Auxiliary Function
Reference: The correct connections for the auxiliary cylinders are illustrated in the hydraulic schematic. Reference the Service Manual module for Systems Operation, SENR1389, "950G Wheel Loader, 962G Wheel Loader and IT62G Integrated Toolcarrier, Hydraulic System", "General Information".
Note: The auxiliary spool is enabled when the fourth function switch is actuated. The tilt lever is used to control the auxiliary valve spool.
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| Illustration 1 | g00490485 |
View of Lift Spool and Auxiliary Spool in the HOLD Position (1) Chamber for pilot oil (2) Springs (3) Passage for the rod end of the auxiliary cylinders (4) Passage for the head end of the auxiliary cylinders (5) Inlet passage for the implement pump oil (6) Auxiliary valve spool (7) Chamber for pilot oil (8) Passage (9) Outlet passage to the hydraulic oil tank | |
Supply oil flows from the tilt and auxiliary main control valve to the lift and auxiliary main control valve. The oil then flows through inlet passage (5) and into auxiliary valve spool (6). Auxiliary valve spool (6) is spring centered. The auxiliary valve spool is controlled by pilot pressure oil. The auxiliary valve spool has an open center.
Note: Some valve spools may differ slightly but the basic principles of operation are similar.
HOLD Position
Springs (2) keep auxiliary valve spool (6) in the HOLD position when there is no pilot pressure oil in chambers (1) or (7). Spool movement is controlled by pilot pressure oil in chambers (1) and (7) .
When auxiliary valve spool (6) is in the HOLD position, implement pump oil flows from inlet passage (5) to passage (8). The oil then flows through outlet passage (9) to the hydraulic oil tank. The position of the auxiliary valve spool prevents the flow of oil to passages (3) and (4). The auxiliary valve spool blocks the oil in both ends. This prevents the auxiliary cylinders from moving.
TILT BACK Position
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| Illustration 2 | g00490482 |
Main Control Valve View of the Lift Spool in the TILT BACK Position and the Auxiliary Spool in the HOLD Position (1) Chamber for pilot oil (3) Passage for the rod end of the auxiliary cylinders (4) Passage for the head end of the auxiliary cylinders (5) Inlet passage for the implement pump oil (6) Auxiliary valve spool (9) Outlet passage to the hydraulic oil tank (10) Passage (11) Spring (12) Check valve for the auxiliary circuit (13) Passage (14) Lift valve spool | |
When the tilt control lever is moved to the TILT BACK position, pilot oil flows to chamber (1). This causes auxiliary valve spool (6) to move to the right. This allows pressure oil to flow from inlet passage (5) to check valve (12) .
Check valve (12) does not open until the oil pressure becomes greater than the combined force of spring (11) and the oil pressure in passage (10). When the check valve opens, oil flows through passage (10) and out of passage (4) to the head end of the auxiliary cylinders. This causes the cylinders to extend.
Oil from the rod end of the auxiliary cylinders flows in through passage (3). Oil from passage (3) flows around auxiliary valve spool (6) and into passage (13).
The oil then flows around lift valve spool (14) and through outlet passage (9) to the hydraulic oil tank. This causes the oil from the rod end of the auxiliary cylinders to bypass the lift circuit. This also prevents simultaneous operation of extending the lift cylinders and raising the lift arms.
Note: When auxiliary valve spool (6) moves fully to the right, implement pump oil will not flow to lift valve spool (14). The lift circuit will not operate.
DUMP Position
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| Illustration 3 | g00490486 |
Main Control Valve View of Lift Spool in the DUMP Position and the Auxiliary Spool in the HOLD Position (3) Passage for the rod end of the auxiliary cylinders (4) Passage for the head end of the auxiliary cylinders (5) Inlet passage for the implement pump oil (6) Auxiliary valve spool (7) Chamber for pilot oil (9) Outlet passage to the hydraulic oil tank (10) Passage (11) Spring (12) Check valve for the auxiliary circuit (13) Passage (14) Lift valve spool (15) Spring (16) Makeup valve for the rod end of the auxiliary cylinders | |
When you move the tilt control lever to the DUMP position, pilot oil flows to chamber (7). Auxiliary valve spool (6) moves to the left. Oil then flows from inlet passage (5) to check valve (12) .
Check valve (12) does not open until the oil pressure becomes greater than the combined force of spring (11) and the oil pressure in passage (10). When the check valve opens, oil flows through passage (10) and out of passage (3) to the rod end of the auxiliary cylinders. This causes the cylinders to retract.
Oil from the head end of the auxiliary cylinders flows through passage (4). Oil from passage (4) then flows around auxiliary valve spool (6) and into passage (13).
The oil then flows around lift valve spool (14) and through outlet passage (9) to the hydraulic oil tank. This causes the oil from the head end of the auxiliary cylinders to bypass the lift circuit. This prevents simultaneous operation of retracting the lift cylinders and raising the lift arms.
If the auxiliary cylinders retract too fast, the implement pump can not supply enough oil flow to the rod end of the auxiliary cylinders. This causes the oil pressure in passage (5) to decrease. This causes makeup valve (16) to compress spring (15). This allows the addition of return line oil to the implement pump oil in order to prevent damage from cavitation (vacuum) in the hydraulic system.
Note: When auxiliary valve spool (6) is moved fully to the left, implement pump oil will not flow to lift valve spool (14). The lift circuit will not operate.
Lift Function
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| Illustration 4 | g00491095 |
Main Control Valve View of Lift Spool and Auxiliary Spool in the HOLD position (3) Passage for the rod end of the auxiliary cylinders (4) Passage for the head end of the auxiliary cylinders (5) Inlet passage for the implement pump oil (6) Auxiliary valve spool (8) Passage (9) Outlet passage to the hydraulic oil tank (14) Lift valve spool (17) Chamber for pilot oil (18) Springs (19) Makeup valves for the rod end of the lift cylinders (20) Passage for the head end of the lift cylinders (21) Chamber | |
HOLD Position
Oil from the implement pump flows through inlet passage (5) and around auxiliary valve spool (6) before the oil reaches lift valve spool (14). Lift valve spool (14) is spring centered. The lift valve spool is controlled by pilot pressure oil. The lift valve spool has an open center.
Springs (18) keep lift valve spool (14) in the HOLD position when there is no pilot pressure oil in chambers (17) and (21). Spool movement is controlled by pilot pressure oil in chambers (17) and (21) .
When lift valve spool (14) is in the HOLD position, implement pump oil flows from inlet passage (5) to passage (8). The oil then flows through outlet passage (9) to the hydraulic oil tank. The position of the lift valve spool prevents the flow of oil to passages (19) and (20). The lift valve spool blocks the oil in both ends of the lift cylinders. This prevents the lift cylinders from moving.
RAISE Position
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| Illustration 5 | g00491090 |
Main Control Valve Auxiliary Valve Spool in the HOLD Position and Lift Valve Spool in the RAISED Position (5) Inlet passage for the implement pump oil (8) Passage (14) Lift valve spool (17) Chamber for pilot oil (20) Passage for the head end of the lift cylinders (22) Passage (23) Check valve for the lift circuit (24) Spring | |
When the lift control lever is moved to the RAISE position, pilot oil flows to chamber (17). This causes lift valve spool (14) to move to the right. Oil from the implement pump flows into inlet passage (5). The oil then flows through passage (8) to check valve (23) .
Check valve (23) does not open until the oil pressure becomes greater than the combined force of spring (24) and the oil pressure in passage (22). When check valve (23) opens, oil flows through passage (22) and out of passage (20) to the head end of the lift cylinders. This causes the lift arms to raise.
LOWER Position
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| Illustration 6 | g00491131 |
Main Control Valve Auxiliary Valve Spool in the HOLD Position and Lift Valve Spool in the LOWER Position (5) Inlet passage for the implement pump oil (8) Passage (14) Lift valve spool (17) Chamber for pilot oil (20) Passage for the head end of the lift cylinders (22) Passage (23) Check valve for the lift circuit (24) Spring (25) Makeup valve for the rod end of the lift cylinders (26) Vent passage to the pilot valve (oil manifold) (27) Spring | |
When the lift control lever is moved to the LOWER position, pilot oil flows to chamber (21). Lift valve spool (14) moves to the left. Oil from the implement pump flows from inlet passage (5), through passage (8), and to check valve (23) .
Check valve (23) does not open until the oil pressure becomes greater than the combined force of spring (24) and the oil pressure in passage (22). When check valve (23) opens, oil flows through passage (22) and into passage (19). The oil will then flow to the rod end of the lift cylinders. This causes the lift arms to lower.
Oil from the head end of the lift cylinders flows through passage (20), and around lift valve spool (14). The oil then flows through outlet passage (9) to the hydraulic oil tank.
If the lift cylinder rods retract too fast the implement pump can not supply enough oil flow to the rod end of the lift cylinders. The pressure then decreases in passage (19).
This causes makeup valve (25) to move against spring (27). This allows the addition of return line oil to the implement pump oil in order to prevent damage from cavitation (vacuum) in the hydraulic system.
FLOAT Position
When the lift control lever is moved to the FLOAT position, pilot oil flows to chamber (21) and lift valve spool (14) moves to the left. Oil from the pilot valve (oil manifold) opens vent passage (26). This allows makeup valve (25) to open.
Implement oil pressure keeps makeup valve (25) open. The oil from passage (22) and the oil in passage (19) flow through passage (13). The oil then flows through outlet passage (9) to the hydraulic oil tank.
The lift cylinders can move freely in either direction according to the force on the bucket. As the lift cylinders move, excess oil from the lift cylinders flows to passage (9). The oil then flows to the hydraulic oil tank.