Abstract:
A novel deformation motion mechanism with precise motion precise motion and structural robustness is achieved. A deformation motion mechanism includes: an elastic ring member shaped symmetrically with respect to a center line, wherein one end of the elastic ring member is fixed and the other end is movable along the center line; a drive unit which is placed within the elastic ring member and is arranged to rotate a feed screw engaged with both ends of the elastic ring member along an operating line orthogonal to the center line, to press or stretch the elastic ring member along the center line; and a plurality of flexible arms which connects the drive unit to the elastic member in at least a direction of the center line.

Description:
BACKGROUND 
       [0001]    The present invention relates to a mechanism which produces predetermined motion by a predetermined deformation. 
         [0002]    With the increasing market demand for precision technology, a linear motion actuator providing high precision has become important for machinery requiring precise displacement such as multiple-degree-of-freedom displacement mechanism, micro-manipulator or the like. In most cases, such a fine linear motion actuator employs reduction gearing mechanism, which requires not only a plurality of parts such as different gears but also backlash adjustment of gears and other alignments during its assembly. 
         [0003]    In order to eliminate the need of backlash adjustment and other alignments, there has been proposed a simplified linear motion mechanism using a combination of elastic plates to allow fine linear displacement (see Japanese Patent Unexamined Publication No. JP2003-075572). More specifically, two elastic plates are fixed to a fixed block at one ends and to a movable block at the other ends. The two elastic plates placed in parallel are connected by a curve elastic plate in the approximate shape of a letter H. The movable block is supported by an elastic plate orthogonal to a plane formed by the H-shaped elastic plates. The curve elastic plate is connected to the slider of a micrometer at the center thereof. Accordingly, extension or contraction of the slider causes the curve elastic plate to push or pull the parallel elastic plates in widening or narrowing directions, which linearly moves the movable block in the retracting or extending direction. 
       SUMMARY 
       [0004]    However, the above-mentioned linear motion actuator using reduction gearing mechanism requires a plurality of parts, complicated assembly process and complicated adjustment operations. The above-mentioned linear motion mechanism using the elasticity of combined elastic plates has the spatial arrangement of a plurality of elastic plates, resulting in weakness in structural strength, which makes it difficult to achieve precise displacements. Accordingly, the existing techniques cannot achieve a light-weight, miniaturized and simply-manufactured linear motion mechanism providing high precision. 
         [0005]    An object of the present invention is to provide a novel deformation motion mechanism with precise motion and structural robustness. 
         [0006]    According to the present invention, a deformation motion mechanism includes: an elastic ring member shaped symmetrically with respect to a center line, wherein one end of the elastic ring member is fixed and the other end is movable along the center line; a drive unit which is placed within the elastic ring member and is arranged to rotate a feed screw engaged with both ends of the elastic ring member along an operating line orthogonal to the center line, to press or stretch the elastic ring member along the center line; and a plurality of flexible arms which connects the drive unit to the elastic member in at least a direction of the center line. 
         [0007]    According to the present invention, a deformation motion method includes: preparing an elastic ring member shaped symmetrically with respect to a center line, wherein one end of the elastic ring member is fixed and the other end is movable along the center line wherein a drive unit is placed within the elastic ring member and is arranged to rotate a feed screw engaged with both ends of the elastic member along an operating line orthogonal to the center line; connecting the drive unit to the elastic ring member through a plurality of flexible arms in at least a direction of the center line; and by the drive unit, rotating the feed screw to press or stretch the elastic ring member along the operating line. 
         [0008]    As described above, according to the present invention, the drive unit is placed within the elastic ring member and is flexibly connected to the elastic ring member through the flexible arms in at least a direction of the center line. Accordingly, the drive unit is placed at the center of the elastic ring member irrespective of the presence or absence of elongated deformation of the elastic ring member. Further, the flexible arms are flexible in the center line direction but rigid in the operating line direction. Accordingly, the flexible arms prevents the drive unit from rotating when the drive unit rotates the feed screw. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a plan view illustrating a deformation motion mechanism according to an exemplary embodiment of the present invention. 
           [0010]      FIG. 2  is a sectional view taken along lines A-A of  FIG. 1 . 
           [0011]      FIG. 3  is a diagram showing a typical operation of the deformation motion mechanism shown in  FIG. 1 . 
           [0012]      FIG. 4  is a diagram showing an analytical example of the operation of the deformation motion mechanism as shown in  FIG. 1 . 
           [0013]      FIG. 5  is a diagram showing another analytical example of the operation of the deformation motion mechanism as shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
     1. Outline of Embodiment 
       [0014]    According to an exemplary embodiment of the present invention, a deformation motion mechanism is arranged to use a pressure mechanism to deform a symmetrically shaped elastic ring member along a center line of the symmetrically shaped elastic member to produce a linear motion. More specifically, the pressure mechanism is composed of a feed screw and a drive unit which are provided within the elastic ring member. The feed screw is screwed into a pair of nuts provided at the respective ends of the elastic ring member. The feed screw may have left-handed and right-handed screw sections which are screwed in the pair of nuts, respectively. The drive unit is arranged to rotate the feed screw to press or stretch the hard spring in the minor-axis direction to produce a linear motion in a direction of the major axis of the hard spring. 
         [0015]    In the above-mentioned structure, since the drive unit rotates the feed screw, the drive unit has to be fixed to something secured so as not to rotate itself. However, the drive unit cannot be fixed rigidly because the drive unit joined to the feed screw moves in the major-axis direction of the hard spring when pressing or stretching the hard spring in the minor-axis direction. For instance, if the drive unit is fixed rigidly to the hard spring, the drive unit causes hard deformation of the hard spring, resulting the linear motion with a low degree of accuracy. If the drive unit is fixed rigidly to the base plate of the deformation motion mechanism, the drive unit cannot be moved, which may cause unexpected deformation of the hard spring. 
         [0016]    Accordingly, it is important to fix the drive unit flexibly to the hard spring. Preferably, the drive unit is fixed to the hard spring through symmetrically arranged flexible arms so as to place the drive unit at the center of the elliptical ring of the hard spring before or after deformed. Further preferably, the flexible arms are flexible in the major-axis direction of the hard spring but rigid in a direction orthogonal to the plane including the elliptical ring of the hard spring. As an example, each of the flexible arms may be formed using an elastic plate or a leaf spring. Hereinafter, an exemplary embodiment of the present invention will be describe with references to figures. 
       2. Exemplary Embodiment 
     2.1) Arrangement 
       [0017]    Referring to  FIGS. 1 and 2 , a deformation motion mechanism  10  includes a hard spring  101  shaped like an elliptical ring symmetrically with respect to a center line L 1  and an operating line L 2  orthogonal to the center line L 1 . The hard spring  101  is connected to a fixed section  102  and a movable section  103  at both ends of the major axis of the hard spring  101 . The hard spring  101  is joined to a pressure mechanism composed of a pair of nuts  104  and  105 , a feed screw  106  and an input mechanism  107 . 
         [0018]    The feed screw  106  may have left-handed and right-handed screw sections which are screwed into the nuts  104  and  105 , respectively. The nuts  104  and  105  are fixed respectively to both sides of the hard spring  101  in the direction of the minor axis so that the hard spring  101  is sandwiched between the nuts  104  and  105 . The input mechanism  107  rotates the feed screw  106  to press or stretch the hard spring  101  depending on rotation direction. In  FIG. 1 , when rotating the feed screw in a direction  108 , the hard spring  101  is pressed in the operating direction  109  to move the movable section  103  in the linear motion direction  110 . 
         [0019]    The input mechanism  107  is a drive unit for rotating the feed screw  106  which rotatably passes through the drive unit as shown in  FIG. 2 . The input mechanism  107  is placed within the elliptical ring of the hard spring  101  and is flexibly joined to the hard spring  101  through an even number of elastic arms (here, four elastic arms S 1 -S 4 ). The elastic arms S 1 -S 4  having the same elasticity are placed symmetrically with respect to a center point O, the line (or plane) L 1 , and/or the line (or plane) L 2  so as to keep the input mechanism  107  at the center of the elliptical ring of the hard spring  101  irrespective of the presence or absence of the deformation. 
         [0020]    Preferably, the elastic arms S 1 -S 4  are placed in parallel along their retracting or extending direction which is the same direction as the major axis of the hard spring  101 . In this example, the elastic arms S 1 -S 4  are formed using an elastic plate or a leaf spring and are shaped like an accordion to be made flexible in the major-axis direction of the hard spring  101 . However, as shown in  FIG. 2 , the elastic arms S 1 -S 4  are installed vertically, that is, in a direction L 3  orthogonal to the plane L 1 , causing them to be hardly bent in the direction L 3 . Accordingly, the elastic arms S 1 -S 4  prevents the input mechanism  107  from rotating when the input mechanism  107  rotates the feed screw  106 . 
       2.2) Operation 
       [0021]    Referring to  FIG. 3 , when the input mechanism  107  rotates the feed screw in the direction  108 , the nuts  104  and  105  presses and deforms the hard spring  101  in the direction  109 . More specifically, pressure in the direction  109  causes the elliptical ring of the hard spring  101  to be elongated in the direction of its major axis, thereby extending the elastic arms S 1 -S 4  and shifting the feed screw  106  and the input mechanism  107  by a displacement  201  while shifting the movable section  103  by a displacement  202 . 
         [0022]    As shown in  FIG. 4 , the respective elastic arms S 1 -S 4  are fixed to the input mechanism  107  at points P 1 -P 4 , which are symmetric about the center point O of the elliptic ring of the hard spring  101 . Accordingly, even when the hard spring  101  is elongated, the input mechanism  107  is kept at the center position of the elongated elliptic ring of the hard spring  101 . 
         [0023]    Similarly, as shown in  FIG. 5 , the respective elastic arms S 1 -S 4  connecting between the hard spring  101  and the input mechanism  107  are placed symmetrically with respect to the center point O of the elliptic ring of the hard spring  101 . Accordingly, even when the hard spring  101  is elongated, the input mechanism  107  is kept at the center position of the elongated elliptic ring of the hard spring  101 . 
       2.3) Advantageous Effects 
       [0024]    According to the exemplary embodiment of the present invention, the input mechanism  107  which is arranged to rotate the feed screw  106  to deform the hard spring  101  is placed within the elliptic ring of the hard spring  101  and is flexibly connected to the hard spring through elastic arms S 1 -S 4  which are symmetrically arranged along the major axis of the elliptic ring of the hard spring  101 . Accordingly, the input mechanism  107  is placed at the center of the elliptical ring of the hard spring  101  irrespective of the presence or absence of elongated deformation of the elliptic ring. 
         [0025]    Further, the elastic arms S 1 -S 4  are flexible in the major-axis direction of the hard spring but rigid in a direction orthogonal to the plane including the elliptical ring. Accordingly, the elastic arms S 1 -S 4  prevents the input mechanism  107  from rotating when the input mechanism  107  rotates the feed screw  106 . 
       3. Other Exemplary Embodiment 
       [0026]    The present invention is not limited to the above-mentioned embodiment as shown  FIGS. 1 and 2 . Any symmetric arrangement of elastic arms supporting the input mechanism or the drive unit within the elliptic ring can be employed, provided that the symmetrically arranged elastic arms allow the input mechanism or the drive unit to be placed at the center of the elliptical ring irrespective of the presence or absence of deformation of the elliptic ring. 
         [0027]    The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The above-described exemplary embodiment and examples are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.