A hydraulic pump is a hydraulic component that provides pressurized liquid for hydraulic transmission and is a type of pump. Its function is to convert the mechanical energy of the power machine (such as electric motor and internal combustion engine, etc.) into the pressure energy of the liquid. The figure shows the working principle of a single plunger pump. The cam is rotated by an electric motor. When the cam pushes the plunger to move upward, the sealing volume formed by the plunger and the cylinder decreases, and the oil is squeezed out from the sealing volume and discharged to the required place through the one-way valve. When the cam rotates to the descending part of the curve, the spring forces the plunger downward to form a certain vacuum, and the oil in the oil tank enters the sealed volume under the action of atmospheric pressure. The cam makes the plunger rise and fall continuously, the sealing volume decreases and increases periodically, and the pump continuously absorbs and discharges oil.