The present invention relates to actuation, and more specifically actuation of valve-lift modes in a valve train assembly of an internal combustion engine.
With more demanding legislation for Internal Combustion (IC) engines more complex valve train assemblies with different valve-lift 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 valve train with different complexity and different integration cost. For example, a valve train may include Switchable Rocker Arm. Switchable Rocker Arms with external actuation of latching pins (applied to both or just one exhaust position of each cylinder) can provide full iEGR functionality for standard Type II valve train system with very low integration cost. Such rocker arms may also be used for other functions, such as, for example, Early Exhaust Valve Opening (EEVO), or the like.
Switchable rocker arms for control of valve actuation by alternating between at least two or more modes of operation (e.g. valve-lift modes) 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 (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). Typically, a moveable latch pin is used to switch between the two modes of operation.
In some switchable rocker arms the latch pin is actuated internally, that is, it is actuated by a mechanism internal to the valve train assembly of which the rocker arm is part. Although internal actuation mechanisms can save overall space, such internal actuation mechanisms typically require modification of one or more components of the valve train, which can be expensive and complex.
In an embodiment, the present invention provides an actuator for actuating valve-lift modes of a valve train assembly of an internal combustion engine. The valve train assembly is capable of being switched between a first valve-lift mode and a second valve-lift mode. The actuator includes a first body and a second body. The second body is mounted for reciprocal movement with respect to the first body between a first position to cause the first valve-lift mode and a second position to cause the second valve-lift mode. The actuator includes a third body supported by the second body, the third body for moving a first component of the valve train assembly to cause the second valve-lift mode. The third body is moveable relative to the second body. The actuator includes a first biaser for biasing the third body away from the second body towards the first component of the valve train assembly.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
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. All features described and/or illustrated herein can be used alone or combined in different combinations in embodiments of the invention. The 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:
An external actuation mechanism can be 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. However, the inventors have recognized that such a leaf spring mechanism can take up a relatively large amount of space, and is relatively inflexible with respect to the position at which it can be located relative to the valve train.
Embodiments of the present invention provide improved external latch pin actuation mechanisms, and provide improved external actuation of valve lift modes in valve train assemblies capable of being switched between a first valve-lift mode and a second valve-lift mode.
According to an embodiment of the present invention, there is provided an actuator for actuating valve-lift modes of a valve train assembly of an internal combustion engine, the valve train assembly capable of being switched between a first valve-lift mode and a second valve-lift mode, the actuator comprising: a first body; a second body mounted for reciprocal movement with respect to the first body between a first position to cause the first valve-lift mode and a second position to cause the second valve-lift mode; a third body supported by the second body, the third body for moving a first component of the valve train assembly to cause the second valve-lift mode, wherein the third body is moveable relative to the second body; and a first biasing (first biaser) means for biasing the third body away from the second body towards the first component of the valve train assembly.
According to an embodiment of the present invention, there is provided a valve train assembly of an internal combustion engine, the valve train assembly capable of being switched between a first valve-lift mode and a second valve-lift mode, the valve train assembly comprising: the actuator according to the first aspect.
According to an embodiment 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, 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; a respective hydraulic actuator for each latch pin; and a common supply gallery connected to each of the hydraulic actuators for supplying pressurised hydraulic fluid to the hydraulic actuators.
Referring again to the example of
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
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
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 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 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 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 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
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 mounted pivotally on a further lash adjuster and which pivots in response to an intake cam 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
As is also best seen from
As seen in
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 piston 98. In the default unlatched configuration, the actuator piston 98 does not contact the latching arrangement 40. To enter the latched configuration, as described in more detail below, the actuator piston 98 extends to contact the roller 90 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 piston 98 retracts and no longer contacts the roller 90. (The roller 90 and/or the latching arrangement 40 are examples of a first component of the valve train assembly.)
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.
As previously mentioned, in an alternative arrangement 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.
Referring now to
The housing 462 comprises a bore 478 extending from an open end 480 of the housing 462 to bore end 482 within the housing 462. A stopper 472 is received in the bore 478 of the housing 462 at the bore end 482, and extends partially within the bore 478 of the housing. The stopper 472 is fixedly connected to the housing 462, for example, by a threaded connection. The stopper 472 comprises a bore 484 extending from a first open end 486 of the stopper 472 to a second open end 488 of the stopper 472. The second open end 488 of the stopper 472 is of a smaller diameter to the first open end 486 of the stopper 472, and there is a bore step 490 formed between the two diameters. The second open end 488 of the stopper 472, and the bore step 490, are towards and slightly beyond the open end 480 of the housing 462.
The main piston 432 is partially received in the bore 484 of the stopper 472 for reciprocal sliding movement with respect to the stopper 472 (and hence the housing 462). The main piston 432 extends beyond the first open end 486 of the stopper 472 and into the bore 478 of the housing 462 towards the bore end 482 within the housing 462. There is a main spring 464 (an example of a second biasing means (second biaser), other biasing means (other biasers) may be used), one end of which is connected to the main piston 432, and the other of which is connected to the stopper 472. The main spring 464 biases the main piston 432 out of the bore 484 of the stopper 472 and towards the bore end 482 within the housing 462, i.e. away from the roller 90 of the latching arrangement 40. The main piston 432 is moveable within the bore 484 of the stopper 472 between two positions with respect to the housing 462, over a total stroke A. The sliding movement of the main piston 432 within the bore 484 of the stopper 472 is restricted at one end by contact of the main piston 432 with the bore end 482 of the housing 462, and is restricted at the other end by the bore step 490 of the stopper 472.
The main piston 432 comprises a bore 476 that extends into the main piston 432 from an open end 492 of the main piston 432 to a bore end 494 of the main piston 432. The open end 492 of the bore 476 of the main piston 432 is towards the open end 488 of the stopper 472. The compliance piston 468 is received in the bore 476 of the main piston 432 for reciprocal sliding movement with respect to the main piston 432. The compliance piston 468 extends beyond the open end 492 of the main piston 432. Moreover, the compliance piston 468 extends through and beyond the second open end 488 of the stopper 472, for engagement with a roller 90 of a latching arrangement 40.
The compliance piston 468 comprises a bore 496 that extends partially into the compliance piston 468 from an open end 402 of the compliance piston 468 to a bore end 498 of the compliance piston 468. The open end 402 of the compliance piston 468 is towards the bore end 494 of the main piston 432.
There is a compliance spring 496 (an example of a first biasing means, other biasing means may be used), one end of which is attached to bore end 498 of the compliance piston 468, and the other end of which is connected to the bore end 494 of the main piston 432. The compliance spring 496 biases the compliance piston 468 away from bore end 494 of the main piston 432 and out through the open end 492 of the main piston 432, i.e. towards the roller 90 of the latching arrangement 40.
The main piston 432 comprises a pin 470 that extends radially from a side wall of the main piston 432 partially into the bore 476 of the main piston 432. The compliance piston 468 comprises a slit 404, for example a rounded rectangular slit 404, in the side wall of the compliance piston 468 into which the pin 470 extends. The sliding movement of the compliance piston 468 with respect to the main piston 432 is limited to between two positions, one by contact of the pin 470 with a first end 406 of the slit 404 of the compliance piston, and another by contact of the pin 470 with a second end (not visible in
The main piston 432 comprises a second bore 470 partially extending into the main piston 432 from a second open end 410 of the main piston 432 to a second bore end 408 of the main piston 432. The second open end 482 of the second bore 410 has a countersink, and the second bore end 408 is concave in shape with respect to the second open end 482. The second open end 410 of the second bore 470 is on the opposite side of the main piston 432 to the open end 493 of the bore 476 of the main piston 432. There are holes 466a and 466b on opposite sides of the main piston 432 that extend from the outer surface of the main piston 432 into the second chamber 470 of the main piston 432 such that hydraulic fluid may flow from the bore 478 of the housing 462 into the second bore 470 of the main piston 432.
The actuator 94a as shown in
When actuation of the latching arrangement 40 is required, an oil control valve is operated to increase the oil pressure in an oil gallery. The oil gallery is in fluid connection with the actuator 94a. High pressure oil enters the housing 462 through a hole 460a/460b in the housing wall (an example of a fluid connection), flows through holes 466a/466b of the main piston 432, and into the second bore 470 of the main piston 432. The high pressure oil flowing into the second bore 470 of the main piston causes the main piston 432 to move outwardly of the housing 462 (i.e. to the left as shown in the figures) through total stroke A. Although reference is made to oil, it will be readily appreciated that any other suitable hydraulic fluid may be used.
As described in more detail below with respect to
In broad overview,
In
As described above, when actuation is required, high pressure oil flows into the second bore 470 of the main piston 432, and the main piston 432 moves outwardly of the housing 462 (i.e. to the left in the figures) through total stroke A, that is the main piston 432 moves from the first position to the second position.
In the situation illustrated in
In the situation illustrated in
The compliance piston 468 and compliance spring 454 therefore ensure that regardless of the time the main piston 432 is caused to move from the first position to the second position, the latching arrangement 40 will be actuated into the latched position at the next possible window, i.e. the next time the secondary lift roller 26 is engaging the base circle 38b of the secondary lift cam 38. Correct timing of actuation can therefore be easily and consistently achieved.
It will be appreciated that if the secondary lift roller 26 is already engaging the base circle 38b of the secondary lift cam 38 when the main piston 432 is moved from the first position to the second position, then the movement of the main piston 432 to the left (in the sense of
When deactuation of the latching arrangement 40 is required, the oil control valve is operated to decrease the oil pressure in the oil gallery, which in turn decreases the oil pressure behind and in second bore 470 of the main piston 432. The main piston 432 returns from the second position to the first position (i.e. moves to the right in the figures) under the force of main spring 464. This in turn causes the compliance piston 468 (via compliance spring 454) to move to the right such that no significant force is applied to the roller 90 of the latching arrangement 40. The latch pin 80 therefore returns to the default unlatched position under the force of the spring 85 of the latch assembly.
Referring now to
At a forward end 372 of the housing 368 there is a hole 378 extending from the outside of the housing 368 to a cylindrical chamber 370 within the housing. The solenoids 336a, 336b are received in the chamber 370 and are attached to the housing 368. One solenoid 336a is located at a forward end 372 of the housing 368, and the other solenoid 336b is located at a rear end 374 of the housing 368. The solenoids 336a, 336b are separated by a gap 376 within the chamber 370. Each solenoid 336a, 336b has an annular soft iron plate 340a, 340b respectively, placed against a flat surface of the solenoid 336a, 336b facing towards the gap 376 (only one soft-iron plate 340a is visible in
The piston 332 is received into the hole 378 in the forward end 372 of the housing 368, through the centre of the solenoids 336a, 336b, and through the annular soft iron plates 340a, 340b, for reciprocal sliding movement with respect to the housing 368. The piston 332 extends out beyond the hole 378 in the forward end 372 of the housing. The movement of the piston 332 with respect to the housing 368 is restricted to within the total stroke C by the magnet 338 to which the piston 332 is attached coming into contact with the soft iron plates 340a, 340b of the respective solenoids 336a, 336b on either side of the magnet 338. The piston 332 is made of a non-magnetic material.
The piston 332 comprises a bore 362 partially extending from an open end 382 of the piston 332 to a bore end 380 within the piston 332. The open end 382 of the piston 332 faces out and away from the housing 368. The piston 332 comprises a rounded rectangular slit 360 in the side of the piston 332 through the wall of the piston 332 into the bore 362. The rounded rectangular slit 360 extends part way along the length of the piston 332 in a portion of the piston 332 extending beyond the hole 378 of the housing 368.
The contact plate 356 comprises a contact portion 384 and a connecting portion 386. A first part 358 of the connecting portion 386 is pivotally connected to the forward end 372 of the housing 368. A second part 364 of the connecting portion 386 is received in the rounded rectangular slit 360 of the piston 332 for reciprocal sliding movement with respect to the piston 332. The movement of the contact plate 356 with respect to the piston 332 is limited to a compliance stroke D between the ends of the rounded rectangular slit 360.
The contact portion 384 of the contact plate 356 is curved such that when the actuator is in a fully extended “actuation” state (see
The bore 362 of the piston 332 has received therein a compliance spring 354 (an example of a first biasing means, other biasing means can be used), one end of which is connected to (or pushes against) the second part 364 of the connecting portion 386 of the contact plate 356, and the other end of which is connected to (or pushes against) the bore end 380 of the bore 362 of the piston 362. The compliance spring 354 biases the contact plate 356 out and away from the piston 362 and towards the roller 90 of the latching arrangement 40, that is it biases the contact plate 356 anticlockwise in the sense of
The actuator 94b as shown in
When actuation is required, an electronic controller causes current to pass through the solenoids 336a, 336b. The current is controlled to flow in the same direction in both of the solenoids 336a, 336b, say clockwise when viewed from the forward end 372 of the housing 368. Such a current flowing in the solenoid 336a at the forward end 372 of the housing 368 will cause the soft iron plate 340a attached thereto to become magnetised so as to attract the South side 338a of the permanent magnet 338. Conversely, such a current flowing in the solenoid 336b at the rear end 374 of the housing 368 will cause the soft iron plate 340b (best seen in
Similarly to as above for hydraulic actuator 94a, and as described in more detail below with respect to
In
As described above, when actuation is required, a current is provided through the solenoids 336a, 336b, and the magnet 338 and hence piston 332 moves outwardly of the housing 462 (i.e. to the left in the figures) through total stroke C, that is the piston 332 moves from the first position to the second position.
In the situation illustrated in
In the situation illustrated in
The compliance spring 354 therefore ensures that regardless of the time the piston 332 is controlled to move to from the first position to the second position, the latching arrangement 40 will be actuated into the latched position at the next possible window, i.e. the next possible time the secondary lift roller 26 is engaging the base circle 38b of the secondary lift cam 38. Correct timing of actuation can therefore be easily and consistently achieved.
It will be appreciated that if the secondary lift roller 26 is already engaging the base circle 38b of the secondary lift cam 38 when the piston 332 is moved from the first position to the second position, then the movement of the piston 332 to the left will therefore (via compliance spring 354) immediately cause the contact plate 356 to move to the left, which will in turn immediately cause the roller 90 of the latching arrangement 40, the latching arrangement 40, and the latch pin 80 to move to the left and into the latched position. That is, the actuator 94b will go from the deactuation state of
When deactuation of the latching arrangement 40 is required, electronic controller is operated to cause current to flow through the solenoids 366a, 366b in the opposite sense to as during actuation, i.e. anticlockwise when viewed from the contact plate 356. The magnet 338 is therefore caused to move to the right under the respective attraction and repulsion of the soft iron plates of solenoids 336b, 336a. The piston 332 therefore correspondingly moves to the right in the figures from the second position to the first position. This in turn causes the contact plate 356 (via compliance spring 354) to move to the right such that no significant force is applied to the roller 90 of the latching arrangement 40. The latch pin 80 therefore returns to the default unlatched position under the force of the spring 85 of the latching arrangement 40.
It will be appreciated that although the surface of the compliance piston 468 of actuator 94a is flat, this need not necessarily be the case, and a curved contact plate such as contact plate 356 of actuator 94b may be used instead.
It will be appreciated that although in the above example, two solenoids 336, two soft-iron plates 340a, 340b, and one permanent magnet 338 was used, this need not necessarily be the case, and in some examples actuator 94b may comprise one or more solenoids, one or more soft iron-plates 340a, 340b, and one or more permanent magnets 338.
It will be appreciated that the soft-iron plates 340a, 340b may instead be made of any suitable magnetisable material.
The above description included an example of an actuator 94, 94a, 94b actuating a latching arrangement 40 in a rocker arm 2 comprising a plurality of bodies that move relative to one another, and which are latched together to provide one mode of operation (valve-lift mode) and are unlatched, and hence can move with respect to each other, to provide a second mode of operation (valve-lift mode). However, it will be appreciated that the actuator 94, 94a, 94b is not limited to use in this example, or to use with a dual-body rocker arm. It will be appreciated that the actuator 94a, 94b may be used to actuate valve-lift modes in any valve train assembly capable of being switched between a first valve-lift mode and a second valve-lift mode, for example, valve train assemblies for Variable Valve Actuation in Medium and/or Heavy Duty Engines known in the art.
The four groups W, X, Y, Z extend side by side along the length of the cam shaft 32. The main lift cam 1136 of the standard valve train assembly 1a is in phase with the main lift cams 34, 36 of the valve train assembly 1, per group. The secondary lift cam 38 of the valve train assembly 1 is out of phase with the main lift cams 34, 36 of the valve train assembly 1 as described above, per group. The main lift cams 1136, 34, 38 of any one group W, X, Y, Z are out of phase with respect to the main lift cams 1136, 34, 38 of any one other group to allow for exhaust gas release from the correspondingly out of phase combustion in each cylinder.
Each hydraulic actuator 94a of each “dual lift” valve train assembly 1 of each group W, X, Y, Z is in fluid communication with a common oil gallery 1104. The common oil or supply gallery 1104 is connected to each of the hydraulic actuators 94a and is for supplying pressurised oil to the hydraulic actuators 94a. Specifically, the common oil gallery 1104 is in fluid communication with the second bore 470 of each actuator 94a via one of the holes 460a/460b in the housing wall of each actuator 94a. In the example illustrated, the other of the holes 460a/460b is closed off. In other examples, the common oil gallery 1104 may run through each actuator 94a from one hole 460a/460b to the other hole 460a/460b. The common oil gallery 1104 may be defined in the cam carrier. This may save space.
Oil (or any hydraulic fluid) is supplied to the common oil gallery 1104 by an oil control valve (OCV) 1102. The oil control valve is controllable (for example by electrical signal) to increase or decrease the pressure of the oil in the common oil gallery 1104. When the OCV 1102 is controlled to deliver high pressure oil (for example when actuation of the latching arrangement is required, for example when an iEGR active mode is required in the engine), the pressure in the common oil gallery 1104 increases, and hence high pressure oil enters the housing 462 of each hydraulic actuator 94a of each group W, X, Y, Z, which (as described above) causes the main piston 432 of each hydraulic actuator 94a to move outwardly of the housing 462 through the total stroke A (as described above with reference to
As described above, depending on the phase of the secondary lift cam 38 of the valve train assembly 1 to which the actuator 94a corresponds when the main piston 432 extends, the extension of the main piston 432 will either cause an immediate actuation of the latching arrangement 40 to the latched position, or cause a delayed actuation of the latching arrangement 40 to the latched position. However, within (at most) one full rotation of the cam shaft 32, the secondary lift roller 26 of each valve train assembly 1 will have engaged the corresponding base circle 38b of the secondary lift cam 38 of each valve train assembly, and hence within (at most) one full rotation of the cam shaft 32, the extension of the main piston 432 of each actuator 94a will have caused actuation of the latching arrangement 40 of each respective valve train assembly 1 to the latched position.
When actuation of the latching arrangement 40 of each valve train assembly 1 is no longer required, the oil control valve 1102 may be controlled to reduce the oil pressure in the common oil gallery 1104, and hence the main piston 432 of each hydraulic actuator 94a may return to the default de-actuated position under the force of the return spring 464 as described above with reference to
Controlled actuation of the latching arrangement 40 of each valve train assembly 1 (within (at most) one revolution of the cam shaft 32) is thereby achieved by controlling a single oil control valve 1102 in fluid communication with each of the actuators 94a via the common oil gallery 1104. This may reduce complexity and cost, and provide space savings, as compared for example to controlling the actuation of each latching arrangement 40 separately.
Similarly to as mentioned above, in an alternative arrangement 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 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 the above example described hydraulic actuation of the latching arrangements 80 of the respective valve train assemblies 1 using the hydraulic actuator described above with reference to
In embodiments, an actuator for actuating valve-lift modes of a valve train assembly of an internal combustion engine is provided. The valve train assembly is capable of being switched between a first valve-lift mode and a second valve-lift mode. The actuator comprises a first body. A second body is mounted for reciprocal movement with respect to the first body between a first position to cause the first valve-lift mode and a second position to cause the second valve-lift mode. A third body is supported by the second body, the third body being for moving a first component of the valve train assembly to cause the second valve-lift mode. The third body is moveable relative to the second body. A first biaser (biasing means) biases the third body away from the second body towards the first component of the valve train assembly. Also presented is a valve train assembly.
All of the above embodiments are to be understood as illustrative examples of the invention only. 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.
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.
Number | Date | Country | Kind |
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1517728.0 | Oct 2015 | GB | national |
1522386.0 | Dec 2015 | GB | national |
This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2016/074099, filed on Oct. 7, 2016, and claims benefit to British Patent Application No. GB 1517728.0, filed on Oct. 7, 2015, and British Patent Application No. GB 1522386.0, filed Dec. 18, 2015. The International Application was published in English on Apr. 13, 2017 as WO 2017/060490 under PCT Article 21(2).
Filing Document | Filing Date | Country | Kind |
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PCT/EP2016/074099 | 10/7/2016 | WO | 00 |