JP6298642B2 - Metal shell manufacturing method, spark plug manufacturing method, and metal shell manufacturing apparatus - Google Patents

Description

  The present invention relates to a spark plug technology.

  The metal shell used for the spark plug is generally composed of an iron-based material such as carbon steel, and a plating layer such as galvanization may be formed on the surface thereof for corrosion protection. Here, when a plating layer is formed on the ground electrode attached to the metal shell in addition to the metal shell, it may cause welding failure when the noble metal tip is welded to the ground electrode, or the ground electrode may be bent. As a result, the plating layer is peeled off, and the peeled plating layer comes into contact with the center electrode, causing problems such as no spark discharge. Therefore, in order to suppress the formation of the plating layer on the ground electrode, a technique for suppressing the contact between the ground electrode and the plating solution by covering the ground electrode with a rubber tube or the like is known (for example, Patent Document 1).

JP 2001-68250 A

  Generally, a heat shrink member is used as a member such as a rubber tube. The ground electrode is covered with the heat shrink member, and the heat shrink member is contracted to suppress contact between the ground electrode and the plating solution. However, when contracting the heat-shrinkable member, a gap may be generated between the heat-shrinkable member and the ground electrode, or the heat-shrinkable member may not be contracted uniformly in the circumferential direction. In this case, when the plating layer is formed on the metal shell, the plating layer may be formed in a wide range of the ground electrode due to the contact between the ground electrode and the plating solution.

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

(1) According to one form of this invention, the manufacturing method of a metal fitting provided with the ground electrode used for a spark plug and extending linearly is provided. The metal shell manufacturing method includes a mounting step of covering the ground electrode from a base end portion to a tip end portion thereof using a heat shrinkable member, and heating the heat shrinkable member using a heat source after the mounting step. A heat shrinking step of shrinking the heat shrinkable member in order from the base end side to the tip end side, and a plating step of plating the surface of the metal shell after the heat shrinking step. According to this embodiment, the heat contraction member is contracted sequentially from the base end side to the tip end side, so that the base end side of the heat contraction member is in close contact with the ground electrode before the tip end side. Thereby, the range (exposed range) in which the base end side of the ground electrode is not covered with the heat shrinkable member can be suppressed within a predetermined range.

(2) In the method of manufacturing the metal shell according to the above aspect, the heat shrinking step heats the heat shrinkable member by directly applying the hot air blown from the nozzle as the heat source to the heat shrinkable member. A step of heating the heat shrinkable member by reflecting the hot air blown from the nozzle with a reflecting plate disposed at a position facing the nozzle across the ground electrode and hitting the heat shrinkable member. But it ’s okay. According to this embodiment, the entire air in the circumferential direction of the heat shrinkable member can be heat-shrinked more uniformly by reflecting the hot air with the reflector and applying it to the heat-shrinkable member.

(3) In the method of manufacturing a metal shell according to the above aspect, the heat shrinking step moves the metal shell so as to be arranged at a different work position, and is heated by a heat source every time the metal shell is moved to the different work position. This may be implemented by moving the portion to be moved from the base end side to the tip end side. According to this aspect, it is possible to shorten the time for contracting the heat-shrinkable member at each different work position as compared with the case of contracting the heat-shrinkable member at the same work position. Therefore, since the time required for the heat shrinking process performed at one work position can be shortened, the production efficiency of the metal shell can be improved.

(4) In the method for manufacturing the metal shell of the above aspect, a plurality of the heat sources may be provided, and the plurality of heat sources may be fixed at different positions. According to this aspect, since the heat source is fixed, the predetermined range of the heat shrinkable member can be reliably heat shrunk by the heat source.

(5) In the method for manufacturing the metal shell according to the above aspect, the heat shrinkable member has a hole on the tip end side in a state of covering the ground electrode, and the heat shrinking step includes the heat shrinkable member. The step of letting the gas existing inside the air escape to the outside through the hole may be included. According to this embodiment, gas can be prevented from escaping from the base end side to the outside of the heat shrink member, so that the base end side can be more closely attached to the ground electrode first than the front end side. Can do. That is, the heat contraction of the heat shrinkable member is stably performed, so that a range (exposed range) in which the base end side of the ground electrode is not covered with the heat shrinkable member is suppressed to a predetermined range with higher accuracy. be able to. In addition, the degree of adhesion between the heat shrinkable member and the ground electrode can be improved by allowing the gas to escape to the outside of the heat shrinkable member.

(6) A method of manufacturing a metal shell according to the above aspect, further comprising a cooling step that is performed between the heat shrinking step and the plating step, and that applies a cooling gas to at least the heat shrinkable member of the metal shell. You may have. Here, since the plating process is generally performed at a place different from the heat shrinking process, it is necessary to move the metal shell. According to this aspect, by having a cooling step between the heat shrinking step and the plating step, it is possible to promote hardening of the heat shrinkable member by the cooling step before moving the metal shell to perform the plating step. . As a result, it is possible to reduce the risk of deviation of the heat-shrinkable member that occurs when the posture of the metal shell changes during movement or when an external force is applied to the metal shell. That is, since the shrinkage of the heat shrinkable member is stably performed by having the cooling step, a range (exposed range) in which the base end side of the ground electrode is not covered with the heat shrinkable member is more highly accurate. It can be suppressed within a predetermined range. Moreover, hardening of a heat contraction member can be accelerated | stimulated by cooling the heat contraction member heated by the heat contraction process by the cooling process. Thereby, possibility that a heat contraction member will be damaged can be reduced.

(7) In the method of manufacturing a metal shell according to the above aspect, the cooling step moves the metal shell so that the metal shell is arranged at a different work position. You may implement by applying the gas for cooling. According to this embodiment, it is possible to shorten the time for cooling the metal shell at different work positions as compared to cooling the metal shell at the same work position. Therefore, since the time required for the cooling process performed at one work position can be shortened, the production efficiency of the metal shell can be improved.

(8) It is a manufacturing method of the metal shell of the above-mentioned form, and cooling gas may be blown out from a plurality of nozzles. According to this aspect, since the cooling gas is blown out from the plurality of nozzles, it is possible to reduce the possibility that a deviation occurs in the degree of cooling of a member to be cooled such as a heat shrinkable member.

(9) In the method of manufacturing a metal shell according to the above aspect, the heat shrinking step is performed in a state where the metal shell is held by a holding member, and the cooling step is performed by the main body to which the ground electrode is bonded. A step of applying the cooling gas to the metal fitting and the holding member may be included. According to this aspect, since the cooling of the metal shell and the holding member can be promoted, deterioration of the metal shell and the holding member due to exposure to a high temperature environment can be suppressed.

(10) Moreover, according to the other form of this invention, the manufacturing method of a spark plug can be provided. The spark plug manufacturing method includes a center electrode disposing step of disposing a center electrode inside an axial hole of an insulator, a metal fitting manufacturing step of manufacturing the metal shell using the metal shell manufacturing method of the above-described form, An insulator disposing step of disposing the insulator inside the metal shell, and a bending step of bending the ground electrode so that the center electrode and the tip of the ground electrode face each other. According to this aspect, since the gap between the heat shrinkable member and the base end can be suppressed within a predetermined range, it is possible to manufacture a spark plug in which the range of plating applied to the ground electrode is suppressed.

(11) Moreover, according to the other form of this invention, the metal shell manufacturing apparatus which manufactures the metal shell for spark plugs provided with the ground electrode extended linearly can be provided. The metal shell manufacturing apparatus includes a mounting means for covering the base electrode from the base end portion to the tip end portion with a heat shrink member, and heating the heat shrink member using a heat source. Heat shrink means for shrinking the heat shrink member in order toward the tip end side. According to this aspect, the gap between the heat-shrinkable member and the base end portion can be suppressed within a predetermined range by the heat-shrinking means.

  The present invention can be realized in various forms, for example, a metal shell manufacturing method, a spark plug manufacturing method, a metal shell manufacturing apparatus, a metal shell manufacturing method, or a spark plug manufacturing method. The present invention can be realized in the form of a program for realizing the method, a metal shell manufactured using these manufacturing methods, a spark plug, an ignition system including a spark plug, or the like.

It is a partially broken sectional view showing a spark plug as an embodiment of the present invention. It is a flowchart which shows the manufacturing method of a spark plug. It is a flowchart which shows the detail of a metal shell manufacturing process. It is a figure for demonstrating the detail of a heat contraction process. It is a figure for demonstrating the detail of a cooling process. It is a figure for demonstrating the heat shrink process as a comparative example. It is a figure for demonstrating the manufacturing apparatus of the metal shell used in 2nd Embodiment. It is a figure for demonstrating the detail of a heat contraction process.

A. First embodiment and comparative example:
FIG. 1 is a partially broken cross-sectional view showing a spark plug 100 as an embodiment of the present invention. In FIG. 1, the direction along the axis CL (also referred to as “axis direction”) CLD of the spark plug 100 is defined as the vertical direction in the drawing. In FIG. 1, the lower side of the drawing is the front end side FS of the spark plug 100, and the upper side of the drawing is the rear end side BS of the spark plug.

  As shown in FIG. 1, the spark plug 100 includes an insulator 10 as an insulator, a metal shell 50, a center electrode 20, a terminal metal fitting 40, and a ground electrode 30.

  The insulator 10 as an insulator is formed by firing alumina or the like. The insulator 10 has a cylindrical shape in which an axial hole 12 extending in the axial direction CLD is formed. The insulator 10 is provided on the outer periphery of the center electrode 20 so as to hold the center electrode 20 in the shaft hole 12. Of the insulator 10, a flange portion 19 having the largest outer diameter is formed at substantially the center in the axial direction CLD. Further, in the insulator 10, a rear end side body portion 18 is formed on the rear end side (upper side in FIG. 1) from the flange portion 19. Further, in the insulator 10, a front end side body portion 17 having an outer diameter smaller than that of the rear end side body portion 18 is formed on the front end side FS from the flange portion 19. Further, in the insulator 10, a leg length portion 13 having an outer diameter smaller than that of the front end side body portion 17 is formed on the front end side FS of the front end side body portion 17. The long leg portion 13 is reduced in diameter toward the distal end side. When the spark plug 100 is attached to the engine head 600 of the internal combustion engine, the leg portion 13 is exposed to the combustion chamber. A step portion 15 is formed between the leg length portion 13 and the distal end side trunk portion 17 in the axial direction CLD.

  The metal shell 50 is a cylindrical metal fitting formed of a low carbon steel material. Further, the metal shell 50 has a plating layer such as galvanizing or nickel plating formed on the surface of the metal fitting. The metal shell 50 fixes the spark plug 100 to the engine head 600 of the internal combustion engine. The metal shell 50 is provided on the outer periphery of the insulator 10 and holds the insulator 10. Specifically, in the insulator 10, a part extending from a part of the rear end side body part 18 to the leg long part 13 is surrounded by the metal shell 50.

  The metal shell 50 includes a tool engaging portion 51 and a mounting screw portion 52. The tool engaging part 51 is a part into which a spark plug wrench (not shown) is fitted. The mounting screw portion 52 of the metal shell 50 is a portion where a screw thread is formed, and is screwed into a mounting screw hole 601 of the engine head 600 provided in the upper part of the internal combustion engine.

  Between the tool engaging portion 51 and the mounting screw portion 52 of the metal shell 50, a bowl-shaped seal portion 54 is formed. An annular gasket 5 formed by bending a plate is fitted between the mounting screw portion 52 and the seal portion 54. The gasket 5 is crushed and deformed when the spark plug 100 is attached to the engine head 600. Due to the deformation of the gasket 5, the gap between the spark plug 100 and the engine head 600 is sealed, and airtight leakage in the engine through the mounting screw hole 601 is prevented.

  A caulking portion 53 is provided on the rear end BS from the tool engaging portion 51 of the metal shell 50. Between the inner peripheral surface of the metal shell 50 from the tool engaging portion 51 to the caulking portion 53 and the outer peripheral surface of the rear end side body portion 18 of the insulator 10, annular ring members 6 and 7 are interposed. Has been. Further, a powder of talc (talc) 9 is filled between the ring members 6 and 7. When the crimping portion 53 is bent inwardly, the insulator 10 is pressed toward the front end side FS in the metal shell 50 via the ring members 6, 7 and the talc 9. Thereby, the step part 15 of the insulator 10 is supported by the step part 56 formed in the inner periphery of the metal shell 50, and the metal shell 50 and the insulator 10 are integrated. At this time, the airtightness between the metal shell 50 and the insulator 10 is maintained by the annular plate packing 8 interposed between the step portion 15 of the insulator 10 and the step portion 56 of the metal shell 50, and combustion is performed. Gas outflow is prevented.

  The center electrode 20 is a rod-shaped member extending in the axial direction CLD. The center electrode 20 is made of nickel or an alloy containing nickel as a main component. The electrode tip 21 located on the tip side FS of the center electrode 20 protrudes outward from the insulator 10. The center electrode 20 extends in the shaft hole 12 toward the rear end side, and is electrically connected to the terminal fitting 40 via the seal body 4 and the ceramic resistor 3. A high voltage cable (not shown) is connected to the terminal fitting 40 via a plug cap (not shown), and a high voltage is applied.

  The ground electrode 30 has a proximal end portion 33 attached to the distal end 57 of the metal shell 50 and a distal end portion 35 disposed at a position facing the electrode distal end portion 21 of the center electrode 20. The ground electrode 30 is formed of nickel or an alloy containing nickel as a main component. The ground electrode 30 is a member having a substantially rectangular cross section perpendicular to the direction in which the ground electrode 30 extends. The ground electrode 30 is bent at a portion between the proximal end portion 33 and the distal end portion 35. As a result, a spark gap for forming a spark discharge is formed between the electrode tip 21 and the tip 35. A noble metal tip 31 is bonded to the surface of the tip portion 35 facing the electrode tip portion 21. The noble metal tip 31 is formed of, for example, platinum (Pt), an alloy containing platinum as a main component, iridium (Ir), or an alloy containing iridium as a main component.

  FIG. 2 is a flowchart showing a method for manufacturing the spark plug 100. The manufacturing method of the spark plug 100 includes processes from the center electrode arrangement process (step S10) to the bending process (step S50). First, as a method for manufacturing the spark plug 100, a center electrode arrangement step is performed (step S10). The center electrode placement step includes a step of placing the center electrode 20 inside the shaft hole 12 of the insulator 10. Further, in the center electrode arranging step, the center electrode 20 is arranged on the front end side FS of the shaft hole 12, the seal body 4 and the ceramic resistor 3 are filled in the shaft hole 12, and then the terminal fitting 40 is placed on the rear end side of the shaft hole 12. It includes a step of assembling the members 3, 4, 20, and 40 to the insulator 10 by placing them on the BS and performing heat sealing at a high temperature.

  Next, a metal shell manufacturing process is performed (step S20). The metal shell manufacturing process is a process of manufacturing the metal shell 50 to which the ground electrode 30 is attached. Details of this will be described later. Note that step S10 and step S20 are not limited to this order, and step S20 may be performed before step S10.

  Next, an insulator arrangement process is performed (step S30). The insulator placement step includes a step of placing the insulator 10 inside the metal shell 50 after steps S10 and S20. Specifically, the talc 9 and the ring members 6 and 7 (FIG. 1) are arranged between the inner peripheral surface of the metal shell 50 and the outer peripheral surface of the insulator 10, and the crimping portion 53 of the metal shell 50 is placed inside. Clamp it as if it were bent. Thereby, the insulator 10 is held by the metal shell 50.

  Next, as shown in FIG. 2, a noble metal tip attachment process is performed (step S40). The noble metal tip attaching step includes a step of joining the noble metal tip 31 to the tip portion 35. A bending process is performed after step S40 (step S50). The bending step includes a step of bending the ground electrode 30 extending linearly toward the center electrode 20 side. By the bending process, as shown in FIG. 1, the electrode tip portion 21 and the tip portion 35 are arranged at positions facing each other in the axial direction CLD.

  FIG. 3 is a flowchart showing details of the metal shell manufacturing process (step S20). In the metal shell manufacturing process, first, a base material manufacturing process with an electrode is performed (step S22). The electrode-made base material manufacturing step includes a step of attaching the ground electrode 30 extending linearly to the metal shell 50 by welding. Step S22 includes a step of removing the welding sag after attaching the ground electrode 30 to the metal shell 50 by welding, and a step of forming the mounting screw portion 52 on the outer peripheral surface of the metal shell 50 (screw rolling step). Including. Here, the metal shell 50 to which the ground electrode 30 manufactured in step S22 is attached is also referred to as a base material W.

  After step S22, a heat shrinking member mounting step is performed (step S24). The mounting step is a step of covering the ground electrode 30 from the proximal end portion 33 to the distal end portion 35 using the heat shrinkable member 90. The step of covering the ground electrode 30 with the heat shrink member 90 may be performed manually by an operator, or mounting means 97 for holding the heat shrink member 90 and covering the ground electrode 30 with the heat shrink member 90 (FIG. You may perform automatically using 3).

  In the present embodiment, the heat-shrinkable member 90 uses a heat-shrinkable tube 90 that shrinks into a previously stored shape when heated. Step S24 is performed by arranging the heat shrinkable tube 90 so as to surround the entire circumference from the proximal end portion 33 to the distal end portion 35 of the ground electrode 30. A hole 94 is formed in the distal end side FS of the heat shrinkable tube 90. Further, the heat shrinkable tube 90 is longer than the ground electrode 30 by a predetermined value or more in the axial direction CLD of the ground electrode 30.

  After step S24, a heat shrinking process is performed (step S26). The heat shrinking step is a step of shrinking the heat shrinkable tube 90 by heating the heat shrinkable tube 90 using a heat source as heat shrinking means. The shrinkage of the heat-shrinkable tube 90 is sequentially performed from the base end portion 33 side to the tip end portion 35 side. By contracting the heat shrinkable tube 90, the heat shrinkable tube 90 is brought into close contact with the ground electrode 30.

  FIG. 4 is a diagram for explaining the details of the heat shrinking process. As shown in FIG. 4, the heat source used in the heat shrinking process is a nozzle 92, and hot air is blown out from the nozzle 92 toward the heat shrinkable tube 90. The nozzle 92 is disposed on one side surface of the ground electrode 30. A reflector 99 is disposed at a position facing the nozzle 92 with the ground electrode 30 in between. The reflector 99 is made of a metal such as stainless steel, for example. Further, when the heat shrinking process is performed, the position of the base material W is fixed by a metal chuck 102. In the present embodiment, the position of the substrate W is fixed by sandwiching the seal portion 54 of the substrate W by the chuck 102.

  The nozzle 92 moves from the proximal end portion 33 side to the distal end portion 35 side along the direction (axial direction) CLD in which the ground electrode 30 extends. Then, hot air is applied to the heat-shrinkable tube 90 with the nozzle 92 kept stationary for a predetermined time. Specifically, the nozzle 92 is stopped at the first to third operation positions that are different in the position of the axial direction CLD in order, and hot air is blown from the nozzle 92 in a stationary state to apply hot air to the heat shrinkable tube 90.

  When hot air blows out from the nozzle 92 located in the first operation position, a portion in the vicinity of the base end portion 33 of the heat shrinkable tube 90 is heated and contracted. After the operation at the first operation position, the nozzle 92 moves to the second operation position located closer to the distal end portion 35 than the first operation position. Then, by blowing hot air from the nozzle 92 located at the second operation position, an intermediate portion of the base end portion 33 and the tip end portion 35 in the heat shrinkable tube 90 is heated and contracted. After the operation at the second operation position, the nozzle 92 moves to the third operation position located on the distal end portion 35 side with respect to the second operation position. And a hot air blows off from the nozzle 92 located in a 3rd operation position, The part near the front-end | tip part 35 among the heat contraction tubes 90 is heated and shrink | contracts. At the first to third operation positions, the heat shrinking process is completed by blowing hot air from the nozzle 92 onto the heat shrinkable tube 90 to shrink the entire heat shrinkable tube 90.

  Further, as the heat shrinkable tube 90 contracts, the gas (air) present inside the heat shrinkable tube 90 escapes to the outside through the hole 94. Thereby, it can suppress that gas interposes between the heat contraction tube 90 and the ground electrode 30, and can improve the grade of contact | adherence with the heat contraction tube 90 and the ground electrode 30. FIG. Moreover, the hole 94 is formed in the front end side FS of the heat contraction tube 90 (FIGS. 3 and 4). As a result, it is possible to suppress the escape of gas (air) from the base end 33 side to the outside of the heat shrinkable tube 90, so that the base electrode 33 side is more surely grounded first than the tip end 35 side. 30. That is, since the heat shrinkable tube 90 is stably contracted, a range (exposed range) in which the proximal end 33 side of the ground electrode 30 is not covered with the heat shrinkable tube 90 is further increased with a predetermined accuracy. Can be kept within the range.

  As described above, in the heat shrinking process, the heat shrinkable tube 90 is shrunk in order from the base end 33 side to the tip end 35 side, so that the heat shrinkable tube 90 is shrunk in order from the base end 33 side to the tip end 35 side. To do. As a result, first, the proximal end 33 side of the ground electrode 30 and the heat shrinkable tube 90 are in close contact with each other, so that the heat shrinkable tube 90 is pulled toward the distal end 35 side starting from the contracted portion in the shrinking process of the heat shrinkable tube 90. Can be suppressed. Therefore, a range (exposed range) that is not covered with the heat shrinkable tube 90 on the base end 33 side of the ground electrode 30 can be suppressed within a predetermined range. That is, the length (gap size) of the axial direction CLD that is not covered with the heat shrinkable tube 90 in the ground electrode 30 can be maintained within a predetermined range. Thereby, it is possible to suppress the range of plating applied to the ground electrode 30 in the plating step (step S29 in FIG. 2) described later.

  Here, in each of the first to third operation positions, the heat shrinkable tube 90 is contracted by being heated by the hot air blown from the nozzle 92 directly hitting the heat shrinkable tube 90. Further, in each of the first to third operation positions, the heat shrinkable tube 90 is contracted by heating the hot air blown from the nozzle by being reflected by the reflecting plate 99 and hitting the heat shrinkable tube 90. Done. Thereby, the whole circumferential direction of the heat shrinkable tube 90 can be shrunk more uniformly.

  In the above embodiment, the nozzle 92 is moved from the base end portion 33 side to the tip end portion 35 side. However, the plurality of nozzles 92 are fixed at different positions in the direction (axial direction) CLD in which the ground electrode 30 extends. May be arranged. For example, in the case of this embodiment, three nozzles 92 shown in the first to third operation positions shown in FIG. 4 are provided. And the nozzle 92 which blows off hot air is switched in order of a 1st-3rd operation position. By fixing the nozzle 92 in this way, the hot air blown from the nozzle 92 can be reliably applied to a predetermined range of the heat shrinkable tube 90. Thereby, the heat contraction tube 90 can be reliably contracted in order from the base end portion 33 side to the tip end portion 35 side.

  As shown in FIG. 3, a cooling process is performed after step S26 (step S28). The cooling step is a step of applying a cooling gas to at least the heat shrinkable tube 90 in the metal shell 50 in which the heat shrinkable tube 90 is attached to the ground electrode 30 by the heat shrinking step. The cooling process is performed until the substrate W and the chuck 102 are at a predetermined temperature (for example, 40 ° C.) or lower. In the present embodiment, air at normal temperature (for example, 20 ° C.) is used as the cooling gas. Note that the cooling gas is not limited to room temperature air, and air having a temperature lower than room temperature or a gas other than air may be used.

  FIG. 5 is a diagram for explaining the details of the cooling process. As shown in FIG. 5, the position of the base material W is fixed by the chuck 102 used in the heat shrinking process also in the cooling process. In the cooling step, cooling gas is blown out from a plurality (ten in this embodiment) of nozzles 96. The five nozzles 96 are disposed on one side surface (first side surface) of the ground electrode 30, and the other five nozzles 96 are side surfaces (second side surface) opposite to the one side surface of the ground electrode 30. Side). Further, the five nozzles arranged on the first side surface side or the second side surface side have different positions in the direction (axial direction) CLD in which the ground electrode 30 extends.

  In the cooling step, cooling gas is blown out from the plurality of nozzles 96 and the cooling gas is applied to the substrate W and the chuck 102. Thereby, the heat-shrinkable tube 90 heated by the heat-shrink process can be cooled to accelerate the curing of the heat-shrinkable tube 90. Therefore, the possibility that the heat shrinkable tube 90 is damaged can be reduced. Moreover, since the cooling of the base material W and the chuck 102 heated by the heat shrinking process can be promoted, deterioration of the base material W and the chuck 102 due to exposure to a high temperature environment can be suppressed. In addition, since the cooling gas is blown out from the plurality of nozzles 96 to cool the base material W and the chuck 102, the possibility of occurrence of bias in the degree of cooling of the base material W and the chuck 102 can be reduced.

  As shown in FIG. 3, a plating process is performed after step S28 (step S29). The plating step is a step of applying a Ni plating layer, a zinc plating layer, or a chromate layer to the surface of the substrate W. In this embodiment, after forming the galvanized layer on the surface of the substrate W, the chromate layer is formed on the galvanized layer. The plating layer is formed, for example, by immersing the base material W in a plating solution and causing a current to flow between the anode part and the cathode part. After the plating process is completed, the heat shrinkable tube 90 that is in close contact with the ground electrode 30 is removed.

  As described above, in the present embodiment, in the heat shrinking step, the heat shrinkable tube 90 is shrunk in order from the base end 33 side to the tip end 35 side, so that the heat shrinkable tube 90 is formed on the base end 33 side of the ground electrode 30. An uncovered range can be suppressed within a predetermined range. As a result, it is possible to suppress the formation of a plating layer on the surface of the ground electrode 30, and the occurrence of defects caused by the formation of the plating layer on the ground electrode 30 (for example, poor welding between the ground electrode 30 and the noble metal tip 31). ) Can be reduced. Here, since the place where the heat shrinking process (step S26 in FIG. 3) is performed is different from the place where the plating process (step S29 in FIG. 3) is performed, it is necessary to move the substrate W. However, by having a cooling step between the heat shrinking step and the plating step, it is possible to promote curing of the heat shrinkable tube 90 by the cooling step before moving the substrate W to the place where the plating step is performed. Thereby, the danger of the shift | offset | difference of the heat contraction tube 90 etc. which generate | occur | produce in the condition where the attitude | position of the base material W changes at the time of a movement, etc., or the condition where an external force is added to the base material W can be reduced. That is, since the heat shrinkable tube 90 is stably contracted by having the cooling step, a range (exposed range) in which the base end 33 side of the ground electrode 30 is not covered with the heat shrinkable tube 90 is further increased. It can be suppressed within a predetermined range with high accuracy.

  FIG. 6 is a diagram for explaining a heat shrinking process as a comparative example. In the comparative example shown in FIG. 6, the heat shrinkable tube 90 is contracted by blowing hot air from the nozzle 92 and heating the entire heat shrinkable tube 90 from the beginning. In this case, the portion Ps between the proximal end portion 33 and the distal end portion 35 of the ground electrode 30 in the heat shrinkable tube 90 may shrink first. In this case, when the tube is pulled toward the portion Ps from the portion Ps as a starting point, a portion CH (exposed portion CH) where the ground electrode 30 is not covered by the heat shrinkable tube 90 on the base end portion 33 side increases. Thereby, the range in which the plating layer is formed on the ground electrode 30 is increased by the plating step, and defects such as poor welding between the ground electrode 30 and the noble metal tip 31 may occur. Further, since the exposed portion CH is increased, the surface area of the ground electrode 30 on which the plating layer is formed increases. Accordingly, the plating layer may be peeled off when the ground electrode 30 is bent in the bending process (step S50 in FIG. 2), which is a post process. When the plating layer is peeled off, the peeled plating layer may come into contact with the center electrode 20 to cause a problem that spark discharge does not occur stably.

B. Second embodiment:
FIG. 7 is a diagram for explaining a manufacturing apparatus 80 for the metal shell 50 used in the second embodiment. The manufacturing apparatus 80 is used to perform steps S24 to S28 (FIG. 3) in the metal shell manufacturing process (step S20 and FIG. 3 in FIG. 2) in the first embodiment. The difference between the first embodiment and the second embodiment is a manufacturing apparatus used in the metal shell manufacturing process. Since other points (for example, the configuration of the spark plug 100) are the same as those of the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  The manufacturing apparatus 80 includes a disk-shaped installation table 82 for installing the base material W. Work positions P1 located at substantially regular intervals along the circumferential direction of the installation table 82 on the installation tables 82 at the work positions P1 to P16 located at regular intervals along the circumferential direction of the installation table 82. Each of .about.P16 is provided with a chuck 102 (FIG. 4). The installation table 82 rotates counterclockwise as indicated by an arrow Ra, so that the substrate W arranged on the installation table 82 is conveyed.

  At the work position P1, the base material W manufactured by the base material manufacturing process with electrodes (step S22 in FIG. 3) is supplied to the manufacturing apparatus 80. Specifically, the base material W is fixed using the chuck 102 on the installation table 82 located at the work position P1.

  At the work positions P2 to P7, a mounting process (step S24 in FIG. 3) is performed. Specifically, the ground electrode 30 of the base material W that has moved to the work positions P <b> 2 to P <b> 7 is covered with the heat shrinkable tube 90. The ground electrode 30 may be covered with the heat-shrinkable tube 90 at at least one of the work positions P2 to P7.

  At the work positions P8 to P10, a heat shrink process (step S26 in FIG. 3) is performed. Specifically, the process performed at the first operation position in FIG. 4 is performed at the work position P8, the process performed at the second operation position in FIG. 4 is performed at the work position P9, and the process illustrated in FIG. A step performed at the third operation position is performed. A peripheral member 84 is provided at the work positions P8 to P10. The working positions P8 to P10 are formed in a tunnel shape by the peripheral member 84. The substrate W moves inside the peripheral member 84.

  FIG. 8 is a diagram for explaining the details of the thermal contraction process performed at the work positions P8 to P10. In FIG. 8, the base material W moves from the back side to the near side of the drawing. In the range from the work position P8 to the work position P10, a peripheral member 84 is disposed on the installation table 82. The peripheral member 84 is formed in a tunnel shape and covers the periphery of the substrate W. Further, the nozzles 92 disposed at the respective work positions P8 to P10 are fixed, and the heights of the nozzles 92 from the installation base 82 are different. Specifically, the nozzle 92 at the work position P8, the nozzle 92 at the work position P9, and the nozzle 92 at the work position P10 are arranged in this order so as to be away from the installation table 82. In each of the work positions P8 to P10, a reflector 99 is disposed at a position facing the nozzle 92 with the ground electrode 30 interposed therebetween, as in the first embodiment.

  When hot air blows out from the nozzle 92 located in the work position P8, a portion of the heat shrinkable tube 90 in the vicinity of the base end 33 is heated and contracted. After the operation at the work position P8, the substrate W moves to the work position P9. Then, by blowing hot air from the nozzle 92 located at the work position P9, the intermediate portion between the base end portion 33 and the tip end portion 35 of the heat shrinkable tube 90 is heated and contracted. After the operation at the work position P9, the substrate W moves to the work position P10. And a hot air blows off from the nozzle 92 located in the work position P10, The part of the heat shrink tube 90 vicinity of the front-end | tip part 35 is heated and shrink | contracts.

  As described above, the heat shrinking process performed in the manufacturing apparatus 80 of the second embodiment moves the base material W so as to be arranged at different work positions P8 to P10 and moves to the different work positions P8 to P10. This is implemented by moving the portion heated by the nozzle 92 as a heat source from the base end 33 side to the tip end 35 side. Thereby, in addition to the effect of 1st Embodiment, there exist the following effects. That is, compared with the case where the heat shrinkable tube 90 is contracted at the same work position, the time for contracting the heat shrinkable tube 90 at each different work position can be shortened. For example, when it is necessary to heat the heat-shrinkable tube 90 for about 3 seconds at each work position P8 to P10, all of the heat-shrinkable tube 90 from the base end 33 side to the tip end 35 side is shrunk at one work position. It takes about 9 seconds to do this. Therefore, when shrinking the heat-shrinkable tube 90 at one work position, the base metal W can be moved only at intervals of about 9 seconds, so that the production efficiency of the metal shell 50 is lowered. On the other hand, since the base material W can be moved at intervals of about 3 seconds by dividing and carrying out the thermal contraction process at each work position P8 to P10, the production efficiency of the metal shell 50 can be improved.

  Returning to FIG. 7, the heat shrinking process and subsequent steps will be described. A cooling step (step S28 in FIG. 3) is performed at the work positions P11 to P12. Specifically, at each work position P11 to P12, cooling air is blown out from the plurality of nozzles 96 shown in FIG. 5 to cool the substrate W and the chuck 102. For example, cooling is performed for about 3 seconds at each of the work positions P11 and P12.

  As described above, the cooling process performed in the manufacturing apparatus 80 of the second embodiment moves the base material W so as to be disposed at different work positions P11 and P12, and moves to the different work positions P11 and P12 each time. This is performed by applying a cooling gas to the metal shell 50. Thereby, compared with the case where the metal shell 50 is cooled at the same work position, the time for cooling the metal shell 50 at different work positions can be shortened. For example, when cooling for about 6 seconds is required, cooling for about 3 seconds may be performed at the work positions P11 and P12. Therefore, the production efficiency of the metal shell can be improved.

  As shown in FIG. 7, at the work positions P13 to P16, the substrate W that has obtained the cooling process is discharged from the manufacturing apparatus 80 (discharge process). In the discharging step, before removing from the chuck of the manufacturing apparatus 80, a step of inspecting whether or not the gap dimension between the heat shrinkable tube 90 and the ground electrode 30 is within a predetermined range may be performed. As for the discharged | emitted base material W, a plating layer is formed by the plating process shown in FIG.

C. Variations:
C-1. First modification:
In the said embodiment, although the heat-shrinkable tube was used as a heat-shrinkable member, it is not limited to this, What is necessary is just a member which shrinks by heating. The heat source is the nozzle 92 that blows out hot air. However, the nozzle 92 may not be used as long as it can heat the heat-shrinkable member. For example, a heating wire or the like may be used as the heat source.

C-2. Second modification:
Although the cooling process of the said embodiment was performed by spraying the gas for cooling toward the base material W and the chuck | zipper 102 from the several nozzle 96 (FIG. 5), you may perform using the one nozzle 96, A plurality of nozzles 96 may be arranged only on one side of the ground electrode 30. Further, the cooling gas may be blown toward the substrate W and the chuck 102 while moving at least one nozzle 96 or each time it moves.
Further, in the cooling process, if the cooling gas can be blown onto the heat shrinkable member 90 and the cooling can be promoted, the cooling gas may not be blown onto the other members.

C-3. Third modification:
In the above embodiment, the reflector 99 (FIG. 4) is used in the heat shrinking step, but may be omitted. That is, the heat shrinkable member 90 may be contracted by directly heating the heat shrinkable member 90 using a heat source.

C-4. Fourth modification:
In the said 2nd Embodiment, although the manufacturing apparatus 80 moved the base material W to the circumferential direction, it is not limited to this, The base material W is fixed to the linear installation stand, and moves linearly. You may let them.

C-5. Fifth modification:
In the above embodiment, the spark plug 100 includes the noble metal tip 31 (FIG. 1), but the noble metal tip 31 may not be provided. Moreover, although the manufacturing method of the spark plug 100 was provided with the noble metal tip attachment process (step S40 of FIG. 2), it does not need to be provided with this.
Moreover, although the heat shrinkable tube 90 has the hole 94 (FIG. 4) for letting gas escape outside, it does not need to have the hole 94.

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

DESCRIPTION OF SYMBOLS 3 ... Ceramic resistance 4 ... Sealing body 5 ... Gasket 6 ... Ring member 8 ... Plate packing 9 ... Talc 10 ... Insulator 12 ... Shaft hole 13 ... Leg long part 15 ... Step part 17 ... Front end side trunk part 18 ... Rear end side trunk Numeral 19: Gutter 20 ... Center electrode 21 ... Electrode tip 30 ... Ground electrode 31 ... Precious metal tip 33 ... Base end 35 ... Tip 40 ... Terminal fitting 50 ... Metal fitting 51 ... Tool engaging portion 52 ... Mounting screw portion 53 ... Caulking part 54 ... Sealing part 56 ... Step part 57 ... Tip 80 ... Manufacturing device 82 ... Installation base 84 ... Surrounding member 90 ... Heat shrinkable tube (heat shrinkable member)
92 ... Nozzle 94 ... Hole 96 ... Nozzle 97 ... Mounting means 99 ... Reflector 100 ... Spark plug 102 ... Chuck 600 ... Engine head 601 ... Hole CL ... Axis CLD ... Axis direction W ... Base material CH ... Exposed part FS ... Tip side BS ... Rear end side

Claims (11)

In a method for manufacturing a metal shell including a ground electrode that is used for a spark plug and extends linearly,
A mounting step of covering the base electrode from the base end to the tip using a heat shrinkable member,
A heat shrinking step of shrinking the heat shrinkable member in order from the base end side to the tip end side by heating the heat shrinkable member using a heat source after the mounting step;
And a plating step of plating the surface of the metal shell after the heat shrinking step. In the manufacturing method of the metal shell according to claim 1,
The heat shrinking step includes
The hot air blown from the nozzle as the heat source is directly applied to the heat shrink member to heat the heat shrink member, and the hot air blown from the nozzle is opposed to the nozzle across the ground electrode. A method of manufacturing a metal shell, comprising the step of heating the heat shrinkable member by reflecting the light with a reflector disposed at a position and applying the light to the heat shrinkable member. In the manufacturing method of the metal shell according to claim 1 or claim 2,
The heat shrinking step includes
It is carried out by moving the metal shell so that it is arranged at a different work position, and moving the portion heated by a heat source from the base end side to the tip end side every time it moves to the different work position. The manufacturing method of the metal shell characterized by the above-mentioned. In the manufacturing method of the metal fitting as described in any one of Claim 1- Claim 3,
A plurality of the heat sources are provided,
The method for manufacturing a metal shell, wherein the plurality of heat sources are fixed at different positions. In the manufacturing method of the metal fitting as described in any one of Claim 1- Claim 4,
The heat shrinkable member has a hole on the tip end side in a state of covering the ground electrode,
The heat shrinking step includes
The manufacturing method of the metal shell characterized by including the process of releasing the gas which exists inside the said heat contraction member outside through the said hole. In the manufacturing method of the metal shell according to any one of claims 1 to 5,
A method for manufacturing a metal shell, comprising: a cooling step that is performed between the heat shrinking step and the plating step and that applies a cooling gas to at least the heat shrinkable member of the metal shell. In the manufacturing method of the metal shell according to claim 6, the cooling process includes
The metallic shell is manufactured by moving the metallic shell so as to be arranged at different working positions and applying the cooling gas to the metallic shell each time the metallic shell is moved to the different working positions. Method. In the manufacturing method of the metal shell according to claim 6 or 7,
The method of manufacturing a metal shell, wherein the cooling gas is blown out from a plurality of nozzles. In the manufacturing method of the metal shell according to any one of claims 6 to 8, the heat shrinking process is performed in a state where the metal shell is held by a holding member,
The cooling step includes
A method of manufacturing a metal shell, comprising the step of applying the cooling gas to the metal shell to which the ground electrode is bonded and the holding member. In the spark plug manufacturing method,
A center electrode placement step of placing the center electrode inside the shaft hole of the insulator;
A metal fitting manufacturing process for manufacturing the metal shell using the method for manufacturing the metal shell according to any one of claims 1 to 9,
An insulator placement step of placing the insulator inside the metal shell;
And a bending step of bending the ground electrode so that the center electrode and the tip of the ground electrode face each other. In a metal shell manufacturing apparatus for manufacturing a metal shell for a spark plug having a linearly extending ground electrode,
A mounting means for covering the base electrode from the proximal end portion to the distal end portion with a heat shrinkable member,
A heat-shrinking means for shrinking the heat-shrinkable member in order from the base end side to the tip-end side by heating the heat-shrinkable member using a heat source; apparatus.

Images