JPH08107663A - Actuator - Google Patents

Abstract

PURPOSE: To avoid breaking resonance frequency which is related to a disc device and tends to be generated in a high-frequency range by a method, wherein a drive device is linked with a driven device only with a linking means and, furthermore, the both devices are insulated from each other to transmit ordinary vibration and high-frequency vibration is suppressed for braking. CONSTITUTION: A drive device D is linked with a driven device only with a linking means. The drive device D generates ordinary vibration upto a predetermined maximum frequency and generates a high-frequency resonance vibration or other breaking vibration at a predetermined excessive frequency, which is higher than the maximum frequency or in a frequency range higher than that. An elastic bonding means bonds the drive device to the driven device in a viscous elastic linking part V-E and, since the elastic shearing is produced in a frequency range of the excessive frequency and higher, the vibration is attenuated between both the devices. By insulating the driven device from the drive device D to a satisfactory extent, the linking means transmits ordinary vibration with relatively little variation and conversely, suppresses the high-frequency vibration to brake.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to electromagnetic actuator components, and more particularly to a new and improved linear voice coil component adapted for reciprocating magnetic conversion means relative to a magnetic recording surface.

[0002]

BACKGROUND OF THE INVENTION Present day computers typically use magnetic disk files for recording and storing data. Disk files have the advantage of facilitating data transfer to randomly selected address locations (tracks) without the need for "serial seek" like magnetic tape. Such a translator must move between selected address locations (tracks) with high precision and ultra high speed. That is, the system tracks the transducer between the address locations at very high speed and in close contact.
You must move between addresses with high density. This constraint becomes more stringent as the density of trucks increases.

The disk file system mounts a conversion head on an arm that is typically carried by a block supported by a carriage. This conversion head is installed on the truck and usually moves back and forth by a common actuator. The present application relates to improvements in the capabilities of such actuators, particularly linear voice coil positioners. Conventional Positioners : Actuators commonly used in magnetic disk files have some severe requirements. For example, typical of these systems include stacks over several magnetic disks. Each disk has hundreds of concentric recording tracks, and a head carrying arm is provided to access each pair of opposed disk surfaces. This arm typically carries 2 to 10 heads and reciprocates with a stroke of about 1 inch to position it near a selected track.
Thus, in order to shorten the access time, most of which is used for head positioning, it can be seen that ultra-high speed transfer and high positioning accuracy are required.

Moving the transducer between data positions at very high speed,
Accurate positioning between close track addresses is very important for an actuator system and becomes more troublesome as the track density increases. With fast access, computers can process data as fast as possible. The processing time of the computer is expensive, so any large delay that exceeds the data processing time will add huge cost (the "travel time" between head to track and track to track is "dead time" as far as data processing is concerned. is there).

At present, there is a tendency to further increase the track density, increase the capacity of the device, and shorten the access time.
Of course, as the track density increases, an actuator mechanism for accurately positioning the conversion head on any selected track so that the signal will not be significantly distorted or recorded or read without proper positioning control. The precise control of is necessary.

Computer manufacturers typically impose specifications requiring movement between tracks in a few ms or less. Such high speed movement is a very demanding requirement for actuators. It requires a relatively lightweight and powerful motor, even with the weight of a carriage. Another requirement for such head positioning is to have a relatively long stroke (a few inches) to reduce the number of heads required per disk.

Many prior art devices have been disclosed, including those intended for use in magnetic disk memory systems. For example, U.S. Patent 3,135,880
No. 3,314,057; 3,619,673; 3,922,720; 4,0
01,889; 3,544,980; 3,646,536; 3,665,433
No .; 3,666,977; 3,827,081; 3,922,718.

[0008]

Voice coil motors : Those skilled in the art are familiar with linear magnetic actuators, especially those adapted for reciprocating magnetic transducers such as on magnetic disk surfaces. Such an actuator is a well-known voice coil motor (VCM or moving coil actuator device).
Is. This structure is known to consist of an E-type magnetic structure including a central core in which a moving coil is movably mounted. The "operating magnetic flux" circulates from the magnet, traverses the gap between the pole section and the core, and is interrupted by the coil. When the coil is driven by a predetermined current and crosses the central magnetic flux, when a current I is passed through a coil of length L under a predetermined magnetic flux density B, a constant force of F = BLI is generated, and an arrow A in the figure
A motion as indicated by x is induced. As is well known, the operating direction depends on the polarity of the current with respect to the magnetic flux.

A "voice coil" motor (VCM) consists of a solenoid such as that used to drive audio speakers. In disk devices, a magnetic read / write head contains a moving electrical coil, usually in a magnetic field, that contains a moving electrical coil that is supplied with a current of a predetermined strength and polarity.
It is carried by a carriage driven by a C motor. This magnetic field is produced by permanent magnet means arranged around the moving coil.

Such a VC linear positioner presents certain disadvantages. For example, the need for undesired weight and high power, and the demand for power to obtain maximum acceleration puts a heavy burden. Such VC actuators are not particularly effective at converting electrical power into power.
The present invention is shown to improve output capability and control the operation of the apparatus for VC positioning.

Such actuators usually have problems with "eddy currents". Eddy currents create a "drag" on the actuator, hindering the acceleration required for speed.

[0012]

A feature of the present invention is to avoid the destructive resonant frequencies associated with disk devices that tend to occur at high frequencies. In particular, the viscoelastic connecting member VE provides a selective insulator, which strongly connects to the inner head carriage structure at low frequency vibrations and not at high frequency vibrations.

[0013]

DETAILED DESCRIPTION Eddy current drag : Those skilled in the art know that voice coil motors are prone to eddy current effects. Usually we try to minimize eddy current effects as much as possible. For example, moving a device as discussed below at high actuator speeds without reducing speed can be very catastrophic. Although not yet clear here, in some cases, for example only at "high speed", the eddy current drag can easily be adapted to brake the actuator.

The general goal here is to promote "vortex drag" at high actuator speeds (eg, about 55 to 60 ips) to deliberately increase drag with simple configuration changes. 1 to 4 show a special embodiment of the invention named Actuator (core device) A. Here, the effect of eddy currents is controlled.

With particular reference to FIGS. 1, 2 and 4, the actuator core device A comprises a central hub portion Ch mounted on the carriage means (not shown), as is well known, The electromagnetic force caused by the current flowing through the coil CL causes a controlled movement along the axis AX-AX. As shown in FIG. 4, the hub Ch is mounted on four arms C-BR that are equidistantly spaced, and each arm C-BR carries its own actuator arm. I understand. This time, h for each arm in Figure 2
A read / write head device, such as the one briefly shown in Figure 3, is installed.
It can be seen that it moves linearly in the X direction. According to the present invention, the arm ring C-BR is wound around and connected to the installation ring CR. This time the ring CR is connected to the outer "damping ring" member DR "viscoelastically". Ring DR is a coil installation drum
Part of D, with flat tail part DM, has actuator coil CL. The connection between the coil installation DM and the annulus DR is according to the invention by means of "rib-like means" DR-R which are installed at equal intervals around the circumference of the drum D. The coil CL may be configured in a well-known shape. For example, the drum surface DM is closely wound with an insulator, and the current input end of the coil crosses one of the ribs DR-R and the ring DR. It is guided to the elastic strip conductor means CS installed above.
The strip conductor CS can be connected at its opposite end to a known current input terminal. The band-shaped conductor means CS may be installed on the ring DR via a known connecting arm CS-BR as well shown in FIG. The hub Ch and the arm CS-BR may be a non-magnetic, light and hard metal such as an aluminum alloy having a cobalt-chromium surface. On the other hand, the drum D is preferably made of aluminum or a non-magnetic metal. Drum Ring DR : As one notable feature, the drum ring (braking wheel) DR has a predetermined width W (as in FIG. 3) and has a cut across the width. The gap is a predetermined gap g-
1 (FIG. 5) and during high speed operation (when coil CL is interacting with a known outer magnet, not shown here), increases resistance and increases eddy current braking force.

The ring DR may be thick enough to maintain the shape.
For example, 0.1 to 145 grams as shown here.
With a 0.2 Watt actuator, the drum D is about 2.5 to 3 inches long (DM under CL is about 3/4 inch wide).
About 40 to 60 ips along the axis of AX-AX for about 1.2
The device would have to be reciprocated by an inch, which appears to be satisfactory with a ring DR of about 2.0 inches in diameter and a gap g-1 of about 0.04 inches long. Width W
, Or increasing the length of gap g-1,
Resistance increases and eddy current braking increases.

The technician is aware that a predetermined summed resistance (see FIG. 11)
It can be seen that by changing the R ₁ , R ₂ of the vortex braking force F _BR sufficient to reduce excessive speeds (V _{max in} FIG. 11) to safe levels. Thus, it can be seen from FIG. 11 that the summed resistance R ₂ gives a certain braking force F ₁ , while the higher resistance R ₁ gives a greater braking force F ₂ . It is clear that the adjustment of the control gap g-1 and the thickness of the ribs can be used to control the vortex braking force. Rib-like member DR-R : As a related feature, the connecting part of the drum D that connects the ring DR and the coil supporting surface DM is connected to the set of rib-like members DR-R that are cut out and relatively thinly extended in the axial direction. There is. Since the width (thickness) and the thickness are sufficiently small, the resistance (eddy voltage V) of the entire housing increases, and the high operating speed (for example, about 60 to 70 ips; 90 + ips to 70).
It has been studied to decelerate to ~ 75 ips) and increases the braking force. The length of the ribs should be reduced as much as possible to keep the drum short and the resonance frequency high.

For example, in the embodiment shown in FIGS.
The width WR of the rib-like member DR-R is about 1/8 inch. However, we have found that doubling this width to about 1/4 inch can reduce the eddy current drag by about 15% at intermediate speeds (20-40 ips). Further, as described below, it was also noticed that the drum DM and the ring DR are connected to each other by a thin rib-like member to weaken heat conduction from the coil CL to the viscoelastic connecting portion VE of the ring DR and the ring CR. This is of great help, especially as the coil CL becomes very hot (eg above 180 ^° F), such as during a "seek" operation.

In a sense, the above-described notched configuration of the annulus DR applies to "coarse adjustment" of eddy current values, whereas the configuration of thin rib members is "fine adjusted". For engineers, the effect of controlling eddy currents to reduce drag at normal processing speeds and maximize drag at higher speeds is generally satisfactory. It is also satisfactory that this is done by a simple structural adjustment (of the ring and the rib-like member), and the simplicity of this automatic brake control is also satisfactory. As a distinctive feature of the viscoelastic connecting member VE , the ring DR is connected to the support ring CR by "viscoelastic" means, and acts as a selective "insulator" or "low pass filter", in short, as is well known, the drum D.
Effectively transmits only predetermined low frequency vibrations to the inner structures (Ch, C-BR etc., especially the arms and heads carried thereby).

The rings DR and CR, together with the viscoelastic connecting member VE, provide a selective damping ring or insulator, and are strongly connected to the inner head carrier structure at low frequency vibrations and not at high frequency vibrations. This is especially important to avoid the destructive resonant frequencies associated with disk devices that tend to occur at high frequencies. As such, the VE-coupling arrangement is specifically designed to avoid coupling at known resonance frequencies. The technician has found that the connecting member VE becomes a “coupling” that is relatively stiff and force-transmittable at a given low frequency (up to about 60 KH _{Z in} this example), as seen in FIGS. 4 and 6, while At high frequencies (including high shear), the connecting member VE is designed to shear and act as an elastic damping material that absorbs most of the high frequency strong vibrations from the drum D. Technicians are aware that shear braking is superior (eg, compression braking).

The connecting member VE is realized by, for example, a product of 3M Co. of Minneapolis, and the "Isotax / chlorpicrin-added adhesive replacement tape (Adkesnie Tr) is used.
ansler Tape with Isotacs PS Additine), Y947
3 "is an elastic cloth with a width of return DR and CR of about 10 mils and adhesive on both sides. Normal 3M tape is about 10 mils thick, but hard as described below. Can be compressed to about 9 mils thick without overwhelming.

This tape fulfills the invention satisfactorily and gives a very satisfactory viscoelastic connection, exhibits surprising hardness at low frequencies and good insulating elasticity (shear damping) at high frequencies. For example, under static bench testing, the return DR was rigidly connected to the CR and reduced about 100 pounds of axial force without causing more than a small shear braking. Even if it exceeds this, the elastic limit cannot be exceeded. Technicians are "adhesive tapes" that have been used for stickiness only.
Is amazed at how effectively it works as shear damping of vibration. Of course, similar adhesive tapes or the like with little or no elastic properties are not preferred (eg perfectly hard cloth). Filter Performance, FIGS. 7 and 8 : The intended actuator servo system may be a "closed loop" servo of the type shown in FIG. 7, the input having a negative feed back (-H) as is known. Amplified by a positive gain amplifier G along with the feedback loop. An equivalent closed loop system consists simply of an amplifier of gain G / (1 + GH), the gain becomes infinite as the product GH goes to -1, and of course the system becomes unstable.

FIG. 8 is a plot of gain and phase with respect to frequency. Gain (slope m = a) is lowered at a predetermined minimum frequency of about -2 to (here about 6KH _Z), resonance occurs in a manner more shown in 8KH _Z. A major goal of system designers is to keep system behavior from breaking (crossing) the zero decibel axis through such soullike resonances. Of course, that is the objective effect of our method, the "filter" using the viscoelastic means VE described above.

In the gain plot of FIG. 8, there is the normal process along curve a (which does not use the filter connecting member VE of the present invention) and there are some resonance peaks as shown by curve b. To do. However, the present invention (the connecting member V-
When corrected by the use of a mechanical filter with E) it follows curve d. That is, the resonance peak is controlled, the inclination (dB / f) becomes steeper per 6KH _Z. This is one of the effects seen for using the connecting member VE (similarly with the electric filter, the curve c
It is also possible to give a similar effect as shown idealized to.

In comparison, the prior art method of manipulating such a resonance problem has been to provide the drive amplifier with an electrical feedback and reduce it at the resonance frequency.
This, as is known, gives undesirable results such as a noticeable "loss of phase margin" if there is something that must be kept to a minimum. This is simply shown by the curve cc in the phase plot of FIG. Here, “phase margin loss”
Are much larger than those using the present invention (eg, at dB = 0, the loss is L ₁ , and at 7-8 KH _Z is L
₂ ).

The engineer now knows that the problem is that there is a maximum resonance on the phase curve, for example giving a gain of -1 at phase 180 ^° . In FIG. 8, the phase margin is indicated as L ₁ at zero decibel. As the engineer appreciates, it is desirable to minimize the phase margin there (or beside it) so that the system does not lose stability. Ideally, the connecting member VE provides the above result. That is, the connecting member VE is sufficiently hard unless it is subjected to "excessive" vibrational force, and furthermore, due to elastic shear, it has some elasticity and weakens the amplitude. Preferred assembly of the return and connection member VE : As another feature, a simple and preferred method of assembling this connected braking structure was found.

As shown in FIG. 6, the connecting member V-
E and the ring CR are placed in the braking ring DR, where the braking ring DR has an inner diameter of 1.944 inches and the floating ring CR has an outer diameter of 1.924 inches when stationary and without pressure. This leaves approximately 10 mils (0.010 inches) of gap radially between the CR and DR. In this case, the above-mentioned 3M # of about 10 mils thick under static conditions (on both sides with all fabrics bonded)
It has been found that a method of using a tape VE such as Y9473 and sticking it inside the ring DR is advantageous, as shown briefly in FIG. Then, make an axially transverse cut (eg, about 40 mils wide) in the ring CR and squeeze to reduce the outer diameter for easy insertion into the tape VE. In this way, press the CR to close this cut, and tape VE
Insert a CR in the region (not filled, but the CR break g-2 does not match the break g-1 on the ring DR). When CR is released, it will be pushed out by the natural elasticity and the tape VE will be thinned from 10 mils to 9 mils while the tape VE is pressed and the elastic cloth remains elastic. The elastic cloth should not be pressed too strongly so as not to lose the required elasticity. Of course, the ring CR should be chosen to give proper resilience to the tape VE (when it is scored, squeezed and released) and to be lightly squeezed (eg, no more than about 6-7 mils thick). , Otherwise it will be too hard). Furthermore, it has been found that, surprisingly, the nicked ring CR does not impair the low / high frequency characteristics of the operating device described above. Result : The above-mentioned connecting member VE offers surprisingly good benefits, especially for its simplicity.

For example, a test was conducted to compare the frequency characteristics of this embodiment with a control device lacking a braking structure (VE and CR on DR). In the vibration test, the current is applied to the coil
CL was excited and the device was oscillated in the range of the prescribed frequency.
The accelerometer was installed in the carriage (Ch etc.). The output of the accelerometer was plotted as shown in FIG. 9B as a frequency characteristic of the "control" device (without the viscous connecting member VE) and as shown in FIG. 9A for the device with connecting member VE.
The improvement is obvious, especially in view of the relatively few simple modifications to the actuator structure.
Correction: Technicians can selectively couple the (vibration) energy from this result to the sensitive structure (such as the carriage Ch above) that is connected to it and at high frequencies (eg at resonance) it will It will be appreciated that can also be achieved with other viscoelastic means, such as that which acts as an elastic shearing force and acts as a "filter" as described above (eg, to dampen resonant vibrations). Others come to mind, for example, a thin elastic cloth held in a ring of vibrating parts (such as DR, CR). And, in some cases, when using a tape as described, one may choose based on desirable "filter characteristics", etc., by the gaps that allow insertion of a given thickness between the rings of the components. Let's do it. Also, in some cases, one or more tapes and an inner ring may be further connected within a floating ring such as a CR to create a "mixture filter." Overview : One of ordinary skill in the art will appreciate that an improved control drag actuator with a modified eddy current configuration is more effective than conventional constructions with little or no substantial change. This actuator provides the desired automatic "self-braking" at high frequencies, eg against "runaway vibrations". Thus, it can be seen that this actuator component is "well balanced" with improved linearity and stability and more efficient use of magnetic flux.
Also, in the characteristic part of the eddy current control (for example, the supporting member),
In particular, since cooling air enters through the gaps of the supporting ribs, it acts as a "filter" (for example, by providing excessive insulation to the VE connection below the ring DR and protecting the tape from heat from the coil). Works as well.

It will be appreciated by those skilled in the art that the design of this actuator may be variously modified within the technical concept including the whole concept. It should be emphasized that the viscoelastic coupling member VE can and must be used as the only joint between the driven and driven configurations to achieve the desired effect. For example, the previous example where VE is the only junction of the CR and DR rings, and the tape is used primarily for the CR and DR connection, and the viscoelastic connection is essentially a hard metal connection. The "control unit" (CU) when "avoided" was tested and compared.

12A and 12B show a clear contrast. In FIG. 12A, there are two cases of vibration (displacement / current) in this VE connection example (curve c) and in a non-contact structure without a tape or in the case where metal connection is made between CR and DR (curve 2a). , Is plotted against frequency. The case of the control unit (CU) (curve c) is likewise compared in FIG. 12B. The contrast is striking and makes it very clear what benefits are gained by simply using the connecting member VE (eg the tape described above) as the only connecting point, rather than simply adding a metal connection. For example, looking at the "effect" of the steep slope provided by curve c near f = f ₁ , some "braking" can be seen but without the "roll-off" provided in this example. Compared to the curve b (CU), no matter how f =
Is the next resonance level near f ₂ pushed down? This is why it emphasizes that the connecting member VE, which was used as the only joint, has achieved a significant "insulating" or "quasi-filter" function.

In addition, the technician is aware that similar electrical filter means
Therefore, although resonance can be weakened (by increasing Q),
This "roll-off" effect cannot be provided.
I understand. This means that the connecting member V-E is
Not only weakens resonance by wave number, but also insulation (roll-off)
It has a remarkable and unique effect. Conclusion : Technician Actuator of this controlled drag
But the converter parts of devices such as disk drive devices
How well it is combined to drive
I understand. Especially, this actuator is praised by those skilled in the art.
As a result, the drive capacity and cost effectiveness of the converter actuator
Used to improve and improve the flux capability accordingly
I know what I can do. Technicians are
The "Cheater" is a step mechanism on the rotary actuator.
Other like load-carrying loads.
Also understand that it can be used. Preferred disclosed herein
The embodiment is merely an example, and the structure and arrangement are included in the embodiment.
And many modifications and variations in use are possible.

Further modifications of the disclosed embodiments are possible. For example, the means and methods disclosed herein also apply to the stable positioning of similar systems and other surrounding transducers and associated loads. In addition, as a related specific example, like an object in which data is optically recorded and reproduced,
It may be used to position transducers forming other recording / playback systems.

[0033]

According to the present invention, the destructive resonance frequency associated with the disk device, which tends to occur at a high frequency, can be avoided. In particular, the viscoelastic connecting member VE provides a selective insulator, which strongly connects to the inner head carriage structure at low frequency vibrations and not at high frequency vibrations.

[Brief description of drawings]

FIG. 1 is a life-size sketch of a preferred embodiment consisting of a portion of a disk device / actuator.

FIG. 2 is a simplified cross-sectional view of FIG.

FIG. 3 is an enlarged view of a connecting portion of FIG.

FIG. 4 is an end view of FIG.

5 is a schematic enlarged end view of the two concentric ring configuration of FIG. 1. FIG.

FIG. 6 shows a separate inner ring.

FIG. 7 is a block diagram of a feedback amplification arrangement used to describe the functionality of this embodiment.

FIG. 8 is a diagram showing an ideal type of function of the present embodiment.

FIG. 9A is a diagram showing an example of performance with respect to frequency in the present embodiment.

FIG. 9B is a diagram showing an example of performance with respect to frequency of a conventional control structure.

FIG. 10 is a diagram showing an idealized plot of phase variation.

FIG. 11 is a diagram showing ideal plots of actuator speed and eddy current braking force for the structure according to the present embodiment.

FIG. 12A is a diagram plotting vibration with respect to frequency in the present embodiment.

FIG. 12B is a plot of frequency-dependent vibration of a conventional control structure.

Front Page Continuation (72) Inventor Kroetsutsu-Whitstonii-Bi. 94086, California, Sanny Vail, Smoke Tree Way 651

Claims (6)

[Claims] 1. An actuator comprising a driven device M and a driving device D connected to the outside of the driven device M via a cylindrical ring DR, the driving device being driven only by a connecting means C. The connecting means C is held between the driving device D and the driven device M to adhere the two devices well along most or all of the two surfaces, and the transient frequency f _E or more. Comprises a thin elastic "viscoelastic" member E, which is a layer of one or more somewhat squeezed elastic adhesive means B, which is susceptible to elastic shearing, said drive device D having a predetermined maximum frequency f _max. until it generates a normal vibration, f _{ma x} higher predetermined excessive frequency f _E
Alternatively, high frequency resonance or other destructive vibration is generated at a frequency higher than the above, the elastic bonding means B bonds the both devices in the viscoelastic connection, and elastic shearing occurs at a frequency higher than the transient frequency f _E or higher. This results in a damping of the vibration between the two devices, and by at least some degree of insulation of the driven device M from the drive device D, the connecting means C causes the normal vibration to An actuator which is characterized in that the high-frequency vibrations are transmitted without any change, and the high-frequency vibrations function to dampen and brake. 2. The driven device M is connected to the driving device D via a floating ring CR, and the layer B of the elastic adhering means.
The actuator according to claim 1, wherein a compression force is applied to the actuator. 3. The floating ring CR has elasticity, and is pressed before being bonded to the elastic bonding means B and then released, and the elastic bonding means B is lightly pressed to bond the entire surface well. An actuator according to claim 2, characterized by ensuring. 4. The drive device D comprises a cylindrical actuator coil mount including a cylindrical ring DR, and the driven device M carries the drive device D and a cylinder via at least one floating ring CR. 4. The actuator according to claim 3, comprising an actuator-carriage structure connected to the inside of the ring shape DR. 5. A viscoelastic means is applied as said elastic adhesive means B and is arranged to weaken at least one expected resonance frequency with a relatively small loss of phase margin. Actuator described. 6. A drive device D which is a cylindrical voice coil base.
And a driven device M, which is an actuator / carriage including a connecting plate CR connected to the driving device D, significantly reduces vibration by elastic shearing at a predetermined high frequency f _E and above. Attaching one or more viscoelastic members E consisting of an elastic adhesive tape applied to one or several thicknesses, which significantly insulates the driven device M from the driving device D, the connection being between Is affected only by the viscoelastic member E contained in the viscoelastic member E, and the viscoelastic member E has the necessary shear elasticity at the predetermined high frequency f _E and above, so that at the predetermined high frequency f _E A method characterized in that vibrations between the driving device D and the driven device M are selectively filtered and damped in the form of a mechanical high frequency insulating filter.