Air-Cooled Multi-Cylinder Internal Combustion Engine

The present invention relates to an air-cooled multi-cylinder internal combustion engine whose cylinders, arranged in a row (in-line) and clamped-in between the associated cylinder heads and the crankcase, are cast individually and are provided externally with transversely extending ribs for cooling purposes.

Such an internal combustion engine is disclosed in the DE-AS No. 12 05 772. The cooling air flowing transversely to the cylinders flows along the wide side of the cross ribs and is then deflected at the rear cooling air discharge side of the cylinders by columns shaped favorably from an aerodynamic point of view. Additionally, guide baffle or deflector plates are attached at the columns, however, nothing is stated in this prior art publication about how these plates are to be fastened. Customarily, such guide baffle or deflector plates are threadably secured and cause an undesired noise emission.

It is the object of the present invention to provide an air guide arrangement which can be manufactured and installed at low cost and does not represent an additional noise source.

A one-piece deflection member covering all cylinders at their cooling-air discharge side serves as solution to the underlying problems, which can be cast of light metal or even injection-molded of plastic material. For purposes of increasing its form rigidity, it is constructed double-walled. This deflection part is threadably connected either with the crankcase or with the cylinders. In the latter case, it can be used at the same time as knock bridge in that it further transmits the knock noises of all cylinders connected with the same to a knock sensor threadably secured thereon in the center thereof. If the deflection part is made of a material that has the same thermal coefficient of expansion as the crankcase, it follows the length expansions thereof during temperature changes so that the deflection part can be rigidly screwed onto the cylinders secured in the crankcase. Otherwise, also a compensating threaded connection can be selected which enables a differing length expansion of the deflection part and of the crankcase.

These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, two embodiments in accordance with the present invention, and wherein:

FIG. 1 is a cross-sectional view through a cylinder row of an air-cooled six-cylinder internal combustion engine in accordance with the present invention;

FIG. 2 is a longitudinal cross-sectional view through a cylinder together with the deflection part taken along line II--II of FIG. 1;

FIG. 3 is a side elevational view of a modified deflection part with a knock sensor in accordance with the present invention;

FIG. 4 is a cross-sectional view through a cylinder row taken along line IV--IV of FIG. 3; and

FIG. 5 is a cross-sectional view taken along line V--V of FIG. 4 with longitudinal cross section through a cylinder.

Referring now to the drawing wherein like reference numerals are used throughout the various views to designate like parts, according to FIGS. 1 and 2, three individually cast cylinders 2, 3 and 4 are arranged in a row adjacent one another within a crankcase 1 of an internal combustion engine and are threadably secured to the crankcase 1 together with the cylinder heads 6 mounted on the cylinders 2, 3 and 4 by expansion bolts 5. The cylinders 2, 3 and 4 are provided externally about the circumference thereof with ribs extending transversely to their longitudinal axis, between which cooling air is blown through. A deflection part 8, which covers all of the cylinders, is arranged at the cooling-air discharge side of the cylinders; the deflection part 8 is cast in one piece of light metal and is placed over the crankcase at its three fastening eyes 9 disposed axially with respect to the cylinders 2, 3 and 4 and is threadably secured thereat with the crankcase 1. For increasing the form rigidity, the deflection part 8 is constructed double-walled. The fastening eyes 9 are disposed centrally with respect to the air discharge openings 10 which are arranged in the area of the center planes 2', 3', 4' of the cylinders 2, 3, 4, proceed radially to the cylinders and extend over their entire height. Within the area between the cylinders 2, 3, and 3, 4 the deflection part 8 includes V-shaped bent-in portions 11 pointing toward the cylinders 2, 3 and 4 along which the cooling air flowing through the cylinders is deflected by 90.degree. and is conducted to the air discharge openings 10.

In an embodiment of the present invention according to FIGS. 3, 4 and 5, the deflection part 12 differs from the deflection part 8 in that it includes eyes 13 extending radially to the cylinders, by means of which it is mounted on corresponding eyes 14 of the cylinders 2, 3 and 4 and is screwed together with the same.

In addition to the air guidance, this deflection part 12 serves at the same time as knock-bridge in that it further conducts the noises coming from the cylinders and caused by knocking combustion, to a knock sensor 15 which is threadably secured at the deflection part 12 approximately in the center of its longitudinal dimension.

While we have shown and described only two embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to those skilled in the art, and we therefore do not wish to be limited to the details shown and described herein, but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.