The hydraulic system is composed of the following five parts:

1. Hydraulic oil tank (oil tank) ;

2. The pump (Hydraulic Pump) ;

3. The hydraulic control valve (Hydraulic Control Valve) ;

4. Hydraulic actuator (hydraulic actuator) ;

5. Hydraulic accessory .

1-1-1 Components Function of Hydraulic Control System P 331 TOP

( I ) Hydraulic Tank P 331

( Two ) hydraulic pump (Hydraulic Pump)

( Three ) hydraulic control valve (Hydraulic Control Valve)

( Four ) hydraulic actuator (Hydraulic Actuator)

( Five ) hydraulic parts subsidiary (Hydraulic Accessory)

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Features of 1-2 hydraulic control system P 337 TOP

Comparison of characteristics of 1-2-1 hydraulic pressure and air pressure

n1. Compressibility: The air is compressible, so it is not easy to control in the control accuracy, especially at low speed.

n2. Cleanliness: The compressed air is clean, but the exhaust gas will have lubricating oil mist. Leakage of hydraulic oil can cause contamination.

n3. Pressure range: Generally, the air pressure is low and the speed is fast, and most of them are used for small output and fast impact control.

The hydraulic pressure is high pressure and slow speed, which is mostly used for high output and high density energy.

n4. Lubricity: The oil has lubricity and less wear on the parts; the air pressure system must be equipped with drying, filtering and oil feeding devices.

n5. Explosion-proof: hydraulic oil is flammable, compressed air10bar or lessThere is no danger of explosion.

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Advantages of 1-2-2 hydraulic device P 337 TOP

n-1. small size and output ( torque ) large, high power density (power density)

n2.Can automatically adjust the output

n3. It is easy to achieve stepless control or adjustment of speed, torque, stroke, etc.

n-4. Overload (over load) protection is very simple

n5. Remote control and easy automation

n6.Can be used for continuous or intermittent exercise

n-7. The tool durability

n8.Good reversibility

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Disadvantages of 1-2-3 hydraulic device P 338 TOP

n1. Poor piping may cause oil leakage, pollute the environment and cause fire

n-2. hydraulic oil ViscosityWill change due to changes in oil temperature, affecting speed control

n3. The installation of pipeline is not as simple as electrical wiring

n-4. drive actuator slow

n5. The horsepower of the motor needs to be increased

n6. High processing accuracy and installation technology, cost is more expensive

n7. Others: If the oil contains air bubbles, it will cause the hydraulic device to malfunction. Impurities in the oil can damage components and cause failures, so a filter is required in the system to remove the impurities. The installation cost is high, the volume is large, the weight is heavy, and there are problems such as hydraulic oil pollution.

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1-3 Basic Principles of Hydraulic Control System P 339 TOP

[ Pascal's law (Pascal's Law)]

n1. The direction of pressure is perpendicular to the fluid contact surface .

n2. The pressure of each point in the fluid in a stationary state should be equal in all directions.

n3. In a closed container, when any point in the liquid is subjected to pressure, this pressure will be transmitted to other parts of the container with the same pressure intensity.

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Hydraulic jack principle P 342 TOP

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Flow change of choke port and orifice P 343 TOP

Choke port:

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Orifice (Orifice , opening limiting ) : P 345 the TOP

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Application examples of choke and orifice P 347 TOP

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Laminar flow (Laminar Flow) , turbulence (Turbulent Flow) and the pipe, the valve pressure loss P348 laminar flow : when the flow rate is small, the fluid distributionlayerflow, and do not mix, calledlaminar flow, referred to as sheet orstream TOP

Turbulent flow: When the flow velocity increases to a large value, many small vortices are generated in the flow field, which is called turbulent flow.

Reynolds number TOP

D : diameter of the inner tube, [m]

: Pingjunsudu, [m / S]
[rho] : Density, [kg / m ^{. 3} ] [mu] : viscosity, [kg / m ‧ per S , or Pa ‧ per S]

Re <2,100 laminar flow

Re> 4,000 chaos stream

2,100 <Re <4,000 transition flow

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Pressure loss in the pipeline P 348 TOP

1. Tube friction coefficient f:

The main loss calculated for large flow rates is about 1.75 times that of small flow rates, so when a smaller flow rate is used, it will have a positive effect on the reduction of pipes, cavitation and cavitation ( the pipeline at the pump inlet lift). .