JP6744244B2 - Differential reducer - Google Patents

Description

The present invention relates to an internal oscillating differential reducer including an internal gear and an external gear that is inscribed in and meshes with the internal gear.

The differential reduction gear includes an internal gear and an external gear that is inscribed in and meshes with the internal gear, and the external gear eccentrically moves in the internal gear due to the rotation input from the input shaft. Relative rotation is generated between the gears, and rotation is output to the output shaft at a speed reduction ratio due to the difference in rotation speed between eccentric motion and relative rotation. For example, in Patent Document 1, a carrier is supported in a casing supporting an internal gear via an angular ball bearing, and an input shaft to which a motor shaft of a motor is connected is supported in the carrier via a ball bearing. Then, the external gears are respectively incorporated through rollers into the plurality of eccentric bodies provided on the outer periphery of the input shaft, and the pin members provided on the carrier are loosely inserted into the through holes provided in each external gear. An invention of a speed reducer in which an external gear is oscillated (eccentric) by rotation of an input shaft and a carrier is rotated via a pin member is disclosed.

JP, 2014-152894, A

In the above conventional speed reducer, since the input shaft is supported by the carrier through the ball bearing and the carrier is supported by the casing through the angular ball bearing, the coaxiality between the input shaft and the casing is poor. There was a risk of becoming.

Therefore, an object of the present invention is to provide a differential speed reducer in which the coaxiality between the input shaft and the casing can be increased and the input shaft can be assembled accurately.

In order to achieve the above-mentioned object, the invention according to claim 1 is such that an output portion supported in a casing via an outer bearing, an internal gear provided in the casing, and the output portion and the internal gear are coaxial. And an external gear that is externally mounted on the eccentric part provided on the input shaft through the bearing for the eccentric part and meshes with the internal gear by inscribed in the internal gear. A carrier that is connected to the output unit via a pin that loosely inserts the gear, and the external gear rotates eccentrically with respect to the internal gear by the rotation of the input shaft. A differential speed reducer that rotates an output section via a pin at a reduction ratio based on the number of teeth of a gear and the number of teeth of an external gear,
The outer ring of the inner bearing is supported by the casing and the carrier.
According to a second aspect of the present invention, in the configuration of the first aspect, the outer ring of the inner bearing is fitted in the casing and/or the carrier with a clearance.
According to a third aspect of the present invention, in the configuration of the second aspect, a grease groove is formed on a sliding surface between the outer ring fitted in the clearance and the casing and/or the carrier.
According to a fourth aspect of the present invention, in the configuration of the third aspect, the grease groove is formed in the casing and/or the carrier.
According to a fifth aspect of the present invention, in the configuration of the third or fourth aspect, the grease groove is formed over the entire circumference of the sliding surface.
According to a sixth aspect of the present invention, in the configuration of any of the first to fifth aspects, a seal member that seals between the casing and the input shaft is arranged outside the inner bearing in the axial direction of the input shaft. It is characterized by being

According to the first aspect of the invention, the outer ring of the inner bearing is supported by the casing and the carrier, so that the coaxiality between the input shaft and the casing can be increased and the input shaft can be assembled accurately.
According to the invention described in claim 2, in addition to the effect of claim 1, since the outer ring of the inner bearing is fitted in the casing and/or the carrier with a clearance, the sliding surface can be slid. , Rotation resistance is reduced.
According to the invention described in claim 3, in addition to the effect of claim 2, since the grease groove is formed on the sliding surface between the outer ring fitted in the clearance and the casing and/or the carrier, Grease is retained on the moving surface and can be slid with low friction.
According to the invention of claim 4, in addition to the effect of claim 3, since the grease groove is formed in the casing and/or the carrier, a standard bearing can be adopted, and an increase in cost can be suppressed. ..
According to the invention of claim 5, in addition to the effect of claim 3 or 4, since the grease groove is formed over the entire circumference of the sliding surface, the grease groove can be easily processed by a lathe or the like. it can.
According to the invention of claim 6, in addition to the effect of any one of claims 1 to 5, a seal member for sealing between the casing and the input shaft is provided outside the inner bearing in the axial direction of the input shaft. Is disposed, the seal member can be accurately brought into contact with the input shaft between the casing having a high degree of coaxiality and the input shaft, and the risk of grease leakage can be reduced.

It is a central longitudinal cross-sectional view of a series of differential reduction gears. 1A to 1C are cross-sectional views of the differential reduction gears 1A to 1C taken along the line AA in FIG. FIG. 2 is an enlarged view of part F of FIG. 1. It is a graph which compared the efficiency when the dislocation coefficient of internal gear 4 differs.

Embodiments of the present invention will be described below with reference to the drawings.
1 and 2 show a series S including three types of differential speed reducers 1A, 1B and 1C. However, since the structures of the differential speed reducers 1A to 1C are substantially the same, FIG. 1 shows a central vertical cross-sectional view of the differential speed reducer 1A as a representative, and FIGS. The cross-sectional views of the differential reduction gears 1A to 1C taken along the line AA are respectively shown. When distinguishing the constituent parts for each of the differential speed reducers 1A to 1C, alphabetical characters such as 14A to 14C are added.
In the differential reduction gear 1A (1B, 1C), 2 is a casing, and this casing 2 has a cylindrical middle case 3 integrally provided with an internal gear 4 inside and one of the axial direction of the middle case 3 The disk-shaped case cover 5 is arranged on the end surface (input side, right side in FIG. 1), and the cylindrical outer case 6 is arranged on the other end surface (output side, left side in FIG. 1). The inner case 3, the case cover 5, and the outer case 6 are integrally coupled by a plurality of bolts 7, 7... Which penetrate the middle case 3 from the case cover 5 side and are screwed into the outer case 6. ..

A disc-shaped output shaft 9 is rotatably supported inside 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 casing 2 via ball bearings 10 and 11 that serve as input shaft bearings. However, in the ball bearing 10 as the inner bearing on the input side, an axial input side half of the outer ring 10a is supported by the case cover 5, and an axial output side half of the outer ring 10a is supported by a carrier 24 described later.
In this input shaft 12, a pair of eccentric parts 14A, 14A (14B) having the same outer diameter and 180° different phases on the maximum eccentric sides are provided between the shaft support parts 13, 13 in which the ball bearings 10, 11 are arranged. , 14B and 14C, 14C) are formed adjacent to each other in the axial direction. Each eccentric portion 14A, 14A (14B, 14B and 14C, 14C) is a bearing for the eccentric portion, and is composed of a plurality of needles 16, 16... The needle bearing 15 is provided, and external gears 17A, 17A (17B, 17B and 17C, 17C) having the same outer shape are rotatably mounted via the needle bearing 15 respectively. Therefore, each needle 16 is in direct contact with 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 in which the ball bearings 10 and 11 are arranged and the outer diameter D2 of the eccentric portion 14A (14B, 14C) in which the needle bearing 15 is provided are D1>D2. Are formed to have a relationship of. By thus reducing the outer diameter D2 of the eccentric portion 14A (14B, 14C), the size (outer diameter) of each needle 16 provided on the outer circumference can be increased. In addition, between the shaft support portion 13 and the eccentric portion 14A (14B, 14C), a disc-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. They are arranged around each other. The retainer portion 18 restricts the movement of the needle 16 outward in the axial direction and the movement of the ball bearings 10 and 11 inward 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 restricted by a cover portion 19 provided on the inner peripheral edge of the case cover 5 and overlapping the outer ring 10a from the outside, and the outward movement of the ball bearing 11 is provided on the output shaft 9. It is regulated by the step portion 20.

As shown in FIG. 2, the external gears 17A to 17C have a smaller number of teeth than the internal gear 4 and are inscribed in the internal gear 4 at an eccentric position. Here, in the differential reduction gears 1A to 1C, each internal gear 4 has the same shape with 120 teeth. On the other hand, in each of the external gears 17A to 17C, the external gear 17A has a reduction ratio of 1/19 when the number of teeth is 114 and the difference in the number of teeth from the internal gear 4 is 6, and the external gear 17B is , The number of teeth is 116 and the difference in the number of teeth with the internal gear 4 is 4, the reduction ratio is 1/29, and the external gear 17C has the number of teeth 118 and the difference in the number of teeth with the internal gear 4 is 2. The reduction ratio is 1/59. Therefore, the eccentricity amounts δ1, δ2, and δ3 from the center O1 (the center of the input shaft 12) of the internal gear 4 of the center O2 of each of the external gears 17A to 17C (the center of the eccentric portions 14A to 14C) are δ1. >δ2>δ3.
Here, the internal teeth of the internal gear 4 and the external teeth of the external gear 17 are involute tooth type, respectively, and the dislocation coefficient of the internal gear 4 exceeds 1 to 1.9. It is set.

Further, in each of the external gears 17A to 17C, eight circular pin holes 21A to 21C are formed concentrically around the center O2 at equal intervals in the circumferential direction, and the pin holes 21A to 21C are formed. , And pins 22, 22... Are loosely inserted therein, respectively. The pin 22 is installed between the output shaft 9 and the disk-shaped carrier 24 arranged inside the case cover 5 in a concentric circle centered on the axis of the internal gear 4 and parallel to the axis. A cylindrical metal 23 is integrally packaged on the shaft body at the loosely inserted portion of the external gear 17A to 17C on the outer periphery of the pin 22. The carrier 24 supports the inner half of the outer ring 10 a of the ball bearing 10 inside the case cover 5, and is rotatable integrally with the output shaft 9 via the pin 22. Here, the pin 22 and the output shaft 9 connected via the pin 22 serve as an output unit.

In each pin 22, the outer circumference of the metal 23 is inscribed in the inner circumference of the pin holes 21A to 21C of the front and rear external gears 17A, 17A (17B, 17B and 17C, 17C) at a phase different from each other by 180 degrees. The hole diameters of the pin holes 21A to 21C of the external gears 17A to 17C are set for the differential speed reducers 1A to 1C, respectively. That is, the diameter of the pin holes 21A to 21C in the external gears 17A to 17C is a dimension obtained by adding twice the eccentricity amount δ1 to δ3 of the external gears 17A to 17C to the diameter of the pin 22 including the metal 23. Thus, the hole diameters of the pin holes 21A to 21C are different for each of the differential speed 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 are all the same.

On the other hand, the ball bearing 10 is fitted into the inner peripheral surfaces of the case cover 5 and the carrier 24 with a gap, and is inserted between the case cover 5 and the carrier 24 supporting the outer ring 10a, as shown in FIG. A gap A is formed in the axial direction of the shaft 12 and communicates with the inside of the casing 2. In addition, ring-shaped grease grooves 25, 25 are formed on the inner peripheral surfaces of the case cover 5 and the carrier 24 over the entire circumference.
Further, an oil seal 27 as a seal member is interposed between the ring-shaped protrusion 26 protruding from the front surface of the case cover 5 and the outer peripheral surface of the input shaft 12. An oil seal 28 is also provided on the output side of the cross roller bearing 8 between the outer case 6 and the output shaft 12. An oil seal 29 is also provided on the output side of the ball bearing 11 between the output shaft 9 and the input shaft 12.

In the differential reduction gears 1A to 1C configured as described above, when the input shaft 12 is rotationally input and the input shaft 12 rotates, the front and rear eccentric portions 14A to 14C symmetrically perform eccentric movements, respectively, and the external teeth. The gears 17A to 17C are eccentrically and rotated while being inscribed in the internal gear 4. Therefore, the pin holes 21A to 21C also move eccentrically and rotate, but since the pin holes 21A to 21C are formed to have a larger diameter than the pin 22 including the metal 23, the pin holes 21A to 21C are formed. The eccentric component is absorbed by the eccentric movement in a state of being inscribed in, and only the rotation component is extracted from each 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 reduction ratio described above. Here, in the series S, the differential speed reducer 1A has a reduced speed, the differential speed reducer 1B has a medium speed reduction, and the differential speed reducer 1C has a high speed reduction.

At this time, the grease filled in the casing 2 is supplied to the grease grooves 25, 25 from the gap A through the outer ring 10a, the inner peripheral surface of the case cover 5 and the inner peripheral surface of the carrier 24, and lubrication is performed. Retained and reduced friction. Further, even if the grease is supplied in this manner, since the oil seal 27 is interposed between the case cover 5 and the input shaft 12, the grease does not leak.

(Effect of the invention related to the series of differential reduction gears)
As described above, according to the series S of the differential reduction gears 1A to 1C of the above-described embodiment, the pin holes 21A to 21C of the external gears 17A to 17C are respectively arranged according to the number of external gears. By forming the internal gears 4, the pins 22, and the metal 23 in common for each of the 17C, the external gears 17A to 17C have pin holes 21A to 21C each having a hole diameter corresponding to one reduction ratio. It is sufficient to form only 21C. Therefore, the parts can be shared and the manufacturing cost can be suppressed without reducing the strength of the external gears 17A to 17C.
Particularly here, since the center positions of the pin holes 21A to 21C coincide with each other among the external gears 17A to 17C, the output shaft 9 and the carrier 24 can be shared.

The tooth profile of the internal gear 4 and the external gears 17A to 17C is an involute tooth profile.
According to JGMA (Japan Gear Manufacturers Association standard) (JGMA 611-01) "ISO standard compliant cylindrical gear shift method", which is a gear standard of the Japan Gear Manufacturers Association, involute internal teeth are considered in consideration of gear meshing efficiency. It is recommended that the total value of the shift coefficient of the gear and the shift coefficient of the involute external gear be 1 or less.
However, in the present embodiment, the dislocation coefficient of the internal gear 4 is set to more than 1 and up to 1.9 to increase the root diameter of the external gears 17A to 17C meshing with the internal gear 4. Therefore, it is possible to secure the wall thickness of the tooth bottoms of the external gears 17A to 17C and the pin holes 21A to 21C.
Note that FIG. 4 is a graph comparing changes in efficiency (transmission efficiency) when the input torque is changed to 1 N·m at an input of 2000 rpm with the dislocation coefficient of the internal gear 4 set to 1.9 and 0.2. No. The solid line of No. 1 is the dislocation coefficient 1.9 (the number of teeth is 76, the number of teeth difference is 1, the reduction ratio is 1/75), and The dotted line 2 indicates the case where the dislocation coefficient is 0.2 (the number of teeth is 60, the number of teeth difference is 1, and the reduction ratio is 1/59).
Here, the maximum efficiency is about 68% at a dislocation coefficient of 1.9 and about 70% at a dislocation coefficient of 0.2, and it can be seen that even if the dislocation coefficient becomes 1.9, the efficiency is not significantly affected. ..

Furthermore, since the number of the pins 22 of the output section is eight, the rigidity of the differential speed reducers 1A to 1C can be increased. Particularly, 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, the number of the pins 22 can be easily set to eight or more.
Further, in order to increase the rigidity of the differential speed reducers 1A to 1C, it is effective to make the pin 22 thick. When many inner roller holes are formed in the external gear for each reduction gear ratio as in the background art mentioned above, it is difficult to make the inner roller holes close to each other and thicken the pin. Since only the pin holes 21A to 21C corresponding to one reduction ratio are formed in the tooth gears 17A to 17C, the distance between the pin holes 21A to 21C can be secured. Therefore, it is possible to easily increase the rigidity by increasing the thickness of the pin 22.

In addition, since only the pin holes 21A to 21C corresponding to one reduction gear ratio need to be formed in the external gears 17A to 17C, each differential reduction gear 1A to 1C can be used as a series of three different reduction gear ratios. Therefore, the strength of the external gears 17A to 17C does not decrease. Therefore, three or more types of series can be configured with the internal gear 4, the pin 22, the metal 23, the output shaft 9, and the carrier 24 being common.
Further, by making the input shaft 12 hollow, 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 types of differential reduction gears is illustrated, but the reduction ratio and the number of differential reduction gears are not limited to this, and two or four or more types of differential reduction gears having different reduction ratios are used. Even in the series, it is possible to share the internal gear and the output section. Each reduction ratio is also not limited to the above-mentioned form. The number of external gears provided in each differential speed reducer can be increased or decreased.
Further, in the above-described embodiment, the pin is covered with a metal, but a rolling element such as a roller may be mounted on the pin, or the pin alone may not be armed with such a separate member.

(Effects of Invention of Eccentric Bearing and Outer Diameter of Eccentric Part)
As described above, according to the differential reduction gears 1A to 1C of the above-described embodiment, the eccentric portion bearing is the full-roller needle bearing 15, and the outer diameter D2 of the eccentric portions 14A to 14C of the input shaft 12 is the ball bearing. Since the outer diameter of the needle 16 is smaller than the outer diameter D1 of the shaft support 13, the outer diameter of the needle 16 can be increased, leading to an increase in strength.
In particular, here, a retaining portion is provided between the ball bearings 10 and 11 and the needle bearing 15 on the outer periphery of the input shaft 12 so as to abut the side surfaces of the ball bearings 10 and 11 to regulate the axial movement of the input shaft 12. Since the eccentric portions 14A to 14C are formed to be lower than the retaining portion 18 over the entire circumference by providing 18, 18, the needle 16 is provided over the entire circumference of the eccentric portions 14A to 14C as a total roller. The movement in the axial direction can be restricted. Further, the retaining portion 18 can be commonly used for retaining both the ball bearings 10 and 11 and the needle 16. Further, the retaining portion 18 also serves as a retaining stopper for the input shaft 12 itself.

Further, since the retaining portion 18 has a disc shape that is integrally formed coaxially with the input shaft 12, the retaining portion 18 can be easily processed by a lathe or the like.
Further, since a plurality of sets of eccentric portions 14A to 14C, needle bearings 15 and external gears 17A to 17C are provided to make the outer diameters of the eccentric portions 14A to 14C all equal, the same needle is used for each eccentric portion 14A to 14C. The bearing 15 can be arranged, and the outer diameter of the needle 16 of each needle bearing 15 can be increased.
In addition, since the external gears 17A to 17C and the needle bearings 15 have the same shape, further cost reduction can be expected.
Since the needle 16 of the needle bearing 15 can be arranged at a position close to the center O1 of the internal gear 4 (axial center of the input shaft 12), the diameter of the pin 22 for taking out the rotation motion from the external gears 17A to 17C is set to be small. Can be large. Therefore, the strength of the differential speed reducers 1A to 1C can be increased.

It should be noted that the shape of the retaining portion is not necessarily a disc shape, and may be a gear shape in which a plurality of protrusions are formed on the outer periphery as long as the movement of the needle can be restricted, or a shape separate from the input shaft It may be a member.

(Effect of Invention of Differential Reduction Gear for Supporting Ball Bearing)
As described above, according to the differential reduction gears 1A to 1C of the above-described embodiment, the outer ring 10a of the ball bearing 10 is supported by the case cover 5 of the casing 2 and the carrier 24, so that the input shaft 12 and the casing 2 are separated from each other. The coaxiality can be increased and the input shaft 12 can be assembled accurately.
In particular, here, since the outer ring 10a of the ball bearing 10 is fitted in the case cover 5 and the carrier 24 with a gap, the outer ring 10a can be slid on the sliding surface and the rotational resistance is reduced.

Further, since the grease grooves 25, 25 are formed on the sliding surface between the outer ring 10a fitted in the clearance and the case cover 5 and the carrier 24, the sliding surface retains the grease and slides with low friction. be able to.
Further, since the grease groove 25 is formed in the case cover 5 and the carrier 24, the standard ball bearing 10 can be adopted, and the cost increase can be suppressed.
In addition, since the grease groove 25 is formed over the entire circumference of the sliding surface, the grease groove 25 can be easily processed by a lathe or the like.
Since the oil seal 27 that seals between the casing 2 and the input shaft 12 is arranged outside the ball bearing 10 in the axial direction of the input shaft 12, the casing 2 and the input shaft 12 having a high degree of coaxiality are provided. The oil seal 27 can be brought into contact with the input shaft 12 with high accuracy during the interval, and the risk of grease leakage can be reduced.

In the above embodiment, the outer ring of the ball bearing is fitted in both the case cover and the carrier with a gap, but may be fitted into only one of the case cover and the carrier. Therefore, the grease groove may be provided only on the sliding surface on one side where the clearance is fitted.
When the grease groove is provided, it can be provided not only over the entire circumference of the sliding surface but also intermittently in the circumferential direction.

Other than the above, the structure of the casing is not limited to the combination of the middle case, the case cover, and the outer case, and the number of parts may be increased or decreased, or the casing may be formed by one member. It doesn't matter.
Further, the outer bearing is not limited to the cross roller bearing, other bearings such as a ball bearing can be adopted, and the number of bearings may be increased.
Further, the structures of the input shaft and the output shaft are not limited to the above-described forms, and the design can be changed as appropriate, such as making the input shaft solid rather than hollow.

1A to 1C ··· Differential reducer 2··Casing 3·· Medium case 4·· Internal gear 5·· Case cover 6·· Outer case 7·· Bolt 8·· Cross roller Bearing, 9... Output shaft, 10... Ball bearing, 10a... Outer ring, 11... Ball bearing, 12... Input shaft, 13... Shaft support, 14... Eccentric part, 15... Needle bearing, 16 ..Needles, 17A to 17C..External gears, 18...Retaining portions, 21A to 21C..Pin holes, 22..Pins, 23..Metal, 24..Carriers, 25..Grease grooves, 27 , 28, 29..Oil seal, S..Series, A..Gap, D1..outer diameter of shaft support, D2..outer diameter of eccentric part, O1..center of internal gear, O2..outer Center of tooth gear, δ1 to δ3...Eccentricity.

Claims (6)

An output part supported in the casing via an outer bearing, an internal gear provided in the casing, an input shaft penetrating the output part and the internal gear coaxially, and supported via an inner bearing. And an external gear that is externally mounted on an eccentric portion provided on the input shaft via a bearing for the eccentric portion and internally meshes with the internal gear and meshes with the output gear via a pin that loosely inserts the external gear. A carrier connected to the internal gear, and the external gear rotates eccentrically with respect to the internal gear due to the rotation of the input shaft, whereby the number of teeth of the internal gear and the external gear is increased. A differential speed reducer for rotating the output section via the pin at a speed reduction ratio based on a difference and the number of teeth of the external gear,
A differential reduction gear characterized in that an outer ring of the inner bearing is supported by the casing and the carrier. The differential reduction gear according to claim 1, wherein an outer ring of the inner bearing is fitted in the casing and/or the carrier with a gap. The differential reduction gear according to claim 2, wherein a grease groove is formed on a sliding surface between the outer ring fitted in the clearance and the casing and/or the carrier. The differential reduction gear according to claim 3, wherein the grease groove is formed in the casing and/or the carrier. The differential reducer according to claim 3 or 4, wherein the grease groove is formed over the entire circumference of the sliding surface. The seal member which seals between the casing and the input shaft is arranged outside the inner bearing in the axial direction of the input shaft. Differential reducer.

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