Viscous Fluid Clutch Assembly

Abstract

A viscous fluid clutch ( 1 ) for use as a clutch for a cooling fan for a vehicle, the clutch includes an input shaft ( 10 ), a rotor assembly ( 20, 30 ), a first housing portion ( 52 ), a second housing portion ( 42 ), a coil assembly ( 80 ), and a brush box ( 105 ). The rotor assembly is coupled to the input shaft. The first housing portion is coupled to the second housing portion and the second housing portion is rotatably disposed on the input shaft. The first and second housing portions define a fluid reservoir ( 16 ) for receiving the rotor assembly and a viscous fluid, preferably of the magnetorheological type. The coil assembly is coupled to the first housing portion. The brush box is operably coupled to the coil assembly. When the coil assembly is energized by the brush box, a magnetic field is created that acts upon the magnetorheological fluid to vary the torque transfer of the input shaft to the housing and the fan connected thereto.

1 . A viscous fluid clutch for use in a vehicle comprising: 
 a rotor having a rotor hub driven by an input shaft and a rotor surface having an end connected to an outer periphery of the rotor hub, the rotor surface including:    a first portion;    a second portion; and    a grooved portion disposed between the first and second portions and having a W-V shaped profile;    wherein the first and second portions of the rotor each have a thickness sufficiently greater than a thickness of the grooved portion such that a magnetic flux path in the fluid clutch will have a substantial portion of a magnetic field flow around the grooved portion as compared to a portion of the magnetic field flow that flows through the grooved portion.    
   
   
       2 . A magnetorheological fluid clutch, comprising: 
 an input shaft;    a coil assembly for generating a magnetic field;    a housing comprising a stator; and    a rotor disposed in the housing;    wherein the rotor includes a radially extending hub driven by the input shaft and an annular rotor ring connected to the hub; and    wherein the rotor ring includes a first portion, a second portion, and a portion of reduced thickness disposed between the first and second portions to prevent a shunt in the magnetic field, and    wherein the portion of reduced thickness has a W-V shaped cross-section.    
   
   
       3 . The magnetorheological fluid clutch of  claim 2 , wherein the thickness of the first portion and the thickness of the second portion are at least seven times greater than the thickness of the portion of reduced thickness.  
   
   
       4 . The magnetorheological fluid clutch of  claim 2 , wherein the portion of reduced thickness is formed to include grooves and protrusions.  
   
   
       5 . The magnetorheological fluid clutch of  claim 4 , wherein the grooves and protrusions form a W-shape.  
   
   
       6 . The magnetorheological fluid clutch of  claim 2 , wherein the portion of reduced thickness is formed without cutting.  
   
   
       7 . The magnetorheological fluid clutch of  claim 2 , wherein the rotor ring comprises a ferrous metal.  
   
   
       8 . The magnetorheological fluid clutch of  claim 2 , wherein the rotor ring comprises a non-ferrous material.  
   
   
       9 . A fan drive assembly for use in a vehicle, the fan drive assembly including the magnetorheological fluid clutch of  claim 2 .  
   
   
       10 - 48 . (canceled)  
   
   
       49 . A fluid clutch for use in a vehicle, the fluid clutch including a rotor having a rotor hub driven by an input shaft and a rotor surface having an end connected to an outer periphery of the rotor hub, the fluid clutch comprising: 
 the rotor surface including a first portion, a second portion, and a roll formed portion disposed between the first and second portions,    wherein the first and second portions of the rotor each have a thickness sufficiently greater than a thickness of the roll formed portion such that a magnetic flux path in the fluid clutch will have a substantial portion of a magnetic field flow around the roll formed portion as compared to a portion of the magnetic field flow that flows through the roll formed portion.    
   
   
       50 . The fluid clutch of  claim 49 , wherein the roll formed portion of the rotor has a saw tooth profile.  
   
   
       51 . The fluid clutch of  claim 49 , wherein the roll formed portion of the rotor has a W-W shaped profile.  
   
   
       52 . A magnetorheological fluid clutch, comprising: 
 an input shaft;    a coil assembly for generating a magnetic field;    a housing comprising a stator; and    a rotor disposed in the housing,    wherein the rotor includes a radially extending hub driven by the input shaft and an annular rotor ring connected to the hub, and    wherein the rotor ring includes a first portion, a second portion, and a thinned center portion disposed between the first and second portions to prevent a shunt in the magnetic field, and    wherein the thinned portion has a saw tooth shaped profile.    
   
   
       53 . The magnetorheological fluid clutch of  claim 52 , wherein the thickness of the first portion and the thickness of the second portion are at least seven times greater than the thickness of the rolled portion.  
   
   
       54 . The magnetorheological fluid clutch of  claim 52 , wherein the roll formed portion is formed without cutting.  
   
   
       55 - 61 . (canceled)  
   
   
       62 . A method of making a rotor assembly for use in a viscous fluid clutch, the method comprising the steps of: 
 providing a magnetic material;    forming the magnetic material into a rotor ring;    roll forming the rotor ring to include a thinned central portion, wherein the first and second portions each have a thickness greater than a thickness of the thinned central portion;    providing a hub member; and    connecting the rotor ring to the hub member.    
   
   
       63 . The method of  claim 62 , wherein the step of forming the magnetic material into a rotor ring includes the steps of providing a sheet of the magnetic material, cup drawing the magnetic material into a cup-shaped member, trimming the cup-shaped member to form a ring, and roll forming the ring.  
   
   
       64 . The method of  claim 63 , further comprising the step of stamping the hub member and forming a curved portion between an inner periphery of the hub member and an outer periphery of the hub member.  
   
   
       65 . The method of  claim 62 , wherein the step of connecting the rotor ring to the hub member includes crimping one of the first portion and the second portion of the rotor ring to an outer periphery of the hub member.  
   
   
       66 - 71 . (canceled)