EP2201298B1 - Glow plug having coking-optimized design - Google Patents

Description

The invention relates to a glow plug for installation in the cylinder head of an internal combustion engine. A glow plug having the features specified in the preamble of claim 1 is known from EP 1 637 806 as well as from the DE 10 2006 008 350 A1 known.

Similar glow plugs are z. B. also from the DE 10346295 known. This has the disadvantage that during normal operation of the glow plugs in an internal combustion engine coking of the glow plugs between the heating element and cylinder head and takes place in the annular gap of the glow plug, thereby causing problems in disassembly of the cylinder head mounted glow plugs and Drucksensorglühkerzen, and in the heat conduction to or in the glow plug.

From the DE 195 06 711 C1 is a flame glow plug for installation in the intake manifold of an internal combustion engine known. In this flame glow plug, a glow plug is surrounded by a radial distance from a flame tube, which has passage openings in a lateral surface.

It is the object of the invention to avoid the above-mentioned disadvantages and to provide a glow plug which permits coking-free operation of the internal combustion engine or prevents coking of the glow plug in the cylinder head or in the annular gap of the glow plug.

This object is achieved by a glow plug according to claim 1. It is advantageous that is provided by the inventive design for a reliable gas exchange, which ensures a complete oxidation at the contact points cylinder head / glow plug or body / heater and thus prevents carbon deposits.

Through this design of the annular gap and the free space, the coking of the glow plugs in the cylinder head bore between the heating element and the cylinder head is permanently prevented. As a result, the heat history or the thermal behavior of the glow plug remains unchanged over its entire life. For moving heating elements, the mobility remains unchanged over their entire life.

A difficult disassembly or a resulting damage by a possible coking with excessive disassembly torque can be reliably prevented.

Advantageous embodiments and further developments of the invention are described in the subclaims.

In the following the invention is explained in more detail with reference to the drawings.

Figur 1:

Einbausituation der Glühkerze mit Volumen im Zylinderkopf gemäß dem Stand der Technik

Figur 2:

Einbausituation der Glühkerze mit variiertem Volumen

Figur 3:

Glühkerze mit variiertem Volumen sowie zweiteiligem Körper

Figur 4:

Glühkerze mit Volumen im Zylinderkopf

Figur 5:

Volumen und Ringspalt Beschreibung

Figur 6:

Einbausituation einer herkömmlichen Drucksensorglühkerze, die kein Ausführungsbeispiel der beanspruchten Erfindung ist,

Figur 7:

Variante mit 2teiligem Körper

Figur 8:

Drucksensor, der kein Ausführungsbeispiel der beanspruchten Erfindung ist.

Show it:

FIG. 1:

Installation situation of the glow plug with volume in the cylinder head according to the prior art

FIG. 2:

Installation situation of the glow plug with varied volume

FIG. 3:

Glow plug with varied volume and two-part body

FIG. 4:

Glow plug with volume in the cylinder head

FIG. 5:

Volume and annular gap Description

FIG. 6:

Installation situation of a conventional pressure sensor glow plug, which is not an embodiment of the claimed invention,

FIG. 7:

Variant with 2-part body

FIG. 8:

Pressure sensor which is not an embodiment of the claimed invention.

FIG. 2 shows a arranged in a cylinder head 5 glow plug having an arranged between the heating element 1 and body 2 of the glow plug annular gap 3 and an adjoining the annular gap 3 space 4, which communicates by means of annular gap 3 with the combustion chamber of the internal combustion engine in such a way that oxygen-containing Gas enters the room 4. Through this annular gap 3 and the space 4, there is the possibility of a volume flow from the combustion chamber of the internal combustion engine in the space 4, which ensures a reliable gas exchange and thus for a sufficient oxygen content in the area of contact surfaces between the cylinder head and glow plug. Thus, very high temperatures are achieved in the annular gap 3 and in the space 4 by means of oxidative processes. As a result of these high temperatures, the carbon present in this region is burned, which thus can not be deposited in the region relevant for trouble-free operation of an internal combustion engine.

The inventive design of the annular gap 3, the volume flow and thus the gas exchange can be adjusted so that there is no carbon deposits.

It is important that sufficient oxygen content enters the annular gap 3 and thus supports or enables complete combustion.

This possibility of gas exchange also increases the temperature in the annular gap between the cylinder head 5 and the heating element 1.

For applications where a moving heating element 1 is used, as in FIG. 6 is shown, this annular gap 3 / space 4 combination for movably holding the heater 1 is provided.

With a defined annular gap 3 and the associated space 4, a corresponding volume can be achieved, which comprises in a particularly advantageous embodiment about 140 mm ³ , to allow sufficient combustion gas flow.

The defined annular gap 3 and the space 4 corresponding to it, which permits a volume as described above for gas exchange in the combustion process, is based on the principle of the so-called Helmholtz resonator.

It consists of a gas volume with a narrow opening, the annular gap 3 to the outside. The elasticity of the volume of air in the interior in combination with the inertial mass of the air in the opening creates a mechanical mass-spring system with a pronounced self-resonance.

• c : Schallgeschwindigkeit
• V : Volumen des Hohlkörpers
• r : Radius des Rohres
• l : Länge des Rohres

The value of the correction member for the interfaces of the tube is only about half as large as in the formula given below: $$f=\frac{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">c</figure-callout>}}{2\cdot \pi }\sqrt{\frac{\pi \cdot r^2}{V\cdot \left(l+\pi r/2\right)}}$$

• c: speed of sound
• V: volume of the hollow body
• r: radius of the pipe
• l: length of the tube

Correction element for the boundary surfaces of the pipe: + π r / 4

Since the transition between gas regions, which act as a mass, or as a spring, is fluent, the exact frequency of a Helmholtz resonator is difficult to calculate.

• l: Länge des Tunnels
• A: Fläche des Tunnels
• V: Innenvolumen der Box.

Approximation formula for calculating the resonance frequency: $$fb=\sqrt{\frac{3000A}{Vl+0.846V\sqrt{A}}}$$

• l: length of the tunnel
• A: surface of the tunnel
• V: inner volume of the box.

The volume of the Helmholtz hollow body settles, as in FIG. 5 can be seen, composed of the annular gap volume formed from b and c. The radius of the Helmholtz tube results, as also in FIG. 5 can be seen from the measure at the annular gap 3, wherein the inner length of the annular gap 3 corresponds to the length of the tube 1 of the Helmholtz formula.

Due to the gas exchange and the associated supply of the volume of the space 4 and the annular gap 3 with oxygen-containing fuel gas ensures that the temperatures in the annular gap 3 and in space 4 rise so far that the carbon is burned especially in the problematic contact zones.

The effect can be enhanced by a targeted and advantageous coating of the surfaces with a catalytically active material. For example, a platinum coating is particularly advantageous here.

When using patterns in special engine runs and Versottungsdauerläufe showed no traces of carbon or carbon deposits in the annular gap 3 or in space 4. Also in the bellows 7, as in FIG. 6 is shown, no soot or soot deposits could be determined by the inventively applied endurance runs.

In an advantageous embodiment it is provided that at least one element such as the bellows is coated with a catalyst-containing coating and / or consists of a catalyst-containing material pairing to lower the ignition temperature for combustion residues.

Suitable catalyst materials are, for example, platinum and / or palladium, cerium iron, Raney nickel, rhodium, hopkalite, vanadium pentoxide and samarium oxide. Any other element of the described glow plug may also be catalyst coated. In temperature measurements with the described inventive configurations, temperatures were measured at which the carbon burns without residue.

In FIG. 2 is arranged in a cylinder head 5 glow plug having an arranged between the heating element 1 and body 2 of the glow plug annular gap 3 and an adjoining the annular gap 3 space 4, which communicates by means of annular gap 3 with the combustion chamber of the internal combustion engine in such a way that oxygen-containing Gas enters the room 4, shown. Through this annular gap 3 and the space 4, there is the possibility of a volume flow from the combustion chamber of the internal combustion engine in the space 4, which ensures a reliable gas exchange and thus for a sufficient oxygen content in the area of contact surfaces between the cylinder head and glow plug. Thus, in the annular gap 3 and in the space 4 by means of complete combustion temperatures above 600 degrees or less, when a corresponding catalyst surface is present, Celsius is reached. As a result of these high temperatures, the carbon present in this region is burned, which thus can not be deposited in the region relevant for the trouble-free operation of an internal combustion engine.

FIG. 3 shows a arranged in a cylinder head 5 glow plug having an arranged between the heating element 1 and two-part body 2 of the glow plug annular gap 3 and an adjoining the annular gap 3 space 4, which communicates by means of annular gap 3 with the combustion chamber of the internal combustion engine in such a way that oxygen-containing gas enters the room 4. Through this annular gap 3 and the space 4, there is the possibility of a volume flow from the combustion chamber of the internal combustion engine in the space 4, which ensures a reliable gas exchange and thus for a sufficient oxygen content in the area of contact surfaces between the cylinder head and glow plug. Thus, very high temperatures are achieved in the annular gap 3 and in the space 4 by means of oxidative processes. As a result of these high temperatures, the carbon present in this region is also burned, which thus can not be deposited in the region relevant for trouble-free operation of an internal combustion engine.

In FIG. 4 is arranged in a cylinder head 5 glow plug, which is arranged between a heating element 1 and body 2 of the glow plug, with the additional space 8, whose length is the length of the tube in the Helmholtz formula, annular gap 3, the radius of the radius of the tube in the Helmholtz formula corresponds and has a subsequent to the annular gap 3 space 4, which communicates by means of annular gap 3 with the combustion chamber of the internal combustion engine in such a way that oxygen-containing gas enters the room 4, shown. Through this annular gap 3 and the space 4, in conjunction with space 8, there is the possibility of a volume flow from the combustion chamber of the internal combustion engine into the space 4, which ensures a reliable gas exchange and thus for a sufficient oxygen content in the contact surfaces between the cylinder head and glow plug. Thus, temperatures above 600 degrees Celsius are achieved in the annular gap 3 and 4 in the room by means of complete combustion. As a result of these high temperatures, the carbon present in this region is burned, which thus can not be deposited in the region relevant for trouble-free operation of an internal combustion engine.

In an alternative embodiment, the space 4 is defined by a two-part body 2, as shown in FIG FIG. 7 is shown produced by means of body upper part and lower body part, wherein the body parts are arranged around the heating element 1.

The body parts are connected by a weld 9.

In FIG. 6 a movable heating element 1 is shown with a bellows 7, which together with the body 2, a glow plug in a cylinder head 5 results. Between body 2 and heating element 2 there is an annular gap 3. The bellows 7 is arranged in a movable space 4. The space 4 and the annular gap 3 communicate with the arranged in the cylinder head 5 combustion chamber, which also not expressly. illustrated internal combustion engine. By the constant movement of the space 4 with oxygen-containing fuel gas a reliable oxidation of any carbon black particles is realized, a coking of the area on the heating element, in particular in the area of the annular gap 3 or in the space 4 is already in the approach prevented, which is beneficial because this keeps the bellows movable over the life of the glow plug.

In FIG. 8 a pressure sensor is shown which, as in FIG. 6 is arranged in a cylinder head 5 of an internal combustion engine, not shown. The pressure sensor comprises a two-part housing 2, 2a, which also, as in FIG. 6 shown, can be one-piece. In a space 4, a bellows 7 between the housing 2 and push rod 1a is arranged thereon, that the push rod 1a is movable together with the bellows 7 substantially along its longitudinal axis.

LIST OF REFERENCE NUMBERS

1.

heater

Second

body

2a.

Lower body part

Third

annular gap

4th

room

5th

cylinder head

6th

press fit

7th

bellow

8th.

room

9th

Weld

a.

Annular gap width

b.

Wide room 4

c.

Length of room 4

Claims (3)

1. Glow plug for mounting in a cylinder head of a combustion engine, comprising a heating rod (1) and a body (2), an annular gap (3) between the heating rod (1) and the body (2), wherein a chamber (4) arranged between the heating rod (1) and the body (2) is connected to the annular gap, characterized in that the combustion of carbon is increased in the chamber (4) by a surface coated with a catalytically effective material, wherein the catalytically effective material comprises Raney nickel, vanadium pentoxide, samarium oxide and hopcalite.
2. Glow plug according to any one of the preceding claims, characterized in that the annular gap (3) has a smaller width than the chamber (4) and that the chamber (4) is in communication with the combustion chamber of the combustion engine via the annular gap (3).
3. Glow plug according to any one of the preceding claims, characterized in that the annular gap (3) forms a Helmholtz-resonator with the chamber (4)

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