Cam Phaser Spring Retainer for Friction Reduction
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Solution Overview
Problem
Camshaft phasers face challenges in aligning a lock pin to its seat at an intermediate rotor position when oil pressure is low, as traditional bias spring systems either fail to bias correctly or cause unwanted advancement past the lock point, leading to frictional drag and assembly issues.
Innovation Solution
A spring retainer system captures and pre-loads a bias spring within a phaser cover plate, with a tapered rotor pocket and retainer slot features that manage the spring's active leg, preventing friction during retardation and arresting spring torque during advancement to allow self-alignment at the lock position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a simple spring-arm system is used to bias the rotor, then the phaser can advance the rotor from full retard position, but the bias spring causes unwanted advancement past the lock point when resistive torque is less than spring torque
Solution Approach 1:
The spring retainer slot is designed with a specific geometry that allows the active leg to engage and disengage dynamically based on rotor position. The slot wall captures the active leg during retardation but releases it during advancement, allowing the system to adapt its mechanical connection state based on operational requirements.
Solution Approach 2:
The spring retainer acts as an intermediary component between the bias spring and the rotor. It mediates the interaction by capturing the active leg in a controlled manner, allowing torque transmission only when needed (during retardation) while preventing unwanted advancement during rotor advance by releasing the active leg from the slot wall.
2Reliability
If the bias spring is pre-loaded to bias the rotor toward the lock position, then alignment assistance is provided during low oil pressure, but frictional drag occurs between the spring and retainer slot wall during rotor retardation
Solution Approach 1:
The spring is pre-loaded during assembly to establish the correct bias force before operation. The spring retainer slot is designed with a tapered geometry that guides the active leg into proper alignment, preliminarily establishing the correct mechanical relationship before the rotor begins to move during operation.
Solution Approach 2:
The tapered slot wall geometry creates a dynamic interaction where the active leg is captured during retardation but lifted off during advancement. This dynamic engagement/disengagement eliminates continuous frictional contact while maintaining the necessary bias force for alignment assistance.
3Reliability
If the active leg of the bias spring contacts the end of the spring retainer slot during rotor advancement, then spring torque is removed to prevent further advancement, but the spring may tip from axial alignment and continue contacting the rotor bottom face
Solution Approach 1:
The potential harmful effect of the spring tipping and continuing to contact the rotor bottom face is converted into a beneficial self-aligning mechanism. The spring's natural tendency to tip and contact the rotor bottom face actually helps return the rotor to its correct axial alignment, transforming a potential failure mode into a corrective feature.
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 reduces frictional drag, improves assembly efficiency, and ensures proper alignment of the lock pin, enhancing the phaser's performance and durability by eliminating unwanted spring torque and facilitating cost-effective manufacturing.
Implementation Method 1
a pre-loaded bias spring is active through only a portion of the range of authority of rotor rotation
Implementation Method 2
Lifting the active tang of the bias spring removes any friction between the bias spring and the retainer slot wall
Data Source
AI summary
During assembly of an improved phaser, a rotor bias spring is captured by a spring retainer that is fitted or formed into the cover, allowing the spring to be installed in a pre-load position and forming a sub-assembly that is then attached to the remaining components. Grounded and active spring tangs are captured in separate slots in the spring retainer. A pocket within the rotor receives the active tang of the bias spring. The pocket has a tapered bottom ramp that lifts the active tang from the slot wall in the retainer and positions the active tang within the pocket in a retarding direction. Lifting the active tang of the bias spring prevents friction between the spring and the retainer slot wall as would occur as the rotor moves in a retarded direction. In advancing, spring rotation stops when the active tang contacts the end of the retainer slot.