GB2569036A

GB2569036A - Assembly of shape memory alloy actuators

Info

Publication number: GB2569036A
Application number: GB1817743.6A
Authority: GB
Inventors: Eddington Robin; Henry Reddall Nicholas; Howarth James
Original assignee: Cambridge Mechatronics Ltd
Current assignee: Cambridge Mechatronics Ltd
Priority date: 2017-10-30
Filing date: 2018-10-30
Publication date: 2019-06-05
Anticipated expiration: 2038-10-30
Also published as: GB2569036B; GB201817743D0

Abstract

A Shape Memory Alloy (SMA) actuator comprises a moveable component able to move in two orthogonal directions perpendicular to a primary optical axis e.g. to provide Optical Image Stabilisation (OIS) for a miniature camera. The actuator comprises four SMA wires connected between the movable component and a support structure 102. The support structure 102 comprises a conductive component 104 such as a conductive layer to provide electrical terminals 108 and conduction paths to wire attach structures such as crimps 106. Terminals may be provided on a single side, or on two different sides of the support structure. The support structure 102 may be made from an insulator e.g. polymer, or may be provided with an insulating layer, or the conductive component may be attached using an insulating adhesive.

Description

The present application generally relates to shape memory alloy (SMA) actuators, and in particular to techniques for simplifying the manufacture/assembly or improving the construction of the SMA actuators.

In a first approach of the present techniques, there is provided a shape memory alloy (SMA) actuation apparatus comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component; and a total of four shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; the support structure comprising a conductive component comprising: electrical terminals and conduction paths for electrically connecting together each SMA actuator wire to control circuitry, and wire attach structures for coupling one end of each SMA actuator wire to the support structure.

In a second approach of the present techniques, there is provided a shape memory alloy (SMA) actuation apparatus comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component; and a total of four shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; the support structure comprising a conductive component comprising: electrical terminals and conduction paths for electrically connecting together each SMA actuator wire to control circuitry, and wire attach structures for coupling one end of each SMA actuator wire to the support structure; and the apparatus further comprising: a flexible printed circuit for electrically connecting the wire attach structures of the moveable component to an electrical common.

In a third approach of the present techniques, there is provided a shape memory alloy (SMA) actuation apparatus comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component; and a total of four shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; the support structure comprising a conductive component comprising: electrical terminals and conduction paths for electrically connecting together each SMA actuator wire to control circuitry, and wire attach structures for coupling one end of each SMA actuator wire to the support structure; and a suspension system supporting the moveable component on the support structure in said manner allowing movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to the notional primary axis, the suspension system comprising a plurality of flexible posts arranged parallel to the primary axis.

In a fourth approach of the present techniques, there is provided a shape memory alloy (SMA) actuation apparatus comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component; a total of four shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; the support structure comprising a conductive component comprising: electrical terminals and conduction paths for electrically connecting together each SMA actuator wire to control circuitry, and wire attach structures for coupling one end of each SMA actuator wire to the support structure; at least one bearing that bears the metal plate of the moveable component on the support structure, allowing movement of the metal plate relative to the support structure orthogonal to the primary axis; and at least one magnet to apply a force on the at least one bearing with a component of force parallel to the primary axis.

In a fifth approach of the present techniques, there is provided a shape memory alloy (SMA) actuation apparatus comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component; a total of four shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; the support structure comprising a conductive component comprising: electrical terminals and conduction paths for electrically connecting together each SMA actuator wire to control circuitry, and wire attach structures for coupling one end of each SMA actuator wire to the support structure; at least one bearing that bears the metal plate of the moveable component on the support structure, allowing movement of the metal plate relative to the support structure orthogonal to the primary axis; wherein the SMA actuator wires are angled relative to a plane perpendicular to the primary axis and, when powered, apply a force on the at least one bearing with a component of force parallel to the primary axis.

In a sixth approach of the present techniques, there is provided a shape memory alloy (SMA) actuation apparatus comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component; a total of four shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; and a conductive component for attaching the SMA actuator wires to the support structure and moveable component, the conductive component comprising: a sacrificial body portion, and eight wire attach structures held apart by the sacrificial body portion and holding the four SMA actuator wires by being folded and pressed over the SMA actuator wires, the sacrificial body portion being removable from the wire attach structures.

In a seventh approach of the present techniques, there is provided a method for manufacturing a shape memory alloy (SMA) actuation apparatus comprising: providing a support structure, a moveable component supported on the support structure in a manner allowing movement of the moveable relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component, and a total of four shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; providing a conductive component for attaching the SMA actuator wires to the support structure and moveable component, the conductive component comprising a sacrificial body portion, and eight wire attach structures held apart by the sacrificial body portion; attaching each of the four SMA actuator wires to two wire attach structures; attaching the wire attach structures to the support structure and moveable component; and removing the sacrificial body portion from the wire attach structures, leaving the wire attach structures attached to the support structure and the moveable component.

In an eighth approach of the present techniques, there is provided an apparatus comprising an SMA actuation apparatus of the types described herein.

The apparatus may be any one of: a smartphone, a camera, a foldable smartphone, a foldable image capture device, a foldable smartphone camera, a foldable consumer electronics device, an image capture device, a 3D sensing device or system, a consumer electronics device, a mobile computing device, a mobile electronic device, a laptop, a tablet computing device, an e-reader (also known as an e-book reader or e-book device), a computing accessory or computing peripheral device (e.g. mouse, keyboard, headphones, earphones, earbuds, etc.), a security system, a medical device (e.g. an endoscope), a gaming system, a gaming accessory (e.g. controller, headset, a wearable controller, etc.), an augmented reality system, an augmented reality device, a virtual reality system, a virtual reality device, a wearable device, a drone (aerial, water, underwater, etc.), an autonomous vehicle, and a vehicle (e.g. an aircraft, a spacecraft, a submersible vessel, a car, etc.). It will be understood that this is a non-exhaustive list of example apparatus.

The SMA actuation apparatus described herein may be used in devices/systems suitable for, for example, image capture, 3D sensing, depth mapping, aerial surveying, terrestrial surveying, surveying in or from space, hydrographic surveying, underwater surveying, scene detection, collision warning, security, medical imaging, facial recognition, augmented and/or virtual reality, advanced driver-assistance systems in vehicles, autonomous vehicles, gaming, gesture control/recognition, and robotic devices.

Preferred features are set out in the appended dependent claims.

Implementations of the present techniques will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1A shows a schematic cross-sectional view of a camera apparatus;

Figure IB shows a plan view of an arrangement of SMA actuator wires along the optical axis of the camera apparatus of Figure 1A;

Figure 1C shows a perspective view of an arrangement of SMA actuator wires in the camera apparatus of Figure 1A;

Figures 2A and 2B show, respectively, a plan view and a perspective view of a support structure comprising a conductive component ;

Figures 3A and 3B show, respectively, a perspective view of an alternative support structure comprising a conductive component, and a perspective view of a moveable component supported on the support structure ;

Figures 4A and 4B show perspective views of a spring plate of a moveable component formed from two materials, and Figure 4C shows a plan view of the spring plate;

Figure 5 shows elements of a support structure of an SMA actuation apparatus;

Figures 6A and 6B show perspective views of an SMA actuation apparatus comprising a flexible printed circuit;

Figure 7A shows a plan view of an SMA actuation apparatus comprising flexible posts to suspend the moveable component on the support structure, and Figure 7B shows a close-up view through a corner of the SMA actuation apparatus;

Figure 8A shows a cross-sectional view of a magnetic mechanism to apply a force/downforce on a bearing of an SMA actuation apparatus;

Figure 8B shows a cross-sectional view of a magnetic mechanism to couple together components of an SMA actuation apparatus;

Figure 9 shows a cross-sectional view of an angled SMA actuator wire arrangement to apply a force/downforce on a bearing of an SMA actuation apparatus; and

Figures 10A and 10B show plan views of, respectively, a conductive component for attaching SMA actuator wires to an SMA actuation apparatus, and the conductive component on an SMA actuation apparatus with a sacrificial body portion removed.

Broadly speaking, embodiments of the present techniques provide ways to simplify the manufacture/assembly, or improve the construction of, shape memory alloy (SMA) actuators. Advantageously, the present techniques may enable SMA actuators to be constructed from fewer components, which may simplify the manufacture and/or lower the cost of manufacture.

A shape memory alloy (SMA) actuator assembly for actuating movement of a movable element in two dimensions perpendicular to a primary axis is described in International Patent Publications WO2013/175197 and WO2014/083318 . Such actuators may be used for Optical Image Stabilization (OIS) in miniature cameras. These actuators comprise four SMA wires connected between a movable element and a fixed support. Each wire is connected at one of its ends to the movable element at a crimp (the moving crimp) and at its other end to the support structure (the static crimp). The actuator of WO2013/175197 is now described in more detail with reference to Figures 1A to 1C.

Figure IA shows a schematic cross-sectional view of a camera apparatus 1 that is an example of an SMA actuation apparatus, and is taken along the optical axis 0 (which is a notional, primary axis). In order to clearly describe the main parts of the camera apparatus 1, the SMA actuator wires are not shown in Figure IA, but subsequently described with reference to Figures IB and 1C. The camera apparatus 1 may be incorporated into any number of devices, such as a smartphone, a foldable smartphone, a foldable image capture device, a foldable smartphone camera, a foldable consumer electronics device, an image capture device, a 3D sensing device or system, a consumer electronics device, a mobile computing device, a mobile electronic device, a laptop, a tablet computing device, an e-reader (also known as an e-book reader or e-book device), a computing accessory or computing peripheral device, a security system, a medical device (e.g. an endoscope), a gaming system, a gaming accessory, an augmented reality system, an augmented reality device, a virtual reality system, a virtual reality device, a wearable device, a drone (aerial, water, underwater, etc.), an autonomous vehicle, and a vehicle (e.g. an aircraft, a spacecraft, a submersible vessel, a car, etc.). It will be understood that this is a non-exhaustive list of example apparatus. In some cases, miniaturisation is an important design criterion of the camera apparatus 1.

The camera apparatus 1 comprises a lens element 2 supported on a support structure 4 by a suspension system 7, in a manner allowing movement of the lens element 2 relative to the support structure 4 in two orthogonal directions each perpendicular to the optical axis 0. Thus, the lens element 2 is a moveable element/component.

The support structure 4 is a camera support supporting an image sensor 6 on the front side of the base 5 thereof. On the rear side of the base 5 there is mounted an IC (integrated circuit) chip 30 in which the control circuit 40 is implemented, and also a gyroscope sensor 47.

The lens element 2 comprises a lens carrier 21 in the form of a cylindrical body supporting a lens 22 arranged along the optical axis O, although in general any number of lenses 22 may be provided. The camera apparatus 1 is a miniature camera in which the lens 22 (or lenses 22 if plural lenses are provided) has a diameter of less than or equal to 10mm, preferably less than or equal to 20mm.

The lens element 2 is arranged to focus an image onto the image sensor 6. The image sensor 6 captures the image and may be of any suitable type, for example a CCD (charge-coupled device) ora CMOS (complimentary metal-oxidesemiconductor) device.

The lens(es) 22 may be fixed relative to the lens carrier 21, or alternatively may be supported on the lens carrier in a manner in which the lens 22 (or at least one lens 22 if plural lenses are provided) is moveable along the optical axis O, for example to provide focussing. Where the lens 22 is moveable along the optical axis O, a suitable actuation system (not shown) may be provided, for example using a voice coil motor or SMA actuator wires, such as that described in International Patent Publication No. WO2007/113478.

In operation, the lens element 2 is moved orthogonally to the optical axis O in two orthogonal directions, shown as X and Y relative to the image sensor 6, with the effect that the image on the image sensor 6 is moved. This is used to provide optical image stabilisation (OIS), compensating for image movement of the camera apparatus 1, caused by, for example, hand shake.

In many known arrangements using SMA actuator wire to provide an OIS function, for example as disclosed in International Patent Publications W02010/029316 and W02010/089529, the OIS is provided by tilting the entire camera unit including the lens element and the image sensor, substantially as a rigid body. This method of compensating for user handshake does in principle give the best OIS performance, because aligning the lens element to the image sensor is difficult in miniature cameras and the manufacturing tolerances are very tight. In addition, the user handshake being compensated for is essentially a tilt to the camera, and so it makes intuitive sense that the compensation should also tilt the camera. However, in this example, OIS is performed differently in order to mitigate several other problems.

The first problem is that with the 'camera tilt' method, the image sensor is moving, relative to the fixed camera structure. This presents extreme difficulties in routing electrical connections from the image sensor to the fixed structure of the camera, and onto the mobile phone motherboard. Solutions to this centre around flexible printed circuits (FPCs) to route connections, but the FPC design remains challenging, owing to the large number of connections, and the high data rates. Therefore, it is highly desirable for the image sensor to remain stationary and fixed.

The second problem is that the camera tilt method implies that there is a camera structure comprising as a minimum the lens and image sensor, with support structures that must tilt inside a surrounding support structure. Because the camera has a finite footprint, the tilt of the camera means that the camera thickness (height) of the OIS camera must be greater than for an equivalent camera without OIS. In mobile phones, it is highly desirable to minimise the camera height.

The third problem is that by tilting the whole camera, it is difficult to package the tilting actuators without increasing the footprint of the camera over that of the camera without OIS.

Accordingly, in Figure IA the lens element 2 is moved linearly in two orthogonal directions, both perpendicular to the optical axis 0 which may be termed shift or OlS-shift. The resulting image compensation does not entirely reverse the effects of user handshake, but the performance is deemed sufficiently good, given the constraints described above, and in particular allows the size of the camera apparatus 1 to be reduced as compared to an apparatus using tilt.

Figure IB shows a plan view of an arrangement of SMA actuator wires along the optical axis of the camera apparatus of Figure IA. Each of the SMA actuator wires 11 to 14 is arranged along one side of the lens element 2. Thus, the SMA actuator wires 11 to 14 are arranged in a loop at different angular positions around the optical axis 0. Thus, the four SMA actuator wires 11 to 14 consist of a first pair of SMA actuator wires 11 and 13 arranged on opposite sides of the optical axis 0 and a second pair of SMA actuator wires 12 and 14 arranged on opposite sides of the optical axis 0. The first pair of SMA actuator wires 11 and 13 are capable on selective driving to move the lens element 2 relative to the support structure 4 in a first direction in said plane, and the second pair of SMA actuator wires 12 and 14 are capable on selective driving to move the lens element 2 relative to the support structure 4 in a second direction in said plane transverse to the first direction. Movement in directions other than parallel to the SMA actuator wires 11 to 14 may be driven by a combination of actuation of these pairs of the SMA actuator wires 11 to 14 to provide a linear combination of movement in the transverse directions. Another way to view this movement is that simultaneous contraction of any pair of the SMA actuator wires 11 to 14 that are adjacent each other in the loop will drive movement of the lens element 2 in a direction bisecting those two of the SMA actuator wires 11 to 14 (diagonally in Figure IB, as labelled by the arrows X and Y).

As a result, the SMA actuator wires 11 to 14 are capable of being selectively driven to move the lens element 2 relative to the support structure 4 to any position in a range of movement in two orthogonal directions perpendicular to the optical axis O. The magnitude ofthe range of movement depends on the geometry and the range of contraction ofthe SMA actuator wires 11 to 14 within their normal operating parameters.

Figure 1C shows a perspective view of an arrangement of SMA actuator wires in the camera apparatus of Figure 1A. The actuator arrangement 10 comprises a total of four SMA actuator wires 11 to 14 connected between a support block 16 that forms part of the support structure 4 and is mounted to the base 5 and a movable platform 15 that forms part of the lens element 2 and is mounted to the rear ofthe lens plate 73 as shown in Figure 1A.

Each of the SMA actuator wires 11 to 14 is held in tension, thereby applying a force between the movable platform 15 and the support block 16 in a direction perpendicular to the optical axis 0. In operation, the SMA actuator wires 11 to 14 move the lens element 2 relative to the support block 16 in two orthogonal directions perpendicular to the optical axis 0.

The SMA actuator wires 11 to 14 are connected at one end to the movable platform 15 by respective crimping members 17 and at the other end to the support block 16 by crimping members 18. The crimping members 17 and 18 crimp the wire to hold it mechanically, optionally strengthened by the use of adhesive. The crimping members 17 and 18 also provide an electrical connection to the SMA actuator wires 11 to 14. However, any other suitable means for connecting the SMA actuator wires 11 to 14 may alternatively be used.

The present techniques provide improvements to the design and assembly of an actuator and camera module of the type shown in Figures IA to 1C.

In the following, the term support structure is used interchangeably herein with the term static component.

One technique for connecting the crimps of the support structure/static component to control circuitry (to enable the SMA actuator wires held by the crimps to be powered/driven), is by using a flexible printed circuit (FPC). However, the FPC is an expensive component and it is necessary to solder the FPC to the crimps and electrical terminals, which is a difficult process. Therefore, it is desirable to remove the need for the FPC to connect the static crimps (i.e. the crimps of the support structure/static component) to control circuitry. Figures 2A and 2B show, respectively, a plan view and a perspective view of a portion 100 of a support structure comprising a conductive component 104. The conductive component 104 comprises electrical terminals 108, conduction paths and wire attach structures 106. The conductive component 104 is an alternative to the FPC.

The conductive component 104 is part of the support structure of the SMA actuation assembly, and comprises four wire attach structures 106 for coupling one end of each of four SMA actuator wires to the support structure. The wire attach structures 106 (which may be crimps) are provided in pairs at opposite corners of the conductive component 104. The conductive component 104 also comprises electrical terminals 108 and conduction paths (as indicated by the arrows) for electrically coupling together each SMA actuator wire (i.e. via the wire attach structure 106) to control circuitry. A flexible printed circuit (FPC) may be used to connect the electrical terminals 108 to control/drive circuitry, to enable each SMA actuator wire to be driven. The terminals 108 may be foldable tabs which are able to fold down and connect to an FPC (not shown). Each wire attach structure 106 is connected to a terminal 108a,b,d,e via a separate conduction path, such that each SMA actuator wire can be driven separately/individually.

The conductive component 104 may comprise one terminal 108a-d for each of the four SMA actuator wires and two additional connectors 108c,f to provide an electrical common. The conduction paths for each wire attach structure 106 to the associated connector 108a-d are isolated from each other by gaps 107 in the conductive component 104 - the gaps 107 may be formed by etching the conductive component 104. As shown in Figures 2A and 2B, the terminals 108 may be provided on two sides of the conductive component 104. The two sides may be adjacent sides or opposing sides. Alternatively, the terminals 108 may be provided on a single side of the conductive component 104.

Since the conductive component 104 comprises the terminals 108 and the wire attach structures 106, the conductive component 104 both holds the SMA actuator wires in position and enables the SMA actuator wires to be connected to control circuitry. Therefore, the conductive component 104 avoids the need for a separate FPC, and advantageously simplifies the construction of the SMA actuation apparatus.

Thus, Figures 2A and 2B show how track connections may be provided on an etched component 104. As mentioned above, the etched component 104 may reduce the cost of carrying connections from the camera PCB tabs to the 4 SMA wire crimps and the spring foot weld locations. This may be achieved by using the same etched and formed component that crimps the wires to conduct to the camera PCB. Separate conduction paths are created as the crimps/wire attach structures 106 and terminals 108 are cut from a frame or sacrificial body portion of the conductive/etched component 104.

The support structure may comprise one or more bearings 109 which facilitate the movement of the moveable component relative to the support structure.

The support structure may comprise a mechanical support component 102. Figures 2A and 2B show one form of support component. The conductive component 104 is supported on, and attached to, the support component 102. The support component 102 must be electrically-isolated. Thus, the support component 102 may be formed of an insulator (e.g. a polymer) and the conductive component 104 may be attached to the support component 102 by an adhesive. Alternatively, the support component 102 may be formed of a metal or metal alloy, and the conductive component 104 may be attached to the support component 102 by an electrically insulative adhesive material. Alternatively, the support component 102 may have a laminate structure, comprising a layer of insulating material provided on a metal structural layer. The conductive component 104 may be attached to the layer of insulating material by an adhesive.

Figures 3A and 3B show, respectively, a perspective view of an alternative support structure comprising a conductive component, and a perspective view of a moveable component supported on the support structure.

A portion 200 of the support structure is shown. Support structure comprises a support component 202 and a conductive component 204. The conductive component 204 comprises four wire attach structures 206 for coupling one end of each of four SMA actuator wires 208 to the support structure/static component. The wire attach structures 206 (which may be crimps) are provided in pairs at opposite corners of the conductive component 204. The conductive component 204 may comprise terminals 210 and conduction paths for electrically connecting each SMA actuator wire to control circuitry. The terminals 210 may be foldable tabs which are able to fold down and connect to control circuitry. A flexible printed circuit (FPC) may be used to connect the electrical terminals 210 to control/drive circuitry, to enable each SMA actuator wire to be driven. Each wire attach structure 206 is connected to a terminal 210 via a separate conduction path, such that each SMA actuator wire can be driven separately/individually. The conductive component 204 may comprise one terminal 210 for each of the four SMA actuator wires 208. The conduction paths for each wire attach structure 206 to the associated terminal 210 may be formed by etching the conductive component 204. As shown in Figures 3A and 3B, the terminals 210 may be provided on two sides of the conductive component 204. The two sides may be adjacent sides or opposite sides. Alternatively, all the terminals 210 may be provide on one side of the conductive component 204.

The conductive component 204 may be formed of a material that is both conductive and suitable for attaching to SMA actuator wires 208. Thus, conductive component 204 may be formed from phosphor bronze, as this material is suitable for forming wire attach structures 206.

The support structure may comprise a mechanical support component 202. Figures 3A and 2B show another form of support component. The conductive component 204 is supported on, and attached to, the support component 202. The support component 202 must be electrically-isolated. Thus, the support component 202 may be formed of an insulator (e.g. a polymer) and the conductive component 104 may be attached to the support component 102 by an adhesive. In embodiments where the SMA actuation apparatus described herein is used in a camera assembly, the support component 202 may be a sensor bracket which holds/supports an image sensor of the camera.

The arrangement shown in Figures 3A and 3B may solve the problem of the cost of having an FPC layer to make the electrical connections. The solutions shown here comprise having terminals on two sides, which allows connection to the phosphor bronze layer 204 directly, and bending the terminals of the conductive component 104 down from the spring foot, which allows connection to them directly.

Figure 3B shows how a part of a moveable component of an SMA actuator may be supported on the support structure. The moveable component may comprise a metal spring plate 212 which is able to move relative to the support structure. The metal spring plate may comprise flexure arms 216 which extend from the metal spring plate and which are connected to the conductive component 204 of the support structure. The moveable component may also comprise wire attach structures 214 for coupling another end of each SMA actuator wire to the moveable component.

Thus, the present techniques provide a shape memory alloy (SMA) actuation apparatus comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component; and a total of four shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; the support structure comprising a conductive component comprising: electrical terminals and conduction paths for electrically connecting together each SMA actuator wire to control circuitry, and wire attach structures for coupling one end of each SMA actuator wire to the support structure.

The electrical terminals of the conductive component may be provided on one side of the conductive component.

Alternatively, the electrical terminals of the conductive component may be provided on a first side and a second side of the conductive component. The electrical terminals on the first side of the conductive component comprise terminals for two of the four SMA actuator wires and a common terminal, and the electrical terminals on the second side of the conductive component comprise terminals for the remaining two of the four SMA actuator wires and a common terminal. The first side may be adjacent to the second side, such that the electrical terminals are on adjacent sides of the conductive component. Alternatively, the first side is opposite to the second side, such that the electrical terminals are on opposing sides of the conductive component. If the SMA actuation apparatus is used as part of a camera assembly, then image noise issues that arise due electrical interference with the image sensor of the camera assembly may be reduced if the electrical terminals are on adjacent sides of the conductive component or along a single side of the conductive component.

The conductive component may be formed of any material which is suitable for welding, forming, crimping, and/or etching. In embodiments, the conductive component may be formed of steel or stainless steel. The conduction paths for each SMA actuator wire may be formed in the conductive component by etching the conductive component e.g. using a chemical etching or laser etching process.

The support structure may further comprise a support component, and the conductive component is attached to the support component. The support component may be an electrically-isolated support component. In embodiments, the electrically-isolated support component may be a sensor bracket.

In embodiments, the electrically-isolated support component may be formed of an insulative material (e.g. a polymer) and the conductive component may be attached to the electrically-isolated support component by an adhesive. Alternatively, the electrically-isolated support component may have a laminate structure, comprising a layer of insulating material provided on a metal structural layer. The conductive component may be attached to the layer of insulating material by an adhesive. The layer of insulating material may have a thickness of less than 20pm, and preferably less than or equal to 10pm, and the metal structural layer may have a thickness of less than 100pm, and preferably less than or equal to 50pm.

In embodiments, the support component may be formed of metal or metal alloy, and the conductive component may be attached to the metal support component using an electrically insulating adhesive.

Figures 4A and 4B show perspective views of a spring plate of a moveable component formed from two materials, and Figure 4C shows a plan view of the spring plate.

In embodiments, a moveable component of an SMA actuation apparatus may comprise a metal spring plate 302 comprising flexure arms 307 extending from the metal spring plate 302. The flexure arms 307 are typically connected to the conductive component 104, 204 of the support structure. The flexure arms 307 may be connected to the portion of the conductive component 104 which is connected to an electrical common (i.e. an OIS common). The moveable component may comprise wire attach structures 304 for coupling another end of each SMA actuator wire to the moveable component.

As mentioned above, ideally, the wire attach structures/crimps 304 are formed from a material that is suitable for forming a good electrical and mechanical connection to the SMA actuator wires without damaging the wires. However, the spring arms/flexure arms 307 are ideally be formed from a resilient material. If the flexure arms 307 and wire attach structures 304 are formed from a single material and as a single component, the height of the actuation assembly may be reduced but a single material may not satisfy the material requirements for both the wire attach structures 304 and the flexure arms 307. A solution to this problem is shown in Figures 4A and 4B: Weld two metals (e.g. one high yield for the spring arms 307 to one ductile for the crimps 304).

A frame 300 may comprise a sacrificial body portion and wire attach structures 304. The frame 300 may be used to ensure the wire attach structures 304 are spaced apart from each other by the required distance during the welding process. A metal spring plate 302 comprising flexure arms 307 is welded to the wire attach structures 304, where the weld points are indicated by arrows 306.

The wire attach structures 304 are then detached (e.g. by cutting) from the sacrificial body portion of the frame 300, as shown in Figure 4B.

In embodiments, the metal spring plate and flexure arms are formed of a first material, and the wire attach structures may be formed of a second material. The first material may be a resilient material, and the second material may be a ductile material. The first material may be stainless steel, and the second material may be a softer steel or softer stainless steel, in one particular example.

Figure 5 shows elements of a support structure 400 of an SMA actuation apparatus. Generally speaking, if an SMA actuation apparatus is used as part of a camera assembly (e.g. to provide autofocus and/or optical image stabilisation), image noise may arise due to electromagnetic interference with an image sensor caused by the SMA actuator wires being driven using pulse width modulated (PWM) drive signals. However, a problem arises if shielding for PWM image noise is provided by having a number of shield layers underneath the current carrying layers because these shield layers increase the actuator z-height. Figure 5 shows one way to reduce image noise without increasing the height of the SMA actuation apparatus.

In embodiments therefore, the SMA actuation apparatus may be a camera apparatus further comprising an image sensor fixed to the support structure, and the moveable component comprises a camera lens element comprising at least one lens arranged to focus an image on the image sensor, the primary axis being the optical axis of the camera lens element. Four SMA actuator wires 406 may be driven using pulse width modulated (PWM) drive signals. In such embodiments, the conductive component 104 may be supported on a support component 102, as previously described. The support component 102 may shield the image sensor from the SMA actuator wires 406 and from the conductive component 104. The support component 102 may have a laminate structure comprising a layer of insulation/insulating material (e.g. of thickness lOpm) provided on top of a metal structural layer (e.g. of thickness 50pm and possibly formed of stainless steel). The layer of insulating material may have a thickness of less than 20pm, and preferably less than or equal to 10pm, and the structural layer may have a thickness of less than lOOpm, and preferably less than or equal to 50pm.

The support structure 400 may further comprise a base layer 402, where the support component 102 is supported on, and attached to, the base layer 402. The base layer 402 may electrically isolate the image sensor from the SMA actuator wires 406 and other conductive elements (e.g. conductive component 104). Thus, in embodiments, the support component 102 may form a thin secondary shielding layer in addition to the shielding provided by the main Base Plate/base layer 402.

In embodiments, the base layer 402 may be formed from stainless steel and may provide the shielding functionality by being coated with a layer of copper/copper-plated. In alternative arrangements, the support structure 102 may be formed of or coated with copper in addition to, or instead of, having a copper-plated base layer 402.

As mentioned above with reference to Figures 4A to 4C, the moveable component may comprise spring arms or a bias spring. A problem with using bias springs in the optical image stabilisation (OIS) part of an SMA actuator is that they limit the footprint reduction of the OIS part (and space available for welding externally). In other words, it would be useful to remove the bias springs in order to reduce the overall size of the SMA actuator. However, removing the bias spring from the OIS requires an alternative method for:

1. Connecting the moving crimps to an OIS common (and connecting to the AF in embodiments where the bias spring also connects to the AF)

2. Providing downforce on the OIS bearings for low tilt

3. Providing a centring spring

Some possible alternatives to the bias spring arms are now described with reference to Figures 6A to 9. In the embodiments shown in Figures 6A to 9, the moveable component comprises: a metal plate, and wire attach structures for coupling another end of each SMA actuator wire to the moveable component.

Figures 6A and 6B show perspective views of an SMA actuation apparatus 500 comprising a flexible printed circuit 506. The SMA actuation apparatus may comprise a screening can 502 to protect the actuation assembly, and a lens holder 504. Here, an FPC 506 is used to connect from the static portion to the AF. The FPC 506 can also carry OIS common as well as all the connections required for the AF (open or closed loop). The FPC 506 comprises a section 510 which can connect to the OIS common, and a section 508 which connects to the electrical terminals on the AF component. The FPC 506 therefore satisfies requirement 1 above, but may not provide a downforce to compensate for the pre-load provided by the spring arms (requirement 2) or a centring function (requirement 3). Thus, the FPC 506 may need to be combined with other components to meet all the requirements.

The SMA actuation apparatus may comprise a flexible printed circuit for electrically connecting the wire attach structures of the moveable component to an electrical common (i.e. the OIS common).

Figure 7A shows a plan view of an SMA actuation apparatus 600 comprising flexible posts 602 to suspend the moveable component 606 on the support structure 604, and Figure 7B shows a close-up view through a corner of the SMA actuation apparatus. Section A-A is taken diagonally through a corner of the apparatus 600. Here, the spring arms are replaced by posts (stilts) 602 in the corners of the OIS to connect directly from the static portion to the AF. These same stilts 602 could replace the centring springs within the OIS (also carrying OIS common to the moving portion) enabling further size reduction. The posts 602 may be flexible posts or flexures, which are integrated with the AF. The flexible posts 602 meet all three requirements above.

Thus, in embodiments, the SMA actuation apparatus may comprise a suspension system supporting the moveable component on the support structure in said manner allowing movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to the notional primary axis, the suspension system comprising a plurality of flexible posts arranged parallel to the primary axis.

The plurality of flexible posts may electrically couple together the wire attach structures of the moveable component to an electrical common (i.e. OIS common). The plurality of flexible posts may provide a centring function.

Figure 8A shows a cross-sectional view of a magnetic mechanism to apply a force/downforce on a bearing of an SMA actuation apparatus, and thereby replace the spring arms. Here, one or more magnets 700 are provided to apply a downforce on bearings 702. Thus, the problem of how to replace the spring arms is solved by using magnetic attraction to provide both the downforce on the bearing(s) and centring.

Thus, in embodiments, the SMA actuation apparatus comprises at least one bearing that bears the metal plate of the moveable component on the support structure, allowing movement of the metal plate relative to the support structure orthogonal to the primary axis; and at least one magnet to apply a force on the at least one bearing with a component of force parallel to the primary axis of the SMA actuation apparatus.

Figure 8B shows a cross-sectional view of a magnetic mechanism to couple together components of an SMA actuation apparatus. Could use AF magnets 700 to attract an OIS moving part 704 to a ferritic static OIS part 706 (e.g. 420 SST).

Figure 9 shows a cross-sectional view of an angled SMA actuator wire arrangement to apply a force/downforce on a bearing of an SMA actuation apparatus. Here, the problem of how to replace the spring arms is solved by dimensioning the moving crimps 900 to always be higher than the static crimps 902, such that the SMA actuator wire 906 held between the crimps 900, 902 will provide a downforce on the OIS bearings when the OIS is powered.

Thus, in embodiments, the SMA actuation apparatus may comprise at least one bearing that bears the metal plate of the moveable component on the support structure, allowing movement of the metal plate relative to the support structure orthogonal to the primary axis; wherein the SMA actuator wires are angled relative to a plane perpendicular to the primary axis and, when powered, apply a force on the at least one bearing, with a component of force parallel to the primary axis of the SMA actuation apparatus.

In each of the above-described techniques, the SMA actuator wire may be attached to the crimps/wire attach structures once the SMA actuator has been assembled, i.e. once the moveable component has been supported on the support structure. However, it is difficult to insert the SMA actuator wire once the other components have been assembled. Therefore, a technique for improving the wire attachment process is now described.

Figures 10A and 10B show plan views of, respectively, a conductive component 800 for attaching SMA actuator wires to an SMA actuation apparatus, and the conductive component 800 on an SMA actuation apparatus with a sacrificial body portion removed. The conductive component 800 is for attaching the SMA actuator wires 808 to the support structure (i.e. to wire attach structures 812) and moveable component (i.e. to wire attach structures 810). The conductive component 800 comprises a sacrificial body portion 802, and eight wire attach structures 810, 812 held apart by the sacrificial body portion. There are four wire attach structures 810 for coupling one end of each SMA actuator wire

808 to the moveable component, and four wire attach structures 812 for coupling the other end of each SMA actuator wire 808 to the support structure/static component. Each wire attach structure 810, 812 may hold the four SMA actuator wires 808 by being folded and pressed over the SMA actuator wires 808. The sacrificial body portion 802 holds the wire attach structures 810, 812 at the required distance apart from each other and in a required position/orientation. The sacrificial body portion 802 is removable from the wire attach structures 810, 812.

As shown in Figure 10B, once the SMA actuator wires 808 have been crimped, the entire conductive component 800 may be provided over an assembled SMA actuator. The assembled SMA actuator comprises a static component/support structure 816 and a metal plate 814 of a moveable component. (The metal plate 814 may comprise spring arms/flexure arms). The conductive component 800 may be aligned over the SMA actuator and the wire attach structures 810, 812 may be attached to the moveable component and support structure by welding. The crimps 810,812 may then be detached from the frame 802.

Thus, this technique allows crimping off-board. The structural laminate layer may only be required to hold the static crimps together for wiring. This structural function could be performed by the main Base Plate layer after the wire is crimped. Thus, the SMA actuator wires 808 may be crimped into a frame 802 off board from the actuator. These crimps can then be welded to the rest of the actuator and detabbed from their carrier frame 802. The laser weld points are indicated by circles 806, and the laser detabs are indicated by circles 804.

The present techniques may provide a shape memory alloy (SMA) actuation apparatus comprising: a support structure; a moveable component supported on the support structure in a manner allowing movement of the moveable relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component; a total of four shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; and a conductive component for attaching the SMA actuator wires to the support structure and moveable component, the conductive component comprising: a sacrificial body portion, and eight wire attach structures held apart by the sacrificial body portion and holding the four SMA actuator wires by being folded and pressed over the SMA actuator wires, the sacrificial body portion being removable from the wire attach structures.

There is also provided a method for manufacturing a shape memory alloy (SMA) actuation apparatus comprising: providing a support structure, a moveable component supported on the support structure in a manner allowing movement of the moveable relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component, and a total of four shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; providing a conductive component for attaching the SMA actuator wires to the support structure and moveable component, the conductive component comprising a sacrificial body portion, and eight wire attach structures held apart by the sacrificial body portion; attaching each of the four SMA actuator wires to two wire attach structures; attaching the wire attach structures to the support structure and moveable component; and removing the sacrificial body portion from the wire attach structures, leaving the wire attach structures attached to the support structure and the moveable component.

Further embodiments of the present techniques are set out in the following numbered clauses:

1. An SMA actuator assembly wherein electrical connections between the camera PCB and four SMA wires are made at static crimps on a single connector component etched and formed to provide four separate conduction paths to the four static crimps.

2. An SMA actuator assembly of clause 1 wherein the connector component is supported on an insulating support layer.

3. An SMA actuator assembly of clause 2 wherein the support layer is a laminate of an insulator on top of a structural layer.

4. The SMA actuator assembly of clause 3 wherein the laminate acts as a PWM noise shield.

5. The SMA actuator assembly of clause 4 wherein the insulator layer has a thickness of less than 20 microns, preferably 10 microns or less, and the structural layer has a thickness of less than 100 microns, preferably 50 microns or less.

6. A camera assembly for autofocus and OIS wherein the OIS actuator is a an SMA wire actuator and connections to the autofocus mechanism and to the moving crimps of the OIS mechanism are made through a single FPC.

7. A camera assembly for autofocus and OIS wherein the OIS actuator is an SMA wire actuator and the movable element is suspended on the support structure by flexible posts at the corners which act as electrical connectors to the AF

8. A camera assembly for autofocus and OIS wherein the OIS actuator is an SMA wire actuator and the movable element is suspended on the support structure by flexible posts at the corners wherein the posts provide a centring function

9. A camera assembly for autofocus and OIS wherein the OIS actuator is an SMA wire actuator and the movable element is suspended on the support structure by flexible posts at the corners which act as electrical connectors to the AF and also provide a centring function.

10. An SMA wire actuator assembly wherein the downforce on to the bearings is provided by the AF magnets.

11. The SMA wire actuator assembly of clause 10 wherein the static OIS part is a ferritic stainless steel, preferably of the 420 type.

12. An SMA wire actuator assembly wherein the downforce on to the bearings is provided by inclined OIS wires.

Those skilled in the art will appreciate that while the foregoing has described what is considered to be the best mode and where appropriate other modes of performing present techniques, the present techniques should not be limited to 5 the specific configurations and methods disclosed in this description of the preferred embodiment. Those skilled in the art will recognise that present techniques have a broad range of applications, and that the embodiments may take a wide range of modifications without departing from any inventive concept as defined in the appended claims.

Claims

1. A shape memory alloy (SMA) actuation apparatus comprising:

a support structure;

a moveable component supported on the support structure in a manner allowing movement of the moveable relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component; and a total of four shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component;

the support structure comprising a conductive component comprising: electrical terminals and conduction paths for electrically connecting together each SMA actuator wire to control circuitry, and wire attach structures for coupling one end of each SMA actuator wire to the support structure.

2. The SMA actuation apparatus as claimed in claim 1 wherein the electrical terminals of the conductive component are provided on one side of the conductive component.

3. The SMA actuation apparatus as claimed in claim 1 wherein the electrical terminals of the conductive component are provided on a first side and a second side of the conductive component.

4. The SMA actuation apparatus as claimed in claim 3 wherein the electrical terminals on the first side of the conductive component comprise terminals for two of the four SMA actuator wires and a common terminal, and the electrical terminals on the second side of the conductive component comprise terminals for the remaining two of the four SMA actuator wires and a common terminal.

5. The SMA actuation apparatus as claimed in claim 3 or 4 wherein the first side is adjacent to the second side.

6. The SMA actuation apparatus as claimed in claim 3 or 4 wherein the first side is opposite to the second side.

7. The SMA actuation apparatus as claimed in any preceding claim wherein the conductive component is formed of steel or stainless steel.

8. The SMA actuation apparatus as claimed in any preceding claim wherein the conduction paths for each SMA actuator wire are formed by etching the conductive component.

9. The SMA actuation apparatus as claimed in any preceding claim wherein the support structure further comprises an electrically-isolated support component, and the conductive component is attached to the electrically-isolated support component.

10. The SMA actuation apparatus as claimed in claim 9 where the electricallyisolated support component is a sensor bracket.

11. The SMA actuation apparatus as claimed in claim 9 wherein the electricallyisolated support component is formed of a polymer and the conductive component is attached to the electrically-isolated support component by an adhesive.

12. The SMA actuation apparatus as claimed in claim 9 wherein the electricallyisolated support component has a laminate structure, comprising a layer of insulating material provided on a metal structural layer, and wherein the conductive component is attached to the layer of insulating material by an adhesive.

13. The SMA actuation apparatus as claimed in claim 12 wherein the layer of insulating material has a thickness of less than 20pm, and preferably less than or equal to 10pm, and the metal structural layer has a thickness of less than lOOpm, and preferably less than or equal to 50pm.

14. The SMA actuation apparatus as claimed in any one of claims 1 to 8 wherein the support structure further comprises a metal support component, and the conductive component is attached to the metal support component using an electrically insulating adhesive.

15. The SMA actuation apparatus as claimed in any one of claims 11 to 14 wherein the support structure further comprises a base layer, wherein the support component is attached to the base layer.

16. The SMA actuation apparatus as claimed in any preceding claim wherein the SMA actuation apparatus is a camera apparatus further comprising an image sensor fixed to the support structure, and the moveable component comprises a camera lens element comprising at least one lens arranged to focus an image on the image sensor, the primary axis being the optical axis of the camera lens element.

17. The SMA actuation apparatus as claimed in claim 16, when dependent on any one of claims 12 to 14, wherein the four SMA actuator wires are driven using pulse width modulated (PWM) drive signals, and wherein the support structure shields the image sensor from the SMA actuator wires.

18. The SMA actuation apparatus as claimed in claim 16, when dependent on claim 15, wherein the four SMA actuator wires are driven using pulse width modulated (PWM) drive signals, and wherein the base layer shields the image sensor from the SMA actuator wires.

19. The SMA actuation apparatus as claimed in any preceding claim wherein the moveable component comprises:

a metal spring plate comprising flexure arms extending from the metal spring plate and connected to the conductive component of the support structure; and wire attach structures for coupling another end of each SMA actuator wire to the moveable component.

20. The SMA actuation apparatus as claimed in claim 19 wherein the metal spring plate and flexure arms are formed of a first material, and the wire attach structures are formed of a second material.

21. The SMA actuation apparatus as claimed in claim 20 wherein the first material is a resilient material, and the second material is a ductile material.

22. The SMA actuation apparatus as claimed in claim 20 or 21 wherein the first material is stainless steel, and the second material is a softer steel or softer stainless steel.

23. The SMA actuation apparatus as claimed in any one of claims 1 to 18 wherein the moveable component comprises:

a metal plate; and wire attach structures for coupling another end of each SMA actuator wire to the moveable component.

24. The SMA actuation apparatus as claimed in claim 23 further comprising:

a flexible printed circuit for electrically connecting the wire attach structures of the moveable component to an electrical common.

25. The SMA actuation apparatus as claimed in claim 23 further comprising a suspension system supporting the moveable component on the support structure in said manner allowing movement of the moveable component relative to the support structure in two orthogonal directions perpendicular to the notional primary axis, the suspension system comprising a plurality of flexible posts arranged parallel to the primary axis.

26. The SMA actuation apparatus as claimed in claim 25 wherein the plurality of flexible posts electrically connect the wire attach structures of the moveable component to an electrical common.

27. The SMA actuation apparatus as claimed in claim 25 or 26 wherein the plurality of flexible posts provide a centring function.

28. The SMA actuation apparatus as claimed in claim 23 further comprising:

at least one bearing that bears the metal plate of the moveable component on the support structure, allowing movement of the metal plate relative to the support structure orthogonal to the primary axis; and at least one magnet to apply a force on the at least one bearing with a component of force parallel to the primary axis.

29. The SMA actuation apparatus as claimed in claim 23 further comprising:

at least one bearing that bears the metal plate of the moveable component on the support structure, allowing movement of the metal plate relative to the support structure orthogonal to the primary axis;

wherein the SMA actuator wires are angled relative to a plane perpendicular to the primary axis and, when powered, apply a force on the at least one bearing with a component of force parallel to the primary axis.

30. A shape memory alloy (SMA) actuation apparatus comprising:

a support structure;

a moveable component supported on the support structure in a manner allowing movement of the moveable relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component;

a total of four shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component; and a conductive component for attaching the SMA actuator wires to the support structure and moveable component, the conductive component comprising:

a sacrificial body portion, and eight wire attach structures held apart by the sacrificial body portion and holding the four SMA actuator wires by being folded and pressed over the SMA actuator wires, the sacrificial body portion being removable from the wire attach structures.

31. A method for manufacturing a shape memory alloy (SMA) actuation apparatus comprising:

providing a support structure, a moveable component supported on the support structure in a manner allowing movement of the moveable relative to the support structure in two orthogonal directions perpendicular to a notional primary axis extending through the moveable component, and a total of four shape memory alloy (SMA) actuator wires connected between the moveable component and the support structure and arranged to, on contraction, move the moveable component;

providing a conductive component for attaching the SMA actuator wires to the support structure and moveable component, the conductive component comprising a sacrificial body portion, and eight wire attach structures held apart by the sacrificial body portion;

attaching each ofthe four SMA actuator wires to two wire attach structures; attaching the wire attach structures to the support structure and moveable component; and removing the sacrificial body portion from the wire attach structures, leaving the wire attach structures attached to the support structure and the moveable component.

32. An apparatus comprising an SMA actuation apparatus as claimed in any of claims 1 to 30.

33. The apparatus as claimed in claim 32 where the apparatus is any one of: a smartphone, a camera, a foldable smartphone, a foldable image capture device, a foldable smartphone camera, a foldable consumer electronics device, an image capture device, a 3D sensing device or system, a consumer electronics device, a mobile computing device, a mobile electronic device, a laptop, a tablet computing device, an e-reader, a computing accessory, a computing peripheral device, a security system, a medical device, a gaming system, a gaming accessory, an augmented reality system, an augmented reality device, a virtual reality system, a virtual reality device, a wearable device, a drone, an autonomous vehicle, and a vehicle.