Technical Field

The present invention relates to an assembly for an internal combustion engine. Background

With more demanding legislation for Internal Combustion (IC) engines more complex valvetrain assemblies with different functions are required. For diesel engines one of the required functions is an internal Exhaust Gas Recirculation (iEGR). The iEGR function could be achieved with different types of valvetrain with different complexity and different integration cost. Switchable Rocker Arms (RR/A) (also reffered to herein as "dual-lift rocker arms") with external actuation of latching pins (applied to both or just one exhaust position of each cylinder) provides full iEGR functionality for standard Type II valvetrain system with very low integration cost.

Dual lift rocker arms for control of valve actuation by alternating between at least two or more modes of operation are known. 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 and are unlatched, and hence can pivot with respect to each other, to provide a second mode of operation. Typically, a moveable latch pin is used to switch between the two modes of operation.

WO 2013/156610 Al [EATON SRL] discloses such a dual lift rocker arm with a moveable latch pin. The default position of the latch pin is unlatched, and it is retained in this position using biasing means. When required, the latch pin is actuated to the latched position using an external actuation mechanism based on a leaf spring. When actuation is required, the leaf spring is controlled to rotate a certain amount so as to engage with a roller of the latch pin, and hence push the latch pin into the latched position.

Summary

According to a first aspect of the present invention, there is provided an assembly for an internal combustion engine, the assembly comprising: a plurality of rocker arms each for operating a respective engine valve of a plurality of engine valves, each rocker arm comprising a first body, a second body and a latch pin that is 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 un-latched to allow pivotal motion of the second body relative to the first body; and an actuating arrangement for actuating the latch pins; wherein the actuating arrangement comprises an elongate shaft carrying a respective flexible strip for each latch pin, and an actuator for moving the elongate shaft, wherein, when the actuator moves the shaft from a first shaft position to a second shaft position, each flexible strip causes a respective one of the latch pins to be urged from one of its first position and second position to the other of its first position and second position.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings. In the following, like parts are given like reference numerals.

Brief Description of the Drawings

Figure 1 illustrates a schematic perspective view of a valve train assembly including a rocker arm;

Figure 2 illustrates another perspective view of the valve train assembly;

Figure 3 is an exploded view of the rocker arm;

Figures 4a and 4b schematically illustrate the valve train assembly at two different points in engine cycle when the inner and outer bodies are latched;

Figures 5a and 5b schematically illustrate the valve train assembly at two different points in engine cycle when the inner and outer bodies are un-latched; Figure 6 illustrates a graph showing valve lift against cam shaft rotation; Figure 7 illustrates schematically a perspective view of an exemplary exhaust valve train assembly; and

Figure 8 illustrates schematically a perspective view of an exemplary exhaust valve train assembly.

Detailed Description

Figures 1 and 2 illustrate schematically a valve train assembly 1 comprising a rocker arm 2 according to an example. Although the example rocker arm 2 is referred to in the below, it will be appreciated that the rocker arm 2 may be any rocker arm comprising a plurality of bodies that move relative to one another, and which are latched together to provide one mode of operation (a latched valve-lift mode) and are unlatched, and hence can move with respect to each other, to provide a second mode of operation (an un-latched valve-lift mode).

Referring again to the example of Figures 1 and 2, a valve train assembly 1 comprises a rocker arm 2, an engine valve 4 for an internal combustion engine cylinder (not shown) and a lash adjustor 6. The rocker arm 2 comprises an inner body or arm 8 and an outer body or arm 10. The inner body 8 is pivotally mounted on a shaft 12 which serves to link the inner body 8 and outer body 10 together. A first end 14 of the outer body 10 engages the stem 16 of the valve 4 and at a second end 20 the outer body 10 is mounted for pivotal movement on the lash adjustor 6 which is supported in an engine block (not shown). The lash adjuster 6, which may for example be a hydraulic lash adjuster, is used to accommodate slack between components in the valve train assembly 1. Lash adjusters are well known per se and so the lash adjuster 6 will not be described in detail.

The rocker arm 2 is provided with a pair of main lift rollers 22a and 22b rotatably mounted on an axle 24 carried by the outer body 10. One of the main lift rollers 22a is located one side of the outer body 10 and the other of the main lift rollers 22b is located the other side of the outer body 10. The rocker arm 2 is further provided with a secondary lift roller 26, located within the inner body 8 and rotatably mounted on an axle (not visible in Figures 1 and 2) carried by the inner body 8. A three lobed camshaft 30 comprises a rotatable camshaft 32 mounted on which are first 34 and second 36 main lift cams and a secondary lift cam 38. The secondary lift cam 38 is positioned between the two main lift cams 34 and 36. The first main lift cam 34 is for engaging the first main lift roller 22a, the second main lift cam 36 is for engaging the second main lift roller 22b and the secondary lift cam 38 is for engaging the secondary lift roller 26. The first main lift cam 34 comprises a lift profile (i.e. a lobe) 34a and a base circle 34b, second main lift cam 36 comprises a lift profile 36a and a base circle 36b and the secondary lift cam 38 comprises a lift profile 38a and a base circle 38b. The lift profiles 34a and 36a are substantially of the same dimensions as each other and are angularly aligned. The lift profile 38a is smaller than the lift profiles 34a (both in terms of the height of its peak and in terms of the length of its base) and is angularly offset from them.

The rocker arm 2 is switchable between a dual lift mode which provides two operations of the valve 4 (a valve operation is an opening and corresponding closing of the valve) per engine cycle (e.g. full rotation of the cam shaft 32) and a single lift mode which provides a single operation of the valve 4 per engine cycle. In the dual lift mode, the inner body 8 and the outer body 10 are latched together by a latching arrangement 40 (see Figure 2) and hence act as a single solid body. With this particular arrangement, the dual lift mode provides a higher main valve lift and a smaller secondary valve lift per engine cycle. The single lift mode provides just the main valve lift per engine cycle. The single lift mode is an example of a first valve-lift mode, and the dual lift mode is an example of a second valve-lift mode of the valve train assembly 1.

During engine operation in the dual lift mode, as the cam shaft 32 rotates, the first main lift cam's lift profile 34a engages the first main lift roller 22a whilst, simultaneously, the second main lift cam's lift profile 36a engages the second main lift roller 22b and together they exert a force that causes the outer body 10 to pivot about the lash adjuster 6 to lift the valve stem 16 (i.e. move it downwards in the sense of the page) against the force of a valve spring (not shown) thus opening the valve 4. As the peaks of the lift profiles 34a and 36a respectively pass out of engagement with the first main lift roller 22a and the second main lift roller 22b, the valve spring (not shown) begins to close the valve 4 (i.e. the valve stem 16 is moved upwards in the sense of the page). When the first main lift cam's base circle 34b again engages the first main lift roller 22a and the second main lift cam's 36 lift profile engages the second main lift roller 22b the valve is fully closed and the main valve lift event is complete.

As the camshaft 32 continues to rotate, then, the secondary lift cam's lift profile 38a engages the secondary lift roller 26 exerting a force on the inner body 8 which force, as the inner body 8 and the outer body 10 are latched together, is transmitted to the outer body 10 causing the outer body 10 to pivot about the lash adjuster 6 to lift the valve stem 16 against the force of a valve spring (not shown) thus opening the valve 4 a second time during the engine cycle. As the peak of the lift profile 38a passes out of engagement with the secondary lift roller 26 the valve spring (not shown) begins to close the valve 4 again. When the secondary lift cam's base circle 38b again engages the secondary lift roller 26 the valve 4 is fully closed and the second valve lift event for the current engine cycle is complete.

The lift profile 38a is shallower and narrower than are the lift profiles 34a and 36a and so consequently the second valve lift event is lower and of a shorter duration than is the first valve lift event.

In the single lift mode the inner body 8 and the outer body 10 are not latched together by the latching arrangement 40 and hence in this mode, the inner body 8 is free to pivot with respect to the outer body 10 about the shaft 12. During engine operation in the single lift mode, as the cam shaft 32 rotates, when the first main lift cam's lift profile 34a engages the first main lift roller 22a and the second main lift cam's lift profile 36a engages the second main lift roller 22b, the outer body 10 pivots about the lash adjuster 6 and, in an identical way as in the dual lift mode, a main valve lift event occurs. As the camshaft 32 continues to rotate, then, the secondary lift cam's lift profile 38a engages the secondary lift roller 26 exerting a force on the inner body 8. In the single lift mode, however, as the inner body 8 and the outer body 10 are not latched together, this force is not transmitted to the outer body 10 which hence does not pivot about the lash adjuster 6 and so there is no additional valve event during the engine cycle. Instead, as the secondary lift cam's lift profile 38a engages the secondary lift roller 26, the inner body 8 pivots with respect to the inner body 10 about the shaft 12 accommodating the motion that otherwise would be transferred to the outer body 10. A torsional lost motion spring (not shown in Figures 1 and 2) is provided to return the inner body 8 to its starting position relative to the outer body 10, once the peak of the lift profile 38a has passed out of engagement with the secondary lift roller 26.

In one embodiment, this arrangement may be used to provide switchable Internal Exhaust Gas Recirculation (IEGR) control. For example, if the valve 4 is an exhaust valve for an engine cylinder, the main valve lift acts as the main exhaust lift of an engine cycle, and the timing of the secondary valve lift may be arranged so that it occurs when an intake valve for that cylinder, controlled by a further rocker arm (not shown) mounted pivotally on a further lash adjuster (not shown) and which pivots in response to an intake cam (not shown) mounted on the cam shaft 32, is open. The simultaneous opening of the intake and exhaust valves in this way ensures that a certain amount of exhaust gas remains in the cylinder during combustion which, as is well known, reduces NOx emissions. Switching to the single lift mode deactivates the IEGR function, which deactivation may be desirable under certain engine operating conditions. As will be appreciated by those skilled in the art, this switchable IEGR control may also be provided if the valve 4 is an intake valve with the timing of the secondary valve lift arranged to occur when an exhaust valve for that cylinder is open during the exhaust part of an engine cycle.

As is best understood from Figure 3, the secondary lift roller 26 is mounted on a hollow inner bushing/ axle 43 which is supported in the apertures 48a and 48b. The axle 24 extends through the inner bushing/axle 43 (and hence through the inner roller 26) and the diameter of the axle 24 is somewhat smaller than the inner diameter of the inner bushing/axle 43 to allow movement of the assembly of the inner body 8, axle 43 and inner roller 26 relative to the outer body 10. The main lift rollers 22a and 22b are therefore arranged along a common longitudinal axis and the secondary lift roller 26 is arranged along a longitudinal axis that is slightly offset from this. This arrangement of axles and rollers ensures that the rocker 2 arm is compact and facilitates manufacturing the first 10 and second bodies from stamped metal sheets.

As is also best seen from Figure 3, the latching arrangement 40 comprises the latch pin 80 and an actuation member 84. The actuation member 84 comprises a sheet bent along its width to form first 84a and second 84b rectangular portions which define a right angle. The first portion 84a defines a hole 84c. The actuation member 82 further comprises a pair of winged portions extending rearwardly from the second portion 84c each of which defines a respective one of a pair of apertures 86a, 86b for supporting a shaft 88 on which is mounted a roller 90. The actuation member 84 straddles the end wall 66 of the outer body 10 with the second portion 84c slidably supported on the end wall 66 with the first portion 84a positioned between the end wall 66 and the inner wall 68 of the outer body 10. At one end, the latch pin 80 defines an upward facing latch surface 92.

As seen in Figures 4 and 5, the latch pin 80 extends through the holes 74a in the end wall 66 and the hole 84c in the actuation member 82 and its end 93 engages the wing portions of the actuation member 84. Figures 4a and 4b illustrate the valve train assembly 1 when the rocker arm 2 is in the single lift mode (i.e. unlatched configuration). In this configuration, the actuation member 82 and latch pin 80 are positioned so that the latch surface 92 does not extend through the hole 74b and so does not engage the latch contact surface 54 of the inner body 8. In this configuration, the inner body 8 is free to pivot, with respect to the outer body 10, about the shaft 12 when the secondary roller 26 engages the lift profile 38a and hence there is no additional valve event. It will be appreciated that the amount of movement available to the inner body 8 relative to the outer body 10 (i.e. the amount of lost motion absorbed by the inner body 8) is defined by the size difference between the diameter of the axle 24 and the inner diameter of the inner bushing/axle 43. The torsional spring 67, which is installed over the top of the valve stem 16 and is located inside the inner body 10 by the shaft 12, acts as a lost motion spring that returns the inner body 8 to its starting position with respect to the outer body 10 after it has pivoted.

Figures 5a and 5b illustrate the valve train assembly 1 when the rocker arm 2 is in the dual lift mode (i.e. a latched configuration). In this configuration, the actuation member 82 and latch pin 80 are moved forward (i.e. to the left in the Figures) relative to their positions in the unlatched configuration so that the latch surface 92 does extend through the hole 74b so as to engage the latch contact surface 54 of the inner body 8. As explained above, in this configuration, the inner body 8 and the outer body 10 act as a solid body so that when the when the secondary roller 26 engages the lift profile 38a there is an additional valve event.

An actuator 94 is provided to move the latching arrangement 40 between the un-latched and latched positions. In this example, the actuator comprises an actuator shaft 96 carrying a biasing means 98, which in this example comprises a flexible strip, preferably a leaf spring. In the default unlatched configuration, the leaf spring 98 does not engage the latching arrangement 40. To enter the latched configuration, the shaft 96 is rotated a certain amount (for example 12 degrees) causing the leaf spring 98 to engage the roller 88 and to push the latching arrangement 40 into the latched position. A spring 85 mounted over the latch pin 80 and supported between an outer face of the end wall 66 and the winged members of the member 84 is biased to cause the latching arrangement 40 to return to its unlatched position when the actuator shaft 96 is rotated back to its unlatched position and the leaf spring 98 disengages the roller 88.

Advantageously, when the base circle 38b engages the inner bushing/axle 43, the inner bushing axle 43 stops always on the axle 24 which ensures that the orientation of the various components is such that the latch pin 80 is free to move in and out of the latched and unlatched positions.

Figure 4a illustrates the valve train assembly 1 when the rocker arm 2 is in the single lift mode (i.e. the un-latched configuration) at a point in an engine cycle when the main lift rollers 22a and 22b are engaging the respective base circles 34b and 36b of the first main lift cam 34 and the second main lift cam 36. At this point in the engine cycle, the valve 4 is closed. Figure 4b illustrates the valve train assembly 1 when the rocker arm 2 is in the single lift mode at another point in an engine cycle when the main lift rollers 22a and 22b are engaging the respective peaks of the lift profiles 34a and 36a of the first main lift cam 34 and the second main lift cam 36. At this point in the engine cycle the valve 4 is fully open and the 'maximum lift' of the main valve event is indicated as M.

Figure 5a illustrates the valve train assembly 1 when the rocker arm 2 is in the dual lift mode (i.e. the latched configuration) at a point in an engine cycle when the main lift rollers 22a and 22b are engaging the respective base circles 34b and 36b of the first main lift cam 34 and the secondary lift roller 26 is engaging the base circle 38b of the secondary lift cam 38. At this point in the engine cycle, the valve 4 is closed. Figure 5b illustrates the valve train assembly 1 when the rocker arm 2 is in the single lift mode at another point in an engine cycle when the main lift rollers 22a and 22b are engaging the respective base circles 34b and 36b of the first main lift cam 34 and the second main lift cam 36 and the secondary lift roller 26 is engaging the peak of the lift profile 38a of the secondary lift cam 38. At this point in the engine cycle the valve 4 is fully open during the additional valve event and the 'maximum lift' of the secondary valve event is indicated as M'.

Figure 6 illustrates a graph in which the Y axis indicates valve lift and the X axis indicates rotation of the cam shaft. In the example of the valve 4 being an exhaust valve, the curve 100 represents the main lift of the exhaust valve during an engine cycle and the curve represents 101 the additional lift of the exhaust valve during the subsequent engine cycle. The curve 102 represents the lift of intake valve (not shown in the figures), during the subsequent engine cycle, operated by an intake rocker arm (again not shown in the Figures) in response to an intake cam (not shown in the Figures) mounted on the cam shaft. It can be seen that the cams are arranged so that in any given engine cycle, the additional smaller opening of the exhaust valve occurs when the intake valve is open to thereby provide a degree of internal exhaust gas recirculation.

As previously mentioned, in an alternative arrangement (not illustrated) the valve 4 is an intake valve rather than an exhaust valve (making the rocker arm 2 an intake rocker arm) and an exhaust rocker arm operates an exhaust valve in response to an exhaust cam mounted on the cam shaft. In this alternative arrangement the cams are arranged so that in any given engine cycle, the additional smaller opening of the intake valve occurs when the exhaust valve is open to thereby provide a degree of internal exhaust gas recirculation.

Figure 7 illustrates a portion of an exhaust valve train assembly 701 of a four cylinder internal combustion engine (not shown). The exhaust valve train assembly 701 comprises a main cam shaft 32 held in a cam carrier (not shown). The cam shaft 32 drives the opening of in total eight exhaust valves 4. There are four groups W, X, Y, Z of two exhaust valves 4 each, one group per cylinder (not shown). One exhaust valve 4 per group is driven by a respective part 701a of the valve train assembly 701 as described above with reference to Figures 1 to 6, the latch pin 80 (not visible in Figure 7) of which being actuated using the actuator 94 as described above with reference to Figures 4a to 5b. This part 701a of the valve train assembly 701 per group W, X, Y, Z provides, for example, internal Exhaust Gas Recirculation on demand as described above. The other exhaust valve 4 per group is driven by a respective part 701b of the valve train assembly 701 similar to that as described above with reference to Figures 1 to 5b, except that the part 701b of valve train assembly 701 comprises a standard, single lift, i.e. non-switchable, rocker arm 2a driven in a fashion as is known per say by a single main lift cam 736 of the cam shaft 32. This standard part 701b of the valve train assembly 701 per group W, X, Y, Z provides standard exhaust valve opening as is known per say.

The four groups W, X, Y, Z extend side by side along the length of the cam shaft 32. In each group, the main lift cam 736 of the standard part 701b of the valve train assembly 701 is in phase with the main lift cams 34, 36 of the part 701a of the valve train assembly 701. In each group, the secondary lift cam 38 of the part 701a of the valve train assembly 701 is out of phase with the main lift cams 34, 36 of the part 701a of the valve train assembly 701 as described above. The main lift cams 736, 34, 36 of any one group W, X, Y, Z are out of phase with respect to the main lift cams 736, 34, 36 of any one other group to allow for exhaust gas release from the correspondingly out of phase combustion in each cylinder (not shown).

The latch pin 80 of each dual lift rocker arm 2 of each valve train assembly 1 of the four groups W, X, Y, Z is actuated by an actuating arrangement 795. The actuating arrangement 795 comprises a flexible strip, preferably a leaf spring 98 as described above, for each respective valve train assembly 1 for each respective group W, X, Y, Z. However, in the actuating arrangement 795 illustrated in Figure 7, each flexible strip or leaf spring 98 is connected by a common shaft 96. The common shaft 96 is elongate and extends substantially parallel with the cam shaft 32 and spans the four groups W, X, Y, Z. Each leaf spring 98 comprises a first portion connected to the common shaft 96 and a second portion for contacting the respective latch pin 80 in each respective group W, X, Y, Z. One end 96a of the common shaft 96 is attached to an actuator or drive 768 for moving the common shaft 96. In this example, the drive 768 is a twostep electric motor (or rotational solenoid, or the like) 768 arranged to rotate the common shaft 96 about its axis. The motor 768 comprises a default biasing means such as a return spring (not shown) for returning the common shaft 96 to its original position, for example so that the default position for the leaf springs 98 is disengaged with the latch pins 80. The electric motor 768 is controllable (for example by electrical signal) to rotate the common shaft 96.

When the motor 768 is controlled to rotate the common shaft 96 (for example when actuation of the latching arrangement 40 is required, for example when an iEGR active mode is required in the engine), the motor 768 rotates the common shaft 96, for example by 20-25 degrees, such that the leaf springs 98 (simultaneously) rotate towards the respective latch assemblies 40 of the respective valve train assemblies 1 of the respective groups W, X, Y, Z. This rotation of each of the leaf spring 98 causes the actuation of the latch pins 80 of the respective dual-lift rocker arms 2 of the respective parts 701a of the valve train assembly 701 into the latched position. When de-actuation is required, the motor 768 is controlled to rotate the common shaft 96 in the opposite direction, which causes each leaf spring 98 to (simultaneously) disengage from the respective latch pins 80. Each latch pin 80 may then return to the unlatched position under force of the associated return spring 85, as described above with reference to Figures 4a to 5b. Alternatively or additionally, the motor 768 may be controlled to cease exerting a torque on the common shaft 96, and hence the torque of the return spring (not shown) of the motor 768 may rotate the common shaft 96 back such that each leaf spring 98 (simultaneously) disengages from (or ceases to apply a substantial force to) the respective latch pins 80. Each latch pin 80 may then return to the unlatched position under force of an associated return spring 85 as described above with reference to Figures 4a to 5b.

Figure 8 illustrates the same valve exhaust valve train assembly 701 as described above with respect to Figure 7, except in the exhaust valve train assembly 801 illustrated in Figure 8, the actuator arrangement 895 comprises a hydraulic assembly 868 rather than an electric motor (786 in Figure 7) as the actuator 868, and rather than being connected to and moveable (e.g. rotatable) by the electric motor (768 in Figure 7), the common shaft 96 is instead connected to and moveable (e.g. rotatable) by the hydraulic assembly 868.

The hydraulic assembly or actuator 868 comprises a hydraulic drive 868a and a lever 868b. The hydraulic drive 868a comprises a piston (not visible) mounted for reciprocal sliding movement in an outer body 868c. The sliding axis of the hydraulic actuator 868a is perpendicular to the axis of the common shaft 96. Hydraulic fluid is supplied to the hydraulic drive 868a, for example from an oil control valve (not shown), to push the piston (not visible) out of the outer body 868c towards the common shaft 96. The hydraulic drive 868a comprises a return spring (not shown) that urges the piston (not visible) inwardly of the outer body 868c, such that the default position of the piston is retracted.

The lever 868b is connected to and extends radially out from the common shaft 96. A distal end (not visible) of the lever 868b is connected to (or is for contact with) the piston (not visible). The lever 868b thereby converts the linear sliding movement of the piston (not visible) into rotational movement of the common shaft 96 about its axis.

When the oil control valve (not shown) is controlled (for example via an electrical signal) to supply high pressure hydraulic fluid (such as oil) to the hydraulic drive 868a (for example when actuation of the latching arrangements 40 is required, for example when an iEGR active mode is required in the engine), the piston (not visible) is caused to extend out of the outer body 868c. The piston (not visible) thereby applies a torque, via the lever 868b, to the common shaft 96, that is the lever 868b converts the outward linear sliding movement of the piston (not shown) into rotational movement of the common shaft 96 about its axis. Rotation of the common shaft 96, for example by 20-25 degrees, causes the leaf springs 98 to (simultaneously) rotate towards the respective latch assemblies 40 of the respective parts 701a of the valve train assembly 801 of the respective groups W, X, Y, Z. This rotation of each of the leaf springs 98 causes the actuation of the latch pins 80 of the respective dual-lift rocker arms 2 of the respective parts 701a of the valve train assembly 801 into the latched position.

When deactuation is required (for example when the iEGR active mode is no longer required), the oil control valve (not shown) is controlled to reduce the oil pressure supplied to the hydraulic drive 868a, and hence under the force of the return spring (not visible) of the hydraulic drive 868a, the piston (not visible) moves back toward (inwardly of) the outer body 868c. This causes the common shaft 96, via the lever 868, to rotate back in the opposite direction, which causes each leaf spring 98 to (simultaneously) disengage from the respective latch pins 80. Each latch pin 80 may then return to the unlatched position under force of the associated return spring 85, as described above with reference to Figures 4a to 5b. The hydraulic assembly 868 may be positioned at any location along the length of the common shaft 96, for example part way along the length of the common shaft 96, as is illustrated in Figure 8. This may provide space savings and flexibility in the placement of the drive 868.

Advantageously, such actuation by a common actuation shaft 96 reduces the complexity of the exhaust valve train assembly 701, 801 as compared to individual actuation, and may save space.

Although the common shaft 96 is illustrated in Figure 7 and Figure 8 as being a straight cylindrical rod, this need not necessarily be the case, and the shape of the shaft 96 in-between the leaf springs 98 can be any shape, so long an overall rotation axis of the common shaft 96 is maintained. This may be advantageous to minimise the space impact of the common shaft 96. Although in the above examples, the common shaft 96 was rotated to cause the leaf springs 98 to actuate the respective latch assemblies 40, this need not necessarily be the case, and in other examples the common shaft 96 may be caused to move, for example translate, rotate, or any combination thereof, in order to cause the leaf springs 98 to actuate the respective latch assemblies 40. For example, the hydraulic actuator 866a may push (translate) the common shaft 96 towards the latch assemblies 40 thereby causing the flexible strips or leaf springs 98 attached thereto to apply a force to and thereby actuate the respective latch assemblies 40.

Similarly to as mentioned above, in an alternative arrangement (not illustrated) to that illustrated in Figure 7 or Figure 8, the valves 4 are instead intake valves rather than an exhaust valves (making the rocker arms 2 of the valve train assemblies 1 an intake rocker arm) and an exhaust rocker arm operates an exhaust valve in response to an exhaust cam mounted on the cam shaft. In this alternative arrangement the cams are arranged so that in any given engine cycle, the additional smaller opening of the intake valve occurs when the exhaust valve is open to thereby provide a degree of internal exhaust gas recirculation.

Although some of the above examples above referred to actuation of the latching arrangement 40 causing an internal Exhaust Gas Recirculation active mode of the associated valve train assembly 1, this need not necessarily be the case. The actuation may be of the respective latching arrangements of any a plurality of rocker arms each for operating a respective engine valve, each rocker arm comprising a first body, a second body and a latch pin that is 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 un-latched to allow pivotal motion of the second body relative to the first body. For example, one or more of the valve train assemblies 1 may be configured for Early Exhaust Valve Opening (EEVO), and hence actuation of the latching arrangement 40 may cause an EEVO active mode of the associated valve train assembly 1.

Although in the examples above the default position of the latch pin 80 was an unlatched position, and the leaf spring 98 moves the latch pin 80 between the un-latched and latched positions, this need not necessarily be the case, and in other examples the default position of the latch pin 80 may be a latched position, and the leaf spring 98 may move the latching arrangement 40 between a latched and an un-latched position. Accordingly, in some examples, the latch pin 80 may be moveable between a first position in which the latch pin 80 latches the outer body 10 and the inner body 8 together and a second position in which the outer body 10 and the inner body 8 are un-latched to allow pivotal motion of the inner body 8 relative to the outer body 10, and the leaf spring 98 may cause the latch pin to be urged from one of its first position and second position to the other of its first position and second position. Similarly, when the actuator 768, 868 moves the common shaft 96 from a first shaft position to a second shaft position, each flexible strip 98 may cause a respective one of the latch pins 80 to be urged from one of its first position and second position to the other of its first position and second position.

Although in some of the above examples, the leaf spring 98 was described as contacting the latch pin 80 indirectly via the roller 90 of the latching arrangement 40, this need not necessarily be the case, and in other examples, the leaf spring 98 may contact the latch pin 80 directly.

It is to be understood that any feature described in relation to any one embodiment 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 embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.