1. Working principle
It can be seen from Figure 1-1 that when the piston of the oil pump moves to the left at a certain speed under the action of external force F, the oil in the left cavity of the oil pump is pushed into the right cavity of the cylinder through the oil pipe; due to the pressure oil The piston of the oil cylinder overcomes the external force F2 and moves to the left at the speed of V2. The oil in the left cavity of the oil cylinder flows through the oil pipe to the right cavity of the oil pump. When the oil pump piston moves to the right, it produces a movement opposite to the above. In this way, if the oil pump piston is continuously moved to the left and right, the left and right movement of the oil cylinder piston can be generated. This is the simple working principle of hydraulic transmission.
Composition diagram of hydraulic system
1-2 is a schematic diagram of a simple hydraulic system. When the power machine (internal combustion engine or electric motor) drives the oil pump 3 to rotate, the hydraulic sleeve is sucked from the oil tank 2 and the pressure oil is output into the oil pipe 7. When the valve stem 11 of the reversing valve is in the middle position, the oil enters the reversing valve from the right end of the oil pipe 7 and returns directly to the oil tank through the oil pipe 10. When the valve stem moves to the right of the valve to the right, the pressure oil enters the reversing valve from the left end of the oil pipe 7 and enters the small cavity (left cavity) of the oil cylinder 6 through the oil tube 8 to push.
The piston 13 moves to the right. At this time, the oil in the large cavity (right cavity) of the oil cylinder 6 flows back to the oil tank through the pipeline 9, the left cavity of the directional valve, the oil pipe 10, and the oil filter 1. When the valve rod moves to the left end, the pressure oil will enter the large cavity (right cavity) of the oil cylinder 6 through the left branch pipe of the oil pipe 7, the directional valve, and the oil pipe 9, and push the piston rod 13 to extend. At this time, the oil in the small cavity (left cavity) of the oil cylinder enters the oil tank through the right branches of the pipelines 8 and 10 and the oil filter 1.
Safety valve is to prevent system overload. That is, when the piston rod is subjected to excessive resistance and the oil pressure reaches the designed maximum allowable pressure, the spring force in the safety valve 4 is overcome to open it, and the oil flows directly back to the oil tank. Otherwise, the oil pressure will be too high, which will cause damage to the components in the system and other accidents. The oil filter 1 is used to filter the impurities in the oil to reduce the wear of the hydraulic components during the movement.
From the above analysis, it can be seen that the hydraulic system is set up to complete a specific task. In fact, in order to meet the action requirements of various machines, various control elements have to be added to the hydraulic system. Therefore, a complete hydraulic system should be composed of the following parts;,
1. Power element-an oil pump. It is an energy conversion device used to convert mechanical energy into liquid pressure energy.
2. Actuator one by one oil cylinder or oil motor. It is an energy conversion device that converts liquid pressure energy into linear reciprocating or rotary motion mechanical energy.
3. Control elements-including direction, pressure, flow and other control valves. Used to control the transmission device to meet the requirements of the work.
4. Auxiliary components-including oil tank, oil filter, heater, cooler, accumulator, pipeline and joints, etc. Some are used to improve the quality of the transmission.
5. Working medium-oil. Used to transfer energy.
Connect and combine various hydraulic components with pipelines in a certain way to achieve the mechanical operation requirements, called hydraulic system. Drawing these elements and their relationship with specific simple symbols is called hydraulic system diagram (also known as oil circuit diagram). The hydraulic system diagram only reflects the basic relationship of the components in the system, and does not represent the specific structure.
In the hydraulic system diagram, commonly used symbols of hydraulic components are shown in Table 1-1.
