Magnetic fluid seal

Abstract

The application relates to a magnetic fluid seal, which comprises a shell, a pole shoe ring, a magnetic conducting ring, a permanent magnet and a winding. The application provides a magnetic fluid seal, which is provided with a winding passing through a controllable current at the position between pole shoes, so as to achieve the purpose of regulating the magnetic field at the position of the permanent magnet of the magnetic fluid seal and the sealing gap. The structure solves the problems that the permanent magnet of the commonly used magnetic fluid seal is easy to demagnetize, difficult to magnetize and the magnetic field is uncontrollable. Meanwhile, the regulation of the winding function is realized by regulating the current in the winding. The strong current, the variable frequency current and the weak current can respectively achieve the functions of magnetizing the permanent magnet, demagnetizing the permanent magnet and resisting high pressure, so that the magnetic fluid seal has high pressure resistance. Meanwhile, the difficulty problem that the permanent magnet is easy to demagnetize in engineering is solved, so that the magnetic fluid seal can complete the function of remagnetizing the permanent magnet without disassembly after demagnetization.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of mechanical engineering seal, and particularly relates to a magnetic fluid seal. BACKGROUND

[0002] The magnetic fluid seal uses permanent magnets to generate magnetic field force in the sealing gap to firmly fix the magnetic fluid in the sealing gap, and resist the pressure difference on both sides, so as to achieve the sealing effect. The research on the magnetic fluid seal using electromagnets as the magnetic source is relatively blank. The main reason is that under the conventional working conditions, the magnetic field of the sealing gap is stable at a certain value, which can meet the sealing requirements. However, with the development of science and technology and the complexity of application conditions, it is necessary to improve the pressure resistance range of the magnetic fluid seal.

[0003] In the application conditions of complex occasions, such as high temperature, mechanical vibration, impact, chemical corrosion, reverse magnetic field, radiation, etc., irreversible demagnetization of permanent magnets will occur, among which demagnetization caused by high temperature and reverse magnetic field is the most common. Irreversible demagnetization may cause weakening of the sealing capacity of the magnetic fluid seal, or even cause sealing failure and leakage. The conventional magnetic fluid seal needs to go through a complex disassembly and assembly process to magnetize the permanent magnet, which may cause temporary sealing failure, damage the pole shoes and pole teeth, and is inconvenient to operate. For key sealing application parts, sealing failure and disassembly are not allowed during use, so the problem of permanent magnet demagnetization cannot be solved. SUMMARY

[0004] The present application proposes a magnetic fluid seal, which is provided with a winding with controllable current at the position between the pole shoes, so as to achieve the purpose of regulating the position of the permanent magnet of the magnetic fluid seal and the magnetic field at the sealing gap. This structure solves the problems of easy demagnetization, difficult magnetization and uncontrollable magnetic field of the permanent magnet commonly used in the magnetic fluid seal. Through the regulation of the current in the winding, the function of the winding is adjusted. The strong current, variable frequency current and weak current can achieve the functions of magnetizing the permanent magnet, demagnetizing the permanent magnet and resisting high pressure respectively, so that the magnetic fluid seal has high pressure resistance. At the same time, the problem of easy demagnetization of the permanent magnet in engineering is solved, so that the magnetic fluid seal can complete the function of re-magnetizing the permanent magnet without disassembly after demagnetization.

[0005] The present application carries out finite element simulation and experimental verification on a large number of magnetic fluid seal examples, analyzes the results, and obtains a reasonable design scheme of the number of turns of the winding and the voltage range of the power supply.

[0006] The technical scheme of the present application is as follows: the magnetic fluid seal comprises a shaft, a shell, a pole shoe ring, a magnetic conducting ring, a winding and a permanent magnet; the pole shoe ring and the magnetic conducting ring are arranged on the inner wall of the shell, the winding is arranged between the two pole shoe rings, and a gap is left between the inner circular surface of the pole shoe ring and the outer circular surface of the shaft; the shaft is composed of two shafts, and the permanent magnet is arranged between the two shafts, wherein the permanent magnet and the winding are parallel in the radial direction, the two shafts are connected through a shaft coupling or a thread to ensure the coaxiality of the two shafts; the inner circular surface of the pole shoe ring is provided with pole teeth extending along the radial direction to the inner circular surface of the pole shoe ring, and a gap is left between the inner circular surface of the pole shoe ring and the outer circular surface of the shaft, which is filled with magnetic fluid for sealing; the winding is a cylindrical ring tightly pressed by copper wires, wherein a gap is left between the inner circular surface of the winding and the outer circular surface of the shaft, and the gap between the winding and the shaft is larger than the gap between the inner circular surface of the pole shoe ring and the outer circular surface of the shaft; the shell and the magnetic conducting ring are provided with radial through holes, the through holes are provided with threads, and aviation plugs are installed on the threads, the lead wires of the winding are connected with the power supply through the aviation plugs, and the winding is supplied with power by an adjustable voltage power supply, wherein the power supply can output constant current direct current and variable frequency alternating current; the sizes of the winding and the permanent magnet are simulated to generate an axial magnetic field in the permanent magnet part, and the maximum magnetic field strength is 5 times the intrinsic coercive force H cj of the permanent magnet.

[0007] The magnetic fluid seal is characterized in that the number of the pole teeth on the inner circular surface of the pole shoe ring is 4-10.

[0008] The magnetic fluid seal is characterized in that the gap between the pole teeth on the inner circular surface of the pole shoe ring and the outer circular surface of the shaft is 0.05-3 mm.

[0009] The magnetic fluid seal is characterized in that the permanent magnet is a magnet material without magnetization or an axially magnetized permanent magnet; when the permanent magnet is a magnet material without magnetization, high-voltage direct current is passed through the winding according to the relevant standards of magnetization equipment, so as to generate an axial magnetic field in the permanent magnet part, and the maximum magnetic field strength is 2 times the intrinsic coercive force H cj of the permanent magnet; the whole magnetization process includes a boosting and a reducing process, and the whole process lasts more than 10 ms; when the permanent magnet is an axially magnetized permanent magnet or an irreversible axially magnetized permanent magnet, the process of demagnetization and then magnetization is needed according to the relevant standards of magnetization equipment; 50 Hz variable frequency alternating current is passed through the winding, so as to generate a demagnetization magnetic field in the permanent magnet part, and the demagnetization time lasts more than 30 ms; then high-voltage direct current is passed through the winding, so as to generate an axial magnetic field in the permanent magnet part, and the maximum magnetic field strength is 2 times the intrinsic coercive force H cj5 times, the whole magnetizing process including boosting and reducing process, the whole process lasts more than 10 ms; it is worth mentioning that the whole process is carried out on the installed seal, and the sealing ability of the seal can be maintained during magnetizing; in order to realize the control of pressure resistance, the control of the magnetic field of the sealing gap is realized, which includes two aspects, the first aspect is to control the intrinsic coercive force H cj of the permanent magnet by controlling the winding voltage during magnetizing, so as to control the size of the magnetic field of the sealing gap; the second aspect is to control the magnetic field of the sealing gap by controlling the size of the winding voltage during sealing, and the direct current voltage is passed in the winding during sealing, so as to improve the pressure resistance of the seal; the magnetizing power supply of the winding should have sufficient capacity, and should be able to continuously and smoothly change the magnetic field in the whole required range, and the instability of the magnetizing voltage should not be more than 0.1% / min.

[0010] The magnetic fluid seal is characterized in that the pole shoe ring and the magnetic conducting ring (4) are made of soft magnetic material with coercive force not greater than 100 kA / m, the thickness of the pole shoe ring and the difference between the inner and outer diameters of the magnetic conducting ring are greater than the radius of the shaft to avoid local magnetic saturation, the pole shoe ring is made of laminated rolled material, the pole surface is parallel or perpendicular to the magnetic field direction, the outer surface of the pole shoe ring is provided with a ring groove, and an O-shaped sealing ring is arranged in the ring groove to prevent leakage along the path between the outer shell and the pole shoe ring.

[0011] The magnetic fluid seal is characterized in that it further comprises an end cover and a bearing; the end cover is used to ensure the axial positioning of the pole shoe ring and the bearing, so that the pole shoe ring and the bearing have good coaxiality with the shaft.

[0012] The magnetic fluid seal is characterized in that the bearing is sleeved on the shaft, and the outer surface of the bearing is in contact with the inner wall of the outer shell. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 A structural schematic diagram of the magnetic fluid seal provided by the application, in which the numbers and corresponding names are as follows: 1-shaft, 2-outer shell, 3-pole shoe ring, 4-permanent magnet, 5-winding, 6-right pole shoe ring, 7-end cover, 8-bearing; Figure 2 A curve diagram of the magnetizing magnetic field; Figure 3 A curve diagram of the demagnetizing magnetic field. DETAILED DESCRIPTION

[0014] The application will be further described below in combination with the drawings.

[0015] The magnetic fluid seal comprises a shaft, a shell, a pole shoe ring, a magnetic conducting ring, a winding and a permanent magnet; the pole shoe ring and the magnetic conducting ring are arranged on the inner wall of the shell, the winding is arranged between the two pole shoe rings, and a gap is left between the inner circular surface of the pole shoe ring and the outer circular surface of the shaft; the shaft is composed of two shafts, the permanent magnet is arranged between the two shafts, the permanent magnet and the winding are parallel in the radial direction, the two shafts are connected through a shaft coupling or a thread to ensure the coaxiality of the two shafts; the inner circular surface of the pole shoe ring is provided with pole teeth extending along the radial direction to the inner circular surface of the pole shoe ring, and a gap is left between the inner circular surface of the pole shoe ring and the outer circular surface of the shaft, which is filled with magnetic fluid for sealing; the winding is a cylindrical ring tightly compressed by copper wires, and a gap is left between the inner circular surface of the winding and the outer circular surface of the shaft; the gap between the winding and the shaft is larger than the gap between the inner circular surface of the pole shoe ring and the outer circular surface of the shaft; the shell and the magnetic conducting ring are provided with radial through holes, the through holes are provided with threads, and aviation plugs are installed on the threads, the lead wires of the winding are connected with the power supply through the aviation plugs, the winding is powered by an adjustable voltage power supply, and the power supply can output constant current direct current and variable frequency alternating current; the sizes of the winding and the permanent magnet are simulated to generate an axial magnetic field in the permanent magnet part, and the maximum magnetic field strength is 5 times the intrinsic coercive force H cj of the permanent magnet.

[0016] The magnetic fluid seal is characterized in that the number of the pole teeth on the inner circular surface of the pole shoe ring is 4-10.

[0017] The magnetic fluid seal is characterized in that the gap between the pole teeth on the inner circular surface of the pole shoe ring and the outer circular surface of the shaft is 0.05-3 mm.

[0018] The magnetic fluid seal is characterized in that the permanent magnet is a magnet material without magnetization or an axially magnetized permanent magnet; when the permanent magnet is a magnet material without magnetization, high-voltage direct current is passed through the winding according to the relevant standards of magnetization equipment, so as to generate an axial magnetic field in the permanent magnet part, and the maximum magnetic field strength is 2 times the intrinsic coercive force H cj of the permanent magnet; the whole magnetization process includes a boosting and a reducing process, and the whole process lasts more than 10 ms; when the permanent magnet is an axially magnetized permanent magnet or an irreversible axially magnetized permanent magnet, the magnetization process needs to be carried out after demagnetization according to the relevant standards of magnetization equipment; 50 Hz variable frequency alternating current is passed through the winding, so as to generate a demagnetization magnetic field in the permanent magnet part, and the demagnetization time lasts more than 30 ms; then high-voltage direct current is passed through the winding, so as to generate an axial magnetic field in the permanent magnet part, and the maximum magnetic field strength is 2 times the intrinsic coercive force H cj5 times, the whole magnetizing process including boosting and reducing process, the whole process lasts more than 10 ms; it is worth mentioning that the whole process is carried out on the installed seal, and the sealing ability of the seal can be maintained during magnetizing; in order to realize the control of pressure resistance, the control of the magnetic field of the sealing gap is realized, which includes two aspects, the first aspect is to control the intrinsic coercive force H cj of the permanent magnet by controlling the winding voltage during magnetizing, so as to control the size of the magnetic field of the sealing gap; the second aspect is to control the size of the winding voltage during sealing application, and the direct current voltage is passed through the winding during sealing, so as to control the magnetic field of the sealing gap and improve the pressure resistance of the seal; the magnetizing power supply passed through the winding should have sufficient capacity, and should be able to continuously and smoothly change the magnetic field in the whole required range, and the instability of the magnetizing voltage should not be more than 0.1% / min.

[0019] The magnetic fluid seal, characterized in that: the pole shoe ring and the magnetic conducting ring (4) are made of soft magnetic material with coercive force not more than 100 kA / m, in order to avoid the occurrence of local magnetic saturation, the difference between the thickness of the pole shoe ring and the inner and outer diameters of the magnetic conducting ring is greater than the radius of the shaft, the laminated material is rolled, the pole surface needs to be parallel or perpendicular to the magnetic field direction, the outer circular surface of the pole shoe ring is provided with a ring groove, and an O-shaped sealing ring is arranged in the ring groove to prevent leakage along the path between the outer shell and the pole shoe ring.

[0020] The magnetic fluid seal, characterized in that: the end cover is used to ensure the axial positioning of the pole shoe ring and the bearing, so that the pole shoe ring and the bearing have good coaxiality with the shaft.

[0021] The magnetic fluid seal, characterized in that: the bearing is sleeved on the shaft, and the outer circular surface of the bearing is in contact with the inner wall of the outer shell.

Claims

1. A magneto fluid seal comprising a shaft (1), a housing (2), a pole shoe ring (3), a magnetically permeable ring (4), a winding (5) and a permanent magnet (6); characterized in that: The pole shoe ring (3) and the magnetic conducting ring (4) are arranged on the inner wall of the shell (2), the winding (5) is arranged between the two pole shoe rings (3), and a gap is left between the inner circular surface of the pole shoe ring (3) and the outer circular surface of the shaft (1); the shaft (1) is composed of two shafts, the permanent magnet (6) is arranged between the two shafts (1), wherein the permanent magnet and the winding (5) are parallel in the radial position, and the two shafts are connected through a shaft coupling or a thread to ensure the coaxiality between the two shafts; the inner circular surface of the pole shoe ring (3) is provided with pole teeth, the pole teeth extend along the radial direction to the inner circular surface of the pole shoe ring (3), and a gap is left between the inner circular surface of the pole shoe ring (3) and the outer circular surface of the shaft (1), the gap is filled with magnetic fluid for sealing, the winding (5) is a cylindrical ring tightly pressed by copper wires, wherein the inner circular surface of the winding (5) leaves a gap with the outer circular surface of the shaft (1), and the gap between the winding and the shaft is greater than the gap between the inner circular surface of the pole shoe ring (3) and the outer circular surface of the shaft (1); the shell (2) and the magnetic conducting ring (4) are provided with radial through holes, the through holes are provided with threads, and an aviation plug is installed, the lead wire of the winding (5) is connected with the power supply through the aviation plug, the winding is powered by an adjustable voltage power supply, wherein the power supply can output constant current direct current and variable frequency alternating current; through the simulation design of the size of the winding and the permanent magnet, in order to realize the magnetization of the permanent magnet, the axial magnetic field is generated at the position of the permanent magnet, the maximum magnetic field strength required by the permanent magnet which is not magnetized is 2 times the intrinsic coercive force of the permanent magnet H cj , the maximum magnetic field strength required by the permanent magnet which is demagnetized and then magnetized is 5 times the intrinsic coercive force of the permanent magnet H cj , and the whole magnetizing process includes boosting and step-down processes, and the whole process lasts more than 10ms.

2. A magnetic fluid seal as claimed in claim 1, wherein: The inner circular surface of the pole shoe ring (3) is provided with 4-10 pole teeth.

3. A magnetic fluid seal as claimed in claim 1, wherein: The gap between the pole teeth on the inner circular surface of the pole shoe ring (3) and the outer circular surface of the shaft (1) is 0.05-3 mm.

4. A magnetic fluid seal as claimed in claim 1, wherein: The permanent magnet (6) is an uncharged magnet material or an axial charged permanent magnet. When the permanent magnet is an uncharged magnet material, according to the relevant standards of magnet charging equipment, high-voltage direct current is directly passed through the winding to generate an axial magnetic field at the permanent magnet part. The maximum magnetic field strength required by the uncharged permanent magnet is twice the intrinsic coercive force of the permanent magnet H cj The entire magnet charging process includes boosting and reducing processes, and the whole process lasts more than 10 ms. When the permanent magnet is an axial charged permanent magnet and an irreversible axial charged permanent magnet, according to the relevant standards of magnet charging equipment, the process of demagnetizing and then charging is required. First, 50Hz variable frequency alternating current is passed through the winding to generate a demagnetizing magnetic field at the permanent magnet part, and the demagnetizing time lasts more than 30 ms. Then, high-voltage direct current is passed through the winding to generate an axial magnetic field at the permanent magnet part. The maximum magnetic field strength required by the permanent magnet after demagnetization and then charging is five times the intrinsic coercive force of the permanent magnet H cj The entire magnet charging process includes boosting and reducing processes, and the whole process lasts more than 10 ms. When the permanent magnet is an axial charged permanent magnet and an irreversible axial charged permanent magnet, according to the relevant standards of magnet charging equipment, the process of demagnetizing and then charging is required. First, 50Hz variable frequency alternating current is passed through the winding to generate a demagnetizing magnetic field at the permanent magnet part, and the demagnetizing time lasts more than 30 ms. Then, high-voltage direct current is passed through the winding to generate an axial magnetic field at the permanent magnet part. The maximum magnetic field strength required by the permanent magnet after demagnetization and then charging is five times the intrinsic coercive force of the permanent magnet H cj The first aspect is to control the intrinsic coercive force of the permanent magnet by controlling the winding voltage during magnetization, thereby controlling the magnetic field size of the sealing gap. The second aspect is to control the sealing gap magnetic field by controlling the winding voltage during sealing. Direct current voltage is passed through the winding during sealing, which can control the sealing gap magnetic field and improve the pressure resistance of the seal. The magnetization power supply of the winding should have sufficient capacity and should be able to continuously and smoothly change the magnetic field within the entire required range. The instability of the magnetization voltage should not exceed 0.1% / min.

5. A magnetic fluid seal as claimed in claim 1, wherein: The pole shoe ring (3) and the magnetic conducting ring (4) are made of soft magnetic material with coercive force not greater than 100 kA / m. In order to avoid local magnetic saturation of the magnetic conducting material, the difference between the inner and outer diameters of the magnetic conducting ring and the thickness of the pole shoe ring are both greater than the radius of the shaft. The pole surface of the laminated rolled material is parallel or perpendicular to the direction of the shaft. The outer circular surface of the pole shoe ring is provided with a ring groove, and an O-shaped sealing ring is arranged in the ring groove to prevent leakage along the path between the outer shell (2) and the pole shoe ring (3).

6. A magnetic fluid seal as claimed in claim 1, wherein: The device further comprises an end cover (7) and a bearing (8). The end cover (7) is used to ensure the axial positioning of the pole shoe ring (3) and the bearing (8), so that the pole shoe ring (3) and the bearing (8) have good coaxiality with the shaft (1).

7. A magnetic fluid seal as claimed in claim 6, wherein: The bearing (8) is sleeved on the shaft (1), and the outer circular surface of the bearing is in contact with the inner wall of the outer shell (2).

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