Patent ID: 6428117
Filing Date: 2002-08-06
Classification: B60T

Abstract:
A control system for an actuator assembly of a parking brake for a vehicle, the actuator assembly being moved into a brake apply position by resilient means and being moved into a brake release position by hydraulic means, said hydraulic means having a solenoid valve with a housing, said housing having a bore therein with an inlet port connected to a source of pressurized fluid, an outlet port connected to said actuator assembly and a relief port connected to a reservoir, said solenoid valve having a plunger located in said bore and coil means associated with said plunger, said coil means being connected to a source of electrical current, and an electronic control unit responsive to operational parameters of the vehicle and an operator input to control the communication of electrical current to said coil means for developing a magnetic force to move said plunger from a first position where said actuator assembly is connected to said reservoir by way of said outlet port and relief port and in the brake apply position to a second position where pressurized fluid is supplied to said actuator assembly by way of said inlet port and outlet port to the brake release position, said solenoid valve being characterized by said coil means having a first circuit connected to directly receive a first current from an electrical source and a second circuit connected to receive a second current from said electrical source through an ignition switch, said second current being subjected to changes as a function of the operational characteristics of the vehicle, and by a parking brake switch responsive to a signal for concurrently allowing current to flow in said first and second circuits and developing first and second magnetic forces in said coil means sufficient to jointly move said plunger to said second position where pressurize fluid is communicated to move said actuator assembly to said brake release position, said first magnetic force and said second magnetic force being insufficient to independently move said plunger from said first position to said second position but sufficient to maintain said plunger in said second position once said plunger is located in said second position to assure that said pressurized fluid is not released from said actuator assembly with an interruption of current flow in said first or second circuits.