JP2008095862A - Moving mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw-structure moving mechanism comprising a screw shaft, and a motion converting part to be moved with the rotation of the screw shaft in the axial direction of the screw shaft, for improving the constant velocity property of the motion converting part. <P>SOLUTION: The moving mechanism 1 comprises the screw shaft 5 rotatably journaled to a non-movable member 11, and the motion converting part 6 threaded to the screw shaft so as to be moved with the rotation of the screw shaft in the axial direction of the screw shaft herein, a spring member 8 is provided which has one end 8a locked to the outer face of the motion converting part and the other end 8b locked to the non-movable member, for giving energizing force to the motion converting part in the axial direction of the screw part. One side face of a female screw formed on the motion converting part in its moving range and one side face of a male screw formed on the screw shaft in opposition to one side face of the female screw hold good contact with each other at all times with thrust generated in the direction of operating the energizing force during moving the motion converting part to actualize high running accuracy of a sliding unit independently of the direction of moving the motion converting part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a screw structure moving mechanism including a screw shaft and a motion conversion unit that moves in the axial direction of the screw shaft in accordance with the rotation of the screw shaft.

  A moving mechanism that uses a screw structure such as a feed screw (sliding screw) or a ball screw, and obtains a linear motion by converting the rotational motion when the screw shaft is rotated by a motion conversion unit (nut) is widely used. ing. In such a screw structure, it is known that a movement position error factor called backlash occurs depending on the state of engagement between the male screw (screw thread) of the screw shaft and the female screw (thread groove) of the motion converting portion. This phenomenon of backlash does not pose a problem in equipment that does not require positioning accuracy, but becomes an error factor that must be reduced when precise positioning and speed stability are required in machine tools, optical equipment, and the like.

  FIG. 11 is an explanatory diagram of backlash that occurs between the feed screw shaft 31 and the motion converting portion (nut) 32 in the conventional moving mechanism having no preload structure, and the rotational motion of the feed screw shaft 31 is changed to a linear motion. If no preload is applied to the motion converting portion 32 to be converted, due to variations in machining accuracy of each portion, the motion converting portion 32 of the feed screw shaft 31 on the left side of the male screw (thread) 31a as shown in FIG. When the right side facing the left side of the male screw 31a of the female screw (thread groove) 32a contacts, or as shown in FIG. 5B, the female screw (thread groove) 32a of the motion converter 32 is placed on the right side of the male screw 31a. When the left side surface opposite to the right side surface of the male screw 31a comes into contact, backlash occurs, and the motion converting portion 32 repeats unstable contact with the feed screw shaft 31, thereby reducing the constant velocity. Only a part of the feed screw shaft 31 is shown.

  FIG. 12 is an explanatory view of backlash that occurs between the ball screw shaft 33 and the motion converting portion (nut) 34 in the conventional moving mechanism having no preload structure, and the rotational motion of the ball screw shaft 33 is changed to a linear motion. If no preload is applied to the motion converting portion 34 to be converted, due to variations in processing accuracy of each portion, the female screw (thread groove) of the motion converting portion 34 is pointed with respect to the point B of the ball screw shaft 33 as shown in FIG. ) With respect to the position of point A1 when 34a is shifted to the left, or the point B of the ball screw shaft 33 as shown in FIG. A difference from the position of point A2 in the case of deviation occurs, resulting in backlash. For this reason, unstable contact is repeated among the ball screw shaft 33, the ball 35, and the motion converting portion (nut) 34, and the constant velocity is lowered. Only a part of the ball screw shaft 33 is shown.

  Therefore, when the moving mechanism of the above configuration requires constant velocity, that is, stability of the moving speed of the motion conversion unit, it is possible to deal with it by applying a preload to the normal motion converting unit to suppress backlash and increase mechanical rigidity. is doing. There are two types of preloading methods, the fixed position preloading method and the constant pressure preloading method. The fixed position preloading method includes a double nut method in which a spacer is interposed between two nuts, There is an offset preload system that applies preload by changing the groove pitch of the nut without using a seat.

  The constant pressure preload system is a system in which a spring structure (elastic body) is provided at the approximate center position of the nut and the preload is applied by changing the groove pitch at the center of the nut. A simple nut offset preload type in which a phase is applied to the screw and the axial clearance is less than or equal to zero (preload state), a double nut offset preload type in which a spacer is inserted between two nuts, so that the gap between the nuts is negative There are oversize ball preload types that apply preload using hard balls of various dimensions. About a countermeasure against backlash, a constant pressure preload system is adopted as a typical system for a ball screw that is generally used.

Further, as a moving mechanism, a screw hole (first nut) in which a threaded portion that meshes with a lead screw that is rotationally driven by a stepping motor is formed integrally with a table, and a nut housing that is formed coaxially with the screw hole. A nut (second nut) that meshes with the lead screw is inserted into the hole so as to be movable only in the axial direction, and the nut is urged in a direction away from the screw hole by a coil spring to form a motion conversion portion. A table feed mechanism has been proposed that does not remove the lead screw from the table and that there is no backlash in the meshing part of both members, so that the table can be moved at high speed and the table can be positioned with high accuracy. (For example, refer to Patent Document 1).
Japanese Unexamined Patent Publication No. 2000-149467 (page 3-4, FIG. 2)

  If a preload is applied to the motion converter, the constant velocity can be ensured, but the structure of the motion converter is complicated and the shape becomes large. Further, in the ball screw shaft, the rotational torque increases due to the differential slip and spin phenomenon of the ball, the load on the motor increases, and the efficiency decreases. Since excessive load always acts on the contact surface of the motion converter, wear of nuts, screws, and balls progresses in a short period of time, reducing the amount of preload, increasing backlash, decreasing constant velocity and shortening the service life. Become. Lubricating oil is subject to repeated repeated shearing, and there are problems such as deterioration that progresses early due to contamination of wear powder and frequent maintenance is required. ) Is correlated and difficult to achieve.

  In addition, for example, a moving mechanism having a screw structure is employed as an imaging mechanism in a semiconductor device that performs optical shape measurement, and the speed (moving speed) of a motion conversion unit (table) may be used as a reference signal. In this case, the stability (constant velocity) of the moving speed of the motion converting unit is the most important. This is not the positioning accuracy at the stop position, but the accuracy in the sense that the speed during constant speed movement is a stable and constant value, so the above-mentioned prior art has insufficient stability (constant speed) of the movement speed. May be.

  In addition, the technique disclosed in Patent Document 1 is improved with respect to positioning accuracy, but is not a content that takes into consideration constant velocity (stability), and is insufficient as constant velocity performance. is there. In other words, the mechanism that makes the constant speed insufficient is that the pitch between the male screw and the female screw is not completely constant even if the screw is precisely manufactured, and minute dimensional errors and changes in the contact state should be avoided. I can't.

  In addition, the technique disclosed in Patent Document 1 has a structure that is substantially divided into two parts, that is, a first nut integrally formed with a table and a second nut that meshes with a lead screw are very small. Since the screw structure including pitch error meshes with two different places at a specific distance, the relative speed of both changes slightly, causing contact surface contact and uneven wear, resulting in fluctuations in rotational torque. And the isokineticity is impaired. In particular, when the minute change is amplified as a vibration phenomenon due to the elasticity of the spring, the constant velocity property is further adversely affected. Furthermore, since the spring is accommodated in the motion conversion part, it is not possible to easily confirm the breakage of the screw.

  SUMMARY OF THE INVENTION An object of the present invention is to improve the constant velocity of a motion converting portion in a moving mechanism of a screw structure including a screw shaft and a motion converting portion that moves in the axial direction of the screw shaft according to the rotation of the screw shaft. It is to provide a moving mechanism.

In order to solve the above-described problems, the moving mechanism according to the present invention is:
In a moving mechanism comprising a screw shaft rotatably supported by a non-movable member, and a motion conversion unit that is screwed to the screw shaft and moves in the axial direction of the screw shaft according to the rotation of the screw shaft. ,
A spring member is disposed so that one end is locked to the outer surface of the motion converting portion and the other end is locked to the non-movable member to exert a biasing force in the axial direction of the screw shaft with respect to the motion converting portion. ,
The spring member maintains the urging force in the movement range of the motion conversion portion, so that one side surface of the female screw formed on the motion conversion portion and one side surface of the male screw facing the one side surface of the female screw of the screw shaft are The contact force is always maintained regardless of the movement direction of the motion conversion portion by the pressing force generated in the direction in which the urging force acts during the movement of the motion conversion portion.

  A spring that exerts an urging force in the screw shaft direction on the motion conversion portion between the non-movable member that supports the screw shaft of the moving mechanism and the motion conversion portion that moves in the screw shaft direction according to the rotation of the screw shaft. By providing a member and maintaining a biasing force in the movement range of the motion conversion unit, one side surface of the female screw formed on the motion conversion unit and one side surface of the male screw facing the female screw side of the screw shaft are The pressing force generated in the direction in which the urging force is applied during movement always maintains good contact regardless of the moving direction of the motion conversion unit. Further, the holding accuracy of the slide unit 16 is improved by holding the spring member by the holding members 13 and 14 that are firmly fixed and applying an urging force to the motion conversion portion in the screw shaft direction. As a result, it is possible to prevent the occurrence of backlash between the male screw of the screw shaft and the female screw of the motion converting portion, and to realize high constant velocity of the motion converting portion.

  A moving mechanism according to a second aspect of the present invention is the moving mechanism according to the first aspect, wherein the screw shaft is a feed screw shaft or a ball screw shaft.

  Even when either a feed screw shaft or a ball screw shaft is used as the screw shaft, it is possible to prevent the occurrence of backlash between the screw shaft and the motion converting portion and to improve the running accuracy of the slide unit.

  A moving mechanism according to claim 3 of the present invention is the moving mechanism according to claim 1 or 2, wherein the spring member is a compression spring or a tension spring.

  A compression spring may be used as a spring member to apply a biasing force so as to press the motion conversion unit against the moving direction of the screw shaft, or a tension spring may be used to move the motion converting unit in the moving direction of the screw shaft. On the other hand, a spring force may be applied in the pulling direction. In any case, the occurrence of backlash between the screw shaft and the motion conversion unit can be prevented.

  According to the present invention, the biasing force in the screw shaft direction with respect to the motion conversion unit between the non-movable member that supports the screw shaft of the moving mechanism and the motion conversion unit that moves in the screw shaft direction according to the rotation of the screw shaft. By providing the spring member so as to exert a backlash, the occurrence of backlash between the screw shaft and the motion conversion portion can be prevented, and high constant velocity of the motion conversion portion can be realized.

  In addition, there is no need to change the internal structure of the motion converter, the structure is simple, easy to change and inexpensive. In addition, since the influence on the rotational torque can be reduced and an appropriate load is applied to the motion converting portion, the constant velocity is stabilized, wear is reduced, and the life is prolonged. Further, the deterioration of the lubricating oil can be reduced, and it is possible to achieve both constant speed and life (maintenance) such as maintenance-free or reduction of maintenance.

  Hereinafter, a moving mechanism according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the moving mechanism 1 includes a base 2, holding members 3 and 4 that are suspended from the left and right ends of the upper surface of the base 2, a screw shaft 5, a motion conversion unit 6 as a moving body, The rail 7, the spring member 8, and the drive motor 9 are configured. The base 2 and the holding members 3 and 4 constitute a non-movable member 11.

  As shown in FIGS. 1 and 2, the base 2 is a thick plate body that is horizontally long when viewed from the upper surface, and the lower surfaces of the holding members 3 and 4 are placed vertically at both ends of the upper surface and Opposed and fixed. These holding members 3 and 4 are provided with screw shaft holding members 13 and 14 on the same straight line and horizontally facing each other as indicated by a dotted line at a substantially upper central position. Further, a rail 7 is provided on the upper surface of the base 2 between the holding members 3 and 4 and along the longitudinal direction at the center position in the width direction.

  The screw shaft 5 is, for example, a feed screw shaft (sliding screw shaft), one end portion (tip portion) 5a is rotatably supported by the screw shaft holding member 13 of the holding member 3, and the other end portion (base end portion) 5b is supported. It is rotatably supported by the screw shaft holding member 14 of the holding member 4 and protrudes outward from the holding member 4 (hereinafter referred to as “feed screw shaft 5”).

  The motion conversion unit 6 is, for example, a cylindrical nut and is made of a thick metal cylindrical member such as brass. As shown in FIG. 3, the upper and lower portions (upper and lower diameters) of the outer peripheral surface are in the longitudinal direction. The upper flat surface portion 6a and the lower flat surface portion 6b are cut out in a flat shape along the flat surface, and an internal thread (thread groove) 6c that engages with an external thread (thread) 5c of the feed screw shaft 5 on the inner peripheral surface. It is engraved. And the flat table 15 is mounted in the upper side plane part 6a of the motion conversion part 6, and is fixed with the screw which is not shown in figure.

  As shown in FIGS. 2 and 3, the slide unit 16 has side plates 16 b vertically suspended along the longitudinal direction on both sides of the thick bottom plate 16 a, and these side plates 16 b serve as the motion conversion unit 6. The upper end surface of the table 15 is fixed to the lower surface of the table 15 with a screw (not shown). Further, a fitting recess 16c is formed at the center of the bottom surface of the bottom plate 16a so as to be slidably fitted to the upper portion of the rail 7 along the longitudinal direction. End plates 17 and 18 are fixed to both left and right ends of the slide unit 16 with screws (not shown). The end plates 17 and 18 are formed with holes 17a and 18a through which the feed screw shaft 5 can freely rotate with a slight gap.

  The table 15 may be formed in a block shape by integrally forming the single plates 17 and 18. The basic configuration of the table 15 may be a block, a motion conversion unit, and a slide unit. A part of the block may be carved to fix the motion conversion unit and fix the block to the slide unit. .

  The motion converting portion 6 is disposed between the holding members 3 and 4, the feed screw shaft 5 is screwed through, and the fitting recess 16 c of the slide unit 16 is fitted to the upper portion of the rail 7. The slide unit 16 prevents rotation and roll when the motion conversion unit 6 moves along the feed screw shaft 5. Thereby, the motion conversion unit 6 can move horizontally and smoothly along the longitudinal direction on the rail 7 via the slide unit 16 according to the rotation of the feed screw shaft 5.

  The spring member 8 is a compression coil spring (hereinafter referred to as “compression spring”) having an inner diameter slightly larger than the outer diameter of the feed screw shaft 5, and is fixed to the motion conversion unit 6 outside the feed screw shaft 5. The end plate 18 and the holding member 4 are attached in a contracted state so as to be concentric with the feed screw shaft 5. As shown in FIG. 3, the compression spring 8 has a circular recess (hereinafter referred to as “counterbore”) 18 b formed so that one end 8 a is concentric with the feed screw shaft 5 on the outer surface of the end plate 18. The other end portion 8b is fitted to a circular concave portion (hereinafter referred to as “counterbore”) 4b formed on the inner side surface 4a of the holding member 4 so as to be concentric with the feed screw shaft 5. It has been stopped.

  Since both ends 8a and 8b of the compression spring 8 are held by the counterbore 18b and 4b, the seat of the spring is stabilized and the center deviation and the body bending are prevented. The compression spring 8 always applies a spring force (biasing force) to the motion conversion unit 6 in the left axial direction in the drawing. In addition, instead of the end plate 18 and the counterbore 18b, 4b of the holding member 4, cylindrical boss portions concentric with the feed screw shaft 5 are formed, and both end portions of the compression coil spring 8 are formed on the outer periphery of these boss portions. 8a and 8b may be fitted and locked.

  As shown in FIGS. 1 and 2, the end 5 b protruding from the holding member 4 of the feed screw shaft 5 is connected to the motor shaft 10 of the driving motor 9 through the shaft coupling 19. Then, the feed screw shaft 5 rotates with the rotation of the drive motor 9, and the motion conversion unit 6 moves horizontally on the rail 7 along the axial direction of the feed screw shaft 5 according to the rotation of the feed screw shaft 5. Moving. In this way, the moving mechanism 1 is configured. An imaging mechanism (not shown) such as a semiconductor device device that performs optical shape measurement such as three-dimensional measurement of an object to be measured using moire fringes as shown in, for example, Japanese Patent Application Laid-Open No. 2004-125652 is attached to the table 15. It is done.

  Thus, by installing the compression spring 8 on the feed screw shaft 5 on the motor 9 side, an appropriate axial load is applied in the direction of the motor 9, and the central axis of the compression spring 8 is deviated, bent or dropped off. Is prevented. And there is no preload of the motion converter 6, and the optimal axial load can be set from the stroke, spring rate, and free length of the motion converter 6.

Returning to FIG. 1, the -side movement limit point P1 (mm) of the motion conversion unit 6, the + side movement limit point P2 (mm), the end face positions T1, T2 of the motion conversion unit 6, and the T1 position P3 at the-side maximum stroke. (Mm), T1 position P4 (mm) at the + side maximum stroke, allowable maximum deflection rate Fw of compression spring 8, free length Lf (mm) of compression spring 8, depth X1 of counterbore 18b of end plate 18, If the depth X2 (mm) of the counterbore 4b of the holding member 4, the spring constant Cs (N / mm) of the compression spring 8, the initial deflection amount 010 Lw (mm), and the coordinate system origin of the motion conversion unit 6 are P1,
It is confirmed that the allowable deflection rate Fw of the compression spring 8 is not exceeded by the equation (Lf × Fw <P3−P1 + X1 + X2) in the motor 9 side moving stroke (hereinafter referred to as “Equation 1”).

  In the non-motor 9 side moving stroke, the free length Lf of the compression spring 8 for securing the initial deflection Lw is confirmed by the equation (Lf> P4−P1 + X1 + X2 + Lw) (hereinafter referred to as “Equation 2”).

  The spring load Fb (N) in the direction of the feed screw shaft 5 generated when the compression spring 8 pushes the motion conversion unit 6 is calculated by the expression “Fb = (Lf− (T1−P1 + X1 + X2) × Cs” (hereinafter, “expression”). 3 ”).

  FIG. 4 is a cross-sectional view of the feed screw shaft 5 and the motion converting portion 6 at the time of stop. The female screw (thread groove) 6c of the motion converting portion 6 holds the male screw (thread) 5c of the feed screw shaft 5 in the direction opposite to the motor (holding). This represents a state where the spring load Fb is pressed in the direction of the member 3). Only a part of the feed screw shaft 5 is shown. In FIG. 4, on the contact surface A2, the sliding surface of the male screw (thread) 5c and the sliding surface of the female screw (thread groove) 6c are in close contact, and on the contact surface A1, the sliding surface of the male screw (thread) 5c and the female screw The sliding surface of the (nut) 6c is separated. When the screw 5 rotates and the female screw (nut) 6c moves at a constant speed in the P1 direction, the female screw (screw groove) 6c operates so as to be pulled by the male screw (thread) 5c in the P1 direction. ) It moves with the right surface of 5c and the left surface of the female screw (thread groove) 6c in contact.

  On the contrary, when the female screw (screw groove) 6c moves at a constant speed in the P2 direction, the female screw (screw groove) 6c operates so as to be pulled by the male screw (screw thread) 5c in the P2 direction. On the contact surface A2, the sliding surface of the male screw (thread) 5c and the sliding surface of the female screw (thread groove) 6c are separated from each other, and on the contact surface A1, the sliding surface of the male screw (thread) 5c and the female screw (nut) 6c. Although the sliding surface is in close contact with each other, the female screw (screw groove) 6c of the motion converting portion 6 is pushed in the anti-motor direction (direction of the holding member 3) with the spring load Fb. The sliding surface of the thread 5c and the sliding surface of the female screw (thread groove) 6c are in close contact with each other, and the sliding surface of the male screw (screw thread) 5c and the sliding surface of the female screw (nut) 6c are separated at the contact surface A1. Hold.

  In order to obtain sufficient constant velocity, all contact surfaces are always in the state shown in FIG. 4 even when the slide unit 16 is moved at a constant speed, even when it is affected by disturbances such as friction and resistance. It is important that

  That is, the surface on one side of the internal thread (screw groove) 6c of the motion conversion section 6 and the sliding surface of the external thread (thread) 5c facing the internal thread 6c of the feed screw shaft 5 are moved during the movement of the motion conversion section 6. The pressing force generated in the direction in which the urging force of the compression spring 8 acts is always kept in good contact regardless of the moving direction of the motion conversion unit 6.

When the slide unit 16 is reciprocated horizontally, the axial load Fa when moving at a constant speed is the conveyance weight m (kg), the friction coefficient μ of the guide surface (sliding surface with the rail 7), the gravitational acceleration g, and the guide surface. If resistance (no load) f (N) and disturbance load N (N),
The axial load Fa2 (N) at the constant speed in the P2 direction is represented by (Fa2 (N) = μ × m × g + f + N−Fb) (hereinafter referred to as “Expression 4”).

  The axial load Fa1 (N) at the constant speed in the P1 direction is expressed by (Fa1 (N) = − μ × m × g−f + N−Fb) (hereinafter referred to as “Formula 5”). The disturbance load N is assumed to be a random load generated by vibration or impact.

  In the above “Expression 4”, if the axial load Fa2 is small under the condition of the axial load Fa2 ≧ 0 and is affected by friction, resistance fluctuations or disturbance load, the left surface of the male screw (thread) 5c is temporarily 4 may contact the right surface of the female screw (thread groove) 6c, and the state of FIG. 4 may not be continuously maintained. In this state, sufficient constant velocity cannot be satisfied. In order to prevent this, regarding the movement in the P2 direction, the setting of Fb is made on condition that (μ × m × g + f + N <Fb) when Fa2 <0 (hereinafter referred to as “Expression 6”).

  The setting of Fb in the movement in the P1 direction is conditional on (−μ × m × g−f + N <Fb) when Fa1 <0 (hereinafter referred to as “Expression 7”). Since Fa1 acts so as to increase Fa1 by the movement in the direction in which the right surface of male screw (thread) 5c and the left surface of female screw (thread groove) 6c contact, Fa1 acts as shown in FIG. 4 unless an abnormal disturbance load is applied. It is easy to maintain the state.

  In addition, since the feed screw axial spring load Fb (N) varies depending on the position of the motion conversion unit 6 (table 15), “Expression 6” and “Expression 7” are determined within the maximum stroke (P3 to P4). It is necessary to satisfy. Then, by setting the minimum necessary spring load Fb (N) in the direction of the screw shaft, the wear and friction of the feed screw shaft 5 and the motion converting portion 6, that is, the male screw (screw thread) 5c and the female screw (screw groove) 6c. Resistance can be reduced.

  FIG. 5 is a graph showing the constant velocity in the moving mechanism configured as described above, that is, the relationship between the position (μm) and the speed (μm / s) of the motion conversion unit 6 (table 15), and FIG. It is a graph showing the constant velocity in the moving mechanism of the structure without preload shown, that is, the relationship between the position (μm) and the speed (μm / s) of the motion conversion unit 32. In any case, the command speed is 1 (mm / s).

  In the configuration of the moving mechanism according to the present invention shown in FIGS. 1 to 3, the speed variation (amplitude of a large wave) of the motion converting unit 6 is significantly reduced as compared with the moving mechanism having the conventional structure shown in FIG. In addition, the speed variation (amplitude of thorn-like thin waves) in a slight change amount (during short distance movement) of the position of the motion conversion unit 6 is also greatly reduced. The moving mechanism having such a configuration is suitable for a moving mechanism that is small and has a relatively short stroke, and is suitable for a moving mechanism that includes an imaging mechanism such as a semiconductor device device as described above.

  FIG. 7 is a cross-sectional view of the motion converter 34 when a ball screw shaft 33 is used instead of the feed screw shaft 5 as a screw shaft. The basic concept of the ball screw shaft 33 is the same as that of the feed screw shaft 5, and it is possible to apply “Formula 1” to “Formula 7”. The operation and effect are the same as in the case of the feed screw shaft 5. In any case, the spring 8 may be a tension spring instead of the compression spring.

  As described above, the compression spring 8 is arranged so as to be concentric on the outer side (outside) of the motion conversion unit 6, one end 8 a of the compression spring 8 is on the outer surface of the motion conversion unit 6, and the other end 8 b is not movable. By being configured to be locked or fixed to the holding member 4 as a portion, the screw portion of the feed screw shaft 5 can be disposed at a place where the screw portion can be seen from the outside, and breakage of the screw portion can be easily confirmed. In addition, by arranging the compression spring 8 so as to be concentric outside the feed screw shaft 5, it is possible to prevent the spring from falling off when the compression spring 8 is damaged.

  Furthermore, the compression spring 8 can be easily replaced as compared with the structure disclosed in Patent Document 1. Then, after roughly designing a spring that sufficiently reduces backlash and keeps the friction of the screw part low, the labor of selecting a more appropriate spring while testing several types of springs is greatly reduced. Therefore, it becomes easy to realize a mechanism in which the constant velocity of the motion conversion unit 6 is stable and wear is reduced.

  8 to 10 show a second embodiment of the moving mechanism according to the present invention. In addition, the same code | symbol is attached | subjected to the member same as the member shown in FIG.1 and FIG.2, and detailed description is abbreviate | omitted. As shown in FIGS. 8 and 9, the moving mechanism 21 has a structure in which a compression spring 25 as a spring member is installed on a side opposite to the motor of the feed screw shaft 5 via a spring guide 24. That is, the moving mechanism 21 has a stopper member (holding member) 23 that is suspended from one end (left side in the figure) of the upper surface of the base 2 so as to face the holding member 4, and the screw shaft holding member of the holding member 4. A hole 23 a having a diameter larger than that of the screw shaft holding member 14 is formed so as to be opposed to the screw shaft 14. The feed screw shaft 5 has a cantilever structure, and as shown by a dotted line in FIG. 10, one end (front end) 5 a side is inserted into the spring guide 24, and the other end (base end) 5 b is inserted by the screw shaft holding member 14. It is pivotally supported.

  As shown in FIG. 10, the spring guide 24 has a bottomed cylindrical shape, the inner diameter of the cylindrical portion 24a is slightly larger than the outer diameter of the feed screw shaft 5, and a flange 24b as a spring seat at the open end. Is formed over the entire circumference. The spring guide 24 is mounted in a state where it is covered on the tip end side of the feed screw shaft 5, the flange 24 b comes into contact with the end plate 17 fixed to the left end portion of the slide unit 16, and the tip end side is a stopper member. 23 is inserted through the hole 23a. The feed screw shaft 5 is rotatable in the spring guide 24 with a slight gap.

  The compression spring 25 has an inner diameter slightly larger than the outer diameter of the spring guide 24, and is concentric between the stopper member 23 and the flange 24 b of the spring guide 24 and outside the spring guide 24. Arranged in a contracted state, one end 25 a is locked to the stopper member 23, and the other end 25 b is locked to the flange 24 b of the spring guide 24. The spring guide 24 is for preventing the center deviation and the bending of the compression spring 25.

  Thus, by installing the compression spring 25 on the side opposite to the motor of the feed screw shaft 5, an appropriate axial load is applied in the direction of the motor 9, and the center axis of the compression spring 25 is displaced by the spring guide 24. , Torso bending and falling off are prevented. And there is no preload of the motion converter 6, and the optimal axial load can be set from the stroke, spring rate, and free length of the motion converter 6. The actions and effects are the same as in the case of the first embodiment described above.

  The application conditions of the compression spring 25 can be considered in the same manner as in the case of the compression spring 8 in the first embodiment. In this case, the spring 25 is not limited to the compression spring, and a tension spring may be used.

It is a top view which shows 1st Embodiment of the moving mechanism which concerns on this invention. It is a front view of the moving mechanism shown in FIG. It is an expanded sectional view of the motion conversion part of the moving mechanism shown in FIG. It is explanatory drawing which shows the relationship between the screw shaft at the time of operation | movement of the moving mechanism shown in FIG. 1, and a motion conversion part. It is a characteristic view which shows an example of the relationship between the position of the motion conversion part of the moving mechanism shown in FIG. 1, and speed (constant velocity). It is a characteristic view which shows an example of the relationship between the position and speed (constant velocity property) of the motion conversion part in the moving mechanism of the conventional no preload structure shown in FIG. It is explanatory drawing which shows the relationship between a ball screw shaft at the time of operation | movement at the time of operation | movement at the time of using a ball screw shaft instead of a feed screw shaft in the moving mechanism shown in FIG. It is a top view which shows 2nd Embodiment of the moving mechanism which concerns on this invention. It is a front view of the moving mechanism shown in FIG. It is a principal part enlarged view which shows the relationship between the motion conversion part of the moving mechanism shown in FIG. 8, and a spring. It is explanatory drawing of the backlash which generate | occur | produces between the feed screw and the motion conversion part in the moving mechanism of the conventional no preload structure, Fig.11 (a) is a female screw of the motion conversion part on the left surface of the external thread of a feed screw axis | shaft. FIG. 11B is an explanatory diagram showing a case of contact, and FIG. 11B is an explanatory diagram showing a case where the female screw of the motion conversion unit contacts the right surface of the male screw of the feed screw shaft. It is explanatory drawing of the backlash which generate | occur | produces between the ball screw axis | shaft and the motion conversion part in the movement mechanism of the conventional no preload structure, Fig.12 (a) is a female screw of a motion conversion part on the left with respect to a ball screw axis. FIG. 12B is an explanatory diagram showing a case where the female screw of the motion converting portion is shifted to the right with respect to the ball screw shaft.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Movement mechanism 2 Base 3 Holding member 4 Holding member 4a Inner side surface 4b Counterbore 5 Feed screw shaft (screw shaft)
5a One end (tip)
5b The other end (base end)
5c Male thread (thread)
6 motion conversion part 6a upper plane part 6b lower plane part 6c female thread (thread groove)
7 Rail 8 Compression spring (spring member)
8a one end 8b other end 9 driving motor 10 motor shaft 11 non-movable member 13, 14 screw shaft holding member 15 table 16 slide unit 16a bottom plate 16b side plate 16c fitting recess 17 end plate 17a hole 18 end plate 18a hole 18b seat Boring 19 Shaft coupling 21 Moving mechanism 23 Stopper member (holding member)
23a hole 24 spring guide 24a tube portion 24b flange (spring seat)
25 compression spring 25a one end 25b other end 31 feed screw shaft 31a male screw (thread)
32 Motion conversion part (nut)
32a Female thread (thread groove)
33 Ball screw shaft 34 Motion converter (nut)
34a Female thread (thread groove)
35 Ball P1-Side movement limit point P2 + Side movement limit point P3-T1 position with maximum side stroke P4 + T1 position with maximum side stroke Fw Allowable maximum deflection of compression spring Lf Free length of compression spring X1 End plate Counterbore depth X2 Depth of counterbore of holding member Cs Spring constant of compression spring Lw Initial deflection of compression spring Fa Axial load during constant speed movement Fb Spring load in screw shaft direction m Conveyance weight μ Coefficient of friction of guide surface g Gravitational acceleration f Guide surface resistance (no load)
N Disturbance load Fa1 Axial load at P1 direction constant speed Fa2 Axial load at P2 direction constant speed A1 Contact surface A2 Contact surface T1 End face position of motion converter T2 End face position of motion converter │AB│ Backlash

Claims (3)

In a moving mechanism comprising a screw shaft rotatably supported by a non-movable member, and a motion conversion unit that is screwed to the screw shaft and moves in the axial direction of the screw shaft according to the rotation of the screw shaft. ,
A spring member is disposed so that one end is locked to the outer surface of the motion converting portion and the other end is locked to the non-movable member and exerts a biasing force on the motion converting portion in the axial direction of the screw shaft. ,
The spring member maintains the urging force in the movement range of the motion conversion portion, so that one side surface of the female screw formed on the motion conversion portion and one side surface of the male screw facing the one side surface of the female screw of the screw shaft are A moving mechanism characterized in that a good contact is always maintained regardless of the moving direction of the motion converting portion by a pressing force generated in a direction in which the urging force acts during the movement of the motion converting portion.   The moving mechanism according to claim 1, wherein the screw shaft is a feed screw shaft or a ball screw shaft.   The moving mechanism according to claim 1, wherein the spring member is a compression spring or a tension spring.

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