Variable Valve Train Cylinder-Specific Fuel Trim for Torque Balance
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Solution Overview
Problem
Internal combustion engines with variable valve trains face issues of unsmooth running and reduced driving comfort due to fabrication-related tolerances, which cause perceptible differences in torque between cylinders, especially in lower load ranges and idling modes.
Innovation Solution
A method for controlling the variable valve train by successively reducing fuel quantity in each cylinder until predefined unsmooth running limiting values are reached, taking into account cylinder-specific values to minimize torque variations, with different operating points prioritizing either fuel supply or air supply faults to optimize valve control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If variable valve train control is used to operate without throttling in lower load ranges, then fuel consumption is reduced, but fabrication tolerances cause cylinder-specific torque differences that reduce driving comfort
Solution Approach 1:
The control device determines cylinder-specific operating parameters for the valve train before actual operation at the first operating point. By pre-determining these parameters based on preliminary testing at a second operating point, the system compensates for fabrication tolerances in advance, ensuring smooth operation when variable valve train control is activated for fuel efficiency
Solution Approach 2:
The system changes operating parameters of the valve train (such as valve lift, duration, or timing) based on determined cylinder-specific values. This allows the system to optimize charging for each cylinder individually, compensating for manufacturing variations while maintaining the fuel-efficient non-throttled operation
2Ease of operation
If cylinder-specific valve control is implemented to compensate for fabrication tolerances, then driving comfort is improved, but the complexity of the control system increases
Solution Approach 1:
The control device uses the engine's own operational data and predetermined test results to automatically determine cylinder-specific operating parameters. The system self-calibrates by comparing actual performance with target values and adjusts valve train parameters accordingly, eliminating the need for external manual calibration or complex additional hardware
Solution Approach 2:
The system determines cylinder-specific values by comparing measured operating parameters with target values and uses this feedback to adjust the valve train control. The control device continuously monitors charging conditions and modifies valve parameters to maintain optimal performance across all cylinders
3Measurement precision
If fuel quantity is reduced for each cylinder to determine charging faults, then cylinder-specific fault detection is achieved, but the time required for determination increases
Solution Approach 1:
The system performs preliminary determination of cylinder-specific operating parameters at a second operating point where fuel supply faults have larger influence. These predetermined values are stored and reused when controlling the valve train at the first operating point, avoiding repeated time-consuming measurements while maintaining precision
Solution Approach 2:
The system determines operating parameters for all cylinders systematically by sequentially adjusting fuel quantity for each cylinder. Rather than attempting simultaneous determination, the method uses controlled sequential adjustment with predetermined limiting values to achieve complete cylinder assessment efficiently
Data Source
AI summary
A method is disclosed for controlling a variable valve timing mechanism of an internal combustion engine having a plurality of cylinders, wherein, at a first operating point of the internal combustion engine, the fuel quantity which is fed in in each case is reduced successively for each cylinder until a predetermined unsmooth-running limiting value is reached. The variable valve timing mechanism is controlled with consideration of the cylinder-individual values for the fuel-quantity reduction at the first operating point.