 | |
| Illustration 1 | g00476300 |
(PIN: 8DN1-5431DR1-1092) (1) Top cover (2) Three-point hitch control valve (3) Implement control valves ("+" quick coupler port for extended cylinder and "-" quick coupler port for retracted cylinder) (4) Inlet manifold | |
 | |
| Illustration 2 | g00476304 |
(PIN: 8DN544-UP1DR1093-UP7DM1-UP) (1) Top cover (2) Three-point hitch control valve (3) Implement control valves ("+" quick coupler port for extended cylinder and "-" quick coupler port for retracted cylinder) (4) Inlet manifold | |
The implement valve bank consists of the following components: top cover (1), three-point hitch control valve (2), three or four implement control valves with quick couplers (3) and inlet manifold (4). The implement valve bank is mounted on top of the rear axle housing and tilts slightly downward toward the rear of the machine.
 | |
| Illustration 3 | g00476342 |
(1) Top cover (2) Three-point hitch control valve (3) Implement control valves ("+" quick coupler port for extended cylinder and "-" quick coupler port for retracted cylinder) (4) Inlet manifold (5) Passage for the load sensing signal to the pressure and flow compensator valve (6) Inlet passage for supply oil from the implement hydraulic pump (7) Return oil passage (8) Port for low pressure return oil (AA) Supply oil (LL) Sump oil | |
Inlet manifold (4) contains the inlet passage (6) for supply oil from the implement hydraulic pump. Also, inlet manifold (4) contains outlet passage (5) for the load sensing signal to the pressure and flow compensator valve.
A port for low pressure return oil (8) is available by removing the plug from the left rear of inlet manifold. The use of a port for low pressure return oil (8) reduces the restriction in the return line from the implement.
The port for low pressure return oil is desired for the following uses: operation of hydraulic motors, hydraulic control valves that are mounted on the implement and application with case drains.
Implement control valves (3) have both O-rings and shims between the valve sections. The O-rings are used in order to seal the fluid passages. The shims are required in order to provide the proper preload on the O-rings.
The bottom implement control valve (#1 implement control valve) has flow priority over the other implement control valves and over the three-point hitch. Priority flow allows the demand of a particular implement control valve to be satisfied first if the total demand exceeds the pump output. This is accomplished by the unique porting and components in the valve body.
The #1 implement control valve and the #2 implement control valve contain load check valves in the EXTEND position. The load check valves are operated by pilot pressure. Hydraulic pressure is used in order to open the load check valves. Therefore, the engine must be running in order to release pressure from components that are attached to the #1 implement control valve or to the #2 implement control valve. The #3 implement control valve and the #4 implement control valves contain no load check valves. The #3 implement control valve and the #4 implement control valve are constructed in the same manner.
HOLD Position
 | |
| Illustration 4 | g00663816 |
Implement control valve (#1 valve with priority) (3) Implement control valves (5) Passage for the load sensing signal to the pressure and flow compensator valve (6) Inlet passage for supply oil from the implement hydraulic pump (9) Passage for supply oil to other valves (10) Adjustable flow control assembly (11) Flow control spool (12) Metering sleeve for the flow control (13) Main control valve spool (14) Quick couplers (15) Load check valve (16) Detent (17) Orifice (18) Pressure limiter valve for the detent (19) Adjustment screw (20) Primary resolver (21) Secondary resolver (22) Passage for the resolved load sensing signal from the previous control valve (23) Orifice (29) Cross-drilled passage (AA) Supply oil (BB) Reduced supply oil (DD) Pilot signal oil (HH) Blocked oil (LL) Sump oil | |
Note: All implement control valves (3) have comparable components with two exceptions. Only the #1 implement control valve and the #2 implement control valve have the porting for the load check valves (15). The #1 implement control valve has different porting in the flow control assembly.
The #1 implement control valve has flow priority over the other implement control valves and over the three-point hitch. The three-point hitch has priority once the demands of the #1 implement control valve is met. The remaining circuits are supplied in the following order: #4 implement control valve (if equipped) and #3 implement control valve and #2 implement control valve.
The #4 implement control valve (if equipped) and #3 implement control valve are in parallel with each other. The #2 implement control valve receives the last flow priority because of the higher spring force in flow control spool (11) .
Note: See Systems Operation/Testing and Adjusting, "Three-Point Hitch Control Valve" for more information about priority flow.
When the engine is not running, the springs at the left end of the flow control spool (11) keep the spool shifted to the right in the #1 implement control valve.
 | |
| Illustration 5 | g00663769 |
Flow control assembly (11) Flow control spool (12) Metering sleeve for the flow control (29) Cross-drilled passage (30) Inlet holes (31) Exhaust holes (32) Center land (33) Outlet to main control valve spool | |
When the engine is started and the #1 implement control valve is in the HOLD position, all of the supply oil from passage (6) is routed to inlet holes (30). Inlet holes (30) are located on the metering sleeve for the flow control (12). The supply oil flows around center land (32) of flow control spool (11). Next, the supply oil exits the flow control assembly through outlet (33). The supply oil is then blocked by main control valve spool (13).
 | |
| Illustration 6 | g00663755 |
Flow control assembly (29) Cross-drilled passage (30) Inlet holes (31) Exhaust holes (32) Center land (33) Outlet to main control valve spool | |
Supply oil flows through cross-drilled passage (29) in flow control spool (11). The supply oil fills the cavity at the right end of the spool. As the pressure increases, oil forces flow control spool (11) to the left against the springs. This causes center land (32) to partially close inlet holes (30) in the metering sleeve for the flow control (12) .
Inlet holes (30) do not close completely. A pressure that is equal to the spring force value of 965 kPa (140 psi) is maintained at main control valve spool (13). This improves the response to the implement when main control valve spool (13) is shifted.
If there is no flow demand in the #1 implement control valve, the position of flow control spool (11) allows all of the supply oil to enter through inlet holes (30). The supply oil will then exit out exhaust holes (31) to common passage (9). Passage (9) provides supply oil to the balance of the implement valve bank.
Each of the remaining implement control valves have access to supply oil that is routed from the #1 implement control valve.
In the HOLD position, each flow control spool (11) shifts in order to maintain a pressure that is equal to the spring force value of flow control spool (11) at the main control valve spool (13) .
Flow control spool (11) is actually a pressure reducing valve. Flow control spool (11) is controlled by the combination of the spring force value and the load sensing signal. Flow control spool (11) is used in order to control flow across an orifice.
The orifice size will vary depending on the position of flow control assembly (10) and the orifice size will vary depending on the pressure of the load sensing signal that is applied to flow control spool (11) .
RAISE Position
 | |
| Illustration 7 | g00476785 |
Implement control valve (#1 valve with priority) (3) Implement control valves (5) Passage for the load sensing signal to the pressure and flow compensator valve (6) Inlet passage for supply oil from the implement hydraulic pump (9) Passage for supply oil to other valves (10) Adjustable flow control assembly (11) Flow control spool (12) Metering sleeve for the flow control (13) Main control valve spool (14) Quick couplers (15) Load check valve (16) Detent (17) Orifice (18) Pressure limiter valve for the detent (19) Adjustment screw (20) Primary resolver (21) Secondary resolver (22) Passage for the resolved load sensing signal from the previous control valve (23) Orifice (AA) Supply oil (BB) Reduced supply oil (DD) Pilot signal oil (LL) Sump oil | |
"-" Quick coupler port (14) opens to the tank when main control valve spool (13) is shifted to the RAISE position. Also, the "-" passage for the load sensing signal opens to the tank.
In the #1 implement control valve, the supply oil is initially blocked from "+" quick coupler port (14) by load check valve (15). Also, the supply oil is blocked from the passage to the tank by main control valve spool (13) .
Working pressure at "+" quick coupler port (14) is initially blocked from the passage for supply oil by load check valve (15). The initial pressure of the supply oil at the bottom of the load check valve (15) is not enough to unseat the valve.
Pressure from the load sensing signal enters primary resolver (20). If the "-" quick coupler port is opened to the tank, the pressure of the load sensing signal is directed to both the secondary resolver (21) and to the spring chamber of the flow control spool (11). If only the #1 implement control valve is activated, the pressure of load sensing signal (5) will be sensed by the pressure and flow compensator valve. This causes the implement hydraulic pump to slightly upstroke.
Pressure from the load sensing signal (5) plus the spring force value in the spring chamber move flow control spool (11) to the right. This allows a greater pressure into the passage to "+" quick coupler port (14). The higher pressure will be sensed at the implement hydraulic pump.
The pump output pressure and pressure at the "+" quick coupler port (14) continue to increase until the pressure at the bottom of the load check valve (15) is great enough to unseat the load check valve.
If another implement control valve is operating at a higher pressure, the load sensing signal from the #1 implement control valve is blocked by the secondary resolver (21) .
The pressure of the load sensing signal in the spring chamber would still continue to increase until the load check valve (15) is unseated. Orifice (23) in the passage to the spring chamber provides a slight pressure drop.
Orifice (23) meters the rate of the pressure increase in the spring chamber. This will ultimately control the rate of the pressure increase in the passage to "+" quick coupler port (14) .
The load check valve (15) has a 10:1 ratio. In order to unseat the load check valve, the supply pressure must be at 1/10 of the value of the load pressure.
When the load check valve (15) is unseated, the load pressure at "+" quick coupler port (14) is felt in the supply passage to "+" quick coupler port (14). The load pressure at "+" quick coupler port (14) is the pressure that is sensed in the signal passage to primary resolver (20) .
When the "-" quick coupler port is still open to the tank, the pressure of the load sensing signal is directed to the secondary resolver (21). Also, the pressure of the load sensing signal is directed to the spring chamber of flow control spool (11). The pressure of the load sensing signal is compared to the highest resolved pressure from the previous valves through passage (22) .
If the #1 implement control valve has the higher load sensing signal, the higher pressure is communicated to the pressure and flow compensator valve. This causes the implement hydraulic pump to upstroke.
 | |
| Illustration 8 | g00663852 |
The increase in supply oil from the implement hydraulic pump now flows into flow control spool (11) through inlet holes (30) in the metering sleeve for the flow control (12). If the #1 implement control valve has full priority flow, the pressure of the load sensing signal works with the spring force value of flow control spool (11) in order to force the spool to the right. This moves center land (32) to the right. All of the pump flow is now routed through inlet holes (30) to the outlet to main control valve spool (33) .
Next, the oil flows past main control valve spool (13) to "+" quick coupler port (14). Once the demands of #1 implement control valve have been satisfied, center lands (32) on flow control spool (11) move back to the left. This allows the remaining supply oil to exit through exhaust holes (31) to the remaining implement control valves.
A decrease in pressure occurs as the oil is metered through the small holes in the metering sleeve for the flow control (12). The decrease in pressure is controlled by the following items: back pressure from the load sensing signal, spring force value of 965 kPa (140 psi) in flow control spool (11) and orifice that is created at the main control spool.
In the #1 implement control valve and #2 implement control valve, the oil flows past the main control valve spool (13). Next, the oil flows through the open load check valve (15) and out "+" quick coupler port (14). The load check valves help prevent implement drift that may occur when an implement is raised and left in the HOLD position.
In the #1 implement control valve, the pressure of the resolved load sensing signal from the primary resolver (20) is routed to the left end of flow control spool (11). Next, the pressure of the resolved load sensing signal flows to the secondary resolver (21). For the remaining implement control valves, the pressure of the resolved load sensing signal from the secondary resolver (21) flows to the left end of flow control spool (11).
The pressure of the load sensing signal works with the spring force value of the flow control spool (11) in order to force the spool to the right. At the same time, the pump supply pressure that is on the right end of the spool tries to push the spool to the left. These opposing forces balance the flow control spool (11) in order to maintain the pressure at the main control valve spool (13) .
The balancing of the flow control spool (11) provides a constant flow to the implement for a given movement of the lever. Since the #3 implement control valve and the #4 implement control valve do not have the porting for load check valves, the oil flows past the main control valve spool to "+" quick coupler port (14) .
Note: Flow control spool (11) also acts as a load check valve which prevents oil from flowing back into the system when pressure at the quick coupler port is higher than supply pressure. Flow control spool (11) works as a load check valve in order to prevent implement drift when an implement hydraulic circuit is initially activated. The initial pressure of the load sensing signal is sensed at the flow control spool (11). This shifts the spool completely to the right. This also prevents oil from "+" quick coupler port (14) from flowing back through the main control valve spool and into the main system. If the pump supply pressure becomes higher than the combined pressure that is required at "+" quick coupler port (14) plus the spring force value of 965 kPa (140 psi), the supply pressure shifts flow control spool (11) back to the left. This permits oil to flow past the main control valve spool (13) to "+" quick coupler port (14) .
LOWER Position
 | |
| Illustration 9 | g00477111 |
Implement control valve (#1 valve with priority) (3) Implement control valves (5) Passage for the load sensing signal to the pressure and flow compensator valve (6) Inlet passage for supply oil from the implement hydraulic pump (9) Passage for supply oil to other valves (10) Adjustable flow control assembly (11) Flow control spool (12) Metering sleeve for the flow control (13) Main control valve spool (14) Quick couplers (15) Load check valve (16) Detent (17) Orifice (18) Pressure limiter valve for the detent (19) Adjustment screw (20) Primary resolver (21) Secondary resolver (22) Passage for the resolved load sensing signal from the previous control valve (23) Orifice (AA) Supply oil (BB) Reduced supply oil (DD) Pilot signal oil (LL) Sump oil | |
When the main control valve spool (13) is shifted to the LOWER position, the pump supply passage (6) is open to both the bottom of the load check valve (15) and "-" quick coupler port (14) .
When there is no load pressure in the "+" quick coupler port (14), the initial pump supply pressure is able to unseat the load check valve (15). This opens both "+" quick coupler port (14) and the passage for the load sensing signal to the tank. The passage between the pump supply and the tank is blocked by the main control valve spool (13) .
The pressure at "-" quick coupler port (14) is sensed in the passage for the load sensing signal. The pressure of the load sensing signal enters the primary resolver (20). The highest resolved pressure which is in "-" quick coupler port (14) is directed to the secondary resolver (21) .
The pressure of the load sensing signal from the "-" quick coupler port (14) is compared to the highest resolved pressure from the previous valves. The highest resolved load sensing signal from "-" quick coupler ports (14) causes the load sensing signal pressure to be directed through passage (5) to the pressure and flow compensator valve. This causes the pump output to increase.
Flow control spool (11) performs the same function that is described in the previous section with respect to providing flow for "-" quick coupler port (14). See "RAISE Position" for more information. The #1 implement control valve has flow priority over the other implement control valves in the LOWER position.
FLOAT Position
 | |
| Illustration 10 | g00477381 |
Implement control valve (#1 valve with priority) (3) Implement control valves (5) Passage for the load sensing signal to the pressure and flow compensator valve (6) Inlet passage for supply oil from the implement hydraulic pump (9) Passage for supply oil to other valves (10) Adjustable flow control assembly (11) Flow control spool (12) Metering sleeve for the flow control (13) Main control valve spool (14) Quick couplers (15) Load check valve (16) Detent (17) Orifice (18) Pressure limiter valve for the detent (19) Adjustment screw (20) Primary resolver (21) Secondary resolver (22) Passage for the resolved load sensing signal from the previous control valve (23) Orifice (24) Cross-drilled passage (AA) Supply oil (BB) Reduced supply oil (DD) Pilot signal oil (LL) Sump oil | |
When the implement control lever is moved to the FLOAT position, implement valve detent (16) holds main control valve spool (13) in that position.
When the FLOAT position is selected, supply oil from flow control spool (11) is blocked. However, main control valve spool (13) has a cross-drilled passage (24) between the two center lands.
Cross-drilled passage (24) provides a path for the pressure of the supply oil which is used in order to unseat load check valve (15) .
When load check valve (15) is unseated, both "-" quick coupler port (14) and "+" quick coupler port (14) are open to the tank.
Detent Positions
 | |
| Illustration 11 | g00477420 |
Implement Valve Detent (13) Main control valve spool (16) Detent balls (17) Orifice (18) Pressure limiter valve for the detent (19) Adjustment screw (25) Detent positions (26) Centering spring (27) Piston (DD) Pilot signal oil (LL) Sump oil | |
Each implement control valve has the following detent positions (25) : HOLD, RAISE, LOWER and FLOAT. When the implement control lever is moved to either the RAISE position or the LOWER position, detents (25) hold both the spool and the respective implement control lever in the position that is selected. Detents (25) are located on the end of main control valve spool (13) .
A selected detent position is constant until the implement control lever is moved to a different position or until the pressure of the load sensing signal becomes greater than 15500 kPa (2250 psi).
If the pressure of the load sensing signal is greater than 15500 kPa (2250 psi), the pressure of the load sensing signal will move pressure limiter valve (18) to the left. When pressure limiter valve (18) moves, the pressure of the load sensing signal is felt at piston (27). Piston (27) holds the detent balls (16) in place. The pressure that is required to move piston (27) must first overcome the leak path to the tank that is created by orifice (17). The leak path to the tank helps prevent the premature release of detents (25) due to shock loads.
When the pressure increases, piston (27) will move to the left. This allows detent balls (16) to fall away from the RAISE position of the detent (25). Centering spring (26) then moves the main control valve spool (13) to the HOLD position. When main control valve spool (13) is moved to the "HOLD" position, pressure limiter valve (18) closes. This is due to the loss of the load sensing signal that is from the quick coupler port. Oil that is behind piston (27) flows to the tank through orifice (17) .
Note: The kickout pressure is adjusted by turning adjustment screw (19). Adjustment screw (19) is located on the left side of the implement control valve.
Pump Signal Control Network
 | |
| Illustration 12 | g00652181 |
Pump Signal Control Network (2) Hitch valve (3) Implement control valve (4) Inlet manifold (5) Passage for the load sensing signal to the pressure and flow compensator valve (6) Inlet passage for supply oil from the implement hydraulic pump (7) Return oil passage (11) Flow control spool (13) Main control valve spool (20) Primary resolver (21) Secondary resolver (28) Check ball (AA) Supply oil (LL) Sump oil | |
Each implement control valve (3) and hitch valve (2) has a primary resolver (20) and secondary resolver (21). A resolver is a double check valve which compares two load sensing signals. The resolver will then send the highest resolved pressure to the next component in the circuit.
Primary Resolver
When main control valve spool (13) is shifted in order to direct the output flow, primary resolver (20) compares the pressures of the load sensing signals that are from the two quick coupler ports of the circuit. The highest pressure of the load sensing signals blocks the low pressure side which permits the load sensing signal to flow to secondary resolver (21) .
Secondary Resolver
Secondary resolver (21) compares the pressure of the load sensing signal of one implement control valve to the previous implement control valve.
The pump signal control network works from the top of the implement valve bank to the bottom of the implement valve bank. The resolved pressure from hitch valve (2) is compared against the #4 implement control valve (if equipped), or against the #3 implement control valve.
The resolved pressures are compared throughout the implement valve bank so that the highest resolved pressure of the load sensing signals is sent from inlet manifold (4) through passage (5) to the pressure and flow compensator valve.
The highest resolved pressure of a load sensing signal will signal the implement pump in order to adjust the displacement.
When the implement control valves are in the HOLD position, both sides of the primary resolver (20) are open to the tank.
The chamber for flow control spool (11) on hitch valve (2) and the #1 implement control valve are ported differently than the remainder of the implement control valves.
The chamber for flow control spool (11) that is in the #1 implement control valve senses the resolved pressure between the two quick coupler ports. The chamber for flow control spool (11) does not sense the resolved pressure between implement control valves.
The chamber for the flow control spool (11) that is in the remaining implement control valves compares the highest resolved pressure of the load sensing signals from the above implement control valves.
A higher pressure requirement that is in hitch valve (2) causes the flow control spools (11) to partially close when the system pressure is higher than the demand of the following valves: #2 implement control valves, #3 implement control valve and #4 implement control valve.
The #1 implement control valve has flow priority over the other implement control valves due to the different porting. The #1 implement control valve is not affected by the resolver network or the hitch valve (2) .