JPS60218A - Self-regulating type ceramic glow plug - Google Patents

Abstract

PURPOSE:To improve electrical and chemical stabilities by integrally forming a heat generating wire having a high heat-resistant property and a resistor body by embedding them in a ceramic sintered body. CONSTITUTION:A ceramic heater 1 is integrally formed in such a manner that two resistor coils 4-1, 4-2 are respectively connected to both ends of a coiled heat generating wire 2 bent in the U-shape through a lead wire 3, and after embedding them in the ceramic powder consisting of, for example, Si3N4 and forming such into a cylindrical shape, the ceramics is sintered by a hot press method. The ceramic heater 1 is disposed in a hollow of a metallic outer cylinder 5 that covers the outer surface of the heater, and its end is retained in such a manner that the end slightly protrudes from the end of the metallic outer cylinder 5. Because of this arrangement, electrical and chemical stabilities can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rapid heating type glow plug that is mainly installed in a diesel engine, and more particularly to a self-control type glow plug that is effective for preventing overheating of a heating element when the temperature increases.

Diesel engines generally have poor startability at low temperatures, so a method is to install a glow plug in the auxiliary combustion chamber of the engine/gin head to partially burn and preheat the fuel injected into the chamber, thereby improving engine startability. However, glow plugs are required to have rapid temperature rise characteristics at startup.

As a rapid heating type glove that achieves this purpose, magnesia is placed inside a metal sheath with a closed tip.

There is a conventional example of using a metal type glow plug, which is made by filling heat-resistant insulating powder such as alumina and embedding a heating wire such as nickel (N1) in the powder, but in this type of glow plug, the heating element is covered with a metal sheath. Because of this, the heating efficiency is poor, and there is a risk that the heating wire may melt due to rapid heating.
In order to prevent this, a problem arises in that a controller 2 or the like is required to control the heating time and temperature.

Another conventional example is to use tungsten (W), which has particularly excellent heat resistance, for the heating wire, and replace it with silicon nitride (S").
There is a ceramic globe 2-g whose heating element is a ceramic heater embedded in a ceramic sintered body whose main component is Because it is not covered with a metal sheath, it has good temperature raising efficiency, and because it uses a highly heat-resistant metal wire for the heating wire.

Although there is little risk of melting even at high temperatures, the surface of the heating element, which is exposed directly to the combustion chamber such as the vortex chamber and has become hot due to rapid temperature rise, is subject to thermal shock due to the cooling effect of the injected fuel and swirling air. There is a risk that ceramic cracking may occur, and as in the case of the metal glow plug, a controller or other auxiliary circuit means for controlling energization is required to prevent this.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a rapid heating type glow rig that solves the above problems and has a self-control function with excellent heating efficiency and durability.

Embodiments of the self-regulating ceramic glow plug of the present invention will be described in detail below using diagrams.

Fig. 1 shows a longitudinal cross-sectional view of the self-regulating ceramic glow plug of the present invention. In the figure, 1 is a ceramic heater serving as a heating element, which has a coil shape bent into a U-shape at the center of the diaphragm. Two resistor coils 4-0 and 4-2 are connected to both ends of the heating wire 2 via connecting wires 3, respectively, and are embedded in ceramic powder mainly composed of, for example, Si 3N and prepared in a cylindrical shape. After molding, the ceramic is sintered using a pot press method, the external shape is finished by polishing or grinding, and the product is integrally molded. This ceramic heater 1 is fitted into the inner cavity of a metal outer cylinder m5 formed to cover its outer periphery, and its tip is connected to the metal outer cylinder 5.
It is held so that it protrudes slightly (1 to 2 feet) from the tip of the wire. Sa L (5~10
A gap 1 is formed between the portion corresponding to M) and the inner wall of the metal outer cylinder 5.

Incidentally, a plurality of oval or circular ventilation holes 5-1 may be provided on the outer periphery of the tip of the metal outer cylinder 5, as shown in FIG. 2(C). As shown in FIG. 1, the lead wire 6-1 welded to the resistor coil 4x is electrically connected to the metal outer cylinder 5, and the metal outer cylinder 5 is inserted into the inner cavity of the distal end of the mounting bracket 8. The lead wire 6-2, which is connected to form an electrode and is welded to the paper antibody coil 4-2, is electrically connected to the lead rod 9 that is brazed to the rear end side of the ceramic heater 1. This lead rod 9 is further welded to the center shaft 10, and the center shaft 10 is tightened with a round nut 12 with an insulator 11 interposed between it and the mounting bracket 8, and has a structure that becomes an electrode. It is something.

Note that the connection structure between the heating wire and the resistor coil of the ceramic heater 1 shown in FIG. However, it is not limited to this, and for example, the third
As shown in the figure, as a heating element 1', a heating wire 2' and a resistor coil 4' are connected at one end a,
The other end of the resistor coil 4' may be pulled out as it is and used as a lead wire, while the other end of the heating wire 2' may be drawn out through the center of the coil and used as a lead wire C.

By the way, the heating wire coil used in the ceramic heater having the structure described above and the metal wire of the resistor coil connected in series with the heating wire coil are designed to have an excellent heat generation control function.

It is assumed that the temperature coefficient of resistance is positive and the wire of the resistor coil has a larger value than that of the heating wire. It is preferable that there is a difference in the ratio (to the resistance value), and as a result of the inventors' various trial production studies,
The wire of the heating wire has a low temperature coefficient of resistance such that the temperature-resistance coefficient is 4 times or less.W-Re, W-Co, W
- Tungsten (W) alloy such as Mo or W-Zr alloy is used, and the wire material of the resistor coil has a temperature-resistance coefficient of 5 to 5.
It has been found that good results can be obtained by combining pure W or pure MO with a temperature coefficient of resistance that is 6 times as large.

The ceramic heater 1 in the glow plug of the embodiment shown in FIG.
A W alloy containing 15% by weight of
-1 and 4-2 wires are made of pure W, and when the glow plug is energized, the temperature rises rapidly (900°C).
As a result of actually measuring the temperature of a part of the heater by keeping the current flowing (within 6 seconds), the temperature of a part of the heater was measured.
It has been demonstrated that saturation occurs within 00'Q.

As can be understood from the above description, the self-regulating ceramic globe of the present invention includes a ceramic heater having an integrated structure in which a highly heat-resistant heating wire and a resistor are embedded in a ceramic sintered body. Since it is a heating element, it has excellent electrical and chemical stability under the usage conditions and environment.

A W alloy wire with a small temperature-resistance coefficient is used for the heating wire,
The wire of the resistor connected in series with this wire is made of pure W or pure MO, which has a higher temperature-resistance coefficient than the heat-generating wire, so when the current is applied and the temperature rises, the resistance value of the resistor increases the heat generation. The heating current increases faster than that of the wire, reduces the heating current, and prevents the heating element from overheating through self-control. In the combustion chamber, the injected fuel and the cold air of the swirling air can be prevented from coming into direct contact with the surface of the high-temperature heating element, thereby preventing the occurrence of ceramic cracking due to thermal shock. Since there is a gap between the two, the ignitability of the fuel is not hindered, and it has many advantages, such as eliminating the need for expensive and complicated energization control controllers, which solves the problems of conventional methods. It can be provided as a rapid heating glow plug.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of an embodiment of the self-regulating ceramic globe 2 of the present invention, Fig. 2 (A) is an enlarged longitudinal cross-sectional view of the main part showing the tip structure of the ceramic heater in Fig. 81, and Fig. B) is an end view of the tip, and the same figure shows another embodiment of the structure of the tip of the metal outer cylinder, and FIG. FIG. 7 is a longitudinal cross-sectional view of a main part of a body coil showing an example of another connection structure. 1.1': Ceramic heater, 2,2': Heat generating wire, 3
: Connection wire, 41, 42.4': Resistor coil, 5: Metal outer cylinder * 5 x 'Vent hole, 61.62 and 61.62', c: Lead wire, 7: Gap, 8: Mounting bracket, 9: Lead stick, 10
: Center shaft, 11: Insulator, 12: Marunatsu agent Patent attorney Mamoru Takeuchi - 8 Figure 1 Figure 2 Figure 3 C c]

Claims (3)

[Claims] (1) In a self-control glow plug in which a current control resistor is connected in series to the heating element in order to control the temperature of the heating element when the temperature is increased by energization, a coil-shaped heating wire connected in series is used. The resistor and the resistor are embedded in the ceramic sintered body and integrated to form a two-layer heater. A self-controlling ceramic glow plug, characterized in that the glow plug is held in a closed position, and a gap is provided between the outer periphery of the heating wire buried portion at the tip of the ceramic heater and the inner wall of the metal outer cylinder. . (2) The heating wire has a temperature-resistance coefficient (normal temperature - 1 (100℃)
) is 4 times or less, and the resistor is pure W or ktl.
A self-regulating ceramic glow plug according to claim 1, characterized in that the plug is made of a wire rod. (3) A plurality of ventilation holes are provided on the outer periphery of the tip of the metal outer cylinder with a gap provided between the outer periphery of the tip of the ceramic heater and the outer periphery of the tip of the ceramic heater. The self-regulating ceramic glow plug described in item 2.