JPH11273236A - Spindle motor for magnetic disk drive - Google Patents

Abstract

(57) [Problem] To provide a fixed shaft type magnetic disk drive spindle motor, which secures a fastening strength between a shaft and a housing. SOLUTION: An adhesive groove 25 having a predetermined width is provided in an adhesive portion,
The ratio of the sum of the width of the adhesive groove to the width of the adhesive is within a predetermined range, and the adhesive gap is formed according to the viscosity of the adhesive. Further, the bonding gap is not constant in the range of the bonding width, but is changed monotonically in a part of the range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed shaft type magnetic disk drive spindle motor using an adhesive for fixing members.

[0002]

2. Description of the Related Art As devices such as personal computers are further downsized and have higher capacities, spindle motors for driving recording media (for example, magnetic disks) incorporated therein are required to be further downsized and higher in accuracy. Have been.

Conventionally, in a spindle motor for driving a magnetic disk of the ball bearing type, the ball bearing is fastened by press-fitting. With the demand for low noise, spindle motors that use ball bearings may deteriorate noise due to deformation of the inner and outer rings and indentation of the race surface during assembly. Fastening using an adhesive is increasing for fastening the bearing and the shaft, and the ball bearing and the housing.

[0004] Japanese Utility Model Application Laid-Open No. 6-36353,
As disclosed in Japanese Patent No. 68153, three adhesive grooves are provided on the outer peripheral surface of the shaft when the adhesive is fastened between the inner race of the ball bearing and the shaft, and the housing is fastened with the adhesive between the outer race of the ball bearing and the housing (or frame). 1 on the inner surface of
It has a structure in which a strip of adhesive grooves is provided. That is, the adhesive grooves for the adhesive fastening of the inner and outer rings of the ball bearing are different from each other. It is stated that the adhesive easily penetrates into the adhesive groove in the assembling work, and the adhesive strength is increased.

As shown in Japanese Utility Model Application Laid-Open No. 6-84553, in fastening an adhesive between an inner ring of a ball bearing and a shaft, a single adhesive groove is provided on the outer peripheral surface of the shaft, and an outer ring of the ball bearing and a housing (or frame) are provided. In this case, one adhesive groove is also provided on the inner peripheral surface of the housing. The number of adhesive grooves for the adhesive fastening of the inner and outer rings of the ball bearing is one. Also in this case, the adhesive easily penetrates into the adhesive groove in the assembling work, and the adhesive strength is increased.

As disclosed in Japanese Utility Model Laid-Open Publication No. Hei 7-39266, an outer ring of a ball bearing is provided in which three adhesive grooves are provided on a shaft by fastening an adhesive between the ball bearing and the shaft, and the width of the middle groove is increased. In the fastening of the adhesive between the housing and the frame (or frame), three adhesive grooves are provided on the inner peripheral surface of the housing, and the width of the middle one of the grooves is increased. Also in this case, the adhesive easily penetrates into the adhesive groove in the assembling work, and the adhesive strength is increased.

A method of providing such an adhesive groove to increase the adhesive fastening strength is adopted for a ball bearing.

Conventionally, ball bearings are often used as bearings for spindle motors. However, as spindle motors have become smaller, especially smaller outer diameters, the use of ball bearings with smaller outer diameters has reduced the bonding width, making it impossible to provide sufficient bonding grooves.
Although light press-fitting fastening is being adopted for miniaturized spindle motors, even if components are assembled with great care, they tend to be deformed during assembly due to the small ball bearings.

Due to the fact that the inner and outer races are liable to be deformed during the assembly of the motor, it is actually difficult to realize sufficient rotational accuracy, which makes it difficult to achieve a high capacity.

[0010] For this reason, bearings using hydrodynamic bearings instead of ball bearings have begun to be used. In a spindle motor using such a hydrodynamic bearing, adhesive fastening is often used for bearing fastening.

[0011] Compared to a spindle motor of a ball bearing specification, a spindle motor of a hydrodynamic bearing specification is far superior in impact resistance.

[0012] As a method of fastening the bearing portion, a method such as bonding or press fitting is employed. Spindle motors are also available in shaft rotation type and shaft fixed type. In the shaft fixed type, there are places where the fastening method is fluid besides the bearing. That point is the connection between the shaft and the housing. Although press-fitting is the mainstream, the width of press-fitting cannot be ensured due to thinning, and the bonding process is being studied actively.

In the fixed-shaft type, if the inclination of the shaft with respect to the housing is large, the line between the magnetic disk surface and the magnetic head is inclined, which hinders an increase in capacity. Fastening is required in a process in which the inclination is reduced, and it is necessary to determine an adhesive and bonding conditions.

Further, since there are many kinds of adhesives, a wide range of viscosity and a wide variety of adhesives, it is necessary to select an adhesive to be used for a fastening portion of a spindle motor for driving a magnetic disk in accordance with an application such as a bonding portion.

[0015]

If the shaft and the housing are not properly fastened, the parts of the spindle motor may be deformed during assembly, resulting in poor rotation accuracy, making it difficult to achieve a high capacity.

In recent years, in order to improve impact resistance, if the fastening strength between the shaft and the housing is low, the shaft may be damaged by an impact.

Further, in the type in which one end of the shaft is fastened to the upper lid with a screw, there is a problem that the shaft fastened to the housing comes off when the screw is tightened. Therefore, it is necessary to determine the adhesive and the bonding conditions at the time of design.

[0018]

When the shaft and the housing are fastened using an adhesive, the bonding conditions are set according to the properties of the adhesive, and the work of filling the adhesive in the bonding operation varies. Less.

For this purpose, (1) an adhesive groove is provided in the adhesive portion.

(2) The width of each of the adhesive reservoir grooves is a predetermined width. (3) The ratio of the sum of the adhesive groove width to the adhesive width is within a predetermined range.

(4) An adhesive gap is formed according to the viscosity of the adhesive. (5) The gap is not constant in the range of the bonding width, and a portion where the gap changes monotonously is provided in a part of the range so that the adhesive fills the bonding portion.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a housing body, a shaft fixed to the housing, and a rotor hub rotatable relative to the shaft via a bearing. Wherein the relationship between the viscosity of the adhesive and the adhesive gap is 3.3 logX-5.9 ≦ δ ≦ 9.0 logX-5.6. Here, X is the viscosity of the adhesive (cps, at 25 ° C.), δ is the magnetic disk drive spindle motor that becomes the adhesive gap (μm), and the rate at which the adhesive fills the gap increases.
In addition to increasing the bonding strength, the bonding strength is stable without variation in bonding strength. In addition, the calculation can be predicted in advance by combining with the calculated value of the adhesive strength. Also, since the bonding time is stable, the shaft runout after assembly work is small,
This has the effect of improving the reliability in assembling the spindle motor.

According to a second aspect of the present invention, there is provided a housing body, a shaft fixed to the housing, and a rotor hub rotatable relative to the shaft via a bearing. In fastening using an adhesive in the gap between the housing and the housing, two diameters, a small-diameter portion in which the diameter of the end surface of the shaft is reduced and a large-diameter portion opposite to the end surface in the range of the bonding width of the bonding portion. In the housing-side inner peripheral range corresponding to the shaft and the bonding portion of the shaft, the range corresponding to the small diameter portion of the shaft has a cylindrical shape, and the gap in the small diameter portion has the viscosity of the adhesive used. 3.3 log X-5.9 ≦ δ ≦ 9.0 log X-5.6 where X is the viscosity of the adhesive (cps, at 25 ° C.), δ is the adhesive gap (μm), and the shaft diameter is large. Corresponding to the housing The inner peripheral portion has a conical shape, and is a magnetic disk drive spindle motor which is a tapered adhesive gap such that the gap on the end face side of the housing is large. Accordingly, the gap becomes smaller. Since the adhesive enters the narrow adhesive gap due to the insertion resistance due to the wedge effect of the gap, the adhesive has an effect of improving the filling rate of the adhesive in the gap and increasing the adhesive strength.

According to a third aspect of the present invention, the inner peripheral portion of the housing corresponding to the large-diameter portion of the shaft has a conical shape, and is a tapered adhesive gap such that the gap on the end face side of the housing is increased. The average bonding gap between the minimum and the maximum of the bonding gaps is 3.3 log X−5.9 ≦ average bonding gap (μm) ≦ 9.
0 log X-5.6 where X is the viscosity of the adhesive (cps, at 25 ° C.), wherein the magnetic disk drive spindle motor according to claim 2, wherein the adhesive groove stably adheres the adhesive, The adhesive has the effect of filling gaps.

According to a fourth aspect of the present invention, there is provided the magnetic disk drive spindle motor according to the second aspect, wherein an adhesive groove is provided on an adhesive surface of the conical portion of the housing corresponding to the large shaft diameter portion. The adhesive groove stabilizes the adhesion of the adhesive and has the effect of filling the gap with the adhesive.

According to a fifth aspect of the present invention, there is provided a housing body, a shaft fixed to the housing, and a rotor hub rotatable relative to the shaft via a bearing. Fastened with an adhesive in the gap between the housing and the adhesive gap is 50 μm
In the following, a magnetic disk drive spindle motor having an adhesive groove width of 0.5 mm or less is provided, which has an effect of increasing the adhesive adhesion rate and increasing the adhesive strength.

According to a sixth aspect of the present invention, there is provided a housing body, a shaft fixed to the housing, and a rotor hub rotatable relative to the shaft via a bearing. Fastened with an adhesive in the gap between the housing and the adhesive gap is 50 μm
The magnetic disk drive spindle motor according to claim 4, wherein the total width of the adhesive groove is 40% or less of the adhesive width, and the filling rate of the adhesive into the adhesive gap is improved. This has the effect of improving the rate of adhesion to the bonding surface, increasing the bonding strength, and evenly filling the adhesive grooves with the adhesive and squeezing excess adhesive.

According to a seventh aspect of the present invention, there is provided a housing main body, a shaft fixed to the housing, and a rotor hub rotatable relative to the shaft via a bearing. Fastened with an adhesive in the gap between the housing and the adhesive gap is 50 μm
7. The method according to claim 4, wherein the number of adhesive grooves is two or more.
And has the effect of increasing the adhesion rate of the adhesive and increasing the adhesive strength.

[0029]

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

(Embodiment 1) FIG. 1 is a cross-sectional view of a spindle motor for driving a magnetic disk according to the present invention, FIG. 2 is a diagram showing the relationship between the adhesive adhesion ratio of an adhesive surface and relative adhesive strength, and FIG. FIG. 4 is a diagram showing the relationship between the viscosity of the adhesive and the bonding gap, FIG. 5 is a diagram showing the relationship between the bonding groove width and the relative bonding strength,
FIG. 6 is an explanatory model diagram of the bonding, FIG. 7 is a process explanatory diagram of applying the adhesive and inserting the shaft, FIG. 8 is a diagram showing the relationship between the total bonding groove width ratio and the adhesion ratio, and FIG. It is a relation diagram of an adhesion rate.

A magnetic disk (not shown) is attached to the rotor hub 1
The device for mounting the magnetic disk drive spindle motor, which is mounted and driven to rotate, has a hermetically sealed interior and extremely dislikes dust. The use of chemicals or the like that may damage the magnetic disk surface is restricted. Therefore, an adhesive that does not generate harmful outgas such as an adhesive used is used.

First, a magnetic disk drive spindle motor will be briefly described. The rotor hub 1 is rotatably supported by ball bearings 3 and 4 fixed to a shaft 2. The shaft 2 is provided with a screw portion 5, and the shaft 2 is adhesively fixed to a housing 6.

The housing 6 has an annular recess 6a having an upper opening.
Has an upwardly projecting cylindrical portion 6b on the inner peripheral side, and has a flange portion 6c on the outer peripheral side of the annular concave portion 6a. The housing can be formed integrally with the base of the magnetic disk drive, for example. Housing 6
The annular concave portion 6a is a magnetic disk mounting portion 1a of the rotor hub.
At the position where it escaped, and the hole 7
However, a transparent seal is attached to the outer peripheral portion of the hole 7 at the final time when the device is incorporated into the device, thereby sealing the device from the outside. Further, a thinned portion is provided in a part of the outer peripheral portion of the annular concave portion 6a of the housing 6, a flexible printed circuit board 8 is adhered thereto, and lead wires 9 such as coil terminals of a motor are soldered to the flexible printed circuit board 8. To conduct to the external drive circuit.

Since the rotor hub 1 is a magnetic material, the magnet 10 is directly adhered and fixed inside the rotor hub 1 to form a magnetic circuit. One end of the magnetic disk clamping screw portion 11 provided on the rotor hub is closed with an adhesive for fixing the magnet 10. A bearing holder 12 is interposed between the rotor hub 1 and the lower ball bearing 4.

The stator core 13 of the motor is bonded and fixed to the shaft 2, and the stator core 13 is
The outer periphery of the stator core 13 is coated with a rust preventive film 15 such as Nittor. A coil 16 is wound around a stator core 13 insulated by a powder coating film 14. The terminal of the coil 16 is conductively connected to a printed circuit board 17, and holes 18 a and 18 b formed in the shaft 2 through the lead wire 9 from the printed circuit board 17 through the housing 6.
And is connected to the flexible printed circuit board 8. The printed circuit board 17 is also provided with a hall element 19 for drive detection which is positioned at a rotational position, and the electric wires of these electronic components are passed through holes 18 a and 18 formed in the shaft 2.
b is led out of the housing 6 using a lead wire 9 and connected to the flexible printed circuit board 8.

Magnetic fluid seals 20 and 21 are provided near the ball bearings 3 and 4 so that dust and dust generated from the stator core 13 and the ball bearings 3 and 4 of the motor do not go outside.

Next, a method of assembling the magnetic disk drive spindle motor of this embodiment will be described.

(1) First, a stator assembly is manufactured as follows. A printed circuit board assembly in which the lead wire 9 is soldered and connected to a printed circuit board 17 on which electronic components are mounted is fixed to the shaft 2 with an ultraviolet curing adhesive.

The coil 16 is wound around the stator core 13 on which the powder coating film 14 and the rust-preventive film 15 are applied, and the coil terminal is set to a predetermined length in advance so as to be easily soldered to the printed circuit board 17. The tip of is soldered to make a coil assembly.

Next, the coil assembly is bonded and fixed to the shaft 2 to which the printed board assembly is fixed,
The preprocessed coil terminals are soldered to the printed circuit board 17 to form a stator assembly.

(2) Next, the magnet 10 magnetized on the rotor hub 1 is bonded and fixed, and further, the ball bearing 3 is bonded and fixed to form a hub assembly.

(3) Further, the ball bearing 4 is bonded and fixed to the bearing holder 12 to form a lower ball bearing assembly.

(4) Assemble the stator assembly, the hub assembly, and the lower ball bearing assembly. An adhesive is applied to the shaft 2 of the stator assembly at the inner ring portion of the ball bearing 4, and the lower ball bearing assembly is inserted and fixed. Next, an adhesive is applied to the outer peripheral portion of the bearing holder 12, and further the adhesive is applied to the shaft 2 of the inner ring portion of the ball bearing 3, and the hub assembly is inserted. Further, a preload is applied to the ball bearing 3 so that the ball bearing 3 is cured.

(5) The magnetic fluid seals 20, 21 are hardened and fixed near the ball bearings 3, 4 of the assembly assembled in the above (4) with an ultraviolet curing adhesive. Further, the washer 22 is fixed to the vicinity of the bearing 3 with an ultraviolet-curing adhesive to form a sub motor assembly.

(6) An adhesive is applied to the inner peripheral portion of the cylindrical portion 6b of the housing 6, and the shaft 2 of the sub motor assembly of (5) is inserted and fixed by bonding to form a spindle motor. .

The spindle motor is assembled as described above. When this spindle motor is incorporated into the device and used, the upper cover 23 of the device is screwed and fixed to the screw portion 5 opened at the tip of the shaft as shown by the broken line in FIG.

Since the magnetic disk drive tightened by the screw 24 is used within the operating temperature range, the components expand and contract within the temperature range, so that the upper lid 23 exerts a force to pull the shaft 2 out of the housing 6. Works. When the force to pull out is greater than the adhesive strength between the shaft 2 and the housing 6, the shaft 2 moves slightly. Since there is a possibility that the position of the magnetic disk and the magnetic head are displaced and the reliability of information is impaired, the bonding portion is so formed that the bonding strength between the shaft 2 and the housing 6 becomes larger than the force for removing the information. Need to design.

In general, the following calculation is made for the adhesive strength of a shaft and a housing as a calculation method. The bonding strength P is given by the following equation, where the bonding area S, the shear strength Q of the adhesive, and the environmental coefficient K are:

P = S × Q × K This K is a coefficient depending on the bonding state, the bonding operation, the surface condition of the material, and the like. If the shaft diameter is D and the bonding width is L, the area S of P = S × Q × K is given by the following equation.

S = π × D × L For example, D = 8 mm, L = 4.4 mm, K = 1, Q = 30
If it is 0 kgf / cm ² , the area S = 1.1 cm ^{2 and the} adhesive strength P = 330 kgf.

In an actual design, it is necessary to clearly grasp the design strength actually required.

Further, when the adhesive is completely present on the bonding surface, the bonding strength required by P = S × Q × K can be almost obtained. However, depending on the selection of the adhesive, due to the bonding work,
Adhesive unevenness occurs. In order to make the adhesive strength of the adhesive non-dimensional, it is represented by a relative adhesive strength where the adhesive strength in a state where there is no unevenness of the adhesive is set to 1. The state of the adhesive unevenness is represented by an adhesion rate (residual rate) of the adhesive adhering to the bonding surface. An adhesion rate of 1 indicates that 100% of the adhesive has adhered to the bonding surface.

FIG. 2 is a diagram showing the relationship between the relative adhesive strength and the adhesion rate of adhesives having different viscosities using a test piece having a shaft diameter of 10 mm and a hollow cylinder having an adhesive width of 5 mm.

As can be seen from FIG. 2, the relationship between the adhesion rate of the adhesive and the relative adhesive strength of the adhesives having different viscosities is on the same straight line and is almost directly proportional. In addition, the place where the adhesive residual ratio is small is a result obtained from a sample having a small gap, and the measured value is larger than the straight line due to the distortion of strength measurement.

Although the data in FIG. 2 vary, the measured values are close to the adhesion rate of 0.5, and data close to the adhesion rate of 1 were not obtained. It speculates that the adhesive surface did not cause the adhesive to squeeze sufficiently due to the cylinder.

FIG. 3 shows the relationship between the bonding gap in the adhesive and the relative bonding strength. The relationship in FIG. 3 is that the material of the housing 6 is aluminum material A5052, and the material of the shaft 2 is S
In the case of US420J2, it is represented by a white circle (○), and in the case of SUS416, it is represented by a black circle (●).

As can be seen from FIG. 3, as the bonding gap increases, the relative bonding strength increases proportionally. However, when the bonding gap exceeds a certain value, the relative bonding strength becomes 1. There is a phenomenon in which the relative adhesive strength becomes worse as the bonding gap is further increased, but such a phenomenon is not often seen when the bonding gap is 50 μm or less. However, if the bonding gap is too large, the shaft will be tilted and bonded to the housing, and the disk mounting surfaces of the housing and the rotor hub will also be tilted. Therefore, when the standard of the inclination of the disk mounting surface of the housing and the rotor hub in the case of the magnetic disks of 5 inches and 3.5 inches is applied to determine the allowable size limit of the size of the adhesive gap, as shown in FIG. , Relative adhesive strength is 1
However, there was a case where the shake was large, and the data was represented by (x). The range of the bond gap when the run-out is within the standard range and the relative bond strength is large is set as the optimum bond gap range.
This is shown in FIG.

In FIG. 3, only data having a large relative adhesive strength are displayed for the same adhesive and the same bonding gap, so that in the case of a cylindrical gap, the same adhesive and the same bonding gap are actually used. And the relative adhesive strength is smaller than that shown in FIG. That is, FIG. 3 shows the maximum value of the relative adhesive strength in the same adhesive gap, and the range in direct proportion is considered to be the effect of the adhesion rate.

When the viscosity increases, the relative adhesive strength is unlikely to reach an adhesion rate of 1. Therefore, a large amount of adhesive is applied so that the adhesion rate is possible, and the protruding adhesive is wiped off. When an agent is used, the bonding operation is stabilized by forming the bonding groove on the bonding surface.

The optimum bonding gap range obtained as shown in FIG. 3 exists regardless of whether the viscosity of the adhesive is large or small. When the optimum bonding gap range is determined by experiment using adhesives of each viscosity. Results such as 4 were obtained. Temperature 25
The viscosity of the adhesive at ℃ is 100cps to 30000cps
The adhesive up to was evaluated.

From FIG. 4, the lower and upper limits of the optimum bonding gap range corresponding to the viscosity at a temperature of 25 ° C. are indicated by straight lines, respectively, so as to match the viscosity of the adhesive used.
The optimum bonding gap can be known in advance. As compared with general bonding, bonding with a magnetic disk may cause outgassing, and the type is limited. In the case of a magnetic disk drive, the inclination of the shaft with respect to the housing is severe, which is different from a general clearance condition.

Therefore, in order to secure the adhesive strength, an optimum adhesive gap δ depending on the viscosity is required. The relationship is as follows.

3.3 × logX−5.9 ≦ δ ≦ 9.0 × logX−5.6 where X is the viscosity of the adhesive (cps, at 25 ° C.) δ is the adhesive gap (μm) FIG. The groove 25 is provided at one location on the inner diameter of the hollow cylindrical plate 27 (see FIG. 6), and the relationship between the adhesive groove width and the relative adhesive strength when the adhesive width is changed is shown. FIG. 6 is a model for the explanation, 25 is an adhesive groove, 26 is a shaft, 27 is a hollow cylindrical plate, 28 is an adhesive, L is an adhesive width, D is a shaft diameter, and δ is an adhesive gap. . Although the entrance of the hole of the hollow cylindrical plate 27 is chamfered, the chamfered portion is not included in the bonding width because it is large with respect to the bonding gap.

As shown in FIG. 5, when the width of the bonding groove is increased, the adhesion ratio is deteriorated, and the relative bonding strength is reduced. There is a limit that the width of the bonding groove cannot be increased. The limit is shown by the following equation.

Adhesion groove width ≦ 0.5 mm The mechanism of the decrease in the adhesion rate will be described. FIG. 7 is a diagram illustrating a process of applying an adhesive and inserting a shaft.

The adhesive is applied to the shaft insertion side of the inner surface of the cylindrical portion (FIG. 7A). When the shaft is inserted, the adhesive applied to a diameter smaller than the diameter of the shaft is applied to the shaft. As a result of the influence of the end face, the adhesive in the gap is wrung out and fills the gap between the shaft and the housing, and the adhesive adheres to the adhesive groove in the adhesive groove due to the surface tension together with the adhesive on the end face of the shaft (FIG. 7 ( b)). However, if the width of the bonding groove is large, the adhesive is divided and adheres to a part of the bonding groove and the end face of the shaft (FIG. 7C). When the shaft is further inserted, the adhesive on the end face of the shaft comes to be present in a range larger than the outer diameter of the shaft due to the surface tension, and the adhesive comes into contact with the adhesive groove, and a part of the adhesive groove is formed. Adheres,
The adhesive enters the adhesive gap with insertion, and the adhesive starts to fill the adhesive gap (FIG. 7D).

If the width of the adhesive groove is large by such a mechanism, the adhesive is not filled in the adhesive groove, so that the adhesion rate is reduced.

In the case of a thin spindle motor, it may not be possible to form several adhesive grooves. If the total ratio of the adhesive groove width to the adhesive width (hereinafter referred to as the total adhesive groove width ratio) is large, the strength may be reduced, and the range was examined. Since the bonding width is specified and the bonding groove width is changed to change the total bonding groove width ratio, the fact that the total bonding groove width ratio is large means that the bonding groove width is large. FIG. 8 shows the relationship between the total adhesive groove width ratio and the adhesion rate in the case of one adhesive groove,
As the overall bonding groove width ratio increases, the adhesion rate decreases. In addition, the fact that the overall bonding groove width ratio is small means that the bonding groove width is small. If the bonding groove width is too small, the state becomes close to a state without grooves, and conversely, the adhesion rate decreases. As can be seen, there is an optimal overall bonding groove ratio that maximizes the adhesion rate in relation to the overall bonding groove width ratio.

FIG. 9 shows the relationship between the total bonding groove width ratio and the adhesion ratio in the case of three bonding grooves. FIG. 9 shows a tendency similar to that of FIG. 8. As the total bonding groove ratio increases, the adhesion rate decreases. Further, when the total bonding groove width ratio is close to 0, the state is close to a state without grooves, and conversely, the adhesion rate decreases. Therefore,
Even in the case of three adhesive grooves, there is an optimal overall adhesive groove width ratio that maximizes the adhesion rate in relation to the overall adhesive groove width ratio.

The same tendency was obtained when the number of the adhesive grooves was 6 or less. There is no evaluation of Article 6 or higher, but it is thought that the same result as Article 6 or lower is obtained.

Therefore, in order to secure the bonding strength, the total bonding groove width ratio needs to have the following relationship.

Total adhesive groove width ratio ≦ 0.4 When there are several adhesive grooves, the adhesion rate becomes large as a whole and 3
When the number is more than the number, the adhesion rate often becomes 1. Therefore, it is more suitable to calculate the environmental coefficient K in the following equation as 1.

3.3 log X−5.9 ≦ δ ≦ 9.0 log X−5.6 where X is the viscosity of the adhesive (cps, at 25 ° C.) δ is the adhesive gap (μm) Incorporation in the bonding portion increases the bonding strength, reduces variation, and provides stable bonding strength.

(Embodiment 2) FIG. 10 is a sectional view of a spindle motor for driving a magnetic disk of the present invention, and FIG. 11 is a detailed sectional view of a bonding portion.

The spindle motor of FIG. 10 is a spindle motor for driving a magnetic disk of a fluid bearing type, and the spindle motor of the first embodiment is of a ball bearing type.

The spindle motor according to the second embodiment will be described below. The cylindrical housing 31 has a cylindrical portion 31 at the center.
a, a flange portion 31b at an outer peripheral portion, a convex cylindrical portion 31c at a position facing the rotor hub 32, and a cylindrical portion 31d at an outer peripheral position facing the rotor hub 32;
By forming the rotor hub 32 between c and 31d, a narrow gap is provided to obtain a labyrinth effect. Further, the inner peripheral surface of the cylindrical portion 31a of the housing 31 has an adhesive groove width ≦
Three adhesive grooves satisfying 0.5 mm are provided, and the adhesive groove satisfies the relationship of overall adhesive groove width ratio ≦ 0.4.

The lower portion of the shaft 33 is fixed by bonding. A screw hole 34 is provided in the upper end surface of the shaft 33. When this spindle motor is incorporated in the apparatus and used, the upper cover 35 indicated by a broken line is fastened and fixed to a screw hole 34 formed in the shaft with a screw 36.

The rotor hub 32 made of a stainless steel material has a bottomed double cylindrical shape, the outer cylindrical portion 32b forms a magnetic disk mounting cylindrical portion, and the outer cylindrical portion 32b has a flange portion 32c serving as a disk mounting surface. . The outer peripheral cylindrical portion further has a hanging portion 32d, and the hanging portion 32d is sandwiched between the cylindrical portions 31c and 31d of the housing with a narrow gap. As shown in FIG. 10, a labyrinth effect is provided by narrowing a gap between the housing 31 and the vicinity of the hanging portion 32d of the rotor hub 32. Also, a labyrinth effect is obtained in the gap between the magnet end face and the housing 31.

A cylindrical bush 38 for mounting the stator core 37 is fixed to the outer periphery of the inner cylindrical portion 31a of the housing 31. A coil 39 is attached to the insulated stator core 37.
Is wound and fixed to the thin cylindrical bush 38,
A terminal wire (also referred to as a lead wire) of the coil 39 is drawn downward through a lead hole 40 penetrating the bottom surface of the housing 31 and is connected to an external flexible printed board 41 by soldering. Stator core 37 by energization
In order to reduce the influence of the torsional resonance of the cylindrical bush 38, the cylindrical bush 38 is formed to be thin.

A large-diameter flange 42 is formed on the upper portion of the shaft 33 adhered and fixed to the housing 31, and a spiral groove is formed on either the flange 42 or the end surface 32a of the rotor hub 32, and fluid flows into the gap. A filled thrust dynamic pressure bearing is configured. A thrust holding plate 43 is fitted inside the rotor hub 32 on the upper surface side of the flange 42 and is adhered to the rotor hub 32 with an adhesive so as not to move. The thrust holding plate 43
Fluid is also filled in the gap between the upper surface of the flange 42 and the upper surface of the flange 42 to constitute a thrust dynamic pressure bearing that generates dynamic pressure of a spiral groove formed on the upper surface of the flange 42. The flange 42 is connected to the rotor hub 32 and the thrust holding plate 43.
, The vertical movement of the rotor hub 32 relative to the shaft 33 is restricted.

The inner peripheral cylindrical portion 32e of the rotor hub 32 is provided with a herringbone groove for generating a dynamic pressure, and a gap between the herringbone groove and the radial receiving portion of the shaft 33 is filled with a fluid. A radial dynamic pressure bearing is configured so that the rotor hub 32 can rotate in a non-contact manner by dynamic pressure generated in the groove.

The inner peripheral cylindrical portion 32 of the rotor hub 32 shown in FIG.
e, a first space 44 is formed on the open end side of the lower part of the herringbone groove, the diameter of which is suddenly enlarged to be reduced as it extends downward in the figure, and is increased when it is further extended downward. As a result, a second space 45 asymptotically reduced in diameter is formed. The maximum gap between the first and second spaces is set to be at least four times the gap where the radial dynamic pressure is generated. When the rotor hub 32 rotates, the fluid adhering to the first space 44 and the second space 45 moves on the inclined portion of the space by centrifugal force, and the oil film is cut between the first space 44 and the second space 45, The surface of the broken oil film has a different property from the wet surface, the contact angle of the surface tension increases, and the scattering of the fluid is prevented.

A spiral groove is formed in the upper and lower annular surfaces of the flange 42 of the shaft 33 so as to be folded at the center position, and is a groove similar to a herringbone shape. Since the spiral groove is formed on the upper and lower surfaces of the flange 42 of the shaft 33, the dynamic pressure during rotation causes the rotor hub 3 to rotate.
2. The thrust holding plate 43 rotates in a non-contact manner with a small gap with respect to the flange 42. An annular groove 46 is formed in the inner peripheral portion of the thrust holding plate 43 facing the shaft 33, and a gap formed between the shaft 33 and the annular groove 46 is formed with a labyrinth so that the lubricating fluid does not scatter. I have. It is also possible to obtain a further labyrinth effect by performing an oil repellent treatment or applying an oil repellent. In addition, the corner of the inner peripheral portion of the thrust holding plate 43 is chamfered positively, and a gap in the chamfered portion is filled with a lubricating fluid to prevent a surplus fluid from leaking outside the spindle motor. Has an effect. Further, there is a gap formed between the outer peripheral surface of the flange 42 of the shaft 33 and the thrust holding plate 43, and this gap is formed for the purpose of buffering fluid movement when an impact acts on the rotor hub 32, and is a relatively large gap. It has become. The gap also has a function of retaining oil in the fluid, thereby improving the reliability of the spindle motor.

The shaft 33 is adhered and fixed to the housing 31. There are three adhesive grooves 47 on the inner periphery of the inner cylindrical portion 31a of the housing 31, the adhesion rate is almost 1, and the adhesive strength is almost equal to the value obtained by calculation. However, when the adhesive is applied in one place, uneven application of the adhesive occurs, so the application is performed in two places.

[0086] Depending on the contents of the work steps, the adhesive strength tends to fluctuate because the adhesion rate fluctuates greatly. for that reason,
As another embodiment of the bonding portion shape, as shown in FIG.
The shaft 50 is located within the range of the bonding width of the bonding portion.
0 has a small diameter portion 51 with a small diameter on the end face side and a large diameter portion 52 on the opposite side to the end face side. In the inner peripheral region on the housing 53 side corresponding to the bonding portion of the shaft 50, a region corresponding to the small diameter portion 51 of the shaft 50 includes a cylindrical portion 54 having a cylindrical shape. The inner peripheral portion of the housing 53 corresponding to the large shaft diameter portion 52 has a conical portion 55 having a conical shape. The conical portion 55 is a tapered adhesive gap such that the gap on the end face side of the housing 53 is increased, and an adhesive groove 56 is provided on the adhesive surface.
The bonding groove 56 is not a rectangle but an arc-shaped semicircle.

The conical shape of the conical portion 55
As a result of evaluating whether there was a decrease in the adhesive strength, no decrease was observed when the adhesive gap was 50 μm. In addition, since the gap is conical, a minimum gap and a maximum gap are formed, and an average gap between the minimum gap and the maximum gap is defined as a cone average bonding gap. The adhesion rate changes depending on the viscosity of the resin.

The relationship between the cone average adhesive gap δm of the conical portion 55 and the viscosity of the adhesive used is 3.3 log X−5.9 ≦ δm ≦ 9.0 log X−5.6, where X is the viscosity of the adhesive ( (cps, at 25 ° C.) δm is the average conical adhesive gap (μm), which is a relationship in which the gap of the cylindrical portion is replaced with the average conical adhesive gap.

In the small diameter portion of the shaft, the relationship between the adhesive gap δ of the cylindrical portion and the viscosity of the adhesive used is 3.3 log X−5.9 ≦ δ ≦ 9.0 log X, as in the first embodiment. −5.6 where X is the viscosity of the adhesive (cps, at 25 ° C.) and δ is the adhesive gap (μm).

The bonding gap has a cylindrical shape and a conical shape,
By inserting the shaft 50 from the side with the larger gap, the tapered portion of the cone serves as an insertion guide, and the insertion can be performed smoothly without any twisting at the time of insertion. Further, by inserting the shaft 50, the adhesive in the gap between the conical portions 55 is filled into the cylindrical portion 54 by being wedged by the wedge effect. Therefore, the adhesive is easily filled in the adhesive gap of the cylindrical portion 54, the adhesion rate is improved, and the adhesive strength is stabilized.

[0090]

As is clear from the description of the above embodiment,
According to the first aspect of the present invention, by setting the adhesive gap in accordance with the viscosity of the adhesive used, the adhesion rate is improved, the adhesive strength is increased, the dispersion is small, and the strength is stable. Is obtained.

According to the second to fourth aspects of the present invention as well, the gap is large at the time of insertion and the gap is reduced as the insertion is made, so that the adhesive is bonded by the wedge effect of the gap. Since the agent enters the narrow adhesive gap due to the insertion resistance, the filling rate of the adhesive in the gap is improved, and the adhesive strength is increased.

Further, according to the fifth to seventh aspects of the present invention, the adhesion rate is improved, the adhesive strength is increased, the dispersion is small, and a stable strength is obtained.

Therefore, the adhesive strength of the small and thin magnetic disk drive spindle motor of the hydrodynamic bearing specification is increased, and the effect of improving the impact resistance is exhibited.

[Brief description of the drawings]

FIG. 1 is a sectional view of a spindle motor for driving a magnetic disk according to a first embodiment of the present invention;

FIG. 2 is a diagram showing a relationship between an adhesive adhesion rate of an adhesive surface and a relative adhesive strength.

FIG. 3 is a diagram showing a relationship between an adhesive gap and a relative adhesive strength.

FIG. 4 is a diagram showing the relationship between the viscosity of the adhesive and the adhesive gap.

FIG. 5 is a diagram showing a relationship between an adhesive groove width and a relative adhesive strength.

FIG. 6 is an explanatory model diagram of bonding.

FIG. 7 is an explanatory view of a process of applying an adhesive and inserting a shaft.

FIG. 8 is a diagram showing the relationship between the total adhesive groove width ratio and the adhesion ratio.

FIG. 9 is a diagram showing the relationship between the total adhesive groove width ratio and the adhesion ratio.

FIG. 10 is a sectional view of a magnetic disk drive spindle motor of the present invention.

FIG. 11 is a cross-sectional view of a bonding portion.

[Explanation of symbols]

 1, 32 Rotor hub 2, 26, 33, 50 Shaft 6, 31, 53 Housing 25, 47, 56 Adhesion groove 27 Cylindrical plate 28 Adhesive 51 Small diameter part 52 Large diameter part 54 Cylindrical part 55 Conical part

Claims (7)

[Claims] 1. A housing body, a shaft fixed to the housing, and a rotor hub rotatable relative to the shaft via a bearing, wherein an adhesive is provided in a gap between the shaft and the housing. , And the viscosity of the adhesive and the bonding gap (the gap of the bonding gap is a half of the difference between the housing diameter and the shaft diameter).
3.3 log X-5.9 ≦ δ ≦ 9.0 log X-5.6 where X is the viscosity of the adhesive (cps, at 25 ° C.), and δ is the adhesive gap (μm). 2. A housing body, a shaft fixed to the housing, and a rotor hub rotatable relative to the shaft via a bearing, wherein an adhesive is provided in a gap between the shaft and the housing. In the fastening using the shaft, the shaft having two diameters of a small diameter portion in which the diameter of the end surface side of the shaft is reduced and a large diameter portion opposite to the end surface side in the range of the adhesion width of the adhesion portion, In the inner peripheral area on the housing side corresponding to the adhesive portion of the shaft, the area corresponding to the small diameter portion of the shaft has a cylindrical shape, and the gap in the small diameter portion has the following relationship with the viscosity of the adhesive used. 3logX-5.9 ≦ δ ≦ 9.0logX-5.6 where X is the viscosity of the adhesive (cps, at 25 ° C.), δ is the adhesive clearance (μm), and the inner circumference of the housing corresponding to the large part of the shaft diameter. The part has a conical shape, A magnetic disk drive spindle motor having a tapered adhesive gap such that the gap on the end face side of the housing is increased. 3. An inner peripheral portion of the housing corresponding to the large diameter portion of the shaft has a conical shape, and is a tapered adhesive gap such that a gap on the end face side of the housing is increased. Is 3.3 logX-5.9 ≦ average bonding gap (μm) ≦ 9.
3. The magnetic disk drive spindle motor according to claim 2, wherein X is the viscosity of the adhesive (cps, at 25 ° C.). 4. A housing body, a shaft fixed to the housing, and a rotor hub rotatable relative to the shaft via a bearing, wherein a gap is provided between the shaft and the housing. In the case of using the joint, the diameter of the shaft in the range of the bonding width of the bonding portion is reduced to a smaller diameter portion on the end face side and a larger diameter portion on the opposite side to the end face side.
The inner peripheral portion of the housing corresponding to the bonding portion of the shaft is a cylindrical portion, the portion corresponding to the small shaft diameter portion is a cylindrical portion, and the inner peripheral portion of the housing corresponding to the large shaft diameter portion is 3. The spindle motor for driving a magnetic disk according to claim 2, wherein an adhesive groove is provided on an adhesive surface with a tapered adhesive gap having a conical shape so that a gap on an end face side of the housing is increased. 5. A housing body, a shaft fixed to the housing, and a rotor hub rotatable relative to the shaft via a bearing, wherein a gap is provided between the shaft and the housing. A magnetic disk drive spindle motor having an adhesive gap of 50 μm or less and an adhesive groove width of 0.5 mm or less. 6. A housing body, a shaft fixed to the housing, and a rotor hub rotatable relative to the shaft via a bearing, wherein an adhesive is provided in a gap between the shaft and the housing. 6. The magnet according to claim 4, wherein the bonding gap is 50 μm or less, and the total width of the bonding groove is such that the total bonding groove width / the bonding width ≦ 0.4 with respect to the bonding width. Spindle motor for disk drive. 7. A housing body, a shaft fixed to the housing, and a rotor hub rotatable relative to the shaft via a bearing, wherein an adhesive is provided in a gap between the shaft and the housing. 7. The magnetic disk drive spindle motor according to claim 4, wherein the adhesive gap is 50 μm or less, and the number of adhesive grooves is two or more.