The regulators for the drive pump and the idler pump 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 drive pump 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 proportional reducing valve on the pump regulators. Proportional reducing valve controls the output flow of the pump by changing the hydraulic signal pressure that flows to the actuator piston in the pump regulators.
The machine ECM controls the PWM driver sent to the PRV 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.
Drive pump displacement - Determined by the drive pump swashplate angle sensor.
Idler pump displacement - Determined by the idler pump swashplate angle sensor.
Negative flow control pressure - Determined by the drive pump pressure sensor and the idler pump pressure sensor.
Drive pump delivery pressure - The drive pump delivery pressure is measured by the drive pump pressure sensor located on the main control valve.
Idler pump delivery pressure - The Idler pump delivery pressure is measured by the idler pump pressure sensor located on the main control valve.
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| Illustration 1 | g03163679 |
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Partial schematic (1) Negative flow control pressure sensor (drive pump) (2) Negative flow control pressure sensor (idler pump) (3) Main control valve end plate (15) Actuator piston (31) Proportional reducing valve (33) Swashplate angle sensor (drive pump) (34) Horsepower control spool (38) Drive pump pressure sensor (39) Idler pump pressure sensor (45) Swashplate angle sensor (idler pump) | |
The machine ECM sends a PWM driver to the proportional reducing valve (PRV) to control the angle of the pump swashplate. When current decreases below 1 amp the pump destrokes. Proportional reducing valve (31) directs oil from the large end of the actuator piston (15) to the pump case drain passage. This action causes the pump to destroke.
When current increases to greater than 1 amp the pump upstrokes. Proportional reducing valve (31) directs pump oil to the large end of actuator piston (15) in order to upstroke the pump.
Note: The machine ECM supplies a current of 1 amp in order to maintain spool (34) in the NEUTRAL position.
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| Illustration 2 | 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
- Drive pump displacement
- Idler pump displacement
- Drive pump negative flow control pressure
- Idler pump negative flow control pressure
- Drive pump delivery pressure
- Idler pump 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 3 | g02932719 |
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Drive pump regulator (11) Maximum angle end of actuator piston (13) Small end of actuator piston (15) Actuator piston (16) Large end of actuator piston (17) Minimum angle end of actuator piston (21) Swashplate (31) Proportional reducing valve (32) Swashplate sensor target (33) Swashplate angle sensor (34) Horsepower control spool | |
Illustration 3 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 small end of the actuator piston (13) in order to destroke the pump toward the minimum angle. A regulated signal pressure is directed to the large end of the actuator piston (16) in order to upstroke the pump toward the maximum angle.
The horsepower control spool (34) directs some of the system pressure oil to and from the large end of the actuator piston (16). The pump swashplate is connected to actuator piston (15).
Pump pressure acting on the small end of actuator piston (13) works with horsepower control spool (34) in order 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 large end of actuator piston (16) works with horsepower control spool (34) in order to upstroke the swashplate when the hydraulic demand increases.
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| Illustration 4 | g02933080 |
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Pump regulator (section view) (13) Small end of actuator piston (15) Actuator piston (16) Large end of actuator piston (31) Proportional reducing valve (32) Swashplate sensor target (33) Swashplate angle sensor (34) Horsepower control spool (35) Drive pump oil supply passage (36) Passage (37) Passage (40) Spring (41) Passage (42) Passage | |
Illustration 4 shows a sectional view of the pump regulator components and passages.
Horsepower control spool (34) is controlled by proportional reducing valve (31) and spring (40).
Swashplate angle sensor (33) is used to determine the swashplate position. The machine ECM uses the swashplate angle sensor signal to determine pump displacement. The swashplate sensor target (32) is mechanically connected to the swashplate and swashplate angle sensor (33) is connected to the pump housing.
Pump oil is supplied to passage (35) and flows to the small end of actuator piston (13). Pump oil also flows through passage (41) and passage (37). The oil pressure in passage (36) can now be regulated by horsepower control spool (34) in order to supply a signal pressure to the large end of actuator piston (16).
When proportional reducting valve (31) receives a PWM driver from the machine ECM, horsepower control spool (34) shifts. Oil pressure can now flow through passage (37), passage (36), and passage (42) to the large end of actuator piston (16). This action causes the pump to upstroke.
Regulator Operation (Standby - Full Destroke)
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| Illustration 5 | g02933116 |
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Drive pump regulator (standby - full destroke position) (13) Small end of actuator piston (15) Actuator piston (16) Large end of actuator piston (21) Swashplate (31) Proportional reducing valve (34) Horsepower control spool (35) Drive pump oil supply passage (36) Passage (37) Passage (40) Spring (41) Passage (42) Passage (43) Passage (44) Case drain oil | |
Illustration 5 shows the pump regulator and swashplate in the destroked position. When all hydraulic control valves are in NEUTRAL position, the pump swashplate is held in the STANDBY condition.
Pump pressure enters passage (35) and acts on the small end of actuator piston (13). This oil pressure causes actuator piston (15) to shift towards the minimum angle position.
The machine ECM sends a PWM driver to PRV (31) that is less than 1 amp. Proportional reducing valve (31) causes horsepower control spool (34) to shift to the right by the force of spring (40). Oil pressure in passage (37) is blocked from passage (36) by horsepower control spool (34). No signal oil can flow to the large end of actuator piston (16).
Horsepower control spool (34) directs the signal pressure on the large end of actuator piston (16) to the case drain passage of the pump. When horsepower control spool (34) is shifted to the right, oil from the large end of actuator piston (16) flows through passage (42), to passage (36). From passage (36) the return signal oil flows through horsepower control spool (34), passage (43) to case drain oil (44).
Regulator Operation (Constant Flow)
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| Illustration 6 | g02934500 |
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Pump regulator (constant flow) (13) Small end of actuator piston (15) Actuator piston (16) Large end of actuator piston (21) Swashplate (31) Proportional reducing valve (34) Horsepower control spool (35) Drive pump oil supply passage (36) Passage (37) Passage (40) Spring (41) Passage (42) Passage (43) Passage (44) Case drain oil | |
Pump pressure enters passage (35) and acts on the small end of actuator piston (13). Part of the pump pressure flows through passage (41) to horsepower control spool (34).
The machine ECM sends a PWM driver to PRV (31) that is greater than 1 amp. Proportional reducing valve (31) causes horsepower control spool (34) to shift to the left against the force of spring (40). Oil pressure in passage (37) is supplied to passage (36) by horsepower control spool (34). Metered signal oil then flows through passage (42) to the large end of actuator piston (16).
Flow to and from the large end of the actuator piston (16) is metered by horsepower control spool (34). The angle of swashplate (21) remains constant until the machine ECM changes the electrical signal to proportional reducing valve (31).
Regulator Operation (Flow Increase - Full Upstroke)
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| Illustration 7 | g02933645 |
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Pump regulator (flow increase - full upstroke) (13) Small end of actuator piston (15) Actuator piston (16) Large end of actuator piston (21) Swashplate (31) Proportional reducing valve (34) Horsepower control spool (35) Drive pump oil supply passage (36) Passage (37) Passage (40) Spring (41) Passage (42) Passage (43) Passage (44) Case drain oil | |
The machine ECM sends a PWM driver which determines the amount of pump upstroke. When the current supplied to PRV (31) is greater than 1 amp, the pump will upstroke until actuator piston (15) contacts maximum angle stop screw.
PRV (31) directs full signal pressure to the large end of actuator piston (16) which is equal to the pump pressure. Since the large end of actuator piston (16) is a larger diameter than the small end of actuator piston (13), the actuator piston shifts to the right or UPSTROKED position.