JP3860991B2 - Magnetic disk drive and carriage used therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic disk device. More specifically, the present invention relates to a carriage used for magnetic head positioning of a magnetic disk device.
[0002]
[Prior art]
Magnetic disk devices are required to improve recording density in order to increase recording capacity. For this purpose, it is important to increase the positioning accuracy of the magnetic head. Factors that hinder the improvement in positioning accuracy include positioning errors caused by vibrations of the mechanical system due to disk rotation and carriage positioning operations, and positioning errors that occur when vibrations are applied from outside the magnetic disk device. In order to reduce these positioning errors, it is necessary to widen the control band of positioning control or reduce the vibration of the mechanism system.
[0003]
Among them, in the vibration of the mechanical system due to the positioning operation of the carriage, each part of the carriage is excited by the driving force input to the carriage during the positioning to the target track in the head moving operation from the track to the other track. The generated vibration component is large.
In particular, a vibration mode involving in-plane bending of a carriage arm (hereinafter simply referred to as an arm) has a great influence on a swing type carriage because the head at the tip of the arm is swung around. Examples of such vibration modes include a main resonance mode and an in-plane bending primary mode of the arm. The main resonance mode is a mode in which the deformation of the bearing portion and the bending deformation of the entire carriage are combined. The in-plane bending primary mode of the arm is the primary bending of the cantilever with each of a plurality of arms. It is a mode that transforms as follows.
[0004]
Furthermore, there is a problem that the read / write speed of the disk device decreases because the time until data can be read or written increases due to residual vibration in the positioning operation. As a method of reducing such residual vibration, there is a method of reducing vibration using a dynamic vibration absorber as described in JP-A-11-66773.
[0005]
In addition, the main resonance mode, which is the primary vibration mode of the carriage, greatly affects the transmission characteristics in which the force generated in the coil is input and the displacement of the magnetic head in the positioning direction is the output. To do. In general, in order to increase the bandwidth of positioning control, the gain margin at the natural frequency (hereinafter referred to as the main resonance frequency) of the main resonance mode is a limiting condition. Therefore, by increasing the main resonance frequency or reducing the gain on the transfer characteristics, it is possible to secure a gain margin and increase the bandwidth. For example, in the example of Japanese Patent Laid-Open No. 2000-48497, the main resonance frequency is increased by increasing the rigidity by changing the fastening method of the carriage bearing.
[0006]
[Problems to be solved by the invention]
In the method using a dynamic vibration absorber for the carriage vibration that appears as residual vibration during head positioning, it is difficult to adjust the frequency of the target vibration mode. If high damping is not applied to the dynamic vibration absorber, it is necessary to accurately match the target vibration frequency. By using a material with a high damping effect. Even if it is going to cope with the dispersion | variation in a frequency, the vibration reduction effect will fall correspondingly.
[0007]
Similarly, if a high damping material is used, applying a member with a direct damping effect to the site that generates the residual vibration reduces the amplitude of the residual vibration in question and accelerates the convergence of the vibration due to the damping. Thus, it can be easily understood that fine adjustment can be omitted.
[0008]
On the other hand, the main resonance mode, which is the key to increase the bandwidth, is a mode in which the deformation of the bearing portion and the bending deformation of the entire carriage are combined. Therefore, in order to increase the main resonance frequency, it is effective to increase the rigidity of the bearing and the entire carriage, or to reduce the carriage. However, in an actual magnetic disk device, the increase in rigidity of the bearing is approaching its limit. As for the carriage, a significant increase in rigidity and weight is in the opposite direction, and it is difficult to significantly increase the main resonance frequency. In other words, increasing the main resonance frequency and widening the control band is now approaching the limit. Therefore, it is necessary to widen the control band by lowering the main resonance gain on the transfer characteristics.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems. By increasing a control band to improve positioning accuracy and reduce positioning errors, a recording disk is improved and a magnetic disk device having a large recording capacity is realized. That is. Another object is to provide a magnetic disk device capable of reducing residual vibration during head positioning operation, improving read / write speed, and capable of high-speed transfer.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problems of the present invention, a first arm portion and a second arm portion are provided on the carriage arm in a direction parallel to the disk surface, and the first arm portion and the second arm portion are provided. A member having a viscoelastic body is provided between them. A member having a viscoelastic body includes a rigid body portion having higher rigidity than the viscoelastic body and viscoelastic bodies provided at both ends of the rigid body portion, and the viscoelastic body is provided at each end of the rigid body portion. Elastic bodies are attached to the first arm and the second arm, respectively. As a result, in the vibration mode with in-plane bending of the arm, relative displacement between the first arm portion and the second arm portion occurs, resulting in a large strain in the viscoelastic body provided between the both arm portions. . Therefore, the damping effect of the viscoelastic body can be enhanced.
Furthermore, in the first arm portion and the second arm portion, the damping effect is obtained by making the width of the central portion larger than the width of the suspension side end portion or the end portion on the opposite side to this end portion. Can be further enhanced. This is because, when compared with the same head displacement in arm bending deformation, the rigidity of the end portion is relatively low, so that the wide portion at the center is not deformed, and deformation occurs at the end portion. This is because the relative displacement between the first arm portion and the second arm portion becomes larger and a larger strain is generated.
In addition, the viscoelastic body is provided at both ends of a rigid body having a higher rigidity than the viscoelastic body, specifically, a thin plate-like member (hereinafter referred to as a restraining member), and the viscoelastic bodies provided at both ends are respectively provided. If it is configured to be affixed to a surface substantially parallel to the disk surface of the center portion of the first arm portion and the center portion of the second arm portion, the area of the viscoelastic body to be affixed to a portion where the width of the center portion is wide is large. Thus, the effect can be further increased by expanding the portion where the damping effect occurs.
Even if the first arm portion and the second arm portion are configured such that the central wide portion is connected via the viscoelastic body without using the restraining member, By relatively displacing the second arm portion so as to rotate about the end portion as a fulcrum , strain is generated in the viscoelastic body, and a high damping effect can be obtained. The cost can be reduced because there is no restraining member.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0012]
FIG. 1 is a perspective view of a carriage according to a first embodiment to which the present invention is applied, and FIG. 2 is a top view of the carriage. FIG. 3 is a side view of the carriage. FIG. 4 shows an example of a magnetic disk device equipped with the carriage of the present invention. A slider 3 on which a magnetic head (not shown) is mounted is attached to the tip of the carriage 1 via a suspension 2. When a current is passed through the coil 4, a force is generated between the voice coil motor 5 and the coil 4, the carriage 1 rotates around a bearing portion around a rotation axis parallel to the rotation axis of the disk, and the slider 3 moves to the disk 6 It can be positioned at any radial position (target track) above.
[0013]
The carriage 1 is configured such that the width of the arm front end 8 and the arm rear end 9 of each of the arm portions 7a and 7b of the carriage arm is smaller than the width of the arm central portion 10. Here, a or b is represented by a subscript “a” on the right side and a “b” on the left side from the body portion 11 toward the suspension fixing portion 12 in FIG. For example, 8a is the front end portion of the arm portion 7a of the arm. The arm portions 7a and 7b are arranged on the carriage arm in a direction parallel to the disk surface.
[0014]
A restraining plate (restraining member) 14 is bonded to a surface parallel to the disk surface of the arm central portions 10a and 10b via a viscoelastic body 13. That is, the viscoelastic body 13 is provided between the arm central portions 10a and 10b. At this time, a member having a viscoelastic body 13 such as a constraining plate (restraining member) 14 and a viscoelastic body 13 may be provided between the arm central portions 10a and 10b. In this example, the constraining plate 14 is a stainless steel plate having a thickness of about 50 to 200 μm, the viscoelastic body 13 is an adhesive material having a thickness of about 50 to 100 μm, and the constraining plate 14 is placed on the central portions 10a and 10b. It also serves as a supporting role. The restraining plate (restraining member) 14 constitutes a rigid body portion (different from the rigid body portion 15) having higher rigidity than the viscoelastic body 13.
[0015]
FIG. 5 is a diagram showing the bending deformation shape of the arm in the main resonance mode. In the arm shape of FIG. 2, the width of the arm front end 8 and the arm rear end 9 reduces the width of the arm central portion 10, so that the rigid body portion 15 and the rotating portion 16 as shown in FIG. It can be modeled by a four-bar link structure expressed by At this time, the central portions 10a and 10b corresponding to the rigid body portion 15 move so as to rotate about the rear end portion 9a or 9b as a fulcrum, thereby causing a relative displacement as indicated by an arrow 17 in FIG. Therefore, since the restraint plate 14 is sufficiently rigid, its length is not changed, and shear stress in the in-plane direction is generated in the viscoelastic body 13. The viscoelastic body 13 converts this strain energy into heat energy and dissipates it to produce a damping effect. According to this mechanism, the greater the strain generated in the viscoelastic body 13, that is, the greater the relative displacement between the restraining plate 14 and the central portion 10 of each arm, the greater the energy consumed and the more the damping effect. Also. It can be seen that if the area pasted to the arm center 10 of the viscoelastic body 13 is large, energy is consumed in more parts and the damping effect is enhanced.
[0016]
In order to increase the bandwidth of positioning control, the frequency of the main resonance mode, which is the primary vibration mode of the carriage, in the transfer characteristics in which the force generated in the coil is input and the displacement of the magnetic head in the positioning direction is output. It is necessary to increase or decrease the gain. FIG. 12 shows the effect of the present invention on the transfer characteristics. Compared to the transfer characteristic 29 when the present invention is not used, the gain of the main resonance mode is reduced in the transfer characteristic 30 when the present invention is applied. FIG. 13 shows a positional deviation signal from the target track when it reaches the vicinity of the target track during the positioning operation. FIG. 13A shows a case where the present invention is not applied, and FIG. 13B shows a waveform when the present invention is applied. It can be seen that the vibration amplitude of the high frequency indicated by the arrow 31 is reduced.
[0017]
In this embodiment, as shown in FIG. 3, the restraint plate 14 is attached to all the arms with a viscoelastic body 13. By doing so, it is possible to obtain a damping effect at the time of bending deformation in all the arms. However, in a carriage in which all the arms are connected to the body portion 11, the vibration mode with in-plane bending of the arm represented by the main resonance mode is a vibration mode in which the entire carriage is deformed as one structure. Thus, even if a part that generates a damping effect is provided, the damping ratio for the vibration mode in the carriage as the entire system increases, so that the vibrations of all the arms can also be reduced. .
[0018]
Therefore, it is possible to give a damping effect to the vibrations of all the arms by simply attaching them to the outside of the arms 19 at both ends without attaching the restraining plate 14 or the viscoelastic body 13 to the intermediate arm 18 shown in FIG. . This is because, in an actual magnetic disk apparatus, the restraint plate 14 is attached to the arms 19 at both ends with the viscoelastic body 13, so that the gain in the vibration mode accompanied by bending in the arm plane is reduced in the transfer characteristics of all the magnetic heads. It shows that it is possible. Thus, by not sticking the restraint plate 14 to the intermediate arm 18, it is possible to reduce the number of parts to be attached and reduce the number of assembly steps.
[0019]
In general, the intermediate arm 18 is arranged alternately with the disk 6 in the height relationship in the magnetic disk device. For this reason, there are many cases where there is a dimension limitation in the thickness direction of the arm. In that case, as shown in FIG. 7, a groove 20 is provided in the thickness direction of the arm, and a restraint plate 14 is attached to the inside via a viscoelastic body 13, thereby avoiding an increase in dimension in the thickness direction. Can do. In this case, there is a concern about the decrease in arm rigidity due to the provision of the groove 20, but when compared with the bending rigidity of the beam, the arm thickness only has a proportional effect on the in-plane rigidity of the arm. Therefore, the rigidity reduction is less than the arm arm width that affects the in-plane direction by the third power. In particular, in the case of the present embodiment, the position where the restraint plate 14 is attached is the central portion 10 where the arm width is widened so that it can be regarded as a rigid body, and therefore the influence on the bending deformation of the arm is very small.
[0020]
Further, the bending stiffness in the out-of-arm direction is via the viscoelastic body 13 but the rigid constraining plate 14 is supported on the outside thereof, so that the out-of-plane rigidity by providing the groove 20 is provided. The decrease is very small, and further, if the strain concentration in the groove 20 is taken into consideration, the viscoelastic body 13 is distorted, and a damping effect can be obtained even with respect to the out-of-plane bending vibration of the arm.
[0021]
In assembling, when the restraint plate 14 is stuck on the arm central portion 10a or 10b, it is desirable that the viscoelastic body 13 is stuck only on a portion where the restraint plate 14 and the central portion 10 face each other. This is because the restraint plate 14 has sufficient rigidity even if the viscoelastic body 13 is present in the portion of the surface facing the arm of the restraint plate 14 that is exposed in the space between both arm centers 10a and 10b. In this case, since no distortion occurs in the viscoelastic body 13, a damping effect at this portion cannot be expected. In addition, the viscoelastic body 13 is greatly exposed, which also means that a part of the viscoelastic body 13 is microscopically peeled off to avoid dust. As another method for solving these problems, a method of further attaching an additional restraining plate to the viscoelastic body 13 exposed in the space between the arm center portions 10a and 10b is also conceivable. There is also an advantage that the rigidity of the restraint plate 14 can be improved.
[0022]
FIG. 8 shows a second embodiment of the present invention. As shown in FIG. 8A, the arm widths of the arm portions 7a and 7b of the carriage arm are fixed, and the thickness and length of the arm portions 7a and 7b are set so as to cause the arm deformation as shown in FIG. 8B. The dimensions and rigidity are designed. Even in this case, a relative displacement occurs in the vicinity of the intermediate portion between the arm portions 7a and 7b. Therefore, the viscoelastic body 13 between the restraint plate 14 is distorted by the same mechanism as described above, and a damping effect can be obtained. Since each of the arm portions 7a and 7b is gradually bent over the entire area of the arm portion, the relative displacement in the vicinity of the center portion becomes smaller than that in the first embodiment, and the damping effect is reduced. If the arm width is increased in order to increase the region where the viscoelastic body 13 is applied, the bending rigidity of the arm is further increased, so that the amount of deformation is reduced and the damping effect is reduced. The resonance frequency of the vibration mode including bending in the arm plane including the resonance mode can be increased.
[0023]
FIG. 9 shows a third embodiment of the present invention. As in the first embodiment, the shape of the carriage arm is such that the width of the arm front end portion 8 and the arm rear end portion 9 of each of the arm portions 7a and 7b of the carriage arm is small. . Further, a restraining member 21 shown in an enlarged manner in the figure is sandwiched between the arm centers 10a and 10b using two viscoelastic bodies 13. By doing so, as in the first embodiment, the viscoelastic body 13 sandwiched between the restraining members 21 is distorted with respect to the relative displacement between the arm centers 10a and 10b, and a damping effect is generated. Can do. In this case, by increasing the thickness of the restraining member 21 to the same level as the thickness of the arm, it is possible to suppress an increase in the dimension outside the arm surface. Further, even if the restraining member 21 is affixed to all the arms or a part of the arms, a damping effect can be expected in all the arms as in the first embodiment.
[0024]
FIG. 10 shows a fourth embodiment of the present invention. As in the first and third embodiments, the carriage arm has the same width as that of the arm central portion 10 in which the width of the arm front end 8 and the arm rear end 9 of each of the arm portions 7a and 7b of the carriage arm is small. It is configured. Here, the thermoplastic damping member 22 is filled along the shape of the arm center portions 10a and 10b. As the damping member 22, it is desirable to mix and shape a viscoelastic body having high attenuation with a thermoplastic resin, or to use an elastic member with high attenuation such as rubber. In this embodiment, there is no restraining member as in the first to third embodiments, but the damping member 22 is formed when the arm central portions 10a and 10b serve as restraining members and are relatively displaced. As a result of the distortion, a damping effect can be generated as before. By adopting such a configuration, a restraining member is unnecessary and a simpler structure can be achieved.
[0025]
FIG. 11 shows an assembling method of this embodiment. In the state A before the suspension 2 is attached, the horizontal shaping mold 23 is inserted between the arms in the in-plane direction. Further, the vertical shaping die 24 is inserted from the out-of-plane direction to obtain a state B. The vertical shaping mold 24 has cylindrical portions 25 and 26 whose outer shapes are determined in accordance with a hole formed between the arm arms 7a and 7b, and a pipe line 27 is provided on the central axis thereof. Further, the injection holes 28 are formed in the side surfaces of the cylindrical portions 26 and 27 in accordance with the positions of the arms. In the state B, a space surrounded by the horizontal shaping mold 23, the vertical shaping mold 24, and the arm is formed between the center portions 10a and 10b. In this state, the damping material melted at a high temperature from one side of the pipe line 27 is extruded from the injection hole 28 into the above space and shaped, and then cooled and hardened to shape the damping member 22. Through the above steps, the damping member 22 is shaped near the center of the arm arm. The surface of the arm central portion 10a or 10b that opposes the attenuation member 22 is depicted as a plane in FIG. 10, but is not necessarily a plane, and irregularities are used to increase the contact area with the attenuation member 22. It is more desirable to provide it. In the assembling process shown in FIG. 11, it is possible to shape the damping member 22 to all the arms at the same time. Therefore, it is effective to apply the damping member 22 to all the arms. It can also be given only to the arm.
[0026]
By using the carriage according to the first to fourth embodiments of the present invention, a high damping effect can be given to various vibration modes involving in-plane bending of the arm, and in particular, the gain in the transfer function of the main resonance mode can be increased. By lowering, the control band can be widened to improve the positioning accuracy, and a high recording density magnetic disk device can be provided. Furthermore, it is possible to provide a magnetic disk device capable of reducing the residual vibration during the head positioning operation in the target mode, improving the read / write speed, and capable of high-speed transfer.
[0027]
In the above description, the “main resonance mode” is a mode in which the deformation of the bearing and the bending deformation of the entire carriage are combined, and the document “Analytical and Experimental Study of the Effect of Basa-plate and Top Cover Stiffness”. on Actuator and Diskpack Dynamics "(Yih-Jen Dennis et al., 10th Annual Symposium on Information Storage and Processing Systems June 28-30, 1999)," Active Damping in HDD Actuator "(Fu-Ying Huang et al.) , IEEE TRANSACTIONS ON MAGNETICS, VOL.37, No2., MARCH 2001), "Development of a Single Coil Coupled Force VCM Actuator for High TPI Magnetic Recording" (Huai Lin et al., IEEE TRANSACTIONS ON MAGNETICS, VOL .37, No2., MARCH 2001) means the same deformation mode as “QRmode”. “In-plane bending primary mode of arm” is a mode in which each of a plurality of arms is deformed like a primary bending of a cantilever beam, and “end arm mode” in the above-mentioned document “Active Damping in HDD Actuator” Refers to the same vibration mode.
[0028]
In the above description, “in-plane” refers to a direction along a plane parallel to the disk surface, and “out-of-plane” refers to an axial direction perpendicular to the disk surface.
[0029]
In the drawings used in the above description, the aspect ratio and the dimensional ratio of each part are not necessarily correct for the sake of explanation.
[0030]
【The invention's effect】
According to the present invention, it is possible to provide a high damping effect to various vibration modes with in-plane bending of the arm, and to suppress positioning vibration by suppressing carriage vibration to provide a high recording density magnetic disk device. it can. Further, it is possible to provide a magnetic disk device capable of reducing the residual vibration during the head positioning operation, improving the read / write speed, and capable of high-speed transfer.
[Brief description of the drawings]
FIG. 1 is a perspective view of a carriage according to a first embodiment of the present invention.
FIG. 2 is a top view of the carriage according to the first embodiment of the present invention.
FIG. 3 is a side view of the carriage according to the first embodiment of the present invention.
FIG. 4 is a schematic diagram of a magnetic disk device using the first embodiment of the present invention. FIG. 5 is a diagram showing arm deformation of the first embodiment of the present invention.
FIG. 6 is a diagram showing a principle model of arm deformation according to the first embodiment of the present invention.
FIG. 7 is an enlarged side view of the arm of the first embodiment of the present invention.
FIG. 8 is a top view of a carriage according to a second embodiment of the present invention.
FIG. 9 is a perspective view of a carriage according to a third embodiment of the present invention.
FIG. 10 is a perspective view of a carriage according to a fourth embodiment of the present invention. FIG. 11 is a view for explaining assembly of the carriage according to the fourth embodiment of the present invention.
FIG. 12 is a transfer characteristic diagram of the first embodiment of the present invention.
FIG. 13 is a diagram showing a positioning residual vibration waveform of the first example of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Carriage, 2 ... Suspension, 3 ... Slider, 4 ... Coil, 5 ... Voice coil motor, 6 ... Disk, 7 ... Carriage arm, 8 ... Arm front end part, 9 ... Arm rear end part, 10 ... Arm center part, DESCRIPTION OF SYMBOLS 11 ... Body part, 12 ... Suspension fixing | fixed part, 13 ... Viscoelastic body, 14 ... Restraint board, 15 ... Rigid beam, 16 ... Link part, 17 ... Middle part deformation | transformation, 18 ... Middle arm, 19 ... Both-ends arm, 20 ... Groove, 21 ... restraining member, 22 ... attenuating member, 23 ... horizontal shaping type, 24 ... vertical shaping type, 25 ... front cylindrical part, 26 ... body side cylindrical part, 27 ... pipe, 28 ... injection hole, 29 ... invention Unapplied transfer characteristics, 30 ... Transfer characteristics after applying the invention, 31 ... Residual vibration amplitude.

Claims (5)

A slider for mounting a magnetic head is supported on a disk by a suspension for applying a predetermined load to the slider and a carriage arm to which the suspension is fixed, and the opposite side of the end of the carriage arm to which the suspension is fixed. In a magnetic disk device that drives and rotates a carriage arm around a rotation axis provided at the end of the disk, positions the magnetic head on a target track on the disk, and reads and writes information.
A first arm portion and a second arm portion are provided side by side in a direction parallel to the disk surface between an end portion on the carriage arm where the suspension is fixed and an end portion on the rotating shaft side. A member having a viscoelastic body is provided between the first arm portion and the second arm portion ,
The member having the viscoelastic body includes a rigid body portion having rigidity higher than that of the viscoelastic body and viscoelastic bodies provided at both ends of the rigid body portion, and is provided at each end of the rigid body portion. And a viscoelastic body attached to each of the first arm and the second arm . In a carriage having a slider mounted with a magnetic head for reading and writing information on a disk, a suspension for holding the slider and applying a predetermined load to the slider, and a carriage arm for fixing the suspension,
A carriage arm includes a suspension fixing portion and first and second arm portions arranged substantially in parallel with the disk surface, and a restraining member having surfaces facing the first arm portion and the second arm portion. The carriage is characterized in that the restraining member and the first arm portion, and the restraining member and the second arm portion are connected via a viscoelastic body. A slider on which a magnetic head for reading and writing information on a disk is mounted; a suspension for holding the slider and applying a predetermined load to the slider; a carriage arm for fixing the suspension; and a body portion to which the carriage arm is connected; In a carriage having
The carriage arm includes a suspension fixing portion and first and second arm portions arranged substantially in parallel with the disk surface. In the first arm portion and the second arm portion, the width of each central portion is A restraining member that is larger than the width of the body side end or the suspension side end and has a surface facing the first arm and the second arm is provided, and the restraining member and the first A carriage characterized in that the central portion of the arm portion and the restraining member and the central portion of the second arm portion are connected via a viscoelastic body. 4. The carriage according to claim 3 , wherein the restraining member is a thin plate-like member, and is attached to a surface substantially parallel to a disk surface of a central portion of the first arm portion and a central portion of the second arm portion. A carriage characterized by having a structure attached via an elastic body. A slider on which a magnetic head for reading and writing information on a disk is mounted; a suspension for holding the slider and applying a predetermined load to the slider; a carriage arm for fixing the suspension; and a body portion to which the carriage arm is connected; In a carriage having
The carriage arm includes a suspension fixing portion and first and second arm portions arranged substantially parallel to the disk surface.
The first arm portion and the second arm portion have a central portion whose width is larger than the width of the body side end or suspension side end ,
A viscoelastic body connecting the first arm portion and the second arm portion at the central portion;
The carriage is characterized in that the central portion moves so as to rotate with the end portion on the body portion side as a fulcrum .

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