JP2004048825A - Coil arm assembly molding method for voice coil motor, coil arm assembly for voice coil motor, voice coil motor, and magnetic disk unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coil arm assembly molding method for a VCM(voice coil motor) which can lessen the dispersion of properties and improve the accuracy and properties, and to provide a coil arm assembly for the VCM, this VCM, and an inexpensive magnetic disk unit of high performance using this VCM. <P>SOLUTION: When an air core coil 14, which is trapezoidal in external shape and in which the lengths L1 and L2 of the two sides between a short side part and a long side part in the above trapezoidal form are the same and at least partial parts 14a and 14b are asymmetrical, is fixed to an arm member 13, it is fitted in a mold which has a projection having external form roughly equal to the spool forming the air core coil 14 and a cavity corresponding to the arm member in a specified outer section of this projection, and this mold is charged with resin so as to integrally mold the air core coil and the arm member. The coil arm assembly of the VCM and the VCM are adopting this molding method, and the magnetic device uses this VCM. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic disk device used as an external storage device of a personal computer or the like, and further relates to a swing type voice coil motor (hereinafter, abbreviated as VCM) and a VCM of the magnetic disk device. The present invention relates to a coil arm assembly and a method of forming the same.
[0002]
[Prior art]
As disclosed in JP-A-5-266609 and JP-A-2001-344916, an oscillating VCM in a conventional general magnetic disk device is connected to a main surface of a chassis via a pivot bearing. An arm supported so as to be swingable substantially in parallel, an air-core coil attached to one end of the arm, a pair of yokes disposed on the upper and lower surfaces of the air-core coil, and a pair of yokes; And permanent magnets respectively mounted on the air-core coil side of the yoke. Then, by passing a current through the air-core coil, thrust is generated in the arm by electromagnetic force based on Fleming's left-hand rule, and the magnetic head attached to the other end of the arm is moved to the target track for positioning. Configuration.
[0003]
In recent years, personal computers have been further reduced in size and improved in performance, and there has been an increasing demand for improved performance of magnetic disk devices. For this reason, the appearance of a small, large-capacity, high-speed and inexpensive magnetic disk device has been strongly desired.
[0004]
[Problems to be solved by the invention]
However, in order to satisfy these demands in the conventional magnetic disk drive, it is necessary to promote the miniaturization of the components constituting the VCM and to improve the dimensional accuracy. For this reason, the cost of the component itself increases, and furthermore, at the fitting portion, etc., the gap is reduced for improving the accuracy, so that it becomes difficult to insert the component, and the workability is reduced. It may be difficult to determine the front and back and directionality. Therefore, if all the assembly processes are mechanized, defects due to human judgment errors can be prevented, but equipment investment increases, resulting in an increase in cost.
[0005]
In particular, variations in positional accuracy caused by fixing the air-core coil to the arm with an adhesive, and variations in VCM characteristics caused by differences in the material of the adhesive cause variations in seek characteristics of the magnetic disk device. As well as a cause for poor performance.
[0006]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and a VCM capable of suppressing variations in characteristics of a coil used in an oscillating VCM and improving accuracy and characteristics by a simple method. It is an object of the present invention to provide a coil arm assembly molding method, a VCM coil arm assembly, a VCM, and an inexpensive and high-performance magnetic disk drive using the VCM.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is characterized in that the outer shape is a trapezoidal shape, and the two sides between the short side and the long side of the trapezoidal shape have the same length and have at least one length. Preparing a winding form in which the shape of the part is asymmetrically formed, winding the conductive wire having a fusion layer adhered to the surface thereof a plurality of times around the winding form to form an air-core coil, A step of fusing the fusion layers of the conductive wires to each other, and providing a mold having a projection having an outer shape substantially equal to that of the bobbin and a cavity corresponding to the arm member holding the air-core coil. A method for molding a coil arm assembly of a VCM, comprising a step of fitting a coil and a step of filling a mold with resin to integrally mold an air core coil and an arm member.
By this method, it is possible to reliably determine the front and back of the air-core coil without losing the weight balance, to eliminate the error of the winding direction, to eliminate the step of checking the winding direction, and to reduce the cost. Become.
[0008]
According to a second aspect of the present invention, in the method for forming a coil arm assembly of a VCM according to the first aspect, the step of winding the conductive wire around the bobbin to form an air-core coil and the step of fusing the fusion layer are performed. Perform in the same process.
According to this method, the two steps can be treated as one step, so that the steps are simplified and the cost can be reduced.
[0009]
According to a third aspect of the present invention, in the method for forming a coil arm assembly of a VCM according to the first or second aspect, the fusion layers of the adjacent conductors are fused to each other by Joule heat generated by energizing the conductors. .
According to this method, the disconnection can be confirmed without adding a special step, and the cost can be reduced and the reliability can be improved.
[0010]
According to a fourth aspect of the present invention, in the method of the third aspect, a pulse current is applied to the conductive wire.
According to this method, the short circuit between the coils can be confirmed in the same process, and the electrical variation of the coils can be managed, so that the reliability can be improved.
[0011]
According to a fifth aspect of the present invention, in the method of forming a coil arm assembly for a VCM according to the first or second aspect, the fusion layers of the adjacent conductors are mutually fused by applying hot air to the conductors.
According to this method, the mechanical stress on the coil can be reduced, so that the reliability can be improved.
[0012]
According to a sixth aspect of the present invention, in the method of forming a coil arm assembly of a VCM according to the first or second aspect, the fusion layers of the adjacent conductive wires are fused to each other by applying an organic solvent.
According to this method, mechanical stress on the coil can be reduced, and at the same time, oil content is also removed, so that reliability can be improved.
[0013]
According to a seventh aspect of the present invention, in the method for forming a coil arm assembly of a VCM according to any one of the first to sixth aspects, the conductor has a rectangular flat cross section, and the flat main surfaces overlap. Wrap around.
By this method, reliable fusion can be performed with a favorable coil winding shape, and the accuracy and characteristics are improved.
[0014]
The invention according to claim 8 is an arm member whose base end is rotatably held, and which is fixed to the distal end of the arm member, the external shape is a trapezoidal shape, and the short side portion and the long side of the trapezoidal shape are long. An air core coil in which two sides between the side portions have the same length and at least a part of the shape is asymmetrically formed, wherein the arm member is formed of a resin molded product; This is a VCM coil arm assembly in which an arm member is integrally formed.
With this configuration, it is possible to reliably determine the front and back of the air-core coil when the coil is mounted in the mold. As a result, in the integrally formed coil, the winding direction is not reversed, and the cost can be reduced. Further, since the effective lengths in the radial direction are substantially the same, there is no difference in generated force, so that the balance is good and unnecessary vibration is not generated.
[0015]
According to a ninth aspect of the present invention, in the coil arm assembly of the VCM according to the eighth aspect, the air-core coil is formed by winding a conductive wire having a surface to which a fusion layer is applied a plurality of times in a trapezoidal shape, and adjacently winding the conductive wire. The fused layers of the turned conductive wires are fused together.
With this configuration, the coil shape can be firmly held, and the discrimination between the front and back sides when the coil is mounted in the mold is more reliable.
[0016]
According to a tenth aspect of the present invention, in the coil arm assembly of the VCM according to the eighth or ninth aspect, the conductive wire has a rectangular and flat cross section, and is wound so that the flat main surfaces overlap.
With this configuration, reliable fusion can be performed with a favorable coil winding shape, and the accuracy and characteristics are improved.
[0017]
According to an eleventh aspect of the present invention, in the VCM coil arm assembly according to any one of the eighth to tenth aspects, the conductive wire is mainly composed of aluminum.
With this configuration, the air core coil can be made lighter, so that the acceleration characteristics of the VCM are improved, and in the case of the same acceleration, the current consumption can be reduced.
[0018]
According to a twelfth aspect of the present invention, in the VCM coil arm assembly according to any one of the eighth to tenth aspects, the conductive wire is a copper-clad aluminum wire.
According to this configuration, copper having high thermal conductivity is arranged outside the air-core coil, so that heat radiation can be improved. Therefore, it is also possible to improve acceleration characteristics by supplying a larger current.
[0019]
According to a thirteenth aspect of the present invention, in the coil arm assembly of the VCM according to any one of the eighth to twelfth aspects, the length of a portion where the air-core coil generates a thrust by an electromagnetic force is made substantially equal.
With this configuration, a thrust characteristic equivalent to that of an air-core coil that is symmetrical with respect to a virtual line segment passing through the center of rotation of the arm member can be obtained, and it is possible to replace the conventional VCM without any change. .
[0020]
According to a fourteenth aspect of the present invention, a pair of yokes arranged opposite to each other, a permanent magnet attached to at least one of the opposing surfaces of the pair of yokes, and a magnetic gap formed between the permanent magnet and the other yoke. And a coil whose base end is rotatably held. The coil has an arm member whose base end is rotatably held, and is fixed to a tip end of the arm member, and has an outer shape. An air core coil having a trapezoidal shape, two sides between the short side and the long side of the trapezoidal shape having the same length and at least a part of the shape being asymmetrically formed; Is a VCM which is formed of a resin molded product, and in which an air core coil and an arm member are integrally formed.
With this configuration, since the air-core coil is not bonded to the arm, variations in characteristics caused by variations in positional accuracy and variations in the material of the adhesive can be reduced, and stable seek characteristics of the magnetic disk device can be obtained. Can be Further, contamination due to gas generated from the adhesive can be reduced.
[0021]
According to a fifteenth aspect of the present invention, a magnetic disk held rotatably substantially in parallel with the main surface of the chassis, and a magnetic disk held in a position separated from the magnetic disk substantially in parallel with the main surface of the chassis and mutually predetermined A pair of yokes held so as to face each other at a distance, a permanent magnet attached to at least one of the opposing surfaces of the pair of yokes, and a longitudinal middle portion can be rotated substantially parallel to the main surface of the chassis. And a coil extending from the center of rotation to one end and holding the magnetic head and a coil extending from the center of rotation to the other and movable in a magnetic gap formed between a pair of yokes. With an actuator,
The coil has an arm member whose base end portion is rotatably held, and is fixed to a distal end portion of the arm member, and has an outer shape of a trapezoidal shape, between a short side portion and a long side portion of the trapezoidal shape. And the arm member is formed of a resin molded product, and the air core coil and the arm member are integrally formed. This is a molded magnetic disk device.
With this configuration, since there is no step of bonding the air-core coil to the arm, variations in positional accuracy and variations in VCM characteristics caused by variations in the material of the adhesive can be reduced, and stable seek characteristics of the magnetic disk device can be achieved. can get. In addition, contamination due to outgassing caused by the adhesive can be reduced, and a highly reliable magnetic disk device can be obtained.
[0022]
The invention according to claim 16 is the magnetic disk drive according to claim 15, wherein the resin is a thermoplastic resin.
With this configuration, an ordinary injection molding machine can be diverted, so that it is not necessary to add equipment and an increase in cost can be prevented. Further, since there is little outgas from the resin, contamination can be reduced, and a highly reliable magnetic disk device can be realized.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings.
FIG. 1 is a plan view showing a schematic configuration of an embodiment of a magnetic disk drive (hereinafter abbreviated as HDD) according to the present invention. In particular, a series of assemblies excluding an electric circuit portion of the HDD, that is, a series of assemblies, 1 shows a head disk assembly (hereinafter, abbreviated as HDA). The HDA 1 includes a rectangular box-shaped chassis 2 made of aluminum and having an upper end opened, and a cover (not shown) for closing the upper end opening of the chassis 2. Inside the HDA1, a disk as a magnetic recording medium is formed by depositing a magnetic material such as Co-Cr based on a non-magnetic base material such as aluminum or glass by sputtering or the like to form a required lubricant or a protective film. 6 is mounted. A spindle motor 7 for rotating the disk 6 at a constant speed is mounted below the disk 6. A fluid bearing is used as a bearing of the spindle motor 7, and the form of the motor is a circumferentially opposed DD motor. With such a configuration, the disk 6 can be rotated with high precision. The radial runout of the disk 6 is designed to satisfy the requirement of high precision as specified by RRO / NRRO.
[0024]
A magnetic head 11 for recording or reproducing information on or from the disk 6 is attached to a gimbal spring (not shown) at the tip of a suspension 12 as a support member for supporting the magnetic head 11, and a biasing force is transmitted by a load beam. It has become. A thin-film head for writing and a GMR (Giant Magneto resistance) head for reading are attached to a slider (not shown) on the magnetic head 11. The slider is a negative pressure slider having an ABS (Air Bearing Surface) surface having a required shape.
[0025]
The suspension 12 is supported by the pivot bearing 5 so as to be rotatable in the track arrangement direction (radial direction) of the disk 6. The actuator 10 includes a suspension 12 and a coil arm 13 as an arm member in which an air-core coil 14 described later is integrally formed. The actuator 10 is rotated and positioned by the VCM, whereby the magnetic head 11 is moved to a desired track position to perform positioning. A ramp block 8 is provided on the radially outer side of the disk 6 at a retracted position of the actuator 10, and when the operation of the HDD is stopped, the actuator 10 is unloaded to the retracted position, and when the HDD is not operated. Then, the actuator 10 is held at the retracted position.
[0026]
A circuit board on which a drive circuit (not shown) for controlling the spindle motor 7 and the like, a read / write circuit, a hard disk controller (HDC: Hard Disk Controller), and the like are mounted is housed and fixed at the bottom of the chassis 2 to hold the HDD. Make up. Such HDDs take the form of a load / unload mechanism instead of a CSS (Contact Start Stop). The disk 6 is rotated and stopped by the spindle motor 7 when the HDD is operating and not operating. Although not shown, tracks on which data and servo information are recorded are concentrically arranged on the surface of the disk 6. The track is further divided into sectors such as 512-byte units. Also, zone bit recording is performed so that the linear recording density becomes substantially constant depending on the track position.
[0027]
The suspension 12 and the coil arm 13 that constitute the actuator 10 are rotatably supported by the pivot bearing 5, and are disposed in opposite positional relations with respect to the pivot bearing 5. Further, a tab 9 is provided at the tip of the suspension 12 so as to be evacuated to the ramp block 8. The tab 9 is a portion that is held by the ramp block 8 when it moves to the retracted position, and has a projection (not shown) that contacts the ramp block 8. This is to reduce the friction with the ramp block 8 to prevent contamination and to prevent the magnetic head 11 from changing position when the disk 6 is retracted from the disk 6 or when the disk 6 is moved in the opposite direction, thereby preventing the disk 6 from contacting. That's why.
[0028]
The HDA 1 in the present embodiment is referred to as one platter and one head, in which only the upper surface of the disk 6 is used as a recording surface and one magnetic head is used. The magnetic head 11 records data on the disk 6 from a circuit board (not shown), and reads data recorded on the disk 6. For recording, code conversion is performed on a byte-by-byte basis using a 16-17 modulation method to improve storage capacity and recording and reproduction characteristics. These signals are exchanged with the magnetic head 11 via a flexible printed circuit (FPC) connected to the head amplifier.
The magnetic head 11 is attached to a slider and is pressed against the disk by a biasing force provided by a suspension 12. As described above, the slider is a negative pressure slider having an ABS surface having a desired shape. Due to the inflow of air generated by the rotation of the disk 6, required positive and negative pressures are generated, and a very slight floating occurs. It floats stably in an amount (10 to 30 nm).
[0029]
FIG. 2 is a perspective view showing a detailed configuration of a main part of the VCM. In the figure, a VCM 16 includes an air-core coil 14 mounted on a plate-shaped coil arm 13, an upper yoke (front yoke), and a lower yoke (not shown) disposed opposite to the front and back surfaces of the coil arm 13, respectively. (Back yoke) 4 and a permanent magnet 17 fixed to the lower yoke 4. That is, the permanent magnet 17 is disposed opposite to the lower end surface of the air-core coil 14 fixed to the coil arm 13 of the actuator 10 via a predetermined gap. An upper yoke is opposed to the upper end surface of the air-core coil 14 via a predetermined gap. Thereby, a magnetic circuit is formed, and the air-core coil 14 is rotatable because the air-core coil 14 is disposed in the magnetic gap sandwiched between the upper yoke and the permanent magnet 17. The permanent magnet 17 is made of a Nd-Fe sintered product having a high energy product, a surface of which is subjected to a rust-proofing treatment with Ni or the like, and has two poles magnetized in one plane. I have.
[0030]
Here, the permanent magnet 17 includes a permanent magnet 17S having an S pole on the upper surface, a permanent magnet 17N having an N pole on the upper surface, and a neutral zone 17A sandwiched therebetween. I have. The permanent magnet 17 is fixed to the lower yoke 4 with an anaerobic adhesive or the like. The chassis 2 is provided with a mounting hole 3 for loosely mounting the lower yoke 4, and the lower yoke 4 has three mounting portions 4b projecting from the peripheral side, and through holes 4c provided in the mounting portions 4b, respectively. A screw is inserted into the chassis 2 so that it can be attached to the chassis 2. An arcuate guide portion 3a is formed in a portion of the mounting hole of the chassis 2 near the pivot bearing 5 so as to be concentric with the axis 5c of the pivot bearing 5. Similarly, an arc-shaped guide wall 4a is formed in a portion of the lower yoke 4 near the pivot bearing 5 so as to move concentrically with the pivot bearing 5 with respect to the guide portion 3a.
[0031]
A gap is provided around the yoke 4, and the lower yoke 4 and the permanent magnet 17 are concentrically moved about the pivot bearing 5 as the rotation center of the VCM 16 by sliding the guide portion 3a and the guide wall 4a. become able to. An adjusting portion 4 d is provided on an end surface of the lower yoke 4 located far from the pivot bearing 5, and can be adjusted with the adjusting portion 2 b of the chassis 2. The positioning hole 2 a provided in the chassis 2 is a long hole that is long in the radial direction with respect to the pivot bearing 5. On the other hand, the through-holes 4c provided in the mounting portions 4b of the lower yoke 4 are elongated holes in the direction of the arrow A in which the coil arm 13 moves around the pivot bearing 5. The dimensions of the gap and hole between the chassis 2 and the yoke 4 can be appropriately set. When the HDA is formed, dust or the like in the outside air is mixed by a suitable seal or a thin film film (not shown). The air gap is sealed so as to prevent
[0032]
Next, the operation of the HDD will be described. The spindle motor 7 is driven by the circuit board, and the disk 6 rotates at a predetermined rotation speed. In the present embodiment, it is 3000 rpm. The magnetic head 11 retracted by the ramp block 8 rotates around the pivot bearing 5 by the VCM, and loads the magnetic head 11 onto the disk surface. The air flow generated by the rotation of the disk 6 passes between the slider and the disk 6. Thus, the slider stably floats with the disk 6 with a very small flying height (10 to 30 nm) against the urging force of the suspension 12. Thus, the loading of the magnetic head 11 is completed. Subsequently, a series of operations such as track recognition and the like called track acquisition are performed.
[0033]
Next, the operation of the VCM will be described. When the VCM is energized, the VCM generates a thrust by the magnetic flux of the permanent magnet 17 and the current of the air-core coil 14 according to Fleming's left-hand rule. At this time, since the permanent magnet 17 is fixed, a thrust acts on the air-core coil 14 as a reaction of the permanent magnet 17 to rotate the actuator 10 with respect to the pivot bearing 5. As a result, the actuator 10 is rotated by an angle corresponding to the amount of current supplied to the air core coil 14. The magnetic head 11 supported by the suspension 12 moves in a floating state on the disk along the radial direction of the disk 6, is positioned on a desired track, and records and reproduces information on the disk 6.
[0034]
The thrust of the VCM 16 is affected by the mounting accuracy of the permanent magnet 17 with respect to the pivot 5c of the pivot bearing 5. That is, it is affected by the magnetic flux linked to the air core coil 14. This is because the generation of thrust is based on the BIL rule determined by the magnetic flux B, the current I, and the length L, and the main factor is considered to be the mounting accuracy of the permanent magnet. Due to a decrease in the mounting accuracy of the permanent magnet 17, the thrust may change depending on the position in the rotation direction or may be insufficient as a whole. For these, the value of the current flowing through the air core coil 14 with respect to the position in the rotating direction, that is, the position of the track, the gain of the servo loop is adjusted for each HDA, and the firmware (Firmware) is used. In such cases, processing steps such as current adjustment were added.
[0035]
As a result, factors that lower the mounting accuracy include the mounting accuracy of the lower yoke 4 to the chassis 2, the positioning accuracy of the permanent magnet 17 with respect to the lower yoke 4, and the positioning accuracy during magnetization. Further, the size of the upper yoke and the lower yoke themselves is set so as not to be affected by positional accuracy. However, the meaning of the positional accuracy is not to arrange the permanent magnet 17 at a required position with respect to the pivot bearing 5, but to arrange the permanent magnet magnetically in a required positional relationship. In addition, it is necessary to balance the generated force as viewed from the rotation axis with respect to the interlinkage magnetic flux. For this reason, the effective length in the radial direction of the coil that generates thrust in the rotation direction It is important that are substantially the same.
[0036]
Even if the thrust of the coil as a whole is the same, if the force generated by each component in the radial direction of the trapezoid is different, a moment acts in the radial direction, which may cause inadvertent vibration. Further, this is true not only in the thrust direction but also in other two axes orthogonal to the thrust direction. However, since the rotating shaft generally has high axial rigidity in two directions other than the rotating direction, it is often sufficient to consider only the thrust in the rotating direction.
[0037]
FIG. 3 is an enlarged perspective view of the coil 15 of the VCM 16. 4A, the core 21 made of aluminum having a circular cross section is surrounded by a clad 22 made of electrolytic copper, for example, as shown in FIG. A so-called self-fusing conductive wire 20 covered with an insulating layer 23 made of, for example, a fusion layer 24 made of polyamide is applied thereon. The air-core coil 14 is wound in a trapezoid such that the center angle is the same θ with respect to a virtual line segment X passing through the rotation center 5c of the pivot bearing 5. The hatched portions in the drawing are effective portions that generate electromagnetic force in the direction of rotation.
[0038]
The wide portion of the tip of the air-core coil 14 has corner portions 14a and 14b. In the present embodiment, the radii of curvature of the inner corners of the air core coil 14 in this portion are R1 and R2, respectively, and a relationship of R1 <R2 is provided therebetween. In order to realize this shape, it is known to use a winding frame provided with the required shape to a winding frame for winding a coil and having walls on both sides (partly or entirely in the thickness direction). This winding frame is set in a winding machine and winding is performed as shown in FIG. 4 (b). In order to enhance the characteristics (efficiency) of the VCM 16, the air-core coil 14 is mounted as shown in FIG. 4 (c). In addition, it is desirable to increase the space factor as an aligned winding so that the thickness is T and the width is W.
[0039]
Further, in the present embodiment, a relationship of L1 = L2 is provided between the lengths L1 and L2 of the portion generating the electromagnetic force in the rotating direction. As described above, the effective length in the radial direction for generating torque with respect to the interlinkage magnetic flux is the same, and the same electromagnetic force is applied to the rotation center 5c in the rotation direction and the components in directions other than the rotation direction. This is because consideration is given to the occurrence of As a result, unnecessary vibrations can be prevented from occurring as the VCM 16 or the HDD, so that good results are obtained for the seek characteristics, settling characteristics, and the like. This also takes into account that the HDD can be replaced without changing the firmware or the like.
[0040]
As shown in FIG. 5A, the conductor forming the air-core coil 14 is such that a core 31 made of aluminum having a rectangular and flat cross section is surrounded by a clad 32 made of electrolytic copper, and this is made of polyurethane. A self-fusing conductive wire 30 covered with an insulating layer 33 made of, for example, and a fusion layer 34 made of, for example, polyamide is adhered thereon can also be used. In this case, winding is performed as shown in FIG. 5B, but by laminating the flat main surfaces 35, the thickness is T and the width is W as shown in FIG. The layers are stacked so that the space factor is higher than that of a circular cross section shown in FIG. The improvement of the space factor improves the thrust of the VCM, and the seek speed can be improved in accordance with the improvement of the thrust, and thus the performance of the HDD can be improved.
[0041]
When the conductor 20 or 30 having a core whose main component is aluminum having a circular or rectangular cross section is used, the air core coil can be made lighter, so that the acceleration characteristics of the VCM are improved. Can be reduced. In addition, an alloy whose main component is aluminum and whose weight is reduced may be used for the conductor portion without distinction between the core and the clad. In this case, since the relationship between the conductivity and the density can be appropriately selected, there is also an effect of increasing the degree of freedom in design. Furthermore, when the one covered with the clad made of copper is used, the heat conductivity of copper is high, so that the heat radiation property is improved, and it is possible to flow a larger current to improve the acceleration characteristics. .
[0042]
The air-core coil 14 or 14A formed as described above is integrally formed of resin and fixed to the coil arm 13. A pivot hole 13a for fitting and fixing to the pivot bearing 5 is formed at a predetermined position in the coil arm 13. Then, the pivot bearing 5 is fitted into the pivot hole 13a, and becomes the center of rotation of the VCM 16. As a material of the coil arm 13, a resin such as PPS is used. It is desirable to use a material having good moldability and low dust generation. In addition, the vibration damping effect can be enhanced by using an additive that easily converts vibration energy into heat energy due to displacement inside. Since the coefficient of restitution is lower than that of a metal material, it is also effective in reducing noise.
[0043]
Although not shown, the conductor forming the air-core coil 14 is self-fused by covering a circular or rectangular electrolytic copper with polyurethane as an insulating layer and then coating polyamide as a fusion layer thereon. Landing can also be used.
[0044]
Next, the fusion of the air-core coil will be described. As described with reference to FIG. 4 or FIG. 5, the fusion layers 24 and 34 applied to the outermost sides of the conductive wires 20 and 30 are made of polyamide. These fusion layers 24 and 34 can be fused while winding. In this case, hot air is applied by a drier or the like, or an organic solvent such as alcohol is applied. Further, in the case of performing the fusion after the winding, the conductor is energized to generate Joule heat to perform the fusion. In any method, the material and composition of the fusion layer suitable for each method are appropriately selected. In the method of energizing the coil, if the wire is broken, no heat is generated and the coil is not fused, so that the coil can be detected by fraying. Further, by applying the pulse current, it is possible to confirm that there is a short circuit between the lines in the middle of the lines (called a rare short circuit) and that the number of turns and the resistance value are within predetermined ranges. When the fusion is completed, the shape of the air core coil is preserved as a required shape.
[0045]
By the way, the mechanical stress on the coil can be reduced when the conductor is fused by applying hot air, and the mechanical stress on the coil is reduced when the conductor is fused while applying an organic solvent such as alcohol. In addition to reducing oil content, it can also remove oil, and when welding by applying a pulse current, the short circuit between coils can be confirmed in the same process, and the advantage that the electrical variation of the coil can be managed. There is.
[0046]
FIG. 6 shows a waveform when a pulse current is applied to the coil. In FIG. 6, (a) shows a voltage waveform 40 of a pulse current to be supplied, and (b) shows a waveform of a voltage generated in the coil. (B) shows a voltage waveform 41 of a good coil and a voltage waveform 42 of a coil whose number of turns is reduced due to a rare short. An air-core coil having a reduced number of turns due to a rare short can have a different transient waveform because of its low resistance and low inductance. The characteristics of the coil can be selected by appropriately giving an allowable range for the period, the peak value, the position, and the like.
[0047]
Next, the integral molding of the air core coil 14 (14A) and the coil arm 13 will be described with reference to FIG. In FIG. 7, the mold 51 on the fixed side has a shape corresponding to the winding frame, and in the present embodiment, a projection 51a having the same shape is provided. The protrusion 51a has a radius of curvature corresponding to the radii of curvature R1 and R2 of the wide inner diameter portion of the trapezoid of the air-core coil 14 so that the air-core coil 14 can be distinguished from each other so as not to be line-symmetric. A cavity 51c having a projection 51b for forming the pivot hole 13a of the coil arm 13 is formed in the fixed mold 51. A cavity 52c that also forms a coil arm is formed in the movable mold 52. Further, a gate 51d for feeding the resin from the nozzle of the molding machine to the cavities 51c and 52c is provided in the fixed mold 51. Therefore, after the air core coil 14 is mounted on the projection 51a of the fixed mold 51, the two molds 51 and 52 are closed, filled with a thermoplastic resin and integrally molded. Thereby, the air core coil 14 and the coil arm 13 are integrated, and the coil arm assembly 18 can be formed.
[0048]
Next, the molding procedure will be described with reference to FIG. Although the description will be partially duplicated, first, the winding process will be described. In step 101, a self-fusing lead wire for an air-core coil is set on the bobbin, and in step 102, the winding machine is rotated to wind the lead wire around the bobbin. In the procedure of Step 102, Step 102A for fusing with hot air or Step 102B for fusing with an organic solvent may be included. Then, in step 103, an air-core coil is formed. In the case where welding is performed by energizing without performing the above steps 102A or 102B, a step 102C for energizing this coil and fusing with Joule heat is inserted after the coil is wound in step 102. For the fusion, one of the three types shown here can be appropriately selected. The air-core coil that has been fused is removed from the bobbin at step 104, thereby completing the air-core coil.
[0049]
In step 104A, if necessary, a pulse test is performed to inspect the coil, and a defective coil such as a rare short circuit is removed. The process of step 104 can be performed in a state where the air core coil is on the bobbin or in a state where it is removed from the bobbin. Subsequently, the steps after step 105 are integrated molding steps. That is, in step 105, the front and back sides are uniformly determined by attaching the air-core coil to the shape corresponding to the mold winding frame. In the next step 106, the coil and the coil arm having a required shape are integrally formed by closing the mold and injecting resin. Thereafter, in step 107, the mold is opened, and the VCM coil in which the coil and the coil arm are integrally formed is completed. The completed VCM coil is assembled into a VCM in step 108, and is assembled into an HDD in the final step 109 to complete the HDD.
[0050]
As described above, the present invention has been described based on the preferred embodiments. However, it is apparent that the present invention can be appropriately modified using the technical concept of the present invention.
[0051]
【The invention's effect】
As is apparent from the above description, according to the method of molding a coil arm assembly of a VCM according to the present invention, the outer shape is trapezoidal, and two portions between the short side and the long side of the trapezoid are formed. An air-core coil is formed by winding a conductor having a fusion layer adhered to the surface thereof a plurality of times around a winding frame having the same side length and at least a part of the shape formed asymmetrically. The fused layers of the turned conductive wires are fused to each other, and this air-core coil is fitted into a mold having a projection having an outer shape substantially equal to the winding frame and a cavity corresponding to an arm member holding the air-core coil. Then, the mold is filled with resin to form the air core coil and the arm member integrally, so that the weight balance is not lost, the front and back of the air core coil can be reliably identified, and the wrong winding direction can be detected. Eliminates the need to check the winding direction Together, it is possible to reduce the cost.
[Brief description of the drawings]
FIG. 1 is a plan view showing a schematic configuration of an embodiment of a magnetic disk drive according to the present invention.
FIG. 2 is a perspective view showing a detailed configuration of a main part of a voice coil motor constituting the embodiment shown in FIG. 1;
FIG. 3 is an enlarged perspective view of a coil constituting the voice coil motor shown in FIG. 2;
FIG. 4 is a cross-sectional perspective view and a cross-sectional view showing a laminated state of a conductor constituting the air-core coil shown in FIG. 3;
FIG. 5 is a cross-sectional perspective view and a cross-sectional view showing a laminated state of another conductor forming the air-core coil shown in FIG. 3;
FIG. 6 is a waveform chart for explaining a rare short test of the air-core coil shown in FIG. 3;
FIG. 7 is a perspective view showing the configuration of a mold for integrally molding the coil shown in FIG. 3;
FIG. 8 is a flowchart showing a procedure for forming the coil arm assembly of the voice coil motor shown in FIG. 3;
[Explanation of symbols]
1 Head disk assembly (HDA)
2 chassis
4 Lower yoke (back yoke)
5 Pivot bearing
6 disks
7 Spindle motor
8 lamp block
9 tabs
10 Actuator
11 Magnetic head
12 Suspension (support member)
13 Coil arm (arm member)
14, 14A air core coil
15 coils
16 Voice coil motor
17 permanent magnet
18 Coil arm assembly
20, 30 conductor
21, 31 core
22, 32 clad
23, 33 insulating layer
35 main surface
24, 34 Fusion layer
51 Fixed side mold
52 Movable mold

Claims (16)

An outer shape is a trapezoidal shape, a length of two sides between a short side portion and a long side portion of the trapezoidal shape is the same, and at least a part of the winding form is asymmetrically prepared. Forming an air-core coil by winding the conductive wire to which the fusion layer is applied a plurality of times around the bobbin;
Fusing the fused layers of the conductive wires wound adjacent to each other;
Preparing a mold having a projection having substantially the same outer shape as the winding frame and a cavity corresponding to an arm member holding the air core coil, and fitting the air core coil to the projection,
Filling the resin in the mold and integrally molding the air core coil and the arm member,
A method for forming a coil arm assembly of a voice coil motor provided with the same. 2. The method of claim 1, wherein the step of forming the air core coil by winding the conductive wire around the bobbin and the step of fusing the fusion layer are performed in the same step. 3. . 3. The method for forming a coil arm assembly of a voice coil motor according to claim 1, wherein the fusion layers of the adjacent wires are fused to each other by Joule heat generated by energizing the wires. 4. The method according to claim 3, wherein a pulse current is applied to the conductor. 3. The method of claim 1, wherein a fusion layer of the adjacent wires is fused to each other by applying hot air to the wires. 4. 3. The method for forming a coil arm assembly of a voice coil motor according to claim 1, wherein the fusion layers of the adjacent wires are fused to each other by applying an organic solvent. The method for forming a coil arm assembly of a voice coil motor according to any one of claims 1 to 6, wherein the conductive wire has a rectangular shape and a flat cross section, and is wound such that the flat main surfaces overlap. An arm member whose base end is rotatably held;
The outer shape is trapezoidal, and the two sides between the short side and the long side of the trapezoid have the same length and at least a part of the shape is asymmetric. With the formed air core coil,
A coil arm assembly for a voice coil motor, wherein the arm member is formed of a resin molded product, and the air core coil and the arm member are integrally formed. The air-core coil is formed by winding a wire having a fusion layer adhered to the surface a plurality of times in a trapezoidal shape, and fusing the fusion layers of the adjacently wound wires to each other. 9. A coil arm assembly for a voice coil motor according to claim 8. The coil arm assembly for a voice coil motor according to claim 8 or 9, wherein the conductive wire has a rectangular cross section and is flat and is wound so that the flat main surfaces overlap. The coil arm assembly of a voice coil motor according to any one of claims 8 to 10, wherein the conductive wire is mainly composed of aluminum. The coil arm assembly of a voice coil motor according to any one of claims 8 to 10, wherein the conductive wire is a copper clad aluminum wire. The coil arm assembly for a voice coil motor according to any one of claims 8 to 12, wherein portions of the air core coil that generate thrust by electromagnetic force are substantially equal. A pair of yokes arranged facing each other,
A permanent magnet attached to at least one opposing surface of the pair of yokes,
A coil that is disposed in a magnetic gap formed between the permanent magnet and the other yoke and that is held by an arm member whose base end is rotatably supported,
An air-core coil in which the coil has a trapezoidal outer shape, and two sides between a short side and a long side of the trapezoid have the same length and at least a part of the coil is asymmetrically formed. Wherein the arm member is formed of a resin molded product, and the air core coil and the arm member are integrally formed. A magnetic disk held rotatably substantially parallel to the main surface of the chassis,
A pair of yokes that are held substantially parallel to the main surface of the chassis at a position separated from the magnetic disk, and that are held so as to face each other at a predetermined interval,
A permanent magnet attached to at least one opposing surface of the pair of yokes,
A longitudinal middle portion is rotatably held substantially parallel to the main surface of the chassis, a support member holding a magnetic head at a tip extending to one side from a rotation center, and a support member extending to the other from the rotation center to the other. An actuator comprising a coil movable in a magnetic gap formed between the pair of yokes,
The coil has an arm member whose base end is rotatably held, and is fixed to the distal end of the arm member, the outer shape is a trapezoidal shape, and a short side and a long side of the trapezoidal shape are formed. An air-core coil in which the length of two sides between them is the same and at least a part of the shape is formed asymmetrically, the arm member is formed of a resin molded product, and the air-core coil and the arm A magnetic disk drive in which a member is integrally formed. 16. The magnetic disk drive according to claim 15, wherein the resin is a thermoplastic resin.

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