Implement Control Valve Without a Line Relief Valve
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| Illustration 1 | g03617879 |
Typical implement control valve without a line relief valve in the HOLD position (1) Check valve (2) Piston (3) Check valve (4) Stem (5) Solenoid (6) Check valve for signal network (7) Compensator spool (8) Signal port (9) Solenoid | |
The following implement circuits do not have line relief valves:
- Articulation
- Centershift
- Circle drive
- Wheel lean
Control stem (4) has metering holes and slots that are designed to match the flow requirements for each circuit. If the components become damaged or worn, the components in the control valves are replaceable.
Check valve (1) and check valve (3) are incorporated into the control valve body. A guided poppet is used in order to reduce leakage. The reduction in leakage reduces cylinder drift.
Piston (2) will shift when pressurized oil is directed to one side of the piston. Piston (2) will unseat one of check valves. Pressurized oil will open the other check valve.
When the total flow demand exceeds the maximum pump flow, compensator spool (7) distributes the hydraulic pump flow that is available. Compensator spool (7) creates an additional restriction in each circuit. This is done so a single circuit cannot use all of the available pump flow. Compensator spool (7) maintains an equal pressure drop across each opening. The oil flow from each implement control valve is proportional to the opening of stem (4) .
Check valve (6) allows pressurized oil to travel out of the implement control valve through a passage and into the signal network. The check valve also prevents back pressure from the other control valves from acting on the control valve. The highest load pressure is the only pressure that passes through the signal check valve. All other signal check valves will remain seated. The signal oil also becomes the input signal to the back of compensator spool (7) . The signal oil enters through port (8) . Signal oil plus the force of the spring act on compensator spool (7) . Compensator spool (7) regulates the flow of oil to the cylinders when multiple implement circuits are being used.
Solenoid (5) and solenoid (9) work independently of each other in order to shift control stem (4) . When the operator moves the joystick, an electrical signal will cause one solenoid to energize. The energized solenoid will direct pilot oil to the end of control stem (4) . The de-energized solenoid will have a passage open to the hydraulic tank. The pilot oil on one side of control stem (4) will shift control stem (4) against the spring on the opposite side. Solenoid (5) and solenoid (9) are variable.
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| Illustration 2 | g03618557 |
Typical implement control valve without a line relief valve in operation (1) Check valve (2) Piston (3) Check valve (4) Stem (5) Solenoid (6) Check valve for signal network (7) Compensator spool (8) Signal port (9) Solenoid | |
When the operator moves the joystick, an electrical signal will cause one solenoid to energize. When solenoid (5) is energized, solenoid (5) will direct pilot oil to the end of control stem (4) . When solenoid (9) is de-energized, solenoid (9) will have a passage open to the hydraulic tank. The pilot oil on one side of the control stem (4) will shift control stem (4) . Pump supply oil will flow into the internal passages of the control valve. Pump supply oil will flow past compensator spool (7) and shift piston (2) to the left. Piston (2) will unseat check valve (1) . Pump supply oil will flow past check valve (3) to the cylinder. The opposite end of the cylinder will be open to the hydraulic tank by check valve (1) .
Pump supply oil will also unseat check valve (6) . The oil that flows past check valve (6) will flow into the signal network. The signal network will send pilot oil to the implement piston pump in order to upstroke the pump. The implement piston pump will maintain oil flow in order to meet the system demands.
Implement Control Valve With a Line Relief Valve
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| Illustration 3 | g03618899 |
(1) Check valve (2) Piston (3) Check valve (4) Stem (5) Solenoid (6) Check valve for signal network (7) Compensator spool (8) Signal port (9) Solenoid | |
The following implement circuits include one line relief valve:
- Blade lift
- Blade tip
- Blade sideshift
- Ripper
- Scarifier
- Snow plow/dozer lift
- Snow plow/dozer angle
The following implement circuits include two line relief valves:
- Snow wing lift
- Snow wing tilt
Check valve (3) contains a check valve and a relief valve. The relief valve protects the rod end of the circuit from high pressures. If the pressure in the rod end of the circuit rises above the setting of the relief valve, the relief valve will open. The relief valve will drain the excessive pressure to the hydraulic tank.
Implement Control Valves with Float
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| Illustration 4 | g03849183 |
(1) Check valve (2) Pistons (3) Check valve (4) Stem (5) Solenoid (6) Check valve for signal network (7) Compensator spool (8) Signal port (9) Solenoid (10) Orifice (11) Orifice | |
The following implement valves have a float function:
- Blade lift
- Snow plow/dozer lift
Solenoid (9) is energized to the maximum of one amp in the float position. The solenoid directs pilot oil to the back of stem (4) . Pilot oil shifts stem (4) all the way to the left. Orifice (11) meters pressurized oil from the pump supply port into the internal passages of the control valve. Pressurized oil flows through the internal passages in the control valve to pistons (2) . Pressurized oil moves pistons (2) outward. Pistons (2) push check valve (1) and check valve (3) open. Orifice (10) and orifice (11) are different sizes. Orifice (10) is smaller. Orifice (10) will meter a small amount of pressurized oil to the hydraulic tank in order to limit the pressure of the oil inside the control valve. Orifice (10) maintains the pressure inside the control valve in order to keep pistons (2) shifted outward. In the float position, both cylinder ports are vented to the hydraulic tank.
Control Valve Operation
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| Illustration 5 | g03620596 |
Blade control valve in the LOWERED position (1) Check valve (2) Pistons (3) Check valve (4) Stem (5) Solenoid (6) Check valve for signal network (7) Compensator spool (8) Signal port (9) Solenoid | |
When the operator moves the joystick, an electrical signal will cause one solenoid to energize. Solenoid (9) is energized in the LOWERED position. Solenoid (9) will direct pilot oil to the end of control stem (4) . The de-energized solenoid will have a passage open to the hydraulic tank. The pilot oil on one side of control stem (4) will shift control stem (4) . Pump supply oil will flow into the internal passages of the control valve. Pump supply oil will flow past compensator spool (7) and shift pistons (2) outward. Pistons (2) will unseat check valve (1) and check valve (3) . Pump supply oil will flow past check valve (1) to the head end of the cylinder. The rod end of the cylinder will be open to the hydraulic tank by check valve (3) .
Pump supply oil will also unseat check valve (6) . The oil that flows past check valve (6) will flow into the signal network. The signal network will send pilot oil to the implement piston pump in order to upstroke the pump. The implement piston pump will maintain oil flow in order to meet the system demands.