Internal Planetary Gear Preload Structure for Backlash-Free Robot Joints
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Solution Overview
Problem
Existing internal-meshing planetary gear devices and joint devices for robots suffer from angle transmission errors due to backlash caused by gaps between the inner peripheral surface of the inner pin hole and the inner roller, and between the inner peripheral surface of the inner roller and the inner pin.
Innovation Solution
The proposed solution involves an internal-meshing planetary gear device with a bearing member, an internally toothed gear, a planetary gear, multiple inner pins, and a support structure. The inner pins are configured to revolve in inner pin holes formed in the planetary gear, with a pre-pressure applied to the inner pins to minimize backlash, and a support structure is used to counteract moments generated by the pre-pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If gaps are ensured between the inner peripheral surface of the inner pin hole and the inner roller, and between the inner peripheral surface of the inner roller and the inner pin, then the inner roller can rotate smoothly relative to the inner pin, but backlash occurs resulting in angle transmission error
Solution Approach 1:
The patent applies pre-pressure to the inner pin by pressing its outer peripheral surface against the inner peripheral surface of the inner pin hole, changing the physical state from loose fit to pressed contact. This eliminates gaps and backlash while maintaining smooth rotation, thereby resolving the contradiction between ease of operation and manufacturing precision
Solution Approach 2:
The support structure is configured to counteract moments generated from the inner pin due to pre-pressure before operation begins. This preliminary structural arrangement ensures that the inner pin remains centered and stable during operation, preventing angle transmission errors while maintaining smooth rotation
2Manufacturing precision
If pre-pressure is applied to the inner pin to reduce backlash, then angle transmission error is suppressed, but moment is generated from the inner pin due to pre-pressure
Solution Approach 1:
The patent converts the harmful moment generated by pre-pressure into a beneficial effect by using the support structure to counteract it. The support structure transforms the destabilizing moment into a stabilizing force that centers the inner pin, thereby eliminating backlash and improving angle transmission precision
3Measurement precision
If the inner pin is pressed to apply pre-pressure, then centering precision is improved, but the support structure must counteract the generated moment
Solution Approach 1:
The support structure serves multiple functions: it supports the inner pin, counteracts the moment generated by pre-pressure, and maintains the inner pin's centering precision. By combining these functions into a single structure, the patent improves centering precision without proportionally increasing device complexity
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 configuration effectively suppresses angle transmission errors by reducing backlash and improving centering precision of the inner pins, leading to enhanced transmission efficiency and reduced vibration.
Implementation Method 1
An inner peripheral surface of each of multiple inner pin holes is configured to press against each corresponding inner pin of multiple inner pins to apply a pre-pressure to each corresponding inner pin of multiple inner pins
Implementation Method 2
The support structure is configured to support each of multiple inner pins to counteract moment generated from each of multiple inner pins due to the pre-pressure
Implementation Method 3
The planetary gear is provided with external teeth partially meshing with the internal teeth
Data Source
AI summary
An internally meshing planetary gear apparatus includes a bearing component, an internal gear, a planetary gear, a plurality of inner pins, and a support structure. The plurality of inner pins are configured to be respectively inserted into a plurality of inner pin holes formed by the planetary gear. The inner pins are configured to revolve within the inner pin holes, and simultaneously rotate relative to the internal gear. When the plurality of inner pins are not rotating relative to the internal gear, a respective inner circumferential face of each pin hole among the plurality of inner pin holes presses against each pin among the plurality of inner pins, and the pin holes exert a pre-pressure on each pin among the plurality of inner pins. The support structure is configured to support each pin among the plurality of inner pins.