JP2020051570A - Reduction gear - Google Patents

Abstract

To improve transmission efficiency of rotation torque while miniaturizing a device as a whole, in a reduction gear for axially transmitting rotation torque through rolling elements.SOLUTION: A reduction gear 1 includes: an input rotary portion 2; an output rotary portion 3 disposed coaxially with the input rotary portion 2; a fixing member 5; a first rolling element engagement groove 13 formed on the input rotary portion 2, and disposed along a circle having a center of curvature O1 eccentric from a center of rotation X of the input rotary portion; a second rolling element engagement groove 16 formed on the fixing member 5 and disposed along wavy curves alternately crossing a pitch circle having a center of curvature on a straight line including the center of rotation X; a plurality of balls 4 engaged with the first rolling element engagement groove 13 and the second rolling element engagement groove 16 axially opposed to each other; and a plurality of pockets 17 formed on the output rotary portion 3, and holding the plurality of balls 4 in a circumferential direction in a state of being radially movable axially between the first rolling element engagement groove 13 and the second rolling element engagement groove 16.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a speed reducer.

  For example, in Patent Document 1, as shown in FIG. 10, an input plate 110 having a ball engaging groove 111 and an output plate 120 having a ball engaging groove 121 are arranged so as to face each other in the axial direction. A reduction gear that transmits a rotational torque from the input plate 110 to the output plate 120 via the balls 130 engaged with the ball engaging grooves 111 and 121 is shown.

  More specifically, the reduction gear transmission includes an input plate 110 and an output plate 120 rotatably provided around a common rotation center X, a plurality of balls 130 interposed therebetween, and a holding member fixed to the housing 160. And a vessel 140. The first ball engaging groove 111 provided on the input plate 110 is formed in a circular shape, and the second ball engaging groove 121 provided on the output plate 120 is formed in a waveform (see FIG. 11). The input plate 110 is attached to the outer periphery of the input shaft 170 via the eccentric cam 180, whereby the center of curvature O1 of the circular first ball engaging groove 111 is eccentric from the rotation center X by the amount of eccentricity a. . When the input shaft 170 rotates, the input plate 110 revolves around the rotation center X with a whirling radius a. Accordingly, the balls 130 engaged with the first ball engaging grooves 111 are provided on the retainer 140. Reciprocate in the radial direction within the pocket 141. The output plate 120 is rotated by the component of the contact force between the ball 130 and the corrugated second ball engaging groove 121 in the rotation direction.

  For example, when the center line O1 of the input plate 110 revolves in the arrow direction from the position shown in FIG. 11 with the rotation of the input shaft 170, the ball 130 (A) located above the rotation center X has the second waveform. The ball 130 (B) located below the center of rotation X is pressed against the inner diameter side portion of the corrugated second ball engagement groove 121. At this time, the output plate 120 is rotated by the component force F (see the arrow) of the contact force applied from the ball 130 to the second ball engaging groove 121 in the rotation direction. As described above, in the above-described reduction gear transmission, among the plurality of balls 130, not only the ball 130 (A) above the rotation center X but also the ball 130 (B) below the rotation center X transmit torque. This contributes to an increase in load capacity and a reduction in vibration.

JP 2018-021602 A

  However, in the above-described speed reducer, as shown in FIG. 12, the ball 130 and the ball engaging grooves 111 and 121 come into contact with each other at an angle inclined with respect to the axial direction. The contact forces F3 'and F4' received from 130 (reactions of the contact forces F3 and F4 applied to the ball 130) have radial components F3a 'and F4a' and axial components F3b 'and F4b'. Therefore, it is necessary to use bearings 151 and 152 for supporting the input plate 110 and bearings 153 and 154 for supporting the output plate 120 that can receive loads in both radial and axial directions. As such bearings, deep groove ball bearings and angular ball bearings are generally used.However, these bearings have a smaller tolerance in the axial direction than in the radial direction, so that they can withstand loads in both the radial and axial directions. If an attempt is made to select one that can withstand, the size of the bearing increases, and as a result, the size of the entire reduction gear increases. Further, when the bearing is used in an environment where loads in both the radial and axial directions act, the torque loss inside the bearing increases, and as a result, the transmission efficiency of the entire reduction gear transmission decreases.

  In view of the above circumstances, an object of the present invention is to reduce the size of the entire device and to improve the transmission efficiency of the rotational torque in a speed reducer that transmits rotational torque in the axial direction via rolling elements.

  In order to solve the above problems, the present invention provides an input rotating unit, an output rotating unit coaxially arranged with the input rotating unit, a fixed member, and the input rotating unit, wherein the input rotating unit and the input rotating unit are formed. A first rolling element engaging groove provided along a circle having a center of curvature eccentric from the center of rotation of the output rotating portion, and a pitch circle formed on the fixed member and having a center of curvature on the center of rotation. Rolling element engaging grooves provided along alternately intersecting waveform curves, and engaging the first rolling element engaging grooves and the second rolling element engaging grooves axially opposed to each other. And a plurality of rolling elements formed in the output rotating portion and circumferentially holding the plurality of rolling elements in an axial direction between the first rolling element engaging groove and the second rolling element engaging groove. A speed reducer having a plurality of pockets is provided.

  Since the second rolling element engaging groove is formed in the fixing member as described above, the contact force generated between the rolling element and the second rolling element engaging groove can be supported by the fixing member. Thus, a bearing for supporting this contact force is not required. Further, in the above-described reduction gear transmission, the first rolling element engaging groove engages with the rolling element while eccentrically rotating with the rotation of the input rotary unit, so that the rolling element forms a waveform formed on the fixed member. Move along the second rolling element engaging groove. The rolling element is rotated in a circumferential direction by engaging with a pocket provided in the output rotating section, thereby rotating the output rotating section. At this time, since only a circumferential (rotational) contact force is generated between the rolling element and the peripheral wall of the pocket, an axial load is not applied to the output rotating portion provided with the pocket. As a result, the bearing that supports the output rotating unit only needs to support the radial load, so that the load applied to the bearing is reduced. For example, the output rotating unit (output plate 120) in the conventional reduction gear transmission shown in FIG. ) Can be reduced in size as compared with the bearings 153 and 154 that support the above, and the torque loss inside the bearing can be reduced.

  A ball or a roller can be used as a rolling element that engages with both rolling element engagement grooves and transmits torque in the axial direction. In particular, if a roller (for example, a cylindrical roller) having a cylindrical outer peripheral surface is used as a rolling element, a load in the axial direction hardly occurs between the outer peripheral surface of the roller and the side wall of each rolling element engaging groove. . Therefore, the bearings that support the input rotary unit and the output rotary unit that receive the above-described contact force from each rolling element engaging groove need only support the radial load, so that the size can be reduced while maintaining the durability. Can be. Further, since the load applied to the bearing is limited in the radial direction, torque loss inside the bearing can be reduced.

  When a roller is used as a rolling element, friction is present on at least one of the outer peripheral surface of the roller and the first rolling element engaging groove, the second rolling element engaging groove, and the contact portion with the pocket. It is preferable to provide a reduction member (for example, a needle bearing or a slide bearing). As described above, by bringing the roller and each member (the input rotation unit, the output rotation unit, or the fixed member) into contact with each other via the friction reducing member, the friction loss of the contact unit is reduced as compared with the case where these members are brought into direct contact. Since it is greatly reduced, the torque transmission efficiency is further increased.

  As described above, by using the member having the corrugated second rolling element engaging groove as the fixing member, a bearing for supporting the contact force between the second rolling element engaging groove and the rolling element becomes unnecessary. In addition, by using a member having a pocket as an output rotating portion, the bearing that supports the output rotating portion can be reduced in size to reduce the overall size of the reduction gear transmission, and torque loss inside the bearing can be reduced to increase torque transmission efficiency. Can be.

It is a sectional view of a reduction gear concerning one embodiment of the present invention. FIG. 2 is a front view of the input member as viewed from an output side (the right side in FIG. 1). It is the front view which looked at the output member from the input side (left side of FIG. 2). It is a front view of a retainer. FIG. 5 is an enlarged view of a portion V in FIG. 4. FIG. 3 is an exploded perspective view schematically illustrating an input member, an output member, a fixing member, and a roller. It is a front view which shows the contact force applied to a ball. It is a sectional view of a reduction gear concerning another embodiment. It is a sectional view of a reduction gear concerning another embodiment. It is sectional drawing of the conventional speed reducer. It is a front view of the output plate and ball of the reduction gear of FIG. It is an enlarged view of the reduction gear of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a reduction gear transmission 1 according to one embodiment of the present invention includes an input rotary unit 2, an output rotary unit 3, a ball 4 as a rolling element, a fixed member 5, and a housing for accommodating these components. 6 is mainly provided. In the illustrated example, the housing 6 includes a first housing member 6a provided on the input side (the left side in FIG. 1) and a second housing member 6b provided on the output side (the right side in FIG. 1). The input rotation unit 2 and the output rotation unit 3 are coaxially arranged and have a common rotation center X. The fixing member 5 is fixed to the housing 6.

  The input rotating unit 2 has an input shaft 7, an eccentric cam 8, a rolling bearing 9, and an input member 10. The input shaft 7 has a shaft portion 7a and a flange portion 7b provided near an input side end (the left end in FIG. 1) of the shaft portion 7a. The input shaft 7 is rotatable around the rotation center X with respect to the housing 6. In the present embodiment, the rolling bearing 11 mounted between the outer peripheral surface of the flange portion 7b and the inner peripheral surface 21 of the first housing member 6a of the housing 6, and the outer peripheral surface of the shaft portion 7a The input shaft 7 is rotatably supported by the housing 6 with the rolling bearing 12 mounted between the input shaft 7 and the peripheral surface. The eccentric cam 8 is fitted and fixed to the outer peripheral surface of the shaft portion 7a of the input shaft 7. The center line O1 of the cylindrical outer peripheral surface 8a of the eccentric cam 8 is eccentric in the radial direction by an eccentric amount a with respect to the rotation center X.

  The input member 10 is formed in an annular shape, and in the illustrated example, has a cylindrical portion 10a and a disk portion 10b extending from the output end of the cylindrical portion 10a toward the inner diameter. The center line O1 of the cylindrical outer peripheral surface 8a of the eccentric cam 8 is also the center line of the cylindrical portion 10a and the disk portion 10b of the input member 10. A rolling bearing 9 is mounted between the cylindrical outer peripheral surface 8 a of the eccentric cam 8 and the inner peripheral surface of the cylindrical portion 10 a of the input member 10. Thus, the input member 10 is rotatable relative to the eccentric cam 8.

  In the flange portion 7b and the eccentric cam 8 of the input shaft 7, axial through holes 27 and 28 for reducing the weight are formed at a plurality of positions in the circumferential direction. In addition, the input rotating unit 2 is provided with a balancer 26 for improving the weight balance of the bearing 9 and the input member 10 that swing around via the eccentric cam 8 during rotation. The center of gravity of the balancer 26 is provided eccentrically with respect to the rotation center X in a direction 180 ° out of phase with the eccentric direction of the center line O1 of the input member 10. In the illustrated example, the balancer 26 is fixed to the outer peripheral surface of the eccentric cam 8 and is disposed between the bearing 9 and the bearing 11 in the axial direction.

  The fixing member 5 has an annular shape and is fixed to the second housing member 6b of the housing 6 by an appropriate means such as a bolt 23 or the like. The input member 10 and the fixed member 5 are arranged side by side at predetermined intervals in the axial direction. A first rolling element engaging groove 13 and a second rolling element engaging groove 16 are formed on the side surfaces of the input member 10 and the fixing member 5 that face each other in the axial direction.

  As shown in FIG. 2, the track center line L1 of the first rolling element engaging groove 13 formed on the disk portion 10b of the input member 10 is formed in a circular shape with a radius r. The center of curvature of the track center line L1 of the first rolling element engaging groove 13 coincides with the cylindrical outer peripheral surface 8a of the eccentric cam 8 and the center line O1 of the input member 10. That is, the center of curvature of the orbit center line L1 (that is, the center line O1) is eccentric with respect to the rotation center X of the input rotation unit 2 by the amount of eccentricity a. By engaging with the first rolling element engaging groove 13, each ball 4 is held at a predetermined radial position while being movable in a circumferential direction (a direction along the track center line L1). The orbit center line L1 of the first rolling element engaging groove 13 means a locus of the center of the ball 4 when the ball 4 is moved along the first rolling element engaging groove 13.

  As shown in FIG. 3, the track center line L2 of the second rolling element engaging groove 16 formed in the fixing member 5 is alternately arranged at a constant pitch with respect to the reference pitch circle C centered on the rotation center X. It is formed by intersecting wavy curves. That is, the second rolling element engaging groove 16 is formed by a wavy curve in which the distance R from the rotation center X increases and decreases with respect to the reference pitch circle radius PCR. In the present embodiment, in the wavy curve of the trajectory center line L2, there are ten peaks whose distance R to the rotation center X is larger than the reference pitch circle radius PCR, and the distance R to the rotation center X is smaller than the reference pitch circle radius PCR. Ten valleys are provided. The orbital center line of the second rolling element engaging groove 16 means the locus of the center of the ball 4 when the ball 4 is moved along the second rolling element engaging groove 16.

  As shown in FIG. 1, the output rotation unit 3 includes a disk part 3a functioning as an output member and a shaft part 3b functioning as an output shaft. In the illustrated example, the disk portion 3a and the shaft portion 3b are formed separately. Further, the shaft portion 3b has a cylindrical portion 3b1 and a lid portion 3b2 for closing an opening of the cylindrical portion 3b1 as separate bodies. The lid 3b2 is provided with a connecting portion to which another member to transmit the reduced rotation is connected. The output rotation unit 3 is rotatable around the rotation center X with respect to the housing 6. In the present embodiment, the rolling bearing 14 mounted between the outer peripheral surface of the cylindrical portion 3b1 of the shaft portion 3b and the inner peripheral surface of the fixing member 5, the inner peripheral surface of the cylindrical portion 3b1 of the shaft portion 3b and the input shaft 7 The output rotary unit 3 is rotatably supported by the housing 6 by a rolling bearing 12 mounted between the shaft unit 7a and the outer peripheral surface of the shaft unit 7a. In the illustrated example, two rolling bearings 12 are arranged in the axial direction.

  The disk part 3 a of the output rotating part 3 has a plurality of pockets 17 for holding the ball 4. In the present embodiment, as shown in FIG. 4, the pocket 17 is formed by an elongated hole radially extending in the radial direction about the rotation center X of the rotating members 2 and 3. In the illustrated example, each pocket 17 is open on the outer peripheral surface of the disk portion 3a. The pockets 17 are formed at equal intervals in the circumferential direction, and one ball 4 is arranged in each pocket 17. The number of pockets 17 (that is, the number of balls 4) is 11 which is one more than the number of peaks or valleys (10) of the wavy curve of the track center line L2. As shown in FIG. 5, the ball 4 can move within a range of a predetermined amount m in the radial direction around the reference pitch circle C in each pocket 17. In the present embodiment, a pair of parallel flat surfaces 17a facing each other in the circumferential direction are provided on the peripheral wall of each pocket 17, and the circumferential distance between the flat surfaces 17a is substantially equal to the outer diameter of the ball 4 (slightly larger). Diameter). Thereby, each ball 4 is held at a predetermined circumferential position by each pocket 17 in a state where it can move in the radial direction.

  As shown in FIG. 6, the input rotation unit 2 and the output rotation unit 3 have a common rotation center X, and the axis of the fixed member 5 is arranged on the rotation center X. The center of curvature O1 of the track center line L1 of the first rolling element engaging groove 13 formed in the input member 10 is eccentric with respect to the rotation center X by the amount of eccentricity a. The ball 4 arranged in each pocket 17 of the output rotation unit 3 projects from the pocket 17 to the input side (left side in the figure) and the output side (right side in the figure). The first rolling element engaging groove 13 of the fixed member 5 is engaged with the first rolling element engaging groove 13. In FIG. 6, each member is schematically illustrated. For example, the pocket 17 is represented by an elongated hole that is not opened on the outer peripheral surface of the disk portion 3 a of the output rotation unit 3.

In the reduction gear transmission 1 of the present embodiment, the number of peaks on the track center line L2 of the second rolling element engaging groove 16 is 10 (the number of valleys is also 10), and the number of balls 4 is 11 Therefore, the reduction ratio i obtained by the following equation is 1/11.
Reduction ratio i = (number of balls−number of ridges) / number of balls The number of ridges is the number of balls ± 1. If the reduction ratio i is a negative value, the rotation of the input rotary unit 2 This means that the rotation direction of the output rotation unit 3 is opposite to the direction.

The shape of the trajectory center line L2 of the second rolling element engaging groove 16 is set such that the reduced rotational motion is transmitted from the input rotary unit 2 to the output rotary unit 3 by synchronous rotation. Specifically, assuming that the reduction ratio of the reduction gear 1 is i, the output rotary unit 3 is engaged with the first rolling element engaging groove 13 with the rotation angle iθ at the rotation angle θ of the input shaft 7. The shape of the second rolling element engaging groove 16 is set such that the ball 4 is engaged with the second rolling element engaging groove 16 to transmit torque. More specifically, the second rotation distance X between the rotation center X of the input rotation unit 2 and the output rotation unit 3 and the track center line L2 of the second rolling element engagement groove 16 satisfies the following expression (1). The shape of the rolling element engaging groove 16 is set.
R = a · cos (ψ / i) + {r ² − (a · sin (ψ / i)) ² } (1)
However,
R: distance between rotation center X and track center line L2 of second rolling element engaging groove 16 a: eccentric amount i of center O1 of track center line L1 of first rolling element engaging groove 13 with respect to rotation center X : Rotation ratio ψ: Rotation angle r of output rotating part 3: Radius of track center line L1 of first rolling element engaging groove 13

  At least one of the input member 10, the output member (the disk portion 3a of the output rotating portion 3), and the fixed member 5 has a side wall of the first rolling element engaging groove 13 that contacts the ball 4, and a second rolling element engaging groove. It is preferable that the side wall 16 and the peripheral wall of the pocket 17 have the same surface hardness as the surface of the ball 4 in order to reduce abrasion due to the difference in surface hardness with the ball 4. For example, it is preferable that the surface hardness of the side wall of the first rolling element engaging groove 13, the side wall of the second rolling element engaging groove 16, and the peripheral wall of the pocket 17 be in the range of HRC50-60. Specifically, the input member 10, the output member, and the fixing member 5 are formed using carbon steel for mechanical structure such as S45C or S50C, or alloy steel for mechanical structure such as SCM415 or SCM420, and Alternatively, the above surface hardness can be obtained by performing a carburizing heat treatment. Alternatively, the above surface hardness can also be obtained by forming each of the above members using bearing steel such as SUJ2 and performing a whole heat treatment or a high frequency heat treatment thereon.

  Next, the operation of the reduction gear transmission 1 of the present embodiment will be summarized and described. When the input shaft 7 of the input rotating unit 2 shown in FIG. 1 is rotated, the input member 10 revolves around a rotation center X with a whirling radius a. At this time, since the input member 10 is rotatable with respect to the eccentric cam 8 provided on the input shaft 7, the input member 10 hardly rotates. Thereby, the relative amount of friction between the first rolling element engaging groove 13 and the ball 4 is reduced, and the transmission efficiency of the rotational torque is increased.

  When the input member 10 makes a revolving motion, each ball 4 engaging with the first circular rolling element engaging groove 13 moves along the second rolling element engaging groove 16 formed on the fixed member 5. I do. Specifically, when the center line O1 of the input member 10 revolves from the position shown in FIG. 4 in the direction of the arrow, the first rolling element engaging groove 13 formed in the input member 10 engages the ball 4 as shown in FIG. When the ball 4 is engaged, a substantially upward contact force F1 acts on the ball 4. When the ball 4 engages with the second rolling element engaging groove 16, a contact force F 2 ′ with the ball 4 acts on the second rolling element engaging groove 16, and at the same time, the ball 4 The contact force F2 due to the contact with the rolling element engaging groove 16 acts. Due to the circumferential component F2a of the contact force F2, the ball 4 moves in the circumferential direction along the second rolling element engaging groove 16. The ball 4 circumferentially engages with the pocket 17 of the output rotating unit 3, and the contact force F 3 ′ generated thereby acts as a force for rotating the output rotating unit 3 in the same direction as the input shaft 7 (FIG. 4). reference).

  A force for rotating the output rotation unit 3 (that is, a contact force F3 ′ acting on the pocket 17 of the output rotation unit 3 from the ball 4) ≒ a circumferential component of a contact force F2 that the ball 4 receives from the second rolling element engaging groove 16 F2a) changes depending on the state of contact between the ball 4 and the corrugated second rolling element engaging groove 16, and therefore, the size differs depending on the position of each ball 4 (see FIG. 4). Since the ball 4 is arranged around the rotation center X of the input rotation unit 2 and the output rotation unit 3, the force for rotating the output rotation unit 3 is distributed around the rotation center X. Specifically, in the corrugated second rolling element engaging groove 16, it comes into contact with the vicinity of the center between the crest of the crest and the crest of the crest (a part having a large inclination angle with respect to the pitch circle around the rotation center X). In the figure, the upper and lower balls 4 at the upper and lower ends have a large force for rotating the output rotating unit 3 and have a peak near a peak or a valley of the corrugated second rolling element engaging groove 16 (with the rotation center X as the center). The ball 4 at each of the left and right ends in the figure in contact with a portion having a small inclination angle with respect to the pitch circle described above has a small force for rotating the output rotation unit 3.

  In the reduction gear transmission 1 described above, the contact force F2 ′ between the ball 4 and the second rolling element engaging groove 16 is supported by the fixing member 5 fixed to the housing 6, and thus supports the contact force F2 ′. Eliminates the need for large bearings. Further, since the ball 4 reciprocates in the radial direction and engages with the pocket 17 in the rotational direction, only the contact force F3 'in the rotational direction is applied from the ball 4 to the output rotating unit 3. Since the direction of the contact force F3 'is limited to the rotation direction in this way, the bearings 12 and 14 that support the output rotating unit 3 can be downsized, and thus the reduction gear 1 can be downsized, and the inside of the bearing can be reduced. The torque loss is reduced, and the torque transmission efficiency of the reduction gear 1 is increased.

  As described above, at the time of torque transmission, a circumferential contact force F <b> 3 ′ due to contact with the ball 4 is applied to the pillar portion provided between the pockets 17 in the disk portion 3 a of the output rotating portion 3. Therefore, there is a concern that the column portion provided between the pockets 17 of the disk portion 3a may be damaged by the contact force F3 'received from the ball 4. In particular, when the number of the pockets 17 (that is, the number of the balls 4) is increased to increase the reduction ratio, the circumferential width of the pillar between the pockets 17 becomes narrower, and the contact force F3 ′ with the ball 4 causes the pillar to become smaller. There is a growing concern about damage.

  In this regard, in the present embodiment, as shown in FIG. 4, not only the ball 4 above the rotation center X but also the ball 4 below the rotation center X has a contact force F3 ′ with the pocket 17. And contribute to torque transmission. For this reason, the contact force F3 'applied to the disk portion 3a from each ball 4 is dispersed, as compared with a case where torque is transmitted only by the balls 4 above the rotation center X, for example, so that each column portion of the disk portion 3a The load applied to is reduced. Further, in the present embodiment, as described above, the surface hardness of the peripheral wall of the pocket 17 is increased to HRC 50 or more by selecting the material of the disk portion 3a or performing heat treatment. As described above, the durability of the pillar portion between the pockets 17 of the disk portion 3a of the output rotating portion 3 can be improved, or the load capacity can be increased while maintaining the durability of the pillar portion.

  Thus, the rotation input to the input shaft 7 of the input rotation unit 2 is transmitted to the output rotation unit 3 via the ball 4. At this time, the second R is set so that the distance R between the rotation center X of the input rotary unit 2 and the output rotary unit 3 and the track center line L2 of the second rolling element engaging groove 16 satisfies the above equation (1). Since the orbital center line L2 of the rolling element engaging groove 16 is designed, the output rotating unit 3 always rotates synchronously with the input shaft 7 at a reduced rotation speed.

  Embodiments of the present invention are not limited to the above. Hereinafter, other embodiments of the present invention will be described, but the description of the same points as the above embodiments will be omitted.

  In the embodiment shown in FIG. 8, a roller 25 having a cylindrical outer peripheral surface is used as a rolling element that engages with both rolling element engaging grooves 13 and 16. In the illustrated example, cylindrical rollers are used as the rollers 25. When the input shaft 7 rotates, the rotation is transmitted to the output rotation unit 3 via the roller 25 while the outer peripheral surface of the roller 25 is in contact with the outer diameter side or the inner diameter side wall of the both rolling element engagement grooves 13 and 16. You. Both end faces in the axial direction of the roller 25 and the bottom faces of the rolling element engaging grooves 13 and 16 may be brought into contact with each other, or an axial gap may be provided therebetween.

  In this embodiment, the direction of the contact force generated between the outer peripheral surface of the roller 25 and each of the rolling element engaging grooves 13 and 16 is a direction orthogonal to the axial direction. Thus, the direction of the load applied to the bearing 9 supporting the input member 10 and the bearings 11 and 12 (see FIG. 1) supporting the input shaft 7 is limited, so that the load applied in both the radial and axial directions is reduced. As a result, the bearing can be downsized while maintaining durability, and the overall reduction gear 1 can be further downsized. In addition, since the load applied to the bearings 9, 11, 12 is limited in the radial direction, torque loss inside these bearings is reduced, so that the transmission efficiency of the rotational torque is further increased.

  Note that the roller 25 is not limited to a cylindrical roller, and for example, a barrel roller having a slightly larger diameter in the axial center of the outer peripheral surface or a tapered roller having a tapered outer peripheral surface may be used. In these cases, a slight axial load is applied to the input rotary unit 2 via the roller 25, but since the size is smaller than when a ball is used as a rolling element, the size of the bearing that supports the input rotary unit 2 is reduced. The effect can be obtained.

  When the roller 25 is used as the rolling element as described above, as shown in FIG. 9, the outer peripheral surface of the roller 25, the first rolling element engaging groove 13, the second rolling element engaging groove 16, and the pocket 17 are formed. A friction reducing member 30 may be provided at a contact portion with the contact member. As the friction reducing member 30, for example, a needle bearing or a slide bearing (for example, a sintered oil-impregnated bearing) can be used. As described above, the roller 25 comes into contact with the first rolling element engaging groove 13, the second rolling element engaging groove 16, and the pocket 17 via the friction reducing member 30, so that the friction at each contact portion is increased. Since the loss is greatly reduced, the torque transmission efficiency is improved.

  As described above, the friction reducing member 30 (needle) is provided at the contact portion between the roller 25 and all three elements of the first rolling element engaging groove 13, the second rolling element engaging groove 16, and the pocket 17. It is most effective to provide a friction reducing member 30 at a contact portion between the roller 25 and at least one of the above three elements. The effect of improving the transmission efficiency is obtained. In particular, if the friction reducing member 30 is provided at a contact portion between the roller 25 and at least two of the above three elements, the contact with the remaining one element becomes a rolling contact, thereby improving the torque transmission efficiency. The effect increases.

  Further, in the above-described embodiment, the case where the first rolling element engaging groove 13 is continuous over the entire circumference is shown. However, the present invention is not limited to this. It may be composed of a plurality of (for example, the same number as the rolling elements) arc-shaped grooves formed along a circle centered on the line O1.

  Further, in the above embodiment, the input member 10 is rotatable with respect to the eccentric cam 8 provided on the input shaft 7, but the input member 10 and the input shaft 7 may be configured to rotate integrally. Further, in the above-described embodiment, the configuration in which the separate eccentric cam 8 is fitted to the input shaft 7 has been described as an example. However, the configuration is not limited thereto, and the input shaft 7 and the eccentric cam 8 may be integrated. Further, in the above-described embodiment, the disc portion 3a of the output rotating portion 3, the cylindrical portion 3b1 and the lid portion 3b2 of the shaft portion 3b are formed separately for manufacturing convenience. The disk portion 3a and the cylindrical portion 3b1 of the shaft portion 3b may be integrated.

  In the above embodiment, the case where the present invention is applied to the speed reducer 1 in which the magnitude of the speed reduction ratio i is 1/11 has been exemplified. However, the present invention is not limited to this. The present invention can be suitably applied to a reduction gear having a reduction ratio of an arbitrary size of the above. In this case, the number of peaks / valleys of the wavy curve of the orbital center line of the rolling element engaging groove, and the number of pockets and rollers of the fixing member may be appropriately set according to the reduction ratio i.

DESCRIPTION OF SYMBOLS 1 Reduction gear 2 Input rotation part 3 Output rotation part 3a Disk part (output member)
4 ball (rolling element)
5 Fixing member 6 Housing 7 Input shaft 8 Eccentric cam 10 Input member 13 First rolling element engaging groove 16 Second rolling element engaging groove 17 Pocket 25 Roller (rolling element)
30 Friction reducing members F1, F1 'Contact force F2 between ball and first rolling element engaging groove F2, Contact force F2 between ball and second rolling element engaging groove F3, F3' Contact between ball and pocket Force L1 Track center line L2 of first rolling element engaging groove Track center line O1 of second rolling element engaging groove Center of curvature of track center line of first rolling element engaging groove (center line of input member)
X Rotation center of input rotation part and output rotation part

Claims (5)

  An input rotation unit, an output rotation unit disposed coaxially with the input rotation unit, a fixed member, and a center of curvature formed on the input rotation unit and eccentric from the rotation centers of the input rotation unit and the output rotation unit. A first rolling element engaging groove provided along a circle having the first member and a wavy curve alternately intersecting a pitch circle formed on the fixing member and having a center of curvature on the rotation center. A second rolling element engaging groove, a plurality of rolling elements engaging with the first rolling element engaging groove and the second rolling element engaging groove, which face each other in the axial direction; A reduction gear having a plurality of pockets formed and axially holding the plurality of rolling elements in a circumferential direction between the first rolling element engaging groove and the second rolling element engaging groove.   The reduction gear according to claim 1, wherein the rolling element is a ball.   The reduction gear according to claim 1, wherein the rolling element is a roller.   4. A friction reducing member is provided on at least one of an outer peripheral surface of the roller, a contact portion between the first rolling element engaging groove, the second rolling element engaging groove, and the pocket. 3. The reduction gear transmission according to claim 1. The reduction gear according to claim 4, wherein the friction reducing member is a needle bearing or a slide bearing.

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