Planetary Gear Train for Automatic Transmission with Compound Set
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Solution Overview
Problem
Existing automatic transmissions with more than eight speeds require multiple planetary gear sets and control elements, increasing complexity, weight, and production costs, which deteriorates installability and shift feel.
Innovation Solution
A planetary gear train design incorporating a compound planetary gear set and two simple planetary gear sets, along with six control elements and brakes, to achieve ten forward speeds and one reverse speed with minimal parts, improving power delivery and fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of planetary gear sets is increased to achieve more shift stages, then fuel consumption and driving efficiency are improved, but device complexity and total length increase, deteriorating installability
Solution Approach 1:
The patent combines two simple planetary gear sets into one compound planetary gear set where the sun gear, planet gears, and ring gear of the first simple planetary gear set are integrated with those of the second simple planetary gear set through shared components and selective connectability. This merging achieves the functional equivalent of multiple planetary gear sets while reducing the total number of separate gear sets and control elements required in the transmission system.
2Productivity
If the number of control elements is increased to achieve more shift stages, then fuel consumption is improved, but device complexity and weight increase
Solution Approach 1:
The control elements in the compound planetary gear set are designed to perform multiple functions. Each control element can selectively connect different shafts (first shaft connected to third and sixth rotation elements, second shaft connected to ninth rotation element, etc.), allowing a single control element to manage multiple gear ratio transitions and shift stages, thereby reducing the total number of control elements needed compared to traditional designs.
3Productivity
If traditional planetary gear sets are used to achieve ten forward speeds, then shift stages are obtained, but applicable structure is restricted and shift feel deteriorates
Solution Approach 1:
The patent implements a dynamic control system where control elements can selectively connect various shafts in different operating conditions to achieve ten forward speeds. The selective connectability between shafts (first shaft to third and sixth rotation elements, second shaft to ninth rotation element, third shaft to first rotation element, fourth shaft to fourth rotation element, fifth shaft to fifth and eighth rotation elements, sixth shaft to seventh rotation element) allows the system to adapt its structure dynamically, providing smooth shifts and improved shift feel while maintaining broad applicability.
Data Source
AI summary
A planetary gear train may include input and output shafts a compound planetary gear set having first, second, third and fourth rotation elements by combination of first and second planetary gear sets; a third planetary gear set having fifth, sixth, and seventh rotation elements; a fourth planetary gear set having eighth, ninth, and tenth rotation elements, the first rotation element selectively connectable to the fifth rotation element and the tenth rotation element, respectively, the second rotation element and the tenth rotation element selectively connectable to the transmission housing, the third rotation element fixedly connected to the sixth rotation element, and fixedly connected to the input shaft, the fourth rotation element selectively connectable to the seventh shaft, the fifth rotation element fixedly connected to the eighth shaft, the seventh rotation element selectively connectable to the ninth shaft, the ninth rotation element fixedly connected to the output shaft.