Toroidal CVT Traction System for Hybrid Vehicles
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Solution Overview
Problem
Existing hybrid traction systems for vehicles face inefficiencies due to the use of toroidal continuously variable transmissions (CVTs) that experience torque reduction with increased speed, require complex and costly auxiliary systems, and suffer from energy dissipation and increased dimensions, leading to reduced overall efficiency.
Innovation Solution
A traction system incorporating a toroidal CVT with a speed variator and epicyclic differential configuration that allows continuous variation of transmission ratios without discrete gear ratios or brakes, enabling independent control of power sources and optimizing energy use by maintaining maximum efficiency across all operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a toroidal CVT with oscillating roller is used, then the transmission can provide continuous variable ratios, but the torque transmission capability progressively decreases with increased speed
Solution Approach 1:
The patent applies dynamics by making the roller's charge direction independent of its oscillation motion. The roller oscillates to vary the transmission ratio, but the charge direction (normal force orientation) is dynamically adjusted separately through a control system that varies the charge direction angle, allowing optimal torque transmission at each operating point regardless of speed
Solution Approach 2:
The patent changes the parameter of charge direction angle independently from the transmission ratio. By varying the charge direction angle as a separate controllable parameter, the system can optimize torque transmission capability at different speeds while maintaining continuous variable ratio operation
2Power
If auxiliary systems are added to compensate for torque deficiency, then the torque limitation can be improved, but the device complexity and cost increase significantly
Solution Approach 1:
The patent merges the torque control function into the existing CVT structure by utilizing the roller's dual motion capability. The same oscillating roller that provides continuous variable ratio also controls torque transmission through its charge direction, eliminating the need for separate auxiliary torque limitation systems
Solution Approach 2:
The oscillating roller is given multi-functionality: it simultaneously provides continuous variable transmission ratio through its oscillation and controls torque transmission capability through its charge direction. This universal component replaces multiple specialized auxiliary systems
3Power
If a hydraulic pump is used to vary the charge between CVT elements, then the normal force can be adjusted, but continuous energy consumption increases
Solution Approach 1:
The system uses the roller's own oscillation motion and controlled charge direction adjustment to vary the normal force distribution, rather than requiring an external hydraulic pump. The CVT elements themselves facilitate the force adjustment through their geometric configuration and controlled interaction
4Device complexity
If fixed transmission ratios are used for the electric motor, then the connection is simplified, but the motor speed cannot be controlled independently of vehicle speed
Solution Approach 1:
The patent applies dynamics by making the transmission ratio between the electric motor and wheels continuously variable rather than fixed. The CVT allows the transmission ratio to change dynamically, enabling the electric motor speed to be independently controlled from vehicle speed while maintaining a simplified single-stage connection
5Reliability
If the internal combustion engine is disconnected from the transmission at low speed, then neutral running is prevented, but kinetic energy is dissipated through braking
Solution Approach 1:
The patent applies dynamics by maintaining the engine continuously connected to the transmission through the CVT. The continuous variable ratio capability allows the engine to remain connected across all operating conditions including low speed and standstill, eliminating the need for disconnection and subsequent braking energy dissipation
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
The system enhances vehicle efficiency by maintaining optimal power delivery and reducing energy dissipation, eliminating the need for complex control systems and auxiliary devices, thereby improving performance and reducing costs.
Implementation Method 1
at least two roller members (268) having a spherical surface and in contact with two toroidal friction discs (266, 270) arranged coaxially and rotating in opposed directions
Data Source
AI summary
A traction system for vehicles comprises a first power source of the non-reversible type, a second power source of the reversible type and a transmission which is connected to the power sources and which includes a first differential device. The transmission further comprises a speed variator which is interposed between the first source and the first differential device and which comprises a continuous speed variation device, and a second differential device. The continuous speed variation device is of the toroidal friction wheel type and comprises a lateral motion input disc, a lateral motion output disc and at least two idle oscillating friction roller members. The lateral motion input and output discs have a friction surface of toroidal shape and the idle oscillating roller members have a friction surface shaped in the form of a spherical dome.