CN200989445Y - Magnetic fluid centring seal bearing - Google Patents

Abstract

Magnetic fluid centering sealed bearing is a dynamic sealing device for rotating (or translational) machinery. It uses the "self-centering" law of magnetic fluid to change the external magnetic field (permanent magnet) in the traditional magnetic fluid sealed bearing into a built-in magnetic field, cancel the magnetic pole piece of the traditional sealed bearing, and replace the "liquid O" of the magnetic fluid Shaped ring" has become a "liquid cylindrical piston", which solves the three major problems of traditional magnetic fluid sealed bearings: 1. Under the same sealing pressure condition, the volume is reduced by more than 60% compared with traditional magnetic fluid sealed bearings; 2. Utilizing the "automatic centering" rule, the requirements for the machining accuracy of the sealed bearing can be significantly reduced; 3. Since the magnetic fluid works in a basically closed environment, the drying time of the magnetic fluid is greatly prolonged.

Description

Magnetic Fluid Centering Sealed Bearings

technical field

The utility model belongs to the technical field of mechanical engineering sealing, and is particularly suitable for the sealing of rotating shafts.

Background technique

Magnetic fluid (also known as magnetic liquid) is a new type of liquid magnetic material, which has both the magnetism of magnetic materials and the fluidity of liquid, and can be attracted by a magnetic field. It has been widely used in many fields such as machinery, electronics, aviation, and medicine.

At present, the basic principle of the magnetic fluid sealing device designed by utilizing the characteristic that the magnetic fluid can be attracted by the magnetic field is shown in Figure 1: it is composed of a permanent magnet 1, a magnetic pole piece 2, a rotating shaft 3 and a magnetic fluid 4. According to whether the rotation axis is magnetically permeable (as shown in Figure 1-a) or non-magnetically permeable (as shown in Figure 1-b), two structures a and b can be designed. These two structures can attract and fix the magnetic fluid around the rotating shaft, forming a liquid "O" type sealing ring, which plays the role of sealing and lubrication. However, the structure of this "liquid O-ring" is formed by the magnetic fluid 4 being attracted around the rotating shaft 3 by the magnetic force provided by the external permanent magnet 1 through the magnetically conductive pole piece 2 . Since the magnetic field provided by the permanent magnet needs to be transmitted to the rotating shaft through the magnetic pole piece, the magnetic force is attenuated, resulting in a lower pressure that the "liquid O-ring" can withstand, and each stage of the sealing ring can withstand about 0.015 ~ 0.020MPa pressure. To improve the pressure resistance, the above structure must be repeated many times, that is, a plurality of magnetically conductive pole pieces are arranged on the bearing, and the total pressure resistance is the sum of the pressure resistance of all levels. If the designed total pressure resistance is 0.20 MPa, the above structure will need to be repeated more than ten times, resulting in a more complicated structure and larger volume of the bearing. In order to reduce the volume, US Patent No. 6,672,592 has made beneficial improvements to the above defects, integrating multiple magnetically conductive pole pieces together, so that the pressure resistance of the sealed bearing with the same volume is doubled. Chinese patent ZL200320126699.3 also provides a "magnetic fluid sealing device with reduced radial space size". The common features of the above-mentioned patents are: due to the existence of the magnetically conductive pole piece, the above-mentioned improved structure is still very complicated, and the space size is still relatively large. In addition, in this structure, the magnetic fluid works in a semi-open environment, and the bearing is prone to seal failure due to the volatilization of the magnetic fluid.

In view of the above disadvantages, the utility model provides a sealed bearing with small volume and simple structure, and the magnetic fluid works in a substantially closed environment.

The utility model is designed according to the natural phenomenon that the magnetic fluid has the function of "self-centering".

When we put a small magnet into a beaker filled with ferrofluid, we found that the small magnet will be just floating in the middle of the ferrofluid; even if you push the small magnet to one side of the beaker with a large external force , but once the external force is removed, the small magnet will immediately re-float to the middle of the ferrofluid (see Figure 2). The reason for this self-centering phenomenon is that there is a fixed magnetic field around the permanent magnet, and the distribution of the magnetic field can be represented by the magnetic field lines in the figure (as shown in Figure 2-a). When the permanent magnet is placed in the ferrofluid (as shown in Figure 2-b), under the action of the magnetic field, the ferrofluid has a tendency to reposition according to the distribution of the magnetic field line, that is, there is a magnetic force around the magnet that attracts the ferrofluid, its size It is determined by the density of the magnetic field lines. The closer to the permanent magnet, the denser the lines of force, and thus the greater the magnetic force. This causes the ferrofluid to pack tightly around the permanent magnet, automatically positioning the permanent magnet in the "center" of the ferrofluid.

Contents of the invention

The technical problem to be solved by the utility model is: to overcome the shortcomings of the magnetic fluid sealed bearing in the prior art, such as complex structure, large space size, and easy volatilization of the magnetic fluid, to provide a sealed bearing centered by the magnetic fluid, so that the sealed bearing can In the case of constant pressure resistance, the volume can be reduced by more than 60%, the requirements for machining accuracy are significantly reduced, and the service life can also be significantly improved.

The technical scheme of the utility model is: using the law of "automatic centering" of magnetic fluid, the external magnetic field (permanent magnet) in the traditional magnetic fluid sealed bearing is changed into a built-in magnetic field with automatic centering effect, which can not only greatly The simplification of the design of the range, and the "liquid O-ring" of the magnetic fluid can be changed into a "liquid cylindrical piston" (see Figure 3), which greatly improves the pressure resistance of the sealed bearing.

The beneficial effects of the utility model are: after adopting the built-in magnetic field, the magnetic pole piece of the traditional sealed bearing is canceled, and the magnetic field in the new bearing is directly transmitted from the permanent magnet to the magnetic fluid, so that the magnetism of the permanent magnet is fully utilized. The permanent magnet is suspended in the center of the cavity of the housing under the "self-centering" action of the magnetic fluid, and together with the magnetic fluid forms a "liquid cylindrical piston" that can withstand high pressure, so that the entire bearing has low frictional resistance and zero Leakage sealing function. At the same time, since the magnetic fluid is in a substantially sealed cavity, the volatilization rate is lower than that in an open environment, which effectively prolongs the service life of the magnetic fluid.

Description of drawings

Figure 1 Schematic diagram of magnetic fluid sealed bearing;

Fig. 2 Schematic diagram of "self-centering" of magnetic fluid;

Fig. 3 Schematic diagram of magnetic fluid centering sealed bearing;

Fig. 4 Schematic diagram of multi-stage seal of magnetic fluid centering sealed bearing.

In Fig. 3 and 4: shell 1, permanent magnet 2, rotating shaft 3, magnetic fluid 4.

Detailed ways

The utility model is further described with accompanying drawing 3 as specific embodiment:

The magnetic fluid centering sealed bearing consists of four main components: a housing 1, a permanent magnet 2, a rotating shaft 3 and a magnetic fluid 4. The casing 1 is composed of a casing and a casing cover. The shape and size of the shell and the cover can be the same or different. It can be two parts that are radially symmetrical or asymmetrical, or two parts that are axially symmetrical or asymmetrical. The combination method can be bolted connection, threaded cover screw connection, riveting, welding, adhesive bonding, etc., and can also be directly embedded in the bearing seat of the equipment. Two symmetrical round holes are arranged on both sides of the housing axially, and the diameter of the holes is slightly larger than the diameter of the rotating shaft 3 . The shell and the rotating shaft are made of non-magnetic and non-magnetic materials, such as stainless steel, copper, aluminum, engineering plastics, ceramics, etc. The permanent magnet 2 is designed as a ring, and its axial thickness is generally 0.1-0.5 times the outer diameter of the magnetic ring. The material of the permanent magnet can be determined according to the pressure resistance of the bearing. The greater the magnetic field strength of the permanent magnet, the greater the pressure resistance of the bearing. In general, different magnetic materials such as NdFeB, SmCo, AlNiCo, and ferrite can be selected. The N and S poles of the permanent magnet are distributed along the axial direction (as shown in Figure 3). The type of magnetic fluid 4 can be determined according to the sealed medium and the working environment temperature. For the vacuum sealing of the ambient temperature above 40°C, the low-volatility BH-2 magnetic fluid developed by Beihang University can be selected. If the sealed environment is gas and normal temperature below 35°C, the general-purpose BH-1 ferrofluid developed by Beihang University can be used, or even more volatile kerosene-based ferrofluid can be used.

Assembly of the magnetic fluid centering sealed bearing: the annular permanent magnet 2 is sleeved on the rotating shaft 3 . There can be a tight fit without relative motion, or a loose fit with relative motion between the two. When there is relative movement between the two, the rotary shaft can also perform linear axial movement. The gap between the permanent magnet and the inner wall of the shell is 0.1-0.5mm. The magnetic fluid is filled in the space inside the casing, and forms a "liquid cylindrical piston" together with the permanent magnet, which isolates the environment on both sides of the bearing and acts as a seal.

A magnetic fluid sealed bearing with multi-stage sealing capability can be formed by combining multiple annular permanent magnets closely in the order of NS, SN, NS... in the axial direction. The n-stage sealed bearing composed of n annular permanent magnets has n times the pressure resistance of the single-stage seal.

Magnetic fluid centering sealed bearings can also be used as non-sealed ordinary bearings. If the bearing capacity of the sealed bearing is to be greatly improved, ordinary ball bearings can also be installed on both sides of the bearing housing.

Application example 1: Process a magnetic fluid centering sealed bearing according to the principle shown in Figure 3: the shell size is φ24×12.8mm, and the material is brass. The wall thickness is 4mm. The shell and the shell cover are composed of two axially asymmetrical parts, which are fastened and connected by non-magnetic bolts. A symmetrical φ5.1mm through hole is reserved on both axial sides of the housing. The permanent magnet is a φ15×3.8mm NdFeB magnetic ring with an inner hole of φ5.0mm. The rotation axis is a stainless steel round bar of φ5.0×20.0mm. The rotating shaft is directly inserted into the inner hole of the magnetic ring, and the two are closely matched without relative movement. The gap between the permanent magnet and the inner wall of the housing is 0.5 mm, and the space formed by the permanent magnet and the housing is filled with 0.35 grams of BH-2 magnetic fluid. The static ultimate pressure resistance capacity of the magnetic fluid centering sealed bearing is 0.04Mpa, which is twice the single-stage pressure resistance capacity of the traditional magnetic fluid sealed bearing. The volume is about 60% smaller than that of traditional magnetic fluid sealed bearings with the same pressure resistance.

Example 2: Process a tertiary-sealed ferrofluid centering seal bearing according to Figure 4. The shell size is φ26.5×15.0mm and the material is brass. The wall thickness is 5mm. The shell and the shell cover are composed of two axially asymmetrical parts, which are screwed through the threaded cover. A symmetrical φ5.6mm through hole is reserved on both axial sides of the housing. The permanent magnets are three φ10×1.5mm NdFeB magnetic rings with an inner hole of φ5.0mm, which are arranged in the order of NS, SN, and NS, and are forcibly connected together by the rotating shaft. The rotation axis is two stainless steel round rods of φ5.0×15.0mm, the diameter of the part inserted into the inner hole of the magnetic ring is φ≤5.0mm, and the diameter of the part outside the inner hole of the magnetic ring is φ5.5mm, and the two are set on the rotating shaft The threaded screws are screwed together. The gap between the permanent magnet and the inner wall of the casing is 0.25 mm, and the space formed by the permanent magnet and the casing is filled with 0.15 grams of BH-2 magnetic fluid. The static ultimate pressure resistance capacity of the magnetic fluid centering sealed bearing is 0.12Mpa, which is twice the three-stage pressure resistance capacity of the traditional magnetic fluid sealed bearing. The volume is more than 60% smaller than the traditional magnetic fluid sealed bearing with the same pressure resistance.

Claims (7)

1, magnetic fluid centering stuffing box bearing is made up of shell, permanent magnet, running shaft, four critical pieces of magnetic fluid, it is characterized in that: with the permanent magnet in the conventional magnetic fluid stuffing box bearing by external change into built-in.

2, magnetic fluid centering stuffing box bearing according to claim 1, it is characterized in that: described shell and running shaft adopt non-magnetic nonmagnetic substance manufacturing.

3, magnetic fluid centering stuffing box bearing according to claim 1, it is characterized in that: described shell is connected by bolt with cap by housing or threaded cap spins or rivet or weld or mode such as adhesive bonds is combined, and housing and cap also can directly be embedded in the bearing support of equipment.

4, magnetic fluid centering stuffing box bearing according to claim 1, it is characterized in that: described permanent magnet is designed to an annular, and the axial thickness of annular solid is generally 0.1-0.5 times of magnet ring external diameter.

5, magnetic fluid according to claim 1 centering stuffing box bearing, it is characterized in that: the gap between described permanent magnet and outer casing inner wall is 0.1-0.5mm, magnetic fluid is filled in the enclosure the space.

6, magnetic fluid centering stuffing box bearing according to claim 4, it is characterized in that: the order combination of pressing NS, SN, NS... by n annular permanent magnet vertically, can form the magnet fluid sealing bearing with n level sealability, its total voltage endurance capability is n a times of single-stage sealing.

7, magnetic fluid centering stuffing box bearing according to claim 1 is characterized in that: can install plain ball bearing additional in bearing shell both sides.

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