The engine, hydraulic pump and distribution valve are the three important parts of the excavator. The excavator drives the hydraulic pump to rotate through the engine, and the high-pressure hydraulic oil drives the whole vehicle through hydraulic actuators such as hydraulic motor and hydraulic cylinder. The engine provides power for the hydraulic pump, the hydraulic pump, hydraulic oil pipeline, hydraulic motor and hydraulic cylinder are hydraulically driven, and the distribution valve is hydraulically controlled.
Hydraulic pump converts mechanical energy into liquid pressure energy, which is divided into gear pump and plunger pump. Both generate pressure on the liquid through volume change.
However, their mechanisms are different and their volume positions are different. The liquid volume of the gear pump is between the two gears, and the liquid volume is changed by gear rotation. The volume of the plunger pump is in each plunger cylinder.
Common large and medium-sized excavators generally combine the plunger pump and gear pump to form a hydraulic pump assembly. Generally, the main pump is the plunger pump. Because the output hydraulic oil pressure is large, it is used to supply oil to the hydraulic travel motor, hydraulic rotary motor and hydraulic oil cylinder; The pilot pump is a gear pump. Because the output hydraulic oil pressure is small, it supplies oil to the distribution valve.
The main characteristics and disadvantages of gear pump and plunger pump are briefly introduced below.
1. Gear pump
The gear pump works by the closed movement of two meshing gears when they rotate. Gear pump is driven by gear to provide power. Gear pump is a quantitative pump, which is mostly used for low-precision medium and low-pressure control.
The utility model has the advantages of simple structure, convenient manufacture, low cost, low price, small volume, light weight, good self-priming performance, insensitive to oil pollution and reliable operation. However, it has the main disadvantages of large flow and pressure pulsation, high noise and non adjustable displacement.
It is widely used in various low-voltage systems. The gear pump has the lowest requirements for oil. At the earliest time, because of its low pressure, it is generally used as the pilot pump in the low-pressure system. Now the gear pump pressure can be about 25MPa, which is commonly used in machinery with low pressure requirements. However, its oil pulsation is large and cannot be variable. The good thing is its good self-priming performance.
2. Plunger pump
The plunger pump is powered by the reciprocating motion of the piston. The plunger pump is a variable displacement pump, which is mostly used for high-precision high-pressure control. The plunger pump has high working pressure, which is generally 20 ~ 40MPa, up to 1000MPa; Compact structure; High efficiency and convenient flow regulation.
Plunger pump has high pressure, stable performance, high cost, minimum pulsation and variable. It is often used in high-pressure system and construction machinery. But his self-priming performance is the worst.
