JPH1066295A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle motor which is simple-structure and can be made thin and assembled easily. SOLUTION: A magnetic fluid sealing device 11 is installed outside in the axis direction of a ball bearing 3a through a flat ring-shaped spacer 20 made of non-magnetic material which abuts against an outer end face 19 of an outer ring 15 of the ball bearing 3a. The ring-shaped spacer 20 and the magnetic fluid sealing device 11 are preliminarily formed as an integral combination body with an outer edge of the ring-shaped spacer with an larger diameter projecting outside. The combination body is abutted against a ring-shaped side face of a rotor 4 and is adhered to it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor provided with a magnetic fluid sealing device.

[0002]

2. Description of the Related Art In recent years, a spindle motor used in a disk drive device is provided with a magnetic fluid sealing device to prevent grease or the like of a ball bearing from leaking out of the motor and affecting reading and writing of the disk. There are many. Conventionally, as shown in FIG. 6, for example, this kind of spindle motor is provided with a shaft a, a rotor c rotatably fitted to the shaft a via bearings b, b, and housed in the rotor c. A stator d externally fitted and fixed to the shaft a;
And a magnetic fluid sealing device e is disposed axially outward of one of the bearings b via a flat annular spacer f.

[0003] That is, as shown in FIG. 7, a magnetic fluid sealing device e comprises a flat annular magnet g and the magnet g
And a pair of pole pieces h, h sandwiching the
A magnetic fluid i held between the inner peripheral edges of the pole pieces h, h and the outer peripheral surface of the shaft a, and an annular bush m fitted into an annular recess k of the yoke j, and the yoke j.
Adhesively fixed. The above-mentioned annular spacer f and annular bush m are made of a non-magnetic material such as aluminum, and magnetically shut off the magnetic fluid sealing device e and the surrounding magnetic material so that the magnetic flux of the magnetic fluid sealing device e causes the bearings b to It prevents leakage to the yoke j side and weakening of the holding force of the magnetic fluid.
Further, the annular bush m abuts on the outer peripheral edge of the magnetic fluid sealing device e, thereby performing concentric positioning between the device e and the shaft a. Further, a protection cap n is disposed on the axially outer side of the magnetic fluid sealing device e to prevent foreign matter from entering from outside.

[0004]

That is, in the conventional spindle motor shown in FIGS. 5 and 6, as described above, the annular bush m for securing the holding force of the magnetic fluid and positioning the magnetic fluid sealing device. , Which requires a large number of parts and is difficult to assemble. The protective cap n has its outer peripheral edge bonded and fixed to the yoke j.
A curved portion p protruding outward in the axial direction is formed on the outer peripheral edge side to prevent contact with the adhesive s for fixing the annular bush, and the protective cap is formed on the inner peripheral edge side. n
A curved portion q protruding toward the magnetic fluid sealing device e is formed in order to achieve the stability of the magnetic fluid sealing device.

Since the magnetic fluid sealing device e, the annular spacer f and the annular bush m are fixed with the adhesive s, the adhesive s rises up to the vicinity of the protective cap n. Therefore, the curved portion p is provided as described above to secure a space, and the contact between the adhesive s and the protective cap n is prevented. Also, in order to eliminate the curved portion p and to provide a flat protective cap n for thinning, it is necessary to eliminate the swelling of the adhesive s. For this purpose, it is conceivable to secure the space for the adhesive pool by lowering the position of the annular bush m. However, as is apparent from the drawing, when the annular bush m is further lowered, the magnetic fluid sealing device e and the annular bush m come into contact with each other. The number of parts was reduced, making it difficult to perform proper positioning, and the adhesive s had to rise to some extent as long as there was the annular bush m. Therefore, the shape of the protective cap n is extremely complicated, it is difficult to manufacture, and the assembling work of the protective cap n is troublesome. Further, since the protection cap n has the curved portion p projecting outward in the axial direction as described above, the axial length of the entire motor cannot be reduced.

Accordingly, an object of the present invention is to provide a spindle motor which can reduce the number of parts as a whole and shorten the axial length of the entire motor and can be easily assembled.

[0007]

In order to achieve the above-mentioned object, one spindle motor according to the present invention comprises a columnar fixed body and a rotatable support for the fixed body via a ball bearing. A cylindrical rotating body, and a ring made of a non-magnetic material that abuts the outer end surface of the ball bearing in a space formed on the axially outward side of the ball bearing with the fixed body and the rotating body facing each other. In the spindle motor in which the magnetic fluid sealing device is disposed via a spacer, the annular spacer and the magnetic fluid sealing device are arranged such that the annular spacer has an outer peripheral portion on an outer diameter side from an outer peripheral edge of the magnetic fluid sealing device. A combined body is formed so as to have a large diameter protruding therefrom, and the combined body is fixed by bringing its outer peripheral portion into contact with the annular side surface of the rotating body or the fixed body. At this time, an adhesive is formed in a concave portion formed by an outer peripheral portion of the annular spacer, an annular step portion provided on a side surface of the rotating body or the fixed body with which the outer peripheral portion contacts, and an outer peripheral edge of the magnetic fluid sealing device. To fix the combination.

In another spindle motor according to the present invention, there is provided a cylindrical fixed body, a cylindrical rotary body rotatably supported on the fixed body via a ball bearing, A magnetic fluid seal device is provided in a space formed on the outer side in the axial direction of the ball bearing with the rotating body facing each other via an annular spacer made of a non-magnetic material in contact with an outer end surface of the ball bearing. In the spindle motor, the annular spacer and the magnetic fluid sealing device form an assembly such that the annular spacer has a small diameter whose inner peripheral portion projects toward the inner diameter side from the inner peripheral edge of the magnetic fluid sealing device. The assembly is fixed by bringing its inner peripheral portion into contact with the annular side surface of the rotating body or the fixed body. At this time, an inner peripheral portion of the annular spacer, an annular step portion provided on a side surface of the rotating body or the fixed body with which the inner peripheral portion abuts, and a concave portion formed by an inner peripheral edge of the magnetic fluid sealing device. It is preferable to fill the adhesive to fix the combination.

Further, in these spindle motors, it is preferable that a protective cap of a flat annular body is disposed on an axially outer side of the magnetic fluid sealing device so as to cover the magnetic fluid sealing device.

Further, another spindle motor according to the present invention includes a cylindrical fixed shaft made of a magnetic material, a rotor yoke rotatably supported by a pair of ball bearings on the fixed shaft, and made of a magnetic material. A magnetic fluid sealing device disposed on an upper end surface of an outer ring of at least one of the ball bearings via an annular spacer made of a non-magnetic material in a space between an outer peripheral surface of the fixed shaft and an inner peripheral surface of the rotor yoke. In the motor, the annular spacer and the magnetic fluid sealing device form an assembly such that the outer periphery of the annular spacer has a large diameter protruding outward from the outer peripheral edge of the magnetic fluid sealing device. At the same time, the outer peripheral portion is brought into contact with the step formed on the annular side surface of the rotor yoke, and the outer peripheral portion, the step of the rotor yoke and the outer peripheral edge of the magnetic fluid sealing device are An adhesive is filled in the recesses formed, it is intended to fix the said set coalescence. In this case, it is preferable to dispose a protective cap of a flat annular body on the rotor yoke so as to cover the magnetic fluid sealing device on the axially outer side of the magnetic fluid sealing device.

[0011]

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

FIG. 3 shows a spindle motor according to the present invention. This spindle motor is composed of a shaft 1 made of a magnetic material as a fixed body, a stator 2 fitted externally to the shaft 1, and a ball mounted on the shaft 1. A rotor 4 as a rotating body rotatably fitted to the outside via bearings 3a and 3b,
Is provided. The rotor 4 includes a cylindrical hub 5 and a rotor magnet 7 attached to the inner peripheral surface of the hub 5 via a rotor yoke 6, and is generally called a fixed shaft type spindle motor.

The rotor yoke 6 has a bulging portion 8 bulging toward the inner diameter side at one end opening side, and one ball is provided between the bulging portion 8 and a part of the shaft 1 corresponding thereto. The bearing 3a is fitted. That is, in the ball bearing 3a, the outer ring 15 is fixed to the inner peripheral surface of the bulging portion 8, and the inner ring 16 is fixed to the shaft 1. Also, at the other end opening of the rotor yoke 6,
The spacer 9 is fitted, and the other ball bearing 3b is fitted between the spacer 9 and a part of the shaft 1 corresponding thereto. That is, the outer race 17 of the ball bearing 3 b is fixed to the inner peripheral surface of the spacer 9, and the inner race 18 is fixed to the shaft 1.

Thus, a magnetic fluid sealing device 11 is disposed axially outward of one of the ball bearings 3a. As shown in FIG. 1, the magnetic fluid sealing device 11 includes a magnet 12 formed of a flat annular body, a pair of annular pole pieces 13, 13 for sandwiching the magnet 12 in a sandwich shape, and pole pieces 13, 13. A magnetic fluid 14 held between the corresponding part of the shaft 1.

The magnetic fluid seal device 11 is bonded and fixed to the rotor yoke 6 together with an annular spacer 20 which abuts on the outer end surface 19 of the outer ring 15 of one of the ball bearings 3a. That is, the annular spacer 20 has a large diameter whose outer peripheral portion 21 projects outward from the outer peripheral edge of the magnetic fluid seal device 11 (that is, the outer peripheral edge of the magnet 12 and the outer peripheral edges of the pole pieces 13, 13). At the same time, the hole 22 has a large diameter. The annular spacer 20 is made of, for example, a non-magnetic material such as synthetic resin or aluminum, and prevents the magnetic flux of the magnetic fluid sealing device 11 from leaking to the ball bearings 3a to the rotor yoke 6 side and preventing the magnetic fluid holding force from weakening. doing. The thickness dimension of the annular spacer 20 is, for example, about 0.05 to 1.00 mm.

In this case, the bulging portion 8 of the rotor yoke 6
It has a first step 23 and a second step 24, and the corner of the first step 23 is
It is slightly chamfered to make it easier to insert the annular spacer 20. The outer peripheral portion 21 of the annular spacer 20 is fitted to the annular side surface of the first step portion 23.
An adhesive S is filled in an annular recess formed by the annular side surface of the step portion 23 and the outer peripheral edge of the magnetic fluid seal device 11, and the magnetic fluid seal device 11 is bonded and fixed to the rotor yoke 6 together with the annular spacer 20. As the adhesive S, for example, an ultraviolet curable resin or an epoxy-based adhesive is used. Further, the magnetic fluid sealing device 11 of the outer peripheral portion 21 of the annular spacer 20 is provided.
The amount of protrusion from the outer edge is, for example, 0.5 to 5.0 mm. If it is smaller than 0.5 mm, the bonding cost is too small and 5.
If it is larger than 0 mm, the protrusion amount is too large, and it is necessary to make the first step portion 23 large.

Further, a protection cap 25 made of a flat plate annular body is provided on the axially outward side of the magnetic fluid seal device 11 to prevent foreign substances from entering the motor and from coming into contact with the inside of the motor. The protection cap 25 has a larger diameter than the annular spacer 20,
The outer peripheral portion 26 is fitted to the second step portion 24 of the bulging portion 8 of the rotor yoke 6 so as to cover the magnetic fluid sealing device 11, and the outer surface of the outer peripheral portion 26 is filled with an adhesive S. 6 is fixed by adhesion. The protective cap 25 is made of, for example, aluminum, stainless steel, or the like, and has a thickness dimension of, for example, about 0.1 to 0.5 mm.

When assembling the spindle motor, as shown in FIG. 2, when the magnetic fluid sealing device 11 and the annular spacer 20 are fixed with an adhesive, these concentric alignments are completed and integrated. After forming the union, it is bonded and fixed to the rotor yoke 6. The assembly is assembled using a positioning jig (not shown). However, the assembly is more restricted in space than the conventional method of directly incorporating the annular spacer f and the magnetic fluid seal device e on the motor side. Because it is not received, it can be done easily and accurately. Therefore, when installing this combination, the magnetic fluid sealing device 11 is previously aligned with the annular spacer 20, and the outer peripheral portion 21 of the annular spacer 20 in this combination is formed by the first step portion 24 of the rotor yoke 6. By contacting the annular side surface, the magnetic fluid sealing device
Since the alignment between the shaft 11 and the shaft 11 can be achieved naturally, the work of assembling these unions becomes easy. (On the other hand, in a conventional spindle motor requiring an annular bush, the positioning of the magnetic fluid sealing device is performed by the bush, and without the bush, the positioning cannot be performed, which is extremely troublesome. Note that the positional relationship between the magnetic fluid sealing device 11 and the shaft 1 determines the holding stability of the magnetic fluid, so that the positioning is extremely important.
The combined body is fixed by filling the above-mentioned annular concave portion with the adhesive S. However, since the adhesive can be filled on the lower annular spacer 20, a space for an adhesive pool is secured, and the vicinity of the protective cap 25 is secured. There is no fear of swelling up to this point, and there is no need to provide a curved portion p in the protective cap n as in the conventional case.

As described above, according to the present invention, the annular bush, which has been conventionally required, is not required, the number of parts can be reduced accordingly, the assembling is facilitated, and the protective cap 25 is used as the protective cap 25. Can also be formed as a flat annular body, which does not require a curved portion on the outer peripheral edge side as in the related art, is easy to manufacture, and has a reduced axial length of the entire motor (that is, a reduced thickness). ) Can be achieved.
In the spindle motor shown in FIGS. 1 and 3, since the rotor yoke 6, the ball bearings 3a and 3b, and the shaft 1 are made of iron, they have substantially the same coefficient of thermal expansion and have an advantage of being resistant to thermal change. . Further, in the present embodiment, the protection cap 25 is a flat plate-shaped body, but a curved portion protruding toward the magnetic fluid seal device 11 is provided on the inner peripheral edge side thereof so that the stability of the cap 25 is achieved. It may be. In this case, since the length in the axial direction is not increased, the thickness is not affected.

Next, FIG. 4 shows another embodiment. In this case, the spindle motor is provided with a hub 30 made of a non-magnetic material such as aluminum as a rotating body.
A first step portion 31 and a second step portion 32 are formed in
The outer peripheral portion 21 of the annular spacer 20 is fitted to the step portion 31, the outer surface of the outer peripheral portion 21 is filled with an adhesive S, and the magnetic fluid sealing device 11 is adhesively fixed to the hub 30 together with the annular spacer 20. Further, an adhesive S is filled on the outer surface of the outer peripheral portion 26 of the protective cap 25, and is adhered and fixed to the hub 30. Therefore, also in this case, the same operation and effect as those of the spindle motor shown in FIG. 1 can be obtained.

FIG. 5 shows another embodiment. In this case, the type is substantially the same as that of the spindle motor shown in FIG. 3, and the difference is that the magnetic fluid sealing device 40 is disposed on the fixed body side. It is in. That is, the annular spacer 41
The inner peripheral portion 42 has a small diameter that protrudes radially inward from the inner peripheral edge of the magnetic fluid seal device 40 and abuts against the outer end surface 43 of the inner ring 16 of the ball bearing 3a. An adhesive S is filled in the formed concave portion and fixed. In this case, the same operation and effect as those of the spindle motor shown in FIG. 1 can be obtained.

Although the embodiments of the spindle motor according to the present invention have been described above, the scope of application of the present invention is not limited to these configurations. For example, in the above-described example, a shaft fixed type spindle motor including a shaft as a fixed body and a hub as a rotating body is used. The combination of the present invention can be provided on the body side or the fixed body side, and the same operation and effect can be obtained.

[0023]

Since the present invention is configured as described above, the following effects can be obtained.

According to the first aspect, since the outer peripheral portion of the combination abuts the annular side surface of the rotating body or the fixed body for both the shaft fixed type and the shaft rotating type spindle motors, the conventional annular bush can be used. The positioning of the magnetic fluid sealing device can be easily and reliably achieved without using it. According to the second aspect, the inner peripheral portion of the combined body abuts the annular side surface of the rotating body or the fixed body for both the shaft fixed type and the shaft rotating type spindle motors. And the positioning of the magnetic fluid sealing device can be easily and reliably achieved. According to the third aspect, it is easy to secure a groove for the adhesive for fixing the union in which the outer periphery is filled with the adhesive.
The swelling of the adhesive to the outside can be suppressed, and the axial length of the motor can be reduced (that is, the motor can be made thinner). According to the fourth aspect, since it is easy to secure a groove for the adhesive for fixing the combination that fills the inner peripheral portion with the adhesive,
The swelling of the adhesive to the outside can be suppressed, and the axial length of the motor can be reduced (that is, the motor can be made thinner). According to the fifth aspect, the use of a protective cap can prevent foreign matter from entering from outside and can provide a safer magnetic fluid sealing device. In addition, since there is no swelling of the adhesive of the assembly, it is manufactured with a flat plate. A spindle motor provided with an easy-to-use protection cap can be provided. According to the sixth aspect, the magnetic fluid sealing device can be easily and securely fixed to the shaft fixed type spindle motor without using the conventional annular bush, and the swelling of the adhesive is suppressed, so that the thickness is reduced. This is a spindle motor that can achieve this. According to the seventh aspect, it is possible to provide a spindle motor having a protective cap, which is provided with a safer magnetic fluid sealing device, and which has a protective cap which is easy to manufacture with a flat plate because there is no swelling of the adhesive of the combination. .

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part of a spindle motor according to the present invention.

FIG. 2 is a simplified perspective view of a magnetic fluid sealing device and an annular space of a spindle motor according to the present invention.

FIG. 3 is a sectional view of a spindle motor according to the present invention.

FIG. 4 is an enlarged sectional view of a main part showing another embodiment of the spindle motor according to the present invention.

FIG. 5 is an enlarged sectional view of a main part showing another embodiment of the spindle motor according to the present invention.

FIG. 6 is a half sectional view of a conventional spindle motor.

FIG. 7 is an enlarged sectional view of a main part of a conventional spindle motor.

[Explanation of symbols]

 3a Ball bearing 6 Rotor yoke 11 Magnetic fluid seal device 15 Outer ring 19 Outer end surface 20 Annular spacer 21 Outer peripheral portion 25 Protective cap 40 Magnetic fluid seal device 41 Annular spacer 42 Inner peripheral portion 43 Outer end surface

Claims (7)

[Claims] 1. A cylindrical fixed body, a cylindrical rotary body rotatably supported by a ball bearing on the fixed body,
The magnetic fluid sealing device is provided in a space formed between the fixed body and the rotating body facing each other in an axially outer side of the ball bearing through an annular spacer made of a non-magnetic material that abuts on an outer end surface of the ball bearing. In the spindle motor provided, the annular spacer and the magnetic fluid sealing device are configured such that the annular spacer has a large diameter whose outer peripheral portion projects outward from the outer peripheral edge of the magnetic fluid sealing device. A spindle motor, wherein a combined body is formed, and the combined body is fixed by bringing an outer peripheral portion thereof into contact with an annular side surface of the rotating body or the fixed body. 2. A cylindrical fixed body, a cylindrical rotary body rotatably supported on the fixed body via a ball bearing,
The magnetic fluid sealing device is provided in a space formed between the fixed body and the rotating body facing each other in an axially outer side of the ball bearing through an annular spacer made of a non-magnetic material that abuts on an outer end surface of the ball bearing. In the spindle motor provided, the annular spacer and the magnetic fluid sealing device are combined so that an inner peripheral portion of the annular spacer has a small diameter protruding toward the inner diameter side from an inner peripheral edge of the magnetic fluid sealing device. A spindle motor which forms a body and is fixed by bringing its inner peripheral portion into contact with the annular side surface of the rotating body or the fixed body. 3. A recess formed by an outer peripheral portion of the annular spacer, an annular step provided on a side surface of the rotating body or the fixed body with which the outer peripheral portion abuts, and an outer peripheral edge of the magnetic fluid sealing device. The spindle motor according to claim 1, wherein the assembly is fixed by filling with an adhesive. 4. An inner peripheral portion of the annular spacer, an annular step provided on a side surface of the rotating body or the fixed body with which the inner peripheral portion abuts, and an inner peripheral edge of the magnetic fluid sealing device. 3. The spindle motor according to claim 2, wherein the recess is filled with an adhesive to fix the assembly. 5. The spindle motor according to claim 3, wherein a protection cap of a flat annular body is disposed on an axially outer side of the magnetic fluid sealing device so as to cover the magnetic fluid sealing device. 6. A cylindrical fixed shaft made of a magnetic material, a rotor yoke rotatably supported by a pair of ball bearings on the fixed shaft, and a rotor yoke made of a magnetic material, an outer peripheral surface of the fixed shaft and an inner periphery of the rotor yoke. A magnetic fluid sealing device disposed on the upper end surface of the outer ring of at least one of the ball bearings via a circular spacer made of a non-magnetic material in a space between the ring spacer and the magnetic fluid. The sealing device is formed by forming the annular spacer such that the outer peripheral portion thereof has a large diameter projecting to the outer diameter side from the outer peripheral edge of the magnetic fluid sealing device, and the outer peripheral portion thereof is formed in an annular shape of the rotor yoke. An adhesive is filled into a recess formed by contacting the outer peripheral portion, the outer peripheral portion of the rotor yoke, and the outer peripheral edge of the magnetic fluid sealing device. Spindle motor, characterized in that to fix the. 7. The rotor yoke is provided with a protective cap of a flat plate-like body on the rotor yoke so as to cover the magnetic fluid sealing device on the axially outward side of the magnetic fluid sealing device.
The spindle motor as described.