Powertrain Downshift Control Using Temporary Two-Stroke Operation

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Solution Overview

Problem

In critical vehicle situations like steep uphill or downhill driving, existing powertrain control methods struggle to achieve rapid downshifting while minimizing torque interruption, which can lead to loss of vehicle control due to inadequate engine speed synchronization with gear rotational speed.

Innovation Solution

A method and control device that temporarily operate the engine in a two-stroke mode during downshifting, using independently operable valves to rapidly increase engine speed and synchronize it with the rotational speed of a lower gear, and then resume four-stroke operation for reduced fuel consumption and emissions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the engine operates in four-stroke mode during downshifting, then fuel consumption and emissions are reduced, but engine speed increases too slowly to synchronize with gear rotational speed in critical situations

Engineering Contradiction:

Improveengine speed increase rateVSAvoidfuel consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The engine dynamically switches between four-stroke and two-stroke operation modes based on driving conditions. During critical downshifting situations, the engine transitions to two-stroke mode to achieve rapid speed synchronization, then returns to four-stroke mode for efficient cruising, optimizing both response time and fuel economy

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The valve timing and duration parameters are dynamically adjusted to enable two-stroke operation. By modifying these parameters, the engine can switch between operational modes to achieve the required balance between rapid acceleration and fuel efficiency

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the drivetrain is disconnected from the engine during downshifting, then gear engagement is enabled, but torque transmission is interrupted leading to vehicle speed loss or unsafe conditions

Engineering Contradiction:

Improvevehicle control stabilityVSAvoidtorque interruption duration

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The engine speed is rapidly increased using two-stroke mode before the drivetrain reconnection occurs. This preliminary speed buildup ensures that when torque transmission resumes, the engine and transmission are already synchronized, eliminating torque interruption and maintaining vehicle control stability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The two-stroke operation mode provides continuous rapid acceleration of the engine during the entire downshifting process, ensuring that engine speed continuously tracks with the required synchronization speed, thereby maintaining continuous useful action despite drivetrain disconnection

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS12103532B2Method for controlling a powertrain

Publication Date: 2024.10.01 VOLVO TRUCK CORP

AI summary

A method for controlling a powertrain of a vehicle, the powertrain comprising:an engine comprising mutually independently operable valves, the engine being configured to be operated in a four-stroke operation mode, anda drivetrain comprising a transmission,the method comprising:while operating the engine in the four-stroke operation mode, identifying that a critical situation applies or is expected to apply, in which a fast downshift of the transmission is required,initiating a downshift process in response to the identification of the critical situation,during at least a part of the downshift process, increasing an engine speed by controlling at least the mutually independently operable valves of the engine such that the engine is temporarily operated in a two-stroke operation mode.