Multi-speed Transmission Shifting Between Ranges
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Solution Overview
Problem
Current automatic transmissions in vehicles lack the ability to seamlessly shift between low and high range while moving, particularly in four-wheel drive vehicles, limiting torque and speed control options, especially during off-road or high-torque situations.
Innovation Solution
A transmission system incorporating four simple planetary gear sets and a controller that selectively engages brakes and clutches to establish various speed ratios, allowing for smooth shifting between low and high ranges, including reverse and forward drive modes, by coordinating the engagement of shift elements to achieve desired speed ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If transfer case gearing is provided in four-wheel drive vehicles, then torque multiplication and speed control capabilities are improved, but the system becomes unavailable to two-wheel drive vehicles and cannot shift while moving under engine power
Solution Approach 1:
The transmission system is divided into two separate gearing arrangements: a first gearing arrangement that provides variable speed ratios (including low and high range) between the input shaft and intermediate shaft, and a second gearing arrangement that provides fixed speed reduction between the intermediate shaft and output shaft. This segmentation allows the variable ratio shifting to occur independently in the first arrangement while the second arrangement maintains a constant linear speed relationship, enabling smooth shifts while moving.
Solution Approach 2:
An intermediate shaft is introduced as a mediator between the input shaft and output shaft. The first gearing arrangement establishes speed ratios between the input shaft and intermediate shaft, while the second gearing arrangement establishes a fixed linear speed relationship among the intermediate shaft, input shaft, and output shaft. This intermediary element enables the decoupling of variable ratio changes from the final output, allowing shifts to occur without interrupting power flow to the wheels.
2Adaptability or versatility
If multiple planetary gear sets and shift elements are used to enable dynamic range shifting, then speed control precision and adaptability are improved, but device complexity increases
Solution Approach 1:
The first gearing arrangement serves multiple functions: it provides low range gear multiplication for high torque situations, high range gear reduction for fuel-efficient cruising, and enables smooth shifting between ranges while moving. The four planetary gear sets are configured to alternately establish four positive speed ratios and two negative speed ratios, allowing a single gearing arrangement to replace what would traditionally require separate transfer case low/high range mechanisms.
Solution Approach 2:
The patent combines the functions of traditional transfer case low/high range gearing directly into the automatic transmission system. By merging the variable ratio capability into the main transmission and using a fixed linear speed relationship in the second gearing arrangement, the system eliminates the need for a separate shiftable transfer case, reducing overall system complexity while maintaining adaptability.
Data Source
AI summary
A transmission gearing arrangement includes four simple planetary gear sets, three brakes, and four clutches. The transmission produces two reverse gear ratios and twelve forward speed ratios in response to engagement of the brakes in clutches in combinations of three. The transmission is suitable for use with a range selector. In a low range, one of the reverse ratios and all twelve of the forward ratios are utilized. In a high range, the other reverse ratio and eleven of the forward ratios are utilized.