VALVE GP-MAIN CONTROL 2566935 - Caterpillar

Illustration 1 g03718610
Travel brake valve
(1) Crossover relief valve
(2) Spring
(3) Valve
(4) Spool
(5) Passage
(6) Passage
(7) Spool
(8) Valve
(9) Spool
(10) Crossover relief valve
(11) Check valve
(12) Passage
(13) Check valve
(14) Left travel motor
(15) Passage
(16) Passage
(17) Spring chamber
(18) Counterbalance valve
(19) Spool
(20) Spring
(21) Passage
(22) Check valve
(23) Passage
(24) Passage
(25) Passage
(26) Port
(27) Passage
(28) Passage
(29) Passage
(30) Port
(31) Passage
(32) Passage
(33) Check valve
(34) Spring The travel counterbalance valve consists of counterbalance valve (18), crossover relief valve (1) and crossover relief valve (10). The travel counterbalance valve is bolted to travel motor (14). The travel counterbalance valve has the following four functions.
The travel counterbalance valve prevents a shock load when travel is stopped.
The travel counterbalance valve prevents overspeed while the machine is traveling down a slope.
The travel counterbalance valve prevents cavitation.
The travel counterbalance valve routes a portion of the oil to the travel parking brake in order to release the brake.Counterbalance Valve Operation During Level Travel
Illustration 2 g03036138
Left travel motor and travel brake valve
(1) Crossover relief valve for reverse travel
(10) Crossover relief valve for forward travel
(14) Left travel motor
(18) Counterbalance valve
(26) Port
(30) Port Counterbalance valve (18) consists of valve (3), valve (8), check valve (11), check valve (13), spring (20) and spring (34). All of these components are located in counterbalance valve (18). During forward travel on level ground, pump oil is supplied to port (26). The oil flows from port (26) through passage (23) to check valve (11). The pressure oil forces check valve (11) to open. Oil flows through passage (25) to motor (14) in order to drive the motor.A portion of the oil delivery from the left pump in port (23) flows past check valve (22) through passage (21) and passage (12). The oil proceeds to flow into spring chamber (17). The oil in spring chamber (17) pushes spool (7) to the right against the force of spring (34). This action connects passage (15) and passage (32).As spool (7) shifts to the right, return oil from the travel motor flows through passage (15), passage (32), passage (29) and port (30) to the hydraulic tank.When the oil flow from port (26) is blocked, the pressure in spring chamber (17) decreases. The force of spring (20) shifts spool (7) to the right. Return oil from the travel motor is blocked and the rotation of the travel motor stops.When the direction of travel is reversed, pump oil flows to spool (7) through port (30). Spool (7) shifts to the left. The return oil flows through port (26). During reverse travel, the travel counterbalance valve operates in the same manner as the forward travel operation.Counterbalance Valve Operation During Slope Travel
When the machine travels down a slope, the travel motors rotate at a higher speed. The higher speed is due to the mass (weight and size) of the machine. When this condition occurs, the pumps cannot maintain the oil supply to the travel motors. The lack of oil supply will cause cavitation in the travel motor. A pressure decrease occurs at port (26). A pressure decrease occurs in spring chamber (17) as well.Spool (7) in counterbalance