Komatsu PC220-5 excavator main pump control system consists of closed valve NC, shut-off valve CO and constant torque valve TVC, servo valve and other components. Closing valve NC is controlled by the pressure difference (Pt-Pd) signal detected by the jet sensor (Pt is the outlet pressure of the sensor and Pd is the inlet pressure) according to the opening of the main ring valve. Due to throttling effect of the NC valve , So that the output of the control pressure Pecn change, thereby controlling the pump displacement; cut-off valve CO used to pump the main pump for regulation. When the main pump outlet load pressure close to the main relief valve to set the pressure, the valve that plays the role of throttling, thereby reducing the pump displacement, reducing the overflow power loss; constant torque valve TVC role is to pass The throttling control of the two main pump displacement control, that is, the total power regulation, so that the engine and hydraulic pump power at the best match, the effective power of the engine to take full advantage of the servo valve to accept from the NC Valve, CO valve, TVC valve control signal to promote its servo piston action, thereby controlling the pump swashplate angle, so that the displacement of the pump changes.
1, the main pump, pilot pump pressure debugging
Two pressure gauges each measuring 60 MPa are respectively connected to the outlets of the two main pumps to monitor the maximum working pressure of the system (ie, the set pressure of the main relief valve). The valve set pressure should be 32.5MPa, if not allowed within the scope (see the table), should loosen the main pump corresponding to the main safety valve on the lock nut, turn the adjustment screw clockwise when the pressure increases , Counterclockwise rotation when the pressure decreases, adjust the screw each turn a change of about 12.8MPa pressure.
A pressure gauge with a range of 6MPa is connected to the outlet of the pilot pump to start the engine. The working pressure of the pilot pump should be measured to be 3.2MPa at idle idle. If it is not within its allowable range, loosen the lock nut on the pilot pump safety valve, increase the pressure when turning the adjustment screw clockwise, and decrease the pressure when turning anticlockwise. The pressure change per revolution is about 0.45MPa.
2, CO valve, NC valve output pressure debugging
(1) Since the CO valve and the NC valve are used for single-pump adjustment of the main pump only, the first pump can be adjusted before the second pump is adjusted. A pressure gauge with a range of 6MPa is connected to the outlet of the NC valve, and two pressure gauges each measuring 2.5MPa are connected to the front and back pressure points of the jet sensor respectively.
(2) First test the jet pressure difference (Pt-Pd) value. When the operating handle on the machine is in the middle, the pressure drop (Pt-Pd) should be 1.6MPa; when the walking handle is placed at the end of the stroke, the value of (Pt-Pd) should not exceed 0.2MPa. If not in the main control valve on the jet valve relief nut on the lock nut, clockwise adjustment screw will make the pressure rise, counterclockwise rotation will make the pressure decreases, the pressure change per revolution is about 1.66MPa.
(3) CO valve debugging: The main control valve is operated to unload the main pump. At this time, the CO valve action (throttling), the NC valve does not operate, the output pressure of the NC valve should not exceed 0.55MPa; if not in this range, Loosen the lock nut on the CO valve (the pressure increases when turning the adjusting screw clockwise and the pressure decreases when turning counterclockwise). The pressure change per revolution is about 014MPa.
(4) NC valve debugging: the main control valve handle placed in the middle, at this time, CO valve does not move, NC valve action, NC valve output pressure should not exceed 0.7MPa; if not, should be released NC nut on the lock nut, clockwise rotation can make the pressure rise, counterclockwise rotation pressure decreases, the pressure change per revolution of about 0.43MPa.
(5) Repeat check CO, NC valve output pressure. Support the corresponding side of the pump track and make it to do full-speed automatic rotation (CO, NC valve no action), then CO, NC valve output pressure should be 1.6MPa, if not within the allowable range should be repeated above CO NC valve debugging. Then carry on the debugging of CO, NC valve of another main pump.
3, TVC valve output pressure debugging
In the TVC valve outlet connected to a range of 6MPa pressure gauge, start the engine idling idle, the operating handle on the machine all placed in the middle, then the outlet pressure TVC valve 2.1MPa; the main control valve operation so that a main pump Unloading, TVC valve output pressure should be 1.5MPa. If it is not within its allowable range, adjust the TVC valve (loosen the lock nut on the TVC valve and raise the pressure when turning the adjusting screw clockwise. When the adjusting screw is rotated counterclockwise, the pressure drops. The pressure changes approximately one turn per turn of the adjusting screw. 0.35 MPa).
4, servo valve debugging
If the above pressures are normal, but the machine does not work, then the formation of servo piston before and after the pump to measure, and the servo valve to adjust.
(1) measurement tools. Prepare a servo piston cover (spring-loaded end) and a dumper brake wear gauge. Then, install the measuring instrument on this cover with the centering wire (1/4 ") of the prepared servo piston cover.
(2) Remove the front pump (or rear pump) servo piston cap (spring-loaded end) and attach the measuring tool.
(3) When the engine is stopped, push the measuring instrument push rod down to measure the stroke of servo piston.
(4) Install the driving track corresponding to the front pump (or rear pump) equipped with the measuring instrument and make it run at high speed, measuring the stroke of the servo piston. The standard value of this stroke should be 7.22mm. If not, then the servo valve should be loosen (close to the end of the servo piston) on the adjustment screw to lock the nut, turn the adjustment screw clockwise to make the stroke smaller, the pump displacement becomes smaller; counterclockwise rotation of the adjustment screw The stroke becomes larger, the displacement of the pump also becomes larger. At the same time, check whether the movement of the measuring rod is smooth or not; if the stroke of the walking rod is well matched. After setting, and then follow the above steps for the other main pump debugging.
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