WO2017220314A1

WO2017220314A1 - Apparatus for controlling poppet valves in an internal combustion engine

Info

Publication number: WO2017220314A1
Application number: PCT/EP2017/063465
Authority: WO
Inventors: Thomas Johnson; Samuel Jenkinson
Original assignee: Jaguar Land Rover Limited
Priority date: 2016-06-22
Filing date: 2017-06-02
Publication date: 2017-12-28
Also published as: DE112017003125T5; GB2551550B; GB201610871D0; GB2551550A

Abstract

An apparatus (3) for controlling poppet valves in an internal combustion engine (5), comprising: a first piston (21a), arranged to control a lift of a first inlet poppet valve (23a) of a first combustion chamber (25a); a second piston (21b), arranged to control a lift of a second inlet poppet valve (23b) of the first combustion chamber; a third piston (21c), arranged to control a lift of a first inlet poppet valve (23c) of a second combustion chamber (25b); a fourth piston (21d), arranged to control a lift of a second inlet poppet valve (23d) of the second combustion chamber; a first hydraulic control system (29a) arranged to operate, at different times, the first piston and the third piston, but not the second piston and the fourth piston; and a second hydraulic control system (29b) arranged to operate, at different times, the second piston and the fourth piston, but not the first piston and the third piston.

Description

APPARATUS FOR CONTROLLING POPPET VALVES IN AN INTERNAL COMBUSTION

ENGINE TECHNICAL FIELD

The present disclosure relates to apparatus for controlling poppet valves in an internal combustion engine. In particular, but not exclusively it relates to apparatus for controlling movement of inlet poppet valves of combustion chambers of an internal combustion engine.

Aspects of the invention relate to an apparatus, a method, a system, an internal combustion engine, a vehicle, a controller and a computer readable medium.

BACKGROUND

At a predetermined time during a combustion cycle of an internal combustion engine, an inlet poppet valve is lifted away from a valve seat and into a combustion chamber, to open an inlet port and allow the intake of air into the combustion chamber through the inlet port. At a later predetermined time during the combustion cycle, the inlet poppet valve is returned to the valve seat to close the inlet port.

It is known for the lifting of an inlet poppet valve to be controlled by apparatus (e.g. a camshaft and valve train). The valve train may comprise a hydraulic control system actuated by the camshaft. The displacement of fluid within the hydraulic control system during actuation by the camshaft moves a small piston within a cylinder. The piston pushes a valve stem of an inlet poppet valve to lift the inlet poppet valve.

A combustion chamber may comprise a plurality of inlet ports, each inlet port opened and closed by an inlet poppet valve. It would be desirable to improve independent adjustability of the lifting of poppet valves sharing a combustion chamber.

It is an aim of the present invention to address disadvantages of the prior art.

SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide an apparatus, a method, a system, an internal combustion engine, a vehicle, a controller and a computer readable medium. According to an aspect of the invention there is provided an apparatus for controlling opening of valves of combustion chambers of a multi-cylinder internal combustion engine, the apparatus comprising at least: a first actuator, arranged to control opening of a first valve of a first combustion chamber; a second actuator, arranged to control opening of a second valve of the first combustion chamber; a third actuator, arranged to control opening of a first valve of a second combustion chamber; a fourth actuator, arranged to control opening of a second valve of the second combustion chamber; a first hydraulic control system arranged to operate, at different times, the first actuator and the third actuator, but not the second actuator and the fourth actuator; and a second hydraulic control system arranged to operate, at different times, the second actuator and the fourth actuator, but not the first actuator and the third actuator.

This provides the advantage of a simple apparatus with a small number of hydraulic control systems, for improving emissions, efficiency and/or performance of an internal combustion engine. The valves are preferably inlet valves, but might instead (or additionally) be exhaust valves. The valves are preferably poppet valves, and the actuators control the lift of the poppet valves, but it will be appreciated that other types of valve might be used instead. Preferably, the actuators are pistons, but it will be appreciated that other types of actuator might be used instead.

The improvement to the internal combustion engine is enabled by lifting inlet poppet valves of a same combustion chamber in a continuously variable manner and substantially independently of one another. Continuous variability refers to the fluid displacement in each hydraulic control system being continuously variable, wherein the fluid displacement may in fact be controllable in a very large but not infinite number of ways, limited by physical constraints. Substantially independent lifting refers to separate adjustability of the lifting of the inlet poppet valves of the same combustion chamber. Substantially independent continuously variable valve lift is enabled because each of the inlet poppet valves to a same combustion chamber is operated by means of a separate hydraulic control system. The apparatus is simple because the overall number of separate hydraulic control systems is smaller than the overall number of inlet poppet valves to be controlled. This is because each hydraulic control system is arranged to operate multiple pistons, and therefore control multiple inlet poppet valves, at different times over the course of a combustion cycle.

It would be appreciated that controlling a lift of an inlet poppet valve may comprise controlling an opening time, a closing time, and/or a lift distance of the inlet poppet valve. The apparatus may comprise switching means for controlling whether the first piston or the third piston is caused to be moved in dependence on application of fluid displacement within the first hydraulic control system, and whether the second piston or the fourth piston is caused to be moved in dependence on separate application of fluid displacement within the second hydraulic control system.

This provides the advantage of a simple means for ensuring that each hydraulic control system operates its pistons at different times. The switching means may be in the form of a spool valve. The switching means may comprise at least one fluid routing switch comprising at least one inlet and multiple outlets, and arranged to switch passage of fluid to different ones of the multiple outlets at different times. The fluid routing switch may be a control valve in the form of a directional control valve, and may be a spool valve. This provides the advantage of a simple apparatus with few components, because each hydraulic control system requires only one control valve.

The switching means may comprise a plurality of fluid blocking switches, each fluid blocking switch having a single inlet and a single outlet, and each fluid blocking switch being arranged to regulate fluid passage from the inlet to the outlet. This provides the advantage of an apparatus with improved switching dynamics. Each fluid blocking switch may be compact, so that full regulation of fluid passage is achieved by blocking movement of a very small distance. The switching means may comprise locking means for regulating movement of at least one of the first piston, the second piston, the third piston, the fourth piston. The locking means may comprise a locking element. This provides the advantage of an apparatus with improved switching dynamics. Full regulation of movement of pistons is achieved by locking movement over a very small distance.

The switching means may comprise at least one actuation mechanism for actuation by a camshaft and/or by electronic means and/or by hydraulic means and/or by pneumatic means, to cause the switching means to complete a cycle through a plurality of switching states over the course of one revolution of the camshaft. This provides the advantage of a simpler apparatus, because existing vehicle systems such as a camshaft, an electrical system, an engine oil system, can be adapted to operate the switching means.

The first hydraulic control system may be arranged to control a first hydraulic fluid displacement in use, and the second hydraulic control system may be arranged to control separately a second hydraulic fluid displacement in use. This provides the advantage of improved dynamics and responsiveness, because hydraulic fluid is substantially incompressible. Hydraulic fluid displacement changes take effect quickly throughout the fluid in the hydraulic control system, enabling each hydraulic control system to control the hydraulic fluid displacement differently for each combustion cycle associated therewith. The hydraulic fluid may be engine oil, to minimize any additional servicing requirements.

The first hydraulic control system may comprise: a master piston for actuation by a camshaft; a solenoid valve for regulating fluid passage to an accumulator; a passage extending between the master piston and the solenoid valve; a first valve passage between the solenoid valve and the first piston; and a second valve passage between the solenoid valve or first valve passage and the third piston. The second hydraulic control system may comprise a master piston for actuation by a camshaft; a solenoid valve for regulating fluid passage to an accumulator; a passage between the master piston and the solenoid valve of the second hydraulic control system; a first valve passage between the solenoid valve of the second hydraulic control system and the second piston; and a second valve passage between the solenoid valve or first valve passage of the second hydraulic control system and the fourth piston. A solenoid valve controls the extent to which camshaft actuation causes fluid displacement to operate a piston, or fill a hydraulic accumulator. This provides the advantage that each hydraulic control system enables continuously variable lift of each inlet poppet valve associated therewith. Switching means as described herein may be disposed on or adjacent to the first valve passage and the second valve passage.

Solenoid valves may be expensive and may require additional computing resources to control solenoid timing. However each hydraulic control system only requires one such solenoid valve to operate a plurality of pistons, the relatively inexpensive, simple and reliable switching means determining which pistons are operated at any one time.

The apparatus may be for a three cylinder internal combustion engine, the apparatus further comprising: a fifth piston, arranged to control a lift of a first inlet poppet valve of a third combustion chamber; and a sixth piston, arranged to control a lift of a second inlet poppet valve of the third combustion chamber. The first hydraulic control system may be arranged to operate, at different times, the first piston and the third piston and the fifth piston, but not the second piston and the fourth piston and the sixth piston; and the second hydraulic control system may be arranged to operate, at different times, the second piston and the fourth piston and the sixth piston, but not the first piston and the third piston and the fifth piston. In this example, no additional hydraulic control systems are used compared to a two combustion chamber example. In some, but not necessarily all examples the apparatus may be for a four cylinder internal combustion engine, the apparatus further comprising: a fifth piston, arranged to control a lift of a first inlet poppet valve of a third combustion chamber; a sixth piston, arranged to control a lift of a second inlet poppet valve of the third combustion chamber; a seventh piston, arranged to control a lift of a first inlet poppet valve of a fourth combustion chamber; a eighth piston, arranged to control a lift of a second inlet poppet valve of the fourth combustion chamber; a third hydraulic control system arranged to operate, at different times, the fifth piston and the seventh piston, but not the sixth piston and the eighth piston; and a fourth hydraulic control system arranged to operate, at different times, the sixth piston and the eighth piston, but not the fifth piston and the seventh piston. This provides the advantage of an apparatus scalable to large internal combustion engines.

According to another aspect of the invention there is provided a system comprising the apparatus as described herein, and means for actuating the first hydraulic control system and/or the second hydraulic control system. The means may comprise at least one actuator, which may comprise an electronic or electro-mechanical actuator such as a solenoid, or a hydraulic actuator, or a pneumatic actuator, or a camshaft may comprise the at least one actuator. In some, but not necessarily all examples, the camshaft may comprise at least one first lobe at a first axial location on the camshaft to actuate the first hydraulic control system, and at least one second lobe at a second different axial location on the camshaft to actuate the second hydraulic control system. This provides the advantage of a simple system having a small number of hydraulic control systems, because the camshaft lobes actuate each hydraulic control system, via its respective master piston, more than once over the course of a camshaft revolution, enabling each hydraulic control system to operate multiple pistons at different times.

The camshaft may comprise a single first lobe and a single second lobe. A camshaft:crankshaft gear ratio may be 1 :1 causing the first lobe to actuate the first hydraulic control system twice for each crankshaft revolution, and the second lobe to actuate the second hydraulic control system twice for each crankshaft revolution. In other examples the camshaft:crankshaft gear ratio may be different. In some, but not necessarily all examples, the camshaft may comprise first lobes at a same axial location on the camshaft and extending in different radial directions, to actuate the first hydraulic control system, and second lobes at a same axial location on the camshaft and extending in different radial directions, to actuate the second hydraulic control system. An azimuthal offset between each of the first lobes may be correlated with the number of lobes of the first lobes, which may be correlated with the number of pistons operated by the first hydraulic control system. An azimuthal offset between each of the second lobes may be correlated with the number of lobes of the second lobes, which may be correlated with the number of pistons operated by the second hydraulic control system. Example azimuthal offsets may be 120 degrees (±30 degrees) or 180 degrees (±45 degrees). The azimuthal offset between lobes may determine lifting timing. This provides the advantage of a simple system for ensuring that each hydraulic control system is actuated when at least one of its associated combustion chambers requires an inlet air charge. The azimuthal offset may be measured from lobe nose to lobe nose. In some, but not necessarily all examples, the first hydraulic control system comprises a plurality of master pistons each aligned with at least one first lobe of the camshaft such that the at least one first lobe actuates each master piston over the course of a camshaft revolution. The second hydraulic control system may comprise a plurality of master pistons arranged to radially surround at least one second lobe of the camshaft, for respective actuation by the at least one second lobe. This provides the same advantages as described above.

The camshaft may comprise switching portions arranged to cause switching operations to occur in the apparatus, to control whether the first piston or the third piston is caused to be moved in dependence on application of fluid pressure by the first hydraulic control system, and/or whether the second piston or the fourth piston is caused to be moved in dependence on separate application of fluid pressure by the second hydraulic control system. This provides the advantage of a simple system with good switching dynamics, because the camshaft is an existing component of the system and is proximal to the apparatus. Camshaft switching portions provide mechanical control of switching, obviating the need for electronic control of switching requiring additional computing resources. The switching operation may be carried out by the switching means as described above. According to a further aspect of the invention there is provided an internal combustion engine comprising the apparatus as described herein or the system as described herein.

According to a further aspect of the invention there is provided a vehicle comprising the internal combustion engine as described herein.

According to a further aspect of the invention there is provided a method of controlling opening of valves of combustion chambers of a multi-cylinder internal combustion engine, the method comprising at least: controlling fluid displacement applied by a first hydraulic control system to control opening of a first valve of the first combustion chamber; controlling fluid displacement applied by a separate second hydraulic control system to control opening of a second valve of the first combustion chamber; controlling fluid displacement applied by the first hydraulic control system to control opening of a first valve of a second combustion chamber; and controlling fluid displacement applied by the separate second hydraulic control system to control opening of a second valve of the second combustion chamber. The valves are preferably inlet valves, but might instead (or additionally) be exhaust valves. The valves are preferably poppet valves, and the control steps control the lift of the poppet valves, but it will be appreciated that other types of valve might be used instead. Preferably, the actuators are pistons, but it will be appreciated that other types of actuator might be used instead.

This provides the advantage of making an internal combustion engine more efficient by causing inlet poppet valves of a same combustion chamber to be lifted in a continuously variable manner and substantially independently of one another to optimize mixing of an air- fuel charge. The first and second hydraulic control systems are separate. This refers to hydraulic control systems which are substantially independent from one another, for example they are separate hydraulic circuits.

The above method may be carried out over a single camshaft revolution and/or over a complete four-stroke cycle of the internal combustion engine. This provides the advantage of improving the dynamics and responsiveness of the apparatus, because each hydraulic control system controls fluid displacement differently for each combustion cycle associated therewith. The method may be repeated continually during internal combustion engine operation.

Controlling fluid displacement applied by the first hydraulic control system may comprise transmitting electronic control signals to a solenoid valve of the first hydraulic control system to open or close the solenoid valve, and controlling fluid displacement applied by the second hydraulic control system may comprise transmitting electronic control signals to a solenoid valve of the second hydraulic control system to open or close the solenoid valve. This provides the advantage that a simple electronic control signal, for example a timed current of predetermined strength, is sufficient to enable substantially independent continuously variable valve lift. According to a further aspect of the invention there is provided a controller: at least one processor; and at least one memory, including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause an apparatus at least to perform the method as described herein. According to a further aspect of the invention there is provided a computer readable medium storing computer program instructions that, when performed by at least one processor, causes the method as described herein to be performed. According to a further aspect of the invention there is provided an apparatus for an internal combustion engine comprising at least: first means for controlling a first valve of a first combustion chamber; second means for controlling a second valve of the first combustion chamber; third means for controlling a first valve of a second combustion chamber; fourth means for controlling a second valve of the second combustion chamber; a first system arranged to operate the first means and the third means, but not the second means and the fourth means; and a second system arranged to operate the second means and the fourth means, but not the first means and the third means.

It would be appreciated that the above apparatus may control inlet poppet valves, and additionally or alternatively exhaust poppet valves to control exhaust of matter from the combustion chambers.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig 1 illustrates an example of a vehicle.

Fig 2 illustrates an example of an apparatus. Figs 3A to 3D illustrate another example of an apparatus, in use over a four stroke combustion cycle.

Fig 4 illustrates another example of an apparatus.

Figs 5A to 5D illustrate another example of an apparatus, in use over a four stroke combustion cycle.

Fig 6A and Fig 6B illustrate example cross-sections through a camshaft.

Fig 7 illustrates an example of a controller.

Fig 8 illustrates an example of a computer readable storage medium.

Fig 9A illustrates an example of operation of a first hydraulic control system, Fig 9B illustrates an example of operation of a second hydraulic control system, Fig 9C illustrates an example of corresponding cycling of switching means through a plurality of switching states, and Figs 9D to 9G illustrate an example of corresponding lifting of inlet poppet valves. DETAILED DESCRIPTION

Examples in the present disclosure relate to apparatus 3 for lifting inlet poppet valves 23 of a same combustion chamber 25 in a continuously variable manner and substantially independently of one another.

It will be helpful when initially describing an example of an apparatus 3 for controlling valve lifts of inlet poppet valves 23 of combustion chambers 25 of a multi-cylinder internal combustion engine 5 to refer to features of Fig 1 . Fig 1 illustrates a vehicle 1 . The vehicle 1 may be any suitable type of vehicle 1 , such as a passenger vehicle 1 .

The vehicle 1 comprises an internal combustion engine 5, for providing motive power to the vehicle 1 . The vehicle 1 comprises a camshaft 7 associated with the internal combustion engine 5. The vehicle 1 comprises an apparatus 3. The apparatus 3 may be a valve train module 3 arranged to control movement of inlet poppet valves 23a-23d of the internal combustion engine 5 as described below in relation to Fig 2. The vehicle 1 further comprises a controller 9 for controlling the apparatus 3. The internal combustion engine 5, the apparatus 3, the camshaft 7, the controller 9, and inlet poppet valves 23a-23d may form a system 1 1 for controlling lifting of inlet poppet valves 23 of combustion chambers 25 of a multi-cylinder internal combustion engine 5. Fig 2 is a simplified diagram illustrating an example of an apparatus 3 for controlling valve lifts of inlet poppet valves 23a-23d of combustion chambers of a multi-cylinder internal combustion engine 5, the apparatus 3 comprising at least: a first piston 21 a, arranged to control a lift of a first inlet poppet valve 23a of a first combustion chamber 25a; a second piston 21 b, arranged to control a lift of a second inlet poppet valve 23b of the first combustion chamber 25a; a third piston 21 c, arranged to control a lift of a first inlet poppet valve 23c of a second combustion chamber 25b; a fourth piston 21 d, arranged to control a lift of a second inlet poppet valve 23d of the second combustion chamber 25b; a first hydraulic control system 29a arranged to operate, at different times, the first piston 21 a and the third piston 21 c, but not the second piston 21 b and the fourth piston 21 d; and a second hydraulic control system 29b arranged to operate, at different times, the second piston 21 b and the fourth piston 21 d, but not the first piston 21 a and the third piston 21 c. The first piston 21 a, second piston 21 b, third piston 21 c and fourth piston 21 d are arranged to move, pushing their respective inlet poppet valves 23a-23d in dependence upon application of fluid displacement via a hydraulic control system 29. Pushing is achieved for example via surface-to-surface contact between each piston 21 a-21 d and valve stems of the associated inlet poppet valves 23a-23d. In other examples the inlet poppet valves 23a-23d and pistons 21 a-21 d may be integrally formed, or mechanically coupled via intervening elements.

In the example of Fig 2, the first hydraulic control system 29a comprises passages C1 V1 , C4V1 leading to the first piston 21 a and the third piston 21 c respectively, as illustrated by the lines, but not to the second piston 21 b and the fourth piston 21 d. The second hydraulic control system 29b comprises passages C1 V2 and C4V2 leading to the second piston 21 b and the fourth piston 21 d respectively, as illustrated by the lines, but not to the first piston 21 a or the third piston 21 c. Fluid displacement changes in the respective hydraulic control systems 29a, 29b, through the passages C1 V1 , C1 V2, C4V1 , C4V2, operate the respective pistons 21 a-21 d by causing them to move at required times. Piston movement causes movement of a respective inlet poppet valve 23a-23d. When the apparatus 3 shown in Fig 2 is in use on a vehicle 1 , the vehicle 1 and internal combustion engine 5 may be adapted to house the apparatus 3 and supply hydraulic fluid, for example engine oil, to the apparatus 3, for example via a supply port (not shown) of the apparatus 3.

The first hydraulic control system 29a may be a first hydraulic circuit arranged to control its internal hydraulic fluid displacement in a continuously variable manner. The second hydraulic control system 29b may be a second hydraulic circuit independent from the first hydraulic circuit, for separately controlling its internal hydraulic fluid displacement in a continuously variable manner.

According to some, but not necessarily all examples, the first hydraulic control system 29a is arranged to operate, at different times, only the first piston 21 a and only the third piston 21 c. The second hydraulic control system 29b is arranged to operate, at different times, only the second piston 21 b, and only the fourth piston 21 d.

As described above in relation to Fig 2, the apparatus 3 comprises only half the number of hydraulic control systems 29a, 29b relative to the number of inlet poppet valves 23a-23d to be controlled. Further, each of the inlet poppet valves 23a, 23b of the first combustion chamber 25a is operated by means of a separate hydraulic control system, enabling continuously variable lifting of the inlet poppet valves 23a, 23b of the first combustion chamber 25a to be performed substantially independently of one another. Similarly, each of the inlet poppet valves 23c, 23d of the second combustion chamber 25b is operated by means of a separate hydraulic control system, enabling continuously variable lifting of the inlet poppet valves 23c, 23d of the second combustion chamber 25b to be performed substantially independently of one another.

Fig 3A illustrates another example of the apparatus 3, based upon the simplified apparatus 3 described above in relation to Fig 2.

Fig 3A illustrates the apparatus 3, a camshaft 7 and a four-cylinder four-stroke internal combustion engine 5. The apparatus 3 is illustrated using at least some hydraulic circuit diagram symbols. The internal combustion engine 5 is illustrated in cross-section through a point between top dead centre and bottom dead centre. Inlet poppet valves 23a-23h are illustrated intersecting the combustion chambers 25a-25d, however they would in fact be positioned above top dead centre. The camshaft 7 is illustrated in cross-section along its axial length, with lobes extending radially at right angles to its axial length. As shown in Fig 3A, the internal combustion engine 5 comprises a first combustion chamber 25a and a second combustion chamber 25b, as described above in relation to Fig 2, and further a third combustion chamber 25c and a fourth combustion chamber 25d.

A first set 20a of inlet poppet valves for the first combustion chamber 25a comprises a first inlet poppet valve 23a and a second inlet poppet valve 23b. A second set 20b of inlet poppet valves for the second combustion chamber 25b comprises a first inlet poppet valve 23c and a second inlet poppet valve 23d. A third set 20c of inlet poppet valves for the third combustion chamber 25c comprises a first inlet poppet valve 23e and a second inlet poppet valve 23f. A fourth set 20d of inlet poppet valves for the fourth combustion chamber 25d comprises a first inlet poppet valve 23g and a second inlet poppet valve 23h.

Figs 3A-3D illustrate use of the apparatus 3 at four different times within a four-stroke combustion cycle, the internal combustion engine 5 having a firing order of 25b-25c-25a- 25d.

Fig 3A represents a particular point in time within a four-stroke combustion cycle. A cylinder piston 27a of the first combustion chamber 25a is performing its intake stroke. A cylinder piston 27b of the second combustion chamber 25b is performing its combustion stroke. A cylinder piston 27c of the third combustion chamber 25c is performing its compression stroke. A cylinder piston 27d of the fourth combustion chamber 25d is performing its exhaust stroke.

In the example of Fig 3A, the apparatus 3 comprises a first hydraulic control system 29a, a second hydraulic control system 29b, a third hydraulic control system 29c, and a fourth hydraulic control system 29d. Each hydraulic control system 29a-29d is an independent hydraulic circuit arranged to control its internal hydraulic fluid displacement in a continuously variable manner. The first hydraulic control system 29a of Fig 3A comprises a master piston 41 a for actuation by a camshaft 7. Actuation of the master piston 41 a comprises pushing the master piston 41 a inside a small cylinder (not shown), following a path corresponding to a circumferential profile of a camshaft 7 lobe or lobes. The camshaft 7 illustrated in Fig 3A comprises a first pair of lobes 71 a, 73a, separated azimuthally by 180 degrees. The first lobes 71 a, 73a are at a same axial location along the camshaft 7 to align with the master piston 41 a of the first hydraulic control system 29a, and have maximum lifts associated therewith for pushing the master piston 41 a. As there are two lobes, the camshaft 7 is shaped to push the master piston 41 a twice per revolution of the camshaft 7.

The first hydraulic control system 29a of Fig 3A further comprises a solenoid valve 43a and hydraulic accumulator 45a. A passage 47a extends between the master piston 41 a and a port of the solenoid valve 43a. The solenoid valve 43a is for regulating fluid passage through a port coupled directly or indirectly to the hydraulic accumulator 45a.

The solenoid valve 43a of the first hydraulic control system 29a comprises a solenoid- operated spool (not shown), the spool being movable within an internal chamber of the solenoid valve 43a in dependence on an electric current magnitude through the solenoid. The spool is movable between a closed position blocking the port to the hydraulic accumulator 45a, and an open position opening the port to the hydraulic accumulator 45a, or intermediate positions therebetween. The solenoid valve 43a comprises at least one port coupled directly or indirectly to two passages: a passage C1 V1 extending towards the first inlet poppet valve 23a of the first combustion chamber 25a, and a passage C4V1 extending towards the first inlet poppet valve 23c of the second combustion chamber 25b.

The passage C1 V1 terminates at a first slave piston 21 a for controlling a lift of the first inlet poppet valve 23a of the first combustion chamber 25a. The passage C4V1 terminates at a third slave piston 21 c for controlling a lift of the first inlet poppet valve 23c of the second combustion chamber 25b.

The second hydraulic control system 29b of Fig 3A comprises a master piston 41 b for actuation by a camshaft 7. Actuation of the master piston 41 b comprises moving the master piston 41 b inside a small cylinder (not shown), following a path corresponding to a circumferential profile of a camshaft 7 lobe or lobes. The camshaft 7 illustrated in Fig 3A comprises a second pair of lobes 71 b, 73b, separated azimuthally by 180 degrees. The second lobes 71 b, 73b are at a same axial location along the camshaft 7 to align with the master piston 41 b of the second hydraulic control system 29b, and have maximum lifts associated therewith for pushing the master piston 41 b. As there are two lobes, the camshaft 7 is shaped to push the master piston 41 b twice per revolution of the camshaft 7.

The second hydraulic control system 29b of Fig 3A further comprises a solenoid valve 43b and hydraulic accumulator 45b. A passage 47b extends between the master piston 41 b and a port of the solenoid valve 43b. The solenoid valve 43b is for regulating fluid passage through a port coupled directly or indirectly to the hydraulic accumulator 45b.

The solenoid valve 43b of the second hydraulic control system 29b comprises a solenoid- operated spool (not shown), the spool being movable within an internal chamber of the solenoid valve 43b in dependence on an electric current magnitude through the solenoid. The spool is movable between a closed position blocking the port to the hydraulic accumulator 45b, and an open position opening the port to the hydraulic accumulator 45b, or intermediate positions therebetween. The solenoid valve 43b comprises at least one port coupled directly or indirectly to two passages: a passage C1 V2 extending towards the second inlet poppet valve 23b of the first combustion chamber 25a, and a passage C4V2 extending towards the second inlet poppet valve 23d of the second combustion chamber 25b.

The passage C1 V2 terminates at a second slave piston 21 b for controlling a lift of the second inlet poppet valve 23b of the first combustion chamber 25a. The passage C4V2 terminates at a fourth slave piston 21 d for controlling a lift of the second inlet poppet valve 23d of the second combustion chamber 25b.

The third hydraulic control system 29c of Fig 3A comprises a master piston 41 c for actuation by a camshaft 7. Actuation of the master piston 41 c comprises moving the master piston 41 c inside a small cylinder (not shown), following a path corresponding to a circumferential profile of a camshaft 7 lobe or lobes. With reference to Fig 3B, the camshaft 7 comprises a third pair of lobes 71 c, 73c, separated azimuthally by 180 degrees. The third lobes 71 c, 73c are not visible in the illustration of Fig 3A because they are azimuthally perpendicular to the first lobes 71 a, 73a and second lobes 71 b, 73b on the camshaft 7, and therefore radially extend perpendicular to the plane of the cross-section at the time represented in Fig 3A. The third lobes 71 c, 73c are at a same axial location along the camshaft 7 to align with the master piston 41 c of the third hydraulic control system 29c, and have maximum lifts associated therewith for pushing the master piston 41 c. As there are two lobes, the camshaft 7 is shaped to push the master piston 41 c twice per revolution of the camshaft 7.

The third hydraulic control system 29c of Fig 3A further comprises a solenoid valve 43c and hydraulic accumulator 45c. A passage 47c extends between the master piston 41 c and a port of the solenoid valve 43c. The solenoid valve 43c is for regulating fluid passage through a port coupled directly or indirectly to the hydraulic accumulator 45c.

The solenoid valve 43c of the third hydraulic control system 29c comprises a solenoid- operated spool (not shown), the spool being movable within an internal chamber of the solenoid valve 43c in dependence on an electric current magnitude through the solenoid. The spool is movable between a closed position blocking the port to the hydraulic accumulator 45c, and an open position opening the port to the hydraulic accumulator 45c, or intermediate positions therebetween. The solenoid valve 43c comprises at least one port coupled directly or indirectly to two passages: a passage C2V1 extending towards the first inlet poppet valve 23e of the third combustion chamber 25c, and a passage C3V1 extending towards the first inlet poppet valve 23g of the fourth combustion chamber 25d.

The passage C2V1 terminates at a fifth slave piston 21 e for controlling a lift of the first inlet poppet valve 23e of the third combustion chamber 25c. The passage C3V1 terminates at a seventh slave piston 21 g for controlling a lift of the first inlet poppet valve 23g of the fourth combustion chamber 25d.

The fourth hydraulic control system 29d of Fig 3A comprises a master piston 41 d for actuation by a camshaft 7. Actuation of the master piston 41 d comprises moving the master piston 41 d inside a small cylinder (not shown), following a path corresponding to a circumferential profile of a camshaft 7 lobe or lobes. With reference to Fig 3B, the camshaft 7 comprises a fourth pair of lobes 71 d, 73d, separated azimuthally by 180 degrees. The fourth lobes 71 d, 73d are not visible in the illustration of Fig 3A because they are azimuthally perpendicular to the first lobes 71 a, 73a and second lobes 71 b, 73b on the camshaft 7, and therefore radially extend perpendicular to the plane of the cross-section at the time represented in Fig 3A. The fourth lobes 71 d, 73d are at a same axial location along the camshaft 7 to align with the master piston 41 d of the fourth hydraulic control system 29d, and have maximum lifts associated therewith for pushing the master piston 41 d. As there are two lobes, the camshaft 7 is shaped to push the master piston 41 d twice per revolution of the camshaft 7.

The fourth hydraulic control system 29d of Fig 3A further comprises a solenoid valve 43d and hydraulic accumulator 45d. A passage 47d extends between the master piston 41 d and a port of the solenoid valve 43d.The solenoid valve 43d is for regulating fluid passage through a port coupled directly or indirectly to the hydraulic accumulator 45d.

The solenoid valve 43d of the fourth hydraulic control system 29d comprises a solenoid- operated spool (not shown), the spool being movable within an internal chamber of the solenoid valve 43d in dependence on an electric current magnitude through the solenoid. The spool is movable between a closed position blocking the port to the hydraulic accumulator 45d, and an open position opening the port to the hydraulic accumulator 45d, or intermediate positions therebetween. The solenoid valve 43d comprises at least one port coupled directly or indirectly to two passages: a passage C2V2 extending towards the second inlet poppet valve 23f of the third combustion chamber 25c, and a passage C3V2 extending towards the second inlet poppet valve 23h of the fourth combustion chamber 25d.

The passage C2V2 terminates at a sixth piston 21 f for controlling a lift of the second inlet poppet valve 23f of the third combustion chamber 25c. The passage C3V2 terminates at an eighth slave piston 21 h for controlling a lift of the second inlet poppet valve 23h of the fourth combustion chamber 25d.

Any number of intervening elements may be provided between each master piston 41 a-41 d and its respective camshaft lobe or lobes, such as pushrods, rocker arms, roller finger followers, tappets etc.

The apparatus 3 of Fig 3A further comprises switching means 31 , in the form of directional control valves 31 . Each hydraulic control system 29a-29d is associated with a single directional control valve 31 , which may be a spool valve 31 . A spool valve 31 of the first hydraulic control system 29a comprises an inlet port 33a coupled directly or indirectly to a port of solenoid valve 43a, an outlet port 35a coupled to passage C1 V1 , and an outlet port 35c coupled to passage C4V1 . The switching means 31 of the first hydraulic control system 29a, in this example spool valve 31 , may have two switching states. In a first switching state, shown in Fig 3A, fluid passage through the outlet port 35c is blocked and fluid passage through the outlet port 35a is unblocked. Consequently the hydraulic circuit between master piston 41 a and first slave piston 21 a is closed circuit so that the first slave piston 21 a can be caused to be moved in dependence on application of fluid displacement by the master piston 41 a. The hydraulic circuit between master piston 41 a and the third slave piston 21 c is open circuit so that the third slave piston 21 c cannot be caused to be moved in dependence on application of fluid displacement by the master piston 41 a. In a second switching state, fluid passage through the outlet port 35a is blocked and fluid passage through the outlet port 35c is unblocked. Consequently the hydraulic circuit between master piston 41 a and third slave piston 21 c is closed circuit so that the third slave piston 21 c can be caused to be moved in dependence on application of fluid displacement by the master piston 41 a. The hydraulic circuit between master piston 41 a and the first slave piston 21 a is open circuit so that the first slave piston 21 a cannot be caused to be moved in dependence on application of fluid displacement by the master piston 41 a.

Therefore, a spool valve 31 for the first hydraulic control system 29a is arranged to switch passage of fluid to different ones of the multiple outlet ports 35a, 35c at different times.

A spool valve 31 of the second hydraulic control system 29b comprises an inlet port 33b coupled directly or indirectly to a port of solenoid valve 43b, an outlet port 35b coupled to passage C1 V2, and an outlet port 35d coupled to passage C4V2. The switching means 31 of the second hydraulic control system 29b, in this example the spool valve 31 , may have two switching states. In a first switching state, shown in Fig 3A, fluid passage through the outlet port 35d is blocked, and fluid passage through the outlet port 35b is unblocked. Consequently the hydraulic circuit between master piston 41 b and second slave piston 21 b is closed circuit so that the second slave piston 21 b can be caused to be moved in dependence on application of fluid displacement by the master piston 41 b. The hydraulic circuit between master piston 41 b and the fourth slave piston 21 d is open circuit so that the fourth slave piston 21 d cannot be caused to be moved in dependence on application of fluid displacement by the master piston 41 b.

In a second switching state, fluid passage through the outlet port 35b is blocked and fluid passage through the outlet port 35d is unblocked. Consequently the hydraulic circuit between master piston 41 b and fourth slave piston 21 d is closed circuit so that the fourth slave piston 21 d can be caused to be moved in dependence on application of fluid displacement by the master piston 41 b. The hydraulic circuit between master piston 41 b and the second slave piston 21 b is open circuit so that the second slave piston 21 b cannot be caused to be moved in dependence on application of fluid displacement by the master piston 41 b. Therefore, a spool valve 31 for the second hydraulic control system 29b is arranged to switch passage of fluid to different ones of the multiple outlet ports 35b, 35d at different times.

A spool valve 31 of the third hydraulic control system 29c comprises an inlet port 33c coupled directly or indirectly to a port of solenoid valve 43c, an outlet port 35e coupled to passage C2V1 , and an outlet port 35g coupled to passage C3V1 .

The switching means 31 of the third hydraulic control system 29c, in this case spool valve 31 , may have two switching states. In a first switching state, fluid passage through outlet port 35g is blocked and fluid passage through outlet port 35e is unblocked. Consequently the hydraulic circuit between master piston 41 c and fifth slave piston 21 e is closed so that the fifth slave piston 21 e can be caused to be moved in dependence on application of fluid displacement by the master piston 41 c. The hydraulic circuit between master piston 41 c and the seventh slave piston 21 g is open so that the seventh slave piston 21 g cannot be caused to be moved in dependence on application of fluid displacement by the master piston 41 c.

In a second switching state, shown in Fig 3A, fluid passage through outlet port 35e is blocked and fluid passage through outlet port 35g is unblocked. Consequently the hydraulic circuit between master piston 41 c and seventh slave piston 21 g is closed so that the seventh slave piston 21 g can be caused to be moved in dependence on application of fluid displacement by the master piston 41 c. The hydraulic circuit between master piston 41 c and the fifth slave piston 21 e is open so that the fifth slave piston 21 e cannot be caused to be moved in dependence on application of fluid displacement by the master piston 41 c.

Therefore, a spool valve 31 for the third hydraulic control system 29c is arranged to switch passage of fluid to different ones of the multiple outlet ports 35e, 35g at different times.

A spool valve 31 of the fourth hydraulic control system 29d comprises an inlet port 33d coupled directly or indirectly to a port of solenoid valve 43d, an outlet port 35f coupled to passage C2V2, and an outlet port 35h coupled to passage C3V2.

The switching means 31 for the fourth hydraulic control system 29d, in this case a spool valve 31 , may have two switching states. In a first switching state, fluid passage through outlet port 35h is blocked and fluid passage through outlet port 35f is unblocked. Consequently the hydraulic circuit between master piston 41 d and sixth slave piston 21 f is closed so that the sixth slave piston 21 f can be caused to be moved in dependence on application of fluid displacement by the master piston 41 d. The hydraulic circuit between master piston 41 d and the eighth slave piston 21 h is open so that the eighth slave piston 21 h cannot be caused to be moved in dependence on application of fluid displacement by the master piston 41 d.

In a second switching state, shown in Fig 3A, fluid passage through outlet port 35f is blocked and fluid passage through outlet port 35h is unblocked. Consequently the hydraulic circuit between master piston 41 d and eighth slave piston 21 h is closed so that the eighth slave piston 21 h can be caused to be moved in dependence on application of fluid displacement by the master piston 41 d. The hydraulic circuit between master piston 41 d and the sixth slave piston 21 f is open so that the sixth slave piston 21 f cannot be caused to be moved in dependence on application of fluid displacement by the master piston 41 d.

Therefore, the spool valve 31 of the fourth hydraulic control system 29d is arranged to switch passage of fluid to different ones of the multiple outlet ports 35f, 35h at different times. The operation of the switching means 31 may be controlled by any suitable means, for example via pushing by an additional lobe of the camshaft 7. Other means are possible, such as electronic or hydraulic or pneumatic means. An example of operation of the apparatus 3 at a first point in time is described below, with reference to Fig 3A.

At the time represented in Fig 3A, one of the first lobes 71 a biases the first master piston 41 a of the first hydraulic control system 29a. The first master piston 41 a is visibly displaced by the lobe 71 a relative to the positions of the master pistons 41 c, 41 d of the third and fourth hydraulic control systems 29c, 29d. The first hydraulic control system 29a is filled with substantially incompressible hydraulic fluid. Solenoid valve 43a is closed, blocking a port to the hydraulic accumulator 45a. The spool valve 31 of the first hydraulic control system 29a is in its first switching state. The movement of the first master piston 41 a displaces the hydraulic fluid along passage C1 V1 , causing first slave piston 21 a to move the first inlet poppet valve 23a of the first combustion chamber 25a (movement not shown).

At the time represented in Fig 3A, one of the second lobes 71 b biases the second master piston 41 b of the second hydraulic control system 29b. The second master piston 41 b is visibly displaced by the lobe 71 b relative to the positions of the master pistons 41 c, 41 d of the third and fourth hydraulic control systems 29c, 29d. The second hydraulic control system 29b is filled with substantially incompressible hydraulic fluid. Solenoid valve 43b is closed, blocking a port to the hydraulic accumulator 45b. The spool valve 31 of the second hydraulic control system 29b is in its first switching state. The movement of the second master piston 41 b displaces the hydraulic fluid along passage C1 V2, causing second slave piston 21 b to move the second inlet poppet valve 23b of the first combustion chamber 25a (movement not shown).

Figs 3B to 3D show the operation of the apparatus 3 of Fig 3A at three sequential later points in time of the four-stroke combustion cycle. The internal combustion engine 5, sets 20a-20d of inlet poppet valves, hydraulic control systems 29a-29d and camshaft 7 are as described above in relation to Fig 3A. At the time represented in Fig 3B, the internal combustion engine 5 has completed the intake stroke in the first combustion chamber 25a, the combustion stroke of the second combustion chamber 25b, the compression stroke of the third combustion chamber 25c, and the exhaust stroke of the fourth combustion chamber 25d. The cylinder piston 27d of the fourth combustion chamber 25d is performing its intake stroke. The cylinder piston 27c of the third combustion chamber 25c is performing its combustion stroke.

At the time represented in Fig 3B, the camshaft 7 has rotated by 90 degrees about its axial length since the time represented in Fig 3A. The first lobes 71 a, 73a and second lobes, 71 b, 73b are no longer visible in Fig 3B as they now radially extend perpendicular to the plane of the camshaft 7 cross-section of Figs 3A-3D. The master pistons 41 a, 41 b of the first and second hydraulic control systems 29a, 29b have returned to resting positions. The third lobes 71 c, 73c and fourth lobes 71 d, 73d are visible in Fig 3B as they now radially extend parallel to the plane of the camshaft 7 cross-section of Figs 3A-3D.

At the time represented in Fig 3B, one of the third lobes 71 c biases the third master piston 41 c of the third hydraulic control system 29c, causing third master piston 41 c to move. The third hydraulic control system 29c is filled with substantially incompressible hydraulic fluid. Solenoid valve 43c is closed, blocking a port to the hydraulic accumulator 45c. The spool valve 31 of the third hydraulic control system 29c is in its second switching state. The movement of the third master piston 41 c displaces the hydraulic fluid along passage C3V1 , causing seventh slave piston 21 g to move the first inlet poppet valve 23g of the fourth combustion chamber 25d (movement not shown). At the time represented in Fig 3B, one of the fourth lobes 71 d biases the fourth master piston 41 d of the fourth hydraulic control system 29d, causing fourth master piston 41 d to move. The fourth hydraulic control system 29d is filled with substantially incompressible hydraulic fluid. Solenoid valve 43d is closed, blocking a port to the hydraulic accumulator 45d. The spool valve 31 of the fourth hydraulic control system 29d is in its second switching state. The movement of the fourth master piston 41 d displaces the hydraulic fluid along passage C3V2, causing eighth slave piston 21 h to move the second inlet poppet valve 23h of the fourth combustion chamber 25d (movement not shown). Referring now to Fig 3C, at the time represented in Fig 3C, the internal combustion engine 5 has completed the intake stroke in the fourth combustion chamber 25d and the combustion stroke in the third combustion chamber 25c. The cylinder piston 27a of the first combustion chamber 25a is performing its combustion stroke. The cylinder piston 27b of the second combustion chamber 25b is performing its intake stroke.

At the time represented in Fig 3C, the camshaft 7 has rotated by 90 degrees about its axial length since the time represented in Fig 3B. The third lobes 71 c, 73c and fourth lobes 71 d, 73d are no longer visible in Fig 3C as they now radially extend perpendicular to the plane of the camshaft 7 cross-section of Figs 3A-3D. The master pistons 41 c, 41 d of the third and fourth hydraulic control systems 29c, 29d have returned to resting positions. The first lobes 71 a, 73a and second lobes 71 b, 73b are visible in Fig 3C as they now radially extend parallel to the plane of the camshaft 7 cross-section of Figs 3A-3D. At the time represented in Fig 3C, the other of the radially opposing first lobes 71 a, 73a mentioned in relation to Fig 3A, in this case lobe 73a, biases against the first master piston 41 a of the first hydraulic control system 29a, causing first master piston 41 a to move. Solenoid valve 43a is closed, blocking a port to the hydraulic accumulator 45a. The spool valve 31 of the first hydraulic control system 29a is in its second switching state, having switched from its first switching state to its second switching state at or near the time described in Fig 3B. The movement of the first master piston 41 a displaces the hydraulic fluid along passage C4V1 , causing third slave piston 21 c to move the first inlet poppet valve 23c of the second combustion chamber 25b (movement not shown). At the time represented in Fig 3C, the other of the radially opposing second lobes 71 b, 73b mentioned in relation to Fig 3A, in this case lobe 73b, biases against the second master piston 41 b of the second hydraulic control system 29b, causing second master piston 41 b to move. Solenoid valve 43b is closed, blocking a port to the hydraulic accumulator 45b. The spool valve 31 of the second hydraulic control system 29b is in its second switching state, having switched from its first switching state to its second switching state at or near the time described in Fig 3B. The movement of the second master piston 41 b displaces the hydraulic fluid along passage C4V2, causing fourth slave piston 21 d to move the second inlet poppet valve 23d of the second combustion chamber 25b (movement not shown). Referring now to Fig 3D, at the time represented in Fig 3D, the internal combustion engine 5 has completed the above intake stroke in the second combustion chamber 25b and the combustion stroke in the first combustion chamber 25a. The cylinder piston 27c of the third combustion chamber 25c is performing its intake stroke. The cylinder piston 27d of the fourth combustion chamber 25d is performing its combustion stroke.

At the time represented in Fig 3D, the camshaft 7 has rotated by 90 degrees about its axial length since the time represented in Fig 3C. The first lobes 71 a, 73a and second lobes, 71 b, 73b are no longer visible in Fig 3D as they now radially extend perpendicular to the plane of the camshaft 7 cross-section of Figs 3A-3D. The master pistons 41 a, 41 b of the first and second hydraulic control systems 29a, 29b have returned to resting positions. The third lobes 71 c, 73c and fourth lobes 71 d, 73d are visible in Fig 3D as they now radially extend parallel to the plane of the camshaft 7 cross-section of Figs 3A-3D. At the time represented in Fig 3D, the other of the radially opposing third lobes 71 c, 73c mentioned in relation to Fig 3B, in this case lobe 73c, biases against the third master piston 41 c of the third hydraulic control system 29c, causing third master piston 41 c to move. Solenoid valve 43c is closed, blocking a port to the hydraulic accumulator 45c. The spool valve 31 of the third hydraulic control system 29c is in its first switching state, having switched from its second switching state to its first switching state at or near the time described in Fig 3C. The movement of the third master piston 41 c displaces the hydraulic fluid along passage C2V1 , causing fifth slave piston 21 e to move the first inlet poppet valve 23e of the third combustion chamber 25c (movement not shown). At the time represented in Fig 3D, the other of the radially opposing fourth lobes 71 d, 73d mentioned in relation to Fig 3B, in this case lobe 73d, biases against the fourth master piston 41 d of the fourth hydraulic control system 29d, causing fourth master piston 41 d to move. Solenoid valve 43d is closed, blocking a port to the hydraulic accumulator 45d. The spool valve 31 of the fourth hydraulic control system 29d is in its first switching state, having switched from its second switching state to its first switching state at or near the time described in Fig 3C. The movement of the fourth master piston 41 d displaces the hydraulic fluid along passage C2V2, causing sixth slave piston 21 f to move the second inlet poppet valve 23f of the third combustion chamber 25c (movement not shown). Referring to the above description of Figs 3A-3D, it has been shown that the movements of inlet poppet valves of each combustion chamber are controlled by separate hydraulic control systems, beneficially enabling independent valve opening. Referring to the above description of Figs 3A-3D, at least one of the solenoid valves 43a-43d could have been opened to open its port to its hydraulic accumulator 45a-45d. This would have caused the internal volume within the respective hydraulic control system 29a-29d to reduce by a lesser extent, or not reduce at all. This would have controlled the timing and extent of lifting of the respective inlet poppet valves 23a-23h. The solenoid valves 43a-43d therefore enable continuously variable control of valve lifting in each respective hydraulic control system 29a-29d.

Referring to the above description of Figs 3A-3D, it has been shown that the switching means 31 , in the form of spool valves 31 , cycled through a plurality of switching states, which prevented all of the inlet poppet valves associated with each hydraulic control system from opening at once, thereby preventing inlet poppet valves from opening during combustion strokes, avoiding damage to the internal combustion engine 5.

Fig 4 shows another example of an apparatus 3 with another switching means 31 . The internal combustion engine 5, sets 20a-20d of inlet poppet valves, hydraulic control systems 29a-29d and camshaft 7 are as described above in relation to Fig 3A.

Fig 4 represents a variation of the switching means 31 in the form of fluid blocking switches 31 , able to achieve equivalent results to the switching means described in Figs 3A to 3D. Each hydraulic control system 29a-29d is associated with a plurality of fluid blocking switches 31 . Instead of each hydraulic control system 29a-29d comprising a single switching means 31 located before the bifurcation of the passages C1 V1 -C4V2, each hydraulic control system 29a-29d now comprises two switching means 31 located after the bifurcation of the passages C1 V1 -C4V2.

Each fluid blocking switch 31 has a single inlet port and a single outlet port, instead of the multiple outlet ports shown in Figs 3A-3D. Each fluid blocking switch 31 is arranged to regulate fluid passage from the inlet port to the outlet port. The fluid blocking switches 31 may be located at the distal end of the passages C1 V1 -C4V2 from the respective solenoid valves 43a-43d. The fluid blocking switches 31 may be located adjacent the slave pistons 21 a-21 h.

According to Fig 4, the first hydraulic control system 29a comprises a fluid blocking switch 31 having a single inlet port 33aa coupled to passage C1 V1 and a single outlet port 35a coupled directly or indirectly to the first slave piston 21 a, and a fluid blocking switch 31 having a single inlet port 33ac coupled to passage C4V1 and a single outlet port 35c coupled directly or indirectly to the third slave piston 21 c. The second hydraulic control system 29b comprises a fluid blocking switch 31 having a single inlet port 33bb coupled to passage C1 V2 and a single outlet port 35b coupled directly or indirectly to the second slave piston 21 b, and a fluid blocking switch 31 having a single inlet port 33bd coupled to passage C4V2 and a single outlet port 35d coupled directly or indirectly to the fourth slave piston 21 d.

The fluid blocking switches 31 of the first hydraulic control system 29a and second hydraulic control system 29b collectively have a first switching state and a second switching state as described above in relation to the spool valves 31 of the first hydraulic control system 29a and second hydraulic control system 29b of Fig 3A.

The third hydraulic control system 29c comprises a fluid blocking switch 31 having a single inlet port 33ce coupled to passage C2V1 and a single outlet port 35e coupled directly or indirectly to the fifth slave piston 21 e, and a fluid blocking switch 31 having a single inlet port 33cg coupled to passage C3V1 and a single outlet port 35g coupled directly or indirectly to the seventh slave piston 21 g.

The fourth hydraulic control system 29d comprises a fluid blocking switch 31 having a single inlet port 33df coupled to passage C2V2 and a single outlet port 35f coupled directly or indirectly to the sixth slave piston 21 f, and a fluid blocking switch 31 having a single inlet port 33dh coupled to passage C3V2 and a single outlet port 35h coupled directly or indirectly to the eighth slave piston 21 h.

The fluid blocking switches 31 of the third hydraulic control system 29c and fourth hydraulic control system 29d collectively have a first switching state and a second switching state as described above in relation to the spool valve 31 of the third hydraulic control system 29c and fourth hydraulic control system 29d of Fig 3A.

Each fluid blocking switch 31 is smaller than a spool valve 31 described in relation to Fig 3A because each fluid blocking switch 31 has only one outlet port, so full regulation of fluid passage from the inlet to the outlet is achieved by movement of an internal valve or locking element within a fluid blocking switch over a very small distance.

The time represented by Fig 4 within a four-stroke combustion cycle is identical to the time represented by Fig 3A. The first combustion chamber 25a requires an intake stroke. The fluid blocking switches 31 of the first hydraulic control system 29a and second hydraulic control system 29b are in the first switching state, so that the first set 20a of inlet poppet valves can open upon movement of the first and second master pistons 41 a, 41 b, allowing air into the first combustion chamber 25a, but not the second set 20b of inlet poppet valves. This beneficially prevents the second set 20b of inlet poppet valves from opening during the combustion stroke in the second combustion chamber 25b, avoiding damage to the internal combustion engine 5. The fluid blocking switches 31 of the third hydraulic control system 29c and fourth hydraulic control system 29d are in the second switching state in preparation for the next intake stroke which will be for the fourth combustion chamber 25d.

The fluid blocking switches 31 may cycle through their switching states over the course of a four-stroke combustion cycle and/or a camshaft 7 revolution, as described above in relation to Figs 3A-3D. The operation of the fluid blocking switches 31 may be controlled by any suitable means, for example via hydraulic means. Other means are possible, such as electronic or mechanical means or pneumatic means. The operation of the fluid blocking switches 31 may be controlled by hydraulic control input, as shown by the illustrated passages in Fig 4 contacting each fluid blocking switch 31 . Although the illustrated passages appear to intersect the combustion chambers 25a-25d in Fig 4, the passages would in fact be outside the combustion chambers 25a-25d. The hydraulic fluid may be engine oil, and separate hydraulic valves may control the order in which the fluid blocking switches 31 cycle through their switching states. For simplicity of design, neighbouring fluid blocking switches 31 for each combustion chamber 25a may share a hydraulic control input. Figs 5A to 5D illustrate an example of an apparatus 3 with another switching means 31 . The internal combustion engine 5, inlet poppet valves 23a-23h, hydraulic control systems 29a- 29d and camshaft 7 are as described above in relation to Fig 3A.

Fig 5A represents a variation of the switching means 31 comprising locking means 31 , able to achieve equivalent results to the switching means described in relation to Figs 3A to 3D and Fig 4. Like Fig 4, each hydraulic control system 29a-29d comprises two switching means 31 located after the bifurcation of the passages C1 V1 -C4V2. However instead of fluid blocking switches 31 , locking means 31 are used, comprising locking elements 37a-37h. The locking elements 37a-37h are for regulating movement of the slave pistons 21 a-21 h, even if fluid pressure is applied to the slave pistons 21 a-21 h. Each hydraulic control system 29a- 29d is associated with a plurality of locking elements 37a-37h.

Each locking means 31 has a single control input which may be electrical, hydraulic, pneumatic and/or mechanical, and a single output in the form of a movable locking element. The locking element is movable between a non-interference position in which it does not interfere with the movement of a slave piston, and an interference position in which it interferes with the movement of the slave piston. In the interference position, the locking element 31 may prevent the slave piston from moving at least in a direction towards its inlet poppet valve, regardless of hydraulic pressure applied to the slave piston. The distance moved by each locking element between its interference position and its non-interference position may be very small relative the distance moved by a spool of an above-described spool valve 31 .

The locking means 31 may be located at the distal ends of the passages C1 V1 -C4V2 from the respective solenoid valves 43a-43d. The locking means 31 may be located adjacent the slave pistons 21 a-21 h. According to Fig 5A, the first hydraulic control system 29a comprises a first locking element 37a to lock the first slave piston 21 a and a third locking element 37c to lock the third slave piston 21 c. The second hydraulic control system 29b comprises a second locking element 37b to lock the second slave piston 21 b and a fourth locking element 37d to lock the fourth slave piston 21 d. In a first switching state of the locking means 31 of the first hydraulic control system 29a and the second hydraulic control system 29b, the first locking element 37a and second locking element 37b are unlocked while the third locking element 37c and fourth locking element 37d are locked. In a second switching state of the locking means 31 of the first hydraulic control system 29a and the second hydraulic control system 29b, the first locking element 37a and second locking element 37b are locked while the third locking element 37c and fourth locking element 37d are unlocked. The result is equivalent to that described in Figs 3A-3D and Fig 4 in relation to the other switching means 31 .

The third hydraulic control system 29c comprises a fifth locking element 37e to lock the fifth slave piston 21 e and a seventh locking element 37g to lock the seventh slave piston 21 g. The fourth hydraulic control system 29d comprises a sixth locking element 37f to lock the sixth slave piston 21 f and an eighth locking element 37h to lock the eighth slave piston 21 h.

In a first switching state of the locking means 31 of the third hydraulic control system 29c and the fourth hydraulic control system 29d, the fifth locking element 37e and sixth locking element 37f are unlocked while the seventh locking element 37g and eighth locking element 37h are locked. In a second switching state of the locking means 31 of the third hydraulic control system 29c and the fourth hydraulic control system 29d, the fifth locking element 37e and sixth locking element 37f are locked while the seventh locking element 37g and eighth locking element 37h are unlocked. The result is equivalent to that described in Figs 3A-3D and Fig 4 in relation to the other switching means 31 . An example of operation of the apparatus 3 at a first point in time is described below, with reference to Fig 5A.

Fig 5A represents a particular point in time within the four-stroke combustion cycle, the same time as described above in relation to Fig 3A. The locking means 31 of the first hydraulic control system 29a and the second hydraulic control system 29b are in the first switching state, so that the first set 20a of inlet poppet valves can open upon movement of the first and second master pistons 41 a, 41 b, allowing air into the first combustion chamber 25a, but not the second set 20b of inlet poppet valves. This beneficially prevents the second set 20b of inlet poppet valves from opening during the combustion stroke in the second combustion chamber 25b, avoiding damage to the internal combustion engine 5. The locking means 31 of the third hydraulic control system 29c and the fourth hydraulic control system 29d are in the second switching state in preparation for the next intake stroke which will be for the fourth combustion chamber 25d.

Fig 5B represents a particular point in time within the four-stroke combustion cycle, the same time as described above in relation to Fig 3B. The locking means 31 of the third hydraulic control system 29c and the fourth hydraulic control system 29d are in the second switching state, so that the fourth set 20d of inlet poppet valves can open upon movement of the third and fourth master pistons 41 c, 41 d, allowing air into the fourth combustion chamber 25d, but not the second set 20c of inlet poppet valves. This beneficially prevents the third set 20c of inlet poppet valves from opening during the combustion stroke in the third combustion chamber 25c, avoiding damage to the internal combustion engine 5. The locking means 31 of the first hydraulic control system 29a and the second hydraulic control system 29b have switched to their second switching states in preparation for the next intake stroke which will be for the second combustion chamber 25b.

Fig 5C represents a particular point in time within the four-stroke combustion cycle, the same time as described above in relation to Fig 3C. The locking means 31 of the first hydraulic control system 29a and the second hydraulic control system 29b are in the second switching state, so that the second set 20b of inlet poppet valves can open upon movement of the first and second master pistons 41 a, 41 b, allowing air into the second combustion chamber 25b, but not the first set 20a of inlet poppet valves. This beneficially prevents the first set 20a of inlet poppet valves from opening during the combustion stroke in the first combustion chamber 25a, avoiding damage to the internal combustion engine 5. The locking means 31 of the third hydraulic control system 29c and the fourth hydraulic control system 29d have switched to their first switching state in preparation for the next intake stroke which will be for the third combustion chamber 25c. Fig 5D represents a particular point in time within the four-stroke combustion cycle, the same time as described above in relation to Fig 3D. The locking means 31 of the third hydraulic control system 29c and the fourth hydraulic control system 29d are in the first switching state, so that the third set 20c of inlet poppet valves can open upon movement of the third and fourth master pistons 41 c, 41 d, allowing air into the third combustion chamber 25c, but not the fourth set 20d of inlet poppet valves. This beneficially prevents the fourth set 20d of inlet poppet valves from opening during the combustion stroke in the fourth combustion chamber 25d, avoiding damage to the internal combustion engine 5. The locking means 31 of the first hydraulic control system 29a and the second hydraulic control system 29b have switched to their first switching state in preparation for the next intake stroke which will be for the first combustion chamber 25a, and is described in Fig 5A.

The operation of the locking means 31 may be controlled by any suitable means, for example via hydraulic means. Other means are possible, such as electronic, pneumatic or mechanical means. The operation of the locking means 31 may be controlled by hydraulic fluid, as shown by the illustrated passages of Figs 5A-5D extending to each locking element 37a-37h. The hydraulic fluid may be engine oil, and separate hydraulic switching valves may control the order in which the locking elements 37a-37h cycle through their switching states. For simplicity of design, neighbouring locking means 31 for each combustion chamber 25a- 25d may share a hydraulic control input.

Although the illustrated passages in Figs 5A-5D appear to intersect the combustion chambers 25a-25d, the passages would in fact be outside the combustion chambers 25a- 25d.

In the preceding description, three designs for switching means 31 have been shown. It will be appreciated that any other suitable designs for the switching means 31 may be used to achieve the above-described activation of pistons 21 a-21 h at different times. Each of the examples shown above can be used in various combinations for separate hydraulic control systems within a single apparatus 3.

Fig 6A illustrates an example transverse cross section through a camshaft 7. The camshaft 7 comprises first lobes 71 a, 73a as a double lobe formation at a single axial position on the camshaft 7, and third lobes 71 c, 73c as a double lobe formation at a different single axial position on the camshaft 7. Second lobes 71 b, 73b and fourth lobes 71 d, 73d are not shown.

In the example of Fig 6A, each double lobe formation has two noses associated therewith, each nose defining a maximum lift. The noses are azimuthally separated by 180 degrees (±45 degrees) on the camshaft 7. Flanks extend from both sides of the noses to a base circle 76 of the camshaft 7. The base circle 76 corresponds to zero lift of an inlet poppet valve. The maximum lift of each lobe is derived by subtracting the base circle radius from the maximum radius of the each lobe. The exposed base circle 76 may be negligibly small if the flanks converge at single points. The flanks may extend into regions associated with exhaust strokes of combustion chambers, allowing opening times of inlet poppet valves to occur earlier than closing times of exhaust poppet valves. Each lobe may be symmetrical in transverse cross-section, or asymmetrical, to control the lift path of the inlet poppet valve.

As already described in relation to Figs 3A-3D, lobe 71 a of the first lobes 71 a, 73a pushes the master piston 41 a of the first hydraulic control system 29a when the switching means 31 is in the first switching state, causing operation of the first piston 21 a for the first combustion chamber 25a. The other lobe 73a of the first lobes 71 a, 73a pushes the master piston 41 a of the first hydraulic control system 29a when the switching means 31 is in the second switching state, causing operation of the third piston 21 c for the second combustion chamber 25b. Lobe 71 b of the second lobes 71 b, 73b pushes the master piston 41 b of the second hydraulic control system 29b when the switching means 31 is in the first switching state, causing operation of the second piston 21 b for the first combustion chamber 25a. The other lobe 73b of the second lobes 71 b, 73b pushes the master piston 41 b of the second hydraulic control system 29b when the switching means 31 is in the second switching state, causing operation of the fourth piston 21 d for the second combustion chamber 25b.

In some, but not necessarily all examples, lobes may be differently shaped to vary the inlet poppet valve lifting characteristics Maximum lifts of lobes may be identical, or different to enable different maximum inlet poppet valve lift amounts.

Fig 6B is another cross-section of the camshaft 7 illustrating switching portions 75a, 77a on the camshaft 7, at a different axial location on the camshaft 7 from the first lobes 71 a, 73a. The switching portions 75a, 77a are for causing switching operations to occur in the apparatus 3, causing the switching means 31 of at least the first hydraulic control system 29a to cycle through a plurality of switching states over the course of one revolution of the camshaft 7.

The switching portions 75a, 77a rise from the base circle 76 to define flanks 75a, 77a of a single switching lobe 78. The single switching lobe 78 comprises a broad nose 78 having a substantially constant radius over approximately half the circumference of the camshaft. The base circle 76 of the camshaft 7 may be exposed over approximately half the circumference of the camshaft 7. The switching portions 75a, 77a are arranged to ensure that a switching operation of the switching means 31 of at least the first hydraulic control system 29a does not interrupt operation of at least the first hydraulic control system 29a. This is achieved by aligning the switching portions 75a, 77a with sections of exposed base circle 76 shown in Fig 6A between the first lobes 71 a, 73b.

Further switching portions of a similar design may be provided at different axial locations on the camshaft 7, associated with switching means 31 of other hydraulic control systems 29b- 29d. Figs 7-9G relate to a method and a controller 9 for implementing the method.

Fig 7 illustrates an example controller 9. The controller 9 may be a chip or a chip set. The controller 9 may form part of one or more systems comprised in a vehicle 1 . The controller 9 may be operable in use to control the valve train apparatus 3 of the vehicle 1 .

Implementation of a controller 9 may be as controller circuitry. The controller 9 may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware). As illustrated in Fig 7 the controller 9 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions of a computer program 95 in a general-purpose or special-purpose processor 91 that may be stored on a computer readable storage medium (disk, memory etc) to be executed by such a processor 91 . The processor 91 is configured to read from and write to the memory 93. The processor 91 may also comprise an output interface via which data and/or commands are output by the processor 91 and an input interface via which data and/or commands are input to the processor 91 . The memory 93 stores a computer program 95 comprising computer program instructions 97 (computer program code) that controls the operation of the controller 9 when loaded into the processor 91 . The computer program instructions 97, of the computer program 95, provide the logic and routines that enables the controller 9 to control the solenoid valves 43a-43d. The processor 91 by reading the memory 93 is able to load and execute the computer program 95.

Although the memory 93 is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable and/or may provide permanent/semi-permanent/ dynamic/cached storage.

Although the processor 91 is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable. The processor 91 may be a single core or multi-core processor.

As illustrated in Fig 8, the computer program 95 may arrive at the controller 9 via any suitable delivery mechanism 99. The delivery mechanism 99 may be, for example, a non- transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a compact disc read-only memory (CD-ROM) or digital versatile disc (DVD), an article of manufacture that tangibly embodies the computer program 95. The delivery mechanism 99 may be a signal configured to reliably transfer the computer program 95. The controller 9 may propagate or transmit the computer program 95 as a computer data signal.

For purposes of this disclosure, it is to be understood that the controller(s) 9 described herein can each comprise a control unit or computational device having one or more electronic processors. A vehicle 1 and/or a system 1 1 thereof may comprise a single control unit or electronic controller or alternatively different functions of the controller(s) may be embodied in, or hosted in, different control units or controllers. A set of instructions could be provided which, when executed, cause the controller(s) or control unit(s) to implement the control techniques described herein (including the described method(s)). The set of instructions may be embedded in one or more electronic processors, or alternatively, the set of instructions could be provided as software to be executed by one or more electronic processor(s). For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present disclosure is not intended to be limited to any particular arrangement. In any event, the set of instructions described above may be embedded in a computer-readable storage medium (e.g., a non-transitory storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM ad EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions. Fig 9A illustrates an example time history demonstrating operation of a first hydraulic control system 29a to control lifting of the first and third pistons 21 a, 21 c for a two or a four cylinder internal combustion engine. Fig 9B illustrates an example time history demonstrating operation of a second hydraulic control system 29b to control lifting of the second and fourth pistons 21 b, 21 d for the two or four cylinder internal combustion engine. A common time axis is shown for Figs 9A-9B, representing two complete revolutions of a crankshaft, corresponding to a complete four-stroke combustion cycle. Timings may differ as appropriate for different internal combustion engine configurations.

The y-axes of Figs 9A-9B represent open or closed states of ports in the solenoid valves 43a and 43b respectively as commanded by electronic control signals 101 , 103, 105, 107. The ports are for the respective hydraulic accumulators 45a, 45b. Closed ports to hydraulic accumulators enable greater inlet poppet valve lift and open ports to hydraulic accumulators disable inlet poppet valve lift. The electronic control signals 101 , 103, 105, 107 may represent high signals causing a normally open accumulator port to be closed, or low signals causing a normally closed accumulator port to be closed. The electronic control signals 101 , 103, 105, 107 may be permitted to have a plurality of levels for commanding partially closed accumulator ports for continuously variable poppet valve opening. The electronic control signals 101 , 103, 105, 107 may be transmitted by a controller 9 in accordance with a method. The method comprises at least: controlling 101 fluid displacement applied by a first hydraulic control system 29a to control a lift of a first inlet poppet valve 23a of the first combustion chamber 25a; controlling 103 fluid displacement applied by a separate second hydraulic control system 29b to control a lift of a second inlet poppet valve 23b of the first combustion chamber 25a; controlling 105 fluid displacement applied by the first hydraulic control system to control a lift of a first inlet poppet valve 23c of a second combustion chamber 25b; and controlling 107 fluid displacement applied by the separate second hydraulic control system to control a lift of a second inlet poppet valve 23d of the second combustion chamber 25b.

In the example, the electronic control signals 101 , 105 are transmitted to solenoid valve 43a of the first hydraulic control system 29a. The electronic control signals 103, 107 are transmitted to solenoid valve 43b of the second hydraulic control system 29b.

In the above example, the electronic control signals 101 , 103, 105, 107 command the respective solenoid valves 43a, 43b to close their respective hydraulic accumulator ports. The resulting fluid displacement and motion of slave pistons is as described above in relation to Figs 3A-3D. The y-axis of Fig 9C represents a switching state of a switching means 31 , with 'A' representing a first switching state and 'B' representing a second switching state. The resulting lifting of the inlet poppet valves 23a-23d is described with reference to an example illustrated in Figs 9D-9G. The y-axes of Figs 9D-9G represent lift distances of inlet poppet valves 23a-23d respectively, with 'h' representing high lift. The time axes of Figs 9C- 9G are aligned with the time axes of Figs 9A-9B.

Between 0 and 180 degrees, an intake stroke occurs in the first combustion chamber 25a. During this time, the lobes 71 a and 71 b of the camshaft 7 push the master pistons 41 a and 41 b of the first and second hydraulic control systems 29a and 29b respectively. The solenoid valves 43a and 43b are operable to control the resulting poppet valve lift profiles. The switching means 31 of the first and second hydraulic control systems 29a and 29b are in the first switching state 'A' to control which of slave pistons 21 a-21 d are operated by the pressure rise. In the example but not necessarily all examples, the electronic control signal 101 to the solenoid valve 43a of the first hydraulic control system 29a is transmitted before the electronic control signal 103 to the solenoid valve 43b of the second hydraulic control system 29b. The first inlet poppet valve 23a of the first combustion chamber 25a opens earlier than the second inlet poppet valve 23b of the first combustion chamber 25a. Figs 9D and 9E show corresponding lifts of the first and second inlet poppet valves 23a, 23b of the first combustion chamber 25a respectively. The late opening of the second inlet poppet valve 23b means that its maximum lift is reduced.

Between 180 degrees and 360 degrees, neither the first combustion chamber 25a nor the second combustion chamber 25b requires an intake stroke. If the internal combustion engine 5 comprises four combustion chambers, such as in Fig 3A, electronic control signals to a third hydraulic control system 29c and a fourth hydraulic control system 29d may be transmitted within this period. During this time the switching means 31 of the first and second hydraulic control systems 29a and 29b switch to the second switching state 'B'.

Between 360 degrees and 540 degrees, an intake stroke occurs in the second combustion chamber 25b. During this time, the lobes 73a and 73b of the camshaft 7 push the master pistons 41 a and 41 b of the first and second hydraulic control systems 29a and 29b respectively. The solenoid valves 43a and 43b are operable to control the resulting poppet valve lift profiles. The switching means 31 of the first and second hydraulic control systems 29a and 29b are in the second switching state 'B'. In the example but not necessarily all examples, the electronic control signal 107 to the solenoid valve 43b of the second hydraulic control system 29b is transmitted before the electronic control signal 105 to the solenoid valve 43a of the first hydraulic control system 29a. The second inlet poppet valve 23d of the second combustion chamber 25b opens before the first inlet poppet valve 23c of the second combustion chamber 25b. Figs 9F and 9G show corresponding lifts of the first and second inlet poppet valves 23c, 23d of the second combustion chamber 25b respectively. The late opening of the first inlet poppet valve 23c means that its maximum lift is reduced.

Between 540 degrees and 720 degrees, neither the first combustion chamber 25a nor the second combustion chamber 25b requires an intake stroke. If the internal combustion engine 5 comprises four combustion chambers, such as in Fig 3A, electronic control signals to a third hydraulic control system 29c and a fourth hydraulic control system 29d may be transmitted within this period. During this time the switching means 31 of the first and second hydraulic control systems 29a and 29b switch to the first switching state 'Α', in preparation for the next combustion cycle, starting with an intake stroke in the first combustion chamber 25a.

The above example relates to control of inlet poppet valve opening and closing time by solenoid valves 43a, 43b. In other examples, the solenoid valve 43a, 43b may control the inlet poppet valve lift amount without changing the timing. A same inlet poppet valve can even be lifted multiple times within a single engine cycle.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

Alternatives to solenoid valves are possible. Any suitable valves may be used, achieving equivalent effect.

Whilst the terms 'inlet' and 'outlet' have been used in relation to hydraulic ports, this language is not intended to suggest that fluid can only travel in one direction through the port.

The term 'base circle' of the camshaft is not intended to suggest a specific camshaft radius or azimuthal position. The term 'base circle' can merely be regarded as any region of the camshaft incapable of pushing an element adjacent the camshaft. Whilst the term 'piston' has been used, it would be appreciated that the term is intended to cover any element, at least a portion of which moves in dependence upon a pressure difference, and which is capable of causing, at least indirectly, movement of an inlet poppet valve. Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1 . An apparatus for controlling opening of valves of combustion chambers of a multi- cylinder internal combustion engine, the apparatus comprising at least:

a first actuator, arranged to control opening of a first valve of a first combustion chamber;

a second actuator, arranged to control opening of a second valve of the first combustion chamber;

a third actuator, arranged to control opening of a first valve of a second combustion chamber;

a fourth actuator, arranged to control opening of a second valve of the second combustion chamber;

a first hydraulic control system arranged to operate, at different times, the first actuator and the third actuator, but not the second actuator and the fourth actuator; and

a second hydraulic control system arranged to operate, at different times, the second actuator and the fourth actuator, but not the first actuator and the third actuator.

2. An apparatus as claimed in claim 1 , wherein the valves are inlet valves.

3. An apparatus according to claim 1 or claim 2, wherein the valves are poppet valves, and the actuators control the lift of the poppet valves.

4. An apparatus according to any one of claims 1 to 3, wherein the actuators are pistons.

5. An apparatus as claimed in claim 4, comprising switching means for controlling whether the first piston or the third piston is caused to be moved in dependence on application of fluid displacement by the first hydraulic control system, and whether the second piston or the fourth piston is caused to be moved in dependence on separate application of fluid displacement by the second hydraulic control system.

6. An apparatus as claimed in claim 5, wherein the switching means comprises at least one fluid routing switch comprising at least one inlet and multiple outlets, and arranged to switch passage of fluid to different ones of the multiple outlets at different times.

7. An apparatus as claimed in claim 5 or 6, wherein the switching means comprises a plurality of fluid blocking switches, each fluid blocking switch having a single inlet and a single outlet, and each fluid blocking switch being arranged to regulate fluid passage from the inlet to the outlet.

8. An apparatus as claimed in any one of claims 5 to 7, wherein the switching means comprises locking means for regulating movement of at least one of the first piston, the second piston, the third piston, the fourth piston.

9. An apparatus as claimed in any one of claims 5 to 8, wherein the switching means comprises at least one actuation mechanism for actuation by a camshaft and/or by electronic means and/or by hydraulic means and/or by pneumatic means, to cause the switching means to complete a cycle through a plurality of switching states over the course of one revolution of the camshaft.

10. An apparatus as claimed in any one of claims 4 to 9, wherein the first hydraulic control system is arranged to control a first hydraulic fluid displacement in use, and wherein the second hydraulic control system is arranged to control separately a second hydraulic fluid displacement in use.

1 1 . An apparatus as claimed in any one of claims 4 to 10, wherein the first hydraulic control system comprises:

a master piston for actuation by a camshaft;

a solenoid valve for regulating fluid passage to an accumulator;

a passage extending between the master piston and the solenoid valve;

a first valve passage between the solenoid valve and the first piston; and a second valve passage between the solenoid valve or first valve passage and the third piston.

12. An apparatus as claimed in any one of claims 4 to 1 1 , wherein the second hydraulic control system comprises:

a master piston for actuation by a camshaft;

a solenoid valve for regulating fluid passage to an accumulator;

a passage between the master piston and the solenoid valve ;

a first valve passage between the solenoid valve and the second piston; and a second valve passage between the solenoid valve or first valve passage and the fourth piston.

13. An apparatus as claimed in any one of claims 4 to 12 , for a four cylinder internal combustion engine, and wherein the apparatus comprises:

a fifth piston, arranged to control a lift of a first inlet poppet valve of a third combustion chamber;

a sixth piston, arranged to control a lift of a second inlet poppet valve of the third combustion chamber;

a seventh piston, arranged to control a lift of a first inlet poppet valve of a fourth combustion chamber;

a eighth piston, arranged to control a lift of a second inlet poppet valve of the fourth combustion chamber;

a third hydraulic control system arranged to operate, at different times, the fifth piston and the seventh piston, but not the sixth piston and the eighth piston; and a fourth hydraulic control system arranged to operate, at different times, the sixth piston and the eighth piston, but not the fifth piston and the seventh piston.

14. A system comprising the apparatus as claimed in any one of claims 4 to 13, and means for actuating at least the first hydraulic control system and/or the second hydraulic control system.

15. A system as claimed in claim 14, wherein the means comprises a camshaft, the camshaft comprising at least one first lobe to actuate the first hydraulic control system, and at least one second lobe to actuate the second hydraulic control system.

16. A system as claimed in claim 14 or 15, wherein the camshaft additionally comprises switching portions arranged to cause switching operations to occur in the apparatus, to control whether the first piston or the third piston is caused to be moved in dependence on application of fluid displacement by the first hydraulic control system, and/or whether the second piston or the fourth piston is caused to be moved in dependence on separate application of fluid displacement by the second hydraulic control system.

17. An internal combustion engine comprising the apparatus of any one of claims 1 to 13 or the system of any one of claims 14 to 16.

18. A vehicle comprising the internal combustion engine of claim 17.

19. A method of controlling opening of valves of combustion chambers of a multi-cylinder internal combustion engine, the method comprising at least:

controlling fluid displacement by a first hydraulic control system to control opening of a first valve of the first combustion chamber;

controlling fluid displacement by a separate second hydraulic control system to control opening of a second valve of the first combustion chamber;

controlling fluid displacement by the first hydraulic control system to control opening of a first valve of a second combustion chamber; and

controlling fluid displacement by the separate second hydraulic control system to control opening of a second valve of the second combustion chamber.

20. A method as claimed in claim 19, wherein the valves are inlet valves.

21 . A method according to claim 19 or claim 20, wherein the valves are poppet valves, and the poppet valves are lifted by the control steps.

22. A method according to any one of claims 19 to 21 , wherein the actuators are pistons.

23. A method as claimed in claims 20, 21 and 22, wherein the first hydraulic control system is arranged to operate, at different times, a first piston and a third piston but not a second piston and a fourth piston, and wherein the second hydraulic control system is arranged to operate, at different times, the second piston and the fourth piston but not the first piston and the third piston; and wherein the first piston is arranged to control the lift of the first inlet poppet valve of the first combustion chamber, wherein the second piston is arranged to control the lift of the second inlet poppet valve of the first combustion chamber, wherein the third piston is arranged to control the lift of the first inlet poppet valve of the second combustion chamber, and wherein the fourth piston is arranged to control the lift of the second inlet poppet valve of the second combustion chamber.

24. A method as claimed in claim 22 or 23 carried out over a single camshaft revolution and/or over a complete four-stroke cycle of the internal combustion engine.

25. A method as claimed in claim 22, 23 or 24, wherein controlling fluid displacement by the first hydraulic control system comprises transmitting electronic control signals to a solenoid valve of the first hydraulic control system to open or close the solenoid valve, and wherein controlling fluid displacement by the second hydraulic control system comprises transmitting electronic control signals to a solenoid valve of the second hydraulic control system to open or close the solenoid valve.

26. A controller comprising: at least one processor; and at least one memory, including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause an apparatus at least to perform the method of any one of claims 19 to 25.

27. A computer readable medium storing computer program instructions that, when performed by at least one processor, causes the method of any one of claims 19 to 25 to be performed.