JPH1194252A - Glow plug and manufacture of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glow plug and a method of manufacturing the same in which an airtight characteristic between a housing and a heater can be easily held. SOLUTION: This glow plug 1 is comprised of a housing 5 having an inner hole 50 therein, a heater 10 press fitted and fixed in the inner hole 50 of the housing 5, and an inner shaft 4 for applying an electrical energy to the heater 10. Press fitting and fixing of the housing 5 and the heater 10 are carried out such that a fitting part 55 arranged in the inner hole 50 of the housing 5 and a press fitting part 15 arranged at an outer circumference of the heater 10 are press fitted. Either an outer circumferential surface of the press fitting part 15 or the inner circumferential surface of the fitting part 55 is provided with a corrugated surface 60 having a corrugation part 6 arranged in non- parallel with an axial direction of the glow plug 1. A surface roughness (Rz) of the corrugated surface is less than 25 μm and it occupies more than 20% of a surface area of the press fitting part or the fitting part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As a glow plug for preheating a diesel engine, there is a sheath type glow plug 9 as shown in FIG. As shown in the figure, the glow plug 9 has a heater 90 in which a metal tube 91 having a U-shaped cross section whose end is closed is filled with the insulating powder 2 and the heat coil 3 for heat generation is housed. Also, the heater 90 includes
From the open end of the metal tube 91, the leading end of the central shaft 4 for energization is embedded in the insulating powder 2 and connected integrally.

As shown in FIG. 1, the heat coil 3 has one end 31 joined to the inner surface of the tip of a metal tube 91 and the other end 32 connected to the tip of the center shaft 4. The heater 90 and the housing 5 are fixed by press-fitting the press-fit portion 95 of the heater 90 to the fitting portion 55 of the housing 5. In FIG. 9, reference numeral 71 denotes a nut, 72 denotes a resin bush, 73 denotes an O-ring made of an insulating elastic material, and 74 denotes a resin washer.

In manufacturing the glow plug 9, first, a step of inserting the heat coil 3 and the center shaft 4 into the metal tube 91, a step of filling the insulating powder, and a swaging process for compressing and compressing the entire metal tube 91 from the outer periphery. Through the steps, a heater 90 in which the center shaft 4 is integrally joined is manufactured. After that, the heater 90 and the housing 5 are press-fitted and fixed.

[0005]

However, the above-mentioned conventional glow plug and its manufacturing method have the following problems. That is, it is necessary that the press-fitting and fixing between the heater 90 and the housing 5 be performed so as to maintain sufficient airtightness to withstand a high pressure (about 150 atm) when the glow plug is used. For this reason, conventionally, the roundness of the press-fit portion 95 of the heater has been increased, and the surface roughness has been reduced to a mirror surface state. For that purpose, it was necessary to use a very expensive high-performance swaging machine. Therefore, in the conventional method of manufacturing a glow plug by press-fitting and fixing,
It was not easy to maintain the airtightness between the heater and the housing.

On the other hand, conventionally, as a manufacturing method without press-fitting and fixing, for example, Japanese Patent Publication No. 59-52726
As shown in the publication, a circumferential groove is provided on the outer periphery of the heater, which is inserted into the housing, and the housing is crimped from the outside to fit the circumferential groove of the heater with the inner surface of the housing. There is a method to obtain airtightness. However, this method has a problem that a step of caulking the housing is newly required.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a glow plug capable of easily maintaining the airtightness between a housing and a heater, and a method for manufacturing the same.

[0008]

According to a first aspect of the present invention, there is provided a housing having an inner hole, a heater press-fitted and fixed in the inner hole of the housing, and a center shaft for supplying power to the heater. In the glow plug, the housing and the heater are press-fitted and fixed by press-fitting a fitting portion provided in an inner hole of the housing and a press-fitting portion provided on the outer periphery of the heater. The glow is characterized in that the outer peripheral surface of the press-fitting portion or the inner peripheral surface of the fitting portion has an uneven surface having uneven portions arranged in a pattern non-parallel to the axial direction of the glow plug. In the plug.

It is most remarkable in the present invention that the outer peripheral surface of the press-fitting portion or the inner peripheral surface of the fitting portion has uneven portions arranged in a pattern not parallel to the axial direction of the glow plug. Is provided.

As described above, the uneven surface has uneven portions arranged in a pattern non-parallel to the axial direction of the glow plug. Examples of the non-parallel pattern include linear and lattice patterns provided in a direction orthogonal to the axis of the glow plug or in a direction oblique with a predetermined inclination angle. Further, a pattern in which non-parallel lines in the axial direction are randomly arranged, or a scattered pattern can be used.

[0011] Further, the uneven portion means a portion having at least one of a protruding portion protruding from the other surface or a concave portion recessed from the other surface. The non-parallel pattern means a pattern of the arrangement of the concave and convex portions. Further, the uneven surface is provided on either the press-fitting portion or the fitting portion. In this case, it is preferable to determine which of the uneven surfaces is to be provided based on the hardness of both, and to provide the higher hardness. Thereby, the adhesion between the two can be further improved.

Next, the operation and effect of the present invention will be described.
In the glow plug according to the present invention, the uneven surface is provided on the press-fitting portion or the fitting portion which is a press-fitting fixed portion between the heater and the housing. Therefore, the heater and the press-fitting fixed portion of the housing can maintain sufficient airtightness.

The reason is considered as follows. That is, when the press-fitting portion or the fitting portion has an uneven surface, the press-fitting is performed so that the uneven surface of the uneven surface is sunk into the opposing surface or the opposing surface is contacted. It is in a state of being immersed. Also, this uneven part
As described above, they are arranged non-parallel to the axial direction of the glow plug.

Therefore, of the contact portions between the press-fitting portion and the fitting portion, the portion where the uneven portion is disposed is very firmly adhered to and plays a role as a barrier for preventing air conduction. Therefore, even when the glow plug is used under a high pressure, it is considered that air entering between the heater and the housing can be blocked and airtightness can be maintained.

Therefore, according to the present invention, the airtightness between the housing and the heater can be easily maintained by providing the uneven surface on the outer peripheral surface of the press-fitting portion or the inner peripheral surface of the fitting portion. A glow plug that can be provided.

Next, as in the second aspect of the present invention, the surface roughness (Rz) of the uneven surface is preferably 25 μm or less. If it exceeds 25 μm, there is a problem that the effect of improving the airtightness between the heater and the housing is small.

It is preferable that the uneven surface occupies 20% or more of the surface area of the press-fitting portion or the fitting portion. If less than 20%
There is a problem that the effect of improving the airtightness due to the presence of the uneven surface is not sufficiently exhibited. Therefore, it is more preferably 90% or more. Note that the upper limit is physically 100%.

Further, it is preferable that the pattern of the uneven surface is a linear pattern. The linear pattern referred to here is, for example, a pattern in which oblique lines having a predetermined angle with respect to the axial direction of the glow plug are continuously or intermittently arranged as shown in the drawings described later. In this case, for example, the concave and convex portions can be easily provided simultaneously with the cutting or grinding.

Further, it is preferable that the linear pattern is inclined at least 30 degrees with respect to the axial center direction of the glow plug. If it is less than 30 degrees, there is a problem that the effect of improving the airtightness between the heater and the housing cannot be sufficiently obtained.

Next, as in the sixth aspect of the present invention, there is provided a housing having an inner hole, a heater press-fitted and fixed in the inner hole of the housing, and a center shaft for supplying electricity to the heater. The press-fitting between the housing and the heater is performed by press-fitting a fitting portion provided in an inner hole of the housing and a press-fitting portion provided on the outer periphery of the heater. In the manufacturing method, before performing the step of press-fitting the heater and the housing, the outer peripheral surface of the press-fit portion or the inner peripheral surface of the fitting portion is non-parallel to the axial direction of the glow plug. There is a method for manufacturing a glow plug characterized by providing an uneven surface having uneven portions arranged in a simple pattern.

It should be noted that in the present manufacturing method, before performing the press-fitting step, the uneven surface is provided on the outer peripheral surface of the press-fit portion or the inner peripheral surface of the fitting portion in advance. . As described above, the uneven surface has uneven portions arranged in a pattern that is not parallel to the axial direction of the glow plug. Therefore, by performing the subsequent press-fitting step, it is possible to obtain a press-fitting fixed part having excellent airtightness.

Therefore, according to the present manufacturing method, it is possible to provide a method for manufacturing a glow plug which can easily maintain the airtightness between the housing and the heater.

The method of providing the above-mentioned uneven surface is as follows.
Various methods can be taken. In particular, it is preferable that the uneven surface is provided by cutting or grinding the press-fit portion or the fitting portion. This makes it possible to easily form the uneven surface while easily securing the roundness of the press-fit portion or the fitting portion.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment A glow plug according to an embodiment of the present invention and a method of manufacturing the glow plug will be described with reference to FIGS. As shown in FIG. 1, the glow plug 1 of the present embodiment includes a housing 5 having an inner hole 50, a heater 10 press-fitted and fixed in the inner hole 50 of the housing 5, and a center shaft 4 for energizing the heater 10. And

The press-fitting of the housing 5 and the heater 10 is performed by press-fitting a fitting portion 55 provided in the inner hole 50 of the housing 5 and a press-fitting portion 15 provided on the outer periphery of the heater 10. On the outer peripheral surface of the press-fitting portion 15, an uneven surface 60 having uneven portions 6 arranged in a pattern non-parallel to the axial direction of the glow plug 1 is provided.

The heater 10 is provided as shown in FIG.
Metal tube 11 having a U-shaped cross section with its tip 111 closed
And the heat coil 3 housed via the insulating powder 2 filled in the metal tube 11. Also, the center shaft 4 has its tip 41 connected to the insertion side end of the heater 10 (the metal tube 1).
1 (opening end of the opening) 112 and is buried in the insulating powder 2. The heat coil 3 has one end 31 welded to the inner surface of the distal end of the metal tube 11 and the other end 32 welded to the distal end of the center shaft 4. Others are the same as the conventional example.

Next, a method of manufacturing the glow plug 1 will be described. In this embodiment, first, a metal tube 11 for the heater 10 is prepared, and the heat coil 3
A central shaft 4 having one end welded is prepared. Next, the heat coil 3 is inserted into the metal tube 11 and the other end of the heat coil 3 and the inner surface of the tip 111 of the metal tube 11 are welded.

Next, the insulating powder 2 is filled in the metal tube 11 so as to fill the ends of the heat coil 3 and the center shaft 4.
(MgO) powder as a filler. Next, a swaging process is performed from the outer peripheral surface of the metal tube 11, and the metal tube 11 is compressed and reduced in diameter. Thereby, the packing density of the insulating powder 2 in the metal tube 11 is improved, and the center shaft 4 and the heater 10 are integrated.

Next, in the present embodiment, as shown in FIG. 2, the press fitting portion 15 of the heater 10 is subjected to grinding.
This grinding process is for improving the roundness of the press-fitting portion 15 of the heater 10 and for providing the uneven surface 60.
More specifically, the roundness of the press-fitting portion 15 is adjusted by adjusting the feed of a grindstone for grinding, and the uneven portion 6 having a linear pattern is provided.

The uneven portion 6 is provided uniformly on the entire surface of the press-fit portion 15. That is, the uneven surface 60 of this example is provided so as to occupy 100% of the surface area of the press-fitting portion 15. Further, as shown in FIG. 2, the pattern of the concavo-convex portions 6 in this example is an intermittent linear pattern, and is provided so as to intersect in a direction substantially perpendicular to the axis direction.

Next, as shown in FIG. 3, the housing 5 is prepared, and a press-fitting step of press-fitting and fixing the heater 10 to the housing 5 is performed. As shown in the figure, the housing 5 has an inner hole 50 penetrating in the axial direction thereof, and has a fitting portion 55 at a position slightly inside the heater insertion opening 51. The material of the housing 5 is a heater 10.
The one with lower hardness than that is adopted.

The housing 5 is, as shown in FIG.
The housing 5 is placed on the housing jig 86 with the heater insertion port 51 facing upward. Next, the heater 10 held by the heater fixing jig 81 is moved from the center shaft 4 to the top.
The heater 10 is inserted into the inner hole of the housing 5 and the heater 10 and the housing 5 are temporarily assembled.

Next, the heater 10 is strongly pressed by the heater fixing jig 81 to press-fit the press-fit portion 15 into the fitting portion 55 of the housing 5. At this time, a lubricant is applied to the press-fitting portion 15 of the heater 10 in advance. This lubricant is for preventing an increase in the pressing load at the time of press-fitting and fixing due to the provision of the uneven surface 60. In this example, fluorine-based grease was used as the lubricant. Instead of this, silicon-based grease, synthetic hydrocarbon-based grease, polyglycol-based grease, phenyl ether-based grease, or the like can also be used.

Upon completion of the press-fitting and fixing, the glow plug 1 in which the heater 10 and the housing 5 are firmly integrated as shown in FIG. 1 is obtained. A nut 71, a resin bush 72, an O-ring 73 made of an insulating elastic material, and a resin washer 74 are disposed on the center shaft protruding side of the housing 5 as in the related art.

The glow plug 1 thus obtained
The airtightness between the heater 10 and the housing 5 is extremely excellent. That is, since the press-fit portion 15 is provided with the uneven surface 60, the press-fitting causes the uneven portion 6 of the uneven surface 60 to be sunk or sunk into the fitting portion 55 that comes into contact therewith. It will be in a state where it was not. The uneven portions 6 are arranged in a direction substantially orthogonal to the axial direction of the glow plug as described above.

Therefore, the uneven portion 6 in the press-fit fixed portion
Plays a role such as a barrier that tightly adheres tightly to the fitting portion 55 and prevents air conduction. Therefore, even when the glow plug 1 is used under high pressure, the uneven portion 6 can block the air that is going to enter between the heater 10 and the housing 5 and maintain the airtightness.

The glow plug 1 having excellent airtightness can be easily manufactured by forming the uneven surface 60 in the above-mentioned grinding process. Therefore, according to this example, it is possible to provide the glow plug 1 and the method for manufacturing the glow plug 1 that can easily maintain the airtightness between the housing 5 and the heater 10.

Embodiment 2 In this embodiment, as shown in FIG. 4, a concave-convex surface 62 is provided in the press-fitting portion 15 of the heater 10 by performing cutting instead of grinding in Embodiment 1. . Uneven surface 6 of this example
As shown in FIG. 2, the unevenness portion 6 is arranged in a spiral pattern on the entire surface of the press-fit portion 15, as shown in FIG. Other configurations are the same as those of the first embodiment. In this case, the same effect as that of the first embodiment can be obtained.

Embodiment 3 As shown in FIG. 5, the present embodiment relates to the uneven surface 62 of Embodiment 2.
Instead, a press-fit portion 15 is provided with a concave-convex surface 63 having a concave-convex portion 6 of a lattice pattern by grinding, knurling, or the like. Others are the same as the second embodiment. In this case, the same effect as that of the first embodiment can be obtained.

Fourth Embodiment As shown in FIG.
This is an example in which a concave-convex surface 64 is provided. That is, the press-fit portion 15 of the heater 10 according to the first embodiment does not need to be provided with the uneven surface 60 only by grinding. Then, on the surface of the fitting portion 55 of the housing 5, an uneven surface 64 in which the uneven portion 6 of an intermittent linear pattern was provided in a direction substantially perpendicular to the axial direction was formed by grinding. The housing 5
Is harder than the heater 10. Other configurations are the same as those of the first embodiment. In this case, the same effect as that of the first embodiment can be obtained.

Fifth Embodiment As shown in FIG. 7, in this embodiment, an uneven surface 65 is provided in the fitting portion 55 of the housing 5 by performing cutting instead of grinding in the fourth embodiment. is there. As shown in the figure, the uneven surface 65 of the present example has the uneven portion 6 arranged in a spiral pattern on the entire surface of the fitting portion 55. Others are the same as the fourth embodiment. In this case, the same effect as that of the first embodiment can be obtained.

Embodiment 6 As shown in FIG. 8, the present embodiment relates to the uneven surface 65 of Embodiment 5.
Instead, the fitting portion 55 is provided with an uneven surface 66 having the uneven portion 6 in a lattice pattern by grinding, knurling, or the like. Others are the same as the fifth embodiment. In this case, the same effect as that of the first embodiment can be obtained.

[Brief description of the drawings]

FIG. 1 is a partially cutaway sectional view of a glow plug according to a first embodiment.

FIG. 2 is an explanatory view showing an uneven surface of a heater in the first embodiment.

FIG. 3 is an explanatory diagram showing a press-fit fixed state between a heater and a housing in the first embodiment.

FIG. 4 is an explanatory view showing an uneven surface of a heater in a second embodiment.

FIG. 5 is an explanatory diagram showing an uneven surface of a heater in a third embodiment.

FIG. 6 is an explanatory diagram showing an uneven surface of a housing in a fourth embodiment.

FIG. 7 is an explanatory view showing an uneven surface of a housing in a fifth embodiment.

FIG. 8 is an explanatory view showing an uneven surface of a housing in a sixth embodiment.

FIG. 9 is a partially cutaway cross-sectional view of a conventional glow plug.

[Explanation of symbols]

 1. . . Glow plug, 10. . . Heater, 11. . . Metal tube, 15. . . Press-fit part, 2. . . 2. insulating powder; . . Heat coil, 4. . . Center axis, 5. . . Housing, 50. . . Inner bore, 55. . . Fitting part, 6. . . Irregularities, 60. . . Uneven surface,

Claims (7)

[Claims] 1. A housing having an inner hole, a heater press-fitted and fixed in the inner hole of the housing, and a center shaft for energizing the heater. Is fixed by press-fitting a fitting portion provided in an inner hole of the housing with a press-fitting portion provided on the outer periphery of the heater. A glow plug characterized in that an uneven surface having uneven portions arranged in a pattern non-parallel to the axial direction of the glow plug is provided on an inner peripheral surface of the joining portion. 2. The glow plug according to claim 1, wherein the surface roughness (Rz) of the uneven surface is 25 μm or less. 3. The glow plug according to claim 1, wherein the uneven surface occupies at least 20% of a surface area of the press-fit portion or the fitting portion. 4. The method according to claim 1, wherein:
The glow plug, wherein the pattern on the uneven surface is a linear pattern. 5. The glow plug according to claim 4, wherein the linear pattern is inclined at least 30 degrees with respect to the axial direction of the glow plug. 6. A housing having an inner hole, a heater press-fitted and fixed in the inner hole of the housing, and a center shaft for energizing the heater. The method of manufacturing a glow plug by press-fitting a fitting portion provided in an inner hole of the housing and a press-fitting portion provided on an outer periphery of the heater in the method of manufacturing a glow plug. Before performing the press-fitting step, the outer peripheral surface of the press-fitting portion or the inner peripheral surface of the fitting portion has irregularities arranged in a pattern non-parallel to the axial direction of the glow plug. A method for manufacturing a glow plug, comprising providing an uneven surface. 7. The method of manufacturing a glow plug according to claim 6, wherein the uneven surface is provided by cutting or grinding the press-fit portion or the fitting portion.