JP2002543549A - Method and apparatus for balancing a spindle in a hard disk drive - Google Patents

Abstract

(57) Abstract: The balance of a disk is maintained, including a sensor for generating a signal indicating a deviation of the disk from a desired dimension, and a movable reference surface for moving the disk in response to the signal from the sensor. Device for centering. The apparatus includes a microprocessor connected to a balance analyzer. Feedback from the balance analyzer can be used to correct for set-up errors, thermal drift, and tool wear.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention generally relates to a method and apparatus for balancing a circular disk on a spindle. More particularly, the present invention relates to a method and apparatus for balancing one or more magnetic recording disks and spacer rings on a spindle for use in a computer hard drive.

[0002]

[Prior art]

A disk stack assembly ("DSA") is a major component of many computer hard disk drives. DSA generally comprises a plurality of alternating magnetic recording disks and spacer rings mounted on a spindle. Drive motors are usually (typically, revolutions per minute or "R
Rotate the DSA around the axis of rotation at high speed (represented by "PM"). If the center of mass of the DSA is not on its axis of rotation, an imbalance occurs. This condition creates unacceptable vibrations and noise, which leads to premature failure of the motor bearing and reduces user satisfaction.

One partial solution to this imbalance problem is the use of balance weights. These weights can be strategically added to or removed from the DSA to correct the imbalance. One problem with this solution is that the balance weight takes up space inside the drive enclosure. This space occupation problem is significant as disk drive manufacturers are constantly striving to increase the data storage capacity of the drive without increasing the size of the drive. Therefore, there is a need for a proposal for a balancing method that does not require a separate balancing weight, so that the designer can more efficiently use the available enclosure volume.

[0004] Another problem with using balance weights to balance the DSA is the complex and time-consuming installation process required by this solution.
When using balance weights, manufacturers usually (1) use mechanical fasteners to
Centering the ring and disc as accurately as possible; (2) clamping the spacer ring and disc on the spindle; (3) testing for any imbalance; (4) the necessary balance weight. And (5) retesting the DSA to verify that the drive is within its specifications. Therefore, DS
A faster and less complicated method for balancing A is awaited.

[0005] Another solution is to attempt to form the outer diameter ("OD") of the DSA in a concentric cylinder centered on its axis of rotation. This method typically uses two fixed rigid fasteners and one spring-loaded fastener for each disk and spacer ring. The rigid fasteners are generally positioned at an angle of 120 degrees to each other and are mechanically installed for the intended OD dimension. One problem with this method is that it only works successfully if the disks in the DSA all have the same OD. Another problem with this method is that the tolerance of the OD dimension of the disc is generally larger than the balance specification allows. As a result, OD tolerances prevent accurate centering and balancing. This problem becomes more acute as the drive industry increases the drive's specified speed. As can be seen from the above, it removes some of the inadequacies of the current system, produces accurate results, and has a low response time (turnaround time: TA).
In T), a proposal for a low-cost and versatile centering and balancing device is awaited.

[0006]

[Means for Solving the Problems]

The present invention provides a method and apparatus for balancing a disk drive disk stack assembly using a small offset value of a magnetic recording disk to compensate for unbalanced masses found near the axis of rotation. About. In embodiments, most of the mass of a disk has its outer diameter ("O") rather than its inner diameter ("ID").
D ") and the fact that an important, specific, unbalanced mass is directly proportional to its radial distance from the axis of rotation.

Accordingly, one embodiment of the present invention provides a sensor that generates a signal indicative of a deviation of at least one disk from a predetermined dimension, and moves at least one disk in response to the signal from the sensor. And a movable reference plane. This embodiment further includes a balance analyzer, a sensor, and a microprocessor connected to the movable reference surface. Feedback from the balance analyzer can be used to calibrate misaligned spacer rings or other set-up errors, unbalanced drive motors, and wear or time-varying errors. Embodiments of the present invention can be used to balance multiple disks and spacer rings stacked in a disk stack assembly. In one such embodiment, the disk stack assembly is divided into at least two groups. Thereafter, embodiments displace the position of the disks within each group based on the average deviation from the desired or expected dimension. This embodiment can be used to obtain either a one-plane ("stationary") balance or a two-plane ("coupled" or "dynamic") balance.

[0008] Another embodiment of the present invention generates a bias member adapted to bias at least one of the plurality of disks relative to a disk reference plane and a signal indicative of a deviation of each disk from a desired dimension. And a positioning member for moving a disk reference surface in response to a signal from the sensor, thereby balancing the disk stack assembly.

The present invention, in another aspect, relates to a method for balancing a disk on a spindle. One embodiment of the method includes generating a signal indicative of a deviation of the disk from a desired dimension, and moving the disk in response to the signal. The method further includes providing a movable reference surface and biasing the disk against the movable reference surface. The invention, in another aspect, relates to a method for balancing a disk stack assembly independent of variations in the outer diameter of the disk member. One embodiment of the method includes providing a plurality of movable reference surfaces, biasing the plurality of disks against the plurality of movable reference surfaces, and an average deviation of the plurality of disks from a predetermined dimension. And a step of moving a plurality of disks according to the signal.

The present invention, in two further aspects, relates to a method of centering a disk on a spindle and to at least one unbalanced disk stack assembly. One embodiment of a method of centering a disk includes providing a movable reference surface, biasing the disk against the movable reference surface, and generating a signal indicative of a deviation from a predetermined dimension of the disk. And moving the disk in response to the signal. One embodiment of a disk stack assembly includes a spindle and an offset disk rotatably coupled to the spindle. Offset in this embodiment
The disc compensates for at least one imbalance. Another aspect of the invention is a method of centering a disk on a spindle, one embodiment of which provides a movable reference surface, biases the disk against the movable reference surface, Generating a signal indicating a deviation from a predetermined dimension of the disk, and moving the disk in response to the signal.

One feature and advantage of the present invention is that the magnetic recording disk is displaced in order to balance the DSA, thereby eliminating the need to specify a location for placing the balance weight. This saves volume space inside the drive enclosure. Another feature of the present invention is that it can compensate for set-up errors and wear. This feature is balanced
The accuracy of the process can be increased. These and other features, aspects, and advantages of the present invention will be better understood with reference to the following description, appended claims, and accompanying drawings.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an embodiment of an apparatus 10 used to balance one or more disks 12 about a rotation axis 13. Each disk 12 has a generally cylindrical inner surface 14 defining (defining) a central opening 15 and two substantially flat surfaces 16, each of which at least partially forms a magnetic recording surface. 16 and a substantially cylindrical outer edge 20. The outer edge 20 is predetermined or designated (
That is, a circumference having an outer diameter (“OD”) different from a normal value is defined. Apparatus 10
Includes two movable cylindrical reference surfaces 24 and 26, and a movable bias member 28, which are slidable mounts 30, 32 and 3, respectively.
4 and fixedly attached. The apparatus 10 also includes a position sensor 36, which includes a transducer 38 mounted on a slidable mount 34 by a mounting bracket 40. The position sensor 36 is connected to the microprocessor 41 by an electric connector 42.

The biasing member 28 is any device that can hold the disk 12 against the reference surfaces 24 and 26 during operation. A suitable biasing member 28 is a leaf spring. Leaf springs are desirable because they are relatively inexpensive and can compensate for some misalignment of the initial disk 12 arrangement. However, any biasing member 28 that can assist in holding the disc 12 against the reference surfaces 24 and 26 also falls within the scope of the present invention. For example, biasing member 28 may be a common planar member biased by a compression spring or air cylinder.

As the position sensor 36, any device that can measure a deviation between the actual disk OD and a desired (or standard) disk OD can be employed. The deviation between them may be measured directly or indirectly. For example, a direct measurement can be achieved by measuring the distance to the outer edge 20 of the disk 12. Indirect measurement can be achieved by measuring the distance to the bottom surface 44 of the biasing member 28. The position sensor 36 needs to provide accurate and precise results with a relatively short sampling period. Suitable transducers 38 include, but are not limited to, non-contact sensors such as laser interferometers, diode arrays, or eddy current transducers, and contact bases such as linear variable differential transformers ("LVDTs"). Is applicable.

The movable reference surfaces 24 and 26 and the biasing member 28 support the disk 12 while the disk 12 is measured and positioned. The reference surfaces 24 and 26 are preferably made of a relatively rigid material having sufficient durability and corrosion resistance, and a low coefficient of thermal expansion. One example of a suitable reference surface 24 and 26 is a cylindrical column made of nickel-plated steel. This embodiment is desirable because it allows the disk and spacer ring to be held in place while secured. That is, the disk and spacer ring move slightly axially when secured to the motor hub by a preheated collar, tether collar, or other suitable method. Therefore, the cylindrical reference surfaces 24 and 26, and the planar biasing member 28 are preferred because they allow the disk and spacer ring to move axially without changing their center position. . However, reference surfaces 24 and 26 made of other materials or having other shapes and orientations are within the scope of the present invention.

The slidable mountings 30, 32 and 34 are provided in a controlled manner in a reference plane 2.
4 and 26, and any device capable of moving the biasing member 28. Mounts 30, 32 and 34 include actuator devices (not shown) that can separately or integrally slide the mount in the X direction. Suitable actuator devices include, but are not limited to, cams, gears, powered by electromechanical actuator devices, hydraulic or electric motors, and controlled by suitable devices such as linear encoders or LVDTs. Or screws.

Referring to FIGS. 2A and 2B, a method using an embodiment of the present invention for centering the OD of the disk 12 on the DSA rotation axis 13 will be described. FIG. 2A
Shows a standard normal disc of radius R ₀ with the center 52 of the OD aligned with the axis of rotation 13. When biasing member 28 presses the disc 12 on the reference surface 24 and 26, the position sensor 36 to measure the distance X ₀ between the (bottom 40 of the or biasing member 28) the outer edge 20 of the transducer 38 and the disk 12 Can be. FIG. 2B shows a disc 12 having a radius R slightly greater than the desired radius R ₀ . When the biasing member 28 presses the disk 12 against the reference surfaces 24 and 26, the center 50 of the actual OD of the disk is displaced from the axis of rotation 13 by a distance "d". This displacement “d” is calculated in this embodiment using the equation d = 2 · s / 3. Here, “s” is a change in the distance between the actual disk and the standard disk measured by the position sensor 36. However, columns 24 and 26,
And if the biasing member 28 is other than 120 degrees apart, another equation should be used. The two reference surfaces 24 and 26 and the biasing member 28 are moved along the "X" axis to remove the displacement "d". That is, the disk 12 is displaced until the center 50 of its actual OD is at the same position as the rotation axis 13.

Some current hard disk designs arrange several magnetic disks in a disk stack separated by a spacer ring. This disk stack should be integrally balanced and centrally located. This step can be accomplished in several ways. One suitable method places each disk in a disk stack using the steps described with reference to FIGS. 2A and 2B. While this method is effective, it is complicated and time consuming because each disk is moved separately. In a second method, all of the disks 12 in the disk stack are displaced based on their averaged displacement d. This method results in one plane (or “stationary”) balance,
If the height of the center of the axis of the disc pack is small compared to the disc radius (ie, "low aspect ratio"), it is a practical solution. The third method described with reference to FIGS. 3A-3C can be used on large aspect ratio disc packs (ie, packs with four or more discs 12). In this method, balancing and centering are performed along the entire length of the axis of rotation by appropriately positioning the group of magnetic recording disks. The centering and positioning of the axis of inertia (mass) parallel and coincident with this axis of rotation is called coupling (or "dynamic") equilibrium.

FIGS. 3A-3C are plan, side, and front views of an embodiment used to balance a DSA having two or more separate disks 12. The device 10
Transducer 38 and bias member 28 for each disk 12
including. The disk 12 is divided into an “upper group” 60 and a “lower group” 62. Each group 60 and 62 has its own reference surface 24 and 26 which is mounted on its own slidable mounting 30 and 32. In order to obtain a connection balance, the second method described above is used to balance each group 60 and 62. In situations where the motors and / or spacer rings are sufficiently alone to achieve the desired overall DSA equilibrium, the disks 12 in each group will have an average displacement of the disks 12 in that group. By moving the stop in the X-axis direction by d, it is centered with respect to the rotation axis 13.

Each group 60 and 62 in this embodiment has the same number of disks 12 or one more than the other group to accommodate a variable number of disks in a pack.
Have more disks. The displacement calculation for each group 60 and 62 is performed including all the disks 12 in that group. In this embodiment, two groups are used, but those skilled in the art understand that dividing the stack into any number of groups is within the scope of the present invention. Will be done. Larger numbers of groups can produce more accurate results, but require additional hardware and increase complexity. Those skilled in the art will appreciate that the method can be used to balance a disk pack holding any number of disks 12.

The present invention also provides a method for displacing the magnetic recording disk 12 from the rotating shaft 13 by an appropriate amount, thereby causing a repetitive imbalance (imbalance) such as a misaligned spacer ring.
Can be used to correct for Since the spacer ring is approximately one-tenth the mass of the hard disk, any false centering of the spacer ring can be easily offset by shifting the hard disk 12. That is, if the spacer rings are located at the same distance and angle of rotation within the subassembly from one subassembly to the next, the spacer rings need not be exactly centered. This constant but repetitive mis-centering of the spacer ring with respect to the axis of rotation can lead to an imbalance from one imbalance.
The offset is achieved by correcting the hard disk in the 80 degree direction by a certain small amount. Thus, in one embodiment, first, Bowen et al.
US patent application Ser. No. 09 / 505,033 filed on Mar. 16 (“Bowen”);
), The angle and magnitude of the imbalance are measured by using a balance analyzer (not shown). That patent application is incorporated herein by reference in its entirety. The apparatus 10 then uses the information gathered by the balance analyzer and the known formula to calculate the appropriate disk offset and offset the disk accordingly. For example, an imbalance of 0.5 g-mm (gram-millimeter) in the direction of 273 degrees would cause a 50 g disc to be 93
It is corrected by shifting in the direction of degrees by 0.01 mm. Another embodiment measures the OD of the spacer ring in the same manner as described with reference to FIGS. 2A and 2B. Then, the average diameter d is calculated for the spacer ring.
The disks and / or rings are offset to null the mean diameter d of the spacer rings and their associated mass.

[0022] Motor imbalance is also a significant contributor to repeated drive imbalances in certain harsh applications. As with the misaligned spacer ring, the present invention provides a known motor unbalance (magnitude and angle) by offsetting the disk 12 by an appropriate amount 180 degrees from the unbalanced condition. ) Can be corrected. In one embodiment, a set of calibration signal transducers that sense vibrations that occur when the motor is operated;
Or the magnitude of the motor imbalance in relation to a readable mark ("index mark") permanently placed on the spindle using a standard balance analyzer, such as a transducer indicated by Bowen or the like. And the angle.
This balance analyzer is located at any convenient point in the assembly process, and usually before the disks and rings are installed. The data from the balance analyzer is provided to the microprocessor 41 and used to calculate the appropriate disk offset using known formulas.

[0023] Companies that manufacture motors typically use balance analyzers to achieve their own motor balance specifications. Thus, providing the motor manufacturer with its data along with each motor shipped can eliminate the need for a motor balance analyzer on the DSA assembly line. Thus, in one embodiment, a machine readable tag, such as a bar code, is used to associate each particular motor with its corresponding imbalance data. This embodiment is desirable because it eliminates the balancing step in the DSA assembly line.

The present invention can also correct for time-varying errors such as wear and thermal drift. One embodiment detects long-term changes by recording data from a balance analyzer on a computer-readable medium.
This embodiment then compares the average displacement of some previously produced disk packs with the average displacement of some recently produced disk packs. However, in other embodiments, to identify and quantify data changes,
More sophisticated statistical techniques can be used. If a change is identified, the microprocessor 41 can calculate an appropriate disk offset value to correct for the change. This feature can reduce the "time to failure" due to having to replace parts and / or recalibrate the device 10, which is consequently simpler and more reliable. This is desirable because the manufacturing process can be performed.

The present invention offers a number of advantages over known disk balancing and centering devices. For example, the disclosed apparatus 10 measures the OD dimension of each individual disk 12 in a pack before centering. With this approach, a high degree of equilibrium can be achieved even with a sufficient range of OD dimensions in one pack. Furthermore, the present invention eliminates the need for a tool to add (or remove) the balance weight, since the magnetic recording disk is used as the balance weight. The advantages are capital cost, labor cost, and response time (TAT
) To decrease. Further, the disclosed centering device simply requires feedback from a balancing tool in the assembly line. This results in eliminating the need for a second balancer, saving additional capital costs, labor and throughput.

Although the present invention has been described in detail with reference to particular embodiments, various modifications are possible. For example, while the embodiment shown in FIGS. 1-3 merely displaces the disk 12 in the X-axis direction, those skilled in the art will appreciate the principles described in this disclosure. Will be understood to be applicable to displacing the disk 12 along any axis of. Also, the reference planes 24 and 26 may be arranged at other angles with respect to each other, or additional reference planes may be added. Further, the present invention can be used in various balancing and centering applications other than computer hard drives.

[0027] Thus, those skilled in the art will appreciate that the accompanying figures and this description illustrate and describe embodiments of the present invention and the features and components thereof. . With respect to the means for fasteners, if not specifically stated otherwise, secure, attach, attach, or connect components of the invention to form a mechanism as a whole. Unless otherwise stated, such means include machine screws, nuts and bolts.
It is intended to include conventional fasteners, such as connectors, machine thread connectors, snap rings, screw clamps, rivets, nuts and bolts, toggles, pins, and the like. Where appropriate, components may also be welded,
The connection may be made by soldering, hard brazing, frictional fittings, adhesives, or the like.
Unless specifically disclosed or otherwise indicated, the materials for making the components of the present invention are selected from suitable materials such as metals, metal alloys, fibers, polymers, and the like, Appropriate manufacturing or production methods are used, including casting, extrusion, molding, and machining. Further, references to front and back, right and left, top and bottom, and top and bottom are intended for convenience of description and are not intended to limit the invention or its components to any fixed position or spatial direction. It does not do. Therefore, the embodiments described herein are to be considered in all respects as illustrative rather than restrictive, and are intended to be references to the appended claims to determine the scope of the invention. Should.

[Brief description of the drawings]

FIG. 1 is a plan view of one embodiment of the present invention used to center a disk.

FIG. 2A is a plan view of the embodiment of FIG. 1 with a standard disc. FIG. 2B is a plan view of the embodiment of FIG. 1 with an actual disk.

FIG. 3A is used to balance a disk stack assembly;
It is a top view of an embodiment of the present invention. FIG. 3B is a side view of the embodiment of FIG. 3A showing a plurality of planar bias members. FIG. 3C is a front view of the embodiment of FIG. 3A.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, TZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL , IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, UZ, VN, YU, ZW (72) Inventor Wheeler, Michael Earl Minnesota, United States of America State 55559, Manterville, 231 Avenue 60661 (72) Inventor Armand, Robert Duane 55116, Rochester, Minnesota, USA 3116 F-term (reference) 5D109 DA05 DA13 5D138 UA11 UA24

Claims (24)

[Claims] 1. An apparatus for balancing at least one disk on a spindle, wherein the sensor is connected to the at least one disk and generates a signal indicative of a deviation from a desired dimension, and in response to the signal from the sensor. And a movable reference surface for moving at least one disk. 2. The apparatus according to claim 1, further comprising: a biasing member for biasing at least one disk with respect to a movable reference plane. 3. The apparatus of claim 1, wherein the apparatus further comprises a plurality of disks arranged in a disk stack assembly. 4. The apparatus of claim 3, wherein the disk stack assembly is divided into at least two groups, and wherein the movable reference surface is configured to move the at least two groups within at least two groups based on an average deviation from a desired dimension. An apparatus characterized by being configured to move each group. 5. Apparatus according to claim 3, wherein the movable reference plane moves a plurality of disks to achieve equilibrium in one plane. 6. The apparatus of claim 3, wherein the movable reference surface is configured to move the plurality of disks to achieve a coupled balance. 7. The apparatus of claim 1, wherein the apparatus further comprises a microprocessor connected to the sensor and the movable reference surface. 8. The apparatus of claim 7, wherein the apparatus further comprises a balance analyzer connected to the microprocessor for producing a signal indicative of the imbalance. 9. The apparatus of claim 8, wherein the signal from the balance analyzer is a signal indicative of a recurring imbalance condition. 10. The apparatus of claim 8, wherein the signal from the balance analyzer is:
An apparatus wherein the signal is indicative of an unbalanced spacer ring. 11. The apparatus according to claim 8, wherein the signal from the balance analyzer is:
An apparatus, wherein the signal is indicative of an unbalanced motor. 12. The apparatus of claim 8, wherein the signal from the balance analyzer is:
An apparatus, wherein the signal is a signal indicating a setup error. 13. The apparatus of claim 8, wherein the signal from the balance analyzer is:
An apparatus characterized by being a signal indicative of wear. 14. The apparatus of claim 8, wherein the signal from the balance analyzer comprises:
An apparatus, wherein the signal is indicative of a thermal drift. 15. The apparatus of claim 8, wherein the microprocessor is configured to calculate a disk correction value for dynamically balancing a plurality of disks arranged as a disk stack assembly. An apparatus characterized by using a signal from a computer. 16. The apparatus according to claim 1, wherein at least one disk comprises:
An apparatus comprising an outer surface defining an outer diameter, wherein the desired dimension is the outer diameter. 17. A disk stack assembly balancing device, comprising: a biasing member adapted to bias at least one of a plurality of disks against one of a plurality of disks relative to a disk reference plane; An apparatus, comprising: a sensor for generating a signal indicative of the signal; and a positioning member for balancing a disk stack assembly by moving a disk reference surface in response to the signal from the sensor. 18. A method for balancing a disk on a spindle, comprising: generating a signal indicative of a deviation of the disk from a desired dimension; and moving the disk in response to the signal indicative of the deviation. A method comprising: 19. The method of claim 18, further comprising: providing a movable reference surface; and biasing the disk against the movable reference surface. 20. The method according to claim 18, wherein the disk includes an outer surface defining an outer diameter, wherein the desired dimension is the outer diameter. 21. A method for balancing a disk stack assembly independent of variations in the outer diameter of a disk member, the method comprising: providing a plurality of movable reference surfaces; Biasing the plurality of disks, generating a signal indicating an average deviation of the plurality of disks from a predetermined dimension, and moving the plurality of disks in response to the signals. how to. 22. The method of claim 21, further comprising: dividing the plurality of disks into at least two groups; and generating a signal indicative of a mean deviation of a first group in the at least two groups. And moving the first group in response to a signal indicative of a mean deviation of the first group. 23. A method for centering a disk on a spindle, providing a movable reference surface, biasing the disk against the movable reference surface, and deviation of the disk from a desired dimension. Generating a signal indicative of: and moving the disk in response to the signal. 24. At least one unbalanced disk stack assembly, comprising: a spindle; and an offset disk rotatably coupled to the spindle for calibrating at least one unbalance. Disc stack assembly.