JP2007093102A - Glow plug and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glow plug having improved accuracy of coaxiality at the front end and reduced run out at the front end while suppressing an increase in manufacturing cost, and to provide its manufacturing method. <P>SOLUTION: The glow plug 1 comprises a cylindrical metal shell 2 and a heater 3 mounted at the front end of the metal shell 2. The metal shell 2 consists of a cylindrical round body portion 2a formed on the front end side, an engine mounting screw portion 2b formed on the rear end side of the round body portion 2a, and a tool engaging portion 2c formed on the rear end side beyond the screw portion 2b. The metal shell 2 also has a joint portion 10 between a small diameter portion 4a of a shaft hole 4 as a heater holding site and the front end of the screw portion 2b. A rear end side portion including its rear end such as the tool engaging portion 2c and the screw portion 2b is joined to a front end side portion including its front end into one unit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a glow plug used for preheating a diesel engine and the like and a method for manufacturing the same.

  Generally, the glow plug is provided with a cylindrical metal shell, and is mounted with a heater protruding from the front end side of the metal shell. A tool engaging part for engaging a tool such as a torque wrench is formed on the outer peripheral surface of the metal shell when the glow plug is attached to the diesel engine. The thread portion is formed. The glow plug is attached to the diesel engine so that the heater on the front end side is located in the combustion chamber.

Conventionally, a metal shell is formed by, for example, using a solid steel rod or a cylindrical steel pipe as a material and performing plastic working or cutting. However, in recent years, there is a tendency for the glow plug to become longer in accordance with the structural change of the diesel engine. Therefore, the processing load is increased for the glow plug having a relatively long length, and there is a concern about an increase in manufacturing cost.
On the other hand, in recent years, a glow plug in which a metal fitting is formed by forming a tool engaging portion and a portion other than the tool engaging portion including the screw portion separately and joining them together is also seen. (For example, refer to Patent Document 1).
JP-A-4-260719

  However, in general, since the tip end side of the metallic shell is not supported when the threaded portion of the metallic shell is rolled, in the invention described in the above Japanese Patent Laid-Open No. 4-260719, In this case, the accuracy of the concentricity of the front end portion of the metal shell relative to the thread portion is lowered, and there is a risk that the front end portion may sway when the glow plug is attached to the diesel engine. Such a defect is more prominent as the glow plug having a relatively longer length on the tip side than the threaded portion of the metal shell is more prominent.

  The present invention has been made in view of the above circumstances, and its object is to improve the accuracy of the concentricity of the tip, reduce the run-out of the tip, and suppress the increase in manufacturing cost. It is to provide a plug and a manufacturing method thereof.

  Hereinafter, each configuration suitable for solving the above-described problems will be described in terms of items. In addition, the effect etc. peculiar to the structure which respond | corresponds as needed are added.

Configuration 1. The glow plug of this configuration is
A glow plug comprising a cylindrical metal shell having a shaft hole, and a heater held in the shaft hole in a state of protruding from the front end side of the metal shell,
On the outer peripheral surface of the metal shell, a screw portion for engine attachment formed on the rear end side in the axial direction from the heater holding portion in the shaft hole where the heater is held, and the rear end side in the axial direction from the screw portion Comprising a tool engaging portion formed on
The metallic shell is formed by joining a first metallic shell intermediate body in which the thread portion is formed and a second metallic shell intermediate body in which the heater is held, and a joint portion that forms the joint is the axial member in the axial direction. It is formed between the heater holding part and the screw part.

  According to the above-described configuration 1, the metallic shell can be formed by forming the portion including the tool engaging portion and the screw portion and the portion on the tip side from the screw portion separately and joining them together. Therefore, the processing load can be reduced and the increase in manufacturing cost can be suppressed. Furthermore, since the joining portion is formed between the heater holding portion and the screw portion, it is possible to improve the accuracy of the coaxiality of the distal end portion of the metal shell with respect to the screw portion. As a result, it is possible to suppress the forward swing of the tip when the glow plug is attached. In addition, the said structure is more effective in the glow plug whose length of the front end side is relatively long (for example, 30 mm or more) from the thread part of a metal shell. In order to obtain this effect more effectively, it is desirable to form the joint portion closer to the screw portion than half the length on the tip side from the screw portion.

Configuration 2. The glow plug of this configuration is the above-described configuration 1,
The joint portion is formed on the tip end side in the axial direction from the tip end of the screw portion.

  If the joint is formed on the rear end side in the axial direction from the tip of the screw part, for example, the hole part is formed inside the screw part, when the thread part is rolled after the joint part is formed, As a result of this stress, the shape of the joint is distorted, so that problems such as run-out and misalignment of the coaxiality may occur when joining. In that respect, according to the above-described configuration 2, the occurrence of such a problem is reduced as compared to a configuration in which the joint portion is formed on the rear end side in the axial direction from the tip of the screw portion.

Configuration 3. The glow plug of this configuration is the above-described configuration 1,
The joining portion is formed on the distal end side in the axial direction from the screw portion so as to be separated from the tip of the screw portion.

  According to the configuration 3, the same effects as the configuration 2 are achieved. Further, when forming the joint after rolling the threaded portion, a predetermined chuck allowance for holding the metal shell can be secured. In addition, when a junction part is shape | molded after rolling of a thread part, the precision of a coaxial degree can be improved further.

Configuration 4. The manufacturing method of the glow plug of this configuration is as follows:
A cylindrical metal shell having a shaft hole, and a heater held in the shaft hole in a state of protruding from the front end side of the metal shell,
On the outer peripheral surface of the metal shell, a screw portion for engine attachment formed on the rear end side in the axial direction from the heater holding portion in the shaft hole where the heater is held, and the rear end side in the axial direction from the screw portion A glow plug manufacturing method comprising a tool engaging portion formed on
Forming a first metal shell intermediate body corresponding to a rear end side portion of the metal shell including the screw portion and the tool engaging portion;
Forming a second metal shell intermediate corresponding to the tip side portion of the metal shell;
Joining the first metal shell intermediate body and the second metal shell intermediate body,
In the step of forming the first metal shell intermediate,
The threaded portion is rolled after forming a joint for joining with the second metal shell intermediate.

  According to the said structure 4, a junction part can be provided in the position nearer the front-end | tip part of a screw part. As a result, since the portion of the first metal shell intermediate body on the tip side is smaller than the screw portion, it is possible to suppress a decrease in the coaxiality of the metal shell tip portion.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1A is an overall view showing an example of a glow plug, and FIG. 1B is a longitudinal sectional view thereof.
As shown in FIGS. 1A and 1B, the glow plug 1 includes a cylindrical metal shell 2 and a heater 3 attached to the tip of the metal shell 2 (lower side in FIG. 1).
The metal shell 2 has a shaft hole 4 penetrating in the axial direction. And the small diameter part 4a for hold | maintaining the heater 3 is formed in the front-end | tip part of this axial hole 4, or its vicinity. A large-diameter portion 3b formed on the rear end side of the sheath tube 3a constituting the outer shape of the heater 3 is press-fitted into the small-diameter portion 4a, so that the heater 3 protrudes from the tip of the metal shell 2 and the metal shell 2 is fixed. The method for mounting the heater 3 is not limited to press-fitting, and other methods such as shrink fitting and brazing may be used. That is, a portion where the heater 3 is held, such as the small diameter portion 4a of the present embodiment, corresponds to the heater holding portion.

  The heater 3 includes two resistance wire coils, more specifically, a heating coil disposed on the distal end side and a control coil connected in series at the rear end, on the inside of the sheath tube 3a with the distal end closed, such as magnesia powder. Enclosed with insulating material. In addition, the front-end | tip part of a resistance coil is joined to the front end side of the sheath tube 3a.

  Further, the shaft hole 4 of the metal shell 2 is inserted with a center shaft 5 having its tip inserted into the sheath tube 3a and electrically connected to the resistance wire coil. The rear end of the middle shaft 5 protrudes from the rear end of the metal shell 2. At the rear end of the metal shell 2, the rubber-made O-ring 6, the resin-made insulating bush 7, and the insulating bush 7 are removed. The holding ring 8 for preventing and the nut 9 for connecting a cable for energization are fitted and fixed to the middle shaft 4 in this order.

  The metal shell 2 includes a cylindrical round body 2a formed on the front end side, a screw part 2b for mounting the internal combustion engine formed on the rear end side of the round body 2a, and the screw part 2b. It consists of a tool engaging portion 2c having a hexagonal cross section formed on the rear end side. In addition, the tool engaging part 2c is not limited to the said cross-sectional hexagon shape, You may form in another polygonal shape. The glow plug 1 in the present embodiment has a comparatively long shape, for example, the total length L1 = 145 mm, the length L2 = 53 mm of the round body portion 2a, and the length L3 = 27 mm of the screw portion 2b.

  Further, in the round body portion 2a (in the vicinity of the boundary with the screw portion 2b in the present embodiment), the joint portion 10 is provided between the small diameter portion 4a of the shaft hole 4 serving as a heater holding portion and the tip portion of the screw portion 2b. Is formed. That is, the metal shell 2 includes a rear end side portion including its own rear end portion such as the tool engagement portion 2c and the screw portion 2b, and a front end side portion including its own front end portion that is closer to the front end side than the rear end side portion ( A large portion of the round body 2a) is integrated by joining at the joint 10.

Here, the manufacturing method of the metal shell 2 and the configuration of the joint 10 will be described in detail.
First, in the first step, the rear end of the metal shell 2 in which the tool engaging portion 2c is formed by performing plastic working, cutting, or the like using a hexagonal steel pipe having a hole corresponding to the shaft hole 4 as a material. A first metal shell intermediate body 11 (see FIG. 2A) corresponding to the side portion is manufactured. In this embodiment, the hexagonal steel pipe has an inner hole diameter larger than the inner diameter of the shaft hole 4 of the first metal shell intermediate body 11.

  In the subsequent second step, by cutting the outer peripheral surface of the distal end portion of the first metal shell intermediate body 11, the annular protrusion protruding from the distal end portion along the inner peripheral surface of the shaft hole 4 toward the distal end side in the axial direction. While forming the part 11a, the annular notch part 11b is formed in the outer peripheral side.

  Thereafter, in the third step, the outer peripheral surface of the first metal shell intermediate body 11 is subjected to a rolling process to form the screw portion 2b. In this embodiment, the annular convex part 11a and the annular notch part 11b are formed without being separated from the tip part of the screw part 2b.

  On the other hand, in a 4th process, the 2nd metal shell intermediate body 12 which hits the front end side part of the metal shell 2 by giving plastic processing, cutting, etc. by using a round steel pipe which has a hole corresponding to shaft hole 4 as a material. [See FIG. 2 (a)].

  In the subsequent fifth step, the annular convex portion 12a that protrudes from the front end portion toward the rear end side in the axial direction along the outer peripheral surface by cutting the inner peripheral surface of the rear end portion of the second metal shell intermediate body 12. And an annular notch 12b is formed on the inner peripheral side thereof.

Then, in the sixth step, as shown in FIG. 2 (b), the annular projection 11a of the first metal shell intermediate body 11 is guided into the annular projection 12a of the second metal shell intermediate body 12 while being guided. The annular protrusions 11a and 12a and the annular notches 12b and 11b are butted together. As a result, the metal shell 2 in which the first metal shell intermediate body 11 and the second metal shell intermediate body 12 are integrated is obtained using the annular protrusions 11a, 12a and the annular cutout portions 12b, 11b as the joint portion 10.
Thereafter, the heater 3 and the center shaft 5 are assembled to the metal shell 2 to obtain the glow plug 1.

  The glow plug 1 thus obtained is inserted into a plug mounting hole formed in an engine head or the like of a diesel engine, and a threaded portion 2b (male threaded portion) of the metal shell 2 is replaced with a threaded portion formed in the plug mounting hole ( It is fixed by screwing into a female thread part) with a tool such as a torque wrench.

  As described in detail above, in the present embodiment, the rear end side portion (first metal shell intermediate body 11) including the rear end portion such as the tool engaging portion 2c and the screw portion 2b, and the rear end side portion. The metal shell 2 is molded by molding the tip side portion (second metal shell intermediate body 12) including the tip portion of the front end side as a separate body and joining them together. Therefore, when manufacturing a relatively long glow plug 1 as in the present embodiment, it is possible to reduce the processing burden and to suppress an increase in manufacturing cost.

  Moreover, in this embodiment, the junction part 10 is formed between the small diameter part 4a of the shaft hole 4 which is a heater holding | maintenance site | part, and the front-end | tip part of the screw part 2b. In particular, the joint portion 10 of the present embodiment is provided on the tip end side in the axial direction from the tip end of the screw portion 2b without being separated from the tip end portion of the screw portion 2b. Therefore, it is possible to improve the accuracy of the coaxiality of the distal end portion of the metal shell 2 with respect to the screw portion 2b. As a result, it is possible to suppress the forward swing of the tip portion when the glow plug 1 is attached.

  Moreover, in this embodiment, the hexagonal steel pipe is used as a material, the first metal shell intermediate body 11 corresponding to the rear end side portion of the metal shell 2 on which the tool engaging portion 2c is formed, the round steel pipe is used as a material, The second metal shell intermediate body 12 corresponding to the tip side portion of the metal shell 2 is formed. Thus, the process of forming the shaft hole 4 can be omitted by using the pipe material in advance. In other words, it is possible to eliminate an enormous processing burden when forming the shaft hole 4 of the relatively long metal shell 2 as in this embodiment, and to suppress an increase in manufacturing cost. In addition, by using a pipe material close to the outer peripheral shape of each of the metal shell intermediate bodies 11 and 12 in advance, the amount of scrap generated by processing can be reduced, and the manufacturing cost can be further reduced.

In addition, it is not limited to the description content of embodiment mentioned above, For example, you may implement as follows.
(A) In the above embodiment, the joint portion 10 (the annular convex portion 11a and the annular notch portion 11b) is formed without being separated from the tip portion of the screw portion 2b, but the position where the joint portion 10 is formed is It is not limited to this. For example, as shown in FIG. 3, it may be formed spaced apart from the tip of the screw part 2b by a predetermined distance L4. In this way, even after the threaded portion 2b is rolled, it is possible to secure a chuck margin for sandwiching the first metal shell intermediate body 11, and molding the annular convex portion 11a and the annular notch portion 11b. Can do. In order to secure such an effect more reliably, it is preferable to set L4 = 10 mm or more. Furthermore, when joining the joining part 10 by brazing or the like, it is possible to reduce thermal effects such as deformation and softening that the threaded part 2b undergoes during joining.

  (B) The length of each part of the glow plug 1 and the metal shell 2 is not limited to the numerical values shown in the above embodiment. However, the present invention is more effective in a glow plug that is relatively long (for example, L2 = 30 mm or more) on the tip side of the threaded portion 2b of the metal shell 2.

  (C) The joint portion 10 of the above embodiment has a structure in which the annular convex portions 11a and 12a are press-fitted and joined to the annular notches 12b and 11b. However, the joining method and the structure of the joining portion are not limited to this.

  For example, as a joining method, other methods such as shrink fitting, brazing, screwing, and laser welding may be used.

  Moreover, as a structure of a junction part, it is good also as a taper-shaped structure which each tapered the annular convex parts 11a and 12a, for example. However, in such a structure, since the alignment of both the intermediate bodies 11 and 12 is somewhat difficult, the above embodiment is more preferable in order to increase the accuracy of the coaxiality.

  In contrast to the above embodiment, as shown in FIG. 4, as shown in FIG. 4, on the first metal shell intermediate body 11 side, an annular convex portion 21 a that protrudes along the outer peripheral surface toward the axial front end side, and an annular notch on the inner peripheral side thereof The structure which formed the part 21b, the annular convex part 22a which protruded to the axial direction rear end side along the inner peripheral surface of the axial hole 4 in the 2nd metal shell intermediate body 12 side, and the annular notch part 22b in the outer peripheral side It is good. In the case of such a structure, if the annular notch 21b is formed up to the inside of the screw part 2b, there is a step of rolling the screw part 2b after the formation of the annular notch 21b. There is a possibility that the shape of the annular notch 21b may be distorted by the stress. Therefore, particularly in the case of such a structure, it is preferable that the annular notch portion 21b is formed on the tip end side in the axial direction from the tip end of the screw portion 2b.

  (D) The heater 3 is not limited to the above sheathed type in which the resistance wire coil is enclosed in the sheath tube 3a. For example, the heater 3 is a ceramic body embedded with a heating element or a conductive ceramic. May be. The heater 3 in the above embodiment is a heater including two resistance wire coils, but the number of resistance wire coils is not limited to this, and may be one, for example, or may be three or more. May be. Moreover, the shape of a heater is not ask | required and a straight shape with a substantially constant outer diameter may be sufficient.

  (E) The small diameter portion 4a of the shaft hole 4 corresponding to the heater holding portion may be omitted, and the heater 3 may be fixed to the shaft hole 4 having a straight shape in the axial direction by press fitting, brazing, or the like. Of course, even in this case, the part holding the heater 3 corresponds to the heater holding part.

(A) is the whole figure which shows the glow plug of this embodiment, (b) is the longitudinal cross-sectional view. (A), (b) is a partial expanded sectional view for demonstrating the joining structure of a main metal fitting. It is a partial expanded sectional view for demonstrating the joining structure of the metal shell in another embodiment. It is a partial expanded sectional view for demonstrating the joining structure of the metal shell in another embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Glow plug, 2 ... Main metal fitting, 2a ... Round body part, 2b ... Screw part, 2c ... Tool engaging part, 3 ... Heater, 4 ... Shaft hole, 10 ... Joining part, 11 ... 1st main metal fitting intermediate body , 12 ... second metal shell intermediate body, 11a, 12a ... annular projection, 11b, 12b ... annular notch.

Claims (4)

A glow plug comprising a cylindrical metal shell having a shaft hole, and a heater held in the shaft hole in a state of protruding from the front end side of the metal shell,
On the outer peripheral surface of the metal shell, a screw portion for engine attachment formed on the rear end side in the axial direction from the heater holding portion in the shaft hole where the heater is held, and the rear end side in the axial direction from the screw portion Comprising a tool engaging portion formed on
The metallic shell is formed by joining a first metallic shell intermediate body in which the thread portion is formed and a second metallic shell intermediate body in which the heater is held, and a joint portion that forms the joint is the axial member in the axial direction. A glow plug formed between a heater holding portion and the screw portion.   The glow plug according to claim 1, wherein the joint portion is formed on the tip end side in the axial direction from the tip of the screw portion.   2. The glow plug according to claim 1, wherein the joint portion is formed at a distal end side in the axial direction from the screw portion so as to be separated from the tip of the screw portion. A cylindrical metal shell having a shaft hole, and a heater held in the shaft hole in a state of protruding from the front end side of the metal shell,
On the outer peripheral surface of the metal shell, a screw portion for engine attachment formed on the rear end side in the axial direction from the heater holding portion in the shaft hole where the heater is held, and the rear end side in the axial direction from the screw portion A glow plug manufacturing method comprising a tool engaging portion formed on
Forming a first metal shell intermediate body corresponding to a rear end side portion of the metal shell including the screw portion and the tool engaging portion;
Forming a second metal shell intermediate corresponding to the tip side portion of the metal shell;
Joining the first metal shell intermediate body and the second metal shell intermediate body,
In the step of forming the first metal shell intermediate,
A method for manufacturing a glow plug, comprising: forming a joint for joining to the second metal shell intermediate, and then rolling the threaded portion.

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