Main Pump Regulator
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| Illustration 1 | g00335678 |
Regulator (Upper Pump) (5) Passage (7) Passage (8) Housing (9) Outlet port (upper pump) (10) Outlet passage (11) Line (upper pump negative control) (12) Port (13) Piston (14) Control piston (15) Passage (17) Passage (18) Spring (19) Bushing (20) Passage (21) Pin (22) Spring (23) Line (power shift pressure) (24) Control piston (25) Passage (26) Spring chamber (27) Spring (28) Spring (29) Spring spacer (30) Spring (31) Trunnion (32) Piston (33) Bolt (34) Ring (35) Passage (37) Piston chamber (38) Bolt (57) Upper pump delivery pressure (58) Lower pump delivery pressure (59) Negative flow control pressure (60) Power shift pressure | |
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| Illustration 2 | g00297423 |
Pump Compartment (11) Line (upper pump negative control) (23) Line (power shift pressure) (39) Regulator (upper pump) (40) Port (41) Regulator (lower pump) (42) Line (lower pump negative control) | |
See the following list for the pump regulator operation.
- The pump regulator receives power shift pressure (60) from the electronic control system. The pump regulator controls the pump flow.
- The pump regulator maintains a constant horsepower between the engine and the pump. The pump regulator receives a summation of upper pump delivery pressure (57) and lower pump delivery pressure (58). This operation is called the horsepower control characteristic.
- When the control levers are in NEUTRAL position or in PARTIAL position, the pump regulator receives the negative flow control pressure (59). Negative flow control pressure (59) controls the pump output flow. This is called the negative flow control.
The pump regulator of the upper pump and lower pump are identical in construction and in operation. The following description identifies the upper pump regulator.
Oil from the upper pump flows to pump regulator (39). Oil from the upper pump goes through passages (10) and (7) in housing (8) to passages (15) and (17). Oil through passage (15) controls piston (14). Oil through passage (17) goes to passage (25). Also, oil goes to piston chamber (37) through passage (35). Oil from the lower pump goes through passage (5) to control piston (14) .
Power shift pressure (60) goes through line (23) to port (40). Port (40) is common to upper pump regulator (39) and lower pump regulator (41) .
During the horsepower control characteristic, both upper pump delivery pressure (57) and lower pump delivery pressure (58) act against the rings of control piston (14) while power shift pressure (60) is acting against the top end face of control piston (14). Control piston (14), pin (21), and control piston (24) shift in order to control the pump output.
During negative flow control, negative flow control pressure (59) from line (11) acts against the top surface of piston (13). Control piston (14) shifts in order to move control piston (24) for pump flow control.
Note: For further information on the horsepower control characteristic and negative flow control, refer to the "Regulator Operation" section in this module.
Regulator Operation
Horsepower Control Characteristic (Period Before Decreased Pump Stroke)
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| Illustration 3 | g00335679 |
Regulator Operation (5) Passage (14) Control piston (15) Passage (17) Passage (21) Pin (22) Spring (24) Control piston (25) Passage (26) Spring chamber (27) Spring (30) Spring (31) Trunnion (32) Piston (33) Bolt (34) Ring (35) Passage (37) Piston chamber (38) Bolt (45) Upper pump (57) Upper pump delivery pressure (58) Lower pump delivery pressure (60) Power shift pressure | |
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| Illustration 4 | g00335680 |
Regulator Operation (Partial View) (5) Passage (14) Control piston (15) Passage (17) Passage (20) Passage (21) Pin (22) Spring (24) Control piston (25) Passage (26) Spring chamber (27) Spring (47) Top surface (48) Passage (49) Passage (57) Upper pump delivery pressure (58) Lower pump delivery pressure (60) Power shift pressure | |
When the machine operates with a low load, pump pressure acts on control piston (14). Upper pump delivery pressure (57) from passage (15) and lower pump delivery pressure (58) from passage (5) act on the ring grooves of control piston (14). Control piston (14) pushes down against pin (21). The force tries to move control piston (24) in the downward direction. Control piston (24) does not move down because the total forces of upper pump delivery pressure (57), lower pump delivery pressure (58) and power shift pressure (60) are less than the combined forces of springs (22), (27) and (30). The force of spring (30) is less than spring (27). Spring (30) is compressed before spring (27) is compressed. Passage (48) closes and passage (49) opens making an open connection between passage (25) and spring chamber (26). Tank pressure in spring chamber (26) acts on the bottom surface of ring (34). Upper pump delivery pressure (57) in piston chamber (37) pushes down piston (32) and ring (34). When bolt (33) comes in contact with bolt (38) movement stops. The mechanical linkage of piston (32) and the cylinder through trunnion (31) hold the cylinder at the maximum angle position. This allows the pump to maintain the maximum output flow.
Horsepower Control Characteristic (Before The Pump Destrokes)
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| Illustration 5 | g00335681 |
Regulator Operation (5) Passage (14) Control piston (15) Passage (17) Passage (20) Passage (21) Pin (22) Spring (24) Control piston (25) Passage (26) Spring chamber (27) Spring (28) Spring (30) Spring (31) Trunnion (32) Piston (34) Ring (35) Passage (37) Piston chamber (45) Upper pump (50) Set screw (57) Upper pump delivery pressure (58) Lower pump delivery pressure (60) Power shift pressure | |
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| Illustration 6 | g00335682 |
Regulator Operation (Partial View) (5) Passage (14) Control piston (15) Passage (17) Passage (20) Passage (21) Pin (22) Spring (24) Control piston (25) Passage (26) Spring chamber (27) Spring (47) Top surface (48) Passage (49) Passage (50) Set screw (57) Upper pump delivery pressure (58) Lower pump delivery pressure (60) Power shift pressure | |
An increased load on the main pump increases upper pump delivery pressure (57) from passage (15) and increases lower pump delivery pressure (58) from passage (5). The force acts on ring grooves of piston (14) .
The combined forces of increased power shift pressure (60) through passage (20) acts on top surface (47) of control piston (14) to overcome the total forces of springs (22) and (30). Control piston (14) pushes down on control piston (24) through pin (21). Passage (49) closes and passage (48) opens. Therefore, upper pump delivery pressure (57) from passage (17) goes through passage (25) to the bottom surface of ring (34) .
Upper pump delivery pressure (57) acts on the top surface of ring (34). Therefore, oil is supplied to piston chamber (37) through passage (35). Upper pump delivery pressure (57) is common to both top and bottom surfaces of ring (34). The bottom surface area of ring (34) is larger than the top surface area. Therefore, ring (34) pushes up piston (32) against the forces of springs (30) and (28). The mechanical linkage of piston (32) and the cylinder through trunnion (31) cause the cylinder to move in a smaller angular direction. Therefore, the pump stroke decreases.
As piston (32) moves up, spring (30) compresses. Spring (30) pushes up on control piston (24). Passage (48) closes and passage (49) partially opens. Therefore, oil flows from passage (25) to spring chamber (26). Because spring chamber (26) is open to tank pressure, the pressure on the bottom surface of ring (34) becomes less than upper pump delivery pressure (57). Piston (32) starts to stop upward movement. When the force of upper pump delivery pressure (57) on the top surface of ring (34) becomes more than the force on the bottom surface, piston (32) starts to move down. Because of the decreased compression force of spring (30), control piston (24) also starts to move down. Passage (49) now closes and passage (48) partially opens. Piston (32) now starts to move up again because of upper pump delivery pressure (57) through passage (25) to the bottom surface of the ring.
When the upper pump delivery pressure (57) compresses spring (27), pistons (24) and (32) operate.
Upper pump delivery pressure (57) is equal to the combined force of springs (28), (30), and (27). Piston (32) is in a balanced position and the angle of the cylinder is held at this point. Control piston (24) is held at a balanced position by keeping the openings slightly opened at passages (48) and (49) .
Turning set screw (50) changes the compression force of spring (22) which changes the pump output flow. Increased compression force of the spring increases the pump output flow.
Negative Flow Control
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| Illustration 7 | g00335683 |
Negative Flow Control Operation (Partial View) (11) Line (upper pump negative control) (12) Port (13) Piston (14) Control piston (17) Passage (19) Bushing (21) Pin (24) Control piston (27) Spring (28) Spring (30) Spring (32) Piston (45) Upper pump (47) Top surface (48) Passage (49) Passage (51) Passage (52) Center bypass passage (53) Negative flow control orifice (54) Main control valve (55) Spring spacer (56) Spring spacer (57) Upper pump delivery pressure (58) Lower pump delivery pressure (59) Negative flow control pressure (60) Power shift pressure | |
The rate of oil flow through center bypass passage (52) in main control valve (54) is maximum when all control levers are in NEUTRAL position. When the control levers are partially moved for a levelling operation, part of upper pump oil flows to passage (51) in order to decrease the rate of oil flow in passage (52) .
The oil flow in center bypass passage (52) is then restricted at negative flow control orifice (53). Negative flow control pressure (59) now develops in line (11). Negative flow control pressure (59) is dependent on the rate of oil flow through center bypass passage (52). Negative flow control pressure (59) is maximum when all control levers are in NEUTRAL position. The pump output flow is minimum.
Note: For more information on negative flow control pressure (59), see Systems Operation, "Main Control Valve".
Negative flow control pressure (59) in line (11) enters the regulator through port (12). The force acts on the top surface of piston (13). Piston (13) tries to move down. Power shift pressure (60) acts on top surface (47) of control piston (14). Upper pump delivery pressure (57) and lower pump delivery pressure (58) act on the body of control piston (14). The combination acts on the inner surface of bushing (19). Bushing (19) tries to push up on piston (13) .
Negative flow control pressure (59) acts on piston (13). The force which acts on piston (13) becomes greater than the force which acts on bushing (19). Piston (13) moves down allowing the negative flow control to function. When piston (13) moves down, bushing (19) is pushed down. Bushing (19) pushes down control piston (14). The cylinder decreases the angle of the cam which destrokes the pump. This operation is similar to the horsepower control characteristic.
All control levers are in NEUTRAL position because negative flow control pressure (59) is maximum. Control piston (14) pushes down against pin (21). Pin (21) moves control piston (24) down opening passage (48). Upper pump delivery pressure (57) or lower pump delivery pressure (58) from passage (17) pushes piston (32) up. The movement of piston (32) compresses springs (27), (28) and (30). When the top surface of spring spacer (56) comes in contact with spring spacer (55), control piston (24) and piston (32) are pushed up by the force of upper pump delivery pressure (57) or lower pump delivery pressure (58). A pressure balance is attained. Control piston (24) remains in the balance position in order to keep the openings of passages (48) and (49) slightly open. This operation is similar to the horsepower control characteristic. The cylinder is now held at the minimum angle position for minimum pump output flow.
When the control levers are partially moved, negative flow control pressure (59) gradually decreases force on piston (13). The forces of compressed springs (27) and (30) overcome the force of the decreased negative flow control pressure (59). Therefore, control piston (24) moves up before spring spacer (56) comes in contact with spring spacer (55). During a levelling operation, the pump output flow is controlled between a minimum and a maximum. The flow depends on negative flow control pressure (59) .
When piston (13) moves up due to a lower negative flow control pressure (59), the total horsepower control functions.
Pressure/Flow Characteristic Curves
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| Illustration 8 | g00297449 |
P-Q Characteristic Curves (1) Destroked position (2) Horsepower characteristics | |
The output characteristics of each pump depends on the following four pressures.
- Pump output circuit pressure of top pump
- Pump output circuit pressure of bottom pump
- Power shift pressure
- Negative flow control pressure
After a pump starts to operate, each pump has a set of pressure/flow characteristic curves. The pressure/flow characteristic curve represents a set of flow rates for distinct pump circuit pressures. Each point on horsepower characteristic (2) represents the respective flow rate and the respective pressure in order to maintain a constant output from the pump.