JPS60103229A - Self-controlling type ceramic glow plug - Google Patents

Abstract

PURPOSE:To obtain a current flow control function in which the heat radiation state of a resistor at the time of a temperature rise due to the curret flow is predetermined by caulking a metal tube at a part of the drum part of a metal fitting in the inner cavity of the metal fitting, and bringing a part of the outer periphery of the metal tube into contact partly with the inner wall of the metal fitting. CONSTITUTION:A connection component including a resistor coil 7, a middle shaft 8 and a lead electrode shaft 6 is covered with a metal tube 12, and is formed into an assembly body 14 embedded into a heat insulative material such as a magnesia powder or the like filled in the inner cavity of the connection component and is integrally formed. The metal tube 12 of the assembly body 14 inserted into the inner cavity of the metal fitting 4 is caulked at the drum part 4a of the metal fitting 4, and a part of the metal tube 12 is hermetically connected to the inner wall of the metal fitting. Therefore, even when a clearance (t) between the coils 7 exceeds 0.1mm., it becomes actually 0.1mm. or less, and hence it is stable. As a result, it is possible to obtain a self-controlled type ceramic glow plug in which the heat radiating condition of the resistor is easily predetermined, the durability is improved and further mass-productivity is excellent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a rapid low heat type glow plug that is installed in a diesel engine and preheats the auxiliary combustion chamber etc. at the time of starting.

Generally speaking, diesel engines operate at low temperatures (at the beginning of the second cycle!
Because of its low power, the engine head is preheated by installing glow plugs in the combustion chamber, etc., and burning a part of the fuel that is injected into the room. This method requires a rapid temperature rise characteristic at the time of starting (= sudden and rapid temperature rise), and even after starting (nearly B91), a long period of afterglow is used to stabilize combustion. There is a growing need for improved durability.

A rapid heating type glow plug suitable for this purpose uses a ceramic heater as a heating element, which is made by embedding a heating wire of a high melting point metal in a ceramic sintered body.

In addition, during rapid temperature rise (in order to prevent ceramic cracking due to melting of the heating wire or thermal shock in the second case), it is necessary to A self-controlling ceramic globe lag is known which has a structure in which resistors made of wires having a certain temperature coefficient of resistance are connected in series and which controls the heating current.

Fig. 1 shows a vertical cross-sectional view showing the Wi construction of a conventional example of this Maki Glow Bag. One end 2 of the heating wire 2 is soldered to the inner cavity of the cylinder 3.
a is electrically connected.

The metal outer cylinder 3 is brazed to the inner cavity of the distal end of the mounting bracket 4 and
The other end 2b of the heating wire 2 is electrically connected to the resistor coil 1 through a lead electrode shaft 6 welded to a metal cap 5 fitted to the rear end of the ceramic heater 1. The other end of the resistor coil T is connected to the tip of the center shaft 8.

The inner cavity of the mounting fitting 4 is filled with glass powder 9 so that the above-mentioned component is embedded in the inner cavity,
The center shaft 8 is configured such that an insulator 10 is interposed between it and the mounting fitting 4, and is tightened and fixed with a round nut 11 to form a sleeping pole.

Conventional self-controlling gloves 2 of this kind with such a structure have a structure in which the temperature of the resistor increases faster than that of the heating wire due to the difference in the temperature coefficient of resistance between the resistor wire and the wire of the heating wire when electricity is applied and the temperature rises. This (′-) has an excellent feature of reducing the heating current of the heating wire and preventing overheating of the heating element due to the increase in resistance value, but the glove 2 group during mass production In order to provide a stable heating current control function to the glow plug, it is necessary that the temperature of the resistor of each glow plug remains constant as the temperature rises. It is desired to improve the storage structure in the inner cavity of the metal fitting, and furthermore, as shown and explained in FIG.
Since the connecting components of the inner shaft 8 and the ceramic heater 1 are sealed in the inner cavity of the mounting bracket 4 with glass (two-way seal), the resistance coil T and the glass are repeatedly heated and cooled by the resistor coil 7. Due to the difference in the coefficient of expansion between the resistor coil 7 and the resistor coil 7, the glass is broken and the sealing performance is impaired, and the outside air enters through the cracked portion, accelerating oxidation of the resistor coil 7 and reducing its durability.

The present invention solves the above-mentioned problems, and aims to provide a self-regulating ceramic globe 2 which has improved durability and is easy to manufacture in mass production. The resistor coils connected in series are formed as an assembly by being embedded in a metal tube filled with a heat-resistant insulating material, including the center shaft and the connection part to the heating element, and the assembly is further stabilized in the inner cavity of the mounting bracket. It has a structure in which it is stored in the same condition.

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

FIG. 2 is a longitudinal cross-sectional view of an embodiment of the self-regulating ceramic glow plug of the present invention.The same parts as in FIG. 1 are designated by the same reference numerals.

In the figure, 7 indicates that the wire is made of nickel (nickel), which has a large temperature coefficient of resistance.
A resistor coil made of N1) or iron (WE), one end of which protrudes from the rear end of the mounting bracket 4 and is connected to the tip 3alZ of the center shaft 8, which becomes the ■ side electrode.

The other end is a wire with a smaller temperature coefficient of resistance than the resistor coil, such as tungsten (W) or rhenium (Rθ).
To L IW8>4. rJA+-h-J+ ”y S
'The lead electrode shaft 6 (two connections are made, and the connection including the resistor coil 1, the center shaft 8, and the lead electrode shaft 6) is connected to the heating wire of V force y-4-1 (omitted and not shown in the figure). The component is formed as an integral assembly 14 covered by a metal tube 12 and embedded in a heat-resistant insulating material 13, such as magnesia powder, which is filled with a lumen of -t-. is inserted from the rear end opening of the mounting bracket 4, is crimped from the outer circumference by a portion 4a of its body, and is held in close contact with a portion of the inner wall C of the lumen of the mounting bracket 4. That is.

Note that the metal tube 12 of the assembly 14 (the part 4a of the body of the pair of mounting brackets 4) is crimped by rolling crimping as shown in the mark in FIG. As shown in the figure, it is crimped using a polygonal chair such as a square, hexagon, hexagon, etc., and the crimping point is not limited to one place, but if necessary, it can be crimped in multiple places in the axial direction as shown in the same figure ←. The parts may be tightened.

The above-mentioned assembly 14 includes six bodies 13 preformed with heat-resistant insulating powder such as magnesia in the internal space of the coil, as shown in FIG. 4 (the same parts as in FIG.
-1 inserted into the resistor coil 1 is connected to the center shaft 8 and the lead electrode shaft 6, and the six bodies 1 are connected to the outside of these connection components.
Insert a preformed tube 13-3 made of the same material as 3-1, further insert it into the metal tube 12', seal the openings at both ends with rubber seals 17, and process it with a swaging machine, roll machine, etc. As shown in the same figure (b), the connection component including the resistor coil 1, the center shaft 8, and a part of the lead electrode shaft 6 is made of a heat-resistant insulating material 1 inside the metal tube 12.
It is obtained as an assembly 14 embedded and fixed in 3.

The rest of the structure of the self-regulating ceramic glow plug in this embodiment is the same as that of the conventional example shown in FIG. 1, so the explanation will be omitted.

Figure 5 is a graph showing the results of a test conducted to determine the effect of the gap t between the outer periphery of the metal tube of the assembly and the inner wall of the lumen of the mounting bracket on the temperature of the heating element when the temperature is increased by energization. In the test, the above gap t is 0 (close) and 0.1MM.
Six types of metal tubes 12a having outer diameters such as This was done for a glow plug arranged as shown in the figure.

As shown in the figure, since the resistor coil 7 is connected in series with a wire having a positive temperature coefficient of resistance larger than that of the heating wire, the temperature (resistance value) of the resistor coil 1 increases when energized.
(heating wire) increases rapidly, and by decreasing the conducting current, the temperature of the heating element reaches the maximum temperature and then gradually decreases, and the gap t with the inner wall of the mounting bracket lumen is 0 to 0.
．． The one in which the metal tubes 12a are arranged so as to give a maximum weight of 1200°C to 1250°C maintains approximately 900°C even after the temperature gradually decreases, showing extremely good temperature characteristics. If t is set to 0.2 gm, the amount of heat dissipated to the mounting bracket 4 side will be small, and the temperature (resistance value) of the built-in resistor coil 7 will be too high, causing the current to flow. If the temperature decreases too much, as shown by the dotted curve in Figure 1, the temperature of the heating element will not be able to maintain the conventionally required 900°C and will not be able to demonstrate its performance as a glow plug. It can be seen that the gap t between the metal fitting 4 and the inner wall of the lumen needs to be 0Aiy or less.

However, considering mass production during actual manufacturing, there may be manufacturing variations in the outer diameter of the metal tube 12a and the inner diameter of the lumen of the mounting bracket 4, and the outer peripheral surface of the metal tube 12a and the inner wall of the lumen of the mounting bracket 4 should be completely close together (gap t=
Q) Uniformly setting the concentration of 0.1H11 or less hinders mass production and is accompanied by manufacturing difficulties.

On the other hand, in the resistor storage structure according to the present invention, as shown and explained in FIG.
Since the metal tube 12 of 4 is crimped by the body 4a of the mounting bracket 4 and has a structure in which a part of the metal tube 12 is brought into close contact with the inner wall of the lumen, it is effective even if the above-mentioned gap t exceeds o, 1 nor. In other words, the current is 0.111W or less, resulting in a stable effect, and the heat dissipation state of the resistor can be easily maintained at a constant level. ゛Figure 7 shows a diagram of the glow plug according to the present invention. This shows the test results conducted for 1.
The test was conducted when the gap t was 0.05 mm, 0.1 mm, and 0.0 mm.
Three types of metal tubes 1 with outer diameters such as 21'jl
Insert the assembly 14 with the second
As shown in the figure, a part of the outer circumference is attached to the body 4a of the mounting bracket 4.
This study was carried out on a housing structure in which the parts were crimped closely together, and the graph shows the relationship between the gap t and the temperature of the heating element when the temperature is increased by energization.

As seen in the graph of FIG. 7, in the case of the storage structure of the present invention, even if the gap t is 0.211M, a part of the outer periphery of the scrap metal tube 12 is in the inner cavity of the fitting 4 and touches the inner wall thereof. Because they were in close contact, the effect was to effectively narrow the gap t, and the temperature of the heating element reached a maximum of 1200°C or more when the temperature was increased by energization, as in the case of t-=0.05+u and 0.1cm. It was proved that even if the temperature was gradually reduced, the temperature remained at 900°C or higher, and the temperature performance required for glove 2 was sufficiently satisfied.

As can be understood from the above explanation, the self-regulating ceramic glow plug of the present invention consists of a resistor connected in series to a heating element, a resistor coil inside a metal tube filled with a heat-resistant insulating material, a central shaft, and a heating element. Even the buried part, including the connection part with the lead electrode shaft connected to the body, has a sheathed resistor structure that is formed as an integrated assembly, so it is extremely strong and has significantly improved durability. The structure is such that the metal tube of the assembly is crimped in the inner cavity of the fitting by a part of the body of the fitting, and a part of its outer periphery is brought into partial contact with the inner wall of the fitting. By doing so, variations in the gap t between the inner wall of the lumen of the mounting bracket and the outer periphery of the metal tube during manufacturing are absorbed, resulting in an effect of effectively narrowing the gap. It has the characteristics of a constant heat dissipation state and a stable energization control function with a constant D1.It solves the problems of conventional products, has improved durability, and can be provided as a self-control ceramic glow plug with excellent mass production. It is something.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view showing a conventional example of a self-controlling ceramic glow plug, Fig. 2 is a longitudinal cross-sectional view showing an embodiment of the self-controlling ceramic glow plug of the present invention, and Fig. 3 is a mounting bracket in the present invention. Figure 4 is a front view of the main parts of the embodiment showing the crimped shape by the body, Figure 4 is an explanatory diagram of the manufacturing procedure of the assembly according to the present invention, and Figure 6 is a diagram showing the relationship between the outer periphery of the metal tube and the inner wall of the fixture in the inner cavity of the fixture. Figure S is a vertical cross-sectional view of the main part showing the structure of the glow plug sample used in the test conducted to find out the relationship between the gap t and the temperature of the heating element during temperature rise. Figure S is a graph showing the results. This is a graph showing similar test results for the 71st invention self-regulating ceramic glow plug. 1: ceramic heater, 2: heating wire, 3: metal outer cylinder,
4: Mounting bracket, 6: Lead electrode shaft, 7: Resistor coil,
8: Center shaft, 9, 13: Heat-resistant insulation material, 10: Insulator, 11
: Round nut, 12: Metal tube, 14: Assembly agent Patent attorney Mamoru Takeuchi Figure 1 Figure 3 C4) (υ) (c) Figure 4

Claims (1)

[Claims] A self-control system that uses a ceramic heater with heating wires embedded in a ceramic sintered body as a heating element provided at the tip of the mounting bracket, and a resistor is connected in series to the heating element within the inner cavity of the mounting bracket. In the type ceramic glow plug,
The coil of the resistor is arranged in a metal tube with both ends open, and one end of the metal tube extends from the rear end τ10 and is connected to a central shaft that becomes a terminal electrode, and the other end is connected to a heating element. The connecting portion in the metal tube is embedded in a heat-resistant insulating material filled in the lumen of the metal tube to form an integrated assembly, and the metal tube of the assembly is connected to a mounting bracket. The outer diameter is such that the gap between the inner wall of the inner cavity and the inner wall of the mounting bracket is as narrow as possible. Ceramic glow plug.