RU2472991C2 - Harmonic gear transmission - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: harmonic gear transmission contains housing (1), rigid gear (2), flexible gear (3) deformed by disk wave generator (4), drive shaft (5), disk in the form of in the form of maltese cross (6) designed together with output shaft (7). Rigid gear with inner tooth crown (b) is fixed in housing. Flexible gear is connected to output shaft by means of mechanism of maltese cross type with rolling friction. There are supports (11) on flexible ring, on them rolling bearings (12) are installed.

EFFECT: increasing load-carrying capacity and efficiency.

Description

The invention relates to mechanical transmissions and can be used as part of electronic engineering products in other industries using wave transmissions with small overall mass characteristics, smooth and silent operation.

Known wave gear [1, 2], comprising a housing, two hard wheels, one of which is fixedly mounted in the housing, and the other is made integral with the output shaft, a flexible short wheel with two external gear crowns, one of which forms a wave transmission with a crown a fixed hard wheel, and the other is a wave gear connection with the output shaft; the flexible wheel is made of monolithic steel in the form of a thin ring with small module teeth, deformable by one two-wave generator. A similar wave gear transmission is known with the difference that the flexible wheel is integral with the outer ring of the flexible bearing of the wave generator [3].

The closest in technical essence of the invention is a wave gear [4], comprising a housing, two hard wheels with internal gear rims, one of which is stationary in the housing and forms a wave transmission, and the other forms a wave connection, made integral with the output shaft, a short flexible wheel with two external gear crowns, deformable by a two-wave generator, a flexible assembly wheel, of increased flexibility, made of a complex structure tape consisting of a middle bearing layer - Coy elastic cylindrical metal shell - and an elastic binder, bonded to the steel backing ring; the generator is made disk (DG). Significant advantages of this transmission are small dimensions in the axial direction, large-modular gearing, low requirements for manufacturing accuracy - a prototype.

The main disadvantages of the above gears [1-4] are: low values of efficiency and load capacity.

The technical task of the claimed invention is to increase the efficiency and load capacity of the wave gear with a short flexible wheel.

To this end, according to the invention, a wave gear reducer is proposed in which the wave connection is replaced by a mechanism in which rolling bearings mounted on a flexible wheel enter the grooves of a disk in the shape of a Maltese cross integral with the output shaft.

As shown in [2], the reason for the reduced (almost double) load capacity of a VM with a short HA, one of the gears of which is a wave connection, is the unfavorable condition in the gear wave connection — the presence of high sliding speeds and loads. The combination of high sliding speeds with force factors contributes to the emergence of a significant amount of work of the sliding friction forces in the engagement of the wave gear connection, a sharp decrease in efficiency and transmission load capacity.

It is possible to reduce the work of sliding friction forces, to increase the efficiency and transmission load capacity by replacing sliding friction with rolling friction. The present invention provides for the replacement of sliding friction in the engagement of the wave connection by rolling friction in the connection of the HA with the output shaft of the transmission. This is achieved as follows.

On figa (section along the longitudinal axis) shows a wave gear reducer containing a housing 1, a hard wheel 2, a flexible wheel 3, deformable by a disk wave generator 4, a drive shaft 5, a disk in the shape of a Maltese cross 6, made integral with the output shaft 7 The hard wheel 2 with the internal gear rim b is fixedly mounted in the housing 1. The flexible wheel 3 is prefabricated (Fig. 2), of increased flexibility, made of a complex structure tape consisting of a supporting layer - a thin middle elastic metal shell 9 placed in an elastic binder 10 s at with an external gear rim g, which engages with the rim b of the hard wheel, the tape is fastened with a steel washer ring 8. The bearings 11 are mounted on the flexible wheel, on which the rolling bearings 12 are mounted. The disk generator 4 and the drive shaft 5 are shown schematically, since carry the features of the present invention. To fix in the axial direction of the HA on the grooves of the disk from two sides should be installed restrictive straps 13 (figure 1)

It is proposed on the washer ring (see Fig. 1) to make supports (along with the ring or by welding) for installing rolling bearings. The number and dimensions of rolling bearings can be preliminarily determined by the static load-bearing capacity C ₀ , having, for example, given the internal diameter of the bearing equal to the thickness of the spacer ring, followed by a check of the bearing performance using known methods [5].

The thickness of the backing ring s _k can be determined by the following dependence [6]:

under the condition

where T _o - torque wave transmission; b _to and E _to - width and elastic modulus of the material of the washer ring; R _to and r _to are the radii of the neutral layer of the underlay ring deformed on arcs with an angle α and in undeformed states; [σ _and ] is the permissible bending stress for the material of the backing ring; m is the modulus of engagement.

When using a flexible wheel such as a toothed belt (GZKR) [4, 7], in addition to installing bearings for rolling bearings on the washer ring (Fig. 1b) (in this case, the immobility of the connection of the tape with the washer ring, in addition to the friction forces in the joint, is provided by additional fastening using glue or vulcanization); the invention provides for two more options (see figure 2):

a) in the manufacture of a non-standard gear belt with external teeth, the supports are installed under the middle of the tooth during the manufacturing process; while the carrier layer (thin metal cylindrical shell [4]) is placed in the slot of the supports (see figure 2, isp. I);

b) when using a standard gear belt - the supports are pressed under the middle of the tooth above the supporting cables (see figure 2, version II).

We estimate the value of the VM efficiency according to the design claimed in the invention. To do this, you can use, for example, the data given in [7] for a comparative assessment of wave reducers with a metal flexible wheel (BPM) and with a flexible wheel GZKR in the form of a gear belt (VRP) with a diameter of the flexible wheel d _gk = 84 mm and the limit the magnitude of the torque on the output shaft T _o = 56.5 Nm.

We accept for the VRP reducer radial rolling bearings No. 1000092 (d × D × B = 2 × 6 × 2.3). The required number of bearings n is determined by the static load capacity equal to c ₀ = 90 N, in a first approximation, by the formula:

The efficiency of two bearings in the calculations is usually taken equal to η _p = 0.99. Therefore, the total loss in engagement of the bearings with the grooves of the disk of the output shaft can be estimated by the value:

Thus, the friction loss in the claimed design of the HA joint with the output shaft is ~ 7%, while in the BPM wave joint according to the results of [7], the losses are estimated at ~ 40% (η≈0.6).

It is easy to see that the design of the short HA connection with the output shaft proposed in the invention contributes to a sharp increase in the efficiency of such wave reducers.

In the case of particularly stringent requirements for the minimum value of the moment of inertia of the wave gear, replacement of rolling bearings with sliding bearings may be proposed; in this case, the efficiency of the mechanism can be slightly reduced.

Information sources

1. US patent No. 2943513.

2. M.N. Ivanov. Wave gears. M .: "Higher School", 1981. - 184 p.

3. USSR patent No. 1772468.

4. Patent No. 2405993 - prototype.

5. I.A. Birger, B.F. Shorr, G. B. Ioselevich. Strength calculation of machine parts. Directory. - M.: Mechanical Engineering. 1979.- 702 p.

6. V.Z. Grebenkin, R.I. Akulov, P.V. Vasiliev. The choice of the rational tension of the flexible link of the wave gear mechanism with a disk generator. // The defense complex to the scientific and technological progress of Russia. 2010. No1. p. 61-66.

7. V.Z. Grebenkin, R.I. Akulov, P.V. Vasiliev. Use in the mechanisms of interoperational transporting devices of microelectronics of wave reducers with the design of a flexible wheel such as a toothed belt / Defense complex to the scientific and technological progress of Russia. 2009. No3. p. 26-32.

Claims (1)

A wave gear train comprising a rigid wheel with an internal gear ring that is fixedly mounted in the housing, a short flexible wheel with an external gear ring, a two-wave generator, characterized in that the flexible wheel is connected to the output shaft using a Maltese type mechanism with rolling friction.

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