Double vane pump and two-stage vane pump
Double vane pump and two-stage vane pump
1. Double vane pump
Double vane pump is composed of two independent vane pumps installed on the same drive shaft. The external oil circuits of the two pumps are independent of each other. Two pumps can share the same oil inlet, but their oil pressure ports are independent. The two pumps can be installed in the same shell, or they can be provided with separate shells. As shown in Figure H (a), it is a duplex pump with two pumps sharing the same housing but independent oil outlets, which are jointly driven by drive shaft 7. Figure H (b) shows its graphical symbols.
This double vane pump is often used in mechanical transmission with requirements of fast movement and slow working feed. At this time, the double pump is often composed of a small flow pump and a large flow pump. When rapid movement is required, large flow pump can be used for oil supply, or two pumps can supply oil at the same time; When a slow working feed is required, the oil is supplied by the small flow pump and the large flow pump is unloaded at the same time, so as to save power and prevent the heating of oil. This kind of pump often adopts the double structure of a low-pressure large flow pump and a high-pressure small flow pump.
2. Two stage vane pump
Two stage vane pump refers to the oil circuit relationship between two pumps installed on the same drive shaft in series to form the front and rear stages, that is, the oil outlet of the former pump is the oil inlet of the latter pump, and the two vane pumps are installed in one pump body and connected in series with each other on the oil circuit.
The working principle of two-stage vane pump is shown in Figure I. The rotors of two single-stage vane pumps are installed on the same transmission shaft. When the transmission shaft rotates, it drives the two rotors to rotate together. The first stage pump sucks oil from the oil tank through the oil suction pipe, the output oil is directly sent to the oil suction port of the second stage pump, and the output oil of the second stage pump is sent to the working system through the pipeline, thus forming the oil supply relationship between the front and rear stages.
If the output pressure of the first stage pump is P1 and the output pressure of the second stage pump is P2, the final output pressure of the pump is P1 + P2:. But this requires a basic condition: the output flow of the first pump should just meet the needs of the input flow of the second stage pump, otherwise it will cause oil cavitation, cause noise and reduce the efficiency of the pump. Because the inner wall curve and width of the stator of the two pumps cannot be exactly the same, the capacity of each revolution of the two single-stage pumps cannot be completely equal. In order to balance the flow and load relationship of the two pumps, as shown in figure I, a load balancing valve is set in the pump body to connect the oil output of the first stage pump with the large end 1 of the balancing valve and the output oil circuit of the second stage pump with the small end 2 of the balancing valve. In this way, when the output flow of the first stage pump is greater than the input flow of the second stage pump, The excess oil pushes the balance valve through the large end of the balance valve and flows back to its oil inlet through the oil drain port, so as to balance the flow and load of the two pumps; If the output flow of the first stage pump is less than the demand of the second stage pump, the oil pressure P1 shall be reduced so that the balance valve is pushed to the left, the first stage oil drain port of the balance valve will be closed, and the balance oil port on the right side of the valve will be opened. Part of the oil output from the second stage pump flows back to the oil inlet of the second stage pump through the valve port from pipeline 2 to obtain flow supplement and balance.
Generally, the single-stage pressure of this pump can reach 7.0Mpa, and the working pressure of two-stage pump can reach 14.0mpa. This kind of pump is generally used in slightly higher pressure.