JP4511449B2 - Protection element and battery pack provided with the protection element - Google Patents

Description

  The present invention relates to a protection element that is mainly used for a battery pack and protects the battery, and a battery pack including the protection element.

  The pack battery has a protective element connected in series with the battery in order to prevent the battery from being charged and discharged in an abnormal state. A protective element used for this purpose has been developed (see Patent Document 1). This protective element cuts off the current when the battery is charged and discharged in an abnormal state. In order to cut off the battery current in the event of an abnormality, the protective element has a built-in low-melting-point metal fuse that is heated by overcurrent Joule heat and blows. Furthermore, a heating resistor is provided that blows the fuse in a short time in the event of an abnormality such as overcharging of the battery. The heating resistor is heated by Joule heat generated by an energized current. The heated heating resistor heats and melts the low melting point metal fuse. This is because the heating resistance is thermally coupled to the low melting point metal fuse.

The protection element is built in the battery pack in the circuit diagram of FIG. As shown in this circuit diagram, the fuse 195 of the protection element 192 is connected in series with the battery 191. Therefore, when the fuse 195 is blown by heat, the current of the battery 191 is cut off. When an overcurrent flows, the fuse 195 is heated by Joule heat and blown. The blown fuse 195 blocks the current of the battery 191. Further, the protection element 192 in the circuit diagram shown in the figure is blown by heating the fuse 195 with the heating resistor 194. The heating resistor 194 is connected to a switching element 193 such as an FET, and energization is controlled by the switching element 193. The switching element 193 is controlled to be turned on / off by the control circuit 196. The control circuit 196 detects an abnormality of the battery 191 and switches the switching element 193 on and off. When the battery 191 enters an abnormal state, for example, an overcharged state, the control circuit 196 switches the switching element 193 on. The switching element 193 in the on state energizes the heating resistor 194. The energizing heating resistor 194 is heated by Joule heat to blow the low melting point metal fuse 195.
JP 2000-340267 A

  The heat generated by the heating resistance increases in proportion to the square of the supply voltage. Therefore, the amount of heat generated from the heating resistor varies greatly as the supply voltage increases. For example, as shown in FIG. 1, a battery pack in which four batteries 191 are connected in series has one battery 191 short-circuited and one battery 191 is overcharged. In 191, it is necessary to heat the heating resistor 194 to blow the fuse 195. Further, when all of the four batteries 191 are overcharged to heat the heating resistor 194, the four battery voltages cause an excessive heating current to flow through the heating resistor 194. That is, the battery pack having this structure needs to be designed so that the fuse 195 can be blown by heating the heating resistor 194 with one battery 191. For this reason, when a high voltage from a plurality of batteries is applied to the heating resistor 194 and a heating current flows, the heating current becomes extremely large.

  For example, as shown in FIG. 1, in a battery pack in which four batteries are connected in series, when three batteries are short-circuited and a heating current is passed by one battery, and when a heating current is passed by four batteries, The heating current changes 4 times. For this reason, when a large current flows through the heating resistor, if the heating resistor is burned out before the fuse is blown, there is a problem that the fuse cannot be blown by the heating resistor.

The present invention has been developed for the purpose of solving such drawbacks. An important object of the present invention is to provide a protective element capable of reliably fusing a fuse with a heating resistor even when the battery voltage built in the battery pack fluctuates greatly, and a pack battery including the protective element.
Furthermore, another important object of the present invention is to provide a protective element that can surely prevent the heating resistance from being burned out and a battery pack equipped with this protective element.

The protection element of the present invention has the following configuration in order to achieve the above-described object.
The protective element includes a low melting point metal 5 that is fused when heated, and a heating resistor 4 that is thermally coupled to the low melting point metal 5 and heats the low melting point metal 5 with Joule heat generated by an energized current. The heating resistor 4 connects a plurality of shunt circuits 4A in parallel. Each shunt circuit 4 </ b> A includes a resistance element 7 having different electric resistances, and a current control element 8 is connected in series with the resistance element 7 to at least one shunt circuit 4 </ b> A. The current control element 8 is an element that controls the current of the shunt circuit 4A by changing the electric resistance depending on the temperature or current. When a predetermined supply voltage is supplied to the heating resistor 4, the protection element controls the current flowing through the shunt circuit 4 </ b> A by the current control element 8, and heats the low melting point metal 5 with the Joule heat of the resistance element 7 to melt it. To do.

  In the protection element of the present invention, the current control elements 8 and 48 are PTCs 8A and 48A whose electrical resistance increases as the temperature rises. When the PTCs 8A and 48A are heated by the Joule heat of the flowing current and become higher than the set temperature, The resistance increases, and the current of the resistance elements 7 and 47 connecting the PTCs 8A and 48A in series can be reduced.

  In the protection element of the present invention, when the current control elements 98 and 108 are NTC 98D and 108D whose electric resistance decreases as the temperature increases, the NTC 98D and 108D are heated to the Joule heat of the flowing current and become higher than the set temperature. , NTC 98D and 108D can be increased in current through the resistance elements 97 and 107 connected in series.

  The protection element of the present invention uses the current control elements 78 and 88 as the breaker 8C that cuts off the current when a predetermined current flows. When the current flowing through the breakers 78C and 88C becomes larger than the set current, the breakers 78C and 88C It can interrupt | block and can interrupt | block the electric current of the resistance elements 77 and 87 which connected the breakers 78C and 88C in series.

  The protection element of the present invention uses the current control elements 58 and 68 as the fuses 58B and 68B that cut off the current when a predetermined current flows. When the current flowing through the fuses 58B and 68B becomes larger than the set current, the fuses 58B and 68B The current can be cut off, and the current of the resistance elements 57 and 67 connecting the fuses 58B and 68B in series can be cut off.

  In the protection element of the present invention, the heating resistor 4 can connect the current control element 8 to the shunt circuit 4A excluding one shunt circuit 4A.

  The protection element of the present invention can connect one end of the heating resistor 4 to the middle of the low melting point metal 5.

The battery pack of the present invention has the following configuration in order to achieve the aforementioned object.
The battery pack includes a battery 1 and a protective element 2 connected to the battery 1 in series. The protection element 2 includes a low melting point metal 5 that is fused when heated, and a heating resistor 4 that is thermally coupled to the low melting point metal 5 and heats the low melting point metal 5 with Joule heat generated by an energized current. . The heating resistor 4 connects a plurality of shunt circuits 4A in parallel. Each shunt circuit 4 </ b> A includes a resistance element 7 having different electric resistances, and at least one of the shunt circuits 4 </ b> A is connected to a current control element 8 in series with the resistance element 7. The current control element 8 is an element that controls the current of the shunt circuit 4A by changing the electric resistance depending on the temperature or current. When a predetermined supply voltage is supplied to the heating resistor 4, the protection element 2 controls the current flowing through the shunt circuit 4 </ b> A by the current control element 8 to heat the low melting point metal 5 with the Joule heat of the resistance element 7. Fusing.

  In the battery pack of the present invention, the current control elements 8 and 48 of the protection elements 2 and 42 are set to PTCs 8A and 48A whose electric resistance increases as the temperature rises, and the PTCs 8A and 48A are set by being heated by the Joule heat of the flowing current. When the temperature becomes higher than the temperature, the electrical resistance increases, and the current of the resistance elements 7 and 47 connecting the PTCs 8A and 48A in series can be reduced.

  In the battery pack of the present invention, the current control elements 98 and 108 of the protection elements 92 and 102 are set as NTC 98D and 108D whose electric resistance decreases as the temperature rises, and the NTC 98D and 108D are heated by Joule heat of the flowing current. When the temperature is higher than the temperature, the currents of the resistance elements 97 and 107 connecting the NTC 98D and 108D in series can be increased.

  In the battery pack of the present invention, the current control elements 78 and 88 of the protection elements 72 and 82 are the breakers 78C and 88C that cut off the current when a predetermined current flows, and the current flowing through the breakers 78C and 88C is larger than the set current. Then, the breakers 78C and 88C cut off the current, and the currents of the resistance elements 77 and 87 connecting the breakers 78C and 88C in series can be cut off.

  In the battery pack of the present invention, the current control elements 58 and 68 of the protection elements 52 and 62 are used as fuses 58B and 68B that cut off the current when a predetermined current flows, and the current flowing through the fuses 58B and 68B is larger than the set current. Then, the fuses 58B and 68B cut off the current, and the currents of the resistance elements 57 and 67 connecting the fuses 58B and 68B in series can be cut off.

  In the battery pack of the present invention, the heating resistor 4 of the protection element 2 can connect the current control element 8 to the shunt circuit 4A except for one shunt circuit 4A.

  In the battery pack of the present invention, the protective element 2 can connect one end of the heating resistor 4 to the middle of the low melting point metal 5.

  In this specification, the heating resistance is burned out means that the electrical resistance of the heating resistance is extremely large and substantially no current flows (may be cut off in some cases).

  The protection element of the present invention and the battery pack provided with this protection element have the feature that the fuse can be surely blown by the heating resistance even if the battery voltage built in the battery pack fluctuates significantly. That is, the protection element of the present invention heats the low melting point metal with a heating resistor in which a plurality of shunt circuits are connected in parallel, and each shunt circuit includes a resistance element having a different electric resistance and at least one of them. The current control element is connected in series with the resistance element to the current shunt circuit, and this current control element is an element for controlling the current of the shunt circuit with temperature or current, and a predetermined supply voltage is supplied to the heating resistor. This is because the current control element controls the current flowing through the shunt circuit, and the low melting point metal is heated and melted by the Joule heat of the resistance element. The protection element of this structure is optimal because the current control element connected to the shunt circuit controls the current of the resistance element connected in series when a predetermined supply voltage is supplied to the heating resistor. The low-melting-point metal can be heated and melted by Joule heat generated by a current passed through a resistance element having a high electrical resistance. For this reason, the protection element and the battery pack of the present invention can reliably melt the low melting point metal by heating even if the voltage supplied to the heating resistor changes significantly.

  In particular, a protection element having a current control element as a PTC and a battery pack equipped with this protection element have an increase in the electrical resistance of the PTC when the temperature of the PTC becomes higher than a set temperature, and the resistance element connected in series with the PTC. Since the current is reduced, it is possible to effectively prevent a large current from flowing through the resistance element and burning the resistance element.

  In addition, a protection element using a current control element as a breaker or a fuse and a battery pack equipped with this protection element, when the flowing current becomes larger than the set current, the breaker or fuse cuts off the current, so that a large current flows through the resistance element. Thus, the resistance element can be reliably prevented from burning.

  Furthermore, the protection element in which the current control element is NTC and the battery pack provided with this protection element increase the current of the resistance element connected in series with the NTC when the temperature of the NTC becomes higher than the set temperature. A low current metal can be blown by heating a low melting point metal with Joule heat of a resistance element having an optimum electrical resistance by causing a large current to flow through the resistor element.

  Embodiments of the present invention will be described below with reference to the drawings. However, the examples shown below exemplify a protective element for embodying the technical idea of the present invention and a battery pack provided with the protective element. The present invention includes the protective element and the battery pack as follows. Not specified.

  Further, in this specification, in order to facilitate understanding of the scope of claims, numbers corresponding to the members shown in the examples are indicated in the “claims” and “means for solving problems” sections. It is added to the members. However, the members shown in the claims are not limited to the members in the embodiments.

  The battery pack shown in the circuit diagram of FIG. 2 includes a control circuit 6 that detects an abnormality of the battery 1, a switching element 3 that is turned on and off by an output signal of the control circuit 6, and an abnormality that is controlled by the switching element 3. A protection element 2 for cutting off the current of the battery 1 is provided.

  As shown in FIG. 3, the protection element 2 includes a low melting point metal 5 and a heating resistor 4 that is thermally coupled to the low melting point metal 5 and heats and melts the low melting point metal 5. The low-melting-point metal 5 is connected in series with the battery 1 and is melted when an abnormality occurs to block the current of the battery 1. The heating resistor 4 is heated by Joule heat and melts the low-melting metal 5 that is thermally bonded by heat.

  The protection element 2 includes a battery terminal 11 connected to the battery 1, a charging terminal 12 connected to a charger or a load, and a switch terminal 13 connected to the switching element 3. The low melting point metal 5 has one end connected to the low melting point metal 5 and the other end connected to the charging terminal 12. The heating resistor 4 has one end connected to the middle of the low melting point metal 5 and the other end connected to the switch terminal 13.

  The control circuit 6 detects that the battery 1 is in an abnormal state, and outputs a signal for turning on the switching element 3 when the battery 1 is in an abnormal state. The abnormal state of the battery 1 detected by the control circuit 6 is, for example, a state in which a fully charged battery is further charged, or a state in which an overcurrent flows through the battery. However, the present invention does not specify an abnormal state of the battery as this state. An abnormal battery state is not only charging a fully charged battery or overcurrent, but also charging a battery that cannot be used safely or normally, such as when the battery temperature has risen to an abnormal temperature. Or it shall mean the state discharged. A battery pack incorporating a plurality of batteries 1 detects an abnormal state of each battery 1 and outputs a signal for turning on the switching element 3 when any one of the batteries 1 is used in an abnormal state. . When all the batteries 1 are in a normal state, the control circuit 6 does not output a signal for turning on the switching elements 3 and keeps the switching elements 3 off.

  The switching element 3 is an FET. The FET has a gate connected to the output terminal of the control circuit 6, a source connected to the ground side, and a drain connected to the heating resistor 4. As the switching element 3, other switching elements such as a transistor can be used instead of the FET. The transistor has a base connected to the control circuit, an emitter connected to ground, and a collector connected to a heating resistor. In a battery pack using a transistor as a switching element, when the battery is in an abnormal state, the control circuit outputs a signal for turning on the transistor. Further, a relay can be used as the switching element. In the relay, the contact on the normally open side is connected between the ground and the heating resistor, and the exciting coil is connected to the ground and the output side of the control circuit. In this battery pack, when the battery is in an abnormal state, the relay exciting coil is energized, the normally open contact is closed, and the heating current flows through the heating resistor.

  The battery pack of FIG. 2 has a battery terminal 11 of the protection element 2 connected to the battery 1 and a charge terminal 12 connected to the output terminal 10, and the low melting point metal 5 of the protection element 2 between the output terminal 10 and the battery 1. Are connected in series. The low melting point metal 5 is a fuse that cuts off current when it is heated to a predetermined temperature. Even when the fuse is not heated by the heating resistor 4, the fuse can be blown by the excessive Joule heat flowing through the fuse, and the current can be cut off. That is, the fuse can be blown by self-heating. However, in the present invention, the low melting point metal does not necessarily need to be a fuse, and the low melting point metal is not blown by the Joule heat of the current flowing through itself, but can be blown by being heated by a heating resistor.

  As shown in FIG. 3, the protection element 2 has a heating resistor 4 connected in the middle of the low melting point metal 5 and a pair of low melting point metals 5 connected in series. One low melting point metal 5 is connected to the battery 1 via the battery terminal 11, and the other low melting point metal 5 is connected to the output terminal 10 of the battery pack via the charging terminal 12. The intermediate connection point 18 of the pair of low melting point metals 5 connected in series is connected to the heating resistor 4. The protection element 2 can block both the discharge current and the charge current of the battery 1. The low melting point metal 5 connected to the battery 1 is melted to cut off the discharge current of the battery 1, and when connected to the charger, the low melting point metal 5 connected to the charger is melted and charged. The current can be cut off.

  The protective element 2 is thermally coupled to the low melting point metal 5 and disposed with the heating resistor 4 so that the low melting point metal 5 can be heated and melted by the heating resistor 4. The heating resistor 4 is disposed close to the low melting point metal 5 or is laminated with an insulating material interposed therebetween. A heating resistor 4 disposed close to the low melting point metal 5 or laminated in an insulating state heats the low melting point metal 5 by radiant heat or heat conduction. Further, the protection element 2 of FIG. 3 has a heating resistor 4 connected to an intermediate connection point 18 of a pair of low melting point metals 5 connected in series. This heating resistor 4 also heats the low melting point metal 5 by heat conducted through the intermediate connection point 18. The heating resistor 4 thermally coupled to the low melting point metal 5 heats and melts the low melting point metal 5 with Joule heat generated by an energized current.

  The heating resistor 4 has one end connected to the low melting point metal 5 and the other end connected to the switching element 3 via the switch terminal 13. The heating resistor 4 shown in the figure has one end connected to an intermediate connection point 18 between a pair of low melting point metals 5. The heating resistor 4 connects a plurality of shunt circuits 4A in parallel. The protection element 2 in FIG. 3 connects two shunt circuits 4A in parallel, and the protection element 42 in FIG. 4 connects three shunt circuits 44A in parallel. Each of the shunt circuits 4A and 44A includes resistance elements 7 and 47 having different electric resistances, and at least one of the shunt circuits 4A and 44A is connected with current control elements 8 and 48 in series with the resistance elements 7 and 47. Yes.

  The current control elements 8 and 48 are elements that control the current of the shunt circuits 4A and 44A by changing the electric resistance depending on temperature or current. The current control elements 8 and 48 are elements such as PTC, NTC, breaker, and fuse. When the PTC (Positive Temperature Coefficient) is heated by the Joule heat of the flowing current and becomes higher than a set temperature, the electric resistance increases rapidly. The PTC whose electrical resistance has increased reduces the current of the resistance elements connected in series. NTC (Negative Temperature Coefficient) has an electrical characteristic that electrical resistance decreases as the temperature increases. The NTC is heated by the Joule heat of the flowing current and the temperature rises. When heated by Joule heat and the temperature of the NTC becomes higher than the set temperature, the electrical resistance decreases rapidly, increasing the current of the resistance elements connected in series. The breaker cuts off the current when the energized current becomes larger than the set current, and cuts off the current of the resistance elements connected in series. Similarly to the breaker, the fuse is blown to cut off the current when the energized current becomes larger than the set current. When the fuse is blown, the current of the resistance element connected in series is cut off.

  Resistance elements 7 and 47 having different electric resistances are connected to the respective shunt circuits 4A and 44A. Since the resistance elements 7 and 47 have different electric resistances, even if the supply voltages of the heating resistors 4 and 44 are the same, the amount of heat generated by Joule heat is different. The protection elements 2 and 42 heat and melt the low melting point metals 5 and 45 with the heat generated by the heating resistors 4 and 44. However, if the heating value of the resistance elements 7 and 47 due to Joule heat is too small, 45 cannot be blown by heat.

  The amount of heat generated by Joule heat of the resistance element is proportional to the power consumption W. The calorific value Q (cal) of the resistance element is represented by the following formula (1).

Q = 0.24WT ………… (1)
In this equation, W is power consumption and T is time (sec).

  From this equation, the resistance element generates a large amount of heat in proportion to the power consumption. In other words, the power consumption specifies the amount of heat generated. For example, if the power consumption of the resistance element is doubled, the amount of heat generated is also doubled. The power consumption W of the resistance element is specified by the electrical resistance and the supply voltage, as shown by the following formula (2).

^{W = E 2 / R ............ (} 2)
In this equation, E is the supply voltage of the resistance element, and R is the electrical resistance.

  As shown in this equation, the power consumption of the resistance element increases in inverse proportion to the electrical resistance. Therefore, the resistance element doubles power consumption and heat generation when the electrical resistance is halved, and triples power consumption and heat generation when the electrical resistance is ３. For this reason, the resistance elements connected in parallel have different power consumption and heat generation depending on the electric resistance, and those having a small electric resistance have a larger heat generation than those having a large electric resistance.

  As shown in FIG. 12, the conventional protection element 182 having the heating resistor 184 as one resistance element 187 heats and melts the low melting point metal 185 with the heat of the heating resistor 184. Since the heating resistor 184 itself burns out, the electric resistance of the heating resistor 184 needs to be a large electric resistance that itself does not burn out while being small enough to melt the low melting point metal 185. That is, the heating resistor 184 sets the electric resistance within a predetermined range. If the electrical resistance of the heating resistor is too large, the amount of heat generation becomes small and the low melting point metal cannot be blown out. On the other hand, if the electrical resistance is too small, the amount of heat generation becomes too large and itself burns out. From this, the electric resistance of the heating resistor is determined so as to be a calorific value at which a low melting point metal can be heated and melted without burning out at a predetermined supply voltage.

  However, even if the electrical resistance is constant, the power consumption and the amount of heat generated by the heating resistor increase in proportion to the square of the supply voltage. Therefore, if the supply voltage exceeds the specified value, the amount of heat generation increases rapidly. It burns out. For example, when the supply voltage of the heating resistor is twice the specified voltage, the amount of heat generation is increased four times, causing the heating resistor to burn out. The burned-up heating resistor has an extremely small current and does not generate Joule heat. This heating resistance makes it impossible to heat the low-melting point metal due to the extremely small amount of heat generated after burning.

  For the above reason, the supply voltage that can heat and melt the low melting point metal without damage by the heating resistor composed of one resistive element is limited to a specified range. If the supply voltage is lower than the specified range, the power consumption is reduced and the low melting point metal cannot be heated and blown out.On the other hand, if the supply voltage is higher than the specified range, the power consumption increases and the product itself burns out, resulting in a low melting point. The metal cannot be heated and blown. For this reason, the voltage range in which the heating resistance composed of one resistance element can heat and melt the low melting point metal is limited to a specified range.

As shown in FIGS. 3 to 10, the protective element of the present invention is a low melting point metal even if the voltage supplied to the heating resistors 4, 44, 54, 64, 74, 84, 94, 104 changes significantly. A plurality of shunt circuits 4A, 44A, 54A, 64A, 74A, 84A, 94A, 104A constitute a heating resistor so that 5, 45, 55, 65, 75, 85, 95, 105 can be heated and blown. Resistive elements 7, 47, 57, 67, 77, 87, 97, 107 having different electric resistances are connected to the respective shunt circuits 4 A, 44 A, 54 A, 64 A, 74 A, 84 A, 94 A, 104 A. A resistance element having a small electric resistance consumes a large amount of power and generates heat at a low supply voltage, and heats and melts the low melting point metal 5, 45, 55, 65, 75, 85, 95, 105 in a low supply voltage state. . A resistance element having a large electric resistance consumes a large amount of power and generates heat at a high supply voltage, and heats and melts the low melting point metal 5, 45, 55, 65, 75, 85, 95, 105 in a state where the supply voltage is high. . The protection elements 2, 42, 52, 62, 72, 82, 92, 102 shown in FIG. 3 to FIG. 10 are low resistance resistance elements that are low melting point metals 5, 45, 55, 65, 75, 85, 95, and 105 are heated and melted. In this state, since the high resistance resistance element has low power consumption and heat generation, the low melting point metal 5, 45, 55, 65, 75, 85, 95, 105 cannot be heated and blown. When the supply voltage is increased, the power consumption and the heat generation amount of the high-resistance resistance element are increased, and the low melting point metal 5, 45, 55, 65, 75, 85, 95, 105 is heated and melted. When the supply voltage of the heating resistors 4, 44, 54, 64, 74, 84, 94, 104 is increased, the resistance element having low resistance increases in power consumption and heat generation. The protective elements 2, 42, 52, 62, 72, and 82 shown in FIG. 5 cut off the current of the low-resistance resistance elements at the current control elements 8, 48, 58, 68, 78, and 88 when the supply voltage increases. Also, the protection elements 92 and 102 shown in FIG. 9 and FIG. 10 cause the current control elements 98 and 108 to increase the current of the low-resistance resistance elements and burn out when the supply voltage increases.
In the embodiment shown in FIGS. 4 to 10, the same components as those in the embodiment shown in FIGS. 2 and 3 are assigned to the lower digits except the first digit in FIGS. 4 to 9 and the upper two digits in FIG. 10. The same sign is attached to the lower digits excluding, and the description is omitted.

  The protection elements 2, 42, 52, 62, 72, and 82 shown in FIGS. 3 to 8 are low resistance resistance elements when the voltage supplied to the heating resistors 4, 44, 54, 64, 74, and 84 increases. The current is reduced or cut off by the current control elements 8, 48, 58, 68, 78, 88 to prevent burning of the low resistance resistance element in a state where the supply voltage is increased.

  3 and FIG. 4, when the supply voltage is increased, the electrical resistance of the PTCs 8A and 48A increases rapidly, and the current of the resistance elements 7 and 47 connected thereto is remarkably reduced. , Virtually no flow. As shown in FIG. 3, the protective element 2 that connects the two shunt circuits 4A in parallel is connected to the PTC 8A of the current control element 8 in series with the low-resistance resistance element 7A having a small electrical resistance. A current control element is not connected to the large resistance element 7C. The PTC 8A is an element whose electric resistance is small at a voltage lower than the trip voltage and whose electric resistance increases rapidly when the applied voltage becomes higher than the trip voltage. The voltage at which the electrical resistance of the PTC 8A increases rapidly is the trip voltage.

  In the protection element 2 having the current control element 8 as the PTC 8A, when the applied voltage of the PTC 8A becomes higher than the trip voltage, the electrical resistance of the PTC 8A increases rapidly. In this state, the current of the low-resistance resistance element 7A is remarkably reduced, and the current is substantially cut off. Since the voltage supplied to the heating resistor 4 is divided into the PTC 8A and the low-resistance resistance element 7A, the supply voltage is divided and supplied to the PTC 8A. When the applied voltage of the PTC 8A exceeds the trip voltage, the PTC 8A Electrical resistance increases rapidly. When the applied voltage of the PTC 8A supplied by dividing is lower than the trip voltage, the PTC 8A is in a very low resistance state. Therefore, in this state, the PTC 8A does not cut off the current of the low-resistance resistance element 7A connected in series therewith. In this state, the low-resistance resistance element 7A connected in series with the PTC 8A flows without current being interrupted to the PTC 8A and generates heat due to Joule heat. Therefore, in the low-resistance resistance element 7A, the current is not cut off by the PTC 8A when the supply voltage is low, and the current is cut off by the PTC 8A when the supply voltage is high. For this reason, the low-resistance resistance element 7A generates heat due to Joule heat when the supply voltage is low, and the current is cut off by the PTC 8A when the supply voltage becomes high. Therefore, the resistance element 7A having a low resistance is not burned by a large current even when the supply voltage of the heating resistor 4 is increased.

  When the supply voltage of the heating resistor 4 is increased, the current of the low-resistance resistance element 7A is cut off. Instead, the high-resistance resistance element 7C heats the low melting point metal 5 and blows out. This is because the power consumption of the high-resistance resistance element 7C increases and Joule heat increases. That is, when the supply voltage is low, the low resistance resistance element 7A heats and melts the low melting point metal 5, and when the supply voltage is high, the high resistance resistance element 7C heats and melts the low melting point metal 5 To do.

  As described above, when the supply voltage is low, the low-resistance resistance element 7A heats and melts the low melting point metal 5, and when the supply voltage increases, the high resistance resistance element 7C blows the low melting point metal 5. The electrical resistances of the low-resistance resistance element 7A and the high-resistance resistance element 7C are specified.

  The electric resistances of the resistance elements 7A and 7C are specified in consideration of the supply voltage, the power consumption, the heat generation amount, and the heat amount capable of fusing the low melting point metal 5. For example, it is assumed that the power consumption of the resistance elements 7A and 7C is 5 W or more, the low melting point metal 5 can be heated and melted by heating, and the low melting point metal 5 is heated with a supply voltage of 5 V or more with the low resistance resistance element 7A. If it is blown out, the electric resistance of the low-resistance resistance element 7A is 5Ω.

  The resistance element 7A having a low resistance is burned out due to an increase in power consumption when the supply voltage increases. When the power consumption by which the resistive element 7A burns out is greater than 15 W, the maximum voltage that can be supplied to the low-resistance resistive element 7A is 8.6V. This is because if the supply voltage of the resistance element 7A exceeds this voltage, the power consumption exceeds 15 W and burns out. The PTC 8A connected in series with the low-resistance resistance element 7A has an increased electrical resistance when the supply voltage of the low-resistance resistance element 7A increases, and the supply voltage of the low-resistance resistance element 7A is 8.6V. Restrict to: For example, when the supply voltage of the low-resistance resistance element 7A exceeds 8V, the PTC 8A trips and the electric resistance increases rapidly. Since the PTC 8A is connected in series with the low-resistance resistance element 7A, when the voltage of the low-resistance resistance element 7A is 8 V or less, the electric resistance is extremely small and the current of the low-resistance resistance element 7A is not limited to a small value.

  In a state where the PTC 8A trips and the electric resistance increases, the high resistance resistance element 7C heats and melts the low melting point metal 5. The high-resistance resistance element 7C has an electric resistance of 10Ω. The high-resistance resistance element 7C consumes 5 W or more when the supply voltage is 7.1 V or more, and melts the low melting point metal 5. When the supply voltage is 12.2V, the high-resistance resistance element 7C has a power consumption of 15 W. Therefore, the high-resistance resistance element 7C generates heat until the supply voltage of the high-resistance resistance element 7C reaches 12.2V. The melting point metal 5 is melted.

  From the above, the two resistance elements 7A and 7C capable of fusing the low melting point metal 5 within the range of power consumption from 5W to 15W, the resistance element 7A having an electrical resistance of 5Ω and the resistance element 7C having a resistance of 10Ω. Can be blown by heating the low melting point metal 5 in a wide range where the supply voltage of the resistance element 7 is 5V to 12.2V. In this protection element 2, in the range where the supply voltage is 5V to 8V, the resistance element 7A having an electric resistance of 5Ω heats and melts the low melting point metal 5, the supply voltage exceeds 8V, and the PTC 8A trips. After the electrical resistance increases, the resistance element 7C having an electrical resistance of 10Ω heats the low melting point metal 5 and blows out.

  As shown in FIG. 4, the protective element can further increase the usable voltage range by using three shunt circuits 44 </ b> A. For example, the protection element 42 having the shunt circuit 44A as three circuits has an electric resistance of 5Ω, 10Ω, and 20Ω as the resistance elements 47A, 47B, and 47C, and the voltage range supplied to the resistance elements 47A, 47B, and 47C is 5V to It can be as wide as 17.3V. However, in this protection element 42, a PTC 48A of the current control element 48 is connected in series to 5Ω and 10Ω resistance elements 47A and 47B. The PTC 48A trips before the power consumption of the resistance elements 47A and 47B connected in series burns out. The tripped PTC 48A has an increased electrical resistance and substantially cuts off the current of the resistance elements 47A and 47B connected in series.

  The protective element 42 includes a plurality of shunt circuits 44A, and the current control element is not connected to the resistance element 47C having the largest electrical resistance, but the current control element is connected in series to all the resistance elements. You can also. Each of the current control elements increases the electric resistance before the resistance elements connected in series are burned out, thereby substantially cutting off the current of the resistance elements.

  The protective elements 2 and 42 described above have a constant power consumption range of 5 W to 15 W in which each of the resistance elements 7 and 47 can be melted by heating the low melting point metals 5 and 45. It is not necessary to make the power consumption range that can melt the melting point metal constant. This is because, for example, each resistance element can have different power consumption ranges in which the low melting point metal can be fused. For example, in the resistance element, the power consumption range in which the low melting point metal can be fused varies depending on the thermal coupling state with the low melting point metal. A resistance element with low thermal coupling and low thermal conductivity from the resistance element to the low melting point metal increases power consumption that can melt the low melting point metal. Conversely, a resistor element having a large thermal coupling and a large thermal conductivity from the resistor element to the low melting point metal can melt the low melting point metal with low power consumption.

  The protective element can increase the number of shunt circuits and increase the supply voltage range that can be used, that is, the voltage range in which the low-melting-point metal can be melted with a heating resistor. The protection element can correspond to the number of shunt circuits connected in parallel to the number of batteries connected in series. However, the protection element does not necessarily need to equalize the number of shunt circuits connected in parallel and the number of batteries connected in series. For example, a resistor having a wide voltage range that can melt a low melting point metal can be used, and a plurality of batteries can be made to correspond to one shunt circuit. That is, the number of shunt circuits connected in parallel can be made smaller than the number of batteries connected in series.

  5 and 6 use fuses 58B and 68B instead of PTC for the current control elements 58 and 68, respectively. The fuses 58 </ b> B and 68 </ b> B are blown and interrupted when a predetermined current flows. The protection elements 52 and 62 having the current control elements 58 and 68 as the fuses 58B and 68B are the voltages at which the PTCs 8A and 48A of the protection elements 2 and 42 in FIGS. 3 and 4 are tripped, and the fuses 58B and 68B are fused. The current of the resistance element connected in series with this is cut off. Since the protective elements 52 and 62 blow the fuses 58B and 68B to cut off the current of the resistance elements 57A, 67A and 67B, the resistance elements 57A, 67A and 67B are not burned even when the supply voltage is increased.

  7 and 8 use breakers 78C and 88C as current control elements 78 and 88 in place of the PTC. Breakers 78C and 88C cut off the current when a predetermined current flows. Therefore, the protection elements 72 and 82 having the current control elements 78 and 88 as the breakers 78C and 88C are voltages at which the PTCs 8A and 48A of the protection elements 2 and 42 in FIGS. 3 and 4 are tripped, and the resistance elements in the breakers 78C and 88C. Since the currents 77A, 87A, and 87B are cut off, the resistance elements 77A, 87A, and 87B are not burned even when the supply voltage increases.

  Further, the protection elements 92 and 102 of FIGS. 9 and 10 use NTC 98D and 108D instead of PTC as the current control elements 8 and 48 of the protection elements 2 and 42 of FIGS. In contrast to PTC, NTC 98D and 108D decrease in electrical resistance as the temperature increases. Therefore, the protection element 2 in FIG. 9 is connected to the NTC 98D in series by decreasing the electrical resistance of the NTC 98D and increasing the current of the resistance element 97A connected in series with the protection element 2 in FIG. The resistance element 97A is surely burned out. Further, the low melting point metal 95 is heated and melted by the resistance element 97C that does not burn. In addition, when the supply voltage increases, the protection element 102 in FIG. 10 decreases the electrical resistance of the NTC 108D and increases the current of the resistance element 107 connected in series therewith. Furthermore, the protective element 102 heats and melts the low melting point metal 105 with the resistance element 107 that is not burned, that is, the resistance element 107 optimum for the supply voltage, while sequentially burning the 102 and the resistance element 107.

  In the battery pack incorporating the above protective element, the control circuit 6 keeps the switching element 3 off when the battery 1 is in a normal state. When the switching element 3 is in the off state, no current flows through the heating resistor 4. Therefore, the low melting point metal 5 is not heated by the heating resistor 4 and the low melting point metal 5 is not blown out. Therefore, the battery 1 is connected to the output terminal 10 of the battery pack via the low melting point metal 5. In this state, the battery pack is charged or discharged.

  When the battery 1 becomes abnormal, the control circuit 6 switches the switching element 3 from OFF to ON. The switching element 3 that has been turned on passes a heating current through the heating resistor 4. The heating resistor 4 is heated by Joule heat generated by a heating current. The heated heating resistor 4 heats and melts the low melting point metal 5. When the low melting point metal 5 is melted, the battery 1 is disconnected from the output terminal 10 of the battery pack and the current is cut off.

  When the supply voltage of the protection element 2 is high, the current control element 8 controls the current of the resistance element 7, and the low resistance metal 5 is heated and melted by the remaining resistance element 7. The number of resistance elements 7 whose current is controlled by the current control element 8 varies depending on the supply voltage. In other words, the number of resistance elements 7 for current control varies depending on the number and type of batteries 1 incorporated in the battery pack. In a battery pack in which a plurality of batteries 1 are connected in series, as the number of batteries 1 connected in series increases and the voltage increases, the number of current-controlled resistance elements 7 increases.

  In a battery pack in which the number of batteries 1 connected in series is increased to increase the output voltage, a resistance element 7 having a small electrical resistance heats and supplies the low melting point metal 5 with the switching element 3 turned on. When the voltage is high, the current control element 8 controls the current of the resistance element 7 connected in series with the current control element 8, and the resistance element 7 having the optimum electrical resistance heats the low-melting-point metal 5 and blows out.

The circuit diagram of FIG. 11 shows a battery pack according to another embodiment of the present invention. In the battery pack of this figure, one low melting point metal 115 is connected between the battery battery output terminal 1110 and the battery 111. In this battery pack, when the battery 111 is in an abnormal state, the switching element 113 is turned on and a heating current flows through the heating resistor 114. The heating resistor 114 through which the heating current flows is heated by Joule heat, and the low melting point metal 115 is thermally melted to cut off the current. In this battery pack, if the number of batteries 111 connected in series is increased to increase the output voltage, the current control element 118 controls the current flowing through the resistance element 117 having a small electrical resistance. The low melting point metal 115 is heated and melted by the resistance element 117 having a large electric resistance. The number of resistance elements 117 to be current controlled varies depending on the number of batteries 111 connected in series, in other words, the supply voltage of the heating resistor 114. When the supply voltage increases, the number of resistance elements 117 to be current controlled increases. When the voltage is low, the number of resistance elements 117 for current control decreases.
In the embodiment shown in FIG. 11, the same components as those of the above-described embodiment are denoted by the same reference numerals in the lower digits except the upper two digits, and the description thereof is omitted.

It is a circuit diagram of the conventional battery pack. 1 is a circuit diagram of a battery pack according to an embodiment of the present invention. It is a circuit diagram of the protection element of the battery pack shown in FIG. It is a circuit diagram which shows another example of a protection element. It is a circuit diagram which shows another example of a protection element. It is a circuit diagram which shows another example of a protection element. It is a circuit diagram which shows another example of a protection element. It is a circuit diagram which shows another example of a protection element. It is a circuit diagram which shows another example of a protection element. It is a circuit diagram which shows another example of a protection element. It is a circuit diagram of the battery pack according to another embodiment of the present invention. It is a circuit diagram which shows the conventional protection element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,111 ... Battery 2,42,52,62,72,82,92,102,112 ... Protective element 3,113 ... Switching element 4,44,54,64,74,84,94,104,114 ... Heating Resistors 4A, 44A, 54A, 64A, 74A, 84A, 94A, 104A, 114A ... Shunt circuit 5, 45, 55, 65, 75, 85, 95, 105, 115 ... Low melting point metal 6, 116 ... Control circuit 7, 47, 57, 67, 77, 87, 97, 107, 117 ... resistance element 7A, 47A, 57A, 67A, 77A, 87A, 97A, 107A ... resistance element 47B, 67B, 87B, 107B ... resistance element 7C, 47C, 57C, 67C, 77C, 87C, 97C, 107C ... Resistance element 8, 48, 58, 68, 78, 88, 98, 108, 118 ... Current control element A, 48A ... PTC
58B, 68B ... fuse 78C, 88C ... breaker 98D, 108D ... NTC
10, 1110 ... Output terminal 11, 411, 511, 611, 711, 811, 911, 1011, 1111 ... Battery terminal 12, 412, 512, 612, 712, 812, 912, 1012, 1112 ... Charging terminal 13, 413, 513, 613, 713, 813, 913, 1013, 1113 ... Switch terminal 18, 418, 518, 618, 718, 818, 918, 1018 ... Intermediate connection point 182 ... Protection element 184 ... Heating resistance 185 ... Low melting point metal 187 ... Resistance element 191 ... Battery 192 ... Protection element 193 ... Switching element 194 ... Heating resistance 195 ... Fuse 196 ... Control circuit

Claims (14)

A protective element comprising a low melting point metal that is blown when heated, and a heating resistor that is thermally coupled to the low melting point metal and that heats the low melting point metal with Joule heat generated by an energized current,
A heating resistor connects a plurality of shunt circuits in parallel, and each shunt circuit includes a resistance element having a different electrical resistance, and at least one shunt circuit has a current control element connected in series with the resistor element. And
The current control element is an element that controls the current of the shunt circuit by changing the electric resistance with temperature or current.
A protective element in which when a predetermined supply voltage is supplied to the heating resistor, the current control element controls the current flowing in the shunt circuit, and the low melting point metal is heated and melted by the Joule heat of the resistance element. The protection element according to claim 1,
The current control element is a PTC whose electrical resistance increases as the temperature rises. When the PTC is heated by the Joule heat of the flowing current and becomes higher than the set temperature, the electrical resistance increases, and the PTC is connected in series. A protective element that reduces the current of the resistive element. The protection element according to claim 1,
The current control element is an NTC whose electric resistance decreases as the temperature rises. When the current control element is heated by the Joule heat of the flowing current and becomes higher than the set temperature, the current of the resistance element connecting the NTC in series is changed. A protective element that is made to increase. The protection element according to claim 1,
The current control element is a breaker that cuts off the current when a predetermined current flows. When the current flowing through the breaker becomes larger than the set current, the breaker cuts off the current and the current of the resistance element that connects the breakers in series A protective element that is designed to shut off. The protection element according to claim 1,
The current control element is a fuse that cuts off the current when a predetermined current flows. When the current flowing through the fuse becomes larger than the set current, the fuse cuts off the current and the current of the resistance element that connects the fuses in series A protective element that is designed to shut off. The protection element according to claim 1,
A protective element in which a heating resistor connects a current control element to a shunt circuit except for one shunt circuit. The protection element according to claim 1,
A protective element formed by connecting one end of a heating resistor to the middle of a low melting point metal. A battery pack comprising a battery and a protective element connected in series to the battery,
The protective element comprises a low melting point metal that is blown when heated, and a heating resistor that is thermally coupled to the low melting point metal and that heats the low melting point metal with Joule heat generated by an energized current,
A heating resistor connects a plurality of shunt circuits in parallel, and each shunt circuit includes a resistance element having a different electrical resistance, and at least one shunt circuit has a current control element connected in series with the resistor element. And
The current control element is an element that controls the current of the shunt circuit by changing the electric resistance with temperature or current.
When a predetermined supply voltage is supplied to the heating resistor, the current control element controls a current flowing in the shunt circuit, and includes a protection element configured to heat and melt the low melting point metal with the Joule heat of the resistance element. Pack battery. The battery pack according to claim 8, wherein
The current control element of the protective element is a PTC whose electrical resistance increases as the temperature rises. When the PTC is heated by the Joule heat of the flowing current and becomes higher than the set temperature, the electrical resistance increases and the PTC is connected in series. A battery pack including a protection element configured to reduce a current of a connected resistance element. The battery pack according to claim 8, wherein
The current control element of the protection element is an NTC whose electric resistance decreases as the temperature rises, and when the NTC is heated by the Joule heat of the flowing current and becomes higher than the set temperature, the resistance element that connects the NTCs in series A battery pack comprising a protective element configured to increase the current of the battery. The battery pack according to claim 8, wherein
The current control element of the protective element is a breaker that cuts off the current when a predetermined current flows. When the current flowing through the breaker becomes larger than the set current, the breaker cuts off the current and the breaker is connected in series. A battery pack comprising a protective element configured to cut off the current of the element. The battery pack according to claim 8, wherein
The current control element of the protection element is a fuse that cuts off the current when a predetermined current flows, and when the current flowing through the fuse becomes larger than the set current, the fuse cuts off the current and connects the fuse in series A battery pack comprising a protective element configured to cut off the current of the element. The battery pack according to claim 8, wherein
A battery pack comprising a protection element in which the heating resistance of the protection element is formed by connecting a current control element to a shunt circuit except for one shunt circuit. The battery pack according to claim 8, wherein
A battery pack provided with a protective element in which the protective element has one end of a heating resistor connected to the middle of a low melting point metal.

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