JP2017185968A - Actuator and active truss - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator having such an effect that the responsiveness of dimension control becomes early.SOLUTION: When a piezoelectric element 6 is extended, a wedge 3 moves to a negative X-direction, and a bias spring 7 is contracted by the moving amount. When the moving amount of the wedge 3 is set as ΔX, a distance between a lower plate 10 and an upper plate 11 is increased by 2ΔXtanα. That is, the displacement of the piezoelectric element 6 in the X-direction is converted to displacement in a Z-direction in the figure. Static friction coefficients of contact faces 4, 5 are set as μ. In this embodiment, an angle α of the wedge 3 is set so as to satisfy tanα<μ (1) in advance.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an actuator used in a field where a large load is applied and high dimensional stability is required, and an active truss using the actuator.

  In order to perform advanced observations on satellites and spacecraft that observe the earth and astronomy, high dimensional stability of antennas and telespheres is required. However, CFRP (carbon-fiber-reinforced plastic), a material widely used in satellites and spacecraft, is known to swell with humidity, and its dimensions stabilize for months as it dries in space after launch. There are things that do not. In addition, the artificial satellite has a problem that the temperature environment changes according to the orbit of the earth, and the structural material undergoes thermal deformation, so that the dimensions are not stable. Therefore, the idea of actively controlling dimensions while monitoring the dimensions of structures was born.

  In Patent Document 1 entitled “Dimension Stabilized Structure”, a structure is proposed in which the temperature is controlled by thermal expansion by controlling the temperature of a metal joint. One embodiment shown in FIG. 1 of Patent Document 1 includes a CFRP frame 1 that is not partially or entirely covered with a metal foil, such as a metal end fitting 2 made of an aluminum alloy or a titanium alloy, a metal joint 3, and a metal. Heater 4 attached to the entire circumference of the joint made of metal, low thermal expansion metal rod 5 made of an invar type alloy such as iron-nickel alloy having a smaller thermal expansion coefficient than aluminum alloy or titanium alloy, strain gauge 6, strain measurement unit 7 The heater temperature control unit 8, the CFRP unit 18, and the like. In this embodiment, the strain amount of the low thermal expansion metal rod 5 is measured by the strain gauge 6, a measurement signal is sent to the heater temperature control unit 8, and positive linear expansion is performed so that the strain of the low thermal expansion metal rod 5 becomes zero. The length of the frame structure in which the CFRP frame 1, the metal end fitting 2, and the metal joint portion 3 are combined in series by heating the metal joint 3 having the metal joint portion 3 by heating with the heater 4. It is adjusted and the deformation of the frame structure is suppressed.

Japanese Patent Laid-Open No. 11-245899

  However, in the invention described in the cited document 1, since heat control is performed by a heater, there is a problem that the cooling has to rely on natural cooling and the response is slow. There is also a problem that the invention described in the cited document 1 cannot be used when the heat generation of the member cannot be allowed. For example, in an infrared telescope for space use, since it is necessary to cool the member gently in order to minimize infrared rays emitted from the member, heat generation may not be allowed. Furthermore, since a member having a large linear expansion coefficient is used, when the temperature control mechanism fails, there is also a problem that the temperature stability is deteriorated.

  On the other hand, there are a piezoelectric element and a magnetostrictive element as an actuator generally used when controlling a minute displacement. However, since these elements are made of ceramic, they are fragile and have a drawback of being weak against an impact load. For this reason, when mounted on an artificial satellite or the like, it is necessary to use a launch lock mechanism or the like so that the load at the time of launch is not directly applied to the element. However, the launch lock mechanism is complicated and effective, and causes an increase in mass and also causes a decrease in reliability.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an actuator that solves the above problems, and an active truss using this actuator.

An actuator according to the present invention includes a first drive member and a second drive member, a wedge disposed between the first drive member and the second drive member, and a relative relationship between the first drive member and the second drive member. Restraining means for restraining the movement in a first direction in which both approach or leave, driving means for driving the wedge in a second direction perpendicular to the first direction, the first driving means and the second Pressurizing application means for applying a pressurizing force in a direction in which the driving means is pressed against the wedge, wherein the sliding direction of the first driving member and the wedge is the first sliding direction, and the second driving member is When the sliding direction of the wedge is the second sliding direction, one or both of the first sliding direction and the second sliding direction has an angle α with respect to the second direction. A contact surface between the first drive member and the wedge, and A static friction coefficient of the contact surface of the wedge and the second drive member is mu, between the angle α and the coefficient of static friction mu,
tanα <μ
The angle α and the coefficient of static friction are adjusted so that the following relationship holds.

  As the driving means, a piezoelectric element or a magnetostrictive element can be used.

  As the restraining means, a pair of parallel hinge springs or leaf springs can be used.

  The first drive member, the second drive member, and the wedge are provided with fitting portions, and the first drive member and the wedge, and the second drive member and the wedge are separated from each other by the fitting portion. It can be fitted to prevent.

  A film is formed on the contact surface between the first drive member and the wedge and the contact surface between the second drive member and the wedge, and the frictional force can be controlled by this film.

  The coating can be a composite ceramic coating mainly composed of chromium oxide.

  An active truss according to the present invention includes any one of the actuators described above, a truss, and a length measuring unit that measures a length from a reference point.

  The length measuring means may include a laser length measuring device.

  Since the present invention controls the dimension in the first direction using the drive member as described above, the response of the dimension control is faster than when thermal expansion is used, and the temperature of the member is arbitrarily controlled. it can. Since the drive member does not need to be energized except during driving, the drive member generates little heat and has little heat fluctuation when a failure occurs. By setting the relationship between the angle α and the static friction coefficient μ as described above, the resistance to damage is high even when a large load is applied. Further, by providing the fitting portion and fitting the first drive member, the second drive member, and the wedge with each other, the launch lock becomes unnecessary. And when mounted on a spacecraft, it is possible to provide technical effects such as providing structural members with little dimensional change in orbit.

It is the side view which showed the actuator which concerns on 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of the actuator shown in FIG. It is a figure for demonstrating operation | movement of the actuator shown in FIG. It is the side view which showed the actuator which concerns on 2nd Embodiment of this invention. It is sectional drawing which cut the actuator of FIG. 4 with the cut surface of the center part. It is the side view which showed the active truss which concerns on 3rd Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1
FIG. 1 is a side view showing an actuator according to Embodiment 1 of the present invention. In FIG. 1, the code | symbol 101 has shown the coordinate system used for description of a structure of an actuator. The first driving member 1 is fixed to the lower plate 10. A wedge 3 is disposed on the first drive member 1, and both can slide on the contact surface 4 of the first drive member 1 and the wedge 3. The second drive member 2 is disposed on the wedge 3, and both can slide on the contact surface 5 of the wedge 3 and the second drive member. An upper plate 11 is fixed to the second drive member 2. The contact surface 4 is inclined clockwise by an angle α with respect to the X direction in the figure, and the contact surface 5 is inclined counterclockwise by an angle α with respect to the X direction in the figure. Here, it is assumed that both the contact surface 4 and the contact surface 5 are inclined by the angle α, but it is also possible that only one of them is inclined and the other is not inclined.

  The first drive member 1, the second drive member 2, and the wedge 3 are made of a stainless alloy as an example, and a composite ceramic coating (CDC-ZAC manufactured by Tocalo Corporation) whose main component is chromium oxide is formed on the sliding surface. A film is formed. With this coating, a relatively stable frictional force having a static friction coefficient on the sliding surface of about 0.4 can be obtained. This film is also characterized by a small difference in frictional force between air and vacuum.

  Arm portions 13a and 13b are connected to the left and right sides of the lower plate 10 via elastic hinge springs 12a and 12b, respectively. Arm members 13c and 13d are connected to the left and right sides of the upper plate 11 via elastic hinge springs 12c and 12d, respectively. The arm members 13a and 13c are connected to the side plate 15 via elastic hinge springs 14a and 14c, respectively. The arm members 13b and 13d are connected to the side plate 16 via elastic hinge springs 14b and 14d, respectively. Between the side plate 15 and the wedge 3, a piezoelectric element 6 as a driving means is disposed, and between the side plate 16 and the wedge 3, a bias spring 7 is disposed. Although a piezoelectric element is used as the driving means, a magnetostrictive element can also be used.

  With such a structure, the first drive member 1 and the second drive member 2 are restrained by an elastic hinge spring parallel to each other so as to be relatively movable only in the Z direction (the direction in which both approach or leave) in the figure. Yes. Further, a leaf spring can be used as the restraining means. Due to the elasticity of the elastic hinge springs 12a to 12d and 14a to 14d, a pressure is applied to the first drive member 1 and the second drive member 2 in a direction in which both approach each other. Apart from this, a tension spring may be arranged between the lower plate 10 and the upper plate 11 to apply pressure.

Next, the operation of the actuator of this embodiment will be described with reference to FIGS. As shown in FIG. 2, when the piezoelectric element 6 extends, the wedge 3 moves in the minus X direction in the figure, and the bias spring 7 contracts accordingly. When the movement amount of the wedge 3 is ΔX, the distance between the lower plate 10 and the upper plate 11 is 2ΔXtan ⁻¹ α.
Only increase. That is, the displacement of the piezoelectric element 6 in the X direction is converted into a displacement in the Z direction in the figure. Since the displacement in the Z direction is generally minute compared to ΔX, it is possible to realize dimensional control with high accuracy using the displacement in the Z direction.

As shown in FIG. 3, the operation when the compressive force F acts between the lower plate 10 and the upper plate 11 will be described. Here, the coefficient of static friction on the contact surfaces 4 and 5 is μ. In this embodiment, the angle α of the wedge 3 is set in advance.
tanα <μ (1)
Set to be.

Considering the contact surface 5, the force F at the contact surface 5 is the force Fsinα in the sliding direction.
And the force Fcosα in the direction perpendicular to the contact surface
Can be broken down into The maximum frictional force at the contact surface 5 is μFcosα
So from (1)
Fsinα <μFcosα (2)
Thus, the wedge 3 does not slide regardless of the size of F. The same applies to the contact surface 4. That is, no force is transmitted to the piezoelectric element 6. Therefore, even when a large compressive load is applied to the actuator, the piezoelectric element is not damaged.

  On the other hand, when a tensile force is applied to the actuator, the first driving member 1 and the second driving member 2 are separated from the wedge 3 when the pressure applied by the elastic hinge springs 14a to 14c is exceeded. Therefore, when using this actuator, it is necessary to use it within a range where the tensile force does not exceed the applied pressure.

  When this actuator fails, the distance between the lower plate 10 and the upper plate 11 varies depending on the ambient temperature, but the material of the first drive member 1, the second drive member 2 and the wedge 3 is subjected to low linear expansion. By using a coefficient material, it is possible to reduce temperature fluctuations.

[Second Embodiment]
Next, the actuator according to the second embodiment will be described with reference to FIGS. First, components 201 to 211 in FIG. 4 correspond to components 1 to 11 in the first embodiment.

  Plate springs 213 a and 213 b are connected to the left and right sides of the lower plate 210, and plate springs 213 c and 213 d are connected to the left and right sides of the upper plate 211. The leaf springs 213a and 213c are connected to the side plate 215, and the leaf springs 213b and 213d are connected to the side plate 216. The leaf springs 213a to 213d function in the same manner as the arm members 13a to 13d and the elastic hinge springs 14a to 14d of the first embodiment.

  FIG. 5 is a cross-sectional view taken along the cutting plane 220 in FIG. In the present embodiment, as shown in FIG. 5, the first drive member 201 and the wedge 203 are fitted together, and similarly, the second drive member 202 and the wedge 203 are fitted together. The fitting portion includes a first driving member and second driving members 210 and 211, and a wedge 203 when a tensile force exceeding the pressure applied by the leaf springs 213a to 213d is applied between the lower plate 210 and the upper plate 211. Prevent them from leaving each other. In FIG. 5, the gap of the fitting portion is drawn large for the sake of explanation, but it is desirable that the gap size be as small as possible within a tolerance range.

  With the configuration as described above, the actuator of the present embodiment can withstand not only a compressive force but also a large tensile force. In addition, due to the above configuration, when incorporated in the main structural member of the spacecraft, it is possible to withstand the launch load without using a launch lock.

[Third Embodiment]
Next, an active truss will be described as a third embodiment. In FIG. 6, reference numeral 330 denotes the actuator of the second embodiment shown in FIG. A hole is formed in the center of the actuator 330 so that the laser beam 335 can pass therethrough. Reference numerals 331a and 331b denote hollow end fittings made of metal, and reference numeral 332 denotes a hollow truss made of CFRP.

  The laser length measuring device 333 and the reflector 334 are attached to the reference point of the structure. The laser length measuring device 333 oscillates the laser beam 335 and measures the distance from the reflector 334. The laser beam 335 passes through the actuator 330, the hollow end fitting 331a, the hollow truss 332, and the hollow end fitting 331b. With such a configuration, it is possible to freely arrange devices around the truss. By performing feedback control so that the output of the laser length measuring device 333 is always constant, a structure having a stable dimensional accuracy that is not affected by temperature can be obtained.

CFRP, which is a material of the hollow truss 332, generally has a linear expansion coefficient of about 10 ^−6, but if the truss length is 1 m, the fluctuation when exposed to a temperature change of 10 ° C. on the orbit is about 10 μm. . When the wedge angle α of the actuator 330 is 16.7 degrees, the displacement of the actuator is approximately 0.6 with respect to the displacement 1 of the piezoelectric element. That is, when the truss length is 1 m, the temperature variation on the orbit can be corrected by using a piezoelectric element having a stroke of 16.7 μm or more.

  According to the present invention, since high dimensional stability can be obtained, the actuator and active truss of the present invention can be applied to antennas, telescopes and other devices that are mounted on artificial satellites and spacecrafts to observe the earth and astronomy. . Needless to say, the present invention can be applied not only to space but also to terrestrial applications to equipment that requires high dimensional stability.

1, 201 First driving member 2, 202 Second driving member 3, 203 Wedge 4, 5 Contact surface 6, 206 Piezoelectric element 7, 207 Bias spring 10, 210 Lower plate 11, 211 Upper plate 12a, 12b, 12c, 12d Elastic hinge springs 13a, 13b, 13c, 13d Arm members 213a, 213b, 213c, 213d Leaf spring 330 Actuator 331a, 331b Hollow end fitting 332 Hollow truss 333 Laser length measuring device 334 Reflector 335 Laser light

Claims (10)

A first drive member and a second drive member;
A wedge disposed between the first drive member and the second drive member;
Restraining means for restraining the relative movement of the first driving member and the second driving member in a first direction in which both approach or leave;
Driving means for driving the wedge in a second direction perpendicular to the first direction;
Pressurization application means for applying a pressurization in a direction in which the first drive means and the second drive means are pressed against the wedge,
When the sliding direction of the first drive member and the wedge is the first sliding direction, and the sliding direction of the second drive member and the wedge is the second sliding direction, the first sliding One or both of the direction and the second sliding direction has an angle α with respect to the second direction;
The static friction coefficient of the contact surface of the first drive member and the wedge and the contact surface of the second drive member and the wedge is μ, and between the angle α and the static friction coefficient μ,
tanα <μ
An actuator in which the angle α and the coefficient of static friction are adjusted so that the above relationship is established.   The actuator according to claim 1, wherein the driving unit is a piezoelectric element.   The actuator according to claim 1, wherein the driving unit is a magnetostrictive element.   The actuator according to any one of claims 1 to 3, wherein the restraining means is a pair of parallel hinge springs.   The actuator according to any one of claims 1 to 3, wherein the restraining means is a leaf spring.   The first driving member, the second driving member, and the wedge have a fitting portion, and the first driving member and the wedge, and the second driving member and the wedge are separated from each other by the fitting portion. The actuator according to any one of claims 1 to 5, wherein the actuator is fitted so as to prevent the above.   The coating for controlling the frictional force is formed on the contact surface between the first drive member and the wedge and the contact surface between the second drive member and the wedge. The actuator according to any one of 1 to 6.   The actuator according to claim 7, wherein the coating is a composite ceramic coating mainly composed of chromium oxide. The actuator according to any one of claims 1 to 8,
A truss,
A length measuring means for measuring the length from the reference point;
An active truss characterized by comprising:   The active truss according to claim 9, wherein the length measuring unit includes a laser length measuring device.

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