Three-plunger digital displacement pump based on dynamic coupling actuating valve

Abstract

The utility model provides a scheme of a three-plunger digital displacement pump based on a dynamic coupling actuating valve, which comprises three groups of flow distribution units, and each group of flow distribution units comprises a reciprocating plunger and two high-speed switch valves. The plungers are connected to the crankshaft through the connecting rods, in the rotating process of the crankshaft, the 120-degree phase difference is kept between the plungers, electrical energy consumption and throttling loss in the control process can be reduced, and the multi-plunger digital displacement pump can be expanded in the crankshaft direction according to requirements. The valve element of the check cartridge valve structure is lighter, and the switch valve has higher rated flow. The topological structure of the coupling iron core can significantly improve the transient mechanical property of the dynamic coupling actuator, and significantly reduces the operation time of the switching valve. A dynamic sealing system is converted into a static sealing system through the thin film sealing structure, the situation that magnetorheological fluid leaks and pollutes a hydraulic oil way can be completely avoided, and the motion resistance of the system is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of digital hydraulic pressure, and particularly relates to a three-plunger digital displacement pump based on a power coupling actuating valve. Background Technique

[0002] The plunger variable pump is the core component to ensure the normal operation of the hydraulic systems of various major equipment. Since its variable displacement operation is generally based on an analog control method, it is extremely sensitive to the working environment, which greatly improves the manufacturing technology threshold. Due to factors such as the dead volume, leakage and shear friction at the port plate, and throttle at the pump port, the plunger variable pump has the inherent disadvantage of extremely low working efficiency at low displacements. On the one hand, continuously iterating and developing the manufacturing technology of high-performance hydraulic components in China may keep the hydraulic field in China in the stage of catching up with the world's advanced technology for a long time; on the other hand, even if China completes the technology iteration of high-performance hydraulic components, the inherent disadvantages of traditional plunger variable pumps cannot be eliminated. In recent years, digital displacement pumps / motors based on digital displacement technology have been widely concerned due to their advantages of high energy efficiency in the full displacement working range and low sensitivity to the working environment. The basic unit for realizing digital displacement technology is called a digital distribution unit, which consists of a plunger and two high-speed switching valves. Multiple digital distribution units are combined to form a digital displacement pump / motor. This technology realizes the suction and discharge of oil by independently controlling the high-speed switching valves of the distribution unit. The function realization of the digital displacement pump / motor depends on high-speed switching valves with low pressure loss and fast response. Therefore, its structural design also has great differences according to the special structure of the high-speed switching valves. In the digital pump technology disclosed in China at present, the switching valves applied to the digital distribution unit are mostly commercial cartridge solenoid valves, which cannot simultaneously take into account the low pressure loss and fast response performance, resulting in unsatisfactory energy efficiency in the research and development of digital pumps.

[0003] As Figure 1 shown, the left figure is a five-plunger radial digital displacement motor developed by Shanghai Jiao Tong University. Its design feature is that each plunger is equipped with two high-speed switching valves, which are respectively connected to the high-pressure end and the low-pressure end of the hydraulic system. During the working process, the switching valves keep high-frequency alternating continuous switching to achieve displacement adjustment. This technology is similar to the duty cycle speed regulation principle in the field of electronic technology, and adjusts the digital motor displacement by controlling the ratio of the opening time of the valve within a single cycle. The working characteristic of the switching valves in this digital motor is that the switching valves need to be continuously switched multiple times within a single plunger stroke.

[0004] As Figure 1Shown is the prior art 1. The right figure is a digital displacement pump designed by Taiyuan University of Science and Technology. Its design features are similar to those of a traditional swashplate piston variable pump. The pistons are evenly distributed along the circumference, and each piston is equipped with a high-speed switching valve and a one-way check valve. The high-speed switching valve is connected to the low-pressure end, and the check valve is connected to the high-pressure end. During operation, when the piston sucks oil, the high-speed switching valve opens, and the oil is sucked into the piston cavity from the low-pressure end; when the piston discharges oil, the high-speed switching valve closes, and the oil in the piston cavity is pumped into the high-pressure oil end through the check valve, thus completing the pumping function. In this design, variable displacement control is achieved by changing the number of working pistons and the opening and closing phases of the switching valves. This technology has a relatively low requirement for the response of the switching valve. The switching valve only needs to complete one opening and closing within one piston stroke.

[0005] The digital motor solution of Shanghai Jiao Tong University has a relatively high switching frequency for the high-speed switching valve. It is difficult to ensure the service life of the switching valve during use. Moreover, due to the small valve stroke, a relatively high throttling loss will be generated during the flow distribution process, making it difficult to ensure the high energy efficiency characteristics of the digital motor.

[0006] The digital displacement pump solution of Taiyuan University of Science and Technology is relatively in line with the digital displacement concept. However, on the one hand, it retains the slipper structure of the swashplate piston pump, and the fluid shear and friction losses during the low-displacement high-pressure operation are inevitable and it is relatively sensitive to the working environment; on the other hand, its high-pressure port uses a passive check valve, and its switching characteristics depend on the pressure difference at both ends of the valve, which means that throttling loss always exists at this port. In addition, this design uses an electromagnetic cartridge valve to replace the high-speed switching valve, and the pressure loss and response time of the switching valve are difficult to meet the requirements of digital displacement technology. This design retains the digital variable displacement control feature of digital displacement technology, but it cannot give full play to the advantages of high energy efficiency and insensitivity to the working environment of digital displacement technology.

[0007] As Figure 2 shown, the prior art 2 is the concept of a digital flow distribution mechanism based on a power coupling actuating valve proposed by the inventor in the early stage, and it has the following 3 defects:

[0008] 1. Coupling drive defect: When the coil is energized, due to the relatively large lateral dimension of the coupling iron core, the magnetic diffusion phenomenon in the iron core during the transient response cannot be ignored. At the initial stage of energization, the magnetic flux in the center of the iron core is much smaller than the magnetic flux at the edge. The rapid saturation of the magnetic flux on the surface of the iron core is an important condition to ensure the rapid response of the valve. For a large-area characteristic coupling iron core, this structure cannot ensure the rapid response of the switching valve.

[0009] 2. Sealing defect: The box body is filled with magnetorheological fluid. To prevent the magnetorheological fluid from contaminating the hydraulic oil in the hydraulic system, an O-ring is required to seal the magnetorheological fluid. On the one hand, the translating part needs to achieve high-frequency reciprocating motion during operation. Therefore, the O-ring needs to be designed with an appropriate compression amount to ensure the sealing effect, and the compression amount should not be designed too large to increase the motion resistance of the translating part. On the other hand, this type of dynamic sealing method cannot completely ensure the sealing of the magnetorheological fluid. During the high-frequency reciprocating motion, the magnetorheological fluid will always leak into the hydraulic system along the mating gap of the O-ring.

[0010] 3. Switch valve defect: A spool valve structure is used as the switch valve. The digital flow distribution unit based on this valve structure has two defects in the digital displacement pump: 1. The low-pressure loss spool valve core requires a longer spool shoulder or a larger-diameter spool shoulder, which results in a multiple increase in its mass compared to the seat valve core, thus reducing the response speed. 2. The spool valve is hardly affected by the system pressure during operation. Therefore, it is necessary to continuously energize the actuator to ensure the position of the spool valve core, which increases its power consumption. Summary of the Utility Model

[0011] The present utility model redesigns the digital flow distribution mechanism based on the concept of the power coupling actuator digital flow distribution mechanism (prior art 2), including the adaptability of the determinant pair of plunger mother pumps, and the improvement of the sealing structure, cartridge valve structure and coupling drive structure, reducing the transient response time and energy loss of the valves in the flow distribution mechanism. In addition, the present utility model gives an integrated solution for the digital flow distribution mechanism to form a multi-plunger digital displacement pump, and gives a variable displacement control strategy for the digital displacement pump / motor. For the coupling drive defect, the present utility model gives a double-coil topology structure to reduce the influence of the magnetic diffusion process on the transient response of the switch valve. For the sealing defect, the present utility model proposes a new flexible film sealing method, converting the dynamic seal into a static seal, which not only achieves the complete sealing of the magnetorheological fluid, but also reduces the system resistance. For the switch valve defect, the present utility model designs a low-pressure loss check valve structure suitable for the power coupling actuator, and the flow distribution mechanism composed of this valve can fully utilize the pressure difference between the plunger cavity and the working oil port to ensure the position of the valve core, and only needs to be energized for a short time at a specified phase to realize the opening and closing of the switch valve, thus greatly reducing the power consumption during operation.

[0012] In view of the problems existing in the background technology, the present utility model designs a three-plunger digital displacement pump / motor based on the power coupling actuator, including a determinant radial three-plunger mother pump, a pump head, a partition plate, an oil seal gasket, a main oil seal, a sealing packing, a sealing positioning ring, a sealing sleeve, a secondary oil seal, an L-shaped connecting plate and 3 groups of digital flow distribution units;

[0013] The high-pressure port is connected to the high-pressure end of the hydraulic oil circuit;

[0014] The low-pressure port is connected to the low-pressure end of the hydraulic oil circuit;

[0015] The digital flow distribution unit includes 1 reciprocating plunger and 2 high-speed switching valves; the reciprocating plunger is connected to the crankshaft through a connecting rod; during the rotation of the crankshaft, a 120° phase difference is maintained between the plungers; on one side of the pump head, there are 3 non-communicating plunger cavities, corresponding to the plungers of the mother pump respectively; oil passage branches are respectively arranged in the plunger cavities for installing pressure sensors; the auxiliary oil seal is embedded in the sealing sleeve, and is sequentially sleeved on the plunger together with the sealing positioning ring, sealing packing, main oil seal, and sealing washer; the plunger is inserted into the plunger cavity of the pump head; a partition is arranged between the mother pump and the pump head; the L connecting plate is fixed below the pump head; the partition is detachably connected to the pump head and the L connecting plate respectively, so as to realize the sealed connection between the pump head and the mother pump. There are 3 oil holes communicating with the plungers on the partition for adding lubricating oil.

[0016] The utility model designs a determinant radial three-plunger digital displacement pump (motor) based on the aforementioned digital flow distribution unit, and this structure can be extended to a multi-plunger digital displacement pump (motor) along the crankshaft direction according to requirements.

[0017] On the basis of the above scheme, the digital flow distribution unit includes a bottom oil return pan, a top oil return pan, a main valve block, a sealing connecting rod, a thin-film sealing structure, cartridge valves, and a power coupling actuator;

[0018] The bottom oil return pan is fixed above the pump head and is provided with 3 working oil holes and 6 oil return holes; the 3 working holes are respectively connected to the 3 plunger cavities of the pump head and the 3 working oil ports at the bottom of the main valve block and are non-communicating with each other, and the 6 oil return holes are communicated to the oil return port through internal channels; the main valve block is provided with 6 cartridge valve holes, corresponding to the 6 oil return holes of the bottom oil return pan respectively, and is inserted and connected with the bottom oil return pan; a sealing groove is opened at the bottom of each cartridge valve hole, and an O-ring is provided; the bottom oil return pan and the main valve block are connected and locked, and are sealed by pressing the sealing ring; each working oil hole of the main valve block is respectively communicated with the cartridge valve holes on both sides through inclined holes, so that each plunger cavity is directly communicated with 2 switching valves, forming a set of flow distribution units;

[0019] There are 6 external ports perpendicular to the cartridge holes above the main valve block. Each external port corresponds to a cartridge valve hole and they are not interconnected. The external ports are used for connecting the cartridge valves to the high-pressure port or low-pressure port of the hydraulic system. The cartridge valves are directly inserted into the cartridge holes of the main valve block, and the bottom is embedded in the oil return port insertion groove of the bottom oil return pan. The 2 cartridge valves configured for each plunger cavity are inserted in opposite directions. Sealing grooves are provided on the outside of the cartridge valves and O-rings are embedded. The outer wall of the cartridge valve is closely attached to the inner wall of the cartridge hole, pressing the O-ring. The two cartridge valves in each flow distribution unit are inserted in opposite directions. Taking the valve opening direction as the positive direction, the cartridge valve connected to the high-pressure port is inserted forward, and the cartridge valve of the low-pressure port is inserted backward. There are 6 oil return ports below the top oil return pan, and all 6 oil return ports are connected to the oil return port through internal channels. There are insertion grooves below the 6 oil return ports of the top oil return pan, which are inserted and connected to the main valve block. The outer wall of the cartridge valve is closely attached to its inner wall, and clearance sealing is achieved by pressing the O-ring. One end of the sealing link is threadedly connected to the cartridge valve spool, and the other end is connected to the power coupling actuator through the thin film sealing structure at the oil return port of the top oil return pan.

[0020] On the basis of the above solution, the cartridge valve includes a spring, a spool, a cartridge valve sleeve and a set of spool slideways.

[0021] Sealing grooves are provided on the outer wall of the cartridge valve sleeve for installing O-rings. The spool slideways are respectively arranged at both ends of the cartridge valve sleeve for restricting the spool. The spool slideways are connected to the oil return ports of the bottom oil return pan, and positioning holes are provided in the slideways above them for restricting the opening degree of the spool. Three grooves are provided on the mating surface of the spool and the spool slideway to prevent oil leakage from the gap. Threaded holes for connecting the sealing rod are provided at both ends of the spool. The spring is used to keep the cartridge valve in an open state, and there is no pre-tightening force in the natural state of the spring.

[0022] Further, the spool and the spool slideway adopt a clearance fit, and the clearance is controlled within 0 - 13 microns. The present invention designs a check cartridge valve structure adapted to the power coupling actuator, the spool has a lighter mass, and the on-off valve has a higher rated flow rate.

[0023] On the basis of the above solution, the thin film sealing structure includes a sealing seat, a sealing film, a skeleton, a sealing link and a sealing cap. The sealing cap buckles the sealing film on the sealing link, and the skeleton is detachably connected to the sealing link and presses the sealing cap and the sealing film. The sealing film has enough margin and is pressed by the sealing seat above the oil return port of the top oil return pan. The sealing seat is detachably connected to the top oil return pan. Sealing grooves are provided on the contact surface between the sealing seat and the sealing film, and O-rings are arranged inside.

[0024] Further, the sealing film uses a strong plastic PE material with a specification of 3 filaments to 5 filaments to reduce the system movement resistance.

[0025] The film sealing structure of the present utility model converts the dynamic sealing system into a static sealing system, which can completely avoid the leakage of magnetorheological fluid, pollute the hydraulic oil circuit, and reduce the movement resistance of the system.

[0026] On the basis of the above solution, the power coupling actuator includes a box cover, a turntable, a bearing, a bearing end cover, a rotating shaft, a box body, and a coupling iron core;

[0027] The box body is fixed on the top oil return disc through a locking ear; three turntables are fixed on the rotating shaft, the rotating shaft passes through the box body and forms a rotating shaft system structure with the bearing, Y-shaped sealing ring, bearing end cover and necessary positioning rings arranged on the box body; the bearing end cover is fixed on the box body; the turntable is provided with a circular coupling groove along the radial direction, and the skeleton is inserted into the coupling groove in parallel; one end of the skeleton is connected to the insertion valve, and the other end is constrained by a linear bearing on the box cover; the skeleton is in the center of the coupling groove, and working gaps are respectively formed between its two sides and the turntable; a coupling iron core is embedded in the skeleton, and the coil wiring ends in the coupling iron core pass through the round holes on the side of the skeleton and are led out of the box body through the box cover and connected to an external excitation power supply.

[0028] Further, the inside of the box body is filled with magnetorheological fluid. To save magnetorheological fluid, box body fillers are installed in the internal space of the box body that does not participate in work. The filler material needs to ensure low density, magnetic insulation, and not easy to corrode.

[0029] On the basis of the above solution, the coupling iron core includes an iron core, a main coil, an iron ring, and a secondary coil; the main coil is connected in series with the secondary coil through the small hole of the iron ring, and the current directions of the two coils are opposite. The iron core, the magnetorheological fluid in the working gap, the turntable and the iron ring form a closed magnetic circuit, so that the magnetic induction lines pass through the iron core and the iron ring, thereby solidifying the magnetorheological fluid between the iron core and the gap of the iron ring to form an effective coupling working surface. The secondary coil is nested on the outer ring of the iron ring, and its current flows in the opposite direction to that of the main coil, thereby forming magnetic induction lines in the same direction in the iron ring, increasing the magnetic flux density of the coupling surface, and preventing the magnetic flux in the closed magnetic circuit from leaking.

[0030] Further, the turn ratio of the inner and outer coils of the coupling iron core is 7:3.

[0031] The present utility model gives the topological structure of the coupling iron core, which can significantly improve the transient mechanical performance of the power coupling actuator and significantly reduce the operation time of the switching valve. For large-area coupling iron cores, this topological idea can be extended to multi-layer coil structures to ensure the transient mechanical performance of the system.

[0032] The beneficial effects of the present utility model:

[0033] The digital displacement pump / motor of the present utility model can realize digital variable displacement operation within the full displacement range.

[0034] The working efficiency of the digital displacement pump / motor described in this utility model is above 90% within the full displacement range.

[0035] The three flow distribution units of the digital displacement pump / motor described in this utility model work independently without affecting each other, improving the reliability of the digital pump / motor.

[0036] The thin film sealing structure described in this utility model can completely avoid the leakage of magnetorheological fluid and pollute the oil circuit system. At the same time, this structure reduces the movement resistance of the system.

[0037] The digital flow distribution mechanism described in this utility model can save a large amount of electrical energy loss and throttling loss during the flow distribution process.

[0038] The coupled iron core structure described in this utility model can greatly improve the transient mechanical performance of the power coupling actuator and can reach the driving force saturation state in a short time. Description of the Drawings

[0039] This utility model has the following drawings:

[0040] Figure 1 For the prior art 1, the digital motor scheme of Shanghai Jiao Tong University (left figure) and the digital pump scheme of Taiyuan University of Science and Technology (right figure);

[0041] Figure 2 For the prior art 2, the digital flow distribution mechanism diagram of China Agricultural University based on the power coupling actuator valve;

[0042] Figure 3 For the disassembly diagram of each part of this utility model;

[0043] Figure 4 For the assembly diagram of the three-plunger digital variable pump;

[0044] Figure 5 For the structure diagram of the cartridge valve;

[0045] Figure 6 For the thin film sealing structure diagram;

[0046] Figure 7 For the cross-section and magnetic field line distribution diagram of the coupled iron core.

[0047] Reference numerals: 01 mother pump, 02 angle sensor, 03 linear bearing, 04 locking lug, 05 tank cover, 06 sealing seat, 07 bottom oil return pan, 08 coupling turntable, 09 bearing, 10 Y-shaped sealing ring, 11 bearing end cover, 12 top oil return pan, 13 rotating shaft, 14 box body, 15 main valve block, 16 pump head, 17 spring, 18 valve core, 19 sealing film, 20 partition board, 21 oil seal washer, 22 main oil seal, 23 sealing packing, 24 sealing positioning ring, 25 sealing sleeve, 26 plunger, 27 auxiliary oil seal, 28 crankshaft, 29 skeleton, 30 sealing connecting rod, 31 coupling iron core, 32 cartridge valve sleeve, 33 sealing cap, 34 L connecting plate, 35 valve core slideway, 36 box body packing, CP plunger cavity, HP high-pressure port, LP low-pressure port, T oil return port, SP oil passage branch. Detailed implementation manners

[0048] To make the objectives, advantages and features of the present utility model more obvious, the following provides a detailed description in conjunction with the accompanying drawings and specific implementation manners.

[0049] The following details the implementation manners of the present utility model. Examples of the implementation manners are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The implementation manners described below with reference to the accompanying drawings are exemplary and are only used to explain the present utility model, and should not be construed as a limitation of the present utility model.

[0050] Those skilled in the art of the present technology can understand that unless specifically stated otherwise, the singular forms "a", "an", "the" and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of the present utility model means the presence of the described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups. It should be understood that when we say an element is "connected" or "coupled" to another element, it can be directly connected or coupled to other elements, or there may also be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or coupling. The phrase "and / or" used herein includes any unit and all combinations of one or more related listed items.

[0051] Those skilled in the art of the present technology can understand that unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those of ordinary skill in the art to which the present utility model belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless defined as such here.

[0052] As Figure 3 and Figure 4 shown is a specific embodiment of the present utility model. It shows the assembly and external structure of a three-plunger digital displacement pump (or motor) based on a power coupling actuating valve. It includes a row-type radial three-plunger mother pump 01, a bottom oil return disc 07, a main valve block 15, a pump head 16, a partition plate 20, an oil seal gasket 21, a main oil seal 22, a sealing packing 23, a sealing positioning ring 24, a sealing sleeve 25, a secondary oil seal 27, an L-shaped connecting plate 34 and a digital flow distribution unit. Three non-communicating plunger chambers CP are provided on one side of the pump head 16, corresponding to the three plungers 26 of the mother pump 01 respectively. Oil passage branches SP for installing pressure sensors are provided in the corresponding plunger chambers CP. The secondary oil seal 27 is embedded in the sealing sleeve, and is sequentially sleeved on the mother pump plunger together with the sealing positioning ring 24, the sealing packing 23, the main oil seal 22 and the sealing washer 21. The mother pump plunger 26 is inserted into the plunger chamber of the pump head 16, and a partition plate 20 is provided between the mother pump 01 and the pump head 16. The L-shaped connecting plate 34 is fixed below the pump head 16 by bolts, and the partition plate 20 is connected to the pump head 16 and the L-shaped connecting plate 34 by bolts respectively, so as to realize the sealed connection between the pump head and the mother pump. Three oil holes communicating with the plungers are opened on the partition plate 20 for adding lubricating oil.

[0053] The digital flow distribution unit includes a bottom oil return pan 07, a top oil return pan 12, a main valve block 15, a sealing link 30, a thin-film sealing structure, cartridge valves, and a power coupling actuator. The bottom oil return pan 07 is fixed above the pump head by bolts. It has 3 working oil holes and 6 oil return holes T. The 3 working holes are respectively connected to the three plunger chambers of the pump head and the three working oil ports at the bottom of the main valve block 15 and are not interconnected. The 6 oil return holes are connected to the oil return port T through internal channels. The main valve block 15 is provided with 6 cartridge valve holes, which correspond to the 6 oil return holes of the bottom oil return pan 07 respectively, and is connected to the bottom oil return pan 07 in a cartridge manner. A sealing groove is opened at the bottom of each cartridge valve hole, and an O-ring is provided. The bottom oil return pan 07 and the main valve block 15 are connected and locked by bolts, and the sealing of the clearance between the two is ensured by pressing the sealing ring. Each working oil hole of the main valve block 15 is connected to the cartridge valve holes on both sides through inclined holes, ensuring that each plunger chamber can be directly connected to two switching valves to form a set of flow distribution units. Six external ports perpendicular to the cartridge holes are provided above the main valve block 15. Each port corresponds to a cartridge valve hole and is not interconnected. This port ensures the connection of the cartridge valve to the high-pressure port HP or the low-pressure port LP of the hydraulic system. The cartridge valve is directly inserted into the cartridge hole of the main valve block 15, and the bottom is embedded in the oil return port insertion groove of the bottom oil return pan 07. The two cartridge valves configured for each plunger chamber are inserted in opposite directions. A sealing groove is opened on the outside of the cartridge valve, and an O-ring is embedded. The outer wall of the cartridge valve is closely attached to the inner wall of the cartridge hole, and the O-ring is pressed to achieve sealing. The two cartridge valves in each set of flow distribution units are inserted in opposite directions. Taking the valve opening direction as the positive direction, the cartridge valve connected to the high-pressure port HP is inserted forward, and the cartridge valve of the low-pressure port LP is inserted backward. Six oil return ports are opened below the top oil return pan 12. The oil return ports are located inside the machine. Each set of cartridge valves (such as Figure 3 ) The structure and the connection position of each set of cartridge valves to the oil return ports located inside the machine and the top oil return pan 12 are all connected to the oil return port T through internal channels. An insertion groove is provided below the 6 oil return ports of the top oil return pan 12, and it is inserted into the cartridge hole of the main valve block 15 and fastened with bolts. The outer wall of the cartridge valve is closely attached to its inner wall, and the clearance sealing is achieved by pressing the O-ring. One end of the sealing link 30 is threadedly connected to the cartridge valve spool 18, and the other end is connected to the power coupling actuator through a specific thin-film sealing structure through the oil return port of the top oil return pan 12.

[0054] The cartridge valve such as Figure 5As shown: It includes a spring 17, a valve core 18, a cartridge valve sleeve 32, and a group of valve core slide ways 35. Sealing grooves are provided on the outer wall of the cartridge valve sleeve 32 for installing O-rings to achieve cartridge sealing. The slide ways 35 are respectively inserted at both ends of the valve sleeve 32 to restrict the valve core 18. The valve core 18 and the slide ways 35 adopt a clearance fit, and the clearance is controlled within 0 - 13 microns to ensure smooth movement of the valve core and a small leakage amount. The slide ways 35 are connected to the oil return port of the oil return disc to ensure that the valve core is not affected by static hydraulic resistance during movement. Positioning holes are provided on the upper slide way to limit the opening degree of the valve core. Three grooves are provided on the mating surface between the valve core 18 and the slide ways to prevent oil from leaking through the clearance. Threaded holes for connecting with the sealing rod 30 are provided at both ends of the valve core 18. The spring 17 ensures that the cartridge valve is in an open state, and there is no pre-tightening force in the natural state of the spring.

[0055] The described film sealing structure is as Figure 6 As shown: It includes a sealing seat 06, a top oil return disc 12, a sealing film 19, a skeleton 29, a sealing link 30, and a sealing cap 33. The sealing cap 33 presses the sealing film 19 onto the sealing link 30. The bottom end thread of the skeleton 29 is connected and fixed to the upper threaded hole of the sealing link 30, pressing the sealing cap 33 and the sealing film 19 tightly. The sealing film 19 has sufficient margin and is pressed by the sealing seat 06 above the oil return port of the top oil return disc 12. The sealing seat 06 and the top oil return disc 12 are connected by screws. Sealing grooves are provided on the contact surface between the sealing seat 06 and the sealing film 19, and O-rings are arranged inside to enhance the sealing effect. Its working principle is: The sealing methods between the sealing seat 06 and the oil return disc 12 and between the skeleton 29 and the sealing rod 30 are both static seals. The sealing film 19 completely isolates the magnetorheological fluid in the upper power coupling actuator from the oil in the lower oil return disc. When the actuator drives the valve core to move, the skeleton 29 drives the sealing rod 30 to drive the valve core to move. Due to the flexible characteristics of the sealing film and sufficient margin, the sealing film hardly provides resistance to the system during the movement process. This sealing structure relies on the flexible characteristics of the sealing film to convert the dynamic sealing problem into a static seal, avoiding leakage and movement resistance caused by the traditional O-ring sealing method.

[0056] It should be noted that the sealing film 19 is recommended to use a strong plastic PE material with a specification of 3 - 5 filaments to reduce the system movement resistance.

[0057] The power coupling actuator includes a box cover 05, a turntable 08, a bearing 09, a bearing end cover 11, a rotating shaft 13, a box body 14, a skeleton 29, a coupling iron core 31, and box body packing 36. The box body is fixed on the top oil return pan 12 through a locking ear 04, and oil sealant is applied to the fitting gaps to prevent the leakage of magnetorheological fluid. Three groups of turntables 08 are fixed on the rotating shaft 13 through screws. The rotating shaft 13 passes through the box body and forms a complete rotating shaft system structure with the bearing 09, Y-shaped sealing ring 10, bearing end cover 11, and necessary positioning rings (not shown in the figure) through the bearing seats provided on the box body. The bearing end cover is fixed on the box body 14 through screws. The turntable 08 is provided with a circular coupling groove with a diameter of 6 mm in the radial direction. The thickness of the skeleton 29 is 5 mm, and it is inserted into the coupling groove in parallel. One end of the skeleton is connected to the insertion valve, and the other end is constrained by a linear bearing on the box cover to ensure that the skeleton can drive the valve core to move smoothly in the longitudinal direction. The position of the fine-tuning turntable 08 on the rotating shaft 13 is adjusted to ensure that the skeleton 29 is in the center of the coupling groove, and a working gap of 0.5 mm is formed between the two sides of the skeleton and the turntable respectively. The coupling iron core 31 is embedded in the skeleton 29. The coil wiring terminals in the coupling iron core pass through the round holes on the side of the skeleton and are led out of the box body through the box cover and connected to an external excitation power supply (not shown in the figure). The inside of the box body 14 is filled with magnetorheological fluid. To save magnetorheological fluid, box body packing 36 is installed in the internal space of the box body that does not participate in the work. It should be noted that the packing material should ensure low density, magnetic insulation, and corrosion resistance.

[0058] The working principle of the power coupling driver is as follows: The rotating shaft 13 is externally connected to a driving motor, which drives the turntable 08 to rotate. The turntable rotates clockwise from the LP side to the HP side. When the coil of the coupling iron core 31 is energized, a strong magnetic field is formed between the coupling iron core and the turntable. Since the working gap between the coupling iron core and the turntable is filled with magnetorheological fluid with instantaneous reversible rheological characteristics, under the action of the strong magnetic field, the magnetorheological fluid in the gap will quickly solidify, so that the coupling iron core and the turntable are coupled and adhered. The turntable provides a downward shear driving force for the coupling iron core, and this driving force is approximately proportional to the area of the coupling iron core under the condition of magnetic saturation. Under the action of the shear force, the skeleton is driven to move downward, closing the switching valve. When the coil is de-energized, under the action of the spring, the valve core returns to its original position.

[0059] The detailed topological structure of the said coupling iron core 31 is as Figure 7As shown in the figure: It includes an iron core 31-1, a main coil 31-2, an iron ring 31-3, and a secondary coil 31-4. Among them, the main coil 31-1 is connected in series with the secondary coil 31-4 through the small hole of the iron ring 31-3, and the current directions of the two coils are opposite. The iron core, the magnetorheological fluid in the working gap, the turntable and the iron ring form a closed magnetic circuit, enabling the magnetic induction lines to pass through the iron core and the iron ring, thereby solidifying the magnetorheological fluid between the iron core and the iron ring and the turntable gap to form an effective coupling working surface. The secondary coil is nested on the outer ring of the iron ring, and its current flows in the opposite direction to that of the main coil, thereby forming magnetic induction lines in the same direction in the iron ring, increasing the magnetic flux density of the coupling surface, and preventing the magnetic flux from leaking in the closed magnetic circuit. The magnetorheological fluid has a saturation magnetic flux density, that is, beyond this magnetic flux density, its yield stress no longer increases. For the design of a large-area coupling iron core structure, due to the magnetic diffusion effect in the prior art 2, the magnetic flux in the central area of the coupling surface cannot quickly reach the saturation requirement instantaneously when powered on, thus prolonging the saturation time of the shear driving force. The advantage of this design compared to the coupling iron core structure mentioned in the prior art 2 is that it eliminates the disadvantage of the significant decline in the transient performance of the large-area coupling iron core driver caused by the magnetic diffusion phenomenon in the original design. Under the conditions of the same area coupling surface, the same number of coil turns, and the same external driving voltage, it can reach the saturation magnetic flux density faster, that is, the transient response performance of the driving force is significantly improved. It is recommended that the number of turns of the inner and outer coils be 7:3, and the saturation shear force can be basically reached within 2 ms. In addition, due to the reduction of the perimeter of the main coil, this scheme also has a smaller moving mass, further improving the transient performance of the driver.

[0060] The working principle of the digital displacement pump / motor is as follows: HP and LP are respectively connected to the high-pressure end and the low-pressure end of the hydraulic oil circuit, the T port is connected to the fuel tank, and a pressure sensor is installed on the SP. It includes three groups of flow distribution units, and each group of flow distribution units includes a reciprocating plunger and two high-speed switching valves. The plunger is connected to the crankshaft through a connecting rod. During the rotation of the crankshaft, a 120° phase difference is maintained between the plungers, and its absolute phase is monitored by the angle encoder 02. The crankshaft rotates uniformly under the action of the power motor, thereby driving the plunger to reciprocate in the plunger cavity. When the plunger reaches the top dead center, the plunger cavity completes the oil discharge action, and the plunger reaches the bottom dead center; when the plunger reaches the bottom dead center, the plunger cavity completes the oil suction action.

[0061] Taking a group of flow distribution units as an example, its pumping mode control method is as follows: At startup, the pressure in the plunger chamber CP is the same as the pressure on the LP side, and the LP side cartridge valve is in the open state; since the pressure on the HP side is higher than the pressure in the plunger chamber CP, under the action of the pressure difference, the HP side switching valve is in the closed state. The pumping process includes four stages: oil suction - compression - oil discharge - expansion. The plunger starts the oil suction stroke from the top dead center, and the oil enters the plunger chamber CP from the LP side. When the plunger reaches the bottom dead center, the valve needs to be completely closed under the action of the LP side actuator, and at this time, the compression stroke begins. Since it takes a certain time for the switching valve to be completely closed, the energization phase of the coupling iron core needs to be earlier than the bottom dead center, and its leading phase is determined by the pump speed and the switching valve operation time. During the compression stroke, the pressure in the plunger chamber CP gradually increases during the compression of the oil. At this time, the LP side coupling iron core is de-energized, and the pressure difference formed by LP and CP ensures that the LP side check valve is closed. The pressure in the plunger chamber continues to increase to the pressure level of the high-pressure port HP, and the HP side cartridge valve quickly opens under the action of the spring and the valve port pressure difference, and the system enters the oil discharge stroke. When the plunger reaches the top dead center during the oil discharge stroke, the valve needs to be completely closed under the action of the HP side actuator, and at this time, the expansion stroke begins. Since it takes a certain time for the switching valve to be completely closed, the energization phase of the coupling iron core needs to be earlier than the top dead center, and its leading phase is determined by the pump speed and the switching valve operation time. During the expansion stroke, the pressure in the plunger chamber CP drops from the HP side pressure to the LP side pressure level. During this process, the HP side coupling iron core is de-energized, the HP side check valve is closed under the action of the valve port pressure difference, and the LP side switching valve quickly opens under the action of the spring and the valve port pressure difference, and re-enters the oil suction stroke, completing a pumping and flow distribution cycle. Three groups of flow distribution units work in parallel and alternately. The crankshaft phase is monitored by an angle sensor, and the power coupling actuator is controlled to drive the switching valve to achieve the full displacement pumping function of the three-plunger digital displacement pump.

[0062] Taking a group of flow distribution units as an example, the operating method in the motor mode is as follows: The oil circuit connection method is the same as that in the pumping mode. The crankshaft is connected to the rotating load system as the output end. In the motor mode, pre-start is required at a certain speed. In the motor operating mode, the plunger chamber CP includes four stages: oil suction - expansion - oil discharge - compression. Under the action of the oil in the high-pressure port HP, the plunger moves from the top dead center to the bottom dead center, entering the oil suction stroke. At this time, the oil in the HP port does external work, driving the crankshaft to rotate. During this process, the LP-side switching valve is closed under the action of the valve port pressure difference. The switching valve needs to be completely closed before the plunger enters the expansion stroke from the oil suction stroke. The phase of entering the expansion stroke is related to the compressibility of the hydraulic oil. Since it takes a certain time for the switching valve to be completely closed, the energizing phase of the coupling iron core needs to be ahead of the phase of entering the expansion stroke, and its leading phase is determined by the motor speed and the operating time of the switching valve. After entering the expansion stroke, the driver is powered off, and the plunger continues to move towards the bottom dead center. During this process, since the pressure in the plunger chamber drops and is higher than the LP-side pressure level, both the switching valves at both ends are in the closed state under the action of the valve port pressure difference. When the plunger reaches the bottom dead center, the pressure in the plunger chamber drops to the LP pressure level. Under the action of inertia, the plunger starts to move towards the top dead center. Under the action of the valve port pressure difference and the spring, the LP-side check valve quickly opens, and the plunger chamber enters the oil discharge stroke. At this time, the crankshaft drives the plunger to discharge the hydraulic oil in the plunger chamber according to the system relationship. When the plunger enters the compression stroke from the oil discharge stroke, the LP switching valve should be completely closed. The phase of entering the compression stroke is related to the compressibility of the hydraulic oil. Since it takes a certain time for the switching valve to be completely closed, the energizing phase of the coupling iron core needs to be ahead of the phase of entering the compression stroke, and its leading phase is determined by the motor speed and the operating time of the switching valve. After entering the compression stroke, the driver is powered off, and the pressure in the plunger chamber CP gradually rises. When approaching the top dead center, the internal pressure is higher than the HP-side pressure level. Under the action of the valve port pressure difference and the spring, the HP-side switching valve quickly opens, and the plunger relies on the system inertia to cross the top dead center and re-enter the oil suction stroke, completing a motor oil distribution cycle. Three groups of flow distribution units work in parallel and alternately. The crankshaft phase is monitored by an angle sensor, and the power coupling actuator is controlled to drive the switching valve to achieve the function of a three-plunger digital displacement full-displacement motor.

[0063] Taking the variable displacement control strategy in the pumping mode as an example: it includes two types, i.e., equal flow ratio control and stroke ratio control. When using the equal flow ratio control method: the three groups of flow distribution units work independently. When the power coupling actuator is not energized, the pump is in an idling state, and the oil suction and discharge process of the plunger flows in / out through the LP port. At this time, the displacement of the plunger pump is 0. When only the power coupling actuator of one group of flow distribution units is phase-excited, the plunger pump realizes 1 / 3 displacement. Similarly, when two groups of flow distribution units work simultaneously and three groups of flow distribution units work simultaneously, 2 / 3 displacement and full displacement are realized; when using the stroke ratio control method, the plunger works at full displacement during the oil suction stroke. When the plunger is in the oil discharge stroke, the excitation phase of the power coupling driver on the LP side is determined according to the plunger stroke position, so as to control the proportion of the oil in the plunger chamber returning to the LP, thereby controlling the displacement of a single flow distribution unit. For example, when the plunger moves from the bottom dead center to 1 / 2 of the full stroke during the oil discharge stroke, the switching valve on the LP side is completely closed. During this process, 1 / 2 of the oil is returned to the fuel tank, and only the remaining 1 / 2 of the oil enters the HP end to participate in the work during the oil discharge stroke, thus realizing 1 / 2 displacement. Combining the two control methods of equal flow ratio and stroke ratio, the digital displacement pump can theoretically realize variable displacement control within the full displacement range. The control strategy in the motor mode is similar to the pumping control strategy, and variable displacement control within the full displacement range in the motor mode can be realized through the equal flow ratio and stroke ratio control methods.

Claims

1. A three-plunger digital displacement pump based on a power-coupled actuating valve, characterized in that: It comprises a matrix radial mother pump (01), a pump head (16), a partition (20), an oil seal pad (21), a main oil seal (22), a sealing filler (23), a sealing positioning ring (24), a sealing sleeve (25), a secondary oil seal (27), an L-shaped connecting plate (34) and three sets of digital flow distribution units; The high-pressure port (HP) is connected to the high-pressure end of the hydraulic oil circuit; the low-pressure port LP is connected to the low-pressure end of the hydraulic oil circuit; the digital flow distribution unit includes a reciprocating plunger and two high-speed switch valves; the reciprocating plunger is connected to the crankshaft through a connecting rod; during the rotation of the crankshaft, the plungers maintain a phase difference of 120°; the pump head (16) is provided with three mutually unconnected plunger cavities (CP) on one side, respectively corresponding to the plungers (26) of the mother pump (01); the plunger cavities (CP) are respectively provided with oil channel branches (SP) for installing pressure sensors; the auxiliary oil seal (27 ) is embedded in a sealing sleeve (25), and is sequentially mounted on a plunger (26) together with a sealing positioning ring (24), a sealing packing (23), a main oil seal (22), and a sealing gasket (21); the plunger (26) is inserted into a plunger cavity (CP) of a pump head (16); a partition (20) is provided between the mother pump (01) and the pump head (16); the L-shaped connecting plate (34) is fixed under the pump head (16); the partition (20) is detachably connected to the pump head (16) and the L-shaped connecting plate (34), respectively, so as to realize a sealed connection between the pump head (16) and the mother pump (01).

2. The three-plunger digital displacement pump according to claim 1, characterized in that: The digital flow distribution unit comprises a bottom oil return plate (07), a top oil return plate (12), a main valve block (15), a sealing connecting rod (30), a film sealing structure, a cartridge valve and a power coupling actuator; The bottom oil return plate (07) is fixed above the pump head (16) and is provided with 3 working oil holes and 6 oil return holes; the 3 working holes are respectively connected to the 3 plunger cavities (CP) of the pump head (16) and the 3 working oil ports at the bottom of the main valve block (15) and are not connected to each other, and the 6 oil return holes are connected to the oil return port (T) through internal channels; the main valve block (15) is provided with 6 cartridge valve holes, which respectively correspond to the 6 oil return holes of the bottom oil return plate (07) and are plug-connected to the bottom oil return plate (07); a sealing groove is opened at the bottom of each cartridge valve hole and an O-ring is provided; the bottom oil return plate (07) is connected and locked with the main valve block (15) and is sealed by a compression sealing ring; each working oil hole of the main valve block (15) is respectively connected to the cartridge valve holes on both sides through an inclined hole, so that each plunger cavity (CP) is directly connected to two switch valves to form a group of distribution units; The main valve block (15) is provided with 6 external ports perpendicular to the insertion hole, each external port corresponds to a cartridge valve hole and is not connected to each other, and the external ports are used to connect the cartridge valve to the high pressure port (HP) or the low pressure port (LP) of the hydraulic system; The cartridge valve is directly inserted into the insertion hole of the main valve block (15), and the bottom is embedded in the oil return port insertion groove of the bottom oil return plate (07); the two cartridge valves configured for each plunger cavity (CP) are inserted in opposite directions; a sealing groove is opened on the outside of the cartridge valve, and an O-ring is embedded; the outer wall of the cartridge valve is tightly fitted with the inner wall of the insertion hole to compress the O-ring; the two cartridge valves in each group of distribution units are inserted in opposite directions, with the valve opening direction as the positive direction, the cartridge valve connected to the high-pressure port (HP) is inserted in the forward direction, and the cartridge valve of the low-pressure port (LP) is inserted in the reverse direction; Six oil return ports are arranged below the top oil return plate (12), and the six oil return ports are connected to the oil return port (T) through internal channels; a plug-in slot is arranged below the six oil return ports of the top oil return plate (12), and is plug-in connected to the main valve block (15); the outer wall of the plug-in valve is tightly fitted to the inner wall thereof, and a gap seal is achieved by pressing the O-ring; one end of the sealing connecting rod (30) is connected to the plug-in valve core (18) through a thread, and the other end is connected to the power coupling actuator through the oil return port of the top oil return plate (12) and the film sealing structure.

3. The three-plunger digital displacement pump according to claim 2, characterized in that: The cartridge valve comprises a spring (17), a valve core (18), a cartridge valve sleeve (32) and a set of valve core slideways (35); The outer wall of the cartridge valve sleeve (32) is provided with a sealing groove for installing an O-ring; the valve core slideway (35) is respectively provided at both ends of the cartridge valve sleeve (32) for constraining the valve core (18); the valve core slideway (35) is connected to the oil return port (T) of the bottom oil return plate (07), and a positioning hole is provided on the slideway above it for limiting the opening degree of the valve core; three grooves are provided on the matching surface of the valve core (18) and the valve core slideway (35) for preventing oil from leaking from the gap; threaded holes connected to the sealing rod (30) are provided at both ends of the valve core (18), and the spring (17) is used to keep the cartridge valve in a normally open state, and there is no pre-tightening force in the natural state of the spring.

4. The three-plunger digital displacement pump according to claim 3, characterized in that: The valve core (18) and the valve core slideway (35) are clearance matched, and the clearance is controlled within a range of 0 to 13 microns.

5. The three-plunger digital displacement pump according to claim 2, characterized in that: The film sealing structure comprises a sealing seat (06), a sealing film (19), a frame (29), a sealing connecting rod (30) and a sealing cap (33); The sealing cap (33) buckles the sealing film (19) onto the sealing connecting rod (30); the frame (29) and the sealing connecting rod (30) are detachably connected and press the sealing cap (33) and the sealing film (19); the sealing film (19) has sufficient margin and is pressed by the sealing seat (06) above the oil return port (T) of the top oil return plate (12); the sealing seat (06) and the top oil return plate (12) are detachably connected; the contact surface between the sealing seat (06) and the sealing film (19) is provided with a sealing groove, and an O-ring is provided inside.

6. The three-plunger digital displacement pump according to claim 5, characterized in that: The dynamic coupling actuator comprises a box cover (05), a rotating disk (08), a bearing (09), a bearing end cover (11), a rotating shaft (13), a box body (14), and a coupling iron core (31); The housing (14) is fixed to the top oil return plate (12) through a locking ear (04); three sets of rotating disks (08) are fixed to the rotating shaft (13); the rotating shaft (13) passes through the housing (14) and forms a rotating shaft system structure through a bearing seat and a bearing (09), a Y-shaped sealing ring (10), a bearing end cover (11) and necessary positioning rings arranged on the housing; the bearing end cover (11) is fixed to the housing (14); the rotating disk (08) is provided with a circular coupling groove along the radial direction, and the skeleton (29) is inserted into the coupling slot in parallel; one end of the skeleton (29) is connected to the cartridge valve, and the other end is constrained by the linear bearing on the box cover (05); the skeleton (29) is located in the center of the coupling slot, and its two sides form a working gap with the turntable (08) respectively; the coupling iron core (31) is embedded in the skeleton (29), and the coil connection terminal in the coupling iron core passes through the circular hole on the side of the skeleton (29) and is led out of the box body (14) through the box cover (05), and is connected to an external excitation power supply.

7. The three-plunger digital displacement pump according to claim 6, characterized in that: The interior of the box (14) is filled with magnetorheological fluid, and the interior space of the box that does not participate in the work is installed with a box filler (36).

8. The three-plunger digital displacement pump according to claim 6, characterized in that: The coupling iron core (31) comprises an iron core (31-1), a main coil (31-2), an iron ring (31-3), and a secondary coil (31-4); the main coil (31-1) is connected in series with the secondary coil (31-4) through a small hole in the iron ring (31-3), and the currents of the two coils are in opposite directions; the iron core, the magnetorheological fluid in the working gap, the turntable, and the iron ring form a closed magnetic circuit, so that the magnetic induction line passes through the iron core and the iron ring, thereby solidifying the magnetorheological fluid between the iron core and the iron ring and the gap of the turntable, and forming an effective coupling working surface.

9. The three-plunger digital displacement pump according to claim 8, characterized in that: The ratio of the number of turns of the inner and outer coils of the coupling iron core (31) is 7:3.

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