Planetary Gear Train Merging for 10-Speed Transmission
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Solution Overview
Problem
Automatic transmissions with increased shift stages face challenges in installability, production cost, weight, and power flow efficiency due to the need for more parts, which complicates achieving better fuel consumption and drivability.
Innovation Solution
A planetary gear train design incorporating four single pinion planetary gear sets and six control elements, including clutches and brakes, to achieve at least ten forward speeds and one reverse speed, optimizing the number of parts for improved efficiency and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of planetary gear sets and control elements is increased to achieve more shift stages, then the fuel consumption and drivability are improved, but the device complexity, weight, and installability deteriorate
Solution Approach 1:
The patent merges multiple planetary gear sets into a integrated structure where gear sets share common elements. Specifically, the first and second planetary gear sets share a common ring gear, and the third and fourth planetary gear sets share another common ring gear. This combining approach reduces the total number of independent parts while maintaining multiple shift stages (10 forward speeds and 1 reverse speed), thereby improving fuel consumption without proportionally increasing device complexity
Solution Approach 2:
The planetary gear sets are designed with multi-functionality where each gear set can serve multiple purposes across different shift stages. The control elements (clutches and brakes) are strategically positioned to control different combinations of sun gears, planet carriers, and ring gears, enabling the same physical components to achieve various gear ratios. This universality allows 10 forward speeds and 1 reverse speed to be achieved with a relatively compact arrangement of four planetary gear sets and six control elements
2Productivity
If the number of planetary gear sets is increased to achieve more shift stages, then the fuel consumption is improved, but the weight increases
Solution Approach 1:
The patent reduces weight by merging planetary gear sets through shared common elements. The first ring gear is shared by the first and second planetary gear sets, and the second ring gear is shared by the third and fourth planetary gear sets. This sharing arrangement means that instead of having eight completely independent planetary gear sets for 10 forward speeds and 1 reverse speed, the system uses four planetary gear sets with shared components, significantly reducing the total weight of the transmission system while maintaining the required number of shift stages
3Ease of operation
If the number of control elements is increased to achieve more shift stages, then the drivability is improved, but the device complexity and installability deteriorate
Solution Approach 1:
The six control elements (clutches and brakes) are designed with multi-functionality to control multiple gear sets simultaneously. Each control element can engage or disengage specific combinations of sun gears, planet carriers, and ring gears to achieve different gear ratios. This multi-functional design allows the same six control elements to manage four planetary gear sets and deliver 10 forward speeds and 1 reverse speed, avoiding the need for a separate control element for each shift stage and thereby reducing device complexity while maintaining good drivability
Data Source
AI summary
A planetary gear train may include input and output shafts, first to fourth planetary gear sets respectively having first to third, fourth to sixth, seventh to ninth, and tenth to twelfth elements, a first shaft connected to the second element and the input shaft, a second shaft connected to the twelfth element and the output shaft, a third shaft connected to the first and seventh elements, a fourth shaft connected to the fifth and eleventh elements, a fifth shaft connected to the eighth and tenth elements, and a plurality of shafts each selectively connecting a corresponding element to a transmission housing, the corresponding element being an element of the first, second and third planetary gear sets which is not interconnected.