JP2020051572A - Power transmission device - Google Patents

Abstract

To miniaturize a power transmission device for axially transmitting rotation torque through rolling elements.SOLUTION: A reduction gear 1 includes: an input member 10 (first member) having first rolling element engagement grooves 13 on side surfaces at axial both sides; a pair of fixing members 5 (second members) disposed at axial both sides of the input member 10 and having second rolling element engagement grooves 16; a plurality of balls 4 respectively disposed between the input member 10 and the pair of fixing members 5, and engaged with the first rolling element engagement grooves 13 and the second rolling element engagement grooves 16; and a pair of output members 31, 32 (third members) respectively disposed axially between the input member 10 and the pair of fixing members 5, and having a plurality of pockets 17 for holding the plurality of balls 4 in a circumferential direction. The first rolling element engagement grooves 13 are formed along a circle having a center of curvature eccentric from a center of rotation X. The second rolling element engagement grooves 16 are formed along wavy curves alternately crossing a pitch circle having a center of curvature on the center of rotation X.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power transmission device that transmits a rotation input to an input rotation unit to an output rotation unit disposed coaxially at a predetermined gear ratio.

  For example, in Patent Document 1, as shown in FIG. 9, an input plate 110 having a ball engaging groove 111 and an output plate 120 having a ball engaging groove 121 are disposed 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. 10). 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 direction of the arrow from the position shown in FIG. 10 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 speed reducer, as shown in FIG. 11, 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 (the reaction forces 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.

  In view of the circumstances described above, an object of the present invention is to reduce the size of the entire power transmission device that transmits rotational torque in the axial direction via rolling elements.

  In order to solve the above problem, the present invention is a power transmission device that transmits rotation input to an input rotation unit to an output rotation unit disposed coaxially at a predetermined speed ratio, and includes a side surface on both axial sides. A first member having a first rolling element engaging groove, a pair of second members provided on both axial sides of the first member and each having a second rolling element engaging groove, and the first member. And a plurality of balls provided in the axial direction between the first rolling element engaging groove and the second rolling element engaging groove, respectively provided in the axial direction between the first rolling element engaging groove and the pair of second members. A pair of third members each provided between the first member and the pair of second members in the axial direction and having a plurality of pockets for holding the plurality of balls in a circumferential direction; One of the moving body engaging groove and the second rolling body engaging groove is connected to the input rotating portion and the output rotating portion. The other of the first rolling element engaging groove and the second rolling element engaging groove is formed along a circle having a center of curvature eccentric from the center of rotation of the portion. The first member, the pair of second members, and the pair of third members are formed on the input rotating unit, and are formed along a wavy curve that alternately intersects a pitch circle having And a power transmission device in which any one of the first member, the pair of second members, and the pair of third members is provided in the output rotation unit.

  As described above, in the power transmission device of the present invention, a pair of second rolling element engaging grooves having the second rolling element engaging grooves centered on the first member having the first rolling element engaging grooves formed on both side surfaces in the axial direction. Two members, a pair of third members having pockets, and a plurality of balls are arranged symmetrically in the axial direction. As a result, contact forces with the ball are applied to the first member from both sides in the axial direction, and the axial components of these contact forces are cancelled. Accordingly, no load is applied to the first member in the axial direction, so that a load applied to a support portion such as a bearing that supports the first member is reduced, and the size of the support portion can be reduced.

  When the power transmission device has a bearing that rotatably supports the first member, the bearing that rotatably supports the first member only needs to support a radial load, and thus maintains durability. The size can be reduced. Further, by limiting the direction of the load applied to the bearing, torque loss inside the bearing can be reduced.

  In the above power transmission device, for example, the first member can be provided on the input rotation unit, the pair of third members can be provided on the output rotation unit, and the pair of second members can be fixed members. Since the contact force generated between the ball and the second rolling element engagement groove can be supported by the fixing member by using the second member as the fixing member, the contact force is supported. Large bearings are not required. In addition, since the third member is provided in the output rotation unit, only the circumferential (rotational) contact force is generated between the ball and the pocket of the output rotation unit (third member), and thus the third member is supported. The load applied to the bearing is reduced, the size of the bearing can be reduced, and the torque loss inside the bearing can be reduced. In this case, if the pair of third members provided on the output rotating unit can be integrally rotated, the power transmitted from the first member provided on the input rotating unit to the balls on both sides in the axial direction is transmitted again. Can be combined and output.

  In the power transmission device described above, since the second member and the third member are provided in pairs, respectively, there is a concern about an increase in cost due to an increase in the number of components. Therefore, if the pair of second members and the pair of third members are formed to have the same shape, it is possible to reduce the manufacturing cost of each member by sharing the components, thereby suppressing an increase in cost due to an increase in the number of components.

  As described above, according to the present invention, since no axial load is applied to the first member, it is possible to reduce the size of a support portion such as a bearing that supports the first member, thereby reducing the size of the entire power transmission device. Can be achieved.

It is a sectional view of a reduction gear concerning one embodiment of the present invention. It is a front view of an input member (1st member). It is a front view of a fixing member (2nd member). It is a front view of an output member (third member). FIG. 5 is an enlarged view of a portion V in FIG. 4. FIG. 3 is an exploded perspective view schematically showing an input member, an output member, a fixing member, and a ball. It is a front view which shows the contact force applied to a ball. FIG. 2 is an enlarged view of the speed reducer of FIG. 1. It is sectional drawing of the conventional speed reducer. FIG. 10 is a front view of an output plate and balls of the reduction gear transmission of FIG. 9. FIG. 10 is an enlarged view of the reduction gear transmission of FIG. 9.

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

  As shown in FIG. 1, a speed reducer 1 as a power transmission device 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 6 for accommodating them. 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 housing members 6a and 6b are fixed by appropriate means such as bolts 23 or the like. 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 rotary unit 2 includes an input shaft 7, an eccentric cam 8, a rolling bearing 9, and an input member 10. The input shaft 7 is rotatable around the rotation center X with respect to the housing 6. In the present embodiment, the input shaft 7 is rotatably supported on the housing 6 by a plurality of rolling bearings 11 mounted between the output rotating unit 3 and the inner peripheral surface. In the illustrated example, two bearings 11 are provided on each side of the eccentric cam portion 8 in the axial direction. A seal member 21 is provided between the outer peripheral surface of the input shaft 7 and the inner peripheral surface of the first housing member 6a to prevent leakage of grease or oil filled in the housing 6. The eccentric cam portion 8 is provided on the outer periphery of the input shaft 7, and is provided integrally with the input shaft 7 in the illustrated example. The center line O1 of the cylindrical outer peripheral surface 8a of the eccentric cam portion 8 is eccentric in the radial direction by an eccentric amount a with respect to the rotation center X. The input member 10 has a substantially disk shape, and the center line of the input member 10 coincides with the center line O1 of the cylindrical outer peripheral surface 8a of the eccentric cam portion 8. A rolling bearing 9 is mounted between the cylindrical outer peripheral surface 8 a of the eccentric cam portion 8 and the inner peripheral surface of the input member 10. As a result, the input member 10 is relatively rotatable with respect to the eccentric cam portion 8.

  The fixing members 5 are provided on both axial sides of the input member 10. The fixing member 5 has an annular shape, and in the illustrated example, both fixing members 5 are formed of the same material in the same shape. Each fixing member 5 is fixed to the housing 6 by an appropriate means. In the illustrated example, a regulating member 24 that regulates the circumferential movement of the fixing member 5 with respect to the housing 6 is provided. The regulating member 24 is mounted on key grooves provided on the inner peripheral surface of each of the housing members 6 a and 6 b and the outer peripheral surface of each of the fixing members 5. In the circumferential direction.

  The input member 10 and each fixing member 5 are arranged side by side in the axial direction at a predetermined interval. First rolling element engaging grooves 13 are respectively formed on the side surfaces on both axial sides of the input member 10. Each of the fixing members 5 is formed with a second rolling element engaging groove 16 that faces the first rolling element engaging groove 13 in the axial direction. That is, in the present embodiment, the first member having the first rolling element engaging groove 13 is provided on the input rotary unit 2 as the input member 10, and the second member having the second rolling element engaging groove 16 is fixed. Member 5.

  As shown in FIG. 2, the track center line L1 of the first rolling element engaging groove 13 formed in 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 portion 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 has a constant pitch with respect to a reference pitch circle C having a center of curvature on the rotation center X. It is formed by alternating 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 second rolling element engaging grooves 16 formed on both fixing members 5 have the same shape and are arranged to have the same phase. 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 rotating unit 3 includes a first output member 31 provided on one side (left side in the figure) of the input member 10 in the axial direction, and another side (right side in the figure) of the input member 10 in the axial direction. And a connecting member 33 that connects the first output member 31 and the second output member 32. The first output member 31 has a cylindrical shaft portion 31a and a disk portion 31b extending from the shaft portion 31a to the outer diameter side. The second output member 32 has a shaft portion 32a functioning as an output shaft, and a disk portion 32b extending from the shaft portion 32a to the outer diameter side. The shaft portion 32a of the second output member 32 has a cylindrical portion 32a1 and a lid portion 32a2 for closing an opening of the cylindrical portion 32a1. The lid 32a2 is provided with a connecting portion for connecting another member to which the reduced rotation is to be transmitted. In the illustrated example, the shaft portion 31a and the disk portion 31b of the first output member 31 are integrally formed, and the shaft portion 32a and the disk portion 32b of the second output member 32 are integrally formed.

  The output rotation unit 3 is rotatable around the rotation center X with respect to the housing 6. In the present embodiment, the outer diameter end of the disk portion 31b of the first output member 31 and the outer diameter end of the disk portion 32b of the second output member 32 are connected by the connection member 33, whereby both output members 31, 32 are connected. It can be rotated integrally. Specifically, the rolling bearing 14 mounted between the outer peripheral surface of the shaft portion 31a of the first output member 31 and the inner peripheral surface of the fixing member 5 on one axial side, and the shaft portion of the second output member 32 The output rotating unit 3 is integrally and rotatably supported on the housing 6 by the rolling bearing 15 mounted between the outer peripheral surface of the fixing member 5 and the inner peripheral surface of the fixing member 5 on the other side in the axial direction. A seal member 22 for preventing leakage of grease or oil filled in the housing 6 is provided between the outer peripheral surface of the shaft portion 32a of the second output member 32 and the inner peripheral surface of the second housing member 6b. Provided.

  A plurality of pockets 17 for holding the balls 4 are formed in the disk portion 31b of the first output member 31 and the disk portion 32b of the second output member 32, respectively. That is, in the present embodiment, a pair of third members having the pockets 17 are provided in the output rotation unit 3 as the output members 31 and 32. As shown in FIG. 4, the pocket 17 is formed by an elongated hole radially extending radially around the rotation center X of the rotating members 10 and 20. In the illustrated example, each pocket 17 is open on the outer peripheral surface of the disk portions 31b and 32b. The pockets 17 are formed at equal circumferential intervals on the same circumference. In the present embodiment, the pockets 17 provided on both the output members 31 and 32 are provided at the same position in a plane orthogonal to the axial direction, and one ball 4 is arranged in each pocket 17. The number of the pockets 17 formed in each of the output members 31 and 32 (that is, the number of the balls 4 arranged between each of the output members 31 and 32 and the input member 10) is determined by the peak of the wavy curve of the track center line L2. The number is 11 more than the number (10) of the parts or valleys.

  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 member 10 and the two output members 31 and 32 have a common rotation center X, and the axes of the fixed members 5 are arranged on the rotation center X. The center axis O1 of the input member 10 (that is, the center of curvature of the track center line L1 of the first rolling element engaging groove 13) is eccentric with respect to the rotation center X by the amount of eccentricity a. The balls 4 arranged in the pockets 17 of the output members 31 and 32 project from the pockets 17 on both sides in the axial direction, and the projecting portions correspond to the first rolling element engaging groove 13 of the input member 10 and the fixing member. 5 is engaged with the second rolling element engaging groove 16 (see FIG. 1). 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 surfaces of the output members 31 and 32.

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

  Of the input member 10, the output members 31, 32, and the fixing members 5, at least the side wall of the first rolling element engaging groove 13 which contacts the ball 4, the side wall of the second rolling element engaging groove 16, and It is preferable that the peripheral wall of the pocket 17 has the same surface hardness as the surface of the ball 4 in order to reduce wear due to a 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 members 31, 32, and the fixing member 5 are formed using mechanical structure carbon steel such as S45C or S50C, or mechanical structure alloy steel such as SCM415 or SCM420. The above surface hardness can be obtained by performing the whole heat treatment or the 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 that time, since the input member 10 is rotatable with respect to the eccentric cam portion 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 engaged, a substantially upward contact force F1 acts on each 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).

  The force for rotating the output rotating unit 3 (that is, the contact force F3 ′ acting on the pocket 17 of each of the output members 31 and 32 from the ball 4) ≒ the circumference of the contact force F2 that the ball 4 receives from the second rolling element engaging groove 16 Since the direction component F2a) changes depending on the contact state between the ball 4 and the corrugated second rolling element engaging groove 16, 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 pair of fixing members 5, the pair of output members 31, 32, and the plurality of balls 4 are arranged axially symmetrically with the input member 10 as a center. As a result, as shown in FIG. 8, the input member 10 receives the contact force F1 'from the balls 4 provided on both sides in the axial direction, and the axial component F1a' of the contact force F1 'is canceled. As a result, the axial load is not transmitted to the bearing 9 supporting the input member 10 and the bearing 11 (see FIG. 1) supporting the input shaft 7, so that the bearings 9 and 11 can be downsized, and the reduction gear 1 can be downsized. Can be In addition, since the direction of the load applied to the bearings 9 and 11 is limited, torque loss inside the bearing is reduced, and the torque transmission efficiency of the reduction gear transmission 1 is increased.

  In the above-described reduction gear transmission 1, 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, so that the contact force F2' is reduced. Large supporting bearings are not required. 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 14 and 15 that support the output rotating unit 3 can be downsized, so that the reduction gear 1 can be downsized. The loss is reduced, and the torque transmission efficiency of the reduction gear transmission 1 is increased.

  As described above, at the time of torque transmission, the circumferential contact force F3 ′ due to the contact with the ball 4 is applied to the column portion provided between the pockets 17 of the disk portions 31b and 32b of the output members 31 and 32. . Therefore, there is a concern that the column portion provided between the pockets 17 of the disk portions 31b and 32b 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 portions 31b and 32b 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 the disk portions 31b and 32b The load applied to each column is reduced. In particular, in the present embodiment, by providing the output members 31 and 32 on both sides of the input member 10, the number of contact points between the ball 4 and the output members 31 and 32 increases, so that the load at each contact point can be further reduced. Further, in the present embodiment, as described above, the surface hardness of the peripheral wall of the pocket 17 is increased to HRC50 or more by selecting the material of the disk portions 31b and 32b and performing heat treatment. As described above, the durability of the column between the pockets 17 of the output members 31 and 32 can be increased, or the load capacity can be increased while maintaining the durability of the column.

  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 above-described embodiment, the case where the circular first rolling element engaging groove 13 is continuous over the entire circumference is shown. However, the present invention is not limited to this. (For example, the same number as the rolling elements) formed along the orbit center line L1.

  Further, in the above embodiment, the input member 10 is rotatable with respect to the input shaft 7, but the input member 10 and the input shaft 7 may be integrally rotated. Further, in the above-described embodiment, the configuration in which the input shaft 7 and the eccentric cam portion 8 are integrally formed is exemplified. However, the present invention is not limited to this, and the input shaft 7 and the eccentric cam portion 8 are formed separately, The eccentric cam 8 may be fixed to the outer peripheral surface of the cam 7.

  Further, in the above embodiment, the shaft portion 31a and the disk portion 31b of the first output member 31 and the shaft portion 32a and the disk portion 32b of the second output member 32 are integrally formed, respectively. It may be formed on the body. Further, if the first output member 31 and the second output member 32 are formed of the same material and in the same shape, the manufacturing cost of these can be reduced.

  Further, in the above-described embodiment, the case where the first output member 31 and the second output member 32 are connected by the connection member 33 has been described. However, the present invention is not limited thereto. Alternatively, they may be integrated by welding. The output members 31 and 32 do not necessarily need to be connected to each other, and may be independently rotatable.

  Further, 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. The present invention can be suitably applied to a reduction gear having a reduction ratio of an arbitrary size within the range. 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.

  In the above embodiment, the first member having the first rolling element engaging groove 13 has the input member 10, the second member having the second rolling element engaging groove 16 has the fixing member 5, and the pocket 17. Although the case where the third member is the output members 31 and 32 has been described, the present invention is not limited to this, and the first member, the second member, and the third member may be changed to the input rotation unit depending on the specification required by the user and the use environment. The power transmission form can be arbitrarily changed by appropriately allocating to each of the fixing member, the fixing member, and the output rotating unit.

1 speed reducer (power transmission device)
2 Input rotating unit 3 Output rotating unit 4 Ball 5 Fixed member (second member)
6 Housing 7 Input shaft 8 Eccentric cam part 10 Input member (first member)
13 First rolling element engaging groove 16 Second rolling element engaging groove 17 Pocket 31, 32 Output member (third member)
33 Connecting members F1, F1 'Contact force F2, F2' between ball and first rolling element engaging groove F3, F3 'Contact force between ball and second rolling element engaging groove Contact force between ball and pocket L1 Track center line L1 of first rolling element engaging groove L2 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 (6)

A power transmission device that transmits the rotation input to the input rotation unit to an output rotation unit coaxially arranged at a predetermined gear ratio,
A first member having first rolling element engaging grooves on both side surfaces in the axial direction, and a pair of second members provided on both axial sides of the first member and each having a second rolling element engaging groove; The first rolling element engaging groove and the second rolling element engaging groove are provided between the first member and the pair of second members, respectively, in the axial direction, and are axially opposed to each other. A plurality of balls, and a pair of third members each provided between the first member and the pair of second members in the axial direction and having a plurality of pockets for holding the plurality of balls in a circumferential direction,
One of the first rolling element engaging groove and the second rolling element engaging groove is formed along a circle having a center of curvature eccentric from the rotation center of the input rotation unit and the output rotation unit. The other of the first rolling element engaging groove and the second rolling element engaging groove is formed along a wavy curve that alternately intersects a pitch circle having a center of curvature on the rotation center. And
One of the first member, the pair of second members, and the pair of third members is provided in the input rotation unit, and the first member, the pair of second members, and the pair of third members are provided on the input rotation unit. A power transmission device in which any one of the three members is provided in the output rotation unit.   The power transmission device according to claim 1, further comprising a bearing that rotatably supports the first member.   The power transmission device according to claim 1, wherein the first member is provided on the input rotation unit, the pair of third members is provided on the output rotation unit, and the pair of second members are fixed members.   The power transmission device according to claim 3, wherein the pair of third members are integrally rotatable.   The power transmission device according to any one of claims 1 to 4, wherein the pair of second members have the same shape. The power transmission device according to claim 1, wherein the pair of third members have the same shape.

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