Functions and Advantages of Hydraulic Pumps

1. The role of the hydram pump

The hydram pump is the heart of the hydraulic system. In a hydraulic system, there must be one or more pumps. The pump is the power element in the hydraulic transmission system. It is driven by the prime mover (motor or engine) to obtain mechanical energy from the output power, and converts it into the pressure energy of the fluid to provide pressure oil for the system, and then in the place where work is required, The fluid is converted into mechanical output by the actuator (hydraulic cylinder or motor).

Generally speaking, the pump is either a positive displacement pump or a non-positive displacement pump, and the pump in the hydraulic system belongs to the positive displacement pump. The so-called positive displacement pump refers to a pump that absorbs and discharges oil by relying on the change of the sealing volume. The existence of the sealing volume and the performance change of the sealing volume are the working principles of all positive displacement pumps.

2. The advantages of hydraulic pumps

The development of hydraulic pump is developing in the direction of high pressure and high speed, and at the same time, higher requirements are put forward for the leakage of hydraulic pump. There are two main forms of preventing hydraulic oil from leaking: static seal and dynamic seal, both of which are used to prevent or reduce the leakage of hydraulic oil in the hydraulic pump cavity to the outside of the pump cavity, and at the same time prevent external dust and foreign matter from entering the pump cavity.

Generally speaking, the static seal of the hydram pump may achieve the ideal situation of zero leakage through reasonable design, but for the dynamic seal, any relative displacement of the contact surface will create conditions for the leakage on the joint surface, so it is difficult to achieve Zero leakage. The external leakage of the hyd pump is an important indicator, and it is usually required that no leakage is allowed at the static seal, and the leakage index per unit time is given at the dynamic seal. As a form of dynamic seal, mechanical seal has the following advantages: low leakage, low material loss, reliable use; low friction power loss; long service life; wide range of use, suitable for low speed, high speed, low temperature, high temperature and high pressure.

Due to the high rotation speed of the input shaft of the high-speed hydraulic pump, the shaft diameter cannot be small due to the limitation of the transmission torque strength, etc., so the linear speed is very high, coupled with the high sealing pressure and high working temperature, the rotary oil seal can no longer meet the requirements, so it is a good solution to take a mechanical seal. A sealing device formed by relative rotation. This isolates the internal working fluid of the hydraulic pump from the outside. When the hydraulic pump is working, the moving ring rotates with the shaft, and the fixed ring is fixed in the end cover. Through the mutual friction of the mating surfaces of the movable and fixed rings, the sealing end face is formed to complete the dynamic sealing.

The rest of the auxiliary sealing is done by the sealing ring. Due to processing and installation, the sealing end face of the initial work will have a certain taper, and the existence of this taper will cause the seal to initially converge or diffuse. During use, the action of pressure and thermal deformation changes the shape of the sealing end face, thereby generating high contact stress on the sealing end face. The movable ring or fixed ring with better self-adaptive wear can reduce the contact stress, and the design and analysis of the seal of the shaft tail mechanism of the high-speed hydraulic pump can quickly rebuild the sealing surface to achieve the sealing function.