1. Working principle
When the piston of the oil pump moves to the left at a certain speed under the action of an external force F, the oil in the left cavity of the oil pump is pushed into the right cavity of the oil cylinder through the oil pipe; due to the push of the pressure oil, the piston of the oil cylinder overcomes the external force F2 , Move to the left at the speed of V2, the oil in the left cavity of the oil cylinder flows into the right cavity of the oil pump through the oil pipe. When the oil pump piston moves to the right, the opposite movement is produced. In this way, if the oil pump piston is continuously moved left and right, the left and right movement of the oil cylinder piston can be produced. This is the simple working principle of hydraulic transmission.
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 directly returns to the oil tank through the oil pipe 10. When the valve stem moves to the right to the right end of the valve, 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 pipe 8, and pushes.
The piston 13 moves to the right. At this time, the oil in the large cavity (right cavity) of the cylinder 6 flows back to the oil tank through the pipeline 9, the left cavity of the reversing 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 cylinder 6 from the left branch pipe of the oil pipe 7, the reversing valve, and the oil pipe 9, and push the piston rod 13 out. At this time, the oil in the small cavity (left cavity) of the oil cylinder enters the oil tank through the right branch pipes of pipelines 8 and 10 and the oil filter 1.
Safety valve is to prevent system overload. That is, when the piston rod receives excessive resistance and the oil pressure reaches the maximum allowable pressure of the design, it overcomes the spring force in the safety valve 4 to open it, and the oil flows directly back to the oil tank. Otherwise, the oil pressure is too high, it will cause the damage of various parts in the system and other accidents. The oil filter 1 is used to filter out the impurities in the oil, so as to reduce the abrasion of the hydraulic parts during the movement.
It can be seen from the above analysis that the hydraulic system is set up to complete a certain specific task. In fact, in order to meet the requirements of various mechanical actions, various control elements are added to the hydraulic system. Therefore, a complete hydraulic system should consist 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. The actuator is one oil cylinder or oil motor. It is an energy conversion device that converts liquid pressure energy into linear reciprocating or rotating mechanical energy.
3. Control components-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 fuel tanks, oil filters, heaters, coolers, accumulators, pipelines and joints, etc. Some are used to improve the quality of the transmission.
5. Working medium-oil. Used to transfer energy.
Various hydraulic components are connected and combined with pipelines in a certain way to meet the requirements of mechanical operations, which is called a hydraulic system. Use specific simple symbols to draw a diagram of these components and their relationships, which is called a hydraulic system diagram (also known as an oil circuit diagram). The hydraulic system diagram only reflects the basic relationship of the components in the system, not the specific structure.
