JPS6231776A - Magnetic-fluid sealing device - Google Patents

Abstract

PURPOSE:To prevent the generation of leaked magnetic flux of a magnetic fluid sealing mechanism due to the reduction of dimension by catching magnetic fluid between an annular pole piece for shielding the leaked magnetic flux and a shaft and between a permanent magnet and the shaft. CONSTITUTION:An annular pole piece 12 which possesses soft magnetism and has a section in L-figure form and a permanent magnet 13 magnetized in the radial direction are installed onto a shaft 11 which possesses soft magnetism, separated by a certain interval. Magnetic fluid 14 is magnetically caught in the part between the pole piece 12 and the shaft 11 and the part between the permanent magnet 13 and the shaft 11. Therefore, though a portion of the leaked magnetic flux of the permanent magnet 13 passes through the pole piece 12 and the rest leaks outside, the leak of magnetic flux outside the pole piece 12 side is prevented, since the pole piece 12 covers the permanent magnet 13 is the radial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic fluid sealing device suitable for application to a sealing structure for a rotating shaft portion of a hard disk serving as a magnetic recording medium.

Various improvements have been made to hard disks as magnetic recording media to improve their reliability. For example, the cleanliness of the space inside the disc pack containing the disc is particularly important. To maintain this cleanliness, a magnetic fluid seal is attached to the spindle of the disk.
It has been improved to prevent grease mist from the spindle bearings or dust from outside the disk pack from entering the disk pack.

However, as hard disks tend to become smaller and thinner, magnetic fluid seals are also required to be smaller and thinner, but with the miniaturization, magnetic flux leakage from the magnetic fluid seal itself has become a problem. There is.

The structure of a conventional magnetic fluid seal, for example, as shown in FIG. 1, includes a soft magnetic pongee 1, two annular ball pieces 2,
A permanent magnet 3 sandwiched between them and magnetized in the axial direction,
It consists of a magnetic fluid film 4 that is magnetically trapped in an air gap.

According to such a structure, a leakage magnetic field is generated from the outer (radial direction) portion of the seal, resulting in a disadvantage that it has an adverse effect on the electronic components of the pond.

In view of these points, the present invention is provided with an annular ball piece having a permanent magnet magnetized in the radial direction and an annular portion for blocking leakage magnetic flux generated to the side surface by the permanent magnet, and between the ball piece and the shaft. The purpose of this invention is to eliminate the above-mentioned drawbacks by configuring the magnetic fluid to be magnetically trapped between the permanent magnet and the shaft.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a sectional view showing an example of the present invention. Reference numeral 11 indicates a soft magnetic shaft, and the shaft 11 includes a circular soft magnetic ball piece 12 having a cross-section shape and a permanent magnet 13 magnetized in the radial direction.
are set up in isolation for a certain period of time. A magnetic fluid 14 is magnetically captured between the ball piece 12 and the pongee 11, and between the permanent magnet 13 and the sleeve 11. Therefore, one side of the leakage magnetic flux due to the permanent magnet 13 passes through the ball piece 12 and the other leaks to the outside (in the direction of the arrow in the figure), but the ball piece 12 covers the permanent magnet 13 in the radial direction. Therefore, leakage magnetic flux to the outside of the ball piece 12 side is prevented from occurring.

FIG. 3 is a sectional view showing another embodiment of the present invention. In this example, the combination of the ball piece 12 and the permanent magnet 13 of the example in FIG.
It was installed as a set. In this case, the magnetization direction of the permanent magnet 13 is formed in the axial direction. Therefore, permanent magnet 1
No leakage magnetic flux due to No. 3 is generated.

FIG. 4 is a sectional view showing an example of a pond according to the present invention. In this example, an annular soft magnetic housing 15 is bonded to the inner peripheral surface of the ball piece 12 in the structure of the example shown in FIG. In this case, the magnetization direction of the permanent magnet 13 is formed in the axial direction. Therefore, one side of the leakage magnetic flux due to the permanent magnet 13 passes through the ball piece 12 and the other side leaks to the outside. However, since the ball piece 12 covers the permanent magnet 13 in the radial direction, the ball piece 12 No magnetic flux leaks to the outside on the 12 side.

FIG. 5 is a sectional view showing a further embodiment of the pond of the present invention.

In this example, a soft magnetic housing 15 is integrated with the ball piece 12 of the example shown in FIG.
The ball piece 16 is provided with a stepped portion having a size corresponding to that of the ball piece 16.

In this case, the magnetization direction of the permanent magnet 13 is formed in the axial direction. One side of the leakage magnetic flux due to the permanent magnet 13 passes through the ball piece 12 and the other leaks to the outside. However, since the ball piece 12 covers the permanent magnet 13 in the radial direction, the magnetic flux on the ball piece 12 side No magnetic flux leaks to the outside.

FIG. 6 is a sectional view showing another embodiment of the present invention. In this example, in the combination of the ball piece 12 and the permanent magnet 13 of the example shown in FIG. 2, the annular portion 22 of the ball piece 12 is further extended in the axial direction. In this case, the magnetization direction of the permanent magnet 13 is formed in the axial direction. Therefore, one side of the leakage magnetic flux due to the permanent magnet 13 passes through the ball piece 12 and the other side passes through the annular portion 22 and leaks to the outside, but the ball piece 12 covers the permanent magnet 13 in the radial direction. Therefore, magnetic flux leakage to the outside of the ball pieces 12 and 22 is prevented from occurring.

FIG. 7 is a sectional view showing an embodiment of the pond of the present invention. In this example, in the combination of the ball piece 12 and the permanent magnet 13 of the example in FIG. 2, the gap between the side surfaces of the ball piece 12 and the permanent magnet 13 is eliminated so that they are in close contact with each other. In this case, the magnetization direction of the permanent magnet 13 is formed in the axial direction. Therefore, one side of the leakage magnetic flux due to the permanent magnet 13 passes through the ball piece 12 and the other side passes through the annular portion 23 and leaks to the outside, but the ball piece 12 covers the permanent magnet 13 in the radial direction. Therefore, leakage magnetic flux to the outside of the ball piece 12 side is prevented from occurring.

FIG. 8 is a sectional view showing another embodiment of the present invention. In this example, in the combination of the ball piece 12 and permanent magnet 13 of the example in FIG. 7, the outer diameter dimensions of the ball piece 24 and the permanent magnet 13 are made to match, and a soft magnetic housing 25 is fitted to the peripheral end surfaces of both. It is a combination of In this case, the magnetization direction of the permanent magnet 13 is formed in the axial direction. Therefore, one side of the leakage magnetic flux due to the permanent magnet 13 passes through the ball piece 24 and the other side passes through the annular portion 25 and leaks to the outside. However, in the radial direction of the permanent magnet 13, the annular portion 25 Since it is covered, magnetic flux leakage to the outside will not occur.

As described above, according to the present invention, in a magnetic fluid sealing device in which a magnetic fluid is magnetically captured on a soft magnetic shaft,
A permanent magnet magnetized in the radial direction and an annular ball piece having an annular portion for blocking leakage magnetic flux generated toward the side surface by the permanent magnet are provided, and the opening between the ball piece and the shaft and the opening between the permanent magnet and the shaft are provided. Since the magnetic fluid is magnetically captured between the permanent magnets, one side of the leakage magnetic flux generated by the permanent magnets passes through the ball piece and the other side leaks to the outside. Since the ball piece covers the ball piece in the radial direction, leakage magnetic flux to the outside of the ball piece side will not occur, and the problem of leakage magnetic flux in the magnetic fluid seal mechanism that accompanies miniaturization will be solved. have an effect.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a conventional sealing device, FIG. 2 is a sectional view showing an example of the present invention, FIGS. 3, 4, 5,
FIGS. 6, 7, and 8 are cross-sectional views showing embodiments of the pond of the present invention. DESCRIPTION OF SYMBOLS 11... Soft magnetic shaft, 12... Annular soft magnetic ball piece, 13... Permanent magnet, 14... Magnetic fluid. Applicant's agent Patent attorney Takashi Akiyama Figure 5 Figure 7 Figure 6

Claims (1)

[Claims] A magnetic fluid seal device in which a magnetic fluid is magnetically captured on a soft magnetic shaft, comprising a permanent magnet magnetized in the radial direction and an annular shape for blocking leakage magnetic flux generated to the side by the permanent magnet. 1. A magnetic fluid sealing device, characterized in that an annular ball piece having a section is provided, and a magnetic fluid is magnetically captured between the ball piece and the shaft and between the permanent magnet and the shaft.