JPH03282122A - Manufacture of glow plug for diesel engine - Google Patents

Abstract

PURPOSE:To accurately position an electrode cap without damaging a lead part, improve the workability, and reduce the cost by a method wherein the electrode cap having a common lead part is soldered to the electrode take-out end of a rodtype ceramic heater and the common lead part is cut at a desired position. CONSTITUTION:An electrode cap 30 for joining a metallic conductor, formed of a conduction metal, having a common lead part is mounted and soldered to electrode take-out ends 21a and 21a on the rear of a rodtype ceramic heater 11 formed of a conductive ceramic material such that a heat generating part 20 and a pair of lead parts 21 and 22 extended in parallel in the rear of the heat generating part are integrally formed of a conductive ceramic material. Thereafter, a lead part 30a of an electrode cap 30 is cut at a desired position by a cutting tool to form terminal caps 31 and 32 secured to the electrode take-out ends 21a and 22a, respectively. Cut terminal cap lead parts 31a and 32a are electrically connected to metallic conductors 16 and 17 lead out from first and second external connection terminals 13 and 14, respectively.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a glow plug for a diesel engine equipped with a rod-shaped ceramic heater integrally formed of a conductive ceramic material, and in particular to The present invention relates to a method of manufacturing a glow plug for a diesel engine with an improved structure.

(Prior Art) Glow plugs for diesel engines having various structures have been known, but in recent years, ceramic heater type glow plugs have been attracting attention because of their quick heating properties and high-temperature durability.

As a structure for taking out electrodes for external connection from this type of ceramic heater, Japanese Patent Application Laid-Open No. 114629/1984 discloses a pair of electrode take-out ends provided at the rear end of the heater, each of which is fitted with a terminal cap and brazed. discloses a bipolar two-wire structure in which the two wires are connected. Also, JP-A-63-
Publication No. 91432 discloses that an electrode cap, in which a metal conductor wire is locked and held at the rear end of a ceramic heater, is attached to the electrode extraction end and brazed, and then this electrode cap is cut at a position corresponding to each lead section. A structure has been disclosed.

(WII, which the invention aims to solve) However, the method disclosed in JP-A-60-114629 requires two terminal caps to be joined to each electrode lead-out end, resulting in a complicated structure and problems in terms of workability and cost. Furthermore, since the relative positions of the terminal caps during bonding are unstable, there are problems such as electrical short circuits.

Furthermore, the method disclosed in JP-A No. 63-91432 has limitations on the cutting location due to its structure, and has poor workability and reliability, such as the possibility of damaging the metal conductor wire and the lead portion of the ceramic heater when cutting the electrode cap. This will cause problems in terms of.

SUMMARY OF THE INVENTION An object of the present invention is to provide a manufacturing method that does not damage the lead portion of a ceramic heater, accurately positions an electrode cap to be joined, improves workability, and reduces costs.

(Means for Solving the Problems) In order to achieve the above object, a method of manufacturing a glow plug for a diesel engine according to the present invention includes a heat generating part and a pair of lead parts extending in parallel behind the heat generating part. An electrode cap for joining metal conductors made of a conductive metal material having a common lead portion is attached to the rear end of a rod-shaped ceramic heater integrally formed of a ceramic material, and then brazed to the rear end of the rod-shaped ceramic heater made of a ceramic material. This method involves cutting the section at the desired position.

(Function) Since the electrode cap is divided into two parts after joining the integral electrode cap to the pair of electrode extraction ends, the electrode can be extracted very easily and reliably.

(Example) Hereinafter, the present invention will be explained in detail with reference to Examples.

In this embodiment, a two-pole two-wire structure will be explained.

1, 3, and 4 are explanatory diagrams for explaining the manufacturing method according to the present invention, and FIG. 2 is a schematic vertical sectional view of a glow plug for a diesel engine according to the present invention. Further, FIGS. 5 and 6 are schematic perspective views showing a modification of the electrode cap, which is a main part of the present invention, and FIG. 7 is a schematic longitudinal sectional view showing an embodiment of the present invention. First, the general structure of the glow plug shown in FIG. 2 by reference numeral 10 will be briefly explained. This glow plug 10 includes a rod-shaped ceramic heater 11 whose distal end functions as a heat generating portion, and a substantially tubular metal holder 12 that holds the heater 11 at its distal end. A terminal assembly 15 in which first and second external connection terminals 13 and 14 are penetrated and embedded in an insulating material such as a synthetic resin material is fitted and held at the rear end of the holder 12. Each terminal 13.14 is connected to a lead portion (described later) made of a conductive ceramic material constituting the heater 11 via a metal conductor 1s16.17 made of a flexible wire or the like. These metal leads! 16.17, the various vibrations and tightening applied to the external connection terminals 13.14 are for the purpose of strongly protecting the heater 11 from external mechanical forces such as torque, and it is preferable to use terminals with a certain degree of flexibility. Note that 12a is a threaded portion formed on the outer periphery of the holder 12 to be screwed into a threaded hole on the cylinder head side of an engine (not shown). Further, the terminal assembly 15 includes a first external connection terminal 13 having a rod portion 13a on its inner end side, and is arranged around the first external connection terminal 13 at a predetermined interval, and extends from a part of the inner end thereof. A cylindrical second external connection terminal 14 having a lead piece 14a, and a resin molding that insulates between both terminals 13 and 14 and integrates them by having an insulating layer on the outer periphery thereof. This main body 1 has an assembly 15a according to
A metal tube 15b for connection reinforcement is fitted around the outer periphery of 5a. and.

This metal tube 15b is caulked with a high pressure at the peripheral edge of the opening at the rear end of the holder 12, and is buckled and deformed along the axial direction. It is firmly pressed against the inner wall and can eliminate problems caused by external forces and thermal contraction. 1 more
8a and 18b are insulating rings and washers 18 fitted to the second terminals 14 protruding rearward of the holder 12;
c is an insulating member fitted to the first terminal 13 side at the outer end of this washer 18b, and 18d and 18e are spring washers and tighteners screwed into the threaded portion of the outer end of this first terminal 13. is a nut. Leads 1a (not shown) from the battery are interposed and held between the washer 18b and the insulating member 18c, and between the insulating member 18c and the spring washer 18d.
14 is electrically connected to the battery terminal side. moreover,
16a and 17a are insulating tubes for covering the conducting wires 16 and 17.

According to this embodiment, as is clear from FIGS. 1 and 2, the rod-shaped ceramic heater 11 held at the tip of the holder 12 is arranged parallel to the U-shaped heating section 2o and backward from both ends thereof. A pair of external connection lead portions 21 and 22 extending from each other are integrally formed of a conductive ceramic material, so that the entire structure has a substantially U-shape. Furthermore, insulating coating layers 23 and 24 are provided as insulating layers on the outer surfaces of both the lead parts 21 and 22. Then, it is held at the tip of the holder 12 via the insulating coating layers 23 and 24. A terminal cap 31.32, which will be described later, is connected to the rear end of each lead portion 21.22.

Each terminal cap 31.32 has a respective metal conductor 16.32.
17, the first and second external connection terminals 13.1
4 is connected.

To explain this in detail, the ceramic heater 11 has a lead portion 2
1.22 has a heat generating part 20 made of a conductive ceramic material formed in a small diameter so that the wall thickness is thinner than that of 1.22, and a heater 11 is provided in the center thereof along the length of the heater 11 from the heat generating part 20 to between the lead parts 21 and 22. A slit 25 is formed along the direction. Further, within this slit 25, an insulating sheet 26 made of an insulating ceramic material is interposed at least in a portion corresponding to the tip of the holder 12 between the lead parts 21 and 22 on the rear end side, and a lead made of a conductive ceramic material is interposed. 21 and 22, thereby closing the slit 25 with the tip of the holder 12 to reliably seal combustion pressure and combustion heat, thereby preventing leakage. In addition, an insulating coating layer 23 is provided on the outer periphery of the lead portion 21.22, which is integrally formed with the heat generating portion 2° and a conductive ceramic material, at approximately the center in the longitudinal direction.
．． 24 is formed, and these two layers 23, 24 and a silver/palladium layer (not shown) formed on the surface of the ceramic heater 11 are bonded and fixed to the tip of the holder 12 with silver soldering or the like and held. It is designed to allow

In this case, it is preferable to form a silver/palladium layer on the bonding surface side of the holder 12 as well, if necessary, but it goes without saying that this is not limiting. Furthermore, ceramic heater 1
Electrode extraction ends 21a and 22a are formed at the rear end portions of the electrodes 1, respectively.

Here, as the conductive ceramic material forming the above-mentioned ceramic heater 11, titanium nitride (T
It is preferable to use Sialon, etc., which can obtain conductivity by adjusting the amount of N) added. However, the conductive ceramic material that becomes the resistor in the ceramic heater 11 described above is not limited to the above-mentioned Sialon, but may be any suitable material. It will be readily understood that it is possible to use ceramic materials.

According to the present invention, as described above, the heat generating section 20 and the pair of lead sections 21 extending in parallel behind the heat generating section 20.
As is clear from FIGS. 1 and 3, conductive electrodes 22 are formed integrally with a conductive ceramic material and have a common lead portion at the electrode extraction ends 21a and 22a at the rear end of the rod-shaped ceramic heater 11, respectively. An electrode cap 3o made of metal for joining metal conductor wires is attached and brazed, and then the lead portion 30a of the electrode cap 30 is cut at a desired position with a cutting tool as shown in FIG. , 22a.

In this embodiment, the above-mentioned electrode cap 30 is made of, for example, stainless steel and has a substantially semicircular bottom surface and a guide portion on the circumference thereof along the outer periphery of each of the electrode extraction ends 21a and 22a, and each Metal conductor wire 16.1 from a part of the bottom
A case is shown in which the bonding layer common lead portion 30a is formed to be connected to the bonding layer 7. After bonding the electrode cap to a position facing each of the electrode extraction ends 21a and 22a, the common lead portion 30a is cut at a desired position, and the terminal cap 3
We get 1.32. In this case, each electrode extraction end 21
a, 22a and the electrode cap 30 are made of, for example, Ti-A.
It is preferable to join by heat treatment in vacuum or in an inert atmosphere using activated silver solder such as g-Cu.

Then, the electrode cap 3 brazed in this way
As shown in FIG. 4, the common lead part 30a of 0 is cut at a desired position using, for example, a rotary cutter 35, so that the electrodes can be taken out from each of the electrode extraction ends 21a and 22a at the same time, easily and reliably. It is. Further, each of the cut terminal cap lead portions 31a, 32a is electrically connected to the metal groove MA16.17 drawn out from the first and second external connection terminals 13.14. here,
Rod portion 1 of first and second external connection terminals 13 and 14
3a lead piece 14a and one end of each metal groove 1s16.17,
And each cut terminal cap lead part 31a, 3
The other ends of 2a and each of the metal conductive wires 16 and 17 are welded together by spot welding or the like to be connected and fixed.

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, the electrode cap 30 used to form the electrode lead-out portion from the ceramic heater 11 can have various shapes.For example, as shown in FIG. By using a structure in which the positioning portion 32b is formed by combining the electrode caps 30 and the like, it is possible to easily and reliably position the electrode cap 30 in the rotational direction when joining the electrode caps 4121a and 22a described above. Furthermore, as shown in FIG. 6, by using a shape that is cut out in advance at the desired cutting position described above, workability during cutting can be improved.

Further, in the above-described embodiment, the case where the glow plug 10 having a two-pole two-wire structure was applied was explained, but the present invention is not limited thereto. As shown in FIG. Even if the glow plug 10 has a structure in which only the lead part 22 is connected to the outside by the external connection terminal 13 held at the rear end of the holder 12 via the insulating bushing 60, and the other lead part 22 is connected to the ground on the holder 12 side. As will be easily understood, in this embodiment, the metal conductor 17 is fitted around the outer periphery of the insulating bushing 60 and the holder 12
Although the terminal piece 61 extending from the metal vibro 0a connected to the side is used for connection, the connection is not limited to this.
Various modifications can be considered as the connection means to 2.

(Effects of the Invention) As described above, according to the present invention, the rod-shaped ceramic heater held at the tip of the holder is electrically conductive through the heat generating portion and the pair of lead portions extending rearward in parallel from both ends of the rod-shaped ceramic heater. An electrode cap for joining metal conductor wires, which is made of a conductive metal material and has a common lead part, is attached to the electrode extraction end of the rear end of the ceramic heater and brazed. Then, the common lead part of the electrode cap was cut at the desired position, so although it was a simple method, the structure of the electrode extraction part from the ceramic heater was simple, and the work was extremely easy. There are various excellent effects such as excellent relative positional accuracy of each electrode cap after bonding.

[Brief explanation of the drawing]

FIGS. 1, 3, and 4 are explanatory diagrams for explaining the manufacturing method according to the present invention, and FIG. 2 shows an example of a glow plug for a diesel engine employing the manufacturing method according to the present invention. FIGS. 5 and 6 are schematic longitudinal sectional views showing a modification of the electrode cap which is the main part of the present invention, and FIG. 7 is a schematic longitudinal sectional view showing an embodiment of the present invention. 10...Glow plug for diesel engine, 11
... Rod-shaped ceramic heater, 12 ... Hollow holder, 13.14 ... First and second external connection terminals, 15 ... Terminal assembly, 16.17 ... Metal conductor wire, 20... Heat generating part, 21.22... Lead part, 21a, 22a... Electrode extraction end, 23.24
...Insulating coating layer (insulating layer), 25...
Slit, 26...Insulating sheet, 30...Electrode cap, 30a...Common lead part, 31.32...
...Terminal cap, 31a, 32a...Terminal cap lead part, 32b...Positioning part

Claims (1)

[Claims] In a rod-shaped ceramic heater in which a heat generating part and a pair of lead parts extending behind the heat generating part are integrally formed from a conductive ceramic material, an electrode cap having a common lead part is attached to the electrode extraction end of the rear end. brazing,
A method of manufacturing a glow plug for a diesel engine, comprising: thereafter cutting the common lead portion of the electrode cap at a desired position.