What are the methods to realize flow control in hydraulic transmission system?

There are two ways to realize flow control in hydraulic transmission system: throttle valve and speed regulating valve.

The flow control valve is a kind of hydraulic control valve, which controls the movement speed of the actuator by changing the flow area of the valve port. Commonly used flow valves are throttle valve and speed regulating valve. The key component used is the throttle valve.

Hydraulic transmission is a hydraulic system composed of hydraulic components (hydraulic oil pump), hydraulic control components (various hydraulic valves) and hydraulic executive components (hydraulic cylinders and hydraulic motors). ), hydraulic accessories (pipelines, accumulators, etc. ) and hydraulic oil.

component

1) Power element, namely hydraulic pump, whose function is to convert the mechanical energy of the prime mover into kinetic energy of liquid pressure (manifested as pressure and flow), and its function is to provide pressure oil for the hydraulic system, which is the power source of the system.

2) The executive element refers to a hydraulic cylinder or a hydraulic motor, and its function is to convert hydraulic energy into mechanical energy and do external work. The hydraulic cylinder can drive the working mechanism to realize reciprocating linear motion (or swing), and the hydraulic motor can complete rotary motion.

3) Control elements refer to various valves that use these elements to control and adjust the pressure, flow and direction of the liquid in the hydraulic system, so as to ensure that the actuator can work as expected.

4) Auxiliary components, including oil tank, oil filter, pipeline and joint, cooler, pressure gauge, etc. Their function is to provide necessary conditions for the normal work of the system and facilitate monitoring and control.

5) Working medium, namely transmission fluid, is usually called hydraulic oil. The hydraulic system realizes movement and power transmission through the working medium. In addition, hydraulic oil can also lubricate moving parts in hydraulic components.

basic circuit

1. Pressure control circuit

A circuit that uses a pressure control valve (see hydraulic control valve) to control the pressure of the whole system or a local range. According to different functions, the pressure control circuit can be divided into four circuits: pressure regulation, pressure transformation, pressure relief and voltage stabilization.

① Pressure regulating circuit: This circuit uses an overflow valve to set the highest constant pressure of the hydraulic source, and the overflow valve in the figure plays this role. When the pressure is greater than the set pressure of the relief valve, the opening of the relief valve increases to reduce the output pressure of the hydraulic pump and keep the system pressure basically constant.

② Variable pressure circuit: used to change the pressure in the local area of the system. If the pressure reducing valve is connected to the circuit, the pressure behind the pressure reducing valve can be reduced; Connecting a supercharger can make the pressure behind the supercharger higher than the pressure of the hydraulic source.

(3) Pressure relief circuit: When the system does not need pressure or only needs low pressure, the system pressure is reduced to zero pressure or low pressure through the pressure relief circuit.

④ Pressure stabilizing circuit: used to reduce or absorb the pressure fluctuation in the local area of the system and keep the system pressure stable, such as using an accumulator in the circuit.

2. Speed control loop

A loop that controls the movement speed of the actuator by controlling the flow rate of the medium. According to different functions, it is divided into speed regulating circuit and synchronous circuit.

① Speed regulating circuit: It is used to control the movement speed of a single actuator, and the flow can be controlled by throttle valve or speed regulating valve, as shown in the figure. The throttle valve controls the flow of the hydraulic pump into the hydraulic cylinder (the excess flow flows back to the oil tank through the overflow valve), thus controlling the movement speed of the hydraulic cylinder. This form is called throttling speed regulation. It can also be used to change the output flow of hydraulic pump to speed regulation, which is called volume speed regulation.

② Synchronization loop: a loop that controls the synchronous operation of two or more actuators, for example, by rigidly connecting the two actuators to ensure synchronization; Adjust the flow of two actuators with throttle valve or speed regulating valve to make them equal and ensure synchronization; Connect the pipelines of the hydraulic cylinders in series to ensure the same flow into the two hydraulic cylinders, so as to synchronize the two hydraulic cylinders.

3. Direction control loop

A circuit for controlling the flow direction of hydraulic medium. The circuit that uses directional control valve to control the movement direction of a single actuator so that it can move forward or backward is called reversing circuit, and the reversing valve in the figure plays this role. When the actuator stops, the circuit that prevents the actuator from acting due to leakage caused by external factors such as load is called a blocking circuit.