The regulators for the drive pump and the idler pump are identical in construction and operation. The following description is given for the idler 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. The 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 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 | g00687567 |
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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 output circuit pressure
- Power shift pressure
- Negative flow control pressure
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 | g06320776 |
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Pump compartment (2) Proportional reducing valve (power shift pressure) (3) Line (pilot oil flow to proportional reducing valve) (19) Line (negative flow control pressure to drive pump regulator) (20) Line (negative flow control pressure to idler pump regulator) | |
Regulator Operation (Standby - Full Destroke)
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| Illustration 3 | g06318086 |
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Pump regulator (standby - full destroke position) (2) Pump solenoid (3) Pilot supply (5) Piston (6) Actuator spool (7) Actuator (8) Idler pump (9) Swashplate (12) Drive pump (13) Swashplate (14) Actuator (15) Actuator spool (16) Piston (17) Piston (18) Piston (19) Line (negative flow control pressure to drive pump regulator) (20) Line (negative flow control pressure to idler pump regulator) | |
Note: The following description refers only to drive pump components, however idler pump works the same.
Pilot oil enters the pump at passage (3), but is blocked by pump solenoid (2). Piston (16) shifts the spool (15) to the right-most position. This action allows pump oil to flow through the spool and fill the cavities on both sides of actuator (14). The pressure is equal on both side of the actuator, but there is more surface area on the left side of the actuator. This allows the oil to move the actuator to the right moving swashplate (13) to the minimum angle resulting in decreased flow.
Regulator Operation (Constant Flow)
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| Illustration 4 | g06318087 |
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Pump regulator (constant flow) (2) Pump solenoid (3) Pilot supply (5) Piston (6) Actuator spool (7) Actuator (8) Idler pump (9) Swashplate (12) Drive pump (13) Swashplate (14) Actuator (15) Actuator spool (16) Piston (17) Piston (18) Piston (19) Line (negative flow control pressure to drive pump regulator) (20) Line (negative flow control pressure to idler pump regulator) | |
Note: The following description refers only to drive pump components, however idler pump works the same.
Pilot oil enters the pump at passage (3). The ECM determines that more flow is needed and sends current flow to pump solenoid (2). This action allows pilot oil to flow through the solenoid valve to piston (17). The pressure on the piston pushes spool (15) to the left. This action allows oil to the left of actuator (14) to flow to tank. With no resistance at the left of the actuator, pressurized oil at the right of the actuator moves the actuator to the left. This action increases the angle of swashplate (13) resulting in increased flow.
The ECM then varies the current flow to solenoid (2) based on machine conditions. This action allows spool (15) to shift back and forth modulating oil flow to the actuator to stabilize the swashplate at the correct angle for machine conditions.
Regulator Operation (Flow Increase - Full Upstroke)
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| Illustration 5 | g06318090 |
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Pump regulator (flow increase - full upstroke) (2) Pump solenoid (3) Pilot supply (5) Piston (6) Actuator spool (7) Actuator (8) Idler pump (9) Swashplate (12) Drive pump (13) Swashplate (14) Actuator (15) Actuator spool (16) Piston (17) Piston (18) Piston (19) Line (negative flow control pressure to drive pump regulator) (20) Line (negative flow control pressure to idler pump regulator) | |
Note: The following description refers only to drive pump components, however idler pump works the same.
Pilot oil enters the pump at passage (3). The ECM determines that more flow is needed and sends maximum current flow to pump solenoid (2). This action allows unrestricted pilot oil to flow through the solenoid valve to piston (17). The pressure on the piston pushes spool (15) to the left. This action allows oil to the left of actuator (14) to flow to tank. With no resistance at the left of the actuator, pressurized oil at the right of the actuator moves the actuator to the left. This action increases the angle of swashplate (13) resulting in increased flow.