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| Illustration 1 | g00786761 |
(1) Swing motor (2) Travel motor (3) Makeup line (4) Drain line (5) Drain line (6) Control valve (7) Center bypass passage (8) Center bypass passage (9) Return passage (10) Orifice (11) Orifice (12) Drain line (13) Return passage (14) Return line (15) Bypass check valve (16) Oil cooler (17) Slow return check valve (18) Left pump (19) Hydraulic tank (20) Suction line (21) Right pump | |
The oils from right pump (21) and left pump (18) enter main control valve (6). Then, the oil flows to the return passages in one of the following conditions.
- When all joysticks and/or travel levers/pedals are in the NEUTRAL position, oil from left pump (18) flows through center bypass passage (7) through orifice (11) to return passage (13). Oil from right pump (21) flows through center bypass passage (8) through orifice (10) to return passage (13) .
- When any one of the joysticks and/or travel levers/pedals is shifted from the NEUTRAL position, center bypass passages (7) and (8) are blocked. The return oil from the cylinders and/or motors now flows through return passage (9) .
The return oil from return passage (13) and return passage (9) flows through slow return check valve (17) back to hydraulic tank (19) in one of the following conditions.
- When the oil temperature is very low, most of the oil is returned through bypass check valve (15) to hydraulic tank (19). The remainder of the oil flows into oil cooler (16) to hydraulic tank (19) .
- When the oil temperature increases, the rate of oil flow through bypass check valve (15) decreases. This causes the rate of oil flow through oil cooler (16) to increase.
Reference: For more information concerning the bypass check valve, refer to Systems Operation, "Bypass Valve (Return)".
The makeup line will route return oil to the inlet port of the swing motor if a vacuum condition occurs at the swing motor during swing stop.
For more information concerning the makeup operation of the return hydraulic system at the swing motor, refer to the following sections in this manual.
- Systems Operation, "Check Valve (Return Makeup)"
- Systems Operation, "Oil Makeup (Swing System)"
- Systems Operation, "Relief Valve (Swing)"