An internal shoe drum brake has a body (1) carrying a plurality of circumferentially spaced friction elements (2) movable into engagement with a rotatable drum (3) by a hydraulic system including an actuator (5) having a pressure-applying cylinder (2) in which a pressure-generating piston (21) is driven by an electrical stepper motor (28), slave cylinders (4) which actuate the friction elements, and internal ducts (7, 8) for transmitting pressure from piston (21) to slave cylinders (4).
A method of accommodating wear in an electrically operated brake assembly includes setting a home position when a brake shoe engages a brake drum. A stepper motor drives the brake shoes into engagement with the drum. Upon engagement of the brake shoes with the drum, the stepper motor slips. Slipping of a stepper motor indicates that a home position has been reached. Upon release of the brake, the brake shoe is moved away from the drum a fixed distance. The fixed distance is an optimal distance between the friction member and the rotating member such that regardless of wear, the distance relationship between the brake shoe and drum is maintained.
A brake system comprising a hydraulic brake, wherein the brake includes a displaceable braking surface, wherein the hydraulic brake requires low pressure to effect displacement during initiation of a brake apply and increased pressure to effect displacement as brake apply progresses, wherein the increased pressure exponentially increases in a non-linear response curve, a motor driven hydraulic actuator having a rotary input provided by a motor and a hydraulic output coupled to the hydraulically actuated brake, wherein the rotary input requires low torque during the initiation of brake apply to effect displacement of the hydraulically actuated brake and requires increased torque to effect rotary motion and displacement of the hydraulically actuated brake as brake apply progresses, the motor characterized by a progressively changing non-linear operation having a low torque mode and a high torque mode, and a control apparatus for the motor controlling the motor to effect displacement of the hydraulic brake, wherein the motor provides increased torque versus displacement in an exponentially increasing non-linear response curve and wherein the motor provides maximum velocity versus displacement in an exponentially decreasing non-linear response curve, wherein the brake system minimizes apply time of the hydraulically actuated brake.