GENERATOR AR 3870792 - Caterpillar

Service Brake Pedal Operation
Service Brakes Engaged
Illustration 2 g01381671
Service brakes engaged. (1) Parking brake solenoid (2) Secondary brake solenoid (7A) Pressure reducing spool for the left brake (7B) Pressure reducing spool for the right brake (12) Proportional brake solenoid (16A) Passage to right brake (16B) Passage to left brakeWhen the operator pushes the service brake pedal toward the floor, the rotary sensor sends a signal to the electronic control module (ECM). This signal tells the ECM the brake pedal position. The electronic control module (ECM) decreases the current to proportional solenoid valve (12) relative to the brake pedal position.The decreased current reduces pilot oil pressure, which causes reducing spools (7A) and (7B) to move upward. This movement relieves oil pressure in brake circuit (16A) and in brake circuit (16B) by partially opening the brake circuits to the tank.The current to proportional solenoid valve (12) is dependent upon the position of the brake pedal. The solenoid converts pilot pressure oil to reduced pilot pressure oil. The pressure in the brake circuits is directly affected by the position of the brake pedal.When the brake pedal is partially depressed, the pilot pressure is reduced. The machine brakes lightly. When the brake pedal is fully depressed, the pilot pressure is reduced until the pressure reaches zero kPa (0 psi). The oil is drained from the brake circuit and the machine brakes fully.Once the pedal is to the floor, the switch (end of travel) for the service brake opens. The switch connects secondary solenoid valve (2) to the battery. The energized solenoid valve opens the secondary brake valve (3), which exhausts any remaining pilot pressure to the drain. When the pilot oil is drained the machine brakes fully.Service Brakes Released
Illustration 3 g01381678
Service brakes released. (1) Parking brake solenoid (2) Secondary brake solenoid (7A) Pressure reducing spool for the left brake (7B) Pressure reducing spool for the right brake (12) Proportional brake solenoid (16A) Passage to right brake (16B) Passage to left brakeWhen the operator releases the service brake pedal, the rotary sensor sends a signal to the electronic control module (ECM). This signal tells the ECM that the brake pedal is released. The electronic control module (ECM) increases the current to proportional solenoid valve (12) .The increased current increases pilot oil pressure, which moves reducing spools (7A) and (7B) downward. The movement allows the oil to flow into brake circuit (16A) and into brake circuit (16B). The oil pressure acts on the brake piston and compresses the belleville springs, which releases the brakes.