Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and...
Reexamination Certificate
2001-03-16
2004-08-31
Gulakowski, Randy (Department: 1746)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
C029S623100
Reexamination Certificate
active
06783887
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for manufacturing a battery module composed of unit cells and an apparatus for manufacturing it to which the method can be applied. The unit cells are each composed of a metallic case incorporating cell elements such as a positive electrode, a negative electrode, a separator, an electrolyte, etc. and an terminal with one polarity and a sealing body sealing an opening of the case through an insulating body and serving a terminal with the other polarity, and connected in series by welding the sealing body of the one of the adjacent unit cells and the case of the other thereof. This invention also relates to the unit cell for use in the battery module to which these manufacturing method and apparatus can be effectively applied.
2. Description of the Related Art
Generally, the alkaline battery such as a nickel-hydride battery and nickel-cadmium battery is constructed so that an electrode body is formed by winding spirally a positive electrode and a negative electrode with a separator interposed therebetween and connecting a collector to the end of the positive electrode or negative electrode; with the batterybody housed in a metallic case, a lead portion extending from the collector is welded to a sealing body; and thereafter the sealing body is mounted in an opening of a battery case through an insulating gasket so that it is hermetically sealed. Where such an alkaline battery is used in an electric tool and an electric vehicle, it needs high power. For this reason, the battery is generally used as a battery module composed of unit cells connected in series.
Such a battery module is manufactured, as shown in
FIG. 10
, in such a manner that one end of a lead plate
85
is welded to a positive polarity cap
82
which is provided as a positive polarity terminal on a sealing plate
81
of a unit cell
80
b,
the other end of the lead plate
85
is welded on a bottom
84
of a metallic case
83
of a unit cell
80
a,
and thereafter the central portion of the lead plate
85
is bent in an U-shape so that the plurality of unit cells
80
a
and
80
b
are connected.
Meanwhile, when the plurality of unit cells
80
a
and
80
b
are discharged through the lead plate
85
bent in a U-shape, a discharged current flows through the lead plate
85
. Therefore, the drop of the voltage across a resistor becomes large as the lead plate
85
becomes long or thin. Where the discharging current is small, this voltage drop is not so problematic. However, where the battery is used in the electric tool or electric vehicle with a large current flowing, the voltage drop presented a problem of reducing an operating voltage.
In order to avoid such a problem, it was proposed to connect the unit cells directly by soldering the opposite electrodes to each other. However, the soldering presented a problem that it is difficult to assure the connection because of a small strength of a soldered portion. In addition, it was troublesome and poor in workability to connect the opposite electrodes of the unit cells.
As a result of various experiments, the inventors of this application developed an epoch-making welding technique of connecting the adjacent electrodes of unit cells directly by passing a welding current in a charging or discharging direction of a battery. As seen from
FIG. 11
, this welding technique is to align a plurality of unit cells
90
a
and
90
b
in a line housed in a holding cylinder not shown, and thereafter arrange one welding electrode
96
on a positive polarity cap
92
at the upper end of these unit cells and the other welding electrode
97
on a bottom
94
of a metallic case
93
at the lower end of these unit cells.
Thereafter, this technique is to apply a voltage under applied pressure between both electrodes
96
and
97
to pass a large pulse current. Thus, the contact portions between the bottom
94
of the metallic case
93
of the unit cell
90
a
and the positive polarity cap
92
of the unit cell
90
b
are molten so that they are welded to each other.
This technique directly weld the adjacent electrodes of the unit cells so that the voltage drop at the welding portion is reduced, thereby improving the operating voltage of the battery module.
However, the method for manufacturing a battery module as shown in
FIG. 11
, in which the pair of welding electrodes
96
and
97
serve as pressurizing members, presented a problem that it is difficult to adjust accurately the pressure to be applied between the plurality of unit cells
90
a
and
90
b.
Specifically, excessively large pressurizing force applied between the plurality of unit cells
90
a
and
90
b
give excessively large pressurizing force to the positive polarity cap
92
. This presented a problem that the positive polarity cap
92
is shrunk or deformed. Since a pressure valve is arranged in the positive polarity cap
92
, this led to another problem that the pressure valve does not operate properly.
On the other hand, excessively small pressurizing force applied between the plurality of unit cells
90
a
and
90
b
presented a problem that the terminals of the adjacent unit cells are not welded sufficiently to each other to generate poor welding. This is because impossibility of applying sufficient pressurizing force between the plurality of unit cells
90
a
and
90
b
increases the contact resistance at the welding portion and hence voltage drop so that sufficient current cannot be supplied to this portion. Therefore, where the number of unit cells to be connected is increased to provide a battery module with a high voltage, the number of the connecting portions is increased. This further makes it impossible to supply the welding current and further generates the poor welding.
Further, since the plurality of unit cells
90
a,
90
b
inserted in a holding cylinder are aligned in a line, there was a problem that when the inner diameter of the holding cylinder is smaller than the outer diameter of the unit cells
90
a
,
90
b
, it is difficult to insert the unit cells
90
a
and
90
b
into the holding cylinder, and inversely, when the inner diameter of the holding cylinder is excessively larger than the outer diameter of the unit cells
90
a
,
90
b
, the unit cells
90
a,
90
b
cannot be aligned in a line within the holding cylinder.
This invention has been accomplished in order to solve the problems described above.
SUMMARY OF THE INVENTION
The first object of this invention is to provide a method of welding a battery module which can easily weld a large number of unit cells without injuring them and generating poor welding when they are welded.
The second object of this invention is to provide a manufacturing apparatus capable of realizing such a manufacturing method.
Further, the third object of this invention is to provide a connecting structure of the battery to which these method and apparatus can be applied effectively applied.
In order to attain the first object, the method for manufacturing a battery module comprises the steps of:
preparing a plurality of unit cells each provided with a case serving as a terminal with one polarity and incorporating cell elements with a positive electrode and a negative electrode with an electrolyte interposed therebetween and a sealing body serving as a terminal with the other polarity electrically isolated from the case;
aligning the plurality of unit cells in a line so that their adjacent terminals are brought into contact with each other; and
welding the adjacent terminals to each other by passing a welding current through at least one battery elements of the plurality of unit cells aligned in a line.
Preferably, the step of aligning is to align the plurality of unit cells in a line so that the bottom of the case with the one polarity of the one unit cell of the adjacent unit cells is brought into contact with the terminal with the other polarity of the other unit cell; and comprises
a welding electrode arranging step of arranging a pair of welding electrodes so that they are brough
Oda Takashi
Okajima Hideki
Okumura Yoshinobu
Tanaka Hitoshi
Uesugi Yukichi
Gulakowski Randy
Nixon & Vanderhye P.C.
Sanyo Electric Co,. Ltd.
Wills Monique
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