Patent ID: 6211590
Filing Date: 2001-04-03
Classification: F16D

Abstract:
An electric brake assembly, comprising:a housing;a rotary shaft having an axis extending into the housing;a brake rotor mounted on the rotary shaft for rotation therewith;a first armature mounted in the housing and being free to move axially for a limited distance relative to the housing;a second armature mounted in the housing and being free to move axially for a limited distance relative to the housing;a first spring located between the housing and the first armature for urging the first armature toward the rotor;a second spring located between the housing and the second armature for urging the second armature toward the rotor to frictionally engage the rotor and prevent rotation of the rotor relative to the housing;a single electromagnetic coil mounted in the housing for urging both of the armatures away from the rotor when energized to compress the springs and allow the rotor to freely rotate;an electronic controller which de-energizes the coil to cause a first level of braking force to be applied to the rotor by the second armature before the first spring overcomes a magnetic attraction of the coil on the first armature; whereinthe controller causes an electrical current supplied to the coil to gradually decay rather than abruptly stop such that the second armature will apply the first level of braking force to the rotor before the first spring overcomes the magnetic attraction of the coil on the first armature; and whereinwhen the coil is energized there is an absence of braking force.