U.S. patent application number 09/793410 was filed with the patent office on 2001-07-19 for suspension for disc drive and manufacturing method therefor.
This patent application is currently assigned to NHK Spring Co., Ltd.. Invention is credited to Hanya, Masao, Saito, Noriyuki, Takagi, Yasuji, Uozumi, Koji.
Application Number | 20010008475 09/793410 |
Document ID | / |
Family ID | 27335246 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008475 |
Kind Code |
A1 |
Takagi, Yasuji ; et
al. |
July 19, 2001 |
Suspension for disc drive and manufacturing method therefor
Abstract
A suspension for disc drive comprises a base plate, a load beam
attached to the base plate, and a flexure attached to the load
beam. The load beam includes a rigid body portion, formed of a
thick plate independent of the base plate, and a spring portion,
formed of a spring member in the form of a thin sheet independent
of the rigid body portion. The spring member connects the rigid
body portion and the base plate. The spring member is thinner than
the rigid body portion and has a lower spring constant. The spring
portion is more flexible than the rigid body portion.
Inventors: |
Takagi, Yasuji; (Ebina-shi,
JP) ; Uozumi, Koji; (Isehara-shi, JP) ; Hanya,
Masao; (Yokohama-shi, JP) ; Saito, Noriyuki;
(Aiko-gun, JP) |
Correspondence
Address: |
FRISHAUF, HOLTZ, GOODMAN &
LANGER & CHICK, PC
767 THIRD AVENUE
25TH AVE
NEW YORK
NY
10017-2023
US
|
Assignee: |
NHK Spring Co., Ltd.
Yokohama-shi
JP
|
Family ID: |
27335246 |
Appl. No.: |
09/793410 |
Filed: |
February 26, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09793410 |
Feb 26, 2001 |
|
|
|
09450148 |
Nov 29, 1999 |
|
|
|
Current U.S.
Class: |
360/244.8 ;
G9B/5.149; G9B/5.153 |
Current CPC
Class: |
Y10T 29/49121 20150115;
Y10T 29/49798 20150115; G11B 5/4833 20130101; Y10T 29/49027
20150115; G11B 5/4826 20130101; Y10T 29/49032 20150115; G11B 5/4813
20130101; Y10T 29/49025 20150115 |
Class at
Publication: |
360/244.8 |
International
Class: |
G11B 005/48; G11B
021/16 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 1999 |
JP |
11-263705 |
Feb 29, 2000 |
JP |
2000-054097 |
Claims
What is claimed is:
1. A suspension for disc drive, comprising: a base plate; a load
beam attached to the base plate; and a flexure attached to the load
beam and adapted to be fitted with a head portion, the load beam
including: a rigid body portion which is formed as a separate
member from the base plate and to which the flexure is fixed; and a
spring portion formed of a spring member which connects the rigid
body portion and the base plate together and which has a spring
constant lower than that of the body portion.
2. A suspension for disc drive according to claim 1, wherein said
rigid body portion of said load beam is formed of a light metal or
synthetic resin.
3. A suspension for disc drive according to claim 1, wherein said
load beam is a laminated member that is made up of at least two
kinds of materials including a light metal.
4. A suspension for disc drive according to claim 3, wherein said
load beam is a laminated member that is made up of an
aluminum-based metal plate and a stainless steel plate.
5. A suspension for disc drive according to claim 1, wherein said
load beam is a laminated member that is made up of an
aluminum-based metal plate and a stainless steel plate, said base
plate is a laminated member that is made up of an aluminum-based
metal plate and a stainless steel plate, and said spring member is
formed of stainless steel and laser-welded to both the stainless
steel plate of the load beam and the stainless steel plate of the
base plate.
6. A suspension for disc drive according to claim 1, wherein said
base plate is an arm-type long base plate and is made as a
laminated member that is made up of at least two kinds of materials
including a light metal.
7. A suspension for disc drive according to claim 1, wherein said
flexure and said spring portion are formed of one integral
sheet.
8. A method for manufacturing a suspension for disc drive,
comprising: a process for manufacturing a semi-finished suspension
product integrally including a base plate, a rigid body portion of
a load beam, and a pair of connecting portions connecting the base
plate and the rigid body portion; a process for fixing a spring
member, formed independently of the semi-finished suspension
product, to the base plate and the rigid body portion of the
semi-finished product; and a process for cutting off the connecting
portions, projecting individually from the opposite sides of the
spring member, from the base plate and the rigid body portion after
the spring member is fixed to the semi-finished suspension
product.
9. A method for manufacturing a suspension according to claim 8,
wherein the distance between said pair of connecting portions is
greater than the width of the spring member.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a Continuation-in-Part application of U.S. patent
application Ser. No. 09/450,138, filed Nov. 29, 1999, the entire
contents of which are incorporated herein by reference.
[0002] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Applications No. 11-263705,
filed Sep. 17, 1999; and No. 2000-054097, filed Feb. 29, 2000, the
entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to a suspension for disc drive
incorporated in an information processing apparatus, such as a
personal computer, and a manufacturing method therefor.
[0004] A hard disc drive (HDD) for recording on or retrieving
information from a rotating magnetic disc or magneto-optical disc
includes a carriage that can turn around a shaft. The carriage is
turned around the shaft by means of a positioning motor.
[0005] As described in U.S. Pat. No. 4,167,765, for example, the
carriage is provided with an arm, a suspension on the distal end
portion of the arm, a head portion including a slider attached to
the suspension, etc. When the slider is slightly lifted from the
disc as the disc rotates at high speed, an air bearing is formed
between the disc and the slider.
[0006] The suspension comprises a load beam formed of a precision
thin plate spring, a flexure formed of a very thin plate spring
that is fixed to the distal end portion of the load beam by laser
welding or the like, and a base plate fixed to the proximal portion
of the beam by laser welding or the like. The base plate is fixed
to a suspension mounting surface of the arm.
[0007] In modern disc drives of this type, the density of
information to be recorded tends to be enhanced, and the disc
rotation has an inclination to higher speed. Accordingly, the
suspensions for disc drive require a good vibration characteristic
such that they can be positioned highly accurately with respect to
the recording surface of discs. Further, the suspensions should not
be easily influenced by air turbulence that is caused by high-speed
rotation of the discs. To meet the demand for various new
functions, moreover, the suspensions of this type also tend to be
subjected to more complicated machining.
[0008] As the density of information to be stored in each disc
increases, the suspensions are expected to have high stiffness and
a low spring constant. FIG. 14 shows one such conventional
suspension 1, which comprises a load beam 2 that integrally
includes a rigid body portion 2a of length L1 and a spring portion
2b of length L2. Conventionally, therefore, the necessary
performance (high stiffness) for the rigid body portion 2a and the
performance (low spring constant) required by the spring portion 2b
cannot be secured at the same time.
[0009] The material and thickness of the whole rigid body portion
2a, in particular, are inevitably restricted by the required
properties of the spring portion 2b. In order to enhance the
stiffness of the body portion 2a, therefore, it is necessary to
form bent edges 3 by bending the opposite side edges of the rigid
body portion 2a or to form ribs 4 by embossing. Accordingly, the
load beam 2 must be subjected to high-accurately machining, thus
entailing a lot of processes for machining, and therefore, high
costs.
[0010] The bent edges 3 or ribs 4 on the load beam 2 may hinder a
flow of air. When a disc rotates at high speed, therefore, the load
beam 2 is easily influenced by air turbulence and flutters. A base
plate 5 is fixed to the proximal portion of the load beam 2.
Further, a flexure 6 is fixed to the distal end portion of the load
beam 2. The flexure 6 is fitted with a slider 8 that constitutes a
head portion 7.
[0011] In a load beam described in Jpn. Pat. Appln. KOKAI
Publication No. 9-191004, for example, the thickness of a spring
portion is partially reduced by partial etching in order to lower
the spring constant of the load beam. Since the thickness of the
spring portion cannot be accurately controlled by partial etching,
however, it is unstable, so that the spring constant is liable to
variation.
[0012] In the case of the suspension described in Jpn. Pat. Appln.
KOKAI Publication No. 9-128919, a plurality of narrow plate spring
portions are formed around a slider mounting portion of a load beam
by etching or pressing. The plate spring portions are deformed in
the thickness direction. In this prior art example, the plate
spring portions should be formed in a narrow region on the distal
end of the load beam. Therefore, the load beam requires very
delicate machining, so that its shape and spring constant are
liable to variation and its quality is unstable.
BRIEF SUMMARY OF THE INVENTION
[0013] Accordingly, the object of the present invention is to
provide a high-performance suspension for disc drive, capable of
ensuring required performance, and a manufacturing method
therefor.
[0014] In order to achieve the above object, a suspension for disc
drive according to the present invention comprises a base plate, a
load beam attached to the base plate, and a flexure attached to the
load beam and adapted to be fitted with a head portion. In this
suspension, the load beam includes a rigid body portion,
independent of the base plate and fixedly fitted with the flexure,
and a spring portion formed of a spring member formed independently
of the rigid body portion, connecting the body portion and the base
plate, and having a spring constant lower than that of the body
portion.
[0015] In this suspension, the rigid body portion and the spring
portion that constitute the load beam are separate components. In
order to obtain the necessary performance for the suspension,
therefore, suitable materials, thicknesses, etc. may be selected
individually for the rigid body portion and the spring portion. For
example, a thick plate is used for the rigid body portion of the
load beam, while a high-accuracy spring member with a low spring
constant, such as a thin rolled steel sheet is used for the spring
portion.
[0016] For example, stainless steel may be used for the rigid body
portion of the load beam. If the rigid body portion is formed of an
alloy of a light metal (lighter than iron), such as a titanium or
aluminum, or a synthetic resin, however, further reduction of
weight and higher stiffness can be reconciled. Alternatively, the
load beam and other structural components may be made of a
laminated member made up of a light metal (e.g., aluminum-based
metal, titanium, or the like) and a metal other than the light
metal. Instead of the light metal, an alloy containing the light
metal as its main ingredient may be used. The "laminated member"
referred to in the present specification may be a clad member
obtained by forcibly pressing different kinds of metals against one
another, or an integral member obtained by bonding different kinds
of metals together. In the present specification, the term
"aluminum-based metal" is intended to cover not only an aluminum
alloy but also pure aluminum. In this manner, the load beam or the
arm-type long base plate is made of a laminated member, and this
laminated member is formed of an aluminum-based metal, a Ti alloy,
or a material containing at least two kinds of light metal alloys.
Accordingly, the load beam and/or other structural components is
light in weight, and improved in frequency and vibration
characteristics. It should be noted that the components may be
homogenized by forming the flexure and the spring portion
integrally with each other from one continuous metal plate.
[0017] According to the invention, the material and thickness of
the rigid body portion that constitutes the load beam cannot be
restricted by the spring portion of the load beam. Therefore,
suitable materials and thicknesses may be selected individually for
the rigid body portion and the spring portion to meet their
respective requirements, so that the necessary performance for the
suspension can be fulfilled. If the rigid body portion of the load
beam is formed of a thick plate, for example, its stiffness can be
further enhanced and air resistance against it can be reduced
without forming bent edges or ribs on the load beam. Thus, the
influence of air turbulence is lessened when a disc rotates at high
speed, and suspension fluttering can be restrained.
[0018] According to the suspension of the invention, the spring
portion can enjoy a steady low spring constant, and high accuracy
of the spring portion can be reconciled with the low spring
constant. Since the rigid body portion of the load beam and the
spring portion are separate components, the rigid body portion can
be formed of a material softer than that of the spring portion.
Thus, the rigid body portion can be formed with a higher degree of
freedom of work, such as pressing.
[0019] Preferably, according to the invention, the rigid body
portion of the load beam is formed of a light metal or synthetic
resin. If the load beam is formed of a material with a low specific
gravity, such as an aluminum or titanium alloy or synthetic resin,
in this case, the load beam is reduced in weight, and its frequency
and vibration characteristics are improved. By using the
low-gravity material for both the load beam and the base plate,
moreover, the whole suspension can be further reduced in weight,
and the operation of the disc drive can be speeded up.
[0020] Preferably, moreover, the flexure and the spring portion are
formed of one integral metal sheet. With this arrangement, the
number of components that constitute the suspension can be reduced,
and the accuracy of relative positioning of the flexure and the
spring portion can be improved.
[0021] A method for manufacturing a suspension according to the
invention uses a semi-finished suspension product, which integrally
includes a base plate, a rigid body portion of a load beam, and a
pair of connecting portions connecting the base plate and the rigid
body portion. The method also uses a spring member that is formed
independently of the semi-finished suspension product. The distance
between the connecting portions of the semi-finished product is
greater than the width of the spring member. After the spring
member is fixed to the base plate and the rigid body portion of the
semi-finished product, the connecting portions, which project
individually from the opposite sides of the spring member, are cut
off from the base plate and the rigid body portion. According to
this manufacturing method, the base plate and the rigid body
portion can be handled as one body in some preceding processes for
manufacturing the suspension. Thus, a common material can be used
for the base plate and the rigid body portion, so that the number
of components used in the suspension can be reduced, and the base
plate and the rigid body portion can be positioned with higher
accuracy as the spring member is fixed to them.
[0022] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0023] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the invention, and together with the
general description given above and the detailed description of the
preferred embodiments given below, serve to explain the principles
of the invention.
[0024] FIG. 1 is a perspective view of a suspension for disc drive
according to a first embodiment of the present invention;
[0025] FIG. 2 is an exploded perspective view of the suspension
shown in FIG. 1;
[0026] FIG. 3 is a side view, partially in section, showing a hard
disc drive provided with the suspension shown in FIG. 1;
[0027] FIG. 4 is a perspective view of a suspension for disc drive
according to a second embodiment of the invention;
[0028] FIG. 5 is a perspective view of a suspension for disc drive
according to a third embodiment of the invention;
[0029] FIG. 6 is a perspective view of a suspension for disc drive
according to a fourth embodiment of the invention;
[0030] FIG. 7 is a perspective view of a suspension for disc drive
according to a fifth embodiment of the invention;
[0031] FIG. 8 is a perspective view showing a semi-finished
suspension product and a spring member used in the suspension shown
in FIG. 7;
[0032] FIG. 9 is a perspective view of a suspension for disc drive
according to a sixth embodiment of the invention;
[0033] FIG. 10 is an exploded perspective view of a suspension for
disc drive according to a seventh embodiment of the invention;
[0034] FIG. 11 is a perspective view of a suspension according to
an eighth embodiment of the present invention;
[0035] FIG. 12 is a perspective view of a suspension according to a
ninth embodiment of the present invention;
[0036] FIG. 13 is a graph showing resonance characteristics of a
SUS/Al Clad-Beam, a SUS-Beam and Al-Beam; and
[0037] FIG. 14 is a perspective view of a conventional disc-drive
suspension.
DETAILED DESCRIPTION OF THE INVENTION
[0038] A first embodiment of the present invention will now be
described with reference to FIGS. 1 to 3. A hard disc drive (HDD)
10 shown in FIG. 3 includes a carriage 12 that can turn around a
shaft 11. The carriage 12 is turned around the shaft 11 by means of
a positioning motor 13 such as a voice coil motor.
[0039] The carriage 12 is provided with a plurality of arms
(actuator arms) 16, suspensions 17 mounted individually on the
respective distal end portions of the arms 16, head portions 18
provided individually on the respective distal end portions of the
suspensions 17, etc. When the carriage 12 is actuated by the motor
13, each head portion 18 moves to a desired track of its
corresponding disc 19.
[0040] Each head portion 18 includes a slider 20, which is situated
in a position such that it can face the tracks of the disc 19, a
transducer (not shown) held thereon, etc. When the disc 19 rotates
at high speed, the slider 20 is slightly lifted from the disc 19 by
air between the two members, whereupon an air bearing is formed
between the disc 19 and the slider 20.
[0041] As shown in FIG. 1, each suspension 17 includes a base plate
30, a load beam 31 attached to the plate 30, etc. As shown in FIG.
3, the base plate 30 is fixed to its corresponding arm 16. The base
plate 30 is formed having a circular hole 33 into which a boss
portion (not shown) of the arm 16 is to be inserted.
[0042] As shown in FIG. 2, each load beam 31 is provided with a
rigid body portion 40, which is independent of the base plate 30,
and a spring portion 42 formed of a spring member 41 fixed to the
body portion 40. The rigid body portion 40 is thicker than the
spring member 41. That portion of the spring member 41 which
corresponds to length L in FIG. 1 is a region that functions as the
spring portion 42. The spring portion 42 has a spring constant
smaller than that of the body portion 40, and therefore, is more
flexible. To reconcile lightweight and high stiffness, the
illustrated body portion 40 is formed of a light alloy, such as an
aluminum alloy, and is penetrated by apertures 45 in the thickness
direction.
[0043] The apertures 45 may be replaced with recesses that are
formed by partially reducing the thickness of the rigid body
portion 40 by, for example, etching. A light metal (lower in
specific gravity than iron), such as a titanium or aluminum alloy,
or a synthetic resin may be used when forming the load beam 31. To
be specific, the load beam 31 may be made of a laminated member
made up of an Al alloy plate and a stainless steel plate. With use
of one such low-gravity material, the load beam 31 can be reduced
in weight, and its frequency and vibration characteristics can be
improved. If necessary, the load beam 31 may be subjected to
bending.
[0044] The plate-like spring member 41 that constitutes the spring
portion 42 is formed of a springy rolled stainless-steel sheet, for
example. One end portion 41a of the spring member 41 is put on and
fixed to an end portion 40a of the rigid body portion 40 by laser
welding or the like. The other end portion 41b of the spring member
41 is put on and fixed to the base plate 30 by laser welding or the
like.
[0045] The spring member 41 may be fixed to the rigid body portion
40 of the load beam 31 with use of an adhesive in place of welding.
In the case where the body portion 40 is formed of a synthetic
resin, the spring member 41 may be fixed to it by the so-called
in-mold forming. In this in-mold forming, the spring member 41 is
set in a mold for molding the rigid body portion 40, and a resin
material is poured into the mold in this state and cured.
[0046] A flexure 50, a very thin plate spring, is attached to the
rigid body portion 40. The flexure 50, which is formed of a rolled
stainless-steel sheet, for example, is fixed to the load beam 31 by
laser welding or the like. As shown in FIG. 2, a protuberance 51 is
provided on an end portion 40b of the body portion 40. The
protuberance 51 is in contact with a tongue portion 52 of the
flexure 50. The protuberance 51 projects toward the tongue portion
52. The slider 20, which constitutes each head portion 18, is
mounted on the flexure 50.
[0047] In the suspension 17 constructed in this manner, the rigid
body portion 40 and the spring portion 42 that constitute each load
beam 31 are separate components. Suitable materials and thicknesses
may be selected individually for the body portion 40 and the spring
portion 42. Accordingly, it is easy to reconcile the necessary
performance (e.g., high stiffness) for the body portion 40 and the
required performance (e.g., low spring constant) for the spring
portion 42. Since a high-accuracy rolled sheet is used for the
spring member 41, moreover, the spring portion 42 can enjoy a
steady low spring constant.
[0048] A thick plate can be used for the load beam 31 according to
this embodiment. As compared with the prior art example of FIG. 14
that is provided with the bent edges and ribs, therefore, the load
beam 31 can be shaped so that it cannot easily disturb a flow of
air, and stiffness of the load beam 31 is enhanced. Thus, the
influence of air turbulence is lessened even though the disc
rotates at high speed.
[0049] FIG. 4 shows a suspension 17A according to a second
embodiment of the invention. A spring portion 42 of the suspension
17A includes bent portions 60, which are formed by bending the
longitudinally intermediate portion of a spring member 41. For
other arrangements, the suspension 17A resembles the suspension 17
according to the first embodiment, so that common reference
numerals are used to designate portions that are common to the
first and second embodiments, and a description of those portions
is omitted.
[0050] FIG. 5 shows a suspension 17B according to a third
embodiment of the invention. The suspension 17B has an aperture 61
formed in the central portion of a spring member 41. The opposite
sides of the aperture 61 of the spring member 41 serves as a spring
portion 42 with a low spring constant. Bent portions 60 are formed
by partially bending the spring member 41. For other arrangements,
the third embodiment resembles the first embodiment, so that common
reference numerals are used to designate portions that are common
to the first and third embodiments, and a description of those
portions is omitted.
[0051] FIG. 6 shows a suspension 17C according to a fourth
embodiment of the invention. The suspension 17C is provided with a
base plate 30C of the so-called arm type (i.e., a base plate having
an arm) and a flexure 50C which has a wiring board. The wired
flexure 50C includes a metal substrate 65, such as a springy rolled
stainless-steel sheet, an electric insulating layer formed on the
surface of the substrate 65, and conductive lines 66 on the
insulating layer. One end of each conductive line 66 is connected
electrically to terminals 67 of a head portion 18, and the other
end to terminals 68 on the base plate 30C. A part of a spring
member 41 is formed having bent portions 60 and an aperture 61. For
other arrangements, the fourth embodiment resembles the first
embodiment, so that common reference numerals are used to designate
portions that are common to the first and fourth embodiments, and a
description of those portions is omitted. The arm of the arm-type
base plate 30C may be made of: a light metal such as Ti, Al alloy,
or the like (i.e., a metal lower in specific gravity than iron); a
laminated member made up of Al and stainless steel; a synthetic
resin; or fiber-reinforced plastics. By use of these materials, the
weight can be as light as possible, and the frequency and vibration
characteristics can be improved.
[0052] FIG. 7 shows a suspension 17D according to a fifth
embodiment of the invention. The suspension 17D is manufactured
using a semi-finished suspension product 70, such as the one shown
in FIG. 8. The semi-finished product 70 includes a base plate 30, a
rigid body portion 40 of a load beam 31, and a pair of connecting
portions 71, right and left, connecting the plate 30 and the body
portion 40. The semi-finished product 70 is formed having the
elements 30, 40 and 71 by press working, for example. The distance
(W1) between the two connecting portions 71 is greater than the
width (W2) of the spring member 41. When the spring member 41 is
put on the base plate 30 and the rigid body portion 40, as shown in
FIG. 7, the connecting portions 71 project individually from the
opposite sides of the member 41.
[0053] The spring member 41 is put on both the rigid body portion
40 of the semi-finished suspension product 70 and the base plate
30, and is fixed to the plate 30 and the body portion 40 by laser
welding or the like. Thereafter, the connecting portions 71 that
project from the opposite sides of the spring member 41 are cut off
from the body portion 40 and the base plate 30 by press working or
the like.
[0054] According to this embodiment, the base plate 30 and the
rigid body portion 40 are connected by means of the connecting
portions 71 so that they form one integral part before the spring
member 41 is fixed to the semi-finished suspension product 70.
Thus, the base plate 30 and the body portion 40 can be handled with
ease, and their relative positions can be regulated more
accurately.
[0055] FIG. 9 shows a suspension 17E according to a sixth
embodiment of the invention. The suspension 17E has a spring
portion 42 and a flexure 50 that are formed from one platelike
spring member 41E. In this case, the components can be homogenized
by forming the spring portion 42 and the flexure 50 integrally with
each other. Further, a rigid body portion 40 and a base plate 30,
like those of the semi-finished suspension product 70 according to
the fifth embodiment, are connected by means of a pair of
connecting portions 71. The distance (W1) between the two
connecting portions 71 is greater than the width (W2) of the spring
member 41E. After the spring member 41E is fixed to the
semi-finished product 70, the connecting portions 71 that project
individually from the opposite sides of the spring member 41E are
cut off.
[0056] FIG. 10 shows a suspension 17F according to a seventh
embodiment of the invention. In the suspension 17F, a spring
portion 42 and a portion 80 to be put on a base plate 30 are formed
integrally on a platelike spring member 41F that constitutes a
flexure 5OF which has a wiring board. The wired flexure 50F
includes an electric insulating layer formed on the surface of a
metal substrate 65, such as a springy rolled stainless-steel sheet,
and conductive lines 66 on the insulating layer. One end of each
conductive line 66 is connected electrically to terminals 67 of a
head portion, and the other end to terminals 68 on the portion 80
that is put on the base plate 30. A body portion 40 and the base
plate 30 according to this embodiment, like those of the
semi-finished suspension product 70 according to the fifth
embodiment, are connected by means of a pair of connecting portions
71. After the spring member 41F is fixed to the semi-finished
product 70, the connecting portions 71 that project individually
from the opposite sides of the spring member 41F are cut off.
[0057] FIG. 11 shows a suspension 17G of the eighth embodiment of
the present invention. According to the eighth embodiment, the
rigid body portion 40 of the load beam 31 is a laminated member
(referred to as "SUS/Al Clad-beam" herein) made up of: a first
plate AL1 formed of an aluminum alloy and having a thickness of 100
.mu.m, and a second plate ST1 formed of a stainless steel and
having a thickness of 30 .mu.m. Likewise, the base plate 30 is a
laminated member made up of: a first plate AL2 formed of a light
alloy such as an aluminum alloy; and a second plate ST2 formed of a
stainless steel. The spring member 41 is formed of a stainless
steel. The spring member 41 is laser-welded to the stainless steel
plate ST1 of the rigid body portion 40 and the stainless steel
plate ST2 of the base plate 30. In FIG. 11, reference symbol "P"
indicates the welded portions.
[0058] FIG. 12 shows a suspension 17H of the ninth embodiment of
the present invention. According to the ninth embodiment, the rigid
body portion 40 of the load beam 31 is a laminated member (referred
to as "SUS/Al Clad-beam" herein) made up of: a first plate ST3
formed of a stainless steel; and a second plate ALl formed of an
aluminum alloy. The spring member 42 is made by part of the first
plate ST3. The base plate 30 is made of a second plate AL2 formed
of a light alloy such as an aluminum alloy. This second plate AL2
is overlaid with the first plate ST3 of stainless steel.
[0059] FIG. 13 is a graph showing the first torsion mode resonance
frequency. As shown in this graph, the first torsion mode resonance
frequency of the SUS/Al Clad-beam is higher than that of the load
beam (SUS-beam) formed only of stainless steel. In addition, the
SUS/Al Clad-beam is lighter in weight than the SUS-beam whose
thickness is 100 .mu.m. Hence, the SUS/Al Clad-beam is reliable in
frequency and vibration characteristics. As indicated by the
one-dot-chain lines in FIG. 13, an Al-beam formed of aluminum alone
and having a thickness of 160 .mu.m may show satisfactory frequency
characteristics. However, the Al-beam cannot be easily laser-welded
to a flexure or base plate formed of stainless steel.
[0060] It is to be understood that the components of the
suspension, such as the base plate, load beam, flexure, rigid body
portion, spring member, etc., may be suitably modified without
departing from the scope or spirit of the invention in carrying out
the invention.
[0061] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *