JP4890901B2 - Glow plug and manufacturing method thereof - Google Patents

Description

  The present invention relates to a glow plug used for assisting starting a diesel engine and the like, and a method of manufacturing the same.

  Conventionally, glow plugs used to assist in starting diesel engines have a metallic metallic shell made of metal, and project the tip of a rod-shaped heater held at the tip end in the shaft hole. ing. Further, a metal rod-shaped central shaft protrudes from the rear end side of the metal shell, and is held in the shaft hole while being insulated from the metal shell. Both electrodes for energizing the heater are electrically connected to the metal shell and the central shaft, respectively.

  In recent years, diesel engines using glow plugs with such a structure are shifting to direct-injection diesel engines instead of conventional sub-chamber type diesel engines due to demands for smaller size, higher fuel consumption, higher output, etc. . Along with this, the mounting structure to the engine may be changed, and the glow plug is required to have a smaller diameter or a longer length. Further, ceramic heaters with high corrosion resistance are often used for glow plugs.

  By the way, if the total length of the central shaft is increased with the increase in the length of the glow plug, the natural frequency of the central shaft is lowered. As a result, the frequency of the vibration load generated with the operation of the diesel engine increases the chance of matching the natural frequency of the central shaft, and resonance may occur frequently. If resonance occurs, a portion corresponding to the antinode of the center shaft may come into contact with the inner peripheral surface of the metal shell and insulation may not be maintained. Moreover, if the amplitude becomes large, the bending of the central shaft also becomes large, and there is a possibility of breaking. Furthermore, there is a possibility that the ceramic heater disposed on the tip side of the middle shaft may be damaged by internal stress transmitted from the middle shaft.

  Therefore, a tube-shaped flexible member (insulating coating) is attached to the center shaft (lead member) to prevent short-circuiting due to contact between the center shaft and the metal shell, and a glow that restricts the amplitude of the vibration of the center shaft due to resonance. A plug has been proposed (see, for example, Patent Document 1). When a flexible member is attached to the central shaft in this way, in order to suppress resonance of the central shaft, the clearance between the outer peripheral surface of the flexible member and the inner peripheral surface of the metal shell should be designed to be smaller. Is effective.

However, in the case of a glow plug designed to have a small clearance as described above, when a flexible member is inserted between the center shaft in the shaft hole of the metal shell after the middle shaft is manufactured, the insertion of the flexible member It gets caught inside and takes time to insert. Therefore, the glow plug is assembled in the order of steps in which a flexible member is attached to the center shaft in advance and the center shaft is inserted into the shaft hole of the metal shell.
Japanese Patent Laid-Open No. 11-2406

  However, when inserting the middle shaft with the flexible member as described above into the shaft hole of the metal shell, the outer peripheral surface of the flexible member comes into contact with the inner surface of the shaft hole of the metal shell, and the drag is reduced. If it is received and misalignment occurs, the flexible member may not be arranged at a desired position. In addition, the metal shell is joined to the holding member that holds the heater member on the tip end side of the shaft hole. However, if the end of the flexible member is caught in the joining position, there is a risk of causing poor joining. It was.

  The present invention has been made to solve the above problems, and in the manufacturing process, when the center shaft is inserted into the shaft hole of the metal shell, preventing the displacement of the flexible member attached to the center shaft, It is an object of the present invention to provide a glow plug and a method for manufacturing the same that can prevent the occurrence of defective joining of the metal shell.

In order to achieve the above object, a glow plug according to a first aspect of the present invention includes a central shaft extending along the axial direction, a heater member having a heating element that generates heat when energized, and a shaft hole. The central shaft is inserted through the metal shell, the metal shell that holds the heater member on its tip side, and a cylinder that is interposed between the central shaft and the shaft hole and that can be inserted into the central shaft and is flexible. in the glow plug with a variable Shiwasei member that have a gender, an outer diameter of said flexible member, said shaft is formed smaller than the inner diameter of the hole of the metal shell, the outer peripheral surface of the middle axle In addition, a locking portion for locking the inner peripheral surface of the flexible member is formed.

  According to a second aspect of the present invention, in the glow plug according to the second aspect of the invention, in addition to the configuration of the first aspect, the locking portion is an end portion on the side where the heater member is disposed in the axial direction of the central shaft. It is formed in the outer peripheral surface of the one end part which is.

According to a third aspect of the present invention, there is provided a glow plug manufacturing method comprising: a holding member that holds the heater member in a radial direction; and the holding member is joined to the front end side of the metal shell. a method of manufacturing a glow plug according to the flexible member, the center shaft of the first intermediate fixing the heater member held in the holding member to the inner shaft, one end of the center shaft A flexible member that is inserted from the other end side opposite to the side of the flexible member and that has an opening end on the side where the middle shaft of the flexible member is inserted is located closer to the heater member than the locking portion of the middle shaft An insertion step, and the intermediate shaft of the second intermediate body, in which the flexible member is inserted through the intermediate shaft of the first intermediate body, is inserted into the shaft hole of the metal shell from the other end side of the intermediate shaft. The metal shell insertion step to be performed, and the locking portion of the middle shaft In over data member side, and a welding step of welding the metal shell and the holding member of the second intermediate.
According to a fourth aspect of the present invention, there is provided a glow plug manufacturing method comprising: a middle shaft extending along an axial direction; a heater member having a heating element that generates heat when energized; a shaft hole; Is inserted, and a metal shell for holding the heater member on its front end side, a tube-like flexible member interposed between the middle shaft and the shaft hole and having flexibility, A holding member that holds the heater member in the radial direction, and a locking portion that locks the inner peripheral surface of the flexible member is formed on the outer peripheral surface of the central shaft, and the holding member is the metal shell The glow plug joined at the distal end side of the first intermediate body, the intermediate shaft of the first intermediate body in which the heater member held by the holding member is fixed to the flexible shaft, Inserted from the other end side opposite to one end of the middle shaft A flexible member insertion step of disposing an opening end of the flexible member on the side where the middle shaft is inserted closer to the heater member than the locking portion of the middle shaft, and the middle shaft of the first intermediate body A metal shell insertion step of inserting the middle shaft of the second intermediate body into which the flexible member is inserted into the shaft hole of the metal shell from the other end side of the middle shaft; and the engagement of the middle shaft A welding step of welding the holding member of the second intermediate body and the metal shell closer to the heater member than the stopper.

  In the glow plug of the invention according to claim 1, since the inner peripheral surface of the flexible member can be locked to the locking portion formed on the outer peripheral surface of the middle shaft, the flexible member is manufactured in the process of manufacturing the glow plug. When the middle shaft with the metal member is inserted into the shaft hole of the metal shell, the flexible member remains in contact with the inner surface of the shaft hole of the metal shell, The position is not displaced. In particular, in a glow plug in which a heater member is held by a holding member, and the holding member is joined and integrated with the metal shell, the metal shell and the holding member are not provided if the flexible member is not displaced as described above. The flexible member is not caught at the joining position, and the occurrence of poor joining can be reliably prevented.

  And if the latching | locking part is formed in the outer peripheral surface of the one end part of a center axis | shaft like the invention which concerns on Claim 2, a center axis | shaft will be in a flexible member from the other end part side on the opposite side to the one end part of a center axis | shaft. When inserted, there is no insertion resistance due to the locking portion until one end of the flexible member contacts the flexible member, and the middle shaft can be easily inserted into the flexible member.

In the method for manufacturing a glow plug according to the third aspect of the present invention, in the flexible member insertion step, the intermediate shaft is inserted into the flexible member in advance, and the flexible member is locked to its own locking portion. Then, in the metal shell insertion step, the central shaft on which the flexible member is mounted is inserted into the shaft hole of the metal shell, so that the flexible member has its own outer peripheral surface and the inner peripheral surface of the shaft hole of the metal shell. Even when the drag generated by the contact is received, the locking portion prevents the displacement of the flexible member. In the subsequent welding process, the metal shell and the holding member are welded. However, if there is no displacement of the flexible member, the flexible member will not be caught at the joint position between the two, so that the joint failure will not occur. Occurrence can be reliably prevented.
In the glow plug manufacturing method of the invention according to claim 4, in the flexible member insertion step, the middle shaft is inserted into the flexible member in advance, and the flexible member is locked to its own locking portion. Then, in the metal shell insertion step, the central shaft on which the flexible member is mounted is inserted into the shaft hole of the metal shell, so that the flexible member has its own outer peripheral surface and the inner peripheral surface of the shaft hole of the metal shell. Even when the drag generated by the contact is received, the locking portion prevents the displacement of the flexible member. In the subsequent welding process, the metal shell and the holding member are welded. However, if there is no displacement of the flexible member, the flexible member will not be caught at the joint position between the two, so that the joint failure will not occur. Occurrence can be reliably prevented. In particular, in a method for manufacturing a glow plug in which a heater member is held by a holding member, and the holding member is joined to and integrated with the metal shell, the metal shell is free from displacement as described above. The flexible member is not caught at the joining position between the holding member and the holding member, and it is possible to reliably prevent the occurrence of poor bonding.

  Hereinafter, an embodiment of a glow plug embodying the present invention and a manufacturing method thereof will be described with reference to the drawings. First, an overall structure of a glow plug 100 as an example will be described with reference to FIG. FIG. 1 is a longitudinal sectional view of the glow plug 100. FIG. 2 is an enlarged perspective view of the vicinity of the tip 31 of the middle shaft 30. Note that the side where the ceramic heater 20 is disposed (the lower side in FIG. 1) in the direction of the axis O will be described as the tip side of the glow plug 100.

  A glow plug 100 shown in FIG. 1 is attached to a combustion chamber (not shown) of a direct injection diesel engine, for example, and is used as a heat source for assisting ignition at the time of engine start. The glow plug 100 generally includes a central shaft 30, a ceramic heater 20 having a heating element 27, a cylindrical body 80 that holds the ceramic heater 20 in the radial direction, and the central shaft 30 inserted into a shaft hole 43. Is composed of a metal shell 40 joined to the cylindrical body 80 and a tube 90 interposed between the central shaft 30 and the metal shell 40.

  First, the ceramic heater 20 will be described. The ceramic heater 20 has a round bar shape, and a heating element 24 having a substantially U-shaped cross section made of a conductive ceramic is embedded in a base 21 made of an insulating ceramic whose tip 22 is hemispherically curved. Have The heating element 24 is disposed at the tip 22 of the ceramic heater 20 and is connected to the heating element 27 whose both ends are folded back in a substantially U shape in accordance with the curved surface thereof, and to both ends of the heating element 27, respectively. And lead portions 28 and 29 extending substantially in parallel along the axis O toward the rear end portion 23. The heating element 27 is shaped so that its cross-sectional area is smaller than the cross-sectional area of the lead portions 28 and 29, and heat is generated mainly in the heating element 27 during energization. Further, on the outer peripheral surface on the rear end side from the center of the ceramic heater 20, electrode extraction portions 25 and 26 protruding from the lead portions 28 and 29 are exposed at positions shifted from each other in the axis O direction. . The ceramic heater 20 corresponds to the “heater member” in the present invention.

  Next, the cylindrical body 80 will be described. The cylindrical body 80 is formed of a cylindrical metal member extending in the direction of the axis O, and holds the body portion of the ceramic heater 20 in the radial direction in its own cylindrical hole 84, and the front end portion 22 and the rear end portion 23 are respectively provided. The cylindrical hole 84 is exposed from both ends. The cylindrical body 80 is formed with a collar portion 82 thicker than the trunk portion 81 on the rear end side of the trunk portion 81, and further, at the rear end thereof, the metallic shell 40 for joining with a metallic shell 40 described later. A step-like engaging portion 83 is formed to engage with the inner periphery of the distal end portion 41. Of the electrode extraction portions 25 and 26 of the ceramic heater 20, the electrode extraction portion 25 formed on the distal end side is in contact with the inner peripheral surface of the cylindrical hole 84 of the cylindrical body 80, and the electrode extraction portion 25 and the cylindrical body are in contact with each other. 80 is electrically connected. Further, a metal-made cylindrical connection ring 75 is fitted to the rear end portion 23 of the ceramic heater 20 exposed rearward from the engaging portion 83 of the cylindrical body 80. The electrode extraction part 26 of the ceramic heater 20 is in contact with the inner peripheral surface of the connection ring 75, and the electrode extraction part 26 and the connection ring 75 are electrically connected. And the front-end | tip part 41 of the metal shell 40 is joined to the engaging part 83 of the cylindrical body 80, and the metal shell 40 and the cylindrical body 80 are electrically connected. At this time, the rear end portion 23 and the connection ring 75 of the ceramic heater 20 are disposed in the metal shell 40. However, the ceramic heater 20 and the metal shell 40 are respectively positioned on the cylindrical body 80, and the metal shell 40 and the connection ring are positioned. Since 75 is maintained in a non-contact state, both are electrically insulated. The cylindrical body 80 corresponds to the “holding member” in the present invention.

  Next, the metal shell 40 will be described. The metal shell 40 is a long and thin cylindrical metal member having a shaft hole 43 penetrating in the direction of the axis O, and a glow plug 100 is attached to the engine head (not shown) of the internal combustion engine on the rear end side of the body portion 44. A male screw portion 42 is formed. In addition, a tool engaging portion 46 is formed at the rear end of the body portion 44 so as to engage with a tool used for attachment to the engine head. In the present embodiment, the tool engaging portion 46 has a hexagonal cross section, and a diameter-enlarged portion 45 in which the diameter of the shaft hole 43 is increased is formed in the tool engaging portion 46. On the other hand, the front end portion 41 of the metal shell 40 is engaged with the outer periphery of the engaging portion 83 of the cylindrical body 80 described above, and the joint portion of both is laser-welded from the outer periphery. 40 and the cylindrical body 80 are joined together.

  Next, the middle shaft 30 will be described. The middle shaft 30 is a metal rod extending in the direction of the axis O, and is inserted into the shaft hole 43 of the metal shell 40. A thin diameter portion 33 having a reduced outer diameter is formed on the distal end side of the middle shaft 30. Further, a small-diameter engaging portion 34 is formed at the distal end portion 31 on the distal end side with respect to the small-diameter portion 33 so as to engage with the inner periphery of the connection ring 75. By engaging the engagement portion 34 with the connection ring 75, the ceramic heater 20 and the middle shaft 30 are integrally coupled along the axis O via the connection ring 75. In addition, as for the front-end | tip part 31 of the center axis | shaft 30, and the connection ring 75, the joint part of both is welded by the laser from the outer periphery. Thereby, the middle shaft 30 is electrically connected to the electrode extraction portion 26 of the ceramic heater 20 via the connection ring 75. As described above, since the ceramic heater 20 and the metal shell 40 are respectively positioned on the cylindrical body 80, the middle shaft 30 and the metal shell 40 are maintained in a non-contact state within the shaft hole of the metal shell 40 and are electrically connected. Is electrically insulated.

  Further, an insulating O-ring 70 is fitted to the rear end portion 32 of the middle shaft 30 and is arranged in contact with a tapered surface 47 formed on the front end side in the enlarged diameter portion 45 of the metal shell 40. . Further, an insulating support ring 60 is fitted to the rear end portion 32 to position the middle shaft 30 in the enlarged diameter portion 45 and press the O-ring 70 toward the front end side in the axis O direction. Thereby, the O-ring 70 is in contact with each of the outer peripheral surface of the intermediate shaft 30, the tapered surface 47 of the enlarged diameter portion 45, and the tip surface of the support ring 60, and the airtightness inside and outside the shaft hole 43 is maintained. Further, a hook-like flange 61 is provided on the rear end side of the support ring 60, and this flange 61 abuts against the rear end surface of the tool engaging portion 46, and a pin terminal 50, a metal shell 40, which will be described later, Both are insulated by interposing between them.

  Next, the pin terminal 50 is fitted into a portion of the rear end portion 32 of the middle shaft 30 that protrudes to the rear end side from the flange portion 61 of the support ring 60. The pin terminal 50 includes a cap-shaped body portion 52 that covers and covers the rear end portion 32 of the intermediate shaft 30, a pin-shaped protrusion portion 53 that protrudes from the body portion 52 toward the rear end side, and a front end side of the body portion 52. It is comprised from the collar part 51 protrudingly provided by radial direction. The pin terminal 50 is fixed to the rear end portion 32 of the middle shaft 30 by crimping the outer periphery of the body portion 52, and the pin terminal 50 and the middle shaft 30 are electrically connected. When the glow plug 100 is attached to the engine head (not shown), a plug cap (not shown) is fitted to the protrusion 53, and power is supplied from an external circuit.

  Next, the tube 90 will be described. The tube 90 is a flexible member made of insulating silicon and has a cylindrical shape. The inner diameter of the tube 90 is substantially the same as or slightly smaller than the outer diameter of the intermediate shaft 30, and the outer diameter is smaller than the inner diameter of the shaft hole 43 of the metal shell 40. As will be described later, the tube 90 is attached to the intermediate shaft 30, and the distal end portion 91 of the tube 90 is engaged with the engagement portion 35 (see FIG. 2) of the distal end portion 31 of the intermediate shaft 30. Further, the rear end portion 92 of the tube 90 extends to the vicinity of the rear end portion 32 of the middle shaft 30, and the outer periphery of the middle shaft 30 excluding a part of the front end portion 31 and the rear end portion 32 is covered by the tube 90. Yes. The tube 90 is interposed in the clearance between the outer peripheral surface of the middle shaft 30 and the inner peripheral surface of the shaft hole 43 of the metal shell 40, prevents contact between the middle shaft 30 and the metal shell 40, and resonates with the middle shaft 30 due to resonance. The amplitude of the vibration belly is limited. The tube 90 corresponds to a “flexible member” in the present invention.

  By the way, the center shaft 30 of the glow plug 100 of the present embodiment having the above-described structure is connected to the ceramic heater 20 whose tip 31 is press-fitted into a cylindrical body 80 joined to the metal shell 40. It is fixed by. On the other hand, the rear end portion 32 is supported by the support ring 60 and the O-ring 70 in the shaft hole 43 (in the enlarged diameter portion 45) at the rear end of the metal shell 40, but is not fixed. Therefore, when the glow plug 100 is attached to the engine head (not shown), the weight of the plug cap fitted to the pin terminal 50 fixed to the rear end portion 32 of the middle shaft 30 and the cord connected to the plug cap Is supported by the middle shaft 30, there is a possibility that the middle shaft 30 may be broken by an impact caused by external vibration such as engine vibration on the middle shaft 30. Therefore, in the present embodiment, the outer diameter of the middle shaft 30 is configured to be 70% or more of the inner diameter of the shaft hole 43 of the metal shell 40. As an example, in the glow plug 100 of the present embodiment, the inner diameter of the shaft hole 43 of the metal shell 40 is configured as Φ5.4, and the outer diameter of the middle shaft 30 is configured as Φ4.0.

  In the glow plug 100 having such a structure, in the manufacturing process, the intermediate shaft 30 is inserted into the tube 90 and the tube 90 is attached to the intermediate shaft 30, and then the intermediate shaft 30 is inserted into the shaft hole 43 of the metal shell 40. It is inserted. At this time, the outer peripheral surface of the tube 90 and the inner peripheral surface of the shaft hole 43 of the metal shell 40 come into contact with each other, and the tube 90 that has received the drag may be displaced with respect to the middle shaft 30. In order to prevent the displacement of the tube 90, in the present embodiment, a knurled locking portion 35 shown in FIG. 2 is provided on the outer peripheral surface of the distal end portion 31 of the center shaft 30 over the entire circumference. The tube 90 is fixed to the middle shaft 30 by the distal end portion 91 of the tube 90 being locked to the locking portion 35. The tip 31 of the middle shaft 30 corresponds to the “one end” in the present invention.

  Next, a method for manufacturing the glow plug 100 will be described with reference to FIGS. 3 and 4 are diagrams schematically showing the manufacturing process of the glow plug 100. FIG.

[Heater formation process]
As shown in FIG. 3, first, an element molded body 251 that is an original shape of the heating element 24 of the ceramic heater 20 is formed by injection molding using a conductive ceramic powder, a binder, or the like as a raw material. On the other hand, the base body molded body 252 that is the original form of the base body 21 is molded into two parts by performing die press molding using an insulating ceramic powder as a raw material and having a concave portion in which the element molded body 251 is accommodated on its mating surface. Form as. The element molded body 251 is accommodated in the concave portion of the base molded body 252 and subjected to press compression, and then subjected to a baking process such as binder removal processing and hot pressing, and the outer peripheral surface thereof is formed into a hemispherical rod shape. The ceramic heater 20 is formed by polishing and shaping.

[Heater press-fitting process]
Next, the connection ring 75 forms a steel material such as stainless steel into a pipe shape, and press-fits the ceramic heater 20 from the front end portion 22 side to make the electrode extraction portion 26 conductive. Similarly, the cylindrical body 80 is also formed into a predetermined shape, and is press-fitted into the ceramic heater 20 from the tip end portion 22 side so as to make the electrode extraction portion 25 conductive. In order to stabilize electrical continuity, plating such as Au or Cu may be performed.

[Center shaft engagement process]
The middle shaft 30 is formed by performing plastic working, cutting, or the like on a rod-shaped member made of an iron-based material (for example, Fe—Cr—Mo steel) cut to a certain size. Then, the engaging portion 34 provided at the distal end portion 31 of the middle shaft 30 on the inner periphery of the connecting ring 75 of the heater integrated member 250 in which the ceramic heater 20 and other members (the cylindrical body 80 and the connecting ring 75) are integrated. The outer periphery is engaged.

[Center shaft joining process]
Then, a laser beam is irradiated from the outer periphery to the joint portion between the distal end portion 31 of the middle shaft 30 and the connection ring 75 and welded to obtain a middle shaft integrated member 260 in which the middle shaft 30 and the heater integrated member 250 are integrally joined. The central shaft integral member 260 corresponds to the “first intermediate body” in the present invention.

[Tube insertion process]
Next, as shown in FIG. 4, insulative silicon is formed into a cylindrical shape by extrusion molding, and a tube 90 is obtained by cutting into a predetermined dimension. The middle shaft 30 of the middle shaft integrated member 260 is inserted into the tube 90 from the rear end portion 32 side. At this time, by moving the tube 90 until the opening end 95 on the distal end portion 91 side of the tube 90 is positioned on the distal end side with respect to the locking portion 35, the inner peripheral surface of the distal end portion 91 of the tube 90 is moved to the middle shaft 30. It is made to latch on the latching part 35 formed in the outer peripheral surface of the front-end | tip part 31. In this way, the tube 90 is attached to the middle shaft 30 to obtain the tube integrated member 270 in which the middle shaft integrated member 260 and the tube 90 are integrated. The tube insertion process corresponds to the “flexible member insertion process” in the present invention, and the tube integrated member 270 corresponds to the “second intermediate body” in the present invention. Further, the rear end portion 32 of the middle shaft 30 corresponds to the “other end portion” in the present invention.

[Fitting engagement process]
Next, a cylindrical metal shell 40 having a tool engaging portion 46 and the like formed from an iron-based material such as S45C is formed, and a thread is rolled on the male screw portion 42. The central shaft 30 of the tube integrated member 270 is inserted into the shaft hole 43 of the metal shell 40 from the rear end portion 32 side. At this time, the outer peripheral surface of the tube 90 attached to the middle shaft 30 comes into contact with the inner peripheral surface of the metal shell 40, receives drag, and the tube 90 is pressed toward the distal end portion 31 side of the middle shaft 30. However, since the inner peripheral surface of the distal end portion 91 of the tube 90 is locked to the locking portion 35 of the distal end portion 31 of the middle shaft 30, the tube 90 is not displaced with respect to the middle shaft 30. And the inner periphery of the front-end | tip part 41 of the metal shell 40 is engaged with the outer periphery of the engaging part 83 of the cylindrical body 80, and the tube 90 is between the inner peripheral surface of the metal shell 40 and the outer peripheral surface of the center shaft 30. It will be interposed in the clearance. Since the clearance is reduced by interposing the tube 90, the amplitude when the central shaft 30 resonates can be effectively limited. The fitting engagement process corresponds to the “metal fitting insertion process” in the present invention.

[Metal fitting process]
Then, laser welding is performed by irradiating a laser beam from the outer periphery to the joint portion of the metal shell 40 and the cylindrical body 80, and the cylindrical body 80 and the metal shell 40 of the tube integrated member 270 are joined together. In order to avoid the metal shell 40, which is an iron-based material, from being rusted, a rust prevention treatment such as plating or painting may be performed after joining the cylindrical body 80. The metal fitting joining process corresponds to the “welding process” in the present invention.

[Terminal assembly process]
Thereafter, the O-ring 70 and the support ring 60 are engaged with the rear end portion 32 of the middle shaft 30 and accommodated in the enlarged diameter portion 45 of the metal shell 40. Further, the pin terminal 50 is fitted into the rear end portion 32 of the intermediate shaft 30, and the pin terminal 50 is attached to the intermediate shaft 30 by caulking the outer periphery of the trunk portion 52 in a state where the support ring 60 is pressed toward the distal end side with the flange portion 51. The glow plug 100 is completed by fixing.

  The present invention can be variously modified. For example, like the middle shaft 130 shown in FIG. 5, the surface shape of the locking portion 135 formed on the outer peripheral surface of the tip portion 131 may be a bellows shape. Alternatively, like the middle shaft 230 shown in FIG. 6, a thread may be rolled on the outer peripheral surface of the tip portion 231 and this may be used as the locking portion 235. Or you may form the latching | locking part 335 which provided the some protrusion part in the outer peripheral surface of the front-end | tip part 331 like the center axis | shaft 330 shown in FIG. In either case, a larger frictional force can be generated on the inner peripheral surface of the distal end portion 91 of the tube 90 than when it is not formed, and the tube 90 can be reliably locked.

  Further, the formation position of the locking portion 35 provided on the middle shaft 30 may not be on the outer peripheral surface of the tip portion 31. For example, like the middle shaft 430 shown in FIG. 8, a knurled locking portion 435 similar to that of the present embodiment may be provided on the middle barrel portion 436 on the rear end portion 432 side with respect to the front end portion 431. Of course, the shape of the locking portion 435 may be the shape of the locking portions 135, 235, and 335 shown in the above modifications. However, when the engaging portion is provided at a portion having a reduced outer diameter, such as the small-diameter portion 433, there is a possibility that sufficient frictional force cannot be obtained on the inner peripheral surface of the tube 90. As described above, it is effective to provide the locking portion 435 at a portion having a large outer diameter. However, in order to reduce the insertion resistance when the central shaft is inserted into the tube and to obtain easy insertion, it is desirable to form the locking portion 35 at the distal end portion 31 of the central shaft 30 as in the present embodiment. .

  Note that an anti-slip structure such as a groove or a protrusion may be provided on the inner peripheral surface of the distal end portion 31 of the tube 90. However, in view of production costs and the like, as described in the present embodiment, the tube 90 has a cylindrical shape. It is preferable to produce the tube 90 by performing extrusion molding and then cutting to a desired length, and for that purpose, it is preferable to have a configuration in which a locking portion 35 is provided on the side of the middle shaft 30.

  Further, in the present embodiment, the tube 90 made of insulating silicon is described as an example of the flexible member. However, since it is only necessary to be able to limit the amplitude of the central axis when resonating, for example, insulating rubber or soft plastic You may produce a tube from etc. Further, a conductive tube may be used as long as the middle shaft 30 is covered with an insulating coating or the like.

  Further, in the present embodiment, the ceramic heater 20 is provided as a heater member provided in the glow plug 100, and the manufacturing method thereof is described. However, the manufacturing method is not limited to this, and any known manufacturing method may be used. . Furthermore, the heater member is not limited to the ceramic heater 20, and may be a sheathed heater in which a coil-shaped heating resistor or control resistor is arranged in a metal sheath tube whose tip is closed in a hemispherical shape. That is, the present invention is not limited to the shape of the heater member, and the heat generation specifications of the heater may be set as appropriate.

  The present invention can be used not only for a glow plug having only a heat generation function but also for a glow plug incorporating a temperature sensor, a pressure sensor, or the like.

1 is a longitudinal sectional view of a glow plug 100. FIG. 3 is an enlarged perspective view of the vicinity of a tip portion 31 of a middle shaft 30. FIG. 5 is a diagram schematically showing a manufacturing process of the glow plug 100. FIG. 5 is a diagram schematically showing a manufacturing process of the glow plug 100. FIG. It is the perspective view which expanded the front-end | tip part 131 vicinity of the center axis | shaft 130 as a modification. It is the perspective view which expanded the front-end | tip part 231 vicinity of the center axis | shaft 230 as a modification. It is the perspective view which expanded the front-end | tip part 331 vicinity of the center axis | shaft 330 as a modification. It is a perspective view of the center axis | shaft 430 as a modification.

DESCRIPTION OF SYMBOLS 20 Ceramic heater 27 Heat generating body 30 Middle shaft 31 Front-end | tip part 32 Rear-end part 34 Engagement part 35 Locking part 40 Main metal fitting 41 Front-end part 43 Shaft hole 75 Connection ring 80 Cylindrical body 83 Engagement part 90 Tube 91 Front-end | tip part 92 Rear End 95 Open end 100 Glow plug 260 Central shaft integral member 270 Tube integral member

Claims (4)

A central axis extending along the axial direction;
A heater member having a heating element that generates heat when energized;
A metal shell that has a shaft hole, the middle shaft is inserted into the shaft hole, and holds the heater member on its tip side;
Interposed between the center pole and said shaft hole, the glow plug with a variable Shiwasei member that have a and flexible consists insertable cylindrical in the middle axle,
The outer diameter of the flexible member is formed smaller than the inner diameter of the shaft hole of the metal shell,
A glow plug, wherein a locking portion for locking the inner peripheral surface of the flexible member is formed on the outer peripheral surface of the middle shaft.   2. The glow plug according to claim 1, wherein the locking portion is formed on an outer peripheral surface of one end portion which is an end portion on a side where the heater member is disposed in the axial direction of the central shaft. . A method for producing a glow plug according to claim 1 or 2, comprising a holding member for holding the heater member in a radial direction, wherein the holding member is joined on a distal end side of the metal shell.
Said flexible member, said center shaft of the first intermediate fixing the heater member held in the holding member to the center pole, is inserted from the other end side opposite to the one end of the center shaft A flexible member insertion step of disposing the opening end of the flexible member on the side where the middle shaft is inserted closer to the heater member than the locking portion of the middle shaft;
Metal shell insertion for inserting the middle shaft of the second intermediate body having the flexible member inserted through the middle shaft of the first intermediate body into the shaft hole of the metal shell from the other end side of the middle shaft. Process,
A glow plug manufacturing method comprising: a welding step of welding the holding member of the second intermediate body and the metallic shell closer to the heater member than the locking portion of the middle shaft. A central axis extending along the axial direction;
A heater member having a heating element that generates heat when energized;
A metal shell that has a shaft hole, the middle shaft is inserted into the shaft hole, and holds the heater member on its tip side;
A tube-like flexible member interposed between the middle shaft and the shaft hole and having flexibility;
A holding member for holding the heater member in a radial direction;
With
On the outer peripheral surface of the middle shaft, a locking portion that locks the inner peripheral surface of the flexible member is formed, and
A method of manufacturing a glow plug in which the holding member is joined on the front end side of the metal shell,
Inserting the intermediate shaft of the first intermediate body, in which the heater member held by the holding member is fixed to the intermediate shaft, from the other end side opposite to the one end portion of the intermediate shaft; A flexible member insertion step in which an opening end of the flexible member on the side where the middle shaft is inserted is disposed closer to the heater member than the locking portion of the middle shaft;
Metal shell insertion for inserting the middle shaft of the second intermediate body having the flexible member inserted through the middle shaft of the first intermediate body into the shaft hole of the metal shell from the other end side of the middle shaft. Process,
A welding step of welding the holding member of the second intermediate body and the metal shell closer to the heater member than the locking portion of the middle shaft;
A method for manufacturing a glow plug, comprising:

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