JP2002237159A - Base plate of suspension for disk drive and method of manufacturing for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base plate which is capable of caulking a boss portion to an actuator arm without any problems and can suppress the deformation at points other than the boss portion. SOLUTION: The base plate 20 to be fixed to a load beam has a plate body section 30 to be superposed on the load beam and the boss portion 31 formed by plastic working, such as pressing. The boss portion 31 is provided with a caulking coupling portion 36 to be inserted into the mounting hole of the actuator arm. The base plate 20 is fixed to the actuator arm by caulking the caulking coupling portion 36. The caulking coupling portion 36 is partially annealed by irradiating the boss portion 31 with a laser beam in such a manner that the hardness is made lower than the hardness of work hardening induced when the boss portion 31 is molded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base plate for a disk drive suspension incorporated in an information processing apparatus such as a personal computer, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A hard disk drive (HDD) for recording and reproducing information on a rotating magnetic disk or a magneto-optical disk or the like has a carriage that can turn about an axis. The carriage is driven to rotate about the axis by a positioning motor. The carriage includes an actuator arm (an arm member also called a stack arm), a suspension provided at a distal end of the arm member, a head unit including a slider attached to the distal end of the suspension, and the like.

When the disk rotates, the slider of the head part slightly floats from the disk surface, and an air bearing is formed between the disk and the slider. This suspension includes a base portion including a base plate, a load beam formed of a precision thin leaf spring, and a flexure fixed to the load beam by laser welding or the like.

A base plate made of a metal such as stainless steel has a plate body fixed to the base of the load beam by laser welding or the like. Further, a short cylindrical boss may be formed on the base plate by plastic working such as pressing. The boss has a caulking joint inserted into the hole of the arm member, and is fixed to the arm member by plastically deforming the caulking joint radially with a jig or the like.

In the base plate, when the boss is formed by pressing, work hardening occurs in the plastically deformed portion including the boss. If the boss portion whose hardness has been increased by work hardening is directly caulked to the arm member, the caulking joint portion is too hard to be plastically deformed, so that satisfactory caulking cannot be performed. Therefore, conventionally, after forming the boss, the entire base plate is placed in a furnace and heated, and the hardness of the base plate is reduced by heat treatment such as annealing.

[0006]

When the entire base plate is heated to an annealing temperature after the boss is formed as described above, the residual stress generated when the boss is formed is released. The base plate may be deformed. Further, since the entire base plate is softened by annealing, portions other than the boss portion are easily deformed by external force.

When a suspension whose entire base plate is softened is attached to an arm member, if the base plate is mishandled, parts other than the boss may be plastically deformed by some external force. When the base plate is deformed, the positional relationship between the arm member and the load beam may be disturbed in a state where the suspension is assembled to the arm member. In such a case, it is difficult to accurately control the relative position between the recording surface of the disk and the head portion of the suspension, or the flying height of the slider with respect to the disk is adversely affected. Cannot be exhibited.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a base plate which can caulk a boss portion to an arm member without any problem and make it difficult to deform portions other than the boss portion, and a method of manufacturing the same. .

[0009]

A base plate according to the present invention for achieving the above object is made of a metal material such as stainless steel, and has a plate main body superposed on a load beam;
A boss portion provided with a caulking connection portion fixed to an arm member such as an actuator arm, wherein the caulking connection portion is heat-treated to a hardness equal to or less than the hardness of the plate body portion.

Further, in the method of manufacturing a base plate according to the present invention, there is provided a step of forming a boss by plastically processing a part of a metal base plate, and locally heating and hardening the boss by the plastic working by heating means. And a heat treatment step of softening the boss portion from the hardness at the time of work hardening by heating the boss portion.

In the manufacturing method of the present invention, preferably, a laser beam is used for the heating means, and the laser beam is applied to a region (for example, a circular or square region) centered on the boss portion, thereby obtaining the boss portion. Is heated to the annealing temperature. More preferably, in the present invention, an optical fiber bundle is used as an optical system for transmitting the laser beam, and the laser beam emitted by the laser oscillator is transmitted to the laser beam emitting end side via the optical fiber bundle. Good.

The base plate has a first surface on which the boss protrudes and a second surface on which the boss does not protrude (a surface on the back side of the base plate). The boss may be irradiated from the second surface side.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. A hard disk drive 10 shown in FIG. 1 includes a suspension 12 for recording and reproducing information on a recording surface of a disk 11 as a recording medium, an actuator arm 13 as an example of an arm member to which the suspension 12 is attached, and a suspension 12. A head section 14 and the like provided at the distal end are provided. The actuator arm 13 is an example of an arm member also called a stack arm. The actuator arm 13 is turned around an axis (not shown) by a positioning motor (not shown).

Disk drive suspension 12
As shown in an example in FIG. 3, a suspension 21 including a base plate 21 including a base plate 20 is provided.
A load beam 22 extending in the direction of the second head portion 14;
A flexure 23 attached to the load beam 22 is provided. The load beam 22 is made of a material having a spring property (for example, stainless steel having a thickness of about 60 μm, or a clad material of aluminum and stainless steel). The flexure 23 is made of a leaf spring that is thinner than the load beam 22, and has a thickness of, for example, about 20 μm. A slider 24 constituting the head unit 14 is attached to the tip of the flexure 22.

The base plate 20 is made of, for example, stainless steel having a thickness of about 200 μm. The base plate 20 is fixed to the base 22 a of the load beam 22 by laser welding while being superposed on the base 22 a of the load beam 22. The base plate 20 has a plate main body 30 to be superimposed on the load beam 22 and a short cylindrical boss 31 formed by plastic working such as pressing.

The boss portion 31 is connected to the actuator arm 13.
2 and a through-hole 37 that penetrates the caulking connection portion 36 in the axial direction of the boss 31. When a plurality of suspensions 12 are mounted adjacent to each other on the actuator arm 13 as shown in FIG. 1, a spacer 41 having a hole 40 is provided between the base plates 20 of each suspension 12.

The base plate 20 has a first surface 20a on the side from which the caulking joint 36 protrudes, and a caulking joint 3
The second surface 20 on the side from which the protrusion 6 does not project (the back side of the boss portion 31)
b. As shown in FIG.
Protrudes from the first surface 20a to the outside of the plate body 30 by a height H.

As shown in FIG. 2, the caulking connection portion 36 is inserted into the mounting hole 35 of the actuator arm 13 and the caulking connection portion 36 is caulked, so that the base plate 2
0 is fixed to the actuator arm 13. For example, a jig or a steel ball having an outer diameter slightly larger than the inner diameter D of the through hole 37 of the boss portion 31 is passed through the through hole 37, and the caulking portion 36 is plastically deformed so as to expand in the radial direction. The connecting portion 36 is fixed to the inner peripheral surface of the mounting hole 35.

When the boss portion 31 of the base plate 20 is plastically worked by a press or the like, the boss portion 31 and an area around the boss portion 31 are hardened. Since the boss portion 31 needs to plastically deform the caulking joint portion 36 when attaching the base plate 20 to the actuator arm 13, the boss portion 31 is partially annealed by the heat treatment device 50 described below to have a hardness higher than the hardness at the time of work hardening. Softened.

If the plate body 30 is pressed in the thickness direction when the boss 31 is formed, the plate body 30 will also be hardened to some extent. However, since it is desired that the plate main body 30 is hard and hardly deformed, it is better that the work hardening of the plate main body 30 is maintained. An example of the hardness of the base plate 20 before forming the boss portion 31 is HV18 in Vickers hardness.
0 to 190. The hardness of the boss 31 when the boss 31 is formed and hardened is, for example, HV300 or more.

When the boss 31 is partially annealed by the heat treatment apparatus 50 shown in FIG.
Softens to V180 or less. As described above, the hardness of the caulked joint portion 36 after the annealing is smaller than the hardness of the hardest portion of the plate body 30. That is, the caulked joint 36 is annealed to a hardness equal to or less than the hardness of the plate body 30.

The heat treatment apparatus 50 shown in FIG. 4 includes a YAG laser oscillator 51 for emitting a laser beam, and a power supply 52
A cooling table 53, a movable table 55 having a holder 54 for holding the base plate 20, a table controller 56, a laser emission port 57, a monitor camera 58 using a CCD or the like, and laser emission from the laser oscillator 51. An optical system 59 for transmitting a laser beam to the opening 57 and a monitor display device 60 are provided.

An optical system 59 whose one example is shown in FIG. 5 includes an incident side lens 62 facing the exit end of a YAG rod 61, an optical fiber bundle 63 which is an aggregate of many optical fibers, and
A lens 64 facing the exit end of the optical fiber bundle 63;
A beam reflection mirror 65, an exit lens 66, and the like are provided. The base plate 20 is provided at a position farther than the focal length f of the emission side lens 66, and the laser beam B emitted from the emission side lens 66 toward the boss portion 31 passes through the focal point f, and The boss portion 31 is irradiated so as to draw a circular outline B ′ (shown in FIG. 6) concentric with the portion 31.

In the case of the optical system 59 shown in FIGS. 4 and 5,
The base plate 20 on the movable table 55 is imaged by the monitor camera 58 whose optical axis coincides with the emission side lens 66, and the image is displayed on the monitor display device 60. In this way, the position of the movable table 55 can be adjusted by the table controller 56 so that the center C (shown in FIG. 6) of the boss portion 31 of the base plate 20 matches the center of the laser beam B.

The base plate 20 includes a caulking connection 36
Has a first surface 20a protruding from the boss portion 31 and a second surface 20b behind the boss portion 31. The boss portion 31 is irradiated with the laser beam B from the second surface 20b side. . Although the reason is not clear when the laser beam B is irradiated from the second surface 20b side as described above, the deformation due to heating is smaller than when the laser beam B is irradiated from the first surface 20a side. It is known from experiments by the present inventors.

In order to suppress discoloration due to heating when the boss 31 is irradiated with the laser beam B, an inert gas such as a nitrogen gas is supplied into the chamber 70 accommodating the base plate 20, and an inert gas atmosphere is supplied. The annealing heating by the laser beam B may be performed in the inside.

As shown in FIG. 6, the boss 31 can be annealed by irradiating the boss 31 with the laser beam B such that the contour B 'of the laser beam B is concentric with the boss 31 as a center. The temperature, for example, in the case of stainless steel, is heated to a transformation point (about 940 to 950 degrees) which becomes an austenite state and a melting temperature or less, and then gradually cooled, so that at least the caulking joint portion 36 has a hardness at the time of work hardening. Than soften.

The reason why the optical fiber bundle 63 is used for the optical system 59 is to make the energy distribution of the laser beam B uniform to some extent. That is, the laser beam B such as a YAG laser passes through the optical fiber bundle 63, so as to be within a certain range S from the center of the laser beam B, regardless of the distance from the center of the laser beam B, as indicated by L1 in FIG. There is a characteristic that the energy distribution becomes flat to some extent.

If the energy distribution is averaged in this way, even if the accuracy of the laser irradiation position on the boss portion 31 is somewhat poor, there is no large difference in the energy applied by the laser beam B to the boss portion 31. That is, by using the optical fiber bundle 63 in the transmission path of the laser beam B, the accuracy of the irradiation position, which is one of the factors that cause the heating to vary, is reduced, so that the heating by the laser beam B can be easily controlled. By changing the cross section of the optical fiber bundle from a circular shape to a substantially square shape, the energy distribution can be made more uniform, and the control of the laser irradiation position can be further facilitated.

In a fixed optical system that does not use the optical fiber bundle 63 (when a laser beam is transmitted only by a reflecting surface or a lens), the energy distribution becomes close to an approximate normal distribution as shown by a two-dot chain line L2 in FIG. . That is, when the optical fiber bundle 63 is not used, high energy is concentrated at the center portion of the laser beam, and the energy distribution is such that the energy decreases rapidly as the distance from the center of the laser beam increases.

Therefore, when the boss 31 is heated by a fixed optical system that does not use the optical fiber bundle 63, a portion where the energy of the laser beam is low is used, and unless the laser irradiation position is managed with high precision, Boss part 3
There is a problem that the variation in the energy received by 1 increases.

On the other hand, the heat treatment apparatus 50 of the above embodiment
In the case of (1), by using the optical fiber bundle 63 in the transmission path of the laser beam B, the accuracy of the irradiation position, which is one of the factors that cause the heating to vary, is reduced.
This makes it easier to control heating.

The base plate 20 is manufactured through a step of forming the boss 31 on the base plate 20 by plastic working such as pressing, and a heat treatment step of partially annealing the boss 31 that has been hardened by the heat treatment apparatus 50. Since the boss portion 31 is partially annealed by the heat treatment device 50, deformation due to release of residual stress generated during the formation of the base plate 20 can be suppressed as compared with the case where the entire base plate is annealed. Further, since the portion other than the boss portion 31 is not softened, it is possible to avoid, for example, the plate body portion 30 being deformed by some external force.

In practicing the present invention, including the embodiments described above, the constituent elements of the present invention, such as the shapes of the base plate, the plate main body and the boss, the shape of the heating means and the optical system, are described in the gist of the present invention. It goes without saying that various changes can be made without departing from the scope of the present invention. For example, the heating means may locally heat the boss by heating, radiant heat, high frequency heating, or other means other than the laser beam to perform partial annealing.

[0035]

According to the base plate of the present invention, the swaged joint of the boss can be swaged to the arm member without any problem, and the portions other than the boss can be hardly deformed. it can. According to the present invention,
Compared with the case where the entire base plate is annealed, the deformation of the base plate due to the release of the residual stress at the time of forming the boss portion can be suppressed.

According to the manufacturing method of the present invention, the hardness of the boss portion hardened by plastic working such as pressing is reduced by partial annealing, so that the boss portion can be caulked to the actuator arm without any problem. In addition, since the entire base plate is not annealed, it is possible to prevent the portions other than the boss portion from being softened. According to the manufacturing method of the third aspect, the desired range of the boss can be heated to the annealing temperature by the laser beam applied to the boss.

According to the manufacturing method of the fourth aspect, by using the optical fiber bundle for the optical system for transmitting the laser beam, the energy distribution of the laser beam applied to the boss can be kept within a certain range from the center of the beam. If so, it can be averaged to some extent. Therefore, the energy loss of the laser beam is small, and the accuracy required for the laser irradiation position can be reduced. Claim 5
According to the manufacturing method described in (1), deformation of the base plate caused by heating when the boss is irradiated with the laser beam can be minimized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a part of a disk drive including a suspension having a base plate according to an embodiment of the present invention.

FIG. 2 is an exemplary sectional view showing a part of the disk drive shown in FIG. 1 in an enlarged manner;

FIG. 3 is a plan view of the suspension shown in FIG. 1;

FIG. 4 is a side view partially showing a heat treatment apparatus for partially annealing a boss portion of a base plate.

FIG. 5 is a side view of an optical system of the heat treatment apparatus shown in FIG.

FIG. 6 is a bottom view of the base plate of the suspension shown in FIG. 1;

FIG. 7 is a diagram showing an energy distribution of a laser beam transmitted by an optical fiber bundle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 ... Suspension for disk drive 13 ... Actuator arm (arm member) 20 ... Base plate 22 ... Load beam 30 ... Plate body 31 ... Boss 35 ... Mounting hole 36 ... Crimping joint 37 ... Through hole 50 ... Heat treatment device

Claims (5)

[Claims] 1. A metal base plate fixed to a load beam of a disk drive suspension, wherein the plate main body is overlapped with the load beam, and the arm is inserted into a hole of an arm member for mounting the suspension, and the arm is swaged. A boss portion having a caulking connection portion fixed to a member, wherein the caulking connection portion is heat-treated to a hardness equal to or less than the hardness of the plate body portion, wherein the base plate for a disk drive suspension is characterized in that . 2. A step of forming a boss portion by plastically processing a part of a metal base plate; and locally heating the boss portion hardened by the plastic working by a heating means to form the boss portion. A heat treatment step of softening the part from the hardness at the time of the work hardening, and a method of manufacturing a base plate for a disk drive suspension. 3. The base plate according to claim 2, wherein the boss is heated by using a laser beam for the heating means and irradiating the laser beam to a range centered on the boss. Production method. 4. The method according to claim 3, wherein an optical fiber bundle is used as an optical system for transmitting the laser beam emitted from the laser oscillator to an emission end side. 5. The base plate has a first surface on which the boss protrudes and a second surface on which the boss does not protrude.
The method for manufacturing a base plate according to claim 3, wherein the laser beam is applied to the boss portion from the second surface side.