Vibration damping device using ER fluids having multiple electrodes

Abstract

A vibration damping device for mounting between two spaced portions of a vehicle for absorbing road forces exerted on the vehicle. An inner metal cylindrical housing forms an internal piston chamber and is connected at one end to one portion of the vehicle, with the outer end of the rod of a piston which is slidably mounted within the piston chamber, being connected to the other portion of the vehicle. An outer housing surrounds a portion of the inner housing and forms a fluid transfer duct between fluid chambers formed on opposite sides of the piston within the piston chamber. A plurality of spaced metal electrode bands are mounted on an inner surface of the outer housing and are electrically isolated therefrom and communicate with the fluid transfer duct for applying voltages across the duct to affect the viscosity of an electrorheological (ER) fluid flowing therethrough to increase the damping force of the device. Certain of the electrode bands may be formed with a plurality of circumferentially spaced, longitudinally extending splines and intervening grooves, which grooves align with splines and grooves formed in a dielectric insulating sleeve mounted adjacent the fluid transfer duct.

We claim:  
     
       1. A vibration damping device using an electrorheological fluid (ER) including: 
       a metal cylindrical inner housing having an outer diameter and an inner diameter forming a piston chamber;  
       a piston axially movable within the piston chamber and dividing the piston chamber into two separate fluid chambers;  
       a cylindrical outer housing formed of a dielectric material having an inner diameter forming an inner cylindrical surface larger than the outer diameter of the cylindrical inner housing and an outer diameter surrounding at least a portion of the cylindrical inner housing, the outer housing including an annular recesses  in the inner diameter;  
       annular fluid transfer duct means formed between said inner and outer housings and surrounding said piston chamber providing fluid communication between said fluid chambers on opposite sides of said piston, said fluid chambers filled with an electrorheological (ER) fluid;  
       a plurality of spaced metal electrode bands, each band being mounted in the annular recesses  of the cylindrical outer housing and being in communication with the duct means, for applying electric fields across portions of the duct means to increase the flow resistance of the ER fluid passing therethrough, each electrode band being isolated from the adjacent electrode band by an intervening band of dielectric material;  
       a piston rod connected at one end to the piston and extending beyond a first end of the damping device with another end of said piston being adapted to be connected to a first support structure;  
       electrical connector means extending through the outer housing electrically connected to the electrode bands for applying an electrical voltage to the metal electrode bands on the inner diameter of the outer housing; and  
       mechanical connection means mounted on a second end of the damping device for connecting said second end of said device to a second structure spaced from the first structure.  
     
     
       2. The vibration damping device defined in claim  1  in which the mechanical connection means is attached to an end of the inner housing, whereby a load on said damping device is supported by said inner housing and piston rod. 
     
     
       3. The vibration damping device defined in claim  2  in which certain of the electrode bands are cylindrical metal members and have conical ends which merge into the inner cylindrical surface of the outer housing. 
     
     
       4. The vibration damping device defined in claim  1  in which the outer housing includes first and second cylindrical portions; in which the annular recess is formed in at least one of said portions; in which a  the intervening band of dielectric material is seated in said annular recess between adjacent annular metal electrode bands; and in which the damping device further includes assembly means for joining said first and second cylindrical portions axially together and for securing said annular metal bands and band of dielectric material in said recess. 
     
     
       5. The vibration damping device defined in claim  4  in which the first and second cylindrical portions of the outer housing are axially joined; and in which the assembly means includes a pair of end retention members and an intervening adjustment screw ring. 
     
     
       6. The vibration damping device defined in claim  1  in which the metal electrode bands have annular surfaces which coincide with the inner cylindrical surface of the outer housing to provide a constant spacing between the inner cylindrical surface of the outer housing and the outer cylindrical surface of the inner housing substantially throughout the length of the fluid transfer duct means. 
     
     
       7. The vibration damping device defined in claim  1  in which the metal electrode bands have annular surfaces which extend beyond the inner cylindrical surface of the outer housing and provide a reduced flow area in the fluid transfer duct means. 
     
     
       8. The vibration damping device defined in claim  1  in which a pressurized gas reservoir is formed within the inner housing adjacent the second end of said damping device. 
     
     
       9. The vibration damping device defined in claim  8  including a movable partition means mounted within the inner housing for separating the gas reservoir from the fluid chambers. 
     
     
       10. The vibration damping device defined in claim  1   14 in which at least one of the electrode bands is formed with a plurality of circumferentially spaced splines and intervening grooves extending longitudinally throughout at least a portion of the fluid transfer duct means. 
     
     
       11. The vibration damping device defined in claim  10  in which the cross-sectional area of the fluid transfer duct means is constant throughout the length of said one electrode band. 
     
     
       12. The vibration damping device defined in claim  11  in which a plurality of circumferentially spaced, longitudinally extending splines and grooves are formed in the inner cylindrical surface of the outer housing and align with the splines and grooves of the said one electrode bands. 
     
     
       13. The vibration damping device defined in claim  12  in which the cross-sectional area of the annular fluid transfer duct means is constant throughout the duct means. 
     
     
       14. A vibration damping device using an electrorheological fluid (ER) including: 
       a metal cylindrical inner housing having an outer diameter and an inner diameter forming a piston chamber;  
       a piston axially movable within the piston chamber and dividing the piston chamber into two separate fluid chambers;  
       a cylindrical outer housing having an outer portion formed of metal, the outer portion having an inner cylindrical surface and an outer cylindrical surface, and an inner portion formed of a dielectric material having an outer cylindrical surface which contacts the inner cylindrical surface of the outer portion, and an inner diameter forming an inner cylindrical surface, the inner diameter of the inner portion being larger than the outer diameter of the cylindrical inner housing, so that the inner portion of the outer housing is between the outer portion of the cylindrical outer housing and the cylindrical inner housing and surrounding at least a portion of the cylindrical inner housing, the inner portion of the cylindrical outer housing including annular recesses in the inner diameter;  
       annular fluid transfer duct means formed between the cylindrical inner housing and the inner portion of the cylindrical outer housing and surrounding said piston chamber, providing fluid communication between said fluid chambers on opposite sides of said piston, said fluid chambers filled with an electrorheological (ER) fluid;  
       a plurality of spaced metal electrode bands, each band being mounted in the annular recesses of the inner portion of the cylindrical outer housing and being in communication with the duct means, for applying electric fields across portions of the duct means to increase the flow resistance of the ER fluid passing therethrough, each electrode band being isolated from the adjacent electrode band by the dielectric inner portion of the cylindrical outer housing;  
       a piston rod connected at one end to the piston and extending beyond a first end of the damping device with another end of said piston being adapted to be connected to a first support structure;  
       electrical connector means extending through the metal outer portion and the dielectric inner portion of the outer housing and electrically connected to the electrode bands for applying an electrical voltage to the metal electrode bands on the inside diameter of the outer housing; and  
       mechanical connection means mounted on a second end of the damping device for connecting said second end of said device to a second structure spaced from the first structure.  
     
     
       15. The vibration damping device defined in claim  14  in which the mechanical connection means is attached to an end of the inner metal housing, whereby a load on said damping device is supported by said inner housing and piston rod. 
     
     
       16. The vibration damping device defined in claim  15  in which the cylindrical metal member has  metal electrode bands have conical ends which merge into an inner cylindrical surface of the inner portion of the outer housing. 
     
     
       17. The vibration damping device defined in claim  14  in which the annular surfaces of the metal electrode bands coincide with the inner cylindrical surface of the inner portion of the outer housing to provide a constant spacing between the inner cylindrical surface of the inner portion of the outer housing and an outer cylindrical surface of the inner housing substantially throughout the length of the fluid transfer duct means. 
     
     
       18. The vibration damping device of claim  14  in which at least one of the metal electrode bands is formed with a plurality of circumferentially spaced splines and intervening grooves throughout at least a portion of the fluid transfer duct means. 
     
     
       19. The vibration damping device defined in claim  18  in which a plurality of circumferentially spaced, longitudinally extending splines and grooves are formed in the inner portion of the inner cylindrical surface of the outer housing and align with the splines and grooves of the electrode bands. 
     
     
       20. The vibration damping device defined in claim  19  in which the cross-sectional area of the annular fluid transfer duct means is constant throughout the duct means. 
     
     
       21. A vibration damping device using an electrorheological fluid (ER) including: 
       a metal cylindrical inner housing having an outer cylindrical surface with an outer diameter and an inner diameter  cylindrical surface forming a piston chamber;  
       a piston axially movable within the piston chamber and dividing the piston chamber into two separate fluid chambers;  
       a cylindrical outer housing formed of a dielectric material having an outer diameter and an inner diameter forming an inner cylindrical surface larger than the outer diameter of the cylindrical inner housing and surrounding at least a portion of the cylindrical inner housing, the cylindrical outer housing including at least one annular recesses in the inner diameter;  
       annular fluid transfer duct means formed between said inner and outer housings and surrounding said piston chamber providing fluid communication between said fluid chambers on opposite sides of said piston, said fluid chambers filled with an electrorheological (ER) fluid;  
       at least one spacedan annular metal electrode band for applying electric fields across portions of the duct means to increase the flow resistance of the ER fluid passing therethrough, the electrode band having an inner diameter forming an inner cylindrical surface and an outer diameter forming an outer cylindrical surface, said electrode band having annular recesses formed in the inner cylindrical surface, the outer cylindrical surface of the spaced  metal electrode band contacting the dielectric outer housing at the corresponding annular recess of the cylindrical outer housing and being isolated by the dielectric outer housing , the diameter of the inner cylindrical surface of the metal electrode band being lessgreater than the outer diameter of the cylindrical inner housing, said electrode band and  being in communication with the duct means, the metal electrode band having annular recesses: 
       annular dielectric bands mounted in the annular recesses of the metal electrode band, each annular dielectric band having an inner diameter greater than the outer diameter of the cylindrical inner housing;  
       a piston rod having a first end connected at one end  to the piston and a second end extending beyond a first end of the damping device with another end of said piston  and being adapted to be connected to a first support structure;  
       electrical connector means extending through the outer housing electrically connected to the electrode bands  band for applying an electrical voltage to the metal electrode bands on  at the inside diameter of the outer housing; and  
       mechanical connection means mounted on a second end of the damping device for connecting said second end of said device to a second structure spaced from the first structure.  
     
     
       22. The vibration damping device defined in claim  21  in which the inner diameter of the metal electrode band coincides with the inner cylindrical surface of the cylindrical outer housing and the inner diameter of the annular dielectric bands to provide a constant spacing with an  the outer cylindrical surface of the inner housing substantially throughout the length of the fluid transfer duct means. 
     
     
       23. The vibration damping device of claim  21  in which the metal electrode band is formed with a plurality of circumferentially spaced splines and intervening grooves throughout at least a portion of the fluid transfer duct means. 
     
     
       24. The vibration damping device defined in claim  23  in which a plurality of circumferentially spaced, longitudinally extending splines and grooves are formed in the inner cylindrical surface of the outer housing and the inner diameter of the annular dielectric bands and align each other and with the splines and grooves of the electrode band. 
     
     
       25. The vibration damping device defined in claim  24   21 in which the cross-sectional area of the annular fluid transfer duct means is constant throughout the said duct means. 
     
     
       26. The vibration damping device defined in claim  1  wherein the inner diameter of the cylindrical inner housing defines a cylindrical inner surface; and in which a coating of a low friction material is applied to said inner surface. 
     
     
       27. The vibration damping device defined in claim  26  wherein said coating of low friction material is selected from the group consisting of nickel, ceramic and chromium plated stainless steel. 
     
     
       28. The vibration damping device defined in claim  14  wherein the inner diameter of the cylindrical inner housing defines a cylindrical inner surface; and in which a coating of a low friction material is applied to said inner surface. 
     
     
       29. The vibration damping device defined in claim  28  wherein said coating of low friction material is selected from the group consisting of nickel, ceramic and chromium plated stainless steel. 
     
     
       30. The vibration damping device defined in claim  21  wherein the inner diameter of the cylindrical inner housing defines a cylindrical inner surface; and in which a coating of a low friction material is applied to said inner surface. 
     
     
       31. The vibration damping device defined in claim  30  wherein said coating of low friction material is selected from the group consisting of nickel, ceramic and chromium plated stainless steel.