Ball Speed Reducer Structure for Lower Bearing Load and Torque Loss
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Solution Overview
Problem
Conventional speed reducers require larger bearings to support both radial and axial loads, leading to increased size and torque loss due to the use of deep groove and angular ball bearings, which are less tolerant in the axial direction.
Innovation Solution
The design incorporates a second rolling element engaging groove that supports contact forces, allowing only radial loads on the bearings, and uses rollers or balls to transmit torque, eliminating the need for large bearings and reducing friction through the use of friction reducing members like needle or slide bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If deep groove ball bearings or angular ball bearings are used to support both radial and axial loads, then the speed reducer can handle axial loads, but the bearing size increases and torque loss increases
Solution Approach 1:
The patent divides the load support function into two separate components: the second rolling element engaging groove supports axial loads through its corrugated structure, while the bearings only support radial loads. This segmentation allows each component to be optimized for its specific function, reducing bearing size and torque loss.
Solution Approach 2:
The second rolling element engaging groove acts as an intermediary structure that intercepts and supports axial loads before they reach the bearings. By introducing this intermediate load path, the bearings are relieved of axial load responsibilities, enabling the use of smaller, more efficient radial-only bearings.
2Force
If deep groove ball bearings or angular ball bearings are used to support both radial and axial loads, then the speed reducer can handle axial loads, but the bearing size increases
Solution Approach 1:
The patent segments the load support responsibilities: the second rolling element engaging groove handles axial loads through its corrugated geometry, while bearings handle only radial loads. This division allows selection of smaller, more appropriately-sized bearings that don't need to be oversized for axial load capacity.
Solution Approach 2:
The patent changes the load parameters borne by the bearings from combined radial and axial loads to purely radial loads. This parameter change enables the use of smaller bearing dimensions while maintaining adequate load support capability for the radial component only.
3Loss of energy
If rollers are used as rolling elements, then torque transmission efficiency improves, but friction reducing members are needed at contact parts
Solution Approach 1:
The patent extracts the friction reduction function into separate friction reducing members (needle bearings or slide bearings) that are placed at specific contact interfaces. This allows the main rolling elements to focus on torque transmission while the extracted friction reducing members handle localized friction issues at contact parts.
Solution Approach 2:
Friction reducing members act as intermediary elements between the rollers and the grooves/pockets. These intermediaries reduce direct friction contact while maintaining the torque transmission function, effectively decoupling the rolling element's primary function from frictional losses at contact interfaces.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach miniaturizes the speed reducer while improving torque transmission efficiency by reducing the load on bearings and minimizing torque loss, as the bearings only need to support radial loads and are optimized for reduced friction.
Implementation Method 1
The input plate 110 is attached to an outer circumference of an input shaft 170 via an eccentric cam 180, and thus a curvature center O1 of the circular first ball engaging groove 111 is eccentric from the rotation center X by an eccentric amount 'a'.
Implementation Method 2
A rotational torque is transmitted from the input plate 110 to the output plate 120 via balls 130 engaging with the ball engaging grooves 111 and 121.
Implementation Method 3
minimizing torque loss, as the bearings only need to support radial loads and are optimized for reduced friction
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A speed reducer 1 includes an input rotating part 2, an output rotating part 3 disposed coaxially with the input rotating part 2, a fixed member 5, a first rolling element engaging groove 13 disposed in the input rotating part 2 and provided along a circle having a curvature center O1 eccentric from a rotation center X of the input rotating part, a second rolling element engaging groove 16 disposed in the fixed member 5 and provided along a corrugated curve alternately intersecting a pitch circle having a curvature center on a straight line including the rotation center X, a plurality of balls 4 engaging with the first rolling element engaging groove 13 and the second rolling element engaging groove 16 facing each other in an axial direction, and a plurality of pockets 17 disposed in the output rotating part 3 and holding the plurality of balls 4 in a circumferential direction so as to radially movable between the first rolling element engaging groove 13 and the second rolling element engaging groove 16 in a radial direction.