JPH026413B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a glow plug used for preheating the sub-combustion chamber or combustion chamber of a diesel engine, and particularly to a glow plug for a diesel engine using a ceramic heater as a heating element. The present invention relates to a method for manufacturing a glow plug.

[Conventional technology]

Generally, diesel engines have poor starting performance at low temperatures, so a glow plug is installed in the auxiliary combustion chamber or combustion chamber, and by passing an electric current through it and generating heat, it is possible to raise the intake air temperature or to use it as an ignition source. A method has been adopted to improve starting performance. This type of glow plug has a structure called a so-called sheath-type glow plug, in which a heat-resistant metal sheath is filled with heat-resistant insulating powder and a coiled heating wire is embedded.
Various structures are known, including ceramic heater types that use rod-shaped heaters with resistors embedded in ceramic material, etc. The latter ceramic heater type in particular has a higher heat transfer efficiency than the sheath type. It has attracted attention in recent years because it has excellent properties and can demonstrate its performance as a rapid heating type.

To briefly explain its schematic structure using a glow plug for a diesel engine as shown in FIG. 10) embedded therein, the rod-shaped ceramic heater 2 is made entirely of a heat-resistant and insulating ceramic material, and a metal holder 3 having a substantially tubular shape that holds the ceramic heater 2 at its tip. An external connection terminal 5 is fitted and held concentrically at the rear end of the holder 3 via an insulating bushing 4 made of synthetic resin, and the external connection terminal 5 is connected to the rear end of the heater 2. A metal conducting wire 6 such as a flexible wire extending from the wire is connected to the tip by spot welding or the like.

As is well known, the above-mentioned ceramic heater 2 has a substantially elliptical cross section, and is molded by pressurizing and firing ceramic powder filled with the above-mentioned resistor held in the mold. It is something that
In this case, the reason why the cross section is approximately elliptical is to improve the density of the ceramic material compared to the circular shape, and to make the heat resistance strength, thermal conductivity, etc. more effective.
The ceramic heater 2 is made of silicon, a so-called fine ceramic material that is stable in performance even at high temperatures (up to about 1700 degrees Celsius) and has excellent insulation and thermal shock resistance. Non-oxides such as silicon-based nitrides are preferred.

In addition, 2a and 2b in the figure are metal coating layers formed on the outer periphery of the central portion in the axial direction, the outer periphery of the rear end portion, and the end surface of the ceramic heater 2, and these are metal coating layers formed at both ends of the resistor embedded in the heater 2, respectively. connected via. That is, since the above-mentioned ceramic heater 2 generally causes some problems when bonded to metal materials, the above-mentioned metal coating layers 2a and 2b are formed on the surface of the ceramic material in advance to ensure adhesion with the metal material. The purpose is to ensure the strength of the bond. and,
A metal coating layer 2a at the center of the heater 2 is connected to a reinforcing metal pipe 7 fitted and fixed to its outer periphery, and is connected to the holder 3 side through this. is covered with a terminal cap 8 and connected to the conductive wire 6. In this case, the metal pipe 7 is connected to the heater 2
This serves as a reinforcing member to hold the heater 2 at the tip of the holder 3, and the through hole inside the heater 2
The heater 2 and the holder 3 are each fixed to the heater 2 and the holder 3 by silver brazing or the like. Further, the terminal cap 8 is similarly formed to match the cross-sectional shape of the heater 2, and is fixed by silver brazing or the like while the conductor wire 6 is connected by welding or the like.

On the other hand, the screw portion formed on the rear end side of the external connection terminal 5 includes an insulating ring 9a, a fixing nut 9b, a spring washer 9c, and a washer 9.
d, and a nut 9e for tightening the external lead is screwed together, and the external connection terminal is connected by sandwiching the lead wire from the battery (not shown) between the washer 9d and the nut 9e and tightening the nut 9e. 5 is electrically connected to the battery terminal. By screwing the threaded portion 3a formed on the outer periphery of the holder 3 into a threaded hole formed in the cylinder head of the engine, the resistor in the ceramic heater 2 is electrically connected via the holder 3. is connected to ground.

Note that 4a in the figure is fitted onto the outer periphery of an insulating bushing 4 that holds an external connection terminal 5 at the rear end of the holder 3, and is buckled in the axial direction due to the high pressure applied by the rear end of the holder 3, which is caulked during assembly. This is a metal tube for integrating the insulating bushing 4 with the holder 3 side with the required mechanical strength and creating a structure that is less susceptible to temperature effects. In addition, the reason why the external connection terminal 5 is connected to the heater 2 made of the ceramic material described above using the metal conductor wire 6 is to prevent the heater 2 from being damaged by mechanical external forces such as various vibrations and tightening torques applied to the external connection terminal 5. This is for protection, and it is preferable to use a material that has a certain degree of flexibility as the material for the conducting wire 6. Here, 6a in the figure is a heat-resistant insulating tube covered with the conducting wire 6.

[Problem that the invention seeks to solve]

By the way, in the conventional ceramic heater type glow plug 1 having the above-described configuration, the ceramic heater 2 is usually pre-assembled with the metal pipe 7 and the terminal cap 8 having the metal conductive wire 6 by silver brazing or the like as a subassembly. Although it is attached to the holder 3 in an assembled state, some problems occur when the metal pipe 7 is welded and fixed to the tip of the holder 3 by silver brazing or the like during this assembly. There is. That is, as shown in FIG.
The part fitted into the holder 3 along the axial direction is silver-brazed to the inner circumferential surface of the holder 3, and the metal pipe on which the ring-shaped brazing filler metal 11 is placed during this brazing is 7 and holder 3
It is necessary to apply flux to the joint portion (indicated by A in FIG. 4). If this flux accidentally adheres to the joint between the heater 2 and the metal pipe 7 fitted around its outer periphery (indicated by B in the figure), the flux will be removed during heating by the high frequency coil 12 or the like. The melted water enters the gap between the heater 2 and the metal pipe 7 due to capillary action, which not only makes it impossible to maintain the joint strength and conductivity of this part, but also causes the As shown, the lead portion 10 of the resistor 10 embedded in the heater 2 is
There is a possibility that the particles may enter the heater 2 through the lead portion 10a and the resistor 10 from the joint portion of one of the electrodes a and 10b (10a) with the metal pipe 7, resulting in deterioration of its performance.

That is, the heater 2 and metal pipe 7 described above
Due to the poor bonding between the ceramic and the metal, it is practically impossible to achieve complete brazing on the bonded surface by brazing, which results in a slight gap. Therefore, when the flux melts as described above, it enters the resistor 10 side through the joint between the heater 2 and the metal pipe 7, and further into the heater 2 through the lead portion 10a, which impairs the assembly. If the heater 2 is energized during a quality inspection after work is completed, the heat generated by the heater 2 may cause the moisture that has entered the product to vaporize and expand, leading to problems such as damage to the heater 2. It was something that had this. In particular, such problems can occur depending on the specifications of the engine, as shown in the diagram.
This is noticeable when the amount of protrusion of the metal pipe 7 from the tip of the holder 3 is required to be small, and it is necessary to be very careful when applying the flux. This is troublesome and complicated, and it is desired that some kind of countermeasure be taken to eliminate the need for such consideration.

That is, due to the increased use of engines in recent years, the amount of protrusion of the heater 2 from the holder 3 and the amount of protrusion of the metal pipe 7 that holds it (indicated by L in FIG. 1) with respect to the glow plug 1 described above have changed. It is desired that the metal pipe 7 and the heater 2 be made as small as possible, and the junction between the metal pipe 7 and the heater 2 is connected to the ground of the resistor 10 in the heater 2 to the holder 3 side, and is also connected to the ground inside the engine when the engine is installed. It is also important to obtain strength against explosions, and there is a great need to eliminate the problems that occur when the metal pipe 7 and holder 3 are brazed together.

The present invention has been made in view of the above-mentioned circumstances, and in a glow plug for a diesel engine, when a metal pipe that holds a ceramic heater is brazed to the tip of the holder, flux is mixed with the metal pipe. Problems caused by adhesion to excess parts that connect to the heater, and the heating during brazing melts the flux and causes moisture to flow from the joint between the heater and metal pipe to the resistor side inside the heater. This eliminates the problem of intrusion and performance deterioration, and also makes it possible to perform the brazing work easily and properly, simplifying the manufacturing work of glow plugs.
The object of the present invention is to provide a method for manufacturing a glow plug for a diesel engine that can greatly improve assembly efficiency and ensure the strength and operational reliability of each part.

[Means for solving problems]

A method of manufacturing a glow plug for a diesel engine according to the present invention involves fitting a metal pipe, which is fitted and fixed to the axial center of a rod-shaped ceramic heater in which a resistor is embedded, into the tip of a hollow holder. Next, flux is applied to the upper end of the joint between the holder and the metal pipe, and a brazing material is placed.Then, by heating the outer circumference of the holder with the heater energized, the holder and the metal pipe are heated. It is designed to be brazed to a manufactured pipe.

[Effect]

According to the present invention, when the holder and the metal pipe are brazed, the ceramic heater is energized and the internal resistor is configured to generate heat, so that the metal pipe and the ceramic heater are connected. Even if flux intrudes into the welded brazed parts, it will be evaporated and vaporized by the heat generated by the heater, making it possible to easily and reliably prevent flux from entering.

〔Example〕

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

Figures 1 and 2 show an embodiment of the method for manufacturing a glow plug for a diesel engine according to the present invention, and in these figures, parts that are the same as or correspond to those in Figure 4 described above are designated by the same numbers. The explanation will be omitted.

Now, according to the present invention, in the ceramic heater type glow plug 1, the resistor 10;
Rod-shaped ceramic heater 2 formed by embedding 10b
is held at the tip of the holder 3 via a metal pipe 7 that is fitted and fixed in the axial center of the heater 2 and brazed to the tip of the holder 3. Next, flux is applied to the upper end of the joint between the holder 3 and the metal pipe 7 (indicated by A in the figure), and the brazing material 11 is placed. After that, with the heater 2 energized, A feature is that the holder 3 and the metal pipe 7 are brazed together by heating the outer circumference of the holder 3 with a high-frequency coil 12 or the like.

To explain this in detail, first, the outline of the high-frequency brazing device 20 for glow plugs shown in FIG. 2 will be briefly explained.
Reference numeral 22 denotes a lifting platform which is supported by the pillar 21 so as to be able to rise and fall freely; 23 is a cylinder that drives the lifting table 22;
A glow plug holding section 24 is provided for holding the heater 2 in an upright position. Reference numeral 25 denotes a ceiling plate that spans the upper end of the support column 21, and a high-frequency device 26 that holds the high-frequency coil 12 is disposed below the ceiling plate. Reference numeral 27 denotes an elevating plate that moves up and down at the small diameter portion 21a at the upper end of the pillar 21, and in the center thereof, the tip side of the holder 3 of the glow plug 1 erected by the glow plug holding portion 24 can be freely rotated. Rotation holding part 2 held in
8 is provided. In addition, 29 is this elevating plate 2
7. This spacer 29 is for adjusting the amount of upward movement of the elevating plate 27, that is, the positional relationship between the glow plug 1 and the high-frequency coil 12, as described above. heater 2 from holder 3 in glow plug 1;
This is selected and used when the amount of protrusion of the metal pipes 7 is different.

A "-" terminal is taken out from the elevating plate 27 that holds the holder 3 of the glow plug 1 and connected to the ground, and the "-" terminal is connected to the external connection terminal 5 of the glow plug 1 in the glow plug holding part 24. A conductive sleeve 33 and a leaf spring 34 are provided via a carbon brush 30, a conductive cylinder 31, and a screw member 32, which connect the "+" terminal, so that the heater 2 of the glow plug 1 can be energized. has been done. In addition, in the figure, 35 and 36 are the glow plug 1 in the glow plug holding part 24.
An insulator that holds the rear end of the holder 3, and a part of the insulator is fitted into the inside of the holder 3 from the rear end and locks the insulating bushing 4, thereby connecting the heater 2, external connection terminal 5, etc. to the holder 3. A locking portion 36a is formed for positioning in the axial direction.
Further, 37 is a support portion that rotatably supports the glow plug holding portion 24 on the lifting platform 22, and 38 is a rubber belt that transmits rotation from a motor (not shown) to the holding portion 24.

Brazing of the holder 3 of the glow plug 1 and the metal pipe 7 on the heater 2 side using the apparatus 20 having the above-described configuration is as follows.

That is, the heater assembly consisting of the heater 2, the metal pipe 7, etc. and the external connection terminal 5 are assembled via the conductor wire 6, and then fitted into the holder 3, and in this state, the glow plug is held. The heater 2 is held facing upward relative to the section 24. At this time, the elevating table 22 is lowered below the apparatus. Next, holder 3 of glow plug 1
Flux is applied to the upper end of the joint between the upper end and the metal pipe 7, and the brazing material 11 is fitted and arranged. Then, turn on the switch and lift platform 2.
2 to a desired position, the holder 3 is held by the rotation holding part 28 of the elevating plate 27, and the joint between the holder 3 and the metal pipe 7 is loosely fitted into the high frequency coil 12. .

In this state, glow plug 1 is connected to the "+" terminal.
The heater 2 is energized, and while the flux adhering to the joint between the heater 2 and the metal pipe 7 is evaporated by the heat generated by the heater 2, the high frequency coil 12 is energized to melt the brazing material 11 and attach the holder. 3
and the metal pipe 7 are brazed. At this time, the glow plug 1 is rotated by the rotation mechanism described above, and is configured to perform uniform brazing. When the brazing is completed, the lifting platform 24 is lowered and the glow plug 1 is lowered.
It is a good idea to remove it.

Here, the heater 2 and the high frequency coil 12 described above are
The state of energization is shown in Figures 3a and 3b. First, a voltage of 4 to 6 V is applied to the heater 2, and the temperature rises to about 350 to 450°C in about 4 to 6 seconds. to rise. Then, while the heater 2 is still energized, the high frequency coil 12 is
Apply a voltage of 1.5KV for about 7 to 9 seconds,
The holder 3 and the metal pipe 7 are melted by melting the brazing material 11.
and brazing. Further, after the completion of this brazing, the heater 2 is kept energized for approximately 1 to 3 seconds to completely prevent flux from entering the heater 2 side.

According to the manufacturing method of the present invention as described above, when the holder 3 and the metal pipe 7 are brazed, the ceramic heater 2 is energized to cause the resistor 10 inside thereof to generate heat. Therefore, metal pipe 7 and heater 2
Even if flux intrudes into the brazed part that joins the two, it will evaporate and vaporize due to the heat generated by the heater 2 mentioned above, making it possible to easily and reliably prevent flux from entering, making the brazing work simple. Moreover, it can be done reliably, and as a result, it is highly effective in eliminating the conventional problems and stabilizing the performance quality and improving the durability of the glow plug 1.

Note that the present invention is not limited to the structure of the embodiment described above, and the shape, structure, etc. of each part may be modified or changed as appropriate. For example, in the above-mentioned embodiment, a case has been described in which the ceramic heater 2 and the external connection terminal 5 are assembled into the holder 3 in a state where they are connected in advance with the conductor wire 6, but the present invention is not limited to this, and the The above-mentioned brazing operation may be performed while the wire is pulled out from the rear end of the holder 3, and the conductive wire 6 and the external connection terminal 5 may be connected after the brazing. Furthermore, the structure of the glow plug 1 for a diesel engine to which the present invention is applied is not limited to that shown in FIG. pipe 7
The effect can be exhibited when the metal pipe 7 is brazed.In this case, it goes without saying that the metal pipe 7 may be applied to a pipe in which the amount of protrusion from the holder 3 is relatively long.

〔Effect of the invention〕

As explained above, according to the method for manufacturing a glow plug for a diesel engine according to the present invention, a metal pipe is fitted and brazed in the axial center of a rod-shaped ceramic heater in which a resistor is embedded. In order to braze this metal pipe to the tip of the holder, the metal pipe fitted to the heater is fitted and positioned to the tip of the holder, and then this holder and the metal pipe are connected. The holder and the metal pipe are brazed together by applying flux to the upper end of the joint with the metal pipe and placing the brazing material thereon, and then heating the outer circumference of the holder with the heater energized. Despite being a simple and inexpensive method, we have solved the problem of the flux applied during brazing melting and its moisture entering the brazed joint surface of the metal pipe and ceramic heater through capillary action. This can be easily and reliably prevented by generating heat on the heater side, which stabilizes the performance and quality of the glow plug, and also prevents cracking and deterioration of each component, especially the heater part, improving durability. Moreover, it has various excellent effects such as a simple overall structure and excellent ease of assembly.

[Brief explanation of drawings]

Fig. 1 is an enlarged longitudinal sectional side view of the main parts showing an embodiment of a glow plug for a diesel engine to which the manufacturing method according to the present invention is applied, Fig. 2 is a schematic configuration diagram showing an example of the manufacturing apparatus, and Fig. 3a , b are time charts showing the energization state of the heater and the high-frequency brazing coil that characterize the present invention, and FIG. 4 is a schematic longitudinal sectional side view showing an example of a glow plug for a diesel engine to which the present invention is applied. 1...Glow plug for diesel engine, 2
... Ceramic heater, 3 ... Hollow holder, 5
...External connection terminal, 6...Metal conductor wire, 7...Metal pipe, 8...Terminal cap, 10...
Resistor, 11... ring-shaped brazing material, 12... high frequency coil, 20... high frequency brazing device for glow plug.

Claims (1)

[Claims] 1. A method for manufacturing a glow plug for a diesel engine, which comprises holding a rod-shaped ceramic heater having a resistor embedded in a hollow holder tip via a metal pipe fitted in the axial center of the rod-shaped ceramic heater. , with a metal pipe fitted and fixed to the outer periphery of the central part of the heater, the heater is fitted and positioned at the tip of the holder, and then the upper end of the joint between the holder and the metal pipe is fitted and fixed. A glow plug for a diesel engine, characterized in that the holder and a metal pipe are brazed by applying flux to the holder and placing a brazing material thereon, and then heating the outer peripheral part of the holder while energizing a heater. manufacturing method.