product overview of hydraulic pump and hydraulic motor

Created on 2025.02.26

1.8 product overview of hydraulic pump and hydraulic motor

At present, the domestic production and sales of hydraulic pump and hydraulic motor products have basically formed a diversified pattern, mainly covering the following categories: domestic self-developed products; products manufactured by imported technology; products produced by Sino foreign joint ventures; products imitated and digested; products wholly owned by foreign companies, etc. In addition, users can download product samples directly from the Internet or ask for product samples by letter according to their needs and specific conditions of use,

1.9 selection of hydraulic pump and motor

1.9.1 selection principle and key points of hydraulic pump

In the design and use of hydraulic system, the factors to be considered when selecting hydraulic pump include structure type, working pressure, flow rate, speed, efficiency (volumetric efficiency and total efficiency), quantitative or variable, variable mode, service life, type of prime mover, noise, pressure pulsation rate, self-priming capacity, etc., as well as compatibility with hydraulic oil, size, weight and economy (purchase cost) Cost, maintainability, source and product history. Some of these factors have been written in the product samples of the hydraulic pump manufacturer or the technical charts and data in the design manual. It is necessary to study them carefully and strictly follow the provisions in the product manual. If it is not clear, it is better to ask the source unit or the manufacturer.

(1) The principle of selection is that the main engine type of hydraulic transmission is fixed equipment and walking machinery. The working conditions of these two kinds of machines are different, so the main characteristic parameters of hydraulic system and the selection of hydraulic pump are also different. The main differences between the two types of hydraulic transmission are shown in the table below.

The main difference of hydraulic transmission between two kinds of main engine

Projects	Fixed equipment	Traveling machinery
Speed	Fixed speed, medium speed (1000～1800r/min)	Speed changes, high speed (2000~3000r/min or higher), minimum only 500~600r/min
pressure	Machine tools are generally lower than 7MPa, and most others are lower than 14MPa	Generally higher than 14MPa, more often higher than 21MPa
Operating temperature	Medium (＜70℃)	High (70-93℃, maximum 105℃)
Ambient temperature	Moderate, little change	A lot of changes
Environmental cleanliness	Cleaner	Dirty and dusty
noise	Low noise is required, generally 70dB (A), not exceeding 80dB (A)	Generally not too emphasized, but should be lower than 90dB
Size and total amount	Ample space, no worries about size and weight	Space is limited, size should be small, weight should be light

(2) Hydraulic pump type selection gear pump, vane pump, screw pump and plunger pump have different characteristics, advantages and prices, which should be based on the host type and working conditions, power size, system pressure and system requirements for pump performance. At present, the pressure of l2mpa is higher than that of ordinary gear pump system

The piston pump is widely used in the hydraulic system. In addition, we should also consider the quantitative or variable, prime mover type, speed, volumetric efficiency, total efficiency, self-priming capacity, noise and other factors.

It needs to be carefully demonstrated whether to use a constant displacement pump or a variable displacement pump. Quantitative pump is simple and cheap, variable pump is complex and expensive, but it can save energy. See the table below for the application occasions of fixed displacement pump and variable displacement pump. Vane pump, axial piston pump and radial piston pump have quantitative pump and variable pump. The variable mechanism of variable displacement pump (especially axial variable displacement piston pump) has many forms. The control methods include manual control, internal pressure control, external pressure control, solenoid valve control, sequence valve control, proportional valve control, servo valve control, etc. The control results include proportional variable, constant voltage variable, constant current variable, constant torque variable, constant power variable, load sensing variable and so on. Not all variable pumps have the above variables and control methods. The choice of variable mode should adapt to the requirements of the system, and the static and dynamic characteristics and use methods of these variable modes should be clarified in practical use. Different types of pumps, different manufacturers, the variable machine

The product sample or instruction manual should be consulted carefully when selecting the structure.

Application of fixed displacement pump and variable displacement pump

Dosing pump	Variable displacement pump
①Hydraulic power is less than 10kW, and energy cost is not an important factor ②The working cycle is on-off, and the pump can be completely unloaded when not working. ③Although the load varies greatly, the pump needs to output the full flow in most working conditions ④The work system is not heavy and temperature rise is not a problem	①Hydraulic power is greater than 10kW, and flow demand varies greatly ②Requires small and quiet movement under heavy load and fast movement under variable load ③The pump serves multiple loads that can be combined in any way ④Requires large load-bearing capacity ⑤ One prime mover drives multiple pumps, and the installed capacity of the pump is greater than the power of the prime mover

The hydraulic pump can also be made into several pumps (which can be the same type of hydraulic pump or different types of pumps) in parallel, and use the same drive shaft of the multi pump, or can be made into a multi-stage pump with oil circuit in series. When the flow of the hydraulic system changes greatly in a working cycle, the multi pump can be selected. Multi pump usually has one oil suction port and several oil outlets. The pressure oil from each outlet can supply oil to different actuators of the system separately or together. When selecting the type and structure of the hydraulic pump, other requirements of the system for the hydraulic pump should also be considered, such as weight, price, service life, reliability, installation mode of the hydraulic pump, driving mode of the pump, connection mode between the pump and the prime mover, shaft extension form of the pump (cylindrical shaft extension, conical shaft extension with external thread, involute spline, etc.), and whether it can bear certain radial load Connection form of oil port (thread, flange), etc.

In the selection of specific products, should also consider the selection of hydraulic pump manufacturer's reputation and maintenance and accessories supply.

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