Abstract:
A method is provided for diagnosing the integrity of a swirl generating system for an internal combustion engine. The swirl generating system includes, but is not limited to swirl controlling elements that are individually located in a respective air passage connecting the intake manifold of the engine to an intake port of an engine combustion chamber, an actuator having a movable shaft, a cinematic chain for mechanically connecting the swirl controlling elements to the actuator movable shaft, an actuator control unit for normally moving the actuator movable shaft in a first direction towards a first final position, and in a second opposite direction towards a second final position, and actuator sensor for sensing the position of the actuator movable shaft. The method providing to arrange at least a mechanical stop for directly acting on one component of the cinematic chain, in order to indirectly limit the movement of the actuator movable shaft in the first direction at a first checking position coincident or beyond the first final position, command the actuator control unit for moving the actuator movable shaft in the first direction towards the first checking position, and verify through the position sensing means whether the actuator movable shaft stops in the first checking position (CP 1 ) or goes beyond.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to British Patent Application No. 0916054.0, filed Sep. 14, 2009, which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to internal combustion engines, especially of Diesel type, which are equipped with an air induction system arranged for generating swirl in the combustion chambers of the engine. 
       BACKGROUND 
       [0003]    In the field of internal combustion engines, it is known that turbulence may improve the preparation of the air-fuel mixture in the combustion chamber and the combustion thereon, to thereby improving the performance of the engine. Conventional air induction system generally provides each combustion chamber of the engine with at least a straight inlet port, which is formed for minimizing the resistance to the intake airflow, and thereby increasing the volumetric efficiency. 
         [0004]    When the engine is operating at high load, although the flow resistance of the inlet port is low, sufficient turbulence is caused in the combustion chamber for keeping the air-fuel mixing and combustion at acceptable level. On the contrary, when the engine is operating at low and medium load, the low flow resistance of the inlet port and the low velocity of the intake airflow are not generally sufficient to generate adequate turbulence in the combustion chamber. 
         [0005]    In order to improve turbulence, have been proposed air induction systems which provide each combustion chamber of the engine not only with a straight inlet port, but also with a further swirl inlet port specifically designed for imparting swirling motion to the intake airflow. A swirl inlet port of this kind is the so called helical port, which extends helically around the axis of the intake valve seating surface. Such air induction systems further comprises a swirl controlling element for each combustion chamber of the engine, typically in form of a rotating flap. 
         [0006]    This swirl controlling flap is located in a passageway connecting the intake manifold to the straight inlet port of the combustion chamber, for selectively close said passageway in accordance with engine load conditions. When the engine is operating at low or medium load, the swirl controlling flap is kept in closed position for preventing the intake air to flow through the straight inlet port. Therefore, the major portion of the intake air flows into the combustion chamber through the swirl inlet port, achieving a strong turbulence. 
         [0007]    When the engine is operating at high load, the swirl controlling flap is kept in open position for allowing intake air to flow into the cylinder through the straight port. The major portion of the intake air flows into the combustion chamber through the straight inlet port, due to the less flow resistance of the latter relative to the swirl inlet port, to thereby reducing pressure drop and achieving a high volumetric efficiency. 
         [0008]    All swirl controlling flaps are simultaneously rotate between their open and closed position by means of a common electromechanical actuator. The electromechanical actuator generally comprises a movable shaft which is called actuator shaft. The electromechanical actuator can be of the rotational or linear kind, such that the actuator shaft is a rotating shaft or a reciprocating shaft respectively. 
         [0009]    The actuator shaft is mechanically coupled with the swirl controlling flaps by means of a proper cinematic chain, which shall comprise gears or levers. The cinematic chain is provided for transforming any rotation or linear movement of the actuator shaft to a correspondent rotation of the swirl controlling flaps. 
         [0010]    The electromechanical actuator further comprises an embedded position sensor for real time sensing the angular or linear position of the actuator shaft. The electromechanical actuator is controlled by an engine control unit, on the base of the signal from the position sensor and the engine operating condition. 
         [0011]    Alternatively, the electromechanical actuator can be provided with an embedded microprocessor based controlled, which control the rotations of the actuator shaft on the base of the signal from the position sensor, and which is connected to the engine control unit, for receiving from the latter instructions about the positions to reach in response of engine operating conditions. As a matter of fact, the engine control unit detects the position of the actuator shaft and the operating condition of the engine, and when the engine is operating at low or medium load, commands the electromechanical actuator to rotate the swirl controlling flaps in closed position, and when the engine is operated at high load, commands the electromechanical actuator to rotate the swirl controlling flaps in open position. Therefore, during normal operation, the actuator shaft is commanded for moving in both directions between a first and a second final position, which respectively correspond to open and closed position of the swirl controlling flaps. 
         [0012]    At least one aim is to detect the integrity of the cinematic chain connecting the actuator movable shaft to the swirl controlling valves. Another aim of the present invention is to meet the goal with a rather simple, rational and inexpensive solution. In addition, other aims, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background. 
       SUMMARY 
       [0013]    The invention provides a method for diagnosing the integrity of a swirl generating system for an internal combustion engine, wherein the swirl generating system comprises: a plurality of swirl controlling elements which are individually located in a respective air passage connecting the intake manifold of the engine to an intake port of an engine combustion chamber, an actuator having a movable shaft, a cinematic chain for mechanically connecting the swirl controlling elements to the actuator movable shaft, actuator controlling means for normally moving the actuator movable shaft in a first direction towards a first final position, and in a second opposite direction towards a second final position, and actuator sensing means for sensing the position of the actuator movable shaft. 
         [0014]    The diagnostic method according to the invention provides to arrange at least a mechanical stop for directly acting on one component of the cinematic chain, in order to indirectly limit the movement of the actuator movable shaft in the first direction at a first checking position, which is coincident or beyond the first final position, command the actuator controlling means for moving the actuator movable shaft in the first direction towards said first checking position, and verify through the position sensing means of the actuator, whether the actuator movable shaft stops in the first checking position or goes beyond. If the actuator movable shaft stops in the first checking position defined by the mechanical stop, than the cinematic chain connecting the actuator movable shaft to the swirl controlling elements is integral and properly working. On the contrary, if the actuator movable shaft goes beyond the first checking position defined by the mechanical stop, than the cinematic chain is broken and a failure signal can be produced by the engine control system. 
         [0015]    For a better diagnosis, the method according to the invention preferably further provides to arrange at least a second mechanical stop for directly acting on one component of the cinematic chain, in order to indirectly limit the movement of the actuator movable shaft in the second direction at a second checking position, which is coincident or beyond the second final position, command the actuator controlling means for moving the actuator movable shaft in the second direction towards the second checking position, and verify through the position sensing means of the actuator, whether the actuator movable shaft stops in said second checking position or goes beyond. Using the position sensor embedded in the actuator, the method according to the invention can perform the integrity diagnosis of the cinematic chain without the installation of any other position sensor, thereby reducing the system costs and simplifying the system design. 
         [0016]    The diagnostic method can be performed by the engine control unit (ECU) after each engine switching off, or cyclically after a predetermined number of kilometers traveled by the vehicle on which the engine is installed. 
         [0017]    An internal combustion engine is also provided that is specially arranged for carrying out the diagnostic method. Further objects, features and advantages of the present invention will be apparent from the detailed description of preferred embodiments that follows, when considered together with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and 
           [0019]      FIG. 1  is a schematic view of a single bank engine equipped with an air induction system according to an embodiment of the present invention; and 
           [0020]      FIG. 2  is a section II-II of  FIG. 1  that shows possible rotations of actuator shaft; 
           [0021]      FIG. 3  in section III-III of  FIG. 1 ; 
           [0022]      FIG. 4  is a detail of  FIG. 1  which shows a single cylinder; 
           [0023]      FIG. 5  is section V-V of  FIG. 3 ; 
           [0024]      FIG. 6  is a schematic view of a two bank engine equipped with an air induction system according to an embodiment of the present invention; and 
           [0025]      FIG. 7  is section VII-VII of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    The following detailed description is merely exemplary in nature and is not intended to limit application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description. 
         [0027]      FIG. 1  schematically illustrates a single bank Diesel engine  1  (for example an inline engine). As a matter of fact, the engine  1  comprises a single cylinder bank  2  having a plurality of cylinder bores  3  whose axis are aligned in a common plane. As shown in  FIG. 5 , each cylinder bore  3  is provided with a respective reciprocating piston  4 . 
         [0028]    A cylinder head  5  closes the top of each cylinder bores  3 , defining a combustion chamber  30  above the piston  4 . For each cylinder bore  3 , the cylinder head  5  comprises two exhaust ports  6  and  7 , and two inlet ports  8  and  9 , which are defined by four openings in the upper surface of the combustion chamber  30  (see  FIG. 4 ). 
         [0029]    The exhaust ports  6  and  7  are opened and closed by means of a respective exhaust valve  60  and  70 , and similar to that the inlet ports  8  and  9  are opened and closed by means of a respective inlet valve  80  and  90 . The inlet and exhaust valves are opened and closed by means of a well known driving apparatus. The first inlet port  8  is constructed as a helical type inlet port, which is suitable for imparting a swirling motion to the air flowing there through, to thereby generating turbulence into the combustion chamber  30 . The second inlet port  9  is constructed as convention straight type inlet port, which has a low flow resistance for reducing air pressure drop. 
         [0030]    Two separate inlet passages  81  and  91  are formed in the cylinder head  5 . The inlet passages  81  and  91  communicate with the first inlet port  8  and the second inlet port  9  respectively. The inlet passages  81  and  91  further communicate with the intake manifold  10  of the engine  1 , through a common air pipe  11  which is fixed to the cylinder head  5 . 
         [0031]    A control valve  12  is held between the air pipe  11  and the cylinder head  5 . The control valve  12  comprises a valve body  120  having two separate channels  121  and  122 , which connect the air pipe  11  with the air passages  81  and  91  respectively. The control valve  12  further comprises a swirl controlling flap  123  which is arranged for rotating into the channel  122  between an open and a closed position. 
         [0032]    When the swirl controlling flap  123  is in closed position, the inlet passage  91  is blocked, and accordingly the major portion of the intake air flows into the combustion chamber  30  through the inlet passage  81  and the swirl inlet port  8 . When the swirl controlling flap  123  is in open position, the inlet passage  91  is open, and the major portion of the intake air flows into the combustion chamber  30  through the inlet passage  91  and the straight inlet port  9 , due to the less flow resistance of the latter relative to the swirl inlet port  8 . 
         [0033]    As shown in  FIG. 1 , all swirl controlling flaps  123  of the single bank engine  1  are fixed on a common rotating shaft, which is called swirl shaft  13 . The swirl shaft  13  is driven by an electromechanical actuator  14 , for simultaneously rotating the flaps  123  between the opened and closed position. 
         [0034]    The electromechanical actuator  14  is of a rotational kind, and thereby comprises a rotating shaft  140  which is called actuator shaft. The swirl shaft  13  is mechanically coupled to the actuator shaft  140  by means of gears  15 , such that any rotation of the actuator shaft  140  corresponds to a rotation of the swirl shaft  13  and thereby of the flaps  123 . The swirl shaft  13  and the gears  15  globally form the cinematic chain allowing the electromechanical actuator  14  to drive the swirl controlling flaps  123 . 
         [0035]    A position sensor  141  is embedded on the electromechanical actuator  14  for real time sensing the angular position of the actuator shaft  140 . The electromechanical actuator  14  is controlled by an engine control unit  16 , on the base of the signal from the position sensor  141  and the engine operating condition. Alternatively, the electromechanical actuator  14  can be provided with an embedded microprocessor based controlled (not shown), which control the rotations of the actuator shaft  140  on the base of the signal from the position sensor  141 , and which is connected to the engine control unit  16 , for receiving from the latter instructions about the positions to reach in response of engine operating conditions. 
         [0036]    As a matter of fact, the engine control unit  16  detects the position of the actuator shaft  140  and when the engine is operating at predetermined conditions, such as low or medium load, commands the electromechanical actuator  14  to rotate the swirl controlling flaps  123  in closed position, and when the engine is operating at different conditions, such as high load, commands the electromechanical actuator  14  to rotate the swirl controlling flaps  123  in open position. 
         [0037]    As shown in  FIG. 2 , during normal operation, the actuator shaft  140  is arranged for rotating in both senses between a first and a second final position, FP 1  and FP 2 , which correspond to the swirl flaps open and closed positions respectively. Such final positions FP 1  and FP 2  defines the “nominal angular range” NAR of the actuator shaft  140 . In the present example, the nominal angular range NAR is about 90°. 
         [0038]    For sake of clarity, the rotations of the actuator shaft  140  towards the first final position FP 1  are indicated with arrow A, and are hereinafter called rotations in “forward sense”. The opposite rotations of the actuator shaft  140  towards the second final position FP 2  are indicated with arrow B, and are hereinafter called rotations in “backward sense”. 
         [0039]    Conventionally, the electromechanical actuator  14  comprises two internal mechanical stops, which are schematically illustrated and labeled as  142  and  143  in  FIG. 1 . The internal mechanical stop  142  directly acts on the actuator shaft  140  for mechanically limiting the rotations of the actuator shaft  140  in forward sense A at a first extreme position, which is indicated with EP 1  in  FIG. 2 . The internal mechanical stop  143  directly acts on the actuator shaft  140  for mechanically limiting the rotations of the actuator shaft  140  in backward sense B at a second extreme position, which is indicated with EP 2  in  FIG. 2 . Such extreme positions EP 1  and EP 2  define the “potential angular range” PAG of the actuator shaft  140 . 
         [0040]    According to an embodiment of the invention, the internal mechanical stop  142  shall allow the actuator shaft  140  to rotate in forward sense A beyond the first final position FP 1 . In other words, the first extreme position EP 1  defined by the internal mechanical stop  142  is beyond the first final position FP 1  relative to the forward sense of rotation A. 
         [0041]    Similar to that, the internal mechanical stop  143  shall allow the actuator shaft  140  to rotate in backward sense B beyond the second final position FP 2 . In other words, the second extreme position EP 2  defined by the internal mechanical stop  143  is beyond the second final position FP 2  relative to backward sense of rotation B. Therefore, the nominal angular range NAR of the actuator shaft  140  shall be a subset of the potential angular range PAR defined by the internal mechanical stops  142  and  143 . In the present example, the potential angular range PAG is about 180°. The internal mechanical stops  142  and  143  are per se known and are not described in further details. 
         [0042]    As shown in  FIG. 1 , the invention provides two external mechanical stops  17  and  18 , which are associated to the cinematic chain connecting the actuator shaft  140  to swirl controlling flaps  123 . The mechanical stop  18  directly acts on the swirl shaft  13  for thereby indirectly limiting the rotation of the actuator shaft  140  in forward sense A at a first checking position, indicated with CP 1  in  FIG. 2 . Similar to that, the mechanical stop  17  directly acts on the swirl shaft  13  for thereby indirectly limiting the rotation of the actuator shaft  140  in backward sense B to a second checking position, indicated with CP 2  in  FIG. 2 . Such checking positions CP 1  and CP 2  defines the “control angular range” CAR of the actuator shaft  140 . 
         [0043]    According to an embodiment of the invention, the external mechanical stop  18  shall allow the actuator shaft  140  to rotate in forward direction A up to or beyond the first final position FP 1 , but shall stop the actuator shaft  140  before it reaches the first extreme position EP 1  defined by the internal mechanical stop  142 . Similar to that, the external mechanical stop  17  shall allow the actuator shaft  140  to rotate in backward direction B up to or beyond the second final position FP 2 , but shall stop the actuator shaft  140  before it reaches the second extreme EP 2  position defined by the internal mechanical stop  143 . As a matter of fact, the first checking position CP 1  shall be interposed between the first final position FP 1  and the first extreme position EP 1 , and the second checking position CP 2  shall be interposed between the second final position FP 2  and the second extreme position EP 2 . Alternatively, the first checking position CP 1  can coincide with the first final position FP 1  and/or the second checking position CP 2  can coincide with the second final position FP 2 . Therefore, the control angular range CAR shall be a subset of the potential angular range PAR, and shall be equal or comprise the nominal angular range NAR. 
         [0044]    As shown in  FIG. 3 , the external mechanical stops  17  and  18  can be realized by two protruding elements integral with the intake manifold  10 , and one protruding element  19  integral with the swirl shaft  13 , which is arranged for contacting the protruding element  17  in consequence of a rotation of the actuator shaft  140  in forward sense, and for contacting the protruding element  18  in consequence of a rotation of the actuator shaft  140  in backward sense. 
         [0045]    For verifying the integrity of the cinematic chain connecting the actuator shaft  140  to the swirl controlling flaps  123 , the embodiments of the invention provide to implement in the engine control unit  16  the diagnosis routine which is disclosed hereinafter. The engine control unit  16  commands the electromechanical actuator  14  for rotating the actuator shaft  140  in forward sense A towards the first extreme position EP 1  defined by the internal mechanical stop  142 . 
         [0046]    Through the position sensor  141  embedded in the electromechanical actuator  14 , the engine control unit  16  senses the angular position of the actuator shaft  140  when it stops. If the angular position of the actuator shaft  140  corresponds to the first checking position CP 1  defined by the external mechanical stop  18 , then the cinematic chain connecting the actuator shaft  140  to the swirl flaps  123  is integral and properly working On the contrary, if the angular position of the actuator shaft  140  actually corresponds to the first extreme position EP 1  defined by the internal mechanical stop  142 , than the cinematic chain is broken and a failure signal can be produced by the engine control unit  16 . This control could be sufficient for verifying the cinematic chain integrity but, for a better verification, the diagnosis routine preferably provides to repeat the control also in the opposite sense of rotation. 
         [0047]    Therefore, the engine control unit  16  commands the electromechanical actuator  14  for rotating the actuator shaft  140  in backward sense B towards the second extreme position EP 2  defined by the internal mechanical stop  143 . Through the position sensor  141  embedded in the electromechanical actuator  14 , the engine control unit  16  senses the angular position of the actuator shaft  140  when it stops. If the angular position of the actuator shaft  140  corresponds to the second checking position CP 2  defined by the external mechanical stop  17 , than the cinematic chain connecting the actuator shaft  140  to the swirl controlling flaps  123  is integral and properly working. On the contrary, if the angular position of the actuator shaft  140  actually corresponds to the second extreme position defined by the internal mechanical stop  142 , than the cinematic chain is broken and a failure signal can be produced by the engine control unit  16 . 
         [0048]      FIG. 6  schematically illustrates a two bank Diesel engine  1 ′ (for example e V engine). As a matter of fact, the engine  1 ′ comprises two separate cylinder bank  2 . Each cylinder bank  2  has a respective plurality of cylinder bores  3  therein, such that the cylinder bores  3  are globally aligned in two separate planes. Each cylinder bore  3  is substantially identical to that shown in  FIG. 3  and  FIG. 4 . As a matter of fact, each cylinder bore  3  is provided with a respective reciprocating piston  4 , and is closed on top by a cylinder head  5  which defines a combustion chamber  30  above the piston  4 . 
         [0049]    The combustion chamber  30  is provided with a control valve  12  which is held between the respective air pipe  11  of intake manifold  10  and the cylinder head  5 . Therefore, the two banks engine  1 ′ globally comprises two separate groups of swirl controlling flaps  123 , which are associated to a respective engine bank  2 . The swirl controlling flaps  123  of each group are fixed on a common rotating swirl shaft, which is labeled  13 ′ and  13 ″ respectively. The swirl shafts  13 ′ and  13 ″ are driven by a common electromechanical actuator  14 , which is suitable for simultaneously rotating all the swirl controlling flaps  123  between the open and closed position. 
         [0050]    The electromechanical actuator  14  is identical to that previously disclosed for the single bank engine  1 . The swirl shafts  13 ′ and  13 ″ are mechanically coupled to the actuator shaft  140  by means of gears  15 ′, such that any rotation of the actuator shaft  140  corresponds to a simultaneous rotation of both swirl shafts  13 ′ and  13 ″, and thereby of the swirl controlling flaps  123 . The swirl shaft  13 ′ and  13 ″ and the gears  15 ′ form the cinematic chain allowing the electromechanical actuator  14  to drive the swirl controlling flaps  123 . 
         [0051]    As previously disclosed, the electromechanical actuator  14  comprises the embedded position sensor  141  for real time sensing the angular position of the actuator shaft  140 . The electromechanical actuator  14  is controlled by the engine control unit  16 , on the base of the signal from the position sensor  141  and the engine operating condition. Also in this case, the electromechanical actuator  14  can alternatively be provided with an embedded microprocessor based controlled, which control the rotations of the actuator shaft  140  and which is connected to the engine control unit  16 . 
         [0052]    During normal operation, the actuator shaft  140  is commanded for rotating in both senses between the first and a second final position FP 1  and FP 2 , which respectively correspond to the swirl controlling flaps  123  open and closed positions. The electromechanical actuator  14  further comprises the two internal mechanical stops  142  and  143 , which directly acts on the actuator shaft  140  for mechanically limiting the rotation of the latter between the first and second extreme positions EP 1  and EP 2 . The setting of the extreme positions EP 1  and EP 2  relative to the final positions FP 1  and FP 2  is identical to that previously described for the single bank engine  1 . 
         [0053]    Two external mechanical stops  17 ′ and  18 ′ are provided in association with the cinematic chain connecting the actuator shaft  140  to the swirl flaps  123 . In this embodiment, the external mechanical stop  17 ′ directly acts on the swirl shaft  13 ′ for thereby indirectly limiting the rotation of the actuator shaft  140  in forward sense A at the first checking position CP 1 . The external mechanical stop  18 ′ directly acts on the swirl shaft  13 ″ for thereby indirectly limiting the rotation of the actuator shaft  140  in backward sense B at the second checking position CP 2 . The setting of the checking positions CP 1  and CP 2  relative to the final positions FP 1  and FP 2  and extreme positions EP 1  and EP 2  is identical to that previously described for the single bank engine  1 . 
         [0054]    As shown in  FIG. 7 , the external mechanical stops  18 ′ can be realized by a single protruding element integral with the intake manifold  10 , and a protruding element  19 ″ integral with the respective swirl shaft  13 ″, which is arranged for contacting the protruding element  18 ′ in consequence of a rotation of the actuator shaft  140  in the backward sense. 
         [0055]    Similar to that, the external mechanical stops  17 ′ can be provided by a single protruding element integral with the intake manifold  10 , and a protruding element  19 ′ integral with the respective swirl shaft  13 ′, which is arranged for contacting the protruding element  17 ′ in consequence of a rotation of the actuator shaft  140  in the forward sense. 
         [0056]    During the diagnosis routine, the engine control unit  16  commands the electromechanical actuator  14  for rotating the actuator shaft  140  in the forward sense A towards the first extreme position EP 1  defined by the internal mechanical stop  142 . Through the position sensor  141  embedded in the electromechanical actuator  14 , the engine control unit  16  senses the angular position of the actuator shaft  140  when it stops. 
         [0057]    If the angular position of the actuator shaft  140  corresponds to the first checking position CP 1  defined by the external mechanical stop  17 ′, than the cinematic chain connecting the actuator shaft  140  to the swirl controlling flaps  123  of the swift shaft  13 ′ is integral and properly working On the contrary, if the angular position of the actuator shaft  140  actually corresponds to the first extreme position EP 1  defined by the internal mechanical stop  142 , than the cinematic chain is broken and a failure signal can be produced by the engine control unit  16 . The diagnosis routine further provides to repeat the control check also in the opposite sense of rotation. 
         [0058]    The engine control unit  16  commands the electromechanical actuator  14  for rotating the actuator shaft  140  in the backward sense B towards the second extreme position EP 2  defined by the internal mechanical stop  143 . Through the position sensor  141  embedded in the electromechanical actuator  14 , the engine control unit  16  senses the angular position of the actuator shaft  140  when it stops. If the angular position of the actuator shaft  140  corresponds to the second checking position CP 2  defined by the external mechanical stop  18 ′, than the cinematic chain connecting the actuator shaft  140  to the swirl flaps  123  of the swirl shaft  13 ″ is integral and properly working On the contrary, if the angular position of the actuator shaft  140  actually corresponds to the second extreme position CP 2  defined by the internal mechanical stop  143 , than the cinematic chain is broken and a failure signal can be produced by the engine control unit  16 . Even if in the preceding embodiments the electromechanical actuator  14  is of rotational kind, the electromechanical actuator  14  could be of linear kind, such that the actuator shaft  140  is a reciprocating shaft which is mechanically coupled with the swirl shaft(s) by means of levers. 
         [0059]    While the present invention has been described with respect to certain preferred embodiments and particular applications, it is understood that the description set forth herein above is to be taken by way of example and not of limitation. Those skilled in the art will recognize various modifications to the particular embodiments are within the scope of the appended claims. Therefore, it is intended that the invention not be limited to the disclosed embodiments, but that it has the full scope permitted by the language of the following claims.