CN112128318A

CN112128318A - Speed reducer

Info

Publication number: CN112128318A
Application number: CN202010160038.0A
Authority: CN
Inventors: 镰形州一; 三好洋之
Original assignee: Nabtesco Corp
Current assignee: Nabtesco Corp
Priority date: 2019-06-25
Filing date: 2020-03-10
Publication date: 2020-12-25
Also published as: JP2021004611A; JP7440218B2

Abstract

The invention provides a speed reducer. The speed reducer according to an aspect of the present invention includes: a housing having internal teeth; an external gear having external teeth meshing with the internal teeth and a through hole; a crankshaft provided in the through hole; and a crankshaft bearing. The crankshaft bearing includes: a retainer whose movement in the axial direction of the crankshaft is restricted by the external gear; and a rolling element held by the cage in the through hole.

Description

Speed reducer

Technical Field

The present invention relates to a speed reducer.

Background

Reduction gears are used in industrial robots, machine tools, and various machines other than these that operate by input torque. The decelerator decelerates rotation input from a drive source such as an electric motor and outputs the decelerated rotation to a device to be driven. As one type of reduction gear, an eccentric oscillating type reduction gear is known. A conventional eccentric oscillating type reduction gear is described in japanese patent application laid-open No. 5-180278.

The eccentric swinging type speed reducer comprises: a crankshaft having an eccentric body; an external gear attached to the crankshaft via the eccentric body; a housing having internal teeth meshing with the external gear; and a carrier provided to be rotatable relative to the casing. In such an eccentric oscillating type reduction gear, rotation from a drive source is transmitted from an input gear to a crankshaft. When the crankshaft rotates, the external gear is also pressed by the eccentric member and rotates. In response to the rotation of the external gear, the carrier rotates relative to the housing. Thereby, the decelerated rotation is output from the carrier or the casing to the other device.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 5-180278

Disclosure of Invention

Problems to be solved by the invention

The crankshaft is coupled to the external gear via a crankshaft bearing, and is supported by a carrier via a taper bearing. Conventional speed reducers include washers to limit axial movement of the crankshaft bearings. The washer is provided, for example, between one axial end of the crankshaft bearing and the inner race of the tapered bearing. The movement of the washer in the axial direction is limited by the tapered bearing.

The conventional speed reducer has the following problems: the gasket that limits the movement of the crankshaft bearing in the axial direction wears.

The present invention has been made to solve or alleviate the above-described problems of the conventional art. It is a particular object of the present invention to provide a new speed reducer that is capable of supporting a crankshaft bearing without the problem of gasket wear. Objects of the invention other than those described above will become apparent by reference to the specification as a whole.

Means for solving the problems

The speed reducer according to an aspect of the present invention includes: a housing having internal teeth; an external gear having external teeth meshing with the internal teeth and a through hole; a crankshaft provided in the through hole; and a crankshaft bearing. The crankshaft bearing includes: a retainer whose movement in the axial direction of the crankshaft is restricted by the external gear; and a rolling element held by the cage in the through hole.

In one aspect of the present invention, the external gear has a bearing surface in a direction intersecting with an axial direction of the crankshaft, and the retainer is supported by the external gear at the bearing surface.

In one aspect of the present invention, the retainer has a flange in a direction intersecting with an axial direction of the crankshaft, and the retainer is supported by the support surface of the external gear at the flange.

In one aspect of the present invention, the retainer has a peripheral wall in a direction around the rotational axis of the crankshaft, and the flange is formed from the peripheral wall in a direction opposite to the rotational axis of the crankshaft.

A speed reducer according to an aspect of the present invention includes another external gear having external teeth that mesh with the internal teeth. In one aspect, the outer gear is disposed such that the bearing surface opposes the other outer gear.

A reduction gear according to an aspect of the present invention includes a carrier provided to be rotatable relative to the casing. In one aspect, the crankshaft is supported by the carrier via another crankshaft bearing, and the retainer is provided separately from the other crankshaft bearing.

The speed reducer according to an aspect of the present invention includes: a housing having internal teeth; an external gear having external teeth meshing with the internal teeth and a through hole; a crankshaft provided in the through hole; a crankshaft bearing having rolling elements held by a cage; a carrier provided to be rotatable relative to the casing; and another crankshaft bearing. The other crankshaft bearing includes an outer ring supported by the carrier, an inner ring that restricts movement of the cage in the axial direction of the crankshaft, and another rolling element provided between the inner ring and the outer ring.

In one aspect of the present invention, the retainer is in contact with the inner race over a range of 180 ° or more in a circumferential direction around the rotation axis of the crankshaft.

In one aspect of the present invention, the inner ring has a bearing surface that supports the cage, and the bearing surface of the inner ring has a vickers hardness of 650HV or more.

In one aspect of the present invention, the cage has an end surface that contacts the bearing surface of the inner ring, and a difference between a vickers hardness of the end surface of the cage and a vickers hardness of the bearing surface of the inner ring is 100HV or less.

ADVANTAGEOUS EFFECTS OF INVENTION

By adopting the technical scheme of the invention, the crankshaft bearing can be supported on the premise of not causing the problem of gasket abrasion.

Drawings

Fig. 1 is a cross-sectional view showing a section of a reduction gear according to an embodiment of the present invention, the section being taken along a rotation axis thereof.

Fig. 2 is an enlarged sectional view showing a crankshaft of the reduction gear of fig. 1 in an enlarged manner.

Fig. 3 is an enlarged cross-sectional view of a crankshaft of a reduction gear according to another embodiment of the present invention.

Fig. 4 is a cross-sectional view schematically showing the crankshaft of fig. 3 cut along line B-B.

Description of the reference numerals

1. 101, a speed reducer; 12. a crankshaft; 20. a speed reduction mechanism; 23a, 23b, an external gear; 23a1, 23b1, crankshaft through hole; 23a2, 23b2, external teeth; 23a4, 23b4, bearing surface; 24. a gear carrier; 25a, 25b, 125a, 125b, bearings; 27. a pin; 28. a housing; 31a, 31b, 131a, 131b, a holder; 31a4, 31b4, flange; a1, central axis; a2, axis.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. In addition, the same reference numerals are given to the components common to the respective drawings. It should be noted that for ease of illustration, the drawings are not necessarily drawn to scale.

A reduction gear 1 according to an embodiment of the present invention will be described with reference to fig. 1 and 2. Fig. 1 is a cross-sectional view showing a section of the reduction gear 1 along a central axis a1, and fig. 2 is an enlarged view showing a crankshaft 12 included in the reduction gear 1.

In these figures, an eccentric rocking type reduction gear 1 as one type of reduction gears to which the present invention can be applied is shown. The speed reducer 1 includes a spur gear 11, a crankshaft 12, and a speed reduction mechanism 20.

The spur gear 11 is an example of a rotation transmission mechanism that transmits rotation input from a drive source, not shown, to the crankshaft 12. The spur gear 11 may be meshed with an input gear to which rotation from a drive source is input. The rotation transmission mechanism applicable to the speed reducer 1 is not limited to the spur gear 11. As the rotation transmission mechanism for the speed reducer 1, any mechanism capable of transmitting an input from the drive source to the crankshaft 12 can be used.

The crankshaft 12 is a substantially cylindrical member extending along the axial center a 2. In the illustrated embodiment, the crankshaft 12 is spline-coupled to the spur gear 11. Thereby, the rotational input from the drive source is transmitted to the crankshaft 12 via the spur gear 11.

The speed reduction mechanism 20 reduces the speed of the rotation input from the crankshaft 12 and transmits the rotation to the other device to be driven. The decelerated rotation is output to the partner apparatus as rotation around the center axis a 1. The reducer 1 may also be provided in an industrial robot. In this case, the partner device to be driven is, for example, an arm of an industrial robot. The reduction mechanism 20 will be described in detail later.

Next, the crankshaft 12 will be described more specifically. The crankshaft 12 is a substantially cylindrical member extending along the axis a2, and rotates (spins) around the axis a2 by a rotational input transmitted from the spur gear 11. The crankshaft 12 has a1 st journal portion 12a, a2 nd journal portion 12b, an eccentric portion 12c, an eccentric portion 12d, and a head portion 12 e. The 1 st journal portion 12a, the 2 nd journal portion 12b, the eccentric portion 12c, the eccentric portion 12d, and the head portion 12e may be formed in one body. In other words, the 1 st journal portion 12a, the 2 nd journal portion 12b, the eccentric portion 12c, the eccentric portion 12d, and the head portion 12e may have an integral structure that does not move relative to each other in the circumferential direction around the axis a 2.

The 1 st journal portion 12a and the 2 nd journal portion 12b each have a cylindrical shape extending in the direction of the shaft center a 2. The 1 st journal portion 12a is supported by the carrier 24 (specifically, the 1 st carrier body 24a) by a bearing 25a, and the 2 nd journal portion 12b is supported by the carrier 24 (specifically, the 2 nd carrier body 24b) by a bearing 25 b.

The eccentric portion 12c is provided on the X2 side of the 1 st journal portion 12a in the axial center a2 direction. The eccentric portion 12d is provided on the X2 side of the eccentric portion 12c in the axis a2 direction. In one embodiment, the eccentric portion 12c and the eccentric portion 12d each have a cylindrical shape. In this case, the eccentric portion 12c and the eccentric portion 12d are circular portions having centers displaced in the radial direction from the axial center a2 when viewed in the direction of the axial center a 2. That is, the eccentric portion 12c and the eccentric portion 12d are eccentric with respect to the axial center a 2. The eccentric portion 12c and the eccentric portion 12d have phases different from each other. For example, the phase of the eccentric portion 12c and the phase of the eccentric portion 12d are shifted from each other by 180 °.

The head portion 12e is provided on the X1 side with respect to the 1 st journal portion 12a in the axial center a2 direction. That is, the head portion 12e is provided on the opposite side of the eccentric portion 12c with respect to the 1 st journal portion 12 a. The head portion 12e has a substantially cylindrical shape. The head portion 12e is spline-coupled to the spur gear 11.

Next, the details of the speed reducing mechanism 20 will be described more specifically. In the illustrated embodiment, the reduction mechanism 20 includes

external gears

23a and 23b, a carrier 24, and a case 28.

The

external gears

23a and 23b each have a substantially annular shape. A through hole extending along the center axis a1 is provided in the center of each of the

external gears

23a and 23 b. A cable, for example, is accommodated in the through hole extending along the center axis a 1. The external gear 23a has a crankshaft through hole 23a1, and the external gear 23b has a crankshaft through hole 23b 1. For simplicity of description, the crank through-hole 23a1 is simply referred to as the through-hole 23a1, and the crank through-hole 23b1 is simply referred to as the through-hole 23b 1. The through hole 23a1 is a through hole that penetrates the external gear 23a in the axial direction along the central axis a1 at a position shifted radially outward from the central axis a 1. The through hole 23b1 is a through hole that penetrates the external gear 23b in the axial direction along the central axis a1 at a position shifted radially outward from the central axis a 1. The crankshaft 12 is provided in the through hole 23a1 and the through hole 23b 1. The through hole 23a1 and the through hole 23b1 receive a part of the crankshaft 12. In the illustrated embodiment, the crankshaft 12 is configured to: the eccentric portion 12c is positioned in the through hole 23a1, and the eccentric portion 12d is positioned in the through hole 23b 1.

A crank bearing 30a is provided between the eccentric portion 12c and the through hole 23a1, and a crank bearing 30b is provided between the eccentric portion 12d and the through hole 23b 1. Thus, the external gear 23a is supported by the eccentric portion 12c of the crankshaft 12 by the crankshaft bearing 30a, and the external gear 23b is supported by the eccentric portion 12d of the crankshaft 12 by the crankshaft bearing 30 b. In the illustrated embodiment, the crankshaft bearing 30a and the crankshaft bearing 30b are needle bearings. The crank

bearings

30a and 30b may be other types of bearings than needle bearings.

The crankshaft bearing 30a includes a cage 31a and rolling elements 32a held by the cage 31 a. As shown in fig. 2, the holder 31a has: a peripheral wall 31a1 provided around the axis a 2; a holding portion 31a2 extending radially inward from the end of the peripheral wall 31a1 on the X1 side; another holding portion 31a3 extending radially inward from the end of the peripheral wall on the X2 side; and a flange 31a4 extending radially outward from the end of the peripheral wall 31a1 on the X2 side. The peripheral wall 31a1 may be formed to surround the axial center a 2. The flange 31a4 is located in the opposite direction of the axial center a2 with respect to the peripheral wall 31a 1. The holding portions 31a2, 31A3 and the flange 31a4 each extend in a direction intersecting the axial center a 2. The holding portions 31a2, 31A3 and the flange 31a4 extend in a direction orthogonal to the axial center a2, for example. In one embodiment, the flange 31a4 is disposed at a position facing the bearing surface 23a4 of the external gear 23 a. The bearing surface 23a4 of the external gear 23a is a surface of the external gear 23a facing the X2 direction. The bearing surface 23a4 of the external gear 23a extends in a direction intersecting the axial center a 2. The support surface 23a4 may extend in a direction perpendicular to the axis a 2.

In the illustrated embodiment, the crank bearing 30b is configured similarly to the crank bearing 30 a. Specifically, the crankshaft bearing 30b includes a cage 31b and rolling elements 32b held by the cage 31 b. The holder 31b has: a peripheral wall 31b1 provided around the axis a 2; a holding portion 31b2 extending radially inward from the end of the peripheral wall 31b1 on the X2 side; another holding portion 31b3 extending radially inward from the end of the peripheral wall on the X1 side; and a flange 31b4 extending radially outward from the end of the peripheral wall 31b1 on the X1 side. The peripheral wall 31b1 may be formed to surround the axial center a 2. The flange 31b4 is located in the opposite direction of the axial center a2 with respect to the peripheral wall 31b 1. The holding portions 31b2, 31b3 and the flange 31b4 each extend in a direction intersecting the axial center a 2. The holding portions 31b2, 31b3 and the flange 31b4 extend in a direction perpendicular to the axial center a2, for example. In one embodiment, the flange 31b4 is disposed at a position facing the bearing surface 23b4 of the external gear 23 b. The bearing surface 23b4 of the external gear 23b is a surface of the external gear 23b facing the X1 direction and extends in a direction intersecting the axial center a 2. The support surface 23b4 may extend in a direction perpendicular to the axis a 2.

In one embodiment, the bearing surfaces 23a4 of the external gears 23a face the bearing surfaces 23b4 of the external gears 23 b.

The end of the holder 31a on the X2 side thereof is in contact with the end of the holder 31b on the X1 side. In one embodiment, retaining portion 31a3 of retainer 31a is in contact with retaining portion 31b3 of retainer 31b and flange 31a4 of retainer 31a is in contact with flange 31b4 of retainer 31 b.

Since the retainer 31a is supported by the external gear 23a at the flange 31a4, the movement of the retainer in the X1 direction along the axial center a2 is restricted. Since the retainer 31b is supported by the external gear 23b at the flange 31b4, the movement of the retainer in the X2 direction along the axial center a2 is restricted. The end of the holder 31a on the X2 side is in contact with the end of the holder 31b on the X1 side, and therefore the movement of the holder 31a in the X2 direction is restricted by the holder 31 b. Similarly, the movement of the holder 31b in the X1 direction is restricted by the holder 31 a.

Specific shapes, structures, and arrangements of the holder 31a, the holder 31b, the support surface 23a4 supporting the holder 31a, and the support surface 23b4 supporting the holder 31b are not limited to the shapes, structures, and arrangements explicitly shown in the present specification and the drawings.

The

external gears

23a and 23b have through holes into which projections 24b2 of the 1 st gear frame body 24a described later are inserted. Specifically, the external gear 23a has a through hole 23A3 radially outward of the central axis a1, and the external gear 23b has a through hole 23b3 radially outward of the central axis a 1. The through hole 23a3 and the through hole 23b3 are provided at positions facing each other. In fig. 1, a single through hole 23a3 and a single through hole 23b3 are shown, but the external gear 23a may have a plurality of through holes 23a3, and the external gear 23b may have a plurality of through holes 23b 3.

The

external gears

23a, 23b each have external teeth. Specifically, the external gear 23a has external teeth 23a2, and the external gear 23b has external teeth 23b 2. The shapes of the external gear 23a and the external gear 23b2 viewed in the direction of the center axis a1 are, for example, cycloidal curves.

The housing 28 is provided radially outside the

external gears

23a and 23 b. The housing 28 has: a housing main body 28a having a hollow cylindrical shape; and a flange 28b provided radially outside the housing main body 28 a. The flange 28b has a bolt hole 28c extending parallel to the central axis a 1. The flange 28b is connected to a partner device (not shown) to be driven, for example. The partner device to be driven is, for example, an arm of an industrial robot. The device to be driven can be coupled to the flange 28b by bolts.

A plurality of grooves 28a1 extending along the center axis a1 are formed in the inner peripheral surface of the case main body 28 a. In other words, the housing body 28a has a plurality of slots 28a1 extending along the central axis a 1. The plurality of grooves 28a1 are provided with pins 27, respectively. The number of pins 27 is different from the number of teeth of the

external gears

23a, 23 b. In the illustrated embodiment, the number of pins 27 is one more than the number of teeth of the

external gears

23a, 23 b. The pin 27 is an example of internal teeth that mesh with the external teeth 23a2 of the external gear 23a and the external teeth 23b2 of the external gear 23 b.

A carrier 24 is provided radially inside the casing 28. The carrier 24 is provided to be rotatable relative to the casing 28. The carrier 24 has a1 st carrier body 24a and a2 nd carrier body 24 b. The 1 st carrier body 24a is provided closer to the X1 side than the 2 nd carrier body 24b in the axial direction along the center axis a 1. The 1 st and 2 nd

gear frame bodies

24a and 24b are coupled by bolts 26. A gap is provided between the 1 st and 2 nd

gear frame bodies

24a and 24 b. The

external gears

23a and 23b are disposed in a gap between the 1 st and 2 nd

gear frame bodies

24a and 24 b.

The 1 st gear frame body 24a has a substantially circular disk shape. The 2 nd carrier body 24b has: a base portion 24b1 having a generally disc shape; and a protrusion 24b2 protruding in the X1 direction at a position radially outward of the central axis a 1. The protrusion 24b2 is provided with a bolt hole into which the bolt 26 is inserted.

The 1 st gear frame body 24a is supported by the housing 28 via a main bearing 29 a. The 2 nd gear frame body 24b is supported by the housing 28 via a main bearing 29 b. Thus, the 1 st and 2

nd carrier bodies

24a, 24b are mounted for relative rotation with respect to the housing 28. Since the 1 st carrier body 24a and the 2 nd carrier body 24b are coupled by the bolts 26, the 1 st carrier body 24a and the 2 nd carrier body 24b rotate integrally relative to the housing 28.

The 1 st and 2 nd

gear frame bodies

24a and 24b are respectively provided with through holes into which the crankshaft 12 is inserted. The crankshaft 12 is supported by the 1 st carrier body 24a via a bearing 25a and is supported by the 2 nd carrier body 24b via a bearing 25 b. Thus, the crankshaft 12 is able to rotate relative to the 1 st and 2

nd carrier bodies

24a, 24 b.

The bearing 25a has: an outer race 25a1 attached to the 1 st gear carrier body 24 a; an inner race 25a2 attached to the 1 st journal portion 12a of the crankshaft 12; and a rolling element 25a3 provided between the outer ring 25a1 and the inner ring 25a 2. Movement of the outer ring 25a1 in the X1 direction is restricted by the stopper ring 25a 4. The bearing 25b is configured substantially similarly to the bearing 25 a. Specifically, the bearing 25b includes: an outer race 25b1 mounted to the 2 nd gear carrier body 24 b; an inner race 25b2 attached to the 2 nd journal portion 12b of the crankshaft 12; and a rolling element 25b3 provided between the outer ring 25b1 and the inner ring 25b 2. Movement of the outer ring 25b1 in the X2 direction is restricted by the stopper ring 25b 4. The

bearings

25a and 25b are tapered roller bearings, for example.

The bearing 25a is provided at a position apart from the holding portion 31a2 in the X1 direction so as to provide a gap Ga with the holding portion 31a 2. In one embodiment, gap Ga extends 360 ° about axis a 2. The bearing 25b is provided at a position separated from the holding portion 31b2 in the X2 direction so as to form a gap Gb with the holding portion 31b 2. In one embodiment, the gap Gb extends 360 ° around the axis a 2. This allows the lubricant to smoothly flow into the crankshaft 12 from the gap Ga and the gap Gb.

In one embodiment, carrier 24 is connected to other components to limit the rotation of carrier 24. When the housing 28 is coupled to an arm of an industrial robot, for example, the carrier 24 is connected to a base of the industrial robot, and rotation of the carrier 24 is restricted. The base of the industrial robot fixes the industrial robot to a fixed surface such as a floor in an installation place of the industrial robot. In another embodiment, the housing 28 is connected to other components to limit the rotation of the housing 28.

Next, the operation of the reducer 1 will be described. When the spur gear 11 is rotated by a rotational driving force from the driving source, the rotation is transmitted from the head 12e meshing with the spur gear 11 to the crankshaft 12. The eccentric portion 12c and the eccentric portion 12d of the crankshaft 12 eccentrically rotate about the axis a2 by the rotation input from the drive source. Therefore, when the crankshaft 12 rotates one revolution, the

external gears

23a, 23b rotate relative to the housing 28 by an amount corresponding to the difference between the number of pins 27 of the housing 28 and the number of teeth of the

external gears

23a, 23 b. When the rotation of the carrier 24 is restricted, the housing 28 rotates by the difference between the number of pins 27 and the number of teeth of the

external gears

23a and 23b, that is, by one tooth. In this way, the rotation of the crankshaft 12 is decelerated at a reduction gear ratio of (the number of teeth of the

external gears

23a, 23 b)/(the number of pins 27 — the number of teeth of the

external gears

23a, 23 b) and then transmitted to the housing 28.

As described above, the rotation input from the drive source is reduced in the speed reduction ratio described above by the speed reduction mechanism 20, and then output from the housing 28 to the partner device.

Next, a reduction gear 101 according to another embodiment of the present invention will be described with reference to fig. 3 and 4. A reduction gear 101 according to another embodiment of the present invention is different from the reduction gear 1 in that: it includes crankshaft bearing 130a instead of crankshaft bearing 30a, crankshaft bearing 130b instead of crankshaft bearing 30b, bearing 125a instead of bearing 25a, and bearing 125b instead of bearing 25 b. Of the components of the speed reducer 101 shown in fig. 3 and 4, those components that are the same as or similar to those of the speed reducer 1 shown in fig. 1 are given the same reference numerals as or similar to those of fig. 1, and detailed description of those components that are the same as or similar to those of fig. 1 is omitted. The components of the speed reducer 101 other than the crank bearing 130a, the crank bearing 130b, the bearing 125a, and the bearing 125b may be the same as those of the speed reducer 1.

In the reduction gear 101 shown in fig. 3, the crankshaft bearing 130a includes a retainer 131a and rolling elements 32a retained by the retainer 131 a. The holder 131a has: a peripheral wall 131a1 extending about the axis a 2; a holding portion 131a2 extending radially inward from the end of the peripheral wall 131a1 on the X1 side; and another holding portion 131a3 extending radially inward from the end of the peripheral wall on the X2 side. In the illustrated embodiment, unlike the retainer 31a, the retainer 131a does not have a flange extending radially outward from the end of the peripheral wall on the X2 side. The retainer 131a may have a flange extending radially outward from the end of the peripheral wall 131a1 on the X2 side. The peripheral wall 131a1, the one holding portion 131a2, and the other holding portion 131a3 are configured similarly to the peripheral wall 31a1, the one holding portion 31a2, and the other holding portion 31a3 of the holder 31a, respectively.

The crank bearing 130b is configured similarly to the crank bearing 130 a. Specifically, the crankshaft bearing 130b includes a retainer 131b and rolling elements 32b retained by the retainer 131 b. The holder 131b has: a peripheral wall 131b1 extending about the axis a 2; a holding portion 131b2 extending radially inward from the end of the peripheral wall on the X2 side; and another holding portion 131b3 extending radially inward from the end of the peripheral wall on the X1 side. In the illustrated embodiment, unlike the holder 31b, the holder 131b does not have a flange extending radially outward from the end of the peripheral wall on the X1 side. In another embodiment, the retainer 131b may have a flange extending radially outward from the end of the peripheral wall 131b1 on the X1 side. The peripheral wall 131b1, the one holding portion 131b2, and the other holding portion 131b3 are configured similarly to the peripheral wall 31b1, the one holding portion 31b2, and the other holding portion 31b3 of the holder 31b, respectively.

The bearing 125a has: an outer race 125a1 attached to the 1 st gear carrier body 24 a; an inner race 125a2 attached to the 1 st journal portion 12a of the crankshaft 12; and a rolling body 125a3 provided between the outer race 125a1 and the inner race 125a 2. The movement of the outer race 125a1 in the X1 direction is restricted by the stopper 125a 4. The dimension of the inner ring 125a2 in the axial center a2 direction is greater than the dimension of the stopper ring 125a4 in the axial center a2 direction by at least 2 times, at least 3 times, at least 4 times, or at least 5 times. The inner race 125a2 is in contact with a holding portion 131a2 of the holder 131 a. In one embodiment, the inner ring 125a2 has a protrusion 126a that protrudes radially outward from an end in the X2 direction thereof. In one embodiment, the inner race 125a2 contacts a retaining portion 131a2 of the retainer 131a at the protrusion 126 a. The inner ring 125a2 supports the end surface of the holder 131a2 in the X1 direction on the support surface S1. The bearing surface S1 is at least a part of the end surface of the inner race 125a2 in the X2 direction. Thereby, the inner ring 125a2 restricts the movement of the retainer 131a in the X1 direction.

The inner ring 125a2 is formed, for example, by: a carburized layer is formed by carburizing a base material layer made of chromium steel (SCr) according to a conventional method. In one embodiment, the vickers hardness of the bearing surface S1 of the inner race 125a2 is 650HV or more. In one embodiment, the difference between the vickers hardness of the holding portion 131a2 of the retainer 131a and the vickers hardness of the supporting surface S1 is 100HV or less.

The bearing 125b includes: an outer race 125b1 mounted to the 2 nd gear carrier body 24 b; an inner race 125b2 attached to the 2 nd journal portion 12b of the crankshaft 12; and a rolling body 125b3 provided between the outer ring 125b1 and the inner ring 125b 2. The movement of the outer race 125b1 in the X2 direction is restricted by the stopper 125b 4. The dimension of the inner ring 125b2 in the axial center a2 direction is greater than the dimension of the stopper ring 125b4 in the axial center a2 direction by at least 2 times, at least 3 times, at least 4 times, or at least 5 times. The inner race 125b2 is in contact with a holding portion 131b2 of the holder 131 b. In one embodiment, the inner ring 125b2 has a protrusion 126b that protrudes radially outward from an end in the X1 direction thereof. In one embodiment, the inner race 125b2 contacts a retaining portion 131b2 of the retainer 131b at the protrusion 126 b. The inner ring 125b2 supports the end surface of the holder 131b2 in the X2 direction on the support surface S2. The bearing surface S2 is at least a part of the end surface of the inner race 125b2 in the X1 direction. Thereby, the inner ring 125b2 restricts the movement of the retainer 131b in the X2 direction.

The inner ring 125b2 is formed, for example, by: a carburized layer is formed by carburizing a base material layer made of chromium steel (SCr) according to a conventional method. In one embodiment, the vickers hardness of the bearing surface S2 of the inner ring 125b2 is 650HV or more. In one embodiment, the vickers hardness of the holding portion 131b2 of the retainer 131b is smaller than the vickers hardness of the supporting surface S2 by 100HV or more.

The outer ring 125a1, the rolling elements 125a3, and the retainer rings 125a4 are configured similarly to the outer ring 25a1, the rolling elements 25a3, and the retainer rings 25a4 of the bearing 25a, respectively. The outer ring 125b1, the rolling elements 125b3, and the retainer rings 125b4 are configured similarly to the outer ring 25b1, the rolling elements 25b3, and the retainer rings 25b4 of the bearing 25b, respectively.

As shown in fig. 4, in one embodiment, the holding portion 131a2 of the holder 131a contacts the inner race 125a2 over 180 ° in the circumferential direction around the axis a2 when viewed along the axis a2 direction. As shown in the drawing, when viewed along the axial center a2, each of the holding portion 131a2 and the inner ring 125a2 has a circular shape. The center C1 of the inner race 125a2 is eccentric from the axial center a2, and the holding portion 131a2 is eccentric from the axial center a2 to the side opposite to the inner race 125a 2. Therefore, when viewed along the axis a2 direction, the holding portion 131a2 and the inner ring 125a2 overlap in a region R1 extending around the axis a 2. In one embodiment, the region R1 extends more than 180 ° circumferentially about the axis a 2. The relationship between holder 131b2 and inner race 125b2 may be the same as the relationship between holder 131a2 and inner race 125a 2. For example, the holding portion 131b2 of the holder 131b may contact the inner race 125b2 over 180 ° in the circumferential direction around the axis a2 when viewed along the axis a2 direction.

Next, the operational effects obtained by the above embodiment will be described. According to the above-described embodiment, since the retainer 31a is supported by the external gear 23a at the flange 31a4, the movement in the X1 direction along the axial center a2 is restricted. Therefore, the movement of the retainer 31a in the X1 direction can be restricted without providing a washer. The retainer 31b is supported by the external gear 23b at the flange 31b 4. Therefore, the movement of the retainer 31b in the X2 direction can be restricted without providing a washer.

According to the above-described embodiment, the bearing 25a supporting the crankshaft 12 is disposed with the gap Ga with the retainer 31 a. This allows the lubricant to smoothly flow into the crankshaft 12 from the gap Ga. The bearing 25b supporting the crankshaft 12 is disposed with a gap Gb from the holder 31 b. This allows the lubricant to smoothly flow into the crankshaft 12 through the gap Gb.

According to the above-described embodiment, the inner ring 125a2 of the bearing 125a supports the end face of the holding portion 131a2 of the holder 131a facing the X1 direction on the support surface S1. Thus, even if no washer is provided, the movement of the cage 131a in the X1 direction can be restricted by the inner ring 125a2 of the bearing 125 a. Similarly, the inner race 125b2 of the bearing 125b supports the end face of the holding portion 131b2 of the holder 131b facing the X2 direction on the support surface S2. Thus, even if no washer is provided, the movement of the cage 131b in the X2 direction can be restricted by the inner ring 125b2 of the bearing 125 b.

According to the above-described embodiment, the retainer 131a is in contact with the inner race 125a2 over a range of 180 ° or more in the circumferential direction around the rotation axis of the crankshaft 12. This can suppress inclination of the retainer 131a with respect to the inner race 125a2 during operation of the reduction gear 101. Further, the cage 131a is in contact with the inner ring 125a2 over a range of 180 ° or more in the circumferential direction around the rotation axis of the crankshaft 12, so the contact area of the inner ring 125a2 and the cage 131a can be increased, whereby wear of the inner ring 125a2 and the cage 131a can be suppressed. The effects described for the holder 131a and the inner race 125a2 also apply to the holder 131b and the inner race 125b 2.

The dimensions, materials, and arrangements of the respective components described in the present specification are not limited to those explicitly described in the embodiments, and the respective components may be modified to have any dimensions, materials, and arrangements that can be included in the scope of the present invention. Further, components not explicitly described in the present specification may be added to the embodiments described above, and a part of the components described in each embodiment may be omitted.

The above embodiments may be combined as appropriate. An embodiment realized by combining a plurality of embodiments can also be an embodiment of the present invention.

Claims

1. A speed reducer, wherein,

the speed reducer is provided with:

a housing having internal teeth;

an external gear having external teeth meshing with the internal teeth and a through hole;

a crankshaft provided in the through hole; and

a crankshaft bearing having: a retainer whose movement in the axial direction of the crankshaft is restricted by the external gear; and a rolling element held by the cage in the through hole.

2. A decelerator according to claim 1 wherein,

the external gear has a bearing surface in a direction intersecting with an axial direction of the crankshaft,

the retainer is supported by the outer gear at the support surface.

3. A decelerator according to claim 2 wherein,

the retainer has a flange in a direction intersecting with an axial direction of the crankshaft, and the retainer is supported by the bearing surface of the external gear at the flange.

4. A decelerator according to claim 3 wherein,

the retainer has a peripheral wall in a direction around a rotational axis of the crankshaft,

the flange is formed from the peripheral wall toward a direction opposite to the rotational axis of the crankshaft.

5. A decelerator according to any one of claims 2 to 4 wherein,

the speed reducer includes another external gear having external teeth meshing with the internal teeth,

the outer gear is disposed such that the bearing surface opposes the other outer gear.

6. A decelerator according to any one of claims 1 to 5 wherein,

the speed reducer includes a carrier provided to be rotatable relative to the casing,

the crankshaft is supported on the carrier by means of a further crankshaft bearing,

the retainer is provided separately from the other crankshaft bearing.

7. A speed reducer, wherein,

this reduction gear includes:

a housing having internal teeth;

a crankshaft provided in the through hole;

a crankshaft bearing having rolling elements held by a cage;

a carrier provided to be rotatable relative to the casing; and

and another crankshaft bearing having an outer ring supported by the carrier, an inner ring restricting movement of the cage in an axial direction of the crankshaft, and another rolling element provided between the inner ring and the outer ring.

8. A decelerator according to claim 7 wherein,

the retainer is in contact with the inner race over a range of 180 ° or more in a circumferential direction around a rotation axis of the crankshaft.

9. A decelerator according to claim 7 or 8 wherein,

the inner race has a bearing surface that supports the cage,

the Vickers hardness of the bearing surface of the inner ring is 650HV or more.

10. A decelerator according to claim 8 or 9 wherein,

the retainer has an end surface contacting the bearing surface of the inner race,

the difference between the Vickers hardness of the end surface of the retainer and the Vickers hardness of the bearing surface of the inner ring is 100HV or less.