Classification, principle and structure of diverter collector valve
Classification, principle and structure of diverter collector valve
1. Purpose and classification
Diverter collector valve is used to ensure that two or more actuator elements can still obtain the same or proportional flow when bearing different loads, so as to make the actuator move at the same displacement or the same speed (synchronous movement), so it is also called synchronous valve. According to different liquid flow directions, the diversion and collection valve can be divided into diversion valve, collection valve and diversion and collection valve. Combined with one-way valve, it can also form one-way diversion valve, one-way collection valve and other composite valves.
The diverter valve automatically divides the input single liquid flow into two branches for output according to a fixed proportion; The collecting valve automatically synthesizes two liquid streams into a single liquid stream for output according to a fixed proportion; When the single diverter valve and one-way collecting valve make the actuator move in the opposite direction, the liquid flows through the one-way valve to reduce the pressure loss; Diverter valve, one-way diverter valve, collecting valve and one-way collecting valve can only make the actuator play a synchronous role in one direction of movement, but not in the reverse direction. The diverter collector valve can synchronize the two-way movement of the actuator.
According to different structural principles, the diverter and collector valve can be divided into reversing piston type, hook type, adjustable type and self-adjusting type.
2. Working principle
(1) Diverter valve and one-way diverter valve. The structural principle and graphic symbols of the diverter valve are shown in Figure 106 (a) and (b). It is composed of two thin cut round hole fixed orifices 1 and 2 with identical structural dimensions, valve body 5, valve core (slide valve) 6, two centering springs 7 and other main parts. P is the oil inlet and a and B are the shunt outlet. The middle boss of spool 6 divides the valve into completely symmetrical left and right parts. The oil chamber a on the left is connected with the spring chamber at the right end of the slide valve through the central hole D of the spool, and the oil chamber B on the right is connected with the spring chamber at the left end of the slide valve through another central hole C of the spool. During assembly, the centering spring ensures that the valve core is in the middle position, and the shoulders at both ends of the valve core are exactly the same as the two variable throttle ports 3 and 4 composed of the valve body.
Under steady-state conditions, the inlet pressure oil of the diverter valve is divided into two parallel branches, which enter the oil chambers a and B respectively through the fixed orifices 1 and 2, and then pass through the variable throttle ports 3 and 4 through the outlets A and B of the valve. The pressure is PA and Pb respectively, and the flow is QA and QB respectively. Since the variable throttle ports 3 and 4 are the same, the pressures P1 and P2 of solid oil cavities A and B are equal, and the pressure difference before and after the fixed orifice △ P1 = ps-p1 = ps-p2 = △ P2. According to the flow formula, the flow through the orifice, that is, the flow of the two branches to the actuator, QA = QB = QS / 2. Therefore, when the structural dimensions of the two actuators are exactly the same, the movement speed will remain synchronous.
During operation, if the load pressures of the outlet oil circuits of a and B are different, for example, the load pressure PA of the oil circuit at port a increases, but Pb does not change. At this time, it suddenly changes from the state of PA = PB to PA > Pb, resulting in the instantaneous increase of P1, which makes the valve core P1 > P2 move to the left. Therefore, the opening of the variable throttle port 3 weakens the throttling effect, and the closing of the variable throttle port 4 enhances the throttling effect, so as to reduce P1 and increase P2 until P1 = P2, The valve core stays at a new equilibrium position to make △ P1 = ps-p1 and ps-p2 = △ P2 equal, and finally make PA and PS equal. Therefore, the diverter valve is a flow control valve that uses the load pressure feedback principle to compensate the change caused by load change. It only controls the distribution of traffic, not the size of traffic.
The one-way diverter valve can be formed by adding two one-way valves on the basis of the above diverter valve. Its structural principle and graphic symbols are shown in Figure 107 (a) and (b). P is the oil inlet and a and B are the shunt outlet. When the pressure oil enters from port P and flows out from shunt ports a and B, check valves 5 and 6 are closed, and the oil is shunted through the shunt valve; When the oil flows reversely from port a and port B and flows out from port P, the check valves 5 and 6 are opened, the diverter valve does not work, and the resistance loss when the oil flows through the valve is very small. Limit screws 3 and 4 are used to limit the left and right movement position of diverter valve element 2.
(3) Diverter and collector valve. Figure 109 shows the structural principle and graphical symbols of the diverter and collector valve, in which figure 109 (a) shows the working condition of the diverter valve and figure 109 (b) shows the working condition of the collector valve. For the convenience of description, the center line O-O is marked on figure 109 (a), and the closing O-O is called the inner side, and the deviation from O-O is called the outer side. The conditions of (PA) and (b) are all in the condition of (PA > 109).
In Figure 109 (a), 1 and 2 are left and right symmetrical valve cores, 3 is the valve body, DA and DB are the fixed orifices on the left and right valve cores respectively, at this time, the diameters of the two orifices should be equal, and Ba and BB are the variable throttling ports formed by the round holes of the left and right valve cores and the corresponding undercut grooves on the valve body respectively. In the collecting condition, the variable orifice is composed of a round hole and the inner side of the undercut. A left oil chamber a is formed between the left fixed orifice DA and the variable throttle port Ba, and the pressure in the chamber is P1. The right oil chamber B is formed between the right fixed orifice dB and the variable throttle port BB, and the pressure in the chamber is P2. The main function of an inner spring 4 and a pair of outer springs 5A and 5b in the valve is to determine the initial state of the shunt and collecting valve. A and B are the two working oil ports of the diverter and collector valve, which are respectively connected with two load actuators, and the pressures are PA and Pb respectively. The main oil port P (T) introduces the high-pressure oil from the pump source into the valve under the shunting condition. At this time, it is the oil inlet. Since this port is used as the oil drain port under the collecting condition, it is recorded as P (T) port in Figure 109 (a); The main oil port discharges the low-pressure oil in the valve under the condition of collecting flow. At this time, it is the oil drain port, so it is recorded as t (P) port in Figure 109 (b).
Under the split flow condition shown in Figure 109 (a), the high-pressure oil entering the P (T) port is divided into two streams and flows to the two fixed orifices DA and DB respectively. After passing through the fixed orifices, the pressure drops △ P1 = ps-p1 and ps-p2 = △ P2 are generated respectively. The internal planing pressure of the left and right valve cores 1 and 2 is high pressure Ps, and the external pressure is the pressure P1 and P2 lower than PS respectively, forcing the valve cores 1 and 2 to the left Move the right outer side away from each other until the hooks on the valve core hook each other, the two valve cores form a whole, and the hooks will not loosen in the whole shunting condition.
Under the steady-state condition of PA = Pb, the valve cores 1 and 2 are in the symmetrical position due to the symmetry of external conditions. The opening degrees of the variable throttle ports Ba and BB are equal. The oil pressure drop through the fixed orifices DA and dB on the left and right sides △ P1 = ps-p1 = ps-p2 = △ P2. According to the flow formula, the oil flow through the two working oil circuits QA = QB. When the load pressures are different, for example, the load pressure Pb on the right side suddenly increases, while the pressure PA on the left side does not change. At this time, it suddenly changes from the state of PA = PB to Pb > PA, causing transient pressure feedback, causing the pressure P2 to rise sharply, pushing the overall valve core to move to the left, reducing the variable throttle port Ba on the left, enhancing the throttling effect, and increasing the pressure in the left oil chamber a; At the same time, due to the increase of P2, the right oil flow QB decreases and the left oil flow QA increases. This factor also cooperates with the throttling effect to increase P1 until P1 = P2, and the whole valve core stays at the new balance position on the left. The opening of variable throttle ports Ba and BB on both sides are not equal, but the oil pressure drop △ P1 = ps-p1 and ps-p2 = △ P2 through fixed orifices DA and dB on the left and right sides return to the same state, and finally the two oil flows return to the same state (new steady state), which is the result of negative pressure feedback.
Under the collecting condition shown in Figure 109 (b), the load flow QA and QB flow into the valve through the oil ports a and B from the loads on both sides, and then flow out through the variable throttle ports Ba and BB and the fixed orifice DA and dB at the port t (P). The process principle is the same as that under the shunting condition. However, in order to realize negative feedback under the collecting condition, the variable throttle ports Ba and BB must be composed of the addition of the round hole of the valve core and the inner side of the sinking groove of the valve body. In this way, the two valve cores cannot be hooked, but must be on the top of the inner side to form a whole. In fact, due to the characteristics of collecting flow, the pressure P1 and P2 on the outside of the two valve cores are greater than the pressure Pt on the inside (i.e. the pressure oil discharged from port T), forcing the two valve cores to face each other.
The shunt collecting valve can only keep the two flows equal under steady-state conditions, which is suitable for the speed synchronous control of the actuator; In the transient process time, the two flows are not equal. If it is used to control the position synchronization of the two actuators, the position synchronization error will be generated. The diverter and collector valve itself has no ability to correct the position synchronization error under transient conditions. For position synchronization control, the application of shunt and collecting valve is an open-loop control.
Even under steady-state conditions, due to the manufacturing error of fixed orifice, different load pressure, the asymmetry of hydraulic force, spring force and leakage flow on both sides and other factors, each factor works alone, and its structure will cause the difference of two-way flow, These will cause the position synchronization error that cannot be corrected by the valve body itself when the shunt and collecting valve is used in the position synchronization control system. However, the combined effect of these factors will sometimes increase the synchronization error and sometimes reduce the synchronization error. In addition, when the diverter collecting valve works below the design flow, the difference of load pressure will make its ability to control equal flow worse.
3. Typical structure
(1) Diverter valve. Fig. 110 shows the structure of the reversing piston diverter valve (tubular connection). The ends of the two reversing pistons 5 and 7 are provided with a slender hole type fixed orifice 6. The reversing piston moves according to the comparison and balance relationship between the pressure difference P1 and P2 behind the orifice, so as to automatically adjust the opening of the variable orifice 10 and realize equal control.
(2) Collecting valve. Fig. 111 shows a structure of the slide valve type collecting valve, and its working principle is the same as that of the diverter valve, except that the pressure P1 of the collecting valve oil chamber a acts in the direction of reducing the variable throttle port 5 at the oil chamber a, and the pressure P2 at the oil chamber B acts in the direction of reducing the variable throttle port 6. The specific content will not be repeated.
(3) Diverter and collector valve. In addition to the hook type diverter and collector valve shown in Figure 111, the reversing piston type is also a common structure of the diverter and collector valve. The structure of the reversing piston diverter and collector valve is similar to that of the diverter valve shown in Figure 110, except for a pair of variable throttle holes.