1 Introduction In the late 1980s, China developed a new type of component-hydraulic valve for hydraulic systems, and then began to use it in the hydraulic system of the combined machine tool, with good results.
The hydraulic system composed of the superposition valve has the advantages of compact structure, light weight, small integrated volume, convenient installation and maintenance, flexible configuration, less oil leakage and less noise.
2 Introduction of the superposition valve 2.1 Features The superposition valve and the general valve have little difference in the working principle, but have their own characteristics in the specific structure and connection mode, so it is a self-contained series. When the stacking valve is composed of the hydraulic system, no additional connecting parts are needed, and the valve body of the superimposed valve is directly connected to each other. Each superposition valve functions both as a control element and as a channel body. The position and number of the main oil passages of the superimposed valves of each size are the same as those of the corresponding main reversing valves. The superimposed valves of the same path series can be superposed to form different systems.
2.2 Technical Specifications The superimposed valve developed in China has five series of diameters. The nominal flow rate of each path is: 10L/min, nominal pressure: 20MPa minimum stable flow: 0.3. The hydraulic system with superimposed valve is designed to be more Intuitively explain the design process of the hydraulic system of the combined machine tool. Here is an example of the hydraulic system of the X6170Z diesel engine cylinder head line Ci station XWC-09-Ci horizontal double-sided combination drilling machine.
3.1 Machine Overview and Design Parameters The overall design of the XWC-09-Ci machine tool uses a mechanical slide and a hydraulic slide. One side of the hydraulic sliding table is used, the axial cutting force during machining is 26kN. The rapid moving speed of the sliding table is about 5m/min, the working speed is divided into two levels, and the first working speed is 0.045m/min. The speed is 0.02m/min. The machine tool is hydraulically positioned and clamped.
3.2 Analysis of the hydraulic system After understanding the general situation of the machine tool, the following analysis, judgment and selection of several key issues in the design of the hydraulic system.
3.2.1 System energy device selection and determination of a pump In the combined machine tool hydraulic system, the vane pump is used more, because the working pressure and flow range of the vane pump are more in line with the requirements of the combined machine tool hydraulic system, and the vane pump has Small size, smooth operation and so on.
In the feed line of the machine tool hydraulic pressure, when the slide table is rapidly fed and quickly retracted, a large flow rate and a small pressure are required; when the slide table is fed, a small flow rate and a large pressure are required. In the positioning clamping circuit of the machine tool hydraulic pressure, when the positioning clamping part moves, a large flow rate and a small pressure are required; when the positioning clamping is completed, only a large pressure and a leakage flow are required to be maintained.
In view of the above characteristics, the energy part of the hydraulic system mainly adopts a double metering pump or a variable pump. The double metering pump is used in this design. This is because the quality and performance of the double pump is more stable than that of the variable pump, and it is easy to manufacture and the system is safer. At the same time, when it is used on a general load machine, the temperature rise is not a big problem; to reduce the temperature rise, appropriate measures can be taken. Solve, for example, the unloading of the oil pump (when the slide table is not working, the large pump oil is unloaded through the relief valve Y-Fa6D-P/O).
2 Differential connection of cylinders In the hydraulic system of the machine tool, the slide cylinders are usually differentially connected. This type of connection allows the larger power components to move forward quickly with pumps of smaller flow sizes, while allowing the slides to move forward and backward at equal speeds. This design also uses a differential connection. When the slide cylinder is fast-forward, the oil discharged from the non-working chamber flows into the cylinder working chamber together with the oil from the oil pump via the check valve A-F10D-B/P.
3.2.3 Choice of “Import Throttling†and “Export Throttling†The “inlet throttling†or “exit throttling†can be applied in the hydraulic system of the machine tool. They have their own advantages and disadvantages, but the “import throttling†system is more reliable. There are few problems, so the design uses / import throttling '.
4 Determination of the action switching control mode The automatic or semi-automatic control of the action conversion of the hydraulic system of the machine tool is realized by mechanical, electrical and hydraulic cooperation. The control modes include stroke control, pressure control and time control.
Action requirements and conversion in the hydraulic feed system In this design, the slide is required to complete the following actions: fast forward y first-class work y second-level work y to stop at the dead stop iron 4s* rewind - to stay in place.
The motion conversion control process is as follows: fast forward y slide table stroke block iron pressure two-stage stroke speed control valve one gear y slide table first stage work y slide table stroke block iron pressure two-stage stroke speed control valve second gear y The secondary work of the sliding table - the work enters the dead stop iron, the slide stops, the pressure relay starts to delay, after 4s delay, the pressure relay sends the y slide retracts y to the original position, the stroke is under the pressure The travel switch is activated and the slide is stopped.
Action requirements and conversion in the hydraulic positioning and clamping system In this design, the positioning cylinder and the clamping cylinder are required to complete the following actions: the positioning cylinder pin y pin is completed, the stroke block is pressed down and the stroke switch is issued, and the y clamping cylinder is clamped to the y-clamp. After the pressure is completed, the pressure relay will start, the slide table will start working, and the pressure switch y cylinder will be released. When the release is completed, the pressure relay will send the y cylinder to pull the pin, the pullout is completed, the travel switch will be sent, and the hydraulic actions will be completed. .
From the above analysis, the design requires a two-stage speed control valve and three pressure relays and multiple stroke switch contacts. 3.3 Calculation and selection 3.3.1 Determination of slide cylinder diameter The technical parameters of the hydraulic slide are shown in Table 1. According to the comparison between the feed force and the maximum cutting force of the machine, we choose HY50A slide, the inner diameter of the cylinder is 125mm, the diameter of the piston rod is Table 1 Hydraulic slide technical parameters Model Feed force Cylinder inner diameter / Piston rod diameter Oil pump flow L/mm Fast forward speed Minimum feed 3.3.2 Determine oil pump flow Since the slide cylinder is differentially connected, its flow calculation formula is: V Forward cylinder forward speed, m/min. From the above formula, when the V-input is 0.045m/min, the flow is Qi=0. When positioning the cylinder latch, the flow rate is calculated as: according to the above values, it can be judged small The pump flow rate is not too large, tentatively set to 4L/min. It is also possible to calculate the total flow rate when the four clamping cylinders are clamped: jV clamping when the known slide table cylinder is fast forward at 5m/min, the required flow rate is 25L/ Min's double pump.
3.3.3 Determination of the motor The technical specifications of the standard pump device can be seen. When the diameter of the double 3.3.4 superimposed valve is selected according to the technical specifications of the superimposed valve, we use the superimposed valve of the blue 10 mm diameter. However, for the circuit of the positioning cylinder, since the flow rate is always small, a stacking valve of S6mm diameter can be selected.
3.4 Precautions when drawing the hydraulic system schematic diagram According to the electromagnet action (see Table 2), the following points should be noted when drawing the schematic diagram of the hydraulic system using the superposition valve: First, determine the function and pressure of the various valves in the system. Trail and so on. The diameter and connection dimensions between the connected blocks in a stack of valves must be the same.
In a stack of valves, the main reversing valve in the system (the main reversing valve is not a superimposed valve, which is a standard plate element) is mounted on the top, the bottom plate block for connecting the actuator parts is placed at the bottom, and the stacking valves are installed. Between the main reversing valve and the floor block, the order is determined by the system's operating requirements.
The interface on each stacking valve and the bottom plate block has different letters, different meanings. When drawing the schematic diagram, pay attention to the identification position of the above letters.
The position of the pressure gauge switch should be close to the floor block.
Some of the stacking valves are constrained in their mutual mounting position and cannot be modified at will.
4 Application Conclusion The application of the superposition valve to realize the design of the hydraulic system of the combined machine tool has been applied in some diesel engine factories for three years. This system overcomes the shortcomings of the hydraulic system with large oil leakage and high noise. It is easy to install and maintain, flexible in configuration, stable and reliable in operation. The effect is good. Has a wide range of promotional applications.
(Received on September 28, 2004) Fu Dongmei, the State Council, approved the construction of two nuclear power plants to promote China's nuclear power autonomy. The State Council approved the construction of the second phase of the Guangdong Lingao Nuclear Power Plant and the first phase of the Zhejiang Sanmen Nuclear Power Plant on the 21st, marking China's nuclear power. The construction of autonomy has taken substantial steps.
Member of the Political Bureau of the CPC Central Committee and Vice Premier of the State Council Zeng Peiyan stressed at the nuclear power development work conference that all relevant parties should combine nuclear power technology development, equipment manufacturing and project construction in accordance with the State Council's deployment, actively adopt advanced technology, and strive to achieve nuclear power industry independence. And localization. It is necessary to attach great importance to nuclear safety work, ensure the quality of nuclear power plant construction, and better meet the demand for power growth in economic and social development.
So far, China has 11 nuclear power units in operation or construction. While adhering to the self-reliance policy, we will actively introduce advanced technologies, improve nuclear power research and development capabilities, enhance nuclear power equipment manufacturing and nuclear fuel production capacity, and narrow the gap with the world's advanced level. In accordance with international standards, a relatively perfect nuclear safety management and nuclear accident emergency response system has been established. But at the same time, we must also see that the proportion of nuclear power in China's electricity supply is still very low. Existing nuclear power plants have many types of reactors, high cost, inadequate design and manufacturing capabilities, and imperfect management systems, which still restrict the development of nuclear power.
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