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| Illustration 1 | g03345006 |
Oil makeup operation (1) Travel motor (2) Relief valve (3) Passage (4) Line (5) Check valve (6) Check valve (7) Passage (8) Motor rotary group (9) Line (10) Hydraulic oil tank (11) Travel control valve (12) Passage (13) Return passage (14) Passage | |
In order to prevent cavitation in the travel motor during travel stop, makeup oil is supplied to the travel motor.
During travel stop, the travel control pedal is moved to the NEUTRAL position. The oil delivery from the main pumps is blocked at passage (12) of travel control valve (11). The oil from the main pumps cannot reach the travel motors.
Since no oil is supplied to travel motor (1), the travel motor will attempt to stop. However, the travel motor will continue to rotate because of the inertia (weight and size) of the machine causing a vacuum condition in passage (7) of the travel motor.
When travel control valve (11) is in the NEUTRAL position, return oil flows from passage (13) to passage (14). The return oil then flows through line (4), check valve (5), passage (7) and to motor rotary group (8) as makeup oil. This makeup oil prevents cavitation in the travel motor during travel stop.
If pressure in passage (3) should be greater than setting of relief valve (2), oil will flow from passage (3) to tank (10) through line (9). Oil from relief valve (2) can also travel through check valve (6) if pressure is less than oil in line (9) .
Makeup oil is supplied for reverse travel in the same manner as forward travel.