CA2385112A1 - Conversion of rectilinear reciprocating motion into rotational motion - Google Patents

Abstract

A device por converting a reciprocating rectilinear motion into a rotational motion and vice versa, comprising a connecting rod (4) mounted on a planet wheel (3) engaging a ring gear (1, 27) with external (27) or internal (1) toothing. The radii of the pitch circle of the ring wheel (1; 27) and of the planet wheel (3) give rise to the gear ratio 2:1. The connecting rod pin (15 ) of the connecting rod (4) performs a rectilinear motion, and this allows to obtain several advantages, particularly in internal combustion engines.</SDO AB>

Description

Description Cgaversion of rectilinear reciprocating motion into rotational motion Technical Field The present irriention relates to a device which may be used in place of the classical crank mechanism, in order to comrert a reciprocating linear motion into a rotational motion, and vice versa.
Specifically, the present device may be applied to reciprocating volumetric internal combustion engines, or to compressors, even if it is not limited to such applications.
Background Art The conventional crank mechanism of an internal combustion engine has several drawbacks.
One of said drawbacks is the frictional force, briefly denoted as "Fin", which is exerted between the piston lateral surface and the cylinder wall, during the sliding movement of the piston, and which is due to the reaction to the thrust of the connecting rod.
There results that all kinds of volumetric reciprocating engines exhibit a large efficiency drop, caused by energy dissipation due to said force, and particularly two-stroke (two-cycle) engines employ a large amount of oil in the gasoline (2%) in order to ensure a good operation and sliding, whose combustion gives rise to high pollution levels.
An additional drawback resides in the turnover force, which is exerted by the connecting rod on the piston, leading to the requirement that the lather must have a length, which avoids piston seizure. However, a greater size leads to a larger weight and consequently to higher inertia, thereby lowering the efficiency.
Noticeable lightening of the components of the mechanism, together with a greater cylinder cooling efficiency, could be achieved if it were possible to obtain a certain AMENDED SHEET

swept volume, using small cylinder bores and large strokes. The classical crank mechanism has in this connection certain limits, because it generally comprises a connecting rod, which translates and oscillates at the same time during its motion, thereby preve~ing to go beyond certain limits of the stroke, due to space (obstruction) problems.
An object of the preset invention is to realize a device suited to convert a rectilinear reciprocating motion into a rotational motion, and vice versa, based on a totally different principle, according to which the end of the auxiliary crank, instead of performing a rotational motion, will move along a straight line.
A further object of the invention - when applied to internal combustion engines -, is to realize a device which eliminates the above mentioned disadvantages of the known art.
In particular, the device will allow the piston to more effectively transmit to the driving shaft the force generated inside the combustion chamber, by generating, in each cycle, a diagram of the moment of the engine, which is much more advantageous. Since the engine power is instantaneously given by the product of the angular velocity and the torque, it can be deduced that the overall power will increase.
An additional object of the present invention is to use, in order to realize the device for converting the linear reciprocating motion into rotational motion, members or components, which perform rotational motions and which, are naturally balanced due to their shapes. Therefore, they will not require the addition of counterweights.
Even if the rotation occurs at a very high rpm value, the driving shaft vibrations are extremely reduced and the motion will be very smooth.
Disclosure of Invention The present invention attains the above mentioned objects, by means of a device for converting a rectilinear reciprocating motion into a rotational motion, or vice versa, AMENDED SHEET

comprising:
- only one auxiliary crack (4) and only one rotor (30) containing the axis of rotation of the auxiliary crank (4), which are both arranged on only one side of the auxiliary crank pin (15);
- means (1,3) which impose to the auxiliary crank (4) and to the rotor (30), rotational motions such that when the auxiliary crank (4) performs a rotation in one direction, said rotor (30) rotates by half that angle and in the opposite direction;
- said means (1,3) comprising a planet wheel (3) integral with said auxiliary crank (4), and which is located between two supports arranged inside the rotor (30), and a IO .ring gear (1) with internal toothing, integral with a housing (7}; said tutor (30) being monolithic and located inside the housing ('7~;
- the pitch circle diameter of the planet wheel (3) being equal to half the pitch circle diameter of the ring gear ( 1 ) with internal toothing; and - the input or drawing of power being perfomaed by means of a shaft (16) which is integral with the rotor (30) and rotates with it.
In applications concerning internal combustion engines, the pin of the auxiliary crank is connected by a rod or bar to the piston of the cylinder. The auxiliary crank pin will perform a rectilinear, or almost rectilinear, reciprocating motion. In case the motion is rectilinear, the rod or bar must not be necessarily connected to the piston in the form of an articulated joint, but may be rigidly connected thereto.
Therefore, said rod or bar for the connection to the movable member may also be called "plunger".
In case of internal combustion engines the movable member is a piston which performs a reciprocating linear motion. It obviously follows that the piston stroke may be much larger than the piston diameter. This will allow to choose (select) the size of the device components in relation to the force acting on the piston, which will be lower in case of swept volumes having small cylinder bores and large strokes.
Thus, the engine weight will be reduced Said means for imposing to the auxiliary AMENDED SHEET

crank and to the rotor the above mentioned relative movements, preferably are embodied by geaJVVheels.
By mounting the auxiliary crank on a crown wheel, according to claim 1, wherein the diameter of the pitch circle of the crown wheel or planet wheel is equal to half the diameter of the pitch circle of the "fellow" wheel (ring gear with internal toothing), it is possible to obtain a rotation by an angle 2a of the crown or planet wheel around its own axis. Simultaneously, the rotor, and the planet wheel center (or center of auxiliary crank), will have moved by an angle a in the opposite direction, around the rotor center, the latter being the rotating member which for instance (in the application concerning internal combustion engines) is directly or indirectly connected to the engine driving shaft.
The effect which is thereby obtained, and which is the actual goal of the imrention, is that the auxiliary crank pin will move along an almost rectilinear path, and said path is perfectly rectilinear provided that, the centers of the two engaging wheels (planet wheel and fellow wheel or ring gear) define a segment, equal to the radius of the orbit of the rotation center of the planet wheel, which exactly corresponds to the distance between the auxiliary crank pin, and the center of the planet wheel (crown wheel).
It is of primary importance that the diameter of the fellow wheel toothing (thc pitch circle diameter) be always equal to twice the diameter of the planet wheel (planet wheel toothing).
According to claim 2, several devices of the same kind, designed according to the present inventive concept, may be used to built a machine in which the power is drawn (collected) by means of a single driving shaft which simultaneously engages the various rotors of the devices.
The present invention and its several advantages will be more easily underst~d by considering the following detailed description of its preferred embodiment.
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26-11-2001 (T0000337 Brief Description of Drawing The present invention will now be described for illustrative and non-limitative purposes, with reference to a preferred embodiment, which is shown in the drawings, wherein:

Fig. 1 is a schematic drawing of the only principle of operation of the device of the present invention, known per se, as compared with the classical crank mechanism;
Fig. 2 is a view of the assembly formed by the ring gear, ar fellow wheel, with internal toothing, by the planet wheel which is integral with the auxiliary crank, and by the auxiliary crank itself, in the position corresponding to the top dead center (TDC) of the movable member having a reciprocating rectilinear motion, this drawing showing the use of two gearwheels for the device implementation;
Fig. 3 is a view of the assembly shown in Fig. 2, showing - in an intermediate position of the planet wheel - how the conditions of the principle of operation regarding the angles of relative rotation, are satisfied, and how the auxiliary crank pin moves along a straight line (X axis);
Fig. 4 illustrates the sequence of movements of the planet wheel (crown wheel) according to four different positions;
Fig. 5 shows an application according to which a disk is used instead of the auxiliary crank, in order to pmvide thereon a plurality of pins whose loci correspond to "reciprocating" rectilinear trajectories, out of phase with respect to each other, Fig. 6a is a view of the preferred embodiment of the device according to the present invention;
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Best Mode of Carrvi~,lr out the Invention The principle on which the invention is based, which is known per se, is that of dividing up the arm of the classical crank mechanism in two articulated {hinged) parts, and to impose thereto, during the motion, opposite rotations in which one rotation is twice the rotation of the other part.
In order to better explain this principle, in Fig. 1 the classical system of a volumetric reciprocating engine, made up by a connecting rod and a crank, is depicted in the left side of the figure, in the position TDC (top dead center) and in a generic position respectively, while on the right hand side, the same engine is illustrated, but with a crank subdivided in two parts, corresponding to segmerrts OC and CB, hinged to each other at C, wherein segment CB is forced to rotate - around hinge C - by angles which arc twice as large as those covered by segment OC during the motion, in the opposite direction.
In both figures, center O represents the axis of the driving shaft (or better, the intersection of this axis with the plane of the drawing).
Consider for each case a generic position following the position TDC shown at the top of Fig. 1. In the classical crank mechanism the crank pin B, for a certain displacement s of the piston, will have moved through an angle a along the circular trajectory t of radius OB. In the arrangement according to the invention, during the same displacement s of the piston, segment OC will rotate clockwise (anticlockwise) around the axis O, through an angle b, and segment BC will rotate anticlockwise (clockwise) around hinge C.
This relative movement generates a trajectory of the point B, which in general is almost rectilinear, with a slight convexity facing to the right or the left, with respect to the piston axis xX, depending on whether the length of segment BC is greater or less than that of segment OC (in Fig. 1 BC is greater than OC, and the trajectory has a convexity to the right, as rilustrated).
Obviously, if OC = CB, the trajectory of point B will be perfectly rectilinear and will AMENDED SHEET

" 26-11-2001 fT0000337 pass through the center O. ' For the impleme~ation of this principle, gearvvheels may be employed, which allow to realize during the motion - by their gear ratios - the constraint according to which, when segment OC covers an angle b around its center O, segment CB covers an angle which is twice that angle, in the opposite direction of rotation.
To this end we employ a fellow wheel ar ring gear 1 with internal toothing 2 and a plaaet wheel or crown wheel 3 (see Fig. 2), configured in such a way that the pitch circle diameter of the former is twice the pitch circle diameter of the latter.
Fig. 2 schematically shows the anangemern of the essential members or components whose relative movement is used to generate the desired reciprocating motion.
In this figure, by comparison with the right side of Fig. I, it may be seen that the center O1 of the ring wheel I corresponds to point O, the center 02 of the planet wheel 3 corresponds to point C, and finally, that the auxiliary crank 4, integral with the planet wheel, is schematically represemed by segment CB; its point 03 corresponds to point B and "covers", i.e. coincides with, point T where the two pitch circles of the toothings 2, 5 are tangent to each other, in the top dead center TDC.
Imagine now that we force segment Ol-02 to perform a right-handed (clockwise) rotation by a generic angle a about center Ol, and that the position of the ring gear 1 is always in the same plane, as shown in Fig.3.
24 The planet wheel 3, which engages with the ring gear 1, will also rotate around its axis 02, due to the rotation of its center 02 around O1, and said rotation of the planet wheel wilt correspond to an angle 2a (since the gear transmission ratio between these two members is 2: I ) and will occur in the opposite direction (anticlockwise).
The auxiliary crank 4, which - as mentioned above - is integral with the planet wheel 3, will rotate by the same angle as the latter, thereby shifting its point 03 once again along the axis X of Fig. 2.
In Fig. 4 there are shown some of the infinite number of positions the system may assume during the rotation, in order to better illustrate the dynamics of the AMENDED SHEET

_ CA 02385112 2002-03-12 movement, and the same figure also shows the two points S and I which correspond to the end-of stroke positions.
It is interesting to note, that if a disk b which is also integral with the planet wheel, is used instead of the auxiliary crank 4 of Fig. 2, as shown in Fig. 5, by fixing on the disk a generic point 04 rotated by a certain angle 2a with respect to 02 and located on the same circumference as 03, the said poic~t will move - during the rotation -along a different rectilinear trajectory, which is tilted by an angle a with respect to the first trajectory (X-axis).
In conclusion, a plun~lity of movable members with rectilinear reciprocating motion and out of phase one with respect to the other by arbitrary angles, may be connected to the disk 6 and around the same.
At this point, for clarity, it is advisable to define - in conformity with their fvactioa -as "plunger", the segment AB (Fig. 1 ), "auxiliary crank", the segment BC, "rotor", a cylinder having its axis passing through O and containing the axis intersecting the plane of the drawing at C. .
Fig. 6a shows a cross-section of the preferred embodiment of the device.
In Fig. 6a, the ring gear 1 is received inside the block or frame 7 provided with cover 8.
The planet wheel 3 of radius R/2 is actually introduced inside the rotor 30, and the latter, is provided with a cylindrical seat 9. The toothing of the planet wheel 3, denoted by numeral 5, engages the fellow wheel or ring gear 1 with internal toothing of double radius (equal to R) with respect to that of the planet wheel 3.
In Fig. 6a it may be noted, in particular, that the cylindrical seat 9 has a discontinuity, that is, it does not extend along the whole longitudinal extension of the rotor 30, so that the toothing 5 of the planet wheel 3 can engage the fellow wheel or ring gear 1 whose toothing is denoted by 2.
it can also be noted - in Fig. 6a -, that the planet wheel 3 of radius RI2 has an integral hub 1 I lodged inside an extension of rotor 30.
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The hub 11 is received inside bearings or a bearing brass (hatched portion).
Also the planet wheel 3 and the rotor 30 are supported by bearings or a bearing brass respectively indicated by 12 and 13.
The portion of the rotor 30 indicated by numeral 10, adjacent to the wall 8, rnay form a gearwheel. The gearwheel 10 may remain uncovered (the upper wall 7 of Fig.
6a is omitted) and may be used for the synchronization of several devices of the same kind, through a synchronization shaft (not shown) which draws and collects the power from the plurality of devices.
In Fig, 6a the driving shaft is denoted by numeral 16 and is integral with the rotor 30;
it projects out of wall 8. It can also be observed that the driving shaft 16 is supported by a bearing brass 17.
In Fig. 6a it is obvious that the axes 18, 19, 20 respectively indicate the axes of components 1 b, 3, 15.
It is appropriate to recall and stress the fact that in case more than one mechanism are assembled together in the same engine, it is necessary to synchronize these mechanisms.
This may be achieved as follows:
- a gear wheel 10 is rigidly connected, e. g. keyed, or directly formed on each rotor 30, and each of said gear wheels has the same pitch circle diameter as the other ones (see for instance in Fig. 6a the region between the ring wheel 1 and the cover 8;
portion 10 of.rotor 30);
- a transversal shaft is added to the assembly, which has a number of gearwheels corresponding to the number of devices (mechanisms), wherein each of the gearwheels of the transversal shaft engages a corresponding gearwheel 10.
Naturally, since the additional shaft, besides the function of synchronization, also accomplishes the task of collecting the work done by each mechanism, it will provide a single power take-off of the engine or machine at the output of its flame.
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)nduStt181 A~~IOn Some goals which are absolutely impossible to reach by means of the traditional system composed of a crank and a connecting rod, can be reached by means of the new "cantilever" device, which is designed to transform a rectilinear reciprocating 5 motion into a rotational motion.
In short, some of these goals are the following:
- increase in the value of Mm (torque of the engine);
- total elimination of the traditional force (Fia) which represents the frictional force, which is one among the most prejudicial ones which act against the motion, and 10 which is exerted during the sliding movement of the piston, between the lateral surface thereof and the cylinder wall due to the reaction to the thrust of the crank. As a direct consequence of this fact, there is a considerable reduction in the amount of oil used for lubricating said walls;
- possibility to use large swept volumes and small cylinder bore diameters, without being forced to excessively increase the volume of the engine. Consequently, very large strokes can be obtained, and therefore also very long lateral cylinder surfaces associated to these strokes, which for this reason give the possibility to much more effectively dissipate the generated heat;
- noticeable weight reduction of the device components (a direct consequence of the foregoing paragraph);
- in the device, the componems or members which rotate, are naturally balanced due to their shapes. Therefore, no counterweights are required for this system by said components.
Practical tests have shown that for the same constant swept volume, as compared with traditional engines, a higher power is obtained and a much smoother (regular) rotation of the driving shaft, with a high reduction of vibrations.
Finally, it is possible to rigidly connect the piston located at the end of the "plunger"
(segment AB of Fig. 1 ), to the plunger itself without any kind of hinge being AMENDED SHEET

necessary for this, and said piston may have a minimal longitudinal size, which is only large enough to ensure the provision of the piston rings.
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Claims (3)

claims

1. A device for converting a rotational motion into a rectilinear reciprocating motion, and vice versa, in particular for the use in volumetric internal combustion engines, and in compressors, characterised in that it comprises:
- only one auxiliary crank (4) and only one rotor (30) containing the axis of rotation 2\1Z<Z0of the auxiliary crank (4), which are both arranged on only one side of the auxiliary crank pin (15);
- means (1, 3) which impose to the auxiliary crank (4) and to the rotor (30), rotational motions such that when the auxiliary crank (4) performs a rotation in one direction, said rotor (30) rotates by half that eagle and in the opposite direction;
- said means (1, 3) comprising a planet wheel (3) integral with said auxiliary crank (4), and which is located between two supports arranged inside the rotor (30), and a ring gear (1) with internal toothing, integral with a housing (7); said rotor (30) being monolithic and located inside the housing (7) ;
- the pitch circle diameter of the planet wheel (3) being equal to half the pitch circle diameter of the ring gear (1) with internal toothing; and the input or drawing of power being performed by means of a shaft (16), which is integral with the rotor (30) and rotates with it.

2. A device according to claim 1, wherein the device can be used for the construction of machines comprising several devices of the same kind, which are synchronised with respect to each other by means of a shaft simultaneously engaging the rotor (30) of each of said devices; the axis of said shaft being arranged so as to not hinder the rectilinear reciprocating motions of the pin (15) of the auxiliary crank (4) of each device.

3. A device according to claim 2, wherein said shaft, besides performing the synchronisation of the various devices, also collects the torque of each device, and outputs them at a single power take-off.