree, 5 degrees, 10 degrees, 20 degrees, 30 degrees, and 40 degrees, respectively.
- each sample was disassembled, and the depth in the axial direction of the scratches generated at the tip portions (tip surface 13A and curved surface portion 13C) of the insulator 10 was measured using a three-dimensional shape measuring instrument (specifically, Measurement was performed using an X-ray CT scanner. Then, the maximum value of the measured depth of the scratch was taken as the amount of shaving of the sample.
- the evaluation of a sample with a scraping amount of less than 0.1 mm was “ ⁇ ”, and the evaluation of a sample with a scraping amount of 0.1 mm or more was “x”.
- the reason for this is estimated as follows.
- the taper angle ⁇ 1 is 0 degree or more, the volume of the insulator 10 becomes smaller as it approaches the tip.
- taper angle (theta) 1 is large, the volume of the front-end
- the larger the taper angle ⁇ 1 the higher the temperature of the tip of the insulator 10.
- the discharge voltage of the spark discharge passing through the tip surface 13A of the insulator 10 is lowered, and the spark energy is reduced.
- the taper angle ⁇ 1 is more preferably 5 degrees or more and 30 degrees or less. In this way, the amount of scraping of the tip of the insulator 10 due to spark discharge can be suppressed, so that the durability of the spark plug can be improved. Moreover, it is possible to suppress the occurrence of erroneous ignition such as pre-ignition due to the tip of the overheated insulator 10. *
- the suppression of penetration failure of the spark plug 100 of the above embodiment is brought about by satisfying 0 ⁇ ⁇ H ⁇ H1 and 0.2 mm ⁇ R ⁇ 0.8 mm. Conceivable. Therefore, elements other than these parameters, for example, the material and details of the metal shell 50 and the material and details of the insulator 10 can be variously changed.
- the material of the metal shell 50 may be a low carbon steel plated with nickel or zinc, or may be a low carbon steel not plated.
- the insulator 10 may be made of various insulating ceramics other than alumina. *
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Abstract
Description
軸線の方向に延びる貫通孔を有する絶縁体と、
前記貫通孔に挿設され、前記軸線の方向に延びる棒状の中心電極と、
前記絶縁体の外周に配置される主体金具と、
前記主体金具と電気的に導通し、前記中心電極との間でギャップを形成する接地電極と、
を備えるスパークプラグであって、
前記絶縁体の先端部分は、先端面と、前記先端面より前記軸線の方向の後端に向かって延びる外周面と、前記先端面と前記外周面との間に形成された曲面部を有し、
前記軸線を含む断面において、
前記主体金具の内周面の先端は、前記曲面部と、前記軸線と垂直な方向に対向し、
前記曲面部の曲率半径は、0.2mm(ミリメートル)以上、かつ、0.8mm(ミリメートル)以下である、スパークプラグ。
前記絶縁体の前記外周面の外径は、前記外周面の先端から後端に向かって大きくなる、スパークプラグ。
前記軸線を含む断面において、前記絶縁体の2つの前記外周面がなす鋭角は、5度以上、かつ、30度以下である、スパークプラグ。
も、曲面部13Cの曲率半径Rが、0.2mm未満であると、曲面部13Cが鋭利なエッジに近くなるので、曲面部13Cに電界が集中して、曲面部13Cが破壊されて絶縁碍子10の貫通破壊が発生する可能性が高くなる。
主体金具50の先端部近傍の内径φ3:7.2mm
ΔH:0.05mm
曲率半径R:0.4mm
第1の外径φ1:4.1mm
Claims (3)
- スパークプラグであって、
軸線の方向に延びる貫通孔を有する絶縁体と、
前記貫通孔に挿設され、前記軸線の方向に延びる棒状の中心電極と、
前記絶縁体の外周に配置される主体金具と、
前記主体金具と電気的に導通し、前記中心電極との間でギャップを形成する接地電極と、
を備えるスパークプラグであって、
前記絶縁体の先端部分は、先端面と、前記先端面より前記軸線の方向の後端に向かって延びる外周面と、前記先端面と前記外周面との間に形成された曲面部を有し、
前記軸線を含む断面において、
前記主体金具の内周面の先端は、前記曲面部と、前記軸線と垂直な方向に対向し、
前記曲面部の曲率半径は、0.2mm(ミリメートル)以上、かつ、0.8mm(ミリメートル)以下である、スパークプラグ。 - 請求項1に記載のスパークプラグであって、
前記絶縁体の前記外周面の外径は、前記外周面の先端から後端に向かって大きくなる、スパークプラグ。 - 請求項1または請求項2に記載のスパークプラグであって、
前記軸線を含む断面において、前記絶縁体の2つの前記外周面がなす鋭角は、5度以上、かつ、30度以下である、スパークプラグ。
Priority Applications (3)
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US15/025,609 US9742157B2 (en) | 2013-10-28 | 2014-08-20 | Spark plug |
CN201480057645.7A CN105659452B (zh) | 2013-10-28 | 2014-08-20 | 火花塞 |
EP14858231.5A EP3065238B1 (en) | 2013-10-28 | 2014-08-20 | Spark plug |
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JP2013222947A JP5755310B2 (ja) | 2013-10-28 | 2013-10-28 | スパークプラグ |
JP2013-222947 | 2013-10-28 |
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WO2015063987A1 true WO2015063987A1 (ja) | 2015-05-07 |
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PCT/JP2014/004262 WO2015063987A1 (ja) | 2013-10-28 | 2014-08-20 | スパークプラグ |
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US (1) | US9742157B2 (ja) |
EP (1) | EP3065238B1 (ja) |
JP (1) | JP5755310B2 (ja) |
CN (1) | CN105659452B (ja) |
WO (1) | WO2015063987A1 (ja) |
Cited By (1)
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WO2021176949A1 (ja) * | 2020-03-04 | 2021-09-10 | 株式会社デンソー | 内燃機関用のスパークプラグ |
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JP6419747B2 (ja) * | 2016-03-31 | 2018-11-07 | 日本特殊陶業株式会社 | スパークプラグ |
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WO2011125306A1 (ja) * | 2010-04-02 | 2011-10-13 | 日本特殊陶業株式会社 | スパークプラグ |
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-
2013
- 2013-10-28 JP JP2013222947A patent/JP5755310B2/ja active Active
-
2014
- 2014-08-20 EP EP14858231.5A patent/EP3065238B1/en active Active
- 2014-08-20 US US15/025,609 patent/US9742157B2/en active Active
- 2014-08-20 CN CN201480057645.7A patent/CN105659452B/zh active Active
- 2014-08-20 WO PCT/JP2014/004262 patent/WO2015063987A1/ja active Application Filing
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JPH0927379A (ja) | 1995-07-13 | 1997-01-28 | Ngk Spark Plug Co Ltd | スパークプラグの製造方法 |
JPH09266056A (ja) | 1996-03-28 | 1997-10-07 | Ngk Spark Plug Co Ltd | スパークプラグ |
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Also Published As
Publication number | Publication date |
---|---|
CN105659452A (zh) | 2016-06-08 |
EP3065238A4 (en) | 2017-06-21 |
JP5755310B2 (ja) | 2015-07-29 |
US9742157B2 (en) | 2017-08-22 |
EP3065238B1 (en) | 2020-10-28 |
EP3065238A1 (en) | 2016-09-07 |
JP2015088224A (ja) | 2015-05-07 |
CN105659452B (zh) | 2017-12-12 |
US20160218486A1 (en) | 2016-07-28 |
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