How to solve the trapped oil of the hydraulic gear pump

For a HYDRAULIC GEAR PUMP to work continuously and smoothly, the overlap coefficient of gear meshing must be greater than 1, that is, at least two pairs of gear teeth should be meshing at the same time. Therefore, a part of the oil is trapped between the closed cavity formed by the two pairs of gear teeth, which is also called the trapped oil area. The trapped oil area is not connected to the high and low-pressure oil chambers of the pump, and changes with the rotation of the gear. The reduction of the volume of the trapped oil area of the HYDRAULIC GEAR PUMP will cause the trapped oil to be squeezed and overflow through the gap, which not only generates high pressure, but also makes the drive shaft and bearing of the pump subject to additional periodic loads, and causes the oil to heat up. The trapped oil problem not only affects the working quality of external gear pumps but also shortens their service life. Therefore, finding a solution is critical.

Here is the content list:

• Open the corresponding unloading tank

• Pay attention to the size and spacing of the unloading slots

Open the corresponding unloading tank

A common measure to solve the problem of trapped oil is to open unloading grooves corresponding to the trapped oil area on the inner surfaces of the front and rear end covers of external gear pumps. In addition to the double rectangular structure symmetrically arranged relative to the gear centerline, the unloading grooves of HYDRAULIC GEAR PUMP also have double circular unloading grooves and double chamfered unloading grooves arranged symmetrically relative to the gear centerline and are asymmetrical relative to the gear centerline Arrangement (the unloading groove is offset to the low-pressure side, that is, the oil suction area) and other structural forms such as thin strip unloading grooves. Its features are different, but the unloading principle is the same, that is, under the premise of ensuring that the high and low-pressure chambers of HYDRAULIC GEAR PUMP do not communicate with each other, try to make the trapped oil area communicate with the high-pressure chamber (oil pressure port) when the volume of the trapped oil decreases, and the trapped oil When the area volume increases, it communicates with the low-pressure chamber (suction port).

Pay attention to the size and spacing of the unloading slots

To ensure a better unloading effect of the HYDRAULIC GEAR PUMP without causing the suction and pressure oil areas to collude, the size of the unloading groove (such as the width and depth of the rectangular unloading groove or the aperture and depth of the circular unloading groove) and the two unloading grooves The spacing of the load tanks should be appropriate. Generally, the two unloading grooves of the HYDRAULIC GEAR PUMP are often opened asymmetrically with an offset to the oil-absorbing area. The distance between the two grooves (minimum dead volume) must ensure that the oil-absorbing chamber and the oil-pressing chamber cannot communicate with each other at any time. For a modulus of m standard involute gear (the pressure angle of the graduation circle is a), its a=2.78m, when the unloading groove is asymmetrical, b=0.8m must be ensured on the side of the pressure oil chamber, and the groove width cmin>2.5 m, groove depth h≥0.8m.

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