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| Illustration 1 | g01145183 |
Hydraulic schematic for SWING RIGHT (1) Swing parking brake (2) Swing parking brake (3) Swing motor (4) Swing motor (5) Pilot line (6) Return line (7) Line (8) Line (9) Main control valve (10) Passage (11) Swing control valve (12) Center bypass passage (13) Center bypass passage (14) Negative flow control orifice (15) Passage (16) Load check valve (17) Parallel feeder passage (18) Passage (19) Return passage (20) Pilot control valve (swing and stick) (21) Return line (22) Pilot line (23) Line (24) Negative flow control line (25) Pilot line (26) Swing brake solenoid valve (27) Pilot oil manifold (28) Drive pump (29) Idler pump (30) Pilot pump | |
The oil delivery for the swing hydraulic circuit is supplied by idler pump (29) only. When either one of the joysticks is moved from the NEUTRAL position, swing parking brake (1) and swing parking brake (2) are released. Motor rotary group (3) and motor rotary group (4) start to rotate. The swing motors are mounted on top of the swing drives. The swing drives are installed on the upper structure. The swing drives reduce the motor speed by two stages. The swing drives rotate the upper structure.
ReferenceFor more information concerning the operation of the swing motor, refer to Systems Operation, "Swing Motor".
ReferenceFor more information concerning the operation of the swing drive, refer to Systems Operation, "Swing Drive".
ReferenceFor more information concerning the operation of the swing parking brake and the swing brake solenoid valve, refer to Systems Operation, "Pilot Valve (Swing Parking Brake)".
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| Illustration 2 | g01123717 |
Main control valve compartment (3) Swing motor (4) Swing motor (7) Line (8) Line (21) Return line | |
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| Illustration 3 | g01140575 |
(26) Swing brake solenoid valve (27) Pilot oil manifold | |
The oil delivery from idler pump (29) flows through center bypass passage (13) in main control valve (9) to swing control valve (11) . The oil delivery from drive pump (28) flows through center bypass passage (12) in main control valve (9) . Illustration 1 shows the main control valve when only the swing hydraulic circuit is activated.
When the hydraulic activation control lever is in the UNLOCKED position, the oil delivery from pilot pump (27) flows to pilot oil manifold (27) and swing brake solenoid valve (26) . The oil delivery from the pilot pump also flows to pilot control valve (20) .
When the swing joystick is moved to the RIGHT position, a signal is sent from the implement/swing pressure switch to the pump control. The pump sends a signal to the swing brake solenoid valve. The swing brake solenoid valve shifts. Pilot oil flows through pilot line (5) to swing parking brake (1) and swing parking brake (2) . The swing parking brake releases in order to enable a swing operation.
The oil delivery from pilot pump (30) flows from pilot control valve (20) through pilot line (25) and into swing control valve (11) . The spool in swing control valve (11) shifts downward. The pilot oil on the upper end of the spool in the swing control valve flows through pilot line (22) and to return passage (19) . The pilot oil then flows to the hydraulic tank.
Since the spool in swing control valve (11) is fully shifted, center bypass passage (12) is blocked. None of the oil delivery from the idler pump flows to negative flow control orifice (14) and no negative flow control pressure is created in center bypass passage (12) . Since no negative flow control pressure is sent through negative flow control line (24) to the idler pump regulator, the idler pump regulator moves the swashplate of the idler pump toward the maximum angle position. The output flow rate of the idler pump increases. The oil delivery from the idler pump flows through parallel feeder passage (17) , load check valve (16) , passage (18) , swing control valve (11) , passage (10) and line (7) to the swing motors. The oil enters the swing motors and flows to motor rotary group (3) and motor rotary group (4) . The motor rotary groups rotate.
The oil delivery for the swing hydraulic circuit is supplied by the idler pump only. Since only a swing operation is being performed, the control valves that receive the oil delivery from drive pump (28) are in the NEUTRAL position. The negative flow control pressure in center bypass passage (13) is not blocked by any of the control valves. Drive pump (28) remains at the destroked position.
ReferenceFor more information concerning the negative flow control operation, refer to Systems Operation, "Negative Flow Control".
Return oil from the motor rotary groups flows through line (8) to the main control valve. The return oil flows through swing control valve (11) , return passage (15) , and return line (21) to the hydraulic tank. The upper structure swings to the right (clockwise direction).
The SWING LEFT operation is similar to the SWING RIGHT operation.
When the swing joystick is moved to the SWING LEFT position, pilot oil from pilot control valve (20) flows through pilot line (22) and into swing control valve (11) . The spool in the swing control valve shifts upward. The oil delivery from the idler pump in parallel feeder passage (17) flows through passage (18) and line (8) . The oil delivery enters motor rotary group (3) and motor rotary group (4) . For a swing left operation, the supply ports and return ports are reverse of the swing right operation. This causes the upper structure to swing to the left (counterclockwise direction).
When the swing joystick is returned to the NEUTRAL position, the springs on each end of the swing control valve maintain the spool in the swing control valve in the NEUTRAL position. The oil flow to the swing motor and the oil flow from the swing motor is blocked by the swing control valve.
Swing Priority
The pilot oil pressure from the pilot control valve directly corresponds to the amount of movement or position of the joystick. The pilot oil pressure from the pilot control valve acts on the pressure reducing valve for swing priority and the variable swing priority valve. As the swing joystick is moved farther from the NEUTRAL position, the pilot oil pressure increases. This gradual increase in pilot oil pressure causes a gradual change to swing priority. Thus, swing priority is controlled by the position of the swing joystick and swing priority automatically activates when the joystick reaches a certain position.
When swing priority is activated, the output flow from the idler pump supplies hydraulic oil to the swing hydraulic circuit. Since swing priority increases the swing acceleration, swing priority is useful for loading operations. Swing priority is also useful for leveling operations and trenching operations when higher swing force is required.
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| Illustration 4 | g01439475 |
SWING RIGHT operation (swing priority OFF) (11) Swing control valve (17) Parallel feeder passage (20) Pilot control valve (swing and stick) (23) Pilot line (25) Pilot line (28) Drive pump (29) Idler pump (30) Pilot pump (31) Swing motor (32) Stick I control valve (33) Valve (34) Parallel feeder passage (35) Variable swing priority valve (36) Spring (37) Pilot line (38) Passage (39) Line (40) Pressure reducing valve for swing priority (41) Spring (42) Pilot line | |
When the swing joystick is in the NEUTRAL position, no pilot oil pressure acts on the pressure reducing valve for swing priority (40) . Full pilot oil pressure flows through pilot line (42) , the pressure reducing valve for swing priority (40) , line (39) and passage (38) to variable swing priority valve (34) . The variable swing priority valve is shifted upward against the force of spring (36) . The oil delivery from idler pump (29) in parallel feeder passage (17) flows through parallel feeder passage (34) and variable swing priority valve (35) . The oil delivery enters stick I control valve (32) .
When the swing joystick is moved slightly from the NEUTRAL position in order to perform a SWING RIGHT operation, reduced pilot oil pressure from pilot control valve (20) flows through pilot line (23) . The pilot oil then divides into two flow paths. Part of the pilot oil flows through pilot line (25) to swing control valve (11) . The spool in the swing control valve shifts a slight amount that corresponds to the amount of movement of the swing joystick. The remainder of the pilot oil flows through pilot line (37) and passage (38) . The pilot oil pressure causes the pressure reducing valve for swing priority (40) to shift a small amount which causes the pilot flow to be reduced.
Since the reduced pilot oil pressure in passage (38) is still greater than the force of spring (36) valve (35) is shifted slightly. Oil is able to flow through valve (35) which allows valve (33) to open. Valve (33) now allows oil to flow. Oil is able to flow to the stick control valve from idler pump (29) without restriction. Swing priority is not activated.
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| Illustration 5 | g01439479 |
SWING RIGHT operation (swing priority ON) (11) Swing control valve (17) Parallel feeder passage (20) Pilot control valve (swing and stick) (23) Pilot line (25) Pilot line (28) Drive pump (29) Idler pump (30) Pilot pump (31) Swing motor (32) Stick I control valve (33) Valve (34) Parallel feeder passage (35) Variable swing priority valve (36) Spring (37) Pilot line (38) Passage (39) Line (40) Pressure reducing valve for swing priority (41) Spring (42) Pilot line | |
As the swing joystick is moved to the FULL STROKE position during a SWING RIGHT operation, the pilot oil pressure in pilot line (25) increases. The spool in swing control valve (11) shifts fully downward. The pilot oil pressure in pilot line (37) and passage (39) also increases. The pressure reducing valve for swing priority (40) shifts fully against the force of spring (41) .
Pilot oil flow from pilot line (42) through the pressure reducing valve for swing priority (40) is restricted. The pilot oil pressure in line (39) and passage (38) also decreases. The decrease in pilot oil pressure causes valve (35) to not shift. Valve (35) blocks oil flow to valve (33) .
The oil delivery from idler pump (29) in parallel feeder passage (34) is restricted by valve (33) . Swing priority is now activated. Most of the oil delivery from the idler pump is dedicated to the swing system and flows through the swing control valve to the swing motor. As a result, swing priority and higher swing force can be achieved with the swing joystick.
Pilot oil pressure that flows from passage (38) into variable swing priority valve (20) corresponds to the position of the swing joystick.