U.S. patent application number 10/842450 was filed with the patent office on 2004-11-18 for electrode plate unit for rechargeable battery and manufacturing method thereof.
This patent application is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Fujioka, Noriyuki, Kajiya, Hiromi, Karasawa, Shoji, Masaki, Masaru, Taniguchi, Akihiro, Tokutome, Yoshihiro.
Application Number | 20040226153 10/842450 |
Document ID | / |
Family ID | 17438691 |
Filed Date | 2004-11-18 |
United States Patent
Application |
20040226153 |
Kind Code |
A1 |
Karasawa, Shoji ; et
al. |
November 18, 2004 |
Electrode plate unit for rechargeable battery and manufacturing
method thereof
Abstract
A plurality of positive electrode plates and negative electrode
plates are stacked alternately upon one another with intervening
separators therebetween, wherein lateral edges of the positive
electrode plates protrude beyond the negative electrode plates on
one side, and lateral edges of the negative electrode plates
protrude beyond the group of positive electrode plates on the
opposite side. Collector plates are brought in tight contact with
respective lateral edges of the positive and negative electrode
plates, and heat is applied to the collector plate on an opposite
surface of the electrode plates from a non-contact type heat source
at several locations in lines along a direction in which the
electrode plates are stacked.
Inventors: |
Karasawa, Shoji; (Kosai-shi,
JP) ; Kajiya, Hiromi; (Toyohashi-shi, JP) ;
Tokutome, Yoshihiro; (Toyota-shi, JP) ; Taniguchi,
Akihiro; (Toyohashi-shi, JP) ; Fujioka, Noriyuki;
(Kosai-shi, JP) ; Masaki, Masaru; (Nisshin-shi,
JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1950 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
Matsushita Electric Industrial Co.,
Ltd.
Osaka
JP
Toyota Jidosha Kabushiki Kaisha
Aichi
JP
|
Family ID: |
17438691 |
Appl. No.: |
10/842450 |
Filed: |
May 11, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10842450 |
May 11, 2004 |
|
|
|
09664323 |
Sep 18, 2000 |
|
|
|
6761993 |
|
|
|
|
Current U.S.
Class: |
29/2 ;
29/623.4 |
Current CPC
Class: |
H01M 50/54 20210101;
Y10T 29/10 20150115; H01M 10/0413 20130101; Y10T 29/49114 20150115;
Y02P 70/50 20151101; H01M 4/48 20130101; Y02E 60/10 20130101 |
Class at
Publication: |
029/002 ;
029/623.4 |
International
Class: |
B23K 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 21, 1999 |
JP |
11-267001 |
Claims
What is claimed is:
1. A method of manufacturing an electrode plate unit for a battery
comprising: stacking a plurality of positive electrode plates and a
plurality of negative electrode plates alternately upon one another
with intervening separators therebetween; bringing a collector
plate .in tight contact with lateral edges on one lateral side of
the positive or negative electrode plates; and applying heat to the
collector plate on an opposite surface of the electrode plates from
a non-contact type heat source at several locations in lines along
a direction in which the electrode plates are stacked.
2. The method of manufacturing an electrode plate unit for a
battery according to claim 1, wherein a solder material is attached
on the collector plate on a surface which is contacted with the
electrode plates along a plurality of lines in the direction in
which the electrode plates are stacked, and heat is applied upon
said solder material.
3. The method of manufacturing an electrode plate unit for a
battery according to claim 1, wherein the positive or negative
electrode plates are pressed against a locating means so that the
lateral edges on one lateral side of the positive or negative
electrode plates are aligned, and heat is applied to the collector
plate in a state wherein the collector plate is tightly pressed
against the lateral edges of the positive or negative electrode
plates.
4. The method of manufacturing an electrode plate unit for a
battery according to claim 1, wherein heat is applied to the
collector plate by irradiating an electronic beam within a
vacuum.
5. The method of manufacturing an electrode plate unit for a
battery according to claim 4, wherein the collector plate, together
with the electrode plates in contact therewith, is demagnetized
before the application of heat.
6. A method of manufacturing an electrode plate unit for a battery
comprising: stacking a plurality of positive electrode plates and a
plurality of negative electrode plates alternately upon one another
with intervening separators therebetween, such that lateral edges
of the positive electrode plates protrude beyond the negative
electrode plates on one side, and lateral edges of the negative
electrode plates protrude beyond the group of positive electrode
plates on the opposite side; and welding a collector plate to the
lateral edges of at least one of the positive electrode plates and
the negative electrode plates, wherein a solder material is
arranged in advance to the collector plate at locations to be
bonded to the lateral edges of the positive or negative electrode
plates.
7. The method of manufacturing an electrode plate unit for a
battery according to claim 6, wherein the solder material is
applied on the collector plate by electrolytic or non-electrolytic
plating.
8. The method of manufacturing an electrode plate unit for a
battery according to claim 6, wherein the solder material is
attached on the collector plate by welding a sheet-like solder
material to the collector plate.
9. The method of manufacturing an electrode plate unit for a
battery according to claim 6, wherein the solder material is
attached on the collector plate on a surface which is contacted
with the electrode plates along a plurality of lines in the
direction in which the electrode plates are stacked, and heat is
applied upon said solder material.
10. A method of manufacturing an electrode plate unit for a battery
comprising: stacking a plurality of positive electrode plates and a
plurality of negative electrode plates alternately upon one another
with intervening separators therebetween, such that lateral edges
of the positive electrode plates protrude beyond the negative
electrode plates on one side, and lateral edges of the negative
electrode plates protrude beyond the group of positive electrode
plates on the opposite side; pressing the positive or negative
electrode plates against a locating means so that the lateral edges
on one lateral side of the positive or negative electrode plates
are aligned; bringing a collector plate in tight contact with said
aligned lateral edges on one lateral side of the positive or
negative electrode plates; and applying heat to the collector plate
on an opposite surface of the electrode plates from a non-contact
type heat source at several locations in lines along a direction in
which the electrode plates are stacked.
11. The method of manufacturing an electrode plate unit for a
battery according to claim 10, wherein heat is applied to the
collector plate by irradiating an electronic beam within a
vacuum.
12. The method of manufacturing an electrode plate unit for a
battery according to claim 11, wherein the collector plate,
together with the electrode plates in contact therewith, is
demagnetized before the application of heat.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present disclosure relates to subject matter contained
in Japanese Patent Application No. HEI 11-267001, filed on Sep. 21,
1999, the contents of which are expressly incorporated herein by
reference in their entirety. Further, the present application is a
divisional of U.S. patent application Ser. No. 09/664,323, filed on
Sep. 18, 2000, the contents of which are expressly incorporated
herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an electrode plate unit for
a rechargeable battery and a manufacturing method of same.
[0004] 2. Description of Related Art
[0005] Batteries are classified into primary batteries and
secondary batteries or rechargeable batteries, and there are
various configurations for each of these two types of battery. FIG.
17 shows a conventional battery module made by connecting a
plurality of rechargeable batteries and coupling them together as
one so as to obtain the necessary power. In this battery module, a
plurality of cells 41 (41a to 41j) made of sealed alkaline
rechargeable batteries as shown in FIG. 18 are arranged side by
side, with the long lateral walls of their battery cases 42
adjacent each other. End plates 52 are arranged against the outside
of the cells 41a and 41j at both ends, and the group of batteries
and the two end plates 52 are bound together with binding bands 53
so as to couple the cells together as one piece.
[0006] For the cells 41, an electrode plate group 47, comprising
positive electrode plates and negative electrode plates layered
with intervening separators, thereby constituting elements for
electromotive force, is accommodated in a battery case 42 together
with a liquid electrolyte, and the open end of the battery case 42
is closed with a lid 46 provided with a safety vent 45. From the
upper end at one side of the positive electrode plates forming the
electrode plate group 47, leads 49 extend upward and are connected
to a positive electrode terminal 43 above them, and similarly, from
the upper end of the other side of the negative electrode plates,
leads 49 extend upward and are connected to an negative electrode
terminal 44 above them. The positive electrode terminal 43 and the
negative electrode terminal 44 are attached to the lid 46.
[0007] The positive electrode terminals 43 and negative electrode
terminals 44 of coupled neighboring cells 41 are connected by
connection plates 51, thereby connecting all cells 41 in series.
When the battery cases 42 are coupled, ribs 48, which protrude
vertically from the long lateral walls of the battery cases 42, are
abutted against each other, forming coolant passages running in the
vertical direction along the long lateral walls of the battery
cases 42 in the space between ribs 48. The cells 41a to 41j are
cooled by flowing air through these coolant passages.
[0008] The leads 49 are integrated to the electrode plate group 47
by welding. For the welding of the leads, according to Japanese
Laid-Open Patent Application 7-220715, for example, laser welding
is used more favorably than resistance welding, because, in
resistance welding, the welding defects are often formed by the
generation of sparks caused by oxide films or other foreign
substances that exist in the welding portion, and uniform welding
cannot always be accomplished. Thus laser welding is more favorably
applied, and specifically, leads are usually provided with
through-holes, through which laser beams are passed, whereby these
through-holes are closed with molten metal, and when the metal
eventually cools down and sets, the leads are integrally welded
together.
[0009] With the configuration for the cells 41 of this conventional
battery module, leads 49 extend from a portion at the upper end on
one side of the electrodes and are connected to the electrode
terminals 43 and 44, and consequently, there were the problems that
the internal resistance of the battery was large, because the
average distance from the surface of the electrodes to the
collector portions of the leads 49 was long, and that the power
output was low, because the utilization rate of the electrode
active material was low.
[0010] The inventors of the present application have proposed an
electrode plate unit for a rechargeable battery, wherein collector
plates are abutted on the entire surface of the opposite lateral
ends of the group of electrode plates, with lateral edges of each
of electrode plates being integrally welded to the collector
plates. In connecting the lateral edges of the electrode plates to
the collector plates, however, sufficient bond cannot be achieved
in the case of employing a seam-welding method, with the result
that power output of the battery is decreased, or the welding
strength is low. On the other hand, if laser welding is used, it is
difficult to accomplish secure bonding of electrode plates with the
collector plates without causing any adverse effects to the
electrode plates. Accordingly, there is the need for a method of
bonding lateral edges of electrode plates with collector plates in
a favorable condition.
SUMMARY OF THE INVENTION
[0011] In view of these problems of the prior art, it is an object
of the present invention to provide an electrode plate unit for a
rechargeable battery, in which one lateral edge of an electrode
plate group is securely bonded to a collector plate, and to a
manufacturing method thereof.
[0012] To achieve the above object, a battery according to one
aspect of the present invention comprises an electrode plate unit,
including:
[0013] a plurality of positive electrode plates and a plurality of
negative electrode plates that are alternately stacked upon one
another with intervening separators therebetween, thereby
constituting a group of electrode plates, wherein lateral edges of
the positive electrode plates protrude beyond the negative
electrode plates on one side, and lateral edges of the negative
electrode plates protrude beyond the group of positive electrode
plates on the opposite side; and
[0014] a positive electrode collector plate and a negative
electrode collector plate that are respectively bonded to said
protruded lateral edges of the positive electrode plates and the
negative electrode plates, wherein the positive electrode collector
plate and the negative electrode collector plate are formed with
protruded portions on a surface which is to be bonded to the
lateral edges of the positive electrode plates and the negative
electrode plates.
[0015] While novel features of the invention are set forth in the
preceding, the invention, both as to organization and content, can
be further understood and appreciated, along with other objects and
features thereof, from the following detailed description and
examples when taken in conjunction with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is an external perspective view of a battery module
according to one embodiment of the present invention;
[0017] FIG. 2 is a partial lateral cross-sectional view of the
same;
[0018] FIG. 3 is a cross-sectional view taken in the direction of
the arrows along the line III-III in FIG. 2;
[0019] FIG. 4 is a front view of an electrode plate unit of the
same embodiment;
[0020] FIG. 5 is a cross-sectional view taken in the direction of
the arrows along the line V-V in FIG. 4;
[0021] FIG. 6A is a front view, FIG. 6B is a top plan view, and
FIG. 6C is an enlargement of VIC in FIG. 6B, showing a positive
electrode plate in the same embodiment;
[0022] FIG. 7A is a front view, FIG. 7B is a top plan view, and
FIG. 7C is an enlargement of VIIC in FIG. 7B, showing a negative
electrode plate in the same embodiment;
[0023] FIG. 8 is a flow chart of a manufacturing method of the
electrode plate unit;
[0024] FIG. 9A is a partial front view and FIG. 9B is a partial
side view showing one process step of manufacturing the electrode
plate unit;
[0025] FIG. 10 is a perspective view showing one process step of
welding a collector plate to the electrode plate group;
[0026] FIG. 11A is a partial front view and FIG. 11B is a partial
side view showing the welding step of FIG. 10;
[0027] FIG. 12A is a front view, FIG. 12B is a longitudinal side
elevation view, FIG. 12C is an enlargement of XIIC in FIG. 12B, and
FIG. 12D is an enlargement of XIID in FIG. 12B, showing a collector
plate in the same embodiment;
[0028] FIG. 13A is a front view, FIG. 13B is a longitudinal side
elevation view, FIG. 13C is an enlargement of XIIIC in FIG. 13B,
and FIG. 13D is an enlargement of XIIID in FIG. 13B, showing a
modification of the collector plate;
[0029] FIGS. 14A-14E are diagrams given in explanation of various
modifications of the arrangement of a corrugated portion of the
collector plate and a nickel solder material attached thereto;
[0030] FIG. 15A is a front view showing one modified example of a
lead portion of the electrode plate, FIGS. 15B and 15C are diagrams
given in explanation of another modified example; and FIG. 15D is a
partial front view showing yet another modified example;
[0031] FIGS. 16A and 16B are diagrams given in explanation of
another modified examples of the lead portion of the electrode
plate;
[0032] FIG. 17 is an external perspective view of a conventional
battery module; and
[0033] FIG. 18 is a partially cutaway perspective view of a cell of
the same conventional example.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0034] One embodiment of a battery module, to which an electrode
plate unit for a battery according to the present invention is
applied, will be hereinafter described with reference to FIGS. 1 to
12.
[0035] First, the overall construction of the battery module 1 in
accordance with this embodiment is described with reference to
FIGS. 1 to 7. The battery module of this embodiment is a nickel
metal hydride battery, which is suitable for use as a drive power
source for an electric vehicle. As shown in FIGS. 1 to 3, the
battery module 1 is made up of a plurality of (six in the example
shown in the drawing) cells 6, arranged in a row. Cell cases 3 of
each of the cells 6, which are formed in a prismatic fashion with
short lateral walls, long lateral walls, and open top ends, are
mutually integrated on their short lateral walls, thereby
constituting an integral battery case 2. The upper open ends of the
cell cases 3 are closed all together by an integral lid member
4.
[0036] Each of the battery cases 3 constitutes a cell 6,
accommodating therein an electrode plate unit 5 together with
electrolyte. The electrode plate group 5 comprises a large number
of positive electrode plates and negative electrode plates arranged
parallel to the long lateral walls of the cell cases 3 and layered
in the direction of the short lateral walls of the cell cases 3,
with intervening separators therebetween. The construction inside
the battery case will be described later in more detail.
[0037] Connection holes 7 are formed at the upper edge portions of
the outer short lateral walls of the cell cases 3 at the two ends
of the integral battery case 2 and between each two cell cases 3.
Positive and negative connection terminals 8 are respectively
mounted to the connection holes 7 at the outer short lateral walls
of the two outer cell cases 3, and connection fittings 9 for
serially connecting two adjacent cells 6 are mounted to the
connection holes 7 in the intermediate short lateral walls between
each two cell cases 3. In addition, the lid member 4 is provided
with one safety vent 10 for each of the cell case 3, so as to
release pressure when the internal pressure in the cell cases 3 has
exceeded a certain value. Moreover, a sensor mounting hole 11 for
mounting a temperature detection sensor for detecting the
temperature of the cells 6 is formed at suitable cells 6 or for
each cell 6.
[0038] The long lateral walls of six cells 6 together form an
integral side wall 12 of the integral battery case 2. On this side
wall 12 of the integral battery case 2, protruding ribs 13 that
extend vertically are provided at positions corresponding to the
lateral edges of two adjacent cell cases 3. Further, a large number
of relatively small circular protrusions 14 are formed at suitable
intervals in matrix fashion between each two ribs 13. The ribs 13
and the protrusions 14 have the same height. Furthermore, coupling
ribs 15a and 15b having the same height as the ribs 13 and the
protrusions 14 are formed on the side walls of the upper edge of
the cell cases 3 and the side walls of the lid member 4, such as to
bridge across the side walls of the cell cases 3 and the lid member
4, at positions corresponding to an extension of the ribs 13 and
the protrusions 14. A plurality of protrusions 16 and indentations
17, for positioning and fitting together integral battery cases 2
when their side walls 12 are abutted on each other, are arranged at
an upper portion and a lower portion of the outer surface of the
two ribs 13 near both ends of the side wall 12 of the integral
battery case 2. When a plurality of integral battery cases 2 are
arranged in a row in parallel to constitute a battery module, the
ribs 13, the protrusions 14 and the coupling ribs 15a and 15b form
coolant passages for cooling the cell cases 3 effectively and
uniformly.
[0039] The aforementioned electrode plate groups 5 are explained in
detail with reference to FIGS. 4 to 7. In FIGS. 4 and 5, a
plurality of positive electrode plates 18 and negative electrode
plates 19 are arranged alternately, and the positive electrode
plates 18 are covered with separators 20 in the form of a bag
having an opening on one side. The positive electrode plates 18 and
the negative electrode plates 19 are stacked upon one another with
separators 20 therebetween, thereby constituting the electrode
plate unit 5. In FIG. 4, the region where the positive electrode
plates 18 and the negative electrode plates 19 oppose each other
with the intervening separators 20 and generate electric power is
indicated by oblique lines. The lateral edges of the group of
positive electrode plates 18 protrude beyond the group of negative
electrode plates 19 on one side, and the lateral edges of the group
of negative electrode plates 19 protrude beyond the group of
positive electrode plates 18 on the opposite side, and these
protruding lateral portions form the lead portions 18a and 19a, to
the lateral ends of which collector plates 21 and 22 are welded,
respectively. The outer edges of the collector plates 21 and 22 are
bent toward the inside as shown in FIG. 5, in order to restrict the
dimensions of the electrode plates 18, 19 during the collector
plates 21, 22 are welded to the electrode plates 18, 19, so that
the electrode plates 18, 19 do not spread outwards as pressure is
applied thereto. Numeral 23 denotes external separators arranged at
the outer faces of the electrode plate unit 5 between the collector
plates 21 and 22.
[0040] The positive electrode plates 18 are made of Ni foamed
metal. As shown in FIGS. 6A-6C, the lead portion 18a is constructed
by compressing one lateral edge of the plate of foamed metal and
attaching a lead plate 24 on one surface of the lead portion 18a by
ultrasonic welding or seam welding. The negative electrode plates
19 shown in FIGS. 7A-7C are made of Ni punched metal coated with an
active material except for lead portions 19a. "L" denotes the
length of a side of the positive electrode plate 18 and the
negative electrode plate 19 where the lead portions 18a and 19a are
provided, and "D" denotes the length of the side in a direction
perpendicular thereto. The positive and negative electrode plates
18, 19 are configured so that "L" is larger than "D", but not
larger than four times "D". In FIGS. 4, 6A-6C, and 7A-7C, numeral
25 denotes pairs of locating holes formed in the lead portions 18a
and 19a at a suitable distance from the top and the bottom
thereof.
[0041] The detailed construction of the electrode plate unit 5 and
the manufacturing method thereof will be described below with
reference to FIGS. 8 to 12. FIG. 8 is a flow chart of the
manufacturing steps. First, the positive electrode plates 18 and
the negative electrode plates 19 fabricated as shown in FIGS. 6A
and 7A respectively are completely dried, and then a predetermined
number of positive and negative electrode plates 18, 19 are
alternately stacked upon one another, with a separator 20
interposed between each pair of positive and negative electrode
plates, whereby a group of electrode plates as shown in FIG. 5 is
obtained but without collector plates 21, 22. These stacked
electrode plates 18, 19 are then set in a suitable mold equipped
with locating pins 26, such that the locating pins 26 are passed
through corresponding locating holes 25 in the positive and
negative electrode plates 18, 19. Then, the lateral edges of the
electrode plates 18, 19 are pressed with a press 27 as shown in
FIGS. 9A and 9B, so that the lateral edges of the electrode plates
together form a flat end surface. Thereafter, the thus formed
lateral end surface is inspected if it is flat. In case there is an
electrode plate which is not flush with the flat end surface, such
is removed as a defective one and replaced. Such inspection of end
surface can be performed efficiently by way of laser focusing
method or the like, so that the variation of electrode plates in
their dimensions is less than 100 .mu.m.
[0042] Next, collector plates 21, 22 are attached on each of the
end surfaces of the electrode plate groups formed by the lateral
edges of the groups of positive and negative electrode plates 18,
19 respectively, and the collector plates 21, 22 are demagnetized
by applying an alternating magnetic field thereto. Then, an
electronic beam 28 is irradiated to the backside, or the opposite
side of the electrode plate group, of the collector plates 21, 22
within a vacuum, in a state wherein the collector plates 21, 22 are
pressed against the electrode plates. The electronic beam 28 is
scanned in directions in which the electrode plates are stacked as
indicated by the arrow in FIG. 10, whereby the collector plates 21,
22 are welded to the lateral edges of the positive and negative
electrode plates 18, 19, respectively. This welding operation is
repeated in several locations at certain intervals along the
lengthwise direction of the electrode plates 18, 19 simultaneously
or successively. While the collector plates 21, 22 may be
magnetized during the fabrication or transportation process
thereof, since they are demagnetized beforehand as noted above,
there is no risk that the electronic beam 28 is adversely affected
by any magnetic force and welding performance fails.
[0043] Various other lasers such as CO.sub.2 laser, YAG laser,
semiconductor laser, or excimer laser can be used instead of
electronic beam 28.
[0044] The collector plates 21, 22 are constructed of a nickel
sheet or nickel-plated steel sheet, and formed with corrugated
portions 29 at a plurality of positions (seven positions in the
drawing) at suitable intervals in a lengthwise direction of the
sheet, as shown in FIGS. 12A through 12D. The corrugated portion 29
partly protrudes toward the side of the electrode plates 18, 19,
and a solder material 30 such as nickel solder is attached to a
portion that makes contact with the lateral edges of the positive
and negative electrode plates 18, 19. FIG. 12D shows in detail one
example of the corrugated portion 29, wherein a groove 29b is
formed on the top of the ridge 29a of the corrugated portion 29,
this groove 29b being filled with the nickel solder material 30.
Reference numeral 31 denotes part of the collector plate 21 or 22
on one end thereof which makes a welding portion to be welded with
a connection fitting 9.
[0045] When attaching the nickel solder 30 on the collector plates
21, 22, the collector plates heed to be thoroughly cleaned to
remove oil components therefrom. The nickel solder may be obtained
by mixing powder consisting of nickel metal alloy with binder into
a paste. This is applied on the collector plates 21, 22 at desired
locations in a predetermined amount, and the collector plates 21,
22 are then heated in a vacuum furnace at 450 to 800.degree. C. for
10 to 30 minutes, whereby the nickel solder paste is reflowed. The
collector plates 21, 22 should preferably be pressed afterwards to
correct warping of the plates and to flatten out the reflowed
portions.
[0046] According to the construction of the electrode plate unit
and the manufacturing method thereof described above, lateral edges
of the electrode plates 18, 19 can be brought in secure contact
with collector plates 21, 22 and bonded reliably thereto, since the
electrode plates 18, 19 have their respective lead portions 18a,
19a along one lateral edge, which is to be welded with a collector
plate, where no active material is packed, and since these lead
portions 18a, 19a include locating holes 25 for positioning the
electrode plates with respect to the collector plate. Further,
since the lead portion 18a of the positive electrode plate 18 that
is made of metal foam and thus is low in strength is reinforced
with the lead plate 24, sufficient strength for the lead portion
18a can be achieved, and the lead portion 18a is prevented from
being irregularly deformed during welding, ensuring secure bond to
the collector plate.
[0047] Furthermore, lateral edges of the positive and negative end
plates 18, 19 are aligned straight by pressing the edges of the
electrode plates, that have been located in position by means of
the locating pins 26 and the corresponding holes 25, before placing
the collector plates 21, 22 on the end surfaces of the electrode
plate groups. Heat is applied to the collector plates 21, 22 as
they are pressed against the edges of the electrode plates 18, 19,
the collector plates 21, 22 remain in secure contact with the
electrode plates during the welding, thus achieving secure bond
therewith.
[0048] For the welding, with a single or a plurality of electronic
beam 28 or using any other non-contact type heat source, heat is
applied to the collector plates 21, 22 on the opposite surface of
the electrode plate group along a line in the direction in which
the electrode plates are stacked. Therefore, welding can be
performed at high speed without affecting other parts of the
electrode plate group that is in tight contact with the collector
plates. Since the electrode plates 18, 19 are welded together along
a plurality of lines in the plate-stacking direction, they can be
securely bonded to the collector plates 21, 22.
[0049] The plurality of corrugated portions 29 that extend in the
plate-stacking direction are formed at suitable intervals, whereby,
the edges of the group of positive electrode plates 18 and the
edges of the negative electrode plates 19 are reliably bonded to
the collector plates 21, 22 respectively at several locations. Thus
an electrode plate unit 5, wherein the collector plates 21, 22 and
the electrode plates 18, 19 are securely bonded together, can be
obtained.
[0050] The solder material 30 is attached to the corrugated
portions 29 of the collector plates 21, 22 that are in contact with
the lateral edges of the electrode plates 18, 19. Since the solder
material melts at a relatively low temperature, the collector
plates 21, 22 can be bonded to the edges of the electrode plates
18, 19 without arising any problems caused by thermal effect to the
electrode plates 18, 19. Further, since both of the collector
plates 21, 22 and the electrode plates 18, 19 are mainly composed
of nickel, they can be favorably bonded together to constitute an
electrode plate unit 5 for a nickel-alkaline rechargeable
battery.
[0051] The electronic beams 28 for heat application are irradiated
within a vacuum, so that the metal will not oxidize by the heat
during the welding. Due to the absence of any oxide films, no
welding defects are formed and bonding can be accomplished
favorably, and the battery performance will not deteriorate.
Moreover, since the collector plates 21, 22 are demagnetized as
being coupled to the electrode plates 18, 19 before applying heat
with the electronic beams 28, any magnetic force that the collector
plates 21, 22 may have acquired during the fabrication or
transportation process can be removed, whereby electronic beams 28
will not be affected by a magnetic force, and bonding can be
accomplished favorably.
[0052] Next, modifications of the corrugated portion 29 in the
collector plates 21, 22 will be described. Instead of forming
several corrugated portions 29 as shown in FIGS. 12A-12D, wherein a
groove 29b is formed on the top of the ridge 29a on the backside,
the corrugated portion may simply be formed as an groove as shown
in FIGS. 13A- 13D, the backside of which protrudes as a ridge 29a
on the side facing the lateral end surface of the electrode plates
18, 19. The solder material 30 is attached on the ridge 29a.
Reference numeral 32 in FIGS. 13A-13C represents a connection
projection that is formed to protrude at one end of the collector
plate 21 or 22. The connection projection 32 is inserted into the
connection hole 7 formed in the short lateral walls of the cell
cases 3, so that the leading ends 32a of two connection projections
32 of the collector plates in two neighboring cells 3 are abutted,
these being welded together. Thus, according to this structure, the
collector plates 21, 22 of adjacent cells 6 can be directly
connected without using a connection fitting 9.
[0053] The shape of the corrugated portion 29 and the arrangement
of the solder material 30 can variously be modified as shown in
FIGS. 14A-14E. FIG. 14A shows one example that is basically the
same as that shown in FIG. 12D, but with the surface of the solder
material 30 filled in the groove 29b protruding slightly more than
the ridge 29a. FIG. 14B shows another example wherein the ridge 29a
is formed to protrude rather sharply, with a narrower and shallower
groove 29b being formed on the top thereof, so that the solder
material 30 can be projected more prominently. FIG. 14C shows yet
another example which is basically the same as that shown in FIG.
13D, but with the ridge 29a being protruded higher and more
sharply, and the solder material 30 being attached on the top of
the ridge 29a and over the both sides thereof. FIG. 14D shows yet
another example wherein the solder material 30 is applied in a
strip on the surface of the collector plate 21 or 22, so that the
solder material 30 itself constitutes a ridge 29b. FIG. 14E shows
yet another example, wherein the solder material 30 is applied over
the surface of the collector plates 21, 22 by non-electrolytic
plating. The thickness of the solder material 30 may suitably be
set within the range of 20 to 200 .mu.m.
[0054] FIGS. 15A-15D show various modifications to the electrode
plates 18, 19. While the lead portions 18a, 19a of the electrode
plates 18, 19 have been described as being straight at lateral
edges in the foregoing embodiments, FIG. 15A shows one example of
modification, wherein the edge of the lead portion 18a or 19a of
the electrode plate 18 or 19 is formed with cuts or indents 34, so
that the portions to be welded to the collector plate 21 or 22 can
be bent more easily. Alternatively, the lateral edges of the lead
portions 18a, 19a of the positive and negative electrode plates 18,
19 can be provided with bent portion 33 as shown in FIG. 15B. By
doing so, even when, because of the dimensional tolerances for
example, there is a difference d in the position of the lateral
edges of the electrode plates 18, 19 that are aligned straight by
the locating pins 26, the edge position of the electrode plates 18,
19 can be aligned more easily along a straight line as shown in
FIG. 15C when a collector plate 21 or 22 is pressed against the
electrode plates, because of the bent portion 33 smoothly bending
and adjusting, so that the edges of the electrode plates 18, 19
together form a uniform, flat end surface, which will be in
favorable contact with the collector plates 21, 22. More
preferably, the examples shown in FIG. 15A and FIGS. 15B, 15C can
be applied in combination, such that bent portions 33 are formed by
making cuts or slits 35 on both sides of the bent portions 33 as
shown in FIG. 15D, at locations corresponding to the corrugated
portions 29 of the collector plates 21, 22.
[0055] The shape of the bent portion 33 should not be limited to
the example shown in FIGS. 15B and 15C, wherein the edge of the
electrode plate is bent at an angle, but can be variously arranged,
such as to be bent round at more than 90.degree. as shown in FIG.
16A, or bent round at nearly 180.degree. as shown in FIG. 16B.
[0056] In the foregoing embodiment, a method of attaching the
solder material 30 on the corrugated portions 29 of the collector
plates 21, 22, wherein a row material of solder paste is applied
and reflowed, has been described as one example. However, the
solder material 30 can be attached by any other means, for example,
using an adhesive, or by thermal welding.
[0057] Alternatively, a material that is similar to the nickel
solder material 30, such as a metal alloy comprising nickel, can be
applied over the entire surface of the collector plates 21, 22 by a
non-electrolytic plating method or the like. In the case wherein
the collector plates 21, 22 are made of a nickel-plated steel
sheet, a material that is similar to that of the nickel solder
paste 30 may suitably selected for the plating of the steel sheet.
In this case, a ridge of solder material 30 can be formed by
locally increasing the thickness of the nickel plate.
[0058] Although the present invention has been fully described in
connection with the preferred embodiment thereof, it is to be noted
that various changes and modifications apparent to those skilled in
the art are to be understood as included within the scope of the
present invention as defined by the appended claims unless they
depart therefrom.
* * * * *