Tubular heating or measurement device

Details Tubular heating or measurement device Tubular heating or measurement device

1999-10-20

2001-11-13

Kwon, John (Department: 3747)

Internal-combustion engines

Igniters

Incandescent

C219S270000

Reexamination Certificate

active

06314930

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to tubular or sleeve-shaped heating and measurement devices, especially glow plugs, heating plugs for preheating water, measurement and sensor elements.
2. Description of Related Art
It is desirable to produce glow plugs, heating plugs for preheating water, measurement and sensor elements to be as slender as possible for reasons of minimization of material consumption, the amount of space required, and weight. However, thermal stresses occur during the operation of the more slender and narrowly-dimensioned glow plugs known in the prior art lead to adverse effects on the function of these prior art glow plugs. In conventional glow plugs produced with an annular gap, vapor bubble formation and coking occurs in the annular gap thereby resulting in faulty measurements from a correspondingly built sensor.
Due to the reduction in the diameter of these devices though slenderizing together with the simultaneous demand for longer dimensioned rod glow plugs, major technical difficulties arise because of the required tolerances and the necessity of economical production of these devices. In particular, major technical problems in the manufacturing of such devices include adherence to concentricity tolerances, difficulties in sealing between the glow plug body and the glow tube and space problems in the area of the control spiral in rod glow plugs.
As an example, the prior art glow plug
100
as shown in
FIG. 1
consists of the glow plug body
15
, into which glow plug tip tube
16
is installed. The glow tube
16
includes a heating element
4
and a control element
5
that are embedded in an electrically insulating material for conducting heat, such as MgO. In the terminal-side area in the body
15
, there is provided a connection lead
10
. This area of the glow plug
100
is sealed by a seal
2
relative to the glow plug tip tube
16
. The terminal-side area includes a cavity around the connection lead
10
which connects to an electric terminal
6
. This cavity is sealed by another seal
3
. This terminal-side of the glow plug body
15
has a thread
7
and a polyhedron
8
. An annular gap
14
is provided proximate to the glow plug tip tube
16
in the combustion space-side exit area between the glow plug tip tube
16
and the glow plug body
15
. As can be seen, the annular gap
14
is formed by increasing the diameter of the hole in the glow plug body
15
. As can be readily appreciated, such prior art glow plugs are relatively complicated with many parts which are difficult to manufacture and assemble.
SUMMARY OF THE INVENTION
One object of the present invention is to overcome the limitation of prior art devices by enabling slenderizing of glow plugs, heating plugs for preheating water, measurement and sensor elements without adversely affecting their operation.
Another object of the present invention is to reduce deviations from concentricity of these devices.
Still another object of the present invention is to reduce the number of parts used in such glow plugs, heating plugs for preheating water, measurement and sensor elements.
These and other objects and advantages of the subject invention are obtained by a glow plug including a glow plug body formed from a single piece tube, the single piece tube including a plug tip area with a glow element disposed therein, a control area with a control element disposed therein, and a connection area with an inside connection lead adapted to be connected to an electrical terminal where the plug tip area has a different diameter than the control area and/or the connection area of the single piece tube.
These and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the invention when viewed in conjunction with the accompanying drawings.


REFERENCES:
patent: 6062185 (2000-05-01), Chiu et al.
patent: 6064039 (2000-05-01), Kumada
patent: 6130410 (2000-10-01), Kita
patent: 6144015 (2000-11-01), Chiu et al.
patent: 6150634 (2000-11-01), Haussner et al.
patent: 0 887 592 (1998-12-01), None

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