Drivetrain Controller Valve Timing for Pump Loss Reduction
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Solution Overview
Problem
Reciprocating engines in motor vehicle drivetrains experience undesirably strong resistance moments due to pump losses during intake and exhaust strokes, which can brake the vehicle excessively when tow-started or in coasting mode, especially when driving an electrical generator.
Innovation Solution
A method and system for controlling the drivetrain that activates start and coasting modes by modifying engine operations, including intermittent opening of cylinders during intake strokes and keeping valves closed during volume-enlarging and -reducing strokes to reduce compression work and pump losses, using actuators and camshaft controllers to manage valve operations and coupling with driving wheels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the reciprocating engine operates with standard valve timing during intake and exhaust strokes, then the engine can perform normal combustion cycles, but pump losses build up resistance that excessively brakes the vehicle during tow-start or coasting mode
Solution Approach 1:
The patent applies reverse engineering by keeping intake and exhaust valves closed during volume-reducing strokes that normally would be compression strokes, thereby converting harmful pump losses into beneficial reduced resistance. This inversion of normal valve operation timing eliminates the resistance moment that normally opposes vehicle rolling during coasting or tow-start conditions.
Solution Approach 2:
The patent dynamically adjusts valve operation based on operating mode. During coasting or tow-start, the control device keeps valves closed during specific strokes to reduce resistance. During normal combustion operation, standard valve timing is restored to maintain combustion efficiency. This dynamic adaptation resolves the contradiction between reducing pump losses and maintaining normal engine function.
2Use of energy by moving object
If the reciprocating engine is used to drive an electrical generator during coasting mode, then energy can be recovered, but the resistance moment from pump losses excessively brakes the vehicle
Solution Approach 1:
The patent changes the operational parameters of the engine during coasting mode by modifying valve timing to keep valves closed during volume-reducing strokes. This parameter change reduces the resistance moment while maintaining sufficient engine rotation to drive the electrical generator for energy recovery, thereby resolving the contradiction between energy recovery and excessive braking.
3Extent of automation
If the engine is tow-started using vehicle inertia, then the engine can be started without external assistance, but the resistance moment excessively brakes the rolling vehicle
Solution Approach 1:
The patent uses inverted valve operation during the start sequence, keeping valves closed during volume-reducing strokes to minimize resistance moment. This allows the vehicle's rolling inertia to more effectively crank the engine without excessive opposing force, enabling successful tow-start while preserving vehicle momentum.
Data Source
AI summary
A method for controlling a drivetrain of a motor vehicle is disclosed. Either a start mode for starting the reciprocating engine is activated via the driving vehicle wheel, or a coasting mode is activated for driving the reciprocating engine via the driving vehicle wheel. At least one volume-reducing stroke is executed that follows an intake stroke for at least one cylinder of the reciprocating engine with at least intermittently open cylinder. Alternately at least one volume-enlarging stroke is executed for at least one cylinder of the reciprocating engine, which is followed by a compression stroke of this cylinder, and at least one volume-reducing stroke of this cylinder, which follows an expansion stroke that follows the compression stroke, with a cylinder that is closed, if possible, in this operating mode.