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发表于 2017-8-13 22:10:24
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【APS机械笔试题一(附答案)】
The graphic below shows a typical hydraulic circuit and some important components. Please explain firstly the principle of the whole system and then each simple component.
Brief answer:
Principle of the whole system:
This is the structure of a 4 way 3 position directional valve. The 4 ways mean that the whole system has A, B, P and T ways to connect the hydraulic pipes. 3 positions mean that the system has three working positions thus left position, right position and neutral (original) position.
When the neutral position is connected, the circuit is blocked up, P and T will be connected so the hydraulic oil will flow back in the tank, so the system doesn’t work.
When the left position is connected, P and A also B and T will be connected with each other, the oil will flow to the left side of the piston cylinder and push the rod to move outward, the oil in the right side will flow back through BT to the tank.
When the right position is connected, P and B also A and T will be connected with each other, the oil will flow to the right side of the piston cylinder and push the rod to move back. The oil in the left side will flow back through AT to the tank.
Simple component:
Hydraulic pump: supply fluid to the components in the system. According to the displacement there are constant pump and variable pump. The commonly used pumps are gear pump and vane pump. (If there is enough time, please also explain the principle of gear pump and vane pump)
One way valve: Valves are used to regulate, direct and coXXXol the oil and system by opening, closing or partially obstructing various passageways. By using one way valve in the system the oil can just flow in one direction, the opposite direction will be blocked up. In this system the one way valve is used after the pump in order to protect the oil from flowing backward in the pump. |
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