Air-Cooled Internal Combustion Engine

This invention relates to an air-cooled internal combustion engine wherein air conducted past the engine cylinders is available to heat the driver's area of a vehicle in which the engine is used.

Heretofore, the cooling air provided to cool air-cooled internal combustion engines is also used to provided heating after it has been warmed up as it is conducted past the cylinder and the cylinder head. The Lloyd twin-cylinder four-stroke engine, for example, uses this kind of warmed-up cooling air for heating the driver's compartment. However, in such a "prior art" system, the heating air frequently becomes contaminated by oil mist and combustion gases passing into the warmed-up cooling air. A particular cause of this contamination entering the flow of cooling air is a leaky cylinder head gasket. In order to avoid this problem, a supplementary heat exchanger is installed in the air-cooled four-cylinder double-piston engine of the Volkswagon "Beetle" automobile to provide heating air separate from the warmed-up cooling air.

It is an object of this invention to provide a simple means to route the cooling air which flows past the cylinders of an air-cooled internal combustion engine directly to the driver's area to provide heating without contamination from engine combustion gases such as may escape from a leaky cylinder head gasket.

It is a further object to provide a single gas-tight partition in a multi-cylinder air-cooled engine of the type having a plurality of separately formed cylinder and cylinder head units, whereby the cooling air, which is warmed as it flows past the cylinders, is separate from the other engine cooling air and flows to the driver's area without being contaminated in the process, even in the event of a combustion gas leak between the cylinder head and the cylinder.

It is preferable that the partition of this invention designed for use between the cylinders and the cylinder heads of a multi-cylinder-bank internal combustion engine be made of a metallic material such as, for example, a metal plate. The partition is provided with an opening for each cylinder which corresponds to the outer contour of the upper end of the associated cylinder. The opening permits the partition to be fitted over the upper end of the cylinder and brought into sealing engagement with the uppermost radially extending cooling fin of the cylinder before installation of the cylinder head. In order to establish a gas-tight seal around the opening for the cylinder, an elastic seal is provided between the partition and the uppermost cooling fin which deforms on installation to form a seal which is gas-tight at every point of its encircling path around the cylinder. The elastic seal preferably is vulcanized or bonded to the underside of the partition and has a semicircular section profile in its unstressed noninstalled condition. Indentations may be provided in the cylinder openings of the partition for receiving sealing elements for tie rods securing the cylinder head and the associated cylinder to the crank case so as to seal the tie rod relative to the uppermost cooling fin of the associated cylinder. The partition preferably extends outwardly over a cooling air shroud surrounding the cylinders and the cylinders and the shroud are substantially perpendicular to the partition. The partition, as herein described, is effective to prevent exhaust gases, which would escape in the event of a leak between the cylinder head and cylinder, from entering the flow of cooling air which is used for heating the driver's area.

One embodiment of the invention is shown in the drawings, in which:

FIG. 1 is a partial vertical section of two cylinder units of an engine on which the partition of this invention is installed;

FIG. 2 is a view taken along the line II--II in FIG. 3 showing a tie rod and its sealed relationship with the upper cooling fin of the associated cylinder;

FIG. 3 is a partial top plan view of the partition shown in FIG. 1; and

FIG. 4 is a view taken along the line IV--IV in FIG. 3.

FIGS. 1 and 2 of the drawings show parts of two side-by-side cylinder units of an air-cooled internal combustion engine. Each cylinder unit includes a cylinder head 1 and a cylinder 3. Each cylinder head 1 of the bank of cylinder units has an annular flat shoulder surface 11 which is held in sealed relation with the upper end of its associated cylinder 3 by a plurality of tie rods 12, only one of which is shown. The tie rods 12 are connected at their lower end to the engine crank case, not shown, and at their upper end to the cylinder head 1. A conventional cylinder head gasket 2 is installed between the surface 11 and the flat annular surface 13 of the flanged upper end 14 of the cylinder 3 to provide a gas-tight seal. The cylinder head includes a flange 16 which extends downwardly below the shoulder surface 11 and in outboard lapped relation to the upper end 14 of the cylinder 3 so as to encompass it.

The bank of side-by-side cylinders 3 are provided with vertically spaced and radially extending cooling fins 4 along their exteriors which are surrounded by an upright cooling baffle or shroud 5. A special horizontal dividing wall or partition 6 is positioned between cylinder heads 1 and cylinders 3 near their plane of juncture. The partition 6 is provided with openings 8 which correspond to the cylindrical outer contour of the upper end 14 of each cylinder 3 in the area of its flanged coupling with its corresponding cylinder head 1. The common partition 6 is pushed over the upper end or flange part 14 of each cylinder 3 so as to rest on the uppermost cooling fin 4a. In order to maintain a gas-tight seal between the partition 6 and the cylinder 3, an elastic seal 7 is vulcanized onto the partition 6. This extends, as can be seen in FIG. 3, in a closed quadrate loop or square configuration around the opening 8. The elastic seal 7 extends around the entire circumference of each cylinder 3 and engages the top surface of the uppermost cooling fin 4a. The predetermined thickness of the elastic seal 7 is selected to ensure that when the cylinder head is installed, the partition fits securely between and sealingly engages the cylinder head 1 and cylinder 3 under all operating conditions of the internal combustion engine. The partition 6 extends laterally out over the upright cooling shroud 5 and sealingly engages it. In the event of a leak in the cylinder head gasket 2, the exhaust gases which escape from the combustion chamber 19 cannot mix with the cooling air which flows around cylinders 3 en route to the driver's area, not shown, of the vehicle in which the engine is used.

Referring to FIGS. 3 and 4, the common partition 6 is shown in a non-installed condition. The partition 6 is generally rectangular in shape, a shape which is only interrupted at its periphery or edge by indentations 10. The valve operating push rods, not shown, extend through these indentations 10 and sealing bushings, not shown, are used to prevent movement of cooling air between the top and bottom sides of the partition by way of the indentations 10. Circumferentially spaced indentations 9 for accommodating the tie rods 12 are provided at the edge of openings 8 of the partition 6. The indentations 9 lie within the arc encircled by the seal 7. The tie rods 12, which connect the cylinder head 1 and the cylinder 3 with the internal combustion engine crank case, are sealed in relation to the uppermost cooling fin 4a by elastic seals 18 each of which has an opening for receiving a tie rod. The annular seal 18 has an outer groove permitting it to be pushed into an indentation 9. The elastic seals 7 are vulcanized to the underside of the partition 6 and are connected to each other at 17 as can be seen in FIGS. 1 and 3. In the noninstalled condition of the partition 6, the seal 7 has a semicircular section profile.

When an air-cooled engine incorporating this invention is used in a vehicle having an operator's station or compartment, the partition 6 provides a gas-tight separation or division of engine cooling air so that the cooling air passing beneath the partition and warmed up by the cylinders will not be contaminated by combustion gases in passing to the driver's area. The partition 6 is located below the plane of juncture between the cylinder heads 1 and cylinders 3 and, thus, any combustion gases escaping from the juncture because of a leaky cylinder head gasket 2 will not pass into the warmed air used to heat the driver's area. The elastic seal 7 is sufficiently pliable to accommodate dimensional tolerances and to conform to and sealingly engage the upper surface of the uppermost cooling fin 4a. By bonding the seal 7 to the partition 6 and by pushing the grommet shaped seals 18 into the indentations 9 before assembly, a preassembled partition 6 is made available to the assembler. Thus, sealing elements will not be forgotten during assembly of the cylinder 3 and cylinder head 1 with the partition 6 of this invention.