JP2006185853A - Method of manufacturing spark plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a spark plug capable of making compatible the maintenance of durability by preventing a chip from being peeled off an electrode base metal with the reduction in production cost. <P>SOLUTION: In a welding step, the chip T10 is welded to the electrode base metal M10 by forming a molten part W10 formed by fusing a part of the electrode base metal M10 and a part of the chip T10. In a re-fusing step, a fused part W10 is re-fused by heating those other than the electrode base metal M10, the chip T10, and the fused part W10 by a laser beam L with a focal point F to a temperature lower than the melting points of the electrode base metal M10 and the chip T10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a spark plug.

  As shown in FIG. 5, a general spark plug 100 includes a cylindrical metal shell 91, a cylindrical insulator 92, a rod-shaped center electrode 93, a ground electrode 94, and a terminal 95. The insulator 92 has a shaft hole 92 b and extends in the axial direction of the metal shell 91, and is fixed in the metal shell 91 with both ends projecting from both ends of the metal shell 91. The center electrode 93 extends in the axial direction in the insulator 92, the tip (lower side in FIG. 5) projects from the tip of the insulator 92, and the rear end (upper side in FIG. 5) in the insulator 92. The tip of the terminal 95 is electrically connected. The terminal 95 protrudes from the rear end of the insulator 92 at the rear end. The ground electrode 94 is disposed such that one end 94 a is fixed to the tip of the metal shell 91 and the other end 94 b is opposed to the tip of the center electrode 93, thereby forming a discharge gap g between the ground electrode 94 and the center electrode 93. is doing.

  In order to exhibit high durability, in the spark plug 100, a tip T10 made of a spark-resistant consumable material is formed at a position where the discharge gap g of at least one of the center electrode 93 and the ground electrode 94 (both in FIG. 5) is formed. T20 may be welded (Patent Document 1).

  Such a center electrode 93 and a ground electrode 94 are formed by, for example, a part of the electrode base material M10 for the ground electrode 94 and the electrode base material M20 for the center electrode 93 and chips T10 and T20 in a welding process such as resistance welding or laser welding. It is obtained by welding the tips T10 and T20 to the electrode base materials M10 and M20 by forming the melted portions W10 and W20 in which a part of them is melted. In the spark plug 100, the consumption of the electrode base materials M10 and M20 can be reduced by the chips T10 and T20.

Japanese Patent No. 2079952

  By the way, when performing the welding process as described above, the center electrode 93 and the ground electrode 94 are welded during the welding process so that the chips T10 and T20 can be prevented from being separated from the electrode base materials M10 and M20 due to insufficient welding. Is stipulated. Here, the welding conditions refer to pressure, electric energy, energization time, etc. when the welding process is performed by resistance welding, for example, and when the welding process is performed by laser welding, for example, In addition to the light shot interval, the number of shots of laser light, etc., it also refers to the material of the electrode base materials M10 and M20 and the material of the chips T10 and T20.

  However, under the welding conditions in this welding process, as shown in FIG. 6, there is a possibility that welding sag W11 and spatter W12 may be generated in the melted portions W10 and W20. 6 illustrates the ground electrode 94, the same applies to the center electrode 93.

  These weld sag W11 and spatter W12 not only impair the appearance of the spark plug 100 before use, but also peel off from the electrode base materials M10 and M20 during use in an internal combustion engine or the like, and the center electrode 93 and the ground electrode 94 are peeled off. There is a risk of short circuiting. For this reason, the spark plug 100 may cause a decrease in durability. For this reason, conventionally, with regard to the extreme welding sag W11 and spatter W12, it is intended to maintain durability after use by removing them by troublesome work at the time of manufacture, which causes an increase in manufacturing cost. It was.

  The present invention has been made in view of the above-described conventional situation, and it is possible to achieve both maintenance of durability and reduction in manufacturing cost by preventing the chip from peeling from the electrode base material. It is an issue to be solved to provide a method for manufacturing a spark plug.

The spark plug manufacturing method of the present invention includes a cylindrical metal shell, a cylindrical insulator that is fixed to the metal shell so as to surround the metal shell, and has a shaft hole; A center electrode protruding from the insulator and fixed to the insulator, and a ground electrode having one end fixed to the metal shell and forming a discharge gap between the other end and the center electrode. And at least one of the ground electrodes is a method of manufacturing a spark plug having an electrode base material and a tip welded to a position where the discharge gap of the electrode base material is formed,
A welding step of welding the tip to the electrode base material by forming a melted portion obtained by melting a part of the electrode base material and a part of the tip;
And a re-melting step of re-melting the molten portion by heating at a temperature lower than the melting point of the electrode base material and the tip after the welding step.

  The method for manufacturing a spark plug according to the present invention includes a welding step of welding the tip to the electrode base material by forming a melted portion obtained by melting a part of the electrode base material and a part of the tip. For this reason, a chip | tip can be welded to an electrode base material on the welding conditions which can prevent a chip | tip peeling from an electrode base material by insufficient welding.

  And the manufacturing method of the spark plug of this invention is equipped with the remelting process which remelts a fusion | melting part by heating at the temperature lower than melting | fusing point of an electrode base material and a chip | tip after a welding process. As a result, it is possible to remelt the welding sag and spatter generated in the melted part during the welding process, and it is difficult for the welding sag and spatter to remain in the resulting spark plug.

  For this reason, the spark plug obtained by the spark plug manufacturing method of the present invention is difficult to cause welding sag and spatter to short-circuit the center electrode and the ground electrode during use, and does not require troublesome work as in the past. High durability can be exhibited. Moreover, the spark plug obtained in this way can also eliminate the concern that the quality may vary due to welding sagging or sputtering.

  Therefore, according to the spark plug manufacturing method of the present invention, it is possible to easily prevent the chip from being peeled off from the electrode base material, and to realize both maintenance of durability and reduction in manufacturing cost.

  Needless to say, the melting part is an alloy of the electrode base material and the tip, and the melting point of the melting part is lower than the melting point of the electrode base material and the tip. For this reason, it cannot be overemphasized that in a remelting process, it heats at temperature higher than melting | fusing point of a fusion | melting part. Further, the melted portion includes not only a part (B10 in FIG. 6) in which a part of the electrode base material and a part of the tip are melted, but also welding sag and spatter.

  Furthermore, in the spark plug manufacturing method of the present invention, it is preferable that the melted portion is irradiated with laser light in the remelting step. In this manner, the manufacturing cost can be reduced by performing the remelting process using laser light.

  In the spark plug manufacturing method of the present invention, it is preferable that the laser beam has a focus other than the electrode base material, the tip, and the melted portion. Since the laser beam focused on other than the electrode base material, the tip, and the melted part does not concentrate energy on the electrode base material, the chip, and the melted part more easily than the laser light focused on these, the electrode base is easily The melting point can be lower than the melting point of the material and the chip and higher than the melting point of the melting part.

  Furthermore, in the spark plug manufacturing method of the present invention, it is preferable to irradiate the laser beam so that at least all of the melted portion is included. When the focal point of the laser beam is other than the electrode base material, the chip, and the melted part, the entire melted part can be remelted at a time by irradiating the laser beam so as to include the melted part at a reduced cost. The effect is increased.

  In the spark plug manufacturing method of the present invention, it is preferable that the focal point is located on the side opposite to the tip with respect to the electrode base material when cut by a virtual cross section passing through the axis. Rather than the focal point being disposed on the tip side with respect to the electrode base material, the refocusing condition of the laser beam can be easily obtained by the focal point being located on the opposite side of the chip with respect to the electrode base material.

  In the spark plug manufacturing method of the present invention, resistance welding, laser welding, electron beam welding, or the like can be employed as the welding step before the remelting step. Among these, it is preferable to employ laser welding as a welding process. Thereby, since a welding process and a remelting process can be performed by the same installation, a spark plug can be mass-produced cheaply.

  In the case of the ground electrode, the tip end surface that forms the discharge gap of the chip after remelting may be covered with the melted portion by welding sag or the like. At this time, if the entire chip is covered by the melted portion, the distance of the discharge gap changes, and the performance of the spark plug may be reduced. Further, when the tip end surface of the chip is entirely covered, blow holes (bubbles) or the like are formed in the melted portion covering the tip end surface of the chip, and the performance of the spark plug may be deteriorated. Therefore, at least a part of the tip end surface of the chip is preferably exposed, more preferably 50% or more of the tip end surface is exposed, and more preferably 80% or more is exposed.

(Test Example 1)
The spark plug 1 of the embodiment will be described. Since this spark plug 1 has the same configuration as the spark plug 100 described in the background art, the description will be given with reference to FIG.

  As shown in FIG. 5, the spark plug 1 according to the present embodiment includes a cylindrical metal shell 91, an insulator 92 fitted in the metal shell 91 so that the tip portion protrudes, and a state in which the tip portion protrudes. The center electrode 93 provided on the inner side of the insulator 92, one end is coupled to the metal shell 91, and the other end side is provided with a ground electrode 94 disposed so as to face the tip of the center electrode 93. A discharge gap g is formed between the ground electrode 94 and the center electrode 93.

  The metal shell 91 is made of carbon steel or the like, and a mounting thread portion 911 is formed on the outer peripheral surface of the metal shell 91 on the tip side (the lower side in FIG. 5). Further, on the rear end side of the threaded portion 911, a tool engaging portion 913 to which a tool is applied when the flange portion 912 and the spark plug 1 are attached to a cylinder head or the like is formed. The spark plug 1 is attached to, for example, a cylinder head of a gasoline engine (internal combustion engine) by the screw portion 911. In this state, a high voltage is applied between a ground electrode 94 and a center electrode 93, which will be described later, to cause a spark discharge in the discharge gap g and to serve as an ignition source for the engine.

  On the other hand, a stepped portion 914 that is reduced in diameter toward the distal end side is formed on the inner periphery of the metal shell 91, and a stepped portion 924 of an insulator 92 described later is engaged with the stepped portion 914 via the packing 6. The insulator 92 is fixed to the metal shell 91.

  The insulator 92 has a flange portion 921 formed at the central portion in the axial direction, and further, an intermediate diameter portion 922 and a small diameter portion 923 are formed toward the tip side. A step portion 924 that connects the medium diameter portion 922 and the small diameter portion 923 is formed, and the step portion 924 engages with the step portion 914 of the metal shell 91. On the other hand, a corrugation portion 925 is formed on the rear end side of the flange portion 921.

  The insulator 92 has an axial hole 926 formed in the axial direction, a terminal 95 is inserted and fixed on the rear end side, and a center electrode 93 is inserted and fixed on the distal end side. In the shaft hole 926, the conductive glass seal layer 7, the resistor 8, and the conductive glass seal layer 9 that electrically connect the center electrode 93 and the terminal 95 are disposed in this order from the front end side. Note that the resistor 8 may be omitted, and the terminal 95 and the center electrode 93 may be joined by a single conductive glass seal layer.

  In the center electrode 93, the electrode base material M20 is made of a Ni alloy such as Inconel (registered trademark). And the chip | tip T20 is welded to the front end side using the method mentioned later. The chip T20 is made of a noble metal such as a Pt alloy such as Pt-13Ir or an Ir alloy such as Ir-5Pt. On the other hand, a core material 931 such as Cu is inserted into the center electrode 93. The center electrode 93 may not have the core material 931.

  In the ground electrode 94, the electrode base material M10 is made of a Ni alloy such as Inconel. And tip T10 is welded to the tip side using the below-mentioned method. The chip T10 is made of a noble metal such as a Pt alloy such as Pt-20Ir or Pt-10Ni or an Ir alloy.

  Next, the manufacturing method of the spark plug 1 of this embodiment is demonstrated. In addition, about a well-known manufacturing method, it simplifies or abbreviate | omits and demonstrates centering on the welding process of the electrode base materials M10 and M20 of this invention, and chip | tip T10 and T20, and a subsequent remelting process. The following description will explain the welding process and the remelting process of the electrode base material M10 for the ground electrode 94 and the tip T10, but the welding process and the remelting process of the electrode base material M20 for the center electrode 93 and the tip T20. The same applies to.

  First, the metal shell 91, the insulator 92, and the center electrode 93 are respectively produced to the respective dimensions by a known method. In the center electrode 93, a tip T20 is welded to the tip side of an electrode base material M20 which will be described through a welding process and a remelting process described later. Then, the center electrode 93 is inserted from the rear end side of the insulator 92. Thereafter, the conductive glass seal layer 7, the resistor 8, and the conductive glass seal layer 9 are filled in order, and a terminal 95 is further inserted on the rear end side and sealed by a known method. Thereafter, the stepped portion 924 of the insulator 92 is engaged with the metal shell 91 via the packing 6, and is crimped by a crimping portion 915 provided on the rear end side of the metal shell 91. The insulator 92 is fixed to the substrate. Thereafter, one end of the electrode base material M10 is joined to the tip of the metal shell 91 by a known method.

  Then, the tip T10 is welded to the rear end side of the electrode base material M10. In addition, resistance welding, laser welding, etc. can be used for the welding method of electrode base material M10 and tip T10. Hereinafter, it demonstrates concretely using drawing.

  First, as shown in FIG. 1, an electrode base material M10 for the ground electrode 94 and a chip T10 were prepared. The electrode base material M10 is a rod-shaped member made of Ni alloy of Inconel 601 and having a width of 2.7 mm and a thickness of 1.3 mm. The chip T10 has a cylindrical shape made of a platinum alloy and having a diameter of 1.1 mm and a thickness of 0.4 mm.

  Next, as a welding process, resistance welding was performed by providing the tip T10 on the electrode base material M10. The conditions of resistance welding were set to cycle 10 (up slope 5 cycles), current 900A, and applied pressure 25 kgf so that the tip T10 would not be peeled off from the electrode base material M10 due to insufficient welding.

  As a result, a melted portion W10 was formed by melting a part of the electrode base material M10 and a part of the tip T10, and the tip T10 was welded to the electrode base material M10. An optical micrograph of the cut surface after the welding process is shown in FIG. Figure (a) is a 20x photograph and Figure (b) is a 40x photograph. Here, as shown in FIG. 2, welding sag W1 and spatter W2 were generated in each obtained melted portion W10.

  For this reason, as the remelting step, the laser beam L having the focal point F disposed on the opposite side of the chip T10 from the electrode base material M10 was irradiated to remelt the melting portion W10. The laser irradiation apparatus is a YAG laser apparatus “JK702H” manufactured by Sumitomo Heavy Industries, Ltd. The shot interval of the laser beam L has a pulse width of 2.5 seconds and a pulse frequency of 10 Hz. The focal point F was set at a position 3 mm away from the surface of the electrode base material M10 on the chip T10 side. Then, at least the melted portion W10 was included in the laser beam L, and the laser beam L with an electric energy of 150 W was shot five times. In this way, the ground electrode 94 was obtained.

  Then, the cross section of the ground electrode 94 was observed. At this time, each ground electrode 94 is cut by a surface passing through the center of the chip T10 and perpendicular to the surface of the electrode base material M10 on the chip T10 side, and the cut surface is corroded, and then an optical micrograph is taken. It was. An optical micrograph of this cut surface is shown in FIG. Figure (a) is a 20x photograph and Figure (b) is a 40x photograph.

  As can be seen from FIG. 3, the ground electrode 94 does not remain after the welding sag W1 or the spatter W2 is remelted, and an extremely smooth melted portion W10 is formed.

  For this reason, as shown in FIG. 5, the spark plug 1 employing this ground electrode 94 does not cause a welding sag W1 or the like to short-circuit the center electrode 93 and the ground electrode 94 during use, and is troublesome as in the prior art. High durability can be exhibited even without performing a difficult operation. Moreover, the spark plug 1 obtained in this way can also eliminate the concern that the quality may vary due to the welding sag W1 or the like.

  Therefore, it is possible to realize both maintenance of durability of the spark plug 1 and reduction in manufacturing cost.

  Furthermore, since this manufacturing method irradiates the melted portion W10 with the laser beam L in the remelting step, the manufacturing cost can be reduced.

  Further, the laser beam L having the focal point F other than the electrode base material M10, the chip T10, and the melting portion W10 is more easily concentrated because the energy does not concentrate on the melting portion W10 than the laser beam L having the focal point F as a focal point. Further, the melting point can be lower than the melting points of the electrode base material M10 and the chip T10 and higher than the melting point of the melting portion W10.

  Furthermore, since this manufacturing method irradiates the laser beam L so as to include at least all the melted portion W10, the entire melted portion W10 can be remelted at one time, and the effect of reducing the manufacturing cost is great.

  Also, in this manufacturing method, when the cutting is performed in a virtual cross section passing through the axis, the focal point F is located on the side opposite to the tip T10 with respect to the electrode base material M10, so that the remelting condition of the laser light L is easily obtained. be able to.

(Test Example 2)
In Test Example 2, after the ground electrode 94 shown in FIG. 5 was produced, a durability test using a burner was performed.

  First, as in Test Example 1, as shown in FIG. 1, a plurality of electrode base materials M10 for the ground electrode 94 and tips T10 were prepared, and welding processes by resistance welding were respectively performed. Thus, two of the ground electrodes 94 obtained without performing the remelting step are referred to as comparative products 1 and 2.

  Next, a remelting process was performed in the same manner as in Test Example 1 for the remaining ground electrodes 94. The obtained ground electrode 94 is designated as test samples 1 and 2.

  Subsequently, an endurance test using a burner was performed on the ground electrodes 94 of the obtained test products 1 and 2 and comparative products 1 and 2. The cooling condition with the burner was set to 1000 cycles when the burner was turned on for 2 minutes, kept at a temperature of 900 ° C., and then turned off for 1 minute as one cycle.

  A cross section similar to that of Test Example 1 of each ground electrode 94 was observed. Then, as shown in FIG. 4, the length H on the cut surface of the surface of the chip T10 on the electrode base material M10 side is generated between the surface of the chip T10 on the electrode base material M10 side and the electrode base material M10. The length A on the cut surface of the crack C (value obtained by adding A1 and A2 in FIG. 4) was measured. And ratio A / H was computed as a crack rate (%). The laser conditions and the results are shown in Table 1.

  From Table 1, it can be seen that in the test products 1 and 2 and the comparative products 1 and 2, the crack C hardly progresses even by a durability test using a burner. For this reason, even if it remelts, it turns out that the peeling resistance of chip | tip T10 can be maintained.

  Next, another embodiment of the method for manufacturing the spark plug 1 will be described. In another embodiment, the welding process and the subsequent remelting process are different from those of the present embodiment, and other manufacturing methods are omitted, and the welding process and the remelting process will be mainly described.

  First, as a welding process, the tip T10 is provided on the electrode base material M10, and laser welding is performed by irradiating the laser beam L so that the focal point F is disposed at the boundary. As a result, a melted portion W10 is formed by melting a part of the electrode base material M10 and a part of the tip T10. In this melting part W10, welding sag W1 and spatter W2 are generated.

  Next, the melting part W10 is remelted using the laser beam L in the welding process as the remelting process. Specifically, the focal point F of the laser beam L located at the boundary between the electrode base material M10 and the chip T10 is shifted to a predetermined position on the side opposite to the chip T10 with respect to the electrode base material M10, so Melting was performed.

  Thus, by performing the welding process and the remelting process using the same laser beam L, the spark plug 1 can be mass-produced at low cost.

  In the above, the present invention has been described with reference to Test Examples 1 and 2, but it goes without saying that the present invention can be applied with appropriate modifications without departing from the spirit of the present invention. For example, the present invention can naturally be applied to the center electrode 93.

  The present invention can be used in a method for manufacturing a spark plug.

It is sectional drawing of a ground electrode in connection with Test Examples 1 and 2. The cross section of the ground electrode after the welding process according to Test Example 1 is shown. FIG. (A) is a 20 × optical micrograph and FIG. (B) is a 40 × optical micrograph. The cross-section of the ground electrode after the remelting process according to Test Example 1 is shown. FIG. (A) is a 20 × optical micrograph, and FIG. (B) is a 40 × optical micrograph. 6 is a cross-sectional view of a ground electrode of Test Example 2. FIG. It is a partially broken sectional view of a spark plug. It is sectional drawing of the conventional ground electrode.

Explanation of symbols

91 ... metal shell 92a ... shaft hole 92 ... insulator 93 ... center electrode 94a ... one end 94b ... other end g ... discharge gap 94 ... ground electrode M10, M20 ... electrode base material T10, T20 ... tip 1 ... spark plug W10 ... Melting zone (W1 ... welding sagging, W2 ... spatter)
L ... Laser beam F ... Focus

Claims (6)

A cylindrical metal shell, a cylindrical insulator having a shaft hole, fixed to the metal shell so as to surround the metal shell, and a tip projecting from the tip of the insulator and fixed to the insulator. A center electrode and a ground electrode having one end fixed to the metal shell and forming a discharge gap between the other end and the center electrode, wherein at least one of the center electrode and the ground electrode is an electrode. A spark plug manufacturing method comprising a base material and a tip welded to a position where the discharge gap of the electrode base material is formed,
A welding step of welding the tip to the electrode base material by forming a melted portion obtained by melting a part of the electrode base material and a part of the tip;
A spark plug manufacturing method comprising: a remelting step of remelting the molten portion by heating at a temperature lower than the melting point of the electrode base material and the tip after the welding step.   The spark plug manufacturing method according to claim 1, wherein the remelting step irradiates the melting portion with laser light.   The method of manufacturing a spark plug according to claim 2, wherein the laser beam is focused on a portion other than the electrode base material, the tip, and the melting portion.   The method of manufacturing a spark plug according to claim 3, wherein the laser light is irradiated so as to include at least all of the melted portion.   5. The method for manufacturing a spark plug according to claim 3, wherein the focal point is located on a side opposite to the tip with respect to the electrode base material when cut along a virtual cross section passing through an axis. 6. In the welding step, the tip is welded to the electrode base material by irradiating a laser beam,
The spark plug manufacturing method according to any one of claims 2 to 5, wherein the remelting step is performed using laser light in the welding step.