Powershift Transmission 24 Forward Modes
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Solution Overview
Problem
Powershift transmissions for work machines typically have limited forward modes and large gear steps, which affect their efficiency at low and high speeds, and often require a high number of components, increasing production costs.
Innovation Solution
A powershift transmission design with 9 clutches and 18 gears, providing 24 forward modes, a high total transmission ratio of 26.2, and smooth shift steps of 16% or less, while minimizing the number of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of forward modes is increased to improve versatility and reduce gear steps, then the transmission ratio range and shift smoothness are improved, but the number of components (clutches and gears) increases
Solution Approach 1:
The transmission is segmented into multiple shafts (input shaft, two countershafts, output shaft) with gears distributed across them. Each shaft carries specific gears that engage with clutches to provide different forward modes. This segmentation allows 24 forward modes to be achieved with a manageable number of components by organizing them across multiple shafts rather than requiring all gears to be on single shafts.
Solution Approach 2:
The patent introduces an additional dimension by using two countershafts (S2 and S3) instead of a single countershaft. This multi-shaft arrangement creates more engagement combinations between clutches and gears, enabling 24 forward modes with 9 clutches and 18 gears. The dimensional expansion from single to multi-shaft architecture resolves the contradiction between mode quantity and component count.
2Power
If the total transmission ratio is increased to improve low-speed performance, then the ability to propel at low speeds with high torque is improved, but the gear step size between modes increases
Solution Approach 1:
The total transmission ratio range is segmented across 24 discrete forward modes distributed from ratio 1.0 to 26.2. By dividing the overall ratio range into many smaller incremental steps (maximum 16% step size), the system achieves both high total ratio for low-speed torque and small incremental steps for smooth transitions. The segmentation of ratio distribution across multiple clutch-gear combinations resolves this contradiction.
Solution Approach 2:
The patent employs non-uniform parameter distribution of gear ratios across the 24 forward modes. The gear ratios are specifically designed to provide finer steps at lower ratios and coarser steps at higher ratios, optimizing both low-speed torque capability and overall versatility. This parameter optimization allows the maximum step size to be constrained to 16% while achieving a total ratio of 26.2:1.
Data Source
AI summary
The powershift transmission comprises nine clutches and eighteen gears, not including the clutches and gears necessary for reverse modes. The powershift transmission provides twenty-four forward modes; a high total transmission ratio of 26.2; and smooth shift steps that are, generally, 15% or less. As such, the transmission utilizes a minimum number of components, while still being extremely functional and versatile.