Shape memory alloy device

Abstract

A shape memory alloy device (1) comprising a member (3) comprising a first end portion (5) and a second end portion (7), and a shape memory alloy component (9) connected to the member (3). The shape memory alloy component (9) is configured to change a separation between the first end portion (5) and the second end portion (7) of the member (3) upon contraction, the member (3) being configured to be under tension during the contraction of the shape memory alloy component (9), wherein the separation is changed in a direction that is at an angle to the direction of contraction.

Description

TECHNICAL FIELD

[0001] The present invention relates to a shape memory alloy (SMA) device, a method for controlling an SMA device and a method of manufacturing a shape memory alloy device. BACKGROUND

[0002] The use of SMA components as actuators is known, and their use has particular advantages in miniature devices. For example, such actuators can be used in miniature cameras for driving the camera lens elements along their optical axis for purposes such as auto focus, zoom and stabilisation.

[0003] By way of example, PCT application publication no. WO2011 / 104518 discloses an SMA actuation arrangement for providing optical image stabilisation (OIS) and auto focus (AF). The SMA actuation arrangement uses eight SMA actuator wires to move a moveable element on a support structure, wherein the SMA wires are each arranged obliquely with respect to an imaginary principal axis. More specifically, the SMA wires are arranged such that a pair of SMA wires is disposed on each of four sides about the principal axis. The SMA wires are connected by a crimp member such that, on contraction, two groups of four SMA actuator wires provide a force along the principal axis with components in opposite directions, such that the two groups are able to provide movement control of all six degrees of freedom.

[0004] There are also other mechanisms, such as scissor jack arrangements, which can be used in miniature devices to effect movement of a moveable element. However, such arrangements only allow linear movement in one direction. SUMMARY

[0005] In the SMA device described herein, buckling of the device is prevented by placing the member or biasing element under tension only during contraction of the SMA component, which would otherwise be likely to occur if the member or biasing element were continuously under tension. Good resistance to buckling is highly beneficial in view of the long term high frequency use of such actuators in, for example, camera lens arrangements.

[0006] Furthermore, the inventors have recognised the benefit of being able to increase and decrease the spacing between the two end portions of the member by contraction of the SMA component, as opposed to the contraction of the SMA component only being able to increase the spacing in a conventional scissor jack arrangement.

[0007] The shape memory alloy actuation device can be or can be provided in any of the following devices: a smartphone, a camera, a foldable smartphone, a foldable smartphone camera, a foldable image capture device, an array camera, a 3D sensing device or system, a servo motor, a consumer electronic device (including a domestic appliance such as a vacuum cleaner, a washing machine and a lawnmower), a mobile or portable computing device, a mobile or portable electronic device, a laptop computer, a tablet computing device, an e-reader (also known as an e-book reader or e-book device), a computing accessory or peripheral (e.g. a mouse, a keyboard, a headset, earphones, earbuds, etc.), an audio device (e.g. a headset, a headset, earphones, etc.), a security system, a gaming system, a gaming accessory (e.g. a controller, a headset, a wearable controller, a joystick, etc.), a robot or robotic device, a medical device (e.g. an endoscope, an inhaler, a medication dispenser, etc.), an augmented reality system or device, a virtual reality system or device, a wearable device, a drone (airborne, waterborne, underwater, etc.), an aircraft, a spacecraft, a submarine, a vehicle, an autonomous vehicle (e.g. a self-driving car), a tool, a surgical tool, a display screen and a touch screen.

[0008] The application has particular advantages when applied to miniature cameras (e.g. where the camera lens elements comprise one or more lenses having a diameter of no more than 15mm, such as in a mobile phone).

[0009] The application is defined by the independent claims, which should now be consulted. Optional features are set out in the dependent claims.

[0010] According to a first aspect of the application, there is provided a shape memory alloy device comprising: a member comprising a first end portion and a second end portion; and a shape memory alloy component connected to the member and configured to change a separation between the first end portion and the second end portion of the member on contraction, the member being configured to be under tension during contraction of the shape memory alloy component, wherein the separation is changed in a direction at an angle to the direction of contraction.

[0011] In other words, the member can exert an output force to change the separation between the first end portion and the second end portion of the member, wherein the output force is misaligned (e.g. 0° and 180°) to an input force exerted by the contraction of the shape memory alloy component.

[0012] More specifically, the member is configured to react to tension in the SMA component by putting itself under tension. Thus, when the SMA component contracts, the SMA component can pull on the member, thereby putting the member under tension. By only putting the member under tension during contraction of the shape memory alloy component, the member and thus the device cannot buckle. This makes the device more stable. This can be achieved by arranging the member outside of the shape memory alloy component, such that the member is only under tension when the wire contracts. That is, the shape memory alloy component can be arranged outside of the region defined by the first and second portions of the member. Furthermore, during actuation, the member in the scissors jack can be put under stress, and thus in a micro actuator the member is highly prone to bending or buckling.

[0013] The term "shape memory alloy (SMA) component" can refer to any element comprising SMA, preferably the SMA component comprises an SMA wire. The SMA wire can have any shape suitable for the purposes described herein. The SMA wire can be elongate and can have a circular cross-section or a cross-section of any other shape. The cross-section can vary along the length of the SMA wire. It is also possible that the length of the SMA wire, however defined, can be similar to one or more of the other dimensions of the SMA wire. The SMA wire can be compliant, or in other words flexible. In some examples, the SMA wire can only exert a tensile force urging two elements together when connected in a straight line between the two elements. In other examples, the SMA wire can be bent around the elements and can exert a force to the elements when the SMA wire tends to straighten under tension. The SMA wire can be beam-like or rigid and can be able to exert different (e.g. non-tensile) forces to the elements. The SMA wire can or can not comprise material and / or components that are not SMA. For example, the SMA wire can comprise a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term "SMA wire" can refer to any configuration of SMA wire used as a single actuation element, e.g. which can be controlled individually to produce a force on an element. For example, the SMA wire can comprise two or more portions of SMA wire arranged mechanically in parallel and / or in series. In some arrangements, the SMA wire can be part of a larger piece of SMA wire. Such a larger piece of SMA wire can comprise two or more portions that are individually controllable, thereby forming two or more SMA wires.

[0014] The SMA wires can be formed of any suitable shape memory alloy material (typically a nickel-titanium alloy (such as Nitinol)), which can also contain a third component such as copper. The SMA wires can have any cross-sectional profile and diameter suitable for the application. For example, the SMA wires can have a cross-sectional diameter of 25 pm or 30 pm or 35 pm, capable of producing a maximum force between 120 mN and 400 mN, while keeping the strain in the SMA wire within safe limits (e.g. a length reduction of 2-3% from the original length). Increasing the diameter of each SMA wire from 25 pm to 35 pm approximately doubles the cross-sectional area of the SMA wire, and thus approximately doubles the force provided by each SMA wire.

[0015] The shape memory alloy device can further comprise a support structure to which the first end portion of the member is connected, and a movable element to which the second end portion of the member is connected, such that a change in the spacing between the first and second end portions of the member is configured to drive the movable element to move in a first direction relative to the support structure along a movement axis and / or to rotate the movable element in a first rotational direction about a first axis perpendicular to the movement axis. The contraction of the shape memory alloy component can equally apply a force to the movable element and the support structure.

[0016] By applying a force on one side of the movable component at a location away from the movement axis, the pair of members can drive the movable element to rotate about the x-axis or the y-axis (which are perpendicular to the movement axis (e.g. the z-axis)). In other words, due to having the ability to pivot about the x-axis and the y-axis, such an arrangement can enable the movable element to tilt in any direction at an angle to the movement axis.

[0017] The shape memory alloy device can further comprise a second member comprising a first end portion and a second end portion, the member and the second member forming a pair of members. The shape memory alloy component can be arranged between the members of the pair of members, and configured to change the spacing between the first and second end portions of each member upon contraction.

[0018] The pair of members can be a first pair of members, and the shape memory alloy device can further comprise: a second pair of members, each member of the second pair of members comprising a first end portion and a second end portion, the first portion of each member being connected to the support structure, and the second portion of each member being connected to the moveable element; and a second shape memory alloy component arranged between the members of the second pair of members and configured to, on contraction, change the spacing between the first end portion and the second end portion of each member of the second pair of members to drive the moveable element to move in a first direction or a second direction relative to the support structure along the movement axis, and / or to drive the moveable element to rotate about the first axis in a second rotational direction. The second direction can be opposite to the first direction, and the second rotational direction is opposite to the first rotational direction. In other words, the second pair of members can drive the moveable element to move in the same direction (or the same rotational direction) or in the opposite direction (or the opposite rotational direction) as the first pair of members.

[0019] The first pair of members and the second pair of members can be arranged on opposite sides of the moveable element with respect to a plane perpendicular to the movement axis. The first shape memory alloy component can be configured to, on contraction, increase the spacing between the first end portion and the second end portion of each member of the first pair of members, and the second shape memory alloy component can be configured to, on contraction, increase the spacing between the first end portion and the second end portion of each member of the second pair of members. In this way, the first pair of members and the second pair of members act as opposing pairs. That is, the first shape memory alloy component and the second shape memory alloy component drive the moveable element in opposite directions (or opposite rotational directions) on contraction. This allows for precise adjustment of the moveable element relative to the support structure. This also advantageously achieves improved compensation for thermal changes over prior art systems in which contraction of different shape memory alloys both cause the moveable element to move in the same direction (or the same rotational direction). Furthermore, this can improve bidirectional movement control in the moveable element compared to systems using a return biasing element.

[0020] Alternatively, the first pair of members and the second pair of members can be arranged on the same side of the movable element with respect to a plane perpendicular to the movement axis. The first shape memory alloy component can be configured to increase the spacing between the first end portion and the second end portion of each member of the first pair of members upon contraction. The second pair of members can be arranged in an inverted arrangement to the arrangement of the first pair of members to enable the movable element to move in an opposite direction to the first pair of members. The pair of inverted members is a pair of members configured to decrease the spacing between the first arm and the second arm of the members upon contraction of the shape memory alloy component arranged between the members. Accordingly, the second shape memory alloy component can be configured to decrease the spacing between the first end portion and the second end portion of each member of the second pair of members upon contraction. Similar to the previous arrangement, the first pair of members and the second pair of members act as opposite pairs of members. The first shape memory alloy component and the second shape memory alloy component drive the movable element to move in opposite directions (or opposite rotational directions) upon contraction, respectively, but in this arrangement the first pair of members and the second pair of members can be arranged on the same side of the movable element.

[0021] In another alternative arrangement, the first pair of members and the second pair of members can be arranged on the same side of the movable element with respect to a plane perpendicular to the movement axis, but in this arrangement both the first shape memory alloy component and the second shape memory alloy component can be configured to increase the spacing between the first end portion and the second end portion of their respective pair of members. In this way, the two pairs of members drive the movable element to move in the same (first) direction. The shape memory alloy device can further comprise a reset or bias mechanism, such as a spring, to reset or bias the movable element in the second direction after the shape memory alloy components have contracted and the movable element has moved. The pairs of members can be arranged on opposite sides of the movable element when viewed along the movement axis.

[0022] The shape memory alloy device can further comprise a third pair of members and a fourth pair of members. Each member of the third and fourth pair of members can comprise a first end portion and a second end portion, and the first end portion of each member can be connected to the support structure and the second end portion of each member can be connected to the movable element. The shape memory alloy device can further comprise a third shape memory alloy component and a fourth shape memory alloy component, which can be arranged between the members of the third pair of members and the members of the fourth pair of members, respectively, and can be configured to change the spacing between the first and second end portions of each member of the third and fourth pair of members, respectively, on contraction, to drive the movable element to move relative to the support structure along the movement axis in the first and second directions, respectively, or to drive the movable element to perform rotational movement about the first axis in the respective first and second rotational directions. Thus, similar to the first and second pair of members, the third and fourth pair of members can act in opposition to each other. By providing four pairs of members in this way, two of the pairs of members are used to move the movable element in the first direction, and two of the pairs of members are available to move the movable element in the second direction. The second direction can be the same or opposite direction to the first direction, which provides even more precise control of the movable element.

[0023] Each of the four pairs of members can be arranged about the movement axis on a respective one of the four sides of the movable element. In other words, the four pairs of members can surround the movable element when viewed along the movement axis. Opposite pairs of the pairs of members (e.g. the first and second pairs, and the third and fourth pairs) can be arranged on adjacent sides of the movable element.

[0024] The opposite pairs of members compensate for temperature changes and allow the use of the faster heating contraction of the shape memory alloy components to drive the movable element in both the first and second directions, rather than relying on cooling to move the movable element in the second direction as in the prior art. By individual control of all four pairs of members (and all four shape memory alloy components), the movable element can be tilted. This allows for optical image stabilization using lens tilt, which can be used to reduce motion blur on the image. The tilt control can be used in an independent autofocus module to compensate for static tilt assembly tolerances, which avoids the need for a more expensive active alignment process to eliminate static tilt.

[0025] The pairs of members can be arranged in various ways in order to provide pairs of members that act in opposition. The first and third pairs of members can be arranged on opposite sides of the movable element with respect to a plane perpendicular to the movement axis compared to the second and fourth pairs of members. In this case, the first and third shape memory alloy parts can be configured to increase the spacing between the first and second end portions of each of the first and third pairs of members upon contraction, respectively; and the second and fourth shape memory alloy parts can be configured to increase the spacing between the first and second end portions of each of the second and fourth pairs of members upon contraction, respectively.

[0026] Alternatively, the first, second, third and fourth pairs of members can be arranged on the same side of the movable element with respect to a plane perpendicular to the movement axis. In this case, the first and third shape memory alloy parts can be configured to increase the spacing between the first and second end portions of each of the first and third pairs of members upon contraction, respectively; and the second and fourth shape memory alloy parts can be configured to decrease the spacing between the first and second end portions of each of the second and fourth pairs of members upon contraction, respectively. The first and third pairs of members can be identical to the second and fourth pairs of members, so they operate in opposite directions. Alternatively, the first and third pairs of members can be inverted with respect to the second and fourth pairs of members, so they operate in the same direction.

[0027] In another alternative arrangement, the pair of members is a first pair of members, and the shape memory alloy device further comprises: a second pair of members, each member of the second pair of members comprising a first end portion and a second end portion, the first portion of each member being connected to the support structure and the second portion of each member being connected to the movable element; and a second shape memory alloy part arranged between the members of the second pair of members and configured to change the spacing between the first and second end portions of each of the second pair of members upon contraction in order to drive the movable element to rotate movement about a second axis in a second rotational direction, the second axis being perpendicular to both the first axis and the movement axis.

[0028] In alternative embodiments, the first and second pairs of members can be arranged on adjacent sides of the movable element about a plane perpendicular to the movement axis; the first shape memory alloy component can be configured to drive rotational movement of the movable element about a first axis perpendicular to the movement axis; and the second shape memory alloy component can be configured to drive or drive rotational movement of the movable element about a second axis perpendicular to the movement axis and the first axis. By applying a force to one side of the movable component at a location away from the movement axis, the pairs of members can drive rotational movement of the movable element about two perpendicular axes (e.g., x and y axes, which are perpendicular to the movement axis (e.g., z axis)). In other words, with the ability to pivot about the x and y axes, such an arrangement can enable the movable element to tilt in any direction at an angle to the movement axis.

[0029] The shape memory alloy device can further include a reset mechanism or biasing mechanism, such as a reset spring or flexure, to rotate the movable element in an opposite direction after the shape memory alloy component contracts and the movable component rotates.

[0030] Optionally, a third and fourth pair of members can be arranged on adjacent sides of the movable element and opposite the first and second pairs of members, respectively; a third shape memory alloy component configured to drive rotational movement of the movable element about the first axis and in an opposite direction to that achieved by the first shape memory alloy component; and a fourth shape memory alloy component configured to drive rotational movement of the movable element about the second axis and in an opposite direction to that achieved by the second shape memory alloy component. That is, the third and fourth shape memory alloy components can be used in place of the reset spring or flexure in the previous example in order to provide more precise and effective control over tilting.

[0031] Alternatively, a third and fourth pair of members can be arranged on the sides of the movable element having the first and second pairs of members, respectively; a third shape memory alloy component configured to drive rotational movement of the movable element about the first axis and in an opposite direction to that achieved by the first shape memory alloy component; and a fourth shape memory alloy component configured to drive rotational movement of the movable element about the second axis and in an opposite direction to that achieved by the second shape memory alloy component.

[0032] The image sensor can be mounted to the support structure. The movable element can be a lens carrier including at least one lens, and the lens carrier can be arranged to focus an image onto the image sensor. The movement axis can be along an optical axis of the lens element. The at least one lens can include a liquid lens. The combination of vertical and tilt actuation can be used to move a top surface of the liquid lens, which can be used to provide autofocus and stabilization functions. The members can suspend the camera lens element on the support structure.

[0033] The shape memory alloy device can further comprise a controller arranged to provide a drive signal to the shape memory alloy component for moving the moveable element along the movement axis. For example, the controller can provide a drive signal to heat the shape memory alloy component to cause it to contract, which changes the spacing between the first end portion and the second end portion of the members to which the shape memory alloy component is attached, which in turn moves the moveable element relative to the support structure.

[0034] According to a second aspect of the application, there is provided a shape memory alloy device comprising: a support structure; a moveable element; a first pair of members and a second pair of members, each member comprising a first end portion and a second end portion; a first shape memory alloy component arranged between members of the first pair of members and configured to, on contraction, change the spacing between the first end portion and the second end portion of the members of the first pair of members to drive movement of the moveable element relative to the support structure along a movement axis in a first direction and / or to drive rotational movement of the moveable element about a first axis perpendicular to the movement axis; and a second shape memory alloy component arranged between members of the second pair of members and configured to, on contraction, change the spacing between the first end portion and the second end portion of the members of the second pair of members to drive movement of the moveable element relative to the support structure along the movement axis in a second direction and / or to drive rotational movement of the moveable element about a second axis, wherein the second direction is opposite to the first direction. With this arrangement, the first pair of members and the second pair of members act in opposite directions to move the moveable element in opposite directions on contraction of the shape memory alloy components, or the first pair of members and the second pair of members are used to rotate or tilt the moveable element on two different axes. The opposite pairs of members compensate for temperature changes and allow the use of the faster heating contraction of the shape memory alloy components to drive the moveable element in both the first and second directions or in both rotational directions, rather than only being able to drive movement in a single direction or a single rotational direction on heating and contraction.

[0035] The first pair of members and the second pair of members can be arranged on opposite sides of the moveable element with respect to a plane perpendicular to the movement axis. In this case, the first shape memory alloy component can be configured to, on contraction, increase the spacing between the first end portion and the second end portion of each member of the first pair of members; and the second shape memory alloy component can be configured to increase the spacing between the first end portion and the second end portion of each member of the second pair of members.

[0036] Alternatively, the first and second pairs of members can be arranged on the same side of the movable element with respect to a plane perpendicular to the movement axis. In this case, the first shape memory alloy component can be configured to increase the separation between the first and second end portions of each member of the first pair of members; and the second shape memory alloy component can be configured to decrease the separation between the first and second end portions of each member of the second pair of members.

[0037] The shape memory alloy device can further include a third pair of members and a fourth pair of members, each member of the third and fourth pairs of members including a first end portion and a second end portion. The first end portion of each member can be connected to the support structure, and the second end portion of each member can be connected to the movable element. Such connection can be achieved by heat staking or gluing. The shape memory alloy device can further include a third shape memory alloy component and a fourth shape memory alloy component, which can be arranged between the members of the third pair of members and between the members of the fourth pair of members, respectively, and can be configured to change the separation between the first and second end portions of each member of the third and fourth pairs of members, respectively, to drive the movable element to move relative to the support structure along the movement axis in the first and second directions, or to rotate about the first axis in the respective first and second rotational directions.

[0038] Each pair of members is arranged about the movement axis on a respective one of the four sides of the movable element. In other words, the four pairs of members can enclose the movable element when viewed along the movement axis. Opposite pairs of the pairs of members (e.g., the first and second pairs, and the third and fourth pairs) can be arranged on adjacent sides of the movable element.

[0039] The pairs of members can be arranged in various ways in order to provide oppositely acting pairs of members. For example, the first and third pairs of members can be arranged on opposite sides of the movable element with respect to a plane perpendicular to the movement axis as the second and fourth pairs of members. The first and third shape memory alloy components can be configured to increase the separation between the first and second end portions of each member of the first and third pairs of members, respectively, upon contraction; and the second and fourth shape memory alloy components can be configured to increase the separation between the first and second end portions of each member of the second and fourth pairs of members, respectively, upon contraction.

[0040] Alternatively, the first pair of members, the second pair of members, the third pair of members, and the fourth pair of members can be arranged on the same side of the movable element with respect to a plane perpendicular to the movement axis. The first shape memory alloy component and the third shape memory alloy component can be configured to increase the spacing between the first end portion and the second end portion of each of the first pair of members and the third pair of members, respectively, upon contraction; and the second shape memory alloy component and the fourth shape memory alloy component can be configured to decrease the spacing between the first end portion and the second end portion of each of the second pair of members and the fourth pair of members, respectively, upon contraction.

[0041] In another alternative arrangement, the first pair of members and the second pair of members can be arranged on the same side of the movable element with respect to a plane perpendicular to the movement axis, but in this arrangement, both the first shape memory alloy component and the second shape memory alloy component can be configured to increase the spacing between the first end portion and the second end portion of their respective pair of members. In this way, the two pairs of members drive the movable element to move in the same (first) direction. The shape memory alloy device can further include a reset structure or biasing mechanism, such as a spring, to reset or bias the movable element in the second direction after the shape memory alloy components contract and the movable element moves. The pairs of members can be arranged on opposite sides of the movable element when viewed along the movement axis.

[0042] In another alternative arrangement, the first pair of members and the second pair of members can be arranged on adjacent sides of the movable element with respect to a plane perpendicular to the movement axis; the first shape memory alloy component can be configured to drive rotational movement of the movable element about a first axis perpendicular to the movement axis; and the second shape memory alloy component can be configured to or drive rotational movement of the movable element about a second axis perpendicular to the movement axis and the first axis. By applying a force on one side of the movable component at a position offset from the center, the pairs of members can drive rotational movement of the movable element about two perpendicular axes (e.g., x-axis and y-axis) perpendicular to the movement axis (e.g., z-axis). In other words, due to the ability to pivot about the x-axis and y-axis, such an arrangement can enable the movable element to tilt in any direction at an angle to the movement axis.

[0043] The shape memory alloy device can further include a reset mechanism or biasing mechanism, such as a reset spring or flexure, to rotate the movable element in the opposite direction after the shape memory alloy components contract and the movable component moves.

[0044] Optionally, a third pair of members and a fourth pair of members can be arranged on adjacent sides of the movable element and opposite the first pair of members and the second pair of members, respectively; the third shape memory alloy component is configured to drive rotational movement of the movable element about the first axis and in an opposite direction to the first shape memory alloy component; and the fourth shape memory alloy component is configured to drive rotational movement of the movable element about the second axis and in an opposite direction to the second shape memory alloy component. That is, the third shape memory alloy component and the fourth shape memory alloy component can be used in place of the return spring or flexure in the previous example in order to provide more precise and effective control of the tilt.

[0045] Alternatively, a third pair of members and a fourth pair of members can be arranged on sides of the movable element having the first pair of members and the second pair of members, respectively; the third shape memory alloy component is configured to drive rotational movement of the movable element about the first axis and in an opposite direction to the first shape memory alloy component; and the fourth shape memory alloy component is configured to drive rotational movement of the movable element about the second axis and in an opposite direction to the second shape memory alloy component.

[0046] In a second aspect of the application, the members can or can not be tension-based members, i.e. members that are placed under tension only in reaction to a tension in the shape memory alloy component when the shape memory alloy component contracts.

[0047] The image sensor can be mounted to the support structure. The movable element can be a lens carrier comprising at least one lens, and the lens carrier can be arranged to focus an image onto the image sensor. The movement axis can be along an optical axis of the lens element. The at least one lens can comprise a liquid lens. The members can suspend the camera lens element on the support structure.

[0048] In such an arrangement, the members can provide sufficient mechanical advantage for use with a miniature camera. The mechanical advantage can be 5.5:1. A shape memory alloy component stroke of 220 pm can achieve a mechanical stroke of 600 pm. In order to achieve full stroke, the force required to overcome the flexure or deformation of the flexure members can be less than 20 mN.

[0049] The shape memory alloy component can be connected to the members at a location between the first end portion and the second end portion. The shape memory alloy component can be connected to the members at a midpoint between the first end portion and the second end portion.

[0050] The members can be flexures. A flexure is a flexible element configured to be compliant in a particular degree of freedom. The members or flexures can define at least a V-shaped structure. The V-shaped structures can each comprise a pivot, which can be located at a point where the first end portion meets the second end portion. The shape memory alloy components can be connected to their respective flexures at the pivot. Optionally, the angle defined between the shape memory alloy component and its respective flexure first end portion and second end portion is 10 to 45 degrees, preferably 20 to 30 degrees, more preferably 22 to 26 degrees, and most preferably 23 degrees. Alternatively, the flexures can define at least a curved shape. For example, each flexure can define at least a semi-circular shape. The members or flexures can comprise or be entirely made of stainless steel, spring steel, or a copper alloy, such as phosphor bronze which is particularly suitable for lower electrical resistance. In some embodiments, the flexures are electrical conductors for forming electrical communication between the SMA wire and an electrical terminal.

[0051] The shape memory alloy components can be secured to the members by crimped portions. The crimped portions can be crimped joints attached to the members by laser welding. The members can be connected to the movable element and the support structure by heat staking or gluing. The members can comprise folded portions which fold out of the plane of movement of the member to transfer loads and ensure that the member moves and flexes in the right place by stiffening the folded regions.

[0052] According to a third aspect of the application, there is provided a method of controlling a shape memory alloy device, the method comprising: causing a shape memory alloy component to contract; placing a member under tension by causing the shape memory alloy component to contract; and changing a separation between a first end portion and a second end portion of the member by placing the member under tension, wherein the separation is changed in a direction at an angle to the direction of contraction. By this method, the member is only placed under tension during contraction of the shape memory alloy component, and is not under tension or compression when at rest (when the shape memory alloy component is not contracting), which eliminates the possibility of the member buckling when the device is at rest. The method can be a method of controlling any shape memory alloy device as previously described.

[0053] The change in separation between the first end portion and the second end portion of the member can drive movement of the movable element relative to the support structure along an axis of movement, or rotational movement about an axis perpendicular to the axis of movement.

[0054] The device controlled by the method can be used for one or more of autofocus, optical image stabilisation, zoom, and haptics.

[0055] There is also provided another method of controlling a shape memory alloy device, the method comprising: causing a first shape memory alloy component to contract; changing a separation between first and second end portions of a first member due to the contraction of the first shape memory alloy component to drive a movable element to move in a first direction relative to a support structure along a movement axis; causing a second shape memory alloy component to contract; and changing a separation between first and second end portions of a second member due to the contraction of the second shape memory alloy component to drive the movable element to move in a second direction relative to the support structure along the movement axis, the second direction being opposite to the first direction. By this method, the movable element can be moved in the first direction as well as in the second direction by causing the first shape memory alloy component or the second shape memory alloy component to contract, respectively. This therefore allows the faster heating contraction of the shape memory alloy components to be used to drive the movable element in both the first and second directions, rather than only being able to drive movement in a single direction when heated and contracted. This method can also be used to control any of the shape memory alloy devices as previously described.

[0056] Movement of the movable element can cause the movable element to tilt about an axis perpendicular to the movement axis. The image sensor can be mounted to the support structure. The movable element can be a lens carrier comprising at least one lens. The movement axis can be along an optical axis of the lens element. Movement of the lens carrier can provide one or both of optical image stabilisation and autofocus of an image acquired at the image sensor. The device can be used for one or more of autofocus, optical image stabilisation, zoom and haptics.

[0057] According to a fourth aspect of the present application, there is provided a method of manufacturing a shape memory alloy device, the method comprising: etching at least one member onto a single sheet; assembling the single sheet comprising the at least one member into a frame; placing the at least one member from the frame onto a surface; and securing a shape memory alloy component to the at least one member. The manufacturing method can be a method of manufacturing any of the shape memory alloy devices as previously described. BRIEF DESCRIPTION OF DRAWINGS

[0058] Certain presently claimed embodiments of the present application will now be described, by way of example only, with reference to the accompanying drawings in which:

[0059] Figure 1 is a perspective view of a shape memory alloy device embodying an aspect of the present application;

[0060] Figure 2 is a perspective view of a shape memory alloy device embodying an aspect of the present application;

[0061] Figure 3 is a plan view of a shape memory alloy device embodying an aspect of the present application; and

[0062] Figure 4 is a perspective view of a shape memory alloy device embodying an aspect of the application.

[0063] Like features are denoted by like reference numerals. DETAILED DESCRIPTION

[0064] Reference will now be made, by way of example, to Figures 1 to 4 An example shape memory alloy device will now be described.

[0065] Figure 1 A shape memory alloy device 1 is shown, which comprises a member 3. The member 3 comprises a first end portion 5 and a second end portion 7. In this example, the member is a phosphor bronze flexure 3. The flexure 3 is connected to a shape memory alloy component 9 by a crimp portion 8. In this example, the SMA component is an SMA wire 9. The crimp portion 8 is a crimp, which in this example is connected to the flexure 3 by laser welding. The first end portion 5 of the flexure 3 is connected to a support structure 11. The second end portion 7 of the flexure 3 is connected to a moveable element 13. In this example, the end portions 5, 7 are glued to the support structure 5 and the moveable element 13.

[0066] When in a rest state, the flexure 3 is not under tension. The flexure 3 is only tensioned when the SMA wire 9 contracts. SMA material has the property that, upon heating, it undergoes a solid state phase transition, which causes the SMA material to contract. At low temperatures, the SMA material enters a martensite phase. At high temperatures, the SMA enters an austenite phase, which causes a deformation, resulting in the SMA material contracting. Due to the statistical distribution of the transition temperature in the SMA crystal structure, the phase transition occurs over a certain temperature range. Thus, heating of the SMA component or wire 9 causes the length of this SMA component or wire to decrease.

[0067] During use, a drive signal is provided to the SMA wire 9 by a controller (not shown). The drive signal heats the SMA wire 9 and causes it to contract. This places the flexure 3 under tension. In this example, when the SMA wire 9 contracts, the flexure 3 is pulled, and thus the separation between the first end portion 5 and the second end portion 7 increases. Since the end portions are connected to the support structure 11 and the moveable element 13, the moveable element 13 moves in a first direction relative to the support structure 11 along the movement axis 4.

[0068] The gearing achieved by the member depends on the angle of the first end portion 5 and the second end portion 7 of the member relative to the direction of movement, and is shown in equation 1 below.

[0069]

[0070] where θ is the external angle between the horizontal plane (defined as the plane of the shape memory alloy component) and the first portion 5 or the second portion 7 of the member, and L f is the length of the member 5, 7. The transmission ratio is not linearly related to the angle. When the angle of the member approaches the horizontal, the transmission ratio tends to infinity. The angle can be between 10 and 45 degrees, for example 20 to 30 degrees, for example 22 to 26 degrees, or 23 degrees.

[0071] Figure 2 A shape memory alloy device 1 is shown as Figure 1 shown, but also comprises a second member, which in this example is also a flexure 15. The flexure 15 comprises a first end portion 17 and a second end portion 19. The SMA wire 9 is connected to the flexure 15, which SMA wire 9 is also connected to the flexure 15 by a crimp 18. The first end portion 17 and the second end portion 19 are heat staked to the support structure 11 and the movable element 13, respectively. The member 3 and the second member 15 form a pair of members 21.

[0072] In use, the SMA wire 9 contracts as described above, which places both flexures 3, 15 in tension, respectively, and increases the separation of the first end portion 5 and the second end portion 7, the separation of the first end portion 15 and the second end portion 17. Due to the connection with the support structure 11 and the movable element 13, this causes the movable element 13 to move in a first direction, which in this example is a direction along the movement axis 4 away from the support structure.

[0073] Figure 2 A second pair of members 23 is also shown, which is similar in many respects to the pair of members 21, but significantly differs in that the flexures 25, 27 are arranged such that contraction of the SMA wire 29 moves the movable element 13 relative to the support structure 11 in a second direction. The second direction is opposite to the first direction. Thus, in this example, the movable element 13 moves along the movement axis 4 towards the support structure 11 by contraction of the SMA wire 29. Thus, the pair of members 21 and the second pair of members 23 act opposite to each other. In Figure 2 this example shown, the flexures 25, 27 in the pair of flexures 23 are reverse flexures compared to the flexures 3, 15 in the pair of flexures 21. This allows the pair of flexures 21, 23 to be arranged on the same side of the movable element 13 relative to a plane perpendicular to the movement axis 4. Alternative arrangements of the pair of flexures are shown in the Figure 4 explanation below. By providing opposite pairs of flexures, the movable element can be tilted.

[0074] As Figure 2The illustrated embodiment is also capable of tilting the movable element 13 about two perpendicular axes perpendicular to the movement axis 4, e.g. to achieve rotational movement or tilting about the x- and y-axes. By way of example of the second pair of members 23, when the SMA wire 29 is contracted, it can cause the respective side of the movable element 13 to move in a second direction relative to the support structure 11. If the movable element 13 is allowed to pivot about the support structure 11, therefore, such contraction will cause the movable element 13 to tilt towards the respective side of the shape memory alloy device.

[0075] In some embodiments, a return spring or flexure can be provided such that, when the SMA wires 9, 29 cool, the return spring or flexure biases the movable element 13 to return to its default position.

[0076] In some embodiments, the first and second pairs of members can be placed on the same side (where the two pairs of members act in opposite directions when the SMA wires are actuated) or on opposite sides (where the two pairs of members act in one direction when the SMA wires are actuated) to provide bidirectional controlled movement in the movable element 13.

[0077] Figure 3 A plan view of an arrangement of Figure 2 is shown. In addition to the pair of flexures 21 and the second pair of flexures 23, there is a third pair of flexures 31 and a fourth pair of flexures 33. The third pair of flexures 31 is identical to the pair of flexures 21 in all respects except for its position on the device. The third pair of flexures 31 is arranged on the opposite side to the pair of flexures 21 and on a side of the movable element 13 perpendicular to the second pair of flexures 23 when viewed along the movement axis 4. The third pair of flexures 31 is used to drive movement of the movable element 13 relative to the support structure 11 in a first direction. The fourth pair of flexures 33 is identical to the second pair of flexures 23 in all respects except for its position on the device. The fourth pair of flexures 33 is used to drive movement of the movable element 13 relative to the support structure 11 in a second direction. The fourth pair of flexures 33 is arranged on the opposite side to the second pair of flexures 21 and on a side of the movable element 13 perpendicular to the pair of flexures 21 and the third pair of flexures 31 when viewed along the movement axis 4. Thus, the four pairs of flexures 21, 23, 31, 33 are arranged on respective ones of the four sides of the movable element 13 about the movement axis 4.

[0078] In use, the SMA wires arranged between each pair of flexures can be heated individually and thus contracted. Thus, the movable element 13 can be moved both away from and towards the support structure 11, but also tilted, e.g. rotated about an axis perpendicular to the main axis 4, by contracting only selected SMA wires. In this example, asFigure 2 As shown, these flexural pairs are all arranged on the same side of the movable element 13 relative to a plane perpendicular to the moving axis 4, which is achieved by having reverse flexural pairs and non-reverse flexural pairs that act in opposite directions.

[0079] Figure 4 An alternative arrangement of the shape memory alloy device is shown. In this example, the movable element 13 is a lens holder movable through a hole in the support structure 11 along the direction of the movement axis 4. Two pairs of flexures 23a, 23b are arranged on two adjacent sides of the movable element 13, similar to the arrangement described above. In other embodiments, an additional pair of flexures is provided opposite each pair of flexures 23a, 23b. Figure 2 Compared to the illustrated embodiment, only reverse flexures 23a and 23b are used. By using the same type of flexures to achieve bidirectional movement, this arrangement advantageously simplifies control and force balance between the flexures.

[0080] like Figure 4 As shown, the reverse flexure pairs 23a and 23b are stacked. When the SMA line contracts, the spacing between the end portions of each flexure pair decreases. For example, the first flexure pair 23a connects the upper portion of the movable element 13 and the support structure 11. When the SMA line 9a contracts, the flexure pair 23a pulls the movable element 13 downwards. The second flexure pair 23b connects the lower portion of the movable element 13 and the support structure 11. When the SMA line 9b contracts, the flexure pair 23b pulls the movable element 13 upwards.

[0081] In some embodiments, the flexural members 23a, 23b can be made of, for example Figure 2 The non-reverse flexure pair 21 shown is used instead. In such an embodiment, when the SMA line is actuated, the first flexure pair connected between the upper portions of the movable element can pull the movable element in an upward direction, and the second flexure pair connected between the lower portions of the movable element can pull the movable element in a downward direction.

[0082] Similar to Figure 3 In the illustrated embodiment, the SMA lines arranged between each pair of flexural elements can be individually heated and thus contracted. Therefore, the movable element 13 can be tilted, for example, rotated about an axis perpendicular to the main axis 4, by contracting only selected SMA lines.

[0083] Similar to the example above, a combination of non-reverse flexures and reverse flexures, or flexures placed on the same or opposite sides of the movable element 13 relative to a plane perpendicular to the moving axis 4, can be used.

[0084] Embodiments of the application have been described. It is to be understood that variations and modifications can be made to the described embodiments within the scope of the present application. For example, the arrangement, positioning, and type of various flexure pairs are not limited to those described above, and any combination of flexure positions and types falls within the scope of the present application.

Claims

1. A shape memory alloy device, comprising: Support structure; Movable components; The first pair of components and the second pair of components, each component including a first end portion and a second end portion; A first shape memory alloy component is disposed between the components of the first pair of components and is configured to change the spacing between the first end portion and the second end portion of the components of the first pair of components during contraction, so as to drive the movable element to move relative to the support structure along a movement axis in a first direction and / or drive the movable element to rotate about a first axis perpendicular to the movement axis in a first rotation direction. as well as A second shape memory alloy component is disposed between the components of the second pair of components and is configured to change the spacing between the first end portion and the second end portion of the components of the second pair of components during contraction, so as to drive the movable element to move relative to the support structure along the movement axis in a second direction and / or drive the movable element to rotate about a second axis perpendicular to both the first axis and the movement axis or about the first axis in a second rotational direction. Wherein, the second direction is opposite to the first direction, and the second rotation direction is opposite to the first rotation direction.

2. The shape memory alloy device according to claim 1, wherein: The first pair of components and the second pair of components are arranged on opposite sides of the movable element about a plane perpendicular to the axis of movement; The first shape memory alloy component is configured to increase the spacing between the first end portion and the second end portion of each of the first pair of components when shrinking; and The second shape memory alloy component is configured to increase the spacing between the first end portion and the second end portion of each of the second pair of components.

3. The shape memory alloy device according to claim 1, wherein: The first pair of components and the second pair of components are arranged on the same side of the movable element about a plane perpendicular to the axis of movement; The first shape memory alloy component is configured to increase the spacing between the first end portion and the second end portion of each of the first pair of components; and The second shape memory alloy component is configured to reduce the gap between the first end portion and the second end portion of each of the second pair of components.

4. The shape memory alloy device according to claim 1, further comprising: The third pair of components and the fourth pair of components, each of the third pair of components and the fourth pair of components includes a first end portion connected to the support structure and a second end portion connected to the movable element; as well as A third shape memory alloy component and a fourth shape memory alloy component are respectively arranged between components in the third pair of components and between components in the fourth pair of components, and are configured to change the spacing between the first end portion and the second end portion of each component in a corresponding pair of components in the third pair of components and the fourth pair of components, respectively, to drive the movable element to move relative to the support structure along the moving axis in the first direction and the second direction, or to drive the movable element to rotate about the first axis in a corresponding first rotational direction and a second rotational direction.

5. The shape memory alloy device according to claim 4, wherein, Each of the first pair of components, the second pair of components, the third pair of components, and the fourth pair of components is arranged around the moving axis on a corresponding side of the four sides of the movable element.

6. The shape memory alloy device according to claim 5, wherein: The first pair of components and the third pair of components are arranged on opposite sides of the movable element about a plane perpendicular to the axis of movement. The first shape memory alloy component and the third shape memory alloy component are configured to increase the spacing between the first end portion and the second end portion of each of a corresponding pair of components in the first pair of components and the third pair of components, respectively, during shrinkage; and The second shape memory alloy component and the fourth shape memory alloy component are configured to increase the interval between the first end portion and the second end portion of each of the respective pairs of components in the second pair and the fourth pair of components during shrinkage.

7. The shape memory alloy device according to claim 5, wherein: The first pair of components, the second pair of components, the third pair of components, and the fourth pair of components are arranged on the same side of the movable element about a plane perpendicular to the moving axis; The first shape memory alloy component and the third shape memory alloy component are configured to increase the spacing between the first end portion and the second end portion of each of a corresponding pair of components in the first pair of components and the third pair of components, respectively, during shrinkage; and The second shape memory alloy component and the fourth shape memory alloy component are configured to reduce the gap between the first end portion and the second end portion of each of the respective pairs of components in the second pair and the fourth pair of components during shrinkage.

8. The shape memory alloy device according to claim 1, wherein: The first pair of components and the second pair of components are arranged on adjacent sides of the movable element about a plane perpendicular to the axis of movement; The first shape memory alloy component is configured to drive the movable element to rotate about a first axis perpendicular to the axis of movement; and The second shape memory alloy component is configured to drive the movable element to rotate about a second axis perpendicular to the moving axis and the first axis.

9. The shape memory alloy device according to claim 8, wherein: The third pair of components and the fourth pair of components are arranged on adjacent sides of the movable element and are respectively opposite to the first pair of components and the second pair of components; The third shape memory alloy component is configured to drive the movable element to rotate about the first axis and in a direction opposite to that of the first shape memory alloy component; and The fourth shape memory alloy component is configured to drive the movable element to rotate about the second axis and in a direction opposite to that of the second shape memory alloy component.

10. The shape memory alloy device according to claim 8, wherein: The third pair of components and the fourth pair of components are arranged on the corresponding sides of the movable element having the first pair of components and the second pair of components; The third shape memory alloy component is configured to drive the movable element to rotate about the first axis and in a direction opposite to that of the first shape memory alloy component; and The fourth shape memory alloy component is configured to drive the movable element to rotate about the second axis and in a direction opposite to that of the second shape memory alloy component.

11. The shape memory alloy device according to any one of claims 4-7 and 9-10, wherein: The image sensor is mounted to the support structure; The movable element is a lens holder including at least one lens; and The moving axis is along the optical axis of the lens element.

12. The shape memory alloy device according to claim 11, wherein, The at least one lens includes a liquid lens.

13. The shape memory alloy device according to claim 11, wherein, The first pair of components, the second pair of components, the third pair of components, and the fourth pair of components suspend the camera lens element on the support structure.

14. The shape memory alloy device according to any one of claims 4-7, 9-10 and 12-13, further comprising a controller arranged to provide drive signals to the first shape memory alloy component, the second shape memory alloy component, the third shape memory alloy component and the fourth shape memory alloy component for moving the movable element along the movement axis.

15. The shape memory alloy device according to any one of claims 4-7, wherein, Each of the first shape memory alloy component, the second shape memory alloy component, the third shape memory alloy component, and the fourth shape memory alloy component is connected to the component at a position between the first end portion and the second end portion of each of the corresponding pair of components in the first pair of components, the second pair of components, the third pair of components, and the fourth pair of components.

16. The shape memory alloy device according to any one of claims 4-7, wherein, Each of the first pair of components, the second pair of components, the third pair of components, and the fourth pair of components is a flexural member.

17. The shape memory alloy device according to claim 16, wherein, The flexural element defines at least a V-shaped structure, the V-shaped structure including a pivot, and the first shape memory alloy component, the second shape memory alloy component, the third shape memory alloy component and the fourth shape memory alloy component are connected to their respective pivots.

18. The shape memory alloy device according to claim 17, wherein, The angle defined between each of the first, second, third, and fourth shape memory alloy components and the first and second end portions of the corresponding flexure of that shape memory alloy component is between 10 and 45 degrees.

19. The shape memory alloy device according to claim 17, wherein, The angle defined between each of the first, second, third, and fourth shape memory alloy components and the first and second end portions of the corresponding flexure of that shape memory alloy component is 20 to 30 degrees.

20. The shape memory alloy device according to claim 17, wherein, The angle defined between each of the first, second, third, and fourth shape memory alloy components and the first and second end portions of the corresponding flexure of that shape memory alloy component is 22 to 26 degrees.

21. The shape memory alloy device according to claim 17, wherein, The angle defined between each of the first, second, third, and fourth shape memory alloy components and the first and second end portions of the corresponding flexure of that shape memory alloy component is 23 degrees.

22. The shape memory alloy device according to claim 16, wherein, The flexural element at least defines a bending shape.

23. The shape memory alloy device according to claim 16, wherein, The flexural element is at least defined as having a semi-circular shape.

24. The shape memory alloy device according to any one of claims 4-7, 9-10, 12-13 and 17-23, wherein, Each of the first shape memory alloy component, the second shape memory alloy component, the third shape memory alloy component, and the fourth shape memory alloy component is fixed to a corresponding pair of components in the first pair of components, the second pair of components, the third pair of components, and the fourth pair of components by a press-fit portion.

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