JP2008131753A - Electrostatic actuator and control method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic actuator and a control method for the actuator wherein a ball can be prevented from coming off from a groove at an end of the groove or reduction in produced thrust can be prevented and coming-off can be prevented by resetting the operating state to the initial state. <P>SOLUTION: A guide groove 21A (21A1, 21A2, 21A3) is so formed that its groove length L1 is equal to or larger than 1/2 times the length obtained by subtracting the diameter of a ball from an operation range length Lm. The frequency of a ball 41 hitting against an end face 22a of the guide groove 21A is reduced as long as a moving element 30 is used within a range less than the operation range length Lm, more preferably, a practical use range length shorter than it. As a result, the ball 41 can be prevented from coming off. When the moving element 30 is reciprocated once on either side or on both sides, the operating state can be reset to the initial state and the ball 41 can be prevented from coming off. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrostatic actuator driven by an electrostatic force generated between an electrode on a stator side and an electrode on a mover side, and in particular, via a ball provided between the stator and the stator. The present invention relates to a moving electrostatic actuator and a control method thereof.

  Patent Document 1 below describes an electrostatic actuator in which a plurality of stator electrodes and mover electrodes are respectively arranged on opposite surfaces of a stator and a mover that are arranged to face each other.

  In the stator and / or the movable element, a pair of left and right long grooves extending in the moving direction are formed on the opposing surfaces, respectively. In these long grooves, for example, a guide protrusion having a low friction coefficient, a cylindrical shape, and the like are formed. Rollers or balls are arranged.

When a predetermined voltage is applied between the stator electrode and the mover electrode, an electrostatic force generated between both electrodes acts as a repulsive force or an attractive force on the mover. For this reason, it is possible to move the mover in the moving direction by sliding the guide convex portion in the groove or rolling the roller or the ball.
JP-A-2005-333756

  In the configuration using the guide convex portion, the guide convex portion and the groove are formed of a material having a low friction coefficient, so that the influence of the dynamic friction resistance can be reduced. However, since there is a limit to reducing the effect of static frictional resistance when starting from a stationary state, it is difficult to shorten the rise time (response time), which improves the response of the actuator at the time of starting. There is a problem that it is difficult. In addition, a phenomenon in which the actuator does not operate depending on the state of the static frictional resistance, for example, temperature, humidity, dust, or the like is a relatively frequent problem with this type of actuator.

  On the other hand, in the structure using a roller, the upper surface or the bottom surface of the roller is always in contact with the inclined surface of the groove. For this reason, there exists a problem that it is difficult to reduce the influence of the sliding frictional resistance in the said contact part.

  In addition, in the device described in Patent Document 1 using a ball, in order to move the mover in a balanced and stable state, the opposing portion of the stator and the mover is opposed to the vertical direction 1. It is necessary to dispose at least two or more balls between the two grooves, and to provide a predetermined distance in the moving direction between the ball positioned in the front and the ball positioned in the rear.

  However, if the mover is reciprocated many times in the moving direction, the ball may be displaced due to the effect of frictional resistance, and the predetermined interval may be gradually reduced. In this case, the mover It is difficult to drive the battery stably.

  Further, in the structure in which the ball is provided in the holding groove so as to be able to roll, the ball may come into contact with the end face of the holding groove. At this time, if the frictional resistance between the ball and the end surface is large, the thrust generated in the mover is reduced, or the mover is lifted at the moment of contact, and the ball is removed from the holding groove. A malfunction occurs.

  The present invention is for solving the above-described conventional problems, and it is possible to effectively prevent the thrust generated in the mover at the end of the groove from being reduced or the ball from being removed from the wheel. It aims to provide an actuator.

  In addition, the present invention is able to prevent the above-mentioned malfunction phenomenon by resetting it to the initial state before the ball contacts the end of the groove and malfunctions such as an increase in frictional resistance and wheel removal occur. It is an object of the present invention to provide a method for controlling an electric actuator.

The present invention includes at least a stator having a first long groove formed along the moving direction, and a second long groove formed along the moving direction, and the movement in a state facing the stator. A movable element that is movable in a direction, a plurality of rolling elements that are arranged to roll between the first long groove and the second long groove, and a plurality of fixed elements that are provided on the stator. And a plurality of mover electrodes provided on the mover, and the rolling element can move without contacting the end of the first long groove or the second long groove in the moving direction. An electrostatic actuator that can reciprocate within the operating range length of
At least one of the first long groove and the second long groove is formed with a length dimension equal to or smaller than the other long groove, and the length dimension of the one long groove having the short length dimension is as follows: It is characterized by being formed with a length dimension equal to or more than ½ times the length obtained by subtracting the diameter of the rolling element from the operating range length.

  In the present invention, among the long grooves formed in the mover and the stator, the lower limit value of the shorter long groove is set to a length that is 1/2 times the length obtained by subtracting the diameter of the rolling element from the operation range length of the mover. The length is longer than the dimension. For this reason, as long as the mover is used below the operation range length, preferably below the practical use range length having a slight margin, the ball can be prevented from hitting the end of the short long groove. For this reason, it is possible to prevent the ball from getting on the groove and coming off the wheel.

Further, as a more preferable upper limit value, for example, when the mover is moved in one direction of the moving direction on the stator, it is provided on the end side in the moving direction in the long groove formed in the mover. The end portion provided at the end side position of the long groove formed coincides with the end portion provided at the front end side position of the long groove provided at the end side among the long grooves formed in the mover. When the mover is moved in the other direction opposite to the one direction from the first coincidence position, the long groove formed in the mover is provided on the end side in the moving direction. The end provided at the end of the long groove coincides with the end provided at the tip of the long groove provided at the end among the long grooves formed in the stator. When the movement distance to the second matching position is the driving range length
Of the groove length of the mover and the groove length of the stator, the length dimension of the other long groove having the short length dimension is 1 / of the length dimension obtained by subtracting the diameter of the rolling element from the drive range length. Formed with less than twice the length dimension.

  For example, the length dimension of the second long groove provided in the mover can be configured to be longer than the length dimension of the first long groove provided in the stator.

  In the above, the friction coefficient of both end surfaces forming the short sides of the first long groove and the second long groove is determined from the friction coefficient of the inner wall surface forming the long sides of the first long groove and the second long groove. Is also preferable.

  In the above means, when the ball hits the end face of the groove, the ball does not ride on the end face, and the frequency of wheel removal can be reduced.

Further, the present invention includes at least a stator having a first long groove formed along the moving direction, and a second long groove formed along the moving direction and facing the stator. A mover provided movably in a moving direction, a rolling element arranged movably between the first long groove and the second long groove, and a plurality of stators provided on the stator An electrostatic actuator control method having an electrode and a plurality of mover electrodes provided on the mover,
(A) moving the mover by a predetermined distance in one of the moving directions;
(B) returning the mover to a predetermined neutral position;
The rolling element is returned to a predetermined position by passing through.

  In the present invention, the operation state of the electrostatic actuator can be returned to the initial state by a simple process of moving the mover in one direction of movement and then returning it to the neutral position (one-way one-way reciprocation). For this reason, it is possible to prevent the ball from coming out of the groove.

Furthermore, after the step (b),
(C) moving the mover by a predetermined distance to the other of the moving directions opposite to the one;
(D) returning the mover to a predetermined neutral position on the stator;
It can have.

  If the steps (a) and (b) alone cannot be completely reset, the steps (c) and (d) are subsequently performed (one reciprocation on both sides), so that the operation state of the electrostatic actuator can be surely changed. It is possible to return to the initial state.

  Further, when the predetermined distance moves the mover from a predetermined neutral position on the stator to one or the other in the moving direction, any one of the rolling elements from the predetermined neutral position It is preferable that the rolling range length is between the end of any one of the first long grooves and the end of any of the second long grooves.

  In the above means, since the range in which the mover moves can be limited, it is possible to reliably prevent problems such as wheel removal during the reset operation.

  In the electrostatic actuator of the present invention, the ball can be prevented from being positioned at the end of the groove.

  Further, even if the ball is positioned at the end of the groove, it is difficult for the ball to climb over the groove and the wheel can be prevented from being derailed. Can be suppressed.

  Further, in the present invention, since the operation state of the electrostatic actuator can be reset to the initial state before the ball is derailed, the derailment can be prevented in advance.

  1 is a perspective view showing an electrostatic actuator according to a first embodiment of the present invention, FIG. 2 is a sectional view of the electrostatic actuator taken along line II-II in FIG. 1, and FIG. 3 is a stator electrode and a mover electrode. FIG. 4 is a plan view of the stator showing the arrangement relationship of the stator electrodes. In FIG. 2, the stator electrode and the mover electrode are omitted for simplification.

  The electrostatic actuator 10A described below is mounted, for example, in a camera body of a camera with a zoom function, and is used as a moving mechanism that moves a lens along the optical axis direction.

  As shown in FIG. 1, the electrostatic actuator 10A according to the present invention includes a stator 20 provided on the Z2 side in the height direction and a mover 30 provided on the Z1 side.

  The stator 20 is a flat plate-like member extending in the Y direction that is the moving direction, and is formed of, for example, a silicon base material. In the present embodiment, three pieces extending linearly at a predetermined groove length L1 along the moving direction (Y direction) at the right end in the width direction (X direction) of the facing surface 20a (Z1 side) of the stator 20. Guide grooves (first long grooves) 21A (indicated by 21A1, 21A2 and 21A3 individually) are formed in a line. Similarly, at the left end in the width direction (X direction) of the facing surface 20a, three guide grooves (first long grooves) 21B linearly extending with a predetermined groove length L1 along the movement direction (Y direction) are also provided. (Indicated individually by 21B1, 21B2, and 21B3) are formed in a line. The pair of left and right guide grooves 21A1 and 21B1, the pair of left and right guide grooves 21A2 and the same guide groove 21B2, and the pair of left and right guide grooves 21A3 and 21B3 are parallel to each other in the direction of movement of the stator 20. They are formed at equal positions from the ends. Furthermore, the guide groove 21A and the guide groove 21B are formed with a fixed dimension pair W1 in the width direction.

  Of the guide grooves 21A arranged in a line in the movement direction, the plate thickness in the Y direction in the figure is ΔL1 between the guide grooves 21A1 and the guide grooves 21A2 and between the guide grooves 21A2 and the guide grooves 21A3. Are separated by partition walls 21a and 21a. Similarly, the guide groove 21B1 and the guide groove 21B2 and the guide groove 21B2 and the guide groove 21B3 are also partitioned by partition walls 21b and 21b each having a plate thickness ΔL1 in the Y direction in the drawing. .

  As shown in FIG. 3, the cross-sectional shapes of the guide grooves 21A and 21B are substantially V-shaped (V-grooves) that are concave in the Z2 direction shown in the figure, and are different from the opposing surface 20a of the stator 20 made of a silicon wafer. It is formed by performing isotropic etching. On the surfaces of the guide grooves 21A and 21B, an oxide film (not shown) that is resistant to heat and dirt and excellent in insulation is formed by heating a silicon crystal to a high temperature in oxygen. The oxide film may be formed on the entire surface of the opposing surface 20a, or may be formed only on the surface of the inclined inner wall surface that forms the guide groove 21A and the three guide grooves 21B. Also good. Then, on the surface of the inner wall surface that forms the guide grooves 21A and 21B, and on the surface of the oxide film, a conductive portion 25 formed by plating using, for example, gold, copper, chromium, or the like is provided. Yes. One end of the conductive portion 25 is led out to the outside through a lead wire 25a formed on the facing surface 20a of the stator 20.

  The conductive portions 25 are not formed on the end faces 22a and 22b (including both sides of the partition walls 21a and 21a) at both ends (short side) in the moving direction of each guide groove 21A and each guide groove 21B, and the oxide film Is exposed. The surface of the oxide film has a smaller coefficient of friction with the metal than the surface of the conductive portion 25. For this reason, in the guide grooves 21A and 21B, the end faces 22a and 22b on the short side are balls described later, rather than the surface of the conductive portion 25 forming the inner wall surface provided on the long side of the V groove. The frictional resistance with the surface metal is small.

  On the other hand, the mover 30 has a width dimension in the X direction shown in the figure that is substantially the same as that of the stator 20, but a length dimension in the movement (Y) direction is shorter than that of the stator 20. . A pair of holding grooves (first grooves) that extend linearly in the moving direction and oppose the guide grooves 21A and 21B are provided at both left and right ends in the width direction (X direction) of the facing surface (Z2 side surface) 30a of the mover 30. 2 long grooves) 31 and 32 are provided. Similarly to the guide grooves 21A and 21B, the holding grooves 31 and 32 have a substantially V-shaped cross section (V-groove), an oxide film (not shown) is formed on the surface, and a conductive portion 35 is further formed on the surface. Is formed.

  End faces 31a and 31a and end faces 32a and 32a are formed at both ends in the Y direction of the holding grooves 31 and 32, respectively. The moving surfaces of the end faces 31a, 31a, 32a, 32a are the front face 30A and the rear face 30B of the mover 30. Similar to the end faces 22a and 22b, oxide films are exposed on the end faces 31a, 31a, 32a and 32a provided at the ends of the holding grooves 31 and 32 in the moving direction. For this reason, also in the holding grooves 31 and 32, the end faces 31a, 31a, 32a, and 32a are more susceptible to friction with the metal on the ball surface described later than the conductive portion 35 formed on the inner surface of the V-groove. The resistance is low. Here, as shown in FIG. 2, assuming that the length of the pair of left and right holding grooves 31 and 32 on the movable element 30 side in the moving direction is L2, in the first embodiment, the holding grooves 31 and 32 are as follows. A relationship of at least L1 <L2 is established between the groove length L2 and the groove length L1 of each guide groove 21A, 21B on the stator 20 side.

  As shown in FIGS. 1 and 3, the stator 20 shown in the present embodiment has a plurality of stator electrodes 23 formed in a convex shape on the facing surface 20a. The stator electrode 23 is a brush in which comb-like electrodes arranged in a row at a predetermined interval along the movement (Y) direction are arranged in a plurality of rows along a width (X) direction orthogonal to the movement direction. Electrode. The plurality of stator electrodes 23 as a whole are regularly arranged in a matrix (also referred to as a grid or a grid).

  Each of the stator electrodes 23 is formed in a cubic shape or a rectangular parallelepiped shape. A predetermined gap dimension is formed between the stator electrode 23 and the stator electrode 23 adjacent to each other in the width (X) direction, and a mover electrode 33 described later is disposed in the gap.

  Similarly, a plurality of mover electrodes 33 having a convex shape are also formed on the facing surface 30 a of the mover 30. The movable element electrode 33 is provided with a plurality of comb-like electrodes arranged in a line along the movement (Y) direction in a plurality of rows in the width (X) direction orthogonal to the movement direction, and the whole is substantially a matrix. Are arranged in a regular pattern. Each mover electrode 33 is formed in a cubic shape or a rectangular parallelepiped shape.

  The stator electrode 23 and the mover electrode 33 are provided with a resist layer having a plurality of exposed portions opened in a matrix at a predetermined pitch on the conductive layers 24 and 33A formed on, for example, a silicon substrate, A conductive metal such as copper is plated on the surfaces of the conductive layers 24 and 33A appearing in the exposed portions so as to be perpendicular to the Z direction.

  A conductive layer 33A of the mover 30 on which one of the mover electrodes 33 is formed is formed with a predetermined area of one sheet on the surface of the facing surface 30a, and each mover electrode 33 is a conductive layer. Conductive connection is established via 33A. That is, the conductive layer 33 </ b> A functions as a common electrode that electrically connects the individual mover electrodes 33. The conductive layer 33A is connected to the conductive portion 35 formed on the surfaces of the holding grooves 31 and 32.

  On the other hand, the conductive layer 24 of the stator 20 on which the stator electrode 23 is formed has a strip-like shape separated for each row as shown in FIG. The mover electrodes 33 (six in FIG. 4) formed on one band-like conductive layer 24 are electrically connected to each other, and these form one phase electrode. The phase electrodes adjacent to each other in the movement (Y) direction are insulated, and a plurality of phase electrodes are arranged on the stator electrode 23 at a predetermined pitch along the movement (Y) direction. Has been.

  The end 24a of the conductive layer 24 is led to the lower surface (Z2 side surface) of the stator 20 through the through hole 26 formed in the stator 20, and the lead wire provided on the lower surface side. 27 is pulled out to the outside. For this reason, it is possible to apply a voltage having a different timing for each phase electrode to the stator electrode 23 via the lead wire 27. Moreover, in FIG. 4, although the phase electrode is shown by five poles of A phase or E phase, the number of poles of a phase electrode is not restricted to this.

  As shown in FIGS. 1 and 3, the stator 20 and the mover 30 are assembled in a state where the opposing surfaces 20a and 30a face each other. In the assembled state, the mover electrode 33 provided on the mover 30 side is disposed between the stator electrode 23 provided on the stator 20 and the stator electrode 23, and at the same time the mover 30 side The stator electrode 23 of the stator 20 is disposed between the mover electrode 33 and the mover electrode 33.

  In this state, each guide groove 21A1, 21A2, 21A3 is provided with a ball (rolling element) 41 (indicated individually by 41a, 41b, 41c), and each guide groove 21B1, 21B2, 21B3 is also provided. One ball 42 (indicated by 42a, 42b and 42c individually) is provided.

  The upper parts of the three balls 41a, 41b, 41c are arranged in one holding groove 31 provided on the X1 side of the movable element 30 side. Similarly, the upper portions of the three balls 42a, 42b, and 42c are disposed in the other holding groove 32 on the movable element 30 side provided on the X2 side of the movable element 30 side.

  For this reason, the mover 30 is provided in each of the three balls 41 provided in the three guide grooves 21A on the X1 side of the stator 20 and the three guide grooves 21B on the X2 side of the stator 20 side. The three balls 42 are supported. In this state, a constant gap dimension h is formed between one opposing surface 20a on the stator 20 side and the other opposing surface 30a on the mover 30 side. At the same time, the tip (upper end) of each stator electrode 23 on the stator 20 side and the conductive layer 33A on the mover 30 side oppose each other through a gap, and the tip (lower end) of each mover electrode 33 on the same mover 30 side. ) And the conductive layer 24 on the stator 20 side are opposed to each other through a gap.

  The balls 41 and 42 are, for example, a hard plastic material, a surface of the hard plastic material covered with a conductive layer made of metal such as gold or copper, or the balls 41 and 42 themselves are made of a conductor such as gold or copper. It is formed with a metal sphere.

  In this state, when a force in the moving direction (Y1-Y2 direction) is applied to the mover 30, the plurality of balls 41, 42 roll between the guide grooves 21A, 21B and the holding grooves 31, 32, respectively. Therefore, it is possible to move the mover 30 while maintaining a constant horizontal posture linearly in the moving direction. That is, the guide grooves 21A and 21B, the holding grooves 31 and 32, and the plurality of balls 41 and 42 in this embodiment function as guide members that guide the mover 30 in the moving direction.

  In a state in which the mover 30 is incorporated on the stator 20, as shown in FIG. 3, when viewed from the stator 20 side, the stator electrode 23 and the stator electrode 23 adjacent to each other in the width (X) direction The movable element electrode 33 is provided without being in contact therewith. Similarly, when viewed from the mover 30 side, the stator electrode 23 is provided between the mover electrode 33 and the mover electrode 33 without contact.

  In this state, one side surface (electrode surface) adjacent to the side surface (electrode surface) of one movable element electrode 33 faces the surface. When a predetermined drive voltage is applied between the plurality of conductive layers 24 provided on the stator 20 side and the electrode layer on the mover 30 side, the electrode surface of the stator electrode 23 and the mover electrode 33 are applied. An electrostatic force is generated between the portion facing the electrode surface.

  For this reason, the movable element 30 is moved by switching the driving voltage applied between each phase electrode (each conductive layer 24) on the stator 20 side and the conductive layer 33A on the movable element 30 side at a predetermined timing. It functions as an electrostatic actuator 10A that can be moved in the direction (Y1-Y2 direction). Therefore, a power control unit (not shown) that switches the drive voltage at a predetermined timing is provided outside the electrostatic actuator 10A.

  The power control unit and each stator electrode 23 are connected to each phase via the lead wire 27, the through hole 26, and the conductive layer 24. Between the power control unit and the mover electrode 33, the lead wire 25a provided on the stator 20 side is connected to the ball 41 from the conductive unit 25, and further provided on the mover 30 side from the ball 41. The conductive portion 35 is connected to the conductive layer 33A (see FIG. 3).

The operation and control of the electrostatic actuator will be described.
5, 6 and 7 are cross-sectional views similar to FIG. 2, showing the operating state of the electrostatic actuator. 5 to 7A shows a state in which the mover is moved in the Y1 direction which is one of the moving directions, and B in FIGS. 5 to 7 shows a state in which the mover has been moved in the Y2 direction which is the other of the moving directions. Yes. FIG. 5 is a view for explaining the moving range (practical use range) of the mover when the ball does not contact the end portions on both sides of the guide groove. FIG. 6 shows the ball as a comparative example of FIG. FIG. 7 is a view for explaining a moving range (operation range (upper limit of use range)) of the mover when the abutment comes into contact with both ends of the guide groove. FIG. It is a figure for demonstrating a movement range (driving range (ideal operation range)).

  In the following, for the convenience of the drawing, one guide groove (first long groove) 21A (21A1, 21A2, 21A3), one ball 41 (41a, 41b, 41c) and one provided mainly on the X1 side in the figure are shown. The holding groove (second long groove) 31 is shown and described, but these operations are performed on the other guide groove (first long groove) 21B (21B1, 21B2, 21B3) provided on the X2 side in the drawing, and on the other ball The same applies to 41 (42a, 42b, 42c) and the other holding groove (second long groove) 32.

  In the initial state (neutral position) shown in FIG. 2A, each of the balls 41 (41a, 41b, 41c) has three guide grooves 21A (21A1, 21A2, 21A3) provided on the left and right sides of the stator 20 side. It is located near the center L1 / 2 of the groove length L1. On the mover 30 side, the ball 41b located in the center is located near the center L2 / 2 of the groove length L2 of the holding groove 31. Note that the same fixed interval is set between the ball 41a and the ball 41b and between the ball 41b and the ball 41c.

  When the power control unit (not shown) is driven and the predetermined drive voltage is applied between the stator electrode 23 and the mover electrode 33, the mover 30 is moved to an electrostatic force as shown in FIGS. Is moved in the Y1 direction or the Y2 direction.

  Here, reference numeral Lu shown in FIGS. 5A and 5B indicates that when the mover 30 is moved in the Y1 direction and the Y2 direction, the balls 41a, 41b, and 41c become the guide grooves 21A1, 21A2, 21a3, and the holding grooves 31. The practical use range length of the needle | mover 30 which can move without abutting on any of the end surfaces 22a and 31a is shown.

  6 indicates the operation range length of the mover 30. In FIG. That is, the operation range length Lm is a position where the balls 41a, 41b, 41c are in contact with the respective end surfaces 22a on one y1 side of the guide grooves 21A1, 21A2, 21a3 when the mover 30 is moved in the Y1 direction (FIG. 6) and when the mover 30 is moved in the Y2 direction, the balls 41a, 41b, 41c are in contact with the other end surfaces 22a on the other y2 side of the guide grooves 21A1, 21A2, 21a3 (see FIG. 6 (see B in FIG. 6), which has a meaning as an upper limit (maximum value) of the use range length Lu.

  In the state shown in FIG. 6A, the ball 41a located on the downstream side at the time of movement has an end face 31a located on the end (Y2 side) of the holding groove 31 on the mover 30 side and a guide groove on the stator 20 side. In the state shown in FIG. 6B, the ball 41c located between the end surface 22a on the tip (Y1) side of 21A1 and the downstream side at the time of movement moves the tip (Y1 of the holding groove 31 on the mover 30 side). And the end surface 22a on the end (Y2) side of the guide groove 21A1 on the stator 20 side.

  In this case, the groove lengths L1 of the guide grooves 21A1, 21A2, and 21a3 are at least 1/2 times the length dimension obtained by subtracting the diameter R of the ball 41 from the operation range length (upper limit of the use range) Lm (L1). ≧ (Lm−R) / 2). However, it is shorter than the groove length L2 of the holding groove 31 (L2> L1).

  Next, a symbol Ld shown in FIGS. 7A and 7B indicates the length dimension (drive range length) of the ideal operating range of the mover 30. That is, A in FIG. 7 is a case where the mover 30 is virtually moved in the Y1 direction in the state in which the ball 41 is ignored, and in the moving direction of the holding groove 31 on the mover 30 side. The end surface 31a located at the end (Y2 side) shows a state in which the end surface 22a on the tip (Y1) side of the guide groove 21A1 on the stator 20 side coincides at the first coincidence position Q1. Similarly, B in FIG. 7 is a case where the mover 30 is virtually moved in the Y2 direction in the state where the ball 41 is ignored, and the tip of the holding groove 31 on the mover 30 side (Y1 The end surface 31a located on the side (side) coincides with the end surface 22a on the terminal (Y2) side of the guide groove 21A3 on the stator 20 side at the second matching position Q2. The ideal operating range length (driving range length) Ld indicates the moving distance when the mover 30 moves in the moving direction from the first matching position Q1 to the second matching position Q2. is there. The drive range length Ld has a meaning as the maximum value of the operation range length Lm in an ideal state when the ball 41 is ignored.

  The groove lengths L1 of the guide grooves 21A1, 21A2, and 21a3 here are formed to be less than 1/2 the length of the driving range length Ld minus the diameter R of the ball (( Ld-R) / 2> L1).

  In summary, the groove lengths L1 of the guide grooves 21A1, 21A2, and 21a3 are L2> (Ld−R) / 2> L1 ≧ (Lm−R) / 2.

  Thus, in the first embodiment, the shorter one of the guide groove (first long groove) 21A on the stator 20 side and the holding groove (second long groove) 31 on the mover 30 side is shorter. The lower limit value of the groove length L1 of the guide groove 21A on the stator 20 side is not less than ½ times the length dimension obtained by subtracting the diameter dimension R of the ball 41 from the operation range length Lm which is the upper limit of the use range. (L1 ≧ (Lm−R) / 2).

  The practical use range length Lu and the operation range length (upper limit of use range) Lm satisfy Lm> Lu. For this reason, as long as the mover 30 is used within the operation range length (upper limit of the use range) Lm, preferably less than or equal to the practical use range length Lu, the moving ball 41 is guided to the stator 20 side. There is no contact with the end surface 22a on the tip (Y1) side or the end surface 22a on the end (Y2) side of the groove 21A. That is, the ball 41 comes into contact with either the end face 22a or the end face 31a of the guide groove (first long groove) 21A on the stator 20 side or the holding groove (second long groove) 31 on the mover 30 side. Can move without. For this reason, it is possible to reliably prevent the ball 41 from being removed from the guide groove 21A.

  Even if the mover 30 is misaligned in the balls 41 for some reason, the balls 41 are located on the Y1 side or Y2 side of the guide groove 21A on the stator 20 side. It is possible to reduce the removal of the mover 30 that is likely to occur when it comes into contact with the end face 22a. That is, the friction coefficient of the end surface 22a is smaller than the friction coefficient of the conductive portion 25 formed on the inner wall surface of the guide grooves 21A and 21B and the conductive portion 35 formed on the holding groove 31. For this reason, when the ball 41 abuts against the end surface 22a of the guide groove 21A, the sliding friction resistance generated between the surface of the ball 41 and the end surface 22a is the surface of the ball 41, the conductive portion 25, and It becomes smaller than the sliding frictional resistance generated between the holding grooves 31. Therefore, when each ball 41 comes into contact with the end surface 22a of the guide groove 21A, slip occurs between the surface of each ball 41 and the surface of the end surface 22a, and the probability that each ball 41 idles on the spot increases. For this reason, it is possible to reduce the frequency with which each ball 41 rides on the end face 22a and derails.

  Next, a control method (reset method) will be described in order to eliminate the positional deviation when the positional deviation occurs in each of the balls 41.

  FIG. 8 is a cross-sectional view similar to FIG. 2 showing a reset method of the electrostatic actuator, wherein A is a misalignment state, B is a first reset step, C is a state after the first reset step, and D is a second state. The reset process, E, shows the state after the second reset process.

  When the mover 30 provided in the guide grooves 21A and 21B reciprocates repeatedly in the Y1 and Y2 directions shown in the drawing, the ball 41 is displaced. FIG. 8A shows a state after the mover 30 has reciprocated repeatedly.

  8A, when the mover 30 is positioned at a neutral position on the stator 20, the ball 41a is positioned on the left side of the perpendicular bisector P1 of the guide groove 21A1, and the ball 41b is positioned on the guide groove 21A2. A case where the ball 41c is displaced to the left side of the vertical bisector P3 of the guide groove 21A3 is shown on the right side of the vertical bisector P2.

  In the first reset process shown in FIG. 8B, the distance between the movable element 30 and the neutral position corresponding to approximately half of the operation range length Lm (hereinafter referred to as “rolling range length”) Lr is illustrated. Move in the Y1 direction. At this time, the balls 41a and 41c located at both ends come into contact with the end surfaces 22a and 22a on the Y1 side of the guide grooves 21A1 and 21A3.

  As shown in FIG. 8C, when the mover 30 is moved in the Y2 direction by the rolling range length Lr from the state shown in FIG. 8B and returned to the neutral position, the moving direction The balls 41a and 41c located at both ends coincide with the vertical bisectors P1 and P3, and these positional deviations are eliminated. However, the central ball 41b has the vertical bisector from the initial position shown in FIG. 8A. Although it is close to the line P2, it still does not reach the point where the complete displacement is eliminated. Therefore, the second reset process is tried.

  As shown in FIG. 8D, in the second reset step, the mover 30 is moved from the neutral position in the Y2 direction by the rolling range length Lr. At this time, all the balls 41a, 41b, and 41c are moved to positions where they contact the end surfaces 22a, 22a, and 22a on the Y2 side of the guide grooves 21A1, 21A2, and 21A3. In this state, the same distance is set between the balls 41a and 41b and between the balls 41b and 41c.

  As shown in E of FIG. 8, when the movable element 30 is moved again in the Y1 direction by the rolling range length Lr from the state shown in D of FIG. 8 to return to the neutral position, the three balls 41a , 41b, and 41c coincide with the vertical bisectors P1, P2, and P3, and the positional deviation states of all the balls 41a, 41b, and 41c can be eliminated.

  In addition, since the 1st reset process and the 2nd reset process are only the directions to which the needle | mover 30 is moved, the same result can be acquired even if these order are replaced.

  As described above, in the first embodiment, the ball 41a is simply moved by reciprocating the mover 30 once, that is, moved once in the Y1 direction and the Y2 direction and then returned to the neutral position. , 41b, 41c can be reset to return to the initial state. For this reason, by periodically performing such control, it is possible to prevent the mover 30 from being removed.

  FIG. 9 is a cross-sectional view similar to FIG. 2 showing the second embodiment of the present invention, FIG. 10 is a cross-sectional view similar to FIG. 6 illustrating the operating state in the second embodiment, and A is a mover of the mover FIG. 11 is a cross-sectional view similar to FIG. 7 showing the state of movement in the Y1 direction which is one of the directions, B is the state where the mover is moved in the Y2 direction which is the other of the movement directions, and FIG. A is a state where the mover is moved in the Y1 direction which is one of the moving directions, B is a state where the mover is moved in the Y2 direction which is the other of the moving directions, and FIG. 12 shows a method for resetting the electrostatic actuator. FIG. 9 is a cross-sectional view similar to FIG. 8, wherein A indicates a misalignment state, B indicates a reset process, and C indicates a state after the first reset process. 9 to 12, only one guide groove 21A, holding groove (second long groove) 31A and ball 41 are shown, but the other guide groove 21B, holding groove (second long groove) 32A and The same applies to the ball 42.

  The electrostatic actuator 10B shown as the second embodiment in FIGS. 9 to 12 has substantially the same structure as the electrostatic actuator 10A shown in the first embodiment. For this reason, the following description will focus on parts that are different from the first embodiment. The same members as those of the electrostatic actuator 10A will be described with the same reference numerals.

  As shown in FIG. 9, in the electrostatic actuator 10B shown in the second embodiment, the holding groove (second long groove) 31 provided on the facing surface 30a of the mover 30 is guided on the stator 20 side. Similar to the groove (first long groove) 21A, it is divided into three along the moving direction, and is greatly different in that each is formed with the same groove length.

  Three holding grooves (second long grooves) provided on the X1 side in the width direction are 31A (indicated individually by 31A1, 31A2, and 31A3), and three holding grooves (second long grooves) provided on the X2 side Is 32A (indicated by 32A1, 32A2, and 32A3 individually), the groove length in the movement (Y) direction of all the holding grooves 31A1, 31A2, and 31A3 (the same applies to the holding grooves 32A1, 32A2, and 32A3) is constant at L3. It is.

  In the second embodiment, as shown in FIGS. 10A and 10B, when the mover 30 is moved in one of the moving directions, each ball 41 moves in the moving direction of each (first long groove) 21A. The mover 30 is moved toward the other side in the moving direction from a position (see A in FIG. 10) sandwiched between the end on the leading end side of each of the holding grooves 31A and the end on the end side in the moving direction of each holding groove 31A. 10 when each ball 41 is sandwiched between the end of each (first long groove) 21A in the moving direction and the end of each holding groove 31A in the moving direction (end of FIG. 10). The movement distance of the mover 30 up to B) is the operation range length Lm.

  Also in the second embodiment, of the guide groove (first long groove) 21A on the stator 20 side and the holding groove (second long groove) 31A on the mover 30 side, the groove length L1 of the shorter groove Alternatively, the lower limit value of L3 (both groove lengths in the case of the same) is set to at least 1/2 times the length dimension obtained by subtracting the diameter R of the ball 41 from the operation range length Lm which is the upper limit of the above-described use range. (L1, L3 ≧ (Lm−R) / 2). In this case, the upper limit value is less than 1/2 the length of the drive range length Ld minus the diameter R of the ball 41 ((Ld−R) / 2> L1, L3). .

  Therefore, as long as the mover 30 is used within the range of the operation range length Lm, preferably within the practical use range length Lu, the ball 41 is formed on the end surface 22a of the guide groove 21A or the holding groove 31A. The frequency of hitting the end faces 31a and 32a at both ends can be reduced.

  As described above, the end surfaces 31 a and 31 a at both ends of the holding groove 31 </ b> A have a smaller friction coefficient than the surface of the conductive portion 35. Therefore, also in the electrostatic actuator 10B shown in the second embodiment, the balls 41 are misaligned for some reason, and the balls 41 are guided by the guide grooves 21A and 21B on the stator 20 side. When the ball 4 is in contact with the end face 22a located on the Y1 side or Y2 side of the figure, or on the end faces 31a, 31a located on the Y1 side or Y2 side of the holding groove 31A of the movable element 30 side. It is possible to reduce the frequency of the unmoving of the mover 30 that is likely to occur when it comes into contact.

  As shown in FIG. 11A, when the case where the ball 41 is ignored and the mover 30 is virtually moved in the Y1 direction is considered, the end of the mover 30 side in the moving direction (Y2 side) is considered. A position where the end surface 31a of the holding groove 31A1 positioned coincides with the end surface 22a on the tip (Y1) side of the guide groove 21A1 on the stator 20 side is a first matching position Q1. Similarly, as shown in FIG. 11B, when considering the case where the ball 41 is ignored and the mover 30 is virtually moved in the Y2 direction in the figure, the end of the move direction on the mover 30 side (Y1 side) ), The position where the end surface 31a located at the end (Y1 side) of the holding groove 31A3 coincides with the end surface 22a on the tip (Y2) side in the moving direction of the guide groove 21A3 on the stator 20 side is the second coincidence. This is the position Q2. Also in the second embodiment, the drive range length Ld (ideal operation range length) is that the mover 30 moves in the moving direction from the first coincidence position Q1 to the second coincidence position Q2. It shows the distance traveled. First, the mover 30 is at the position shown in FIG. 11B (in this case, Q2 corresponds to the first matching position), and then the mover 30 moves in the Y1 direction to move to the position shown in FIG. , Q1 corresponds to the second matching position), the drive range length Ld is the same length dimension.

  Here, the shorter length of the groove length L1 of the guide groove 21A and the groove length L3 of the holding groove 31A is the same as that of the first embodiment described above, from the drive range length Ld to the ball diameter R. (Ld−R) / 2> L1, L3).

  Next, a description will be given of an electrostatic actuator control method (reset method) that eliminates the displacement when the balls 41 and 42 are displaced in the second embodiment.

  As shown in FIG. 12A, when the mover 30 is repeatedly reciprocated many times, the balls 41a, 41b, 41c during the operation may be displaced. In FIG. 12A, for example, when the ball 41c coincides with the vertical bisector P3, the balls 41a and 41b are displaced to the right side of the vertical bisector P1 and P2. Show.

  As shown in FIG. 12B, in the first reset step, the mover 30 is moved from the neutral position in the Y1 direction by the rolling range length Lr as described above. At this time, all the balls 41a, 41b, 41c are pushed and moved by the Y2 side end surfaces 31a, 31a, 31a of the holding grooves 31A1, 31A2, 31A3. All the balls 41a, 41b, 41c are connected to the Y2 side end surfaces 31a, 31a, 31a of the holding grooves 31A1, 31A2, 31A3 and the Y1 side end surfaces 22a, 22a, 22a of the guide grooves 21A1, 21A2, 21A3, Is held between the two. In this state, the same distance is set between the balls 41a and 41b and between the balls 41b and 41c.

  Next, as shown in FIG. 12C, when the mover 30 is moved in the Y2 direction by the rolling range length Lr from the state shown in FIG. 12B and returned to the neutral position, the three balls 41a, 41b, and 41c coincide with the perpendicular bisectors P1, P2, and P3, and all the balls 41a, 41b, and 41c are displaced.

  In the reset process shown in FIG. 12B, the mover 30 may be moved in the Y2 direction from the neutral position by the rolling range length Lr.

  As described above, in the second embodiment, the movable element 30 is moved back and forth on one side, that is, the movable element 30 is moved in the Y1 direction or the Y2 direction in the figure in the rolling range length Lr (equivalent to approximately ½ of the operating range length Lm). The position shift generated in the balls 41a, 41b, 41c can be reset and returned to the initial state by a simple operation of moving the distance 41) and then returning to the neutral position.

  Therefore, by periodically performing such a reset operation, the ball can be returned to the initial state, and it is possible to prevent the mover 30 from being removed.

  In the first embodiment, the case where the length of the guide groove on the stator side is longer than the length of the holding groove on the mover side is described. However, the length of the guide groove and the holding groove is long. There is a relative relationship. For this reason, when the groove length of the holding groove on the mover side is longer than the groove length of the guide groove on the stator side, it can be made to function in the same manner by exchanging the relationship between the two.

The perspective view which shows the electrostatic actuator which shows the 1st Embodiment of this invention, Sectional drawing of the electrostatic actuator in the II-II line | wire of FIG. Sectional drawing of the actuator which shows the state which a stator electrode and a mover electrode oppose, A plan view of the stator showing the arrangement relationship of the stator electrodes, It is sectional drawing of the electrostatic actuator for demonstrating the moving range (practical use range) of a needle | mover when a ball | bowl does not contact | abut the both ends of a guide groove, A is a needle | mover moving to a Y1 direction. , B is the state where the mover has moved in the Y2 direction, It is sectional drawing of the electrostatic actuator for demonstrating the moving range (operation | movement range (upper limit of use range)) of a needle | mover when a ball | bowl contacts the edge part of the both sides of a guide groove, A is a needle | mover in Y1 direction. The state in which the mover has moved in the Y2 direction, It is sectional drawing for demonstrating the movement range (driving range length (ideal operation range length)) of the needle | mover in the ideal state which disregarded the ball | bowl, A is the state which the needle | mover moved to the Y1 direction, B is movable The child has moved in the Y2 direction, It is sectional drawing similar to FIG. 2 which shows the reset method of an electrostatic actuator, A is a position shift state, B is a 1st reset process, C is the state after a 1st reset process, D is a 2nd reset process, E is the state after the second reset step, Sectional drawing similar to FIG. 2 which shows the 2nd Embodiment of this invention, FIG. 7 is a cross-sectional view similar to FIG. 6 illustrating an operation state in the second embodiment, and A is a state in which the mover is moved in the Y1 direction which is one of the movement directions. FIG. 8 is a cross-sectional view similar to FIG. 7 illustrating an operation state in the second embodiment, where A is a state where the mover is moved in the Y1 direction which is one of the moving directions, and B is Y2 which is the other moving direction Moved in the direction, FIG. 7 is a cross-sectional view similar to FIG. 6 illustrating a reset method of the electrostatic actuator, wherein A is a misalignment state, B is a reset process, C is a state after the first reset process,

Explanation of symbols

10 Electrostatic actuator 20 Stator 21A, 21A1, 21A2, 21A3 X1 side guide groove (first long groove)
21B, 21B1, 21B2, 21B3 X2 side guide groove (first long groove)
22a, 22b End face 23 of guide groove 23 Stator electrode 25 Conductive portion 30 Movable element 31, 31A, 31A1, 31A2, 31A3 X1 side holding groove (second long groove)
32, 32A, 32A1, 32A2, 32A3 X2 side holding groove (second long groove)
31a, 32a End surface 33 of holding groove (second long groove) Movable electrode 33A Conductive layer 35 Conductive portions 41, 41a, 41b, 41c Ball on X1 side (rolling element)
42, 42a, 42b, 42c X2 side ball (rolling element)
L1 Guide groove (first long groove) groove length L2, L3 Holding groove (second long groove) groove length Ld Driving range length Lm Operating range length Lr Rolling range length Lu Practical use range length

Claims (7)

At least a stator having a first long groove formed along the moving direction, and a second long groove formed along the moving direction, and movable in the moving direction in a state of facing the stator A plurality of rolling elements disposed in a freely movable manner between the first long groove and the second long groove, a plurality of stator electrodes provided on the stator, A plurality of mover electrodes provided on the mover, and a predetermined operating range length in which the rolling element can move without contacting an end of the first long groove or the second long groove in the moving direction. An electrostatic actuator capable of reciprocating movement in,
At least one of the first long groove and the second long groove is formed with a length dimension equal to or smaller than the other long groove, and the length dimension of the one long groove having the short length dimension is as follows: An electrostatic actuator characterized in that it is formed with a length dimension equal to or more than ½ times the length obtained by subtracting the diameter of the rolling element from the operating range length. When the movable element is moved on the stator in one direction of the moving direction, the position of the long groove provided on the terminal side in the moving direction among the long grooves formed in the movable element on the terminal side From the first coincidence position in which the end provided on the distal end side of the long groove provided on the end side of the long groove formed on the movable element coincides with the end provided on the mover, When the mover is moved in the other direction opposite to the one direction, among the long grooves formed in the mover, at the position on the end side of the long groove provided on the end side in the moving direction. The moving distance to the second coincidence position where the provided end and the end provided at the position on the distal end side of the long groove provided on the end side among the long grooves formed in the stator coincide with each other Is the drive range length,
Of the groove length of the mover and the groove length of the stator, the length dimension of the other long groove having the short length dimension is 1 / of the length dimension obtained by subtracting the diameter of the rolling element from the drive range length. The electrostatic actuator according to claim 1, wherein the electrostatic actuator is formed with a length dimension less than twice.   3. The electrostatic actuator according to claim 1, wherein a length dimension of the second long groove provided in the movable element is longer than a length dimension of the first long groove provided in the stator.   The friction coefficient of the both end surfaces forming the short sides of the first long groove and the second long groove is smaller than the friction coefficient of the inner wall surface forming the long sides of the first long groove and the second long groove. Item 4. The electrostatic actuator according to any one of Items 1 to 3. At least a stator having a first long groove formed along the moving direction, and a second long groove formed along the moving direction, and movable in the moving direction in a state of facing the stator A movable element provided on the stator, a rolling element disposed so as to roll between the first long groove and the second long groove, a plurality of stator electrodes provided on the stator, and the movable A control method of an electrostatic actuator having a plurality of mover electrodes provided on the child,
(A) moving the mover by a predetermined distance in one of the moving directions;
(B) returning the mover to a predetermined neutral position;
The method of controlling an electrostatic actuator, wherein the rolling element is returned to a predetermined position by passing through the above. After step (b)
(C) moving the mover by a predetermined distance to the other of the moving directions opposite to the one;
(D) returning the mover to a predetermined neutral position on the stator;
The method for controlling an electrostatic actuator according to claim 5.   When the predetermined distance moves the mover from a predetermined neutral position on the stator to one or the other of the moving directions, any one of the rolling elements from the predetermined neutral position is The method of controlling an electrostatic actuator according to claim 5 or 6, wherein the length is a rolling range length until it is sandwiched between an end of the first long groove and an end of any of the second long grooves.

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