Five-Set Planetary Gear Train for Ten-Speed Automatic Transmission
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Solution Overview
Problem
Conventional automatic transmissions face challenges in achieving optimal power delivery performance and fuel economy due to limited gear ratio span and increased complexity with higher speed stages, leading to deteriorated drivability and efficiency.
Innovation Solution
A planetary gear train with five planetary gear sets and six engaging elements, including three clutches and three brakes, is designed to achieve ten forward speeds and one reverse speed, minimizing component count and optimizing torque delivery efficiency while ensuring linearity of step ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of speed stages is increased to enhance fuel economy and optimize drivability, then power delivery performance and fuel economy are improved, but the number of internal components increases leading to deteriorated mountability, cost, weight, and transmission efficiency
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 gears, and ring gear. This merging approach enables the system to achieve ten forward speeds and one reverse speed without proportionally increasing the number of independent components, thereby improving fuel economy while controlling device complexity.
Solution Approach 2:
The planetary gear sets are designed with multi-functional capability where the same gear set can provide multiple gear ratios through different engagement configurations of clutches and brakes. The first through fifth planetary gear sets collectively provide ten forward speeds and one reverse speed, allowing a single gear set to perform the work of multiple traditional gear stages, thus reducing overall component count while maintaining high speed stage capability.
2Ease of operation
If the gear ratio span is increased to secure linearity of step ratios, then drivability and acceleration performance are improved, but the complexity of the planetary gear train increases
Solution Approach 1:
The patent employs dynamic engagement and disengagement of clutches (first through fourth clutches) and brakes (first through third brakes) to achieve different gear ratios. The selective engagement of these elements allows the planetary gear sets to dynamically reconfigure torque transmission paths, providing ten forward speeds and one reverse speed with linear step ratios without requiring a fixed complex mechanical structure for each gear stage.
Solution Approach 2:
The system achieves a gear ratio span of 9.7 or more by changing the engagement state parameters of the clutches and brakes. By varying which clutches are engaged and which brakes are applied, the system can smoothly transition between different gear ratios while maintaining linearity of step ratios, thereby improving drivability without proportionally increasing mechanical complexity.
3Power
If five planetary gear sets are used to achieve ten forward speeds and one reverse speed, then power delivery performance and fuel economy are improved, but drag loss of clutches and brakes increases
Solution Approach 1:
The patent designs the torque transmission path to maintain continuous useful action through the planetary gear sets. By configuring the first through fifth planetary gear sets with shared components and optimized torque distribution, the system ensures that torque is continuously transmitted through gear meshing rather than through multiple clutch engagement/disengagement cycles. This reduces drag loss while maintaining high power delivery performance across ten forward speeds and one reverse speed.
Data Source
AI summary
A planetary gear train apparatus of automatic transmission may include first planetary gear set including first to third rotation elements, second planetary gear set including fourth to sixth rotation elements, third planetary gear set including seventh to ninth rotation elements, fourth planetary gear set including tenth to twelfth rotation elements, fifth planetary gear set including thirteenth to fifteenth rotation elements, first shaft fixed to the second rotation element and the input shaft, second shaft fixed to the fourteenth rotation element and the output shaft, third shaft fixed to the third and seventh rotation elements, fourth shaft fixed to the fifth and thirteenth rotation elements, fifth shaft fixed to the sixth rotation element, sixth shaft fixed to the eleventh and fifteenth rotation elements, seventh shaft fixed to the first, fourth, and eighth rotation elements, eighth shaft fixed to the ninth and tenth rotation elements, and ninth shaft fixed to the twelfth rotation element.