JP2010156452A - Planetary rotation/linear motion converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planetary rotation/linear motion converter for enlarging a stroke of a sun shaft, and improving productivity and durability. <P>SOLUTION: The planetary rotation/linear motion converter includes: the sun shaft 1 having a sun gear 11 and a helical ridge 12; planetary shafts 4 having planetary gears 41 meshing with the sun gear 11 of the sun shaft 1 and helical grooves 42 meshing with the helical ridge 12 of the sun shaft 1; and a nut 2 having an internal gear 21 meshing with the planetary gears 41 of the planetary shafts 4 and meshing with the helical grooves 42 in the planetary shafts 4. When the sun shaft 1 is rotated relative to the nut 2, the planetary shafts 4 linearly move relative to the sun shaft 1 in the axis direction of the sun shaft 1. Regions of the planetary shafts 4 in which the planetary gears 41 are formed and regions of the planetary shafts 4 in which the helical grooves 42 are formed are separated from each other in the axis direction of the planetary shafts 4. The sun gear 11 meshing with the planetary gears 41 of the planetary shafts 4 is formed on the helical ridge 12 of the sun shaft 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a planetary rotation-linear motion conversion device that converts rotational motion into linear motion using a planetary gear mechanism.

  As a planetary rotation-linear motion conversion device that converts rotational motion into linear motion, it is arranged between the sun shaft, a nut that surrounds the sun shaft with an annular space, and is arranged between the sun shaft and the nut. There is known a planetary rotation-linear motion conversion device including a plurality of planetary shafts (see Patent Document 1). The sun shaft has both a helical sun gear and a threaded sun gear. The planetary shaft also has a helical planetary gear and a threaded planetary gear. The nut also has a helical internal gear and a threaded internal gear. The helical sun gear of the sun shaft, the helical planet gear of the planetary shaft, and the helical internal gear of the nut constitute the first planetary gear mechanism, and the threaded sun gear of the sun shaft, the planetary shaft of the planetary shaft The screw-like planetary gear and the screw-like internal gear of the nut constitute a second planetary gear mechanism. The threaded sun gear of the sun shaft, the threaded planetary gear of the planetary shaft, and the threaded internal gear of the nut have the same pitch, and constitute a second planetary gear mechanism that meshes with each other. Then, the rotational movement of the nut is converted into the linear movement of the sun axis by making the gear ratio of the first planetary gear mechanism and the second planetary gear mechanism different.

  That is, in the planetary rotation-linear motion conversion device described in Patent Document 1, the ratio of the number of teeth of the helical sun gear of the solar shaft to the helical planetary gear of the planetary shaft is expressed by the screw-type planetary gear of the planetary shaft. The ratio of the number of teeth (the ratio of the number of teeth) of the threaded sun gear on the sun shaft is different. On the other hand, the ratio of the number of teeth of the helical internal gear of the nut to the helical planetary gear of the planetary shaft is matched to the ratio of the number of threads of the internal screw of the nut to the screw-type planetary gear of the planetary shaft. .

  The operation principle of the planetary rotation-linear motion conversion device described in Patent Document 1 is described as follows. When the nut is rotated relative to the sun axis, the planetary axis revolves while rotating around the sun axis. Here, since the gear ratio of the first planetary gear mechanism and the second planetary gear mechanism is different, assuming that the sun axis does not move in the axial direction, the revolution position of the planetary axis of the first planetary gear mechanism Then, the revolution position of the planetary shaft of the second planetary gear mechanism is shifted in the circumferential direction. However, since the helical planetary gear and the screw planetary gear of the planetary shaft are coupled to each other, the revolution position of the helical planetary gear cannot be shifted from the revolution position of the screw planetary gear. When the sun axis moves in the axial direction, the revolution position of the helical planetary gear changes, whereas the revolution position of the screw-like planetary gear changes. Therefore, the sun axis moves in the axial direction.

JP 2007-56952 A (refer to FIG. 1 and FIG. 14)

  However, in the conventional planetary rotation-linear motion conversion device, the sun axis moves linearly relative to the planet axis in the axial direction, and the sun-shaped screw sun gear is the planetary-axis screw planetary gear. There is a problem in that the screw-shaped sun gear of the sun axis hits the helical planetary gear of the planetary shaft when it deviates from this region. For this reason, the stroke amount of the sun shaft is limited to a range in which the screw sun gear of the sun shaft does not hit the helical planet gear of the planet shaft. Furthermore, since a helical planetary gear is provided only on one side in the axial direction of the screw-type planetary gear of the planetary shaft and the gear is driven only on one side, a bending moment that tilts the planetary shaft is likely to act, There is also a problem that transmission efficiency deteriorates.

  In order to increase the amount of stroke of the sun axis and to prevent a bending moment from acting on the planetary axis, in FIG. Also disclosed is a planetary rotation-linear motion conversion device in which a large number of convex portions that fit into the sun shaft recesses are arranged on the planetary shaft.

  However, since a large number of spiral dents on the outer peripheral surface of the solar shaft cannot be manufactured by any means other than rolling, a new problem arises that it becomes difficult to manufacture the solar shaft. Even if the solar shaft can be manufactured by a rolling die, it is impossible to correct the pitch errors of a large number of dents due to processing errors, distortion after quenching, and the like. This is because it is practically impossible to grind many dents. In addition, a large number of recesses on the sun axis and a large number of projections on the planetary shaft are intermittently engaged with each other, and many recesses and a large number of projections are manufactured by rolling as described above. Therefore, rattling (clearance) is likely to occur between the sun shaft recess and the planetary shaft projection, and there is also a problem that the durability of the sun shaft recess and the planetary shaft projection is adversely affected.

  The present invention has been made in order to solve the above-described problems of the conventional planetary rotation-linear motion conversion device, and can increase the stroke amount of the sun shaft or nut, thereby improving productivity and durability. It is an object of the present invention to provide a practical planetary rotation-linear motion conversion device that can be used.

The present invention will be described below.
In order to solve the above-described problems, one embodiment of the present invention includes a sun gear, a sun shaft having a spiral ridge or a circumferential ridge, and a planetary gear that meshes with the sun gear of the sun shaft. A planetary shaft having a spiral groove or a circumferential groove that meshes with the spiral ridge of the sun shaft or the circumferential ridge, and an internal gear that meshes with the planetary gear of the planetary shaft, and the spiral of the planetary shaft A groove or a nut meshing with the circumferential groove, and the sun gear of the sun shaft, the planetary gear of the planetary shaft, and the internal gear of the nut constitute a planetary gear mechanism, and In the planetary rotation-linear motion conversion device in which the planetary axis moves linearly relative to the sun axis in the axial direction of the sun axis when the sun axis is rotated relatively, the planet of the planetary axis gear The formed region and the region in which the spiral groove or the circumferential groove of the planetary shaft is formed are separated in the axial direction of the planetary shaft, and the spiral ridge or the circumferential ridge of the solar shaft is separated. Is a planetary rotation-linear motion conversion device that forms the sun gear meshing with the planetary gear of the planetary shaft on the convex portion of the planetary shaft.

  Another aspect of the present invention has a sun gear, a sun shaft having a spiral ridge or a circumferential ridge, a planetary gear meshing with the sun gear of the sun shaft, and the spiral projection of the sun shaft. A planetary shaft having a spiral groove or a circumferential groove meshing with a strip or the circumferential convex strip, and an internal gear meshing with the planetary gear of the planetary shaft, and meshing with the spiral groove or the circumferential groove of the planetary shaft A nut having a spiral ridge or a circumferential ridge, and the sun gear of the sun shaft, the planetary gear of the planetary shaft, and the internal gear of the nut constitute a planetary gear mechanism, and the sun shaft In the planetary rotation-linear motion conversion device in which the planetary shaft moves linearly relative to the nut in the axial direction of the nut when the nut is rotated relative to the nut, the planet of the planetary shaft A region in which the wheel is formed and a region in which the spiral groove or the circumferential groove of the planetary shaft is formed are separated in an axial direction of the planetary shaft, and the spiral protrusion or the circumferential protrusion of the nut is separated. It is a planetary rotation-linear motion conversion device that forms the internal gear meshing with the planetary gear of the planetary shaft on the convex portion of the strip.

  According to one aspect of the present invention, the sun gear that meshes with the planetary gear of the planetary shaft is formed on the spiral ridge or the circumferential ridge of the solar shaft, so that the planetary shaft is relative to the sun axis in the axial direction. The spiral ridges or circumferential ridges of the sun axis do not interfere with the planetary gears of the planetary axis even when the Engagement with the directional groove is maintained, and engagement between the sun gear of the sun shaft and the planet gear of the planet shaft is maintained. Therefore, the relative stroke amount of the nut in the axial direction with respect to the sun axis can be increased. In addition, the solar shaft can be manufactured by either cutting or rolling, and the pitch can be corrected by grinding after the quenching of the solar shaft, improving the productivity of the solar shaft. To do. Furthermore, the region where the planetary gear of the planetary shaft is formed and the region where the spiral groove or circumferential groove of the planetary shaft is formed are separated in the axial direction of the planetary shaft, so that the planetary shaft is also cut and rolled. Both of them can be manufactured, and the manufacture of the planetary shaft becomes easy.

  According to another aspect of the present invention, an internal gear that meshes with the planetary gear of the planetary shaft is formed on the convex portion of the spiral or circumferential ridge of the nut, so that the planetary shaft is relative to the nut in the axial direction. Even if it moves to, the helical ridge or circumferential ridge of the nut does not interfere with the planetary gear of the planetary shaft, and the helical ridge or circumferential ridge of the nut and the helical groove or circumferential groove of the planetary shaft And the meshing between the nut internal gear and the planetary gear of the planetary shaft is maintained. Therefore, the relative stroke amount in the axial direction of the sun shaft with respect to the nut can be increased. Further, the nut can be manufactured by either cutting or rolling, and the pitch can be corrected by grinding or the like after the nut is quenched, so that the productivity of the nut is improved. Furthermore, the region where the planetary gear of the planetary shaft is formed and the region where the spiral groove or circumferential groove of the planetary shaft is formed are separated in the axial direction of the planetary shaft, so that the planetary shaft is also cut and rolled. Both of them can be manufactured, and the manufacture of the planetary shaft becomes easy.

The perspective view of the planetary rotation-linear motion conversion apparatus in 1st embodiment of this invention. Solar axis side view Side view of planetary shaft Sectional view along the axis of the nut Schematic diagram showing the revolution angle of the planetary axis when the sun axis is rotated once. Conceptual diagram of the total lead calculation method Diagram showing the crowning applied to the planetary axis Sectional view perpendicular to the axis showing the meshing of the male screw of the sun shaft, the male screw of the planetary shaft, and the female screw of the nut Comparison of planetary rotation-linear motion converters with different spur gear modules (module 0.68 (a) and module 0.42 (b)) The perspective view which shows the meshing | engagement of the external thread of a planetary axis, and the external thread of a solar axis (module 0.68 (a) and module 0.42 (b)) Cross-sectional views orthogonal to the axis of the solar axis (module 0.68 (a) and module 0.42 (b)) The perspective view of the planetary rotation-linear motion converter in 2nd embodiment of this invention Sectional view of the planetary rotation-linear motion converter Cross section of nut The perspective view of the planetary rotation-linear motion conversion apparatus in 3rd embodiment of this invention. Sectional view of the planetary rotation-linear motion converter Solar axis side view Sectional perspective view of an actuator incorporating the planetary rotation-linear motion conversion device of the first embodiment of the present invention.

  Hereinafter, the planetary rotation-linear motion conversion device of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a perspective view of a planetary rotation-linear motion conversion device in a first embodiment of the present invention (a state in which a nut is divided in half for easy understanding of the internal structure). The planetary rotation-linear motion conversion device includes a sun shaft 1 and an annular nut 2 that extend along a common axis 3. In the annular space between the sun shaft 1 and the nut 2, a plurality of, for example, nine planetary shafts 4 that mesh with these are arranged. The axis of the planetary axis 4 is parallel to the axis of the sun axis 1 and the nut 2. The nine planetary axes 4 are arranged around the sun axis 1 at equal intervals in the circumferential direction. When the sun shaft 1 is rotated relative to the nut, the nut 2 linearly moves in the axial direction.

  The sun shaft 1 is formed with a spur gear 11 as a sun gear and a male screw 12 as a spiral ridge. The planetary shaft 4 is formed with a spur gear 41 as a planetary gear and a male screw 42 as a spiral groove. The nut 2 is formed with a spur gear 21 as an internal gear and a female screw 22 as a spiral protrusion. The sun gear of the sun shaft 1, the planetary gear of the planetary shaft 4, and the internal gear of the nut 2 mesh with each other to constitute a planetary gear mechanism. The sun gear, the planetary gear, and the internal gear are gears having a twist angle of 25 degrees or less, and include gears having a twist angle of 0 degrees, that is, spur gears. The spiral ridges of the sun shaft 1, the spiral groove of the planetary shaft 4, and the spiral ridges of the nut also mesh with each other at the same pitch to constitute a planetary roller screw mechanism.

  As shown in FIG. 2, a plurality of, for example, eight male threads 12 as spiral ridges are formed on the outer peripheral surface of the sun shaft 1. The male screw 12 is formed along a spiral winding on a cylindrical outer peripheral surface and has a predetermined lead angle. The cross-sectional shape of the cut surface of the male screw 12 by a plane including the axis of the sun axis 1 is a trapezoid. Of course, the outer diameter of the male screw 12 is larger than the diameter of the valley of the male screw 12.

  As shown in FIG. 1, when the pitch of the male screw 12 as the spiral protrusion of the sun shaft 1 is matched with the pitch of the male screw 42 as the spiral groove of the planetary shaft 4, the male screw 12 of the solar shaft 1 is changed to the male screw 42 of the planetary shaft 4. Can be engaged.

  A spur gear 11 as a sun gear is formed on the convex portion of the male screw 12 of the sun shaft 1. The spur gear 11 is formed in an involute tooth profile, for example, like a general spur gear. The total tooth depth of the spur gear 11 is smaller than the height of the thread of the male screw 12, and a contact surface 12 a is formed on the male screw 12 inside the tooth bottom of the spur gear 11. In other words, the root circle of the spur gear 11 is set larger than the diameter of the valley of the male screw 12 of the sun shaft 1. The male screw 42 of the planetary shaft 4 is in contact with the contact surface 12a.

The spur gear 11 of the planetary shaft 4 meshes with the spur gear 11 of the sun shaft 1. The phases of the spur gears 11 of the sun shaft 1 formed on the eight male threads 12 coincide with each other when viewed from the axial direction of the sun shaft 1. When the number of teeth of the spur gear 11 of the sun shaft 1 is S _z1 and the number of teeth of the spur gear 41 of the planetary shaft 4 is P _z1 , the distance between the spur gear 11 of the sun shaft 1 and the spur gear 41 of the planetary shaft 4 is The rotation is transmitted at a speed ratio (ratio of rotation speed) according to the number of teeth S _z1 and P _z1 .

  The spur gear 11 of the sun shaft 1 is formed on the convex portion of the male screw 12 of the sun shaft 1. For this reason, the region where the spur gear 11 of the sun shaft 1 is formed overlaps the region where the male screw 12 of the sun shaft 1 is formed in the axial direction of the sun shaft 1. Even if the planetary shaft 4 is displaced relative to the solar shaft 1 in the axial direction of the solar shaft 1, the solar shaft 1 can maintain the meshing of the spur gear 11 of the solar shaft 1 with the spur gear 41 of the planetary shaft 4. 1 spur gear 11 is formed.

  Nine planet axes 4 are arranged around the sun axis 1. The number of arranged planetary shafts 4 is a common divisor of the sum of the number of teeth of the spur gears 11 and 21 of the sun shaft 1 and nut 2 and the sum of the number of threads of the male screw 12 and female screw 22 of the sun shaft 1 and nut 2. It is.

  As shown in FIG. 3, each planetary shaft 4 is provided with, for example, two male screws 42 as spiral grooves, and a pair of spur gears 41 as planetary gears. The two male threads 42 are formed at the center of the planetary shaft 4 in the axial direction. The pair of spur gears 41 is formed at both ends in the axial direction of the male screw 42 of the planetary shaft 4. The phases of the pair of spur gears 41 as seen from the axial direction of the planetary shaft 4 coincide with each other. By forming the spur gear 41 at both ends of the male screw 42 of the planetary shaft 4, the planetary shaft 4 can be gear-driven at both ends in the axial direction, and the planetary shaft 4 can be prevented from tilting.

  In the sun shaft 1, a region where the male screw 12 is formed and a region where the spur gear 11 is formed overlap in the axial direction of the sun shaft 1. On the other hand, in the planetary shaft 4, the male screw 42 and the spur gear 41 are independent, and the region where the male screw 42 is formed and the region where the spur gear 41 is formed are separated in the axial direction of the planetary shaft 4. ing. The male screw 42 of the planetary shaft 4 meshes with the male screw 12 of the sun shaft 1, and the spur gear 41 of the planetary shaft 4 meshes with the spur gear 11 of the sun shaft 1. By making the male screw 42 of the planetary shaft 4 and the spur gear 41 independent, there is no need to form the spur gear 41 at the bottom of the male screw 42 of the planetary shaft 4, making the planetary shaft 4 easy to manufacture, and the planetary shaft 4. And the sun shaft 1 can be prevented from intermittently meshing with each other.

  In order to increase the stroke amount of the sun shaft 1 while maintaining the meshing of the male screws 42 and 12 and the spur gears 41 and 11 of the planetary shaft 4 and the sun shaft 1, the spur gear 11 is provided on the male screw 12 of the sun shaft 1. It is formed. When a spur gear is formed on the male screw 12 of the sun shaft 1, it appears that the male screw 12 of the sun shaft 1 intermittently meshes with the male screw 42 of the planetary shaft 4. However, since the male screw 42 of the planetary shaft 4 contacts inside the root circle of the spur gear 11 of the male screw 12 of the sun shaft 1, the male screw 42 of the planetary shaft 4 intermittently meshes with the male screw 12 of the solar shaft 1. There is nothing.

  As shown in FIG. 1, each planetary shaft 4 is supported by an annular plate carrier (not shown) at both ends in the axial direction so as to be rotatable around the axis. The carrier is supported by the nut 2 so that it can freely rotate around the axis relative to the nut 2. Of course, the inner diameter of the carrier 2 is larger than the outer diameter of the sun shaft 1.

  As shown in FIG. 4, the nut 2 is formed in a substantially cylindrical shape. A flange 2a for attaching the nut 2 to another member is formed at one end of the nut 2 in the axial direction. The nut 2 is connected to other members (not shown) so as not to rotate relative to each other. At both ends in the axial direction of the inner peripheral surface of the nut 2, a pair of ring step portions 2 b having an enlarged inner diameter is formed. A pair of ring gear members 5 is fixed to the pair of ring stepped portions 2b by press fitting or the like (see FIG. 1). The pair of ring gear members 5 are formed with a pair of internal gears 21 that mesh with a pair of spur gears 41 of the planetary shaft 4. Further, on the inner peripheral surface of the central portion 2c of the nut 2, a plurality of, for example, ten female threads 22 that are screwed with the male threads 42 of the planetary shaft 4 are formed as spiral ridges. The female screw 22 has a predetermined lead angle along the helical winding on the inner peripheral surface of the nut 2. The cross-sectional shape of the cut surface of the female screw 22 in a plane including the axis of the nut 2 is a trapezoid.

  When assembling the planetary rotation-linear motion conversion device, first, the planetary shaft 4 is held in an annular shape inside the nut 2. At the stage where the positional relationship between the planetary shaft 4 and the nut 2 is fixed so as not to be shifted by the carrier, the sun shaft 1 is screwed into the planetary shaft 4.

  As shown in FIG. 1, the spur gear 11 of the sun shaft 1, the spur gear 41 of the planetary shaft 4, and the internal gear 21 of the nut 2 work together to form a planetary gear mechanism, and the sun gear, the planetary gear, Functions as an internal gear. The male screw 12 of the sun shaft 1, the male screw 42 of the planetary shaft 4, and the female screw 22 of the nut 2 constitute a planetary roller screw mechanism that functions as a spiral ridge, a spiral groove, and a spiral ridge, respectively. To do.

  The male screw 12 of the sun shaft 1, the male screw 42 of the planetary shaft 4, and the female screw 22 of the nut 2 that constitute the planetary roller screw mechanism mesh with each other. The male screw 12 and the male screw 42 have leads in opposite directions, and the male screw 42 and the female screw 22 have leads in the same direction. The pitches of the male screw 12, the male screw 42, and the female screw 22 are equal to each other. The lead angle of the male screw 42 of the planetary shaft 4 is the same as the lead angle of the female screw 22 of the nut 2 in the other screw lead reference pitch circle. For this reason, even if the planetary shaft 4 revolves inside the nut 2, the planetary shaft 4 does not stroke in the axial direction with respect to the nut 2. On the other hand, the lead angle of the male screw 42 of the planetary shaft 4 is different from the lead angle of the male screw 12 of the sun shaft 1. For this reason, when the planetary axis 4 revolves around the sun axis 1, the planetary axis 4 linearly moves in the axial direction with respect to the sun axis 1. Accordingly, the nut 2 also moves linearly with respect to the sun axis 1 in the axial direction.

  The spur gear 11 of the sun shaft 1, the spur gear 41 of the planetary shaft 4 and the internal gear 21 of the nut 2 that constitute the planetary gear mechanism also mesh with each other. In this planetary rotation-linear motion converter, the number of teeth of the spur gear 11, the spur gear 41, and the internal gear 21 is 69, 24, and 120, respectively.

  When the sun shaft 1 is rotated once, the stroke amount (total lead) of the sun shaft 1 relative to the nut 2 is calculated as follows. As shown in FIG. 5, when the sun axis 1 is rotated once, the planetary axis 4 revolves while rotating around the sun axis 1. The planetary shaft revolution reduction ratio, which is the revolution speed of the planetary shaft 4, is obtained by the following equation.

Entering specific numbers,

Since the pitch of the male screw 12 of the solar shaft 1 is 7 mm and the number of strips is 8, the lead per rotation of the solar shaft 1 is 7 × 8 = 56 mm. As shown in FIG. 6, when the S _PC of the external thread 12 of the sun shaft 1 (sun shaft thread lead reference pitch) and 28.75Mm, sun shaft 1 per revolution, a reference pitch circle of (28.75 × [pi) At 56 mm in the axial direction.

On the other hand, since the pitch of the male screw of the planetary shaft 4 is 7 mm and the number of threads is 2, the lead is 7 × 2 = 14 mm. When the planetary shaft 4 of the external thread of the P _PC (the planetary shaft thread lead reference pitch) to 10 mm, the planetary shaft 4 is per revolution, it proceeds 14mm in reference pitch of (10 × [pi).

  The planetary axis 4 revolves around the sun axis 1. The length of the contact portion 7 (see FIG. 5) when the sun shaft 1 is rotated once is 28.75 × π × 0.6349 from the planetary shaft revolution reduction ratio. The difference between the lead of the sun axis 1 and the lead of the planetary axis 4 at that time is the total lead L.

That is, the total lead L is the lead of the solar axis 1-the lead of the planetary axis 4,
L = 56 × 0.6349−28.75 × π × 0.6349 / (10 × π) × 14 = 10 mm.

When expressed by a general formula, the total lead L is expressed by the following calculation formula.

  As shown in FIG. 7, the male screw 42 of the planetary shaft 4 is provided with a crowning 42a. The crowning 42 a is formed in an arc shape when viewed in a cross section including the axis of the planetary shaft 4 or when viewed in a cross section perpendicular to the lead of the male screw 42 of the planetary shaft 4. By applying the crowning 42a, the male screw 12 of the sun shaft 1 and the male screw 42 of the planetary shaft 4 can be brought into point contact. The contact point between the planetary axis 4 and the sun axis 1 is arranged in the vicinity of the point where the male screw 42 of the planetary axis 4 rolls without sliding with respect to the male screw 12 of the sun axis 1. By doing in this way, the differential slip between the external thread 12 of the sun shaft 1 and the external thread 42 of the planetary shaft 4 can be reduced, and the transmission efficiency of rotation can be improved.

  As shown in FIG. 8, when viewed from the axial direction of the sun shaft 1, a part of the outer diameter circle 43 of the male screw 42 of the planetary shaft 4 enters inside the root circle 13 of the spur gear 11 of the sun shaft 1. The point P where the male screw 42 of the planetary shaft 4 contacts the male screw 12 of the sun shaft 1 is the contact surface 12a of the male screw 12 of the sun shaft 1 (inside the root circle 13 of the spur gear 11 of the sun shaft 1, 10). When a load in the axial direction is applied to the sun shaft 1, the contact point P between the male screw 12 of the sun shaft 1 and the male screw 42 of the planetary shaft 4 is elastically deformed, and the contact area becomes wide. The load in the axial direction of the solar shaft 1 is received by the contact surface 12a of the external thread 12 of the solar shaft 1 that has been elastically deformed. By bringing the male screw 42 of the planetary shaft 4 into contact with the contact surface 12 a of the male screw 12 of the sun shaft 1, the male screw 42 of the planetary shaft 4 is prevented from contacting only the spur gear 11 formed on the male screw 12 of the solar shaft 1. be able to. For this reason, the male screw 42 of the planetary shaft 4 hits the spur gear 11 of the male screw 12 of the sun shaft 1 intermittently (that is, when the male screw 42 of the planetary shaft 4 hits the spur gear 11 of the male screw 12 of the sun shaft 1). Can be prevented, and the male screw 42 of the planetary shaft 4 can be brought into stable contact with the male screw 12 of the sun shaft 1. Further, since the male screw 42 of the planetary shaft 4 can be prevented from intermittently hitting the spur gear 11 of the male screw 12 of the sun shaft 1, the screw is resistant to shear stress and bending moment.

  In the present embodiment, since the male screw 42 of the planetary shaft 4 is desired to be brought into contact with the contact surface 12a of the male screw 12 of the sun shaft 1, the male screw 42 of the planetary shaft 4 is thickened. When the male screw 42 of the planetary shaft 4 is extremely thickened, it interferes with the adjacent planetary shaft 4. For this reason, the number of arranged planetary shafts 4 is reduced to nine.

  The lead angle of the male screw 42 of the planetary shaft 4 is different from the lead angle of the male screw 12 of the sun shaft 1. Therefore, strictly speaking, the contact point P between the male screw 42 of the planetary shaft 4 and the male screw 12 of the solar shaft 1 is slightly shifted from the line 15 connecting the center of the solar shaft 1 and the center of the planetary shaft 4. . On the other hand, the lead angle of the male screw 42 of the planetary shaft 4 is equal to the lead angle of the female screw 22 of the nut 2. For this reason, the contact point Q between the male screw 42 of the planetary shaft 4 and the female screw 22 of the nut 2 is located on a line 15 connecting the center of the sun shaft 1 and the center of the planetary shaft 4.

  FIG. 9 shows an example in which the spur gear module is changed. If the spur gear module is reduced from 0.68 to 0.42, for example, while maintaining the speed ratio and meshing phase of the spur gear, the circular pitch of the spur gear 11 of the male screw 12 of the sun shaft 1 is reduced. As shown in FIG. 10, when the module of the spur gear 11 is reduced from 0.68 to 0.42, the total tooth clearance of the spur gear 11 formed on the male screw 12 of the sun shaft 1 can be reduced. The thickness of the contact surface 12a in the radial direction can be increased. For this reason, the male screw 42 of the planetary shaft 4 is easily brought into contact with the contact surface 12 a of the male screw 12 of the sun shaft 1. Furthermore, as shown in FIG. 11, the meshing pitch circle (shown by the meshing area in the figure) of the male screw 12 of the sunshaft 1 can be increased by the amount that the total tooth depth of the spur gear 11 of the sunshaft 1 can be reduced. The circle can be brought close to the zero-slip region where no slip occurs, and the rotation transmission efficiency can be improved. The meshing pitch circle is a locus on the point where the male screw 12 of the sun shaft 1 and the male screw 42 of the planetary shaft 4 are engaged with each other. The zero slip region is a locus on a point where no slip occurs between the male screw 12 of the sun shaft 1 and the male screw 42 of the planetary shaft 4. A region where the helical orbit length drawn by the planetary axis 4 that revolves and the helical orbit length of the sun shaft 1 coincides with the zero-slip region.

  As shown in FIG. 1, the male screw 42 of the planetary shaft 4 also contacts the female screw 22 of the nut 2 in the vicinity of the point of rolling contact so that no differential slip occurs. By making the male screw 42 of the planetary shaft 4 oversized, it is possible to apply a preload and to eliminate backlash.

  In the above embodiment, the example in which the planetary shaft 4 is displaced relative to the solar shaft 1 in the axial direction has been described.

  Conversely, the planetary shaft may be displaced relative to the nut in the axial direction. In this case, the gear which comprises an internal gear is provided in the convex part of the helical internal thread of the nut which comprises a spiral groove. The planetary shaft is provided with a male screw constituting a spiral groove and a pair of spur gears constituting a planetary gear on both sides in the axial direction of the male screw, separated in the axial direction of the planetary shaft. The sun shaft is provided with a male screw constituting a spiral ridge and a pair of spur gears constituting a sun gear on both sides of the male screw in the axial direction, separated in the axial direction. According to this example, even if the planetary shaft makes a stroke with respect to the nut, the screw-shaped internal gear of the nut does not interfere with the planetary gear of the planetary shaft. Therefore, the relative stroke amount in the axial direction of the sun shaft with respect to the nut can be increased.

  12 to 14 show a planetary rotation-linear motion conversion device according to a second embodiment of the present invention. FIG. 12 is a perspective view of the planetary rotation-linear motion conversion device (a state in which the nut 52 is divided in half for easy understanding of the internal structure), and FIG. 13 is a cross section of the planetary rotation-linear motion conversion device. The figure is shown. The planetary rotation-linear motion converter of this embodiment also includes a sun shaft 51, a plurality of planet shafts 54 arranged around the sun shaft 51, an annular nut 52 surrounding the sun shaft 51 and the planet shaft 54, Is provided.

  The sun shaft 51 is formed with a spur gear 55 as a sun gear and a male screw 56 as a spiral ridge. Similar to the planetary rotation-linear motion conversion device of the first embodiment, the spur gear 55 of the sun shaft 51 is formed on the convex portion of the male screw 56. The male screw 56 has a predetermined lead angle.

  The planetary shaft 54 is formed with a pair of spur gears 57 as planetary gears, and a circumferential groove 58 is formed between the pair of spur gears 57. The circumferential groove 58 is formed by arranging a large number of single ring-shaped grooves extending in the circumferential direction in the axial direction of the planetary shaft 4. The spur gear 57 of the planetary shaft 54 meshes with the spur gear 55 of the sun shaft 51, and the circumferential groove 58 of the planetary shaft 54 meshes with the male screw 56 of the sun shaft 51. As shown in the sectional view of the nut 52 in FIG. 14, the lead angle of the circumferential groove 58 of the planetary shaft 54 is 0 degree. The pitch of the circumferential grooves 58 of the planetary shaft 54 is the same as the pitch of the male threads 56 of the sun shaft 51.

  As shown in FIGS. 12 and 13, the nut 52 is formed with a pair of spur gears 59 as internal gears, and a circumferential ridge 60 is formed between the pair of spur gears 59. The pair of spur gears 59 of the nut 52 mesh with the pair of spur gears 57 of the planetary shaft 54, and the circumferential ridge 60 of the nut 52 meshes with the circumferential groove 58 of the planetary shaft 54. As shown in FIG. 14, the circumferential ridge 60 of the nut 52 is also formed by arranging a plurality of single ring-shaped ridges extending in the circumferential direction. The lead angle of the circumferential ridge 60 is 0 degree.

  The spur gear 55 of the sun shaft 51, the spur gear 57 of the planetary shaft 54, and the spur gear 59 of the nut 52 constitute a planetary gear mechanism. When the sun shaft 51 is rotated relative to the nut 52, the planetary shaft 54 revolves while rotating around the sun shaft 51.

  The male screw 56 of the sun shaft 51, the circumferential groove 58 of the planetary shaft 54, and the circumferential ridge 60 of the nut 52 mesh with each other. Unlike the planetary rotation-linear motion conversion device of the first embodiment, the lead angle of the circumferential groove 58 of the planetary shaft 54 and the circumferential protrusion 60 of the nut 52 is 0 degree. Similarly, when the planetary shaft 54 revolves around the sun shaft 51 while rotating, the difference between the lead angle of the male screw 56 of the sun shaft 51 and the lead angle of the circumferential groove 58 of the planet shaft 54 causes the planet shaft 54 and The nut 52 moves in the axial direction.

  According to the planetary rotation-linear motion conversion device of this embodiment, the following effects can be obtained. 1. Since the circumferential ridge 60 of the nut 52 and the circumferential groove 58 of the planetary shaft 54 are not helical, the manufacturing accuracy is improved (the machining accuracy is not affected by the index accuracy when machining the helical groove). Depends only on the feed accuracy of the processing machine). 2. Since the lead angle of the circumferential ridge 60 of the nut 52 and the circumferential groove 58 of the planetary shaft 54 is 0, relative displacement due to a lead error does not occur. 3. Since the lead angle of the circumferential ridge 60 of the nut 52 and the circumferential groove 58 of the planetary shaft 54 is 0, the number of threads is defined as 0, increasing the degree of freedom of the number of arrangement of the planetary shaft 54 and increasing the strength. Is easy to get. 4). Since the number of threads of the sun shaft 51 can be designed to be small, accuracy is easily obtained. 5. The reverse efficiency can be designed extremely small without reducing the normal efficiency.

  15 to 17 show a planetary rotation-linear motion conversion device according to a third embodiment of the present invention. FIG. 15 is a perspective view of the planetary rotation-linear motion conversion device, and FIG. 16 is a cross-sectional view. The planetary rotation-linear motion conversion device of this embodiment also includes a sun shaft 61, a plurality of planet shafts 64 arranged around the sun shaft 61, an annular nut 62 surrounding the sun shaft 61 and the planet shaft 64, and Is provided.

  The sun shaft 61 is formed with a spur gear 65 and a circumferential ridge 66 as sun gears. As shown in the side view of the sun shaft 61 in FIG. 17, the circumferential ridge 66 is formed by arranging a plurality of single ridges extending in the circumferential direction in the axial direction of the sun shaft 61. The lead angle of the circumferential ridge 66 is 0 degree. The spur gear 65 of the sun shaft 61 is formed on the convex portion of the circumferential ridge 66.

  As shown in FIG. 15, a pair of spur gears 67 as planetary gears are formed on the planetary shaft 64, and a male screw 68 as a spiral groove is formed between the pair of spur gears 67. A pair of spur gears 67 of the planetary shaft 64 mesh with the spur gear 65 of the sun shaft 61, and a male screw 68 of the planetary shaft 64 meshes with the circumferential ridge 66 of the sun shaft 61. The pitch of the male screw 68 of the planetary shaft 64 is the same as the pitch of the circumferential ridge 66 of the sun shaft 61. The male screw 68 of the planetary shaft 64 has a predetermined lead angle.

  The nut 62 is formed with a spur gear 69 as an internal gear and a female screw 70 as a spiral protrusion. The spur gear 69 of the nut 62 meshes with the spur gear 67 of the planetary shaft 64, and the female screw 70 of the nut 62 meshes with the male screw 68 of the planetary shaft 64. The female screw 70 of the nut 62 has the same lead angle in the opposite direction as the male screw 69 of the planetary shaft 64.

  The spur gear 65 of the sun shaft 61, the spur gear 67 of the planetary shaft 64, and the spur gear 69 of the nut 62 constitute a planetary gear mechanism. When the sun shaft 61 is rotated with respect to the nut 62, the planetary shaft 64 revolves while rotating around the nut 62.

  The circumferential ridge 66 of the sun shaft 61, the male screw 68 of the planetary shaft 64, and the female screw 70 of the nut 62 mesh with each other. Unlike the planetary rotation-linear motion conversion device of the first embodiment, the lead angle of the circumferential ridge 66 of the sun shaft 61 is 0 degrees, so the circumferential ridge 66 of the sun shaft 61 is a screw gear. Does not constitute. However, when the planetary shaft 64 revolves around the sun shaft 61 while rotating, the sun shaft 61 is rotated by the difference between the lead angle of the circumferential projection 66 of the sun shaft 61 and the lead angle of the male screw 68 of the planet shaft 64. Move in the direction.

  According to the planetary rotation-linear motion conversion device of this embodiment, the following effects can be obtained. 1. Since the circumferential ridge 66 of the sun shaft 61 is not spiral, the manufacturing accuracy is improved. 2. Since the lead angle of the circumferential ridge 66 of the sun shaft 61 is 0, relative displacement due to lead error does not occur. 3. Since the lead angle of the circumferential ridge 66 of the sun axis 61 is 0, the number of threads is defined as 0, the degree of freedom of the number of arrangement of the planetary axes 64 is increased, and the strength is easily obtained. 4). Since the number of threads of the sun shaft 61 can be designed to be zero, it is easy to obtain accuracy. 5. The reverse efficiency can be designed extremely small without reducing the normal efficiency.

  FIG. 18 shows an actuator incorporating the planetary rotation-linear motion conversion device of the first embodiment of the present invention. In this actuator, the nut 2 is rotated by the hollow motor 73 so that the sun shaft 1 moving in the axial direction enters and exits the housing 74.

  Both ends of the nut 2 in the front-rear direction are rotatably supported by bearings 76 and 77. The bearings 76 and 77 are incorporated in the housing 74.

  The motor 73 is integrally incorporated in the housing 74. A permanent magnet 71 serving as a rotor of the motor 73 is fixed to the outer peripheral surface of the nut. A three-phase coil 72 serving as a stator of the motor 73 is integrally fixed to the housing 74 so as to surround the permanent magnet 71.

  The front wall 75 of the housing 74 is formed with a spline groove 75a that prevents the sun shaft 1 from rotating about its axis and allows the sun shaft 1 to linearly move in the axial direction. The sun shaft 1 is formed with a spline protrusion 1 a that engages with the spline groove 75 a of the housing 75. These spline grooves 75a and spline ridges 1a constitute a detent mechanism.

  When the motor 73 rotates the nut 2, the planetary shaft 4 revolves while rotating around the sun shaft 1. As the planetary shaft 4 rotates and revolves, the sun shaft 1 that meshes with the planetary shaft 4 moves in the axial direction. Since the rotation of the sun shaft 1 around the axis is limited by the rotation preventing mechanisms 1a and 75a, the sun shaft 1 does not rotate together with the nut 2.

  According to the actuator of this embodiment, since the planetary rotation-linear motion conversion device with low reverse efficiency is incorporated, the power of the motor 73 for maintaining the axial position of the sun shaft 1 can be reduced. In order to hold the position of the sun axis 1 against the axial load acting on the sun axis 1, the motor 73 must continue to generate torque while the position of the sun axis 1 is being held. Since the planetary rotation-linear motion conversion device has a lower reverse efficiency (efficiency to change the axial load into the rotational torque) than the ball screw, the torque required to maintain the position of the sun shaft 1 is applied to the ball screw. Compared to an extremely small size. Therefore, the capacity and size of the motor 73 can be reduced, and the heat generation of the motor 73 can be suppressed.

  The present invention is not limited to being embodied in the above-described embodiment, and can be variously modified without departing from the scope of the present invention. The design specifications such as the number of teeth shown in the above embodiment are examples, and can be appropriately changed according to the total lead and the axial load.

DESCRIPTION OF SYMBOLS 1,51,61 ... Sun shaft, 2, 52, 62 ... Nut, 3 ... Axis, 4, 54, 64 ... Planetary shaft, 11, 55, 65 ... Spur gear (sun gear) of solar shaft, 12, 56 ... Male axis of the sun axis (spiral ridge of the sun axis), 66 ... Circumferential ridges of the sun axis, 12a ... Contact surface, 13 ... Root circle of the spur gear of the sun axis, 21, 59, 69 ... Spur gear of the nut (Internal gears), 22, 70 ... nut internal threads (nut spiral ridges), 60 ... nut circumferential ridges, 41, 57, 67 ... planetary shaft spur gears (planetary gears), 42, 68 ... planets Shaft male screw (planetary spiral groove), 58 ... circumferential groove of planetary shaft, 42a ... crowning, P ... contact point between male screw of solar shaft and male screw of planetary shaft

Claims (8)

A sun shaft having a sun gear and a spiral or circumferential ridge,
A planetary gear having a planetary gear meshing with the sun gear of the sun shaft, and having a spiral groove or a circumferential groove meshing with the spiral ridge or the circumferential ridge of the sun shaft;
An internal gear that meshes with the planetary gear of the planetary shaft, and a nut that meshes with the spiral groove or the circumferential groove of the planetary shaft,
The sun gear of the sun shaft, the planetary gear of the planetary shaft, and the internal gear of the nut constitute a planetary gear mechanism,
In the planetary rotation-linear motion conversion device in which when the sun axis is rotated relative to the nut, the planetary axis is linearly moved relative to the sun axis in the axial direction of the sun axis.
The region of the planetary shaft where the planetary gear is formed and the region of the planetary shaft where the spiral groove or the circumferential groove is formed are separated in the axial direction of the planetary shaft,
A planetary rotation-linear motion conversion device that forms the sun gear meshing with the planetary gear of the planetary shaft on the spiral ridge of the sunshaft or the convex portion of the circumferential ridge.   The contact position between the spiral ridges or the circumferential ridges of the sun axis and the spiral grooves or the circumferential grooves of the planetary axis is the position of the sun gear of the sun axis when viewed from the axial direction of the sun axis. The planetary rotation-linear motion conversion device according to claim 1, wherein the planetary rotation-linear motion conversion device is inside the root circle.   The spiral groove or the circumferential groove of the planetary shaft is viewed in a cross section including the axis of the planetary shaft, or viewed in a cross section perpendicular to the lead of the spiral groove or the circumferential groove of the planetary shaft. The crowning is performed so that the spiral groove or the circumferential groove of the planetary shaft and the spiral ridge or the circumferential ridge of the sun axis are in point contact with each other. The planetary rotation-linear motion conversion device described. The spiral groove or the circumferential groove is formed in the center of the planetary shaft in the axial direction,
The planetary rotation-linear motion conversion device according to any one of claims 1 to 3, wherein a pair of the planetary gears are formed at both ends of the planetary shaft in the axial direction.   When the sun axis is rotated relative to the nut, the spiral ridge of the sun axis or the planetary axis moves linearly relative to the sun axis in the axial direction of the sun axis or 5. The planetary rotational-linear motion according to claim 1, wherein a lead angle of the circumferential ridge is different from a lead angle of the spiral groove or the circumferential groove of the planetary shaft. Conversion device. A sun shaft having a sun gear and a spiral or circumferential ridge,
A planetary gear having a planetary gear meshing with the sun gear of the sun shaft, and having a spiral groove or a circumferential groove meshing with the spiral ridge or the circumferential ridge of the sun shaft;
And having an internal gear that meshes with the planetary gear of the planetary shaft, and a nut having a spiral ridge or a circumferential ridge that meshes with the spiral groove or the circumferential groove of the planetary shaft,
The sun gear of the sun shaft, the planetary gear of the planetary shaft, and the internal gear of the nut constitute a planetary gear mechanism,
In the planetary rotation-linear motion conversion device in which when the nut is rotated relative to the sun shaft, the planetary shaft moves linearly relative to the nut in the axial direction of the nut,
The region of the planetary shaft where the planetary gear is formed and the region of the planetary shaft where the spiral groove or the circumferential groove is formed are separated in the axial direction of the planetary shaft,
A planetary rotation-linear motion conversion device for forming the internal gear meshing with the planetary gear of the planetary shaft on the convex portion of the spiral ridge or the circumferential ridge of the nut.   When the nut is rotated relative to the sun axis, the spiral ridge of the nut or the circumferential direction so that the planetary shaft linearly moves relative to the nut in the axial direction of the nut. The planetary rotation-linear motion conversion device according to claim 6, wherein a lead angle of the ridge and a lead angle of the spiral groove or the circumferential groove of the planetary shaft are different from each other. The planetary rotation-linear motion conversion device according to any one of claims 1 to 7,
A drive source for rotating the nut of the planetary rotation-linear motion converter with respect to the sun axis;
A detent mechanism that prevents the sun axis from rotating about its axis and allows the sun axis to linearly move in its axial direction;
An actuator that linearly moves the sun axis relative to the nut in the axial direction of the sun axis when the drive source rotates the nut with respect to the sun axis.