WO2001021947A1

WO2001021947A1 - Conversion of rectilinear reciprocating motion into rotational motion

Info

Publication number: WO2001021947A1
Application number: PCT/IT2000/000337
Authority: WO
Inventors: Andrea Di Foggia
Original assignee: Andrea Di Foggia
Priority date: 1999-09-24
Filing date: 2000-08-09
Publication date: 2001-03-29
Also published as: EA200200402A1; JP2003510528A; EP1214507A1; CA2385112A1; BR0014228A; ITRM990593A0; AU6724400A; IT1309063B1; EA003724B1; CN1376237A; ITRM990593A1

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.

Description

Conversion of rectilinear reciprocating motion into rotational motion

Technical Field

The present invention relates to a device which may be used in place of the classical crank mechanism, in order to convert 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 "Fia", 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 latter 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 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 preventing to go beyond certain limits of the stroke, due to space (obstruction) problems. An object of the present 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 connecting rod, 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, comprising:

- a connecting rod;

- a rotor which includes the connecting rod rotation axis, and wherefrom/whereto power may be drawn/transmitted, directly or indirectly, for example by means of a synchronization shaft;

- means for imposing rotational movements to the connecting rod and to the rotor such that, when the connecting rod rotates in one direction, the rotor rotates by half of this angle and in the opposite direction. In applications concerning internal combustion engines, the pin of the connecting rod is connected by a rod or bar to the piston of the cylinder. The connecting rod 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 connecting rod and to the rotor the above mentioned relative movements, preferably are embodied by gearwheels. By mounting the connecting rod on a crown wheel, according to claim 2, 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 or external 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 connecting rod), 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 invention, is that the connecting rod pin will move along an almost rectilinear path, and said path is perfectly rectilinear provided that - according to claim 6 - , 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 connecting rod pin, and the center of the planet wheel (crown wheel). The device implementation by means of gearwheels may also make use of a "fellow wheel" or ring gear with an external -instead of internal- toothing, as indicated in claim 3 and claim 4. In both cases, it is of primary importance that the diameter of the fellow wheel toothing (the pitch circle diameter) be always equal to twice the diameter of the planet wheel (planet wheel toothing).

According to claim 7, 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 understood by considering the following detailed description of some of its preferred embodiments.

Brief Description of Drawings

The present invention will now be described for illustrative and non-limitative purposes, with reference to two preferred embodiments, which are shown in the drawings, wherein:

Fig. 1 is a schematic drawing of the principle of operation of the device of the present invention, as compared with the classical crank mechanism;

Fig. 2 is a view of the assembly formed by the ring gear, or fellow wheel, with internal toothing, by the planet wheel which is integral with the connecting rod, and by the connecting rod 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 connecting rod 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 connecting rod, in order to provide 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 a first possible embodiment of the device according to the present invention, which is especially suited for relatively small strokes of the movable member performing a rectilinear reciprocating motion;

Fig. 6b is an exploded perspective view of the embodiment of Fig. 6a;

Fig. 7 is a sectional view of a second possible embodiment of the device according to the present invention, particularly suited for larger strokes of the piston inside the cylinder, and in which the fellow wheel, or ring gear, has an external toothing.

Best Modes of Carrying out the Invention

The principle on which the invention is based 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 segments OC and CB, hinged to each other at C, wherein segment CB is forced to rotate - around hinge C - by angles which are twice as large as those covered by segment OC during the motion, in the opposite direction. In both figures, center 0 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 0, through an angle b, and segment BC will rotate anticlockwise (clockwise) around hinge C. This relative movement generates a trajectory of the connecting rod pin (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 illustrated) . Obviously, if OC = CB, the trajectory of point B will be perfectly rectilinear and will pass through the center 0. For the implementation of this principle, gearwheels 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 0, segment CB covers an angle which is twice that angle, in the opposite direction of rotation.

For relatively short piston strokes it is advisable, in order to have mechanical members of noticeable resistance, to employ a fellow wheel or ring gear 1 with internal toothing 2 and a planet 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 arrangement 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. 1, it may be seen that the center 01 of the ring wheel 1 corresponds to point 0, the center 02 of the planet wheel 3 corresponds to point C, and finally, that the connecting rod 4, integral with the planet wheel, is schematically represented 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 01-02 to perform a right-handed (clockwise) rotation by a generic angle a about center 01, and that the position of the ring gear 1 is always in the same plane, as shown in Fig.3. 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 01, and said rotation of the planet wheel will correspond to an angle 2a (since the gear transmission ratio between these two members is 2:1) and will occur in the opposite direction (anticlockwise). The connecting rod 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 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 6 which is also integral with the planet wheel, is used instead of the connecting rod 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 point 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 plurality 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 function - as "plunger" , the segment AB (Fig. 1), "connecting rod", 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 a first embodiment of the device, selected among several possible embodiments, and which is preferably used when the stroke of the piston is limited.

Fig. 6b shows the same embodiment of fig. 6a, with some slight variants, and according to a perspective exploded view.

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, as best shown in Fig. 6b, 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. 6b 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 R/2 has an integral hub 11 lodged inside an extension of rotor 30. 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, may form a gearwheel in the variant of Fig. 6b, in which said gearwheel 14 remains uncovered (the upper wall 7 of Fig. 6a is omitted) and may be used for the synchronization of several devices of the same kind as that shown in Fig. 6b, through a synchronization shaft (not shown) which draws and collects the power from the plurality of devices. A further modification with respect to Fig. 6a is that (see Fig. 6b) symmetrically with respect to the connecting rod pin 15 of connecting rod 4, the device of the invention is "duplicated", in the sense that the further planet wheel 3' may be introduced inside a second rotor 30 in order to increase the resistance of the mechanism. 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 16, 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 14 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 14. 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 frame.

The description made till now refers to one of a large number of possible constructive realizations used in order to put into practice the principle of operation which consists in imposing, during the rotation, that segments OC and CB (Fig. 1) cover angles around their respective center, which are opposite to each other and wherein one of them is half of the other. The above description, as may be seen from Fig. 2, has made use of the solution comprising a ring gear and a planet wheel, which offers the possibility , as stated above, to use mechanical members with an appreciable resistance, for piston strokes which are relatively short. In case of long piston strokes, a similar result may be achieved by the solution of Fig. 7.

The latter is only a suggestion among many proposals for a design whose aim is to put into practice the above mentioned kinematic principle. Fig. 7 shows the following essential elements: - a support 21 of the mechanism, receiving therein two shafts 22, 23 freely movable inside a respective bearing brass (hatched);

- a primary synchronization shaft 22, integral with two gearwheels 24, 25 of radius R2 , R3 respectively; - a secondary synchronization shaft 23 integral with two further gearwheels 26, 27 of radius R4 and Rl respectively;

- a rotor 30 integral with a gearwheel 28 of radius R5; - a connecting rod 4 having a pin or shaft 15 for the connection to the "plunger", and a further gearwheel 29 of radius R6 integral with said connecting rod. Moreover, each gearwheel must have the following values of pitch circle radius: Rl = 2r R2 = 3r R3 = 4r R4 = 2r R5 = 3r R6 = r where r is arbitrary.

Suppose that the element 30 rotates in an arbitrary direction, by an angle a; then, the gearwheel 28 of radius R5 which is integral thereto will transmit an identical rotation - in the opposite direction - to the gearwheel 24 of radius R2 , and therefore also to the gearwheel 25 (R3), because R5 and R2 have a gear ratio = 1; therefore, the gearwheel 25 of radius R3 will rotate by an angle -a. This latter gearwheel engages the gearwheel 26 of radius R4, and will transmit to it a rotation corresponding to twice this latter angle and in the opposite direction, that is a rotation by an angle 2a, since the gear ratio between them is 2:1. The gearwheel 27, which is integral (rigidly connected) with the gearwheel 26, will rotate by an angle 2a, thereby performing a relative rotation equal to 2a - a = a - with respect to element 30 causing the rotation and which has rotated by an angle a -.

The gearwheel 29 and therefore the connecting rod provided with the spindle or pin 15 integral thereto (segment CB in Fig. 1), will rotate by an angle -2a, by engaging with gearwheel Rl and having its center of rotation on the element 30, said rotation being twice as large (gear ratio 2:1) and of opposite direction with respect to the relative angle a of rotation of the elements 23 and 30. In conclusion, it has been shown that if element 30 (rotor) rotates by an angle a, the element 4 (connecting rod) rotates in the opposite direction by an angle equal to 2a, that is, twice a large, thereby confirming the above principle.

Industrial Application

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 device, which is designed to transform a rectilinear reciprocating 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 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 components 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 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.

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, characterized in that it comprises:

- a connecting rod (4);

- a rotor (30) containing the axis of rotation of the connecting rod (4), and to or from which the energy of rotational motion may be transmitted, directly or indirectly, and

- means (1, 3; 22, 24, 25, 23, 26, 27, 29) which impose to the connecting rod (4) and to the rotor (30), rotational motions such that when the connecting rod (4) performs a rotation in one direction, said rotor (30) rotates by half that angle and in the opposite direction.

2. A device according to claim 1, characterized in that the connecting rod (4) is mounted on, or is integral with, a planet wheel (3) whose diameter is equal to half the diameter of its fellow wheel or ring gear (1; 27).

3. A device according to claim 2, wherein the fellow wheel or ring gear (1) is a gearwheel with internal toothing.

4. A device according to claim 2, wherein the fellow wheel or ring gear is a gearwheel having an external toothing ( 27 ) .

5. A device according to claim 3 or 4, wherein the centers of the two engaging gearwheels, that is of the fellow wheel (1; 27) and of the planet wheel (3), define a segment which is equal to the radius of the orbit of the center of rotation of the planet wheel (3), and therefore of the connecting rod (4) integral thereto; said segment being equal , less, or greater than the distance between the connecting rod pin (15) and the center of the planet wheel (3).

6. A device according to claim 5, wherein, when said segment is equal to said distance between the connecting rod pin (15) and the center of the planet wheel (3), the connecting rod pin (15) will perform, during the device motion, a perfectly linear reciprocating motion.

7. A device according to any of the preceding claims, wherein the device can be used for the construction of machines comprising several devices of the same kind, which are synchronized 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 connecting rod pin (15) of each device.

8. A device according to claim 7, wherein said shaft, besides performing the synchronization of the various devices, also collects the torque of each device, and outputs them at a single power take-off.

9. A device according to the preceding claims, wherein in place of the connecting rod (4), a disk (6) is rigidly mounted on said planet wheel (3), such that, internally with respect to the disk periphery and at a certain distance with respect to the center (02) of the disk (6), equal to the pitch circle radius of said planet wheel (3), there may be provided several "connecting rod" pins (04) which are out of phase with respect to each other by arbitrary angles, and which individually perform separate reciprocating rectilinear motions.

AMENDED CLAIMS

[received by the International Bureau on 11 December 2000 (1 1.12.00); original claims 1-9 replaced by new claims 1-5 (2 pages)]

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 connecting rod (4) and only one rotor (30) containing the axis of rotation of the connecting rod (4), which are both arranged on only one side of the crankshaft pin ( 15), and comprising also means (1, 3; 22, 24, 25, 23, 26, 27, 29) which impose to the connecting rod (4) and to the rotor (30), rotational motions such that when the connecting rod (4) performs a rotation in one direction, said rotor (30) rotates by half that angle and in the opposite direction.

2. A device accord ng to claim 1, characterised in that it comprises a housing (7), an internal rotor (30) which is formed by a monolithic block, a planet wheel (3) integral with said connecting rod (4), and which is located between two supports arranged inside the rotor (30), and a ring gear (1) with internal toothing, which is integral with said housing (7), wherein the input or drawing of power is performed by means of a shaft (16) which is integral with the rotor (30) and rotates with it.

3. A device according to claim 1, wherein the connecting rod (4) is integral with the planet wheel (29), and the latter engages a fellow wheel (27) having an external toothing.

4. A device according to any of the preceding claims, 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 connecting rod pin (15) of each device.

5. A device according to claim 4, 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.