In the hydraulic system, the mechanical energy into liquid pressure energy components called hydraulic gear pump. It is the heart of the hydraulic transmission system, the role is to provide enough pressure oil to the hydraulic system. Although there are many kinds of hydraulic pumps, they all have a common law. The following external gear oil pump as an example to clarify this law.
As shown in figure 1 a 1, a pair of gears with the same parameters with intermesh 1 and 2, 3 contained in the pump body and cover (collar or side panel) (not shown) of the figure of the closed space, two gears addendum and the gap between the hole in the pump body surface is very small, gear face the clearance between the cover plate (collar or side panel) and also is very small, Therefore, two separated closed oil cavities are formed along the contact line of the gear meshing point along the tooth width direction. When the driving gear rotates clockwise, the closed volume on the left side of the engagement point becomes larger, resulting in a local vacuum. The oil in the tank enters into this space under the action of atmospheric pressure, forming the other side of the oil suction chamber. The closed volume becomes smaller and the oil is hydraulic out, forming the oil discharge chamber P. This is the process of oil absorption and pressure of gear pump. When the gear oil pump rotates continuously, the space volume of oil suction cavity and oil pressure cavity changes continuously, and the gear oil pump continuously absorbs and presses oil.
Obviously, in the working process of gear oil pump, as long as the rotation direction of the two gears is unchanged, the position of the suction and discharge cavity is also fixed. Here the tooth surface contact line at the meshing point always plays the role of separating the high and low pressure cavity.
Hydraulic pumps used in actual hydraulic systems are of course much more complex than this example, but several common characteristics of hydraulic pumps can be generalized from this example:
(1) The hydraulic pump must have a closed cavity that can be changed. This is the root cause of hydraulic pump suction and drainage work.
(2) The suction and discharge cavity of the hydraulic pump must be separated. Basic guarantee, flow device, such as valve, plate or shaft, etc. This is the hydraulic pump can work and some hydraulic pumps must be set up
(3) The absolute pressure of the liquid in the tank must be equal to or greater than the atmospheric pressure. This is a positive displacement hydraulic pump can suck liquid external conditions. Therefore, the tank must always be in contact with the atmosphere, or a closed charged tank must be used.
