Created on:2021-05-10 11:00

Classification and expression of hydraulic pump and motor

Classification and expression of hydraulic pump and motor

 

1.3.1 classification

(1) There are many types of hydraulic pumps and motors, and the classification methods and names vary with the focus.

It can be divided into gear type, vane type, plunger type and screw type

According to the periodic change of the working chamber, the volume of liquid entering and discharging can be adjusted, which can be divided into quantitative type and variable type.

In addition, according to its speed and torque, hydraulic motors are traditionally divided into three types: high-speed small torque type and low-speed large torque type, and swing motor which can only realize limited angle rotation. Generally, the motor with rated speed higher than 500 R / min is called high-speed motor, while the motor with rated speed lower than 500 R / min is called low-speed motor. The basic forms of high-speed hydraulic motors include gear type, screw type, vane type and axial piston type. Their structures are similar to those of the same type of hydraulic pumps, and their working principles are reversible. However, due to their different purposes of use, there are many differences in their structures, which generally can not be directly reversed. High speed hydraulic motor has the advantages of high speed, small moment of inertia, easy to start and brake, high sensitivity of adjustment and commutation, but the output torque is small (only tens to hundreds of n · m). When driving low-speed load, acceleration and deceleration device is needed. The basic form of low-speed motor is plunger type, including single acting and multi acting. Low speed hydraulic motor has the advantages of large displacement, low speed, large output torque (up to thousands to tens of thousands of n · m), and can be directly connected with its working mechanism without deceleration device, but its volume is large. Swing hydraulic motor can be divided into piston type and vane type, and vane type is mostly used. The structure of the swing hydraulic motor is simpler than that of the continuous rotary hydraulic motor. The outstanding advantage of the swing hydraulic motor is that the output shaft directly drives the load to swing, without any speed change mechanism, the output torque can reach tens of thousands of n · m, and the minimum stable speed can reach 0.001 rad / s.

(2) The detailed classification of hydraulic pump and hydraulic motor is shown in Figure B and figure C.

A

1.3.2 graphic symbols

(1) The graphic symbols of common hydraulic pumps and motors and their significance the schematic diagrams of hydraulic components and systems including hydraulic pumps and motors are generally drawn with standard graphic symbols. As the graphic symbols only represent the function, operation (control) method and external connection of hydraulic components, but not the specific structure, performance parameters, actual position of connection and installation position of components, they are used to express the functions of various components in the system and the composition, oil circuit connection and working principle of the whole system. They are simple and clear, and convenient for drawing and technical exchange .

In 1965, 1976, 1993 and 2009, China promulgated the hydraulic graphic symbol standards. The current standard is GB / T 786.1-2009 fluid power systems and components - Graphical symbols and circuit diagrams - Part 1: Graphical symbols for general use and data processing. The standard establishes the basic elements of various symbols (including line, connection and pipe joint, flow path and direction indication, basic mechanical elements, control mechanism elements, regulation elements, etc.), and formulates the design and application rules of hydraulic and pneumatic components (hydraulic: valve, pump and motor, cylinder, accessories; pneumatic: valve, air compressor and motor, cylinder, accessories) and symbols in circuit diagram (including The CAD symbols are introduced in the form of informative appendix.

The graphic symbols of common hydraulic pumps and motors drawn in GB / T 786.1-2009 are shown in the table below, and the meaning of the graphic symbols is as follows.

A

④ The graphic symbol of hydraulic pump is represented by a circle plus a solid equilateral triangle or two solid equilateral triangles. The outward arrow of equilateral triangle indicates the direction of pressure oil. A solid triangle for one-way pump, two solid triangle for two-way pump. The upper and lower vertical line segments of the circle represent the oil drain and oil suction pipes (oil ports) respectively. No arrow for quantitative pump, arrow for variable pump. The double line and arc arrows on the side of the circle represent the pump drive shaft and the rotary motion respectively.

② The graphic symbol of hydraulic motor is represented by a circle plus a solid equilateral triangle or two solid equilateral triangles. The inward arrow of equilateral triangle indicates the direction of pressure oil. One solid equilateral triangle represents unidirectional motor, and two solid equilateral triangles represent bidirectional motor. The upper and lower vertical line segments of the circle represent the oil inlet and oil outlet respectively. The motor without arrow is quantitative motor, and the motor with arrow is variable motor. The double horizontal and arc arrows on the side of the circle indicate the motor drive shaft and the rotary motion respectively.

(2) Precautions for the use of graphic symbols the following precautions should be paid attention to when using GB / T 786.1-2009 to draw the schematic diagram of hydraulic components and systems.

① According to the size and needs of the drawing, the size of the graphic symbols of the components can be changed according to the appropriate proportion to draw, based on the principle of clear and beautiful.

② The components and circuit diagrams are generally drawn in the non working state without excitation (such as the working position of electromagnetic directional valve after power failure).

③ On the premise of not changing the meaning of the initial state defined in the standard, the direction of the component can be drawn according to the specific situation of horizontal turnover or 90 ° rotation, but the hydraulic tank must be drawn horizontally and the opening upward.

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