What are the three categories of hydraulic pumps? What are the advantages and disadvantages of each?

There are many ways to classify hydraulic pumps, which can be divided into low pressure pumps, medium pressure pumps and high pressure pumps according to the size of the pressure. It can also be divided into quantitative pumps and variable pumps according to whether the flow is adjustable. It can also be divided into gear pump, vane pump and plunger pump according to the structure of the pump

advantage
1) Smooth transmission
In hydraulic transmission, due to the very small amount of oil compression, it can be considered incompressible under normal pressure, relying on the continuous flow of oil for transmission. Oil containing
Vibration absorption capacity, hydraulic buffer device can also be set in the oil circuit, so unlike the mechanical mechanism due to processing and assembly errors will cause vibration button impact, so that the transmission is very smooth, easy to achieve frequent
Reversing; Therefore, it is widely used in machinery requiring smooth transmission, such as grinding machines almost all use hydraulic transmission.
2) Light weight and small volume
Hydraulic transmission compared with mechanical, electric and other transmission methods, under the condition of output the same power, the volume and mass can be reduced a lot, so the inertia is small and the action is spirit
Quick; This is particularly important for hydraulic copying, hydraulic automatic control and machines that require mass reduction. For example, the 1m3 excavator produced in China is more than a machine after using hydraulic transmission
The mass of mechanical transmission is reduced by 1t.
3) Large carrying capacity
Hydraulic transmission is easy to obtain a lot of force and torque, so it is widely used in pressing machines, tunnel boring machines, ten thousand tons of wheel steering gear and ten thousand tons of hydraulic press.

5) Easy to achieve overload protection
Many safety protection measures are taken in the hydraulic system, which can automatically prevent overload and avoid accidents.
6) Hydraulic components can be lubricated automatically
Because the hydraulic oil is used as the working medium, the hydraulic transmission device can be automatically lubricated, so the service life of the components is long.
7) Easy to achieve complex actions
The use of hydraulic transmission can obtain a variety of complex mechanical actions, such as the hydraulic copying lathe tool holder, CNC milling machine hydraulic workbench, can be processed out
Regular shaped parts.
8) Simplify the organization
The use of hydraulic transmission can greatly simplify the mechanical structure, thus reducing the number of mechanical parts.
9) Easy to automate
In the hydraulic system, the pressure, flow and direction of the liquid are very easy to control, coupled with the cooperation of the electrical device, it is easy to achieve complex automatic working cycle
Ring. At present, hydraulic transmission is widely used in combination machine tools and automatic lines.
10) Easy to achieve “three”
Hydraulic components are easy to achieve series comparison, standardization and universality. It is also easy to design and organize professional mass production, which can improve productivity and increase output
Quality, cost reduction.

shortcoming
1) The manufacturing accuracy of hydraulic components is high
Due to the high technical requirements of the components and the more difficult assembly, the use of maintenance is more strict.
2) It is difficult to achieve constant ratio transmission
Hydraulic transmission is based on hydraulic oil as the working medium, there is inevitably leakage between the relative moving surfaces, and the oil is not absolutely incompressible. Due to the
This is not suitable for use in situations where the transmission ratio is strict, such as the drive system of thread and gear machining machines.
3) Oil is affected by temperature
Because the viscosity of the oil changes with the change of temperature, it is not suitable to work in high or low temperature environment.
4) Not suitable for long-distance transmission of power
Because the pressure oil is transmitted by tubing, the pressure loss is large, so it is not suitable for long-distance transmission of power.
5) Air mixed into the oil is easy to affect the working performance
When air is mixed into the oil, it is easy to cause crawling, vibration and noise, and the working performance of the system is affected.
6) Oil is easy to pollute
Oil contamination will affect the reliability of the system.
7) Failure is not easy to check and eliminate.