JP2017054599A - Spark plug and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve peeling resistance of an electrode tip in a spark plug.SOLUTION: An electrode tip in a spark plug comprises: a first metal layer which forms a facing surface; and a second metal layer which has a linear thermal expansion coefficient at a level between those of the first metal layer and an electrode base material, and which is arranged on a rear side of the facing surface of the first metal layer. A fusion interface between the electrode tip and a melting part includes: a first partial interface, extending on one end side in the surface direction, where the first metal layer and the melting part abut against each other; and a second partial interface, extending on the other end side from the first partial interface in the surface direction, where the second metal layer and the melting part abut against each other.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a spark plug and a manufacturing method thereof.

  As a spark plug, there is known a spark plug in which an electrode tip is joined to an electrode base material in order to improve durability (consumption resistance) against electrode consumption (see, for example, Patent Documents 1 and 2). ). Such an electrode tip is made of a material that is more resistant to spark discharge and oxidation than the electrode base material. The material of the electrode tip is, for example, a noble metal (for example, platinum, iridium, ruthenium, rhodium, etc.) or an alloy containing the noble metal as a main component. A melted portion is formed between the electrode tip and the electrode base material. The melted portion is a portion (so-called weld bead) in which the electrode base material once melted by laser welding and the metal derived from the electrode tip are solidified when the electrode tip is joined to the electrode base material.

  When the spark plug is used in an internal combustion engine, thermal stress is generated in the melted portion formed between the electrode tip and the electrode base material due to the combustion heat of the internal combustion engine. Therefore, cracks and oxide scales are likely to occur at the boundary between the electrode tip and the molten part and at the boundary between the electrode base material and the molten part. When at least one of cracks and oxide scales develops excessively at these boundaries, the electrode tip may be peeled off and dropped from the electrode base material. Therefore, the spark plug in which the electrode tip is bonded to the electrode base material is required to have improved durability (peeling resistance) against peeling and dropping of the electrode tip.

JP 2010-238498 A JP 2010-238499 A

  In the spark plugs of Patent Documents 1 and 2, there is room for improvement in suppressing the thermal stress generated in the weld formed between the electrode tip and the electrode base material.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms.

(1) One aspect of the present invention provides a spark plug. The spark plug includes: a first electrode; an electrode chip having an opposing surface that forms a gap between the first electrode; an electrode base material to which the electrode chip is bonded; the electrode chip and the electrode And a second electrode including a melting portion formed between the opposite surface of the electrode tip and the opposite surface of the electrode tip toward the other end. It forms a shape that spreads in the direction, and is exposed with the maximum thickness at one end side in the plane direction. In this form of the spark plug, the electrode tip has a first metal layer constituting the facing surface; a linear thermal expansion coefficient intermediate between the first metal layer and the electrode base material; A second metal layer disposed on the back surface of the first metal layer with respect to the facing surface, and a melting interface between the electrode tip and the melting portion extends to one end side in the surface direction, A first partial interface in which the metal layer and the melted part are adjacent to each other; a first partial interface extending from the first partial interface to the other end in the surface direction, and the second metal layer and the melted part are adjacent to each other. 2 partial interfaces. According to this embodiment, the change in the thermal expansion characteristics from the first metal layer to the electrode base material can be gradually changed by the second metal layer and the melted part at the portion sandwiching the second partial interface. . As a result, thermal stress generated between the first metal layer and the electrode base material can be suppressed on the other end side where it is relatively difficult to ensure the thickness of the melted portion of the melted portion spreading in the plane direction. Therefore, the peel resistance of the electrode tip can be improved. In addition, since the first metal layer, not the second metal layer, is exposed at one end side in the surface direction of the electrode tip, it is possible to avoid a decrease in wear resistance of the electrode tip due to the exposure of the second metal layer. .

(2) In the spark plug described above, the first metal layer is mainly composed of at least one of platinum (Pt) and iridium (Ir), and the second metal layer constitutes the first metal layer. It may consist mainly of an alloy containing the component which forms and the component which comprises the said electrode base material. According to this form, the wear resistance of the electrode tip can be sufficiently ensured by the first metal layer, and the peel resistance of the electrode tip can be improved by the second metal layer.

(3) In the spark plug described above, the thickness A of the melted portion at one end in the surface direction at the melt interface and the melt at the other end in the surface direction at the melt interface. The relationship with the thickness B of the part may satisfy 0.7 ≦ B / A <1.0. According to this aspect, the thermal stress generated between the first metal layer and the electrode base material can be sufficiently suppressed on the other end side of the melted portion spreading in the surface direction.

(4) In the spark plug described above, the melting portion passes through the second metal layer from the first metal layer and faces the end surface on the other end side of the electrode tip. May be reached. According to this form, compared with the case where a fusion | melting part does not reach | attain the surface of an electrode base material in the other end side, the joining strength which joins an electrode tip and an electrode base material can be improved.

(5) In the spark plug described above, the electrode base material has a base material surface adjacent to the electrode chip and facing the same direction as the facing surface, and the second metal layer is formed in the surface direction. You may exist in the position away from the said opposing surface from the said base material surface in the perpendicular direction. According to this aspect, it is possible to avoid a decrease in wear resistance of the electrode tip due to the second metal layer being exposed on the opposite surface side from the base material surface.

(6) In the spark plug described above, the second electrode is preferably a ground electrode. According to this aspect, it is preferable that the peeling resistance of the electrode tip can be improved in the ground electrode that is easily affected by the combustion heat of the internal combustion engine.

(7) One form of this invention provides the manufacturing method of a spark plug. The spark plug includes: a first electrode; an electrode chip having an opposing surface that forms a gap between the first electrode; an electrode base material to which the electrode chip is bonded; the electrode chip and the electrode And a second electrode including a melting portion formed between the opposite surface of the electrode tip and the opposite surface of the electrode tip toward the other end. It forms a shape that spreads in the direction, and is exposed with the maximum thickness at one end side in the plane direction. In this embodiment, the spark plug manufacturing method has an intermediate linear thermal expansion coefficient between the first metal layer and the electrode base material on the back side of the first metal layer constituting the facing surface with respect to the facing surface. By thermocompression bonding the second metal layer, an electrode chip in which the second metal layer is thickly present on the back side and deviated from one end side in the surface direction toward the other end side; the second metal layer; The electrode tip and the melting portion are formed by laser welding in which a laser is incident from one end side to the other end side in the surface direction with respect to the chip back surface opposite to the facing surface of the electrode chip that is thermocompression bonded. A melt interface between the first metal layer and the melted portion is adjacent to the first partial interface, and the first partial interface is the other in the plane direction. Spread to the end side, the second gold It is said the layer melting portion forming the molten portion so as to include a second portion surface adjacent. According to this aspect, in the electrode tip before being joined to the electrode base material, the second metal layer that is easier to melt than the first metal layer is biased to the other end side. The melted portion can be formed with a sufficient thickness toward the end side. As a result, it is possible to manufacture a spark plug that achieves both peeling resistance and wear resistance of the electrode tip.

  The present invention can be realized in various forms other than the spark plug and the manufacturing method thereof. For example, the spark plug electrode, the spark plug manufacturing apparatus, the computer program for controlling the manufacturing apparatus, and the computer program are recorded. It can be realized in the form of a non-temporary recording medium.

It is explanatory drawing which shows the partial cross section of a spark plug. It is explanatory drawing which shows the part by the side of the front-end | tip of a ground electrode. It is process drawing which shows the manufacturing method of a spark plug. It is explanatory drawing which shows the ground electrode in the middle of manufacture. It is explanatory drawing which shows the ground electrode in the middle of manufacture in a 1st modification. It is explanatory drawing which shows the ground electrode in the middle of manufacture in a 2nd modification. It is explanatory drawing which shows the ground electrode in the middle of manufacture in a 3rd modification. It is explanatory drawing which shows the ground electrode in the middle of manufacture in a 4th modification. It is explanatory drawing which shows the ground electrode in the middle of manufacture in a 5th modification. It is explanatory drawing which shows the ground electrode in the middle of manufacture in a 6th modification. It is explanatory drawing which shows the ground electrode in the middle of manufacture in the 7th modification. It is a graph which shows the result of having evaluated the relationship between the shape of a fusion | melting part, and durability. It is a graph which shows the result of having evaluated the relationship between the shape of a fusion | melting part, and durability. It is a graph which shows the result of having evaluated the relationship between the shape of a fusion | melting part, and durability.

A. Embodiment FIG. 1 is an explanatory view showing a partial cross section of a spark plug 10. FIG. 1 shows the external shape of the spark plug 10 on the left side of the drawing surface with respect to the axis AL, which is the axis of the spark plug 10, and the cross-sectional shape of the spark plug 10 on the right side of the drawing. ing. In the description of the present embodiment, the lower side of the spark plug 10 in FIG. 1 is referred to as “front end side”, and the upper side of FIG. 1 is referred to as “rear end side”.

  FIG. 1 shows the XYZ axes. The XYZ axes in FIG. 1 have an X axis, a Y axis, and a Z axis as three spatial axes orthogonal to each other. In the present embodiment, the Z axis is an axis along the axis AL of the spark plug 10. Among the X-axis directions along the X-axis, the + X-axis direction is a direction from the front of the paper to the back of the paper, and the −X-axis direction is a direction opposite to the + X-axis direction. Among the Y-axis directions along the Y-axis, the + Y-axis direction is a direction from the right side of the drawing to the left side of the drawing, and the −Y-axis direction is a direction opposite to the + Y-axis direction. Among the Z-axis directions (axial directions) along the Z-axis, the + Z-axis direction is a direction from the front end side to the rear end side, and the −Z-axis direction is a direction opposite to the + Z-axis direction. The XYZ axes in FIG. 1 correspond to the XYZ axes in the other drawings.

  The spark plug 10 includes a center electrode 100, an insulator 200, a metal shell 300, and a ground electrode 400. In the present embodiment, the axis AL of the spark plug 10 is also the axis of each member of the center electrode 100, the insulator 200, and the metal shell 300.

  The spark plug 10 has a gap SG formed between the center electrode 100 and the ground electrode 400 on the tip side. The gap SG of the spark plug 10 is also called a spark gap. The spark plug 10 is configured to be attachable to the internal combustion engine 90 in a state where the tip end side where the gap SG is formed protrudes from the inner wall 910 of the combustion chamber 920. When a high voltage (for example, 10,000 to 30,000 volts) is applied to the center electrode 100 with the spark plug 10 attached to the internal combustion engine 90, a spark discharge occurs in the gap SG. The air-fuel mixture in the combustion chamber 920 is ignited by the spark discharge generated in the gap SG.

  The center electrode 100 of the spark plug 10 is a first electrode having conductivity. The center electrode 100 has a rod shape extending about the axis AL. In the present embodiment, the center electrode 100 is made of a nickel alloy (for example, Inconel 601 (“INCONEL” is a registered trademark)) containing nickel (Ni) as a main component. In the description of the present specification, the “main component” means a component that is contained most. The outer surface of the center electrode 100 is electrically insulated from the outside by an insulator 200. The distal end side of the center electrode 100 protrudes from the distal end side of the insulator 200. The rear end side of the center electrode 100 is electrically connected to the rear end side of the insulator 200. In the present embodiment, the rear end side of the center electrode 100 is electrically connected to the rear end side of the insulator 200 via the terminal fitting 190.

  The insulator 200 of the spark plug 10 is an insulator having electrical insulation. The insulator 200 has a cylindrical shape extending around the axis AL. In this embodiment, the insulator 200 is produced by firing an insulating ceramic material (for example, alumina). The insulator 200 has a shaft hole 290 that is a through hole extending about the axis AL. In the shaft hole 290 of the insulator 200, the center electrode 100 is held on the axis AL in a state where the center electrode 100 protrudes from the distal end side of the insulator 200.

  The metal shell 300 of the spark plug 10 is a metal body having conductivity. The metal shell 300 has a cylindrical shape extending around the axis AL. In the present embodiment, the metal shell 300 is a member obtained by applying nickel plating to a low carbon steel formed into a cylindrical shape. In other embodiments, the metallic shell 300 may be a member that has been galvanized or a member that has not been plated (no plating). The metal shell 300 is fixed to the outer surface of the insulator 200 by caulking while being electrically insulated from the center electrode 100. An end face 310 is formed on the front end side of the metal shell 300. From the center of the end surface 310, the insulator 200 together with the center electrode 100 protrudes toward the tip side. A ground electrode 400 is joined to the end face 310.

  The ground electrode 400 of the spark plug 10 is a second electrode having conductivity. The ground electrode 400 includes an electrode base material 410 and an electrode tip 450. The electrode base material 410 has a shape bent toward the axis AL after extending from the end surface 310 of the metal shell 300 to the front end side. The rear end side of the electrode base material 410 is joined to the metal shell 300. An electrode tip 450 is joined to the tip side of the electrode base material 410. The electrode tip 450 forms a gap SG between the electrode tip 450 and the center electrode 100.

  FIG. 2 is an explanatory diagram showing a portion on the tip side of the ground electrode 400. In the upper part of FIG. 2, the tip side portion of the ground electrode 400 viewed from the + Z-axis direction is illustrated. The lower part of FIG. 2 shows a partial cross section of the ground electrode 400 as viewed from the upper arrow F2-F2.

  The electrode base material 410 of the ground electrode 400 has base material surfaces 411, 412, 413, 414, and 415. The base material surface 411 of the electrode base material 410 is a surface facing the + Z-axis direction. The base material surface 411 is adjacent to the electrode tip 450. The base material surface 412 of the electrode base material 410 is a surface facing the −Z axis direction. The base material surface 413 of the electrode base material 410 is a surface facing the + X-axis direction. The base material surface 414 of the electrode base material 410 is a surface facing the −X axis direction. The base material surface 415 of the electrode base material 410 is a surface facing the + Y-axis direction. In the present embodiment, the electrode base material 410 is made of a nickel alloy (for example, Inconel 601 (“INCONEL” is a registered trademark)) whose main component is nickel (Ni).

  The electrode tip 450 of the ground electrode 400 has a facing surface 451 that forms a gap SG with the center electrode 100. In the present embodiment, the facing surface 451 is located on the + Z-axis direction side from the base material surface 411 of the electrode base material 410. In the present embodiment, the shape of the facing surface 451 is a square. The electrode tip 450 has end surfaces 455 and 456 in addition to the facing surface 451. The end surface 455 of the electrode tip 450 is a surface facing the + Y axis direction. The end surface 455 constitutes one end of the facing surface 451. The end surface 456 of the electrode tip 450 is a surface facing the −Y axis direction. The end surface 456 constitutes the other end of the facing surface 451.

  In the ground electrode 400, a melting part 430 is formed between the electrode base material 410 and the electrode tip 450. The melting portion 430 is a portion (so-called weld bead) in which the electrode base material 410 once melted by laser welding and the metal derived from the electrode tip 450 are solidified when the electrode tip 450 is joined to the electrode base material 410. Melting portion 430 contains a component derived from electrode base material 410 and a component derived from electrode tip 450.

  On the back side (−Z axis direction side) with respect to the facing surface 451 of the electrode tip 450, the melting part 430 is directed in a surface direction (−Y axis direction) from one end (end surface 455) to the other end (end surface 456). It has a shape that spreads out. The melting part 430 is exposed with the maximum thickness (length in the Z-axis direction) on one end side (+ Y-axis direction side) in the surface direction. In the present embodiment, the melting part 430 is formed over the entire region on the −Z axis direction side of the electrode tip 450. A broken line shown in the upper part of FIG. 2 indicates a range where the melting part 430 is formed.

  The electrode tip 450 of the ground electrode 400 includes a first metal layer 461 and a second metal layer 462. The electrode tip 450 is a clad material in which a first metal layer 461 and a second metal layer 462 are joined by thermocompression bonding. The first metal layer 461 in the electrode tip 450 constitutes the facing surface 451. The second metal layer 462 in the electrode chip 450 is disposed on the back surface 461b of the first metal layer 461 with respect to the facing surface 451. The second metal layer 462 is atomically bonded to the back surface 461b of the first metal layer 461. The second metal layer 462 is unevenly distributed on the −Y axis direction side.

  In the present embodiment, the melting part 430 passes from the first metal layer 461 through the second metal layer 462 and reaches the end surface 419 of the electrode base material 410. The end surface 419 of the electrode base material 410 is a surface facing the end surface 456 of the electrode tip 450. The end surface 419 is one of surfaces constituting a groove that fits into the electrode tip 450. In other embodiments, the melting part 430 may not reach the end surface 419 of the electrode base material 410.

  In the present embodiment, the second metal layer 462 is located away from the facing surface 451 from the base material surface 411 in the Z-axis direction. In other words, the second metal layer 462 is located on the −Z axis direction side from the base material surface 411. In another embodiment, the second metal layer 462 may be at the same position as the base material surface 411 in the Z-axis direction, or may be positioned on the + Z-axis direction side from the base material surface 411.

  A point P in FIG. 2 is a point where the end surface 455 of the electrode tip 450 and the melting part 430 are connected. A point Q in FIG. 2 is a point where the end portion on the + Y-axis direction side of the second metal layer 462 and the melting portion 430 are connected. A point R in FIG. 2 is a point where the end portion on the −Y-axis direction side of the second metal layer 462 and the melting portion 430 are connected.

  The melting interface PQR connecting the points P, Q, and R is a boundary surface where the electrode tip 450 and the melting part 430 are in contact with each other. The melt interface PQR between the electrode tip 450 and the melt part 430 includes a first partial interface PQ and a second partial interface QR. The first partial interface PQ is a boundary surface that extends toward the + Y-axis direction and is adjacent to the first metal layer 461 and the melted portion 430. The second partial interface QR is a boundary surface that extends to the −Y axis direction side from the first partial interface PQ, and the second metal layer 462 and the melted portion 430 are adjacent to each other.

  The length L of the electrode tip 450 shown in FIG. 2 is the length of the electrode tip 450 in the Y-axis direction. The thickness A of the melted part 430 shown in FIG. 2 is the thickness at the end part on the one end side (+ Y axis direction side) of the melt interface PQR, and is located at a position of L / 10 from the point P in the −Y axis direction. The drawn imaginary line parallel to the Z-axis indicates a length that overlaps the melted part 430. The thickness B of the melted portion 430 shown in FIG. 2 is the thickness at the end portion on the other end side (−Y-axis direction side) of the melt interface PQR, and the position L / 10 from the point R to the + Y-axis direction. The imaginary line parallel to the Z-axis drawn in FIG. The relationship between the thickness A and the thickness B preferably satisfies 0.4 ≦ B / A <1.0, and more preferably satisfies 0.7 ≦ B / A <1.0.

  In the present embodiment, the material of the first metal layer 461 is an alloy containing platinum (Pt) as a main component and containing 10% by mass of iridium (Ir). In other embodiments, the material of the first metal layer 461 may be any material that is more durable than the electrode base material 410, and may be a pure noble metal (for example, platinum (Pt), iridium (Ir), ruthenium ( Ru), rhodium (Rh), etc.), and other alloys mainly composed of these noble metals.

  The second metal layer 462 in the electrode tip 450 has an intermediate linear expansion coefficient between the first metal layer 461 and the melting part 430. In the present embodiment, the second metal layer 462 is mainly composed of an alloy containing a component constituting the first metal layer 461 and a component constituting the electrode base material 410. In the present embodiment, the material of the second metal layer 462 is mainly composed of platinum (Pt), which is a component constituting the first metal layer 461, and nickel (Ni), which is a component constituting the electrode base material 410. Is an alloy containing 20% by mass. In other embodiments, the nickel (Ni) contained in the second metal layer 462 may be 30% by mass or 40% by mass. The material of the second metal layer 462 is not limited to each component of the electrode base material 410 and the first metal layer 461, but may be a component having an intermediate linear expansion coefficient between the first metal layer 461 and the melting portion 430. That's fine.

  FIG. 3 is a process diagram showing a method for manufacturing the spark plug 10. FIG. 4 is an explanatory diagram showing the ground electrode 400p being manufactured. That is, the ground electrode 400p indicates a state in which the electrode base material 410 and the electrode tip 450 are not joined to each other. The upper part of FIG. 4 shows a portion on the tip side of the ground electrode 400p as viewed from the + Z-axis direction. The lower part of FIG. 4 shows a partial cross section of the ground electrode 400p as viewed from the upper arrow F4-F4.

  In the manufacturing process of the spark plug 10, the manufacturer of the spark plug 10 performs thermocompression bonding of the second metal layer 462 on the back side (the −Z axis direction side) of the first metal layer 461 with respect to the facing surface 451. An electrode chip 450 is produced in which the second metal layer 462 is present thickly on the back side of the first metal layer 461 while being biased toward the −Y-axis direction (step P110). In the present embodiment, the electrode tip 450 forms a rectangular parallelepiped having an opposing surface 451 that forms a square. In the present embodiment, the first metal layer 461 has a counter surface 451 that forms a square, and forms a rectangular parallelepiped with the −Y-axis direction side cut out of the back side of the counter surface 451. In the present embodiment, the second metal layer 462 forms a rectangular parallelepiped that fits into the notched portion of the first metal layer 461.

  After manufacturing the electrode tip 450 (process P110), the manufacturer performs laser welding that irradiates the tip back surface 452 of the electrode tip 450 fitted in the groove 418 of the electrode base material 410 along the tip back surface 452. Thus, the melting part 430 constituting the electrode tip 450 and the melting interface PQR (see FIG. 2) is formed (process P120). As a result, the electrode base material 410 and the electrode tip 450 are joined. In the present embodiment, the irradiation direction DL for laser irradiation is the −Y axis direction. In other embodiments, the irradiation direction DL may be inclined in the + Z-axis direction or may be inclined in the −Z-axis direction. In the present embodiment, the scanning direction DM for scanning the laser is the + X-axis direction. In another embodiment, the scanning direction DM may be the −X axis direction.

  After joining the electrode base material 410 and the electrode tip 450 by laser welding (process P120), the manufacturer assembles the members (process P180). Thereby, the spark plug 10 is completed.

  FIG. 5 is an explanatory diagram showing the ground electrode 400Bp in the middle of manufacture in the first modification. The ground electrode 400Bp of the first modified example is the same as that in the above-described embodiment except that a gap GP is formed between the end surface 419 of the electrode base material 410 and the end surface 456 of the electrode tip 450.

  FIG. 6 is an explanatory view showing a ground electrode 400Cp in the middle of manufacture in the second modification. The ground electrode 400Cp of the second modified example is the same as that of the above-described embodiment except that the electrode tip 450C is joined to the electrode base material 410 instead of the electrode tip 450. The electrode tip 450C is the same as that of the above-described embodiment except that the second metal layer 462 forms a right triangle in the cross section cut along the YZ plane. In the right triangle formed by the second metal layer 462, the short side forms the end face 456, the oblique side forms the back surface 461b, and the long side forms the chip back surface 452.

  FIG. 7 is an explanatory view showing a ground electrode 400Dp in the middle of manufacture in the third modified example. The ground electrode 400Dp of the third modification is the same as that of the above-described embodiment except that the electrode tip 450D is joined to the electrode base material 410 instead of the electrode tip 450. The electrode tip 450D is the same as that in the above-described embodiment except that the second metal layer 462 forms a right trapezoid in the cross section cut along the YZ plane. In the right trapezoid formed by the second metal layer 462, the first side constitutes the end surface 455, the second side constitutes the end surface 456, the third side constitutes the back surface 461b, and the fourth side A chip back surface 452 is formed. The first side constituting the end surface 455 is shorter than the second side constituting the end surface 456. Of the portion of the second metal layer 462 in the ground electrode 400Dp, the portion on the + Y-axis direction side disappears with the formation of the melting portion 430.

  FIG. 8 is an explanatory view showing a ground electrode 400Ep in the middle of manufacture in the fourth modified example. The ground electrode 400Ep of the fourth modification is the same as that of the above-described embodiment except that the electrode tip 450E is joined to the electrode base material 410 instead of the electrode tip 450. The electrode tip 450E is the same as the second modification example of FIG. 6 except that the back surface 461b forms a curve in the cross section cut along the YZ plane.

  FIG. 9 is an explanatory diagram showing the ground electrode 400Fp in the middle of manufacture in the fifth modification. The ground electrode 400Fp of the fifth modification is the same as that of the above-described embodiment except that the electrode tip 450F is joined to the electrode base material 410 instead of the electrode tip 450. The electrode tip 450F is the same as that of the above-described embodiment except that the back surface 461b has a stepped shape in a cross section cut along the YZ plane. Of the portion of the second metal layer 462 in the ground electrode 400Fp, the portion on the + Y-axis direction side disappears with the formation of the melting portion 430.

  FIG. 10 is an explanatory diagram showing the ground electrode 400Gp in the middle of manufacture in the sixth modification. The ground electrode 400Gp of the sixth modified example is the same as that of the above-described embodiment except that the electrode base material 410G is provided instead of the electrode base material 410 and that the electrode tip 450G is provided instead of the electrode tip 450. . The electrode tip 450G of the sixth modification is the same as the electrode tip 450 except that it forms a rectangular parallelepiped having a rectangular opposing surface 451 whose longitudinal direction is the Y-axis direction. The electrode base material 410G of the sixth modification is the same as the electrode base material 410 except that the electrode base material 410G is configured to fit with the electrode tip 450G.

  FIG. 11 is an explanatory diagram showing a ground electrode 400Hp in the middle of manufacture in the seventh modification. The ground electrode 400Hp of the seventh modified example is the same as that of the above-described embodiment except that the electrode base material 410H is provided instead of the electrode base material 410 and that the electrode tip 450H is provided instead of the electrode tip 450. . The electrode tip 450H of the seventh modified example is the same as the electrode tip 450 except that it forms a cylinder having a circular opposing surface 451. The electrode base material 410H of the seventh modified example is the same as the electrode base material 410 except that the electrode base material 410H is configured to fit with the electrode tip 450H.

  12, 13 and 14 are graphs showing the results of evaluating the relationship between the shape of the melted part 430 and the durability. The horizontal axis in FIG. 12 indicates the ratio B / A between the thickness A on one end side and the thickness B on the other end side in the melted portion 430. The vertical axis in FIG. 12 indicates the damage rate, which is the ratio of the length of the crack and the oxide scale confirmed after the durability test with respect to the length L of the electrode tip 450 in the Y-axis direction (see FIG. 2). The same applies to the axes in FIGS. 13 and 14.

  The tester produced an electrode in which an electrode base material and an electrode tip were joined by laser welding as a sample. The tester prepared a plurality of electrode tips having different materials and shapes. The tester produced a plurality of samples having different ratios B / A for each specification of the electrode tip by adjusting the laser intensity and the processing speed as the laser welding conditions. The combination of the electrode base material and the electrode tip used for the preparation of the sample is as follows.

<Combination A1 (FIG. 12)>
The shape of the electrode tip: a rectangular parallelepiped having a square (1.8 mm × 1.8 mm) facing surface corresponding to the second modification (FIG. 6) The material of the first metal layer: platinum (Pt) as a main component Alloy containing 10% by mass of iridium (Ir) Material of the second metal layer: Alloy mainly containing platinum (Pt) and containing 20% by mass of nickel (Ni) Electrode base material: Inconel 601 Square material <combination A2 (FIG. 12)>
The shape of the electrode tip: a rectangular parallelepiped having a square (1.3 mm × 1.3 mm) facing surface corresponding to the second modification (FIG. 6) The material of the first metal layer: platinum (Pt) as a main component Alloy containing 10% by mass of iridium (Ir) Material of the second metal layer: Alloy mainly containing platinum (Pt) and containing 20% by mass of nickel (Ni) Electrode base material: Inconel 601 Squarewood consisting of

<Combination B1 (FIG. 13)>
The shape of the electrode tip: a rectangular parallelepiped having a square (1.3 mm × 1.3 mm) facing surface corresponding to the second modification (FIG. 6) The material of the first metal layer: platinum (Pt) as a main component Alloy containing 10% by mass of ruthenium (Ru) Material of the second metal layer: Alloy mainly containing platinum (Pt) and containing 20% by mass of nickel (Ni) Electrode base material: Inconel 601 Square material <combination B2 (FIG. 13)>
The shape of the electrode tip: a cylinder having a cross section corresponding to the second modification (FIG. 6) and a circular (diameter 1.0 mm) facing surface corresponding to the seventh modification (FIG. 11) Material of the metal layer: Platinum (Pt) as a main component and an alloy containing 10% by mass of ruthenium (Ru). Material of the second metal layer: Platinum (Pt) as a main component and 20% by mass of nickel ( Ni) -containing alloy / electrode base material: Square member made of Inconel 601

<Combination C1 (FIG. 14)>
The shape of the electrode tip: a rectangular parallelepiped having a square (1.5 mm × 1.5 mm) facing surface corresponding to the second modification (FIG. 6) The material of the first metal layer: platinum (Pt) as a main component Alloy containing 10% by mass rhodium (Rh) Material of the second metal layer: Platinum (Pt) as a main component Alloy containing 20% by mass nickel (Ni) Electrode base material: Inconel 601 Square material <combination C2 (FIG. 14)>
The shape of the electrode tip: a cylinder having a cross section corresponding to the second modification (FIG. 6) and a circular (diameter 1.0 mm) facing surface corresponding to the seventh modification (FIG. 11) Material of the metal layer: platinum (Pt) as a main component and alloy containing 10% by mass of rhodium (Rh) Material of the second metal layer: Platinum (Pt) as a main component and 20% by mass of nickel ( Ni) -containing alloy / electrode base material: Square member made of Inconel 601

The tester performed a thermal cycle test in which the following procedures 1 and 2 were repeated 1000 times for each sample.
(Procedure 1) Heat the electrode chip bonded to the electrode base material with a burner for 2 minutes so that the maximum temperature of the electrode chip is 1050 ° C. (Procedure 2) Cool the electrode chip by blowing air for 1 minute

  After completing the cooling cycle test, the tester cuts each sample along the YZ plane at the center in the X-axis direction, measures the thicknesses A and B of the melted part 430, and generates cracks in the melted part 430 and The length of the oxide scale was measured. Cracks and oxide scales tended to occur at sites on the −Y axis direction side of the melted part 430.

  After measuring each part of the sample cross section, the tester calculated the ratio B / A and calculated the damage ratio based on the length of the cracks and oxide scale. The tester evaluated two samples for each laser welding condition, and calculated each average value of the ratio B / A and the damage ratio. As a result, the tester obtained the results shown in FIG. 12, FIG. 13 and FIG. 12, 13, and 14, white dots indicate that the melted portion 430 has not reached the end surface 419 of the electrode base material 410 and has not been penetrated, and the filled points indicate melting points. It shows that the part 430 is a sample penetrating to the end surface 419 of the electrode base material 410.

  According to the results shown in FIGS. 12, 13, and 14, it can be seen that the rate of damage can be reduced by penetration of the melted portion 430 into the end surface 419 of the electrode base material 410. Further, from the viewpoint of reducing the damage ratio, the ratio B / A preferably satisfies 0.4 ≦ B / A <1.0, and more preferably satisfies 0.7 ≦ B / A <1.0. .

  According to the embodiment described above, the change in the thermal expansion characteristics from the first metal layer 461 to the electrode base material 410 in the region sandwiching the second partial interface QR is changed to the second metal layer 462 and the melt. The portion 430 can be used to make a gentle transition. As a result, the first metal layer 461 and the electrode mother are formed on the other end side (−Y-axis direction side) where it is relatively difficult to ensure the thickness of the melted part 430 among the melted parts 430 extending in the plane direction (Y-axis direction). The thermal stress generated between the material 410 can be suppressed. Therefore, the peel resistance of the electrode tip 450 can be improved. In addition, since the first metal layer 461 is exposed instead of the second metal layer 462 on one end side (+ Y-axis direction side) in the surface direction of the electrode chip 450, the electrode formed by exposing the second metal layer 462 is exposed. A decrease in wear resistance of the chip 450 can be avoided.

  The first metal layer 461 is mainly made of platinum (Pt), and the second metal layer 462 contains a component constituting the first metal layer 461 and a component constituting the electrode base material 410. Mainly made of alloy. Therefore, the wear resistance of the electrode tip 450 can be sufficiently secured by the first metal layer 461, and the peel resistance of the electrode tip 450 can be improved by the second metal layer 462.

  Further, the relationship between the thickness A and the thickness B of the melted part 430 satisfies 0.7 ≦ B / A <1.0, and therefore the other end side (− of the melted part 430 spreading in the surface direction (Y-axis direction)). In the Y-axis direction side), the thermal stress generated between the first metal layer 461 and the electrode base material 410 can be sufficiently suppressed.

  In addition, since the melting part 430 passes through the second metal layer 462 from the first metal layer 461 and reaches the end surface 419 of the electrode base material 410, the melting part 430 does not reach the end surface 419 of the electrode base material 410. Compared to the case, the bonding strength for bonding the electrode tip 450 and the electrode base material 410 can be improved.

  In addition, since the second metal layer 462 is located farther from the facing surface 451 than the base material surface 411 of the electrode base material 410 in the direction perpendicular to the surface direction (Z-axis direction), the second metal layer 462 is opposed to the base material surface 411. A reduction in wear resistance of the electrode tip 450 due to the exposure of the second metal layer 462 on the 451 side can be avoided.

  In addition, in the electrode tip 450 before being bonded to the electrode base material 410, the second metal layer 462 that is more easily melted than the first metal layer 461 is biased to the other end side (the −Y axis direction side). The fusion zone 430 can be formed with sufficient thickness from one end side (+ Y-axis direction side) to the other end side (−Y-axis direction side) by laser welding. As a result, it is possible to manufacture the spark plug 10 that achieves both peeling resistance and wear resistance of the electrode tip 450.

B. Other Embodiments The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, among the technical features in the embodiments, examples, and modifications, those corresponding to the technical features in each embodiment described in the summary of the invention are to solve a part or all of the above-described problems, or In order to achieve part or all of the above-described effects, replacement and combination can be performed as appropriate. Further, technical features that are not described as essential in the present specification can be appropriately deleted.

  Laser welding for joining the electrode tip 450 to the electrode base material 410 is not limited to a mode in which laser is irradiated from the base material surface 415 side of the electrode base material 410, but the base material surface 413 side (+ X-axis direction side) of the electrode base material 410 ) From the base material surface 414 side (−X-axis direction side) of the electrode base material 410 may be used.

  The present invention is not limited to the form applied to the ground electrode 400 as in the above-described embodiment, but may be applied to the center electrode 100 to which the electrode chip is joined, and each of the center electrode 100 and the ground electrode 400 may be applied. The form applied to an electrode may be sufficient.

DESCRIPTION OF SYMBOLS 10 ... Spark plug 90 ... Internal combustion engine 100 ... Center electrode 190 ... Terminal metal fitting 200 ... Insulator 290 ... Shaft hole 300 ... Main metal fitting 310 ... End surface 400 ... Ground electrode 400p, 400Bp-400Hp ... Ground electrode 410, 410G, 410H ... Electrode Base material 411, 412, 413, 414, 415 ... Base material surface 418 ... Groove 419 ... End face 430 ... Melting part 450, 450C-450H ... Electrode chip 451 ... Opposing surface 452 ... Chip back surface 455, 456 ... End face 461 ... First Metal layer 461b ... Back surface 462 ... Second metal layer 910 ... Inner wall 920 ... Combustion chamber PQR ... Melting interface PQ ... First partial interface QR ... Second partial interface

Claims (7)

A first electrode;
An electrode tip having an opposing surface that forms a gap with the first electrode, an electrode base material to which the electrode tip is bonded, and a fusion zone formed between the electrode tip and the electrode base material And a second electrode comprising:
The melting part is formed on the back side of the electrode chip with respect to the opposing surface, and has a shape that extends in a surface direction from one end of the opposing surface toward the other end, and is exposed with a maximum thickness on one end side of the surface direction. A spark plug,
The electrode tip is
A first metal layer constituting the facing surface;
A second metal layer having an intermediate linear thermal expansion coefficient between the first metal layer and the electrode base material and disposed on the back surface of the first metal layer with respect to the facing surface;
The melting interface between the electrode tip and the melting part is:
A first partial interface extending to one end side in the plane direction, and adjacent to the first metal layer and the molten portion;
A spark plug, comprising: a second partial interface extending from the first partial interface to the other end side in the planar direction and adjacent to the second metal layer and the molten portion. The spark plug according to claim 1,
The first metal layer mainly comprises at least one of platinum (Pt) and iridium (Ir),
The second metal layer is a spark plug mainly composed of an alloy containing a component constituting the first metal layer and a component constituting the electrode base material.   The relationship between the thickness A of the melted portion at one end in the surface direction at the melt interface and the thickness B of the melted portion at the other end in the surface direction at the melt interface is: The spark plug according to claim 1, wherein 0.7 ≦ B / A <1.0 is satisfied.   The melted portion passes from the first metal layer through the second metal layer and reaches the surface of the electrode base material facing the end surface on the other end side of the electrode tip. The spark plug according to any one of Items 3 to 3. The spark plug according to any one of claims 1 to 4, wherein
The electrode base material has a base material surface adjacent to the electrode chip and facing the same direction as the facing surface;
The spark plug, wherein the second metal layer is located away from the facing surface from the base material surface in a direction perpendicular to the surface direction.   The spark plug according to any one of claims 1 to 5, wherein the second electrode is a ground electrode. A first electrode;
An electrode tip having an opposing surface that forms a gap with the first electrode, an electrode base material to which the electrode tip is bonded, and a fusion zone formed between the electrode tip and the electrode base material And a second electrode comprising:
The melting part is formed on the back side of the electrode chip with respect to the opposing surface, and has a shape that extends in a surface direction from one end of the opposing surface toward the other end, and is exposed with a maximum thickness on one end side of the surface direction. A spark plug manufacturing method for manufacturing a spark plug, comprising:
Thermocompression bonding a second metal layer having a linear thermal expansion coefficient between the first metal layer and the electrode base material on the back side of the first metal layer constituting the facing surface with respect to the facing surface. To produce an electrode chip in which the second metal layer is present thickly on the back side from the one end side in the plane direction to the other end side,
By laser welding in which a laser is incident from one end side to the other end side in the surface direction with respect to the chip back surface opposite to the facing surface in the electrode chip on which the second metal layer is thermocompression bonded, The melting interface between the electrode tip and the melting part is
A first partial interface extending to one end side in the plane direction, and adjacent to the first metal layer and the molten portion;
A spark plug that extends from the first partial interface to the other end in the plane direction and forms the melted part so as to include the second partial interface adjacent to the second metal layer and the melted part. Manufacturing method.

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