CN110234907B

CN110234907B - Differential speed reducer

Info

Publication number: CN110234907B
Application number: CN201880009531.3A
Authority: CN
Inventors: 原口国弘
Original assignee: Nissei Corp
Current assignee: Nissei Corp
Priority date: 2017-03-15
Filing date: 2018-03-12
Publication date: 2023-03-10
Anticipated expiration: 2038-03-12
Also published as: JP6803273B2; WO2018168763A1; JP2018155264A; CN110234907A

Abstract

The invention aims to increase the outer diameter of a roller to improve the strength even if a roller bearing is adopted for shaft support of an external gear. For this purpose, the differential speed reducer (1A-1C) comprises: an internal gear (4) disposed within the housing (2); an input shaft (12) coaxially penetrating the internal gear (4); external gears (17A-17C) externally fitted to eccentric portions (14A-14C) provided on the input shaft (12) via eccentric portion bearings and internally engaged with the internal gear (4); and an output shaft (9) having pins (22, 22 … …) loosely inserted into the external gears (17A to 17C) and having ball bearings (10, 11) interposed between the output shaft and the input shaft (12), wherein the external gears (17A to 17C) eccentrically move with respect to the internal gear (4) by rotation of the input shaft (12), thereby rotating the output shaft (9) at a predetermined reduction ratio by the pins (22), wherein the eccentric portion bearings are needle roller bearings (15) full of rollers, and the outer diameter (D2) of the eccentric portions (14A to 14C) in the input shaft (12) is made smaller than the outer diameter (D1) of the shaft support portion (13) where the ball bearings (10, 11) are provided.

Description

Differential speed reducer

Technical Field

The present invention relates to an internal oscillating type differential speed reducer including an internal gear and an external gear that is in internal-contact engagement with the internal gear.

Background

The differential reduction gear includes an internal gear and an external gear that is internally meshed with the internal gear, and the external gear is eccentrically moved within the internal gear by a rotational input from the input shaft, thereby generating relative rotation between the two gears and outputting rotation to the output shaft at a reduction ratio based on a difference between the rotational speeds of the eccentric movement and the relative rotation. For example, patent document 1 discloses a power transmission device in which a hollow input shaft is supported by a pair of front and rear support flanges via a pair of bearings, two external gears are arranged in different phases between the bearings via roller bearings, a pair of front and rear eccentric bodies provided on the outer periphery of the input shaft are arranged between the bearings, and an inner pin is bridged between the support flanges, wherein the inner pin is loosely inserted into an inner pin hole provided in each external gear. That is, when the input shaft rotates, the external gear oscillates (eccentrically moves) within the internal gear via the eccentric member, and the relative rotational component of the difference in the number of teeth between the internal teeth and the external teeth is extracted and output to the support flange.

Prior art documents

Patent document

Patent document 1: international publication No. 2006/085536

Disclosure of Invention

(problems to be solved by the invention)

In order to improve the strength of the differential speed reducer, it is effective to increase the outer diameter of the roller that supports the external gear. However, in the invention of patent document 1, since the outer diameter of the input shaft is enlarged in stages, the inner diameter of the roller bearing is larger than the inner diameter of the bearing of the input shaft, and the outer diameter of the roller is restricted, so that it is difficult to improve the strength.

Accordingly, an object of the present invention is to provide a differential speed reducer capable of increasing the outer diameter of a roller and improving the strength even when a roller bearing is used for shaft support of an external gear.

(means for solving the problems)

In order to achieve the above object, the invention described in claim 1 is a differential speed reducer including: an inner gear disposed within the housing; an input shaft coaxially penetrating the internal gear; an external gear externally fitted to an eccentric portion provided in the input shaft via an eccentric portion bearing and internally engaged with the internal gear; and an output portion including a pin loosely inserted into the external gear, the pin being interposed between the input shaft and the input shaft, the output portion being rotated by the pin at a speed reduction ratio determined based on a difference between the number of teeth of the internal gear and the number of teeth of the external gear by eccentrically moving the external gear with respect to the internal gear by rotation of the input shaft,

the differential speed reducer has an eccentric portion bearing as a full roller, and an outer diameter of an eccentric portion of an input shaft is smaller than an outer diameter of a portion where the input shaft bearing is provided.

The invention described in claim 2 is characterized in that, in the structure of claim 1, a retaining portion is provided on the outer periphery of the input shaft between the input shaft bearing and the eccentric portion bearing, the retaining portion abuts against a side surface of the input shaft bearing to restrict movement of the input shaft in the axial direction, and the eccentric portion is formed lower than the retaining portion over the entire periphery.

The invention described in claim 3 is characterized in that, in the structure of claim 2, the retaining portion has a disk shape formed coaxially with and integrally with the input shaft.

The invention described in claim 4 is characterized in that, in the structure according to any one of claims 1 to 3, the eccentric portion, the bearing for the eccentric portion, and the external gear are provided in plural sets, and the outer diameters of the respective eccentric portions are all equal.

The invention described in claim 5 is characterized in that, in the structure of claim 4, the shape of each external gear is the same, and the shape of each eccentric portion bearing is the same.

(effect of the invention)

According to the invention described in claim 1, the eccentric portion bearing is made full of rollers, and the outer diameter of the eccentric portion of the input shaft is made smaller than the outer diameter of the portion where the input shaft bearing is provided, whereby the outer diameter of the rollers can be increased, contributing to strength improvement.

According to the invention described in claim 2, in addition to the effect of claim 1, by providing the retaining portion that abuts against the side surface of the input shaft bearing to restrict the movement of the input shaft in the axial direction on the outer periphery of the input shaft and forming the eccentric portion so as to be lower than the retaining portion over the entire periphery, the movement of the roller in the axial direction can be restricted over the entire periphery of the eccentric portion even when the roller is full. Further, the retaining portion can be used for retaining both the input shaft bearing and the roller.

According to the invention described in claim 3, in addition to the effect of claim 2, since the retaining portion is formed in a disk shape that is formed coaxially with and integrally with the input shaft, the retaining portion can be easily machined by a lathe or the like.

According to the invention described in claim 4, in addition to the effect of any one of claims 1 to 3, since a plurality of sets of the eccentric portion, the eccentric portion bearing, and the external gear are provided and the outer diameters of the respective eccentric portions are all made equal, the same eccentric portion bearing can be disposed in each eccentric portion, and the outer diameter of the roller of each eccentric portion bearing can be increased.

According to the invention described in claim 5, in addition to the effect of claim 4, since the shapes of the respective external gears and the respective eccentric portion bearings are made the same, it is possible to expect further cost reduction.

Drawings

FIG. 1 is a central longitudinal section view of a series of differential reducers.

Fig. 2 (base:Sub>A) to (C) show cross-sectional views of the differential reducers 1base:Sub>A to 1C at the linebase:Sub>A-base:Sub>A of fig. 1, respectively.

Fig. 3 is an enlarged view of a portion F of fig. 1.

Fig. 4 is a graph comparing efficiencies when the internal gear 4 has different displacement coefficients.

Detailed Description

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

Fig. 1 and 2 show a series S of three

differential gear units

1A, 1B, 1C. Since the differential speed reducers 1A to 1C have substantially the same structure, fig. 1 typically showsbase:Sub>A central longitudinal sectional view of the differential speed reducer 1A, and fig. 2 (base:Sub>A) to (C) show sectional views of the differential speed reducers 1A to 1C taken along the linebase:Sub>A-base:Sub>A in fig. 1. In addition, when the components are distinguished for each of the differential reducers 1A to 1C, english letters are labeled as in 14A to 14C.

In the differential speed reducer 1A (1B, 1C), 2 is a casing, and the casing 2 is composed of a cylindrical middle case 3 in which an internal gear 4 is integrally provided inside, a disk-shaped case cover 5 disposed on one end surface (input side, right side in fig. 1) in the axial direction of the middle case 3, and a cylindrical outer case 6 disposed on the other end surface (output side, left side in fig. 1). The middle casing 3, the casing lid 5, and the outer casing 6 are integrally coupled by a plurality of

bolts

7, 7 … … that penetrate the middle casing 3 from the casing lid 5 side and are screwed to the outer casing 6.

A disk-shaped output shaft 9 is rotatably supported on the inner side of the outer case 6 via a cross roller bearing 8 as an outer bearing. A hollow cylindrical input shaft 12 is coaxially and rotatably supported inside the housing 2 via

ball bearings

10 and 11 serving as bearings for the input shaft. Of these, in the ball bearing 10 as an input-side inner bearing, an axial input-side half of the outer ring 10a is supported by the housing cover 5, and an axial output-side half of the outer ring 10a is supported by a carrier 24 described later.

In the input shaft 12, a pair of

eccentric portions

14A and 14A (14B and 14C) having the same outer diameter and the phase difference of 180 degrees between the maximum eccentric side are formed adjacent to each other in the axial direction between the shaft support

portions

13 and 13 on which the

ball bearings

10 and 11 are disposed. Each of the

eccentric portions

14A and 14A (14B and 14C) is provided with a full-roller needle bearing 15 as an eccentric portion bearing, which is composed of a plurality of

needle rollers

16 and 16 … … having a circular cross-sectional shape and arranged over the entire circumference, and externally mounted with

external gears

17A and 17A (17B and 17C) having the same outer shape so as to be rotatable via the needle bearing 15. Therefore, the needle rollers 16 directly contact the inner eccentric portions 14A to 14C and the outer external gears 17A to 17C.

Here, in the input shaft 12, the outer diameter D1 of the shaft support portion 13 on which the

ball bearings

10 and 11 are disposed and the outer diameter D2 of the eccentric portion 14A (14B and 14C) on which the needle roller bearing 15 is provided are set in a relationship of D1 > D2. By reducing the outer diameter D2 of the eccentric portion 14A (14B, 14C) in this way, the size (outer diameter) of each needle roller 16 provided on the outer periphery thereof can be increased. Further, between the shaft support portion 13 and the eccentric portion 14A (14B, 14C), a disk-shaped retaining portion 18 that protrudes higher toward the outer peripheral side than the eccentric portion 14A (14B, 14C) over the entire circumference is provided in the circumferential direction. The retaining portion 18 can restrict the movement of the needle roller 16 to the outside in the axial direction and the movement of the

ball bearings

10 and 11 to the inside in the axial direction over the entire circumference. As a result, the movement of the input shaft 12 in the axial direction is also restricted. The outward movement of the ball bearing 10 is regulated by a cover portion 19 provided on the inner peripheral edge of the housing cover 5 and overlapping the outer ring 10a from the outside, and the outward movement of the ball bearing 11 is regulated by a step portion 20 provided on the output shaft 9.

As shown in fig. 2, the external gears 17A to 17C have fewer teeth than the internal gear 4, and are inscribed in the internal gear 4 at eccentric positions. Here, in the differential speed reducers 1A to 1C, the same-shaped ring gears having the number of teeth of 120 are used for the ring gears 4. On the other hand, for each of the external gears 17A to 17C, the external gear 17A has a number of teeth of 114 and a difference in number of teeth from the internal gear 4 is 6, and the reduction ratio is 1/19, the external gear 17B has a number of teeth of 116 and a difference in number of teeth from the internal gear 4 is 4, and the reduction ratio is 1/29, and the external gear 17C has a number of teeth of 118 and a difference in number of teeth from the internal gear 4 is 2, and the reduction ratio is 1/59. Therefore, the amounts of eccentricity δ 1, δ 2, δ 3 of the centers O2 (the centers of the eccentric portions 14A to 14C) of the external gears 17A to 17C from the center O1 (the axial center of the input shaft 12) of the internal gear 4 are in a relationship of δ 1 > δ 2 > δ 3.

Here, the internal teeth of the internal gear 4 and the external teeth of the external gear 17 are of involute tooth type, and the coefficient of displacement of the internal gear 4 is set to be more than 1 and 1.9 or less.

In addition, eight circular pin holes 21A to 21C are formed in each of the external gears 17A to 17C so as to be circumferentially spaced at equal intervals on a concentric circle centered on the center O2, and the

pins

22 and 22 … … are loosely inserted into the pin holes 21A to 21C, respectively. The pin 22 is a shaft body that is disposed between the output shaft 9 and a disk-shaped carrier 24 disposed inside the housing cover 5 and extends parallel to the axis of the internal gear 4 on a concentric circle about the axis, and a tubular metal fitting 23 is integrally attached to the outer periphery of the pin 22 at loosely inserted portions of the external gears 17A to 17C. The carrier 24 supports an inner half of the outer ring 10a of the ball bearing 10 inside the housing cover 5, and is rotatable integrally with the output shaft 9 via the pin 22. Here, the pin 22 and the output shaft 9 coupled via the pin 22 serve as an output portion.

The pins 22 inscribe the outer periphery of the metal fitting 23 and the inner peripheries of the pin holes 21A to 21C of the front and rear

external gears

17A, 17A (17B, 17B and 17C, 17C) at phases different by 180 degrees from each other, and the hole diameters of the pin holes 21A to 21C of the external gears 17A to 17C are set for each of the differential reducers 1A to 1C. That is, the diameters of the pin holes 21A to 21C in the external gears 17A to 17C are set to a size obtained by adding 2 times the eccentric amounts δ 1 to δ 3 of the external gears 17A to 17C to the diameter of the pin 22 including the metal 23, and the hole diameters of the pin holes 21A to 21C are different for each of the differential reducers 1A to 1C. However, even if the hole diameters are different, the center positions of the pin holes 21A to 21C of the external gears 17A to 17C all coincide.

On the other hand, the ball bearing 10 is fitted with a clearance between the housing cover 5 and the inner peripheral surface of the carrier 24, and a clearance a is formed between the housing cover 5 supporting the outer ring 10a and the carrier 24 in the axial direction of the input shaft 12 to communicate with the inside of the housing 2 as shown in fig. 3. Further,

annular grease grooves

25, 25 are formed on the inner circumferential surfaces of the case cover 5 and the carrier 24 over the entire circumference.

Further, an oil seal 27 as a sealing member is interposed between an annular projecting strip 26 provided projecting on the front surface of the housing cover 5 and the outer peripheral surface of the input shaft 12. An oil seal 28 is also interposed between the outer housing 6 and the output shaft 9 on the output side of the cross roller bearing 8. An oil seal 29 is also interposed between the output shaft 9 and the input shaft 12 on the output side of the ball bearing 11.

In the differential speed reducer 1A to 1C configured as described above, when the input shaft 12 is rotated by a rotational input to the input shaft 12, the front and rear eccentric portions 14A to 14C perform eccentric motions symmetrically, respectively, and the external gears 17A to 17C perform eccentric and rotational motions while being inscribed in the internal gear 4. Therefore, although the pin holes 21A to 21C also perform eccentric and rotational motions, since the pin holes 21A to 21C are formed to have a larger diameter than the pin 22 including the metal fitting 23, the pin 22 relatively eccentrically moves while being inscribed in the pin holes 21A to 21C, and absorbs the eccentric component, and only the rotational component is taken out from the pin 22. Therefore, the output shaft 9 and the carrier 24 rotate synchronously via the pin 22, and the output shaft 9 rotates in a state of being decelerated at the above-described reduction ratio. In the series S, the differential reduction gear 1A performs low deceleration, the differential reduction gear 1B performs medium deceleration, and the differential reduction gear 1C performs high deceleration.

At this time, the grease filled in the housing 2 is supplied from the gap a to the

grease grooves

25 and 25 through the gap between the inner circumferential surfaces of the outer ring 10a and the housing cover 5 and the inner circumferential surface of the carrier 24, thereby ensuring lubrication and reducing friction. Further, even if grease is supplied in this way, since the oil seal 27 is interposed between the housing cover 5 and the input shaft 12, grease leakage does not occur.

(effect of the invention relating to the series of differential speed reducers)

As described above, according to the series S of the differential reducers 1A to 1C of the above-described embodiment, it is sufficient that the pin holes 21A to 21C of the external gears 17A to 17C are formed with different diameters for the external gears 17A to 17C according to the number of external teeth, and the internal gear 4, the pins 22, and the metal fittings 23 are commonly used, so that only the pin holes 21A to 21C having a diameter corresponding to one reduction ratio are formed in the external gears 17A to 17C. Therefore, the parts can be shared without reducing the strength of the external gears 17A to 17C, and the manufacturing cost can be suppressed.

In particular, the center positions of the pin holes 21A to 21C are matched between the external gears 17A to 17C, and therefore the output shaft 9 and the carrier 24 can be shared.

The tooth profiles of the internal gear 4 and the external gears 17A to 17C are involute tooth profiles.

In accordance with JGMA (japan gear association standard) (JGMA 611-01) "which is a gear standard of japan gear association" and conforms to the modification method of ISO standard cylindrical gears ", the total value of the modification coefficient of the involute inner gear and the modification coefficient of the involute outer gear is recommended to be designed to be 1 or less in consideration of the meshing efficiency of gears.

However, in this embodiment, by setting the displacement coefficient of the internal gear 4 to be in a range exceeding 1 and 1.9 or less, the root circle diameter of the external gears 17A to 17C meshing therewith can be increased, and the thickness of the roots of the external gears 17A to 17C and the thickness of the pin holes 21A to 21C can be ensured.

Fig. 4 is a graph comparing changes in efficiency (transmission efficiency) when the input torque is changed to 1N · m when 2000rpm is input with the displacement coefficients of the ring gear 4 set to 1.9 and 0.2, and a solid line of No.1 shows a case where the displacement coefficient is 1.9 (the number of teeth 76, the difference in the number of teeth 1, and the reduction ratio 1/75), and a broken line of No.2 shows a case where the displacement coefficient is 0.2 (the number of teeth 60, the difference in the number of teeth 1, and the reduction ratio 1/59).

Here, the maximum efficiency was approximately 68% at a displacement coefficient of 1.9 and approximately 70% at a displacement coefficient of 0.2, and it was found that the degree of influence on efficiency was not so large even when the displacement coefficient was 1.9.

Further, the number of the pins 22 of the output portion is eight, so that the rigidity of the differential speed reducers 1A to 1C can be improved. In particular, since it is sufficient to form only the pin holes 21A to 21C corresponding to one reduction gear ratio in the external gears 17A to 17C, it is possible to easily perform the number of the pins 22 to be eight or more.

In addition, in order to increase the rigidity of the differential reducers 1A to 1C, it is effective to thicken the pins 22. In the above-described aspect, although it is difficult to increase the pin diameter by making the inner roller holes closer to each other when forming a plurality of inner roller holes for each reduction ratio in the external gear as in the above-described related art, since only the pin holes 21A to 21C corresponding to one reduction ratio are formed in the external gears 17A to 17C, the distance between the pin holes 21A to 21C can be secured. Therefore, thickening the pin 22 to make the rigidity higher can be easily performed.

Further, since the external gears 17A to 17C only need to be formed with the pin holes 21A to 21C corresponding to one reduction ratio, even if three types of series having different reduction ratios are used, the strength of the external gears 17A to 17C does not decrease in the differential speed reducers 1A to 1C. Therefore, three or more series can be configured while maintaining the state in which the internal gear 4, the pin 22, the metal fitting 23, the output shaft 9, and the carrier 24 are shared.

Further, the input shaft 12 is hollow, so that weight reduction can be achieved. Further, even if the input shaft 12 is hollow, the strength of the external gears 17A to 17C can be maintained.

In the above embodiment, a series of three differential speed reducers is exemplified, but the reduction gear ratio and the number of differential speed reducers are not limited thereto, and even a series of two or four or more differential speed reducers having different reduction gear ratios can be used to share the internal gear and the output unit in the same manner. The reduction ratios are not limited to the above embodiment. The number of external gears provided in each differential speed reducer can also be increased or decreased.

In the above-described embodiment, the pin is externally fitted with a metal fitting, but a rolling element such as a roller may be externally fitted, or a separate pin that is not externally fitted with such other member may be provided.

(effects of the invention of the bearing for eccentric section and the differential speed reducer relating to the outer diameter of eccentric section)

In this way, according to the differential speed reducers 1A to 1C of the above-described aspect, the eccentric portion bearing is the needle roller bearing 15 with full rollers, and the outer diameter D2 of the eccentric portions 14A to 14C in the input shaft 12 is set smaller than the outer diameter D1 of the shaft support portion 13 on which the

ball bearings

10 and 11 are provided, whereby the outer diameter of the needle roller 16 can be increased, contributing to strength improvement.

In particular, since the retaining

portions

18, 18 that abut against the side surfaces of the

ball bearings

10, 11 to restrict the movement of the input shaft 12 in the axial direction are provided on the outer periphery of the input shaft 12 between the

ball bearings

10, 11 and the needle roller bearing 15, and the eccentric portions 14A to 14C are formed lower than the retaining portion 18 over the entire periphery, the movement of the needle roller 16 in the axial direction can be restricted over the entire periphery of the eccentric portions 14A to 14C even if the roller is full. The retaining portions 18 can be used for retaining both the

ball bearings

10 and 11 and the needle roller 16. The retaining portion 18 also serves as retaining of the input shaft 12 itself.

Further, since the retaining portion 18 is formed in a disk shape that is formed coaxially with and integrally with the input shaft 12, the retaining portion 18 can be easily machined by a lathe or the like.

Further, since the eccentric portions 14A to 14C, the needle roller bearings 15, and the external gears 17A to 17C are provided in plural sets, and the outer diameters of the eccentric portions 14A to 14C are all made equal, the same needle roller bearings 15 can be arranged in the eccentric portions 14A to 14C, and the outer diameters of the needle rollers 16 of the needle roller bearings 15 can be increased.

Further, since the external gears 17A to 17C and the needle bearings 15 are formed in the same shape, further cost reduction can be expected.

Further, since the needle rollers 16 of the needle roller bearing 15 are disposed at positions close to the center O1 of the internal gear 4 (the axial center of the input shaft 12), the diameter of the pins 22 for taking out the rotation motion from the external gears 17A to 17C can be increased. Therefore, the strength of the differential reducers 1A to 1C can be improved.

The shape of the retaining portion is not necessarily a circular plate shape, and may be a gear shape having a plurality of projections formed on the outer periphery thereof or a member separate from the input shaft as long as the movement of the needle roller can be regulated.

(effect of the invention of the differential speed reducer relating to the support of the ball bearing)

In this way, according to the differential speed reducers 1A to 1C of the above-described embodiment, the outer ring 10a of the ball bearing 10 is supported by the housing cover 5 and the carrier 24 of the housing 2, so that the coaxiality of the input shaft 12 and the housing 2 can be improved, and the input shaft 12 can be assembled with high accuracy.

In particular, since the outer ring 10a of the ball bearing 10 is fitted into the housing cover 5 and the carrier 24 with a clearance therebetween, the sliding surfaces can slide, and the rotational resistance can be reduced.

Further, since the

grease grooves

25, 25 are formed on the sliding surfaces of the outer ring 10a, the housing cover 5, and the carrier 24 that are fitted in the clearance, grease can be retained on the sliding surfaces to slide with low friction.

Further, since the grease groove 25 is formed in the housing cover 5 and the carrier 24, the standard ball bearing 10 can be used, and an increase in cost can be suppressed.

Further, since the grease groove 25 is formed over the entire circumference of the sliding surface, the grease groove 25 can be easily machined by a lathe or the like.

Further, since the oil seal 27 for sealing between the housing 2 and the input shaft 12 is disposed outside the ball bearing 10 in the axial direction of the input shaft 12, the oil seal 27 and the input shaft 12 can be brought into contact with each other with high accuracy between the housing 2 and the input shaft 12 having high coaxiality, and the risk of grease leakage can be reduced.

In the above-described aspect, the outer ring of the ball bearing is fitted with a clearance between both the housing cover and the carrier, but may be fitted with a clearance only with either one. Therefore, the grease pocket may be provided only on the sliding surface on one side to which the clearance is fitted.

In addition, when the grease groove is provided, the grease groove may be provided intermittently in the circumferential direction, in addition to being provided over the entire circumference of the sliding surface.

In each aspect, the structure of the outer case is not limited to the combination of the middle case, the case cover, and the outer case as described above, and the number of components may be increased or decreased, or the outer case may be formed of one member.

The outer bearing is not limited to the cross roller bearing, and other bearings such as a ball bearing may be used, and the number of bearings may be increased.

Further, the structure of the input shaft and the output shaft is not limited to the above-described embodiment, and design changes can be appropriately made, for example, the input shaft is made solid, not hollow, and the like.

Description of the symbols

1A-1C differential speed reducer, 2 outer shell, 3 middle shell, 4 inner gear, 5 shell cover, 6 outer shell, 7 bolt, 8 cross roller bearing, 9 output shaft, 10 ball bearing, 10a outer ring, 11 ball bearing, 12 input shaft, 13 shaft support part, 14 eccentric part, 15 needle bearing, 16 needle roller, 17A-17C outer gear, 18 anti-slip part, 21A-21C pin hole, 22 pin, 23 metal piece, 24 bearing part, 25 grease groove, 27, 28, 29 oil seal, S series, A clearance, the outer diameter of D1 shaft support part, the outer diameter of D2 eccentric part, the center of O1 inner gear, the center of O2 outer gear, and the eccentricity of delta 1-delta 3.

Claims

1. A differential reducer, comprising:

an inner gear disposed within the housing;

an input shaft coaxially penetrating the internal gear;

an external gear externally fitted to an eccentric portion provided in the input shaft via an eccentric portion bearing and internally engaged with the internal gear; and

an output part having a pin loosely inserted into the external gear and having an input shaft bearing interposed between the output part and the input shaft,

rotating the output portion by the pin at a reduction ratio determined based on a difference between the number of teeth of the internal gear and the number of teeth of the external gear by eccentrically moving the external gear with respect to the internal gear by rotation of the input shaft,

the differential speed reducer has the eccentric portion bearings as full rollers, and the input shaft bearings are arranged in a pair in the axial direction of the input shaft in front of and behind the external gear, and the outer diameter of the eccentric portion of the input shaft is set to be smaller than the outer diameter of a portion where each of the input shaft bearings is provided.

2. Differential reducer according to claim 1,

a stopper portion that abuts against a side surface of the input shaft bearing to restrict movement of the input shaft in an axial direction is provided on an outer periphery of the input shaft between the input shaft bearing and the eccentric portion bearing, and the eccentric portion is formed lower than the stopper portion over an entire periphery.

3. A differential reducer according to claim 2,

the anti-drop part is in a disc shape which is coaxial with and integrally formed with the input shaft.

4. A differential reducer according to any one of claims 1-3,

the eccentric portion, the bearing for the eccentric portion, and the external gear are provided in plural sets, and the outer diameters of the eccentric portions are all equal.

5. A differential reducer according to claim 4,

the external gears have the same shape, and the eccentric portion bearings have the same shape.