JP6996994B2 - Decelerator - Google Patents

Description

The present invention relates to a speed reducer.

A first disk on the input side with a ball engagement groove, a second disk on the output side with a ball engagement groove, a plurality of balls engaging with the ball engagement groove, and a first. A speed reducer having a cage interposed between a disk and a second disk to hold a ball has already been proposed (for example, Patent Documents 1 and 2). This type of reducer is excellent in that it is compact and can obtain a large reduction ratio.

The speed reducer proposed in Patent Document 1 has a winding first groove in which a first reference circle on a plane intersects at a constant pitch and a second reference circle on the plane intersecting at a constant pitch. The first and second discs having the two grooves, the first disc and the second disc, respectively, are held by the first and second cages, respectively, with the first and second discs. The first cage is fixed and the second cage is rotatably supported so as to face each other via the rolling elements 2. Since this speed reducer is a differential type, it is described that a large 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 that engages with the ball and is eccentric from the rotation axis by a certain distance, a driven cam having a petal-shaped cam groove that engages with the ball, and a driven cam. A cage having a groove for holding the ball so as to be movable in the radial direction is provided, and the cage is sandwiched between the cages, and the drive cam and the driven cam are placed on both sides of the cage with the surfaces having the respective cam grooves facing each other. , Rotably connected around the same axis, decelerates the rotation of the drive cam via the movement of the ball and transmits it to the driven cam. It is described that this reduction gear is small, can be manufactured at low cost by relatively simple processing, and can obtain a reduction gear ratio of about 6.

Japanese Unexamined Patent Publication No. 60-168954 Japanese Unexamined Patent Publication No. 5-203009

In recent years, high rotational accuracy and vibration suppression of the reducer are desired depending on the intended use. On the other hand, we focused on the non-uniform velocity of the rotational motion between the input side and the output side of the reducer, and the accompanying high-dimensional problems such as rotational speed fluctuation on the output side and vibration generation. Came to the idea that is necessary. However, the speed reducers described in Patent Documents 1 and 2 are considered to be excellent in terms of being compact and obtaining a large reduction ratio, but the rotational movement between the input side and the output side as described above is described. No attention was paid to the non-constant velocity of the above, and the accompanying problems of rotational speed fluctuation and vibration generation on the output side, and there was no concrete proposal so far in other literature, so we focused on this. Is the present invention.

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

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

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

However, since the ball makes a linear motion in the pocket of the cage and the rotation speed of the ball is determined, the contact between the ball and the pocket of the cage causes slippage, which reduces efficiency or durability. There is a concern that it will worsen.

The cage that holds the ball is a component that does not contribute to the power transmission of the reducer, and it is important to reduce the frictional force between the ball and the pocket of the cage in order to improve efficiency. The frictional force generated by the contact between the ball and the pocket of the cage acts only in the radial direction about the rotation axis of the input shaft or 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 makes it possible to obtain a small size and a high reduction ratio, suppress rotation speed fluctuations and vibrations on the output side, and improve efficiency due to slippage generated in the pockets of the ball and the cage. It is an object of the present invention to provide a speed reducer having improved deterioration and deterioration of durability.

As a result of various studies to achieve the above object, the present inventors first create a new ball engaging groove in which synchronous rotation is obtained in the deceleration rotation motion between the input side and the output side. The idea was made, and further, by lowering the coefficient of friction between the ball and the pocket of the cage, it is possible to improve the durability, improve the transmission efficiency, and reduce the vibration, which led to the present invention.

As a technical means for achieving the above-mentioned object, the present invention relates to an input-side rotating member having an input plate portion on which a first ball engaging groove is formed, and coaxially with the rotation axis of the input-side rotating member. A plurality of rotating members on the output side having an output plate portion arranged and having a second ball engaging groove formed, and a plurality of engaging with both ball engaging grooves of the input plate portion and the output plate portion facing in the axial direction. The cage is provided with a cage having a plurality of pockets for holding the ball so as to be movable in the radial direction. In the speed reducing device in which the rotation of the input side rotating member is decelerated via the matching ball and transmitted to the output side rotating member, the trajectory center line of the second ball engaging groove is formed by a wavy curve. When the reduction ratio of the speed reducer is i, the wavy curve is such that the output side rotating member has a rotation angle (θ / i) at an arbitrary rotation angle (θ) of the input side rotating member. The ball engaged with the first ball engaging groove has a shape of engaging with the second ball engaging groove, and the friction coefficient with the ball is at least on the contact surface of the cage pocket with the ball. It is characterized by using a material having a friction coefficient smaller than the friction coefficient of the contact surface of the ball engaging groove or a surface treatment.
With the above configuration, it is possible to realize a deceleration device that is compact, can obtain a high reduction ratio, and can suppress rotation speed fluctuations and vibrations on the output side.

Specifically, the center of the ball engaged with the first ball engaging groove is located on the trajectory center line of the second ball engaging groove. As a result, the first ball engaging groove and the second ball engaging groove can be reliably set.

In addition, by using a material with a lower coefficient of friction than the ball engaging groove (usually steel is used) of the input / output rotating member in the pocket of the cage, the ball is held while being rolled by the contact between the ball and the ball engaging 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 rotating shaft of the input-side rotating member, and the input plate portion is rotatably mounted on the eccentric portion via a rolling bearing. As a result, the relative amount of friction 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 trajectory center line of the first ball engagement groove is circular, and the center of curvature thereof is eccentric with respect to the axis of rotation of the input side rotating member, and the axis of the rotation axis and the second ball. It is preferable that the distance (R) of the engaging groove from the track center line satisfies the following equation.

However,
R: Distance between the axis of the rotation axis and the trajectory center line of the second ball engagement groove a: Eccentricity i: Reduction ratio ψ: Rotation angle of the output side rotating member r: Trajectory of the first ball engagement groove Radius of center line This makes it possible to simplify the shape of the ball engaging groove as a whole of the first ball engaging groove and the second ball engaging groove, and it is possible to facilitate manufacturing and reduce the cost.

According to the present invention, it is possible to realize a reduction gear that is compact, can obtain a high reduction ratio, and can suppress rotation speed fluctuations and vibrations 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 vertical sectional view which shows the whole of the speed reduction apparatus which concerns on one Embodiment of this invention. It is an exploded perspective view which shows the main part of FIG. It is a schematic diagram of FIG. (A) is a side view of the input plate portion taken along the line EE of FIG. 1, and (b) is a cross-sectional view of the input plate portion taken along the line GG of FIG. 1 (a). (A) is a side view of the output plate portion taken along the line FF of FIG. 1, and FIG. (B) is a cross-sectional view of the output plate portion taken along the line HF of FIG. 1 (a). (A) is a side view of the cage as seen by the line I-I of FIG. 1, and (b) is an enlarged view of part J of FIG. 1 (a). It is a graph which shows the time change of the transmission efficiency when only the coefficient of friction between a ball and a cage is compared with 0.1 and 0.05. 3 is a graph showing 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. 7. It is a figure which shows the ball engagement groove of an output plate part, and the arrangement state of a ball. It is a figure which shows the movement of a ball with respect to a ball engaging groove. It is a schematic diagram which derives the reference curve of the ball engagement groove of an output plate part.

The speed reducing device according to the embodiment of the present invention will be described with reference to FIGS. 1 to 9. FIG. 1 is a vertical sectional view showing the entire speed reducing device according to the present embodiment. The speed reducing device 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 to the outer diameter surface of the rotating shaft 7. The center O1 of the cylindrical outer diameter surface 8a of the eccentric cam 8 is eccentric in the radial direction by the amount of eccentricity a with respect to the axial center X1 of the rotating shaft 7. A rolling bearing 9 is mounted between the cylindrical outer diameter surface 8a of the eccentric cam 8 and the cylindrical inner diameter surface 10a of the input plate portion 10, and the input plate portion 10 is rotatably supported by the eccentric cam 8. The center O1 of the cylindrical outer diameter surface 8a of the eccentric cam 8 is also the center of the input plate portion 10. Therefore, when the rotation shaft 7 rotates, the input plate portion 10 revolves around the axis X1 of the rotation shaft 7 with a radius a. The rotary shaft 7 is rotatably supported by a rolling bearing 11 mounted on the inner diameter surface 21 of the case 6a and a rolling bearing 12 mounted on the inner diameter surface 5a of the cage 5.

As shown in FIGS. 1, 4 (a) and 4 (b), the first ball engaging groove 13 is formed on the side surface 10b of the input plate portion 10. 4 (a) is a side view of the input plate portion 10 taken along the line EE of FIG. 1, and FIG. 4 (b) is a side view of the input plate portion 10 taken along the line GG of FIG. 4 (a). It is a cross-sectional view. In FIGS. 4A and 4B, 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 circle having 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 L1 is located at the cylindrical outer diameter surface 8a of the eccentric cam 8 and the center O1 of the input plate portion 10. The center O1 is eccentric with respect to the axis X1 of the rotating shaft 7 by an eccentric amount a. The center Ob of the ball 4 is located on the track center line L1 of the first ball engaging groove 13. In the present specification and claims, the trajectory center line of the first ball engaging groove is the trajectory 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 rotating member 3 is composed of 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 step outer diameter surface 5b of the cage 5.

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

The orbital center line L2 of the second ball engaging groove 16 is formed by a wavy curve, and the axial center X2 of the shaft portion 3b, the orbital center line L2, and the distance R fluctuate with respect to the reference pitch circular radius PCR. In the embodiment, the wavy curve of the orbital 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. There is. The axis X2 of the shaft portion 3b is arranged coaxially with the axis X1 of the rotating shaft 7. The center Ob of the ball 4 is located on the trajectory center line L2 of the second ball engaging groove 16.

In the present specification and claims, the wavy curve of the orbital center line of the second ball engaging groove means a curve that alternately intersects the reference pitch circle of the radius PCR at a constant pitch. Further, the trajectory center line of the second ball engaging groove means the trajectory of the center Ob of the ball 4 when the ball 4 is moved along the second ball engaging groove 16. The 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 arranged between the side surfaces 10b and 28 of the input plate portion 10 and the output plate portion 3a facing in the axial direction. 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, a pin 19 is fitted into the through hole 18, and the cage 5 is non-rotatably attached to the cases 6a and 6b. As a result, the cage 5 becomes non-rotatable with respect to the rotating shaft 7 of the input-side rotating member 2. In this state, the fixing bolt 24 is fitted into the through hole 25 of the case 6b and the through hole 23 of the cage 5 and screwed into the screw hole 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 of elongated holes extending radially around the axis X1 of the rotating shaft 7. 6 (a) is a side view of the cage viewed along the line I-I of FIG. 1, and FIG. 6 (b) is an enlarged view of the J portion of FIG. 6 (a). 6 (a) and 6 (b) omit the illustration of the through holes 18 and 23 on the outer peripheral side of the cage 5 and the inner diameter surface 5a to which the rolling bearing 12 is mounted in FIG.

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

In the present invention, the ball is used in the cage 5 or the pocket 17 by using a material having a lower coefficient of friction than the ball engaging grooves 13 and 16 (usually steel is used) 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 of at least the contact point of the pocket 17 (the part surrounded by M in FIG. 6B) where the ball 4 reciprocates in the radial direction of the ball, the heat generation between the ball 4 and the cage 5 is reduced. It is possible to make it.

FIG. 7 shows the analysis result of the transmission efficiency of this speed reducer using the general-purpose mechanism analysis software (ADAMS). FIG. 7 shows the transmission efficiency values when only the coefficient of friction between the ball 4 and the cage 5 is compared between 0.1 and 0.05. In FIG. 7, the coefficient of friction of other contacts is set to 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. When the coefficient of friction between the ball 4 and the cage 5 is 0.3 or more or 0.01 or less, there is almost no change.

By lowering 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. The transmission efficiency is effective when the friction coefficient between the ball 4 and the cage 5 or the pocket 17 is lowered to less than that when the friction coefficient between the steel and the steel contact (with grease) is 0.01 to 0.3. There is.

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

The coefficient of friction values shown below indicate the coefficient of dynamic friction of steel vs. "each material" in the dry state. In addition to the material of the contact surface, the coefficient of friction also changes depending on the presence or absence of lubricant such as oil and the surface roughness, so in this case, the friction coefficient in a dry state where the conditions are relatively the same is compared. I 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 with a small coefficient of friction 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 coefficient of friction can be reduced by applying the following surface treatment to the cage 5 or the pocket 17.
The surface treatment is 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, etc .: 0.08 to 0. 12. Hard chrome plating: 0.1 to 0.16, and other treatments that reduce the coefficient of friction may be used.

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 pool on the contact surface to reduce the influence of slippage.

As described above, by lowering 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 speed reducing device 1 of the present embodiment, the number of peaks of the track center line L2 of the second ball 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 is obtained by the following equation, and the reduction ratio i is -1/10.
Reduction ratio i = (number of peaks-number of balls) / number of peaks The minus sign of the reduction ratio i is that the rotation direction of the output side rotating member 3 is opposite to the rotation direction of the input side rotating member 2. Means that

Next, the combined state of the input plate portion 10, the cage 5, the ball 4, and the output plate portion 3a will be described with reference to FIGS. 2 and 3. 2 is a perspective view showing a main part of FIG. 1, and FIG. 3 is a schematic view of a state in which the ball of FIG. 2 is arranged in a pocket of a cage. In FIG. 3, the outer diameter chamfer of the input plate portion 10 in FIG. 2, the inner diameter surface 10a for bearing mounting, the outer diameter side through holes 18 and 23 of the cage 5, the inner diameter surface 5a for bearing mounting, and the bearing mounting of the output plate portion 3a are shown. The 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 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 rotation shaft 7 by the amount of eccentricity a.

FIG. 2 shows a state in which the ball 4 is engaged with the second ball engaging groove 16 of the output plate portion 3b. The ball 4 is arranged in the pocket 17 of the cage 5, and the drawing is made 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 drawing of the ball 4 in the pocket 17 of the cage 5 engages with the first ball engaging groove 13 (see FIG. 1) of the input plate portion 10, and the drawing of the ball 4 The back side engages with the second ball engaging groove 16 of the output plate portion 3b.

The overall configuration of the speed reducer 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 with respect to the input side rotating member and rotates synchronously will be described with reference to FIGS. 9 to 11. FIG. 9 is a diagram showing a second ball engaging groove and a ball arrangement state of the output plate portion, and FIG. 10 is an enlargement of the K portion of FIG. 9 to show the movement of the ball with respect to the second ball engaging groove. In the figure, 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 movably in the radial direction by the pocket 17 of the cage 5. As shown in FIG. 9, the ball 4 engages with the second ball engaging groove 16 of the output plate portion 3a at equiangular positions in the circumferential direction. In the present embodiment, since the number of balls 4 is 11, when the angle formed by the straight line connecting the center Ob ₀ and Ob'of the balls 4 adjacent to the axis X2 in the circumferential direction is α, α = 360 °. It becomes / 11, and the angle α between all the adjacent balls 4 is an equal angle.

A state in which the output side rotating member 3 is decelerated with respect to the input side rotating 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 shown by the solid line in FIG. 10 does not move in the circumferential direction. The horizontal center line in FIG. 10 indicates the position where the rotation angle θ of the rotation axis 7 of the input side rotation member 2 is 0 °. The ball 4 is located on the outermost side in the radial direction in the pocket 17. This is because, in the revolution motion of the input plate portion 10, the swing radius a of the rotation shaft 7 of the input plate portion 10 with respect to the axis X1 is on the horizontal center line of FIG. The ball 4 that engages with the ball engagement groove 13 is located on the outermost side in the radial direction in the pocket 17.

Since the rotation shaft 7 rotates at a rotation angle θ1 and the position of the swing radius a of the input plate portion 10 moves to the position of the rotation angle θ ₁ , it engages with the first ball engagement groove 13 of the input plate portion 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 of Ob ₁ . Since the ball 4 engages with the second ball engaging groove 16 of the output plate portion 3a while the center of the ball 4 is Ob ₁ , in other words, the center Ob ₁ of the ball 4 engages with the second ball. Since the groove 16 is located on the track center line L2, the output plate portion 3a rotates at the rotation angle iθ shown in FIG. 10 by ₁ minute. Subsequently, when the rotation axis 7 rotates at the rotation angles θ ₂ and further at the rotation angles θ ₃ and θ ₄ , the output plate portion 3a rotates at the rotation angles i θ ₂ , i θ ₃ and i θ ₄ in the same manner as described above. .. As a result, the decelerated (reduction ratio i = -1/10) rotational motion is transmitted from the input-side rotary member 2 to the output-side rotary member 3.

The speed reducing device 1 of the present embodiment is characterized in that the rotational movement decelerated from the input side rotating member 2 to the output side rotating member 3 is transmitted by synchronous rotation. As a result, high rotation accuracy and vibration suppression can be achieved. Since the rotational movement 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 trajectory center line L2 of the second ball engaging groove 16 of the output plate portion 3a. Is set.

A method of 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 of FIG. 11 corresponds to the horizontal center line of FIG. 10, and indicates a position where the rotation angle θ of the rotation axis 7 of the input side rotation member 2 is 0 °. The orbital center line L1 ₀ of the first ball engaging groove 13 of the input plate portion 10 when the rotation angle θ of the rotation axis 7 is 0 ° is indicated by a broken line, and the first ball when the rotation angle θ is arbitrary. The track center line L1θ of the engagement groove 13 is represented by a solid line.

The track center line L1 of the first ball engaging groove 13 of the input plate portion 10 is a circle having a radius r with respect to the axis X1 of the rotating shaft 7 of the input side rotating member 2, and the center O1 is the eccentricity a. Only eccentric. Therefore, when the rotation angle θ is 0 °, the center of the orbital center line L1 is at _{O10, and the center of the ball 4 is Ob 0} and _is located at the outermost position in the radial direction. With the pocket 17 of the cage 5,
The ball 4 is constrained on the line n and can move in the radial direction. Then, when the rotation axis 7 has an arbitrary rotation angle θ, the center of the orbital 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 center Obθ of the ball 4 is located on the trajectory center line L2 (see FIG. 10) of the second ball engaging groove 16. In this positional relationship, 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, which establishes synchronous rotation between the rotation shaft 7 and the output plate portion 3a. Based on this, the distance R between the axis X1 of the rotating shaft 7 and the trajectory center line L2 of the second ball engaging groove is geometrically obtained.

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 trajectory center line of the second ball engaging groove a: Eccentric amount i: Reduction ratio ψ: Rotation angle of the output side rotating member r: Trajectory of the first ball engaging groove Centerline radius

Finally, the operation of the speed reducer 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 rotating shaft 7, the input member 10 hardly rotates. As a result, the relative amount of friction 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 revolves, each ball 4 engaged in the first ball engaging groove 13 formed of the circular track center line L1 is restrained in the pocket 17 of the cage 5 provided so as not to rotate. And each moves in the radial direction.

Since each ball 4 is engaged with the second ball engaging groove 16 of the output plate portion 3a of the output side rotating member 3, it is shown in FIG. 8 corresponding to the radial movement operation of each ball 4. As described above, the output-side rotating member 3 rotates after the rotation of the rotating shaft 7 of the input-side rotating member 2 is decelerated. At that time, since the reference curve of the trajectory center line L2 of the second ball engaging groove 16 of the output plate portion 3a is set as described with reference to FIG. 9, the output side rotating member 3 is relative to the rotating shaft 7. It rotates synchronously at the decelerated rotation speed.

The operation of the speed reducer 1 of the present embodiment is as described above, and it is possible to realize a speed reducer that is compact, has a high reduction ratio, and can suppress rotation speed fluctuations and vibrations on the output side. Further, the first ball engaging groove formed of the circular track center line and the second ball engaging groove formed of the wavy curve track center line can simplify the shape of the ball engaging groove as a whole and are easy to manufacture. It is possible to reduce the cost and cost.

In the speed reducing device 1 of the present embodiment, a circular track center line L1 of the first ball engaging groove 13 provided in the input plate portion 10 is exemplified, but the speeding device 1 is not limited to this, and the reduction ratio i is used. It may be a polygonal orbital center line. In this case, the distance R between the axis of the rotating shaft and the trajectory 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. In this way, the track center line of the first ball engaging groove and the track center line of the second ball engaging groove for the input side rotating member and the output side rotating member to rotate synchronously can be appropriately set.

In the speed reducing 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 rotating shaft 7, but the input plate portion and the rotating shaft are integrally configured. You may do it. Further, in the speed reducing device 1 of the present embodiment, a configuration in which a separate eccentric cam 8 is fitted to the rotating shaft 7 is exemplified, but the present invention is not limited to this, and the rotating shaft and the eccentric cam may be integrally configured. good.

In the reduction gear 1 of the present embodiment, the reduction ratio i is exemplified as -1/10, but for example, the reduction ratio i is about 1/5 to 1/20 and can be appropriately set as needed. In this case, the number of peaks / valleys of the wavy curve of the track centerline of the ball engaging 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 embodiment, 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. Further, it goes without saying that it can be carried out in various forms without departing from the gist of the present invention, and the scope of the present invention is indicated by the scope of claims and further described in the scope of claims. Meaning of equality, and includes all changes within the scope.

1 Speed reducer 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 First ball engaging groove 16 Second Ball engagement groove 17 Pocket L1 Track center line L2 Track center line O1 Center of input plate
Ob Ball center PCR Reference pitch Circle radius R Distance between the axis of the rotation axis and the trajectory centerline of the second ball engagement groove X1 The axis of the rotation axis X2 The axis of the output side rotating member a Eccentricity i Deceleration Ratio r Radius of the trajectory center line of the first ball engagement groove θ Rotation angle of the rotation axis of the input side rotation member ψ Rotation angle of the output side rotation axis

Claims (6)

An input-side rotating member having an input plate portion on which a first ball engaging groove is formed, and an output plate portion arranged coaxially with the rotation axis of the input-side rotating member and forming a second ball engaging groove. The output side rotating member having the The cage is provided with a cage having a pocket so as to be non-rotatable with respect to the rotation shaft, and the rotation of the input-side rotating member is decelerated via the balls engaging with both ball engagement grooves. In the speed reducing device transmitted to the output side rotating member
The trajectory centerline of the second ball engaging groove is formed by a wavy curve.
When the reduction ratio of the speed reducing device is i, the wavy curve is the first in a state where the output side rotating member has a rotation angle (iθ) at an arbitrary rotation angle (θ) of the input side rotating member. The ball engaged with the ball engaging groove of the above has a shape of engaging with the second ball engaging groove.
A speed reducer characterized in that a material or surface treatment is used on at least the contact surface of the cage pocket with the ball, whose coefficient of friction with the ball is smaller than the coefficient of friction of the contact surface between the ball and the ball engaging groove. The speed reducing device 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 the material of the member constituting the pocket of the cage is copper or a copper alloy. The speed reducing device according to claim 1 or 2, wherein the material of the member constituting the cage or the pocket is a resin-based material. The speed reducer according to any one of claims 1, 3 and 4, wherein the material of the ball is ceramics. The speed reducer according to any one of claims 1 to 5, wherein at least the contact surface of the pocket of the cage with the ball is dimple-processed.

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