TECHNICAL FIELD

The present disclosure relates to gear reducers and particularly to epicycloidal high-ratio gear reducers. More particularly, the present invention relates to a compact pericycloidal high-ratio gear reducer.

BACKGROUND

A fundamental requirement of majority of devices that utilize mechanical power is transmission of the rotational movement of a power source, such as an electric motor or an internal combustion engine to a low speed power consumer or end effector. One way to address this requirement may be utilization of conventional gear boxes with multistage gear trains. However, such multistage gear boxes may be relatively large and heavy for applications where high reduction ratios are required.

To obtain higher reduction ratios while maintaining the compactness of power transmission systems, gear reducers may be utilized instead of conventional multistage gear boxes. Planetary gear transmissions (PGTs), cycloidal speed reducers (CSRs), worm and gears (WGs), and harmonic drives (HDs) are among the well-known gear reducers that may provide high gear reduction ratios and maintain the compactness of the transmission systems.

In comparison with conventional gearboxes with simple gear trains, single-stage PGTs have several advantages and some disadvantages. Coaxial input and output, as well as two degrees of freedom are important benefits which enable the PGTs to provide several gear ratios when several stages of PGTs are mounted consecutively. In short, the advantages of PGTs in comparison with ordinary gear boxes may include compact structure, light weight, small moment of inertia, high power density, high efficiency, coaxial input-output shafts, low backlash, low pitch line velocity in gears, multiplicity in reduction ratios, and multiple degrees of freedom. However, PGTs may have disadvantages, such as having a large number of elements which makes the system overly complex, requiring an exceedingly high precision manufacturing process which makes PGTs expensive, having indeterminate load distribution on gears, high fatigue due to high repetition of loading on teeth of sun gear and bidirectional bending loads on teeth of planet gears, having weak heat transfer capabilities, and finally a narrow range of reduction ratios per stage.

In comparison with conventional gearboxes, a CSR may have all the above-mentioned advantages of a PGT, except having multiplicity in reduction ratios, and multi degrees of freedom. A CSR may further have drawbacks, such as non-involute-cut gears, load alternation on gears and bearings and internal speed fluctuation as well as centrifugal forces which altogether increase internal vibrations and probability of fatigue failure. Additionally, it can offer reduction ratios only in a range of 10 to 100, which are limited to integer numbers and getting decimal ratios is impossible. A CSR may also require high precisions and high technology level in production due to complexity in its components' shape and their accurate assembly. The advantages of a CSR may include a high reduction ratio in a single stage, a very compact design, smooth running with moderate noise, low backlash, high shock absorbance, smaller number of parts, high reliability and long life. However, a CSR may have disadvantages, such as internal vibrations and non-steady output velocity, requiring balancing, expensive manufacturing process, limited range and numbers of possible reduction ratios, and indeterminate load distribution on rollers.

Compared to PGTs, HDs may have advantages, such as considerably larger reduction ratios per stage, high torque capacity per weight, excellent positioning accuracy and repeatability, compact design, near zero backlash, self-locking property, and high torsion stiffness. On the other hand, HDs may have drawbacks, such as high elasticity requirement in its flex spline, together with nonlinear stiffness damping resulting in a low efficiency, a restricted reduction range: i.e. 30:1 up to 320:1 in normal applications. Furthermore, HDs cannot be back driven. HDs may further require high technology level both in gear production and bearing production. In addition, HDs may be applicable only in small sizes since for larger sizes, larger deflections and stresses may occur, which might go beyond the resistance margins of materials.

SUMMARY

This summary is intended to provide an overview of the subject matter of the present disclosure and is not intended to identify essential elements or key elements of the subject matter, nor is it intended to be used to determine the scope of the claimed implementations. The proper scope of the present disclosure may be ascertained from the claims set forth below in view of the detailed description and the drawings.

According to one or more exemplary embodiments, the present disclosure is directed to a pericyclic gear reducer. An exemplary pericyclic gear reducer may include an input shaft that may be rotatable about a longitudinal axis of an exemplary input shaft, a middle planet ring gear, and an output sun gear that may be meshed with an exemplary middle planet ring gear. An axis of rotation of an exemplary output sun gear may be parallel with a central normal axis of an exemplary middle planet ring gear and an exemplary output sun gear may be rotatable with an exemplary middle planet ring gear.

An exemplary pericyclic gear reducer may further include a driver ring gear that may be coupled to an exemplary input shaft and rotatable with an exemplary input shaft about a first rotational axis coinciding with an exemplary longitudinal axis of an exemplary input shaft. An exemplary driver ring gear may be coupled to an exemplary middle planet ring gear from a first side of an exemplary middle planet ring gear utilizing a first prismatic joint. An exemplary first rotational axis may be parallel with an exemplary central normal axis of an exemplary middle planet ring gear. An exemplary first prismatic joint may be disposed on a plane perpendicular to an exemplary first rotational axis and an exemplary central normal axis. An exemplary driver ring gear may be configured to transfer the rotational movement of an exemplary input shaft to an exemplary middle planet ring gear.

An exemplary pericyclic gear reducer may further include a driven wheel that may be coupled to an exemplary middle planet ring gear from a second side of an exemplary middle planet ring gear utilizing a second prismatic joint. An exemplary second prismatic joint may be disposed on a plane perpendicular to an exemplary first rotational axis. An exemplary second prismatic joint may be perpendicular to an exemplary first prismatic joint. An exemplary driven wheel may be rotatable about a second rotational axis, where an exemplary second rotational axis may be parallel with an exemplary first rotational axis.

An exemplary pericyclic gear reducer may further include a central output shaft that may be coupled to an exemplary output sun gear. An exemplary central output shaft may be rotatable with an exemplary output sun gear about a central axis, where an exemplary central axis may be along and parallel with a longitudinal axis of an exemplary central output shaft.

