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| Illustration 1 | g01317784 |
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Right side drive loop (1) Actuator piston (2) Feedback lever (3) Solenoid (4) Passage (5) Servo valve (6) Port for the drive loop (7) Input shaft (8) Swashplate (9) Piston (10) Barrel (11) Spring (12) Port Plate (13) Port for drive loop (14) Adapter group | |
When the engine is running, shaft (7) and barrel (10) are rotating. There are nine pistons (9) in barrel (10). Port plate (12) and swashplate (8) are stationary within the pump housing. Port plate (12) and swashplate (8) do not rotate. Spring (11) maintains a force against barrel (10) and port plate (12). When barrel (10) is rotating, each piston (9) follows the angle of swashplate (8).
If the angle of swashplate (8) is zero, pistons (9) do not move in and out of barrel (10) and there is no oil flow. Pilot oil from the charge pump maintains oil pressure in the pump in order to perform the following tasks:
- Keep barrel (10) full of oil.
- Lubricate the pump components.
- Provide makeup oil for internal loss of oil that is due to leakage.
- Provide pilot oil to servo valve (5) in order to shift actuator piston (1) and change the angle of swashplate (8).
- The charge pump provides pilot oil in order to release the parking brakes.
The position of swashplate (8) is determined by actuator piston (1). The transmission control lever that is located on the left console sends signals to the electronic control module (ECM). The ECM interprets the signals and the ECM sends pulse width modulated signals to solenoids (3) on either side of servo valve (5). As servo valve (5) is shifted to either direction, signal oil gets filtered through the pilot oil screens. The signal oil then travels through passage (4) to the corresponding end of actuator piston (1).
As actuator piston (1) begins to move, the angle of swashplate (8) begins to increase. As piston (9) follows swashplate (8), pistons (9) begin to move in and out of barrel (10). As piston (9) moves out of barrel (10), oil is drawn from the passage of port (6) of the drive loop through port plate (12). As piston (9) follows swashplate (8) and the piston moves into barrel (10), the oil is pushed through port plate (12) into the passage to port (13) of the drive loop.
As the angle of swashplate (8) increases, the output flow of the pump also increases.
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| Illustration 2 | g01960585 |
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(32) Drive gear
(33) Idler gear (A) Outlet (B) Inlet | |
The right charge pump is a fixed displacement external gear pump. This pump supplies flow to the following systems:
- Pilot pressure to both of the hystat controls
- Pilot supply to the implement control valve
- Pilot pressure for the brakes
- Makeup to the right hystat loop
- Lubrication of pump components and of motor components
- Cooling of pump components and of motor components
When the pump is viewed from the drive end, the pump shaft rotates clockwise. The pump is mounted on the right hystat pump.
A gear pump carries oil from inlet port (B) to outlet port (A) in the spaces between the gear teeth.
The drive shaft turns drive gear (32). This forces idler gear (33) to rotate. When the gear teeth separate, a partial vacuum is formed. Oil fills the spaces between the teeth at inlet port (B). The gears carry oil around the circumference of the pump to outlet port (A). A seal is formed by the gear teeth against the pump housing. Oil is forced out of the spaces between the gear teeth as the gear teeth mesh together at outlet port (A). Oil will not return to inlet port (B) because the meshing of the gears will fill the spaces between the gear teeth.
The flow rate of oil that is supplied by the pump is controlled by the rate of the rotation of the shaft.
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| Illustration 3 | g01317716 |
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Left side drive loop (1) Actuator piston (2) Feedback lever (3) Solenoid (4) Passage (5) Servo valve (6) Port for the drive loop (7) Input shaft (8) Swashplate (9) Piston (10) Barrel (11) Spring (12) Port Plate (13) Port for drive loop (15) Charge pump (16) Gerotor pump | |
When the engine is running, shaft (7) and barrel (10) are rotating. There are nine pistons (9) in barrel (10). Port plate (12) and swashplate (8) are stationary within the pump housing. Port plate (12) and swashplate (8) do not rotate. Spring (11) maintains a force against barrel (10) and port plate (12). When barrel (10) is rotating, each piston (9) follows the angle of swashplate (8).
If the angle of swashplate (8) is zero, pistons (9) do not move in and out of barrel (10) and there is no oil flow. Charge oil from charge pump (15) maintains oil pressure in the pump in order to perform the following tasks:
- Keep barrel (10) full of oil.
- Lubricate the pump components.
- Provide makeup oil for internal loss of oil that is due to leakage.
For additional information, refer to "Head of the Piston Pump and Left Charge Pump Assembly".
The position of swashplate (8) is determined by actuator piston (1). The transmission control lever that is located on the left console sends signals to the electronic control module (ECM). The ECM interprets the signals and the ECM sends pulse width modulated signals to solenoids (3) on either side of servo valve (5). As servo valve (5) is shifted to either direction, signal oil gets filtered through the pilot oil screens. The signal oil then travels through passage (4) to the corresponding end of actuator piston (1).
As actuator piston (1) begins to move, the angle of swashplate (8) begins to increase. As piston (9) follows swashplate (8), pistons (9) begin to move in and out of barrel (10). As piston (9) moves out of barrel (10), oil is drawn from the passage of port (6) of the drive loop through port plate (12). As piston (9) follows swashplate (8) and the piston moves into barrel (10), the oil is pushed through port plate (12) into the passage to port (13) of the drive loop.
As the angle of swashplate (8) increases, the output flow of the pump also increases.
Head of the Piston Pump and Left Charge Pump Assembly
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| Illustration 4 | g01355821 |
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(17) Passage
(18) Crossover relief valve (19) Passage (20) Blocked passage (21) Passage (22) Supply passage for the charge pump (23) Passage (24) Charge relief valve (25) Crossover relief valve (26) Oil filter (27) Passage (28) Passage (16) Gerotor pump (29) Filter bypass passage (30) Passage (31) Supply passage for charge oil from the hydraulic tank | |
The charge pump is a gerotor pump that is located on the rear of the left hydrostatic pump. This pump supplies flow to the following systems:
- Makeup to the left hystat loop
- Lubrication of pump components and of motor components
- Cooling of pump components and of motor components
As gerotor pump (16) rotates, oil is drawn from supply passage (31). The oil is forced out of passage (30) to hydraulic oil filter (26). For additional information regarding the hydraulic oil filter, refer to Systems Operation, "Hydraulic Oil Filter".
The oil returns from hydraulic oil filter (26) through passage (27) to passage (28). The oil flows from passage (28) to supply passage (22).
The oil also flows from supply passage (22) to the following components:
- Crossover relief valve (18)
- Charge relief valve (24)
- Crossover relief valve (25)
Refer to the following topics for additional information:
- Systems Operation, "Relief Valve (Crossover)"
- Systems Operation, "Relief Valve (Charge Pressure) (Pump)"