Variable Displacement Oil Pump Control for VCT Shifts
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Solution Overview
Problem
Variable cam timing (VCT) systems in internal combustion engines often face insufficient oil pressure during abrupt shifts, leading to degraded performance, including delayed engine response, turbo lag, noise, harshness, and vibration issues, due to conventional oil pressure control methods that fail to provide sufficient pressure under certain operating conditions.
Innovation Solution
A method to adjust oil pressure supplied to the VCT system based on engine speed, load, and temperature, with an increase to a higher level during specific conditions, such as abrupt shifts, using a variable displacement oil pump to ensure sufficient oil pressure is provided without adding supplementary pumps, thereby reducing parasitic losses and improving fuel economy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional oil pressure control methods are used based on engine temperature, load, and speed, then fuel economy is improved by minimizing parasitic losses, but oil pressure becomes insufficient during abrupt VCT shifts causing degraded performance
Solution Approach 1:
The oil pump control system transitions from static calibration based solely on engine parameters to dynamic control that adapts to VCT system demands. The controller monitors VCT operating conditions and dynamically adjusts oil pump output to provide high pressure during abrupt shifts while maintaining reduced pressure during steady-state operation, resolving the contradiction between fuel economy and VCT reliability.
Solution Approach 2:
The system implements feedback control by monitoring VCT operating conditions and using this information to adjust oil pump output. The controller receives input about VCT phase position and shift demands, then modulates oil pressure accordingly, ensuring sufficient pressure during abrupt shifts while minimizing parasitic losses during normal operation.
2Reliability
If an auxiliary oil pump and accumulator are added to supply high flow rate pulses to the VCT system, then sufficient oil pressure is provided during abrupt shifts, but system complexity and cost increase
Solution Approach 1:
The existing variable displacement oil pump is made multi-functional by enabling it to serve both the general engine lubrication needs and the specific high-demand VCT shifting requirements. By controlling the oil pump to deliver high pressure during VCT shifts and reduced pressure during steady-state, the single pump system replaces what would otherwise require an auxiliary pump and accumulator, reducing system complexity while maintaining reliability.
Solution Approach 2:
The oil pump output parameters (pressure and flow) are dynamically changed based on VCT system demands. The controller adjusts the oil pump to deliver high pressure during abrupt shifts and reduces pressure during normal operation, allowing the existing pump to meet varying demands without requiring additional hardware components.
3Reliability
If a fixed rate oil pump is upsized to meet periodic high demands of the VCT system, then sufficient oil pressure is always available, but parasitic losses increase and fuel economy degrades
Solution Approach 1:
The variable displacement oil pump provides dynamic adjustment of oil output, delivering high pressure only when VCT shifts are demanded and reducing pressure during steady-state operation. This dynamic capability eliminates the need for an oversized fixed pump, maintaining reliable oil pressure availability while minimizing parasitic losses and preserving fuel economy.
4Reliability
If computationally intensive models are used to adjust oil pressure based on modeled vs. actual phasing rate, then oil pressure can be optimized for VCT performance, but computation time increases and response speed decreases
Solution Approach 1:
The system uses a simplified control approach that monitors key VCT operating conditions and applies appropriate oil pressure adjustments without performing computationally intensive modeling. This partial action approach provides sufficient VCT performance by focusing on the most critical parameters, achieving reliable phasing control while maintaining fast computation speed and responsive operation.
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 enhances engine responsiveness and performance by expeditiously supplying the necessary oil pressure for rapid shifting, minimizing issues like turbo lag and noise, while maintaining efficient fuel economy and reducing system costs.
Implementation Method 1
Many variable cam timing systems use a vane type cam phaser that may be controlled by an electromechanically actuated spool valve that directs oil flow to one side or the other of the vane in order to actuate the phaser
Data Source
AI summary
Methods and systems are provided for adjusting an oil pressure supplied to an engine and a variable cam timing (VCT) responsive to a condition of the VCT system. In one example, a method may include adjusting the oil pressure based on engine speed, engine load, and engine oil temperature, and responsive to a request to shift the VCT system during specific engine operating conditions, increasing the oil pressure to an upper threshold oil pressure for the duration of the shift.