溢流阀与减压阀在原理、作用和结构上分别有什么不同？
参考答案：
相同点：都是由液压力与弹簧力进行比较来控制阀口动作；两阀都可以在先导阀的遥控口接远程调压阀实现远控或多级调压。
不同点：
1）不工作时溢流阀阀口常闭，进出油口不通；减压阀阀口常开，进出油口相通。
2）溢流阀由进口压力控制，阀口开启后保证进口压力稳定；减压阀由出口压力控制，工作时保证出口压力稳定。
3）溢流阀出口接油箱，先导阀弹簧腔的先导油经阀体内流道内泄至出口；减压阀出口压力油去工作，压力不为零，先导阀弹簧腔的先导油由单独的泄油口引回油箱。
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| My holiday is coming. Yesterday I asked my American friends about the best way to travel within the United States. They said it was best to go by 1 and gave me the 2 . To fly, of course, is the fastest way, but one can't see anything during a 3 except the blue sky and white clouds. So it is not very interesting to one who wants to see the 4 . Besides, airfare is very 5 . To travel by train is 6 , because passengers can walk and buy food and drinks on a train. They can also see cities and the country through the windows. But trains don't leave or 7 at a place every day, and don't go to many cities. To travel by bus, my friends tell me, is easy, cheap and convenient, though not so fast as traveling by plane or so 8 by train. You can find buses almost in every city, big or small. That makes travel arrangement easy. I take their 9 . Now I have decided to go to the east coast with an interesting 10 by bus. | |||
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