The present invention relates, in general, to a hybrid machine including an internal combustion engine and two or more electrical machines.

A hybrid machine of the type identified above, is known, for example, from CN 104514627 .

In such known solution, the hybrid machine includes an internal combustion engine of six cylinders with the respective axes, oriented in parallel to one another and located as an angle and separated along a circumference. Each cylinder is provided with its respective piston, which is axially located. The piston of each cylinder is provided with a square- section rod, which prevents it from rotating around its own axis. The rod of each section is connected to a ball screw that cooperates with a nut, which is connected in turn - by means of a clutch - to a pinion, so that the pinion always rotates in only one direction, even if the nut rotates in both directions because of the alternate linear movement of the screw, which is rigidly connected to the piston. All pinions gear to the same output sprocket wheels, which is firmly fitted by rotation on an output shaft. Furthermore, the hybrid machine includes - for each cylinder - a respective linear electrical machine with a stator set around the piston rod of the respective cylinder; every electrical machine is configured to operate - depending on the movement direction of the respective rod - as an electrical motor to control the transfer motor of the respective rod, or as a generator to exploit the transfer movement of the respective rod to generate electric power.

The hybrid machine known from CN 104514627 has a rather complex and costly architecture. Furthermore, the maintenance of the electrical machines is far from being easy and therefore - it is also particularly costly.

Object of the present invention is developing a hybrid machine of an improved type as compared to known techniques, in particular a hybrid machine of a simpler structure and less costly than the known techniques .

This and other objects are fully achieved by the present invention thanks to a hybrid machine whose characteristics are defined in the enclosed independent claim 1. Advantageous embodiments of the invention are specified in the dependent claims, whose content is to be considered as an integral and integrating part of the description reported hereinafter.

In short, the invention is based on the idea of developing a hybrid machine including: an internal combustion engine, with a first cylinder provided with a lengthwise axis and a first piston axially sliding in the first cylinder in order to define - with the first cylinder - a first variable volume combustion chamber;

a first electrical machine and a second electrical machine, each of which is a rotary electrical machine including a respective stator and a respective rotor;

a ball screw and nut assembly fitted between the first piston of the internal combustion engine and the rotor of every aforementioned first and second electrical machines; the ball screw and nut assembly includes a screw that extends along the lengthwise axis and is solidly connected to the first piston to transfer - together with the latter - along the lengthwise axis, and at least one nut that is located coaxially to the screw and engages with the latter so that the transfer movement of the first piston and - therefore - of the screw along the lengthwise axis becomes a rotary movement of the latter at least one nut around the lengthwise axis; a rotating output organ;

first means of connection set to connect in a disconnectable way at least one nut to the rotor of the first electrical machine depending on the relative direction of rotation of said at least one nut as related to the rotor of the first electrical machine, so that the first electrical machine, which operates from the motor, is set to control - through said at least one nut - the transfer of the screw and - subsequently - of the first piston, in a first direction;

second means of connection set to connect in a disconnectable way at least one nut to the rotor of the second electrical machine depending on the relative direction of rotation of said at least one nut as related to the rotor of the second electrical machine, so that the second electrical machine, which operates as a motor, is set to control through said at least one nut - the transfer of the screw and - therefore - of the first piston, in a second direction, opposite to the first one; and

third means of connection set to connect in a disconnectable way said at least one nut to the rotating output organ so that the rotating output organ is controlled by the rotation of said at least one nut in a given direction, irrespectively on the rotation direction of said at least one nut, i.e. irrespectively on the transfer direction of the first piston.

Thanks to such configuration, a hybrid machine in compliance with the invention allows giving up the crankshaft and the cranking mechanism that are typically utilized in the internal combustion engines.

The absence of the crankshaft and of the cranking mechanism allows for a remarkable structural simplification of the internal combustion engine, with all subsequent advantages related to reduced weight, friction, wear, etc., as well as with an increased combustion efficiency and with an increased motion transmission efficiency.

Furthermore, a hybrid machine in compliance with the present invention allows for the selective optimization of some internal combustion engine parameters, in particular, allows varying the bottom dead center and the top dead center of the internal combustion engine piston, as function of the used fuel, or of the specific performance requested, thus allowing to select optimum displacement and compression ratio.

Furthermore, as compared to the aforementioned known technique, a hybrid machine in compliance with the present invention has a simpler structure and can be developed at a lower cost, thanks to the use of rotary electrical machines. Furthermore, the use of rotary electrical machines makes simpler and more cost-effective the maintenance of the hybrid machine in compliance with the invention as compared to the aforementioned known technique.

Further characteristics and advantages of the present invention will be more clearly shown in the detailed description hereinafter, which are provided as a mere example without limitations, with reference to the enclosed drawings, where:

figure 1 is a sectional view of a hybrid machine in compliance with an embodiment of the present invention;

figure 2 is a sectional view of a hybrid machine in compliance with a further embodiment of the present invention;

figure 3 is a schematic view of a vehicle including a hybrid machine in compliance with the present invention;

figure 4 is a schematic view of a hybrid machine in compliance with a further embodiment of the present invention; and

figure 5 is a schematic view of a hybrid machine in compliance with a further embodiment of the present invention.

With initial reference to figure 1, a hybrid machine in compliance with the embodiment of the present invention is indicated as a whole by 10 and essentially includes an internal combustion engine 12 and a pair of rotary electrical machines, respectively marked in the figure with reference numbers 14a and 14b and - from now on - indicated respectively as first and second electrical machine.

The hybrid machine 10 is set to control in rotation - in a given direction - a rotating output organ 0, which is a hub in the embodiment in figure 1, but which can also be a shaft, as in the embodiment in figure 2, or any other type of rotary organ. As it results more clearly further on in the description, the hybrid machine 10 can be used to operate as an engine, in order to generate mechanical power through which one can control - for instance - the drive wheels of a vehicle in rotation, in which case the rotary output organ shall be connected through an appropriate transmission system, which includes - for instance - a transmission shift and a differential gear, to the vehicle drive wheels. As an alternative, the hybrid machine 10 can be utilized to operate as a generator to generate electric power, in which case the output organ shall be connected to the rotor of an electrical generator.

The embodiments shown in the figures refer to this second case, i.e. to the case in which the hybrid machine 10 is coupled to an electrical generator to generate electric power.

The internal combustion engine 12 can operate utilizing any fuel (fossil fuel, biofuel, hydrogen, etc.) and it can further operate at either two or four strokes. The following description refers to a four-stroke internal combustion engine using a fossil fuel, being understood that the internal combustion engine can be - in alternative - a two-stroke engine and/or can - in alternative

- utilize other types of fuel.

The internal combustion engine 12 includes a cylinder 16, which extends along a lengthwise axis x. A piston 18 is slidingly fitted to the cylinder 16 along the lengthwise axis x and defines with the cylinder 16 a variable volume combustion chamber 20, with minimum volume when the piston 18 is at its top dead center and a maximum volume when the piston 18 is at its bottom dead center.

Furthermore, the internal combustion engine 12 includes an intake and exhaust system 22 to control the intake and exhaust phases of the engine operational cycle, whose operation is known per se.

The intake and exhaust system 22 includes

- as known per se - at least one intake valve 24 to allow for the entry of a mixture of air and fuel inside the combustion chamber 20 of cylinder 16 during the intake stage and one exhaust valve 26, able to allow for the exhaustion of the combusted gases to the outside of the combustion chamber 20 during the exhaust step. The number of the intake and exhaust valves 24 and 26 can vary and be of different types, which are known per se. The intake and exhaust valves 24 and 26 can be operated as know per se, e.g. by mechanical or electro-mechanical actuators.

The internal combustion engine 12 generates in sequence - as known per se - an intake step, a compression step, an expansion step and an exhaust step.

Each of the two electrical machines 14a and 14b includes - as known per se - a rotor (which is indicated by 28a for the first electrical machine 14a and by 28b for the second electrical machine 14b) and a stator (indicated by 30a for the first electrical machine 14a and by 30b for the second electrical machine 14b) , which are coaxially located onto the cylinder 16 of the internal combustion engine 12, so that the rotor 28a, 28b of every electrical machine 14a, 14b rotates around the lengthwise axis x. The electrical machines 14a and 14b of the brushless type are preferable.

Furthermore, the hybrid machine 10 includes a ball screw and nut assembly 32, in particular of the recirculating ball type, fitted between piston 18 and rotors 28a and 28b of the first and second electrical machines 14a and 14b to allow converting the transfer movement of piston 18 along the lengthwise axis x into a rotation movement of rotor 28a and/or of rotor 28b around the longitudinal axis x, and vice-versa.

The screw-nut 32 includes a screw 34 and a cross head screw 36, one of which is rigidly connected to the piston 18 of the internal combustion engine 12 so that it is connected to it in the alternate transfer movement along the lengthwise axis x. In particular, in the proposed embodiment, the screw 34 is rigidly connected to the piston 18 and - precisely - on the opposite side of the piston as related to the combustion chamber 20. As an alternative, in any case, the piston 20 could be rigidly connected to the nut 36, instead of the screw 34.

The unit consisting of piston 18 and screw 34 is provided with an anti-rotation system, so that it is bound to transfer along the lengthwise axis x, and it cannot rotate around such axis.

Even though the embodiment shown in figure 1 includes only one cross head screw 36, associated to both rotors 28a and 28b of the electrical machines 14a and 14b, a nut could in any case be provided on each electrical machine; each nut would be associated to the rotor of the respective electrical machine and each of them gearing with the screw 34.

Each of the rotors 28a and 28b of the first and second electrical machine 14a and 14b is connected to the rotation of the nut 36 in disconnectable mode through a respective clutch device (indicated as 38a for rotor 28a and as 38b for rotor 28b) , which can be an overrunning clutch, as in the embodiment in figure 1, or - as an alternative - an electromagnetic clutch or another similar clutch device of known type, so that it is connected to rotate with the nut 36 only when the rotor 28a or 28b and the nut 36 rotate one related to the other in a given rotation direction and they are instead free to rotate as related to the nut 36 when rotor 28a or 28b and nut 36 rotate one related to the other in the other rotation direction.

More specifically, the two clutch devices 38a and 38b are configured so that they connect in rotation the respective rotors 28a and 28b with the nut 36 when the rotors 28a and 28b rotate related to nut 36 in opposite directions one to the other, as will be more clearly explained in the description of the hybrid machine operation, which is provided further on in this document. Each of the two electrical machines 14a and 14b can operate as a motor to control in rotation the nut 36 around the lengthwise axis x in a respective direction, and therefore to generate the axial transfer of the screw 34 and of the piston 18, which is connected thereto in a respective direction. In particular, the direction by which the first electrical machine 14a controls in rotation the nut 36, and therefore controls the transfer of screw 34, is opposite to the direction by which the second electrical machine 14b controls in rotation the nut 36, and therefore controls the transfer of screw 34. In this way, the two electrical machines 14a and 14b allow operating the internal combustion engine 12, developing the variations in volume of the combustion chamber 20 as required for the intake, compression and exhaustion phases. Obviously, the two clutch devices 38a and 38b are configured so to make the respective rotor 28a and 28b connected in rotation with the nut 36 in a first direction and - respectively - in a second direction as opposite to the first one.

Preferably, one of the two electrical machines 14a and 14b, and - precisely - the electrical machine (in this case, the first electrical machine 14a) which results to be connected in rotation to the nut 36 when the piston 18 is thrust by the combustion of the fuel in the combustion chamber 20 during the expansion step, can also operate as generator to generate electric power during such step of the work cycle of the internal combustion engine 12.

Each of the two electrical machines 14a and 14b is associated - in a way which is known per se - to a respective drive and control device 40a and 40b managed by an Electronic Control Unit.

The Electronic Control Unit manages the general operation of the hybrid machine 10, controlling not only the electrical machines 14a and 14b, but also - for example - the intake and exhaust valves 24 and 26, in compliance with set, programmable and/or updatable control logics.

In the embodiment shown in figure 1, the rotary output organ 0 is a hub located around the nut 36, coaxial with the nut itself, so that the latter controls it around the lengthwise axis x.

To this purpose, a clutch device 46 is fitted between the nut 36 and the rotary output 0. In this case, the device is an overrunning clutch, but it could be an electro-magnetic clutch or another similar clutch device of a known technique, configured to connect in rotation the rotary output organ 0 to the nut 36 in a given rotation direction.

Furthermore, the embodiment shown in figure 1, where the hybrid machine 10 is used to generate electric power, includes an electric generator 42 with a rotor 44 located around the rotary output organ 0, coaxial thereto and rigidly connected in rotation to the latter around the lengthwise axis x. Thanks to the clutch device 46, the rotor 44 of the electric generator 42 is connected in rotation to the nut 36 only in a given direction of relative rotation between rotor 44 and nut 36, and - precisely - when the nut 36 is set into rotation by the screw 34 during the expansion step of the internal combustion engine 12. During such step, therefore, the rotor 44 is set into rotation by the ball screw and nut assembly 32 and thus the electric generator 42 generates electric power .

Instead of being a hub that is coaxially located to the nut 36, the rotary output organ O could be - as an alternative - a shaft located parallel and at a distance to the lengthwise axis x and connected to the nut 36 through transmission means that are known per se, such as - for instance - belts. Also in this case, one or more clutch devices would be provided: for instance, one or more overrunning clutches, able to allow the transmission of the rotary motion from the nut 36 to the rotary output organ 0 only when the nut 36 is controlled in rotation by the screw 34 during the expansion step of the internal combustion engine. Such alternative location of rotary organ 0 and - therefore - of the electric generator associated thereto shall be described in detail further on in this document with reference to the embodiment shown in figure 2.

The electric generator 42 is preferably connected to a storage battery 48 to store the electric power generated by the electrical generator 42. Furthermore, in case one of the two electrical machines 14a and 14b is set to operate also as generator, as is the case of the first electrical machine 14a, the storage battery 48 shall be connected to such electrical machine, through the respective driving and control device (in this case the driving and control mechanism 40a) .

The hybrid machine 10 which has been described above operates as follows.

In a first step (intake step) the first electrical machine 14a is operated by the respective driving and control device 40a to operate as a motor, using electric current retrieved from the storage battery 48, and therefore to set into rotation the nut 36, in such a direction that the screw 34, and with it the piston 18, is transferred along the lengthwise axis x towards the left, as referred to the point of view of the observer of figure 1, in order to increase the volume of the combustion chamber 20. In other words, in this step the piston 18 is moved from the top dead center to the bottom dead center.

In this step, the nut 36 is connected in rotation to the rotor 28a of the first electrical machine 14a through the clutch device 38a associated to said machine. The rotor 28b of the second electrical machine 14a is - instead - disconnected from the nut 36 thanks to the clutch device 38b associated thereto. As related to the rotor 44 of the electric generator 42, in case of use of an overrunning clutch like the clutch device 46 to connect the rotary output organ 0 with the nut 36, the rotor 44, at such stage, shall be connected in rotation to the nut 36, while, in case of use of an electro-magnetic clutch, or of a similar controllable clutch device, as a clutch device for the connection of the rotary output organ 0 with the nut 36, at this step the rotor 44 shall be preferably disconnected from the nut 36 and therefore, it will not be dragged into rotation by the latter.

During this step, the intake valve 24 is opened in order to allow for the intake of the air-fuel mix within the combustion chamber 20. The advantage is that the Electronic Control Unit can control - at this stage - the first electrical machine 14a, through the respective driving and control device 40a, in order to vary the bottom dead center of piston 18, for instance as function of the power required and/or as function of the type of fuel used, thus obtaining a variable displacement internal combustion engine.

In a second step (compression step) , which starts once the piston 18 has reached the bottom dead center, the second electrical machine 14b is operated by the respective drive and control 40b to operate as a motor, utilizing electric current retrieved from the storage battery 48, and then setting into rotation the nut 36 in the opposite direction as related to the one of the previous intake step, so that the screw 34 - and with it the piston 18 - is transferred along the lengthwise axis x towards the right, in order to reduce the volume of the combustion chamber 20. In this stage, therefore, the piston 18 moves from the bottom dead center to the top dead center.

In this step, the nut 36 is connected in rotation to the rotor 28b of the second electrical machine 14b through the clutch device 38a associated to that machine. Both the rotor 28a of the first electrical machine 14a and the rotating output organ 0, and therefore the rotor 44 of the electrical generator 42, are instead disconnected from the nut 36 thanks to the clutch devices 38a and 46 that are associated thereto.

During such step, the intake and exhaust valves 24 and 26 are kept closed in order to allow for the compression of the air-fuel mix within the combustion chamber 20.

The advantage is that the Electronic Control Unit at this step can control the second electric machine 14a in order to vary the top dead center of piston 18, for instance as function of the compression ratio and/or of the combustion pressure required.

Once the compression step is completed, i.e. once the piston 18 has reached the top dead center, the combustion of the fuel is primed either by a spark plug or as a result of the compression itself of the fuel, depending upon the fuel utilized, in compliance with modes that are known per se.

As a result of the increased volume of the combustion chamber 20 after the combustion, the piston 18 is axially displaced, in the direction from the top dead center to the bottom dead center (expansion step) . Consequently, also the screw 34, which is rigidly connected to the piston 18, is transferred axially in the same direction, thus generating the rotation of the nut 36. In this step, the nut 36 is connected in rotation to the rotary input organ 0, and therefore to the rotor 44 of the generator 42, through the clutch device 46 and - preferably - also to the rotor 28a of the first electrical machine

14a through the clutch device 38a. Therefore, the generator 42 and - preferably - also the first electrical machine 14a operate at this stage as generators to generate electric power; the generated energy is transferred to the storage battery 48.

After the expansion step, the last step (exhaustion step) of the internal combustion engine 12 takes place; during this stage the exhaust valve 26 is opened to allow for the exhaustion of the combusted gases from the combustion chamber 20 and the piston 18 is moved from the bottom dead center to the top dead center using, as a motor, the second electrical machine 14b, as it was previously described as referred to the compression step.

A further embodiment of a hybrid machine in compliance with the present invention is shown in figure 2, where identical parts and elements, or elements corresponding to those of the hybrid machine shown in figure 1 are identified by identical or similar reference numbers. The hybrid machine 10 shown in figure 2 differs from the one shown in figure 1 mainly because the internal combustion engine includes a second cylinder 16', which is coaxially located as related to the cylinder 16 (from now on indicated as first cylinder 16), where a second piston 18' is axially sliding in order to define with the second cylinder 16' a second variable volume combustion chamber 20' . The second cylinder 20' is provided with second intake and exhaustion valves, which are respectively indicated as 24' and 26'.

Also the second piston 18' is rigidly connected to the screw 34 of the screw nut 32, in particular to the end of screw 34, which is opposite to the one 18 (from now on indicated as first piston 18) to which it is connected. The two cylinders 16 and 16' are therefore oppositely located, with the relevant pistons 18 and 18', which - being rigidly connected to the opposite ends of the screw 34 - axially move in opposite directions to each other, together with the screw 34. For instance, when the first piston 18 moves from the bottom dead center to the top dead center, the second piston 18' will move from the top dead center to the bottom dead center and vice versa.

As in the embodiment shown in figure 1, also in the embodiment shown in figure 2 the hybrid machine 10 is used to control an electrical generator 42, which is able to generate electric power using the transfer movement of the screw 34 during the combustion stages of the internal combustion engine 12.

Unlike the embodiment shown in figure 1, where - since the sole cylinder 16 is provided - the screw 34 moves in only one directions (from right to left for the observer of figure 1) during the expansion step, in the embodiment shown in figure 2, the screw 34 will move in one direction (from the right to the left) during the expansion step in the first cylinder 16 and in the opposite direction (from the left to the right) during the expansion step of the second cylinder 16'. The electrical generator 42 can therefore exploit the movement of the screw 34 in both directions, in order to generate electric power.

For this purpose, the embodiment shown in figure 2 includes two nuts 36a and 36b, from now on indicated respectively as first nut and second nut, which engage respectively to the screw 34 and that are respectively associated to the first electrical machine 14a and to the second electrical machine 14b. In particular, the two nuts 36a and 36b engage with respective portions of the screw 34, which are respectively indicated as 34a and 34b, with opposite winding directions one to the other, so that the two nuts 36a and 36b are set into rotation in opposite directions one to the other one when the screw 34 moves in a given direction.

Furthermore, in the embodiment shown in figure 2, the rotary output organs 0 is located non-coaxial to the screw 34, as is instead in the embodiment shown in figure 1, turns around a rotation axis x' parallel and set at a distance to the lengthwise axis x. In particular, the rotary output organ 0 is - in this case - developed as a shaft.

The rotary output organ 0 is connected both to the first nut 36a - e.g. through a first belt 52a and a first pulley 54a - and to the second nut 36b, e.g. through a second belt 52b and a second pulley 54b. The two pulleys 54a and 54b are fitted on the rotary output organ 0, in particular at the opposite ends of the same organ, each of them by means of a respective clutch device (such as an overrunning device, as in the embodiment shown in figure 2), which is respectively indicated as 46a for the first pulley 54a and as 46b for the second pulley 54b.

The rotor 44 of the electrical generator 42 is fitted, fixed to rotate, on the rotary output organ 0 to rotate with it around the rotation axis c' .

A variation embodiment, which is not shown, would include two rotary output organs, which are coaxially located to the screw and each of them connected - through a respective clutch device - to a respective nut (in case of two cross-head nuts) or to the nut (in case of only one nut) .

The operation of a hybrid machine 10 according to the embodiment shown on figure 2 will now be described, again on the assumption of a 4-stroke operation of the internal combustion engine 12 (even though, as already mentioned, the internal combustion engine 12 could also operate at two strokes) .

The first electrical machine 14a, operating as a motor, retrieves electric power from the storage battery 48 and sets into rotation in a given direction the first nut 36a, which is connected in rotation to the rotor 28a of said machine through the clutch device 38a. The rotation of the first nut 36a is converted into axial transfer of the screw 34, and then of the pistons 18 and 18' that are connected thereto, in a first direction (from right to left for the observer of figure 2) . The first piston 18 then moves in the first cylinder 16 in the direction from the top dead center to the bottom dead center. At the same time, the first intake valve 24 (i.e. the intake valve of the first cylinder 16) is opened, in order to allow for the intake of the air-fuel mix within the combustion chamber 20.

During this step, it would be convenient - only during the starting of the machine - to keep the second intake and exhaust valves 24' and 26' open, in order to minimize the forces to be counteracted along the lengthwise axis x .

At the end of the intake step in the first cylinder 16, the second electrical machine 14b is operated as a motor to control the second nut 36b in rotation in a given direction. This generates the transfer of screw 34 along the lengthwise axis x, and - with it - of the two pistons 18 and 18' connected to it, in a second direction opposite to the first one (i.e. from left to right for the observer of figure 2) .

The first piston 18 is therefore moved from the bottom dead center to the top dead center and - at the same time - the first intake and exhaust valves 24 and 26 are kept closed, in order to allow for the compression of the air-fuel mix within the combustion chamber 20 in the first cylinder 16.

At the same time, the second piston 18' is moved from the top dead center to the bottom dead center, while the second intake valve 24' is opened to allow for the introduction of the air-fuel mix into the second combustion chamber 20 ' . Therefore, while the compression step takes place in the first cylinder 16, the second cylinder 16' performs the intake stage.

Once the compression step is completed in the first cylinder 16, the combustion is primed in the combustion chamber 20 of said cylinder. As a consequence of the increased volume in the combustion chamber 20 of the first cylinder 16, the first piston 18 is thrust along the lengthwise axis in the aforementioned first direction, thrusting with it the screw 34 and the second piston 18'. At this step, since the rotor 28a of the first electrical machine 14a is preferably connected in rotation with the first cross head screw 36a through the clutch device 38a, the first electrical machine 14a can operate as a generator to generate electric power.

At this stage, also the rotor 44 of the electrical generator 42 is set into rotation through the ball screw and nut assembly 32, as a result of the transfer of the screw 34 in said first direction, and thus generates electric power to be sent to the storage battery 48.

At the same time, the second intake and exhaust valves 24' and 26' are kept closed, in order to allow for the compression of the air- fuel mix within the second combustion chamber 20'. Part of the mechanical energy obtained from the combustion in the first combustion chamber 20 is then transferred from the screw 34 to the second piston 18' in order to allow for the compression of the air-fuel mix inside the second combustion chamber 20'.

Therefore, while the expansion step takes place in the first cylinder 16, the second cylinder 16' performs the compression step.

Once the compression step is completed in the second cylinder 16', the combustion of the mix contained in the second combustion chamber 20' is primed. As a result of the combustion in the second combustion chamber 20', the second piston 18' is thrust along the lengthwise axis x in the aforementioned second direction, and therefore from the top dead center to the bottom dead center, thrusting with it the screw 34 and the first piston 16.

As already described above as related to the expansion step in the first cylinder 16, during the expansion step in the second cylinder 16', the rotor 28b of the second electrical machine 14b and the rotor 44 of the electrical generator 42 are set into rotation around the respective axes x and x'; subsequently, both the second electrical machine 14b and the electrical generator 42 generate electric power.

At the same time, the first exhaust valve 26 opens to allow for the exhaustion of the combusted gases from the first combustion chamber 20.

A hybrid machine 10 in compliance with the present invention can be used for the most diversified requirements of power generation, be it mechanical or electric, within the framework of transport, with particular reference to the automotive sector, in the industrial or agricultural environments, etc.

In particular, a hybrid machine in compliance with the present invention can be advantageously utilized on a motorcar, as schematically shown in figure 3 of the enclosed drawings.

With reference to figure 3, the vehicle can include one or more electrical motors 58, appropriate to control in rotation one or more wheels 60 of a vehicle. In this example, relevant to a four-wheel vehicle 5, four electrical motors 58 are included, each of them associated to a respective wheel 60. The electrical motors 58 are preferably motors of the brushless type and are controlled by a drive and control system 62, under the management of the Electronic Control Unit, using the electric power stored in the storage battery 48.

As an alternative, the rotary output organ of the hybrid machine could be connected - through a transmission shift and a differential gear - to the drive wheels of the vehicle to control them in rotation.

A hybrid machine in compliance with the present invention has several advantages.

First of all, the absence of a crankshaft and of a cranking mechanism to convert the piston transfer movement into rotary motion allows for a remarkable simplification of the internal combustion engine layout.

Furthermore, the elimination of the crankshaft and of the cranking mechanism involves the elimination of the so-called "parasite" absorbed torsional moments, with a subsequent reduction of the energy requirements and - finally - of fuel consumption. Furthermore, the absence of crankshaft allows - with the presence of a sufficient number of cylinders - to disengage the management of a cylinder from the one of the other one, and - subsequently - to adjust the machine so to distribute the load and the power requirements in a diversified way among the cylinders, with the support - for instance - of the Electronic Control Unit.

In general, the reduction in the number of the internal combustion engine components allows reducing both the weight and the design and development costs, besides simplifying the maintenance of the engine.

The best tribological features of the contact components (nuts and screws of the ball screw and nut assembly) allow for a significant reduction of friction and wear. Consequently, this also reduces the consumption of oil thanks to a lower heat exchange between the components to be lubricated, besides a lower number of components to be lubricated.

Furthermore, the use of a recirculating ball screw-nut to convert the transfer movement of the piston/s into rotary motion allows for remarkable compactness of the system.

Furthermore, if is it allowed acting on the positions of the top and bottom dead centers, the hybrid machine in compliance with the invention allows optimizing the combustion process by acting - either jointly or separately - on two parameters: the displacement and the compression ratio, i.e. the compression pressure. Both parameters can be adjusted by controlling the axial transfer of the screw, i.e. of the rotation of the nuts. In particular, at start-up, the displacement can be adjusted as a function of the power required, thus reducing the power requirement. The absence of the starter motor, whose function is instead covered by an electrical machine, allows for a faster more efficient start-up of the internal combustion engine .

Furthermore, the ability to use different control and programming strategies for the use of different fuels allows optimizing the combustion also with the variation of the type of used fuel.

As related to the performance of the system, the hybrid machine in compliance with the invention allows improving the useful torque curves, an enhancement of the operational interval and - subsequently - a general increment of the efficiency.

Essentially, the optimization of the combustion process, the reduction of weight and the reduction of the mechanical losses contribute to the general reduction of the vibrations and of the polluting and acoustic emissions - at the same power delivered, which is particularly advantageous in view of the application of the invention to the automotive industry or - in more general terms - within the framework of the means of transport.

With reference to Figures 4 and 5, two further embodiments of the hybrid machine of the invention will be described below. This is an innovative system of a combustion engine with two opposed pistons which move in a single cylinder. In the system, in a four- stroke cycle, the cylinder is equipped with a intake valve to allow air or a mixture to enter, and with an exhaust valve to allow gas to go out at the end of the combustion. In the system in a two-stroke cycle, instead, the cylinder is not equipped with valves, but is equipped with openings, suitably placed, which are opened or closed during the stroke of the piston into the cylinder. This machine has a great flexibility and modularity in managing independent strokes and displacement speeds for every single piston in the cylinder; this allows optimizing at a maximum the steps of intake (air, mixture) and exhaust (burnt gases) , improving engine thermal and mechanical efficiency, and providing a strong reduction of weight due to the lack, with respect to current endothermic engines, of the assembly for transforming the linear motion into rotary motion: rod - crank and camshafts for moving the valves, where provided, while no heavy and costly mechanical transmission members are necessary any more, through the use of power on a single shaft.

In fact, energy which derives from the active mixture combustion step, the expansion, generates the relative displacement to move away the two pistons in the same cylinder: every piston is rigidly connected (also with a rotation-preventing system) with a ball screw, which linearly moves along the cylinder-piston axis. The screw, during its translation, impresses a rotary motion to the nuts connected thereto, which are fixed in their seats.

The nuts of both screws are made integral, by means of a clutch or free wheel (to allow the rotation along a single working direction) , with one or more rotors of brushless motors, and in a redundant way, by means of a clutch or a free wheel, to the rotor of a generator of electric energy (alternator, dynamo) . The electric energy produced during the rotation is sent to a suitable accumulator.

The screws have a threading with one pitch inverse with respect to the other (a rightward one and a leftward one, or vice versa) , to be able to always move the rotor of the electric generator always along a single rotation direction. The rotor, not being on the same axis of cylinder, piston, screws and nuts, can rotate by means of belts (of the toothed, trapezoidal type, etc.) on suitable pulleys.

The operating cycle for a four-stroke engine will now be described with reference to Figure 4.

Firstly, in the hybrid machine, a first brushless motor 43, with its own first actuation and control 44, managed by a first ECU 42, takes the electric current from a first accumulator 411 and rotates a first nut 45 (made integral with a suitably placed clutch or free wheel) and a first screw 46 coupled thereto translates with a first piston 47 connected thereto, from the central dead center of a first cylinder 41 at the opposite end. With a suitably open first intake valve 413', intake of air or mixture in the first cylinder 41 occurs.

Similarly, the machine is composed of a second piston 47' integral with a second screw 46', with a contrary pitch to the corresponding first screw 46, of a second nut 45' and of second and third brushless motors 43' and 49', and moves in a mirror and simultaneous way to the first brushless motor 43, the intake step thereby occurring. The piston stroke can change to generate the most suitable displacement to satisfy a required power .

Moreover, a fourth brushless motor 49, with its own second actuation and control 410, takes the electric current from the first accumulator 411, checks the intake end-of- stroke and rotates the first nut 45 (made integral with a suitably placed clutch or free wheel) , which translates the first screw 46 keyed to the first piston 47 till the central dead center in the first cylinder 41, with closed valves, performing the compression step . Similarly, the system behaves in a mirror and simultaneous way with its second and third brushless motors 43' and 49', completing the compression step. The piston stroke can change to obtain the most suitable compression ratio to optimize the cylinder combustion.

Moreover, the first brushless motor 43 with its own first actuation and control 44, managed by the first ECU 42, takes the electric current from the first accumulator 411, and checks the final stroke of the first piston 47 in the compression step. In the first cylinder 41, at this time, the combustion occurs and the related pressure increase operates onto the head of the first piston 47, and translates it from the central dead center towards the opposite end, and the expansion step occurs. The first piston 47 is rigidly connected to the first screw 46, which, during its movement along the axis of the hybrid machine, rotates the first nut 45, the rotor of the first brushless motor 43 and, by means of a connection with a belt-pulley system, etc., the shaft carrying the rotor of a second electric generator 412 (made integral by suitably placed clutches or free wheels, which generate electric energy to send to a second accumulator 311. This occurs similarly, in a mirror and simultaneous way, for the second and third brushless motors 43' and 49' completing the expansion step.

Moreover, the fourth brushless motor 49, with its own second actuation and control 410, managed by the second ECU 42, takes the electric current from the first accumulator 411 and, at the end of the expansion, rotates the first nut 45 (made integral thereto by a suitably placed clutch or free wheel) which translates the first screw 46 with its related first piston 47 to the central dead center. With the suitably open first valve 413, the exhaust step occurs for the burnt gas in a suitable duct. Simultaneously, the second and third brushless motors 43' and 49' operates in the same way, completing the exhaust step.

The operating cycle for a two-stroke engine will now be described with reference to Figure 5.

Differently from the four-stroke endothermal engine, in which the complete working cycle occurs with four stokes of the piston in the cylinder, in the two-stroke endothermal engine, the working cycle is completed only with two strokes of the piston.

Firstly, in the hybrid machine, a fifth brushless motor 29, with its own third actuation and control 210, managed by a third ECU 22, takes the electric current from a third accumulator 211, and checks the expansion end-of-stroke by rotating a third nut 25 (made integral thereto by a suitably placed clutch or free wheel) and a third screw 26, coupled thereto, translates, with a third piston 27 connected thereto, till the central dead center of a third cylinder 21. During its stroke, the third piston 27 covers the openings, suitably obtained in the third cylinder 21, namely the entering opening 213 for air or mixture from the intake duct, and the exiting opening 214 of the burnt gas from the exhaust duct. These openings 213, 214, uncovered by the third piston 27 during its stroke in the expansion step, have allowed so far a flow of air or mixture to enter (intake step) and a flow of burn gas to exit (exhaust step) from the third cylinder 21. The third piston 27, after having covered the intake and exhaust openings 213, 214, compresses air or the mixture till it gets to the central dead center of the third cylinder 21.

Similarly, the hybrid device comprises a fourth piston 27' integral with the fourth screw 26' , with a contrary pitch to its corresponding third screw 26, a fourth nut 25' , a sixth and a seventh brushless motors 23' and 29' , and moves in a mirror way with respect to the fifth brushless motor 29, completing the compression step.

Also in this case, the hybrid engine is very flexible and modular: the piston stroke can change to obtain the most suitable compression ratio, to optimize the cylinder combustion. The piston speeds can change during the stroke, to optimize the intake and/or exhaust steps.

Moreover, the eight brushless motor 23, with its own fourth actuation and control 24, managed by a fourth ECU 22, takes the electric current from the third accumulator 211, checks the end-of-stroke of the compression step, activating the third nut 25 (made integral thereto by a suitably placed clutch or free wheel) . During the end of compression step, a combustion occurs in the mixture, with its related, sudden pressure increase, which acts on the head of the third piston 27, which translates from the central dead center towards the opposite end of the third cylinder 21, and the expansion step occurs. The third piston 27 is rigidly connected to a third screw 26, which, during its movement along the axis of the third cylinder 21, rotates the third nut 25, the rotor of the eighth brushless motor 23 and, by means of a connection with a belt-pulleys system etc., the shaft carrying the rotor of the second electric generator 212 (made integral thereto by suitably placed clutches or free wheels), which generate the electric energy to be sent to the third accumulator 211. Similarly, this occurs in a mirror and simultaneous way for the sixth and seventh brushless motors 23' and 29' .

An hybrid machine equipped with a four- stroke operating cycle could easily pass to a two-stroke operating cycle, with much higher thermal efficiency due to its extreme flexibility in moving the valves.