SMA tactile components and assembly of SMA tactile components

Abstract

An SMA actuator assembly includes two parts movable relative to each other along a motion axis and a length of SMA wire, with each end of the SMA wire connected to one of the parts. One part includes a contact portion, while the other part includes more than one contact portion, the contact portions contacting the SMA wire on opposite sides along the motion axis. The contact portions alternate in a direction normal to the motion axis and are positioned to guide the SMA wire along a zigzag path, such that the parts are driven in opposite directions when the SMA wire contracts. Considering intermediate sections of the SMA wire between contact with adjacent contact portions, the rate of change of the wire length of each intermediate section during contraction of the SMA wire is equal to the total strain of the SMA wire, and there is no slippage of the SMA wire.

Description

Technical Field

[0001] The present invention relates to an actuator that uses a shape memory alloy (SMA) wire to provide relative movement between two components. The present invention also relates to a method for assembling an actuator that uses an SMA wire to provide relative movement between two components. In particular, it relates to such an actuator for use in a haptic assembly. Background Art

[0002] SMA actuators are known for use in handheld electronic devices, such as cameras and mobile phones. In particular, they can be used to provide haptic functionality, providing tactile feedback, for example, in response to a user selecting a specific area of ​​a screen or pressing a button. Such actuators typically function by using the contraction of an SMA wire to induce relative motion between two components. The SMA wire contacts parts (e.g., teeth) of two opposing bodies, which are forced apart due to the change in length of the wire as it contracts.

[0003] However, providing this functionality requires the SMA wire to be in contact with two opposing bodies. Furthermore, the SMA wire is attached at its ends to the bodies to be forced apart. In many prior art devices, as the SMA wire extends from its attachment point to the first tooth, it comes into contact with the body to which it is attached. As the SMA wire contracts, its change in length can cause it to slip relative to the body parts it contacts. This slippage can wear the SMA wire and, due to the variable flexing of the SMA wire around the body parts, can lead to fatigue. This increases the risk of wire failure during repeated actuation of the assembly, resulting in shortened device life and / or loss of functionality.

[0004] Wear caused by this slippage can be reduced by, for example, using low-friction coatings on parts of the body that come into contact with the SMA wire. However, this can increase manufacturing complexity and, therefore, the cost of the device and the manufacturing process. Furthermore, fatigue due to flexure can be reduced by, for example, ensuring that the surfaces in contact with the SMA wire have a large radius of curvature. However, this can increase the size of the device, which is undesirable in many cases. Summary of the Invention

[0005] It would therefore be desirable to provide an SMA actuator assembly having a configuration that reduces slippage of the SMA wire and thereby reduces the potential for wire failure.

[0006] Furthermore, to precisely manufacture SMA actuator assemblies, the SMA wire length and the dimensions of the features relative to the body must be very carefully controlled. This means very high manufacturing tolerances are required to produce satisfactory performance in the finished device. Equipment and processes that allow for sufficiently high tolerances are very expensive and can result in high losses of scrapped parts. Such equipment and processes are also more time-consuming and difficult to control.

[0007] Therefore, it would also be desirable to provide a method of assembling haptic components using shape memory alloy wire that allows the components to be precisely produced without requiring high manufacturing tolerances.

[0008] According to one aspect of the present invention, an SMA actuator assembly is provided, the SMA actuator assembly comprising a first part and a second part movable relative to each other along a travel axis, and a length of SMA wire, each end of the length of SMA wire being connected to the first part or the second part, wherein the first part includes at least one contact portion that contacts the length of SMA wire on a first side of the length of SMA wire along the travel axis, and the second part includes more than one contact portion that contacts the length of SMA wire on a second side of the length of SMA wire opposite the first side along the travel axis, the at least one contact portion of the first part and the more than one contact portion of the second part alternating in a direction normal to the travel axis and relatively positioned so as to guide the length of SMA wire along a tortuous path such that the first part and the second part are driven in opposite directions along the travel axis upon contraction of the length of SMA wire, and wherein the SMA actuator assembly is configured such that, taking into account intermediate SMA segments of the length of SMA wire extending between center points of contact with adjacent contact portions of the first and second parts, a fractional change in length of each intermediate SMA segment upon contraction of the length of SMA wire is proportional to the change in length of the wire. The contact length is at least substantially equal to the total strain of the SMA wire and at least substantially no slippage of the SMA wire is present at the center point of contact.

[0009] Because the strain of a length of SMA wire is the rate of change of the wire length as the material of the SMA wire contracts, by configuring the SMA actuator assembly to match the rate of change of the wire length of each intermediate segment of the length of SMA wire to the total strain of the length of SMA wire, the length of SMA wire is prevented from slipping relative to the point of contact between the contact portion of the SMA wire and the first and second parts. This reduces wear and / or deflection of the length of SMA wire and reduces the likelihood of wire failure.

[0010] In some embodiments, a length of SMA wire is connected at each end to either of the first part and the second part by respective connecting elements that retain the SMA wire.

[0011] The connecting element holds the end of a length of SMA wire in a fixed position relative to the associated parts so that the behavior of the length of SMA wire and the SMA actuator assembly is well defined.

[0012] In some embodiments, also considering an end SMA segment in a length of SMA wire extending from an exit point where the length of SMA wire exits a connecting element to a center point of contact with an adjacent contact portion, the SMA actuator assembly is configured such that as the length of SMA wire contracts, for each of the intermediate SMA segments and the end SMA segments, the rate of change of the wire length of each SMA segment is at least substantially equal to the total strain of the length of the SMA wire, and there is no slippage of the length of the SMA wire at the center point of contact with the contact portion adjacent to the connecting element.

[0013] Advantageously, the rate of change of wire length is appropriately matched across all segments of a length of SMA wire, including at the edges of a component where the wire connects to a part. This is especially true if the end segments have a different geometry than the segments at the center of the component. If the end segments are not designed correctly, slippage and increased wear on a length of SMA wire can still occur.

[0014] In some embodiments, the connecting element is a crimp portion.

[0015] The crimp section provides a convenient connection method that is simple to manufacture and assemble and can also provide an electrical connection to a length of SMA wire.

[0016] In some embodiments, the connecting element further comprises an adhesive between the crimping portion and the adjacent contact portion.

[0017] Including adhesive in addition to the crimp portion means that the exit point of the connecting element is closer to the adjacent contact portion and therefore reduces the likelihood of contact between a length of SMA wire and any component between the exit point and the adjacent contact portion, which contact could increase wear on the SMA wire.

[0018] In some embodiments, the linear length of the SMA segments and the angle of the SMA segments with a plane normal to the axis of movement vary between SMA segments.

[0019] These changes may be advantageous in certain applications.

[0020] In some embodiments, for each SMA segment, a ratio (d / ε) of the relative movement (d) along the axis of movement developed between the first part and the second part at each end of the SMA segment to the rate of change ε ​​of the linear length of the SMA segment is at least substantially equal to a ratio ((L / sin(θ)) of the linear length (L) of the SMA segment to the sine of the angle (sin(θ)) formed by the SMA segment with a plane normal to the axis of movement.

[0021] In some embodiments, the spacing between center points of contact with adjacent contact portions of the first and second parts, along a direction normal to the axis of movement, varies between intermediate SMA sections.

[0022] Allowing the spacing between a line of contact with adjacent contact portions to vary may allow for a greater range of functionality and design flexibility in haptic assemblies.

[0023] In some embodiments, the height of each intermediate SMA segment along the axis of movement between center points of contact with adjacent contact portions of the first and second parts is the same.

[0024] Matching the heights of the SMA sections, particularly the height in the rest position when the SMA wire is not contracted, means that all contacting portions of the first and second parts can be made to the same shape, thereby simplifying manufacture.

[0025] In some embodiments, each of the first and second parts is rigid such that relative movement along the axis of movement between the first and second parts at each end of the intermediate SMA segments is the same for each of the intermediate SMA segments.

[0026] Where the first and second parts are rigid, the first and second parts may be used to provide a uniform tactile response across their entire surfaces.

[0027] In some embodiments, at least one of the first part and the second part is flexible, flexing the at least one of the first part and the second part at least partially provides relative movement between the first part and the second part along the movement axis at each end of the intermediate SMA segment, the relative movement being different between the intermediate SMA segments.

[0028] The flexible member allows for greater design flexibility and a wider variety of possible tactile responses, such as being able to provide variations in the amplitude of the tactile signal across the surface of the SMA actuator assembly.

[0029] In some embodiments, one of the first part and the second part is a beam that extends between two fixed ends that do not move relative to the other of the first part and the second part, and the beam is flexible such that relative movement along the axis of movement of the first part and the second part at each end of the intermediate SMA section increases with increasing distance from the fixed ends to a central portion of the beam.

[0030] An advantage of using a flexible beam with fixed ends is that the ends of the beam at the edges of the SMA actuator assembly can remain flush with the surrounding material even when the assembly is actuated to provide relative movement of two parts at the center of the SMA actuator assembly. This can provide a more aesthetically pleasing appearance or reduce the possibility of fluid or dirt entering the assembly.

[0031] In some embodiments, the separation in a direction normal to the axis of movement between center points of contact with adjacent contact portions of the first and second parts increases with increasing distance from the fixed end to the center portion of the beam.

[0032] Varying the spacing of the contacts with the contact portion allows varying the angle of a length of SMA wire in different SMA segments to provide different magnitudes of relative movement in different regions of the SMA actuator assembly, even if, for example, the heights of the SMA segments along the axis of movement are the same.

[0033] In some embodiments, one of the first part and the second part is a flexible part of a housing of the electronic device.

[0034] In some embodiments, a length of SMA wire is connected to the first part at each end.

[0035] The advantage of connecting both ends of a length of SMA wire to the same part in the component is that no net force is applied between the parts perpendicular to the direction of movement. This can reduce the stress on the suspension mechanism used to suspend the two parts relative to each other.

[0036] In some embodiments, each part has more than one contact portion. This increases the total force applied by a length of SMA wire while minimizing the height along the axis of movement.

[0037] In some embodiments, the parts are configured to be pushed together only by a force applied by a user. This eliminates the need to provide a pushing member to move the parts together.

[0038] In some embodiments, the first part includes a first body, the second part includes a second body, at least one contact portion of the first body includes at least one tooth, more than one contact portion of the second body includes more than one tooth, the teeth of the first body and the second body alternate in a direction normal to the axis of movement and overlap in a direction parallel to the axis of movement, and contact of a length of SMA wire with the teeth of the first body and the second body alternates between the teeth of the first body and the teeth of the second body.

[0039] According to another aspect of the present invention, an SMA actuator assembly is provided, the SMA actuator assembly comprising a first part and a second part movable relative to each other along a travel axis, and a length of SMA wire, each end of the length of SMA wire being connected to the first part or the second part, wherein the first part includes at least one contact portion that contacts the length of SMA wire on a first side of the length of SMA wire along the travel axis, and the second part includes at least one contact portion that contacts the length of SMA wire on a second side of the length of SMA wire opposite the first side along the travel axis, the at least one contact portion of the first part and the at least one contact portion of the second part being relatively positioned so as to guide the length of SMA wire along a tortuous path such that upon contraction of the length of SMA wire, the first part and the second part are driven in opposite directions along the travel axis, wherein the length of SMA wire is connected to the first part or the second part at each end by a respective connecting element that retains the SMA wire; and wherein at each end, the length of SMA wire extends from an exit point of the length of SMA wire from the connecting element to an adjacent contact portion without contacting the part to which the end of the length of SMA wire is connected.

[0040] By ensuring that a length of SMA wire does not come into contact with the part to which it is attached before contacting the contact portion of the device, wear and / or flexing of the wire is reduced. Thus, the life of the SMA assembly can be increased.

[0041] In some embodiments, the shape of each connecting element is designed so that a section of SMA wire extends inside the connecting element in a direction with an exit angle of up to 15° relative to a line from the exit point to the point where the section of SMA wire first contacts an adjacent contact portion to the point where the section of SMA wire exits the connecting element.

[0042] Having a length of SMA wire with a high bend angle at the exit point can increase wear and / or flexing of the wire at that point and increase the likelihood of wire failure. Therefore, ensuring the angle is sufficiently small can further improve the life of the assembly.

[0043] In some embodiments, the outlet angle is at most 10° relative to the line. In another embodiment, the outlet angle is at most 5° relative to the line.

[0044] A smaller exit angle may reduce wear and / or deflection at the exit point, thereby increasing the life of the component.

[0045] In some embodiments, the connecting element is a crimp portion secured to the first part and includes a crimp tab that closes around the length of SMA wire to retain the length of SMA wire.

[0046] Using a crimp tab can be a convenient way to attach a length of SMA wire to a part, providing for simple and quick assembly of the SMA actuator.

[0047] In some embodiments, the crimping portion is made of a sheet material that is bent to provide a portion extending normal to the axis of movement and a portion including the exit point extending at an acute angle greater than 0° relative to a plane normal to the axis of movement.

[0048] Using a curved crimp section allows the wire exit angle to be kept small while allowing the wire to be held at a different angle in another portion of the crimp. This provides greater flexibility in the design of the crimp and also in the manner in which a length of SMA wire is attached to the first and second parts.

[0049] In some embodiments, a portion of the crimping portion extending normal to the axis of movement is fixed to the first part.

[0050] Securing the portion of the crimp normal to the axis of movement to the part allows for a secure and consistent bond to the part regardless of the particular angle selected for the bend.

[0051] In some embodiments, the portion of the crimping portion comprising the exit point of the length of SMA wire protrudes beyond the portion of the first part to which the crimping portion is secured.

[0052] Having an exit point on a protruding portion of the crimp allows the assembly to easily provide both of the following features: a sufficiently small exit angle for a length of SMA wire and no contact between the length of SMA wire and the part it is secured to before contact with the adjacent contact portion. The protrusion ensures that contact is impossible and allows the protruding portion to be angled without interfering with contact with the first part. It also allows for greater space efficiency in the direction of the axis of movement.

[0053] In some embodiments, the line makes an acute angle greater than 0° with respect to a plane normal to the axis of movement.

[0054] This feature means that when a length of SMA wire contracts, the portion of the length of SMA wire between the connecting element and the adjacent contact portion may also contribute to providing the force to separate the two parts.

[0055] In some embodiments, a length of SMA wire is connected to the first part at each end.

[0056] The advantage of attaching both ends of a length of SMA wire to the same part is that no net force is applied between the parts perpendicular to the direction of movement. This can reduce the strain on the suspension mechanism used to suspend the two parts relative to each other.

[0057] In some embodiments, the first part has at least one contact portion, preferably more than one contact portion, and the second part has more than one contact portion, the contact portions of the two parts alternating in a direction normal to the axis of movement, and the contact of a length of SMA wire with the contact portion alternates between the first part and the second part. This increases the total force applied by the length of SMA wire while minimizing the height along the axis of movement.

[0058] In some embodiments, the first part includes a first body, the second part includes a second body, at least one contact portion of the first body includes at least one tooth, at least one contact portion of the second body includes at least one tooth, the teeth of the first body and the teeth of the second body overlap in a direction parallel to the axis of movement, and contact of a section of the SMA wire with the teeth of the first body and the teeth of the second body alternates between the teeth of the first body and the teeth of the second body.

[0059] According to another aspect of the present invention, a method of manufacturing an SMA actuator assembly is provided, the SMA actuator assembly comprising a first part and a second part movable relative to each other along a travel axis, and a length of SMA wire, each of the ends of the length of SMA wire being connected to the first part or the second part, wherein the first part includes at least one contact portion that contacts the length of SMA wire on a first side of the length of SMA wire along the travel axis, and the second part includes at least one contact portion that contacts the length of SMA wire on a second side of the length of SMA wire opposite the first side along the travel axis, the at least one contact portion of the first part and the at least one contact portion of the second part being relatively positioned to guide the length of SMA wire along a tortuous path such that upon contraction of the length of SMA wire, the first part and the second part are driven in opposite directions along the travel axis, wherein the method includes controlling the tension in the length of SMA wire and / or the path length of the length of SMA wire between the connected ends of the length of SMA wire when assembling the SMA actuator assembly.

[0060] Thus, a method is provided in which the characteristics of a finished SMA actuator assembly can be determined very accurately without requiring very high manufacturing tolerances on the component parts. This is achieved by compensating for variations that have occurred in the manufacture of the components of the SMA actuator assembly during assembly of the SMA actuator assembly.

[0061] In some embodiments, the method includes connecting a length of SMA wire at each end to either one of a first part and a second part, and assembling the first part and the second part, wherein the length of SMA wire extends between the first part and the second part, the first part and the second part are provided with adjustable end stops that limit relative movement of the first part and the second part toward each other, and adjusting the adjustable end stops to control tension in the length of SMA wire while applying a predetermined force between the first part and the second part.

[0062] Adjustment of the end stops provides a convenient way to adjust the length of the tortuous path between the parts, thereby providing the correct tension in the length of the SMA wire. This is convenient in situations where adjusting the length of the wire is difficult or undesirable.

[0063] In some embodiments, the adjustable end stop arrangement comprises at least one mechanically adjustable end stop.

[0064] Mechanically adjustable end stops provide an easy mechanism to adjust to the correct size.

[0065] In some embodiments, the adjustable end stop includes at least one end stop mounted in a bed of adhesive, the step of adjusting the adjustable end stop includes adjusting the at least one end stop when the adhesive is uncured, and the method further includes curing the adhesive after adjusting the adjustable end stop.

[0066] The use of adhesive is a convenient method of adjusting the position of the end stop because the deformation of the adhesive during assembly maintains the correct position of the end stop. The curing of the adhesive fixes this position in the final product.

[0067] In some embodiments, the method includes assembling a first part and a second part with a length of SMA wire extending between the first part and the second part, and connecting an end of the length of SMA wire to either of the first part and the second part, and controlling the tension in the SMA wire between the ends of the length of SMA wire while holding the parts in a fixed position relative to each other before the end of the length of SMA wire is fully connected to either of the first part and the second part.

[0068] This embodiment allows the tension in the wire to be controlled to match the length of the tortuous path defined by the fixed relative positions of the parts. This is useful if a specific relative position of the parts is required in the finished product.

[0069] In some embodiments, during the step of connecting the ends of a length of SMA wire to either the first part and the second part, the wire length of the length of SMA wire between the ends of the length of SMA wire is fixed, and the tension is controlled by selecting at least one of the positions where the ends of the length of SMA wire are connected to either the first part and the second part.

[0070] Selecting the location at which the end of a length of SMA wire is connected is a convenient way to adjust the tension in the wire during assembly because the location can be selected while still applying the desired tension.

[0071] In some embodiments, the step of connecting an end of a length of SMA wire to either of the first part and the second part includes connecting one of the ends of the length of SMA wire to either of the first part and the second part, and controlling the tension by adjusting the position at which the other end of the end of the length of SMA wire is connected to either of the first part and the second part while holding the parts in a fixed position relative to each other.

[0072] Fixing one end of the line and adjusting the position where the other end is fixed means that the position can be set in a controlled manner to provide the correct tension, while only the position of a single component needs to be adjusted.

[0073] In some embodiments, a length of SMA wire is connected to either the first part or the second part by crimping a crimping portion that crimps an end of the length of SMA wire, and the location where the end of the length of SMA wire is connected to either the first part or the second part is selected by selecting the location where the crimping portion is fixed to either the first part or the second part.

[0074] Crimp sections are a particularly convenient choice for fixing because they are easy to assemble and can be compact in their assembled state. Crimp sections can also be used to provide an electrical connection to a length of SMA wire.

[0075] In some embodiments, the step of assembling the first part and the second part with a length of SMA wire extending between the first part and the second part is performed with the length of SMA wire held by a fret comprising a sacrificial body and two crimping portions crimping ends of the length of SMA wire, the sacrificial body having an elastic portion arranged to apply a predetermined tension to the length of SMA wire, the step of connecting the ends of the length of SMA wire to either of the first part and the second part comprises fixing the crimping portions to either of the first part and the second part at selected positions while the tension of the length of SMA wire between the ends of the length of SMA wire is controlled by the elastic portion of the fret, and after connecting the crimping portions to either of the first part and the second part, removing the sacrificial body, leaving the crimping portions fixed to either of the first part and the second part.

[0076] The use of a compression structure simplifies the process of assembling the SMA actuator assembly by allowing a standard tension to be applied to the wire in a controlled manner during assembly. Removing the sacrificial portion allows the crimp section to be compact in the completed assembly while still allowing a standard predetermined tension to be applied consistently during assembly.

[0077] In some embodiments, in the step of connecting an end of a length of SMA wire to either the first part or the second part, the positions at which the end of the length of SMA wire is connected to either the first part or the second part are fixed, and the tension is controlled by adjusting the wire length of the length of SMA wire between these positions.

[0078] Adjusting the wire length provides a way to match the wire tension to the tortuous path length where a length of SMA wire is required to be connected at a specific location and the relative positions of the parts are also predetermined.

[0079] In some embodiments, the step of assembling the first part and the second part with a length of SMA wire extending between the first part and the second part is performed with the length of SMA wire located in a crimping portion that partially crimps an end of the length of SMA wire, and the step of connecting an end of the length of SMA wire to either the first part or the second part includes: connecting the crimping portion to either the first part and the second part at a fixed position; controlling tension in the length of SMA wire by adjusting the length of the SMA wire between the crimping portions; and compressing the crimping portion to complete the crimping of the length of SMA wire by the crimping portion.

[0080] Partially crimping the crimp portion allows a length of SMA wire to be securely held and correctly positioned in an assembly during assembly, while still allowing the wire length to be adjusted by applying tension to the length of SMA wire.

[0081] In some embodiments, the first part and the second part are provided with end stops that limit relative movement of the first part and the second part toward each other, and the first part and the second part are maintained in a fixed position relative to each other by holding the first part and the second part together against the end stops.

[0082] The use of end stops allows the relative position of a first part and a second part to be fixed during assembly if a specific component size or part position is required in the final assembly.

[0083] In some embodiments, a length of SMA wire is connected at each end to the same one of the first part and the second part.

[0084] Connecting both ends of a length of SMA wire to the same part reduces the force applied between the parts in a direction normal to the direction of movement, thereby reducing undesirable movement and reducing strain on any suspension mechanism holding the parts.

[0085] In some embodiments, the method includes: assembling a first of a first part and a second part with a length of SMA wire using another part that shapes the length of SMA wire to follow a path of a predetermined length; connecting an end of the length of SMA wire to the first part, and adjusting the tension of the length of SMA wire between the ends of the length of SMA wire while holding the first part and the other part in a fixed position relative to each other before completing the connection of the end of the length of SMA wire to the first part; removing the other part; and assembling the second part with the first part and the length of SMA wire extending between the first part and the second part.

[0086] In some cases where it is difficult to set the wire length or tension of a length of SMA wire in situ at the time of assembly, it may be convenient to use another part to predetermine the wire length of the length of SMA wire.

[0087] In some embodiments, during the step of connecting the ends of a length of SMA wire to the first part, the connection points where the ends of the length of SMA wire connect to the first part are in fixed positions, and the tension is adjusted by adjusting the wire length of the length of SMA wire between the connection points.

[0088] Adjusting the wire length may be the preferred method where the connection point is required to be at a specific location on the first part.

[0089] In some embodiments, during the step of connecting the ends of a length of SMA wire to the first part, the wire length of the length of SMA wire between the ends of the length of SMA wire is fixed, and the tension is adjusted by adjusting the position of at least one of the connection points where the ends of the length of SMA wire connect to the first part.

[0090] When the relative positions of the parts are predetermined, adjusting the position of the connection point can be a convenient way to set the tension in a length of SMA wire and allow the correct tension to be applied consistently.

[0091] In some embodiments, the length of SMA wire is connected to either of the first and second parts by crimping an end of the length of SMA wire and securing it to a crimped portion of either of the first and second parts.

[0092] The crimp section provides a convenient way to secure a length of SMA wire to a first part and a second part using purely mechanical means and without the need for adhesives or a curing process. If the crimp is conductive, they can also be used to make an electrical connection to a length of SMA wire.

[0093] In some embodiments, at least one part, and preferably each part, has more than one contact portion, the contact portion of the first part and the contact portion of the second part alternate in a direction normal to the axis of movement, and contact of a length of SMA wire with the contact portion alternates between the contact portion of the first part and the contact portion of the second part.

[0094] In some embodiments, the tension in a length of SMA wire and / or the path length of a length of SMA wire between connected ends of the length of SMA wire is controlled by components being in specific relative positions. The specific positions may correspond to the rest positions of the SMA actuator assembly.

[0095] In some embodiments, the first part includes a first body, the second part includes a second body, at least one contact portion of the first body includes at least one tooth, at least one contact portion of the second body includes at least one tooth, and the teeth of the first body and the teeth of the second body overlap in a direction parallel to the movement axis.

[0096] According to yet another aspect of the present invention, an SMA actuator assembly is provided, the SMA actuator assembly comprising a first part and a second part movable relative to each other along a travel axis, and a length of SMA wire, each of the ends of the length of SMA wire being connected to the first part or the second part, wherein the first part includes at least one contact portion that contacts the length of SMA wire on a first side of the length of SMA wire along the travel axis, and the second part includes at least one contact portion that contacts the length of SMA wire on a second side of the length of SMA wire opposite to the first side along the travel axis, the at least one contact portion of the first part and the at least one contact portion of the second part being relatively positioned so as to guide the length of SMA wire along a tortuous path such that when the length of SMA wire contracts, the first part and the second part are driven in opposite directions along the travel axis, the SMA actuator assembly having means for providing control of the tension in the length of SMA wire and / or the path length of the length of SMA wire between the connected ends.

[0097] According to yet another aspect of the present invention, there is provided a set (e.g., >100) of SMA actuator assemblies manufactured using the method, each SMA actuator assembly in the set having substantially the same tension in a length of SMA wire and / or substantially the same path length of the length of SMA wire between connected ends of the length of SMA wire (e.g., within 5%, 1%, 0.5%, or 0.1%). BRIEF DESCRIPTION OF THE DRAWINGS

[0098] Embodiments of the invention will now be described, by way of non-limiting examples, with reference to the accompanying drawings, in which:

[0099] Figure 1 An SMA actuator assembly is shown;

[0100] Figure 2 Shows Figure 1 sections of the component in before and during actuation;

[0101] Figure 3 An assembly is shown wherein the spacing perpendicular to the direction of movement of contact with a length of SMA wire varies across the assembly;

[0102] Figure 4 An assembly having a flexible body is shown during actuation;

[0103] Figure 5 An assembly having a connecting element including a crimp portion and an adhesive is shown;

[0104] Figure 6 Another SMA actuator assembly is shown;

[0105] Figure 7 A section of an SMA actuator assembly is shown;

[0106] Figure 8 shows a section of an SMA actuator assembly according to an embodiment of the present invention;

[0107] Figure 9 The assembly is shown with a protruding crimp portion;

[0108] Figure 10 shows the crimped portion before the bent portion is formed;

[0109] Figure 11 A crimping portion formed with a bent portion is shown;

[0110] Figure 12 An SMA actuator assembly is shown;

[0111] Figure 13 shows assembling the SMA actuator assembly by adjusting the end stops;

[0112] Figure 14 shows assembling an SMA actuator assembly by adjusting the position of the connection points of a length of SMA wire;

[0113] Figure 15 Shows the available Figure 14 The compression piece used in the assembly shown in ;

[0114] Figure 16 shows assembling an SMA actuator assembly by adjusting the wire length of a length of SMA wire;

[0115] Figure 17 shows the assembly of the SMA actuator assembly using another part;

[0116] Figure 18 is a flow chart of a manufacturing method including adjusting an end stop;

[0117] Figure 19 is a flow chart of a manufacturing method including adjusting a connection point between a length of SMA wire and a part;

[0118] Figure 20 is a flow chart of a manufacturing method comprising adjusting a wire length of a length of SMA wire; and

[0119] Figure 21 is a flow chart of a manufacturing method that includes using another part. DETAILED DESCRIPTION

[0120] Figure 1 An SMA actuator assembly 2 of the type in which the present disclosure may be implemented is shown. The SMA actuator assembly 2 comprises a first body 4 and a second body 6 movable relative to each other along a movement axis M. The first body 4 and the second body 6 are examples of first and second parts. Figure 1 The first body 4 and the second body 6 shown are solid bodies that can be formed by injection molding or milling. However, it is not necessary to form the parts in this way, and in some embodiments, the parts can take other forms, such as being hollow or formed from sheet material. The first part and the second part provide two parts that can move relative to each other so that a tactile signal can be provided to the user. Throughout the description, the embodiments will generally be described with reference to the first body 4 and the second body 6 of the embodiment shown in the figures. However, any of the embodiments described herein can also be implemented using other types of first parts and second parts in addition to the first and second bodies.

[0121] Although not in Figure 1 , the SMA actuator assembly 2 may include a suspension system that holds the two bodies 4, 6 relative to each other and permits them to move along the axis of movement M. The suspension system may permit the two bodies 4, 6 to move relative to each other along the axis of movement M while limiting or preventing relative movement of the two bodies 4, 6 in a plane perpendicular to the axis of movement M. The suspension system (or some other device) may also limit or prevent relative rotation of the two bodies 4, 6 due to, for example, off-center forces applied to the SMA actuator assembly 2 by a user.

[0122] In some embodiments, the SMA actuator assembly 2 is integrated into a larger device. In some embodiments, the first body 4 can be a stationary body that does not move relative to the device during actuation of the SMA actuator assembly 2, while the second body 6 can be a moving body that moves relative to the device during actuation of the SMA actuator assembly 2. Alternatively, both bodies 4, 6 can move during actuation.

[0123] The first body 4 has at least one tooth 8, and the second body 6 has more than one tooth 8. The teeth 8 of the first body 4 and the teeth 8 of the second body 6 are examples of the contact portion of the first part and the contact portion of the second part. In the embodiment shown in the figures, the teeth 8 of the first body 4 and the teeth 8 of the second body 6 are substantially solid and integrally formed with the respective bodies. However, this is generally not necessary, and the contact portions of the parts may take other forms, such as being hollow, formed separately from the body, or formed from other materials such as metal.

[0124] exist Figure 1 In the embodiment shown, the first body 4 has two teeth and the second body 6 has three teeth. The teeth 8 of the first body 4 and the teeth 8 of the second body 6 alternate in a direction normal to the axis of movement M and overlap in a direction parallel to the axis of movement M. This means that for any tooth 8 on either body, the nearest adjacent tooth 8 will be a tooth 8 on the other body. The overlapping of the teeth means that the uppermost portion of a tooth 8 on the first body is higher than the lowermost portion of an adjacent tooth 8 on the second body 4 (where "upper" for this purpose is defined as in the direction of movement of the second body 6 relative to the first body 4 when the SMA wire 10 contracts).

[0125] The shape of the teeth 8 can be any suitable shape to provide contact with a length of SMA wire 10 as described below. In the embodiment shown in the figures, the uppermost portion of the teeth 8 has a curved shape. However, other shapes can also be used. For example, the uppermost portion of the teeth 8 can have a pointed shape, or the uppermost portion of the teeth can be flat. In addition, the lowermost portion of the teeth 8 can be triangular as shown, or can be rectangular or any other shape. In embodiments such as Figure 1 In the embodiment shown, each of the bodies has more than one tooth 8 .

[0126] The SMA actuator assembly 2 also includes a length of SMA wire 10 connected at each end to either the first body 4 and the second body 6. In some embodiments, the ends of the length of SMA wire 10 are connected to different ones of the two bodies. Preferably, the length of SMA wire 10 is connected to the same body at each end, that is, both ends of the length of SMA wire 10 are connected to the first body 4 or both ends are connected to the second body 6. Connecting both ends to the same body reduces the force between the first body 4 and the second body 6 in a direction perpendicular to the moving axis M during actuation of the SMA actuator assembly. In some embodiments, the length of SMA wire 10 is connected to the first body 4 at each end. This may be preferred in embodiments where the first body 4 is a stationary body. In Figure 1 In the embodiment shown, both ends of a length of SMA wire 10 are connected to the first body 4 .

[0127] In some embodiments, a length of SMA wire 10 is connected to either the first body 4 or the second body 6 at each end by a respective connecting element 18 that holds the length of SMA wire 10. Any suitable means or wire attachment device can be used as the connecting element 18 to hold the length of SMA wire 10. In some embodiments, one or both of the connecting elements 18 are crimping portions. The crimping portions can be secured to the first body 4 or the second body 6. The crimping portions crimp the ends of the length of SMA wire 10. This can be achieved by compressing the ends of the wire 10 between two deformable materials. Using a metal crimping portion may be desirable, particularly where crimping is used to both electrically connect the length of SMA wire 10 and secure the length of SMA wire 10 to the first body 4 or the second body 6.

[0128] In some embodiments, the connecting element 18 includes a crimping portion 17 and an adhesive 19 between the crimping portion 17 and the adjacent teeth 8. Figure 5 , and can be applied to any of the SMA actuator assemblies 2 disclosed herein. When the SMA wire within the adhesive 19 is secured, the adhesive 19 can be used to effectively reduce the length of the end SMA segment between the exit point of the connecting element 18, now formed by the adhesive 19, and the adjacent tooth 8, compared to using the crimp portion 17 alone. This can be used, in part, to meet the following condition (discussed further below): the rate of change of the wire length of each SMA segment matches the strain of the length of the length of the SMA wire 10.

[0129] The teeth 8 of the first body 4 contact the SMA wire 10 from below on a first side of the SMA wire 10 along the axis of movement, and the teeth 8 of the second body 6 contact the SMA wire 10 from above on a second side of the SMA wire 10, opposite the first side, along the axis of movement. The SMA wire 10 extends between the first and second bodies 4, 6 and is guided by the teeth 8 along a tortuous path between the first and second bodies 4, 6, and contacts the teeth 8. A tortuous path is any path that is not a straight line between the end of the SMA wire 10 and the point where it connects to the first or second body. Therefore, the tortuous path followed by the SMA wire 10 will have a line length (i.e., the length of the path followed by the SMA wire 10) that is greater than the shortest distance between the connecting elements 18. The tortuosity of the tortuous path can be measured using the ratio of the length of the tortuous path to the shortest distance between the connecting elements 18.

[0130] The contact of the length of SMA wire 10 alternates between the teeth 8 of the first body 4 and the teeth 8 of the second body 6. In some embodiments, the length of SMA wire crosses from the first body 4 to the second body 6 (and back again) two or more times. In some embodiments, for example Figure 1 In the embodiment shown, a length of SMA wire 10 contacts all of the teeth 8 of the first body 4 and all of the teeth 8 of the second body 6 in the alternating manner described above.

[0131] The teeth 8 of the first body 4 and the teeth 8 of the second body 6 are positioned relative to each other, and alternating contact of a length of SMA wire 10 with the teeth 8 of the first body 4 and the teeth 8 of the second body 6 causes the first body 4 and the second body 6 to be driven apart along the movement axis M when the length of SMA wire 10 contracts. The length of SMA wire 10 is arranged so that when the length of SMA wire 10 contracts, the first and second bodies move away from each other. This is caused by the overlap of the teeth 8 of the first body 4 and the teeth 8 of the second body 6, so that when the length of SMA wire contracts, the length of SMA wire exerts a force on the teeth 8. In other embodiments, the first body 4 and the second body 6 can move together as long as the first body 4 and the second body 6 move in opposite directions.

[0132] In some embodiments, the two bodies are provided with end stops 12 that limit the relative movement of the two bodies toward each other. The end stop 12 may be provided on the same of the two bodies, for example, Figure 11 and 2. The end stops 12 are shown on the first body 4. Alternatively, the end stops 12 may be provided on different of the two bodies, for example, at different ends of the SMA actuator assembly 2, or the end stops 12 may be provided on both bodies, for example, at both ends of the SMA actuator assembly 2. The end stops 12 define a minimum separation between the first body 4 and the second body 6. In some embodiments, when the SMA actuator assembly 2 is not actuated, i.e., when the length of SMA wire 10 is not contracted, the minimum separation will be the separation in the rest position. In the rest position, the two bodies are in contact with the end stops 12.

[0133] In some embodiments, the SMA actuator assembly 2 includes a device (e.g., a resilient element such as a spring) to provide a force ("return force") that pushes the two bodies 4, 6 together along the axis of movement M, such that when power to the length of SMA wire 10 is reduced or stopped, the length of SMA wire 10 expands as the length of SMA wire 10 cools, and the two bodies 4, 6 move back, e.g., toward a rest position. In other embodiments, the SMA actuator assembly 2 does not include such a device, in which case the return force can be provided by a user (e.g., by finger pressure) on the area of ​​the electronic device to which the SMA actuator assembly 2 is coupled.

[0134] like Figure 2 As shown, a length of SMA wire 10 can be considered to be composed of a series of segments 44, wherein the boundaries between the segments 44 are the contact points 40, 42 with adjacent teeth 8. In embodiments where a length of SMA wire 10 contacts each tooth 8 for a distance (e.g., if the uppermost point of the tooth 8 has a curved or flat surface), the boundaries between the segments 44 are the middle of the contact area where the length of SMA wire 10 contacts the adjacent tooth 8. For ease of understanding, reference will generally be made to the following. Figure 2 The embodiment shown is one in which a section of SMA wire 10 contacts each tooth 8 at one point, or at least over a very short distance. However, the description also applies, mutatis mutandis, to embodiments in which a section of SMA wire 10 contacts each tooth 8 over a distance, in which case parameters such as θ and L (see below) may be defined with reference to the complete section 44 or only to those portions of the section 44 that are in space (i.e., not in contact with any tooth 8).

[0135] In some embodiments, the height h of each intermediate SMA segment 44 along the movement axis M between the center points of contact with adjacent teeth 8 of the first and second bodies 4, 6 is the same. The height h along the movement axis M is the projection of the intermediate SMA segment 44 onto the movement axis M. In particular, the height h of each intermediate SMA segment 44 is the same in the rest position prior to actuation of the SMA actuator assembly 2. In the case where the first and second bodies 4, 6 are rigid, the height of each intermediate SMA segment 44 is also the same in the actuated position.

[0136] Considering the intermediate SMA segments 44 of a length of SMA wire 10 extending between the center points 40, 42 of contact with adjacent teeth 8 of the first and second bodies 4, 6, the SMA actuator assembly 2 is configured such that, as the length of SMA wire 10 contracts, the rate of change of the wire length of each intermediate SMA segment 44 is equal to the strain of the length of SMA wire 10. Since the strain of a length of SMA wire 10 is the rate of change of the wire length of the material of the SMA wire 10, configuring the first and second bodies 4, 6 such that each intermediate SMA segment 44 has the same rate of change of wire length means that the length of SMA wire 10 does not slip at the point of contact when the length of SMA wire 10 contracts, causing the first and second bodies 4, 6 to move relative to each other. This can be achieved by configuring the first body 4 and the second body 6, for example, configuring the length and angle of a section of SMA wire 10 between the contact points 40, 42, so that for a given relative movement of the first body 4 and the second body 6, the rate of change of the wire length in all intermediate sections 44 of the section of SMA wire 10 is the same and matches the total strain of the section of SMA wire 10.

[0137] Preventing slippage of the length of SMA wire 10 prevents damage to the length of SMA wire 10 where it contacts the teeth 8 of the first body 4 and the teeth 8 of the second body 6. Such damage could occur due to friction and wear and / or flexure and fatigue if the length of SMA wire 10 slips on the teeth 8. Preventing this type of damage can substantially increase the life expectancy of the actuator assembly 2.

[0138] In some embodiments, also taking into account the end SMA segments of a length of SMA wire 10 extending from an exit point of the length of SMA wire 10 from the connecting element 18 to a center point of contact with an adjacent tooth 8, the SMA actuator assembly 2 is configured such that as the length of SMA wire 10 contracts, for each of the intermediate SMA segments 44 and the end SMA segments, the rate of change of the wire length of each SMA segment is equal to the strain of the length of the length of SMA wire 10.

[0139] In this embodiment, slippage of a length of SMA wire 10 on portions of the first body 4 and / or second body 6 is also avoided at the end of the length of SMA wire 10 where the wire is connected to the body and where it contacts the first and / or last teeth during actuation. To avoid such slippage, the connecting element 18 (and / or any other component at the end of the SMA actuator assembly 2 that holds the length of SMA wire, such as where the connecting element 18 includes a crimp portion and adhesive) is positioned so that the length of SMA wire 10 contracts in an equivalent manner on either side of the first / last tooth. This is achieved by ensuring that the end SMA segments are subject to the same constraints as the middle SMA segment 44.

[0140] The condition to prevent a section of SMA wire 10 from sliding relative to the tooth 8 is given by Figure 2 The parameters in FIG. 1 are shown. The solid line shows the configuration of the SMA actuator assembly 2 in the rest position when a section of SMA wire 10 is not contracted. The dashed line shows the configuration in the actuated state when a section of SMA wire 10 is contracted. Figure 2 In the embodiment of the invention, the first body 4 is the stationary body and the relative motion of the two bodies 4, 6 is entirely due to the movement of the second body 6. The condition of avoiding slip can be achieved when the distance d of the relative movement of the two bodies 4, 6 along the movement axis M during actuation has the same relationship to the rate of change ε ​​of the wire length of each SMA segment of a length of SMA wire 10. This applies to the intermediate SMA segment 44 as well as the end SMA segments in the embodiment where the end segments are subject to the same constraints as the intermediate SMA segment 44. Considering that the intermediate SMA segment 44 (which, as described above, spans the length of the length of SMA wire 10 between the center points 40, 42 of contact between two adjacent teeth of the first body 4 and the second body 6) forms an angle θ with respect to the plane normal to the movement axis M, the segment length L of the length of the wire should be given by the following formula:

[0141]

[0142] like Figure 2As shown, angle θ and length L are defined, for example, when the SMA actuator assembly 2 is in a rest position, wherein the length of SMA wire 10 is uncontracted and the first and second bodies 4, 6 are separated by a minimum separation. Equation 1 reflects the gearing effect created by providing the SMA segments at an angle relative to the axis of motion M, i.e., the relative movement d of the two bodies is greater than the change in the length of the SMA segments (Lε) multiplied by a factor that increases as the angle θ decreases (e.g., 1 / sin(θ)). Also according to Equation 1, the ratio of the relative movement between the two bodies to the rate of change of the wire length of each SMA segment (d / ε) is equal to the ratio (L / sin(θ)) and can be controlled by appropriately controlling angle θ and the length L of the SMA segments. In the case where both bodies 4, 6 are rigid, these ratios should be the same for each SMA segment. Broadly speaking, in such an assembly 2, an SMA segment at a greater angle θ relative to a plane normal to the axis of motion M must have a greater wire length L than another SMA segment.

[0143] exist Figure 3 In the embodiment shown, the spacing in the direction normal to the axis of movement M between the center points 40, 42 of contact with adjacent teeth 8 of the first and second bodies 4, 6 varies between the intermediate SMA sections 44. This variation in spacing may occur because the spacing of the teeth 8 on the first body 4 in the direction normal to the axis of movement M is different from the spacing of the teeth 8 on the second body 6. Alternatively or additionally, the variation in spacing may occur because the spacing of the teeth 8 on one or both bodies is different along the entire length of the body. Figure 3 In an embodiment of the present invention, the spacing of the teeth 8 on the second body 6 varies along the second body 6 and is also different from the spacing of the teeth 8 on the first body 4. Therefore, the spacing a is different from the spacing b. In such an embodiment, if the parameters are not carefully selected, slippage of the length of SMA wire 10 relative to the teeth 8 is particularly likely. Therefore, in such an embodiment, it is particularly advantageous to ensure that the angle θ and length L of the segment of SMA wire 10 obey the above conditions.

[0144] In general, the angle θ and length L of the SMA segments vary along the length of the SMA actuator assembly 2. If a higher force is required on a particular tooth 8, then the angle θ is increased (i.e., the angle between the line and the axis of movement M is decreased) for a corresponding intermediate SMA segment 44 of the same length, for example. If greater motion or force is required, then the length L of the SMA segment is preferably increased.

[0145] In some embodiments, for example Figure 3In the illustrated embodiment, each of the first body 4 and the second body 6 is at least substantially rigid such that the relative movement along the axis of movement M between the first body 4 and the second body 6 at each end of the intermediate SMA segments 44 is the same for each of the intermediate SMA segments 44. In such an embodiment, in order to comply with the above-mentioned constraints on the lengths and angles of the SMA segments, the SMA actuator assembly 2 can be configured such that the angle between the center points 40, 42 of contact with adjacent teeth 8 of the first body 4 and the second body 6 varies between the intermediate SMA segments 44. This ensures that the angles can be properly matched if the spacing between the center points 40, 42 of contact with adjacent teeth in a direction normal to the axis of movement M varies for different intermediate SMA segments. Figure 3 The variation shown—i.e., SMA segments having larger angles θ (and therefore higher forces on the teeth 8) toward the end of a length of SMA wire 10—may be advantageous in some applications, such as for increasing rotational stability and / or for counteracting uneven forces associated with, for example, having to move a beam-like body (which may be part of a device housing).

[0146] One or both of the first body 4 and the second body 6 can be flexible. In embodiments where the first body 4 is a stationary body fixed to the device in which the SMA actuator assembly 2 is used, the second body 6 can be flexible. This may be particularly true where the second body 6 is constrained from movement at both ends but is able to flex to produce movement at the center. In such cases, different displacements and / or forces may be required at different locations along the SMA actuator assembly 2, and these can be achieved by appropriately varying the angle θ and length L of the SMA segments along the length of the SMA actuator assembly 2.

[0147] Figure 4 An embodiment is shown in which at least one of the first and second bodies 4, 6 is flexible such that flexure thereof at least partially provides relative movement of the first and second bodies 4, 6 along the movement axis M, whereby the relative movement along the movement axis M between the first and second bodies 4, 6 developed at each end of the intermediate SMA segments 44 is different between the intermediate SMA segments 44. In embodiments where one of the bodies is flexible, it is advantageous to vary the spacing in a direction normal to the movement axis M between the center points 40, 42 of contact with adjacent teeth 8. As discussed above, this will vary the angle θ between the SMA segments so as to provide different forces and relative displacements of the two bodies at different points along the SMA actuator assembly 2. Figure 4 In the example shown, the first body 4 is rigid and the second body 6 is flexible, although in general either or both of the bodies may be flexible.

[0148] exist Figure 4 In the embodiment of FIG. 5 , the SMA actuator assembly 2 is designed such that the height of the teeth 8 of the first body along the axis of movement M is constant along the length of the SMA actuator assembly 2 to maintain a constant Z height. However, at the edges of the device, the angle between the line and the direction of movement is smaller (and therefore the angle θ defined above is larger) to account for the reduced displacement in the direction of the axis of movement M possible at the edges of the SMA actuator assembly 2.

[0149] Figure 4 Example parameters for the embodiment shown in are given in Table 1 below. Although shown Figure 4 The SMA actuator assembly is in an actuated state (wherein the center of the second body 6 is displaced on the movement axis M), but the parameters angle θ and length L are measured in the rest position (ie, non-actuated state) as described above.

[0150] Table 1

[0151]

[0152]

[0153] In some embodiments, one of the first and second bodies 4, 6 is a beam extending between two fixed ends that do not move relative to the other of the first and second bodies 4, 6. The beam is flexible such that relative movement along the axis of movement M of the first and second bodies 4, 6 at each end of the intermediate SMA segment 44 increases with increasing distance from the fixed ends to the center of the beam. In such embodiments, the spacing between the center points 40, 42 of contact with adjacent teeth 8 of the first and second bodies, along a direction normal to the axis of movement M, can increase with increasing distance from the fixed ends to the center of the beam. This reduces the angle θ near the center compared to the angle θ near the fixed ends, thereby providing greater relative movement of the two bodies near the center of the SMA actuator assembly 2. This also provides the effect of causing the center of the SMA actuator assembly 2 to bulge upward, providing a tactile effect even when the ends of the beam are fixed and do not move relative to the other body.

[0154] In some embodiments, one of the first body 4 and the second body 6 is a flexible portion of the housing of the electronic device. Using a flexible body in such an embodiment of the SMA actuator assembly 2 is particularly advantageous because the flexibility means that the edges of the assembly 2 can be seamless and flush with the housing of the electronic device.

[0155] According to another aspect of the present invention, there is also provided an SMA actuator assembly, wherein a length of SMA wire is connected at each end to a first part or a second part by a corresponding connecting element that holds the SMA wire; and wherein, at each end, a length of SMA wire extends from an exit point of the length of SMA wire from the connecting element to an adjacent contact portion without contacting the part to which the end of the length of SMA wire is connected. Figures 6 to 11 This aspect of the present invention is described.

[0156] Figure 6 Another SMA actuator assembly 2 of the type in which the present disclosure may be implemented is shown. The SMA actuator assembly 2 includes a first body 4 and a second body 6 movable relative to each other along a movement axis M. The first body 4 and the second body 6 are examples of first and second parts. Figure 6 The first and second bodies 4, 6 shown are solid bodies that can be formed by injection molding or milling. However, it is not necessary to form the parts in this way, and in some embodiments, the parts can take other forms, such as being hollow or formed from sheet material. The first and second parts provide two parts that can move relative to each other so that a tactile signal can be provided to the user. Throughout the description, the embodiments will generally be described with reference to the first and second bodies 4, 6 of the embodiments shown in the figures. However, any of the embodiments described herein can also be implemented using other types of first and second parts in addition to the first and second bodies.

[0157] Although not in Figure 6 , the SMA actuator assembly 2 may include a suspension system that holds the two bodies 4, 6 relative to each other and allows them to move along the movement axis M. The suspension system may allow the two bodies 4, 6 to move relative to each other along the movement axis M while limiting or preventing relative movement of the two bodies 4, 6 in a plane perpendicular to the movement axis M and / or limiting or preventing relative rotation of the two bodies 4, 6.

[0158] In some embodiments, the SMA actuator assembly 2 is integrated into a larger device. In such embodiments, the first body 4 can be a stationary body that does not move relative to the device during actuation of the SMA actuator assembly 2, while the second body 6 can be a moving body that moves relative to the device during actuation of the SMA actuator assembly 2. Alternatively, both bodies can move during actuation.

[0159] Each of the first and second bodies 4, 6 has at least one tooth 8. The teeth 8 of the first and second bodies 4, 6 are examples of contact portions between the first and second parts. In the embodiment shown in the figures, the teeth 8 of the first and second bodies 4, 6 are substantially solid and integrally formed with the respective bodies. However, this is generally not necessary, and the contact portions of the parts may take other forms, such as being hollow, formed separately from the body, or formed from sheet material.

[0160] exist Figure 6 In the embodiment shown, the first body 4 has two teeth, while the second body 6 has three teeth. The teeth 8 of the first body 4 and the teeth 8 of the second body 6 overlap in a direction parallel to the axis of movement M. The overlapping of the teeth means that the uppermost portion of a tooth 8 on the first body 4 is higher than the lowermost portion of an adjacent tooth 8 on the second body 6 (where "upper" for this purpose is defined in the direction of movement of the second body 6 relative to the first body 4 when the SMA wire 10 is contracted). In some embodiments, the first body 4 has at least one tooth 8 and the second body 6 has more than one tooth 8, the teeth 8 of the two bodies alternate in a direction normal to the axis of movement M, and contact of a length of SMA wire 10 with the teeth 8 alternates between the teeth 8 of the first body 4 and the teeth 8 of the second body 6.

[0161] The shape of the teeth 8 can be any suitable shape to provide contact with a length of SMA wire 10, as described below. In the embodiment shown in the figures, the uppermost portion of the teeth 8 has a curved shape. However, other shapes can also be used. For example, the uppermost portion of the teeth 8 can have a pointed shape, or the uppermost portion of the teeth can be flat. In addition, the lowermost portion of the teeth 8 can be triangular as shown, or can be rectangular or any other shape. In embodiments such as Figure 6 In the embodiment shown, each of the bodies has more than one tooth 8 .

[0162] The SMA actuator assembly 2 also includes a length of SMA wire 10 connected at each end to either the first body 4 and the second body 6. In some embodiments, the ends of the length of SMA wire 10 are connected to different ones of the two bodies. Preferably, the length of SMA wire 10 is connected at each end to the same one of the bodies, i.e., both ends of the length of SMA wire 10 are connected to the first body 4 or both ends are connected to the second body 6. This reduces the forces between the first body 4 and the second body 6 in a direction perpendicular to the axis of movement M during actuation of the SMA actuator assembly. In some embodiments, the length of SMA wire 10 is connected at each end to the first body 4. This may be preferred in embodiments where the first body 4 is a stationary body. In Figure 6 In the embodiment shown, both ends of a length of SMA wire 10 are connected to the first body 4 .

[0163] A length of SMA wire 10 is connected to either the first body 4 or the second body 6 at each end via a respective connecting element 18 that holds the SMA wire 10. Any suitable means or wire attachment device may be used as the connecting element 18 to hold the length of SMA wire 10. For example, the connecting element 18 may include an adhesive, wherein the length of SMA wire 10 is disposed in the adhesive before curing the adhesive. In some embodiments, one or both of the connecting elements 18 are crimping portions. The crimping portions crimp the ends of the length of SMA wire 10. The crimping portions can be secured to the first body 4 or the second body 6. In some embodiments, the crimping portions include crimping tabs that close around the length of SMA wire 10 to hold the length of SMA wire 10. The crimping portions crimp the ends of the length of SMA wire 10. This can be achieved by compressing the ends of the wire 10 between two deformable materials. Using a metal crimping portion may be desirable, particularly when crimping is used to both electrically connect the length of SMA wire 10 and secure the length of SMA wire 10 to the first body 4 or the second body 6.

[0164] The teeth 8 of the first body 4 contact the length of SMA wire 10 from below on a first side of the length of SMA wire 10 along the axis of movement, while the teeth 8 of the second body 6 contact the length of SMA wire 10 from above on a second side of the length of SMA wire 10, opposite the first side, along the axis of movement. The length of SMA wire 10 extends between the first and second bodies 4, 6 and is guided by the teeth 8 along a tortuous path between the first and second bodies 4, 6, and contacts the teeth 8. A tortuous path is any path that is not a straight line between the end of the length of the length of the SMA wire 10 and the point where it connects to the first or second body 4, 6. Therefore, the tortuous path followed by the length of the SMA wire 10 will have a length that is greater than the shortest distance between the connecting elements 18. The tortuosity of the tortuous path can be measured using the ratio of the length of the tortuous path to the shortest distance between the connecting elements 18.

[0165] The contact of the length of SMA wire 10 alternates between the teeth 8 of the first body 4 and the teeth 8 of the second body 6. In some embodiments, the length of SMA wire crosses from the first body 4 to the second body 6 (and back again) two or more times. In some embodiments, for example Figure 6 In the embodiment shown, a length of SMA wire 10 contacts all of the teeth 8 of the first body 4 and all of the teeth 8 of the second body 6 in the alternating manner described above.

[0166] The teeth 8 of the first body 4 and the teeth 8 of the second body 6 are positioned relative to each other, and alternating contact of the length of SMA wire 10 with the teeth 8 of the first body 4 and the teeth 8 of the second body 6 causes the first body 4 and the second body 6 to be driven apart along the movement axis M when the length of SMA wire 10 contracts. The length of SMA wire 10 is arranged so that when the length of SMA wire 10 contracts, the first body 4 and the second body 6 move away from each other. This is caused by the teeth 8 of the first body 4 and the teeth 8 of the second body 6 overlapping, so that the length of SMA wire 10 applies a force to the teeth 8 when the length of SMA wire 10 contracts. In other embodiments, the first body 4 and the second body 6 can move together as long as the first body 4 and the second body 6 move in opposite directions.

[0167] In some embodiments, the two bodies are provided with end stops 12 that limit the relative movement of the two bodies toward each other. The end stop 12 can be provided on the same of the two bodies, for example, Figure 6 1 and 2. The end stops 12 are shown on the first body 4. Alternatively, the end stops 12 may be provided on different of the two bodies, for example, at different ends of the SMA actuator assembly 2, or the end stops 12 may be provided on both bodies, for example, at both ends of the SMA actuator assembly 2. The end stops 12 define a minimum separation between the first body 4 and the second body 6. In some embodiments, the minimum separation will be the separation when the SMA actuator assembly 2 is not actuated, i.e., when the length of SMA wire 10 is not contracted, in the rest position. In the rest state, the two bodies are in contact with the end stops 12.

[0168] In some embodiments, the assembly 2 includes a device (e.g., a resilient element such as a spring) to provide a force (a "return force") that pushes the two bodies 4, 6 together along the axis of movement M, such that when the power to the length of SMA wire 10 is reduced or stopped, the length of SMA wire 10 expands as the length of SMA wire cools, and the two bodies 4, 6 move back, for example, toward a rest position.

[0169] Figure 7 A section of an SMA actuator assembly is shown as a comparative example rather than an embodiment of the present invention. Figure 7 In the SMA actuator assembly of FIG. 4 , the end of a length of SMA wire 10 is attached to the first body 4 via a connecting element 18. The length of SMA wire 10 exits the connecting element 18 at an exit point 46 and then contacts another portion 48 of the first body 4 before extending through a gap to the first tooth 8 of the second body 6. When the length of SMA wire 10 contracts during actuation, the wire will rub against and flex around the point 48 of the first body 4, and this may cause damage to the wire.

[0170] like Figure 8 and Figure 9 As shown in the embodiment of FIG. 1 , at each end, a length of SMA wire 10 extends from an exit point 46 where the length of SMA wire 10 leaves the connecting element 18 to an adjacent tooth 8 without contacting the body to which the end of the length of SMA wire 10 is connected. Ensuring that the length of SMA wire 10 extends in this manner prevents damage to the length of SMA wire 10 where it contacts the body to which it is attached.

[0171] The length of SMA wire 10 exits the connecting element 18 to the point where the length of SMA wire 10 contacts the first of the teeth 8 of the body. Preferably, the angle between the direction 50 of the length of SMA wire 10 as it exits the connecting element 18 and the line 52 between the point where the SMA wire 10 exits the connecting element 18 and the point where the length of SMA wire 10 contacts the first tooth is minimized. Minimizing this angle reduces bending of the length of SMA wire 10 at the exit point 46, thereby reducing wear on the length of SMA wire 10. Thus, in applications such as Figure 8 In the illustrated embodiment, the connecting element 18 is shaped such that a length of SMA wire 10 extends from the connecting element 18 within the connecting element 18 to an exit point 46 of the length of SMA wire 10, with the exit direction 50 having an exit angle θ of at most 15° relative to a line 52 extending from the exit point 46 to the point 40 where the length of SMA wire 10 first contacts an adjacent tooth 8. In some embodiments, the line 52 forms an acute angle greater than 0°, optionally greater than 5°, and optionally greater than 10° relative to a plane normal to the axis of movement M. This means that the length of SMA wire 10 can exert a force on the teeth of the body when it contracts. In some embodiments, the exit angle θ relative to the line 52 is at most 10°, optionally at most 5°.

[0172] The outlet angle θ can be limited in various ways. For example, Figure 8 As shown, the connecting element 18 can be shaped so that it holds a length of SMA wire 10 at an angle that is not aligned with an outer dimension of the connecting element 18, such that even if the connecting element 18 is mounted on the body perpendicular to the axis of movement M, the length of SMA wire 10 is not perpendicular to the axis of movement M inside the connecting element 18. Alternatively or additionally, the surface of the body to which the connecting element 18 is secured may not be perpendicular to the axis of movement M. This ensures that even if the connecting element 18 is mounted on the body perpendicular to the axis of movement M and holds the length of SMA wire 10 at an angle that is aligned with an outer dimension of the connecting element 18, the length of SMA wire 10 is not perpendicular to the axis of movement M inside the connecting element 18.

[0173] Another configuration to achieve the restriction on the outlet angle θ is shown in Figure 9 In. Figure 9In an embodiment of the present invention, the connecting element 18 is a crimping portion, wherein the crimping portion is made of a sheet material that is bent to provide a portion 54 extending normal to the movement axis M and a portion 56 extending at an acute angle greater than 0° relative to a plane normal to the movement axis M. In some embodiments, the portion 54 of the crimping portion extending normal to the movement axis M is fixed to the first body 4. In an embodiment such as Figure 9 In the embodiment shown, the portion of the crimp portion that includes the exit point 46 for the length of SMA wire 10 protrudes beyond the portion of the first body 4 to which the crimp portion is secured. The use of a protrusion in this manner ensures that the curved connecting element 18 can be easily mounted to the body and does not come into contact with the body to which the connecting element 18 is secured (and therefore also without contacting the end of the length of SMA wire 10).

[0174] The crimping portion may be formed as follows Figure 10 and Figure 11 As shown. Figure 10 As shown, the metal sheet to be formed into the crimped portion is placed in a plane normal to the moving axis M and is placed between the punch 60 and the anvil 62. Then, as shown in FIG. Figure 11 As shown, the metal sheet is compressed between the punch 60 and the anvil 62. Although the process Figure 10 and Figure 11 , wherein a length of SMA wire 10 is present in the connecting element 18, but this is not essential, and the formation of the crimping portion can be performed without the presence of a length of SMA wire 10, and the subsequent introduction of a length of SMA wire 10. As a result, the crimping portion retains the length of SMA wire 10 such that the length of SMA wire 10 extends along a line that makes an acute angle with the plane of the sheet material, which is a plane perpendicular to the axis of movement M.

[0175] According to another aspect of the present invention, a method of manufacturing an SMA actuator assembly is provided, wherein the method includes controlling the tension in a length of SMA wire and / or the path length of a length of SMA wire between connected ends when assembling the SMA actuator assembly. Figures 12 to 21 This aspect of the present invention is described.

[0176] The present disclosure relates to methods of manufacturing SMA actuator assemblies. Figure 12 An SMA actuator assembly 2 of the type that may be assembled using embodiments of the manufacturing methods disclosed herein is shown. The SMA actuator assembly 2 includes two bodies 4, 6 movable relative to each other along a movement axis M. The two bodies 4, 6 are examples of first and second parts. Figure 12The two bodies 4, 6 shown in the figure are solid bodies that can be formed by methods such as injection molding or milling. However, it is not necessary to form the parts in this way, and in some embodiments, the parts can take other forms, such as being hollow or formed from sheet material. The first part and the second part provide two parts that can move relative to each other so that a tactile signal can be provided to the user. Throughout the description, the embodiments will generally be described with reference to the two bodies 4, 6 of the embodiment shown in the figures. However, any of the embodiments described herein can also be implemented using types of first and second parts other than two bodies.

[0177] Although not in Figure 12 , the SMA actuator assembly 2 may include a suspension system that holds the two bodies 4, 6 relative to each other and allows them to move along the movement axis M. The suspension system may allow the two bodies 4, 6 to move relative to each other along the movement axis M while limiting or preventing relative movement of the two bodies 4, 6 in a plane perpendicular to the movement axis M and / or limiting or preventing relative rotation of the two bodies 4, 6.

[0178] In some embodiments, the SMA actuator assembly 2 is integrated into a larger device. In some embodiments, one of the two bodies 4, 6 can be a stationary body that does not move relative to the device during actuation of the SMA actuator assembly 2, while the other of the two bodies 4, 6 can be a moving body that moves relative to the device during actuation of the SMA actuator assembly 2. Alternatively, both bodies can move during actuation.

[0179] Each of the two bodies 4, 6 has at least one tooth 8. The teeth 8 of the two bodies 4, 6 are examples of contact portions between the first and second parts. In the embodiment shown in the figures, the teeth 8 of the two bodies 4, 6 are substantially solid and molded integrally with the respective bodies. However, this is generally not necessary, and the contact portions of the parts may take other forms, such as being hollow, formed separately from the bodies, or formed from sheet material.

[0180] exist Figure 12 In the illustrated embodiment, the two bodies 4, 6 of the SMA actuator assembly 2 include a lower body 4 having three teeth 8 and an upper body 6 having four teeth 8. The teeth 8 of the two bodies 4, 6 overlap in a direction parallel to the axis of movement M. The overlapping teeth means that the uppermost portion of the teeth 8 on the lower body 4 is higher than the lowermost portion of the adjacent teeth 8 on the upper body 6 (where "upper" for this purpose is defined in the direction of movement of the body 6 relative to the body 4 when the SMA wire 10 contracts). In some embodiments where one of the two bodies 4, 6 is a stationary body and the other of the two bodies 4, 6 is a moving body, the lower body 4 is preferably the stationary body.

[0181] The shape of the teeth 8 can be any suitable shape to provide contact with a length of SMA wire 10, as described below. In the embodiment shown in the figures, the uppermost portion of the teeth 8 has a curved shape. However, other shapes can also be used. For example, the uppermost portion of the teeth 8 can have a pointed shape, or the uppermost portion of the teeth 8 can be flat. In addition, the lowermost portion of the teeth 8 can be triangular as shown in the figures, or can be rectangular or any other shape. In some embodiments, at least one of the bodies 4, 6 has more than one tooth 8, and the teeth 8 of the two bodies 4, 6 alternate in a direction normal to the movement axis M. This means that for any tooth 8 on either of the two bodies 4, 6, the nearest adjacent tooth 8 will be a tooth 8 of the other of the two bodies 4, 6. In a case such as Figure 12 In the embodiment shown, each body has more than one tooth 8 .

[0182] The SMA actuator assembly 2 also includes a length of SMA wire 10 connected at each end to either of the first body 4 and the second body 6. In some embodiments, the ends of the length of SMA wire 10 are connected to different ones of the two bodies 4, 6. Preferably, the length of SMA wire 10 is connected at each end to the same one of the two bodies 4, 6. Connecting both ends to the same body reduces the forces between the two bodies 4, 6 in a direction perpendicular to the axis of movement M during actuation of the SMA actuator assembly. In some embodiments where one of the bodies 4, 6 is a stationary body, the length of SMA wire 10 may be connected at each end to the stationary body. Figure 12 In the illustrated embodiment, both ends of a length of SMA wire 10 are connected to the lower body 4. In some embodiments, each end of the length of SMA wire 10 is connected to either body 4 or 6 via a respective connecting element 18 that holds the SMA wire. Any suitable means or wire attachment device can be used as the connecting element 18 to hold the length of SMA wire 10. For example, the connecting element 18 can include an adhesive, wherein the length of SMA wire 10 is disposed in the adhesive before curing the adhesive. Preferably, the connecting element 18 is a crimping portion. The crimping portion can be secured to either body 4 or 6. In some embodiments, the length of SMA wire 10 is connected to either body 4 or 6 via the crimping portion, wherein the crimping portion is secured to either body 4 or 6. The crimping portion crimps the ends of the length of SMA wire 10. The crimping can be achieved by compressing the ends of the wire 10 between two deformable materials. Using a metal crimping portion may be desirable, particularly when the crimping portion is used to both electrically connect the length of SMA wire 10 and secure the length of SMA wire 10 to either body 4 or 6.

[0183] The teeth 8 of the first body 4 contact the length of SMA wire 10 from below on a first side of the length of SMA wire 10 along the axis of movement, and the teeth 8 of the second body 6 contact the length of SMA wire 10 from above on a second side of the length of SMA wire 10, opposite the first side, along the axis of movement. The length of SMA wire 10 extends between the two bodies 4, 6 and is guided by the teeth 8 along a tortuous path between the two bodies 4, 6 and in contact with the teeth 8. A tortuous path is any path that is not a straight line between the points where the ends of the length of the SMA wire 10 connect to the two bodies 4, 6. Therefore, the length of the tortuous path followed by the length of the SMA wire 10 will be greater than the shortest distance between the connecting elements 18. The tortuosity of the tortuous path can be measured using the ratio of the length of the tortuous path to the shortest distance between the connecting elements 18.

[0184] The teeth 8 of the first body 4 and the teeth 8 of the second body 6 are positioned relative to each other, and a length of SMA wire 10 is in contact with the teeth 8, so that the two bodies 4 and 6 are driven apart along the axis of movement when the length of SMA wire 10 contracts. The length of SMA wire 10 is arranged so that when the length of SMA wire 10 contracts, the two bodies 4 and 6 move away from each other. This is caused by the teeth 8 of the two bodies 4 and 6 overlapping, so that when the length of SMA wire contracts, it exerts a force on the teeth 8. In other embodiments, the first body 4 and the second body 6 can move together as long as the first body 4 and the second body 6 move in opposite directions.

[0185] In some embodiments where at least one of the bodies has more than one tooth 8 and the teeth 8 of the two bodies 4, 6 alternate in a direction normal to the axis of movement M, the contact of the length of SMA wire 10 with the teeth 8 alternates between the teeth 8 of the two bodies 4, 6. In some embodiments, the length of SMA wire 10 crosses two or more times from one of the two bodies 4, 6 to the other of the two bodies 4, 6. In some embodiments, for example Figure 12 In the embodiment shown, a length of SMA wire 10 contacts all of the teeth 8 of both bodies 4, 6 in the alternating manner described above. This alternating contact of the length of SMA wire with the teeth 8 of the two bodies 4, 6 helps drive the two bodies 4, 6 apart along the movement axis M when the length of SMA wire 10 contracts.

[0186] In some embodiments, the two bodies 4, 6 are provided with end stops 12 that limit the relative movement of the two bodies 4, 6 toward each other. The end stops 12 may be provided on the same of the two bodies 4, 6, for example, as in Figure 12The lower body 4 is shown. Alternatively, the end stop 12 can be provided on different of the two bodies 4, 6, for example, at different ends of the SMA actuator assembly 2, or the end stop 12 can be provided on both bodies, for example, at both ends of the SMA actuator assembly 2. The end stop 12 defines a minimum separation between the two bodies 4, 6. In some embodiments, the minimum separation will be the separation in the rest position when the SMA actuator assembly 2 is not actuated, i.e., when the length of SMA wire 10 is not contracted. In the rest state, the two bodies 4, 6 are in contact with the end stop 12.

[0187] In some embodiments, the end stop 12 is an adjustable end stop. For example, the adjustable end stop can include at least one mechanically adjustable end stop, such as a grub screw. Alternatively or additionally, the adjustable end stop can include at least one end stop 14 mounted in a bed of adhesive 16, such as a component located on the glue bed.

[0188] In some embodiments, the assembly includes a device (e.g., a resilient element, such as a spring) that pushes the two bodies 4, 6 together along the movement axis M so that when the power to the section of SMA wire 10 is reduced or stopped, the section of SMA wire 10 expands as the section of SMA wire 10 cools and the two bodies 4, 6 move back toward the rest position.

[0189] The manufacture of a Figure 12 In order to accurately manufacture the SMA actuator assembly 2, it is necessary to very accurately control the path length (where the path length is the length of the meandering path along which a section of SMA wire 10 extends between the two bodies 4, 6) and the difference between the SMA wires 10. In the SMA actuator assembly 2, where the section of SMA wire 10 contacts a part of the assembly (e.g., the teeth 8 of the two bodies 4, 6) (i.e., a part other than the point at which the section of SMA wire 10 connects to the bodies 4, 6), the path length depends on the tolerance of the contact between the section of SMA wire 10 and the part of the assembly.

[0190] Therefore, it is desirable to provide a manufacturing method that minimizes the error in the difference between the path length and the wire length of a length of SMA wire 10. This error can arise due to variations in the path length from component tolerances, as well as variations in the wire length of a length of SMA wire 10. One method of achieving this is to use high-tolerance parts and high-tolerance assembly processes to ensure that both the wire length and the path length of a length of SMA wire 10 are precisely controlled, thereby ensuring precise control of the difference between the path length and the wire length. However, such high-precision assemblies and parts are expensive and difficult to control. Therefore, embodiments of the manufacturing method disclosed herein provide an adjustment method to directly control the difference between the wire length and the path length of a length of SMA wire 10 by adjusting either the path length or the wire length of the length of the length of the SMA wire 10 based on the length of the other.

[0191] The manufacturing method includes controlling the tension in a length of SMA wire 10 and / or the path length of a length of SMA wire 10 between connected ends of the length of SMA wire 10 when assembling the SMA actuator assembly 2 .

[0192] exist Figure 18 In some embodiments shown, the method includes a step (S10) of connecting a length of SMA wire 10 at each end to either of the bodies 4, 6. As described above, this can be achieved in any suitable manner. Preferably, both ends of the length of SMA wire 10 are connected to the same body of the two bodies 4, 6. In some embodiments where one of the bodies is stationary, the length of SMA wire 10 can be connected to the stationary body at both ends. The method also includes a step (S12) of assembling the two bodies 4, 6 with the length of SMA wire 10 extending therebetween. For a given wire tension, the gap between the bodies will depend on the tolerances of the bodies.

[0193] like Figure 13 As further shown in FIG. 4 , the method further includes step S14 of adjusting the adjustable end stop 12 to control the tension in the length of SMA wire 10 while applying a predetermined force F between the two bodies 4 , 6 . The adjustable end stop 12 is configured to precisely pass through the gap L1 between the bodies when the correct force (and therefore the wire tension) is applied. The adjustable end stop 12 is adjusted to adjust the path length (i.e., the length of the tortuous path along which the length of SMA wire 10 extends between the two bodies 4 , 6 ). Adjusting the path length when the correct force is applied between the bodies ensures that, regardless of tolerances on the bodies and the wire length of the length of SMA wire 10 , the path length is correctly matched to the tension in the length of SMA wire 10 resulting from the applied force.

[0194] A force F can be applied to one of the two bodies 4, 6 while holding the other of the two bodies 4, 6 in a fixed position, such as Figure 13As shown. This may be preferred in the case where the other of the two bodies 4, 6 is the stationary body of the SMA actuator assembly 2 and one of the two bodies 4, 6 is the moving body of the SMA actuator assembly 2. In the case where the adjustable end stop 12 of the SMA actuator assembly 2 includes at least one end stop 14 mounted in a bed of adhesive 16, the step S14 of adjusting the adjustable end stop 12 includes adjusting the at least one end stop 14 when the adhesive 16 is uncured, and the method further includes the step S16 of curing the adhesive 16 after adjusting the adjustable end stop 12.

[0195] exist Figure 19 and Figure 20 In the illustrated embodiment, the method includes a step S20 of assembling two bodies 4, 6 with a length of SMA wire 10 extending between the two bodies, and a step S22 of connecting an end of the length of SMA wire 10 to either of the bodies. Connecting the end of the length of SMA wire 10 to either of the bodies can be performed by connecting a connecting element 18 (which can be any type of wire attachment component, such as a crimp or adhesive) to both ends of the length of SMA wire 10, and then connecting the connecting element 18 to either of the bodies. Alternatively, the connecting element 18 can be first connected to either of the bodies, and then the connecting element 18 can be connected to the end of the length of SMA wire 10. As described above, the connecting element 18 can be connected to the same of the two bodies 4, 6, or to different of the two bodies 4, 6. In some embodiments where one of the two bodies 4, 6 is a stationary body, the connecting elements 18 are preferably both connected to the stationary body.

[0196] During the step S22 of connecting the ends of a length of SMA wire 10 to either of the bodies, the tension of the SMA wire 10 between the ends of the length of SMA wire 10 is controlled while the bodies 4, 6 are held in a fixed position relative to each other before the connection of the ends of the length of SMA wire 10 to either of the bodies 4, 6 is completed. In some embodiments, for example, Figure 14 and Figure 16 In the embodiment shown in , the two bodies 4, 6 are provided with end stops 12 that limit relative movement of the two bodies 4, 6 toward each other, and the two bodies 4, 6 are held together against the end stops 12, thereby maintaining the two bodies 4, 6 in a fixed position relative to each other. For example, in some embodiments where one of the two bodies 4, 6 is a stationary body, the end stop 12 is provided on the stationary body, and the moving body provided by the other of the two bodies 4, 6 is placed in contact with the end stop 12 on the stationary body.

[0197] In these embodiments, the fixed position of the bodies 4, 6 relative to each other fixes the path length of the tortuous path between the two bodies 4, 6 along which the length of SMA wire 10 extends. Controlling the wire tension while keeping the path length fixed ensures that the wire tension is correctly matched to the path length regardless of tolerances on the bodies and the length of SMA wire 10.

[0198] In the step of connecting the end of a length of SMA wire 10 to the body, the tension in the length of SMA wire can be controlled in different ways. One method of controlling the tension is to adjust the position at which the length of SMA wire 10 is attached to the body. This method is Figure 19 is displayed in the Figure 14 is shown in the figure.

[0199] exist Figure 19 In the embodiment of the present invention, in step S22 of connecting the end of a length of SMA wire 10 to either of the bodies, the wire length of the length of the length of SMA wire 10 between the ends of the length of SMA wire 10 is fixed, and the tension is controlled by selecting the location at which the end of the length of SMA wire 10 is connected to either of the bodies. The fixed position of the bodies relative to each other fixes the path length of the meandering section of the path length between the teeth of the two bodies 4 and 6, and selecting the connection location adjusts the path length exceeding the meandering section of the path, i.e., the length of the path portion between the connection point of the length of SMA wire 10 to the body and the first of the teeth of the body. This ensures that the wire tension and total path length are matched regardless of the tolerances on the body and the length of SMA wire 10.

[0200] In some embodiments, step S22 of connecting the ends of the length of SMA wire 10 to either of the bodies 4, 6 includes connecting one of the ends of the length of SMA wire 10 to either of the bodies 4, 6 and, while maintaining the bodies 4, 6 in a fixed position relative to each other, controlling the tension by adjusting the position of the other end of the length of SMA wire 10 connected to either of the bodies 4, 6 in step S24. As described above, the bodies 4, 6 can be maintained in a fixed position relative to each other using the end stop 12. Then, in step S26, the other end of the length of SMA wire 10 is fixed to either of the bodies.

[0201] exist Figure 14 In the embodiment shown, a length of SMA wire 10 is connected to the body using a connecting element 18. When a length of SMA wire 10 is connected to the body using a connecting element 18, the end of the length of SMA wire 10 is the point where the length of SMA wire 10 exits the connecting element 18 along a tortuous path. Figure 14In the embodiment of the present invention, the connecting element 18 is a crimping portion that crimps the end of a length of SMA wire 10. The location where the end of the length of SMA wire 10 is connected to either of the bodies is selected by selecting the location where the crimping portion is fixed to either of the bodies.

[0202] The position at which the end of the length of SMA wire 10 is connected can be selected by applying a force perpendicular to the movement axis M to adjust the position at which the end of the length of SMA wire 10 is connected to the body. Force can be applied to both ends of the length of SMA wire 10, or force can be applied to one end of the length of SMA wire 10 after the position of the other end of the length of SMA wire 10 has been fixed. Figure 14 In the embodiment shown, a length of SMA wire 10 is connected via a connecting element 18, a force is applied to the connecting element 18, and the application of force adjusts the position of the connecting element 18, which in this embodiment is on the lower body 4. The applied force creates a known tension in the length of SMA wire 10, and the position of the connection of the length of SMA wire 10 to the body under the applied force will depend on the tolerances of the dimensions of the two bodies 4, 6 and the length of the length of SMA wire 10. Once the position is selected under the application of force, the length of SMA wire 10 is secured to the body, for example, by securing the connecting element 18 to the body at that position.

[0203] One way to apply force to a length of SMA wire 10 is to crimp the length of SMA wire 10 onto a compression member 20, such as Figure 15 As shown. In some such embodiments, the step of assembling two bodies 4, 6 with a length of SMA wire 10 extending therebetween is performed by retaining the length of SMA wire 10 via a compression member 20. The compression member 20 includes a sacrificial body 22 and two crimping portions 18 that crimp the ends of the length of SMA wire 10. The sacrificial body 22 has a resilient portion 24 that is configured to apply a predetermined tension to the length of SMA wire 10. The resilient portion 24 may include a spring. When using the compression member 20, the step of connecting the ends of the length of SMA wire 10 to either body 4, 6 includes securing the crimping portion 18 to either body 4, 6 at a selected position while the resilient portion 24 of the compression member 20 controls the tension between the ends of the length of SMA wire 10. Connecting the ends of the length of SMA wire 10 also includes, after the crimping portion 18 is connected to either body 4, 6, removing the sacrificial body 22, leaving the crimping portion 18 secured to either body 4, 6. This provides a reliable and repeatable way of applying a desired force to a length of SMA wire 10 .

[0204] An alternative method of controlling the tension of a length of SMA wire 10 during the step of connecting the ends of the length of SMA wire 10 to the bodies 4, 6 is to adjust the length of the length of the SMA wire 10 according to the path length. Figure 20 is displayed in Figure 16 is shown in the figure.

[0205] exist Figure 20 In this embodiment, during step S32 of attaching the end of a length of SMA wire 10 to either of the bodies 4 and 6, the position at which the end of the length of SMA wire 10 is attached to either of the bodies 4 and 6 is fixed, and the tension is controlled by adjusting the length of the length of SMA wire 10 between these positions in step S34. The end of the length of SMA wire 10 can then be fixed in step S36. The length of the length of SMA wire 10 will depend on the tolerances. In this embodiment, the fixed positions of the bodies 4 and 6 relative to each other and the fixed position at which the end of the length of SMA wire 10 is attached to the bodies fix the path length of the tortuous path along which the length of SMA wire 10 extends between the two bodies 4 and 6. While keeping the path length fixed, adjusting the length of the length of SMA wire 10 controls the wire tension to ensure that the wire tension is correctly matched to the path length regardless of the tolerances on the two bodies 4 and 6.

[0206] exist Figure 16 In the embodiment shown, the step S30 of assembling the two bodies 4, 6 with a length of SMA wire 10 extending therebetween is performed by positioning the length of SMA wire 10 in a crimp portion that partially crimps the end of the length of SMA wire 10. The step S22 of connecting the end of the length of SMA wire 10 to either of the bodies then includes connecting the crimp portion to either of the bodies 4, 6 at a fixed position. In some embodiments, this includes attaching an open crimp portion at either end of the SMA actuator assembly 2 (preferably to a stationary body if one of the bodies 4, 6 is a stationary body). Figure 16 In the embodiment of the present invention, no sacrificial or disposable element (e.g., crimp coupon) is used between the crimp portions when connecting the crimp portions to either of the bodies 4, 6, but in other embodiments, a similar crimp coupon may be used. Figure 15 The step S22 of connecting the ends of the SMA wire 10 further includes controlling the tension in the SMA wire 10 by adjusting the length of the SMA wire 10 between the crimping portions, and compressing the crimping portions to complete the crimping of the SMA wire 10 through the crimping portions. This process may also be referred to as on-board crimping.

[0207] By applying tension to a length of SMA wire 10 and then compressing the crimping portion to attach the length of SMA wire 10 to the crimping portion, the crimping portion may be compressed. Figure 16 As shown, the wire length of a length of SMA wire 10 between the crimped portions is adjusted. The wire length is adjusted by feeding the length of SMA wire into the crimped portions, compressing the crimped portion holding one end of the length of SMA wire 10 to form a crimp at one end, applying force to the other end of the length of SMA wire 10 (i.e., the end with the open crimp) to achieve the correct wire length in the SMA actuator assembly 2, and finally compressing the crimped portion holding the other end of the length of SMA wire 10, i.e., closing the second crimp. Alternatively, the wire length can be adjusted by applying force to both ends of the length of SMA wire 10 simultaneously and then compressing both crimped portions simultaneously.

[0208] The end stop 12 is used, for example, to hold the two bodies 4, 6 in a fixed position relative to each other during control of tension in a length of SMA wire 10. In the event that one of the two bodies 4, 6 is a stationary body and the other of the two bodies 4, 6 is a moving body, the end stop 12 can be provided on the stationary body and the moving body brought into contact with the end stop 12 on the stationary body.

[0209] In any of the embodiments discussed above, the steps S12, S20, S30 of assembling the two bodies 4, 6 may include assembling one of the two bodies 4, 6 with a dummy body or another component. In embodiments where one of the two bodies 4, 6 is a stationary body and the other of the two bodies 4, 6 is a moving body, the dummy body or another component is preferably assembled with the stationary body 4. The profile of the dummy body or another component is designed for the purpose of setting the correct wire length of a length of SMA wire 10 and is configured such that the path length of the tortuous path extending between the dummy body and one of the two bodies 4, 6 matches the desired path length in the final assembled SMA actuator assembly 2. The profile of the dummy body may be different from the profile of either of the two bodies 4, 6 (and therefore the shape of the tortuous path may be different). Figure 17 Such a body 30 is shown. In some embodiments where a dummy body or additional part is used, the method further comprises the steps of removing the dummy body or additional part and assembling one of the two bodies 4, 6 with the other of the two bodies 4, 6 and a length of SMA wire 10 extending between the two bodies 4, 6, as shown. Figure 21 It will be understood that in case a dummy body or an additional part is used, tolerances relative to the other of the two bodies 4, 6 (eg the mobile body 6) will not have to be compensated.

[0210] In embodiments where a crimping portion is used to connect the end of a length of SMA wire 10 to, for example, a first body, the two crimping portions may be connected by a similar Figure 15 The disposable connecting portion shown is connected to the first body, but the disposable connecting portion does not have an elastic portion. During the step of connecting the end of a length of SMA wire 10 to the crimping portion, the length of SMA wire 10 is laid between the two crimping portions and then deflected using, for example, a clamp to increase the length of the wire 10 between the two crimping portions to correspond to the desired wire length. The crimping portion is then closed, connected to the first body, and the disposable connecting portion is removed.

[0211] You can use Figure 12 The illustrated SMA actuator assembly 2 implements an embodiment of the above-described method. The SMA actuator assembly 2 includes two bodies 4, 6, and a length of SMA wire 10. The two bodies 4, 6 are movable relative to each other along a movement axis M. Each of the two bodies 4, 6 has at least one tooth 8 that overlaps in a direction along the movement axis M. The length of SMA wire 10 is connected to one of the bodies at each end and extends along a zigzag path between the two bodies 4, 6, contacting the teeth 8 so that when the length of SMA wire 10 contracts, the two bodies 4, 6 are driven apart along the movement axis M. The SMA actuator assembly 2 includes a device that provides control over the tension in the length of SMA wire 10 and / or the length of the path of the length of SMA wire 10 between the connected ends. This device can correspond to any embodiment of the above-described assembly method, such as an adjustable end stop 12.

[0212] Thus, as described above, the tension in a length of SMA wire 10 and / or the path length of a length of SMA wire 10 between the connected ends of the length of SMA wire 10 can be controlled, and in particular, the tension in a length of SMA wire 10 and / or the path length of a length of SMA wire 10 between the connected ends of the length of SMA wire 10 can be controlled for a particular relative position of the two bodies 4, 6. This position can correspond to the rest position of the SMA actuator assembly or some other position (e.g., the midpoint of the operating range of relative movement of the two bodies 4, 6). Thus, for example, the tension is appropriately controlled throughout the operating range of movement.

Claims

1. An SMA actuator assembly comprising: a first part and a second part, the first part and the second part being movable relative to each other along a movement axis; and a length of SMA wire, each end of the length of SMA wire being connected to the first part or the second part, in, The first part includes at least one contact portion that contacts the length of SMA wire on a first side of the length of SMA wire along the axis of movement, and the second part includes at least one contact portion that contacts the length of SMA wire along a second side of the length of SMA wire opposite the first side along the axis of movement, the at least one contact portion of the first part and the at least one contact portion of the second part being relatively positioned to guide the length of SMA wire along a tortuous path such that the first part and the second part are driven in opposite directions along the axis of movement when the length of SMA wire contracts. wherein the length of SMA wire is connected at each end to the first part or the second part by a respective connecting element holding the length of SMA wire; wherein, at each end, the length of SMA wire extends from a point at which the length of SMA wire exits the connecting element to an adjacent contact portion without contacting a component to which the end of the length of SMA wire is connected; and wherein taking into account an intermediate SMA segment of the length of SMA wire extending between center points of contact with adjacent contact portions of the first part and the second part, and an end SMA segment of the length of SMA wire extending from the exit point to the center point of contact with the adjacent contact portions, the SMA actuator assembly is configured such that upon contraction of the length of SMA wire, for each of the intermediate SMA segment and the end SMA segment, a rate of change of wire length of each SMA segment is equal to a total strain of the length of SMA wire, and there is no slippage of the length of SMA wire at the center point of contact.

2. The SMA actuator assembly of claim 1 , wherein: Each connecting element is shaped so that the length of SMA wire extends inside the connecting element in a direction that makes an exit angle of at most 15° relative to a line from the exit point to the point where the length of SMA wire first contacts the adjacent contact portion to the exit point of the length of SMA wire from the connecting element.

3. The SMA actuator assembly of claim 2, wherein: The outlet angle relative to the line is a maximum of 10°.

4. The SMA actuator assembly of claim 3, wherein: The outlet angle relative to the line is a maximum of 5°.

5. The SMA actuator assembly according to any one of claims 1 to 3, wherein: The connecting element is a crimping portion fixed to the first part and includes a crimping tab that closes around the length of SMA wire to retain the length of SMA wire.

6. The SMA actuator assembly of claim 5, wherein: The crimping portion is made of a sheet material that is bent to provide a portion extending normal to the movement axis and a portion including the exit point extending at an acute angle greater than 0° relative to a plane normal to the movement axis.

7. The SMA actuator assembly of claim 6, wherein: The portion of the crimping portion extending normally to the movement axis is fixed to the first part.

8. An SMA actuator assembly according to any one of claims 6 to 7, wherein: A portion of the crimping portion including the exit point of the length of SMA wire protrudes beyond a portion of the first part to which the crimping portion is fixed.

9. An SMA actuator assembly according to any one of claims 2 to 4, wherein: The line forms an acute angle greater than 0° with respect to a plane normal to the axis of movement.

10. The SMA actuator assembly of any one of claims 1-4 and 6-7, wherein: The first part has at least one contact portion, the second part has more than one contact portion, the contact portions of the first part and the contact portions of the second part alternate in a direction normal to the axis of movement, and contact of the length of SMA wire with the contact portions of the first part and the contact portions of the second part alternates between the contact portions of the first part and the contact portions of the second part.

11. The SMA actuator assembly of claim 10, wherein: Each of the first part and the second part has more than one contact portion.

12. The SMA actuator assembly of any one of claims 1-4, 6-7, and 11, wherein: The first part includes a first body; The second part includes a second body; said at least one contact portion of said first body comprising at least one tooth; said at least one contact portion of said second body comprising at least one tooth; The teeth of the first body and the teeth of the second body overlap in a direction parallel to the movement axis; and Contact of the length of SMA wire with the teeth of the first body and the teeth of the second body alternates between the teeth of the first body and the teeth of the second body.

13. The SMA actuator assembly of claim 1 , wherein: The connecting element is a crimping portion.

14. The SMA actuator assembly of claim 13, wherein: The connecting element further includes an adhesive between the crimping portion and the adjacent contact portion.

15. The SMA actuator assembly of any one of claims 1-4, 6-7, 11, and 13-14, wherein: The linear length of the SMA segments and the angle formed by the SMA segments with a plane normal to the axis of movement vary between the SMA segments.

16. The SMA actuator assembly of any one of claims 1-4, 6-7, 11, and 13-14, wherein: For each SMA segment, a ratio (d / ε) of the relative movement (d) developed between the first part and the second part along the movement axis at each end of the SMA segment to the rate of change (ε) of the linear length of the SMA segment is equal to a ratio ((L / sin(θ)) of the linear length (L) of the SMA segment to the sine of the angle (sin(θ)) formed by the SMA segment with a plane normal to the movement axis.

17. The SMA actuator assembly of any one of claims 1-4, 6-7, 11, and 13-14, wherein: A spacing between the center points of contact with adjacent contact portions of the first and second parts in a direction normal to the axis of movement varies between the intermediate SMA sections.

18. The SMA actuator assembly of any one of claims 1-4, 6-7, 11, and 13-14, wherein: In a rest position of the SMA actuator assembly, the height of each intermediate SMA segment along the axis of movement between the center points of contact with adjacent contact portions of the first and second parts is the same.

19. The SMA actuator assembly of any one of claims 1-4, 6-7, 11, and 13-14, wherein: Each of the first part and the second part is rigid such that the relative movement along the movement axis between the first part and the second part at each end of the intermediate SMA segments is the same for each of the intermediate SMA segments.

20. The SMA actuator assembly of any one of claims 1-4, 6-7, 11, and 13-14, wherein: At least one of the first part and the second part is flexible, flexure of the at least one of the first part and the second part at least partially providing relative movement along the movement axis between the first part and the second part at each end of the intermediate SMA segment, the relative movement at each end of the intermediate SMA segment being different between the intermediate SMA segments.

21. The SMA actuator assembly of claim 19, wherein: One of the first part and the second part is a beam, the beam extending between two fixed ends, the fixed ends not moving relative to the other of the first part and the second part, and the beam being flexible such that relative movement along the axis of movement of the first part and the second part at each end of the intermediate SMA section increases with increasing distance from the fixed ends to a central portion of the beam, wherein a separation between the center points of the contacts with adjacent contact portions of the first part and the second part in a direction normal to the axis of movement increases with increasing distance from the fixed ends to the central portion of the beam.

22. The SMA actuator assembly of claim 19, wherein: One of the first part and the second part is a flexible portion of a housing of the electronic device.

23. The SMA actuator assembly of any one of claims 1-4, 6-7, 11, 13-14, and 21-22, wherein: The parts are configured to be urged together only by force applied by a user.

24. The SMA actuator assembly of any one of claims 1-4, 6-7, 11, 13-14, and 21-22, wherein: The first part includes a first body; The second part includes a second body; said at least one contact portion of said first body comprising at least one tooth; The more than one contact portions of the second body include more than one tooth; The teeth of the first body and the teeth of the second body alternate in a direction normal to the movement axis and overlap in a direction parallel to the movement axis; and Contact of the length of SMA wire with the teeth of the first body and the teeth of the second body alternates between the teeth of the first body and the teeth of the second body.

25. The SMA actuator assembly of claim 1, wherein the SMA actuator assembly has means for providing control over the tension in the length of SMA wire and / or the path length of the length of SMA wire between connected ends.

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