A metal skeleton for magnetic fluid sealing, and a sealing performance testing device and method

Abstract

The present invention provides a metal skeleton for magnetic fluid sealing, a magnetic fluid sealing performance testing device and method. The metal skeleton adopts an annular belt structure and is sleeved outside the rotating shaft during use, and there is a gap for filling magnetic fluid between the metal skeleton and the rotating shaft; there is a gap for filling magnetic fluid between the metal skeleton sleeved outside the rotating shaft and the rotating shaft. When the rotating shaft rotates at a high speed, a micro-motion pressure effect and a labyrinth sealing effect are formed. Under the combined action of the rotation of the rotating shaft and the applied external magnetic field, a dense sealing liquid film is formed, which can resist the sealing pressure. The metal skeleton has good shear resistance. Under the action of the external magnetic field, the magnetic fluid in the gap can be adsorbed on the skeleton to form a "meat wrapping bone" structure, which can better fill the sealing gap and strengthen the heat dissipation of the magnetic fluid.

Description

Technical Field

[0001] The present invention belongs to the fields of application of intelligent materials and magnetic fluid sealing, and relates to a metal skeleton for magnetic fluid sealing, a magnetic fluid sealing performance testing device and a method. Background Art

[0002] Fluid sealing technology has been widely applied in high-tech fields such as aerospace, national defense, nuclear energy, etc., and important technical fields of national economic industries such as petroleum, chemical industry, machinery, electric power, and light industry. Although sealing technology is not a leading technology, it is a decisive technology and has always been the focus of attention of countries around the world. Conducting research on sealing technology can not only achieve energy conservation, consumption reduction, emission reduction and environmental protection, but also provide essential important basic components for high-tech equipment such as space shuttles, deep-sea robots and super-large shield machines.

[0003] Magnetic fluid sealing is an important application field of magnetic fluid, and mainly uses magnetic fluid as a sealing medium to seal a rotating shaft. Magnetic fluid sealing uses a magnetic field to control the magnetic fluid between fixed and rotating components, eliminate the gap of the sealing pair, resist the pressure of the sealed medium, and achieve the sealing of the working medium. Compared with hydrodynamic mechanical seals, the structure of magnetic fluid seals is simpler. Through reasonable structural improvements, the sealing pressure can be further increased, such as optimizing the tooth profile structure parameters and using bevel pole shoes. However, magnetic fluid is a mixture, and magnetic particles, active agents and base carrier liquids are sensitive to temperature. The shear motion of the friction pair / sealing pair will cause viscous dissipation, which is the main factor causing the temperature rise and viscosity reduction of magnetic fluid, and has a significant impact on the magnetic fluid sealing performance. Research shows that the pressure resistance of magnetic fluid decreases with the increase of the sealing temperature, decreases with the increase of the rotational speed, and decreases with the increase of the sealing gap. In addition, when used for liquid sealing, the sealed liquid is in direct contact with the magnetic fluid, and the liquid-liquid interface between the two liquids is unstable, which easily dilutes or flushes the magnetic fluid, resulting in seal failure.

[0004] Investigation found that traditional magnetorheological fluid materials can no longer meet the development requirements of high-tech and equipment. The research and development of new magnetorheological materials suitable for high temperature, low temperature, high-frequency high-speed vibration and other special environments is extremely urgent, which makes the magnetoresponsive functional materials composed of magnetorheological fluid and other materials increasingly attracting attention. For example, on the basis of the porous sponge magnetorheological fluid damper, after years of development, a series of magnetorheological fluid-filled porous metal materials have been formed, improving and enhancing the energy absorption characteristics of the porous materials, and realizing the controllability and intelligence of the energy absorption structure and materials. Aiming at the problem of the decline in the force transmission performance of magnetorheological fluid at high temperature, a composite transmission method of magnetorheological fluid and slider friction driven by shape memory alloy under thermal effect is proposed, which makes up for the defects of magnetorheological fluid at high temperature. The magnetorheological fluid-filled hollow 3D printed lattice structure made by advanced manufacturing technology has a rapid increase in material stiffness under the excitation of a magnetic field, which provides a new idea for the development of magnetorheological fluid-containing composite materials. In addition, there are hydrogel hollow spheres with ferromagnetic particles as capsules developed at the micro- and nano-scale, three-dimensional graphene aerogels modified with ferromagnetic particles, and magnetoresponsive surfaces prepared on the surfaces of glass, aluminum and paper, etc., fully demonstrating the broad application prospects of magnetorheological fluid and its composite materials.

[0005] To sum up, as an important basic component commonly used in many industries, the technological innovation of fluid dynamic seal equipment is of great significance. After decades of development, the application of magnetorheological fluid in the fields of lubrication and sealing has achieved remarkable results. However, due to the limitations of material stiffness, saturation magnetic induction intensity and operating temperature, it is difficult to further improve the sealing performance of magnetorheological fluid. If limited to the sealing medium itself, it is difficult to make a breakthrough. By compounding magnetorheological fluid with other materials to prepare composite materials with more excellent performance, reducing the influence of frictional heat and rotational speed on the sealing performance, the sealing performance parameters can be effectively improved, and the application field of magnetorheological fluid sealing can be further broadened. Summary of the Invention

[0006] Aiming at the problems existing in the current magnetorheological fluid seal, such as low sealing parameters and inability to be used under high rotational speed and high pressure, the present invention provides a metal skeleton for magnetorheological fluid seal for rotating shaft seal; another object of the present invention is to provide a magnetorheological fluid sealing performance testing device.

[0007] Another object of the present invention is to provide a magnetorheological fluid automatic sealing control method.

[0008] The technical solution of the present invention is as follows:

[0009] A metal framework for magnetic fluid sealing, the metal framework adopts an annular belt structure, and when in use, it is sleeved outside the rotating shaft and there is a gap for filling magnetic fluid between it and the rotating shaft; the metal framework is surrounded by several metal sheets, and several fins are provided on the metal sheets, and the fins are arranged in a staggered array, each fin is rectangular and has an opening structure formed by cutting three sides of the rectangle, and the unfolding direction of the fins is the same as the rotating direction of the rotating shaft; the metal framework and the magnetic fluid filled in the gap form a sealing liquid film under the action of an external magnetic field to realize magnetic fluid sealing.

[0010] Further, the external magnetic field is formed by pole shoes connected to the outside of the metal framework and several groups of evenly distributed electromagnets connected to the pole shoes. Under the action of the magnetic circuit of the external magnetic field, the magnetic fluid fills the gap to form a seal.

[0011] Further, the magnetic field lines direction of each group of electromagnets is perpendicular to the axis of the rotating shaft.

[0012] Further, the electromagnet adopts a U-shaped electromagnet, and there are two groups corresponding to the metal framework and the pole shoes. The two groups of metal frameworks are sleeved outside the rotating shaft in parallel at intervals, and the two extreme ends of the U-shaped electromagnet correspond to the positions of a group of pole shoes and a group of metal frameworks respectively.

[0013] Further, the thickness of the metal framework is 0.1 - 0.5 mm.

[0014] Further, the gap distance between the metal framework and the rotating shaft is 0.15 - 0.5 mm.

[0015] Further, the rectangular opening specification of the fins on the metal framework is a*b; wherein, the value range of a is 2 - 4 mm, the value range of b is 1 - 3 mm, and a > b.

[0016] A magnetic fluid sealing performance testing device using the above metal framework for sealing a rotating shaft. The magnetic fluid sealing device includes a housing, a sealing unit, a magnetic field generating device, a temperature control unit, a data acquisition unit, a data processing unit and a control unit;

[0017] One end of the housing is sealed, and the other end is sleeved on the rotating shaft;

[0018] The sealing unit includes two groups of metal frameworks arranged in the housing and magnetic fluid; the two groups of metal frameworks are sleeved outside the rotating shaft in parallel and there are gaps between them and the rotating shaft respectively, and the magnetic fluid fills the gaps;

[0019] The magnetic field generating device includes two sets of pole shoes disposed inside the housing and connected to the outside of the metal skeleton, and several sets of evenly distributed electromagnets disposed outside the housing and cooperating with the pole shoes. The electromagnets are U-shaped electromagnets, and the two extreme ends of the U-shaped electromagnets respectively correspond to a set of pole shoes and a set of metal skeletons. The magnetic field intensity generated by the magnetic field generating device is changed by changing the current of the electromagnet. Inside the housing, a first sealed cavity is formed between the inner pole shoe and the sealed end of the housing, and a second sealed cavity is formed between the two pole shoes.

[0020] The temperature control unit includes a cooling water jacket disposed between and connected to the two pole shoes, and a cooling water circulation device connected to the cooling water jacket.

[0021] The data acquisition unit includes a first pressure sensor and a first temperature sensor disposed in the first sealed cavity, a second pressure sensor and a second temperature sensor disposed in the second sealed cavity, a torque sensor disposed on the output shaft of the motor, and a rotational speed sensor disposed on the rotating shaft. The first pressure sensor and the first temperature sensor are used to measure the medium pressure and temperature. The second pressure sensor and the second temperature sensor are used to measure the magnetic fluid film pressure and temperature.

[0022] The data processing unit is connected to the data acquisition unit and the control unit.

[0023] The control unit is also connected to the controller of the motor, the magnetic field generating device, and the temperature control unit.

[0024] A magnetic fluid automatic sealing control method, based on the above magnetic fluid sealing performance testing device, includes the following steps:

[0025] 1) Installation of the magnetic fluid sealing performance testing device;

[0026] 2) Turn on the magnetic field generating device so that the magnetic fluid in the gap is polarized and fills the gap.

[0027] 3) Rotate the rotating shaft at a rotational speed n1.

[0028] 4) Determine whether the magnetic fluid is sufficient:

[0029] Measure the frictional torque T at the standby rotational speed by the torque sensor f , and compare it with the frictional torque T d when the magnetic fluid is sufficient, and determine whether to supplement the magnetic fluid according to the frictional torque, and supplement the magnetic fluid to sufficiency.

[0030] 5) Adjust the rotational speed of the rotating shaft;

[0031] Adjust the rotational speed n1 of the rotating shaft to the test target rotational speed n2, measure the rotational speed n of the rotating shaft by the rotational speed sensor, and measure the pressure P of the first sealed cavity by the first pressure sensorn The temperature T of the magnetic fluid liquid film is measured by the second temperature sensor m and fed back to the data processing unit. The control unit adjusts the magnetic field intensity of the magnetic field generating device and the opening and closing of the temperature control unit to maintain the sealing stability of the magnetic fluid sealing system. The basis for judging the sealing stability is the temperature T of the magnetic fluid liquid film m and the pressure P of the first sealing cavity n to be stable and the fluctuation range to be within 15%;

[0032] 6) Fill in the sealing medium;

[0033] Fill the sealing medium into the first sealing cavity and gradually increase the pressure. The pressure of the first sealing cavity, that is, the pressure P of the sealing medium, is measured by the first pressure sensor group n and fed back to the data processing unit. The control unit adjusts the magnetic field intensity of the magnetic field generating device and the opening and closing of the temperature control unit according to the threshold value of the preset ultimate sealing pressure P max and the relationship between the medium pressure P n to maintain the sealing stability of the magnetic fluid sealing system. Among them, the preset ultimate sealing pressure P max can be determined by experiments.

[0034] Furthermore, when the pressure P of the sealing medium n fluctuates, that is, P n exceeds the threshold range by more than 15% and lasts for more than ts, the current I of the electromagnet in the magnetic field generator is changed to adjust the magnetic field intensity;

[0035] When the magnetic field intensity has reached the saturation magnetization intensity of the magnetic fluid, or the temperature rises and causes the apparent viscosity of the magnetic fluid to drop significantly, the temperature control system is started to take out the heat from the magnetic fluid sealing system and stabilize the sealing system.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The metal skeleton for magnetic fluid sealing of the present invention adopts an annular belt structure, which is sleeved outside the rotating shaft and there is a gap for filling magnetic fluid between it and the rotating shaft. When the rotating shaft rotates at a high speed, a micro-motion pressure effect and a labyrinth sealing effect are formed. Under the combined action of the rotation of the rotating shaft and the applied magnetic field, a dense sealing liquid film is formed, which can resist the sealing pressure. The metal skeleton has good shear resistance. Under the action of the external magnetic field, the magnetic fluid in the gap can be adsorbed on the skeleton, forming a "meat wrapping bone" structure, which can better fill the sealing gap and strengthen the heat dissipation of the magnetic fluid.

[0038] The magnetic fluid sealing performance testing device of the present invention uses magnetic fluid as the response material, with a fast response speed, which can respond to the external field within the millisecond level, and the physical property change range of the magnetic fluid is relatively wide, which can be optimized specifically according to the sealing medium or the operating conditions, and has strong adaptability;

[0039] The magnetic fluid seal performance testing device of the present invention uses a metal skeleton material as a sealing reinforcement body to enhance the heat dissipation and shear resistance of the magnetic fluid. At the same time, it is inserted into the magnetic fluid and can play a better role in fixing and maintaining the magnetic fluid after being polarized. The combination of the two can better improve the existing magnetic fluid seal parameters and expand the application scenarios of magnetic fluid seals.

[0040] The magnetic fluid seal performance testing device of the present invention uses a magnetic field to control the physical properties of the magnetic fluid, and then controls the pressure of the sealing liquid film. This belongs to non-contact control, and the seal performance testing device has little impact on the operation of the overall device.

[0041] In the magnetic field generating device of the magnetic fluid seal performance testing device of the present invention, a number of U-shaped electromagnets are evenly arranged to provide an approximate magnetic field distribution of a point source (sink). The polarities of adjacent two magnetic poles are opposite, which avoids the mutual cancellation of the magnetic fields between the same poles, makes the magnetic field distribution more uniform, and has a smaller heating power, without causing too much load on the temperature control unit.

[0042] In the magnetic fluid automatic seal control method of the present invention, the control unit can adjust the seal performance testing device according to the set threshold and the real-time parameters of the system feedback by the data acquisition unit to optimize the seal state.

[0043] In the magnetic fluid automatic seal control method of the present invention, a control method combining temperature and magnetic field is used, which can control the physical properties of the magnetic fluid to change within a large range, improve the anti-interference ability of the system, and expand the adaptability of the seal performance testing device. Description of the Drawings

[0044] Figure 1 It is a schematic diagram of the metal skeleton structure:

[0045] Figure 2 It is a schematic diagram of the metal sheet structure;

[0046] Figure 2 In it: 1 - metal sheet

[0047] Figure 3 It is a schematic diagram of the fins unfolded on the metal sheet;

[0048] Figure 3 In it: 2 - cutting line; 3 - fin

[0049] Figure 4 It is a schematic diagram of the structure of the magnetic fluid seal performance testing device;

[0050] Figure 4In the figure: 1 - nitrogen cylinder; 2 - first temperature and pressure sensor group; 3 - second temperature and pressure sensor group; 4 - cooling water inlet and outlet; 5 - cooling water jacket; 6 - pole shoe; 7 - sealing unit; 8 - circulating water-cooled tank; 9 - control unit; 10 - data processing unit; 11 - terminal; 12 - servo motor; 13 - torque sensor; 14 - bearing pair; 15 - rotating shaft; 16 - electromagnet; 17 - coil; 18 - magnetic isolation ring; 19 - sealing ring; 20 - first sealing cavity; 21 - bearing; 22 - housing

[0051] Figure 5 It is a partial structure diagram of a magnetic fluid sealing performance test device

[0052] Figure 6 It is a schematic diagram of metal sheet processing Specific implementation manners

[0053] Embodiment 1:

[0054] A metal skeleton for magnetic fluid sealing, as Figure 1 shown, the metal skeleton adopts an annular belt structure, and when in use, it is sleeved outside the rotating shaft and there is a gap for filling magnetic fluid between it and the rotating shaft; the metal skeleton is formed by surrounding several metal sheets, and there are several fins on the metal sheets, and the fins can be arranged in a staggered array through laser cutting and stamping; the array arrangement can make the magnetic induction intensity at the tip of the fins the largest, so that the magnetic fluid can be more kept at the tip of the fins under the action of an external magnetic field, which helps the combination of the metal skeleton and the magnetic fluid, and at the same time can better form a magnetic circuit with the magnetic focusing structure, while the staggered arrangement of the fins can make the magnetic field peaks inside the magnetic field more concentrated

[0055] Each fin is rectangular and has an opening structure formed by cutting three sides of the rectangle. The unfolding direction of the fin is the same as the rotating direction of the rotating shaft, and the fin is finger-shaped after unfolding; the metal skeleton and the magnetic fluid filled in the gap form a sealed liquid film under the action of an external magnetic field to realize magnetic fluid sealing

[0056] In this example, the external magnetic field is formed by a pole shoe connected to the outside of the metal skeleton and several groups of evenly distributed electromagnets connected to the pole shoe. The magnetic force lines of each group of electromagnets are perpendicular to the axis of the rotating shaft. The magnetic fluid fills the gap under the action of the magnetic circuit of the external magnetic field to form a seal. The metal skeleton has good shear resistance. Under the action of the external magnetic field, the magnetic fluid in the gap can be adsorbed on the skeleton to form a "meat-wrapping-bone" structure, which can better fill the sealing gap and strengthen the heat dissipation of the magnetic fluid

[0057] Embodiment 2:

[0058] A further optional design of this example lies in that: in this example, a U-shaped electromagnet is adopted, and there are two sets of corresponding metal skeletons and pole shoes. The two sets of metal skeletons are sleeved outside the rotating shaft in parallel at intervals. The two extreme ends of the U-shaped electromagnet correspond to the positions of a set of pole shoes and a set of metal skeletons respectively, and the magnetic pole polarities of adjacent U-shaped electromagnets are opposite.

[0059] Example Three:

[0060] A further optional design of this example lies in that: in this example, the thickness of the metal skeleton is 0.1 - 0.5 mm. The gap distance between the metal skeleton and the rotating shaft is 0.15 - 0.5 mm. The rectangular opening specifications of the fins on the metal skeleton are a*b; where, the value range of a is 2 - 4 mm, the value range of b is 1 - 3 mm, and a > b.

[0061] Example Four:

[0062] The further design of the metal skeleton of the present invention in this example is as follows. The metal skeleton is formed by surrounding 8 metal sheets. As Figure 2 shown, each metal sheet 1 has the same structure and is formed by laser cutting or stamping to ensure the processing accuracy of the fins. The fins 3 on the metal sheet 1 are of rectangular structure, and an opening structure is formed by cutting three sides of the rectangle. The cutting line 2 and the unfolded structure are as Figure 3 shown, and the dimensions of the fins are shown in Table 1:

[0063] Table 1 shows the fin structure parameters

[0064] Fin parameters Dimensions Blank thickness t 0.3 mm Fin opening shape a*b 2*1 mm Bending radius ρ 0.3 mm Bending angle θ 10° Sealing gap h 0.3 mm

[0065] Example Five:

[0066] Adopt the magnetic fluid sealing performance test device of the metal skeleton in the above example for the sealing of the rotating shaft. The rotating shaft 15 is installed on the bearing pair 14 and is connected to the output shaft of the servo motor 12. As Figure 4 and Figure 5 shown, the magnetic fluid sealing device includes a housing 22, a sealing unit 7, a magnetic field generating device, a temperature control unit, a data acquisition unit, a data processing unit 10 and a control unit 9;

[0067] One end of the housing 22 is sealed, and the other end is sleeved on the rotating shaft 15; the sealed end is provided with a sealing end cover.

[0068] The sealing unit includes two sets of metal skeletons and magnetic fluid arranged in the housing 22; the two sets of metal skeletons are sleeved outside the rotating shaft 15 in parallel and there are gaps between them and the rotating shaft 15 respectively, and the magnetic fluid is filled in the gaps; the magnetic fluid can adopt an optimized ferromagnetic fluid, and this magnetic fluid uses Fe 2+ and Fe 3+Nano-sized Fe3O4 particles are generated by coprecipitation method under an excessive alkaline environment, and are prepared after steps such as washing, ultrasonic oscillation and static settlement. The volume fraction is 4.5%, and the apparent viscosity at room temperature is 270.4 mPa·s. This magnetic fluid has good paramagnetism and high magnetic saturation intensity. At the same time, the magnetic fluid is modified by changing the surfactant and the base carrier liquid in the preparation process to enhance the thermal conductivity and high temperature resistance of the magnetic fluid.

[0069] The magnetic field generating device includes two sets of pole shoes 6 arranged inside the housing 22 and connected to the outside of the metal skeleton, and eight sets of evenly distributed electromagnets 16 arranged outside the housing 22 and cooperating with the pole shoes 6; the pole shoes and the metal skeleton can be connected by cold brazing or polymer adhesive, and as close to the rotating shaft as possible without contacting the rotating shaft, so that the magnetic fluid can be better maintained between the sealing gaps. The direction of the magnetic force lines generated by the magnetic field generating device is perpendicular to the axis of the rotating shaft, and the axial direction is a point source or point sink distribution starting from the center of the rotating shaft. The electromagnet 16 uses a U-shaped electromagnet, and the two extreme ends of the U-shaped electromagnet correspond to the positions of a set of pole shoes 6 and a set of metal skeletons respectively; the magnetic pole polarities of the U-shaped electromagnet are opposite to ensure that the magnetic field distribution is as uniform as possible and avoid the interference of the same-pole magnetic fields. Considering the resistance and heating power, the coil 17 of the U-shaped electromagnet is made of enameled copper wire with a diameter of 1 mm, the resistivity is 0.0037 Ω / m, the working current is 0.5 - 3 A, the number of turns of the coil 17 for each magnetic pole is 400 - 600 turns, and it is powered by a DC power supply. The magnetic poles of the electromagnet 16 use silicon steel, and the magnetic yoke is selected from the magnetic conductive material Q235 to strengthen the magnetic field.

[0070] The magnetic field intensity generated by the magnetic field generating device is changed by changing the current of the electromagnet 16; inside the housing 22, a first sealing cavity 20 is formed between the inner pole shoe (the inner pole shoe is the pole shoe 6 close to the sealed end of the housing 22) and the sealed end of the housing 22, and a second sealing cavity is formed between the two pole shoes; a magnetic isolation ring 18 and a sealing ring 19 are arranged inside the first sealing cavity, the magnetic isolation ring 18 is arranged close to the inner pole shoe, the sealing ring 19 is arranged at the connection between the housing and the sealed end cover, and the first sealing cavity is also connected to a sealing medium source, and this sealing medium source can be a nitrogen cylinder 1.

[0071] The temperature control unit includes a cooling water jacket 5 arranged between the two pole shoes 6 and connected to them, and a cooling water circulation device connected to the cooling water jacket 5; among them, the cooling water circulation device can adopt a circulating water cooling tank 8; the cooling water enters the cooling water jacket from the cooling water inlet and outlet 4 opened in the non-sealed area of the housing 22, exchanges heat with the pole shoes 6, and the heat is conducted from the magnetic fluid and the metal skeleton to the pole shoes 6 and then taken out of the sealing performance test device, and the temperature can be adjusted according to the test requirements and the control unit 9.

[0072] The data acquisition unit includes a first pressure sensor and a first temperature sensor disposed in the first sealed cavity, a second pressure sensor and a second temperature sensor disposed in the second sealed cavity, a torque sensor 13 disposed on the output shaft of the servo motor 12, and a rotational speed sensor disposed on the rotating shaft 15; the first pressure sensor and the first temperature sensor are used to measure the medium pressure and temperature, constituting the first temperature and pressure sensor group 2; the second pressure sensor and the second temperature sensor are used to measure the magnetorheological fluid film pressure and temperature, constituting the second temperature and pressure sensor group 3;

[0073] The data processing unit 10 is connected to the data acquisition unit and the control unit 9;

[0074] The control unit 9 is further connected to the controller of the motor, the magnetic field generating device, and the temperature control unit. In this example, an external terminal 11 is also provided, and the control unit 9 is connected to the terminal 11.

[0075] When there is no external magnetic field in this magnetorheological fluid sealing performance testing device, the key to resisting the medium pressure is the fretting pressure effect and the labyrinth sealing effect formed by a single fin; while under an external magnetic field, this fretting pressure effect increases due to the change of the physical properties of the magnetorheological fluid, and together with the polarized magnetorheological fluid, it resists the sealing medium pressure, which can improve the existing magnetorheological fluid sealing parameters.

[0076] During installation, a set of bearings ( Figure 4 not shown in the figure) is provided on both sides of the two sets of pole shoes, such as bearing 21. The rotating shaft is supported in the housing through the bearing. The bearing selected is a rolling ball bearing, which is convenient for the installation and positioning of the magnetic field generating device and has a certain dust-proof and sealing effect. In addition, since the sealing gap is 0.1 - 0.3 mm, after installing the bearing, it can better support the rotating shaft and ensure its rotational accuracy.

[0077] Example Six:

[0078] In this example, the fluid sealing performance testing device of the present invention is further designed as follows. In this device, the diameter of the rotating shaft is 40 mm, the pole shoe is a cylinder with a length of 15 mm, an inner diameter of 41.2 mm, and an outer diameter of 62 mm, and the sealing gap between the rotating shaft and the metal skeleton is 0.3 mm.

[0079] Considering that during actual processing, if the bending angle of the metal sheet is too large, the fins will be deformed or even damaged. Therefore, in this example, a total of 8 metal sheets with a length of 15.6 mm, a width of 15 mm, and a thickness of 0.3 mm are processed. Each metal sheet is bent at a central angle of approximately 45°, and then connected to the pole shoe through an adhesive. The fins on the metal sheets are arranged in a staggered array. Five fins are provided in each of the 1st, 3rd, and 5th columns, and four fins are provided in each of the 2nd and 4th columns. The distance between adjacent two columns is 2 mm, and the distance between adjacent fins in each column is 1 mm. The distances from the fins arranged in a staggered array to the edge of the metal sheet are 0.8 mm, 2.3 mm, and 1 mm respectively. The processing parameters of the metal sheet are as Figure 6 shown.

[0080] Example Seven:

[0081] The magnetic fluid automatic sealing control method of the present invention, based on the magnetic fluid sealing performance test device in Example Four, is used to study the influence of magnetic field intensity and temperature on the sealing performance of the composite structure formed by the metal skeleton and the magnetic fluid. The specific steps are as follows:

[0082] Step 1) Installation of the magnetic fluid sealing performance test device;

[0083] Step 2) Turn on the magnetic field generating device so that the magnetic fluid in the gap is polarized and fills the gap;

[0084] Step 3) Turn on the servo motor connected to the rotating shaft so that the rotating shaft rotates at a speed of n1;

[0085] Step 4) Determine whether the magnetic fluid is sufficient:

[0086] Measure the frictional torque T at the standby speed by the torque sensor f , and compare it with the frictional torque T when the magnetic fluid is sufficient d (the frictional torque T when the magnetic fluid is sufficient d can be determined by pre-experiment), and judge whether it is necessary to supplement the magnetic fluid according to the frictional torque, and supplement the magnetic fluid until it is sufficient;

[0087] Step 5) Adjust the rotating shaft speed;

[0088] Adjust the rotating shaft speed n1 to the test target speed n2. Measure the rotating shaft speed n by the speed sensor, measure the pressure P in the first sealing cavity by the first pressure sensor n , measure the temperature T of the magnetic fluid liquid film by the second temperature sensor m and feedback it to the data processing unit. The control unit adjusts the magnetic field intensity of the magnetic field generating device and the opening and closing of the temperature control unit to maintain the sealing stability of the magnetic fluid sealing system; the basis for judging the sealing stability is that the temperature T of the magnetic fluid liquid film m and the pressure P in the first sealing cavity n are stable and the fluctuation range is within 15%;

[0089] Step 6) Fill in the sealing medium;

[0090] Keep the rotational speed n of the rotating shaft and the liquid film temperature T m , the electromagnet current I unchanged, fill in the sealing medium into the first sealing cavity and gradually increase the pressure. Measure the pressure of the first sealing cavity by the first pressure sensor group, that is, the sealing medium pressure P n , and feedback it to the data processing unit. The control unit adjusts the magnetic field intensity of the magnetic field generating device and the opening and closing of the temperature control unit according to the threshold value of the preset limit sealing pressure P max and the relationship between the medium pressure P n to maintain the sealing stability of the magnetic fluid sealing system; collect the response curves of the pressure (liquid film pressure) P m of the second sealing cavity, the liquid film temperature T m , the frictional torque T f , and the sealing medium pressure P n when the magnetic field intensity changes; among them, the preset limit sealing pressure P max can be obtained by the following method: when the sealing pressure fluctuates by more than 15% instantaneously, it is considered that the seal fails, and the pressure at the time of failure is defined as the limit sealing pressure P max under this working condition.

[0091] On the basis of the above control, the following can be further designed:

[0092] When the sealing medium pressure P n fluctuates, that is, P n exceeds the threshold range by more than 15% and lasts for more than ts, change the electromagnet current I in the magnetic field generator to adjust the magnetic field intensity; (P n The change rate per second is more than 15% and the duration is ts)

[0093] When fluctuations in the rotational speed of the rotating shaft, the current of the magnetic field generator, and the temperature of the magnetic fluid cause the magnetic fluid liquid film pressure P max to change and P n exceeds the threshold range by more than 15% and lasts for more than ts, increase the current of the magnetic field generator to increase the magnetic field intensity and increase the sealing liquid film pressure;

[0094] When the magnetic field intensity has reached the saturation magnetization intensity of the magnetic fluid, or when the temperature rises and causes the apparent viscosity of the magnetic fluid to drop significantly, start the temperature control system to take out the heat from the magnetic fluid sealing system and stabilize the sealing system.

Claims

1. A metal skeleton for magnetic fluid sealing, characterized in that: The metal framework adopts an annular belt structure. When in use, it is sleeved outside the rotating shaft, and there is a gap for filling magnetic fluid between it and the rotating shaft; the metal framework is formed by surrounding a number of metal sheets, and a number of fins are provided on the metal sheets, and the fins are arranged in a staggered array. Each fin is rectangular and has an opening structure formed by cutting three sides of the rectangle. The unfolding direction of the fins is the same as the rotation direction of the rotating shaft; the metal framework and the magnetic fluid filled in the gap form a sealed liquid film under the action of an external magnetic field to achieve magnetic fluid sealing; The external magnetic field is formed by pole shoes connected to the outside of the metal framework and a number of groups of evenly distributed electromagnets connected to the pole shoes. The magnetic fluid fills the gap under the action of the magnetic circuit of the external magnetic field to form a seal; The magnetic force line directions of each group of electromagnets are all perpendicular to the axis of the rotating shaft; The electromagnet adopts a U-shaped electromagnet. There are two groups corresponding to the metal framework and the pole shoes. The two groups of metal frameworks are sleeved outside the rotating shaft in parallel at intervals. The two extreme ends of the U-shaped electromagnet correspond to the positions of a group of pole shoes and a group of metal frameworks respectively, and the magnetic pole polarities of adjacent U-shaped electromagnets are opposite.

2. The metal framework for magnetic fluid sealing according to claim 1, characterized in that: The thickness of the metal framework is 0.1 - 0.5 mm.

3. The metal framework for magnetic fluid seal according to claim 1, wherein: The gap distance between the metal framework and the rotating shaft is 0.15 - 0.5 mm.

4. The metal framework for magnetic fluid seal according to claim 1, wherein: The rectangular opening specifications of the fins on the metal skeleton are ; among them, a ranges from 2 to 4 mm, b ranges from 1 to 3 mm, and a > b .

5. A magnetic fluid sealing performance testing device using the metal framework according to any one of claims 2 to 4, for sealing a rotating shaft, characterized in that: This magnetic fluid sealing performance test device includes a housing, a sealing unit, a magnetic field generating device, a temperature control unit, a data acquisition unit, a data processing unit and a control unit; One end of the housing is sealed, and the other end is sleeved on the rotating shaft; The sealing unit includes two groups of metal frameworks arranged in the housing and magnetic fluid; the two groups of metal frameworks are sleeved outside the rotating shaft in parallel and there are gaps between them and the rotating shaft respectively, and the magnetic fluid is filled in the gaps; The magnetic field generating device includes two groups of pole shoes arranged in the housing and connected to the outside of the metal framework, and a number of groups of evenly distributed electromagnets arranged outside the housing and cooperating with the pole shoes. The electromagnet adopts a U-shaped electromagnet. The two extreme ends of the U-shaped electromagnet correspond to the positions of a group of pole shoes and a group of metal frameworks respectively; by changing the current of the electromagnet, the magnetic field intensity generated by the magnetic field generating device is changed; inside the housing, a first sealed cavity is formed between the inner pole shoe and the sealed end of the housing, and a second sealed cavity is formed between the two pole shoes; The temperature control unit includes a cooling water jacket arranged between and connected to the two pole shoes, and a cooling water circulation device connected to the cooling water jacket; The data acquisition unit includes a first pressure sensor and a first temperature sensor arranged in the first sealed cavity, a second pressure sensor and a second temperature sensor arranged in the second sealed cavity, a torque sensor arranged on the output shaft of the motor, and a rotational speed sensor arranged on the rotating shaft; the first pressure sensor and the first temperature sensor are used to measure the medium pressure and temperature; the second pressure sensor and the second temperature sensor are used to measure the magnetic fluid liquid film pressure and temperature; The data processing unit is connected to the data acquisition unit and the control unit; The control unit is also connected to the controller of the motor, the magnetic field generating device and the temperature control unit.

6. A magnetic fluid automatic sealing control method, based on the magnetic fluid sealing performance testing device described in claim 5, characterized in that: It includes the following steps: 1) Installation of the magnetic fluid sealing performance test device; 2) Turn on the magnetic field generating device so that the ferrofluid in the gap is polarized and fills the gap; 3) Rotate the rotation axis at a rotational speed of n 1 rotation; 4) Determine whether the ferrofluid is sufficient: Measure the frictional torque at the standby speed by the torque sensor T f , and compare it with the frictional torque when the magnetorheological fluid is sufficient T d , determine whether it is necessary to replenish the magnetorheological fluid according to the frictional torque, and replenish the magnetorheological fluid to sufficiency; 5) Adjust the rotational speed of the rotating shaft; Adjust the rotational speed of the rotating shaft n 1 to the test target rotational speed n 2. Measure the rotational speed of the rotating shaft by the rotational speed sensor n , and measure the pressure of the first sealing cavity by the first pressure sensor P n , and measure the temperature of the magnetic fluid liquid film by the second temperature sensor T m And feedback to the data processing unit. The control unit adjusts the magnetic field intensity of the magnetic field generating device and the opening and closing of the temperature control unit to maintain the sealing stability of the magnetic fluid sealing system; the basis for judging the sealing stability is the temperature of the magnetic fluid liquid film T m and the pressure of the first sealing cavity P n being stable and the fluctuation range being within 15%; 6) Fill in the sealing medium; Keep the rotational speed of the rotating shaft n and the liquid film temperature T m constant, fill the sealing medium into the first sealing cavity and gradually increase the pressure. Measure the pressure of the first sealing cavity by the first pressure sensor group, that is, the pressure of the sealing medium I n P n , and feedback it to the data processing unit. The control unit adjusts the magnetic field intensity of the magnetic field generating device and the opening and closing of the temperature control unit according to the threshold value of the preset limit sealing pressure P max and the relationship between the medium pressure P n to maintain the sealing stability of the magnetic fluid sealing system; among them, the preset limit sealing pressure P max can be determined according to experiments.

7. The magnetic fluid automatic sealing control method according to claim 6, characterized in that: When the pressure of the sealed medium P n fluctuates, that is P n exceeds the threshold range by more than 15% and lasts t for more than s, change the current of the electromagnet in the magnetic field generating device I to adjust the magnetic field strength; When the magnetic field strength has reached the saturation magnetization intensity of the ferrofluid, or when the temperature rises and causes a significant decrease in the apparent viscosity of the ferrofluid, start the temperature control system to remove heat from the ferrofluid sealing system and stabilize the sealing system.

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