Electric Vehicle Transmission Unit with Segmented Planetary Gears
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Solution Overview
Problem
Existing automatic transmission units for electric vehicles with two forward speeds experience increased torque amplification and acceleration/deceleration rates due to high step ratios during gear shifts, necessitating a smaller motor size and lower high-speed rotation.
Innovation Solution
A power transmission unit with a 3-speed configuration using a first and second planetary gear mechanism, along with a third engagement element, allowing for reduced step ratios and synchronized rotational speeds across gear positions, reducing power loss and layout constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the transmission gear ratio at the first speed is increased to reduce motor size, then the torque amplification effect increases, but the step ratio increases and acceleration/deceleration rates during shifting increase
Solution Approach 1:
The transmission system is segmented into two planetary gear mechanisms (first and second) with different gear ratios. The first planetary gear mechanism provides a first transmission gear ratio while the second provides a second transmission gear ratio. By segmenting the transmission into multiple mechanisms with intermediate gear ratios, the step ratio between adjacent speeds is reduced, thereby lowering acceleration and deceleration rates during shifting while still achieving torque amplification to reduce motor size.
2Device complexity
If a two-speed configuration is used, then the structure is simpler, but the step ratio is large causing high acceleration/deceleration rates during shifting
Solution Approach 1:
The transmission system is segmented into two planetary gear mechanisms (first and second) that can be engaged independently or in combination. This segmentation enables the creation of multiple gear ratios (first, second, and third transmission gear ratios) without significantly increasing structural complexity. The intermediate gear ratios provided by the segmented structure reduce the step ratio between adjacent speeds, thereby lowering acceleration and deceleration rates during shifting while maintaining relatively simple transmission structure.
3Speed
If three or more gear positions are achieved, then the step ratio is reduced and acceleration/deceleration rates during shifting are reduced, but the device complexity increases
Solution Approach 1:
The first and second planetary gear mechanisms are merged into a single transmission system with shared components. The input element is connected to both mechanisms, and the engagement elements control both mechanisms simultaneously. This merging allows three or more gear positions to be achieved through coordinated engagement of the first, second, and third engagement elements, reducing the step ratio and acceleration/deceleration rates during shifting while avoiding the complexity of completely separate transmission systems.
Data Source
AI summary
Provided is a unit including: an input element; an output element; first to third engagement elements; a first planetary gear mechanism in which the first to third rotational elements are arranged in this order on an alignment chart; and a second planetary gear mechanism in which fourth to sixth rotational elements are arranged in this order on the alignment chart. The input element is connected to the first rotational element and the sixth rotational element, the output element is connected to the second rotational element, one side of the first engagement element is connected to the third rotational element and the fifth rotational element, the other side of the first engagement element is fixed, one side of the second engagement element is connected to the fourth rotational element, the other side of the second engagement element is fixed, and the third engagement element connects two rotational elements that are selected from the first to sixth rotational elements and are not connected to each other.