Ball-Planetary CVT Control for Stable Forward and Reverse Drive

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Solution Overview

Problem

Existing continuously variable transmissions (CVTs) face challenges in efficiently switching between forward and reverse directions while maintaining stable speed ratios and torque control, particularly in scenarios involving rollback or changing load conditions.

Innovation Solution

The implementation of a control system that adjusts the offset angle (psi) and skew angle (zeta) of trunnions relative to the pitch circle, allowing for independent control of tilt angles (gamma) to dynamically change the speed ratio and maintain stability and sensitivity, enabling operation in both forward and reverse directions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the CVT operates in forward direction with a given speed ratio, then the output speed and torque are maintained, but switching to reverse direction causes instability and rollback damage

Engineering Contradiction:

Improveprevention of rollback damageVSAvoidswitching between forward and reverse directions

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies dynamics by making the trunnion offset angle (psi) a variable parameter that changes based on operating conditions. The control system dynamically adjusts psi independently of the tilt angle (gamma), allowing the CVT to adapt its configuration when switching between forward and reverse directions, thereby maintaining stability and preventing rollback damage during directional transitions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter configuration by introducing an independent control of the trunnion offset angle (psi) separate from the tilt angle (gamma). By varying psi as a distinct parameter, the system can optimize performance for different operating modes (forward/reverse) without being constrained by fixed geometric relationships, thus resolving the contradiction between reliability during switching and adaptability to different directions

Inventive Principle:

Principle #35Parameter changes

2Speed

If the control system increases sensitivity to detect direction changes, then the response time is reduced, but the stability during operation is compromised

Engineering Contradiction:

Improveresponse time to direction changesVSAvoidoperational stability

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

The control system dynamically adjusts the trunnion offset angle (psi) based on real-time operating conditions and detected direction changes. This dynamic adjustment allows the system to respond quickly to directional transitions while maintaining operational stability during steady-state operation, as psi can be optimized for each specific operating phase

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control system uses feedback from sensors detecting rotation direction and operating conditions to continuously adjust the trunnion offset angle (psi). This closed-loop control enables the system to respond rapidly to direction changes while maintaining stability, as the feedback mechanism allows for real-time optimization of the geometric configuration based on actual operating state

Inventive Principle:

Principle #23Feedback

3Stability of the object's composition

If the CVT maintains a fixed geometric configuration for stability, then the speed ratio control is precise, but the ability to switch between forward and reverse directions is limited

Engineering Contradiction:

Improvespeed ratio stabilityVSAvoiddirectional switching capability

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The patent makes the trunnion offset angle (psi) a dynamic variable that can be adjusted independently of the tilt angle (gamma). This dynamic configuration allows the CVT to maintain precise speed ratio control through stable gamma control while simultaneously enabling directional switching through independent psi adjustment, thus resolving the contradiction between fixed configuration stability and directional adaptability

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent segments the control of geometric parameters by separating the control of tilt angle (gamma) from the trunnion offset angle (psi). This segmentation allows independent optimization of each parameter for different functions: gamma for speed ratio stability and psi for directional switching, thereby resolving the contradiction between maintaining fixed configuration for stability and enabling directional versatility

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS11530739B2Reversible variable drives and systems and methods for control in forward and reverse directions

Publication Date: 2022.12.20 ENVIOLO BV

AI summary

A ball-planetary continuously variable transmission (CVT) capable of stable control in forward and reverse rotation over a range of speed ratios including underdrive and overdrive is provided. Imparting a skew angle (zeta) causes unbalanced forces that change the tilt angle (gamma), resulting in a change in speed ratio of the CVT. Angularly orientating a control system of the CVT with a positive offset angle (psi) configures the CVT for operation in a first direction of rotation or angularly orientating the control system with a negative offset angle (psi) configures the CVT for operation in a reverse direction of rotation. A control system for configuring the offset angle (psi) may lead or trail the planets. The control system may configure a larger offset angle for more stable control or may configure a smaller offset angle for higher sensitivity in potential rollback scenarios.