JPH01203768A - Sealing device utilizing magnetic fluid - Google Patents

Abstract

PURPOSE:To cut cost by reducing the number of parts, securing the coercive force of magnetic fluid by retreating the peripheral surface of an annular pole piece to an operating member side, in comparison with the peripheral surface of an annular magnetic body. CONSTITUTION:Though a portion of the magnetic fluxes of an annular magnet body 2 passes through a fixed housing 5 side, and a portion passages through a rotary shaft 7 side, the magnetic fluxes which pass through the fixed housing 5 side shall pass the magnetic pole surface exposure parts 20 and 21 having each large magnetic resistance, and the magnetic fluxes which pass through this part reduce. Therefore, the magnetic fluxes which pass through the rotary shaft 7 side increase, and the coercive force of the magnetic fluid 8, 9 can be secured. Therefore, even if a conventional annular surrounding member is not used, the coercive force of the magnetic fluid 8, 9 can be secured, and the number of parts of a sealing device can be reduced, enabling cost reduction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sealing device using a magnetic fluid, and particularly to a sealing device suitable for dustproof sealing, vacuum sealing, and the like.

(Prior Art) A magnetic fluid is a fluid made by suspending ferromagnetic particles, such as magnetite particles, with a particle size of about 100 μm in a base solvent via a surfactant. The ferromagnetic particles are suspended in suspension by colliding with molecules in the base solvent that undergo random thermal motion, and the action of the stabilizer permanently prevents their agglomeration, so that the magnetic fluid It is a stable and homogeneous colloidal liquid. As is well known, this magnetic fluid has the property that its position can be controlled by the magnetic force of an external magnetic field.

A conventional example of a seal device using such a magnetic fluid is shown in FIG. As shown in the same figure, this sealing device is constructed by overlapping annular pole pieces 41 and 42 made of a magnetic material on both sides of an annular magnet 40 having different poles arranged in the thickness direction. An annular surrounding member 44 made of a non-magnetic material surrounding the outer circumferential side is attached to the cylindrical fixed housing 4 made of a magnetic material.
It is attached to the inner peripheral surface of 5. Then, the inner circumferential surface of the seal body 43 is opposed to the circumferential surface of a rotating shaft 47 made of a magnetic material rotatably supported in the fixed housing 45 via a bearing 46, and the annular pole piece 41.
Magnetic fluids 48 and 49 are interposed between the inner peripheral surface of 42 and the outer peripheral surface of rotating shaft 47. This magnetic fluid 48.4
9 is an annular pole piece 41, 42 and a rotating shaft 47
It is held in place by the magnetic flux generated between the two and can perform a sealing function.

(Problems to be Solved by the Invention) The above-mentioned sealing device includes the annular surrounding member 44 made of a non-magnetic material for the following reason.

That is, in general, when a magnetic body is placed in a magnetic field formed by a magnet, most of the magnetic flux has a property of passing through the magnetic body. Therefore, when the outer peripheral surfaces of the annular pole pieces 41 and 42, which are magnetic materials, are directly attached to the fixed housing 45, which is also magnetic, a large amount of the magnetic flux generated by the annular magnet body 40 passes through the fixed housing 45 side. As a result, the magnetic flux passing through the rotating shirt 1-47m is reduced, and the holding force of the magnetic fluid 48, 49 is reduced. Therefore, an annular surrounding member 44 made of a non-magnetic material with a high magnetic resistance is interposed between the annular pole pieces 41 and 42 and the fixed housing 45 to reduce the magnetic flux passing through the fixed housing 45 side, thereby preventing the rotating shaft 47 side from flowing. This increases the magnetic flux passing through the magnetic fluid 48, 49 to ensure the holding force of the magnetic fluid 48,49.

However, in this sealing device, by providing the annular surrounding member 44 in this manner, the number of parts increases, making the sealing device expensive.

This invention was made in view of the above-mentioned conventional problems, and its purpose is to use a magnetic fluid that can reduce the number of parts while ensuring the holding force of the magnetic fluid, and therefore reduce costs. The object of the present invention is to provide a sealing device that achieves this.

(Means for Solving the Problems) Therefore, in the sealing device using magnetic fluid of the present invention, an annular pole piece made of a magnetic material is superimposed on the magnetic pole surface of an annular magnet body with different poles arranged in the thickness direction. to form a seal body, one circumferential surface of the seal body is attached to the circumferential surface of the non-actuating member, and the other circumferential surface of the seal member is opposed to the circumferential surface of the actuating member. and the actuating member, the sealing device comprising a magnetic fluid interposed between the seal body and the actuating member, wherein the circumferential surface of the annular pole piece is positioned closer to the actuating member than the circumferential surface of the annular magnet body on the attachment side of the seal body. are retreating.

(Function) As a result of the above, when the operating member and the non-operating member are each magnetic, one of the magnetic fluxes due to the annular magnet passes through the non-operating member side and the other passes through the operating member side. However, since the magnetic flux passing through the non-operating member side has to pass through the exposed part of the magnetic pole face of the annular magnet body, which has a large magnetic resistance, the magnetic flux passing through this part decreases. As a result, the magnetic flux passing through the actuating member increases, and the holding force of the magnetic fluid is ensured.

(Example) Next, a specific example of a sealing device using a magnetic fluid of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a first embodiment of the invention.

In the figure, 1 is a seal body, and this seal body 1
is an annular pole consisting of an annular magnet body 2 with different poles arranged in the thickness direction (N pole on the left side in the figure, S pole on the right side) and a magnetic material superimposed on both magnetic pole surfaces of this annular magnet body 2. It is composed of pieces 3 and 4. Details of this seal body 1 will be described later. The outer peripheral surface of this seal body I is
It is attached to the inner peripheral surface of a cylindrical fixed housing 5 as a non-operating member. The inner circumferential side of the annular pole piece 3.4 is disposed opposite to the outer circumferential surface of a rotary shaft 7, which is an operating member rotatably supported in the fixed housing 5 via a bearing 6. A magnetic fluid 8.9 is interposed between each inner peripheral portion and the outer peripheral surface of the rotating shaft 7. It is assumed that the fixed housing 5 and the rotating shaft 7 are each made of a magnetic material.

By the way, in the seal body 1, the thickness of the inner circumferential side of the annular magnet body 2 is made smaller than the thickness of the outer circumferential side via the stepped portions 10 and 11, and the annular ball heath 3.4 is
The seal body 1 is overlapped with both magnetic pole faces of the annular magnet body 2 so that both surfaces of the seal body 1 are planar, with their outer peripheral portions in contact with the step portions 10.11. That is, the outer circumferential surface of the annular pole piece 3.4 is set back toward the rotating shaft 7 side than the outer circumferential surface of the annular magnet body 2, so that there is a gap between a part of the annular magnet body 2 and the inner circumferential surface of the fixed housing 5. Exposed magnetic pole face portions 20 and 21 are formed in the magnetic pole faces. Note that the annular magnet body 2 in the seal body 1 can easily obtain the above-described shape by injection molding, for example, and can also be integrally molded with the annular pole piece 3.4.

In the above embodiment, a part of the magnetic flux generated by the annular magnet body 2 passes through the fixed housing 5 side, and a - part passes through the rotating shaft 7 side, but the magnetic flux passing through the fixed housing 5 side is Since the magnetic flux must pass through the exposed magnetic pole face portions 20 and 21 of the annular magnet body 2, which have a large magnetic resistance, the magnetic flux passing through this portion is reduced. As a result, the magnetic flux passing through the rotating shaft 7 side increases, and the holding force of the magnetic fluid 8.9 is ensured.

As described above, in the above embodiment, the holding force of the magnetic fluid 8.9 can be ensured without using the conventional annular surrounding member 44 (see FIG. 5), and therefore the parts of the sealing device This means that you can reduce your score,
It is possible to reduce the cost of the sealing device.

FIG. 2 shows a second embodiment of the invention. The difference from the first embodiment is that a rotary housing 13 is used as an operating member, and a fixed shaft 14 is used as a non-operating member.
The point is that each of them is adopted. Also, Figures 3 and 4
The figures show third and fourth embodiments of the invention, respectively. In each of the embodiments, the annular pole piece 3 is superimposed on one magnetic pole surface of the annular magnet body 16, and a bearing 18 is placed adjacent to the other surface, and this bearing 18 is made of a magnetic material and forms part of a magnetic circuit. The structure is such that a bearing 18 is used in this case. As is clear from the figures, in the third embodiment, the rotating shaft 7 is used as the operating member, and the fixed housing 5 is used as the non-operating member, and in the fourth embodiment, the rotating housing 13 is used as the operating member. A fixed shaft 14 is respectively employed as a non-operating member. In addition, also in the above-mentioned second to fourth embodiments,
It is possible to achieve the same effect as the first embodiment, and therefore in the second to fourth embodiments, the first embodiment
The same reference numerals are given to the same parts as in the embodiment, and the explanation thereof is omitted.

Specific embodiments of the sealing device using magnetic fluid of the present invention have been described above, but in this invention, for example, the thickness of the annular magnet body is made constant in the radial direction, and the non-operating member in the annular pole piece is It is also possible to form an exposed portion of the magnetic pole face in a part of the annular magnet body by retracting the side circumferential surface from the circumferential surface of the annular magnet body toward the actuating member. Further, the present invention can also be applied to an actuating member that is reciprocated in the axial direction. Further, in the above embodiments, a single seal body is shown, but it is also possible to arrange a plurality of seal bodies in multiple stages.

(Effects of the Invention) As described above, the sealing device using the magnetic fluid of the present invention has the above structure, so while maintaining the holding force of the magnetic fluid, the annular surrounding member as in the conventional case is not required. This makes it unnecessary, and therefore the number of parts can be reduced, making it possible to reduce costs.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing the first embodiment of the present invention, and the second
4 are partial sectional views showing second to fourth embodiments, respectively, and FIG. 5 is a partial sectional view of a conventional sealing device. ■... Seal body, 2.16... Annular magnet body, 3.4
... Annular pole piece, 5... Fixed housing (non-operating member), 6.18... Bearing, 7... Rotating shaft (operating member), 8.9... Magnetic fluid, 13
...Rotating housing (operating member), 14... Fixed shaft (non-operating member), 20.21... Air gap. Patent applicant Nippon Ferro Fluidics Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. Construct a seal body by overlapping an annular pole piece made of a magnetic material on the magnetic pole surface of an annular magnet body with different poles arranged in the thickness direction, and place one circumference of the seal body on the circumferential surface of the non-operating member. A sealing device comprising: a surface attached to the seal member, the other circumferential surface of the seal member facing the circumferential surface of the actuating member, and a magnetic fluid interposed between the seal body and the actuating member. ,
A sealing device using a magnetic fluid, characterized in that, on the attachment side of the seal body, the circumferential surface of the annular pole piece is set back toward the operating member side from the circumferential surface of the annular magnet body.