Drive device

The driving device includes a bendable shape memory alloy member, a resilient member for applying a tension to the shape memory alloy member in a longitudinal direction thereof, a bending member for bending the shape memory alloy member, and a movable body moved by a displacement of the shape memory alloy member. The bending member contacts the shape memory alloy member, so that the tension is applied to the shape memory alloy member in the longitudinal direction thereof. Compared with the driving device in which the shape memory alloy member is linearly disposed, the decrease in the amount of displacement can be suppressed, so that a space efficiency can be enhanced and the downsizing of the driving device can be accomplished.

TECHNICAL FIELD

This invention relates to a driving device, and particularly relates to a driving device that utilizes the characteristics of a shape memory alloy to generate a driving force.

BACKGROUND ART

Conventionally, there is known a driving device using a shape memory alloy in the form of a wire, as disclosed in, for example, Japanese Laid-Open Patent Publication Nos. 2000-310181 (see Page 2, FIG. 11) and HEI 5-224136 (see Page 3, FIG. 3). Such a driving device utilizes the characteristics of the shape memory alloy member that changes to a memorized shape when the shape memory alloy member is heated to a temperature higher than a transformation temperature, and returns to its original shape when the shape memory alloy member is cooled to a temperature lower than the transformation temperature. The amount of displacement of the shape memory alloy member is several percents of the entire length of the shape memory alloy member, and therefore it is necessary to increase the entire length of the shape memory alloy member in order to obtain the sufficient output (the amount of displacement) of the driving device. However, if the shape memory alloy member is linearly disposed, it is necessary to provide a large space.

Therefore, a driving device is recently proposed, in which the shape memory alloy member is wound around a winding member so that the shape memory alloy member whose entire length is long can be disposed in a small space. Such a driving device is disclosed in, for example, Japanese Laid-Open Patent Publication Nos. 2000-31018 (see Page 6, FIG. 1), HEI 8-226376 (see Pages 3-5, FIG. 1), HEI 10-148174 (see Pages 2-3, FIG. 1), and HEI 8-77674 (see Page 5, FIG. 5).

However, if the shape memory alloy member is wound around the winding member as disclosed in these publications, the amount of displacement of the shape memory alloy member decreases, compared with the case in which the shape memory alloy member is linearly disposed.

DISCLOSURE OF INVENTION

The present invention is intended to solve the above described problems, and an object of the present invention is to provide a driving device capable of suppressing the decrease in the amount of displacement compared with a driving device in which a shape memory alloy member is linearly disposed, and capable of being disposed in small space (i.e., capable of enhancing a space efficiency).

A driving device according to the present invention includes a bendable shape memory alloy member, an urging means that applies a tension to the shape memory alloy member in a longitudinal direction thereof, a bending means which bends the shape memory alloy member and has a plurality of contact portions contacting the shape memory alloy member, the contact portions being disposed along a closed path, wherein the contact. portions contact the shape memory alloy member so that the tension is applied to the shape memory alloy member in the longitudinal direction thereof.

According to the present invention, it becomes possible to suppress the decrease in the amount of displacement of a shape memory alloy member, and capable of enhancing a space efficiency so as to accomplish the downsizing of the driving device.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 and 2are a plan view and a perspective view showing a driving device1according to Embodiment 1 of the present invention. As shown inFIGS. 1 and 2, a base6of the driving device1has a placing surface6aand a wall surface6bperpendicular to the placing surface6a. On the placing surface6a, a pin-shaped bending member5is planted on a position distanced from the wall surface6b. A shape memory alloy member2is wound around the circumferential surface of the bending member5at a winding angle θ of 180 degrees, with one end (fixed end) being fixed to a wall surface6b, with the other end (movable end) being fixed to a side of a movable body3. The expression that the winding angle is 180 degrees means that the shape memory alloy member2contacts the bending member5and is bent at 180 degrees. An end of a resilient member4made of a tension coil spring is fixed to the wall surface6b, and the other end of the resilient member4is fixed to the other side (the side opposite to the side fixed to the shape memory alloy member2) of the movable body3in such a manner that the resilient member4is slightly stretched to cause a predetermined tension.

In the driving device1, an energizing circuit7causes a direct current to flow between the fixed end of the shape memory alloy2and the fixed end (the end fixed to the wall surface6b) of the resilient member4, so as to heat the shape memory alloy member2by means of heat (Joule heat) caused by the electric resistance of the shape memory alloy member2. For this purpose, a conducting material is used for the resilient member4and the movable body3. However, the method for heating the shape memory alloy member2is not limited to this method. It is possible that the movable body3contacts the placing surface6a. In such a case, the friction generated between the movable body3and the placing surface6awhen the movable body3moves is negligible compared to the tension applied to the shape memory alloy member2.

The bending member5constitutes a bending means that bends the shape memory alloy member2. A portion of the circumferential surface of the bending member5contacting the shape memory alloy member2constitutes a contact portion of the bending means contacting the shape memory alloy member2. The base6constitutes a holding means that holds the bending member5.

In the above constructed driving device1, when the energizing circuit7causes a predetermined direct current (for example, 100 mA) to flows through the shape memory alloy member2, the shape memory alloy member2is heated and contracted, so that the movable body3moves in the direction of an arrow A resisting the urging force of the resilient member4. When the energization of the shape memory alloy member2is stopped, the temperature of the shape memory alloy member2decreases and the shape memory alloy member2is expanded to its original length, so that the movable body3moves in the direction of an arrow B by the urging force of the resilient member4.

FIG. 3is a plan view showing a driving device according to a comparative example with respect to this embodiment, i.e., a driving device100in which a shape memory alloy member101is linearly disposed. An end of the shape memory alloy member101is fixed to a fixed wall104a, and the other end is fixed to a side (a right side inFIG. 3) of a movable body102. The other side (a left side inFIG. 3) of the movable body102is fixed to an end of a resilient member103. The other end of the resilient member103is fixed to another fixed wall104b. Due to the urging force of the resilient member103, a tension is applied to the shape memory alloy member101in the longitudinal direction thereof, so that the shape memory alloy member101is linearly disposed without slackening. The heating of the shape memory alloy member101is carried out by the energization of an energizing circuit105. When the shape memory alloy member101is energized by the energizing circuit105, the shape memory alloy member101is contracted, so that the movable body102moves in a direction shown by an arrow A. When the energization of the shape memory alloy member101is stopped, the movable body102moves in a direction. shown by an arrow B. However, in the driving device100, since the shape memory alloy member101is linearly disposed, it is difficult to reduce the dimension of the device in the longitudinal direction of the shape memory alloy member101.

FIG. 4is a view showing another comparative example with respect to the embodiment, i.e., a driving device110in which a shape memory alloy member101is wound around a cylindrical winding member106having a large diameter (for example, a diameter of 10 mm) at about 360 degrees. By winding the shape memory alloy member101around the winding member106at about 360 degrees, the shape memory alloy member101whose entire length is long can be disposed in a small space (i.e., the space efficiency can be enhanced). However, the amount of displacement of the movable body102becomes smaller compared with the driving device100shown inFIG. 3.

An experimental result on the driving devices100and110according to the comparative examples will be described.FIG. 5shows an experimental method in the case where a shape memory alloy member101is linearly disposed (corresponding to the driving device100ofFIG. 3). Crimp contacts120are fixed to both ends of the shape memory alloy member101in the form of a wire having a diameter of 60 μm and a length of 50 mm. One of the crimp contacts120is fixed to a fixing pin121a, and the other of the crimp contacts120is fixed to an end of a resilient member103. The other end of the resilient member103is fixed to another fixing pin121b. The amount of displacement of the movable body102(FIG. 3) is evaluated by measuring the amount of displacement of the crimp contact120connecting the shape memory alloy member101and the resilient member103. The resilient member103(tension coil spring) is expanded by 1 mm in a state where the shape memory alloy member101is not energized. A resilient member103causes the tension of about 49×10−3N when the resilient member103is expanded by 1 mm, and causes the tension of about 98×10−3N when the resilient member103is further expanded by 1 mm (i.e., when the shape memory alloy member2is contracted by 1 mm).

Moreover, as shown inFIGS. 6(a) and (b), the same experiment is carried out in such a manner that the shape memory alloy member101in the form of a wire is wound around a cylindrical winding member106having a diameter of 10 mm at about 180 degrees. The winding member106is made of POM (polyoxymethylene) or ABS (Acrylonitrile-Butadiene-Styrene resin). The length C of the shape memory alloy member101from the winding member106to each crimp contact120is set to be 17.1 mm. Further, as shown inFIGS. 7(a) and (b), the same experiment is carried out in such a manner that the shape memory alloy member101is wound around the winding member106at 360 degrees. The lengths C1and C2of the shape memory alloy member101from the winding member106to the respective crimp contacts120are set to be 9.3 mm. Furthermore, as shown inFIGS. 8(a) and (b), the same experiment is carried out in such a manner that the shape memory alloy member101is wound around the winding member106at 450 degrees. The length C of the shape memory alloy member101from the winding member106to each crimp contact120is set to be 11 mm.

As a result of the experiment, when the shape memory alloy member101is linearly disposed as shown inFIG. 5, the amount of displacement of the end of the shape memory alloy member101is 1.6 mm. In contrast, in the experiment in which the shape memory alloy member101is wound around the winding member106having a diameter of 10 mm at about 180 degrees as shown inFIG. 6, the amount of displacement is about 1.0 mm in each of cases where POM and ABS are used. Moreover, in the experiment in which the shape memory alloy member101is wound at about 360 degrees as shown inFIG. 7, the amount of displacement is 0.5 mm (when the winding member106is POM) and 1.0 mm (when the winding member106is ABS). Moreover, in the experiment in which the shape memory alloy member101is wound at about 450 degrees as shown inFIG. 8, the amount of displacement is 0.3 mm (when the winding member106is POM) and 0.6 mm (when the winding member106is ABS). That is, it is understood that the amount of displacement of the shape memory alloy member101decreases to about 35% (POM) and about 61% (ABS) when the winding angle is 360 degrees, and decreases to about 20% (POM) and about 36% (ABS) when the winding angle is 450 degrees, compared with the case in which the shape memory alloy member101is linearly disposed (FIG. 5).

Next, the result of the same experiment on the driving device1according to the embodiment (FIGS. 1 and 2) will be described. The experiment is carried out in the same method as that shown inFIG. 5. The bending member5is a pin-shaped member made of metal having a diameter of 1 mm. The shape memory alloy member2is formed in the form of a wire having a diameter of about 60 μm and the length of 50 mm. When the shape memory alloy member2is not energized, the length of the shape memory alloy member2from the movable body3(the crimp contact) to the pin5is 11.8 mm. The resilient member4causes the tension of about 49×10−3N when the resilient member4is expanded by 1 mm, and causes the tension of about 98×10−3N when the resilient member4is further expanded by 1 mm (i.e., when the shape memory alloy member2is contracted by 1 mm).

In the experiment using the driving device1according to the embodiment, when the direct current of 100 mA flows through the shape memory alloy member2so that the shape memory alloy member2is heated and contracted, the amount of displacement of the end of the shape memory alloy member2is 1.5 mm. That is, the amount of displacement of about 94% is obtained, with respect to the amount (1.6 mm) of displacement when the shape memory alloy member is linearly disposed. In other words, it is understood that, by bending the shape memory alloy member2using the winding member5(a metal pin having a diameter of 1 mm), it is possible to obtain the amount of displacement of about 94% with respect to the case in which the shape memory alloy member2is linearly disposed.

As described above, according to the driving device1of the embodiment, the shape memory alloy member2is bent by the bending member5so that the tension is applied to the shape memory alloy member2in the longitudinal direction thereof, and therefore the decrease in the amount of displacement of the movable body3can be suppressed, and the shape memory alloy member2whose entire length is long can be disposed in a smaller space. In other words, the space efficiency can be enhanced.

FIG. 9is a plan view showing a driving device11according to Embodiment 2 of the present invention. The driving device11is different from the driving device1of the above described Embodiment 1 (FIGS. 1 and 2) in that an additional bending member12is added for bending the shape memory alloy member2at two positions and two wall portions13band13care formed on a base13. In the driving device11, parts in common with the driving device1of Embodiment 1 are assigned the same reference numerals.

In this driving device11, the wall portions13band13care formed on both sides of the base13. In addition to the bending member5, a bending member12is planted on the placing surface13aof the base13on the wall portion13bside with respect to the bending member5. An end (fixed end) of the shape memory alloy member2is fixed to the wall portion13c. The shape memory alloy member2is wound around the bending members5and12so that each winding angle is about 180 degrees. The other end (movable end) of the shape memory alloy member2is fixed to the movable body3.

The bending member5is disposed on a position so that opposing portions2aand2bof the shape memory alloy member2bent around the bending member5become almost parallel to each other and do not interfere with the movement of the movable body3. As an example of dimension, in the direction in which the opposing portions2aand2bextend (the moving direction of the movable body3), an interval C2between the movable member3and the bending member5is 12.6 mm, an interval C3between the bending members5and12is 10 mm, an interval C4between the bending member12and the wall portion13cis 22.5 mm. An interval C1between the bending portions5and12in a direction perpendicular to the direction in which the opposing part2aand2bextend is 5 mm.

The bending members5and12constitute a bending means which bends the shape memory alloy member2. Portions of the circumferential surfaces of the bending members5and12contacting the shape memory alloy member2constitute a contact portion of the bending means contacting the shape memory alloy member2. The base13constitutes a holding means which holds the bending members5and12.

In the above described configuration, the experiment that has been described with reference toFIG. 5is carried out. In this case, the pin-shaped bending members5and12each having a diameter of 1 mm are used. The other measurement conditions are the same as those described with reference toFIG. 5. When the direct current of 100 mA flows through the shape memory alloy member2so that the shape memory alloy member2is heated and contracted, the amount of displacement of the movable body3is about 1.3 mm.

In other words, the amount of displacement of the movable body3becomes about 81% with respect to the case in which the shape memory alloy member2is linearly disposed. It is understood that the decrease in the amount of displacement (which may accompany the enhancement of the space efficiency) can be suppressed.

As described above, according to the driving device of this embodiment, since the shape memory alloy member2is bent two times by means. of two pin-shaped bending members5and12, it becomes possible to suppress the decrease in the amount of displacement of the movable body3, and to enhance the space efficiency. Further, since two bending members5and12are used, it becomes possible to dispose the walls13band13ccloser to each other, and therefore the space efficiency can be further enhanced.

FIG. 10is a perspective view showing the driving device21according to Embodiment 3 of the present invention. This driving device21is different from the driving device1of Embodiment 1 (FIGS. 1 and 2) in that two bending portions are provided and a plurality of portions for bending the shape memory alloy member22(guide grooves) are formed on the respective bending members23and24. In the driving device21, parts in common with the driving device1of Embodiment 1 are assigned the same reference numerals.

In this driving device21, two bending members24and23are planted on the base6in this order from the side closer to the wall portion6b. Four guide grooves23aare formed on the circumferential surface of the bending member23at intervals in the axial direction of the bending member23. Three guide grooves24aare formed on the circumferential surface of the bending member24at intervals in the axial direction of the bending member24. An end (fixed end) of the shape memory alloy member22is fixed to the wall portion6b, and the other end (movable end) is fixed to the movable body3. The shape memory alloy member22is wound around four guide grooves23aof the bending member23and three guide grooves24aof the bending member24so that each winding angle is about 180 degrees. In other words, two bending member23and24have contact portions at seven positions in total, which contact the shape memory alloy member22so as to bend the shape memory alloy member22. In this embodiment, in order to avoid the short circuit of the shape memory alloy member22, the bending members23and24are made of insulation material or the like.

Two bending members23and24constitute a bending means which bends the shape memory alloy member22. Portions of the respective guide grooves23aand24acontacting the shape memory alloy member22constitute a contact portion of the bending means contacting the shape memory alloy member22. The base6constitutes a holding means which holds the bending members23and24. The resilient member4constitutes an urging means that urges the shape memory alloy member22.

In the above described configuration, as is the case with Embodiment 1, the movable body3can be displaced by causing a predetermined direct current (for example, 100 mA) to flow through the shape memory alloy member22by means of the energizing circuit7so that the shape memory alloy member22is heated and contracted.

As described above, according to the driving device21of this embodiment, it is possible to efficiently dispose the longer shape memory alloy member22, and therefore it is possible to suppress the decrease in the amount of displacement of the movable body3and to further enhance the space efficiency.

Moreover, since the guide grooves23aand24aare formed on the bending members23and24, the shape memory alloy member22can be easily wound, the deviation of the winding position of the shape memory alloy member22can be prevented, and the short circuit of the shape memory alloy member22can be prevented.

FIG. 11is a perspective view showing a driving device31according to Embodiment 4 of the present invention. This driving device31is different from the driving device1(FIGS. 1 and 2) of Embodiment 1 in that four pin-shaped bending member33,34,35and36are provided. In the driving device31, parts in common with the driving device1of Embodiment 1 are assigned the same reference numerals.

In this driving device31, four pin-shaped. bending members33through36are provided at positions corresponding to four corners of a rectangle of the placing surface6aof the base6. An end (fixed end) of the shape memory alloy member32is fixed to the wall portion6b, and the shape memory alloy member32is wound around the bending members33through36in about two turns and half so that each winding angle is 90 degrees. The other end (movable end) of the shape memory alloy member32is fixed to the movable body3. The shape memory alloy member32is wound around the bending members34and35at three positions axially apart from each other, and wound around the bending members33and36at two positions axially apart from each other. That is, four bending members33through36have ten contact portions in total that contact the shape memory alloy member32so as to bend the shape memory alloy member32. For example, in this embodiment, in order to avoid the short circuit of the shape memory alloy member32, the bending members33through36are made of insulating material. Moreover, it is possible to provide the guide groove (the guide grooves23aand24ashown inFIG. 10) described in Embodiment 3 on the bending members33and36.

Four bending members33through36constitute a bending means which bends the shape memory alloy member32. Portions of the bending members33through36contacting the shape memory alloy member32constitute a contact portion of the bending means. The base6constitutes a holding means which holds the bending members33through36.

In the above described configuration, the movable body3can be displaced by causing a predetermined direct current (for example, 100 mA) to flow through the shape memory alloy member32using the energizing circuit7so that the shape memory alloy member32is heated and contracted.

Although the bending portions33and36are disposed on four apexes of the rectangle, it is also possible to properly change the number and positions of the bending members, as long as the contact portions contacting the shape memory alloy member32are formed along a closed path. Further, in this example, although four bending members32have contact portions at ten positions in total, it is also possible to properly change this.

As described above, according to the driving device31of this embodiment, it is possible to efficiently dispose the longer shape memory alloy member32, and therefore it is possible to suppress the decrease in the amount of displacement of the movable body3and to further enhance the space efficiency.

FIG. 12is a plan view showing a driving device41according to Embodiment 5 of the present invention. This driving device41is different from the driving device1(FIGS. 1 and 2) of Embodiment 1 in that a shape memory alloy member42is wound around projections44aand44bprojecting from corners of a housing44so that each winding angle is 90 degrees. In the driving device41, parts in common with the driving device1of Embodiment 1 are assigned the same reference numerals.

In the driving device41, a housing44in the form of, for example, a rectangular parallelepiped is formed on a placing surface43aof a base43. The projections44aand44bare formed on two corners of the housing44on the sides farther from a wall portion43b. The projections44aand44bproject in directions almost perpendicular to each other, and have contact surfaces (for example, cylindrical surfaces) around which the shape memory alloy member42is wound. The shape memory alloy member42is wound around each contact surface of the projections44aand44bso that the winding angle (corresponding to a bending angle) is 90 degrees.

An end (fixed end) of the shape memory alloy member42is fixed to the wall portion43bof the base43, and the shape memory alloy member42is wound around projections44aand44bso that each winding angle is 90 degrees. The other end (movable end) of the shape memory alloy member42is fixed to the movable body3.

The projections44aand44bconstitute a bending means which bends the shape memory alloy member42. Portions of the respective projections44aand44bcontacting the shape memory alloy member42constitute a contact portion of the bending means that contacts the shape memory alloy member42. The base43constitutes a holding means which holds the housing44having the projections44aand44b.

In the above described configuration, the movable body3can be displaced by causing a predetermined direct current (for example, 100 mA) to flow through the shape memory alloy member42by means of the energizing circuit7as in Embodiment 1 so that the shape memory alloy member42is heated and contracted.

In this embodiment, the projections44aand44bproject from the corners of the housing44. However, the projections44aand44bare is not limited to this configuration, but can be fixed to proper positions (in terms of designing) on the housing44. The winding angle of the shape memory alloy member42is not limited to 90 degrees.

Moreover, it is possible to form the guide grooves23aand24a(FIG. 10) described in Embodiment 3 on the projections44aand44b. Further, it is also possible to form a step44con a position where the shape memory alloy member42is wound, so that it becomes easy to wind the shape memory alloy member42.

As described above, according to the driving device41of this embodiment, since the shape memory alloy member42is bent two times (at 90 degrees for each) by a pair of projections44aand44b, the longer shape memory alloy member42can be efficiently disposed. Further, the housing44constituting a part of the driving device41can be utilized, and therefore the space efficiency can be further enhanced.

FIG. 14is a perspective view showing a driving device51according to Embodiment 6 of the present invention. This driving device51is different from the driving device11(FIG. 9) of Embodiment 2 in that a bending member54having convex portions on a circumferential surface thereof is provided. In the driving device51, parts in common with the driving device11of Embodiment 2 are assigned the same reference numerals.

As shown inFIG. 14, the bending member54is formed on the placing surface13aof the base, and the bending member54is approximately in the form of a cylinder having minute convex portions on the circumferential surface thereof. The minute convex portions of the bending member54constitute contact portions54athat contact the shape memory alloy member2. The contact portions54are elongated in the axial direction of the bending member54, and a large number of the contact portions54aare disposed in the circumferential direction of the bending member54.

An end (fixed end) of the shape memory alloy member2is fixed to the wall portion13c, and the shape memory alloy member2is wound around the bending member54in one turn so that the total of the bending angles at the respective contact portions54ais 360 degrees. The other end (movable end) of the shape memory alloy member2is fixed to one side of the movable body3. The other side of the movable body3is fixed to an end of the resilient member4, and the other end of the resilient member4is fixed to the wall portion13b.

The bending member54constitutes a bending means which bends the shape memory alloy member2. The contact portions54aconstitute contact portions (convex portions) that contacts the shape memory alloy member2in the bending means. The base31constitutes a holding means which holds the bending member54.

In the above described configuration, the movable body3can be displaced by causing a predetermined direct current (for example, 100 mA) to flow through the shape memory alloy member2using the energizing circuit7so that the shape memory alloy member2is heated and contracted, as is the case with Embodiment 1.

Next, the experiment on the driving device51according to this embodiment will be described. As is the case with the experiments shown in the above describedFIGS. 5 through 8, the crimp contacts120and the fixing pins121are arranged as shown inFIGS. 15 through 17.

As shown inFIGS. 15(a) and (b), the shape memory alloy member2in the form of a wire is wound around the bending member54(having the contact portions54a) at about 180 degrees, and the bending member54is made of POM or ABS in the form of a cylinder having a diameter of 10 mm.

The crimp contact120at an end of the shape memory alloy member2is fixed to the fixing pin121, and the crimp contact120at the other end of the shape memory alloy member2is fixed to another fixing pin121via a resilient member4. The length C of the shape memory alloy member2from the bending member54to the crimp contacts120at both ends of the shape memory alloy member2are set to be 17.1 mm. As shown inFIGS. 16(a) and (b), the shape memory alloy member2is wound around the bending member54at 360 degrees, and the experiments are carried out similarly. The lengths C1and C2of the shape memory alloy member2from the bending member54to the crimp contacts120at both ends are set to be 9.3 mm. As shown inFIGS. 17(a) and (b), the shape memory alloy member2is wound around the bending member54at 450 degrees, and the experiment is carried out similarly. The length C of the shape memory alloy member2from the bending member54to the crimp contacts120are set to be 11 mm.

FIG. 18(a) is a perspective view showing an outline shape of the bending member used in the respective experiments.FIGS. 18(b) through (d) are plan views showing three kinds of shapes used in the respective experiments. The bending member54is an approximately cylindrical member having a diameter D of 10 mm, and has the contact portions54aformed on the circumferential surface thereof with a pitch (P) of 1.56 mm. Each contact portion54ahas a circular-arc cross section having a radius of 5 mm. The widths W1of the contact portion54aare, respectively, 1.05 mm (FIG. 18(b)), 0.78 mm (FIG. 18(c)) and 0.52 mm (FIG. 18(d)). Moreover, the widths W2of the grooves between adjacent contact portions54aare, respectively, 0.52 mm (FIG. 18(b)), 0.78 mm (FIG. 18(c)) and 1.05 mm (FIG. 18(d)).

The other experimental conditions are the same as those of Embodiment 1. The direct current of 100 mA flows through the shape memory alloy member2so that the shape memory alloy member2is heated and contracted, and the displacement of the movable end is measured. The result of the measurement is shown in Tables 1 and 2. Table 1 shows the case where the bending member54is made of ABS, Table 2 shows the case where the bending member54is made of POM.

FIG. 19is a graph showing the experimental result when ABS is used as the bending member54, which corresponds to Table 1.FIG. 20is a graph showing the experiment result when POM is used as the bending member54, which corresponds to Table 2. InFIGS. 19 and 20, a vertical axis indicates a displacement ratio H (%), i.e., a ratio of the measured displacement of the movable body3with respect to the displacement when the shape memory alloy member2is linearly disposed. A horizontal axis indicates a contact ratio S (%), i.e., a ratio of the width W1of the contact portion54awith respect to the pitch P (1.56 mm) of the contact portion54a. For example, if the width W1of the contact portion54ais 0.52 mm (FIG. 18(d)), the contact ratio S is 100×0.52 mm/1.56 mm=33%. InFIGS. 19 and 20, marks a, b, and c indicate data respectively when the winding angle of the shape memory alloy member2around the bending member54is 450 degrees, 360 degrees and 180 degrees.

According toFIGS. 19 and 20(Tables 1 and 2), the displacement ratio H of the movable body3becomes close to 100% (i.e., the amount of displacement when the shape memory alloy member2is linearly disposed), as the width W1of the contact portion54abecomes small. Moreover, as the width W1of the contact portion54abecomes small, the difference in amount of displacement caused by the difference in winding angle or material of the bending members54(ABS or POM) becomes small. In particular, when the width W1of the contact portion54ais ⅓ of the pitch P (the contact ratio S is about 35%), the displacement ratio H further becomes closer to 100%, and the difference in amount of displacement caused by the difference in winding angle or material of the bending members (ABS or POM) almost disappears. In the above describedFIGS. 6 through 8, the amount of displacement of the movable body3largely changes according to the difference in material of the winding member106or winding angle of the shape memory alloy member2. Conversely, in this embodiment, it is possible to suppress the deviation of the amount of displacement caused by the difference in winding angle of the shape memory alloy member2or material of the bending members54. Therefore, the space efficiency can be enhanced, the configuration of the driving device can be simplified, and the operation efficiency of the manufacturing process can be enhanced.

In this embodiment, although the contact portions54aare formed along the approximately circular circumference of the contact member54as shown inFIG. 21(a), the contact portions54aare not limited to this configuration. For example, the contact portions54acan be formed along a closed path (the circumference of the closed figure), such as a circumference of a approximately rounded triangle or oval, as shown inFIGS. 21(b) and (c).

FIG. 22is a plan view showing a driving device61according to Embodiment 7 of the present invention. This driving device61is different from the driving device1(FIG. 1) in that a shape memory alloy member62is made in the form of a coil spring. In the driving device61, parts in common with the driving device1of Embodiment 1 are assigned the same reference numerals.

As shown inFIG. 22, the shape memory alloy member62is made in the form of a coil spring, and is wound around a pin-shaped bending member63planted on a placing surface6aof a base6so that the winding angle is 180 degrees. An end of the shape memory alloy member62is fixed to wall portion6b, and the other end is fixed to the movable body3.

The pin-shaped bending member63constitutes a bending means which bends the shape memory alloy member62. A portion of the circumferential surface of the bending member63contacting the shape-memory alloy member62constitutes a contact portion of the bending means contacting the shape memory alloy member62. The base6constitutes a holding means which holds the bending member63.

In the above described configuration, the movable body3can be displaced by causing a predetermined direct current (for example, 100 mA) to flow through the shape memory alloy member62by means of the energizing circuit7so that the shape memory alloy member62is heated and contracted. Since the shape memory alloy member62takes the form of a coil spring, the amount of expansion and contraction of the shape memory alloy member62becomes large, with the result that the amount of displacement of the movable body3can be largely increased.

In this embodiment, although the bending member63is pin-shaped, the bending member63is not limited to the pin shape, but it is possible to chose the shape of the bending member63suitable for the shape memory alloy member62(in the form of the coil-spring) in terms of designing.

As described above, according to the driving device61of this embodiment, since the shape memory alloy member62is made in the form of the coil spring, the amount of expansion and contraction of the shape memory alloy member62becomes larger, and therefore the amount of displacement of the movable body3can be largely increased. Therefore, the space efficiency can be further enhanced, and the downsizing of the driving device61can be accomplished.

FIG. 23is a perspective view showing a driving device71according to Embodiment 8 of the present invention. This driving device71is different from the driving device1of Embodiment 1 (FIGS. 1 and 2) in that a shape memory alloy member72in the form of a band is used. In the driving device71, parts in common with the driving device1of Embodiment 1 are assigned the same reference numerals.

In the driving device71, the shape memory alloy member72is not in the form of a wire but in the form of a band. The shape memory alloy member72is wound around a pin-shaped bending member5planted on a base6so that the winding angle is 180 degrees. An end of the shape memory alloy member72is fixed to a wall portion6b, and the other end is fixed to a movable body3.

The pin-shaped bending member5constitutes the bending means which bends the shape memory alloy member72. A part of the circumferential surface of the bending member5contacting the shape memory alloy member72constitutes a contact portion of the bending means contacting the shape memory alloy member72. The base6constitutes a holding means which holds the bending member5.

In the above described configuration, the movable body3can be displaced by causing a predetermined direct current (for example, 100 mA) to flow through the shape-memory alloy member72by means of the energizing circuit7so that the shape memory alloy member72is heated and contracted.

In this embodiment, although the bending member.5is pin-shaped, the bending member5is not limited to the pin shape. It is possible to chose the shape of the bending member5suitable for the shape memory alloy member72(in the form of the band) in terms of designing.

As described above, according to the driving device71of this embodiment, in addition to the advantage of Embodiment 1 that enhances the space efficiency, it becomes possible to generate a large force because the shape memory alloy72is in the form of a band. Therefore, it becomes possible to move the movable body3with a large force.

FIGS. 24(a) and (b) are a front view and a side view showing a driving device81according to Embodiment 9 of the present invention. As shown inFIGS. 24(a) and (b), a base83has a pair of fixing walls83aand83bopposing to each other. Both ends of the shape memory alloy member2are fixed to one fixing wall83a. The center part of the shape memory alloy member2is wound around a bending member84in a plurality of turns (2.5 turns) so that the winding angle is about 900 degrees. The bending member84is approximately in the form of a cylinder. This bending member84is composed by adding a rotation axis84ato the above described bending member54(FIG. 14)having a plurality of contact portions54a. Both ends of the rotation axis84aare rotatably supported by a holding frame85. A resilient member4is stretched between the center of a connecting portion85aof the holding frame85and the fixing wall83bof the base83, so that the shape memory alloy member2is kept in a state where the shape memory alloy member2is not slackened. By the above described configuration, the shape memory alloy member2is not slackened, and the position of the bending member84is stably determined.

The bending member84constitutes a bending means which bends the shape memory. alloy member2. A part of the circumferential surface of the bending member84contacting the shape memory alloy member2constitutes a contact portion of the bending means that contacts the shape memory alloy member2. The base83constitutes a holding means which holds the bending member84.

In the above described configuration, when the energizing circuit7causes a current to flow through the shape memory alloy member2, the shape memory alloy member2is heated and contracted, so that the bending member84(and the holding frame85) is displaced in the direction of an arrow C resisting the force of the resilient member4. When the energization of the shape memory alloy member2is stopped, the shape memory alloy member2is expanded to its original length, and the bending member84(and the holding frame85) is displaced in the direction of an arrow D due to the force of the resilient member4. Here, although the direction of the movement of a movable body (the bending member83and the holding frame85) shown by arrows C and D is aligned with the direction of the gravity, the direction is not necessarily aligned with the direction of the gravity, as long as the movable body3is able to smoothly move in the direction indicated by the arrows C and D. Further, in this embodiment, the bending member84uses an approximately cylindrical member having contact portions54aon a circumferential surface thereof. However, as was described with reference toFIG. 21(Embodiment 6), it is possible to freely design the shape of the bending member84such as oval shape, rounded triangle or the like, according to the conditions of the driving device81.

As described above, according to the driving device81of this embodiment, it is possible to suppress the decrease in the amount of displacement of the movable body (bending member84and holding frame85). Further, by using the shape memory alloy member2whose entire length is long, it is possible to obtain a large driving force and to accomplish the downsizing of the driving device81.

FIGS. 25(a) and (b) are perspective views showing a driving device91according to Embodiment 10 of the present invention, as seen from different directions. This driving device91is different from the driving device41of the Embodiment 5 in that a pin93is further provided on a housing44for further bending a shape memory alloy member92, in addition to the projections44aand44b. In the driving device91, parts in common with the driving device41of Embodiment 5 are assigned the same reference numerals.

As shown inFIG. 25(a), the housing44is provided on, for example, a placing surface43aof a base43. The projections44aand44bdescribed in Embodiment 5 are formed on the corners of this housing44. In addition, the pin93(protrusion) is planted on the side surface of the housing44as shown inFIG. 25(b).

An end (fixed end) of the shape memory alloy member92is fixed to a wall portion43bof the base43. The shape memory alloy member92is wound around the projections44aand44bso that each winding angle is 90 degrees, then bent by the pin93at 180 degrees, and again wound around the projections44aand44bso that each winding angle is 90 degrees. The other end (movable end) of the shape memory alloy92is fixed to the movable body3.

The housing44with the projections44aand44bconstitutes a bending means which bends the shape memory alloy member92. Portions of the circumferential surfaces of the projections44aand44bcontacting the shape memory alloy member92constitutes a contact portion of the bending means that contacts the shape memory alloy member92. The base43constitutes a holding means which holds the housing44with the projections44aand44b.

In the above described configuration, the movable body3can be displaced by causing a current to flow through the shape memory alloy member92by means of the energizing circuit7so that the shape memory alloy member92is heated and contracted.

The driving device91according to this embodiment has the pin93and the protruding portions44aand44b, so that the shape memory alloy member92is wound around a pair of projections44aand44band the pin93in five turns (90 degrees and 180 degrees). Therefore, the shape memory alloy member92whose entire length is long can be disposed in a small space. Additionally, since a part of the housing44constituting the driving device91can be utilized, the downsizing of the driving device can be accomplished, while the decrease in the amount of displacement of the movable body3can be suppressed and the space efficiency can be enhanced.

FIG. 26is a perspective view showing a driving device151according to Embodiment 11 of the present invention. This driving device151is different from the driving device41(FIGS. 12 and 13) of Embodiment 5 in that minute convex portions153are formed on the circumferential surfaces of projections152aand152bof a housing152. In the driving device151, parts in common with the driving device41of Embodiment 5 are assigned the same reference numerals.

In the driving device41, the housing152is provided on, for example, a placing surface43aof a base43. The projections152aand152bare formed on corners of the housing152and project in directions perpendicular to each other. Minute convex portions153are formed on the circumferences of the projections152aand152b, and elongated in the vertical direction. An end (movable end) of the shape memory alloy member42is fixed to the wall portion43bof the base43, and the shape-memory alloy member42is wound around the projections152band152a(in contact with the convex portions153) so that each winding angle is 90 degrees. The other end (fixed end) of the shape memory alloy member42is fixed to a movable body3.

The housing152with the projections152aand152bconstitutes a bending means which bends the shape memory alloy member42. Convex portions153of the projections152aand152bconstitute a contact portion of the bending means that contacts the shape memory alloy member42. The base43constitutes a holding means which holds the housing152.

In the above described configuration, the movable body3can be displaced by causing the direct current to flow through the shape memory alloy member42by means of the energizing circuit7so that the shape memory alloy member42is heated and contracted.

When the shape memory alloy member42is to be bent, it is necessary to prevent the stress concentration caused by the rapid change of the stress, and to prevent a bent habit to thereby enhance a reliability. For this purpose, the diameters of the projections152aand152b(in the case where the projections152aand152bhave circular-arc cross sections) are preferably from 20 to 40 times the diameter of the shape memory alloy member42. However, in such a case, a contact length with which the shape memory alloy member42contacts the projections152aand152bincreases, and therefore there is a possibility that the amount of displacement may decrease compared with the case in which the shape memory alloy member42is linearly disposed.

However, in this embodiment, the convex portions153are formed on the projections152aand152bin the direction perpendicular to the winding direction of the shape memory alloy member42, so that the contact length between the shape memory alloy member42and the projections152aand152b(the convex portions153) is short. Therefore, even when the diameters of the projections152aand152bare set to be large, it is possible to prevent the decrease in the amount of displacement of the shape memory alloy member42.

FIG. 27is a plan view showing an experimental method for verifying the effect by the provision of the convex portions153. As shown inFIG. 27, in this experiment, the shape memory alloy member2with the crimp contacts120fixed to both ends thereof is wound around a bending member155aat 360 degrees. The crimp contact120at an end (movable end) is fixed to a resilient member4, and the crimp contact120at the other end (fixed end) is fixed to the fixing pin121(FIG. 7(a)). The other end of the resilient member4is fixed to another fixing pin121(FIG. 7(a)). The energizing circuit105(FIG. 7(a)) causes a current to flow between two fixing pins121. The shape memory alloy member2has a length of 50 mm, and a diameter of 60 μm. The length C of the shape memory alloy member2from the bending member155ato the fixing pin121on the fixed end is set to be about 8 mm. Moreover, the tension of about 392×10−3N is applied to the shape memory alloy member2on a normal condition (when the shape memory alloy member2is not energized). Under such a condition, when the direct current of 140 mA flows through the shape memory alloy member2, the amount of displacement (for example, the amount of displacement of the crimp contact120connected to the resilient member4) of the movable end of the shape memory alloy member2is measured.

The bending member155ais a rectangular column having a square cross section with projections156formed on the four corners, and each projection156has a circular-arc cross section. The projections156correspond to the projections152aand152bof the driving device151(FIG. 26) of Embodiment 11. By measuring the amount of displacement when the shapes of the projections156is varied, it is possible to determine the tendency of the change in the amount of displacement when the respective shapes are adopted to the projections152aand152b(FIG. 26).

FIGS. 28(a) and (d) show plan views showing the respective shapes of the bending members155athrough155dused in this experiment. The bending member155athrough155dare made of POM.

The bending member155ashown inFIG. 28(a) is a rectangular column having an approximately square cross section, and the projections156(having a radius R of 3.3 mm) are formed on four corners of the rectangular column. Concaves having a depth t of 0.2 mm are formed between the projections156. The ratio of the length of four projections156contacting the shape memory alloy member2with respect to the entire circumferential length of the bending member155a, i.e., the contact ratio is 66%. Each projection156is in the form of sector whose central angle θ is 90 degrees. In the experiment using this bending member155a, the amount of displacement of the movable end of the shape memory alloy member2is 1.16 mm, and the ratio (i.e., the displacement ratio) thereof to the amount of displacement on the same condition in the case where the shape memory alloy member2is linearly disposed (2.1 mm) is 55.2%.

The bending member155bshown inFIG. 28(b) is a rectangular column with an approximately square cross section, and the projections156(having a radius R of 1.6 mm) are formed on four corners of the rectangular column. Concaves having a depth t of 0.2 mm are formed between the projections156. The ratio of the length of four projections156contacting the shape memory alloy member2with respect to the entire circumferential length of the bending member155b(the contact ratio) is 33%. In the experiment using this bending member155b, the amount of displacement of the movable end of the shape memory alloy member2is 1.48 mm, and the displacement ratio thereof to the amount of displacement in the case where. the shape memory alloy member2is linearly disposed (2.1 mm) is 70.5%.

The bending member155cshown inFIG. 28(c) is made by forming two concaves having a depth t of 0.2 mm (so as to form three convex portions156a) on each projection156of the bending member155ashown inFIG. 28(a). The ratio of the length of the convex portions156aof four projections156contacting the shape memory alloy member2with respect to the entire circumferential length of the bending member155c(the contact ratio) is 33%. In the experiment using this bending member155c, the amount of displacement of the movable end of the shape memory alloy member2is 1.38 mm, and the displacement ratio thereof to the amount of displacement in the case where the shape memory alloy member2is linearly disposed (2.1 mm) is 65.7%.

The bending member155dshown inFIG. 28(d) is made by forming four concaves having a depth t of 0.2 mm (so as to form five convex portions156b) on each projection156of the bending member155ashown inFIG. 28(a). The ratio of the length of the convex portions156bof four projections156contacting the shape memory alloy member2with respect to the entire circumferential length of the bending member155c(the contact ratio) is 33%. In the experiment using this bending member155d, the amount of displacement of the movable end of the shape memory alloy member2is 1.42 mm, and the displacement ratio thereof to the amount of displacement in the case where the shape memory alloy member2is linearly disposed (2.1 mm) is 67.6%.

The result of the above described experiment is shown in Table 3 andFIG. 29. InFIG. 29, the vertical axis indicates the displacement ratio H (%). Marks a, b, c, and d of a horizontal axis respectively indicate the experiment results when the bending members155a,155b,155c, and155d(FIG. 28(a) through (d)) are used.

As seen from the experimental result shown in Table 3 andFIG. 29, it is understood that the amount of displacement of the movable body (the movable end of the shape memory alloy member2) increases, as the contact. ratio of the shape memory alloy member decreases. Therefore, in driving device151(FIG. 26), it is understood that the amount of displacement of the movable body3can be increased by forming the convex portions153on the projections152aand152bso as to reduce the ratio of the contact portion contacting the shape memory alloy member42to the entire circumferential length.

As described above, according to the driving device151of this embodiment, since the minute convex portions153are formed on the projections152aand152bcontacting the shape memory alloy member42, the amount of displacement of the movable end of the shape memory alloy member42can be increased, and the stress concentration on the shape memory alloy member42can be prevented, so that the bent habit can be prevented.

FIG. 30is a perspective view showing the driving device161according to Embodiment 12 of the present invention. The driving device161is different from the driving device51(FIG. 14) according to Embodiment 6 of the present invention in that a bending member162having projections162bis in the form of a multangular column. In the driving device161, parts in common with the driving device51of Embodiment 6 are assigned the same reference numerals.

As shown inFIG. 30, the bending member2is planted on a placing surface13aof a base13, and has a plurality of projections162b(contact portion) on the circumferential surface thereof. An end (fixed end) of the shape memory alloy member2is fixed to a wall portion13c, and the shape memory alloy member2is wound around the circumferential surface of the bending portion162so that the total of bending angles at the respective projections162bis 360 degrees. The other end (movable end) of the shape memory alloy member2is fixed to a movable body3.

The bending member162constitutes a bending means which bends the shape memory alloy member2. Portions of the circumferential surface of the bending member162contacting the shape memory alloy member2constitutes a contact portion of the bending means contacting the shape memory alloy member2. The base13constitutes a holding means which holds the bending member162.

In the above described configuration, the movable body3can be displaced by causing a current to flow through the shape memory alloy member2by means of the energizing circuit7so that the shape memory alloy member2is heated and contracted.

In the above described Embodiment 6 (FIGS. 14 through 20), it has been described that the decrease in the amount of displacement of the shape memory alloy member2can be suppressed by reducing the contact ratio of the shape memory alloy member2contacting the bending member54. However, if the bending member54is made of resin, as a contact width of the projection54a(a length with which the projection54acontacts the shape memory alloy member2) decreases, there is a possibility that the bending member54may be molten by the heat of the shape memory alloy member2. Therefore, it is preferable to increase the contact width of each projection54aand to reduce the contact ratio, if a resin or other material which does not have high heat resistance property is used as the bending member54. In this respect, the experiment using the bending members of various sectional shapes will be described.

FIG. 31is a perspective view of a main part of an experimental arrangement. As shown inFIG. 31, in this experiment, a crimp contact120is fixed to an end (fixed end) of the shape memory alloy member2, and the crimp contact120is also fixed to a fixing pin121. Another crimp contact120is fixed to another end (movable end) of the shape memory alloy member2, and the crimp contact120is fixed to another fixing pin121via a resilient member4. The shape memory alloy member2has a length of 50 mm and a diameter of 60 μm. The tension applied to the shape memory alloy member2is about 392×10−3N when the shape memory alloy member2is not energized.

When a direct current of 140 mA flows through the shape memory alloy member2, the amount of displacement of the movable end (for example, the amount of displacement of the crimp contact120fixed to the resilient member4) of the shape memory alloy member2is measured.

FIG. 32(a) through (d) are plan views for illustrating the experiments using four kinds of bending members162through165. In the experiment shown inFIG. 32(a), the bending member162in the form of a column having an approximately triangular cross section is used. In the experiment shown inFIG. 32(b), the bending member163in the form of a column having an approximately rectangle cross section is used. In the experiment shown inFIG. 32(c), the bending member164in the form of a column having an approximately hexagonal cross section is used. In the experiment shown inFIG. 32(d), the bending member165in the form of a cylinder having an approximately circular cross section is used. The bending members162through165are made of POM. In each case, the distance C from the bending portion162through165to the fixed end of the shape memory alloy member2is 8 mm.

FIGS. 33 through 36are plan views showing the concrete sectional shapes of the bending members162through165.

The bending member162shown inFIG. 33(a) is a triangular column with projections162ahaving a radius R of 0.5 mm formed on the respective corners thereof, and the contact ratio is 10%. The interval S between the adjacent projections162ais 9.4 mm. The bending member162shown inFIG. 33(b) is a triangular column with projections162bhaving a radius R of 1.6 mm formed on the respective corners thereof, and the contact ratio is 33%. The interval S between the adjacent projections162bis 9.4 mm. The bending member162shown inFIG. 33(c) is a triangular column with projections162chaving a radius R of 2.5 mm formed on the respective corners thereof, and the contact ratio is 50%. The interval S between the adjacent projections162cis 5.2 mm. The bending member162shown inFIG. 33(d) is a triangular column with projections162dhaving a radius R of 3.3 mm formed on the respective corners thereof, and the contact ratio is 66%. The interval S between the adjacent projections162dis 3.6 mm. The above describedFIGS. 29 and 30show the cases in which the bending members shown inFIGS. 33(a) through (d) are used.

Similarly, the bending member163shown inFIG. 34(a) is a rectangular column with projections163ahaving a radius R of 0.5 mm formed on the respective corners thereof, and the contact ratio is 10%. The interval S between the adjacent projections163ais 7.1 mm. The bending member163shown inFIG. 34(b) is a rectangular column with projections163bhaving a radius R of 1.6 mm formed on the respective corners thereof, and the contact ratio is 33%. The interval S between the adjacent projections163bis 5.3 mm. The bending member163shown inFIG. 34(c) is a rectangular column with projections163cehaving a radius R of 2.5 mm formed on the respective corners thereof, and the contact ratio is 50%. The interval S between the adjacent projections163cis 3.9 mm. The bending member163shown inFIG. 34(d) is a rectangular column with projections163dhaving a radius R of 3.3 mm formed on the respective corners thereof, and the contact ratio is 66%. The interval S between the adjacent projections163dis 2.7 mm.

Similarly, the bending member164shown inFIG. 35(a) is a hexagonal column with projections164ahaving a radius R of 0.5 mm formed on the respective corners thereof, and the contact ratio is 10%. The interval S between the adjacent projections164ais 4.7 mm. The bending member164shown inFIG. 35(b) is a hexagonal column with projections164bhaving a radius R of 1.6 mm formed on the respective corners thereof, and the contact ratio is 33%. The interval S between the adjacent projections164bis 3.6 mm. The bending member164shown inFIG. 35(c) is a hexagonal column with projections164chaving a radius R of 2.6 mm formed on the respective corners thereof, and the contact ratio is 50%. The interval S between the adjacent projections164cis 2.6 mm. The bending member164shown inFIG. 35(d) is a hexagonal column with projections164dhaving a radius R of 3.3 mm formed on the respective corners thereof, and the contact ratio is 66%. The interval S between the adjacent projections164dis 1.8 mm.

The bending member165shown inFIG. 36(a) is a cylinder having a diameter D of 10 mm, and the contact ratio is 100%. The bending member165shown inFIG. 35(b) is a cylinder having a diameter D of 10 mm on which 20 projections165bhaving a width W1of 0.52 mm are formed at a pitch of 1.56 mm, and the contact ratio is 33%. The width W2of the groove between the adjacent projections165bis 1.05 mm. The bending member165shown inFIG. 35(c) is a cylinder having a diameter D of 10 mm on which 20 projections165chaving a width W1of 0.78 mm are formed at a pitch of 1.56 mm, and the contact ratio is 50%. The width W2of the groove between the adjacent projections165cis 0.78 mm. The bending member165shown inFIG. 35(d) is a cylinder having a diameter D of 10 mm on which20projections165dhaving a width W1of 1.05 mm are formed at a pitch of 1.56 mm, and the contact ratio is 66%. The width W2of the groove between the adjacent projections165dis 0.52 mm.

Using these bending members162through165, the displacement of the movable end of the shape memory alloy member2is measured as shown inFIGS. 32(a) through (d). The result is shown in Table 4 andFIG. 37. InFIG. 37, the vertical axis indicates the displacement ratio H, and the horizontal axis indicates the contact ratio S (%). Moreover, inFIG. 37, marks a, b, c and d respectively indicate the results of the experiments shown inFIGS. 32(a), (b), (c) and (d).

Based on Table 4 andFIG. 37, it is understood that the amount of displacement of the shape memory alloy member2does not depend on the shape of the bending members162through165(triangular column, rectangular column or the like), but depends on the contact ratio S. Further, it is understood that the amount of displacement becomes larger, as the contact ratio S becomes smaller. Therefore, it is understood that it is preferable to chose the bending member162(FIG. 33) having a triangular cross section with small number of sides, in order to increase the amount of displacement of the shape memory alloy member2and to increase the width of the contact portion (for preventing the melting due to the heat of the shape memory alloy member2).

As described above, according to the driving device161(FIG. 30) of this embodiment, since the bending member is approximately in the form of a multangular column, it is possible to suppress the decrease in the amount of displacement of the movable body3and to chose the width of the contact portion so as to prevent the melting. Thus, the melting of the projection of the bending member can be prevented, while the decrease in the amount of displacement of the movable body3can be suppressed and the space efficiency can be enhanced. That is, the downsizing of the driving device can be accomplished.

FIG. 38 and 39are views for illustrating a fixing method (a crimping method) of a shape memory alloy member202and a crimp contact208. The crimp contact208is used for fixing an end of the shape memory alloy member202to a resilient member (for example, the resilient member4shown inFIG. 1), a fixing pin or the like.

As shown inFIG. 38(a), the crimp contact208is composed of a plate-like member made of metal. The crimp contact208has a base portion208bapproximately in the form of oblong, a ring portion208cformed on an end in the longitudinal direction of the base portion208b, and crimp portions208aformed on both sides in the width direction of the base portion208b. An end of the shape memory alloy member202is placed on almost the center of the base portion208bof the crimp contact208, and then the crimp portions208aare bent as shown inFIG. 38(b), so that the shape memory alloy member202and the crimp contact208are fixed (crimped) to each other. Moreover, as shown inFIG. 38(c), it is also possible to wind the shape memory alloy member202around one of the crimp portions208a, and then bend the crimp portion208aas shown inFIG. 38(d).

In this embodiment, as shown inFIG. 39, the energizing circuit207causes a current to flow between the crimp contact208and the shape memory alloy member202. The energizing circuit207is connected to an arbitrary position on the crimp contact208(including a part202bof the shape memory alloy member202fixed to the crimp contact208) and to a position202aon the shape memory alloy member202close to the crimp contact208. The energizing circuit207causes the current (excess current) to flow through the shape memory alloy member202, and the current is sufficient for heating the shape memory alloy member202to a temperature at which the shape memory alloy member202loses the memory of the shape. Therefore, on the crimp contact208side of the shape memory alloy member202with respect to the above described position202a, the memory of the shape is lost.

The effect of this embodiment is as follows. If the shape memory alloy member202is simply fixed to the crimp contact208, the reliability of the fixed part of the shape memory alloy member202and the crimp portion208amay decreases when the shape memory alloy member202is repeatedly expanded and contracted due to the heating and cooling caused by the energizing (or the change in an environmental temperature). In such a case, there is a possibility that the shape memory alloy member202may be dropped out of the crimp portion208aor may be cut. In this embodiment, the part202bof the shape memory alloy member202fixed to the crimp contact208loses its memory of shape so that the part202bis not expanded or contracted, utilizing the characteristics that the shape memory alloy member202loses its memory of shape when the shape memory alloy member202is heated to a predetermined temperature or higher. As a result, it is possible to enhance the reliability of the connection of the shape memory alloy member202and the crimp portion208a, and to prevent that the shape memory alloy member202from being dropped out of the crimp contact208or being cut.

FIG. 40is a perspective view showing a driving device211according to Embodiment 14 of the present invention. The driving device211shown inFIG. 40has pin-shaped bending members215a,215b,215cand215dplanted on a base216so that the bending members215a,215b,215cand215dare disposed on four apexes of quadrangle. On the base216, fixing pins219aand219bare planted in this order from the side closer to the bending member215a. A shape memory alloy member212in the form of a wire is wound around the bending members215a,215b,215cand215d. A crimp contact218ais fixed to an end (fixed end) of the shape memory alloy member212, and the crimp contact218ais fixed to the fixing pin219a. A crimp contact218bis fixed to the other end (free end) of the shape memory alloy member212, and the crimp contact218bis fixed to an end of a resilient member214. The other end of the resilient member214is fixed to the fixing pin219b. Among the bending members215athrough215d, the energizing circuit217is connected to the bending member215awhich is the closest from the fixed end (the crimp contact218a) of the shape memory alloy member212and to the bending member215dwhich is the closest from the movable end (the crimp contact218b). Other configuration is the same as Embodiment 1.

Here, the bending members215athrough215dconstitute a bending means which bends the shape memory alloy member212. Portions of the circumferential surfaces of the bending members215athrough215dcontacting the shape memory alloy member212constitute a contact portion of the bending means contacting the shape memory alloy member212. The base216constitutes a holding means which holds the bending members215athrough215d.

In the above described configuration, the movable body (the crimp contact218b) can be displaced by causing the current to flow through the shape memory alloy member212via the bending members215aand215bby means of the energizing circuit217, so that the shape memory alloy member212is heated and contracted. The current flows through a part of the shape memory alloy member212between the bending member215aand the bending member215d, and does not flow through the crimp contacts218aand218bat both ends of the shape memory alloy member212. Therefore, parts of the shape memory alloy member212fixed to crimp portions218cof the crimp contacts218aand218bare not expanded or contracted. As a result, the connection between the crimp contacts218aand218band the shape memory alloy member212is enhanced.

In order to verify the effect of this embodiment, a comparative example shown inFIG. 41(a) will be described. In a driving device211a, a shape memory alloy member212is linearly disposed, and crimp contacts218aand218bare fixed to both ends of the shape memory alloy member212. One crimp contact218ais fixed to a fixing pin219aplanted on a base126, the other crimp contact218bis fixed to an end of a resilient member214. The other end of the resilient member214is fixed to a fixing pin219bplanted on the base216. A wiring portion217a(for example, a cable) of the energizing circuit217is connected to a fixed end (the crimp contact218a) and a movable end (the crimp contact218b) of the shape memory alloy member212. The movable body (the crimp contact218b) is displaced by causing the current to flow through the shape memory alloy member212by means of the energizing circuit217.

However, in such a driving device211a, the crimp contact218bto which the wiring portion217aof the energizing circuit217is connected moves, and therefore it is necessary to provide a space or the like so as to prevent an unnecessary external force from being exerted on the movable body (the crimp contact218b). Further, there is a possibility that the reliability of the electrical connection (by soldering) between the wiring portion217aand the crimp contact218bmay decrease.

Further, in a driving device211bshown inFIG. 41(b), the shape memory alloy member212is bent in V-shape. Crimp contacts218are fixed to both ends of the shape memory alloy member212, and the crimp contacts218are fixed to two fixing pins219aplanted on the base216. A movable body213is fixed to a bent portion of V-shape of the shape memory alloy member212. The movable body213is fixed to an end of a resilient member214, and the other end of the resilient member214is fixed to another fixing pin219bplanted on the base216. An energizing circuit217is connected to two fixing pin219a, and supplies a current to the shape memory alloy member212via the fixing pins219aand the crimp contacts218.

However, in such a driving device211b, the current flows through the crimp contacts218, and therefore portions of the shape memory alloy member212fixed to the crimp contacts218are repeatedly expanded and contracted, with the result that the reliability of the connecting portion may decrease. Therefore, the problems such as the dropping of the shape memory alloy member212out of the crimp contacts218and the cutting of the shape memory alloy member212may easily occur.

In contrast, in the driving device211of this embodiment, the wiring portions of the energizing circuit217can be connected to the bending members215aand215d, and therefore it is possible to prevent the movable body (the crimp contact218b) from being influenced by the wiring portions. Therefore, it is not necessary to provide a space or the like around the wiring portions. Thus, it becomes possible to simplify the configuration of the driving device211, and to accomplish the downsizing of the driving device211. Further, since the current does not flow through the crimp contacts218aand218b, the portions of the shape memory alloy member212fixed to the crimp contacts218aand218bis not expanded or contracted. Therefore, the reliability of the connection between the crimp contacts218aand218band the shape memory alloy member212is enhanced.

FIG. 42is a perspective view showing a configuration of a driving device221aaccording to Embodiment 15 of the present invention. In the above described Embodiment 14 (FIG. 40), the current is supplied through the bending members215dand215arespectively closest from the movable end and the fixed end of the shape memory alloy member212. In this embodiment, an electric potential V1is applied to a bending member225aclosest to the fixed end (the crimp contact228a) of the shape memory alloy member222, and its adjacent bending member225bis grounded. Further, an electric potential V2is applied to a further adjacent bending member225c, and the bending member225dclosest to the movable end (the crimp contact228b) of the shape memory alloy member222is grounded. The electric potential V1is applied to a pin229ato which the crimp contact228ais fixed, so that a current does not flow through the crimp contact228a. Other configuration is the same as Embodiment 14.

The bending members225athrough225dconstitute a bending means which bends the shape memory alloy member222. Portions of the circumferential surfaces of the bending members225athrough225dcontacting the shape memory alloy member222constitute a contact portion of the bending means contacting the shape memory alloy member222.

In the above described configuration, the current flows through a section of the shape memory alloy member222from the bending member225cto the bending member225b, a section from the bending member225cto the bending member225d, and a section from the bending member225ato the bending member225b. As a result, each section of the shape memory alloy member222is heated and contracted, so that the movable body (the crimp contact228b) is displaced.

That is, the current does not flow uniformly throughout the shape memory alloy member222, but flows respective sections independently. The resistance to the current flowing through the respective sections of the shape memory alloy member222is smaller than the case where the current flows uniformly. Therefore, even in the case of obtaining the same current to that of Embodiment 14, the required voltage can be reduced.

Further, it becomes possible to select a portion through which the current flows. For example, by setting the voltage applied to the bending member225ato 0, the current flows through two sides of the shape memory alloy member222(between the bending members225band225cand between the bending members225cand225d). With such an arrangement, only a portion of the shape memory alloy member202through which the current flows is expanded and contracted, and therefore it becomes to chose the amount of the displacement of the movable body (the crimp contact228b).

In a configuration in which the amount of displacement is varied by causing the current flows partially in the longitudinal direction of the shape memory alloy member, the method of electrical supply by supplying electricity via the contact between the shape memory alloy member and the electric supply member such as pins (here, the bending members225athrough225b) is effective. There is another considerable method in which lead wires are attached to the shape memory alloy member. However, in such a case, it is necessary to attach a multiple lead wires in order to increase the variation of the amount of displacement. Thus, in order to prevent the shape memory alloy member from being influenced by the external force, it is necessary to provide a large space for disposing the lead wires, and therefore the downsizing of the driving device becomes difficult. Further, if crimp contacts are used (in the case where the reliability of the soldering of the shape memory alloy member is not high), there is a problem that a large space is needed as the number of the crimp contacts increases. In contrast, in this embodiment, the method of supplying electricity via pin-shaped bending members225athrough225dcontacting the shape memory alloy member222is employed, it is not necessary to attach a multiple lead wires. Therefore, it is possible to enable the selection of the amount of displacement, and to accomplish the downsizing of the driving device.

In this embodiment, the shape memory alloy member222is wounded around the pin-shaped bending members225athrough225d(electrical supply members) at about 90 degrees for each. However, the winding angle is not limited to about 90 degrees. Further, the bending members225athrough225are not limited to the pin-shape. Further, spring contacts or other contacts can be used to connect the shape memory alloy member222and the electrical supply members for electrical supply. With these arrangement, it is possible to accomplish the downsizing of the driving device.

Moreover, as shown inFIG. 43, in the case where the shape memory alloy member222is wound around the bending members225athrough225din a plurality of turns, the current flows the same sections (between the bending members225aand225b) of the shape memory alloy member222in parallel. Therefore, it is possible to provide the same electrical supply as the case in which the shape memory alloy member222is wound around the bending members225athrough225din one turn (FIG. 42). Further, since the entire length of the shape memory alloy member222can be increased, it is possible to obtain a sufficient amount of displacement of the movable body (the crimp contact228b) even when the deriving device221bis downsized.

As described above, according to this embodiment, since the current flows through the respective sections of the shape memory alloy member222, it becomes possible to suppress the voltage to be low, and to enable the choosing of the amount of displacement of the movable body. Particularly, in a portable terminal such as a mobile phone device in which the available voltage is generally limited to be low, the driving device according to this embodiment (operable at low voltage and suitable for downsizing) is greatly valuable.

FIG. 44is a perspective view showing a driving device231aaccording to Embodiment 16 of the present invention. In the above described Embodiment 14, the current flows uniformly throughout the entire length of the shape memory alloy member212. In contrast, in this embodiment, the current varies with sections of the shape memory alloy member232. This is based on the consideration that a friction load applied to the shape memory alloy member232due to the contact with the other components (in addition to the urging force of the resilient member234) varies according to the position in the longitudinal direction of the shape memory alloy member232.

An experiment providing the basis of this embodiment will be described. In the experiment shown inFIG. 45, the shape memory alloy member232in the form of a wire is wound around a cylindrical bending member235having a contact ratio of 33%. An energizing circuit237causes a current to flow only a straight portion of the shape memory alloy member232(a portion not wound around the bending member235). The length of the energized portion of the shape memory alloy member232is set to be 50 mm. An end (fixed end) of the energized portion of the shape memory alloy member232is fixed to the fixing pin239a. The amount of displacement of the other end (a movable end233) of the energized portion is measured. Instead of a resilient member, a weight234awhich weighs 30 g is fixed to the movable end of the shape memory alloy member232in order to prevent the change of the load. The bending member235is made of POM, and is an approximately cylindrical member having a diameter of 10 mm whose contact ratio is 33% as shown inFIG. 36(b). In order to evaluate the influence of the friction load by winding the shape memory alloy member232around the bending member235, the experiment is carried out in a state where the shape memory alloy member232is wound around the bending member235in one turn (360 degrees), two turns (720 degrees) and three turns (1080 degrees). As the number of windings increases, the friction load becomes large. Table 5 andFIG. 46show the result of the measurement of the amount R of displacement of the above described movable end233when the current value is varied from 60 mA to 180 mA. InFIG. 46, the vertical axis indicates the amount R (mm) of displacement of the above described movable end233of the shape memory alloy member232, and the horizontal axis indicates a current I (mA) flowing through the shape memory alloy member232. Moreover, marks a, b and c respectively correspond to data when the shape memory alloy member232is wound in one turn (360 degrees), two turns (720 degrees), and three turns (1080 degrees).

Based on Table 5 andFIG. 46, in the case (a) where the shape memory alloy member232is wound in one turn, it is understood that there is an extreme point at about 80 mA of current I, and the amount R of displacement does not change greatly when the current exceeds 80 mA. Moreover, in the case (b) where the shape memory alloy member232is wound in two turns, it is understood that there is an extreme point at about 100 mA of current I, and the amount R of displacement does not change greatly when the current exceeds 100 mA. In the case (c) where the shape memory alloy member232is wound in three turns, it is understood that there is an extreme point at about 160 mA of current, and the amount R of displacement does not change greatly when the current exceeds 160 mA. Based on this result, it is understood that it is possible to suppress the power consumption of the driving device231, and to obtain the almost maximum amount of displacement, by choosing the optimum current according to the frictional force.

Based on this result, the driving device231aaccording to this embodiment will be described. As shown inFIG. 44, in the driving device231aaccording to this embodiment, four bending members235a,235b,235cand235dare disposed on a base236respectively on positions corresponding to four tops of a rectangle. Inside the bending members235athrough235d, four bending members235e,235f,235gand235hare disposed. Inside the bending members235ethrough235h, four bending member235i,235j,235kand235lare disposed. At a substantial center of the base236, a thirteenth bending member235mand a fixing pin239bare disposed.

The shape memory alloy member232in the form of a wire is wound around the total thirteen bending members235athrough235mon the base236. That is, the shape memory alloy member232is wound around the most outside bending members235athrough235d, then wound around the inside bending members235ethrough235h, then wound around further inside bending members235ithrough235l, and bent at the bending member235m. A crimp contact239dis fixed to an end (fixed end) of the shape memory alloy member232, and the crimp contact239dis fixed to an end of a resilient member234in the vicinity of the outer periphery of the base236. The other end the resilient member234is fixed to a fixing pin239aplanted on the base236.

The bending member235athrough235mconstitute a bending means which bends the shape memory alloy member232. Portions of the circumferential surfaces of the bending members235athrough235mcontacting the shape memory alloy member232constitute a contact portion of the bending means contacting the shape memory alloy member232. The base236constitutes a holding means which holds the bending members235athrough235m.

An electric potential Va is applied to the bending member235aclosest to the movable end of the shape memory alloy member232. The bending member235eat a position where the shape memory alloy member232is wound in one turn with respect to the bending member235ais grounded. In addition, an electric potential Vb is applied to the bending member235iat a position where the shape memory alloy member232is wound in two turns with respect to the bending member235a. The bending member235kat the position where the shape memory alloy member232is wound in two turns and half is grounded. An electric potential Vc is applied to the bending member235mclosest to a fixed end of the shape memory alloy member232. As a result, a current Ia flows through the section from the bending member235ato the bending member235eof the shape memory alloy member232. A current Ib flows through the section from the bending member235ito the bending member235e. Moreover, a current Ic flows through the section from the bending member235ito the bending member235k. A current Id flows through the section from the bending member235mto the bending member235k. A conductive coil spring is used as the resilient member234so that the same voltage (Va) as the bending member235ais applied to the fixing pin239a, in order to prevent the current from flowing through the crimp contact239c. Moreover, the same voltage (Vc) as the bending member235mis applied to the fixing pin239b, in order to prevent the current from flowing through the crimp contact239d. Since the current does not flow through the crimp contacts239cand239das described above, the shape memory alloy member232is not expanded and contracted at crimp portions239eof the crimp contacts239cand239d, and therefore the reliability of the connection is enhanced.

In the shape memory alloy member232, the friction load when the current flows becomes smaller, as the portion is closer to the movable end (the crimp contact239c). Moreover, as the section through which the current flows is long, the amount of displacement caused by the same current is large, and therefore the necessary current becomes small with regard to the same friction load. In the section from the bending member235ato the bending member235e(the section where the current Ia flows), the friction load is larger and the section length is shorter, compared with the section from the bending member235eto the bending member235i(the section where the current Ib flows), and therefore the current Ib is set larger than the current Ia. Referring to the experiment result ofFIG. 46, the current Ia is set to, for example, 80 mA, and the current Ib is set to, for example, 100 mA. Further, in the section from the bending member235ito the bending member235k(the section where the current Ic flows), the friction load is larger and the section length is shorter, compared with the section from the bending member235eto the bending member235i(the section where the current Ib flows), and therefore the current Ic is set larger than the current Ib. Furthermore, in the section from the bending member235mto the bending member235k(the section where the current Id flows), the friction load is larger and the section length is almost the same, compared with the section from the bending member235ito the bending member235k(the section where the current Ic flows), and therefore the current Id is larger than or equals to the current Ic. Referring to the experiment result ofFIG. 46, the current Ic and Id are set to, for example, 160 mA.

As described above, by changing the value of the current flowing through the shape memory alloy member232in consideration of the friction load according to the winding position of the shape memory alloy member232, it is possible to suppress a power consumption, and to obtain the maximum amount of displacement.

In the configuration shown inFIG. 44, although the movable end239c(and the resilient member234) is disposed on the outermost side, the fixed end239dcan be disposed on the outermost side and the movable end239con the innermost side. However, it is possible to obtain larger displacement at a low power consumption, when the movable end239cis disposed on the outermost side. This is because, when the movable end239cis disposed on the outermost side, the length of the outer portion of the shape memory alloy member232becomes longer (and therefore the amount of displacement becomes larger), and the summation of the load applied by the resilient member234and the friction load applied by the bending members becomes relatively small (with respect to the amount of displacement), so that the required current for obtaining the desired amount of displacement can be reduced.

FIG. 47is a perspective view showing another example of electric supply according to this embodiment. In the example shown inFIG. 47, the bending member235ais grounded, and an electric potential Va is applied to the bending member235cat a position where the shape memory alloy member232is wound a half. Similarly, the bending member235eat a position where the shape memory alloy member232is wound in one turn is ground. An electric potential Vb is applied to the bending member235gof the position where the shape memory alloy member232is wound in one turn and a half. In addition, the bending member235iat a position where the shape memory alloy member232is wound in two turns is grounded. An electric potential Vc is applied to the bending member235kat a position where the shape memory alloy member232is wound in two turns and half. In addition, the bending member235iat a position where the shape memory alloy member232is wound in three turns is grounded. As a result, the current Ia flows from the bending member235cto the bending member235a, and the current Ib flows from the bending member235cto the bending member235e. Moreover, the current Ic flows from the bending member235gto the bending member235e, and the current Id flows from the bending member235gto the bending member235i. In addition, the current Ie flows from the bending member235kto the bending member235i, and the current If flows from the bending member235kto the bending member235m. The values of the respective current can be set as Ia≦Ib≦Ic≦Id≦Ie≦If. For example, based on the experimental result ofFIG. 46, the current Ia and the current Ib can be set to about 80 mA, the current Ic and the current Id can be set to about 100 mA, and the current Ie and the current If can be set to about 160 mA. In the example shown inFIG. 47, both of a constant voltage circuit and a constant current circuit can be used as a power supply circuit.

Moreover, instead of causing the current Ia through If to flow, it is possible to cause the current to partially flow. With respect to the entire length of the shape memory alloy member232, a part where the current flows and a part where the current does not flow can be selectable, so that the amount of the displacement of the shape memory alloy member232can be varied.

FIG. 48is a perspective view showing a driving device231caccording to this embodiment. The energizing circuit237chas constant current circuits238a,238band238c. A terminal of the constant current circuit238ais connected to the bending member235m, and the other terminal of the constant current circuit238ais connected to the bending member235a. A terminal of the constant current circuit238bis connected to the bending member235m, and the other terminal of the constant current circuit238bis connected to the bending member235e. A terminal of the constant current circuit238cis connected to the bending member235m, and the other terminal of the constant current circuit238cis connected to the bending member235i. Between the bending member235mand the bending member235i, the constant current circuits238a,238band238ccause the current Ia+Ib+Ic to flow. Between the bending member235iand the bending member235e, the constant current circuits238aand238bcause the current Ia+Ib to flow. Between the bending member235eand the bending member235a, the constant current circuits238acauses the current Ia to flow. That is, in the shape memory alloy member232, the current flowing between the bending member235mand the bending member235iis the largest, the current flowing between the bending member235iand the bending member235eis the second largest, and the current flowing between the bending member235eand the bending member235ais the smallest. In concrete, considering the experimental result ofFIG. 46, the largest current (Ia+Ib+Ic) can be set to 160 mA, the second largest current (Ia+Ib) can be set to 100 mA, and the smallest current (Ia) can be set to 80 mA. In this case, the current Ib can be set to 20 mA, and the current Ic can be set to 60 mA.

FIG. 49is a block diagram of the energizing circuit237cshown inFIG. 48. As shown inFIG. 49, an entire length L of the shape memory alloy member232(the length from the bending member235ato the bending member235m) is set to be 15 mm. The length L3between the bending members235aand235eof the shape memory alloy member232, the length L2between the bending members235eand235i, and the length L1between the bending members235iand235mare respectively set to 5 mm. The resistance of the shape memory alloy member232is set to 0.5 Ω/mm. If the current Ia+Ib+Ic (160 mA) flows between the bending member235mand the bending member235iof the shape memory alloy member232, the current Ia+Ib (100 mA) flows between the bending member235iand the bending member235e, and the current Ia (80 mA) flows between the bending member235eand the bending member235a,the entire power consumption is 0.105 W. In contrast, in a block chart of a comparative example shown inFIG. 50, when a constant current 160 mA flows throughout the entire length L (15 mm) of the shape memory alloy member232, the power consumption is 0.192 W. Base on this result, it is understood that it becomes possible to decrease the power consumption to 55% by separately supplying the current as shown inFIG. 49.

FIG. 51is a circuit diagram for illustrating the constant current circuits238athrough238cshown inFIG. 48. In the constant current circuit238c, a resistance238d(R0) is a current value detection resistance. When the current238e(IC) flows through the resistance238d(R0), the potential difference of Ic×R0is caused between both ends of the resistance238d(R0) This potential difference is an input voltage to a minus input terminal238gof an operational amplifier238f. Moreover, an input voltage (reference voltage) to a plus input terminal238jof the operational amplifier238fis determined by a resistance238h(R1) and a variable resistance238i(VR). The operational amplifier238foperates to change the electric potential of a G-terminal238lof an FET (field-effect transistor)238k, and to adjust the current flowing from a D-terminal238m to a S-terminal238nso that the electric potential of the minus input terminal238gof the operational amplifier238fis the same as the electric potential of the plus input terminal238j. As a result, the electric potential of the minus input terminal238gof the operational amplifier238fbecomes constant, and the current (Ic=V/R0)238ebecomes constant, irrespective of the resistance of the shape memory alloy member232. The constant current circuits238aand238boperate in a similar manner to the constant current circuit238c.

The constant current circuit238athough238care described as being sink-type circuits, but not limited to this. It is possible to use a source-type circuit. In this case, a ground electric potential is applied to the bending member235mclosest to the fixed end of the shape memory alloy member2, and the directions of the respective currents Ia, Ib and Ic are opposite to those shown inFIG. 49.

As described above, according to this embodiment, since the current flows through the respective portions of the shape memory alloy member232in accordance with the friction load or the like, it becomes possible to obtain a large amount of displacement at a small power consumption.

FIG. 52is a perspective view showing a configuration of a driving device241aaccording to Embodiment 17 of the present invention. In the above described Embodiments 14 through 16, the shape memory alloy member is wound around a plurality of pin-shaped bending members, and the current is supplied to the shape memory alloy member via the bending members. In this embodiment, the pin-shaped bending members are further mechanically and electrically connected to an electric circuit board.

As shown inFIG. 52, in the driving device241a, pin-shaped bending members245a,245b,245cand245dare planted on an electric circuit board249in such a manner that the bending members245a,245b,245cand245dare mechanically connected to the electric circuit board249. Further, among the bending members245a,245b,245cand245d, at least the bending members245aand245dare electrically connected to the electric circuit board249. Between the bending members245aand245d, fixing pins249aand249bare planted in this order from the side closer to the bending member245a.

An end (fixed end) of the shape memory alloy member242is fixed to a fixing pin249aby means of a crimp contact248a, and the shape memory alloy member242is wound around the bending member245a,245b,245cand245dat 90 degrees for each. The other end (movable end) of the shape memory alloy member242is fixed to an end of the resilient member244by means of a crimp contact248b, and the other end of the resilient member244is fixed to the fixing pin249b. Other configuration is the same as Embodiment 14.

The bending members245athrough245dconstitute a bending means which bends the shape memory alloy member242. Portion of the circumferential surfaces of the bending members245athrough245dcontacting the shape memory alloy member242constitute a contact portion of the bending means contacting the shape memory alloy member242. The electric circuit board249constitutes a holding means which holds the bending members245athrough245d.

In the above described configuration, the movable body (the crimp contact248b) can be displaced by causing the current to flow through the shape memory alloy member242by means of the electric circuit board249via the bending members245aand245dso that the shape memory alloy member242is heated and contracted.

According to this embodiment, the bending members245athrough245dare held by the electric circuit board249, and therefore it is not necessary to provide a separate base. Thus, the number of components can be reduced, with the result the downsizing of the driving device can be easily accomplished. Particularly, if this driving device241ais applied to the above described Embodiments 14 through 16 (FIGS. 40,42through44and47through48), it becomes possible to form the energizing circuit (for example, the energizing circuit237ofFIG. 40or the energizing circuit217cofFIG. 48) on the electric circuit board249. Therefore, it becomes easy to supply electricity to the bending members215,225and235(FIGS. 40,42through44and47through48). Moreover, since the bases216,226and236(FIGS. 40,42through44and47through48) can be composed of the electric circuit board249, the number of components can be reduced, and the downsizing of the driving device can be easily accomplished.

FIG. 53is a perspective view showing another configuration example of the driving device according to this embodiment. In the driving device241bshown inFIG. 53, the bending members245a,245b,245cand245dare planted on the base246. Between the bending members245aand245d, the fixing pins249aand249bare planted in this order from the side closer to the bending member245a. An end (fixed end) of the shape memory alloy member242is fixed to the fixing pin249aby means of the crimp contact248a, and the shape memory alloy member242is wound around the bending member245a,245b,245cand245dat abut 90 degrees for each. The other end (movable end) of the shape memory alloy member242is fixed to an end of a resilient member244by means of a crimp contact248b, and the other end of the resilient member244is fixed to the fixing pin249b.

In the driving device241bshown inFIG. 53, in addition, an electric circuit board249is provided on the side opposite to the base246with respect to the shape memory alloy member242. The bending members245athrough245dare mechanically connected to the electric circuit board249. The pin-shaped bending members245athrough245dengage four penetration holes punched on the electric circuit board249. Moreover, among the bending members245athrough245d, the bending members245aand245dneeded for energizing the shape memory alloy member242are electrically connected to electric circuit board249. It is also possible to connect all bending members245athrough245dto the electric circuit board249electricity and mechanically.

In the above described driving device241aofFIG. 52, the bending members245athrough245dare connected to the electric circuit board249. Therefore, when the driving force generated by the expansion and contraction of the shape memory alloy member242is relatively small, the bending members245athrough245dcan be stably held. However, when the driving force generated by the expansion and contraction of the shape memory alloy member242is relatively large, it is difficult to stably hold the bending members245athrough245d, and therefore the reliability of the electric connection may decrease. In contrast, according to the driving device241bshown inFIG. 53, the bending member245athrough245dare held by the base246, and therefore it is possible to stably hold the bending members245athrough245dby designing the base246according to the load exerted on the bending members245athrough245d. Moreover, the mechanical connection of the electric circuit board249and the bending members245athrough245dhelps the electric circuit board249to hold the bending members245athrough245d, and therefore it is possible to stably hold the bending members245athrough245deven when the force exerted on the bending members245athrough245dis relatively large. Moreover, by placing the electric circuit board249on the side opposite to the base246with respect to the shape memory alloy member242, it is possible to prevent the shape memory alloy member242from dropping out of the bending members245athrough245d.

In the case of the driving device241b, it is also possible to use a seat-like flexible board, so-called the FPC (Flexible Printed Circuit) board, because the electric circuit board249is not needed to have a strength.

FIG. 54is a perspective view showing the configuration of a driving device251according to Embodiment 18 of the present invention. In the above described Embodiments 14 through 17, the shape memory alloy member is wound around the pin-shaped bending members (for example, the bending members215athrough215dshown inFIG. 40). In contrast, in the driving device251according to this embodiment, a shape memory alloy member252is wound around a bending member252composed of a structural body made of a non-conductive member (for example, a plastic) on which a conductive member is formed.

As shown inFIG. 54, the driving device251has a bending member255made by forming four approximately cylindrical projections255athrough255don four corners of a structural body255emade of an insulation material (for example, a plastic) in the form of, for example, a quadrangular column. On a surface of the projections255aand255dside of the bending member255, fixing members258band258aare formed in this order from the side closer to the projection255a. An end (fixed end) of the shape memory alloy member252is fixed to the fixing member258bof the bending member255, and the shape memory alloy member252is wound around the projections255a,255b,255cand255dat 90 degrees for each. The other end (movable end) of the shape memory alloy member252is fixed to an end of the resilient member254via a movable body253, and the other end of the resilient member254is fixed to the fixing member258a.

The bending member255has a conductive member259aon the projection255aclosest from the fixed end of the shape memory alloy member252, and has another conductive member259bon the projection255dclosest from the movable end of the shape memory alloy member252. An energizing circuit257is connected to the conductive members259aand259b. The energizing circuit257causes the current to flow through the shape memory alloy member252via the conductive members259aand259b, so that the shape memory alloy member252is heated and the movable member253fixed to the movable end is displaced. Although the energizing circuit257is illustrated to be apart from the bending member255inFIG. 54, it is possible to form the energizing circuit257on the surface of the bending member255, and to form a solid circuit board.

The bending member255having the projections255athrough255dconstitute a bending means which bends the shape memory alloy member252. Portions of the circumferential surfaces of the projections255athrough255dcontacting the shape memory alloy member252constitute a contact portion of the bending means contacting the shape memory alloy member252. The bending member255constitutes a holding means which holds the projections255athrough255d.

In the above described configuration, the movable body253can be displaced by causing the current to flow through the shape memory alloy member252by means of the energizing circuit257via the bending members259aand259bso that the heating shape memory alloy member252is heated and contracted.

According to this embodiment, since the shape memory alloy member252is wound around the contact portions258athrough258dintegrally formed with the bending member255, it is possible to enhance the rigidity of the contact portions258athrough258d. Therefore, even when a load applied to the contact portions258athrough258dis large, it is possible to prevent the deformation of the contact portions258athrough258d, and to enhance the reliability of the electrical connection between the conductive members259aand259band the energizing circuit257. Particularly, compared with the case in which the shape memory alloy member252is wound around pin-shaped bending members (for example,FIG. 52), the strength of the mechanical connection between the energizing circuit257and the conductive members259aand259bis high, and the reliability of the electrical connection is high. Further, since the energizing circuit257is formed on the bending member255to form a solid circuit, it is not necessary to employ a configuration in which the pin-shaped bending members245athrough245dis sandwiched between the base246and the electric circuit board249ashown inFIG. 53. As a result, it is possible to accomplish the downsizing of the driving device, while maintaining the reliabilities of the electrical connection and the mechanical connection.

FIG. 55is a perspective view showing the configuration of a driving device261aaccording to Embodiment 19 of the present invention. In the driving device261ashown inFIG. 55, a bending member265arespectively in the form of a cylinder having minute convex portions265eon the circumferential surface thereof is rotatably supported on a base266. An end (fixed end) of a shape memory alloy member262is fixed to a fixing pin269a provided on the base266, and the shape memory alloy member262is wound around the bending member265aat about 180 degrees in such a manner that the shape memory alloy member262contacts the convex portions265eof the bending member265a. The other end (movable end) of the shape memory alloy member262is fixed to an end of a resilient member264via a movable body263, and the other end of the resilient member264is fixed to a fixing pin269bplanted on the base266. The energizing circuit267is connected with the fixing pins269aand269b. Other configuration is the same as Embodiment 1.

The bending member265aconstitutes a bending means which bends the shape memory alloy member262. Portions of the convex portions265eof the bending member265acontacting the shape memory alloy member262constitutes a contact portion of the bending means contacting the shape memory alloy member262. The base266constitutes a holding member for holding the bending member265a.

In the above described configuration, the movable body263can be displaced by causing the current to flow through the shape memory alloy member262by means of the energizing circuit267via the fixing pins269aand269bso that the shape memory alloy member262is heated and contracted.

FIGS. 56(a) through (c) are perspective views showing experimental arrangements261b,261cand261dfor verifying the effect of the driving device261a. In the experimental arrangement261bshown inFIG. 56(a), a wire-shaped memory alloy member262is wound around a cylindrical bending member265bhaving a diameter of 10 mm which is not rotatable and which has no convex portions. An end (fixed end) of the shape memory alloy member262is fixed to a fixing pin269a, and a weight264a which weighs 50 g is fixed to the other end (movable end) of the shape memory alloy member262. When the energizing circuit267causes a direct current of 140 mA to flow through an area of the shape memory alloy member262including a portion wound around the bending member265b, the amount of displacement of the movable end of the shape memory alloy member262is measured. In the experimental arrangement261cshown inFIG. 56(b), a cylindrical bending member265chaving a diameter of 10 mm which has no convex portion is rotatably supported on the base266, and the other conditions are the same as those of the experimental arrangement261bofFIG. 56(a). In the experimental arrangement261dshown inFIG. 56(c), a bending member265dhaving a diameter of 10 mm which has convex portions265eon the circumferential surface thereof is rotatably supported on the base266, and the other conditions are the same as those of the experimental arrangement261bofFIG. 56(b). The contact ratio of the bending member25(ratio of a length with which the convex portion265econtacts the shape memory alloy member262with respect to an entire circumferential length of the bending member265d) is 33%. The bending members261b,261cand261dshown inFIGS. 56(a) through (c) are made of POM.

Using the experimental apparatuses shown inFIGS. 56(a) through (c), the amount of displacement on a movable end of the shape memory alloy member262is measured on condition that the winding angle is set to 360 degrees (one turn), 450 degrees (1 turn and half) and 720 degrees (two turns). A further experiment is carried out on condition that the rotation of the bending member265dis locked in the experimental arrangement261dshown inFIG. 56(c). The result thereof is shown in Table 6 andFIG. 57. InFIG. 57, the vertical axis indicates a displacement ratio H (%), and the horizontal axis indicates a winding angle θ (degrees). InFIG. 57, the mark a indicates the data when the non-rotatable cylindrical bending member265b(FIG. 56(a)) is used. The mark b indicates the data when the rotatable cylindrical bending member265c(FIG. 56(b)) is used. The mark c indicates the data when the non-rotatable bending member (not shown) having a contact ratio of 33% (FIG. 56(c)) is used. The mark d indicates the data when the rotatable bending member265bhaving a contact ratio of 33% (FIG. 56(c)) is used.

Based onFIG. 57, it is understood that, when the rotatable bending member265c(the mark b) is used instead of the non-rotatable bending member265b(the mark a), the displacement of the shape memory alloy262increases approximately 1.2 to 1.5 times. Moreover, when the rotatable bending member265d(the mark d) having the contact ratio of 33% is used, the displacement of the shape memory alloy262increases approximately 2.7 to 3.2 times.

Based on the above described result, according to this embodiment, it becomes possible to increase the amount of displacement of the movable body263by using the rotatable bending member261ahaving convex portions on the circumferential surface thereof. While the driving devices having wire-shaped shape memory alloy members wound around pulleys are disclosed in Japanese Laid-Open Patent Publication Nos. HEI 8-776743 and HEI 10-148174, it becomes possible to obtain a large amount of displacement by forming convex portions on these pulleys so as to reduce the contact ratio.

The rotatable bending member is not limited to a cylindrical shape, but can be in the form of a polygonal column such as a triangular column as was described in Embodiment 12, and further can be made of a plurality of pins disposed along a closed path.

FIG. 58is a perspective view showing the configuration of a driving device271aaccording to Embodiment 20 of the present invention. The driving device271aaccording to this embodiment is different from the driving device261a(FIG. 55) according to Embodiment 19 in that a shape memory alloy member272is wound around a pin279cplanted on a circumferential surface of the bending member275a.

As shown inFIG. 58, the driving device271ahas a rotatable bending member275ain the form of an approximately cylindrical shape having a lot of minute convex portions275eformed on the circumferential surface thereof. On the circumferential surface of this bending member275a, a pin (protrusion)279cis provided, in addition to the convex portion275e. The pin279cprotrudes in the radial direction of the bending member275a, in addition to the convex portion275e. An end (fixed end) of the shape memory alloy member272in the form of a wire is fixed to a fixing pin279bon a base276by means of a crimp contact278b. The shape memory alloy member272is wound around bending member275aat, for example, 360 degrees. Moreover, the shape memory alloy member272is also wound around the pin279cat, for example, 360 degrees while the shape memory alloy member272is wound around the bending member275a. The other end (movable end) of the shape memory alloy member272is fixed to an end of a resilient member274by means of a crimp contact278a, and the other end of resilient member274is fixed to a fixing pin279aformed on the base276.

The bending member275aconstitutes a bending means which bends the shape memory alloy member272. The pin279cconstitutes a protrusion that protrudes from the bending member275aso that the shape memory alloy member272is wound around the pin279c. Portions of the convex portions275eof the bending member275acontacting the shape memory alloy member272constitute a contact portion of the bending means contacting the shape memory alloy member272. The base276constitutes a holding means which holds the bending member275a.

In the above described configuration, the movable body (the crimp contact278a) can be displaced by causing the current to flow through the shape memory alloy member272by means of an energizing circuit277so that the shape memory alloy member272is heated and contracted. With this, the bending member275aalso rotates. When the current flowing through the shape memory alloy member272is stopped, the shape memory alloy member272is cooled and expanded to its original length, so that the movable body (the crimp contact278a) returns to its original position, and the bending member275areturns to its original rotational position.

Although the above described Embodiment 19 (FIG. 55) is effective when the rotational position of the bending member265can be arbitrary as a pulley, this embodiment is effective when the rotational position of the bending member265is limited.

FIG. 59is a perspective view showing an experimental arrangement271bfor measuring the amount of displacement of the movable body of the driving device271aaccording to Embodiment 20. The experimental arrangement271bincludes a bending member275brotatably provided on a base276, and the bending member275bhas convex portions and a pin279con the circumferential surface thereof. The contact ratio of the bending members275bis 33%. An end (fixed end) of the shape memory alloy member272is fixed to a fixing pin279bfixed to the base276by means of a crimp contact278b. The shape memory alloy member272is wound around the bending member275bat about 360 degrees, then wound around the pin279cat about 360 degrees, and further wound around the bending member275bat about 360 degrees. The other end (movable end) of the shape memory alloy member272is fixed to an end of a resilient member274composed of a coil spring by means of a crimp contact278a, and the other end of the resilient member274is fixed to a fixing pin279aplanted on the base276. An energizing circuit277is connected to the fixing pins279aand279b, so that a current flows through the shape memory alloy member272via the fixing pins279aand279b. The shape memory alloy member272has a diameter of about 60 μm and a length of about 83 mm. The urging force of the resilient member274is about 392×10−3N when the shape memory alloy member272is not energized. The current caused to flow through the shape memory alloy member272by means of the energizing circuit277is 140 mA. The length c of the shape memory alloy member272from the bending member275bto the crimp contact278ais about 1.5 mm.

Using the experimental arrangement shown inFIG. 59, the amount of displacement of the crimp contact278a(when the energizing is carried out by the energizing circuit277) is measured. Additionally, the amount of displacement is measured also in the case where the shape memory alloy member272is not wound around the pin279c, or in the case where the rotation of the bending member275bis locked. The result thereof is shown in Table 7 andFIG. 60. InFIG. 60, the vertical axis indicates the displacement ratio H (%). In the horizontal axis, the mark b indicates data in the case where the shape memory alloy member272is wound around the pin279cas shown inFIG. 59. The mark a indicates data in the case where the shape memory alloy member272is not wound around the pin279c. The mark c indicates data in the case where the rotation of the bending member275bis locked (the shape memory alloy member272is not wound around the pin279c).

Based onFIG. 60, it is understood that it is possible to obtain the almost same amount of displacement when the shape memory alloy member272is wound around the pin279c(mark b) and when the shape memory alloy member272is not wound around the pin279c(mark a). Moreover, it is understood that in both of these cases (marks a and b), it is possible to obtain a larger amount of displacement than in the case where the rotation of the bending member275bis locked (mark c). That is, it is understood that the decrease in the amount of displacement due to the winding of the shape memory alloy member272around the pin279c(i.e., the fixing of the shape memory alloy member272to the bending member275) is very small, and almost the same advantage as Embodiment 19 can be obtained.

As described above, according to this embodiment, it is possible to obtain the same advantage as Embodiment 19 even in the case where the rotational position of the bending member275is limited (not arbitrary).

The rotatable bending member275ais not limited to the cylindrical shape, but may be in the form of a polygonal column such as a triangular column as was described in Embodiment 12. In such a case, it is possible to obtain the same advantage.

FIG. 61(a) is a perspective view of a configuration example (referred to as a driving device281a)in the case where the driving devices1,11,21and31(FIGS. 1,2and9through11) are applied to a lens drive in a camera. The camera to which this driving device281ais applied has a cylindrical barrel286aand a circuit board289dprovided on a side (rear side) of the barrel286aopposite to an object. A lens283e(FIG. 64(a)) is fixed to a tip of the barrel286a. A lens283b(FIG. 64(a)) held by a lens frame283ais provided in the barrel286a. The lens frame283ais movably supported by guide axes283cand283d(FIG. 64(a)) along an optical axis X of the lens. A part of the lens frame283apenetrates a groove axially formed on the barrel286aand projects outward. Moreover, the circuit board289dhas a solid state image sensing device289c(FIG. 64(a)) at a position where the image is focused by lens283eand283b.

On the circumferential surface of the barrel286a, a plurality of pin-shaped bending members285are planted. These bending members285are disposed at intervals in a circumferential direction of the barrel286a. The bending member285has a main part that projects in the radial direction of the barrel286aand an orthogonal member that projects from the main part in the direction almost parallel to the axial direction of the barrel286a.

An end (fixed end) of a shape memory alloy member282in the form of a wire is fixed to a fixing member289bin the vicinity of the rear end of the barrel286a. The shape memory alloy member282turns around the barrel286aalmost in one turn in such a manner that the shape memory alloy member282is wound around the bending members285, and further extends in the axial direction of the barrel286a. The other end (movable end) of the shape memory alloy member282is fixed to the rear end of the above described lens frame283a. An end of a resilient member284is fixed to a front end of the lens frame283a, and the other end of this resilient member284is fixed to a fixing member289aprovided in the vicinity of the front end of the barrel286a. An energizing circuit287is connected to both ends of the shape memory alloy member282.

When the energizing circuit287causes the current to flow through the shape memory alloy member282to heat the shape memory alloy member282, the shape memory alloy member282is contracted resisting the urging force of the resilient member284, so that the lens frame283amoves rearward (direction of an arrow A). When the energizing of the shape memory alloy member282is stopped, the shape memory alloy member282is cooled and expanded to its original length, so that the lens frame283amoves frontward (direction of an arrow B) by means of the urging force of the resilient member284. As a result, the lens283b(FIG. 64(a)) moves in the direction of the optical axis X, and, for example, a zooming operation or a focusing operation is carried out.

As constructed above, it becomes possible to dispose the shape memory alloy member282whose entire length is long (i.e., a amount of displacement is large) around the barrel286awithout increasing the length of the barrel286aof the camera. Moreover, since the shape memory alloy member282is wound around the pin-shaped bending members285, it is possible to reduce the ratio of the length with which the shape memory alloy member282contacts the bending members285to the entire circumferential length of the barrel286a(i.e., a contact ratio). As a result, it is possible to reduce the decrease in the amount of displacement, compared with the case in which the shape memory alloy member282is linearly disposed.

FIG. 61(b) is a perspective view showing a configuration example (referred to as a driving device281b)in the case where the driving device51(FIG. 14)of Embodiment 6 is applied to the lens drive of the camera. In this driving device281b, a large number of convex portions285bsimilar to the convex portions54a(FIG. 14) described in Embodiment 6 are formed in the circumferential direction of the barrel286a. Only one bending member285a, for example, is formed on the rear side of the lens frame283a. An end (fixed end) of the shape memory alloy member282is fixed to a fixing member289b, and the shape memory alloy member282is wound around the barrel286ain almost one turn in such a manner that the shape memory alloy member282contacts the convex portions285b, and then the shape memory alloy member282is wound around the bending member285aat about 90 degrees. The other end (movable end) of the shape memory alloy member282is fixed to the lens frame283a. Each convex portion285bis elongated in the axial direction of the barrel286a. Other configuration is the same as the driving device281ashown inFIG. 61(a).

Using the driving device281b, it becomes possible to dispose the shape memory alloy member282whose entire length is long (i.e., a amount of displacement of the movable end is large) around the barrel286awithout increasing the length of the barrel286aof the camera. Moreover, since the shape memory alloy member282is wound around the bending member285aand the convex portion285b, it is possible to reduce the ratio of the length with which the shape memory alloy member282contacts the bending member285aand the convex portions285bto the entire circumferential length of the barrel286a(i.e., a contact ratio). As a result, it is possible to reduce the decrease in the amount of displacement, compared with the case in which the shape memory alloy member282is linearly disposed.

FIG. 62(a) is a perspective view showing a configuration example (referred to as a driving device281c)in the case where the driving device261a(FIG. 55)of Embodiment 18 is applied to the lens drive of the camera. In this driving device281c, a cylindrical ring285cis provided on the circumference of the barrel286a, and the cylindrical ring285cis rotatable in the circumferential direction of the barrel286a. A number of convex portions285bdescribed with reference toFIG. 61(b) are formed on a circumference of the cylindrical ring285cat intervals in the circumferential direction of the cylindrical ring285c. An end (fixed end) of the shape memory alloy member282is fixed to a fixing member289b. The shape memory alloy member282is wound around the cylindrical ring285cin almost one turn in such a manner that the shape memory alloy member282contacts the convex portions285b, and then the shape memory alloy member282is wound around the bending member285aat about 90 degrees. The other end (movable end) of the shape memory alloy member282is fixed to the lens frame283a. The cylindrical ring285chas a cutaway portion285fin order not to interfere with the fixing member289bwhen the cylindrical ring285crotates. Other configuration is the same as the driving device281bshown inFIG. 61(b).

According to this driving device281c, the contact ratio is small and the cylindrical ring285cis rotatable, and therefore it is possible to increase the amount of displacement of the shape memory alloy member282as was described in Embodiment 18.

FIG. 62(b) is a perspective view showing a configuration example (referred to as a driving device281d)in the case where the driving device271a(FIG. 58)of Embodiment 19 is applied to the lens drive of the camera. In this driving device281d, the pin-shaped bending member285eis planted on the circumferential surface of the cylindrical ring285d, and is located behind the bending member285aplanted on the circumferential surface of the barrel286a. The shape memory alloy member282is wound around the convex portions285bto turn around the cylindrical ring285cin ¼ turn, and then wound around the bending member285e. The shape memory alloy member282is further wound around the convex portions285bto turn around the cylindrical ring285cin almost one turn, and-then bent by the bending member285at 90 degrees. Other compositions are the same as those of the driving device281cshown inFIG. 62(a).

According to the driving device281d, the positional relationship between the shape memory alloy member282and the cylindrical ring285dis regulated by the pin-shaped bending member285e, and therefore the rotational position of the cylindrical ring285ddoes not deviate even if the shape memory alloy member282is repeatedly expanded and contracted. Therefore, it is possible to keep constant the positional relationship between the fixing member289bthat fixes the fixed end of the shape memory alloy member282and the cutaway portion285fof the cylindrical ring285d.

FIGS. 63(a) and (b) are a perspective view and a front view showing a configuration example (referred to as a driving device281e) in the case where the driving devices41and151of Embodiments 5 and 11 (FIGS. 12 and 26)is applied to the lens driving of the camera.FIG. 63(c) is another perspective view of the driving device281eseen from the direction different fromFIG. 63(a).

As shown inFIGS. 63(a) and (b), the driving device281ehas a bending member285gformed in the vicinity of the front end of a barrel286a, and a bending member285fformed in the vicinity of the rear end of the barrel286a. The lens frame283ais disposed between the bending members285gand285fin the axial direction of the barrel286a. A bending member285his formed on and projects from the circumferential surface of the barrel286a, and is located on a further front position with respect to the bending member285g. A number of minute convexes are formed on the circumferential surfaces of the bending members285g,285fand285h, which contact the shape memory alloy member282. On the circumferential surface of the barrel286a,a fixing member289bis disposed on a position shifted from the lens frame283ain the circumferential direction of the barrel286a. A fixing member289ais provided between the lens frame283aand the bending member285g. A resilient member284is provided between the fixing member289aand the lens frame283a.

An end (fixed end) of the shape memory alloy member282is fixed to the fixing member289b(FIG. 63(c)). The shape memory alloy member282is led frontward from the fixing member289bin the axial direction of the barrel286a. In the vicinity of the front end of the barrel286a, the shape memory alloy member282is bend by the bending member285gat about 180 degrees, and is led rearward almost in the axial direction of the barrel286a. Moreover, the shape memory alloy member282is wound by the bending member285fat about 180 degrees in the vicinity of the rear end of the barrel286a, and is led frontward almost in the axial direction of the barrel286a. The other end (movable end) of the shape memory alloy member282is fixed to the lens frame283a. As shown inFIG. 63(b), where the shape memory alloy member282is wound around the bending member285gat 180 degrees, the shape memory alloy member282also contacts the bending member285h, so that the shape memory alloy member282does not contact the circumferential surface of the barrel286a.

According to the driving device286a, it is possible to dispose the shape memory alloy member282whose entire length is long (i.e., the amount of displacement of the movable end is large) around the barrel286awithout increasing the length of the barrel286aof the camera. Moreover, because the shape memory alloy member282is wound around the bending member285h,285g, and285fhaving minute convex portions on the outer sides thereof, it is possible to suppress the decrease in the amount of displacement.

In the above described Embodiment 12, it has been described that, if the bending member is in the form of a polygonal column, an almost triangular column (whose cross section is almost triangle) is preferable. However, if the bending member is not in the form of the polygonal column, the configuration in which the shape memory alloy member is wound around two bending members is advantageous in terms of reducing the contact ratio (to thereby suppress the decrease in the amount of displacement) while keeping the contact length between one bending member and the shape memory alloy member as was described in Embodiment 3. The above described driving device281eis an example of such a configuration being applied to the lens driving.

Next, in order to facilitate the understanding of the effect of the driving device according to this embodiment, a configuration example in the case where a driving device in which a shape memory alloy member is linearly disposed is used for driving the lens in the camera will be described.

FIGS. 64(a) and (b) are a side sectional view and a perspective view showing the configuration example (referred to a driving device281f) in the case where the driving device in which the shape memory alloy member2is linearly disposed is used for driving the lens of the camera. In this driving device281f, an end (fixed end) of a shape memory alloy member282is fixed to a fixing member289bprovided in the vicinity of the rear end of the barrel286aand the other end (movable end) of the shape memory alloy member282is fixed to a lens frame283a. A fixing member289ais provided in the vicinity of the front end of the barrel286a, and a resilient member284is provided between the fixing member289aand the lens frame283a. An energizing circuit287is connected to both ends of the shape memory alloy member282. However, in such a configuration, because the shape memory alloy member282is linearly disposed on the barrel286a, only a shape memory alloy member282whose entire length is short can be provided in the camera whose length is short in the direction of the barrel286a. Moreover, if the shape memory alloy member282whose entire length is short is provided, there is a problem that a sufficient driving distance of the lens283bcan not be obtained, since the amount of displacement of the shape memory alloy member282is about 3 through 5% with respect to the entire length of the shape memory alloy member282.

In contrast, according to the driving device281a(FIG. 61(a)) of this embodiment and the driving devices281bthrough281e(FIGS. 61(b) through63(c)) of other example of this embodiment, the shape memory alloy member282whose entire length is long can be wound around the circumferential surface of the barrel286aby means of the bending member285(or the bending members285athrough285h). Therefore, even in a small-sized camera, there is an advantage that a sufficient driving length of the lens283bis ensured by using the shape memory alloy member282whose entire length is long.

In the above described Embodiments 1 through 21, although the shape memory alloy member is heated and deformed by causing the direct current to flow through the shape memory alloy member, the embodiments are not limited to this. It is also possible to use an alternating current instead of the direct current. Moreover, it is possible to cause a pulse current to flow through the shape memory alloy member to heat the shape memory alloy member as disclosed in Japanese Laid-Open Patent Publication No. HEI 6-324740, and it is possible to use a heater to heat the shape memory alloy member as disclosed in Japanese Laid-Open Patent Publication No. HEI 6-32296. Furthermore, it is possible to use other components to heat the shape memory alloy member, as disclosed in Japanese Laid-Open Patent Publication No. HEI 5-224136. Further, it is possible to heat the shape memory alloy member by means of a change in environmental temperature, as disclosed in Japanese Laid-Open Patent Publication Nos. 2000-318698, HEI 5-118272, 2003-28337, HEI 7-14376 and HEI 8-179181.

Moreover, in a configuration in which the shape memory alloy member is bent by the bending member and is heated to obtain the amount of displacement, the decrease in the amount of displacement is large when the contacting part between the shape memory alloy member and the bending member is large, and the decrease in the amount of displacement is small when the contacting part between the shape memory alloy member and the bending member is small, as described above. This seems to be because, in the contacting part between the shape memory alloy member and the bending member, the heat is drawn from the shape memory alloy member via the bending member, so that the temperature increase of the shape memory alloy member is suppressed. With consideration given to this, it is effective to heat the shape memory alloy member by energizing in terms of obtaining a large amount of displacement. Moreover, in the case where the temperature increase of the bending member is slow (in the case where the heat of the shape memory alloy member does not tend to be drawn), it is also effective to heat the shape memory alloy member by means of the change in environmental temperature, an external heater and the like. In contrast, in a configuration that indirectly heats the shape memory alloy member by means of heat transfer by heating a member around which the shape memory alloy member is wound (for example, a configuration disclosed in Japanese Laid-Open Patent Publication No. HEI 5-224136), it is not possible to obtain a sufficient amount of displacement.

Besides the reduction of the contacting part between the shape memory alloy member and the bending member, it is also possible to suppress the decrease in the amount of displacement of the shape memory alloy member by using a material having a low coefficient of thermal conductivity as the bending member (or the contact portion contacting the shape memory alloy member).

Moreover, in the above described Embodiments 1 through 21, although a tension coil spring is used as a resilient member for urging the shape memory alloy member, the resilient member is not limited to this. It is also possible to use a compressive coil spring, a torsion coil spring, a plate spring, a rubber or the like. Furthermore, the resilient member is not limited to a conductive material such as metal. If a material other than the conductive material is used as the resilient member, and if the shape memory alloy member is heated by energizing, it is only necessary to energize between both ends of the shape memory alloy member. Furthermore, instead of using the resilient member, it is possible to employ various methods for urging the shape memory alloy member, for example, urging the movable body by means of gravity.