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| Illustration 1 | g03418690 |
Pilot oil creation circuit included in both the upper and lower manifolds of the MH3049 (1) Filter (2) Check Valve (3) Relief Valve (4) Orifice (5) Pilot valve (6) Resolver valve | |
Pilot pressure is created by converting high pressure hydraulic oil to pilot pressure oil. The hydraulic conversion circuit is included in the upper and lower main control valves. In the last step of this conversion process the oil is filtered.
High-pressure oil enters orifice (4). Pilot valve (5) is open to allow the pilot fluid to pass. The fluid passes ball resolver valve (6) and passes through filter (1) on the way to the motor shifting and park brake solenoids.
As filter (1) fills with debris, pressure increases downstream of the filter. Ball resolver valve (6) prevents the oil from flowing from the filter back to the solenoid. The increased pressure above ball resolver valve (6) causes check valve (2) to open allowing oil to bypass the filter.
When the pressure in the circuit builds to a specific level, relief valve (3) opens and oil is passed to the hydraulic tank. When the relief valve opens, pilot valve (5) also receives pilot pressure to shift the spool of the valve. The shift in the spool reduces flow into the pilot circuit. The spool is actuated when pilot pressure increases beyond 3503 kPa (508 psi).