Dual-Input Transmission Shifting With Intermediate Gear Engagement
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Solution Overview
Problem
Existing transmission systems that use dog clutches to shift gears face challenges in synchronizing rotational speeds, leading to increased electric power consumption or generation, which necessitates larger batteries and higher costs, and result in rough gear shifts.
Innovation Solution
A transmission system that utilizes two electric machines to simultaneously engage different gears, allowing dog clutch transitions to be spread over a wider speed range, reducing the need for high-capacity batteries and ensuring smooth gear shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If dog clutch rotational speed is increased or decreased to match gear rotational speed quickly, then gear engagement smoothness is improved, but electric power consumption increases and battery capacity must be increased
Solution Approach 1:
The patent divides the single dog clutch engagement task into two separate dog clutch engagements. The first dog clutch engages the first gear while the second dog clutch engages the second gear, allowing the speed synchronization process to be distributed across two independent operations rather than requiring one clutch to handle the entire speed mismatch alone.
Solution Approach 2:
The patent dynamically adjusts the engagement timing of the two dog clutches based on the rotational speeds of the electric machines. By controlling when each clutch engages relative to the others, the system optimizes the speed synchronization process to reduce peak power demands on the battery while maintaining smooth gear transitions.
2Reliability
If dog clutch rotational speed is increased or decreased to match gear rotational speed, then possibility of teeth skipping is reduced, but rate of speed change increases causing rough shifts
Solution Approach 1:
The patent segments the gear shifting process into two independent dog clutch engagements. Each clutch handles a portion of the speed synchronization task, allowing for more controlled and gradual speed matching that reduces both tooth skipping and abrupt speed changes that cause rough shifts.
Solution Approach 2:
The second dog clutch acts as an intermediary mechanism that shares the speed synchronization burden. By having two clutches working in parallel, the system can achieve reliable tooth engagement while distributing the speed adjustment across multiple components, thereby reducing the rate of speed change and improving shift smoothness.
3Device complexity
If single electric machine is used for torque supply, then system complexity is reduced, but ability to meet driver demand torque during gear shift deteriorates
Solution Approach 1:
The patent segments the torque supply function across two electric machines. During gear shifts, one electric machine can maintain torque output while the other adjusts speed for clutch engagement, ensuring continuous and reliable driver demand torque delivery without requiring a single machine to handle all functions alone.
Solution Approach 2:
The patent combines the functions of two electric machines to work together during gear shifts. One machine focuses on speed synchronization for its associated clutch while the other maintains power delivery, and their torque outputs are combined to meet the total driver demand, achieving both reliable power delivery and smooth shifting.
Data Source
AI summary
Methods and systems for shifting a transmission that includes two input shafts configured to be driven via two different power sources is shown. The systems and methods include shifting into an intermediate gear mode where two different gears coupled to an output shaft of a transmission are driven simultaneously. The approach allows battery power to be conserved during gear shifting and simplification of performing off-road maneuvers.