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| Illustration 1 | g01043968 |
Signal resolver network schematic for the machine (1) Stick circuit (2) Bucket circuit (3) Boom circuit (4) Orifice with Bypass (5) Swing circuit and Auxiliary backhoe circuit (If Equipped) (6) Left stabilizer circuit (7) Right stabilizer circuit (8) Extendable stick circuit (9) Lift circuit (10) Tilt circuit (11) The auxiliary circuit for the loader (12) Signal line from the steering circuit (13) Resolver for the priority valve (14) Line to the pump controller (A) Primary resolver (B) Secondary resolver (C) Bank Valve for the Boom, Bucket and Stick (D) Bank Valve for the Stabilizers, Swing, and Extendable Stick (E) Bank Valve for the Loader | |
Note: The arrows that are shown reflect the direction of flow of the signal oil.
Each control valve in the implement hydraulic system is part of the signal resolver network. Each resolver compares two signal pressures. Control valves in backhoe control valve (C) have a single resolver (A) in each valve. The resolver is installed parallel to the control spool. The boom, the bucket and the stick have internal passages in the control spool which serve the same function as primary resolvers. Control valve section (D) and control valve section (E) in the implement hydraulic system has two resolvers, the primary resolver (A) and the secondary resolver (B). The priority valve has only one resolver. The resolver in the priority valve (13) is a secondary resolver with an orifice.
A resolver is a double check valve which compares two pressure signals. The higher pressure signal goes to the next resolver.
The primary resolver is installed parallel to the control spool. The ball check valve is built into the resolver. The secondary resolver is installed perpendicular to the primary resolver. The ball check valve is not contained in a housing. A plug holds the ball check valve in the valve body.
The primary resolver compares the pressure between the two work ports in each control valve section. This resolver compares the head end pressure to the rod end pressure of the same cylinder.
The network for the secondary signal resolver is arranged in a series. The network begins at the bank valves for the stick control on mechanical backhoe controls. The network begins at the lower function of the pilot control valve for pilot backhoe controls. The secondary resolvers for the loader control are connected to the resolver for the priority valve (13) .
The signal network starts out at the cover end of the backhoe control valve (C). The highest signal pressure from a backhoe control valve is sent to the stabilizer control valve (D) through the Orifice with Bypass (4) .
Signal pressure from the backhoe control valve (C) flows through the Orifice with Bypass (4) and signal pressure enters the stabilizer valve (D) at the left cover end. That signal pressure is then compared to any signal pressure in the stabilizer control valve (D). The highest resolved signal pressure is sent to the loader control valve (E). That signal pressure is then compared to any signal pressure in the loader control valve (E). The ball check valve in the priority valve then compares the highest resolved signal pressure from the loader valve (E) to any signal pressure from the hand metering unit. Finally, the highest signal pressure is sent to the pump compensator valve.
Now, the signal instructs the pump to vary the pump output in order to meet the highest load requirements. The compensator valve adds margin pressure to the load requirements. The pump will not change the pump pressure until the resolver network identifies a different highest resolved signal.
Note: The resolver network does not add the various loads together. Instead, the single highest resolved load plus the margin governs pump output pressure. The hydraulic system is supplied with 2100 ± 100 kPa (305 ± 15 psi) extra pressure. The extra pressure is supplied in order to handle the single largest load.
When the spool in a stabilizer or the loader control valve is shifted, the primary resolver valve compares the pressure between the two work ports in the control valve section. The resolver compares the head end pressure of the cylinder to the rod end pressure of the same cylinder.
Secondary resolver check valve (B) in each valve section works similarly. The resolver compares the pressure signals between two control valves. Secondary resolver check valve (B) compares the highest primary pressure signal in the control valve to the highest resolved signal from the previous control valve. The highest resolved pressure is sent through the line to the next control valve.