JP4480663B2 - Glow plug manufacturing method and glow plug - Google Patents

Description

  The present invention relates to a method for manufacturing a glow plug and a glow plug manufactured by the manufacturing method.

  Conventionally, the glow plug of patent document 1 is known. As shown in FIG. 5, the glow plug 100 has a cylindrical metal shell 3 extending in the direction of the axis O and a cylinder extending in the direction of the axis O. A heating tube 4 fixed in the metal shell 3 with its own tip 4a protruding, and a rod shape extending in the direction of the axis O, its tip is located in the heating tube 4, and its rear end is the main A middle shaft 6 projecting from the rear end of the metal fitting 3 and a spiral extending in the direction of the axis O, and its own tip 5 a is joined to the tip 4 a of the heat generating tube 4 in the heat generating tube 4, and its rear end is the center shaft 6. A heating coil 5 joined to the tip is provided. In this glow plug, the middle shaft 6 includes a first middle shaft 8, and a second middle shaft 9 in which a rear end 8b of the first middle shaft 8 and a front end 9a thereof are joined.

  According to the publication, the glow plug 100 is manufactured as follows. That is, as a first step, as shown in FIG. 6, the insertion portion 8 a formed at the tip of the first central shaft 8 is inserted into the insertion portion 5 b formed at the rear end of the heating coil 5. In addition, an overlapping portion 90a is provided in which the insertion portion 8a of the first middle shaft 8 and the inserted portion 5b of the heating coil 5 are in contact with each other in the radial direction. Thereby, the first glow plug intermediate 90 is obtained.

  Then, as the second step, the overlapping portion 90a is sandwiched between the two electrodes 81 and 82 in the radial direction. Both electrodes 81 and 82 are connected to a power source 80 via a switch S80. Then, the switch S80 is turned on to energize the electrodes 81 and 82. In this way, the insertion portion 5b of the heating coil 5 and the insertion portion 8a of the first center shaft 8 are welded to form the welded portion 90b, and the second glow plug intermediate 91 is obtained.

  As shown in FIG. 5, the second glow plug intermediate 91 is assembled with the metal shell 3 and the like to form a glow plug.

  At this time, first, a cylindrical heating tube 4 having both ends opened is prepared, and the tip 5 a of the heating coil 5 of the second glow plug intermediate 91 is inserted into the heating tube 4. In this state, the heat generating tube 4 and the tip 5a of the heat generating coil 5 are spot welded, and the tip 4a of the heat generating tube 4 is closed. Then, an insulating material 7 such as magnesia powder is enclosed in the heat generating tube 4, and a sealing material 11 such as fluorine rubber or silicon rubber is inserted between the rear end 4b of the heat generating tube 4 and the first middle shaft 8, Swaging the outer periphery of the heat generating tube 4. Thereby, the sheathed heater 2 is obtained.

  Then, the front end 9 a of the second middle shaft 9 is welded to the rear end 8 b of the first middle shaft 8, thereby forming the middle shaft 6. Thereafter, the sheathed heater 2 is inserted into the cylindrical metal shell 3, and the sheathed heater 2 is fixed in the metal shell 3 with the tip 4 a of the heat generating tube 4 protruding from the tip of the metal shell 3. Thereafter, an O-ring 16, an insulation bush 14 and a nut 15 are provided on the second middle shaft 9 of the middle shaft 6 protruding from the rear end of the metal shell 3, and the second middle shaft 9 is fixed to the metal shell 3 in an insulated state. The glow plug thus obtained is used for a diesel engine.

FIG. 4 of JP-A-4-15408

  By the way, recent glow plugs tend to be reduced in diameter to increase the temperature rising rate and to reduce the diameter of the glow hole due to the demand for miniaturization and weight reduction of diesel engines. For this reason, in the recent glow plug, the heat generating tube 4 in which the inner shaft 6 and the heat generating coil 5 are housed has a larger cross-sectional reduction rate than that of the conventional case, and the processing load acting on the welded portion 90b is increased. Is also larger than before.

  For this reason, in order to increase the welding strength between the insertion portion 8a of the first middle shaft 8 and the insertion portion 5b of the heating coil 5, in the conventional glow plug manufacturing method, as shown in FIG. There was a problem that the shaft core was bent more on the tip side than the welded portion 90b.

  When the second glow plug intermediate body 91 in which such a defect has occurred is assembled with the metal shell 3 or the like to form a glow plug, the heat generating coil 5 is likely to come into contact with the inner cylindrical surface of the heat generating tube 4, and the short There was a risk of quality defects such as defects and variations in current-carrying performance.

  The present invention has been made in view of the above-described conventional situation, and an object to be solved is to provide a method for manufacturing a glow plug that can suppress a quality defect such as a short-circuit defect or a variation in energization performance.

  The inventors have studied various causes of quality defects such as short-circuit defects and variations in energization performance in the conventional manufacturing method. And the cause was elucidated as follows and it came to complete this invention.

  That is, one of the causes is that when the current flowing between the electrodes 81 and 82 is increased in order to increase the welding strength in the conventional manufacturing method, the amount of welding penetration of the heating coil 5 inevitably increases. As a result, the heat generating coil 5 is greatly deformed at the tip position C of the welded portion 90b.

  Another cause is that in the conventional manufacturing method, the welded portion 90b is formed so that the tip position A of the overlapped portion 90a substantially coincides with the tip position C of the welded portion 90b. In other words, in the conventional manufacturing method, the electrodes 81 and 82 are arranged so that the tip position A of the overlapping portion 90a almost coincides with the tip surface B of the electrodes 81 and 82.

  The method for manufacturing the glow plug of the first invention thus completed has a cylindrical metal shell extending in the axial direction and a cylinder extending in the axial direction, the tip of which is closed, and the tip of the metal shell is A heat generating tube fixed in the metal shell with the tip protruded, and a rod shape extending in the axial direction, its own tip is located in the heat generating tube, and its rear end is behind the metal shell. A heat generating coil having a middle shaft projecting from the end, a spiral extending in the axial direction, a front end of the heat generating tube joined to a front end of the heat generating tube, and a rear end of the heat generating coil joined to the front end of the middle shaft A method of manufacturing a glow plug comprising:

  By inserting the insertion portion formed at the tip of the middle shaft into the insertion portion formed at the rear end of the heating coil, the insertion portion and the insertion portion overlap each other in the radial direction. A first step of providing

  A second step of forming a welded portion by welding the inserted portion and the inserted portion by energizing each electrode while holding the overlapping portion in a radial direction by a plurality of electrodes. Prepared,

  The welded portion is formed between the tip position of the welded portion and the tip position of the overlapping portion so that the heat generating coil is present at least 1/2 turn without being welded to the insertion portion. To do.

  The method for manufacturing a glow plug according to the second aspect of the present invention comprises a cylindrical metal shell extending in the axial direction and a cylinder extending in the axial direction, the tip of which is closed, and the tip of the metal shell from the tip of the metal shell A heat generating tube fixed in the metal shell in a protruding state, and a rod-like shape extending in the axial direction, with its own tip positioned in the heat generating tube, and its rear end being the rear end of the metal shell A heat generating coil having a spiral shape extending in the axial direction and having a tip thereof joined to a tip of the heat generating tube and a rear end thereof joined to a tip of the center shaft. A method for manufacturing a glow plug comprising:

  By inserting the insertion portion formed at the tip of the middle shaft into the insertion portion formed at the rear end of the heating coil, the insertion portion and the insertion portion overlap each other in the radial direction. A first step of providing

  A second step of forming a welded portion by welding the inserted portion and the inserted portion by energizing each electrode while holding the overlapping portion in a radial direction by a plurality of electrodes. Prepared,

  Each of the electrodes is arranged so that the heating coil is present at least 1/2 turn between the tip surface of each electrode and the tip position of the overlapping portion.

  In the manufacturing method of the first invention, the overlapping portion and the welded portion are specified in the first and second steps. And between the front-end | tip position of a welding part and the front-end | tip position of an overlap part, a heating coil is made to exist 1/2 turn or more in the state which is not welded with an insertion part.

  In the manufacturing method of the second invention, each electrode and the overlapping portion are specified in the first and second steps. Then, there are 1/2 or more heating coils between the tip surface of each electrode and the tip position of the overlapping portion.

  The second glow plug intermediate obtained by the manufacturing method according to the first and second inventions is welded with 1/2 turn or more from the tip position of the welded portion, even if the deformation of the heating coil becomes large at the tip position of the welded portion. Since no heat generating coil is supported by the insertion portion of the middle shaft, it is possible to prevent the shaft core of the heat generating coil from being bent at the front end side of the front end position of the welded portion.

  For this reason, the glow plug obtained by this second glow plug intermediate increases the current flowing between the electrodes in order to increase the welding strength between the insertion portion of the central shaft and the insertion portion of the heating coil, Even if the welding penetration amount is increased, the heating coil is difficult to come into contact with the inner cylindrical surface of the heating tube, and it is difficult to cause quality defects such as short-circuit defects and variations in energization performance.

  Therefore, according to the method for manufacturing a glow plug of the first and second inventions, it is possible to suppress a quality defect such as a short-circuit defect or a variation in energization performance.

  For this reason, the glow plugs obtained by the manufacturing methods of the first and second inventions can be reduced in diameter, can increase the rate of temperature rise, and can grow glow holes due to demands for miniaturization and weight reduction of diesel engines. It is possible to cope with smaller diameters.

  In addition, the manufacturing method of 1st invention is a method of manufacturing so that an overlapping part and a welding part may satisfy | fill said positional relationship, It is related with the multiple body electrode arrange | positioned around an overlapping part when forming a welding part. Is not stipulated. That is, in manufacturing the second glow plug intermediate body, a welding portion is formed in which the insertion portion of the central shaft and the insertion portion of the heating coil are welded, and the heating coil In this method, the inserted portion is a non-welded portion that only engages with the inserted portion of the middle shaft, so that the middle shaft can support the heating coil from the inside.

  In this way, the electrodes of the welding machine for manufacturing the second glow plug intermediate may be arranged as shown in the manufacturing method of the second invention. If the second glow plug intermediate is manufactured by arranging the electrodes in this manner, the heating coil is not welded to the insertion portion between the distal end position of the welded portion and the distal end position of the overlapping portion, and more than 1/2 turn. A weld is formed to exist. The first manufacturing method places importance on the accuracy of completion of the second glow plug intermediate, whereas the manufacturing method of the second invention can be said to be a manufacturing method that places importance on work efficiency.

  In the method for manufacturing a glow plug according to the first aspect of the present invention, the welded portion is formed between the distal end position of the welded portion and the distal end position of the overlapping portion so that the heating coil does not exist more than three turns without being welded to the insertion portion. It is preferable.

  In the method for manufacturing a glow plug according to the second aspect of the invention, it is preferable that each electrode is arranged so that there are not three or more heating coils between the tip surface of each electrode and the tip position of the overlapping portion.

  In these cases, the effect of the present invention can be achieved without unnecessarily lengthening the unwelded portion in the insertion portion of the central shaft. If the unwelded portion in the insertion portion of the middle shaft is made longer than necessary, the resistance value is likely to fluctuate and the variation in the current-carrying performance increases, which is not preferable.

  In the glow plug manufacturing method of the first and second inventions, the outer diameter of the insertion portion in the overlapping portion is preferably larger than the inner diameter of the insertion portion. In this case, the heat generating coil is easily supported by the inserting portion of the tightened middle shaft, and the axial center of the heat generating coil is further prevented from being bent at the front end side than the welded portion.

  In the method for manufacturing a glow plug according to the first and second inventions, the insertion portion of the central shaft can have a chamfered edge. The insertion portion has a small diameter toward the tip, a first tapered surface that forms at least a part of the overlapping portion, and a diameter that is continuous with the first taper surface toward the tip, and is smaller than the inner diameter of the insertion portion. And a second tapered surface. In this case, in the first step, the operation of inserting the insertion portion of the middle shaft into the insertion portion of the heating coil can be easily performed, and as a result, the work efficiency can be improved.

  In the method for manufacturing a glow plug according to the first and second inventions, the middle shaft has a large-diameter portion adjacent to the rear end of the insertion portion and having an outer diameter equal to or greater than the sum of the inner diameter of the insertion portion and the wire diameter of the heating coil. Is preferably formed. In this case, in the first step, the insertion portion of the middle shaft is inserted into the insertion portion of the heating coil, and the leading end surface of the large-diameter portion is held against the rear end of the heating coil, thereby providing an overlapping portion of a certain length. Work can be performed easily. As a result, work efficiency can be improved.

  The glow plug of the present invention is obtained by the manufacturing method of the present invention. That is, the glow plug of the present invention has a cylindrical metal shell extending in the axial direction and a cylinder extending in the axial direction, the tip of which is closed, and the tip of the metal shell protrudes from the tip of the metal shell. A heat generating tube fixed in the metal shell in a state and a rod-like shape extending in the axial direction, a central shaft whose own tip is located in the heat generating tube and whose rear end protrudes from the rear end of the metal shell And a heating coil having a spiral shape extending in the axial direction, a heating coil in which the tip of the heating tube is joined to the tip of the heating tube, and the rear end of the heating tube is joined to the tip of the center shaft. In the plug,

  The insertion portion formed at the tip of the central shaft is inserted into the insertion portion formed at the rear end of the heat generating coil, so that the insertion portion and the insertion portion overlap each other in the radial direction. A welded portion is formed by welding the insertion portion and the inserted portion at the overlapping portion, and the heating coil is disposed between the tip position of the welding portion and the tip position of the overlapping portion. Is characterized in that there are 1/2 or more turns in a state in which it is not welded to the insertion portion.

  The glow plug of the present invention having such a structure can be reduced in diameter for the reasons described above, can increase the rate of temperature rise, and can be used for a glow hole due to a demand for downsizing and weight reduction of a diesel engine. It is possible to cope with smaller diameters.

  In the present invention, the central shaft may be composed of a plurality of members. When the central shaft is composed of a plurality of members, an insertion portion is formed at the distal end of the distal end side member. When the middle shaft is formed of a single member, an insertion portion is formed at the tip of the member.

  The electrodes are not limited to two bodies and even bodies as long as the overlapping portion can be sandwiched in the radial direction.

  Embodiments 1 and 2 embodying the present invention will be described below with reference to the drawings. In each drawing excluding FIG. 3, the right side is the front end side, and the left side is the rear end side.

  As shown in FIG. 5, the glow plug 1 according to the manufacturing method of the first embodiment is substantially the same as the conventional glow plug 100, and the same reference numerals are given to the same configuration as the conventional mechanical configuration shown in FIG. The description will be omitted.

  This glow plug 1 is manufactured as follows. First, as shown in FIGS. 1 and 2, a heating coil 5 is prepared. The material of the heating coil 5 is a Co—Ni—Fe alloy, Fe alloy, Ni alloy or the like. The heating coil 5 has an inner diameter D1 of 2.6 mm and a wire diameter d of 0.25 mm.

  Also, the first center shaft 8 is prepared. The first middle shaft 8 is a rod-shaped member extending in the direction of the axis O, and is a member on the distal end side among a plurality of members constituting the middle shaft 6. The material of the first middle shaft 8 is, for example, SCM435, and a cylindrical insertion portion 8c is formed at the tip of the first middle shaft 8, and a large diameter portion 8d is formed adjacent to the rear end of the insertion portion. The outer diameter D3 of the insertion portion 8c is 2.65 mm, which is slightly larger than the inner diameter D1 of the heat generating coil 5, and the outer diameter D2 of the large diameter portion 8d is greater than or equal to the sum of the inner diameter D1 of the heat generating coil 5 and the wire diameter d of the heat generating coil 5. Is 2.9 mm. The length L1 in the direction of the axis O between the distal end position A1 of the insertion portion 8c and the distal end surface of the large diameter portion 8d is 1.75 mm.

  Next, as a first step, the insertion portion 8c of the first middle shaft 8 and the insertion portion 5b of the heating coil 5 are inserted by inserting the insertion portion 8c of the first middle shaft 8 into the insertion portion 5b of the heating coil 5. Are overlapped with each other in the radial direction. At this time, the rear end of the heating coil 5 is brought into contact with the front end surface of the large-diameter portion 8d, so that an overlapping portion 10a having a certain length can be provided. That is, the length in the axis O direction of the overlapping portion 10a is always equal to the length L1 in the axis O direction between the distal end position A1 of the insertion portion 8c and the distal end surface of the large diameter portion 8d. Furthermore, since the outer diameter D3 of the insertion portion 8c is slightly larger than the inner diameter D1 of the inserted portion 5b, the heating coil 5 is in a state of tightening the insertion portion 8c. Thus, the first glow plug intermediate 10 is obtained.

  And as a 2nd process, a part of overlapping part 10a of the 1st glow plug intermediate body 10 obtained at the 1st process is clamped with the two electrodes 81 and 82 which mutually oppose. Here, each of the electrodes 81 and 82 is the same as the conventional one, and the length Le in the direction of the axis O is 1.25 mm. On the other hand, the length L1 in the axis O direction between the distal end position A1 of the insertion portion 8c and the distal end surface of the large diameter portion 8d is approximately the same as the length Le of the electrodes 81 and 82 in the axis O direction. It was extended to 1.75 mm. For this reason, the heating coil 5 is set to have a length of 0.5 mm (about 1 turn) between the tip surface B of each electrode 81, 82 and the tip position A1 of the overlapping portion 10a.

  Next, a predetermined load is vertically applied to the overlapping portion 10 a via the electrodes 81 and 82. Here, as shown in FIG. 3, substantially semicircular recesses 81 a and 82 a are provided at portions of the electrodes 81 and 82 that contact the inserted portion 5 b of the heating coil 5. Therefore, when the electrodes 81 and 82 apply a load to the overlapping portion 10a, the electrodes 81 and 82 can be centered with respect to the inserted portion 5b of the heating coil 5, and the load can be easily applied to the overlapping portion 10a. . The electrodes 81 and 82 are connected to the power source 80 via the switch S80. When the switch S80 is turned on and energized between the electrodes 81 and 82, the insertion portion 8c of the first middle shaft 8 and the heating coil 5 are connected. The inserted portion 5b is welded. As a result, as shown in FIGS. 1 and 2, the heating coil 5 is not welded to the insertion portion 8c of the first middle shaft 8 between the tip position C1 of the welded portion 10b and the tip position A1 of the overlapping portion 10a. The welded portion 10b is formed so that there is one turn (length: 0.5 mm). In this way, the second glow plug intermediate body 11 in which the first middle shaft 8 and the heating coil 5 are joined is obtained.

  Here, with respect to the second glow plug intermediate body 11 manufactured by the above-described process, it was evaluated whether the axis of the heating coil 5 was bent on the tip side of the welded portion 10b. Specifically, when the axis of the heating coil 5 is tilted by 3 ° or more with respect to the axis O on the tip side of the welded portion 10b, it was determined that bending occurred. As a result, the bending of the axis of the heating coil 5 did not occur in all of the ten second glow plug intermediate bodies 11.

  On the other hand, the length L1 in the axis O direction between the distal end position A1 of the insertion portion 8c and the distal end surface of the large diameter portion 8d is set to 1.25 mm, which is the same as the length Le in the axis O direction of the electrodes 81 and 82. The second glow plug intermediate body 11 of Comparative Example 1 was manufactured by the above process. And also about the 2nd glow plug intermediate body 11 of the comparative example 1, it was evaluated whether the axial center of the heat generating coil 5 had bent on the front end side rather than the welding part 10b. As a result, the bending of the axis of the heating coil 5 occurred in seven of the ten second glow plug intermediate bodies 11.

  The second glow plug intermediate body 11 of Example 1 and Comparative Example 1 manufactured as described above is assembled with the metal shell 3 and the like as the conventional one shown in FIG. Since the assembly procedure and the like are the same as the conventional one, the description thereof is omitted. The glow plug 1 thus obtained is used for a diesel engine.

  Here, from the viewpoint of process control, the method for manufacturing the glow plug 1 of Example 1 specifies the electrodes 81 and 82 and the overlapping portion 10a in the first and second processes described above. Then, between the front end surface B of each electrode 81, 82 and the front end position A1 of the overlapping portion 10a, about 1 turn of the heating coil 5 is present.

  From the viewpoint of the manufactured product, the method for manufacturing the glow plug 1 of Example 1 specifies the overlapping portion 10a and the welded portion 10b in the first and second steps described above. And between the front-end | tip position C1 of the welding part 10b and the front-end | tip position A1 of the overlap part 10a, about 1 turn of the heat generating coil 5 is made to exist in the state which is not welded with the insertion part 8c.

  For this reason, the second glow plug intermediate body 11 obtained by the manufacturing method of Example 1 is 1/0 from the tip position C1 of the welded part 10b even if the deformation of the heating coil 5 becomes large at the tip position C1 of the welded part 10b. Since the heating coil 5 which is not welded by two or more windings is supported by the insertion portion 8c of the first middle shaft 8, the axial center of the heating coil 5 is prevented from being bent at the tip side from the tip position C1 of the welding portion 10b. Yes.

  For this reason, the glow plug 1 obtained by the second glow plug intermediate body 11 is formed between the electrodes 81 and 82 in order to increase the welding strength between the insertion portion 8c of the first middle shaft 8 and the insertion portion 5b of the heating coil 5. Even if the current to be applied to the heating coil is increased and the welding penetration amount of the heating coil 5 is increased, the heating coil 5 is difficult to contact the inner cylindrical surface of the heating tube 4, and short-circuit failure, variation in current-carrying performance, etc. It is difficult to cause quality defects.

  Therefore, according to the method for manufacturing the glow plug 1 of the first embodiment, it is possible to suppress quality defects such as short-circuit defects and variations in energization performance.

  For this reason, the glow plug 1 obtained by the method for manufacturing the glow plug 1 can be reduced in diameter, can increase the rate of temperature rise, and can grow glow holes due to demands for miniaturization and weight reduction of diesel engines. It is possible to cope with smaller diameters.

  On the other hand, the second glow plug intermediate body 11 of Comparative Example 1 is obtained from the second glow plug intermediate body 11 of Example 1 because the bending of the axis of the heating coil 5 occurs with a probability of 7/10. The glow plug 1 to be used is also not preferable because quality defects such as short-circuit defects and variations in energization performance occur with a certain probability.

  Further, in the method of manufacturing the glow plug 1 according to the first embodiment, the heating coil 5 is not more than 3 turns between the tip surface B of each electrode 81, 82 and the tip position A1 of the overlapping portion 10a. Electrodes 81 and 82 are disposed. In other words, from the viewpoint of the manufactured product, in the method for manufacturing the glow plug 1 of the first embodiment, the heating coil 5 is between the tip position C1 of the welded portion 10b and the tip position A1 of the overlapping portion 10a. A welded portion 10b is formed so that there are no more than three turns in a state where the intermediate shaft 8 is not welded to the insertion portion 8c. For this reason, in this method of manufacturing the glow plug 1, the portion that is not welded in the insertion portion 8c of the first middle shaft 8 is not unnecessarily long, so that the resistance value is difficult to vary while achieving the effects of the present invention. Also, the variation in energization performance can be reduced.

  Further, in the method for manufacturing the glow plug 1, the outer diameter D3 of the insertion portion 8c in the overlapping portion 10a is larger than the inner diameter D1 of the inserted portion 5b, so that the heating coil 5 is inserted into the tightened first middle shaft 8. It becomes easy to be supported by the part 8c, and it is further prevented that the axial center of the heating coil 5 bends in the front end side rather than the welding part 10b.

  In the method for manufacturing the glow plug 1, the first middle shaft 8 is adjacent to the rear end of the insertion portion 8 c and is an outer diameter that is equal to or greater than the sum of the inner diameter D 1 of the insertion portion 5 b and the wire diameter d of the heating coil 5. A large diameter portion 8d having a diameter D2 is formed. For this reason, in the first step, the insertion portion 8c of the first middle shaft 8 is inserted into the inserted portion 5b of the heating coil 5, and the front end surface of the large diameter portion 8d is held against the rear end of the heating coil 5, The operation of providing the overlapping portion 10a having a certain length can be easily performed. As a result, work efficiency can be improved.

  The glow plug 1 according to the second embodiment is manufactured by using a cylindrical surface 8f adjacent to the front end side of the cylindrical surface 8f instead of the insertion portion 8c of the first central shaft 8 described in the method for manufacturing the glow plug 1 according to the first embodiment. An insertion portion 8e having a first tapered surface 8g and a second tapered surface 8h adjacent to the distal end side of the first tapered surface 8g is employed. Since other configurations are the same as those of the method for manufacturing the glow plug 1 of the first embodiment, description thereof is omitted.

  The first tapered surface 8g has a smaller diameter toward the tip, and forms at least a part of the overlapping portion 12a. Since the outer diameter D4 of the tip of the first tapered surface 8g is made equal to the inner diameter D1 of the inserted portion 5b, the tip position A2 of the overlapping portion 12a is the tip of the first tapered surface 8g. For this reason, when the insertion portion 8e of the first middle shaft 8 is inserted into the insertion portion 5b of the heating coil 5, the first tapered surface 8g acts to guide the insertion portion 8e into the heating coil 5. The length L2 in the direction of the axis O between the tip position A2 of the overlapping portion 12a and the tip surface of the large diameter portion 8d is 2.25 mm.

  The second tapered surface 8h has a smaller diameter toward the tip continuously with the first tapered surface 8g, and is smaller than the inner diameter D1 of the inserted portion 5b. For this reason, the operation | work which inserts the front-end | tip of the insertion part 8e of the 1st center shaft 8 in the to-be-inserted part 5b of the heat generating coil 5 becomes still easier.

  In the method of manufacturing the glow plug 1 of Example 2 having the insertion portion 8e of the first middle shaft 8 as described above, the first glow plug intermediate body 12 provided with the overlapping portion 12a is obtained in the first step.

  In the second step, a part of the overlapping portion 12a of the first glow plug intermediate body 12 obtained in the first step is sandwiched between two electrodes 81 and 82 facing each other. Here, each of the electrodes 81 and 82 is the same as the conventional one, and the length Le in the direction of the axis O is 1.25 mm. On the other hand, the length L2 in the axis O direction between the tip position A2 of the overlapping portion 12a and the tip surface of the large diameter portion 8d is approximately the same as the length Le of the electrodes 81 and 82 in the axis O direction. However, it was further extended to 2.25 mm. Therefore, the heating coil 5 is set to have a length of 1.0 mm (about 2 turns) between the tip surface B of each electrode 81, 82 and the tip position A2 of the overlapping portion 12a.

  Next, the overlapping portion 12a is welded by the electrodes 81 and 82 in the same manner as in the method for manufacturing the glow plug 1 of the second embodiment. As a result, there are about two turns (length 1.0 mm) between the tip position C2 of the welded portion 12b and the tip position A2 of the overlapping portion 12a in a state where the heating coil 5 is not welded to the insertion portion 8e of the first middle shaft 8. Thus, the welded portion 12b is formed. In this way, the second glow plug intermediate body 13 in which the first middle shaft 8 and the heating coil 5 are joined is obtained.

  The second glow plug intermediate 13 is also the glow plug 1 in the same manner as the second glow plug intermediate 11 of the first embodiment.

  Here, from the viewpoint of process management, the method for manufacturing the glow plug 1 of Example 2 specifies the electrodes 81 and 82 and the overlapping portion 12a in the first and second processes described above. Then, between the front end surface B of each electrode 81, 82 and the front end position A2 of the overlapping portion 12a, about two turns of the heating coil 5 are present.

  Further, from the viewpoint of the manufactured product, the method for manufacturing the glow plug 1 of Example 2 specifies the overlapping portion 12a and the welded portion 12b in the first and second steps described above. Then, between the distal end position C2 of the welded portion 12b and the distal end position A2 of the overlapping portion 12a, about two turns of the heating coil 5 are present without being welded to the insertion portion 8e.

  For this reason, the second glow plug intermediate body 13 obtained by the manufacturing method of the second embodiment also has the axial core of the heating coil 5 for the same reason as the second glow plug intermediate body 11 obtained by the manufacturing method of the first embodiment. Bending at the tip side of the welded portion 12b is prevented.

  For this reason, the glow plug 1 obtained by the second glow plug intermediate body 13 is also less likely to cause a quality defect such as a short-circuit defect or a variation in energization performance.

  Therefore, even with the method for manufacturing the glow plug 1 according to the second embodiment, it is possible to suppress quality defects such as short-circuit defects and variations in energization performance.

  Further, in the method for manufacturing the glow plug 1, the insertion portion 8e of the first middle shaft 8 has the first tapered surface 8g and the second tapered surface 8h in addition to the cylindrical surface 8f. For this reason, in the first step, the operation of inserting the insertion portion 8e of the first middle shaft 8 into the inserted portion 5b of the heating coil 5 can be easily performed, and as a result, the work efficiency can be improved. Is done.

  In the above, the present invention has been described with reference to the first and second embodiments. However, the present invention is not limited to the first and second embodiments, and can be appropriately modified and applied without departing from the spirit of the present invention. Needless to say.

  For example, the heat generating coil is not limited to the case where the heat generating coil is composed of one material as in the heat generating coil 5 of the first and second embodiments, and is made of a plurality of materials having different resistance temperature coefficients (so-called control coil and heat generating coil). May have a self-control function).

  The inner diameter D1 of the heating coil 5 described in the first and second embodiments may be at least the inner diameter D1 in the inserted portion 5b of the heating coil 5, and the inner diameter other than the inserted portion 5b may be larger than D1. .

  The present invention is applicable to a glow plug.

FIG. 6 is a schematic diagram showing first and second steps in the method for manufacturing a glow plug of Example 1. FIG. 6 is an enlarged schematic view of the main part showing the first and second steps in the method for manufacturing the glow plug of Example 1. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 1 according to the method for manufacturing the glow plug of the first embodiment. FIG. 6 is a schematic diagram showing first and second steps in a method for manufacturing a glow plug of Example 2. It is sectional drawing of a glow plug in connection with the manufacturing method of the conventional glow plug. It is a schematic diagram which shows the 1st, 2nd process in connection with the manufacturing method of the conventional glow plug. It is a principal part expansion schematic diagram which shows the 1st, 2nd process in connection with the manufacturing method of the conventional glow plug.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,100 ... Glow plug 3 ... Main metal fitting 4 ... Heat generating tube 4a ... The tip of a heat generating tube 5 ... Heat generating coil 5a ... The tip of a heat generating coil 5b ... Insertion part of a heat generating coil 6 ... Middle shaft 8 ... 1st center shaft 9 ... 2nd Middle shaft 8a, 8c, 8e ... Middle shaft insertion portion 8d ... Large diameter portion 8f ... Cylindrical surface 8g ... First taper surface 8h ... Second taper surface 10a, 12a, 90a ... Overlapping portion 10b, 12b, 90b ... Welded portion 80 ... Power source S80 ... Switch 81, 82 ... Electrodes A, A1, A2 ... End position of overlapping part B ... End face of electrode C, C1, C2 ... End position of welded part D1 ... Inner diameter of inserted part D2 ... Of large diameter part Outer diameter D3 ... Outer diameter of insertion part D4 ... Outer diameter of tip of first taper surface d ... Wire diameter of heating coil

Claims (8)

A cylindrical metal shell extending in the axial direction and a cylinder extending in the axial direction, the tip of itself is closed, and the tip of the metal shell is protruded from the tip of the metal shell and is fixed in the metal shell. A heat generating tube, a rod shape extending in the axial direction, a tip end of which is located in the heat generating tube, a rear shaft projecting from the rear end of the metal shell, and a spiral shape extending in the axial direction A glow plug manufacturing method comprising a heating coil having its own tip joined to the tip of the heating tube in the heating tube and its rear end joined to the tip of the middle shaft,
By inserting the insertion portion formed at the tip of the middle shaft into the insertion portion formed at the rear end of the heating coil, the insertion portion and the insertion portion overlap each other in the radial direction. A first step of providing
A second step of forming a welded portion by welding the inserted portion and the inserted portion by energizing each electrode while holding the overlapping portion in a radial direction by a plurality of electrodes. Prepared,
The welded portion is formed between the tip position of the welded portion and the tip position of the overlapping portion so that the heat generating coil is present at least 1/2 turn without being welded to the insertion portion. Manufacturing method for glow plugs.   2. The glow according to claim 1, wherein the welded portion is formed between the distal end position of the welded portion and the distal end position of the overlapping portion so that the heating coil does not exist in three or more turns without being welded to the insertion portion. Plug manufacturing method. A cylindrical metal shell extending in the axial direction and a cylinder extending in the axial direction, the tip of itself is closed, and the tip of the metal shell is protruded from the tip of the metal shell and is fixed in the metal shell. A heat generating tube, a rod shape extending in the axial direction, a tip end of which is located in the heat generating tube, a rear shaft projecting from the rear end of the metal shell, and a spiral shape extending in the axial direction A glow plug manufacturing method comprising a heating coil having its own tip joined to the tip of the heating tube in the heating tube and its rear end joined to the tip of the middle shaft,
By inserting the insertion portion formed at the tip of the middle shaft into the insertion portion formed at the rear end of the heating coil, the insertion portion and the insertion portion overlap each other in the radial direction. A first step of providing
A second step of forming a welded portion by welding the inserted portion and the inserted portion by energizing each electrode while holding the overlapping portion in a radial direction by a plurality of electrodes. Prepared,
A method for manufacturing a glow plug, characterized in that each of the electrodes is arranged so that the heat generating coil is ½ or more turns between the tip surface of each electrode and the tip position of the overlapping portion.   The method for manufacturing a glow plug according to claim 3, wherein each of the electrodes is arranged so that there are not three or more turns of the heating coil between a tip surface of each of the electrodes and a tip position of the overlapping portion.   The glow plug manufacturing method according to claim 1, wherein an outer diameter of the insertion portion in the overlapping portion is larger than an inner diameter of the insertion portion.   The insertion portion has a small diameter toward the tip, a first tapered surface that forms at least a part of the overlapping portion, and a small diameter toward the tip continuously with the first taper surface, and an inner diameter of the inserted portion. The method for manufacturing a glow plug according to claim 5, further comprising a second tapered surface having a smaller diameter.   The large diameter part which has an outer diameter which adjoins the rear end of the said insertion part and has the outer diameter which is more than the sum total of the internal diameter of the said to-be-inserted part, and the wire diameter of this heat generating coil is formed in the said center shaft. 6. A method for producing a glow plug according to 6. A cylindrical metal shell extending in the axial direction and a cylinder extending in the axial direction, the tip of itself is closed, and the tip of the metal shell is protruded from the tip of the metal shell and is fixed in the metal shell. A heat generating tube, a rod shape extending in the axial direction, a tip end of which is located in the heat generating tube, a rear shaft projecting from the rear end of the metal shell, and a spiral shape extending in the axial direction A glow plug having a heating coil in which the tip of the heating tube is joined to the tip of the heating tube in the heating tube, and the rear end of the heating tube is joined to the tip of the center shaft,
The insertion portion formed at the tip of the central shaft is inserted into the insertion portion formed at the rear end of the heat generating coil, so that the insertion portion and the insertion portion overlap each other in the radial direction. A welded portion is formed by welding the insertion portion and the inserted portion at the overlapping portion, and the heating coil is disposed between the tip position of the welding portion and the tip position of the overlapping portion. The glow plug is characterized in that there are 1/2 or more turns in a state where the insertion is not welded to the insertion portion.

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