Vehicle Powertrain Freewheeling Control for Downhill Speed Management

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Solution Overview

Problem

Conventional internal combustion engine vehicles consume unnecessary fuel and emit excess emissions when idling, and existing stop-and-start systems do not efficiently manage powertrain operations during varying driving conditions, particularly in heavy-duty vehicles.

Innovation Solution

A computer system controls the powertrain system to operate in freewheeling, coasting, and engine braking modes, using processing circuitry to manage transitions based on topography and vehicle data to optimize fuel efficiency and emissions, especially during downhill segments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the engine operates continuously during vehicle inactivity, then the vehicle can maintain readiness and respond quickly, but fuel consumption increases and emissions are generated

Engineering Contradiction:

Improvevehicle readinessVSAvoidfuel consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent segments the traditional continuous engine operation into distinct operational phases: freewheeling mode (engine disconnected from drive wheels), coasting mode (engine disconnected, fuel supply interrupted), and engine braking mode (engine connected, generating braking effect). This segmentation allows the engine to be decoupled from the drivetrain during vehicle inactivity or downhill segments, eliminating the need for continuous fuel consumption while maintaining vehicle controllability through inertial momentum and regenerative braking capabilities.

Inventive Principle:

Principle #1Segmentation

2Use of energy by moving object

If the engine is shut off during vehicle inactivity, then fuel consumption is reduced, but the vehicle loses acceleration capability and requires longer restart time

Engineering Contradiction:

Improvefuel consumptionVSAvoidacceleration capability

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The patent implements preliminary action by maintaining the engine in a rotated but disconnected state during freewheeling mode, or by pre-charging the battery and pre-conditioning the engine startup system. This allows the engine to be quickly restarted when acceleration is needed, reducing the penalty associated with engine shutdown. Additionally, the system uses coasting and engine braking modes to maintain vehicle momentum, reducing the frequency of acceleration events required.

Inventive Principle:

Principle #10Preliminary action

3Speed

If the engine is restarted frequently during downhill segments, then the vehicle can maintain speed control, but the exhaust aftertreatment system is exposed to cold gases reducing its effectiveness

Engineering Contradiction:

Improvespeed controlVSAvoidexhaust aftertreatment temperature

Core Design Contradiction:

SpeedVSTemperature

Solution Approach 1:

The patent dynamically adjusts engine operation based on real-time driving conditions, particularly during downhill segments. The system transitions between freewheeling mode (engine rotated, disconnected), coasting mode (engine disconnected, fuel interrupted), and engine braking mode (engine connected, braking effect generated). This dynamic operation allows the engine to remain disconnected from the drivetrain during downhill coasting, preventing cold exhaust gases from entering the aftertreatment system, while still providing speed control through inertial momentum and selective engine re-engagement only when necessary.

Inventive Principle:

Principle #15Dynamics

4Speed

If the vehicle uses mechanical brakes for speed control during downhill segments, then speed can be maintained, but brake wear increases and braking effectiveness decreases over time

Engineering Contradiction:

Improvespeed controlVSAvoidbrake lifespan

Core Design Contradiction:

SpeedVSDuration of action of moving object

Solution Approach 1:

The patent replaces the traditional mechanical braking system with an engine braking system that utilizes the engine's compression resistance to generate braking effect. During downhill segments, the engine is reconnected to the drivetrain and operated in engine braking mode, where the engine's internal compression forces create a retarding torque that slows the vehicle without wearing down mechanical brake components. This substitution significantly extends brake lifespan while maintaining effective speed control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP4600099A1System and method for controlling a powertrain system of a vehicle

Publication Date: 2025.08.13 VOLVO TRUCK CORP

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AI summary

The present disclosure relates to a computer system (100) for controlling a powertrain system (11) of a vehicle (10), the powertrain system comprising an internal combustion engine (12) connectable to one or more drive wheels, the computer system comprising processing circuitry (102) configured to selectively operate the powertrain system in: a first freewheeling mode (FM1); a second freewheeling mode (FM2); a coasting mode (CM); and an engine braking mode (EBM); wherein the processing circuitry (102) is further configured to: determine a vehicle target speed; determine that a freewheeling mode condition is fulfilled based on any one of topography data and vehicle data; determine that the powertrain system is operating in either the first freewheeling mode or the second freewheeling mode; if the powertrain system is operating in the first freewheeling mode and an acceleration level fulfills an acceleration level condition, control the powertrain system from the first freewheeling mode to the coasting mode; and if the powertrain system is operating in the second freewheeling mode, further determine to maintain the second freewheeling mode.