A rotary internal combustion engine

Abstract

 A rotary internal combustion or heat engine has a reciprocable double piston (3) moving in a cylinder (2). In one embodiment the cylinder (2) itself is rotatable and linked to an engine drive shaft (12) which turns at twice the speed of rotation of the cylinder. In another embodiment the cylinder (2) is fixed and the engine shaft (11) performs a planetary motion. The double piston (5) provides the working cycle and the variations in volume are obtained from the reciprocating motion of the piston within the cylinder (3) which is closed at both ends. Fuel induction takes place through centrally located ports (20,30) at a radially inner position and exhaust of the combustion products is effected at a radially outer position through exhaust ports (21,31).

Description

[0001] The present invention relates to a rotary internal combustion engine.

[0002] Conventional internal combustion engines comprise at least one cylinder in which a piston is linearly movable with reciprocating motion, which piston is connected, by means of a connecting rod, to a crank shaft of conventional crank shape. This configuration, whilst being universally adopted, has the disadvantage of generating unbalanced reciprocating forces and has a large numer of moving parts.

[0003] In order to seek to resolve these balancing problems various alternative configurations have been tried, the nearest to achieving success being the so-called rotary engine, in particular the Wankel engine which employs a trochoidal piston and epitrochoidal "cylinder". Other configurations using toroidal cylinders and with oscillating pistons having rotating or oscillating blades, lobes or rotating pistons have all been tried: these all have significant constructional problems, however, and in many cases have an insufficient gas tightness, above all during the compression stroke, because of the unnusual form of the combustion chamber.

[0004] The present invention seeks to overcome the above indicated disadvantages by providing a rotary internal combustion engine which benefits from the absence of unbalanced forces, has relatively few moving parts, and is of very small dimensions and low weight, without having any need for components the shape of which is difficult to manufacture.

[0005] The invention also seeks to provide a rotary internal combustion engine in which the mechanism is charact­erised by having a stationary overall centre of gravity.

[0006] A rotary internal combustion engine made in accordance with the principles of the present invention has particular constructional characteristics which enable it to offer the widest guarantees of reliability and security in use.

[0007] According to the present invention, a rotary internal combustion engine is characterised by the fact that it comprises at least one double piston sealingly movable within the interior of a cylinder, the said double piston being reciprocable in the said cylinder and connected via an eccentric to a drive shaft such that the drive shaft rotates twice for each complete stroke of the said double piston.

[0008] The present invention has the advantage of providing a rotary internal combustion engine which can be made easily using component parts and working operations which are common in the motor industry, such as cylinders, pistons, piston rings, cylinder heads which, of course, is advantageous from an economic point of view.

[0009] In a first embodiment of the invention a first gear is keyed onto the engine drive shaft, the first gear meshing with a second gear, having inwardly directed teeth, rigidly connected to the cylinder, the first gear having a diameter equal to the radius of the second gear, and the said gears having respective axes separated by a distance equal to one quarter of the total stroke of the piston.

[0010] In the preferred embodiment the said cylinder is rotatable coaxially with respect to a fixed casing of the engine.

[0011] Various embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic side view of a rotary internal combustion engine formed as an embodiment of the present invention;

Figure 2 is a schematic view similar to Figure 1 showing the engine in a different working phase;

Figures 3, 4, 5 and 6 are schematic diagrams illustrating the engine according to the invention in a construction having a fixed cylinder and rotary shaft;

Figure 7 shows the same engine in transverse section;

Figure 8 shows the engine in axial section; and

Figures 9 to 12 schematically represent four successive working phases of a two-stroke embodiment of the engine.

[0012] Referring now to the drawings, the engine illustrated in Figures 1 and 2 is constituted, from a theoretical point of view, as an internal combustion or heat engine, having a construction in which a double piston performs the working cycle within a cylinder which rotates about an axis transversely of its length within a fixed outer body or casing, and the volume variations are obtainable from the reciprocating motion of the piston within the cylinder. The linear movement of the piston is converted into rotary motion of the engines output shaft by an eccentric gear arrangement which will be described in more detail below. The engine shaft is driven to rotate at twice the speed of the cylinder as will be described in more detail below. The piston performs the various phases of the working cycle and its kinetic characteristics, with respect to the cylinder, are similar to those of a conventional reciprocating piston heat engine.

[0013] The engine of the invention can easily be designed to run with an Otto cycle or with a Diesel cycle and may be formed as a four stroke or a two stroke engine to burn any type of fuel delivered by any type of fuel supply system (carburettor, fuel injection etc.) and may have any number of cylinders as required.

[0014] Moreover, the engine of the invention may easily be used as a volumetric pump by applying drive to the output shaft and operating the valves appropriately: this is true of most positive-displacement engines.

[0015] To operate properly, the double piston of the engine of the present invention must move within the cylinder along the longitudinal axis thereof, and to restrict the forces of friction of the piston against the cylinder walls, the arrangement must be such that the two bodies (piston and cylinder) one within the other, both rotate in the same direction about fixed axes parallel to one another and at a distance equal to one quarter of the total piston stroke, whilst the angular velocity of one must be twice that of the other; the "throw" of the crank of the crank shaft or eccentric must, also, be of a length equal to one quarter of the stroke of the double piston in the cylinder.

[0016] A construction able to satisfy these conditions is found in the application of a particular trochoid. Trochoids are the curves followed by each point on a circle rolling, without slip on a fixed line or circle. Any point in the plane of the rolling circle describes a curve called a trochoid. If the point considered is located on the rolling circle and this circle rolls on the inside of a circle the curve described is called a hypocycloid.

[0017] The operating principle of the engine of the present invention is that the transformation of the recipro­cating motion of the piston into rotary motion of the engine shaft can be based on the fact that if the rolling circle rolls internally of a fixed circle and has a diameter equal to the radius of the fixed outer circle, the hypocycloid described coincides with a diameter of the outer circle. This diameter represents the locus of the successive positions of the piston over the entire stroke, and the radius of the rolling circle thus represents the length of the effective crank arm of the engine itself. The engine of the invention, in a manner similar to conventional reciprocating piston engines, transforms the rectilinear reciprocating motion of the piston into rotary motion of the engine shaft but, differently from conventional engines, does not transmit the thrust of the expanding gas from the piston to the engine shaft via a connecting rod, but directly from the piston to the engine shaft itself in a manner which will be described in more detail hereinbelow.

[0018] By way of interpretation of what has been discussed above, and in relation to the embodiment of the engine, it can also be seen that: the fixed point on the smaller, rolling circle represents the axis of rotation of the piston; the smaller, rolling circle itself represents the primitive circle of a gear positioned on the engine shaft; and the larger, fixed circle represents the primitive circle of a gear rigidly connected to the cylinder. Moreover, the engine constituting the subject of the present invention can be made in various different practical arrangements (which are, however, conceptually analogous) with a simple kinetic transformation relating to the development of the motion, that is to say by holding the centres of the two circles fixed and making the circles rotate, or by holding fixed the circumference of the larger circle and making the smaller circle rotate.

[0019] In the first arrangement, which is illustrated schematically in Figures 1 and 2, which shows a compound piston which may be considered as a rotary piston, both the internal body constituted by the double piston proper, and the outer body constituted by the cylinder, turn in the same directional sense about respective transverse axes of rotation, the first with an angular velocity twice that of the second. Between the piston and the cylinder is formed the chamber, of variable volume, in which the working process takes place.

[0020] In the second arrangement, schematically illustrated in Figures from 3 to 6, there is shown an engine with a rotatable shaft; in this case the outer body constituted by the cylinder remains fixed and the inner body constituted by the piston moves with reciprocating rectilinear motion and drives the engine shaft to perform a planetary motion.

[0021] Figures from 7 to 12 illustrate a practical embodiment of the first arrangement, that is to say an arrangement in which the cylinder and piston both rotate. The embodiment shown is designed to operate with a two stroke Otto cycle although, obviously, the basic considerations of engine design apply equally to a four stroke engine or to one in which the second arrangement with a fixed cylinder is utilised. Referring now to Figures 7 and 8, the engine constituting the subject of the invention substantially comprises an outer fixed casing indicated 1, which rotatably supports a cylinder body 2 which has an interior cavity with a cylindrical wall 3. At each end of the cylinder there are provided respective spark plugs 4. Within the cylinder 3 there is a movable double piston capable of reciprocating motion. The double piston is composed of two oppositely facing piston crowns 5, which are provided with piston rings in the normal way in a sealing zone 6, and by a piston body 7 which connects the piston crowns 5. In the median portion of the piston body 7 engages a crank pin 10 which is eccentrically supported by a crank shaft 11.

[0022] Keyed on the crank shaft 11 there is an externally toothed pinion 12 which meshes with an inner toothing 13 defined on the body of the cylinder 2. The body of the cylinder 2 defines induction ports 20 and exhaust ports 21. On the fixed casing 1 there are provided an induction duct 30 and an exhaust duct 31.

[0023] In Figures from 9 to 12 there are illustrated, in succession, the operative phases of the engine illustrated in Figures 7 and 8. In Figure 9, in the upper part of the cylinder there is, respectively, an upper chamber 41 above the piston, that is between the piston and the cylinder head in which ignition and combustion are just commencing whilst beneath the piston in a lower chamber 42, the induction phase is just comming to an end. In the lower part of the cylinder, on the other hand, the piston defines an upper chamber 43 in which the pre-compression phase is just being completed, and a lower chamber 44 between the piston and the cylinder head, in which the exhaust and washing stage is just terminating.

[0024] In Figure 10 there is shown a subsequent stage in which the upper chamber 41 in the upper part of the cylinder is undergoing combustion and expansion whilst beneath the piston, in the lower chamber 42 of the upper part of the cylinder, the pre-compression phase is taking place. At the same time, in the lower part of the cylinder, in the upper chamber 43 the induction phase is taking place whilst in the lower chamber 44 between the pistons and the cylinder head the commencement of compression is taking place.

[0025] Figure 11 represents the same engine slightly later in the cycle. Now the upper chamber 41 has moved to become the right hand chamber in the right hand part of the cylinder, and here the expansion phase continues whilst the pre-compression phase continues on the other side of this end of the piston in the chamber 42. In the left part of the cylinder the induction and compression phases continue respectively in the chambers 43 and 44.

[0026] Figure 12 illustrates the position when the engine has come almost to the end of the working cycle. In what has now become the upper part of the cylinder, the upper chamber 44 has reached the end of compression and is ready for ignition whilst on the other side of this end of the double piston, in the lower chamber 43, the induction phase is complete. Similarly, in what has now become the lower part of the cylinder, in the upper chamber 42 the pre-compression phase has come to an end and, in the lower chamber 41, the expansion phase has finished and exhausting has commenced.

[0027] From what has been described above it will be seen that the double piston is substantially constituted by two counterposed piston crowns of a reciprocating engine, connected by a central body in the centre of which rotates the crank pin of the crankshaft. In this two-stroke embodiment the piston has been designed with the pumping zone also in the region of the piston body so that the induction of active gases and the subsequent washing are obtained in this region. It will be seen that the piston body slides within the cylinder and rotates at the same time as performing its rectilinear motion, so that the compound motion is a planetary one. In the chamber between the two ends of the piston and the cylinder those operating phases take place which in a two stroke engine of conventional form take place in the crank case chamber.

[0028] The planetary movement of the piston results from the composition of the relative movement of rotation about its axis and the "tied" movement which this latter performs about the axis of the cylinder. In other words the displacement of the piston with respect to the cylinder is equal to that of a reciprocating engine having a connecting rod of infinite length with all the positive results deriving from such a linkage, in particular an avoidance of the tendency in a conven­tional reciprocating piston engine for the connecting rod to apply lateral forces tending to rock the piston and increase the frictional forces between the piston and cylinder.

[0029] In fact, an aspect which distinguishes the engine forming the subject of the invention is the absence of such reciprocating inertia forces of the second order; for this reason, in the engine forming the subject of the invention, there is only the problem of balancing the inertia forces of the first order and these are resolved at the level of the static and dynamic balancing of a crank shaft of a reciprocating engine. Thus, with the absence of a connecting rod, the problems tied to the reciprocating forces of the second order, and the component of force exerted thereby on the piston laterally against the walls of the cylinder, permit an optimum realisation of the stroke/diameter ratio, as well as the possibility of a high speed of rotation.

[0030] Finally, again because of the absence of a conventional connecting rod, the piston does not have need of a skirt and therefore the region of the sealing rings can be very limited with great advantage as far as friction with the cylinder is concerned.

[0031] The cylinder turns axially, with respect to the outer casing 1, and carries the gears for transmission of the rotary motion from a crank shaft gear. The cylinder gear has a primitive circle with a diameter twice that of the crank shaft gear. At the end of the cylinder there are formed two cylinder heads which can be similar to those used in conventional engines.

[0032] The supply of fuel and exhaust of combustion products takes place by means of openings formed in the cylinder in the zone of contact with the casing. These openings are covered and uncovered by the angular displacement of the cylinder with respect to the casing, which supports both the carburettor and the exhaust manifold. There is, consequently, realised a distribution of rotary type obtaining in a simple manner the most appropriate diagram of distribution. In particular the induction duct is provided in the central part of the engine in order to exploit the centrifugal effect on the fuel charge caused by the outward motion of the piston, and to emphasise the direct current towards the discharge openings created by the departing combustion gases, thus obtaining an improved filling of the cylinder.

[0033] As far as all the cooling, lubrication, ignition and similar problems are concerned, the solutions are entirely similar to those of conventional engines.

Claims

1. An internal combustion engine, characterised by the fact that it comprises at least one double piston (5) sealingly movable within the interior of a cylinder (3), the said double piston (5) being reciprocable in the said cylinder (3) and connected via an eccentric (10) to a drive shaft (11) such that the drive shaft rotates twice for each complete stroke of the said double piston (5).

2. An internal combustion engine according to Claim 1, characterised by the fact that a first gear (12) is keyed onto the engine drive shaft (11) meshing with a second gear (13), having inwardly directed teeth, the first gear rigidly connected to the cylinder (3), the first gear (12) having a diameter equal to the radius of the second gear (13), and the said gears having respective axes separated by a distance equal to one quarter of the total stroke of the piston (5).

3. A rotary internal combustion engine according to Claim 1 or Claim 2 characterised by the fact that the said cylinder (3) is rotatable coaxially with respect to a fixed casing (1) of the engine.

4. A rotary internal combustion engine according to Claim 3, characterised by the fact that the double piston (5) turns about an axis substantially parallel to the axis of rotation of the cylinder (3) but spaced therefrom by one quarter of the stroke of the double piston (5).

5. An internal combustion engine according to Claim 1 or Claim 2, characterised by the fact that the cylinder (3) is fixed, the double piston (5) moves with a reciprocating rectilinear motion, and the engine drive shaft (11) performs a planetary motion driven by its interconnection with the double piston (5).

6. An internal combustion engine according to any preceding Claim, in which the space between the two opposite piston crowns of the double piston (5) is subdivided into different working chambers by bulkheads transversing the central portion of the cylinder (3).

7. An internal combustion engine according to any preceding Claim, characterised by the fact that the central region of the engine is provided with an induction conduit for deliverying fuel to the central region of the engine such that the centrifugal actions of the rotating parts encourages radially outward motion of the fuel charge towards the working chambers of the engine.

Drawing