JP2013114028A - Driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the progress of metal fatigue of an SMA due to a repeated movement and to prevent deterioration of SMA performance, in a driving device using an SMA actuator.SOLUTION: The driving device 100 comprises: a linear SMA wire 3L that causes a displacement input part to generate driving force used to move a target drive body by being pulled or pressed; a holding member 33a projected from a base member and fixing a part of the SMA wire 3L to the interior along a first direction AR1; and driving means for pulling or pressing the SMA wire 3L. In the driving device 100, the first direction AR1 is made to coincide with a second direction AR2 that is one of directions ARms between the force points of the holding member during driving, which is from the holding member 33a to the displacement input part, which changes when the SMA wire 3L is pulled or pressed by the driving means. Thereby deterioration of the SMA performance can be prevented.

Description

  The present invention relates to a drive device using a shape memory alloy actuator.

  In recent years, there has been a dramatic increase in image quality, such as an increase in the number of pixels in an image sensor mounted on a camera-equipped mobile phone, etc. In addition to this, in addition to the basic function of image shooting, a focus function and zoom function Etc. are required.

  In order to add these functions, a lens driving device that moves the lens in the optical axis direction is necessary. Recently, a lens driving device using a shape memory alloy (SMA) actuator has been applied. Various studies have been made. This device generates contraction force by, for example, energizing and heating SMA, and uses the contraction force as a lens driving force. It is easy to reduce the size and weight and obtain a relatively large driving force. There is an advantage that can be.

  As a lens driving device to which the SMA actuator is applied, for example, in the configuration of the driving device disclosed in Patent Document 1, the lens driving device has a fulcrum and an action point that contacts the sliding member, and swings around an axis passing through the fulcrum. A lever member that has a greater distance from the axis to the action point when viewed in the optical axis direction of the photographic lens than the distance from the axis to the edge of the photographic lens; And a shape memory alloy that drives

  Further, in the configuration of the driving device disclosed in Patent Document 2, since the lever member is formed by integrally molding the lever portion and the fixed portion, the lever portion is moved with respect to the fixed portion by elastic deformation. Since it can be displaceably supported, it is possible to create a stroke in which the deformation amount of the wire member is increased without using a generally bulky shaft support.

  Furthermore, in the configuration of the driving device disclosed in Patent Document 3, the SMA is non-parallel to the moving direction of the driven body, and is a plane including the first contact point and the swing axis of the support shaft. Since they are arranged so as to be non-parallel to each other, the SMA deformation force can be efficiently converted into the rotation of the lever member.

  That is, in any configuration of Patent Documents 1 to 3, a configuration is employed in which the operation direction of the SMA is changed or the operation amount is increased by a lever mechanism.

  On the other hand, as a method for holding and fixing the SMA, for example, in the configuration of the driving device disclosed in Patent Document 4, there is a rod-shaped member made of metal that penetrates the base member that is the base of the driving device and is fixed to the base member. The rod-like member is caulked on one end side of the rod-like member to sandwich the SMA, and the other end side of the rod-like member is provided with a current-carrying connection portion for supplying current to the SMA. Yes.

JP 2007-58075 A JP 2007-58076 A JP 2007-60530 A JP 2008-291834 A

  By the way, when a high-performance focus function, zoom function, or the like is added to a camera-equipped cellular phone or the like, it is necessary to control the position of the lens and stop it at a predetermined position. Of course, since the camera must also function during the period in which the mobile phone or the like is used, it is necessary for the device to be able to repeatedly operate.

  However, since SMA is a metal material, metal fatigue occurs due to repeated operations, and deterioration progresses. In general, the progress of metal fatigue of SMA applied with a stress of 500 MPa or more is fast, and there is a possibility of rupture within several thousand times. In other words, it is a fatal defect that a device does not function as a camera device after thousands of repeated operations.

  On the other hand, the configurations of Patent Documents 1 to 4 do not particularly take into account the configuration that suppresses metal fatigue due to SMA repetitive operation, and further, degradation of SMA performance.

  The present invention has been made in view of such circumstances, and in the case of continuously using a drive device using an SMA actuator, the progress rate of SMA metal fatigue due to repeated operations can be reduced, and the SMA performance can be degraded. It is an object of the present invention to provide a drive device that can be suppressed.

  In order to solve the above-mentioned problems, the invention of claim 1 is a driven body driven to reciprocate in a predetermined direction and a line that generates a driving force for moving the driven body by expansion and contraction at a predetermined force point. A drive device comprising: a shape memory alloy; a holding member that internally fixes a part of the shape memory alloy along a first direction; and a drive unit that expands and contracts the shape memory alloy. 1 direction from the holding member to the predetermined force point, and the second direction, which is one of the directions between driving holding member force points that changes when the shape memory alloy is expanded and contracted by the driving means. Characterized by matching.

  Further, the invention of claim 2 is the drive device according to claim 1, wherein the second direction is a range in which the direction between the holding member force points during driving varies around the holding member by the driving means. Including a straight line direction that bisects the angle.

  The invention according to claim 3 is the drive device according to claim 1 or 2, wherein the holding member includes a caulking portion that internally holds the shape memory alloy along the first direction. It is characterized by having.

  According to a fourth aspect of the present invention, there is provided the driving device according to any one of the first to third aspects, wherein the driven body is a lens unit, and a direction in which the driven body is driven is an optical axis. It is a direction.

  According to the first to fourth aspects of the present invention, the driving direction of the holding member force point changes from the holding member to the predetermined force point and changes when the shape memory alloy is expanded and contracted by the driving means. The driving device is characterized in that it coincides with the second direction which is one direction. As a result, the bending angle generated between the driving holding member force point direction and the first direction, which changes from time to time during driving, is made smaller than when the first direction does not coincide with the driving holding member force point direction. be able to. For this reason, the maximum stress generated in the shape memory alloy such as a bending stress having a positive correlation with the bending angle can be reduced. As a result, the progress rate of metal fatigue inside the shape memory alloy due to repeated operations can be reduced, and deterioration of the shape memory alloy can be suppressed.

  According to the second aspect of the present invention, the second direction includes a linear direction that bisects an angle of a range in which the direction between the holding member force points during driving varies around the holding member by the driving means. As a result, the maximum value of the bending angle generated between the driving holding member force point direction and the first direction (= second direction), which change from moment to moment during driving, can be minimized. For this reason, the maximum stress generated inside the shape memory alloy can be further reduced, the progress rate of the metal fatigue inside the shape memory alloy due to repeated operations can be further reduced, and the deterioration of the shape memory alloy can be further suppressed. It becomes possible.

  According to the third aspect of the present invention, the holding member includes the crimping portion that sandwiches the shape memory alloy, whereby the shape memory alloy can be stably held.

  According to the invention of claim 4, the driven body is a lens unit, and the direction in which the driven body is driven is the optical axis direction, so that the same effects as the inventions of claims 1 to 3 are achieved. A lens driving device can be obtained.

It is a top view which shows roughly the structural example of the drive device which concerns on embodiment of this invention. FIG. 2 is a side view schematically showing the configuration of the drive device of FIG. 1. FIG. 2 is a side view schematically showing the configuration of the drive device of FIG. 1. It is a top view which shows roughly the structural example of the manufacturing apparatus of a SMA actuator. It is a figure which illustrates typically the general stress characteristic of an SMA wire. It is a figure which illustrates typically the general stress characteristic of an SMA wire. It is a figure explaining the periphery of the holding member of the SMA wire of the drive device which concerns on embodiment of this invention. It is a figure explaining the periphery of the holding member of the SMA wire of the drive device which concerns on embodiment of this invention. It is explanatory drawing which shows 1 process in the manufacturing method of the drive device which concerns on embodiment of this invention. It is explanatory drawing which shows 1 process in the manufacturing method of the drive device which concerns on embodiment of this invention. It is explanatory drawing which shows 1 process in the manufacturing method of the drive device which concerns on embodiment of this invention. It is explanatory drawing which shows 1 process in the manufacturing method of the drive device which concerns on embodiment of this invention. It is explanatory drawing which shows 1 process in the manufacturing method of the conventional drive device. It is explanatory drawing which shows 1 process in the manufacturing method of the conventional drive device. It is explanatory drawing which shows 1 process in the manufacturing method of the conventional drive device. It is explanatory drawing which shows 1 process in the manufacturing method of the conventional drive device. It is a figure explaining the periphery of the holding member of the SMA wire of the conventional drive device. It is a figure explaining the periphery of the holding member of the SMA wire of the conventional drive device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, parts having the same configuration and function are denoted by the same reference numerals, and redundant description is omitted in the following description. Further, the drawings are schematically shown, and the sizes, positional relationships, and the like of various structures in the drawings are not accurately illustrated. For convenience of explanation, FIGS. 4 and 5 are attached with three orthogonal XYZ axes. Further, the angles shown in FIGS. 7, 8, 11, 14, 15 and 17 are shown as + in the counterclockwise direction and as-in the clockwise direction.

<1. Overview of Driving Device and Manufacturing Method of Driving Device>
Prior to the description of the embodiments of the present invention, the basic configuration of an application example of an actuator using SMA (SMA actuator) will be described with reference to FIGS. 1 to 3, and the SMA actuator in the drive device using the SMA actuator as a drive source will be described. A manufacturing method will be described with reference to FIG.

<1-1. Overall Configuration of Drive Device>
1 to 3 schematically show main components of a driving apparatus 100 using an actuator using SMA as a driving source, and FIG. 1 is a plan view seen from the lens side. 3 shows a side view as seen from the direction of arrow A1 in FIG. 2 shows a state before driving, and FIG. 3 shows a state after driving.

  The drive device 100 is a drive device that mainly moves the driven body 1 (for example, a lens unit including an imaging lens) in the axis line (for example, the optical axis) AX direction, and has a base member having a through-hole portion 4a. 4 and a driven body 1 that is driven to reciprocate in the direction along the axis AX of the through-hole portion 4a, and a driving force that moves the driven body 1 by expansion and contraction is applied to a predetermined force point (to a displacement input portion 2a described later). A linear shape memory alloy 3 (SMA actuator) 3 that is generated) and a lever member 2 that moves the driven body 1 by receiving a driving force from the SMA actuator 3. The top plate 5, the parallel plate springs 6 a and 6 b, the bias spring 7, and the like are provided, and the driven body 1 and the like are assembled to the base member 4. The top plate 5 and the parallel leaf springs 6a and 6b are omitted in FIG. 1 for convenience. The driving device 100 is mounted on a battery-driven portable device or the like.

  The base member 4 is fixed to a member (for example, a frame of a mobile phone or a mount substrate) to which the driving device 100 is attached, and is a non-moving member that constitutes the bottom side of the driving device 100. The base member 4 is formed in a square plate shape in plan view, and is entirely made of a resin material or the like. Although an imaging sensor is attached to the base member 4, illustration is omitted.

  The driven body 1 has a cylindrical shape, and includes an imaging lens 10, a lens driving frame 12 that holds the imaging lens 10, and a lens barrel 14 that stores the lens driving frame 12. The imaging lens 10 includes an objective lens, a focus lens, a zoom lens, and the like, and constitutes an imaging optical system for a subject image with respect to an imaging element (not shown). The lens drive frame 12 is a so-called ball frame (also referred to as “carrier”), and moves in the direction of the axis AX together with the lens barrel 14. A pair of support portions 16 project from the outer peripheral edge portion of the lens drive frame 12 at the distal end on the object side with an angular difference of 180 ° in the circumferential direction.

  The driven body 1 is disposed on the base member 4 in a state of being inserted into an opening formed in the top plate 5. Specifically, the pair of support portions 16 are arranged so as to be positioned in the vicinity of the pair of diagonals of the base member 4 (see FIG. 1).

  Parallel plate springs 6a and 6b are fixed to the base member 4 and the top plate 5, respectively, and the driven body 1 is fixed to the parallel plate springs 6a and 6b. As a result, the driven body 1 is supported so as to be displaceable with respect to the base member 4 and the like, and the degree of freedom of displacement is restricted in the direction along the axis AX. In addition, the top plate 5 may be fixed to the base member 4 through a post or the like (not shown), or may be a structure integrated with the base member 4.

  The lever member 2 applies a driving force in the direction of the axis AX to the driven body 1 by engaging with the driven body 1 via the support portion 16.

  The lever member 2 is installed on the side of the driven body 1, specifically, at a corner portion of the base member 4 other than the corner portion where the support portion 16 of the driven body 1 is located. ing. The lever member 2 is supported so as to be swingable around an axis that is orthogonal to the axis AX and extends in the direction in which the pair of support portions 16 are arranged (the vertical direction in FIG. 1).

  As shown in FIG. 2, the lever member 2 has an inverted L-shape in a side view including an arm portion 21 and an extending portion 22 extending from the proximal end portion of the arm portion 21 in the axis AX direction. The bent portion of the extended portion 22 located in the vicinity of the boundary between the arm portion 21 and the extended portion 22 is supported by the tip of the support leg 8 erected on the base member 4, so that the base member 4. Supported on top.

  The tip of the support leg 8 (hereinafter referred to as lever support portion 8a) has a substantially cylindrical shape extending in a direction orthogonal to the axis AX direction (a direction orthogonal to the paper surface of FIG. 2). Accordingly, the lever member 2 is supported so as to be swingable about an axis perpendicular to the direction of the axis AX, with the lever support portion 8a as a fulcrum.

  The arm portion 21 is formed in an arc shape in plan view. Specifically, as shown in FIG. 1, the extended portion 22 is divided into two forks on both sides of the driven body 1, and extends evenly in the vicinity of the outer peripheral surface of the driven body 1. It is formed so as to surround one half of each. The distal ends (both ends) of the arm portion 21 reach the positions of the support portions 16 of the driven body 1, respectively. Then, the SMA actuator 3 is bridged over the extended portion 22, and the moving force F1 (see FIG. 3) in the direction orthogonal to the axis AX direction is input to this bridge position (referred to as the displacement input portion 2a). The lever member 2 swings. Along with this swinging, the tip of the arm portion 21 (referred to as the displacement output portion 2b) is displaced in the direction of the axis AX, and the displacement output portion 2b engages with each support portion 16 to drive the driven body 1 in the direction of the axis AX. Power will be given.

  The SMA actuator 3 applies a moving force F1 (see FIG. 3) to the lever member 2, and is a linear actuator composed of, for example, a SMA wire 3L (see FIG. 4 described later) such as a Ni—Ti alloy. It is. The SMA actuator 3 expands when given a predetermined tension in a state where the elastic modulus is low (martensite phase) at a low temperature. When heat is applied in this extended state, the SMA actuator 3 undergoes phase transformation and has a high elastic modulus (austenite). Phase: parent phase) and return to its original length from its extended state (recover shape). That is, the SMA actuator 3 is an actuator that moves the object using the shape restoring force due to the temperature change of the SMA wire 3L.

  In this example, the configuration in which the SMA actuator 3 is energized and heated to cause the above-described phase transformation is employed as the driving means for expanding and contracting the shape memory alloy. That is, since the SMA actuator 3 is a conductor having a predetermined resistance value, Joule heat is generated by energizing the SMA actuator 3 itself, and transformation from the martensite phase to the austenite phase is performed by self-heating based on the Joule heat. It is supposed to be configured. For this reason, the first electrode 30a and the second electrode 30b for energization heating are fixed to both ends of the SMA wire 3L. These electrodes 30a and 30b are fixed to predetermined holding members 33a and 33b protruding from the base member 4, respectively. The holding members 33a and 33b fix a part of the SMA wire 3L along the first direction AR1 (refer to FIG. 17 described later in the vicinity of the holding member 33a). In addition, the holding members 33a and 33b have a crimped portion SP that internally holds the SMA wire 3L along the first direction AR1 (refer to FIG. 18 described later in the vicinity of the holding member 33a). Thereby, the SMA wire 3L can be stably held.

  As shown in FIG. 1, the SMA actuator 3 is bridged between the electrodes 30a and 30b with a portion engaging with the extending portion 22 of the lever member 2 as a turning point. With this configuration, when the SMA actuator 3 is energized and heated via the electrodes 30a and 30b and is operated (shrinks), the lever member 2 is given a moving force F1 (see FIG. 3), and the moving force F1 causes the lever member to move. 2 will swing.

  The electrodes 30 a and 30 b are respectively disposed in the vicinity of the support portion 16 of the driven body 1 in the base member 4. The lengths of the SMA actuator 3 from the electrodes 30a and 30b to the turn-back point are set to be equal to each other, so that the amount of expansion / contraction of the SMA actuator 3 on both sides of the displacement input portion 2a becomes equal. Rubbing between the lever member 2 and the SMA actuator 3 is prevented. Further, a V-groove 21a (corresponding to the displacement input portion 2a) is formed in the extended portion 22, and the SMA actuator 3 is bridged so as to be fitted into the V-groove 21a, whereby the lever member 2 is On the other hand, the SMA actuator 3 is stably suspended.

  The bias spring 7 biases the driven body 1 in the direction of the axis AX in the direction opposite to the direction in which the displacement output unit 2b moves due to the operation (contraction) of the SMA actuator 3. The bias spring 7 is formed of a compression coil spring having a diameter substantially matching the peripheral size of the lens drive frame 12, and one end side (lower end side) is in contact with the top surface of the lens drive frame 12. The inner wall N is a surface on the base member 4 side of the surface of a frame member (not shown), and the frame member is fixed to the base member 4 by a post (not shown). The frame member is provided with an opening having a diameter substantially matching the diameter of the imaging lens 10, and the other end side (upper end side) of the bias spring 7 is in contact with the peripheral edge portion of the opening on the inner wall N. Is done.

  Note that, when the SMA actuator 3 is not in operation, the line length is set so that the SMA actuator 3 is tensioned by receiving the pressing force of the bias spring 7 acting via the driven body 1 (support portion 16) and the lever member 2. Has been. That is, the line length is set so that the lever member 2 (arm portion 21) is always brought into contact (pressure contact) with the driven body 1 (support portion 16) regardless of the operating state. With this configuration, in this embodiment, the lever member 2 is swingably supported at the tip of the support leg 8 without directly connecting the support leg 8 and the lever member 2, and when the SMA actuator 3 is operated. The lever member 2 is swung by quickly transmitting the displacement.

<1-2. Manufacturing apparatus for manufacturing drive device>
FIG. 4 schematically shows a configuration example of main components of the manufacturing apparatus 300 for the SMA actuator 3 used for manufacturing the driving apparatus 100 (FIGS. 1 to 3) according to the present embodiment. FIG. 4 is a plan view of the manufacturing apparatus 300 as seen from the axial direction of the imaging lens 10.

  The manufacturing apparatus 300 mainly includes punches 51a and 51b, a displacement meter 52, sliders 53a and 53b, and a control unit 55. The manufacturing apparatus 300 manufactures the SMA actuator 3 in a workpiece by stretching the SMA wire 3L on a set of driving devices 100 (also referred to as “work”) in a semi-complete state where the SMA wire 3L is not yet stretched. Device. The SMA actuator 3 is manufactured by the manufacturing apparatus 300 in a state where the work is placed on the adjustment table 56.

<1-2-1. Control unit 55>
The control unit 55 is a control processing device that controls each functional element of the manufacturing apparatus 300. The control unit 55 is configured by, for example, a general-purpose computer or a dedicated hardware circuit. The control unit 55 processes a signal indicating the displacement of the lens driving frame 12 acquired by the displacement meter 52, and controls the punches 51a and 51b and the sliders 53a and 53b based on the result of the processing.

<1-2-2. Slider 53a, 53b>
The sliders 53a and 53b are stretching portions that hold the SMA wire 3L in a stretched state before the SMA wire 3L is fixed to the electrodes 30a and 30b provided on the holding members 33a and 33b, respectively. The sliders 53a and 53b include SMA wire holding portions 54a and 54b that can respectively hold a part of the SMA wire 3L. A part of the SMA wire 3L held in part by the SMA line holding part 54a passes through the electrode 30a, the V-groove 21a provided in the extended part 22 and the electrode 30b in order, and a part thereof is supplied to the SMA line holding part 54b. Is retained. The sliders 53a and 53b have wheels at the bottom and a drive mechanism for the wheels, and are movable on the adjustment table 56 along arrows Ya and Yb. The sliders 53a and 53b move along the arrows Ya and Yb while the SMA wire 3L is held in a stretched state by the SMA wire holding portions 54a and 54b via the V-groove 21a and the like. The tension applied to the SMA wire 3L can be adjusted. The operations of the sliders 53a and 53b are controlled by the control unit 55 via a communication line.

  In FIG. 4, the positions of the sliders 53a and 53b indicated by solid lines indicate the state before driving the SMA wire 3L, and the positions of the sliders 53a and 53b indicated by broken lines indicate the state during driving of the SMA wire 3L. Show.

<1-2-3. Displacement meter 52>
The displacement meter 52 is configured by, for example, a laser displacement meter or the like, and is held on the lens drive frame 12 of the drive device 100 via a post (not shown). The displacement meter 52 measures the distance between the lens drive frame 12 and the displacement meter 52, that is, the displacement of the lens drive frame 12 with respect to the displacement meter 52, and supplies a signal indicating the measured distance to the control unit 55 via the communication line. To do. The control unit 55 acquires the displacement of the lens driving frame 12 with respect to the base member 4 based on the distance and the distance between the displacement meter 52 and the base member 4 acquired in advance.

<1-2-4. Punches 51a and 51b>
The punches 51a and 51b function as a heating unit that heats the shape memory alloy wire in a state where the SMA wire 3L is stretched by the sliders 53a and 53b, and the SMA wire 3L is provided on the holding members 33a and 33b, respectively. It also functions as a fixing portion for fixing to the electrodes 30a and 30b.

  The operations of the punches 51a and 51b are controlled by the control unit 55 via a driving device (not shown). The positions of the punch 51a and the punch 51b can be moved along the Z-axis direction by the driving device, and the moving force can be changed by the driving device. In addition, the frame member which concerns on the inner wall (refer FIG. 2) of the drive device 100, and the top plate 5 (refer FIG. 2), the intersection part of each flow line along each Z-axis direction of punch 51a and 51b Are provided with through holes through which the punches 51a and 51b can respectively pass.

  The punches 51a and 51b heat the SMA wire 3L by energizing the SMA wire 3L in contact with the electrodes 30a and 30b in a state where the respective tip portions (not shown) are in contact with the electrodes 30a and 30b. It is configured to be possible. Further, the current relating to the energization is configured to be changeable.

  In the process of fixing the SMA wire 3L to the electrodes 30a and 30b by the punches 51a and 51b, first, the control unit 55 sets the heating state of the SMA wire 3L by the punches 51a and 51b to a preset heating state. The energization current to the SMA wire 3L by the punches 51a and 51b is controlled to a preset value. Further, the control unit 55 causes the sliders 53a and 53b to be applied to the SMA wire 3L based on the output signal of the displacement meter 52 so that the lens driving frame 12 is held at a preset position by the heated SMA wire 3L. Adjust the tension to be applied. In a state in which the tension is adjusted, the punches 51a and 51b increase the moving force under the control of the control unit 55 to caulk the holding members 33a and 33b that are in contact with the tip portions, respectively. The wires 3L are fixed to the crimping portions SP, respectively.

  In a state where the SMA wire 3L is fixed to the crimping portion SP, the control unit 55 controls a cutting unit (not shown) to move from the electrodes 30a and 30b to the SMA line holding units 54a and 54b side of the SMA wire 3L. The SMA actuator 3 in the drive device 100 is manufactured by cutting each protruding part.

<1-3. General Stress Characteristics of SMA Wire and Situations in Application to Drives>
Here, general stress characteristics of the SMA wire 3L will be described with reference to FIGS. FIG. 5 is a diagram for schematically explaining a numerical calculation result of a stress state generated in the SMA wire 3L itself when a part of the SMA wire 3L is bent. Among these, FIG. 5A shows + X on the YZ plane. FIG. 5B is a diagram in which the stress state of the side surface of the SMA wire 3L on the axis side is vertically projected to the + X axis side, and FIG. 5B is the stress on the side surface of the SMA wire 3L on the + Z axis side (or −Z axis side) of the XY plane. FIG. 5C is a diagram in which the state is vertically projected to the + Z axis side (or −Z axis side), and FIG. 5C is a vertical projection of the stress state of the side surface of the SMA wire 3L on the −X axis side of the YZ plane to the −X axis side. FIG.

  As shown in FIGS. 5A and 5B, in the area Rc inside the portion where the SMA wire 3L is bent, the compressive stress is maximum (the tensile stress is minimum), and conversely, FIG. ) And FIG. 5C, it can be seen that the compressive stress is minimum (the tensile stress is maximum) in the area Rt outside the portion where the SMA wire 3L is bent. Thus, as a general stress characteristic of the SMA wire 3L, compressive stress is dominant in the bent inner region (area Rc in FIG. 5) of the SMA wire 3L, and conversely, the bent outer region of the SMA wire 3L ( In the area Rt) in FIG. 5, the tensile stress is dominant.

  Hereinafter, the bending stress is a combination of the compressive stress and the tensile stress of the SMA wire 3L, and the stress at the portion where the sum of the absolute value of the compressive stress and the absolute value of the tensile stress is relatively largest is defined as the maximum stress. If defined, the bending stress acting inside the SMA wire 3L has a positive correlation with the bending angle, and the stress in the bent region (around the areas Rc and Rt in FIG. 5) becomes the maximum stress.

  FIG. 6 is a graph schematically illustrating the strength with respect to the load applied to the SMA wire 3L when the SMA wire 3L is incorporated in the drive device, and the vertical axis represents the load applied to the SMA wire 3L. The axis indicates the number of repetitive operations until the SMA wire 3L breaks.

  As shown in the graph of FIG. 6, when a load is applied to the SMA wire 3L, the number of repeated operations until the SMA wire 3L breaks tends to decrease, and a load of about 500 MPa is applied. When given, it can be seen that breakage occurs after several thousand repeated operations. This is because the stress generated in the SMA wire 3L increases as the load increases, and the progress of metal fatigue of the SMA wire 3L is promoted. Thus, as a general stress characteristic of the SMA wire 3L, when a load of 500 MPa or more is applied to the SMA wire 3L, the progress of metal fatigue of the SMA wire 3L is fast, and the number of repeated operations within a few thousand times. May lead to breakage.

  Next, the situation in application of the SMA wire 3L to the driving device will be described below.

  13-16 is a figure which illustrates typically the conventional apparatus incorporating method of the SMA wire 3L in a drive device. As shown in FIGS. 13 to 16, in the drive device, the conventional device assembling method of the SMA wire 3 </ b> L is roughly divided into the following four steps (i) to (iv).

  (I) First, as shown in FIG. 13, in a state where the SMA wire 3L is passed through one electrode 30a, the electrode 30a is caulked to fix one side of the SMA wire 3L (see FIG. 14).

  (Ii) Next, as shown in FIG. 14, the SMA wire 3L is guided to the other electrode 30b while rotating around the electrode 33a, and the SMA wire 3L is passed through the electrode 30b.

  (Iii) Further, as shown in FIG. 15, the SMA wire 3L is fixed by caulking to the other electrode 30b in the state shown in FIG.

  (Iv) Finally, as shown in FIG. 16, unnecessary portions on both sides of the fixed SMA wire 3L are cut and removed to complete the installation of the SMA wire 3L.

  FIG. 17 is an enlarged view of the periphery of the electrode 30a and the holding member 33a of the SMA wire 3L thus constructed, and FIG. 18 is an enlarged view of the region R1 of FIG. Hereinafter, for the sake of convenience, after the SMA wire 3L is crimped and fixed, the SMA wire extends from the holding member 33a (holding member 33b) to the manufacturing apparatus 300 outside the base member 4 including the inside of the holding member 33a (holding member 33b). 3L is referred to as SMA wire 3L1, and SMA wire 3L from the holding member 33a (holding member 33b) to the displacement input portion 2b is referred to as SMA wire 3L2. However, in general, when expressing SMA wire, SMA wire 3L Called.

  As shown in FIGS. 17 and 18, in the conventional driving device in the initial state (non-driving state) before being driven, the direction of the SMA wire 3L2 is the boundary point BP located at the inner / outer boundary of the holding member 33a. Is installed in a direction rotated by an angle + α1 with respect to the forming direction of the SMA wire 3L1 (first direction AR1) (see FIG. 17). This corresponds to the state in which the SMA wire 3L is crimped to the electrodes 30a and 30b in the above steps (i) and (iii). When the SMA wire 3L2 is driven, the SMA wire 3L2 is contracted to be bent at the boundary point BP in the direction further rotated by the angle + α2 than the non-driven state. As a result, as shown in FIG. 18, the SMA wire 3L2 at the time of driving is bent outside due to the tension Ft of the SMA wire 3L with respect to the boundary point BP of the bent region and its vicinity as in FIG. While tensile stress is generated in the area Rt, compressive stress is dominant in the inner area Rc of bending. That is, the maximum bending stress exists at the boundary point BP and in the vicinity thereof.

  Thus, in the drive device by the conventional apparatus incorporating method, the state of the step (i) (see FIG. 13) to the step (ii) (see FIG. 14) or the state of the step (ii) (see FIG. 14). Bending stress generated when the SMA wire 3L2 is rotated by an angle + α1 (holding member 33a side) or an angle −α (holding member 33b side) during the transition from the step (see) to the step (iii) (see FIG. 15). Will occur.

  When the SMA wire 3L2 is moved from the non-driving state to the driving state, the SMA wire 3L2 is further bent up to the angle + α2 as a movable range. Therefore, when driving, the SMA wire 3L2 is bent to the maximum angle + (α1 + α2) It will be. That is, the SMA wire 3L is operated so that the angle generated between the SMA wire 3L1 and the SMA wire 3L2 during driving varies in the range of the angle + α2 or the angle −α2, and thus the bending stress is further increased.

  Accordingly, the tension applied to the SMA wire 3L and the tension generated by driving the SMA wire 3L correspond to the stress generated by the load shown in FIG. The metal fatigue proceeds at and near the boundary point BP. For this reason, as described above, when the stress exceeds a certain level, it is repeatedly broken within a few thousand times, and the camera device becomes fatal.

  Under such a background, in the present invention, by reducing the maximum stress generated inside the SMA wire 3L of bending stress, the progress rate of metal fatigue inside the SMA wire 3L due to repeated operations can be reduced, and the SMA A drive device that suppresses the deterioration of the wire 3L is realized.

  Hereinafter, a specific configuration that is a characteristic part of the embodiment will be described.

<2. Specific Configuration of Embodiment>
Therefore, in the driving device 100 according to the embodiment of the present invention, the first direction AR1 is changed from the holding member 33a (or the holding member 33b) that changes when the SMA wire 3L is expanded or contracted by the driving unit described above to the displacement input unit 2b ( By adopting a configuration that matches the second direction, which is one direction, among the driving-point holding member force point directions to a predetermined force point), the above-described problem is solved.

  7 and 8 are enlarged views showing the periphery of the electrode 30a and the holding member 33a of the SMA wire 3L of the driving apparatus 100 according to the embodiment of the present invention. Among these, FIG. 7 shows the state of the SMA wire 3L in the initial state (non-driving state) before driving, and FIG. 8 shows the state of the SMA wire 3L in the driving state of the driving device 100.

  As shown in FIG. 7, the center of the SMA wire 3L2 when driving in the first direction AR1 bisects the angle of the range in which the driving member holding point force direction ARm of the SMA wire 3L2 varies about the boundary point BP. The line direction is set to the center line direction AR2c that matches the center position of the fluctuation range when the SMA wire 3L is driven. On the other hand, since the SMA wire 3L2 is in the most extended state in the non-driven state, the direction AR20 of the SMA wire 3L2 does not coincide with the first direction AR1 of the SMA wire 3L1 fixed inside the holding member 33a. The SMA wire 3L1 is installed around the point BP in a direction rotated by an angle −θ1 with respect to the first direction AR1 (= centerline direction AR2c).

  On the other hand, the driving holding member force point direction ARm of the SMA wire 3L2 in the driving state is within a movable range reaching the direction AR22 rotated + (2 × θ1) with respect to the direction AR20, as shown in FIG. It fluctuates with. That is, the rotation direction is an angle ± θ1 with respect to the first direction AR1 of the SMA wire 3L1 around the centerline direction AR2c. Thus, due to the expansion and contraction of the SMA wire 3L during driving, the driving holding member force point direction ARm of the SMA wire 3L varies between the directions AR20 to AR22. In the driving device 100, the present embodiment employs a configuration in which the first direction AR1 is made to coincide with the second direction AR2 that is one of the driving holding member force point directions ARm.

  At this time, as shown in FIGS. 7 and 8, the second direction AR2 has two angles (± θ1) in a range in which the driving holding member force point direction ARm fluctuates around the boundary point BP by the driving means. It is desirable to set the linear direction to be equally divided (center line direction AR2c).

  Note that the periphery of the electrode 30b of the SMA wire 3L and the holding member 33b of the driving apparatus 100 according to the embodiment of the present invention is the same as in FIGS. 7 and 8, but in this case, as shown in FIG. The SMA wire 3L1 is installed in a direction rotated by an angle + θ1 with respect to the first direction AR1 (= centerline direction AR2c).

  As described above, in the driving device 100 according to the present embodiment, the first direction AR1 is driven from the holding member 33a (or the holding member 33b) that changes when the SMA wire 3L is expanded or contracted by the driving unit to the displacement input unit 2b. Of the hour holding member force point direction ARm, the second holding direction AR2 that is one direction is made to coincide. Thus, the bending angle generated between the driving holding member force point direction ARm and the first direction AR1 of the SMA wire 3L2, which changes momentarily during driving, is set to be the first in any of the driving holding member force point directions ARm. The direction AR1 can be reduced compared to the conventional configuration (see FIG. 17) in which the directions AR1 are not matched. For this reason, the maximum stress generated in the SMA wire 3L having a bending stress having a positive correlation with the bending angle can be reduced. As a result, the progress rate of metal fatigue inside the SMA wire 3L due to repetitive operation can be reduced, and deterioration of the SMA wire 3L can be suppressed.

  Further, as the second direction AR2, the linear direction of the center line that bisects the angle of the range in which the driving holding member force point direction ARm varies around the boundary point BP by the driving means (center line direction AR2c in FIG. 8). ), The maximum bending angle (1/1 of the movable angle) generated between the driving holding member force point direction ARm and the first direction AR1 (= centerline direction AR2c), which changes every moment during driving. 2, | θ1 |) can be minimized in the examples of FIGS. For this reason, the maximum stress generated inside the SMA wire 3L can be further reduced, the progress rate of the metal fatigue inside the SMA wire 3L due to repeated operations can be further reduced, and the deterioration of the SMA wire 3L can be further suppressed. It becomes possible.

  With respect to the driving apparatus 100 according to the present embodiment as described above, when the driven body 1 is a lens unit and the axis AX direction is the optical axis direction, a lens driving apparatus having the same effects as described above is obtained. Can do. As a result, it is possible to realize a lens driving device in which the number of repetitions until the breakage exceeds 100,000 times.

<3. Method for Manufacturing Drive Device 100>
Next, a method for incorporating the SMA wire 3L in the driving apparatus 100 according to the present embodiment will be described below.

  9-12 is a figure which illustrates typically the apparatus incorporating method of the SMA wire 3L in the drive device 100 which concerns on this embodiment. As shown in FIGS. 9 to 12, the method of incorporating the SMA wire 3L in the driving apparatus 100 according to the present embodiment is roughly divided into the following five steps (I) to (V).

  (I) First, as shown in FIG. 9, the SMA wire 3L is passed through one electrode 30a. At this time, the electrode 30a is not yet crimped in this state.

  (II) Next, as shown in FIG. 10, the SMA wire 3L is guided to the other electrode 30b while rotating around the electrode 30a, and the SMA wire 3L is passed through the electrode 30b.

  (III) Energize the SMA wire 3L in the state shown in FIG.

  (IV) Then, as shown in FIG. 11, while driving the SMA wire 3L, the first direction of the SMA wire 3L1 in one direction out of the driving member holding point force direction ARm of the SMA wire 3L that varies during driving. The SMA wire 3L is fixed by caulking the two locations of the electrodes 30a and 30b so that the directions AR1 of the two are aligned.

  (V) Finally, as shown in FIG. 12, unnecessary portions on both sides of the fixed SMA wire 3L are cut and removed to complete the installation of the SMA wire 3L.

  Here, returning to FIG. 7 and FIG. As shown in FIG. 7, in the initial state before being driven (non-driven state), the SMA wire is rotated in the direction rotated about the boundary point BP by the angle −θ1 with respect to the first direction AR1 of the SMA wire 3L1. 3L2 is installed, but this is achieved by energizing the SMA wire 3L in the above steps (III) and (IV) to drive it, and crimping the SMA wire 3L to the electrodes 30a and 30b. (See FIGS. 10 and 11). As described above, the first direction AR1 of the SMA wire 3L1 is changed between the driving holding member force point direction ARm in the driving state by passing through the steps (III) and (IV) as shown in FIG. Among these, the structure which makes it correspond to 2nd direction AR2 which is one direction is implement | achieved.

  Further, as described above, in the second direction AR2, it is more preferable that the driving holding member force point direction ARm includes the center line direction AR2c of FIG.

<3-1. Specific Manufacturing Method Using Manufacturing Apparatus 300>
Hereinafter, a specific method of assembling the device into the driving device 100 of the SMA wire using the manufacturing apparatus 300 will be described in detail.

<3-1-1. About Step (I) and Step (II)>
First, the drive device 100 (also referred to as “work”) in an unfinished state in which the SMA wire 3L is not stretched and the sliders 53a and 53b are installed on the adjustment base 56. When the installation of the workpiece and the sliders 53a and 53b on the adjustment base 56 is completed, a stretching process is performed in which the SMA wire 3L is loosely stretched between the workpiece and the sliders 53a and 53b (see FIG. 10). Then, the sliders 53a and 53b are moved in a direction relatively away from the workpiece, so that a stronger tension is applied to the SMA wire 3L.

<3-1-2. About Step (III) and Step (IV)>
A predetermined current for setting the first direction AR1 of the SMA wire 3L1 is supplied from the punch 51a and the punch 51b so that the SMA wire 3L can be stabilized in the middle of the transformation process from the austenite phase to the martensite phase. Thus, the driving device 100 is brought into a driving state.

  Here, the first direction AR1 of the SMA wire 3L1 is adjusted so as to coincide with the second direction AR2 that is one of the driving holding member force point directions ARm. That is, as shown in FIG. 11, the energizing current to the SMA wire 3L is controlled so that the SMA wire 3L is in a preset heating state, and the holding member force point direction ARm during driving is changed to the centerline direction AR2c. After the SMA wire 3L is stabilized at the position, the sliders 53a and 53b are moved. That is, the positions of the sliders 53a and 53b indicated by the solid lines in FIG. 4 are rotated by ± θ1 to the positions of the sliders 53a and 53b indicated by the broken lines. In this way, the first direction AR1 of the SMA wire 3L1 inside the holding member 33a (or 33b) is fixed by performing the caulking process described below so as to coincide with the center line direction AR2c.

  In the caulking process, the driving holding member force point direction ARm is stable (when the driving holding member force point direction ARm is equal to the center line direction AR2c), and the SMA wire 3L1 passes through the tip of each of the punches 51a and 51b. This is a process of caulking the groove portions of the electrodes 30a and 30b. In this way, by performing the caulking process, the caulking portion SP is caulked to the electrodes 30a and 30b of the holding members 33a and 33b in a state where the first direction AR1 of the SMA wire 3L1 is aligned with the center line direction AR2c. Thereby, the SMA wire 3L1 is fixed (see FIG. 11).

<3-1-3. About Process (V)>
When the SMA wire 3L is fixed to each of the electrode fixing portions 33a and 33b by the above-described caulking process, the control unit 55 controls a cutting unit (not shown) to start from the electrodes 30a and 30b of the SMA wire 3L. A process of cutting each part protruding to the SMA line holding parts 54a and 54b side is performed (see FIG. 12).

DESCRIPTION OF SYMBOLS 1 Driven body 2 Lever member 2a Displacement input part 2b Displacement output part 3 Shape memory alloy (SMA) actuator 3L, 3L1, 3L2 SMA wire 4 Base member 6a, 6b Parallel leaf spring 8 Support leg 8a Lever support part 10 Imaging lens 30a , 30b Electrode 33a, 33b Holding member 53a, 53b Slider 54a, 54b SMA line holding unit 55 Control unit 100 Drive device 300 Manufacturing device SP Caulking portion AR1 First direction AR2 Second direction AR2c Center line direction ARm Holding member during driving Direction between power points

Claims (4)

A driven body driven to reciprocate in a predetermined direction;
A linear shape memory alloy that generates a driving force to move the driven body by expansion and contraction at a predetermined force point; and
A holding member for internally fixing a part of the shape memory alloy along the first direction;
Driving means for expanding and contracting the shape memory alloy;
In a drive device comprising:
The first direction is a second direction which is one of driving-holding member force point directions that change when the shape memory alloy is expanded and contracted by the driving means from the holding member to the predetermined force point. Characterized by matching the direction,
Drive device. The drive device according to claim 1,
The second direction is
The driving means includes a linear direction that bisects an angle of a range in which the direction between the holding member force points during driving varies around the holding member,
Drive device. The drive device according to claim 1 or 2, wherein
The holding member has a caulking portion that internally holds the shape memory alloy along the first direction.
Drive device. The drive device according to any one of claims 1 to 3,
The driven body is a lens unit;
A direction in which the driven body is driven is an optical axis direction,
Drive device.

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