JP2019132401A - Reduction gear - Google Patents

Abstract

To provide a reduction gear which is small in a size, can obtain a high reduction ratio, is high in rotation accuracy, and can suppress vibration.SOLUTION: A reduction gear 1 comprises: an input-side rotating member 2 in which a first ball engagement groove 13 is formed; an output-side rotating member 3 which is arranged coaxially with a rotating shaft 7 of the input-side rotating member 2, and in which a second ball engagement groove 16 is formed; a plurality of balls 4 engaged with both the ball engagement grooves 13, 16 which oppose each other in an axial direction; and a cage 5 having a plurality of pockets 17 for movably holding the balls 4 in a radial direction. The cage 5 is arranged so as to be non-rotatable with respect to the rotating shaft 7, the rotation of the input-side rotating member 2 is reduced in speed, and transmitted to the output-side rotating member 3 via the balls 4 which are engaged with both the ball engagement grooves 13, 16. A material or surface treatment whose friction coefficient with the ball is lower than the that of contact between the ball and the ball engagement groove, is used on at least a surface of a member constituting the pockets of the cage.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a reduction gear.

  A first disk on the input side provided with a ball engaging groove, a second disk on the output side provided with a ball engaging groove, a plurality of balls engaged with the ball engaging groove, and a first There have already been proposed reduction gears that are interposed between a disc and a second disc and have a cage for holding a ball (for example, Patent Documents 1 and 2). This type of speed reducer is excellent in that it is small and provides a large reduction ratio.

  The speed reducer proposed in Patent Document 1 has a winding first groove that intersects a first reference circle of a plane with a constant pitch and a winding first groove that intersects a second reference circle of the plane with a constant pitch. The first and second discs each having two grooves, and the first and second discs are respectively held by the first and second cages. The first retainer is fixed and the second retainer is rotatably supported by two rolling elements facing each other. Since this speed reducer is a differential type, it is described that a large speed reduction ratio can be obtained and a small speed reducer is possible.

  The speed reducer proposed in Patent Document 2 includes a drive cam having a circular cam groove engaged with a ball and decentered from the rotation axis by a certain distance, a driven cam having a petal-shaped cam groove engaged with the ball, A cage having a groove for holding the ball movably in the radial direction, with the cage sandwiched between the drive cam and the follower cam on opposite sides of the surface having the respective cam grooves. These are coupled so as to be rotatable around the same axis, and the rotation of the drive cam is decelerated and transmitted to the driven cam via the movement of the ball. It is described that this reduction gear is small and is manufactured at a low cost by relatively simple processing and can obtain a reduction gear ratio of about 6.

Japanese Patent Application Laid-Open No. 60-168954 JP-A-5-203209

  In recent years, high rotational accuracy and vibration suppression of a reduction gear are desired depending on the intended use. On the other hand, pay attention to the non-uniformity of the rotational motion between the input side and the output side of the reducer, and accompanying high-order problems such as fluctuations in the rotational speed of the output side and vibration generation. It came to the idea that is necessary. However, the reduction gears described in Patent Documents 1 and 2 are excellent in terms of being small and providing a large reduction ratio, but the rotational motion between the input side and the output side as described above. No attention has been paid to the inconstant speed, the accompanying fluctuations in the rotational speed of the output side, and the occurrence of vibrations. In other literature, there have been no specific proposals so far. This is the present invention.

  By the way, the main parts of this type of reduction gear are composed of a ball, an input plate, an output plate, and a cage.

  This type of reducer is a mechanism that converts the eccentric rotational motion of the input plate into a reciprocating linear motion of the ball, converts it back into a rotational motion again by the wavy groove of the output plate, and transmits the driving force by decelerating it. Since the rolling bearing is rotatably provided in the eccentric part on the side, it is possible to absorb the rotational difference between the input plate and the output plate and transmit torque while the ball rolls.

  Therefore, the rotation speed of the ball rotation is determined by the rotation speed of the input plate and the rotation speed of the output plate.

  However, since the ball moves linearly in the cage pocket and the rotation speed of the ball is determined, slip occurs at the contact between the ball and the cage pocket, resulting in reduced efficiency or durability. There is concern that it will get worse.

  The cage that holds the ball is a component that does not contribute to the power transmission of the speed reducer, and it is important to improve the efficiency to reduce the frictional force between the ball and the pocket of the cage. The frictional force generated by the contact between the ball and the pocket of the cage acts only in the radial direction around the input shaft or the rotation shaft of the output plate. Therefore, it can be seen that the frictional force generated between the ball and the cage does not contribute to power transmission.

  Therefore, in view of the above problems, the present invention can achieve a small and high reduction ratio, and can suppress fluctuations in rotational speed and vibration on the output side, and can improve efficiency due to slip generated in the balls and the pockets of the cage. An object of the present invention is to provide a speed reducer that has improved deterioration and deterioration of durability.

  As a result of various studies to achieve the above-described object, the present inventors firstly create a new ball engagement groove capable of obtaining a synchronous rotational property in a decelerating rotational motion between the input side and the output side. The present invention has been achieved by the idea that the durability can be improved, the transmission efficiency can be improved, and the vibration can be reduced by reducing the coefficient of friction between the ball and the pocket of the cage.

As technical means for achieving the above-described object, the present invention includes an input-side rotating member having an input plate portion in which a first ball engaging groove is formed, and coaxially with the rotation axis of the input-side rotating member. An output-side rotating member that is disposed and has an output plate portion in which a second ball engaging groove is formed, and a plurality of members that engage with both the ball engaging grooves of the input plate portion and the output plate portion facing in the axial direction. And a cage having a plurality of pockets for holding the ball so as to be movable in the radial direction. The cage is provided so as not to rotate with respect to the rotating shaft, and is engaged with both the ball engaging grooves. In the speed reducer in which the rotation of the input side rotating member is decelerated through the balls to be combined and transmitted to the output side rotating member, the track center line of the second ball engaging groove is formed as a wavy curve, When the reduction ratio of the speed reducer is i, The wavy curve indicates that the ball is engaged with the first ball engagement groove when the output side rotation member is at a rotation angle (θ / i) at an arbitrary rotation angle (θ) of the input side rotation member. Has a shape that engages with the second ball engagement groove, and the friction coefficient between the ball and the ball engagement groove is greater than the friction coefficient between the ball and the ball engagement groove. It is characterized by using a small material or surface treatment.
With the above configuration, it is possible to realize a reduction device that is small and has a high reduction ratio, and that can suppress rotational speed fluctuation and vibration on the output side.

  Specifically, the center of the ball engaged with the first ball engaging groove is positioned on the track center line of the second ball engaging groove. Thereby, the 1st ball engagement groove and the 2nd ball engagement groove can be set up certainly.

  In addition, by using a material with a lower friction coefficient than the ball engagement groove (usually steel is used) of the input / output rotating member for the cage pocket, the ball is held while rolling by contact between the ball and the ball engagement groove. It is possible to suppress heat generation with the pocket of the vessel.

  It is preferable that an eccentric portion is formed on the rotation shaft of the input side rotating member, and an input plate portion is rotatably mounted on the eccentric portion via a rolling bearing. Thereby, the relative friction amount between the pocket of the cage or the ball engaging groove and the ball can be reduced, and the transmission efficiency from the input side rotating member to the output side rotating member can be improved.

但し、
Ｒ：回転軸の軸心と第２のボール係合溝の軌道中心線との距離
ａ：偏心量
ｉ：減速比
ψ：出力側回転部材の回転角
ｒ：第１のボール係合溝の軌道中心線の半径
これにより、第１のボール係合溝と第２のボール係合溝の全体としてボール係合溝の形状を簡素化でき、製造の容易化、低コスト化を図ることができる。 The track center line of the first ball engaging groove is circular, the center of curvature is eccentric with respect to the axis of the rotation shaft of the input side rotation member, and the axis of the rotation shaft and the second ball It is preferable that the distance (R) between the engagement groove and the track center line satisfies the following formula.

However,
R: distance between the axis of the rotating shaft and the orbit center line of the second ball engaging groove a: eccentricity i: reduction ratio ψ: rotation angle of the output side rotating member r: orbit of the first ball engaging groove Thus, the shape of the ball engaging groove can be simplified as a whole of the first ball engaging groove and the second ball engaging groove, and the manufacturing can be facilitated and the cost can be reduced.

According to the present invention, it is possible to realize a reduction gear that is small and has a high reduction ratio, and that can suppress fluctuations in rotational speed and vibration on the output side.
By reducing the coefficient of friction between the ball and the pocket of the cage, it is possible to improve durability, improve transmission efficiency, and reduce vibration.

It is a longitudinal section showing the whole reduction gear device concerning one embodiment of the present invention. It is a disassembled perspective view which shows the principal part of FIG. FIG. 3 is a schematic diagram of FIG. 2. (A) is a side view of the input plate portion taken along line EE in FIG. 1, and (b) is a cross-sectional view of the input plate portion along line GG in (a). (A) The figure is a side view of the output board part which looked at the FF line | wire of FIG. 1, and (b) figure is sectional drawing of the output board part in the HH line | wire of (a) figure. (A) A figure is a side view of the holder | retainer seen from the II line | wire of FIG. 1, (b) A figure is an enlarged view of the J section of (a) figure. It is a graph which shows the time change of the transmission efficiency at the time of comparing only the friction coefficient between a ball | bowl and a holder | retainer with 0.1 and 0.05. It is a graph which shows the influence amount on the transmission efficiency with respect to the friction coefficient calculated like FIG. 7 between the ball | bowl and a cage | basket. It is a figure which shows the ball engagement groove of an output board part, and the arrangement | positioning state of a ball | bowl. It is a figure which shows the motion of the ball | bowl with respect to a ball engaging groove. It is a schematic diagram which derive | leads out the reference | standard curve of the ball engaging groove of an output board part.

  A speed reducer according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view showing the entire reduction gear device according to the present embodiment. The speed reducer 1 mainly includes an input side rotating member 2, an output side rotating member 3, a ball 4, and a cage 5, and is incorporated in cases 6a and 6b.

  As shown in FIG. 1, the input side rotating member 2 includes a rotating shaft 7, an eccentric cam 8, a rolling bearing 9 and an input plate portion 10. An eccentric cam 8 is fitted on the outer diameter surface of the rotating shaft 7. The center line O1 of the cylindrical outer diameter surface 8a of the eccentric cam 8 is eccentric in the radial direction with respect to the axis X1 of the rotating shaft 7 by the amount of eccentricity a. A rolling bearing 9 is mounted between the cylindrical outer diameter surface 8 a of the eccentric cam 8 and the cylindrical inner diameter surface 10 a of the input plate portion 10, and the input plate portion 10 is rotatably supported by the eccentric cam 8. The center line O1 of the cylindrical outer diameter surface 8a of the eccentric cam 8 is also the center line of the input plate portion 10. For this reason, when the rotating shaft 7 rotates, the input plate portion 10 performs a revolving motion with a swaying radius a around the axis X1 of the rotating shaft 7. The rotating shaft 7 is rotatably supported by a rolling bearing 11 attached to the inner diameter surface 21 of the case 6a and a rolling bearing 12 attached to the inner diameter surface 5a of the cage 5.

  As shown in FIGS. 1, 4 (a) and 4 (b), a first ball engaging groove 13 is formed on the side surface 10 b of the input plate portion 10. 4A is a side view of the input plate 10 taken along the line EE in FIG. 1, and FIG. 4B is a diagram of the input plate 10 taken along the line GG in FIG. 4A. It is sectional drawing. 4 (a) and 4 (b), the chamfering of the outer diameter surface of the input plate portion 10 and the illustration of the inner diameter surface 10a (see FIG. 1) on which the rolling bearing 9 is mounted are omitted.

  As shown in FIG. 4A, the track center line L1 of the first ball engaging groove 13 is formed in a circular shape with a radius r, and the first ball engaging groove 13 is formed of a part of the torus surface. The center of curvature of the track center line L <b> 1 is located at the cylindrical outer diameter surface 8 a of the eccentric cam 8 and the center line O <b> 1 of the input plate portion 10. The center of curvature O1 is eccentric with respect to the axis X1 of the rotating shaft 7 by the amount of eccentricity a. The center Ob of the ball 4 is positioned on the track center line L1 of the first ball engaging groove 13. In the present specification and claims, the track center line of the first ball engaging groove is the track of the center Ob of the ball 4 when the ball 4 is moved along the first ball engaging groove 13. Means.

  As shown in FIG. 1, the output side rotation member 3 includes an output plate portion 3a and a shaft portion 3b, and the output plate portion 3a and the shaft portion 3b are integrally formed. The shaft portion 3b serves as an output shaft. The output side rotating member 3 is rotatably supported by a rolling bearing 14 mounted on the inner diameter surface 20 of the case 6b and a rolling bearing 15 mounted on the stepped outer diameter surface 5b of the cage 5.

  As shown in FIGS. 1, 5A, and 5B, the second ball engaging groove 16 is formed on the side surface 28 of the output plate portion 3a. FIG. 5A is a side view of the output plate portion 3a taken along the line FF in FIG. 1, and FIG. 5B is a view of the output plate portion 3a taken along the line H-H in FIG. It is sectional drawing. 5A and 5B, illustration of the chamfering of the outer diameter surface of the output plate portion 3a and the inner diameter surface 22 (see FIG. 1) on which the rolling bearing 15 is mounted is omitted.

  The orbit center line L2 of the second ball engaging groove 16 is formed in a wavy curve, and the axis X2, the orbit center line L2 and the distance R of the shaft portion 3b vary with respect to the reference pitch circle radius PCR. In the embodiment, the wavy curve of the trajectory center line L2 is formed with 10 peaks having a distance R larger than the reference pitch circle radius PCR and 10 valleys having a distance R smaller than the reference pitch circle radius PCR. Yes. The shaft center X2 of the shaft portion 3b is arranged coaxially with the shaft center X1 of the rotating shaft 7. The center Ob of the ball 4 is positioned on the track center line L2 of the second ball engaging groove 16.

  In the present specification and claims, the wavy curve of the track center line of the second ball engaging groove means a curve that alternately intersects the reference pitch circle of radius PCR at a constant pitch. The track center line of the second ball engaging groove means the locus of the center Ob of the ball 4 when the ball 4 is moved along the second ball engaging groove 16. Details of the wavy curve of the track center line L2 of the second ball engaging groove 16 will be described later.

  As shown in FIG. 1, the cage 5 is disposed between the side surfaces 10 b and 28 facing the axial direction of the input plate portion 10 and the output plate portion 3 a. The cage 5 is provided with a pocket 17 for holding the ball 4. A through hole 18 is provided on the outer peripheral side of the cage 5, and a pin 19 is fitted into the through hole 18. The cage 5 is attached to the cases 6 a and 6 b so as not to rotate. As a result, the cage 5 cannot rotate with respect to the rotation shaft 7 of the input side rotation member 2. In this state, the fixing bolts 24 are fitted into the through holes 25 of the case 6b and the through holes 23 of the cage 5, and are screwed into the screw holes 26 of the case 6a to fasten the cases 6a, 6b and the cage 5. .

  As shown in FIGS. 1, 6 (a), and 6 (b), the pocket 17 of the cage 5 is formed with elongated holes that extend radially in the radial direction about the axis X 1 of the rotating shaft 7. Fig.6 (a) is a side view of the holder | retainer seen from the II line | wire of FIG. 1, FIG.6 (b) is an enlarged view of the J section of Fig.6 (a). 6 (a) and 6 (b), illustration of the inner surface 5a on which the through holes 18 and 23 on the outer peripheral side of the cage 5 and the rolling bearing 12 in FIG. 1 are mounted is omitted.

  The number of pockets 17 of the cage 5 is 11, which is one more than the number of ridges or valleys (10) of the wavy curve of the track center line L2, and the pockets 17 are formed at equal intervals in the circumferential direction. Yes. One ball 4 is arranged in each pocket 17. Since each pocket 17 is formed of a long hole extending radially in the radial direction, the balls 4 in each pocket 17 are within a predetermined amount m in the radial outer side and the radial inner side with respect to the reference pitch circle radius PCR. Can move. The cage 5 is provided so as not to rotate, and the ball 4 is held by a pocket 17 of the cage 5 so as to be movable in the radial direction.

  In the present invention, the cage 5 or the pocket 17 is made of a material having a lower friction coefficient than the ball engaging grooves 13 and 16 (usually using steel) of the input side rotating member 2 and the output side rotating member 3. It is possible to suppress heat generation with the pocket 17 while rolling the ball 4 due to contact between the ball 4 and the ball engaging grooves 13 and 16.

  By reducing the friction coefficient at least at the contact point of the pocket 17 (reciprocating in the radial direction of the ball) (portion surrounded by M in FIG. 6B), heat generation between the ball 4 and the cage 5 is reduced. It becomes possible to make it.

  FIG. 7 shows the analysis result of the transmission efficiency of the speed reducer using general-purpose mechanism analysis software (ADAMS). FIG. 7 shows transmission efficiency values when only the friction coefficient between the ball 4 and the cage 5 is compared between 0.1 and 0.05. In FIG. 7, the friction coefficients of other contacts are all 0.1.

  When compared in a stable state, the transmission efficiency is improved by about 9% on average by changing the friction coefficient from 0.1 to 0.05.

  FIG. 8 shows the amount of influence on the transmission efficiency with respect to the coefficient of friction between the ball and the cage calculated in the same manner as in FIG. There is almost no change when the friction coefficient between the ball 4 and the cage 5 is 0.3 or more or 0.01 or less.

  By reducing the coefficient of friction between the ball 4 and the cage 5 or the pocket 17, durability can be improved, transmission efficiency can be improved, and vibration can be reduced. The transmission efficiency is effective when the friction coefficient between the ball 4 and the cage 5 or the pocket 17 is lowered below that when the friction coefficient between the steel and steel contact (with grease) is 0.01 to 0.3. There is.

As a material of the cage 5, a material having a low friction coefficient such as a resin or a copper alloy is selected.
For example, when the ball 4 is made of steel, the friction coefficient can be lowered by changing the cage 5 or the pocket 17 to the following material. It is known that the dynamic friction coefficient in a dry state (solid vs. solid) is about 0.4 to 0.6 in the case of steel vs. steel.

  The value of the friction coefficient shown below indicates the dynamic friction coefficient of the steel vs “each material” in the dry state. In addition to the material of the contact surface, the friction coefficient changes depending on the presence or absence of lubricants such as oil and the surface roughness. In this case, the friction coefficient in the dry state where the conditions are relatively consistent is compared. It was decided to do.

Copper alloys including brass, bronze and lead bronze: 0.15 to 0.3 ⁽ Note ⁾ , resin materials with excellent lubricity (PTFE, nylon, polyacetal, UHPE, PEEK, etc.): 0.05 to 0.4 ⁽ Note ⁾ , ceramics: 0.2 to 0.5 ⁽ Note ⁾ Other materials having a small friction coefficient may be applied.
Note: Source: W. Beitz, K.-H. Kuttner (editors) “Taschenbuch fur den Maschinenbau”, 18th edition, Springer 1995 / “Formulaen und Tafeln”, 2md edition, Orell Fussli Zurich 1981, Mechanical Engineering Handbook

Similarly, when the ball 4 is made of steel, the friction coefficient can be lowered by applying the following surface treatment to the cage 5 or the pocket 17.
Surface treatment includes DLC (diamond-like carbon): 0.05 to 0.1, resin coating such as fluorine: 0.08 to 0.12, electroless nickel plating including fluorine resin composite: 0.08 to 0. 12. Hard chrome plating: 0.1 to 0.16, and any other treatment that reduces the friction coefficient.

  The surface treatment may be at least one of the contact surfaces of the balls 4 or the balls 4 of the cage 5.

  In addition, dimples may be processed on the contact surface of the ball 4 or the ball 4 of the cage 5 to form an oil sump on the contact surface, thereby reducing the influence of sliding.

  As described above, by reducing the coefficient of friction between the ball 4 and the cage 5 or the pocket 17, it is possible to improve durability, improve transmission efficiency, and reduce vibration.

In the reduction gear 1 of the present embodiment, the number of crests of the track center line L2 of the second ball engagement groove 16 is 10 (the number of troughs is 10 similarly), and the number of balls 4 is 11. Therefore, the reduction ratio i is obtained by the following equation, and the reduction ratio i is -1/10.
Reduction ratio i = (number of ridges−number of balls) / number of ridges Note that the minus sign of the reduction ratio i indicates that the rotation direction of the output side rotation member 3 is opposite to the rotation direction of the input side rotation member 2. It means that.

  Next, with reference to FIG. 2 and FIG. 3, the combination state of the input board part 10, the holder | retainer 5, the ball | bowl 4, and the output board part 3a is demonstrated. 2 is a perspective view showing a main part of FIG. 1, and FIG. 3 is a schematic view showing a state in which the ball of FIG. 2 is arranged in the pocket of the cage. 3, the outer diameter chamfer of the input plate portion 10 in FIG. 2, the inner diameter surface 10a for mounting the bearing, the outer diameter side through holes 18 and 23 of the cage 5, the inner diameter surface 5a for mounting the bearing, and the bearing mounting of the output plate portion 3a. Illustration of the inner diameter surface 22 and the shaft portion 3b is omitted.

  The axis X1 of the rotating shaft 7 of the input side rotating member 2 and the axis X2 of the output side member 3 are arranged coaxially, and the axis of the cage 5 is also arranged coaxially with the axes X1 and X2. The center of curvature O1 (see FIG. 4A) of the track center line L1 of the first ball engaging groove 13 of the input plate portion 10 is eccentric with respect to the axis X1 of the rotating shaft 7 by an eccentric amount a.

  In FIG. 2, the ball 4 is shown in a state of being engaged with the second ball engaging groove 16 of the output plate portion 3 b, but this ball 4 is disposed in the pocket 17 of the cage 5 and is shown in the drawing from the pocket 17. The ball 4 protrudes toward the front side, and the ball 4 engages with the first ball engaging groove 13 (see FIG. 1) of the input plate portion 10. That is, as shown in FIG. 3, the front side of the ball 4 in the pocket 17 of the cage 5 is engaged with the first ball engagement groove 13 (see FIG. 1) of the input plate portion 10, and the drawing of the ball 4 is made. The back side engages with the second ball engaging groove 16 of the output plate portion 3b.

  The overall configuration of the reduction gear 1 of the present embodiment is as described above. Next, the details of the ball engaging groove in which the output side rotating member is decelerated relative to the input side rotating member and rotates synchronously will be described with reference to FIGS. FIG. 9 is a view showing the second ball engaging groove and the ball arrangement state of the output plate portion, and FIG. 10 is an enlarged view of the K portion of FIG. 9 to show the movement of the ball with respect to the second ball engaging groove. FIG. 11 is a schematic diagram for deriving a reference curve of the second ball engaging groove of the output plate portion.

As described above, the cage 5 is provided so as not to rotate, and the ball 4 is held by the pocket 17 of the cage 5 so as to be movable in the radial direction. As shown in FIG. 9, the ball 4 engages with the second ball engagement groove 16 of the output plate portion 3a at an equiangular position in the circumferential direction. In this embodiment, since the number of balls 4 is 11, α = 360 °, where α is an angle formed by a straight line connecting the axis X2 and the centers Ob ₀ and Ob ′ of the balls 4 adjacent in the circumferential direction. / 11, and the angle α between all adjacent balls 4 is equal.

  A state in which the output side rotation member 3 is decelerated relative to the input side rotation member 2 and rotates synchronously will be described with reference to FIG. As described above, the cage 5 is configured to be non-rotatable with respect to the rotation of the input side rotating member 2 and the output side rotating member 3. Therefore, the pocket 17 indicated by the solid line in FIG. 10 does not move in the circumferential direction. A horizontal center line in FIG. 10 indicates a position where the rotation angle θ of the rotation shaft 7 of the input side rotation member 2 is 0 °. The ball 4 is located in the outermost radial direction in the pocket 17. This is because, in the revolving motion of the input plate portion 10, the swing radius a with respect to the axis X1 of the rotation shaft 7 of the input plate portion 10 is on the horizontal center line in FIG. The ball 4 that engages with the ball engaging groove 13 is located in the radially outermost side in the pocket 17.

Rotary shaft 7 is rotated a rotation angle .theta.1, since the position of the whirling radius a of the input plate 10 is moved to the position of the rotation angle theta _1, to engage the first ball engagement groove 13 of the input plate 10 The ball 4 moves in the pocket 17 toward the inner diameter side in the radial direction, and the center of the ball 4 is at the position Ob ₁ . In center of the Ob ₁ state of the ball 4, since the ball 4 is engaged with the second ball engagement groove 16 of the output plate portion 3a, in other words, the center Ob ₁ of the ball 4 is a second ball engaging Since it is positioned on the track center line L2 of the groove 16, the output plate portion 3a rotates by the rotation angle iθ ₁ shown in FIG. Subsequently, when the rotary shaft 7 rotates at the rotation angle θ ₂ and further at the rotation angles θ ₃ and θ ₄ , the output plate portion 3 a rotates at the rotation angles iθ ₂ , iθ ₃ , and iθ ₄ as described above. . Thereby, the rotational motion decelerated (reduction ratio i = −1 / 10) is transmitted from the input side rotating member 2 to the output side rotating member 3.

  The speed reduction device 1 of the present embodiment is characterized in that the rotational motion decelerated from the input side rotation member 2 to the output side rotation member 3 is transmitted in a synchronous rotation. Thereby, high rotation accuracy and vibration suppression can be achieved. Since the rotational motion decelerated from the input-side rotating member 2 to the output-side rotating member 3 is transmitted by synchronous rotation, the shape of the wavy curve of the track center line L2 of the second ball engaging groove 16 of the output plate portion 3a. Is set.

A method for deriving the wavy curve of the track center line L2 of the second ball engaging groove 16 of the output plate portion 3a will be described with reference to FIG. FIG. 11 is a schematic diagram for deriving a wavy curve of the track center line L2 of the second ball engaging groove 16. The horizontal center line in FIG. 11 corresponds to the horizontal center line in FIG. 10 and indicates a position where the rotation angle θ of the rotation shaft 7 of the input side rotation member 2 is 0 °. The track center line L1 ₀ of the first ball engagement groove 13 of the input plate 10 when the rotational angle θ of 0 ° of the rotary shaft 7 is represented by a broken line, the first ball at any rotation angle θ The track center line L1θ of the engagement groove 13 is indicated by a solid line.

With respect to the axis X1 of the rotation shaft 7 of the input side rotating member 2, the track center line L1 of the first ball engaging groove 13 of the input plate portion 10 is a circle with a radius r, and the center of curvature O1 is the amount of eccentricity. Only a is eccentric. For this reason, when the rotation angle θ is 0 °, the center of curvature of the trajectory center line L1 is O1 ₀ , and the center of the ball 4 is Ob ₀ and is located on the outermost side in the radial direction. The ball 4 is restrained on the line n by the pocket 17 of the cage 5 and can move in the radial direction. When the rotation axis 7 reaches an arbitrary rotation angle θ, the center of curvature of the track center line L1 moves to O1θ, and the center of the ball 4 moves to Obθ. The ball 4 at this position engages with the second ball engaging groove 16 of the output plate portion 3a. That is, the relationship is such that the center Obθ of the ball 4 is positioned on the track center line L2 (see FIG. 10) of the second ball engaging groove 16. With respect to this positional relationship, when the rotation angle of the output plate portion 3a is always iθ with respect to an arbitrary rotation angle θ of the rotation shaft 7, synchronous rotation of the rotation shaft 7 and the output plate portion 3a is established. Based on this, the distance R between the axis X1 of the rotating shaft 7 and the track center line L2 of the second ball engaging groove is obtained geometrically.

但し、
Ｒ：回転軸の軸心と第２のボール係合溝の軌道中心線との距離
ａ：偏心量
ｉ：減速比
ψ：出力側回転部材の回転角
ｒ：第１のボール係合溝の軌道中心線の半径 As shown in FIG. 11, the distance R between the axis X1 of the rotating shaft 7 and the track center line L2 of the second ball engaging groove is expressed as follows.

However,
R: distance between the axis of the rotating shaft and the orbit center line of the second ball engaging groove a: eccentricity i: reduction ratio ψ: rotation angle of the output side rotating member r: orbit of the first ball engaging groove Centerline radius

  Finally, the operation of the reduction gear 1 of the present embodiment will be summarized and described. When the rotating shaft 7 of the input side rotating member 2 is rotated, the input plate portion 10 revolves around the axis X1 of the rotating shaft 7. At that time, since the input plate portion 10 is rotatable with respect to the eccentric cam 8 provided on the rotation shaft 7, the input member 10 hardly rotates. Thereby, the relative friction amount between the pocket of the cage or the ball engaging groove and the ball can be reduced, and the transmission efficiency from the input side rotating member to the output side rotating member can be improved.

  When the input plate portion 10 performs a revolving motion, each ball 4 that engages with the first ball engaging groove 13 formed of the circular track center line L1 is restrained in the pocket 17 of the cage 5 that is provided so as not to rotate. And move in the radial direction respectively.

  Since each ball 4 is engaged with the second ball engaging groove 16 of the output plate portion 3a of the output side rotation member 3, the ball 4 is shown in FIG. As described above, the output-side rotating member 3 rotates while the rotation of the rotating shaft 7 of the input-side rotating member 2 is decelerated. At this time, the reference curve of the track center line L2 of the second ball engaging groove 16 of the output plate portion 3a is set as described with reference to FIG. Rotate synchronously at the reduced speed.

  The operation of the reduction gear 1 of the present embodiment is as described above, and it is possible to achieve a reduction device that is small and has a high reduction ratio, and that can suppress fluctuations in rotational speed and vibration on the output side. Further, the first ball engaging groove formed of a circular track center line and the second ball engaging groove formed of a wavy curved track center line can simplify the shape of the ball engaging groove as a whole, and are easy to manufacture. And cost reduction.

  In the speed reduction device 1 of the present embodiment, the circular track center line L1 of the first ball engagement groove 13 provided in the input plate portion 10 is exemplified as a circular shape, but the present invention is not limited to this and corresponds to the speed reduction ratio i. It may be a polygonal orbit centerline. In this case, the distance R between the axis of the rotating shaft and the track center line of the second ball engaging groove can be derived in the same manner as described with reference to FIG. 9, and R = a · cos (ψ / i ) + R. Thus, the track center line of the first ball engagement groove and the track center line of the second ball engagement groove for synchronously rotating the input side rotation member and the output side rotation member can be appropriately set.

  In the speed reduction device 1 of the present embodiment, the input plate portion 10 is configured to be rotatable with respect to the eccentric cam 8 provided on the rotation shaft 7, but the input plate portion and the rotation shaft are integrated. It may be. Further, in the speed reduction device 1 of the present embodiment, the configuration in which the separate eccentric cam 8 is fitted to the rotating shaft 7 is illustrated, but the present invention is not limited to this, and the rotating shaft and the eccentric cam are configured integrally. Good.

  In the speed reduction device 1 of the present embodiment, the speed reduction ratio i is -1/10. However, for example, the speed reduction ratio i is about 1/5 to 1/20, and can be appropriately set as necessary. In this case, the number of peaks / valleys of the wavy curve of the track center line of the ball engagement groove, the number of pockets of the cage, and the number of balls may be appropriately set according to the reduction ratio i.

  The present invention is not limited to the above-described embodiments, and the pocket of the cage may be formed of a member different from the cage, and the cage may be composed of a plurality of members. In addition, the present invention can of course be implemented in various forms without departing from the scope of the present invention, and the scope of the present invention is shown by the claims and further described in the claims. Including the equivalent meaning of and all changes within the scope.

DESCRIPTION OF SYMBOLS 1 Deceleration apparatus 2 Input side rotating member 3 Output side rotating member 3a Output plate part 3b Shaft part 4 Ball 5 Cage 6a Case 6b Case 7 Rotating shaft 8 Eccentric cam 10 Input plate part 13 1st ball engaging groove 16 2nd Ball engaging groove 17 Pocket L1 Orbit center line L2 Orbit center line O1 Input plate center line Ob Ball center PCR Reference pitch circle radius R Center axis of rotation axis and orbit center line of second ball engaging groove Distance X1 Rotational shaft axis X2 Shaft center of output-side rotating member a Eccentricity i Reduction ratio r Radius of track center line of first ball engagement groove Rotational angle ψ of rotating shaft of input-side rotating member Output Rotation angle of side rotation axis

Claims (6)

An input side rotation member having an input plate portion in which a first ball engagement groove is formed, and an output plate portion arranged coaxially with the rotation axis of the input side rotation member and having a second ball engagement groove formed An output-side rotating member having a plurality of balls, engaging a plurality of balls engaging with both the ball engaging grooves of the input plate portion and the output plate portion facing in the axial direction, and a plurality of balls holding the balls movably in the radial direction. A cage having a pocket, the cage is provided so as not to rotate with respect to the rotation shaft, and the rotation of the input side rotation member is decelerated through the balls engaged with the both ball engagement grooves. In the speed reducer transmitted to the output side rotating member,
The center line of the orbit of the second ball engaging groove is formed as a wavy curve;
When the reduction ratio of the speed reducer is i, the wavy curve indicates that the first rotation member is at a rotation angle (iθ) at an arbitrary rotation angle (θ) of the input side rotation member. The ball engaged with the ball engagement groove of the second shape is engaged with the second ball engagement groove,
A speed reducer comprising a material having a friction coefficient with a ball smaller than that of a contact surface between a ball and a ball engagement groove, or a surface treatment, at least on a contact surface of the cage with a ball.   2. The reduction gear according to claim 1, wherein the contact between the ball and the ball engaging groove is steel and steel.   The speed reducer according to claim 1 or 2, wherein a material of a member constituting the pocket of the cage is copper or a copper alloy.   The speed reducer according to claim 1 or 2, wherein a material of a member constituting the cage or pocket is a resin material.   5. The reduction gear according to claim 1, wherein the material of the ball is ceramic.   The speed reducer according to any one of claims 1 to 5, wherein dimple processing is performed on at least a contact surface of the pocket of the cage with the ball.

Images