Location and Function
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| Illustration 1 | g00942402 |
The axle propel motor is located under the machine. The motor is bolted to the final drive planetary. The axle propel motor receives oil from the axle propel pump. Power is transmitted from the motor to the rear axle.
Components of the Axle Propel Motor
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| Illustration 2 | g00942404 |
Axle Propel Motor (1) Drive shaft (2) Motor case (3) Retainer (4) Pistons (5) Spring (6) Barrel (7) Adjustment screw (minimum displacement) (8) Head (9) Control spool (10) Flushing valve (11) Control piston (12) Adjustment screw (maximum displacement) (13) Control plate (14) Control slot (15) Control slot (16) Pivot Pin | |
The axle propel motor is a variable displacement axial piston motor with a bent axis.
The axle propel motor in LOW speed has the following characteristics:
- High torque
- Large displacement
The axle propel motor in HIGH speed has the following characteristics:
- Low torque
- Small displacement
In LOW speed, the motor has a displacement of 55 cc/rev (3.35 cu in/rev). In HIGH speed, the motor has a displacement of 28 cc/rev (1.71 cu in/rev). When the machine is shifted from LOW to HIGH, the displacement and the torque of the axle propel motor are decreased by one half. At the same time, the rotating speed is doubled. The axle propel motor can operate in either direction.
The following four lines are connected to the motor:
- Two high pressure loop lines
- One displacement selector pilot line
- One case drain line
Oil is supplied to the axle propel motor by the axle propel pump. The direction of the motor rotation is controlled by the oil flow direction from the propel pump. The displacement and the speed are controlled by the shift valve.
The following components of the axle propel motor are the components that rotate:
- Drive shaft (1)
- Retainer (3)
- Pistons (4)
- Barrel (6)
The following components of the axle motor are the components that do not rotate:
- Motor case (2)
- Head (8)
- Control plate (13)
Oil Flow
Propel Lever in NEUTRAL Position
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| Illustration 3 | g00942443 |
(7) Adjustment screw (minimum displacement) (10) Flushing valve (11) Control piston (12) Adjustment screw (maximum displacement) (13) Control plate (17) Rotating group (18) Control spool (19) Charge oil port (shift) (20) Check valves (21) Flushing relief valve (22) Flushing shuttle spool (23) Pivot pin (AA) Charge pressure (AB) Sump (AC) Activated components | |
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| Illustration 4 | g00942535 |
Hydraulic Schematic (11) Control piston (17) Rotating group (18) Control spool (21) Flushing relief valve (22) Flushing shuttle spool (24) Line to thermal bypass and return manifold (25) Line from axle propel pump (26) Line to axle propel pump (27) Line from shift valve (AA) Charge pressure (AB) Sump (AC) Activated components (AD) Trapped oil | |
The axle propel motor will turn when a pressure differential exists between the forward and reverse ports. When the propel lever is in the NEUTRAL position, the directional control valve in the axle propel pump will block the flow of pressure oil to the servo piston in the pump. There will be equal pressure on both sides of the servo piston. This will cause the swashplate in the axle propel pump to be at zero angle position. As a result, the axle propel pump will not produce any output oil flow.
Control spool (18) will allow oil from control piston (11) to flow to the hydraulic tank. As a result, the swashplate in the axle propel motor will be a zero degree angle. The motor will not rotate.
When the propel lever is in the NEUTRAL position, the springs in flushing shuttle spool (22) will center the spool. Flushing relief valve (21) is closed. As a result, the oil between the flushing relief valve and the flushing shuttle spool is trapped. In this condition, no flushing oil flow will occur.
The axle propel motor is lubricated by oil leakage from the pistons and the barrel.
The axle propel motor operates at either a large displacement or a small displacement. When the propel motor operates at a large displacement, the barrel and the shaft are at the maximum angle. At this point, the barrel and the shaft are against adjustment screw (12) (maximum displacement). When the propel motor operates at a small displacement, the barrel and the control plate are at the minimum angle against adjustment screw (7) (minimum displacement).
Propel Lever in the FORWARD Position and the Propel Range Switch in the LOW SPEED Position
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| Illustration 5 | g00942454 |
(1) Drive shaft (3) Retainer (4) Pistons (5) Spring (6) Barrel (7) Adjustment screw (minimum displacement) (10) Flushing valve (11) Control piston (12) Adjustment screw (maximum displacement) (13) Control plate (17) Rotating group (18) Control spool (19) Charge oil port (shift) (20) Check valves (21) Flushing relief valve (22) Flushing shuttle spool (23) Swivel pin (AB) Sump (AC) Activated components (AE) System pressure (AF) First pressure reduction | |
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| Illustration 6 | g00942537 |
Hydraulic Schematic (11) Control piston (17) Rotating group (18) Control spool (21) Flushing relief valve (22) Flushing shuttle spool (24) Line to thermal bypass and return manifold (25) Line from axle propel pump (26) Line to axle propel pump (27) Line from shift valve (AA) Charge pressure (AB) Sump (AC) Activated components (AE) System pressure (AF) First pressure reduction | |
The axle propel motor will turn when a pressure differential exists between the forward and reverse ports. When the propel lever is in the FORWARD position, the directional control valve in the axle propel pump will control the amount of output oil by moving the swashplate in the axle propel pump. The output oil flow from the axle propel pump is directly proportional to the mechanical input from the propel lever to the directional control valve.
When the propel range switch is in the LOW SPEED position, charge oil (19) (shift port) is vented to the hydraulic tank. The spring in control spool (18) moves the control spool to the right. In this condition, the control spool allows the system pressure from the axle propel pump to flow through the control spool (18) to the top of control piston (11). Control piston (11) will shift control plate (13) downward. The bottom of the servo piston is vented to the motor case drain.
Note: To shift the axle propel motor to HIGH SPEED, the propel range switch should be in the HIGH SPEED position. Charge pressure oil that is coming from the line from shift valve (27) will shift control spool (18). This will allow system pressure oil to enter control piston (11). As a result, the angle of the swashplate in rotating group (17) will become larger. This will cause the speed of the axle propel motor to increase to HIGH SPEED.
Spring (5) pushes barrel (6) against control plate (13). This makes a high pressure seal between the barrel and the control plate. A seal is also made between the control plate and the head.
When high pressure oil is at the high pressure loop line, oil from the port also flows to control slot (14). Oil in the control slot goes into the cylinders of barrel (6) that are over the control slot.
The spherical piston heads are held in the sockets in drive shaft (1) by retainer (3). Seven pistons (4) are held by barrel (6). The barrel rotates around pivot pin (16) which is at an angle to the axis of the drive shaft (1). The design of the bent axis between the barrel and the shaft causes each piston to move. The pistons, the barrel, and the drive shaft rotate as pressure oil enters the cylinders.
The pistons are fully retracted when the pistons are in the top center position. The cylinder overlaps control slot (14) on the low pressure side of the loop at this point. When the piston starts to move down, the oil is pushed out of the cylinder. The oil also moves out of the control slot, the high pressure loop line and exits to the low pressure side of the loop.
Whenever the axle propel pump produces output flow, closed loop flushing will occur. Oil in the system pressure side of the closed loop circuit will act on flushing shuttle spool (22). This will allow system pressure oil to flow to flushing relief valve (21). The flushing relief valve will open allowing a metered amount of oil to flow to thermal bypass valve and return manifold (24) .
Note: The orifice in the flushing valve is designed to allow 9 ± 2 L/min (2.4 ± 0.5 US gpm) to flow to the thermal bypass and return manifold.
The orifice is a sharp edged type that allows a constant amount of oil to flow regardless of the viscosity (temperature) of the oil.