Two-Stage EV Transmission Reducing Motor Capacity
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Solution Overview
Problem
Conventional electric vehicle transmissions with single gear ratios increase motor capacity and production costs, necessitating a solution to reduce costs while maintaining driving performance.
Innovation Solution
A two-stage transmission system for electric vehicles incorporating a gearbox unit with a sun gear, planetary gear, carrier, ring gear, first and second synchro units, and a clutch unit, allowing for adjustable shifting and reduced component count, including an electric motor unit and control unit to manage power delivery and shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If only motor torque is utilized or only an electric reducer is used, then motor capacity relatively increases, but production costs increase accordingly
Solution Approach 1:
The transmission system is segmented into two distinct stages: a first stage using a planetary gear mechanism for low-speed high-torque operation, and a second stage using a worm gear mechanism for high-speed operation. This segmentation allows the motor to operate at optimal capacity across different speed ranges, reducing the need for oversized motor capacity while maintaining production cost efficiency
Solution Approach 2:
The system dynamically switches between two transmission modes based on operating conditions. A switching mechanism enables transition between the planetary gear stage (for starting and low-speed operation) and the worm gear stage (for high-speed operation), allowing the motor to maintain optimal capacity without requiring excessive power for peak demands
2Device complexity
If a single gear ratio reducer is used, then the transmission structure is simple, but motor capacity must increase to satisfy all driving conditions
Solution Approach 1:
The transmission is divided into two functional stages with different gear mechanisms. The first stage uses a planetary gear mechanism for torque multiplication during starting and acceleration, while the second stage uses a worm gear mechanism for efficient power transmission during cruising. This segmentation eliminates the need for a single high-capacity motor by matching transmission characteristics to operational requirements
Solution Approach 2:
The planetary gear mechanism is nested within the overall transmission structure, with the sun gear connected to the motor output and planetary gears providing torque multiplication. This compact nested arrangement achieves complex transmission functions within a space-efficient design, avoiding the need for oversized motor components
Data Source
AI summary
A two-stage transmission for an electric vehicle of the present invention comprises: a gearbox unit; a driving unit for providing power into the gearbox unit; a sun gear unit embedded in the gearbox unit and rotated by being axially connected to the driving unit, a planetary gear unit embedded in the gearbox unit, and provided in engagement with an outer side part of the sun gear unit; a carrier unit embedded in the gearbox unit and rotatably supporting the planetary gear unit; a ring gear unit embedded in the gearbox unit, and provided on the outer side of the carrier unit and engaged with the planetary gear unit; a first synchro unit axially connected to the driving unit so as to rotate together with the sun gear unit, and selectively connected to the carrier unit so as to adjust variable speeds; and a second synchro unit mounted in the gearbox unit, and selectively coupled to the ring gear unit so as to adjust variable speeds.