JPS59157423A - Self-control type glow plug - Google Patents

Abstract

PURPOSE:To improve the durability of a heating part and contrive to prevent the heating element from over-heating due to a self-control by a method wherein an electric current limiting resistance element is connected to a ceramic heater in series, the ceramic heater is made by sinter forming after imbedding of a heating wire made of high heat-resisting metal in a ceramic powder material. CONSTITUTION:A coil-shaped heating wire 2 is imbedded in a ceramic powder material which is mainly composed of Si3N4, SiC and the like, and preformed in cylindrical shape, then the ceramic is sintered by a hot-press method, thus, the external form of a ceramic heater 1 is finished by abrasion or grinding process. A metal outer cylinder 3 is fitted and brazed at the outer side of a rear half part, simultaneously, one end 2a of a heating wire 2 is connected to the outer side of the rear half part. The metal outer cylinder 3 is brazed to be (-) side electrode on a bore at the end part of a fitting 4, meanwhile, the other end 2b of the heating wire 2 is brazed to a cap 5 fitted to the rear end part of the ceramic heater 1, and connected to a metal coil-shaped resistance element 7 via a lead rod 6 welded to the cap 5, the other end of the resistance element 7 is welded to a center shaft 8. A heat-resistant insulating filler material 9 such as MgO or glass and the like is filled inside of the bore of the fitting 4 and the metal outer cylinder 3. The center shaft 8 is formed to be (+) electrode by locking and fixing to the fitting 4 with a circular nut 11 by interposing an insulating element 10 between the shaft and the fitting.

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 is effective for preheating the inside of a cylinder or sub-combustion chamber at the time of starting.

Diesel engines generally have poor startability at low temperatures, so a method is used in which a Darrow plug is installed in the cylinder or sub-combustion chamber to raise the temperature inside the chamber and improve the engine's starting characteristics. It is required to have suitable temperature rise characteristics.

Magnesia is placed inside a metal sheath with a closed end to create a rapidly heating glow plug that achieves this purpose.

There is a conventional example of using a metal type glow plug filled with heat-resistant insulating powder such as alumina and with an N1 heating wire embedded in it, but in this type of glow plug, the heating wire melts when a rapid heating current is applied. To prevent this, a controller is used to control the heating current to regulate the heating time and temperature.In addition to being expensive, the heating part is covered with a metal sheath. However, it had the disadvantage of poor heat conduction efficiency.

In addition, as another conventional example, tungsten (W), which has particularly excellent heat resistance, is used for the heating wire, and this is replaced with silicon nitride (B15).
M4) or silicon carbide (810) as the main component, and is sintered to form a heating element and used as a rapid heating ceramic glow plug.
In this case, the heating element is not covered with a metal sheath, so the temperature raising efficiency is good, and since the heating wire is made of highly heat-resistant metal, there is little risk of melting even at high temperatures, but the rapid temperature rise causes thermal shock. Since there is a risk of ceramic cracking, there is a problem in that a controller or other auxiliary circuit means for controlling energization is required, as in the case of the conventional example described above.

Other conventional examples of rapid heating glow plugs include:
In order to further improve temperature raising efficiency, there is a self-control glow plug that has a structure in which the heating wire is exposed as it is as a heating element, and a current limiting resistor is connected in series to this heating element. In the case of this glow plug, it is possible to rapidly raise the temperature with a small amount of electricity, and the heating current decreases due to the increase in resistance as the temperature of the resistor connected in series increases, and the temperature reaches saturation within a range where the heating wire does not melt. It has the advantage that it does not require any control means such as a controller, but it has the disadvantage that the heating wire is easily oxidized and corroded because there is no coating on the heating part, resulting in insufficient durability. It had a

As mentioned above, conventional rapid heating type glow plugs particularly require a controller and other auxiliary circuit means to control the heating current in order to prevent heating wires from melting due to rapid temperature rise or ceramic cracking due to thermal shock. Both systems have their drawbacks, such as the system becoming complicated and expensive, and self-regulating glow plugs with exposed heating wires having insufficient durability of the heating part. Especially in recent years, there has been a trend that glow plugs are not only used when starting an engine, but also used for a long time after engine startup as an afterglow to stabilize combustion. Physical and chemical durability are particularly required.

In view of the above circumstances, the present invention aims to provide a glow plug having a self-control function that improves the durability of the heat generating part and solves the problems of the above-mentioned conventional examples. A ceramic heater is used in which a heat-generating wire made of a high heat-resistant metal is embedded in ceramic powder and then sintered, and a current-limiting resistor is connected in series to this ceramic heater within the bore of the mounting bracket. It has a structure in which the surrounding area is filled with a heat-resistant insulating filler.

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

FIG. 1 shows a longitudinal cross-sectional view of an embodiment of the self-regulating glow plug of the present invention. In the ceramic heater 1, a coiled heating wire 2 is made of ceramic powder mainly composed of 513N4, SiC, etc. After being buried in the body and pre-formed into a cylindrical shape, the ceramic is sintered using a hot press method, and the outer shape is finished by polishing or grinding.The outside of the rear half is made of metal. The outer cylinder 3 is fitted and soldered, and at the same time, one end 2a of the heating wire 2 is connected. The metal outer cylinder 3 is soldered to the inner cavity of the tip end of the mounting bracket 4 to form the e-side electrode9. On the other hand, the other end 2b of the heating wire 2 is soldered to a cap 5 fitted to the rear end of the ceramic heater 1, and connected to a metal coiled resistor 7 via a lead rod 6 welded to the cap 5. Further, the other end of the resistor 7 is welded to the center shaft 8. The inner cavities of the mounting bracket 4 and the metal outer cylinder 3 have, for example, a dragonfly shape so that each of the components disposed in the inner cavities are embedded therein. Alternatively, it is filled with a heat-resistant insulating filler 9 such as glass, and the center shaft 8 has an insulator 10 interposed between it and the mounting bracket 4, and is tightened with a round nut 11 to form an electrode. be.

In addition, the metal wires of the heating wire 2 used in the ceramic heater 1 mentioned above and the resistor 7 inserted and connected in series with the metal wire have a positive temperature coefficient of resistance in order to provide an excellent heat generation control function. It is desirable that there is a difference in temperature-resistance coefficient (ratio of resistance value at room temperature and resistance value at high temperature of 1000'C) between the two.
If possible, it is preferable to use a wire material for the heating wire 2 that has a temperature-resistance coefficient of 3 times or less, and to use a wire material for the resistor that has a temperature-resistance coefficient of 5 times or more. However, in this embodiment, tungsten (W) was used as the wire for the heating wire 2, and nickel (N1), which has a larger temperature-resistance slow wave than the heating wire 2, was used for the resistor 70 wire.

By selecting the heating wire 2 and the wire of the resistor 70 and connecting them in series as described above, heating current is passed through 1. In the rapid temperature rise by i, the temperature-resistance coefficient of the resistor 7 is
Because the heating wire 2 is smaller than that of the heating wire 2, the resistance of the resistor increases faster than that of the heating wire 2, reducing the heating current and preventing the heating wire 2 of a part of the heater from overheating. This is the result.

FIG. 2 (the same parts as in FIG. 1 are designated by the same reference numerals) is a longitudinal cross-sectional view of another 5V embodiment of the self-regulating glow plug of the present invention, in which the distal end is made of a disk-shaped ceramic material. This ceramic heater is equipped with a heating wire 2' wound in the shape of a spring coil, as shown in FIGS. 3(A) and 3(B). After being embedded in a powder shell and preformed, the ceramic is sintered using a hot press method, and the external shape is finished by polishing or grinding. The central end 2'a of the heating wire 2' wound into a spring coil is pulled out and welded to the lead rod 6', and the other end 2/b is inserted into the outside of the ceramic heater 1'. It is connected to the tip of the metal outer cylinder 3' which is to be welded together. The rest of the structure of the self-regulating glow plug of this embodiment is the same as that of the previous embodiment, so the explanation will be omitted.

Incidentally, the glow plug according to the embodiment of the present invention was energized, the temperature was rapidly raised (reaching 900°C within 6 seconds), and the energization was continued.
'As a result of actually measuring the temperature of a part of the heater when it continues, 1
It was possible to demonstrate saturation within 150°C.

As can be understood from the above description, the self-regulating glow plug according to the present invention has a high-performance ceramic heater in which a high heat-resistant heating wire is embedded in the ceramic in the heat generating part.
In addition to having excellent electrical and chemical stability under the usage conditions and environment, the metal resistor wire connected in series with this heater has a temperature-resistance coefficient that matches the heat generated by the heater. Since the combination uses a wire that is larger than that of the heating wire, when the current is applied and the temperature is raised, the resistance value of the resistor increases faster than the resistance value of the heating wire, thereby reducing the heating current and self-controlling. This prevents the heating element from overheating, and it has the advantage of reducing costs by not requiring the expensive and complicated current control controllers, etc., as in the past, and has improved the drawbacks and problems of the past. It can be said to be a thing.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of an embodiment of the self-regulating glow plug of the present invention, FIG. 2 is a vertical cross-sectional view of another embodiment of the self-regulating glow plug of the present invention, and FIG. (A) is a front view, (A) is a front view, (A) is a front view, (A) is a front view,
B) is a vertical cross-sectional view taken along the line x-X in (A). 1.1': Ceramic heater, 2,2': Heat generating wire, 2
'a: Lead wire, '3.3': Metal outer cylinder, 4: Mounting bracket, 5: Cap, 6.6': Lead rod, 1: Resistor, 8
: Center axis, 9: Filler agent Patent attorney Mamoru Takeuchi Procedural amendment (spontaneous) June 13, 1982 Commissioner of the Japan Patent Office Kazuo Wakasugi 1 Indication of case 1989 Patent Application No. 28452 2 Invention Name Relationship with the case of self-regulating glow plug 6 corrector Patent applicant address 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi Name (454) NGK Spark Plug Co., Ltd. Representative Osamu Ogawa 4 Agent residence Postal code 101 No. 7, Uchikanda 2-15-13, Chiyoda-ku, Tokyo
On the 5th line of the page, between r(Ni)J and "Used."
, iron (11'e), etc." is added.

Claims (1)

[Claims] In a self-control glow plug, a current limiting resistor is connected in series to a heating element provided at the tip of an engine mounting bracket in order to control the temperature of the heating element when the temperature rises due to energization. As the heating element provided at the tip of the mounting bracket, a ceramic heater with a heating wire embedded in ceramic is used. A self-regulating glow plug characterized by being filled with a heat-resistant electrically insulating filler.