Variable speed fan drive

Abstract

The invention relates to a variable speed fan drive. There is a need for a variable speed fan drive with fewer seals and bearings, which is operated by system hydraulic pressure, which has fewer parts and which is simpler to assemble. A variable speed fan drive is provided for a vehicle powered by an internal combustion engine. The fan drive has a driver variable sheave unit, a driven variable sheave unit and a belt engaging both the driver and driven variable sheave units. The driver variable sheave unit includes a driver shaft drivingly coupled to an engine output shaft, a first axially fixed half sheave mounted for rotation with the driver shaft, and a first axially movable half sheave member mounted for rotation with the driver shaft and movable axially on the driver shaft. The first axially movable half sheave member includes a belt engaging flange formed integrally with an axially movable piston member mounted for rotation with the driver shaft and movable axially in response to hydraulic pressure.

1 . A variable speed fan drive for a vehicle powered by an internal combustion engine, the fan drive having a driver variable sheave unit, a driven variable sheave unit and a belt engaging both the driver and driven variable sheave units, characterized by the driver variable sheave unit comprising:
 a driver shaft drivingly coupled to an engine output shaft;   a first axially fixed half sheave mounted for rotation with the driver shaft; and   a first axially movable half sheave member mounted for rotation with the driver shaft and movable axially on the driver shaft, the first axially movable half sheave member comprising a belt engaging flange formed integrally with an axially movable piston member mounted for rotation with the driver shaft and movable axially in response to hydraulic pressure.   
   
   
       2 . The variable speed fan drive of  claim 1 , wherein the driven variable sheave unit comprises:
 a shaft having an end rotatably supported by bearings in a housing, a second axially fixed half sheave fixed to the shaft for rotation therewith, an second axially movable half sheave mounted on the shaft for rotation therewith, a spring retainer mounted on the shaft for rotation therewith, and a plurality of return springs mounted between the retainer and the second axially movable half sheave, the return springs being spaced apart from each other and spaced apart from an exterior surface of the shaft, and the second axially movable half sheave being located between the second axially fixed half sheave and the return springs, and the shaft having a member formed thereon which engages the spring retainer and holds the spring retainer on the shaft against a bias of the return springs.   
   
   
       3 . The variable speed fan drive of  claim 1 , wherein:
 the piston member and the driver shaft cooperate to form a pressure chamber therebetween, and the piston member being movable axially in response to fluid pressure in said chamber.   
   
   
       4 . The variable speed fan drive of  claim 1 , wherein:
 the driver shaft includes a larger diameter part connected to a smaller diameter part by an axially facing annular shoulder; and   the piston member includes a hollow hub having a larger diameter bore receiving the larger diameter part of the driver shaft, a smaller diameter bore receiving the smaller diameter part of the driver shaft, and an axially facing annular wall connecting the larger diameter bore with the smaller diameter bore, the smaller diameter part, the wall, the shoulder and a wall of the larger diameter bore enclosing a pressure chamber, and the piston member being movable axially in response to fluid pressure in said chamber.   
   
   
       5 . A variable speed fan drive for a vehicle powered by an internal combustion engine, the fan drive having a driving variable sheave assembly, a driven variable sheave assembly and a belt engaging both the driving variable sheave assembly and the driven variable sheave assembly, characterized by:
 the driving variable sheave assembly being driven by an engine output shaft, the driving variable sheave assembly having a first axially fixed half sheave and a first axially movable half sheave movable axially in response to hydraulic pressure;   the driven variable sheave assembly drivingly coupled to a fan, the driven variable sheave assembly comprising:   a shaft having an end rotatably supported by bearings in a housing, a second axially fixed half sheave fixed to the shaft for rotation therewith, an second axially movable half sheave mounted on the shaft for rotation therewith, a spring retainer mounted on the shaft for rotation therewith, and a plurality of return springs mounted between the retainer and the second axially movable half sheave, the return springs being spaced apart from each other and spaced apart from an exterior surface of the shaft, and the second axially movable half sheave being located between the second axially fixed half sheave and the return springs, and the shaft having a member formed thereon which engages the spring retainer and holds the spring retainer on the shaft against a bias of the return springs.   
   
   
       6 . The variable speed fan drive of  claim 5 , further comprising:
 plurality of spaced apart projecting tabs which are mounted for rotation with the second axially movable half sheave; and   a magnetic sensor mounted on the housing for generating a speed signal as the tabs move past the sensor.   
   
   
       7 . The variable speed fan drive of  claim 6 , wherein:
 the tabs project from the spring retainer.   
   
   
       8 . The variable speed fan drive of  claim 6 , wherein:
 the shaft includes an outwardly facing fustroconical surface formed thereon; and   the spring retainer includes a hollow hub including an inwardly facing fustroconical surface formed thereon, the inwardly facing fustroconical surface engaging the outwardly facing fustroconical surface to hold the spring retainer on the shaft and to center the spring retainer thereon.   
   
   
       9 . The variable speed fan drive of  claim 6 , wherein the driving variable sheave assembly comprises:
 a non-rotating hydraulic member for communicating with a source of hydraulic pressure, the hydraulic member having a first passage extending therethrough; and   a driver shaft coupled for rotation with the engine output shaft, the first axially movable half sheave being mounted on the driver shaft, the driver shaft and the first axially movable half sheave forming pressure chamber therebetween, the first axially movable half sheave being movable in response to fluid pressure in said pressure chamber, the driver shaft having a blind bore in an end thereof, the hydraulic member being rotatably received in the blind bore, and the driver shaft having a second passage therein, the second passage communicating the first passage to the pressure chamber.   
   
   
       10 . The variable speed fan drive of  claim 6 , further comprising:
 a plurality of coupling members which couple the spring retainer to the second axially movable half sheave.   
   
   
       11 . The variable speed fan drive of  claim 10 , wherein:
 each coupling member extends through a corresponding one of the return springs.   
   
   
       12 . The variable speed fan drive of  claim 10 , wherein:
 each coupling member comprises a bolt which is screwed into a threaded bore in the spring retainer.   
   
   
       13 . A variable speed fan drive for a vehicle powered by an internal combustion engine, the fan drive assembly comprising:
 a driver shaft coupled for rotation with an output shaft of the engine;   a first axially fixed half sheave coupled for rotation with the driver shaft;   a first axially movable half sheave mounted on the driver shaft for rotation with the driver shaft, the driver shaft and the first axially movable half sheave forming a pressure chamber, and the first axially movable half sheave being movable axially in response to hydraulic pressure in said chamber;   a driven shaft supported for rotation on a housing of the engine;   a second axially fixed half sheave fixed to the driven shaft for rotation therewith;   a second axially movable half sheave mounted on the driven shaft for rotation therewith;   a spring retainer mounted on the shaft for rotation therewith;   a plurality of return springs mounted between the retainer and the second axially movable half sheave, the return springs being spaced apart from each other and spaced apart from an exterior surface of the shaft, and the second axially movable half sheave being located between the second axially fixed half sheave and the return springs, and the shaft having a member formed thereon which engages the spring retainer and holds the spring retainer on the shaft against a bias of the return springs; and   a belt engaging all the half sheaves.   
   
   
       14 . The variable speed fan drive of  claim 13 , wherein:
 the driven shaft includes a first fustroconical surface formed thereon; and   the spring retainer includes a hollow hub including a second fustroconical surface formed thereon, the first fustroconical surface engaging the second fustroconical surface to hold the spring retainer on the shaft and to center the spring retainer thereon.