2-Speed EV Transmission Using CMDs for Seamless Direction Shifts
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Solution Overview
Problem
Existing vehicle powertrains with electric motors and planetary gear systems face inefficiencies in shifting between forward and reverse gears, particularly in electric vehicles, due to the limitations of conventional clutch mechanisms.
Innovation Solution
A vehicle drive system utilizing a 2-speed transmission with controllable mechanical diodes (CMDs) and one-way clutches that allow for seamless gear shifting by changing the rotational direction of the electric motor, enabling direct engagement of either the first or second gearset based on the motor's direction, thereby facilitating quick and efficient shifts between forward and reverse gears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional clutch mechanisms are used for gear shifting in electric vehicle powertrains, then the shifting between forward and reverse gears can be achieved, but torque interruption occurs during shifting which reduces efficiency
Solution Approach 1:
The patent introduces controllable mechanical diodes (CMDs) as intermediary elements that enable seamless transition between forward and reverse gears. The CMDs act as mediators that can selectively engage different gearsets (first gearset for forward, second gearset for reverse) without requiring traditional clutch mechanisms that interrupt torque flow. This allows continuous power transmission while switching between opposing rotational directions.
Solution Approach 2:
The system dynamically changes the rotational direction of the electric motor to select between different gearsets. By making the motor's rotational direction controllable and changeable, the system can seamlessly switch between forward and reverse operations without mechanical interruption. The CMDs dynamically engage/disengage based on the motor's rotation direction, enabling smooth gear transitions.
2Adaptability or versatility
If traditional multi-speed transmission systems are implemented, then multiple forward and reverse gears are achieved, but the system complexity increases with multiple clutch elements and concentric architectures
Solution Approach 1:
The electric motor serves multiple functions: it acts as both the power source and the directional control mechanism. By changing the motor's rotational direction, the same motor controls both forward and reverse operations across multiple gears, eliminating the need for separate mechanisms for each direction. The CMDs also serve dual purposes by enabling both gear selection and directional control.
Solution Approach 2:
The patent extracts and eliminates traditional clutch mechanisms from the transmission system. Instead of using multiple clutch elements to engage/disengage gears, the system uses CMDs that control gearset selection through motor direction changes. This extraction of the clutch function simplifies the overall architecture while maintaining multi-speed capability.
3Productivity
If conventional gear shifting mechanisms are used, then gear changes are achieved, but the shifting process causes torque interruption which reduces productivity
Solution Approach 1:
The system maintains continuous power transmission during gear shifts by using CMDs that enable seamless transitions between gearsets. The electric motor's ability to change rotational direction allows the power flow to continue uninterrupted while switching between forward and reverse gears. This eliminates the torque interruption that occurs in conventional systems during clutch engagement/disengagement.
Solution Approach 2:
The CMDs are positioned and configured in advance to enable immediate engagement of the appropriate gearset when the motor changes direction. The system prepares the mechanical diode states beforehand so that when a gear change is needed, the transition occurs instantly without interruption, maintaining continuous productivity.
Data Source
AI summary
A vehicle transmission using a gearset. Multi-mode clutches selectively couple components of the gearset. The transmission operates in and shifts between a first forward gear and a second forward gear using a change in input rotation. An electric motor coupled to the input may be used to change the input rotation direction.