JP2007170210A - Actuator and actuator bending drive mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make compatible a large output force and a large rate of shrinkage in an actuator using a wire shrunk by external irritation such as a shape memory alloy and a polymer actuator. <P>SOLUTION: This actuator is shrunk in a predetermined shrinking direction (Y-direction) according to the shrinkage of the wire material 1 shrunk by external irritation. The wire material 1 is disposed diagonally relative to the shrinking direction. Also, the wire material has a width restraining member 3 suppressing the relative movement of both ends of the wire material 1 disposed diagonally relative to the shrinking direction in the direction (X-direction) vertical to the shrinking direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an actuator suitable for bending, for example, a joint of a robot and an actuator bending drive mechanism.

  In addition to industrial applications, robots are expected to be used in homes for the purpose of welfare, crime prevention, and housework, and many researches and developments have been conducted for that purpose. For welfare and home use, contact with humans is unavoidable, and the development of technology that enhances affinity with humans has become important. Nowadays, it is also possible to understand human language and recognize human faces. However, there has been no significant progress in robot safety and comfort for humans. The main reason for this is thought to be the delay in the development of actuators that are compatible with humans.

  As an actuator having affinity with humans, a shape memory alloy (SMA) and a polymer actuator (see, for example, Patent Document 1) are attracting attention. By using SMA or a polymer actuator, a flexible and noise-free robot actuator can be configured. However, it is difficult for SMA and polymer actuators to achieve both a large amount of deformation and a large generated force. For example, in the case of a contraction type SMA wire, the generated stress is relatively large at about 100 MPa, while the contraction rate is about 5%. And small. On the other hand, when the wire rod is coiled and the shrinkage rate is 100% or more, the generated stress is as small as about 1 MPa.

On the other hand, the example which tries coexistence with generated force and a contraction | shrinkage rate is comprised by comprising SMA in mesh shape (refer patent document 2).
JP 2005-111245 A JP 2002-48053 A

  An object of the present invention is to achieve both a large generation force and a large contraction rate in an actuator using a wire material that contracts by an external stimulus such as SMA and a polymer actuator and an actuator bending drive mechanism using the same.

  In order to achieve the above object, an actuator according to the present invention is an actuator that contracts in a predetermined contraction direction in response to contraction of a wire contracted by an external stimulus, wherein at least a part of the wire is oblique to the contraction direction. And a width restraining member that suppresses relative movement in a direction perpendicular to the contraction direction of both ends of the wire rod disposed obliquely with respect to the direction.

  Further, the actuator bending drive mechanism according to the present invention includes an actuator that contracts in a predetermined contraction direction in accordance with contraction of the wire contracted by an external stimulus inside the bending portion, and at least a part of the wire is in the contraction direction. And a width restricting member that suppresses relative movement in the direction perpendicular to the contraction direction of both ends of the wire rod disposed obliquely with respect to the contraction direction.

  According to the present invention, it is possible to achieve both a large generation force and a large contraction rate in an actuator using a wire that contracts by an external stimulus such as SMA or a polymer actuator and an actuator bending drive mechanism using the same.

  First, the principle of the present invention will be described with reference to FIGS. In the embodiment of the present invention, a wire that contracts by an external stimulus is used, and a force generated in a direction perpendicular to the length direction of the wire is used. Thereby, it is possible to achieve both a large generated force and a large shrinkage rate.

FIG. 1 shows an analysis model. Both ends 2 of the wire 1 are fixed. Let L be the distance between both ends 2 of the wire 1. Consider a case where an external force f is applied to the center of the wire 1. The direction of the external force f (Y direction) is perpendicular to the direction connecting the both ends 2 of the wire (X direction). The wire 1 is a shape memory alloy or a conductive polymer material, and has a property of contracting by stimulation such as an electric signal. It is assumed that the contraction rate of the wire 1 is ε, the maximum generated force (allowable maximum tension) is F, and no force other than the tension is generated in the wire 1. Further, the tension of the wire 1 before contraction is T ₀ , the tension after contraction is T ₁ , and the length of the wire 1 before contraction is L ₀ . The angle between the straight line connecting both ends 2 of the wire (X direction) and the wire 1 before contraction is θ _0, and the angle between the straight line connecting both ends 2 of the wire and the contracted wire 1 is θ ₁ . . However, both θ ₀ and θ ₁ are larger than 0 ° and smaller than 90 °.

The length L ₁ of the wire after contraction,
L ₁ = L ₀ (1-ε)
It can be expressed.

  When the distance between the straight line connecting both ends 2 of the wire and the center point of the wire 1 before contraction (the point of action of the external force f) is h, and the movement distance of the center point of the wire 1 before and after contraction is Δh, the shrinkage rate is Δh / H.

  The following relationship holds from the geometric relationship.

cos θ ₀ = L / L ₀ = α (0 <α <1-ε)
cos θ ₁ = L / L ₀ (1-ε) = α / (1-ε) (1)
_{Δh = h- (L 1/2} ) sinθ 1, h = (L 0/2) sinθ 0 (2)
T ₀ = f / (2sin θ ₀ ), T ₁ = f / (2 sin θ ₁ ) (3)
From Expression (1) and Expression (2), Δh / h is expressed as the following expression.

Next, the maximum generated force f _max will be considered. The conditions for preventing the wire from plastic deformation are:
T ₁ ≦ F (5)
It is. The following equation is obtained from the equations (3) and (5).

f _max / F = 2√ [1- {α / (1-ε)} ² ] (6)
FIG. 2 shows the shrinkage rate and the maximum generated force expressed by the equations (4) and (6) when ε = 0.05. The horizontal axis is L / L ₀ . The shrinkage rate Δh / h increases as L / L ₀ increases, and reaches a maximum value Δh / h = 1 when L ₀ = L / (1−ε). On the other hand, when L / L ₀ increases, f _max / F decreases and decreases rapidly near L ₀ = 1 / (1-ε). However, since the maximum generated force can be increased by decreasing L and increasing the number N of triangular elements as shown in FIG. 3, when actually designing an actuator, first, from the required shrinkage rate Δh / h to L It is possible to optimize by determining the value of / L ₀ and reducing L as much as possible.

  As described above, it is possible to obtain a large shrinkage rate by the configuration as shown in FIG. 1, but in the actual configuration, both ends of the wire cannot be completely fixed. The influence can be estimated by considering a model as shown in FIG. Assuming that one of the fixed ends 2 has a spring having a spring constant k, the contraction rate Δh / h can be expressed by the following equation.

Δh / h = 1- (1-ε) √ {(1-γ ² ) / (1-α ² )} (7)
Here, γ = {α / (1-ε)} / {1+ (Fα) / kL (1-ε)}
The maximum generated force is as follows.

f _max / F = 2√ (1-γ ² ) (8)
FIG. 5 shows the ratio between the contraction rate Δh / h obtained from the equations (7) and (8) when ε = 0.05 and L / L ₀ = 0.9, and the maximum generated force and the allowable maximum tension. It is a figure which shows _fmax / F. The horizontal axis is F / kL. When the rigidity of the wire fixed end is weak and the width L is reduced, the shrinkage rate is drastically reduced.

  Therefore, in order to obtain a large contraction rate with the actuator element having the configuration shown in FIG. 1, it is important that the width L is not reduced as much as possible when an external force is applied.

  Next, specific embodiments of the actuator and the actuator bending drive mechanism according to the present invention will be described.

[First Embodiment]
The actuator bending drive mechanism according to the first embodiment of the present invention will be described with reference to FIG. The restraint plate 3 is a flat plate extending in the XY plane direction. The restraint plate 3 has anisotropy that is difficult to contract or bend in the X-axis direction and is easily contracted or bent in the Y-axis direction. A number of attachments 4 are attached to the upper surface of the restraint plate 3, and the wire 1 is passed between these attachments 4. The wire 1 is disposed in an oblique direction with respect to the X axis and the Y axis.

  The wire 1 is a shape memory alloy, a conductive polymer material, or the like, and has a property of contracting by stimulation such as current. In the case where the wire 1 is a shape memory alloy, for example, when the current passes through the wire 1, the wire 1 generates heat, and thereby the temperature rises, and when it rises to a specific temperature, the shape changes and contracts.

  When the wire 1 contracts in this way, the restraint plate 3 receives a force through the attachment 4. At this time, since the restraint plate 3 is relatively easily deformed in the Y direction, the restraint plate 3 is curved or bent with the X direction as an axis. Here, since the restraint plate 3 has anisotropy and does not easily contract in the X direction, the contraction rate in the Y direction increases due to the above-described principle. Thereby, the restraint plate 3 can be bent largely compared with the case where the restraint plate 3 has no anisotropy.

  In the embodiment shown in FIG. 6, the fixture 4 and the wire 1 are arranged only on the upper surface side of the restraint plate 3. However, as a modification, the fixture 4 and the wire 1 are arranged on both surfaces of the restraint plate 3. You can also. In this case, if the constraining plate 3 is made of a material that contracts in the Y-axis direction, the constraining plate 3 can be contracted in the Y-axis direction instead of being bent or bent. In this case, the contraction rate of the restraint plate 3 can be increased as compared with the case where the restraint plate 3 has no anisotropy. In addition, the actuator bending drive mechanism can be configured by combining the contraction element thus formed with another element as an inner element of the actuator bending drive mechanism.

[Second Embodiment]
Next, an actuator bending drive mechanism according to a second embodiment of the present invention will be described with reference to FIG. Here, the same or similar parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In this embodiment, as in the first embodiment, the restraint plate 3 is a flat plate extending in the XY plane direction, and is not easily contracted or curved in the X-axis direction, and contracted or curved in the Y-axis direction. It has easy anisotropy. In this embodiment, a large number of small through holes 5 are arranged in the restraint plate 3, the wire 1 that contracts by external stimulation passes through these through holes 5, and the wire 1 is passed between the through holes 5. . The wire 1 is disposed in an oblique direction with respect to the X axis and the Y axis. Each time the wire 1 passes through the through hole 5, the wire 1 moves back and forth between the upper surface and the lower surface of the restraint plate 3. In the example shown in FIG. 7, the wire 1 on the upper surface side is longer than the wire 1 on the lower surface side.

  When the wire 1 contracts due to an external stimulus, the restraint plate 3 is bent or bent as in the first embodiment. In this embodiment, the wire 1 is also present on the lower surface of the restraint plate 3, but the wire 1 existing on the upper surface is longer, so the force due to the contraction of the wire 1 on the upper surface side is larger, and the upper surface side is more. It is pulled strongly.

  As a modification of this embodiment, the lengths of the wires 1 on the upper and lower surfaces of the restraint plate 3 can be arranged at the same level. In this case, if the restraint plate 3 is made of a material that shrinks in the Y-axis direction, Instead of bending or bending the plate 3, it can be contracted in the Y-axis direction.

[Third Embodiment]
Next, an actuator according to a third embodiment of the present invention will be described with reference to FIG. Here, parts that are the same as or similar to those in the first or second embodiment are denoted by common reference numerals, and redundant description is omitted.

  In this embodiment, two elongated restraining plates 3 are arranged in parallel in the X direction with their long sides facing each other in the Y direction. In this embodiment, the restraint plate 3 is difficult to bend and contract. A large number of through holes 5 are arranged in the restraint plate 3 in the longitudinal direction (X direction). The wire 1 is arranged so as to pass through these through holes 5, and the wire 1 is passed so as to connect the through holes 5 of the two constraining plates 3 facing each other. The wire 1 is disposed in an oblique direction with respect to the X direction and the Y direction.

  In this embodiment, when the wire 1 is contracted by an external stimulus, the two restraining plates 3 are attracted to each other in the Y direction, and the distance between them is reduced. At this time, since the distance in the X direction at both ends of each wire 1 is restrained by the restraining plate 3, the contraction rate in the Y direction of the actuator is increased.

  Although the actuator shown in FIG. 8 only contracts in the Y direction and does not cause bending or bending, an actuator bending drive mechanism is realized by combining such an actuator with other mechanical elements such as a joint. Can do.

  As a modification of this embodiment, instead of connecting the restraint plates 3 to each other through the wire 1 to the through hole 5 of the restraint plate 3, the restraint plate 3 shown in FIG. It is also possible to connect the restraint plates 3 by fixing the protrusion (not shown) and engaging the wire 1 with the fixture 4 or the protrusion.

[Fourth Embodiment]
Next, an actuator bending drive mechanism according to a fourth embodiment of the present invention will be described with reference to FIG. Here, the same or similar parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In this embodiment, the actuator bending drive mechanism has a substantially cylindrical shape as a whole, and when the cylindrical axis is horizontal, the lower half of the figure is a semi-cylindrical actuator 10. The actuator 10 is formed in a mesh shape by knitting a wire 1 that contracts by an external stimulus. Each wire 1 is coated with, for example, an electrical insulating material so that a current flows through each wire 1.

  The upper half of the cylindrical actuator bending drive mechanism in FIG. 9 is a semi-cylindrical restraint plate 3, and is joined to the lower half semi-cylindrical actuator 10. The restraining plate 3 includes a semi-cylindrical width restraining rubber sheet 11 and a plurality of anti-stretch fibers 11 fixed to the width restraining rubber sheet 11 and arranged in the axial direction so as to extend in the circumferential direction. Have.

  When an external stimulus such as an electric current is applied to each wire 1 of the actuator 10, each wire 1 contracts and the actuator 10 contracts in the cylindrical axis direction. When the actuator 10 contracts in the axial direction, the entire actuator bending drive mechanism bends with the actuator 10 inside. At this time, since the deformation (shrinkage) of the restraint plate 3 in the width direction is suppressed by the width restraint rubber sheet 11 and the extension preventing fiber 12, the contraction rate in the axial direction of the actuator 10 is increased according to the above principle.

[Fifth Embodiment]
Next, an actuator bending drive mechanism according to a fifth embodiment of the present invention will be described with reference to FIG. This embodiment is a modification of the fourth embodiment (FIG. 9), and the same or similar parts as those of the fourth embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In this embodiment, as in the fourth embodiment, the actuator bending drive mechanism has a substantially cylindrical shape as a whole, and when the cylindrical axis is horizontal, the lower half is a semi-cylindrical actuator 10. The actuator 10 is formed in a mesh shape by knitting a wire 1 that contracts by an external stimulus. Each wire 1 is coated with, for example, an electrical insulating material so that a current flows through each wire 1.

  In this embodiment, the restraining body 15 that restrains deformation in the width direction of the actuator 10 includes a plurality of annular members 16 arranged in the axial direction with a common axis, and upper ends of the plurality of annular members 16 extending in the axial direction. And a connecting member 17 for connecting the two. The annular member 16 has a rigid structure that is difficult to deform including expansion and contraction. The connecting member 17 is, for example, an elongated plate-like member extending in the axial direction, and has a structure that is difficult to expand and contract but can be bent in the vertical direction shown in the figure. The actuator 10 is formed in a semi-cylindrical shape so as to cover the outer side of the lower half of the annular member 16, and is fixed to the annular member 16.

  When an external stimulus such as an electric current is applied to each wire 1 of the actuator 10, each wire 1 contracts and the actuator 10 contracts in the cylindrical axis direction. At this time, since the axial length of the connecting member 17 does not change, the entire actuator bending drive mechanism bends with the actuator 10 on the inside and the connecting member 17 on the outside. At this time, deformation (contraction) in the width direction of the tutor 10 is suppressed by the annular member 16, so that the contraction rate in the axial direction of the actuator 10 is increased according to the above principle.

[Sixth Embodiment]
Next, an actuator bending drive mechanism according to a sixth embodiment of the present invention will be described with reference to FIG. This embodiment is a modification of the fifth embodiment (FIG. 10), and the same or similar parts as those of the fifth embodiment are denoted by common reference numerals, and redundant description is omitted.

  In this embodiment, as in the fifth embodiment, the actuator bending drive mechanism has a substantially cylindrical shape as a whole, and a plurality of annular members 16 arranged in the axial direction with the axis of this cylinder as a common axis, and in the axial direction And a connecting member 17 that extends and connects the upper ends of the plurality of annular members 16. The annular member 16 has a rigid structure that is difficult to deform including expansion and contraction. In FIG. 11, five annular members 16 are arranged, but this number is arbitrary. The connecting member 17 is, for example, a long and narrow plate extending in the axial direction, and has a structure that is difficult to expand and contract but can be bent in the vertical direction shown in the figure.

  A large number of through holes (not shown) are arranged in the lower part of each annular member 16, and the wire 1 that contracts by external stimulation passes through these through holes, and the wire 1 is passed between the through holes. ing. Each wire 1 is disposed obliquely with respect to the axial direction as in the third embodiment (FIG. 8).

  When an external stimulus such as an electric current is applied to each wire 1, each wire 1 contracts, and the lower part of the entire actuator bending drive mechanism contracts in the axial direction. At this time, since the axial length of the connecting member 17 does not change, the entire actuator bending drive mechanism bends with the lower part on the inside and the connecting member 17 on the outside. At this time, the deformation (shrinkage) of the actuator 10 in the width direction is suppressed by the annular member 16, so that the contraction rate of the actuator 10 in the axial direction is increased according to the above principle.

  As a modification of this embodiment, as described as a modification of the third embodiment, instead of connecting the annular members 16 to each other through the wire 1 to the through hole 5 of the restraint plate 3, It is also possible to connect the annular members 16 by fixing many attachments 4 and other protrusions (not shown) shown in FIG. 6 and engaging the wire 1 with the attachments 4 and protrusions.

  As mentioned above, although various embodiment was described, these are illustrations, Comprising: This invention is not limited to these. In the description of the above embodiment, the upper part and the lower part are described separately for convenience of explanation, and the gravity direction is not relevant in the present invention.

It is model explanatory drawing for demonstrating the basic principle of the actuator which concerns on this invention. It is a graph which shows the example of the analysis result in the model of FIG. 1, Comprising: A contraction rate (DELTA) h / h and the ratio _fmax / F of the maximum generation force and the allowable maximum tension | _{tensile_strength of} a wire are set to a vertical axis | shaft, the ratio L / L ₀ a retracted front member length is a graph showing the horizontal axis. It is a model explanatory drawing which shows the example which arranged the actuator of FIG. 1 in parallel. It is model explanatory drawing for demonstrating the basic principle of the actuator which concerns on this invention. FIG. 5 is a graph showing an example of an analysis result in the model of FIG. 4, wherein the vertical axis is the contraction rate Δh / h and the ratio f _max / F of the maximum generated force and the allowable maximum tension of the wire, and the allowable maximum tension is the spring constant. It is a graph which shows the value F / kL divided by the distance between fixed points on both ends of a wire as the horizontal axis. It is a perspective view which shows the actuator bending drive mechanism which concerns on the 1st Embodiment of this invention. It is a perspective view which shows the actuator bending drive mechanism which concerns on the 2nd Embodiment of this invention. It is a top view which shows the actuator which concerns on the 3rd Embodiment of this invention. It is a perspective view which shows the actuator bending drive mechanism which concerns on the 4th Embodiment of this invention. It is a perspective view which shows the actuator bending drive mechanism which concerns on the 5th Embodiment of this invention. It is a perspective view which shows the actuator bending drive mechanism which concerns on the 6th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wire 2 ... Both ends 3 of a wire rod ... Restraint plate 4 ... Mounting tool 5 ... Through-hole 10 ... Actuator 11 ... Width restraint rubber sheet 12 ... Stretch prevention fiber 15 ... Restraint body 16 ... Ring member 17 ... Connecting member

Claims (9)

In an actuator that contracts in a predetermined contraction direction according to contraction of a wire that contracts by an external stimulus,
At least a part of the wire is disposed obliquely with respect to the contraction direction, and
Having a width restraining member that suppresses relative movement in a direction perpendicular to the contraction direction of both ends of the wire rod arranged obliquely with respect to the direction;
An actuator characterized by.   2. The actuator according to claim 1, wherein the width restricting member has an anisotropy that is easily deformed in the contraction direction and hardly deforms in a direction perpendicular to the contraction direction. The width restricting members are a plurality of elongated plates extending in a direction substantially parallel to each other and substantially perpendicular to the contraction direction;
The wire is disposed so as to connect the width restraining members adjacent to each other;
The actuator according to claim 1. An actuator that contracts in a predetermined contraction direction according to contraction of the wire contracting by an external stimulus is provided inside the bent portion,
At least a part of the wire is disposed obliquely with respect to the contraction direction, and
Having a width restraining member that suppresses relative movement in a direction perpendicular to the contraction direction at both ends of the wire rod arranged obliquely with respect to the contraction direction;
An actuator bending drive mechanism.   5. The actuator bending drive mechanism according to claim 4, wherein the width restricting member has anisotropy that is easily deformed in the contraction direction and is not easily deformed in a direction perpendicular to the contraction direction. The width restricting member is configured to be partially cylindrical outside the bent portion, and is arranged so that deformation in a direction perpendicular to the cylindrical axis is suppressed,
The wire is configured in a partially cylindrical shape on the inner side of the bent portion, and is arranged so that a cylindrical axis direction coincides with the contraction direction,
The width restricting member and the wire are joined to form a whole in a cylindrical shape,
The actuator bending drive mechanism according to claim 4 or 5, wherein:   The actuator bending drive mechanism according to claim 6, wherein the width restricting member includes an extension preventing fiber extending in a circumferential direction of the partial cylindrical portion. The width restraining member has a plurality of annular members arranged along the contraction direction and extending in a plane substantially perpendicular to the contraction direction,
The wire is fixed to the annular member so as to connect between the annular members;
The actuator bending drive mechanism according to claim 4.   The actuator according to claim 8, wherein the plurality of annular members are connected to each other in the contraction direction, and a connection member made of a material that hardly stretches in the contraction direction is disposed outside the bent portion. Bending drive mechanism.

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