BACKGROUND OF THE INVENTION

1. Field of the Invention

This present invention relates to a transmission apparatus, more particularly, to a

transmission apparatus that employs gears having movable gear teeth. This type of device can be used for a broad range of applications, which require motion and power to be

transmitted continuously from an input element to an output element with a predetermined

velocity ratio.

2. Description of the Related Art

There are known mechanical power transmission devices comprise gears having a

plurality of movable gear teeth that mesh with stationary gears, such as U.S. patent

No.4.798,104. Chinese patent No.CN85,10T,702A. Chinese patent No.CN86,200.768U. and Russian patent No. SU-1.307.129. Since sliding occurs between moving pairs among the

wave generators, the movable gear teeth and their carriers, and the stationary gears, these

types of devices have low transmission efficiency and high wear.

Sliding also occurs in the variable speed transmission apparatus of U.S. patent

No.4.856,378 because the rollers can only rotate with either the eccentric cam or the

stationary gear but not both at the same time. This type of device has limited transmission

ratios and loading capacity since the number of inner teeth of the stationary gear is two less

than that of the rollers of the special gear, so that only a few gear teeth are engaged at any

time. Furthermore, because the eccentricity of the extendable cam varies, the transmission

ratio is not constant. Similarly, the loading capacity and transmission ratio of U.S. patent

No.3,468,175 are also limited because it requires the number of the movable gear teeth to be a

harmonic of the number of the casing teeth. In addition, this design requires complicated

movable gear teeth comprising five different rollers.

U.S. patent No.4, 713,985 provides a pure rolling-style transmission. However, the

connecting elements on the carrier disk not only reduce the number of driving rollers but also

increase their size. This type of transmission device has limited loading capacity because it

has less engaged gear teeth. It also has limited transmission ratio because fewer driving

rollers can be arranged on the carrier disk. Furthermore, the asymmetrical gear tooth profile of the casing and the structure of the connecting elements make this transmission suitable

only for rotating in the pulling direction of the connecting elements.

In Chinese patent No.CNl,020,383C one of the present inventors Zhi Chen proposes

an oscillatory tooth transmission which eliminates sliding from all relative moving pairs. As

it is shown by Fig. 10, the oscillatory tooth gear comprises two gear tooth carriers, staggered

at a half pitch of a gear tooth, and connected by a plurality of screws. Holding a row of

oscillatory teeth, each gear tooth carrier comprises a force-transmitting disk 23 and an

oscillatory tooth disk 22. This arrangement is difficult to produce and subject to assembly

error. In addition, the oscillatory gear carrier has limited strength and stiffness.

SUMMARY OF THE INVENTION

Accordingly, the present invention has the following advantages and objectives: first,

the relative movements among all components are of rolling style; second, there are many

engaged gear teeth at any time; third, it has a high transmission ratio; fourth, the oscillatory

roller gear can be easily produced and accurately assembled; thereby overcoming the

inherent shortcomings of the prior arts. Further objects and advantages of our invention will

become apparent from a consideration of the drawings and ensuing description.

Referring to Fig. 1 and 2. the present invention is a transmission apparatus comprising

three components: a wave actuator, an oscillatory roller gear, and a stationary gear. Said

wave actuator comprises a wave-actuating disk 4 mounted on a rolling bearing 15 which is

attached to an eccentric cam 1. Said oscillatory roller gear comprises Zh number of oscillatory rollers assembled in Zh radial roller slots 36 on the oscillatory roller carrier 31,

where Zh = i, i is the transmission ratio. Each of the oscillatory rollers comprises a rolling

ring 10 mounted on a rolling bearing 40 supported by an axle pin 11. Both ends of said axle

pin rest in one of the Zh pin slots 37 of the oscillatory roller carrier. Said stationary gear 2

has Zg number of inner teeth, where Zg = Zh ± 1. Each inner tooth has a tooth profile of the

envelope curve of the oscillatory rollers. Any one of the three components: the wave

actuator, the oscillatory roller gear, and the stationary gear, may be chosen as a fixed

component, the other two then form a speed-reducing or a speed-increasing transmission. If

none of the components are fixed, they will form a two-in/one-out differential transmission.

When operating, each of the oscillatory rollers is in contact with three parts: the wave-

actuating disk 4 of the wave actuator, the stationary gear 2, and the oscillatory roller carrier

31, forming three associated moving pairs. Take, for example, a speed reducer configuration

in which the stationary gear is the fixed component: The wave actuator is connected to a high

speed input shaft and the oscillatory roller carrier to a slow speed output shaft. Rotating with

the input shaft, the wave actuator pushes the oscillatory rollers. The oscillatory rollers move

radially while they are rolling along the inner surface of the stationary gear, driving the

oscillatory roller carrier to rotate, thereby transmitting movement and power to the slow

speed output shaft. Since the wave- actuating disk 4 is mounted on the eccentric cam 1

through the rolling bearing 15, the wave actuating disk can rotate freely with the oscillatory

rollers. Furthermore, since the rolling ring 10 of the oscillatory roller is mounted on the axle pin 11 through the rolling bearing 40, the rolling ring and the axle pin are separated from each

other, presenting two separate and freely rotating surfaces. The axle pin rests loosely in the

pin slot 37 of the oscillatory roller carrier, so that the axle pin can roll radially on the surface

of the pin slot. The roller slot 36 of the oscillatory roller carrier is wider than the diameter of

the rolling ring 10, allowing the rolling ring to retract in the roller slot without contacting the

oscillatory roller carrier. This arrangement separates the above-mentioned three associated

moving pairs, such that each moving pair can rotate independently, achieving a rolling style

of movement between each transmission pair.

Generally, the gear tooth profile of the stationary gear 2 is an envelope curve of the

rolling ring 10, generated when the oscillatory roller, pushed by the wave actuator, moves

radially while circling at a constant speed according to a transmission ratio i (See Figure 3a).

To improve the engaging in/out conditions between the rolling ring and the inner teeth of the

stationary gear, the gear tooth profile of the stationary gear can be a corrected envelope curve

of the oscillatory rollers (See Figure 3b). Said corrected envelope curve is a curve such that

the peak and valley of a gear tooth are trimmed 0.05-0.3 mm more than the theoretical

envelope curve, and with a gradual transition to the theoretical envelope curve within 0-30°

and 150-180° of the according 0-180° working range of the wave actuator. To simplify the

manufacture process, the gear tooth profile of the stationary gear can also be an approximated

envelope curve of the oscillatory rollers smoothed from three to five segments of circles (See

Figure 3c). Said circles should be decided by the radius of the curvature of three to five

points on the theoretical envelope curve (i.e. ab. be, cd of Figure 3c).

The merits of this invention are:

A. High loading capacity and high shock overload tolerance:

The oscillatory roller transmission has more engaged teeth. In the present embodiment

approximately 50% of the teeth are engaged at any time, achieving a loading capacity 5-6

times that of a similar sized conventional transmission. For the same reason, it also

withstands high shock overload and eliminates catastrophic failure.

B. High efficiency, low heat generation, and low operation noise:

Within the moving mechanism of present invention all contacts are rolling contacts. It

achieves a transmission efficiency of 90%-96% within its general range of transmission

ratio. Rolling contacts also reduces the heat and noise generated during operation.

C. High transmission ratio and small size:

The transmission ratio of the present invention ranges from 4: 1 - 60:1 for a single stage,

and from 60: 1 - 3600: 1 for a double stage. For a similar power and transmission ratio, the

size of the present invention may be 1/3 that of a conventional transmission and 1/2 that

of a worm drive.

D. Simple structure and low production cost:

The present invention has simplified the structure of our previous design, particularly the

construction of the oscillatory roller carrier. This new design makes it easier to produce

and assemble accurately, reducing manufacturing costs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a transverse sectional view, partially broken away, of the oscillatory roller

transmission apparatus.

FIG. 2 is a cross-sectional view along the shaft of the oscillatory roller transmission

apparatus.

FIG. 3 shows the tooth profile of the inner teeth of the stationary gear.

(3a) is the envelope curve generated when the oscillatory roller, pushed by the wave

actuator, moves radially, while rotating at a constant speed according to a transmission

ratio i.

(3b) is the corrected envelope curve trimmed at the peak and bottom of a tooth.

(3c) is the approximated envelope curve smoothed from three segments of circle ab, be,

cd.

FIG. 4 shows the structure variations of the oscillatory roller of the present invention.

(4a) shows an oscillatory roller comprising a standard rolling bearing mounted on an axle

pin.

(4b) shows an oscillatory roller comprising a rolling wheel mounted on a needle bearing

which is supported by an axle pin.

(4c) shows an oscillatory roller comprising a rolling wheel supported by a sleeve, which

is attached to an axle pin.

(4d) shows an oscillatory roller comprising a rolling wheel supported directly by an axle

pin.

Fig. 5 shows the structures of the oscillatory roller carrier of the present invention.

(5a) shows an assembled oscillatory roller carrier.

(5b) shows the three major components of an oscillatory roller carrier: an oscillatory roller

disk and two force-transmitting disks.

(5c) is the lateral view of the force-transmitting disk from direction K.

(5d) is the lateral view of the oscillatory roller disk from direction N.

Fig. 6 shows a variation of the structure of the oscillatory roller carrier of the present

invention.

(6a) is the design of an oscillatory roller carrier in which the oscillatory roller disk and

two force-transmitting disks assembled together through a plurality of rods.

(6b) shows a connecting rod.

(6c) shows the connections of the oscillatory roller disk and the force-transmitting disk.

(6d) is the lateral view of the force-transmitting disk from direction K.

(6e) is the lateral view of the oscillatory roller disk from direction N.

Fig.7 shows a four-row configuration of an oscillatory roller carrier.

(7a) shows the assembled four-row design of an oscillatory roller carrier.

(7b) is the lateral view of the force-transmitting disk from direction K.

(7c) is the lateral view of the oscillatory roller disk from direction N.

Fig. 8 is a transverse sectional view of an embodiment of the oscillatory roller transmission

apparatus.

Fig. 9 is the cross-sectional view along the shaft of an embodiment of the oscillatory roller

transmission apparatus.

Fig. 10 is the cross-sectional view along the shaft of an embodiment of a prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to Fig. 8 and Fig. 9, the preferred embodiment of this invention is an

oscillatory roller speed reducer in which Zg = Zh + 1 , transmission ratio i = + Zh. In other

words, the low- speed output shaft 5 rotates in the same direction as the high-speed input

shaft 14. A twin row arrangement is applied in order to increase the numbers of engaged

gears and to form a symmetrical layout, thus keeping the internal loads balanced.

Accordingly, this speed reducer comprises two wave actuators, an oscillatory roller gear, and

a stationary gear. Rolling bearings 16 and 17 support the input shaft. The two wave actuators

are mounted on the high-speed input shaft and positioned by ring 9. The peaks of the

eccentric cams 1 of the two wave actuators are staggered 180° in phase. The oscillatory roller gear comprises an oscillatory roller carrier 31 and two rows of oscillatory rollers. The

oscillatory roller carrier comprises an oscillatory roller disk 3 and two force-transmitting

disks 8 and 12 connected altogether via screw 21. The two rows of oscillatory rollers are

assembled in phase on the oscillatory roller carrier. The two wave actuators sit inside the

oscillatory roller gear between the oscillatory roller disk and the force-transmitting disks,

such that the wave-actuating disks 4 contact the oscillatory rollers. The stationary gear 2 has

two rows of inner teeth. To match the positions of the wave actuators, the two rows of inner

teeth are staggered at a half pitch of a gear tooth. Each row of the stationary gear has Zg

number of inner teeth in mesh with the oscillatory rollers. The oscillatory roller carrier 31 is

attached to the low speed shaft 5 through the force-transmitting disk 8 to form the output

rotor of the speed reducer. The rolling bearing 18 on the large cover 13 and the rolling

bearing 19 on the case 7 support the output rotor. The small cover 6 fixed the output rotor

axially.

Referring to Fig.5, the oscillatory roller carrier 31 comprises an oscillatory roller disk

3 and two force-transmitting disks 8 and 12. The oscillatory roller disk has Zh number of

radial roller slots 36 and Zh number of radial pin slots 37 at both ends. The roller slots at the

opposite ends of the oscillatory roller disk are in phase and the pin slot is in the center of the roller slot. The force-transmitting disks also have Zh number of radial pin slots. The two

force-transmitting disks are assembled at the ends of the oscillatory roller disk 3. The pin

slots on the oscillatory roller disk align with the pin slots on the force-transmitting disks, such

that both ends of the axle pin 11 of the oscillatory roller rest in the radial pin slots. Figure 6 shows the design in which the oscillatory roller carrier 31 comprises an oscillatory roller disk

3, and two force-transmitting disks 8 and 12. The force-transmitting disks are assembled at

both ends of the oscillatory roller disk through a plurality of rods 38. Both the oscillatory

roller disk and the force-transmitting disks have radial pin slots 37. The pin slots on the

oscillatory roller disk align with the pin slots on the force-transmitting disks, so that the gaps

between pairs of rods form the oscillatory roller slots.

Each wave actuator comprises an eccentric cam 1, a rolling bearing 15, and a wave-

actuating disk 4. Obviously, the wave actuator can also be just a rolling bearing mounted on

an eccentric cam. Each oscillatory roller comprises a rolling ring 10 supported by an axle pin

11, allowing the rolling ring to rotate freely on the axle pin. The gear tooth profile of the

stationary gear 2 is the corrected envelope curve of the rolling ring generated when the

oscillator}' roller moves radially, while circling at a constant speed according to transmission

ratio i. When the eccentric cam 1 rotates clockwise, it pushes the rolling ring 10 to move

radially through the wave-actuating disk 4. The rolling ring engages with the stationary gear

2 and rolls along the surface of the stationary gear, so that the rolling ring circles clockwise

while moving radially. Both ends of the axle pin 11 of each oscillatory roller rest loosely in

the pin slot 37. so that the axle pin can roll radially on the side surfaces of the pin slot. The

plates 20 on the force-transmitting disks decide the axial position of the axle pins. The roller

slot 36 on the oscillatory roller carrier is wider than, the diameter of the rolling ring 10,

permitting the rolling ring to retract in the roller slot without contacting the oscillatory roller

carrier. The axle pin transmits the circumferential movement and force of the rolling ring to

the oscillatory roller carrier. Since the rolling ring rotates freely on the pin. the movements of

the oscillatory rollers are of pure rolling style.

When the peak of the wave-actuating disk 4 engages with the rolling ring 10, and the

rolling ring is at a tooth valley of the stationary gear 2, the instantaneous radial movement

and circumferential force of the rolling ring are zero. When the peak of the wave-actuating

disk 4 has passed the rolling ring 10, the circumferential movement of the oscillatory roller

carrier 31 transmits to the axle pin 11, and thereafter to the rolling ring through the back wall

of the pin slot 37. The rolling ring rolls along the inner surface of the stationary gear,

generating a radial force that pushes the axle pin to roll along the surface of the pin slot,

thereby retracting the oscillatory roller in the roller slot 36. When the lowest point of the

wave-actuating disk 4 engages with the rolling ring 10, the inward radial movement of the

oscillatory roller reaches its limit and retraction stops. The rolling ring will then be ready to

engage with the next tooth of the stationary gear to start another working cycle. Among the

Zh oscillatory rollers, half of them are in working cycle ahead of the peak of the wave-

actuating disk, while the other half are in retracting cycle. The movements of the oscillatory

rollers during both working and retracting cycles are of pure rolling style.

There are various designs to further increase the loading capacity of the speed reducer

for applications requiring high power and compact structure, such as oil drilling and

pumping. The gears of the speed reducer can be arranged in n rows, where n is an integer

greater than two. To keep the internal force in balance, the peaks of the eccentric cams of the

n wave actuators are staggered evenly or symmetrically in phase, while the n rows inner teeth

of the stationary gear matching the distribution of the wave actuators. For example, Fig. 7

shows a four-row design of an oscillatory roller carrier. In one arrangement, the peaks of the

4 wave actuators are 360°/4 in phase while the 4 rows of inner teeth of the stationary gear are

staggered 1/4 pitch of a gear tooth. Another arrangement involves placing two pairs of the 4

wave actuators 180° in phase, and accordingly the inner teeth of the stationary gear are

staggered a half pitch of a gear tooth.

There can be several variations in the structure of the oscillatory rollers to produce

speed reducers of various sizes and transmission ratios. For speed reducers of large size or

small transmission ratio, the oscillatory roller can be a standard rolling bearing 30 supported

on an axle pin 11 (See Fig. 4a). For speed reducers of medium size or transmission ratio, the

oscillatory roller can be a roller ring 10 mounted on an axle pin 11 via the rolling pin 40 (Fig.

4b). For speed reducers of small size or large transmission ratio, the roller ring 10 can be

mounted on the axle pin 11 via the sleeve 50 (Fig. 4c), or the roller ring 10 may be directly

supported by the axle pin 11 (Fig. 4d).