Application of Double Pumping and Shunting and Pilot Pressure Unloading Technology

At present, the loader steering and working devices are controlled by the hydraulic system to complete the majority of the loader uses a dual-pump confluence system that does not turn when the loader steering hydraulic steering pump output hydraulic control system forced by the hydraulic valve All of the confluence to work hydraulic control system go. The system requires a high pressure and low flow when the loader bucket excavation material, while the current loader hydraulic control system provided by the quantitative pump is a high pressure and high flow, so a lot of hydraulic oil overflow pressure relief valve Back to the tank. As a result, the working hydraulic control system has low power utilization rate, large energy consumption and large pollution, meanwhile the heating of the hydraulic system causes the heat balance temperature of the hydraulic system to be too high, which affects the reliability of the hydraulic system and reduces the traction during operation of the loader performance. XCMG LW820G wheel loader steering system uses a dual-pump shunt pilot pressure unloading hydraulic system, which includes hydraulic steering gear, priority flow control valve, pilot control unloading valve, limit valve and other components, the system The application greatly improves the performance of the whole machine and improves the reliability of the whole machine. one. System Features: 1. The use of smaller flow of pilot oil to promote the flow of the main valve spool movement to control the steering pump over a large flow of pressure oil into the steering cylinder to achieve low pressure small flow control of high pressure flow purposes and reduce the operator's labor strength. 2. In addition to preferentially supplying the steering system, the steering excess oil can be merged into the work system to achieve double-pump confluence, reducing the displacement of the working pump, improving the reliability, saving energy and improving three items and performance. 3. Pilot oil-controlled unloader valve enables the steering pump to direct low-pressure unloading back to the oil during loader shovel operation to improve the traction of the loader and at the same time to meet the rapid boom-lift boom Request. 4. By unloading valve directly to the oil, reducing the system heat, improve the thermal balance of the system and improve system reliability. two. System composition and working principle: 1. System components in different working conditions, the basic structure of the control system is different. Shown in Figure 1 2. Working principle of hydraulic system: The working device control system is supplied by two oil pumps. The main pump is P7600-F100, which is used to control the movement of the boom and bucket cylinder. The pilot pump is P124-G16, which is used to control the proportional pilot valve. Control the displacement of the main reversing valve core, to control the working speed of boom and bucket cylinder. Pilot pump oil first into the brake valve, to ensure that the brake oil, the pilot system to provide control of oil, the oil through the pressure reducing valve to pilot control system required control pressure into the control circuit, Control the completion of the work of the device. Schematic diagram of the hydraulic system shown in Figure 2 1. Working pump 2. Double pump 3. Pilot control unloading valve 3. Steering 4. Limit valve 6. Priority flow amplification valve 7. Steering cylinder 8. Dispensing valve 9. Boom cylinder 10. Tipping bucket cylinder 11. Pilot valve 12. Hydraulic tank 2.1 boom up Pull the operating handle to move backwards, the pilot oil into the proportional pilot valve, pilot oil from the proportional pilot valve to control the movement of the main valve spool so that the working pump to the oil Into the boom cylinder boom boom. Proportional pilot pressure relief valve the greater the output pressure, the control of the main valve spool displacement greater the main valve flow through the greater the boom up faster. When the operating handle is pulled to the limit position, the limit electromagnet in the handle is energized and the handle is pulled in the limit position. When the boom is raised to the position limited by the boom upper limit switch, the handle limit electromagnet is de-energized, the handle automatically returns to the neutral position, and the boom is held in the defined position. If the boom needs to stay in a certain position during boom-up, the operator must be returned to the neutral position. In the promotion and other operations, the pilot control valve unloading valve is closed, the steering pump to open the one-way valve to the work of the oil flow system, the working unit hydraulic oil increased to meet the needs of the operation of low-pressure high flow requirements, The boom lift and other operations to improve speed, shortening the cycle of operations, is an extremely efficient high-performance hydraulic system is extremely significant. 2.2 Bucket load handling bucket control handle to the right, the control pressure from the proportional pressure relief valve pilot oil control the main control valve in the bucket control spool, the bucket cylinder to complete the loading action. In the excavation, loading operations, the pilot control oil to promote unloading valve spool movement, steering pump to the oil through the opening of the unloading valve spool directly unloaded back to the oil. So that the work flow to the hydraulic equipment to reduce, reduce the hydraulic load, this part of the power is assigned to the drive wheel. At this moment, it meets the requirements of high pressure and small flow rate and large tractive force required by the operation, thus reducing the heat balance temperature and power loss of the system, improving the working efficiency of the machine, improving the traction force, and enabling the digging and loading capacity to be stronger. Pilot-controlled unloading valve can automatically achieve double-pump confluence according to the operating conditions, direct unloading oil, reducing system temperature and power loss, improve the traction when the loader shoveling; When working, boom boom requirements. Pilot control unloading valve in the solenoid valve is an option, the optional control signal can be used to achieve automatic unloading, the operator can send an electrical signal to the solenoid valve according to the actual conditions, the unloading valve spool open Unloading oil. This machine no use of electrical signals, but the direct use of pilot oil as the control signal also achieved good results. XCMG LW820G Wheel Loader is a self-developed product. The dual-pump combined flow diversion and pilot pressure unloading technology has been successfully applied to the aircraft. It won acclaim for its outstanding performance, high work efficiency and good appearance.

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