Hydraulic Schematic for the Brake System (High Speed Machine)
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| Illustration 1 | g00418740 |
Hydraulic Schematic for the Brake system (High Speed Machine) (1) Implement pump. (2) Steering and brake pump. (3) Priority valve. (4) Priority valve spool. (5) Hydraulic line to metering pump (HMU). (6) HMU supply line. (7) Load sensing line from metering pump (HMU). (8) Relief valve. (9) Inching Valve. (10) Left pedal assembly. (11) Right pedal assembly. (12) Flow control valve. (13) Master cylinder circuit. (14) Relief valve. (15) Brake Boost. (16) Master cylinder. (17) Hydraulic brake oil (remote reservoir). (18) Front service brakes. (19) Rear service brakes. | |
The hydraulic pump is a two-section pump that consists of an implement pump (1) and a steering and brake pump (2) . The steering and brake pump (2) is a gear pump that supplies the hydraulic oil to the steering system and the brake system. Oil flows from the pump (2) to the priority valve (3) . The priority valve (3) contains a priority valve spool (4) and a relief valve (8) . The relief valve (8) limits the oil pressure in the steering circuit. The priority valve spool (4) gives priority to the steering system. The priority valve spool (4) directs flow to hydraulic line (6) . When steering is in the neutral position, the load sensing line (7) is open to the hydraulic tank. The oil pressure in line (6) is felt on the left side of the priority valve. The pressure overcomes the spring and the oil pressure in the load sensing line (7) . The priority valve spool (4) shifts to the left. The pump supply oil is directed to hydraulic line (5) . Hydraulic line (5) supplies oil to the HMU and to the master cylinder circuit (13) .
The master cylinder circuit (13) consists of a brake boost (15) , a master cylinder (16) , a flow control valve (12) , and a relief valve (14) . The hydraulic oil from the priority valve (3) supplies oil to the brake boost (15) . When the brake pedals (10) and (11) are not applied, the brake boost (15) is open to the hydraulic tank. When one of the brake pedals (10) and (11) is applied, the brake boost (15) increases the applied pedal force. The brake boost (15) hydraulically transfers the force to the master cylinder (16) . The first 25 to 50 mm (1.0 to 2.0 inch) of travel of either service brake pedal (10) and (11) actuates the inching valve (9) . This causes the hystat pump signal to open to the hydraulic tank. The flow from the hystat pump to the motor is redirected to the hydraulic oil tank. There is a decrease in the pressure of the hystat pump signal. This signals the pump to gradually destroke and this signals the motor to upstroke. The speed of the machine decreases, while full engine rpm is maintained.
Reservoir (17) supplies brake oil to master cylinder (16) . When either brake pedals (10) and (11) are engaged the brake oil is directed to the service brakes. High speed machines are equipped with front service brakes (19) and rear service brakes (18) .