JPH0228044B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-wire glow plug that is mainly installed in a diesel engine and preheats a sub-combustion chamber or the like provided in the engine head.

Diesel engines generally have poor starting performance, especially at low temperatures, so a glow plug is installed in the auxiliary combustion chamber installed in the engine head, and when electricity is applied to the glow plug, it becomes red hot and burns a portion of the fuel injected into the engine. In recent years, there has been a trend for it to be used as an afterglow for combustion stabilization even after the engine has started.

Ceramic glow plugs are known as this type of glow plug, whose heating element is a ceramic heater with excellent temperature-raising characteristics, in which a heating wire of a high-melting point metal is embedded in a ceramic combustion body. Single-wire ceramic glow plugs are often used, with one end connected to the center shaft that serves as the electrode terminal on the ○+ side that is insulated from the mounting bracket, and the other end electrically connected to the mounting bracket to form a ground electrode. There is.

By the way, these single-wire glow plugs are usually installed in each cylinder of a multi-cylinder engine, and each glow plug is connected in parallel to the power supply, but these multiple glow plugs are used during startup and startup. Since it is necessary to perform heating control according to the heating conditions required during afterglow, etc., an external circuit is required to control current flow without changing the power supply voltage by switching each glow plug in parallel or series. There is a need for a two-wire glow plug that has a terminal electrode part that connects to a 2-wire glow plug, and efforts are being made to put it into practical use and improve it.

A conventional example of a two-wire ceramic glow plug that uses a ceramic heater as a heating element has the structure shown in Figure 1 (Utility Model Application No. 119045/1982).
is known, and the ceramic heater 1 serving as the heating element is made by embedding the heating wire 2 in ceramic powder and sintering it, and inserting it from the opening at the tip of the mounting bracket 3 and forming a large diameter wire in the center. The shoulder portion 1a of the mounting bracket 3 is brought into contact with the tip side step seat 3a of the small diameter portion formed in the inner cavity of the tip portion of the mounting bracket 3, and is bonded and fixed.
One end 2a of the heating wire 2 is connected to a center shaft 4 serving as one terminal electrode at the rear end of the heater 1, and the other end 2b is connected to an electrode tube 5 fitted on the outside of the rear end of the heater 1. , the electrode tube 5
The central shaft 4 has its inner cavity filled with heat-resistant insulating material 6.
is sealed and supported, protrudes from the rear end side of the mounting bracket 3 and is insulated from the mounting bracket 3 by an insulator 7, and a terminal plate 8 is fixed to serve as the other terminal electrode. be.

However, the ceramic heater 1 in the conventional two-wire ceramic glow plug described above,
The connection structure between the center shaft 4 and the electrode tube 5, which serve as terminal electrodes, is based on the heating wire 2 buried in the heater 1.
Since the surfaces of the respective joint parts with exposed end parts 2a and 2b are metallized by metallization, vapor deposition, etc., and directly soldered to the center shaft 4 and the inner cavity of the electrode tube, the joining work is labor-intensive and makes it difficult to mass-produce. It had the disadvantage of hindering the development of

The present invention has been made for the purpose of providing a two-wire ceramic glow plug that solves the above-mentioned problems, and the rear end of the ceramic heater is formed with a small diameter part that is stepped with respect to the outer diameter of the heater body. Then, on the outer peripheral surfaces of this small diameter part and the large diameter part of the main body, electrode parts are formed with exposed ends of the heating wires, and each of these electrode parts has an inner diameter smaller than the outer diameter of each electrode part. By fitting a cylindrical terminal fitting with a cut portion in the axial direction and welding the lead wires protruding from the cylindrical terminal fitting to the central shaft and electrode tube, the ceramic heater and both terminals can be connected. This improves workability when connecting the center shaft and electrode tube, which serve as electrodes, and facilitates manufacturing.

The present invention will be explained below with reference to the drawings.

FIG. 2 is a longitudinal cross-sectional view showing the structure of an embodiment of the two-wire ceramic glow plug according to the present invention. Along with being
The metal outer cylinder 12 is joined and held in the inner cavity of the distal end of the mounting bracket 13, and the rear end of the ceramic heater 11 has a small diameter part 11a formed by providing a step with respect to the outer diameter of the heater body, and a small diameter part 11a is formed on the outer peripheral surface of the ceramic heater 11. heating wire 1
A cylindrical terminal fitting 15 is provided, in which one end 14a of the cylindrical part 15b is exposed to form an electrode part A, a lead wire 15a is protruded from the electrode part A, and a cut part 15c is provided in the axial direction of the cylindrical part 15b. The end of the lead wire 15a that is fitted and protrudes from the terminal fitting 15 is welded to the tip 16a of the center shaft 16 to form one terminal electrode, and the other end 14b of the heating wire 14 is connected to the ceramic heater 11. The other electrode part B is formed by exposing the outer circumferential surface of the main body large diameter part 11b close to the electrode part A on the rear end side, and the lead wire 1 is connected to the electrode part B.
A cylindrical terminal fitting 17 having a protruding portion 7a and a cut portion 17c in the axial direction of the cylindrical portion 17b is fitted,
The tip of the lead wire 17a is joined to the tip of an electrode tube 18 that is inserted into the outside of the center shaft 16 and has the center shaft 16 insulated and sealed in its inner cavity. 20 is fixed to serve as the other terminal electrode.

The cylindrical terminal fittings 15 and 17 fitted into the electrode parts A and B are shown enlarged in FIG. 3 (the cylindrical terminal fittings 15 and 17 have different dimensions but the same shape, so A cylindrical part 15 is punched out of a heat-resistant metal plate into a predetermined shape with lead wires 15a and 17a protruding from it, as shown in the drawing, and has an inner diameter smaller than the outer diameter of each of the electrode parts by bending.
b, 17b and the cut portions 15c, 1 in the axial direction thereof.
7c. Such cut section 1
Since the cylindrical terminal fitting provided with the cylindrical terminal fittings 5c and 17c has elasticity in the radial direction, it is easy to fit and hold the electrode parts A and B, and there is an advantage that the soldering work is easy.

In addition, the connection with the connecting fittings in the electrode part A and the electrode part B is made at the end 14 of the heating wire 14.
For example, a glass layer formed by coating and baking glass powder or a metallized layer is interposed on the outer circumferential surfaces of a and 14b excluding exposed portions, and the outer peripheral surfaces are firmly soldered together.

The two-wire ceramic glow plug according to the present invention having such a structure is particularly suitable for a ceramic heater,
The connection structure between the center shaft and the electrode tube that becomes the terminal electrode on the rear end side of the mounting bracket is such that there is a small diameter part with a step at the rear end of the heater, and both ends of the heating wire on the outer peripheral surface of the large diameter part of the main body adjacent to this. A cylindrical terminal fitting with a cut portion is fitted onto the electrode portion formed by exposing each terminal, and a lead wire protruding from each terminal fitting is connected to the center shaft and the electrode tube. Compared to the conventional method of directly joining the electrode part of the heater to the center shaft or mounting bracket, workability during joining is greatly improved, and the joined part is soldered with a glass layer intervening, providing sufficient strength. It can be provided as a two-wire ceramic glow plug that has excellent bi-productivity and solves the problems of the conventional method.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing a conventional example of a two-wire ceramic glow plug, FIG. 2 is a vertical cross-sectional view showing an embodiment of the two-wire ceramic glow plug of the present invention, and FIG.
The figure is an enlarged perspective view of the cylindrical terminal fittings 15 and 17 in FIG. 2. 1, 11: Ceramic heater, 2, 14: Heat generating wire, 3, 13: Mounting bracket, 4, 16: Center shaft,
5, 18: Electrode tube, 11a: Small diameter part, 11
b: Large diameter part, 15: Cylindrical terminal fitting, 15a, 17
a: Lead wire, 17: Cylindrical terminal fitting, A, B: Electrode portion, 15b, 17b: Cylindrical portion, 15c, 17
c: Cut portion.

Claims (1)

[Claims] 1. On the heating element exposed at the tip of the mounting bracket,
It uses a ceramic heater made by embedding a heating wire of a high-melting point metal in ceramic powder and sintering it, and has a structure in which both ends of the heating wire of the ceramic heater are insulated and led out from the rear end side of the mounting bracket. In the two-wire ceramic glow plug, the ceramic heater has one electrode portion having a stepped portion at its rear end and having a smaller diameter than the outer diameter of the heater body, with one end of the heating wire exposed on the outer peripheral surface; The other electrode portion is formed by exposing the other end of the heating wire on the outer peripheral surface of the large diameter portion of the heater body that is close to and separated from the small diameter portion, and the outer diameter of each electrode portion is attached to both electrode portions. A cylindrical terminal fitting with a smaller inner diameter and a cut in the axial direction is fitted,
The end of the lead wire protruding from the cylindrical terminal fitting is
A two-wire ceramic glow plug characterized by having a connection structure that is joined to a terminal fitting at the rear end of the mounting fitting.