Negative-Torque Downshift for Fixed-Gear Hybrid Powertrains

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Solution Overview

Problem

Fixed-gear transmissions in hybrid powertrains face challenges in managing shift execution torque effectively, particularly during downshifts, where maintaining consistent output torque is difficult due to changes in speed ratios and torque multiplication, leading to inefficiencies in regenerative braking and vehicle deceleration.

Innovation Solution

A method is introduced that involves a two-phase approach for downshift execution in fixed-gear powertrains, comprising a torque phase where an oncoming clutch is engaged to change the speed ratio, and an inertia phase where regenerative input torque is calculated and applied to maintain consistent output torque, utilizing the electric machine to manage torque multiplication and overcome rotational inertia.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If regenerative braking torque is applied during downshift, then energy recovery is improved, but transmission component loading and potential damage increase

Engineering Contradiction:

Improveregenerative braking efficiencyVSAvoidtransmission component durability

Core Design Contradiction:

Use of energy by moving objectVSStrength

Solution Approach 1:

The control system pre-calculates the maximum safe regenerative torque based on current transmission state (clutch engagement level, gear ratio, rotational speeds) before applying regenerative braking. This preliminary assessment ensures that regenerative torque is applied within safe limits that prevent component damage while maximizing energy recovery.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts the amount of regenerative torque applied during downshift based on real-time transmission conditions. As the clutch engages and gear ratio changes, the control system continuously modifies the regenerative torque magnitude to optimize energy recovery while preventing excessive loading on transmission components.

Inventive Principle:

Principle #15Dynamics

2Loss of time

If clutch engagement is accelerated during torque phase, then shift execution time is reduced, but torque ripple and vibration increase

Engineering Contradiction:

Improvedownshift execution timeVSAvoidtorque smoothness

Core Design Contradiction:

Loss of timeVSStability of the object's composition

Solution Approach 1:

The control system applies periodic or pulsed torque management during the clutch engagement phase, modulating the clutch torque in a controlled manner rather than applying continuous maximum torque. This periodic action allows the clutch to engage more quickly while minimizing torque ripple and vibration by allowing brief relaxation periods during the engagement process.

Inventive Principle:

Principle #19Periodic action

3Use of energy by moving object

If regenerative torque is maximized during inertia phase, then energy recovery is improved, but output torque consistency deteriorates

Engineering Contradiction:

Improveregenerative energy recoveryVSAvoidoutput torque consistency

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The control system continuously monitors output torque levels during the inertia phase and uses feedback control to adjust the regenerative torque application. When output torque deviation is detected, the system modulates the regenerative torque to maintain consistent output torque while still maximizing energy recovery within the constraints of torque consistency requirements.

Inventive Principle:

Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This method ensures consistent output torque throughout the downshift process, improving the efficiency of regenerative braking and deceleration by precisely managing torque phase and inertia phase transitions, thereby enhancing the overall performance of hybrid powertrains.

Implementation Method 1

calculating a starting regenerative input torque at the input node... applying the starting regenerative input torque with the electric machine at the beginning of the torque phase

Methodology Applied

Scientific EffectRegenerative braking:

Implementation Method 2

executing a torque phase by engaging an oncoming clutch

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 3

Different gears or modes of the transmission provide different, selectable speed ratios or gear ratios, and also different levels of torque multiplication

Methodology Applied

Scientific EffectMechanical Advantage: Mechanical Advantage

Data Source

PatentUS9242545B2Negative-torque downshift execution for fixed-gear transmissions

Publication Date: 2016.01.26 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A method of executing a downshift in a fixed-gear powertrain having an input node and an output node related by a starting speed ratio before the downshift and a finishing speed ratio after is provided. The downshift includes a torque phase and an inertia phase. A starting output torque is calculated as a function of a starting driver request. An electric machine applies a starting regenerative input torque which is calculated as substantially equal to the starting output torque divided by the starting speed ratio. A finishing output torque is calculated as a function of a finishing driver request. The electric machine applies a finishing regenerative input torque which is calculated as substantially equal to the finishing output torque divided by the finishing speed ratio.