Clutch assembly

Abstract

A viscous fluid clutch for use as a clutch for a cooling fan for a vehicle , the clutch includes an input shaft, a rotor assembly, a first housing portion, a second housing portion, a coil assembly, and a brush box. 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 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 magnetorheological fluid clutch comprising:
 an input shaft;   a rotor including a radially extending hub coupled to the input shaft and an annular rotor ring coupled to the hub, the rotor ring having a radially outer surface and a radially inner surface;   a housing rotatably coupled to the input shaft, the housing including an annular slot for receiving the rotor ring, the slot having a radially outer surface proximate the radially outer surface of the rotor ring and a radially inner surface proximate the radially inner surface of the rotor ring; and   a coil assembly coupled to the housing for generating a magnetic field;   wherein at least one of the radially outer surface of the rotor ring, the radially inner surface of the rotor ring, the radially outer surface of the slot, and the radially inner surface of the slot is roughened.   
     
     
         2 . The magnetorheological fluid clutch of  claim 1 , wherein the at least one of the radially outer surface of the rotor ring, the radially inner surface of the rotor ring, the radially outer surface of the slot, and the radially inner surface of the slot is has a surface roughness between approximately 8 to 12 microns. 
     
     
         3 . The magnetorheological fluid clutch of  claim 2 , wherein the radially outer surface of the rotor ring, the radially inner surface of the rotor ring, the radially outer surface of the slot, and the radially inner surface of the slot art each roughened. 
     
     
         4 . The magnetorheological fluid clutch of  claim 1 , wherein at least one of the radially outer surface of the rotor ring, the radially inner surface of the rotor ring, the radially outer surface of the slot, and the radially inner surface of the slot is knurled. 
     
     
         5 . A fluid clutch for use in a vehicle comprising:
 a rotor having a rotor hub coupled to an input shaft and a rotor ring having an end connected to an outer periphery of the rotor hub, the rotor ring having a radially outer edge and a radially inner edge and including:
 a first portion; 
 a second portion; and 
 a grooved portion disposed between the first and second portions and including a rectangular groove extending radially inwardly from the radially outer edge of the rotor ring; 
   wherein the radially inner edge of the grooved portion is flush with the radially inner edge of the first portion and the radially inner edge of the second portion; and   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.   
     
     
         6 . A viscous fluid clutch having a back side and a front side, the viscous fluid clutch comprising:
 an input shaft;   a rotor assembly coupled to the input shaft, the rotor assembly including a radially extending rotor hub and a rotor ring extending axially rearward from a distal end of the rotor hub, the rotor ring having a rear end coupled to the distal end of the rotor hub, a front end opposite the rear end, a radially outer surface, and a radially inner surface;   a housing substantially surrounding the rotor assembly and defining a fluid reservoir, the fluid reservoir including an axial slot for receiving the rotor ring, the slot having a radially outer surface proximate the radially outer surface of the rotor ring and a radially inner surface proximate the radially inner surface of the rotor ring, the housing including a first housing portion rotatably disposed on the input shaft and a second housing portion connected for rotation with the first housing portion;   a coil assembly coupled to the second housing portion, the coil assembly including a radially extending coil cover located on the front side of the rotor hub;   wherein the radially outer surface of the rotor ring is spaced apart from the radially outer surface of the slot by a first distance and the radially inner surface of the rotor ring is spaced apart from the radially inner surface of the slot by the first distance.   
     
     
         7 . The viscous fluid clutch of  claim 6 , wherein a corner between the radially outer surface of the slot and a front end of the slot is radiused. 
     
     
         8 . The viscous fluid clutch of  claim 7 , wherein the radius of the corner is between approximately 1.5 and 1.9 times the first distance. 
     
     
         9 . The viscous fluid clutch of  claim 6 , wherein the distance between the front end of the rotor ring and a front end of the slot is between approximately 2.0 and 2.4 times the first distance. 
     
     
         10 . The viscous fluid clutch of  claim 6 , wherein the distance between the distal end of the rotor hub and a wall portion of the housing behind the distal end of the rotor hub is between approximately 3.0 and 3.4 times the first distance. 
     
     
         11 . The viscous fluid clutch of  claim 6 , wherein the distance between the distal end of the rotor hub and the portion of the coil cover in front of the distal end of the rotor hub is between approximately 1.4 and 1.8 times the first distance. 
     
     
         12 . The viscous fluid clutch of  claim 6 , wherein a corner between the radially outer surface of the slot and a rear end of the slot is radiused. 
     
     
         13 . The viscous fluid clutch of  claim 12 , wherein the radius of the corner is between approximately 2.0 and 2.4 times the first distance.