Created on:2021-09-09 14:09

Construction machinery_ Maintenance of excavator_ Improvement of hydraulic control system

Construction machinery_ Maintenance of excavator_ Improvement of hydraulic control system

Realizing the electro-hydraulic proportional control and remote wireless control of the excavator can greatly reduce the repeated operation labor of the driver and liberate the excavator driver from the traditional lever operation and harsh working environment. Based on the above ideas, the lever operating system of a WYI. 5 hydraulic excavator is refitted into an electro-hydraulic proportional control hydraulic system, and the control of the whole vehicle is realized based on E1 mobile vehicle controller( 1) Hydraulic system of WYI. 5 excavator

The hydraulic system of WYI. 5 excavator is composed of oil tank, triple gear pump (one 3ml / R, two 8ml / R), multi-channel, throttle valve, boom hydraulic cylinder, stick hydraulic cylinder, bucket hydraulic cylinder, working device deflection hydraulic cylinder, bulldozer hydraulic cylinder, left and right, complete machine swing motor, radiator and filter. The bulldozer supply oil is completed by a 3ml / R gear pump alone. When the bulldozer does not work, its high-pressure oil directly returns to the oil tank. A reversing valve is installed behind the control valve of the rotary motor of the whole machine to realize the oil circuit switching control between the rotary motor of the whole machine and the deflection hydraulic cylinder of the working device. Other hydraulic systems are typical double pump, double circuit, medium oil return and confluent systems.

(2) Improvement of electric hydraulic system

① The electro-hydraulic proportional hydraulic system is designed to realize the electro-hydraulic proportional control of each mechanism, and a set of electric control system is connected in parallel without changing the function of the original lever control system. For the sake of safety, the two systems are designed not to work at the same time. In terms of priority, the lever control system cannot be used when the electronic control system works, and the lever control system automatically returns to normal work when the electronic control system stops working. As shown in Figure K, in order to realize this function, two position and two-way solenoid directional valves 1 and 2 are selected to realize the switching of high-pressure oil in electric control system and lever control system. The control of the solenoid valve is based on software programming, and its response time and response speed have nothing to do with the proficiency of the operator. Therefore, the solenoid directional valve 3 is selected to realize the unloading (reflux) when the whole system is not working. Solenoid directional valve 4 is used for the confluence of two pumps in the system. When the original lever control system lifted the boom, it was found that it dropped briefly and then lifted normally. The reason is that when the hydraulic system does not work, all directional valves are in the middle oil return position, and the pressure at the pump outlet is in the low pressure state. When the boom is to be lifted, the directional valve is switched to the lifting position. At this time, the pressure in the pipeline between the pump outlet and the lever control valve is still in the low pressure state, and the hydraulic oil in the lower chamber of the boom hydraulic cylinder should support the whole boom, stick The gravity of the bucket and its hydraulic cylinder has considerable pressure, so when the change-over valve is just switched to the lifting position, the hydraulic oil in the lower chamber of the boom hydraulic cylinder will flow to the pipeline system with low pressure, which shows that the boom drops early; With the operation of the gear pump, the pressure of the system increases continuously. When it is equal to the pressure in the lower chamber of the boom hydraulic cylinder, the boom stops falling; After that, the system pressure is gradually higher than the pressure in the lower chamber of the boom hydraulic cylinder, and the boom begins to lift. The time of this process is very short, and the decline range of boom is not large, but it is a potential safety hazard for excavator operation. Therefore, a hydraulic control check valve 5 is added in the new electric control system design to ensure the safety and accuracy of boom lifting. The design of other control systems basically adopts the scheme of the original lever control system. Its working principle is shown in Figure K.

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② After consulting a large number of data and comparing the hydraulic valve samples, the hydraulic valve body of Foshan meikemas Hydraulic Co., Ltd. is finally selected.

The function of the slide valve is shown in Figure K, which is A-type directional valve. The direct acting electromagnetic proportional valve that controls the action of each actuator can only be selected in two models with diameter of 6 and 10. In order to reduce the design difficulty and processing cost of hydraulic valve plate, the directional valve is also selected in diameter 6 and 10. In order to reduce the loss of coil burning caused by misoperation, wet replaceable coil electromagnet is selected. The minimum stable speed of l375 diesel engine matched with the hydraulic pump in Figure 7-11 is less than 650r / s, the maximum speed is 2650r / s, and the minimum fuel consumption point in the external characteristic curve is 1950r / s. The displacement of a single gear pump is 8ml / R. it can be calculated that the flow of directional valves 1, 2 and 3 should be 5.2 ~ 21.2l/min, and the economic fuel consumption flow is 15.6l/min. The flow of directional valve 4 is twice that of directional valves 1, 2 and 3. According to the characteristic curve of type a wet replaceable coil electromagnet directional valve with diameter 6 and 10, it can be seen that the flow directions P-A and p-b. when the flow of directional valve with diameter 6 and 10 is less than 20L / min, the pressure drop difference is small, both between 0.1 and 0.2MPa; When the flow is greater than 20L / tnin, the pressure drop of 6-way directional valve increases rapidly with the increase of flow. Therefore, the directional valves 1, 2 and 3 adopt 6-way diameter, i.e. 3we6a-61b / cg24n9zsl; The directional valve 4 adopts 10 diameter, i.e. 3we10a-31b / cg24n925l.

There are six actuators in the excavator (left travel, right travel and complete machine rotation motor); The control of boom, stick and bucket (hydraulic cylinder) adopts proportional directional valve, and the function of proportional directional valve is E-type as shown in Figure K. Because the bucket trajectory of the electric excavator needs to be accurately controlled, the 4wre proportional directional valve with electrical feedback of valve core position is selected for the control of boom, stick and bucket hydraulic cylinder. Ordinary 4wra proportional directional valve is used for left travel, right travel and complete machine rotation motors.

The flow of a single pump is between 5.2 ~ 21.2l/min, and the economic fuel consumption flow is 15.6l/min. Combined with the actual working conditions of the hydraulic excavator, each motor is basically supplied by a pump during walking; The whole vehicle has a large moment of inertia during rotation, and the impact vibration generated when stopping rotation will have a great impact on the service life of vehicle rotating parts, so the rotation speed should not be too large, that is, double pump confluence should not be used. Combined with the characteristic curves of flow, input value and valve pressure drop of 6-way, 10-way 4wra proportional directional valve, it can be seen that under the condition of low control accuracy requirements, the proportional directional valve with 6-way and nominal flow of 17L / min can meet the requirements of left travel, right travel and rotary motor of the whole machine, so 4wre6e20-10b / 24n24 / M proportional directional valve is selected.

According to the actual working conditions of the hydraulic excavator, the oil supply of the boom, stick and bucket hydraulic cylinder has the condition of double pump confluence. The flow of the control valve is 5.2 ~ 21.4l/min for single pump oil supply and 10.2 ~ 42.4l/min for double pump oil supply, and the corresponding economic fuel consumption flow is 15.6l/min or 31.2l/min. Combined with the analysis of the characteristic curves of flow, input value and valve pressure drop of 6-way and 10-way 4wre proportional directional valves, it can be seen that all curves are the most straight between 30% ~ 80% of their input value, with good linearity and easy to realize accurate control. In addition, when realizing the electro-hydraulic proportional control of excavator, it is hoped that the total pressure drop on the shoulder at the inlet and outlet of the hydraulic valve will be the smallest. Combined with the above data and principles, the proportional directional valve with 10 diameter and nominal flow of 64l / min is selected, i.e. 4wre10e64-10b / 24za / M proportional directional valve.

The selection of other overflow valves, throttle valves, one-way throttle valves and are determined according to the directional valves connected with them and the designed working pressure and flow of the original machine.

(3) Summary

After the transformation of the electro-hydraulic proportional control hydraulic system of the excavator, the system control adopts the E1 mobile vehicle controller of German inter control company. The software is developed and debugged successfully. It can be operated by short-range wired remote control or automatically complete the predetermined actions according to the program, realizing all the functions that the original lever control system can complete, It lays a solid foundation for realizing the remote control operation of excavator in the next step.

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