A new type of oil makeup valve with floating funct

2022-10-12
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New type oil replenishing valve with floating function

1 characteristics of multi-way directional valve of wheel loader

the operation mode of hydraulic multi-way valve of wheel loader mainly has two forms: one is manual type, that is, the operation lever with a certain lever ratio is used to operate the direction change through steel wire flexible shaft or directly connected to the sliding valve end; The other is pilot controlled hydraulic type. The valve group is composed of pilot valve and main reversing hydraulic valve. The two valves are connected by pilot control oil circuit. The operator operates the pilot valve, inputs secondary pressure to both ends of the main valve in linear proportion, and pushes the slide valve of the main valve to move left and right to realize the direction change of the main valve. With the large-scale wheel loader, the hydraulic system is also developing in the direction of high pressure and large flow. Using lever to directly operate the multi-way directional valve requires a lot of control force, even beyond human physical strength. With the increase of flow, it is difficult for the pipeline to be arranged in a proper position near the cab. With pilot control, because the pilot valve is a low-pressure and small flow element, the stroke and spring return force of the slide valve can be designed to be very small, and the control torque can be greatly reduced. According to relevant information, the control torque is only 1/3 ~ 1/5 of the manual type. This is particularly important for construction machinery whose working mechanism moves frequently. Secondly, through the reasonable matching of the main valve and the pilot valve, the fine-tuning range of the main reversing valve can be increased and the speed regulation performance of the multi-channel valve can be improved. In addition, because there is no rigid connection between the main valve and the pilot valve, its layout on the host is more free, which provides convenience for the piping of the hydraulic system. Therefore, in the construction machinery industry, the pilot proportional control of multi-channel directional valve of large and medium-sized loaders will become a development trend

The working device of the loader mainly includes boom lifting and bucket overturning. In addition to the working conditions of lifting, lowering and stopping, the boom also has a floating position, that is, the upper and lower chambers of the boom hydraulic cylinder are connected with the oil return chamber and are in a low-pressure state. The floating position of the boom enables the working device to float freely with the ground conditions when the loader is shoveling, which can improve the operating efficiency of the loader, and also realize the rapid descent of the boom when the boom is lightly loaded or empty, so as to shorten the cycle time. In addition, when the boom descends, the boom descends faster and faster because the direction of self weight is consistent with the direction of boom descent. When the amount of oil required in the upper chamber exceeds the rated flow of the pump, a "vacuum" may appear in the upper chamber of the boom hydraulic cylinder, causing the oil to vaporize, and external air may also penetrate, thereby affecting the normal operation of the hydraulic system. In order to avoid "vacuum", an oil makeup valve should be installed in the upper chamber of the boom. When the oil pressure in the upper chamber is lower than the return oil pressure of the system, the oil makeup valve opens and enters the upper chamber of the boom cylinder to realize oil makeup to the upper chamber of the boom cylinder

in order to meet the floating and oil replenishment functions, we have designed two different structural forms, which are described separately

2 pilot controlled hydraulic multi-way directional valve with four position valve structure

the structural diagram of the boom device of the pilot controlled hydraulic multi-way directional valve is shown in Figure 1. The hydraulic schematic diagram of the tool should be checked frequently, as shown in Figure 2. The multi-channel valve boom device is a four position valve structure. The work of the boom device is as follows: when the C port is connected with the pilot international standard or industry standard to measure the physical performance test pressure oil of various materials, the boom stem is in the neutral position, and the hydraulic oil coming from the oil inlet returns to the oil tank through the boom neutral position return passage; When pilot control oil is supplied to ports a and C, the boom valve rod moves to the right, and the pressure oil from the oil inlet enters chamber a to the lower chamber of the boom cylinder to realize boom lifting; When the pilot controlled oil pressure is applied to port B and port C, the boom valve rod moves to the left, and the pressure oil from the oil inlet enters chamber B to the upper chamber of the boom cylinder to realize the lowering of the boom valve rod; When only port B is connected with pilot controlled oil pressure, the boom valve rod continues to move to the left. At this time, the oil inlet P cavity is connected with cavity a, cavity B and cavity T, which are flourishing with the development of plastic processing machinery in China. Each oil cavity is in a low-pressure state, realizing boom floating

1. End cap 2. Nut 3. Limit sleeve 4. limit piston 5. Outer spring 6. Inner spring 7. check valve spring 8. Check valve 9. boom valve rod 10. Valve body 11. Protective cover

Figure 1 structure diagram of boom device of pilot controlled hydraulic multi-way directional valve

1. Boom linkage of pilot valve 2. Boom linkage of multi-way valve

Figure 2 boom linkage hydraulic schematic diagram of pilot controlled hydraulic multi-way directional valve

from the above analysis, In order to realize the floating of boom, it realizes the above floating function through the on-off combination of pilot oil pressure, the movement and limit of limit piston

to overcome 5 During the lowering process of the boom with large LCD screen, due to the self weight and other factors and the insufficient oil supply of the hydraulic pump in the upper chamber of the oil cylinder, the upper chamber of the oil cylinder forms a local "vacuum". Here, it is also necessary to add an oil replenishing device to the upper chamber of the boom oil cylinder separately. The structural diagram of the oil replenishing valve is shown in Figure 3. At present, this kind of hydraulic pilot controlled hydraulic multi-channel directional valve has been applied in the zlm50 loader of Changzhou forestry machinery factory

Figure 3 structure diagram of oil makeup valve

3 pilot controlled hydraulic multiple directional valve with floating and oil makeup functions

the boom device structure diagram of the pilot controlled hydraulic multiple directional valve is shown in Figure 4, and its hydraulic schematic diagram is shown in Figure 5. The multi-way valve boom device is a three position valve structure. The work of the boom device is as follows: when the pilot pressure oil is not available at port a and port B, the boom valve rod is in the neutral position, the oil chambers a and B are closed, and the hydraulic oil from the oil inlet flows back to the oil tank through the return passage at the neutral position of the boom; When pilot controlled oil pressure is applied to port a, the boom valve rod moves to the right, and the pressure oil from the oil inlet opens the check valve 9 in the multi-way valve and enters chamber a to the lower chamber of the boom cylinder to realize boom lifting; When pilot controlled oil pressure is applied to port B, the boom valve rod moves to the left, and the pressure oil from oil inlet P opens check valve 9 and enters port B into the upper chamber of boom cylinder to realize boom lowering; When the boom is in the down position, by operating the pilot valve rod in the floating position, the sequence valve 2 in the pilot valve is opened, so that the pressure oil in chamber B returns to the oil tank through the small hole D on the oil makeup valve and the oil passage in the sequence valve, from which the pressure difference is generated before and after the throttling small hole. When the pressure difference between chamber B and chamber C reaches a certain difference, open the oil makeup valve, so that chamber B is connected with chamber t of the oil return port, so that chamber P of the oil inlet is connected with chamber a, and chamber B is connected with chamber t, The boom cylinder is in a low-pressure state, realizing the floating performance of the boom

1. Left end cover 2. Outer spring 3. Inner spring 4. oil replenishment

valve element 5. oil replenishment valve spring 6. oil replenishment valve cover 7. boom valve rod 8. Valve body 9. Check valve 10. Right end cover

Figure 4 structure diagram of boom device of pilot controlled hydraulic multi-way directional valve

1. Pilot valve boom linkage 2. Sequence valve 3. Multi-way valve boom linkage

Figure 5 Schematic diagram of boom linkage of pilot controlled hydraulic multi-way valve

when boom is descending of During the process, due to self weight and other factors, the upper chamber of the oil cylinder forms a local "vacuum" phenomenon due to insufficient oil supply of the hydraulic pump. At this time, the oil pressure in chamber t is higher than that in chamber B. overcome the pressure of the oil replenishment valve spring 5, and open the oil replenishment valve core 4, so as to replenish oil in chamber B and realize the oil replenishment function of the small chamber of the boom

when the diesel engine suddenly stalls, if the bucket is at a high position, as long as the boom control lever is placed in the "down" position, the working oil in the large chamber of the boom cylinder enters the control chamber at the lower end of the pilot valve through the pressure selection valve under the self weight of the working device. When the pressure reaches a certain value, push the boom spool valve to make it in the "down" position, lower the boom, and the bucket can be placed on the ground. In addition, the pilot valve is also equipped with an electromagnet positioning device in the lifting and floating positions

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