5230B Excavator Hydraulic System Travel Parking Brake Caterpillar


Travel Parking Brake
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5230B Excavator Hydraulic System [RENR3348]
POWER TRAIN
BRAKE GP
5230B Excavator Hydraulic System Travel Parking Brake



Illustration 1g00930183

Travel parking brake system schematic

(1) Left travel lever

(2) Right travel lever

(3) Implement warm-up solenoid valves

(4) Travel pressure switch

(5) Friction discs

(6) Travel brake springs

(7) Travel brake piston

(8) Housing

(9) Friction plates

(10) Rear control valve

(11) Engine control module

(12) Travel alarm

(13) Brake release port

(14) Interface module "number 2" for the Vital Information Management System (VIMS)

(15) Implement warm-up solenoid valve

(16) Dual pressure solenoid valve

(17) Pilot manifold

(18) Load sensing signal relief valve

(19) Machine Control Module (MCM)

(20) Front control valve

(21) Implement pressure switch

(22) Ladder position switch

(23) Pilot gear pump

(24) Pilot hydraulic oil filter

(25) Hydraulic activation control selector valve

(26) Travel parking brake

The travel drive is equipped with a multi-disc parking brake. The parking brake is applied by spring force and released by the force of the pressurized pilot oil.

When left travel pilot lever (1) or right travel pilot lever (2) is moved to a travel position, pilot oil is sent to one end of the travel control spool. The pilot oil moves the valve spool and the travel function is activated. Pilot oil is also sent to implement pressure switch (21) and to travel pressure switch (4). Implement pressure switch (21) is located on front control valve (20). Travel pressure switch (4) is located on rear control valve (10). The force of the travel pilot pressure opens implement pressure switch (21) and the force of the travel pilot pressure closes travel pressure switch (4). Closing travel pressure switch (4) signals machine control module (19) to check ladder position switch (22). If the ladder is raised, ladder position switch (22) will be CLOSED and machine control module (19) energizes the solenoid valve (26) for the travel parking brake.

When the force of the travel pilot pressure opens implement pressure switch (21), the implement pressure switch signals engine control module (11) that the travel function is requested. Engine control module (11) will increase the engine speed to the throttle dial setting if the engine speed is at the Automatic Engine Speed Control setting of 1350 rpm. Engine control module (11) also signals Vital Information Management System (VIMS) interface module number 2 (14) that travel is requested. VIMS interface module number 2 (14) closes implement warm-up solenoid valves (3) that are located on rear control valve (10). The VIMS interface module number 2 also closes two implement warm-up solenoid valves (15) that are located on front control valve (19).

When solenoid valve (26) for the travel parking brake is energized, pilot oil is directed to the travel parking brakes. The travel parking brakes are located in the final drive housings. The force of the pilot oil acts against the force of travel brake springs (6). If the pilot oil pressure is above 3000 kPa (435 psi), the force of the pilot oil overcomes the force of travel brake springs (6) and the travel parking brake is released.

If no other implements have been actuated, machine control module (19) will also energize dual pressure solenoid valve (16). Energizing dual pressure solenoid valve (16) allows low pressure pilot oil to flow to load sensing signal relief valve (18) to increase the main system pressure to 35000 kPa (5080 psi). If any other implements have been actuated, machine control module (19) will not energize dual pressure solenoid valve (16) and the main system pressure will remain at 31000 kPa (4500 psi).

When the travel pilot control levers are returned to NEUTRAL, pilot oil to implement pressure switch (21) and travel pressure switch (4) is blocked. The loss of pilot oil closes implement pressure switch (21). The loss of pilot oil opens travel pressure switch (4). Now, machine control module (19) de-energizes dual pressure solenoid valve (16) and pilot oil to the load sensing signal relief valve (18) is blocked. The loss of low pressure pilot oil to load sensing signal relief valve (18) returns system pressure to 31000 kPa (4500 psi). Machine control module (19) will wait for eight seconds after the travel pilot control levers are returned to NEUTRAL and the machine control module will de-energize solenoid valve (26) for the travel parking brake. When solenoid valve (26) for the travel parking brake is de-energized, the flow of pilot oil is blocked to the travel parking brakes. The low pressure pilot oil, that releases the travel parking brakes, drains to the tank. Travel brake springs (6) apply the travel parking brake.

Travel parking brake inner friction plates (9) are splined to the input shaft of the travel motor.Travel parking brake outer friction discs (5) are splined to travel parking brake housing (8). Travel parking brake springs (6) force brake piston (7) downward. This forces friction plates (9) and friction discs (5) together. Forcing friction plates (9) and friction discs (5) together applies a holding force to the travel motor input shaft.

De-energizing implement pressure switch (21) signals engine control module (11) that travel has stopped. After four seconds, the engine control module will decrease the engine speed to the Automatic Engine Speed Control setting of 1350 rpm if no hydraulic circuits are active and the AESC function is ON.

Information System:

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