Patent Publication Number: US-11047268-B2

Title: Actuator arrangement

Description:
CROSS-REFERENCE TO PRIOR APPLICATIONS 
     This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2018/068455, filed on Jul. 7, 2018, and claims benefit to British Patent Application No. GB 1710960.4, filed on Jul. 7, 2017. The International Application was published in English on Jan. 10, 2019 as WO/2019/008181 under PCT Article 21(2). 
     FIELD 
     The present invention relates to valve train assemblies of internal combustion engines, specifically to actuator arrangements for switchable engine or valve train components of a valve train assembly. 
     BACKGROUND 
     Internal combustion engines may comprise switchable engine or valve train components. For example, valve train assemblies may comprise a switchable rocker arm to provide for control of a valve (for example control of an intake or exhaust valve opening) by alternating between at least two or more modes of operation (e.g. valve-lift modes). Such rocker arms typically involve multiple bodies, such as an inner arm and an outer arm. These bodies are latched together to provide one mode of operation (e.g. a first valve-lift mode) and are unlatched, and hence can pivot with respect to each other, to provide a second mode of operation (e.g. a second valve-lift mode). For example, in a first valve-lift mode the rocker arm may provide for valve opening, whereas in the second valve-lift mode the rocker arm may deactivate valve opening. This can be useful, for example, in applications such as cylinder deactivation. Typically, a moveable latch pin is used and actuated and de-actuated to switch between the two modes of operation. 
     SUMMARY 
     In an embodiment, the present invention provides an actuator arrangement for controlling a first latching arrangement of a first dual body rocker arm for controlling an intake valve of an internal combustion engine, and for controlling a second latching arrangement of a second dual body rocker arm for controlling an exhaust valve of the internal combustion engine, the first and second dual body rocker arms each comprising a first body, a second body, and the latching arrangement controllable to latch and unlatch the first body and the second body, the actuator arrangement comprising: an actuation source; and an actuation transmission arrangement configured to transmit movement of the actuation source to both the first latching arrangement and the second latching arrangement, wherein, in use, movement of the actuation source is configured to cause, via the actuation transmission arrangement, control of the first latching arrangement and of the second latching arrangement in common. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. Other features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following: 
         FIG. 1  illustrates schematically a perspective view of a valve train assembly according to a first example; 
         FIG. 2  illustrates schematically a plan view of a valve train assembly according to the first example; 
         FIG. 3  illustrates schematically a perspective view of a valve train assembly according to the first example; 
         FIG. 4  illustrates schematically a side view of a valve train assembly according to the first example; 
         FIG. 5  illustrates schematically a sectional view of a valve train assembly according to the first example; 
         FIG. 6  illustrates schematically a detail of the sectional view of  FIG. 5 ; 
         FIG. 7  illustrates schematically a perspective cutaway view of a valve train assembly according to a first example; 
         FIG. 8  illustrates schematically a perspective view of a dual body rocker arm according to an example; 
         FIG. 9  illustrates schematically an exploded view of a dual body rocker arm of  FIG. 8 ; 
         FIG. 10  illustrates schematically a table of different cylinder operating modes for different cam orientations; 
         FIG. 11  illustrates schematically a detail of a perspective view of the valve train assembly according to the first example; 
         FIG. 12  illustrates schematically a perspective view of a gear mechanism according to an example; 
         FIG. 13  illustrates schematically a side view of a valve train assembly according to a second example; 
         FIG. 14  illustrates schematically a sectional view of an actuation source according to the second example; 
         FIG. 15  illustrates schematically a sectional view of an actuation assembly according to a third example; 
         FIG. 16  illustrates schematically a perspective view of the actuation assembly of  FIG. 15 ; 
         FIG. 17  illustrates schematically a perspective view of a valve train assembly according to a fourth example; 
         FIG. 18  illustrates schematically a cutaway view of the valve train assembly of  FIG. 17 ; 
         FIG. 19  illustrates schematically two gear mechanisms according to the fourth example; 
         FIG. 20  illustrates schematically a perspective view of a valve train assembly according to a fifth example; 
         FIG. 21  illustrates schematically a sectional view of an actuator according to the fifth example; 
         FIG. 22  illustrates schematically a side view of the actuator of  FIG. 22 ; 
         FIGS. 23 and 24  illustrate schematically perspective views of the actuator of  FIG. 21 , in different configurations; 
         FIG. 25  illustrates schematically a cutaway view of the valve train assembly according to the fifth example; and 
         FIG. 26  illustrates schematically a perspective view of the valve train assembly according to the fifth example. 
     
    
    
     DETAILED DESCRIPTION 
     Throughout, like reference signs denote like features. 
     Referring to  FIGS. 1 to 12 , a first example valve train assembly  1  comprises dual body rocker arms  3   a  (hereinafter, simply, rocker arms) for controlling intake valves  40   a , and rocker arms  3   b  for controlling exhaust valves  40   b , of cylinders of an internal combustion engine. The valve train assembly  1  is for an inline-four (1-4) internal combustion engine having four cylinders. There are a total of eight intake valves  40   a , two for each cylinder, and eight exhaust valves  40   b , again, two for each cylinder. 
     The valve train assembly  1  comprises a first cam shaft  44   a  comprising cams  43   a , one for each intake valve  40   a , and a second cam shaft  44   b  comprising cams  43   b , one for each exhaust valve  40   b . Each cam  43   a ,  43   b  comprises a base circle  43   a ′,  43   b ′ and a lift profile  43   a ″,  43   b ″. The lift profiles  43   a ″ of the first cam shaft  44   a  are arranged to cause opening of the respective intake valves  40   a , via the rocker arms  3   a , at the appropriate times in the engine cycle. Similarly, lift profiles  43   b ″ of the second cam shaft  44   b  are arranged to cause opening of the respective exhaust valves  40   b , via the rocker arms  3   b , at the appropriate times in the engine cycle. 
     The valve train assembly  1  comprises an actuation arrangement  100 . In broad overview, the actuation arrangement  100  is arranged to control the rocker arms  3   a ,  3   b  to provide either a first valve-lift mode, or a second valve-lift mode. 
     As more clearly seen in  FIGS. 6, 8 and 9 , each rocker arm  3   a ,  3   b  comprises an outer body  7  and an inner body  9  that are pivotably connected together at a pivot axis  11 . A first end  7   a  of the outer body  7  contacts a valve stem  41   a ,  41   b  of the valve  40   a ,  40   b  and a second end  7   b  of the outer body  7  contacts a hydraulic lash adjuster (HLA)  42 . The HLA  42  compensates for lash in the valve train assembly  1 . The outer body  7  is arranged to move or pivot about the HLA  42 . The outer body  7  contacts the valve stem  41   a ,  4   lb  via a foot portion  51 . Each rocker arm  3   a ,  3   b  further comprises at the second end  7   b  of the outer body  7  a latching arrangement  13  comprising a latch pin latch pin  15  that can be urged between a first position in which the outer body  7  and the inner body  9  are latched together and hence can move or pivot about the HLA  42  as a single body, and an second position in which the inner body  9  and the outer body  7  are unlatched and hence can pivot with respect to each other about the pivot axis  11 . 
     Each inner body  9  is provided with an inner body cam follower  17 , for example, a roller follower  17  for following the cams  43   a ,  43   b  on the cam shaft  44   a ,  44   b . The roller follower  17  comprises a roller  17   a  and needle bearings  17   b  mounted on a roller axle  17   c . Each valve  40   a ,  40   b  comprises a valve spring for urging the rocker arm  3   a ,  3   b  against the cams  43   a ,  43   b  of the cam shaft  44 . 
     Each rocker arm further comprises a return spring arrangement  21  for returning the inner body  9  to its rest position after it is has pivoted with respect to the outer body  7 . The return spring  21  is a torsional spring supported by the outer body  7 . 
     When the latch pin  15  of a rocker arm  3   a ,  3   b  is in the latched position (as per e.g.  FIG. 6 ), that rocker arm  3   a ,  3   b  provides a first primary function, for example, the valve  40   a ,  40   b  it controls is activated as a result of the rocker arm  3   a ,  3   b  pivoting as a whole about the HLA  42  and exerting an opening force on the valve  40   a ,  40   b  it controls. For example, when the latch pin of the rocker arm  3   a  is in the latched position, and hence the inner body  9  and the outer body  7  are latched together, when the cam shaft  44   a ,  44   b  rotates such that the lift profile  43   a ″,  43   b ″ of the cam  43   a ,  43   b  engages the inner body cam follower  17 , the rocker arm  3   a  is caused to pivot about the HLA  42  against the valve spring, and hence control the valve  40   a  to open. 
     When the latch pin  15  of a rocker arm  3   a ,  3   b  is in the un-latched position, that rocker arm  3   a ,  3   b  provides a second secondary function, for example, the valve  40   a ,  40   b  it controls is de-activated as a result of lost motion absorbed by the inner body  9  pivoting freely with respect to the outer body  7  about the pivot axis  11  and hence no opening force being applied to the valve  40   a ,  40   b . For example, when the latch pin  15  of the rocker arm  3   a  is in the un-latched position, and hence the inner body  9  and the outer body  7  are unlatched, when the cam shaft  44  rotates such that the lift profile  43   a ″,  43   b ″ of the cam  43 ,  44  engages the inner body cam follower  17 , the inner body  9  is caused to pivot with respect to the outer body  7  about the pivot axis  11  against the return spring arrangement  21 , and hence the rocker arm  3   a  is not caused to pivot about the HLA  42 , and hence the valve  40   a ,  40   b  does not open. The cylinder associated with the valve  40   a  may thereby be deactivated (also referred to as cylinder deactivation). 
     In such a way, for example, the position of the latch pin may be used to control whether or not the rocker arm  3   a ,  3   b  is configured for cylinder deactivation. 
     As mentioned above, the rocker arm  3   a ,  3   b  comprises the inner body  9 , the outer body  7 , and the latching arrangement  13  moveable to latch and unlatch the inner body  9  and the outer body  7 . The latching arrangement  13  is at an opposite side of the rocker arm  3   a ,  3   b  to the pivot axis  11 . The latching arrangement  13  comprises the latch pin  15  moveable between a first position in which the latch pin  15  latches the inner body  9  and the outer body  7  together and a second position in which the inner body  9  and the outer body  9  are un-latched. The latching arrangement  13  comprises a lever  102  mounted for pivotal motion relative to the outer body  7 . A first end  102   a  of the lever  102  contacts the latch pin  15 , and a second end  10   b  of the lever  102  is for contacting the actuation arrangement  100 . In broad overview, when the actuation arrangement  100  exerts a force on the second end  102   b  of the lever, the lever  102  is caused to pivot such that the first end  102   a  of the lever exerts a force on the latch pin  15 , thereby moving the latch pin from the first (latched) position to the second (unlatched) position. 
     The lever  102  is arranged to orient the latch pin  15  rotationally with respect to the outer body  7 . Specifically, as best seen in  FIGS. 8 and 9 , the second end  102   b  of the lever  102  defines protrusions  102   c , and the latch pin  15  defines transverse slots  15   a  into which the protrusion  102   c  is received. This prevents the latch pin  15  from rotating relative to the lever  102 , and thereby orients the latch pin  15  rotationally with respect to the lever  102 . Specifically, the latch pin  15  is orientated so that a shelf  15   b  of the latch pin  15  for engaging with the inner body  9  when the latch pin  15  is in the first position, faces towards the inner body  9 . 
     As mentioned above, the rocker arm  3   a ,  3   b  comprises a torsional biasing means or spring  21  supported by the outer body  7  and arranged to bias the inner body  9  relative to the outer body  7 . As best seen in  FIGS. 8 and 9 , the torsional spring  21  (also known as a torsional lost motion spring) comprises two coiled sections  21   a ,  21   b  arranged around and supported by protrusions  8   a ,  8   b  on opposite sides of the outer body  7 , and a non-coiled section  21   c  joining the two coiled sections,  21   a ,  21   b  and extending transversely across the outer body  7 . The lever  102  is mounted on the non-coiled section  21   c  of the torsional biasing means  21 , for pivotal motion relative to the first body  7 . The lever  102  is mounted on the non-coiled section  21   c  of the torsional spring  21  at a point along the lever  102  between the first end  102   a  and the second end  102   b  of the lever  102 . The lever  102  converts a pushing force on the first end  102   a  of the lever into a force that pulls the latch pin  15  away from the inner body  9 , thereby to move the latch pin  15  from the first (latched) position to the second (unlatched) position. 
     The latching arrangement  13  comprises a biasing means or return spring  16  arranged to bias the latch pin  15  towards the first position. As a result, the default configuration of the rocker arm  3   a ,  3   b  is that the inner body  9  and the outer body  7  are latched together to provide the first primary function. The rocker arm  3   a  is arranged such that an actuation arrangement  100  can cause the latch pin  15  to move from the first position to the second position against the return spring  16 . The return spring  16  has an associated washer  16   a.    
     As mentioned above, the outer body  7  comprises protrusions  8   a ,  8   b  to support the torsional spring  21 . The protrusions  8   a ,  8   b  are formed integrally with the outer body  7 . More specifically the protrusions  8   a ,  8   b  are formed from the outer body  7 . For example, the protrusions  8   a ,  8   b  and the outer body  8  are formed from a single sheet of material, such as metal. For example, the protrusions  8   a ,  8   b  and the outer body  7  are formed from a stamped metal sheet. For example, a method of manufacturing the rocker arm  3   a ,  3   b  may comprise providing a sheet of material; and stamping the sheet of material to form the protrusions  8   a ,  8   b . The inner body  9  may also be metal sheet stamped. 
     The torsional spring  21  is arranged to bias the inner body  9  relative to the outer body  7  from a position in which the inner body  9  is pivoted away from the outer body  7 , towards a position in which the inner body  9  is aligned with the outer body  9 . The torsional biasing means  21  is arranged around each protrusion  8   a ,  8   b . Specifically, each protrusion  8   a ,  8   b  comprises a substantially cylindrical cuff  8   a ,  8   b , the cuff  8   a ,  8   b  defining a curved surface  8   c  by which the torsional biasing means  21  is supported. Each protrusion  8   a ,  8   b  is located towards an end  7   b  of the outer body  7  opposite to that end  7   a  where the inner body  9  is connected to the outer body  7 . 
     As mentioned above, the actuation arrangement  100  controls the latching arrangement  13  of the rocker arms  3   a ,  3   b , so as to control the position of the latch pins  15 , so as to control whether or not the rocker arms  3   a ,  3   b  are configured for cylinder deactivation. 
     As best seen in  FIGS. 1 to 4 , the actuation arrangement  100  comprises an actuation source  104 , and an actuation transmission arrangement  106 . The actuation arrangement  100  is incorporated in the cam carrier  122  of the engine. The actuation transmission arrangement  106  is arranged to transmit movement of the actuation source  104  to the latching arrangements  13  of the rocker arms  3   a ,  3   b  of both the intake valves  40   a  and the exhaust valves  40   b . In other words, the actuation source  104  is common to the latching arrangements  13  of the rocker arms  3   a ,  3   b  of both the intake valves  40   a  and the exhaust valves  40   b . In broad overview, in use, movement of the actuation source  104  causes, via the actuation transmission arrangement  106 , control of the latching arrangements  13  of the exhaust valve and intake valve rocker arms  3   a ,  3   b , in common. 
     The actuation transmission arrangement  106  comprises a first shaft  108   a  comprising a first set of cams  110   a  for controlling the latching arrangements  13  of the rocker arms  3   a  controlling the intake valves  40   a . The actuation transmission arrangement  106  comprises a second shaft  108   b  comprising a second set of cams  110   b  for controlling the latching arrangements  13  of the rocker arms  3   b  controlling the exhaust valves  40   b . The actuation source  104  is common to the first shaft  108   a  and the second shaft  108   b . The axis of the rotation of the actuation  104  source is perpendicular to an axis of rotation of the first shaft  108   a  and to an axis of rotation of the second shaft  108   b . In use, a rotation of the actuation source  104  causes, via gear mechanisms  112   a ,  112   b , the first shaft  108   a  and the second shaft  108   b  to rotate, thereby to change an orientation of the first set of cams  110   a  and the second set of cams  110   b  relative the latching arrangements  13  of the rocker arms  3   a ,  3   b  of the intake valves  40   a  and the exhaust valves  40   b , respectively, so as to control those latching arrangements  13 . 
     As best seen in  FIG. 6 , each cam  110  has an associated compliance arrangement  120  intermediate of the cam  110  and the latching arrangement  13  of the associated rocker arm  3   a ,  3   b . The compliance arrangement  120  is supported by a main body  122  external to the rocker arm  3   a , 3   b . Specifically, the compliance arrangement  120  is supported by the cam carrier  122 . The shafts  108   a ,  108   b  and cams  110   a ,  110   b  are housed in a housing  122   a  connected to the cam carrier  122  adjacent to the compliance arrangement  120  (see also  FIG. 7 ). The compliance arrangement  120  comprises a first portion  120   a  for contacting with the cam  110 , a second portion  120   b  for contacting with the latching arrangement  13 . The second portion  120   b  is moveable relative to the first portion  120   a . The compliance arrangement comprises a biasing means  124  arranged to bias the first portion  120   a  and the second portion  120   b  away from one another. The compliance device  120  transmits an actuation force from the cam  110  to the latching arrangement  13  of the rocker arm. 
     Each cam  110  has a base circle  116  and a raised profile  118 . When the cam  110  is orientated such that the base circle  116  is engaged with the compliance arrangement  120 , no actuation force is transmitted to the latching arrangement  13 , and hence the rocker arm  3   a ,  3   b  remains in its default, latched configuration. When the shaft  108  is rotated such that the raised profile  118  is engaged with the compliance arrangement  120 , the raised profile  118  applies a force, via the compliance arrangement  120 , to the latching arrangement  13 . If the latching arrangement  13  is free to move, this force will cause the latch pin  15  to move from its first, default position to its second position in which the inner body  9  and the outer body  7  are unlatched, and hence in a cylinder deactivation configuration. However, if the latching arrangement  13  is in a non-moveable state, the biasing means  124  becomes biased by the cam  110 , and the biasing means  124  causes the latching arrangement  13  to move from its first position to its second position when the latching arrangement  13  is in a moveable state again. For example, the latching arrangement  13  may be in a non-moveable state when the engine cycle is such that the inner body  9  is forced against the latch pin  15  so as to hold it firmly in place. The biasing means  124  if biased by the cam  110  in this time will then, once the engine cycle has moved on such that the inner body  9  is no longer forced against the latch pin  15 , cause the latch pin  15  to move from the first position to the second position, and hence configure the rocker arm  3   a ,  3   b  for cylinder deactivation. The compliance arrangement  120  thereby allows for the actuation of the latching arrangement to be effected as soon as it is physically possible, and hence can simplify timing requirements of actuating the latching arrangements  13 . 
     As best seen in  FIG. 3 , the cams  110  of the first set of cams  110   a  have different shapes to allow control of the latching arrangements  13  on a per cylinder basis. Similarly, the cams  110  of the second set of cams  110   b  have different shapes to allow control on a per cylinder basis. The cams  110  of the first set  110   a  and the second set  110   b  that are associated with the same cylinder have the same shape, so as to allow for deactivation of that cylinder based on deactivation of both the intake and exhaust valves of that cylinder. 
     Specifically, first cams  11  Op for controlling rocker arms  3   a ,  3   b  of valves  40   a ,  40   b  of a first cylinder have a first shape, second cams  1   l Oq for controlling rocker arms  3   a ,  3   b  of valves  40   a ,  40   b  of a second cylinder have a second shape, third cams  1   l Or for controlling rocker arms  3   a ,  3   b  of valves  40   a ,  40   b  of a third cylinder have a third shape, and fourth cams  110   s  for controlling rocker arms  3   a ,  3   b  of valves  40   a ,  40   b  of a fourth cylinder have a fourth shape. 
     As best seen in  FIG. 10 , the shapes of the different cams  11  Op, HOq,  11  Or,  110   s  are different in that the raised profile  118  extends over different proportions of the circumference of the different cams  1   l Op,  1   l Oq,  1   l Or,  110   s . The different shaped cams  110  are phased relative to one another with respect to the shaft  108 . The table of  FIG. 10  shows the orientation of the four different shaped cams  11  Op, HOq,  11  Or,  1  is, associated with the cylinders CYL 1 , CYL 2 , CYL 3 , CYL 4  respectively, relative to the compliance arrangement  120  (indicated in  FIG. 10  by a hatched rectangle), and hence latching arrangement  13 , at five different rotational positions of the shaft  108  to which the cams are attached. 
     In the first row of the table of  FIG. 10 , the shaft  108  is rotated such that all of the cams  11  Op, HOq,  11  Or,  110   s  have their base circles  116  engaged with the compliance arrangements  120 . Hence no force will be applied to the latching arrangements  13  of any of the rocker arms  3   a ,  3   b , and hence all of the rocker arms  3   a ,  3   b  will be in their default, latched, configuration, and hence all will be providing their first primary function, and hence all the cylinders CYL 1 , CYL 2 , CYL 3 , CYL 4  will be active. The engine will therefore be operating in a 4 cylinder operational mode. 
     In the second row of the table of  FIG. 10 , the shaft  108  is rotated by a fifth of a turn (i.e. by 72°) clockwise in the sense of  FIG. 10  as compared to the first row, such that the first cam  1   l Op, third cam  1   l Or, and fourth cam  110   s  still have their base circles  116  engaged with the compliance arrangements  120 , but the second cam HOq has its raised profile  118  engaged with its compliance arrangement  120 . Hence an actuation force will be applied only to the latching arrangements  13  of the rocker arms  3   a ,  3   b  of the second cylinder CYL  2 , and hence only those rocker arms  3   a ,  3   b  will be actuated to be in their unlatched state, and hence only those rocker arms  3   a ,  3   b  will provide their second secondary function of providing cylinder deactivation, and hence only the second cylinder C YL 2  will be deactivated (indicated in  FIG. 10  by a hatched bar extending across the width of the associated cell), whereas the first, third and fourth cylinders CYL 1 , CYL 3 , CYL 4  will remain active. The engine will therefore be operating in a 3 cylinder operational mode. 
     In the third row of the table of  FIG. 10 , the shaft  108  is rotated by a fifth of a turn (i.e. by 72°) clockwise in the sense of  FIG. 10  as compared to the second row, such that the first cam  11  Op and fourth cam  110   s  still have their base circles  116  engaged with their compliance arrangements  120 , but the second cam HOq and third cam  11  Or have their raised profile  118  engaged with their compliance arrangements  120 . Hence an actuation force will be applied only to the latching arrangements  13  of the rocker arms  3   a ,  3   b  of the second cylinder CYL  2  and the third cylinder CYL 3 , and hence only those rocker arms  3   a ,  3   b  will be actuated to be in their unlatched state, and hence only those rocker arms  3   a ,  3   b  will provide their second secondary function of providing cylinder deactivation, and hence only the second cylinder C YL 2  and the third cylinder CYL 3  will be deactivated (indicated in  FIG. 10  by a hatched bar extending across the width of the associated cells), whereas the first and fourth cylinders CYL 1 , CYL 4  will remain active. The engine will therefore be operating in a 2 cylinder operational mode. 
     In the fourth row of the table of  FIG. 10 , the shaft  108  is rotated by a fifth of a turn (i.e. by 72°) clockwise in the sense of  FIG. 10  as compared to the third row, such that only the fourth cam  110   s  still has its base circle  116  engaged with its 
     compliance arrangement  120 , but the first cam  1   l Op, second cam  1   l Oq and third cam  11  Or have their raised profile  118  engaged with their compliance arrangements  120 . Hence an actuation force will be applied to the latching arrangements  13  of the rocker arms  3   a ,  3   b  of the first cylinder CYL 1 , second cylinder CYL  2  and the third cylinder CYL 3 , and hence those rocker arms  3   a ,  3   b  will be actuated to be in their unlatched state, and hence those rocker arms  3   a ,  3   b  will provide their second secondary function of providing cylinder deactivation, and hence the first cylinder CYL 1 , second cylinder CYL 2  and the third cylinder CYL 3  will be deactivated (indicated in  FIG. 10  by a hatched bar extending across the width of the associated cells), whereas the fourth cylinder CYL 4  will remain active. The engine will therefore be operating in a 1 cylinder operational mode. 
     In the fifth row of the table of  FIG. 10 , the shaft  108  is rotated by a fifth of a turn (i.e. by 72°) clockwise in the sense of  FIG. 10  as compared to the fourth row, such that all of the first cam  1   l Op, second cam  1   l Oq, third cam  1   l Or and fourth cam  110   s  have their raised profile  118  engaged with their compliance arrangements  120 . Hence an actuation force will be applied to the latching arrangements  13  of the rocker arms  3   a ,  3   b  of all of the first cylinder CYL 1 , second cylinder CYL  2 , third cylinder CYL 3 , and the fourth cylinder CYL 4 , and hence all of the rocker arms  3   a ,  3   b  will be actuated to be in their unlatched state, and hence the rocker arms  3   a ,  3   b  will provide their second secondary function of providing cylinder deactivation, and hence all of the first cylinder CYL 1 , second cylinder CYL 2 , third cylinder CYL 3 , and the fourth cylinder CYL 4  will be deactivated (indicated in  FIG. 10  by a hatched bar extending across the width of all of the cells). The engine will therefore be operating in a 0 cylinder operational mode, and in effect will be shut off. Further rotation of the shaft  108  by a fifth of a turn (i.e. by 72°) clockwise in the sense of  FIG. 10  would return the shaft and cams  110  to the orientation illustrated in the first row of the table of  FIG. 10 , and hence return the engine to a 4 cylinder operational mode again. 
     As mentioned above, a rotation of the actuation source  104  causes, via gear mechanisms  112   a ,  112   b , the first shaft  108   a  and the second shaft  108   b  to rotate, so as to control the latching arrangements  13  of the rocker arms  3   a ,  3   b , for example using cams  110  as described above. As best seen in  FIGS. 11 and 12 , a gear mechanism  112   a ,  112   b  is arranged to translate a continuous rotation of the actuation source  104  into an intermittent rotation of the shaft  108   a ,  108   b  in steps of a predefined degree. In use, a continuous rotation of the actuation source  104  causes, via the gear mechanism  112   a ,  12   b , the shaft  108   a ,  108   b  to rotate in steps of a predefined degree, thereby to change an orientation of the cams  110  relative the latching arrangements  13  by a predefined amount, so as to control the latching arrangements  13 . Specifically, the gear mechanism  112   a ,  112   b  is arranged to translate the continuous rotation of the actuation source  104  into an intermittent rotation of the shaft  108   a ,  108   b  in steps of 72°, either clockwise or anticlockwise. This allows, as described above, sequential selection of the operational mode of the engine from 0 cylinders to 1 or 4 cylinders, from 1 cylinder to 0 or 2 cylinders, from 2 cylinders to 3 or 1 cylinders, from 3 cylinders to 4 or two cylinders, and from 4 cylinders to 3 or 0 cylinders. 
     The gear mechanism  112   a ,  112   b  is arranged to prevent rotation of the shaft  108   a ,  108   b  between the intermittent rotations of the shaft  108   a ,  108   b . This allows the shaft  108   a ,  108   b  to be held in position, and hence the operational mode selection to remain effective, without the gear mechanism  112   a ,  112   b  or other component needing to absorb a holding force. 
     The gear mechanism  112   a ,  112   b , is a “Malta&#39;s cross” type gear mechanism, also referred to as a “Geneva” type gear mechanism. Specifically, as best seen in  FIG. 12 , the gear mechanism  112   a ,  112   b  comprises a first part  130  connected to the actuation source  104 . The first part  130  comprises a pin  132  distal from the axis of rotation of the first part  130 . The gear mechanism  112   a ,  112   b  also comprises a second part  134  connected to the shaft  108 . The second part  134  comprises a plurality of slots  136 , five as shown, extending radially from the axis of rotation of the second part  134 , and into which the pin  132  is engageable. In use, when the actuation source  104  rotates such that the pin  132  engages into one of the slots  136 , the pin  132  causes the second part  134  to rotate. This allows the shaft  108   a ,  108   b  to be rotated in discrete steps, thereby to allow discrete selection of the engine operational mode. 
     The first part  130  comprises an arcuate protrusion  138  protruding substantially parallel with the axis of rotation of the first part  130 . The second part  134  comprises an arcuate recess  140  between each of the plurality of slots  136 . The arcuate protrusion  138  is engageable with the arcuate recess  140 . In use, when the actuation source  104  rotates such that the arcuate protrusion  138  engages with the arcuate recess  140 , the arcuate protrusion  138  holds the second part  134  so as to prevent rotation of the second part  134 . This allows the shaft  108   a ,  108   b  to be held in position between steps of rotation. 
     The rotation of the actuation source  104  is substantially perpendicular to an axis of the rotation of the shaft  108   a ,  108   b . The second part  134  of the gear mechanism  112   a ,  112   b  is therefore concave such that the slots  136  extend at an angle to the plane of rotation of the second part  134 . Similarly, the pin  132  of the first part  130  of the gear mechanism  112   a ,  112   b  extends at an angle to the plane of rotation of the first part  130 , so as to engage with the correspondingly angled slots  136  of the second part  134 . In use, a continuous rotation of the actuation source  104  causes, via the gear mechanisms  112   a ,  112   b , both the first shaft  108   a  and the second shaft  108   b  to rotate in steps of a common predefined degree, so as to control the respective latching arrangements  13  in common. 
     As best seen in  FIGS. 2 and 3 , the actuation source  104  comprises a rotary electric motor or torque motor  150  comprising an output shaft  156 . The rotary electric motor  150  is controllable by a control unit to rotate an output shaft  156 . For example, the electric motor  150  may be controlled to rotate the output shaft  156  by a predefined amount depending on the engine operational mode desired to be selected. The output shaft  156  is connected at one end to the first shaft  108   a  via the first gear mechanism  112   a , and at the other end to the second shaft  108   b  via the second gear mechanism  112   b . Rotation of the output shaft  156  therefore allows control of the rocker arms  3   a  of the intake valves  40   a  and of the rocker arms  3   b  of the exhaust valves  40   b . The cams  110   a  and/or the gear mechanism  112   a  of the first shaft  108   a  are phased with the cams  110   b  and/or the gear mechanism  112   b  of the second shaft  108   b  so that a given rotation of the output shaft  156  deactivates or activates the intake valves  40   a  and the exhaust valves  40   b  for a given cylinder at substantially the same time. 
     A second example is illustrated in  FIGS. 13 and 14 . This second example may be the same as the first example described above apart from the actuation source  104 ′. The actuation source  104 ′ in the valve train assembly  1   a  of this second example comprises a rotary electric motor  250 , a spur gear  252 , a gear housing  254 , an output shaft  256 , and bearings  258 . The output shaft  256  is supported by the bearings  258 , which are supported by the gear housing  254 . The gear housing  254  houses the spur gear  252 . The rotary electric motor  250  is controllable by a control unit to rotate a drive shaft  260 . For example, the electric motor may be controlled to rotate the drive shaft  260  by a predefined amount depending on the engine operational mode desired to be selected. Rotation of the drive shaft  260  causes, via the spur gear  252 , rotation of the output shaft  256 . The output shaft  256  is connected at one end to the first shaft  108   a  via the first gear mechanism  112   a , and at the other end to the second shaft  108   b  via the second gear mechanism  112   b . Rotation of the drive shaft  260  therefore allows control of the rocker arms  3   a  of the intake valve  40   a  and of the rocker arms  3   b  of the exhaust valves  40   b . The cams  110  and/or the gear mechanism  112   a  of the first shaft  108   a  are phased with the cams  110  and/or the gear mechanism  112   b  of the second shaft  108   b  so that a given rotation of the drive shaft  260  deactivates or activates the intake valves  40   a  and the exhaust valves  40   b  for a given cylinder at substantially the same time. 
     In the above first and second examples, the compliance arrangements  120  were supported by the cam carrier  122 . However, in a third example, illustrated in  FIGS. 15 and 16 , the compliance arrangements  120  are supported by a main body  322  of an actuation assembly  350  connectable to a cam carrier (not shown in  FIGS. 15 and 16 , but see cam carrier  122 ′ of  FIGS. 17 and 18 ) of an internal combustion engine. This third example may be the same as the first and/or second examples except for in the abovementioned respect. Referring to  FIGS. 15 and 16 , the actuation assembly  350  comprises the main body  322 , and a shaft  308  supported by the main body  322 . The shaft  308  is essentially the same as the shafts  108   a ,  108   b  described above, in that it is rotatable by an actuation source (not shown in  FIGS. 15 and 16 ), and comprises a set of cams  310  for moving latching arrangements  13  of rocker arms  3   a ,  3   b  via the compliance arrangements  120 . Although only six compliance arrangement  120  are shown in the actuation assembly  350  of  FIGS. 15 and 16 , it will be appreciated there may be eight, as per the first and second examples described above. The main body  322  supports the compliance arrangements  120 . The compliance arrangements  120  are the same as those described in the above example. The main body  322  comprises a housing  324  connectable to the cam carrier  122 ′. The housing comprises bearings  326  that support two opposing ends of the shaft  308 . The housing  324  comprises hollow cylindrical protrusions  324   a  which support and house the compliance arrangements  120 . The housing  324  houses and encloses the cams  310  of the shaft. The actuation assembly  350  is useful as it can be fitted to the cam carrier  122 ′ in an engine plant, hence providing efficient assembly of the engine. 
     In the above examples, the actuation source  104  was arranged to drive, via the gear mechanisms  112   a ,  112   b , both the first shaft  108   a  and the second shaft  108   b . However, in a fourth example, illustrated in  FIGS. 17 to 19 , an actuation source  404  is arranged to drive only one shaft  408   b , via a gear mechanism  412   b , for example so as to control actuation of latch pins  15  of rocker arms  3   b  of only exhaust valves  40   b  (or of only intake valves, not shown in  FIGS. 17 to 19 ) of an internal combustion engine. This fourth example may be the same as that of the first, second or third examples, except in the abovementioned respect. The shaft  408   b  of this example is the same as the second shaft  108   b  described in the above examples and will not be described again. It will be appreciated that there may be another actuation source arranged to drive another shaft, which another shaft may be the same as the first shaft  108   a  described in the above examples. The actuation source  404  in this example is again an electric motor  404 . The actuation source  404  of the valve train assembly  1   c  of this fourth example is arranged to drive the shaft  408   b  via the gear mechanism  412   b . The gear mechanism  412   b  is similar to the gear mechanisms  112   a ,  112   b  described above in that it is arranged to translate a continuous rotation of the actuation source  404  into an intermittent rotation of the shaft  408   b  in steps of a predefined degree (again, as before, in this example in steps of 72°), so as to orient the cams  410  as described above, so as effect sequential control of the engine operation mode. However, in this example, the axis of rotation of the actuation source  404  is substantially parallel to the axis of rotation of the shaft  408   a . In this case therefore, the second part  434  of the gear mechanism  412   b  is not concave but is generally flat, such that the slots  436  extend in the plane of rotation of the second part  434 . Similarly, the pin  432  of the first part  430  of the gear mechanism  412   b  extends substantially perpendicularly to the plane of rotation of the first part  430 , so as to engage with the slots  436  of the second part  434 . In use, a continuous rotation of the actuation source  404  causes, via the gear mechanism  412   b , the shaft  408   b  to rotate in steps of a predefined degree, thereby to change an orientation of the cams relative to latching arrangements by a predefined amount, so as to control the latching arrangement, so as to ultimately control the engine operation mode. 
     The above examples allow the engine to run different numbers of active cylinders, from all cylinders being active (in a fired mode) to none of the cylinders being active (i.e. all deactivated, i.e. none in a fired mode). As explained above for an 1-4 gasoline engine, the above example actuation arrangements and assemblies allow the engine to run with 4, 3, 2, 1 or none of the cylinders active. This allows flexibility in the selection of the engine operation mode. 
     In the above examples, the latching arrangements  13  of the rocker arms  3   a ,  3   b  were actuated, via the compliance arrangements  120 , by cams  110  of one or more shafts  108   a ,  108   b , the shafts  108   a ,  108   b  being rotated, via one or more gear mechanisms  112   a ,  112   b , by an actuation source  104 . The cams  110  associated with exhaust valves  40   b  (and/or intake valves  40   a ) for a given cylinder had the same shape so that the latching arrangements  13  of the rocker arms  3   a ,  3   b  controlling those valves would be actuated in common. However, in a fifth example, illustrated in  FIGS. 20 to 26 , an actuator  569  comprising a solenoid  570  is arranged to actuate directly a first latching arrangement  13 ′ of a first rocker arm  3   a ′ for controlling a first valve  40   a ′ of a first cylinder, and to actuate a second latching arrangement  13 ″ of a second rocker arm  3   a ″ for controlling a second valve  40   a ″ of the first cylinder, in common. The first valve  40   a ′ and the second valve  40   a ″ controlled in common by one actuator  569  may both be intake valves  40   a ′,  40   a ″ of the first cylinder, controlled by rocker arms  3   a ′,  3   a ″ respectively, or may both be exhaust valves  40   b ′,  40   b ″ of the first cylinder, controlled by rocker arms  3   b ′,  3   b ″ respectively. The fifth example may be the same as the first, second, third, or fourth examples apart from in the above mentioned respects. 
     Referring to  FIGS. 20 to 26 , the actuator  569  of valve train assembly Id of this fifth example comprises the solenoid  570 , a body  572  moveable relative to and by the solenoid  570  from a first position (as per  FIGS. 21 to 23 ) to a second position (as per  FIG. 24 ), and a contact element  574  in mechanical communication with the body  572 . The contact element  574  comprises a first region  574   a  for contacting with the first latching arrangement  13 ′ and a second region  574   b  for contacting with the second latching arrangement  13 ″. When the body  572  is in the first position, the contact element  574  does not apply an actuation force to the latching arrangements  13 ′,  13 ″ of the rocker arms  3   a ′,  3   a ″. However, when the body  572  is in the second position, the contact element  574  contacts and applies an actuation force to the latching arrangements  13 ′,  13 ″ of the rocker arms  3   a ′,  3   a ″. In use, when the solenoid  570  is energised, the solenoid  570  causes the body  572  to move relative to the solenoid  570  from the first position to the second position, thereby causing the contact element  574  to apply an actuation force to both the first latching arrangement  13 ′ and the second latching arrangement  13 ″ in common. The solenoid  570  and the body  572  may be or comprise a “push pull solenoid” device. 
     The actuator  569  comprises a biasing means such as a spring  576  arranged to bias the body  572  away from the solenoid  570 , from the second position to the first position. This provides that when the solenoid  570  is not energised, the body  572  returns under the force of the spring  576  to the default first position. 
     The body  572  is moveable relative to and by the solenoid  570  along a first axis. The contact element  574  extends along an axis substantially perpendicular to this first axis. This allows the contact element to translate a movement of the body  572  along one axis, to movement of the latching arrangements  13 ′,  13 ″ along two, parallel, axes. 
     The contact element  574  is mechanically connected to the body  572  at a point  574   c  between the first region  574   a  and the second region  574   b . The contact element  574  is mounted for pivotal motion relative to the body  572  about the point  574   c . The body  572  is received through the solenoid  570 . The actuator  569  comprises a housing  578  in which the solenoid  570  is housed. The body  572  is partially received in the housing  578 . The body  572  comprises a magnetisable portion  572   a  located at an opposite side of the solenoid  570  to the contact element  574 . This allows for a particularly compact actuator  569 . 
     As best seen in  FIG. 26 , a plurality of the actuators  569  may be used to actuate latching arrangements  13  of rocker arms  3  of the intake valves  40   a ′,  40   a ″ or the exhaust valves  40   b ′,  40   b ″ of a respective plurality of cylinders. Referring to  FIG. 26 , an actuation assembly  580  comprises a plurality of actuators  569 , each actuator  569  being associated with the intake valves  40   a ′,  40   a ″ or the exhaust valves  40   b ′,  40   b ″ of a different cylinder of an internal combustion engine. The actuation assembly  580  comprises a common support  582  connectable to a cam carrier  522  of the internal combustion engine. Each of the plurality of actuators  569  are connected to the common support  582 . The actuation assembly  580  allows for convenient and efficient installment of the plurality of actuators  569  to the engine. 
     As best seen in  FIG. 26 , a first actuation assembly  580   a , comprising two actuators  569 , is arranged for actuation of the latching arrangements  13 ′,  13 ″ of the rocker arms  3   a ′,  3   a ″ of the intake valves  40   a ′,  40   a ″ of each of the second and third cylinder of the internal combustion engine, and a second actuation assembly  580   b , comprising two actuators  569 , is arranged for actuation of the latch pins  13 ′,  13 ″ of the rocker arms  3   b ′,  3   b ″ of the exhaust valves  40   b ′,  40   b ″ of the second and third cylinder of the internal combustion engine. The actuators  569  associated with the intake  40   a ′,  40   a ″ and exhaust  40   b ′,  40   b ″ valves of the third cylinder may be controlled by a control unit to actuate the latching arrangements  13  associated with the valves of the third cylinder in common, thereby to deactivate the third cylinder. Similarly, the actuators  569  associated with the intake  40   a ′,  40   a ″ and exhaust  40   b ′,  40   b ″ valves of the second cylinder may be controlled by a control unit to actuate the latching arrangements  13  associated with the valves of the second cylinder in common, thereby to deactivate the second cylinder. If all four actuators  569  are controlled to actuate their respective latch pins  13 , then both the second and third cylinder will be deactivated. 
     Although not illustrated, it will be appreciated that the first actuation assembly  580   a  may comprise four actuators  569  each arranged to actuate latching arrangements  13  of the rocker arms  3   a  of the intake valves  40   a  of a different one of the four cylinders, and/or the second actuation assembly  580   b  may comprise four actuators  569  each arranged to actuate latching arrangements  13  of the rocker arms  3   a  of the exhaust valves  40   b  of a different one of the four cylinders. In this way, dynamic skip fire control, in which any of the cylinders may be active (fired) or deactivated (skipped) on a continuously variable basis, may be provided. The use of individual solenoid based actuators  569  therefore allows fully independent activation and deactivation of the cylinders, and hence flexibility in the selection of an engine operation mode. 
     In some of the examples above, it was described that a compliance arrangement  120  intermediate of the cam  110  and latching arrangement  13  of the rocker arm  3  may be used. However, in examples where the movement of the cams  110  is synchronised with the engine condition, for example synchronised so that a cam  110  attempts to apply an actuation force to the latching arrangement  13  only when the latch pin  15  of the latching arrangement  13  is free to move, or otherwise, then the valve train assembly  1  may not comprise a compliance arrangement  120 . Further, it is noted that the examples described above having the actuator  569  comprising a solenoid  570  do neither comprise an compliance arrangement, because energising of the solenoid  570  will cause a constant force to be applied to the latching arrangement  13  such that the latch pin  15  of the latching arrangement  13  will be actuated as soon as it is free to do so. 
     It will be appreciated that although the above examples relate to an 1-4 internal combustion engine having four cylinders, this need not necessarily be the case and that there may be a different number of cylinders and/or the cylinders may be in a different configuration. For example there may be six cylinders. 
     It will be appreciated that in some examples cam shapes other than those described above may be used provide the control of the rocker arms  3   a ,  3   b.    
     Although in the above the dual body rocker arms were described as providing a first primary function of a standard valve opening event and a second secondary function of cylinder deactivation, this need not necessarily be the case, and in other examples, other functions or modes of operation may be provided by the dual body rocker arms. Indeed, the dual body rocker arms may be any dual body rocker arm for controlling a valve of a cylinder, the rocker arm comprising a first body, a second body mounted for pivotal motion with respect to the first body, and a latch pin moveable between a first position in which the latch pin latches the first body and the second body together and a second position in which the first body and the second body are unlatched to allow pivotal motion of the second body relative to the first body. Other functionality such as, for example, internal Exhaust Gas Recirculation (iEGR) may be provided. 
     Although in some of the above examples the default position of the latch pin  15  was described as latched and that the latch pin  15  is actuated from an unlatched position to a latched position, this need not necessarily be the case and in some examples, the default position of the latch pin  15  may be unlatched, and the actuation arrangement  13  may be arranged to cause the latch pin to move from the unlatched position to the latched position, i.e. the actuation arrangement  13  and/or the actuator  569  etc may be arranged to actuate the latching arrangement so as to cause the latch pin to move from the unlatched position to the latched position. Indeed, the actuating arrangement may be arranged to move the respective latch pins of one or more dual body rocker arms from one of the latched and unlatched positions to the other of the latched and unlatched positions. 
     It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the examples, or any combination of any other of the examples. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments. 
     The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 ,  1   a ,  1   c ,  1   d  valve train assembly 
               3   a ,  3   b ,  3   a ′,  3   a ″,  3   b ′,  3   b ″ dual body rocker arm 
               7  outer body 
               7   a ,  7   b  ends of outer body 
               8   a ,  8   b  protrusions 
               8   c  curved surface 
               9  inner body 
               11  pivot axis 
               13 ,  13 ′,  13 ″ latching arrangement 
               15  latch pin 
               15   a  slot 
               16  return spring 
               16   a  washer 
               17  roller follower 
               17   a  roller 
               17   b  needle bearings 
               17   c  roller axle 
               21  torsional biasing means 
               21   a ,  21   b  coiled sections 
               21   c  non-coiled section 
               40   a ,  40   a ′,  40   a ″ intake valve 
               40   b ,  40   b ′,  40   b ″ exhaust valve 
               41   a ,  41   b  valve stem 
               42  Hydraulic Lash Adjuster (HLA) 
               43   a ,  43   b  cam 
               44   a ,  44   b  camshaft 
               100  actuation arrangement 
               102  lever 
               102   a  first end 
               102   b  second end 
               102   c  protrusion 
               104 ,  104 ′,  404  actuation source 
               106  actuation transmission arrangement 
               108 ,  108   a ,  108   b ,  308 ,  408   b  shaft 
               110 ,  110   a ,  110   b ,  11 Op,  11 Oq,  11  Or, 
               110   s ,  410  cams 
               112 ,  112   a ,  112   b ,  412   b  gear mechanism 
               116  base circle 
               118  raised profile 
               120  compliance arrangement 
               120   a  first portion 
               120   b  second portion 
               122 ,  122 ′ cam carrier 
               124  biasing means 
               130 ,  430  first part 
               132 ,  432  pin 
               134 ,  434  second part 
               136 ,  436  slots 
               138  arcuate protrusion 
               140  arcuate recess 
               150 ,  250  electric motor 
               156 ,  256  output shaft 
               252  spur gear 
               254  gear housing 
               258 ,  326  bearings 
               260  drive shaft 
               322  main body 
               324  housing 
               324   a  hollow cylindrical protrusion  350  actuation assembly 
               569  actuator 
               570  solenoid 
               572  body 
               572   a  magnetisable portion 
               574  contact element 
               574   a  first region 
               574   b  second region 
               574   c  pivot point 
               576  biasing means 
               578  housing 
               580 ,  580   a ,  580   b  actuation assembly 
               582  common support