Internal-combustion engines – Rotary – With compression – combustion – and expansion in a single...
Reexamination Certificate
2001-07-13
2002-08-13
Denion, Thomas (Department: 3748)
Internal-combustion engines
Rotary
With compression, combustion, and expansion in a single...
C123S244000, C123S04400R, C123S0430AA, C418S253000, C418S270000, C074S024000, C074S052000
Reexamination Certificate
active
06431139
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an oscillating-piston engine, comprising a housing, in which several pistons configured as two-armed levers are arranged pivotably, respectively, around a pivot axis being parallel to a central housing axis and are movable commonly in a revolution direction, wherein the pistons have running surfaces on their side facing away from a housing inner wall, the running surfaces when the pistons revolve in the housing, being guided alongside of at least one control cam of a central housing-fixed cam piece, in order to control the pivot movements of the pistons in revolution.
Such a oscillating-piston engine is known from WO 98/13583, the disclosure of which is herewith explicitly included into the present application.
Oscillating piston-engines belong to a type of internal combustion engines, in which the single working strokes of intake, compression, ignition (expanding) and expulsion of the combustion mixture are mediated by rock-like pivot movements of the single pistons between two end positions.
The known oscillating piston-engine has centrally in the housing a housing-fixed cam piece, which comprises an outer contour configured as a control cam. The pistons have running surfaces on their sides facing away from the housing inner wall, i.e. on their sides facing the central cam piece, the running surfaces being guided, when the pistons revolve in the housing alongside the outer contour of the cam piece, in steady contact with same. The pivot movements of the pistons are controlled in this procedure, when the pistons revolve in the housing, by the guiding of the running surfaces of the pistons alongside the outer contour of the cam piece in combination with a rolling engagement of respectively adjacent pistons.
Although the known oscillating piston-engine has turned out to be particularly favorable for what concerns its running characteristics, it can be improved for what concerns its wear-resistance and fail-safety, in particular in long-term operation and in high performance operation.
Calculations with respect to kinematics of the known oscillating piston-engine have, namely, shown that the centrifugal forces of the oscillating pistons adopt different values between a minimum and a maximum, seen via a full revolution in dependence of the momentous rotation position, which is to be explained by the asymmetric mass position of the oscillating pistons with respect to the center of the pivot axes of the single pistons.
The maximal centrifugal force occurs in each piston when it is in the so-called Upper-Dead-Center (TO) position (12 o'clock position) or in the Bottom-Dead-Center (UT) position (6 o'clock position). This maximal centrifugal force acting on the leading lever arm of the piston being in the TO position, which presses this lever arm to the outward into the direction of the housing inner wall, results in a force of equal amount directed to the cam piece acting on the trailing lever arm of the same piston. As this trailing lever arm is in rolling engagement with the leading lever arm of the next trailing piston, the trailing lever arm of the leading piston presses the leading lever arm and, thus, the running surface arranged on that lever arm with increased force against the cam piece. This is because only a centrifugal force minimum acts upon on the leading lever arm of the trailing piston, which is just in the drawn-in 9 o'clock position or 3 o'clock position, so that this minimal centrifugal force does not compensate the compressive force caused by the centrifugal force in the TO position. The consequence is that the running surface of the trailing piston in the 9 o'clock position or of the piston in the 3 o'clock position is pressed against the cam piece with very high force, whereby both the running surface and the cam piece are excessively loaded.
In long-term operation, this may result in increased wear or even in damage of these parts, in particular when the rotational speed is high and, therefore, the centrifugal forces are high.
It can be seen from the above that the teething of the rolling engagement, which has to absorb opposing forces, is even more force loaded.
Moreover, a centrifugal piston combustion engine is known from DE-OS-15 51 101, which comprises six pistons of an approximately triangle form distanced from each other, which are mounted, pivotably, on a circle-shaped driving wheel such that they are pressed against the inner wall of the housing by the occurring centrifugal forces, when rotating in the housing of the engine. The control of the pivot movement of the single pistons is, in this procedure, caused by a special trochoid-shaped embodiment of the housing inner wall. In the housing, moreover, two stationary guiding cams with an outer contour are arranged, which are to guarantee, at low speed of the engine, when the centrifugal forces are low, that the pistons are pressed against the inner wall of the housing to guarantee working of the engine, when the speed is low. This centrifugal piston engine is disadvantageous, however, already because of the required special noncircular contour of the housing inner wall.
From DE-OS-15 26 408, a combustion engine with revolving pistons which form a closed chain is further known. The pistons form, together with the noncircular, approximately oval cylinder jacket, closed rotating working chambers of changeable volume. The articulation polygon formed by the pistons is a pentagon or a polygon, whereby a regular pentagon is considered as to be the most advantageous. For the control of the piston movement, two auxiliary rotors are provided, which consist of five segments, these segments being articulatedly connected via bolts. On the bolts, rollers are mounted, which, rolling over the race, control the movement of the rotors and by means of further bolts the movement of the pistons, too. This embodiment of an oscillating-piston engine is relatively expensive. Further disadvantages of this embodiment are the noncircular configuration of the housing inner wall and the articulated connection of the segments forming the two auxiliary rotors for controlling the pivot movement of the pistons.
From U.S. Pat. No. 3,642,391, another oscillating-piston engine is known, in which the pistons are in pairs articulatedly connected to each other. The form of the housing inner wall of this oscillating-piston engine is not round, but elliptical. The piston pivot movements are controlled by cam pieces, on which the pistons run with rollers. Also in this oscillating-piston engine, the noncircular contour of the housing inner wall is disadvantageous.
It is therefore an object of the invention to improve an oscillating-piston engine mentioned at the outset in such a way that the disadvantages mentioned before are avoided. The oscillating-piston engine is to be improved with reference to its wear characteristics and fail-safety.
SUMMARY OF THE INVENTION
According to the invention, this object is achieved by an oscillating piston engine, comprising:
a housing having a central housing axis and a housing inner wall;
several pistons configured as two-armed levers, said pistons being arranged in said housing and moving/orbiting together in a revolution direction about said central housing axis;
several pivot axes parallel to said housing axis, each of said pistons arranged pivotably about one of said pivot axes, respectively;
a stationary cam piece with respect to said housing and arranged centrally in said housing, said cam piece having an outer contour and at least one inner contour, said outer contour and said inner contour being configured as control cams, wherein said pistons have, at a side facing away from said housing inner wall, running surfaces,
which are guided alongside said inner contour supportedly to a side of a centrifugal force and alongside said outer contour supportedly into a direction of the housing axis, in order to control pivot movements of said pistons in the revolution about said central housing axis.
The oscillating-piston engine
Denion Thomas
St. Onge Steward Johnston & Reens LLC
Trieu Thai-Ba
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