JP2022126241A - transmission device - Google Patents

Abstract

To provide a transmission device capable of easily decreasing size, and thus saving costs and improving a maintenance property.SOLUTION: A speed reducer 1 includes an input shaft 10 that rotates around a rotation axis O1, an internal gear 20 that is disposed around an eccentric axis O2, is actuated with rotations of the input shaft 10, and has a plurality of internal teeth 21 and a guiding member 30 projecting out to one side in an axial direction, an external gear 40 that is disposed so as to face the internal gear 20 on the other side in the axial direction, is disposed rotatably around the rotation axis O1, and has a plurality of external teeth 41, an output shaft 50 that rotates about the rotation axis O1 with rotations of the external gear 40, and a lower case 65 that is disposed so as to face the internal gear 20 on the one side in the axial direction. In the lower case 65, a storage recessed portion 67 is formed, which receives the guiding member 30 so as to restrain the rotation of the internal gear 20 and accept eccentric rocking around the rotation axis O1 of the internal gear 20.SELECTED DRAWING: Figure 2

Description

The present invention relates to transmission devices.

2. Description of the Related Art Conventionally, a speed reducer that reduces the rotation speed of an output shaft of a motor for output is known as a transmission device that transmits transmitted power. In general, a speed reducer reduces the rotation speed of an output shaft by using a plurality of gears, and is capable of outputting torque inversely proportional to the speed reduction. As a reduction gear of this type, for example, Patent Document 1 below discloses a reduction gear using an external gear that rotates eccentrically with rotation of an input shaft.

The speed reducer described in Patent Document 1 includes an input shaft, an eccentric body that rotates as the input shaft rotates, an external gear that is attached to the eccentric body and can rotate eccentrically, and an external gear that is fixed to a casing. It has an internally meshed internal gear and an output shaft connected to the external gear via spline means for extracting and transmitting only the rotation component of the external gear. The external gear is arranged inside the internal gear while meshing with the internal gear, and is rotatable around an eccentric axis eccentric to the central axis of the internal gear. The number of teeth of the external gear is one less than the number of teeth of the internal gear.

According to the speed reducer described in Patent Document 1, when the input shaft rotates, the rotational force is transmitted to the external gear via the eccentric body. Since the rotation of the external gear is restrained by meshing with the internal gear, the external gear rotates eccentrically so as to oscillate about the eccentric axis while being inscribed with the internal gear. At this time, the external gear rotates eccentrically while being decelerated by the relationship between the number of teeth of the external gear and the number of teeth of the internal gear. Since only the rotation component of the external gear can be extracted by the spline means and transmitted to the output shaft, the output shaft can be rotated in a decelerated state.

Japanese Patent No. 2686337

However, the conventional speed reducer described above has a structure in which the external gear arranged inside the internal gear fixed to the casing is eccentrically rotated so as to oscillate. Therefore, it is necessary to provide spline means or the like between the external gear and the output shaft to absorb the oscillation component of the external gear and extract only the rotation component. As a result, a space is required for providing the spline means, etc., and it is difficult to reduce the size of the speed reducer in the radial direction. Moreover, the provision of the spline means or the like complicates the structure and increases the number of parts.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a transmission device that can be easily miniaturized, can lead to cost reduction, and can be improved in maintainability.

The transmission device of the present invention is arranged around an input shaft that rotates about an axis by transmitted power, and an eccentric axis that is eccentric with respect to the axis, operates as the input shaft rotates, and An internal gear having a plurality of circumferentially spaced internal teeth that revolve around the eccentric axis and a guide member protruding on one side in the axial direction, and the other side in the axial direction with respect to the internal gear. a plurality of external teeth arranged so as to face each other side by side, arranged rotatably about the axis, and meshable with the plurality of internal teeth, wherein the plurality of external teeth are arranged to face the plurality of internal teeth; an external gear having a number of teeth different from the number of teeth of the teeth; and an output shaft that rotates around the axis along with the rotation of the external gear so as to face the internal gear on the one side in the axial direction. and a fixing member disposed in the fixing member receives the guide member so as to constrain the rotation of the internal gear and allow the eccentric oscillation of the internal gear about the axis. A receiving recess is formed.

According to the present invention, when the input shaft is rotated about the axis by the transmitted power, the internal gear tends to rotate eccentrically about the axis with the rotation of the input shaft. However, the rotation of the internal gear is restrained by the guide member and the accommodation recess of the fixed member. As a result, the internal gear eccentrically oscillates about the rotation axis O1 so that the parallel movement component is extracted from the eccentric rotation. As a result, the internal gear eccentrically oscillates with respect to the external gear so that the internal teeth sequentially ride over the external teeth in the circumferential direction while the external teeth are inscribed in the internal teeth. Then, each time the internal teeth get over the external teeth due to the eccentric oscillation of the internal gear, the internal gear presses the external teeth in the circumferential direction via the internal teeth to rotate the external gear and the output shaft around the axis. can be done. In particular, since the number of teeth of the external teeth and the number of teeth of the internal teeth are different, it is possible to decelerate or speed up the external gear by the angular difference in the number of teeth. As a result, the output shaft can be rotated while being decelerated or accelerated with respect to the rotation of the input shaft.

Further, unlike conventional reduction gears and the like, the internal gear side is eccentrically oscillated, so that the external gear can be rotated about its axis in a simple rotational motion. Therefore, it is not necessary to extract only the rotation component of the external gear, for example, and power can be transmitted directly from the external gear to the output shaft to rotate the output shaft about its axis. Therefore, the structure can be made simple with a reduced number of parts, and the size of the entire transmission device can be reduced. In addition, it can lead to cost reduction and improvement of maintainability.

By the way, the receiving recess is made larger than the guide member in the cross section of the transmission in order to allow the eccentric oscillation of the internal gear with the guide member. Here, instead of the guide member and the accommodation recess of the present invention, the fixed member is provided with a guide member projecting toward the internal gear, and the internal gear is provided with an accommodation recess for receiving the guide member of the fixed member. Similarly, a configuration is obtained in which the rotation of the internal gear is restrained and the eccentric oscillation of the internal gear is allowed. Compared to this configuration, according to the present invention, the diameter of the internal gear can be reduced by the amount corresponding to the absence of the accommodation recess formed in the internal gear. Therefore, it is possible to reduce the size of the transmission device in the radial direction.

In the transmission device described above, a rolling bearing may be arranged between the guide member and the inner wall surface of the housing recess.

According to the present invention, direct sliding between the guide member and the inner wall surface of the housing recess can be suppressed. Therefore, it is possible to reduce frictional resistance between the internal gear that eccentrically oscillates with respect to the fixed member and the fixed member, thereby reducing power loss. Therefore, power transmission efficiency can be improved, and power can be efficiently transmitted from the input shaft to the output shaft without waste.

In the transmission device described above, the internal tooth may have a circular outer shape in a plan view seen from the axial direction, and may have a rotatable rolling element.

According to the present invention, since the internal teeth have rolling elements that can rotate on their own axes, the internal gears are arranged relative to the external gears so that the rolling elements sequentially get over the external teeth in the circumferential direction while the rolling elements are rotated. can be eccentrically oscillated. Therefore, frictional resistance between the internal gear and the external gear can be reduced, and power loss can be reduced. Therefore, power transmission efficiency can be improved, and power can be efficiently transmitted from the input shaft to the output shaft without waste.

In the transmission device described above, the internal gear includes an internal gear plate arranged to face the external gear, and a pin projecting from the internal gear, and the rolling elements are formed in a cylindrical shape, It may be rotatably fitted around the pin.

ADVANTAGE OF THE INVENTION According to this invention, an external tooth can be made to point-contact with the outer peripheral surface of a cylindrical rolling element, and the frictional resistance between an internal gear and an external gear can be reduced effectively. Therefore, power transmission efficiency can be further improved.

In the transmission device described above, a bearing arranged around the eccentric axis is provided, the bearing includes an inner ring mounted on the input shaft, and the bearing is arranged so as to surround the inner ring from the outside in the radial direction, and the accommodating recess An outer ring mounted on the internal gear on the other side in the axial direction, and a plurality of balls held between the inner ring and the outer ring so as to be able to roll.

According to the present invention, the input shaft and the internal gear can be combined via the bearing, which is a ball bearing composed of the inner ring, the outer ring, and the balls. The internal gear can be smoothly eccentrically oscillated with the rotation. Moreover, since the outer ring is attached to the internal gear on the other side in the axial direction of the housing recess, the internal gear can be increased in diameter due to the mounting structure of the bearing. It is possible to effectively suppress the increase in the diameter of the Therefore, it is possible to reduce the size of the transmission device in the radial direction.

ADVANTAGE OF THE INVENTION According to this invention, it can be set as the transmission device which can be easily reduced in size, and can lead to cost reduction and improvement of maintainability.

1 is a perspective view showing a speed reducer according to a first embodiment; FIG. 1 is a longitudinal sectional view of a speed reducer according to a first embodiment; FIG. 3 is a cross-sectional view of a portion corresponding to line III-III of FIG. 2; FIG. 3 is a cross-sectional view of a portion corresponding to line IV-IV of FIG. 2; FIG. FIG. 3 is a cross-sectional view of a portion corresponding to the VV line in FIG. 2; It is a longitudinal cross-sectional view of a speed reducer according to a second embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a transmission device of the present invention will be described below with reference to the drawings. In the following description, the same reference numerals are given to components having the same or similar functions. Duplicate descriptions of these configurations may be omitted.

[First embodiment]
FIG. 1 is a perspective view showing a speed reducer according to the first embodiment. FIG. FIG. 2 is a vertical cross-sectional view of the speed reducer according to the first embodiment.
A speed reducer 1 shown in FIG. 1 is an example of a transmission device. As shown in FIGS. 1 and 2, the speed reducer 1 includes an input shaft 10, an internal gear 20 having a plurality of internal teeth 21, an external gear 40 having a plurality of external teeth 41, an output shaft 50, a casing 60 and .

The input shaft 10 and the output shaft 50 are arranged so that their central axes are positioned on a common common axis. In the present embodiment, this common axis is referred to as the rotation axis O1 (the axis according to the present invention), and the direction along the rotation axis O1 is referred to as the axial direction, which intersects the rotation axis O1 in a plan view seen from the rotation axis O1 direction. The direction is called the radial direction, and the direction of rotation around the rotation axis O1 is called the circumferential direction. Further, of the axial directions, the direction from the input shaft 10 to the output shaft 50 is called upward, and the opposite direction is called downward.

As shown in FIG. 2, casing 60 is a stationary system. The casing 60 includes an upper case 61 and a lower case 65 (fixing members) integrally combined with each other. The upper case 61 and the lower case 65 are arranged so that an accommodation space for accommodating the internal gear 20 and the external gear 40 is formed therebetween.

The upper case 61 includes an upper plate 62 that defines the housing space from above, and a peripheral wall portion 63 that protrudes downward from the outer edge of the upper plate 62 and defines the housing space from the outside in the radial direction. The upper plate 62 is formed in a square shape in plan view so as to center on the rotation axis O1 (see FIG. 1). An upper through-hole 64 is formed in the center of the upper plate 62 so as to penetrate the upper plate 62 in the axial direction. The upper through-hole 64 is formed in a circular shape centered on the rotation axis O1 in plan view. An axially outer end (upper end) of the upper through-hole 64 is provided with an enlarged diameter portion 64 a whose inner diameter is enlarged stepwise. The peripheral wall portion 63 extends all around the rotation axis O1. In this embodiment, the peripheral wall portion 63 is formed in a square tubular shape.

The lower case 65 is arranged below the upper case 61 . The lower case 65 defines an accommodation space from below and is arranged to face the internal gear 20 from below. The lower case 65 is formed in a square shape substantially the same as the outer shape of the upper plate 62 in plan view (see FIG. 1). The outer peripheral portion of the lower case 65 faces the lower edge of the peripheral wall portion 63 of the upper case 61 over the entire circumference. Between the outer peripheral portion of the lower case 65 and the lower edge of the peripheral wall portion 63 of the upper case 61, an O-ring 70 is interposed over the entire circumference.

A lower through hole 66 is formed in the center of the lower case 65 so as to axially penetrate the lower case 65 . The lower through hole 66 is formed in a circular shape centering on the rotation axis O1 in plan view. An axially outer end (lower end) of the lower through-hole 66 is provided with an enlarged diameter portion 66 a whose inner diameter is enlarged stepwise.

A housing recess 67 is opened in the upper surface of the lower case 65 . The housing recess 67 is formed in a portion of the lower case 65 that axially faces the internal gear 20 . A plurality of housing recesses 67 (four in this embodiment) are formed around the lower through hole 66 at equal angular intervals around the rotation axis O1 (see FIG. 5). The accommodation recess 67 is formed in a circular shape in plan view. The accommodation recess 67 extends downward with a predetermined inner diameter from the upper opening edge. The number of accommodation recesses 67 is not limited to four, and may be any number other than four.

The input shaft 10 is arranged along the axial direction so as to be rotatable about the rotation axis O1 with respect to the stationary system by power (torque) transmitted from the outside. The input shaft 10 is inserted through the lower through hole 66 of the lower case 65 . The input shaft 10 is made non-contact with the lower case 65 . The input shaft 10 is rotatably supported by the lower case 65 via an input side bearing 80 .

The input side bearing 80 is a rolling bearing. In this embodiment, the rolling bearing is a ball bearing having an inner ring, an outer ring arranged to surround the inner ring, and a plurality of balls held between the inner ring and the outer ring so as to be able to roll (described below. other rolling bearings). The input-side bearing 80 is attached to the input shaft 10 in such a manner that its upward movement is restricted. The input side bearing 80 is arranged inside the enlarged diameter portion 66 a of the lower through hole 66 . The outer ring 80o of the input-side bearing 80 abuts the axially inner end surface of the enlarged diameter portion 66a from the axially outer side. The outer ring 80o of the input-side bearing 80 is restricted from dropping out of the lower through-hole 66 by the lower restricting member 71 . The lower regulating member 71 overlaps the lower surface of the lower case 65 and is fixed to the lower case 65 . The lower regulating member 71 is formed in an annular shape and arranged coaxially with the rotation axis O1. The inner peripheral portion of the lower regulating member 71 abuts the outer ring 80o of the input side bearing 80 from the outside in the axial direction. The lower regulating member 71 is made non-contact with the inner ring 80i of the input side bearing 80 and the input shaft 10 .

A lower seal member 11 is attached to the input shaft 10 . The lower seal member 11 is fixed to the input shaft 10 with set screws. The lower seal member 11 includes a cylindrical portion 12 fitted onto the input shaft 10, and a flange portion 13 that protrudes radially outward from the outer peripheral surface of the cylindrical portion 12 and extends over the entire circumference in the circumferential direction. The upper portion of the cylindrical portion 12 is surrounded by a lower restricting member 71 . The upper edge of the cylindrical portion 12 abuts on the inner ring 80i of the input side bearing 80 from the outside in the axial direction. As a result, the inner ring 80 i of the input side bearing 80 is axially fixed to the input shaft 10 , so that the input shaft 10 is axially fixed to the lower case 65 via the input side bearing 80 . The flange portion 13 faces the lower surface of the lower regulation member 71 . The flange portion 13 and the lower regulating member 71 form an axial labyrinth passage 14 therebetween.

An eccentric bearing 81 is mounted on the input shaft 10 . The eccentric bearing 81 is a rolling bearing. The eccentric bearing 81 is mounted above the input side bearing 80 and below the upper end of the input shaft 10 . The eccentric bearing 81 is arranged around an eccentric axis O2 radially eccentric with respect to the rotation axis O1. The eccentric bearing 81 overlaps at least one of the housing recesses 67 of the lower case 65 in plan view. An inner ring 81 i of the eccentric bearing 81 is attached to the input shaft 10 via an eccentric collar 90 .

An eccentric collar 90 is fitted onto the input shaft 10 . The eccentric collar 90 rotates together with the input shaft 10 . The eccentric collar 90 has an inner peripheral surface centered on the rotation axis O1 and an outer peripheral surface centered on the eccentric axis O2. An outer flange 91 projecting outward is provided at the lower end of the outer peripheral surface. An inner ring 81 i of the eccentric bearing 81 is attached to the outer peripheral surface of the eccentric collar 90 .

The inner ring 81i of the eccentric bearing 81 includes an annular first inner ring portion 81i1 and a second inner ring portion 81i2. The first inner ring portion 81i1 is fitted over the eccentric collar 90 and abuts against the outer flange 91 from above. The second inner ring portion 81i2 is fitted over the eccentric collar 90 above the first inner ring portion 81i1. The first inner ring portion 81i1 and the second inner ring portion 81i2 are integrally combined with each other via the eccentric collar 90 by press-fitting the eccentric collar 90 inside each. Between the first inner ring portion 81i1 and the second inner ring portion 81i2, a V-shaped annular groove in longitudinal cross-section is formed, which serves as the raceway surface of the inner ring 81i.

The internal gear 20 is arranged between the upper case 61 and the lower case 65 . The internal gear 20 is arranged around the eccentric axis O2 and operates as the input shaft 10 rotates. The internal gear 20 is kept out of contact with the casing 60 . The internal gear 20 has a plurality of internal teeth 21 circumferentially spaced around the eccentric axis O2.

The internal gear 20 includes an internal gear plate 22 whose outer shape is circular in plan view, an annular gear wall portion 26 that protrudes upward from the outer peripheral edge of the internal gear plate 22 over the entire circumference, a guide member 30 protruding downward from the internal gear plate 22; The internal gear plate 22 is arranged inside the peripheral wall portion 63 of the upper case 61 so as to axially face the lower case 65 . The gear wall portion 26 protrudes from the upper surface of the internal gear plate 22 toward the upper plate 62 side of the upper case 61 and extends along the outer peripheral edge of the internal gear plate 22 .

FIG. 3 is a cross-sectional view taken along line III-III of FIG.
As shown in FIGS. 2 and 3, a through hole 23 is formed in the central portion of the internal gear plate 22 so as to penetrate the internal gear plate 22 in the axial direction. The entire inner peripheral surface of the through-hole 23 is formed in a circular cross-section centered on the eccentric axis O2 in a plan view. An end portion (lower end portion) of the through hole 23 on the side of the lower case 65 is provided with an enlarged diameter portion 23a whose inner diameter is enlarged in a stepped manner. An outer ring 81o of an eccentric bearing 81 is fitted in the enlarged diameter portion 23a. Thereby, the internal gear 20 is rotatable about the eccentric axis O<b>2 with respect to the input shaft 10 .

A pin hole 24 and a shaft recess 25 are formed in the internal gear plate 22 . The pin hole 24 axially penetrates the internal gear plate 22 . However, the pin holes 24 need only open to the upper surface of the internal gear plate 22 . The pin holes 24 are formed inside the gear wall portion 26 in plan view and at positions corresponding to the internal teeth 21 in the circumferential direction around the eccentric axis O2. A shaft recess 25 is formed in the lower surface of the internal gear plate 22 . The shaft recess 25 is formed at a position overlapping the housing recess 67 in plan view. A shaft recess 25 is formed on the eccentric axis O2 side with respect to the pin hole 24 . In the illustrated example, a through-hole that axially penetrates the internal gear plate 22 is opened in the bottom surface of the shaft concave portion 25, but this through-hole may not be formed.

FIG. 4 is a cross-sectional view taken along line IV-IV of FIG.
As shown in FIGS. 2 and 4, inside the gear wall portion 26, a plurality of internal teeth 21 are provided at equal angular intervals around the eccentric axis O2 over the entire circumference of the gear wall portion 26. It is Each internal tooth 21 protrudes from the gear wall portion 26 toward the eccentric axis O2. A tooth surface of each internal tooth 21 extends in an arc shape in plan view. Each internal tooth 21 has a roller 27 as a rotatable rolling element forming a tooth surface.

The roller 27 is formed in a cylindrical shape. Roller 27 is rotatably supported by roller pin 28 . The roller pin 28 is formed in a cylindrical shape extending in the axial direction and is press-fitted into the pin hole 24 of the internal gear plate 22 . The roller pins 28 are arranged so that their lower ends do not protrude downward from the bottom surface of the internal gear plate 22 and their upper ends protrude upward from the top surface of the internal gear plate 22 . The upper end of the roller pin 28 is provided with a diameter-reduced portion 28a whose outer diameter is reduced stepwise. A roller 27 is rotatably fitted around the reduced diameter portion 28a. Thereby, the rollers 27 are rotatable with respect to the internal gear plate 22 . The upper edge of the roller 27 is located above the upper edge of the roller pin 28 . The internal teeth 21 having the rollers 27 configured as described above are formed to have 31 teeth (ie, 31 rollers 27).

As shown in FIG. 2, a pressing member 29 is superimposed on the gear wall portion 26 from above. The pressing member 29 is formed in an annular shape coaxial with the eccentric axis O2. The pressing member 29 is attached to the upper end portion of the gear wall portion 26 . The pressing member 29 overlaps at least a portion of each roller 27 when viewed from above. As a result, each roller 27 is restricted from dropping upward from the roller pin 28 .

Guide member 30 controls the behavior of internal gear 20 in combination with casing 60 . Specifically, the guide member 30 restrains the rotation of the internal gear 20 and guides the internal gear 20 eccentrically oscillating with respect to the casing 60 about the rotation axis O1 by restraining the rotation.

5 is a cross-sectional view taken along line VV of FIG. 2. FIG.
As shown in FIGS. 2 and 5, the guide members 30 are provided corresponding to the number of the housing recesses 67 formed in the lower case 65 . That is, in this embodiment, four guide members 30 are provided. The guide member 30 is formed to protrude from the internal gear plate 22 toward the lower case 65 . The guide member 30 is formed in a cylindrical shape and is inserted into the shaft recess 25 of the internal gear plate 22 from below. The upper end of the guide member 30 abuts against the bottom surface of the shaft recess 25 from below. The guide member 30 is arranged closer to the eccentric axis O<b>2 than the roller pin 28 .

The guide member 30 is inserted into a housing recess 67 formed in the lower case 65 . The guide member 30 does not come into contact with the inner surface of the housing recess 67 . The guide member 30 is arranged eccentrically with respect to the center line of the housing recess 67 by the amount of eccentricity of the eccentric axis O2 with respect to the rotation axis O1. The guide member 30 includes a mounted portion 31 to which the guide bearing 82 is mounted below the internal gear 20, and a collar portion 32 adjacent to the mounted portion 31 below and having a larger outer diameter than the mounted portion 31. Prepare. The collar portion 32 is positioned at the lower end of the guide member 30 .

Guide bearing 82 is a rolling bearing. The guide bearing 82 is attached to the attached portion 31 of the guide member 30 . An inner ring 82i of the guide bearing 82 is abutted against the flange portion 32 from above. The guide bearing 82 is kept out of contact with the internal gear plate 22 . The guide bearing 82 is arranged between the guide member 30 and the inner wall surface of the housing recess 67 . The outer diameter of the guide bearing 82 is smaller than the inner diameter of the housing recess 67 . The guide bearing 82 is mounted on the guide member 30 so as to be eccentric with respect to the center line of the housing recess 67 by the amount of eccentricity of the eccentric axis O2 with respect to the rotation axis O1. . The outer ring 82o of the guide bearing 82 contacts the inner peripheral surface of the housing recess 67 at one point in plan view.

As shown in FIG. 2, the output shaft 50 is arranged along the axial direction and is rotatable about the rotation axis O1 with respect to the stationary system. The output shaft 50 is inserted through the upper through hole 64 of the upper case 61 . The output shaft 50 is kept out of contact with the upper case 61 . The output shaft 50 is rotatably supported by the upper case 61 via an output side bearing 83 .

The output side bearing 83 is a rolling bearing. The output-side bearing 83 is attached to the output shaft 50 in such a manner that its downward movement is restricted. The output side bearing 83 is arranged inside the enlarged diameter portion 64 a of the upper through hole 64 . The outer ring 83o of the output-side bearing 83 abuts the axially inner end surface of the enlarged diameter portion 64a from the axially outer side. The outer ring 83o of the output-side bearing 83 is restricted from coming off from the upper through-hole 64 by the upper restricting member 72. As shown in FIG. The upper regulation member 72 overlaps the upper surface of the upper case 61 and is fixed to the upper case 61 . The upper regulating member 72 is formed in an annular shape and arranged coaxially with the rotation axis O1. The inner peripheral portion of the upper regulating member 72 abuts the outer ring 83o of the output side bearing 83 from the outside in the axial direction. The upper restricting member 72 is made non-contact with the inner ring 83i of the output side bearing 83 and the output shaft 50 .

The inner ring 83i of the output-side bearing 83 includes an annular first inner ring portion 83i1 and a second inner ring portion 83i2. The first inner ring portion 83i1 is fitted over the output shaft 50 and abuts against the step surface of the output shaft 50 from the outside in the axial direction. The second inner ring portion 83i2 is fitted onto the output shaft 50 axially outside the first inner ring portion 83i1. The first inner ring portion 83i1 and the second inner ring portion 83i2 are integrally combined with each other via the output shaft 50 by press-fitting the output shaft 50 inside them. Between the first inner ring portion 83i1 and the second inner ring portion 83i2, a V-shaped annular groove in longitudinal cross-section is formed, which serves as the raceway surface of the inner ring 83i.

An upper sealing member 55 is attached to the output shaft 50 . The upper seal member 55 is fixed to the output shaft 50 with a set screw. The upper seal member 55 includes a cylindrical portion 56 fitted onto the output shaft 50 and a flange portion 57 that protrudes radially outward from the outer peripheral surface of the cylindrical portion 56 and extends over the entire circumference in the circumferential direction. A lower portion of the cylindrical portion 56 is surrounded by an upper restricting member 72 . A lower edge of the cylindrical portion 56 abuts on the second inner ring portion 83i2 of the output side bearing 83 from the outside in the axial direction. As a result, the first inner ring portion 83i1 and the second inner ring portion 83i2 of the output side bearing 83 are axially fixed to the output shaft 50, so that the output shaft 50 is attached to the upper case 61 via the output side bearing 83. Axially fixed. The flange portion 57 faces the upper surface of the upper restricting member 72 . The flange portion 57 and the upper restricting member 72 form an axial labyrinth passage 58 therebetween.

A concave portion 51 that is recessed upward is formed in the lower end surface of the output shaft 50 . The concave portion 51 is formed in a circular shape centering on the rotation axis O1 in plan view. An intermediate bearing 84 is arranged in the recess 51 . Intermediate bearing 84 is a rolling bearing. An outer ring 84 o of the intermediate bearing 84 is fitted into the recess 51 . The inner ring 84i of the intermediate bearing 84 is attached to the upper end portion of the input shaft 10 . Thereby, the output shaft 50 is connected to the input shaft 10 via the intermediate bearing 84 . The output shaft 50 includes a lower end portion 52 to which the external gear 40 is mounted, and a flange 53 adjacent to the lower end portion 52 and projecting radially outward inside the casing 60 . The external gear 40 attached to the lower end portion 52 is abutted against the lower surface of the flange 53 .

The external gear 40 is arranged between the upper case 61 and the lower case 65 . The external gear 40 is arranged closer to the upper plate 62 than the internal gear 20 is. The external gear 40 is arranged inside the gear wall portion 26 of the internal gear 20 . The external gear 40 is arranged around the rotation axis O1 and is rotatable about the rotation axis O1. The external gear 40 is made non-contact with the casing 60 .

As shown in FIGS. 2 and 4 , the external gear 40 has a plurality of external teeth 41 that are inscribed and can mesh with the plurality of internal teeth 21 . A fitting hole 42 axially penetrating the external gear 40 is formed at the center of the external gear 40 coaxially with the rotation axis O1. A lower end portion 52 of the output shaft 50 is inserted into the fitting hole 42 . An engagement pin 43 is fixed to the external gear 40 so as to protrude toward the flange 53 of the output shaft 50 (upward). The engagement pin 43 is inserted into a notch 53a formed in the flange 53, and is restricted from being displaced relative to the flange 53 about the rotation axis O1. As a result, the external gear 40 cannot rotate with respect to the output shaft 50 and rotates integrally with the output shaft 50 about the rotation axis O1.

The plurality of external teeth 41 are arranged at equal angular intervals around the rotation axis O1. The external teeth 41 are arranged so that the number of teeth is different from that of the internal teeth 21 (31 teeth). Specifically, the external teeth 41 are arranged to have 30 teeth, which is one less than the internal teeth 21 . Furthermore, the external teeth 41 of this embodiment have a tooth profile along a trochoid curve, that is, a so-called trochoid tooth profile. This allows the rollers 27 of the plurality of internal teeth 21 and the plurality of external teeth 41 to be in constant contact.

(Action of reducer)
Next, a case of operating the speed reducer 1 configured as described above will be described.
In this case, for example, when power from an external drive source (for example, a stepping motor or the like) is transmitted to the input shaft 10, the input shaft 10 rotates around the rotation axis O1. As a result, the inner ring 81i of the eccentric bearing 81 rotates eccentrically about the rotation axis O1, and the internal gear 20 tries to rotate eccentrically together with the inner ring 81i of the eccentric bearing 81.

Here, the guide member 30 of the internal gear 20 is inscribed in the inner wall surface of the accommodation recess 67 of the lower case 65 via the guide bearing 82 arranged in the accommodation recess 67 . As a result, the internal gear 20 is restrained from rotating by the guide member 30 and the housing recess 67 of the lower case 65 . The guide member 30 is eccentric with respect to the center line of the housing recess 67 by the amount of eccentricity of the eccentric axis O2 with respect to the rotation axis O1. Therefore, when the internal gear 20 is about to rotate eccentrically, the relative rotation of the inner ring 81i and the outer ring 81o of the eccentric bearing 81 causes the translational component of the eccentric rotation of the inner ring 81i to be taken out. It oscillates eccentrically.

When the internal gear 20 eccentrically oscillates about the rotation axis O1, the internal teeth 21 sequentially get over the external teeth 41 in the circumferential direction while the external teeth 41 are inscribed in the internal teeth 21. The internal gear 20 eccentrically oscillates with respect to the external gear 40 . Each time the internal teeth 21 get over the external teeth 41 due to the eccentric oscillation of the internal gear 20, the internal gear 20 presses the external teeth 41 in the circumferential direction via the internal teeth 21, causing the external gear 40 to rotate. be able to.

As described above, the power transmitted to the input shaft 10 is transmitted to the internal gear 20 to cause the internal gear 20 to eccentrically oscillate. Power can be transmitted to the gear 40 . As a result, the external gear 40 and the output shaft 50 can be rotated about the rotation axis O<b>1 in a direction opposite to the rotation direction of the input shaft 10 . In particular, since the number of teeth of the external teeth 41 (30 teeth) and the number of teeth of the internal teeth 21 (31 teeth) are different, it is possible to decelerate the external gear 40 by the angular difference of the number of teeth. As a result, the output shaft 50 can be rotated while being decelerated with respect to the rotation of the input shaft 10 .

In particular, the speed reducer 1 of the present embodiment differs from conventional speed reducers and the like in that the internal gear 20 side is eccentrically oscillated. can be done. Therefore, for example, it is not necessary to extract only the rotation component of the external gear 40, and power can be transmitted directly from the external gear 40 to the output shaft 50 to rotate the output shaft 50 around the rotation axis O1.
Therefore, the structure can be made simple with a reduced number of parts, and the size of the entire speed reducer 1 can be reduced. In addition, it can lead to cost reduction and improvement of maintainability.

By the way, in order to allow the eccentric oscillation of the internal gear 20 having the guide member 30, the accommodation recess 67 is formed larger than the guide member 30 on the cross section of the speed reducer 1 (on the cross section perpendicular to the axial direction). be. Here, instead of the guide member 30 and the housing recess 67 of the present embodiment, the casing is provided with a guide member projecting toward the internal gear, and the internal gear is provided with a housing recess for receiving the guide member. Similarly, a configuration is obtained in which the rotation of the internal gear is restrained and the eccentric oscillation of the internal gear is allowed. Compared to this configuration, according to the present embodiment, the internal gear 20 can be formed with a smaller diameter because the internal gear 20 is not formed with a housing recess. Therefore, it is possible to reduce the size of the speed reducer 1 in the radial direction.

As described above, according to the speed reducer 1 of the present embodiment, it is easy to achieve miniaturization, which can lead to cost reduction and improvement of maintainability.
In particular, since the speed reducer 1 can be easily miniaturized, it can be suitably used for small parts in various fields. For example, the speed reducer 1 can be used in various devices that move small moving parts (for example, industrial robots, robot arms, robot hands, medical support devices that support the movement of patients, home appliances, AV devices, etc.). It can be used suitably.

Furthermore, in this embodiment, since the guide bearing 82 is arranged between the guide member 30 and the inner wall surface of the accommodation recess 67, direct sliding between the guide member 30 and the inner wall surface of the accommodation recess 67 can be suppressed. . Therefore, it is possible to reduce the frictional resistance between the internal gear 20 eccentrically oscillating with respect to the lower case 65 and the lower case 65, thereby reducing the power loss. Therefore, power transmission efficiency can be improved, and power can be efficiently transmitted from the input shaft 10 to the output shaft 50 without waste.

The internal tooth 21 has a circular outer shape in plan view and has a roller 27 that can rotate. According to this configuration, the internal gear 20 can be eccentrically oscillated with respect to the external gear 40 so that the rollers 27 sequentially get over the external teeth 41 in the circumferential direction while the rollers 27 are rotated. Therefore, frictional resistance between the internal gear 20 and the external gear 40 can be reduced, and power loss can be reduced. Therefore, power transmission efficiency can be improved, and power can be efficiently transmitted from the input shaft 10 to the output shaft 50 without waste.

Further, the roller 27 is formed in a cylindrical shape and provided rotatably. According to this configuration, the external teeth 41 can be brought into point contact with the outer peripheral surface of the cylindrical roller 27, and the frictional resistance between the internal gear 20 and the external gear 40 can be effectively reduced. Therefore, power transmission efficiency can be further improved.

The speed reducer 1 includes an eccentric bearing 81, which is a ball bearing arranged around the eccentric axis O2. ing. According to this configuration, the input shaft 10 and the internal gear 20 can be combined via the ball bearings, so that the ease of assembly can be improved, and the internal gear 20 can be smoothly rotated as the input shaft 10 rotates. can be eccentrically oscillated. Moreover, since the outer ring 81o is mounted on the internal gear 20 above the housing recess 67, the housing recess 67 is formed in the lower case 65 when the internal gear 20 can be increased in diameter due to the mounting structure of the eccentric bearing 81. Therefore, an increase in the diameter of the internal gear 20 can be effectively suppressed. Therefore, it is possible to reduce the size of the speed reducer 1 in the radial direction.

[Second embodiment]
Next, a second embodiment will be described with reference to FIG. The second embodiment differs from the first embodiment in that the internal gear 20A includes balls 34 instead of the rollers 27 and roller pins 28 of the first embodiment. Configurations other than those described below are the same as those of the first embodiment.

FIG. 6 is a vertical cross-sectional view of a speed reducer according to the second embodiment.
As shown in FIG. 6, each internal tooth 21 has a ball 34 as a rotatable rolling element forming a tooth surface. Further, the inner peripheral surface of the gear wall portion 26 is formed with a ball accommodating portion 35 that accommodates and rotatably holds the balls 34 one by one. The balls 34 are accommodated in the ball accommodating portions 35 while being placed on the upper surface of the internal gear plate 22, and are rotatably held by the ball accommodating portions 35 without protruding radially inward. The balls 34 protrude radially inward from the inner peripheral surface of the gear wall portion 26 and are capable of contacting and meshing with the external teeth 41 of the external gear 40 .

As described above, according to the speed reducer 1A of the present embodiment, since the roller pin 28 of the speed reducer 1 of the first embodiment is not provided, the pin hole is not formed in the internal gear 20A. can be Therefore, according to the speed reducer 1A of the present embodiment, further miniaturization can be achieved.

It should be noted that the present invention is not limited to the above-described embodiments described with reference to the drawings, and various modifications are conceivable within its technical scope.
For example, in the above embodiment, the number of teeth of the internal teeth 21 is 31 and the number of teeth of the external teeth 41 is 30. may be changed as appropriate.

Further, in the above embodiment, the inner ring 82i of the guide bearing 82 is attached to the guide member 30, but the configuration is not limited to this. The guide bearing may be arranged such that the outer ring is fitted into the housing recess 67 and the outer peripheral surface of the guide member 30 is inscribed at one point on the inner peripheral surface of the inner ring. Further, the outer peripheral surface of the guide member may be inscribed at one point on the inner peripheral surface of the housing recess without arranging the guide bearing 82 .

Further, although each bearing is a ball bearing in the above embodiment, the present invention is not limited to this configuration. Each bearing may be a roller bearing or a slide bearing.

Further, in the above embodiment, the guide member 30 is described as the guide member according to the present invention, but the guide bearing 82 may be included in the guide member according to the present invention. Further, in a modification in which the guide bearing is fitted into the accommodation recess, the inside of the guide bearing may be the accommodation recess according to the present invention.

In addition, it is possible to appropriately replace the components in the above-described embodiments with well-known components without departing from the scope of the present invention, and the above-described embodiments may be combined as appropriate.

DESCRIPTION OF SYMBOLS 1, 1A... Reduction gear (transmission device) 10... Input shaft 20, 20A... Internal gear 21... Internal tooth 22... Internal gear plate 27... Roller (rolling element) 28... Roller pin (pin) 30... Guide member 34... Ball ( Rolling element) 40 External gear 41 External tooth 50 Output shaft 65 Lower case (fixed member) 67 Housing recess 81 Eccentric bearing (bearing) 81i Inner ring 81o Outer ring 82 Guide bearing (rolling bearing) O1 Axis of rotation (axis) O2... Eccentric axis

Claims (5)

an input shaft that rotates about its axis by the transmitted power;
A plurality of internal teeth arranged around an eccentric axis eccentric with respect to the axis, operating as the input shaft rotates, and spaced apart in a circumferential direction orbiting around the eccentric axis. , and an internal gear having a guide member protruding on one side in the axial direction;
a plurality of external teeth arranged to face the internal gear on the other side in the axial direction, arranged rotatably about the axis, and meshable with the plurality of internal teeth; , an external gear in which the number of teeth of the plurality of external teeth is different from the number of teeth of the plurality of internal teeth;
an output shaft that rotates around the axis as the external gear rotates;
a fixing member arranged to face the internal gear on the one side in the axial direction;
with
The fixed member is formed with a housing recess that receives the guide member so as to constrain rotation of the internal gear and allow eccentric oscillation of the internal gear about the axis.
transmission device. A rolling bearing is arranged between the guide member and the inner wall surface of the housing recess,
A transmission according to claim 1. The internal tooth has a circular outer shape in a plan view seen from the axial direction, and has a rolling element that can rotate.
The transmission device according to claim 1 or 2. The internal gear is
an internal gear plate arranged to face the external gear;
a pin protruding from the internal gear;
with
The rolling element is formed in a cylindrical shape and is rotatably fitted around the pin,
A transmission according to claim 3. a bearing centered about the eccentric axis;
The bearing is
an inner ring mounted on the input shaft;
an outer ring arranged to surround the inner ring from the outside in the radial direction and mounted on the internal gear on the other side in the axial direction relative to the housing recess;
a plurality of balls rotatably held between the inner ring and the outer ring;
comprising
A transmission according to any one of claims 1 to 4.

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