A three-plunger digital displacement pump based on power coupling action valve and variable displacement operation strategy

Abstract

The application provides a scheme of a three-plunger digital displacement pump based on a power coupling action valve, which comprises three groups of flow distribution units, each group of flow distribution units including one reciprocating plunger and two high-speed on-off valves. The plunger is connected to a crankshaft through a connecting rod, and the reciprocating plungers keep a phase difference of 120 degrees during the rotation of the crankshaft, which can save electrical energy consumption and throttling loss during operation, and can be expanded to a multi-plunger digital displacement pump along the direction of the crankshaft according to requirements. The valve core of the check plug-in valve structure has a lighter mass, and the on-off valve has a higher rated flow. The coupling core topology can significantly improve the transient mechanical properties of the power coupling actuator, and significantly reduce the on-off valve operation time. The thin film sealing structure converts the dynamic sealing system into a static sealing system, which can completely avoid the leakage of the magnetorheological fluid, pollute the hydraulic oil circuit, and reduce the system movement resistance.

Description

Technical Field

[0001] The present invention belongs to the field of digital hydraulic technology, and in particular relates to a three-plunger digital displacement pump based on a power-coupled actuating valve and a variable displacement operation strategy. Background Art

[0002] Variable displacement piston pumps are core components that ensure the proper functioning of hydraulic systems in various critical equipment. Because they typically operate using analog control for variable displacement, they are extremely sensitive to the operating environment, significantly raising the technical barriers to manufacturing. Due to factors such as dead volume, leakage and shear friction at the manifold, and throttling at the pump port, variable displacement piston pumps inherently suffer from extremely low efficiency at low displacements. On the one hand, continued iterative development of high-performance hydraulic component manufacturing technology in my country may keep the hydraulics industry at a stage of catching up with advanced global technologies for a long time. On the other hand, even if my country achieves technological advancement in high-performance hydraulic components, it will not eliminate the inherent shortcomings of traditional variable displacement piston pumps. In recent years, digital displacement pumps / motors based on digital displacement technology have attracted widespread attention due to their high energy efficiency across the entire displacement range and low sensitivity to operating environments. The basic unit in digital displacement technology is called a digital manifold unit, which consists of a plunger and two high-speed switching valves. Multiple digital manifold units are combined to form a digital displacement pump / motor. This technology achieves fluid suction and discharge by independently controlling the high-speed switching valves of the manifold units. The functionality of digital displacement pumps / motors relies on high-speed on / off valves with low pressure drop and fast response. Therefore, their structural designs vary significantly depending on the specific structure of these high-speed on / off valves. Currently, in my country's publicly available digital pump technologies, the on / off valves used in digital flow distribution units are mostly commercial cartridge-type solenoid valves. These valves cannot simultaneously achieve low pressure drop and fast response, resulting in unsatisfactory energy efficiency in the development of digital pumps.

[0003] like Figure 1 The left image shows a five-plunger radial digital displacement motor developed by Shanghai Jiao Tong University. Its design features two high-speed on-off valves for each plunger, connected to the high-pressure and low-pressure sides of the hydraulic system. During operation, the on-off valves continuously open and close at high frequency to adjust displacement. This technology, similar to the duty cycle control principle in electronics, adjusts the displacement of the digital motor by controlling the proportion of time the valve is open within a single cycle. The on-off valves in this digital motor operate in such a way that they must open and close multiple times within a single plunger stroke.

[0004] like Figure 1The figure shows prior art 1. The right image shows a digital displacement pump designed by Taiyuan University of Science and Technology. Its design features are similar to those of a traditional swash plate piston variable displacement pump. The pistons are evenly distributed along the circumference, and each piston is equipped with a high-speed on-off valve and a one-way check valve. The high-speed on-off valve is connected to the low-pressure side, and the check valve is connected to the high-pressure side. During operation, when the piston is absorbing oil, the high-speed on-off valve opens, drawing oil from the low-pressure side into the piston cavity. When the piston is discharging oil, the high-speed on-off valve closes, and the oil in the piston cavity is pumped through the check valve to the high-pressure side, completing the pumping function. This design achieves variable displacement control by varying the number of active pistons and the opening and closing phases of the on-off valve. This technology places low demands on the on-off valve's response, requiring the on-off valve to open and close only once within a plunger stroke.

[0005] The digital motor solution of Shanghai Jiao Tong University has a high switching frequency for high-speed switching valves, and the life of the switching valves is difficult to guarantee during use. In addition, due to the small valve stroke, high throttling losses 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 proposed by Taiyuan University of Science and Technology is relatively consistent with the digital displacement concept. However, while it retains the slipper structure of the swash plate plunger pump, fluid shear and friction losses are inevitable during low-displacement, high-pressure operation and are highly sensitive to the operating environment. Furthermore, its high-pressure port uses a passive check valve, whose switching characteristics depend on the pressure differential across the valve, meaning that throttling losses are always present at this port. Furthermore, this design uses a solenoid cartridge valve instead of a high-speed on-off valve. The on-off valve's pressure drop and response time make it difficult to meet the requirements of digital displacement technology. This design retains the digital variable displacement control characteristics of digital displacement technology, but fails to leverage its advantages of high energy efficiency and insensitivity to the operating environment.

[0007] like Figure 2 As shown, prior art 2 is a concept of a digital flow distribution mechanism based on a power-coupled actuated valve proposed by the inventors in the early stage, which has the following three defects:

[0008] 1. Coupling drive defects: When the coil is energized, the large lateral dimensions of the coupled core cause significant magnetic diffusion within the core during transient response. Initially, the magnetic flux in the center of the core is significantly smaller than the flux at the edges. Rapid saturation of the core's surface flux is crucial for fast valve response. However, with a large-area coupled core, this structure cannot guarantee a fast valve response.

[0009] 2. Sealing defect: The tank is filled with MR fluid, and O-ring is needed to seal the MR fluid to prevent the MR fluid from polluting the hydraulic oil in the hydraulic system. On the one hand, the translator needs to realize high-frequency reciprocating motion in the working process, so the O-ring needs to be designed with appropriate compression to ensure sealing effect, and the compression should not be too large to increase the movement resistance of the translator. On the other hand, this kind of dynamic sealing method cannot completely ensure the sealing of the MR fluid, and the MR fluid will always leak into the hydraulic system along the O-ring gap during high-frequency reciprocating motion.

[0010] 3. Switching valve defect: The sliding valve structure is used as a switching valve, and the digital flow distribution unit based on the valve structure has two defects in the digital displacement pump: 1. The low-pressure loss sliding valve spool needs a longer shaft shoulder or a larger diameter shaft shoulder, which results in a fold increase in the mass of the spool compared to the seat valve spool, thereby reducing the response speed. 2. The sliding valve is almost not affected by the system pressure during operation, so the driver needs to be continuously powered to ensure the position of the sliding valve spool, which increases the electrical energy loss. SUMMARY

[0011] The present application redesigns the digital flow distribution mechanism based on the concept of power coupling actuator valve (prior art 2), including the adaptability of the determinant to the plunger mother pump, the improvement of the sealing structure, the plug-in valve structure and the coupling driving structure, which reduces the transient response time and energy loss of the valve in the flow distribution mechanism. In addition, the present application gives an integrated scheme of the digital flow distribution mechanism, forming a multi-plunger digital displacement pump, and gives a variable displacement control strategy for the digital displacement pump / motor. For the coupling driving defect, the present application gives a double-coil topology to reduce the influence of magnetic diffusion process on the transient response of the switching valve. For the sealing defect, the present application proposes a new flexible membrane sealing method, which converts dynamic sealing into static sealing, i.e. realizes complete sealing of the MR fluid, and reduces the system resistance. For the switching valve defect, the present application designs a low-pressure loss check valve structure suitable for power coupling actuators, and the flow distribution mechanism formed by the 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 powered for a short time at a specified phase to realize the opening and closing of the switching valve, thereby greatly reducing the electrical energy consumption in the working process.

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

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

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

[0015] The digital flow distribution unit comprises one reciprocating plunger and two high-speed on-off valves; the reciprocating plunger is connected to the crankshaft through a connecting rod; the crankshaft keeps a phase difference of 120° between the plungers during rotation; the pump head is provided with three plunger cavities on one side, which are not communicated with each other and correspond to the plungers of the master pump respectively; the plunger cavities are respectively provided with oil channel branches for installing pressure sensors; the auxiliary oil seal is embedded in the sealing sleeve and is sequentially sleeved on the plunger with the sealing positioning ring, the sealing packing, the main oil seal and the sealing washer; the plunger is inserted into the plunger cavity of the pump head; the master pump and the pump head are provided with a partition plate therebetween; the L-shaped connecting plate is fixed below the pump head; the partition plate is detachably connected with the pump head and the L-shaped connecting plate, so that the sealed connection between the pump head and the master pump is realized; three oil holes for connecting the plungers are formed in the partition plate for adding lubricating oil.

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

[0017] On the basis of the above-mentioned scheme, the digital flow distribution unit comprises a bottom oil return disc, a top oil return disc, a main valve block, a sealing connecting rod, a diaphragm sealing structure, an inserted valve and a power coupling actuator;

[0018] The bottom oil return disc is fixed above the pump head and is provided with three working oil holes and six oil return holes; the three working holes are connected with the three plunger cavities of the pump head and the three working oil ports at the bottom of the main valve block respectively and are not communicated with each other, and the six oil return holes are communicated with the oil return port through internal channels; the main valve block is provided with six inserted valve holes corresponding to the six oil return holes of the bottom oil return disc and is insertedly connected with the bottom oil return disc; a sealing groove is formed at the bottom of each inserted valve hole and is provided with an O-shaped sealing ring; the bottom oil return disc is connected and locked with the main valve block and is sealed by pressing the sealing ring; each working oil hole of the main valve block is communicated with the inserted valve holes on both sides through inclined holes, so that each plunger cavity is directly communicated with two on-off valves to form a group of flow distribution units;

[0019] The main valve block is provided with six external ports perpendicular to the plug-in holes, each of which corresponds to one plug-in valve hole and is not communicated with each other, and the external ports are used for connecting the plug-in valve with the high pressure port or the low pressure port of the hydraulic system; the plug-in valve is directly plugged into the plug-in hole of the main valve block and the bottom is embedded into the oil return port plug-in slot of the bottom oil return disc; two plug-in valves in each plunger cavity are arranged in opposite directions; the plug-in valve is externally provided with a sealing groove and is embedded with an O-ring; the outer wall of the plug-in valve is tightly fitted with the inner wall of the plug-in hole, and the O-ring is compressed; the two plug-in valves in each flow distribution unit are arranged in opposite directions, the valve opening direction is taken as the positive direction, the plug-in valve connected with the high pressure port is plugged in the positive direction, and the plug-in valve connected with the low pressure port is plugged in the reverse direction; the bottom of the top oil return disc is provided with six oil return ports, and the six oil return ports are communicated to the oil return port through the internal hole; the six oil return ports of the top oil return disc are provided with plug-in slots below and are plugged with the main valve block; the outer wall of the plug-in valve is tightly fitted with the inner wall thereof, and the gap is sealed by compressing the O-ring; one end of the sealing connecting rod is connected with the plug-in valve core through a thread, and the other end is connected with the power coupling actuator through the diaphragm sealing structure through the oil return port of the top oil return disc.

[0020] On the basis of the above scheme, the plug-in valve comprises a spring, a valve core, a plug-in valve sleeve and a set of valve core sliding ways.

[0021] The outer wall of the plug-in valve sleeve is provided with a sealing groove for installing an O-ring; the valve core sliding ways are respectively arranged at both ends of the plug-in valve sleeve and are used for restraining the valve core; the valve core sliding ways are communicated with the oil return ports of the bottom oil return disc, and the sliding ways above are provided with positioning holes for limiting the opening degree of the valve core; the mating surface of the valve core and the valve core sliding way is provided with three grooves for preventing oil leakage from the gap; the valve core is provided with threaded holes at both ends for connecting with the sealing rod; the spring is used to keep the plug-in valve in the normally open state, and the spring has no pre-tightening force in the natural state.

[0022] Further, the valve core and the valve core sliding way are gap-fitted, and the gap is controlled to be 0-13 microns. The invention designs a check plug-in valve structure matched with the power coupling actuator, the valve core has a lighter mass, and the on-off valve has a higher rated flow.

[0023] On the basis of the above scheme, the diaphragm sealing structure comprises a sealing seat, a sealing film, a framework, a sealing connecting rod and a sealing cap; the sealing cap buckles and presses the sealing film on the sealing connecting rod, the framework is detachably connected with the sealing connecting rod and presses the sealing cap and the sealing film; the sealing film has sufficient excess and is pressed above the oil return port of the top oil return disc by the sealing seat, and the sealing seat is detachably connected with the top oil return disc; the contact surface of the sealing seat and the sealing film is provided with a sealing groove and is internally provided with an O-ring.

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

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

[0026] On the basis of the above scheme, the power coupling actuator comprises a box cover, a rotating disc, a bearing, a bearing end cover, a rotating shaft, a box body, and a coupling core.

[0027] The box body is fixed on the top oil return disc through the locking lug; three sets of rotating discs are fixed on the rotating shaft, the rotating shaft penetrates through the box body and forms a rotating shaft system structure with the bearing seat, the bearing, the Y-shaped sealing ring, the bearing end cover, and the necessary positioning ring arranged on the box body; the bearing end cover is fixed on the box body; the rotating disc is provided with a circular coupling groove in the radial direction, and the skeleton is parallelly inserted into the coupling groove; one end of the skeleton is connected with the plug-in valve, and the other end is constrained through the linear bearing on the box cover; the skeleton is located in the center of the coupling groove, and both sides thereof form working gaps with the rotating disc; the coupling core is inlaid on the skeleton, and the coil wire end in the coupling core penetrates out through the side hole of the skeleton and is led out of the box body through the box cover, and is connected with the external excitation power supply.

[0028] Further, the inside of the box body is filled with the magnetorheological fluid, and the inside space of the box body not participating in the work is provided with a box filler for saving the magnetorheological fluid.

[0029] On the basis of the above scheme, the coupling core comprises a core, a main coil, a ring, and a secondary coil; the main coil is connected in series with the secondary coil through the small hole of the ring, and the current directions of the two coils are opposite. The core, the magnetorheological fluid in the working gap, the rotating disc, and the ring form a closed magnetic circuit, so that the magnetic induction lines pass through the core and the ring, thereby solidifying the magnetorheological fluid between the core, the ring, and the rotating disc gap, and forming an effective coupling working surface. The secondary coil is nested in the outer ring of the ring, and the current direction of the secondary coil is opposite to that of the main coil, so that the magnetic induction lines in the same direction are formed in the ring, the magnetic flux density of the coupling surface is increased, and the leakage of the magnetic flux in the closed magnetic circuit is prevented.

[0030] Further, the turns ratio of the inner coil to the outer coil of the coupling core is 7:3.

[0031] The present application provides the topological structure of the coupling core, which can significantly improve the transient mechanical properties of the power coupling actuator, and significantly reduce the switching valve operating time. The topological idea can be extended to a multi-layer coil structure for a large-area coupling core, so as to ensure the transient mechanical properties of the system.

[0032] In the second aspect, a variable displacement operation strategy of a digital displacement pump is provided, which specifically comprises flow ratio control and stroke ratio control.

[0033] When the flow ratio control mode is adopted: three groups of flow distribution units work independently, when the power coupling actuator is not powered, the pump is in an idle state, the plunger oil suction and discharge process flows into or out of the LP port, at this time the plunger pump displacement is 0; only one group of power coupling actuator of the flow distribution unit is phase excited, the plunger pump realizes 1 / 3 displacement, 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.

[0034] When the stroke ratio control mode is adopted: the plunger works in full displacement during the oil suction stroke, when the plunger is in the oil discharge stroke, the LP side power coupling driver excitation phase is determined according to the plunger stroke position, so as to control the proportion of oil returning to the LP in the plunger cavity, so as to control the displacement of a single flow distribution unit.

[0035] The beneficial effects of the present application are as follows:

[0036] The digital displacement pump / motor can realize digital variable displacement control in the full displacement range.

[0037] The digital displacement pump / motor has a working efficiency of more than 90% in the full displacement range.

[0038] The three groups of flow distribution units of the digital displacement pump / motor work independently and do not affect each other, improving the reliability of the digital pump / motor.

[0039] The thin film sealing structure can completely avoid the leakage of the magnetorheological fluid and pollute the oil way system. Meanwhile, the structure reduces the system movement resistance.

[0040] The digital flow distribution mechanism can greatly save the electric energy loss and throttling loss in the flow distribution process.

[0041] The coupling core structure can greatly improve the transient mechanical properties of the power coupling actuator, and can reach the driving force saturation state in a short time. BRIEF DESCRIPTION OF DRAWINGS

[0042] The present application has the following drawings:

[0043] Figure 1 It is prior art 1 Shanghai Jiaotong University digital motor scheme (left figure) Taiyuan University of Science and Technology digital pump scheme (right figure);

[0044] Figure 2 It is prior art 2 China Agricultural University digital flow distribution mechanism based on power coupling actuator;

[0045] Figure 3 It is a disassembled view of each part of the present application;

[0046] Figure 4 It is a three-plunger digital variable displacement pump assembly drawing;

[0047] Figure 5 This is the structural diagram of the cartridge valve;

[0048] Figure 6 This is a diagram of the film sealing structure;

[0049] Figure 7 This is the coupling core cross section and magnetic field line distribution diagram.

[0050] Figure markings: 01 mother pump, 02 angle sensor, 03 linear bearing, 04 lock ear, 05 box cover, 06 sealing seat, 07 bottom oil return plate, 08 coupling turntable, 09 bearing, 10 Y-type sealing ring, 11 bearing end cover, 12 top oil return plate, 13 rotating shaft, 14 box body, 15 main valve block, 16 pump head, 17 spring, 18 valve core, 19 sealing membrane, 20 partition, 21 oil seal gasket, 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, 34L connecting plate, 35 valve core slide, 36 box body packing, CP plunger cavity, HP high pressure port, LP low pressure port, T oil return port, SP oil channel branch. DETAILED DESCRIPTION

[0051] In order to make the objects, advantages and features of the present invention more apparent, a detailed description is given below with reference to the accompanying drawings and specific embodiments.

[0052] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention.

[0053] It will be understood by those skilled in the art that, unless expressly stated otherwise, the singular forms "a", "an", "said" and "the" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the description of the present invention refers to the presence of the 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 groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, "connected" or "coupled" as used herein may include wireless connections or couplings. The term "and / or" used herein includes any unit and all combinations of one or more associated listed items.

[0054] Those skilled in the art will appreciate that unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art in the field of the application. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0055] As Figure 3 and Figure 4 is a specific embodiment of the present application. A three-plunger digital displacement pump (or motor) assembly based on power coupling action valve is shown. It includes a radial three-plunger master pump 01, a bottom oil return plate 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. The pump head 16 is provided with three plunger cavities CP on one side, which are not connected to each other, and are respectively connected to the three plungers 26 of the master pump 01. Oil passage branches SP are arranged corresponding to the plunger cavities CP for installing pressure sensors. The secondary oil seal 27 is embedded in the sealing sleeve, and is sequentially sleeved on the master pump plunger with the sealing positioning ring 24, the sealing packing 23, the main oil seal 22, and the sealing gasket 21. The master pump plunger 26 is inserted into the plunger cavity of the pump head 16, and the partition plate 20 is arranged between the master 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, so as to realize the sealed connection of the pump head and the master pump. Three oil holes for adding lubricating oil are opened on the partition plate 20 to communicate with the plungers.

[0056] The digital flow distribution unit comprises a bottom oil return disc 07, a top oil return disc 12, a main valve block 15, a sealing connecting rod 30, a diaphragm sealing structure, an insert valve and a power coupling actuator. The bottom oil return disc 07 is fixed above the pump head by bolts, and three working oil holes and six oil return holes T are opened in the bottom oil return disc 07. The three working holes are connected with the three plunger cavities of the pump head and the three working oil ports at the bottom of the main valve block 15 respectively and are not connected with each other. The six oil return holes are connected with the oil return port T through internal channels. The main valve block 15 is provided with six insert valve holes corresponding to the six oil return holes of the bottom oil return disc 07 and is connected with the bottom oil return disc 07 in an insert manner. A sealing groove is opened at the bottom of each insert valve hole, and an O-shaped sealing ring is arranged. The bottom oil return disc 07 is connected and locked with the main valve block 15 by bolts, and the sealing of the gap between the two is ensured by pressing the sealing ring. Each working oil hole of the main valve block 15 is connected with two insert valve holes on both sides through inclined holes, so that each plunger cavity can be directly connected with two on-off valves to form a group of flow distribution units. Six external ports perpendicular to the insert holes are arranged above the main valve block 15, and each port corresponds to an insert valve hole and is not connected with each other. The ports ensure that the insert valves are connected with the high-pressure port HP or the low-pressure port LP of the hydraulic system. The insert valves are directly inserted into the insert holes of the main valve block 15, and the bottoms are embedded into the oil return port insert grooves of the bottom oil return disc 07. The two insert valves arranged for each plunger cavity are inserted in opposite directions. A sealing groove is opened on the outer wall of the insert valve, and an O-shaped ring is embedded. The outer wall of the insert valve is tightly combined with the inner wall of the insert hole, and the O-shaped ring is pressed to achieve sealing. The two insert valves in each group of flow distribution units are inserted in opposite directions. Taking the valve opening direction as the positive direction, the insert valve connected with the high-pressure port HP is inserted in the positive direction, and the insert valve connected with the low-pressure port LP is inserted in the reverse direction. Six oil return ports are opened below the top oil return disc 12, and the oil return ports are connected with each group of insert valve structures in the machine through internal channels. The connection position of each group of insert valve structures with the top oil return disc 12 is connected with the oil return port T through internal channels. The insert grooves are arranged below the six oil return ports of the top oil return disc 12, and are inserted into the insert holes of the main valve block 15 and fastened by bolts. The outer wall of the insert valve is tightly combined with the inner wall thereof, and the gap is sealed by pressing the O-shaped ring. One end of the sealing connecting rod 30 is connected with the valve core 18 of the insert valve through threads, and the other end is connected with the power coupling actuator through a specific diaphragm sealing structure through the oil return port of the top oil return disc 12. Figure 3 ) structure and the oil return port in the machine, and the connection position of each group of insert valve structures with the top oil return disc 12 is connected with the oil return port T through internal channels. The insert grooves are arranged below the six oil return ports of the top oil return disc 12, and are inserted into the insert holes of the main valve block 15 and fastened by bolts. The outer wall of the insert valve is tightly combined with the inner wall thereof, and the gap is sealed by pressing the O-shaped ring. One end of the sealing connecting rod 30 is connected with the valve core 18 of the insert valve through threads, and the other end is connected with the power coupling actuator through a specific diaphragm sealing structure through the oil return port of the top oil return disc 12.

[0057] The insert valve is as Figure 5As shown: including spring 17, valve core 18, plug-in valve sleeve 32, and a set of valve core slide 35. Plug-in valve sleeve 32 outer wall with sealing groove, for installing O-ring to achieve plug-in sealing. Slide 35 respectively plug-in valve sleeve 32 both ends, used to constrain valve core 18. Valve core 18 and slide 35 with clearance fit, clearance control in 0~13 microns to ensure smooth movement of valve core and small leakage. Slide 35 communication oil return port of oil pan, ensure valve core movement is not subject to static hydraulic resistance. The upper slide is provided with positioning hole, used to limit the valve core opening degree. Valve core 18 and slide fit surface with 3 groove, prevent oil from leakage. Valve core 18 both ends with sealing rod 30 connected with threaded hole, spring 17 ensure plug-in valve in the open state, and spring natural state without pre-tightening force.

[0058] The film sealing structure is as shown in Figure 6 As shown: including sealing seat 06, top oil return disc 12, sealing film 19, skeleton 29, sealing connecting rod 30 and sealing cap 33. Sealing cap 33 will be sealed film 19 buckled on the sealing connecting rod 30, the bottom end of skeleton 29 is screwed with the upper threaded hole of sealing connecting rod 30 to connect and fix and press sealing cap 33 and sealing film 19. Sealing film 19 has enough excess, and is pressed by sealing seat 06 above the oil return port of top oil return disc 12, sealing seat 06 and top oil return disc 12 are connected by screw. Sealing seat 06 and sealing film 19 contact surface with sealing groove, inside set with O-ring, used to enhance the sealing effect. Its working principle is: the sealing mode between sealing seat 06 and oil return disc 12 and the sealing mode between skeleton 29 and sealing rod 30 are both static sealing, sealing film 19 completely isolates the magnetic rheological fluid in the upper power coupling actuator and the oil in the lower oil pan. When the actuator drives the valve core to move, the skeleton 29 drives the sealing rod 30 to drive the valve core to move, because of the flexible characteristics of the sealing film and the sufficient excess, the sealing film almost does not provide resistance to the system during the movement. The sealing structure relies on the flexible characteristics of the sealing film to convert the dynamic sealing problem into static sealing, avoiding the leakage and movement resistance caused by the traditional O-ring sealing mode.

[0059] It should be pointed out that the sealing film 19 recommends using 3 wire~5 wire specification of strong plastic PE material, to reduce the system movement resistance.

[0060] The power coupling actuator includes a box cover 05, a rotating disc 08, a bearing 09, a bearing end cover 11, a rotating shaft 13, a box 14, a skeleton 29, a coupling core 31, and a box filler 36. The box is fixed on the top oil return disc 12 through the locking lug 04, and the gap is sealed with oil sealant to prevent the leakage of the magnetorheological fluid. Three groups of rotating discs 08 are fixed on the rotating shaft 13 through screws, the rotating shaft 13 penetrates through the box, and a complete rotating shaft structure is formed by the bearing 09, the Y-shaped sealing ring 10, the bearing end cover 11, and the necessary positioning ring (not shown in the figure). The bearing end cover is fixed on the box 14 through screws. The rotating disc 08 is radially provided with a circular coupling groove with a depth of 6 mm, and the skeleton 29 with a thickness of 5 mm is inserted into the coupling groove in parallel. One end of the skeleton is connected with the plug-in valve, and the other end is constrained through the 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 adjustment rotating disc 08 on the rotating shaft 13 is adjusted to ensure that the skeleton 29 is located in the center of the coupling groove, and the two sides of the skeleton form a working gap of 0.5 mm with the rotating disc. The coupling core 31 is embedded in the skeleton 29, the coil wire end of the coupling core penetrates out through the round hole on the side surface of the skeleton and is led out of the box through the box cover, and is connected with the external excitation power supply (not shown in the figure). The inside of the box 14 is filled with magnetorheological fluid, and the inside space of the box which does not participate in the work is provided with the box filler 36 to save the magnetorheological fluid. It should be noted that the filler material should have small density, magnetic insulation, and corrosion resistance.

[0061] The working principle of the power coupling driver is as follows: the rotating shaft 13 is connected with a driving motor to drive the rotating disc 08 to rotate. The rotating disc rotates clockwise from the LP side to the HP side, and when the coil of the coupling core 31 is energized, a strong magnetic field is formed between the coupling core and the rotating disc. Since the working gap between the coupling core and the rotating disc is filled with magnetorheological fluid with instantaneous reversible rheological properties, the magnetorheological fluid in the gap will quickly solidify under the action of the strong magnetic field, so that the coupling core and the rotating disc are coupled and adhered, and the rotating disc provides a downward shear driving force for the coupling core, which is approximately proportional to the area of the coupling core under magnetic saturation. Under the action of the shear force, the skeleton moves downward to close the on-off valve. When the coil is de-energized, the valve core returns to the original position under the action of the spring.

[0062] The detailed topology structure of the coupling core 31 is as follows Figure 7The core 31-1, the main coil 31-2, the iron ring 31-3, and the auxiliary coil 31-4 are shown. The main coil 31-1 is connected in series with the auxiliary coil 31-4 through the small hole of the iron ring 31-3, and the current directions of the two coils are opposite. The core, the magneto-rheological fluid in the working gap, the rotating disc and the iron ring form a closed magnetic circuit, so that the magnetic induction lines pass through the core and the iron ring, thereby solidifying the magneto-rheological fluid between the core and the iron ring and the rotating disc gap, and forming an effective coupling working surface. The auxiliary coil is nested in the outer ring of the iron ring, and the current direction of the auxiliary coil is opposite to that of the main coil, so that the magnetic induction lines in the same direction are formed in the iron ring, the magnetic flux density of the coupling surface is increased, and the magnetic flux leakage in the closed magnetic circuit is prevented. The magneto-rheological fluid has a saturation magnetic flux density, that is, when the magnetic flux density exceeds the saturation magnetic flux density, the yield stress of the magneto-rheological fluid does not increase any more. For the design of the large-area coupling core structure, the design scheme in the prior art 2 causes the magnetic flux in the center region of the coupling surface to be unable to quickly reach the required value due to the magnetic diffusion effect in the power-on moment, thereby prolonging the saturation time of the shear driving force. Compared with the coupling core structure mentioned in the prior art 2, the design has the advantages that the disadvantage of significant decrease in transient performance of the large-area coupling core driver caused by the magnetic diffusion phenomenon in the original design is eliminated, and under the conditions of the same area of the coupling surface, the same number of turns of the coil and the same external driving voltage, the saturation magnetic flux density can be reached more quickly, 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 is 7:3, and the saturation shear force can be reached within 2 ms. In addition, since the circumference of the main coil is reduced, the scheme also has smaller moving mass, and further improves the transient performance of the driver.

[0063] The working principle of the digital displacement pump / motor is as follows: HP and LP are connected with the high-pressure end and the low-pressure end of the hydraulic oil circuit respectively, T is connected with the oil tank, and SP is provided with a pressure sensor. Three groups of flow distribution units are included, each group of flow distribution unit comprising a reciprocating plunger and two high-speed on-off valves. The plunger is connected to the crankshaft through a connecting rod, and during rotation of the crankshaft, the plungers maintain a phase difference of 120°, and the absolute phase is monitored by an angle encoder 02. The crankshaft rotates at a constant speed 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 when the plunger reaches the bottom dead center, the plunger cavity completes the oil suction action.

[0064] The pumping mode control method of a set of flow distribution units is as follows: the pressure in the plunger cavity CP is the same as the pressure on the LP side when starting, and the plug-in valve on the LP side is in an open state; the HP side switch valve is in a closed state due to the pressure on the HP side being higher than the pressure in the plunger cavity CP under the action of the pressure difference. The pumping process includes four stages: oil suction, compression, oil discharge, and expansion. The plunger starts the oil suction stroke from the top dead center, and the oil enters the plunger cavity CP from the LP side. The valve needs to be completely closed under the action of the LP side driver when the plunger reaches the bottom dead center, at which time the compression stroke begins. Since it takes a certain time for the switch valve to be completely closed, the coupling core energizing phase needs to be earlier than the bottom dead center, and the advance phase is determined by the pump speed and the switch valve control time. During the compression stroke, the pressure in the plunger cavity CP gradually increases during the compression process, at which time the LP side coupling core is de-energized, and the pressure difference between the LP and CP ensures that the LP side check valve is closed. The pressure in the plunger cavity continues to increase to the pressure level of the high-pressure port HP, and the plug-in valve on the HP side quickly opens under the action of the spring and the pressure difference of the valve port, and the system enters the oil discharge stroke. When the plunger oil discharge stroke moves to the top dead center, the valve needs to be completely closed under the action of the HP side driver, at which time the expansion stroke begins. Since it takes a certain time for the switch valve to be completely closed, the coupling core energizing phase needs to be earlier than the top dead center, and the advance phase is determined by the pump speed and the switch valve control time. During the expansion stroke, the pressure in the plunger cavity CP decreases from the pressure on the HP side to the pressure on the LP side. During this process, the HP side coupling core is de-energized, the HP side check valve is closed under the action of the pressure difference of the valve port, and the LP side switch valve quickly opens under the action of the spring and the pressure difference of the valve port, and the oil suction stroke is re-entered to complete a pumping and oil distribution cycle. Three sets of flow distribution units work alternately in parallel, the crankshaft phase is monitored by an angle sensor, and the power coupling actuator drives the switch valve to realize the full displacement pumping function of the three-plunger digital displacement pump.

[0065] The motor mode operating method of a set of flow distribution units is as follows: the same as the oil path connection mode in pumping mode, the crankshaft is connected to the rotating load system as the output end, and the motor mode needs to be pre-started at a certain speed. In the motor working mode, the plunger cavity CP contains four stages of 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, enters the oil suction stroke, and at this time the oil in the HP port does work to the outside to drive the crankshaft to rotate. During this process, the LP side switch valve is closed under the action of the valve port pressure difference. The switch valve needs to be completely closed before the plunger enters the expansion stroke from the oil suction stroke, and the phase of entering the expansion stroke is related to the compressibility of hydraulic oil. Since it takes a certain time for the switch valve to be completely closed, the coupling core energizing phase needs to be ahead of the phase of entering the expansion stroke, and the leading phase is determined by the motor speed and the switch valve operating time. After entering the expansion stroke, the driver is de-energized, and the plunger continues to move to the bottom dead center. During this process, the pressure in the plunger cavity decreases and is higher than the pressure level on the LP side, so both end switch valves are closed under the action of the valve port pressure difference. When the plunger reaches the bottom dead center, the pressure in the plunger cavity decreases to the LP pressure level, and under the action of inertia the plunger starts to move to 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 cavity enters the oil discharge stroke. At this time, the crankshaft drives the plunger to discharge the hydraulic oil in the plunger cavity. When the plunger enters the compression stroke from the oil discharge stroke, the LP switch valve should be completely closed, and the phase of entering the compression stroke is related to the compressibility of hydraulic oil. Since it takes a certain time for the switch valve to be completely closed, the coupling core energizing phase needs to be ahead of the phase of entering the compression stroke, and the leading phase is determined by the motor speed and the switch valve operating time. After entering the compression stroke, the driver is de-energized, and the pressure in the plunger cavity CP gradually rises. When it is close to the top dead center, the internal pressure is higher than the pressure level on the HP side. Under the action of the valve port pressure difference and the spring, the HP side switch valve quickly opens, and the plunger relies on system inertia to cross the top dead center and re-enter the oil suction stroke, completing a motor oil distribution cycle. Three sets of flow distribution units work in parallel and alternately, the crankshaft phase is monitored by an angle sensor, and the power coupling actuator drives the switch valve to realize the function of a three-plunger digital displacement full-displacement motor.

[0066] Take the variable displacement control strategy in pumping mode as an example: including two kinds of flow ratio control and stroke ratio control. When using flow ratio control: three groups of valve train units work independently. When the power coupling actuator is not powered, the pump is in idle state, and the plunger suction and discharge oil process flows into / out of LP port, at this time the plunger pump displacement is 0. When only one group of power coupling actuator of valve train unit is excited, the plunger pump realizes 1 / 3 displacement. Similarly, when two groups of valve train units work simultaneously and three groups of valve train units work simultaneously, 2 / 3 displacement and full displacement are realized; when using stroke ratio control, the plunger works at full displacement during suction stroke. When the plunger is in discharge stroke, the excitation phase of LP side power coupling driver is determined according to the position of plunger stroke, so as to control the proportion of oil returning to LP in plunger cavity, and thus control the displacement of single valve train unit. For example, when the plunger moves from bottom dead center to 1 / 2 of full stroke during discharge stroke, the LP side on-off valve is completely closed, and 1 / 2 of the oil is returned to the tank during this process, only the remaining 1 / 2 of the oil enters the HP end to participate in work during the discharge stroke, thereby realizing 1 / 2 displacement. Combined with the two control methods of flow ratio and stroke ratio, the digital displacement pump can theoretically realize variable displacement control in the full displacement range. The control strategy in motor mode is similar to that in pumping mode, and through the control methods of flow ratio and stroke ratio, variable displacement control in the full displacement range in motor mode can be realized.

Claims

1. A three-piston digital displacement pump based on power-coupled acting valves, characterized in that, It comprises a radial matrix pump (01), a pump head (16), a partition (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; The high-pressure port is connected with the high-pressure end of the hydraulic oil circuit, and the low-pressure port is connected with the low-pressure end of the hydraulic oil circuit; the plunger of the matrix pump is connected to the crankshaft through a connecting rod; during rotation of the crankshaft, the plunger maintains a 120° phase difference with each other; the pump head (16) is provided with three plunger cavities on one side, which are not connected with each other and correspond to the plungers (26) of the matrix pump (01); the plunger cavities are respectively provided with oil channel branches for installing pressure sensors; the secondary oil seal (27) is embedded in the sealing sleeve (25) and is sequentially sleeved on the plunger (26) with the sealing positioning ring (24), the sealing packing (23), the main oil seal (22) and the sealing gasket (21); the plunger (26) is inserted into the plunger cavity of the pump head (16); the matrix pump (01) and the pump head (16) are provided with a partition (20) in the middle; the L-shaped connecting plate (34) is fixed below the pump head (16); the partition (20) is detachably connected with the pump head (16) and the L-shaped connecting plate (34), so as to realize sealed connection of the pump head (16) and the matrix pump (01); The digital flow distribution unit comprises a bottom oil return disc (07), a top oil return disc (12), a main valve block (15), a sealing connecting rod (30), a diaphragm sealing structure, a high-speed on-off valve and a power coupling actuator; the high-speed on-off valve is a plug-in valve; The bottom oil return disc (07) is fixed above the pump head (16) and is provided with three working oil holes and six oil return holes; the three working holes are connected with the three plunger cavities of the pump head (16) and the three working oil ports at the bottom of the main valve block (15) and are not connected with each other, and the six oil return holes are connected to the oil return port through internal channels; the main valve block (15) is provided with six plug-in valve holes corresponding to the six oil return holes of the bottom oil return disc (07) and is plug-in connected with the bottom oil return disc (07); a sealing groove is formed at the bottom of each plug-in valve hole and is provided with a sealing ring; the bottom oil return disc (07) is connected and locked with the main valve block (15) and is sealed by pressing the sealing ring; each working oil hole of the main valve block (15) is communicated with the plug-in valve holes on both sides through inclined holes, so that each plunger cavity is directly communicated with two high-speed on-off valves; The main valve block (15) is provided with six external ports perpendicular to the plug-in holes, each of which corresponds to a plug-in valve hole and is not communicated with each other, and is used for connecting the plug-in valve with the high pressure port or the low pressure port of the hydraulic system; the plug-in valve is directly plugged into the plug-in hole of the main valve block (15) and is embedded into the oil return port plug-in slot of the bottom oil return disc (07); the plug-in valve is externally provided with a sealing groove and is embedded with an O-ring; the outer wall of the plug-in valve is tightly combined with the inner wall of the plug-in hole, and the O-ring is compressed; the plug-in valves in each flow distribution unit are oppositely plugged, the valve opening direction is taken as the positive direction, the plug-in valve connected with the high pressure port is plugged in the positive direction, and the plug-in valve connected with the low pressure port is plugged in the reverse direction; the bottom oil return disc (12) is provided with six oil return ports below, and the six oil return ports are communicated to the oil return port through internal channels; the six oil return ports of the top oil return disc (12) are provided with plug-in slots below and are plugged and connected with the main valve block (15); the outer wall of the plug-in valve is tightly combined with the inner wall of the top oil return disc, and the gap is sealed by the compression ring; one end of the sealing connecting rod (30) is connected with the plug-in valve core (18) through threads, and the other end is connected with the power coupling actuator through the oil return port of the top oil return disc (12) and the thin film sealing structure; The plug-in valve comprises a spring (17), a valve core (18), a plug-in valve sleeve (32) and a set of valve core sliding ways (35); The thin film sealing structure comprises a sealing seat (06), a sealing film (19), a framework (29) and a sealing cap (33).

2. The three-piston digital displacement pump of claim 1, wherein, The outer wall of the plug-in valve sleeve (32) is provided with a sealing groove for installing an O-ring; the valve core sliding way (35) is respectively arranged at both ends of the plug-in valve sleeve (32) and is used for restraining the valve core (18); the valve core sliding way (35) is communicated with the oil return port of the bottom oil return disc (07), the upper valve core sliding way is provided with a positioning hole and is used for limiting the opening degree of the valve core; the mating surface of the valve core (18) and the valve core sliding way (35) is provided with three grooves and is used for preventing oil leakage from the gap; the valve core (18) is provided with threaded holes at both ends and is connected with the sealing connecting rod (30); the spring (17) is used for keeping the plug-in valve in the open state, and the spring has no pre-tightening force in the natural state.

3. The three-piston digital displacement pump of claim 2, wherein, The valve core (18) and the valve core sliding way (35) are gap-fitted, and the gap is controlled to be 0-13 microns.

4. The three-piston digital displacement pump of claim 1, wherein, The sealing cap (33) buckles and presses the sealing film (19) on the sealing connecting rod (30), the framework (29) is detachably connected with the sealing connecting rod (30) and compresses the sealing cap (33) and the sealing film (19); the sealing film (19) has sufficient excess and is pressed above the oil return port of the top oil return disc (12) by the sealing seat (06), the sealing seat (06) is detachably connected with the top oil return disc (12); the contact surface of the sealing seat (06) and the sealing film (19) is provided with a sealing groove and is internally provided with an O-ring.

5. The three-piston digital displacement pump of claim 4, wherein, The power coupling actuator comprises a box cover (05), a rotating disc (08), a bearing (09), a bearing end cover (11), a rotating shaft (13), a box body (14) and a coupling iron core (31). The box (14) is fixed on the top oil return disc (12) through the locking lug (04); three groups of rotating discs (08) are fixed on the rotating shaft (13), the rotating shaft (13) penetrates through the box (14) and forms a rotating shaft system structure with the bearing (09), the Y-shaped sealing ring (10), the bearing end cover (11) and the positioning ring through the bearing seat arranged on the box; the bearing end cover (11) is fixed on the box (14); the rotating disc (08) is provided with a circular coupling groove, and the framework (29) is parallelly inserted into the coupling groove; one end of the framework (29) is connected with the plug-in valve, and the other end is constrained through the linear bearing on the box cover (05); the framework (29) is located in the center of the coupling groove, and the two sides thereof form working clearances with the rotating disc (08) respectively; the coupling iron core (31) is inlaid on the framework (29), and the coil wire end in the coupling iron core is led out through the side hole of the framework (29) and the box cover (05) and connected with the external excitation power supply.

6. The three-piston digital displacement pump of claim 5, wherein, The box (14) is filled with the magnetorheological fluid, and the internal space of the box not participating in work is provided with the box filler (36).

7. The three-piston digital displacement pump of claim 5, wherein, 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 (31-2) 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 clearance, the rotating disc 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, the iron ring and the rotating disc gap, and forming an effective coupling working surface.

8. The three-piston digital displacement pump of claim 7, wherein, The secondary coil is located outside the main coil, and the turn ratio of the main coil to the secondary coil of the coupling iron core (31) is 7:

3.

9. A variable-displacement operating method of a digital displacement pump, characterized by, The three-plunger digital displacement pump based on any one of claims 1-8, specifically comprising flow ratio control and stroke ratio control; When the flow ratio control is adopted: three groups of flow distribution units work independently, when the power coupling actuator is not electrified, the pump is in an idle state, and the plunger suction and discharge processes all flow into or out through the low-pressure port, at this time, the plunger pump has a displacement of 0; when only the power coupling actuator of one group of flow distribution units is excited, the plunger pump realizes 1 / 3 displacement, 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 respectively; When the stroke ratio control is adopted: the plunger works at full displacement during the suction stroke, and when the plunger is in the discharge stroke, the excitation phase of the low-pressure side power coupling driver is determined according to the plunger stroke position, so as to control the proportion of oil returning to the low-pressure side in the plunger cavity, thereby controlling the displacement of a single flow distribution unit.

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