Variable Valve Control Preventing Cylinder Negative Pressure
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Solution Overview
Problem
Conventional variable valve timing mechanisms controlled by oil hydraulic systems face response delays, leading to potential simultaneous closure of intake and exhaust valves after the piston passes the intake top dead center, causing negative pressure inside the cylinder, which complicates achieving stable output and fuel efficiency across a wide range of engine revolutions.
Innovation Solution
A variable valve control apparatus with a negative pressure suppression control section that adjusts the phase and working angle of the intake valve, and exhaust valve timing to prevent simultaneous closure, using a combination of hydraulic pressure management, feedback control, and forced opening mechanisms to maintain optimal engine performance and prevent negative pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If variable valve timing mechanism is controlled by oil hydraulic system, then stable output is ensured, but response delay occurs causing negative pressure in cylinder
Solution Approach 1:
The control apparatus predicts when simultaneous valve closure will occur based on current operating conditions and提前 issues advance angle control commands to the variable valve timing mechanism. This preliminary action prevents negative pressure from developing in the first place, resolving the contradiction by acting before the problem occurs rather than reacting after the hydraulic system's response delay causes issues.
Solution Approach 2:
The control apparatus continuously monitors valve timing and engine operating conditions, comparing actual valve closure timing against predicted timing. When deviation indicating potential simultaneous closure is detected, the feedback loop triggers advance angle control adjustments to the variable valve timing mechanism, ensuring stable operation while compensating for hydraulic response delays.
2Reliability
If advance angle control is performed to prevent simultaneous valve closure, then negative pressure is avoided, but fuel efficiency deteriorates
Solution Approach 1:
The control apparatus applies advance angle control selectively only in specific operating conditions where simultaneous valve closure is predicted, rather than continuously. By targeting control only when and where needed (local application), it prevents negative pressure in critical situations while avoiding unnecessary advance angle adjustments that would waste fuel during normal operation.
Solution Approach 2:
The control apparatus dynamically adjusts the degree of advance angle control based on real-time engine operating parameters such as load, speed, and temperature. By varying the control parameter (advance angle magnitude) according to conditions, it achieves reliable prevention of negative pressure when necessary while minimizing fuel efficiency penalties by using smaller or no adjustments when conditions allow.
3Speed
If variable working angle mechanism is controlled by electric motor, then response speed is improved, but device complexity increases
Solution Approach 1:
The control apparatus merges the control of the variable working angle mechanism with the existing variable valve timing control system. Both mechanisms are coordinated through a unified control algorithm that manages them as an integrated system, achieving fast response through the electric motor while reducing overall complexity by consolidating control logic rather than creating separate independent control systems.
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
Ensures stable engine output and improved fuel efficiency by preventing torque variations and addressing response delays in the valve control system, thereby avoiding abnormal combustion due to oil suction and maintaining optimal engine performance across a wide range of engine revolutions.
Implementation Method 1
a variable valve timing mechanism that adjusts actuation timing of a valve and includes a variable valve timing mechanism that adjusts actuation timing of an intake valve and an exhaust valve
Implementation Method 2
a variable working angle mechanism that adjusts a working angle of the intake valve and includes variable valve control section that controls the variable valve timing mechanism or the variable working angle mechanism based on an engine load
Data Source
AI summary
A variable valve control apparatus includes a variable valve timing mechanism that adjusts an actuation timing of an intake valve and an actuation timing of an exhaust valve; a variable working angle mechanism that adjusts a working angle of the intake valve; a variable valve control section that controls at least one of the variable valve timing mechanism and the variable working angle mechanism based on an engine load; and a negative pressure suppression control section. The negative pressure suppression control section suppresses a negative pressure of an inside of a cylinder when the negative pressure suppression control section determines that both of the intake valve and the exhaust valve close after an intake top dead center, based on opening conditions of the intake valve and the exhaust valve.