Working principle of hydraulic system of shield machine
Working principle of hydraulic system of shield machine
The working condition of shield machine is complex, and the geological conditions are very different. The cutterhead is the key component of shield tunneling. The drive of shield cutterhead has the characteristics of high power, large torque variation and wide speed range.
The speed regulating circuit of pump controlled motor has high efficiency and speed stiffness. It is an advanced control method to drive multiple high-speed and small torque hydraulic motors in parallel with multiple large flow variable pumps, and then drive the cutterhead through reducer and gear transmission mechanism. Its characteristic is that the system composition is simple, safe and reliable, and the load change has little influence on the cutter head speed. HD hydraulic control proportional variable pump is adopted, and centralized control is carried out through one control module, which can realize the proportional control, constant power control and safety pressure control under different working modes of the whole system. Through this control module, the simultaneous regulation of multiple pumps and motors and the simultaneous setting of safety pressure can be realized, so the system structure is simplified and the reliability is high.
图16所示液压系统是应用在某地铁隧道施工的盾构刀盘驱动液压系统。
整个液压系统由3个回路组成，包括主驱动回路、补油回路和液压控制回路。主驱动回路是闭式回路，由两台比例变量泵(HD型，最大排量750mL/r)驱动8台变量马达(两点液控型，最大排量500mL/r，高速挡排量300mL/r)。液压控制模块9提供控制油，实现主驱动泵排量的比例控制和恒功率控制以及液压马达排量的控制。调速阀10和减压阀11调节进入马达的控制油流量和压力，换向阀12实现马达排量的两挡控制。蓄能器4用于减少补油油路的压力脉动，溢流阀5设定补油及主驱动泵的换油压力。
The hydraulic control module 9 has three functions: ① adjust the displacement of the main drive pump through the proportional overflow valve; ② Set the maximum working pressure of the system through the sequence valve and overflow valve; ③ The constant power control of the two variable displacement pumps in the system is realized through the power limiting valve, that is, under the feedback system pressure, the displacement of the main drive pump is adjusted to reduce the speed of the cutter head, and at the same time, the system pressure can be reduced to reduce the torque borne by the cutter head. The module adopts the lv06 power limiting valve of Rexroth company, as shown in Figure 17. This power limiting valve is composed of a direct acting overflow valve and a stepped valve core 1. The two ends of the stepped valve core are valve opening control spring 2 and combined adjustment spring 3 respectively, and the adjustment spring resists the hydraulic pressure acting on the stepped valve core. The control port PST is connected with the pilot control oil port of the main drive pump, and the high pressure port PhD is connected with the main circuit through the shuttle valve. If the system pressure exceeds the set pressure of the power limit valve, the step valve core moves to the right to compress the adjusting spring, which reduces the pressure on the valve opening control spring, and the valve port overflows, reducing the control pressure, so that the main drive pump maintains constant power output.
In order to stabilize the pressure of the control circuit, the constant pressure screw pump is selected for the pilot hydraulic pump 8 in Figure 16, that is, the control oil variable pump, and the speed regulating valve and pressure reducing valve are used in the circuit.
