JP2007116796A - Motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor for ensuring a fixing strength of a sleeve to a motor base, preventing an eccentricity and a vibration from being generated and maintaining the capability of a dynamic pressure bearing for a long time. <P>SOLUTION: The motor (50, 50A) is provided with: a rotor (R) comprising a shaft (13) and a hub (2) for fixing the shaft (13); and a stator (S) comprising the sleeve (10) for pivotably supporting the motor base (5) with a penetration hole (5d) and the shaft (13), and having an outer circumference (10d) pressed into or adhered to an inner circumference (5a1) of the penetration hole (5d). The motor (50, 50A) has a plurality of recesses (17, 27) extending in the direction of a rotating shaft (CL) on the inner circumference (5a1) or the outer circumference (10d) in a region in which the inner circumference (5a1) of the penetration hole (5d) and the outer circumference (10d) of the sleeve (10) contact. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a motor, and more particularly to a motor provided with a dynamic pressure bearing.

An example of a conventional motor is described in Patent Document 1.
This motor is a spindle motor equipped with a hydrodynamic bearing suitable for use in an HDD (Hard Disk Drive).
In this motor, a sleeve that supports a shaft in the radial direction is press-fitted and fixed to an inner peripheral surface of a cylindrical wall formed in a motor base. A dynamic pressure groove of a radial dynamic pressure bearing is formed on the inner peripheral surface of the sleeve. Is formed.
JP 2003-289646 A

By the way, various demands have been made on the market for motors for HDDs, such as downsizing, thinning, high density, excellent vibration resistance and shock resistance, low cost, low power consumption characteristics, etc. This demand is becoming increasingly severe year by year.
As a motor for this HDD, it is common to use a hydrodynamic bearing as a bearing because of its excellent dynamic characteristics and high reliability, but how to ensure the performance of the hydrodynamic bearing in response to each demand from the market. It is a challenge to do.
For example, specifically explaining the thinning, in order to meet this requirement, the axial fitting dimension between the sleeve and the shaft must be shortened.

However, as the fitting dimension becomes shorter, the influence on the bearing performance due to the slight deformation of the dynamic pressure grooves provided on the opposing surfaces of the two parts cannot be ignored. In particular, there is a concern that the life of the bearing will be affected when it is used for a long time.
Therefore, it is necessary to consider so that the deformation of the dynamic pressure groove does not occur as much as possible.
As an index indicating the performance of the hydrodynamic bearing, there are a degree of variation in the flying height of the rotor, non-repetitive accuracy (NRRO), and the like.

Further, since the fitting dimension is shortened, the contact area between the motor base and the sleeve press-fitted and fixed thereto is reduced, and the fixing strength of the sleeve is reduced.
When this fixing strength is reduced, the press-fitting part is also affected by slight deformation (thermal expansion and thermal contraction) of each member caused by temperature changes during operation, and the perpendicularity of the sleeve to the motor base changes and the shaft core changes. There is a possibility that the vibration may occur or the motor may vibrate.

The conventional motor described in Patent Document 1 is provided with an annular recess in a range corresponding to the dynamic pressure groove on the inner peripheral surface of the cylindrical wall of the motor base or the outer peripheral surface of the sleeve, so The groove can be prevented from being deformed, but the axial contact range between the motor base and the sleeve is limited. Therefore, when the thickness is extremely reduced, it is desirable to improve the fixing strength of the sleeve. is there.
Further, not only the press-fitting but also the case where the adhesive is fixed by bonding, there is a concern that the dynamic pressure groove may be deformed due to a similar stress generated by the volume change when the adhesive is cured.

  Therefore, the problem to be solved by the present invention is to prevent deformation of the dynamic pressure groove formed on the inner peripheral surface of the sleeve and secure the fixing strength of the sleeve to the motor base even if the motor is thinned. An object of the present invention is to provide a motor capable of preventing the occurrence of vibration and vibration and maintaining the performance of a hydrodynamic bearing for a long period of time.

In order to solve the above problems, the present invention has the following means.
That is, a rotor part (R) including a shaft (13) and a hub (2) to which the shaft (13) is fixed, a motor base (5) having a through hole (5d), and A stator portion comprising a sleeve (10) that supports the shaft (13) and whose outer peripheral surface (10d) is fixed to the inner peripheral surface (5a1) of the through hole (5d) by press-fitting or bonding ( S), and within a range where the inner peripheral surface (5a1) of the through hole (5d) and the outer peripheral surface (10d) of the sleeve (10) are in contact with each other, the inner peripheral surface (5a1) or the outer peripheral surface A motor (50, 50A) having a plurality of recesses (17, 27) extending in the direction of the rotation axis (CL) in any of (10d).

  According to the present invention, even if the motor is thinned, it is possible to secure the fixing strength of the sleeve to the motor base, prevent the occurrence of core runout and vibration, and maintain the performance of the hydrodynamic bearing for a long period of time. .

The preferred embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is a sectional view showing a first embodiment of the motor of the present invention.
FIG. 2 is a plan view for explaining a main part in the first embodiment of the motor of the present invention.
FIG. 3 is a plan view of an essential part for explaining a modification of the first embodiment of the motor of the present invention.
FIG. 4 is a cross-sectional view for explaining a second embodiment of the motor of the present invention.
FIG. 5 is a plan view for explaining a main part in the second embodiment of the motor of the present invention.
FIG. 6 is a graph for explaining the effect in each embodiment of the motor of the present invention.
FIG. 7 is a graph for explaining another effect in each embodiment of the motor of the present invention.
FIG. 8 is a diagram in which FIGS. 6 and 7 are summarized as the relationship of the recess occupation ratio α.

<First embodiment>
The motor 50 of the first embodiment is a three-phase drive motor that is used in a magnetic disk device and rotationally drives a magnetic disk. The motor 50 includes a rotor portion R and a stator portion S, and includes a radial dynamic pressure bearing portion RB and a thrust. The rotor portion R is structured to be rotatably supported with respect to the stator portion S by the dynamic pressure bearing portion SB.
Hereinafter, the stator portion S, the rotor portion R, and the dynamic pressure bearing portions RB and SB will be described in this order.

The stator portion S includes a motor base 5, a sleeve 10 and a core 6 fixed to the motor base 5, and a coil 7 wound around the core 6.
The motor base 5 is formed by cutting aluminum die casting or pressing an aluminum plate or an iron plate plated with nickel.
The motor base 5 has a cylindrical wall portion 5a raised in a cylindrical shape around the through hole 5d, and the sleeve 10 is fixed to the inner peripheral surface 5a1 of the cylindrical wall portion 5a by press-fitting.

The sleeve 10 is made of copper-based saddle-bonding gold or SUS (stainless steel) material.
Moreover, the step part 10c formed in the step shape of 2 steps | paragraphs is formed in the one end side. As will be described later, the counter plate 9 and the thrust ring 12 are accommodated in the stepped portion.

The core 6 has a ring shape having nine poles that are laminated with magnetic materials such as silicon steel plates and project outward, and is fixed to the outer peripheral surface 5a2 of the cylindrical wall portion 5a of the motor base 5. .
An insulating coating is applied to the surface of the core 6 by electrodeposition coating, powder coating or the like, and a coil 7 is wound around each salient pole.
A winding terminal 7 a of the coil 7 is soldered to a flexible substrate 14 attached to the bottom surface 5 c of the motor base 5 through a through hole 5 b formed in the motor base 5.
The flexible substrate 14 is provided with a portion for soldering the terminal 7a of the coil 7 and a land portion (both not shown) for connection to a drive circuit of a magnetic disk device on which the motor 50 is mounted. The soldering portion and the land portion are connected by a pattern.

The rotor portion R includes a shaft 13, a cup-shaped hub 2 having a through-hole into which the shaft 13 is press-fitted and fixed, and a flange 2 a, and a ring-shaped magnet 8 fixed to the hub 2. The Details will be described below.

The shaft 13 is formed of a SUS material.
The bubb 2 is formed by cutting a magnetic SUS material, and the magnetic disk D is placed on the flange 2a.
Further, one end side of the shaft 13 is fixed to the through hole 2b by press-fitting.
The ring-shaped magnet 8 is fixed to the inner peripheral surface 2 c of the hub 2.
The magnet 8 is made of an Nd—Fe—B (neodymium-iron-boron) material, and the surface thereof is coated with an epoxy resin. Moreover, the inner peripheral side is magnetized to 12 poles.

Next, the dynamic pressure bearing portions RB and SB will be described.
The radial dynamic pressure bearing portion RB includes an outer peripheral surface 13a of the shaft 13, an inner peripheral surface 10a1 in the through hole 10a of the sleeve 10 into which the shaft 13 is inserted, and a lubricating oil 20 filled in a gap between the two facing each other. Consists of.
A pair of radial dynamic pressure grooves 16 are formed in the inner peripheral surface 10a1 of the sleeve 10 apart in the direction of the axis CL. In FIG. 1, the radial dynamic pressure groove 16 is illustrated in a planar manner at the position of the shaft for easy understanding.
The radial dynamic pressure groove 16 is formed in a so-called herringbone shape, and in FIG.
When the rotor portion R rotates, dynamic pressure is generated in the lubricating oil 20 by the radial dynamic pressure grooves 16, and the shaft 13 is supported in the radial direction.

A tapered portion 23 is provided at an end of the inner peripheral surface 10a1 of the sleeve 10 on the hub 2 side so as to be inclined so that the inner diameter increases toward the end surface. The filling amount of the lubricating oil 20 is set so that the liquid level of the lubricating oil 20 is located in the middle of the tapered portion 23, and the tapered portion 23 prevents the lubricating oil 20 from leaking to the outside and prevents it from becoming a capillary tube. It functions as a taper seal that seals using the phenomenon.
Further, a predetermined gap 22 is provided between the inner surface 2d of the hub 2 and the end surface 10b of the sleeve 10 facing each other in the direction of the axis CL, thereby preventing the lubricating oil 20 from scattering to the outside.

Next, the thrust dynamic pressure bearing portion SB will be described.
First, a thrust ring 12 is fixed to an end portion of the shaft 13 opposite to the hub 2, and the thrust ring 12 is a first step portion 10 c 1 inside a step portion 10 c formed in the sleeve 10. Are accommodated with a slight gap.

Further, the counter plate 9 is fixed to the second step portion 10c2 on the opening side of the step portion 10c from the outside, and one opening portion (the lower side in FIG. 1) of the through hole 10a of the sleeve 10 is sealed. .
Each dimension is set so that a predetermined gap is generated between the counter plate 9, the thrust ring 12, and the step portion 10 c of the sleeve 10, and the gap is filled with the lubricating oil 20.

A first thrust dynamic pressure groove (not shown) is formed in a herringbone shape on either the end face of the thrust ring 12 on the hub 2 side or the face of the sleeve 10 facing the hub 2 side.
On the other hand, a herringbone-like second thrust dynamic pressure groove (not shown) is formed on either the opposite end face of the hub 2 in the thrust ring 12 or the face of the counter plate 9 facing the hub 2. .
When the rotor portion R rotates, dynamic pressures in opposite directions are generated in the lubricating oil 20 by the first and second thrust dynamic pressure grooves, and the rotor portion R is supported in the thrust direction.

The motor base 5 is provided with a yoke 11 formed in a ring shape with a magnetic material so as to face the end surface 8a of the magnet 8 in a state where the rotor portion R is rotatably supported by the stator portion S in this manner. ing.
Due to the magnetic action of the yoke 11 and the magnet 8, the rotor portion R is attracted to the motor base 5 side and excessive lifting from the stator portion S is prevented. It is comprised so that it may oppose with a predetermined clearance gap with the internal peripheral surface of this.
The hub 2 is made of a magnetic stainless steel as described above, and the hub 2, the core 6 and the magnet 8 constitute a magnetic circuit.
And in the structure mentioned above, the rotor part R rotates with respect to the stator part S by supplying with electricity sequentially to each phase of the coil 7 from a motor drive circuit.

  By the way, in this 1st Example, the recessed part 17 extended in the direction of the axis | shaft CL is provided in the internal peripheral surface 5a1 of the cylindrical wall part 5a of the motor base 5. As shown in FIG. This will be described with reference to FIG.

FIG. 2 is a plan view depicting the core 6 around which the coil 7 is wound around each of the nine salient poles and the cylindrical wall portion 5a fixed to the outer peripheral surface 5a2.
In this figure, the recesses 17 are formed at four locations on the inner peripheral surface 5a1 of the cylindrical wall portion 5a having inner surfaces formed of a part of a cylinder at equal intervals of 90 °.

Assuming that the circumferential length of the recess 17 in the inner peripheral surface 5a1 is W, the total Wt is Wt = W × 4 in this embodiment.
Here, the circumferential length of the inner peripheral surface 5a1 is L, α = Wt / L is obtained as the recess occupation ratio α, and the relationship with the amount of change in cylindricity Δ in the inner peripheral portion of the sleeve 10 is examined. FIG. Show.
Here, the change amount Δ of cylindricity in the inner peripheral portion of the sleeve means that the inner peripheral surface of the sleeve 10 is fixed by press-fitting the sleeve 10 into the motor base 5 or fixed by adhesion, or a temperature change. It means the amount of change in cylindricity that changes due to deformation due to slight deformation (thermal expansion or thermal contraction).

From FIG. 6, it was found that when the recess occupation ratio α is greater than a certain value, the cylindricity change amount Δ is stable at a small value.
If this cylindricity change amount Δ is small, the deformation amount of the radial dynamic pressure groove is also small. Therefore, this change amount Δ is preferably made as small as possible.

Specifically, when α is 0.12 or more, the cylindricity change amount Δ is stabilized at 0.10 μm or less.
Therefore, it is desirable that the recess occupation ratio α be 0.12 or more because the rotation characteristics of the motor are stabilized and a product with little variation is obtained.

  Further, when α is set to 0.20 or more, the cylindricity change amount Δ is approximately constant at about 0.05 μm, which is further desirable.

If it demonstrates using FIG. 2, if the circumferential direction length W of one recessed part 17 is set to 0.05 * L, when the recessed part 17 is formed in 3 or more places, More preferably, 4 or more places, (alpha) will be 0. .15 and 0.20, which are desirable and more desirable.
When the recesses 17 are formed at an equiangular pitch, the deformation balance at the time of press-fitting is improved, and the inner surface shape is most preferably an arc shape as shown in FIG. 2 in order to suppress the occurrence of stress concentration.

As described above in detail, by forming the concave portion 17 extending in the direction of the axis CL, deformation caused by press-fitting in the inner peripheral portion of the cylindrical wall portion 5a is suppressed, and excessively high stress does not occur. .
Therefore, the sleeve 10 does not receive excessive force from the cylindrical wall portion 5a, and the radial dynamic pressure groove 16 formed on the inner peripheral surface 10a1 of the sleeve 10 can be prevented from being deformed.

On the other hand, the outer peripheral surface of the sleeve 10 is in contact with the portion other than the concave portion 17 on the inner peripheral surface 5a1 of the cylindrical wall portion 5a in the entire range where the sleeve 10 is press-fitted.
Therefore, even if the concave portion 17 extending in the direction of the axis CL is provided, the bonding strength does not decrease significantly.
As shown in FIG. 7, this is understood from the fact that even when the recess occupancy ratio is 0.5, the coupling strength ratio β is secured to 0.8 when the recess 17 is not provided. .
The bond strength ratio is a ratio of the bond strength when the recess is provided to the bond strength when no recess is provided, and is preferably close to 1 and preferably 0.8 or more.
Therefore, from this point of strength, it is desirable that the recess occupation ratio α is 0.5 or less.
FIG. 8 is a graph in which the amount of change in cylindricity Δ in FIG. 6 and the coupling strength ratio β in FIG. 7 are plotted with the recess occupancy α being a common parameter as the horizontal axis.
As can be seen from this figure, the recess occupation ratio α is preferably 0.12 ≦ α ≦ 0.5, and more preferably 0.20 ≦ α ≦ 0.5.

Thereby, even if the axial fitting length between the cylindrical wall portion 5a and the sleeve 10 is shortened to reduce the thickness of the motor, the press-fit fixing strength of the sleeve 10 can be increased while preventing the radial dynamic pressure groove from being deformed. Can be secured.
Therefore, according to this embodiment, it is possible to prevent the occurrence of the motor runout and vibration and to maintain the performance of the hydrodynamic bearing for a long period of time.

<Second embodiment>
The second embodiment is an example of a motor 50A in which the concave portion 17 provided on the motor base 5 side in the first embodiment is provided as the concave portion 27 on the sleeve 10 side. Parts of the second embodiment that are different from the first embodiment will be described with reference to FIGS. FIG. 4 is a cross-sectional view of the motor 50A of the second embodiment, and FIG. 5 is a plan view of the sleeve 10 in the motor 50A of the second embodiment.
In FIG. 4, the radial dynamic pressure grooves 16 formed on the inner peripheral surface of the sleeve 10 are illustrated in a planar manner at the position of the shaft for easy understanding.

As shown in FIG. 4, the recess 27 is formed on the outer peripheral surface 10 d of the sleeve 10 so as to extend along the rotation axis CL.
In FIG. 5, the concave portion 27 is formed at four locations on the outer peripheral surface 10 d of the sleeve 10 with an inner surface formed of a part of a cylinder at equal intervals of 90 °.

Assuming that the circumferential length of the recess 27 in the outer peripheral surface 10d is W2, the total Wt is Wt = W2 × 4 in this embodiment.
Further, when the circumferential length of the outer peripheral surface 10d is L, α = Wt / L is obtained as the recess occupation ratio in this embodiment, and the relationship with the cylindricity change amount Δ is examined, the same as in the first embodiment (FIG. 6).
Therefore, also in the second embodiment, by setting the recess occupation ratio α to 0.12 or more, it is desirable that the rotational characteristics of the motor are stabilized and a product with little variation is obtained.

  Furthermore, if α is 0.20 or more, the amount of change in cylindricity Δ becomes almost constant with a small amount, which is further desirable.

As described in detail above, by forming the concave portion 17 extending in the direction along the axis CL, deformation caused by press-fitting in the outer peripheral portion 10d of the sleeve 10 is suppressed, so that the generated stress is reduced.
Therefore, it is possible to prevent the radial dynamic pressure groove 16 formed on the inner peripheral surface 10a1 of the sleeve 10 from being deformed.

On the other hand, the outer peripheral surface 10d of the sleeve 10 is in contact with the outer peripheral surface 10d of the sleeve 10 other than the recess 27 in the entire range of the inner peripheral surface 5a1 of the cylindrical wall 5a.
Therefore, even if the recess 27 is provided, the bonding strength does not decrease significantly.
As in the case of the first embodiment, as shown in FIG. 7, even when the recess occupation ratio α is 0.5, the press-fit strength ratio β with respect to the case where the recess 27 is not provided is 0. It is understood from the fact that 8 or more are secured.
In any case, since the bond strength ratio β is the same as that in FIG. 8, the recess occupation ratio α is preferably 0.12 ≦ α ≦ 0.5, and more preferably in this embodiment. Is 0.20 ≦ α ≦ 0.5.

Each embodiment of the present invention is not limited to the above-described configuration and procedure, and may be modified as follows without departing from the gist of the present invention.
Needless to say, the modifications can be applied in combination.

<First Modification>
In each of the embodiments described above, the inner surface shape of the recesses 17 and 27 that are part of the cylinder may be a combination of planes. That is, when the first embodiment is described as a representative, as shown in FIG. 3, the inner peripheral surface 5a1 of the cylindrical wall portion 5a of the motor base 5 is substantially U-shaped on a plane orthogonal to the rotation axis CL. You may form the recessed part 17 so that it may have a cross section. The U-shape may be a square shape, and the cross-sectional shape is not limited. In any case, it is preferable to provide R at the apex ridgeline in order to reduce stress concentration.

<Second Modification>
The recesses 17 and 27 extending in the direction of the axis CL include a width W16 (see FIG. 1) of the radial dynamic pressure groove in the direction of the axis CL and the axis of the thrust ring 12 in which the thrust dynamic pressure groove is provided on the end surface. It is preferably provided in a range corresponding to the thickness Wsr in the CL direction.
Even if the concave portions 17 and 27 are not formed so as to reach the end surface of the cylindrical wall portion 5a or the sleeve 10, it is possible to effectively generate excessively high stress by press-fitting as shown in the above-described embodiments. Can be suppressed.

  In each of the above-described embodiments and modifications, the sleeve 10 is press-fitted into the motor base 5, but it goes without saying that the sleeve 10 may be fixed not only by press-fitting but also by adhesion. Even in this case, it is possible to similarly prevent the stress generated by the volume change at the time of curing of the adhesive from being excessively high, to provide a motor having a stable rotational characteristic, a small characteristic variation, and a high reliability. it can.

It is sectional drawing which shows 1st Example of the motor of this invention. It is a top view explaining the principal part in 1st Example of the motor of this invention. It is a top view of the principal part for demonstrating the modification of 1st Example of the motor of this invention. It is sectional drawing for demonstrating 2nd Example of the motor of this invention. It is a top view explaining the principal part in 2nd Example of the motor of this invention. It is a graph explaining the effect in each Example of the motor of this invention. It is a graph explaining the other effect in each Example of the motor of this invention. It is the figure which summarized FIG.6 and FIG.7 as the relationship of the recessed part occupation rate (alpha).

Explanation of symbols

2 Hub 2a Flange 2b Through-hole 2c Inner peripheral surface 2d Inner surface 5 Motor base 5a Tubular wall 5a1 Inner peripheral surface 5a2 Outer peripheral surface 5b Through-hole 5c Bottom surface 5d Through-hole 6 Core 7 Coil 7a Terminal 8 Magnet 9 Counter plate 10 Sleeve 10a Through hole 10a1 Inner peripheral surface 10b End surface 10c Stepped portion 10c1 First stepped portion 10c2 Second stepped portion 10d Outer peripheral surface 12 Thrust ring 13 Shaft 13a Outer peripheral surface 14 Flexible substrate 16 Radial dynamic pressure grooves 17, 27 Recessed portion 20 Lubricating oil 23 Tapered part (taper seal part)
50 Motor D Magnetic disk R Rotor part S Stator part △ Change amount α Recess occupancy ratio β Press-fit strength ratio

Claims (1)

A rotor portion including a shaft and a hub to which the shaft is fixed;
A motor base having a through hole, and a stator portion including a sleeve that pivotally supports the shaft and whose outer peripheral surface is fixed to the inner peripheral surface of the through hole by press-fitting or bonding,
A motor having a plurality of recesses extending in a rotation axis direction on either the inner peripheral surface or the outer peripheral surface in a range where the inner peripheral surface of the through hole and the outer peripheral surface of the sleeve are in contact with each other. .

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