Hydraulic and pneumatic transmission is a pressure fluid (pressure oil or compressed air) as the working medium, to achieve a variety of mechanical transmission and automatic control of the transmission form.

Hydraulic transmission power, smooth movement, but because of the liquid viscosity, in the flow of the resistance loss is large, so it is not suitable for long-distance transmission and control;And pneumatic transmission because the air compressibility is big, and the working pressure is low (usually in 1.0MPa below), so the transmission power is not big, the motion is not as smooth as hydraulic transmission, but the air viscosity is small, the resistance in the transmission process is small, the speed is fast, the reaction is sensitive, so pneumatic transmission can be used for long-distance transmission and control.

The working principle of hydraulic and pneumatic transmission

Composition of hydraulic and pneumatic transmission systems

(1) Energy devices

A device that converts mechanical energy into the pressure energy of a fluid, usually a hydraulic pump or an air compressor.

(2) Execution device

A device that converts the pressure energy of a fluid into mechanical energy. It generally refers to a liquid (gas) pressure cylinder in a straight line of motion, a liquid (gas) pressure motor in a rotary motion, etc.

(3) Control and adjustment device

A device that controls and regulates the pressure, flow, and direction of fluid in a liquid (gas) pressure system.Such as relief valve, throttle valve, reversing valve, etc.The different combinations of these components form a liquid (gas) pressure system capable of performing different functions.

(4) Auxiliary devices

Refers to other devices other than the above three, such as oil tank, filter, water separator gas filter, oil mist, accumulator, etc., which play an important role in ensuring the reliable and stable operation of the liquid (gas) pressure system.

(5) Transmission medium

The fluid that transmits energy, namely hydraulic oil or compressed air.

Advantages and disadvantages of hydraulic and pneumatic transmission

1. Drag ability

(1) High power-mass ratio

(2) Force-mass ratio

2. Performance of control mode

Compared with hydraulic transmission, pneumatic transmission has the following advantages:

(1) Air can be taken from the atmosphere, no media costs and supply difficulties, will use more gas into the atmosphere, easy to deal with.Leakage will not seriously affect the work, will not pollute the environment.

(2) The viscosity of the air is very small, the resistance loss in the pipeline is far less than the hydraulic transmission system, suitable for remote transmission and control.

(3) Low working pressure, low material and manufacturing precision of components.

(4) Simple maintenance, safe use, oil-free pneumatic control system is especially suitable for the production process of radio components, food and medicine.

(5) Pneumatic components can be used according to different occasions, the corresponding materials, so that the components can be in the harsh environment (strong vibration, strong impact, strong corrosion and strong radiation, etc.) to carry out normal work.

Compared with electrical and hydraulic transmission, pneumatic transmission has the following disadvantages:

(1) The signal transmission speed of pneumatic transmission device is limited to the speed of sound (about 340m/s), so its working frequency and response speed is far inferior to that of electronic devices. Moreover, the signal has to generate large distortion and delay, and it is not convenient to form a more complex loop, but this disadvantage will not cause difficulties in the industrial production process.

(2) The compressibility of air is much greater than that of hydraulic oil, so it is not as good as hydraulic transmission in terms of response ability and stability of working speed.

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