The regulators for the drive pump and the idler pump are identical in construction and operation. The pump regulators are located on top of the main pump housing. The following description is given for the drive pump regulator.
The main pump regulators are controlled in the following manner.
Power Shift System - The pump regulators are controlled by the electronic control system. The machine ECM continually monitors the engine speed and the load on the engine. The machine ECM sends an electrical signal to the proportional reducing valve for power shift pressure. Proportional reducing valve assists in controlling the output flow of the pumps by changing the hydraulic signal pressure (power shift pressure) that flows to the pump regulators.
Cross sensing control - The pump regulators are controlled by cross sensing control. In order to maintain the engine horsepower to the pumps at a constant rate, the pump regulators receive average delivery pressure of the drive pump and the idler pump through the cross sensing control. This operation is called constant horsepower control.
Negative Flow Control - When the joysticks and/or the travel levers/pedals are in the NEUTRAL position or when the joysticks and/or the travel levers/pedals are partially moved from the NEUTRAL position, the pump regulators receive negative flow control pressure from the main control valve. The main pumps are controlled by negative flow control pressure at this time.
Reference: For more information concerning the power shift system, refer to Systems Operation, "Pilot Hydraulic System".
Reference: For more information concerning the negative flow control operation at the main control valve, refer to Systems Operation, "Negative Flow Control System".
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| Illustration 1 | g02149999 |
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P-Q characteristic curve (A) Pressure/flow point (destroke point) (B) P-Q characteristic curve | |
The output characteristic of each pump depends on the following pressures.
- Pump delivery pressure (PD)
- Cross sensing control pressure (CF)
- Power shift pressure (PS)
- Negative flow control pressure (PI)
The flow rate of each pump is represented on P-Q characteristic curve (B) from pressure/flow point (A). Each point on the P-Q characteristic curve represents the flow rate and pressure when pump output horsepower is maintained at a constant rate.
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| Illustration 2 | g02143256 |
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Drive pump regulator (1) Horsepower control section (2) Horsepower control spool (3) Horsepower control sleeve (4) Pivot pin (5) Torque control lever (6) Negative flow control lever (7) Pivot pin (8) Negative flow control section (9) Pin (feedback lever) (10) Negative flow control piston (11) Maximum angle end of actuator piston (12) Feedback lever (13) Small end of actuator piston (14) Torque control spool (15) Actuator piston (16) Large end of actuator piston (17) Minimum angle end of actuator piston (18) Torque control piston (19) Torque control section | |
Illustration 2 shows the three separate control sections of the pump control group. The three control sections are connected with a series of pins and linkages. The separate control sections work together to regulate pump flow by changing the angle of the pump swashplate, according to demand and hydraulic horsepower requirements.
Pump delivery pressure (PD) is directed to the small end of the actuator piston (13) in order to upstroke the pump toward the maximum angle. A regulated pressure signal is directed to the large end of the actuator piston (16) in order to destroke the pump toward the minimum angle.
The section for horsepower control (1) directs some of the system pressure oil to and from the large end of the large actuator piston (16). The lower end of the feedback lever (12) is connected to actuator piston (15). Feedback lever (12) works as a follow-up linkage in order to move horsepower control spool (2) when actuator piston (15) moves.
Section for negative flow control (8) works with horsepower control section (1) in order to destroke the swashplate when all hydraulic controls are in the NEUTRAL position or during an implement or travel function. The section for torque control (19) works with the section for horsepower control (1) in order to regulate pump flow when the hydraulic circuits are actuated.
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| Illustration 3 | g02143388 |
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Pump regulator (end view) (2) Horsepower control spool (4) Pivot pin (5) Torque control lever (6) Negative flow control lever (7) Pivot pin (9) Pin (feedback lever) (10) Negative flow control piston (12) Feedback lever (14) Torque control spool (15) Actuator piston (20) Large hole (21) Swashplate | |
Illustration 3 shows an end sectional view of the pump controls. NFC piston (10) is connected to the lower end of NFC lever (6) with a pin. The upper end of the NFC lever pivots on pivot pin (7) in the housing.
Torque control spool (14) is connected to the lower end of torque control lever (5) with a pin. The upper end of the torque control lever also pivots on pivot pin (4) in the housing.
The upper end of feedback lever (12) is connected to horsepower control spool (2) with a pin. The lower end of the feedback lever is connected to actuator piston (15).
Pin for the feedback lever (9) fits tightly into feedback lever (12). Pin for the feedback lever (9) extends into large holes in torque control lever (5) and NFC lever (6).
The large holes permit individual control from torque control lever (5) and NFC lever (6). Movement of actuator piston (15) causes feedback lever (12) to pivot on the pin for the feedback lever (9) and move the horsepower control spool (2).
Regulator Operation (Standby - Full Destroke)
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| Illustration 4 | g02143390 |
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Drive pump regulator (standby - full destroke position) (2) Horsepower control spool (6) Negative flow control lever (7) Pivot pin (9) Pin (feedback lever) (10) Negative flow control piston (11) Maximum angle end of actuator piston (12) Feedback lever (15) Actuator piston (17) Minimum angle end of actuator piston (21) Swashplate (22) NFC lever pin (23) NFC adjustment screw (24) Minimum angle stop (PI) Negative flow control pressure | |
Illustration 4 shows the negative flow control section of the pump control group. When all hydraulic control valves are in NEUTRAL, a high NFC pressure (system pressure) from the NFC orifice is directed to the left end of NFC piston (10). The NFC pressure pushes NFC piston (10) to the right against the spring force.
In the STANDBY condition, horsepower control spool (2) directs a signal pressure, which is part of system pressure, to the minimum angle end of the actuator piston (17). The increase in pressure moves actuator piston (15) to the right against minimum angle stop screw (24). The pump flow will remain constant until the NFC pressure from the control valve decreases.
NFC adjusting screw (23) changes the effect of the NFC pressure on NFC piston (10). Turning the screw in (clockwise) causes the NFC pressure to increase higher before NFC piston (10) moves. This condition causes the pump to upstroke sooner (less modulation) when the hydraulic control valve is ACTIVATED.
Turning NFC adjustment screw (23) out (counterclockwise) causes NFC piston (10) to move at a lower NFC pressure. This condition causes the pump to upstroke later (more modulation) when the hydraulic control valve is ACTIVATED.
Regulator Operation (Flow Increase - Start of Upstroke)
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| Illustration 5 | g02143391 |
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Pump regulator (flow increase - start of upstroke) (2) Horsepower control spool (3) Horsepower control sleeve (6) Negative flow control lever (7) Pivot pin (9) Pin (feedback lever) (10) Negative flow control piston (11) Maximum angle end of actuator piston (12) Feedback lever (17) Minimum angle end of actuator piston (21) Swashplate (22) NFC lever pin (25) Maximum angle stop (26) Orifice (PD) Pump delivery pressure (PI) Negative flow control pressure | |
Illustration 5 shows the pump control group at the beginning of an upstroke caused by a decrease in NFC pressure (PI).
Pivot pin (7) is fixed to the pump control housing. NFC lever (6) pivots around this point.
When a hydraulic control valve in the main control valve is shifted, the NFC pressure is decreased. Due to reduced NFC pressure, spring force moves NFC piston (10) to the left. NFC piston (10) moves the lower end of NFC lever (6) to the left.
As the lower end of NFC lever (6) moves to the left, the large hole through the lever also moves to the left. As the large hole moves to the left, spring force pulls horsepower control spool (2) and the upper end of feedback lever (12) to the left because pin for the feedback lever (9) is allowed to move to the left.
Minimum angle end of actuator piston (17) is opened to case drain through right orifice (26) in horsepower control sleeve (3) and the right end of horsepower control spool (2). Pump delivery pressure (PD) pushes maximum angle end of actuator piston (11) to the left to upstroke the pump.
Regulator Operation (Constant Flow)
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| Illustration 6 | g02143648 |
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Pump regulator (constant flow) (2) Horsepower control spool (3) Horsepower control sleeve (6) Negative flow control lever (7) Pivot pin (9) Pin (feedback lever) (10) Negative flow control piston (11) Maximum angle end of actuator piston (12) Feedback lever (15) Actuator piston (17) Minimum angle end of actuator piston (21) Swashplate (22) NFC lever pin (25) Maximum angle stop (26) Orifice (PI) Negative flow control pressure | |
As actuator piston (15) moves, the lower end of feedback lever (12) moves to the left. Feedback lever (12) rotates clockwise with the pin for the feedback lever (9) as the pivot point.
The upper end of feedback lever (12) pulls horsepower control spool (2) to the right until the right land on horsepower control spool (2) reaches a balance point between orifices (26) through the horsepower control sleeve (3).
Flow to and from the minimum angle end of the actuator piston (17) is metered by horsepower control spool (2) and horsepower control sleeve (3). The angle of swashplate (21) remains constant until NFC pressure (PI) is again changed.
Regulator Operation (Flow Increase - Full Upstroke)
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| Illustration 7 | g02143684 |
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Pump regulator (flow increase - full upstroke) (2) Horsepower control spool (3) Horsepower control sleeve (6) Negative flow control lever (7) Pivot pin (9) Pin (feedback lever) (10) Negative flow control piston (11) Maximum angle end of actuator piston (12) Feedback lever (17) Minimum angle end of actuator piston (21) Swashplate (22) NFC lever pin (25) Maximum angle stop (26) Orifice (PI) Negative flow control pressure | |
The amount of reduction in NFC signal pressure (PI) determines the amount of pump upstroke. If NFC pressure is reduced to minimum, the pump will upstroke until actuator piston (15) contacts maximum angle stop screw (25).
Note: A decrease in power shift pressure will cause an increase in flow from the pump in the same manner as described for a decrease in system pressure, since both power shift pressure and system pressures act on torque control piston (18).
Regulator Operation (Flow Decrease - Start of Destroke)
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| Illustration 8 | g02143689 |
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Pump regulator (flow decrease -start of destroke) (2) Horsepower control spool (3) Horsepower control sleeve (5) Torque control lever (7) Pivot pin (9) Pin (feedback lever) (11) Maximum angle end of actuator piston (12) Feedback lever (14) Torque control spool (15) Actuator piston (17) Minimum angle end of actuator piston (18) Torque control piston (26) Orifice (27) Torque control lever pin (28) Horsepower control springs (29) Adjustment screw (first stage of the constant horsepower control) (30) Adjustment screw (second stage of the constant horsepower control) (PD) Pump delivery pressure (PS) Power shift pressure (CF) Cross sensing control pressure | |
Illustration 8 shows torque control piston (18) and horsepower control spool sections of the pump control valve group with the pump in the upstroked position at the beginning of DESTROKE due to an increase in the load on the system.
Pivot pin (7) is fixed to the pump control housing. Torque control lever (5) pivots around pivot pin (7).
Adjustment screw for the first stage of constant horsepower control (29) regulates the pressure or point that the pump starts to destroke (large spring adjustment). Adjustment screw for the second stage of constant horsepower control (30) regulates the rate that the pump destrokes (small spring adjustment).
Power shift pressure (PS) from the power shift PRV solenoid valve enters the pump control group and pushes on the plug at the left end of torque control piston (18). Pump delivery pressure (PD) from the drive pump enters the pump control valve group and goes to the right shoulder area on torque control piston (18).
The cross sensing signal pressure (CF) from the idler pump goes to the left shoulder area on torque control piston (18).
The combination of power shift pressure (PS), pump delivery pressure (PD), and cross sensing control pressure (CF) push torque control piston (18) to the right against the force of the horsepower control adjustment springs (28). Horsepower control spool (2) directs the signal pressure to minimum angle end of the actuator piston (17) to destroke the hydraulic pump.
When pump delivery pressure (PD), cross sensing control pressure (CF) and power shift pressure (PS) push torque control piston (18) to the right:
Torque control piston (18) moves to the right to compress horsepower control springs (28). Torque control piston (18) moves the lower end of torque control lever (5) to the right with fixed pin (7) on the upper end of torque control lever (5) as the pivot point.
Torque control lever (5) pulls pin for the feedback lever (9) and the upper end of the feed back lever (12) to the right.
Feedback lever (12) pulls horsepower control spool (2) to the right against the spring force.
Pump delivery pressure (PD) is directed around horsepower control spool (2) through the center orifice of horsepower control sleeve (3) and to minimum angle end of the actuator piston (17). The increase in pressure in minimum angle piston (17) moves actuator piston (15) to destroke the pump.
Regulator Operation (Flow Decrease - End of Destroke)
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| Illustration 9 | g02143691 |
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Pump regulator (flow decrease - end of destroke) (2) Horsepower control spool (3) Horsepower control sleeve (5) Torque control lever (7) Pivot pin (9) Pin (feedback lever) (11) Maximum angle end of actuator piston (12) Feedback lever (15) Actuator piston (17) Minimum angle end of actuator piston (18) Torque control piston (21) Swashplate (26) Orifice (27) Torque control lever pin (PS) Power shift pressure (CF) Cross sensing control pressure | |
Illustration 9 shows the pump control group at the end of a DESTROKE due to an increase in load on the system.
When actuator piston (15) moves toward minimum angle, the lower end of feedback lever (12) moves to the right, turning the lever counterclockwise with pin for the feedback lever (9) as the pivot point.
Feedback lever (12) movement shifts horsepower control spool (2) to the left so pump delivery pressure (PD) is metered through two orifices (26) to and from the minimum angle end of the actuator piston (17). Pump flow is held constant until one of the signal pressures changes.
An increase in power shift pressure (PS) will cause a decrease in flow from the pump in the same manner as described for an increase in system pressure since both the power shift pressure and system pressure act on torque control piston (18).