JPS6350606Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a rapid heating type glow plug that is mainly attached to a diesel engine and preheats the sub-combustion chamber etc. at the time of startup.

(Prior art) Diesel engines generally have poor startability at low temperatures, so a glow plug is attached to the auxiliary combustion chamber provided in the engine head, and when electricity is applied to the glow plug, it becomes red hot and some of the fuel is injected into the engine. The method of preheating by burning is used, and it is required to have rapid temperature rise characteristics at the time of startup, and recently it is also used for a long time as an afterglow to stabilize combustion even after startup. Therefore, there is an increasing demand for improved durability.

As a rapid heating type glow plug that meets this demand, a ceramic heater in which a heating wire of a high-melting point metal is embedded in a ceramic sintered body is used as the heating element, and the heating wire is melted or fused due to overheating during rapid temperature rise. In order to prevent ceramic cracking due to thermal shock, the heating element is connected in series with a resistor made of a wire that has a larger positive temperature coefficient of resistance than the wire used for the heating wire. A self-controlling ceramic glow plug is known in which the resistance value of the resistor increases faster than the heating wire when current is applied and the temperature rises due to the difference, thereby reducing the heating current of the heating wire and preventing the heating element from overheating. There is.

The inventors of the present invention previously proposed a self-regulating ceramic glow plug of this type having a structure as shown in FIG. (Unexamined Japanese Patent Publication No. 58-217104).

In the glow plug according to this prior art, one end of a resistor coil 1 made of a metal wire having a large temperature coefficient of resistance such as Ni or Fe is attached to the tip of a center shaft 3 that protrudes from the rear end of a mounting bracket 2 and serves as a terminal electrode on the side. At the same time, the other end is connected to the lead electrode shaft 4, and the connection portion including the center shaft 3 and a part of the lead electrode shaft 4 is covered with a metal tube 5, and the inner cavity thereof is filled with a material such as magnesia powder, etc. An integrated assembly 7 is embedded in a heat-resistant insulating material 6, and is fitted onto the lead electrode shaft 4 of this assembly 7 and the rear end of a ceramic heater 8 disposed at the tip of the mounting bracket 2. A metal cap 10 to which one end of the heating wire 9 is connected is connected by a lead wire 11, and the ceramic heater 8 is held by being soldered to the inner cavity of the metal outer cylinder 12. At the same time, the other end of the heating wire 9 is connected to an electric wire. The metal outer cylinder 12 is further connected to the mounting bracket 2.
In the figure, 13 is an insulator, and 14 is an insulator.
is a round nut that fixes the center shaft 3.

(Problems to be solved by the invention) The self-regulating ceramic glow plug according to the above-mentioned prior art has a sheathed resistor structure in which the resistor connected in series with the heating element is embedded in a heat-resistant insulating material inside a metal tube. This makes it extremely robust and improves durability, and since the metal tube containing the resistor is crimped and fixed to the body of the mounting bracket, the heat dissipation of the resistor is constant when the current is applied and the temperature rises, resulting in a stable temperature. However, as shown and explained in Fig. 2, the metal tube 5 and the ceramic heater 8 of the assembly are respectively fixed in the inner cavity of the mounting bracket 2, so when in use, The mounting bracket 2 expands and contracts in the axial direction as the temperature of the resistor 1 changes due to ON and OFF energization, and the lead wire 11 that connects the mounting bracket 2 also expands and contracts repeatedly, which may cause the wire to break. Something became clear after that.

(Means and operations for solving the problems) The present invention was made to solve the problems of the self-regulating ceramic glow plug according to the above-mentioned prior art. Instead of the linear lead wire 11 that connects the lead electrode shaft 4 of the assembly 7 in the plug to the ceramic heater 8, a connecting member formed by forming the lead wire in a spiral shape is used. It is designed to absorb the expansion and contraction in the axial direction.

(Example) Fig. 1 is a longitudinal cross-sectional view showing the main parts of an embodiment of the self-regulating ceramic glow plug of the present invention, and the same parts as in Fig. 2 shown as an example of the prior art are designated by the same reference numerals. .

As seen in the figure, the main part of the glow plug according to the present invention is an assembly having a structure similar to that shown in the prior art example, which is crimped by a part 2a of the body of the mounting bracket 2 and fixed in the inner cavity thereof. Between the lead electrode shaft 4 and the rear end of the ceramic heater 8 disposed at the tip of the mounting bracket 2, there is a connecting member 11' having a lead wire formed in a spiral shape as shown in the figure. The upper end 11'a of the member 11' is fitted and welded to the lead electrode shaft 4 protruding from the lower end surface of the assembly 7, and the tightly wound lower end 11'b is connected to the ceramic heater 8. It has a connection structure in which one end of the heating wire 9 that is fitted and soldered to the rear end of the heater 8 and exposed on the surface of the rear end of the heater 8 is electrically connected. This is similar to the prior art example shown in FIG.

(Effects of the invention) As can be understood from the above, the self-controlling ceramic glow plug of the present invention has a lead wire spirally connected to the connection between the resistor and the ceramic heater, which is the heating element, in the shaft hole of the mounting bracket. By using a connecting member formed in a shape, expansion and contraction caused by temperature changes of the resistor during use can be absorbed and disconnection can be prevented. An electrical connection is made to one end of the heating wire of the heater by fitting and soldering the windings, so conventionally it was attached to the rear end of the heater as a terminal fitting to connect and take out one end of the heating wire. This has the advantage of omitting the process of welding the metal cap 10 and the lead wire to the cap as shown in FIG. This can be further improved.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a main part of an embodiment of the self-regulating ceramic glow plug of the present invention, and FIG. 2 is a vertical cross-sectional view showing a prior art example of the self-regulating ceramic glow plug. 1: Resistor coil, 2: Mounting bracket, 3: Center shaft,
4: Lead electrode shaft, 5: Metal tube, 6: Heat-resistant insulation material, 7: Assembly, 8: Ceramic heater,
9: Heat generating wire, 10: Metal cap, 11: Lead wire, 11': Connection member.

Claims (1)

[Scope of utility model registration request] A heat-resistant insulating material in which a resistor coil connected in series with a heating element is filled in the inner cavity of a metal tube inserted into the shaft hole of the mounting bracket, including the connection part with the center shaft and lead electrode shaft. This assembly is embedded in the mounting bracket and formed as an integrated assembly, and this assembly is fixed by crimping from the outer periphery with a part of the body of the mounting bracket,
In a self-controlling ceramic glow plug, the lead electrode shaft of the assembly is connected by a lead wire to a ceramic heater that is fitted into the tip of the inner cavity of the mounting bracket and serves as a heating element. A connecting member having a lead wire formed in a spiral shape is used at the connecting part between the heater and the ceramic heater.
The upper end of the connecting member is fitted and welded to the tip of the lead electrode shaft of the assembly, and the lower end thereof is fitted and soldered to the rear end of the ceramic heater, so that one end of the heating wire of the heater is connected at the same time. A self-regulating ceramic glow plug that is characterized by