JP5564000B2 - 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.

  The spark plug is attached to, for example, an internal combustion engine (engine) and is used to ignite an air-fuel mixture in a combustion chamber. Generally, a spark plug is provided at the tip of a metal shell, a cylindrical insulator extending in the axial direction, a central electrode inserted into the insulator, a metal shell provided on the outer periphery of the insulator, And a ground electrode that forms a spark discharge gap with the center electrode. Further, the metal shell and the insulator are fixed by inserting the insulator into the metal shell and bending the rear end side opening of the metal shell inward in the radial direction.

  Furthermore, in order to improve the airtightness between the metal shell and the insulator, a technique for providing a talc between the metal shell and the insulator is known (see, for example, Patent Document 1).

JP 2006-92955 A

  By the way, when providing the talc, it is preferable to press the talc and increase the packing density of the talc in order to improve the airtightness more reliably. Here, as a method for pressing the talc, after inserting the metal shell through which the insulator is inserted into the cylindrical cradle, the talc is disposed between the metal shell and the insulator, and then the axis of the insulator It is considered that the talc press jig is moved downward along the axial direction, and the talc is pressed by the tip of the talc press jig. It is done.

  However, although the axis of the insulator and the central axis of the talc press jig are small, there is a slight axial shift, the insulator itself is slightly bent, or there is a difference in the packing density of the talc along the circumferential direction. Due to factors such as the occurrence of the talc, the metal shell and the insulator may move in the radial direction when the talc is pressed. In this case, the axis of the insulator is shifted or tilted with respect to the central axis of the metal shell, so that excessive stress is applied to the insulator and damage (breaking, etc.) of the insulator occurs. There is a risk of it. In addition, due to the axial misalignment of the insulator, the center electrode held by the insulator also causes an axial misalignment, and abnormal spark discharge such as a horizontal spark tends to occur between the central electrode and the metal shell. There is a fear. In particular, in order to meet the demand for a small diameter, the spark plug in which the distance along the radial direction between the center electrode and the metal shell is set to be relatively small, even if the axis deviation and inclination are slight, There is concern about the occurrence of abnormal spark discharge.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress movement along the radial direction of the insulator and the metal shell in the talc pressing process, and consequently the axis and the main body of the insulator. An object of the present invention is to provide a method for manufacturing a spark plug that can effectively suppress axial misalignment with the central axis of a metal fitting.

  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 provided on the tip side of the shaft hole;
A cylindrical metal shell provided on the outer periphery of the insulator, and having a flange that bulges radially outward on the outer periphery;
A spark plug manufacturing method comprising a talc filled between the insulator and the metal shell,
A cylindrical cradle into which the metallic shell is inserted;
An insulator guide that regulates relative movement along the radial direction of the tip of the insulator with respect to the cradle by holding the tip of the insulator;
A cylindrical metal guide that is provided on the outer periphery of the insulator guide and is biased toward the rear end side in the axial direction by the first elastic member, and holds the front end of the metal shell,
A cylindrical talc press jig movable along the axial direction;
Using a talc press device provided with a cylindrical press jig guide in which the front end part of the talc press jig can be moved relative to the front end side in the axial direction with respect to its front end part,
Including a talc pressing step of pressing the talc by moving the talc press jig after the metal shell through which the insulator has been inserted is inserted into the cradle.
In the talc pressing step,
The talc press jig is moved to the metal shell side in a state where the tip end surface of the flange is lifted from the cradle by the metal guide,
Contact between the front end of the press jig guide and the rear end of the metal shell, contact between the front end surface of the flange and the cradle, and pressing of the talc by the talc press jig in this order. There line,
The press jig guide is positioned with respect to the talc press jig via a second elastic member in a state where the front end of the press jig guide is positioned on the rear end side in the axial direction with respect to the front end of the talc press jig. It is attached and the second elastic member is compressed, so that the tip of the talc press jig can move relative to the tip of the talc in the axial direction,
When the talc is pressed by the talc pressing jig, a reaction force of the second elastic member is larger than a reaction force of the first elastic member .

  According to the above configuration 1, the tip of the insulator is held by the insulator guide, and the tip of the metal shell is held by the metal guide. Therefore, it is possible to suppress movement along the radial direction at the distal end portion of the insulator and the distal end portion of the metal shell, and it is possible to more reliably suppress axial deviation (eccentricity) between the distal end portion of the insulator and the distal end portion of the metal shell. can do.

  In addition, when the metal shell is inserted into the cradle, the distal end surface of the collar portion is configured to float from the cradle without contacting the cradle. Therefore, the tip of the metal shell or the tip of the insulator can be brought into contact with the metal guide or the insulator guide more reliably. As a result, the above-described effect of suppressing the axial deviation at the tip can be more reliably exhibited.

On the other hand, if the talc is pressed with the front end surface of the collar part floating from the cradle, the rear end side of the metal shell moves in the radial direction, and the axis between the insulator axis and the center axis of the metal shell There is a risk of deviation or tilt. In this regard, according to the above-described configuration 1, the tip end surface of the collar portion and the cradle are brought into contact with each other before the talc is pressed. Therefore, when pressing the talc, it is possible to suppress the movement of the metal shell along the radial direction, and in combination with the fact that it is possible to suppress the axial deviation between the tip of the insulator and the tip of the metal shell, Axial misalignment and inclination between the body axis and the central axis of the metallic shell can be effectively suppressed. As a result, it is possible to prevent damage to the insulator and to suppress the occurrence of abnormal discharge.
Further, according to the configuration 1, when the talc is pressed by the talc press jig (that is, when the first elastic member and the second elastic member are compressed most in the talc pressing step), The reaction force of the second elastic member is configured to be larger than the reaction force of the first elastic member. Therefore, when the talc press jig is further moved from the state in which the tip of the press jig guide is in contact with the rear end of the metal shell to the metal shell side, the tip of the talc press jig presses the talc. Before, the front end surface of a collar part can be made to contact with a receiving stand more reliably.
The reaction force of the elastic member can be changed by adjusting the spring constant or the amount of compression of the elastic member when pressing the talc.

Configuration 2 . The manufacturing method of the spark plug of this configuration is the above configuration 1 , wherein the insulator guide is biased toward the rear end side in the axial direction by a third elastic member,
A cylindrical portion inserted through the metal fitting guide;
Formed on the rear end side in the axial direction of the cylindrical portion, and having a hook-shaped protruding portion having an outer diameter larger than an inner diameter of the metal fitting guide,
When the talc is pressed by the talc press jig, the reaction force of the second elastic member is the sum of the reaction force of the first elastic member and the reaction force of the third elastic member. It is characterized by being larger than.

According to the above configuration 2 , the hook-shaped protrusion having an outer diameter larger than the inner diameter of the metal fitting guide is provided at the rear end of the insulator guide (tubular portion). Therefore, the upper limit position of the insulator guide with respect to the metal fitting guide is set, and the situation where the insulator guide protrudes excessively with respect to the metal fitting guide can be prevented more reliably. As a result, the metal guide and the insulator guide can hold the distal end portion of the metal shell and the distal end portion of the insulator in a more stable state.

By forming the protruding portion on the insulator guide, the elastic force of the third elastic member biased to the insulator guide is also applied to the metal fitting guide, so that the press jig guide comes into contact with the metal shell. When the talc press jig is further moved toward the metal shell, the sum of the reaction force of the first elastic member and the reaction force of the third elastic member may be applied to the metal shell. In consideration of this point, according to the configuration 2 , when the talc is pressed by the talc press jig, the reaction force of the second elastic member is the reaction force of the first elastic member and the first It is comprised so that it may become larger than the sum total of the reaction force of 3 elastic members. Therefore, before the talc is pressed, the front end surface of the collar portion can be more reliably brought into contact with the cradle, and the configuration 1 can be more reliably realized.

Configuration 3 . In the spark plug manufacturing method according to this configuration, in the above configuration 2 , when the talc is pressed by the talc press jig, the reaction force of the first elastic member is the reaction of the third elastic member. It is characterized by greater than force.

According to the configuration 3 , the reaction force of the first elastic member is configured to be larger than the reaction force of the third elastic member when pressing the talc. Therefore, when the talc is pressed, when the insulator guide moves to the rear end side in the axial direction and the projection is separated from the bracket guide, the bracket guide is moved to the rear end in the axial direction in such a way that the support by the projection is lost. It is possible to more reliably prevent the situation of moving. Therefore, the front end portion of the metal shell can be held in a more stable state by the metal fitting guide, and movement along the radial direction of the front end portion of the metal shell can be more reliably suppressed.

Configuration 4 . In the spark plug manufacturing method according to this configuration, in any one of the above configurations 1 to 3 , the insulator guide has a cylindrical shape and includes a tapered portion whose inner diameter is reduced toward the lower side on the inner periphery of the upper end portion. ,
In the cross section including the central axis of the insulator guide, an acute angle among angles formed by a straight line orthogonal to the central axis and the outline of the tapered portion is 45 ° to 80 °. .

According to the said structure 4 , the force to the axial direction rear-end side applied to an insulator guide by the press of a talc and the dead weight of an insulator is made into the force which suppresses the movement along the radial direction of the front-end | tip part of an insulator. It can be converted efficiently. As a result, the movement along the radial direction of the distal end portion of the insulator can be more reliably suppressed, and the axis of the insulator and the central axis of the metal shell can be aligned with higher accuracy.

Configuration 5 . In the spark plug manufacturing method of this configuration, in any one of the above configurations 1 to 4 , in the spark plug, a rod-shaped ground electrode is welded to a tip portion of the metal shell,
The metal fitting guide is
An electrode insertion portion through which the ground electrode can be inserted;
And a recess for avoiding contact with a welding sag generated by welding the ground electrode to the metal shell.

According to the above configuration 5 , since the metal fitting guide has the electrode insertion portion, even when the talc pressing process is performed after the ground electrode is welded to the metal fitting, the metal guide guide stabilizes the tip portion of the metal fitting. Can be held in a state.

Moreover, according to the said structure 5 , the recessed part is formed in the metal fitting guide, and it is comprised so that the welding sag produced with the welding of a ground electrode may not contact a metal fitting guide. Therefore, it is possible to more reliably prevent a situation where the metal shell is held in an inclined state due to the presence of welding sag. As a result, the axis of the insulator and the central axis of the metal shell can be aligned with higher accuracy.

It is a partially broken front view which shows the structure of a spark plug. It is a partially broken front view which shows structures, such as a receiving stand and an insulator guide. It is a perspective view which shows the structure of a metal fitting guide. It is an expanded sectional view which shows the structure of an insulator guide. It is a partially broken front view for demonstrating one process in a talc pressing process. It is a partially broken front view for demonstrating one process in a talc pressing process. It is a partially broken front view for demonstrating one process in a talc pressing process. It is a partially broken front view for demonstrating one process in a talc pressing process. It is a partially broken front view for demonstrating one process in a talc pressing process. It is a graph which shows the shift | offset | difference amount and the failure | damage ratio in cases 1-3. It is a graph which shows the deviation | shift amount in the sample which changed the angle (alpha) variously. 6 is a graph showing a deviation amount in cases 4 and 5;

  Hereinafter, an embodiment will be described with reference to the drawings. 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. The leg length part 13 formed in diameter smaller than this on the side 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.

  Further, the insulator 2 is formed with a shaft hole 4 extending along the axis CL <b> 1, and a center electrode 5 is inserted and fixed to the tip side of the shaft hole 4. The center electrode 5 includes an inner layer 5A made of copper or a copper alloy and an outer layer 5B made of a Ni alloy containing nickel (Ni) as a main component. The center electrode 5 has a rod shape (cylindrical shape) as a whole, and a tip portion of the center electrode 5 projects from the tip of the insulator 2.

  In addition, 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 screw for attaching the spark plug 1 to a combustion device such as an internal combustion engine or a fuel cell reformer on the outer peripheral surface thereof. A portion (male screw portion) 15 is formed. Further, a flange portion 16 is formed to bulge toward the outer peripheral side at the rear end side of the screw portion 15, and a ring-shaped gasket 18 is fitted into the screw neck 17 at the rear end of the screw portion 15. Further, 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 on the rear end side of the metal shell 3. A caulking portion 20 that bends inward in the radial direction is provided at the rear end portion of the metal shell 3. In the present embodiment, the metal shell 3 is reduced in diameter in order to reduce the diameter of the spark plug 1. Therefore, the screw diameter of the screw portion 15 is a relatively small diameter (for example, M12 or less), and as a result, the screw portion 15 is orthogonal to the axis CL1 between the tip inner peripheral surface of the metal shell 3 and the tip portion of the insulator 2. The distance L along the direction is relatively small (for example, 1.0 mm or less).

  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 rear end of the metal shell 3 is engaged with the step portion 14 of the metal shell 3. It is fixed to the metal shell 3 by caulking the opening on the side inward 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 of both the insulator 2 and the metal shell 3. 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 talc 25 powder. 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.

  In addition, a substantially intermediate portion is bent back at the distal end portion 26 of the metal shell 3, and a ground electrode 27 whose distal side surface faces the distal end portion of the center electrode 5 is joined. A spark discharge gap 28 is formed between the tip of the center electrode 5 and the tip of the ground electrode 27, and spark discharge is performed in the spark discharge gap 28 in a direction substantially along the axis CL1. It has become.

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

  First, the metal shell 3 is processed in advance. That is, a rough shape is formed by subjecting a cylindrical metal material (for example, an iron-based material or a stainless steel material) to cold forging, 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 an Ni alloy is resistance-welded to the front end surface of the metal shell intermediate. Since a so-called welding sag occurs during the welding, at least a portion of the welding sag protruding from the inner peripheral surface of the metal shell intermediate body is removed, and then a threaded portion 15 is formed by rolling at a predetermined portion of the metal shell intermediate body. Is done. Thereby, the metal shell 3 to which the ground electrode 27 is welded is obtained. It should be noted that the welding sag generated due to the welding of the ground electrode 27 remains slightly in a form protruding from the front end surface of the metal shell 3 toward the front end side in the axis CL1 direction.

  Next, the metal shell 3 to which the ground electrode 27 is welded is subjected to zinc plating or nickel plating. 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. For example, by using a raw material powder mainly composed of alumina and containing a binder or the like, a green compact for molding is prepared, and a rubber-molded product is used to form a cylindrical molded body. Is obtained. The obtained molded body is ground and shaped, and the shaped product is fired in a firing furnace, whereby the insulator 2 is obtained.

  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.

  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 injected into the axial hole 4 of the insulator 2 with the resistor 7 interposed therebetween, and then from the rear. While being pressed by the terminal electrode 6, it is fired by being heated in a firing furnace. At this time, the glaze layer may be fired simultaneously on the surface of the rear end side body portion 10 of the insulator 2 or the glaze layer may be formed in advance.

  Next, in the talc pressing step, the insulator 2 and the main body are formed by a talc press device 51 (see FIG. 7 and the like) including a receiving base 31, a metal guide 33, an insulator guide 35, and a pressing jig 41, which will be described later. A talc 25 is filled between the metal fittings 3.

  In the talc pressing step, as shown in FIG. 2, first, after inserting the insulator 2 into the metal shell 3, the axis CL <b> 1 is substantially along the vertical direction with respect to the metal-made cradle 31. The metal shell 3 is inserted so as to extend. At this time, the metal shell 3 is arranged such that its central axis coincides with the central axis of the cradle 31.

  In addition, the receiving stand 31 is arrange | positioned in the state penetrated by the hole of the conveyance stand 32, and the said conveyance stand 32 is movable along a predetermined conveyance direction. Further, a cylindrical metal guide 33 and an insulator guide 35 are attached to the lower side of the inner periphery of the cradle 31.

  The metal fitting guide 33 is formed of a predetermined metal material, and is urged toward the rear end side (upward) in the direction of the axis CL1 by the first elastic member 34 which is provided below and can be expanded and contracted along the vertical direction. It has become a state. Further, at least the inner peripheral side of the upper surface 33A of the metal fitting guide 33 has a tapered shape that gradually decreases toward the outer peripheral side, and when the metal shell 3 is inserted through the cradle 31, the upper surface 33A. The inner periphery of the tip of the metal shell 3 comes into contact with the tapered portion. The front end portion of the metal shell 3 comes into contact with the upper surface 33A (tapered portion) of the metal guide 33 urged upward, so that the front end portion of the metal shell 3 relative to the cradle 31 along the radial direction. Movement is restricted.

  In addition, as shown in FIG. 3, the metal guide 33 is provided with an electrode insertion portion 33 </ b> S that is a space through which the ground electrode 27 can be inserted. When the metal shell 3 is held by the metal guide 33, The ground electrode 27 is accommodated in the electrode insertion portion 33S. Furthermore, a notch-shaped recess 33H is provided between the electrode insertion portion 33S and the upper surface 33A. When the metal shell 3 is held by the metal guide 33, the concave portion 33H prevents the welding sag generated by welding the ground electrode 27 and the metal guide 33 from being contacted.

  Returning to FIG. 2, the insulator guide 35 is arranged on the inner peripheral side of the metal guide 33 in a state where the center axis of the insulator guide 35 coincides with the center axis of the metal guide 33 and is formed of a predetermined resin material. . A third elastic member 36 that can extend and contract along the vertical direction is provided below the insulator guide 35, and the insulator guide 35 is moved toward the rear end side in the axis CL <b> 1 direction by the third elastic member 36. It is in a state of being biased (upward). Further, the inner periphery of the upper end portion of the insulator guide 35 is formed with a tapered portion 35A whose inner diameter gradually decreases toward the lower side, and when the metal shell 3 is inserted into the receiving base 31, The outer periphery of the tip of the insulator 2 is in contact with the tapered portion 35A. The tip of the insulator 2 is brought into contact with the tapered portion 35A of the insulator guide 35 biased upward, thereby restricting relative movement along the radial direction of the tip of the insulator 2 with respect to the receiving base 31. Is done.

  In the present embodiment, as shown in FIG. 4, in the cross section including the central axis of the insulator guide 35, an acute angle among the angles formed by the straight line L1 orthogonal to the central axis and the outline of the tapered portion 35A. α is 45 ° or more and 80 ° or less.

  Returning to FIG. 2, the insulator guide 35 includes a cylindrical cylindrical portion 35 </ b> C inserted through the metal fitting guide 33, and a hook-shaped protrusion 35 </ b> P formed on the distal end side of the cylindrical portion 35 </ b> C. The protruding portion 35 </ b> P is configured to be exposed from the metal guide 33 and to have an outer diameter larger than the inner diameter of the metal guide 33. The protrusion 35P is configured to be able to contact the lower end surface of the metal guide 33, and the upper limit position of the insulator guide 35 with respect to the metal guide 33 is set by the protrusion 35P. On the other hand, since the lower limit position of the insulator guide 35 with respect to the metal fitting guide 33 can be adjusted to some extent, even when manufacturing the spark plug 1 in which the protruding amount of the tip of the insulator 2 with respect to the tip of the metal shell 3 is different, The metal fitting guide 33 and the insulator guide 35 can be used in common. The outer peripheral surface of the metal fitting guide 33 is in contact with the cradle 31 with almost no gap, and the metal fitting guide 33 and the insulator guide 35 cannot move relative to the cradle 31 along their radial direction. It has become.

  Returning to the description of the manufacturing method, when the metal shell 3 is inserted into the cradle 31, the front end surface of the flange portion 16 is lifted from the cradle 31 by the bracket guide 33. In this state, as shown in FIG. 5, in the annular space 40 formed between the insulator 2 (the rear end side body portion 10 and the large diameter portion 11) and the metal shell 3, the ring member 23 and The talc 25 is arranged in this order.

  Next, as shown in FIG. 6, the metal shell 3 is transported below the pressing device 41 by moving the transport table 32, and the central axis CL <b> 2 of the pressing device 41 and the central axis (axis line CL <b> 1 of the receiving device 31). The conveyance table 32 is stopped in a state where the two coincide with each other.

  The pressing device 41 includes a cylindrical talc press jig 42 and a cylindrical press jig guide 43 disposed on the outer periphery of the talc press jig 42.

  The talc press jig 42 moves along the direction of the axis CL <b> 1 and presses the talc 25 at its front end, and the front end is disposed inside the press jig guide 43. .

  The press jig guide 43 is attached to the talc press jig 42 via the second elastic member 44. When the talc 25 is pressed, the second elastic member 44 is compressed, so that the tip of the talc press jig 42 is closer to the tip of the axis CL1 direction than the tip of the press jig guide 43. It is configured to move relative to each other. In addition, an enlarged diameter portion 43 </ b> A whose inner diameter increases toward the lower side is provided on the inner periphery of the tip portion of the press jig guide 43. When the talc 25 is pressed by the talc press jig 42, the enlarged diameter portion 43A comes into contact with the tool engaging portion 19 of the metal shell 3.

  Furthermore, the distance X along the axis CL1 between the front end of the talc press jig 42 and the front end of the press jig guide 43 is sufficiently large. Thereby, when the enlarged diameter portion 43A contacts the metal shell 3 (see FIG. 7), the distance along the axis CL1 between the distal end of the talc press jig 42 and the talc 25 is the distal end surface of the flange portion 16. It is comprised so that it may become larger than the distance along the axis line CL1 between the cradle 31 and the receiving stand 31.

  Moreover, while setting the said distance X as mentioned above and adjusting the spring constant of each elastic member 34,36,44, each said elastic member when pressing the talc 25 with the talc press jig | tool 42 is carried out. The reaction forces of 34, 36, and 44 are set so as to satisfy the following relationship. That is, when pressing the talc 25, the reaction force of the second elastic member 44 is greater than the reaction force of the first elastic member 34, and the reaction force of the first elastic member 34 is the third force. It is set to be larger than the reaction force of the elastic member 36. Further, when the talc 25 is being pressed, the reaction force of the second elastic member 44 is larger than the sum of the reaction force of the first elastic member 34 and the reaction force of the third elastic member 36. Is set to

  In pressing the talc 25 with the talc press jig 42, the talc press jig 42 is moved toward the metal shell 3 along the direction of the axis CL1. As a result, as shown in FIG. 7, the press jig guide 43 moves downward together with the talc press jig 42, and the enlarged diameter portion 43 </ b> A of the press support guide 43 contacts the tool engaging portion 19. When the talc press jig 42 continues to move downward, the elastic members 34, 36, 44 are compressed, and the distal end surface of the flange 16 contacts the cradle 31 as shown in FIG. 8. To do. Then, the second elastic member 44 is further compressed by moving the talc press jig 42 further downward, and the talc 25 is pressed by the tip of the talc press jig 42 as shown in FIG.

  After the talc pressing step, the ring member 24 is disposed on the talc 25 after a portion located on the rear end side in the direction of the axis CL1 of the talc 25 is shaved. Next, the insulator 2 and the metal shell 3 are fixed. More specifically, a load directed toward the front end side in the axis CL1 direction is applied to the opening on the rear end side of the metal shell 3, and the opening is caulked inward in the radial direction, that is, the caulking portion 20 is formed. By doing so, the insulator 2 and the metal shell 3 are fixed.

  Finally, the above-described spark plug 1 is obtained by bending the ground electrode 27 toward the center electrode 5 and adjusting the size of the spark discharge gap 28 between the center electrode 5 and the ground electrode 27.

  As described above in detail, according to the present embodiment, in the talc pressing process, the tip of the insulator 2 is held by the insulator guide 35 and the tip of the metal shell 3 is held by the metal guide 33. Yes. Therefore, the movement along the radial direction at the distal end portion of the insulator 2 and the distal end portion of the metal shell 3 can be suppressed, and the axial deviation (eccentricity) between the distal end portion of the insulator 2 and the distal end portion of the metal shell 3 can be reduced. It can suppress more reliably.

  Further, when the metal shell 3 is inserted into the cradle 31, the front end surface of the flange portion 16 is not in contact with the cradle 31 and is in a state of floating from the cradle 31. In addition, the metal shell 3 and the insulator 2 can be brought into contact with the insulator guide 35 more reliably. Therefore, the effect of suppressing the axial deviation at the tip portion described above can be exhibited more reliably.

  Furthermore, in this embodiment, it is comprised so that the front end surface of the collar part 16 and the receiving stand 31 may contact before the talc 25 is pressed. Therefore, when the talc 25 is pressed, the movement of the metal shell 3 along the radial direction can be suppressed, and it is possible to suppress the axial shift between the tip portion of the insulator 2 and the tip portion of the metal shell 3. Thus, it is possible to effectively suppress the axial deviation and inclination between the axis CL1 of the insulator 2 and the central axis of the metal shell 3. As a result, breakage of the insulator 2 can be prevented and occurrence of abnormal discharge can be suppressed.

  In addition, the upper limit position of the insulator guide 35 with respect to the metal fitting guide 33 is set by the protruding portion 35P provided on the insulator guide 35, and the insulator guide 35 protrudes excessively with respect to the metal guide 33. Can be prevented more reliably. As a result, the metal shell 3 and the insulator 2 can be held in a more stable state by the metal guide 33 and the insulator guide 35.

  In addition, when pressing the talc 25, the reaction force of the second elastic member 44 is larger than the sum of the reaction force of the first elastic member 34 and the reaction force of the third elastic member 36. It is comprised so that it may become. Therefore, when the talc 25 is pressed, the order of steps of pressing the talc 25 with the talc press jig 42 after the tip surface of the flange 16 and the cradle 31 are brought into contact with each other can be realized more reliably.

  In the present embodiment, the reaction force of the first elastic member 34 is configured to be larger than the reaction force of the third elastic member 36 when the talc 25 is pressed. Therefore, when the talc 25 is pressed, the metal fitting guide 33 moves downward in such a manner that the support by the protruding portion 35P is lost, and the holding power of the metal shell 3 by the metal fitting guide 33 is more reliably reduced. Can be prevented. As a result, the metal guide 3 can hold the front end portion of the metal shell 3 in a more stable state, and the movement of the front end portion of the metal shell 3 along the radial direction can be more reliably suppressed.

  Further, since the angle α of the tapered portion 35A is set to 45 ° or more and 80 ° or less, the downward force applied to the insulator guide 35 due to the pressing of the talc 25 or the dead weight of the insulator 2 is applied to the insulator 2. It can convert efficiently into the force which suppresses the movement along the radial direction of the tip. Thereby, the movement along the radial direction of the distal end portion of the insulator 2 can be more reliably suppressed, and the axial deviation and inclination between the axis CL1 of the insulator 2 and the central axis of the metal shell 3 can be further effectively suppressed.

  In addition, a recess 33 </ b> H is formed in the metal guide 33 so that the welding sag does not contact the metal guide 33. Therefore, the situation where the metal shell 3 is held in an inclined state due to the presence of welding sag can be more reliably prevented, and the axis CL1 of the insulator 2 and the center axis of the metal shell 3 can be aligned more accurately. .

  Next, in order to confirm the operational effects achieved by the above embodiment, in the talc pressing step, the contact between the tip of the press jig guide and the tool engaging portion (A), the tip of the flange and the cradle When the contact (B) and pressing of the talc by the talc pressing jig (C) are performed in the order of (A), (B), (C) (case 1; corresponding to the present invention), ( When performed in the order of A), (C), and (B) (Case 2; corresponding to the comparative example), and when performed in the order of (C), (A), and (B) (Case 3; comparison) The amount of deviation between the axis of the insulator and the central axis of the metal shell when the obtained spark plug was viewed from the front end side in the axial direction was measured.

  In addition, the talc pressing process was performed 100 times for each case described above. And the obtained spark plug was observed, while confirming the presence or absence of breakage in the insulator caused by pressing of the talc, the breakage occurrence rate (breakage rate) was calculated.

  In both tests, the talc was pressed after the relative movement along the radial direction of the front end portion of the metal shell and the front end portion of the insulator was restricted by a metal guide or insulator guide. In addition, the angle α of the tapered portion of the insulator guide was set to 60 °, and a recess was provided in the metal guide so that the welding sag did not contact the metal guide.

  FIG. 10 shows the shift amount and the breakage rate in each case. In FIG. 10, the amount of deviation is indicated by a circle, and the percentage calculated is indicated by a square.

  As shown in FIG. 10, the contact between the front end portion of the press jig guide and the metal shell (A), the contact between the front end surface of the flange portion and the cradle (B), and pressing of the talc by the talc press jig (C) When the talc pressing process was performed in this order (case 1), it became clear that the amount of deviation could be made sufficiently small. This is because when the talc was pressed, the movement of the metal shell along the radial direction due to the talc was effectively suppressed because the front end surface of the heel was already in contact with the cradle. It is thought to be caused.

  Moreover, in the case 1, it was confirmed that breakage of the insulator due to pressing of the talc could be prevented more reliably. This is considered to be because an excessive stress was applied to the insulator due to the suppression of the axial misalignment between the insulator and the metal shell.

  From the above test results, in order to suppress the axial deviation and inclination between the axis of the insulator and the central axis of the metal shell, in the talc pressing process, the contact between the tip of the press jig guide and the metal shell, the flange It can be said that it is preferable to perform the contact between the front end surface and the cradle and the talc pressing by the talc press jig in this order.

  Next, after using an insulator guide in which the angle α of the taper portion is variously changed, in the talc pressing process, the contact between the tip portion of the press jig guide and the metal shell, the tip surface of the flange portion and the cradle Contact and pressing of the talc with the talc press jig were performed in this order. And when the obtained spark plug was seen from the axial direction front end side, the deviation | shift amount of the axial line of an insulator and the central axis of a metal shell was measured. FIG. 11 is a graph showing the relationship between the angle α and the shift amount. The talc is pressed after restricting the relative movement along the radial direction of the tip of the metal shell, etc., with a metal guide, etc., and a recess is provided in the metal guide so that the welding sag does not contact the metal guide. did.

  As shown in FIG. 11, it was found that when the insulator guide having an angle α of 45 ° or more and 80 ° or less was used, the deviation amount could be reduced more reliably. This is because, by setting the angle α to the above numerical range, the axial force applied to the insulator guide by the pressing of the talc and the dead weight of the insulator follows the radial direction of the tip of the insulator. This is thought to be due to the efficient conversion to the force to suppress the movement.

  From the results of the above test, it can be said that the angle α of the tapered portion is preferably set to 45 ° or more and 80 ° or less in order to align the axis of the insulator and the central axis of the metal shell with higher accuracy.

  Next, when a recess is provided in the metal fitting guide so that the welding sag does not contact the metal guide and the talc is pressed (case 4), the welding sag can contact the metal guide without providing a recess in the metal guide. In the case where the talc was pressed in a state (Case 5), the amount of deviation between the axis of the insulator and the center axis of the metal shell in the obtained spark plug was measured. FIG. 12 shows the deviation amounts in both cases. The talc was pressed after the tip of the insulator was held by the insulator guide, and the angle α of the tapered portion of the insulator guide was set to 60 °.

  As shown in FIG. 12, it has been clarified that the shift amount can be further reliably reduced by providing the concave portion in the metal fitting guide. This is considered to be because the metal shell was prevented from being inclined due to the presence of welding sag, and the metal shell could be held in a more stable state.

  From the results of the above test, it can be said that it is preferable to provide a recess in the metal guide and avoid contact of the welding sag with the metal guide from the viewpoint of aligning the axis of the insulator and the central axis of the metal shell with higher accuracy.

  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 spark plug 1 in the above embodiment, the metal shell 3 has a relatively small diameter and the distance L is relatively small. However, the spark plug that can be manufactured using the present invention is particularly limited. Is not to be done. Therefore, for example, the present invention may be adopted when manufacturing a spark plug in which the screw diameter of the metal shell 3 exceeds M12 and the distance L is relatively large.

  (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. 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 Patent Laid-Open No. 2006-236906, etc.).

  (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)
DESCRIPTION OF SYMBOLS 3 ... Main metal fitting 4 ... Shaft hole 5 ... Center electrode 16 ... Eaves part 25 ... Tail 27 ... Ground electrode 31 ... Base 33 ... Metal fitting guide 33H ... Recess 33S ... Electrode insertion part 34 ... First elastic member 35 ... Insulator Guide 35A ... Tapered portion 35C ... Cylindrical portion 35P ... Protruding portion 36 ... Third elastic member 42 ... Talstone press jig 43 ... Press jig guide 44 ... Second elastic member 51 ... Tailstone press device CL1 ... Axis

Claims (5)

A cylindrical insulator having an axial hole penetrating in the axial direction;
A center electrode provided on the tip side of the shaft hole;
A cylindrical metal shell provided on the outer periphery of the insulator, and having a flange that bulges radially outward on the outer periphery;
A spark plug manufacturing method comprising a talc filled between the insulator and the metal shell,
A cylindrical cradle into which the metallic shell is inserted;
An insulator guide that regulates relative movement along the radial direction of the tip of the insulator with respect to the cradle by holding the tip of the insulator;
A cylindrical metal guide that is provided on the outer periphery of the insulator guide and is biased toward the rear end side in the axial direction by the first elastic member, and holds the front end of the metal shell,
A cylindrical talc press jig movable along the axial direction;
Using a talc press device provided with a cylindrical press jig guide in which the front end part of the talc press jig can be moved relative to the front end side in the axial direction with respect to its front end part,
Including a talc pressing step of pressing the talc by moving the talc press jig after the metal shell through which the insulator has been inserted is inserted into the cradle.
In the talc pressing step,
The talc press jig is moved to the metal shell side in a state where the tip end surface of the flange is lifted from the cradle by the metal guide,
Contact between the front end of the press jig guide and the rear end of the metal shell, contact between the front end surface of the flange and the cradle, and pressing of the talc by the talc press jig in this order. There line,
The press jig guide is positioned with respect to the talc press jig via a second elastic member in a state where the front end of the press jig guide is positioned on the rear end side in the axial direction with respect to the front end of the talc press jig. It is attached and the second elastic member is compressed, so that the tip of the talc press jig can move relative to the tip of the talc in the axial direction,
A method for producing a spark plug , wherein a reaction force of the second elastic member is larger than a reaction force of the first elastic member when the talc is pressed by the talc press jig . The insulator guide is biased toward the rear end side in the axial direction by a third elastic member,
A cylindrical portion inserted through the metal fitting guide;
Formed on the rear end side in the axial direction of the cylindrical portion, and having a hook-shaped protruding portion having an outer diameter larger than an inner diameter of the metal fitting guide,
When the talc is pressed by the talc press jig, the reaction force of the second elastic member is the sum of the reaction force of the first elastic member and the reaction force of the third elastic member. The method for manufacturing a spark plug according to claim 1 , wherein the spark plug is larger than the above. When presses the talc by the talc pressing jig, the reaction force of the first elastic member, according to claim 2, wherein greater than the reaction force of the third elastic member Spark plug manufacturing method. The insulator guide has a cylindrical shape and includes a tapered portion whose inner diameter is reduced toward the lower side on the inner periphery of the upper end portion,
In the cross section including the central axis of the insulator guide, an acute angle among angles formed by a straight line orthogonal to the central axis and the outline of the tapered portion is 45 ° to 80 °. The method for manufacturing a spark plug according to any one of claims 1 to 3 . In the spark plug, a rod-shaped ground electrode is welded to the tip of the metal shell,
The metal fitting guide is
An electrode insertion portion through which the ground electrode can be inserted;
The spark plug manufacturing method according to any one of claims 1 to 4 , further comprising a concave portion for avoiding contact with a welding sag generated by welding the ground electrode to the metal shell.

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