Electromagnetically actuated engine valve for an internal combustion engine

Abstract

An electromagnetically actuated valve assembly (1) for an internal combustion engine comprises a housing (10) inside of which is a tubular linear electric motor (12) with a central axis (18) and, extending along the axis, an elongate armature body (20) that comprises an elongate main portion that is configured to move in opposite first and second axial directions (41, 42) and a poppet valve (40) having a valve stem and a valve head (46). An armature bearing (45) is configured for sliding motion of the armature body relative to the housing. A controller (16) controls the operation of the linear electric motor (12) to move axially and thereby lift and lower the valve head with respect to a valve seat (48) to open and close a valve (2, 4). A coil spring (51) exerts a force on the armature body in the second direction (42). The linear electric motor comprises a fixed winding pack and a magnet pack with an array of alternating permanent magnets within the armature body main portion. The valve assembly further comprises within the housing a solenoid actuator (14) comprising a solenoid winding (70) and a solenoid armature (60), the solenoid winding being fixed relative to the housing (1) and the solenoid armature (60) being fixed relative to an end of the main portion of the armature body and comprising a magnetic material. The controller is connected to the solenoid winding and is configured, when the poppet valve is to move in the second direction to close the cylinder valve, to energise the solenoid winding and thereby actuate the solenoid armature to move in the second direction and close the cylinder valve.

Description

[0001] Electromagnetically Actuated Engine Valve for an Internal Combustion Engine

[0002] BACKGROUND a. Field of the Invention

[0003] The present invention relates to an electromagnetically actuated engine valve assembly for opening and closing a cylinder valve of a reciprocating piston internal combustion engine, and also a method for operating such an engine valve assembly. b. Related Art

[0004] Conventional spark and compression ignition engines, referred to generally herein as internal combustion engines, contain cams driven off the crankshaft that synchronise the timing of the intake and exhaust valves with the pistons. Various mechanical I hydraulic timing variation mechanisms are known but these are very limited and have a slow response time in comparison to engine demand.

[0005] The use of one or two solenoids, instead of a camshaft, to drive the motion of a valve stem in an internal combustion engine (cylinder inlet and outlet valves), has been known for some time. For example, patent document US 6,575,126 B2 discloses a valve assembly having a housing, an engine valve having a valve stem that extends along a central axis, a movable armature to which the valve stem is coupled, and two solenoids that are spaced apart in an axial direction. One solenoid can be energised to move the valve to an open position, and the other solenoid can be energised to move the valve to a closed position. A spring is provided to provide damping against valve movement.

[0006] All such solenoid-based engine valves suffer from various problems. To move the valves at the requisite speeds in a four-stroke internal combustion engine, operating at up to about 6,000 revolutions per minute (rpm), requires solenoids that are bulky as compared with the available space around a typical engine head, particularly for roadgoing vehicles. For example, at 100 revolutions per second (rps), one stroke will take 5 ms. A valve will need to be both opened and closed within that time, for example, opened within 1 ms, then maintained open for 3 ms, and then closed within 1 ms, approximately. An exhaust valve may weigh about 70 grams, and may need to move up to about 2.5 cm, the required forces needed to complete the movement within the available time are of the order of about 70 N. The use of two solenoids as detailed in patent document US 6,575,126 B2 only provides two states of operation, fully closed or fully open depending on which coil is energised.

[0007] Single solenoid actuators need to operate against a force provided by a biasing spring, which is configured to hold the valve shut when the engine is off. To provide some linearity in the drive current against valve position, the biasing force needs to be comparable to the force needed to complete the movement in the absence of a biasing spring. This can double the required force in one direction. Although energy stored in the spring is then available to help close the valve, there will be energy loses due to friction in the spring mechanism. Greater forces will require higher peak currents and average electrical energy consumption.

[0008] Ohmic heating of the solenoid coil can be a problem. Excess heat can degrade coil insulation as well as damage and demagnetise the permanent magnet to be moved by the solenoid coil. Attempting to minimise the volume of a solenoid actuator will make cooling of the solenoid more difficult.

[0009] For reasons such as these, electromagnetically actuated engine valves have not been widely used, despite the potential for simplifying mechanical complexity by doing away with cam shaft mechanisms and allowing independent control of valve timing.

[0010] It is an object of the invention to provide a more convenient electromagnetically actuated engine valve assembly for opening and closing a cylinder valve of a reciprocating piston internal combustion engine, and also a method for operating such an engine valve assembly. SUMMARY OF THE INVENTION

[0011] According to a first aspect of the invention, there is provided an electromagnetically actuated engine valve assembly for opening and closing a cylinder valve of a reciprocating piston internal combustion engine, the valve assembly comprising: a housing, and within the housing a tubular linear electric motor with a central axis and, extending along the axis, an elongate armature body, the armature body comprising:

[0012] - an elongate main portion, the main portion extending along the central axis between a first end and a second end of the main portion, and being configured to move in opposite first and second axial directions along said axis; and

[0013] - a poppet valve, the poppet valve comprising a valve stem and a valve head, the valve stem being connected to the second end of the main portion of the armature body and extending away from the housing along the central axis towards the valve head; at least one armature bearing configured for sliding motion of the armature body relative to the housing in said opposite axial directions; a controller, the controller being configured to control the operation of the linear electric motor whereby the armature body moves in the first and second axial directions respectively to lift and lower the valve head with respect to a valve seat whereby said cylinder valve is, respectively, moved towards an open position and a closed position; and a spring mechanism, the spring mechanism being configured to exert a force on the armature body along the central axis in the second direction, wherein: the linear electric motor comprises a winding pack and a magnet pack, the winding pack being fixed relative to the housing and comprising a plurality of motor windings, the motor windings extending around the central axis and the winding pack defining a central bore, and the magnet pack being fixed relative to the main portion of the armature body and comprising an array of permanent magnets aligned in alternating and opposing axial directions within the bore, each magnet in the array being separated from an adjacent magnet by a magnetic material spacer and said array extending axially along the central axis of the armature body, whereby the magnet pack is configured to produce a sinusoidal-like magnet field pattern along the central axis; the controller is connected to the motor windings and is configured, when controlling the operation of the linear electric motor, to energise the motor windings; the valve assembly further comprises within the housing, a solenoid actuator, the solenoid actuator comprising a solenoid winding, and a solenoid armature, the solenoid winding being fixed relative to the housing and being coaxial with the central axis and the solenoid armature being fixed relative to the first end of the main portion of the armature body and comprising a magnetic material; and the controller is connected to the solenoid winding and is configured, when the poppet valve is to move in the second direction to close the cylinder valve, to energise the solenoid winding and thereby actuate the solenoid armature to move in the second direction and close the cylinder valve.

[0014] In this application, the term “magnetic material” has its usual meaning, i.e. a material which is attracted towards a magnet. This may be either a non-magnetised material which acquires magnetisation when attracted, or a magnetised magnet material, i.e. a permanent magnet. A magnetic material may more generally be defined as a substance that exhibits permeability p that is significantly different from the permeability of free space po. Magnetic materials are typically metals, semiconductors, or heterogeneous media containing such materials. Examples include iron and ferrite, which consists of iron particles suspended in a ceramic. Magnetic materials are commonly classified according to the physical mechanism responsible for their magnetizability. These mechanisms include paramagnetism, diamagnetism, and ferromagnetism. Ferromagnetism occurs in the transition metals iron, nickel, and cobalt, as well as their alloys and alloys of rare-earth metals.

[0015] Because there is a plurality of windings in the tubular linear electric motor, the windings will, in use, interact with different portions of the sinusoidal-like magnet field pattern along the central axis. The windings can then be energised, either individually or in concert, by the controller to move the winding pack in one direction or another, or to hold the winding pack in a desired position. In this way, the position of the winding pack, and hence the actuator body a poppet valve, is controlled so that the cylinder valve is moved from a closed position towards an open position, which may be partially open or fully open, as desired.

[0016] There is therefore no need for the electric motor to act against a spring mechanism in the same way that a solenoid (which can only act in one direction when the armature is not magnetised) can be used to generate a variable force acting against a spring biasing force, when maintaining a desired position of the valve. Therefore, the necessary strength of the spring is not determined by the forces to be generated by the electric motor.

[0017] In many modes of engine operation, it is desirable to hold a valve open for as long as possible, either for an intake valve during an intake stroke, so that the cylinder receives the maximum charge of air and fuel, or during the exhaust stoke, as the cylinder is being discharged of burnt gasses. In both cases, once the valve is no longer needed open, it is generally desirable that the valve be closed as quickly as possible. The solenoid actuator is therefore energised just during the portion of the cylinder cycle when the valve is to be closed.

[0018] It is therefore not necessary that the spring mechanism be strong enough to bias the valve in the second direction to close the valve in the relatively short interval of time available for the closing of the valve, as it is the solenoid actuator which predominantly provides the required force on the actuator body.

[0019] It will, in general, be desirable that the cylinder valve is held closed against gravity when the engine is not operating. Therefore, force provided by the spring mechanism may be sufficient only to hold the poppet valve closed against gravity, i.e. against the weight of the moving armature / valve assembly of the actuator body, magnet pack, solenoid armature and poppet valve including the valve stem and valve head.

[0020] Preferably, the force exerted by the spring mechanism on the armature body is at least enough to lift the armature body against gravity when the axis is oriented substantially vertically, i.e. a generating an upwards force greater than the weight of the armature body, and more preferably at least about 50% greater than the weight. Preferably the upwards force is not more than about five times the weight of the armature body. Ideally, the force exerted by the spring mechanism on the armature body is less than twice the weight of the armature body.

[0021] The spring mechanism can therefore be relatively weak, as compared with the type of valve-return springs typically used in cam-driven valves. This will reduce the peak and average current requirements for the electric motor used to control the position of the cylinder valve when this is being moved or held in partially or fully open positions.

[0022] In any event, since the spring mechanism will exert a certain minimum force on the poppet valve along the central axis in the second direction, the spring will, in general, cooperate with the solenoid when the cylinder valve is to be closed.

[0023] Optionally, the electric motor may also be energised to move the cylinder valve to the closed position, in which case, the electric valve will also cooperate with the solenoid when the cylinder valve is to be closed.

[0024] In some embodiments of the invention, the spring mechanism is located between the winding pack and the solenoid winding. This has the advantage of providing a physical separation between the magnetic elements of the electric motor and the solenoid actuator, which helps to prevent electromagnetic interference between the two. The spring mechanism therefore magnetically separates the winding pack and the solenoid winding.

[0025] Preferably, the armature body comprises an outer sleeve.

[0026] In this case, both the magnet pack and the magnetic material of the solenoid armature may be secured to the sleeve.

[0027] In general, the sleeve will be of a non-magnetic material, so as not to interfere with magnetic field lines between windings and magnets or magnetic material.

[0028] The spring mechanism may comprise a coil spring. In some embodiments, the coil spring being located between a radially outer surface of the sleeve and the housing.

[0029] Preferably, the armature body comprises a shoulder that extends radially outwards from the sleeve, and the coil spring is held in compression between the shoulder and the winding pack.

[0030] The solenoid winding may extend around a solenoid bore extending around the central axis, and the solenoid armature may then extend axially within the bore.

[0031] When the armature body comprises an outer sleeve, the outer sleeve may extend into the solenoid bore. The magnetic material of the solenoid armature may then be secured to the sleeve within the solenoid bore.

[0032] The shoulder may be provided by a flange affixed externally to the sleeve.

[0033] In one embodiment, the solenoid winding defines a solenoid bore extending around the central axis and the solenoid actuator comprises within the solenoid bore a fixed core of a magnetic material, the fixed core being axially opposed to the magnetic material of the solenoid armature.

[0034] In this case, the solenoid armature may comprise a disc that extends radially away from the first end of the armature body.

[0035] The disc will, in general have, opposite first and second radially extending faces. The first face is then preferably axially opposed to the solenoid winding.

[0036] The second face of the disc may then provide the shoulder against which the coil spring is held in compression.

[0037] In preferred embodiments, the second end of the armature body extends through an aperture in the housing.

[0038] According to a second aspect of the invention, there is provided a method of operating an electromagnetically actuated engine valve assembly for opening and closing a cylinder valve of a reciprocating piston internal combustion engine, the valve assembly being according to the first aspect of the invention, wherein the method comprises: turning the engine in a cycle of cylinder strokes in which the cylinder valve is repeatedly opened and closed by the valve assembly; when the cylinder valve is to be opened, using the controller to drive the motor windings to control the movement of the actuator body and hence the position of the poppet valve in both the first and second directions along the central axis; and when the cylinder valve is to be closed, using the controller to drive the solenoid winding to control the movement of the actuator body in the second direction until the cylinder valve is closed.

[0039] Preferably, the method comprises force exerted on the armature body in the second direction by the spring mechanism is sufficient to hold the cylinder valve closed against gravity when the first direction is vertically downwards.

[0040] Preferably, the method further comprises, when the cylinder valve is to be closed, using the controller to drive the motor windings to move the actuator body in the second direction, whereby the solenoid actuator and the electric motor co-operate to close the cylinder valve.

[0041] BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention will now be further described, by way of example only, and with reference to the accompanying drawings, in which:

[0043] Figure 1 is a partially cut away perspective view of a part of an internal combustion engine cylinder head, having four electromagnetically actuated engine valve assemblies in a first preferred embodiment of the invention, each valve assembly having an axially movable armature body that includes a poppet valve, the poppet vale comprising a valve stem that extends away from main portion of the armature body towards a valve head that is raised and lowered with respect to a valve seat in order to open and close a corresponding cylinder valve;

[0044] Figure 2 is a sectional perspective view of the armature body of Figure 1 , showing how the armature body has a main portion that extends along a central axis defined by a stacked series of four motor windings, and which holds a magnet pack comprising a series of five magnets with alternating polarity;

[0045] Figure 3A is a partially cut away / sectional view of one of the valve assemblies of Figure 1 in an open position, showing how the movable magnet pack and the four windings, which are fixed relative to an external housing, act as a linear motor to move the valve stem in opposition directions along the central axis when the motor windings are energised with electrical current;

[0046] Figure 3B is a partially cut away / sectional view of the valve assembly of Figure 1 when moved to in a closed position, showing how the valve assembly further comprises, separate from the linear motor, a solenoid actuator comprising a solenoid armature including a plate of magnetic material at an end of the armature body, and a solenoid winding fixed relative to the housing which, when energized with electrical current, acts as a solenoid motor to pull the valve stem in along the central axis to close the cylinder valve;

[0047] Figures 4A, 4B and 4C show three further embodiments of a solenoid motor, each having a solenoid armature of magnetic material which, instead of a plate, has a flange at one end of a cylindrical body that moves axially within a bore within a solenoid winding;

[0048] Figure 5 is a schematic representation of the relationship between a sinusoidal- like magnet field pattern generated by the magnet pack of Figures 1 to 3, and shows how the locations of magnetic fields provided by the four motor windings of the linear motor are spaced apart with respect to the magnet field in a four- phase pattern;

[0049] Figures 6 to 8 are views similar to Figures 1 , 3A and 3B showing an electromagnetically actuated engine valve assembly in a second preferred embodiment of the invention, in which the linear motor has six motor windings instead of four, the magnet pack has a series of six magnets instead of five and the solenoid armature has magnetic material in the form of a cylindrical body, rather than a plate, that moves axially within a bore defined by a solenoid winding;

[0050] Figure 9 is a schematic representation of the relationship between a sinusoidal- like magnet field pattern generated by the magnet pack of Figures 6 to 8, and shows how the locations of magnetic fields provided by the six windings of the linear motor are spaced apart with respect to the magnet field in a three-phase pattern that repeats once;

[0051] Figure 10A is a schematic diagram showing how a controller is connected to the four motor windings and the solenoid winding of the first embodiment, showing how the windings are driven in four separate phases.

[0052] Figure 10B is a schematic diagram showing how a controller is connected to the four motor windings and the solenoid winding of the second embodiment, showing how the windings are driven in three separate phases;

[0053] Figures 11 to 13 are views similar to Figures 1 , 3A and 3B, showing an electromagnetically actuated engine valve assembly in a third preferred embodiment of the invention, in which the linear motor has three motor windings instead of four, the magnet pack has a series of six magnets instead of five and the solenoid armature has magnetic material in the form of a cylindrical body, rather than a plate, that moves axially within a bore within a solenoid winding;

[0054] Figure 14 is a schematic representation of the relationship between a sinusoidal-like magnet field pattern generated by the magnet pack of Figures 11 to 13, and shows how the locations of magnetic fields provided by the three windings of the linear motor are spaced apart with respect to the magnet field in a three-phase pattern; Figure 15 is a schematic diagram showing how a controller is connected to the three motor windings and the solenoid winding of the third embodiment, showing how the windings are driven in three separate phases.

[0055] Figure 16 is a partially cut away perspective view of an internal combustion engine cylinder head showing parts of two electromagnetically actuated engine valve assemblies in a fourth preferred embodiment of the invention, in which a spring mechanism acting between the armature body and the housing is provided between the linear motor and the cylinder head, rather than between the linear motor and the solenoid armature or the solenoid winding;

[0056] Figure 17 is a perspective view of a shared housing for four of the engine valve assemblies of Figure 16 when fixed to the cylinder head;

[0057] Figure 18A is a partially cut away perspective view of an internal combustion engine cylinder head and part of a reciprocating piston, showing two cylinder valves at inlet and outlet ports above the piston that are opened and closed by two of the electromagnetically actuated engine valve assemblies of Figures 11 to 13, at the start of the intake stroke, in which the inlet valve is opened using the linear motor and the outlet valve is held closed using the solenoid motor;

[0058] Figure 18B is a view following from Figure 18B, at the start of the compression stroke, in which both the inlet and outlet valves are moved to the closed position using both the solenoid motor and the linear motor;

[0059] Figure 18C is a view following from Figure 18C, during the power stroke, in which both the solenoid motor and the linear motor are de-energised; and

[0060] Figure 18D is a view following from Figure 18C, during the exhaust stroke, in which the inlet valve is held closed using the solenoid motor and the outlet port is held open using the linear motor. DETAILED DESCRIPTION

[0061] Figure 1 shows part of an internal combustion engine cylinder head 3, having for each engine cylinder four electromagnetically actuated engine valve assemblies 1. The valve assemblies actuate a pair of side-by-side inlet valves 2 and a pair of side-by side outlet valves 4. Just one of each valve type is visible in Figure 1 . In this example, both inlet valves are the same as each other and both outlet valves are the same as each other. Each inlet valve controls the flow of air or an air / fuel mixture through a corresponding inlet port 6 and each outlet valve controls the flow of combustion gasses to a corresponding outlet port 8. For the same of brevity, not shown are conventional elements such as a direct or indirect fuel injection system or inlet or outlet manifolds.

[0062] The valve assemblies 1 for the inlet and outlet valves 2, 4 are mechanically the same, but will be driven differently, according to their function in controlling gas flow cylinder operation, as will be explained in more detail below. Figures 3A and 3B therefore show two different modes of operation which are applicable to both the inlet and outlet valves 2, 4. The size of the inlet and outlet valves can be other than shown.

[0063] Each valve assembly 1 is electromagnetically actuated by an electromagnetic actuator system that comprises a tubular linear electric motor 12 and a solenoid actuator 14, both of which are controlled by a controller 16 which is illustrated in a simplified form as a plain circuit board. In this example, each valve assembly has its own outer housing 10, that houses the linear electric motor 12 and the solenoid actuator 14.

[0064] The controller 16 is preferably within the housing, in proximity with the linear electric motor 12 and the solenoid actuator 14, and in general may comprise a microprocessor including memory and program instructions to control the opening and closing of inlet and outlet valves 2, 4 in synchronisation with engine operation, e.g., reciprocating engine cylinders and fuel injection system (not shown). The controller is connected to input and output connections 5 for power and communicating with vehicle electronics, as will be described below in more detail. The connections 5 may be provided in a lid 7 of the housing 10, which is closed after assembly of the components held within the housing. Locating the controller 16 within the housing 10 simplifies electrical connections (not illustrated) for providing electrical currents to drive the linear electric motor 12 and solenoid actuator 14. It would, however, be possible to locate the controller 16 outside the housing. If multiple valve assemblies are housed within a common housing, then the functions of several corresponding controllers may be integrated, for example on the same printed circuit board or using the same integrated circuit chip.

[0065] As shown in Figure 2, the linear electric motor 12 is tubular in form around a central axis 18 and comprises a magnet pack 22 a linear motor winding pack 24. The linear motor winding pack 24 is fixed relative to the housing 10 (i.e. either directly fixed or indirectly fixed to the housing) and comprises a plurality of motor windings 25 that extend around the central axis 18 and preferably also a series of magnetic material spacers, preferably non-magnetised, which in this example are rings 23 that separate adjacent windings 25 that extend in a plane perpendicular to the axis 18. The magnets and rings are stacked in the axial direction, such that the magnet pack extends between opposite first and second ends 17, 19 of the winding pack. The magnetic material rings 23, 23’, preferably non-magnetised and which may be of iron or ferrite, may also be provided at the opposite first and second ends 13, 15 of the magnet pack 22, as in the illustrated embodiment, so that each winding is sandwiched between a pair of adjacent magnetic material rings 23, 23’. Most preferably, the rings 23, 23’, are connected at a common inner radius by a magnetic material cylinder portion 27, preferably non-magnetised. The rings 23, 23’ and cylinder portion 27 may then provide a winding pack bobbin 26 for each winding 25. In this example, the rings 23, 23’ and cylinder portion 27 are of one-piece construction, i.e. a unitary body without any seams or joins, and so provide a unitary multi-flanged winding pack bobbin 26 for all of the windings 25.

[0066] The magnet pack 22 therefore defines a central bore 11 of the linear electric motor 12, and also of the valve assembly 1 . In this example, the central bore 11 is provided by a radially inner surface of the cylinder portion 27 of the linear motor winding pack 24.

[0067] The magnet pack 22 is fixed within the armature body 20 and comprises an array of permanent magnets 28, 28’ that are aligned in alternating and opposing axial directions within the bore 11 . In other words, adjacent magnets have the same magnetic polarity, either North or South, facing each other.

[0068] The array of magnets 28, 28’ extends axially along the central axis 18 and each magnet in the array is separated from an adjacent magnet by a magnetic material spacer 29, preferably non-magnetised and which may be iron or ferrite, which serves to turn the magnetic fields of the opposed North and South poles of adjacent magnets so that these magnetic fields bend radially away from the axis 18. In this way, the magnet pack 22 holds a linear array of alternating magnets configured to produce a sinusoidal-like magnet field pattern 50 along the central axis, as illustrated schematically in Figure 5. In Figure 5, this is shown as a pure sinusoidal pattern for the purposes of explaining principles of operation of the linear magnet motor 12, however in general the pattern may deviate from a perfect sinusoid.

[0069] The housing 10 is elongate along the axis between a opposite first and second end 55, 56 of the housing. The lid 7 is at the first end 55 of the housing and the second end of the housing is provided by an annular wall 77 for mounting the housing to the cylinder block 3.

[0070] The armature body 20 comprises a main portion 30 that is elongate along the axis 18 between opposite first and second ends 31 , 32, the first end 31 being within the housing and the second end 32 projecting out from an end aperture 33 in the annular wall 77 at the second end 56 of the housing. The main portion 30 comprises a substantially cylindrical outer surface 34 that has a clearance gap 37 with the bore 11 and, as shown in Figure 3A and 3B, a clearance gap 37’ with the end aperture 33, such that the main portion 30 may move in opposite first and second axial directions 41 , 42 under the control of the controller 16. To maximise the magnetic interaction between the magnetic fields generated by the motor windings and the magnet pack 22, the clearance gap 37 with the bore 11 should be as close as possible. Preferably, this gap should be between about 0.25 mm and 1 mm. The clearance gap 37 has to be sufficient to prevent contact between the stator and the armature between minimum and maximum operating temperatures of the components held within the housing 10. This and other clearance gaps should also be sufficient to allow air passage to prevent positive / negative air resistance within the empty spaces within the housing 10.

[0071] Optionally, the valve stem 44 may be mounted to thermally insulating material 57 held within the main portion 30 of the armature body 20. This can help reduce heat transmission from the valve head 46 magnet pack 22.

[0072] The main portion provides a housing 21 for the magnet pack 22. The magnet pack housing 21 is of non-magnetic material and has a tubular outer sleeve 39 of nonmagnetic material and having a substantially cylindrical outer surface 36 inside of which is a coaxial cylindrical recess 35 in which the magnets 28, 28’ and spacers 29 of the magnet pack 20 are retained.

[0073] The recess 35 is closed at the first end 31 of the main portion 30 of the armature body 20 by a plug of magnetic material, preferably iron or ferrite, which is preferably nonmagnetised, but which may be a permanent magnet, and which provides a solenoid armature 60 of the solenoid actuator 14. The solenoid armature has opposite first and second sides 61 , 62 that extend in planes perpendicular to the axis 18 and that face, respectively, towards and away from a solenoid winding 70 of the solenoid actuator 14. The first side 61 of the solenoid armature 60 is a circular disc and the second side 62 of the solenoid armature 60 is an annular flange that surrounds a cylindrical walled stem portion 63 of the solenoid armature that is secured inside the cylindrical recess 35 of the magnet pack housing 21 .

[0074] The magnet pack 22 has opposite first and second ends 13, 15, with the magnet pack first end 13 being nearest the first end 31 of the main body, and the magnet pack second end 15 being nearest the second end 32 of the main body. The solenoid armature 60 is spaced apart from the first end 13 of the magnet pack 22 by an end spacer 38. This end spacer 38 is omitted in the view of the partially cut away armature body of Figure 1 , to better illustrate the cylindrical shape of the recess 35. The end spacer 38 physically separates the solenoid armature 60 from the first end 13 of the magnet pack 22 and is also non-magnetic. Both these features help to minimise magnetic interaction between the solenoid armature 60 and the magnet pack 22. The end spacer 38 has a stepped cylindrical form such that this engages both with the cylindrical shape of the recess 35 and the shape of the cylindrical walled stem portion 63 of the solenoid armature 60 where this is secured inside the cylindrical recess 35.

[0075] The main portion housing 21 supports a poppet valve 40, which extends axially away from the second end 32 of the main portion 30 of the armature body 20. The poppet valve 40 comprises a substantially cylindrical valve stem 44 that is joined inside an axially extending bore 43 within the second end 32 of the main portion 30. The valve stem 44 is therefore connected to the main portion 30 and extends axially away from the main portion to a valve head 46.

[0076] Movement of the valve stem and valve head along the axis 18 is directly driven by the corresponding movement of the main portion 30 of the armature body 20. The armature body 20 therefore includes the poppet valve 40.

[0077] When the main portion 30 of the of the armature body 20 moves in the second direction 42, the valve head is moved to engage with a valve seat 48, which is fixed to the cylinder head 3, as shown in Figure 3A. This moves the valve 2, 4 to the closed position (upwards, as drawn). When the main portion 30 of the of the armature body 20 moves in the first direction 41 , the valve head 46 is raised relative to the valve seat 48, as shown in Figure 3B. This moves the valve 2, 4 to the open position (downwards, as drawn).

[0078] The valve assembly 1 also comprises at least one armature bearing configured for sliding motion of the armature body 20 relative to the housing 10 in the opposite axial directions 41 , 42. In this example, there is one such bearing 45, which is external to housing 10, being provided by a sleeve 47 mounted in a bore 49 of the cylinder head 3. Such a sleeve is often referred to as a valve guide.

[0079] Although not illustrated, optionally, an additional coaxial bearing may be provided within the housing, or there may be a single bearing that is provided within the housing, with the valve stem then extending through a clear bore in the cylinder head 3. In general, each such bearing may be provided with oil lubrication (not illustrated), which may also provide cooling for the linear electric motor 12 and solenoid motor 14.

[0080] The valve assembly 1 also comprises a spring mechanism, in this example, a coil spring 51 , that acts between the armature body 20 and the housing 10. The spring 51 is configured to exert a force on the armature body and hence on the poppet valve along the central axis in the second direction 42. As the spring mechanism biases the armature body and the along the central axis in the second direction, the spring mechanism also acts to bias the valve head towards a closed position.

[0081] In this example, opposite first and second ends 52, 53 of the coil spring bear upon, respectively, the second side 62 of the solenoid armature 60 and the first end 17 of the linear motor winding pack 24. In this example, the magnetic material ring 23’ at the first end 17 of the linear motor winding pack 24 has an annular recess 54 in which the second end 53 of the spring 51 is seated. The second side 62 of the solenoid armature 60 therefore serves as an abutment for the first end 52 of the spring.

[0082] The solenoid winding 70 is fixed relative to the housing (i.e. either directly fixed or indirectly fixed to the housing) and is coaxial with the central axis 18. In the first embodiment 1 , the solenoid winding 70 is part of a solenoid winding pack 64 that comprises also a solenoid bobbin 66 of a magnetic material, preferably nonmagnetised, such as iron or ferrite. In this embodiment, the solenoid bobbin has a cylindrical core 65 that makes a close fit within a bore 58 defined by the solenoid winding 70, and also with a cylindrical outer wall 68 an inside surface of which that makes a close fit with an outer cylindrical surface 59 defined by the winding and an outside surface of which makes a close sliding fit with a cylindrical inner surface 9 of the housing 10. The solenoid core 65 is joined to the solenoid bobbin outer wall 68 by a disc-shaped solenoid end plate 69 that also extends over the solenoid winding 70.

[0083] A bore 71 is provided through the solenoid bobbin outer wall 68 for routing wires (not illustrated) between the bobbin winding 70 and the controller 16.

[0084] The solenoid bobbin 66 and the winding pack bobbin 26 are spaced apart by a cylindrical spacing sleeve 72 that has the same outer diameter as the solenoid winding pack 64 and the linear motor winding pack 24 and is bonded to both the solenoid bobbin and 66 and the winding bobbin 26.

[0085] During final assembly of the engine valve assembly 1 , an inner rim 73 of the housing end cap 7 is pressed against the bobbin outer wall 68 as the end cap is closed and joined to the rest of the housing 10. The housing is preferably a moulded plastic material, for example glass reinforced plastic such as polypropylene, for example using an adhesive or by ultrasonic welding.

[0086] Through the cylindrical spacing sleeve 72, the pressure imparted by the end cap inner rim 73 is transmitted to the first end 17 of the linear motor winding pack 24, which causes the second end 19 of the winding pack to bear against the annular end wall 77 of the housing 10 around the end aperture 33 in the housing. This pressure secures the fixed components held within the housing 10 against movement in an axial direction.

[0087] Prior to final assembly, the annular end wall 77 of the housing 10 is fastened into a bore 98 in the cylinder head, this bore 98 has a base 97 in which the bore 49 for the bearing 45 is provided.

[0088] Figures 4A, 4B and 4C show three variations of a solenoid actuator 14A, 14B, 14C, each having a different type of solenoid winding pack 64A, 64B, 64C with different forms of solenoid bobbin 66A, 66B 66C, solenoid winding 70A, 70B, 70C and solenoid armature 60A, 60B, 60C.

[0089] Instead of a cylindrical core 65, each solenoid winding pack 64A, 64B, 64C has a clear bore 74A, 74B, 74D, in each case lined with a cylindrical wall of magnetic material 65A, 65B, 65C, preferably non-magnetised and of iron or ferrite. Each solenoid armature 60A, 60B, 60C therefore has a central rod or pole 75A, 75B, 75C, which is preferably non-magnetised, but which may be magnetised, and which is preferably cylindrical in form, that extends in the second direction 42 from a top side 61 A, 61 B, 61 C of the solenoid armature and that moves axially within the corresponding bore during the operation of the electromagnetically actuated engine valve assembly.

[0090] Figures 4B and 4C show variations of the solenoid bobbin 66B, 66C, which are open radially outwards, so that the solenoid windings 70B, 70C can be wound directly onto the bobbin, rather than being wound separately and inserted into an annular cavity 76, 76A as indicated in Figures 3B and 4A.

[0091] The use of the pole 75A, 75B, 75C can increase the magnetic attraction imparted on the solenoid armature by the solenoid pack. This can allow a reduction in the number of turns in the solenoid winding, or a reduction in the required drive current (thereby also reducing ohmic heating), or a combination of these two.

[0092] If the magnetic material of the solenoid armature 60, 60A-C is not magnetised, the solenoid armature will experience an attractive force 83 in the second direction 42, i.e. towards the solenoid winding pack 64, 64A-C, regardless of the polarity of the magnetic field produced by a drive current through the windings. Although it would be possible to replace the non-magnetised material of the solenoid armature with a permanent magnet in order to further increase this force 83 using one direction for the drive current, it is preferred that the solenoid armature is non-magnetised. This is not just to minimise material cost. As illustrated schematically in Figure 5, the linear motor magnet pack 22 generates an alternating magnetic field pattern 50 that is preferably approximately sinusoidal. If the solenoid armature is a permanent magnet, this will potentially affect the magnetic field pattern 50 at the first end 13 of the magnet pack nearest the solenoid actuator, regardless of whether or not the solenoid windings are energised. This will require a corresponding need to compensate for this in drive current provided to the linear motor windings 25 in order to produce a desired force 81 on the magnet pack 22 in the first direction 41 and or a desired force 82 on the magnet pack in the second direction 42.

[0093] When moving the valve to the closed position, optionally, the linear electric motor 12 may be driven to assist the solenoid, in which case this will add a force 82’ in the second direction. Turning now to Figure 5, this shows schematically, in the case of the first embodiment 1 , the relationship between the magnet field pattern 50 of the magnet pack 22 and the centre locations the four windings 25, which are labelled Pi, P2, P3 and P4

[0094] Figure 5 shows the sinusoidal-like magnet field pattern 50 of the first embodiment 1 of the magnet pack 22 in relation to the position of the linear motor winding pack 24. This is for a particular axial position of the armature body 20 in which the valve head 46 would be close to, or at, the closed position of Figure 3B. The arrow with an extent labelled D indicates the length of travel of the armature body 20 along the axis 18 between the open position of Figure 3A and the closed position of Figure 3B.

[0095] The North and South maxima of the magnet field pattern 50 coincide with centre locations of each spacer 29 in the magnet pack 22. In practice, the exact shape of this curve will depend on many factors, including the radial distance from the axis, and the relative axial lengths of the magnets 28 and spacers 29, however, the variation in the field will be approximately sinusoidal and will repeat in accordance with the magnet polarity. There may also some deviation from a perfectly repeating pattern beyond the first and second ends 13, 15 of the magnet pack 22, where there may be no magnetic material spacer, but for the sake of simplicity the sinusoidal pattern is shown in Figure 5 as extending regularly beyond the ends 13, 15 of the magnet pack 22. These approximations do not change the principles of the invention described below.

[0096] Figure 5 also shows how the centre locations of the four windings 25 of the linear motor winding pack 24, are positioned relative to the sinusoidal-like magnet field pattern 50. In this example, the windings will be individually driven in four phases, and so these four centre locations are respectively labelled with Pi, P2, P3 and P4, this representing the phase for that winding.

[0097] As can be seen, winding centre location for the first phase Pi is at a position of 3TT / 4 in terms of radians, and the winding centre location for the second phase P2 is at a position of 3TT / 2, and so on for the third and fourth phases P3 and P4. This regular separation along the direction of the central axis 18 is referred to herein as a “winding phase distance” along the central axis and is represented in Figure 5 by an arrow labelled with Pw. Using radians as the horizontal scale, as drawn:

[0098] (1 ) PW = 3TT / 4

[0099] Including the winding pack ends, there are four phases. Therefore, in terms of the horizontal scale, the length of winding pack Lw can be defined to be:

[0100] (2) Lw=4Pw=3TT

[0101] The actual length may be slightly longer than this owing to there being one magnetic material spacer 23, 23’ at each end. The repeating period of the magnet field pattern 50 is PM = 2 T and so:

[0102] (3) n = PM / 2

[0103] Substituting (3) into (2):

[0104] (4) Lw = 4Pw = 3PM / 2

[0105] Therefore, the length L of the winding pack, in this example, is three times one-half of the magnetic period distance PM.

[0106] As can be seen from Figure 5, if there were a fifth winding, then this would correspond to a phase distance 3TT + (3TT / 4) which will experience the same magnetic field strength from the magnet pack as for the first winding, but with the opposite polarity. The pattern repeats, and so if the number of permanent magnets and winders were doubled, then the four additional windings would have the same phases Pi, P2, P3 and P4 but with the opposite polarity. These four additional windings could therefore be driven by the same circuity but with the windings connected in the opposite direction in order to reverse the current flow through the windings.

[0107] It should be noted that each of the windings 25 will, in general, be powered with a varying current as the magnet pack moves axially. Because of the regular spacing described above. For example, if it were desired to move the armature body 20 at a steady speed in one direction, then a four-phase sinewave sequence, i.e. with currents 90° out of phase with each other on in the current phases, would be applied to the windings 25.

[0108] Figures 6, 7 and 8 are views similar to Figures 1 , 3A and 3B showing part of an internal combustion engine cylinder head 103 having an electromagnetically actuated engine valve assembly 101 in a second preferred embodiment of the invention. In the second embodiment, features which are the same as those of the first embodiment 1 are indicated using the same reference numerals, and features which are similar to those of the first embodiment are indicated using reference numerals incremented by 100.

[0109] Each valve assembly 101 is electromagnetically actuated by an electromagnetic actuator system that comprises a tubular linear electric motor 112 and a solenoid actuator 114, both of which are controlled by a controller 116 which is illustrated in a simplified form as a plain circuit board. In this example, each valve assembly has its own outer housing 10, that houses the linear electric motor 112 and the solenoid actuator 114.

[0110] The second embodiment differs from the first embodiment in several ways. The linear electric motor 112 has six motor windings 125 instead of four and the magnet pack 122 has a series of six magnets 128, 128’ instead of five. In the solenoid motor 114, the solenoid armature 160 has magnetic material, preferably non-magnetised, although this may be magnetised, and which may be of iron or ferrite, in the form of a cylindrical body connected within a first end 131 of the armature body, rather than a plate, which moves axially within a bore 74 defined by a solenoid winding pack 164.

[0111] As in the first embodiment, the main portion 130 provides a housing 121 for the magnet pack 122. The magnet pack housing 121 is of non-magnetic material and has a tubular outer sleeve 139 of non-magnetic material with a substantially cylindrical outer surface 136 inside of which is a coaxial cylindrical recess 135 in which the magnets 128, 128’ and spacers 129 of the magnet pack 122 are retained. The magnet pack 122 has opposite first and second ends 113, 115, with the magnet pack first end 113 being nearest the first end 131 of the main body, and the magnet pack second end 115 being nearest a second end 132 of the main body. The solenoid armature 160 is spaced apart from the first end 113 of the magnet pack 122 by an end spacer 138 in the form of a cylindrical sleeve 138 that is of non-magnetic material held coaxially within the tubular outer sleeve 139.

[0112] The tubular outer sleeve 139 extends the full length of the main body 130, between the first and second end 131 , 132. The recess 135 is closed at the first end 131 of the main portion 130 of the armature body 120 by a cylindrical plug of magnetic material, preferably non-magnetised, although this may be magnetised, and is preferably of iron or ferrite. The plug of magnetic material is fully within the sleeve and provides a solenoid armature 160 of the solenoid actuator 114. The solenoid armature has opposite first and second sides 161 , 162 that extend in planes perpendicular to the axis 18. The first side 161 is flush with the first end 131 of the main portion 130 of the armature body and the second end 162 faces towards a first end 131 of the magnet pack 122 and being spaced apart from the magnet pack by the cylindrical sleeve 138.

[0113] Another difference with the first embodiment is that the first end 52 of the coil spring 51 bears upon an abutment 91 separate from the solenoid armature 160, that extends radially outwards from the main portion 130 of the of the armature body 120. Preferably, the abutment is a lower side 91 of a self-locking retaining ring 90 on the cylindrical outer surface 136 of the outer sleeve 139. Optionally, this may be located in a groove 92 in the cylindrical outer surface 136 of the outer sleeve 139. Preferably both the retaining ring 90 and sleeve 139 are of a non-magnetic material, for example stainless steel.

[0114] As in the first embodiment, the second end 53 of the coil spring 51 is seated in annular recess 54 in the magnetic material ring 23’ at the first end 117 of the linear motor winding pack 124.

[0115] The rings 23, 23’, are preferably connected at a common inner radius by a magnetic material cylinder portion 127, similar to the cylinder portion 27 described above, but with a different axial length. The rings 23, 23’ and cylinder portion 127 may then provide a winding pack bobbin 126 for each motor winding 125. In this example, the rings 23, 23’ and cylinder portion 127 are of one-piece construction, i.e. a unitary body without any seams or joins, and so provide a unitary multi-flanged winding pack bobbin 126 for all six of the windings 125.

[0116] The solenoid winding pack 164 includes a solenoid winding 170 surrounded by a solenoid casing 166. The solenoid casing may be either of a magnet material, preferably non-magnetised, or a non-magnetic material. In this embodiment, the solenoid casing 166 is annular in shape with a cylindrical radially inner wall 75 defining a bore 74 for receiving the tubular outer sleeve 139 of the magnet pack housing 121 and a radially outer cylindrical wall 78 with an outer surface 168 that makes a close fit with the cylindrical inner surface 9 of the housing 10.

[0117] The final assembly of the engine valve assembly 101 is similar to that of the first embodiment. The inner rim 73 of the housing end cap 7 is pressed against the solenoid casing 166 as the end cap is closed and joined to the rest of the housing 10. The pressure or force imparted by the end cap inner rim 73 is transmitted through the cylindrical spacing sleeve 72 to the first end 117 of the linear motor winding pack 124, which causes the second end 119 of the winding pack to bear against the annular end wall 77 of the housing 10 around the end aperture 33 in the housing. This pressure secures the fixed components held within the housing 10 against movement in an axial direction.

[0118] As can be seen by comparing the first and second embodiments 1 , 101 , the use in the second embodiment of the solenoid armature 160 that extends into the bore 74 of the solenoid winding pack 164 allows an increase in the separation of the solenoid armature 160 and the magnet pack 122. This helps to further minimise magnetic interaction between the solenoid armature 160 and the magnet pack 122.

[0119] Another advantage of this arrangement is that the maximum attraction between the solenoid armature 160 and the solenoid winding 170 becomes relatively insensitive to the axial position of the armature body 120 when the valve head 46 is engaged with the valve seat 48. As is known, the interface between the valve head and valve seat can wear over time with use, and this causes the position of the valve stem 44 to rise. In the first embodiment, the initial gap between the upper surface 61 of the armature body 60 and a lower surface 67 of the solenoid winding pack 64 has to be sufficient to allow for some wear in the inlet or outlet valve 2, 4 over the expected lifetime of the engine valve assembly 1 so that the armature body does not start to hit the lower surface 67 of the solenoid pack. At the same time, there is a desire to make the initial gap as small as possible, as this maximises the motive force of the solenoid motor 14. The second embodiment 101 avoids this inconvenience because the maximum motive force will occur when the length of solenoid armature 160 is approximately centred inside the solenoid bore 74. If needed, therefore, the axial length of the solenoid armature can be shortened, or a greater gap 96 provided between the solenoid winding pack 164 and the end cap 9, to accommodate the expected wear of the inlet or outlet valve 2, 4 over the lifetime of the engine valve assembly.

[0120] Turning now to Figure 9, this shows schematically, in the case of the second embodiment 101 , the relationship between a magnet field pattern 150 of the magnet pack 122 and the centre locations the six windings 125, which are in three phases labelled Pi, P2 and P3. In this example, the number of motor windings 125 is double the number of phases.

[0121] As before, the sinusoidal-like magnet field pattern 150 in shown relation to the position of the linear motor winding pack 124, for a particular axial position of the armature body 120 in which the valve head 46 would be close to, or at, the closed position of Figure 8. The arrow with an extent labelled D indicates the length of travel of the armature body 120 along the axis 18 between the open position of Figure 7 and the closed position of Figure 8.

[0122] The North and South maxima of the magnet field pattern 150 coincide with centre locations of each spacer 129 in the magnet pack 122. As explained above, there may also some deviation from a perfectly repeating pattern beyond the first and second ends 113, 115 of the magnet pack 122. Figure 9 also shows how the centre locations of the six windings 125 of the linear motor winding pack 124, are positioned relative to the sinusoidal-like magnet field pattern 150. In this example, the magnets will be driven as pairs in three phases, and so these six centre locations are respectively labelled with Pi, P2, and P3, this representing the phase for each winding.

[0123] As can be seen, winding centre location for the first phase Pi is at a position of 2TT / 3 in terms of radians. The winding centre location for the second phase P2 is at a position of 4TT / 3. The winding centre location for the third phase P3 is at a position of 2 T , which is of course equivalent to the origin of the plot, and so the pattern repeats for the next three phases, which are therefore the same as Pi - P3. This regular separation along the direction of the central axis 18 is referred to herein as a “winding phase distance” along the central axis and is represented in Figure 9 by an arrow labelled with Pw. Using radians as the horizontal scale, as drawn:

[0124] (5) Pw = 2TT / 3

[0125] Including the winding pack ends, there are three phases, repeated once, for a total of six phases. Therefore, in terms of the horizontal scale, the length of winding pack Lw can be defined to be:

[0126] (6) Lw=6Pw=TT

[0127] The actual length may be slightly longer than this owing to there being one magnetic material spacer 23, 23’ at each end. The repeating period of the magnet field pattern 150 is PM = 2 T and so:

[0128] (7) n = PM / 2

[0129] Substituting (7) into (6) :

[0130] (8) Lw - 6Pw - 2PM Therefore, the length L of the winding pack, in this example, is twice the magnetic period distance PM , which is four times one-half of the magnetic period distance PM.

[0131] Figures 10A and 10B are schematic diagrams that respective show for the first and second embodiments 1 , 101 how each controller 16, 116 is connected to the motor windings 25, 125 and the solenoid winding 70, 170, showing how the windings are driven in separate phases.

[0132] Figures 10A and 10B are schematic diagrams that respectively show for the first and second embodiments 1 , 101 how each controller 16, 116 has outputs is connected to the motor windings 25, 125 and the solenoid winding 70, 170, showing how the windings are driven in separate phases. In Figure 10A the controller 16 has outputs that provide drive current to the linear motor windings 25 in four separate phases and in Figure 10B the controller 16 provides drive current to the linear motor windings 25 in three separate phases, each phase driving a pair of windings 125.

[0133] In addition, the controller 16, 116 has an output, labelled Ps, that provides drive current to the solenoid winding 70, 170.

[0134] Optionally the controller 16, 116 has an input, labelled S, that receives a signal from a linear position sensor 80, 180. The sensor 80, 180 is preferably within the housing 10, and is configured to provide a measure to the controller 16, 1 16 of the position of the actuator body 30, 130 along the central axis, and the controller is configured to use this measure in closed loop operation of the linear electric motor 12, 112.

[0135] In this example, the sensor 80, 180 is an optical sensor with a linear array of LED emitters and detectors (not illustrated) that detects a reflection from either the solenoid armature 60 or the self-locking retaining ring 90. Other types of sensor, such as Hall effect sensors, or capacitive, inductive, laser or ultrasonic sensors may alternatively be used.

[0136] In general, the controller 16, 116 receives a data signal from an engine control unit (ECU) 85 and then independently controls valve timing and position. The data signals may be conveyed via a CANBUS 86 or other type of communication network. The engine control unit continuously monitors engine data including crank position, temperatures, air flow, emissions, load, speed, demand and may also determine the optimal valve timing and opening characteristics. The engine control unit therefore will, in general also have control of other engine functions such as electrical fuel injection in a valve intake system to allow the engine control unit to optimise timing, fuel mixture, burn control, power output and therefore overall reduction in emissions and increase in engine efficiency.

[0137] As an alternative to the main engine control unit directly determining the optimal valve timing and opening characteristics, this function may be delegated to each controller 16, 116. The processing may then be distributed, thereby reducing the demands placed on the engine control unit. The controllers may therefore be pre-programmed with multiple operating positions (20 for example). Therefore, the engine control unit only has to send a single data instruction to the controller 16, 116 to open to a predetermined position. The controller then does the rest. Instead of simply moving from one position to another, the controller 16, 116 can be programmed to operate the valves 2, 4 over a chosen curve characteristic, if required by the engine control unit.

[0138] Figures 11 , 12 and 13 are views similar to Figures 6, 7 and 8 showing part of an internal combustion engine cylinder head 203 having an electromagnetically actuated engine valve assembly 201 in a third preferred embodiment of the invention. In the third embodiment, features which are the same as those of the first or second embodiments 1 , 101 are indicated using the same reference numerals, and features which are similar to those of the second embodiment 101 are indicated using reference numerals incremented by 100.

[0139] Each valve assembly 201 is electromagnetically actuated by an electromagnetic actuator system that comprises a linear electric motor 212 and the same solenoid actuator 114 as the first embodiment, both of which are controlled by a controller 216 which is illustrated in a simplified form as a plain circuit board. In this example, each valve assembly has its own outer housing 10, which is the same as the previous embodiments, that houses the linear electric motor 112 and the solenoid actuator 114. The third embodiment differs from the second embodiment mainly in that the linear electric motor 212 has three motor windings 225 instead of six. The magnet pack 122 and the solenoid motor 114 are, however, the same; these components will, therefore, not be further described.

[0140] As in the first and second embodiments, the coil spring 51 bears against a first end 217 of the linear motor winding pack 224. The rings 23, 23’, are preferably connected at a common inner radius by a magnetic material cylinder portion 227, similar to those 27, 127 described above, to provide a winding pack bobbin 226 for each motor winding 225. In this example, the rings 23, 23’ and cylinder portion 227 are of one-piece construction, extending between opposite first and second ends 217, 219 of the winding pack 224.

[0141] The final assembly of the engine valve assembly 201 is the same as for that of the second embodiment 101 , and so will not be explained again.

[0142] Turning now to Figure 14, this shows schematically, in the case of the third embodiment 201 , the relationship between a magnet field pattern 250 of the magnet pack 122 and the centre locations the three windings 225, which are in three phases labelled Pi, P2 and P3.

[0143] As before, the sinusoidal-like magnet field pattern 250 in shown relation to the position of the linear motor winding pack 224, for a particular axial position of the armature body 120 in which the valve head 46 would be close to, or at, the closed position of Figure 8. The arrow with an extent labelled D indicates the length of travel of the armature body 120 along the axis 18 between the open position of Figure 12 and the closed position of Figure 13.

[0144] The North and South maxima of the magnet field pattern 250 coincide with centre locations of each spacer 129 in the magnet pack 122. As explained above, there may also some deviation from a perfectly repeating pattern beyond the first and second ends 113, 115 of the magnet pack 122. Figure 14 also shows how the centre locations of the three windings 225 of the linear motor winding pack 224, are positioned relative to the sinusoidal-like magnet field pattern 250. In this example, the magnets will be individually driven in three phases, and so these three centre locations are respectively labelled with Pi, P2, and P3, this representing the phase for each winding.

[0145] As can be seen, winding centre location for the first phase Pi is at a position of TT in terms of radians. The winding centre location for the second phase P2 is at a position of 7TT / 3. The winding centre location for the third phase P3 is at a position of 11 TT / 3 . If there were a fourth winding this would be at 5TT and so the pattern would repeat if there were more than three windings. Using radians as the horizontal scale, as drawn, the winding phase distance is:

[0146] (9) Pw = 4TT / 3

[0147] Since there are three phases, in terms of the horizontal scale, the length of winding pack Lw can be defined to be:

[0148] (10) Lw - 3Pw - 4TT

[0149] The actual length may be slightly longer than this owing to there being one magnetic material spacer 23, 23’ at each end. The repeating period of the magnet field pattern 250 is PM = 27T and so:

[0150] (11 ) n = PM / 2

[0151] Substituting (11 ) into (10) :

[0152] (12) Lw - 3Pw - 2PM

[0153] Therefore, the length L of the winding pack, in this example, is twice the magnetic period distance PM , which is four times one-half of the magnetic period distance PM. Figure 15 shows how the motor windings 225 are connected to the controller 216 in three phases Pi, P2, and P3. In addition, the controller 216 has an output, labelled Ps, that provides drive current to the solenoid winding 170, and an optional input, labelled S, that receives a signal from a linear position sensor 180, as described above. The controller 216 is configured to energise each phase separately from the other phases, as described above.

[0154] The principles of operation of the linear motors 12, 112, 212 in three examples 1 , 101 , 201 described above, can be generalised as follows. In each case, there are at least three phases. From equations (4), (8) and (12), it can be seen that the product of winding phase distance Pw along the central axis and the number of phases N is always equal to an integer multiple M of one-half the magnetic period distance PM / 2:

[0155] (13) N PW= M PM / 2

[0156] In terms of radians PM / 2 = T .

[0157] In the first embodiment equation (4), 4Pw = 3PM / 2 and so N = 4 and M = 3.

[0158] In the second embodiment equation (8), 6Pw = 4PM / 2 and so N = 6 and M = 3.

[0159] In the third embodiment equation (12), 3Pw = 4PM / 2 and so N = 3 and M = 4.

[0160] In each case, the phases are spaced evenly apart in terms of the static magnetic field pattern 250. This regular separation in each embodiment ensures that the motor windings 25, 125, 225 can be driven to provide an even response along the full extent of the distance D to be travelled by the armature body 20, 120. In particular, there is never a point when more than one phase of the windings coincides with a minimum in the permanent magnetisation, i.e. where the magnetic field pattern 50, 150, 250 is crossing zero.

[0161] From the above it can be seen that in all embodiments, the sinusoidal-like magnet field pattern repeats with a magnetic period distance along the central axis. The motor windings are connected to the controller in phases, and the controller is configured to energise each phase separately from the other phases. The phases are each positioned regularly apart from an adjacent phase by a corresponding winding phase distance along the central axis. There are at least three such phases and the product of the winding phase distance along the central axis and the number of phases is equal to an integer multiple of one-half the magnetic period distance.

[0162] Figure 16 shows parts of two electromagnetically actuated engine valve assemblies in a fourth preferred embodiment of the invention, and Figure 17 shows the complete assembly 301. Features in Figure 16 and 17 which are the same as previous embodiments are indicated using the same reference numerals, and features which are similar are indicated using reference numerals increments by 100.

[0163] The valve assemblies are each mounted to a corresponding bore 198 in a cylinder head 303. Each bore 198 leads to either an inlet valve 2 or an outlet valve 4 for an engine cylinder (not shown). Not shown are two of the valve assemblies that would be mounted in two additional bores 198 also leading to an inlet valve 2 and an outlet valve 4 of the same cylinder.

[0164] Each valve assembly comprises a housing that is elongate between opposite first and second ends 155, 156 of the housing. Each bore 198 receives an annular end wall 177 at the second end 156 of the housing 110. The end wall 177 has an aperture 133 through which a second end 232 of a main portion 230 of an armature body 220 extends. The poppet valve 40, then extends axially away from this second end 232. A base 197 of the bore 198 in the cylinder head 303 has a bore 149 in which a bearing 145 for the poppet valve is provided. Prior to final assembly, the annular end wall 177 of the housing 110 is fastened into the bore 198 in the cylinder head 303.

[0165] Similar to the embodiments described above, the electromagnetically actuated engine valve assembly 301 has an armature body 220 that is driven to move in the opposite first and second directions 41 , 42, and over a distance D, along the axis 18 by the solenoid motor 112 and the electric linear motor 14. The fourth embodiment 301 has two main differences from the second embodiment. The first is that an abutment and spring mechanism are located towards a second end 232 of a main portion 230 of an armature body 220, rather than towards the first end 131 . Preferably, the abutment is provided by a side 191 of a self-locking retaining ring

[0166] 190 secured on a cylindrical outer surface 236 of an outer sleeve 239 that holds a magnet pack (not shown) and the solenoid armature 160. Preferably, the spring mechanism is a coil spring 151 . A first end 152 of the coil spring bears against the side

[0167] 191 of the retaining ring 190. A second end 153 of the coil spring bears against a base 197 of a cylindrical bore 198 in the cylinder head 303.

[0168] To make this possible, the main portion 230 of the armature body 220 extends sufficiently beyond the first end 155 of the housing 110 so that the self-locking retaining ring 190 does not come into contact with this first end 155 as the poppet valve 40 moves in the second direction 42.

[0169] In the previous embodiments, the spring mechanism was configured to act between the armature body 20, 120 and the housing 10. This is a direct action between the armature body 20, 120 and the housing 10.

[0170] In the fourth embodiment, the spring mechanism is configured to act between the armature body 220 and the cylinder head 303 to which the housing 110 is mounted. However, because the housing is mounted to the cylinder head, it can be seen that the spring mechanism acts indirectly (i.e. through the cylinder head 303) between the armature body 220 and the housing 110.

[0171] Another difference with the previous embodiments is that each housing 110 does not house a controller. Each housing 101 has a connector 105, which may be provided in a lid 107 at the first end 156 of the housing, for making input and output connections for power and data signals. After each housing has been mounted to the corresponding bore 198 in the cylinder head 303, and outer housing 210 is fitted to the cylinder head, covering over all the assemblies. Although not illustrated, the outer housing contains within a controller for controlling the operation of each valve 2, 4. The controller will be connected to each connector 105. An external connector 205 is then provided on the outer housing 210 for making connection to an engine control unit 85.

[0172] Figures 18A-18D illustrate the way in which the engine valve assemblies described above are preferably operated to control flow through inlet and outlet valves 2, 4 in an internal combustion engine, in which a cylinder piston 100 repeats a four-stroke cycle. In this example the engine valve assemblies 201 are the same as those described above in relation to Figures 11 to 13, with the exception that, instead of being mounted at angles to a cylinder axis 84, the engine valve assemblies 201 are mounted on a cylinder head 403 with their axes 18 parallel with the cylinder axis 84. This difference may affect details of the actual valve time timing but does not change the principles of the invention to be described below.

[0173] Figure 18A shows the piston 100 and engine valve assemblies 201 at the start of an intake stroke, in which the inlet valve 2 is opened by energising 82 the linear electric motor 212 to move the armature body 120 for the inlet 2 valve in the first direction (downwards, as drawn). At the same time, the outlet valve 4 is held closed by energising 83 the solenoid motor 114 to impart a force on the armature body 120 for the outlet valve 4 in the second direction 42 (upwards, as drawn). Meanwhile, the piston 100 moves fully down inside the cylinder. During this period, the linear electric motor may vary the amount of opening or the time period during which the inlet valve 2 is opened.

[0174] After the cylinder has been filled with an air fuel mixture, the piston begins to move up, as shown in Figure 18B, during a compression stroke. The inlet valve 2 is rapidly moved in the second direction 42 to the closed position by energising 83 the solenoid motor 114 for the inlet valve 2 to move the armature body 120 in the second direction 42. Optionally, the linear electric motor 212 for the outlet valve 4 may also be energised 81 so that both the solenoid motor 114 and the linear electric motor 212 cooperate in moving the armature body in the second direction 42.

[0175] At or near the top of the compression stoke, the compressed air fuel mixture will be ignited, using either spark ignition or compression ignition. The pressure inside the cylinder, including on the valve heads 46, as represented by arrows 99 in Figure 18C, is sufficient to seal both valve 2, 4 closed, and so there is no need to energise the solenoid motors 114 or the linear electric motors 212, to ensure that both valves 2, 4 remain closed.

[0176] The piston 100 then moves fully down and begins to return upwards in an exhaust stoke, as shown in Figure 18D. During this part of the engine cycle, the inlet valve 2 is held closed by energising 83 the solenoid motor 114 to impart a force in the second direction 42 to ensure that the inlet valve 2 remains closed. Meanwhile, the outlet valve 4 is held open by energising the linear electric motor 212 so that armature body is moved in the first direction 41 .

[0177] Although not illustrated, at some point towards the end of the exhaust stoke, it may be necessary to move the outlet valve 4 rapidly to the closed position to prevent the piston 100 from hitting the open exhaust valve, in which case, the solenoid motor 114 for the exhaust valve would be energised to move the armature body 120 in the second direction 42 and close the exhaust valve 4. Optionally, the linear electric motor 212 may also be energised so that both the solenoid motor 114 and the linear electric motor 212 cooperate in moving the armature body in the second direction 42.

[0178] The invention described herein provides a number of advantages over the prior art. In conventional engines, one or more relatively strong valve springs are utilised to hold the valve shut and so previous approaches have needed to overcome these forces using mechanical, electrical mechanical or electro-pneumatic cylinders to actuate the valves. In the present invention, the main purpose of the spring mechanism is to ensure that the valve is moved to and held in the closed under power-down conditions, thereby preventing contact and damage with the moving piston. During the compression and power strokes, the engine control unit would send a command to the controller 16, 116 to use the solenoid motor 14, 114 and optionally also the linear electric motor 12, 112, 212 to generate a relatively high retraction force, and hence achieve a relatively rapid closing time, thereby avoiding the need to provide a strong spring mechanism.

[0179] Electronic control of electrically actuator valves can provide a number of other benefits in an internal combustion engine. For example, in a four valve per cylinder arrangement, with two inlet and two outlet valves, there can be two separate exhaust manifolds connected to the two outlet ports 8 of each cylinder. Modern engines often use turbos to increase power and efficiency by utilising exhaust gases to power a turbine which drives a compressor turbine increasing inlet pressure and volume entering the cylinder. In an attempt to reduce turbo lag caused by the time it takes for the turbo to spin up to speed, it is common practice to run the turbo harder and use a dump valve to control inlet pressure, however, this is not linear and results in an overall waste of energy.

[0180] By controlling a pair of outlet valves 4 on an exhaust stroke, exhaust gasses and energy can be diverted fully to just one of the exhaust manifolds or be distributed proportionally between two exhaust manifolds, by adjusting the timing or valve opening of the two outlet valves 4. If one manifold were was connected to the turbo, the engine control unit could control the inlet pressure generated by the turbo by controlling the amount of exhaust gases being sent to the turbo in real time, therefore maintaining inlet pressure over a wide range of engine operating conditions.

[0181] Another example is to do with the initial heating of catalytic converters utilising exhaust gases. Ideally, the catalytic converter core needs to be heated quickly to around 375 to 400 degrees Celsius. For maximum efficiency, the quicker the catalytic converters core is heated the quicker unwanted emissions can be reduced. However, passing exhaust gasses through a turbo system will result in significant cooling, which results in a delay before the catalytic converter reaches operational temperature. To deal with this problem, engine manufactures have tended to fit a pre catalytic converter.

[0182] Therefore, if one of the two exhaust manifolds were to be directly connected to the catalytic converter, thereby bypassing the turbo, the catalytic converter could reach operating temperature quickly before the exhaust energy could then be distributed between turbo and catalytic convertor.

[0183] The electromagnetically actuated engine valve assembly may, of course, be used in engines having fewer or more than four inlet / outlet valves per cylinder, and may also be used in other types of engine, for example a two-stroke engine where induction is via an aperture and exhaust is via a mechanical valve.

[0184] The invention therefore provides a more convenient electromagnetically actuated engine valve assembly for opening and closing a cylinder valve of a reciprocating piston internal combustion engine, and also a method for operating such an engine valve assembly.

Claims

CLAIMS1 . An electromagnetically actuated engine valve assembly for opening and closing a cylinder valve of a reciprocating piston internal combustion engine, the valve assembly comprising: a housing, and within the housing a tubular linear electric motor with a central axis and, extending along the axis, an elongate armature body, the armature body comprising:- an elongate main portion, the main portion extending along the central axis between a first end and a second end of the main portion, and being configured to move in opposite first and second axial directions along said axis; and- a poppet valve, the poppet valve comprising a valve stem and a valve head, the valve stem being connected to the second end of the main portion of the armature body and extending away from the housing along the central axis towards the valve head; at least one armature bearing configured for sliding motion of the armature body relative to the housing in said opposite axial directions; a controller, the controller being configured to control the operation of the linear electric motor whereby the armature body moves in the first and second axial directions respectively to lift and lower the valve head with respect to a valve seat whereby said cylinder valve is, respectively, moved towards an open position and a closed position; and a spring mechanism, the spring mechanism being configured to exert a force on the armature body along the central axis in the second direction, wherein: the linear electric motor comprises a winding pack and a magnet pack, the winding pack being fixed relative to the housing and comprising a plurality of motor windings, the motor windings extending around the central axis and the winding pack defining a central bore, and the magnet pack being fixed relative to the main portion of the armature body and comprising an array of permanent magnets aligned in alternating and opposing axial directions within the bore, each magnet in the array being separated from an adjacent magnet by a magnetic material spacer and said array extending axially along the central axis of the armature body, whereby themagnet pack is configured to produce a sinusoidal-like magnet field pattern along the central axis; the controller is connected to the motor windings and is configured, when controlling the operation of the linear electric motor, to energise the motor windings; the valve assembly further comprises within the housing, a solenoid actuator, the solenoid actuator comprising a solenoid winding, and a solenoid armature, the solenoid winding being fixed relative to the housing and being coaxial with the central axis and the solenoid armature being fixed relative to the first end of the main portion of the armature body and comprising a magnetic material; and the controller is connected to the solenoid winding and is configured, when the poppet valve is to move in the second direction to close the cylinder valve, to energise the solenoid winding and thereby actuate the solenoid armature to move in the second direction and close the cylinder valve.

2. The valve assembly of Claim 1 , in which the controller is configured, when the poppet valve is to move in the second direction to close the cylinder valve, to energise the motor windings and thereby actuate the main portion of the armature body to move the armature body in the second direction and close the cylinder valve, whereby the linear motor and the solenoid motor cooperate to close the cylinder valve.

3. The valve assembly of Claim 1 or Claim 2, in which the force exerted by the spring mechanism on the armature body is at least enough to lift the armature body against gravity when the axis is oriented substantially vertically but is not more than five times the weight of the armature body.

4. The valve assembly of any one of the preceding claims, in which the spring mechanism is located between the winding pack and the solenoid winding.

5. The valve assembly of any one of the preceding claims, in which: the armature body comprises an outer sleeve; both the magnet pack and the magnetic material of the solenoid armature are secured to the sleeve; and the sleeve is of a non-magnetic material.

6. The valve assembly of Claim 5, when dependent from Claim 4, in which the spring mechanism comprises a coil spring, the coil spring being located between a radially outer surface of the sleeve and the housing.

7. The valve assembly of Claim 6, in which the armature body comprises a shoulder that extends radially outwards from the sleeve, and the coil spring is held in compression between the shoulder and the winding pack.

8. The valve assembly of any one of the preceding claims, in which the solenoid winding defines a solenoid bore extending around the central axis and the solenoid armature extends axially within the bore.

9. The valve assembly of Claim 8, when dependent from Claim 5, in which: the outer sleeve extends into the solenoid bore; and the magnetic material of the solenoid armature is secured to the sleeve within the solenoid bore.

10. The valve assembly of Claim 8, when dependent from Claim 7, in which: the outer sleeve extends into the solenoid bore; the magnetic material of the solenoid armature is secured to the sleeve within the solenoid bore; and the shoulder is provided by a flange affixed externally to the sleeve.

11. The valve assembly of any of Claims 1 to 7, in which the solenoid winding defines a solenoid bore extending around the central axis and the solenoid actuator comprises within the solenoid bore a fixed core of a magnetic material, the fixed core being axially opposed to the magnetic material of the solenoid armature.

12. The valve assembly of Claim 11 , in which the solenoid armature comprises a disc that extends radially away from the first end of the armature body.

13. The valve assembly of Claim 12, when in which the disc has opposite first andsecond radially extending faces, the first face being axially opposed to the solenoid winding.

14. The valve assembly of Claim 13, when dependent from Claim 7, in which the second face provides the shoulder against which the coil spring is held in compression.

15. The valve assembly of any one of the preceding claims, in which the second end of the armature body extends through an aperture in the housing said aperture providing said armature bearing.

16. The valve assembly of any one of the preceding claims, in which the sinusoidal-like magnet field pattern repeats with a magnetic period distance along the central axis; the motor windings are connected to the controller in phases, the controller being configured to energise each phase separately from the other phases and the phases each being positioned regularly apart from an adjacent phase by a corresponding winding phase distance along the central axis; and there are at least three such phases and the product of said winding phase distance along the central axis and the number of phases is equal to an integer multiple of one-half the magnetic period distance.

17. The valve assembly of Claim 16, in which the phases are duplicated, whereby the number of motor windings is double the number of phases.

18. The valve assembly of any one of the preceding claims, comprising additionally a linear position sensor, the sensor being configured to provide a measure to the controller of the position of the actuator body along the central axis, and the controller is configured to use said measure in closed loop operation of the linear electric motor.

19. The valve assembly of any one of the preceding claims, in which the spring mechanism acts between the armature body and the housing.

20. The valve assembly of any one of Claims 1 to 18, in which the housing isconfigured to be mounted to a cylinder head of an internal combustion engine, and the spring mechanism is configured to act between the armature body and said cylinder head.21 . The valve assembly of any one of the preceding claims, in which the magnetic material is non-magnetised.

22. The valve assembly of any one of Claims 1 to 20, in which the magnetic material comprises a permanent magnet.

23. A method of operating an electromagnetically actuated engine valve assembly for opening and closing a cylinder valve of a reciprocating piston internal combustion engine, the valve assembly being as claimed in any preceding claim, wherein the method comprises: turning the engine in a cycle of cylinder strokes in which the cylinder valve is repeatedly opened and closed by the valve assembly; when the cylinder valve is to be opened, using the controller to drive the motor windings to control the movement of the actuator body and hence the position of the poppet valve in both the first and second directions along the central axis; and when the cylinder valve is to be closed, using the controller to drive the solenoid winding to control the movement of the actuator body in the second direction until the cylinder valve is closed.

24. A method as claimed in Claim 23, in which the force exerted on the armature body in the second direction by the spring mechanism is sufficient to hold cylinder valve closed against gravity when the first direction is vertically downwards.

25. A method as claimed in Claim 23 or Claim 24, in which the method further comprises, when the cylinder valve is to be closed, using the controller to drive the motor windings to move the actuator body in the second direction, whereby the solenoid actuator and the linear electric motor cooperate when the cylinder valve is closed.

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