TRANSMITTING UNIT

Abstract: A transmitting unit used for a transmission with a fixed transmission ratio is provided. The external shape of the unit is similar to an ordinary rolling bearing, and it is able to perform transmission with reduction of speed or increase of speed in a clockwise or anti-clockwise direction, the input and output shafts being arranged on the same axis. The transmitting unit is made up by a dual eccentric sleeve (5), a transmitting race (2) with radial grooves, which house transmitting rods (4) enclosing rolling members (3; 23) at both ends to such an extent that each covered length of a rolling member equals the radius of a rolling member, an internal gear race (1) with a teeth or cam profile (20) and rolling bearings (6,16,9). The transmitting unit can be installed like a rolling bearing in a main machine and no transmission boxes are needed. The unit also may be installed as a variable speed transmission mechanism, and can be used in industries requiring the use of various transmission mechanismus with fixed transmission ratios.

Description: This invention relates to a mechanical transmitting unit comprising an input shaft and an output shaft disposed in the same axial line. Such a transmitting unit can be used to reduce or to increase the rotational speed in both directions, i. e. clockwise or counterclockwise. More specifically the invention relates to a transmitting unit as described in the classifying portion of claim 1. In order to realize a coaxial transmitting unit with a fixed transmission ratio, especially a transmitting unit with a relatively large single stage transmission ratio, it is generally known to make use of an epicyclic gearing mechanism having a fixed transmission ratio. In an ordinary epicyclic gearing mechanism, the design is limited by the conditions of transmission ratio, concentricity, assembling, adjacency, and efficiency of the transmission. In order to overcome the disadvantages of ordinary epicyclic gearing, an epicyclic gearing of cycloid needle type was produced however, such a gearing requires special output mechanism, high precision work and thus it is inconvenient in maintenance and repairing work. Moreover, the bearing of the epicyclic gear is under high stress and owing to the limitation in design structure, larger bearings cannot be used. In another known transmitting unit of the kind mentioned in the classifying portion of claim 1 a relatively large single stage transmission ratio is achieved without the usual epicyclic gearing mechanism. In this known construction there still exist the following problems: transmission efficiency is low; heat is easily produced at the contact locations between the teeth profile or cams and the rolling member and also between the rolling member and the internal gear race; the guide grooves suffer early wear; the roller member and the internal gear race easily produce heat during their meshing; etc. The main causes of those problems are that the linear speed of the meshing contact of the high speed cam and of the rolling members on the transmitting race is too high, and that the rolling member and the guide groove in a radial direction of the transmitting race are in direct contact. When the rolling member is in radial motion at remote center position, there is some displacement of the contact position of the rolling member and the guide groove and also some displacement of the contact position of the rolling member and the internal gear race. If the relative motion between the rolling member and the guide groove is pure rolling, then the rolling member should rotate in clockwise direction. If the relative motion between the rolling member and the internal gear race is pure rolling, then the rolling member should rotate in counterclockwise direction. Of course, the same rolling member cannot simultaneously rotate clockwisely and counterclockwisely, thus the rolling member can be neither in normal rolling nor in normal sliding status. The objects of this invention are to provide a transmitting unit with a relatively large single stage transmission ratio without making use of the common epicyclic gearing mechanism and at the same time to overcome the problems of overheating in operation and early wear of the guide grooves, so as to increase transmission efficiency and life time of the transmitting unit. The unit should be assembled like a usual rolling bearing, i. e. transmission bearing. Thus, the unit should offer a series of standard parts to replace conventional transmission boxes. These and other objects are accomplished by the measures specified in claim 1. According to this invention, two rolling bearings are installed on a dual eccentric sleeve to cooperate with the rolling member on the transmitting rod, so as to separate from the high speed rotation of the dual eccentric sleeve; the two ends of each transmitting rod enclose the rolling members to such an extent that the covered length equals the rolling member radius or exceeds this length so that there is no direct contact between the rolling member and the guide groove of the transmitting race; the transmitting rod and the guide groove are in surface contact and thus the problem of early wear of the transmitting race is overcome. Owing to the fact that the transmitting rod carrying the rolling members only moves in radial direction with respect to its guide groove this does not affect the rolling motion during meshing contact of the rolling member with the teeth profile of the internal gear race, pure rolling is guaranteed when the rolling member is in meshing motion. The transmitting race is coaxial with the dual eccentric sleeve, hence enough space is provided for replacing the rolling bearing on the dual eccentric sleeve with a larger one. The outside shape of the whole body is similar to that of a usual rolling bearing and can be installed directly into the main machine. No transmission cases or boxes are required. Thus, the usual epicyclic gearing mechanism is replaced by a simple structure of a coaxial transmitting unit for transmitting speeds and torques with a large fixed transmission ratio in a single stage. A preferred embodiment of the invention is described in the following at hand of the accompanying drawings, in which Fig. 1 is a front view, partly in cross section and Fig. 2 is a section along line II-II. The main parts of the transmitting unit are formed by an annular internal gear race 1, an annular transmitting race 2 and a dual eccentric sleeve 5. The internal gear race 1 comprises two gear race rings 18,19 and an intermediate spacer ring 10. At the inner periphery of the gear race rings 18,19 teeths or cams 20 are formed. Two cover plates 8 cover the outer side surfaces of the gear race rings 18,19, and the above described parts are hold together by rivets 11. The transmitting race 2 comprises a transmitting ring body 21 which has a centre portion 22 and two rows of radial equidistant disposed guide grooves, one row being arranged to face the gear teeth of cams 20 of ring 18 and the other row being arranged to face the gear teeth 20 of ring 19. Each guide groove accomodates a transmitting rod 4, each end of which enclose a rolling member 3,23, respectively,to such an excent that the covering length is equal to or exceeds the radius of the rolling members 3,23. Outer rolling members 3 are in meshing contact with the gear teeth 20, whereas the inner rolling members 23 are in rolling contact with the outer race of a ball bearing 6 or 16, respectively. The ball bearings 6,16 have similar dimensions and are mounted on eccentric portions 51,52, respectively at both ends of the eccentric sleeve 5, the middle portion 53 of which is in axial alignment with the axis Z of the sleeve 5 and the transmitting race 2. The two eccentric portions 51,52 have an eccentricity, which is equal but offset 180° and the same is true for the eccentricity of the base circles of the teeth of the rings 18,19 with respect to the axis Z. The centre portion 53 of the dual eccentric sleeve 5 carries a ball bearing 9, the outer race of which supports the centre portion 22 of transmitting race 2. Cover plates 7 are riveted to both sides of transmitting a race 2 to guarantee in combination with cover plates 8 that there is only radial motion and no axial displacement of the transmitting rods 4 and rolling members 3,23. Ball bearings 6,16 avoid direct contact of the inner rolling members 23 with the dual eccentric sleeve 52 and provide for a pure rolling movement between inner roller members 23 and outer races of bearings 6,16. The dual eccentric sleeve 5 has a centre bore 54 having a key groove 55 for mounting a rotatable shaft (not shown) for common rotating movement. Moreover a key groove 12 is provided at the outer periphery of internal gear race 1 for connection to a stationary housing or the like. The transmitting unit as described has the shape of an ordinary rolling bearing, the external diameter of which corresponds to the external diameter of the internal gear race 1. The dimensions of the unit can be the same of those of standard series rolling bearings or may be different therefrom. The transmission theory of the transmitting unit of this invention is described as follows: when internal gear 1 race is stationary and the dual eccentric sleeve 5 is driven with high speed, then the transmitting rods 4 and the rolling members 3,23 are subjected to radial motion in the guide groove of transmitting race 2, and the rolling members 3 also roll along the teeth profile 20 of the internal gear 1. This has the result that the transmitting race 1 is rotated at low speed. If according to the theory of relative motion, any one of the three components - internal gear race 1, transmitting race 2, and dual eccentric sleeve 5 - is stationary, then the other two will be driving and driven parts, and one transmitting unit as described can realize a speed or torque transmission of three speed ratios for speed reduction and three speed ratios for speed increase. The number of radial guide grooves at each side of transmitting race 2 is equal to the number of teeth 20 of internal gear race ± 1 divided by a positive integer. Let the number of teeth of internal gear race 1 be za, then the maximum number of transmitting rods 4 is Zbmax = Za±1. The transmitting ratios of reduction of speed are as follows: If internal gear race is stationary, then i = ±Zbmax = ±Za±1 If the transmitting race is stationary, then i = ±Za If the dual eccentric sleeve is stationary, then In case of increasing the speed, the speed ratios are the reciprocals of the values given above. The number of teeth 20 of each row of the internal gear race 1 is an odd number, from 5 to 69, and thus a wide range of speed ratios may be obtained for the single stage in reducing or increasing speed transmission. A theorectical teeth or cam profile according to the generating manufacturing process is used to make the teeth profile 20 of the internal gear race 1. Except for the cases of the transmission of very small power and low requirements in transmission, in the axial direction there are two rows of internal gear races 1 provided at the inner periphery of gear race rings 18,19 and staggered 180° , the dual eccentric sleeve 5 being correspondingly staggered 180° . The transmitting race 2 has two sets of rows of guide grooves in the axial direction and their positions are corresponding to those of internal gear race 1 and dual eccentric sleeve 5, so that the stress is balanced at any instant and thus stable transmission is achieved. At the same time, the loading action line of the bearings 6,16,9 on the dual eccentric sleeve 5 is not static; and this is favourable for increasing the working life of the bearings. Keyway 12 on the outer periphery of internal gear race 1 serves for connection and transmission as mentioned. According to different power transmission conditions a single key, double key, spline, etc. may be used which is conventional standard.Also drill holes or threaded holes may be drilled in the end faces of the internal gear race 1 for connection and transmission. On the end face of the transmitting race 2, there is hole or threaded hole for connection and transmission. The radial guide grooves together with the cover plates 7,8 form hollow spaces which are suitable for accomodating the transmitting rods 4 to perform radial motion only and no rotation. The cross-section profiles of the transmitting rods and the guide grooves should be basically identical. The profiles may be selected at random; but the rectangular cross-section is preferred. The transmitting rods and the guide grooves of the transmitting race are in surface contact and thus,very heavy loads can be carried. Rolling members (not shown) such as rolling needles, etc. can also be placed between the rods and the guide grooves to reduce friction. The transmitting race 2 and the cover plates 7 may also be made in a one-piece structure. One lateral side of the groove is open. The transmitting race 2 and the internal bore 54 of the dual eccentric sleeve 5 are coaxial and therefore there is enough space for a larger rolling bearing 6 to be mounted on the dual eccentric sleeve 5 and thus eliminating the weak link which exists in known transmitting units of the epicyclic type. Two ends of transmitting rod 4 enclose the rolling member 3 to such an extent that the covering length equals radius of rolling member 3 or exceeds it. The exceeding part is the plain surface which extends tangentially to the cylindrical surface; this favors the machining work of the transmitting rod 4 because a spearate structure of transmitting rods 4 and rolling members 3,23 is provided. It is also possible to provide for a flexible link and thus inaccurance in machining is not sensitive, and therefore the production cost of a unit according to this invention may be decreased. The minimum angle between adjacent guide grooves of the transmitting race 2 is equal to 360° divided by the number of teeth of internal gear ±1. This angle may be the integral multiple of the minimum inclined angle. If the suitable number of guide grooves during the designing is selected properly more meshing points as well as sufficient strength of transmitting race may be achieved. The rolling members 3,23 may be rollers or balls of a standard rolling bearing. Instead of the keyway 55 in the internal bore 54 of the dual eccentric sleeve 5 single key, double key or splines may be provided to meet different requirements in power transmissions and types of connections. In the preferred embodiment of this invention, only the eccentric sleeve 5 is a high speed rotating part which is of small mass. Moreover, the ball bearings 6,16 separate the high speed rotating dual eccentric sleeve 5 from other parts. Thus, the inner rolling members 23 have low rotational speed,and all other rotating parts as well have low linear speed. Therefore a stable and low noise transmission can be obtained. When the unit is used for increasing the speed, a larger multiple of increasing speeds may be achieved without any difficulties as regards dynamic balancing. When the transmitting unit of this invention is used for reducing or increasing the speed, the whole transmitting unit can be put directly into the main machine and the use of a particular transmission case or box is not required. It is only necessary to provide for an installation hole at the main machine; thus the layout design of the main machine is convenient. This also makes the structure simple and shortens the transmission chain. As a result, many high speed rotating parts in the main machine are eliminated, and its performance is improved. Moreover, through exchange of the transmitting unit or bearing, the specifications of the main machine may be changed, without any change in the structure of the main machine to suit the different demands of the products processed by this main machine or other changes in functions. The application and manufacture of the transmitting unit of this invention as a standard part offers the possibility to substitute different kinds of transmission cases which are now widely used in many areas. If the transmitting unit is installed at an ordinary machine base and input and output shafts are added having keyways, holes or threaded holes for the purposes of connection and transmission, then a variable speed transmitting unit with an external shape of horizontal or vertical type is formed. Moreover the unit can be directly connected with a d.c. or an a.c. motor. Therefore this kind of variable speed transmitting unit can be used in the areas where transmission caes having fixed speed or torque ratios are used such as in food and chemical industries, light industry, construction, mining, textile and dyeing industries. The transmission efficiency of a produced transmitting unit reducing the speed is 90 - 94 %, and of a transmitting unit used for increasing the speed is somewhat lower by 20 % to 4 %.

Claims: 1. A transmitting unit of fixed speed transmission ratio comprising an eccentric mechanism (5), an internal gear race (1) and a transmitting race (2) disposed between the internal gear race (1) and the eccentric mechanism (5), one of these elements being connected to a rotatable input shaft, a second one being stationary and a third one being connected to a rotatable output shaft, wherein said transmitting race (2) contains radial guide grooves equidistantly disposed about the periphery of the transmitting race and transmitting rods (4) are housed in the guide grooves and inner and outer rolling members (3; 23) are arranged at the ends of the transmitting rods (4), the outer rolling members (3) cooperating with a teeth profile formed at the internal gear race (1) and the inner rolling members (23) cooperating with a surface of the eccentric mechanism, respectively, characterized in that the two ends of the transmitting rods (4) enclose the rolling members (3; 23) to such an extent that the covering length is equal to or exceeds the radius of the rolling members (3; 23); and in that two rolling bearings (6,16;9) are mounted on an eccentric sleeve (5), which forms the eccentric mechanism, wherein the first rolling bearing (6,16) is mounted on an eccentric portion (51,52) of the eccentric sleeve (5) and cooperates with the inner rolling members (23) and wherein the second rolling bearing (9) is mounted on a portion (53) of the eccentric sleeve (5), which is coaxial with the internal bore(54) of the eccentric sleeve (5) and supports the transmitting race (2). 2. A transmitting unit according to claim 1, characterized in that a keyway (12) is provided at the outside periphery of the internal gear race (1), and at least one hole or threaded hole is provided in the radial end face of the internal gear race (1) for connection to a stationary housing, the output shaft or the input shaft, respectively. 3. A transmitting unit according to claim 1 or 2, characterized in that a hole or threaded hole is provided on the end face of the transmitting race (2) for connection to the output shaft, the input shaft, or a stationary housing, respectively. 4. A transmitting unit according to one of claims 1 to 3, characterized in that rolling members are installed between each guide groove and each transmitting rod (4) of transmitting race (2). 5. A transmitting unit according to one of claims 1 to 4, characterized in that the number of radial guide grooves is equal to the number of internal gear teeth (20) plus 1 divided by a positive integer. 6. A transmitting unit according to one of claims 1 to 5, characterized in that a second internal gear race (1) is arranged at the other side of the unit and connected to the first internal gear race (1), that the transmitting race (2) contains a second set of radial guide grooves equidistantly disposed about the periphery of the transmitting race, transmitting rods (4) being housed in each guide groove and rolling members (3,23) being disposed at each end of the transmitting rod (4), that the inner rolling members (23) in the second radial guide grooves cooperate with the outer race of a third rolling bearing (16) arranged on a second eccentric portion (52) of the eccentric sleeve (5) and that the eccentricity of the second eccentric portion (52) is of the same value but angularly offset 180° with respect to the eccentricity of the first eccentric portion of the eccentric sleeve (5). 7. A transmitting unit according to one claims 1 to 5, characterized in that the transmitting race (2) and the or each internal gear race (1) are covered by cover plates (7,8) at both sides, and that the transmitting race (2) and the corresponding cover plates (7), respectively and also the or each internal gear race or races (1) and the corresponding cover plates (8), respectively, are connected by axial connecting means, e. g. rivets, to form a single unit having an outside shape and being mountable similar to a usual rolling bearing. 8. A transmitting unit according to claim 6 or 7, characterized in that a spacer ring (10) is inserted between the two internal gear races (1).

Inventors: REN, ZHU SHAO
Applicants: HUBEI INSTITUTE OF MACHINERY
Application year: 1986
Main classification: F16H25
IPC codes: F16H13, F16H25