TW201435466A - Auto-focus device with shape memory actuator - Google Patents

Abstract

An auto-focus device comprises a lens carrier (LC) slidably received for a reciprocating motion within a stationary housing frame (HF), said reciprocating motion being provided by an actuator that includes at least one V-shaped SMA actuating member (SW), the lens carrier (LC) being provided with a guide pin (GP) embedded in a corner projection (CP) and whose ends are received within bushing holes (BH) formed respectively in the housing frame (HF) and in a bottom plate (BP).

Description

Autofocus device with shape memory actuator

The present invention relates to a shape memory actuator, that is, an actuator in which the actuating member is composed of an element (for example, a wiring member) made of a shape memory alloy (hereinafter referred to as "SMA"), And particularly relevant to actuators for adjusting the position of the lens in an auto-focus device. Although a specific reference for using the wire as an actuating member is provided below, it should be noted that the description is also applied to other similar shapes in one dimension that are much larger than other generally two-dimensionally very small dimensions, such as strips. Wait.

It is known that the shape memory phenomenon consists of mechanical parts made of an alloy exhibiting this phenomenon that can be converted between two shapes preset at the time of manufacture in a very short time and in a manner that does not require an intermediate equilibrium position when the temperature changes. . The first mode in which this phenomenon may occur is referred to as the "single pass" of the mechanical component that changes shape in a single direction as the temperature changes, for example, from shape A to shape B, but from shape B to shape A. Mechanical force needs to be applied.

Conversely, in the so-called "two-way" mode, both transitions can be This is the application of the present invention due to temperature changes. This is due to the fact that the microcrystalline structure of the component is transferred from a species that is stable at low temperatures, called Matian bulk (M), to a species that is stable at high temperatures, called Vostian (A), and vice versa ( M/A and A/M transitions occur.

The SMA wire must be forged such that it can exhibit the characteristics of a shape memory component, and the forging process of the SMA wire often allows the induction of the Matian bulk/Worstian (M/A) phase change when the wire is heated in a highly repeating manner. And when the line is cooled, induce a phase change of the Worthian/Massa loose body (A/M). In the M/A transition, the line is shortened by 3-5%, and when the line is cooled, it recovers and returns to its original length via the A/M transition.

In particular, it is advantageous to utilize this feature that the SMA wire shrinks when heated and re-extends upon cooling, with a piezoelectric actuator and motor that are conventionally used in autofocus devices, which is very simple, compact, reliable, Quiet, low-cost actuators. The configuration of the present invention is also provided with respect to other SMA-based autofocus devices, such as the autofocus device as described in International Patent Application No. WO 2011/122438, which will be described later.

It is therefore an object of the present invention to provide an autofocus device having a shape memory actuator that achieves the advantages mentioned above. This object is achieved by an autofocus device comprising a frame slidably received in a fixed outer frame for reciprocating motion, the reciprocating action being provided by an actuator comprising at least one V-shaped SMA actuating member, the erection Embedded in the corner bulge and at the end of it Guide pins are formed in the outer frame and in the bushing holes in the bottom plate, respectively. Other advantageous features are disclosed in the scope of the related patent application.

BH‧‧‧ bushing hole

BP‧‧‧floor

CP‧‧ horn bulge

CS‧‧‧ coil spring

DIC‧‧‧Drive integrated circuit

EC‧‧‧Electrical connection

FPC‧‧‧Flexible Printed Circuit Board

FS‧‧‧Flexible spring

GP‧‧‧ guide pin

HF‧‧‧ frame

HS‧‧‧ Hall sensor

L‧‧‧ lens

LC‧‧‧ frames

M‧‧‧ magnet

P1, P2‧‧ points

SA‧‧‧ soldering area

SP‧‧‧ pads

SW‧‧‧SMA line

T1, T2‧‧‧ crimp terminal

From the following detailed description of embodiments of an autofocus device having a shape memory actuator in accordance with the present invention, and with reference to such additional figures, advantages and features thereof will be apparent to those skilled in the art, in which: Figure 1 is a front perspective view of the device; Figure 2 is a top plan view of the device; Figure 3 is a top plan view of the frame; Figure 4 is a side view of the frame; Figure 5 is a special view of the guide pin and associated bushing A partially perspective side view of the device in the position of the hole; Figure 6 is a partial perspective side view of the device showing the position of the return spring; Figure 7 is a bottom view of the device with the bottom plate removed; Figure 8 shows in particular A partially perspective perspective view of the device in the position of the flexible spring; Figure 9 is a partially cutaway perspective view of the device showing the position of the SMA wire terminal and the SMA wire.

Figure 10 is a partially cutaway perspective view of the device particularly showing the position of the control electronics of the device mounted on the flexible printed circuit board; Figure 11 is a position sensor specifically showing the position of the frame for detecting the frame a partially cutaway perspective view of the device; Figure 12 particularly shows a partially cutaway perspective view of the device for electrical connection between the position sensor and the control electronics; and Figure 13 particularly shows the device for electrical connection between the SMA wire terminal and the control electronics Partial cutaway perspective.

1 to 6, it can be seen that the autofocus apparatus according to the present invention includes a lens holder LC that carries the lens L and is slidably received in the fixed outer frame HF to implement an autofocus function for realizing a camera module or the like. Reciprocating action. This action is preferably guided by a metal guide pin GP that is embedded in the frame at the corner of the frame LC. The guide pin GP and the frame can be made by overmolding (also referred to as insert molding, that is, pre-inserting the guide pin GP into the plastic frame mold) or by assembling the two parts later. LC integration.

The ends of the guide pins GP are housed in a pair of concentric bushing holes BH formed in the corners of the outer frame HF and the bottom plate BP, respectively, which can be placed on or integrated with the outer frame.

The guide pin of the present invention controls the tilting performance of the control module itself due to the presence of a guide pin extending above the overall height of the frame and limited by the bushing hole, and the international patent application mentioned above In WO 2011/122438, there is only a retaining element for a return spring, the autofocus device according to the invention being different in architecture and function from that disclosed in WO 2011/122438.

The gap between the guide pin GP and the bushing hole BH will control the dynamic tilting efficiency of the actuator and the key factors for aligning the movement of the frame LC and the guide pin GP. child. For simplification, the gap of the guide pin can be exemplified as the difference between the diameter of the bushing hole BH and the diameter of the guide pin GP. The inventors have found that with enhanced performance, the gap is equal to or less than 0,75% of the height of the frame LC. Therefore, the preferred gap result is included between a minimum of 0,1% and a maximum of 0,75% to ensure freedom of movement.

As mentioned previously, the device according to the invention comprises a shape memory actuator, wherein the SMA actuating member, preferably the SMA wire SW, engages the frame LC such that when it is contracted by heating the SMA wire SW This contraction causes the sliding motion of the frame LC. The returning operation of the frame LC is preferably provided by at least one return spring, but it can also be provided by a second SMA wire acting on the frame LC in the reverse direction. The return spring is disposed above the guide pin GP between the outer frame HF and the frame LC, and the coil spring CS in the position formed in the corner projection CP of the latter is preferable to cool and return to the SMA wire SW. The return force is provided when the state is not contracted. For this purpose, the coil spring CS is designed with a compression length to provide a preload force to the frame LC.

The ends of the SMA wires SW are pre-compressed on the two terminals T1, T2, which are used for assembly alignment and for electrical connection. Then, by hooking the wire SW through the V-shaped structure located closer to the recess of the corner protrusion CP of the bottom plate BP than the crimp connection to the terminals T1, T2, it is preferable to hook it onto the frame LC for actuation. .

The movement of the frame LC is fixed by fixing one end of the flexible spring FS depicted in FIGS. 7 and 8 to the bottom plate BP at a point P1 and fixing the other end of the flexible spring FS to the frame LC at a point P2. Use flexible spring FS during Prevent it from rotating better. The restriction provided by the flexible spring FS limits the movement of the frame LC to only the axis component without the tilt component to achieve alignment of the optical center of the frame LC after the device is integrated into the camera or the like.

Referring also to Figures 9 through 13, it should be noted that the apparatus also typically includes a position sensing mechanism, such as a Hall sensor HS mounted on the outer frame HF, which is placed on the frame LC in the facing position detection. The position of the magnet M (other types of sensors can also be used, for example, a reflective optical sensor). The sensing integrated circuit is placed on the flexible printed circuit board FPC corresponding to the position of the magnetic polarization, and the magnet M is attached to the frame LC so that the Hall sensor HS can move the frame LC The feedback is easily provided to the control electronics for compensation.

The laser direct configuration (LDS) process is applied to the device for providing an electrical connection EC between the crimp terminals T1, T2 (between the pads SA) and the pad SP on the flexible printed circuit board FPC The driver integrated circuit DIC placed on the FPC can apply a current to the SMA line SW.

Embodiments of an autofocus device having a shape memory actuator according to the present invention, which are obviously described and illustrated above, are merely examples that are susceptible to various modifications. In particular, in addition to the variations mentioned above, it should be noted that the SMA actuating members (etc.) and the return springs (etc.) can be configured in many different ways within the knowledge of those skilled in the art.

To understand the performance of the auto-focusing device in accordance with a preferred embodiment of the present invention, the angle indicated by the division (1/60 degrees) is used to provide a reference for the tilt of the module.

Evaluate the AF modules M1-M5 with different pin gaps and frame heights and report the corresponding tilt; be emphasized due to the parasitic movement of the tilting AF module Side effects are unfavorable phenomena, so the lower the better.

As can be observed, the AF apparatus according to the preferred embodiment of the present invention, i.e., having a gap/frame height ratio (M1-M3) comprised between 0, 1 and 0, 75%, is provided with a low The enhanced performance of the tilt angle of 10 points that is considered to be the limit of the high-end AF module. Since this tilt represents dynamic tilt (inclination during the movement of the deflector), the smaller the dynamic tilt, the better, as it will not affect the optics. An actuator for the camera moves the lens along the image/optical axis toward the image sensor, so less tilt results in more uniform image formation/sharpness (or optical projection).

BP‧‧‧floor

CP‧‧ horn bulge

CS‧‧‧ coil spring

GP‧‧‧ guide pin

HF‧‧‧ frame

HS‧‧‧ Hall sensor

L‧‧‧ lens

LC‧‧‧ frames

M‧‧‧ magnet

SW‧‧‧SMA line

T1, T2‧‧‧ crimp terminal

Claims (13)

An autofocus device comprising a frame (LC) slidably received in a fixed outer frame (HF) for reciprocating motion, the reciprocating action being provided by an actuator comprising at least one V-shaped SMA actuating member, characterized The frame (LC) is provided with a guide pin (GP) embedded in the corner protrusion (CP) of the frame (LC), and is equal to the diameter of the bushing hole (BH) and the guide pin (GP) The gap between the diameters accommodates the ends of the guide pins (GP) in the bushing holes (BH) formed in the outer frame (HF) and the bottom plate (BP), respectively. The autofocus device of claim 1, wherein the ratio of the gap of the guide pin (GP) to the height of the frame (LC) is between 0, 1% and 0, 75%. An autofocus device according to claim 1 or 2, wherein the action of the SMA actuating member is resisted by at least one return spring (CS). An autofocus device according to claim 1 or 2, wherein the SMA actuating member is an SMA wire (SW) placed on the outer frame (HF). An autofocus device according to claim 4, wherein the SMA wire (SW) is crimped to the terminals (T1, T2), and the terminals are electrically connected to the flexible printed circuit board carrying the control electronics of the device. (FPC). An autofocus device according to claim 5, wherein the SMA wire (SW) is closer to the bottom plate (BP) by passing it through a crimp connection located to the terminals (T1, T2). The V-shaped structure of the depressed portion of the (CP) engages the frame (LC) at the angular projection (CP). An autofocus device as claimed in claim 3, wherein The return spring (CS) is coaxially disposed above the guide pin (GP) in a position formed in the angular projection (CP). An autofocus device according to claim 7, wherein the return spring (CS) is compressed between the angular projection (CP) and the outer frame (HF) to provide a direction toward the bottom plate (BP). Preload force. An autofocus device as claimed in claim 1, further comprising a flexible spring (FS) disposed between the frame (LC) and the outer frame (HF) or the bottom plate (BP). An autofocus device according to claim 9, wherein the flexible spring (FS) is fixed to the frame (LC) and the outer frame (HF) or the bottom plate (BP) at opposite corners of the device. The autofocus device of claim 1, wherein the method further comprises a position sensing mechanism. The autofocus device of claim 11, wherein the position sensing mechanism is mounted on the frame (LC) by a magnet (M) mounted on the frame (LC) facing the position and placed on the outer frame (HF) The Hall sensor (HS) is composed. An autofocus device according to claim 5, wherein the electrical connection between the control electronics and the terminals (T1, T2) of the crimped SMA wire (SW) is obtained by direct laser configuration.