JP2001309609A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle motor capable of assembling and disassembling with high reliability having a dynamic-pressure fluid-bearing mechanism solving a problem how to prevent a deformation caused by fixing a fixing shaft 11 and a bracket 13 employing a screw-type structure by use of a screw 14 for fixing the fixing shaft to a holding member. SOLUTION: A female screw 11a is formed at the center of one-end face of the shaft 11 by which the shaft 11 and the bracket 13 are fixed. The shaft 11 and the bracket 13 are so formed as to press-contact each other at the side of an inside-diameter 11b of the shaft-end face and as to make a gap between each other at the side of an outside diameter 11c. Also, a concave groove lid is grooved at the mid point between the sides of the inside and outside diameters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor having a hydrodynamic bearing mechanism, and more particularly to a bearing mechanism thereof.

[0002]

2. Description of the Related Art Spindle motors having a hydrodynamic bearing mechanism are frequently used in equipment requiring precise and high-speed rotation. Among them, it is common to use air as the fluid particularly in high-speed rotating equipment. In air bearings, the bearing diameter is increased to increase the load capacity. The bearing portion is formed with the sleeve and the shaft facing each other, and the rotor structure is generally simpler when the sleeve is on the rotating side. In this manner, the dynamic pressure gas bearing mechanism often has a shaft fixing structure.
This hydrodynamic bearing mechanism is particularly precise, the bearing clearance is very small, and the shaft and sleeve that make it up must have dimensions and shapes that are the target values not only when processing parts but also when assembling. Must not change. Therefore, in general, for example,
In many cases, as shown in Japanese Patent Publication No. 9, a shaft is shrink-fitted to the holding member.

FIG. 6 shows the structure. In this spindle motor, a fixed shaft 91 and a rotating sleeve 92 constitute (a radial part of) a hydrodynamic bearing mechanism. A polygon mirror 93 is attached to the rotating sleeve. The fixed shaft 91 is shrink-fitted (or pressed) to the shaft holding member 94 and fixed.

[0004] Incidentally, this fixed shaft is extremely accurate and expensive. In many cases, the sleeve must be selectively fitted. If this is shrink-fitted and fixed to the shaft holding member 94 in this way, it will hinder the replacement work. For this reason, the motor of this example may have
Can be separated from the casing 95, but there is still a lot of waste.

When a fixed shaft is shrink-fitted as in this example, a certain axial length is required.
Therefore, the motor has a long shape in the axial direction.

[0006]

Therefore, the present invention seeks a structure in which the shrink-fitting method is not used to fix the fixed shaft to the holding member, and a structure in which the fixed shaft is fastened by a screw mechanism. However, fastening by means of a screw mechanism will in part have very high stresses, which may lead to deformation of the fixed shaft. Therefore, the present invention
With the adoption of a screw mechanism, the issue was how to prevent deformation due to the fastening between the fixed shaft and the holding member while maintaining the structural rigidity of the spindle motor. It is an object of the present invention to obtain a spindle motor having a highly reliable hydrodynamic bearing mechanism that can be performed.

[0007]

SUMMARY OF THE INVENTION To solve the above problems, a spindle motor according to the present invention comprises a fixed shaft and a rotating sleeve which are fitted together to form a hydrodynamic bearing mechanism, and an end face of the shaft. A shaft support member disposed so as to be pressed against and adhered to the shaft, and a male screw or a female screw is formed at the center of one end surface of the shaft, thereby fastening the shaft and the shaft support member. The term “comprising” means that the shaft is pressed and adhered on the inner diameter side of the end face of the shaft and a gap is formed on the outer diameter side.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The invention according to claim 1 of the present invention is characterized in that: a) they are fitted together to form a hydrodynamic bearing mechanism;
A fixed shaft and a rotating sleeve, and a shaft support member arranged so as to press against the end face of the shaft, and b) a male screw or a female screw is formed at the center of one end face of the shaft, whereby The shaft support member is fastened to the shaft support member. C) The shaft and the shaft support member are a spindle motor in which the shaft is pressed and adhered on the inner diameter side of the shaft end face and the gap is formed on the outer diameter side.

Thus, the radial distortion caused by pressing the end face of the shaft is limited only to the inner diameter side. Accordingly, expansion and deformation of the outer diameter of the shaft can be reduced, and reliability is improved by improving the accuracy of the bearing. In addition, the bearing can be used up to just below the pressing portion, and the height of the entire bearing can be reduced. Alternatively, the height of the motor can be reduced. Further, it is possible to tighten with a strong torque, and it is possible to prevent deterioration of accuracy and reliability over time (shaft fall, loosening due to vibration at high speed rotation, etc.). In addition, it is possible to adopt a screw fastening structure, it is possible to re-disassemble in the process, and it becomes easy to regenerate defective products.

According to a second aspect of the present invention, there is provided the spindle motor according to the first aspect, wherein the width of the gap provided on the outer diameter side is one third or more of the width of the end face. This prevents radial distortion due to pressing on the shaft end face from substantially affecting the outer diameter of the shaft. Therefore, the expansion of the outer diameter of the shaft can be kept within the allowable range as a fluid bearing,
The accuracy of the bearing can be improved, and the reliability is improved. Also, it can be used as a bearing up to the very end of the pressing portion. Here, the end face width is a value obtained by dividing a dimension obtained by subtracting the diameter of the fastening portion from the shaft diameter by two.

According to a third aspect of the present invention, there is provided a) a fixed shaft and a rotating sleeve, which are fitted to each other to form a hydrodynamic bearing mechanism, and b) a pressure-contacting end face of the shaft. C) an external thread or an internal thread is formed at the center of one end face of the shaft, thereby fastening the shaft and the shaft support member, and d) an end face of the shaft. Has a concave groove in the middle part from the inner diameter side to the outer diameter side,
Further, the spindle motor has a gap formed between the groove support and the shaft support member on the outer diameter side of the groove.

As described above, the continuity between the inner peripheral side and the outer peripheral side of the shaft end face is interrupted by the concave groove. Then, the radial distortion generated on the inner peripheral side is reduced from affecting the outer diameter of the shaft. Therefore, expansion and deformation of the outer diameter of the shaft can be more reliably prevented. Further, the shape and the contact area of the contact portion can be managed uniformly. Therefore, the contact state does not vary depending on the product, and the bearing performance can be stably managed.

According to a fourth aspect of the present invention, there is provided the spindle motor according to the third aspect, wherein the concave groove provided in the intermediate portion has a depth of 0.1 mm or more. The continuity between the inner peripheral side and the outer peripheral side of the shaft end face is clearly blocked by the concave groove, and radial distortion generated on the inner peripheral side is prevented from reaching the outer diameter of the shaft.

According to a fifth aspect of the present invention, in the spindle according to any one of the first to third aspects, the axial distance from the pressing portion of the shaft end face to the sleeve end face is one third or less of the shaft diameter. It is a motor. Since the bearing is used just up to the pressing portion, the overall height of the bearing can be reduced. Alternatively, the height of the motor can be reduced.

The invention according to claim 6 is the spindle motor according to any one of claims 1 and 3, wherein the sleeve and the shaft are made of an aluminum alloy. By using an aluminum-based alloy for the sleeve, the weight and inertia of the rotor can be reduced, and a motor suitable for high-speed rotation can be obtained. By using the same material for the shaft and the sleeve, a change in clearance due to a change in temperature can be reduced.

However, a shaft made of an aluminum alloy has a smaller longitudinal elastic modulus than iron and is easily deformed by stress. For this reason, conventionally, a screw fastening structure could not be adopted in such a portion, but by combining with the invention of claim 1 or 3, the deformation of the outer diameter can be prevented, and the assembly can be reassembled while keeping the height low. Thus, a spindle motor capable of rotating at a high speed and covering a wide temperature range can be provided.

[0017]

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

FIG. 1 is a side sectional view showing the structure of a spindle motor according to an embodiment of the present invention. FIG. 2 is an enlarged sectional view of the shaft fastening portion. FIG. 3 is a diagram illustrating the relationship between the gap forming width 'k' and the amount of change in the shaft diameter for explaining the operation. FIG. 4 is a graph showing the relationship between the groove depth 'q' and the amount of change in the shaft diameter. FIG. 5 is a diagram showing the relationship between the gap forming width 'k' and the axial profile of the amount of shaft deformation.

In FIG. 1, the spindle motor is formed as a drive source for driving the polygon mirror 51 to rotate at high speed. The bearing is a hydrodynamic bearing mechanism, and the radial bearing portion is composed of a fixed cylindrical shaft 11 and a sleeve 22 that surrounds and rotates around the shaft. A dynamic pressure generating groove (not shown) is formed in any of them. Both the sleeve 22 and the shaft 11 are made of an aluminum alloy, and the surface of the shaft is plated with electroless nickel. The thrust bearing portion includes a hard flat plate 12 embedded in an end face of the shaft,
It is composed of a resin spherical plate 23 opposed thereto.

The motor is divided into a stator (all of the fixed members) and a rotor (all of the rotating members).
Around the shaft 11, a bracket 13 for supporting the shaft 11,
It is composed of a shaft mounting screw 14 for the connection, a metal substrate 15 for mounting the bracket to the device, a stator assembly fixed to the bracket and driving the rotor to rotate. The stator assembly is performed by winding the winding 17 around the stator core 16.
The inner circumference of the stator core is supported by brackets 13. A retaining hook 40 is attached to the inner periphery of the stator core.

On the other hand, the rotor is constructed around a rotor frame 21. The sleeve 22 is a cylindrical portion formed on a part of the rotor frame and surrounding the shaft to form a bearing.
At the end of the rotor frame, there is a thrust cover 24 for holding the resin spherical plate 23 described above. A multi-pole magnetized magnet 25 is fixed inside the rotor frame at a position facing the stator assembly. A polygon mirror 51 is mounted on the upper part of the rotor frame, and a mirror retainer 52 is mounted on the polygon mirror 51 and fixed with a mirror fixing screw 53. When the winding 17 of the motor configured as described above is externally supplied with power and driven, the rotor rotates.

FIG. 2 is an enlarged sectional view of a shaft fastening portion which is a main portion of the present invention. As already mentioned, the shaft 1
1 is supported by a bracket 13 (shaft support member). That is, the end face of the shaft 11 is pressed and adhered to the bracket 13 by the shaft mounting screw 14. For this purpose, a female screw 11 a (may be a male screw) is formed at the center of one end face of the shaft 11, thereby fastening the shaft 11 and the bracket 13.

The shaft 11 and the bracket 13 are pressed and adhered on the inner diameter side 11b of the shaft end face, and a gap is formed on the outer diameter side 11c. The width k of the gap formed here is a large gap that is substantially half or more than the width j of the end face of the shaft and covers about two thirds. Further, the axial distance s from the shaft end face to the sleeve end face is kept small. Further, in this embodiment, the shaft 1
A groove 11d is provided at an intermediate portion from the inner diameter side 11b to the outer diameter side 11c on the end face of the bracket 1 and a gap is formed between the bracket 13 and the outer diameter side of the groove 11d.

As described above, in the present embodiment, the width j of the shaft end surface is not brought into contact with the entire surface of the bracket 13 and contact is avoided in the range of the gap forming width k. Then, the generation of the radial distortion due to the pressing of the shaft end face is reduced to the inner diameter side 11.
b only.

This will be described with reference to FIG. The figure shows the relationship between the gap formation width 'k' and the amount of change in the shaft outer diameter Da. The horizontal axis is the tightening torque of the shaft mounting screw 14, the vertical axis is the diameter change amount due to the tightening, and the parameter 'k' is the gap formation width described in FIG. In this embodiment, the shaft outer diameter Da is 10 mm, and the shaft fastening portion diameter Dd is 5 mm.

In FIG. 3, the diameter change increases with the increase in the tightening torque. However, the amount of change greatly varies depending on the gap formation width k. When 'k = 0.2 mm', which is only a small chamfer, a maximum diameter change of about 1.2 μm occurs, but when a large gap forming width 'k = 1.5 mm' as shown in FIG. 2 is used. Remains at a maximum of about 0.3 μm. Even in the case of “k = 0.8 mm” in the middle, the variation is within 0.4 μm. It is of course better that the amount of change is small, but the allowable amount of change is up to about 0.4 μm in the case of the hydrodynamic air bearing as in this embodiment.

As can be seen from the above, the width k of the gap provided on the outer diameter side is preferably not less than one third of the end face width j.
It is better to be 0.8 mm or more in numerical terms. At this time, the radial distortion caused by pressing the end face of the shaft can be substantially prevented from reaching the outer diameter of the shaft, and the expansion of the outer diameter of the shaft can be kept within an allowable range as a fluid bearing. Therefore, the accuracy of the bearing is improved and the reliability is improved, and the bearing can be used just up to the pressing portion.
Furthermore, it is possible to tighten with a strong torque. This can prevent deterioration in accuracy and reliability over time (shaft fall, loosening due to vibration at high speed rotation, etc.), and it is possible to adopt a screw tightening and fixing structure instead of the conventional shrink fit structure. Re-decomposition, selection fitting, and regeneration of defective products.

In this embodiment, a concave groove 11d is provided at an intermediate portion from the inner diameter side to the outer diameter side on the end surface of the shaft, and a gap is formed between the shaft 13 and the bracket 13 on the outer diameter side from the groove 11d. are doing. In this way, the continuity between the inner peripheral side and the outer peripheral side of the shaft end face is interrupted by the concave groove 11d,
Radial distortion generated on the inner peripheral side is reduced from affecting the outer diameter of the shaft.

This will be described with reference to FIG. The figure is a relationship diagram between the groove depth 'q' and the amount of change in the shaft outer diameter Da. The horizontal axis is the tightening torque of the shaft mounting screw 14, the vertical axis is the diameter change amount due to the tightening, the parameter 'q'.
Is the groove depth of the concave groove 11d described in FIG.

In FIG. 4, the amount of change in the diameter increases as the tightening torque increases. However, the amount of the change depends on the groove depth q. When 'q = 0.0 mm' without a groove, a diameter change of slightly more than 0.5 μm occurs, but when a groove is provided and the groove depth is 'q = 0.1 mm', 0.4 μm or less, 0.3μ when groove depth is 'k = 0.2mm'
m.

As can be seen from the above, it is preferable that the depth of the concave groove provided in the intermediate portion is 0.1 mm or more. Thereby, the continuity between the inner peripheral side and the outer peripheral side of the shaft end face can be clearly blocked by the concave groove, and the radial distortion generated on the inner peripheral side is prevented from reaching the outer diameter of the shaft. In combination with the provision of the gap on the outer peripheral end surface of the shaft, the expansion and deformation of the outer diameter of the shaft can be more reliably prevented. Also, by providing this concave groove, the shape of the contact portion can be controlled uniformly.
The contact state does not vary from product to product, and bearing performance can be managed stably.

In this embodiment, the axial distance s from the shaft end face to the sleeve end face is kept small. This is because the expansion of the shaft outer diameter Da is reduced by providing a gap on the outer peripheral end surface of the shaft, and the range usable as a bearing is expanded.

This will be described with reference to FIG. The figure shows the relationship between the gap forming width 'k' and the axial profile of the amount of shaft deformation. The horizontal axis indicates the measurement point of the shaft diameter by the distance from the end face. The vertical axis is the diameter change amount due to the tightening, and the parameter 'k' is the gap formation width described in FIG.

In FIG. 5, the amount of change in diameter decreases as the measurement point moves away from the end face. The amount of change depends on the gap formation width k. In the case of 'k = 0.2 mm' where only a small chamfer is applied, in order for the amount of change in diameter to be less than 0.4 μm, the gap must be at least 3.5 mm from the end face of the shaft. When it is set to 0.8 mm ', the diameter changes only about 1.0 mm from the shaft end face. That is, according to the present invention, the axial distance s from the shaft end face to the sleeve end face can be made smaller than about one third of the shaft outer diameter Da. When the axial distance s is equal to or less than one third of the shaft diameter Da, the effective length of the bearing can be made longer than before. Alternatively, the height of the motor can be made lower than before.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various applications and developments can be made within the scope of the present invention.

[0036]

As described above, according to the present invention, the shaft and the shaft supporting member are pressed and contacted on the inner diameter side of the shaft end face, and a gap is formed on the outer diameter side.
Deformation due to fastening between the fixed shaft and the holding member can be prevented. Thus, it is possible to obtain a spindle motor having a highly reliable hydrodynamic bearing mechanism that can be assembled and disassembled while keeping the height low.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a structure of a spindle motor according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the shaft fastening portion.

FIG. 3 is a diagram showing the relationship between the gap forming width 'k' and the amount of change in shaft diameter.

FIG. 4 is a diagram showing the relationship between the groove depth 'q' and the amount of change in the shaft diameter.

FIG. 5 is a graph showing the relationship between the gap formation width 'k' and the axial profile of the amount of shaft deformation.

FIG. 6 is a side sectional view showing the structure of a conventional spindle motor.

[Explanation of symbols]

Reference Signs List 11 shaft 11a female screw 11b inner diameter side of shaft end face 11c outer diameter side of shaft end face 11d concave groove in shaft end face 13 bracket (shaft support member) 14 shaft mounting screw 21 rotor frame 22 sleeve j width (end face width) of shaft end face k gap Formed width s Axial distance from shaft end face to sleeve end face q Groove depth of concave groove Da Shaft outer diameter (shaft diameter) Dd Shaft fastening part diameter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 26/10 102 G02B 26/10 102 5H607 H02K 5/16 H02K 5/16 Z 5H621 21/22 21/22 M 29/00 29/00 Z F term (reference) 2H045 AA13 AA24 3J011 AA01 BA04 BA10 DA01 KA03 MA12 PA03 QA05 SB04 SC01 3J017 AA01 DB01 5H019 AA00 CC04 DD01 FF01 FF03 5H605 AA00 BB05 BB09 BB10 BB10 BB10 BB10 BB10 BB10 5H607 AA00 AA12 BB01 BB07 BB09 BB14 BB17 BB25 DD03 DD09 DD14 FF12 GG01 GG03 GG09 GG12 GG14 JJ05 KK04 KK10 5H621 GA01 JK13 JK17 JK19

Claims (6)

[Claims] A fixed shaft and a rotating sleeve that fit together to form a hydrodynamic bearing mechanism;
A shaft support member disposed so as to be pressed and adhered to the end surface of the shaft, and a male screw or a female screw is formed at the center of one end surface of the shaft, thereby fastening the shaft and the shaft support member. A spindle motor in which the shaft and the shaft support member are pressed and contacted on the inner diameter side of the shaft end face, and a gap is formed on the outer diameter side. 2. The spindle motor according to claim 1, wherein the width of the gap provided on the outer diameter side is one third or more of the width of the end face. 3. A fixed shaft and a rotating sleeve that fit together to form a hydrodynamic bearing mechanism;
A shaft support member disposed so as to be pressed and adhered to the end surface of the shaft, and a male screw or a female screw is formed at the center of one end surface of the shaft, thereby fastening the shaft and the shaft support member. A spindle motor, wherein a groove is provided at an intermediate portion from an inner diameter side to an outer diameter side at an end surface of the shaft, and a gap is formed between the shaft and the shaft support member at an outer diameter side from the groove. 4. The groove provided in the intermediate portion has a depth of 0.1
4. The spindle motor according to claim 3, wherein the diameter is not less than mm. 5. The spindle motor according to claim 1, wherein the axial distance from the pressing portion of the shaft end surface to the sleeve end surface is one third or less of the shaft diameter. 6. The sleeve and the shaft are made of an aluminum alloy.
A spindle motor according to the item.