Magnetic reluctance actuator

Abstract

Magnetic reluctance actuator comprising a magnet, a ferromagnetic armature, and a ferromagnetic mover forming at least part of a magnetic circuit carrying a magnetic flux, wherein the magnetic flux generates a first magnetic force on the mover which acts in a first direction, wherein the magnetic circuit further comprises at least a variable air gap and an air gap actuator arranged to control the size of the variable air gap, wherein the magnetic reluctance of the magnetic circuit is increased or decreased by respectively increasing or decreasing the size of the air gap, thereby respectively decreasing and increasing the magnitude of the magnetic flux and the magnitude of the first magnetic force, wherein the actuator is arranged to adjust the position of the mover by adjusting the size of the variable air gap.

Description

[0001] MAGNETIC RELUCTANCE ACTUATOR

[0002] The present invention relates to a magnetic reluctance actuator.

[0003] Magnetic actuators are known that make use of a magnetic field to produce a magnetic force to move a part of the actuator, which part may be referred to as the mover. In known variants of such magnetic actuators, electromagnets, in particular coils, are employed to generate a magnetic field of controllable strength, in particular a magnetic field with a controllable magnetic flux magnitude, to produce a controllable magnetic force acting on the mover to move said mover, thereby providing the actuating function of the magnetic actuator. A permanent magnet may be included in the magnetic actuator to provide a constant magnetic force acting on the mover, which may augment the controllable magnetic force provided by one or more coils.

[0004] Such magnetic actuators are particularly useful in micro or nanoscale applications. In addition, such magnetic actuators are used in environments operating in a vacuum, as well as at very low temperatures. A particular drawback of magnetic actuators making use of electromagnetic coils is that a relatively large amount of heat is generated by said coils when a current is applied to generate a magnetic field. In addition, at very small scales, the construction of appropriately sized coils may be complicated.

[0005] It is an object of the present invention to provide a magnetic actuator that at least partially alleviates one or more of the aforementioned problems. This is at least partially achieved by a magnetic reluctance actuator comprising a magnet, a ferromagnetic armature, which is preferably at least partially fixed to the magnetic reluctance actuator, and a ferromagnetic mover forming at least part of a magnetic circuit carrying a magnetic flux, wherein the magnetic flux generates a first magnetic force on the mover which acts in a first direction, wherein the magnetic circuit further comprises at least a variable air gap and an air gap actuator arranged to, preferably mechanically, control the size of the variable air gap, wherein the magnetic reluctance of the magnetic circuit is increased or decreased by respectively increasing or decreasing the size of the air gap, thereby respectively decreasing and increasing the magnitude of the magnetic flux and the magnitude of the first magnetic force, wherein the actuator is arranged to adjust the position of the mover by adjusting the size of the variable air gap.

[0006] The magnetic force exerted on the mover is thus preferably provided by a permanent magnet, which does not require additional energy to energize in contrast to an electromagnet. To vary the force exerted on the mover, the reluctance of the magnetic circuit that carries the magnetic flux provided by the (permanent) magnet is varied by adjusting the air gap. This requires less energy than powering (a plurality of) electromagnets. However, benefits may also be obtained when using an electromagnet, or another non-permanent magnet, in combination with the magnetic reluctance actuator described herein.

[0007] The size of the air gap may relate to the overall (average) length of the air gap, as well as the (average) cross section of the air gap. The magnetic reluctance of an element is determined by the formula R = L / (A x u), wherein R is the reluctance of an element, L is the (average) length of the element in a direction parallel to the magnetic flux lines of the magnetic flux carried by the element, and A is the (average) cross sectional area of the element in a plane perpendicular to the magnetic flux lines carried. The air gap can thus be seen as an element in a magnetic circuit. The reluctance may be increased by increasing the size, i.e. a dimension, i.e. the length and / or area of the air gap. Increasing the length of the air gap may involve moving elements of the circuit between which the air gap extends further apart from each other, while adjusting the area of the air gap may involve adjusting the dimensions and / or the relative position of elements of the circuit between which the air gap extends. In other words, the geometry of the actuator is adapted to adjust the reluctance in the magnetic circuit.

[0008] Magnetic reluctance actuators as such are known, in combination with a magneto restrictive element comprising magneto restrictive material. By compressing said magneto restrictive material, for example constructed out of so-called ‘terfenol’, the magnetic reluctance of said magneto restrictive material is increased. As the magneto restrictive element comprises part of the magnetic circuit which carries a magnetic flux which exerts a magnetic force on a mover, said magnetic force may be decreased or increased by respectively compressing and decompressing / relieving the magneto restrictive element. In known embodiments, the magneto restrictive element is held between two other elements, such as plates. An air gap may also extend between said elements, which decreases in size, in particular in length, as the magneto restrictive material is compressed. However, the increased reluctance of the compressed magneto restrictive element more than offsets the decreased reluctance of the accompanying smaller air gap . In other words, the magnitude of the increased reluctance of the compressed magneto restrictive element is larger than the magnitude of the decreased reluctance of the narrowed air gap. Thus, in such actuators, a decrease of the size of the air gap in fact results in a decrease in the magnetic flux and thus the force exerted on the mover. Thus, these magnetic reluctance actuators function fundamentally different than the magnetic reluctance actuator described herein. In an embodiment, the ferromagnetic armature is monolithic (i.e., made in one piece, made integrally, et cetera). Accordingly, the construction of the actuator has a relatively small number of moving parts, which may reduce maintenance intervals and / or mitigate potential mechanical issues.

[0009] Preferably, the magnetic reluctance actuator further comprises a biasing means arranged to movably support the mover relative to the magnetic reluctance actuator and apply a first biasing force on the mover which acts in a direction with at least a component opposite the first magnetic force.

[0010] The resulting interaction between the first biasing force and the first magnetic force allows for a more accurate control of the displacement of the mover.

[0011] Preferably, the biasing means comprises a spring member arranged to at least partially support the mover and preferably provide the first biasing force.

[0012] A spring member beneficially comprises a positive spring coefficient, meaning the biasing force exerted by a spring member increased with displacement. This counteracts a possible negative stability of the first magnetic force. This negative stability may occur as a result of a deflection of the mover resulting from an increase in the (first) magnetic force moving the mover closer to a part of the armature, reducing the size of an air gap extending therebetween, decreasing the reluctance of said air gap. Thus, the magnetic flux further increases, increasing the magnetic force, and pulling the mover again closer to the other part of the armature.

[0013] Preferably, the air gap actuator comprises a linear actuator. As the air gap is preferably increased and decreased with a linear movement of an element forming of the magnetic circuit relative to another element forming part of the magnetic circuit, a linear actuator is particularly suitable. Alternatively, other actuators may be used, such as rotary, shape memory, and / or bending actuators, and / or motors such as servo motors and / or linear motors.

[0014] In an embodiment, the magnetic reluctance actuator does not comprise a piezo electric actuator. Alternatively, the magnetic reluctance actuator, in particular the aforementioned linear actuator thereof, may comprise a piezo electric actuator.

[0015] Preferably, the variable air gap extends between the armature and the mover. The size, such as average length or area, preferably length, may thus be adjusted by moving the armature relative to the mover. This can be achieved by for example moving the armature as a whole, preferably using the air gap actuator, or deforming the armature, preferably using the air gap actuator. Adjusting the size of the variable air gap by moving and / or deforming (part of) the armature allows for a relatively simple construction of the magnetic reluctance actuator.

[0016] Preferably, the armature comprises a fixed armature part, which is substantially fixed to the magnetic reluctance actuator, and at least one movable armature part. This allows for more functionality.

[0017] Preferably, the variable air gap extends between the fixed armature part and the movable armature part. The variable air gap may thus be adjusted in size, for example length, by moving the movable armature part relative to another part of the magnetic circuit, such as another part of the armature, for example a fixed armature part, and / or the mover. In an embodiment, the movable armature part is arranged between a face of the fixed armature and a face of the mover, wherein said faces extend at a nonparallel angle. A movement of the movable armature part to and from the fixed armature part with a certain distance then results in a movement of the movable armature part to and from the mover with a different distance. In another embodiment, said faces of the armature and mover may extend perpendicular. This allows a distance, i.e. air gap between the movable armature part and the mover to remain constant while the movable armature part moves to and from the armature face, decreasing and increasing a variable air gap therebetween (the mover assumed to remain stationary, which it would not in practice). The movable armature part may be monolithic with the fixed armature part, and be movable relative to the fixed armature part by the magnetic reluctance actuator.

[0018] Preferably, the movable armature part extends adjacent to the mover, such that an air gap extends between adjacent faces of the movable armature part and the mover, wherein the combined surface area of the adjacent faces of the fixed armature part and the movable armature part is different than the combined surface area of the adjacent faces of the movable armature part and the mover.

[0019] Thus, two air gaps are created, one of which comprises the variable air gap as described above. The other air gap may also be variable, for example as a result of an adjustment of the size of the ‘main’ variable air gap. The average cross-sectional areas of the two air gaps are thus preferably different. A movement of the movable armature part may then increase the length of one air gap and simultaneously decrease the length of the other air gap with the same amount. As the (average) areas of the two air gaps are different, the reluctance of one air gap will increase in magnitude more than the reluctance of the other air gap decreases, and vice versa. This allows for more tunability of the magnetic reluctance actuator.

[0020] Preferably, the fixed armature part extends between the movable armature part and the mover, the movable armature part and the mover thereby extending on substantially opposing sides of the armature. This provides for a relatively simple construction of the magnetic reluctance actuator. In addition, the movable armature part and the mover may thus not extend adjacently to each other. This allows the size of the variable air gap to be increased and decreased without significantly changing the reluctance of an air gap between the mover and movable armature part. After all, a sort of air gap will in most cases remain between the movable armature part and the mover, even when the fixed armature part extends between the movable armature part and the mover. However, as this air gap is (much) larger than the variable air gap between the fixed armature part and the movable armature part, a change in reluctance resulting from a change in the distance between the movable armature part and the mover does not have a significant effect, or at least a smaller effect than the associated change in size of the variable air gap.

[0021] Preferably, the variable air gap extends between the movable armature part and the mover. This means that the aforementioned negative stability properties of the magnetic force are increased, as a movement of the mover towards the movable armature part as a result of a decrease of the air gap (which caused an increase in the (first) magnetic force) will further increase the (first) magnetic force. In comparison, in embodiments wherein a change of the size of the variable air gap does not directly change the distance between the mover and the (movable) armature (part), this ‘negative’ stability is less severe. Having a larger or smaller degree of negative stability may be desirable depending on the application.

[0022] Preferably, the armature comprises at least a first and second magnetic circuit arranged to transmit magnetic flux lines originating from the permanent magnet through at least two loops, each passing through the mover, wherein the magnetic fluxes passing through the first and second circuit respectively generate the first magnetic force on the mover, as well as at least one second magnetic force on the mover. This thus provides a second parameter which may be adjusted to affect the position of the mover, compared to embodiments with a single magnetic circuit and / or a substantially single magnetic force acting on the mover. In addition, the first and second magnetic force may balance each other, and / or either magnetic force may provide at least part of the biasing force as described above. Preferably, the first and second magnetic circuits each respectively comprise at least a first and a second variable air gap as well as, preferably, at least a first and second air gap actuator to preferably respectively control at least the first and second air gap, wherein the first and second variable air gaps are preferably arranged to control the magnetic reluctance of respectively the first and second magnetic circuit. The two variable air gaps may thus be used to change the magnetic reluctance of the two magnetic circuits independently of each other. This increases the functionality of the magnetic reluctance actuator.

[0023] In an embodiment, the magnetic flux flows substantially in a flux plane, wherein the armature and / or the flux lines are substantially asymmetrical relative to the magnetic flux lines extending through the magnet. In particular in embodiments wherein the armature is shaped to carry the magnetic flux provided by the magnet through two or more magnetic circuits, thereby exerting magnetic forces on the mover in two directions, for example a first and a second direction associated with a first and second magnetic force, adjusting the asymmetrical shape of the armature may allow movement of the mover as a result of increases or decreases in the size(s) of air gap(s) in the two magnetic circuits to be tuned.

[0024] In an embodiment, the ferromagnetic armature may be asymmetric with reference to a central actuator axis. The central actuator axis may be through a permanent magnet. Magnetic flux lines may originate from the permanent magnet, that may transmit in opposite directions through the mover and / or transmit through faces of the armature that face the mover, also called the ‘poles’ (i.e., transmit through opposite poles of the ferromagnetic armature between which opposite poles the mover is located).

[0025] Alternatively, the ferromagnetic armature may be symmetric with reference to a central actuator axis through the permanent magnet from which the magnetic flux lines originate, which may thus transmit through opposite directions through the armature and mover, as well as through faces of the armature that face the mover, also called the ‘poles’. This provides for a more predictable movement of the mover as a result of changes in the size(s) of air gap(s) in the magnetic circuit(s).

[0026] Preferably, the armature comprises a first armature part and a second armature part, substantially separate from each other, wherein the mover extends between the first and second armature parts. Preferably, the magnetic reluctance actuator then comprises at least two movable armature parts. Preferably, the first fixed and movable armature parts and the second fixed and movable armature parts respectively form a first and second magnetic circuit, carrying a first and second magnetic flux which exert a first and second magnetic force on the mover. This embodiment may comprise a single magnet, of which the flux is conducted by the at least two magnetic circuits. However, preferably, separate magnets are arranged on or near the first and second fixed armature parts to provide the magnetic fluxes carries by the first and second magnetic circuits. Preferably, at least one permanent magnet is thus arranged on either side of the mover

[0027] Preferably, the first and second magnetic forces act respectively in the first direction and a second direction, wherein the first and second directions extend in directions with at least a component opposite each other. This allows the first and second magnetic forces to at least partially balance each other.

[0028] The present invention is further illustrated by the following Figures, which show preferred embodiments of the device according to the invention, and are not intended to limit the scope of the invention in any way, wherein:

[0029] Figures 1A, B show a schematic overview of an embodiment of a magnetic reluctance actuator;

[0030] Figures 2A, B show another schematic overview of an embodiment of a magnetic reluctance actuator;

[0031] Figures 3A, B show another schematic overview of an embodiment of a magnetic reluctance actuator;

[0032] Figure 4 shows another schematic overview of an embodiment of a magnetic reluctance actuator;

[0033] Figures 5A, B show another schematic overview of an embodiment of a magnetic reluctance actuator; and

[0034] Figures 6A, B show another schematic overview of an embodiment of a magnetic reluctance actuator.

[0035] Figures 1A, B show a schematic overview of an embodiment of a magnetic reluctance actuator 1. The reluctance actuator 1 comprises a mover 2, movably mounted on the reluctance actuator 1 by means of flexible members, preferably leaf spring members, 5. A fixed armature part 3 is fixedly mounted on the reluctance actuator 1, and is formed to conduct flux lines originating from a magnet M, in particular a permanent magnet M, in two loops Fl and F2. In this embodiment, the fixed armature part 3 is E shaped. The magnetic actuator 1 further comprises two movable armature parts 4a, b arranged on either side of the mover 2. The mover 2, fixed armature part 3 form, together with movable armature parts 4a, b respectively two magnetic circuits Fl and F2 which carry magnetic flux lines originating from the magnet M through the mover 2 and the respective movable armature parts 4a, b. Actuators, preferably linear actuators 7a, b control the position of the movable armature parts 4a, b, in this embodiment particularly towards and away from the mover 2, in particular respective surfaces 21a, b of the mover. The actuators 7a, b thereby control the distance, or air gap, Ga, Gb between respective pole faces 41a, b of movable armature parts 4a, b and corresponding surfaces 21a, b of the mover 2. The mover 2 is mounted on the magnetic reluctance actuator through members 5, preferably spring members 5, which produce a biasing force depending on the displacement of the mover 2. Movable armature parts 4a, b are mounted on the magnetic reluctance actuator 1 through members 6, which may or may not produce a biasing force depending on the displacement of the movable armature parts 4a, b. The polarity of the magnet M is shown with the north pole facing the mover 2. This is however not essential, as the magnet M may also be reversed.

[0036] The magnetic reluctance of a magnetic circuit or part of a magnetic circuit, such as F 1 and F2, is determined by the formula R = L / (A x u), wherein R is the magnetic reluctance, L is the length of the relevant part in the magnetic circuit, A is the cross sectional area of the relevant part in the magnetic circuit, and u is the magnetic permeability of the material of the relevant part in the magnetic circuit. The total magnetic reluctance of a magnetic circuit, such as Fl and F2, corresponds to the sum of the magnetic reluctances that make up the magnetic circuit. In the present case, an air gap Ga, b can be regarded as a part of a magnetic circuit Fl, F2. By increasing or decreasing the length of the air gap Ga, b, the magnetic reluctance of the air gap Ga, b may be increased or decreased, thereby increasing or decreasing the magnetic reluctance of the complete circuit Fl, F2.

[0037] The magnetic force exerted on an element in a magnetic circuit, such as the mover 2, is proportional to the magnitude of the magnetic flux in the respective magnetic circuit. The magnetic flux carried by the magnetic circuit is inversely proportional to the total magnetic reluctance of said circuit. In the shown embodiment, magnetic forces resulting from the magnetic fluxes flowing through magnetic circuits Fl, F2 are applied to the mover 2, in particular towards the movable armature parts 4a, b.

[0038] Figure IB shows the effect of a movement of one of the movable armature parts 4a, b, in particular the left part 4a. A movement Df, of the movable armature part 4a towards mover 2, in particular a movement Df of surface, or pole face, 41a of the movable armature part 4a towards the surface 21a of the mover reduces the size of the air gap Ga to G’a, thereby reducing the magnetic reluctance of the air gap G’a relative to the initial reluctance of the air gap Ga. The magnetic flux in circuit Fl thus increases proportionally, increasing the magnetic force applied to the mover, in particular the magnetic attraction force pulling the mover 2 towards the movable part 4a which acts in a first direction. The mover 2 thus moves towards the movable armature part 4a with a movement Dm as the opposing biasing force applied by the spring members 5 and the magnetic force acting in the opposite (second) direction towards the right movable part 4b is overcome. In the shown embodiment, this movement of the mover 2 to the left also increases the air gap Gb to G’b, reducing the magnetic force acting in the second direction towards the right movable armature part 4b.

[0039] Figures 2A, B show another embodiment of the magnetic reluctance actuator 1. The shown embodiment comprises a single movable armature part 4. The magnet M produces a magnetic field which is conducted by a fixed armature 3, in particular parts 3a-c through two magnetic circuits Fl, F2. An air gap G extends between the armature parts 3a-c and the movable armature part 4, in particular between surface 41 of the movable armature part 4 and the surfaces 3 la-c of the armature 3a-c facing the movable armature part 4. By moving the movable armature part 4, using actuator 7, away from the fixed armature parts 3a-c, the air gap G is increased. This reduces the magnitude of the magnetic fluxes carried through magnetic circuits Fl, F2, and the magnetic force exerted on the mover 2. The mover 2 is mounted on biasing members 5, which produce a biasing force acting away from the armature 3 which opposes the magnetic force exerted on the mover. In Figure 2B, the movable armature part 4 is moved closer to the fixed armature 3a-c, decreasing the air gap to G’ . The magnetic reluctance of the magnetic circuits F 1, F2 is thus decreased, increasing the magnetic force exerted on the mover 2, moving the mover 2 towards the armature 3a-c.

[0040] Figures 3A, B show another embodiment of the magnetic reluctance actuator 1. The fixed armature 3a-d essentially comprises two main sections 3a, b and 3c, d, extending on either side of a mover 2. Two permanent magnets, respectively Ml, M2 and M3, M4, are arranged on either armature section 3a, b and 3c, d. The polarity of the magnets on either section is opposite, such that two magnets together, respectively Ml, M2 and M3, M4, produce magnetic fluxes that reinforce each other, to flow through respective magnetic circuits Fl, F2. Thus, a first magnetic force, acting to the magnets Ml, M2, and a second magnetic force, acting to the magnets M3, M4, is exerted on the mover 2. Said two magnetic forces oppose each other. Air gaps Ga, Gb respectively extend between faces 3 la, b and movable part 4a, and faces 3 lb, c and movable part 4b. By increasing either air gap Ga, b relative to the other air gap the magnetic force acting on the mover 2 towards the respective air gap is reduced, moving the mover 2 in the opposite direction. For example, as shown in figure 3B, by moving the movable part 4a away from the armature section 3a, b, the air gap Ga is increased to G’a, reducing the magnetic force exerted on the mover 2 as a result of the magnetic flux conducted through magnetic circuit Fl, relative to the opposing magnetic force originating from magnetic circuit F2. As a result, the mover 2 moves in the direction of the magnetic circuit F2. It should be noted that movable parts 4a, b may be controlled separate from each other, to tune the behaviour of the magnetic reluctance actuator 1, in particular in combination with spring members 5 which produce a biasing force that opposes the movement of the mover 2.

[0041] Figure 4 shows another embodiment of a magnetic reluctance actuator 1. The magnetic reluctance actuator comprises movable armature parts 4a, b which extend between surfaces, or surface pairs, 3 la, b of a fixed armature 3 and a mover 2, on either side of the mover 2. By moving for example movable armature part 4a towards the mover 2, and thus away from surfaces 31a, the air gap Ga between the movable armature part 4a, in particular surface 41a, and surfaces 3 la is increased, while the air gap Gc between the movable armature part 4a, in particular surface 42a, and the mover 2, in particular surface 21, is decreased. The total area of surfaces 3 la (as well as 3 lb) is smaller than the total area of surface 21. Thus, an increase of the air gap Ga will result in a higher increase of the magnetic reluctance of circuit Fl than a corresponding decrease of the air gap Gc. The same applies to magnetic circuit F2, air gaps Gb, Gd, movable armature part 4b and surfaces 41b, 42b and 3 lb. Thus, an increase of one of air gap Ga, Gb relative to the other of air gaps Ga, Gb will result in the mover 2 moving away from the increased air gap Ga, b. By adapting the sizes of the surfaces 3 la, b, 41a, b, 42a, b and 21, the movement of the mover 2 resulting from a movement of either one or both movable parts 4a, b can be adapted.

[0042] Figures 5A, B show another embodiment of a magnetic reluctance actuator 1. The shown magnetic reluctance actuator 1 functions in a similar manner as the embodiment shown in figure 4. Movable armature parts 4a, b extend between respective surfaces, or surface pairs, 3 la, c and 3 lb, d and surfaces 21 of the mover 2. The areas of surface pairs 3 la-d are smaller than the adjacent surfaces 21 of the mover 2, resulting in the behaviour described in relation to the embodiment of figure 4. For example, an increase of air gap Ga to air gap G’a by a movement of movable armature part 4b in direction Df, away from surfaces 3 lb, d increases the reluctance of magnetic circuits Fla, b, reducing the magnetic force pulling the mover 2 towards surfaces 3 lb, d relative to the magnetic force pulling the mover 2 towards the opposing surfaces 3 la, c, moving the mover 2 in the direction Dm, towards the surfaces 3 la, c.

[0043] Figures 6A, B show another embodiment of a magnetic reluctance actuator 1. A fixed armature 3, a magnet, preferably a permanent magnet M, movable armature part 4 and a mover 2 form a magnetic circuit F carrying the magnetic flux originating from the magnet M. A variable air gap G extends between the movable part 4 and the mover 2, in particular between surface 41 of the movable part and surface 21 of the mover. An actuator, preferably a linear actuator 7 controls the position of the movable part 4, and thus the size of the air gap G. A decrease of the size of the air gap G reduces the magnetic reluctance of the air gap G and thus the magnetic reluctance of the magnetic circuit F, thereby increasing the magnetic flux in the circuit F, and the magnetic force applied to the mover 2, which acts towards the movable armature part 4. In figure 6B the movable armature part 4 is moved in direction Df towards the mover 2, thereby decreasing the air gap. As a result, the mover 2 is pulled towards the movable armature part 4, thereby further reducing the size of the air gap G’. The interaction between the movable armature part 4 and the mover 2 thus has a negative stability, as a reduction of the air gap G increases the force exerted on the mover 2, which then further decreases the air gap G. A spring member 5 may thus be provided to support the mover 2 and provide a biasing force that (at least partially) counters the magnetic force. In addition, the biasing force of the spring members 5 increase as the mover 2 moves towards the movable part 4, thereby at least partially counteracting the negative stability of the magnetic interaction between the mover 2 and the movable part 4.

[0044] The disclosure further comprises the following clauses, which correspond exactly to the Dutchlanguage claims:

[0045] CLAUSES

[0046] 1. Magnetic reluctance actuator comprising a magnet, a ferromagnetic armature, and a ferromagnetic mover forming at least part of a magnetic circuit carrying a magnetic flux, wherein the magnetic flux generates a first magnetic force on the mover which acts in a first direction, wherein the magnetic circuit further comprises at least a variable air gap and an air gap actuator arranged to control the size of the variable air gap, wherein the magnetic reluctance of the magnetic circuit is increased or decreased by respectively increasing or decreasing the size of the air gap, thereby respectively decreasing and increasing the magnitude of the magnetic flux and the magnitude of the first magnetic force, wherein the actuator is arranged to adjust the position of the mover by adjusting the size of the variable air gap.

[0047] 2. Magnetic reluctance actuator according to clause 1, wherein the magnetic reluctance actuator further comprises a biasing means arranged to movably support the mover relative to the magnetic reluctance actuator and apply a first biasing force on the mover which acts in a direction with at least a component opposite the first magnetic force.

[0048] 3. Magnetic reluctance actuator according to the previous clause, wherein the biasing means comprises a spring member arranged to at least partially support the mover and provide the first biasing force. Magnetic reluctance actuator according to any of the preceding clauses, wherein the air gap actuator comprises a linear actuator. Magnetic reluctance actuator according to the preceding clause, not comprising a piezo electric actuator. Magnetic reluctance actuator according to any of the preceding clauses, wherein the magnetic flux flows substantially in a flux plane, wherein the armature and / or the flux lines are substantially asymmetrical relative to the magnetic flux lines extending through the magnet. Magnetic reluctance actuator according to any of the preceding clauses, wherein the variable air gap extends between the armature and the mover. Magnetic reluctance actuator according to any of the preceding clauses, wherein the armature comprises a fixed armature part, which is substantially fixed to the magnetic reluctance actuator, and at least one movable armature part. Magnetic reluctance actuator according to the preceding clause, wherein the variable air gap extends between the fixed armature part and the movable armature part. Magnetic reluctance actuator according to the preceding clause, wherein the movable armature part extends adjacent to the mover, such that an air gap extends between adjacent faces of the movable armature part and the mover, wherein the combined surface area of the adjacent faces of the fixed armature part and the movable armature part is different than the combined surface area of the adjacent faces of the movable armature part and the mover. Magnetic reluctance actuator according to at least clause 8, wherein the fixed armature part extends between the movable armature part and the mover, the movable armature part and the mover thereby extending on substantially opposing sides of the armature. Magnetic reluctance actuator according to at least clause 8, wherein the variable air gap extends between the movable armature part and the mover. Magnetic reluctance actuator according to any of the preceding clauses, wherein the armature comprises at least a first and second magnetic circuit arranged to transmit magnetic flux lines originating from the permanent magnet through at least two loops, each passing through the mover, wherein the magnetic fluxes passing through the first and second circuit respectively generate the first magnetic force on the mover, as well as at least one second magnetic force on the mover. Magnetic reluctance actuator according to the preceding clause, wherein the first and second magnetic circuits each respectively comprise a first and a second variable air gap as well as a first and second air gap actuator to respectively control the first and second air gap, wherein the first and second variable air gaps are arranged to control the magnetic reluctance of respectively the first and second magnetic circuit. Magnetic reluctance actuator according to at least clause 13 and 14, wherein the armature comprises a first armature part and a second armature part, substantially separate from each other, wherein the mover extends between the first and second armature parts. Magnetic reluctance actuator according to any of the preceding clauses 13-15, wherein the first and second magnetic forces act respectively in the first direction and a second direction, wherein the first and second directions extend in directions with at least a component opposite each other.

Claims

CLAIMS1. Magnetic reluctance actuator comprising a magnet, a ferromagnetic armature, and a ferromagnetic mover forming at least part of a magnetic circuit carrying a magnetic flux, wherein the magnetic flux generates a first magnetic force on the mover which acts in a first direction, wherein the magnetic circuit further comprises at least a variable air gap and an air gap actuator arranged to control the size of the variable air gap, wherein the magnetic reluctance of the magnetic circuit is increased or decreased by respectively increasing or decreasing the size of the air gap, thereby respectively decreasing and increasing the magnitude of the magnetic flux and the magnitude of the first magnetic force, wherein the actuator is arranged to adjust the position of the mover by adjusting the size of the variable air gap, thereby adjusting the magnetic reluctance of the magnetic circuit, thereby adjusting the magnitude of the first magnetic force, thereby adjusting the position of the mover.

2. Magnetic reluctance actuator according to claim 1, wherein the magnetic reluctance actuator further comprises a biasing means arranged to movably support the mover relative to the magnetic reluctance actuator and apply a first biasing force on the mover which acts in a direction with at least a component opposite the first magnetic force.

3. Magnetic reluctance actuator according to the previous claim, wherein the biasing means comprises a spring member arranged to at least partially support the mover and provide the first biasing force.

4. Magnetic reluctance actuator according to any of the preceding claims, wherein the air gap actuator comprises a linear actuator.

5. Magnetic reluctance actuator according to the preceding claim, not comprising a piezo electric actuator.

6. Magnetic reluctance actuator according to any of the preceding claims, wherein the magnetic flux flows substantially in a flux plane, wherein the armature and / or the flux lines are substantially asymmetrical relative to the magnetic flux lines extending through the magnet.

7. Magnetic reluctance actuator according to any of the preceding claims, wherein the variable air gap extends between the armature and the mover.

8. Magnetic reluctance actuator according to any of the preceding claims, wherein the armature comprises a fixed armature part, which is substantially fixed to the magnetic reluctance actuator, and at least one movable armature part.

9. Magnetic reluctance actuator according to the preceding claim, wherein the variable air gap extends between the fixed armature part and the movable armature part.

10. Magnetic reluctance actuator according to the preceding claim, wherein the movable armature part extends adjacent to the mover, such that an air gap extends between adjacent faces of the movable armature part and the mover, wherein the combined surface area of the adjacent faces of the fixed armature part and the movable armature part is different than the combined surface area of the adjacent faces of the movable armature part and the mover.

11. Magnetic reluctance actuator according to at least claim 8, wherein the fixed armature part extends between the movable armature part and the mover, the movable armature part and the mover thereby extending on substantially opposing sides of the armature.

12. Magnetic reluctance actuator according to at least claim 8, wherein the variable air gap extends between the movable armature part and the mover.

13. Magnetic reluctance actuator according to any of the preceding claims, wherein the armature comprises at least a first and second magnetic circuit arranged to transmit magnetic flux lines originating from the permanent magnet through at least two loops, each passing through the mover, wherein the magnetic fluxes passing through the first and second circuit respectively generate the first magnetic force on the mover, as well as at least one second magnetic force on the mover.

14. Magnetic reluctance actuator according to the preceding claim, wherein the first and second magnetic circuits each respectively comprise a first and a second variable air gap as well as a first and second air gap actuator to respectively control the first and second air gap, wherein the first and second variable air gaps are arranged to control the magnetic reluctance of respectively the first and second magnetic circuit.

15. Magnetic reluctance actuator according to at least claim 13 and 14, wherein the armature comprises a first armature part and a second armature part, substantially separate from each other, wherein the mover extends between the first and second armature parts.

16. Magnetic reluctance actuator according to any of the preceding claims 13-15, wherein the first and second magnetic forces act respectively in the first direction and a second direction, wherein the first and second directions extend in directions with at least a component opposite each other.

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