CN113404820A

CN113404820A - Adjustable-gap multi-crank variable-tooth-thickness precision transmission device

Info

Publication number: CN113404820A
Application number: CN202110725776.XA
Authority: CN
Inventors: 宋朝省; 邓自立; 闫国帅; 朱才朝
Original assignee: Chongqing University
Current assignee: Chongqing University
Priority date: 2021-06-29
Filing date: 2021-06-29
Publication date: 2021-09-17
Anticipated expiration: 2041-06-29
Also published as: CN113404820B

Abstract

The invention belongs to the field of reducers, and relates to an adjustable-gap multi-crank variable-tooth-thickness precision transmission device, comprising a casing, a first-stage planetary gear train and a second-stage variable-tooth-thickness gear train; the second-stage variable-tooth-thickness gear train It includes two pairs of side-by-side internal meshing gear pairs and an anti-backlash mechanism. The anti-backlash mechanism includes a backlash-eliminating external hexagon external thread nut, a hollow shaft and a backlash-eliminating internal hexagon cylinder head screw connected with it, the backlash-eliminating external gear and the device. The elastic element disc spring at one end of the anti-backlash external gear presses the disc spring through the anti-backlash internal hexagon socket head screw and the anti-backlash external hexagon external thread nut to make the two pairs of gear pairs closely fit to reduce the backlash, so as to eliminate the two pairs of internal The gear backlash caused by the manufacture and installation of the meshing gear pair realizes the precise transmission without backlash; the backlash elimination structure of the present invention is simple and can be disassembled and assembled repeatedly, which can effectively eliminate the backlash of the gears, improve the transmission accuracy, and realize no backlash. Poor precision transmission, and can automatically compensate for the backlash caused by wear to ensure the longevity of transmission accuracy.

Description

Adjustable-gap multi-crank variable-tooth-thickness precision transmission device

Technical Field

The invention belongs to the field of speed reducers, and relates to a gap-adjustable multi-crank variable-tooth-thickness precise transmission device.

Background

The variable tooth thickness RV reducer is a novel precision reducer developed by a cycloid reducer, and structurally adopts a first-stage planetary gear train and a second-stage variable tooth thickness gear train. The cycloidal gear reducer has the advantages of large transmission ratio, high motion precision, large torsional rigidity, high transmission efficiency and the like, and can also utilize the anti-backlash structure to adjust the axial position of the variable tooth thickness gear according to the structural characteristics of the variable tooth thickness gear, further adjust the meshing backlash of a gear pair, realize low backlash or backlash-free precision transmission, and effectively solve the defect that the cycloidal gear reducer can realize small backlash only when the manufacturing precision is very high. However, the elimination of the meshing backlash is one of the difficult problems to be solved by a precise transmission system, the existing backlash eliminating structure is complex and various, most of the problems of unreasonable backlash eliminating structure, difficulty in ensuring backlash eliminating precision, reduction of backlash eliminating capability after long-term work and the like exist, and the problems of poor backlash eliminating effect, sliding friction between mutually meshed gear teeth, aggravation of abrasion between running parts, influence on the stability of the transmission system, reduction of the service life and the transmission efficiency of the transmission mechanism and increase of use and maintenance cost are caused.

Disclosure of Invention

In view of this, the invention aims to provide an adjustable-gap multi-crank variable-tooth-thickness precision transmission device, which solves the problem of backlash of a transmission gear pair of the conventional variable-tooth-thickness RV reducer.

In order to achieve the purpose, the invention provides the following technical scheme:

a gap-adjustable multi-crank variable-tooth-thickness precise transmission device comprises an input disc, an output disc, a first-stage planetary gear train and a second-stage variable-tooth-thickness gear train, wherein the input disc and the output disc are arranged oppositely, the first-stage planetary gear train is arranged between an end cover and the input disc, and the second-stage variable-tooth-thickness gear train establishes a transmission relation with the first-stage planetary gear train through a crank shaft; the first-stage planetary gear train comprises an input shaft, a planetary-stage sun gear connected with the input shaft and a planetary-stage planet gear meshed with the planetary-stage sun gear;

the second-stage variable-tooth-thickness gear train comprises two pairs of inner meshing gears arranged in parallel and a gap eliminating mechanism; one pair of internal gear pairs comprises a first anti-backlash external gear and a first internal gear meshed with the first anti-backlash external gear, and the other pair of internal gear pairs comprises a second anti-backlash external gear and a second internal gear meshed with the second anti-backlash external gear; the first anti-backlash outer gear and the second anti-backlash outer gear are sleeved on the crankshaft;

the clearance eliminating mechanism comprises a hollow shaft, a first hollow shaft bearing, a second hollow shaft bearing, a disc spring and a clearance eliminating inner hexagonal socket head cap screw; the hollow shaft is mounted on the output disc through a first hollow shaft bearing and mounted on the input disc through a second hollow shaft bearing, a disc spring is arranged between the first hollow shaft bearing and the second anti-backlash outer gear, and a disc spring is arranged between the second hollow shaft bearing and the first anti-backlash outer gear; one end of the anti-backlash inner hexagonal socket head cap screw is arranged on the outer side of the output disc, and the other end of the anti-backlash inner hexagonal socket head cap screw is in threaded fit with one end, facing the output disc, of the hollow shaft.

Optionally, the anti-backlash mechanism further comprises an anti-backlash washer arranged between the output disc and the anti-backlash inner hexagonal socket head cap screw, and an outer tongue stop washer arranged between the anti-backlash washer and the anti-backlash inner hexagonal socket head cap screw.

Optionally, the hollow shaft is provided with an anti-backlash outer hexagonal external thread nut matched with the output disc through threads, and a sleeve is arranged between the anti-backlash outer hexagonal external thread nut and the first hollow shaft bearing.

Optionally, the gear-driven generator further comprises a shell, wherein the shell comprises a variable-tooth-thickness box body and an end cover, the first internal gear is fixed on the variable-tooth-thickness box body, and the end cover is fixedly arranged at one end, far away from the output disc, of the input disc; the second internal gear and the variable tooth thickness box body are designed integrally.

Optionally, two phase adjusting screws which are symmetrically arranged and used for adjusting the phase difference between the first internal gear and the second internal gear are arranged on the variable tooth thickness box body.

Optionally, an angular contact ball bearing is mounted between the input disc and the variable tooth thickness box body to support the input disc; and an angular contact ball bearing is arranged between the output disc and the variable tooth thickness box body to support the output disc.

Optionally, a corresponding shaft section on the crank shaft for sleeving the first anti-backlash outer gear and the second anti-backlash outer gear is an eccentric shaft section, and a needle bearing for supporting the outer gears is correspondingly installed on the eccentric shaft section.

Optionally, tapered roller bearings for supporting the crankshaft are respectively installed between the crankshaft and the input disc and between the crankshaft and the output disc, and a clamp spring for axially limiting the tapered roller bearings is configured.

Optionally, a reinforced shaft sealing element is respectively installed between the variable tooth thickness box body and the input disc and between the variable tooth thickness box body and the output disc so as to complete the sealing of the whole speed reducer.

Optionally, deep groove ball bearings are respectively installed between the planetary-grade sun gear and the end cover and between the planetary-grade sun gear and the input disc to support the planetary-grade sun gear; the planet-stage planet wheels are axially limited on the crankshaft by two shafts which are symmetrically arranged through clamp springs.

The invention has the beneficial effects that:

(1) according to the invention, the second-stage variable-tooth-thickness gear train realizes gap adjustment by arranging the gap elimination mechanism, the left disc spring generates a certain compression amount by controlling the length of the thread of the gap elimination outer hexagonal external thread nut screwed into the output disc at the beginning, and the small end of the second gap elimination outer gear is pushed to align with the large end of the second inner gear under the action of axial force generated by compression of the disc spring, so that the meshing gear pair is tightly attached together; then make the right dish spring produce the compression amount through the length that control clearance-eliminating hexagon socket head cap screw screwed in the quill shaft, thereby promote first clearance-eliminating external gear tip and first internal gear main aspects alignment under the effect of the axial force that the dish spring compression produced, make the vice close laminating of meshing gear be in the same place, and then eliminate the tooth side clearance that two pairs of inside meshing gear pairs lead to because of machining error or assembly error, in addition because clearance-adjusting elastic element is the dish spring, the backlash that again can the automatic compensation produce because of wearing and tearing, guarantee transmission precision.

(2) The anti-backlash inner hexagonal socket head cap screw and the anti-backlash outer hexagonal external thread nut are combined to realize the one-side backlash adjustment of the external gear, compared with other backlash adjusting structures, the anti-backlash inner hexagonal socket head cap screw is more convenient to design and operate, higher in adjustment efficiency, capable of adjusting the meshing backlash of two meshing gears better and achieving a state that the backlash is very small or zero, further capable of achieving precision transmission without return difference, and further capable of achieving the anti-loosening treatment of the anti-backlash inner hexagonal socket head cap screw by adopting the outer tongue locking washer, and capable of guaranteeing the durability of an anti-backlash effect.

(3) According to the invention, the two thickened inner teeth are manufactured in a mode of integrally machining and then cutting off, so that the phase difference between the two thickened inner teeth is required to be ensured, the phase difference between the first inner gear and the second inner gear is adjusted by controlling the screwing-in length of the two phase adjusting screws on the variable-tooth-thickness box body, and the position of the first inner gear on the variable-tooth-thickness box body is fixed through the cylindrical pin after the adjustment is finished.

(4) In the invention, the whole gap eliminating process is only carried out on the hollow shaft, and the hollow shaft does not have any rotary motion, so that other parts of the speed reducer cannot be influenced in the gap eliminating process. Compared with the gap elimination structure on the crank shafts, the gap elimination structure solves the problem that the gap adjustment amount is inconsistent when the gaps of the plurality of crank shafts are adjusted simultaneously, and effectively reduces the precision loss caused by the gap elimination structure.

(5) According to the invention, the smooth outer gear gasket is added on the contact surface of the disc spring and the gap eliminating outer gear, so that the friction generated when the outer gear and the disc spring rotate relatively is effectively reduced, the efficiency loss of a transmission mechanism is reduced, and the transmission efficiency is improved.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.

Drawings

For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of an adjustable-gap multi-crank variable-tooth-thickness precision transmission device of the present invention;

FIG. 2 is a cross-sectional view of the phasing screw of FIG. 1;

fig. 3 is a cross-sectional view of the relief structure of fig. 1.

Reference numerals: the variable tooth thickness box body 1, a first inner gear 2, a first anti-backlash outer gear 3, a second inner gear 4, an angular contact ball bearing 5, a reinforced shaft sealing element 6, a second anti-backlash outer gear 7, an output disc 8, a crankshaft 9, an anti-backlash gasket 10, an anti-backlash inner hexagonal socket head cap screw 11, an outer tongue stop gasket 12, an anti-backlash outer hexagonal external thread nut 13, a sleeve 14, a first hollow shaft bearing 15, a first hole clamp spring 16, a tapered roller bearing gasket 17, a tapered roller bearing 18, a crankshaft gasket 19, a needle bearing 20, a cylindrical pin 21, an angular contact ball bearing gasket 22, an input disc 23, an inner hexagonal socket head cap screw 24, a shaft clamp spring 25, a planet-stage planet wheel 26, a first deep groove ball bearing 27, an input shaft 28, a planet-stage sun gear 29, a second deep groove ball bearing 30, a second hole clamp spring 31, an end cover 32, a hollow shaft 33, a second hollow shaft bearing 34, a first deep groove ball bearing 27, a second groove bearing 31, a second groove bearing, a third groove bearing, a fourth groove bearing, a sixth groove bearing, a fourth groove bearing, a sixth groove bearing, a fourth groove bearing, a, A stop washer 35, a disc spring 36, an external gear washer 37, a phasing screw 38, and an assembly screw 39.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.

Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not an indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes, and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific situations.

Please refer to fig. 1 to 3, which illustrate a gap-adjustable multi-crank variable tooth thickness precision transmission device. The variable tooth thickness box body 1 and the end cover 32 connected with the right end of the input disc 23 through the hexagon socket cap head cap screw 24 form a shell together. A first-stage planetary gear train and a second-stage variable-tooth-thickness gear train matched with the first-stage planetary gear train are arranged in the shell.

The second-stage variable-tooth-thickness gear train comprises two pairs of internal gear pairs and anti-backlash mechanisms which are arranged side by side, wherein one pair of internal gear pairs close to the input end is composed of a first anti-backlash outer gear 3 and a first inner gear 2 meshed with the first anti-backlash outer gear, and the other pair of internal gear pairs is composed of a second anti-backlash outer gear 7 and a second inner gear 4 meshed with the second anti-backlash outer gear; the first anti-backlash external gear 3 and the second anti-backlash external gear 7 are sleeved on the crankshaft 9 through a needle bearing 20; the anti-backlash mechanism comprises an anti-backlash washer 10, an anti-backlash inner hexagonal socket head cap screw 11, an outer tongue stop washer 12, an anti-backlash outer hexagonal external thread nut 13 matched with the output disc 8, a sleeve 14, a first hollow shaft bearing 15, a hollow shaft 33, a second hollow shaft bearing 34, a stop washer 35, a disc spring 36 and an external gear washer 37, and the stop washer 35 and the disc spring 36 are pressed through the anti-backlash inner hexagonal socket head cap screw 11 and the anti-backlash outer hexagonal external thread nut 13.

The phase difference between the first internal gear 2 and the second internal gear 4 is adjusted by two phase adjusting screws 38 symmetrically arranged on the variable tooth thickness box body 1, the first internal gear 2 is fixed on the variable tooth thickness box body 1 through a cylindrical pin 21 after the phase adjustment is completed, and the second internal gear 4 and the variable tooth thickness box body 1 are integrally designed.

The first stage planetary gear train comprises an input shaft 28, a planetary stage planetary gear 26 fixedly connected to the crankshaft 9 through splines, and a planetary stage sun gear 29 fixedly connected to the input shaft 28 through interference fit, wherein the planetary stage planetary gear 26 is axially positioned on the crankshaft 9 through two shafts which are symmetrically arranged by using clamp springs 25.

The corresponding shaft section of the crankshaft 9 for sleeving the first anti-backlash outer gear 3 and the second anti-backlash outer gear 7 is an eccentric shaft section, and needle roller bearings 20 are mounted at corresponding positions, so that the anti-backlash requirements are met, and the first anti-backlash outer gear 3 and the second anti-backlash outer gear 7 can be supported. Accordingly, the first and second external

anti-backlash gears

3 and 7 are eccentrically arranged. The left needle bearing 20 is axially restrained by a corresponding shoulder on the crankshaft 9 and the crankshaft washer 19, and the right needle bearing 20 is also axially restrained by a corresponding shoulder on the crankshaft 9 and the crankshaft washer 19.

Tapered roller bearings 18 used for supporting the crankshaft 9 are respectively arranged between the right end of the crankshaft 9 and the input disc 23 and between the left end of the crankshaft 9 and the output disc 8, the tapered roller bearings 18 at the left end are axially limited through a clamp spring 16 for a first hole and a shaft shoulder on the crankshaft 9, similarly, the tapered roller bearings 18 at the right end are axially limited through the shaft shoulder on the crankshaft 9 and a blocking shoulder of the input disc 23, and tapered roller bearing gaskets 17 are further arranged between the output disc 8 and the tapered roller bearings 18.

A first deep groove ball bearing 27 and a second deep groove ball bearing 30 are respectively arranged between the planetary stage sun gear 29 and the end cover 32 and the input disc 23, and are used for supporting the planetary stage sun gear 29. The first deep groove ball bearing 27 is axially limited by a retaining shoulder on the end cover 32 and a shaft shoulder on the planetary-stage planetary gear 29, and the first deep groove ball bearing 27 is a sealing bearing; the second deep groove ball bearing 30 is axially limited by a shoulder on the input disc 23 and a shoulder on the planet-stage sun gear 29.

An angular contact ball bearing 5 is arranged between the output disc 8 and the variable tooth thickness box body 1 to support the output disc 8; an angular contact ball bearing gasket 22 is also arranged between the angular contact ball bearing 5 and the variable tooth thickness box body 1. The angular contact bearing 5 close to the left end realizes axial limit through a retaining shoulder on the output disc 8 and a retaining shoulder on the variable tooth thickness box body 1; in the same way, an angular contact ball bearing 5 for supporting the input disc 23 is also arranged between the input disc 23 and the variable tooth thickness box body 1, and the axial limiting is realized through a retaining shoulder on the input disc 23 and a retaining shoulder on the variable tooth thickness box body 1.

A first hollow shaft bearing 15 and a second hollow shaft bearing 34 are respectively installed between the hollow shaft 33 and the output disc 8 and the input disc 23 for supporting the hollow shaft 33, the first hollow shaft bearing 15 is axially limited by the left sleeve 14 and the right stop washer 35, and the second hollow shaft bearing 34 is axially limited by the left and right second holes by the clamp springs 31.

The end cover 32 and the input disc 23 are assembled together through the hexagon socket head cap screws 24; the input disc 23 and the output disc 8 are assembled together by assembly screws 39; and reinforced shaft sealing elements 6 are respectively arranged between the variable-tooth-thickness box body 1 and the input disc 23 and the output disc 8 so as to complete the sealing work of the whole speed reducer.

The anti-backlash principle of the transmission device is as follows: firstly, the sleeve 14 and the first hollow shaft bearing 15 are pushed by rotating the anti-backlash outer hexagonal external thread nut 13 to enable the disc spring 36 at the left end to generate a certain compression amount, so that the second anti-backlash external gear 7 moves axially to the right under the action of axial force generated by compression deformation of the disc spring 36 at the left end, and the second anti-backlash external gear 7 is forced to be meshed with the second internal gear 4; the disc spring 36 and the first hollow shaft bearing 15 are separated by a stop washer 35 to reduce the mutual friction between the two and thus reduce the loss of efficiency. After the second anti-backlash external gear 7 finishes backlash elimination, the thread length of the second anti-backlash external gear 7 screwed into the hollow shaft 33 is controlled to pull the hollow shaft 33 to move leftwards integrally to adjust the compression amount of the right disc spring 36, so that the first anti-backlash external gear 3 moves leftwards axially under the action of axial force generated by the right disc spring 36 due to compression deformation, meanwhile, the anti-loosening treatment is carried out on the anti-backlash internal hexagonal head screw 11 by adopting the outer tongue stop washer 12 to force the first anti-backlash external gear 3 and the first internal gear 2 to be meshed to finish backlash elimination, the bearing capacity of a gear pair can be effectively improved after backlash elimination is finished, and precision transmission without backlash is realized.

The first internal gear 2 and the second internal gear 4 are integrally processed and then separated, and the phase difference caused by the processing turnover can be adjusted by controlling the screwed length of two phase adjusting screws 38 symmetrically arranged on the variable tooth thickness box body 1.

When the variable-tooth-thickness gear transmission system works, power is input through an input shaft 28, the power is output to a crank shaft 9 of a second-stage variable-tooth-thickness gear transmission system through the transmission of a first-stage planetary gear train through a planetary-stage planetary gear 26, the crank shaft 9 drives two pairs of internal-meshing gear pairs to transmit, the rotation of a first anti-backlash outer gear 3 and a second anti-backlash outer gear 7 is transmitted to an output disc 8 through the crank shaft 9, and torque output is completed; meanwhile, the backlash eliminating effect of the disc spring 36, the first internal gear 2, the first backlash eliminating external gear 3, the second internal gear 4 and the second backlash eliminating external gear 7 ensures the transmission precision of the transmission device, and improves the bearing capacity of the transmission device.

Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.

Claims

1. The utility model provides a but adjustable gap multiple crank becomes thick accurate transmission of tooth which characterized in that: the gear-type speed reducer comprises an input disc, an output disc, a first-stage planetary gear train and a second-stage variable-tooth-thickness gear train, wherein the input disc and the output disc are oppositely arranged, the first-stage planetary gear train is arranged between an end cover and the input disc, and the second-stage variable-tooth-thickness gear train establishes a transmission relation with the first-stage planetary gear train through a crank shaft; the first-stage planetary gear train comprises an input shaft, a planetary-stage sun gear connected with the input shaft and a planetary-stage planet gear meshed with the planetary-stage sun gear;

2. The adjustable gap multi-crank variable tooth thickness precision transmission device according to claim 1, wherein: the anti-backlash mechanism further comprises an anti-backlash gasket arranged between the output disc and the anti-backlash inner hexagonal socket head screw, and an outer tongue stop gasket arranged between the anti-backlash gasket and the anti-backlash inner hexagonal socket head screw.

3. The adjustable gap multi-crank variable tooth thickness precision transmission device according to claim 1, wherein: the hollow shaft is provided with an anti-backlash outer hexagonal external thread nut matched with the output disc through threads, and a sleeve is arranged between the anti-backlash outer hexagonal external thread nut and the first hollow shaft bearing.

4. The adjustable gap multi-crank variable tooth thickness precision transmission device according to claim 1, wherein: the first internal gear is fixed on the variable tooth thickness box body, and the end cover is fixedly arranged at one end of the input disc, which is far away from the output disc; the second internal gear and the variable tooth thickness box body are designed integrally.

5. The adjustable gap multi-crank variable tooth thickness precision transmission of claim 4, wherein: and two phase modulation screws which are symmetrically arranged and used for adjusting the phase difference between the first internal gear and the second internal gear are arranged on the variable-tooth-thickness box body.

6. The adjustable gap multi-crank variable tooth thickness precision transmission of claim 4, wherein: an angular contact ball bearing is arranged between the input disc and the variable tooth thickness box body to support the input disc; and an angular contact ball bearing is arranged between the output disc and the variable tooth thickness box body to support the output disc.

7. The adjustable gap multi-crank variable tooth thickness precision transmission device according to claim 1, wherein: and the corresponding shaft section on the crank shaft for sleeving the first anti-backlash outer gear and the second anti-backlash outer gear is an eccentric shaft section, and a needle bearing for supporting the outer gears is correspondingly installed.

8. The adjustable gap multi-crank variable tooth thickness precision transmission device according to claim 1, wherein: tapered roller bearings used for supporting the crankshaft are respectively arranged between the crankshaft and the input disc and between the crankshaft and the output disc, and clamping springs used for axially limiting the tapered roller bearings are arranged.

9. The adjustable gap multi-crank variable tooth thickness precision transmission of claim 4, wherein: and reinforced shaft sealing elements are respectively arranged between the variable tooth thickness box body and the input disc and between the variable tooth thickness box body and the output disc so as to complete the sealing of the whole speed reducer.

10. The adjustable gap multi-crank variable tooth thickness precision transmission of claim 4, wherein: deep groove ball bearings are respectively arranged between the planetary sun gear and the end cover and between the planetary sun gear and the input disc so as to support the planetary sun gear; the planet-stage planet wheels are axially limited on the crankshaft by two shafts which are symmetrically arranged through clamp springs.