JP2012154412A - Actuator and link mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator and a link mechanism having an apparently nonlinear elastic modulus.SOLUTION: A first pulley 22a and a second pulley 22b are integrally rotatably supported by a linearly movably supported base 20. A first wire 17a is wound on the first pulley 22a, and the output end To of the first wire 17a is connected to a load. A second wire 17b is wound in the inverse direction of the first wire 17a on the second pulley 22b. An installation member 12 is connected to a base 14. A driving source 3 integrally linearly moves the base 14 and the installation member 12. One end of a spring 4 is connected to the installation member 12, and the other end of the spring 4 is connected to the second wire 17b.

Description

  The present invention relates to an actuator used for various robot arms, manipulators, or operation support devices for workers and care recipients, and a link mechanism including the actuator.

In recent years, in the development of various robot arms and manipulators, it has been considered to realize flexible and agile movement by adopting a musculoskeletal structure similar to the structure of a living body and to apply it to various work. ing. Here, it is generally known that the muscle strength F generated by the muscles of living organisms is expressed by the following equation (1) (see Non-Patent Document 1).
F = U−K · U · X−b · U · (dX / dt) (1)

  In equation (1), U is the muscle contraction force, X is the amount of displacement (contraction), dX / dt is the displacement speed, and k and b are constants. Here, the second term on the right side is a force corresponding to an elastic force, the elastic coefficient is -k · U, the third term is a force corresponding to a viscous force, and the viscosity coefficient is -b · U. Thus, the point that the elastic coefficient and the viscosity coefficient are proportional to the contraction force U is a characteristic of the muscle. In Non-Patent Documents 1 and 2, the characteristic represented by the equation (1) is expressed by an actuator model in which a drive source, an elastic element, and a viscous element are connected in parallel and one end thereof is an output end.

Here, an actuator having an output characteristic represented by the following equation (2) in which the third term (viscous force) is omitted from the equation (1) is assumed.
F = Uk ・ U ・ X (2)

  The link mechanism of the robot arm is configured by arranging two actuators having such output characteristics so as to antagonize on both sides of a link rotatably supported by a joint such as a robot arm. The driving torque around the joint is determined by the difference between the contraction forces (tensile forces) U of both actuators, and the rigidity is determined by the sum of the contraction forces U of both actuators. That is, by adjusting the contraction force U of both actuators separately, it is possible to independently change the torque and rigidity around the joint, and application to biological, flexible and agile operations can be expected.

  As a means for realizing an actuator having such characteristics, a motor and a gear as a drive source are connected in series to a spring as an elastic element, one end of the spring is driven by the drive source, and the other end is output as an output end. Has been disclosed (see Patent Document 1). In this example, driving the spring with the driving source corresponds to generation of the contraction force U.

  Further, in Patent Document 1, a spring having non-linear characteristics, such as an unequal pitch coil spring or a taper coil spring, in which the rate of change in elastic force, that is, the elastic coefficient (spring constant), decreases as the displacement (shrinkage) amount X increases. An example for use as an elastic element is disclosed. When one end of the spring having such characteristics is driven, a curve representing the output characteristics translates in the X-axis direction. When the displacement amount X is constant, the output F increases as the spring is driven, and at the same time, the spring constant increases. That is, an actuator having characteristics close to the characteristics expressed by the above formula (2) can be realized.

JP-A-2005-96020

Written by Kumamoto Mizuyori: Humanoid Engineering, Tokyo Denki University Press

  Here, the elastic coefficient (spring constant) of a general spring is constant regardless of displacement, but as disclosed in Patent Document 1, a special shape such as an unequal pitch coil spring or a taper coil spring is used. It is known that the characteristic of elastic modulus can be made non-linear. However, even if the shape and size of a simple spring composed of a single member is changed depending on the part, the variable ratio (maximum value / minimum value) of the obtained elastic coefficient is limited.

  Moreover, since it is not practically desirable to make the change in the elastic force with respect to the displacement excessively steep, the change in the elastic force should be moderately moderate with respect to the displacement. In that case, however, in order to increase the variable ratio of the elastic modulus, it is necessary to increase the amount of displacement of the spring. As a result, the spring itself is longer than the stroke required for the actuator, and further the total length of the actuator is increased. There is a problem of becoming longer.

Further, since the elastic coefficient is a differential coefficient with respect to the displacement of the elastic force, in order to realize a characteristic in which the elastic coefficient (−k · U) is proportional to the contraction force U as shown in the above equation (2) A spring having a characteristic close to an exponential function of displacement is required. That is, the relationship between the elastic force Fs of the spring and the displacement X is expressed by the following equation (3), and the elastic coefficient dFs / dX is expressed by the equation (4). Here, B and C are constants.
Fs = C · e ^{B · X} (3)
dFs / dX = B · C · e ^{B · X} (4)

  However, it is very difficult to design and manufacture a spring composed of a single member and having characteristics expressed in such a special function form.

  Therefore, an object of the present invention is to provide an actuator and a link mechanism having an apparently nonlinear elastic coefficient.

  The present invention provides an actuator that applies a tensile force to a load, a base that is supported so as to be linearly movable, a first pulley that is rotatably supported by the base, and a rotation that is integrated with the first pulley. A second pulley rotatably supported by the base, and the load is connected to the load, and the first pulley is wound around the first pulley when rotating in the first rotation direction, A first connection wound around the outer circumference of the first pulley so that the first pulley is drawn out from the first pulley when the first pulley rotates in a second rotation direction opposite to the first rotation direction. When the member and the first pulley wind up the first connecting member, the member is fed out from the second pulley, and when the first pulley feeds out the first connecting member, the member is wound around the second pulley. To be taken The second connecting member wound around the outer periphery of the second pulley, the mounting member disposed on the opposite side of the load with respect to the base and connected to the base, the base and the base A drive source for linearly moving the mounting member, one end connected to the mounting member, the other end connected to the second connecting member, and the second connecting member being fed out from the second pulley An elastic member capable of expanding and contracting to apply a tensile force to the second connecting member, wherein the first pulley and the second pulley are rotation centers of the first pulley and the second pulley. A ratio R1 / of a distance R1 from the center of rotation of the first connecting member to a terminal end of the portion where the second connecting member is wound R1 R2 is the first pulley and the second pulley Characterized in that it is formed in a shape that varies according to the rotation of the over Li.

  Further, the present invention provides an actuator that applies a tensile force to a load, a base that is supported so as to be linearly movable, a first gear that is rotatably supported by the base, and a base that is rotatable. A second gear supported and meshed with the first gear; a first pulley rotatably supported by the base so as to rotate integrally with the first gear; and the second gear. A second pulley rotatably supported on the base so as to rotate integrally with the base, and connected to the load, and when the first pulley rotates in the first rotation direction, the first pulley The first pulley is wound around the outer periphery of the first pulley so that the first pulley is drawn out from the first pulley when the first pulley rotates in the second rotation direction opposite to the first rotation direction. A first connecting member and the first pulley When the first connecting member is wound up, the second pulley is fed out, and when the first pulley is fed out the first connecting member, the second pulley is wound up. A second connecting member wound around the outer periphery, an attachment member disposed on the opposite side of the load with respect to the base, and connected to the base, and the base and the attachment member are linearly moved integrally. A driving source to be connected to the second connecting member, one end of which is connected to the mounting member, the other end is connected to the second connecting member, and the second connecting member is extended from the second pulley. An elastic member capable of expanding and contracting to apply a tensile force, and the first gear and the second gear are connected to the first gear and the second gear from the rotation center of the second gear. Distance R12 to the meshing position of the The ratio R12 / R21 of the distance R21 from the rotation center of the first gear to the meshing position of the first gear and the second gear changes according to the rotation of the first gear and the second gear. It is formed in a shape.

  According to the present invention, it is possible to realize an actuator having an apparently nonlinear elastic coefficient that has a variable ratio larger than the variable ratio of the elastic coefficient of the elastic member. In particular, an actuator having elastic characteristics expressed in a special function form such as an exponential function can be easily designed and manufactured. Even when the variable ratio of the elastic coefficient is increased, it is not necessary to increase the amount of displacement of the elastic member, and the overall length of the actuator can be shortened.

It is a figure which shows schematic structure of the link mechanism which has an actuator which concerns on 1st Embodiment of this invention. It is sectional drawing which shows the structure of the actuator which concerns on 1st Embodiment of this invention. It is a figure which shows the structure of the displacement conversion mechanism of the actuator which concerns on 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of an actuator, (a) is a figure which shows the state which is not driving a base, (b) is the state from which the external force acted on the output end of the 1st wire from the state of (a). It is a figure which shows a case. (C) is a figure which shows the state which driven the base only by Xd, (d) is a figure which shows the case where an external force acts on the output end of a 1st wire from the state of (c). It is a figure which shows the characteristic of an actuator, (a) is a figure which shows the case where there is a displacement conversion mechanism, (b) is a figure which shows the case where there is no displacement conversion mechanism. It is sectional drawing which shows the structure of the actuator which concerns on 2nd Embodiment of this invention. It is a figure which shows the structure of the displacement conversion mechanism of the actuator which concerns on 2nd Embodiment of this invention. It is a figure for demonstrating operation | movement of an actuator, (a) is a figure which shows the state which is not driving a base, (b) is the state from which the external force acted on the output end of the 1st wire from the state of (a). It is a figure which shows a case. (C) is a figure which shows the state which driven the base only by Xd, (d) is a figure which shows the case where an external force acts on the output end of a 1st wire from the state of (c). It is a figure which compares the characteristic of an actuator.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a diagram showing a schematic configuration of a link mechanism having an actuator according to the first embodiment of the present invention. Reference numeral 30 shown in FIG. 1 denotes a first link, and a second link 31 is supported by the first link 30 via a joint 32 so as to be rotatable. The link mechanism 100 includes a pair of actuators 1 and 1 connected to the first link 30 and the second link 31. In the first embodiment, the second link 31 is a load driven by the actuator 1. Of the two actuators 1 and 1, one actuator is the first actuator 1a, the other actuator is the second actuator 1b, and the actuators 1a and 1b have the same configuration. The first control circuit 33 a controls the pulling force (contraction force) of the first actuator 1 a that is applied to the second link 31, and the second control circuit 33 b is the second that is applied to the second link 31. The pulling force (contraction force) of the actuator 1b is controlled.

  The first actuator 1a and the second actuator 1b are fixed to both sides of the first link 30, and the second actuator 1a and the output end To2 of the second actuator 1b are antagonized with each other. It is attached to the link 31.

Here, the contraction force generated by the first actuator 1a is U1, and the contraction force generated by the second actuator 1b is U2. If the distance from the rotation center of the joint 32 to the output ends To1 and To2 of the actuators 1a and 1b is r and the rotation angle of the second link 31 is φ, the total torque T acting on the second link 31 is given by It becomes like (5).
T = (U1-U2) · r-k · (U1 + U2) · r 2 · φ (5)

  In Expression (5), the first term on the right side is drive torque, and the second term is elastic torque. The driving torque is proportional to the contraction force difference U1-U2 between the two actuators 1a, 1b, while the elastic torque is proportional to the rotational angle φ of the second link 31 and the sum U1 + U2 of the contraction forces of the two actuators 1a, 1b. To do. Accordingly, by separately controlling the contraction force U1 generated by the first actuator 1a and the contraction force U2 generated by the second actuator 1b by the first control circuit 33a and the second control circuit 33b, the driving torque and rigidity are controlled. And can be adjusted independently. The second link 31 rotates at the joint 32 when a driving torque acts. The second link 31 is given rigidity by the action of elastic torque.

  FIG. 2 is a cross-sectional view showing the configuration of the actuator according to the first embodiment of the present invention. The actuator 1 includes a housing 2, a drive source 3 built in the housing 2, a spring 4 that can be expanded and contracted as an elastic member, a displacement conversion mechanism 5, a guide 6, and an attachment for attaching one end of the spring 4. And a member 12. The spring 4 used here does not need to have a non-linear characteristic, and is a tension coil spring having a linear characteristic with a constant elastic coefficient (spring constant).

  The drive source 3 includes a stator 10 fixed in the housing 2 and a mover 11 linearly driven by the stator 10 in directions indicated by arrows X + and X−. It is assumed that the back drivability of the drive source 3 itself is sufficiently low and is not reversely driven even if an external force acts on the mover 11. As such a drive source 3, a motor combined with an ultrasonic motor or a reduction gear having a large reduction ratio can be used. In addition, when a rotary motor is used, a mechanism for converting rotational motion into linear motion is required separately. Such a mechanism can be configured by known means such as screws and nuts, racks and pinions, pulleys and belts (wires), crank mechanisms, and the like.

  An attachment member 12 is attached to the tip of the mover 11. Thereby, the attachment member 12 moves linearly in the directions indicated by the arrows X + and X− by the drive of the drive source 3. One end T1 of the spring 4 and one end of the support member 13 are connected to the mounting member 12.

  The displacement conversion mechanism 5 includes a base 14, a first pulley 16a, a second pulley 16b, a first wire 17a that is a flexible first connection member, and a flexible second connection. It is comprised by the 2nd wire 17b which is a member. In the present embodiment, the case where a wire is used as the connecting member will be described. However, any wire-like member having flexibility such as a belt may be used.

  The base 14 is disposed on the other end T <b> 2 side of the spring 4, and is connected to the other end of the support member 13. In other words, the base 14 and the mounting member 12 disposed on the side opposite to the second link 31 (FIG. 1) that is a load with respect to the base 14 are connected by the support member 13. That is, the spring 4 is disposed between the mounting member 12 and the base 14. And since the attachment member 12 and the base 14 are connected, the base 14 and the spring 4 move integrally with the attachment member 12 moved by the drive source 3.

  The base 14 supports the rotating shaft 15 in a state where the rotating shaft 15 can rotate in the forward and reverse rotation directions. The first pulley 16 a and the second pulley 16 b are fixed to the rotating shaft 15 so as to rotate integrally with the base 14. That is, the first pulley 16a and the second pulley 16b are supported by the base 14 via the rotating shaft 15 so as to be rotatable together. In addition, although the case where the rotating shaft 15 was provided in the base 14 was demonstrated, a fixed shaft is fixed to a base, and a 1st pulley and a 2nd pulley rotate to a normal / reverse rotation direction integrally around a fixed shaft. You may comprise as follows.

  The base 14 is guided by the guide 6 and the moving direction is restricted to the directions indicated by the arrows X + and X−. Thereby, the base 14 is supported by the housing 2 through the guide 6 so as to be linearly movable in the directions indicated by the arrows X + and X−. The drive source 3 drives the base 14 together with the one end T1 of the spring 4 in the directions indicated by the arrows X + and X-.

  The first wire 17a has an output end To, which is one end thereof, drawn in a direction opposite to that of the drive source 3, and is connected to a second link 31 (FIG. 1) that is a load. The other end of the first wire 17a is connected to the first pulley 16a, and is wound around the outer periphery of the first pulley 16a from the other end side. One end of the second wire 17 b is pulled out in the direction opposite to the output end To (the driving source 3 side), and is connected to the other end T <b> 2 of the spring 4. The other end of the second wire 17b is connected to the second pulley 16b, and is wound around the outer periphery of the second pulley 16b from the other end side.

  Details of the displacement conversion mechanism 5 are shown in FIG. Here, the end (winding end) of the portion where the first wire 17a is wound on the first pulley 16a from the rotation center Q (center of the rotation shaft 15) of the first pulley 16a and the second pulley 16b. ) Let R1 be the distance to S1. Further, the distance from the rotation center Q to the end (winding end) S2 of the portion where the second wire 17b is wound in the second pulley 16b is R2.

  The outer periphery of the first pulley 16a and the second pulley 16b has a shape in which the ratio R1 / R2 between the distance R1 and the distance R2 changes according to the rotation of the first pulley 16a and the second pulley 16b. Is formed.

  Here, it is preferable that the outer periphery of at least one of the first pulley 16a and the second pulley 16b is formed in a spiral shape in section with the rotation center Q as the center. In the first embodiment, the outer periphery of the second pulley 16b is formed in a spiral cross section, and the outer periphery of the first pulley 16a is formed in a circular cross section. Therefore, since the outer periphery of the first pulley 16a has a circular cross section, the distance (rotation radius) R1 between the terminal end (winding end) S1 of the portion wound on the first wire 17a and the rotation center Q is as follows. It is constant. On the other hand, the second pulley 16b has a terminal end (winding end) of the portion wound around the second wire 17b as the rotation angle θ increases in the direction of winding the second wire 17b. This is a spiral shape in which the distance (rotation radius) R2 between S2 and the rotation center Q increases. That is, the outer circumferences of the first pulley 16a and the second pulley 16b are formed in such a shape that the ratio R1 / R2 decreases as the first wire 17a is drawn out from the first pulley 16a. In other words, the outer circumferences of the first pulley 16a and the second pulley 16b are formed in a shape in which the ratio R1 / R2 increases as the first wire 17a is wound around the first pulley 16a.

  Here, the first wire 17a is wound around the first pulley 16a when the first pulley 16a rotates in the first rotation direction A, and the first pulley 16a is opposite to the first rotation direction A. When rotating in the second rotation direction B, the first pulley 16a is fed out. The second wire 17b is wound around the second pulley 16b in the direction opposite to the winding direction of the first wire 17a. Thus, when the first pulley 16a winds up the first wire 17a when the second pulley 16b rotates in the first rotation direction A integrally with the first pulley 16a, the second wire 17b To pay out. The second pulley 16b winds the second wire 17b when the first pulley 16a unwinds the first wire 17a when the first pulley 16a rotates in the second rotation direction B integrally with the first pulley 16a. take.

  Next, the operation of the actuator 1 will be described. FIG. 4 is a diagram for explaining the operation of the actuator 1 and shows only the main part. FIG. 5 is a diagram illustrating the characteristics of the output F with respect to the displacement X of the output end To in each operation state. In FIG. 5A, the curves Lo1 and Lo2 indicate the characteristics of the actuator 1 according to the present embodiment. For comparison, the characteristic when assuming that the displacement conversion mechanism 5 is not provided and the other end T2 of the spring 4 is directly connected to the second link 31 as a load is indicated by a straight line Ls. In this case, the output F is the elastic force generated by the spring 4 itself.

  FIG. 4A shows a state in which the drive source 3 does not drive the spring 4 (base 14), the output F from the output end To is 0, and there is no action of external force on the output end To. That is, the spring 4 that is a tension coil spring has a free length, and no tension is applied to the second wire 17b. The position X of the output end To at this time is set to 0 (reference position). In FIG. 5A, this state is indicated by an operation position O (0, 0). Then, the rotation angle θ of the pulleys 16a and 16b in this state is set to 0 degree.

  In FIG. 4B, an external force is applied in the direction of drawing the first wire 17a to the output end To from the state of FIG. The displaced state is shown. At this time, the first pulley 16a rotates, and at the same time, the second pulley 16b also rotates together with the first pulley 16a, so that the first wire 17a is fed out from the first pulley 16a, while the second pulley 16a rotates. The wire 17b is wound around the second pulley 16b. As a result, the other end T2 of the spring 4 is pulled by the second wire 17b wound around the second pulley 16b, and the spring 4 expands by −Xs1. The spring 4 biases an elastic force Fs1 that is a pulling force to the second wire 17b in a direction in which the second wire 17b is drawn out from the second pulley 16b. As a result, an output (tensile force) Fo1 that balances the external force is generated at the output end To. Here, the leftward displacement in FIG. 4 is positive (+), and the rightward displacement is negative (−). In the present embodiment, the pulleys 16a and 16b rotate within a range of 0 degree or more and less than 360 degrees.

  Next, the displacement and force conversion action by the displacement conversion mechanism 5 will be described. The ratio between the rotation radius R1 at the winding end S1 of the first wire 17a of the first pulley 16a shown in FIG. 3 and the rotation radius R2 at the winding end S2 of the second wire 17b of the second pulley 16b. A (θ) = R1 / R2 varies depending on the rotation angle θ of the pulleys 16a and 16b.

Here, if the minute displacement of the first wire 17a is ΔXo and the minute displacement of the second wire 17b is ΔXs, the relationship ΔXo = A (θ) · ΔXs is established. Further, if the tension acting on the first wire 17a is Fo and the tension acting on the second wire 17b is Fs, the relationship Fo = Fs / A (θ) is established. Therefore, when the elastic coefficient of the spring 4 to which the second wire 17b is connected is ks and the apparent elastic coefficient at the output end To is ko, the following expression (6) is established.
ko = ks / A (θ) ² (6)

As a result, even if the elastic coefficient ks of the spring 4 is a constant value, a non-linear change in the elastic coefficient ko can be obtained by the change in the value of the coefficient 1 / A (θ) ² accompanying the change in the rotation angle θ. It can be done.

  The characteristic in the case where there is no displacement conversion mechanism 5 indicated by the straight line Ls in FIG. 5A is converted into the characteristic indicated by the curve Lo1 by such a conversion action of the displacement conversion mechanism 5. Also, the operating position Ps1 (−Xs1, Fs1) of the spring 4 corresponding to the state of FIG. 4B is converted into the operating position Po1 (−Xo1, Fo1) of the output end To.

  Next, in FIG. 4C, from the state of FIG. 4A (a state in which there is no external force applied to the output end To), the drive source 3 moves the one end T1 and the base 14 of the spring 4 in the direction opposite to the output end To. It shows a state in which driving is performed by Xd in the direction indicated by the arrow X +, and the position X of the output end To is displaced to Xd. In this state, the length of the spring 4 is the same as that shown in FIG. 4A, and no elastic force is generated. Further, the first pulley 16a and the second pulley 16b do not rotate.

  FIG. 5B shows the characteristics in this state. The characteristic at the output end To is a characteristic indicated by a curve Lo2 translated from the curve Lo1 indicating the state of FIG. 4A by Xd in the X-axis direction. Accordingly, the operation position moves from O (0, 0) to Po2 (Xd, 0). That is, the operating position of the spring 4 can be displaced by moving the mounting member 12 and the base 14 by the drive source 3.

  Next, FIG. 4 (d) is displaced by -Xo1 due to an external force acting in the direction (indicated by arrow X-) in which the first wire 17a is fed out from the state of FIG. 4 (c) to the output end To. A state where the position X of To is Xd-Xo1 is shown. At this time, the first pulley 16a rotates, and at the same time, the second pulley 16b also rotates together with the first pulley 16a, so that the first wire 17a is fed out from the first pulley 16a, while the second pulley 16a rotates. The wire 17b is wound around the second pulley 16b. As a result, the other end T2 of the spring 4 is pulled by the second wire 17b wound around the second pulley 16b, the spring 4 is extended by -Xs1, and the second wire 17b is pulled by the spring 4 by a tensile force. A certain elastic force Fs1 is generated. As a result, an output Fo1 that balances the external force is generated at the output end To, and the operation position moves to Po3 (Xd-Xo1, Fo1).

In this embodiment, the conversion characteristic, that is, the shape of the curve Lo1 in FIG. 5 is determined by the ratio A (θ) = R1 / R2 of the first pulley 16a and the second pulley 16b, and the elastic coefficient conversion coefficient is As shown in the equation (6), 1 / A (θ) ² = (R2 / R1) ² .

As described above, since the conversion characteristics can be determined only by the geometry of the pulleys 16a and 16b, the design and manufacture thereof are very easy. For example, when the elastic force realizes a desired function with respect to the displacement, for example, the same characteristic as the characteristic of the non-linear spring shown in Expression (4), the apparent elastic coefficient ko at the output end To is expressed by the following expression (7 )become that way.
ko = B ・ C ・ e ^{B ・ X} (7)

From the above equations (6) and (7), the rotational radii R1 and R2 of the first pulley 16a and the second pulley 16b may be designed so that A (θ) satisfies the following equation (8). Become.
A (θ) = {ks / (B · C · e ^{B · X} )} ^1/2 (8)

  In the present embodiment, the rotation radius R1 of the first pulley 16a is constant regardless of the rotation angle θ, and only the rotation radius R2 of the second pulley 16b changes according to the rotation angle θ. This is not a limitation. As long as the above equation (8) can be satisfied, either or both of the rotation radius R1 and the rotation radius R2 may be changed according to the rotation angle θ. That is, in the present embodiment, the outer periphery of the first pulley 16a is formed in a spiral shape and the outer periphery of the second pulley 16b is formed in a circular shape, but the outer periphery of the second pulley 16b is formed in a spiral shape, The first pulley 16a may be formed in either a circular shape or a spiral shape. By forming the first pulley 16a and the second pulley 16b in this way, the apparent elastic coefficient of the actuator 1 becomes an exponential characteristic. If the characteristics of the spring 4 are not linear but nonlinear, A (θ) may be designed in consideration of the characteristics.

  Further, in the present embodiment, with the rotation of the second pulley 16b, the position of the winding end S2 of the second wire 17b is in a direction perpendicular to the second wire 17b (up and down direction in FIG. 3). Displace. For this reason, the spring 4 and the second wire 17b are inclined, and the extension amount of the spring 4 is also affected. If the inclination is sufficiently small, it can be ignored. However, if necessary, the shape of the pulley 16b can be designed so as to correct the influence of the inclination.

  If the average value of A (θ) over the entire stroke of the actuator 1 is Aa, the stroke of the output end To is larger than the stroke of the spring 4 if Aa> 1, and the displacement conversion mechanism 5 simultaneously displaces. It will also have an expansion effect. In the present embodiment, this condition can be satisfied by making the rotation radius R1 of the first pulley 16a larger than the maximum value of the rotation radius R2 of the second pulley 16b. That is, the outer peripheries of the pulleys 16a and 16b are formed so that the distance R1 from the rotation center Q to the outer periphery of the first pulley 16a is larger than the distance R2 from the rotation center Q to the outer periphery of the second pulley 16b. ing. As a result, since the stroke of the spring 4 is smaller than the stroke required for the output end To of the actuator 1, the entire length of the spring 4 itself can be shortened. As a result, the entire length of the actuator 1 can be shortened.

  Furthermore, in the present embodiment, as shown in the equation (6), since the conversion coefficient of the elastic coefficient is inversely proportional to the square of A (θ), the variable ratio of the elastic coefficient ko at the output end To can be increased. Easy. For example, when the variable ratio (maximum value / minimum value) of the elastic modulus ko is desired to be 10, the maximum value / minimum value of A (θ) may be about 3.2.

  As described above, in the present embodiment, it is possible to realize the actuator 1 having an apparently nonlinear elastic coefficient ko that has a variable ratio larger than the variable ratio of the elastic coefficient ks of the spring 4. In particular, the actuator 1 having elastic characteristics expressed in a special function form such as an exponential function can be easily designed and manufactured. Even when the variable ratio of the elastic coefficient ko is increased, it is not necessary to increase the amount of displacement of the spring 4, and the overall length of the actuator 1 can be shortened.

[Second Embodiment]
Next, an actuator according to a second embodiment of the present invention will be described. FIG. 6 is a cross-sectional view showing the configuration of the actuator according to the second embodiment of the present invention. An actuator 1A shown in FIG. 6 includes a housing 2, a drive source 3, a spring 4 as an elastic member, a displacement conversion mechanism 5A, and a guide 6. The actuator 1A is used for the link mechanism as in the first embodiment. In the actuator 1A of the second embodiment, since the configuration other than the displacement conversion mechanism 5A is the same as that of the first embodiment, detailed description thereof is omitted.

  The displacement conversion mechanism 5A includes a base 20, a first pulley 22a, a second pulley 22b, a first gear 23a, a second gear 23b, a first wire 17a as a first connecting member, and a second gear. It is comprised by the 2nd wire 17b which is a connection member. In the present embodiment, the case where a wire is used as the connecting member will be described. However, any wire-like member having flexibility such as a belt may be used.

  The base 20 is disposed on the other end T <b> 2 side of the spring 4, and is connected to the other end of the support member 13. In other words, the base 20 and the mounting member 12 disposed on the side opposite to the second link side that is a load with respect to the base 20 are connected by the support member 13. That is, the spring 4 is disposed between the mounting member 12 and the base 20. And since the attachment member 12 and the base 20 are connected, the base 20 and the spring 4 move integrally with the attachment member 12 moved by the drive source 3.

  The base 20 supports the first rotating shaft 21a and the second rotating shaft 21b in a state where the first rotating shaft 21a and the second rotating shaft 21b can rotate in the forward and reverse rotating directions. The first pulley 22a and the first gear 23a are fixed to the first rotating shaft 21a so as to rotate integrally with the base 14. The second pulley 22b and the second gear 23b are fixed to the second rotating shaft 21b so as to rotate integrally with the base 20. That is, the first pulley 22a and the first gear 23a are supported by the base 20 via the first rotating shaft 21a so as to be rotatable integrally. Further, the second pulley 22b and the second gear 23b are supported by the base 20 via the second rotating shaft 21b so as to be integrally rotatable. And the 1st gearwheel 23a and the 2nd gearwheel 23b have meshed | engaged in the state which can rotate centering on each rotating shaft 21a, 21b.

  Although the case where the rotary shafts 21a and 21b are provided on the base 20 has been described, the first fixed shaft is fixed to the base, and the first pulley and the first gear are integrated around the first fixed shaft. It may be configured to rotate in the forward and reverse rotation directions. Similarly, the second fixed shaft may be fixed to the base, and the second pulley and the second gear may be configured to rotate integrally in the forward and reverse rotation directions around the second fixed shaft. In the present embodiment, the first pulley 22a and the first gear 23a are integrally formed, and the second pulley 22b and the second gear 23b are integrally formed.

  The base 20 is guided by the guide 6 and the moving direction is restricted to the directions indicated by the arrows X + and X−. Thus, the base 20 is supported by the housing 2 via the guide 6 so as to be linearly movable in the directions indicated by the arrows X + and X−. The drive source 3 drives the base 20 together with the one end T1 of the spring 4 in the directions indicated by the arrows X + and X-.

  The first wire 17a has an output end To which is one end thereof drawn out in a direction opposite to that of the drive source 3, and is connected to a second link which is a load. The other end of the first wire 17a is connected to the first pulley 22a, and is wound around the outer periphery of the first pulley 22a from the other end side. One end of the second wire 17 b is pulled out in the direction opposite to the output end To (the driving source 3 side), and is connected to the other end T <b> 2 of the spring 4. The other end of the second wire 17b is connected to the second pulley 22b, and is wound around the outer periphery of the second pulley 22b from the other end side.

  Details of the displacement conversion mechanism 5A are shown in FIG. Here, the distance from the rotation center Q1 of the first gear 23a (the center of the first rotation shaft 21a) to the meshing position S21 between the first gear 23a and the second gear 23b is R21. The distance from the rotation center Q2 of the second gear 23b (the center of the second rotation shaft 21b) to the meshing position S12 between the first gear 23a and the second gear 23b is R12.

  The outer periphery of the first gear 23a and the second gear 23b has a shape in which the ratio R12 / R12 between the distance R12 and the distance R21 changes according to the rotation of the first gear 23a and the second gear 23b. Is formed.

  Here, the outer circumferences of the first gear 23a and the second gear 23b are formed in a cross-sectional spiral shape. The first gear 23a has a spiral shape in which the distance (rotation radius) R21 between the meshing position S21 with the second gear 23b and the rotation center Q1 increases as the rotation angle θ1 increases. The second gear 23b has a spiral shape in which the distance (rotation radius) R12 between the meshing position S12 with the first gear 23a and the rotation center Q2 decreases as the rotation angle θ2 increases.

  On the other hand, the first pulley 22a has a circular cross section, and the distance (rotation radius) R11 between the winding end S11 of the first wire 17a and the rotation center Q1 is constant. The second pulley 22b has a circular cross section, and the distance (rotation radius) R22 between the winding end S22 of the second wire 17b and the rotation center Q2 is constant.

  The outer circumferences of the first gear 23a and the second gear 23b are formed in such a shape that the ratio R12 / R21 decreases as the first wire 17a is drawn out from the first pulley 22a. In other words, the outer periphery of the first gear 23a and the second gear 23b is formed in a shape in which the ratio R12 / R21 increases as the first wire 17a is wound around the first pulley 22a.

  Here, the first wire 17a is wound around the first pulley 22a when the first pulley 22a rotates in the first rotation direction A, and the first pulley 22a is opposite to the first rotation direction A. When rotating in the second rotation direction B, the first pulley 22a is fed out.

  Since the second gear 23b meshing with the first gear 23a rotates in the opposite direction to the first gear 23a, the second pulley 22b rotates in the opposite direction to the first pulley 22a. The second wire 17b is wound around the second pulley 22b in the same direction as the winding direction of the first wire 17a. Thereby, when the first pulley 22a rotates in the first rotation direction A and winds up the first wire 17a, the second wire 17b rotates in the direction opposite to the first pulley 22a. It is fed out from the pulley 22b. The second wire 17b is a second pulley 22b that rotates in the opposite direction to the first pulley 22a when the first pulley 22a rotates in the second rotation direction B and feeds the first wire 17a. Rolled up.

  Next, the operation of the actuator 1A will be described. FIG. 8 is a diagram for explaining the operation of the actuator 1A, and shows only the main part. The characteristics in each operation state are the same as those in the first embodiment, and will be described with reference to FIG.

  FIG. 8A shows a state in which the drive source 3 does not drive the spring 4 and the output F from the output end To is 0, and there is no external force applied to the output end To. That is, the spring 4 that is a tension coil spring has a free length, and no tension is applied to the second wire 17b. The position X of the output end To at this time is set to 0 (reference position). In FIG. 5A, this state is indicated by an operation position O (0, 0). The rotation angles θ1 and θ2 of the pulleys 22a and 22b in this state are set to 0 degrees.

  In FIG. 8B, an external force is applied in the direction of drawing the first wire 17a to the output end To from the state shown in FIG. The displaced state is shown. At this time, the first pulley 22a and the first gear 23a around which the first wire 17a is wound rotate integrally in the second rotation direction B. At the same time, the second pulley 22b rotates together with the second gear 23b meshing with the first gear 23a in the direction opposite to the first gear 23a. As a result, the first wire 17a is fed out from the first pulley 22a, while the second wire 17b is wound around the second pulley 22b. As a result, the other end T2 of the spring 4 is pulled by the second wire 17b wound around the second pulley 22b, and the spring 4 expands by −Xs1. The spring 4 biases an elastic force Fs1, which is a pulling force, to the second wire 17b in a direction in which the second wire 17b is drawn out from the second pulley 22b. As a result, an output (tensile force) Fo1 that balances the external force is generated at the output end To. Here, the leftward displacement in FIG. 8 is positive (+), and the rightward displacement is negative (−). In the present embodiment, the pulleys 22a and 22b rotate within a range of 0 degree or more and less than 360 degrees.

  Next, the displacement and force conversion action by the displacement conversion mechanism 5 will be described. The ratio A1 (θ1) = R11 / R21 of the rotation radius R11 at the winding end S11 of the first wire 17a of the first pulley 22a and the rotation radius R21 at the meshing position S21 shown in FIG. 22a and the rotation angle θ1 of the first gear 23a. The ratio A2 (θ2) = R12 / R22 of the rotation radius R12 at the meshing position S12 and the rotation radius R22 at the winding end S22 of the second wire 17b of the second pulley 22b is the same as that of the second pulley 22b and the second pulley 22b. It changes with the rotation angle θ2 of the gear 23b.

Here, assuming that the minute displacement of the first wire 17a is ΔXo and the minute displacement of the second wire 17b is ΔXs, the relationship ΔXo = A1 (θ1) · A2 (θ2) · ΔXs is established. Further, if the tension acting on the first wire 17a is Fo and the tension acting on the second wire 17b is Fs, the relationship Fo = Fs / (A1 (θ1) · A2 (θ2)) is established. Accordingly, when the elastic coefficient of the spring 4 is ks and the apparent elastic coefficient at the output end To is ko, the following equation (9) is established.
ko = ks / (A1 (θ1) · A2 (θ2)) ² (9)

As a result, even if the elastic coefficient ks of the spring 4 is a constant value, a non-linear change is caused by a change in the value of the coefficient 1 / (A1 (θ1) · A2 (θ2)) ² accompanying the change in the rotation angles θ1 and θ2. It is possible to obtain an elastic coefficient ko for In the present embodiment, the first pulley 22a and the second pulley 22b are circular, and the distances R11 and R22 are constant. In practice, the rotational radii of the second gear 23b and the first gear 23a Only the ratio R12 / R21 contributes to nonlinear conversion.

  The characteristic when the displacement converting mechanism 5 indicated by the straight line Ls in FIG. 5A is not converted to the characteristic indicated by the curve Lo1 by the converting action of the displacement converting mechanism 5A. Further, the operating position Ps1 (−Xs1, Fs1) of the spring 4 corresponding to the state of FIG. 8B is converted into the operating position Po1 (−Xo1, Fo1) of the output end To.

  Next, in FIG. 8C, from the state of FIG. 8A (the state where the output end To is not subjected to external force), the drive source 3 moves the one end T1 of the spring 4 and the base 20 in the opposite direction to the output end To. It shows a state in which driving is performed by Xd in the direction indicated by the arrow X +, and the position X of the output end To is displaced to Xd. In this state, the length of the spring 4 is the same as that shown in FIG. 8A, and no elastic force is generated. Further, the first pulley 22a and the second pulley 22b do not rotate.

  FIG. 5B shows the characteristics in this state. The characteristic at the output end To is a characteristic indicated by a curve Lo2 translated from the curve Lo1 indicating the state of FIG. 8A by Xd in the X-axis direction. Accordingly, the operation position moves from O (0, 0) to Po2 (Xd, 0). That is, the operating position of the spring 4 can be displaced by moving the mounting member 12 and the base 20 by the drive source 3.

  Next, FIG. 8 (d) is displaced by −Xo1 due to an external force acting in the direction of drawing the first wire 17a to the output end To from the state of FIG. 8 (c) (direction indicated by the arrow X-). A state where the position X of To is Xd-Xo1 is shown. At this time, the first pulley 22a rotates, and at the same time, the first gear 23a, the second gear meshing with the first gear 23a, and the second pulley 22b rotate together. Accordingly, the first wire 17a is drawn out from the first pulley 22a, while the second wire 17b is wound around the second pulley 22b. As a result, the other end T2 of the spring 4 is pulled by the second wire 17b wound around the second pulley 22b, the spring 4 is extended by -Xs1, and the second wire 17b is pulled by the spring 4 by a tensile force. A certain elastic force Fs1 is generated. As a result, an output Fo1 that balances the external force is generated at the output end To, and the operation position moves to Po3 (Xd-Xo1, Fo1).

In this embodiment, the conversion characteristic, that is, the shape of the curve Lo1 in FIG. . The conversion coefficient of the elastic coefficient is 1 / (A1 (θ1) · A2 (θ2)) ² = (R21 · R22) ² / (R11 · R12) ² as shown in the equation (9).

As described above, since the conversion characteristics can be determined only by the geometric dimensions of the gears 23a and 23b, the design and manufacture thereof are very easy. For example, when the elastic force realizes a desired function with respect to the displacement, for example, the same characteristic as the characteristic of the non-linear spring shown in Expression (4), the apparent elastic coefficient ko at the output end To is expressed by the following expression (10 )become that way.
ko = B ・ C ・ e ^{B ・ X} (10)

From the above equations (9) and (1), the first pulley 22a, the first gear 23a, the second pulley 22b, so that A1 (θ1) and A2 (θ2) satisfy the following equation (11): The rotational radii R11, R21, R22, and R12 of the second gear 23b may be designed.
A1 (θ1) · A2 (θ2) = {ks / (B · C · e ^{B · X} )} ^1/2 (11)

  In this embodiment, since the rotation radius R11 of the first pulley 22a and the rotation radius R22 of the second pulley 22b are constant, the first gear needs to be changed according to the rotation angles θ1 and θ2. Only the rotation radius R21 of 23a and the rotation radius R12 of the second gear 23b are provided. However, in order for the first gear 23a and the second gear 23b to mesh with each other, R12 + R21 must be constant. That is, the ratio R12 / R21 may be designed under the condition that R12 + R21 = constant. In addition, when the spring 4 is not linear but nonlinear, A1 (θ1) · A2 (θ2) may be designed in consideration of the characteristics.

  If the average value of A1 (θ1) and A2 (θ2) over the entire stroke of the actuator 1A is Aa, the stroke of the output end To is larger than the stroke of the spring 4 if Aa> 1, and the displacement conversion mechanism At the same time, 5A also has the effect of expanding the displacement. In the present embodiment, this condition can be satisfied by making the rotation radius R11 of the first pulley 22a larger than the rotation radius R22 of the second pulley 22b. That is, the outer peripheries of the respective pulleys 22a and 22b are formed so that the distance R11 from the rotation center Q1 to the outer periphery of the first pulley 22a is larger than the distance R22 from the rotation center Q2 to the outer periphery of the second pulley 22b. ing. As a result, since the stroke of the spring 4 becomes smaller than the stroke required for the output end To of the actuator 1A, the entire length of the spring 4 itself can be shortened. As a result, the entire length of the actuator 1A can be shortened.

  Furthermore, in the present embodiment, as shown in the equation (9), since the conversion coefficient of the elastic coefficient is inversely proportional to the square of A1 (θ1) · A2 (θ2), the variable ratio of the elastic coefficient ko at the output end To is Easy to enlarge. For example, when the variable ratio (maximum value / minimum value) of the elastic modulus ko is set to 10, the maximum value / minimum value of A1 (θ1) · A2 (θ2) may be about 3.2.

  As described above, in the present embodiment, it is possible to realize the actuator 1A having an apparently nonlinear elastic coefficient ko that has a variable ratio larger than the variable ratio of the elastic coefficient ks of the spring 4. In particular, it is possible to easily design and manufacture the actuator 1A having elastic characteristics expressed in a special function form such as an exponential function. Even when the variable ratio of the elastic coefficient ko is increased, it is not necessary to increase the amount of displacement of the spring 4, and the overall length of the actuator 1A can be shortened.

  In both the first and second embodiments, when the drive source 3 drives one end T1 of the spring 4, the base 14 or 20 needs to be driven integrally. Assuming that the drive source 3 drives only one end T1 of the spring 4 and does not drive the base 14 or 20, it is shown in FIG. 4 (c), FIG. 4 (d), FIG. 8 (c), or FIG. In the illustrated operation, the elastic force generated by the spring 4 is only applied as an offset by driving. Therefore, the characteristic of the output end To indicated by the curve Lo1 in FIG. 5B translates in the F-axis direction and does not cause the necessary translation in the X-axis direction.

  As described above, the actuators according to the first and second embodiments can be combined with a displacement conversion mechanism having nonlinear characteristics even when the characteristics of the spring used are linear (the spring constant is constant). It is possible to realize an apparently non-linear elasticity characteristic.

  Here, the characteristics of the actuators 1 and 1A are compared with the characteristics represented by the above equation (2). FIG. 9A is a diagram showing the characteristics of the output F of the actuators 1 and 1A. The characteristics obtained by the displacement conversion mechanisms 5 and 5A can be driven and translated by an arbitrary amount by the driving source 3 to obtain the characteristics indicated by the curve group Lo, and any position on these curve groups Lo can be obtained. It can be an operating position. Here, the value at the intersection (X = 0) with the F axis of each curve group Lo corresponds to the contraction force U in Equation (2), and the inclination at the operating position corresponds to the elastic coefficient ko. Similarly, FIG. 9B shows the characteristics of the output F when the contraction force U is changed in the above equation (2) as a straight line group Lm.

  Here, it is assumed that the operation range required for practical use is a rectangular region Xmin ≦ X ≦ Xmax, 0 ≦ F ≦ Fmax, and the characteristics in this operation range are compared. In FIG. 9A and FIG. 9B, the characteristics that the elastic modulus increases as the contraction force U increases match. In particular, as described above, when the elastic coefficient ko is a characteristic represented by an exponential function of the displacement X, the elastic coefficient ko is proportional to the contraction force U at an arbitrary value of X. The same characteristics as those expressed by) can be realized.

  The characteristics of the output F of the actuators 1 and 1A are different from the characteristics expressed by the expression (2) in that they are not linear with respect to the displacement X, but the change is sufficiently slow in the range of Xmin ≦ X ≦ Xmax. If so, there is no practical problem.

DESCRIPTION OF SYMBOLS 1,1A ... Actuator, 3 ... Drive source, 4 ... Spring, 12 ... Mounting member, 14 ... Base, 16a ... First pulley, 16b ... Second pulley, 17a ... First wire, 17b ... Second 20 ... base, 22a ... first pulley, 22b ... second pulley, 23a ... first gear, 23b ... second gear, 30 ... first link, 31 ... second link, 32 ... Joint, 100 ... Link mechanism

Claims (6)

In an actuator that applies a tensile force to a load,
A base supported so as to be linearly movable;
A first pulley rotatably supported on the base;
A second pulley rotatably supported by the base so as to rotate integrally with the first pulley;
When connected to the load and the first pulley rotates in a first rotational direction, the first pulley is wound around the first pulley, and the first pulley is rotated in a second direction opposite to the first rotational direction. A first connecting member wound around an outer periphery of the first pulley so as to be fed out from the first pulley when rotating in a direction;
When the first pulley winds up the first connecting member, the first pulley is fed out from the second pulley, and when the first pulley is fed out from the first connecting member, the first pulley is wound up by the second pulley. A second connecting member wound around the outer periphery of the second pulley;
An attachment member disposed on the opposite side of the load with respect to the base and connected to the base;
A drive source for linearly moving the base and the mounting member together;
One end is connected to the attachment member, the other end is connected to the second connection member, and a tensile force is applied to the second connection member so as to extend the second connection member from the second pulley. An elastic member capable of stretching,
The first pulley and the second pulley include a distance R1 from a rotation center of the first pulley and the second pulley to a terminal end of the portion where the first connecting member is wound, The ratio R1 / R2 with the distance R2 from the center of rotation to the end of the portion where the second connecting member is wound is a shape that changes according to the rotation of the first pulley and the second pulley. An actuator characterized by being formed.   The first pulley and the second pulley are formed in such a shape that the ratio R1 / R2 decreases as the first connecting member is drawn out from the first pulley. The actuator according to claim 1. In an actuator that applies a tensile force to a load,
A base supported so as to be linearly movable;
A first gear rotatably supported on the base;
A second gear rotatably supported by the base and meshing with the first gear;
A first pulley rotatably supported by the base so as to rotate integrally with the first gear;
A second pulley rotatably supported by the base so as to rotate integrally with the second gear;
When connected to the load and the first pulley rotates in a first rotational direction, the first pulley is wound around the first pulley, and the first pulley is rotated in a second direction opposite to the first rotational direction. A first connecting member wound around an outer periphery of the first pulley so as to be fed out from the first pulley when rotating in a direction;
When the first pulley winds up the first connecting member, the first pulley is fed out from the second pulley, and when the first pulley is fed out from the first connecting member, the first pulley is wound up by the second pulley. A second connecting member wound around the outer periphery of the second pulley;
An attachment member disposed on the opposite side of the load with respect to the base and connected to the base;
A drive source for linearly moving the base and the mounting member together;
One end is connected to the attachment member, the other end is connected to the second connection member, and a tensile force is applied to the second connection member so as to extend the second connection member from the second pulley. An elastic member capable of stretching,
The first gear and the second gear include a distance R12 from a rotation center of the second gear to a meshing position of the first gear and the second gear, and rotation of the first gear. The ratio R12 / R21 of the distance R21 from the center to the meshing position of the first gear and the second gear is formed in a shape that changes according to the rotation of the first gear and the second gear. An actuator characterized by that.   The first gear and the second gear are formed in a shape in which the ratio R12 / R21 decreases as the first connecting member is extended from the first pulley. The actuator according to claim 3.   The first pulley and the second pulley are formed in a shape in which the distance from the rotation center to the outer periphery of the first pulley is larger than the distance from the rotation center to the outer periphery of the second pulley. The actuator according to any one of claims 1 to 4, wherein the actuator is provided. The first link,
A second link pivotally supported at one end of the first link via a joint;
The actuator according to claim 1, wherein the actuator is connected to the first link and the second link and pivots the second link by a difference in tensile force. A link mechanism characterized by that.

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