Hydraulic transmission is an ideal transmission device of construction machinery. The progress and development of construction machinery depend on hydraulic technology. At present, construction machinery is the largest market in the hydraulic industry. More than half of the hydraulic parts are used in construction machinery. Construction machinery puts forward high requirements for hydraulic technology. The development of hydraulic technology is mainly to meet the needs of construction machinery. The level of hydraulic technology is mainly reflected in construction machinery, such as the large-scale, miniaturization and high-pressure of hydraulic parts. The maximum service pressure has reached 70MPa. Construction machinery and hydraulic technology promote each other and develop together.
Therefore, it is necessary to deeply analyze the characteristics and existing problems of hydraulic transmission and the requirements of construction machinery for hydraulic transmission, so as to further improve and improve the performance of hydraulic transmission.
Hydraulic transmission transmits energy through pipeline connection, just like biological blood vessels. It only needs pipelines to transmit energy to the place where it is needed. It brings great flexibility and convenience to the design and layout. The hydraulic transmission is easy to realize various motion forms. It is very suitable for the requirements of multiple power and operation devices of construction machinery to realize complex motion.
Hydraulic transmission has high power density (power transmitted by unit volume or unit weight), compact structure and light weight, which is suitable for the requirements of strong, heavy and high horsepower of construction machinery.
Hydraulic transmission has excellent transmission performance, stable transmission, easy to prevent overload, simple speed regulation, stepless speed change performance, simple maintenance and long service life, which can well meet the transmission performance requirements of construction machinery.
Hydraulic transmission has good handling and control performance. Hydraulic pressure is the interface between machinery and electronics, and electro-hydraulic control is the key technology of the integration of machinery and telecommunications.
However, there are some unsatisfactory deficiencies in hydraulic transmission, some of which have been improved, and the problems that need to be solved need further thinking. There are the following problems to be solved in the use of construction machinery.
1. Energy saving requirements: adapt to the load change, provide the hydraulic power (flow and pressure) required by the load, minimize the flow and pressure loss, change the throttle speed regulation to volume speed regulation, and especially provide the flow required by the load according to the load demand.
The hydraulic system is required to absorb the energy of the operation device in reverse and have the energy storage function of energy regeneration and utilization.
2. Speed regulation requirements: it is hoped that when the control valve controls the speed regulation, it will not be affected by the change of load pressure and the change of oil pump flow, and the speed regulation can be carried out according to the operation instructions of people.
3. Compound action operation requirements: single pump for multiple actuators: when multiple actuators act at the same time, they are required not to interfere with each other and can operate each actuator to supply oil according to the required flow. Reasonably distribute the flow and realize the ideal compound action.
4. Matching problem between hydraulic pump (single pump or multi pump) and prime mover: it can make full use of the power of prime mover, keep working at the maximum power point of engine, and prevent engine flameout at the same time: in order to save energy, it is required that the hydraulic pump and engine work together at the most economical point.
5. Pressure loss of multiple actuators supplied by a single pump: when several actuators are supplied by a single pump, according to Pascal principle, the system pressure is determined by the pressure required to overcome the maximum load. Therefore, there must be pressure loss in the oil circuit with low supply load. People are exploring whether we can use the transformer in the circuit to solve this problem.
