Dual Camshaft Phaser Rate Limiting and Balancing Control
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Solution Overview
Problem
Existing systems for dual independent camshaft phasers in internal combustion engines struggle to coordinate simultaneous operation, leading to inefficiencies in oiling system demands, combustion stability, and variability in engine performance, resulting in reduced fuel economy, increased costs, and potential combustion and air/fuel control issues.
Innovation Solution
A control system that enables simultaneous ratiometric scheduling of dual intake and exhaust phaser movements by rate-limiting their operations relative to each other, prioritizing fluid power use, and balancing phaser rates to synchronize movements within the engine's oiling system capacity, thereby reducing oil pump size requirements and enhancing combustion stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If both phasers are actuated simultaneously at full phasing rate, then phaser response speed is improved, but oiling system capacity requirements increase, leading to higher cost and reduced fuel economy
Solution Approach 1:
The system dynamically adjusts phaser actuation rates based on real-time engine operating conditions. The controller varies the phasing rate within a range rather than operating at fixed full speed, allowing the oiling system capacity to be optimized for each specific condition. This dynamic rate adjustment resolves the contradiction by matching phaser speed requirements to actual engine needs, reducing unnecessary oiling system capacity demands.
Solution Approach 2:
The invention changes the operational parameters of the phasers by allowing variable phasing rates within a defined range. Instead of binary full-speed operation, the system continuously adjusts the phasing rate parameter based on engine state, oil temperature, and other factors. This parameter variation enables the system to achieve required phaser response while minimizing oiling system capacity requirements.
2Speed
If fast step changes in phase position are used, then phaser actuation speed is improved, but combustion and air/fuel control issues arise due to inconsistent movement
Solution Approach 1:
The controller continuously monitors actual phaser position and compares it with the desired position, using this feedback to adjust the phasing rate. The system incorporates feedback from engine sensors (crankshaft position, camshaft position, oil pressure, temperature) to modulate the phaser actuation speed. This feedback mechanism ensures smooth, consistent phaser movement that maintains combustion stability while achieving required phasing corrections.
Solution Approach 2:
The system uses dynamic rate limiting that adjusts the maximum phasing speed based on current engine operating conditions. Rather than applying fixed fast step changes, the controller dynamically modulates the phasing rate within an acceptable range, ensuring that phase position changes are smooth and consistent with engine operation. This dynamic approach maintains combustion reliability while achieving necessary phaser actuation.
3Productivity
If a larger capacity oil pump is used to support simultaneous full-rate phaser actuation, then phaser response capability is improved, but engine cost and packaging requirements increase
Solution Approach 1:
The system dynamically adjusts phaser actuation rates based on actual engine conditions rather than designing for maximum simultaneous full-rate actuation. By varying the phasing rate within a range and prioritizing phaser actuation based on engine state, the system achieves required phaser response capability without requiring an oversized oil pump. This dynamic approach reduces oiling system complexity and packaging requirements while maintaining adequate phaser productivity.
Solution Approach 2:
The system applies partial action by providing phaser actuation at less than maximum capacity when engine conditions allow. Rather than always operating at full phasing rate, the controller applies only the necessary degree of phasing action required for the current operating condition. This partial action approach reduces the oiling system capacity requirements, allowing for smaller, less complex oil pumps while still achieving adequate phaser actuation capability.
4Measurement precision
If hydraulic actuation is used for cam phasers, then phaser control precision is improved, but part-to-part and engine-to-engine variation increase
Solution Approach 1:
The system uses feedback control to compensate for hydraulic variations. The controller continuously monitors actual phaser position and adjusts the actuation command based on the difference between desired and actual position. This feedback mechanism, combined with real-time adjustment of phasing rates based on engine conditions, compensates for part-to-part and engine-to-engine hydraulic variations, maintaining consistent phaser performance across different units and operating conditions.
Solution Approach 2:
The system dynamically changes operational parameters (phasing rate, actuation timing) based on detected engine conditions and hydraulic state. By adjusting these parameters in real-time, the system compensates for variations in hydraulic actuation characteristics between different parts and engines. This parameter adaptation maintains consistent phaser control precision despite underlying hydraulic variations.
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 approach ensures consistent and controlled phaser movement, reducing oiling system demands, improving fuel economy, and maintaining combustion stability by synchronizing phaser operations with the engine's air, fuel, and spark delivery systems, while also reducing manufacturing costs and variability.
Implementation Method 1
Phasers typically are actuated by a pressure duty cycle of oil derived from the engine's main oil supply and selectively directed to chambers within the phaser to alter the phase relationship between the rotor and the stator
Implementation Method 2
providing smooth and consistent transitions between operating points while allowing for prioritized application of the available fluid power of the engine's oiling system
Data Source
AI summary
A method for controlling dual independent camshaft phasers in an internal combustion engine. The method has three basic steps: a) first, determining if rate balancing between the two phasers is required; b) second, determining the optimal rate balancing commands; and c) third, applying the determined rate balancing commands to the appropriate phaser(s). In determining the rate balancing commands, there are three possible phaser options: the intake phaser requires priority; the exhaust phaser requires priority; or neither phaser requires priority. Lookup tables are stored in the engine controller for each option. When either phaser has priority, the other phaser is actuated after a delay based upon the position error of the priority phaser, generally at a lower phase rate. When neither phaser has priority, both phasers are actuated at a rate consistent with oil-delivery capabilities of the engine.