Fabrication of shape memory alloy actuator components

Abstract

An SMA subassembly includes at least one body portion (3) which holds apart a pair of crimping sections / connecting members (10) which at least partially crimp or weld to a length of SMA wire (20) slack between the crimping sections / connecting members. The slack of the SMA wire in the SMA subassembly can subsequently be adjusted and / or the SMA subassembly can be used to manufacture an SMA assembly in which at least one length of slack shape memory alloy wire is connected between a static portion and a movable portion, thereby providing the advantage of increasing the available travel of the SMA wire.

Description

[0001] The present application generally relates to the manufacture of shape memory alloy (SMA) actuator assemblies.

[0002] In a first approach of the present technology, a shape memory alloy subassembly is provided that includes at least one body portion that holds apart a pair of crimp portions that are at least partially closed around a length of shape memory alloy wire slack between the crimp portions.

[0003] In a second method of the present technology, a method of manufacturing a shape memory alloy subassembly is provided, the method comprising: providing at least one main body portion that holds a pair of open crimping portions apart; laying a length of shape memory alloy wire on the pair of open crimping portions or each pair of open crimping portions; and at least partially closing the crimping portions around the length of shape memory alloy wire and providing slack for the length of shape memory alloy wire between the crimping portions. Thus, the SMA subassembly can be manufactured according to the first method of the present technology.

[0004] In both the first and second techniques, since the SMA wire is slack between the crimped portions, there is no need to apply controlled tension to the SMA wire when closing the crimped portions around the length of SMA wire, resulting in simplified manufacturing, thereby increasing manufacturing speed and reducing unit cost.

[0005] In general, the term "slack wire" may mean a wire having zero tension. Alternatively, the term "slack wire" may mean a wire having zero tension when the wire is not energized. Alternatively, the term "slack wire" may mean a wire having zero tension when the wire is not energized and at ambient temperature (which may be 25°C in some cases). In other words, the term "slack wire" may mean a wire held between two crimps / crimped portions (i.e., mechanically coupled to some other element at two points along its length), and when the wire is not energized and at ambient temperature, the wire is not located on a straight line between the two crimped portions. Therefore, in some cases, the length of SMA wire exhibits slack when it is at a temperature of 25°C (which is a typical ambient temperature). When a drive signal is applied to the length of SMA wire in use to cause contraction, the temperature of the SMA wire rises significantly above 25°C. Generally, when the SMA wire is pulled out of a spool (where the wire is under tension), in some cases, the wire may maintain a certain tension due to hysteresis. Thus, alternatively, the term "relaxed wire" may mean that the wire is relaxed after any residual tension has been removed. For example, the tension may be removed by stretching the wire at ambient temperature. Once the tension is removed, if the length of the wire between the two crimps is greater than the distance between the crimps, the wire may be considered relaxed. A further definition of the term "relaxed wire" is a wire that is relaxed when the SMA wire is substantially martensite. It should be understood that any of these definitions may be used in the present technology to provide a relaxed wire.

[0006] As an alternative to crimping, welding may be used to connect the SMA wire in place. The SMA wire may be welded to the crimping portion / crimping section. Alternatively, the crimping portion / crimping section may be replaced by a suitable connecting member (e.g., a tab) to which the SMA wire may be welded. Therefore, it should be understood that where crimping is described herein, crimping may be replaced by welding.

[0007] Thus, in a third approach of the present technology, a shape memory alloy (SMA) subassembly is provided that includes at least one body portion that holds apart a pair of connecting components welded to a length of SMA wire slack between the connecting components.

[0008] As for the crimping arrangement, the body portion may be a sacrificial body portion that is removable from the connecting component.The connecting component may be formed integrally with the body portion.The connecting component may be formed integrally with the body portion from a sheet of material.

[0009] The SMA subassembly may include a single body portion.

[0010] The SMA subassembly may be a composite SMA subassembly comprising a one-dimensional array or a two-dimensional array of body portions connected together. The body portions may be connected together by being integrally formed. The length of the SMA wire relative to each body portion may be the length of the SMA wire of the same piece.

[0011] In a fourth method of the present technology, a method of manufacturing a shape memory alloy (SMA) subassembly is provided, the method comprising: providing at least one body portion that holds a pair of connecting components apart; laying a length of SMA wire on the pair of connecting components or each pair of connecting components; and welding the SMA wire to the connecting components. The step of welding the SMA wire to the connecting components may include any of the following: arc welding, welding using a welding rod, heat-based welding, laser welding.

[0012] The method may further include adjusting the degree of slack or tension in the length of SMA wire prior to welding.

[0013] The step of laying the length of SMA wire over the or each pair of connecting components may be carried out with the length of SMA wire under tension, and the method may further comprise applying a tool to deflect the length of SMA wire laterally between the connecting components and removing the tool after welding the connecting components to the length of SMA wire.

[0014] Alternatively, the step of laying the length of SMA wire over the or each pair of connecting members may be carried out with the length of SMA wire under tension, and the method may further comprise deforming the body portion to provide slack to the length of SMA wire between the connecting members.

[0015] The step of laying a length of SMA wire across each pair of connecting members may include laying the same piece of SMA wire across all pairs of connecting members.

[0016] The SMA subassembly can be used to manufacture an SMA actuator assembly. Therefore, in a fifth method of the present technology, a method of manufacturing a shape memory alloy actuator assembly is provided, the method comprising: providing a static portion, a movable portion movable relative to the static portion, and a shape memory alloy subassembly according to the first method of the present technology; attaching crimping portions to the static portion and the movable portion, respectively; and removing the main body portion, leaving the crimping portions attached to the static portion and the movable portion, respectively.

[0017] Similarly, in a sixth method of the present technology, a method for manufacturing a shape memory alloy (SMA) actuator assembly is provided, the method comprising: providing a static part, a movable part movable relative to the static part, and an SMA subassembly, the SMA subassembly comprising a main body portion that holds a pair of connecting parts apart, the connecting parts being welded to a length segment of shape memory alloy wire relaxed between the connecting parts; attaching the connecting parts to the static part and the movable part, respectively; and removing the main body portion, leaving the connecting parts attached to the static part and the movable part, respectively.

[0018] It is contemplated that the presence of slack SMA wire in an SMA subassembly will not affect the use of the subassembly in manufacturing an SMA actuator assembly for the following reasons.

[0019] In the first case, the degree of slack or tension in the SMA wire may be adjusted (a) after manufacturing the SMA subassembly but before manufacturing the SMA actuator assembly, (b) during manufacturing the SMA actuator assembly (e.g., after the step of attaching the crimp portion to the SMA actuator assembly but before removing the body portion of the SMA subassembly); or (c) after manufacturing the SMA actuator assembly. In this manner, the degree of slack in the SMA wire in the SMA subassembly is not critical when the SMA wire is subsequently adjusted, which facilitates rapid and cost-effective manufacturing.

[0020] For example, to facilitate such adjustment, during manufacture of the SMA subassembly, the crimping portion may be partially closed around a length of shape memory alloy wire. In this state, the crimping portion may hold the SMA wire, but with a sufficiently low compressive force to allow the SMA wire to be adjusted to change the degree of slack or tension. Thereafter, the crimping portion may be fully closed around the SMA wire to hold the SMA wire with a sufficiently high compressive force to resist the tension generated in the SMA wire when a drive signal is applied.

[0021] In the second case, the SMA subassembly can be used to make an SMA actuator assembly where the SMA wire is slack in the unenergized state.

[0022] That is, in the seventh method of the present technology, a shape memory alloy actuator assembly is provided, which includes: a static part; a movable part movable relative to the static part; and a shape memory alloy wire of at least one length segment connected between the static part and the movable part, and the shape memory alloy wire is loose.

[0023] It has been shown by experimentation and analysis that it is not necessary to keep the SMA wire in tension in the unpowered state. In this case, the SMA wire is configured so that a tension suitable for driving the SMA actuator assembly can be applied to the SMA wire by applying a suitable drive signal. This can be achieved by controlling the degree of slack in the SMA wire. During manufacturing, the length of the SMA wire in its driven state can be controlled, for example by precisely controlling the relative position of the crimping portion.

[0024] Furthermore, such a relaxed SMA wire in the unenergized state provides significant advantages. If the SMA wire is under tension in the unenergized state, the SMA actuator assembly typically loses a significant amount of its theoretical travel, for example, on the order of 50 μm to 100 μm in a typical optical device. This is very important because the achievable travel is often the limiting factor in the miniaturization of SMA actuator assemblies. On the other hand, if the SMA wire is relaxed in the unenergized state, the length of the length of SMA wire is increased, thereby increasing the travel capability of the SMA actuator assembly, possibly to its theoretical maximum.

[0025] The SMA actuator assembly according to the seventh method of the present technology can be manufactured according to the fifth method or the sixth method of the present technology. For example, to facilitate this, during the manufacture of the SMA subassembly, the crimping portion can be completely closed around a length of the shape memory alloy wire. In this state, the crimping portion holds the SMA wire with a sufficiently high compression force to resist the tension generated in the SMA wire when the drive signal is applied.

[0026] In an embodiment, an SMA actuator assembly can be manufactured by providing a static portion, a movable portion movable relative to the static portion, and a shape memory alloy subassembly, the shape memory alloy subassembly including at least one main body portion that holds a pair of crimping portions apart, the crimping portions at least partially closed around a length of shape memory alloy wire; attaching the crimping portions to the static portion and the movable portion, respectively; and removing the main body portion, leaving the crimping portions attached to the static portion and the movable portion, respectively. The method may also include fully closing the crimping portions (if the crimping portions were not fully closed before being attached to the SMA actuator assembly). The method may also include forming at least a portion of the SMA actuator assembly or deforming at least a portion of the SMA actuator assembly in a manner that causes the SMA wire between the crimping portions to become slack. That is, the technique includes coupling a taut or tightened SMA wire to the SMA actuator assembly and deforming or shaping or forming the SMA actuator assembly so that the SMA wire becomes slack.

[0027] Alternatively, the SMA actuator assembly according to the seventh method of the present technology can be manufactured by any other technique that provides a slack SMA wire. Some non-limiting examples include:

[0028] Precisely cut over-length SMA wire at a known tension.

[0029] Providing a removable element (such as a pin) to ensure that the SMA wire is not straight when attached to the crimping portion, and then removing the removable element;

[0030] before attaching the SMA wire to the movable part, for example using a clamp to move the movable part to a known position within the travel of the SMA wire; or

[0031] Attaching the SMA wire in a heated state, where the SMA wire partially deforms and contracts so that the SMA wire can be attached in a tensioned state and becomes relaxed when cooled.

[0032] The SMA subassembly will now be discussed further.

[0033] The body portion may be a sacrificial body portion that is removable from the crimp portion / connection component.

[0034] The crimping portion / connection member may be integrally formed with the body portion, for example from a sheet of material.

[0035] The SMA subassembly may include a single body portion. In this case, the SMA subassembly holds a single length of SMA wire. When used to manufacture an SMA actuator assembly that includes multiple lengths of SMA wire, multiple SMA subassemblies may be used.

[0036] Alternatively, the SMA subassembly may be a composite SMA subassembly comprising an array of main body parts connected together, which array may be a one-dimensional array or a two-dimensional array. The term "composite SMA subassembly" as used herein means that the SMA subassembly may be part of (i.e., one of) a larger array of SMA subassemblies, and that a separate SMA subassembly may be disconnected or removed from the array during the actuator manufacturing process. For example, the main body parts may be connected together by integral formation. In this case, the SMA main body parts each hold a single length of SMA wire. Such a composite SMA subassembly may further improve the speed and cost-effectiveness of manufacturing by assembling multiple lengths of SMA wire at the same time. For example, the length of the SMA wire relative to each main body part may be the length of the shape memory alloy wire of the same piece. This allows the piece of SMA wire to be applied to all main body parts. A separate SMA subassembly may be removed from the composite SMA subassembly.

[0037] The eighth and ninth methods of the present technology are directed to simplifying the manufacture of shape memory alloy sub-assemblies.

[0038] In the eighth method of the present technology, a method for manufacturing a shape memory alloy sub-component is provided, the method comprising: providing a material sheet including a plurality of pairs of open crimping portions; laying a length segment of shape memory alloy wire on each pair of open crimping portions; at least partially closing the crimping portions around the length segment of shape memory alloy wire; and cutting a plurality of shape memory alloy sub-components from the material sheet, each shape memory alloy sub-component comprising a main body portion integrally formed with a pair of crimping portions for holding a length segment of SMA wire.

[0039] In a ninth method of the present technology, a method for manufacturing a shape memory alloy (SMA) sub-component is provided, the method comprising: providing a sheet of material comprising a plurality of pairs of connecting components; laying a length of SMA wire on each pair of connecting components; welding the SMA wire to each pair of connecting components; and cutting a plurality of SMA sub-components from the sheet of material, each SMA sub-component comprising a main body portion integrally formed with a pair of connecting components that hold a length of SMA wire.

[0040] The method may also include adjusting the degree of slack or tension in the length of shape memory alloy wire prior to welding.

[0041] The step of welding the length of SMA wire to the connecting components may be performed with the length of shape memory alloy wire relaxed between the connecting components, optionally while the length of shape memory alloy wire is at a temperature of 25°C.

[0042] The step of laying the length of SMA wire on the pair of connecting components or each pair of connecting components may be carried out when the length of shape memory alloy wire is under tension, and the method may further include: before welding the length of SMA wire, applying a tool to cause the length of SMA wire to deflect laterally between the crimping parts, and removing the tool after welding the connecting components to the length of SMA wire.

[0043] Alternatively, the step of laying the length of SMA wire over the or each pair of connecting members may be carried out with the length of SMA wire under tension, and the method may further comprise deforming the body portion to provide slack to the length of SMA wire between the connecting members.

[0044] The step of laying a length of SMA wire across each pair of connecting members may include laying the same piece of SMA wire across all pairs of connecting members.

[0045] These methods can increase the speed and cost-effectiveness of manufacturing by assembling multiple lengths of SMA wire at the same time. For example, the length of the SMA wire relative to each body portion can be the length of the same piece of shape memory alloy wire. This allows the same piece of SMA wire to be used in all SMA subassemblies.

[0046] For example, when the length of shape memory alloy wire is at a temperature of 25°C, the length of SMA wire may be relaxed between the crimped portions, as in the method of the present technology discussed above, and provide the same advantages.

[0047] The SMA actuator assembly will now be discussed further.

[0048] In general, an SMA actuator assembly may be any type of device that includes a static portion and a movable portion that is movable relative to the static portion.

[0049] The SMA actuator assembly can be any of the following devices or can be set in any of the following devices: a smartphone, a camera, a foldable smartphone, a foldable smartphone camera, a foldable consumer electronic device, an image capture device, a foldable image capture device, an array camera, a periscope camera, a 3D sensing device or system, a servo motor, a consumer electronic device (including household appliances such as vacuum cleaners, washing machines, and lawn mowers), a mobile or portable computing device, a mobile or portable electronic device, a laptop computer, 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., a mouse, a keyboard, a headset, headphones, earphones, etc.), an audio device (e.g., a headset, a headset The invention also includes but is not limited to headsets, headphones, etc.), security systems, gaming systems, gaming accessories (e.g., controllers, earphones, wearable controllers, joysticks, etc.), robots or robotic devices, medical devices (e.g., endoscopes, inhalers, medication dispensers, etc.), electronic cigarettes, augmented reality systems, augmented reality devices, virtual reality systems, virtual reality devices, wearable devices (e.g., watches, smart watches, fitness trackers, etc.), drones (aerial, aquatic, underwater, etc.), aircraft, spacecraft, submersibles, vehicles and autonomous vehicles (e.g., driverless cars), tools, surgical tools, remote controls (e.g., for drones or consumer electronic devices), clothing (e.g., clothing, shoes, etc.), display screens, touch screens, sensors, and wireless communication devices (e.g., near field communication (NFC) devices). It should be understood that this is a non-exhaustive list of exemplary devices.

[0050] The SMA actuator assembly may be an optical device, wherein the movable element comprises an optical element.The movable portion may be movable along an optical axis of the optical element.

[0051] For example, the optical element may be a lens element comprising at least one lens, such as a micro device, wherein the at least one lens has a diameter of at most 20 mm. In this case, the SMA actuator assembly may be a camera, wherein the static part has an image sensor mounted thereon, and the lens element is arranged to focus an image on the image sensor. However, the SMA actuator assembly may be any other type of optical device.

[0052] The movable component may be supported on the static part by a suspension system arranged to guide movement of the movable element relative to the static part. For example, the static part may comprise a bearing arrangement.

[0053] The slack wire used in the present technology can be coated with an electrically insulating layer. Such a coated slack wire is described in International Patent Publication No. WO2015 / 036761. When crimping a coated SMA wire, it may be necessary to remove the electrically insulating layer from at least a portion of the coated SMA wire that will be in the crimp in order to achieve an electrical connection between the wire and the crimp. For example, the electrically insulating layer can be removed by laser ablation. An advantage of the present technology of welding an SMA wire in place may be that if the SMA wire is coated with an electrically insulating layer, it may not be necessary to remove the coating prior to the welding process.

[0054] In an embodiment, the present technology can be used to provide an eight wire actuator, such as the actuator described in International Patent Publication No. WO2011 / 104518. Preferably, the eight wire actuator is formed using the present technology and coated slack wires.

[0055] The present technology may be used to provide a haptic assembly or device arranged to deliver tactile feedback, such as the haptic assemblies described in UK patent applications GB1803084.1 and GB1813008.8. Thus, in an SMA actuator assembly, a movable portion may be movable relative to a static portion to deliver tactile feedback. The slack wire may be coated or uncoated in such a haptic assembly or device.

[0056] The present technology can be used to provide a 3D sensing device or system, such as those described in International Patent Publication No. WO2018 / 096347 and UK Patent Application Nos. GB1808804.7 and GB1812818.1. In such a 3D sensing device or system, the slack wire can be coated or uncoated.

[0057] Preferred features are set out in the attached dependent claims.

[0058] Embodiments of the present technology will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0059] Figure 1 is a top view of an SMA subassembly including a single body portion;

[0060] Figure 2 and Figure 3 is a perspective view of a crimped portion in a partially crimped state and a fully crimped state;

[0061] Figure 4 is a flow chart of a method for manufacturing an SMA subassembly;

[0062] Figure 5 is a flow chart of a modified method of manufacturing an SMA subassembly;

[0063] Figure 6 is Figure 5 A perspective view of a method of using a tool to deflect the length of SMA wire;

[0064] Figure 7 is a flow chart of a further modified method of manufacturing the SMA subassembly;

[0065] Figure 8 and Fig. 9 is Figure 7 perspective views of an SMA subassembly before and after deformation in the method;

[0066] Fig.10 is a top view of a one-dimensional array of multiple separated SMA subassemblies during the manufacturing process;

[0067] Fig.11 is a top view of a composite SMA subassembly comprising a one-dimensional array of a plurality of connected SMA subassemblies;

[0068] Fig.12 is a top view of a two-dimensional array of multiple separated SMA subassemblies during a manufacturing process;

[0069] Fig.13 is a top view of a composite SMA subassembly comprising a two-dimensional array of a plurality of connected SMA subassemblies;

[0070] Fig.14 is a flow chart of a method for manufacturing a plurality of SMA subassemblies;

[0071] Fig.15 is a top view of a sheet of material in which a plurality of SMA subassemblies are fabricated in a one-dimensional array;

[0072] Fig.16 is a top view of a sheet of material in which a plurality of SMA subassemblies are fabricated in a two-dimensional array;

[0073] Fig.17is a flow chart of a modified method of manufacturing a plurality of SMA subassemblies;

[0074] Fig.18 is a flow chart of a further modified method of manufacturing a plurality of SMA subassemblies;

[0075] Fig.19 and Fig. 20 is a perspective view of an SMA actuator assembly, the SMA actuator assembly being a camera;

[0076] Figure 21 to Figure 23 are flow charts of three methods of manufacturing an SMA actuator assembly; and

[0077] Figure 24 to Figure 27 is a flow chart of three methods of manufacturing SMA subassemblies.

[0078] In summary, embodiments of the present technology generally relate to the manufacture of shape memory alloy (SMA) actuator assemblies. The SMA subassembly includes at least one body portion that holds apart a pair of crimping portions (or connecting components) that are at least partially closed around (or welded to) a length of SMA wire that is slack between the crimping portions (or connecting components). The slack of the SMA wire in the SMA subassembly can then be adjusted and / or the SMA subassembly can be used to manufacture an SMA assembly in which at least one length of slack shape memory alloy wire is connected between a static portion and a movable portion, thereby providing the advantage of increasing the available travel of the SMA wire.

[0079] SMA actuators are known to be used in handheld electronic devices, such as cameras and mobile phones. For example, such actuators can be used in miniature cameras to achieve focusing, zooming or optical image stabilization (OIS). For example, International Patent Publication No. WO2007 / 113478 discloses an SMA actuator arrangement for a camera that uses a single SMA wire to provide autofocus, and International Patent Publication No. WO2013 / 175197 discloses a compact SMA actuator arrangement for a camera that uses four SMA wires to provide OIS. In addition, International Patent Publication No. WO2011 / 104518 discloses an SMA actuator arrangement that includes eight SMA wires that can achieve both autofocus and OIS. Such actuators can also be used to deliver tactile feedback to a user of the device. For example, British Patent Application No. GB1813008.8 discloses the use of one or more SMA wires to deliver tactile feedback. In each of these disclosures, each SMA wire is fixed to a static part and a moving part at its ends. One method of securing the SMA wire to the static and moving parts is crimping, where the crimping portion is closed (or crimped) around the SMA wire to form a crimp that holds the SMA wire. Another method of securing the SMA wire to the static and moving parts is welding, where segments of the SMA wire are welded directly to the static and moving parts, or by welding segments of the SMA wire to the connecting parts.

[0080] In the prior art examples mentioned above, it has been assumed that it is necessary to attach the SMA wire under tension during manufacturing so that the length and tension of the SMA wire can be accurately known in the unpowered state. In such actuators, the SMA wire is under tension in the unpowered state.

[0081] International Patent Publication No. WO2016 / 189314 discloses a method of manufacturing an SMA actuator assembly by first manufacturing a subassembly in the form of a strut element, the subassembly comprising a sacrificial strut body and a crimping portion that is closed (or crimped) around an SMA wire under the application of a controlled tension such that the crimping portion holds the SMA wire between the crimping portions. The crimping portions are attached to a static portion and a moving portion, respectively. The sacrificial strut body is then removed, leaving the crimping portions attached to the static portion and the moving portion, respectively. WO2016 / 189314 teaches that this provides advantages including providing tight control over the length of the SMA wire in the manufactured SMA actuator assembly, because the sacrificial strut body of the strut element maintains the relative position of the crimping portions, and thereby maintains the length of the SMA wire between the crimping portions.

[0082] While the use of the subassembly disclosed in WO2016 / 189314 provides such advantages, difficulties remain in manufacturing the subassembly while applying controlled tension to the SMA wire.

[0083] In the following, an SMA subassembly including a crimping portion is described (and illustrated in the accompanying drawings). However, it should be understood that the crimping portion of the SMA subassembly can be replaced by a connecting component to which the SMA wire can be welded. Similarly, it should be understood that the manufacturing process described with respect to crimping can be applied to the welding process.

[0084] Figure 1 An SMA subassembly 1 is shown which comprises a fret 2 comprising a body portion 3. The fret 2 is formed from a sheet of material as a flat strip. The material of the fret 2 may be a metal such as phosphor bronze, steel or a laminate containing a conductive component.

[0085] The bridge 2 also includes a pair of crimping portions 10 formed integrally with the main body portion 3 from the same sheet of material. Specifically, the main body portion 3 includes an elongated portion 4 and a laterally projecting arm 5 at the end of the elongated portion 4, and the crimping portions 10 are formed by tabs on the ends of the arm 5. Thus, the crimping portions 10 are held apart by the main body portion 3.

[0086] The SMA subassembly 1 may have a similar construction and arrangement as the bridge disclosed in WO 2016 / 189314.

[0087] The crimping portions 10 are partially or completely closed around a length of SMA wire 20 so that they hold the SMA wire 20. Thus, the crimping portions 10 crimp the length of SMA wire 20 to provide both a mechanical connection and an electrical connection. The SMA wire 20 may be made of any suitable SMA material, such as Nitinol or another titanium alloy SMA material.

[0088] Compared to WO2016 / 189314 (in which the length of SMA wire 20 is under tension in the bridge), the length of SMA wire 20 is slack, the term "slack" being used herein in its normal meaning, i.e. the length of the SMA wire 20 between the crimping portions 10 (i.e. the length of its three-dimensional path) is greater than the distance between the crimping portions 10. Typically, when the SMA wire 20 is slack, the length of the SMA wire 20 will have zero tension, except that this may be affected by hysteresis effects. That is, when a length of SMA wire 20 is pulled under tension (e.g. from a spool), the wire may retain some tension even if it is slack between the crimping portions. Such tension may be removed by stretching the length of SMA wire 20 (before or after the crimping portions 10 are crimped) at a tension of, for example, 300 MPa.

[0089] Generally, the slack or tension of the length of SMA wire 20 depends on its temperature, and in use, a drive signal is applied to the length of SMA wire 20 to cause contraction. However, reference herein to the length of SMA wire 20 being slack refers to the length of SMA wire being slack when at ambient temperature, such as at a temperature of 25°C (which is significantly lower than the temperature of the SMA wire when the drive signal is applied in use). The length of SMA wire 20 can be brought to a temperature of 25°C simply by placing the length of SMA wire 20 within an ambient temperature of 25°C and waiting sufficient time for thermal equilibrium to be reached between the length of SMA wire 20 and any surrounding components.

[0090] The body portion 3 is sacrificial and is removable from the crimping portion 10, for example by mechanical or laser cutting.

[0091] like Figure 2 As shown in , the crimping portion 10 can be partially closed around the length of SMA wire 20. In this case, the crimping portion 10 holds the SMA wire 20 with a sufficiently low compression force to allow the SMA wire 20 to move along its length to change the degree of slack or introduce tension.

[0092] Alternatively, if Figure 3 As shown in , the crimping portion 10 can be completely closed around the length of SMA wire 20. In this case, the crimping portion 10 holds the SMA wire 20 with a sufficiently high compression force to resist the tension generated in the SMA wire 20 when a drive signal is applied in normal use.

[0093] Figure 4 A method of manufacturing the SMA subassembly 1 is illustrated.

[0094] In step S1, a bridge 2 is provided, which includes a main body portion 3 and a pair of crimping portions 10, wherein the crimping portions 10 are open. For example, the bridge 2 can be made (e.g., by mechanical or laser cutting, stamping or pressing) by cutting the main body portion and the pair of crimping portions 10 from a sheet of material.

[0095] In step S2, a length of SMA wire 20 is laid in a predetermined position on a pair of open crimping portions 10. The SMA wire 20 is not under tension and is therefore slack.

[0096] In step S3, the crimping portion 10 is closed around the length of SMA wire 20. This can be done by folding the open crimping portion 10 over the SMA wire 20 and squeezing them, for example, using a conventional crimping tool. The crimping portion 10 thus holds the length of SMA wire 20 in a state in which the length of SMA wire 20 is slack between the crimping portions 10, the degree of slack being controlled by the slack of the length of SMA wire 20 when the crimping portion 10 is crimped around the length of SMA wire 20. As described below, the body portion 3 of the SMA subassembly 1 holds the crimping portion 10 and maintains the length of SMA wire 20 when the length of SMA wire 20 is subsequently tensioned.

[0097] Since the SMA wire 20 is slack between the crimping portions 10, it is not necessary to apply controlled tension to the SMA wire 20 when closing the crimping portion 10 around the length of SMA wire 20. As a result, manufacturing is simplified, thereby increasing the speed of manufacturing and reducing unit costs.

[0098] Step S3 may be performed by completely closing the crimping portion 10 around the length of SMA wire 20. In this case, as mentioned above, the crimping portion 10 holds the SMA wire 20 with a sufficiently high compression force to resist the tension generated in the SMA wire 20 when a drive signal is applied in normal use.

[0099] In this case, the method ends and the Figure 4 The further steps are shown in .

[0100] Alternatively, step S3 may be performed by partially closing the crimping portion 10 around the length of SMA wire 20. In this case, as mentioned above, the crimping portion 10 holds the SMA wire 20 with a sufficiently low compression force to allow a degree of slack or introduce tension into the SMA wire 20 by applying force along the length of SMA wire 20. Thus, step S3 may be performed. Figure 4 The further steps shown in , to condition the SMA wire 20 in this manner, are as follows.

[0101] In step S4, a force is applied along the length of SMA wire 20 to change the degree of slack (i.e., not introduce tension) or to introduce tension into the length of SMA wire 20. The force may be applied by a tool that clamps the length of SMA wire 20 on opposite sides of the bridge 2.

[0102] In step S5, the crimping portion 10 is completely closed around the length of SMA wire 20. In this case, as mentioned above, the crimping portion 10 holds the SMA wire 20 with a sufficiently high compression force to resist the tension generated in the SMA wire 20 under application of a drive signal in normal use.

[0103] Steps S4 and S5 may be performed after manufacturing the SMA subassembly 1, but before using the SMA subassembly in manufacturing the SMA actuator assembly 30 (described below). Alternatively, steps S4 and S5 may be performed during manufacturing the SMA actuator assembly 30, as described further below.

[0104] When the bridge comprises a pair of connecting parts instead of a crimping portion, the Figure 4 Specifically, steps S3, S4 and S5 can be replaced by welding the SMA wire to the connecting parts of the bridge. The modified manufacturing process is Fig.24 Steps S1 and S2 are shown in Figure 4 Once the SMA wire has been positioned in the correct position on the bridge (i.e., on a pair of connecting parts of the bridge held apart by the main body portion), the SMA wire is welded to the connecting parts of the bridge (step S30), and any suitable welding technique may be used to weld the SMA wire to the connecting parts, such as spot welding, arc welding, welding using welding rods, heat-based welding, and laser welding.

[0105] Figure 5 A modified method of making an SMA subassembly 1 is shown which uses a different technique to control the degree of slack in the length of SMA wire 20 and is performed as follows. The steps of the method are the same as those of Figure 4 The steps are the same as shown in .

[0106] In step S1 , as described above, a bridge 2 including a body portion 3 and a pair of crimping portions 10 is provided, wherein the crimping portions 10 are open.

[0107] In step S2, a length of SMA wire 20 is laid on the pair of open crimping portions 10 in a predetermined position, as described above, except that the length of SMA wire 20 is under tension.

[0108] In step S8 as an additional step, the tool 15 is applied to the length of SMA wire 20 between the open crimping portions 10, such as Figure 6 The tool 15 causes the length of SMA wire 20 to be deflected laterally.

[0109] In step S3, as described above, the crimping portion 10 is crimped around the length of SMA wire 20, or welded to the SMA wire. Since the length of SMA wire 20 is in tension, good mechanical contact is formed between the crimping portion 10 and the length of SMA wire 20.

[0110] In step S9, the tool 15 is removed. This causes the length of SMA wire 20 to slack. The amount of slack is controlled by the amount of deflection applied by the tool 15 in step S8. Therefore, this alternative method provides good control over the degree of slack.

[0111] When the bridge comprises a pair of connecting parts instead of a crimping portion, the Figure 5 Specifically, step S3 can be replaced by a step of welding the SMA wire to the connecting member of the bridge. The modified manufacturing process is Fig.25 S1, S2 and S8 are shown in Figure 5 Once the SMA wire has been positioned in the correct position on the bridge (i.e., on a pair of connecting parts of the bridge held apart by the main body portion), the wire is deflected and then the SMA wire is welded to the connecting parts of the bridge (step S30), and any suitable welding technique may be used to weld the SMA wire to the connecting parts, such as spot welding, arc welding, welding using welding rods, heat-based welding, and laser welding. Then, according to Figure 5 The tool for deflecting the SMA wire is removed (step S9).

[0112] Figure 7 Another modified method of making an SMA subassembly 1 is shown, which uses a different technique to control the degree of slack in the length of SMA wire 20, and is performed as follows. The steps of the method are the same as those of Figure 4 The steps are the same as shown in .

[0113] In step S1 , as described above, a bridge 2 including a body portion 3 and a pair of crimping portions 10 is provided, wherein the crimping portions 10 are open.

[0114] In step S2, a length of SMA wire 20 is laid on the pair of open crimping portions 10 in a predetermined position, as described above, except that the length of SMA wire 20 is under tension.

[0115] In step S3, as described above, the crimping portion 10 is crimped around the length of SMA wire 20, or welded to the SMA wire. Since the length of SMA wire 20 is in tension, good mechanical contact is formed between the crimping portion 10 and the length of SMA wire 20.

[0116] In step S10, the body portion 3 is deformed so as to provide slack for the length of SMA wire 20 between the crimping portions 10 by reducing the distance between the crimping portions 10. For example, this may be performed as follows: Figure 8 and Fig. 9 As shown in Figure 8 and Fig. 9 The SMA subassembly 1 is shown before and after step S10 . Figure 8 The dashed line 16 in FIG. 1 shows the edge of a portion 17 of the main body portion 3 , which is deformed out of the plane of the main body portion 3 .

[0117] Further improvements may be achieved by applying similar methods to manufacture arrays of multiple SMA subassemblies 1, for example as will now be described.

[0118] Fig.10 A one-dimensional array of SMA subassemblies 1 separated from each other is shown. The bridge 2 of each SMA subassembly 1 may be cut from the same sheet of material.

[0119] Fig.11 A composite SMA subassembly 11 is shown comprising a one-dimensional array of a plurality of SMA subassemblies 1 connected together by being integrally formed from the same sheet of material (eg, by being cut out from a larger sheet).

[0120] Fig.12 A two-dimensional array of SMA subassemblies 1 separated from each other is shown. The bridge 2 of each SMA subassembly 1 may be cut from the same sheet of material.

[0121] Fig.13 A composite SMA subassembly 12 is shown that includes a two-dimensional array of multiple SMA subassemblies 1 that are connected together by virtue of being integrally formed from the same sheet of material (eg, by being cut from a larger sheet).

[0122] Figures 10 to 13 Each array shown can be used Figure 4 In this case, multiple SMA subassemblies can first be cut out from a larger sheet and arranged as shown in FIG. Figures 10 to 13 In each case, the cutting can be performed, for example, by mechanical or laser cutting, punching or pressing.

[0123] In principle, separate lengths of SMA wire 20 could be laid across each SMA subassembly in step S3, but manufacturing is improved by instead laying the same piece of SMA wire 21 across all pairs of open crimp portions 10 (or connecting components), such that the portion of the piece of SMA wire 21 between each pair of crimp portions 10 forms a corresponding length of SMA wire 20. The piece of SMA wire 21 is then cut into corresponding lengths of SMA wire 20 for each SMA subassembly, as shown by the dashed lines.

[0124] Such fabrication of arrays of multiple SMA subassemblies 1 allows for high volume processing, which reduces unit cost.

[0125] In the case of a composite SMA subassembly 11 or 12, a step of removing the individual SMA subassemblies from the composite shape memory alloy subassembly 11 or 12 may then be performed, such as by mechanically or laser cutting along the Figure 8 and Fig. 9 The cut is made along the dashed line 16 shown in FIG.

[0126] Fig.14 A method of manufacturing a plurality of SMA subassemblies 1 together is illustrated and is performed as follows. The steps of the method are the same as those of Figure 4 The steps shown in are the same as described above.

[0127] In step S11, a material sheet 18 is provided from which a plurality of SMA assemblies 1 arranged in a one-dimensional array or a two-dimensional array are subsequently cut. However, in step S11, only the pair of crimping portions 10 of each SMA subassembly 1 are cut out, for example using mechanical or laser cutting. Fig.15 and Fig.16 An example of such a sheet of material 18 is shown. Fig.15 illustrates the case of a one-dimensional array of SMA subassemblies, and Fig.16 The diagram shows a two-dimensional array of SMA subassemblies. Fig.15 and Fig.16 In FIG. 1 , the cut paired crimped portions are shown by solid lines, and the remainder of the SMA subassembly (which will be cut later) is shown in dashed outline.

[0128] In step S2, a length of SMA wire 20 is laid on each pair of open crimping parts 10 in a predetermined position. The SMA wire 20 is not under tension and is therefore slack. This step is similar to Figure 4 The method of step S2 is the same as that of step S3, except that the same piece of SMA wire 21 is laid across all pairs of open crimping portions 10 so that the portion of the piece of SMA wire 21 between each pair of crimping portions 10 forms a corresponding length of SMA wire 20. Fig.16As shown in FIG. 1 , in the case of a two-dimensional array of SMA subassemblies, a single piece of SMA wire 21 is bent around to span successive rows of SMA subassemblies 1 , but alternatively separate straight pieces of SMA wire may be laid across each row of SMA subassemblies 1 .

[0129] In step S3, the crimping portion 10 is crimped around the length of SMA wire 20 as described above. Figure 4 The above description of step S3 of the method also applies to Fig.14 method.

[0130] As mentioned above Figure 4 The method described above may optionally perform steps S4 and S5.

[0131] When the bridge comprises a pair of connecting parts instead of a crimping portion, the Fig.14 Specifically, steps S3, S4 and S5 can be replaced by the step of welding the SMA wire to the connecting parts of the bridge.

[0132] In step S12, the SMA subassembly 1 is cut from the material sheet 18, for example using mechanical or laser cutting. The cutting process can simultaneously cut (1) the material sheet 18 to cut out the body portion 3, and (2) the piece of SMA wire 21 to separate the multiple lengths of SMA wire 20.

[0133] Such fabrication of arrays of multiple SMA subassemblies 1 allows for high volume processing, which reduces unit cost.

[0134] Fig.17 and Fig.18 A modified method of manufacturing multiple SMA subassemblies 1 together is shown, which is similar to Fig.14 The method is modified in the same way as Figure 5 and Figure 7 Methods and Figure 4 Therefore, for the sake of brevity, with respect to these modifications, reference is made to Figure 5 and Figure 7 The description of is not repeated here. Similarly, Fig.26 and Fig. 27 A manufacturing method is shown in which the step of crimping the SMA wire ( S3 ) is replaced instead by a step of welding the SMA to the connecting parts of the bridge (step S30 ).

[0135] The SMA subassembly 1 as described above may be used to manufacture an SMA actuator assembly, as will now be described.

[0136] Fig.19An example of an SMA actuator assembly 30 is shown which is a camera arranged as follows.

[0137] The SMA actuator assembly 30 includes a support structure 32 having an image sensor 33 mounted thereon. The support structure 32 includes a base 34, which is a rigid plate. The image sensor 33 is fixed to the front side of the base 34. The support structure 32 also includes a chassis 36, which protrudes from the base 34 and can be a molded component. The chassis 36 has a central hole 37 aligned with the image sensor 33.

[0138] The SMA actuator assembly 30 also includes a lens element 40, which is positioned in the hole 37 and includes a lens holder 42, which holds a lens 41, but alternatively, there may be multiple lenses. The lens 41 may be made of glass or plastic. The SMA actuator assembly 30 is a micro-optical device, wherein the lens 41 has a diameter of at most 20 mm, preferably at most 15 mm, and more preferably at most 10 mm.

[0139] The lens element 40 has an optical axis O aligned with the image sensor 33 and is arranged to focus an image on the image sensor 33. The lens element 40 also has a protrusion 43 formed on one side of the optical axis O protruding laterally.

[0140] The SMA actuator assembly 30 also includes a suspension system 50 that supports the lens element 40 on the support structure 32. The suspension system 50 is configured to guide the movement of the lens element 40 relative to the support structure 32 along the optical axis O, while restricting the movement of the lens element 40 relative to the support structure 32 in other degrees of freedom. This relative movement of the lens element 40 changes the focus of the image on the image sensor 33, for example, to provide autofocus or zoom. Thus, in this example, the support structure 32 is a static part, and the lens element 40 is a movable part that is movable relative to the support structure 32 along the optical axis O. The terms "static" and "movable" refer to relative motion.

[0141] In particular, the suspension system 50 comprises a bearing arrangement of a plurality of rolling bearings 51. Each of the rolling bearings 51 comprises a bearing surface 53 on the support structure 32, in particular on the chassis 36, and a bearing surface 52 on the lens element 40, in particular on the lens holder 42. Each of the rolling bearings 51 further comprises a ball 54 arranged between the bearing surface 52 and the bearing surface 53. Thus, the ball 54 acts as a rolling bearing element, however, as an alternative, other types of rolling bearing elements, such as rollers, may be used.

[0142] As an alternative, rolling bearings 51 may be replaced by plain bearings comprising bearing surfaces on each of support structure 32 and lens element 40 which coincide with each other and bear against each other to guide relative movement.

[0143] The SMA actuator assembly 30 also includes two lengths of SMA wire 20 (one of which is at Fig.19 4, which are arranged as follows to drive movement of the lens element 40 along the optical axis O). Each length of SMA wire 20 is connected at one end to the support structure 32 and at the other end to the lens element 40 by a crimping portion 10 (the crimping portion 10 is the crimping portion 10 of the SMA subassembly, as described in more detail below).

[0144] The lengths of SMA wire 20 have an angled V-shaped arrangement of a similar type to that disclosed in International Patent Publication No. WO2007 / 113478. That is, each length of SMA wire 20 is inclined in the same sense and at the same acute angle θ relative to a plane normal to the optical axis O, which is the direction of movement in this example. The angle θ is selected to provide a gain between the change in length of the SMA wire 20 and the movement along the optical axis O, while also reducing the height of the projection along the optical axis relative to the plane normal to the optical axis O, typically ranging from a lower limit of 5 degrees, or more preferably 8 degrees, to an upper limit of 20 degrees, preferably 15 degrees, or more preferably 12 degrees. The lengths of SMA wire 20 also have an angle of 90 degrees between them when viewed along the optical axis O, which is the direction of movement in this example.

[0145] In an alternative, simpler arrangement, one of the lengths of SMA wire 20 may be omitted.

[0146] The SMA actuator assembly 30 also includes a compression spring 45 connected between the support structure 32 and the lens element 40 and acting as a resilient biasing element for the lengths of SMA wire 20. Thus, as the lengths of SMA wire 20 cool, the compression spring 45 drives the lengths of SMA wire 20 to move in opposite directions (in the direction of the optical axis O). Fig.19 and Fig. 20 Therefore, the temperature of the SMA wire 20 of these lengths can be controlled by controlling the power of the drive signal, and thus the position of the lens element 40 along the optical axis O can be controlled.

[0147] The lengths of SMA wire 20 are arranged to be relaxed when no drive signal is applied thereto, for example when the lengths of SMA wire 20 are at a temperature of 25°C. It has been recognised through experimentation and analysis that it is not necessary to maintain the lengths of SMA wire 20 in tension in the unpowered state. However, the SMA wire 20 is configured such that a tension suitable for driving the SMA actuator assembly 30 can be applied to the SMA wire by applying a suitable drive signal to heat the wire and cause it to contract. This can be achieved by controlling the degree of slack in the lengths of SMA wire 20.

[0148] Furthermore, this condition of the SMA wire being relaxed in the unenergized state provides significant advantages. If the SMA wire is under tension in the unenergized state, the SMA actuator assembly will typically lose a significant amount of its theoretical travel, for example, on the order of 50 μm to 100 μm in a typical optical device. This is very important because the achievable travel is often a limiting factor in the miniaturization of SMA actuator assemblies. On the other hand, by providing these lengths of SMA wire 20 that are relaxed in the unenergized state, the length of these SMA wires 20 is increased, thereby improving the travel capability of the SMA actuator assembly 30, possibly to its theoretical maximum value.

[0149] A control circuit implemented in an IC chip (not shown) generates drive signals and provides them to the lengths of SMA wire 20 connected to the control circuit. The control circuit receives an input signal representing a desired position of the lens element 40 along the optical axis O and generates a drive signal having a power selected to drive the lens element 40 to the desired position. The power of the drive signal may be linear or may be varied using pulse width modulation.

[0150] The drive signal may be generated using a resistance feedback control technique, in which case the control circuit measures the resistance of the lengths of SMA wire 20 and uses the measured resistance as a feedback signal to control the power of the drive signal. Such resistance feedback control techniques may be implemented as disclosed in any of the following international patent publications, each of which is incorporated herein by reference: WO2013 / 175197; WO2014 / 076463; WO2012 / 066285; WO2012 / 020212; WO2011 / 104518; WO2012 / 038703; WO2010 / 089529 or WO2010 / 029316. Alternatively, the drive signal may be generated using closed loop control based on the output of a Hall sensor that senses the position of the lens element 40 along the optical axis O.

[0151] Fig. 20 An example of an SMA actuator assembly 30 is shown, which is similar to Fig.19 , but with the following modifications to provide an angled V-shaped arrangement of the type disclosed in International Patent Publication No. WO2007 / 113478. Fig.19 In the embodiment of the present invention, two lengths of SMA wire 20 are provided (the two lengths of SMA wire 20 are separate pieces of SMA wire each connected at each end by a crimping portion 10), a single length of SMA wire 20 is connected to the support structure 32 at each end by a crimping portion 10, and is connected to the lens element 40 by hooking on a hook feature 44 formed on a protrusion 43. As a result, the two portions of the length of SMA wire 20 on either side of the protrusion 43 form a corresponding length of SMA wire 22 having the same Fig.19 The two lengths of SMA wire 20 in the same configuration and therefore have the same function and operation.

[0152] Despite Fig.19 and Fig. 20 , a particular SMA actuator assembly 30 is shown as an example, but the SMA subassembly 1 can be used to make other types of SMA actuator assemblies 30. In one alternative, the SMA actuator assembly 30 can be a camera providing OIS of the type disclosed in International Patent Publication No. WO2013 / 175197, or a camera providing multiple functions of the type disclosed in International Patent Publication No. WO2011 / 104518. In other alternatives, the SMA actuator assembly 30 can be an optical device in which the movable element is a lens element, but there is no image sensor. In other alternatives, the SMA actuator assembly 30 can be an optical device in which the movable part is an optical element other than a lens element, such as a diffractive optical element, a filter, a prism, a reflector, a reflective optical element, a polarizing optical element, a dielectric mirror, a metal mirror, a beam splitter, a grid, a patterned plate, or a grating, which can be a diffraction grating. In other examples, the SMA actuator assembly 30 may be a type of device that is not an optical device and in which the movable element is not an optical element.

[0153] A method of using the SMA subassembly 1 to make an SMA actuator assembly 30 will now be described. The SMA actuator assembly 30 may be, for example, Fig.19 or Fig. 20 The type shown in .

[0154] Fig.21 is a flow chart of a first method of manufacturing an SMA actuator assembly, the method being performed as follows.

[0155] In step T1, a static portion of an SMA actuator assembly 30, a movable portion of an SMA actuator assembly 30, and an SMA subassembly 1 of the type described above are provided. The movable portion (e.g. Fig.19 and Fig. 20 The lens element 40 in the example of FIG. 4 is relative to the static portion (eg Fig.19 and Fig. 20 The supporting structure 32) is movable. Fig.21 In the first method, as described above, in the SMA subassembly 1, the crimping portion 10 is completely crimped around the SMA wire 20, or the connecting component is welded to the SMA wire.

[0156] In step T2, the crimping portions 10 are attached to the static and movable portions, respectively. This can be accomplished by placing the SMA subassembly 1 on the static and movable portions with the crimping portions / connecting components in the desired positions, and then securing the crimping portions / connecting components 10 themselves to the static and movable portions (e.g., by providing adhesive or mechanical securing). The manner in which the crimping portions / connecting components 10 are secured allows a certain degree of freedom in the placement of the SMA subassembly 1, so that the distance between the crimping portions / connecting components 10 and the length of the SMA wire 20 remain the same as set by the configuration of the main body portion 3 of the SMA subassembly 1.

[0157] In step T3, the body portion 3 is removed from the SMA subassembly, for example by mechanical or laser cutting. This leaves the crimping portions / connecting components attached to the static and moving portions, respectively. However, the length of the length of SMA wire 20 remains exactly as set by the spacing between the crimping portions / connecting components 10 in the SMA subassembly.

[0158] exist Fig.21 In the first method, since the crimping portion / connecting component 10 is completely crimped or welded around a length of shape memory alloy wire, no further steps are performed.

[0159] In an alternative case of using an SMA subassembly 1, where the crimping portion 10 is partially crimped around the length of shape memory alloy wire 20, then Fig. 22 The second method shown in Fig.23 As described above, each of these methods includes steps T1 to T3 of the first method, but with the following additional steps.

[0160] exist Fig. 22In the second method, during the manufacture of the SMA actuator assembly 30, in particular after step T2 of attaching the crimping portion 10 to the static and movable portions, but before step T3 of removing the body portion 3 of the SMA subassembly 1, additional steps T4 and T5 are performed.

[0161] The additional steps T4 and T5 correspond to steps S4 and S5 in the method of manufacturing the SMA subassembly. That is, in step T4, a force is applied along the length of SMA wire 20 to change the degree of slack (i.e., not introduce tension) or introduce tension into the length of SMA wire 20, and in step T5, the crimping portion 10 is fully crimped around the length of SMA wire 20 as described above.

[0162] exist Fig.23 In a third method, the same additional steps T4 and T5 are performed, but after manufacturing the SMA actuator assembly 30 , and in particular after step T3 of removing the body portion 3 of the SMA subassembly 1 .

[0163] Those skilled in the art will appreciate that, although the foregoing content has been described as being the best mode and other modes of carrying out the present technology where appropriate, the present technology should not be limited to the specific constructions and methods disclosed in this description of the preferred embodiments. Those skilled in the art will appreciate that the present technology has a wide range of applications and that the embodiments may be modified in a wide range without departing from any inventive concept defined by the appended claims.

Claims

1. A shape memory alloy subassembly for manufacturing a shape memory alloy actuator assembly, the subassembly comprising at least one main body portion that holds a pair of crimping portions apart, the crimping portions at least partially closed around a length segment of shape memory alloy wire, the length segment of shape memory alloy wire being relaxed between the crimping portions, wherein when the length segment of shape memory alloy wire is laid on the crimping portions and when the crimping portions are closed around the length segment of shape memory alloy wire, the length segment of shape memory alloy wire is under tension, and the relaxation of the length segment of shape memory alloy wire is achieved by deforming the main body portion.

2. The shape memory alloy subassembly of claim 1, wherein the crimping portion is partially closed around a length of shape memory alloy wire.

3. The shape memory alloy subassembly of claim 1, wherein the crimping portion is completely closed around a length of the shape memory alloy wire.

4. The shape memory alloy subassembly of any one of claims 1-3, wherein the body portion is a sacrificial body portion that is removable from the crimp portion.

5. The shape memory alloy subassembly according to any one of claims 1 to 3, wherein the crimping portion is formed integrally with the body portion.

6. The shape memory alloy subassembly of claim 5, wherein the crimp portion is integrally formed with the body portion from a sheet of material.

7. A shape memory alloy subassembly according to any one of claims 1 to 3 and 6, comprising a single body portion.

8. The shape memory alloy subassembly according to any one of claims 1 to 3 and 6, which is a composite shape memory alloy subassembly comprising a one-dimensional array or a two-dimensional array of body parts connected together.

9. The shape memory alloy subassembly of claim 8, wherein the body portions are connected together by integral forming.

10. The shape memory alloy subassembly of claim 8, wherein the length of the shape memory alloy wire relative to each main body portion is the length of the same piece of shape memory alloy wire.

11. A method of manufacturing a shape memory alloy subassembly, wherein the subassembly is used to manufacture a shape memory alloy actuator assembly, the method comprising: providing at least one body portion that holds a pair of open crimp portions apart; Laying a length of shape memory alloy wire on the pair of open crimping portions or each pair of open crimping portions; as well as at least partially closing the crimping portion around the length of shape memory alloy wire and providing slack to the length of shape memory alloy wire between the crimping portions, The steps of laying the length of shape memory alloy wire on the pair of open crimping parts or each pair of open crimping parts and closing the crimping parts around the length of shape memory alloy wire are performed when the length of shape memory alloy wire is under tension, and the method further comprises: The body portion is deformed to provide slack to the length of shape memory alloy wire between the crimping portions.

12. The method of claim 11, wherein the crimping portion is completely closed around a length of the shape memory alloy wire.

13. The method of claim 11, wherein the crimping portion is partially closed around a length of shape memory alloy wire.

14. The method according to claim 13, further comprising: adjusting the degree of relaxation or tension of the shape memory alloy wire of the length segment; as well as The shape memory alloy wire surrounding the length completely closes the crimping portion.

15. The method according to any one of claims 11 to 14, further comprising: A tool is applied to deflect the length of SMA wire laterally between the crimp portions before closing the crimp portion around the length of shape memory alloy wire and is removed after closing the crimp portion around the length of shape memory alloy wire.

16. A method according to any one of claims 11 to 14, wherein the body portion is a sacrificial body portion that is removable from the crimp portion.

17. A method according to any one of claims 11 to 14, wherein the crimping portion is integrally formed with the body portion.

18. The method of claim 17, wherein the crimp portion is integrally formed with the body portion from a sheet of material.

19. A method according to any one of claims 11 to 14 and 18, wherein a single body portion is provided.

20. A method according to any one of claims 11 to 14 and 18, wherein a one-dimensional array or a two-dimensional array of body portions is provided.

21. The method of claim 20, wherein the body portion is separate.

22. The method of claim 20, wherein the body portions are connected together.

23. The method of claim 22, wherein the body portions are connected together by integral forming.

24. The method of claim 20, wherein the step of laying a length of shape memory alloy wire over each pair of open crimp portions comprises laying the same piece of shape memory alloy wire across all pairs of open crimp portions.

25. A method of manufacturing a shape memory alloy actuator assembly, the method comprising: providing a static portion, a movable portion movable relative to the static portion, and a shape memory alloy subassembly, the shape memory alloy subassembly comprising a main body portion holding a pair of crimping portions apart, the crimping portions at least partially closed around a length of shape memory alloy wire relaxed between the crimping portions, wherein the length of shape memory alloy wire is under tension when the length of shape memory alloy wire is laid on the crimping portions and when the crimping portions are closed around the length of shape memory alloy wire, and the relaxation of the length of shape memory alloy wire is achieved by deforming the main body portion; attaching the crimping portions to the static portion and the movable portion, respectively; as well as The body portion is removed, leaving the crimping portions attached to the static portion and the movable portion, respectively.

26. The method of claim 25, wherein when providing the shape memory alloy subassembly, the crimping portion partially crimps around a length of shape memory alloy wire.

27. The method of claim 26, wherein the method further comprises adjusting a degree of slack or tension of the shape memory alloy wire, and then completely closing the crimping portion around the shape memory alloy wire.

28. The method of claim 27, wherein the step of adjusting the degree of slack or tension of the shape memory alloy wire and then completely closing the crimping portion around the shape memory alloy wire is performed after the step of attaching the crimping portion to the static portion and the movable portion, respectively; and before or after the step of removing the main body portion.

29. The method of claim 25, wherein when providing the shape memory alloy subassembly, the crimping portion is completely crimped around a length of shape memory alloy wire.

30. A method according to any one of claims 25 to 29, wherein the crimping portion is integrally formed with the body portion.

31. The method of claim 30, wherein the crimp portion is integrally formed with the body portion from a sheet of material.

32. The method of any one of claims 25-29 and 31, wherein the step of providing a shape memory alloy subassembly comprises: providing a composite shape memory alloy subassembly comprising an array of body portions connected together; as well as The shape memory alloy subassembly including the body portion is removed from the composite shape memory alloy subassembly.

33. A method according to any one of claims 25-29 and 31, wherein the movable part is supported on a support structure by a suspension system, the suspension system being arranged to guide movement of the movable part relative to the static part.

34. The method of claim 33, wherein the suspension system comprises a bearing arrangement.

35. The method of any one of claims 25-29, 31 and 34, wherein the movable part is an optical element.

36. A method according to claim 35, wherein the movable part is movable relative to the static part along the optical axis of the optical element.

37. The method of claim 35, wherein the movable portion is a lens element comprising at least one lens.

38. A method according to claim 37, wherein the at least one lens has a diameter of at most 20 mm.

39. A method according to claim 37 or 38, wherein the static part has an image sensor mounted thereon, the lens element being arranged to focus an image on the image sensor.

40. A shape memory alloy (SMA) subassembly for use in making a shape memory alloy actuator assembly, the subassembly comprising at least one main body portion holding a pair of connecting components apart, the pair of connecting components being welded to a length of SMA wire relaxed between the connecting components, wherein the length of SMA wire is under tension when the length of SMA wire is laid on the connecting components and when the connecting components are welded, and the relaxation of the length of SMA wire is achieved by deforming the main body portion.

41. The SMA subassembly of claim 40, wherein the body portion is a sacrificial body portion that is removable from the connecting member.

42. An SMA subassembly according to claim 40 or 41, wherein the connecting member is integrally formed with the body portion.

43. An SMA subassembly as claimed in claim 42, wherein the connecting member is integrally formed with the body portion from a sheet of material.

44. An SMA subassembly according to any one of claims 40, 41 and 43, comprising a single body portion.

45. The SMA subassembly of any one of claims 40, 41 and 43, the SMA subassembly being a composite SMA subassembly comprising a one-dimensional array or a two-dimensional array of body portions connected together.

46. ​​The SMA subassembly of claim 45, wherein the body portions are connected together by being integrally formed.

47. The SMA subassembly of claim 45, wherein the length of the SMA wire relative to each body portion is the length of the same piece of SMA wire.

48. A method of manufacturing a shape memory alloy (SMA) actuator assembly, the method comprising: providing a static portion, a movable portion movable relative to the static portion, and an SMA subassembly, the SMA subassembly comprising a main body portion holding a pair of connecting members apart, the connecting members being welded to a length of shape memory alloy wire relaxed between the connecting members, wherein the length of SMA wire is under tension when the length of SMA wire is laid on the connecting members and when the connecting members are welded, and the relaxation of the length of SMA wire is achieved by deforming the main body portion; attaching the connection members to the static part and the movable part respectively; as well as The main body portion is removed, leaving the connecting components attached to the static portion and the movable portion respectively.

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