JP3455804B2 - Magnetic fluid sealing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic fluid sealing device. FIG. 8 shows a basic configuration of a magnetic fluid rotary shaft seal. A permanent magnet 1, a ring disk-shaped pole piece (yoke) 2 provided on both sides of the permanent magnet 1, and Constitutes the seal body 3. A motor shaft 5 is inserted through the inside of the seal body 3, and a magnetic fluid 4 is interposed between the shaft, the outer peripheral surface of the shaft 5, and the inside of the pole piece 2. As the permanent magnet 1, for example, a ring-shaped permanent magnet such as a value ferrite, an alnico, or a rare earth cobalt magnetized in the axial direction is used. This permanent magnet 1
As a result, a magnetic circuit as shown by an arrow is formed between the shaft 5 and the high-permeability shaft 5, and the magnetic fluid 4 is held in a gap between the shaft 5 and the pole piece 2 to serve as a pressure resistance, and the axial direction of the shaft 5 To block the flow of air and prevent the inflow of dust and the like. FIG. 7 shows a process of assembling a bearing portion of a motor used in a conventional hard disk or the like. As shown in FIG. 7 (a), a seal body 3 is made of a ring-shaped permanent magnet 1 as described above. , And a ring-shaped pole piece 2 arranged on both sides of the permanent magnet 1. A hole 2 for inserting the shaft 5 is provided inside the pole piece 2.
a is perforated. FIG. 7 (b) shows an aluminum housing 6 for holding the seal body 3, and the seal body 3 is disposed inside the housing 6 as shown in FIG. It is designed to be fixed. That is, the outer peripheral portion of the pole piece 2 on the upper side of the seal body 3 in the drawing and the housing 6
Both are fixed between the upper part and the inner part formed obliquely, and a sealing adhesive 7 is applied. In addition, a conductive adhesive 8 is applied between the lower surface of the lower pole piece 2 and the upper surface of the bottom of the housing 6 so that conduction between the seal body 3 and the housing 6 is obtained. [0005] FIG. 7 (d) shows a state incorporating the seal body 3 integrated with the housing 6 to the motor. When assembling the housing 6 in which the seal body 3 is fixed to the motor hub 9, the following is performed. That is, the housing 6 shown in (c) is disposed inside the motor hub 9 in the upside-down direction, and is adhered and fixed to the conductive adhesive 8 between the lower surface outside the housing 6 and the upper surface at the bottom of the motor hub 9. The electrical connection between the motor body 6 and the motor hub 9 is obtained so that the seal body 3 is grounded. Further, an adhesive between the upper part of the outside of the housing 6 and the inner part of the upper part of the motor hub 9 is adhered, and the adhesive 7 fixes and seals the housing 6, that is, the seal body 3 and the motor hub 9. I have. Figure
7 is a bearing 10 shown in (d). [0006] Such a conventional example has the following problems. That is, as shown in FIGS. 7 (c) and 7 (d), the bonding step is required twice to fix and seal the seal body 3 to the motor hub 9, and a conduction process for grounding the seal body 3 is performed. Also, two steps using a conductive adhesive are required. There is also a problem that the accuracy of individual parts is very severe in order to ensure the coaxiality of the inner diameter of the motor shaft 5 and the seal body 3. Further, with the downsizing of the motor, the space in which the seal 3 can be mounted is reduced, and there is no space for bonding the seal 3. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and an object of the present invention is to provide a magnetic fluid sealing device capable of reducing the number of bonding steps during assembly. According to the first aspect of the present invention, there is provided a magnetic fluid sealing apparatus comprising a permanent magnet and a pole piece disposed on both sides of the permanent magnet.
In the magnetic fluid sealing device for holding the magnetic fluid 4 between the pole piece 2 of the seal body 3 and the shaft 5,
The seal body 3 and the conductive plate 12 in contact with the seal body 3 are integrally formed by resin molding to form a seal body 14, and when the seal body 14 is disposed in the motor hub 9, the motor hub 9 The contact portion 13a for making contact with the inner surface of the
4, a rib 16 formed on a cover 15 that covers the seal body 14 is press-fitted between the inner peripheral surface of the motor hub 9 and the outer peripheral surface of the seal body 14 so that the seal body 14 Swelling part 1 for fixing and sealing with motor hub 9
6 a is formed on the rib 16. According to the first aspect of the present invention, the seal body is formed by integrally molding the seal body and the conductive plate in contact with the seal body with a resin mold. This eliminates the need for a bonding step between the seal body 13 and the housing 11 formed by the resin mold, and eliminates the need for a conductive adhesive for contact between the seal body 3 and the conductive plate 12 . In addition, the seal body 14
By simply mounting the tab hub 9, the conductive play of the seal body 14 is achieved.
The contact portion 13a of the motor 12 contacts the inner surface of the motor hub 9
The seal body 3 and the motor housing are
The connection with the bus 9 can be obtained. And cover 15
The sealing body 14 and the motor are
The fixing and sealing with the hub 9 can be performed at the same time.
Bonding in the assembly process of the main body 14 to the motor hub 9
The process can be eliminated. Therefore, the seal body 14
Is formed and the seal body 14 is assembled to the motor hub 9 or the like.
To obtain contact conduction between the seal body 3 and the motor hub 9 or the like.
To eliminate the bonding process in the assembly process
it can. Next, specific embodiments of the magnetic fluid sealing device of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 3, the structure of the seal body 3 for performing the magnetic fluid sealing is the same as that of the prior art, as shown in FIG. 3, and a ring disk-shaped pole piece 2 disposed on both sides of the permanent magnet 1. It is composed of And as shown in FIG.
The seal body 3, the conductive plate 12, and the resin housing 11 are integrally formed to form the seal body 14, and the bonding step for forming the seal body 14 is eliminated. That is, the ring-shaped housing 11 is integrally formed with the ring-shaped seal body 3 and the ring-shaped conductive plate 12 in contact with each other, and a part of the conductive plate 12 (a contact portion 13a described later) is formed. By projecting outward from the housing 11, the conductive plate 12 and the motor hub 9 are brought into contact with each other when assembling the motor hub 9. By integrally forming the conductive plate 12 in this manner, the contact between the conductive plate 12 and the seal body 3 can be obtained, and a conductive adhesive is not required unlike the related art. In addition, by performing molding based on the inner diameter of the seal body 3, the accuracy of the outer diameter dimension of the seal body 3 can be roughly performed. FIG. 5 shows the conductive plate 12, and three tongue pieces 13 project outward from the outer periphery of the conductive plate 12 formed in a ring disk shape. This tongue piece 13
Is formed in a substantially L-shape, and a tip portion is formed in an arc shape to be a contact portion 13a for making contact with the motor hub 9. FIG. 6 shows the seal body 3 and the conductive plate 12.
And a seal body 14 integrally formed with the housing 11, wherein the tongue 13 of the conduction plate 12 is embedded in the lower part of the housing 11, and the contact portion 13 a at the tip of the tongue 13 is Is formed so as to protrude from the outer peripheral surface of the lower part of the lower part. FIG. 6B shows a bottom view of the seal body 14. 2 and 4 show a ring-shaped disk-shaped cover 15 made of resin, and a hole 15 through which the shaft 5 is inserted at the center.
a, and a rib 16 is integrally provided around the outer peripheral portion.
The tip of the rib 16 is a bulged portion 1 bulged from the base.
6a. Here, the inner diameter of the bulging portion 16 a of the cover 15 is formed slightly smaller than the outer peripheral surface of the upper part of the housing 11 of the seal body 14, and the outer diameter of the bulging portion 16 a is slightly larger than the inner diameter of the inner peripheral surface of the motor hub 9. It is formed. Next, assembly of the seal body 14 to the motor hub 9 will be described. As shown in FIG. 1, a seal body 14 in which the seal body 3, the housing 11 and the conductive plate 12 are integrally formed is inserted and arranged inside the motor hub 9.
When the seal body 14 is installed in the motor hub 9, the contact portion 1 of the conductive plate 12 protruding from the housing 11
3a contacts the inner side surface of the motor hub 9, and the seal body 3 contacts the motor hub 9 via the conduction plate 12 to obtain conduction. Therefore, conduction between the conduction plate 12, that is, the seal body 3 and the motor hub 9 can be obtained without requiring a conductive adhesive as in the related art. Next, the cover 15 is attached to the motor hub 9. At this time, the rib 16 of the cover 15 is press-fitted between the outer peripheral surface of the seal body 14 and the inner peripheral surface of the motor hub 9, and the bulging portion 16 a at the tip end of the rib 16 becomes , And the inner peripheral surface of the motor hub 9. Then, the shaft 5 is inserted through the motor hub 9 in which the seal body 14 is incorporated, and the assembly is completed. The swelling portion 16a formed on the rib 16 of the cover 15 allows the seal body 14 to be fixed to the motor hub 9 and sealed at the same time. In other words, the bulging portion of the rib 16 of the cover 15 serves as an O-ring, and can be fixed and sealed to the motor hub 9 without using an adhesive. Note that the seal body 14 and the cover 15 are shipped as separate products,
When the seal main body 14 and the cover 15 are assembled into the motor by the user, the number of assembly steps on the shipping side can be reduced to zero because the main seal 14 is integrally formed.
Further, since the cover 15 has a function of fixing and sealing the seal body 14 to the motor hub 9, a bonding step by the user can be omitted, and a product with added value can be obtained. According to the magnetic fluid sealing device of the first aspect, the step of bonding the sealing body to the housing formed by the resin mold is unnecessary, and the contact between the sealing body and the conductive plate is eliminated. Eliminates the need for conductive adhesive .
Furthermore, just assemble the motor hub into the seal body,
The contact part of the conduction plate of the main body contacts the inner surface of the motor hub.
Without touching conductive adhesive, seal body and motor
Conduction with the hub can be obtained. Further cover ribs
Of the seal body and motor hub with the bulge
Can be performed simultaneously with the seal of the motor hub
The bonding step can be eliminated in the assembling step.
Therefore, when the seal body is formed and when the seal body is
Contact between the seal and motor hub etc.
In the assembly process for obtaining continuity, do not
Can be combed. In addition, smell of molding with resin mold
Is performed based on the inner diameter of the seal body.
The accuracy of the outer diameter of the body can be roughened. further
Because it is integrally molded, a seal and conductive plate
The number of standing steps can be reduced to zero. Also, seal body and cover
By shipping the bar and the product as separate products,
Side, when assembling the seal body and cover to the motor,
The added value can be improved because the bonding process can be omitted.
Product.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a main part showing an assembled state of an embodiment of the present invention. FIG. 2 is a cross-sectional view of a main part of the cover. FIG. 3 is a cross-sectional view of a main part of the seal body according to the first embodiment. FIG. 4 is a cross-sectional view of the cover. FIG. 5 (a) is a view showing the conductive plate A shown in FIG.
FIG. 4A is a cross-sectional view, and FIG. 4B is a plan view of a conduction plate. FIG. 6A is a cutaway side view of the same seal body, and FIG. 6B is a bottom view. FIG. 7 is an explanatory view showing an assembling process of a conventional example. FIG. 8 shows a basic configuration of a magnetic fluid rotary shaft seal.
FIG. [Description of Signs] 1 Permanent magnet 2 Pole piece 3 Seal body 4 Magnetic fluid 5 Shaft 9 Motor hub 11 Housing 12 Conductive plate 13a Contact portion 14 Seal body 15 Cover 16 Rib 16a Swelling portion

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-299044 (JP, A) JP-A-1-2555763 (JP, A) JP-A-3-78177 (JP, U) JP-A 58- 28159 (JP, U) JP-A 1-1118256 (JP, U) JP-A 2-101178 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16J 15/43

Claims (1)

(57) Claims 1. A permanent magnet (1) and the permanent magnet (1)
And a pole piece (2) disposed on both sides of the seal body (3), and a magnetic fluid (4) is held between the pole piece (2) and the shaft (5) of the seal body (3). In the magnetic fluid sealing device, the seal body (3) and the conductive plate (12) in contact with the seal body (3) are integrally formed by resin molding to form a seal body (14), and a motor hub is provided. When the seal body (14) is disposed in (9), the contact portion (13a) for contacting the inner surface of the motor hub (9) is made to protrude outward from the seal body (14) on the conduction plate (12). Cover (1) formed to cover the seal body (14).
The rib (16) formed in 5) is press-fitted between the inner peripheral surface of the motor hub (9) and the outer peripheral surface of the seal body (14) to fix and seal the seal body (14) and the motor hub (9). A magnetic fluid sealing device, wherein a bulging portion (16a) to be performed is formed on the rib (16).