SWITCH AS-PRESSURE 1717570 - Caterpillar

Illustration 1 g02646177
Propel Motors and Final Drives (1) Left motor and final drive (2) Flushing relief valve (3) Right motor and final drive (4) Flushing valve (5) Speed sensorEach propel motor is a piston type motor which drives the rear wheels through a two speed planetary final drive. The ports on the motors are marked for identification. On right motor (3), port "A" is the reverse port and port "B" is the forward port. On left motor (1), port "A" is the forward port and port "B" is the reverse port.Each motor is equipped with speed sensor (5) (right shown). A gear on the output shaft of the motor rotates past the tip of the speed sensor. Each time a tooth passes the sensor, an electrical impulse is sent to the machine ECM. These impulses are out of phase with one another. The machine ECM converts the frequency of the impulses to a vehicle speed and the phase of the impulses into a travel direction. Each propel motor contains flushing valve (4). Flushing valves direct oil from the low-pressure side of the propel loop to flushing relief valve (2). The flushing relief valves open when the pressure in the low-pressure side of the propel loop is greater than the flushing relief pressure setting. Each flushing relief valve directs a metered amount of oil from the low-pressure side of the loop into the motor case drain. The case drain line on each motor directs oil from the motor cases to the cooler bypass manifold.
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Propel Motor Cross Section (6) Flushing relief valve (7) Cylinder block (8) Piston (9) Slipper feet (10) Flushing spool (11) Valve plate (12) Swashplate (13) Output shaftThe right propel motor and left propel motor are identical. Each propel motor is a single speed piston type motor. The motor contains flushing relief valve (6). When the machine is moving, supply oil from the propel pump enters the motor. Supply oil is directed to the inlet port of valve plate (11). Supply oil is also directed to flushing spool (10). The valve plate directs oil into the piston chamber in cylinder block (7). This pressure forces the pistons which are aligned with the inlet port to move out of the cylinder block.As pistons (8) are forced out of cylinder block (7), slipper feet (9) slide along the swashplate; this causes the cylinder block and pistons to rotate. Since the cylinder block is splined to output shaft (13), the output shaft also rotates. As cylinder block (7) rotates, pistons (8) align with the outlet port in valve plate (11). The rotation of the cylinder block forces oil out of the piston chambers and into the low-pressure side of the hydrostatic loop. Low-pressure oil acts against flushing relief valve (6). The low-pressure oil then returns to the inlet side of the hydraulic pump, which completes the hydrostatic circuit.High-pressure oil acts against one side of flushing spool (10), and low-pressure oil acts against the other. The force from the high-pressure oil