JPS6129619A - Ceramic glow plug - Google Patents

Abstract

PURPOSE:To provide a stable junction part by a method wherein an outer cylinder at the extremity end and a ceramic heater are brazed with a brazing material of high melting point, and the outer cylinder at the rear end and the ceramic heater are brazed with a silver brazing material having a superior brazing characteristic. CONSTITUTION:A junction part between the ceramic heater 12 and an inner surface of the outer cylinder 13A at the extremity end is brazed with a brazing material 15 of a high melting point of 1,000 deg.C or more, a junction part with the inner surface of the outer cylinder 13B at the rear end is brazed with a brazing material 16 of low melting point of 800 deg.C, and at the same time it has a junction structure in which the rear end of the metallic outer cylinder 13 containing a junction part 13C between the outer cylinder 13A at the extremity end and the outer cylinder 13B at the rear extremity end is brazed to the inner cavity at the extremity of the fixing unit 17 with a brazing material of low melting point of 600-700 deg.C. With this arrangement, it is possible to provide a ceramic glow plug of which brazing operation is easily performed and it has a stable junction part and a durability as well as a reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ceramic glow plug that is installed in a diesel engine primarily for starting.

(Prior Art and Problems to be Solved by the Invention) Generally, in order to improve starting performance of a diesel engine, a glow plug is attached to an auxiliary chamber such as a vortex chamber provided in the engine head, and the glow plug is energized and injected into the cabin. A method of preheating by heating and combusting a part of the fuel is used, and it is required to have rapid temperature rise characteristics at the time of startup, and recently after-glow is also used to stabilize combustion even after startup. As glow plugs tend to be used for long periods of time, there is an increasing demand for improved durability.For this purpose, we have developed a rapid heating type glow plug with a high melting point metal heating wire embedded in ceramic powder. A ceramic glow plug is known that uses a sintered ceramic heater as a heating element.

Figure 2 is a vertical cross-sectional view of the main part showing the structure of a conventional ceramic glow plug installed in the auxiliary chamber (vortex chamber) of an engine head. The ceramic heater 2 is made of a ceramic heater 2 having a small diameter so as to have rapid heating properties, and its tip protrudes into the inner cavity of a metal outer cylinder 3 inserted on the outside and is reinforced by brazing. The cylinder 3 is further soldered to the inner cavity of the mounting bracket 4, and as shown in the figure, the tip of the ceramic heater 2 covered with the metal outer cylinder 3 is inserted from the inner wall 5 of the auxiliary chamber. It is attached so that it protrudes.

Since this protruding part is directly exposed to high-temperature combustion gas, it is desirable that the ceramic heater 2 and the metal outer cylinder 3 be brazed together using a brazing material with a high melting point. Conventionally, it was 600 to
It was soldered with a single commonly used silver solder having a melting point of 800°C.゛This brazing filler metal has good fluidity during soldering and can provide a joint with excellent strength and airtightness. When this happens, the wax at the joint is burnt out, the joint strength is reduced, and adhesion is lost, causing a change in the temperature characteristics of the heater and an unstable plug performance.

(Means and operations for solving the problems) The present invention has been made in order to solve the problems of the conventional ceramic glow plugs as described above. shall consist of two parts: a front end outer cylinder that projects into the interior when installed in the subchamber of the engine, and a rear end outer cylinder connected to this,
The melting point of the joint between the ceramic heater and the outer cylinder on the tip side is 10.
The joint with the outer cylinder on the rear end side is soldered with a low melting point brazing material with a melting point of approximately 800 °C, and the joint between the front end and rear end parts is Attach a metal outer cylinder containing a melting point of 600 to 70 to the inner cavity of the tip of the fitting.
By brazing with a low melting point brazing material of 0°C, the ceramic heater and the metal outer cylinder are firmly joined with heat resistance at the tip exposed to high temperatures, and at the rear end. The ceramic glow plug is a ceramic glow plug that is bonded with sufficient airtightness in the parts.

(Example〕 Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing the main parts of an embodiment of the ceramic glow plug of the present invention. As seen in the figure, the ceramic glow plug 11 of the present invention is inserted into the outside of the ceramic heater 12 and reinforced. When the metal outer cylinder 13 is installed in the auxiliary chamber (vortex chamber) of the engine, its inner wall 14 (
The tip-side outer cylinder 13 protrudes into the room from the imaginary line in the figure).
With A.

The ceramic heater 12 is divided into two parts, and the rear end outer cylinder 13B is connected to the rear end. Melting point brazing material 15 For example, Ou wax (melting point 1080
°C), N1 solder (melting point 1060°C) or PA wax (melting point 1200°C), etc., and the joint with the inner surface of the rear outer cylinder 13B has a melting point of about 800°C. The melting point brazing material 16 is brazed using a silver brazing material (melting point 780° C.), for example, J-Work 13.BAg-8, and the connecting portion 130 between the front end outer cylinder 13A and the rear end outer cylinder 13B.
The rear end of the metal outer cylinder 13 containing a low melting point wax 18 having a melting point of 600 to 700° C. is placed in the inner cavity of the tip of the fitting 17.
For example, JIS, BAg-1 (melting point 620°C), BAg
-7 (melting point: 650°C), etc., has a joining structure made by soldering with a silver brazing material such as -7 (melting point: 650°C).

Note that the brazing material 18 with a low melting point used for soldering the metal outer cylinder 13 and the mounting bracket 17 has a lower melting point than the brazing material 16 used in soldering the rear end side outer cylinder 33B of the metal outer cylinder and the heater 12. The reason for using the solder metal is to ensure that the joining part of the wax lug 16 is not damaged by the temperature of the soldering filler metal 18.

Furthermore, the metal outer cylinder 13 of the ceramic heater 12 of the present invention is soldered to the heater on the tip side that protrudes into the interior of the engine when it is installed in the subchamber of the engine using a high melting point brazing filler metal, so that it can be heated under high temperatures. In addition to making it strong so that it will not burn out even if it is heated, complete airtightness is maintained by brazing the rear end with a low melting point brazing material with good wax properties. The reason why the metal outer cylinder 13 is divided into a front end outer cylinder 13A and a rear end outer cylinder 13B instead of using a single metal outer cylinder 13 is that if a single metal outer cylinder is used and the heater 12 is combined with the brazing material as described above. If it is in contact, the inner surface of the rear end of the metal outer cylinder will be oxidized by the high melting point brazing filler metal at the tip of the metal outer cylinder, and the wax properties due to the low melting point brazing filler material in this area will be significantly reduced. This is because complete bonding cannot be obtained.

Also, the front end side outer cylinder 13A and the rear end side outer cylinder 1 of the metal outer cylinder 13.
The connecting portion 130 with 3B can be formed by having planar end surfaces in contact with each other as shown in FIG. −
□, 13C-2 (also shown in the same figure)
As shown in the figure, cut out a groove of 13cm1 on the outer periphery of the abutted end face.
It is also possible to insert the brazing filler metal 18 into the groove to increase the bonding strength during soldering with the mounting bracket 17.

(Effects of the Invention) As can be understood from the above explanation, the ceramic glow plug of the present invention has a metal outer cylinder that reinforces the ceramic heater from the outside, and when installed in the subchamber (vortex chamber) of an engine, It is divided into a front end side outer cylinder that protrudes from the front end side outer cylinder and a rear end side outer cylinder connected to this.

Since the tip side outer cylinder and the ceramic heater are brazed with a high melting point brazing filler metal with a melting point of over 1000℃, the strength of the joint will not decrease even if exposed to high temperature combustion gas in the pre-chamber. In addition, the rear end side outer cylinder, which is not directly exposed to high-temperature combustion gas, the ceramic heater 1, and the metal outer cylinder including the connecting parts thereof, and the mounting bracket are soldered with silver solder with excellent waxing properties, so that it is completely soldered. We can provide a ceramic glow plug that provides excellent airtightness, solves the problems with conventional glow plugs of this type, and has improved durability and reliability with easy brazing and stable joints. It is something.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a main part of an embodiment of the ceramic glow plug of the present invention, and FIG. Fig. 2 is a vertical cross-sectional view of a main part showing a conventional example of a ceramic glow plug installed in an auxiliary chamber. 1.11: Ceramic glow plug, 2, 12: Ceramic heater -, 3, 13: Metal outer cylinder, 4° 17: Mounting metal fittings, 5.14: Inner wall, 13A: Front end outer cylinder, 13B: Rear end outer cylinder, 13C: Connecting part. 15: High melting point brazing metal, 16.18: Low melting point waxing agent Patent attorney Mamoru Takeuchi Figure 1

Claims (1)

[Claims] A ceramic heater consisting of a heating wire of a high melting point metal embedded in a ceramic sintered body has its tip protruding from a metal outer cylinder inserted on the outside and is joined to the inner cavity, and this metal outer cylinder is attached to the ceramic heater. In a ceramic glow plug that is joined to the inner cavity of the distal end of a metal fitting, a metal outer cylinder that is inserted on the outside of the ceramic heater has an outer distal end that protrudes into the interior when the glow plug is installed in the subchamber of an engine. It is divided into a cylinder and a rear end outer cylinder connected to the cylinder, and the joint between the ceramic heater and the front end outer cylinder has a melting point of 100.
These metal outer cylinders, including the connecting parts, are brazed with a high melting point brazing material having a melting point of 0°C or higher, and the joint with the outer cylinder on the rear end side is brazed with a low melting point brazing metal having a melting point of approximately 800°C. A ceramic glow plug characterized in that the inner cavity of the distal end of the fitting is soldered with a low melting point brazing material having a melting point of 600 to 700°C.