DE102004030990A1 - Glow plug with a protective layer coated glow plug - Google Patents

Abstract

The invention relates to a glow plug (1; 101) for a fuel-fired engine, consisting essentially of a plug housing (8; 108) and a connecting bolt arranged in the plug housing (8; 108) and a ceramic glow plug (3; 103) with a side projecting into the combustion chamber (2, 102). DOLLAR A According to the invention it is provided that the glow plug (3, 103) with a porous layer (9, 109) is provided at least on the part (3, 103) projecting into the combustion chamber of the fuel engine.

Description

The The invention relates to a glow plug for a fuel engine, consisting essentially of a plug housing and arranged in the plug housing Connecting bolt and a contacted with the connecting bolt ceramic glow pin with a projecting into the combustion chamber side.

diesel engines need for a good start and warm-up behavior at low temperatures a heat source, which preheat either the gas mixture, the intake air or the combustion chamber. For this purpose is usually proposed the use of glow plugs. These consist of a candle housing and a protruding from the candle housing Glow plug made of ceramic material, which in its assembled state in the Burner chamber of a fuel engine protrudes. Usually In direct injection engines, the glow plugs of the glow plugs protrude about 4 mm into the combustion chamber of the fuel engine and heat the Diesel-air mixture. Achieved annealing temperature and afterglow time of glow plug have a considerable influence on the exhaust gas behavior and the fuel consumption of the fuel engine. glow plugs the newer generation are designed in such a way that by current flow the tip of the glow plug to glow is brought. The glow plug itself is round in cross-section and has a diameter for certain types from approx. 3.5 - 6 mm up.

The known glow plugs are made of metal and usually have no protective coating on its outer wall.

The The object of the invention is to improve the functionality of the glow plug.

Solution of the task

Of the Core idea of the invention, which leads to the solution of the problem consists in it, with the glow plug a porous one Layer at least on the in the combustion chamber of the fuel engine To provide projecting part.

Advantages of the invention

by virtue of the applied porous Layer has this better compared to the previous layer Thermal shock resistance on. As a result, the thickness of the porous layer can be significantly increased become. Moreover, in comparison to "massive" layers, no exact adaptation to the Expansion coefficients are made.

The greater layer thickness, the on the glow pin can be applied leads to the advantage that a significantly better chemical protection influences achieved in the combustion chamber. Due to the embedded in the porous layer gases achieved a thermal insulation, creating a low temperature gradient is achieved and this in turn means that low thermal Voltages inside the glow plug occur.

One Another significant advantage in the application of a porous layer on the glow plug is that the flow velocity of the fuel / air mixture is reduced. Due to the longer residence time will the inflammation of the mixture on the hot Glow pin surface relieved, so that the engine has a better start and run behavior.

One Another significant advantage of the invention is that in the layer catalytically active particles are embeddable. in this connection For example, these may be PT metals or rare earth oxides act. By embedding these particles is also the ignition further improved, especially when switched off glow plug. Thus, with the same ignition performance the electrical power consumption of a glow plug candle ge be lowered. This in turn means that due to the lower temperatures and thus the lower load the life of the glow plug elevated becomes.

The Applying the porous Layer on the glow plug a glow plug can be done in different ways:

powder dispersion

For example can be in the form of thick-film pastes or slips, dipping, spraying and Print the application done. In addition, it is conceivable that the porous layer roll up.

sintering

The sintering can be done by both cofiring and postfiring. For a cofiring process, the protective layer is applied to the unsintered glow plug and sintered together with it. The composition of the applied layer must be such that it has the same dimensional changes during the sintering process as the glow plug itself. This can be achieved, for example, by using a layer largely of the insulating layer of the ceramic glow pin selects identical material. The porosity is produced by admixing pore formers, for example acrylates, which completely burn out even in an inert gas atmosphere.

at a postfiring process requires sintering with such small dimensional changes as possible otherwise, would flake off the layer. To ensure this, in addition to reaction sintering processes also sol / gel technologies can be used.

Based on the reaction sintering of Al alloys in combination with various oxides, suitable oxide layers can be made, such as Al ₂ O ₃ , spinel, cordierite, mullite, or composites thereof.

• 1. Ein reaktionsgebundener Mullit, der durch eine Pulvermischung aus 30-gew% Al₇₅Si₂₅-Legierung und 70-gew% Al₆Si₂O₁₃ in Ethanol gemischt, herstellbar ist. Durch einen Tauchprozess wird die Schicht auf den Glühstift aufgebracht, Die Wärmebehandlung erfolgt in Luft bei einer Temperatur von ca. 1200 °C bis zur vollständigen Umsetzung in Mullit.
• 2. Ein reaktionsgebundenes Aluminiumnitrid, das aus einer Pulvermischung aus Al und AlN herstellbar ist, wobei der Reaktionssinterprozess in Stickstoff bei Temperaturen zwischen 1000 und 1200°C erfolgt.
• 3. Ein reaktionsgebundener Spinell/Mullit, der aus einer Pulvermischung von 34-Vol% AlMg₅ Legierung, 16-Vol% MgO und 50 Volk Al₆Si₂O₁₃ gewonnen wird. Die Reaktionssinterung erfolgt in der Luft bei Temperaturen bis 1000 °C.
• 4. Eine Sol-/Gel-Schicht, die aus NH4+ stabilisiertem Siliziumsol in Kombination mit Aluminiumsilikaten eingesetzt werden kann. Die Wärmebehandlung erfolgt bei 1000 °C.
• 5. Katalytische Schicht, die durch die Schaffung einer der unter den Punkten 1-3 genannten Schichten zusammen mit einer Beimengung von katalytisch aktiven Partikeln, wie beispielsweise PT-Metalle oder Seltenerdoxiden erstellbar ist. Durch die relativ niedrigen Herstellungstemperaturen und aufgrund der Zusammensetzung der Schichten muss nicht mit einer Vergiftung des Katalysators gerechnet werden. Aufgrund besonderer mechanischer Eigenschaften der porösen Schicht ist trotz der unterschiedlichen Ausdehungskoeffizienten von Schicht und zum Beispiel Platin eine dauerhafte Einbettung der Partikel in die Schicht möglich. Alternativ kann die poröse Schicht auch mit einer zum Beispiel PT-haltigen Dispersion infiltriert werden. Auch eine Imprägnierung mit einer Katalysator-Salzlösung ist denkbar.

The following substances may be suitable to find application for the invention:

• 1. A reaction-bound mullite, which can be produced by mixing a powder mixture of 30% by weight of Al ₇₅ Si ₂₅ alloy and 70% by weight of Al ₆ Si ₂ O ₁₃ in ethanol. The coating is applied to the glow plug by means of a dipping process. The heat treatment is carried out in air at a temperature of about 1200 ° C. until complete conversion into mullite.
• 2. A reaction bonded aluminum nitride, which can be prepared from a powder mixture of Al and AlN, wherein the reaction sintering process is carried out in nitrogen at temperatures between 1000 and 1200 ° C.
• 3. A reaction bonded spinel / mullite obtained from a powder blend of 34% by volume AlMg ₅ alloy, 16% by volume MgO and 50% by weight Al ₆ Si ₂ O ₁₃ . The reaction sintering takes place in air at temperatures up to 1000 ° C.
• 4. A sol / gel layer, which can be used from NH4 + stabilized silicon sol in combination with aluminum silicates. The heat treatment takes place at 1000 ° C.
• 5. Catalytic layer, which can be produced by creating one of the layers mentioned under points 1-3 together with an admixture of catalytically active particles, such as, for example, PT metals or rare earth oxides. Due to the relatively low production temperatures and the composition of the layers, no poisoning of the catalyst is to be expected. Due to the special mechanical properties of the porous layer, permanent embedding of the particles in the layer is possible despite the different coefficients of expansion of the layer and, for example, platinum. Alternatively, the porous layer can also be infiltrated with a dispersion containing, for example, PT. An impregnation with a catalyst salt solution is conceivable.

Further advantageous embodiments also go from the following description and the claims out.

drawings

It demonstrate:

1 a schematic representation of a portion of a first embodiment of a glow plug according to the invention in section;

2 a schematic representation of a portion of a second embodiment of a glow plug according to the invention in section.

In 1 is a first embodiment of an embodiment of a glow plug according to the invention 1 represented, for simplicity of illustration, only the essential part of the invention, namely the projecting into the combustion chamber not shown in the figure part 2 the glow plug 1 , is shown.

The glow plug 1 owns a glow plug 3 made of a horseshoe-shaped ceramic body 4 consists of electrically conductive material, wherein on the side facing the combustion chamber 5 a rejuvenation 6 is formed so that when current flow this rejuvenation 6 begins to glow. The gap formed by the shape 7 is filled with insulating ceramic material.

The glow plug 3 is in a housing 8th arranged. This is at the top 2 with a porous layer according to the invention 9 made of ceramic foam.

2 shows a second embodiment of an inventive embodiment of a glow plug 101 holding a glow plug 103 Includes, made of a horseshoe-shaped ceramic body 104 consists of electrically conductive material, wherein on the side facing the combustion chamber 105 a rejuvenation 106 is formed so that when current flow this rejuvenation 106 begins to glow. The gap formed by the shape 107 is filled with insulating ceramic material

Also in 2 shown glow plug 101 points to the projecting into the combustion chamber part 102 a coating of the housing 108 with a porous layer 109 made of ceramic foam. This ceramic foam from which the layer 109 consists, as opposed to 1 - finely divided, catalytically active particles 110 ,

Claims (8)

Glow plug for a fuel-power engine, consisting essentially of a plug housing and a arranged in the plug housing connecting bolt and a contactable with the connecting pin ceramic glow plug with a projecting into the combustion chamber side, characterized in that the glow plug ( 3 ; 103 ) with a porous layer ( 9 ; 109 ) is provided at least on the projecting into the combustion chamber of the fuel engine part. Glow plug according to claim 1, characterized in that the layer ( 109 ) additionally catalytically active particles ( 110 ) having. Glow plug according to claim 1 or 2, characterized in that the application of the layer ( 9 ; 109 ) is carried out by powder dispersion. Glow plug according to claim 1 or 2, characterized in that the application of the layer ( 9 ; 109 ) is done by sintering. Glow plug according to claim 1, characterized in that the layer ( 9 ; 109 ) is infiltrated with a PT-containing dispersion A fabric for producing a porous layer for a glow plug according to claim 1, characterized in that the substance is a reaction bonded mullite, which by a powder mixture of 30 wt% Al ₇₅ Si ₂₅ alloy and 70 wt% Al ₆ Si ₂ O ₁₃ mixed in ethanol, can be produced. Fabric for producing a porous layer for a glow plug according to claim 1, characterized in that the substance is a reaction-bound Aluminum nitride is, this from a powder mixture of Al and AlN can be produced. A fabric for producing a porous layer for a glow plug according to claim 1, characterized in that the substance is a reaction bonded spinel / mullite consisting of 34 vol% AlMg ₅ alloy, 16 vol% MgO and 50 vol% Al ₆ Si ₂ O _{13 can be} produced.