Variable Cam Timing Lock Pin Hydraulic Force Balance
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Solution Overview
Problem
Variable Camshaft Timing (VCT) devices experience uncommanded phasing between the camshaft and crankshaft due to hydraulic and mechanical inputs causing the lock pin to unlock, leading to decreased engine efficiency and related issues.
Innovation Solution
A lock pin with multiple diameters and pressure areas is designed to utilize engine oil pressure to maintain the VCT device in a locked position, featuring a dynamic hydraulic seal and unequal pressure areas to induce a net force in the locking direction, preventing uncommanded unlocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional lock pin design is used in the VCT device, then the device can unlock when commanded by the ECU, but the lock pin may unlock uncommanded due to hydraulic and mechanical inputs causing uncontrolled phasing
Solution Approach 1:
The lock pin is designed with different diameter sections (first diameter larger than second diameter) creating distinct pressure areas. The first pressure area (on the nose) responds to oil pressure for unlocking, while the second pressure area (on the body) maintains locking resistance against hydraulic and mechanical inputs. This local differentiation of geometric properties enables the lock pin to simultaneously maintain reliable locking and respond to commanded unlock signals.
2Adaptability or versatility
If engine oil pressure is used to retract the lock pin for timing adjustment, then the VCT device can phase, but the same oil pressure may cause uncommanded unlocking under certain engine conditions
Solution Approach 1:
The lock pin geometry is changed to create unequal pressure areas. The first pressure area (nose) is designed to be smaller than the second pressure area (body). This parameter change in geometric distribution allows the same engine oil pressure to have different effects: when applied to the smaller first area, it generates sufficient force for unlocking; when acting on the larger second area, it creates a stabilizing moment that prevents uncommanded unlocking while maintaining timing adjustment capability.
3Reliability
If a spring is used to maintain lock pin engagement, then the lock pin stays locked, but additional hydraulic input is needed to overcome the spring force for unlocking
Solution Approach 1:
The invention extracts the spring component from the locking mechanism and replaces it with a passive geometric locking feature. The unequal diameter sections of the lock pin create inherent mechanical advantage and pressure distribution that maintains locking without active spring force. This eliminates the need for additional hydraulic energy to overcome spring resistance, while the ECU-controlled oil pressure can still reliably unlock the pin when needed.
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
The solution effectively maintains the VCT device in a locked position until commanded to unlock by the Engine Control Unit (ECU), enhancing engine efficiency by preventing uncontrolled phasing and ensuring reliable operation under various engine conditions.
Implementation Method 1
the lock pin of the present invention has a pressure area in the locking direction, which utilizes engine oil pressure to create a net force in the lock direction to maintain the VCT device in the locked position
Implementation Method 2
The lock pin is received in a bore of the rotor that has multiple diameters that create a dynamic hydraulic seal with the lock pin
Implementation Method 3
When the lock pin is commanded to unlock by the ECU, engine oil pressure is directed to the nose of the lock pin and the lock pin retracts from the pin pocket resulting in an unlocked condition
Data Source
AI summary
A lock pin for a VCT device that has a locked position, locking a housing assembly relative to a rotor assembly of the variable cam timing device, and an unlocked position. The lock pin has a body comprising a first diameter with a first area, a second diameter with a second area, and a chamber formed between the first area of the first diameter and the second area of the second diameter for receiving fluid, the first area being greater than the second area. When fluid is applied to the chamber through the variable cam timing phaser, a difference between first area and the second area defining the chamber creates a force imbalance, such that the oil pressure applied to the chamber of the body assists in maintaining the Sock pin in the locked position.