Multi-speed EV Gearbox with Planetary Differential
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Solution Overview
Problem
Fully electric vehicles typically use single-speed gearboxes, which are insufficient for off-road use, as they lack the lower gear ratios needed for improved torque and control, unlike conventional vehicles with multi-speed transmissions.
Innovation Solution
A multi-speed gearbox design for electric vehicles, featuring a planetary gear set, differential, and shift elements like dog clutches, allowing selective speed ratios between the input and output axes, enabling both HIGH and LOW range speed ratios for enhanced torque and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single-speed gearbox is used in fully electric vehicles, then the structure is simple and the optimal speed range of the electric machine is充分利用, but the vehicle lacks sufficient torque multiplication for off-road conditions and low-speed control
Solution Approach 1:
The patent implements a multi-speed gearbox with shift elements (clutches and brakes) that can dynamically change the gear ratio between high-range and low-range modes. The shift elements selectively engage or disengage to alter the power transmission path, enabling the gearbox to adapt its characteristics based on driving conditions while maintaining a relatively compact structure
Solution Approach 2:
The gearbox design incorporates a planetary gear set that can operate in multiple modes (high-range direct drive, high-range reduced drive, low-range gear ratios) through the selective engagement of shift elements. This allows a single gearbox structure to serve multiple functions - both on-road cruising and off-road low-speed control requirements
2Power
If a multi-speed transmission is added to electric vehicles, then torque multiplication and speed control are improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent employs a planetary gear set where smaller gears are nested within larger gears, creating a compact multi-speed transmission system. The planetary arrangement allows multiple gear ratios to be achieved within a single stage, reducing the overall size and complexity compared to traditional multi-stage gear trains while providing sufficient torque multiplication
Solution Approach 2:
The design merges the high-range and low-range gear systems into a single integrated planetary gear set. By combining the sun gear, planet gears, and ring gear with selective braking and clutching mechanisms, the system achieves multiple speed ratios without requiring separate transmission systems for different ranges, thereby reducing overall complexity
3Productivity
If a planetary gear set with multiple components is used, then multiple speed ratios are achieved, but the manufacturing precision and assembly difficulty increase
Solution Approach 1:
The planetary gear set is divided into distinct functional components (sun gear, planet gears, ring gear, planet carrier) that can be manufactured and assembled separately. The shift elements (clutches and brakes) are also segmented into independent components that can be engaged or disengaged independently, allowing for modular manufacturing and assembly while achieving multiple speed ratios
Data Source
AI summary
A gearbox includes an input gear supported for rotation about an input axis and includes first and second idler gears fixedly coupled to each other and supported for rotation about a transfer axis. The first idler gear is fixedly coupled to the input gear. A planetary gear set is supported for rotation about an output axis of the gearbox and has a first component fixedly coupled to the second idler gear. A differential is supported for rotation about the output axis, co-axial with the planetary gear set, and fixedly coupled to a second component of the planetary gear set.