JPS61195213A - Self-control type ceramic glow plug - Google Patents

Abstract

PURPOSE:To prevent rapid resistance increase of a resistor at the time of raising up the temp. under electrified condition in such a manner that a heating element is connected in series with a primary resistance coil and then a secondary resistance coil having smaller resistance temp. coefficient than that of the former. CONSTITUTION:Wire material of a heater 1 as a heating element is made of tungsten alloy which is composed of tungsten having small resistance temp. coefficient and rhenium being added to. The heater is connected with a resistor 17 in series via leed electrode axis 6. The resistor 17 is connected with a pri mary resistance coil 17-1 and a secondary resistance coil 17-2 in series. The former is made of Ni, Fe, or Ni-Fe alloy having high resistance temp. coefficient and the latter is made of Fe-Cr or Ni-Cr alloy wire having smaller resistance temp. coefficient than that of the former.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rapid heating type glow plug that is mainly installed in a diesel engine and preheats the auxiliary combustion chamber and the like at the time of startup.

[Conventional technology]

Diesel engines generally have poor starting performance at low temperatures, so a glow plug is attached to the auxiliary combustion chamber installed in the engine head, and when electricity is applied to it, it becomes red hot and burns part of the fuel injected into the interior. In addition to being required to have a rapid temperature rise characteristic at the time of starting, there is also a recent tendency for it to be used for a long time as an afterglow to stabilize combustion even after starting. As a result, there is an increasing demand for improved performance.

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.

Furthermore, in order to prevent melting of the heating wire due to overheating during rapid temperature rise or ceramic cracking due to thermal shock, the heating element is made of a wire material that has a larger positive temperature coefficient of resistance than the wire used for the first heating wire. A self-control ceramic glow plug is known which has a structure in which resistors are connected in series and which controls heating current.

FIG. 3 is a vertical cross-sectional view showing the structure of a conventional example of this kind of glove. 1 A ceramic heater (hereinafter simply referred to as a heater) serving as a heating element 1 is made of a wire material with a small temperature coefficient of resistance, such as tungsten (W). A heating wire 2 made of a W alloy containing rhenium (Re) is embedded in a ceramic sintered body 9, and is soldered to the inner cavity of a metal outer cylinder 3, and one end 2a of the heating wire 2 is electrically connected. The metal outer cylinder 3 is soldered to the inner cavity of the tip of the mounting bracket 4 to become the e-side electrode.
On the other hand, the other end 2b of the heating wire 2 is connected to a lead electrode shaft 6 which is welded to a metal cap 5 fitted to the rear end of the heater 1, and is then coated with nickel (Ni) or iron (Fe), which has a large temperature coefficient of resistance. It is electrically connected to a resistor coil 7 used as a wire, and the other end of the resistor coil 7 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 constituent parts in the inner cavity are embedded.
The center shaft 8 has an insulator 10 interposed between it and the mounting fitting 4, and is secured by a round nut 11 to form an electrode.

Another conventional example of this type of self-controlling ceramic globe 2 is a prior application example (Japanese patent application No. 58-209992), and as shown in the figure, the resistor coil T connected to the heating wire (not shown) of the heater 1 (the wire used for the heating wire and the resistor coil is the same as in the conventional example). ) is formed as an assembly 14 that is embedded in the metal tube 12 filled with a heat-resistant insulating material 13, including the connection part with the center shaft 8 and the lead electrode shaft 6, and this assembly 14 is inserted into the inner cavity of the mounting bracket 4. There is a prior art in which a portion 4a of the body is caulked from the outer periphery and partially housed in the inner wall in close contact.

In all conventional self-regulating ceramic globe lugs having such a structure, the temperature of the resistor coil 7 changes due to the difference in the temperature coefficient of resistance between the wire of the resistor coil 7 and the wire of the heating wire of the heater 1 when the temperature is increased by energization. increases faster than the heating wire of the heater 1, and the accompanying increase in resistance reduces the heating current of the heater 1, thereby preventing it from overheating.

In particular, in the prior art example (Japanese Patent Application No. 58-209992) mentioned above, a resistor coil 1 connected in series to a heater 1 has a central shaft 8 and a lead electrode shaft 6 inside a metal tube 12 filled with a heat-resistant insulating material 13. Since it has a sheath type resistor structure that is buried and integrated including the connection part with the TL, it is extremely strong, or it has a structure that is caulked from the outer periphery with part 4a of the mounting bracket and held in its inner cavity. Because it is,
Variations in the gap between the inner wall of the mounting bracket and the outer periphery of the metal tube during manufacture are absorbed, the heat dissipation state of the resistor becomes constant during energization and temperature rise, and a stable energization control function is obtained.

[Problem that the invention seeks to solve]

However, all of the conventional self-regulating ceramic glow plugs mentioned above use a W alloy in which Re is added to W as the heating wire of the heater, and the wire of the resistor coil connected in series to this alloy is Because Ml or Fe, which has an extremely large temperature coefficient of resistance, is used, the resistance value of the resistor coil increases rapidly as the heater heats up during one energization, and the current decreases too much, causing the heater to not meet the specified temperature. It was subsequently discovered that the time required to reach the temperature was delayed and the rapid heating performance tended to be inhibited.

[Means and effects for solving the problems] The present invention has been made to solve the above-mentioned problems, and the resistor connected in series to the heating wire of the heater is replaced with the conventionally used Ni. Or, in the first resistor coil whose wire is IPe,
By combining and connecting in series a second resistor coil made of a wire having a smaller temperature coefficient of resistance than the wire of the coil, sudden resistance of the resistor due to heat generation of the heater when energized and heated is reduced. This is a self-control glow plug that suppresses the current increase, alleviates excessive current reduction, and improves rapid temperature rise performance.

〔Example〕

FIG. 1 is a longitudinal sectional view showing an embodiment of the self-controlled ceramic glow plug of the present invention, in which the same parts as in FIG. 3 are designated by the same reference numerals.

The self-regulating ceramic glow plug of this embodiment uses a W alloy in which Re is added to W, which has a small temperature coefficient of resistance, for the wire of the heating wire (not shown) of the heater 1 serving as the heating element, as in the conventional example. The resistor 11 connected in series to the lead electrode shaft 6 is made of Ni having a large temperature coefficient of resistance.
Or a first resistor coil 17-1 using a wire of Fe or Ni-Fe alloy (30Fe-Ni alloy), and a Fe-cr having a smaller temperature coefficient of resistance than the wire used for the coil.
A second resistor coil 171 made of a wire material made of alloy or Ni-Cr alloy is combined and connected in series.
It has the same structure as the conventional example shown and explained in the drawings.

FIG. 2 is a longitudinal sectional view of another embodiment of the self-regulating ceramic glow plug of the present invention, in which the same parts as in FIG. 4 are designated by the same reference numerals. The resistor 11 consisting of the resistor coil 17-1 and the second resistor coil 17-2 having the same structure as shown in FIG. It is formed as an integrated assembly 14 embedded in a heat-resistant insulating material 13 filled in a metal tube 12, including the connection part with the center shaft 8 and the y-de electrode shaft 6. It has the same structure as the conventional example shown in FIG.

Figure 5 shows a conventional glove 2 having the structure shown in Figure 3.
This is a graph showing the results of a comparative test of the current heating characteristics of Glove 2 and Glove 2 according to the present invention having the structure shown in Figure 1. This figure shows the relationship between the time when the plug is energized and the temperature is raised and the temperature of the heating element.

As can be seen in the graph, compared to conventional glow plugs, the glow plug of the present invention suppresses the rapid increase in resistance of the resistor when the temperature rises after the start of energization, and as a result, the energizing current is extremely reduced. It will be understood that the time required for the heater to reach 900° C. is shortened and the temperature increase performance is clearly improved.

〔Effect of the invention〕

As explained above, the self-regulating ceramic glow plug of the present invention uses not only a resistor coil made of a wire material with a large temperature coefficient of resistance, which has been conventionally used, as a resistor connected in series with the heating wire of a heater.

By combining this with a second resistor coil made of a wire material with a small resistance temperature coefficient and connecting it in series, the resistance of the resistor increases rapidly when the current is applied and the temperature rises, and the accompanying current current flows. This has the effect of suppressing the reduction in temperature and improves the rapid heating performance of the heater, thereby providing a self-regulating ceramic glow plug with excellent heating characteristics that solves the conventional problems.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the self-regulating ceramic glow plug of the present invention, and FIG. 2 is a longitudinal cross-sectional view showing another embodiment of the self-regulating ceramic glow plug of the present invention.
s and 4 are vertical cross-sectional views showing a conventional example of a self-controlling ceramic globe 2g. The graph shows the comparison test of 4 degrees and 4 degrees. 1: upper 2 mix heaters, 2: heating wires, 4: mounting brackets,
6: Lead electrode axis, 7.17: Resistor. 7-,. 7-Snow, 17-s-17-t' Resistor coil, 9 Niglass powder, 12: Metal tube, 13
: Heat-resistant insulation material, 14: Assembly. Agent Patent Attorney Mamoru Takeuchi Figure 1 Figure 3 WJ

Claims (3)

[Claims] (1) As the heating element provided at the tip of the mounting bracket, a ceramic heater with a heating wire embedded in a ceramic sintered body is used, and a resistor is connected in series to the heating element within the inner cavity of the mounting bracket. In the self-regulating ceramic glow plug, the resistor in the mounting fitting lumen includes a first resistor coil made of a material with a large positive temperature coefficient of resistance, and a second resistor made of a material with a smaller temperature coefficient of resistance. A self-regulating ceramic glow plug characterized by being formed by connecting a body coil in series. (2) The material of the first coil is Ni, Fe, or Ni-Fe alloy, and the material of the second coil is N.
The self-regulating ceramic glow plug according to claim 1, which is made of an i-Cr alloy or a Fe-Cr alloy. (3) The first and second resistor coils in the inner cavity of the mounting bracket are arranged in a metal tube with both ends open, and one end thereof is connected to a center shaft that protrudes from the rear end side of the metal tube and serves as a terminal electrode. At the same time, the other end is connected to a lead electrode shaft connected to a heating element, and the connecting part in the metal tube is embedded in a heat-resistant insulating material filled in the lumen of the metal tube, forming an integrated assembly. Claim 1, wherein the metal tube of the assembly is caulked from the outer periphery with a part of the body of the mounting bracket and housed in the inner cavity of the mounting bracket with the outer periphery partially in close contact. Ceramic glow plug.