JPH0310844B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a glow plug used for preheating a sub-combustion chamber or a combustion chamber of a diesel engine.

[Prior art] Diesel engines generally have poor starting performance at low temperatures, so a glow plug is installed in the auxiliary combustion chamber or combustion chamber, and current is passed through it to generate heat, thereby increasing the intake air temperature or igniting the engine. A method has been adopted in which the engine is used as a source to improve engine startability. As this type of glow plug, there are so-called sheath-type glow plugs, in which a heat-resistant metal sheath is filled with heat-resistant insulating powder and a coiled heating wire is embedded, and the resistor is made of ceramic material. Various structures are known, such as a ceramic heater type using an embedded heater rod. In particular, the latter ceramic heater type has attracted attention in recent years because it has superior heat transfer efficiency than the conventional sheath type and can demonstrate its performance as a rapid heating type.

An example of this can be briefly explained using Figure 1.
The glow plug, which is designated as a whole by the reference numeral 10, includes a heater rod 11 having a roughly elliptical cross section (see FIG. 3) made of ceramic material in which a resistor (not shown) that generates heat when energized is embedded, and 11
It is provided with a metal holder 12 having a substantially tubular shape and holding the metal holder 12 at its distal end. At the rear end of this holder 12 is an insulating bushing 13 made of resin.
An external connection terminal 14 is fitted through the heater rod 11, and the external connection terminal 14 is connected to the rear end of the heater rod 11 through a conductive wire 15 such as an iron wire.

Reference numerals 16 and 17 denote metal metallized layers formed on the outer periphery of the center portion, the outer periphery of the rear end portion, and the end surface of the heater rod 11, respectively, and these are lead portions at both ends of the resistor embedded in the heater rod 11, respectively. connected via. And heater rod 11
The central metallized layer 16 is connected to the holder 1 through a reinforcing metal pipe 18 fitted around its outer periphery.
The metallized layer 17 on the rear end side is covered with a terminal cap 19 and connected to the conductive wire 15. Here, the metal pipe 18 holds the heater rod 11 in the holder 12.
It also functions as an auxiliary member to be held at the tip of the heater rod 11, and has a through hole formed to match the irregular cross-sectional shape of the heater rod 11.
1 and holder 12 by welding and fixing, for example, by silver brazing. On the other hand, the terminal cap 19 is similarly formed to match the cross-sectional shape of the heater rod 11, and is welded and fixed by, for example, silver brazing. The conductive wire 15 is connected to this terminal cap 1.
9 at the same time by brazing or the like, or by being fixed and connected in a later process by welding, soldering, etc.

Further, the outer peripheral portion of the electric wire 15 described above is covered with an insulating tube 15a, and the rear end is connected to the inner end of the external connection terminal 14 by welding or the like. The external connection terminal 14 is assembled in such a manner that the insulating bush 13 holding the external connection terminal 14 is locked at the rear end of the holder 12 by caulking the periphery of its opening.
Here, the connection portion of the external connection terminal 14 described above is connected to the holder 12 via the insulating bushing 13.
It is necessary to firmly fix it to the side to prevent it from slipping out and preventing it from rotating, but this can be satisfied by the presence of the metal tube 13a coated on the outer periphery of the resin insulating bush 13. be.

That is, since a rotational force acts on the external connection terminal 14 when tightening the lead wire, when this rotational force is transmitted to the heater rod 11 fixed to the holder 12 side via the conductor 15, the conductor 15 This is a problem in ensuring the strength of the connection part of the heater rod 11 and the connection part of the heater rod 11, and the same applies to the disconnection of the external connection terminal 14. Of course, a highly flexible flexible wire or the like is used as the conducting wire 15, and is configured to function as a cushioning material, and the insulating bushing 13 is press-fitted or insert-molded into the external connection terminal 14 which has been knurled or the like. However, the above-mentioned problems cannot be completely prevented. Furthermore, an insulating bushing 13 which is simply a resin molded product
If only the bushing 13 is used, there is a risk that the bushing 13 will thermally shrink due to the difference in thermal expansion coefficient with the holder 12, creating a gap between the two and loosening.
This is noticeable when the device is used for a long period of time in a place with a large difference in ambient temperature.

On the other hand, the metal tube 13a described above is covered with an insulating bushing 13 made of resin, and these are placed in the holder 12.
After the metal tube 13a is inserted into the holder 12 and its inner end is locked with a step inside the holder 12, the opening edge of the holder 12 is caulked with high pressure.
is clamped with a large force from both ends, resulting in buckling deformation along the axial direction, as shown in FIG. 2 if this is illustrated in an extreme manner. In this state, the outside of the metal tube 13a is connected to the holder 12.
The inner side is firmly pressed and fixed to the insulating bushing 13 side, and as a result, they are integrated with the desired mechanical strength, and even if the resin part shrinks slightly due to heat, it will not shrink. The amount of deformation is absorbed and problems such as loosening are resolved.

The rear end side of the external connection terminal 14 is a threaded portion, into which an insulating ring 20, a nut 21, a spring washer 22, a washer 23, a nut 24 for tightening an external lead, etc. are screwed together. The external connection terminal 14 is electrically connected to the battery terminal by clamping a lead wire from a battery (not shown) between the washer 23 and the nut 24. Further, by screwing the threaded portion 25 formed on the outer periphery of the holder 12 into a screw hole drilled in the cylinder housing of the engine, the heater rod 11 is electrically connected to earth via the holder 12. The tip of the heater rod 11, which is arranged to protrude into the cylinder, becomes red hot by the applied current.

By the way, the glow plug 1 with the above-mentioned configuration
In No. 0, it is desired that the metal pipe 18 to the heater rod 11 and the joint portion of this metal pipe 18 to the holder 12 be connected in a manner that does not cause airtight leakage or poor connection. . In other words, each of the above-mentioned joints faces into the engine and is exposed to the air-fuel mixture and combustion gas atmosphere, and if an airtight leak occurs in this part, fuel oil, moisture, etc. will enter the glow plug 10 through the gap. This may not only affect the durability of the heater rod 11, but also cause poor contact at each electrical connection, causing problems such as the inability to function as a glow plug.
In particular, problems such as airtight leakage often occur due to separation of the welded part between the ceramic heater rod 11 and the metal pipe 18, which have different coefficients of thermal expansion, and moisture etc. in this part. Infiltration of the heater rod 11 may lead to damage due to rapid heat generation, which is a problem in achieving stability of durability and quality. This is clear from the fact that the heater rod 11 portion of this glow plug is alternately heated and cooled during engine operation, including when it generates heat, and when the engine is stopped.

Therefore, in order to prevent such air leakage, the metal pipe 18 and terminal cap 19, as well as the conductor 15 connected thereto, are heated to about 800°C in a furnace, for example. Conventionally, it has been proposed that the parts are welded and fixed in advance by silver brazing to obtain the required bonding strength. This is because in order to silver-braze the metal parts to the ceramic materials mentioned above, it is necessary to heat the entire body in a non-oxidizing atmosphere in a furnace, and if this is not done, It is not possible to obtain a suitable bonding state.

However, according to such a manufacturing method,
In the subsequent process, that is, when the external connection terminal 14 is connected to the heater rod 11 via the conductor wire 15, these are inserted into the holder 12, and the metal pipe 18 is joined at its tip by silver brazing. This caused problems that had an adverse effect on various parts.

That is, when the metal pipe 18 described above is brazed to the holder 12, when the entire assembled state is carried into a furnace and heated, the brazing material welding the heater rod 11 and the metal holder 18 described above will melt. There is a risk that the bond will separate due to melting or a difference in the coefficient of thermal expansion in this portion. Furthermore, during heating in the above-mentioned furnace, the entire glow plug is heated and the resin insulating bush 13 that holds the external connection terminal 14 at the rear end of the holder 12 melts, making it impossible to obtain its function. This gives rise to the following problem. Therefore, with this type of glow plug, it is impossible to simultaneously connect the heater rod 11, metal pipe 18, and holder 12 due to the above-mentioned problem with the insulating bushing 13, and it is necessary to take some countermeasures. has been done.

For this reason, according to Japanese Patent Application Laid-Open No. 58-120028, etc., the above-mentioned insulating bush 13 is replaced with a resin one,
It has been considered that the glow plug could be made of ceramic so that the entire part could be joined by brazing or the like at the same time, but in this case, the joint strength and moldability of each part could be improved, but on the other hand, the insulation of ceramic Since it is necessary to form a metallized layer for bonding to the bush and its metal member side, this causes problems such as increased costs, and is not preferred from a practical standpoint.

[Summary of the invention]

The present invention has been made in view of the above circumstances, and the heater rod and the metal pipe are welded together using a high-melting point metal material, and the metal pipe is attached to the holder with a low temperature when the entire glow plug is assembled. The simple structure of welding and joining with melting point metal materials improves the quality stability and durability of each part without causing problems such as airtight leakage or poor contact as with conventional products, making it suitable for use as a glow plug. The purpose of the present invention is to provide a method for manufacturing an inexpensive glow plug for a diesel engine that can exhibit the following functions.

〔Example〕

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

3 to 5, together with FIGS. 1 and 2, show an embodiment of a glow plug for a diesel engine to which the manufacturing method according to the present invention is applied, and in these figures, the above-mentioned FIG. Identical parts are given the same numbers and their explanations will be omitted.

Now, according to the present invention, the heater rod 11 made of ceramic material and the metal pipe 1 fitted therein
8 are welded together using a high melting point metal material such as silver brazing material, and then external connection terminals 14 and the like are connected to this heater rod 11 via conductive wires 15 and inserted into the holder 12. After that, the metal pipe 18 is attached to the tip of the holder 12 using a low melting point metal material whose melting temperature is lower than that of the silver brazing material, such as silver Ag.
Alloy material consisting of cadmium Cd, tin Sn, silver
It is unique in that it is constructed by welding and joining with an alloy material consisting of Ag, lead Pb, and tin Sn. Then, in the glow plug 10 welded and joined in this way, the rear end of the holder 12 is caulked to lock the insulating bush 13 holding the external connection terminal 14.
This completes the assembly of 0.

To explain this in detail, according to this embodiment, the metal pipe 1 is difficult to join to the ceramic heater rod 11 and is difficult to obtain the required strength.
8. Furthermore, as shown in FIG. 4, the terminal cap 19 and the conductive wire 15 are assembled in advance and heated at a high temperature in a furnace or the like and welded and joined by silver brazing. According to such a method, the metal pipe 18 and the like can be easily and reliably joined to the heater rod 11, and even if thermal contraction occurs due to a difference in coefficient of thermal expansion, separation of the joint can be prevented as much as possible. It's something you get.

Here, reference numeral 30 in FIG. 4 denotes resistors 30a and 30b which are embedded in the heater rod 11 and serve as heating elements.
is a pair of lead parts connected to both ends thereof, one of the lead parts 30a is exposed on the outer periphery of the approximately central part of the heater rod 11 and is electrically connected to the metal pipe 18, and the other lead part 30a is connected to the metal pipe 18; 30b is exposed on the outer periphery of the rear end of the heater rod 11 and on its end face, and can be connected to the conductor 15 via the terminal cap 19. In addition, 31, 3 in the same figure
2 is a silver brazing material placed at each joint when these assemblies are carried into the furnace; for example, in the case shown in the figure, the left end is carried upward, and the whole is heated to melt the silver brazing materials 31 and 32. The molten metal is allowed to flow into each joint portion to ensure a reliable welded joint state.

In this embodiment, the conducting wire 15 and the terminal cap 19 are silver-brazed at the same time during the welding in the furnace described above, but this is not done because the above-mentioned problems such as leakage do not occur in this part. Of course, it is also possible to perform welding and joining in a subsequent process. However, if you do as in this example,
This can be effective in simplifying the manufacturing process and obtaining the required bonding strength.

In addition, as described above, the assembly of the heater rod 11 etc., which is silver-brazed in the furnace, has its conductor 15.
After the tube 15a is covered, the external connection terminal 1 is provided with an insulating bushing 13 made of resin at the rear end.
4, for example, by spot welding, and in that state the whole is as shown in Fig. 5.
It is inserted into the holder 12 from the rear end side.

Then, in this state, the ring 33 made of the low-melting point metal material mentioned above is placed at the tip of the holder 12, and this part is locally heated using, for example, high frequency to create a gap between the holder 12 and the metal pipe 18. It is configured to perform welding and joining. Here, this heating temperature is, for example, about 350°C to 500°C, which is the heating temperature for silver brazing (about 800°C) mentioned above.
It is lower than

Therefore, according to such a method, this part can be welded and joined easily and reliably, and the influence of the heat does not affect the welded joint between the heater rod 11 and the metal pipe 18, and this part Problems such as airtight leakage do not occur, and since the heating is localized as described above, there is no problem such as melting of the insulating bushing 13 at the rear end of the holder 12.

After the above-described joining on the distal end side of the holder 12 is completed, as shown in FIG.
Caulk the rear end opening edge 34 and attach it to the holder 1.
2 side, and then screw the insulating nut 20 and the like onto the external connection terminal 14 to complete the entire assembly.

Note that the present invention is not limited to the structure of the embodiment described above, and the shape and structure of each part may be modified and changed as appropriate. For example, the electrical connection circuit in the glow plug 10, the structure of its external connection terminal, and Various modifications can be made to the insulating bush structure for assembling this to the holder.

〔Effect of the invention〕

As explained above, according to the method of manufacturing a glow plug for a diesel engine according to the present invention, a metal pipe is welded and bonded to a ceramic heater rod using a high melting point metal material, and each part is assembled with a metal pipe. The simple method of welding and joining the manufactured pipe to the holder with a low-melting metal material, then caulking the rear end of the holder and assembling and fixing the resin insulating bushing prevents airtight leakage and contact unlike conventional methods. It is possible to stabilize the quality and improve the durability of each part without causing problems such as defects, and it can be manufactured extremely easily and reliably, and it can perform its function as a glow plug. Its effects are significant, including being advantageous in terms of cost.

[Brief explanation of the drawing]

The figures show an embodiment of a glow plug for a diesel engine to which the manufacturing method according to the present invention is applied, in which Fig. 1 is a vertical cross-sectional side view showing the overall schematic configuration, Fig. 2 is an enlarged view of the main parts, and Fig. 3 FIG. 4 is an exploded perspective view showing the entire device, and FIGS. 4 and 5 are side sectional views showing essential parts, respectively, for explaining the manufacturing sequence. 10...Glow plug for diesel engine,
DESCRIPTION OF SYMBOLS 11... Heater rod, 12... Metal tubular holder, 13... Resin insulating bush, 14... External connection terminal, 15... Conductive wire, 15a... Insulating tube, 16, 17... Metal metallized layer , 18...
...Metal pipe, 19...Terminal cap,
31, 32...Silver brazing material (high melting point metal material), 33
...A ring made of a low melting point metal material, 34...A peripheral edge of the opening at the rear end of the holder (caulked portion).

Claims (1)

[Claims] 1 A ceramic heater rod with a resistor embedded therein, a tubular metal holder that holds the heater rod at its tip via a metal pipe, and a resin insulating bushing at the rear end of this holder. A method for manufacturing a glow plug for a diesel engine comprising an external connection terminal held through the heater rod and connected to the heater rod via a conductive wire, the method comprising heating the heater rod and a metal pipe fitted therein. By doing so, they are welded and joined using high melting point metal materials, and then these are inserted into the holder together with the external connection terminals connected via the conductive wire, and then the metal pipe is connected to the tip of the holder. The holder is welded and joined using a low melting point metal material that melts at a temperature lower than the heating temperature, and then the insulating bushing on the external connection terminal side is locked by caulking the periphery of the rear end opening of the holder. A method for manufacturing glow plugs for diesel engines.