JPH0195221A - Self-control type glow plug - Google Patents

Abstract

PURPOSE:To obtain optimum preheating and after glow times by forming a large diameter part at the upper end of a holding tube, caulking and fixing the large-diameter part to the inner wall of a housing, forming a predetermined gap between the outer periphery of a general part and the inner periphery of the housing, and burying a resistor within a holding tube filled with an insulator. CONSTITUTION:An insulator 5 is filled in a holding tube 1, and a resistor 4 is buried within the lower half part of the tube 1. A metal ring body 13 is brazed and fixed to the outer circumference of the upper end 12 of the holding tube 1 to form a large diameter part. The upper edge 212 of an upper end opening 21 of the housing 2 is caulked so that the upper edge 212 covers the outer periphery of the ring body 13, and the holding tube 1 is fixedly located within the housing 2. That is, the inner periphery of the opening part 21 beforehand has an annular shoulder 211. Under this condition, an interval C having a predetermined size obtained by subtracting a predetermined caulking depth from the difference between the outer diameter of the general part and the outer diameter of the ring body, is formed between the outer periphery of the general part 11 of the holding tube other than the upper end 12 and the inner periphery of the housing 2. In the case of varying the size of the gap, the inner diameter of the housing and the outer diameter of the ring body in accordance therewith are varied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a glow plug, and more particularly to a self-control type glow plug incorporating a sheath-structured heat-controlling resistor.

[Prior art] Fig. 6 shows an example of the above glow plug (Utility Model No. 62-295).
48), the glow plug has a cylindrical housing 2, and is fixed to an engine cylinder head by a threaded portion 2a formed on the outer periphery of the central portion of the housing 2.

A heating element 3 is fitted and fixed into the opening at the tip of the housing 2, and is positioned within the combustion chamber of the engine. A smaller diameter holding tube 1 filled with a heat-resistant insulating material 5 such as magnesia powder is provided inside the housing 2, and a coiled resistor 4 made of nickel or the like having a large temperature coefficient of resistance is embedded within the insulating material 5. It is.

The resistor 4 has one end connected in series to the heating element 3 via a lead electrode shaft 6, and the other end a central shaft 8 that extends into the holding tube 1 through a lid member 7 that seals the proximal opening of the housing 2. It is connected to the.

The holding tube 1 is fixed to the outer periphery of the heating element buried portion slightly above the inner wall of the housing 2 whose diameter is reduced by caulking, and the outer periphery of the buried portion is in a predetermined position with the inner periphery of the housing 2. A gap C is formed.

When electricity is applied through the center shaft 8, the heating element 3 rapidly generates heat, and at the same time, the temperature of the resistor 4 gradually rises due to self-heating. Since the resistor 4 has a large resistance temperature coefficient, its resistance value increases as the temperature rises, limiting the current to the heating element 3, and after that, the state shifts to afterglow in this self-controlled state.

[Problems to be Solved by the Invention] By the way, the size of the gap C formed between the outer periphery of the holding tube 1 and the inner periphery of the housing 2 greatly influences the amount of heat dissipated from the holding tube 1. In order to optimally set the temperature reached and the temperature increase time, it is desirable that the size of the gap C can be varied within a wide range depending on the installation conditions of the glow plug.

Here, in the above-mentioned conventional structure, as described in the above-mentioned publication, the upper limit of the size of the gap was about 0.6 mm in order to prevent deformation cracking of the housing during caulking.

SUMMARY OF THE INVENTION The present invention aims to solve these problems and to provide a self-control glow plug in which the gap between the outer periphery of the holding tube and the inner periphery of the housing can be freely set within a wide range.

[Means for solving pressure points] The structure of the present invention is explained with reference to FIG. 1. The glow plug has the following features:
A cylindrical housing that holds a heating element in its lower end opening, and a large diameter part that is disposed above the heating element in the housing and has a larger diameter than the second part at the upper end, and this part is used for the housing. a holding tube which is caulked and fixed to the inner wall of the housing at a certain depth to form a predetermined gap between the outer periphery of the claw part and the inner periphery of the housing; A resistor with a large resistance temperature coefficient is connected in series with the resistor.

[Function] When the large diameter part at the upper end of the holding tube is caulked and fixed to the inner wall of the housing, the caulking depth is constant, so there is a gap between the outer periphery of the general part of the holding tube and the inner periphery of the housing. A gap of a size corresponding to the difference in diameter of the general portion is formed.

[Effect] According to the present invention, by changing the outer diameter of the large diameter portion of the holding tube, the size of the gap formed between the outer circumference of the general portion of the holding tube and the inner circumference of the housing can be freely set within a wide range. This makes it possible to obtain optimal preheating and afterglow times depending on the installation conditions of the glow plug.

In the present invention, since the amount of deformation of the housing during caulking can be made constant regardless of the size of the gap formed, there is no limitation on the maximum value of the gap due to cracks or the like during caulking as in the conventional case.

[Example] In FIG. 1, a heating element 3 is fixed to a lower end opening of a cylindrical housing 2 having a mounting screw portion 2a formed on its outer periphery. An example of the heating element 3 is shown in FIG. 2, which has a rod-shaped base 31 made of insulating ceramics such as silicon nitride.
An alloy heating wire 32, which is made of tungsten with rhenium added and has a small resistance temperature coefficient, is buried in the lower end of the wire 1, and a tungsten current conduction lead wire 33 and a grounding lead wire 34 extend toward the upper end.

A cylindrical holding fitting 34 which also serves as a ground conductor is fitted on the outer periphery of the heating element 3 having the above structure, and the holding fitting 34 is welded and fixed to the housing opening.

Inside the housing 2, a stainless steel holding tube 1 is disposed above the heating element 3. The holding tube 1 is filled with a heat-resistant insulating material 5 such as magnesia powder, and the lower half of the holding tube 1 is filled with a heat-resistant insulating material 5 such as magnesia powder. A coiled resistor 4 is embedded. The resistor 4 is made of nickel, iron, or an alloy thereof so that the temperature coefficient of resistance is larger than that of the heating wire 32.

The lower end of the resistor 4 is brought into contact with and electrically connected to the lead electrode shaft 6 embedded in the lower end opening of the holding tube 1,
The lead electrode shaft 6 is the lead for energizing the heating element 3 by means of a coil spring 61! ! It is connected to 33.

A current-carrying center shaft 8 is inserted into the upper half of the holding tube 1 from above, and the upper end of the resistor 4 is in contact with the insertion end of the center shaft 8 for conduction. The center shaft 8 extends upwardly through a lid member 7 covering the upper end opening of the housing 2, and a nut 71 for fixing a current-carrying wire terminal is screwed into the screw portion at the upper end.

A metal ring body 13 of a predetermined diameter is brazed or fixed to the outer periphery of the upper end 12 of the holding tube 1 to form a large diameter portion. The holding tube 1 is fixedly positioned within the housing 2 by deforming the holding tube 212 by caulking. That is, the inner periphery of the opening 21 is preliminarily provided with an annular shoulder 211 of a certain depth and has a slightly larger diameter along the outer periphery of the ring body, and after inserting the holding tube, the upper edge 212 is caulked. Transform.

In this state, holding tube other than the upper end 12 - i section 1
A gap C having a predetermined size is formed between the outer circumference of the housing 1 and the inner circumference of the housing 2, which is the difference between the general part outer diameter and the ring body outer diameter minus a fixed caulking depth.

In addition, in the figure, 14 is a welded glass for maintaining airtightness.

When changing the size of the gap in the fi-shaped glow plug mentioned above, by changing the inner diameter of the housing and the outer diameter of the ring body accordingly, the amount of deformation of the housing during caulking can be kept constant and the size of the gap can be changed. You can freely set the size.

Therefore, the maximum value of the gap that can be formed is not limited, and the optimum gap can be set within a wide range depending on the installation conditions of the glow plug.

The structure of the heating element 3 is not limited to the above embodiment, and instead of the heating wire 32, as shown in FIG.
A composite of Si 3 ) and silicon nitride formed into a U-shape and integrally sintered can be used.

FIG. 4 shows another embodiment of the present invention. In the above embodiment, a ring body 13 was provided at the upper end 12 of the holding tube 1 to form a large diameter part, but in this embodiment, the upper end 12 was directly swaged. Expand the diameter. This structure also provides the same effects as the above embodiment, and does not require other parts such as a metal ring.

FIG. 5 shows still another embodiment of the present invention. In this embodiment, the upper end 12 of the holding tube 1 is made into a thick-walled, large-diameter portion by cutting. Such a structure also provides the same effects as the other embodiments described above.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, FIG. 1 is an overall sectional view of a glow plug, FIG. 2 is a sectional view of a heating element, and FIG. 3 is another example of a heating element. 4 is a sectional view of a holding tube showing another embodiment of the present invention; FIG. 5 is a sectional view of a holding tube showing still another embodiment of the present invention;
FIG. 6 is a sectional view of a conventional glow plug. 1... Holding tube 11... - Claw part 12... Upper end 13... Ring body (large diameter part) 2... Housing 3... Heating element 4... Resistor element 5... Insulating material! J1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (3)

[Claims] (1) A cylindrical housing holding a heating element in its lower end opening;
disposed above the heating element in the housing,
a holding tube having a large-diameter portion larger in diameter than the general portion at the upper end and caulked and fixed to the inner wall of the housing at this portion to form a predetermined gap between the outer periphery of the general portion and the inner periphery of the housing; A self-regulating glow plug comprising: a resistor having a large temperature coefficient of resistance embedded in the holding tube filled with an insulating material and connected in series to the heating element. (2) The self-control glow plug according to claim 1, wherein the large diameter portion of the holding tube has the same diameter as the general portion, and a ring body is fitted to the outer periphery of the upper end. (3) The self-control type glow plug according to claim 1, wherein the large diameter portion of the holding tube is formed by deforming the upper end to expand the diameter.