DD290705A5 - CERAMIC GAS CHANNEL EQUIPMENT FOR CYLINDER COILS OF COMBUSTION ENGINES - Google Patents

Abstract

The invention relates to a ceramic Gasfuehrungskanalauskleidung for cylinder heads of internal combustion engines, which causes a favorable heat insulation of the flue gas flowing through the exhaust pipe. The invention is intended to avoid or reduce thermal shock problems during encasing and stress loads due to the different thermal expansion coefficients of the encasing material and of the lining. Erfindungsgemaesz this is done by the liner is divided transversely into individual, at least two segments, of which at least one segment is encapsulated and the other segments are inserted nachtraeglich. Fig. 2 {Gasfuehrungskanalauskleidung, ceramic; Zylinderkoepfe; Combustion engine; Waermeisolierung; Exhaust pipe; exhaust gases; Stress loads; coefficient of thermal expansion; Umguszmaterial; segments}

Description

For this 2 pages drawings

Field of application of the invention

The invention relates to a ceramic gas guide channel lining for cylinder heads of internal combustion engines. Such linings in the form of a hollow body are also referred to as a portliner. It is customary to use these linings as a casting core during casting of the cylinder head.

Characteristic of the known state of the art

Ceramic gas duct liners in the form of a one-piece hollow body are already known (US-PS 3568723 and 3799772). By virtue of its construction with an inner, ceramic core and an outer metal casing cast directly around the core, a favorable thermal insulation of the exhaust gases flowing through the exhaust gas line is achieved. In this way, the Temperaturnivoau remains in the exhaust pipe maintained at such a level that a reuse of the exhaust energy is possible.

Also known are longitudinally split liners (DD-PS 266385). In this case, the structure should compensate for stresses that occur due to different thermal expansion coefficients of the Umgußmaterials and the lining, by an elastic intermediate layer at the abutting surfaces.

It is difficult to find a suitable material for the ceramic core that meets the requirements. This material must withstand, in addition to chemical resistance to the exhaust gas components, the pressure of the solidifying casting material and, on the other hand, have good thermal resistance and thermal shock resistance to withstand the prevailing high steady and peak temperatures and the temperature differences encountered during casting. For this a number of ceramic materials were considered. So it is, for example, according to DE-PS 2163717 and 2354254 known mixtures of silica and alumina or clay chamotte, Muiitt, zirconium u. a. and as a binder alumina or aluminum phosphate and according to DE-AS 2750290 and EP-PS 119499 aluminum titanate use.

The disadvantage, however, turns out that certain materials, such as SiM * ¹ "carbide and aluminum oxide, due to their thermal conductivity have too low insulation, ν / uring other such. As aluminum titanate, have too low strength. Even ceramic materials with silicate fiber content (DE-OS 2549256) satisfy in this respect is not perfect.

Portliner made of welded sheet steel halves are also known (DE-PS 2555166 and DE-OS 2323792), but they have too low a thermal insulation capacity.

Object of the invention

OBJECT OF THE INVENTION It is the object of the invention to develop a technically simple gas duct lining which solves the technological problems encountered in the casting of ceramic bodies due to the different coefficients of thermal expansion of the covering material and of the lining.

Explanation of the essence of the invention

The invention has for its object to provide a gas guide channel lining, with which it is difficult, regardless of the shape of the channel or the lining to allow the Einsau ceramic materials as lining material. Furthermore, an increase in the exhaust gas energy is to be achieved by reducing the heat loss in the cylinder head.

According to the invention the object is achieved by the liner is divided transversely into individual segments, of which a segment of the lining extends from the valve seat to the end of Auslaßkanalkrümmung and has substantially the same curvature. At least one other segment of the liner extends from the exhaust passage curvature to the exhaust passage opening. The non-molded segment or segments of the liner are inserted from the manifold side into the gas guide channel of the cylinder head with an inorganic high temperature resistant adhesive and are locked by means of the flanged manifold. The segments are made of ceramic materials with the same or dissimilar properties but have similar thermal expansion coefficients. The contact surfaces of the lining segments are provided with opposite chamfers, so that they fit positively to each other. The lining according to the invention ensures that the moving medium is surrounded by an insulating layer, which in turn is positively surrounded by a Umgußmaterial or at least fixed by the Umgußmaterial in its position. Due to the decreasing heat transfer between the working gases and the cylinder head, the prerequisite for thermal insulation is created. The encumbrances are compensated by the first part of the lining by the spherical formation or the circular cross-section of the channel. Since the loads no longer reach critical temperature ranges during engine operation, as in the case of an encapsulation, a non-circular cross-section can also be used for the subsequently inserted part of the lining. This saves space on the cylinder head.

embodiment

The solution according to the invention is to be explained in more detail in an exemplary embodiment with associated schematic drawings.

As FIG. 1 shows, the portliner consists of two ATI segments 1 and 2. Segment 1 extends from the valve seat to the end of the exhaust-gas channel curvature and is encircled by sand cores analogously to the encapsulation. Segment 2 is inserted after cooling of the cylinder head in the gas guide channel of the manifold side by means of high temperature resistant adhesive 3, pushed up to segment 1, as shown in Fig. 2. For this purpose, the contact surfaces of the segments are provided with opposite chamfers 4, so that they fit positively to each other.

By attaching the exhaust manifold takes place an additional fixation of the lining in the gas guide channel.

Claims (6)

1. Ceramic gas guide channel lining for cylinder heads of internal combustion engines in the form of a hollow body, from the einsetehar during casting of the cylinder head segments as parts of the casting core, characterized in that the lining is divided transversely into individual segments, of which a segment (1} of the lining vonrfVentilsitz extends to the end of Auslaßkanalkrümmung, having substantially the same curvature and extends at least one further segment (2) of the lining of the Auslaßkanalkrümmung to Auslaßkanalöffnung. 2. Ceramic gas guide channel lining according to claim 1, characterized in that the non-molded segment or segments of the liner are inserted from the manifold side into the gas guide channel of the cylinder head. 3. Ceramic gas guide channel lining according to claim 1 and 2, characterized in that the segments to be inserted are inserted with an inorganic high temperature resistant adhesive (3) in the gas guide channel. 4. Ceramic gas guide channel lining according to claim 1 to 3, characterized in that the inserted segments are locked by means of a flanged manifold. 5. Ceramic gas duct lining according to Anspruoi. 1 to 4, characterized in that the segments of ceramic materials with the same or different properties and have similar thermal expansion coefficients. 6. Ceramic gas guide channel lining according to Ar.apruch 1 to 5, characterized in that the contact surfaces of the lining segments with opposite chamfers (4) are provided.