349E Excavator Hydraulic System Swing Hydraulic System Caterpillar


Swing Hydraulic System
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349E Excavator Hydraulic System [KENR9604]
FRAME AND BODY
SWING GP
349E Excavator Hydraulic System Swing Hydraulic System
349E Excavator Hydraulic System Swing Hydraulic System
1.1. Swing Priority



Illustration 1g03561267

Hydraulic schematic for SWING RIGHT

(1) Swing parking brake

(2) Right swing motor

(3) Swing parking brake

(4) Left swing motor

(5) Pilot line

(6) Line

(7) Line

(8) Return line

(9) Return passage

(10) Passage

(11) Swing control valve

(12) Passage

(13) Passage

(14) Parallel feeder passage

(15) Center bypass passage

(16) Center bypass passage

(17) Main control valve

(18) Negative flow control orifice

(19) Pilot control valve (swing and stick)

(20) Line

(21) Load check valve

(22) Negative flow control line

(23) Return line

(24) Swing pressure sensor

(25) Pilot line

(26) Pilot line

(27) Swing brake solenoid valve

(28) Pilot oil manifold

(29) Pilot pump

(30) Drive pump

(31) Idler pump




Illustration 2g02147013

Swing motor with fine swing

(2) Right swing motor

(4) Left swing motor

(17) Main control valve

(31) Idler pump

(32) Fine swing solenoid valve

The oil delivery for the swing hydraulic circuit is supplied by idler pump (31) only. When either one of the joysticks is moved from the NEUTRAL position, swing parking brake (1) and swing parking brake (3) are released. Motor rotary group (2) 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)".




Illustration 3g02148310

Swing motor compartment

(2) Right swing motor

(4) Left swing motor

(6) Line

(7) Line

(23) Return line




Illustration 4g02148479

(27) Swing brake solenoid valve

(28) Pilot oil manifold

The oil delivery from idler pump (31) flows through center bypass passage (15) in main control valve (17) to swing control valve (11) . The oil delivery from drive pump (30) flows through center bypass passage (16) in main control valve (17) . 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 (29) flows to pilot oil manifold (28) and swing brake solenoid valve (27) . The oil delivery from the pilot pump also flows to pilot control valve (19) .

When the swing joystick is moved to the SWING RIGHT position, swing pressure sensor (24) senses the increase in pilot oil pressure. The swing pressure sensor sends an input signal to the machine ECM. The machine ECM sends a pulse width modulated signal (PWM signal) to swing brake solenoid valve (27) . The swing brake solenoid valve shifts. Pilot oil flows through pilot line (5) to swing parking brake (1) and swing parking brake (3) . The swing parking brake releases in order to enable a swing operation.

The oil delivery from pilot pump (29) flows from pilot control valve (19) through pilot line (25) and into swing control valve (11) . The spool in swing control valve (11) shifts upward.

Since the spool in swing control valve (11) is fully shifted, center bypass passage (15) is blocked. None of the oil delivery from the idler pump flows to negative flow control line (22) and no negative flow control pressure is created in center bypass passage (15) . Since no negative flow control pressure is sent through negative flow control line (22) 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 (14) , passage (13) , load check valve (21) , swing control valve (11) , passage (10) and line (6) to the swing motors. The oil enters the swing motors and flows to motor rotary group (2) 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 (30) are in the NEUTRAL position. The negative flow control pressure in center bypass passage (16) is not blocked by any of the control valves. Drive pump (30) 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 (7) to the main control valve. The return oil flows through swing control valve (11) , return passage (12) , and return line (9) to the hydraulic tank. The upper structure swings to the right (clockwise direction).

The SWING LEFT operation is like the SWING RIGHT operation.

When the swing joystick is moved to the SWING LEFT position, pilot oil from pilot control valve (19) flows through pilot line (26) and into swing control valve (11) . The spool in the swing control valve shifts downward. The oil delivery from the idler pump in parallel feeder passage (14) flows through passage (13) and line (7) . The oil delivery enters motor rotary group (2) and motor rotary group (4) . For a swing left operation, the supply ports and return ports are reverse of the swing right operation. This action 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. During a swing operation, pilot oil flows from pilot control valve (19) to swing control valve (11) . Supply oil from idler pump (31) enters parallel feeder passage (14) . Parallel feeder passage (14) supplies oil to swing priority valve (36) , passage (40) and swing priority solenoid (38) . Pressure sensor (24) for swing control sends an electrical signal to the machine ECM. The machine ECM sends an electrical signal to swing priority solenoid (38) in order to activate swing priority.

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.




Illustration 5g02154928

Swing priority valve (swing priority OFF)

(11) Swing control valve

(34) Stick I control valve

(35) Parallel feeder passage

(36) Valve

(37) Spring

(38) Swing priority solenoid

(39) Passage

(40) Passage




Illustration 6g02709593

SWING RIGHT operation (swing priority OFF)

(11) Swing control valve

(14) Parallel feeder passage

(19) Pilot control valve (swing and stick)

(24) Swing pressure sensor

(25) Pilot line

(29) Pilot pump

(30) Drive pump

(31) Idler pump

(33) Swing motors

(34) Stick I control valve

(35) Parallel feeder passage

(36) Valve

(37) Spring

(38) Swing priority solenoid

(39) Passage

(40) Passage

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 (19) flows through pilot line (25) . The spool in swing control valve (11) shifts a slight amount that corresponds to the amount of movement of the swing joystick. The machine ECM sends an electrical signal to swing priority solenoid (38) in order to energize the solenoid. The swing priority solenoid shifts to the left.

The oil delivery from idler pump (31) supplies oil to parallel feeder passage (14) . Parallel feeder passage (14) supplies oil to swing priority solenoid (38) through passage (40) . Supply oil in passage (40) is blocked by swing priority solenoid (38) to the spring side of swing priority valve (36) . Oil in passage (39) is able to flow through valve (38) which allows valve (36) to open. Valve (36) now allows oil to flow. Oil is able to flow to stick I control valve (34) from idler pump (31) without restriction. Swing priority is not activated.

Swing priority is OFF when the machine ECM energizes swing priority solenoid (38) . Supplying power to swing priority solenoid (38) overrides the spring in the solenoid. Oil delivery from the idler pump is supplied to swing control valve (11) and stick I control valve (34) .




Illustration 7g02313914

Swing priority valve (swing priority ON)

(11) Swing control valve

(34) Stick I control valve

(35) Parallel feeder passage

(36) Valve

(37) Spring

(38) Swing priority solenoid

(39) Passage

(40) Passage

(41) Swing priority check valve




Illustration 8g02709616

SWING RIGHT operation (swing priority ON)

(11) Swing control valve

(14) Parallel feeder passage

(19) Pilot control valve (swing and stick)

(24) Swing pressure sensor

(25) Pilot line

(29) Pilot pump

(30) Drive pump

(31) Idler pump

(33) Swing motors

(34) Stick I control valve

(35) Parallel feeder passage

(36) Valve

(37) Spring

(38) Swing priority solenoid

(39) Passage

(40) Passage

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 to the UP position. Swing pressure sensor (34) senses the increase in pilot pressure. Swing priority solenoid (38) does not shift.

The oil delivery from idler pump (31) supplies oil to parallel feeder passage (14) . Parallel feeder passage (14) supplies oil to swing priority solenoid (38) through passage (40) . Supply oil in passage (39) enters the spring side of swing priority valve (36) . Swing priority valve (36) closes. Oil pressure in parallel feeder passage (14) flows through swing priority check valve (41) to stick I control valve ( 34) . Oil pressure from parallel feeder passage (14) to stick I control valve (34) is restricted by swing priority valve (36) . Limited idler pump oil is supplied to stick I control valve (34) .

The machine ECM de-energizes swing priority solenoid (38) thus enabling swing priority. Swing priority solenoid (38) is now in the OFF position. 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.

Note: The drive pump supplies oil to the stick II control valve during a combined swing and stick operation.

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