JP2007051861A - Glow plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glow plug capable of preventing the rupture of an inner shaft by resonance while reducing breakage or a labor hour in manufacturing. <P>SOLUTION: A tube 200 formed of insulating silicon is interposed in the clearance between the inner shaft 30 and a main metal fitting 40 of the glow plug. The tube 200 includes a split part 210 extending from one extending directional end side to the other end through its own thickness direction. At the time of manufacturing the glow plug, the split part 210 is opened, and the inner shaft 30 is stored on the inner circumferential side, whereby the tube 20 can be easily installed to the inner shaft 30. Since the clearance between the outer circumferential surface of the inner shaft 30 and the inner circumferential surface of a shaft hole 43 of the main metal fitting 40 can be minimized by the tube 200, an amplitude in the resonance of the inner shaft 30 with the vibration of an engine can be restricted to prevent the rupture of the inner shaft 30. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a glow plug used for assisting starting a diesel engine.

  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, since the natural frequency of the middle shaft decreases because the overall length of the glow plug becomes longer, the frequency of the vibration load generated by the operation of the diesel engine increases the chance of matching the natural frequency of the middle shaft, and resonance occurs. There was a risk that it would occur frequently. If resonance occurs, the effect of the contact between the central shaft and the metal shell makes it impossible to maintain insulation, the central shaft breaks due to bending with a large amplitude, or internal stress transmitted from the central shaft causes ceramics to break. There was a risk of the heater being damaged.

Therefore, the intermediate shaft (lead member) is covered with an insulating coating to prevent short circuit between the central shaft and the metallic shell due to resonance, and the outer diameter of the insulating coating is brought close to the inner diameter of the metallic shell, thereby preventing the vibration of the central shaft due to resonance. A glow plug has been proposed in which the amplitude of the above is limited and the generated stress is reduced to prevent breakage of the central shaft (see, for example, Patent Document 1). Thus, if the stress generated by the resonance of the central axis is reduced, the ceramic heater can be prevented from being damaged.
Japanese Patent Laid-Open No. 11-176563

  However, in Patent Document 1, since the insulating coating and the central shaft are in close contact with each other, it is difficult to attach the insulating coating to the central shaft in the process of manufacturing the glow plug, the insulating coating is damaged, or a lubricant such as grease is applied to the central shaft in advance. There was a need.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a glow plug capable of preventing breakage of the central shaft due to resonance and reducing damage and labor during manufacturing. .

  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. And a metal shell that holds the heater member on its tip side, and a flexible member that is interposed between the middle shaft and the shaft hole and has flexibility. When the flexible member is interposed between at least the middle shaft and the shaft hole, the flexible member forms a tube surrounding the periphery of the middle shaft and has a crack that penetrates in the thickness direction of the flexible member, The inner diameter of the flexible member having a tube shape changes with the opening and closing of the crack.

  According to a second aspect of the present invention, in addition to the structure of the first aspect of the present invention, the flexible member is formed in a tube shape and has a crack that penetrates in the thickness direction of the flexible plug, As the opening area of the crack increases, the inner diameter of the flexible member increases.

  According to a third aspect of the present invention, in the glow plug according to the first aspect of the present invention, in addition to the configuration of the first aspect of the present invention, the crack is formed from one end side to the other end in the extending direction of the flexible member having a tube shape. A plurality of flexible members are formed on the side, and the flexible member has at least a part of one of the plurality of cleaves and at least a part of another claw different from the one claw in the circumferential direction of the flexible member. And has a portion arranged together.

  According to a fourth aspect of the present invention, in the glow plug according to the first or second aspect of the invention, in addition to the configuration of the first or second aspect of the invention, the crack is formed from one end to the other end in the extending direction of the flexible member having a tube shape. It is characterized by being formed in a continuous cut shape toward the side.

  In the glow plug of the invention according to claim 1, when the flexible member is interposed between at least the middle shaft and the shaft hole of the metal shell, it forms a tube by surrounding the circumference of the middle shaft. Even if the middle shaft resonates due to vibrations of the attached engine, the antinode amplitude of the middle shaft due to the resonance can be limited. As a result, it is possible to reduce the bending of the central shaft and prevent breakage, and to reliably prevent contact between the metallic shell and the central shaft, and use the metallic shell and the central shaft as an electrode for energizing the heating elements, respectively. In the structure of the glow plug, a short circuit between the two can be prevented. In addition, since the flexible member has a crevice that can change the inner diameter of the flexible member, when the flexible member is attached to the central shaft in the process of manufacturing the glow plug, the crevice is opened and closed. By changing the inner diameter of the flexible member, the contact area between the central shaft and the flexible member can be reduced. For this reason, it is possible to easily attach the flexible member to the middle shaft, there is no fear of damage that may occur due to the forcible attachment, and it is possible to reduce the labor of the attachment. Such a flexible member may be a sheet-like member rolled up and interposed between the middle shaft and the shaft hole of the metal shell, or may be tube-shaped before the intervention. By having a crack that can change the inner diameter of the flexible member, the flexible member can be easily attached to the central shaft. Further, even when the middle shaft has a partially different outer diameter, it can be easily mounted by using a flexible member that can change the inner diameter in this way. Further, the manufacturing tolerance of the central shaft can be absorbed by the change in the inner diameter, and the same flexible member can be used even if the outer diameter is changed by changing the design of the central shaft, thereby reducing the manufacturing cost. be able to.

  Further, as in the invention according to claim 2, it is desirable that the flexible member has a tube shape. In the process of manufacturing the glow plug, the central shaft on which the flexible member is mounted is inserted into the shaft hole of the metal shell in a subsequent process. If this flexible member has a tubular shape and firmly grips the outer peripheral surface of the central shaft with its inner peripheral surface as its own support, it will be an obstacle when the central shaft is inserted into the shaft hole of the metal shell. Therefore, the operation can be easily performed. As a flexible member capable of realizing such a configuration, a member having a size relationship in which the inner circumference of the flexible member is expanded by the outer circumference of the middle shaft when mounted on the middle shaft is generally used. The flexible member of the glow plug according to claim 2 has a configuration in which the inner diameter is increased with an increase in the opening area of the crack portion penetrating in the thickness direction of the glow plug. It is small in size and can be securely held after mounting on the center shaft, and when mounted on the center shaft, it can be easily mounted by expanding its inner diameter, reducing the labor involved in the glow plug manufacturing process. can do. By attaching such a flexible member to the central shaft, when the resonance occurs in the central shaft, the flexible member limits the amplitude of the vibration of the central shaft and reduces the generated stress. Breakage can be prevented.

  Further, as in the invention according to claim 3, if a plurality of cracks are formed from one end side to the other end side in the extending direction of the tube-like flexible member, the flexibility can be obtained by opening each crack. The inner diameter of the member can be increased. Even if the opening area of each crack is small, if the opening areas of all the cracks are summed up, a considerably large opening area can be secured, and the expansion of the inner diameter of the flexible member becomes large. Furthermore, in the circumferential direction of the flexible member, if it is arranged in a staggered manner so that parts of different cracks overlap each other, the entire crack is deformed in three dimensions (deformation along the peripheral wall of the flexible member). In addition to the deformation in the direction of widening or narrowing the peripheral wall, the restriction on the increase of the opening area can be reduced. For this reason, it opens larger than each crack part and can expand the internal diameter of a flexible member more largely. In this way, if the inner diameter of the flexible member can be increased when the flexible member is mounted on the center shaft, the resistance due to friction between the center shaft and the flexible member during mounting can be reduced and mounted easily. It is possible to reduce the trouble in the process of manufacturing the glow plug. Similarly to the above, it is possible to prevent breakage of the central shaft by mounting such a flexible member on the central shaft.

  In order to produce the flexible member having the above-described configuration, it is easy to cut it into a certain length after forming it into a tube shape by extrusion molding. Therefore, as in the invention according to claim 4, if the crack is formed in a continuous cut shape from one end side to the other end side in the extending direction of the flexible member, it is formed into a tube shape by extrusion molding. At the same time, a crack can be formed, and a flexible member can be produced efficiently. Furthermore, in the process of manufacturing the glow plug, when the flexible member is attached to the center shaft, it can be mounted by opening the crack and accommodating the center shaft on the inner peripheral side, so that the labor of the operation can be reduced. Similarly to the above, it is possible to prevent breakage of the central shaft by mounting such a flexible member on the central shaft.

  Hereinafter, an embodiment of a glow plug embodying the present invention will be described with reference to the drawings. First, the entire structure of the glow plug 100 of the present embodiment will be described with reference to FIG. FIG. 1 is a longitudinal sectional view of the glow plug 100. 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 metal shell 40 in which the central shaft 30 is inserted into the shaft hole 43 and holding the ceramic heater 20 in the radial direction, and a rear of the central shaft 30. It is comprised from the pin terminal 50 fitted to an end, and the tube 200 interposed between the center shaft 30 and the metal shell 40.

  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 of the rear end portion 23 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.

  The ceramic heater 20 is held by a cylindrical tubular body 80 so as to surround the outer periphery of the body portion. The electrode extraction portion 25 formed on the distal end side of the electrode extraction portions 25 and 26 is in contact with and electrically connected to the cylindrical body 80 in the cylindrical hole of the cylindrical body 80. The cylindrical body 80 is made of a metal member, and a collar portion 82 that is thicker than the trunk portion 81 is formed on the rear end side of the trunk portion 81. A stepped engagement portion 83 is formed at the rear end of the collar portion 82, and the inner periphery of the distal end portion 41 of the cylindrical metal shell 40 is engaged with the engagement portion 83. At the time of the engagement, the axis of the ceramic heater 20 and the axis of the metal shell 40 coincide with the axis O. In this state, a portion of the rear end portion 23 of the ceramic heater 20 on the rear end side with respect to the cylindrical body 80 is accommodated in the metal shell 40, and the metal shell 40 is positioned by the engaging portion 83 of the cylindrical body 80. Therefore, the electrode extraction portion 26 provided at the rear end portion of the ceramic heater 20 does not contact the metal metal shell 40. The electrode extraction portion 26 is electrically connected to the middle shaft 30 (described later).

  Next, 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 an engine head (not shown) on the rear end side of the body portion 44. ) Is formed. Further, a tool engaging portion 46 having a hexagonal cross section in the axial line is formed at the rear end of the body portion 44 and engages with a tool used for attachment to the engine head. Within the tool engaging portion 46, the shaft hole 43 has an enlarged diameter portion 45 having an enlarged diameter.

  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. The front end portion 31 of the middle shaft 30 is fitted to a connection ring 35 fitted to the rear end portion 23 of the ceramic heater 20 so that the middle shaft 30 and the ceramic heater 20 are integrally connected. In this state, the electrode extraction portion 26 of the ceramic heater 20 is in contact with the inner wall of the cylindrical hole of the connection ring 35, and is electrically connected to the central shaft 30 via the connection ring 35. The metal shell 40 and the middle shaft 30 are electrically insulated with a gap and, as will be described later, a tube 200 is interposed therebetween. Each of the metal shell 40 and the central shaft 30 functions as an electrode for applying a voltage to the heating element 27 of the ceramic heater 20.

  An insulating O-ring 70 is fitted to the rear end portion 32 of the middle shaft 30 and is disposed at a position on the front end side in the enlarged diameter portion 45 of the metal shell 40. Further, an insulating support ring 60 is engaged with the rear end portion 32 and presses the O-ring 70 within the enlarged diameter portion 45. As a result, the O-ring 70 is brought into contact with the outer peripheral surface of the intermediate shaft 30, the inner peripheral surface 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. Also, a flange 61 is provided on the rear end side of the support ring 60 and is in contact with the rear end of the tool engaging portion 46. Both of them are interposed between a pin terminal 50 and a metal shell 40 described later. Is insulated.

  Next, the pin terminal 50 is fitted into a portion of the rear end portion 32 of the middle shaft 30 that protrudes from the flange portion 61 of the support ring 60 toward the rear end side. 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.

  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 the 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.

  Next, the configuration of the tube 200 will be described with reference to FIGS. FIG. 2 is a perspective view of the tube 200. FIG. 3 is a cross-sectional view of the tube 200 as viewed from the direction of the arrows along the one-dot chain line AA in FIG. FIG. 4 is a cross-sectional view of the tube 200 showing a state in which the crack 210 of the tube 200 shown in FIG. 3 is opened. In FIG. 3, in order to show the relationship of the size of the tube 200, the axes of the middle shaft 30 and the metal shell 40 are drawn to be equal.

  The tube 200 shown in FIG. 2 has a cylindrical shape and is a flexible member made of insulating silicon. The tube 200 is formed with a slit 210 that penetrates in the thickness direction of the tube 200 in a continuous cut shape from one end 201 side to the other end 202 side in the extension direction of the tube 200. That is, as shown in FIG. 3, the tube 200 has a C shape in a sectional view. In the state before being assembled as the glow plug 100 (see FIG. 1), the outer diameter C of the tube 200 is configured to be smaller than the inner diameter B of the shaft hole 43 of the metal shell 40. Also, the inner diameter E of the tube 200 is configured to be slightly smaller than the outer diameter D of the middle shaft 30. Furthermore, the thickness F of the tube 200 corresponding to ½ of the difference between the outer diameter C and the inner diameter E is between the two corresponding to ½ of the difference between the inner diameter B of the shaft hole 43 and the outer diameter D of the center shaft 30. The clearance is slightly smaller than G. The tube 200 corresponds to the “flexible member” in the present invention.

  Then, as shown in FIG. 4, the tube 200 opens and closes the cleft 210 (opens or narrows the cross-sections formed by the cuts away from each other in a direction away from each other). Is configured to change (enlarge and reduce). In the present embodiment, the opening area of the crevice 210 is increased by opening the crevice 210 of the tube 200 (expanding from the state of FIG. 3 to the state of FIG. 4), and the inner diameter of the tube 200 is increased accordingly. It is configured. In the present embodiment, the opening area means the size of a range in which the inner peripheral side can be faced from the outer peripheral side of the tube 200 through the crack 210.

  In the glow plug 100 having such a structure, a process of attaching the tube 200 to the central shaft 30 is performed in the manufacturing process, and the inner diameter E can be expanded by opening the crack 210 as described above. Since it is comprised, the mounting | wearing operation | work can be performed easily. Hereinafter, the manufacturing process of the glow plug 100 will be described with reference to FIGS. FIG. 5 is a diagram showing a schematic flow of the manufacturing process of the glow plug 100. FIG. 6 is a cross-sectional view of the glow plug 100 as viewed from the direction of the arrows along the alternate long and short dash line JJ in FIG.

[Heater formation process]
As shown in FIG. 5, first, an element molded body 251 that is the original shape of the heating element 24 of the ceramic heater 20 is formed by injection molding using 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 35 is formed of a steel material such as stainless steel into a pipe shape and press-fitted into the ceramic heater 20 so as to conduct the electrode extraction portion 26. Similarly, the cylindrical body 80 is also formed into a predetermined shape and press-fitted into the ceramic heater 20 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 joining process]
The middle shaft 30 is formed from a rod-shaped member of an iron-based material (for example, Fe—Cr—Mo steel) cut to a certain size by plastic working or cutting. Then, the front end portion 31 of the middle shaft 30 is engaged in the connection ring 35 of the heater integrated member 250 in which the ceramic heater 20 and the other member are integrated, and the outer periphery of the front end portion 31 is connected to the end portion of the connection ring 35 in this state. The intermediate shaft 30 and the heater integrated member 250 are joined together by laser welding.

[Tube mounting process]
Next, the insulating silicon is formed by extrusion molding into a cylindrical shape in which a continuous slit-shaped crack 210 is formed from the one end 201 side to the other end 202 side, and the tube is cut into a predetermined dimension. 200 (see FIG. 2) is obtained. Then, the crack portion 210 of the tube 200 is opened to enlarge the inner diameter E (see FIG. 3), and the central shaft 30 joined to the heater integrated member 250 is guided to the inner peripheral side of the tube 200 through the crack portion 210. As described above, since the inner diameter E of the tube 200 can be enlarged and reduced by opening and closing the crack 210, the friction resistance when the tube 200 is attached to the center shaft 30 is small, and the attachment can be performed smoothly. it can.

  Further, as shown in FIG. 3, since the inner diameter E of the tube 200 is smaller than the outer diameter D of the central shaft 30, after installation, as shown in FIG. Also in the part, the inner peripheral surface of the tube 200 is in close contact with the outer peripheral surface of the central shaft 30. That is, the tube 200 is supported by the inner shaft 30 so as to firmly hold the outer peripheral surface of the middle shaft with its inner peripheral surface, and is held by the middle shaft 30. At this time, the outer diameter C of the tube 200 is similarly increased because the inner diameter E is increased in accordance with the outer diameter D of the middle shaft 30. However, as described above, the thickness F of the tube 200 is slightly smaller than the size G of the clearance between the shaft hole 43 of the metal shell 40 and the middle shaft 30. For this reason, the outer diameter C of the tube 200 is smaller than the inner diameter B of the shaft hole 43 even after being attached to the middle shaft 30.

[Metal fitting process]
Next, as shown in FIG. 5, 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 middle shaft 30 to which the tube 200 is attached is inserted into the shaft hole 43 of the metal shell 40. As described above, the outer diameter C of the tube 200 is smaller than the inner diameter B of the shaft hole 43 even when attached to the middle shaft 30, and a gap is generated between the outer peripheral surface of the tube 200 and the inner peripheral surface of the metal shell 40. Therefore, it is possible to easily insert the central shaft 30 with the tube 200 into the shaft hole 43 of the metal shell 40. By interposing this tube 200, the gap (space) between the outer peripheral surface of the central shaft 30 and the inner peripheral surface of the shaft hole 43 of the metal shell 40 is reduced, so that the amplitude when the central shaft 30 resonates is effective. Can be limited. And the inner periphery of the front-end | tip part 41 of the metal shell 40 is engaged with the engaging part 83 of the cylindrical body 80, and the metal shell 40 and the cylindrical body 80 are joined by laser welding. In addition, in order to avoid that the metal shell 40, which is an iron-based material, is rusted, a rust prevention treatment such as plating or painting may be performed after joining the cylindrical body 80.

[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 middle shaft 30, and the pin terminal 50 is attached to the middle 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 a tube 300 shown in FIG. 7, a slit 310 that is cylindrical and penetrates in its own thickness direction is continuous in a spiral shape from one end 301 side to the other end 302 side in its extension direction. You may use what is called a spiral tube formed. In order to attach the tube 300 having such a configuration to the middle shaft 30, for example, the middle shaft 30 is first accommodated in the tube 300 from the end of the crack 310 on the one end 301 side, and then the other end 302 side of the tube 300. The middle shaft 30 may be accommodated in the crack 310 while rotating in the circumferential direction of the middle shaft 30 in accordance with the spiral direction of the crack 310. In this modification, an example is shown in which the width t2 of the flexible member forming the tube 300 is larger than the width t1 of the crack 301. However, the present invention is not limited to this shape. That is, the width t1 of the crack 301 may be configured to be equal to the width t2 of the flexible member, or the width t1 of the crack 301 is configured to be smaller than the width t2 of the flexible member. May be. However, in order to effectively suppress the contact between the outer peripheral surface of the middle shaft 30 and the inner peripheral surface of the shaft hole 43, flexibility is provided with respect to the width t1 of the crack 301 as in the present modification shown in FIG. It is preferable that the width t2 of the member is increased. Further, the flexible member may be formed such that the thickness t3 thereof is substantially the same as the width t2, and the winding tube 300 is formed around the middle shaft 30.

  Further, like the tube 320 shown in FIG. 8, the cracks 330 and 331 that are cylindrical and penetrate in the thickness direction of the tube 320 are intermittently continuous from one end 321 side to the other end 322 side in the extension direction of the tube 320. You may use what was formed in the shape of a cut. The tube 320 having such a configuration can widen the inner diameter (opening diameter) at both ends of the tube 320 by opening the crack 330 on the one end 321 side and the crack 331 on the other end 322 side, In the intermediate part 323 where the cracks 330 and 331 are not formed, the inner diameter of the tube 320 does not widen. However, when the tube 320 is mounted so as to cover the outer periphery of the middle shaft 30 from the opening of the one end 321 or the other end 322, a portion where a mounting resistance due to friction occurs between the inner peripheral surface of the tube 320 and the outer peripheral surface of the central shaft 30. Can be mainly set in a small range near the intermediate portion 323, and the operation can be easily performed.

  Further, like the tube 340 shown in FIG. 9, a plurality of slits 350 having a cylindrical shape and penetrating in its own thickness direction are formed from one end 341 side to the other end 342 side in its extension direction. May be used. In this case, when the slits 350 are arranged in a staggered manner so that the cut direction of each crack 350 is aligned with the extending direction of the tube 340 and the ends of the cracks 350 overlap each other in the circumferential direction of the tube 340. Good. If the cracks 350 are arranged in this way and the tube 340 is formed so as to have a so-called mesh shape, the restriction on the increase in the opening area when opening the cracks 350 can be reduced. Therefore, as shown in FIG. 10, each crack 350 can be greatly opened, and the inner diameter of the tube 340 can be further expanded. Of course, finer cracks may be formed than in this modification, the cracks may be assembled in a lattice shape, or the cracks may be formed in various shapes of holes. .

  In addition, the tube 200 of the present embodiment is formed by extrusion so as to form a cylindrical shape even before being assembled as the glow plug 100. However, the tube 200 is formed in a sheet shape and is attached to the central shaft 30 in the manufacturing process of the glow plug 100. You may use the flexible member of the form wound. In the case of such a flexible member, it is preferable that plastic deformation is possible because handling in the process after winding around the intermediate shaft 30 is facilitated. In the state where the flexible member is wound around the middle shaft 30, the circumferential edge corresponds to the “crack” of the present invention. However, in view of production costs and the like, it is preferable to produce the tube 200 by extrusion molding as in the present embodiment, and the crack 210 may be formed at the same time during the extrusion molding process.

  Further, in this embodiment, the tube 200 made of insulating silicon is described as an example of the flexible member. However, since it is only necessary to limit the amplitude of the central axis when resonating, for example, insulating rubber or soft plastic is used. 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. 2 is a perspective view of a tube 200. FIG. It is sectional drawing of the tube 200 seen from the arrow direction in the dashed-dotted line AA of FIG. It is sectional drawing of the tube 200 which shows the state which opened the crack part 210 of the tube 200 shown in FIG. 3 is a diagram showing a schematic flow of a manufacturing process of the glow plug 100. FIG. It is sectional drawing of the glow plug 100 seen from the arrow direction in the dashed-dotted line JJ in FIG. It is a perspective view of tube 300 as a modification. It is a perspective view of tube 320 as a modification. It is a perspective view of tube 340 as a modification. It is a figure which shows the state which opened each crack 350 of the tube 340 shown in FIG.

Explanation of symbols

20 Ceramic heater 27 Heating element 30 Middle shaft 40 Metal shell 43 Shaft hole 100 Glow plug 200 Tube 210 Crack

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;
A flexible member interposed between the middle shaft and the shaft hole and having flexibility,
When the flexible member is interposed between at least the middle shaft and the shaft hole, the flexible member forms a tube surrounding the circumference of the middle shaft and has a crack that penetrates in the thickness direction of the flexible member,
A glow plug characterized in that the inner diameter of the flexible member having a tube shape changes with the opening and closing of the crack. The flexible member forms a tube shape and has a crack that penetrates in the thickness direction of the flexible member,
The glow plug according to claim 1, wherein an inner diameter of the flexible member increases with an increase in an opening area of the crack. A plurality of the cracks are formed from one end side to the other end side in the extending direction of the flexible member having a tube shape,
In the circumferential direction of the flexible member, at least a part of one of the plurality of fissures and at least a part of another fissure different from the one fissure are arranged together. The glow plug according to claim 1, wherein the glow plug has a region. The glow plug according to claim 1, wherein the crack is formed in a continuous cut shape from one end side to the other end side in the extending direction of the flexible member having a tube shape.

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