Chemistry: electrical current producing apparatus – product – and – With control means responsive to battery condition sensing...
Reexamination Certificate
2000-04-24
2003-02-25
Dunn, Tom (Department: 1725)
Chemistry: electrical current producing apparatus, product, and
With control means responsive to battery condition sensing...
C429S007000, C429S185000
Reexamination Certificate
active
06524739
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a secondary battery such as a lithium ion secondary battery, which is provided with a battery protection device inside of the battery and which has thereby functions for protecting the battery from overcharging and over-discharging, etc., in the battery itself.
BACKGROUND ART
Various kinds of protective features are built into secondary batteries in order to protect against shorts in battery peripheral circuits in equipment wherein such secondary batteries are used, against shorts between positive and negative electrodes, and against battery damage resulting from abnormal usage as in overcharging or over-discharging. These include PTC elements for blocking excessive discharge currents caused by shorts and the like, and safety valves and the like which interrupt the conducting circuit by the anomalous rises in internal battery voltage associated with overcharging and release that internal voltage. These protective features are commonly known as features wherewith the secondary battery itself is provided. In lithium ion secondary batteries, moreover, protective circuits are provided for preventing overcharging and over-discharging. These protective circuits are generally contained inside a battery pack case and integrated with the lithium ion secondary battery. As well known, such battery pack constructions wherein the battery and the protective circuit are accommodated and integrated in a case are widely used as battery power supplies in portable telephone instruments and mobile computers, etc., that use lithium ion secondary batteries.
The protective circuits described above can also incorporate excessive current interrupting features and battery temperature monitoring features and the like in addition to features for preventing overcharging and over-discharging as described in the foregoing. If these features can be built into the secondary battery itself, it will be no more necessary to construct the battery pack and secondary batteries with protective circuits can be provided for general purposes. Japanese Laid-Open Patent Application No. 8-31460 discloses a battery which is though to have been developed for the purpose of accommodating a protective circuit inside the battery. In this art, a protective circuit and other constituent elements are arranged in an upper part of the battery, and the protective circuit, and the battery, are accommodated inside an outer case. Thus it is nothing different from the conventional battery pack construction. What is demanded in a secondary battery provided with a protective circuit is one which has roughly the same dimensions and shape as a conventional secondary battery having no- protective circuit, with the protective circuit accommodated inside that battery case.
The inventors of the present invention developed a secondary battery having a protective circuit accommodated inside the battery, along the lines described in the foregoing, and proposed that secondary battery in Japanese Laid-Open Patent Application No. 8-178896. One embodiment thereof is diagrammed in FIG.
37
. Therein, a battery protection device containing the protective circuit described earlier is arranged in a sealing member
90
that seals the open end of a battery case accommodating electricity generating elements.
The battery protection device within the sealing member
90
comprises a circuit board constituting an electronic circuit
77
forming a protective circuit, a PTC element
72
that is a critical temperature resistor for blocking excessive currents such as occur with shorts, etc., and a current interrupting mechanism
73
that interrupts the conducting circuit by breaking when the voltage inside the battery rises abnormally thereby to release the abnormal internal voltage. The positive terminal of the electricity generating elements is connected to the circuit board through the current interrupting mechanism
73
and the PTC element
72
, and electrical connections are effected from the circuit board to a positive terminal cap
75
that constitutes the positive terminal of the battery, and to an S pole cap
76
that is for externally connecting the minus side of the electronic circuit
77
.
The construction described in the foregoing is diagrammed in schematic form in FIG.
38
. The electronic circuit
77
is made up of a battery protection IC
80
comprising overcharging and over-discharging control functions, and an FET
81
for turning on and off the conducting circuit on the positive terminal side by control signals from the battery protection IC
80
. The negative terminal side of this electronic circuit
77
is electrically connected to the S pole cap
76
. Therefore, when this secondary battery is installed in equipment wherein it is used or in a charger, an electrical connection is effected across the S pole cap
76
and a battery case
83
constituting the negative terminal of the secondary battery, thereby putting the electronic circuit
77
in an operating state. When this secondary battery is not installed in equipment, no power consumption arises because of the electronic circuit
77
, although it is very slight. As diagrammed, the current interrupting mechanism
73
, PTC element
72
, and electronic circuit
77
are arranged in series in the conducting circuit on the positive terminal side from the electricity generating elements
78
. Thus the secondary battery is equipped with three levels of battery protection features.
However, when the resistance value of the PTC element
72
secured by caulking inside the sealing member
90
rises by self-heating due to excessive currents, the cubic volume thereof expands when a tripped state is reached. When this cycle of expansion and return to normal is repeated again and again, the caulking becomes loosened so that a very small gap develops, leading to the problem of electrolyte leaking out through the gap.
There is also another problem in that, because the circuit board is arranged in proximity to the current interrupting mechanism
73
, limitations are placed on the space available for deformation of the current interrupting mechanism
73
which will deform and rupture due to abnormal rises in the internal battery voltage, making it difficult to obtain deformation/rupture precision.
An object of the present invention is to provide a secondary battery wherein a battery protection device comprising a protective circuit is accommodated inside the battery, wherewith there is but slight change in the size of the battery, and wherewith battery performance is not compromised.
DISCLOSURE OF THE INVENTION
A first aspect of the present invention is a secondary battery wherein electricity generating elements are accommodated inside a battery case formed in a cylindrical shape having a bottom, the open end of the battery case being sealed by a sealing member having a battery protection device built therein, characterized in that the battery protection device comprises a protective circuit, for protecting the battery from overcharging and over-discharging, consisting of an electronic circuit formed on a circuit board, the circuit board being arranged in the sealing member such that an electrode terminal formed in one side thereof is exposed to the outside.
According to this construction, the protective circuit is built into the secondary battery itself, in which the protective circuit is arranged inside the sealing member, and the electrode terminal passed through the electronic circuit forming this protective circuit is attached so that it is externally exposed. Thus the secondary battery is constructed with a protective circuit without resorting to the construction of a battery pack. Battery damage caused by equipment malfunction or abnormal use is prevented by the features provided in this protective circuit for preventing overcharging, over-discharging, and excessive discharge current, etc.
A second aspect of the present invention is a secondary battery wherein electricity generating elements are accommodated inside a battery case formed in a cylindrical s
Ishimaru Tomiya
Iwaizono Yoshinori
Masumoto Kenjin
Mizutani Seiichi
Mori Katsuhiko
Dunn Tom
Greenblum & Bernstein P.L.C.
Pittman Zidia
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