Valve Timing Lock Mechanism Preventing Unintended Release
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Solution Overview
Problem
Existing valve timing control apparatuses are susceptible to unintended lock release due to centrifugal forces and backlash between rotors, particularly at engine startup, leading to inconsistent valve timing and potential engine performance issues.
Innovation Solution
A valve timing control apparatus with a fluid pressure chamber, partitioning portions, and a lock mechanism that includes a lock member and concave portion, where the lock release flow path is isolated during engine startup to prevent fluid flow, generating negative pressure and maintaining the lock state, thereby canceling out centrifugal and external forces that could cause unintended lock release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the lock plate is ejected and retracted in the radial direction to be fitted to the receiving groove, then the lock mechanism can switch between lock state and lock release state, but the lock plate may be retracted unintentionally when centrifugal force exceeds the biasing force of the torsion spring
Solution Approach 1:
The patent applies preliminary action by pre-positioning the lock plate at the rear end of the receiving groove during engine startup before centrifugal force becomes significant. The control unit keeps the solenoid valve closed during startup, preventing operating oil from entering the receiving groove, so the lock plate is already in place before high-speed rotation begins. This prevents the lock plate from being pushed away by centrifugal force later, as it never had the opportunity to be displaced in the first place.
2Ease of operation
If the end portion of the lock plate is formed with a tapered shape to facilitate fitting, then the ejecting and retracting operation is easier, but external force in the retracting direction acts on the lock plate due to backlash between rotors
Solution Approach 1:
The control unit keeps the solenoid valve closed during engine startup, preventing operating oil from entering the receiving groove. This ensures the lock plate remains firmly positioned at the rear end of the groove during the startup period when backlash forces are present. The preliminary prevention of oil entry establishes a stable initial condition that counteracts the retracting forces generated by rotor backlash.
3Reliability
If the lock plate is biased by the torsion spring to be pushed into the receiving groove, then the lock state is maintained, but the lock may be released when centrifugal force is higher than the biasing force
Solution Approach 1:
The control unit keeps the solenoid valve closed during engine startup, preventing operating oil from entering the receiving groove. This preliminary action ensures the lock plate is already positioned at the rear end before centrifugal force becomes significant. By establishing the locked position in advance during the low-speed startup phase, the system prevents centrifugal force from later displacing the lock plate, as the lock mechanism is already engaged and stabilized.
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 ensures reliable valve timing by preventing unintentional lock release, maintaining optimal valve operation across varying engine conditions, and improving engine performance by ensuring consistent relative rotation phases.
Implementation Method 1
The switching between the lock state and the lock release state is performed by supplying and discharging operating oil to the receiving groove through flow paths connecting to the receiving groove
Implementation Method 2
a torsion spring for biasing the lock plate to be pushed so that an end portion of the lock plate is fitted to a receiving groove
Implementation Method 3
there is a danger that the lock plate is retracted from the receiving groove unintentionally and that the lock is released in the case where the centrifugal force generated by the rotation of the engine is higher than the biasing force
Data Source
AI summary
A valve timing control apparatus includes: a drive-side rotor rotating in synchronization with a crankshaft of an internal combustion engine; a driven-side rotor arranged to have the same shaft center as the drive-side rotor, rotating in synchronization with a camshaft for opening and closing valves; a fluid pressure chamber formed between the drive-side driven-side rotors; a partitioning portion provided in at least one of the drive-side and driven-side rotors; a timing advance chamber and a timing delay chamber formed by partitioning the fluid pressure chamber by the partitioning portion; a lock mechanism including a lock member and a concave portion a lock release flow path through which operating fluid supplied and discharged to and from the concave portion is circulated; a valve arranged in the middle of the lock release flow path; and a control unit controlling the operation of the valve.