Actuator assembly

Abstract

An actuator assembly (1) comprising: a support structure (2); a movable member (10); a helical bearing mechanism (20) arranged to guide helical movement of the movable part relative to the support structure about a helical axis (H); a loading mechanism (50) arranged between the support structure and the movable part for loading the helical bearing mechanism; and at least one pair of actuator members (40) arranged, upon actuation, to drive rotation of the movable member in opposite directions about the helical axis, the helical bearing mechanism converting the rotation into said helical movement; wherein the at least one pair of actuator members is arranged to apply an unloading torque about an axis perpendicular to the helical axis in order to reduce the loading of the helical bearing mechanism.

Description

[0001] field

[0002] The present application relates to an actuator assembly.

[0003] background

[0004] It is known to use actuators (e.g., shape memory alloy SMA elements) to drive translational movement of a movable element relative to a support structure. SMAs have particular advantages in micro devices and can be applied in various devices including handheld devices (e.g., cameras and mobile phones). For example, such SMA elements can be used in optical devices (such as cameras) to drive translational movement of a camera lens element along its optical axis, for example to achieve focusing (autofocus, AF) or zooming.

[0005] Some examples of SMA actuation devices for cameras of this type are disclosed in WO 2007 / 113478 A1. Here, the movable element is a camera lens element supported on a support structure by a helical bearing arrangement, the helical bearing arrangement including a flexure that guides translational movement along the optical axis. In one example described therein, the SMA element is a piece of SMA wire connected at its ends to the support structure and hooked on a hook-shaped piece on the camera lens element for driving the translational movement. The straight SMA wire formed by the portions of the piece of SMA wire on either side of the hook-shaped piece extends at an acute angle greater than 0 degrees relative to a direction of movement parallel to the optical axis. Tilting the SMA wire in this way increases the amount of movement compared to an SMA wire extending in the direction of movement and also reduces the range of the actuator in the direction of movement.

[0006] WO 2019 / 243849 A1 discloses an SMA device comprising a helical bearing mechanism that converts a rotation about a helical axis into a helical movement.

[0007] The screw bearing mechanism is loaded in use, i.e. the bearing surfaces are pushed towards each other. It is desirable to reduce the likelihood of the loading force directly affecting the movement of the screw in addition to loading the screw bearing mechanism. It is also desirable to reduce the power and / or energy required to control the movement and / or position of the screw.

[0008] Overview

[0009] According to one aspect of the present invention, an actuator assembly is provided, which includes: a supporting structure; a movable part; a spiral bearing mechanism, which is arranged to guide the spiral movement of the movable part relative to the supporting structure around a spiral axis; a loading mechanism, which is arranged between the supporting structure and the movable part and is used to load the spiral bearing mechanism; and at least one pair of actuator parts, which are arranged to drive the movable part to rotate in opposite directions around the spiral axis when actuated, and the spiral bearing mechanism converts the rotation into the spiral movement; wherein the at least one pair of actuator parts is arranged to apply an unloading torque around an axis perpendicular to the spiral axis so as to reduce the load of the spiral bearing mechanism.

[0010] By applying an unloading torque, the load on the screw bearing mechanism can be controlled. As an example, this allows the load to be low when movement of the movable component is desired and high when movement is not desired. By applying the unloading torque using an actuator component, the number of components can be minimized.

[0011] Optionally, the loading mechanism is arranged to apply a loading moment about an axis perpendicular to the screw axis for loading the screw bearing mechanism.

[0012] By applying a loading moment perpendicular to the screw axis, the lateral forces applied by the loading mechanism can be reduced. This can help to improve the control accuracy of the position of the movable component.

[0013] Optionally, the at least one pair of actuator members are arranged to apply forces to the moveable member relative to the support structure that are offset from each other along the screw axis.

[0014] By means of the biasing force, a moment may be generated by the actuator component. This may help to provide a load-relieving function without excessively generating unwanted forces that may affect the movement of the movable component.

[0015] Optionally, the at least one pair of actuator components are arranged to apply forces in opposite directions perpendicular to the screw axis, such that an unloading moment can be applied without applying an overall force perpendicular to the screw axis.

[0016] By providing forces in opposite directions, the total force applied perpendicular to the screw axis can be reduced. This can help to improve the control accuracy of the movable component, especially towards the extremes of travel.

[0017] Optionally, the spiral bearing mechanism is arranged to have sufficient friction when loaded so that the movable part remains in place when the actuator component does not apply an unloading torque and / or when the actuator component does not drive the rotation of the movable part. Optionally, the spiral bearing mechanism is arranged to have sufficient friction when loaded so that the movable part remains in place in a continuous position when the actuator component does not apply an unloading torque and / or when the actuator component does not drive the rotation of the movable part. When the actuator component does not apply an unloading torque, the friction in the spiral bearing mechanism can be greater than the weight of the movable part (optionally, when the lens assembly is fixed relative to the movable part, including such a lens assembly). When the actuator component does not apply an unloading torque, the friction in the spiral bearing mechanism can be greater than 1.5 times or 2 times the weight of the movable part (optionally, when the lens assembly is fixed relative to the movable part, including such a lens assembly).

[0018] By providing sufficient friction, the power and / or energy requirements to maintain the position of the movable component can be reduced. By providing sufficient friction, the power and / or energy requirements to maintain an arbitrary position of the movable component within the range of motion of the movable component can be reduced. The movable component can be held in place by friction in the screw bearing mechanism without the need to provide power to the actuator component.

[0019] Optionally, the pair of actuator components are arranged to apply an unloading torque upon actuation so as to reduce friction in the screw bearing mechanism.

[0020] By applying an unloading torque, movement of the movable part can be facilitated when required. This can help reduce the likelihood of unwanted sticking of the movable part. The force required to move the movable part along the screw axis can be reduced compared to the case where the friction force is not reduced by the unloading torque.

[0021] Optionally, the spiral bearing mechanism comprises at least one spiral bearing, which is a rolling bearing comprising bearing surfaces on the support structure and the movable element and at least one rolling bearing element arranged between the bearing surfaces.

[0022] By providing rolling bearings, the ease of movement of the movable part can be increased.

[0023] Optionally, where the spiral bearing mechanism comprises at least one spiral bearing, the at least one spiral bearing is a sliding bearing comprising bearing surfaces on the support structure and the movable component arranged to slide against each other. The sliding bearing may provide friction in the spiral bearing mechanism.

[0024] By providing a sliding bearing, friction can be increased, making it easier to maintain the position of the movable parts with reduced power / energy requirements.

[0025] Optionally, the spiral bearing mechanism comprises three spiral bearings.

[0026] By providing three helical bearings, movement of the movable component can be more reliably constrained to movement along the helical axis.

[0027] Optionally, the bearing surfaces of the first and second spiral bearings each include a groove on each of the support structure and the movable component, and the bearing surface of the third spiral bearing includes a groove on one of the support structure and the movable component and a flat surface on the other of the support structure and the movable component.

[0028] By providing the grooves, the spiral bearings can limit the movement of the movable part in two degrees of freedom. This can reduce the number of spiral bearings required. Thus, three spiral bearings can only allow movement of the movable part in a single degree of freedom relative to the support structure, in particular only allow movement along a spiral path.

[0029] Optionally, the first spiral bearing, the second spiral bearing and the third spiral bearing each comprise only a single rolling bearing element.

[0030] By providing rolling bearings, the ease of movement of the movable part can be increased.

[0031] Optionally, the at least one pair of actuator components is arranged to reduce loading of the screw bearing mechanism by less than a load applied by the loading mechanism.

[0032] By providing an unloading that is less than the loading, the screw bearing mechanism can remain loaded during use of the actuator assembly.

[0033] According to another aspect of the present invention, an actuator assembly is provided, which includes: a support structure; a movable part; a spiral bearing mechanism, which is arranged to guide the spiral movement of the movable part around the spiral axis relative to the support structure; at least one actuator part, which is arranged to drive the movable part to rotate around the spiral axis when contracted, and the spiral bearing mechanism converts the rotation into the spiral movement; and a loading mechanism, which is arranged to apply a loading torque around an axis perpendicular to the spiral axis for loading the spiral bearing mechanism.

[0034] By applying a loading moment perpendicular to the screw axis, the lateral force applied by the loading mechanism can be reduced. This can help to improve the control accuracy of the position of the movable component.

[0035] Optionally, the loading mechanism comprises a spring loading mechanism for spring loading the spiral bearing mechanism.

[0036] By providing a resilient loading mechanism, loading can be provided without increasing power requirements.

[0037] Optionally, the spring loading mechanism comprises a pair of spring elements connected between the support structure and the movable part.

[0038] By providing a pair of elastic elements, the applied forces may at least partially cancel each other out in a direction different from the desired rotational direction of the loading moment.

[0039] Optionally, the resilient loading mechanism comprises at least one resilient element (optionally a pair of resilient elements) between the support structure and the movable part, the resilient element or each resilient element comprising at least one portion extending between the support structure and the movable part, the at least one portion being at least as thick in a direction parallel to the helical axis as in a direction perpendicular to the helical axis. Thus, the portion extending between the support structure and the movable part may be thicker in a direction parallel to the helical axis than in a direction perpendicular to the helical axis. The extent of the portion in a direction parallel to the helical axis may be greater than the extent of the portion in a direction perpendicular to the helical axis.

[0040] By providing a resilient element with a greater extent in a direction parallel to the screw axis, lateral forces acting on the movable component may be reduced or minimised. This may help to increase the accuracy of control of the position of the movable component.

[0041] Optionally, the resilient loading mechanism comprises at least one resilient element (optionally a pair of resilient elements) between the support structure and the movable part, wherein the or each resilient element is stressed in its mounted position connected between the support structure and the movable part so as to load the screw bearing mechanism, whereby the portion of the or each resilient element engaging the support structure and the movable part is at a smaller distance in the direction of the screw axis than if the resilient element were not stressed. Thus, the at least one resilient element may be preloaded by a preload force acting in the direction of the screw axis.

[0042] By providing a stressed elastic element, the loading moment can be applied in a mechanically simple manner which is relatively easy to produce.

[0043] Optionally, the difference in distances of the portions of the elastic element that engage the support structure and the movable component along the screw axis is greater than the possible range of movement of the movable component along the screw axis. Thus, the elastic element can be preloaded over the entire possible range of movement of the movable component along the screw axis.

[0044] By providing a greater preloading distance, it is ensured that the loading mechanism applies a loading force over the entire possible range of movement. Thus, the screw bearing mechanism can be reliably held together by the loading mechanism at any position along the range of movement. This can contribute to improving the control accuracy of the position of the movable part.

[0045] Optionally, the resilient loading mechanism includes at least one resilient element (optionally a pair of resilient elements) between the support structure and the movable part, which resilient element or each resilient element is stiffer for bending about an axis perpendicular to the screw axis than for bending about the screw axis.

[0046] By providing stiffness for bending perpendicular to the screw axis, the applied lateral force can be reduced or minimized. This can contribute to improving the control accuracy of the position of the movable part.

[0047] Optionally, the resilient loading mechanism includes at least one resilient element (optionally each of a pair of resilient elements), which at least one resilient element engages with at least one of the support structure and the movable part via a bearing mechanism. The bearing mechanism can allow the resilient element to move in a direction perpendicular to the screw axis relative to the support structure or the movable part.

[0048] By providing a bearing mechanism, the influence of the lateral force on the support structure or the movable part can be reduced. This can contribute to improving the control accuracy of the position of the movable part.

[0049] Optionally, the loading mechanism includes a magnetic loading mechanism.

[0050] By providing a magnetic mechanism, the lateral force on the movable part can be reduced. This can contribute to improving the control accuracy of the position of the movable part.

[0051] Optionally, each actuator part is a shape memory alloy SMA element. The SMA element can also be referred to as an SMA wire.

[0052] By providing an SMA element, actuation can be achieved particularly precisely and simply. Due to its high energy density, SMA can also provide a particularly compact actuator part, thus allowing the actuator assembly to be used in micro applications such as micro cameras.

[0053] Optionally, the movable part includes a lens assembly having at least one lens, wherein the screw axis is parallel to or coincides with the optical axis of the lens assembly.

[0054] For example, by providing a lens assembly, control of the position of the movable part can be achieved in the context of an optical focusing system or an optical athermalization system.

[0055] Optionally, the support structure has an image sensor mounted thereon, and the lens assembly is arranged to focus the image on the image sensor.

[0056] By providing an image sensor, the actuator assembly may be implemented as a camera, for example. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0059] Figure 1 is a schematic diagram of an actuator assembly having a screw bearing mechanism;

[0060] Figure 2 is a schematic diagram of an actuator assembly having a loading mechanism;

[0061] Figure 3 yes Figure 2 a schematic side view of the actuator assembly shown;

[0062] Figure 4 is a schematic diagram of a sliding bearing;

[0063] Figure 5 yes Figure 4 Different schematic diagrams of the sliding bearing shown;

[0064] Figure 6 is a schematic diagram of a sliding bearing;

[0065] Figure 7 yes Figure 6 Different schematic diagrams of plain bearings shown;

[0066] Figure 8 is a schematic diagram of a rolling bearing;

[0067] Fig. 9 is a schematic diagram of a rolling bearing;

[0068] Fig.10 is a schematic diagram of a possible spiral bearing mechanism;

[0069] Fig.11 is a schematic diagram of a portion of a loading mechanism;

[0070] Fig.12 is a schematic diagram of a portion of a loading mechanism;

[0071] Fig.13 is a schematic plan view of a portion of a loading mechanism;

[0072] Fig.14 is a schematic side view of an actuator assembly;

[0073] Fig.15is a schematic side view of an actuator assembly;

[0074] Fig.16 is a schematic side view of an actuator assembly; and

[0075] Fig.17 is a schematic side view of an actuator assembly.

[0076] Detailed Description

[0077] Actuator assembly

[0078] Figure 1 An actuator assembly 1 is schematically shown in . The actuator assembly 1 may be a camera. The actuator assembly 1 is mainly described in the context that the actuator assembly 1 is a camera. However, the actuator assembly 1 need not be a camera and may be implemented as a different type of device.

[0079] The actuator assembly 1 comprises a support structure 2. The support structure 2 may have one or more components fixed thereto, e.g. mounted thereto. For example, when the actuator assembly 1 is a camera, the support structure 2 may have an image sensor 3 mounted thereon. The support structure 2 may take any suitable form, typically comprising a base 4 to which the image sensor is fixed. The support structure 2 may also support an IC chip 5.

[0080] The actuator assembly 1 further comprises a movable part 10 (or movable element). Optionally, the movable part 10 is or comprises a lens assembly 11 having one or more lenses. The movable part 10 has an axis O (e.g. an optical axis) aligned with the image sensor 3 and can be arranged to focus an image on the image sensor 3.

[0081] The actuator assembly 1 may be a microdevice. In some examples of microdevices, the lens (or more than one lens, when provided) of the lens assembly 11 may have a diameter of at most 20 mm, preferably at most 15 mm, preferably at most 10 mm.

[0082] Although the actuator assembly 1 in this example is a camera, this is generally not required. In some examples, the actuator assembly 1 may be an optical device in which the movable component 10 includes a lens assembly 11, but no image sensor. In other examples, the actuator assembly 1 may be a device of a type that is not an optical device and in which the movable component is not a lens element and no image sensor is present. Examples include devices for depth mapping, facial recognition, gaming consoles, projectors, and security scanners.

[0083] The actuator assembly 1 also includes a spiral bearing mechanism 20 (in Figure 1), the spiral bearing mechanism 20 supports the movable part 10 on the support structure 2. The spiral bearing mechanism 20 is arranged to guide the spiral movement of the movable part 10 relative to the support structure 2 about the spiral axis H. In this embodiment, the spiral axis H coincides with the optical axis O, and the spiral movement along the spiral path is Figure 1 , shown by arrow M. Preferably, the spiral motion is along a right-hand spiral, i.e. a spiral with a constant radius, but generally any spiral is possible. The pitch of the spiral can be constant or vary along the spiral motion. Preferably, the spiral motion is generally only a small portion (less than a quarter) of a full turn of the spiral.

[0084] The helical movement of the movable part 10 guided by the helical bearing mechanism 20 comprises components of translational movement along the helical axis H and rotational movement about the helical axis H. The translational movement along the helical axis H is the desired movement of the movable part 10, for example to change the focus of the image on the image sensor 3 and / or to change the magnification (zoom) of the image on the image sensor 3. In this example, the rotational movement about the helical axis H is not required for optical purposes, but is generally acceptable because the rotation of the movable part 10 does not change the focus of the image on the image sensor 3.

[0085] Drive the rotation of movable parts

[0086] Figure 2 is a schematic diagram of an actuator assembly 1. The actuator assembly 1 comprises at least one actuator component. Optionally, the actuator component is an SMA element, such as an SMA wire 40. Figure 2 The actuator assembly 1 depicted in comprises an SMA wire 40 as an actuator component. However, other types of actuator components may be used.

[0087] The actuator member is arranged to drive upon actuation a rotation of the movable part 10 about the helical axis H. The helical bearing mechanism 20 converts the rotation of the movable part 10 into a helical movement of the movable part 10 about the helical axis H relative to the support structure 2 .

[0088] Optionally, only one actuator component is provided. The actuator component can be arranged to drive the movable component 10 to rotate in one direction around the spiral axis H when actuated. The spiral bearing mechanism 20 converts the rotation into a spiral movement along one spiral direction (i.e., in one direction). Another component such as an elastic member can drive the movable component 10 to rotate in the opposite direction around the spiral axis H, and the spiral bearing mechanism 20 converts the rotation into a spiral movement in the opposite direction.

[0089] In a preferred embodiment, the actuator assembly 1 comprises a plurality of actuator components, such as a pair of actuator components. Figure 2As shown, the actuator assembly 1 may include two SMA wires 40 as actuator components. Figure 2 Only one of the SMA wires 40 can be seen from the angle. Figure 2 As shown, optionally, an SMA wire 40 is connected between the support structure 2 and the movable part 10. The SMA wire 40 can be connected to the support structure 2 via a connection element such as a static crimp 41. The SMA wire 40 can be connected to the movable part 10 via a connection element such as a moving crimp 42. In general, any connection element capable of fixing the SMA wire to the support structure 2 and / or the movable part 10 can be used. Figure 2 The second SMA wire 40 which is not visible in the figure is arranged on the lower side of the actuator assembly 1 (at Figure 2 ). Figure 2 A movable crimp 42 for connecting the second SMA wire 40 to the movable part 10 can be seen in FIG.

[0090] Optionally, the actuator assembly 1 includes at least one pair of actuator components (e.g., SMA wires 40) that are arranged to drive the movable component 10 to rotate in opposite directions around the helical axis H when actuated. The helical bearing mechanism converts the rotation of the movable component 10 into a helical movement. The two SMA wires 40 can be actuated to cause helical movement in opposite directions along the helical axis H. The SMA wires 40 can be controlled (i.e., actuated) to control the position of the movable component 10 along the helical axis H, for example, within the range of movement of the movable component 10 relative to the support structure 2.

[0091] Optionally, the SMA wires 40 are driven by a control circuit or controller implemented in the IC chip 5. In particular, the control circuit can generate a drive signal (e.g., a PWM drive signal) for each of the SMA wires 40 and provide the drive signal to the SMA wires. The control circuit receives an input signal representing a desired position of the movable component 10 along the optical axis O, and generates a drive signal selected to drive the movable component 10 to the desired position.

[0092] The drive signal may be generated using a resistance feedback control technique, in which case the control circuit measures the resistance of the lengths of SMA wire 40 and uses the measured resistance as a feedback signal to control the power of the drive signal.

[0093] Alternatively, the control circuit may include a sensor that senses the position of the movable part 10, such as a Hall sensor that senses the position of a magnet fixed to the movable part 10. In this case, the drive signal uses the sensed position as a feedback signal to control the power of the drive signal.

[0094] Loading mechanism

[0095] like Figure 2 As shown, the actuator assembly 1 includes a loading mechanism 50 (which may also be referred to as a biasing mechanism). The loading mechanism 50 is arranged between the support structure 2 and the movable part 10. The loading mechanism 50 is used to load the spiral bearing mechanism 20. Loading the spiral bearing mechanism 20 means pushing different parts (e.g., bearing surfaces) of the spiral bearing mechanism 20 toward each other.

[0096] If the spiral bearing mechanism 20 is not loaded (i.e., unloaded), the spiral bearing mechanism 20 may not be able to convert the rotation of the movable part 10 into a spiral movement. If the spiral bearing mechanism 20 is not loaded, the bearing surfaces of the sliding bearing may lose contact with each other and / or the bearing surfaces may lose contact with the rolling bearing between the bearing surfaces. By loading the spiral bearing mechanism 20, the spiral bearing mechanism 20 can reliably guide the spiral movement of the movable part 10 relative to the support structure 2 around the spiral axis 2.

[0097] exist Figure 2 In the illustrated actuator assembly 1, the loading mechanism 50 comprises a pair of resilient elements 51 (eg springs). The resilient elements 51 apply a force that pushes the spiral bearing mechanism 20 together. The loading mechanism 50 may be provided in a variety of different forms, as explained in further detail below.

[0098] like Figure 2 As shown, optionally, each elastic element 51 is connected between the support structure 2 and the movable part 10. The elastic element 51 can be fixedly connected to the support structure 2 at one end and fixedly connected to the movable part 10 at the other end. The elastic element 51 can include a static portion 52 engaged with the support structure 2. For example, the static portion 52 can be directly fixed to the support structure 2. The elastic element 51 can include a moving portion 53 engaged with the movable part 10. For example, the moving portion 53 can be fixed to the movable part 10.

[0099] like Figure 2 As shown, optionally, the moving part 53 of the elastic element 51 and the moving crimping member 42 can be set as an integral part. However, this is not necessary. In an alternative arrangement, the moving part 53 of the elastic element 51 and the moving crimping member 42 can be set as separate parts. The moving part 53 of the elastic element 51 and the moving crimping member 42 can both be fixed relative to the movable part 10.

[0100] Unloading torque

[0101] Figure 3 yes Figure 2 A schematic side view of the actuator assembly 1 is shown. Figure 3 Two SMA wires 40 can be seen as actuator components.

[0102] Figure 3 A force arrow 45 indicating the direction of the force applied by the SMA wire 40 is shown. These are the forces applied to the movable member 10. Figure 3 The upper force arrow 45 shown indicates the force applied to the movable member 10 to push the movable member in the direction from right to left. When Figure 3 the SMA wire 40 at the top contracts, this force is applied. At Figure 3 the bottom, another force arrow 45 shows the force applied to the movable member 10 by Figure 3 the contraction of the SMA wire 40 shown at the bottom.

[0103] Figure 3 An unloading moment arrow 46 is also shown. The unloading moment arrow 46 indicates the general direction of the unloading moment formed by the combination of the force arrows 45 applied by the SMA wire 40 as the actuator member.

[0104] As Figure 3 shown, optionally, at least one pair of actuator members (e.g., the SMA wire 40) is arranged to apply an unloading moment 46 about an axis perpendicular to the helical axis H, so as to reduce the load on the helical bearing mechanism 20. In Figure 3 the actuator assembly shown, the axis about which the unloading moment 46 is applied is the axis extending into and out of the drawing. The axis can be generally perpendicular to the length of the SMA wire 40 and perpendicular to the helical axis H.

[0105] By providing an unloading moment to reduce the load on the helical bearing mechanism 20, the degree of load on the helical bearing mechanism 20 can be varied in a controlled manner. For example, when it is desired to move the movable element 10 along the helical axis H, the load on the helical bearing mechanism 20 can be reduced by applying the unloading moment 46. By reducing the load on the helical bearing mechanism 20, the friction in the helical bearing mechanism 20 (or generally the resistance to motion in the helical bearing mechanism 20) can be reduced. This allows the movable member 10 to move more freely relative to the support structure 2. Of course, it is desired that the helical bearing mechanism 10 remains loaded at least to a certain extent such that the helical bearing mechanism 20 can continue to reliably convert the rotation of the movable member 10 into a helical movement during the use of the actuator assembly 1. It is desired that the unloading moment 46 is less than a threshold amount that would cause the helical bearing mechanism 20 to become unloaded.

[0106] By providing the unloading moment 46 applied by the actuator member (the actuator member drives the rotation of the movable member 10 and causes the movable member 10 to move helically), the load on the helical bearing mechanism 20 can be controlled without the need for additional components for controlling the load on the helical bearing mechanism 20. The actuator member may already be provided in such an actuator assembly 1. The actuator member is controlled in a new way so as to control the load on the helical bearing mechanism 20.

[0107] By providing an unloading moment 46 about an axis perpendicular to the screw axis H to reduce the load on the screw bearing mechanism 20, the likelihood that the unloading moment 46 itself directly causes a screw movement of the movable part 10 is reduced. For example, if the reduction of the load on the screw bearing mechanism 20 is achieved by applying a force that acts primarily or purely along the screw axis H, the unloading force itself may cause the movable part 10 to move along the screw axis H. As a result, the screw movement of the movable part 10 may be affected in an undesirable manner. By providing an unloading moment 46 about an axis perpendicular to the screw axis H, undesirable effects on the screw movement may be reduced.

[0108] At the same time, when spiral movement of the movable component 10 is not desired (e.g., when it is desired that the movable component 10 maintain its position relative to the support structure 2), the load of the spiral bearing mechanism 20 can be increased. For example, the unloading torque 46 can be reduced to reduce any reduction in the load of the spiral bearing mechanism 20 caused by the unloading torque 46. By increasing the load of the spiral bearing mechanism 20, the friction within the spiral bearing mechanism 20 can be increased. Friction can help to reduce the amount of power required by the actuator component in order to maintain the position of the movable component 10 relative to the support structure 2. It is possible that the power required to maintain the position of the movable component 10 along the spiral axis H can be eliminated. In other words, when the actuator component is not actuated, the friction within the spiral bearing mechanism 20 can be sufficient to maintain the movable component 10 in the appropriate position relative to the support structure 2. This can be referred to as zero holding power.

[0109] like Figure 3 As shown, optionally, at least one pair of actuator components (e.g., SMA wires 40) are arranged to apply forces to the movable component 10 that are offset from each other along the helical axis H relative to the support structure 2. This offset along the helical axis H allows the forces to combine to form an unloading moment 46 about an axis perpendicular to the helical axis H. Figure 3 In the example shown, the actuator components are SMA wires 40. In this case, the SMA wires 40 may be arranged offset from one another along the helical axis H. The axis about which the unloading moment 46 is applied may be between the forces applied by the actuator components, for example, between the SMA wires 40 when the SMA wires 40 are the actuator components. The forces applied by the SMA wires 40 act in the direction of the SMA wires 40.

[0110] like Figure 3 As shown, optionally, at least one pair of actuator components are arranged to apply forces in opposite directions perpendicular to the screw axis H, so that the unloading moment 46 can be applied without applying a total force perpendicular to the screw axis H. Figure 3The force arrows 45 shown in FIG. 4 are generally opposite to each other. The force arrows 45 are generally perpendicular to the helical axis H. The force arrows 45 are in the direction of the SMA wire 40 itself. The SMA wire 40 may be generally perpendicular to the helical axis H. However, typically, the SMA wire 40 may be oriented at an acute angle relative to the direction perpendicular to the helical axis H. The orientation angle of the SMA wire 40 may change as the movable component 10 moves along the helical axis H relative to the support structure 2. However, the force and the SMA wire 40 may remain generally approximately perpendicular to the helical axis H (or at least at an acute angle relative to the direction perpendicular to the helical axis H). Alternatively, the forces applied by the SMA wire 40 may be equal in magnitude to each other but applied in opposite directions. This will result in no total force perpendicular to the helical axis H. However, an unloading torque 46 may still be applied. This means that the loading of the helical bearing mechanism 20 may be controlled without adversely affecting the control of the helical position of the movable component 10 relative to the support structure 2.

[0111] Of course, it may be desirable to apply different forces through different SMA wires 40. For example, it may be desirable to drive the rotation of the movable member 10 to move the movable member 10 in a helical direction. Additionally or alternatively, it may be desirable to control the difference in forces applied by the SMA wires 40 in order to counteract other external forces such as gravity.

[0112] Loading torque

[0113] Figure 3 Also shown is a loading force arrow 55. The loading force arrow 55 shows the loading force generated by the loading mechanism 50, in particular by Figure 3 The force applied to the movable part 10 by the elastic element 51 of the particular loading mechanism 50 shown in FIG. 1 is shown in FIG. 2 . For example, the moving portion 53 of the elastic element 51 engaged with the movable part 10 can push the movable part 10 by a force acting substantially parallel to the screw axis H. Figure 3 As shown, optionally, the loading mechanism 50 is arranged to apply a loading torque 56 about an axis perpendicular to the screw axis H for loading the screw bearing mechanism 20. In embodiments that provide both a loading torque and an unloading torque, the loading torque provided by the loading mechanism 50 may be in a direction opposite to the unloading torque provided by the actuator component.

[0114] like Figure 3 As shown, the force exerted by the elastic element 51 on the movable part 10 acts generally in a direction parallel to the screw axis H. However, the two forces exerted by the two elastic elements 51 of the loading mechanism 50 act on both sides of the screw axis H. The screw axis H is located between the loading force arrows 55. This generates a loading moment 56. The axis about which the loading moment 56 is applied is the axis extending into and out of the drawing.

[0115] By providing that loading of the screw bearing mechanism 20 is achieved by a loading moment 56 about an axis perpendicular to the screw axis H, the likelihood of the force loading the screw bearing mechanism 20 undesirably affecting the screw movement is reduced. Desirably, the force loading the screw bearing mechanism 20 does not act in a direction that may cause screw movement of the movable component 10 relative to the support structure 2.

[0116] For example, Figure 3 As shown, the two loading force arrows 55 for the elastic element 51 of the loading mechanism 50 act substantially in opposite directions to each other. Therefore, the total force in the direction of the helical axis H may be small or even zero. Therefore, the loading mechanism 50 itself may not significantly drive the helical movement of the movable part 10 relative to the support structure 2. This can help to more accurately control the helical movement of the movable part 10 by controlling the rotation of the movable part 10 by the actuator part.

[0117] Zero holding power

[0118] A zero hold power actuator has the advantage of using no power when holding a position. This is particularly advantageous for devices with limited power (e.g., limited peak power) and / or energy (e.g., limited average power). For example, a wearable device may have limited power and / or energy. Other battery powered devices may similarly have limited power and / or available energy.

[0119] It may be desirable that the spiral bearing mechanism 20 have sufficient friction to keep the movable component in place against the inertial path. For example, the spiral bearing mechanism 20 may generally be good at resisting linear forces caused by impacts. Such linear forces may increase friction on one or more spiral bearings of the spiral bearing mechanism 20, thereby actually increasing the resistance to motion.

[0120] Optionally, the spiral bearing mechanism 20 is arranged to have sufficient friction when loaded so that the movable part 10 remains in place when the actuator component is not driving the rotation of the movable part 10. The spiral bearing mechanism 20 is arranged to have sufficient friction when loaded so that the movable part 10 remains in place when the actuator component does not provide an unloading torque. This allows the power and energy requirements of the actuator assembly 1 to be reduced while allowing the position of the movable part 10 to be controlled and maintained. For example, the actuator assembly 1 can be used in the context of an autofocus function of a camera. It may be desirable to maintain the focus position of the movable part 10 relative to the support structure 2 between shots taken by the camera. In another example, the actuator assembly 1 can be used in the context of providing athermalization in an optical system. It may be desirable to maintain the position of the movable part 10 relative to the support structure 2 while the ambient temperature remains constant.

[0121] Optionally, the spiral bearing mechanism 20 is arranged to have sufficient friction when loaded so that the movable part 10 remains in position over a continuous range of positions when the actuator component is not driving rotation of the movable part 10. This can allow the movable part 10 to be controlled to maintain any arbitrary spiral position relative to the support structure 2 at least within the range of movement of the movable part 10 relative to the support structure 2. This is an improvement over ratchet-type systems, which can maintain the position of a part, but only at a set of discrete intervals. The friction within the spiral bearing mechanism 20 can allow the movable part 10 to remain in any position in a continuous range of positions.

[0122] Optionally, the loading mechanism 50 is arranged to load the spiral bearing mechanism 20 so as to generate a friction force therein, which, when the actuator component is not actuated, constrains the movement of the movable component 10 at any position within the range of movement relative to the support structure 2. The constraint on the movable component 10 can cause the movable component 10 to maintain the spiral position relative to the support structure 2. Once the desired position of the movable component 10 is found, there is no need to control the spiral movement of the movable component 10 again to maintain the desired position for subsequent processes (e.g., taking a picture with a camera).

[0123] Optionally, a pair of actuator components are arranged to apply an unloading torque 46 when actuated so as to reduce friction in the screw bearing mechanism 20. Figure 3 As shown, the unloading moment 46 counteracts the loading moment 56. The loading moment 56 and the unloading moment 46 can be around the same axis perpendicular to the spiral axis H. The unloading moment 46 is used to counteract a portion of the loading moment 56. Of course, the loading moment 56 can generally remain greater than the unloading moment 46, so that the spiral bearing mechanism 20 remains loaded at least to a certain extent. By reducing the friction in the spiral bearing mechanism 20, the ease of movement of the movable part 10 relative to the support structure 2 can be controlled. For example, in the case where it is desired to maintain the position of the movable part 10, the friction can be increased by reducing the unloading moment 46. When it is desired to move the movable part 10 spirally (in either direction), the unloading moment 46 can be increased to reduce the friction within the spiral bearing mechanism 20.

[0124] Sliding bearings

[0125] The screw bearing mechanism 20 may take a variety of forms.

[0126] One possibility is that the spiral bearing mechanism 20 comprises one or more spiral bearings 30 (which are sliding bearings), examples of which are shown in Figure 4-Figure 7 In Figure 4 and Figure 5In the first example shown, the sliding bearing is a plain bearing 81, which includes an elongated bearing surface 83 on one of the support structure 2 and the movable part 10. The plain bearing 81 also includes a protrusion 85 formed on the other of the support structure 2 and the movable part 10, and the end of the protrusion 85 forms a bearing surface 86 supported on the elongated bearing surface 83. Although two protrusions 85 are shown in this example, any number of one or more protrusions 85 can generally be provided. The elongated bearing surface 83 and the bearing surface 86 are conformal, and in this example both are planar, so as to allow relative movement of the movable part 10 relative to the support structure 2. The elongated bearing surface 83 and the bearing surface 86 ideally have a friction coefficient of 0.2 or greater. A higher friction coefficient can reduce or eliminate the power and / or energy required to keep the movable part 10 in place.

[0127] exist Figure 6 and Figure 7 In the second example shown, the sliding bearing is a slider bearing 91, which includes a channel 92 on one of the support structure 2 and the movable part 10, and the inner surface of the channel 92 forms a bearing surface 93. The slider bearing 9 includes a protrusion 95 formed on the other of the support structure 2 and the movable part 10, and the end of the protrusion 95 forms a bearing surface 96 supported on the bearing surface 93. Although two protrusions 95 are shown in this example, any number of one or more protrusions 95 can be provided. The elongated bearing surface 93 and the bearing surface 96 are conformal, and both are planar in this example, so as to allow relative movement of the movable part 10 relative to the support structure 2. The elongated bearing surface 93 and the bearing surface 96 ideally have a friction coefficient of 0.2 or greater. A higher friction coefficient can reduce or eliminate the power and / or energy to keep the movable part 10 in place. However, in general, a lower friction coefficient can be used and compensated by a larger loading force to provide zero holding power, and vice versa. Therefore, the friction surfaces of the loading mechanism and the spiral bearing mechanism can be designed to work together to provide zero holding power.

[0128] In each of the slider bearings 81 and 91, the material of the bearing surfaces 83, 86, 93, 96 is selected to provide smooth movement and long life. The bearing surfaces 83, 86, 93, 96 may be integral with the underlying components or may be formed by a surface coating. Suitable materials include, for example, PTFE or other polymer bearing materials or metals.

[0129] In each of the slider bearings 81 and 91, a lubricant may be provided on the bearing surfaces 83, 86, 93, 96. For example, such a lubricant may be a powder or a fluid. Suitable lubricants include: graphite; silicon paste or low viscosity oil.

[0130] Rolling bearings

[0131] As mentioned above, the screw bearing mechanism 20 may take a variety of forms.

[0132] Another possibility is that the spiral bearing mechanism 20 includes one or more spiral bearings 30 (which are rolling bearings), examples of which are shown in Figure 8 and Fig. 9 In Figure 8 and Fig. 9 In each of the spiral bearings 30, a pair of bearing surfaces 31 and 32 and more than one rolling bearing element 33 (e.g., balls) are arranged between the bearing surfaces 31 and 32. One of the bearing surfaces 31, 32 is arranged on the support structure 2, and the other of the bearing surfaces 31, 32 is arranged on the movable part 10.

[0133] The spiral bearing 30 guides the spiral movement of the movable part 10 relative to the support structure 2, as shown by the arrow M. This can be achieved by the bearing surfaces 31 and 32 extending spirally around the spiral axis H (i.e. extending along the line of the spiral). That is, in a practical embodiment, if one or more spiral bearings in the spiral bearing mechanism 20 guide the spiral movement of the movable part 10 relative to the support structure 2, the length of the bearing surfaces 31 and 32 can be short compared to the distance of the bearing surfaces 31 and 32 from the spiral axis H, so that their shape is close to straight or even each is straight. Typically there is more than one spiral bearing 30, which is positioned around the spiral axis H at different angular positions, in which case the spiral bearings 30 have different orientations so that they cooperate and maintain sufficient constraint to guide the spiral movement of the movable part 10 relative to the support structure 2, even if the bearing surfaces 31 and 32 of a single spiral bearing 30 are straight.

[0134] exist Figure 8 In the example of , the bearing surfaces 31 and 32 each comprise a corresponding groove 34 and 35, in which the rolling bearing element 33 is located. In this example, the grooves 34 and 35 constrain the lateral translational movement of the movable part 10 relative to the support structure 2, i.e. transversely to the movement direction indicated by the arrow M. Figure 8The grooves shown in are V-shaped in cross section, but other cross sections are also possible, such as curved sections of a circle or an ellipse. Typically, the grooves 34 and 35 provide two contact points with the corresponding rolling bearing element 33. The grooves 34 and 35 can extend spirally. Alternatively, in a practical embodiment, in the case where one or more spiral bearings 30 in the spiral bearing mechanism 20 guide the spiral movement of the movable part 10 relative to the support structure 2, the length of the bearing surfaces 31 and 32 can be short compared to the distance of the bearing surfaces 31 and 32 from the spiral axis H, in which case the grooves 34 and 35 can be straight or nearly straight.

[0135] exist Fig. 9 In the example of , the first bearing surface 31 includes a groove 36 in which the rolling bearing element 33 is located, and the bearing surface is "planar" in the second bearing surface 32. The first bearing surface 31 including the groove 36 can be provided on either one of the support structure 2 and the movable part 10, and the second bearing surface 32 is provided on the other of the support structure 2 and the movable part 10. Fig. 9 In the example of the spiral bearing 30, the movable part 10 is not constrained in the lateral translation movement relative to the support structure 2, i.e., transverse to the direction of movement shown by the arrow M. The bearing surface 32 is "planar" in the sense that it is a surface that is not a groove and is a surface that only provides a single point contact with the ball. In other words, the bearing surface 32 is actually planar over the entire width scale of the rolling bearing element 33, although it is spiral on a larger scale. For example, as shown in the figure, this "planar" surface is spiral, and in a cross section is a line that is spirally twisted along the direction of movement, maintaining a single point contact with the ball at all times. Alternatively, and as described above, in a practical embodiment, in the case where one or more spiral bearings 30 in the spiral bearing mechanism 20 guide the spiral movement of the movable part 10 relative to the support structure 2, the length of the bearing surfaces 31 and 32 can be short, in which case the bearing surface 32 can be planar or nearly planar.

[0136] Figure 8 and Fig. 9 A single rolling bearing element 33 is shown by way of example in FIG. 1 , but generally any number of rolling bearing elements 33 more than one may be included.

[0137] In some examples, the spiral bearing 30 may comprise a single rolling bearing element 33. In this case, the spiral bearing 30 itself does not constrain the rotational movement of the movable part 10 relative to the support structure 2 about the single rolling bearing element 33 (i.e. about an axis transverse to the direction of movement indicated by the arrow M). However, this minimizes the overall size of the spiral bearing 30, in particular the height of the spiral bearing 30 protruding along the spiral axis H, because it only needs to accommodate the size of the rolling bearing element 33 and the relative travel of the bearing surfaces 31 and 32.

[0138] In other examples, the spiral bearing 30 may include more than one rolling bearing element 33. In this case, the spiral bearing 30 constrains the rotational movement of the movable part 10 relative to the support structure 2 around any one of the rolling bearing elements 33, i.e. around an axis transverse to the direction of movement indicated by the arrow M. However, this increases the overall size of the spiral bearing 30, in particular the height of the spiral bearing 30 protruding along the spiral axis H, compared to the use of a single rolling bearing element 33.

[0139] The spiral bearing mechanism may generally include any number of spiral bearings 30, wherein the configuration of the spiral bearings 30 is selected to guide the spiral movement of the movable part 10 relative to the support structure 2 while constraining the movement of the movable part 10 relative to the support structure 2 in other degrees of freedom. Many spiral bearing mechanisms may include more than one spiral bearing 30, and at least one spiral bearing includes more than one rolling bearing element 30.

[0140] Screw bearing mechanism

[0141] Fig.10 A possible spiral bearing arrangement is illustrated, which comprises only three spiral bearings 71, 72 and 73. Optionally, the three spiral bearings 71, 72 and 73 are equiangularly spaced around the spiral axis H, but alternatively they may be unequally spaced.

[0142] Optionally, the first spiral bearing 71 and the second spiral bearing 72 are Figure 8 The spiral bearing 30 shown is of the same type, wherein the bearing surfaces 31 and 32 each comprise a corresponding groove 34 and 35 .

[0143] The third spiral bearing 73 and Fig. 9 The spiral bearing 30 shown is of the same type, wherein the first bearing surface 31 comprises a groove 36 in which the rolling bearing element 33 is located, and the second bearing surface 32 is planar. Fig.10 The case where the first bearing surface 31 of the third spiral bearing 73 is on the movable part 10 is illustrated, but it may alternatively be on the support structure 2 .

[0144] Each of the three spiral bearings 71, 72 and 73 may comprise a single rolling bearing element or more than one bearing element 33. This is possible because the constraints imposed by the three spiral bearings 71, 72 and 73 and in particular the constraints imposed by the grooves of the first and second spiral bearings 71, 72 are sufficient to constrain the movement of the movable part 10 relative to the support structure 2 in degrees of freedom other than the spiral movement. Due to the use of only a single rolling bearing element 33 in each of the three spiral bearings 71, 72 and 73, the overall dimensions of the three spiral bearings 71, 72 and 73, in particular the height of the three spiral bearings 71, 72 and 73 protruding along the spiral axis H, are reduced.

[0145] Optionally, Fig.10 One or more of the spiral bearings shown in the drawings may be replaced by one or more sliding bearings. For example, the sliding bearing may include a groove in one of the support structure 2 and the movable part 10, and a member of complementary shape in the other of the support structure 2 and the movable part 10. This may provide sufficient constraint to constrain the movement of the movable part 10 relative to the support structure 2 in degrees of freedom other than spiral movement.

[0146] Optionally, at least one pair of actuator components is arranged to reduce the load of the screw bearing mechanism 20 by less than the load applied by the loading mechanism 50. This allows the screw bearing mechanism 20 to continue to accurately convert the rotation of the movable component 10 into a screw movement.

[0147] Elastic element

[0148] Fig.11 is a schematic diagram of one of the elastic elements 51 of the loading mechanism 50. For example, Fig.11 The elastic element 51 shown in FIG. 5 may be Figure 2 and Figure 3 1. Optionally, the loading mechanism 50 comprises a resilient loading mechanism for resiliently loading the spiral bearing mechanism 20. The resilient loading mechanism has the advantage that it does not need to be actuated in order to apply a load to the spiral bearing mechanism 20. For example, the resilient element 51 may be preloaded so that when it is mounted in the actuator assembly 1, it serves to push the movable part 10 relative to the support structure 2 so as to provide the loading moment 56.

[0149] like Figure 3 As shown, optionally, the elastic loading mechanism includes a pair of elastic elements 51. The elastic element 51 is located between the support structure 2 and the movable part 10. For example, the elastic element 51 can be connected between the support structure 2 and the movable part 10. For example, the elastic element 51 can include a static part 52 configured to be fixed to the support structure 2 and a moving part 53 configured to be fixed to the movable part 10.

[0150] By providing a pair of elastic elements 51 , a loading moment can be provided by combining the forces applied to the movable part 10 by the two elastic elements 51 .

[0151] Optionally, the elastic loading mechanism comprises at least one elastic element 51 between the support structure 2 and the movable part 10. The elastic element 51 may comprise at least a portion 54 extending between the support structure 2 and the movable part 10, the portion 54 being at least as thick in a direction parallel to the screw axis H as in a direction perpendicular to the screw axis H. For example, the thickness 57 of the portion 54 of the elastic element 51 in a direction perpendicular to the screw axis H is Fig.11 . Optionally, the thickness of portion 54 parallel to the screw axis H (i.e. the thickness of portion 54 in the direction into and out of the page) is at least as great as the thickness 57 in the direction perpendicular to the screw axis H. This can help to reduce lateral forces (i.e. forces in a direction perpendicular to the screw axis H at the edge of travel, i.e. at the extreme positions of the movable part 10 along the screw axis H (in either direction)). By providing a resilient element 51 that is relatively thick in a direction parallel to the screw axis H, the force applied by the resilient element 51 can be much greater in a direction parallel to the screw axis H than in a direction perpendicular to the screw axis H. This helps to reduce lateral forces.

[0152] As the movable part 10 moves along the screw axis H, the force exerted by the elastic element 51 on the movable part 10 varies. This is because the shape and / or orientation of the elastic element 51 changes. In particular, the distance along the screw axis H between the parts 52, 53 of the elastic element 51 that engage with the support structure and the movable part 10 varies with the movement of the movable part 10. By providing a relatively thick (in the direction of the screw axis H) elastic element 51, the variation of the required preload force within the stroke can be reduced.

[0153] As described above, the elastic element 51 may be preloaded with stress so that when the elastic element 51 is mounted in the actuator assembly 1, it exerts a force on the movable part 10. Optionally, the elastic loading mechanism comprises at least one elastic element 51 between the support structure 2 and the movable part 10. The elastic element 51 is stressed in its mounted position connected between the support structure 2 and the movable part 10 so as to load the spiral bearing mechanism 10. Thereby, the portions 52, 53 of the elastic element 51 that engage with the support structure 2 and the movable part 10 are at a smaller distance in the direction along the spiral axis H than if the elastic element 51 is not stressed.

[0154] During the manufacture of the elastic element 51, the elastic element 51 may be bent, for example, a jog may be included in the elastic element 51. When the elastic element 51 is incorporated into the actuator assembly 1, it is installed in a position that is deformed (for example, deformed to a flatter shape) compared to the bent shape during manufacture. Therefore, when the elastic element 51 is installed in the actuator assembly 1, there is a difference in the distance or range between the parts 52 and 53 of the elastic element 51 along the spiral axis H compared to before installation. Therefore, the elastic element 51 can be preloaded during manufacture. Optionally, the difference is greater than the possible range of movement (i.e., stroke) of the movable part 10 along the spiral axis H. For example, optionally, the possible range of movement of the movable part 10 along the spiral axis is at least 10 μm, and optionally at least 20 μm. Optionally, the possible range of movement of the movable part 10 along the spiral axis H is at most 100 μm, optionally at most 50 μm. At the same time, optionally, the preload distance of the elastic element 51 can be at least 100 μm, optionally at least 200 μm and optionally at least 500 μm. The preload distance is the difference in distance between the parts 52, 53 of the elastic element 51 along the screw axis H before the elastic element is installed in the actuator assembly 1 (but when the parts 52, 53 are oriented perpendicular to the screw axis H) and after installation. By providing a preload distance greater than the stroke, the change in preload within the range of motion of the movable component will be relatively small. This helps to maintain low lateral forces at the stroke limit.

[0155] Fig.12 FIG. 5 is a schematic perspective view of another embodiment of the elastic element 51 of the loading mechanism 50. Fig.12 As shown, the elastic loading mechanism optionally comprises at least one elastic element 51 between the support structure 2 and the movable part 10. The elastic element 51 is stiffer for bending around an axis perpendicular to the screw axis H than for bending around the screw axis H. For example, Fig.12 As shown, optionally, the thickness 58 of the portion 54 between the portions 52, 53 engaging the support structure 2 and the movable part 10 is greater than the thickness 57 in a direction perpendicular to the screw axis H. The thickness 58 is parallel to the screw axis H. For example, Fig.12 As shown, optionally, the elastic element 51 comprises a folded section forming a portion 54. The folded section increases the vertical force without increasing the lateral force. Optionally, the elastic element 51 is rigid in the preload direction and flexible in the lateral direction.

[0156] The elastic element 51 does not have to be folded in order to be flexible in the lateral direction while being rigid in the preload direction. As an alternative, the portion 54 can be fixed to the portions 52, 53 of the elastic element 51. For example, the portion 54 can be welded or adhered (e.g., glued) to produce a low aspect ratio (i.e., the thickness 57 perpendicular to the helical axis H is smaller than the thickness 58 parallel to the helical axis H).

[0157] Fig.13 is a schematic plan view of the actuator assembly 1. Fig.13 As shown, the loading mechanism 50 optionally includes at least one elastic element 51 placed along the side of the actuator (i.e., the support structure 2 and the movable part 10). The elastic element 51 can be bent around the corner to reduce its lateral stiffness. The elastic element 51 can include a bend 59. By providing the bend 59, the elastic element 51 can be more compliant with lateral movement, i.e., movement in a direction perpendicular to the screw axis H. Although in Fig.13 It is not shown, but the elastic element 51 may be fixedly connected to the support structure 2 and the movable part 10 .

[0158] Optionally, the elastic element 51 is thicker in a direction parallel to the helical axis than in a direction perpendicular to the helical axis. This can help reduce the lateral stiffness of the elastic element 51.

[0159] By disposing the elastic element 51 on the side of the actuator, it may not be necessary to perform processes such as welding or complicated folding of the bent elastic element 51. This may help simplify the manufacture of the actuator assembly 1.

[0160] Fig.14 is a schematic side view of the actuator assembly 1. Fig.14 As shown, optionally, the loading mechanism 50 includes at least one elastic element 51, and the elastic element 51 includes a meander. Fig.14 As shown, the elastic element 51 can be serpentine on the side of the actuator. The elastic element 51 can be optionally connected to the support structure 2 and the movable part 10 through parts 52, 53. By arranging the elastic element 51 to have a meander, the overall length of the elastic element 51 (i.e., the length when it is pulled straight out without any bend) can be increased. By increasing the length of the elastic element 51, the lateral force applied by the elastic member 51 can be reduced.

[0161] Fig.14 A resilient element 51 having a meander is shown. As an alternative, the resilient element 51 may be coiled to provide an increased length of the resilient element 51. This may help to reduce the variation of the preload force within the stroke (ie the possible movement of the movable part 10 relative to the support structure 2).

[0162] Fig.15 is a schematic side view of the actuator assembly 1. Fig.15 As shown, optionally, the elastic loading mechanism comprises at least one elastic element 51, which is engaged with at least one of the support structure 2 and the movable part 10 via a bearing mechanism 60. Fig.15 In the example shown, the elastic element 51 can be fixedly connected to the support structure 2. However, the other end of the elastic element 51 is engaged with the movable part 10 via a bearing mechanism 60. Optionally, the bearing mechanism 60 includes a moving part 53 of the elastic element 51. The moving part 53 can define a bearing surface of the bearing mechanism 60. Another bearing surface of the bearing mechanism 60 can be defined by the movable part 10 or a part (e.g., a protrusion) fixedly connected to the movable part 10. Optionally, the bearing mechanism includes a rolling element 61, such as a ball bearing for rolling relative to the bearing surface.

[0163] Optionally, the bearing mechanism is a spiral bearing. However, the bearing mechanism 60 does not necessarily have to include a spiral bearing. By providing engagement via the bearing mechanism 10, the lateral force applied by the elastic element 51 can be reduced or even eliminated. The lateral force element can be relieved by using the bearing mechanism 60. The bearing mechanism 60 can cause the only lateral force to be friction. Although Fig.15 The use of rolling bearings is shown, but in an alternative arrangement, the rolling bearings may be replaced by sliding bearings (e.g., slide bearings). The use of the bearing mechanism 60 helps to separate the normal force of the elastic element 51 from the lateral force. The normal force is desired to be used to transfer the vertical load of the spiral bearing mechanism 20. The lateral component of the force is undesirable. The lateral component of the force is reduced by the bearing mechanism 60.

[0164] Fig.16 is a schematic side view of the actuator assembly 1 . Fig.16 The arrangement shown in is similar to Fig.15 However, Fig.16 The arrangement shown in comprises a sliding bearing as the bearing mechanism 60 instead of a rolling bearing. Fig.16 The bearing mechanism 60 shown may have a Fig.15 The rolling bearing shown has greater friction. However, the amount of friction may depend on the material and design of the bearing mechanism 60.

[0165] although Fig.15 and Fig.16 It is shown that the elastic element 51 may be fixedly connected to the support structure 2 and engage with the movable part 10 via a bearing mechanism 60, but this is not necessary. In an alternative embodiment, the elastic element 51 may be fixedly connected to the movable part 10 and engage with the support structure 2 via a bearing mechanism.

[0166] Fig.17 is a schematic side view of the actuator assembly 1. Fig.17 As shown, optionally, the loading mechanism 50 includes a magnetic loading mechanism. Fig.17 As shown, optionally, the magnetic loading mechanism includes a magnet 65 and a magnetic material 66. Fig.17 In the arrangement shown, there are two magnets 65 and two magnetic materials 66. The magnetic loading mechanism is configured to provide a force for loading the screw bearing mechanism 20. The number of magnets and magnetic materials is not particularly limited. In order to provide the loading torque 56, it is desirable to have at least two magnets and at least two magnetic materials 66. However, for example, the number of magnets 65 can be four and the number of magnetic materials can be four.

[0167] By providing the magnet 65, the loading moment 56 can be applied with little or even no lateral force. The magnet 65 has a small lateral force within the travel of the movable part 10. In particular, if the magnetic material 66 is arranged so that it is wider than the magnet 65 in the direction perpendicular to the helical axis H, it can be expected that the magnetic field changes are not particularly significant within the movement travel of the movable part 10 along the helical axis H. The magnetic material 66 can be arranged, for example, as a metal washer.

[0168] SMA Wire

[0169] The actuator assembly 1 described above includes an actuator component. Optionally, the actuator component is an SMA element, such as an SMA wire. The term "SMA wire" may refer to any element including SMA. The SMA wire may have any shape suitable for the purposes described herein. The SMA wire may be elongated and may have a circular cross section or a cross section of any other shape. The cross section may vary along the length of the SMA wire. It is also possible that the length of the SMA wire (regardless of the definition) may be similar to one or more of the other dimensions of the SMA wire. The SMA wire may be pliable, or in other words, may be flexible. In some examples, when connected in a straight line between two elements, the SMA wire can only apply a tensile force that pushes the two elements together. In other examples, the SMA wire may be bent around the element, and when the SMA wire tends to straighten under tension, the SMA wire may apply force to the element. The SMA wire may be beam-shaped or rigid and may be able to apply different (e.g., non-tensile) forces to the element. The SMA wire may or may not include (one or more) materials and / or (one or more) components that are not SMA. For example, an SMA wire may include a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term "SMA wire" may refer to any configuration of an SMA wire that acts as a single actuating element, for example, which can be individually controlled to generate a force acting on the element. For example, an SMA wire may include two or more portions of an SMA wire that are mechanically arranged in parallel and / or in series. In some arrangements, an SMA wire may be part of a larger piece of SMA wire. Such a larger piece of SMA wire may include two or more portions that can be individually controlled, thereby forming two or more SMA wires.

[0170] Other variants

[0171] It will be appreciated that many other variations of the above examples are possible.

[0172] For example, the actuator assembly 1 may comprise a mixture of sliding bearings and rolling bearings.As a further alternative, the bearing mechanism may comprise a flexure mechanism.

Claims

1. An actuator assembly, include: Support structure; movable parts; a helical bearing mechanism arranged to guide helical movement of the movable member relative to the support structure about a helical axis; a loading mechanism, the loading mechanism being arranged between the support structure and the movable component and being used for loading the spiral bearing mechanism; and at least one pair of actuator components arranged to drive rotation of the movable component in opposite directions about the helical axis when actuated, the helical bearing mechanism converting the rotation into the helical movement; Wherein, the at least one pair of actuator components is arranged to apply an unloading moment about an axis perpendicular to the screw axis so as to reduce the load of the screw bearing mechanism.

2. The actuator assembly according to claim 1, in, The loading mechanism is arranged to apply a loading moment about an axis perpendicular to the screw axis for loading the screw bearing mechanism.

3. The actuator assembly according to claim 1 or 2, in, The at least one pair of actuator members are arranged to apply forces to the movable member relative to the support structure that are offset from each other along the screw axis.

4. An actuator assembly according to any one of the preceding claims, in, The at least one pair of actuator components are arranged to apply forces in opposite directions perpendicular to the screw axis such that the unloading moment can be applied without applying an overall force perpendicular to the screw axis.

5. An actuator assembly according to any one of the preceding claims, in, The screw bearing mechanism is arranged to have sufficient friction when loaded so that the movable member remains in position when the actuator member is not driving rotation of the movable member.

6. The actuator assembly according to claim 5, in, The spiral bearing mechanism is arranged to have sufficient friction when loaded so that the movable member is held in position in a succession of positions when the actuator member is not driving rotation of the movable member.

7. An actuator assembly according to any one of the preceding claims, in, The loading mechanism is arranged to load the screw bearing mechanism so as to generate a friction force therein, which restrains movement of the movable member relative to the support structure at any position within a range of movement when the actuator member is not actuated.

8. The actuator assembly according to claim 7, in, The pair of actuator components are arranged to apply the unloading torque upon actuation so as to reduce the frictional forces in the screw bearing mechanism.

9. An actuator assembly according to any one of the preceding claims, in, The spiral bearing mechanism comprises at least one spiral bearing, which is a rolling bearing comprising bearing surfaces on the support structure and the movable element and at least one rolling bearing element arranged between the bearing surfaces.

10. An actuator assembly according to any one of the preceding claims, in, The spiral bearing arrangement comprises at least one spiral bearing, which is a sliding bearing comprising bearing surfaces on the support structure and the movable part arranged to slide against each other.

11. An actuator assembly according to any one of the preceding claims, in, The spiral bearing mechanism comprises three spiral bearings.

12. The actuator assembly according to claim 11, in, The bearing surfaces of the first and second spiral bearings each include a groove on each of the support structure and the movable component, and the bearing surface of the third spiral bearing includes a groove on one of the support structure and the movable component, and a flat surface on the other of the support structure and the movable component.

13. The actuator assembly according to claim 12, in, The first spiral bearing, the second spiral bearing and the third spiral bearing each comprise only a single rolling bearing element.

14. An actuator assembly according to any one of the preceding claims, in, The at least one pair of actuator components is arranged to reduce the load of the screw bearing mechanism by a load that is less than that applied by the loading mechanism.

15. An actuator assembly, include: Support structure; movable parts; a helical bearing mechanism arranged to guide helical movement of the movable member relative to the support structure about a helical axis; at least one actuator member arranged to drive rotation of said movable member about said helical axis upon contraction, said helical bearing mechanism converting said rotation into said helical movement; and A loading mechanism is arranged to apply a loading moment about an axis perpendicular to the screw axis for loading the screw bearing mechanism.

16. An actuator assembly according to any one of the preceding claims, in, The loading mechanism includes an elastic loading mechanism for elastically loading the spiral bearing mechanism.

17. The actuator assembly according to claim 16, in, The spring loading mechanism includes a pair of spring elements connected between the support structure and the movable component.

18. An actuator assembly according to claim 16 or 17, in, The spring loading mechanism comprises at least one spring element between the support structure and the movable part, the spring element comprising at least a portion extending between the support structure and the movable part, the at least a portion being at least as thick in a direction parallel to the screw axis as in a direction perpendicular to the screw axis.

19. An actuator assembly according to any one of claims 16 to 18, in, The elastic loading mechanism comprises at least one elastic element between the support structure and the movable part, wherein the elastic element is stressed in its mounted position connected between the support structure and the movable part so as to load the spiral bearing mechanism, whereby the distance of the part of the elastic element engaging with the support structure and the movable part in the direction along the spiral axis is smaller than the distance of the elastic element when it is not stressed.

20. The actuator assembly according to claim 19, in, The difference in distances along the screw axis between the portions of the elastic element that engage the support structure and the movable component is greater than the possible range of movement of the movable component along the screw axis.

21. An actuator assembly according to any one of claims 16 to 20, in, The spring-loading mechanism comprises at least one spring element between the support structure and the movable part, the spring element being stiffer for bending about an axis perpendicular to the screw axis than for bending about the screw axis.

22. An actuator assembly according to any one of claims 16 to 21, in, The spring loading mechanism comprises at least one spring element engaged with at least one of the support structure and the movable component via a bearing mechanism.

23. An actuator assembly according to any one of the preceding claims, in, The loading mechanism includes a magnetic loading mechanism.

24. An actuator assembly according to any one of the preceding claims, wherein each actuator component is a shape memory alloy (SMA) element.

25. An actuator assembly according to any preceding claim, in, The movable part is a lens element comprising at least one lens, wherein the helical axis is the optical axis of the lens element.

26. The actuator assembly according to claim 25, in, The support structure has an image sensor mounted thereon, and the lens element is arranged to focus an image on the image sensor.

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