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Illustration 1 | g00826544 |
Front Control Valve (1) Main relief valves (2) Line relief valves (3) Stick control spool (4) Boom control spool (5) Bucket control spool (6) Load check and flow compensator valves (7) Shuttle resolver valve (load signal network) (8) Signal duplication valve (9) Load sensing signal relief valve (10) Implement makeup valves (11) Bucket control spool (12) Boom control spool (13) Stick control spool (14) Warm-up solenoid valves (15) Shuttle resolver valve (load signal network) (16) Shuttle resolver valve (load signal network) (17) Shuttle resolver valve (load signal network) (18) Shuttle resolver valve (load signal network) (19) True load signal pressure from the rear control valve (20) Shuttle resolver valve (load signal network) |
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Illustration 2 | g00826545 |
Schematic of the Front Control Valve (1) Main relief valves (2) Line relief valves (3) Stick control spool (4) Boom control spool (5) Bucket control spool (6) Load check and flow compensator valves (7) Shuttle resolver valve (load signal network) (8) Signal duplication valve (9) Load sensing signal relief valve (10) Implement makeup valves (11) Bucket control spool (12) Boom control spool (13) Stick control spool (14) Warm-up solenoid valves (15) Shuttle resolver valve (load signal network) (16) Shuttle resolver valve (pilot signal network) (17) True load signal pressure from the rear control valve |
Note: The shuttle valves in this control valve are more commonly known as resolver valves.
The front control valve consists of a right body, a left body, and a center manifold. These three components are connected with bolts in order to make one assembly. The left body contains the following control valve spools in parallel:
- Stick control spool (3)
- Boom control spool (4)
- Bucket control spool (5)
The right body contains the following control valves in parallel:
- Bucket control spool (11)
- Boom control spool (12)
- Stick control spool (13)
Stick Control Spool
Stick control spool (3) and stick control spool (13) direct pump flow to the stick cylinders.
Boom Control Spool
Boom control spool (4) and boom control spool (12) direct pump flow to the boom cylinders.
Bucket Control Spool
Bucket control spool (5) and bucket control spool (11) direct pump flow to the bucket curl cylinders.
Implement Warm-up Solenoid Valves
Warm-up solenoid valves (14) are commonly called "warm-up valves" or "neutral bypass valves". An electrical signal from the Vital Information Management System (VIMS) actuates warm-up solenoid valves (14) when the implement and travel controls are in the NEUTRAL position. When all the controls are in the NEUTRAL position, warm-up solenoid valves (14) provide a flow path for a low volume of hydraulic oil through the front control valve. Activation of any function except the swing function causes the VIMS module to de-energize warm-up solenoid valves (14). De-energizing implement warm-up solenoid valve (14) blocks the flow path of the hydraulic oil through implement warm-up solenoid valve (14) .
Load Signal System
The load signal system is a series of internal passages and resolver valves. The load signal system directs true load signal pressure from each control spool to signal duplication valve (8). The highest true load signal pressure will pass through the load signal system to the signal duplication valve (8). The duplicated true load signal pressure is called the load sensing signal pressure. The load sensing signal pressure is directed to the load check and flow compensator valves for each spool in the control valves. The load sensing signal pressure is also directed to the margin relief valves and the regulator control valves for the implement pump.
The resolver valves perform the following functions:
- Resolver valve (6) passes the highest signal pressure which is received from resolver valve (15) and resolver valve (16) .
- Resolver valve (14) passes the highest signal pressure which is received from stick control spool (2) and boom control spool (3) .
- Resolver valve (15) passes the highest signal pressure which is received from resolver valve (14) and bucket control spool (4) .
- Resolver valve (16) passes the highest signal pressure which is received from resolver valve (17) and resolver valve (19) .
- Resolver valve (17) passes the highest signal pressure which is received from bucket control spool (10) and the rear control valve (18) .
- Resolver valve (19) passes the highest signal pressure which is received from stick control spool (12) and boom control spool (11) .
Signal Duplication Valve
Signal duplication valve (7) minimizes the effects of leakage in the load signal system. The signal duplication valve (7) duplicates the true load signal pressure. The duplicated load signal pressure is called load sensing signal pressure.
Load Sensing Signal Relief Valve
Load sensing signal relief valve (8) is a two-stage relief valve for the load sensing signal pressure that is sent to the implement pumps. During an implement function, the pump discharge pressure is regulated to a maximum of 31000 ± 500 kPa (4500 ± 70 psi). During a travel function, pilot pressure is directed to the load sensing signal relief valve (8) and the pump discharge pressure is increased to a maximum of 35000 ± 500 kPa (5080 ± 70 psi).
Line Relief Valves
The boom function, the stick function, and the bucket curl function have a line relief valve (1). Line relief valve (1) limits the maximum pressure in the circuit due to external loads on the cylinders.
The pressure setting for line relief valves (1) is 33500 ± 350 kPa (4860 ± 50 psi).
Implement Makeup Valves
Implement makeup valves (9) are in parallel with the line relief valves in the circuit. The load on an implement can cause the implement to move too quickly and the supply circuit can not supply the cylinders with oil. This can cause the pressure in the return circuit to be greater than the implement circuit pressure. If this occurs, the implement makeup valves (9) allow the tank return line to supply makeup oil to the implement supply circuit.
Main Relief Valves
Each three spool monoblock has a main relief valve (1) in order to limit the pump discharge pressure if the other relief valves malfunction. The pressure setting for the main relief valves (1) is 41375 ± 350 kPa (6000 ± 50 psi).