770G and 772G Off-Highway Truck (OEM) Hydraulic and Braking System: Foot Brake Control (Service), Position Sensor (Foot Brake Control) & Slack Adjuster

1.-Foot Brake Control (Service)

Location of the Foot Brake Control (Service)

(1) Position Sensor (Foot Brake Control) (2) Service Brake Valve (Foot Control) (2A) Brake port (2B) Tank port(2C) Supply port

Position Sensor (Foot Brake Control) (1) provides an input to the Brake ECM. The sensor tells the Brake ECM the position of the service brake pedal. The Brake ECM uses this input to turn on the brake lights. If the truck is equipped with wet brakes, Position Sensor (Foot Brake Control) (1) will cause the Brake ECM to command current to the front service brake solenoid. If the truck is equipped with dry front brakes, and the front brakes are locked out via the front brake lockout switch, the application of the brake pedal results in no braking by the front wheels. If the dry front brakes are not locked out via the front brake lockout switch, the application of the brake pedal will command the front brakes. Position Sensor (Foot Brake Control) (1) is a PWM sensor. The sensor needs no manual calibration or adjustment. Position Sensor (Foot Brake Control) (1) automatically calibrates when the truck is started.

Oil from the brake charging section of Gear Pump (Brake, Brake Cooling, Hoist) flows through the Brake Valve (Front Service Brake) to the supply port (2C) of Service Brake Valve (Foot Control) (2) .

When the service brake pedal is depressed, internal passages in Service Brake Valve (Foot Control) (2) route the supply oil to brake port (2A). Oil from brake port (2A) flows to the Brake Valve (Rear Service Brake, Retarder Control, Traction Control). Brake Valve (Rear Service Brake, Retarder Control, Traction Control) then actuates the rear service brakes.

When the service brake pedal is released, the oil that is returning through brake port (2A) is routed to tank port (2B). Oil from tank port (2B) then flows to the hydraulic tank.

2.-Position Sensor (Foot Brake Control)

(1) Position Sensor (Foot Brake Control)

Position Sensor (Foot Brake Control) (1) is located on the left side of the Foot Brake Control (Service). Position Sensor (Foot Brake Control) (1) is a Pulse Width Modulation position sensor. Position Sensor (Foot Brake Control) (1) sends duty cycle signals to the Brake Electronic Control Module (Brake ECM).

When the service brake is applied, Position Sensor (Foot Brake Control) (1) sends an electrical signal to the Brake Electronic Control Module (Brake ECM). The sensor tells the Brake ECM the position of the service brake pedal. The Brake ECM uses this input to turn on the brake lights. If the truck is equipped with wet brakes, the Brake ECM will command current to the front service brake solenoid. If the truck is equipped with dry front brakes, and the front brakes are locked out via the front brake lockout switch, the application of the service brake pedal results in no braking by the front wheels. If the dry front brakes are not locked out via the front brake lockout switch, the application of the service brake pedal will command the front brakes.

Note: Position Sensor (Foot Brake Control) (1) does not need to be manually calibrated or adjusted. The machine performs an auto-calibration on Position Sensor (Foot Brake Control) (1).

3.-Slack Adjuster

Location of the slack adjusters for the rear service brakes

Location of the Brake Valve (Rear Service Brake, Retarder Control, Traction Control)

Operation of the slack adjusters keeps the timing constant between the pushing of the brake foot pedal valve and the stopping of the machine. Because of the slack adjusters, the same brake application will work with new brakes or with worn brakes. The slack adjusters are full of oil. The slack adjusters are located between the Brake Valve (Rear Service Brake, Retarder Control, Traction Control) and the rear brakes.

Components of slack adjuster (1) Outlet to a brake (2) Piston (3) Inlet from brake valve (4) Oil chamber (5) Small piston (6) Oil passage(7) Passage for makeup oil

When the service brake foot valve is used or when the retarder is used, the Brake Valve (Rear Service Brake, Retarder Control, Traction Control) sends oil to inlet (3) and into the slack adjusters. The oil pressure in the slack adjusters pushes pistons (2) away from the center of the slack adjusters. Pistons (2) push the oil in oil chamber (4) through outlet (1) to the brakes in each wheel. This oil initiates the brake application.

If the brakes have worn, the oil from chamber (4) may not complete the brake application. When piston (2) is against the ends of the slack adjusters, the oil from the Brake Valve (Rear Service Brake, Retarder Control, Traction Control) will fill oil passage (6). If the pressure in passage (6) is higher than the pressure in outlet (1), small piston (5) move away from the piston seats. Additional oil from the Brake Valve (Rear Service Brake, Retarder Control, Traction Control) can flow through the open piston seats to passage (7). This oil flows through outlet (1) in order to complete the brake application.

When you stop applying the brakes, the Brake Valve (Rear Service Brake, Retarder Control, Traction Control) will not send oil to the slack adjusters. The lower pressure in outlet (1) will cause small piston (5) to return to the piston seats. Small piston (5) will block passage (7). When oil stops filling the brakes, the return springs in the brakes will push the service brake pistons. The service brake pistons push the oil from the brake application back into outlet (1) of the slack adjusters. This oil pushes pistons (2) to the center of the slack adjusters. The brake is released completely.

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770G and 772G Off-Highway Truck (OEM) Hydraulic and Braking System: Foot Brake Control (Service), Position Sensor (Foot Brake Control) & Slack Adjuster 2013-01-20T10:44:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown