BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a fan assembly embodying the invention;
FIG. 2 is an end view of the fan assembly of FIG. 1;
FIG. 3 is a side view of the fan assembly of FIG. 1 with the actuator extended; and
FIG. 4 is a simplified schematic diagram of a control system the fan assembly of FIG. 1.
DETAILED DESCRIPTION
Referring to FIGS. 1 and 2, a fan and shroud assembly 10 includes a fan unit 12 which has fan blades 14 mounted on a shaft 16 which is rotated by a conventional fan driving mechanism (not shown). The assembly includes a shroud assembly 18 having a first fixed shroud 20 and a movable shroud 22 coupled thereto. Shroud 20 includes a hollow larger portion 24 and a hollow smaller diameter portion 26. The larger portion 24 may be positioned to at least partially surround a heat exchange device (not shown), such as a vehicle radiator. Shroud portion 26 preferably has a set of helical threads 28 formed on its outer peripheral surface. Movable shroud 22 has a set of internal threads 30 for mating engagement with threads 28.
An actuator 32, such as an extendable piston or hydraulic cylinder has one end coupled to a bracket 34 on shroud 20 and another end coupled to a bracket 36 mounted on shroud 22. As best seen in FIG. 1, when the actuator 32 is retracted, the shroud 22 only overlaps or surrounds a small end portion of the fan 12. As best seen in FIG. 3, when the actuator 32 is extended, the shroud 22 overlaps or surrounds a larger portion of the fan 12. Also, the hydraulic actuator 32 could be replaced with a linear electric or pneumatic actuator (not shown).
Referring now to FIG. 4, the control system 40 includes a fan immersion sensor 42 which senses how much of the fan blades 14 are immersed in or surrounded by the shroud 22, a fan speed or rpm sensor 44, and a coolant temperature sensor 46. An electronic control unit (ECU) 48 receives signals from sensors 42-46 and generates an actuator control signal which is communicated to the actuator 32. The ECU 48 is preferably programmed with an algorithm and look-up tables in accordance with desired static pressures at different fan speeds so that the immersion can be controlled so that the fan operates at maximum efficiency under different conditions. The immersion sensor 42 may e a cylinder position sensor installed in or on the cylinder 32, or an ultrasonic position sensor installed between shroud 22 and shroud 20.
While the present invention has been described in conjunction with a specific embodiment, it is understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. For example, the fan blades could be moved axially with respect to the shroud, instead of moving the shroud relative to the fan. The fan blades could be moved axially by with a sylphon type mechanism (a cylindrically symmetrical bellows), which could be heat actuated or hydraulically actuated. Accordingly, this invention is intended to embrace all such alternatives, modifications and variations which fall within the spirit and scope of the appended claims.
Patent Application
20080031721
