1. Basic information of hydraulic pump and hydraulic motor
1.3 The operating principles of hydraulic pumps and hydraulic motors are different. Different types of hydraulic pumps and hydraulic motors have different operating details, but generally have commonalities. Here, two typical types are selected to analyze their operating principles.
1.3.1 Operating principle of plunger type and gear meshing hydraulic pump. The plunger type hydraulic pump converts the mechanical energy generated by electromagnetic energy into hydraulic energy through the reciprocating motion of the plunger. It mainly drives the lower eccentric wheel to rotate through external motors and other prime movers, thereby driving the piston to perform reciprocating motion and continuously changing the volume of the sealed cylinder body. When the volume increases, the internal pressure decreases to form a vacuum, and hydraulic oil is sucked in by the oil inlet mechanism; When the volume decreases, the internal pressure increases, pushing the hydraulic oil to be output from the oil discharge pipe. Due to the larger diameter of the sealing cylinder compared to the oil discharge pipe, the oil discharge pressure can increase. From its operating principle, it can be seen that a plunger hydraulic pump requires a well sealed chamber and a coordinated oil distribution relationship to ensure that the suction check valve and the oil distribution check valve cannot be opened simultaneously.
The gear meshing hydraulic pump converts mechanical energy into pressure energy through the rotational meshing of gears. The main body of the structure is composed of two gears that mesh with each other, and the outer shell forms a closed structure. When the gears mesh and rotate, the volume of the oil suction port increases, resulting in a decrease in pressure. Hydraulic oil enters the chamber under atmospheric pressure, and at the same time, the gears at the meshing point move towards the oil discharge point, driving the hydraulic oil to continuously run towards the oil discharge point box and supply oil to the system continuously. The gear meshing hydraulic pump system has the characteristics of simple structure, low cost, and strong reliability compared to the plunger hydraulic pump. In addition, the system can also achieve self-priming function and has been widely used in recent years.
1.3.2 Operating principles of axial piston and gear hydraulic motors. The operating principles of hydraulic motors and hydraulic pumps are relatively similar, and they are mutually reversible processes. Taking the axial piston hydraulic motor as an example, the main body of the inclined plate is fixed on the housing with a fixed inclination angle α. Hydraulic oil enters the cylinder body through the high-pressure oil inlet area of the oil distribution plate, pushing the plunger outward. When the plunger terminal acts on the inclined plate, the inclined plate forms a reverse force F on the plunger, which is decomposed into a normal force P perpendicular to the inclined plate and a tangential force Q perpendicular to the cylinder body axis. Among them, the P force pushes the plunger inward, extruding hydraulic oil from the oil distribution plate in the cylinder body. The Q force causes the plunger to generate a certain torque relative to the cylinder body, which changes with the position of the plunger, thereby driving the motor shaft to rotate together with the cylinder body.
The structure of a gear type hydraulic motor is similar to that of a gear mesh hydraulic pump, but the difference is that its gears are connected to the load, and high-pressure hydraulic oil drives the gears to rotate through the gears. The speed mainly depends on the pressure of the hydraulic oil.
