FOUR DEAD CENTERS CRANK MECHANISM

Abstract: In order to improve the organic engine efficiency and the polluting characteristics, as regards the present engines, I propose a new type of crank mechanism - ''four dead centers crank mechanism'' - which has the following most important kinematic characteristics: we can stop the piston at the top dead center for a period corresponding also with a rotation of 120 degrees of the crankshaft; the induction and exhaust strokes are more speed than traditional one (with the same turn velocity omega ). All these characteristics riverberate thermodinamically in a combustion at constant volumes and at minor heat exchanges between evolving fluid and cylinder wall.

Description: " FOUR DEAD CENTERS CRANK MECHANISM " DESCRIPTION The following work wants to propose a new type of crank mechanism and a variant of it, in order to improve thermodinamic efficiency and to reduce quantity of polluting masses for every cycle and to attenuate the closing forces between piston and the cylinder wall. These aims will be pursued operating by means of the particular kinematism on the law that regulates piston displacement in function of crank angle. Crank mechanism considered is composed in its schematic description ( Tab 1/5, Fig. 1 ) and in its real one ( Tab. 3/5, Fig. 1 and 2 ) of a traditi nal crank mechanism in which the crank pin is connected to two rods,one of them has an extremity in agreement with the crankcase, the other one is connected by means of extremity E to other two rods; these last rods have on this way, an extremity coinciding with the point E and the other two extremities are respectively connected to the crankcase (point G.) and to the piston pin (point F). KINEMATIC ANALYSIS The title of this work points out that this crank mechanism has the chara cteristic of having four dead centers, if as dead centers we mean the posi tions of the rods ( namely when there are particular alignments of the rods ) in which piston has null velocity. On this way, we'll be at a dead center position or when piston rod and crank (rods A-B and B-C) are alig ned or when rods C-D and E-C are aligned. These situations are represented on Tab. 2/5, Fig. 1, 2, 3 and 4, and they show respectively the external dead center and the three internal dead centers. Two internal dead centers of these last ones correspond to an end stroke position ( Fig. 2 and 4 ), the other one corresponds to a position too much near the end stroke posi¬ tion ( Fig. 3 ). In other words, from first dead center the piston begins his upward run which has a catch when there is an alignment of rods C.-D and E--C, ( Tab. 2/5, Fig. 2 ). Then the piston reverse s its run moving a- way only a little from preceding occupied position corresponding witi dead center that is own of the component crank mechanism ( Tab. 2/5, Fig. 3 _), and then it goes up again as far as the third dead center which correspond to an alignment of the rods C_-D and E,-C, ( Tab. 2/5, Fig. 4 ); the turn crank completes itself with exhaust stroke, carrying back the piston to the external dead center. Summing up, the piston during the period' time ( that is proportional to the angle θ.. , Tab. 1/5, Fig. 2 ) between the first and the third internal dead center, moves itself with so small velocities and shiftings ( some hundredth of millimetre for an angle € of 60 degrees and a run of 70 mil- limetres)that we can consider it- :as ~ stopped. THERMODYNAMIC ANALYSIS In order that the proposed crank mechanism had an efficient thermodinaπric it is indispensable that the rules regulating piston motion have to give to the evolving fluid some characteristics nearer the ideal criteria; in other words the cycle which has to come out must be, as regards the tradi¬ tional one ( with the same turnvelocity _Zt ) , nearer the lymit cycle which, as well known, is composed of isometric combustions and of compres- 5862 3 sions and expansions without heat-exchanges. The isometric combustion is much more than approximated because the pi ston is just stopped when it is at the internal dead center. We have smaller heat quantities which are exchanged between evolving flu id, and cylinder walls because these last ones are set free from pisto a smaller period of time(proportional to the angles θ. and θ ) than th traditional crank mechanism ( with the same turn velocities u ) . As regards the induction and exhaust strokes, we can declare that durin induction stroke the losses of load are attenuated because we have possi¬ bility of utilizing a part of the angle Θ-. for letting open inlet valve, on this way on requesting of engine-fluid this valve is just almost com¬ pletely opened. We can divide exhaust stroke in three parts ( one more than traditional ones ) : spontaneous exhaust, forced exhaust and, utilizing again a part of angle θ,. , another spontaneous exhaust, obtained delaying the closing of the suitable valve. ECOLOGICAL FACTORS _.. mechanism • _ _ • . . _, . This crank is very interesting also as regards the ecological point of view because it permits a more complete combustion, a reduction of combu¬ stible and lubrificanting oil consumptions; these last one for the minor friction between piston and cylinder wall. FORCES OF INERTIA The complexity of this crank mechanism permits an increase of forces of inertia which oblige us at rather slow rotation runnings. To surmount these disadvantages, when besides a good efficiency we want also high powers, we must opt for the variant of this new crank mechanism represen¬ ted by two views on Tab. 4/5 and 5/5 with Fig. 1, in which the forces in play discharge themself on two rotating in opposite way crankshafts and in which there aren't closing forces of the kinematic couple cylinder-pi¬ ston.

Claims: CLAIMS The crank mechanism and its variant that we want to patent have the chara_ cteristic of giving us the possibility of having four dead centers; thi possibility is due to the particular alignments of the rods which compos these new crank mechanisms. Referring to the schematic representation on Tab. 1/5, Fig. 1, the propo¬ sed crank mechanism is composed of a component crank mechanism ( rods A- and B-C ) with the crank pin (point C) coinciding with the extremities of other two rods (C-D and C-E). These last ones have each another extremity the extremity of one of these rods is encircled in a point in agreement with the crankcase (point D) while at the extremity of the other rod (poin t E) join the last two rods E-F and E-G; one of these rods is connected to the piston by means of the point F, while the other one is connected to a point in agreement with the crankcase (point G). In other words, this crank mechanism is composed of a kinematic chain (arc with four hinges) characterized of three rods C-D, C-E and E-G following one another, in which the initial and final points of the chain are ancho¬ red by means of hinges to the crankcase; the system completes itself with the addition of the piston and of a traditional crank mechanism which are clasped at the system, respectively by means of the rod E-F ( which trans mits piston motion to the system and vice versa ) clasped at the hinge E and putting in common the point C of the system with the crank pin of com¬ ponent crank mechanism ( rods A-B and B-C). On the Tab. 4/5 and 5/5 have been drawed two views of a twin camshaft cran mechanism that we want show as a variant because it has the same characte ristics (four dead centers) and it has been obtained from single camshaft crank mechanism eliminating the rod G-E, the piston pin F and rendering all that remains symmetric as regards the cylinder axis. At last we point out that they have been described only two forms of car¬ rying out the invention, but, it is obvious, that all the possible varian ts are included in the invention.

Inventors: SARNO COSIMO, SARNO, COSIMO
Applicants: SARNO COSIMO, SARNO, COSIMO
Application year: 1989
Main classification: F16H21
IPC codes: F02B41, F16H21