JP3818064B2 - Spindle motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spindle motor for driving a recording medium such as a magnetic disk or a hard disk.
[0002]
[Prior art]
The recording density of HDDs (hard disk drive devices) has doubled in recent years, and the number of tracks per inch (TPI) is 25000 TPI with current notebook computers. In the future, a higher density is required, and it is necessary to further increase the recording density on a limited size disk. By the way, TPI is an index for increasing the recording density. In the current mainstream ball bearings, the rolling element and the inner ring or the outer ring rotate while being in point contact with each other. A shake “NRRO” (asynchronous shake, hereinafter referred to as NRRO) from a perfect circle occurs, and the limit of TPI is beginning to be seen.
[0003]
When this NRRO is large, deviation occurs from the track width of the disk (off-track), and a phenomenon such as generation of noise in the signal or inability to read data occurs.
[0004]
NRRO must be suppressed to 1/10 or less of the track width. For example, at a track width of 30000 TPI, it is 0.8 μm, and therefore, NRRO needs to be 0.08 μm or less. If a fluid bearing is used, the NRRO can be suppressed to 0.04 or less, but a ball bearing cannot be used at about 0.08 μm. Therefore, fluid bearings have attracted attention in place of ball bearings, and the development competition of HDD motors using these fluid bearings has been spurred.
[0005]
On the other hand, along with the miniaturization of devices, HDDs (hard disk drive devices) as means for recording information are further miniaturized and thinned. And the rotational drive part which is the heart part of this type of device has both a bearing and a motor part built in the drive hub, and by attaching a plurality of recording / reproducing disks on the outer periphery of the drive hub, The miniaturization of the device and the increase of the storage capacity are attempted. Further, in order to increase the recording density, it is necessary to dramatically improve the accuracy of the rotating main shaft portion.
[0006]
Here, this type of spindle motor having a hydrodynamic bearing structure will be described with reference to FIG.
[0007]
As shown in FIG. 4, a fixed shaft 1 is fixed on a disc-shaped base 2, and a core 4 around which a winding 3 is wound is fixed on an upper surface. On the outer peripheral surface of the fixed shaft 1, radial direction dynamic pressure generating grooves (herringbone grooves) 1a and 1b are formed, which are spaced apart in the axial direction. Reference numeral 5 denotes a hub assembly including a hub 6 which is a disc fixing portion made of aluminum and a bronze sleeve 7 which is press-fitted into the inside thereof by shrink fitting or the like, and the sleeve 7 is inserted into the fixed shaft 1. As a result, the hub assembly 5 is rotatable about the fixed shaft 1.
[0008]
The sleeve 7 is formed with an oil sump 7a serving as a recess on a surface corresponding to the distance between the radial direction dynamic pressure generating grooves 1a and 1b. The radial direction dynamic pressure generating grooves 1 a and 1 b may be formed in at least one of the fixed shaft 1 and the sleeve 7. In addition, 8 is a screw which fixes the printed circuit board 9 with which the drive circuit components etc. which are arrange | positioned on the base 2 are mounted.
[0009]
A plurality of aluminum disks 10, 10 are attached to the outer periphery of the hub 6 via spacers 11, and these disks 10, 10 are fixed to the hub 6 with screws 13 via fixing plates 12. The yoke 14 fixed to the lower portion of the hub 6 is disposed at a predetermined interval so as to be surrounded by an annular recess 2a formed in the base 2, while the yoke 14 is disposed on the inner surface of the yoke 14 with a predetermined distance from the core 4. A magnetic circuit is formed by fixing the magnet 15 with the interval of.
[0010]
Further, a disk-like flange 16 bulging from the shaft diameter is fixed to the upper end portion of the fixed shaft 1 by means such as screws or press fitting, so that a notch formed in the outer peripheral surface of the flange 16 and the hub 6 is formed. An upper oil sump space 17 is formed between 6a and 6a (the portion a is shown enlarged in FIG. 5).
[0011]
Then, a thrust plate 18 serving as a mounting body is disposed on the flange 16, and the shaft portion is sealed by fixing the thrust plate 18 to the hub 6 with screws 19. The bearing portion configured as described above includes a thrust direction dynamic pressure generating groove 18a such as a pumping groove or a herringbone groove formed on the lower surface of the thrust plate 18, the upper oil reservoir space 17, and the above-described radial direction dynamic pressure generation. By lubricating and applying a lubricant 20 such as oil or grease to the grooves 1a, 1b, etc., the bearing portion can be lubricated.
[0012]
As shown in FIG. 5, when the gap between the upper oil reservoir spaces 17 is small, the filled lubricant 20 rises up to the thrust plate 18 due to capillary action and scatters to the outside, leading to a decrease in the lubricant. On the other hand, if the gap between the upper oil reservoir spaces 17 is too wide as shown in FIG. 6, the contact area between the lubricant 20 and air becomes large, and the lubricant is reduced in the same manner as described above due to evaporation of the lubricant.
[0013]
In this assembled state, the magnet 15 and the yoke 14 are located above the magnetic center of the core 4 which is a magnetic body. Therefore, the hub assembly 5 is always subjected to an attractive force (Pz) to act as the base 2. Drawn to the side.
[0014]
The spindle motor configured as described above generates a magnetic field when the winding 3 is energized, and the hub assembly 5 is rotationally driven in a predetermined direction together with the magnet 15. During this driving, the sleeve 7 is centered with respect to the fixed shaft 1 by the pumping force of the radial direction dynamic pressure generating grooves 1a and 1b, and the axial direction is determined by the thrust direction dynamic pressure generating groove 18a of the thrust plate 18. The thrust plate 18 and the hub assembly 5 float several μm from the flange 16 integral with the shaft, and the hub assembly 5 rotates without contact with the fixed shaft 1 and the flange 16 via the lubricant 20. A magnetic head (not shown) scans the disk 10 relatively in the radial direction to read / write information.
[0015]
By the way, the present situation is that the demand for high precision and high reliability is becoming increasingly strong for spindle motors used in information equipment such as HDDs (hard disk drive devices). As described above, when the flange 16 (for example, the thickness is 1.2 mm) for generating the dynamic pressure for supporting the rotational drive unit is attached to the fixed shaft 1, the shaft end is fixed by the screw 21 as shown in FIG. In the case of fixing on the side, the foreign matter 22 is sandwiched between the shaft end portion and the lower surface of the flange 16, or the perpendicularity between the fixed shaft 1 and the flange 16 cannot be maintained due to burrs at the shaft end portion. This is the cause of the decline in function.
[0016]
In addition, when the flange 16 is fixed to the fixed shaft 1 by press-fitting as shown in FIG. Since the stress to be applied is small and non-uniform as it goes to the shaft end where the press-fitting surface is reduced due to chamfering or the like, the flange 16 is bent in the F direction, and the flatness of the thrust bearing portion deteriorates. In addition, the reliability of the hydrodynamic bearing is reduced.
[0017]
Therefore, the applicant of the present invention has a base having a core around which a fixed shaft and a coil are wound, a rotatable hub that is fitted to the fixed shaft via a lubricant, and either the fixed shaft or the hub. And a dynamic pressure generating groove formed on one of the flange and the thrust plate sealing the flange. A spindle which solves such a problem by forming an annular recess on the press-fitting surface of either the fixed shaft or the disc-shaped flange press-fitted into the fixed shaft at a vertical position corresponding to the thickness of the flange. I have applied for a motor. (JP-A-8-322193)
[0018]
The spindle motor according to the contents will be described below with reference to FIGS. FIG. 9 is a half sectional view of the spindle motor. The same components as those in the prior art are denoted by the same reference numerals, and detailed description of the overlapping portions is omitted. Only the changed portions will be described below.
[0019]
As shown in FIG. 9, the fixed shaft 1 is made of stainless steel (SUS303), and the sleeve 7 is made of bronze. The coefficient of thermal expansion of both is substantially the same (17 × 10 ⁻⁶ / ° C.). On the outer peripheral surface of the sleeve 7 opposite to the inner surface of the fixed shaft 1 side, for example, corresponding to the hub 6 made of aluminum, a thickness (W2) equal to or sufficiently larger than the thickness (W1) of the sleeve 7 is provided. reinforcing sleeve ₇₁ with is fixed. The reinforcing sleeve ₇₁ is small stomach than the thermal expansion coefficient of the stationary shaft 1 and the sleeve 7, for example, stainless steel thermal expansion coefficient is ^{10 × 10 -6 / ° C (} SUS430) or the like is used, the hub 6 It is fixed in the notch recess 6b by a fixing means such as press fitting.
[0020]
Furthermore, the sleeve 7 the reinforcing sleeve 7 _1, for example, which is secured by shrink fitting, by the sleeve portion is constituted by a sleeve 7 and the reinforcement sleeve _71, the fixed shaft 1 The substantial thermal expansion coefficient of the sleeve portion is set to be lower than the thermal expansion coefficient. For this reason, the influence of the change of the clearance gap by the heat | fever of a dynamic pressure generation part is made small.
[0021]
For example, as a method for fixing the flange 16 having a thickness of 1.2 mm to the fixed shaft 1 having a shaft diameter of 3 mm, a press-fitting method is employed. That is, as shown in FIG. 10, annular recesses 23 a and 23 b are formed at the upper and lower surface positions on the inner peripheral portion 16 a that is the press-fitting surface of the flange 16. The depths t of the annular recesses 23a and 23b are uniform, 0.1 mm in this embodiment, and the diameter is about 0.03 mm larger than the diameter of the inner peripheral portion 16a.
[0022]
Therefore, when the flange 16 is press-fitted into the fixed shaft 1, the stress (surface pressure) generated in the inner peripheral portion 16a with respect to the geometric center l of the flange 16 is symmetrical (position L1 = L2 vertically symmetrical with respect to the center l). And uniform, and the perpendicularity and flatness of the flange 16 with respect to the fixed axis 1 can be kept good.
[0023]
11 shows a mode opposite to the mode shown in FIG. 10, and the geometric center l thereof corresponds to the inner peripheral portion 16 a that becomes the press-fitting surface of the flange 16 on the fixed shaft 1 side. On the other hand, annular recesses 24a and 24b are respectively formed at upper and lower positions. Therefore, as in the above embodiment, the stress (surface pressure) generated on the press-fit surface is symmetric and uniform, and the perpendicularity and flatness of the flange 16 with respect to the fixed shaft 1 are improved. Therefore, in both embodiments, the reliability of the hydrodynamic bearing is improved, and a small and highly accurate and highly reliable motor with little vibration can be obtained.
[0024]
By the way, according to the technique described in JP-A-8-322193, the assembly of the shaft 1 to the flange 16 is performed by press-fitting, for example. When the both are assembled by this press-fitting, as shown in FIG. 8 and described later, the inner peripheral portion 16a and the shaft end 1d of the flange 16 are inserted so that the assembly is performed smoothly. Chamfering is required as a guide for this.
[0025]
[Problems to be solved by the invention]
However, as a result of studying this chamfering, the applicant of the present application cannot simply be chamfered. As described later, the chamfering at the tip 1d of the shaft 1 and the inner peripheral part 16a of the flange 16 is large. And the positional relationship between the two after the assembly and not only that both are assembled, it is necessary to be assembled with a predetermined assembly force, each proved to be important . The present invention has been made on the basis of such knowledge, and this will be described below.
[0026]
Here, before entering the description of chamfering, the general relationship between the shaft and the hole during shrink fitting (the relationship between the interference and the assembly force) will be described with reference to FIGS. Keep it. The fastening allowance refers to the difference (D−d) between the diameter (D) of the shaft 1 and the hole diameter (d) of the inner peripheral portion 16a of the flange 16, and the assembling force refers to assembling both. After that, the force which pulls out the flange 16 shall be said. As a matter of course, since the assembly is performed by shrink fitting, by heating the hole diameter (d) of the inner peripheral portion 16a of the flange 16, the hole diameter (d) is expanded and the both are coupled. However, this is the premise. In the description of FIGS. 12 and 13, the chamfered portion is omitted for convenience.
[0027]
FIG. 12 (A) shows the state before shrink fitting, and is an explanatory diagram when the interference is small, that is, when the difference (D−d) between the two is small. As a matter of course, in this case, The range in which the hole diameter (d) of the inner peripheral portion 16a of the flange 16 is expanded is reduced. Accordingly, as in FIG. (B), assembled force G ₁ after shrink fit (assembly) is small. In FIG. 12A, since the range in which the hole diameter (d) is expanded is reduced, the force H _{1 for} trying to warp the flange 16 is small, so that the flange 16 is not easily warped. That is, as described later, although the required assembling force cannot be obtained, the contradictory result that the flatness of the flange 16 is easily obtained is obtained.
[0028]
On the other hand, FIG. 13A shows the state before shrink fitting, and is an explanatory diagram when the interference is large, that is, when the difference (D−d) between the two is large. In this case, the range in which the hole diameter (d) of the inner peripheral portion 16a of the flange 16 is expanded is increased. Therefore, as shown in FIG. 5B, the assembling force G ₂ after shrink fitting (assembling) is large. In FIG. 13A, since the range in which the above-described hole diameter (d) is expanded is increased, the force H ₂ for bending the flange 16 is increased as shown in FIG. 13B. The flange 16 is easily warped. That is, although the required assembling force described later is obtained, the contradictory result is obtained that the flatness of the flange 16 is difficult to obtain.
[0029]
As described above, for spindle motors for HDDs, the use of fluid bearings is becoming mainstream due to the NRRO relationship. However, due to the reduction in NRRO, precise rotation accuracy as a spindle motor has been increased. It has been demanded. Therefore, it is necessary to finish the flatness, surface roughness, groove depth, etc. with high precision as the thrust plate constituting the thrust bearing. Therefore, the flange 16 in contact with the thrust plate also needs to be finished to a predetermined flatness, and is generally desired to be finished to 1 μm or less.
[0030]
Also, the assembly force is required to be 1000 N or more based on the results of various experiments and data of this type of HDD spindle motor currently supplied to the market. The reason for this is that if it is less than this, a deviation occurs at the time of start and stop due to a change with time or the like.
[0031]
Furthermore, if the tightening margin is too large or too small as described above, there is a contradictory result due to the relationship between the force for bending the flange and the assembling force. Therefore, as a result of examining the relationship between the above-described assembly force and various experimental results and data of this type of HDD spindle motor currently being supplied to the market, it is said that about 0.03 mm is necessary. I understood that.
[0032]
That is, the assembly force of this type of HDD spindle motor needs to be 1000 N or more, the tightening margin needs to be about 0.03 mm, and the flatness of the flange needs to be finished to 1 μm or less. There is something.
[0033]
Next, the relationship between the size of the chamfer and the position after assembly is important. If this point is neglected, the reason why the flange 16 is deformed (warped) after shrink fitting (assembly). Will be described with reference to FIG. FIG. 14 is a side view showing a state in which the shaft 1 and the flange 16 are assembled by shrink fitting, for example. In addition, the same code | symbol is used for the same part as the past, and the detailed description is abbreviate | omitted.
[0034]
In FIG. 14, 1 c is a chamfered portion formed annularly at, for example, the upper portion of the tip portion 1 d of the shaft 1, 16 b and 16 c are chamfered portions formed annularly on the inner peripheral portion 16 a of the flange 16, and 16 d is a flange Since the upper surface portion 16d is in contact with the thrust direction dynamic pressure generating groove 18a such as the herringbone groove constituting the thrust bearing as described above, surface accuracy (flatness). Need to be out.
[0035]
In the state of FIG. 14, it can be seen from the flange 16 side that there is a portion that is not in contact with the flange 16 and the shaft 1. That is, in the inner peripheral portion 16a of the flange 16, the chamfered portion 16b continuous with the inner peripheral portion 16a, and the chamfered portion 1c provided on the distal end portion 1d side of the shaft 1, the shaft 1 is viewed from the flange 16 side. It can be seen that a triangular zone (Δ) that is not in contact with is formed.
[0036]
As described above, when there is a portion (triangular zone Δ) that is not in contact with the shaft 1 when viewed from the flange 16 side, the upper surface 16d of the flange 16 warps upward during assembly, as indicated by an arrow. The squeezing force I ₁ is generated and the balance is lost. That is, the flange 16 is deformed. Therefore, the deformation of the flange 16 adversely affects the thrust bearing that is in contact with the flange 16, and consequently, the performance of the spindle motor itself is deteriorated. As can be understood from this fact, it can be understood that depending on the size of the chamfer, the above-described adverse effect, that is, simply chamfering is not sufficient. Therefore, the size of the chamfered portion 1c formed on the tip 1d side of the shaft 1 and the chamfered portion 16b formed on the inner peripheral portion 16a of the flange 16 must be within a predetermined range as will be described later. Can understand.
[0037]
Next, a method for obtaining a predetermined assembling force (surface roughness and assembling force of the inner peripheral portion 16a of the flange 16) will be described with reference to FIGS. 15 is a side view showing a state in which the shaft 1 and the flange 16 are assembled by shrink fitting, for example, and FIG. 16 shows the surface roughness of the inner peripheral portion 16a of the flange 16 at the X portion in FIG. It is shown, (A) is a state where surface roughness is fine, (B) is a side view which shows a state where surface roughness is rough. In addition, the same code | symbol is used for the same part as the past, and the detailed description is abbreviate | omitted.
[0038]
16a ₁ ~16a ₁ n in FIG. 16 (A) shows the surface roughness of the inner peripheral portion 16a of the flange 16 (pitch), in this case, the pitch is fine (Rt: 2 [mu] m). Accordingly, since the contact area between the inner peripheral portion 16a _{1 and the} like and the shaft 1 is large, both have a large frictional force, and as a result, the assembling force is also large.
[0039]
16a ₂ ~16a ₂ n in FIG. 16 (B) shows the surface roughness of the inner peripheral portion 16a of the flange 16 (pitch), in this case, the pitch is rough (Rt: 8 [mu] m). Accordingly, since the contact area between the inner peripheral portion 16a _{2 and the} like and the shaft 1 is small, both have a small frictional force and, as a result, a small assembling force. As can be seen from this example, it is understood that a fine state is desirable for the surface roughness (pitch) of the shaft 1 and the inner peripheral part 16a of the flange 16 in order to obtain a predetermined assembling force.
[0040]
The present invention has been made in view of such a viewpoint, and specifically describes the size of the chamfer on the flange hole edge portion and the shaft tip portion side corresponding to the thickness of the flange, the positional relationship between the flange surface and the shaft tip portion, and the like. The above-mentioned problem is solved by setting to, and this point will be described below.
[0041]
[Means for Solving the Problems]
In order to solve the above problems, the invention described in claim 1 is an annular flange having a hole (16a) into which the shaft (1) is inserted on the tip (1d) side of the shaft (1). 16) is a spindle motor assembled by shrink fitting,
While providing the first chamfered portion (16b) to an edge portion of the hole of the flange (16), a second chamfer (1c) provided at the distal end (1d) side of the shaft (1), wherein The longitudinal chamfering amount of the shaft (1) in the first chamfered portion (16b) is T1, and the end surface (16d) on the distal end (1d) side of the shaft (1) in the flange (16) When the longitudinal distance of the shaft to the chamfer start position of the second chamfered portion (1c) on the outer peripheral surface of the shaft (1) is T2, T1 and T2 are set to T1−T2 ≧ 0.01 mm. In addition, the surface roughness (Rt) of the inner surface of the hole (16a) is 2 μm or less .
[0043]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of the invention will be described with reference to the accompanying drawings. It should be noted that the examples described below are preferred specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless otherwise described, the present invention is not limited to these embodiments.
[0044]
FIG. 1 is a partial view showing an entire assembled state of a fixed shaft and a flange of a spindle motor according to the present embodiment, and FIG. 2 shows an example of an assembled state of the fixed shaft and the flange of the spindle motor according to the present invention. FIG. 3 is a partial view showing a bad assembly state of the fixed shaft and the flange of the spindle motor. The same parts as those in the conventional example are denoted by the same reference numerals, and detailed description thereof is omitted.
[0045]
FIG. 1 is a partial view showing an entire assembled state of the fixed shaft and the flange of the spindle motor according to the present embodiment. For example, the outer diameter of the flange 16 is 7.2 mm, the thickness of the flange 16 is 1.5 mm, When the shaft diameter 1 is set to 4 mm, a spindle motor is manufactured for the purpose of obtaining the above assembly force of 1000 N or more and the flatness of the flange of 1 μm or less.
[0046]
Example 1
Specifically, 0.03 mm of the interference described above, 0.12 mm chamfering amount of the flange holes 16 a of the edge portion 16b, and chamfering of the tip portions 1d side formed chamfered portion 1c of the shaft 1 0. 08Mm, was set a level difference between the upper surface portion 1d of the upper surface portion 16d and the shaft 1 of the flange 16 0.03 mm, surface roughness of the inner surface 16a1~16a1n flange hole 16 a of (Rt) to 2 [mu] m.
[0047]
By specifically configuring the spindle motor as described above, results were obtained that the assembly force was 1100 N and the flatness of the flange was 0.062 μm.
[0048]
(Comparative Example 1)
In the same conditions as in Example 1 described above were set surface roughness of the inner surface 16a2~16a2n flange hole 16 a only (Rt) to 8 [mu] m. As a result, the assembly force has been reduced to 710N. As described above with reference to FIG. 16B, the contact area between the inner peripheral portion 16a2 and the shaft 1 and the shaft 1 becomes small due to the rough pitch (Rt: 8 .mu.m). As a result, the assembly force is also small. Although the surface roughness was changed to 4 μm and 6 μm for Rt, the assembling force was 940 N in the former case and 780 N in the latter, and neither of the predetermined 1000 N could be obtained.
[0049]
(Comparative Example 2)
Under the same conditions as in Example 1 described above, only the chamfering amount of the chamfered portion 1c formed on the tip 1d side of the shaft 1 was set to 0.2 mm. As a result, the flatness of the flange deteriorated to 1.524 μm. FIG. 3 shows the result of Comparative Example 2 as a drawing. As is apparent from FIG. 3, when the chamfering amount of the chamfered portion 1c formed on the tip 1d side of the shaft 1 is as large as 0.2 mm, as described in FIG. As a result, when the shaft 1 rotates at a high speed, a force that warps upward is generated on the upper surface 16d of the flange 16. This is because the balance has been lost. That is, this is an example in which the flange 16 has been deformed.
[0050]
2, the height after the edge portion 16b chamfer of the flange holes 16 a T1, the upper surface portion 16d and the height after the tip portion 1d side to the formed chamfer 1c chamfer of the shaft 1 of the flange 16 and the T2 In this case, the flatness of the flange 16 can be reduced to 1 μm or less by setting the above-described height relationship so as to satisfy the inequality T1-T2 ≧ 0.01 mm.
[0051]
In the description of the present embodiment, the example of the fixed shaft as the shaft of the spindle motor has been described. However, the present invention is not necessarily limited to this, and the same effect can be obtained even if a rotor is used instead of the fixed shaft. It is what
[0052]
【The invention's effect】
According to the present invention, high-precision, high-strength fixed shaft or rotor is obtained, Ru are highly spindle motor reliable less accurate runout obtained.
[Brief description of the drawings]
FIG. 1 is a partial view showing an embodiment of an entire assembled state of a fixed shaft and a flange of a spindle motor according to the present invention.
FIG. 2 is a partial view showing an embodiment of the assembled state of the fixed shaft and the flange of the spindle motor according to the present invention.
FIG. 3 is a partial view showing a badly assembled state of a fixed shaft and a flange of a spindle motor.
FIG. 4 is a half sectional view showing an example of an improved conventional spindle motor.
5 is a partially enlarged view showing a relationship between a fixed shaft and a flange in the spindle motor of FIG. 4;
6 is a partially enlarged view showing another relationship between the fixed shaft and the flange in the spindle motor of FIG. 4;
FIG. 7 is a half sectional view showing an example of a conventional spindle motor.
FIG. 8 is a half sectional view showing an oil pool space of a conventional spindle motor.
FIG. 9 is a half sectional view showing another oil pool space of a conventional spindle motor.
FIG. 10 is a partial view showing an assembled state of a fixed shaft and a flange of a conventional spindle motor.
FIG. 11 is a partial view showing another assembled state of a fixed shaft and a flange of a conventional spindle motor.
FIG. 12 is a partial view showing an example of an assembly process and an assembly state of a fixed shaft and a flange of a spindle motor.
FIG. 13 is a partial view showing another example of the assembly process and assembly state of the fixed shaft and the flange of the spindle motor.
FIG. 14 is a partial view showing an example of an assembled state of a fixed shaft and a flange of a spindle motor.
FIG. 15 is a partial view showing another example of the assembled state of the fixed shaft and the flange of the spindle motor.
16 is a partial view showing the relationship between the fixed shaft and the flange mounting hole in FIG. 15;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixed shaft 1c Chamfer 1d Tip part 2 Base 5 Hub assembly 6 Hub 7 Sleeve 10 Disk 11 Spacer 14 Yoke 15 Magnet 16 Flange 16a Flange hole 16b Edge part (Chamfer)
16c Chamfer 16d Flange upper surface

Claims (1)

In a spindle motor in which an annular flange having a hole into which the shaft is inserted is assembled by shrink fitting on the tip end side of the shaft.
While providing a first chamfered portion on the edge portion of the hole of the flange, a second chamfered portion is provided on the tip side of the shaft,
The amount of chamfering in the longitudinal direction of the shaft in the first chamfered portion is T1, and from the end surface on the tip end side of the shaft in the flange to the chamfering start position of the second chamfered portion on the outer peripheral surface of the shaft. When the longitudinal distance of the shaft is T2, T1 and T2 are set to T1−T2 ≧ 0.01 mm, and the surface roughness (Rt) of the inner surface of the hole is 2 μm or less. Spindle motor.

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