The hydraulic system consists of hydraulic pumps, hydra […]
The hydraulic system consists of hydraulic pumps, hydraulic control valves, hydraulic actuators (hydraulic cylinders and hydraulic motors, etc.) and hydraulic accessories (pipes and accumulators, etc.). The hydraulic pump converts the mechanical energy into the pressure energy of the liquid. The hydraulic control valve and hydraulic accessories control the pressure, flow and flow direction of the hydraulic medium, and transmit the pressure energy output by the hydraulic pump to the actuator, and the actuator converts the liquid pressure energy into mechanical energy To complete the required action.
Working principle The electric motor drives the hydraulic pump to suck oil from the oil tank, and the hydraulic pump converts the mechanical energy of the electric motor into the pressure energy of the liquid. The hydraulic medium enters the left cavity of the hydraulic cylinder through the throttle valve and the reversing valve through the pipeline, pushing the piston to drive the worktable to move to the right, and the hydraulic medium discharged from the right cavity of the hydraulic cylinder flows back to the oil tank through the reversing valve. After the direction of the reversing valve, the hydraulic medium enters the right cavity of the hydraulic cylinder, causing the piston to move to the left and pushing the worktable to move in the opposite direction. Changing the opening of the throttle valve can adjust the movement speed of the hydraulic cylinder. The pressure of the hydraulic system can be adjusted by an overflow valve. When drawing the hydraulic system diagram, for the sake of simplicity, the prescribed symbols are used to represent hydraulic components. This symbol is called a functional symbol.
The basic circuit is a typical oil circuit composed of related hydraulic components to complete specific functions. Any hydraulic transmission system is composed of several basic circuits, each of which has a certain control function. Several basic circuits are combined to control the movement direction, working pressure and movement speed of the actuator according to certain requirements. According to different control functions, the basic loop is divided into pressure control loop, speed control loop and direction control loop.
Pressure control circuit A circuit that uses a pressure control valve (see hydraulic control valve) to control the pressure of the entire system or a partial range. According to different functions, the pressure control loop can be divided into four loops: pressure regulation, pressure transformation, pressure relief and stabilization. (1) Pressure regulating circuit: This circuit uses an overflow valve to adjust the highest constant pressure of the hydraulic source, and the overflow valve plays this role. When the pressure is greater than the set pressure of the overflow valve, the opening of the overflow valve is enlarged to reduce the output pressure of the hydraulic pump and maintain the system pressure basically constant. (2) Variable pressure circuit: It is used to change the pressure of the local range of the system. If a pressure reducing valve is connected to the circuit, the pressure after the pressure reducing valve can be reduced; The pressure is higher than the hydraulic pressure. (3) Pressure relief circuit: When the system does not require pressure or only low pressure, the pressure relief circuit makes the system pressure drop to zero pressure or low pressure. (4) Voltage stabilizing circuit: used to reduce or absorb pressure fluctuations generated in a local range in the system and maintain the system pressure stable, for example, using an accumulator in the circuit.
Speed control loop A loop that controls the movement speed of the actuator by controlling the flow of the medium. According to different functions, it is divided into speed control loop and synchronization loop. (1) Speed control circuit: used to control the movement speed of a single actuator. You can use a throttle valve or a speed control valve to control the flow. The throttle valve in the schematic diagram of the hydraulic transmission system of the simple grinder plays this role. . The throttle valve controls the flow of the hydraulic pump into the hydraulic cylinder (the excess flow flows back to the tank through the overflow valve), thereby controlling the movement speed of the hydraulic cylinder. This form is called throttle speed regulation. The speed can also be adjusted by changing the output flow of the hydraulic pump, which is called volumetric speed control. (2) Synchronous circuit: a circuit that controls the synchronous operation of two or more actuators, for example, the method of rigidly connecting two actuators to ensure synchronization; use a throttle valve or a speed control valve to adjust the two actuators separately Make the flow of the hydraulic cylinder equal to ensure synchronization; connect the pipelines of the hydraulic cylinders in series to ensure the same flow into the two hydraulic cylinders, so that the two hydraulic cylinders are synchronized.
Direction control circuit A circuit that controls the direction of the flow of hydraulic media. The circuit that uses the directional control valve to control the movement direction of a single actuator so that it can move or stop in the forward and reverse directions is called the reversing circuit. The reversing valve in the schematic diagram of the hydraulic transmission system of the simple grinder plays this role. When the actuator is stopped, the circuit that prevents the actuator from moving due to leakage caused by external factors such as load is called a locking circuit.
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