JP5820323B2 - Manufacturing method of spark plug - Google Patents

Description

  The present invention relates to a method for manufacturing a spark plug used for an internal combustion engine or the like.

  In general, a spark plug used for an internal combustion engine or the like is configured to ignite an air-fuel mixture supplied to a combustion chamber by generating a spark in a spark discharge gap between a center electrode and a ground electrode. Yes.

  In recent years, a technique has been proposed in which a tip made of a metal having excellent wear resistance is welded to a portion of the ground electrode facing the center electrode in order to improve ignitability while preventing deterioration of wear resistance. Yes.

  Here, resistance welding is generally used as a technique for welding the tip to the ground electrode. Specifically, with the ground electrode and the chip sandwiched between the ground electrode side member in contact with the ground electrode and the chip side member in contact with the chip, a load is applied from both the members to the ground electrode and the chip, By energizing between the two members, the tip is welded to the ground electrode (see, for example, Patent Document 1). In order to suppress the movement (deformation) of the ground electrode, the load applied from the ground electrode side member to the ground electrode is equal to the load applied from the chip side member to the chip.

JP 2002-198157 A

  By the way, in terms of sufficiently melting the ground electrode and the chip and improving the bondability of the chip to the ground electrode, the contact resistance value of the chip with respect to the ground electrode is made relatively large, and the amount of heat generated between both is increased. Is effective. Therefore, in order to increase the contact resistance value of the chip with respect to the ground electrode, it is conceivable to make the load applied to the chip from the chip side member relatively small.

  However, when the load applied to the chip from the chip side member is reduced, the load applied to the ground electrode from the ground electrode side member is also correspondingly reduced. When the load applied to the ground electrode is reduced, the ground electrode side member locally presses against a part of the ground electrode (not in surface contact but close to point contact), and the chip and ground The energization path between the electrodes is not stable, and there is a risk that a bias may occur. As a result, a part of the contact portion between the ground electrode and the chip is excessively melted, while the other part is not sufficiently melted, and the contact portion between the ground electrode and the chip can be evenly melted. There is a risk that it will not be possible, and as a result, the bondability will be reduced.

  On the other hand, by adjusting the load applied to the chip from the chip side member and the load applied to the ground electrode from the ground electrode side member, the contact resistance value between the ground electrode and the chip is increased to some extent while grounding. A method is considered in which the energization path between the electrode and the chip is relatively free of bias. However, in this method, it is necessary to set the applied load within a very narrow range. Therefore, it is extremely difficult to manage the applied load, and there is a possibility that sufficient bondability cannot be obtained due to slight load fluctuations during manufacturing.

  The present invention has been made in view of the above circumstances, and its purpose is to dramatically improve the bondability of the chip to the ground electrode and to set the applied load in a wide range, which is excellent. An object of the present invention is to provide a method for manufacturing a spark plug capable of stably realizing bonding properties.

  Hereinafter, each configuration suitable for solving the above-described object will be described in terms of items. In addition, the effect specific to the corresponding structure is added as needed.

Configuration 1. A manufacturing method of the spark plug of this configuration includes a cylindrical insulator having an axial hole penetrating in the axial direction;
A center electrode inserted on the tip side of the shaft hole;
A cylindrical metal shell provided on the outer periphery of the insulator;
A ground electrode having its base end fixed to the tip of the metal shell;
A spark plug manufacturing method comprising: a tip that is bonded to the tip of the ground electrode and that forms a gap with the tip of the center electrode;
A joining step of joining the tip to the ground electrode by resistance welding;
In the joining step,
A chip-side member that contacts the chip with a load applied to the ground electrode side with respect to the chip, and a ground electrode that contacts the ground electrode with a load applied to the ground electrode By energizing between the side members, the chip is joined to the ground electrode,
The load applied to the chip from the chip side member is made smaller than the load applied to the ground electrode from the ground electrode side member.

  According to the configuration 1, in the joining process, the load applied to the chip from the chip side member is relatively small. Accordingly, the contact resistance value of the chip with respect to the ground electrode can be increased, and both can be sufficiently dissolved.

  Further, according to the configuration 1, the load applied to the ground electrode from the ground electrode side member in the joining step is relatively large. Accordingly, the ground electrode side member can be more reliably brought into surface contact with the ground electrode, the bias of the energization path between the ground electrode and the chip can be prevented, and the energization path can be formed more evenly. be able to. As a result, the contact portion between the ground electrode and the chip can be uniformly melted over a wide range.

  As described above, according to the configuration 1, the ground electrode and the chip can be sufficiently melted in a wide range of the contact portion between the ground electrode and the chip. As a result, the bondability of the chip to the ground electrode can be dramatically improved.

  When the chip is bonded to the ground electrode, a so-called sag (outer sag) is formed by protruding a melted portion formed by melting the ground electrode or the chip on the outer peripheral side of the bonding surface of the chip and the ground electrode. The According to the configuration 1, since the ground electrode and the chip are sufficiently melted in a wide range of the contact portion between the ground electrode and the chip, an outer peripheral sag is formed over a wide range on the outer peripheral side of the joint surface. It becomes. Therefore, a wide range of the outer periphery of the joint surface is covered with the outer peripheral sag, and gas intrusion to the joint surface can be more reliably prevented. As a result, the formation of oxide scales and the like on the bonding surface can be effectively suppressed, and the bondability can be further enhanced.

  Moreover, according to the said structure 1, since the load applied to a chip | tip from a chip | tip side member and the load applied to a ground electrode from a ground electrode side member can be set separately, each applied load can be set in a wide range. Can be set. Therefore, the applied load can be managed very easily, and a spark plug having excellent bonding properties can be stably manufactured.

  In addition, in order to suppress the movement (deformation) of the ground electrode due to the difference between the load applied from the tip side member to the chip and the load applied from the ground electrode side member to the ground electrode (balance of forces in the load direction is achieved). Therefore, in the joining step, a holding member that holds the ground electrode may be used. In this case, it is preferable to provide a holding member at the position of Configuration 2 described below.

  Configuration 2. The spark plug manufacturing method of the present configuration is the above-described configuration 1, in the configuration 1, in the bonding step, by a holding member that contacts both side surfaces of the ground electrode adjacent to the surface to which the chip is bonded and sandwiches the ground electrode, The ground electrode is held.

  When joining chips while applying a load, the balance of the load may be momentarily broken at the moment when the chip or the like melts, and the ground electrode may move in the load application direction due to inertia. If the ground electrode moves, the load will not be evenly applied from the tip to the ground electrode, and the portion of the contact portion between the ground electrode and the tip that has a relatively small applied load may melt excessively. There is.

  In this regard, according to Configuration 2, the ground electrode is held by the holding member that is in contact with both side surfaces of the ground electrode and sandwiches the ground electrode in the joining step. Therefore, the movement of the ground electrode in the joining process can be restricted, and a load can be applied more evenly from the chip to the ground electrode. As a result, the contact portion between the ground electrode and the chip can be evenly melted over a wider range, and the bondability can be further improved.

  Configuration 3. In the method of manufacturing a spark plug according to this configuration, in the configuration 1 or 2, in the bonding step, the ground electrode side member is in contact with both side surfaces of the ground electrode adjacent to the surface to which the chip is bonded. It is characterized by.

  According to the configuration 3, the movement of the ground electrode in the joining process can be restricted by the ground electrode side member, and a load can be more evenly applied from the chip to the ground electrode. As a result, the contact portion between the ground electrode and the chip can be evenly melted over a wider range, and the bondability can be further improved.

  Moreover, according to the said structure 3, since the ground electrode side member is contacting the both sides | surfaces of a ground electrode, the electricity supply path formed between a ground electrode and a chip | tip can be disperse | distributed moderately. Therefore, a very wide range of the contact portion between the ground electrode and the chip can be evenly melted, and the bondability can be further improved.

  Configuration 4. The spark plug manufacturing method according to this configuration is the manufacturing method of the spark plug according to any one of the above configurations 1 to 3, wherein at least a part of the chip includes the ground electrode corresponding to a portion of the ground electrode that contacts the ground electrode side member. It is characterized by being joined within a range along the longitudinal direction.

  According to the configuration 4, it is possible to more reliably prevent a bias in the energization path formed between the ground electrode and the chip. Therefore, the contact portion between the ground electrode and the chip can be melted more evenly, and the bondability can be further improved.

Configuration 5. The manufacturing method of the spark plug of this configuration is any one of the above configurations 1 to 4, in the joining step,
A columnar metal piece having a cross-sectional area smaller than the area of the surface located on the ground electrode side of the chip is disposed between the center portion of the chip and the ground electrode, and then the chip side member and the ground electrode Between the side members is energized,
When before the load applied to the chip from the winding-up member and A (N), the height of the metal pieces was H (mm),
A (N) <1000 (N / mm) × H (mm) +100 (N)
It is characterized by satisfying.

  According to the configuration 5, the load applied to the chip from the chip side member is set so as to satisfy A <1000 (N / mm) × H + 100. Therefore, in the joining step, the metal piece (so-called projection) can be more reliably melted, and the center portion of the chip can be more reliably joined to the ground electrode. As a result, the bondability can be further improved.

It is a partially broken front view which shows the structure of a spark plug. It is a partially broken expanded front view which shows the structure of the front-end | tip part of a spark plug. It is a front view showing a chip side member, a ground electrode side member, and the like. It is a front view showing a chip side member, a ground electrode side member, and the like. It is a bottom surface schematic diagram for demonstrating the joining position of the ground electrode side chip | tip with respect to a ground electrode. (A) is a front view which shows the chip side member etc. in a joining process, (b) is a side view which shows the chip side member etc. in a joining process. (A) is a front view which shows the chip side member etc. in 2nd Embodiment, (b) is a side view which shows the chip side member etc. in 2nd Embodiment. (A) is a front view which shows the chip side member etc. in 3rd Embodiment, (b) is a side view which shows the chip side member etc. in 3rd Embodiment. (A) is a front view which shows the chip side member etc. in 4th Embodiment, (b) is a side view which shows the chip side member etc. in 4th Embodiment. It is a partial expanded sectional view which shows the ground electrode side chip | tip joined to the ground electrode in 4th Embodiment. It is a schematic diagram which shows a fusion | melting part in case the formation range of outer periphery sagging is 1/2. (A)-(d) is a cross-sectional schematic diagram of the ground electrode etc. for demonstrating the evaluation method at the time of evaluating bondability by the surface of mechanical strength. (A), (b) is a cross-sectional schematic diagram of the ground electrode etc. for demonstrating the evaluation method at the time of evaluating joining property by the surface of thermal strength. It is a figure which shows the chip | tip side member etc. for demonstrating the joining aspect 1 corresponded to a comparative example, (a) is a front view, (b) is a side view. (A) is a side view of the ground electrode and the like for indicating the bonding position α, (b) is a schematic bottom view of the ground electrode and the like for indicating the bonding position α, and (c) is a bonding position. FIG. 4 is a side view of a ground electrode or the like for indicating β, (d) is a schematic bottom view of the ground electrode or the like for indicating a junction position β, and (e) is a ground electrode for indicating the junction position γ. (F) is a schematic bottom view of a ground electrode and the like for indicating a bonding position γ.

Hereinafter, embodiments will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a partially cutaway front view showing a spark plug 1. In FIG. 1, the direction of the axis CL <b> 1 of the spark plug 1 is the vertical direction in the drawing, the lower side is the front end side of the spark plug 1, and the upper side is the rear end side.

  The spark plug 1 includes an insulator 2 as a cylindrical insulator, a cylindrical metal shell 3 that holds the insulator 2, and the like.

  As is well known, the insulator 2 is formed by firing alumina or the like, and in its outer portion, a rear end side body portion 10 formed on the rear end side, and a front end than the rear end side body portion 10. A large-diameter portion 11 that protrudes radially outward on the side, a middle body portion 12 that is smaller in diameter than the large-diameter portion 11, and a tip portion that is more distal than the middle body portion 12. On the side, a leg length part 13 formed with a smaller diameter than this is provided. In addition, of the insulator 2, the large diameter portion 11, the middle trunk portion 12, and most of the leg long portions 13 are accommodated inside the metal shell 3. A tapered step portion 14 is formed at the connecting portion between the middle body portion 12 and the long leg portion 13, and the insulator 2 is locked to the metal shell 3 at the step portion 14.

  Furthermore, a shaft hole 4 is formed through the insulator 2 along the axis CL1, and a rod-like (columnar) center electrode 5 extending in the direction of the axis CL1 is inserted and fixed to the tip side of the shaft hole 4. Has been. The center electrode 5 is composed of an inner layer 5A made of copper or a copper alloy having excellent thermal conductivity, pure nickel (Ni), and an outer layer 5B made of an alloy containing Ni as a main component. Furthermore, the front end surface of the center electrode 5 protrudes from the front end of the insulator 2, and a cylindrical center electrode side chip 31 is joined to the front end portion of the center electrode 5. In the present embodiment, the center electrode side tip 31 is formed of iridium (Ir), platinum (Pt), tungsten (W), palladium (Pd), or an alloy containing at least one of these metals as a main component. ing.

  A terminal electrode 6 is inserted and fixed on the rear end side of the shaft hole 4 in a state of protruding from the rear end of the insulator 2.

  Further, a cylindrical resistor 7 is disposed between the center electrode 5 and the terminal electrode 6 of the shaft hole 4. Both ends of the resistor 7 are electrically connected to the center electrode 5 and the terminal electrode 6 through conductive glass seal layers 8 and 9, respectively.

  In addition, the metal shell 3 is formed in a cylindrical shape from a metal such as low carbon steel, and a spark plug 1 is attached to the outer peripheral surface of the metal shell 3 such as an internal combustion engine or a fuel cell reformer. A threaded portion (male threaded portion) 15 for attachment to the hole is formed. Further, a seat portion 16 protruding radially outward is formed on the rear end side of the screw portion 15, and a ring-shaped gasket 18 is fitted on the screw neck 17 at the rear end of the screw portion 15. Further, on the rear end side of the metal shell 3, a tool engaging portion 19 having a hexagonal cross section for engaging a tool such as a wrench when the metal shell 3 is attached to the combustion device is provided. 1 is provided with a caulking portion 20 for holding the insulator 2.

  A tapered step portion 21 for locking the insulator 2 is provided on the inner peripheral surface of the metal shell 3. The insulator 2 is inserted from the rear end side to the front end side of the metal shell 3, and the step 14 of the metal shell 3 is locked to the step 21 of the metal shell 3. It is fixed to the metal shell 3 by caulking the opening on the rear end side in the radial direction, that is, by forming the caulking portion 20. An annular plate packing 22 is interposed between the step portions 14 and 21. Thereby, the airtightness in the combustion chamber is maintained, and the fuel gas entering the gap between the leg long portion 13 of the insulator 2 exposed to the combustion chamber and the inner peripheral surface of the metal shell 3 is prevented from leaking outside.

  Further, in order to make the sealing by caulking more complete, annular ring members 23 and 24 are interposed between the metal shell 3 and the insulator 2 on the rear end side of the metal shell 3, and the ring member 23 , 24 is filled with powder of talc (talc) 25. That is, the metal shell 3 holds the insulator 2 via the plate packing 22, the ring members 23 and 24, and the talc 25.

  Further, as shown in FIG. 2, the base end portion of the rod-shaped ground electrode 27 is joined to the distal end portion 26 of the metal shell 3. The ground electrode 27 has a rectangular cross section and is bent back at a substantially intermediate portion thereof. A cylindrical ground electrode made of Ir, Pt, W, Pd, or an alloy containing at least one of them as a main component is provided at the tip of the opposing surface 27T located on the center electrode 5 side of the ground electrode 27. The side chip 32 (corresponding to the chip of the present invention) is joined. The ground electrode side tip 32 is formed by resistance welding, and is formed by a melting portion 35 formed by melting the constituent material of the ground electrode 27 and the constituent material of the ground electrode side tip 32 (in FIG. 2, for convenience of illustration, the melting portion 35 is shown to be thicker than the actual thickness). A spark discharge gap 33 is formed between the two chips 31 and 32, and spark discharge is performed in the spark discharge gap 33 in a direction substantially along the axis CL1.

  Next, the manufacturing method of the spark plug 1 comprised as mentioned above is demonstrated.

  First, the metallic shell 3 is manufactured in advance. That is, a rough shape is formed by performing a cold forging process or the like on a cylindrical metal material (for example, an iron-based material or a stainless steel material), and a through hole is formed. Thereafter, the outer shape is adjusted by cutting to obtain a metal shell intermediate.

  Subsequently, a straight bar-shaped ground electrode 27 made of Ni alloy or the like is resistance-welded to the front end surface of the metal shell intermediate. When the welding is performed, so-called “sag” is generated. After the “sag” is removed, the threaded portion 15 is formed by rolling at a predetermined portion of the metal shell intermediate body. Thereby, the metal shell 3 to which the ground electrode 27 is welded is obtained. The metal shell 3 to which the ground electrode 27 is welded is galvanized or nickel plated. In order to improve the corrosion resistance, the surface may be further subjected to chromate treatment.

  On the other hand, the insulator 2 is formed separately from the metal shell 3. That is, by using raw material powder mainly composed of alumina and containing a binder or the like, a green compact for molding is prepared, and by performing rubber press molding using the green granule for molding, a cylindrical molded body Get. And the insulator 2 is obtained by shaping | molding the obtained molded object by baking, and baking the shape | molded thing with a baking furnace.

  Separately from the metal shell 3 and the insulator 2, the center electrode 5 is manufactured. That is, the center electrode 5 is produced by forging a Ni alloy in which a copper alloy or the like for improving heat dissipation is arranged at the center. Further, the center electrode tip 31 is joined to the tip of the center electrode 5 by laser welding or the like.

  Next, the insulator 2 and the center electrode 5, the resistor 7, and the terminal electrode 6 obtained as described above are sealed and fixed by the glass seal layers 8 and 9. The glass seal layers 8 and 9 are generally prepared by mixing borosilicate glass and metal powder, and the prepared material is injected into the shaft hole 4 of the insulator 2 with the resistor 7 interposed therebetween. After being done, it is baked and hardened by heating in the firing furnace while pressing with the terminal electrode 6 from the rear. At this time, the glaze layer may be fired simultaneously on the surface of the rear end body portion 10 of the insulator 2 or the glaze layer may be formed in advance.

  Thereafter, the insulator 2 provided with the center electrode 5 and the terminal electrode 6 and the metal shell 3 provided with the ground electrode 27 are fixed. More specifically, after the insulator 2 is inserted through the metal shell 3, the opening on the rear end side of the metal shell 3 formed relatively thin is caulked radially inward, that is, the caulking portion 20 is By forming, the insulator 2 and the metal shell 3 are fixed.

  Next, by plating at least a portion to be bonded of the ground electrode side chip 32 in the ground electrode 27 in a predetermined acidic stripping solution, the plating covering the portion to be bonded is peeled off.

  Next, in the joining step, as shown in FIG. 3, the ground electrode side chip 32 is joined to the tip of the ground electrode 27 using the chip side member 41 and the ground electrode side member 42 that can be energized therebetween. The The tip-side member 41 is composed of a rod-shaped (needle-shaped) electrode that can move toward and away from the ground electrode 27. The ground electrode side member 42 includes a pair of opposing electrodes that can move toward and away from the ground electrode 27. Further, as shown in FIG. 6B, the portion of the ground electrode side member 42 that contacts the ground electrode 27 has a length L along the longitudinal direction of the ground electrode 27 within a predetermined numerical range (for example, 1 mm). 10 mm or less).

  Returning to the description of the bonding step, first, as shown in FIG. 4, the ground electrode side chip 32 is placed on the chip side member 41, and then the chip side member 41 is placed on the facing surface 27 </ b> T of the ground electrode 27. To approach. 6 (a) and 6 (b), the holding member 43 and the chip side member 41, which are made of an insulating material and are in contact with the back surface 27B located behind the facing surface 27T of the ground electrode 27, Thus, the ground electrode 27 and the ground electrode side chip 32 are sandwiched. Further, the ground electrode side member 42 is brought into contact with both side surfaces 27S1 and 27S2 adjacent to the facing surface 27T of the ground electrode 27, and the ground electrode 27 is sandwiched by the ground electrode side member 42. At this time, as shown in FIG. 5, at least a part of the ground electrode side chip 32 extends along the longitudinal direction of the ground electrode 27 corresponding to the portion of the ground electrode 27 that contacts the ground electrode side member 42. The relative positional relationship between the ground electrode side chip 32 and the ground electrode side member 42 is set so as to be joined within the range RA.

  Next, while applying a load from the tip side member 41 to the ground electrode side tip 32 toward the ground electrode 27 side, and applying a load from the ground electrode side member 42 to the ground electrode 27, the tip side member 41 In addition, a current having a predetermined current value (for example, 500 A or more and 1500 A or less) is passed between the ground electrode side members 42 for a predetermined time (for example, 100 ms or more and 1000 ms or less). As a result, a melting portion 35 is formed by melting the metal constituting the ground electrode 27 and the metal constituting the ground electrode side chip 32, and the ground electrode side chip 32 is joined to the ground electrode 27. In particular, in the present embodiment, in the joining process, a load (for example, 50 N or more and 100 N or less) applied from the tip side member 41 to the ground electrode side chip 32 is applied to a ground electrode 27 from the ground electrode side member 42 (for example, 300N or more).

  After the bonding of the ground electrode side chip 32, the substantially middle portion of the ground electrode 27 is bent toward the center electrode 5 side. Finally, the above spark plug 1 is obtained by performing a process of adjusting the size of the spark discharge gap 33 between the two chips 31 and 32.

  As described above in detail, according to the present embodiment, the load applied from the tip side member 41 to the ground electrode side tip 32 in the joining step is relatively small. Therefore, the contact resistance value of the ground electrode side chip 32 with respect to the ground electrode 27 can be increased, and both can be sufficiently melted.

  Further, in the joining process, a load applied from the ground electrode side member 42 to the ground electrode 27 is relatively large. Therefore, the ground electrode side member 42 can be more reliably brought into surface contact with the ground electrode 27, and it is possible to prevent a bias in the energization path between the ground electrode 27 and the ground electrode side chip 32. An energization path can be formed evenly. As a result, the contact portion between the ground electrode 27 and the ground electrode side chip 32 can be uniformly melted over a wide range.

  As described above, according to the present embodiment, the ground electrode 27 and the ground electrode side chip 32 can be sufficiently dissolved in a wide range of the contact portion between the ground electrode 27 and the ground electrode side chip 32. As a result, the bondability of the ground electrode side chip 32 to the ground electrode 27 can be dramatically improved.

  Further, according to the present embodiment, the melting portion 35 (so-called outer periphery sag) located on the outer peripheral side of the joint surface between the ground electrode 27 and the ground electrode side chip 32 is formed over a wide range of the outer periphery of the joint surface. be able to. Therefore, it is possible to more reliably prevent the gas from entering the bonding surface, and effectively suppress the formation of oxide scale and the like on the bonding surface. As a result, the bondability can be further improved.

  Furthermore, in this embodiment, since the load applied from the tip side member 41 to the ground electrode side chip 32 and the load applied from the ground electrode side member 42 to the ground electrode 27 can be set individually, each application The load can be set in a wide range. Therefore, the applied load can be managed very easily, and the spark plug 1 having excellent bonding properties can be stably manufactured.

  Further, in the joining step, the movement of the ground electrode 27 can be regulated by the ground electrode side member 42, so that a load can be more evenly applied from the ground electrode side chip 32 to the ground electrode 27. As a result, the contact portion between the ground electrode 27 and the ground electrode side chip 32 can be uniformly melted over a wider range, and the joining property can be further improved.

  Further, since the ground electrode side member 42 is in contact with both side surfaces 27S1 and 27S2 of the ground electrode 27, the energization path formed between the ground electrode 27 and the ground electrode side chip 32 can be appropriately dispersed. Therefore, a very wide range of the contact portion between the ground electrode 27 and the ground electrode side chip 32 can be evenly melted, and the bondability can be further improved.

In addition, in the present embodiment, at least a part of the ground electrode side chip 32 is configured to be joined within a range RA corresponding to a portion of the ground electrode 27 with which the ground electrode side member 42 contacts. . Therefore, it is possible to more reliably prevent a bias in the energization path formed between the ground electrode 27 and the ground electrode side chip 32. As a result, the contact portion between the ground electrode 27 and the ground electrode side chip 32 can be melted more evenly, and the bondability can be further improved.
[Second Embodiment]
Next, the second embodiment will be described focusing on differences from the first embodiment. In the first embodiment, the ground electrode side member 42 is configured to contact both side surfaces 27S1 and 27S2 of the ground electrode 27 in the joining step. On the other hand, in the second embodiment, as shown in FIGS. 7A and 7B, the ground electrode side member 45 is in contact with the back surface 27 </ b> B of the ground electrode 27, and between the chip side member 41. The ground electrode 27 and the ground electrode side chip 32 are sandwiched.

  Furthermore, in the second embodiment, the holding member 46 is formed of a pair of insulating members that face each other and can move toward and away from each other. The holding member 46 is in contact with both side surfaces 27S1 and 27S2 of the ground electrode 27 and sandwiches the ground electrode 27, whereby the ground electrode 27 is held.

  In addition, when the ground electrode side chip 32 is joined to the ground electrode 27, the load applied from the chip side member 41 to the ground electrode side chip 32 is applied from the ground electrode side member 45 as in the first embodiment. The load applied to the ground electrode 27 is made smaller. Since the ground electrode 27 is firmly held by the holding member 46, the movement (deformation) of the ground electrode 27 is restricted even if the load applied from the members 41 and 45 is different. .

  Further, at least a part of the ground electrode side chip 32 is joined within a range RB along the longitudinal direction of the ground electrode 27 corresponding to a portion of the ground electrode 27 that contacts the ground electrode side member 45. In addition, the portion of the ground electrode side member 45 that contacts the ground electrode 27 has a length L along the longitudinal direction of the ground electrode 27 and a width W along the width direction of the ground electrode 27. The outer diameter of the side chip 32 is equal to or greater than that.

As described above, in the second embodiment, the movement restriction of the ground electrode 27 realized by the ground electrode side member 42 in the first embodiment is realized by the holding member 46. Therefore, according to the second embodiment, the same operational effects as those of the first embodiment are exhibited.
[Third Embodiment]
Next, the third embodiment will be described focusing on the differences from the second embodiment. In the second embodiment, the holding member 46 is configured to contact both side surfaces 27S1 and 27S2 of the ground electrode 27 and sandwich the ground electrode 27 therebetween. On the other hand, in the third embodiment, as shown in FIGS. 8A and 8B, the holding member 48 is configured to contact the facing surface 27 </ b> T of the ground electrode 27. In the joining step, as in the above embodiment, the load applied from the tip side member 41 to the ground electrode side chip 32 is made smaller than the load applied from the ground electrode side member 45 to the ground electrode 27. In the bonding process, the holding electrode 48 is configured so that the ground electrode 27 does not move in the load application direction even if the load balance is lost at the moment when the ground electrode side chip 32 or the like melts.

As described above, according to the third embodiment, the same functions and effects as those of the above embodiment are basically achieved. That is, it is possible to dramatically improve the bondability of the ground electrode side chip 32 to the ground electrode 27 and to stably manufacture the spark plug 1 having excellent bondability.
[Fourth Embodiment]
Next, a fourth embodiment will be described focusing on differences from the above embodiment. In the above embodiment, in the bonding step, the ground electrode side chip 32 is brought into direct contact with the ground electrode 27 and then the chip side member 41 and the ground electrode side member 42 (45) are energized, whereby the ground electrode The side chip 32 is bonded to the ground electrode 27.

  On the other hand, in the fourth embodiment, in order to improve the bondability, as shown in FIGS. 9A and 9B, a predetermined amount is provided between the ground electrode side chip 32 and the ground electrode 27 in the bonding step. A cylindrical metal piece MP made of metal (for example, a metal including the constituent material of the ground electrode side chip 32 and the constituent material of the ground electrode 27) is interposed. The metal piece MP is arranged at the center of the surface of the ground electrode side chip 32 located on the ground electrode 27 side, and has a smaller cross-sectional area than the surface of the ground electrode side chip 32 located on the ground electrode 27 side. It is comprised so that it may have. In the present embodiment, the outer diameter of the metal piece MP is not more than half of the outer diameter of the ground electrode side chip 32.

  After the placement of the metal piece MP, a load is applied from the chip side member 41 to the ground electrode side chip 32, and a load is applied from the ground electrode side member 45 to the ground electrode 27, and the chip side member 41 and the ground electrode side member 42 are loaded. Energize the space. Thereby, as shown in FIG. 10 (in FIG. 10, the melting portion 37 is shown to be thicker than the actual thickness), the melting portion 37 formed by melting the metal piece MP, the ground electrode 27, and the ground electrode side chip 32 is obtained. The ground electrode side chip 32 is joined to the ground electrode 27 through the melting portion 37.

  In the fourth embodiment, the load applied from the tip side member 41 to the ground electrode side tip 32 is A (N), and the tip side member 41 is grounded as shown in FIGS. 9A and 9B. The load A is set so as to satisfy A <1000 (N / m) × H + 100, where H (mm) is the height of the metal piece MP along the direction in which the load is applied to the electrode side tip 32. .

  As described above, according to the fourth embodiment, basically the same functions and effects as those of the above embodiment are achieved. That is, it is possible to dramatically improve the bondability of the ground electrode side chip 32 to the ground electrode 27 and to stably manufacture the spark plug 1 having excellent bondability.

  In addition, since the load A is set so as to satisfy A <1000 (N / m) × H + 100, the metal piece MP can be more reliably melted. Therefore, the center part of the ground electrode side chip 32 can be more reliably joined to the ground electrode 27, and the joining property can be further improved.

  Next, in order to confirm the operational effects achieved by the above embodiment, the bonding mode when bonding the ground electrode side chip to the ground electrode is set to any one of the bonding modes 1 to 4 to be described later, and in the bonding step. The ground electrode side chip is joined by variously changing the load A (N) applied from the chip side member to the ground electrode side chip and the load B (N) applied from the ground electrode side member to the ground electrode. A plurality of ground electrode samples were prepared. Then, for each of the prepared samples, the formation range of the melted portion (so-called outer peripheral sag) located on the outer periphery of the bonding surface of the ground electrode and the ground electrode side chip is specified, and the bonding property of the ground electrode side chip to the ground electrode is determined. It confirmed from the surface of mechanical strength and thermal strength.

  Here, the formation range of the outer peripheral sag was specified by calculating the ratio of the outer peripheral sag existing range along the circumferential direction of the ground electrode side chip to the entire circumference of the ground electrode side chip. For example, as shown in FIG. 11, in the case where the outer peripheral sag exists in half of the entire circumference of the ground electrode side chip, the formation range of the outer peripheral sag is specified as 1/2.

  In addition, as the formation range of the outer peripheral sag is larger, it is possible to suppress the invasion of gas to the joint surface of the ground electrode and the chip on the ground electrode side, and to suppress the generation of oxide scale and the like on the joint surface. I can say that. In view of this point, a sample having a peripheral sag formation range of 4/5 or more can effectively suppress the invasion of gas to the joint surface, and is evaluated as “☆” as having excellent joint properties. It was decided that In addition, the sample in which the formation range of the peripheral sag is 3/4 or more and less than 4/5 is evaluated as “」 ”as being excellent in the effect of suppressing gas intrusion and excellent in bonding property. The sample having a value of 2/3 or more and less than 3/4 can be sufficiently suppressed from entering the gas, and is evaluated as “◯” because it has good bondability. On the other hand, the sample in which the formation range of the outer peripheral sag is less than 2/3 is evaluated as “x” because there is a concern of gas intrusion.

  Further, the bondability in terms of mechanical strength was confirmed as follows. That is, as shown in FIGS. 12A to 12D, the ground electrode is bent 90 ° around the center of the ground electrode side chip, and after bending, the cross sections of the ground electrode and the ground electrode side chip are observed. The joining state of the ground electrode side chip with respect to the ground electrode was confirmed. Here, as shown in FIG. 12 (a), when both the ground electrode side tip and the melted portion (peripheral sag) are joined to the ground electrode without floating, it has extremely excellent joining properties. It was decided to give a "☆" rating. In addition, as shown in FIG. 12 (b), when the melted portion (peripheral sag) floats with respect to the ground electrode, the ground electrode side chip is joined to the ground electrode without being floated. It was decided to give an evaluation of “◎” because of its excellent properties. Further, as shown in FIG. 12 (c), although a part of the ground electrode side chip floated with respect to the ground electrode, the floating length K is the distance from the center of the ground electrode side chip to the outer periphery thereof. When it was less than 1/3 of D, it was decided to evaluate “◯” as having sufficient bonding properties. On the other hand, as shown in FIG. 12 (d), when the ground electrode side tip is floating with respect to the ground electrode, and the length K of the float is 1/3 or more of the distance D, It was decided to give an evaluation of “x” because of poor bonding.

  Furthermore, the bondability in terms of thermal strength was confirmed as follows. That is, the sample was subjected to 1000 cycles, with 1 cycle consisting of heating for 2 minutes with a burner and then slowly cooling at room temperature for 1 minute so that the temperature of the ground electrode side tip was 900 ° C. Then, the cross section of the sample was observed after 1000 cycles, and as shown in FIG. 13 (a), the oxide scale formed on the joint surface with respect to the length X of the joint surface of the ground electrode and the ground electrode side chip [FIG. 13 (a), a portion Y indicated by a thick line] was measured, and the ratio of the length Y to the length X (oxidized scale ratio) was calculated. Here, the sample with an oxide scale ratio of ¼ or less is evaluated as “☆” because it can extremely effectively suppress the intrusion of gas into the joint surface even under severe cooling and heating cycles, and has excellent jointability. It was decided that In addition, the sample having an oxide scale ratio of more than 1/4 and not more than 1/3 was evaluated as “」 ”because it was excellent in the effect of suppressing gas intrusion to the bonding surface and had excellent bonding properties. Furthermore, the sample having an oxide scale ratio of more than 1/3 and less than 1/2 was evaluated as “◯” as having sufficient bonding properties. On the other hand, a sample having an oxide scale ratio larger than ½ was evaluated as “x” because it was inferior in bondability. When a plurality of oxide scales are formed, the total length of each oxide scale is Y. For example, as shown in FIG. 13B, when a plurality of oxide scales [parts indicated by bold lines in FIG. 13B] are formed, the length Y of the oxide scale is set to the length of each oxide scale. Total (Y1 + Y2).

  Incidentally, in the bonding mode 1 (corresponding to the comparative example), the ground electrode and the ground electrode side chip are sandwiched between the chip side member and the ground electrode side member as shown in FIGS. In this embodiment, the load applied from the side member to the ground electrode side chip is equal to the load applied from the ground electrode side member to the ground electrode, and the ground electrode side chip is joined to the ground electrode.

  Further, in the bonding mode 2 (corresponding to the embodiment), the ground electrode and the ground electrode side chip are sandwiched between the chip side member and the ground electrode side member as shown in FIGS. In this aspect, the load applied from the side member to the ground electrode side chip is made smaller than the load applied from the ground electrode side member to the ground electrode, and the ground electrode side chip is joined to the ground electrode. In bonding mode 2, the opposing surface of the ground electrode was supported by an insulating holding member in order to restrict the movement of the ground electrode during bonding.

  Further, in the bonding mode 3 (corresponding to the embodiment), as shown in FIGS. 7A and 7B, the holding member comes into contact with both side surfaces of the ground electrode, and the ground electrode is held by the holding member. In this state, the load applied to the ground electrode side chip from the chip side member is made smaller than the load applied to the ground electrode from the ground electrode side member, and the ground electrode side chip is joined to the ground electrode.

  In addition, as shown in FIGS. 6A and 6B, the bonding mode 4 (corresponding to the embodiment) is a state in which the ground electrode side member is in contact with both side surfaces of the ground electrode. The load applied to the ground electrode side chip from the ground electrode side member is made smaller than the load applied to the ground electrode from the ground electrode side member, and the ground electrode side chip is joined to the ground electrode. In the bonding mode 4, the back surface of the ground electrode was supported by an insulating holding member in order to restrict the movement of the ground electrode during bonding.

  Table 1 shows the evaluation of each sample. When joining the ground electrode side chip, the current value was 700 A, and the energization time was 200 ms. The ground electrode side tip was made of a Pt-10Ni alloy, and had an outer diameter of 1.5 mm and a thickness of 0.4 mm. Further, the ground electrode is composed of Inconel (registered trademark) 601 and has a thickness of 1.5 mm and a width of 2.8 mm (in the following tests, the constituent materials of the ground electrode side chip and the ground electrode, The size was the same). In addition, the length L of the ground electrode side member is 15 mm, and the entire area of the ground electrode side chip is joined within a range corresponding to a portion of the ground electrode that contacts the ground electrode side member.

As shown in Table 1, samples (samples 1 to 3) in which the ground electrode-side chip is bonded by bonding mode 1 in which load A and load B are equal are insufficient in terms of bondability. It has been found that the peripheral sag is not sufficiently formed. This is considered to be due to the following (1) and (2).
(1) When the load A is relatively large, the contact resistance value of the ground electrode side chip with respect to the ground electrode is relatively low, and the amount of heat generated is small, so that both cannot be sufficiently dissolved.
(2) When the load B is relatively small, the ground electrode side member is locally in contact with a part of the ground electrode (that is, it is close to point contact, not surface contact), and the ground electrode and Since the energization path formed between the ground electrode side tips has been biased, only a part of the contact portion between the ground electrode and the ground electrode side tip has melted excessively.

Samples (samples 4 to 12) in which the tip of the ground electrode side is bonded to the samples 1 to 3 by the bonding modes 2 to 4 in which the load A is smaller than the load B have good bondability. In addition, it has become clear that the outer peripheral sag can be formed in a wide range along the circumferential direction of the ground electrode side chip. This is considered due to the following (3) and (4).
(3) Since the load A was made relatively small, the contact resistance value of the ground electrode side chip with respect to the ground electrode became large, and both could be sufficiently dissolved.
(4) Since the load B is relatively large, a wider area of the ground electrode side member is in contact with the ground electrode, and a current-carrying path is uniformly formed between the ground electrode and the ground electrode side chip. The contact portion with the ground electrode side tip could be uniformly melted over a wide range.

  Further, samples (samples 7 to 12) in which the holding electrode or the ground electrode side member is brought into contact with both side surfaces of the ground electrode, the ground electrode is held, and the ground electrode side chip is joined are the outer peripheral sag. It was confirmed that the formation range was larger and that the bonding property was even better. This is considered to be due to the following reason.

  That is, when the ground electrode side tip is joined while applying a load, when the ground electrode side tip or the like starts to melt, the ground electrode may move along the load application direction. If the ground electrode moves, the load will not be evenly applied from the tip on the ground electrode side to the ground electrode, and the portion of the contact area between the ground electrode and the tip on the ground electrode side will melt excessively. End up.

  On the other hand, in the state where the movement of the ground electrode is regulated by the holding member, the samples 7 to 12 to which the ground electrode side chip is bonded are in a state where a load is applied more evenly from the ground electrode side chip to the ground electrode. Thus, the ground electrode side chip is joined. Therefore, in Samples 7 to 12, the contact portion between the ground electrode and the ground electrode side tip is melted evenly over a wider range, the outer peripheral sagging formation range is larger, and excellent bonding properties are provided. It is thought that it was.

  In particular, samples (samples 10 to 12) in which the ground electrode side chip is joined after the ground electrode side member is brought into contact with both side surfaces of the ground electrode have a larger outer peripheral sagging range. As a result, it has been clarified that it has excellent bonding properties. This is considered to be because the energization path between the ground electrode and the ground electrode side chip is moderately dispersed, and almost the entire contact portion between the ground electrode and the ground electrode side chip is uniformly melted.

  From the above results, in order to improve the bondability of the ground electrode side tip to the ground electrode, the load applied from the tip side member to the ground electrode side tip should be made smaller than the load applied from the ground electrode side member to the ground electrode. Is preferable.

  Further, in order to further improve the bondability, in the bonding step, it is more preferable to bond the chip on the ground electrode side while holding the ground electrode by a holding member that is in contact with both side surfaces of the ground electrode and sandwiches the ground electrode. It can be said.

  Further, from the viewpoint of further improving the bonding property, it can be said that in the bonding process, it is more preferable to bond the ground electrode side chip after bringing the ground electrode side member into contact with both side surfaces of the ground electrode.

  Next, after setting the bonding position of the ground electrode side chip to a bonding position α, β, or γ, which will be described later, a sample of the ground electrode formed by bonding the ground electrode side chip according to the bonding mode 2 was prepared. And about each sample, while identifying the formation range of outer periphery sagging, joining property was confirmed from the surface of mechanical strength. Table 2 shows the results of the test.

  As shown in FIGS. 15A and 15B, the joining position α is from a range R along the longitudinal direction of the ground electrode corresponding to the portion of the ground electrode that contacts the ground electrode side member. This means a position that is out of position, and the ground electrode side chip is bonded to a portion of the ground electrode that is out of the range R. The junction position β means a position across the boundary between the range R and the outside of the range R, as shown in FIGS. 15C and 15D, and is a part of the ground electrode side chip. Is joined to a portion of the ground electrode located within the range R. Furthermore, the bonding position γ means a position within the range R as shown in FIGS. 15E and 15F, and the ground electrode side chip is positioned within the range R of the ground electrodes. It is joined to the part to do.

  In joining the ground electrode side chip, the load A was 100 N and the load B was 200 N. Further, the length L of the ground electrode side member was set to 5 mm or 10 mm.

  As shown in Table 2, samples (samples 23 to 26) in which at least a part of the ground electrode side chip is bonded to a position within the range R of the ground electrode may have even better bonding properties. It became clear. This is considered to be due to the fact that the current path formed between the ground electrode and the ground electrode side chip is prevented from being biased, and the contact portion between the ground electrode and the ground electrode side chip is melted more evenly. .

  In particular, it was confirmed that samples (samples 25 and 26) in which the entire ground electrode-side chip was bonded to a portion located within the range R of the ground electrode had very excellent bonding properties.

  From the result of the above test, from the viewpoint of further improving the bonding property, at least a part of the ground electrode side chip is along the longitudinal direction of the ground electrode corresponding to the portion of the ground electrode that contacts the ground electrode side member. It can be said that it is preferable to be joined within the range. Further, in terms of further improving the bonding property, the entire ground electrode side chip is bonded within the range along the longitudinal direction of the ground electrode corresponding to the portion of the ground electrode that contacts the ground electrode side member. It is even more preferable.

  Next, metal pieces having various heights H (mm) are arranged between the ground electrode and the ground electrode side chip, and the load A (N) applied to the ground electrode side chip from the chip side member is variously changed. A sample of the ground electrode in which the ground electrode side chip was joined by the joining mode 4 was prepared. And about each sample, the joinability from the surface of the outer periphery sagging formation range, mechanical strength, and thermal strength was confirmed. For each sample, by observing the cross section of the ground electrode and the ground electrode side tip, the center and the outer periphery of the ground electrode side tip are joined to the ground electrode, or the outer periphery of the ground electrode side tip It was confirmed whether only the part was joined (center part weldability). Here, when the center part and the outer peripheral part of the ground electrode side chip were bonded to the ground electrode, “☆” was evaluated as being very excellent in bonding property. In addition, when only the outer peripheral portion of the ground electrode side chip is bonded to the ground electrode, the evaluation of “◯” is given as having good bondability. Table 3 shows the results of the test.

  The outer diameter of the metal piece was less than half of the outer diameter of the ground electrode side chip, and the load B applied to the ground electrode from the ground electrode side member was 300N. In Table 3, the height H of 0.00 mm means that the ground electrode side chip is directly joined to the ground electrode without providing a metal piece.

  As shown in Table 3, assuming that the load A is smaller than 1000 (N / mm) × H + 100, samples (samples 32, 33, 35, 36, 38, 39) in which the ground electrode side chip is bonded are as follows: It became clear that the center part and the outer peripheral part of the ground electrode side chip were joined to the ground electrode, and had excellent jointability.

  From the above results, in the case where the ground electrode side chip is joined after the metal piece is arranged between the ground electrode side chip and the ground electrode, the tip side member to the ground electrode can be more reliably improved. When the load applied to the side chip is A (N) and the height of the metal piece is H (mm), A (N) <1000 (N / mm) × H (mm) +100 (N) is satisfied. It can be said that it is preferable to set the load A and the like.

  In addition, it is not limited to the description content of the said embodiment, For example, you may implement as follows. Of course, other application examples and modification examples not illustrated below are also possible.

  (A) In the above embodiment, the center electrode side tip 31 is provided at the tip of the center electrode 5, but the center electrode side tip 31 may not be provided.

  (B) In the above embodiment, the case where the ground electrode 27 is joined to the distal end portion 26 of the metal shell 3 is embodied. However, a part of the metal shell (or the tip metal fitting previously welded to the metal shell) The present invention can also be applied to the case where the ground electrode is formed so as to cut out a part of (see Japanese Unexamined Patent Publication No. 2006-236906).

  (C) In the above embodiment, the tool engaging portion 19 has a hexagonal cross section, but the shape of the tool engaging portion 19 is not limited to such a shape. For example, it may be a Bi-HEX (deformed 12-angle) shape [ISO 22777: 2005 (E)].

1 ... Spark plug 2 ... Insulator (insulator)
3 ... metal shell 4 ... shaft hole 5 ... center electrode 27 ... ground electrode 32 ... ground electrode side tip (chip)
33 ... Gap (spark discharge gap)
41 ... Chip side member 42,45 ... Ground electrode side member 43,46,48 ... Holding member CL1 ... Axis MP ... Metal piece

Claims (5)

A cylindrical insulator having an axial hole penetrating in the axial direction;
A center electrode inserted on the tip side of the shaft hole;
A cylindrical metal shell provided on the outer periphery of the insulator;
A ground electrode having its base end fixed to the tip of the metal shell;
A spark plug manufacturing method comprising: a tip that is bonded to the tip of the ground electrode and that forms a gap with the tip of the center electrode;
A joining step of joining the tip to the ground electrode by resistance welding;
In the joining step,
A chip-side member that contacts the chip with a load applied to the ground electrode side with respect to the chip, and a ground electrode that contacts the ground electrode with a load applied to the ground electrode By energizing between the side members, the chip is joined to the ground electrode,
A method of manufacturing a spark plug, wherein a load applied from the tip side member to the tip is made smaller than a load applied from the ground electrode side member to the ground electrode.   2. The bonding step, wherein the ground electrode is held by a holding member that is in contact with both side surfaces of the ground electrode adjacent to a surface to which the chip is bonded and sandwiches the ground electrode. A method for producing a spark plug as described in 1.   3. The spark plug manufacturing method according to claim 1, wherein, in the joining step, the ground electrode side member is in contact with both side surfaces of the ground electrode adjacent to a surface to which the chip is joined. .   2. The chip according to claim 1, wherein at least a part of the chip is joined within a range along a longitudinal direction of the ground electrode corresponding to a portion of the ground electrode that contacts the ground electrode side member. 4. The method for producing a spark plug according to any one of 3 above. In the joining step,
A columnar metal piece having a cross-sectional area smaller than the area of the surface located on the ground electrode side of the chip is disposed between the center portion of the chip and the ground electrode, and then the chip side member and the ground electrode Between the side members is energized,
When before the load applied to the chip from the winding-up member and A (N), the height of the metal pieces was H (mm),
A (N) <1000 (N / mm) × H (mm) +100 (N)
5. The method for manufacturing a spark plug according to claim 1, wherein:

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