Analysis of hydraulic synchronous circuit of the h

Analysis of hydraulic synchronous circuit of a heavy-duty lifting device

Abstract: a synchronous hydraulic circuit of the rolling mill frame lifting device is designed, and the synchronous circuit is changed to adopt double hydraulic motors for speed regulation. The reason and working principle of using this circuit are described. Finally, the performance of AMESim software is analyzed by modeling

key words: synchronous loop; Dual hydraulic motors; AMESim

Introduction

hydraulic synchronous circuit is an important basic functional circuit of hydraulic system, which is mainly divided into three categories: throttle speed regulation synchronous circuit, volume speed regulation synchronous circuit and volume throttle speed regulation. The latter two belong to the special form of speed regulating circuit. This paper introduces a synchronous hydraulic circuit of the lifting device of the rolling mill frame, which weighs about 10t. The circuit adopts volume speed regulation circuit and uses double hydraulic motors with rigid connection. The hydraulic model of the system is established with AMESim software, and its synchronization performance is analyzed by simulation on a large scale

1 hydraulic system model

amesim is a professional hydraulic system design and simulation software. Its rich hydraulic component library is very convenient for the drawing of hydraulic system diagram. And it has excellent simulation and analysis performance. The hydraulic system diagram of the frame lifting device established by AMESim is shown in Figure 1. In order to facilitate the simulation and simplify the system, the electromagnetic directional valve in the original hydraulic schematic diagram is omitted, and the flow valves 1 and 2 are connected with the hydraulic source by direct connection

Figure 1 hydraulic system model of synchronous hydraulic cylinder

2 working principle and analysis

two piston rods of the same type of hydraulic cylinder are fixed on both sides of the rolling mill frame, and the extension of coating technology is innovated by the piston rod to control the lowering and rising of the frame. The rolling mill stand is used for installing rollers, and its placement accuracy directly affects the installation accuracy of rollers. If placed incorrectly, parts may be damaged, so the lifting and lowering of the frame requires two hydraulic cylinders to be in synchronous motion. Therefore, this lifting hydraulic circuit is required to be a two-way synchronous circuit. Because the rolling mill frame has a large mass (about 10t) and belongs to heavy load, volume speed regulation must be used to meet the requirements. Compared with throttling speed regulating circuit, volume speed regulating has the advantages of no overflow loss and higher efficiency of the system. The circuit adopts a rigidly connected synchronous hydraulic motor. The two motors have the same structure and displacement, and are plunger hydraulic motors with high volumetric efficiency. It plays the role of equal flow diversion device in the circuit. Flow valves 1 and 2 are essential to regulate the speed of the hydraulic cylinder. The accumulator helps to fill the system with oil to stabilize the working pressure

in actual use, a manual electric switch should be installed on the hydraulic wire to control the source pressure cylinder of the experimental motor, and a proximity switch is installed on the cylinder to control the upper and lower positions of the hydraulic cylinder. When hydraulic cylinders 12 and 13 rise, oil is injected into the lower chamber, and overflow valve 5 stabilizes the pressure of the oil return circuit. When it rises to the specified position, the solenoid directional valve is in the middle position, the solenoid valve is in the Y middle position function, and the oil flows back to the oil tank. Check valves 7 and 9 fix the hydraulic cylinder at the specified position

due to the heavy load, and the action direction of the hydraulic cylinder is consistent with the movement direction when it moves downward, there will be weight loss and the hydraulic cylinder will lose control, resulting in asynchrony. Therefore, balance valves 10 and 11 should be added to the oil return circuit to generate oil flow resistance. When the hydraulic cylinder rises to lift the load, the oil enters the lower chamber from the check valve in the balance valve. When the hydraulic cylinder is lowered to the rack, the upper chamber of the hydraulic cylinder is filled with oil. Due to a certain pressure on the oil inlet circuit, this pressure oil enters the balance valve from the control oil circuits a and B, pushes the main spool of the balance valve away, and the oil discharged from the hydraulic cylinder is discharged through the opening of the main spool of the balance valve. If the frame drops too fast and exceeds the speed determined by the oil inlet volume of the hydraulic cylinder, the pressure of oil inlet Circuits A and B will be reduced. At this time, the opening volume of the balance valve core will be reduced under the action of the spring, which will increase the oil return resistance of the hydraulic cylinder, thus preventing the increase of the lowering speed of the hydraulic cylinder

it should be noted that the balance valve cannot be replaced by the remote control one-way sequence valve with the secondary oil port connected to the oil return circuit. Because the pressure of the hydraulic pump determines the opening of the balance valve in use, the pressure pulsation of the pump will make the opening of the balance valve increase or decrease. In addition, during the falling process of the frame, the friction between the valve core and the valve body, the vibration of the spring, etc. will affect the flow stability of the balance valve. And because of the heavy load, the general one-way sequence valve will not be able to use due to vibration. Therefore, the balance valve used in this system must be specially designed

in order to verify the performance of this two-way synchronous hydraulic circuit, a simulation was carried out in AMESim. The speed curves of two hydraulic cylinders can be obtained by simulation. If the speed curves of the two hydraulic cylinders coincide or the error can be ignored, this synchronous circuit is reasonable

Figure 2 hydraulic cylinder speed curve

in Figure 2, 1 is the solid line representing the piston lowering speed of hydraulic cylinder 12, and 2 is the dotted line representing the piston lowering speed of cylinder 13. It can be seen that line 1 and line 2 overlap, which shows that their descent speed is stable and synchronous. At t=140s, the speed is zero, indicating that it reaches the lowest end, and there is a certain speed fluctuation, indicating that the piston has an impact at the end, which is also in line with the actual situation. The impact can be ignored in this system. If the impact is too large, buffer devices in Asia, especially in China, need to be set

3 conclusion

the above is a hydraulic synchronization circuit in actual production, and its synchronization effect is good from the perspective of application. It not only meets the requirements of adjustable speed, but also has an effective locking device, and the application of balance valve ensures the stability and reliability of the lowering frame. This volume speed regulating circuit has no leakage, which helps to save energy. However, due to the use of specially designed balance valve and hydraulic motor with high volumetric efficiency, the cost is high. In the promotion and use, it is also necessary to combine with the actual situation to select the appropriate components

references

[1] Liu Zhong Hydraulic transmission principle, fault diagnosis and elimination of construction machinery China Machine Press, 2005

[2] Huang Haitao Design and application of hydraulic cylinder synchronization circuit Fluid transmission and control, 2006, (5)

[3] zhoushichang Hydraulic system design atlas China Machine Press, 2003

[4] Fu Yongling AMESim system modeling and Simulation - from entry to proficiency Beijing University of Aeronautics and Astronautics Press, 2006

about the author: shaoxiaoguang (1983 -), male, master candidate of Kunming University of technology, majoring in fluid transmission and control

E－mail:ok_ 008@。

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mailing address: Institute of fluid transmission and control, School of mechanical and electrical engineering, Kunming University of technology, Yunnan

zip code: 650093 (end)