Patent Description:
As portable electric products such as video cameras, cellular phones and portable PCs are used more broadly, the importance of secondary batteries mainly used as a driving power source therefor is increasing.

A secondary battery capable of charging and discharging, different from a primary battery cannot be recharged is being actively studied in high-tech fields such as digital cameras, cellular phones, laptop computers, power tools, electric bicycles, electric vehicles, hybrid electric vehicles and mass-capacity power storage devices.

In particular, a lithium secondary battery has a high energy density per unit weight and allows rapid charging, compared to other secondary batteries such as lead storage batteries, nickel-cadmium batteries, nickel-hydrogen batteries and nickel-zinc batteries, and thus it is used more and more.

The lithium secondary battery has an operating voltage of <NUM>. 6V or above. The lithium secondary battery is used as a power source for a portable electronic device, or a plurality of lithium secondary batteries are connected in series or in parallel and used for a high output electric vehicle, a hybrid electric vehicle, a power tool, an electric bicycle, an energy storage system (ESS) or a UPS.

The lithium secondary battery has an operating voltage three times higher than that of a nickel-cadmium battery or a nickel-metal hydride battery and has a high energy density per unit weight. For this reason, the lithium secondary battery tends to be used more and more.

The lithium secondary battery may be classified into a lithium ion battery using a liquid electrolyte and a lithium ion polymer battery using a polymer solid electrolyte depending on an electrolyte type. In addition, the lithium ion polymer battery may be classified into a pure solid lithium ion polymer battery without containing any electrolyte and a lithium ion polymer battery using a gel polymer electrolyte containing an electrolytic solution, depending on a polymer solid electrolyte type.

In the lithium ion battery using a liquid electrolyte, a cylindrical or rectangular metal can is generally used as a container in a welded and sealed form. Since the can-type secondary battery using the metal can as a container has a fixed shape, there is a disadvantage that it restricts the design of an electric product using the can-type secondary battery as a power source, and it is difficult to reduce the volume. Thus, a pouch-type secondary battery prepared by putting an electrode assembly and an electrolyte in a pouch packaging material made of a film and sealing the pouch packaging material has been developed and used.

However, the lithium secondary battery has a risk of explosion when being overheated and thus it is important to secure safety. The lithium secondary battery is overheated due to various factors, one of which is an overcurrent flow above a limit through the lithium secondary battery. If the overcurrent flows, the lithium secondary battery is heated by the Joule heat, so the internal temperature of the battery rises rapidly. In addition, the rapid rise in temperature causes a decomposition reaction of the electrolyte, causing a thermal runaway, which eventually leads to the explosion of the battery. Overcurrent occurs in the case where a sharp metal object penetrates the lithium secondary battery, where the insulation between positive and negative electrodes is destroyed due to the shrinkage of a separator interposed between the positive and negative electrodes, where a rush current is applied to the battery due to abnormality of a charging circuit or a load connected to the outside, or the like. In particularly, in case of an electric vehicle, the battery is installed below a seat, which may make it difficult to detect swelling of the battery cell and thus lead to injury of persons.

Thus, the lithium secondary battery is used in combination with a protecting circuit in order to protect the battery against an abnormal situation such as overcurrent, and the protecting circuit generally includes a fuse element for irreversibly disconnecting a line through which a charging or discharging current flows when overcurrent occurs.

<FIG> is a circuit diagram for illustrating an arrangement and an operating mechanism of a fuse element provided in a protecting circuit coupled to a battery pack including a lithium secondary battery.

As shown in <FIG>, in order to protect the battery pack when overcurrent occurs, the protecting circuit includes a fuse element <NUM>, a sensing resistor <NUM> for sensing overcurrent, a microcontroller <NUM> for monitoring the occurrence of overcurrent and operating the fuse element <NUM> when overcurrent occurs, and a switch <NUM> for switching the inflow of an operating current to the fuse element <NUM>.

The fuse element <NUM> is installed on a main line connected to an outermost terminal of the battery pack. The main line refers to a wiring through which a charging current or a discharging current flows. In <FIG>, it is depicted that the fuse element <NUM> is installed at a high-potential line (Pack+).

The fuse element <NUM> is a three-terminal element, where two terminals are connected to the main line through which a charging or discharging current flows and one terminal is connected to the switch <NUM>. In addition, the fuse element <NUM> includes a fuse 1a connected to the main line in series and melted and cut at a certain temperature and a resistor 1b for applying heat to the fuse 1a.

The microcontroller <NUM> periodically detects the voltage at both ends of the sensing resistor <NUM> and monitors whether overcurrent occurs. If it is determined that overcurrent occurs, the microcontroller <NUM> turns on the switch <NUM>. If so, the current flowing on the main line is bypassed to the fuse element <NUM> and applied to the resistor 1b. Accordingly, the Joule heat generated at the resistor 1b is conducted to the fuse 1a to raise the temperature of the fuse 1a. If the temperature of the fuse 1a rises to the melting temperature, the fuse 1a is melted and broken so that the main line is irreversibly disconnected. If the main line is disconnected, the overcurrent does not flow any more, thereby overcoming the problem caused by the overcurrent.

However, the above conventional technique has several problems. In other words, if the microcontroller <NUM> is broken, the switch <NUM> does not turn on even though overcurrent occurs. In this case, a current does not flow into the resistor 1b of the fuse element <NUM>, and thus the fuse element <NUM> does not operate. Also, a space for disposing the fuse element <NUM> is separately required inside the protecting circuit, and a program algorithm for controlling the operation of the fuse element <NUM> must be loaded in the microcontroller <NUM>. Thus, it is disadvantageous that the space efficiency of the protecting circuit is deteriorated and the load of the microcontroller <NUM> is increased.

The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure is directed to providing a battery pack, which is configured to greatly improve the safety in the use of a secondary battery by preventing the occurrence of an event such as ignition without deteriorating the energy density of battery cells.

In one aspect of the present disclosure, there is provided a battery pack as defined in the appended set of claims, comprising: at least one battery cell; a pack case configured to accommodate the battery cell and having a cooling hole formed therethrough; a flow meter provided at an outer side of the pack case and disposed adjacent to the cooling hole; and an opening and closing unit configured to open or close the cooling hole according to a temperature change inside the pack case.

The flow meter senses the flow of air that flows from the inside of the pack case to the outside.

The flow meter generates an alarm when it is sensed that the flow of air is blocked.

Alternatively the battery pack further comprises an alarm device configured to generate an alarm when the flow meter senses that the flow of air is blocked. Namely, the flow meter has only a function of sensing whether air flows or not, and a device for generating an alarm is provided separately.

The opening and closing unit may include a hole cap shaped and sized to be matched with the cooling hole; a vertical rod connected to the hole cap; and one or two bimetals configured to deform a shape when the temperature inside the pack case rises over a reference temperature so that the vertical rod is moved downward, whereby the hole cap is moved downward to close the cooling hole.

The opening and closing unit may include a first bimetal curved to be convex upward when the temperature rises, the first bimetal having a perforation hole through which the vertical rod is provided; a second bimetal located below the first bimetal and coupled to the vertical rod, the second bimetal being curved to be convex downward when the temperature rises; and a stopper located above the first bimetal to restrict the upward movement of the first bimetal.

The opening and closing unit may further include an elastic member located below the second bimetal to elastically support the second bimetal upward.

The opening and closing unit may include one bimetal coupled to the vertical rod and curved to be convex downward when the temperature rises, and the opening and closing unit may further include a stopper located above the one bimetal to restrict the upward movement of the one bimetal.

The opening and closing unit may include a hole cap shaped and sized to be matched with the cooling hole; a vertical rod having one end connected to the hole cap; a horizontal rod extending in a direction perpendicular to the vertical rod and having one end connected to the other end of the vertical rod; and one or two bimetals configured to deform a shape when the temperature inside the pack case rises over a reference temperature so that the horizontal rod is moved away from the vertical rod, whereby the hole cap connected to the vertical rod is moved downward to close the cooling hole.

The opening and closing unit may include a first bimetal curved to be convex toward the vertical rod when the temperature rises, the first bimetal having a perforation hole through which the horizontal rod is provided; a second bimetal located adjacent to the first bimetal and fixed to the other end of the horizontal rod provided through the perforation hole; and a stopper located between the vertical rod and the first bimetal to restrict the movement of the first bimetal toward the vertical rod.

The opening and closing unit may further include an elastic member configured to elastically support the second bimetal toward the first bimetal.

The opening and closing unit may include one bimetal coupled to the other end of the horizontal rod and curved to be convex in a direction away from the vertical rod when the temperature rises, and the opening and closing unit may further include a stopper located between the vertical rod and the one bimetal to restrict the movement of the one bimetal toward the vertical rod.

According to an embodiment of the present disclosure, since a user may detect an abnormal symptom before the occurrence of an event such as ignition of a battery pack, it is possible to secure the safety in using a secondary battery.

According to another embodiment of the present disclosure, when the risk of ignition event in the battery pack increases, the battery pack is completely isolated from the outside, so that the supply of oxygen introduced to the inside is blocked and the flame is prevented from flowing to the outside, thereby securing the safety.

Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the disclosure. For example, a vertical rod may be provided to pass through a bimetal or not to pass through the bimetal.

The structure of a battery pack according to an embodiment of the present disclosure will be described with reference to <FIG>.

<FIG> is a diagram showing a battery pack according to an embodiment of the present disclosure, <FIG> is a diagram showing that a vertical rod is provided through a first bimetal, at an opening and closing unit depicted in <FIG>, and <FIG> is a diagram showing that a cooling hole is closed as the temperature rises, at the battery pack according to the embodiment depicted in <FIG>.

Referring to <FIG>, the battery pack according to an embodiment of the present disclosure may be implemented to include at least one battery cell <NUM>, a pack case <NUM> for accommodating the battery cell <NUM>, an opening and closing unit <NUM> for opening or closing the pack case <NUM> according to a temperature change inside the pack case <NUM> so that the pack case <NUM> communicates with the outside or not, and a flow meter <NUM> for sensing whether air flows out of the pack case <NUM>.

The battery cell <NUM> is be provided in any kind and in any number. One battery cell <NUM> may be accommodated in the pack case <NUM>, and two or more battery cells <NUM> may be accommodated in the pack case <NUM> in a state of being connected in series or in parallel or in a combination thereof.

Also, as the number of the battery cells <NUM> accommodated in the pack case <NUM> increases, the amount of heat generated in the pack case <NUM> increases, and thus the necessity of applying the opening and closing unit <NUM> of the present disclosure becomes greater.

The pack case <NUM> accommodating at least one battery cell <NUM> further includes a space for accommodating the opening and closing unit <NUM>, explained later, in addition to the space for accommodating the battery cell <NUM>.

The pack case <NUM> has at least one cooling hole 20a formed therethrough. The cooling hole 20a functions as a passage through which hot air heated the heat generated at the battery cell <NUM> flows to the outside. In this way, the battery pack may be cooled.

The cooling hole 20a may have an inlet that is narrowed from the outside to the inside of the pack case <NUM> so that a hole cap <NUM> of the opening and closing unit <NUM>, explained later, may be stably coupled onto the inner surface of the cooling hole 20a. If the cooling hole 20a has an inlet narrowed from the outside to the inside and the hole cap <NUM>, explained later, is shaped to be matched therewith as described above, the hole cap <NUM> may be more easily coupled to the inner surface of the cooling hole 20a.

Meanwhile, the cooling hole 20a may be formed in plural. In this case, the opening and closing unit <NUM> is provided as many as the number of the cooling holes 20a, and all the cooling holes 20a are opened or closed according to a temperature change.

The opening and closing unit <NUM> is installed at a position corresponding to the cooling hole 20a to open or close the cooling hole 20a according to a temperature change inside the pack case <NUM>. That is, the opening and closing unit <NUM> operates to close the cooling hole 20a if the temperature inside the pack case <NUM> rises, and operates to open the cooling hole 20a if the temperature inside the pack case <NUM> falls.

For this operation, the opening and closing unit <NUM> applied to the battery pack according to an embodiment of the present disclosure may be implemented to include a hole cap <NUM>, a vertical rod <NUM>, a first bimetal <NUM>, a second bimetal <NUM> and a stopper <NUM>. In addition, the opening and closing unit <NUM> may further include a fixing member <NUM> such as a bolt to fix the second bimetal <NUM> to the vertical rod <NUM>.

The hole cap <NUM> is located at the outside of the battery pack and is sized and shaped to be matched with the cooling hole 20a as described above. That is, the hole cap <NUM> may have a substantially inverted trapezoidal shape in which its width becomes narrower from an upper portion to a lower portion.

The hole cap <NUM> closes or opens the cooling hole 20a as the vertical rod <NUM> moves due to the deformation of the bimetals <NUM>, <NUM>. The hole cap <NUM> may be made of elastic material such as rubber since the hole cap <NUM> functions to seal the cooling hole 20a by closing.

The vertical rod <NUM> has a long rod shape extending in a vertical direction. One end of the vertical rod <NUM> is connected to the hole cap <NUM> through the cooling hole 20a, and the other end of the vertical rod <NUM> is fixed to the second bimetal <NUM> through the first bimetal <NUM>. Here, the vertical direction means an upper and lower direction, based on <FIG>.

Each of the bimetals <NUM>, <NUM> is formed by bonding a pair of metal plates with different thermal expansion rates and is located inside the pack case <NUM>. Thus, if the temperature rises above a reference value due to the heating of the battery cell <NUM>, each of the bimetals <NUM>, <NUM> is curved to be convex toward a metal plate with a greater thermal expansion rate.

In the present disclosure, in the case of the first bimetal <NUM>, a first metal plate 33a with a relatively higher thermal expansion rate is disposed at the top and a second metal plate 33b with a relatively smaller thermal expansion rate is disposed at the bottom. Also, the two metal plates 33a, 33b are contacted and adhered to each other. As the temperature inside the pack case <NUM> rises, the first bimetal <NUM> deforms its shape so that its center portion is curved to be convex upward, namely toward the cooling hole 20a.

In addition, in the case of the second bimetal <NUM>, as opposed to the first bimetal <NUM>, a third metal plate 34a with a relatively higher thermal expansion rate is disposed at the top, and a fourth metal plate 34b with a relatively smaller thermal expansion rate is disposed at the bottom. Also, two metal plates 34a, 34b are contacted and adhered to each other. As the temperature inside the pack case <NUM> rises, the second bimetal <NUM> deforms its shape so that its center portion is curved to be convex downward, namely in a direction away from the cooling hole 20a, as opposed to the first bimetal <NUM>.

Since the second bimetal <NUM> is connected and fixed to an end of the vertical rod <NUM>, the vertical rod <NUM> is moved downward according to the shape change of the second bimetal <NUM>. Also, the stopper <NUM> is fixed and disposed between the cooling hole 20a and the first bimetal <NUM>. Accordingly, if the first bimetal <NUM> deforms its shape, the first bimetal <NUM> is caught by the stopper <NUM>, and the first bimetal <NUM> pushes the second bimetal <NUM> downward due to its reaction.

Thus, the vertical rod <NUM> moves downward by a distance corresponding to the sum of displacements of the first bimetal <NUM> and the second bimetal <NUM>, and thus the hole cap <NUM> connected and fixed to one end of the vertical rod <NUM> is moved downward to close the cooling hole 20a.

Meanwhile, though not shown in the figures, an elastic member may be additionally applied to a lower portion of the vertical rod <NUM> to elastically support the lower portion of the vertical rod <NUM>. In this case, when the shape deformation of the bimetals <NUM>, <NUM> due to the temperature rise does not occur, the elastic member prevents the vertical rod <NUM> from drooping, thereby keeping the cooling hole 20a in an opened state.

The flow meter <NUM> is installed at an outer side of the pack case <NUM> and is disposed adjacent to the inlet of the cooling hole 20a to sense a flow rate of the air flowing between the cooling hole 20a and the outside. If the cooling hole 20a is closed by the shape deformation of the bimetals <NUM>, <NUM> as described above, the flow meter <NUM> senses that there is no flow of air. At this time, the flow meter <NUM> may directly generate an alarm to notify this situation to a user. Alternatively, the flow meter <NUM> may transmit the information on the sensed flow rate to an alarm device (not shown) separately provided so that the alarm device generates an alarm.

As described above, in the battery pack according to an embodiment of the present disclosure, sufficient displacement are generated using two bimetals <NUM>, <NUM> so that the cooling hole 20a may be quickly and reliably closed when the temperature inside the battery pack rises. Also, the change of flow rate according thereto is sensed and an alarm is generated to notify the abnormal temperature rise to the user rapidly, thereby securing the safety in the use of the battery pack.

Next, a battery pack according to another embodiment of the present disclosure, which is implemented in a mode different from the former embodiment, will be described with reference to <FIG> and <FIG>.

<FIG> is a diagram showing a battery pack according to another embodiment of the present disclosure, and <FIG> is a diagram showing that the cooling hole is closed as the temperature rises, at the battery pack according to the embodiment depicted in <FIG>.

The battery pack according to the embodiment depicted in <FIG> and <FIG> is substantially identical to that of the former embodiment, except that only one bimetal <NUM> is applied instead of two bimetals. Thus, in the description of the battery pack according to the embodiment depicted in <FIG> and <FIG>, the feature identical to the former embodiment will not be described in detail, and only a different feature will be described intensively.

Referring to <FIG> and <FIG>, in the battery pack according to another embodiment of the present disclosure, the upward movement of the bimetal <NUM> is restricted by a stopper <NUM> located above the bimetal <NUM> and directly or indirectly fixed to the inside of the pack case <NUM>.

In addition, in the bimetal <NUM>, the third metal plate 34a located at the bottom has a relatively higher thermal expansion rate compared to the fourth metal plate 34b adhered thereon. Thus, as the temperature inside the pack case <NUM> rises, the bimetal <NUM> deforms its shape so that its central portion is curved to be convex downward.

At this time, since the central portion of the bimetal <NUM> is connected and fixed to an end of the vertical rod <NUM>, as the bimetal <NUM> is bent, the vertical rod <NUM> is also moved downward, and accordingly the hole cap <NUM> connected and fixed to one end of the vertical rod <NUM> is moved downward to close the cooling hole 20a.

As described above, the battery pack according to another embodiment of the present disclosure, which is configured different from the former embodiment, may secure the safety in the use of a secondary battery with a simpler structure since only one bimetal is used.

Next, a battery pack according to still another embodiment of the present disclosure, which is implemented in a mode different from the former two embodiments, will be described with reference to <FIG> and <FIG>.

<FIG> is a diagram showing a battery pack according to still another embodiment of the present disclosure, and <FIG> is a diagram showing that the cooling hole is closed as the temperature rises, at the battery pack according to the embodiment depicted in <FIG>.

The battery pack according to still another embodiment of the present disclosure as depicted in <FIG> and <FIG> is substantially identical to that of the former embodiment depicted in <FIG>, except that a horizontal rod <NUM> and joints <NUM>, <NUM> are applied. Thus, in the description of the battery pack according to still another embodiment of the present disclosure as depicted in <FIG> and <FIG>, the feature identical to the former embodiments will not be described in detail, and only a different feature will be described intensively.

Referring to <FIG> and <FIG>, in the battery pack according to still another embodiment of the present disclosure, one end of the horizontal rod <NUM> is fastened to a lower end of the vertical rod <NUM>. At this time, the horizontal rod <NUM> and the vertical rod <NUM> may be fastened by a rod joint <NUM> so as to be rotatable relative to each other.

Meanwhile, an upper end of the vertical rod <NUM> is fastened to the hole cap <NUM>. At this time, the vertical rod <NUM> and the hole cap <NUM> may also be fastened by a cap joint <NUM> so as to be rotatable relative to each other.

The horizontal rod <NUM> is a long rod-shaped component extending along a direction perpendicular to the extending direction of the vertical rod <NUM>. When the bimetals <NUM>, <NUM> deform their shapes due to the temperature rise inside the pack case <NUM>, the horizontal rod <NUM> is moved in a direction away from the vertical rod <NUM>. If the horizontal rod <NUM> moves away from the vertical rod <NUM> as described above, the lower end of the vertical rod <NUM> also moves in the same direction, and accordingly the hole cap <NUM> pivotally coupled to the upper end of the vertical rod <NUM> is moved downward to close the cooling hole 20a.

As described above, in the battery pack according to still another embodiment of the present disclosure, due to the horizontal rod <NUM> connected and fixed to the second bimetal <NUM> through the first bimetal <NUM>, it is possible to close the cooling hole 20a by converting a horizontal force into a vertical direction, thereby minimizing the space between the cooling hole 20a and the battery cell <NUM>. Thus, it is possible to increase the energy density of the battery pack.

Next, a battery pack according to still another embodiment of the present disclosure, which is implemented in a mode different from the former embodiments, will be described with reference to <FIG> and <FIG>.

<FIG> is a diagram showing a battery pack according to still another embodiment of the present disclosure, different from the embodiment depicted in the above figures, and <FIG> is a diagram showing that the cooling hole is closed as the temperature rises, at the battery pack according to the embodiment depicted in <FIG>.

The battery pack according to the embodiment depicted in <FIG> and <FIG> is substantially identical to that of the former embodiment depicted in <FIG>, except that the horizontal rod <NUM> is applied to convert a horizontal force to a vertical force, and the rod joint <NUM> and the cap joint <NUM> are applied to facilitate the force direction conversion. Thus, in the description of the battery pack according to the embodiment depicted in <FIG> and <FIG>, the feature identical to the former embodiments will not be described in detail, and only a different feature will be described intensively.

Referring to <FIG> and <FIG>, in the battery pack according to still another embodiment of the present disclosure, one end of the horizontal rod <NUM> is fastened to the lower end of the vertical rod <NUM>. At this time, the horizontal rod <NUM> and the vertical rod <NUM> may be fastened using the rod joint <NUM> so that the horizontal rod <NUM> and the vertical rod <NUM> may be pivotal relative to each other.

Meanwhile, the upper end of the vertical rod <NUM> is fastened to the hole cap <NUM>. At this time, the vertical rod <NUM> and the hole cap <NUM> may also be fastened using the cap joint <NUM> so as to be pivotal relative to each other.

The horizontal rod <NUM> is a long rod-shaped component extending along a direction perpendicular to the extending direction of the vertical rod <NUM>. When the bimetal <NUM> deforms its shape due to the temperature rise inside the pack case <NUM>, the horizontal rod <NUM> is moved in a direction away from the vertical rod <NUM>. If the horizontal rod <NUM> moves away from the vertical rod <NUM> as described above, the lower end of the vertical rod <NUM> also moves in the same direction, and accordingly the hole cap <NUM> pivotally coupled to the upper end of the vertical rod <NUM> is moved downward to close the cooling hole 20a.

Claim 1:
A battery pack, comprising:
at least one battery cell (<NUM>);
a pack case (<NUM>) configured to accommodate the battery cell and having a cooling hole (20a) formed therethrough;
a flow meter (<NUM>) provided at an outer side of the pack case (<NUM>) and disposed adjacent to the cooling hole (20a); and
an opening and closing unit (<NUM>) configured to operate to close the cooling hole (20a) if the temperature inside the pack case (<NUM>) rises and operate to open the cooling hole (20a) if the temperature inside the pack case (<NUM>) falls,
wherein the flow meter (<NUM>) is configured to sense the flow of air from the inside of the pack case to the outside and to generate an alarm when it is sensed that the flow of air is blocked, or
the flow meter (<NUM>) is configured to sense that the flow of air is blocked and to transmit the information to an alarm device which is provided separately and which is configured to generate an alarm when the flow meter senses that the flow of air is blocked.