GB2580029A

GB2580029A - Engine valve actuation

Info

Publication number: GB2580029A
Application number: GB1820682.1A
Authority: GB
Inventors: tyrell Richard; Stone Roger; Kelly David
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2018-12-19
Filing date: 2018-12-19
Publication date: 2020-07-15
Anticipated expiration: 2038-12-19
Also published as: GB2580029B; GB201820682D0

Abstract

An electromagnetic valve actuator 100 for at least one valve 300 of an internal combustion engine (40, Fig. 1), the electromagnetic valve actuator 100 comprising: a rotor 102, a stator 101 for rotating the rotor, output means 104, 106 for actuating the valve in dependence on rotation of the rotor 102, mechanical energy storage means 108, 110, 116, 118 arranged to store energy in dependence on rotation of the rotor 102 and release the energy to assist rotation of the rotor 102; and phase varying means 400 for varying a phase between the mechanical energy storage means and the output means. The actuator 100 allows for continuously variable valve lift and improved engine efficiency.

Description

ENGINE VALVE ACTUATION

TECHNICAL FIELD

The present disclosure relates to engine valve actuation, and more particularly to phasing an energy recovery system for an engine valve actuator. In particular, but not exclusively it relates to phasing an energy recovery system for an electromagnetic valve actuator for an engine valvetrain of a vehicle.

Aspects of the invention relate to an electromagnetic valve actuator, a controller, a valve actuation system, an internal combustion engine, a vehicle, a method and a computer program.

BACKGROUND

Conventional camshaft-driven engine valvetrains suffer from limited or no adjustability of poppet valve ('valve' herein) timing and lift. Various systems have been derived to enable discrete variable valve lift (VVL) and even continuously variable valve lift (CVVL). CVVL systems enable improved engine efficiency.

Electromagnetic valve actuators (EVAs) can enable CVVL. Since the EVA is not physically coupled to the engine crankshaft, valves can be lifted at any time during a combustion cycle, to any target peak lift.

EVAs present various challenges, such as their parasitic energy consumption and difficulty to package within a vehicle.

SUMMARY OF THE INVENTION

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

Aspects and embodiments of the invention provide an electromagnetic valve actuator, a controller, a valve actuation system, an internal combustion engine, a vehicle, a method and a computer program as claimed in the appended claims.

According to an aspect of the invention there is provided an electromagnetic valve actuator for at least one valve of an internal combustion engine, the electromagnetic valve actuator comprising: a rotor; a stator for rotating the rotor; output means (output) for actuating the valve in dependence on rotation of the rotor; mechanical energy storage means (mechanical energy storage device) arranged to store energy in dependence on rotation of the rotor and release the energy to assist rotation of the rotor; and phase varying means (phase varying device) for varying a phase between the mechanical energy storage means and the output means. In some examples the mechanical energy storage means is arranged to store energy to decelerate the rotor and release the energy to accelerate the rotor.

The mechanical energy storage means defines a form of energy recovery system (ERS) which recovers energy from the inertia of the moving parts of the valvetrain. The energy is then released to assist with rotor acceleration, allowing a smaller stator rated at a lower torque.

Valvetrain energy consumption is reduced. An advantage of phasing the timing of energy storage and release is that its potential efficiencies are available in a greater variety of operating scenarios. These include at least a scenario in which the inertia is too low for full energy recovery, a scenario of reversing a direction of rotation of the rotor, and a scenario in which the reversal is followed by a full rotation. The scenarios are defined further herein.

In some examples the phase varying means is operable to maintain a first phase between the mechanical energy storage means and the output means, causing the mechanical energy storage means to store energy while the valve is open.

In a first example operating scenario, maintaining the first phase causes the mechanical energy storage means to store the energy while the valve is closing. An advantage is greater efficiency than if the energy storage occurs after valve closing. The energy may then be released after the valve has closed when rotor acceleration is next required.

In a second example operating scenario, the electromagnetic valve actuator is operable to reverse a direction of rotation of the rotor when the valve has reached a target peak lift less than a maximum peak lift, and wherein the mechanical energy storage means causes, at least in part, the reversal. The mechanical energy storage means at the first phase is analogous to a much stiffer valve return spring, enough to cause reversal of rotation. An advantage is less reliance on the stator for supplying negative torque to cause the reversal in a partial lift mode.

In some examples the phase varying means is operable to maintain a second phase between the mechanical energy storage means and the output means, causing the mechanical energy storage means to store energy later with respect to valve opening than in the first phase. An advantage is that when the first phase is no longer useful or efficient, the phasing can occur such that the mechanical energy storage means continues to be useful and efficient for a different type of valve lift event.

In the first example operating scenario, maintaining the second phase may cause the energy storage to occur while the valve is closed. An advantage of retarding the energy storage until after valve closing arises because if the moving parts have insufficient inertia, the mechanical energy storage means could become a parasitic. The stator is burdened with charging the mechanical energy storage means. If the stator has to do this while simultaneously accelerating the rotor to meet a target rotor velocity, the stator may be saturated such that the target rotor velocity cannot be satisfied, and the valve allows too much gas exchange.

Therefore, a retarded second phase enables the energy storage to occur when there are no other higher priority loads on the stator.

In the second example operating scenario, having a second phase for partial valve lift mode enables the mechanical energy storage means to optimize the reversal of rotation in dependence on the target peak lift of the valve. For example, if more deceleration is required, the phase could be advanced to cause reversal at the desired timing without the requirement for additional stator braking energy.

Additionally or alternatively, phasing can be useful when transitioning from partial valve lift mode to full valve lift mode. Phasing enables the mechanical energy storage means to assist with reversal in partial valve lift mode (first phase) when required, and to not resist rotation in full valve lift mode when the rotor completes a full cycle with no reversal (second phase). The second phase may store energy while the valve is closing or after the valve has closed, as per the first example operating scenario.

In some examples the second phase is offset from the first phase by a value from the range 10 to 30 degrees. In an example the offset is around 20 degrees.

In some examples the mechanical energy storage means is configured to supply X Nm of torque when releasing the energy to assist rotation of the rotor, wherein the stator is configured to supply up to Y Nm of torque for rotating the rotor, and wherein X is from the range 40% to 95% of Y. In some examples, X is from the range 60-95% of Y. An advantage is that net torque can be close to 2Y without needing more stator windings contained in a larger stator housing.

Since the mechanical energy storage means is smaller and lighter than the stator, the valvetrain is lighter and easier to package within a small engine bay such as an automobile engine bay.

In some examples Y is less than a torque required to fully open the valve at an engine speed above 5000 rpm. An advantage is that there is no need for a larger stator housing. At high engine speeds the assistance from ERS is necessary and sufficient to meet target rotor velocity.

In some examples the mechanical energy storage means comprises a resilient member. In some examples the mechanical energy storage means comprises a cantilever spring. This is a highly space-efficient design, for system lightness and ease of packaging.

In some examples the mechanical energy storage means comprises a cam or an eccentric. In some examples the phasing does not change the total amount of energy that the mechanical energy storage means stores or is capable of storing, because the maximum storable energy is defined by the lift of the cam. In some examples the output means comprises a cam or an eccentric. Both cams/eccentrics may be on the same rotor. This design enables a single rotor to perform multiple functions which is mechanically simple and space-efficient.

In some examples the phase varying means is configured to vary the phase of the mechanical energy storage means or the output means relative to the rotor. In some examples the phase varying means is configured to vary the phase of the mechanical energy storage means relative to the rotor. In some examples, the cam is detachable from the rotor, causing the cam to slip relative to the rotor, and the cam is re-attachable to the rotor at a different phase.

In some examples the output means is desmodromic. The output means may comprise an opening lobe and a closing lobe. A desmodromic application enables a target rotor velocity for closing the valve to be higher than a target rotor velocity for opening the valve, enabling skewed valve lifts which can improve combustion efficiency. Beyond the inherent advantages of desmodromic systems, an advantage of phasing the ERS in a desmodromic application is to avoid the situation described above in relation to the first example operating scenario, to enable the target rotor velocity for closing the valve to be achieved.

According to another aspect of the invention there is provided a controller configured to control an electromagnetic valve actuator for at least one valve of an internal combustion engine, the electromagnetic valve actuator comprising: a rotor; a stator for rotating the rotor; output means for actuating the valve in dependence on rotation of the rotor; mechanical energy storage means arranged to store energy in dependence on rotation of the rotor and release the energy to assist rotation of the rotor; and phase varying means for varying a phase between the mechanical energy storage means and the output means, wherein the controller comprises: means to control the phase varying means to vary the phase between the mechanical energy storage means and the output means.

According to a further aspect of the invention there is provided a controller as described above, wherein: said means to control the phase varying means to vary the phase between the mechanical energy storage means and the output means comprises an electronic processor having one or more electrical inputs for receiving a parameter indicative of a requirement to vary the phase; and an electronic memory device electrically coupled to the electronic processor and having computer program instructions stored therein; the processor being configured to access the memory device and execute the instructions stored therein such that it is operable to determine a requirement to vary the phase based on the parameter, and control the phase varying means in dependence on the determination.

In some examples, 'means to' perform a function comprises: at least one electronic processor; and at least one electronic memory device electrically coupled to the electronic processor and having instructions stored therein, the at least one electronic memory device and the instructions configured to, with the at least one electronic processor, perform the function.

In some examples the controller comprises means to receive a parameter indicative of kinetic energy (inertia of rotating parts), and to control the phase varying means to vary the phase from a second phase that causes the mechanical energy storage means to store energy after closing of the valve, to a first phase that causes the mechanical energy storage means to store energy during closing of the valve, when the parameter exceeds a threshold. In some examples the parameter is engine speed-dependent. For example the engine-speed dependent parameter could be engine speed or target rotor velocity. This relates to the first example operating scenario. Low rotor velocity or engine speed are example parameters for identifying when the mechanical energy storage means is parasitic rather than functioning as an ERS.

Regarding the first example operating scenario, in some examples the controller comprises means to control the stator while the second phase is in operation, to apply torque to the rotor after closing of the valve to cause the mechanical energy storage means to store energy after closing of the valve. As described above, the phasing is useful when inertia is low because the stator will need to apply torque to charge the (parasitic) mechanical energy storage means. In some examples the controller comprises means to control the stator while at least the second phase is in operation, to apply torque to the rotor during closing of the valve. As described above, the phasing is useful when inertia is low because the stator will need to apply torque prior to valve closing to meet a target rotor velocity for valve closing.

In some examples the controller comprises means to determine a required change from a partial valve lift mode to a full valve lift mode, wherein the partial valve lift mode requires the electromagnetic valve actuator to reverse a direction of rotation of the rotor when the valve has reached a target peak lift less than a maximum peak lift, and comprising means to control the phase varying means to vary the phase from a second phase that causes the mechanical energy storage means to cause, at least in part, reversal of the valve, to a first phase in which energy storage does not occur prior to maximum peak lift. As described above, the phasing is useful when transitioning from partial valve lift mode to full valve lift mode. The determination may arise from an engine control unit map relating engine speed and load to a desired target rotor velocity and efficient valve lift.

Regarding the second example operating scenario, in some examples the controller comprises means to determine a required change of target peak lift of the valve less than a maximum peak lift of the valve, wherein the target peak lift requires the electromagnetic valve actuator to reverse a direction of rotation of the rotor when the valve has reached the target peak lift, wherein the phase is changed in dependence on the required change of target peak lift. As described above, the phasing is useful for optimizing the reversal of rotation by minimizing a stator energy requirement for the reversal. This determination may also arise from said engine control unit map.

According to a further aspect of the invention there is provided a valvetrain comprising the electromagnetic valve actuator, a valve, and a mechanism for coupling the electromagnetic valve actuator to the valve.

According to a further aspect of the invention there is provided a valve actuation system comprising the electromagnetic valve actuator and the controller.

According to a further aspect of the invention there is provided an internal combustion engine comprising the electromagnetic valve actuator or the controller or the valve actuation system.

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

According to a further aspect of the invention there is provided a method of controlling an electromagnetic valve actuator for at least one valve of an internal combustion engine, the electromagnetic valve actuator comprising: a rotor; a stator for rotating the rotor; output means for actuating the valve in dependence on rotation of the rotor; mechanical energy storage means arranged to store energy in dependence on rotation of the rotor and release the energy to assist rotation of the rotor; and phase varying means for varying a phase between the mechanical energy storage means and the output means, wherein the method comprises: controlling the phase varying means to vary the phase between the mechanical energy storage means and the output means.

According to a further aspect of the invention there is provided a computer program that, when run on at least one electronic processor, causes at least: controlling an electromagnetic valve actuator for at least one valve of an internal combustion engine, the electromagnetic valve actuator comprising: a rotor; a stator for rotating the rotor; output means for actuating the valve in dependence on rotation of the rotor; mechanical energy storage means arranged to store energy in dependence on rotation of the rotor and release the energy to assist rotation of the rotor; and phase varying means for varying a phase between the mechanical energy storage means and the output means, such that: the valve phase varying means is controlled to vary the phase between the mechanical energy storage means and the output means.

According to a further aspect of the invention there is provided a non-transitory tangible physical entity embodying a computer program comprising computer program instructions that, when executed by at least one electronic processor, enable a controller at least to perform any one or more of the methods described herein.

According to a further aspect of the invention the mechanical energy storage means as described above is not necessarily mechanical but could be any energy storage means, e.g. electrical or chemical.

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 2A illustrates an example of a controller and Fig 2B illustrates an example of a computer-readable storage medium; Fig 3 illustrates an example of an electromagnetic valve actuator, a mechanism and a poppet valve; Fig 4A illustrates an example of phase-varying means set to a first phase, and Fig 4B illustrates an example of phase-varying means set to a second phase; Fig 5 illustrates valve lift and rotor angle according to an example use case; Fig 6 illustrates valve lift and rotor angle according to an example use case; and Fig 7 illustrates valve lift and rotor angle according to an example use case.

DETAILED DESCRIPTION

Fig 1 illustrates an example of a vehicle 10 in which embodiments of the invention can be implemented. In some, but not necessarily all examples, the vehicle 10 is a passenger vehicle, also referred to as a passenger car or as an 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.

The vehicle 10 comprises an internal combustion engine ('engine') 40. The engine comprises a valvetrain 20. The valvetrain 20 comprises the EVA 100 (not shown in Figure 1) embodying one or more aspects of the invention.

The vehicle 10 comprises a controller 50. An example implementation of the controller 50 is shown in Fig 2A. The controller 50 may consist of a single discrete control unit such as shown in Fig 2A and described below, or its functionality may be distributed over a plurality of such control units. The controller 50 may comprise an engine control unit and/or a dedicated valvetrain control unit and/or any other appropriate control unit(s). The controller 50 and EVA 100 may together define a valve actuation system when together.

The controller 50 includes at least one electronic processor 52; and at least one electronic memory device 54 electrically coupled to the electronic processor and having instructions 56 (e.g. a computer program) stored therein, the at least one electronic memory device and the instructions configured to, with the at least one electronic processor, cause any one or more of the methods described herein to be performed.

Fig 2B illustrates an example of a non-transitory computer-readable storage medium 58 comprising the computer program 56.

An example design of the EVA 100 is now described, with reference to Fig 3. Although the phase varying means is not shown in Fig 3, an example underlying system to which the phase varying means can be applied is shown.

Each EVA 100 may be for actuating a single valve 300 or for actuating a plurality of valves. In an engine 40 having a plurality of combustion chambers, each combustion chamber may be associated with one or more valves for allowing gas exchange to/from the combustion chamber, EVAs may be provided for at least one of the one or more valves. Therefore, the valvetrain 20 may comprise a plurality of EVAs.

Depending on implementation, EVAs may be provided for intake valves, for exhaust valves, or for a combination thereof.

The EVA 100 comprises an electric machine comprising a rotor-stator pair. Energy to the stator 101 can be supplied from any appropriate known energy source on the vehicle 10 such as a battery or the engine. The energy may be supplied via an alternator or inverter.

The rotor 102 opens the valve 300 via any appropriate means. In Fig 3 the rotor 102 comprises output means comprising an opening lobe 104. The opening lobe 104 may be coupled to the valve 300 via any appropriate mechanism 200 such as a conventional tappet. In Fig 3 the mechanism 200 is more complex than a conventional tappet. The mechanism 200 comprises an upper rocker 202, 204 and a lower rocker 208 coupled to each other by a pushrod 206.

Valve movement may be amplified relative to the lift of the opening lobe 104 by a multiple within the range 1.3 to 1.95. This range of mechanical advantage is for optimized tolerances, power consumption and system packaging. The EVA 100, mechanism 200 and valve 300 when supplied together may define a system.

The force required to close the valve 300 can be provided by a valve return spring (not shown) and/or by configuring the EVA 100 for desmodromic operation. In Fig 3, the EVA 100 is configured for desmodromic operation. In Fig 3, but not necessarily in all examples, the output means comprises a closing lobe 106. The opening lobe 104 actuates a clockwise portion 202 of the upper rocker (clockwise from perspective of Fig 3) and the closing lobe 106 actuates a counter-clockwise portion 204 of the upper rocker. The rocker 202, 204 pushes and pulls the pushrod 206. The pushrod 206 causes the lower rocker 208 to push and pull the stem of the valve 300. The lower rocker 208 grips the valve 300 like a claw to enable both opening and closing.

The stator 101 can apply positive and negative torque to accelerate and decelerate the rotor 102 and reverse its direction of rotation. The nominal output of the stator 101 may be capable of supplying up to Y Nm of torque for rotating the rotor 102. In one implementation, Y may be from the range approximately 0.5Nm to approximately 1.5Nm. The valve lift events that can be achieved is limited by the speed/acceleration/jerk of the rotor which is limited by Y and the derivative(s) of Y. To plan valve lift events and control stator current accordingly, the controller 50 may receive information indicative of one or more required properties of one or more upcoming valve lift events, such as valve opening time, peak valve lift, and valve closing time. The controller may determine a target rotor velocity (angular velocity) for achieving the valve lift curve. A relationship between target rotor velocity and stator current is stored in the controller 50. The stator current is determined and an output signal is transmitted which causes any appropriate power electronics to control the stator current. The controller 50 may be equipped to control stator current in various engine operating scenarios, including one or more of: * Perform a full valve lift event by rotating the rotor 102 in a first direction for the valve opening stage and continuing rotation in the first direction for the valve closing stage.

* Perform a partial valve lift event by rotating the rotor 102 in a first direction for the valve opening stage and in a second, opposite direction for the valve closing stage. The reversal occurs when a target peak lift less than the maximum peak valve lift is reached. The reversal requires negative stator current.

* Perform a skewed full or partial valve lift event wherein the target rotor velocity in the valve closing stage is different from the target rotor velocity in the valve opening stage.

* Perform multiple valve lifts in one stage of a combustion cycle. For example, the rotor may be rotated twice rather than once. Or, the rotor may be reversed twice or three times.

* 'Park' the rotor 102 between valve lift events at a park position, in which the target rotor velocity is zero. This requires negative 'braking' torque. The park position may correspond to a detent location for minimal cogging torque, so that little or no energy is required to hold the rotor 102 in the park position. The detent locations are specific to the permanent magnet arrangement of the stator 101.

In one implementation, the size of the stator 101 is constrained by engine bay space. It may be that Y is less than a torque required to fully open the valve 300 at an engine speed above 5000 rpm, e.g. for a gasoline engine. Therefore, the stator 101 may require assistance for achieving one or more of the above-described target rotor velocities. Therefore, as shown in Fig 3, the EVA 100 comprises a mechanical energy storage means, referred to as ERS (energy recovery system) herein. The nominal output of the ERS may be capable of supplying up to X Nm of torque for rotating the rotor 102, wherein X<Y and wherein X is approximately 80% of Y, or any other value from the range approximately 60% to approximately 95% of Y. Working together, the stator 101 and ERS can supply nearly X+Y torque to the rotor 102. If the stator can be larger, X could be from the broader range approximately 40% to approximately 95% because less assistance is required.

In Fig 3, but not necessarily in all examples, the ERS is cam/eccentric -actuated. An ERS lobe 108 is shown on the rotor 102. The ERS lobe 108 directly or indirectly couples to a resilient member for storing elastic deformation energy. In Fig 3 the coupling is via an ERS rocker 110.

In Fig 3, but not necessarily in all examples, the resilient member is a cantilever spring 116 which is deflectable about a fulcrum 118. The stiffness of the cantilever spring 116 can be configured to store elastic potential energy for X Nm of torque assistance when fully actuated by the nose of the ERS lobe 108. No elastic potential energy is stored when on the base circle of the ERS lobe 108. In other examples the resilient member could be a different type of resilient member such as a coil spring or other resiliently deformable component.

The operation of the ERS will now be described, with reference to a typical engine operating scenario. In this scenario, the ERS is charged during valve closing and the energy is released prior to the next valve opening. During the valve opening stage, the contact point between the ERS lobe 108 and the ERS rocker 110 is on the base circle of the ERS lobe 108, so that energy recovery does not commence while the valve 300 is opening. Then, during the valve closing phase the contact point between the ERS lobe 108 and the ERS rocker 110 ascends up a flank of the ERS lobe 108 to bias the cantilever spring 116 away from its equilibrium position. Once peak lift of the ERS lobe 108 is reached, the cantilever spring 116 is fully deflected (ERS fully 'charged'). It may be that the peak lift is aligned with a detent location as described above, so that the ERS is fully charged while the rotor 102 is in a park position. Fig 3 also shows that the ERS lobe 108 has a substantially flat top which is sufficiently flat to increase stability/reduce wobble. As soon as the rotor 102 starts to move for the next valve lift event, the contact point descends down a flank of the ERS lobe 108. If rotation is in the same direction the flank is the opposite flank from that which was ascended. If rotation is in reverse the flank is the same flank which was ascended. The cantilever spring 116 is no longer forced away from its equilibrium position so releases its energy to accelerate the ERS lobe 108. This accelerates the rotor 102. This extra torque assists the stator 101 in meeting the target rotor velocity for the next valve lift event.

The ERS of Fig 3 is also space-efficient for various reasons. One of the most significant packaging constraints for engine bays is the height of the EVA 100. The ERS lobe 108 is integrated into the rotor 102 and therefore does not increase the overall height of the system. The ERS rocker 110 is positioned lower than the top of the stator housing 122. The cantilever spring 116 comprises a coupling 120 at one end to the top of the stator housing 122. The axis of the cantilever spring 116 is substantially horizontal. In Fig 3 the fulcrum 118 is separate from the coupling 120 and located towards the free end of the cantilever spring, but in other examples the fulcrum 118 could be provided by the coupling 120. The fulcrum 118 is above the cantilever spring 116, but the top of the fulcrum 118 is only in the order of tens of millimetres higher than the top of the stator housing 122, for example from the range approximately lOmm to approximately 20mm.

Although the above design is space-efficient, it would be appreciated that various aspects of the invention relate to phasing which can be achieved with a different implementation of the ERS and/or EVA 100 from that shown. In other examples the ERS may be implemented with different mechanical components, or even electronically, electromagnetically, hydraulically or pneumatically. Further, although one ERS lobe 108 is shown, more than one could be provided, or none if a different principle of actuation is provided such as a belt, chain or even an electric machine.

The valve actuation techniques described herein involve varying a phase between components of the actuator. In functional terms, the phase between two components may be an offset between the timing at which those components perform their particular functions. For example, the phase between a cam (which charges the ERS) and the rotor 102 defines a timing at which the ERS is charged and released (by the cam) in relation to the timing at which the valve is opened and closed (by the rotor). In this sense, a change in the phase would be a change in the timing offset between the ERS charging and releasing, and the valve opening/closing. It will be appreciated that the timing offset and change in timing offset may be an offset in duration, or an offset in a cycle (for example as a percentage offset of the cycle) where that cycle can be carried out at different rates.

In structural terms, the phase between two components may be an angular or rotational position of one of the two components with respect to the other of the two components with respect to a common axis. For example, the phase between the cam and the rotor 102 may define an angular position of the cam with respect to the rotor 102. Here, a change in phase involves changing the relative angular position between the cam and the rotor 102 about the common axis.

Figs 4A and 4B illustrate an example implementation of phase varying means 400 in which the phase of a cam relative to the rotor 102 can be changed. This changes the phasing of the ERS with respect to valve timing. In Figs 4A and 4B, but not necessarily in all examples, the phase of the ERS lobe 108 can be changed relative to the output means, wherein the output means are permanently fixed to the rotor 102. For example, the phase of the ERS lobe 108 is changeable relative to the opening lobe 104 and/or the closing lobe 106. In other examples, the phase of the output means can be changed relative to the ERS lobe 108 or the rotor 102.

The ERS lobe 108 is not formed or otherwise permanently fixed to the rotor 102. The ERS lobe 108 is capable of 'floating' on the rotor 102, removing or reducing a relationship between rotation of the rotor 102 and rotation of the ERS lobe 108. At two or more phase positions relative to the rotor 102, the ERS lobe 108 is attachable (can be fixed) to the rotor 102 to lock the phase between the rotor 102 and the ERS lobe 108.

Figs 4A and 4B show a hydraulically-actuated two-pin system. The rotor 102 comprises a hydraulic fluid groove 420. The hydraulic fluid could be engine oil or another fluid. In one implementation, the open face of the groove is covered by a bearing housing (not shown), such that fluid in the groove cannot readily escape. Fluid can be supplied to the groove via an aperture in the bearing housing. The pressure of the fluid can be controlled using a solenoid 422. Other known means of supplying hydraulic fluid are also usable.

Radial drillings in the groove transport fluid into passageways inside the rotor 102. Each passageway extends into (or defines) a rotor chamber 408, 418. Two rotor chambers 408, 418 are shown. The pair of rotor chambers 408, 418 are rotationally offset with respect to the axis of rotation of the rotor, by a fixed amount. Corresponding lobe chambers 406, 416 are also provided in the ERS lobe 108. The pair of lobe chambers 406, 416 are rotationally offset by a fixed amount which is different from the rotor chamber offset. For example, the offset may differ by 10 to 30 degrees. Therefore, it is not possible for both lobe chambers 406, 416 to align with both rotor chambers 408, 418 at once.

A locking pin 402, 412 is in each lobe chamber. As shown in Fig 4A, when a first locking pin 402 extends into both a first rotor chamber 408 and a first lobe chamber 406, the locking pin 402 is in an interference position so the rotor 102 and ERS lobe 108 are locked together. This defines a first phase. As shown in Fig 4B, when a second locking pin 412 extends into both a second rotor chamber 418 and a second lobe chamber 416, the second locking pin 412 is in an interference position so the rotor 102 and ERS lobe 108 are locked together. This defines a second phase.

The locking pins 402, 412 are biased towards the respective rotor chambers 408, 418 by respective springs 404, 414. When a rotor chamber is aligned with a lobe chamber, the locking pin 402, 412 will move to its interference position if hydraulic pressure is low. Raising hydraulic pressure pushes against the spring 404, 414 so that the locking pin 402, 412 is pushed back into the lobe chamber 406, 416 to unlock the ERS lobe 108. To change phase according to the above design, hydraulic pressure within the groove 420 can be increased to detach the ERS lobe 108, and then reduced at a calculated time to re-attach the ERS lobe 108 at the desired phase.

The above implementation is based on raising fluid pressure to unlock. In an alternative implementation, the design is based on lowering fluid pressure to unlock, so constant raised hydraulic pressure is required to maintain the locking pin in the interference position.

In another implementation, the locking pin 402, 412 could be retracted into the rotor chamber rather than the lobe chamber, with corresponding changes to the fluid supply routing.

Although the groove 420 is shown on one side of the ERS lobe 108, it could be on the other side of the ERS lobe 108 in another implementation, with the grooves, pins and springs 25 mirrored.

The above implementation is a two-pin design. However, it is possible to change phase using a one-pin two-chamber design in another implementation. This would require one locking pin 402 in one rotor chamber 408 and at least two lobe chambers 406, 416, or one locking pin 402 in one lobe chamber 406 and at least two rotor chambers 408, 418. When the chamber in which the locking pin 402 is located aligns with one of the corresponding other chambers, the pin can be slid into the interference position by control of hydraulic pressure. When the ERS lobe 108 is detached, then once the pin 402 aligns with the next one of the corresponding other chambers, the pin can again be slid into the interference position if hydraulic pressure is high, and the phase will have been varied depending on the rotational separation of the other chambers relative to each other.

The above principles can readily be applied to a phase varying means with three or more phases, simply by increasing the number of rotationally offset interference positions.

The actuating means described above is hydraulic fluid although other actuating means are also envisaged based on electromagnetics or pneumatics.

In another variation, the attachment of the ERS lobe 108 could be controlled in a different way than by applying hydraulic pressure. For example, the locking pin could have a sloped surface, and be spring biased as disclosed above. When in the interference position, the rotor 102 and ERS lobe 108 could couple at a contact point on the sloped surface. The slope is against the direction of rotation so that acceleration of the rotor 'drags' the ERS lobe 108 with it. Shear force between the ERS lobe 108 and the rotor 102 acts on the contact point on the sloped surface, to lock their speeds together. When shear force is increased by applying a force to slow the ERS lobe 108 relative to the rotor 102, the forces on the contact point are no longer in equilibrium so the locking pin 402 starts to compress the spring 404 and retract away from the interference position. With sufficient shear force, the ERS lobe 108 is unlocked. An advantage is enabling a 'dry' system, because shear force could be controlled by electromagnetic means such as a small electric actuator proximal to or inside the rotor 102 or ERS lobe 108 that controls an electric/magnetic field. Variable cam timing systems exist which work on a similar premise.

A locking pin design is one of many alternative ways in which the phase varying means can be implemented. In another example, no locking pins are involved. For example, the ERS rocker 110 could be actuated to change the phasing between the ERS lobe 108 and the cantilever spring 116.

In view of the above, it would be appreciated that the phase varying means can be implemented in many ways.

Methods of using the phase varying means will now be explained, with reference to Figs 5 to 7.

Each of Figs 5 to 7 illustrates a top graph which shows valve lift (vertical, y-axis) against a time domain (horizontal, x-axis). The time domain is degrees of crank rotation. One or more lower graphs shows rotor angular position (0, y-axis) against the same time domain.

Fig 5 relates to the first example operating scenario as described earlier. Fig 7 relates to the second example operating scenario. Fig 6 relates to changing between the second scenario and the first scenario. The controller 50 is configured to control the phase in the manner described below in relation to one or more of the operating scenarios.

The upper graph of Fig 5 shows two valve lift events.

The middle graph of Fig 5 shows rotor position for 'phase 1' of the phase varying means. Before time A the rotor 102 is in its park position. The ERS is fully charged. At time A the valve 300 starts to open. At time B the valve 300 reaches its maximum peak lift. Between times A and B the contact point between the ERS lobe 108 and the ERS rocker 110 is on the base circle of the ERS lobe 108. At time C the valve 300 is fully closed. Between times B and C the ERS starts to charge. Referring to the hardware example of Fig 3, the ERS lobe 108 starts to deflect the cantilever spring 116. The optimum start time for ERS charging is denoted by the region 1S1' which is between time B and time C, or between time B and after time C. The effect of charging the ERS is illustrated by the visible slowdown of the rotor 102. The rotor 102 slows to a halt at or after time C. The ERS may be fully charged when the rotor 102 is stationary. If the energy recovery is insufficient the stator 101 may assist the charging of the ERS. The rotor 102 halts at a park position which may be aligned with a detent. The rotor 102 remains in the park position until a required time before time D. Time D represents the valve 300 starting to open for a subsequent valve lift event. The rotor 102 begins to rotate with the assistance of the ERS, before time D, in the region R1. The region R1 occurs at a predetermined time between Si and time D. The target rotor velocity for valve opening at time D is therefore achieved with assistance from the ERS. After time E (target peak lift), the ERS may charge again.

The lowest graph of Fig 5 shows rotor position for 'phase 2' of the phase varying means. The phase may be changed in advance, between valve lift events. Stator torque may be supplied to slide the rotor 102 relative to the ERS lobe 108 into the next phase position, if the change occurs while the rotor 102 is in a park position. The ERS is retarded relative to phase 1. Now, ERS charging denoted by region S2 commences after time C. not before. Energy release denoted by region R2 commences before time D, and may or may not be timed to occur at the same time as region R1.

As explained earlier, switching from phase 1 to phase 2 may be performed in response to a parameter indicative of kinetic energy, such as rotor velocity or engine speed, indicating insufficient kinetic energy (inertia) to fully charge the ERS without assistance by the stator 101. Additionally or alternatively, the switch may be performed for another reason such as in response to a determination that the rotor 102 must speed up between times B and C (fast valve close event), or in response to satisfaction of a safety/limp mode condition or other condition.

Fig 7 will be described before Fig 6. The upper graph of Fig 7 illustrates two partial valve lift events, requiring reversal of the direction of rotation of the rotor 102. At time A the valve 300 starts to open. Between times A and B the rotor 102 needs to decelerate to a halt so that a reversal of rotation occurs at time B (target peak lift). The controller 50 determines when the ERS should commence charging and selects an appropriate ERS phase, to minimise a requirement for the stator 101 to apply negative torque. The ERS at phase 1 charges in the region Si between times A and B, which decelerates the rotor 102. At time B the rotor 102 ceases rotation and the target peak valve lift is achieved. The contact point between the ERS lobe 108 and the ERS rocker 110 may still be on the flank rather than on the nose of the ERS lobe 108, to reduce the chance of an overshoot. From time B the rotor 102 reverses direction and the contact point between the ERS lobe 108 and the ERS rocker 110 descends the same flank towards base circle. This energy release in region R1 minimises a requirement for the stator 101 to accelerate the rotor 102 in the reverse direction.

At time C of Fig 7 the valve 300 closes. In Fig 7 the stator 101 then stops the rotor 102 in a park position between times C and D in preparation for the next valve lift event. However, in other examples the rotor 102 could continually rotate or the reverse rotation may even become its forward direction of rotation for the next valve lift event. An event planning function in the controller 50 may determine that the next valve lift event is also a partial valve lift event and plan the rotor 102 behaviour accordingly between times C and D. If the next valve lift event requires a different amount of lift, a different ERS phase may be selected to minimise the requirement for negative stator torque. The phase may be changed between times C and D. Stator energy may be supplied to facilitate the change, if the change occurs once the rotor 102 has already stopped rotating. For example, Fig 7 shows that less lift is required for the next valve lift event. As a result, the ERS charging occurs in the region S2 which is slightly later than the region Si, so that the point of reversal is aligned with time D (beginning of valve opening phase) without the need for additional stator energy. There may be some scenarios in which ERS charging should be advanced when less lift is required, such as when the target rotor velocity is higher.

Fig 6 shows a transition from a partial valve lift such as shown in Fig 7 and a full valve lift such as shown in Fig 5. Between times A to C the ERS phase performs the function of phase 1 (or phase 2) of Fig 7, with charging at Si and release at R1. Between times D and E the ERS phase should perform the function of phase 1 or 2 of Fig 5. An efficient control strategy is to allow the rotor 102 to continue rotating between times C and D in the reverse direction, such that the reverse direction becomes the forward direction for the next valve lift event from times D to E. The ERS phase is changed in advance between times C and D. The charging S2 for phase 2 occurs during the closing phase of the next valve lift event from times E to F, wherein at time F the valve 300 is fully closed. Therefore, 52 occurs later with respect to the respective valve lift event than Si.

For purposes of this disclosure, it is to be understood that the controller(s) 50 described herein can each comprise a control unit or computational device having one or more electronic processors 52. A vehicle 10 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 56 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 58 (e.g., a non-transitory computer-readable 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.

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

CLAIMS1. An electromagnetic valve actuator for at least one valve of an internal combustion engine, the electromagnetic valve actuator comprising: a rotor; a stator for rotating the rotor; output means for actuating the valve in dependence on rotation of the rotor; mechanical energy storage means arranged to store energy in dependence on rotation of the rotor and release the energy to assist rotation of the rotor; and phase varying means for varying a phase between the mechanical energy storage means and the output means.
2. The electromagnetic valve actuator of claim 1, wherein the phase varying means is operable to maintain a first phase between the mechanical energy storage means and the output means, causing the mechanical energy storage means to store energy while the valve is open.
3. The electromagnetic valve actuator of claim 2, wherein maintaining the first phase causes the mechanical energy storage means to release the energy while the valve is closed.
4. The electromagnetic valve actuator of claim 2 or 3, wherein the phase varying means is operable to maintain a second phase between the mechanical energy storage means and the output means, causing the mechanical energy storage means to store energy later with respect to valve opening than in the first phase.
5. The electromagnetic valve actuator of claim 4, wherein maintaining the second phase causes the energy storage to occur while the valve is closed.
6. The electromagnetic valve actuator of claim 4 or 5, wherein the second phase is offset from the first phase by a value from the range 10 to 30 degrees.
7. The electromagnetic valve actuator of any preceding claim, wherein the electromagnetic valve actuator is operable to reverse a direction of rotation of the rotor when the valve has reached a target peak lift less than a maximum peak lift, and wherein the mechanical energy storage means causes, at least in part, the reversal.
8. The electromagnetic valve actuator of any preceding claim, wherein the mechanical energy storage means is configured to supply X Nm of torque when releasing the energy to assist rotation of the rotor, wherein the stator is configured to supply up to Y Nm of torque for rotating the rotor, and wherein X is from the range 40% to 95% of Y.
9. The electromagnetic valve actuator of claim 8, wherein Y is less than a torque required to fully open the valve at an engine speed above 5000 rpm.
10. The electromagnetic valve actuator of any preceding claim, wherein the mechanical energy storage means comprises a cantilever spring.
11. The electromagnetic valve actuator of any preceding claim, wherein the mechanical energy storage means comprises a cam or an eccentric.
12. The electromagnetic valve actuator of any preceding claim, wherein the phase varying means is configured to vary the phase of the mechanical energy storage means or the output means relative to the rotor.
13. The electromagnetic valve actuator of any preceding claim, wherein the output means is desmodromic.
14. A controller configured to control an electromagnetic valve actuator for at least one valve of an internal combustion engine, the electromagnetic valve actuator comprising: a rotor; a stator for rotating the rotor; output means for actuating the valve in dependence on rotation of the rotor; mechanical energy storage means arranged to store energy in dependence on rotation of the rotor and release the energy to assist rotation of the rotor; and phase varying means for varying a phase between the mechanical energy storage means and the output means, wherein the controller comprises: means to control the phase varying means to vary the phase between the mechanical energy storage means and the output means.
15. The controller of claim 14, comprising means to receive a parameter indicative of kinetic energy, and to control the phase varying means to vary the phase from a second phase that causes the mechanical energy storage means to store energy after closing of the valve, to a first phase that causes the mechanical energy storage means to store energy during closing of the valve, when the parameter exceeds a threshold.
16. The controller of claim 15, wherein the parameter is engine speed-dependent.S
17. The controller of claim 15 or 16, comprising means to control the stator while the second phase is in operation, to apply torque to the rotor after closing of the valve to cause the mechanical energy storage means to store energy after closing of the valve.
18. The controller of any of claims 14 to 17, wherein the controller comprises means to control the stator while at least the second phase is in operation, to apply torque to the rotor during closing of the valve.
19. The controller of any of claims 14 to 18, comprising means to determine a required change from a partial valve lift mode to a full valve lift mode, wherein the partial valve lift mode requires the electromagnetic valve actuator to reverse a direction of rotation of the rotor when the valve has reached a target peak lift less than a maximum peak lift, and comprising means to control the phase varying means to vary the phase from a second phase that causes the mechanical energy storage means to cause, at least in part, reversal of the valve, to a first phase in which energy storage does not occur prior to maximum peak lift.
20. The controller of any of claims 14 to 19, comprising means to determine a required change of target peak lift of the valve less than a maximum peak lift of the valve, wherein the target peak lift requires the electromagnetic valve actuator to reverse a direction of rotation of the rotor when the valve has reached the target peak lift, wherein the phase is changed in dependence on the required change of target peak lift.
21. A valve actuation system comprising the electromagnetic valve actuator as claimed in any one or more of claims 1 to 13 and the controller as claimed in any one or more of claims 14 to 20.
22. An internal combustion engine comprising the electromagnetic valve actuator as claimed in any one or more of claims 1 to 13 or the controller as claimed in any one or more of claims 14 to 20 or the valve actuation system as claimed in claim 21.
23. A vehicle comprising the internal combustion engine as claimed in claim 22.
24. A method of controlling an electromagnetic valve actuator for at least one valve of an internal combustion engine, the electromagnetic valve actuator comprising: a rotor; a stator for rotating the rotor; output means for actuating the valve in dependence on rotation of the rotor; mechanical energy storage means arranged to store energy in dependence on rotation of the rotor and release the energy to assist rotation of the rotor; and phase varying means for varying a phase between the mechanical energy storage means and the output means, wherein the method comprises: controlling the phase varying means to vary the phase between the mechanical energy storage means and the output means.
25. A computer program that, when run on at least one electronic processor, causes at least: controlling an electromagnetic valve actuator for at least one valve of an internal combustion engine, the electromagnetic valve actuator comprising: a rotor; a stator for rotating the rotor; output means for actuating the valve in dependence on rotation of the rotor; mechanical energy storage means arranged to store energy in dependence on rotation of the rotor and release the energy to assist rotation of the rotor; and phase varying means for varying a phase between the mechanical energy storage means and the output means, such that: the valve phase varying means is controlled to vary the phase between the mechanical energy storage means and the output means.