Internal-combustion engines – Frame construction – Horizontal cylinder
Reexamination Certificate
2000-05-08
2001-07-03
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Frame construction
Horizontal cylinder
C123S1950HC, C123S1950HC
Reexamination Certificate
active
06253726
ABSTRACT:
The invention concerns a crankcase for a combustion engine with cylinders arranged in a V formation, divided into two halves along a dividing line through the axis of the crankcase, such two halves being connected with each other by bearing screws at right angles to the plane of separation on each side of the crankshaft bearing, and by cylindrical adapters that each lock in a fitting drilling between the two case halves.
Since the crankshaft of a combustion engine with a V-shaped cylinder formation is subjected to particular lateral forces parallel to the plane of separation of the crankcase, these lateral forces must be transmitted via the crankshaft bearings to the two halves of the crankcase bearing the crankshaft. The crankshaft bearings are made of comparatively thin bearing shells inserted in bearing drill holes between the two halves of the crankcase. This means that the two halves of the crankcase cannot be centred via the crankshaft bearings. In order to achieve an appropriate centring of the crankcase halves to be connected to each along a continuous plane, it is known (U.S. Pat. No. 4,674,455) that the two crankcase halves can be screwed together by means of bearing screws on both sides of the crankshaft bearings, such screws having cylindrical adapters in the area of the plane of separation between the two crankcase halves. These adapters lock into fitting drill holes on both sides of the plane of separation at right angles to the plane of separation penetrated by the bearing screws, such that the bearing screw adapters locking in the flush fitting drill holes of the crankcase halves can be used to centre the crankcase halves with respect to the drill holes for the crankshaft bearings and can be connected with each other in a manner permitting the transmission of forces. The disadvantage of this know design is, however, that the fitting drill holes of the two crankcase halves at right angles to the plane of separation require considerable manufacturing effort because of the drilling accuracy needed. Despite the required high drilling accuracy, the take-up of load via the adapters of the bearer screws is impaired by the inevitable tolerances.
Thus the invention is based on the problem of designing a crankcase of the type described at the beginning for a combustion engine with cylinders arranged in a V formation in such a way that an exactly centred and load-transmitting connection between the two halves of the crankcase can be ensured with a minimum of manufacturing effort.
The invention solves the problem set by having the adapters running parallel to the axis of the crankshaft located in the plane of separation and each penetrated by one bearing screw.
Since the adapters are in the plane of separation and run parallel to the axis of the crankshaft, the fitting drill holes for these adapters can be drilled together with the bearing drill holes for the crankshaft bearings, which combines simple construction conditions with high accuracy. Since the centring and the removal of the load parallel to the plane of separation is achieved by the adapters separate from the bearing screws, there is no need for fitting drill holes for the bearing screws, with the result that the seat drill holes for the bearing screws can be made without particular accuracy. Despite the adapters separate from the bearing screws, a compact hardly protruding design is ensured since the adapters are penetrated by the bearing screws. In this way, the bearing screws penetrating the adapters fix the adapters in the axial direction, with the result that there is no need for additional design measures.
If two bearing screws are provided on each side of the crankshaft bearings, it is recommended that the adapters be located in the area of the outer bearing screws in each case in order to keep a small distance between the inner bearing screws and the corresponding bearing drill hole.
In a further embodiment of the invention, at least two bearing screws are positioned on either side of each crankshaft bearing and the adapters are respectively positioned parallel to the crankshaft axis in the plane of separation between any two screws on each side of the crankshaft bearing.
REFERENCES:
patent: 2703263 (1955-03-01), Zernov
patent: 4674455 (1987-06-01), Tsuboi
patent: 4753201 (1988-06-01), Fukuo et al.
patent: 5133313 (1992-07-01), Inoue et al.
patent: 5462366 (1995-10-01), Häusler
patent: 5564837 (1996-10-01), Putman et al.
patent: 5829406 (1998-11-01), Mazzola et al.
patent: 5931135 (1999-08-01), Yamada
patent: 830 443 (1952-01-01), None
patent: 12 95 276 (1969-05-01), None
Glinsner Karl
Koch Thomas
Lippitsch Heinz
Bombardier-Rotax GmbH
McMahon Marguerite
Pillsbury & Winthrop LLP
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