Fastening device

A fastening device includes a fastening member that fixedly fastens fastened members, and a driving member that is capable of releasing a fastening state of the fastening member by applying a driving force to a moving portion provided in the fastening member to drive it, wherein the driving member is formed of a shape memory alloy, and the driving force is a restoring force of the shape memory alloy to its memory shape.

TECHNICAL FIELD

The present invention relates to a fastening device.

Priority is claimed on Japanese Patent Application No. 2004-113231, filed Apr. 7, 2004, the content of which is incorporated herein by reference.

BACKGROUND ART

There is conventionally known a joint retaining member in which among a shaft, a header that fits on one end of the shaft and a nut that fits on the other end of the shaft, at least any one of the members is formed of a shape memory alloy, so that the joint retaining member can release the mechanical binding by shape change of the shape memory alloy in accordance with heating or cooling applied to this member (for example, refer to Patent Document 1).

Also, there is conventionally known a fastening member that is formed of a shape memory alloy molded in such a shape that fastening can be released under heating, in which the fastening member is secondarily processed into a shape capable of fastening at temperatures at which it is not reverted to the memorized shape, and a microwave absorption material or infrared absorption material is coated on the surface of the fastening member or provided inside the fastening member (for example, refer to Patent Document 2).Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2002-5124Patent Document 2: Japanese Unexamined Patent Application, First Publication No. 2003-301815

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

However, in the joint retaining member or the fastening member according to the aforementioned prior art, since the main body of the joint retaining member or the fastening member is formed of a shape memory alloy and has a relatively complicated shape, improving the efficiency of heat transfer during heating is difficult, and problems arise such as accumulation of the energy required until releasing the mechanical binding and fastening. Also, since the joint retention strength and fastening strength are restricted according to the material characteristics of the shape memory alloy, there is a risk that the desired strength cannot be ensured.

The present invention was achieved in view of the aforementioned circumstances, and has as its object to provide a fastening device that can reduce the energy required for fastening release and readily release the fastening, and can ensure the desired fastening strength.

Means for Solving the Problem

In order to solve the aforementioned problems to attain the object, the fastening device according to the present invention is provided with a fastening member that fixedly fastens fastened members, and a driving member that is capable of releasing a fastening state of the fastening member by applying a driving force to a moving portion provided in the fastening member to drive it, wherein the driving member is formed of a shape memory alloy, and the driving force is a restoring force of the shape memory alloy to its memory shape.

According to the fastening device of this constitution, providing the fastening device with the fastening member and the driving member can prevent the shapes of the members from becoming complicated compared to the case of, for example, integrating the fastening member and the driving member, and can improve the versatility of the fastening device. Also, by forming the driving member, which is capable of releasing the fastening state of the fastening member, with a shape memory alloy, the fastening member may be formed of a suitable construction material that can ensure the desired fastening strength so that the fastened members can be fixedly fastened in a suitable manner.

In the fastening device according to the present invention, presupposing the aforementioned invention, is provided with an energizing means that energizes the driving member, wherein the driving member is reverted to the memory shape by being energized by the energizing means.

According to the fastening device of this constitution, the driving member, which is formed of a shape memory alloy, is restored from a deformed state to the memory shape when the temperature rises to the transformation point of the shape memory alloy or higher by resistance heat generation from energization from the energizing means, with the moving portion being driven by the restoring force at this time to release the fastening state of the fastening member.

In the fastening device according to the present invention, presupposing the aforementioned invention, the fastening member is provided with a pin member that is attached to the fastened members, and a clip member that holds the pin member, the clip member includes two pinching members formed as the moving portion to be turnable about a turning axis, with the pin member being held so as to be pinched from both sides by the two pinching members, and the driving member releases the fastening state of the fastening member by turning the pinching members of the clip member about the turning axis.

According to the fastening device of this constitution, the fastened members to which the pin member is attached are fixedly fastened by the clip member that pinches the pin member and a nut member that is attached to one end of the pin member. The driving member releases the pinched state of the pin member by turning the two pinching members constituting the clip member in opposite directions about the turning axis so as to mutually separate, and by separating the pin member from the clip member releases the fastening state of the fastening member.

In the fastening device according to the present invention, presupposing the aforementioned invention, the fastening member is provided with a pin member that is attached to the fastened members, and a clip member that holds the pin member, the clip member includes a notch portion in which the pin member, which is the moving portion, is attached, the pin member is held by an inside wall surface of the notch portion so as to be sandwiched from both sides, the driving member presses the pin member toward an outside of the notch portion of the clip member, and the fastening state of the fastening member is released by separating the pin member from the notch portion.

According to the fastening device of this constitution, the fastened members to which the pin member is attached are fixedly fastened by the clip member that pinches the pin member and a nut member that is attached to one end of the pin member. The driving member separates the pin member from the notch portion by pressing the pin member, which is attached to the notch portion of the clip member, to the outside, thereby releasing the fastening state of the fastening member.

In the fastening device according to the present invention, presupposing the aforementioned invention, the clip member includes a holding member that holds the driving member.

According to the fastening device of this constitution, the driving member is held at the clip member, whereby due to the restoring force when the shape memory alloy of the driving member reverts from the deformed shape to the memory shape, the two pinching members constituting the clip member are turned about the turning axis, and by pressing toward the outside the pin member, which is attached to the notch portion of the clip member, can release the fastening state of the fastening member.

In the fastening device according to the present invention, presupposing the aforementioned invention, the clip member includes a restriction member that restricts driving of the moving portion.

According to the fastening device of this constitution, when the shape memory alloy of the driving member held in the clip member reverts from the deformed shape to the memory shape, excessive turning of the two pinching members constituting the clip member, and excessive deformation of the moving member in the direction that presses the pin member, which is attached to the notch portion of the clip member, outward can be prevented.

In the fastening device according to the present invention, presupposing the aforementioned invention, the pin member includes either one of a mutually fitting concave portion and convex portion, and the clip member includes the other one of the concave portion and convex portion.

According to the fastening device of this constitution, when the pin member is held in the clip member, the pin member and the clip member are firmly fixed, and the desired fastening strength can be ensured by the fitting of either one of the concave portion and convex portion provided in the pin member and either one of the concave portion and convex portion provided in the clip member.

In the fastening device according to the present invention, presupposing the aforementioned invention, the driving member is formed of a shape memory alloy in a coil shape or a U-shape, and being deformed in the fastening state of the fastening member so that a distance between two predetermined positions of the shape memory alloy becomes closer than a distance in the memory shape.

According to the fastening device of this constitution, when the shape memory alloy of the driving member reverts from the deformed shape to the memory shape, the distance between the two predetermined positions of the shape memory alloy increases, whereby the driving force acts on the moving portion provided in the fastening member so that the fastening state of the fastening member is easily released. Moreover, since the driving member has a small cross-sectional area and is formed with a simple shape, resistance heating by directly energizing the driving member is possible, and so the fastening can be readily released while reducing the electrical energy required to raise the temperature of the driving member to the transformation point of the shape memory alloy or higher compared to the case of indirect heating using a heater or the like.

Advantageous Effects of the Invention

According to the fastening device of the present invention, providing the fastening device with the fastening member and the driving member can prevent the shapes of the members from becoming complicated compared to the case of, for example, integrating the fastening member and the driving member, and can improve the versatility of the fastening device. In addition, by forming the driving member, which is capable of releasing the fastening state of the fastening member, with a shape memory alloy, the fastening member may be formed of a suitable construction material that can ensure the desired fastening strength so that the fastened members can be fixedly fastened in a suitable manner.

Furthermore, according to the fastening device of the present invention, when the shape memory alloy of the driving member held in the clip member reverts from the deformed shape to the memory shape, excessive turning of the two pinching members constituting the clip member, and excessive deformation of the moving member in the direction that presses the pin member, which is attached to the notch portion of the clip member, outward can be prevented.

Furthermore, according to the fastening device of the present invention, the pin member and the clip member are firmly fixed, and the desired fastening strength can be ensured.

Furthermore, according to the fastening device of the present invention, the fastening state of the fastening member is easily released by the restoring force when the shape memory alloy of the driving member reverts from the deformed shape to the memory shape. In addition, since the driving member has a small cross-sectional area and is formed with a simple shape, resistance heating by directly energizing the driving member is possible, and so the fastening can be readily released while reducing the electrical energy required to raise the temperature of the driving member to the transformation point of the shape memory alloy or higher compared to the case of indirect heating using a heater or the like.

DESCRIPTION OF THE REFERENCE SYMBOLS

BEST MODE FOR CARRYING OUT THE INVENTION

The first embodiment of the present invention is explained below, referring to the accompanying drawings.

A fastening device10according to the present embodiment is constituted, as shown for example inFIG. 1, by a fastening member11that fixedly fastens fastened members1, a driving member12that is capable of releasing a fastened state of the fastening member11, and an energizing device13. For example, the driving member12is formed by shape memory alloy wire (for example, 1 mm in diameter) having an insulating coating and wound into a coil. The energizing device13connected to both end portions of the driving member12is constituted by a power supply21and a switch22that controls an ON/OFF of energization from the power supply21to the driving member12.

The fastening member11is constituted, as shown for example inFIG. 2, by a clip member31, a clip restriction member32, a pin member33, and a nut34.

As for the clip member31, as shown for example inFIG. 2andFIG. 3, one end portions of two clip pieces41are turnably connected to each other via a pin42, and abutting surfaces41A thereof are formed to be abuttable when the other end portions of the two clip pieces41turn toward each other.

A notch portion41athat is approximately semicircular in plan view is formed on the abutting surface41A of each clip piece41, so that a pin member mounting hole43that is circular in plan view is formed by the notch portions41awhen the abutting surfaces41A of the two clip pieces41abut each other. The inner diameter of the pin member mounting hole43is formed to be a value that is slightly greater than an outer diameter of a reduced diameter portion33bof the pin member33described below.

Also, a projection portion41bthat projects from the top of a surface41B is formed on the other end portion of each clip piece41. Each projection portion41bof the two clip pieces41abuts the outer peripheral surface of the driving member12described below so as to sandwich the driving member12from both sides in the diameter direction. Furthermore, a bolt mounting hole44is formed in a distal end portion of each projection portion41b, and a plate-shaped holding member46disposed at a position separated from the projection portion44bby a predetermined distance is connected to a bolt45that is mounted in the bolt mounting hole44. This holding member46abuts the inner peripheral surface of the driving member12described below, so that the driving member12is sandwiched from both sides in the diameter direction by the pair of holding members46and projection portions41b.

A bend portion46athat extends toward the projection portion41bso as to cover the end portion of the driving member12mounted between the holding member46and the projection portion41bis formed in the holding member46.

An insertion hole32ais formed in the center of the plate-shaped clip restriction member32for insertion of the pin member33. Furthermore, the clip restriction member32is formed into an approximately U-shaped plate in which both end portions32bbend so as to be perpendicular to the center portion. Both end portions32bof the clip restriction member32abut the projection portions41bwhen the other end portions of the two clip pieces41of the clip member31are separated from each other by a predetermined distance so as to restrict the turning of the two clip pieces41.

As shown for example inFIG. 2, a thread portion33aon which the nut34is mounted is formed on one end portion of the pin member33, and a reduced diameter portion33bhaving a diameter reduced by one step is formed at a position shifted from the other end toward the one end. The notch portion41aof each clip piece41of the clip member31is mounted to the reduced diameter portion33b.

As shown for example inFIG. 4, the deformed shape of the driving member12, which constituted of a coil made from a shape memory alloy, is an oblong coil, while the memory shape thereof is a circular coil as shown for example inFIG. 5. When a temperature of the driving member12is less then a predetermined temperature, the driving member12assumes the deformed shape, and when the temperature of the driving member12is the predetermined temperature or higher, the driving member12reverts from the deformed shape to the memory shape.

In the clip member31on which the driving member12is mounted, as described below, the abutting surfaces41A of the two clip pieces41abut each other when the driving member12is in a deformed state, and when the driving member12reverts from the deformed shape to the memory shape, the other end portions of the two clip pieces41turn so as to separate from each other.

As shown for example inFIG. 2, each pin member insertion-hole1ain which the pin member33is inserted and through-holes1bin which both end portions32bof the clip restriction member32are inserted are formed in the plate-shaped fastened members1. In a state of both end portions32bof the clip restriction member32being inserted in the through-holes1bof the fastened members1, each pin member insertion-hole1aof the fastened members1is disposed to be coaxial with the insertion hole32aof the clip restriction member32, and the pin member insertion-holes1aare formed to be continuous while facing the insertion hole32a.

The fastening device10according to the present embodiment has the aforementioned constitution. Next, the step of fixedly fastening the fastened member1with the fastening device10and the step of releasing the fastening will be explained.

When fixedly fastening the fastened members1, at first, the both end portions32bof the clip restriction member32are inserted in the through-holes1bof the fastened members1, and the pin member insertion-hole1aof the fastened members1and the insertion hole32aof the clip restriction member32are made continuous.

Then, the pin member33is inserted in each pin member insertion-hole1aof the fastened members1and the insertion hole32aof the clip restriction member32, and the reduced diameter portion33bof the other end portion of the pin member34, as well as both end portions32bof the clip restriction member32, are made to protrude from the surface of the fastened members1.

Next, the driving member12is mounted on the fastening member11, and in the state of energization of the driving member12from the energizing device13being set to OFF, the notch portion41aof each clip piece41is mounted on the reduced diameter portion33bof the pin member33so that the reduced diameter portion33bof the pin member33is pinched from both sides by the notch portions41aof the two clip pieces41of the driving member12, while deforming the driving member12to a suitable shape by a suitable external force.

Here, the driving member12mounted on the fastening member11has an approximately circular shape, and when the driving member12is in its memory shape, the two clip pieces41of the fastening member11are set so that the other end portions thereof separate from each other. By deforming the driving member12so that the other end portions of the two clip pieces41approach each other, the driving member12deforms from the circular memory shape to the oblong deformation shape. The reduced diameter portion33bof the pin member33is mounted in the pin member mounting hole43formed by the notch portions41aby the abutting of the abutting surfaces41A of the two clip pieces41, and so relative displacement of the pin member33and the fastening member11is restricted along the axial direction of the pin member33.

As shown for example inFIG. 6, the fastened members1are fixedly fastened by attaching the nut34to the thread portion33aat the one end portion of the pin member33that protrudes from the surface of the clip restriction member32.

When releasing the fastening of the fastened members1, the switch22of the energizing device13is set to ON to start energization from the energizing device13to the driving member12. The energization causes the temperature of the driving member12to rise. When the temperature reaches a temperature equal to or greater than the transformation point of the shape memory alloy, a restoring force occurs that causes the driving member12to revert from the deformed shape to the memory shape. Due to this restoring force, the other end portions of the two clip pieces41of the fastening member11turn so as to separate from each other. As shown for example inFIG. 7, the notch portion41aof each clip piece41detaches from the reduced diameter portion33bof the pin member33, whereby the fastening of the fastened members1is released.

At this time, when the other end portions of the two clip pieces41separate from each other by a predetermined distance, as shown for example inFIG. 5, the projection portion41bof each clip piece41abuts both end portions32bof the clip restriction member32, and so excessive turning of the two clip pieces41is restricted.

As stated above, according to the fastening device10of the present embodiment, the fastening device10is constituted by the fastening member11and the driving member12, separable each other. This can prevent complication of the shapes of the members11and12compared to the case of integrally forming the fastening member11and the driving member12and can improve the versatility of the fastening device10. In addition, since the driving member12, which is capable of releasing the fastening state of the fastening member11, is formed of a shape memory alloy, the fastening member11may be formed of a suitable construction material that can ensure the desired fastening strength so that the fastened members1can be fixedly fastened in a suitable manner.

Furthermore, forming the driving member12in a coil with a simple shape can prevent an excessive increase in the electrical energy required when raising the temperature by resistance heating. Also, by altering the number of windings of the coil or the diameter of the coil, the magnitude of the restoring force when reverting from the deformed shape to the memory shape can be readily altered, and so the fastening strength and the driving force required for fastening release can be flexibly set in accordance with the place of application of the fastening device10and the fastened members1.

Furthermore, providing the clip restriction member32can prevent excessive turning of the two clip pieces41when the shape memory alloy of the driving member12that is mounted in the fastening member11reverts from the deformed shape to the memory shape.

In the above-described embodiment, the driving member12was formed with a shaped memory alloy having a coil-shaped, but it is not limited thereto. For example, it may be formed with a shape memory alloy having a suitable shape such as a U-shape.

In addition, as shown for example inFIG. 8andFIG. 9, a spring51such as a belleville spring that applies a counterforce along the axial direction of the pin member33may be provided between the clip restriction member32and the nut34. In this case, when the notch portion41aof each clip piece41detaches from the reduced diameter portion33bof the pin member33, the pin member33can be readily pulled out from the fastened members1.

The second embodiment of the present invention is explained below, referring to the accompanying drawings.

The fastening device10according to this embodiment is constituted by the fastening member11that fixedly fastens fastened members1, the driving member12that is capable of releasing the fastened state of the fastening member11, and the energizing device13, as shown for example inFIG. 10A,FIG. 10B,FIG. 11AandFIG. 11B. For example, the driving member12is formed by shape memory alloy wire (for example, 1 mm in diameter) having an insulating coating and wound into a coil. The energizing device13connected to both end portions of the driving member12is constituted by a power supply21and a switch22that controls the ON/OFF of energization from the power supply21to the driving member12.

The fastening member11is constituted by a pin holding member61, a washer62, a pin member63, and a nut64.

A notch portion61ais formed in one end portion of the plate-shaped pin holding member61, and a hook portion61cthat is bent into a hook-shaped is formed at the other end portion. The driving member12is mounted in this hook portion61c. The inner wall face of the notch portion61ais provided with a shape that follows a peripheral surface of the notch portion63bof the pin member63described below, with the notch portion63bof the pin member63being mounted thereon.

A thread portion (not illustrated) on which the nut64is mounted is formed on one end portion of the pin member64, and a concave portion63ahaving a shape that follows the outer periphery of the driving member12is formed on the other end portion. In addition, the notch portion63bis formed at a position shifted from the concave portion63atoward the one end portion.

As shown for example inFIG. 10A, a deformed shape of the driving member12, which is constituted by a coil made from a shape memory alloy, is an oblong coil, while a memory shape thereof, as shown for example inFIG. 11A, is a circular coil. When a temperature of the driving member12is less then a predetermined temperature, the driving member12assumes the deformed shape, and when the temperature of the driving member12is the predetermined temperature or higher, the driving member12reverts from the deformed shape to the memory shape.

The outer circumference side end portion of the driving member12that is mounted in the pin holding member61, during a deformed state, is disposed at a position shifted more the other end portion side of the pin holding member61than a base of the notch portion61aof the pin holding member61. When the driving member12reverts from the deformed state to a memory state, the outer circumference side end portion of the driving member12moves to a position shifted more to the one end portion side of the pin holding member61than the base of the notch portion61aof the pin holding member61.

When fixedly fastening the fastened members1by the fastening device10according to the second embodiment, first the notch portion63bof the pin member63is mounted in the notch portion61aof the pin holding member61. Thereby, relative displacement of the pin holding member61and the pin member63is restricted along an axial direction of the pin member63.

At this time, in a state of energization of the driving member12from the energizing device13being set to OFF, the outer circumference side end portion of the driving member12is pressed inward in a diameter direction by the concave portion63aof the pin member63. Thereby, the driving member12is made to deform from the circular shape that is the memory shape to the oblong shape that is the deformed shape.

As shown for example inFIG. 10B, by mounting a washer62and the nut64on the pin member63that projects from the surface of the fastened members1, the fastened members1are fixedly fastened.

On the other hand, when releasing the fastening of the fastened member1, the switch22of the energizing device13is set to ON to start energization from the energizing device13to the driving member12. The energization causes the temperature of the driving member12to rise. When the temperature reaches a temperature equal to or greater than the transformation point of the shape memory alloy, a restoring force occurs that causes the driving member12to revert from the deformed shape to the memory shape. Due to this restoring force, the pin member63mounted in the notch portion61aof the pin holding member61is pressed toward an outside of the notch portion61a. Then, as shown for example inFIGS. 11A and 11B, the notch portion63bof the pin member33detaches from the notch portion61aof the pin holding member61, whereby the fastening of the fastened members1is released.

While preferred embodiments of the invention have been described and illustrated above, it should be understood that the present invention is not limited to these embodiments and can be widely applied. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.

INDUSTRIAL APPLICABILITY

The present invention can be appropriately used for example when fastened members to be fastened which are required to be regularly fastened in a firm manner and quickly released during emergencies.