WO1998036189A1

WO1998036189A1 - Compound oscillatory roller transmission

Info

Publication number: WO1998036189A1
Application number: PCT/US1998/002810
Authority: WO
Inventors: Chen Bo; Chen Shixian; Chen Zhi
Original assignee: Chen Bo; Chen Shixian; Chen Zhi
Priority date: 1997-02-17
Filing date: 1998-02-13
Publication date: 1998-08-20
Also published as: CN1191284A; AU6163798A; CN1068664C

Abstract

A speed-changing device comprising a planetary gear stage integrated with an oscillatory roller transmission (ORT) stage. The ORT stage having eccentric wave actuating disk (14) mounted on eccentric portions (18) of crankshafts (11) of the planetary stage, rollers (20) mounted in radial slots (27) of transmission disks via pin (26), with the rollers acting on the internal gear (30).

Description

COMPOUND OSCILLATORY ROLLER TRANSMISSION

Technical Field

This invention relates to a speed-changing device more particularly, to a speed-

changing device that employs movable gear teeth or rollers to transmit movement and

torque.

Background Art

We have previously described a mechanism called Oscillatory Roller Transmission in Chinese patents CN91,01060.2 and CN96,215,504.7. The

transmission ratio of this previous mechanism is limited by the number of rollers that can be arranged on the oscillatory roller gear.

There are also known cycloidal type drives that are widely used in robotics and motion control industries as shown in US patents 4,348,918, 4,690,010 and 5,322,485. The stress on the bearings that support the eccentric crankshafts is very high since those bearings take loads not only directly from the low speed shaft, but also from the eccentric cams and the first stage spur gears. Disclosure of Invention

Accordingly, the objective of the present invention is to provide a speed-

changing device that has high speed-changing ratios, low bearing loads and compact

size, thereby overcoming the inherent shortcomings of the prior arts. Further objects

and advantages of the present invention will become apparent from a consideration of

the drawings and ensuing description.

Referring now to Figs. 1 and 2, the present invention is a speed-changing

device comprising two stages such that the overall transmission ratios of the speed-

changing device can be provided by selecting various ratio combinations of the two stages The first stage comprises a pinion 13 attached to a high speed shaft 10, and to

engage with a plurality of planetary gears 12 coupled with a plurality of crankshafts 11

The crankshafts 11 have eccentric portions 18 that are assembled in a wave-actuating

disk 14 via eccentric bearings 16 to form the wave actuator of the second stage,

whereby the wave-actuating disk 14 has an eccentricity e to the center line 50 The

second stage applies the mechanism of the Oscillatory Roller Transmission (ORT),

which comprises three major components a wave actuator, an oscillatory roller gear

and an internal gear The internal gear 30 is fixed on or an integral part of a casing and

has Zg numbers of inner gear teeth, which have a tooth profile of the envelope curve

of the oscillatory rollers 20 The oscillatory roller gear comprises two force-

transmitting disks 21 and 23 that are linked together by supporting portion 22 via through-holes 15 on the wave-actuating disk 14 Zh number of oscillatory rollers 20,

supported on axle pins 26 via needle bearings 28, are assembled in radial pin slots 27

on the force-transmitting disks 21 and 23 Thus, the wave-actuator orbits around the

center line 50 and pushes oscillatory rollers 20 of the oscillatory roller gear to move in

the axial direction meshing with inner gear teeth of the internal gear 30 The

oscillatory rollers 20 rotate along the surface of the internal gear 30, driving the force-

transmitting disks 21 and 23 to rotate via axle pins 26, thereby transmitting the

movement and force to the low speed shaft 60 The transmission ratio of the ORT

stage equals the numbers of the oscillatory rollers Zh, which can be one more or less

than the number of the inner gear teeth Zg of the internal gear 30 Since the force-

transmitting disks 21 and 23 are connected together through supporting portions 22,

more oscillatory rollers can be arranged on the oscillatory roller gear than a regular

ORT drive which the force-transmitting disks are connected together via rods between the oscillatory rollers The greater number of oscillatory rollers combined with the

reduction provided by the first stage vastly increases the overall transmission ratio of

the speed-changing device In addition, unlike the cycloidal type drives, in the present

invention, the torque of the low speed shaft 60 is applied to the multiple oscillatory

rollers directly, therefore the supporting bearings 17 of the crankshafts only take loads

from the eccentric portions 18 and the planetary gears 12 The multiple rollers/gear

teeth engagement provides the speed-changing device with high load capacity and

especially high shock load tolerance Furthermore, this engagement also enables the speed-changing device to operate even if a few of the oscillatory rollers are missing

Any one of the three components the high speed shaft 10, the internal gear 30

and the low speed shaft 60, can be grounded so that the other two serve as input and output components When none of the components are grounded, the transmission is a differential

The first stage reduction gear can combine with one row or more than one row of ORT reduction gears It is preferable to use two or three rows of ORT reduction gears that are 180 or 120 degrees in phase respectively, so that the forces caused by

the eccentricity can be balanced Brief Description of Drawings

Fig 1 is a transverse sectional view, partially broken away, of the compound oscillatory roller transmission

Fig 2 is a cross-sectional view along the shaft of the compound oscillatory roller

transmission shown in Fig 1

Fig 3 is a transverse sectional view, partially broken away, of an embodiment of the

compound oscillatory roller transmission

Fig 4 is a cross-sectional view along the shaft of the embodiment shown in Fig 3 Best Mode for Carrying Out the Invention

Referring now to Figs 3 and 4, the preferred embodiment of the present

invention is a speed reducer comprising a spur gear reduction stage and an ORT

reduction stage The spur gear reduction stage comprises a pinion 13 coupled with a

high speed input shaft 10, to engage with three planetary gears 12 coupled with three

evenly angular spaced crankshafts 11 Clearly, depending on the size of the speed

reducer, the number of the crankshafts can be less or more than three The ORT

reduction stage comprises two rows of ORT reduction gears, each comprising a wave actuator, an oscillatory roller gear and an internal gear The two rows of ORT

reduction gears are arranged symmetrically to balance the forces caused by the eccentricity It is best to place the spur gears of the first stage between the two rows of oscillatory roller gears to keep the structure compact Nevertheless, an arrangement with the first stage outside the two rows of oscillatory roller gears is

applicable for other purpose The three crankshafts 11 are supported on two force-

transmitting disks 21 and 21a via tapered roller bearings 17 Each of the three

crankshafts 11 has two eccentric portions 18 such that their eccentricities are 180

degrees in phase Obviously, the two eccentric portions 18 can also be two eccentric

cams mounted on a straight crankshaft Two wave-actuating disks 14 are assembled

on the eccentric portions 18 via eccentric bearings 16 to form the two wave actuators

of the ORT stage Each of the mternal gears 30 has Zg numbers of inner gear teeth,

where the inner gear teeth have the profile of the envelope curve of the oscillatory

rollers 20 Each of the oscillatory roller gears comprises Zh numbers of oscillatory

rollers 20 that mesh with the inner gear teeth of the mternal gear 30, where Zh can be

one more or less than Zg The oscillatory rollers 20 supported by axle pins 26 hke

journal bearings are assembled in radial pin slots on the force-transmitting disks 21, 21a and 23. Three supporting portions 22 link the force-transmitting disks 21, 21a

and 23 across the through-holes 15 on the wave-actuating disks 14. The gaps between

each side of the supporting portions 22 and the edges of the through-holes 15 are

larger than twice the eccentricity of the wave actuators, such that the wave actuators

can orbit without interference. The supporting portions 22 are integral portions of the

center force-transmitting disk 23 with a shell-like shape. Obviously, they can be

separated parts and/or different shapes.

The high speed pinion 13 drives the planetary gears 12 and the crankshafts 11

to rotate, whereby the eccentric portions 18 of the crankshafts 11 bring the wave

actuators to orbit around the center line 50. The wave-actuating disks 14 push the

oscillatory rollers 20 to move in the radial direction and to mesh with the internal gears

30. Rotating on the surface of the internal gears 30, the oscillatory rollers 20 drive the force-transmitting disks 21, 21a and 23 through axle pins 26 to rotate, thereby

transmitting movement and torque to the slow speed shaft 60. As we have described previously in the ORT patents, the oscillatory rollers can have different configurations depends on ratio and size of the speed reducer. For

example, the oscillatory rollers can be rolling bearings supported on axle pins. Obviously, the oscillatory rollers may also be rolling wheels mounted on axle pins like

journal bearings or axle pins with both ends supported on small rings.

The speed reducer may be used in various ways. Any one of the three

components: the high speed shaft 10, the internal gear 30 and the low speed shaft 60

can be grounded so that the other two serve as input and output components. When

none of the components are grounded, the transmission is a differential.

Claims

Claims of the Invention

We claim

1 A speed-changmg device comprising

a sun gear attached to a high speed shaft,

a plurality of planetary gears meshing with said sun gear,

a plurality of rotatably mounted crankshafts coupled with said planetary gears and having eccentric portions,

at least one wave-actuating disk which has a plurality of shaft holes angular spaced

evenly to each other, whereby said eccentric portions of said crankshafts being inserted into said shaft holes so that rotation of the crankshafts drives said wave- actuating disk to revolve eccentrically,

said wave-actuating disk having a plurality of through-holes, each through-hole being placed between adjacent shaft holes, at least one oscillatory roller gear comprising

supporting means attached to a slow speed shaft having a plurality of radial pin slots,

connecting means loosely inserted into said through-holes of the wave-actuatmg disk and linking said supporting means, wherein the opposite ends of the supporting means support the crankshafts to rotate,

a plurality of rolling means being supported on axle pms which are assembled in

said pin slots on said supporting means,

at least one internal gear surrounding said oscillatory roller gear and having inner gear

teeth which mesh with said rolling means of the oscillatory roller gear,

whereby, eccentric revolving of the wave-actuating disk pushes said rolling means to

move in the radial direction and to rotate along the gear tooth surface of said internal gear, thereby transmitting movement and torque to said slow speed shaft via the axle

pins

2 A speed-changing device according to claim 1, wherein any one of the three

components said high speed shaft, said low speed shaft and said internal gear can

be grounded so that the other two serve as input and output components of said speed-changing device

3 A speed-changing device according to claim 1, wherein none of the three

components said high speed shaft, said low speed shaft and said internal gear is

grounded so that the speed-changing device is a differential transmission 4 A speed-changing device according to claim 1, wherein the number of said rolling means is one less or more than the number of inner gear teeth of said internal gear

5 A speed-changing device according to claim 1, wherein arranging n rows of the combination of said wave actuator, said oscillatory roller gear and said internal

gear 360°/n in phase so that the internal forces of said speed-changing device

caused by the eccentricity are balanced

6 A speed-changing device according to claim 1, wherein said wave-actuatmg disk

being rotatable mounted on said eccentric portions of said crankshafts via eccentric

rolling bearings, whereby rotation of the crankshafts drives the wave-actuating disk to revolve eccentrically

7 A speed-changmg device according to claim 1 , wherein said eccentric portions of

said crankshafts comprises eccentric cams mounted on straight crankshafts

8 A speed-changing device according to claim 1, wherein said connecting means of

said oscillatory roller gear is loosely inserted into said through-holes of said wave-

actuating disks, such that the gaps between the connecting means and the edges of the through-holes being wide enough to allow the wave-actuating disks revolving

eccentrically without interference.

9. A speed-changing device according to claim 1, wherein said supporting means and

connecting means are separated parts or integrated to one another for easy manufacturing.

10. A speed-changing device according to claim 1, wherein said rolling means of said

oscillatory roll gear are rolling bearings supported on said axle pins.

11. A speed-changing device according to claim 1, wherein said rolling means of said oscillatory roll gear are journal bearings supported on said axle pins. 12. A speed-changing device according to claim 1, wherein the number of said planetary gear and said crankshaft is one.