Variable Valve Timing Lock Mechanism for Centrifugal Force Management
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Solution Overview
Problem
Existing variable valve timing control devices for internal combustion engines struggle to maintain valve timing at an intermediate lock position as engine revolution speed increases, due to centrifugal forces causing the lock pin to release, leading to instability in valve timing control.
Innovation Solution
The implementation of a variable valve timing control device with intermediate lock mechanisms, including phase-advance and phase-retard side lock mechanisms, which utilize working fluid to maintain the valve timing at the intermediate lock position through forced lock control and intermediate position feedback control, ensuring the lock keys engage with recessed portions despite centrifugal forces, and switching between these controls based on engine speed thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lock pin is used to hold valve timing at an intermediate lock position, then valve timing can be maintained at the intermediate position, but when engine revolution speed increases and centrifugal force increases, the lock pin cannot maintain valve timing at the intermediate lock position
Solution Approach 1:
The patent introduces a hydraulic lock mechanism that uses working fluid pressure to maintain the lock keys in the engaged state with recessed portions. The hydraulic actuator applies force to the lock keys, counteracting the centrifugal force that tends to disengage them at high engine speeds. This hydraulic assistance ensures reliable intermediate lock position maintenance across the full engine speed range.
Solution Approach 2:
The patent changes the physical state and parameters of the locking mechanism by introducing hydraulic pressure as a controllable parameter. By adjusting working fluid pressure based on engine speed conditions, the system can maintain adequate locking force at high speeds while allowing normal mechanical locking at lower speeds, thus adapting the locking capability to varying operational parameters.
2Stability of the object's composition
If forced lock control is applied to maintain intermediate lock position, then valve timing stability is improved, but friction against motion increases due to centrifugal force
Solution Approach 1:
The hydraulic actuator provides a controlled force to the lock keys, reducing the reliance on pure mechanical friction to maintain the locked position. By using hydraulic pressure to supplement the locking force, the system achieves stable valve timing maintenance without excessive friction resistance, as the hydraulic force acts in conjunction with the mechanical locking elements.
Solution Approach 2:
The working fluid acts as an intermediary between the control system and the lock keys. Instead of directly applying large mechanical forces that generate high friction, the hydraulic system transmits force through the fluid medium, providing a smoother and more controlled action that reduces direct frictional resistance while maintaining locking stability.
3Reliability
If the lock pin is spring biased towards the lock position, then intermediate lock position can be maintained, but the mechanism releases under sufficient centrifugal force at high engine speeds
Solution Approach 1:
The patent transitions from a static spring-biased mechanical lock to a dynamic hybrid locking system. The lock mechanism now adapts its characteristics based on engine speed: at low speeds, mechanical spring biasing provides the locking force, while at high speeds, hydraulic pressure dynamically supplements or replaces the mechanical force to counteract increased centrifugal effects, thus adapting the locking capability to varying operational conditions.
Solution Approach 2:
By introducing hydraulic pressure control, the system gains adaptability to different engine speed conditions. The working fluid pressure can be dynamically adjusted to match the centrifugal force requirements at various speeds, allowing the lock mechanism to maintain reliability across the entire operating range rather than being limited to a narrow speed range where spring biasing alone is effective.
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 solution effectively maintains valve timing at the intermediate lock position across varying engine speeds, preventing disengagement of lock keys and ensuring stable valve timing control, thereby enhancing engine performance and reducing emissions.
Implementation Method 1
when an engine revolution speed increases and thus a centrifugal force, acting on the lock pin, also increases
Implementation Method 2
utilize working fluid to maintain the valve timing at the intermediate lock position through forced lock control
Data Source
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AI summary
Intermediate position feedback control is executed when valve timing of an intake valve is at an intermediate lock position, an intermediate lock is needed, and an engine revolution speed is greater than a first engine revolution speed R1. Forced lock control is executed when the valve timing of the intake valve is at the intermediate lock position, the intermediate lock is needed, the engine revolution speed is less than the first engine revolution speed R1, and the intermediate position feedback control is not being executed. As a result, even when the engine revolution speed increases in the presence of a demand that the valve timing needs to be in the intermediate lock position, it is possible to maintain the valve timing at the intermediate lock position.