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Working Principle of Gear Pump

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Author : Peter
Update time : 2019-10-09 20:29:43
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Gear pump principle: The most basic form of the gear pump is that two identically sized gears mesh with each other in a tightly fitting housing. The interior of the housing resembles an "8" shape with two gears mounted inside, the outer diameter of the gear and The sides are closely fitted to the housing. The material from the extruder enters the middle of the two gears at the suction port and fills this space, moves along the housing as the teeth rotate, and finally exits when the two teeth mesh.
Gear pump structure features: 1 simple structure; 2 low working requirements; 3 end caps and gears between the interdental grooves constitute a number of fixed sealed working chambers, can only be used as a dosing pump.
 
Gear pump working characteristics
 
Advantages: simple and compact structure, small size, light weight, good processability, low price, strong self-suction, insensitivity to oil pollution, large speed range, impact resistance load, convenient maintenance and reliable operation.
 
Disadvantages: radial force imbalance, large flow artery, high noise, low efficiency, poor interchangeability of parts, difficult to repair after wear, can not be used for variable pumps.
 
Frequent problems with gear pumps
 
1 trapped oil phenomenon: hydraulic oil in the process of involute gear pump operation, because the closed volume of the gear intersection changes with time, often a part of the hydraulic oil is sealed between the teeth, as shown in the figure, called trapped oil phenomenon Because the hydraulic oil is not compressible, the external gear will generate great vibration and noise, which will affect the normal operation of the system.
 
Measure: The principle of opening and unloading the groove on the front and rear cover plates or the floating bushing to open the unloading groove: the distance between the two grooves is the dead volume, and the closed volume is connected to the pressure oil chamber from large to small, and the dead volume is When the small becomes large, it communicates with the oil suction chamber.
 
2 Leakage phenomenon: The leakage of the gear pump is large. The leakage path of the external gear has the following three points: one is the gear head clearance, the second is the gap measurement, and the third is the meshing gap. The leakage of the end face gap is large, accounting for 80%-85% of the total leakage. When the pressure increases, the former will not change, but the deflection of the latter is greatly increased. This is the main reason for the leakage of the external gear pump, volumetric efficiency. It is not suitable for use as a high pressure pump.
 
Solution: Face clearance compensation uses static pressure balancing measures to add a compensation part between the gear and the cover, such as floating bushings and floating side plates.
 
3 Force imbalance: the right side is the pressure oil chamber, the left side is the oil suction chamber, the pressure of the two chambers is unbalanced; in addition, the pressure chamber is leaked due to the tip of the tooth, and the pressure is decreasing. The two unbalanced pressures act on the radial unbalanced pressure of the gear and the shaft. The higher the oil pressure, the greater the force, accelerating the bearing wear, reducing the bearing life, bending the shaft, and increasing the wear of the tooth top and the shaft hole.
 
Preventive measures: Use a pressure balance tank or reduce the pressure oil chamber.
 
Scope of application: generally transporting lubricating liquids, such as petroleum oil and lubricating oil; used in the mechanical industry for medium speed, low force hydraulic systems and lubricating oil systems as auxiliary oil pumps; available in the chemical industry For conveying high viscosity materials such as nylon, polyethylene, polypropylene and other molten resins.