Gear pumps, a type of pump consisting of two meshing gears, belong to the category of positive displacement rotary pumps. They are mainly used to transport lubricating liquids, such as fuel oil and lubricating oil in the oil sector, and viscous oil in oil depots. In addition, gear pumps also play an auxiliary role in simple hydraulic systems and lubrication systems in engineering machinery, mining machinery, agricultural machinery and machine tool industries.
There are many types of gear pumps, and the most common classification method is to classify them according to the gear meshing method. External gear pumps, whose driving gear and driven gear are both external gears, are the most widely used type of gear pumps, and the gear pumps we usually refer to are of this type.
External gear pumps include the following components: driving gears, which are responsible for driving the operation of the pump; discharge ports, which are used to discharge the pumped liquid; pump housings, which protect and support the gears; driven gears, which mesh with the driving gears; driven shafts, which connect the driven gears and transmit power; suction ports, which inhale the liquid to be pumped; and driving shafts, which connect the driving gears and drive them to rotate.
In contrast, the internal gear pump has an internal gear as its driving gear and an external gear as its driven gear. The core components of the internal gear pump include a pair of meshing internal and external gears and a crescent-shaped spacer. The internal gear is concentric with the rotating shaft, while the external gear is eccentrically set. The main function of the spacer is to separate the suction chamber from the discharge chamber. When the internal gear starts to rotate, a partial vacuum is formed at the separation of the gear teeth, and then under the action of atmospheric pressure, the oil enters through the suction port of the pump and fills the gaps between the teeth. As the gears rotate further, the oil between the teeth is squeezed at the meshing point of the gear teeth and discharged into the discharge pipe.
Compared with external gear pumps, internal gear pumps are known for their compact structure, small size and excellent suction performance. However, their tooth shape is relatively complex and the processing difficulty is relatively high. Therefore, internal gear pumps are often used in situations where high-pressure hydraulic systems are required, such as aircraft hydraulic systems, and are also used on 100-95-2 trailer pumps.
In addition, internal gear pumps can be further classified according to the shape of the gear teeth. Among them, spur gear pumps are an important type, characterized by the driving gear and driven gear are spur gears, and the torque is transmitted through key connection. During the operation of the pump, due to the extrusion of liquid at the discharge port, a small amount of liquid is enclosed in the meshing tooth cavity, which forms a closed space. As the enclosed space changes from large to small, the liquid in the tooth cavity is squeezed and produces a higher pressure, which in turn increases the radial force on the pump shaft. At the suction port, the enclosed space undergoes a change from small to large, and low pressure is generated instantly and oil vapor is precipitated. When these oil vapors condense, an erosion effect similar to cavitation will be generated, causing erosion on the smooth surface of the gear teeth. Herringbone gear pumps are usually used in oil depots to meet their high flow and high efficiency requirements. Next, we will explore the working principle of gear pumps in depth. When the prime mover drives the driving gear to rotate, the driven gear meshes with it and rotates. Since the gap between the gear and the pump cover is very small, the suction port and the discharge port are effectively separated.
At the suction port, as the gear rotates, the tooth cavity gradually separates, resulting in an increase in volume and a decrease in pressure, thereby sucking in oil. The oil is brought to the discharge port,
where the tooth cavity re-engages, the volume decreases, the pressure increases, and the oil is finally squeezed out of the discharge pipe.
The main structure of the gear pump mainly includes components such as the driving gear, the driven gear, the pump body and the pump cover. The gear is sealed on both end faces, and the bearing supports the driving gear and the driven gear. The pump body, the pump cover and the inter-tooth groove of the gear together form a sealed working space.
