RU2296903C2 - Magnetic fluid shaft seal - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: magnetic fluid shaft seal comprises ring magnetic system that embraces the shaft and is made of permanent magnet and pole members with teeth that abuts against it. The teeth are formed by ring grooves. The space between the teeth and shaft is filled with a magnetic fluid. The shaft has teeth similar to the teeth of the pole members. The teeth of the pole members are shifted in the axial direction by half of the tooth with respect to the teeth on the shaft.

EFFECT: enhanced reliability.

4 dwg

Description

The present invention relates to sealing technology and can be used in mechanical engineering for sealing rotating shafts.

Known magnetic fluid shaft seal SU 420836, containing a non-magnetic housing, an annular permanent magnet, pole attachments, on the surfaces of the shaft facing which the annular grooves are made for a diamagnetic filler. Its disadvantage is its low holding capacity and reliability.

It is known magnetic SU shaft seal SU 653470. The shaft seal contains a permanent magnet and mounted on a concentrically sealed shaft pole attachments between which magnetic fluid is placed. On the surfaces of the pole consoles and the shaft facing each other, grooves are made with two lateral generatrices in axial section, the protrusions on the shaft opposite the protrusions on the pole consoles.

The disadvantages of the seal are: low holding capacity, therefore, low reliability. This is due to the insufficiently effective form of the working zone of the magneto-liquid seal.

The technical result achieved by the invention is to increase the holding capacity of the magneto-liquid seal and its reliability. This is achieved by the fact that in a magnetically liquid shaft seal containing an annular magnetic system, covering the shaft, including a permanent magnet and adjacent pole attachments with teeth formed by annular grooves, where the gap between the teeth and the shaft is filled with magnetic fluid, the shaft has teeth similar to teeth pole consoles both in shape and their formation, and the teeth of the pole consoles are displaced in the axial direction by half of the tooth division relative to the teeth on the shaft.

Figure 1 shows the design of the seal, figure 2 - the shape of the tooth and the position of the magneto-liquid plugs in the gap, figure 3 - the position of the magneto-fluid plugs in the gap of known seals, figure 4 is a graphical representation of the distribution of magnetic field strength in the working gap of the known and proposed seals.

The seal is arranged as follows. In the housing 1, a permanent magnet 2 is installed with adjacent pole attachments 3. On the surfaces of the pole attachments facing the shaft 4, there are rectangular teeth 5. On the shaft surface under the pole attachments there are also teeth 6, similar to the teeth of the pole attachments both in shape and and their formation, and the teeth of the pole attachments are displaced in the axial direction by half of the tooth division relative to the teeth on the shaft. Magnetic fluid introduced into the working gap forms separate magneto-fluid plugs 7 (Fig. 2) located in the region of the edges of the teeth.

Sealing works as follows. The permanent magnet 2 in the seal serves as a source of magnetic field. The magnetic flux created by it by the pole attachments 3 is brought to the gap between the pole attachments and the shaft. The teeth of the poles 5 and shaft 6 redistribute the magnetic flux in the gap, and the field becomes sharply inhomogeneous. The magnetic fluid is drawn by the magnetic field into the areas where the field has maximum tension and forms sealed plugs with increased internal pressure. Zones with maximum field strength are located between the edges of the teeth of the pole attachments and the shaft. Each magneto-liquid plug is capable of perceiving a pressure drop, which is determined by the formula:

where μ ₀ is the magnetic constant,

M is the magnetization of the magnetic fluid,

N is the magnetic field strength in the gap,

H _max and H _min - the maximum and minimum magnetic field strengths at the boundaries of the magnetofluidic plug at the moment it holds the maximum pressure drop.

The pressure drop held by the seal is determined by the sum of the pressure drops of all the magneto-liquid plugs under the teeth.

If we compare the distribution of the magnetic field strength in the working clearances of the seals (Fig. 4), then we see that for each tooth division of the proposed seal, there are two peaks and two minima of the magnetic field strength, compared with one peak and a minimum in the prototype. Therefore, in the proposed seal under each tooth two magneto-liquid plugs are formed instead of the one existing in known seals. If the pitch of the tooth division in both cases is the same, then the differential pressure that is kept is almost doubled compared to the prototype.

Thus, the proposed magneto-liquid seal allows you to increase the held differential pressure almost doubled and thereby increase the reliability of the seal.

Claims (1)

A magnetically liquid shaft seal comprising an annular magnetic system enclosing the shaft, including a permanent magnet and adjacent pole attachments with teeth formed by annular grooves, where the gap between the teeth and the shaft is filled with magnetic fluid, characterized in that the shaft has teeth similar to the teeth of pole attachments both in shape and in their formation, moreover, the teeth of the pole attachments are displaced in the axial direction by half of the tooth division relative to the teeth on the shaft.

Images