Viscous Fan Drive Bushing Prevents Actuator Sticking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fluid coupling devices used in radiator cooling fans experience 'morning sickness' due to inadequate fluid drain back, leading to unnecessary fan operation and potential overcooling, and the actuator can stick in the 'on' position, causing emissions issues.
Innovation Solution
An electronically controlled viscous fan drive system with a valve disk and actuating piston, using insulated washers and bushings to prevent fluid backflow and actuator locking, allowing precise control of fan operation and fluid flow based on engine conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If fluid coupling devices are used to drive radiator cooling fans, then engine horsepower savings are achieved, but morning sickness occurs due to inadequate fluid drain back
Solution Approach 1:
The housing is segmented into a reservoir chamber and an operating chamber, allowing separate control of fluid storage and fluid operation. This segmentation enables the valve disk to selectively control fluid flow between chambers, preventing morning sickness while maintaining energy savings during normal operation.
Solution Approach 2:
A valve disk acts as an intermediary component between the reservoir chamber and operating chamber. The valve disk controls fluid flow with precision, ensuring complete drain back to the reservoir while allowing controlled fluid transfer during operation. This intermediary mechanism resolves the contradiction by providing reliable fluid management.
2Measurement precision
If electronic activation is used to control fluid flow, then precise control between engaged and disengaged modes is achieved, but the actuator may stick in the on position
Solution Approach 1:
The return spring mechanism extracts the actuator from the magnetic flux path when deactivating. By physically removing the actuator from the flux pattern, the system prevents magnetic sticking while maintaining precise electronic control during active operation. This separation resolves the reliability issue without sacrificing control precision.
Solution Approach 2:
Instead of relying on magnetic field cessation alone to return the actuator, the system uses a return spring to actively push the actuator away from the flux path. This inverted approach ensures reliable return by applying mechanical force opposite to the magnetic attraction, preventing sticking while preserving precise control capability.
3Duration of action of stationary object
If the actuator remains stuck in the on position, then the fan continues operation, but overcooling and additional emissions occur
Solution Approach 1:
The return spring provides mechanical feedback that actively resets the actuator position based on electrical activation state. This feedback mechanism ensures the system returns to the off position reliably, preventing prolonged fan operation and associated emissions while maintaining appropriate operation duration when cooling is 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
Prevents unnecessary fan operation and emissions by ensuring proper fluid drainage and actuator return, minimizing 'morning sickness' and preventing actuator sticking, thus optimizing cooling fan performance and reducing emissions.
Implementation Method 1
The shaft and actuating piston are spring biased by a return spring such that the passageways between the fluid reservoir chamber and the fluid operating chamber are closed when the engine is turned off and no electrical activation is present.
Implementation Method 2
a valve disk is provided which electronically controls movement of viscous fluid from the reservoir to the anti-bleed back chamber by energizing or deenergizing the actuator based on engine operating conditions
Data Source
AI summary
A viscous shear fan drive mechanism for a cooling fan. A moveable valve disk is provided which controls the quantity of fluid in the operating chamber. An electronic actuation system activates piston and shaft members which move the valve disk against the bias of a return spring to open the fill holes, allow fluid communication between the reservoir and working chambers, and allow rotation of the cooling fan. Without activation of the electronic actuation system, the flow of fluid to the working chamber is prevented. A non-magnetic or insulating bushing member adjacent the piston and shaft members prevents the system from sticking in the actuation condition when power is eliminated.