GB2562268A

GB2562268A - Apparatus for moving at least one valve for a combustion chamber of an internal combustion engine

Info

Publication number: GB2562268A
Application number: GB1707487.3A
Authority: GB
Inventors: Richard Johnson Thomas; James Peacock Christopher; Miller Andrew
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-05-10
Filing date: 2017-05-10
Publication date: 2018-11-14
Also published as: GB201707487D0; DE102018206746A1

Abstract

An apparatus 7 for moving a valve(s) 27a for a combustion chamber 5 of an internal combustion engine (3, figure 1) comprises a first piston 23a within a first chamber 25a, configured to actuate the valve, wherein the first piston is arranged to be actuated by a hydraulic control system 21. A second piston 23b within a second chamber 25b, configured to not actuate any valve for any combustion chamber, is arranged to be actuated by the hydraulic control system to move within the second chamber and a resilient means 29b is arranged to resist actuation of the second piston. An adjustment means 30b arranged to control the resistance of the resilient means. The adjustment means may alter a preload applied to the resilient means and / or comprise a mechanical spring and / or enable more than two levels of adjustment. This preferably is a rotary element having a screw thread which may be adjusted by means of electronic control. An internal combustion engine, a valve train, a vehicle, a system and a method of operation are also claimed.

Description

APPARATUS FOR MOVING AT LEAST ONE VALVE FOR A COMBUSTION CHAMBER OF AN INTERNAL COMBUSTION ENGINE

TECHNICAL FIELD

The present disclosure relates to apparatus for moving at least one valve for a combustion chamber of an internal combustion engine. In particular, but not exclusively it relates to apparatus for moving at least one valve for a combustion chamber of an internal combustion engine in a vehicle.

Aspects of the invention relate to an apparatus, an internal combustion engine, a valve train, a vehicle, and a method.

BACKGROUND

At a predetermined time during a combustion cycle of an internal combustion engine (‘engine’), a valve (e.g. poppet valve) is lifted away from a valve seat and into a combustion chamber, to open an inlet or exhaust port in the combustion chamber and allow the exchange of gas into or out of the combustion chamber through the port. At a later predetermined time during the combustion cycle, the valve is returned to the valve seat to close the port.

It is known for the lifting of a 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 a valve contacting the piston to lift the valve. A combustion chamber may comprise a plurality of ports, each port opened and closed by a valve.

Apparatus that enable greater control of valve lift characteristics allow greater control of gas exchange parameters that affect engine performance. Example parameters are fuel-air mixing, aspiration and manifold gas pressure. Such apparatus therefore enable efficient engine management for increased combustion efficiency and engine torque; and reduced noise, vibration and harshness.

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, an internal combustion engine, a valve train, and a vehicle as claimed in the appended claims. The invention is as set out in the claims.

According to a first aspect of the invention, there is provided an apparatus for moving at least one valve for a combustion chamber of an internal combustion engine, the apparatus comprising: a first piston within a first chamber, configured to actuate a first valve for the combustion chamber, wherein the first piston is arranged to be actuated by a hydraulic control system to move within the first chamber, for moving the first valve; a second piston within a second chamber, configured to not actuate any valve for any combustion chamber, wherein the second piston is arranged to be actuated by the hydraulic control system to move within the second chamber; resilient means arranged to resist actuation of the second piston; and adjustment means arranged to control the resistance of the resilient means.

The adjustment means and the resilient means provide the advantage of greater control of the lift (movement) characteristics of the first valve. When the second piston and the first piston are actuated, pumped hydraulic fluid is divided between the two pistons, therefore reducing the total hydraulic displacement of the first piston and correspondingly reducing the lift of the first valve. The second piston is effectively a ‘lift control piston’ because it acts as a hydraulic accumulator to control the lift characteristics of the first valve depending on whether it is actuated. Increasing the resistance of the resilient means causes the second piston to displace (move) less when the second piston is supplied with a same quantity of energy from hydraulic displacement. A lower displacement of the second piston corresponds with a proportionally greater displacement of first piston. Therefore, increasing the resistance of the resilient means causes the maximum lift distance of the first valve to increase.

The resilient means also provides an efficient valve train by returning energy to the hydraulic control system when recovering following its deformation. The resilient means significantly reduces the requirement to pump additional hydraulic fluid into the apparatus to maintain pressure.

In some examples, the adjustment means is arranged to adjust a preload applied to the resilient means.

In examples where the resistance is the preload of the resilient means, changing the preload advantageously enables clipping of the maximum lift of the first valve without substantially delaying or retarding the initial valve opening or the valve closing, to maintain a long duration valve lift event.

In some examples, the resilient means comprises a mechanical spring.

This provides the advantage of a resilient means having a substantially linear force-deformation characteristic, giving a more predictable resistance against actuation and therefore a more predictable valve lift.

In some examples, the adjustment means is arranged to enable more than two levels of adjustment to the resistance of the resilient means.

This provides the advantage of greater control over the lift characteristics of the first valve.

In some examples, the adjustment means comprises a rotary element coupled to the resilient means and having a screw thread for position adjustment.

This provides the advantage of enabling fine control of the lift characteristics of the first valve.

In some examples, the apparatus comprises electronic control means operable to adjust the adjustment means.

This provides the advantage of enabling active control of the lift characteristics of the first valve for efficient engine management.

In some examples, the apparatus comprises at least one further piston, configured to not actuate any valve for any combustion chamber, each at least one further piston being within a further chamber and being arranged to be actuated by the hydraulic control system to move within its further chamber.

This provides the advantage of additional lift control compared to that which would be possible in an apparatus having only one second piston.

In some examples, the apparatus comprises the hydraulic control system wherein the hydraulic control system is arranged to control sequential actuation of the second piston and the at least one further piston.

This provides the advantage of enabling independent control of different stages of lifting the first valve.

In some examples, the apparatus comprises further resilient means arranged to resist actuation of the at least one further piston, and further adjustment means arranged to control the resistance of the further resilient means.

This provides the advantage of enabling fine independent control of different stages of lifting the first valve.

In some examples, the apparatus comprises a limiter arranged to limit a maximum distance of movement of the at least one further piston or the second piston to control sequential actuation of the second piston and the at least one further piston.

The use of a limiter provides the advantage of enabling sequential actuation without the complexity of directional control valves.

In some examples, the apparatus comprises first resilient means arranged to resist actuation of the first piston. In some examples, a resistance of the first resilient means is different from a resistance of the resilient means arranged to resist actuation of the second piston. In some examples, the first chamber comprises a first bore sized to accommodate the first piston, the first bore having a first area, the second chamber comprises a second bore sized to accommodate the second piston, the second bore having a second area, and the first area and the second area are different. In some examples, the further chamber comprises a further bore sized to accommodate the further piston, the further bore having a further area, and wherein the second area and the further area are different. In some examples, the first piston and the first valve have a first combined mass, the second piston has a second mass, and the first combined mass and the second mass are different. In some examples, the further piston (23d) has a further mass, and wherein the second mass and the further mass are different.

This provides the advantage of enabling greater control of the change in lift of the first valve in the second mode.

In some examples, the apparatus comprises the hydraulic control system wherein the hydraulic control system is arranged to: in a first mode, control actuation of the first piston but not the second piston; and in a second mode, control parallel actuation of the first piston and the second piston.

This provides the advantage of greater control of the lift (movement) characteristics of the first valve, wherein at least two different lift characteristics are enabled. When the second piston is actuated, hydraulic fluid is divided between the two pistons, therefore reducing the total hydraulic displacement of the first piston and correspondingly reducing the lift of the first valve.

In some examples, the hydraulic control system is arranged to: in the first mode, control parallel actuation of the first piston and the third piston but not the second piston or the further piston; and in the second mode, control parallel actuation of the first piston and the second piston and the third piston and the further piston.

The apparatus can be employed for various applications. The apparatus can advantageously be employed in a ‘discrete variable valve lift’ (DVVL) application, wherein the first and second modes are DVVL modes. DVVL modes enable the valve or valves to be lifted further or less depending on engine management requirements, resulting in a more efficient and powerful engine.

In another application the apparatus can advantageously be employed with at least one additional valve to be able to switch between dual valve actuation (DVA) (first mode) and single valve actuation (SVA) (second mode) depending on engine management requirements. SVA mode will be described later.

In some examples, the hydraulic control system is arranged to control parallel actuation of the first piston and the second piston in the second mode by controlling simultaneous actuation of the first piston and the second piston using hydraulic pumping means.

This simultaneous parallel actuation provides the advantage that the second piston is usable to provide lift control from when actuation commences.

In some examples, the apparatus comprises means for blocking hydraulic communication between the second piston and hydraulic pumping means in the first mode but not in the second mode.

This provides the advantage of a fast hydraulic switch between the first mode and the second mode.

In some examples, the first piston is movable by a first maximum distance in the first mode and movable by a second maximum distance in the second mode, wherein adjustment of the adjustment means controls the second maximum distance without altering the first maximum distance.

This provides the advantage of greater control of the lift (movement) characteristics of the first valve, wherein the lift distance in the second mode is controllable.

In some examples, the apparatus comprises a third piston within a third chamber, configured to actuate a second valve, wherein the third piston is arranged to be actuated by the hydraulic control system to move within the third chamber for moving the second valve.

This provides the advantage of an efficient apparatus because multiple valves (e.g. multiple valves of one combustion chamber) share one hydraulic control system.

The multiple valve apparatus can be arranged to provide DVVL modes. In some examples, the hydraulic control system is arranged to: in the first mode, control parallel actuation of the first piston and the third piston but not the second piston; and in the second mode, control parallel actuation of the first piston and the second piston and the third piston.

The first and second modes are DVVL modes because both valves are lifted in each mode, lifting further or less depending on the mode.

In some examples, the first piston is movable by a first maximum distance in the first mode and movable by a second maximum distance in the second mode, wherein the third piston is movable by a third maximum distance in the first mode and movable by a fourth maximum distance in the second mode, wherein the first maximum distance is greater than the second maximum distance, and wherein the third maximum distance is greater than the fourth maximum distance.

This advantageously provides a high lift mode in the first mode and a low lift mode in the second mode. Low lift mode is advantageous for smooth and efficient engine operation in low load, low engine speed environments such as urban environments. High lift mode is advantageous for increased gas exchange improving engine torque.

In some examples, adjustment of the adjustment means controls the second maximum distance and the fourth maximum distance without altering the first maximum distance or the third maximum distance.

This provides the advantage that valve lift characteristics in the low lift mode are controllable using the adjustment means to further increase engine torque and/or efficiency.

In some examples, the hydraulic control system is arranged to: in the first mode, control parallel actuation of the first piston and the third piston but not the second piston; and in the second mode, control parallel actuation of the first piston and the second piston but not the third piston.

The actuation of the same number of pistons in both modes provides the advantage of compensating for the tendency of the hydraulic control system to lift the first valve further in SVA mode compared to DVA mode. This compensation provides greater control of gas exchange relative to the combustion chamber and reduces valve interference with a stroke portion of the combustion chamber.

In some examples, the hydraulic control system is arranged to: in the first mode, control parallel actuation of the first piston and the third piston but not at least one of the second piston or the further piston; and in the second mode, control parallel actuation of the first piston and at least one of the second piston orthe further piston, but not the third piston.

In some examples, the first piston is movable by a first maximum distance in the first mode and movable by a second maximum distance in the second mode, wherein the third piston is movable by a third maximum distance in the first mode, and wherein the first maximum distance, the second maximum distance, and the third maximum distance are equal.

This provides the advantage of eliminating the tendency of the hydraulic control system to lift the first valve further in SVA mode compared to DVA mode.

In some examples, the apparatus comprises a closed loop feedback system for adjusting the adjustment means to reduce differences between the first maximum distance and the second maximum distance.

This provides the advantage of actively eliminating the tendency of the hydraulic control system to lift the first valve further in SVA mode compared to DVA mode.

In some examples, the apparatus comprises means for blocking hydraulic communication between the third piston and hydraulic pumping means of the hydraulic control system in the second mode but not in the first mode.

In some examples, the apparatus comprises a movable element, movable to a first position in the first mode in which the movable element blocks actuation of the second piston and allows actuation of the third piston, and movable to a second position in the second mode in which the movable element blocks actuation of the third piston and allows actuation of the second piston.

This movable element for controlling actuation of both pistons provides the advantage of reducing timing and/or control constraints associated with switching modes.

In some examples, the movable element in the first position blocks hydraulic communication between the second piston and hydraulic pumping means of the hydraulic control system and allows hydraulic communication between the third piston and the hydraulic pumping means, and wherein the movable element in the second position blocks hydraulic communication between the third piston and the hydraulic pumping means and allows hydraulic communication between the second piston and the hydraulic pumping means. In some examples, the movable element consists of a single spool arranged to move along a single axis between the first position and the second position.

Blocking and allowing hydraulic communication provides the advantage of a fast switch between the first and second modes.

According to a further aspect of the present invention, there is provided an internal combustion engine comprising the apparatus.

In some examples, the internal combustion engine has a predetermined number of manifold extensions opening into combustion chambers, each manifold extension having an associated lengthwise centre axis, wherein an axis of reciprocation of the second piston does not intersect a lengthwise centre axis of any of the manifold extensions.

This provides the advantage of increasing design freedom over where to locate the second piston, as the second piston is solely for lift control.

According to a further aspect of the present invention, there is provided a valve train comprising the apparatus.

In some examples, there is provided a plurality of the apparatus, the valve train comprising control means arranged to control, in parallel, the hydraulic control systems of the plurality of the apparatus to switch between the first mode and the second mode.

According to a further aspect of the present invention, there is provided a vehicle comprising the internal combustion engine.

According to a further aspect of the present invention, there is provided a system comprising the apparatus and hydraulic fluid in the hydraulic control system.

According to a further aspect of the present invention, there is provided an apparatus for a valve train, the apparatus comprising: an uncoupled piston within a chamber, configured to not actuate any valve for any combustion chamber, wherein the uncoupled piston is arranged to be actuated by a fluid control system to move within the chamber. The fluid control system may be a hydraulic control system or a pneumatic control system.

According to a further aspect of the present invention, there is provided an apparatus for controlling an engine, the apparatus comprising: a piston within a chamber, wherein the piston is arranged to be actuated to move within the chamber; a hydraulic control system arranged to control actuation of the piston; resilient means arranged to resist actuation of the piston; and adjustment means arranged to control the resistance of the resilient means.

According to a further aspect of the present invention, there is provided a method for moving at least one valve for a combustion chamber of an internal combustion engine, the method comprising: in a first mode, causing hydraulic actuation of a first piston but not a second piston; switching from the first mode to a second mode, and in the second mode, causing simultaneous hydraulic actuation of the first piston and the second piston, wherein the first piston is within a first chamber, configured to actuate a first valve for the combustion chamber, and is arranged when hydraulically actuated to move within the first chamber (25a), for moving the first valve; wherein the second piston is within a second chamber, configured to not actuate any valve for any combustion chamber, and is arranged when hydraulically actuated to move within the second chamber, wherein actuation of the second piston is resisted by resilient means, wherein the resistance of the resilient means is controlled by adjustment means.

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 having an engine;

Fig 2 illustrates an example of an apparatus;

Fig 3 illustrates another example of an apparatus;

Fig 4 illustrates another example of an apparatus;

Fig 5 illustrates example valve lift curves for an apparatus; and Fig 6 illustrates an example of adjustment means of an apparatus.

DETAILED DESCRIPTION

The Figures illustrate an apparatus 7 for moving at least one valve 27a for a combustion chamber 5 of an internal combustion engine 3, the apparatus 7 comprising: a first piston 23a within a first chamber 25a, configured to actuate a first valve 27a for the combustion chamber 5, wherein the first piston 23a is arranged to be actuated by a hydraulic control system 21 to move within the first chamber 25a, for moving the first valve 27a; a second piston 23b within a second chamber 25b, configured to not actuate any valve for any combustion chamber, wherein the second piston 23b is arranged to be actuated by the hydraulic control system 21 to move within the second chamber 25b; resilient means 29b arranged to resist actuation of the second piston 23b; and adjustment means 30b arranged to control the resistance of the resilient means 29b.

Fig 1 illustrates an example of a vehicle 1 in which embodiments of the invention can be implemented. In some, but not necessarily all examples, the vehicle 1 is a passenger vehicle, also referred to as a passenger car or automobile. Passenger vehicles generally have kerb weights of less than 5000 kg. In other examples, embodiments of the invention can be implemented for other applications, such as industrial vehicles, air or marine vehicles, or non-vehicle applications.

In Fig 1 the vehicle 1 comprises an engine 3. The engine 3 comprises a combustion chamber 5. In some examples the engine 3 comprises a plurality of combustion chambers 5. The engine 3 comprises a valve train 9 for controlling the operation of valves of the engine 3. The valve train 9 comprises an apparatus 7 in which embodiments of the invention can be implemented.

Fig 2 shows a first valve 27a (e.g. poppet valve) configured to block a port 6 (aperture) in a wall of the combustion chamber 5 of the engine 3 of Fig 1 when the first valve 27a is closed, and to open the port 6 when the first valve 27a is lifted (in an open position) and therefore spaced from its valve seat.

The port 6 is an interface between the combustion chamber 5 and a manifold extension 28. The manifold extension 28 is for supplying or collecting gases associated with a combustion process, and has the form of a pipe in Fig 2. When the first valve 27a is moved (lifted) by the apparatus 7 into an open position, the separation distance of the open first valve 27a from the port 6 controls gas flow into the combustion chamber 5 if the first valve 27a is an inlet valve, or out of the combustion chamber 5 if the first valve 27a is an exhaust valve.

Fig 2 also shows an example of an apparatus 7 in accordance with embodiments of the invention, for controlling movement of the first valve 27a. In some examples, the apparatus 7 is for controlling the movement of more than one valve. In other examples, the total number of valves controlled by the apparatus 7 consists of one valve only.

The apparatus 7 of Fig 2 comprises: a hydraulic control system 21; a valve actuator in the form of a first piston 23a within a first chamber 25a; a second piston 23b within a second chamber 25b; resilient means 29b; and adjustment means 30b.

The first piston 23a is movable within the first chamber 25a, for example by reciprocation caused by hydraulic fluid displacement. The first piston 23a is configured to actuate the first valve 27a for the combustion chamber 5, via a non-hydraulic coupling between the first piston 23a and the first valve 27a, such as direct mechanical coupling (surface-to-surface contact) or indirect mechanical coupling (via one or more intervening mechanical components), or via any other form of coupling independent of hydraulic fluid that actuates the first piston 23a and second piston 23b. The first piston 23a can therefore be regarded as a ‘coupled’ piston 23a. The first chamber 25a may comprise a valve aperture for receiving a stem of the first valve 27a. Movement of the first piston 23a is translated directly into movement of the first valve 27a.

In some, but not necessarily all examples, all coupled pistons are each aligned with a respective manifold extension of the engine 3 when the apparatus 7 is installed in the engine 3. Alignment with a manifold extension means that an axis in which a piston reciprocates substantially intersects a lengthwise centre axis of the manifold extension, for proper valve alignment and minimal side loading.

The second piston 23b is located within the second chamber 25b and is movable within the second chamber 25b, for example by reciprocation caused by hydraulic fluid displacement. The second piston 23a is configured to not actuate any valve for any combustion chamber, such as the first valve 27a. The second chamber 25b does not comprise a valve aperture for receiving a stem of a valve. The second piston 23b can therefore be regarded as a ‘dummy’ piston/'uncoupled’ piston. The second piston 23b in the second chamber 25b defines a hydraulic accumulator that expands in volume as it is filled with hydraulic fluid, due to movement of the second piston 23b.

Uncoupled pistons are locatable such that they are not aligned with any manifold extensions of the engine 3 when the apparatus 7 is installed in the engine 3, as uncoupled pistons are solely for lift control of other coupled pistons.

The resilient means 29b (e.g. resilient member) in the apparatus 7 of Fig 2 is arranged to resist actuation of the second piston 23b. The resilient means 29b is arranged to resist actuation of the second piston 23b by deforming in response to movement of the second piston 23b. The resilient means 29b is arranged to return energy to the hydraulic control system 21 when recovering, following its deformation.

In some, but not necessarily all examples, the resilient means 29b (resilience) comprises a mechanical spring. In some, but not necessarily all examples, the resilient means 29b comprises a compression spring. In some, but not necessarily all examples, the resilient means 29b comprises a coil spring. In other examples, the resilient means 29b comprises another material or system arranged to exhibit a substantially linear restoring force-deformation characteristic.

The adjustment means 30b (adjustor) in the apparatus 7 of Fig 2 is arranged to control the resistance of the resilient means 29b. In some, but not necessarily all examples the adjustment means 30b is arranged to enable a plurality of levels of adjustment of the resistance of the resilient means 29b. For example, the adjustment means 30b may be arranged to enable more than two levels of adjustment.

In some, but not necessarily all examples the resistance refers to a preload and the adjustment means 30b is operable to adjust the preload applied to the resilient means 29b. Preload is a background level of internal stress in the resilient means 29b that is present even while the second piston 23b is not being actuated. For example, if the resilient means 29b is a spring, a preload comprises an initial extension or compression of the spring from its resting (free) length even while the second piston 23b is not being actuated. In use, when actuating force is exerted on the preloaded resilient means 29b by the actuating second piston 23b, this actuating force must exceed the preload before the second piston 23b starts to move. Until the preload is exceeded, the second piston 23b does not move. Therefore until the preload is exceeded, all the hydraulic displacement occurs in the first piston 23a. Once the preload is exceeded, the hydraulic displacement is divided between the pistons 23a, 23b, reducing any further displacement of the first piston 23a.

Fig 5 shows example valve lift curves for a valve (such as the first valve 27a) of the apparatus 7. The x-axis is normalised time t such as crank displacement. The y-axis is the distance d of the first valve 27a from its seat. Line 501 is a first valve lift curve associated with the second piston 23b being immovable due to a high preload (no hydraulic accumulation occurs). Line 501 therefore assumes a normal bell-shape familiar to those skilled in the art. Line 503 is a second valve lift curve associated with the second piston 23b being movable due to a pre-defined finite preload. The second valve lift curve assumes a clipped bell shape. This is explained below.

The second valve lift curve 503 matches the first valve lift curve 501 before a first shoulder point 505 on the second valve lift curve 503. Actuating force on the second piston 23b does not exceed the preload so the second piston 23b does not move before the first shoulder point 505. The first shoulder point 505 corresponds to the second piston 23b starting to move when actuating force on the second piston 23b exceeds the preload. A proportion of the displaced hydraulic fluid now accumulates in the second chamber 25b. Consequently the first valve 27a slows after the first shoulder point 505. The first valve 27a then reaches its peak lift point 507 which is lower than its maximum possible peak lift 509 as shown in the first valve lift curve 501. The first valve 27a then moves back towards its seat with an initial low velocity, then once the preload is no longer exceeded, at the second shoulder point 511, the valve 27a returns to its seat at a high velocity. The second valve lift curve 503 matches the first valve lift curve 501 after the second shoulder point 511.

In other examples, the resistance may be spring rate rather than preload.

Fig 6 illustrates an example implementation of the adjustment means 30b applied to the resilient means 29b. The adjustment means 30b comprises a bucket slider 601 in which an end of the resilient means 29b is seated. The adjustment means 30b comprises a cam 603 for camming the bucket slider 601 to adjust the preload of the resilient means 29b. The cam 603 may be rotatable by a worm gear 605 or other suitable linkage. The worm gear 605 is a rotary element comprising a screw thread 607 rotatable by an actuator such as a stepper motor 609, and helical teeth 611 on the cam 603 or on a separate component linked to the cam 603. The helical teeth 611 engage with the screw thread 607.

The hydraulic control system 21 comprises any suitable hydraulic circuitry (not shown in Fig 2) for controlling the actuation of the first piston 23a and the second piston 23b. ‘Actuation’ of a piston refers to movement of a piston caused by hydraulic displacement. Example hydraulic circuitry includes: - pumping means for displacing hydraulic fluid to actuate the first piston 23a and to actuate the second piston 23b, for example a cam-actuated master piston that pumps hydraulic fluid within the hydraulic circuit in dependence on engine camshaft rotation; - a reservoir of hydraulic fluid, for example an engine oil gallery configured to add or remove hydraulic fluid from the hydraulic circuit depending on requirements; - one or more passages that enable hydraulic communication (hydraulic coupling) between circuit components; and control valves, such as directional control valves for controlling hydraulic communication between hydraulic circuit components and the pumping means. Control valves are examples of hydraulic circuitry able to control actuation of a piston.

Referring now to control aspects of the hydraulic control system 21, in some, but not necessarily all examples the hydraulic control system 21 is arranged to: in a first mode, control actuation of the first piston 23a but not the second piston 23b; and in a second mode, control parallel actuation of the first piston 23a and the second piston 23b. The hydraulic control system 21 is in the first mode or the second mode depending on whether the second piston 23b is actuated.

Parallel actuation of pistons refers to enabling a hydraulic displacement to reach both of the pistons in parallel branches of the hydraulic circuit simultaneously, without actuation of one of the pistons depending on or requiring any prior (in series) actuation of the other of the pistons. The coupled piston(s) and uncoupled piston(s) are all configured to be exposed to a same volume of continuous hydraulic fluid internal to the hydraulic circuit.

In some, but not necessarily all examples, the hydraulic control system 21 is in the first mode when the first piston 23a is in hydraulic communication with pumping means at the beginning of a pumping cycle (e.g. at the beginning of camming of the pumping means by a camshaft lobe) while the second piston 23b is hydraulically isolated from the pumping means. The hydraulic control system 21 is in the second mode when the first piston 23a and the second piston 23b are simultaneously in hydraulic communication with the pumping means at the beginning of the pumping cycle. Therefore, the first piston 23a and the second piston 23b are actuated in parallel in the second mode.

When the second piston 23b is actuated in parallel with the first piston 23a (second mode), pumped hydraulic fluid is divided between the two pistons 23a, 23b, therefore reducing the total hydraulic displacement of the first piston 23a and correspondingly reducing the lift of the first valve 27a. The second piston 23b is a ‘lift control piston’ because it acts as a hydraulic accumulator to control the lift characteristics of the first valve 27a depending on whether it is actuated.

The apparatus 7 is configured to, in the first mode, control actuation of the first piston 23a but not the second piston 23b by enabling movement of the first piston 23a in response to hydraulic displacement and preventing movement of the second piston 23b in response to hydraulic displacement. Enabling movement of the first piston 23a may comprise closing a bleed valve for bleeding hydraulic fluid out of the hydraulic control system 21, to ensure that hydraulic displacement from the pumping means moves the first piston 23a. Preventing movement of the second piston 23b in response to hydraulic displacement may comprise operating a directional control valve to block hydraulic communication between the second piston 23b and the pumping means.

The apparatus 7 is configured to, in the second mode, control parallel actuation of the first piston 23a and the second piston 23b by enabling movement of the first piston 23a in response to hydraulic displacement and enabling movement of the second piston 23b in response to hydraulic displacement. Enabling movement of the second piston 23b in response to hydraulic displacement may comprise operating a directional control valve to allow hydraulic communication between the second piston 23b and the pumping means. Enabling movement of the first piston 23a and the second piston 23b may further comprise closing a bleed valve for bleeding hydraulic fluid out of the hydraulic control system 21, to ensure that hydraulic displacement from the pumping means moves the first piston 23a and the second piston 23b.

The apparatus 7 is not restricted to having one uncoupled piston or to having one coupled piston as shown in Fig 2. Fig 3 denotes an example apparatus 7 comprising a further third, ‘coupled’ piston 23c and a further fourth, ‘uncoupled’ piston 23d in addition to the first, ‘coupled’ piston 23a and the second, ‘uncoupled’ piston 23b of Fig 2. The apparatus 7 is not even restricted to having two coupled pistons, two uncoupled pistons, or even the same number of coupled and uncoupled pistons as shown in Fig 3.

The apparatus 7 of Fig 3 is operable to actuate a plurality of valves in parallel, with multiple uncoupled pistons (second piston 23b and fourth piston 23d) to serve as separate lift control pistons.

The apparatus 7 of Fig 3 also comprises all the elements of the apparatus 7 of Fig 2, namely the first valve 27a, the first piston 23a, the first chamber 25a, the second piston 23b, the second chamber 25b, the resilient means 29b, the adjustment means 30b and the hydraulic control system 21. The apparatus 7 of Fig 3 is therefore a dual-valve apparatus 7.

The third piston 23c is located within a third chamber 25c. The third piston 23c is movable within the third chamber 25c, for example by reciprocation caused by hydraulic fluid displacement. The third piston 23c is configured to actuate a second valve 27c (e.g. poppet valve) for the combustion chamber 5, via a non-hydraulic coupling between the third piston 23c and the second valve 27c, such as direct mechanical coupling (surface-to-surface contact) or indirect mechanical coupling (via one or more intervening mechanical components), or via any other form of coupling independent of hydraulic fluid that actuates the first piston 23a, the second piston 23b and the third piston 23c. The third piston 23c can therefore be regarded as a ‘coupled’ piston. The third chamber 25c may comprise a valve aperture for receiving a stem of the second valve 27c. Movement of the third piston 23c is translated directly and via mechanical forces only into movement of the second valve 27c.

The further piston 23d is a fourth piston 23d of the apparatus 7. The fourth piston 23d is located within a (further) fourth chamber 25d of the apparatus 7 and is movable within the fourth chamber 25d, for example by reciprocation caused by hydraulic fluid displacement. The fourth piston 23d is configured to not actuate any valve for any combustion chamber, such as the first valve 27a and the second valve 27c. The fourth chamber 25d does not comprise a valve aperture for receiving a stem of a poppet valve. The fourth piston 23d can therefore be regarded as a ‘dummy’ piston/’uncoupled’ piston. The fourth piston 23d in the fourth chamber 25d defines a hydraulic accumulator that expands in volume as it is filled with hydraulic fluid, due to movement of the fourth piston 23d.

In the illustration of Fig 3, the first piston 23a is mechanically coupled to first resilient means 29a and the third piston 23c is mechanically coupled to third resilient means 29c. In some examples, the first resilient means 29a and third resilient means 29c are valve return springs configured to return the respective first valve 27a and second valve 27c to their valve seats. In Fig 3, the second piston 23b is mechanically coupled to (second) resilient means 29b which is the same as the resilient means 29b of the apparatus 7 of Fig 2, and the fourth piston 23d is mechanically coupled to fourth resilient means 29d. The fourth resilient means 29d is arranged to resist actuation of the fourth piston 23b by deforming in response to movement of the fourth piston 23d. The fourth resilient means 29d may be of a same construction as the second resilient means 29b, for example the fourth resilient means 29b may comprise a compression spring. The second resilient means 29b and fourth resilient means 29d are arranged to return energy to the hydraulic control system 21 when recovering, following their deformation in the second mode.

In Fig 3, but not necessarily all examples, further adjustment means 30d is provided. The further adjustment means 30d is arranged to control the resistance of the fourth resilient means 29d. The construction of the further adjustment means 30d may be the same as the construction of the adjustment means 30b.

In Fig 3 the adjustment means 30b and/or the further adjustment means 30d is controlled by electronic control means 300 shown in Fig 3. The electronic control means 300 may comprise an electronic controller such as an engine control unit, for controlling the adjustment means in dependence on engine management requirements. In some, but not necessarily all examples, the adjustment means 30b is controlled using closed loop feedback, in which a measured output (e.g. a sensed maximum valve lift) is sensed and fed back to the electronic controller to recalculate the adjustment required by the adjustment means.

In the illustration of Fig 3, components of an example hydraulic control system 21 are shown in detail. In Fig 3, the hydraulic pumping means is provided in the form of a master piston 31 arranged to be actuated by a camshaft or other suitable actuator (not shown). The master piston 31 displaces hydraulic fluid in the hydraulic control system 21 when actuated in use. It is this displacement of hydraulic fluid which causes actuation of the first to fourth pistons 23a-23d. The first to fourth pistons 23a-23d can therefore be regarded as ‘slave’ pistons. A reservoir bleed valve 38 enables hydraulic communication between the apparatus 7 and an external reservoir 36 (e.g. relatively low pressure oil gallery) when the reservoir bleed valve 38 is open. When the reservoir bleed valve 38 is open, any displacement energy of the hydraulic fluid is vented to the reservoir, such that none of the pistons 23a-23d are actuated. In use, the reservoir bleed valve 38 is openable if required to provide zero-valve lift when required. A feed valve 34 supplies hydraulic fluid to the apparatus 7 to replenish any lost hydraulic fluid with hydraulic fluid from the reservoir 36, to maintain a required hydraulic pressure in the apparatus 7.

The hydraulic control system 21 further comprises a directional control valve 33b configured to move (switch) between two switching positions that respectively block and allow hydraulic communication between the second piston 23b and the master piston 31.

The design of directional control valves is herein specified with the nomenclature np/nc, where np is the total number of ports (combined total of input and output ports) connected to the directional control valve 33b and nc is the number of switching positions. The illustrated directional control valve 33b is a 2/2-way valve (analogous to a one-way electrical switch).

The hydraulic control system 21 further comprises a directional control valve 33d configured to move (switch) between two switching positions that respectively block and allow hydraulic communication between the fourth piston 23d and the master piston 31. The illustrated additional directional control valve 33d is a 2/2-way valve. In other examples the directional control valves 33b and 33d are mechanically linked to form a single directional control valve (e.g. 4/2-way directional control valve).

In some, but not necessarily all examples, a bleed valve 39 is provided between the second piston 23b and its associated directional control valve 33b. The bleed valve 39 is configured to drain residual hydraulic fluid trapped in the second chamber 25b while the directional control valve 33b blocks hydraulic communication between the second piston 23b and the master piston 31. This reduces drain-down of hydraulic fluid past a seal between the second piston 23b and the second chamber 25b. A bleed valve 39 is also provided between the fourth piston 23d and its associated directional control valve 33d to perform the same function.

Performing a switch between the above-described first mode and the second mode comprises switching, by control means 37, at least one, or optionally all of the available directional control valves (e.g. 33b, 33d).

The directional control valves 33b and 33d may be of a spool type, and the control means 37 of Fig 3 may comprise hydraulic actuators such as solenoids (not shown) to bias the spools into working positions, and springs to bias the spools into their normal positions. The hydraulic actuators may be in selective hydraulic communication with an engine oil gallery, the hydraulic communication being controlled by at least one solenoid-actuated directional control valve under electronic control by an electronic controller (not shown).

In some, but not necessarily all examples, the valve train 9 comprises a plurality of the apparatus 7, and the solenoid-actuated directional control valve is arranged to control, in parallel, the hydraulic control systems 21 of the plurality of the apparatus 7 to switch between the first mode and the second mode. Every apparatus 7 therefore switches between the first mode and the second mode concurrently.

Referring again to the apparatus 7 in both Figs 2 and 3, the apparatus 7 can advantageously be employed for a ‘discrete variable valve lift’ (DVVL) application, wherein the first and second modes are DVVL modes. DVVL modes enable the first valve 27a or valves to be lifted further or less depending on engine management requirements, resulting in a more efficient and powerful engine 3.

Referring to both Figs 2 and 3, in a first, high valve lift mode the directional control valves 33b, 33d are arranged to control actuation of the coupled piston(s) but not the uncoupled piston(s), for example by blocking passage of hydraulic fluid to the uncoupled piston(s). The valve lift is high because the displaced hydraulic fluid is not divided between the coupled piston(s) and the uncoupled piston(s). In a second, low valve lift mode the directional control valves 33b, 33d are arranged to control parallel actuation of the coupled piston(s) and the uncoupled piston(s). The valve lift is low in the second mode because the displaced hydraulic fluid is divided between the coupled piston(s) and the uncoupled piston(s).

Referring specifically to Fig 3, in the first mode, the directional control valves 33b, 33d are arranged to control parallel actuation of the first piston 23a and the third piston 23c but not the second piston 23b or the fourth piston 23c. In the second mode, the directional control valves 33b, 33d are arranged to control parallel actuation of the first piston 23a, the second piston 23b, the third, uncoupled piston 23c and the fourth, coupled piston 23d.

In the above examples, more slave pistons are actuated overall in the second mode than in the first mode. More specifically, to provide DVVL a greater total slave piston area is displaced in the second mode by a given quantity of displacement energy provided by the pumping means.

In the above-described DVVL example, the first piston 23a moves by a first maximum distance in the first mode and moves by a second maximum distance in the second mode, wherein the first maximum distance is greater than the second maximum distance. The third piston 23c moves by a third maximum distance in the first mode and moves by a fourth maximum distance in the second mode, wherein the third maximum distance is greater than the fourth maximum distance. Adjustment of the adjustment means 30b and/or further adjustment means 30d controls the second maximum distance and the fourth maximum distance without altering the first maximum distance or the third maximum distance. This is because the first maximum distance and third maximum distance occur in the first mode when the uncoupled piston(s) are not in hydraulic communication with the master piston 31.

Various temporal and physical characteristics associated with each of the slave pistons may be controllable to customise valve lift behaviour, such as valve acceleration behaviour and maximum lift distance.

One temporal characteristic is the timing of switching of the directional control valves 33b, 33d. In some, but not necessarily all examples the control means 37 is configured to concurrently (non-sequentially) switch the directional control valves 33b and 33d. In other examples the directional control valves 33b and 33d are switched sequentially. For instance, one of the directional control valves 33b, 33d is switched to perform a switch between the first mode and the second mode. The other of the directional control valves 33b, 33d is then switched part-way through the valve lift event to divert some hydraulic fluid energy away from lifting the valves. Sequential switching enables multiple-stage valve lift control.

In another example of controlling a temporal characteristic (timing), the control means 37 is configured to control switching of individual directional control valves of the apparatus 7 independently of other directional control valves of the apparatus 7. This approach applied to Fig. 3 would provide the apparatus 7 with four DVVL modes (four discrete peak valve lifts). In the first DVVL mode, both directional control valves 33b, 33d are open to minimise valve lift. In the second DVVL mode, only the directional control valve 33b is open for a first intermediate valve lift. In the third DVVL mode, only the directional control valve 33d is open for a second intermediate valve lift. In the fourth DVVL mode, both directional control valves 33b, 33d are closed to maximise valve lift. The number of possible DVVL modes is 2Λη where n is the number of uncoupled pistons of the apparatus 7. Every DVVL mode enables a different peak valve lift if each of the uncoupled pistons is associated with a different physical characteristic. Various example physical characteristics are provided below.

An example physical characteristic is another resistance characteristic of the resilient means 29b, 29d, such as spring constant. In some, but not necessarily all examples, the resistance of the second resilient means 29b is different from the resistance of the fourth resilient means 29d. In some, but not necessarily all examples, the resistances of the resilient means 29b, 29d associated with the uncoupled pistons 23b, 23d are different from, for example greater than, the resistances of the resilient means 29a, 29c associated with the coupled pistons 23a, 23c.

Another physical characteristic is the cross-sectional bores (areas) of the chambers for accommodating the pistons. The actuated surface area of each piston is approximately equal (slightly smaller to allow for thermal effects) to the bore of its chamber. Pistons in chambers with a greater bore displace less when supplied with a same quantity of energy from hydraulic displacement. In some, but not necessarily all examples, the bore of the second chamber 25b is different from the bore of the fourth chamber 25d. In some, but not necessarily all examples, the bores of the chambers of the uncoupled pistons are different from, for example greater than, the bores of the chambers of the coupled pistons.

Another physical characteristic is the maximum distance of movement (stroke) of the pistons. In some, but not necessarily all examples the apparatus 7 comprises a limiter 35 (a stroke limiter) arranged to limit a maximum distance of movement of at least one of the uncoupled pistons. In some examples the limiter 35 is embodied as a base of the chamber or a constriction in the bore of the chamber. A limiter 35 interferes with the stroke of at least one of the uncoupled pistons so that the uncoupled piston hits the limiter 35 before maximum valve lift occurs (e.g. before a camshaft lobe nose cams the master piston 31). A limiter 35 can be employed to limit the stroke of one of the uncoupled pistons relative to the other of the uncoupled pistons. This results in sequential actuation of the uncoupled pistons to enable multi-stage valve lift control.

Another physical characteristic is the masses of the pistons. Those pistons with greater mass exhibit greater inertial effects when supplied with a same quantity of energy (hydraulic displacement). In some, but not necessarily all examples, the mass of the second piston 23b is different from the mass of the fourth piston 23d. In some, but not necessarily all examples, the masses of the uncoupled pistons are different from, for example greater than, the masses of the coupled pistons.

The adjustment means 30b and further adjustment means 30d of Fig 3 can be controlled separately. Additional separately controllable uncoupled pistons can be provided to the apparatus 7, each uncoupled piston being provided with resilient means and adjustment means, to enable additional different valve lift curves for the valve(s) of the apparatus 7, each valve lift curve having a different shape.

In some, but not necessarily all examples, the temporal and/or physical characteristics are chosen to control valve acceleration and deceleration behaviour in the first and second modes in addition to the intended difference in maximum lift distance.

In some, but not necessarily all examples, the temporal and/or physical characteristics are chosen to ensure that the valves start to lift before the uncoupled pistons start to move.

Fig 4 illustrates an example of the apparatus 7 which comprises at least two coupled pistons. In the example of Fig 4, the hydraulic control system 21, in combination with at least one uncoupled piston 23b, is configured to enable the apparatus 7 to lift several valves in the first mode, and to lift fewer valves in the second mode. The apparatus 7 illustrated in Fig 4 has two coupled pistons, therefore in this example the first mode is a ‘dual valve actuation’ mode (DVA), and the second mode is a ‘single valve actuation’ (SVA) mode.

The apparatus 7 of Fig 4 comprises all the elements of the apparatus 7 in Fig 2. In some, but not necessarily all examples, the apparatus 7 of Fig 4 also comprises most of the elements of the apparatus 7 in Fig 3, however the optional fourth piston 23d is not illustrated for clarity and the directional control valves 33b, 33d are replaced with a different, 4/2-way directional control valve 41. The common elements include at least: the first valve 27a, the first piston 23a, the first chamber 25a, the first resilient means 29a, the adjustment means 30b, the second piston 23b, the second chamber 25b, the second resilient means 29b, the third valve 27c, the third piston 23c, the third chamber 25c, the third resilient means 29c, the hydraulic control system 21 including the master piston 31, the reservoir 36, the reservoir bleed valve 38, the feed valve 34, and a bleed valve 39 for the second piston 23b.

The apparatus 7 of Fig 4 comprises first means, such as a directional control valve, for blocking hydraulic communication between the third piston 23c and the master piston 31 in the second mode and allowing hydraulic communication between the third piston 23c and the master piston 31 in the first mode. Therefore, the second valve 27c is only lifted in the second mode. The first valve 27a is lifted in both modes. The directional control valve can be a 2/2-way directional control valve similar to those described in relation to Fig 3, or a portion of the 4/2-way directional control valve 41 shown in Fig 4. The directional control valve is therefore operable to switch the apparatus 7 between the first, DVA mode and the second, SVA mode.

The apparatus 7 also comprises second means, such as a directional control valve, for blocking hydraulic communication between the second piston 23b and the master piston 31 in the first mode and allowing hydraulic communication between the second piston 23b and the master piston 31 in the second mode. The directional control valve can be a 2/2-way directional control valve similar to those described in relation to Fig 3, or another portion of the 4/2-way directional control valve 41 shown in Fig 4.

In some, but not necessarily all examples the first means and the second means, embodied in one directional control valve 41 in Fig 4, are actuated in use to switch between a DVA mode and an SVA mode that compensates for the tendency to hydraulically lift the first valve 27a further in SVA mode. In the first (DVA) mode the directional control valve 41 is arranged to control parallel actuation of the first piston 23a and the third piston 23c but not the second piston 23b. Two pistons are actuated in total in the first mode. In the second (SVA) mode the directional control valve 41 is arranged to control parallel actuation of the first piston 23a and the second piston 23b but not the third piston 23c. The combination of pistons actuated in the second mode is different from the combination of pistons actuated in the first mode. Two pistons are actuated in total in the second mode.

In the above example, but not necessarily all examples, the same number of slave pistons are actuated overall in the second (SVA) mode and in the first (DVA) mode. More specifically, the compensation in SVA mode occurs because a same total slave piston area is displaced in the second mode by a same quantity of displacement energy, despite one of the slave pistons (third piston 23c) being no longer actuated. Therefore, it would be appreciated that variations from the illustrated examples are possible, for example a different number of slave pistons can be actuated in the SVA mode compared to the DVA mode while still providing compensation, if the total slave piston areas or other characteristics of the slave pistons are suitably controlled.

In some, but not necessarily all examples relating to a DVA-SVA implementation, the characteristics associated with the second piston 23b are chosen to match, as closely as possible, the characteristics associated with the third piston 23c. The characteristics can be selected such that in use, the first piston 23a moves by a first maximum distance in the first mode and moves by a second maximum distance in the second mode, the third piston 23c moves by a third maximum distance in the first mode, and the first maximum distance, the second maximum distance, and the third maximum distance are equal (within engineering tolerances). The characteristics include, but are not limited to one or more of: piston mass; chamber bore; piston stroke; timing of switching of the directional control valve(s) 41; resistance of resilient means. Each of these characteristics is described above in relation to Fig 3 in more detail.

Adjustment of the adjustment means 30b controls the second maximum distance without altering the first maximum distance or the third maximum distance. This is because the first maximum distance and the third maximum distance occur when the second piston 23b is not in hydraulic communication with the master piston 31. Closed loop feedback may be used to control the second maximum distance to reduce differences between the first maximum distance and the second maximum distance.

In some, but not necessarily all examples all the above-mentioned characteristics are identical for the first piston 23a, the second piston 23b and the third piston 23c.

In the illustration of Fig 4, the single 4/2-way directional control valve 41 comprises the first means and the second means. The directional control valve 41 consists of a single movable element (e.g. spool) arranged to be moved along a single axis to switch between a normal position and at least a first working position. In the first mode, the movable element is in a first position in which the movable element blocks hydraulic communication between the second piston 23b and the master piston 31 and allows hydraulic communication between the third piston 23c and the master piston 31. In the second mode, the movable element is in a second position in which the movable element blocks hydraulic communication between the third piston 23c and the master piston 31 and allows hydraulic communication between the second piston 23b and the master piston 31.

In some, but not necessarily all examples, the first position is the normal position of the directional control valve 41 and the second position is its working position, so that the apparatus 7 normally operates in DVA mode.

The directional control valve 41 can be of any design that relies on a single movable element providing the first means and the second means.

In the example of Fig 4, but not necessarily all examples, performing a switch between the first mode and the second mode comprises switching, by control means 43, the first means and the second means. The first means and second means are embodied in Fig 4 as the 4/2-way directional control valve 41 comprising a spool. The control means 43 may comprise hydraulic actuator(s) to bias the spool(s) into its working position, and spring(s) or hydraulic actuator(s) to bias the spool(s) into its normal position. The hydraulic actuator(s) may be in selective hydraulic communication with an engine oil gallery, the hydraulic communication being controlled by at least one solenoid-actuated directional control valve under electronic control by an electronic controller (not shown).

In some, but not necessarily all examples, a valve train 9 comprises a plurality of the apparatus 7, and the solenoid-actuated directional control valve is arranged to control, in parallel, the hydraulic control systems 21 of the plurality of the apparatus 7 to switch between the first mode and the second mode. Every apparatus 7 consequently switches between the first mode and the second mode concurrently.

Alternative designs for the apparatus 7 compared to Fig 4 may comprise additional coupled valves and/or additional uncoupled valves. In such designs the directional control valve 41, or additional directional control valves, is/are employed to control actuation of at least one uncoupled valve for each coupled valve that is no longer actuated.

In accordance with some, but not necessarily all examples of the disclosure, there is provided a method for moving at least one valve 27a for a combustion chamber 5 of an internal combustion engine 3, the method comprising: in a first mode, causing hydraulic actuation of a first piston 23a but not a second piston 23b; switching from the first mode to a second mode, and in the second mode, causing simultaneous hydraulic actuation of the first piston 23a and the second piston 23b, wherein the first piston 23a is within a first chamber 25a, configured to actuate a first valve 27a for the combustion chamber 5, and is arranged when hydraulically actuated to move within the first chamber 25a, for moving the first valve 27a; wherein the second piston 23b is within a second chamber 25b, configured to not actuate any valve for any combustion chamber, and is arranged when hydraulically actuated to move within the second chamber 25b, wherein actuation of the second piston 23b is resisted by resilient means 29b, wherein the resistance of the resilient means is controlled by adjustment means 30b.

An electronic controller may comprise means for causing the apparatus 7 to perform the method. The means may comprise at least one processor, at least one memory comprising computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus 7 at least to perform the method. The electronic controller can be arranged to control actuation of the hereinbefore described directional control valves, to operate the apparatus 7 in the above-described DVVL modes (see Fig 3) and/or DVA/SVA modes (see Fig 4).

For purposes of this disclosure, it is to be understood that the electronic controller(s) described herein can each comprise a control unit or computational device having one or more electronic processors. A vehicle and/or a system 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 said 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.

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. For example, independently controllable directional control valves can be provided to control actuation of a plurality of coupled pistons and to control actuation of one or more uncoupled pistons, to provide an apparatus 7 operable in DVVL modes (see Fig 3) and DVA/SVA modes (see Fig 4) at different times. Further, although the preceding description refers to a hydraulic control system, a pneumatic control system is an alternative workable implementation in which the various above-described pistons are actuated using pneumatic gases rather than by hydraulic fluid.

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 endeavouring 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 moving at least one valve for a combustion chamber of an internal combustion engine, the apparatus comprising: a first piston within a first chamber, configured to actuate a first valve for the combustion chamber, wherein the first piston is arranged to be actuated by a hydraulic control system to move within the first chamber, for moving the first valve; a second piston within a second chamber, configured to not actuate any valve for any combustion chamber, wherein the second piston is arranged to be actuated by the hydraulic control system to move within the second chamber; resilient means arranged to resist actuation of the second piston; and adjustment means arranged to control the resistance of the resilient means.

2. An apparatus as claimed in any preceding claim, wherein the adjustment means is arranged to adjust a preload applied to the resilient means.

3. An apparatus as claimed in any preceding claim, wherein the resilient means comprises a mechanical spring.

4. An apparatus as claimed in any preceding claim, wherein the adjustment means is arranged to enable more than two levels of adjustment to the resistance of the resilient means.

5. An apparatus as claimed in any preceding claim, wherein the adjustment means comprises a rotary element coupled to the resilient means and having a screw thread for position adjustment.

6. An apparatus as claimed in any preceding claim, comprising electronic control means operable to adjust the adjustment means.

7. An apparatus as claimed in any preceding claim, comprising at least one further piston, configured to not actuate any valve for any combustion chamber, each at least one further piston being within a further chamber and being arranged to be actuated by the hydraulic control system to move within its further chamber.

8. An apparatus as claimed in claim 7, comprising the hydraulic control system wherein the hydraulic control system is arranged to control sequential actuation of the second piston and the at least one further piston.

9. An apparatus as claimed in claim 7 or 8, comprising further resilient means arranged to resist actuation of the at least one further piston, and further adjustment means arranged to control the resistance of the further resilient means.

10. An apparatus as claimed in claim 7, 8 or 9, comprising a limiter arranged to limit a maximum distance of movement of the at least one further piston or the second piston to control sequential actuation of the second piston and the at least one further piston.

11. An apparatus as claimed in any preceding claim, comprising the hydraulic control system wherein the hydraulic control system is arranged to: in a first mode, control actuation of the first piston but not the second piston; and in a second mode, control parallel actuation of the first piston and the second piston.

12. An apparatus as claimed in claim 11, wherein the hydraulic control system is arranged to control parallel actuation of the first piston and the second piston in the second mode by controlling simultaneous actuation of the first piston and the second piston.

13. An apparatus as claimed in claim 11 or 12, comprising means for blocking hydraulic communication between the second piston and hydraulic pumping means in the first mode but not in the second mode.

14. An apparatus as claimed in any one of claims 11 to 13, wherein the first piston is movable by a first maximum distance in the first mode and movable by a second maximum distance in the second mode, wherein adjustment of the adjustment means controls the second maximum distance without altering the first maximum distance.

15. An apparatus as claimed in any preceding claim, comprising a third piston within a third chamber, configured to actuate a second valve, wherein the third piston is arranged to be actuated by the hydraulic control system to move within the third chamber for moving the second valve.

16. An apparatus as claimed in any preceding claim, comprising first resilient means arranged to resist actuation of the first piston.

17. An apparatus as claimed in claim 16, wherein a resistance of the first resilient means is different from a resistance of the resilient means arranged to resist actuation of the second piston.

18. An apparatus as claimed in any preceding claim, wherein the first chamber comprises a first bore sized to accommodate the first piston, the first bore having a first area, wherein the second chamber comprises a second bore sized to accommodate the second piston, the second bore having a second area, and wherein the first area and the second area are different.

19. An apparatus as claimed in any preceding claim, wherein the first piston and the first valve have a first combined mass, wherein the second piston has a second mass, and wherein the first combined mass and the second mass are different.

20. An apparatus as claimed in claim 15, when dependant on any one of claims 11 to 14, wherein the hydraulic control system is arranged to: in the first mode, control parallel actuation of the first piston and the third piston but not the second piston; and in the second mode, control parallel actuation of the first piston and the second piston but not the third piston.

21. An apparatus as claimed in claim 20, wherein the first piston is movable by a first maximum distance in the first mode and movable by a second maximum distance in the second mode, wherein the third piston is movable by a third maximum distance in the first mode, and wherein the first maximum distance, the second maximum distance, and the third maximum distance are equal.

22. An apparatus as claimed in claim 21, comprising a closed loop feedback system for adjusting the adjustment means to reduce differences between the first maximum distance and the second maximum distance.

23. An apparatus as claimed in any one of claims 20 to 22, comprising means for blocking hydraulic communication between the third piston and hydraulic pumping means of the hydraulic control system in the second mode but not in the first mode.

24. An apparatus as claimed in any one of claims 20 to 23, comprising a movable element, movable to a first position in the first mode in which the movable element blocks actuation of the second piston and allows actuation of the third piston, and movable to a second position in the second mode in which the movable element blocks actuation of the third piston and allows actuation of the second piston.

25. An apparatus as claimed in claim 24, wherein the movable element in the first position blocks hydraulic communication between the second piston and hydraulic pumping means of the hydraulic control system and allows hydraulic communication between the third piston and the hydraulic pumping means, and wherein the movable element in the second position blocks hydraulic communication between the third piston and the hydraulic pumping means and allows hydraulic communication between the second piston and the hydraulic pumping means.

26. An apparatus as claimed in claim 24 or 25, wherein the movable element consists of a single spool arranged to move along a single axis between the first position and the second position.

27. An internal combustion engine comprising the apparatus as claimed in any preceding claim.

28. An internal combustion engine as claimed in claim 27, the internal combustion engine having a predetermined number of manifold extensions opening into combustion chambers, each manifold extension having an associated lengthwise centre axis, wherein an axis of reciprocation of the second piston does not intersect a lengthwise centre axis of any of the manifold extensions.

29. A valve train comprising the apparatus as claimed in any one of claims 1 to 26.

30. A valve train as claimed in claim 29 and comprising a plurality of the apparatus as claimed in any one of claims 1 to 27, the valve train comprising control means arranged to control, in parallel, the hydraulic control systems of the plurality of the apparatus to switch between the first mode and the second mode.

31. A vehicle comprising the internal combustion engine as claimed in claim 27 or 28.

32. A system comprising the apparatus as claimed in any one of claims 1 to 26 and hydraulic fluid in the hydraulic control system.

33. A method for moving at least one valve for a combustion chamber of an internal combustion engine, the method comprising: in a first mode, causing hydraulic actuation of a first piston but not a second piston; switching from the first mode to a second mode, and in the second mode, causing simultaneous hydraulic actuation of the first piston and the second piston, wherein the first piston is within a first chamber, configured to actuate a first valve for the combustion chamber, and is arranged when hydraulically actuated to move within the first chamber, for moving the first valve; wherein the second piston is within a second chamber, configured to not actuate any valve for any combustion chamber, and is arranged when hydraulically actuated to move within the second chamber, wherein actuation of the second piston is resisted by resilient means, wherein the resistance of the resilient means is controlled by adjustment means.