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| Illustration 1 | g02921617 |
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Hydraulic schematic for the steering system (1) Steering cylinder (2) Steering cylinder (3) Implement and steering solenoid valve (4) Portable hydraulic pump quick connect coupler (5) Brake accumulator charging valve (6) Steering cylinder crossover relief valve (7) Steering cylinder crossover relief valve (8) Parking brake solenoid valve (9) Steering control valve (10) Secondary steering pump (11) Spool (12) Line to braking system (13) Line to parking brakes (14) Portable hydraulic pump quick connect coupler (15) Check valve (16) Steering system pressure tap (17) Secondary steering diverter valve (18) Primary steering flow switch (19) Steering neutralizer valve (20) Oil cooler (21) Check valve (22) STIC steering pilot valve (23) Line from implement lift circuit (24) Pilot oil filter (25) Steering neutralizer valve (26) Selector and pressure control valve (27) Dual pilot check valve (28, 29) Check valve (30) Pilot system pressure tap (31) Pilot relief valve (32) Breaker relief valve (33) Secondary steering flow switch (34) Hydraulic oil temperature sensor (35) Hydraulic oil level sensor (36) Hydraulic filters (37) Hydraulic tank (38) Pilot and braking pump (39) Steering pump | |
The optional secondary steering system has two purposes:
- Supplies steering oil should steering pump (39) fail, or the engine stops while the machine is moving.
- Adds oil to the steering pump flow when the engine rpm is low, and the machine is moving.
Secondary steering pump (10) is mounted to the front of the output transfer gears. The secondary steering pump is a ground speed driven pump that turns when the machine is moving.
Secondary steering diverter valve (17) is mounted on the right side of the rear frame near hydraulic tank (37).
Primary steering flow switch (18) is mounted to secondary steering diverter valve (17).
Secondary steering flow switch (33) is mounted to hydraulic tank (37).
With the engine running, oil from steering pump (39) flows past primary steering flow switch (18) to secondary steering diverter valve (17). Oil from steering pump (39) moves the paddle of primary steering flow switch (18). When the paddle moves, the contacts in primary steering flow switch (18) will close and the primary/secondary steering indicator will be off. Oil then flows through secondary steering diverter valve (17) to steering control valve (9). The oil flowing from steering control valve (9) is used to operate steering cylinders (1) and (2).
If steering pump (39) fails there will be a loss of steering oil flow. The contacts in primary steering flow switch (18) will open. A signal will be sent to the primary/secondary steering indicator. The primary/secondary steering indicator will turn on in order to alert the operator that the primary steering system has failed.
When the machine starts to move, secondary steering pump (10) also begins to turn. When ground speed is above
If the primary steering pump cannot supply enough oil, the contacts in secondary steering flow switch (33) will open. A signal will be sent to the primary/secondary steering indicator. The primary/secondary steering indicator will turn on in order to alert the operator that the secondary steering system has failed.
When engine rpm is less than 1350 ± 60 rpm, oil from secondary steering gear pump (10) combines with oil from steering pump (39). The oil combines in secondary steering diverter valve (17). Combined oil flows into steering control valve (9).
As the machine moves, and engine rpm rises above 1350 ± 60 rpm, secondary steering pump oil flows from secondary steering diverter valve (17) back to hydraulic tank (37). Steering pump (39) now provides all of the oil to steering control valve (9). If the primary steering pump cannot supply enough oil, the secondary steering diverter valve allows oil from the secondary steering pump to flow to steering control valve (9).
When pilot oil moves spool (11) the high-pressure oil is directed to steering cylinders (1) and (2). When turning right, the pressure oil flows to the rod end of steering cylinder (2) and to the head end of steering cylinder (1). When turning left, the pressure oil flows to the head end of steering cylinder (2) and to the rod end of steering cylinder (1).
Oil is displaced from the steering cylinder when a turn is made. Oil returns through spool (11) and steering control valve (9) to hydraulic oil cooler (20). The return oil flows through hydraulic oil cooler (20) and hydraulic filters (36) to hydraulic tank (37).
The hydraulic oil cooler (20) has an orifice that bypasses oil cooler (20). Cold oil or a blocked oil cooler causes the oil to flow through the orifice and return to hydraulic tank (37).