Power Shift Transmission Control for Constant Torque Gear Changes

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Solution Overview

Problem

Existing electric powertrain transmissions experience significant torque interruptions and output torque fluctuations during shifting events due to the wide gear ratio spread, leading to decreased shift quality.

Innovation Solution

The method involves engaging a second friction clutch while disengaging a first friction clutch to transition between gear ratios, and operating the traction motor under a peak condition exceeding the maximum continuous torque threshold during the transition to maintain a constant output torque.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a wide gear ratio spread is used in electric transmission, then the power band capability is improved, but torque interruptions during shifting are exacerbated

Engineering Contradiction:

Improvepower band capabilityVSAvoidtorque continuity during shifting

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The traction motor is operated in a peak condition before the actual shift occurs, building up rotational energy in advance. This preliminary energy storage allows the motor to compensate for torque interruptions during the shift event, maintaining output torque continuity despite the wide gear ratio spread

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control system dynamically changes the motor operating parameters by transiently exceeding the maximum continuous torque threshold during shifting. This parameter change enables the motor to deliver peak torque exactly when needed during the transition, compensating for the torque dip that would normally occur with wide gear ratio spread

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If friction clutches are engaged and disengaged during shifting, then gear ratio transition is achieved, but torque interruptions occur at transmission output

Engineering Contradiction:

Improvegear ratio transitionVSAvoidoutput torque stability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The control system continuously monitors clutch engagement status and motor torque output, using this feedback to dynamically adjust motor torque commands. This closed-loop control ensures that the motor compensates for torque variations caused by clutch transitions, maintaining stable output torque throughout the shifting process

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The traction motor acts as an intermediary energy buffer between the friction clutches and the transmission output. While the clutches transition between engaged and disengaged states, the motor maintains rotational energy and torque output, mediating the torque interruptions that would otherwise propagate to the transmission output

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12209658B2Electric power shift transmission and power shift method

Publication Date: 2025.01.28 DANA BELGIUM

AI summary

Systems and methods for an electric powertrain. The method, in one example, includes responsive to receiving a shift command, engaging a second friction clutch while disengaging a first friction clutch to transition from a first operating gear ratio to a second operating gear ratio. The method, further includes during the gear ratio transition, operating a traction motor under a peak condition, the peak condition denotes a condition where the motor speed is greater than a maximum continuous torque curve of the motor.