JPS60114630A - Method for manufacturing glow plug for diesel engine - Google Patents

Abstract

PURPOSE:To improve a stability and durability of each of the portions without producing any leakage of gas or poor contact and the like by a method wherein a metallic pipe is welded and connected to a ceramic heater rod in advance with metallic material having a high melting point and at the same time the metallic pipe is welded and connected to the holder with a metallic material of low melting point under a condition in which each of the portions is assembled to each other. CONSTITUTION:A heater rod 11 made of ceramic material and a metallic pipe 18 fitted to the heater rod are welded and connected to each other by metallic material of high melting point such as, for example, a silver solder material, then an outer connector terminal 14 is connected to the heater rod 11 through a conductor line 15 and inserted into the holder 12, thereafter the metallic pipe 18 is welded and connected to the extremity end of the holder 12 by a metallic material having a lower melting point than that of the silver solder material, for example, alloy material composed of silver, cadmium and tin, alloy material composed of silver, lead and tin. The rear end of the holder 12 is press fitted and an insulation bushing 13 having an outer connector terminal 14 held is engaged, thereby an assembly of the glow plug 10 is completed.

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]

Generally, diesel engines have poor startability at low temperatures, so glow plugs are installed in the auxiliary combustion chamber or combustion chamber.
A method has been adopted in which a current is passed through this to generate heat, thereby raising the intake air temperature or using it as an ignition 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 completely filled with heat-resistant insulating powder and a coiled heating wire is embedded, and the resistor is made of ceramic material. Various types of heaters are known, such as a ceramic heater type that uses an embedded heater rod. /l? The latter ceramic heater type has been attracting attention in recent years because it has superior heat transfer efficiency compared to the conventional sheath type and can demonstrate its performance as a rapid heating type.

An example of this will be briefly explained using FIG. 1. A glow plug, generally designated by the reference numeral 10, is made of a ceramic material and has a roughly elliptical cross section in which a resistor (not shown) that generates heat when energized is embedded. It is equipped with a heater rod 11 having a shape (see Fig. 3), and a metal holder 12 having a substantially tubular shape that holds the heater rod 11 at its tip. An external connection terminal 14 is fitted into the section through an insulating bushing 13 made of resin, and this external connection terminal 14 is further connected to the rear end of the heater rod 11 through a conductive wire 1st made of iron a or the like.

Further, 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 face of the heater rod 11, and these layers are respectively formed on both ends of the resistor embedded in the heater rod 11. Lead section? connected via. The metal metallized layer 16 at the center of the heater rod 71 is connected to the holder 12 side via a reinforcing metal pipe 18 fitted to its outer periphery, while the ore terminal cap 19 is connected to the metal metallized layer 11 at the rear end side. is covered and connected to the conductive wire 15. Here, the metal pipe 18 also functions as an auxiliary member for holding the heater rod 11 at the tip of the holder 12, and has a through hole formed to match the irregular cross-sectional shape of the heater rod 11. The heater rod 11 and the holder 12 are welded and fixed to each of the heater rod 11 and the holder 12 by, for example, silver brazing. On the other hand, the terminal cap 19 is also attached to the heater rod 1 in the same way.
1, and is welded and fixed, for example, by silver brazing. Then, the conductive wire 15
is connected to the terminal cap 19 at the same time by brazing or the like, or by being fixed in a later process by welding, welding, etc.

Further, an insulating tube 15 is provided on the outer periphery of the electric wire 15 described above.
The rear ends of the terminals 7, on which the terminals a and the like are covered, are connected to the inner ends of the external connection terminals 14 by welding or the like. The external connection terminal 14Fi and the insulating bushing 13 holding the external connection terminal 14Fi are assembled at the rear end of the holder 12 in a locked state by tightening the periphery of the opening.

Here, the connecting portion of the external connection terminal 14 described above needs to be firmly fixed to the holder 12 side through the fully insulating bushing 13 to prevent its removal and rotation. However, this is a resin insulation bushing 13.
This can be satisfied due to the presence of the metal tube 13a coated on the outer periphery of the tube.

That is, since a rotational force acts on the external connection terminal 14 when the lead wire is tightened, the rotational force of the wire is applied to the external connection terminal 14.
Heater rod 1 fixed to holder 12 side IC via 5vi-
When the signal is transmitted to the 1 side, the connection part of the conductor 15 and the heater rod 11
This is a problem in ensuring the strength of the external connection terminal 14, and the same problem occurs when the external connection terminal 14 comes off. Of course, a highly flexible 7 lexiple wire or the like is used as the conductor 15,
The insulating bushing 13 is configured to function as a buffer material, and the external connection terminal 1 is knurled or the like.
4 is firmly assembled by press-fitting or insert molding, but the above-mentioned problems cannot be completely prevented. Furthermore, when only the insulating bushing 13, which is a simple resin molded product, is used, the holder 12
There is a risk that the bushing 13 may shrink due to heat shrinkage due to the difference in coefficient of thermal expansion between the bushing 13 and the bushing 13, creating a gap between the bushings and loosening the bushing. It comes out.

On the other hand, the above-mentioned metal tube 13a is covered with a resin insulating bushing 13, and after fitting these into the holder 12 and locking the inner end with a step inside the holder 12, the holder 120 By caulking the opening edge with high pressure,
The metal tube 13a mentioned above is clamped with a large force from both ends @, and as a result, it is buckled and deformed along the axial direction.
An extreme illustration of this is shown in FIG. In this state, the outer side of the metal tube 13a is firmly pressed and fixed to the holder 12 side and the inner side to the insulating bushing 13 side.Thus, these are integrated with the desired mechanical strength, Even if the resin part shrinks somewhat due to heat, the amount of deformation will be absorbed and problems such as loosening will be resolved.

Note that the rear end side of the external connection terminal 14 is a screw portion,
An insulating ring 20, a nut 21, a spring washer 22, a washer 23, and a nut 24 for tightening the external lead are screwed together. The external connection terminal 14 can be connected by holding a lead wire from a battery (not shown) between the washer 23 and the nut 24.
electrically connected to the battery terminals. Furthermore, 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 12t. 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, in the glow plug 10 having the above-described structure, the metal pipe 18 to the heater rod 11 and the joint portion of the metal pipe 18 to the holder 12 are made in such a manner that no air leakage or poor jointing occurs. It is desired to connect each of them. 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, so if an airtight leak occurs in this part, fuel oil, moisture, etc. will leak into the glow plug 1 from the gap.
There is a risk that this will not only affect the durability of the heater rod 11, but also cause poor contact at each electrical connection, causing problems such as the glow plug not being able to function as a glow plug. Ru. 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 also due to the infiltration of moisture etc. in this part. This is mainly because there is a risk that the heater rod 11 may be damaged due to rapid heat generation, which poses a problem in obtaining 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 airtight leakage, the metal pipe 18 and the terminal cap 19, as well as the conductor 15 connected thereto, etc. are all connected to the heater rod 11.
For example, it has been proposed in the past to heat the material to about 800.degree. C. in a furnace and then weld and fix it with silver brazing in advance to obtain the required bonding strength. this is,
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, a reliable bonding condition cannot be obtained. There are things you can't get.

However, according to such a manufacturing method, in the subsequent process, that is, after connecting the external connection terminal 14 to the heater rod 11 via the conductor wire 15, these are inserted into the holder 12, and the metal pipe 18 is inserted at the tip thereof. When joining by silver brazing, there was a problem in that it had an adverse effect on other parts.

That is, when brazing the metal pipe 18 to the holder 12, the heater rod 11 and the metal holder 1 are sometimes brought into a furnace in an assembled state and heated.
8? There is a risk that the welded brazing material may be melted or that the bond may separate due to differences in thermal expansion coefficients in this area. Furthermore, during heating in the furnace as described above, the entire glow plug is heated and the resin insulating bushing 13 held at the rear end of the holder 12 and the external connection terminal 14' melts, making it impossible to obtain its functional value. This is what causes the problem. Therefore, according to this type of glow plug, it is impossible to simultaneously connect the heater rod 11, the metal pipe 18, and the holder 12 due to the above-mentioned problem of the insulating bushing 13, and it is necessary to take some countermeasures. There is.

For this reason, it has been proposed in Japanese Unexamined Patent Publication No. 58-120028 that the insulating bushing 13 mentioned above be made of ceramic instead of made of resin, so that the entire glow plug can be joined by brazing, etc. at the same time. However, in this case, although it is possible to improve the bonding strength and moldability of each part, it is necessary to form a metallized layer to bond the ceramic mix, bushing, and the metal component side. From this point of view, it causes problems such as high cost and noise, which is not desirable from a practical point of view.

[Summary of the invention]

The present invention has been made in view of these circumstances.
The heater rod and the metal pipe are welded together using a high melting point metal material, and the metal pipe is welded to the holder using a low melting point metal material when the entire glow plug is assembled. An inexpensive glow plug for diesel engines that improves the quality stability and durability of each part and allows it to function as a glow plug, without causing problems such as air leakage or poor contact. It provides a manufacturing method.

〔Example〕

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

3 to 5, along 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. 1 and 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 a ceramic material and the metal pipe 18 fitted therein are welded and joined using a high melting point metal material such as gold, for example, silver brazing material,
Next, after all the external connection terminals 14 etc. are connected to this heater rod 11 through all the conductive wires 15 and inserted into the holder 12, the metal pipe 18 is inserted into the tip of the holder 12 with the silver brazing material etc. Low-melting metal materials with low melting temperature, such as silver (A
It is characterized by a structure in which an alloy material consisting of P), cadmium (Cd), and tin (Sn), and an alloy material consisting of silver (Ag), lead (Pb), and tin (Sn) are welded and joined. ing. In the glow plug 10 welded and joined in this manner, the rear end of the holder 12 is caulked to the insulating bushing 1 holding the external connection terminal 14.
3vi- By locking, the assembly of the jigrow plug 10 is completed.

To explain this in detail, 11 According to this embodiment, the metal pipe 18, which is difficult to join to the ceramic heater rod 11 and difficult to obtain the required strength, as well as the terminal cap 1B and the lead #15, As shown in FIG. 4, the components are assembled in advance in a furnace or the like, and are welded and bonded using silver brazing under high-temperature power 11a. and,
According to such a method, the metal pipe 18, etc. can be easily and reliably joined to the heater shaft 11, and even if thermal contraction occurs due to a difference in coefficient of thermal expansion, it is possible to prevent the joint from slipping as much as possible. There's something to be gained.

Here, reference numeral 30 in FIG. 4 is a resistor which is a heating element embedded in the heater rod 11, and 30a and 30b are a pair of lead parts connected to both ends of the resistor, and one of the lead parts (3
0a) is exposed on the outer periphery of the approximately central portion of the heater rod 11 and is electrically connected to the metal pipe 18, and the other lead portion (30b) is exposed on the outer periphery of the rear end of the heater rod 11 and on its tIs surface. It is exposed and can be connected to the conducting wire 15 through the terminal cap 19. In addition, in the same figure, 31° and 32 are silver brazing materials placed at each joint when these assemblies are carried into the furnace. The whole is heated to melt the silver brazing material 31,32'L- and flow into each joint, so that a reliable welded joint state can be obtained.

In addition, in this actual example, during the welding in the furnace mentioned above, the conductor 15 and the terminal cap 19' are silver-brazed at the same time, but this part is not covered by the above-mentioned problems such as airtight leakage (because it does not occur). Of course, it is possible to weld and join this in a later process. However, if it is done as in the present example, it will be effective in simplifying the manufacturing process and obtaining the required joint strength. There's something to be gained.

In addition, as described above, the heater rod 11 and other assemblies silver-brazed in the furnace are connected to the tube 15 by the conductor wire 15.
After a is covered, the rear end is made of resin and the insulating bushing 1 is covered.
3 is connected to the tip of the external connection terminal 14 by, for example, spot welding, and in this state the whole is inserted into the holder 12 from the rear end side, as shown in FIG.

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 with, for example, high frequency, so that the holder 12
It is configured to perform welding and joining between the metal pipe 18 and the metal pipe 18. Here, this heating temperature is, for example, 350
℃ to about 500℃, the heating temperature for silver brazing described above (
(approximately 800°C).

Therefore, according to such a method, the molten N in this part
The joining can be done easily and reliably, and the heat effect will not affect the welded joint between the heater rod 11 and the metal pipe 18, and problems such as airtight leakage will not occur in this part. In addition, since it is melted by local heating as described above, there is no problem that the insulating bushing 13 at the rear end of the holder 12 is melted.

After the above-mentioned joining on the distal end side of the holder 12 is completed, as shown in FIG. The entire assembly is completed by screwing the insulating nuts 20 and the like onto the external connection terminals 14.

Note that the present invention is not limited to the structure of the above-described embodiments, 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, Various modifications can be made to the insulating bushing structure for assembling this to the holder.

〔Effect of the invention〕

As explained above, according to the method for manufacturing a diesel engine plug according to the present invention, a metal pipe is welded to a ceramic heater rod using a metal material with a high melting point, and each part is assembled. By a simple method of welding and joining a metal pipe holder with a low-melting metal material, and then caulking the end of the holder and assembling and fixing a resin insulating bushing, it is possible to eliminate airtight leakage compared to the conventional 571. It is possible to stabilize the quality and improve the durability of each part without causing any problem sounds such as poor contact or poor contact.Furthermore, it is extremely easy and reliable to manufacture, and it is possible to demonstrate its function as a glow plug. The effects are great, such as being cost-effective.

[Brief explanation of drawings]

The figures show an actual example of a glow plug for a diesel engine to which the manufacturing method according to the present invention is applied. 1 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, 11
... Heater rod, 12 ... Metal tubular holder,
13...Resin insulation bushing, 14...External connection terminal, 15...Conductor wire, 15a...φ insulating tube, 16.17@...Metal metallized layer, 18...
... Metal pipe, 19 ... Terminal cap, 31° 32 ... Silver brazing filler metal (high melting point metal material), 33
...Ring made of a low melting point metal material, 34...Rear end opening periphery of holder (caulked portion). Patent applicant: Jidosha Kiki Co., Ltd. Diesel Kiki Co., Ltd. Agent: Kazubin Yamakawa (and 1 other person) Figure 5

Claims (1)

[Claims] A ceramic heater rod with a resistor embedded therein, a tubular metal holder held at the tip of the heater rod via an all-metal pipe, and a resin insulating bushing attached to the rear end of the holder. A method for manufacturing a glow plug for a diesel engine, which is fully equipped with an external connection terminal that is held in place and connected to the heater rod through a conductive wire, and the heater rod and the metal pipe fitted therein are fully heated. Preferably, υ high melting point metal materials are welded and joined, and then these are inserted into the holder together with the external connection terminal connected via the conductive wire, and then the metal pipe is connected to the tip of the holder. Weld and join with a low melting point metal material that melts at a temperature lower than the heating temperature, and then lock the insulating bushing on the external connection terminal side by tightening and tightening the periphery of the opening at the rear end of the holder. A method for manufacturing a glow plug for a diesel engine, characterized in that: