The regulators for pump 1 and pump 2 are identical in construction and operation. The pump regulators are located on the sides of the main pump housing. The following description is given for the pump 1 regulator.
The pump regulators are controlled by the electronic control system. The machine ECM continually monitors various inputs. The machine ECM sends a pulse width modulated (PWM) driver to the pump control solenoid on the pump regulators. Pump control solenoid controls the output flow of the pump by changing the hydraulic signal pressure that flows to the counter piston.
The machine ECM controls the PWM driver sent to the pump control solenoid and determines the required pump flow based off the following inputs.
Desired engine speed - Determined by the engine speed dial.
Actual engine speed - Determined by the engine speed pickup.
Hydraulic torque output - The hydraulic torque output varies depending on the engine speed dial setting.
Pump 1 displacement - Determined by pump 1 control solenoid current.
Pump 2 displacement - Determined by pump 2 control solenoid current.
Flow requested - Determined by the left-hand joystick position, right-hand joystick position, or the travel pilot pressure sensors.
Pump 1 delivery pressure - The pump 1 delivery pressure is measured by the pump 1 pressure sensor on the main control valve.
Pump 2 delivery pressure - The pump 2 delivery pressure is measured by the pump 2 pressure sensor on the main control valve.
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| Illustration 1 | g06614601 |
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Partial schematic (1) Main control valve (2) Pump 1 (3) Pump 2 (15) Counter piston (pump 1) (16) Stroking piston (pump 1) (31) Pump 1 control solenoid (34) Pump displacement spool (38) Pump 1 pressure sensor (39) Pump 2 pressure sensor | |
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| Illustration 2 | g06240362 |
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Pump displacement (approximate current value) | |
The machine ECM sends a PWM driver to pump control solenoid (31) to control the angle of the pump swashplate. When current decreases the pump destrokes. Pump control solenoid (31) directs oil to the stroking piston (16) to destroke the pump.
When current increases the pump upstrokes. Pump control solenoid (31) directs pump oil to the end of counter piston (15) in order to upstroke the pump.
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| Illustration 3 | g02149999 |
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P-Q characteristic curve (A) Pressure/flow point (destroke point) (B) P-Q characteristic curve | |
The P-Q characteristic curve is determined by the machine ECM. The output characteristic of each pump depends on the following inputs.
- Desired engine speed
- Actual engine speed
- Hydraulic torque output
- Pump 1 displacement
- Pump 2 displacement
- Flow requested
- Pump 1 delivery pressure
- Pump 2 delivery 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 4 | g06607872 |
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Pump regulators (31) Pump 1 control solenoid (32) Pump 2 control solenoid | |
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| Illustration 5 | g06287405 |
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Pump 1 regulator (11) Maximum angle stop screw (15) Counter piston (16) Stroking piston (17) Minimum angle end of counter piston (21) Swashplate (31) Pump control solenoid (34) Pump displacement spool | |
Illustration 5 shows the separate control sections of the pump control group. The 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 is directed to the end of the counter piston (15) to upstroke the pump toward the maximum angle. The pump swashplate is connected to counter piston (15).
Pump pressure acting on the end of counter piston (15) works with pump displacement spool (34) to destroke the swashplate when all hydraulic controls are in the NEUTRAL position or during an implement or travel function when hydraulic demand decreases. The counter piston (15) works with pump displacement spool (34) to upstroke the swashplate when the hydraulic demand increases. The stroking piston (16) works with pump displacement spool (34) to destroke the swashplate when the hydraulic demand decreases.
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| Illustration 6 | g06193965 |
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Pump regulator schematic (2) Pump 1 (15) Counter piston (16) Stroking piston (21) Swashplate (31) Pump control solenoid (34) Pump displacement spool (35) Pump 1 oil supply passage (36) Passage (40) Spring (41) Passage (42) Passage | |
Pump displacement spool (34) is controlled by pump control solenoid (31) and spring (40).
Pump oil is supplied to passage (35) and flows to the end of counter piston (15). Pump oil also flows through passage (41) to pump displacement spool (34). The oil pressure in passage (35) can now be regulated by pump displacement spool (34) to supply a hydraulic signal pressure.
When pump control solenoid (31) receives a PWM driver from the machine ECM, pump displacement spool (34) shifts. Oil pressure can now flow through passage (42) to the stroking piston (16). This action causes the pump to upstroke.
Regulator Operation (Standby - Full Destroke)
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| Illustration 7 | g06193972 |
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Pump 1 regulator (standby - full destroke position) (2) Pump 1 (15) Counter piston (16) Stroking piston (21) Swashplate (31) Pump control solenoid (34) Pump displacement spool (35) Pump 1 oil supply passage (36) Passage (40) Spring (41) Passage (42) Passage | |
Illustration 7 shows the pump regulator and swashplate in the destroke position. When all hydraulic control valves are in NEUTRAL position, the pump swashplate is held in the standby condition.
The machine ECM sends a PWM driver decrease the current at pump control solenoid (31). Pump control solenoid (31) causes pump displacement spool (34) to shift by the force of spring (40). Oil then flows through passage (42) to the stroking piston (16). Swashplate (21) moves to the destroke position causing the pump to destroke.
Regulator Operation (Constant Flow)
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| Illustration 8 | g06194194 |
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Pump regulator (constant flow) (2) Pump 1 (15) Counter piston (16) Stroking piston (21) Swashplate (31) Pump control solenoid (34) Pump displacement spool (35) Pump 1 oil supply passage (36) Passage (40) Spring (41) Passage (42) Passage | |
Pump oil enters passage (35) and acts on the end of counter piston (15). Part of the pump oil flows through passage (41) and to pump displacement spool (34).
The machine ECM sends a PWM driver to increase the current at pump control solenoid (31). Pump control solenoid (31) causes pump displacement spool (34) to shift against the force of spring (40). Metered signal oil then flows through passage (42) to the stroking piston (16). The oil to and from the stroking piston (16) is metered by pump displacement spool (34). The angle of swashplate (21) remains constant until the machine ECM changes the electrical signal to pump control solenoid (31).
Regulator Operation (Flow Increase - Full Upstroke)
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| Illustration 9 | g06194209 |
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Pump regulator (flow increase - full upstroke) (2) Pump 1 (15) Counter piston (16) Stroking piston (21) Swashplate (31) Pump control solenoid (34) Pump displacement spool (35) Pump 1 oil supply passage (36) Passage (40) Spring (41) Passage (42) Passage | |
Pump oil enters passage (35) and acts on the end of counter piston (15).
The machine ECM sends a PWM driver to increase the current at pump control solenoid (31) to upstroke the pump. Pump control solenoid (31) causes pump displacement spool (34) to shift against the force of spring (40). The greater the commanded signal supplied to pump control solenoid (31) the greater the pump displacement will be. The pump will upstroke until stroking piston (16) contacts maximum angle stop screw (11).