Three-Speed Planetary Transmission Layout for Smoother EV Shifting
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Solution Overview
Problem
Existing automatic transmission units for electric vehicles with two forward speeds experience high step ratios during shifting, leading to increased acceleration and deceleration rates, which can be problematic for smooth gear transitions.
Innovation Solution
A power transmission unit with a three-speed configuration utilizing a first and second planetary gear mechanism, along with three engagement elements, allowing for reduced step ratios and smoother shifting by connecting the input element to the output element through a series of interconnected components, reducing power transmission loss, and integrating the control unit with a power transmission mechanism, and integrating the control unit with a power transmission mechanism.
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 is improved, but the step ratio at the time of shifting is increased
Solution Approach 1:
The transmission system is divided into two separate 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 independent gear mechanisms, the system achieves both high torque amplification at first speed and reduced step ratio during shifting, as each mechanism can be optimized for its specific function.
2Power
If the transmission gear ratio at the first speed is increased, then a motor with small size can be selected, but the acceleration and deceleration rates of output rotation at the time of shifting is increased
Solution Approach 1:
The transmission system is divided into two separate 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 independent gear mechanisms, the system achieves both high torque amplification at first speed and reduced step ratio during shifting, as each mechanism can be optimized for its specific function.
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 third rotational element, the output element is connected to the second rotational element and the sixth rotational element, one side of the first engagement element is connected to 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 first rotational element and 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.