The existing hydraulic system of the crane is mostly valve control, that is, controlling the flow rate of the hydraulic system by controlling the opening size of the hydraulic multi-way valve so as to control the speed of the actuator. This structure of energy loss, the system heat.
The system uses pump-controlled hydraulic system to ensure the coordination of the engine and hydraulic system, the effective use of the engine power, to avoid unnecessary energy consumption , saving energy, to achieve the work of the institutions stepless regulation.
The system has excellent fretting, greatly reducing the impact of the hydraulic system, helping to protect the hydraulic system and hydraulic components, extending the service life of the hydraulic components and greatly improving the operation safety, reliability and work efficiency of the crane. This system operation and control of the electricity the way, truly intelligent machines, electrical, fluid integration and crane operations. System with retractable mechanism and electrical system telescopic single-cylinder latch function.
Second, an overview
The system through the electro-hydraulic proportional pilot-controlled displacement of the actuator to achieve the implementation of the movement speed changes. The system consists of a closed loop of the rotary circuit, open circuit of the main oil and auxiliary oil circuit composition.
Swing oil circuit using swash plate variable displacement piston pump and closed-loop quantitative motor circuit. The pump's oil outlet is connected to the motor's oil inlet, the motor's oil outlet is connected to the pump's oil inlet to form a closed circuit, and no valve is needed. The pump is changed by adjusting the angle of the variable pump Of the flow and pressure oil direction, thereby changing the rotary motor speed and direction of rotation. Therefore, good mobility and stable rotation. Variable displacement piston pump with a charge pump and charge device, which can effectively improve the pump speed and prevent pump suction empty.
The main oil routes include main and auxiliary lifting oil routes, luffing oil routes and telescopic oil routes. The main pump adopts inclined axis variable double pump, and independent variable control can meet the speed regulation requirements of various agencies under different working conditions of the crane. One of the constant power hyperbola not only depends on the pump's own set point but also on the other pump's load conditions. With power regulators and limit load regulation, the power regulator regulates the displacement of the pump associated with the working pressure and must not exceed the given drive power. Once overloaded, the control pressure output by the proportional pressure relief valve will swing back the dual pump, reducing flow and increasing pump absorption of engine power. Constant power pump override the pilot pressure control, therefore, the variable pump control curve shown in Figure.
The entire system for the pump speed control system, the use of advanced electro-hydraulic proportional pilot control technology, that is, the displacement of the pump is controlled by the pilot oil, the displacement of the size of the pressure by the pilot oil, and the pressure is proportional to the supply. The size of the pilot oil pressure is controlled by a proportional pressure relief valve, the proportional pressure relief valve according to the size of the solenoid current proportional to change the output pressure. The greater the displacement of the electronic remote control pilot handle, the greater the output current, the pressure of the proportional pressure reducing valve will also increase correspondingly. As a result, the displacement of the pump will increase and the actuator will move faster. On the contrary, the electronic remote control pilot The smaller the handle displacement, the slower the actuator will move. On the one hand, the operator controls the direction of movement of each actuator (luffing cylinder, telescopic oil cylinder, main and auxiliary lifting motors) through the main valve commutation; on the other hand, by changing the moving direction and displacement of the pilot handle, Pump displacement to control the actuator speed. Control of pressure can make double pump displacement stepless change, the greater the control pressure, the greater the flow, the faster the movement speed. Dual pumps can supply oil to each actuator independently, and can also be supplied to actuators after merging. The range of speed regulation is large and the stepless speed regulation can be realized with excellent fretting.
Third, the function introduction
1, rotary oil
Large tonnage of engineering crane rotary mechanism for the machine's handling performance, operating efficiency, system efficiency and structural force is essential, so in addition to using on-demand pump control circuit, quantitative motor drive to ensure slewing motion speed performance and Control of the stability, the agency's buffer performance and start-up performance has also given a comprehensive consideration. Slewing process can be smoothly controlled, so that equipment safety can be effectively guaranteed.
Rotary oil circuit is a closed loop, no valve, adjust the angle of the variable pump swashplate to change the flow of the pump and the direction of the pressure oil control rotary motor speed and direction of rotation. The pump has a charge pump and charge device, which can effectively increase the pump speed and prevent pump suction; with filters and luminous pollution indicators. Swivel buffer valve is set for its smooth performance.
Set the free-wheeling solenoid valve, its role is: During the lifting of heavy objects, especially when heavy objects will leave the ground, the boom will be subject to lateral pull, in order to prevent the boom from breaking, then press the free-wheeling Control switch so that the swing brake control solenoid valve and the free-slip solenoid valve at the same time there will be electricity, the swing motor two work port oil communication, while the rotary brake is also opened, so that the entire part of the float in the state, boom in the Wire rope pull automatically placed under the weight center of gravity, thus protecting the boom.
So slewing system has the following advantages:
A, smooth start and stop control features, through the electrical proportional control of the control characteristics of the slewing mechanism to start a smooth, slow pause, to ensure the stability of rotary operations, to avoid the impact.
B, a good pump speed control system, a wide speed curve, the speed of rotation from the engine speed and A4VG pump displacement product of the decision, at any stable engine speed or any pump swing angle can get a good flow control curve .
C, three-speed speed curve adjustment system control, the slewing speed can be three curves to choose control, the maximum swing angle of the pump can be the maximum limit of 33%, 66%, 100% swing pump swing angle control, so much Improve the operator's control accuracy.
2, the main, vice lifting oil Road
Lord, vice lifting mechanism built-in quantitative motor, small size, torsion big rejection. Its internal safety valve installed to protect the motor, which can effectively prevent the motor damage due to overload. With reference to Figure l and its serial number lifting (vice lifting is optional) Hydraulic System Description:
The main and auxiliary winch brake 6, 9 are normally closed, when the control of the main and auxiliary lifting pilot handle, the auxiliary pump 3 to the main control valve 3 to the main valve to change direction 13, while the proportional decompression The pressure oil output by the valve 4 swings the main pump 2 to a certain angle. At this time, the pressure oil in the main oil line is decompressed by the shuttle valve in the lifting balance valve 8 and 11 to open the winch brake 6 , 9, so as to normal lifting or lowering action.
When the pilot handle returns to neutral position, the pilot oil to the main valve 13 is closed and the main valve 13 is also returned to the neutral position. The main circuit pressure oil is returned from the main valve 13 to the tank 1 in the unloading state, so that the winch brake 6, 9 under the action of the brake spring through the oil drain back to the tank 1, so the brake 6, 9 under the action of the spring in a braking state.
The lifting balance valves 8 and 11 in the main and auxiliary lifting oil lines can effectively prevent the stalling phenomenon of the heavy objects during the decentralization process and ensure the steady and reliable lowering speed of heavy objects so as to improve the safety performance.
Lord, vice lifting mechanism built-in quantitative motor 7,10, small size, torsion big rejection. Its internal safety valve installed to protect the motor 7,10, can effectively prevent the motor damage due to overload.
Vice lifting through the quick connector 12 for optional switching.
3, luffing oil road
The maximum swing angle of the pump to the maximum gain can be obtained for the maximum limit of 33%, 66%, 100% of the hydraulic pump maximum swing angle control, declination using advanced gravity reduction principle, luffing balance valve descent with the pilot handle direct Control proportional valve, the pilot handle to control the luffing cylinder descent speed, when the luffing cylinder due to arm length or lifting causes luffing cylinder force increases to the set value, the luffing balance valve will be pressure compensation Control, with the increase of the amplitude of the cylinder and automatically slow down the speed to ensure the stability of the boom when the luffing drop jobs.
4, telescopic oil
The machine has a total of five main boom, single cylinder plus bolt expansion principle, by a telescopic cylinder driven four telescopic boom, telescopic sequence can be manually controlled or pre-set way for automatic control.
When the boom is extended, with the movement of the pilot handle, the cylinder pin will pin the cylinder with the selected boom and the arm pin will be pulled out. The opening of the multi-way reversing valve will increase gradually and the pressure oil will enter Telescopic cylinder rodless chamber, pushing the telescopic cylinder cylinder to drive the boom forward, the arm extended in place by the arm pin locked.
When the boom is retracted, with the movement of the pilot handle, the cylinder pin will pin the cylinder with the selected boom and the arm pin will be pulled out. The valve opening of the multi-way reversing valve will gradually increase and the pressure oil will enter Telescopic cylinder rod chamber, open the balance valve, telescopic cylinder cylinder driven boom retractable, the boom retracted by the arm pin lock.
Telescopic cylinder piston rod with cartridge head-balancing valve, ensures stability during retraction of the boom.
Hydraulic system uses a double loop design to avoid the boom in the electromagnetic valve damage telescopic cylinder can not be retracted.
5, auxiliary oil circuit
Auxiliary circuits include pilot control circuit, counterweight circuit, cooling system. Pilot control of the oil pressure system is set to 3Mpa, its main role is to provide power to the proportional pressure reducing valve and control the main reversing valve. Proportional pressure reducing valve for the quadruple, respectively, to control the variable displacement of dual pump and limit load regulation as well as the control of the luffing down conditions.
The system has automatic cooling function, equipped with a temperature sensor inside the fuel tank . Once the sensor detects that the oil temperature in the tank rises to the set temperature, the gear pump with load-sensing diverter valve drives the fan motor to rotate to cool the system. If the oil temperature is lower than the set temperature, the gear pump is in the low-pressure oil return state, and the fan motor stops rotating.
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