Planetary Gear Train for Automatic Transmission with Torque-In-Parallel Scheme
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Solution Overview
Problem
Existing automatic transmissions with multiple shift stages face challenges in reducing the number of parts, production cost, weight, and power flow efficiency while maintaining gear ratio linearity, which is exacerbated in eight-speed transmissions with gear ratio spans below 9.0.
Innovation Solution
A planetary gear train utilizing five planetary gear sets and six engagement elements, including a torque-in-parallel scheme on the output side, to achieve ten forward speeds and at least one reverse speed, minimizing drag loss and improving power delivery and fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of parts is increased to achieve more shift stages, then the number of shift stages is increased, but the device complexity and production cost increase
Solution Approach 1:
The patent combines multiple planetary gear sets (first, second, third, fourth, and fifth planetary gear sets) into a single integrated transmission system where gear sets share common components such as the sun gear, planet carrier, and ring gear. This merging approach enables the system to achieve ten forward speeds and reverse speeds without proportionally increasing the number of discrete parts, thereby resolving the contradiction between increasing shift stages and maintaining device complexity at acceptable levels.
Solution Approach 2:
The planetary gear sets are designed with universal components that serve multiple functions. For example, the sun gear, planet carrier, and ring gear are shared across different planetary gear sets and can be selectively engaged to produce different gear ratios. This multi-functionality allows a single set of components to contribute to multiple shift stages, reducing the overall number of parts needed while maintaining high productivity in terms of available gear ratios.
2Productivity
If the number of parts is increased to achieve more shift stages, then the number of shift stages is increased, but the weight increases
Solution Approach 1:
The patent merges multiple planetary gear sets into a compact arrangement where components are shared and overlapped. The first, second, third, fourth, and fifth planetary gear sets are integrated such that they share common sun gears, planet carriers, and ring gears. This combining approach significantly reduces the total weight compared to having separate, non-sharing gear sets for each shift stage, as the same physical components serve multiple gear ratio functions simultaneously.
3Manufacturing precision
If the gear ratio span is increased to improve linearity of step ratios, then the linearity is improved, but the torque loads on engagement elements increase
Solution Approach 1:
The patent segments the overall gear ratio range into multiple smaller stages achieved through the coordinated operation of five planetary gear sets. Instead of using a single large gear ratio span that would require high torque engagement elements, the system divides the gear ratio changes into incremental steps. Each planetary gear set contributes to a portion of the overall gear ratio range, allowing engagement elements to operate at lower torque levels while maintaining good linearity of step ratios across the full range.
Solution Approach 2:
The system employs dynamic engagement of multiple planetary gear sets where the active gear set changes depending on the desired output speed and torque requirements. This dynamic operation allows the transmission to optimize the torque distribution across engagement elements, preventing any single engagement element from bearing excessive torque loads while achieving the necessary gear ratio span for linearity.
4Productivity
If more engagement elements are used to control more shift stages, then the number of shift stages is increased, but the drag loss increases
Solution Approach 1:
The patent combines the control functions of multiple engagement elements into a coordinated system where three engagement elements control five planetary gear sets to achieve ten forward speeds and reverse speeds. This merging of control functions reduces the total number of engagement elements compared to having one engagement element per shift stage. The reduced number of engagement elements directly reduces the total drag loss from friction and hydraulic pressure requirements.
Solution Approach 2:
Each engagement element is designed with multi-functionality to control multiple planetary gear sets simultaneously. For example, a single engagement element can engage or disengage multiple planetary gear sets in a coordinated manner to achieve different gear ratios. This universal control approach reduces the total number of engagement elements needed, thereby reducing the cumulative drag loss from having fewer friction interfaces and hydraulic actuators.
Data Source
AI summary
The present disclosure provides a planetary gear train of an automatic transmission including: input and output shaft, first to fifth planetary gear sets respectively having first to third, fourth to sixth, seventh to ninth, tenth to twelfth, and thirteenth to fifteenth rotational elements, a first shaft connected with the second and fifth rotational elements and the input shaft, a second shaft connected with the fourteenth rotational element and the output shaft, a third shaft connected with the eighth and thirteenth rotational elements, a fourth shaft connected with the eleventh and the fifteenth rotational elements, a fifth shaft connected with the sixth rotational element, a sixth shaft connected with the ninth and twelfth rotational elements, a seventh shaft connected with the tenth rotational element, an eighth shaft connected with the first and seventh rotational elements, and a ninth shaft connected with the third and fourth rotational elements.