ELECTRONICS GP-ENGINE RATINGS 2515728 - Caterpillar

Illustration 3 g06197214
Main control valve
(2) Swing brake solenoid
(5) Swing control valve
(6) Swing left solenoid
(21) Swing right solenoidSwing control valve (5) consists of a swing right solenoid (6) and swing left solenoid (21) which are controlled by the machine ECM.
Illustration 4 g06333728
Compartment for the swing motor (typical example)
(10) Line
(17) Main control valve
(28) Swing motor
(31) Line
(32) Make-up line
(33) Line
(34) Line
(38) Check valveThe oil from pump 2 (37) flows through parallel feeder passage (7) into main control valve (17) to swing control valve (5). The oil from pump 1 (36) flows through center bypass passage (15) into the main control valve. Illustration 1 shows the main control valve when only the swing hydraulic circuit is activated.The oil from pump 2 also flows through parallel feeder passage (7) to pressure reducing valve (12). Pilot oil then flows through check valve (14) to swing brake solenoid (2) and to hydraulic lockout solenoid (20). When the hydraulic lockout lever is in the UNLOCKED position, the machine ECM energizes hydraulic lockout solenoid (20). Pilot oil flows through hydraulic lockout solenoid to swing right solenoid (21) and swing left solenoid (6).When the swing joystick is moved to the SWING RIGHT position, the machine ECM energizes swing right solenoid (21). Pilot oil from the pressure reducing valve flows through passage (11), hydraulic lock solenoid (20), swing right solenoid (21), to swing control valve (5). Pilot oil shifts the spool in swing control valve (5). The machine ECM also energizes swing brake solenoid valve (2). Swing brake solenoid valve (2) shifts. Pilot oil flows through line (10) to swing parking brake (27). Swing parking brake (27) releases to enable swing.The oil from pump 2 (37) flows through parallel feeder passage (7) and through swing control valve (5). The oil then flows through line (34) to swing motor (28). Swing motor (28) rotates and the upper structure swings to the right.Return oil from the swing motor flows through line (33) back to the main control valve . The return oil flows through the swing control valve, return passage (4), and slow return check valve (9) to hydraulic tank (32).When the joystick is released back to neutral, the ECM stops current flow to swing right solenoid (21). Swing control valve (5) shifts back to the neutral position stopping pump flow to the swing motor. The ECM also stops current flow to swing brake solenoid valve (2). The discontinued flow from the pump to the swing motor and discontinued pilot oil to the swing brake stops the upper structure from swinging. The orifice in check valve (38) helps dampen the application of the swing brake by restricting the return oil back to tank.Swing left and swing right operate in the same manner. The swing control valve is shifted in the opposite direction when swinging to the right.Swing Priority
When the stick and swing are both in being operated, swing priority restricts oil flow to the stick. Since swing priority increases the swing acceleration, swing priority is useful for loading. Swing priority is also useful