Actuator assembly

Abstract

An actuator assembly (2) comprises: first and second parts (10, 20) which are movable relative to each other in at least one direction in a movement plane and are not movable relative to each other along a primary axis perpendicular to the movement plane; and one or more actuating units (30), each of which comprises: a force-modifying mechanism (32), a coupling link (33) connected between the force- modifying mechanism (32) and the second part (20); and an SMA element (34) connected between the first part (10) and the force-modifying mechanism (32); wherein the extent of each actuating unit (30) when projected onto the primary axis is greater than the extent of the actuating unit (30) when projected onto at least one line in the movement plane.

Description

[0001] ACTUATOR ASSEMBLY

[0002] Field

[0003] The present application relates to a shape memory alloy (SMA) actuator assembly.

[0004] Background

[0005] SMA actuator assemblies have various applications and, for example, can be used to provide optical image stabilisation (OIS) in compact cameras for smartphones and other electronic devices. For instance, WO2013 / 175197 describes an actuator assembly with four SMA wires for moving the movable part in any direction in a plane perpendicular to a primary axis. WO2022 / 084699 describes a so-called high-stroke version of such an actuator assembly.

[0006] Summary

[0007] First aspect

[0008] According to a first aspect of the present invention, there is provided an actuator assembly comprising: first and second parts which are movable relative to each other in at least one direction in a movement plane and are not movable relative to each other along a primary axis perpendicular to the movement plane; and one or more actuating units, each of which comprises: a force-modifying mechanism connected to the first part; a coupling link connected between the force-modifying mechanism and the second part; and an SMA element connected between the first part and the force-modifying mechanism for applying an input force on the force-modifying mechanism thereby causing the forcemodifying mechanism to apply an output force on the coupling link and causing the coupling link to apply an actuating force on the second part; wherein the extent of each actuating unit when projected onto the primary axis is greater than the extent of the actuating unit when projected onto at least one line in the movement plane.

[0009] Thus, the one or more actuating units can be described as having a significant extent along the primary axis. Such a 'vertical' configuration of actuating units can have several different advantages. For example, the extent of the actuator assembly when projected onto the movement plane (also referred to as the footprint of the actuator assembly) can be reduced.

[0010] The extent of each actuating unit when projected onto the primary axis may be at least 2.5, 5 or 10 times the extent of the actuating unit when projected onto at least one line in the movement plane. The extent of each actuating unit when projected onto the primary axis may substantially overlap with the extent of the second part when projected onto the primary axis. The second part may be configured to hold at least one additional part (e.g. the lenses of a camera assembly) and the extent of each actuating unit when projected onto the primary axis may substantially overlap with the extent of the additional part(s) when projected onto the primary axis.

[0011] Herein, substantial overlap means, for example, an overlap of at least 50%, 60%, 70%, 80% or 90%.

[0012] Thus, the vertical configuration of actuating units need not overly increase the extent of the actuator assembly when projected onto the primary axis (also referred to as the height of the actuator assembly). Thus, the actuator assembly can make efficient use of available space (footprint and height).

[0013] Each actuating unit may comprise one or more planar components each of which is oriented substantially parallel to the primary axis. Each actuating unit may be attached to planar regions of the first and second parts each of which is oriented substantially parallel to the primary axis.

[0014] The extent of the first part when projected onto the primary axis may substantially overlap with the extent of the second part (and / or the additional part) when projected onto the primary axis.

[0015] The first part may comprise a space which receives the second part (and / or additional part).

[0016] The actuator assembly may comprise a plurality of (e.g. four) actuating units arranged in a loop around the primary axis.

[0017] Second aspect

[0018] According to a second aspect of the present invention, there is provided an actuator assembly comprising: first and second parts which are movable relative to each other in at least one direction in a movement plane and are not movable relative to each other along a primary axis perpendicular to the movement plane; and one or more actuating units, each of which comprises: a force-modifying mechanism connected to the first part; a coupling link connected between the force-modifying mechanism and the second part; and an SMA element connected between the first part and the force-modifying mechanism for applying an input force on the force-modifying mechanism thereby causing the forcemodifying mechanism to apply an output force on the coupling link and causing the coupling link to apply an actuating force on the second part; wherein the actuating force is directed along a line that is inclined at a non-zero angle to the movement plane.

[0019] Thus, the relative movement of the first and second parts for a given change in length of the SMA element can be increased as a result of both (a) the force-modifying mechanism and (b) the non-zero angle between the actuating force and the movement plane. This increase may be referred to herein as 'amplification'. In relation to (a), amplification can be obtained with a suitable design of the forcemodifying mechanism. In relation to (b), amplification is due to geometrical considerations as described, for example, in GB2569668.

[0020] The angle may, for example, be greater than 10°, 20°, 30°, 40°, 50°, 60°, 70° or 80°. The preferred angle may depend on various design considerations.

[0021] Third aspect

[0022] According to a third aspect of the present invention, there is provided an actuator assembly comprising: first and second parts which are movable relative to each other in at least one direction in a movement plane and are not movable relative to each other along a primary axis perpendicular to the movement plane; and one or more actuating units, each of which comprises: a force-modifying mechanism connected to the first part; a coupling link connected between the force-modifying mechanism and the second part; and an SMA element connected between the first part and the force-modifying mechanism for applying an input force on the force-modifying mechanism thereby causing the forcemodifying mechanism to apply an output force on the coupling link and causing the coupling link to apply an actuating force on the second part; wherein each actuating unit is elongate and has a length that is at least twice any transverse dimension.

[0023] Each actuating unit may have a length that is at least three or four times any transverse dimension. Such a configuration can have various advantages. For example, the actuating unit(s) can be more easily arranged within the actuator assembly, thereby simplifying manufacture. In particular, actuating units need not overlap when viewed along the primary axis, as they generally do in WO2022 / 084699.

[0024] The actuator assembly may comprise four actuating units arranged in a loop around the primary axis, e.g. in a similar way to the SMA elements described in WO2013 / 175197.

[0025] Generally, in each actuating unit, the length of the SMA element is less than the length of the actuating unit. Hence, compared to other actuator assemblies (e.g. as described in WO2013 / 175197) in which each 'actuating unit' consists of just an SMA element, the actuator assembly generally has shorter SMA elements and therefore consumes less power. Moreover, although shorter SMA elements are generally capable of producing less movement, the amplification that can be provided by the force-modifying mechanism compensates for this.

[0026] Features relating e.g. to manufacturability

[0027] Each coupling link may correspond to a coupling flexure and each force-modifying mechanism may correspond to a force-modifying flexure.

[0028] Each actuating unit may comprise only one coupling flexure and only one force-modifying flexure.

[0029] Each force-modifying flexure may be connected to the first part by way of a first connecting portion and each coupling flexure may be connected to the second part by way of a second connecting portion.

[0030] In each actuating unit, the first connecting portion may comprise a terminal portion electrically connected to one end of the SMA element via the force-modifying flexure. The terminal portion may be for connecting to actuator control circuitry.

[0031] Each actuating unit may comprise a body portion to which the SMA element, the force-modifying flexure and the coupling flexure are connected. The SMA element may be connected to the body by way of a first wire connector (e.g. a crimp).

[0032] Each actuating unit may comprise a third connecting portion, wherein the third connecting portion is connected to the second part and comprises a terminal portion electrically connected to the other end of the SMA element. The terminal portion may be for connecting to actuator control circuitry. The SMA element may be connected to the third connecting portion by way of a second wire connector (e.g. a crimp). The actuator assembly may comprise a first actuating unit on a first side of the actuator assembly and a second actuating unit on a second, different side of the actuator assembly, and the first and / or third connecting portions of the first actuating unit may extend, e.g. around a corner of the actuator assembly, so that terminal portions of the first and second actuating units are arranged on the second side of the actuator assembly. This can facilitate connections to the actuator control circuitry.

[0033] The actuator assembly may comprise one or more interconnects for carrying electrical signals between the first and second parts. Each interconnect may comprise a first portion connected to the first part, a second portion connected to the second part, and a flexure between the first and second portions. The one or more interconnects may be for carrying electrical signals to a further actuator, e.g. an autofocus actuator.

[0034] The force-modifying flexure, the first connecting portion, the coupling flexure and the second connecting portion of at least one actuating unit may all be produced from a single sheet of material. The material may comprise metallic material, e.g. steel.

[0035] The third connecting portion of the at least one actuating unit may be produced from the sheet of material. The first portion, the second portion and the flexure of at least one interconnect may be produced from the sheet of material.

[0036] Each first connecting portion may be insert moulded in the first part. Each second connecting portion may be insert moulded in the second part. Each third connecting portion may be insert moulded in the first part. The first portion of each interconnect may be insert moulded in the first part, and / or the second portion of each interconnect may be insert moulded in the second part.

[0037] Thus, several components of the actuator assembly can be manufactured in a cost-effective way.

[0038] There may be provided a method of producing such an actuating assembly. The method may comprise: patterning the sheet of material to produce therein features corresponding to the forcemodifying flexure, the first connecting portion, the coupling flexure and the second connecting portion of the at least one actuating unit; bending the sheet so that the features corresponding to the force-modifying flexure, the first connecting portion, the coupling flexure and the second connecting portion of the at least one actuating unit are all oriented substantially parallel to the same axis; insert moulding in the first part each feature corresponding to the first connecting portion of the at least one actuating unit, and / or insert moulding in the second part each feature corresponding to the second connecting portion of the at least one actuating unit; and removing one or more sacrificial portions (e.g. tabs) of the sheet of material so as to the forcemodifying flexure, the first connecting portion, the coupling flexure and the second connecting portion of the at least one actuating unit.

[0039] The method may comprise patterning the sheet to produce therein feature(s) corresponding to the third connecting portion of the at least one actuating unit. The method may comprise patterning the sheet to produce therein features corresponding to the first portion, the second portion and the flexure of at least one interconnect. The method may comprise bending the sheet so that at least some of these features are oriented substantially parallel to the axis. The method may comprise insert moulding feature(s) corresponding to each third connecting portion in the first part. The method may comprise insert moulding feature(s) corresponding to the first portion of each interconnect in the first part, and / or insert moulding feature(s) corresponding to the second portion of each interconnect in the second part.

[0040] Features relating e.g. to a bearing arrangement

[0041] The actuator assembly may comprise a bearing arrangement configured to guide relative movement of the first and second parts in the at least one direction and to restrict relative movement of the first and second parts along the primary axis.

[0042] The bearing arrangement may comprise a plurality of (e.g. three or more) ball bearings. The bearing arrangement may instead comprise plain bearings, for example as described in WO2017 / 055788, but such plain bearings may require low-friction coatings and may have a higher cost.

[0043] The actuator assembly may comprise a loading arrangement, e.g. comprising flexures or magnets, for loading the bearing arrangement.

[0044] Alternatively or additionally, the actuating force of the one or more actuating units (e.g. of the second aspect) may act as a loading force for loading the bearing arrangement. Hence the cost of having a separate loading arrangement can be avoided or reduced.

[0045] Further features

[0046] The coupling link may be compliant in at least one direction perpendicular to the direction of the actuating force. The actuator assembly may comprise at least two actuating units arranged to apply actuating forces on the second part in perpendicular directions such that the coupling link of each of the two actuating units is compliant in the direction of the actuating force of the other of the two actuating units.

[0047] The actuator assembly may comprise four actuating units arranged so as to be capable of moving the second part relative to the first part in any direction in a plane perpendicular to the primary axis without applying any net torque to the second part about the primary axis. The actuating units may be arranged so as to be capable of rotating the second part relative to the first part about any axis perpendicular to and intersecting the primary axis.

[0048] Instead of the first and second parts being movable relative to each other as specified above (i.e. in at least one direction in a movement plane and not along a primary axis perpendicular to the movement plane), the first and second parts may be rotatable (or, in other words, tiltable) relative to each other about any axis orthogonal to the primary axis.

[0049] Features relating e.g. to larger assemblies

[0050] There may be provided a camera assembly comprising the actuator assembly. One of the first and second parts may comprise a lens with an optical axis parallel to the primary axis, and the other of the first and second parts may comprise an image sensor, The first and second parts may be movable relative to each other so as to provide lens-shift optical image stabilisation. Alternatively, the first and second parts may be movable relative to each other so as to provide sensor-shift optical image stabilisation.

[0051] However, the actuator assembly may be used in any system or device, e.g. a head-mounted display.

[0052] The actuator assembly may comprise a third part that is movable relative to one of the first and second parts along the primary axis. The third part may correspond to the abovedescribed additional part. The third part may be a moulded part. The third part may be movable by a further actuator. The abovedescribed one or more interconnects may be for connecting actuator control circuitry to the further actuator. The further actuator may be, for example, as described in WO2017134456 or WO2019 / 243849, which are incorporated herein by reference. (The support structures described in these documents would correspond to the first or second part described herein, and the movable element described in these documents would corresponding to the third part described herein). The third part may comprise a lens and may be movable so as to provide autofocus.

[0053] Brief description of the drawings Certain embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0054] Figure 1A illustrates a camera apparatus;

[0055] Figure IB illustrates an actuator assembly which may be used in the camera apparatus of Figure 1A;

[0056] Figures 2A is a side view of an example of the actuator assembly of Figure IB;

[0057] Figures 2B is a top view of the same actuator assembly;

[0058] Figure 3A is a top view of a patterned sheet which may be used in the manufacture of the actuator assembly of Figures 2A and 2B;

[0059] Figure 3B is a perspective view of the sheet of Figure 3A after bending;

[0060] Figure 4 illustrates a method which may be used to manufacture the actuator assembly of Figures 2A and 2B;

[0061] Figure 5 is a side view of another example of an actuator assembly which may be used in the camera apparatus of Figure 1A; and

[0062] Figure 6 is a side view of another example of an actuator assembly which may be used in the camera apparatus of Figure 1A.

[0063] Detailed description

[0064] Camera apparatus

[0065] Figure 1A schematically shows an apparatus 1 incorporating an actuator assembly 2 in accordance with an embodiment of the present invention. Figure IB schematically shows a plan view of the actuator assembly 2. The apparatus 1 is, for example, a camera apparatus 1. The apparatus 1 is to be incorporated in a portable electronic device such as a mobile telephone, or tablet computer. Thus, miniaturisation is an important design criterion.

[0066] The apparatus 1 comprises an actuator assembly 2 or may itself be considered an example of an actuator assembly 2. The actuator assembly 2 comprises a support structure 10 (an example of a first part 10) and a movable part 20 (an example of a second part 20). The movable part 20 is supported on the support structure 10. The movable part 20 is movable relative to the support structure 10. For example, the movable part 20 may be supported in a manner allowing movement of the movable part 20 relative to the support structure 10 in a plane orthogonal to a primary axis P. Movement along the primary axis P may be constrained or prevented. Alternatively, the movable part 20 may be supported in a manner allowing tilting of the movable part 20 relative to the support structure 10 about any axes orthogonal to the primary axis P. Movement other than such tilting may be constrained or prevented.

[0067] The support structure 10 is used as a reference point to describe movement of the movable part 20. When the actuator assembly 2 is included in an apparatus or device, such as a camera or a smartphone, the support structure 10 may be fixed relative to a main body of the apparatus or device. However, in general the support structure 10 need not necessarily be stationary and may be movable relative to or within such a device. In some embodiments, the movable part 20 may be fixed relative to a main body of the device. Furthermore, although the support structure 10 is schematically depicted as one part in Figure 1A, in practice the support structure 10 may be formed from a plurality of layers, parts and components that are fixed relative to one another. Similarly, the movable part 20 may be formed from a plurality of layers, parts and components that are fixed relative to one another. The support structure 10 may also include or be attached to additional structure 11, 12.

[0068] The actuator assembly 2 comprises actuating units 30. The actuating units 30 are connected between the support structure 10 and the movable part 20. The actuating units 30 are arranged to apply actuating forces F between the movable part 20 and the support structure 10. Selectively applying and varying the actuating forces F may move the movable part 20 relative to the support structure 10. The actuating units 30 are thus capable, on selective actuation, of driving movement of the movable part 20 relative to the support structure 10.

[0069] The actuator assembly 2 extends primarily in a direction orthogonal to a primary axis P. The extent of the actuator assembly 2 along the primary axis is less than the extent of the actuator assembly 2 along axes orthogonal to the primary axis P.

[0070] The movable part 20 may be supported (so suspended) on the support structure 10 exclusively by the actuating units 30. However, preferably, the actuator assembly 2 comprises a bearing arrangement 40 that supports the movable part 20 on the support structure 10. The bearing arrangement 40 may have any suitable form for allowing movement of the movable part 20 with respect to the support structure 10. According to embodiments, the bearing arrangement 40 may guide movement of the movable part 20 relative to the support structure 10 in a plane, also referred to as a movement plane. In alternative embodiments, the bearing arrangement 40 guides movement of the movable part 20 relative to the support structure 10 such that the movable part 20 tilts about axes orthogonal to the primary axis P. The bearing arrangement 40 may constrain movement of the movable part relative to the support structure in other degrees of freedom. For this purpose, the bearing arrangement 40 may, for example, comprise a rolling bearing (such as a roller bearing or ball bearing), a flexure bearing (i.e. an arrangement of flexures or other resilient elements guiding movement), or a plain bearing or sliding bearing.

[0071] The camera apparatus 1 further comprises a lens assembly 3 and an image sensor 4. The lens assembly 3 comprises one or more lenses configured to focus an image on the image sensor 4. The lens assembly 3 defines an optical axis O, which is aligned with the primary axis P in Figure 1A. The image sensor 4 captures an image and may be of any suitable type, for example a charge coupled device (CCD) or a CMOS device. The lens assembly 3 comprises a lens carrier 50, for example in the form of a cylindrical body, supporting the one or more lenses. The lens carrier 50 may be movable along the optical axis O, for example to provide zoom or focus, such as auto-focus (AF). The lens carrier 50 may be moved by a voice coil motor (VCM) or an SMA actuator 60, which may be as described in WO2017134456 or WO2019 / 243849, for example.

[0072] The apparatus 1 may be a miniature camera apparatus in which each lens of the lens assembly 3 has a diameter of 20mm or less, for example of 12mm or less.

[0073] In the embodiment shown in Figure 1, the movable part 20 may be considered to comprise the lens assembly 3. The image sensor 4 may be fixed relative to the support structure 10, i.e. mounted on the support structure 10. In other embodiments (not shown), the lens assembly 3may be fixed relative to the support structure 10 and the movable part 20 may comprise the image sensor 4. In either embodiment, in operation the lens assembly 3 is moved relative to the image sensor 4. This has the effect that the image on the image sensor 4 is moved. So, optical image stabilization (OIS) may be implemented in the apparatus 1.

[0074] The camera apparatus 1 further comprises a controller 8. The controller 8 may be implemented in an integrated circuit (IC) chip. The controller 8 generates drive signals for the actuating units 30, in particular for SMA wires 34 forming part of the actuating units 30. SMA material has the property that on heating it undergoes a solid-state phase change that causes the SMA material to contract. Thus, applying drive signals to the SMA wires 34, thereby heating the SMA wires 34 by allowing an electric current to flow, will cause the SMA wires 34 to contract and thus actuate the actuating unit 30, so as to move the movable part 20. The drive signals are chosen to drive movement of the movable part 20 in a desired manner, for example so as to achieve OIS by stabilizing the image sensed by the image sensor 4. The controller 8 supplies the generated drive signals to the SMA wires 34. Optionally, the camera apparatus comprises an inertial measurement unit 6. The inertial measurement unit 6 may comprise one or more vibration sensors, such as gyroscopes, accelerometers or magnetometers, although in general other types of sensors could be used. The inertial measurement unit 6 detects changes in the orientation of and / or the forces on the camera apparatus 1 and generates sensor signals representative of the orientation of and / or forces on the camera apparatus 1. The controller 8 receives the sensor signals and generates the drive signals for the SMA wires 34 in response to the sensor signals, for example so as to counteract the changes in orientation and / or forces represented by the output signals. The controller 8 may thus control the SMA wires 34 to achieve OIS.

[0075] Arrangement of actuating units

[0076] Figure IB schematically shows the arrangement of actuating units 30 in the actuator assembly 2. As shown, the actuator assembly 2 may comprise a total of four actuating units 30. The four actuating units 30 may apply actuating forces F between the movable part 20 and the support structure 10. The actuating forces F may be applied to the movable part 20 relative to the support structure 10.

[0077] In the depicted embodiment, the actuating forces F are perpendicular to the primary axis P, and may be parallel to the movement plane. However, in general the actuating forces F may be angled relative to the movement plane. The actuating forces F may thus have a component along the primary axis P. This component along the primary axis P may be resisted by the bearing arrangement 40, for example, to provide movement of the movable part 20 in degrees of freedom allowed by the bearing arrangement 40. In some embodiment it may even be desirable for actuating forces F to have a component in parallel to the primary axis P, for example so as to load plain or rolling bearings arranged between the movable part 20 and the support structure 10.

[0078] In the depicted embodiment, the four actuating units 30 are in an arrangement capable of applying actuating forces F so as to move the movable part 20 relative to the support structure 10 to any positions within a range of movement. The range of movement may be within a movement plane that is perpendicular to the primary axis P.

[0079] In particular, two actuating units 30 (e.g. the top and bottom actuating units in Figure IB) are arranged to apply actuating forces F in opposite directions parallel to a first axis (e.g. the x axis in Figure IB). The other two of actuating units (e.g. the left and right actuating units in Figure IB) are arranged to apply actuating forces F opposite directions parallel to a second axis (e.g. the y axis in Figure IB), orthogonal to the first axis. By appropriately varying the difference in actuation amount between the opposing actuating units 30, the movable part 20 may thus be moved independently along the first and second axes. The opposing actuating forces F are not colinear, but offset from each other in a direction perpendicular to the actuating forces. Providing opposing actuating units 30 allows the tension in the SMA wires 30 of the respective actuating units 30 to be controlled, allowing for more accurate and reliable positioning of the movable part 20 compared to a situation in which actuating units 30 do not oppose each other.

[0080] In embodiments, none of the actuating forces F are collinear. This allows the arrangement of actuating units 30 to translationally move the movable part 20 without applying any net torque to the movable part 20. So, the movable part 20 can be moved translationally in the movement plane without rotating the movable part 20 in the movement plane. In general, the arrangement of actuating units 30 is capable of accurately controlling a torque or moment of the movable part 20 about the primary axis P. So, the actuating units 30 are capable of rotating (or not rotating) the movable part 20 relative to the support structure about the primary axis P.

[0081] In particular, two actuating units 30 (e.g. the top and bottom actuating units in Figure IB) are arranged to apply actuating forces F so as to generate a torque or moment between the movable part 20 and the support structure 2 in a first sense (e.g. clockwise) around the primary axis P. The other two actuating units 30 (e.g. the left and right actuating units 30 in Figure IB) are arranged to apply actuating forces F so as to generate a torque or moment between the movable part 20 and the support structure 2 in a second, opposite sense (e.g. anti-clockwise) around the primary axis P. This allows the movable part 20 to be rotated by simultaneously increasing or decreasing the tension of SMA wires in any of the two actuating units 30.

[0082] As shown, two actuating units 30 may be arranged to apply actuating forces in a corner of the actuator assembly 2. The other two actuating units 30 may be arranged to apply actuating forces in another, opposite corner of the actuator assembly 2. The actuator assembly 2, and in particular the movable part 20 and / or the support structure 10, may have a square or rectangular footprint. Each actuating unit 30 may be provided on one of the four sides of the actuator assembly 2.

[0083] The arrangement of forces F applied between movable part 20 and support structure 10 corresponds to the arrangement of SMA wires 30 described in WO2013 / 175197, which is incorporated herein by reference.

[0084] Although, for illustrative purposes, the arrangement of actuating units 30 was described as moving the movable part 20 in the movement plane (e.g. translationally along the x and y axis, or rotationally about the primary axis P), in other embodiments the movable part 20 may be moved differently. For example, the same arrangement of actuating forces F may be used to tilt the movable part 20 relative to the support structure 10 about axes orthogonal to the primary axis, due to appropriate movement constraints provided by the bearing arrangement 40. For example, the bearing arrangement 40 may comprise a plurality of flexures for guiding tilting of the movable part 20 about the axes orthogonal to the primary axis P. Examples of such bearing arrangement 40 are described in WO2022 / 029441, which is incorporated herein by reference.

[0085] Although the actuator assembly 2 is described herein in the context of four actuating units 30, in general the actuator assembly 2 may comprise fewer actuating units 30. For example, the actuator assembly 2 may comprise two actuating units 30, e.g. the two actuating units 30 depicted in the top left of Figure IB. The forces applied to the movable part 20 by the two actuating units 30 may be opposed by a biasing force of one or more resilient elements, such as springs. With reference to Figure IB, the two actuating units 30 in the bottom right corner may be replaced with springs applying biasing forces along the corresponding depicted arrows, for example.

[0086] Actuator assembly

[0087] Referring in particular to Figures 2A and 2B, an example of an actuator assembly 2 will now be described in more detail.

[0088] Referring in particular to Figure 2A, an actuating unit 30 will now be described in detail. It will be appreciated that the other actuating units 30 may comprise the same components described with reference to this actuating unit 30. The actuating units 30 may be substantially identical, i.e. the structure and components of the actuating units 30 may be the same, but the actuating units' arrangement relative to the support structure 10 and / or movable part 20 may differ.

[0089] The actuating unit 30 comprises a body portion 31 to which several components are connected.

[0090] The actuating unit 30 further comprises a force-modifying flexure 32. The force-modifying flexure 32 is connected between the body portion 31 and the support structure 10. One end of the force-modifying flexure 32 is connected to the body portion 31. The other end of the force-modifying flexure 32 is connected to the support structure 10, in particular via a first connecting portion 36. The first connecting portion 36 is fixed relative to the support structure 10. In the depicted design, the forcemodifying flexure 32 is formed integrally with the first connecting portion 36 and with part of the body portion 31, for example from a single sheet of material (such as metal). The force-modifying flexure 32 may, on flexing, allow the body portion 31 to move relative to the support structure 10 in a direction that is substantially orthogonal to the force-modifying flexure 32. The force-modifying flexure 32 effectively allows the body portion 31 to pivot relative to the support structure 10. The actuating unit 30 further comprises an SMA wire 34. The SMA wire 34 is connected between the body portion 31 and the support structure 10. One end of the SMA wire 34 is connected to the support structure 10, in particular by a crimp 15. The other end of the SMA wire 34 is connected to the body portion 31, in particular by a crimp 35.

[0091] The actuating unit 30 further comprises a coupling flexure 33. The coupling flexure 33 is connected between the body portion 31 and the movable part 20. One end of the coupling flexure 33 is connected to the body portion 31. The other end of the coupling flexure 33 is connected to the movable part 20, in particular via a second connecting portion 37.

[0092] The SMA wire 34 is arranged, on contraction, to apply an input force on the body portion 31. The input force acts parallel to the length of the SMA wire 34. The force-modifying flexure 32 is arranged to modify the input force so as to cause the coupling flexure 33 to apply an actuating force to the movable part 20. In particular, in the depicted embodiment the force-modifying flexure 32 is placed in compression on contraction of the SMA wire 34. The force-modifying flexure 32 is arranged at an angle relative to the SMA wire 34. As a result, the body portion 31 is arranged, on SMA wire contraction, to move at an angle relative to the length of the SMA wire 34. The force-modifying flexure 32 thus converts the input force, in particular the magnitude and direction thereof, into the actuating force.

[0093] The actuating unit 30 can be configured to amplify movement or to amplify force due to contraction of the SMA wire 34.

[0094] In some embodiments, at least one actuating unit 30, preferably each actuating unit 30, is configured such that the force-modifying flexure 32 amplifies an amount of contraction of the SMA wire 34 to a relatively greater amount of movement of the movable part 20 relative to the support structure 10. Such amplification, for example, may be by a factor greater than 1.5, preferably greater than 2, further preferably greater than 3. This may be achieved, for example, by appropriate selection of the angle between the force-modifying flexure 32 and the SMA wire 34. The angle may be in the range from 0 to 45 degrees, preferably from 13 to 40 degrees.

[0095] The coupling flexure 33 is compliant in a direction perpendicular to the actuating force. This allows the movable part 20 to move in a direction perpendicular to the actuating force, and in a direction perpendicular to the coupling flexure 33, for example due to actuation of a different actuating unit 30. The coupling link 33 and hence the actuating force is directed along a line that is inclined at a non-zero angle to the so-called movement plane XY. In this example, the line is at an angle of about 30° to the movement plane XY.

[0096] In the above-described embodiments, the force-modifying flexure 32 is placed in compression on contraction of the SMA wire 34. However, in general, the force-modifying flexure 32 could also be arranged so as to be placed under tension on contraction of the SMA wire 34. This can reduce the risk of buckling of the force-modifying flexure 32.

[0097] In the above-described embodiments, the force-modifying flexure 32 and the SMA wire 34 connect at one end to the support structure 10, and the coupling flexure 33 connects at one end to the movable part 20. In general, this arrangement may also be reversed, with the force-modifying flexure 32 and the SMA wire 34 connecting at one end to the movable part 20, and the coupling flexure 33 connecting at one end to the support structure 10.

[0098] Each actuating unit 30 comprise one or more planar components 32, 33, 34, 36, 37 each of which is oriented substantially parallel to the primary axis P.

[0099] Each actuating unit 30 has a 'vertical' configuration in that its extent when projected onto the primary axis P is ~10 times greater than its extent when projected onto at least one line in the movement plane XY.

[0100] In addition, the extent of each actuating unit 30 when projected onto the primary axis P substantially overlaps with the extent of the movable part 20 when projected onto the primary axis P.

[0101] The support structure 10 includes a a space which receives the movable part 20. Accordingly, the extent of the support structure 10 when projected onto the primary axis P substantially overlaps with the extent of the movable part 20 when projected onto the primary axis P. Similarly, the movable part 20 includes a space for receiving the lens assembly (not shown in Figures 2A and B).

[0102] Furthermore, each actuating unit 30 is elongate and has a length that is at least twice any transverse dimension (e.g. its length is ~4-5 times greater than its height).

[0103] The first connecting portion 36 includes a terminal portion 45 which is electrically connected to the SMA wire 34 via the force-modifying flexure 32 and the crimp 35. The actuator assembly 2 further includes a third connecting portion 43. The third connecting portion 43 is connected to the support structure 10 and includes a terminal portion 46 which is electrically connected to the SMA wire 34 via the crimp 15.

[0104] The terminal portions 45, 46 are for connecting to the controller 8 (Fig. 1A).

[0105] The bearing arrangement 40 includes four ball bearings 41.

[0106] Manufacture

[0107] Referring to Figures 3A, 3B and 4 a method of manufacturing an example of an actuator assembly 2 will now be described.

[0108] The method involves manufacturing certain components of the actuator assembly 2 from a single sheet 90 of metallic material, e.g. steel.

[0109] At a first step SI, the sheet 90 is patterned to produce therein features 91 corresponding, amongst other things, to the force-modifying flexure 32, the first connecting portion 36, the body portion 31, the coupling flexure 33, the second connecting portion 37 and the third connecting portion 44 of each actuating unit 30. In Figure 3A, these features are labelled for one of the four actuating units. The patterning may be carried out by etching or in any other suitable way.

[0110] At a second step S2, the patterned sheet 90 produced at step SI is bent so that some of the features 91 (including those corresponding to the force-modifying flexure 32, the first connecting portion 36, the body portion 31, the coupling flexure 33, the second connecting portion 37 and the third connecting portion 44 of each actuating unit 30) are all oriented substantially parallel to the same axis (i.e. 'upright').

[0111] At a third step S3, the support structure 10 and the movable part 20 are moulded and certain components of the bent sheet 90 produced at step S2 are insert moulded therein. In particular, each first connecting portion 36 and each third connecting portion 44 is insert moulded in the support structure 10, and each second connecting portion 37 is insert moulded in the movable part 20 (see also Figures 2A and B).

[0112] At a fourth step S4, one or more sacrificial portions of the sheet 90 are removed, leaving the desired components of the actuator assembly 2.

[0113] In some examples, the SMA wires 34 and the crimps 15, 35 may then be attached, e.g. using a process as described in WO2016 / 189314, which is incorporated herein by reference. In this example, the actuator assembly 2 includes some additional features which are not present in Figures 2A and 2B.

[0114] In particular, in two of the actuating units 30, the first connecting portions 36 and the third connecting portions 44 extend around a corner of the actuator assembly 2, so that their terminal portions 46, 47 are arranged on the same sides of the actuator assembly 2 as those of the other two actuating units 30. In other words, there are terminal portions 46, 47 on just two sides of the actuator assembly 2.

[0115] In addition, the actuator assembly 2 includes a set of four interconnects 101 for carrying electrical signals between the support structure 10 and the movable part 20. Each interconnect 101 includes a first portion 101a connected to the support structure 10, a second portion 101b connected to the movable part 20, and a flexure 101c between the first and second portions 101a, 101b. In Figure 3A, these features are labelled for one of the four interconnects 101. These interconnects 101 may be for carrying electrical signals to a further actuator, e.g. an autofocus actuator 60 (see Fig. 1).

[0116] The interconnects 101 may be similarly produced from the same sheet 90 as some of the other components of the actuator assembly 2. In particular, step SI may include patterning the sheet 90 to produce features 91 corresponding to the first portion 101a, the second portion 101b and the flexure 101c of each interconnect 101. Step S2 may include bending the patterned sheet 90 so that at least some of these features 91 are upright (in this example, not all of the parts of the interconnects 101 are bent upright, see Fig. 3B). Step S3 may include insert moulding features 91 corresponding to the first portion 101a of each interconnect 101 in the support structure 10, and insert moulding features 91 corresponding to the second portion 101b of each interconnect 101 in the movable part 20.

[0117] In this example, the force-modifying flexure 32 is arranged so that it is in tension rather than compression. This is achieved by providing an extension 36a on the first connection portion 36 and an extension 31a on the body portion 31, as illustrated.

[0118] Other examples of actuator assemblies

[0119] Referring in particular to Figure 5, another example of an actuator assembly 2' will now be described.

[0120] The actuator assembly 2' is similar to that described above. In particular, the actuator assembly 2' can be incorporated in an apparatus 1 (e.g. a camera apparatus 1) as described above with reference to Figure 1A, and the actuator assembly 2' has an arrangement of actuating units 30 that is broadly similar to that described above with reference to Figure IB. However, the actuator assembly 2 has different actuating units 30' as will now be described.

[0121] The actuator assembly 2' has actuating units 30' as illustrated in Figure 5. In particular, as will be appreciated, the actuator assembly 2' has actuating units 30' as illustrated in Figure 5 on two opposite sides of the actuator assembly 2' (e.g. the left and rights sides in Figure IB). Furthermore, the actuator assembly 2' has actuating units 30' on the other two sides that are mirror images of those illustrated in Figure 5 (wherein the mirror plane is perpendicular to the side and passes through the primary axis P, for example).

[0122] Each actuating unit 30' includes similar structural and functional features to those described above with particular reference to Figure 2A.

[0123] In particular, each actuating unit 30' comprises a force-modifying flexure 32', one end of which is connected to the body portion 31' and the other end of which is connected to the support structure 10 (see Fig. 1A) via a first connecting portion 36'. As explained in more detail above, the force-modifying flexure 32' effectively allows the body portion 31' to pivot relative to the support structure 10 (see Fig. 1A).

[0124] Each actuating unit 30' further comprises an SMA wire 34', one end of which is connected to the support structure 10 by a crimp 15' and the other end of which is connected to the body portion 31' by a crimp 35'.

[0125] Each actuating unit 30' further comprises a coupling flexure 33', one end of which is connected to the body portion 31' and the other end of which is connected to the movable part 20 (see Fig. IB) via a second connecting portion 37'.

[0126] As explained in more detail above, the SMA wire 34' is arranged, on contraction, to apply an input force on the body portion 31', and the force-modifying flexure 32' modifies the input force so as to cause the coupling flexure 33' to apply an actuating force to the movable part 20 (see Fig. IB). As explained in more detail above, the coupling flexure 33' is compliant in a direction perpendicular to the actuating force.

[0127] In contrast to the actuating unit 30 described above, the coupling flexure 33' and hence the actuating force is directed along a line that is parallel to the movement plane XY. Each actuating unit 30' may comprise one or more planar components 32', 33', 34', 36', 37' each of which is oriented substantially parallel to the primary axis P. Each actuating unit 30' may have a 'vertical' configuration as explained in more detail above. In addition, the extent of each actuating unit 30' when projected onto the primary axis P may substantially overlap with the extent of the movable part 20 (see Fig. 1A) when projected onto the primary axis P. Furthermore, each actuating unit 30' may be elongate and may have a length that is at least twice any transverse dimension (e.g. its length is ~4-5 times greater than its height).

[0128] In each actuating unit 30', the point at which the force-modifying flexure 32' is connected to the body portion 31' is between the point at which the SMA wire 34' is connected to the body portion 31' and the point at which the coupling flexure 33' is connected to the body portion 31'. Hence, each actuating unit 30' can be considered as a first-class lever.

[0129] Referring in particular to Figure 6, in an alternative example of an actuator assembly 2" (which is otherwise the same as the actuator assembly 2'), the point at which the SMA wire 34" is connected to the body portion 31" is between the point at which the force-modifying flexure 32" is connected to the body portion 31" and the point at which the coupling flexure 33" is connected to the body portion 31". Hence, each such actuating unit 30" can be considered as a third-class lever.

[0130] In each of the above-described examples, the force-modifying flexure 32', 32" is placed in tension on contraction of the SMA wire 34', 34", but it may alternatively be placed in compression.

[0131] In addition, in each of above-described examples, the force-modifying flexure 32', 32" and the SMA wire 34', 34" connect at one end to the support structure 10, and the coupling flexure 33', 33" connects at one end to the movable part 20. However, this arrangement may be reversed, with the force-modifying flexure 32', 32" and the SMA wire 34', 34" connecting at one end to the movable part 20, and the coupling flexure 33', 33" connecting at one end to the support structure 10. This may apply to some or all of the actuating units 30', 30".

[0132] Other variations

[0133] It will be appreciated that there may be many other variations of the above-described examples.

[0134] For example, instead of a coupling flexure 33, the actuator assembly 2 may have a different type of coupling link, e.g. a ball bearing or plain bearing configured to transmit the actuating force F to the movable part 20 while allowing movement of the movable part 20 in directions perpendicular to the actuating force F. Such alternative examples of the coupling link 33 are disclosed in WO 2022 / 084699 Al. The coupling link 33 may (or may not) be formed by an SMA wire, which may (or may not) be integral with the SMA wire 34 and may (or may not) be driven together with the SMA wire 34. Instead of the force-modifying flexure 32, the actuator assembly 2 may have a different type of force-modifying mechanism. Such a force-modifying element may include, for instance, a rigid member with one end connected to the support structure 10 via a suitable pivoting connection (e.g. a pin joint) and the other end connected to the body portion 31. Some examples of different force-modifying mechanisms are described in WO2022 / 084699, which is incorporated herein by reference.

[0135] SMA elements

[0136] The above-described SMA actuator assemblies comprise at least one SMA element. The term 'shape memory alloy (SMA)element' may refer to any element comprising SMA. The SMA element may be described as an SMA wire. The SMA element may have any shape that is suitable for the purposes described herein. The SMA element may be elongate and may have a round cross section or any other shape cross section. The cross section may vary along the length of the SMA element. The SMA element might have a relatively complex shape such as a helical spring. It is also possible that the length of the SMA element (however defined) may be similar to one or more of its other dimensions. The SMA element may be sheet-like, and such a sheet may be planar or non-planar. The SMA element may be pliant or, in other words, flexible. In some examples, when connected in a straight line between two components, the SMA element can apply only a tensile force which urges the two components together. In other examples, the SMA element may be bent around a component and can apply a force to the component as the SMA element tends to straighten under tension. The SMA element may be beam-like or rigid and may be able to apply different (e.g. non-tensile) forces to elements. The SMA element may or may not include material(s) and / or component(s) that are not SMA. For example, the SMA element may comprise a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term 'SMA element' may refer to any configuration of SMA material acting as a single actuating element which, for example, can be individually controlled to produce a force on an element. For example, the SMA element may comprise two or more portions of SMA material that are arranged mechanically in parallel and / or in series. In some arrangements, the SMA element may be part of a larger SMA element. Such a larger SMA element might comprise two or more parts that are individually controllable, thereby forming two or more SMA elements. The SMA element may comprise an SMA wire, SMA foil, SMA film or any other configuration of SMA material. The SMA element may be manufactured using any suitable method, for example by a method involving drawing, rolling, deposition, sintering or powder fusion. The SMA element may exhibit any shape memory effect, e.g. a thermal shape memory effect or a magnetic shape memory effect, and may be controlled in any suitable way, e.g. by Joule heating, another heating technique or by applying a magnetic field.

Claims

Claims1. An actuator assembly comprising: first and second parts which are movable relative to each other in at least one direction in a movement plane and are not movable relative to each other along a primary axis perpendicular to the movement plane; and one or more actuating units, each of which comprises: a force-modifying mechanism connected to the first part; a coupling link connected between the force-modifying mechanism and the second part; and an SMA element connected between the first part and the force-modifying mechanism for applying an input force on the force-modifying mechanism thereby causing the forcemodifying mechanism to apply an output force on the coupling link and causing the coupling link to apply an actuating force on the second part; wherein the extent of each actuating unit when projected onto the primary axis is greater than the extent of the actuating unit when projected onto at least one line in the movement plane.

2. An actuator assembly according to claim 1 wherein the extent of each actuating unit when projected onto the primary axis substantially overlaps with the extent of the second part when projected onto the primary axis.

3. An actuator assembly according to claim 1 or 2 wherein the extent of the first part when projected onto the primary axis substantially overlaps with the extent of the second part when projected onto the primary axis.

4. An actuator assembly according to any preceding claim wherein each actuating unit comprises one or more planar components each of which is oriented substantially parallel to the primary axis.

5. An actuator assembly comprising: first and second parts which are movable relative to each other in at least one direction in a movement plane and are not movable relative to each other along a primary axis perpendicular to the movement plane; and one or more actuating units, each of which comprises: a force-modifying mechanism connected to the first part; a coupling link connected between the force-modifying mechanism and the second part; andan SMA element connected between the first part and the force-modifying mechanism for applying an input force on the force-modifying mechanism thereby causing the forcemodifying mechanism to apply an output force on the coupling link and causing the coupling link to apply an actuating force on the second part; wherein the actuating force is directed along a line that is inclined at a non-zero angle to the movement plane.

6. An actuator assembly comprising: first and second parts which are movable relative to each other in at least one direction in a movement plane and are not movable relative to each other along a primary axis perpendicular to the movement plane; and one or more actuating units, each of which comprises: a force-modifying mechanism connected to the first part; a coupling link connected between the force-modifying mechanism and the second part; and an SMA element connected between the first part and the force-modifying mechanism for applying an input force on the force-modifying mechanism thereby causing the forcemodifying mechanism to apply an output force on the coupling link and causing the coupling link to apply an actuating force on the second part; wherein each actuating unit is elongate and has a length that is at least twice any transverse dimension.

7. An actuator assembly according to any preceding claim wherein each coupling link corresponds to a coupling flexure and each force-modifying mechanism corresponds to a force-modifying flexure.

8. An actuator assembly according to claim 7 wherein each force-modifying flexure is connected to the first part by way of a first connecting portion and each coupling flexure is connected to the second part by way of a second connecting portion.

9. An actuator assembly according to claim 8 wherein, in each actuating unit, the first connecting portion comprises a terminal portion electrically connected to one end of the SMA element via the forcemodifying flexure, wherein the terminal portion is for connecting to actuator control circuitry.

10. An actuator assembly according to claim 9 wherein each actuating unit comprises a third connecting portion, wherein the third connecting portion is connected to the second part and comprisesa terminal portion electrically connected to the other end of the SMA element, wherein the terminal portion is for connecting to actuator control circuitry.

11. An actuator assembly according to any one of claims 7 to 10 comprising one or more interconnects for carrying electrical signals between the first and second parts, wherein each interconnect comprises a first portion connected to the first part, a second portion connected to the second part, and a flexure between the first and second portions.

12. An actuator assembly according to any one of claims 7 to 11 wherein the force-modifying flexure, the first connecting portion, the coupling link and the second connecting portion of at least one actuating unit are all produced from a single sheet of material.

13. An actuator assembly according to claim 12 when dependent on claim 10 wherein the third connecting portion of the at least one actuating unit is produced from the sheet of material.

14. An actuator assembly according to claim 12 or 13 when dependent on claim 11 wherein the first portion, the second portion and the flexure of at least one interconnect are produced from the sheet of material.

15. An actuator assembly according to any preceding claim wherein each first connecting portion is insert moulded in the first part, and / or each second connecting portion is insert moulded in the second part.

16. An actuator assembly according to claim 15 when dependent on claim 10 wherein each third connecting portion is insert moulded in the first part.

17. An actuator assembly according to claim 15 or 16 when dependent on claim 11 wherein the portion of each interconnect is insert moulded in the first part, and / or the second portion of each interconnect is insert moulded in the second part.

18. An actuator assembly according to any preceding claim comprising a bearing arrangement configured to guide relative movement of the first and second parts in the at least one direction and to restrict relative movement of the first and second parts along the primary axis.

19. An actuator assembly according to claim 18 when dependent on claim 5 wherein the actuating force of the one or more actuating units acts as a loading force for the bearing arrangement.

20. An actuator assembly according to any preceding claim comprising at least two actuating units arranged to apply actuating forces on the second part in perpendicular directions such that the coupling link of each of the two actuating units is compliant in the direction of the actuating force of the other of the two actuating units.

21. An actuator assembly according to claim 20, comprising four actuating units arranged so as to be capable of moving the second part relative to the first part in any direction in a plane perpendicular to the primary axis without applying any net torque to the second part about the primary axis.

22. A camera assembly comprising an actuator assembly according to any preceding claim wherein one of the first and second parts comprises a lens with an optical axis parallel to the primary axis and the other of the first and second parts comprises an image sensor and the first and second parts are movable relative to each other so as to provide lens-shift optical image stabilisation.

23. A method of producing an actuating assembly according to any one of claims 15 to 17 when dependent on any one of claims 12 to 14, the method comprising: patterning the sheet of material to produce therein features corresponding to the forcemodifying flexure, the first connecting portion, the coupling flexure and the second connecting portion of the at least one actuating unit; bending the sheet so that the features corresponding to the force-modifying flexure, the first connecting portion, the coupling flexure and the second connecting portion of the at least one actuating unit are all oriented substantially parallel to the same axis; insert moulding in the first part each feature corresponding to the first connecting portion of the at least one actuating unit, and / or insert moulding in the second part each feature corresponding to the second connecting portion of the at least one actuating unit; and removing one or more sacrificial portions of the sheet of material so as to produce the forcemodifying flexure, the first connecting portion, the coupling flexure and the second connecting portion of the at least one actuating unit.

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