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| Illustration 1 | g00489656 |
Front View of Machine (1) Tilt and auxiliary main control valve (2) Lift and auxiliary main control valve | |
The main control valves are located on the front frame of the machine. The implement pump supplies oil pressure to the main control valve (tilt and auxiliary). Lift and auxiliary main control valve (2) is dependent upon the tilt and auxiliary main control valve (1) for supply oil pressure.
Tilt Control Valve (HOLD Position)
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| Illustration 2 | g00474621 |
Tilt Control Valve (HOLD Position) (3) Spring (4) Spring (5) Supply port (6) Inlet chamber (7) Supply port (8) Tilt valve spool (9) Spring (10) Spring (11) Passage (12) Supply chamber (13) Auxiliary valve spool | |
The tilt valve spool is the first control valve in the series of valve spools that make up the main control valves. When the engine is running, oil flows from the implement pump to the tilt and auxiliary main control valve. The oil then flows into inlet chamber (6) .
When tilt valve spool (8) is in the HOLD position, the oil flows around tilt valve spool (8), into passage (11), and to auxiliary valve spool (13). If the auxiliary valve spool is also in the HOLD position, the oil flows around the auxiliary valve spool and to supply chamber (12). The supply oil then flows to the tilt and auxiliary main control valve.
When the tilt control valve is in the HOLD position, tilt valve spool (8) blocks the flow of oil into ports (5) and (7). The oil in the passages to the tilt cylinder is blocked. The tilt cylinder can not move until the tilt control lever and tilt valve spool (8) are moved to the TILT BACK position or to the DUMP position.
Springs (3) and (4) are located on the left end of tilt valve spool (8). Springs (9) and (10) are located on the right end of tilt valve spool (8). The springs keep tilt valve spool (8) centered when no pilot oil is being routed to the spool.
Tilt Control Valve (TILT BACK Position)
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| Illustration 3 | g00489911 |
Tilt Valve Spool in the TILT BACK Position (3) Spring (4) Spring (5) Supply port (6) Inlet chamber (7) Supply port (8) Tilt valve spool (9) Spring (10) Spring (11) Passage (14) Port (15) Port (16) Port | |
When the tilt control lever is moved to the TILT BACK position, pilot oil flows from the tilt pilot control valve and into port (16). Pilot oil combines with the force of springs (9) and (10) on the right end of tilt valve spool (8). This combined force overcomes the force of springs (3) and (4) on the left end of tilt valve spool (8). This causes the spool to move to the left.
When tilt valve spool (8) moves to the left and into the TILT BACK position, pump oil flow from chamber (6) is blocked from entering passage (11). The pump oil in chamber (6) flows into passage (7), and out of port (15). Then, the oil flows to the head end of the tilt cylinder.
The pump oil that flows into the head end of the tilt cylinder extends the cylinder rod and the bucket or attachment tilts back. Return oil from the rod end of the tilt cylinder flows through port (14), and through passage (5). At this point, the oil from the rod end is mixed with the supply oil at inlet chamber (6) .
Tilt Control Valve (DUMP Position)
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| Illustration 4 | g00489903 |
Tilt Valve Spool in the DUMP Position (3) Spring (4) Spring (5) Supply port (6) Inlet chamber (8) Tilt valve spool (9) Spring (10) Spring (11) Passage (14) Port (15) Port (17) Port (18) Return passage to tank | |
When the tilt control lever is moved to the DUMP position, pilot oil flows from the tilt pilot control valve and into port (17). Pilot oil combines with the force of springs (3) and (4) on the left end of tilt valve spool (8). This combined force overcomes the force of springs (9) and (10) on the right end of tilt valve spool (8). This causes the spool to move to the right.
When tilt valve spool (8) moves to the right and into the DUMP position, pump oil flow from chamber (6) is blocked from entering passage (11). The pump oil in passage (6) flows into passage (5), and out of port (14). Then, the oil flows to the rod end of the tilt cylinder.
The pump oil that flows into the rod end of the tilt cylinder retracts the cylinder rod and the bucket or attachment dumps. Return oil from the head end of the tilt cylinder flows through port (15), through passage (18), through the hydraulic oil filter, and to the hydraulic oil tank.
Auxiliary Control Valve
The auxiliary valve spool's operation is similar to the tilt valve spool. The spools may differ slightly but the overall operation is similar.