Variable Oil Pump Discharge Control for Camshaft Unlocking
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Solution Overview
Problem
Existing engine control systems face challenges in performing phase angle control suitable for operating states while reducing unlocking failures of the locking member in the variable valve timing mechanism.
Innovation Solution
A control system that includes a hydraulically-operated variable valve timing mechanism, a variable oil pump, and a hydraulic-pressure control valve, where the pump control device restricts oil discharge to maintain hydraulic pressure within an upper-limit value during unlocking operations, ensuring the locking member can be unlocked effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the timing of hydraulic pressure control is retarded to reduce unlocking failure, then the locking member can be reliably unlocked, but phase angle control suitable for engine operating state cannot be performed
Solution Approach 1:
The patent applies dynamics by making the oil pump discharge amount adjustable in real-time based on operating conditions. The control device dynamically modifies the discharge amount during unlocking operations to prevent excessive pressure buildup, while maintaining normal adaptive phase angle control during regular operation. This resolves the contradiction by making the system behavior flexible rather than fixed, allowing reliable unlocking without sacrificing control adaptability.
Solution Approach 2:
The patent changes the hydraulic pressure parameter dynamically by controlling the oil pump discharge amount. During unlocking operations, the discharge amount is restricted to keep pressure below the upper-limit value, preventing locking member failure. During normal operation, the system returns to adaptive phase angle control. This parameter modification approach resolves the contradiction between reliable unlocking and control adaptability.
2Reliability
If the oil discharge amount is restricted during unlocking, then hydraulic pressure is controlled to prevent unlocking failure, but phase angle control responsiveness may be affected
Solution Approach 1:
The patent applies periodic action by implementing temporary discharge amount restriction only during the specific unlocking operation period, rather than continuously. The control device detects when unlocking is needed and applies the restriction only during that transient phase. After unlocking is complete, the system returns to normal adaptive control mode. This time-limited approach ensures reliable unlocking without permanently affecting phase angle control responsiveness.
Solution Approach 2:
The system dynamically adjusts the oil pump discharge amount based on real-time operating conditions. During unlocking operations, the discharge amount is temporarily restricted to prevent excessive pressure. During normal phase angle control operations, the system resumes adaptive control with full responsiveness. This dynamic switching resolves the contradiction between unlocking reliability and control speed.
3Speed
If the hydraulic pressure is increased to improve phase angle control speed, then control responsiveness improves, but unlocking failure occurs due to excessive pressure
Solution Approach 1:
The patent applies preliminary action by detecting the unlocking condition in advance and proactively restricting the oil pump discharge amount before excessive pressure can build up. The control device monitors the operational state and preemptively adjusts the discharge amount during unlocking operations to keep pressure below the upper-limit value. This preventive approach prevents unlocking failure while allowing normal high-speed control operation.
Solution Approach 2:
The system changes the hydraulic pressure parameter dynamically based on operating conditions. During unlocking operations, the discharge amount is restricted to maintain pressure below the upper-limit value, preventing locking member failure. During normal phase angle control, the system allows higher pressures for faster responsiveness. This conditional parameter modification resolves the contradiction between control speed and unlocking reliability.
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 configuration reduces unlocking failures of the locking member while allowing for suitable phase angle control according to the engine's operating state, enhancing the stability and efficiency of the engine's operation.
Implementation Method 1
The variable oil pump supplies, via a hydraulic-pressure path, oil to hydraulically-operated devices including the variable valve timing mechanism of the engine
Implementation Method 2
The hydraulic-pressure control valve controls the hydraulic pressure to be supplied to the locking mechanism and the advance-side and retard-side operation chambers
Implementation Method 3
a locking mechanism that unlocks, by supplying hydraulic pressure, a locking member for fixing the phase angle of the camshaft with respect to the crankshaft
Data Source
AI summary
A control system for an engine is provided. The system includes a hydraulically-operated variable valve timing mechanism, a variable oil pump, and a hydraulic-pressure control valve. The variable valve timing mechanism has advance-side and retard-side operation chambers and a locking mechanism. The system includes a hydraulic-pressure sensor for detecting hydraulic pressure within a hydraulic-pressure path, and a pump control device for performing a target hydraulic-pressure control. During a change of an engine operating state in a specific operation of the engine, while an unlocking operation of a locking member of the locking mechanism is performed, the pump control device performs, instead of the target hydraulic-pressure control, a discharge amount restricting control to control the hydraulic pressure to be an upper-limit hydraulic-pressure value or lower, which is an upper limit to perform the unlocking operation.