Cylinders Of Internal-combustion Engines

Abstract

Cylinders of internal-combustion engines, reciprocating-piston or rotary-piston type, made of hypereutectoid aluminum-silicon alloy and formed with a labyrinth of grooves, in checkered or spiral pattern for example, in at least the area of the inner surface along which gastight seal members of the piston slide, said grooves being packed with a dystectic material, such as a ferric alloy, molybdenum, metallic carbide, or ceramic, or a mixture thereof, flush with the rest of the inner surface formed of an aluminum-silicon alloy.

Description

This invention relates to cylinders of internal-combustion engines.

For the purpose of the invention the term cylinders means the cases each surrounding each piston of an internal-combustion engine and defining a working chamber or chambers therebetween.

With the view to saving the weight of engines and improving their cooling efficiency to meet increased power output, it is sometimes attempted at using aluminum alloy cylinders without iron sleeves. Usually in such case a hyper-eutectoid aluminum-silicon alloy is used which contains crystallized silicon in the parent metal. The same material has been adopted for the fabrication of side housings of rotary-piston engines having trochoid-shaped cylinders.

The hyper-eutectoid aluminum-silicon alloy cylinders, which contain hard crystallized sillicon as stated above, are superior in abrasion resistance to the cylinders provided with iron sleeves or chrome-plated on the inner surface, provided that the former is adequately lubricated.

It is known, however, that at the time of cold-weather starting the cylinders of this material tend to suffer from objectionable scuffing on the inner surface due to their contact with sliding gastight seal members of the pistons. [Refer to "Aluminum engine will power minicar," Product Engineering, Apr. 27, 1970, published by Margan-Grampin Inc., New York, p.54, or "Light metal casting and its trends", JIDOSHA GIJUTSU (Automobile Technology, a Japanese periodical), 26, 4, 1972, p.395.]

The tendency is presumably sttributed to the following facts.

For starting in cold weather the engine must be fed with a rich fuel-air mixture by means of a choke valve. The fuel thus applied in an increased proportion washes away lubricating oil from the surface along which gastight seal members on each piston slide, thereby leading to very poor lubrication of the surface. (Refer to "The Vega 2300 Engine, "SAE Paper 710/47, p.4.)

As the gastight seal members slide on such surface, they no longer form any lubricant film and come into direct contact with the aluminum alloy surface. When this happens, the latter, which is a metal having a relatively low melting point, readily fuses and wears partly with the seal material. This wear due to fusion results in scuffing on the surface of the aluminum alloy along which the piston works.

Such an objectionable phenomenon seldom takes place with the materials as used in the fabrication of iron sleeves that have higher melting points that aluminum alloys.

Naturally the scuffing is precluded by the use of more dystectic materials, e.g., molybdenum, metallic carbides, and ceramics.

In view of this, we made numerous experiments on combinations of hyper-eutectoid aluminum-silicon alloy and various dystectic materials. The aluminum-silicon alloy is light in weight, easy to cool, and possesses excellent wear resistance under the operating conditions except for the cold-weather start as already pointed out. The experiments were aimed at taking advantage of these features of the alloy and also eliminating the possibility of aforementioned scuffing. As a result, it has now been found that the foregoing purposes can be fulfilled by forming grooves in a certain labyrinth pattern on at least the inner surface portion of the cylinder that is subjected to the sliding contact by gastight seal members of a piston and depositing a material having a higher melting point than the aluminum-silicon alloy in the grooves so that the surface of the dystectic material filling up the grooves can be flush with the rest of the inner surface, i.e., the exposed surface of the hyper-eutectoid aluminum-silicon alloy. The present invention is predicated upon this discovery.

The reason for which the scuffing of the inner surface of cylinders in cold-weather starting of an engine can be avoided by the construction above described is yet to be theoretically clarified. However, it appears most likely that, as the gastight seal members of the piston move in sliding contact with the inner surface of the cylinder, the particles produced by the abrasion of the dystectic material are dispersed and embedded in the aluminum alloy to make it resistant to scuffing.

The invention is illustrated, by way of example, by the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a part of a cylinder for a reciprocating-piston engine;

FIG. 2 is a detail of the portion of the cylinder encircled at A in FIG. 1;

FIG. 3 is a perspective view of a rotor housing of a rotary-piston engine having a trochoid-shaped cylinder; and

FIG. 4 is a perspective view of a side housing of the same rotary-piston engine.

Referring now to FIG. 1, there is shown a cylinder of a reciprocating-piston engine as comprising a cylinder body 1 having an inner surface 3 along which piston rings slide, and also having a labyrinth of a dystectic material provided on the inner surface of the cylinder in a checkered pattern.

The labyrinth of dystectic material is formed, for example, by knurling the inner surface of the cylinder, thereby forming grooves in a checkered pattern, and spraying a ferrous alloy, molybdenum, metallic carbide, or ceramic, in molten form, over the inner surface, and then removing the resulting deposit from the area of the inner surface other than the groove surface.

FIG. 2 is a micrographic representation of the portion encircled at A in FIG. 1. The structure consists of crystallized silicon 7, a hyper-eutectoid base 9 of silicon and aluminum, and a dystectic material 11 deposited on the grooves formed on the inner surface 3 of the cylinder.

FIGS. 3 and 4 illustrates another embodiment of the invention as applied to a rotary-piston engine having a trochoid-shaped cylinder, FIG. 3 showing a rotor housing and FIG. 4 a side housing.

In FIG. 3 the housing 15 is made of a hyper-eutectoid aluminum-silicon alloy and has a trochoid-shaped inner surface 17 along which apex seals of the rotary piston slide. The inner surface is coated with a dystectic material 19 as is the case with the embodiment of FIGS. 1 and 2.

In FIG. 4 is shown a side housing 21 of a hyper-eutectoid aluminum-silicon alloy, having an annular surface 23 along which seal members, such as side, corner, and apex seals, of the rotary piston slide. The annular surface surrounds a spiralling loop of a dystectic material 25.

Claims

1. A cylinder of an internal-combustion engine characterized by the combination of the following features: (1) it is made of a hyper-eutectoid aluminum-silicon alloy, (2) it is formed with grooves in a labyrinth pattern in at least the area of the inner surface along which gastight seal members of a piston move in sliding contact therewith, and (3) a dystectic material having a higher melting point than the said aluminum-silicon alloy is deposited in the grooves and exposed flush with the rest of the inner surface of the cylinder formed by the

2. A cylinder as defined in claim 1 wherein the pattern of the grooves is

3. A cylinder as defined in claim 1 wherein the dystectic material is a ferrous alloy, molybdenum, a metallic carbide, or ceramic, or a mixture

4. A cylinder as defined in claim 1 wherein the cylinder is in a

5. A cylinder as defined in claim 1 wherein the cylinder is a trochoid-shaped cylinder in a rotary-piston internal-combustion engine.