TEE 0985687 - Caterpillar

Pilot Oil Circuit
The pilot circuit pressure is limited by pilot relief valve (35) .The oil delivery from pilot pump (65) performs the following main functions.
Control the output flows of the main and swing pumps.
Automatically operate the control devices.The pilot circuit is classified into the following circuits and each circuit performs one of the above functions.
Main and swing pumps
Power shift pressure system
Proportional valve operation at the main control valve and the swing control valve
Swing parking brake
Automatic travel speed change valveMain and Swing Pumps
Part of the oil delivery from pilot pump (65) flows directly into the front pump, the rear pump and the swing pump through lines (59), (60), and (62). When the front pump, the rear pump, and the swing pump are at low delivery pressure, the pilot oil provides a positive pressure to the pumps in order to control the pump swashplate angles. This controls the output flow of the pumps.Power Shift Pressure System
During machine operation, the machine electronic control module receives input signals from the following components:
Engine speed dial
Work mode control on the keypad
Engine speed sensor that is located on the flywheel housingThe machine electronic control module continually monitors all of the input signals. The input signals are processed by the machine electronic control module and an output signal is sent to proportional reducing valve (15) at pilot oil manifold (27). The proportional reducing valve assists in controlling the output flow of front pump (63) and rear pump (64) .The oil delivery from pilot pump (65) flows through pilot filter (57) and line (14) to pilot oil manifold (27) and to proportional reducing valve (15). The electrical signal that is sent from the machine electronic control module causes proportional reducing valve (15) to regulate the pilot pressure to a reduced pressure. This reduced pressure is called power shift pressure (PS). The proportional reducing valve sends the reduced pilot oil pressure through line (58) to the regulators at front pump (63) and rear pump (64). The output flow of the front pump and the rear pump is controlled in accordance with the power shift pressure. The power shift pressure is used to regulate the maximum allowable hydraulic pump output.The output signal that is sent from the machine electronic control module to the proportional reducing valve will change when the machine electronic control module detects a change in any of the input signals. The power shift pressure that is sent to the regulators at the front pump and the rear pump will change in order to regulate the maximum allowable hydraulic pump output. The desired engine speed is maintained.An increase in engine speed increases the power shift pressure. An increase in power shift pressure causes an upstroke condition of the front pump and the rear pump. The maximum allowable hydraulic power output is increased.A decrease in engine speed decreases the power shift pressure. A decrease in power shift pressure causes destroke condition of the front pump and the rear pump. The maximum allowable hydraulic power output is decreased.Note: For