Patent Application
20180119956
This application claims priority to DE 10 2016 120 578.8, filed Oct. 27, 2016, and also claims priority to DE 10 2016 121 346.2, filed Nov. 8, 2016, both of which are hereby incorporated herein by reference in their entireties.
This disclosure is based on a glow plug comprising a casing, a ceramic glow pin protruding out of the casing and having a tapered end section inside the casing, a protective tube which is made of metal and protrudes out of the casing and surrounds the glow pin, a center electrode, which is arranged in the casing and electrically connected to the glow pin, and an annular or sleeve-shaped contact element, through which the glow pin projects and to which the tapered end section of the glow pin is soldered. Such a glow plug is known from U.S. Publication No. 2011/0215080 A1.
Ceramic glow pins are susceptible to fractures and are therefore protected by a protective tube which is made of metal and projects out of the casing of the glow plug. The ceramic glow pin sits in the protective tube and projects with its combustion chamber side end, i.e., the glow tip, out of the protective tube. In the casing, the glow pin is electrically connected to a center electrode via a tapered end section. This tapered end section is surrounded by an annular or sleeve-shaped contact element which on its inside is shaped to fit the tapered end section, and soldered to the same. Generally, the glow pin is thus connected via the center electrode to potential and via the contact element to earth.
This disclosure shows how the fracture risk of the ceramic glow pin of such a glow plug can be further reduced or in the case of a fracture the risk that fragments fall into the combustion chamber of the engine can be reduced.
In a glow plug according to this disclosure, an end section of the protective tube is widened, i.e., its inner diameter and its outer diameter are increased, for example by plastic deformation. The contact element can therefore be arranged at least partially in the protective tube and the tapered end section of the ceramic glow pin that is particularly susceptible to breakage better protected. By widening the protective tube its wall thickness, compared with enlargement drilling, is substantially retained so that the mechanical stability and consequently the protective function is preserved even in the expanded end section.
An advantageous refinement of this disclosure provides that the glow plug is a pressure measuring glow plug, i.e., the glow pin is moveable in its longitudinal direction relative to the casing and the pressure acting on the glow pin is detected with a pressure sensor. With such a pressure measuring glow plug the protective tube presses on the pressure sensor via a transmission element. Since by way of widening the protective tube the mechanical stability, in particular the radial stability, of the protective tube is not negatively affected, interference signals during the transmission of the pressure acting on the glow pin are avoided.
Preferably, the expanded end section of the protective tube and the transmission element are inserted into one another, for example in that the protective tube is inserted into the transmission element. The end section of the protective tube and the transmission element can be welded to one another.
In order to obtain the advantages according to this disclosure, a small widening of the protective tube, namely an increase in diameter that is large enough to allow the contact element to project into the protective tube and even be entirely arranged inside the protective tube is sufficient. Preferably, the end section of the protective tube is widened by not more than twice the wall thickness of the protective tube, i.e., the inner diameter is not increased by more than double the wall thickness. For example, the expansion can amount to between half of the wall thickness and the wall thickness.
A further advantageous refinement of this disclosure provides that the widened end section of the protective tube has an inner diameter which is smaller than the outer diameter of a cylindrical main section of the protective tube. Between the expanded end section and the cylindrical main section a transition section can be present which is shorter than the end section. The transition section can for example be conically shaped.
The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:
The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.
As is shown in particular by
The conically tapered end section of the ceramic glow pin 1 is soldered to an annular or sleeve-shaped contact element 3. The ceramic glow pin 1 projects through the contact element 3. In the shown embodiment, the earth contact of the glow pin 1 is affected via the contact element 3 while the potential connection is affected via the central electrode 5.
The contact element 3 has a funnel-shaped for example conical inner surface 6 which matches the tapered shape of the end section of the ceramic glow pin 1. An outer surface of the contact element 3, which is preferentially shaped cylindrically, is connected to the widened end section 2.2. of the protective tube 2, for example, welded.
The embodiment shown in
The widened end section 2.2 practically has the same wall thickness as the remaining part of the protective tube 2 and can therefore favourably transmit pressure signals.
For sealing against combustion chamber gases, a section of the protective tube 2 in the casing is surrounded by a bellows 8, which with an end is fastened to the protective tube 2 and with its other end to the casing.
In comparison with the embodiment of the
The protective tube 2 in this case can be so long that the conically tapered end section of the ceramic glow pin 1 is entirely arranged in the protective tube 2. However it is also possible that the conically tapered end section of the glow pin 1 projects out of the expanded end section 2.2.
While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 120 578.8 | Oct 2016 | DE | national |
| 10 2016 121 346.2 | Nov 2016 | DE | national |
